Vanillin cross-linked hydrogel membranes interfacial reinforced by carbon nitride nanosheets for enhanced antibacterial activity and mechanical properties

Biopolymer based hydrogels are highly adaptable, compatible and have shown great potential in biological tissues in biomedical applications. However, the development of bio-based hydrogels with high strength and effective antibacterial activity remains challenging. Herein, a series of Vanillin-cross-linked chitosan nanocomposite hydrogel interfacially reinforced by g-C₃N₄ nanosheet carrying starch-caped Ag NPs were prepared for wound healing applications. The study aimed to enhance the strength, sustainability and control release ability of the fabricated membranes. Starch-caped silver nanoparticles were incorporated to enhance the anti-bacterial activities The fabricated membranes were assessed using various characterization techniques such as FT-IR, XRD, SEM, mechanical testing, Gel fraction and porosity alongside traditional biomedical tests i.e., swelling percentage, moisture retention ability, water vapor transmission rate, oxygen permeability, anti-bacterial activity and drug-release of the fabricated membranes. The mechanical strength reached as high as 25.9 ± 0.24 MPa for the best optimized sample. The moisture retention lied between 87–89%, gel fraction 80–85%, and water vapor transmission up to 104 ± 1.9 g/m²h showing great properties of the fabricated membrane. Swelling percentage surged to 225% for blood while porosity fluctuated between 44% ± 2.1% and 52.5% ± 2.3%. Oxygen permeability reached up to 8.02 mg/L showing the breathable nature of fabricated membranes. The nanocomposite membrane shown excellent antibacterial activity for both gram-positive and gram-negative bacteria with a maximum zone of inhibition 30 ± 0.25 mm and 36.23 ± 0.23 mm respectively. Furthermore, nanoparticles maintained sustainable release following non-fickian diffusion. The fabricated membrane demonstrated the application of inorganic filler to enhance the strength of biopolymer hydrogel with superior properties. These results envisage the potential of synthesized membrane to be used as wound dressing, artificial skin and load-bearing scaffolds.     

Preparation of Bioactive PDMS-Modified CaO–SiO2–TiO2 Hybrids by the Sol-Gel Method

Much attention has been focused on the development of a new type of bioactive material with mechanical properties analogous to those of natural bone. The present authors previously showed that some polydimethylsiloxane (PDMS)-modified CaO–SiO₂–TiO₂ hybrids prepared by sol-gel method show apatite-forming ability in a simulated body fluid (SBF), which is indicative of bioactivity. In the present study, effects of composition of PDMS-modified CaO–SiO₂–TiO₂ hybrids on their bioactivity and mechanical properties were investigated. The bioactivity of the hybrids increased with decreasing PDMS content and increasing TiO₂ content. Their strain at failure increased with increasing PDMS content and decreasing TiO₂ content. Some samples showed high bioactivity, as well as analogous mechanical properties to those of human cancellous bones. This type of hybrids might be useful as a bone-repairing material.     

To Study the Effect of Nanoparticle TiO2 on Sodium (Na+) – Ion Conducting Solid Polymer Electrolyte System: [80PEO:20NaPF6]

To study the effect of nanofiller particle TiO₂ on sodium (Na⁺) – ion conducting solid polymer electrolyte (SPE) film: [80PEO:20NaPF₆] and nanocomposite polymer electrolyte (NCPE): [80PEO:20NaPF₆] + xTiO₂, where x = 1–9 wt. (%) have been prepared. SPE film composition: [80PEO:20NaPF₆] selects as Ist-phase host and nano-sized (<100 nm) filler materials TiO₂ as IInd-phase dispersoid. Both SPE and NCPE films have been prepared by the hot-press technique. Filler particle-dependent conductivity study reveals the NCPE system: [80PEO:20NaPF₆] + 8TiO₂ as the highest conducting composition with σ_rt − 3.53 × 10⁻⁶ S cm⁻¹, which is approximately one order of magnitude higher than the SPE optimum conducting composition (OCC) (σ_rt) ≈ 7.78 × 10⁻⁷ S cm⁻¹. Ion transport properties for both SPE and NCPE system have been evaluated in terms of ionic conductivity (σ) and total ionic (t_ion)/cationic (t₊) transference numbers using combined AC/DC techniques in order to evaluate its usefulness in all-solid-state battery applications. Structural/thermal properties have been characterized using X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques. A cyclic voltammetry (CV) study has been performed in SPE and NCPE OCC film to evaluate the electrochemical performance for battery application.     

Application of sol–gel TiO2 film for an extended-gate H+ ion-sensitive field-effect transistor

In this study, a sol–gel TiO₂ thin film has been spin-coated on a commercial ITO glass substrate as the extended-gate field effect transistor (EGFET) for hydrogen ion sensing. The as-deposited films are further annealed at various temperatures (T_a) under ambient atmosphere. It is found that the bi-layer structure of TiO₂/ITO EGFET exhibits good linear sensitivity from pH 1 to 11. Anatase TiO₂ appeared as early as T_a = 200 °C and a brookite (121) diffraction evolved at T_a = 500 °C. No prominent influence on the surface fine structures could be found at higher T_a. Due to the reduction or disappearance of the surface hydroxyl groups on TiO₂, the sensitivities of the TiO₂/ITO pH-EGFET device are rapidly reduced. However, the influence of the conductivity decay for ITO substrates annealed at high T_a could not be excluded. A maximum sensitivity 61.44 mV/pH is achieved as T_a = 300 °C.The bi-layer structure of TiO₂/ITO exhibits better long-term stability than the traditional ITO sensing membranes. In addition, the asymmetric hysteresis is more significant in alkaline buffer solutions, which could be explained by a site-binding model because the diffusion of H⁺ ions into the buried sites of the sensing film is more rapid than that of OH⁻ ions.     

The fabrication of TiO<Subscript>2</Subscript> nanoparticle/ZnO nanowire arrays bi-filmed photoanode and their effect on dye-sensitized solar cells

Porous TiO₂ nanoparticles coated on ZnO nanowire arrays (TiO₂ NP/ZnO NW) as photoanode for dye-sensitized solar cell (DSSC) has been fabricated and investigated to improve the power conversion efficiency. The TiO₂ NP/ZnO NW photoanode consists of single crystalline ZnO NWs synthesized via hydrothermal method and porous TiO₂ NP film covered on the surface of ZnO NW arrays by screen printing technique. The effect of TiO₂ NPs thickness of the bi-filmed photoanode on the cell performance has been investigated, and TiO₂ NP/ZnO NW DSSC with NP thickness of ~5 μm exhibits the best efficiency of 4.68%, higher than 1.16% of ZnO NW DSSC and 3.18% of TiO₂ NPs DSSC, prepared and tested under identical conditions. The efficiency increase is attributed to the enlarged photocurrent, due to the greatly enhanced surface area for dye absorption and light harvesting efficiency resulted from TiO₂ NPs, and improved open-circuit voltage, due to reduced electron recombination by providing direct conduction pathway along ZnO NWs.     

High photocatalytic degradation activity of polyethylene containing polyacrylamide grafted TiO2

A novel photocatalytic polyacrylamide grafted TiO₂ (PAM-g-TiO₂) nanocomposite was prepared and embedded into a low density polyethylene (LDPE) plastic. Photocatalytic degradation of the LDPE/PAM-g-TiO₂ composite film was carried out under ambient conditions under ultraviolet light irradiation. The properties of composite film were compared with those of the pure LDPE film by measuring the changes in weight loss, carbonyl index, molecular weight, tensile strength and elongation at break. PAM-g-TiO₂ embedded LDPE showed highly enhanced photocatalytic degradation. Irradiating the LDPE/PAM-g-TiO₂ composite film for 520 h under UV light reduced its weight by 39.85% and average molecular weight (M_w) by 94.60%, while that of pure LDPE film was only 1.03% and 69.59%, respectively. The addition of PAM-g-TiO₂ brought about the good dispersion of TiO₂ in LDPE matrix and improved the hydrophilicity of composite film, which were able to facilitate the degradation of LDPE. The photocatalytic degradation mechanism of the films is briefly discussed.     

Electrocatalytic oxidation of nitric oxide at TiO2–Au nanocomposite film electrodes

Structured films of TiO₂ (anatase) nanoparticles (ca. 6 nm diameter) and gold nanoparticles (nominal 20 nm diameter) are formed via a layer-by-layer deposition procedure. TiO₂ nanoparticles are deposited with a Nafion polyelectrolyte binder followed by calcination to give a mesoporous thin film electrode. Gold nanoparticles are incorporated into this film employing a poly(diallyldimethylammonium chloride) polyelectrolyte binder followed by calcination to give a stable mesoporous TiO₂–gold nanocomposite. This methodology allows well-defined and structured films to be formed which are re-usable after a 500 °C heat treatment in air.Electrochemical experiments are performed in aqueous KCl and buffer solutions and for the oxidation of nitric oxide, NO, and nitrite in phosphate buffer solution. It is shown that the NO oxidation occurs as a highly effective electrocatalytically amplified process at the surface of the gold nanocomposite probably with co-evolution of oxygen, O₂. In contrast, the oxidation of nitrite to nitrate occurs at the same potential but without oxygen evolution. A mechanistic scheme for the amplified NO detection process is proposed.     

Long-Term Antibacterial Film Nanocomposite Incorporated with Patchouli Essential Oil Prepared by Supercritical CO2 Cyclic Impregnation for Wound Dressing

Biocompatible skin wound dressing materials with long-term therapeutic windows and anti-infection properties have attracted great attention all over the world. The cooperation between essential oil and non-toxic or bio-based polymers was a promising strategy. However, the inherent volatility and chemical instability of most ingredients in essential oils make the sustained pharmacological activity of essential oil-based biomaterials a challenge. In this study, a kind of film nanocomposite loaded with patchouli essential oil (PEO-FNC) was fabricated. PEO-loaded mesoporous silica nanoparticles (PEO-MSNs) with drug load higher than 40 wt% were firstly prepared using supercritical CO₂ cyclic impregnation (SCCI), and then combined with the film matrix consisting of polyvinyl alcohol and chitosan. The morphology of PEO-MSNs and PEO-FNC was observed by transmission and scanning electron microscope. The mechanical properties, including hygroscopicity, tensile strength and elongation at break (%), were tested. The release behavior of PEO from the film nanocomposite showed that PEO could keep releasing for more than five days. PEO-FNC exhibited good long-term (>48 h) antibacterial effect on Staphylococcus aureus and non-toxicity on mouse fibroblast (L929 cells), making it a promising wound dressing material.     

Development of porous,antibacterial and biocompatible GO/n-HAp/bacterial cellulose/β-glucan biocomposite scaffold for bone tissue engineering

Due to their potential renewable materials-based tissue engineering scaffolds has gained more attention. Therefore, researchers are looking for new materials to be used as a scaffold. In this study, we have focused on the development of a nanocomposite scaffold for bone tissue engineering (using bacterial cellulose (BC) and β-glucan (β-G)) via free radical polymerization and freeze-drying technique. Hydroxyapatite nanoparticles (n-HAp) and graphene oxide (GO) were added as reinforcement materials. The structural changes, surface morphology, porosity, and mechanical properties were investigated through spectroscopic and analytical techniques like Fourier transformation infrared (FT-IR), scanning electron microscope (SEM), Brunauer–Emmett-Teller (BET), and universal testing machine Instron. The scaffolds showed remarkable stability, aqueous degradation, spongy morphology, porosity, and mechanical properties. Antibacterial activities were performed against gram -ive and gram + ive bacterial strains. The BgC-1.4 scaffold was found more antibacterial compared to BgC-1.3, BgC-1.2, and BgC-1.1. The cell culture and cytotoxicity were evaluated using the MC3T3-E1 cell line. More cell growth was observed onto BgC-1.4 due to its uniform interrelated pores distribution, surface roughness, better mechanical properties, considerable biochemical affinity towards cell adhesion, proliferation, and biocompatibility. These nanocomposite scaffolds can be potential biomaterials for fractured bones in orthopedic tissue engineering.     

Thermodynamic properties of calcium titanates: CaTiO3, Ca4Ti3O10, and Ca3Ti2O7

The chemical potentials of CaO in two-phase fields (TiO₂ + CaTiO₃), (CaTiO₃ + Ca₄Ti₃O₁₀), and (Ca₄Ti₃O₁₀ + Ca₃Ti₂O₇) of the pseudo-binary system (CaO + TiO₂) have been measured in the temperature range (900 to 1250) K, relative to pure CaO as the reference state, using solid-state galvanic cells incorporating single crystal CaF₂ as the solid electrolyte. The cells were operated under pure oxygen at ambient pressure. The standard Gibbs free energies of formation of calcium titanates, CaTiO₃, Ca₄Ti₃O₁₀, and Ca₃Ti₂O₇, from their component binary oxides were derived from the reversible e.m.f.s. The results can be summarised by the following equations: CaO(solid) + TiO₂(solid) → CaTiO₃(solid), ΔG° ± 85/(J · mol^?1) = ?80,140 ? 6.302(T/K); 4CaO(solid) + 3TiO₂(solid) → Ca₄Ti₃O₁₀(solid), ΔG° ± 275/(J · mol^?1) = ?243,473 ? 25.758(T/K); 3CaO(solid) + 2TiO₂(solid) → Ca₃Ti₂O₇(solid), ΔG° ± 185/(J · mol^?1) = ?164,217 ? 16.838(T/K).The reference state for solid TiO₂ is the rutile form. The results of this study are in good agreement with thermodynamic data for CaTiO₃ reported in the literature. For Ca₄Ti₃O₁₀ Gibbs free energy of formation obtained in this study differs significantly from that reported by Taylor and Schmalzried at T = 873 K. For Ca₃Ti₂O₇ experimental measurements are not available in the literature for direct comparison with the results obtained in this study. Nevertheless, the standard entropy for Ca₃Ti₂O₇ at T = 298.15 K estimated from the results of this study using the Neumann–Koop rule is in fair agreement with the value obtained from low-temperature heat capacity measurements.     

Adsorption characteristics of malachite green dye onto novel kappa-carrageenan-g-polyacrylic acid/TiO2–NH2 hydrogel nanocomposite

Batch adsorption experiments were carried out for the removal of malachite green (MG) cationic dye from aqueous solution using novel hydrogel nanocomposite that was prepared by graft copolymerization of acrylic acid (AA) onto kappa-carrageenan (κC) biopolymer in the presence of a crosslinking agent, a free radical initiator and aminosilica-functionalized TiO₂ nanoparticles (κC-g-PAA/TiO₂–NH₂). The factors influencing adsorption capacity of the adsorbents such as initial pH value (pH₀) of the dye solutions, TiO₂–NH₂ content (wt%), initial concentration of the dye, amount of adsorbents, and temperature were investigated. The adsorption capacity of hydrogel nanocomposite for MG was compared with hydrogel. The adsorption behaviors of both adsorbents showed that the adsorption kinetics and isotherms were in good agreement with a pseudo-second-order equation and the Langmuir equation. The high adsorption capacity (q _m= 666–833 (mg/g)) and the favorable heterogeneity factor (n = 1.2–1.5) calculated from isotherm equations show the efficiency of the novel adsorbents.     

Microstructure,stability and biocompatibility of hydroxyapatite – titania nanocomposites formed by two step sintering process

In the present work, we report the characterization of TiO₂-hydroxyapatite (HA) nanocomposites obtained by a two-step sintering (TSS) process of a mixture of HA and titanium hydride (TiH₂) powders. The reactions underwent by TiH₂ in the presence of HA and hydrogen release, and subsequently, titanium oxidation was examined by thermal analysis. A longer holding time in the second sintering stage enabled obtaining a homogenous TiO₂-HA (36% rutile) composite with a thermal expansion coefficient of 11.46 · 10⁻⁶ C⁻¹ in the 40–1000 °C range. Unconventional TSS process hinders HA decomposition to detrimental tricalcium phosphate (TCP). Wear rate of ceramics was determined by tribological measurements and the material biocompatibility was evaluated using MTT assay. Overall, cell viability results correlated with morphological observations indicated a good biocompatibility of HA-based composites at all tested concentrations. Incorporation of the TiO₂ phase in HA by TSS process was found to be an efficient way to prepare bioceramics with improved performances.     

Sustainable fabrication of silver-titania nanocomposites using goji berry (Lycium barbarum L.) fruit extract and their photocatalytic and antibacterial applications

Silver-titania nanocomposites (Ag-TiO₂ NCs) have unique functional attributes due to their photocatalytic and antibacterial properties. In this study, titania nanoparticles (TiO₂-NPs) were successfully in-situ decorated with silver nanoparticles (Ag-NPs) using the aqueous extract of goji berries (Lycium barbarum L.) as a bioreducing and stabilizing agent. Different Ag-TiO₂ NCs were synthesized by treating different concentrations of silver nitrate with a specific concentration of TiO₂-NPs in the presence of fruit extract. The green-synthesized NCs were characterized using several techniques viz., ultraviolet–visible spectrophotometry, X-ray diffractometry (XRD), scanning electron microscopy, field-emission transmission electron microscopy (FE-TEM), Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. XRD analysis revealed the formation of face-centered cubic (fcc) crystals, and FE-TEM analysis revealed the embedment of Ag-NPs throughout the surface of TiO₂-NPs. The average size of Ag-NPs on TiO₂-NPs increased from 11.2 ± 3.05 nm to 16.4 ± 4.5 nm with an increase in the concentration of silver ions, and the morphology of Ag-NPs was predominantly quasi-spherical and hexagonal. These NCs exhibited an excellent photocatalytic degradation of an azo dye, methylene blue (MB). The synthesized Ag-TiO₂ NCs (3:1) showed higher photocatalytic degradation efficiency of ∼ 93.4% for MB in 130 min under visible light irradiation. Ag-TiO₂ NC_S also exhibited good antibacterial activities towards Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). Therefore, the formation of Ag-NPs on the surface of TiO₂-NPs to form Ag-TiO₂ NCs exhibits eco-friendly photocatalytic degradation of azo dye contaminants as well as antibacterial activity.     

Au-TiO2/Chit modified sensor for electrochemical detection of trace organophosphates insecticides

In this paper, Au–TiO₂/Chit modified electrode was prepared with Au–TiO₂ nanocomposite (Au–TiO₂) and Chitosan (Chit) as a conjunct. The Au–TiO₂ nanocomposite and the films were characterized by electrochemical and spectroscopy methods. A set of experimental conditions was also optimized for the film's fabrication. The electrochemical and electrocatalytic behaviors of Au–TiO₂/Chit modified electrode to trace organophosphates (OPs) insecticides such as parathion were discussed in this work. By differential pulse voltammetry (DPV) measurement, the current responses of Au–TiO₂/Chit modified electrode were linear with parathion concentration ranging from 1.0 ng/ml to 7.0 × 10³ ng/ml with the detection limit of 0.5 ng/ml. In order to evaluate the performance of the detection system, we also examined the real samples successfully in this work. It exhibited a sensitive, rapid and easy-to-use method for the fast determination of trace OPs insecticides.     

Electrodeposition and characterization of Cu-TiO2 nanocomposite coatings

Cu-TiO₂ nanocomposites were prepared by electrodeposition method onto copper substrate using an acid copper plating bath containing dispersed nanosized TiO₂. The composition of codeposited TiO₂ nanoparticles in the composite coatings was controlled by the addition of different concentrations of TiO₂ nanoparticles in the bath solution. The average crystallite size was calculated by using X-ray diffraction analysis and it was ~32 nm for electrodeposited copper and ~33 nm for Cu-TiO₂ composite coatings. The crystallite structure was fcc for electrodeposited copper and Cu-TiO₂ nanocomposite coatings. The surface morphology and composition of the nanocomposites were examined by scanning electron microscopy and energy dispersive X-ray spectroscopy analysis. The effect of TiO₂ content on the corrosion and wear resistance properties of the nanocomposite coatings was also presented. The codeposited TiO₂ nanoparticles in the deposit increased the corrosion and wear resistance, which were closely related with TiO₂ content in the nanocomposites. The wear resistance and microhardness of the Cu-TiO₂ nanocomposite coatings were higher than electrodeposited copper. The corrosion resistance property of the electrodeposited copper and Cu-TiO₂ nanocomposite coatings was evaluated by electrochemical impedance and Tafel polarization studies. Cu-TiO₂ composite coatings were more corrosion resistant than electrodeposited copper.     

CoFe2O4@Methylcellulose/AC as a New,Green, and Eco-friendly Nano-magnetic adsorbent for removal of Reactive Red 198 from aqueous solution

Methylcellulose (MC) is the most common commercial cellulose ether and the most attractive biopolymer due to its cheap cost of biodegradability, biocompatibility, hydrophilicity, and lack of toxicity. In this study, CoFe₂O₄@MC/activated carbon (AC) was synthesized as a unique magnetic nano-adsorbent in the presence of MC biopolymer for Reactive Red 198 (RR198) dye removal. The nano-magnetic adsorbent was characterized by FESEM (Field emission scanning electron microscopy), EDS (Energy-dispersive X-ray spectroscopy), Mapping, Linescan, BET (Brunauer–Emmett–Teller), FTIR (Fourier Transform Infrared Spectroscopy), XRD (X-Ray Diffraction), and VSM (Vibrating-Sample magnetometer). For simple separation by external magnetic fields, the Ms value was 57.91 emu/g. According to XRD analysis, the nano-adsorbent maintains its crystal structure, with an average crystal size of 11 nm. The maximum removal efficiencies of RR198 for synthetic and real wastewater samples under optimal conditions (an initial concentration of 10 mg/L, pH 3, contact time of 10 min, nanocomposite dose of 1.5 g/L, and a temperature of 25 °C) were 92.2% and 78%, respectively. The adsorption experiments were fitted well with the Freundlich isotherm (R² = 0.989) and pseudo-second-order kinetic (R² = 0.995). The values of entropy changes (ΔS = 35.087 kJ/mol.k), enthalpy changes (ΔH = -9.862 kJ/mol), and negative Gibbs free energy changes (ΔG) showed that the adsorption process was exothermic. Finally, the reusability findings showed that after six recovery cycles, the efficiency decreased slightly (90.1%). In the end, it can be concluded that the prepared CoFe₂O₄@Methylcellulose/AC can be used as an efficient adsorbent for the removal of RR198 from an aqueous solution.     

Fabrication,characterization, and performance evaluation of polyethersulfone/TiO2 nanocomposite ultrafiltration membranes for produced water treatment

In the present work, development of neat and nanocomposite polyethersulfone membranes composed of TiO₂ nanoparticles is presented. Membranes are fabricated using nonsolvent phase inversion process with the objective of improving antifouling, hydrophilicity, and mechanical properties for real and synthetic produced water treatment. Membranes are characterized using scanning electron microscopy, Fourier‐transform infrared, contact angle, porosity measurement, compaction factor, nanoparticles stability, and mechanical strength. The performance of prepared membranes was also characterized using flux measurement and oil rejection. Fourier‐transform infrared spectra indicated that noncovalence bond formed between Ti and polyethersulfone chains. The contact angle results confirmed the improved hydrophilicity of nanocomposite membranes upon addition of TiO₂ nanoparticles owing to the strong interactions between fillers and water molecules. The increased water flux for nanocomposite membranes in comparison with neat ones can be due to coupling effects of improved surface hydrophilicity, higher porosity, and formation of macrovoids in the membrane structure. The membrane containing 7 wt% of TiO₂ nanoparticles was the best nanocomposite membrane because of its high oil rejection, water flux, antifouling properties, and mechanical stability. The pure water flux for this membrane was twice greater than that of neat membrane without any loss in oil rejection. The hydrophilicity and antifouling resistance against oil nominates developed nanocomposite membranes for real and synthetic produced water treatment applications with high performance and extended life span.     

Semiconducting and quartz microbalance (QCM) humidity sensor properties of TiO2 by sol gel calcination method

Titanium dioxide (TiO₂) material was synthesized using the sol gel calcination method. The structural properties of the TiO₂ semiconductor were investigated by atomic force microscopy. The electrical conductivity of the TiO₂ was measured as a function of temperature and TiO₂ exhibits a conductivity of 2.55 × 10⁻⁶ S/m at room temperature with activation energy of 104 meV. The electrical conductivity of the TiO₂ at room temperature is higher than that of nanocrystalline TiO₂ (3 × 10⁻⁷ S/m) and TiO₂ thin film in air (5 × 10⁻⁹ S/m) and in vacuum (8.8 × 10⁻¹⁰ S/m). It was found that the electrical transport mechanism of the TiO₂ is controlled by thermally activated mechanism. The optical band gap of the TiO₂ powder sample was determined to be 3.17 eV, which is good in agreement with the bulk TiO₂ (E_g = 3.2 eV). Up to our knowledge, there is no any reported data about the band gap of TiO₂ nanopowder based on the diffused reflectance calculation. Quartz crystal microbalance (QCM) TiO₂ humidity sensor was prepared. The sensor indicates a large frequency change with an interaction occurred between TiO₂ and humidity molecules. The sensor exhibits a good repeatability when it was exposed to the moist air of 65% RH.     

Effect of calcination temperature on the microstructure of porous TiO<Subscript>2</Subscript> film

To obtain porous TiO₂ film, the precursor sol was prepared by hydrolysis of Ti isopropoxide and then complexed with trehalose dihydrate. The porous TiO₂ film was fabricated by the dip-coating technique on glass substrates using this solution. The TiO₂ film was calcined at 500 °C. The maximum thickness of the film from one-run dip-coating was ca. 740 nm. The film was composed of nanosized particle and pores. The porosity of the TiO₂ film was increased by addition of trehalose dihydrate to the sol. The porous TiO₂ films were calcined at different temperatures. The effects of calcination temperature on the microstructure of the porous TiO₂ film were investigated. The porous film prepared from sol containing trehalose still kept the porous structure after calcination at 950 °C. The phase transition temperature of the film from anatase to rutile was shifted from 650 to 700 °C by addition of trehalose to the sol.