Dry fungus mediated gold bio-nano-composites synthesis: An efficient green and sustainable heterogeneous catalyst for selective nitro reduction

Amar G Deshamukh¹Rajashree Borgohain²Harishkumar Madhyastha³Paresh N Patel^1*

• ¹Uka Tarsadia University, Surat, India
• ²Uka Tarsadia University, Bardoli, India
• ³University of Miyazaki, Miyazaki, Japan

This dry fungus reinforced nanoparticle synthesis is the first and proficient plan of action to replace the use of hazardous chemical, physical and other bio-methods. Here we reports the synthesis of gold bio-nano-composites (GBNCs) via immobilization of dry biomass prepared with conventional and lyophilization methods. Under atmospheric conditions, dried Aspergillus Trinidadensis VM ST01' OL587588 functions as a reducing and capping agent in water without any solvent and buffer interference. The use of dried biomass provides additional benefits for the synthesis of GBNCs such as short synthesis time (24 hr; 36 hr with wet biomass) without incubation, better shelf life (more than 18 months), improved catalytic activity, intact morphology, etc. The generated GBNCs were characterized by verities of analytical techniques and found roughly spherical shape with mono-dispersed diameter of around 25 nm as determined with high-resolution transmission electron microscopy. An influence of stirring and biomass concentration on the kinetics were also studied for GBNCs fabrication process. An optimized stoichiometric results have shown 3.5 x 1015 gold atoms per milligram of dried bio-mass prepared by both the methods. Crystalline nature and surface charge of GBNCs were analyzed by powder X-ray diffraction and Zeta potential studies, respectively. FT-IR studies have shown the participation of various bio-mass functional groups in forming GBNCs. The surface morphology of GBNCs was investigated by Scanning Electron Microscope. A comparative thermal stability of dried biomass and GBNCs were evaluated by thermo-gravimetric analysis with a large difference in residual mass. Here, GBNCs have been proven as a truly potent heterogeneous catalyst for reduction of nitrobenzene in water using sodium borohydride with good isolated yields up to over 95%. Industrial suitability of GBNCs has been established with its broad operational pH (4 to 10) and temperature range (25 to 80 °C), reusability (more than 10 cycles), storage stability (more than 18 months) and successful scale-up investigations (up to 5gm).