Printed Ag/RGO Nanostructure And Sers Performance Research

Surface-enhanced Raman scattering(SERS) spectroscopy is an advanced surface analysis technique. Owing to its high sensitivity, good selectivity, non-destruction, and real-time response, SERS has been considered as one of the most powerful and promising tools for chemical analysis, biological detection, medical diagnosis, food safety inspection and environmental monitoring. In the field of food safety, organic dyes are a very important class of dyes that are widely used in our daily life. The usage of disable additives such as malachite green(MG), rhodamine 6G(R6G), melamine(MA) are becoming more and more serious. SERS has been proved to be an important technique for rapid and low concentration detection of food additives. Although the SERS technology has been widely studied and used, one main obstacle of using SERS as a routine analytical tool is the fabrication of homogeneous, reproducible, and stable SERS-active substrate. Therefore, we aim at to prepare flexible tag SERS active substrate with good stability, good uniformity and repeatability, high strengthen ability, cheap and easy preparation at the same time.In this work, an efficient surface enhanced Raman scattering(SERS) substrate has been developed by inkjet printing of Ag nanoparticles conductive ink(AgNPs ink) and gravure printing of reduced graphene oxide ink(RGO ink). First, a series of AgNPs SERS substrate pattern has been prepared by inkjet printing AgNPs ink on the different substrate(slides, art paper, chromatography paper, weighting paper). Second, the preparation of a series of flexible paper-based Ag/RGO composite structure SERS substrate based on inkjet printing ink AgNPs combined with gravure printing RGO on different flexible paper substrate(art paper, chromatography paper, weighting paper) directly. Finally, in order to study the influence of different composite membrane structure used on the SERS performance, a set of substrates with hybrid structures were printed directly on weighting paper(WP), including RGO films(RGO/WP), Ag nanoparticles(AgNPs/WP), AgNPs on top of RGO(AgNPs/RGO/WP) and AgNPs underneath RGO(RGO/AgNPs/WP).UV-Vis absorption spectra results showed that the absorption peak position of AgNPs ink was 410 nm. TEM and particle size analysis showed that AgNPs evenly dispersed and the average grain size was about 26.9 nm. By electron diffraction lattice figure can be seen that graphene hexagonal crystal structure with high quality. SEM results showed that the pattern of AgNPs was closely arranged and have good dispersity and the average particle size of about 60 nm. Compared with the bare AgNPs, no noticeable morphology change was observed for AgNPs printed on top of RGO. The AFM images showed that the roughness(root mean square(RMS))of the printed RGO thin film is measured to be 18.6 nm. The surface of AgNPs coated on RGO(AgNPs/RGO) exhibits a smaller roughness(RMS) of 5.1 nm compared with that of bare AgNPs(4.4 nm). However, the surface roughness of AgNPs is slightly increased after the deposition of RGO thin film on top of it, with the RMS value increasing from 4.4 to 8.7 nm. The outstanding enhancement ability of the AgNPs/RGO substrate arises from three concurrent effects: electromagnetic enhancement due to surface plasmon resonance of AgNPs, chemical enhancement due to charge transfer of RGO, as well as molecular resonance. In addition, the adhesion and surface roughness of AgNPs are improved by introducing RGO thin film.Their SERS activities were compared using MG, R6 G and MA as probe molecules. The SERS enhancement performance, uniformity, reproducibility, and stability of the printed AgNPs/RGO/WP substrate were systematically investigated. It was found that the AgNPs/RGO/WP possessed higher enhancement ability than the pure RGO and AgNPs. The Raman enhancement factor was calculated to be as large as 2.9×108. The minimum detection limit for MG was as low as 10-7 M with a linear response range from 10-4 M to 10-7 M(r=0.9999). At the same time, the AgNPs/RGO/ WP exhibited strong flexibility, good uniformity with relative standard deviation(RSD) of 4.46%, excellent reproducibility with RSD smaller than 4%, and long-term stability with RSD of about 6% after 40 days and 3.6% after six months by repeated testing, respectively. In addition, this SERS substrate shows excellent ability to recognize MA molecules with a detection limit of approximately 3.125 mg/L.We combined inkjet printing of ink AgNPs with gravure printing of RGO and obtained Ag/RGO composites by using the advantage of printing technique such as good film-forming, simple process and strong operability. The composites realized good SERS performance, which combined the excellent enhancement ability of metal nanostructure and the chemical enhancement ability of of RGO. The Raman enhancement factor was calculated to be as large as 2.9×108. The minimum detection limit for MG was as low as 10-7 M with a linear response range from 10-4 M to 10-7 M(r=0.9999). this SERS substrate shows excellent ability to recognize MA molecules with a detection limit of approximately 3.125 mg/L. The results indicated that the tag AgNPs/RGO/WP substrate exhibited not only excellent enhancement ability but also good stability, uniformity, reproducibility, as well as high strengthen ability, cheap and easy preparation. Therefore, the fully printed, flexible and high-performance substrate can promote the application of SERS analysis in real life, such as food safety inspection and environmental monitoring.