Carbon dots as a 'green' reagent to produce shape and size controlled gold nanoparticles for application in pollutant degradation

Gold nanoparticles (Au NPs) have attracted wide attention as catalysts for in situ degradation of organic pollutants. Current synthetic methods that enable precise control of Au NPs size and shape cause adverse effects on the environment. In this work, a sustainable, one-step method was used to synthesize Au NPs by reducing Au3+ with norepinephrine and ethylamine-based carbon dots (NE/EA CDs). CDs not only act as reducing agent but also stabilize the resulting Au NPs. The mechanism of Au3+ reduction was investigated by studying the effects of functional groups present in the CDs, which were confirmed from UV-Vis and XPS spectral analysis. Three different morphologies of Au NPs were observed after reduction: nanotriangles, nanourchins and nanospheres. Fabricated Au NPs were used to study a model catalytic reaction, reduction of 4-nitrophenol, indicating that CDs are an attractive option for fabrication of Au NPs for water treatment applications.