Facial Fabrication of Large-Scale SERS-Active Substrate Based on Self-Assembled Monolayer of Silver Nanoparticles on CTAB-Modified Silicon for Analytical Applications

Optimization of the Surfactant Ratio in the Formation of Penta-Twinned Seeds for Precision Synthesis of Gold Nanobipyramids with Tunable Plasmon Resonances

The synthesis of high-purity gold nano bipyramids (Au NBPs) with a narrow size distribution and tunable plasmon resonances is of great significance for plasmon resonance-related applications. However, the synthesis Au NBP approach involves multiple steps with many parameters that can affect the purity of the final product. In this work, we were devoted to studying the effect of the molar ratio between hexadecyltrimethylammonium chloride (CTAC) and sodium citrate tribasic dihydrate (CiNa3) on the seed formation stage. The results showed that the yield of Au NBP product has dramatically increased with the seed solution made from the molar ratio of CTAC:CiNa3 at 21:1. Furthermore, using this optimal seed, we can efficiently synthesize Au NBPs with various sizes by adjusting the concentration of the seed but keeping the rest of the parameters constant. In this study, the longitudinal localized surface plasmon resonances (LSPRs) of Au NBPs exhibit tunability beyond 450 nm across the visible and near-infrared regions from 774 to 1224 nm. We were able to successfully fine-tune the LSPRs of Au NBPs in the spectral region to become resonant with the excitation wavelengths of an 808 nm near-infrared (NIR) laser. The photothermal activities of Au NBPs were studied under 808 nm laser irradiation at ambient conditions. The present work demonstrates a paradigm for the synthesis of Au NBPs with tunable LSPRs in a precise and controllable manner, achieved by examining the surfactant ratios in the formation of penta-twinned seeds.

Construction of dense film inside capillary wall and SERS application research

The high-density particle distribution in capillary was a crucial factor for enhancing SERS properties and a difficult point in the preparation process. The direct high-temperature method was used to fuse the particles and form a uniform and dense particle distribution on the capillary's inner wall, providing a foundation for enhancing Raman signals. The prepared capillary SERS substrate strongly enhances the rhodamine 6G (R6G) signal, and the RSD values of several characteristic peaks of R6G are about 10 %, demonstrating high sensitivity, uniformity, and stability. Using capillary SERS substrate for detecting goat serum. Embedding precious metal particles into capillary SERS substrate can effectively encapsulate the tested liquid and avoid contamination, which improves the disadvantage of traditional substrates exposing the liquid to air. The prepared capillary SERS substrate could be used for field and biomedical sensitivity detection, providing a theoretical and experimental basis for developing the capillary SERS substrate.

Alkoxysilane-Mediated Decoration of Si Nanowires Vertical Arrays with Au Nanoparticles as Improved SERS-Active Platforms

The search for improved transducers to fabricate better-performing (bio)sensors is a challenging but rewarding endeavor aiming to better diagnose and treat diseases. In this paper, we report on the decoration of a dense vertical array of ultrathin silicon nanowires (Si NWs), produced by metal-assisted chemical etching, with 20 nm gold nanoparticles (Au NPs) for surface-enhanced Raman scattering (SERS) applications. To optimize the production of a uniform 3D SERS active platform, we tested different Si NW surface functionalizations with various alkoxysilanes before Au decoration. Scanning electron microscopy investigations confirm that Au NPs decorate both bare and (3-glycidiloxypropyl)trimethoxysilane (GPTMS)-modified Si NWs with a high surface coverage uniformity. The SERS response of the decorated NWs was probed using a model dye system (methylene blue; MB) at 633 and 785 nm excitation wavelengths. The GPTMS-modified NWs present the highest enhancements of 2.9 and 2.6 for the 450 cm-1 and 1625 cm-1 peaks under 785 nm excitation and of 10.8 and 5.3 for the 450 cm-1 and 1625 cm-1 peaks under 633 nm excitation. These results demonstrate the perspective role of Si NWs decorated with Au NPs as a low-cost 3D SERS platform.

Surface-enhanced Raman scattering biosensors for detection of oncomiRs in breast cancer

Surface-enhanced Raman scattering (SERS) has emerged as one of the most promising platforms for various biosensing applications. These sensing systems encompass the advantages of specificity, ultra-high sensitivity, stability, low cost, repeatability, and easy-to-use methods. Moreover, their ability to offer a molecular fingerprint and identify the target analyte at low levels make SERS a promising technique for detecting circulating cancer biomarkers with greater sensitivity and reliability. Among the various circulating biomolecules, oncomiRs are emerging as prominent biomarkers for the early screening of breast cancers (BCs). In this review, we provide a comprehensive understanding of different SERS-based biosensors and their application to identify BC-specific oncomiRs. We also discuss different SERS-based sensing strategies, nano-analytical frameworks, and challenges to be addressed for effective clinical translation.