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Reference Module in Materials Science and Materials Engineering || Tip-Enhanced Raman Microscopy: Instrumentation, Techniques and Applications in Practice
摘要： The idea of optical microscopy is to use a set of lenses to magnify the object to see. Scientists changed the idea of this conventional optical microscopy since the scanning probe microscope (SPM) came out in 1980s. Inouye and Kawata proposed to use a sharp metal probe to create an optical image [1]. They scanned the metal tip on a sample surface while recording the optical near-field signals scattered by the tip [1,2]. The spatial resolution is not determined by the numerical aperture (N.A.) of the objective lens but by the tip radius that is typically a few tens of nanometers. The use of a metal tip provides not only high spatial resolution but also an enhancement of optical signals as a result of excitation of surface plasmons at the sharp metal tip. With the tip-enhancement effect, it becomes possible to detect even a very weak optical signal scattered from an extremely tiny volume. One such process is Raman scattering. The application of tip-enhancement to Raman spectroscopy was reported in the year of 2000 by three independent groups led by Kawata, Zenobi, and Anderson, respectively [3–6]. Using TERS, distribution of molecules [7–11] and electronic [12] and chemical properties within nanoscale materials [13–18] have been successfully visualized through Raman signatures with a nanoscale spatial resolution. There are a number of review articles for TERS microscopy and spectroscopy available in literatures [14,19–22]. During the past 20 years, the development of TERS has been mostly driven by research labs having research-grade apparatus operated by skillful researchers. The situation has been changing in the recent years, some companies have started to sell commercial products of TERS microscopes in the market. However, in order to realize TERS microscope as an analytical tool for the routine use of research and industry, challenges in TERS probes, reproducibility issues remain such as stable implementation of atomic force microscopes (AFMs), and peripheral operational techniques.
关键词： Raman spectroscopy,nanoscale imaging,plasmonic enhancement,Tip-Enhanced Raman Microscopy,TERS
更新于2025-09-10 09:29:36
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Over 1000-fold enhancement of upconversion luminescence using water-dispersible metal-insulator-metal nanostructures
摘要： Rare-earth activated upconversion nanoparticles (UCNPs) are receiving renewed attention for use in bioimaging due to their exceptional photostability and low cytotoxicity. Often, these nanoparticles are attached to plasmonic nanostructures to enhance their photoluminescence (PL) emission. However, current wet-chemistry techniques suffer from large inhomogeneity and thus low enhancement is achieved. In this paper, we report lithographically fabricated metal-insulator-metal (MIM) nanostructures that show over 1000-fold enhancement of their PL. We demonstrate the potential for bioimaging applications by dispersing the MIMs into water and imaging bladder cancer cells with them. To our knowledge, our results represent one and two orders of magnitude improvement, respectively, over the best lithographically fabricated structures and colloidal systems in the literature. The large enhancement will allow for bioimaging and therapeutics using lower particle densities or lower excitation power densities, thus increasing the sensitivity and efficacy of such procedures while decreasing potential side effects.
关键词： upconversion nanoparticles,plasmonic enhancement,bioimaging,photoluminescence,metal-insulator-metal nanostructures
更新于2025-09-10 09:29:36
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Total Aqueous Synthesis of Au@Cu <sub/>2?</sub><i> <sub/>x</sub></i> S Core–Shell Nanoparticles for In Vitro and In Vivo SERS/PA Imaging‐Guided Photothermal Cancer Therapy
摘要： Both accurate tumor navigation and nanostructures with high photothermal (PT) conversion efficiency are important but remain challenging to achieve in current biomedical applications. This study reports an anion exchange-based facile and green approach for synthesizing Au@Cu2?xS core–shell nanoparticles (NPs) in an aqueous system. In addition to the PT effect of the suggested NPs, the surface-enhanced Raman scattering (SERS) is also significantly improved due to the tailored localized surface plasmon resonance coupling between the Au metal core and the Cu2?xS semiconductor shell. Using an epitaxial strategy, Au@Cu2O NPs are first obtained by the in situ reduction of cupric hydroxide on a cresyl violet acetate-coated Au core; then, Au@Cu2?xS NPs are obtained via anion exchange between the S2? and Cu2O shell. Both the Cu/S atomic ratio and the Cu2?xS shell thickness can be adjusted conveniently. Hence, the ideal integration of the plasmonic Au core and Cu2?xS shell into a single unit is conducive not only to highly efficient PT conversion but also to the construction of a SERS-based navigator. This new type of SERS-guided NP, with enhanced photoacoustic signals, is an important candidate for both accurate tumor navigation and nondestructive PT treatment guided in vivo by two modes of optical imaging.
关键词： navigation treatment,photothermal therapy (PTT),Au@Cu2?xS core–shell nanoparticles (NPs),plasmonic enhancement,surface-enhanced Raman scattering (SERS)
更新于2025-09-09 09:28:46