Thick Sol-gel Films Research Articles

Bioactive glass–ceramic coatings prepared by pulsed laser deposition from RKKP targets (sol–gel vs melt-processing route)

The deposition of innovative glass–ceramic composition (i.e. RKKP) coatings by Pulsed Lased Deposition (PLD) technique is reported. RKKP was synthesised following two methodologies: melt-processing and sol–gel, the latter being particularly suitable to tailor the compositional range. The PLD advantage with respect to other deposition techniques is the congruent transfer of the target composition to the coating. The physico-chemical properties of films were investigated by Scanning Electron and Atomic Force Microscopies, Fourier Transform Infrared Spectroscopy, Angular and Energy Dispersive X-ray Diffraction, and Vickers microhardness. The deposition performed at 12J/cm2 and 500°C allows to prepare crystalline films with the composition that replicates rather well that of the initial targets. The 0.6μm thin melt-processing RKKP films, possessing the hardness of 25GPa, and the 4.3μm thick sol–gel films with the hardness of 17GPa were obtained.

One-step immobilization of tris(2,2′-bipyridyl)ruthenium(II) via vapor-surface sol–gel deposition towards solid-state electrochemiluminescence detection

A novel method for immobilization of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy) 3Cl 2) on electrode surfaces based on the vapor-surface sol–gel deposition strategy is first demonstrated in this paper. Ru(bpy) 3Cl 2 immobilized sol–gel (Ru(bpy) 3Cl 2/sol–gel) films were characterized by UV–vis spectroscopy and field-emitted scanning electron microscopy (FE-SEM). These results showed that Ru(bpy) 3Cl 2 was successfully incorporated into the silica sol–gel film. It was found that many irregular Ru(bpy) 3Cl 2/sol–gel clusters were formed on surfaces through one deposition and thick sol–gel films were observed after further deposition. Electrochemical properties and electrochemiluminescence (ECL) behaviors of Ru(bpy) 3Cl 2/sol–gel films could be easily adjusted by deposition numbers and time. At last, the Ru(bpy) 3Cl 2/sol–gel film modified electrode was used for solid-state ECL detection of tripropylamine. The linear range was from 5.8 × 10 −8 to 2.4 × 10 −4 M with the detection limit of 5 nM, which was three orders of magnitude lower than that from pure Nafion-modified electrodes. The ECL sensor also exhibited high stability, and still remained 92% response after being stored in air for 35 days. This method for immobilization of Ru(bpy) 3Cl 2 is simple, convenient and low-cost relative to others, so it shows promising applications in solid-state ECL detection.

Preparation and characterization of ultra-thin sol–gel films

The formation and characterization of nanometer thick sol–gel films are reported. The films were prepared by spin-coating of a diluted solution of a silane precursor on a number of different substrates. The effect of dilution, rotation speed and nature of substrate on the thickness and homogeneity of the films was examined. Characterization of the films was carried out by profilometry, reflectance spectroscopy, atomic force microscopy, adhesion test and electrochemistry. We find that the dilution factor has a pronounced effect on the film thickness. Moreover, the time of dilution, namely, whether dilution was carried out before or after a period of hydrolysis, has a noticeable effect on the thickness as well as on the permeability of embedded species.

Preparation of structured sol–gel films using tape casting method

A modification of the tape casting method optimized for preparing either uniform or linearly structured sol–gel films is presented. It is demonstrated that molecular level homogeneous high viscosity sol–gel precursors can be used instead of slurries to prepare surface coatings by the tape casting method. Such method is especially well suited for preparing thick sol–gel films from relatively high viscosity sol precursor materials. The feasibility of the method is demonstrated using linearly structured ATO precursor films.

Reflow and burial of channel waveguides formed in sol-gel glass on Si substrates

A reflow step and an improved burial procedure are demonstrated for channel waveguides formed in sol-gel glass on silicon substrates. Thick sol-gel films are deposited by repetitive spin coating and rapid thermal annealing, and etched to form ridge waveguides. Furnace heating is then used to melt both core and buffer layers simultaneously, providing a smooth surface for burial by further spin-coat deposition. Results are presented for typical core shapes, surface profiles after planarization, and optical insertion losses. >