Snowflake-like gold nanoparticles as SERS substrates for the sensitive detection of organophosphorus pesticide residues

Abstract

Representing tremendous enhancement effect for the Raman signal of trace chemicals, branched gold nanoparticles (Au NPs) are particularly attractive as surface-enhanced Raman spectroscopy (SERS) substrates, though precise morphology control during synthesis might remain challenging. Herein, snowflake-like gold nanoparticles served as SERS substrates were successfully prepared by reducing chloroauric acid (HAuCl4) with ascorbic acid in aqueous solutions of tetradecylpiperidinium (C14PDB) surfactant. At a C14PDB/HAuCl4 molar concentration ratio of 4.2/1 and a reaction time of 6 h, the Au NPs resembled hexagonal snowflakes were produced. The snowflake-like Au NPs substrates performed great SERS activity and afforded limits of detection around 3 × 10−9 mol L−1 in aqueous rhodamine 6G (R6G) solutions and 1 × 10−8 mol L−1 for organophosphorus pesticides in solution. And applying these SERS substrates for practical detection on five fruit or vegetable peels, the detection limit of parathion-methyl, triazophos and phosmet on apple peels was 0.026 ng cm−2, 0.031 ng cm−2 and 0.032 ng cm−2, respectively. SERS results suggest that snowflake-like Au NPs used as SERS substrates hold great promise for the detection of organophosphorus pesticides at trace concentrations.