Fabrication and characterization of nano TiO2 thin films at low temperature

Anatase TiO₂ thin films were successfully prepared on glass slide substrates via a sol–gel method from refluxed sol (RS) containing anatase TiO₂ crystals at low temperature of 100 °C. The influences of various refluxing time on crystallinity, morphology and size of the RS sol and dried TiO₂ films particles were discussed. These samples were characterized by infrared absorption spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission-scanning electron microscopy (FE-SEM) and UV–vis absorption spectroscopy (UV–vis). The photocatalytic activities of the TiO₂ thin films were assessed by the degradation of methyl orange in aqueous solution. The results indicated that titania films thus obtained were transparent and their maximal light transmittance exceeded 80% under visible light region. The TiO₂ thin films prepared from RS-6 sol showed the highest photocatalytic activity, when the calcination temperature is higher than 300 °C. The degradation of methyl orange of RS-6 thin films reached 99% after irradiated for 120 min, the results suggested that the TiO₂ thin films prepared from RS sol exhibited high photoactivities.     

Photocatalytic degradation of gaseous toluene over TiO2–SiO2 composite nanotubes synthesized by sol–gel with template technique

TiO₂–SiO₂ composite nanotubes were successfully synthesized by a facile sol–gel technique utilizing ZnO nanowires as template. The nanotubes were well characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, N₂ adsorption–desorption analysis and UV–vis diffuse reflectance spectroscopy. The nanotubular TiO₂–SiO₂ composite photocatalysts showed diameter of 300–325 nm, fine mesoporous structure and high specific surface area. The results indicated that the degradation efficiency of gaseous toluene could get 65% after 4 h reaction using the TiO₂–SiO₂ composite as the photocatalyst under UV light illumination, which was higher than that of P25.     

Study on activities of vanadium (IV/V) doped TiO2(R) nanorods induced by UV and visible light

Vanadium (IV/V) doped rutile TiO₂ naonorods had been successfully synthesized through a single step hydrothermal method. The photocatalyst was characterized by transmission electron microscopy (TEM), selected area electron diffraction (SAED), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), UV–vis diffusive reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). The results showed that the doping of V ions had significant influence on the band gap energy and the surface state of TiO₂. The photo-activities of the new catalysts were investigated under ultraviolet (UV) and visible light. The UV-photocatalytic activity of the as-prepared catalysts was hardly influenced by doping V ions; while under visible light, the samples with 1 wt% and 0.1 wt% V exhibited enhanced activity to the oxidation of methylene blue (MB) and the reduction of Cr (VI), respectively.     

Preparation and properties of sliver and nitrogen co-doped TiO2 photocatalyst

TiO₂ photocatalysts co-doped with different content of Ag and N were prepared by sol–gel method combined with microwave chemical method. The samples were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), ultraviolet–visible diffuse reflectance spectrum (UV–vis) and photo-luminescence emission spectrum (PL). The photocatalytic activity was investigated by photocatalytic degradation of methylene blue (MB) under irradiation of fluorescent lamp. The results indicate that Ag and N co-doping can restrain the increase of grain size, broaden the absorption spectrum to visible light region, and inhibit the recombination of the photo-generated electron–hole pairs. Moreover, the photocatalytic activity of Ag–N–TiO₂ in MB degradation is remarkable improved. The degradation rate of the sample with Ag:TiO₂ = 0.05 at%, N:TiO₂ = 18.50 wt% in 5 h is 93.44%, which is much higher than that of Degussa P25 (39.40%).     

Effect of NaHCO3 on synthesis of anatase TiO2 nanopowders by thermal processing of the precursor

Titanium dioxide (TiO₂) nanopowders were successfully prepared by thermal processing of the precursor of titanium hydroxide, urea and sodium acid carbonate (NaHCO₃). The products were characterized by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The results show that NaHCO₃ has a certain effect on the average crystallite size and dispersity of TiO₂ nanopowders, at the same time other phases (Na₂SO₄ and Na₂CO₃) will be introduced. However, Na₂SO₄ has distinctive intercalation ability and catalytic activity. TiO₂ (anatase) powders can be prepared at ?600 °C for 2 h with addition of 2–10 wt% NaHCO₃, and the average crystallite size is 20.0–22.3 nm. The surface of the sample mainly consists of Ti, O, C, Na and S five species elements.     

Simple synthesis of MoS2 inorganic fullerene-like nanomaterials from MoS2 amorphous nanoparticles

The amorphous MoS₂ nanoparticles have been synthesized by a simple oxidation–reduction reaction in an aqueous solution. A series of products with different morphologies, such as MoS₂ nanospheres, inorganic fullerene-like nanospheres, nanorods and Mo bended rods, can be obtained by annealing the amorphous MoS₂ nanoparticles under N₂ atmosphere under 400–1200 °C. These products have been characterized by X-ray diffraction, field emission scanning electronic microscopy, transmission electron microscopy and high-resolution transmission electron microscopy in detail. The possible transformation mechanism for the structure has been discussed based on the experimental results. In addition, the optical properties of IF-MoS₂ have also been performed by UV–vis absorption spectroscopy.     

Controllable fabrication of hollow TiO2 spheres as sustained release drug carrier

TiO₂ hollow spheres with controllable size were successfully synthesized through a hydrothermal silica etching method; SiO₂ cores were easily removed without the use of a toxic reagent. The parameters for the synthesis of SiO₂ cores and TiO₂ hollow spheres, including stirring time, ammonia concentration, tetrabutyl titanate content, hydrothermal time, and reflux time, were systematically investigated. SiO₂ cores and TiO₂ hollow structure were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectra (EDX), X-ray photoelectron spectroscopy (XPS), and N₂ adsorption-desorption isotherms. The results revealed that the mean diameter of SiO₂ was ∼280 nm when the concentration of ammonia was 4.8 M and the stirring time was 0.5 h. For hollow TiO₂, when the operation process was optimized (ammonia volume 0.35 mL, TBOT addition 1.5 mL, hydrothermal time 3 h, and reflux time 3 h), the average size and the shell thickness were 270 and 100 nm, respectively. The process exhibited a high drug loading capacity (33.12 ± 0.01%) and encapsulation rate (99.03 ± 0.24%) due to its high specific surface area of 121.62 m²·g⁻¹. In addition, TiO₂ hollow spheres displayed pH-responsive sustained-controlled drug release behavior in vitro which released 80% of doxorubicin at 5.0 pH within 120 h, its release kinetic showed that it fits well with Zero-order kinetic equation, demonstrating that DOX·HCl/hollow TiO₂ maintains constant release rate, and the investigation of blood compatibility showed that the hemolysis rate of hollow TiO₂ did not exceed 3% in the concentration range of 100 and 4000 μg/mL, further confirming that prepared hollow TiO₂ is a relatively safe medical inorganic material.     

Synthesis and photocatalytic activity of N-doped TiO2/ZrO2 visible-light photocatalysts

Visible-light responsive N-doped ZrO₂/TiO₂ photocatalysts were synthesized via a sol–gel process. To obtain the optimum nitrogen doping content and operational conditions for photodegradation of NO, several key factors (including nitrogen doping, initial NO concentration, light intensity, reactor temperature, etc.) were investigated under both UV and visible light irradiation. Physical characterization of the photocatalysts was performed using X-ray diffraction (XRD), UV–visible absorption spectroscopy, transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR). The observed results suggest that nitrogen was doped in the lattice of TiO₂ and had an effect on the translation of phase, photodegradation activity, and visible-light response. Among synthesized photocatalysts, 0.1 M Zr and 0.15 M N supported on TiO₂ exhibited the best visible-light response and the highest NO photodegradation activity.     

Nb2O5 hollow nanospheres as anode material for enhanced performance in lithium ion batteries

Nb₂O₅ hollow nanospheres of average diameter ca. ～29 nm and hollow cavity size ca. 17 nm were synthesized using polymeric micelles with core–shell–corona architecture under mild conditions. The hollow particles were thoroughly characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), infrared spectroscopy (FTIR), thermal (TG/DTA) and nitrogen adsorption analyses. Thus obtained Nb₂O₅ hollow nanospheres were investigated as anode materials for lithium ion rechargeable batteries for the first time. The nanostructured electrode delivers high capacity of 172 mAh g^?1 after 250 cycles of charge/discharge at a rate of 0.5 C. More importantly, the hollow particles based electrodes maintains the structural integrity and excellent cycling stability even after exposing to high current density 6.25 A g^?1. The enhanced electrochemical behavior is ascribed to hollow cavity coupled with nanosized Nb₂O₅ shell domain that facilitates fast lithium intercalation/deintercalation kinetics.     

Experimental study on synthesizing TiO2 nanotube/polyaniline (PANI) nanocomposites and their thermoelectric and photosensitive property characterization

In this paper, TiO₂ nanotube/polyaniline (PANI) nanocomposites were made. The thermoelectric and photosensitive properties of the nanocomposites were studied. The effects of processing time, voltage, concentration of F^? ions and H₃PO₄ on the formation of TiO₂ nanotubes were investigated. The morphologies of the synthesized nanocomposites were revealed by scanning electron microscopy (SEM). The formation of polyaniline was confirmed by both Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). The optimum conditions for the formation of well-organized TiO₂ nanotubes are at 20 V for 60 min in the electrolyte containing 0.2 M fluorine ions. The highest absolute value of the Seebeck coefficient for the TiO₂ nanotube/polyaniline nanocomposites is 124 μV/K at 30 °C. Pure Ti foil does not show photosensitive property, while the TiO₂ nanotubes have strong photosensitivity.     

Poly(hydroxyethyl methacrylate-co-methacryloylamidotryptophane) nanospheres and their utilization as affinity adsorbents for porcine pancreas lipase adsorption

Novel nanospheres with an average size of 350 nm utilizing N-methacryloyl-(l)-tryptophane methyl ester (MATrp) as a hydrophobic monomer were prepared by surfactant free emulsion polymerization of 2-hydroxyethyl methacrylate (HEMA), (MATrp) conducted in an aqueous dispersion medium. MATrp was synthesized using methacryloyl chloride and (l)-tryptophane methyl ester. Specific surface area of the non-porous nanospheres was found to be 1902.3 m²/g. poly(HEMA–MATrp) nanospheres were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and scanning electron microscopy (SEM). Average particle size and size distribution measurements were also performed. Elemental analysis of MATrp for nitrogen was estimated at 1.36 mmol/g nanospheres. Then, poly(HEMA–MATrp) nanospheres were used in the adsorption of porcine pancreas lipase in a batch system. Using an optimized adsorption protocol, a very high loading of 558 mg enzyme/g nanospheres was obtained. The adsorption phenomena appeared to follow a typical Langmuir isotherm. The K_m value for immobilized lipase (16.26 mM) was higher than that of free enzyme (10.34 mM). It was observed that enzyme could be repeatedly adsorbed and desorbed without significant loss in adsorption amount or enzyme activity. These findings show considerable promise for this material as an adsorption matrix in industrial processes.     

Low temperature synthesis of high quality carbon nanospheres through the chemical reactions between calcium carbide and oxalic acid

Carbon nanospheres (CNSs) were synthesized through the chemical reactions of calcium carbide and oxalic acid without using catalysts. The chemical reactions were carried out in a sealed stainless steel pressure vessel with various molar ratios at temperatures of 65–250 °C. The synthesized CNSs have been characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) attached to the SEM, transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The total yield of carbonaceous materials relative to the starting material is about 4% (w/w). SEM and TEM results reveal that the percentage of CNSs is high (>95%). The CNSs that have been synthesized are roe-like spheres of relatively uniform size with diameters of 60–120 nm. The attached EDS result shows that the carbon content of CNSs reaches up to 98%.     

Combustion synthesized TiO2 for enhanced photocatalytic activity under the direct sunlight-optimization of titanylnitrate synthesis

Optimized synthesis of Ti-precursor ‘titanylnitrate’ for one step combustion synthesis of N- and C-doped TiO₂ catalysts were reported and characterized by using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), diffused reflectance UV–vis spectroscopy, N₂ adsorption and X-ray photoelectron spectroscopy (XPS). XRD confirmed the formation of TiO₂ anatase and nano-crystallite size which was further confirmed by TEM. UV-DRS confirmed the decrease in the band gap to less than 3.0 eV, which was assigned due to the presence of C and N in the framework of TiO₂ as confirmed by X-ray photoelectron spectroscopy. Degradation of methylene blue in aqueous solution under the direct sunlight was carried out and typical results indicated the better performance of the synthesized catalysts than Degussa P-25.     

Effects of ZrO2 addition on phase stability and photocatalytic activity of ZrO2/TiO2 nanoparticles

ZrO₂/TiO₂ nanoparticles with various Zr/Ti ratios (0–0.9) were prepared by a polymer complex solution method (PCSM). The prepared samples were characterized using transmission electron microscopy (TEM), the Brunauer, Emmett & Teller (BET) method, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The ZrO₂/TiO₂ photocatalyst showed a high specific area and small crystal size. The XRD pattern for the Zr/Ti = 0.1 sample indicated that the addition of ZrO₂ stabilized the anatase phase of TiO₂ up to 800 °C. The photocatalytic activity of Zr/Ti = 0.1 sample was higher than that of the TiO₂ sample and commercially available Degussa P25. The high photocatalytic activity can be attributed to stronger adsorption in the visible light region, higher specific area, smaller crystal size and increased surface OH groups.     

A novel protocol to design TiO2-Fe2O3 hybrids with effective charge separation efficiency for improved photocatalysis

TiO₂-based heterogeneous photocatalysis has been widely considered as a promising technique for decontamination of water. Herein the hybrid of TiO₂ nanocrystals decorated Fe₂O₃ nanoparticles was successfully synthesized via a mild hydrothermal method, derived from favorable titanium glycolate and water-soluble Fe^II salt precursors. The composition and structure of the as-synthesized TiO₂-Fe₂O₃ hybrids were characterized by Powder X-ray diffraction (XRD), EDX mapping, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The photocatalytic activity was evaluated by the decomposition of Rhodamine B in an aqueous solution under visible-light (λ > 420 nm). The results show that the TiO₂-Fe₂O₃ nanocomposite exhibits superior photocatalytic capability to the bare ones upon Rhodamine B degradation, owing to promoted photo-induced electrons and holes separation and migration on the basis of photoluminescence spectra, photocurrent measurements, and electrochemical impedance (EIS) spectroscopy.     

Microstructural,chemical and textural characterization of ZnO nanorods synthesized by aerosol assisted chemical vapor deposition

ZnO nanorods were synthesized by aerosol assisted chemical vapor deposition onto TiO₂ covered borosilicate glass substrates. Deposition parameters were optimized and kept constant. Solely the effect of different nozzle velocities on the growth of ZnO nanorods was evaluated in order to develop a dense and uniform structure. The crystalline structure was characterized by conventional X-ray diffraction in grazing incidence and Bragg–Brentano configurations. In addition, two-dimensional grazing incidence synchrotron radiation diffraction was employed to determine the preferred growth direction of the nanorods. Morphology and growth characteristics analyzed by electron microscopy were correlated with diffraction outcomes. Chemical composition was established by X-ray photoelectron spectroscopy. X-ray diffraction results and X-ray photoelectron spectroscopy showed the presence of wurtzite ZnO and anatase TiO₂ phases. Morphological changes noticed when the deposition velocity was lowered to the minimum, indicated the formation of relatively vertically oriented nanorods evenly distributed onto the TiO₂ buffer film. By coupling two-dimensional X-ray diffraction and computational modeling with ANAELU it was proved that a successful texture determination was achieved and confirmed by scanning electron microscopy analysis. Texture analysis led to the conclusion of a preferred growth direction in [001] having a distribution width Ω = 20° ± 2°.     

Effect of Na2SiO3 on synthesis of TiO2 nanopowders by thermal processing of the precursor

TiO₂ nanopowders could be prepared by thermal processing of the precursor of titanium hydroxide, urea and Na₂SiO₃. The powders were characterized by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The results show that Na₂SiO₃ has an important effect on the average crystallite size and dispersity of TiO₂ nanopowders, and other phases (Na₂SO₄ and SiO₂) will be introduced. However, Na₂SO₄ has distinctive intercalation ability and catalytic activity; SiO₂ coating layers can effectively inhibit the agglomeration of TiO₂ nanopowders. TiO₂ (anatase) powders with well dispersity can be prepared at ～600 °C for 2 h with addition of 2–6 wt.% Na₂SiO₃, and the average crystallite size is 15.5–22.1 nm. The surface of the sample mainly consists of Ti, O, C, Si, Na and S six species elements.     

Adsorption and photocatalysis of nanocrystalline TiO2 particles prepared by sol–gel method for methylene blue degradation

Titanium dioxide (TiO₂) powders were synthesized by using TiO₂ colloidal sol prepared from titanium-tetraisopropoxide (TTIP) and used as a starting material by applying the sol–gel method. The effect of aging times and temperatures on physical and chemical properties of TiO₂ sol particles was systematically investigated. The results showed that the crystallinity and average particle size of TiO₂ can be successfully controlled by adjusting the aging time and temperature. The samples after calcination of TiO₂ powders were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and nitrogen adsorption measurements. In addition, the photocatalytic activity of synthesized TiO₂ powders was evaluated by studying the degradation of 10 ppm aqueous methylene blue dye under 32 W high pressure mercury vapor lamp with 100 mg of TiO₂ powders. The highest photocatalytic activity was observed in TiO₂ powder synthesized at 90 °C for 0 h attributed to the presence of anatase and rutile phases in an 80:20 ratio.     

Synthesis and characterization of MFe2O4 (M = Mg,Mn, Ni) nanoparticles

MFe₂O₄ nanoparticles were obtained in the presence of natural compounds as carboxymethylcellulose (CMC). The CMC polymer had a double function as a capping agent and as a protecting agent in the growth process of nanoparticles. The synthesized nanoparticles were characterized using thermal analysis (TG, DTA, DTG), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and a vibrating sample magnetometer (VSM). The XRD patterns indicate that all the samples were formed in single phase spinel structure. The results also show that the samples calcinated at 500 °C for 6 h have the best crystallinity and the calculated crystallite size was in the range of 6–13 nm. The thermal analysis and FTIR spectra indicate a core–shell structure of the MFe₂O₄ nanoparticles obtained.     

Synthesis and characterization of rice grains like Nitrogen-doped TiO2 nanostructures by electrospinning–photocatalysis

Rice grain-shaped Nitrogen-doped titanium dioxide (N–TiO₂) nano/mesostructures were fabricated through a combination of sol–gel and electrospinning methods. As-spun nanofibers were continuous and upon thermal treatment at 500° C for 1 h in air, the continuous fibers break into rice grain-shaped TiO₂ nanostructures of average diameter 50–80 nm. The nanostructures were characterized by spectroscopy, microscopy and powder X-ray diffraction. The rice grains consist of spherical particles of average diameter of ~ 18 nm and with N doping, their average diameters decrease from ~ 18 to ~ 12 nm. The presence of N in the TiO₂ lattice was confirmed by X-ray photoelectron spectroscopy (XPS). The band-gap of TiO₂ reduced from 3.19 eV to 2.83 eV upon increasing doping level of N from 0% to 5% (w/w), respectively. The N–TiO₂ rice grains showed an enhanced UV light-assisted photocatalysis compared to pure TiO₂ in the photodegradation of Alizarin Red S dye, an industrially important anthraquinone dye.