貴金屬奈米粒子在吸收光譜中會產生特性吸收帶，此特性稱為粒子電漿共振波帶 (particle plasmon resonance, PPR)。其波長的位置與吸收度對外在環境的改變相當敏感。若要增加貴金屬奈米粒子的感測靈敏性可以從粒子形狀作選擇也可利用光波導多次內反射來增加光學路徑，同時也可透過貴金屬奈米粒子的表面官能化修飾增加感測器的選擇性。由於偵測是靠待分析物結合在奈米粒子的表面導致介電性質的改變，因此不必因為待測分析物沒有特殊的光譜特性 (例如：螢光基團、發光團…等) 而需要額外進行標記的動作。近年來以貴金屬PPR 現象為基礎開發的檢測平台在感測應用上有長足的進展，此法最大的特點是具有免標定、即時偵測以及高靈敏度等優點，而這些優勢使其成為極具潛力的生物分析工具。本文將介紹不同形狀貴金屬的PPR 特性與各式奈米生物感測平台。 Noble metal nanoparticles exhibit a characteristic absorption band in the absorption spectrum, known as “Particle Plasmon Resonance, PPR”. The absorbance and peak wavelength of the PPR band are linearly dependent on the refractive index of the surrounding medium. The sensing sensitivity can be increased by using nanoparticles of different shapes and by using waveguides to increase the optical path. The nanoparticles can also be functionalized to allow the selectivity of the sensor. Since the detection process is based on the change of refractive index of the surrounding medium when the analyte interacts with the molecular recognition group on the nanoparticle surface, the analyte does not require to have a spectroscopic signature (e.g. fluorophore, chromophore, etc.). Thus, noble metal nanoparticles can be used to construct leble-free sensors. Recent developments of biosensors have paved the route toward label-free and real-time optical transducers using the particle plasmon resonance (PPR) of metal nanostructures. These platforms can provide extremely sensitive assays. In this article, the characteristics of noble metal nanoparticles of different shapes and development of biosensors based on these materials will be introduced.
