Xerogels fabrication

ELECTROLUMINESCENT XEROGELS FABRICATED IN POROUS ANODIC ALUMINA... 

Figures. PL intensity of Do-> F2 spectral band (612 ntn) from EU2O3 in In203 xerogel fabricated on mono-Si ( ), Sn02 on mono-Si ( ), In203 on PAA of 5 pm thick ( ), and SnO on PAA (A).

Figure 3. Room temperature PL of (a) - Tb, (b) - Er, and (c) - Eu doped titania xerogels fabricated on silicon and porous anodic alumina. PL spectra of Fig. 3(b) correspond to one (upper curve), five ( medium curve) and ten (lower curve) deposition of erbium-doped xerogel layer.

Tb-implanted thermally grown silicon dioxide film, and (iii) Tb-doped alumina xerogels fabricated onto monocrystalline silicon. Thus, the terbium-doped alumina xerogel/PAA structure was proposed as a basis for green room-temperature luminescent images [17]. 

Figure 5. PLE (a, c) and PL (b, d) spectra measured at 1.53 pm from erbium-doped TiO2/SiO2 xerogels fabricated in PAA (a, b) and from bulk xerogels (c, d) 30 wt. % TiO2/70 wt. % SiO2 (upper spectra), 50 wt. % TiO2/50 wt. % SiO2 (middle spectra), 70 wt. % TiO2/30 wt. % SiO2 (lower spectra).

Silica xerogel monoliths are the major class of sol-gel process materials and their fabrication procedures were described extensively in many reviews and papers [54-58]. The principal concepts of fabrication of silica xerogel monoliths have already been described in Section 10.2, and the effects of parameters such as metal alkoxide precursor types, type of catalyst used, H2O Si molar ratio R), steric effect of precursor ligand groups, and functionality of organically modified silanes have also been discussed. Important pioneering research on the influence of these parameters on xerogel fabrication was presented in Refs [9,59-63]. 

Brinkley et al. demonstrated89 a simple to use, easy to interpret, low cost, and environmentally friendly colorimetric detector of the chemical warfare agent - mustard gas (HD, l,l-thiobis(2-chloroethane)). An optically transparent xerogel encapsulating Cu(II) acetate was fabricated to detect HD analogues and can serve as the optical sensor based on metal-ligand charge-transfer mechanism. 

An array of 10- i,m microlenses was fabricated from the adhesion of an aminated silicasol on a poly[methyl(phenyl)silane-co-methyl(3,3,3-tri-fluoropropyl)silane] (CF3PMPS) film patterned by UV light irradiation.132 By soaking the UV-patterned polysilane film into the sol-gel solution, a convex xerogel layer adhered only to the UV-exposed poly silane, which was cured to form a glass that functioned as a condensing lens. 

A wide variety of approaches are currently being used in the fabrication and technology of columns for capillary electrochromatography (CEC). Continuous polymer bed, or monolithic columns (see Section 3.4), manufactured by in-situ polymerization within the columns, have been used in numerous application areas and have been shown to be highly efficient. In a second approach, a sol-gel process is employed to form a silica xerogel within the capillary, followed by bonding of the stationary-phase group alternatively, the separation medium itself may be polymerized in situ. 

The PL spectra of the fabricated xerogel film structures Tbo isYissAlsO are shown in Fig. 1. They revealed appearance of the bands within the range of... 

EDX-analyses reveal observation of stretched xerogel clusters which fill almost entirely the channels of the PAA after sequential spin-on deposition followed by heat treatment. Unlike to all our earlier works with titania or alumina xerogel, the proposed technology does not allow fabrication of YAG xerogel monolith, whereas only occasional clusters are observed inside the mesoscopic channels of PAA-Fig. 2. 

In this work we report on the method of fabrication the dichromatic luminescent images using intrinsic blue PL of PAA along with europium species deposited within the porous volume from a solution of an appropriate salt. The results are compared with generation of the structure xerogel/PAA. 

For the samples comprising of PAA coated with Eu-doped xerogel typical PL spectrum measured at the excitation wavelength of 368 nm is presented in Fig. 2. It reveals the presence of clearly pronounced PL band at 475 nm visible to the naked eye which corresponds to inherent blue photoluminescence of PAA. Well-resolved optical band at 613 nm corresponding to Do-> F2 electron transition of Eu ions in the fabricated structure is also observed from the spectrum but red emission can not be seen with the naked eye. 

The following results (Figs. 16-18) are for a series of hybrid class II xerogel formulations prepared from TEOS and l,4-bis(trimethoxysilylethyl)benzene (BTEB). Ten formulations were prepared by varying the molar ratio of the two silane precursors in 0.5% increments from 100.0 to 96.0% TEOS, with the final formulation being 95.0% TEOS. These formulations were fabricated manually using micropipettes and with the ALHS. Both sets of formulations were doped with an 02-responsive luminophore then spun cast and pin printed into quenchometric 02 responsive sensor thin films and arrays. 

Figure2. Voltage-current characteristics of EL structure fabricated on PAA of 15 urn thick xerogel Eu203-In203 (curve 1), Eu203-Sn02 (curve 2). Sample dimensions are 5><5 mm. ...

Fabrication of xerogels within the pore volumes after spin-on deposition of a sol followed by drying was confirmed by different experimental techniques. First, it was r evealed i n B SUIR (Belarus) b y S IMS-analyses o f 3 p m t hick P AA s pin-on... 

Figure 2. SEM (a,b) and TEM (c) micrographs of the structure xerogel/anodic alumina (a) - as anodized anodic alumina film of 5 pm thick fabricated on Si, (b) - after one spin-on deposition of Eu-doped titania xerogel (c) - ultramicrotomed sections of the terbium-doped alumina xerogel/PAA structure of 30 pm thick. Bottom of the pore was filled with terbium-doped alumina xerogel after five spin-on depositions.

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