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Abstract：
Fluorescence spectroscopy serves as an ultrasensitive sophisticated tool where background noises which serve as a major impediment to the detection of the desired signals can be safely avoided for detections down to the single-molecule levels. One such way of bypassing background noise is plasmon-enhanced fluorescence (PEF), where the interactions of fluorophores at the surface of metals or plasmonic nanoparticles are probed. The underlying condition is a significant spectral overlap between the localized surface plasmon resonance (LSPR) of the nanoparticle and the absorption or emission spectra of the fluorophore. The rationale being the coupling of the excited state of the fluorophore with the localized surface plasmon leads to an augmented emission, owing to local field enhancement. It is manifested in enhanced quantum yields concurrent with a decrease in fluorescence lifetimes, owing to an increase in radiative rate constants. This improvement in detection provided by PEF allows a significant scope of expansion in the domain of weakly emitting fluorophores which otherwise would have remained unperceivable. The concept of coupling of weak emitters with plasmons can bypass the problems of photobleaching, opening up avenues of imaging with significantly higher sensitivity and improved resolution. Furthermore, amplification of the emission signal by the coupling of free electrons of the metal nanoparticles with the electrons of the fluorophore provides ample opportunities for achieving lower detection limits that are involved in biological imaging and molecular sensing. One avenue that has attracted significant attraction in the last few years is the fast, label-free detection of bio-analytes under physiological conditions using plasmonic nanoparticles for point-of-care analysis. This review focusses on the applications of plasmonic nanomaterials in the field of biosensing, imaging with a brief introduction on the different aspects of LSPR and fabrication techniques.
摘要：
荧光光谱学作为超灵敏的复杂工具，其中背景噪声作为所需信号检测的主要障碍，可以安全地避免以单分子水平进行检测。绕过背景噪声的一种方法是等离子体激元增强荧光(PEF)，其中探测金属或等离子体纳米粒子表面上的荧光团的相互作用。潜在条件是纳米颗粒的局域化表面等离子体共振(LSPR)与荧光团的吸收或发射光谱之间的显著光谱重叠。原理是荧光团的激发态与局部表面等离子体激元的耦合导致增强的发射，由于局部磁场增强。它表现在增强的量子产率与荧光寿命的减少同时，由于辐射率常数的增加。由PEF提供的这种检测改进允许弱发射荧光团的域中的显著扩展范围,否则其将保持不可感知。弱发射器与等离子体激元耦合的概念可以绕过光漂白的问题，开辟了成像的途径，具有明显更高的灵敏度和提高的分辨率。此外，通过金属纳米颗粒的自由电子与荧光团的电子的耦合来放大发射信号提供了实现生物成像和分子传感中涉及的较低检测限的充足机会。在过去几年中吸引了巨大吸引力的一条途径是快速，使用等离子体纳米颗粒在生理条件下对生物分析物进行无标记检测，以进行即时分析。本文综述了等离子体纳米材料在生物传感领域的应用。成像，简要介绍了LSPR和制造技术的不同方面。
