Organically Modified Silicate Film Research Articles

Template-free sol–gel preparation of nanoporous ORMOSIL films with adjustable refractive index

A nanoporous organically modified silicate (ORMOSIL) film with adjustable refractive index from 1.21 to 1.10 was prepared at room temperature via a template-free sol–gel method, using tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) as co-precursors and hexamethylisilazane (HMDS) as surface modifier. Heating the ORMOSIL film, the refractive index of the ORMOSIL film can be further decreased to as low as 1.07. This adjustable refractive index thin film can find potential application in optical and microelectronic fields.

Template‐Free Sol‐Gel Preparation of Superhydrophobic ORMOSIL Films for Double‐Wavelength Broadband Antireflective Coatings

AbstractA double‐layer double‐wavelength antireflective (AR) coating with 100% transmittance at both 1064 nm and 532 nm, which is very important in high power laser systems, is designed using thin film design software (TFCalc). The refractive indices for the bottom and top layers of the designed AR coating are about 1.30 and 1.14. A simple, template‐free sol‐gel route is proposed to prepare the superhydrophobic ORMOSIL (organically modified silicate) thin film, which has an ultralow refractive index, by silica particle surface modification using hexamethylisilazane (HMDS); this treatment decreases the refractive index of the silica thin film from 1.23 to 1.13. The formation mechanism of the ultralow refractive index thin film is proposed. The particle surface modification with HMDS significantly improves the hydrophobicity of the coated film; the water contact angle of the film increases from 23.4° to 160°. The bottom layer, which has a refractive index of 1.30, is prepared from acid‐catalyzed and base‐catalyzed mixed silica sol. A double‐layer silica AR coating is obtained with transmittances of 99.6% and 99.8% at 532 nm and 1064 nm, respectively.

An integrated micro-volume fiber-optic sensor for oxygen determination in exhaled breath based on iridium(iii) complexes immobilized in fluorinated xerogels

A novel integrated fiber-optic sensor with micro detection volume is developed and evaluated for O(2) determination on a breath-by-breath basis in human health monitoring applications. The sensing element was fabricated by dip-coating an uncladded optical fiber with [Ir(piq)(2)(acac)]-doped hybrid fluorinated ORMOSIL (organically modified silicate) film, which was prepared from 3,3,3-trifluoropropyltrimethoxysilane (TFP-TriMOS) and n-propyltrimethoxysilane (n-propyl-TriMOS). The sensor was then constructed by inserting the prepared optical fiber into a transparent capillary. A microchannel formed between the optical fiber and the capillary inner wall acted as a flow cell for the sample flowing through. The evanescent wave (EW) field produced on the fiber core surface can excite the O(2)-sensitive fluorophores of [Ir(piq)(2)(acac)] to produce emission fluorescence. O(2) can be sensed by its quenching effect on the emission fluorescence intensity. Spectroscopic properties have been characterized by FTIR and fluorescence measurements. Stern-Volmer and Demas models were both employed to analyse the sensor sensitivity, which is 13.0 with the LOD = 0.009% (3σ) and the response time is about 1 s. By integrating the sensing and detection elements on the optical fiber, the novel configuration showed advantages of easy fabrication and low cost. Parameters of sensitivity, response time, repeatability, humidity effect and temperature effect were discussed in detail. The proposed sensor showed potential for practical in-breath O(2) analysis application due to its advantages of easy fabrication, low cost, fast response, excellent hydrophobicity, negligible temperature interference and suitable sensitivity.

Tris(2,2′-bipyridyl)ruthenium(II) electrochemiluminescence sensor based on carbon nanotube/organically modified silicate films

In this paper, a novel electrochemiluminescence (ECL) sensor was constructed to determine herring sperm (HS) double-stranded (ds) DNA. Tetramethoxysilane and dimethyldimethoxysilane were selected as co-precursors to form an organically modified silicate (ORMOSIL) film for the immobilization of multiwall carbon nanotubes (MWNTs) wrapped by poly( p-styrenesulfonate) (PSS), and then Tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy) 3 2+) was successfully immobilized on a glassy carbon electrode via ion-association. PSS was employed to increase the conductivity of the ORMOSIL film and disperse the cut MWNTs, which were cut and shortened in a mixture of concentrated sulfuric and nitric acids, in the film. It was found that MWNTs could adsorb Ru(bpy) 3 2+ and acted as conducting pathways to connect Ru(bpy) 3 2+ sites to the electrode. MWNTs also played a key role as materials for the mechanical and thermal properties. The ECL performance of this modified electrode was evaluated in a flow injection analysis (FIA) system, and the detection limit ( S/ N = 3) for HS ds-DNA was 2.0 × 10 −7 g mL −1 with a linear range from 1.34 × 10 −6 to 6.67 × 10 −4 g mL −1 ( R 2 = 0.9876). In addition, the ECL sensor presented excellent characteristics in terms of stability, reproducibility and application life.

Luminescent properties of neodymium organic complexes and as-doped organically modified silicate films

Near-infrared (NIR) luminescent ternary and hydrated binary neodymium β-diketonates emitting at ca. 1330 nm are presented. The effects of ligand moieties on the photoluminescence properties of Nd 3+ ions are discussed. Moreover, the neodymium organic complex neodymium tris(2-theonyltrifluoroacetonate)bis(triphenylphosphine oxide), Nd(TTA) 3(TPPO) 2, which has the best photoluminescence properties among all investigated neodymium complexes, is incorporated into vinyltriethoxysilane-derived ORMOSIL (organically modified silicate) film by a multistep sol–gel process. The Nd doping concentration was up to 5 mol% related to Si. The spectroscopic results about as-doped ORMOSIL films indicate that the ligands around Nd 3+ ions indeed shield effectively Nd 3+ ions from luminescence-quenching impurities in the host matrix, such as OH groups.

Single-Molecule Studies of Diffusion by Oligomer-Bound Dyes in Organically Modified Sol−Gel-Derived Silicate Films

Single-molecule fluorescence spectroscopy is used to study dye diffusion within organically modified silicate (ORMOSIL) films. ORMOSIL films are prepared from sols containing tetraethoxysilane and isobutyltrimethoxysilane in 2:1 and 1:9 molar ratios. Nile red and a new silanized form of nile red that can be covalently attached to the silicate matrix are used as fluorescent probe molecules. The number and rate of single molecules diffusing through these films increases dramatically with increasing film organic content. Autocorrelation of the fluorescence images yields a quantitative measure of the relative populations of fixed and diffusing species. Surprisingly, both "free" and silicate-bound nile red exhibit relatively facile translational motions. Single-molecule/single-point fluorescence correlation spectroscopy (FCS) is used to measure the dye diffusion coefficients in submicrometer-scale film regions. The most common diffusion coefficients for "free" and silicate-bound nile red molecules in the 1:9 films are 3.9 x 10(-10) and 1.6 x 10(-10) cm(2)/s, respectively. The unexpectedly rapid diffusion of silicate-bound nile red is attributed to the presence of liquidlike silicate oligomers in the films. A lower bound for the molecular weight of the oligomers is estimated at 2900. Bulk solution-phase FCS experiments performed on "free" and silicate-bound nile red species extracted into chloroform solutions provide valuable support for these conclusions. Comparison of the results derived from experimental and simulated time transients indicates film heterogeneity occurs on sub-100-nm-length scales and likely results from the presence of inorganic- and organic-rich domains.

Electrochemiluminescent determination of methamphetamine based on tris(2,2′-bipyridine)ruthenium(II) ion-association in organically modified silicate films

Tetramethoxysilane (TMOS) and dimethyldimethoxysilane (DiMe–DiMOS) were used as co-precursor to immobilize poly( p-styrenesulfonate) (PSS), then tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy) 3 2+) was successfully immobilized on a glass carbon electrode via ion-association. The immobilized Ru(bpy) 3 2+ shows good electrochemical and photochemical activities. Electrochemical and electrochemiluminescence (ECL) characterizations of the organically modified silicates (ORMOSILs) modified film electrodes were made by means of cyclic voltammetry and chronocoulometry. The ORMOSIL films were investigated by atomic force microscopy, scanning electrochemical microscope, tunnelling electrochemical microscope, X-ray photoelectron spectroscopy (XPS), UV–vis spectroscopy and fluorescence spectroscopy. XPS in-depth profiles revealed a homogeneous distribution of Ru(bpy) 3 2+ inside the silica thin layers. The modified electrode was used for the ECL determination of methamphetamine (METH) and showed high sensitivity. Detection limit was 2.0 × 10 −7 mol l −1 for METH (S/N = 3) with a linear range from 5.0 × 10 −7 to 1.0 × 10 −3 mol l −1 ( R = 0.986). The relative standard deviation ( n = 6) was 1.1% for the determination of 1.0 × 10 −5 mol l −1 METH. Furthermore, the Ru(bpy) 3 2+ immobilized modified electrode was applied in the ECL determination of methamphetamine (METH) in scout cases.

Preparation and spectral properties of ORMOSIL films doped with neodymium organic complex

Vinyltriethoxysilane-derived organically modified silicate (ORMOSIL) films doped with the organic complex neodymium tris(2-theonyltrifluoroacetonate)bis(triphenylphosphine oxide) by a multistep sol–gel process exhibit near-infrared luminescence at ca. 1330 nm ( 4F 3/2→ 4I 13/2). Spectral properties of as-doped films with a series of doping concentration from 1 to 10 mol.% (Nd related to Si) are investigated for the optimum doping concentration. The vinyltriethoxysilane-derived ORMOSIL host matrix is considered to have little effect on spectral properties of Nd 3+ ions due to the ligands' protection. The effect of heat-treatment on photoluminescence properties is also revealed.

Synchrotron infrared microspectroscopy reveals localized heterogeneities in an organically modified silicate film

High spatial resolution, 7 μm×7 μm confocal image plane masking, and 1 μm step size mapping were used to image small areas of an organically modified silicate (ORMOSIL) film. The film was prepared by the sol–gel process from separately hydrolyzed isobutyltrimethoxysilane and tetraethoxysilane sols that were mixed just prior to being spin cast onto a polished silicon substrate. Detailed mapping was performed in a reflection absorption mode with an infrared microspectrometer at beamline U10B of the National Synchrotron Light Source of Brookhaven National Laboratory. The main objective of this study was to characterize the spatial distribution of organic (i.e. butyl) components within the film. Functional group maps of each film region were produced from the peak areas of the CH, OH, and SiO stretching bands. The organic content (relative to total silicate) was obtained by ratioing the peak areas of the CH and SiO absorption bands. Functional group maps of a relatively large region ( 230 μm×230 μm) with a 10 μm×10 μm mask size and a 10 μm step size reveal heterogeneity on a larger scale. These data demonstrate the utility of IR imaging in the study of ORMOSIL film chemical heterogeneity.

Fabrication of photo-patternable inorganic–organic hybrid film by spin-coating

Organically modified silicate (ORMOSIL) was synthesized by the sol–gel process. The control of the refractive index was achieved by varying the content of phenyltrimethoxysilane as a refractive index modifier. The refractive index variations as a function of UV illumination and baking conditions were analyzed using Fourier transform infrared spectrometer. Incorporation of 3-(trimethoxysilyl)propylmethacrylate as a UV-sensitive functional group allowed to obtain high-resolution patterned films with 7 μm linewidth using a conventional photo-lithography. Relatively thick layers of ORMOSIL film with 11 μm thickness were obtained by a single spin-coating without producing any crack. Heat-treatment at temperatures lower than 150 °C resulted in inorganic–organic hybrid films that exhibited dense microstructure.

ORMOSIL films: Properties and microelectronic applications

The properties, as well as some issues of microelectronic applications of organically modified silicate (ORMOSIL) films, prepared by cohydrolysis in various proportions of tetraethoxysilane (TEOS) and phenyltriethoxysilane (PTEOS), or diphenyldiethylhexyloxydiethoxydisiloxane (DPS)1, are discussed.