Cu^(2+)-Assisted Synthesis of Au@AgI Core/Shell Nanorods via In Situ Oxidation of Iodide:A Strategy for Colorimetric Iodide Sensing

Colorimetric nanoprobes are frequently employed to construct sensitive sensors via various strategies.In this work,a novel strategy for simple and ultrasensitive sensing of iodide(I_(−))was constructed based on Cu^(2+)-assisted generation of Au@AgI core/shell nanorods(NRs),by etching silver-coated gold nanorods(Ag@Au NRs).Ag@Au NRs were first prepared and characterized with UV-visible spectroscopy,transmission electron microscopy,high-angle annular dark-field scanning transmission electron microscopy,and energy-dispersive X-ray spectroscopy before and after iodide treatment.The mechanism of detection was based on the generation of AgI shells via etching Ag shells by I_(2),which was produced from the oxidation of I_(−)with Cu^(2+),resulting in the peak shift of localized surface plasmon resonance(LSPR)while the color changed from green,blue to light-violet.The red-shift of the longitudinal LSPR peak had a linear relationship with I_(−)concentration in the range of 0-50μmol/L with a correlation coefficient of 0.982.Furthermore,the proposed method was used for the quantitative detection of I_(−)in real samples and outstanding recoveries in the range of 91-106%with relative standard deviations lower than 2.5%were observed.

Fabrication of Non-woven Fabric-Based SERS Substrate for Direct Detection of Pesticide Residues in Fruits

In surface-enhanced Raman scattering(SERS),flexible substrate plays an important role in target molecular collection from various shape surfaces and increases the analytical sensitivity.In this study,silver nanoparticles(Ag NPs)were deposited on a non-woven fabric used as an SERS substrate by self-assembly,in situ growing or the self-assembly/in situ growing combination method.4-Aminothiophenol was selected as a model molecular for the evaluation of the SERS performance using the substrates.The Ag NPs substrate prepared by self-assembly/in situ growing method presented the best Raman enhancement effect and its enhancement factor was estimated as high as 3.59106.The substrate was applied to the determination of four pesticide residues on the surfaces of fruit samples through wipe sampling,and the results revealed the good reproducibility of SERS responses and high detection sensitivity.The prepared flexible substrate was simple to fabricate and environmentally friendly.It could be expected to be a useful tool in rapid on-site test of pesticide residues on fruit surfaces because of its high sensitivity,convenience and non-destructive characteristics.