Fluorescence intensity colloidal nanoparticles

The combination of fluorophores and suspended colloid particles could be used in metal-enhanced solution assays. Scheme 8.1 depicts the use of fluorophores and suspended colloid particles. Previous studies on fluorescence intensity enhancement between fluorophores and suspended particles in terms of metal core of nanoparticles, fluorophore type, and spacer used are summarized in Table 8.2. 

Furthermore, the dense, saturation packing of R6G or other dye molecules on colloidal gold/silver surface does not limit Raman intensities in the way that fluorescence intensities are lowered by excited state dipole-dipole interactions. In comparison with flnorescent dyes and quantum dots, the enhanced Raman probes have an intrinsic amplification mechanism, with improved encoding and mnltiplexing capabilities. If multiple (4 or even more) sizes of gold/silver nanoparticles in the 50-300 nm diameter range with a narrow size distribution can be prepared, and then loaded with 20 different dye molecules with unique SERS fingerprints, this would provide 80 probes for each metal nanoparticle. 

Nanomaterials in the form of a colloidal solution or quantum dots are attributed to have a tremendous impact in analytical chemistry for their unique physical and chemical properties (Alivisatos 2004 Katz and Willner 2004). A different methodology has been adopted to analyse vitamin Bi spectro-fluorimetrically by using cadmium selenide quantum dots (CdSe QDs), cadmium telluride (CdTe) nanorods, and silica and gold nanoparticles. A fluorescence resonance Rayleigh scattering (RRS) method was applied for determining vitamin Bi at sub-nanomolar level (Liu et al. 2006). In this technique, vitamin Bi was mixed with acidic buffer and prepared gold nanoparticles. After incubation, the solution mixture was excited in synchronous mode to obtain RRS spectra. The RRS spectral intensity correlated with the concentration of vitamin Bi. 

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