Feasibility of SERS-Active Porous Ag Substrates for the Effective Detection of Pyrene in Water

Exploring Reliable and Efficient Plasmonic Nanopatterning for Surface- and Tip-Enhanced Raman Spectroscopies

Surface-enhanced Raman scattering (SERS) is of growing interest for a wide range of applications, especially for biomedical analysis, thanks to its sensitivity, specificity, and multiplexing capabilities. A crucial role for successful applications of SERS is played by the development of reproducible, efficient, and facile procedures for the fabrication of metal nanostructures (SERS substrates). Even more challenging is to extend the fabrication techniques of plasmonic nano-textures to atomic force microscope (AFM) probes to carry out tip-enhanced Raman spectroscopy (TERS) experiments, in which spatial resolution below the diffraction limit is added to the peculiarities of SERS. In this short review, we describe recent studies performed by our group during the last ten years in which novel nanofabrication techniques have been successfully applied to SERS and TERS experiments for studying bio-systems and molecular species of environmental interest.

MoS2 Nanoplatelets on Hybrid Core-Shell (HyCoS) AuPd NPs for Hybrid SERS Platform for Detection of R6G

In this work, a novel hybrid SERS platform incorporating hybrid core-shell (HyCoS) AuPd nanoparticles (NPs) and MoS₂ nanoplatelets has been successfully demonstrated for strong surface-enhanced Raman spectroscopy (SERS) enhancement of Rhodamine 6G (R6G). A significantly improved SERS signal of R6G is observed on the hybrid SERS platform by adapting both electromagnetic mechanism (EM) and chemical mechanism (CM) in a single platform. The EM enhancement originates from the unique plasmonic HyCoS AuPd NP template fabricated by the modified droplet epitaxy, which exhibits strong plasmon excitation of hotspots at the nanogaps of metallic NPs and abundant generation of electric fields by localized surface plasmon resonance (LSPR). Superior LSPR results from the coupling of distinctive AuPd core-shell NP and high-density background Au NPs. The CM enhancement is associated with the charge transfer from the MoS₂ nanoplatelets to the R6G. The direct contact via mixing approach with optimal mixing ratio can effectively facilitate the charges transfer to the HOMO and LUMO of R6G, leading to the orders of Raman signal amplification. The enhancement factor (EF) for the proposed hybrid platform reaches ~10¹⁰ for R6G on the hybrid SERS platform.

Recent advances in the analysis of polycyclic aromatic hydrocarbons in food and water

Polycyclic aromatic hydrocarbons (PAHs), a class of harmful and persistent organic contaminant, are widely distributed in the environment and eventually accumulated in water and food. Also, they are formed in different varieties and varying amounts during processing of food depending on the food composition, cooking method and processing condition. According to the International Agency for Research on Cancer (IARC), various PAHs are classified under Group 1 to 3 category, with Group 1 designated as carcinogenic to humans, Group 2A as probable carcinogen, Group 2B as possible carcinogen and Group 3 as noncarcinogenic. Therefore, it is imperative to develop rapid and highly sensitive analytical methods for determination of PAHs in food and water. This article aims to overview the recent advances of various chromatographic methods as well as electrochemical and SERS-based optical sensing methods for analysis of PAHs in food and water. Initially, several conventional sample preparation methods along with the advanced extraction for isolation of PAHs were summarized, followed by reviewing various gas chromatographic methods coupled with various detection techniques for PAHs analysis in various food products including meat/meat products, seafood, oil, milk/milk products, baby foods, honey, vegetable, cocoa products, tea/coffee, juice, rice, flour, noodle and cake. In addition, high performance liquid chromatographic methods coupled with fluorescence, diode array or mass/tandem mass detection techniques as well as an emerging supercritical fluid chromatographic technique employed for determination of PAHs in different food and water matrices were also overviewed. Finally, various electrochemical sensors and SERS-based optical sensors developed recently for onsite detection of PAHs were tabulated and discussed. Thus, this review article can provide a research update on chromatography and sensor-based analytical methods for PAH analysis as well as enable elucidation of research gaps for future studies.