Physical Vapor Deposition and Inmobilized metal na Essays

Physical Vapor Deposition and Inmobilized metal nanoparticles Student Name: Institutional Affiliation: Course: Date: The application of metal nanoparticles has grown greatly over the past years. Immobilized metallic particles are much easier to fabricate via normal wet chemistry, giving various choices with regard to shape and size CITATION Mar05 \l 1033 [1] . Furthermore, SERS hotspots can be cheaply realized through the aggregation of immobilized metallic particles from their suspensions through the use of salts or any analyte of interest. Nevertheless, the use of aggregated and dispersed immobilized metallic particles as SERS substrates within real analytical complications is limited as a result of the poor modification factor reproducibility. The issue of reproducibility could be solved through advanced metallic nanoparticles immobilization together with some solid support CITATION LeR09 \l 1033 [2] . The easiest SERS experiments are achieved with metallic nanoparticles under the presence of particular analyte concentration [6] . However, suspension of metallic nanoparticles should be mixed with the SERS analyte solution, a sampling demand that may be hampering some applications. Regardless, of the reproducibility and possible sampling shortcomings, metallic nanoparticles are widely used as SERS substrate because of their good stability, high SERS performance and easy fabrication [9] . Furthermore, they promote the formation of more stable metallic particles. Another methodology comprises of generating some SERS substrates through immobilizing the metallic nanoparticles under a planar foundation [10] . The metallic nanoparticles adhesion to solid supports is occasionally so poor and particular immobilization methodologies have to be devised to retain the performance and integrity of SERS substrate over time [5] . For example the chemical attachment of metallic nanoparticles to solid substrates where bi-functional molecules are used for its immobilization CITATION Fre95 \l 1033 [3] . The ideology behind this is to anchor the molecule to the surface through the use of one of its functional sets, hence leaving the other functional set free to bind the metallic nanoparticle. Glass slides surfaces are functionalized with thiol or amine groups with the aid of a surface polymerization procedure coupled with Deeping the functionalized glass to the metallic nanoparticles suspension for some time period CITATION DMM10 \l 1033 [4] . Benefits of using Glass in this case include large enlargement factor, low cost, electrochemical addressability, flexibility with regard to glass surface geometry, better reproducibility as opposed to metallic nanoparticles in suspension and the fact that glass has a less di-electric constant that affects the Rama/SERS signal compared to other substances such as PDMS [7] . Apart from the above approach, some other efficient surface chemical modification avenues exists which have been used to immobilize metallic nanoparticles. For instance, the introduction of amino functionality to a silicon surface through the application of Silane chemistry [2] . The amino group was successively clapped using a carboxyl alkanethiol. The thiol group then reacted with the metallic nanoparticles. SERS substrates could also be achieved through fabricated biochips by soft lithography CITATION Fre95 \l 1033 [3] . A set of nanofabrication technique is established to build nano-pillars frameworks within a silicon wafer as a parent molding copy, then the other nano - wells frameworks on polydimethylsiloxane. PDMS are established through soft lithography [2] . The selection of metallic deposition on the nanowells is used to establish SERS active sites prior to the integration with glass microfluidic that works as a sample deliv ery device as well as an optical transparent window for imaging of the SERS spectroscopic. PDMS is an off the - shelve available chemically and physically stable silicone rubber. It contains some unique flexibility that cannot be compared to glass with shear elastic modulus as a result of one of the lowest glass temperature transition of any polymer. In addition, PDMS are a bit some low change within the shear elastic modulus as opposed to temperature typically no change in elastic modulus versus high compressibility and frequency. Due to its clean process ability, the high flexibility and low temperature, the chances of change to any of its functional components as well as property drift over temperature and time, as opposed to glass, PDMS is suitable for chemical and mechanical sensors as it has many desirable features than can be found in glass when producing SERS signals and further