No abstract

Surface enhanced Raman is a powerful analytical tool with high sensitivity and unique specificity and promising applications in various branches of analytical chemistry. Despite the fabrication of ingenious enhancement substrate used in laboratory research, the development of simple, flexible, and cost-effective substrate is also great important for promoting the application of SERS in practical analysis. Recently, paper and filter membrane as support to fabricate flexible SERS substrates received considerable attentions. Paper-based SERS substrate has been reviewed but no summary on filter-based SERS substrate is available. Compared with paper, filter membrane has unique advantage in robust mechanics, diverse component, and tunable pore size. These characteristics endow the filter-based substrates great advantages for practical SERS analysis including simple and low-cost substrate preparation, high efficiency in preconcentration, separation and detection procedure. Therefore, filter-based substrates have shown great promise in SERS analysis in environment monitoring, food safety with high sensitivity and efficiency. As more and more work has been emerged, it is necessary to summarize the state of such a research topic. Here, the research on filter involved SERS analysis in the past eight years is summarized. A short introduction was presented to understand the background, and then the brief history of filter-based substrate is introduced. After that, the preparation of filter-based substrate and the role of filter are summarized. Then, the application of filter involved SERS substrate in analysis is presented. Finally, the challenges and perspective on this topic is discussed.

A composite CC/Fe−MoS2@Au composed of gold nanoparticles in‐situ grown on Fe‐doped MoS2 anchored on carbon cloth (CC) was prepared for SERS detection and photo/photo‐Fenton degradation of fungi pesticides. Flower‐like MoS2 grown on CC provides large surface area for in‐situ reduction and immobilization of AuNPs, generating high SERS enhancement effect. Fe‐doping improves MoS2’s SERS activity and photocatalysis and endows the composite with Fenton degradation ability due to the coexistence of Fe3+/Fe2+ confirmed by XPS. Owing to their synergy, the CC/Fe−MoS2@Au can achieve the SERS detection of fungicide crystal violet (CV) and malachite green (MG) with detection limits of 0.1 nM and 10 nM, respectively. The CC endows it flexibility for fungicide sensing on irregular surface, such as fish skin with a LOD of 10−7 M for MG. The composite displayed multimode degradation ability for fungicides: 70 % of 10−5 M CV could be degraded after 75 min photocatalytic degradation by CC/Fe−MoS2@Au under natural light, while it increases to 85 % in the presence of H2O2 through a photo‐Fenton reaction. The synergy mechanism of these components for fungicide degradation were discussed. Such flexible multifunctional composite has great value in SERS analysis, environmental monitoring and remediation.

Sensitive determination of Cr(VI) is of great importance as this is one of the most toxic heavy metal ions in the environment. In this work, a metal–organic framework (MOF) material, UIO-66 (University of Oslo, UIO), was introduced for the first time to develop a composite substrate, UIO-66/Ag/TiO2, for the sensitive SERS detection of Cr(VI) in water. The composition, morphology, crystal structure and optical property of the UIO-66/Ag/TiO2 were characterized by SEM, XRD, EDX, UV-Vis and Raman spectroscopy. The control experiment revealed the introduction of UIO-66 and TiO2 can improve the adsorption to Cr ions and thus greatly enhance the SERS signal of Cr(VI) on this composite substrate. The SERS signal can also be tuned by changing the dosage of TiO2. Under optimized conditions, UIO-66/Ag/TiO2 was used to detect Cr(VI) in water with different concentrations, which showed high sensitivity and good stability. The SERS signals showed a linear increase as the concentration of Cr(VI) increases from 5 × 10−9 M to 5 × 10−6 M. The detection limit was 5 nM, which was lower than the safe drinking water standard of the US Environmental Protection Agency (1 μM). Detection of Cr(VI) in the range of 1 × 10−7 M to 5 × 10−6 M in real lake water was also achieved. These results demonstrate the great potential of UIO-66/Ag/TiO2 composites as SERS substrates for the trace determination of Cr(VI) in the environmental field.