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Abstract: The differences between electromagnetic enhancement and chemical enhancement in surface‐enhanced Raman scattering (SERS) and their deep insight are very important and valuable for the explanation of spectral behaviors and the practical application of SERS technique. In this work, the typical semiconductor substrate TiO2 nanoparticles and noble‐metal substrate Ag colloid were selected as two representative SERS‐active substrates to investigate the differences between the electromagnetic (EM) mechanism and the charge‐transfer (CT) mechanism using 4‐mercaptobenzoic acid as probe molecule. The 4‐mercaptobenzoic acid molecules on two substrates exhibit the obvious differences in spectral behavior and signal intensity of SERS as well as the detectability, which can be attributed to the essential differences between the EM mechanism and the CT mechanism. The EM enhancement more depends on the behavior of the substrate, which more tends to be nonselective for the adsorbed molecules and their enhancement. The CT enhancement not only depends on the behavior of the substrate but also depends on the behavior of the adsorbed molecule due to the CT between substrate and molecule, which more tends to be selective for the adsorbed molecules and their enhancement. Moreover, it is also proved that the semiconductor (TiO2) SERS‐active substrate is characterized by the high stability and the recyclability. [ABSTRACT FROM AUTHOR]

In this paper, anatase and rutile TiO2 nanoparticles as well as their mixed crystal phase structure TiO2 nanoparticles were synthesized by a sol-hydrothermal method, and were served as active substrates for surface-enhanced Raman scattering (SERS) study. The results show that the 4-mercaptobenzoic acid probe molecules exhibit different degree SERS enhancements on the surface of different phase structure TiO2 nanoparticles. The mixed crystal structure TiO2 with an appropriate proportion of anatase and rutile phase is favourable to SERS enhancement of adsorbed molecules. These are mainly attributed to the contributions of the TiO2-to-molecule charge transfer mechanism and the mixed crystal effect. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A metal-organic semiconductor-molecule model was developed with Ag nanoparticles (NPs), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and 4-mercaptobenzoic acid (4-MBA) via the layer-by-layer self-assembly method. In the SERS spectrum of the Ag/PEDOT:PSS/4-MBA system, structural changes in the PEDOT chain were discovered, which provides a deeper understanding of the charge transfer (CT) mechanism in SERS and helps in the development of a method to construct metal-organic semiconductor SERS substrates. A quantitative calculation of the degree of charge transfer (ρ CT(κ)) determines the CT contribution of PEDOT:PSS to the SERS intensity of the Ag/PEDOT:PSS/4-MBA system. On this basis, we propose the formation of a resonance complex between Ag NPs and PEDOT:PSS to explore the CT mechanism, which is beneficial for studying interface CT and for understanding the CT mechanism in SERS. The introduction of organic semiconductors in this study not only broadens the research scope of SERS substrates but also contributes to the exploration of SERS mechanisms. A metal/organic semiconductor/molecule model was fabricated with Ag NPs, PEDOT:PSS and 4-MBA via the layer-by-layer self-assembly method. The structural changes of the PEDOT chain in the SERS spectrum of the Ag/PEDOT:PSS/4-MBA system provide a deeper understanding of the CT mechanism in SERS and helps in the development of a method to construct metal-organic semiconductor SERS substrates. The introduction of organic semiconductors in this study not only broadens the research scope of SERS substrates but also contributes to the exploration of SERS mechanisms. Unlabelled Image • A metal/organic semiconductor/molecule model was fabricated via the layer-by-layer self-assembly method. • SERS spectrum of the Ag/PEDOT:PSS/4-MBA system provided a deeper understanding of the CT mechanism. • The introduction of organic semiconductors in this study not only broadens the research scope of SERS substrates. [ABSTRACT FROM AUTHOR]