Optical properties surface enhanced Raman spectroscopy

Gold received much attention due to their unique size-dependent optical properties, insolubility in nitric acid and resistance to heat, moisture, oxygen and most corrosive reagents. For substrates in surface-enhanced Raman Spectroscopy (SERS), ergonomic electronic contacts, ultra fast data communication and biomedicine surface modified gold nanoparticles are perspective agents, while in the industry of catalysis platinum nanoparticles (Pt NPs) exhibiting excellent anticorrosive and catalytic properties are usually employed. 

This article provides some general remarks on detection requirements for FIA and related techniques and outlines the basic features of the most commonly used detection principles, including optical methods (namely, ultraviolet (UV)-visible spectrophotometry, spectrofluorimetry, chemiluminescence (CL), infrared (IR) spectroscopy, and atomic absorption/emission spectrometry) and electrochemical techniques such as potentiometry, amperometry, voltammetry, and stripping analysis methods. Very few flowing stream applications involve other detection techniques. In this respect, measurement of physical properties such as the refractive index, surface tension, and optical rotation, as well as the a-, //-, or y-emission of radionuclides, should be underlined. Piezoelectric quartz crystal detectors, thermal lens spectroscopy, photoacoustic spectroscopy, surface-enhanced Raman spectroscopy, and conductometric detection have also been coupled to flow systems, with notable advantages in terms of automation, precision, and sampling rate in comparison with the manual counterparts. 

Metal nanocrystals also interact strongly with electromagnetic waves and offer remarkable properties due to the localized surface plasmon resonance (SPR) that induces, through optical excitation, very intense local electrical fields. This property can be exploited for surface-enhanced Raman spectroscopy (SERS) and SPR-based... 

The current widespread interest in size-dependent optical properties of nanomaterials is a consequence of their many applications in research areas such as chemosensors, biosensors,nanoparticle optics, and surface-enhanced spectroscopy. Recently, interest in surface-enhanced Raman spectroscopy (SERS)... 

The unique photonic and condnctive properties of some nanoparticles can be employed to detect biological recognitions on a surface. With dimensions similar to those of biomolecnles, nanoparlicles are a natural choice for detecting biomolecules, which can be nsed in both electrochemically and optically based biosensors. Upon the assembly of nanoparticles on a solid surface, the biomolecules adsorbed on the surfaces of nanoparlicles can be detected by means of surface plasmon resonance (SPR), surface enhanced Raman spectroscopy (SERS), and surface-enhanced fluorescence spectroscopic techniques. Furthermore, the unique size-controlled optical properties of semiconductor nanoparticles imply that the organization of combinatorial hbraries of biomolecule-semiconductor nanoparticle hybrid systems or the assembly of these hybrids in array configurations may lead to the high-throughput parallel analysis of numerous analytes [53]. 

Despite the extensive studies of the anodic layers on Pt with various ultraviolet-visible optical methods, they have not provided a clear indication of the electronic or structural properties of the layers. Rather these optical methods have been more than just another form of readout to complement the electrochemical measurements of charge and current response of the layer to potential and time. Vibrational spectroscopic data from infrared and Raman measurements would be more helpful in establishing the nature of the layers but it is difficult to use these techniques to study metal-electrolyte and similar interfaces because of solvent interference and sensitivity problems. A noteworthy exception is the quite successful in situ use of Raman spectroscopy to study the electrochemically formed oxide layers on silver by Kotz and Yeager. In the instance of silver electrodes, there is a large surface enhanced Raman effect and the signal-to-noise ratio is not a problem. Unfortunately this is not the situation with other metal surfaces such as Pt. Even so, with improved instrumentation there is hope that in situ Raman studies of the anodic layers on Pt will become practical. 

Specular reflection spectroscopy has been actively used in in situ studies of the formation and optical behaviour of monolayer films on surfaces, and for detecting intermediates and products of heterogeneous chemical and electrochemical reactions. The vibrational spectra of the adsorbed species at electrode surfaces are obtained by surface-enhanced Raman scattering and infrared reflectance spectroscopies. Since the mid-1960s, modulated reflection spectroscopy techniques have been employed in elucidating the optical properties and band structure of solids. In the semiconductor electroreflectance, the reflectance change at the semiconductor surface caused by the perturbation of the dielectric properties of... 

Modified anilino squaraines have been widely utilized in surface-enhanced Raman resonance scattering (SERBS) spectroscopy. Their molecular structure displays a quadrupole D-A-D system that is characterized by an electron-deficient cyclobutendione (C Oj) bridge (Figure 5.7). The total structure can be represented in many ways, with the charge homogenously distributed over the entire molecule. Several theoretical studies have been conducted on this class of materials and their unusual nonlinear optical properties [4,81]. 

See also Matrix Isolation Studies By IR and Raman Spectroscopies Nonlinear Optical Properties Nonlinear Raman Spectroscopy, Instruments Nonlinear Raman Spectroscopy, Theory Photoacoustic Spectroscopy, Theory Raman Optical Activity, Applications Raman Optical Activity, Theory Rayleigh Scattering and Raman Spectroscopy, Theory Surface-Enhanced Raman Scattering (SERS), Applications. 

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