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Abstract:
Core-shell metal-semiconductor nanostructures have established worldwide interest due to their magnificent chemical, optical and electrical behavior as compared to their monometallic analogous. Wet chemically synthesized gold-copper oxide (Au@Cu2O) core-shell nanostructures were studied for catalytic activity for the degradation of dyes such as crystal violet (CV) and congo red (CR) and the reduction of organic pollutant, 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) and compared with Au nanoparticles (Au NPs). The Au@Cu2O nanostructures show ten times higher reduction rate for 4-NP than that of monometallic Au NPs. The adsorption followed by degradation of CV, and CR dyes in aqueous solution has been investigated with Au NPs and Au@Cu2O core-shell nanostructures. Kinetics study has been performed using Au NPs and Au@Cu2O core-shell nanostructure for the 4-NP reduction, CV and CR degradation. The synergistic effect in Au@Cu2O core-shell nanostructure facilitates catalytic activity compared to the monometallic Au NPs.

Keywords:
Au@Cu2O, Core-shell nanostructure, 4-Nitrophenol, 4-Aminophenol, Dye degradation

Abstract:
The rapid, ultralow detection, degradation, and complete removal of pesticides demand the design of potential substrates. Herein, we discussed gold nanorods (Au NRs) as the potential substrate for the naked eye detection and degradation of two common and broad-spectrum pesticides, chlorpyrifos (CPF) and malathion (MLT), up to 0.15 ppt concentration within 2 min. Under certain environmental conditions, both the pesticides degraded and adsorbed on the surface of Au NRs. The degraded moieties of CPF and MLT on the surface of Au NRs formed side-to-side and end-to-end interactions, respectively, leading to a long-range assembly. This shows that no external agent is required, and only CPF and MLT analytes are quite enough for the formation of assembly of Au NRs. Assembly of Au NRs is confirmed by transmission electron microscopy (TEM) analysis, and degradation is supported by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and gas chromatography-mass spectrometry (GC-MS) analyses. Au NRs were recovered and reused for four consecutive cycles. The fast and ultralow detection of pesticides demonstrates that Au NRs are a potential substrate for the detection and degradation of pesticides.

Keywords:
gold nanorods, chlorpyrifos, malathion, pesticides, degradation, side to side interaction, end to end interaction