Molecularly imprinted 3D SERS sensor with inorganic frameworks for specific and recyclable SERS sensing application

Poor selectivity and reusability of Au/Ag nanostructures are the main challenges for surface-enhanced Raman spectroscopy (SERS) in real sample detection. Herein, a novel specific and reusable three-dimensional (3D) SERS sensor with dual functions of selective trapping and photocatalytic degradation was designed. Firstly, Au-Ag bimetallic nanoparticles decorated silicon nanowires array (SiNWs-AuAg) were prepared as 3D SERS substrate. Then, silicon-based inorganic-framework molecularly imprinted TiO₂ (TiO₂@SiMIP) was synthesized and immobilized on SiNWs-AuAg by using rhodamine 6G (R6G) as template molecule. Owing to the excellent SERS performance of SiNWs-AuAg and the specific affinity of TiO₂@SiMIP to template molecule, the prepared SERS sensor enables sensitive and selective detection of R6G in food samples with a limit of detection (LOD) of 0.27 nM. In addition, due to the photocatalysis of TiO₂ and the stability of silicon-based inorganic framework, the residual templates in TiO₂@SiMIP can be completely removed by UV irradiation, and the imprinted cavity of regenerated sensors still maintained good selectivity after regeneration by UV irradiation.

Study on surface enhanced Raman scattering of Au and Au@Al2O3 spherical dimers based on 3D finite element method

In this paper, the surface enhanced Raman scattering (SERS) characteristics of Au and Au@Al₂O₃ nanoparticle dimers were calculated and analyzed by using finite element method (3D-FEM). Firstly, the electric field enhancement factors of Au nanoparticles at the dimer gap were optimized from three aspects: the incident angle of the incident light, the radius of nanoparticle and the distance of the dimer. Then, aluminum oxide is wrapped on the Au dimer. What is different from the previous simulation is that Al₂O₃ shell and Au core are regarded as a whole and the total radius of Au@Al₂O₃ dimer is controlled to remain unchanged. By comparing the distance of Au nucleus between Au and Au@Al₂O₃ dimer, it is found that the electric field enhancement factor of Au@Al₂O₃ dimer is much greater than that of Au dimer with the increase of Al₂O₃ thickness. The peak of electric field of Au@Al₂O₃ dimer moves towards the middle of the resonance peak of the two materials, and it is more concentrated than that of the Au dimer. The maximum electric field enhancement factor 583 is reached at the shell thickness of 1 nm. Our results provide a theoretical reference for the design of SERS substrate and the extension of the research scope.

Development of affinity between target analytes and substrates in surface enhanced Raman spectroscopy for environmental pollutant detection

Environmental pollution has long been a social concern due to the variety of pollutants and their wide distribution, persistence and being detrimental to health. It is therefore necessary to develop rapid and sensitive strategies to trace and detect these compounds. Among various detection methodologies, surface enhanced Raman spectroscopy (SERS) has become an attractive option as it enables accurate analyte identification, simple sample preparation, rapid detection and ultra-high sensitivity without any interference from water. For SERS detection, an essential yet challenging step is the effective capture of target analytes onto the surface of metal nanostructures with a high intensity of enhanced electromagnetic field. This review has systematically summarized recent advances in developing affinity between targets and the surface of SERS substrates via direct adsorption, hydrophobic functional groups, boronate affinity, metal organic frameworks (MOFs), DNA aptamers and molecularly imprinted polymers (MIPs). At the end of this review, technical limitations and outlook have been provided, with suggestions on optimizing SERS techniques for real-world applications in environmental pollutant detection.

Applications of surface-enhanced Raman spectroscopy in detection fields

Surface-enhanced Raman spectroscopy (SERS) is a Raman spectroscopy technique that has been widely used in food safety, environmental monitoring, medical diagnosis and treatment and drug monitoring because of its high selectivity, sensitivity, rapidness, simplicity and specificity in identifying molecular structures. This review introduces the detection mechanism of SERS and summarizes the most recent progress concerning the use of SERS for the detection and characterization of molecules, providing references for the later research of SERS in detection fields.