Surface quartz

Here, the structures of interfacial water at a fused quartz surface with and without contact of polyvinyl alcohol (PVA) were investigated by in situ SFG spectroscopy and their role in low friction between PVA and a fused quartz surface is discussed. 

Figure 5.14 shows SFG spectra in the OH-stretching region (2800-3800 cm obtained at a quartz surface in water before (a) and after (b-f) the contact of PVA... 

The SFG intensity decreased when PVA gel was in contact with the quartz surface. Weakening of SFG intensity is mostly due to the change in the Fresnel coefficients upon contact with the PVA gel [99]. 

The shape of the spectra also changed as the PVA gel was pressed toward the quartz surface and the pressure on the PVA gel was increased (Figure 5.14b-f). The SFG signal from the liquid-like water component became dominant as the pressure on the PVA gel surface was increased. 

The friction behavior of PVA gel and solid is strongly dependent on the nature of the solid surface. While the friction is low when the PVA gel is in contact with a quartz surface, which is hydrophilic, it is very high when the PVA gel is in contact with a... 

Although the total intensity of the SFG spectra decreased as the pressure on the PVA gel was increased, the intensity ratio between the peaks corresponding to icelike water and liquid-like water was almost constant. Since the OTS-modified quartz surface was hydrophobic, the water squeezed from the bulk gel was ice-like at the PVA gel/OTS-modified quartz interface. 

These results at the interfaces between the PVA gel and quartz surfaces, with and without modification by OTS, suggest that the weakly hydrogen bonded, that is, liquid-like , water plays an important role for the low friction at the PVA gel/quartz interface. 

The structure of water at the PVA/quartz interface was investigated by SFG spectroscopy. Two broad peaks were observed in the OH-stretching region at 3200 and 3400 cm , due to ice-like and liquid-like water, respectively, in both cases. The relative intensity of the SFG signal due to liquid-like water increased when the PVA gel was pressed against the quartz surface. No such increase of the liquid-like water was observed when the PVA gel was contacted to the hydro-phobic OTS-modified quartz surface where friction was high. These results suggest the important role of water structure for low friction at the polymer gel/solid interfaces. 

Ye, S., Nihonyanagi, S. and Uosaki, K. (2001) Sum frequency generation (SFG) study of the pH-dependent water structure on a fused quartz surface modified by an octadecyltrichlorosilane (OTS) monolayer. Phys. Chem. Chem. Phys., 3, 3463-3469. 

Works [40, 91] surveyed y versus temperature for deactivation of 02( Aj ) on quartz at 350- 900 K. The obtained temperature dependencies were in the Arrhenius form with the activation energy of 18.5kJ/mole. A conclusion was drawn up about the chemisorption mechanism of singlet oxygen deactivation on quartz surface. A similar inference was arrived at by the authors of work [92] relative to 02( A ) deactivation (on a surface of oxygen-annealed gold). 

Photogeneration of singlet oxygen takes place at illumination of an 02-surrounded quartz surface with molecule-dispersed vanadium pentox-ide applied to the surface [93, 94]. A 10 - 10 molecule/cm concentration of 02( A ) in the gaseous phase can be obtained above a quartz... 

Deactivation of Singlet Oxygen on a Glass or Quartz Surface... 

Ap ) on a quartz surface that contains adsorbed V2O5 complexes. 

Note that a similar situation arises in the study of heterogeneous deactivation of electron-excited molecules of N2. Thus, an opinion expressed by Clark et al. [152] states that the coefficients of heterogeneous deactivation of N2(A S, v = 0.1) for all surfaces are close to unity. On the other hand, Vidaud with his coworkers [59, 153] have obtained 3 10 2 and (1.8 + 1.2) 10 values for these coefficients shown by platinum and Pyrex, respectively. Tabachnik and Shub [154] investigated heterogeneous decay of NaC A SJJ ) molecules on a quartz surface by the method of bulk-luminescence spectroscopy. The authors carried out a series of experiments within a broad (about four orders of magnitude) range of active particle concentrations and arrived at a conclusion that at a concentration of N2( A 2 ) in excess of 10 mole/cm , the... 

Thereby, photogeneration of singlet oxygen molecules from the quartz surface containing molecular dispersed molecules of pentoxide... 

Example 1 Attachment of an enzyme to a quartz surface is usually effected via a spacer chain.1119]... 

Quartz surfaces 16-Carbon spacer chain, urease [119]... 

Harper, W.R. Adhesion and charging of quartz surfaces. Proc. Roy. Soc. 

The microarray consists of small DNA fragments, chemically synthesized at specific locations on a coated quartz surface. The number of locations on one array is in the range of millions. DNA is extracted and labeled from experimental samples, and then samples are hybridized on the array. Labels are monitored so that gene- and exon-level expression analysis, novel transcript discovery, genotyping, and resequencing can be carried out. 

The first application of the quartz crystal microbalance in electrochemistry came with the work of Bruckenstein and Shay (1985) who proved that the Sauerbrey equation could still be applied to a quartz wafer one side of which was covered with electrolyte. Although they were able to establish that an electrolyte layer several hundred angstroms thick moved essentially with the quartz surface, they also showed that the thickness of this layer remained constant with potential so any change in frequency could be attributed to surface film formation. The authors showed that it was possible to take simultaneous measurements of the in situ frequency change accompanying electrolysis at a working electrode (comprising one of the electrical contacts to the crystal) as a function of the applied potential or current. They coined the acronym EQCM (electrochemical quartz crystal microbalance) for the technique. 

Tolstoi, V. P. Molotkina, E. V. 1994. The synthesis of copper-peroxide nanolayers on silicon and fused-quartz surfaces by the ionic deposition technique.. Russ J. Inorg Chem. 39 372-374. 

Groendes and Mesler (1982) studied the saturated film boiling impacts of a 4.7 mm water droplet on a quartz surface of 460 °C. The fluctuation of the surface temperature was detected using a fast-response thermometer. The maximal temperature drop of the solid surface during a droplet impact was reported to be about 20 °C. Considering the lower thermal diffusivity of quartz, this temperature drop implies a low heat-transfer rate on the surface. Biance et al. (2003) studied the steady-state evaporation of the water droplet on a superheated surface and found that for the nonwetting contact condition, the droplet size cannot exceed the capillary length. 

The detection limits of FPD can be improved by an approximate factor of 30 by using quartz surface-induced luminescence, at ca 390 nm, instead of the usual tin hydride... 

Here, i// is the surface roughness (surface area per unit area in cross section) of the fracture walls, p is fluid density in g cm-3, and the aperture 8 is taken in cm. For our purposes, it is sufficiently accurate to choose a value of 2 for 1// and set p to 1 g cm-3. In a fracture with an aperture of 10 cm, for example, each kg of water is exposed to 400 cm2 of quartz surface. 

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