TiO2 nanotube, nanowire, and rhomboid-shaped particle thin films fixed on a titanium metal plate

Titanium dioxide thin films having various nanostructures could be formed by various treatments on sodium titanate nanotube thin films approximately 5 μm thick fixed on titanium metal plates. Using an aqueous solution with a lower hydrochloric acid concentration (0.01 mol/L) and a higher reaction temperature (90 °C) than those previously employed, we obtained a hydrogen titanate nanotube thin film fixed onto a titanium metal plate by H⁺ ion-exchange treatment of the sodium titanate nanotube thin film. Calcination of hydrogen titanate nanotube thin films yielded porous thin films consisting of anatase nanotubes, anatase nanowires, and anatase nanoparticles grown directly from the titanium metal plate. H⁺ ion-exchange treatment of sodium titanate nanotube thin films at 140 °C resulted in porous thin films consisting of rhomboid-shaped anatase nanoparticles.     

Comparative study of LiMn2O4 thin film cathode grown at high, medium and low temperatures by pulsed laser deposition

LiMn₂O₄ thin films with different crystallizations were respectively grown at high, medium and low temperatures by pulsed laser deposition (PLD). Structures, morphologies and electrochemical properties of these three types of thin films were comparatively studied. Films grown at high temperature (?873 K) possessed flat and smooth surfaces and were highly crystallized with different textures and crystal sizes depending on the deposition pressure of oxygen. However, films deposited at low temperature (473 K) had rough surfaces with amorphous characteristics. At medium temperature (673 K), the film was found to consist mainly of nano-crystals less than 100 nm with relatively loose and rough surfaces, but very dense as observed from the cross-section. The film deposited at 873 K and 100 mTorr of oxygen showed an initial discharge capacity of 54.3 μAh/cm² μm and decayed at 0.28% per cycle, while the amorphous film had an initial discharge capacity of 20.2 μAh/cm² μm and a loss rate of 0.29% per cycle. Compared with the highly crystallized and the amorphous films, nano-crystalline film exhibited higher potential, more capacity and much better cycling stability. As high as 61 μAh/cm² μm of discharge capacity can be achieved with an average decaying rate of only 0.032% per cycle up to 500 cycles. The excellent performance of nano-crystalline film was correlated to its microstructures in the present study.     

Influence of substrate morphology on organic layer growth: PTCDA on Ag(1 1 1)

By UV-excited photoelectron emission microscopy (UV-PEEM) we investigated the microscopic growth behavior of organic thin films using 3,4,9,10-perylene-tetracarboxylicacid dianhydride (PTCDA) on a Ag(1 1 1) single crystal substrate as example. Direct, real time observation allows to correlate the initial growth modes and the related kinetic parameters with substrate properties like terrace width, step density, and step bunches from the submonolayer range up to 5 layers or more. Above room temperature PTCDA grows in a Stranski–Krastanov fashion: after completion of the first two stable layers three-dimensional islands are formed. The nucleation density strongly depends on the temperature and the substrate morphology thus affecting the properties of the organic film.     

Electrochemical synthesis and surface characterization of poly(3,4-ethylenedioxythiophene) films grown in an ionic liquid

We report a facile method to synthesize poly(3,4-ethylenedioxythiophene) (PEDOT) films at room temperature in a waterproof ionic liquid, 1-ethyl-3-methylimidazolium bis(perfluoroethylsulfonyl)imide (EMIPFSI), by electropolymerization. The ionic liquid leads to the formation of randomly oriented nanofibers and particles confined to submicrometer-sized domains in the film microstructure. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray (EDX) studies provide information about the intercalation of the cation apart from the reported anion in the polymer film, and on how the imidazolium ion controls the growth of PEDOT nanostructures.     

Novel chemical synthesis of polypyrrole thin film electrodes for supercapacitor application

Present investigation describes the cost-effective, novel and simple chemical synthesis of polypyrrole (PPy) thin films for supercapacitor application. These PPy films are characterized by different techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The XRD pattern reveals the amorphous nature of PPy thin film, which is highly feasible for supercapacitors. Further, FTIR study confirms the formation of PPy. The surface morphological study exhibit the coverage of uniform and smooth morphology on thin film. The electrochemical supercapacitive properties of PPy thin films are evaluated using cyclic voltammetry (CV) in 0.5 M H₂SO₄ electrolyte, which exhibits the maximum specific capacitance of 329 Fg⁻¹ at the scan rate of 5 mV s⁻¹. Additionally, an equivalent series resistance (ESR) of PPy thin films is found to be 1.08 Ω using electrochemical impedance measurement.     

Crystallinity and dimensional stability of biaxial oriented poly(lactic acid) films

Transparent biaxial oriented poly(lactic acid) (BOPLA) films with improved dimensional stability were successfully prepared by controlling the crystallization of poly(lactic acid) (PLA). The crystalline morphology of PLA films can be manipulated by changing certain processing parameters, such as stretch ratio, heat setting temperatures, and heat setting time. Optical and mechanical properties as well as dimensional stability of the resulting polymer films are governed by their crystallinity and crystalline morphology. Crystallization behavior and kinetics of PLA, therefore, were investigated using wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS), and differential scanning calorimetry (DSC) techniques. Mechanical properties and the dimensional stability of the biaxial oriented PLA films were obtained and correlated with their processing conditions. Poly(lactic acid) films prepared by melt extrusion methods have great potential for food packaging, shrink labeling and protective film applications. However, shrinkage at elevated processing temperature should be minimized to avoid puckering of the polymer film. Shrinkage of less than 2% was achieved for a BOPLA film stretched 300% in both directions at 75 °C and then annealed at 160 °C for 30 s. Fabrication, properties, and potential applications of a series of biodegradable films will be described.     

Growth of HfO2 films using an alternate reaction of HfCl4 and O2 under atmospheric pressure

HfO₂ films were deposited onto a Si(1 0 0) substrate using an alternate reaction of HfCl₄ and O₂ under atmospheric pressure. Self-limiting growth of the HfO₂ was achieved in the range of the growth temperature above 873 K. The X-ray diffraction of the HfO₂ films showed a typical diffraction pattern assigned to the monoclinic polycrystalline phase. Residual chloride concentration in HfO₂ films were not higher than 0.1 at%. When the growth temperature was 973 K, the HfSiO_x is formed in HfO₂ film. This gives effective permittivity value of 9.6 for the HfO₂ film grown at 573 K.     

Polyaniline and poly(flavin adenine dinucleotide) doped multi-walled carbon nanotubes for p-acetamidophenol sensor

A conductive biocomposite film (MWCNTs-PANIFAD) which contains multi-walled carbon nanotubes (MWCNTs) along with the incorporation of poly(aniline) and poly(flavin adenine dinucleotide) co-polymer (PANIFAD) has been synthesized on gold and screen printed carbon electrodes by potentiostatic methods. The presence of MWCNTs in the MWCNTs-PANIFAD biocomposite film enhances the surface coverage concentration (Γ) of PANIFAD and increases the electron transfer rate constant (k_s) to 89%. Electrochemical quartz crystal microbalance studies reveal the enhancements in the functional properties of MWCNTs and PANIFAD present in MWCNTs-PANIFAD biocomposite film. Surface morphology of the biocomposite film has been studied using scanning electron microscopy and atomic force microscopy. The surface morphology results reveal that PANIFAD incorporated on MWCNTs. The MWCNTs-PANIFAD biocomposite film exhibits promising enhanced electrocatalytic activity towards the oxidation of p-acetamidophenol. The cyclic voltammetry has been used for the measurement of electroanalytical properties of p-acetamidophenol by means of PANIFAD, MWCNTs and MWCNTs-PANIFAD biocomposite film modified gold electrodes. The sensitivity value of MWCNTs-PANIFAD film (88.5 mA mM⁻¹ cm⁻²) is higher than the values which are obtained for PANIFAD (28.7 mA mM⁻¹ cm⁻²) and MWCNTs films (60.7 mA mM⁻¹ cm⁻²). Finally, the flow injection analysis (FIA) has been used for the amperometric detection of p-acetamidophenol at MWCNTs-PANIFAD film modified screen printed carbon electrode. The sensitivity value of MWCNTs-PANIFAD film (3.3 mA mM⁻¹ cm⁻²) in FIA is also higher than the value obtained for MWCNTs film (1.1 mA mM⁻¹ cm⁻²).     

Preparation and properties of a high temperature, flexible and colorless ITO coated polyimide substrate

A new high temperature, flexible and colorless indium-tin-oxide (ITO) coated plastic substrate has been prepared from a thermally stable, high glass transition temperature (T_g) and colorless polyimide film. The polyimide was synthesized from 3,3′-diaminodiphenylsulfone (3,3′-DDS) and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) monomers. Its heat distortion temperature was 278 °C. The ITO was deposited on the polyimide film using the magnetron-sputtering process. After annealing at 250 °C under nitrogen for 1 h, the resistivity of the ITO film was 4.0 × 10⁻⁴ Ω cm, and its transmittance was 83.5%. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to observe the surface and morphology of the ITO film. UV-visible spectroscopy and the four-probe method were used to study their optical and electrical properties. The high performance ITO-plastic substrate can be used in the next generation flat panel displays.     

The porous CuO electrode fabricated by hydrogen bubble evolution and its application to highly sensitive non-enzymatic glucose detection

The porous Cu film was deposited on a Pt/Ti/Si substrate by electrochemical deposition accompanied by hydrogen evolution at very high current densities. CuO films with similar morphologies were obtained by subsequent annealing of the porous copper films. The morphology, composition and structure of the porous Cu and porous CuO were investigated by FE-SEM, EDS and XRD methods. The complete transformation of Cu to CuO after annealing was indicated. The sensing performances of the porous CuO film were evaluated in alkaline solution with the porous CuO film showing a wide linearity range from 1 μM to 2.5 mM with sensitivity of 2.9 mA cm⁻² mM⁻¹, and detection limit of 0.14 μM. The sensor showed good selectivity to conventional intermediates such as AA and UA and long term stability.     

Facile synthesis of PbTe nanoparticles and thin films in alkaline aqueous solution at room temperature

A novel, simple, and cost-effective route to PbTe nanoparticles and films is reported in this paper. The PbTe nanoparticles and films are fabricated by a chemical bath method, at room temperature and ambient pressure, using conventional chemicals as starting materials. The average grain size of the nanoparticles collected at the bottom of the bath is ∼25 nm. The film deposited on glass substrate is dense, smooth, and uniform with silver gray metallic luster. The film exhibits p-type conduction and has a moderate Seebeck coefficient value (∼147 μV K⁻¹) and low electrical conductivity (∼0.017 S cm⁻¹). The formation mechanism of the PbTe nanoparticles and films is proposed.     

Electrochemistry and scanning electron microscopy of polyaniline/peroxidase-based biosensor

An amperometric biosensor was prepared by in situ deposition of horseradish peroxidase (HRP) enzyme on a polyaniline (PANI)-doped platinum disk electrode. The PANI film was electrochemically deposited on the electrode at 100 mV s⁻¹/Ag-AgCl. Cyclic voltammetric characterization of the PANI film in 1 M HCl showed two distinct redox peaks, which prove that the PANI film was electroactive and exhibited fast reversible electrochemistry. The surface concentration and film thickness of the adsorbed electroactive species was estimated to be 1.85×10⁻⁷ mol cm⁻² and approximately 16 nm, respectively. HRP was electrostatically immobilized onto the surface of the PANI film, and voltammetry was used to monitor the electrocatalytic reduction of hydrogen peroxide under diffusion-controlled conditions. Linear responses over the concentration range 2.5×10⁻⁴ to 5×10⁻³ M were observed. Spectroelectrochemistry was used to monitor the changes in UV-vis properties of HRP, before and after the catalysis of H₂O₂. The biosensor surface morphology was characterized by scanning electron microscopy (SEM) using PANI-doped screen-printed carbon electrodes (SPCEs) in the presence and absence of (i) peroxidase and (ii) peroxide. The SEM images showed clear modifications of the conducting film surface structure when doped with HRP, as well as the effect of hydrogen peroxide on the morphology of biosensor.     

Highly selective molecular recognition and high throughput detection of melamine based on molecularly imprinted sol-gel film

Multimode reader has been generally applied in immunoassay, and in the proposed paper, the 96 well micro-plate was modified with molecularly imprinted melamine sol-gel film, based on which the highly selective and high throughput detection of melamine was achieved. Melamine was imprinted into silica sol-gel films directly using phenyltrimethoxysilane and methyltrimethoxysilane as functionalized organosilicon precursors. The binding characteristic of the imprinted film to melamine was evaluated by equilibrium binding experiments and the morphology was studied by scanning electronic microscope (SEM). Scatchard analysis was carried out to estimate the binding parameters of the imprinted film. The proposed method exhibited excellent selectivity because of specific recognition of MM by molecularly imprinted film. Under the optimum conditions, the chemiluminescence (CL) intensity had a linear relationship against the concentration of melamine over the range of 0.1-50 μg mL⁻¹ with a lower detection limit of 0.02 μg mL⁻¹.     

Properties of foam films stabilized with tetraethylammonium perfluorooctane-sulfonate

Properties of single foam films prepared with tetraethylammonium perfluorooctane-sulfonate (TAPOS) were studied. Film thickness was measured as a function of NH₄Cl concentration in the film forming solution. The dependence of the film disjoining pressure versus the film thickness (disjoining pressure isotherms) and the mean lifetime of the films were studied. The dependence of the film thickness on the electrolyte concentration showed the presence of an electrostatic double layer at the film surfaces. The electrostatic double layer component of the disjoining pressure was screened at a NH₄Cl concentration higher than 0.2 M where Newton black films (NBFs) of 6 nm thickness were formed. These films are bilayers of amphiphile molecules and contain almost no free water. The disjoining pressure isotherms of the foam films formed with 0.001 M TAPOS were measured at two different NH₄Cl concentrations (0.005 and 0.0005 M). The Deryaguin-Landau-Verwey-Overbeek (DLVO) theory describes well the isotherms with an electrostatic double layer potential of ∼140 mV. The mean lifetime, a measure of the stability of the NBFs, was measured depending on surfactant concentrations. The observation of NBF was possible above a minimum TAPOS concentration of 9.4 × 10⁻⁵ M. Above this concentration, the lifetime increases exponentially. The dependence of the film lifetime on surfactant concentration is explained by the theory for NBF-rupture by nucleation mechanism of formation of microscopic holes.     

Fabrication and nanoindentation properties of TiN/NiTi thin films and their applications in electrochemical sensing

Nanocrystalline TiN/NiTi thin films have been grown on silicon substrate by dc magnetron sputtering to improve the corrosion and mechanical properties of NiTi based shape memory alloys without sacrificing the phase transformation effect. Interestingly, the preferential orientation of the TiN films was observed to change from (1 1 1) to (2 0 0) with change in nature of sputtering gas from 70% Ar + 30% N₂ to 100% N₂. In present study the influence of crystallographic orientation of TiN on mechanical and corrosion properties of TiN/NiTi thin films was investigated. TiN (2 0 0)/NiTi films were found to exhibit high hardness, high elastic modulus, and thereby better wear resistance as compared to pure NiTi and TiN (1 1 1)/NiTi films. Electrochemical test revealed that TiN coated NiTi film exhibits better corrosion resistance in 1 M NaCl solution as compared to uncoated NiTi film. The application of TiN/NiTi films in the electrochemical sensing of dopamine, which has a critical physiological importance in Parkinson's disease, has been demonstrated. A comparison of voltammetric response of dopamine at silicon based electrodes modified with different nanocrystalline coatings indicated that these films catalyze the oxidation of dopamine.     

A new sensor for ammonia based on cyanidin-sensitized titanium dioxide film operating at room temperature

Design and fabrication of an ammonia sensor operating at room temperature based on pigment-sensitized TiO₂ films was described. TiO₂ was prepared by sol–gel method and deposited on glass slides containing gold electrodes. Then, the film immersed in a 2.5 × 10⁻⁴ M ethanol solution of cyanidin to absorb the pigment. The hybrid organic–inorganic formed film here can detect ammonia reversibly at room temperature. The relative change resistance of the films at a potential difference of 1.5 V is determined when the films are exposed to atmospheres containing ammonia vapors with concentrations over the range 10–50 ppm. The relative change resistance, S, of the films increased almost linearly with increasing concentrations of ammonia (r = 0.92). The response time to increasing concentrations of the ammonia is about 180–220 s, and the corresponding values for decreasing concentrations 240–270 s. At low humidity, ammonia could be ionized by the cyanidin on the TiO₂ film and thereby decrease in the proton concentration at the surface. Consequently, more positively charged holes at the surface of the TiO₂ have to be extracted to neutralize the adsorbed cyanidin and water film. The resistance response to ammonia of the sensors was nearly independent on temperature from 10 to 50 °C. These results are not actually as good as those reported in the literature, but this preliminary work proposes simpler and cheaper processes to realize NH₃ sensor for room temperature applications.     

One step electrochemically deposited nanocomposite film of chitosan-carbon nanotubes-gold nanoparticles for carcinoembryonic antigen immunosensor application

A simple and controllable one-step electrodeposition method for the preparation of a chitosan-carbon nanotubes-gold nanoparticles (CS-CNTs-GNPs) nanocomposite film was used to fabricate an immunosensor for detection of carcinoembryonic antigen (CEA). The porous three-dimensional CS-CNTs-GNPs nanocomposite film, which offered a large specific surface area for immobilization of antibodies, exhibited improved conductivity, high stability and good biocompatibility. The morphology of the formed nanocomposite film was investigated by scanning electron microscopy (SEM), and the electrochemical behaviors of the immunosensor were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Under the optimal conditions, the proposed immunosensor could detect CEA in two linear ranges from 0.1 to 2.0 ng mL⁻¹ and from 2.0 to 200.0 ng mL⁻¹, with a detection limit of 0.04 ng mL⁻¹. The immunosensor based on CS-CNTs-GNPs nanocomposite film as the antibody immobilization matrix could exhibit good sensitivity, stability, and reproducibility for the determination of CEA.     

Effects of substrate temperature on properties of ITO-ZnO composition spread films fabricated by combinatorial RF magnetron sputtering

We have fabricated ITO-ZnO composition spread films to investigate the effects of substrate temperature on their electrical and optical properties by using combinatorial RF magnetron sputtering. It turned out by X-ray measurement that the film with zinc contents above 16.0 at% [Zn/(In+Zn+Sn)] showed amorphous phase regardless of substrate temperature. The amorphous ITO-ZnO film had lower resistivity than polycrystalline films. When the films were deposited at 250 °C, the minimum resistivity of 3.0×10⁻⁴ Ω cm was obtained with the zinc contents of 16.0 at%. The indium content could be reduced as high as ~30 at% compared to that of ITO for the films having similar resistivity (~10⁻⁴ Ω cm). However, a drastic increase of resistivity was observed for the ITO-ZnO films deposited at 350 °C, having zinc contents below 15.2 at%.     

Composite film of carbon nanotubes and chitosan for preparation of amperometric hydrogen peroxide biosensor

A new amperometric biosensor for hydrogen peroxide was developed based on cross-linking horseradish peroxidase (HRP) by glutaraldehyde with multiwall carbon nanotubes/chitosan (MWNTs/chitosan) composite film coated on a glassy carbon electrode. MWNTs were firstly dissolved in a chitosan solution. Then the morphology of MWNTs/chitosan composite film was characterized by field-emission scanning electron microscopy. The results showed that MWNTs were well soluble in chitosan and robust films could be formed on the surface. HRP was cross-linked by glutaraldehyde with MWNTs/chitosan film to prepare a hydrogen peroxide biosensor. The enzyme electrode exhibited excellent electrocatalytic activity and rapid response for H₂O₂ in the absence of a mediator. The linear range of detection towards H₂O₂ (applied potential: −0.2 V) was from 1.67 × 10⁻⁵ to 7.40 × 10⁻⁴ M with correction coefficient of 0.998. The biosensor had good repeatability and stability for the determination of H₂O₂. There were no interferences from ascorbic acid, glucose, citrate acid and lactic acid.     

Thermal diffusivity measurement of low-k dielectric thin film by temperature wave analysis

Thermal diffusivity of thin film with low dielectric constant (k), what is called low-k dielectric thin film, 0.31-1.14 μm, including hydrogen-silsesquioxane (HSQ), methyl-silsesquioxane (MSQ), and poly(arylen ether) was examined by temperature wave analysis. The phase shift of temperature wave was observable up to 100 kHz. Thermal diffusivity of HSQ was 4.7 × 10⁻⁷ m² s⁻¹, on the other hand it was not higher than 1.1 × 10⁻⁷ m² s⁻¹ for MSQ or poly(arylen ether) at room temperature. Temperature dependence of thermal diffusivity/thermal conductivity of MSQ was obtained, thermal diffusivity decreased but thermal conductivity increased in a heating scan at 30-150 °C. It was shown that the thermal diffusivity of low-k thin film was correlated with the chemical and the physical structures, the latter was formed in the spin-coating and the curing process.