Colloidal gold monitoring

The use of gold nanoparticles as an electrochemical label for bionanalysis was introduced by Costa-Garcia and coworkers 62 Adsorptive voltammetry was used to detect the gold signal and monitor biotin-stieptavidin interactions on a pretreated carbon paste electrode with an adsorbed biotinylated albumin layer after immersion into a solution of streptavidin-coated colloidal gold. While colloidal gold had found widespread use as a histochemical label for biomolecules and an optical label based on absorption... 

Gold nanoparticles can be used in conjunction with coenzymes for the continuous monitoring of glucose.118 Results of in vitro experiments show that this glucose sensor has a short response time, high sensitivity and good linearity. This is a demonstration that aqueous colloidal gold particles can enhance the activity of aqueous enzymes. 

Figure 16.9 Transient absorption spectra of 15 nm spherical gold nanoparticles after excitation at 400 nm with 100 fs laser pulses, recorded as different delay times. Also shown is the steady-state UV/Vis-absorption spectrum of the colloidal gold solution. The inset shows the decay of the transient bleach when the particles are monitored at the hleach maximum at 520 nm. Fitting of the decay curve yields electron-phonon and phonon-phonon relaxation times of 3.1 and 90 ps, respectively. (Reproduced with permission from S. Link and M. El-Sayed, 1999. J. Phys. Chem. B 103 8410 8426. Copyright 1999 American Chemical Society.)...

Monitoring the pH value during the preparation of gold sol, which leads to the below reported results, it has been observed that pH moves from ca. 3.2, before NaBH4 addition, to ca. 6.9, after NaBH4 addition. In this section a discussion of the influence of the initial pH value on the properties of the colloidal dispersion stabilized by a large amount (PVA/Au = 0.67) or a low amount (PVA/ Au = 0.05) of stabilizer is presented. Proper amounts of HCl or NaOH were used to produce the reported pH values. 

Controlled reduction of cadmium (or lead) ions on surfaces of nanosized silver (or gold) metallic particles results in the formation of double-layer colloids [532-534]. Depending on the coverage, the second layer can vary from being non-metallic clusters to quasi-metallic and metallic colloids. Growth of the second-layer particles can be monitored by absorption spectrophotometry. For... 

CL measurements. The CL was conducted on a Remex IFFM-E client system (Xi an Remex Analysis Instrument Co., Ltd.). De-ionized, distilled water was used as a carrier for Na2S03 to mix with Ce(IV) with the colloidal solution of gold NPs and NFLX of the optimized concentrations. The CL signals were monitored by a photomultiplier tube (PMT) adjacent to the flow CL cell. 

A short laser pulse ( 200 fs) generates hot electrons in the metal clusters. A second laser pulse monitors the hot electron population. This technique enables the direct observation of electron relaxation as a result of electron-phonon coupling. Electron-phonon coupling is a decisive property enabling differentiation between bulk and molecular properties. Although this possibility has been exploited by different authors, the particles used have not been single-sized, which is necessary if valid results are to be obtained. The use of clusters of a distinct size such as Aun and Auss" and almost monodisperse 15-nm gold colloids and 3 nm and 35 nm Pt particles recently enabled more precise measurements to be made and better results to be obtained than in the past. It could be shown that the hot electron relaxation depends on the particle size in two different ways ... 

Hydrous oxides are of major interest in many areas of technology, e.g., corrosion and passivation of metals, formation of decorative, protective, and insulating films, aqueous battery systems, catalysis and electrocatalysis, electrochromic display systems, pH monitoring devices, soil science, colloid chemistry, and various branches of material science. Detailed accounts of some of the nonnoble hydrous metal oxide systems, especially aluminum,1 have appeared recently. In the case of the noble metals such as platinum or gold most of the electrochemical work to date has been concerned with compact monolayer, and submonolayer, oxide growth. 

N. Nagahori and S.-I. Nishimura, Direct and effieient monitoring of glyeosyl-transferase reactions on gold colloidal nanoparticles by using mass spectrometry, Chem. Eur. J, 12 (2006) 6478-6485. 

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