LSPR is a coherent, collective spatial oscillation of the conduction electrons in a metallic nanoparticle, which can be directly excited by near-visible light. The localized surface plasmon resonance (LSPR) condition is defined by several factors, including the electronic properties of the
nanoparticle, the size and shape of the particle, temperature, the dielectric environment, and so on.
Small changes in the local dielectric environment cause the dysfunction of LSPR. The frequency
of the LSPR spectral peak is very sensitive to the nanostructure environment through the local
refractive index. Thereby, shifts of the LSPR frequency are widely used as a method for the detection of molecular interaction close to the surface of the nanoparticle [161–166]. In addition,the near-field enhancement has led to a very large variety of advances in many fundamental and applied areas of science, particularly for the determination of nanoparticle shapes, dimensions, and compositions. This spectroscopy method is being used to investigate fundamental properties and processes of nanoparticles in (bio)-molecular detection devices, or (bio)-imaging tools with improved single-molecule sensitivity. LSPR spectroscopy can provide thermodynamic and real-time kinetic data for binding processes. LSPR-based tools will be helpful to analyze faster and with higher sensitivity.
The application of LSPR spectroscopy is mainly used for biological and chemical sensing by transducing changes in the local refractive index via a wavelength-shift measurement, due to its sensitivity, wavelength tunability, smaller sensing volumes, and lower instrumentation cost. Single-nanoparticleInt. J. Mol. Sci. 2016, 17, 1534 8 of 34 LSPR spectroscopy is an important tool for understanding the relationship between local structure and spectra. In addition, single nanoparticles can provide even higher refractive-index sensitivity than nanoparticle arrays.