Performance-enhancing methods for Au film over nanosphere surface-enhanced Raman scattering substrate and melamine detection application.

Jun Feng Wang,Xue Zhong Wu,Chao Guang Wang,Rui Xiao,Pei Tao Dong,Alan Stitt

doi:10.1371/journal.pone.0097976

Abstract

A new high-performance surface-enhanced Raman scattering (SERS) substrate with extremely high SERS activity was produced. This SERS substrate combines the advantages of Au film over nanosphere (AuFON) substrate and Ag nanoparticles (AgNPs). A three order enhancement of SERS was observed when Rhodamine 6G (R6G) was used as a probe molecule to compare the SERS effects of the new substrate and commonly used AuFON substrate. These new SERS substrates can detect R6G down to 1 nM. The new substrate was also utilized to detect melamine, and the limit of detection (LOD) is 1 ppb. A linear relationship was also observed between the SERS intensity at Raman peak 682 cm−1 and the logarithm of melamine concentrations ranging from 10 ppm to 1 ppb. This ultrasensitive SERS substrate is a promising tool for detecting trace chemical molecules because of its simple and effective fabrication procedure, high sensitivity and high reproducibility of the SERS effect.

Highlights

Surface-enhanced Raman scattering (SERS) spectroscopy is an important analytical technique for biological sensing and trace analysis because of the enormous Raman enhancement for molecules absorbed on specific SERS substrates
We achieved the preparation of Au film over nanosphere (AuFON) by nanosphere lithography techniques and the synthesis of silver colloidal by the microwave synthesis method
The new Ag nanoparticles (AgNPs)/AuFON SERS substrate was prepared through a simple amination process

Summary

Introduction

Surface-enhanced Raman scattering (SERS) spectroscopy is an important analytical technique for biological sensing and trace analysis because of the enormous Raman enhancement for molecules absorbed on specific SERS substrates. Au film over nanosphere (AuFON) and Ag film over nanosphere (AgFON) are the two commonly used MFON SERS substrates produced by nanosphere lithography techniques [19,20] that use spin-coated microspheres layers as templates for silver or gold deposition. The advantages of these MFON substrates are the high controllability of their relatively simple fabrication process and the high reproducibility of the SERS effect. 10 mL of silver colloids was dropped onto each piece of the AuFON substrate, followed by 5 mL 0.1% NaCl. After drying at RT, the active AgNPs/AuFON SERS substrate was successfully fabricated. The SERS substrate was immersed in 100 mL analyte solution of different concentrations for 1 h before the SERS characterization to assure saturated adsorption

Instrumentation FE-SEM micrographs were acquired using a JEOL JSM-7001F

Results and Discussion

Conclusions