Gel Thin Films Research Articles

Modification of gold electrode with a monolayer of self-assembled microgels

A new method of modification of the gold-electrode surface with a microgel monolayer was developed. Microgel particles contained –S-S– groups to enable modification of the gold surface by self-assembly via the chemisorption process. The particles were obtained by precipitation polymerization of N-isopropylacrylamide with N,N′-bis(acryloyl)cystine cross-linker. Their spherical shape and highly uniform dispersion were confirmed by electron microscopies (SEM and TEM). Thermosensitivity of the microgel was investigated with dynamic light scattering (DLS). The formation of monolayers was monitored with a quartz-crystal microbalance. The morphology of the modified surface in its dry state and in aqueous environment was investigated with atomic force microscopy (AFM). At temperatures below the volume-phase-transition temperature the microgels formed a densely packed structure that well covered the entire surface. A significant change in morphology was observed after raising temperature above the volume-phase-transition temperature. The observed increase in roughness of the modified surface suggested that the surface of electrode could be locally, between the microgel particles, uncovered. The electrochemical properties of the modified electrode were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). A strong influence of the volume phase transition in the microgels attached to the Au surface on CV and EIS responses of the modified electrode was found. The observed behavior was reversed to that of the electrodes modified with a thin thermosensitive gel film based on N-isopropylacrylamide, i.e. the volume phase transition led to a significant increase in the voltammetric current and to a drop in electron transfer resistance. That was related to partial uncovering of the electrode surface after the shrinking process in the microgels.

Nanostructured Titania Templated by Natural Cellulose Substance: Effect of Vanadium-Doping on the Anatase-to-Rutile Phase Transformation.

Vanadium-doped rutile titania nanomaterial was synthesized by calcination of titania/vanadia composite thin gel films pre-coated natural cellulose substance (e.g., ordinary filter paper) at a relatively low temperature (600 °C). A better mixture of titanium and vanadium species is achieved during the layer-by-layer (LbL) deposition process with cellulose nanofiber as a template, leading to more vanadium dopants incorporated in the titania crystal lattices. By sufficient vanadium-doping, the phase transformation temperature from anatase to rutile phase of titania is decreased effectively. The doping mode and existing state of vanadium in the titania nanomaterials and the effect on the anatase-to-rutile phase transformation have been studied. This strategy provides a facile and effective route to facilitate the phase transformation of various nanostructured metal oxides templated by natural cellulose substance through doping appropriate functional metal ions in the LbL deposition process.

Sol–Gel Synthesis of Nickel-Doped Cr2O3 Thin Films

This work presents an experimental study dedicated to the synthesis and characterization of pure and Ni-doped chromium (III) oxide thin films. Sol–gel thin films with doping rates of 3%, 6%, 9%, and 12% were deposited onto glass substrates by the dip-coating method at room temperature using Cr(NO3)3: 9H2O as precursor. Using X-ray diffraction (XRD), infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–Vis), and impedance spectroscopy on solids, we noted that the films are polycrystalline with a grain size ranging from 11.2[Formula: see text]nm to 24.4[Formula: see text]nm, the synthesized materials are highly transparent in the visible light with more than 90% of transmittance and have an optical bandgap less than 3.0[Formula: see text]eV overall, and the equivalent circuit of the deposited films is a resistors and capacitors (RC) parallel circuit.

Characterization of sol–gel thin films by ellipsometric porosimetry

As an extension of spectral ellipsometry, ellipsometric porosimetry has gained considerable importance for the characterization of porous thin films. The in-situ measurement of sorption facilitates the evaluation of open porosity, pore radius distribution, film backbone refractive index and even elastic properties. Multilayer assemblies and gradients within films can be characterized. These features are especially interesting for sol–gel derived thin films that are commonly composed of aggregated nanoparticles and thus may retain significant porosity after thermal treatment. In this paper the general features of Ellipsometric Porosimetry are highlighted and related to the characterization of selected sol–gel films. The examples range from simple assessments of porosity and pore radius distribution, film backbone analysis to the characterization of multilayer assemblies and systematic changes induced by thermal treatment or leaching phenomena. Besides optical properties Ellipsometric Porosimetry can reveal structural features such as open porosity and pore radius distribution of sol-gel derived thin films.

Multi-wavelength spectrophotometric determination of pH using phenol red–doped sol–gel film sensors

ABSTRACTDye leakage and the nonlinear relationship between absorbance and pH affect the pH measurement precision of absorption-based optic sensors and limit their application. Based on the preparation of a transparent sol–gel thin film with a phenol red indicator, this work assumed that the absorbancies had an exponential relationship to the concentrations of the indicator, and the multi-wavelength equation for the pH was derived as follows:where n is the exponential coefficient, e1, e2, and e3 are the extinction coefficient ratios, and R is the ratio of the absorbancies. The calculation parameters for an immobilized phenol red film were pKa = 8.577, e1 = 0.0191, e2 = 1.530, e3 = 0.2992, and n = 0.6322, while those for an immobilized phenol red/Triton X-100 film were pKa = 8.612, e1 = 0.0507, e2 = 1.501, e3 = 0.3687, and n = 0.3931. The correspondence between the calculated pKa and the pKa from the calibration curve verifies the equation. The calculation parameters remain stable as the indicator content is increased, but change with an increase in the Triton X-100 content. Using the equation, the calculated pH shows stable behavior over a long duration regardless of dye leakage, and the calculated precision is 0.0053. The method provides drift-free and precise water pH measurements for R that is not dependent on the total concentration of the indicator, and can be applied to online monitoring.

Opening Opportunities for High-Resolution Isotope Analysis - Quantification of δ15NNO3 and δ18ONO3 in Diffusive Equilibrium in Thin-Film Passive Samplers.

The fate of nitrate transported across groundwater-surface water interfaces has been intensively studied in recent decades. The interfaces between aquifers and rivers or lakes have been identified as biogeochemical hotspots with steep redox gradients. However, a detailed understanding of the spatial heterogeneity and potential temporal variability of these hotspots, and the consequences for nitrogen processing, is still hindered by a paucity of adequate measurement techniques. A novel methodology is presented here, using Diffusive Equilibrium in Thin-film (DET) gels as high-spatial-resolution passive-samplers of δ15NNO3 and δ18ONO3 to investigate nitrogen cycling. Fractionation of δ15NNO3 and δ18ONO3 during diffusion of nitrate through the DET gel was determined using varying equilibrium times and nitrate concentrations. This demonstrated that nitrate isotopes of δ15NNO3 and δ18ONO3 do not fractionate when sampled with a DET gel. δ15NNO3 values from the DET gels ranged between 2.3 ± 0.2 and 2.7 ± 0.3‰ for a NO3- stock solution value of 2.7 ± 0.4‰, and δ18ONO3 values ranged between 18.3 ± 1.0 and 21.5 ± 0.8‰ for a NO3- stock solution of 19.7 ± 0.9‰. Nitrate recovery and isotope values were independent of equilibrium time and nitrate concentration. Additionally, an in situ study showed that nitrate concentration and isotopes provide unique, high-resolution data that enable improved understanding of nitrogen cycling in freshwater sediments.

Ilmenite type nano-crystalline Co–Ti–O ternary oxides: sol–gel thin film on borosilicate glass, characterization and photocatalytic activity in mineralization of reactive red 198

The sol–gel preparation of cobalt titanium oxide nano-crystals using the reaction between cobalt chloride (CoCl2·6H2O) and tetraisopropyl orthotitanate (Ti[OCH(CH3)2]4) with 1:1 molar ratio was studied. The nano-crystals were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDAX), fourier transform infrared spectroscopy (FTIR), thermogravimetric (TG-DTG) analysis and UV–Vis diffuse reflectance spectra (UV–Vis DRS) spectroscopy. TG-DTG results revealed that the weight loss with peak temperatures of 189, 267 and 692 °C. The XRD results showed that the sample calcinated at 550 and 750 °C were mixtures of CoTiO3, Co3O4, and TiO2 phases while at 650 °C a single crystalline phase of CoTiO3 was formed. FESEM results of the cobalt titanium oxide nanocrystalles demonstrate that CoTiO3 is nano-particles with an average size of 70 nm. FTIR results showed the formation of cobalt–oxygen, titanium–oxygen, and titanium–oxygen–cobalt bonds. DRS spectroscopy results of the sample calcinated at 650 °C showed band gap of 1.734 eV (715 nm) and 2.389 eV (519 nm) well in the visible portion of sun light. The cobalt titanium oxide nano crystales thin films on borosilicate glass showed an excellent photocatalytic activity on mineralization of Reactive Red 198 textille dye as environmental pollutant of industrial wastewater. An excellent photocatalytic activity in mineralization of Reactive Red 198 is related to the efficient separation of cobalt titanium oxide nano-crystals and visible-light absorption.

A soluble conjugated porous organic polymer: efficient white light emission in solution, nanoparticles, gel and transparent thin film.

A tetraphenylcyclopentadiene based multifunctional, solution processable, fluorescent, ultramicroporous polymer exhibiting high hydrogen uptake was employed for encapsulation of dyes to obtain enhanced white light emission in solution, nanoparticles, gel and transparent thin film. Hybrid nanoparticles showed a quantum yield of 35% with a high color rendering index.

Electromagnetic-triboeletric hybridized generator based on magnetic levitation for scavenging biomechanical energy

The popularity of various portable electronics and biological health monitoring devices, such as pedometers, pulse oximeters, mobile telephones, wearable watches, has greatly changed our lifestyles and brought significant convenience to us. Energy harvesting has been a key technology for the self-powered mobile terminals, because there are many defects such as limited lifetime, large size, low energy density and environmentally unfriendly feature for the traditional chemical batteries. Lots of devices used for the energy harvesting of the human movement have been reported. However, some problems such as poor efficiency, low output power and low sensitivity need further studying. In this work, we demonstrate a novel magnetically levitated electromagnetic-triboelectric generator. The device size is φ4.8 cm×2.4 cm, and its weight is 80 g. The device uses the magnetically levitation structure as the core components, and the structure contains four magnets to form a magnetic array, in which three cylindrical magnets are placed around a bigger magnet. And two coils with polyvinyl-acetal enameled copper wires of 70 μm areplaced at the top and bottom of the device, respectively. Then two silica gel thin films with inverted tetrahedron patterned on the surface are integrated inside the structure. Then, we analyze the motion feature with the Maxwell simulation software, and discuss output characteristics of the two energy harvest units theoretically. The device possesses a high sensitivity, wide frequency response and high output performance. The dynamic response characteristics are analyzed in this paper.The frequency response range of the device is from 2 Hz to 20 Hz. The wider frequency response means that it can harvest more energy from complicated external environment. Furthermore, we analyze the output signal at low frequency, which has more than one wave crest after an environment perturbation. The triboelectric units can deliver peak output voltages of 70 V and 71 V, respectively, and the electromagnetic units each can deliver a peak output voltage of 10 V. In addition, the triboelectric units can produce peak output powers of 0.12 mW and 0.13 mW, respectively, under a loading resistance of 10 MΩ, while the electromagnetic units produce peak output powers of 36 mW and 38 mW, respectively, under a loading resistance of 1 kΩ. We discuss the energy output and energy conversion efficiency of the device, which are 750.89 μJ and 18%, respectively. Then we use the hybridized generator to charge a capacitor of 33 μF, the output voltage of which can reach 8 V in 2 seconds. Furthermore, the hybridized generator can power a pedometer continuously, which can work steadily and display movement data. This work has a significant step toward human mechanical energy harvesting and potential application in self-powered wearable devices.

Synthesis, characterization and theoretical studies on novel organic–inorganic hybrid ion–gel polymer thin films from a γ-Fe2O3 doped polyvinylpyrrolidone–N-butylpyridinium tetrafluoroborate composite via intramolecular thermal polymerization

Facile one-step synthesis and material study of novel PVP-ion gel thin film and improvement of ionic conductivity, specific conductance and charge density of it by doping high-dielectric γ-Fe2O3 magnetic nanoparticles is presented here.

On the mechanical and electrical properties of self-assembly-based organosilicate porous films

The effect of the replacement of Si–O–Si by Si–CH2–Si groups on the mechanical and electrical properties of silica-based hybrid sol–gel thin films is reported.

Effect of Pt Concentration on the Grain Growth of TiO2sol-gel Films

Pt metallic has been supported on TiO2 surface using different methods, Here, Pt doped TiO2 (Pt-TiO2) sol gel thin film were successfully produced by reducing chloroplatinc acid (H2PtCl6). The structures of prepared composites were investigated using X-ray diffraction (XRD). The physical morphologies of the composites were examined using transmission electron microscope (TEM). The grain size of Pt-TiO2 thin film after annealing was also measured by atomic force microscope (AFM) images.

可塑化PVCゲルアクチュエータ製造のための印刷技術を適用したゲル薄膜形成自動化技術の開発

Plasticized poly vinyl chloride (PVC) gel which has a large deformation by applying a voltage and high driving stability in the atmosphere is considered as a promising material for a soft actuator. To fabricate a more flexible and high performance multilayered PVC gel actuator, in this study, we attempt to develop automation technology for fabricating thin film PVC gel used in multilayered PVC gel actuator based on digital 3D printing technology. We proposed automation system and examined to adjust amount of coating by control the condition of coating. Under the condition of 0.06 mg/shot of the amount of coated gel per shot, the average dot diameter of the point coated gel was about 0. 86 mm and the height was about 8 μm. It was expected that a gel thin film of about several μm can be automatically produced in an arbitrary shape by using the proposed system.

ChemInform Abstract: Photochemical Radical Thiol—Ene Click‐Based Methodologies for Silica and Transition Metal Oxides Materials Chemical Modification: A Mini‐Review

AbstractReview: 137 refs.

Quartz Crystal Microbalance Electrode Modified with Thermoresponsive Crosslinked and Non-Crosslinked N- Isopropylacrylamide Polymers. Response to Changes in Temperature

Electrochemical quartz crystal microbalance (EQCM) electrode was modified with environmentally sensitive polymers. The polymer layers on the electrode were composed of either crosslinked or non-crosslinked thermoresponsive poly(N-isopropylacrylamide). For anchoring thin gel films on the electrode surface the electrochemically induced free-radical polymerization (EIFRP) was employed. The electroreduction of the peroxydisulfate anion led to generation of free radical. This radical initiated the free radical polymerization process that led to the formation of a thin gel layer attached to the electrode surface. To monitor in situ the growth of the polymer film the changes in resonant frequency of the quartz-crystal were recorded. A significant decrease in the frequency (growth of the layer) was seen in the potential range where the reduction of peroxydisulfate anion took place. The morphology of the layers was examined with a scanning electron microscopy (SEM). The phenomenon of volume phase transition (shrinking/swelling process) in the gel layers initiated by a change in temperature was investigated. Unexpected big, sharp and of negative sign minima appeared at the change-in-frequency vs. temperature plots. These minima were not seen in the plots obtained for the polymers without linker. That situation should be useful in the investigation of chemical interactions proceeding under the conditions of volume phase transition. The influence of volume phase transition on the transport of a member of a model red-ox system, ferro- and ferricyanide couple, and therefore on height of its voltammetric response was examined. The changes in electrochemical properties of the layers induced by volume phase transition were monitored with electrochemical impedance spectroscopy.

A method to assess the location and positional stability of supra-choroidal retinal neuroprostheses.

Electrical stimulation of the retina is now firmly established as a means of restoration of rudimentary vision for blindness particularly that caused by retinitis pigmentosa. Of the various approaches, the novel positioning of an ultra-thin stimulating electrode array (SEA) posterior to the choroid has shown promising results. Following their implantation, reliable imaging methods are essential to establish the SEA's location relative to the optic disk and retinal vasculature. Because the opacity of the choroid precludes the use of conventional light-based fundus imaging, we developed an instrument (Wangiscope) that relies on infra-red illumination from LEDs. This instrument generates video from an inexpensive web camera whose optics have been enhanced for wide-angled retinal imaging by adding two plano-concave lenses to the existing lens system. When imaging, the instrument's outer lens, protected by a thin plastic film and methylcellulose gel, contacts the cornea while a probe comprising two 940 nm wavelength LEDS is held against the sclera. This instrument has provided useful retinal images in acute experiments using the Felus catus and also proof of the positional stability over 3 months of SEAs in the Ovis aries.

Amplified spontaneous emission in distributed feedback active microcavities fabricated by the sol–gel dip-coating method

Amplified spontaneous emission (ASE) is demonstrated in a distributed feedback (DFB) active microcavity, formed by rhodamine B molecules in a Bragg grating (BG). The BG was fabricated by alternately depositing titanium dioxide and silicon dioxide sol–gel thin films. The reflectance spectrum of BG simulated by the transfer matrix method was consistent with experimental results, demonstrating that the BG had good periodic structures. With rhodamine B molecules embedded, the ASE was observed from the DFB active microcavity in optical pumped conditions. The full-width-half-maximum and threshold of ASE were 7.5 nm and 0.2 mJ/pulse. The slope efficiency of 3% was measured. The DFB active microcavity is promising for low-cost ASE.

Quartz crystal microbalance electrode modified with thermoresponsive crosslinked and non-crosslinked N-isopropylacrylamide polymers. Response to changes in temperature

Electrochemical quartz crystal microbalance (EQCM) electrode was modified with environmentally sensitive polymers. The polymer layers on the electrode were composed of either crosslinked or non-crosslinked thermoresponsive poly(N-isopropylacrylamide). For anchoring thin gel films on the electrode surface, the electrochemically induced free radical polymerization (EIFRP) was employed. The electroreduction of the peroxydisulfate anion led to generation of free radical. This radical initiated the free radical polymerization process that led to the formation of a thin gel layer attached to the electrode surface. To monitor in situ the growth of the polymer film the changes in resonant frequency of the quartz crystal were recorded. A significant decrease in the frequency (growth of the layer) was seen in the potential range where the reduction of peroxydisulfate anion took place. The morphology of the layers was examined with a scanning electron microscopy (SEM). The phenomenon of volume phase transition (shrinking/swelling process) in the gel layers initiated by a change in temperature was investigated. Unexpected big, sharp, and of negative sign minima appeared at the change-in-frequency vs. temperature plots. These minima were not seen in the plots obtained for the polymers without linker. That situation should be useful in the investigation of chemical interactions proceeding under the conditions of volume phase transition. The influence of volume phase transition on the transport of a member of a model red-ox system, ferro- and ferricyanide couple, and therefore on height of its voltammetric response was examined. The changes in electrochemical properties of the layers induced by volume phase transition were monitored with electrochemical impedance spectroscopy.

Temperature stable Au nanoparticles embedded in Er3 + doped ZrO2 sol–gel thin films prepared by spin coating

Gold nanoparticles (NP) were successfully embedded as single and triple stacks into Er3+ doped spin-coated sol–gel ZrO2 thin films. The effect of different initial Au NP solution concentrations and annealing temperatures on the stack structure has been investigated. The NP coverage was varied by the concentration of the applied NP solution from sub-monolayers to structured networks. Furthermore, the coverage depends on the surface quality, as confirmed by atomic force microscopy (AFM). The existence and characteristics of the embedded Au NPs after annealing up to 1000°C were investigated by UV–Vis spectroscopy and transmission electron microscopy (TEM). Finally, X-ray diffraction (XRD) measurements were used to correlate the annealing temperature with the resulting crystal structure of the ZrO2:Er3+ films.

One-step sol–gel imprint lithography for guided-mode resonance structures

Guided-mode resonance (GMR) structures consisting of sub-wavelength periodic gratings are capable of producing narrow-linewidth optical resonances. This paper describes a sol–gel-based imprint lithography method for the fabrication of submicron 1D and 2D GMR structures. This method utilizes a patterned polydimethylsiloxane (PDMS) mold to fabricate the grating coupler and waveguide for a GMR device using a sol–gel thin film in a single step. An organic–inorganic hybrid sol–gel film was selected as the imprint material because of its relatively high refractive index. The optical responses of several sol–gel GMR devices were characterized, and the experimental results were in good agreement with the results of electromagnetic simulations. The influence of processing parameters was investigated in order to determine how finely the spectral response and resonant wavelength of the GMR devices could be tuned. As an example potential application, refractometric sensing experiments were performed using a 1D sol–gel device. The results demonstrated a refractive index sensitivity of 50 nm/refractive index unit. This one-step fabrication process offers a simple, rapid, and low-cost means of fabricating GMR structures. We anticipate that this method can be valuable in the development of various GMR-based devices as it can readily enable the fabrication of complex shapes and allow the doping of optically active materials into sol–gel thin film.