Facile synthesis of C30-AuNPs for the effective catalytic reduction of nitrophenols and azo dyes

Gold nanoparticles (AuNPs) with a high specific surface area show efficient activity for the reduction of nitroaromatics. In this study, single-stranded DNA chains (ssDNA, T30, C30 or A30) were used as templates to mediate the formation of AuNPs, and the results demonstrated that the morphologies of the C30-AuNPs or A30-AuNPs had more abundant irregular features than the T30-AuNPs. The catalytic properties and applications of the C30-AuNPs were systematically examined using a reaction model for the reduction of 4-nitrophenol by NaBH4. The effect of different temperatures and pH values on the catalytic activity of C30-AuNPs have been investigated. The C30-AuNPs showed the highest catalytic activity (rate constant kapp = 0.2221 min-1) for the reduction of 4-NP at 35 degrees C and pH = 7. The conversion of 4-NP to 4-AP using C30-AuNPs followed the Langmuir-Hinshelwood mechanism, which was explained by the principle of promoting electron transfer, i.e. the surface of C30-AuNPs is rich in active sites that promote the process of electron transfer from BH4- to 4-NP, completing the conversion of 4-nitrophenol to 4-aminophenol. Furthermore, the results confirmed that C30-AuNPs were versatile for catalyzing isomers of 4-NP and azo dyes, such as 2-NP, 3-NP, MO, CR and EBT. The results offer new insights into the construction of Au-based catalysts for efficiently removing environmental pollutants. A facile and green synthesis approach of C30-AuNPs is developed for the effective catalytic reduction of nitrophenols and azo dyes, and the in-depth mechanism investigation is described by thermodynamic and kinetic analysis.