Doped particle size

Figure 16.11 Titania (TiO c)-suppoited (a) and niobium-doped titania (Nbo.o8Tio.920j /Au)-suppoited (b) Au particle-size-dependent specific activities for—CO oxidation at a potential step of 0.5 V vs. RHE. The current densities have been corrected for the TEM-deteimined...

Figure 4. Particle size distributions for the original and ground B-doped carbon from WUT.

In a study that addressed the effect of doping on quantum dots, the donor and acceptor levels were found to be practically independent of particle size [De3]. In other words, shallow impurities become deep ones if the dot size is reduced. Experimental observations show that the luminescence is not affected by doping if a thermal diffusion process, for example using a POCl3 source, is used [Ell]. Implantation, in contrast, is observed to effectively quench the PL [Tal4]. If the pores are filled with a medium of a large low-frequency dielectric constant, such as water or any other polar solvent, it is found that deep impurity states still exist,... 

A variant of CD has been described where ZnS was precipitated as a gel by adding concentrated S to a concentrated solution of a Cd salt. The pH was then reduced by HNO3 to a value between 5 and 7, when a semitransparent sol formed. Heating this sol between 100 and 200°C (in an autoclave) resulted in the formation of zincblende ZnS films [134]. If the S was not in excess (twice the Cd concentration), some ZnO, together with some wurtzite ZnS, also formed. Addition of a CuCli solution to the pH-adjusted sol and heating at 140°C resulted in Cu-doped ZnS (particle size 60 X 10 nm) that showed several photoluminescence bands [135]. 

Since the 1960 s, stamp paper has been treated with fluorescent or phosphorescent phosphors. Since the stamp is stuck to the top right-hand corner of the letter, its recognition by the machine serves to establish the position of the letter and enables machine control of the correct positioning for postmarking and reading. Doped zinc sulfides with average particle sizes of 5-6 pm are used as afterglow phosphors. 

For pure Ti02> the q.y. is higher, for the more concentrated suspension ho wever for the case of both iron-doped TiC>2, the higher q.y. is obtained for the lower concentration of catalyst. The differences can be explained in terms of differences in particle size of the catalysts. Recent results by Navio et al. 

A parameter that determines the performances, as outlined also in patents, is the mean diameter of Pd or doped-Pd particles. This is also one of the claims in Headwaters Nanokinetix Inc. patents. It seems that a maximum in the activity/ selectivity as a function of the particle size is present. Figure 8.11 reports the effect of the Pd-particle size (Pd supported on alumina, prepared by deposition-precipitation method) in the direct synthesis of H202 in water at atmospheric pressure [77]. Low... 

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