Gel Thin Films Research Articles

Design and preparation of thin film gel polymer electrolyte for 3D Li-ion battery

Three-dimensional (3D) configuration of the battery provides a large active surface area of the electrodes to store and utilize more active material, enabling remarkable increase of capacity. Herein, we report on the development of a full 3D battery composed of Ni3Sn4 (Ni–Sn) alloy electrodeposited onto a nickel foam current collector to form a 3D anode, which was coated with a polymer electrolyte-separator film, and LiFePO4/CNT cathode filled into the voids of the resulting 3D structure. An ultrathin polymer coating on the 3D anode was obtained via layer-by-layer technique. The X-ray diffraction investigations confirmed stability of the structure of the anode prior and after the polymer coating, while top and cross-section SEM images proved the uniformity of both the deposited 3D anode and the polymer coating on its surface. It was shown that a thin homogeneous layer of polymer can be obtained on 3D structured anode. This film effectively performed as a gel-like electrolyte in a full 3D battery. Cyclic voltammetry and charge-discharge tests exhibited stable electrochemical response and cyclability of the 3D battery. The prepared full 3D battery successfully operated at 0.1C rate and retained 90% of its initial capacity over 100 galvanostatic charge-discharge cycles.

Stand-Alone Semi-Solid-State Electrochemical Systems Based on Bicontinuous Microemulsion Gel Films.

Bicontinuous microemulsion (BME)-based hydrogel films were integrated with screen-printed electrodes (SPEs) comprising working, counter, and reference electrodes to form stand-alone, semi-solid-state electrochemical systems that do not require an outer electrolyte solution. The gel network of the BME hydrogel only exists in the microaqueous phase and retains the structure of the entire BME gel. Following gelation, a microaqueous phase with sufficient ionic strength ensured effective ionic conductivity, even in thin gel films. This enabled the electrochemical reaction to proceed using a thin gel film as an electrolyte solution. However, an intact micro-oil phase with no gel network enabled efficient extraction from an external oil solution and exhibited rapid electrochemistry that was comparable to that of a BME solution. Cyclic voltammograms of lipophilic redox species in oil using the gel-integrated SPE system demonstrated successfully in the oil itself and in the air with dropped oil onto the system.

Debonding waves in gel thin films.

We develop a mathematical model for the sliding of a gel sheet adhered to a moving substrate. The sliding takes place by the motion of detached region between the gel sheet and the substrates, i.e. the propagation of a Schallamach wave. Efficient numerical methods are developed to solve the problem. Numerical examples illustrate that the model can describe the Schallamach wave and are consistent with the existing experiments qualitatively.

Surface and mechanical analysis of metallized poly(dimethylsiloxane) gel for varifocal micromirrors

Varifocal micromirrors are alternative and miniaturized mirror systems that are used for imaging procedures in biomedical diagnostics, mirror‐based tunable lenses, or the correction of spherical aberration. In this study, we demonstrate a new concept for focal length variation by electrostatic mirror deformation of a compact and integrated electroactive polymer actuator based on metallized poly(dimethylsiloxane) (PDMS) gel thin films. The varifocal micromirrors have a lateral size of 70 × 70 μm2 and are capable of deforming in either convex or concave direction, depending on a defined surface treatment by O2‐plasma or UV/ozone of the PDMS prior to metallization by physical vapor deposition (PVD). Surface and interface analysis by wetting experiments, sputter depth‐profiling X‐ray photoelectron spectroscopy (XPS) combined with scanning electron microscopy (SEM) on cross‐sections processed with focused ion beam (FIB) as well as polymer and metal surfaces are used to understand and to improve the metal film growth and quality with respect to high reflectivity and conductivity. In addition to the high quality of the metallic mirror layer, the mirror displacement is important and inevitably depends on the gel stiffness of the actuator. Therefore, we investigate the gel mechanics and the performance of the actuator with rheology, confocal microscopy, and image formation on the electrically deformed mirrors. Our concept of varifocal micromirrors offers a wide range of applications for tunable mirror‐based optics due to their simple and compact design.

Enhancing the Corrosion Protection of AA2024-T3 Alloy by Surface Treatments Based on Piperazine-Modified Hybrid Sol–Gel Films

The aim of this study was to develop new chrome-free surface pretreatments for AA2024-T3 aluminum alloy. These pretreatments were based on hybrid organic–inorganic sol–gel thin films prepared from mixtures of γ-methacryloxypropyltrimethoxysilane (MAPTMS) and tetramethylorthosilicate (TMOS). Different MAPTMS/TMOS molar ratios were used for optimizing the physical–chemical characteristics of the sol–gel films. The formulation of a set of these sols was modified by incorporating piperazine (1,4-diazacyclohexane) as a corrosion inhibitor. The resulting sol–gel films were characterized by using Fourier transform infrared spectroscopy (FTIR), liquid-state 29Si nuclear magnetic resonance spectroscopy (29Si-NMR) and viscosity measurements. The corrosion performance of the sol–gel films was analyzed by using electrochemical impedance spectroscopy (EIS) and local electrochemical impedance mapping (LEIM). The characterization techniques indicated that piperazine behaved as a catalyst for the condensation reaction during the formation of the MAPTMS/TMOS organopolysiloxane network and produces an increase of the crosslinking degree of the sol–gel films. EIS and LEIM results showed that piperazine is an effective corrosion inhibitor, which can be used to enhance the active corrosion protection performance of sol–gel films.

Measurement of Adsorption/Desorption Rate of Water Vapor to a Silica gel Thin Film Coated on a Surface of a Cross-fin Tube Heat Exchanger

Measurement of Adsorption/Desorption Rate of Water Vapor to a Silica gel Thin Film Coated on a Surface of a Cross-fin Tube Heat Exchanger

Controllable doping and passivation of ZnO thin films by surface chemistry modification to design low-cost and high-performance thin film transistors

Solution-processed metal oxide thin-film transistors have become more popular as they can be used to fabricate transparent and flexible electronics at low cost. However, additional and complex processes for trap-site passivation and doping hinder the potential of the low-cost solution process. This study introduces a surface passivation process involving treatment with 3-aminopropyltriethoxysilane (APTES) that can enhance the electrical properties of ZnO sol–gel thin films. Optical, chemical, and structural analyses of ZnO sol–gel thin films revealed that their trap sites were passivated successfully through APTES treatment under basic conditions. Taking advantage of this process, high-mobility and negligible-hysteresis ZnO thin-film transistors were successfully fabricated, showing an Ion/Ioff of 105, hysteresis as low as 1.13 V, and mobility of up to 0.117 cm2/Vs. Furthermore, a characteristic transition of ZnO sol–gel thin films from semiconductive to semimetallic was observed during investigations with various APTES concentrations.

Synthesis of N-CNT/TiO2 composites thin films: surface analysis and optoelectronic properties

In this study, we have investigated the surface analysis and optoelectronic properties on the synthesis of N-CNT/TiO2 composites thin films, using sol gel method for a dye synthetized solar cell (DSSC) which is found to be simple and economical route. The titanium dioxide based solar cells are an exciting photovoltaic candidate; they are promising for the realization of large area devices. That can be synthetized by room temperature solution processing, with high photoactive performance. In the present work, we stated comparable efficiencies by directing our investigation on obtaining Sol Gel thin films based on N-CNT/TiO2, by dispersing nitrogen (N) doped carbon nanotubes (N-CNTs) powders in titanium tetraisopropoxyde (TTIP). The samples were assessed in terms of optical properties, using UV—visible absorption spectroscopic techniques. After careful analysis of the results, we have concluded that the mentioned route is good and more efficient in terms of optoelectronic properties. The gap of “the neat” 0.00w% N-CNT/TiO2 is of 3eV, which is in a good agreement with similar gap of semiconductors. The incorporated “w%NCNTs” led to diminishing the Eg with increasing N-CNTs amount. These consequences are very encouraging for optoelectronic field.

Application of a composite membrane aerated biofilm with controllable biofilm thickness in nitrogen removal

AbstractBACKGROUNDThe manipulation of aeration and biofilm thickness remain two key factors for membrane aerated biofilm. A composite membrane aerated biofilm (CMAB) reactor coated with microorganisms embedded in hydrogel was developed to quantitatively control the biofilm thickness by introducing the microbial immobilization technique.RESULTSResults show that the thin gel film exhibited high dispersion coefficients of oxygen and substrates, and the crosslinking solution of sodium nitrate (NaNO3) contributed to the highest specific ammonium‐nitrogen (NH4+‐N) removal rate of 615.33 mg/(gVSS d) with respect to partial nitrification. Correspondingly, the microbial activity of this thin gel film was also the strongest. Therefore, with the simultaneous nitrification and denitrification, the gel thickness and air pressure co‐determined its efficiency. The optimum biofilm thickness and air pressure was 0.1 mm and 1 kPa, respectively, achieving the nitrogen removal rate of 1594.95 mg/(gVSS d). Furthermore, two abundant denitrifiers of Rhizobium and Thauera dominated the bacterial community of all four samples, and their proportion varied according to the aeration condition. Nitrosomonas tended to enrich in the thin CMAB under low air pressure and few Nitrospira existed.CONCLUSIONThe thickness of developed CMAB can be quantitatively controlled, and the precise regulation of simultaneous nitrification and denitrification might be achieved by adjusting the gel film thickness and air pressure. The CMAB is supposed to greatly facilitate the application of membrane aerated biofilm for nitrogen removal. © 2019 Society of Chemical Industry

4-Nitro-Azo Dye-Sensitized Optical Behavior of Organic/Inorganic Hybrid Networks in Zirconium-Based Thin Films: Effect of Cu Co-doping

The considerable attention on organic–inorganic compounds motivated us to study the effect of incorporation of new azo derivative, (2-hydroxy-3-methoxy-5-((4-Nitrophenyl)diazenyl) benzaldehyde), as an applicable organic molecule, in the structure of zirconium-based sol–gel thin films. The driving force behind our study is to see whether the possible coordination of organic and inorganic counterparts leads to the modification of the physical characters of the samples. The study on the UV/Vis transmittance and FTIR spectra of samples confirms that a combination of functional groups with the inorganic bonds is created. The improvement in the photoluminescence intensity is observed due to the lower concentration of dimer in the 1% azo-doped thin film. The effect of the addition of copper on the optical characteristics of samples doped with 1% azo is also studied. The increase in the copper concentration showed to be an intelligent method to achieve higher PL intensity.

Oxidation resistant TiO2–SiO2 coatings on mild steel by Sol–Gel

Single and multilayer titania–silica (TiO2–SiO2) oxidation resistant dry gel thin film was applied on mild steel (MS) through sol–gel based dip coating. The coated samples were fired at 410 °C for 30 min and the coating film thickness was found to be 200–400 nm using spectroscopic ellipsometry. The structural and chemical analysis of the films was carried out by XRD, SEM–EDS and TG–DTA. The oxidation resistance of coatings was evaluated by weight gain per unit area after exposing to 400 °C for 20 h in air. Uncoated specimens exhibited a weight gain of 0.72 mg/cm2. However, the weight gain was less by 6 times for single layer and 16 times for 3 layers of coatings (deposition). Further, oxidation kinetics study revealed a reduction of parabolic oxidization rate constant by 43 times (0.026 mg2 cm−4.h−1) for single layer and 325 times (8 × 10−5 mg2 cm−4.h−1) for 3 layer coatings, compared to bare MS exposed to identical conditions. Such a high reduction in oxidation with multilayer deposition is probably due to the effective coverage of micro–cracks, which may be induced due to the thermal mismatch between the coatings and MS. An improvement in adherence of coating was confirmed due to the formation of (Fe0. 927Ti0.073)2.O3 at the interface using XRD. The addition of SiO2 to TiO2 was found to minimise the coating defects associated with sol–gel and also inhibit the formation of anatase. Thus, the present work demonstrated the application of TiO2–SiO2 thin film coating on MS through sol–gel technique to form an impervious layer to substantially enhance the oxidation resistance at elevated temperatures.

Amine Functionalization of Silica Sol-Gel Thin Films via Kinetic Doping: A Novel, Green Approach.

Amine-functionalized thin films are highly desirable technologies for analytical, material, and biochemistry applications. Current functionalization procedures can be costly, environmentally unfriendly, and require many synthetic steps. Here, we present an inexpensive and facile way to functionalize a silica thin film with a 25 000 MW branched polyethylenimine (BPEI), consistent with green chemistry principles. Using UV–vis spectroscopy and scanning electron microscopy, BPEI was determined to be loaded into the film at an approximately 0.5 M concentration, which is a 500× increase from the loading solution used. The films were also tested for copper(II) sequestration to assess their potential for heavy metal sequestration and showed a high loading capacity of 10 ± 6 mmol/g. Films proved to be reusable, using ethylenediaminetetraacetic acid to chelate copper and regenerate the films, with only a 6% reduction in the amount of copper(II) ions sequestered by the third use. The films also proved stable against leaching over the course of 1 week in solution, with less than 1% of the original BPEI lost under various storage conditions (i.e., storage in deionized (DI) water, storage in dilute BPEI solution, storage in DI water after annealing). These films show promise for multiple applications, from heavy metal sequestration to antifouling applications, while being inexpensive, facile, and environmentally friendly to synthesize. To our knowledge, this is the first time that BPEI has been doped into silica thin films.

Exploring the Effect of Porous Structure on Thermal Conductivity in Templated Mesoporous Silica Films

This work elucidates the effect of porous structure on thermal conductivity of mesoporous amorphous silica. Sol–gel and nanoparticle-based mesoporous amorphous silica thin films were synthesized by...

SYNTHESIS AND CHARACTERIZATION OF Fe–ZnO THIN FILMS FOR ANTIMICROBIAL ACTIVITY

Pure and Fe-doped zinc oxide (ZnO) sol–gel thin films were deposited by spin-coating process. Pure ZnO and Fe–ZnO films, containing Fe of 2–8[Formula: see text]wt.%, were annealed at 500∘C for 2[Formula: see text]h. All prepared thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV–visible (UV–vis) spectroscopy. XRD studies show the polycrystalline nature with hexagonal wurtzite structure of pure ZnO and Fe–ZnO thin films. The crystallite size of the prepared samples reduced with increasing Fe doping concentrations. AFM and SEM results indicated that the average grain size decreased as Fe doping concentration increased. The transmittance spectra were then recorded at wavelengths ranging from 300[Formula: see text]nm to 1000[Formula: see text]nm. The films produced yielded high transmission at visible regions. The optical bandgap energy of spin-coated films also decreased as Fe doping concentration increased. In particular, their optical bandgap energies were 3.75, 3.6, 3.5, 3.45 and 3.3 eV at 0-, 2-, 4-, 6- and 8-wt.% Fe concentrations, respectively. Antibacterial activities of pure ZnO and Fe–ZnO against E. coli and S. aureus were evaluated by international recognized test (JIS Z 2801). The results showed that pure and Fe-doped ZnO thin films have antibacterial inhibition zone against E. coli and S. aureus. Gram-positive bacteria seemed be more resistant to pure and Fe-doped ZnO thin films than gram-negative bacteria. The test shows an incremental increase in antibacterial activity of the thin films when dopant ratio increased under UV light.

Optical waveguiding characteristics of TiO2 sol–gel thin films for photonic devices: effects of thermal annealing

We have investigated the effects of thermal annealing (450°C, 500°C, and 550°C) on the titanium dioxide (TiO2) thin film physical and optical waveguiding properties using x-ray diffraction, Raman spectroscopy, scanning electron microscopy, atomic force microscopy, UV–visible spectrophotometry, and m-lines spectroscopy. The results show that the as-deposited film is amorphous, whereas the annealed films are polycrystalline and crystallize only in the anatase tetragonal structure with a preferential orientation of (101). The grain size, morphology, and surface roughness of the TiO2 films are significantly affected by the thermal annealing. The as-deposited TiO2 thin films reveal high transparency with an average transmittance >80 % in the visible region. Moreover, a decrease in the optical transmission and energy bandgap with increasing annealing temperature is also observed. All the TiO2 planar waveguides exhibit only single-mode confinement regardless of the polarization. Both transverse electric and transverse magnetic refractive indices are found to increase upon annealing. Moreover, the as-deposited TiO2 planar waveguide shows a remarkable propagation loss of as low as 0.8 ± 0.1 dB / cm at a 632.8 nm wavelength, which suggests that the fabricated TiO2 films are promising for photonic applications.

Fabrication of Biomimetic Micropatterned Surfaces by Sol–Gel Dewetting

AbstractDewetting of thin polymer films has been extensively investigated as a way to generate patterned surfaces. In this paper, the controlled dewetting of sol–gel thin films induced by solvent annealing is reported. The key factors that control the dewetting process are identified and patterns with tunable diameter between 5 and 80 µm and tunable height between 1 and 10 µm are fabricated on a large scale. By changing the chemistry of the sol–gel system, patterns with wetting contrast, consisting of hydrophilic bumps on a hydrophobic layer, are realized. These surfaces are inspired by the exoskeleton of the Namib desert beetle and are amenable to application in atmospheric water capture, as they facilitate condensation and allow for water droplets to roll off at low critical volumes (6–8 µL), similar to the value predicted for the Namib desert beetle. The approach presented is simple, scalable, and can be applied to a wide range of substrates including glass. Transparent micropatterns are realized with high transmittance in the visible range, suitable for fabrication of coatings on windows or microlens arrays.

2D Image Quantification of Microbial Iron Chelators (Siderophores) Using Diffusive Equilibrium in Thin Films Method.

Siderophores are natural metal chelating agents that strongly control the biogeochemical metal cycles such as Fe in the environment. This article describes a new methodology to detect and quantify at the micromolar concentration the spatial distribution at millimeter scale of siderophores within the root's system. The "universal" CAS assay originally designed for bacterial siderophores detection and later designed for fungus was adapted here for diffusive equilibrium in thin film gel techniques (DET). The method was calibrated against the marketed desferrioxamine mesylate (DFOM) siderophore and applied with experiments performed with sunflower ( Helianthus annuus) and wheat ( Triticum aestivum) cultivated on free iron agar medium plates. We present here the first results with 2D images of the siderophores distribution in the vicinity of the root system of plants. With this technique we detected (i) the production of siderophores on bacteria inoculated ( Pseudomonas fluorescens) environments and (ii) hotspots of natural iron binding ligands production up to 50 μM in the wheat rhizosphere. The lower detection limit in our experiment was 2.5 μmol/L. This new technique offers a unique opportunity to investigate the siderophore production in two dimensions in a wide range of applications from laboratory experiments to natural systems very likely using an in situ and nondestructive tool.

Studies on piezo coefficients of PLD and sol-gel grown PZT thin film for devices

The effect of electrical (DC) contact poling processes on the ferroelectric and piezoelectric properties of sol–gel and pulsed laser-deposited PZT thin films has been investigated as a function of the poling field, temperature and time. The remnant polarization and piezoelectric coefficient are found to increase with and saturate at dc-poling field of 100- 300 kV/cm, temperature of 100–120 °C and poling time of 10–20 min. as compared with un-poled PZT thin films. The P-E hysteresis loops of poled PLD grown PZT films shows sharper switching behaviour as compared to imbalanced loop in sol-gel grown films. An improvement of piezoelectric and ferroelectric properties of sol–gel PZT thin films is found, as compared to those deposited using pulsed laser deposition (PLD), indicating that a poling process is required for sol–gel PZT thin films.

Kinetic Insights into Marangoni Effect-Assisted Preparation of Ultrathin Hydrogel Films.

In a previous work ( ACS Appl. Mater. Interfaces 2017, 9, 34349-34355), a facile approach was reported to prepare thin hydrogel films based on the Marangoni effect. After dripping onto a water surface, a drop of ethanol solution of poly(stearyl acrylate- co-acrylic acid) [P(SA- co-AAc)] spread quickly to form a thin film. The solvent exchange from ethanol to water led to the gelation of polymer solution which turned into a hydrogel film. Here, we investigate the scenario and seek for the governing kinetics of the Marangoni effect-assisted preparation of hydrogel films. By incorporating aggregation-induced emission fluorogens into the P(SA- co-AAc) solution, so that fluorescence appears at the gel state, we found that the spreading usually completed before the full gelation of the entire film. The spreading and formation of the gel films were influenced by the molar fraction of SA, f, and the polymer concentration of ethanol solution, CP. The spreading was blocked when CP was too high, whereas the film was fragmented into small pieces when CP was too low. At an intermediate CP, uniform hydrogel films were obtained. Steady spreading at a constant speed was observed during the processes which yielded uniform hydrogel films. Both CP and f influenced the spreading process by tuning the surface tension of the ethanol solution and the viscoelasticity of the gelated film, as suggested by our theoretical model. This work provided kinetic insights into the Marangoni phenomena of viscous polymer solutions. The strategy and principle should be applicable to other systems on preparing thin supramolecular gel films with versatile functions.

Studying structural, morphological and optical properties of nanocrystalline ZnO:Ag films prepared by sol–gel method for antimicrobial activity

Pure and Ag-doped zinc oxide sol–gel thin films were prepared by spin-coating process. Pure and Ag–ZnO films, containing 2–8% Ag, were annealed at 500 °C for 2 h. All thin films were prepared and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV–visible spectroscopy. X-ray diffraction studies show the polycrystalline nature with hexagonal wurtzite structure of ZnO and Ag:ZnO thin films. The crystallite size of the prepared samples reduced with increasing Ag doping concentrations. AFM and SEM results indicated that the average crystallite size decreased as Ag doping concentration increased. The transmittance spectra were then recorded at wavelengths ranging from 300 to 1000 nm. The films produced yielded high transmission at visible regions. The optical band gap energy of spin-coated films also decreased as Ag doping concentration increased. In particular, their optical band gap energies were 3.75, 3.55, 3.4, 3.3, and 3.23 eV at 0%, 2%, 4%, 6%, and 8%, respectively. Antibacterial activity of pure and Ag-doped zinc oxide against Escherichia coli and Staphylococcus aureus was evaluated by international recognized test (JIS Z 2801). The results showed that pure and Ag-doped ZnO thin film has an antibacterial inhibition zone against E. coli and S. aureus. Gram-positive bacteria seemed to be more resistant to pure and Ag-doped ZnO thin film than gram-negative bacteria. The test shows incrementally increasing in antibacterial activity of the thin films when dopant ratio increased under UV light.