Abstract
Carbon dots (CDs) are a fascinating area of research. Carbon nanodots (CDs), also known as carbon quantum dots (CQDs), carbon nanodots (CNDs), and graphene quantum dots (GQDs), have garnered increasing attention in recent times due to their accessibility, non-toxicity, and affordability as carbon-based materials. This paper highlights several synthetic approaches for creating CDs, including hydrothermal synthesis, pulsed laser ablation, direct carbonization, microwave and ultrasonic aided chemical synthesis, and electrochemical methods. Moreover, CDs also possess excellent photostability as they can maintain their optical properties like photoluminescence (PL), charge transfer properties, etc., even under prolonged light exposure. Owing to their distinct optical and optoelectronic characteristics, C-dots have the potential to serve as crucial components for several fields, including optoelectronics, solar cells, light-emitting diodes, and sensitizers. In addition to encouraging the practical implementation of CDs in many current and future research lines, we hope that the material presented in this review will stimulate further fascinating study on CDs from a fresh angle.
1 Introduction
Among the elements that are most prevalent in the crust of the planet is carbon. Numerous useful materials, including different types of nanomaterials, are based on carbon (Paper and Paper, 2002). Since nanotechnology has advanced so much in recent years, carbon-based materials have transformed from cheap waste to valuable commodities. Adding value is often accomplished via the use of novel synthesis techniques, which enable the simple and controlled manufacture of nanomaterials (Kwee et al., 2021; Lu et al., 2012; Marinovic et al., 2017). The sophisticated subclass of carbon-based nanomaterials known as carbon dots (CDs) was first created in 2004 (Li et al., 2012; Xu et al., 2004). Since carbon nanotubes (CNDs) are believed to consist of sp2/sp3 carbon and oxygen/nitrogen-based groups or polymer groups, CNDs are believed to have more practical uses in a range of fields, such as photocatalysis, photothermal therapy, electrochemical energy storage, biological imaging, light-emitting devices, and pH sensing for accuracy in the biomedical and visual fields (Li et al., 2021). To date, several types of CDs, such as CNDs, GQDs, polymer dots (PDs), and so on have been synthesized (Ghosh et al., 2021; Lee et al., 2021; Lin et al., 2020; Sakthivel et al., 2021; Verma et al., 2021).
A “water-in-oil” emulsion was employed by Rhee and Kwon as a nanoscale self-assembling platform in their initial size-controlling synthesis procedure for CNDs (Kwon et al., 2014; Wang X. et al., 2010). The resulting water micelles were encased in an immiscible oil by surfactant molecules. The temperature was then raised to 250 oC for 2 hours while under an argon atmosphere to generate the CNDs. To optimize the creation of CNDs, they also investigated the effects of two distinct temperatures, 160 oC and 200 oC. In addition, the proper temperature was maintained throughout the CND carbonization and capping operations. The concentration of water-surfactant may control the micelle size, it was discovered. Therefore, this approach may provide size tenability with a limited size dispersion. Furthermore, because of their non-identical band gaps, Rhee and Kwon found that different-sized CNDs had different PL behaviors. The blue shift of the PL peak was about 25 nm as the CNDs grew from 1.5 to 3.5 nm. The sp2 hybridization exhibiting different energy gaps due to its association with oleylamine ligands, which acted as auxo chromes to reduce the energy gaps, provided another explanation for the differing results of the quantum size effect (Figure 1). Band gaps were thus larger in large CNDs than in small CNDs with relatively modest ligand/sp2 clusters. This resulted in the large absorption peak at 370 nm being obscured by enormous CNDs and the highest PL peak being shifted to 360 nm (Behi et al., 2022).
FIGURE 1
The sensor community has focused a lot of interest on CNDs because of their outstanding luminous performance, low cost, low toxicity (Singh et al., 2020), strong biocompatibility (Kim and Kim, 2020), optoelectronics (Astafiev et al., 2021), energy (Bian et al., 2019), chemical stability, photocatalysis (Wang et al., 2020) and biological imaging (Gao et al., 2017). Unmodified CNDs often handle a single physics-chemical property due to the absence of particular groups, which surely restricts their wider uses, including full-color displays, light-emitting diodes (LEDs), and bioimaging (Yang Y. et al., 2021; Wang et al., 2018). Thus, creating CNDs with multicolored emissions is desired (Zhang et al., 2023). The following describes how CDs vary from other carbon nanostructures. Due to its favorable environmental effects, ease of synthesis or fabrication, and widespread commercial availability, carbon compounds such as graphite, graphene, carbon nanotubes, fullerene and diamond have historically found extensive application in the field of material science. The lack of an appropriate band gap makes the macro-sized carbon material challenging to use as an ideal luminous material (Tao et al., 2019). By reducing the size up to dot level, bandgaps can be easily tuned over a wide range. CNDs represent a highly appealing substitute carbon source for the “older generation” of well-researched carbon nanostructures. The polar groups that are formed from the starting materials during their production allow these flexible nanocarbon compounds to also be well-dispersed in water (Goryacheva et al., 2017).
Due to the appealing feature of having electrochemical characteristics that are equal to graphene, GQDs are used far more often than other nanoparticles in a variety of fields, including photocatalysis, biosensing, optoelectronic instruments, bioimaging applications, and biological and environmental purposes (Hassanvand et al., 2021; Karimzadeh et al., 2018). CNDs are characterized primarily by the quantum confinement effect (QCE), which manifests when the CNDs’ size is less than the Bohr exciton radius. The valence band and conduction band transition are covered in the QCE phenomenon. To put it briefly, continuous energy bands become discrete energy levels as a material’s size drops to the nanoscale and the bandgap rises as a result. When the CNDs have insufficient surface chemical groups and a large, conjugated p-system, the QCE of the conjugated p-electrons is what causes fluorescence. The carbon core states are believed to have a fluorescence center located in the bandgap of the conjugated p-system. Moving toward the red region is the emission peak due to the larger conjugated p-system size. The conjugated p-system with limited size affects how the valence band and conduction band of CNDs split apart (Kwon et al., 2014; Sk et al., 2014). Subsequently, the electrons go straight to the valence band’s empty state. It is known as the fluorescence bandgap and results in the electron and hole recombining simply. It is projected that the hue of the CNDs emissions and their variable bandgap will alter with modifications to the size of the conjugated a-systems. Reaction conditions might be changed to increase the conjugated p-system size (Sekar et al., 2021).
This review’s main goal is to present a thorough and critical evaluation of the main carbon dot (CD) synthesis techniques, such as hydrothermal, microwave-assisted, laser ablation, electrochemical, and direct carbonization methods. This review assesses how each synthesis route affects the structural, optical, and optoelectronic properties of CDs, including particle size, photoluminescence behavior, quantum yield, surface functionalization, and charge-transfer characteristics, rather than just listing the various methods. The performance of CDs in optoelectronic applications, including as light-emitting diodes (LEDs), solar cells, sensors, and related devices, is also strongly correlated with these synthesis-dependent features. In order to offer recommendations for choosing suitable fabrication techniques and to determine future research paths, a comparative study highlighting the benefits, drawbacks, and applicability of each synthesis approach is offered.
1.1 Meta-analysis of publication trends
The global amount of scholarly literature on the optoelectronic uses of Carbon Dots (CDs) during the last 10 years is shown in Figure 2 to demonstrate the scientific advancement in this topic.
FIGURE 2
2 Synthesis of carbon nanodots (CNDs)
The first time CNDs were reported by Xu et al., in 2004, as a result of unintended discovery (Xu et al., 2004). Carbon nanotubes were reported for the experiment by using arc-discharge soot as a source. During the procedure, the components of the soot solution were separated using gel electrophoresis, which made a new band of fluorescent material visible. CNDs are now synthesized by a variety of physical and chemical procedures (Sakthivel et al., 2021). A fresh band of fluorescent material became evident throughout the process when the soot solution’s components were separated using gel electrophoresis. These days, CNDs are produced using a range of physical and chemical techniques (Khan et al., 2021; Xu et al., 2015). Two main types of CND synthesis methodologies are i) top-down and ii) bottom-up approaches. Top-down methods concentrate on utilizing chemical, electrochemical and other methods to break larger carbon structures down into nanoscale structures (Goryacheva et al., 2017; Hassanvand et al., 2021; Karimzadeh et al., 2018) or physical techniques such as arc discharge (Sk et al., 2014), laser ablation (a straightforward method for creating CQDs are laser-based) (Behi et al., 2022; Sekar et al., 2021), etc. However, bottom-up methods include creating CNDs from smaller carbon units (small organic compounds) primarily by chemical synthesis, which includes the template technique (Khan et al., 2021; Nguyen et al., 2015; Xu et al., 2015), and hydrothermal and microwave synthesis (De Medeiros et al., 2019; Mitra et al., 2012; Roy et al., 2015; Shi et al., 2016).
Top-down approaches, in general, make it possible to produce CNDs with better features and consequently, performance. But they also have some drawbacks, such as a lower fluorescence quantum yield, challenging collection, complex processes, and expensive instruments. Bottom-up approaches offer the advantage of simpler controllable synthetic conditions, a greater availability of carbon sources that are suited for synthesis and generally better fluorescence quantum yields in the generated CNDs. This approach’s sole drawback is that it requires more time and effort for the subsequent purification stages, which has a major impact on CND performance. These days, the most popular synthesis strategy is the bottom-up approach.
2.1 Top-down synthesis
For top-down approaches (Table 1), the most widely used techniques for producing carbon-based nanomaterials are probably laser ablation and arc discharge. An arc discharge occurs when two electrodes, often graphite rods, are linked to a current that vaporizes the electrodes. This results in the production of soot, which may include various carbon-based nanoparticles. By exposing a solid surface to radiation, a process known as pulse laser ablation releases nanomaterials. A quick and inexpensive method for synthesizing nanomaterials, laser ablation in solution (LAS) single-step top-down technique has drawn attention. Low contamination and byproduct formation rates are only two of LAS’s benefits (Nguyen et al., 2015). Gonçalves et al. produced passivated CNDs by laser ablation in a solution containing NH2-polyethylene glycol (PEG200), N-acetyl-l-cysteine (NAC), and water. Nguyen et al. have evaluated this strategy’s many facets and how they affect CNDs. The mean size of CNDs, for example, decreases with decreasing laser fluence and spot size. Moreover, extending the time of the irradiation reduces CNDs and produces several functional groups (Nguyen et al., 2015). For arc discharge, laser ablation and high-energy ion beam radiation, precursors including graphite powder and carbon-based cement have been frequently employed (Li et al., 2012).
TABLE 1
| Sources | Synthetic approaches | Size (nm) | Applications | Ref |
|---|---|---|---|---|
| Glucosamine hydrochloride | Microwave synthesizer | 2.0 ± 0.7 nm | ROS scavenging | Ji et al. (2019) |
| Citric acid and ethylene diamine | Hydrothermal | 1.9 ± 0.2 nm | Theranostic cancer | Wu et al. (2020) |
| Citric acid and polyethyleneimine | Hydrothermal | 9.8–9.9 nm | Bioimaging in vivo and photothermal | Sun et al. (2019) |
| Citric acid and polyethyleneimine | Microwave | -5 nm | Enhancement of bioavailability of curcumin | Arvapalli et al. (2020a) |
| Milk | Hydrothermal | −20 nm for CNDs doxorubicin complexes | Drug delivery | Yuan et al. (2017) |
| Exopolysaccharides | Hydrothermal | 4.3 nm | Microbial viability assessment | Lin et al. (2018) |
| Beer yeast powder | Hydrothermal | Less than 5 nm | Imaging of bacteria | Gao et al. (2019) |
| Citric acid and urea | Microwave | 2.4 nm | Antioxidation | Ji et al. (2020) |
| Citric acid and ethylenimine | Microwave | 2.4 nm | Detection of Fe(III) Ions | Arvapalli et al. (2020b) |
| Chitosan and different unsaturated amides and carboxylic acid | Hydrothermal | 2.6 ± 0.9 nm | Bioimaging, antioxidant | Wang et al. (2017) |
| Phenylenediamine | Hydrothermal | 4.92 nm | Antioxidant | Gao J. et al. (2020) |
| Citric acid and urea | Microwave synthesizer | 2.4 ± 0.3 nm | Radicals scavenging | Zhang et al. (2017) |
| Carbon fiber powder HNO3 | Hydrothermal | 1.8 ± 0.3 nm | Bioimaging | Liu et al. (2019) |
There are a few top-down and bottom-up synthetic techniques for CDs with very good control on synthesis are discussed (Khan et al., 2021).
As precursors for arc discharge, laser ablation, and high-energy ion beam radiation, carbon-based cement and graphite powder have been extensively used (Nguyen et al., 2015). Arc discharge, high-energy ion beam radiation, and laser ablation have all made extensive use of precursors such graphite powder and carbon-based cement (Li et al., 2012). For top-down CND synthesis, several approaches have been investigated. By oxidizing carbon nanostructure aggregates with a strong acid, chemical oxidation introduces hydrophilic functional groups containing oxygen. For top-down CND synthesis, several approaches have been investigated. Chemical oxidation is a technique that introduces hydrophilic functional groups containing oxygen into carbon nanostructure aggregates by oxidizing them with a strong acid. The re-entry of the carbon nanostructures into the fluid is facilitated by their increased solubility in water. The oxidized carbon nanostructures were made soluble in water by Xu et al.'s extraction of soot from arc-discharged materials, which allowed for their release into the solution. When soot was extracted from arc-discharged materials, 3.3M HNO3 was used to oxidize Luminescent CNDs and the black slurry was purified by gel electrophoresis after extraction with NaOH solution. Redox potentials strong enough to oxidize C-C bonds or water to produce oxygen radicals were used in electrochemical procedures. Ding et al. developed CNDs by using multi-walled CNTs generated by chemical vapor deposition as electrodes. This method’s practical and financial benefits prompted several developments regarding the composition of electrodes and carbon sources. Blue-fluorescent CNDs were created by cycling multi-walled CNTs on carbon paper in tetrabutylammonium perchlorate between −2.0 and +2.0 V. Higher CNDs emerged from lower current levels, and their size depended on the current density between 20 and 180 mA cm2 (Roy et al., 2015).
Additionally, investigated are solvothermal and hydrothermal cutting techniques. Among the first to use these techniques were Pan et al (2010), who used graphene sheets and hydrothermal cutting at 200 °C for 10 h to create CNDs. By using leeks in a one-step pyrolysis and hydrothermal treatment process, blue and green, fluorescent CNDs were created. This allowed for easy reaction condition modification and the production of tunable PL (Shi et al., 2016). Intercalation techniques are another common top-down strategy. These techniques usually entail the incorporation of an element or compound into carbon sources, e.g., graphite sheets. Lin et al. used potassium intercalation to create hydrophilic CNDs from CNTs and graphite flakes. When the CNT walls encountered ethanol, the combination of intercalated K atoms and graphene sheets broke down the barriers. The walls were further broken down to CNDs, among other byproducts, produced by ultrasonication. High degrees of accuracy are expressed by other top-down techniques. Graphene was sliced into desired sizes by Ponomarenko et al. using ultrahigh-resolution beam lithography. Li et al. produced CNDs directly by ultrasonic treatment of activated carbon mediated by hydrogen peroxide. Liu et al. vortexed commercial graphic nanoparticles in ethanol and water, then centrifuged the mixture at 2000 RPM for 30 min to provide a supernatant of sp2 CNDs with an ideal crystalline structure (Khan et al., 2021).
There have also been reports of the synthesis of hydrophilic, hydrophobic, and even amphiphilic carbon dots via microwave-assisted synthesis (De Medeiros et al., 2019). Mitra et al. (2012) described a relatively straightforward one-step microwave-assisted synthesis of hydrophobic CDs from the Pluronic F-68 (PF-68) block copolymer, which is composed of polyoxyethylene, polypropylene, and polyoxyethylene (PEO–PPO–PEO). Jaiswal et al. (2012) created CDs by caramelizing PEG under microwave assistance; in this case, glycol served as the CDs passivating agent and carbon source. Similarly, Zhai et al. (2012) reported pyrolytic reactions between amines and citric acid aided by microwaves. Ma et al. (2012) reported the use of ammonium hydroxide and glucose as a precursor in the ultrasonic synthesis of N-doped CDs. Dang et al. (2016) reported CDs on a massive scale by applying ultrasonic treatment to an oligomer polyamide resin, which served as the carbon source (Sivasankarapillai et al., 2020).
CDs are also extensively produced with the help of pulsed laser ablation method. To create CNDs with UV emission from a graphite target, a PLA (Pulsed Laser Ablation) technique is devised. The CNDs’ graphitic carbon cores are disclosed by TEM, XRD, Raman and XPS data, while their surface groups are functionalized with basic oxygen-related groups. As a result, there is very little excited electron trapping by surfaces and imperfections. Consequently, the CNDs display three sub-bands of intrinsic UV emission at 305 nm, 325 nm, and 335 nm. This study presented a novel method for creating U: V-emissive CNDs, which will greatly advance the use of CNDs in optoelectronics (Yang M. J. et al., 2021).
Direct pyrolysis, often referred to as the pyrolytic process, is a method frequently used in the synthesis of CDs. It entails carbonizing carbon precursors at high temperatures. To degrade the precursors at the nanoscale, a powerful acid or alkali is used. This pyrolytic process can use leftover fruit peels, any kind of juice, carbon-based chemicals, or anything that contains carbon as its carbonaceous source. Zhou et al. illustrated producing CDs using fresh watermelon peel as the starting material. Filtration and centrifugation were used to purify the final product after the peel was carbonized for 2 hours at 220 oC. The particles had significant blue luminescence and were stable and soluble in water (Zhou et al., 2012). High quantum yield and good water solubility CDs are synthesized at 200 oC using citric acid and glutathione as starting ingredients, as presented by Zhuo et al., (2015) and these particles had emission behavior that was independent of excitation and produced blue fluorescence. The addition of ligands and continuous stirring of the fluid, and the introduction of chemical bonds with amidation reactions or electrostatic interactions, are the factors responsible for the modification in the behavior of CDs.
Modification of the nanostructure and electrical distribution of CDs can be accomplished by doping them with heteroatoms, fluorescence may be regulated by nitrogen doping, and excitation-independent behavior can be exploited to infer passivated surface states (Arvapalli et al., 2020b; Gao J. et al., 2020; Wang et al., 2017; Zhang et al., 2017). Furthermore, N-doped carbon dots have been synthesized utilizing bee pollen as the carbon source by the use of hydrothermal carbonization techniques. It was found that the utilized method produced a good yield of 3 g of CDs from 10 g environmentally friendly precursor. Wang F. et al. (2010) employed a straightforward, one-step process to create CDs. The procedure involved loading 1.5 g of 1-hexadecylamine and 15 mL of octadecene into a three-neck flask, heating it to 300 oC with an argon flow. After adding 1 g of CA to the mixture and stirring constantly for 3 hours at 300 oC, the mixture was purified by precipitation and three acetone washes. The final product developed was CDs that were extremely soluble in ordinary non-polar organic solvents (Sivasankarapillai et al., 2020).
2.2 Bottom-up synthesis
To create CNDs from biological material, bottom-up approaches have been completely established as an alternative economic structure (Table 1). CNDs below 10 nm that are photoluminescent and persistent in an aqueous solution are often the product of the original components and circumstances. Gianneli et al. heated organic ammonium and citric acid (CA) monohydrate hydrothermally to produce 7 nm CNDs after acetone washing and filtering. Urea, ethanolamine, cysteine, glycine, ethylenediamine, and other organic materials have all been used in the synthesis of hydrophilic CNDs since the first CNDs were reported to have been produced. Zhu et al. synthesized PEG-200 and a dissolved saccharide using microwave pyrolysis for the first time. The size of the CNDs increased with reaction time when this solution was cooked in a 500 W microwave oven. Microwave pyrolysis increases the yield of CNDs, decreases side reactions, and shortens process times (Cayuela et al., 2016). Nevertheless, certain CNDs made with this technique exhibit reasonable luminescence and blue emission (Das et al., 2014). Qu et al. heated inorganic ions and carbohydrates for a few minutes to produce CNDs. Comparable techniques include heating organic molecules in solution for a duration ranging from seconds to minutes at 300–900 W. Reactants include PEG-200, polysaccharides containing inorganic ions (such 4,7,10-trioxa-1,13-tridecanediamine, or TTDDA), citric acid and amino acids.
For a microwave heating procedure, Stefanakis et al. used aqueous solutions of urea and either 6-aminocaproic acid or citric acid. CNDs were produced using microwave-cooking solutions. It was predicted that citrate molecules would form CNDs. The surface groups were made up of additional organic molecules, resulting in a hydrophilic CND. To create pure CNDs, the product is often dialyzed, centrifuged, or ultra-filtered once it is acquired. Polymers might be added by surface passivation, which usually takes minutes. Following the microwave synthesis of lipoic acid, citric acid, and urea, Chen et al. generated N, S-co-doped CNDs with OH- and NH surface groups, which made them hydrophilic (Chen et al., 2013). As determined by XPS, CNDs with strong graphite components and sp2 character are produced by microwave pyrolysis and laser ablation. The fact is that precursors are heated and carbonized in an inert environment during the process of direct thermal decomposition, which has produced a range of CNDs. Gianneli et al. developed CNDs in 2008 utilizing a direct thermal breakdown method; they had an asymmetric shape and were only stable in organic solvents like DMSO and DMF. After using a different method of thermal breakdown, which included combining citric acid with sodium 11-amminoundecanoate, heating the combination, and centrifuging the mixture, hydrophilic CNDs were produced. The end result was the production of core-shell structured CNDs with an overall size of 10–20 nm and a core size of 5–10 nm. Carbon and nitrogen sources were provided by citric acid and tris(hydroxymethyl)aminomethane to produce nitrogen-doped CNDs (N-CNDs) in a single process (Xu et al., 2015). The template synthesis method was utilized to create CNDs from monodisperse spherical mesoporous silica particles. After thermal decompression and template removal, organosilane was deposited into the pores to produce spherical CNDs (He et al., 2020).
Liu et al.'s assisted synthetic technique uses formaldehyde or phenol resins as carbon precursors and polymer/silica composites as carriers. Heating facilitated the formation of carbon/silica blends, which, by the etching with NaOH, yielded CNDs. The oxidation, neutralization and purifying processes that came next were difficult and time-consuming. Li et al. used nanoreactors composed of silica spheres with holes ranging in size from 2 nm to 50 nm, which simplified this operation. They are stable, PL and comparatively nontoxic CNDs that do not require any further purifying processes. Because concentrated H2SO4 is a potent dehydrator, it has also been used to create a variety of CNDs. This procedure, which includes adding sulfuric acid to sucrose solution, neutralization, dialysis, and neutralization, was initially published by Zhang et al. The molecular weight of pure CNDs was used to distinguish them based on their photoluminescence behavior 2 nm CNDs emitted green light, whereas 5 nm CNDs were photoluminescent following PEG2000 N passivation. Other dehydration syntheses may use organics such as bovine serum albumin, ethylene glycol, or ethylenediaminetetraacetic acid (EDTA). Some employ heat as well; reaction temperatures can range from 40 oC to 200 oC. A plethora of other techniques have been devised to produce CNDs with a consistent size distribution and comparatively elevated purity. Kim et al. created an atomic carbon beam using ethylene gas and Ar plasma, and they carved graphene into CNDs using thermal plasma jets. After dissolving commercial coffee in 90 oC water and centrifuging it at 14,000 RPM, Jiang et al. were able to extract approximately 4.4 nm CNDs by gel filtration chromatography. Li et al. employed ultrasonic treatment to synthesize as shown in Figure 3 (Shi et al., 2016).
FIGURE 3
Usually, four sequential phases in the development of CNDs for optoelectronic application involve (i) tiny organic molecules aggregating; (ii) forming a dense core with an extended shell; (iii) the shell collapsing; and (iv) the core aromatizing (Table 2). Additional heating causes the core to aromatize but does not affect the emissive behavior. They introduced five new CNDs, all of which have an amine-rich ligand shell covering an electron-dense core; as a result, post-synthesis CND functionalization is not necessary to produce a core-shell structure (Figure 4) (Rigodanza et al., 2021).
TABLE 2
| Synthesis method | Typical size (nm) | Optical characteristics | Advantages | Limitations | Suitable optoelectronic applications |
|---|---|---|---|---|---|
| Hydrothermal | 2–10 | High photoluminescence, tunable emission, good quantum yield | Simple, eco-friendly, inexpensive | Long reaction time | LEDs, bioimaging, sensors, solar cells |
| Microwave-assisted | 2–8 | Bright fluorescence, high quantum yield, excitation-dependent emission | Very rapid synthesis, energy efficient | Limited scale-up | LEDs, fluorescent probes, sensors |
| Laser Ablation | 2–6 | High purity, stable emission, narrow size distribution | Chemical-free synthesis | Expensive equipment, low productivity | High-performance optoelectronics |
| Electrochemical | 2–8 | Tunable emission through voltage control, excellent surface functionality | Mild synthesis conditions | Low production yield | Electrochemical sensors, photovoltaics |
| Direct Carbonization | 3–10 | Good photostability, precursor-dependent fluorescence | Low cost, green synthesis | Poor size uniformity | LEDs, photocatalysis, solar cells |
Comparison of carbon dot synthesis methods and their optical/optoelectronic characteristics.
FIGURE 4
Along with preparation, the effect of applied voltage on CD size has been studied. Numerous papers describe the electrochemical method of producing CDs, such as Bao et al. (2011), who detailed the fluorescence behavior and electrochemical tuning of CDs. CDs have been successfully created from low-molecular-weight alcohols (Deng et al., 2014). In a basic medium, alcohols were transformed into carbon particles using the electrochemical carbonization process. Hou et al. (2015) reported an electrochemical process that produced CDs in a single pot and was utilized to detect mercury ions. Zeng et al. (2019) developed superior CDs that, by using a unique bio-electrochemical process, were able to enhance their electrical output and demonstrated outstanding catalytic performance (Sivasankarapillai et al., 2020). The viability of studying microwave-assisted hydrothermal techniques for synthesis has attracted attention. Wang Q. et al. (2011) used graphene oxide as the precursor in a hydrothermal process aided by microwaves to create CDs with favorable luminescence characteristics. Lately, Zheng et al. (2017) presented an additional quick technique that suppresses the quenching of the produced CDs fluorescence by employing N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane.
Biomolecules may also be employed in synthesis. To create luminous CDs in the presence of monopotassium phosphate, Yang et al. (2011) employed glucose. The monopotassium phosphate in this system functioned as a regulating component to adjust the emission spectra. Additionally, biomolecules are employed as synthesis’s precursors. To create luminous CDs in the presence of monopotassium phosphate, (Arvapalli et al. 2020a) employed glucose. The monopotassium phosphate in this system functioned as a regulating component to adjust the emission spectra. Similarly, Chen et al. (2016) described a successful hydrothermal process that synthesized lignin. Zhang et al. (2018) created chiral CDs using a hydrothermal process in one step. The scientists discovered that the CDs might affect the physiology of mung bean plants by using citric acid and cysteine (cis-form) as carbon sources (Sivasankarapillai et al., 2020).
3 Optical properties of CDs
CNDs have drawn a lot of interest in the last decade. From a fundamentally applicable perspective, PL has attracted the interest of several researchers and is considered one of the most promising behaviors of CNDs (Kwee et al., 2021). PL refers to fluorescence, not formed by heating (Greenham et al., 1995). CNDs with distinct ratios of nitrogenous or oxygen-containing groups can arise from nucleation and development under various reaction circumstances and these CNDs have their distinctive PL properties (Figure 5). The excitation wavelength, quantum yield, and PL of CNDs are determined by their synthetic conditions, which include temperature, reaction time, and precursor materials (Bayan and Karak, 2019; Liu et al., 2015; Shen and Liu, 2016; Wang et al., 2016; Xu et al., 2015). The CNDs’ average UV absorbance is in the range of 330–420 nm. It has a tail in the visible area and is affected by photon harvesting. However, a 250–300 nm band may be present in CNDs due to * bond and ketone group transfer. Their emission wavelength typically falls between 400 and 600 nm, depending on their size (Li et al., 2012). Sun et al. have proven that the PL intensity of CNDs is related to their size. CNDs of different sizes and synthesis methods have been seen in the UV to NIR range. The transition gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), which is inversely proportional to size, contributes to the size dependency of CNDs (Roy et al., 2015). Using gel electrophoresis and HPLC, CNDs with uneven size distributions were able to measure their peak lightness PL of 1.2 nm in the UV and 1.5–3.8 nm in the visible and near-infrared ranges (Roy et al., 2015).
FIGURE 5
Furthermore, the PL of 30–50 nm CNDs was lower than that of 10 nm CNDs, which can be attributed to the smaller CND’s greater PL due to their larger surface area to volume ratio. After hydrothermally cutting graphene sheets, CNDs with a size distribution of 5–17 nm and a matching PL wavelength of 450–486 nm were produced. The transformation of the CND from circular to polygonal shape, which raised the PL energy, was the cause of this reversal of the quantum size effect (Roy et al., 2015). Therefore, even across various sizes and shapes, the edge type of differently manufactured CNDs can affect PL. When λex was 470 nm, CNDs made from flower petals emitted a bright green light at 510 nm and showed absorptions from 220 to 400 nm. This might be because the band gap is being lowered by emissive flaws and a high graphite content (Paquin et al., 2015). The emission spectra of coffee-ground-synthesized CNDs changed from 400 to 600 nm, indicating their λex dependency (Li et al., 2012). The surface and core functional groups, as well as surface electronic state changes, can cause CNDs to become excited (Zeng et al., 2017). This characteristic sets them apart from other nanomaterials such as nanoclusters, Au-nanodots, and SQDs (Roy et al., 2015). Li et al. used hydrazine hydrate to decrease graphene oxide and then functionalized the surface with PEG.
The modified CND released photons at a lower wavelength (390–468 nm) when it absorbed several longer wavelength photons (600–800 nm) simultaneously or sequentially. Because CNDs absorb light poorly, oil-synthesized CNDs and CA-CNDs exhibited adjustable emissions that reduced fluorescence intensity with increased excitation (Table 3). This suggested that long λex may be employed to be less hazardous in vivo, limit background noise, and reach deep tissues CNDs produced from petals exhibited a red shift, an increase in PL intensity, and a subsequent drop in λex from 430 to 490 nm. Additionally, the average fluorescence lifetime of CNDs was 5.8934 ns (Paquin et al., 2015). Excited from 250 to 600 nm, hydrophobic N-doped CNDs showed a red-shifted emission that peaked at λex of 390 nm (Cayuela et al., 2016). They also demonstrated up conversion, a feature of CNDs that enables lower energy excitation of live cells, hence reducing harmful effects and aiding in interference elimination. When the excitation wavelength was altered from 700 to 900 nm, the N-doped CNDs exhibited a red shift and a narrowing of their emission peak at 500 nm (Khan et al., 2021).
TABLE 3
| Types | Mode of excitation | Importance/applications | Presence of CDs | Ref. |
|---|---|---|---|---|
| Radioluminescence | Ionizing radiation | Scintillators, biomedicine, dosimetry | CQDs | Stellmer et al. (2015) |
| Photoluminescence | Photon | LEDs, display panel | CQDs | Gupta et al. (2021) |
| Triboluminescence | Frictional and electrical forces, mechanical energy | Sensor, aerospace, defense sector, civil construction | CNDs | Olawale et al. (2011) |
| Chemiluminescence | Chemical process | Pharmaceutical, clinical, analytical, gas analysis | GQDs | Iranifam (2014) |
| Cathodoluminescence | Cathode ray/electron beam | Pharmaceutical, mineralogy, display | SQDs | Barbin (2013) |
| Bioluminescence | Biological process | Imaging, dairy industries, biocidal disinfection | CQDs | Brock (2012) |
Different types of CDs are used in luminescence depending on the mode of excitation.
The charge-transfer chemistry of CNDs, which allows them to function as either electron donors or acceptors, is one of their most remarkable characteristics. Several supramolecular structures with varying dimensions have been created by fusing CNDs with mesoporous surfaces or molecular and particulate building pieces. Charge transfer to or from photoexcited CNDs is how they function. Generally speaking, CNDs have developed into adaptable building blocks for supramolecular structures with specific electrical characteristics, indicating their potential application in low-cost charge-transfer active materials for technological devices (Cadranel et al., 2019). The optical and antioxidation characteristics of CNDs are studied by doping them with phosphorus (P) and boron (B) in varying amounts. Following doping, high P%-CNDs’ UV–vis absorption exhibited a little blue shift (348-345), whereas high B%-CNDs’ absorption revealed a modest redshift (348–351 nm). A study on the scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals was carried out for every CND. The highest scavenging ability was found to be indicated by the high B%-CNDs. This work may provide guidance in the development of CND structures in the core and surface functional groups, as a helpful method for modifying the optoelectronic properties of CNDs for photoluminescence and antioxidation applications (Azami et al., 2023).
Cl-CNDs, or chlorine-doped carbon nitride dots, are also claimed to be produced by thermally treating guanidine hydrochloride, making them both luminous and phosphorescent. The phosphorescence quantum yield of the Cl-CNDs is 2.32% and their phosphorescence lifetime is 657 ms when they are triggered at 360 nm in ambient conditions. Since Cl-CNDs are inexpensive to produce and have changeable optical properties, they may find application in security encryption and optoelectronic systems (Patir and Gogoi, 2022). The green fluorescence nature of CNDs was evaluated at 510 nm for maximum emission using photoluminescence and ultraviolet-visible absorption spectra. In the current study, the scientists employed an easy-to-use and low-cost technique to synthesize vivid green PL CNDs from soft coconut water using acid-assisted ultrasonic with an excitation wavelength of 450 nm. The fluorescence quantum yield of the carbon nanotubes (CNDs) having a carbon core and chemical groups all over their surface was 60.18%. These results and observations offer a foundation for a range of upcoming investigations into the use of CNDs in cell imaging and optoelectronics (Manoharan et al., 2020).
It was described as an oxygen-free synthesis of CNDs with exceptionally low oxygen contents based on the pyrolysis-induced decarboxylation of aromatic carboxylic acids. The creation of CNDs nearly usually involves a certain kind of oxidation process. With an absolute quantum yield that may reach 80%, the CNDs show very strong excitation-independent PL in the visible spectrum’s yellow to orange region. This novel synthetic method, which is predicated on the non-oxidative pyrolysis of ACAs, sheds light on the synthesis of highly luminous CNDs and emphasizes the necessity of giving oxygen’s impact on the chemical, optical, and electrical aspects of CNDs more thought. Using the pre-made CNDs as a stand-alone color filter, vivid orange light was produced (Lee et al., 2021).
The study focused on polyethyleneimine CNDs (PEI CNDs) with concentration-dependent PL properties and unique excitation using a one-pot hydrothermal technique. The findings demonstrated that L-Glu and PEI might be directly connected to the CNDs, allowing the CNDs to handle rich amniotic groups. The carbon core of the PEI CNDs is primarily responsible for the excitation-independent blue PL behavior at low concentrations (0.1 mg/mL and 0.2 mg/mL). The UV–Vis absorption at 350 nm shows a considerable increase when the concentration of PEI CNDs rises from 1 mg/mL to 10.0 mg/mL, and the absorption peaks broaden as the concentration of PEI@CNDs increases. Green, cyan, blue, and greenish-yellow are displayed in the PL colors. The color coordinates of (0.30, 0.31) and (0.39, 0.40) could be produced by combining 10.0 mg/mL of PEI CNDs with polymer PVA and employing light-conversion films of PVA containing PEI CNDs to combine with the blue LEDs to create WLEDs with white and warm white emissions. Results demonstrated that the PEI CNDs may be employed in WLED fabrication, and they show tremendous promise in the field of optoelectronics (Zhang et al., 2023).
A variety of functional groups, including C-O, C=O, C-O-C, and C-N, are attached to the surface and edges of the carbon nucleus of N-CNDs. This was demonstrated by multi-color fluorescent N-CNDs that were created using a microwave technique with CA and L-glutamic acid as carbon sources. Deionized water was used as a dispersion agent. The generated N-CNDs can produce green (546 nm), orange (617 nm), and blue (445 nm) fluorescence, depending on the raw material ratios of 1:1,1:2 and 1:3. Variations in the N concentration doped into N-CNDs can result in distinct surface/edge states, and by adjusting the N concentration in CNDs, one can adjust the wavelength of the PL emission from N-CNDs. The number of C-O groups on the surface or edges of N-CNDs is correlated with their PL intensity. When the concentration of N in N-CNDs increases, the wavelength of the PL emission from these N-CNDs exhibits a redshift (Li et al., 2021).
4 Application of CDs in optoelectronic
CNDs have many benefits, such as abundant and readily accessible raw materials, low cost, multicolored photoluminescence, convenient synthesis, excellent biocompatibility and acceptable renewability. Researchers synthesize these new nanomaterials which are valuable and environment-friendly with novel applications (Figure 6). CDs also show various applications in optoelectronics (Kwee et al., 2021).
FIGURE 6
4.1 Carbon dots as a sensitizer in DSSC
The exceptional electron-donor and acceptor electrochemical properties of CDs (Kwon et al., 2014; Stellmer et al., 2015), in addition to producing both electrochemical and chemical luminescence (Li et al., 2015), give them a broad range of possibilities in sensors, optoelectronics, and catalysis. Numerous solar cells have made use of CDs’ exceptional light-harvesting and conducting qualities (Table 4). As CDs frequently exhibit excellent optical absorptivity throughout a broad visible light spectrum, they might be used as a substitute sensitizer in DSSCs. The most sophisticated DSSCs available today usually use sensitizers based on Ru. The problem is that while Ru-based sensitizers work well most of the time, they are difficult to synthesize and rely on the pricey and rare Ru-metal core, therefore there is an urgent need for a sustainable, eco-friendly alternative. Low current density may result from photo-charged surface recombination, which is also seen when CDs are employed as sensitizers (Gao N. et al., 2020).
TABLE 4
| Classification | CND role | Device architecture | Optimized conditions | Explanation for performance | References |
|---|---|---|---|---|---|
| CQDs | Sensitizer | FTO/TiO2 NPs/CQDs/I3 –: I–/Pt | No optimization | Emissive sites acting as recombination centers, inferior charge injection properties | Mirtchev et al. (2012) |
| GQDs | Sensitizer | FTO/TiO2 NPs/GQDs/I3 –: I–/Pt | No optimization | Low affinity of GQD functional groups for TiO2 | Yan et al. (2010) |
| CNDs | Sensitizer | FTO/TiO2 NPs/CNDs/I3 –: I–/Pt | No Optimization | IR light. Low performance due to high recombination rates with CNDs and poor electron transfer | Wang et al. (2012) |
| CQDs | Electron donor | No device made | No optimization | CQDs promoted photosynthesis by enhancing the electron transfer process; chloroplasts absorbance profile overlaps with CQDs emission profile (390 nm excitation) resulting in electron transfer from CQDs to chloroplasts | Chandra et al. (2014) |
| CQDs | Electron acceptor/dono r | FTO/TiO2 NPs/RhB/CQDs/I3 –:I–/Pt | No optimization | CQDs act as electron/energy transfer bridge between RhB and TiO2 mimicking processes involved in photosynthesis; CQDs enhanced absorbance of RhB and acted as one-way bridge, effectively separating the charge carriers and suppressing recombination | Ma et al. (2013) |
| GQDs | Electron acceptor | ITO/PEDOT:PSS/P3HT:GQDs/LiF/Al | 1 wt% GQDs | Depends on GQD wt%; Appropriate band alignment, improved optical properties and morphology (e.g., nanoscale phase separation) of composite film | Gupta et al. (2011) |
Sensitizer devices.
4.2 Light-emitting diodes (LEDs)
Lately, several study teams have endeavored to use CNDs as an active component in optoelectronic apparatuses, such as light-emitting diodes (LEDs). The Liu and Ma groups showed off the electroluminescence of CNDs made using the noncoordinating solvent approach for LEDs, although achieving an acceptable brightness required an extremely high operation voltage (about 9 V) (Barbin, 2013; Iranifam, 2014). Additionally, phosphor-based LEDs with CNDs made of photonic crystals were disclosed by Chen and colleagues (Guo et al., 2012). Three colors; bright blue, orange, and warm white are rendered satisfactorily; nevertheless, the resulting CNDs only exhibited a small amount of absorption in the deep-blue (long-UV, 360–400 nm) range. As a result, the most popular base LEDs, Gallium nitride (GaN) blue LEDs, are not very effective for this system. Furthermore, aggregation of solid-state CNDs often leads to considerable light quenching, which would considerably restrict the performance of CND-based LEDs (Essner and Baker, 2017; Li et al., 2015).
LEDs are considered the lighting technology of the future because of their high stability, affordability, eco-friendliness and mass manufacture. As a novel kind of carbon-based QDs, CQDs seem to be one of the most promising substitutes for costly rare-earth-based phosphors and hazardous metal-based semiconductor QDs to speed up the development of electroluminescent full-color displays and lighting. Phosphor-converted LEDs (pc-LEDs) and electroluminescent LEDs are the two main types of LEDs based on CQDs. The term “pc-LEDs” describes the optical pumping of CQD-based phosphors using blue/NUV chips as the primary light source. When electrons and holes are introduced into CQDs for electroluminescent LEDs, they undergo radiative recombination, which functions as an active emission layer. Among these, the creation of electroluminescent LEDs with high efficiency is crucial for next-generation displays (Shi et al., 2022).
4.3 Solar cells (SCs)
CQDs have potential uses in solar cells (SCs), including dye-sensitized SCs, organic SCs, and silicon-based SCs, because of their broad spectrum of light absorption (Chandra et al., 2014; Mirtchev et al., 2012; Wang et al., 2012; Yan et al., 2010). Currently, the photocurrent and power conversion efficiency (PCE) of corresponding perovskite solar cells (SCs) may be greatly increased (from 8.81% to 10.15%) by adding a sub-monolayer layer of CQDs between the perovskite and the mesoporous titanium dioxide layers. This work demonstrated that hot electrons from the photo-excited perovskite may be collected because of their sluggish cooling (Shi et al., 2018). Additionally, by adding CQDs to stabilize MAPbI3 by grain boundary passivation, the PCE increased 17.59%–18.81%) and perovskite SC stability enhanced (Guo et al., 2019). Despite the paucity of studies on CQDs in the field of SCs, CQDs remain a viable alternative to inorganic halide perovskites, which are unstable and poisonous (Shi et al., 2022). Another instance is the heterojunction of p-type PbS colloidal quantum dots (CQDs) with n-type wide-band-gap semiconductors, such as ZnO or TiO2. It is anticipated that confinement within these nanostructures would lead to marginal phenomena, such as hot carrier collection and multiple exciton formation, hence raising the theoretical limit of conversion efficiency. In the end, this method may potentially result in the construction of a tandem-type cell that absorbs light in several solar spectrum areas thanks to CQD films (Malgras et al., 2017).
4.4 Phosphor-converted LEDs
Two distinct peaks at 448 and 548 nm are produced by the LED using CQDs as phosphors when compared to the PL spectra of the CQD solution. This phenomenon might be explained by the solid-state CQDs integrated with the LED lens transferring energy through light reabsorption (Kwon et al., 2014; Li et al., 2015; Yan et al., 2010). To create pc-WLEDs, blue/NUV LED chips and CQD phosphors are often mixed (Guo et al., 2012; Kwon et al., 2013). However, because of direct π–π interactions, CQD phosphors are limited to self-quenching in the solid state, which is insufficient for real-world uses. In this instance, phosphors have been embedded into solid matrices (such as polymers, starch, and silica xerogel) conventionally to provide solid-state illumination of CQD-based composites. The realization of high-performance multicolor pc-WLEDs still confronts significant obstacles since there are fewer multicolor CQDs with high QYs in solid states and because solution-processability is a concern. Effective singlet-component CQDs in solid states have been studied in the last several years. To create warm white light emission, for example, R/G/B-SBF-CQRs with high QYs up to 30%–46% have been successfully applied to LEDs. This shows promise for acting as a replacement for conventional rare earth phosphors and realizing industrialization in the future (Gao N. et al., 2020; Wang et al., 2012).
5 Current bottlenecks and future perspectives
Although carbon dots have significant optoelectronic potential, a number of outstanding material issues need to be resolved before commercial translation can take place:
5.1 Low reproducibility of emission properties
Because polymerization, carbonization, and passivation occur simultaneously during bottom-up synthesis, even small changes in batch temperatures or heating rates can drastically change surface topologies (Kwon et al., 2014; Rigodanza et al., 2021). To guarantee consistent optical performance from batch to batch, standardized, automated synthesis processes must be developed. Furthermore, in parallel tracking systems, integrating physics-based rendering with neural network embeddings is essential to maintain multi-source illumination color constancy despite these material variances (Xue et al., 2025).
5.2 Scale-up limitations
High quantum efficiency production techniques, such microwave or hydrothermal synthesis, are usually limited to tiny batch sizes (He et al., 2020). Thermal and mass-transport gradients are frequently introduced when scaling up to commercial levels, which widens particle size distributions and deteriorates color purity. This optical variance presents similar challenges to low-light imaging frameworks, where multiconditional diffusion probabilistic models (such as MCLL-Diff) are deployed to dynamically adapt and enhance contrast under poor visibility conditions (Chen et al., 2025).
5.3 Stability under device operating conditions
CDs are subjected to extended exposure to heat, moisture, and strong UV fluxes when incorporated into high-power LEDs or solar cells. In these circumstances, thermal desorption or photo-oxidation of the surface functional groups that passivate fault states may occur, resulting in irreversible luminescence degradation and device failure (Essner and Baker, 2017). To monitor macro-structural shifts and thermal anomalies linked to this degradation, highly precise diagnostic tools are required, such as using self-mixing interferometry with intracavity frequency-doubling solid-state lasers to trace micro-vibration signatures (Feng et al., 2026).
To accelerate the practical deployment of these materials in complex optical systems, research must also bridge the gap between material synthesis and advanced system-level calibration. In next-generation optoelectronics and light-emitting systems, single-view neural illumination estimation frameworks are now utilized to dynamically edit and adjust complex environmental lighting conditions for high-fidelity light field displays (He et al., 2026). Concurrently, to safeguard long-term stability and catch defects early on a industrial scale, photovoltaic module inspection platforms are implementing advanced electromagnetic induction-assisted scanning photoluminescence imaging (Hong et al.,2026). Bridging these materials-level improvements with systematic, automated imaging diagnostics will be key to unlocking the full potential of next-generation carbon dot optoelectronics.
Although carbon dots have recently emerged as versatile nanomaterials for optoelectronic applications, many of the fundamental concepts governing their optical performance have evolved from extensive studies on conventional semiconductor materials. Wide-bandgap semiconductors have served as benchmark systems for understanding the relationship between crystal quality, defect density, and radiative recombination. Previous investigations have demonstrated that synthesis parameters, including deposition temperature and precursor chemistry, significantly influence crystallinity, carrier transport, and photoluminescence efficiency. Likewise, improvements in epitaxial growth strategies and optimized buffer layers have been shown to enhance optical emission by minimizing structural defects and impurity incorporation. These studies have provided valuable insight into the design principles required for developing highly efficient optoelectronic materials, even though the materials themselves differ substantially from carbon-based quantum dots (Dai et al., 2006; Dai et al., 2007; Dai et al., 2011).
In comparison with inorganic semiconductor films, carbon dots offer several practical advantages, including low toxicity, abundant precursor availability, excellent aqueous dispersibility, facile surface functionalization, and solution-processable synthesis. Nevertheless, both material classes share common objectives in optoelectronic engineering, namely, maximizing light absorption, improving charge-carrier dynamics, reducing non-radiative recombination, and achieving stable photoluminescence. The development of multifunctional ultraviolet optoelectronic devices based further illustrates how careful control of optical and electronic properties can enable integrated light-emitting and photodetecting functions. Such advances provide a useful conceptual framework for interpreting the rapidly expanding applications of carbon dots in light-emitting diodes, photodetectors, bioimaging, optical sensing, and photovoltaic technologies, where similar optimization strategies are increasingly employed through heteroatom doping, surface-state engineering, and hybrid nanocomposite design (Dai et al., 2009; Dai et al., 2010).
6 Conclusion
The main carbon dot synthesis techniques are critically compared in this review, which also shows how the synthesis pathway has a significant impact on the structural, optical, and optoelectronic characteristics of carbon dots. While laser ablation produces extremely pure CDs appropriate for cutting-edge optoelectronic devices despite its greater cost, hydrothermal and microwave-assisted techniques often offer superior photoluminescence performance and high quantum yields with comparatively easy processing. While direct carbonization is a cost-effective and ecologically benign method, improvements in size uniformity and repeatability are still needed. Electrochemical synthesis provides exceptional control over surface chemistry and electrical characteristics. In addition to highlighting the benefits and drawbacks of each synthesis technique, this review’s comparative analysis shows a direct correlation between synthesis conditions and device performance in LEDs, solar cells, sensors, and related optoelectronic applications. These discoveries offer helpful direction for choosing suitable synthesis techniques and point the way forward for the creation of high-performance carbon-dot-based optoelectronic materials.
Statements
Author contributions
AS: Investigation, Methodology, Software, Writing – original draft. TF: Conceptualization, Investigation, Writing – original draft. MS: Formal Analysis, Methodology, Project administration, Writing – review and editing. SD: Data curation, Validation, Writing – review and editing. SM: Formal Analysis, Investigation, Software, Writing – review and editing. SK: Funding acquisition, Resources, Visualization, Writing – review and editing. RA: Data curation, Funding acquisition, Validation, Visualization, Writing – review and editing. SI: Conceptualization, Supervision, Writing – original draft, Writing – review and editing.
Funding
The author(s) declared that financial support was received for this work and/or its publication. The authors extend their appreciation to the Deanship of Scientific Research at Northern Border University, Arar, KSA for funding this research work through the project number “NBU-FFR-2026-3547-04”.
Conflict of interest
The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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References
1
ArvapalliD. M.SheardyA. T.AlladoK.ChevvaH.YinZ.WeiJ. (2020a). Design of curcumin loaded carbon nanodots delivery system: enhanced bioavailability, release kinetics, and anticancer activity. ACS Appl. Bio Mat.3 (12), 8776–8785. 10.1021/acsabm.0c01144
2
ArvapalliD. M.SheardyA. T.AlapatiK. C.WeiJ. (2020b). High quantum yield fluorescent carbon nanodots for detection of Fe (III) ions and electrochemical study of quenching mechanism. Talanta209 (November), 120538. 10.1016/j.talanta.2019.120538
3
AstafievA. A.ShakhovA. M.KritchenkovA. S.KhrustalevV. N.ShepelD. V.NadtochenkoV. A.et al (2021). Femtosecond laser synthesis of nitrogen-doped luminescent carbon dots from acetonitrile. Dye. Pigment.188 (January), 109176. 10.1016/j.dyepig.2021.109176
4
AzamiM.WeiJ.ValizadehderakhshanM.JayapalanA.AyodeleO. O.NowlinK. (2023). Effect of doping heteroatoms on the optical behaviors and radical scavenging properties of carbon nanodots. J. Phys. Chem. C127 (15), 7360–7370. 10.1021/acs.jpcc.3c00953
5
BaoL.ZhangZ. L.TianZ. Q.ZhangL.LiuC.LinY.et al (2011). Electrochemical tuning of luminescent carbon nanodots: from preparation to luminescence mechanism. Adv. Mat.23 (48), 5801–5806. 10.1002/adma.201102866
6
BarbinV. (2013). Application of cathodoluminescence microscopy to recent and past biological materials: a decade of progress, 353–362. 10.1007/s00710-013-0266-6
7
BayanR.KarakN. (2019). Photoluminescent oxygeneous-graphitic carbon nitride nanodot-incorporated bioderived hyperbranched polyurethane nanocomposite anticounterfeiting attribute. ACS Omega4 (5), 9219–9227. 10.1021/acsomega.9b00891
8
BehiM.GholamiL.NaficyS.PalombaS.DehghaniF. (2022). Carbon dots: a novel platform for biomedical applications. Nanoscale Adv.4 (2), 353–376. 10.1039/d1na00559f
9
BianH.WangQ.YangS.YanC.WangH.LiangL.et al (2019). Nitrogen-doped graphene quantum dots for 80% photoluminescence quantum yield for inorganic γ-CsPbI3 perovskite solar cells with efficiency beyond 16. J. Mat. Chem. A7 (10), 5740–5747. 10.1039/c8ta12519h
10
BrockM. (2012). Application of bioluminescence imaging for in vivo monitoring of fungal infections. Int. J. Microbiol.2012, 956794. 10.1155/2012/956794
11
CadranelA.MargrafJ. T.StraussV.ClarkT.GuldiD. M. (2019). Carbon nanodots for charge-transfer processes. Acc. Chem. Res.52 (4), 955–963. 10.1021/acs.accounts.8b00673
12
CayuelaA.Carrillo-CarriónC.SorianoM. L.ParakW. J.ValcárcelM. (2016). One-step synthesis and characterization of N-Doped carbon nanodots for sensing in organic media. Anal. Chem.88 (6), 3178–3185. 10.1021/acs.analchem.5b04523
13
ChandraS.PradhanS.MitraS.PatraP.BhattacharyaA.PramanikP.et al (2014). High throughput electron transfer from carbon dots to chloroplast: a rationale of enhanced photosynthesis. Nanoscale6 (7), 3647–3655. 10.1039/c3nr06079a
14
ChenB.LiF.LiS.WengW.GuoH.GuoT.et al (2013). Large scale synthesis of photoluminescent carbon nanodots and their application for bioimaging. Nanscale, 5 (5), 1967–1971. 10.1039/c2nr32675b
15
ChenW.HuC.YangY.CuiJ.LiuY. (2016). Rapid synthesis of carbon dots by hydrothermal treatment of lignin. Mater. (Basel)9 (3), 184. 10.3390/ma9030184
16
ChenF.YuY.YiJ.ZhangT.ZhaoJ.JiaW.et al (2025). MCLL-Diff: Multiconditional low-light image enhancement based on diffusion probabilistic models. IEEE Sensors J.25 (6), 9912–9924. 10.1109/JSEN.2025.3534566
17
DaiJ.LiuH.FangW.WangL.PuY.JiangF. (2006). Comparisons of structural and optical properties of ZnO films grown on (0001) sapphire and GaN/(0001) sapphire template by atmospheric-pressure MOCVD. Mater. Sci. Eng. B127 (2–3), 280–284. 10.1016/j.mseb.2005.10.024
18
DaiJ.JiangF.PuY.WangL.FangW.LiF. (2007). NH3-Assisted growth approach for ZnO films by atmospheric pressure metal-organic chemical vapor deposition. Appl. Phys. A89 (3), 645–650. 10.1007/s00339-007-4248-6
19
DaiJ. N.WuZ. H.YuC. H.ZhangQ.SunY. Q.XiongY. K.et al (2009). Comparative study on MOCVD growth of a-Plane GaN films on r-Plane sapphire substrates using GaN, AlGaN, and AlN buffer layers. J. Electron. Mater.38 (9), 1938–1943. 10.1007/s11664-009-0847-7
20
DaiJ. N.HanX. Y.WuZ. H.YuC. H.XiangR. F.HeQ. H.et al (2010). Growth of non-polar ZnO films on a-GaN/r-Al2O3 templates by radio-frequency magnetron sputtering. J. Alloys Compd.489 (2), 519–522. 10.1016/j.jallcom.2009.09.098
21
DaiJ. N.HanX. Y.WuZ. H.FangY. Y.XiongH.TianY.et al (2011). Effects of growth temperature on properties of nonpolar a-Plane ZnO films on GaN templates by pulsed laser deposition. J. Electron. Mater.40 (4), 446–452. 10.1007/s11664-011-1511-6
22
DangH.HuangL. K.ZhangY.WangC. F.ChenS. (2016). Large-scale ultrasonic fabrication of white fluorescent carbon dots. Ind. Eng. Chem. Res.55 (18), 5335–5341. 10.1021/acs.iecr.6b00894
23
DasB.DadhichP.PalP.SrivasP. K.BankotiK.DharaS. (2014). Carbon nanodots from date molasses: new nanolights for the in vitro scavenging of reactive oxygen species. J. Mat. Chem. B2 (39), 6839–6847. 10.1039/c4tb01020e
24
De MedeirosT. V.ManioudakisJ.NounF.MacairanJ. R.VictoriaF.NaccacheR. (2019). Microwave-assisted synthesis of carbon dots and their applications. J. Mat. Chem. C7 (24), 7175–7195. 10.1039/c9tc01640f
25
DengJ.LuQ.MiN.LiH.LiuM.XuM.et al (2014). Electrochemical synthesis of carbon nanodots directly from alcohols. Chem. - A Eur. J.20 (17), 4993–4999. 10.1002/chem.201304869
26
EssnerJ. B.BakerG. A. (2017). The emerging roles of carbon dots in solar photovoltaics: a critical review. Environ. Sci. Nano4 (6), 1216–1263. 10.1039/c7en00179g
27
FengY.WangY.ZhouJ.NieX.SunS.LiJ.et al (2026). Micro-vibration measurement using self-mixing interferometry with an intracavity frequency-doubling solid-state laser. Opt. and Laser Technol.198, 114644. 10.1016/j.optlastec.2025.114644
28
GaoT.WangX.YangL. Y.HeH.BaX. X.ZhaoJ.et al (2017). Red, yellow, and blue luminescence by graphene quantum dots: syntheses, mechanism, and cellular imaging. ACS Appl. Mat. Interfaces9 (29), 24846–24856. 10.1021/acsami.7b05569
29
GaoZ.xi ZhaoC.yan LiY.ling YangY. (2019). Beer yeast-derived fluorescent carbon dots for photoinduced bactericidal functions and multicolor imaging of bacteria. Appl. Microbiol. Biotechnol.103 (11), 4585–4593. 10.1007/s00253-019-09782-3
30
GaoJ.LiuY.JiangB.CaoW.KanY.ChenW.et al (2020). Phenylenediamine-based carbon nanodots alleviate acute kidney injury via preferential renal accumulation and antioxidant capacity. ACS Appl. Mat. Interfaces12 (28), 31745–31756. 10.1021/acsami.0c05041
31
GaoN.HuangL.LiT.SongJ.HuH.LiuY.et al (2020). Application of carbon dots in dye-sensitized solar cells: a review. J. Appl. Polym. Sci.137 (10), 1–11. 10.1002/app.48443
32
GhoshD.SarkarK.DeviP.KimK. H.KumarP. (2021). Current and future perspectives of carbon and graphene quantum dots: from synthesis to strategy for building optoelectronic and energy devices. Renew. Sustain. Energy Rev.135 (September 2020), 110391. 10.1016/j.rser.2020.110391
33
GoryachevaI. Y.SapelkinA. V.SukhorukovG. B. (2017). Carbon nanodots: mechanisms of photoluminescence and principles of application. Trac. - Trends Anal. Chem.90, 27–37. 10.1016/j.trac.2017.02.012
34
GreenhamN. C.SamuelI.HayesG.PhillipsR.KessenerY.MorattiS.et al (1995). Measurement of absolute photoluminescence quantum efficiencies in conjugated polymers. Chem. Phys. Lett.241 (1–2), 89–96. 10.1016/0009-2614(95)00584-Q
35
GuoX.WangC. F.YuZ. Y.ChenL.ChenS. (2012). Facile access to versatile fluorescent carbon dots toward light-emitting diodes. Chem. Commun.48 (21), 2692–2694. 10.1039/c2cc17769b
36
GuoQ.YuanF.ZhangB.ZhouS.ZhangJ.BaiY.et al (2019). Passivation of the grain boundaries of CH3NH3PbI3 using carbon quantum dots for highly efficient perovskite solar cells with excellent environmental stability. Nanoscale11 (1), 115–124. 10.1039/c8nr08295b
37
GuptaV.ChaudharyN.SrivastavaR.SharmaG. D.BhardwajR.ChandS. (2011). Luminscent graphene quantum dots for organic photovoltaic devices. J. Am. Chem. Soc.133 (26), 9960–9963. 10.1021/ja2036749
38
GuptaS. K.SudarshanK.KadamR. M. (2021). Optical nanomaterials with focus on rare Earth doped oxide: a review. Mat. Today Commun.27 (September 2020), 102277. 10.1016/j.mtcomm.2021.102277
39
HassanvandZ.JalaliF.NazariM.ParnianchiF.SantoroC. (2021). Carbon nanodots in electrochemical sensors and biosensors: a review. ChemElectroChem8 (1), 15–35. 10.1002/celc.202001229
40
HeP.ShiY.MengT.YuanT.LiY.LiX.et al (2020). Recent advances in white light-emitting diodes of carbon quantum dots. Nanoscale12 (8), 4826–4832. 10.1039/c9nr10958g
41
HeY.WangJ.DengB.GuoC.YangR.ZhangH.et al (2026). Photovoltaic module inspection based on electromagnetic induction-assisted scanning photoluminescence imaging. IEEE Trans. Industrial Inf., 1–11. 10.1109/TII.2026.3685159
42
HongX.XieJ.ShengJ.XieF.ZhangJ.WangK.et al (2026). Single-view neural illumination estimation and editing for dynamic light field display. Light Sci. Appl.15 (1), 147. 10.1038/s41377-026-02234-4
43
HouY.LuQ.DengJ.LiH.ZhangY. (2015). One-pot electrochemical synthesis of functionalized fluorescent carbon dots and their selective sensing for Mercury ion. Anal. Chim. Acta866, 69–74. 10.1016/j.aca.2015.01.039
44
IranifamM. (2014). Analytical applications of chemiluminescence methods for cancer detection and therapy. Trac. - Trends Anal. Chem.59, 156–183. 10.1016/j.trac.2014.03.010
45
JaiswalA.Sankar GhoshS.ChattopadhyayA. (2012). One step synthesis of C-dots by microwave mediated caramelization of poly(ethylene glycol). Chem. Commun.48 (3), 407–409. 10.1039/c1cc15988g
46
JiZ.SheardyA.ZengZ.ZhangW.ChevvaH.AlladoK.et al (2019). Tuning the functional groups on carbon nanodots and antioxidant studies. Molecules24 (1), 1–12. 10.3390/molecules24010152
47
JiZ.YinZ.JiaZ.WeiJ. (2020). Carbon nanodots derived from urea and citric acid in living cells: cellular uptake and antioxidation effect. Langmuir36 (29), 8632–8640. 10.1021/acs.langmuir.0c01598
48
KarimzadehA.HasanzadehM.ShadjouN.de la GuardiaM. (2018). Electrochemical biosensing using N-GQDs: recent advances in analytical approach. Trac. - Trends Anal. Chem.105, 484–491. 10.1016/j.trac.2018.06.009
49
KhanS.DunphyA.AnikeM. S.BelperainS.PatelK.ChiuN. H. L.et al (2021). Recent advances in carbon nanodots: a promising nanomaterial for biomedical applications. Int. J. Mol. Sci.22 (13), 6786. 10.3390/ijms22136786
50
KimY.KimJ. (2020). Bioinspired thiol functionalized carbon dots for rapid detection of lead (II) ions in human serum. Opt. Mat. (Amst).99 (November), 109514. 10.1016/j.optmat.2019.109514
51
KweeY.KristantiA. N.SiimonK.AminahN. S.FahmiM. Z. (2021). Carbon nanodots derived from natural products. South Afr. J. Chem.75 (1), 40–63. 10.17159/0379-4350/2021/v75a6
52
KwonW.DoS.WonD. C.RheeS. (2013a). ACS Appl Mater Interfaces 2013 - Carbon Quantum Dot-based Field-Effect Transistors and their Ligand Length-dependent Carrier Mobility. pdf. Washington, D.C., United States: American Chemical Society (ACS). 10.1021/am3023898
53
KwonW.LeeG.DoS.JooT.RheeS. W. (2014). Size-controlled soft-template synthesis of carbon nanodots toward versatile photoactive materials. Small10 (3), 506–513. 10.1002/smll.201301770
54
LeeT.WonS.ParkY.KwonW. (2021). Oxygen-less carbon nanodots with an absolute quantum yield of 80% for display applications. ACS Appl. Nano Mat.4 (3), 2462–2469. 10.1021/acsanm.0c03011
55
LiH.KangZ.LiuY.LeeS. T. (2012). Carbon nanodots: synthesis, properties and applications. J. Mat. Chem.22 (46), 24230–24253. 10.1039/c2jm34690g
56
LiX.LiuY.SongX.WangH.GuH.ZengH. (2015). Intercrossed carbon nanorings with pure surface states as low‐cost and environment‐friendly phosphors for white‐light‐emitting diodes. Angew. Chem.127 (6), 1779–1784. 10.1002/ange.201406836
57
LiW.TangJ.LiY.BaiH.ZhangW.ZhangJ.et al (2021). Preparation and fluorescent wavelength control of multi-color nitrogen-doped carbon nano-dots. Nanomaterials11 (12), 1–10. 10.3390/nano11123190
58
LinF.LiC.ChenZ. (2018). Exopolysaccharide-derived carbon dots for microbial viability assessment. Front. Microbiol.9 (NOV), 1–10. 10.3389/fmicb.2018.02697
59
LinR.ZhangJ.ShuL.ZhuJ.FuB.SongC.et al (2020). Self-dispersible graphene quantum dots in ethylene glycol for direct absorption-based medium-temperature solar-thermal harvesting. RSC Adv.10 (73), 45028–45036. 10.1039/d0ra08128k
60
LiuH.HeZ.JiangL. P.ZhuJ. J. (2015). Microwave-assisted synthesis of wavelength-tunable photoluminescent carbon nanodots and their potential applications. ACS Appl. Mat. Interfaces7 (8), 4913–4920. 10.1021/am508994w
61
LiuC.BaoL.YangM.ZhangS.ZhouM.TangB.et al (2019). Surface sensitive photoluminescence of carbon nanodots: coupling between the carbonyl group and π-Electron system. J. Phys. Chem. Lett.10 (13), 3621–3629. 10.1021/acs.jpclett.9b01339
62
LuW.QinX.LiuS.ChangG.ZhangY.LuoY.et al (2012). Economical, green synthesis of fluorescent carbon nanoparticles and their use as probes for sensitive and selective detection of mercury(II) ions. Anal. Chem.84 (12), 5351–5357. 10.1021/ac3007939
63
MaZ.MingH.HuangH.LiuY.KangZ. (2012). One-step ultrasonic synthesis of fluorescent N-doped carbon dots from glucose and their visible-light sensitive photocatalytic ability. New J. Chem.36 (4), 861–864. 10.1039/c2nj20942j
64
MaZ.ZhangY. L.WangL.MingH.LiH.ZhangX.et al (2013). Bioinspired photoelectric conversion system based on carbon-quantum-dot- doped dye-semiconductor complex. ACS Appl. Mat. Interfaces5 (11), 5080–5084. 10.1021/am400930h
65
MalgrasV.NattestadA.KimJ. H.DouS. X.YamauchiY. (2017). Understanding chemically processed solar cells based on quantum dots. Sci. Technol. Adv. Mat.18 (1), 334–350. 10.1080/14686996.2017.1317219
66
ManoharanP.DhanabalanS. C.AlaganM.MuthuvijayanS.PonrajJ. S.SomasundaramC. K. (2020). Facile synthesis and characterisation of green luminescent carbon nanodots prepared from tender coconut water using the acid-assisted ultrasonic route. Micro Nano Lett.15 (13), 964–968. 10.1049/mnl.2020.0101
67
MarinovicA.KiatL. S.DunnS.TitiriciM. M.BriscoeJ. (2017). Carbon-nanodot solar cells from renewable precursors. ChemSusChem10 (5), 1004–1013. 10.1002/cssc.201601741
68
MirtchevP.HendersonE. J.SoheilniaN.YipC. M.OzinG. A. (2012). Solution phase synthesis of carbon quantum dots as sensitizers for nanocrystalline TiO 2 solar cells. J. Mat. Chem.22 (4), 1265–1269. 10.1039/c1jm14112k
69
MitraS.ChandraS.KunduT.BanerjeeR.PramanikP.GoswamiA. (2012). Rapid microwave synthesis of fluorescent hydrophobic carbon dots. RSC Adv.2 (32), 12129–12131. 10.1039/c2ra21048g
70
NguyenV.YanL.SiJ.HouX. (2015). Femtosecond laser-induced size reduction of carbon nanodots in solution: effect of laser fluence, spot size, and irradiation time. J. Appl. Phys.117 (8), 084304. 10.1063/1.4909506
71
OlawaleD. O.DickensT.SullivanW. G.OkoliO. I.SobanjoJ. O.WangB. (2011). Progress in triboluminescence-based smart optical sensor system. J. Lumin.131 (7), 1407–1418. 10.1016/j.jlumin.2011.03.015
72
PanD.ZhangJ.LiZ.WuM. (2010). Hydrothermal route for cutting graphene sheets into blue‐luminescent graphene quantum dots. Adv. Mater.22 (6), 734–738. 10.1002/adma.200902825
73
PaperW.PaperW. (2002). “Nanotechnology: clean energy and resources for the future,” in Energy Convers. October.
74
PaquinF.RivnayJ.SalleoA.StingelinN.SilvaC. (2015). Multi-phase semicrystalline microstructures drive exciton dissociation in neat plastic semiconductors. J. Mat. Chem. C3, 10715–10722. 10.1039/b000000x
75
PatirK.GogoiS. K. (2022). Room temperature phosphorescence of chlorine doped carbon nitride dots. Front. Chem.10 (March), 1–10. 10.3389/fchem.2022.812602
76
RigodanzaF.BurianM.ArcudiF.ĐorđevićL.AmenitschH.PratoM. (2021). Snapshots into carbon dots formation through a combined spectroscopic approach. Nat. Commun.12 (2021), 2640. 10.1038/s41467-021-22902-w
77
RoyP.ChenP. C.PeriasamyA. P.ChenY. N.ChangH. T. (2015). Photoluminescent carbon nanodots: synthesis, physicochemical properties and analytical applications. Mat. Today18 (8), 447–458. 10.1016/j.mattod.2015.04.005
78
SakthivelS.ZhouX.GiannelisE. P.KanjM. Y. (2021). Carbon nanodots for enhanced oil recovery in carbonate reservoirs. Energy Rep.7, 8943–8959. 10.1016/j.egyr.2021.11.194
79
SekarA.YadavR.BasavarajN. (2021). Fluorescence quenching mechanism and the application of green carbon nanodots in the detection of heavy metal ions: a review. New J. Chem.45 (5), 2326–2360. 10.1039/d0nj04878j
80
SharmaA.DasJ. (2019). Small molecules derived carbon dots: synthesis and applications in sensing, catalysis, imaging, and biomedicine. J. Nanobiotechnology17 (1), 1–24. 10.1186/s12951-019-0525-8
81
ShenL. M.LiuJ. (2016). New development in carbon quantum dots technical applications. Talanta156 (157), 245–256. 10.1016/j.talanta.2016.05.028
82
ShiL.LiY.LiX.ZhaoB.WenX.ZhangG.et al (2016). Controllable synthesis of green and blue fluorescent carbon nanodots for pH and Cu2+ sensing in living cells. Biosens. Bioelectron.77, 598–602. 10.1016/j.bios.2015.10.031
83
ShiW.YaoJ.BaiL.LuC. (2018). Defect-stabilized triplet state excitons: toward ultralong organic room-temperature phosphorescence. Adv. Funct. Mat.28 (52), 1–8. 10.1002/adfm.201804961
84
ShiY.XuH.YuanT.MengT.WuH.ChangJ.et al (2022). Carbon dots: an innovative luminescent nanomaterial: photovoltaics: special issue dedicated to professor yongfang li. Aggregate3 (3), 1–18. 10.1002/agt2.108
85
SinghS.VaishnavJ. K.MukherjeeT. K. (2020). Quantum dot-based hybrid coacervate nanodroplets for ultrasensitive detection of Hg2+. ACS Appl. Nano Mat.3 (4), 3604–3612. 10.1021/acsanm.0c00317
86
SivasankarapillaiV. S.Vishnu KirthiA.AkksadhaM.InduS.Dhiviya DharshiniU.PushpamalarJ.et al (2020). Recent advancements in the applications of carbon nanodots: exploring the rising star of nanotechnology. Nanoscale Adv.2 (5), 1760–1773. 10.1039/c9na00794f
87
SkM. A.AnanthanarayananA.HuangL.LimK. H.ChenP. (2014). Revealing the tunable photoluminescence properties of graphene quantum dots. J. Mat. Chem. C2 (34), 6954–6960. 10.1039/c4tc01191k
88
StellmerS.SchreitlM.SchummT. (2015). Radioluminescence and photoluminescence of Th:CaF2 crystals. Sci. Rep.5, 1–10. 10.1038/srep15580
89
SunS.ChenJ.JiangK.TangZ.WangY.LiZ.et al (2019). Ce6-Modified carbon dots for multimodal-imaging-guided and Single-NIR-Laser-Triggered photothermal/photodynamic synergistic cancer therapy by reduced irradiation power. ACS Appl. Mat. Interfaces11 (6), 5791–5803. 10.1021/acsami.8b19042
90
TaoS.FengT.ZhengC.ZhuS.YangB. (2019). Carbonized polymer dots: a brand new perspective to recognize luminescent carbon-based nanomaterials. J. Phys. Chem. Lett.10, 5182–5188. 10.1021/acs.jpclett.9b01384
91
VermaN. C.YadavA.RaoC.MishraP. M.NandiC. K. (2021). Emergence of carbon nanodots as a probe for super-resolution microscopy. J. Phys. Chem. C125, 1637–1653. 10.1021/acs.jpcc.0c09695
92
WangX.CaoL.YangS. T.LuF.MezianiM. J.TianL.et al (2010). Bandgap-like strong fluorescence in functionalized carbon nanoparticles. Angew. Chem. - Int. Ed.49 (31), 5310–5314. 10.1002/anie.201000982
93
WangF.PangS.WangL.LiQ.KreiterM.LiuC. Y. (2010). One-step synthesis of highly luminescent carbon dots in noncoordinating solvents. Chem. Mat.22 (16), 4528–4530. 10.1021/cm101350u
94
WangQ.ZhengH.LongY.ZhangL.GaoM.BaiW. (2011). Microwave-hydrothermal synthesis of fluorescent carbon dots from graphite oxide. Carbon N. Y.49 (9), 3134–3140. 10.1016/j.carbon.2011.03.041
95
WangF.ChenY. H.LiuC. Y.MaD. G. (2011). White light-emitting devices based on carbon dots’ electroluminescence. Chem. Commun.47 (12), 3502–3504. 10.1039/c0cc05391k
96
WangC.WuX.LiX.WangW.WangL.GuM.et al (2012). Upconversion fluorescent carbon nanodots enriched with nitrogen for light harvesting. J. Mat. Chem.22 (31), 15522–15525. 10.1039/c2jm30935a
97
WangL.LiB.XuF.ShiX.FengD.WeiD.et al (2016). High-yield synthesis of strong photoluminescent N-doped carbon nanodots derived from hydrosoluble chitosan for Mercury ion sensing via smartphone APP. Biosens. Bioelectron.79, 1–8. 10.1016/j.bios.2015.11.085
98
WangL.LiB.LiL.XuF.XuZ.WeiD.et al (2017). Ultrahigh-yield synthesis of N-doped carbon nanodots that down-regulate ROS in zebrafish. J. Mat. Chem. B5 (38), 7848–7860. 10.1039/c7tb01114h
99
WangX. F.WangG. G.LiJ. B.LiuZ.ZhaoW. F.HanJ. C. (2018). Towards high-powered remote WLED based on flexible white-luminescent polymer composite films containing S, N co-doped graphene quantum dots. Chem. Eng. J.336, 406–415. 10.1016/j.cej.2017.12.056
100
WangX.LiuY.ZhouQ.ShengX.SunY.ZhouB.et al (2020). A reliable and facile fluorescent sensor from carbon dots for sensing 2,4,6-trinitrophenol based on inner filter effect. Sci. Total Environ.720, 137680. 10.1016/j.scitotenv.2020.137680
101
WuD.LiB. L.ZhaoQ.LiuQ.WangD.HeB.et al (2020). Assembling defined DNA nanostructure with nitrogen-enriched carbon dots for Theranostic cancer applications. Small16 (19), 1–8. 10.1002/smll.201906975
102
XuX.RayR.GuY.PloehnH. J.GearheartL.RakerK.et al (2004). Electrophoretic analysis and purification of fluorescent single-walled carbon nanotube fragments. J. Am. Chem. Soc.126 (40), 12736–12737. 10.1021/ja040082h
103
XuZ. Q.LanJ. Y.JinJ. C.DongP.JiangF. L.LiuY. (2015). Highly photoluminescent nitrogen-doped carbon nanodots and their protective effects against oxidative stress on cells. ACS Appl. Mat. Interfaces7 (51), 28346–28352. 10.1021/acsami.5b08945
104
XueX.HuH. M.HeZ.ZhengH. (2025). Towards multi-source illumination color constancy through physics-based rendering and spectral power distribution embedding. IEEE Trans. Comput. Imaging11, 1349–1360. 10.1109/TCI.2025.3598440
105
YanX.CuiX.LiB.LiL. S. (2010). Large, solution-processable graphene quantum dots as light absorbers for photovoltaics. Nano Lett.10 (5), 1869–1873. 10.1021/nl101060h
106
YangZ. C.WangM.YongA. M.WongS. Y.ZhangX. H.TanH.et al (2011). Intrinsically fluorescent carbon dots with tunable emission derived from hydrothermal treatment of glucose in the presence of monopotassium phosphate. Chem. Commun.47 (42), 11615–11617. 10.1039/c1cc14860e
107
YangY.LiuZ.ChenD.GuB.GaoB.WangZ.et al (2021). Multifunctional N-doped graphene quantum dots towards tetracycline detection, temperature sensing and high-performance WLEDs. J. Photochem. Photobiol. A Chem.405 (July 2020), 112977. 10.1016/j.jphotochem.2020.112977
108
YangM. J.ShiJ. X.YinY.ShiC. G. (2021). Preparation of carbon nanodots with ultraviolet emission by pulsed laser ablation. Phys. Status Solidi Basic Res.258 (10), 1–6. 10.1002/pssb.202100110
109
YuanY.GuoB.HaoL.LiuN.LinY.GuoW.et al (2017). Doxorubicin-loaded environmentally friendly carbon dots as a novel drug delivery system for nucleus targeted cancer therapy. Colloids Surfaces B Biointerfaces159, 349–359. 10.1016/j.colsurfb.2017.07.030
110
ZengZ.ZhangW.ArvapalliD. M.BloomB.SheardyA.MabeT.et al (2017). A fluorescence-electrochemical study of carbon nanodots (CNDs) in bio- and photoelectronic applications and energy gap investigation. Phys. Chem. Chem. Phys.19 (30), 20101–20109. 10.1039/c7cp02875j
111
ZengL.LiX.FanS.LiJ.MuJ.QinM.et al (2019). The bioelectrochemical synthesis of high-quality carbon dots with strengthened electricity output and excellent catalytic performance. Nanoscale11 (10), 4428–4437. 10.1039/c8nr10510c
112
ZhangM.HuL.WangH.SongY.LiuY.LiH.et al (2018). One-step hydrothermal synthesis of chiral carbon dots and their effects on mung bean plant growth. Nanoscale10 (26), 12734–12742. 10.1039/c8nr01644e
113
ZhaiX.ZhangP.LiuC.BaiT.LiW.DaiL. (2012). Electronic Supplementary Information Highly luminescent carbon nanodots by microwave-assisted pyrolysis. Chem. Commun., 48 (64), 7955–7957. 10.1039/c2cc33869f
114
ZhangW.ZengZ.WeiJ. (2017). Electrochemical study of DPPH radical scavenging for evaluating the antioxidant capacity of carbon nanodots. J. Phys. Chem. C121 (34), 18635–18642. 10.1021/acs.jpcc.7b05353
115
ZhangJ.YangA.ZhangK. (2023). Photophysical properties of bright luminescent polyethyleneimine@carbon nanodots and their application in white light-emitting diodes. Photonics10 (3), 262. 10.3390/photonics10030262
116
ZhengJ.WangY.ZhangF.YangY.LiuX.GuoK.et al (2017). Microwave-assisted hydrothermal synthesis of solid-state carbon dots with intensive emission for white light-emitting devices. J. Mat. Chem. C5 (32), 8105–8111. 10.1039/c7tc01701d
117
ZhouJ.ShengZ.HanH.ZouM.LiC. (2012). Facile synthesis of fluorescent carbon dots using watermelon peel as a carbon source. Mat. Lett.66 (1), 222–224. 10.1016/j.matlet.2011.08.081
118
ZhuoY.MiaoH.ZhongD.ZhuS.YangX. (2015). One-step synthesis of high quantum-yield and excitation-independent emission carbon dots for cell imaging. Mat. Lett.139, 197–200. 10.1016/j.matlet.2014.10.048
Summary
Keywords
carbon dots, graphene quantum dots, light emitting diodes, optoelectronic, photostability
Citation
Shehzadi A, Fazal T, Shah M, Daud S, Mahmood S, Knani S, Alreshidi R and Iqbal S (2026) Illuminating innovations: leveraging the optoelectronic capabilities of carbon dots for advanced displays, sensors, and renewable energy solutions. Front. Chem. 14:1843453. doi: 10.3389/fchem.2026.1843453
Received
31 March 2026
Revised
09 July 2026
Accepted
10 July 2026
Published
04 August 2026
Volume
14 - 2026
Edited by
Suresh Kumar Kailasa, Sardar Vallabhbhai National Institute of Technology Surat, India
Reviewed by
Kamlesh Shrivas, Pandit Ravishankar Shukla University, India
Pinkesh Sutariya, Sardar Patel University, India
Updates
Copyright
© 2026 Shehzadi, Fazal, Shah, Daud, Mahmood, Knani, Alreshidi and Iqbal.
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Tanzeela Fazal, tanzeelafazal@yahoo.com; Reem Alreshidi, reemalreshidi@outlook.com; Shahid Iqbal, Shahid.Iqbal@nottingham.edu.cn
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