Synthesis of water-soluble gold-aryl nanoparticles with distinct catalytic performance in the reduction of the environmental pollutant 4-nitrophenol

Catalysis under harsh environmental conditions requires robust nanoparticles that can resist leaching of the organic shell and possess significant resistance to aggregation. Robust gold core-carbon shell gold-aryl nanoparticles (AuNPs-COOH) were fabricated by mild reduction of the water-soluble aryldiazonium salt [HOOC-4-C6H4N equivalent to N]AuCl4, and were fully characterized in solution and solid state. The nanoparticles showed high stability in the presence of 0.01-1.00 M NaCl salt, acidic and basic pH values (1-13) and moderate temperatures (20-90 degrees C). DFT calculations of the optimized model system Au-38-C6H4-COOH show an Au-C (aryl) distance of 2.04 angstrom, which is related to a binding energy of -59.2 kcal mol(-1). The 4-nitrophenol (4-NPh) reduction model was used to study the viability of AuNPs-COOH as a catalyst. Nitrophenols are among the most common organic pollutants in industrial and agricultural wastewaters due to their toxicity, anthropogenic and inhibitory nature. The AuNPs-COOH show high catalytic activity, where the reduction of 80 mu M 4-NPh was complete in less than five minutes with a high k(app) (2.26 x 10(-2) s(-1)) and a relatively low E-a (25 kJ mol(-1)) compared to literature values. Catalytic activity decreases with subsequent cycles of the reaction, along with a decrease in intensity and red shift in the LSPR band, and an increase in aggregation of nanoparticles in the TEM following each reaction cycle.