Core-shell magnetic Ag-molecularly imprinted composite for surface enhanced Raman scattering detection of carbaryl

Abstract

Surface-enhanced Raman scattering (SERS) is a promising technique for rapid detection of pesticide residues. However, conventional SERS substrates require extraction processes which are time consuming and they also lack selectivity, stability and reproducibility. Herein, we present a multifunctional stable zero-valent iron based core-shell substrate. It combines magnetic separation, selective adsorption by molecular imprinting technique and sensitive detection of carbaryl by SERS. The core-shell substrate was successfully prepared by immobilizing silver on the surface of zero-valent iron microspheres. Subsequent molecular imprinting on the bimetallic magnetic silver microspheres ensured selective removal and detection. The substrate exhibited magnetization saturation of 8.89 emu/g providing efficient analyte separation. It showed high sensitivity and selectivity toward carbaryl detection to nanomolar concentration level. Linear regression models for peaks at Raman shift 1599 cm⁻¹ and 2233 cm⁻¹ demonstrated a good linear fit with R²=0.9738 and R²=0.8952 respectively. The composite was successfully applied on spiked water samples resulting in average recovery rate of 89%. The findings of this study demonstrate great substrate potential for application in separation and detection of trace quantities of chemical contaminants for environment safety and protection.

Keywords:

• zero-valent iron
• molecularly imprinted polymer
• bimetallic
• pesticide residues
• environment

Appendix

Figure A1. SEM for different concentration of reducing agent a) ratio of FeCl₂.4H₂O: NaBH₄ (1:2) b) ratio of FeCl₂.4H₂O: NaBH₄ (1:5).

Figure A2. Plot of logarithm of the concentration of carbaryl in water with corresponding Raman intensity at 1599 cm⁻¹ (a) and 2233 cm⁻¹ (b).

Table A1. Summary of adsorption studies data.

Table A2. Isotherm parameter for adsorption of Cabaryl on Fe@Ag-MIP.

Additional information

Funding

We are grateful for the financial support of this research from the National Natural Science Foundation of China (51579057, 51779065), and State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology (2019DX11).