Pure TiO2 Nanoparticles Research Articles

Performance of Caesalpinia sappan heartwood extract as photo sensitizer for dye sensitized solar cells

A natural dye extracted from Caesalpinia sappan heartwood was used as photo sensitizer for the first time to fabricate titanium dioxide (TiO2) nanoparticles based dye sensitized solar cells. Brazilin and brazilein are the major pigments present in the natural dye and their optimized molecular structure were calculated using Density functional theory (DFT) at 6-31G (d) level. The HOMO–LUMO were performed to reveal the energy gap using optimized structure. Pure TiO2 nanoparticles in anatase phase were synthesized by sol–gel technique. The pure and natural dye sensitized TiO2 nanoparticles were subjected to structural, optical, spectral and morphological studies. Low cost and environment friendly dye sensitized solar cells were fabricated using natural dye sensitized TiO2 based photo anode. The solar light to electron conversion efficiency of Caesalpinia sappan heartwood extract sensitized dye sensitized solar cell is 1.1%.

Fe-TiO<sub>2</sub> Nanoparticles by Hydrothermal Treatment with Photocatalytic Activity Enhancement

Fe-TiO2 nanoparticles with 5-9 nm sizes were prepared by sol gel method subsequently subjected to hydrothermal treatment at 150°C for 6 h. Titanium (IV) isopropoxide and iron (III) nitrate nonahydrate were used as precursor. The morphology, structure and composition of the Fe-TiO2 were investigated by X-ray diffraction (XRD), Transmission emission microscopy (TEM) and UV-vis spectroscopy (UV-vis). XRD analysis revealed the prepared samples was dominated with anatase phase and a trace of brookite phase. The TiO2 crystallite size was reduced as Fe content was increased. Compared with the pure TiO2 nanoparticles, the Fe-TiO2 nanoparticles exhibited higher photocatalytic activity in decolorizing methyl orange into non-toxic inorganic products under UV irradiation.

Hydrothermal synthesis of TiO2–RGO composites and their improved photocatalytic activity in visible light

Composites of titanium dioxide–reduced graphene oxide (TiO2–RGO) have been prepared via an efficient and facile hydrothermal reaction of graphene oxide and Ti(OH)4 in a ethanol–water solvent. The structure and composition of the composites have been characterized by X-ray diffraction, Scanning electron microscopy, Brunauer–Emmett–Teller specific area analysis, X-ray photoelectron spectroscopy and ultraviolet-visible diffuse reflectance spectroscopy. The results showed that the TiO2–RGO composites exhibited a layered structure with well-dispersed anatase TiO2 on the surface of the reduced graphene oxide. Compared with the pure TiO2 nanoparticles, the composites had larger surface area, and extended the photoresponse range to the visible light region. The photocatalytic activity of the composites was much higher than that of TiO2 in the photodegradation of methyl orange (MO) under visible light irradiation.

Sonocatalytic removal of an organic dye using TiO2/Montmorillonite nanocomposite

The sonocatalytic performance of the synthesized TiO2/Montmorillonite K10 (TiO2/MMT) nanocomposite was studied in removal of Basic Blue 3 (BB3) from water. The TiO2/MMT nanocomposite was prepared by hydrothermal method. Scanning electron microscope, X-ray diffraction and Fourier transform infrared were used to characterize the synthesized nanocomposite. The average size of TiO2 nanoparticles decreased from 60–80nm to 40–60nm through the immobilization of this semiconductor on the surface of MMT. The obtained results indicated that the sonocatalytic activity of TiO2/MMT nanocomposite was higher than that of pure TiO2 nanoparticles and MMT particles. Furthermore, the main influence factors on the sonocatalytic activity such as the BB3 concentration, pH of solution, TiO2/MMT dose, power of ultrasonic generator, and inorganic salts were studied. The intermediates of BB3 degradation during the sonocatalytic process in the presence of the TiO2/MMT nanocomposite have been monitored by gas chromatography–mass spectrometry.

Oxygen defect assisted paramagnetic to ferromagnetic conversion in Fe doped TiO2nanoparticles

Here we report the magnetic properties of Fe doped TiO2 nanoparticles annealed in air and vacuum. Fe doped TiO2 nanoparticles display paramagnetism during air annealing and ferromagnetism when the samples are annealed under vacuum. Ferromagnetism in vacuum annealed pure TiO2 nanoparticles is because of the presence of a high density of paramagnetic oxygen vacancy centers. Ferromagnetism in vacuum annealed Fe doped TiO2 is because of the strong exchange interaction of lattice site Fe3+ ions with the nearest paramagnetic oxygen vacancies by forming bound magnetic polarons (BMPs). A collective contribution of the magnetic moment from the bound magnetic polaron on the lattice site and from the paramagnetic oxygen vacancies on the surface and on the grain boundary results in the conversion of paramagnetism to ferromagnetism in vacuum annealed Fe doped TiO2.

Effect of nanostructured TiO₂ crystal phase on photoinduced apoptosis of breast cancer epithelial cells.

PurposeThe use of nanoparticles has seen exponential growth in the area of health care, due to the unique physicochemical properties of nanomaterials that make them desirable for medical applications. The aim of this study was to examine the effects of crystal phase-nanostructured titanium dioxide particles on bioactivity/cytotoxicity in breast cancer epithelial cells.Materials and methodsCultured Michigan Cancer Foundation (MCF)-7 and human breast adenocarcinoma (MDA-MB-468) breast cancer epithelial cells were exposed to ultraviolet A light (wavelength 350 nm) for 20 minutes in the presence of aqueous dispersions of two different nanostructured titanium dioxide (TiO2) crystal phases: anatase and an anatase–rutile mixture. Detailed characterization of each titanium dispersion was performed by dynamic light scattering. A 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) colorimetric assay was employed to estimate the percentage of viable cells after each treatment. Western blot analysis of protein expression and characterization, as well as a deoxyribonucleic acid (DNA)-laddering assay, were used to detect cell apoptosis.ResultsOur results documented that 100% anatase TiO2 nanoparticles (110–130 nm) exhibited significantly higher cytotoxicity in the highly malignant MDA-MB-468 cancer cells than anatase– rutile mixtures (75%/25%) with the same size. On the contrary, MCF-7 cells (characterized by low invasive properties) were not considerably affected. Exposure of MDA-MB-468 cells to pure anatase nanoparticles or anatase–rutile mixtures for 48 hours resulted in increased proapoptotic Bax expression, caspase-mediated poly(adenosine diphosphate ribose) polymerase (PARP) cleavage, DNA fragmentation, and programmed cell death/apoptosis.ConclusionThe obtained results indicated that pure anatase TiO2 nanoparticles exhibit superior cytotoxic effects compared to anatase–rutile mixtures of the same size. The molecular mechanism of TiO2 nanoparticle cytotoxicity involved increased Bax expression and caspase-mediated PARP inactivation, thus resulting in DNA fragmentation and cell apoptosis.

Study on crystallinity and morphology controlling of titania using acrylamide gel method and their photocatalytic properties

In this study, polyacrylamide gel method was used for preparation of pure and mixed phase TiO2 nanoparticles. The influence of synthesis conditions on the physicochemical properties of products was investigated. It was found that the type of acid, which was used for acidifying the precursor solution together with calcination temperature can affect the phase structure, crystalline size, morphology and thereby photocatalytic activity of obtained TiO2 nanoparticles. Different trends were observed during the phase transformation, particle growth, shift in energy of band gap with the change in tensile strain to compressive strain of the prepared TiO2 nanomaterial. X-ray diffraction (XRD) showed that prepared nanocrystals, which were calcined at 450°C have pure anatase and anatase–rutile mixed structures. The prepared samples having crystallite size between 5nm and 60nm were observed at different calcination temperatures. In addition, the photocatalytic activities of the prepared samples were evaluated by monitoring the degradation of Cresol Red (CR). The results show that the photocatalyst (TECI), exhibits the highest photocatalytic efficiency where 94.7% of CR can be decomposed after UV exposure for 75min.

Study of niobium and tantalum doped titania-supported Pt electrocatalysts for methanol oxidation and oxygen reduction reactions

Niobium and tantalum doped TiO2 nanoparticles were prepared as catalyst substrates by an improved sol–gel method. Catalysts consisting of 20 wt.% Pt supported on these substrates were synthesised and studied for the methanol oxidation reaction (MOR) and the oxygen reduction reaction (ORR). The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Results indicated that the support materials had an average particle size of 26 nm and that the dopants were evenly distributed in the TiO2. The catalysts were also investigated with a range of electrochemical analyses and benchmarked against pure TiO2 nanoparticles and carbon-supported Pt catalysts with the same composition. The samples showed dramatically better stability than the carbon-supported Pt catalysts in an accelerated degradation test (ADT) under various experimental conditions. The MOR activities of these samples were also increased due to the presence of oxide material substrates, which provide active sites at lower potentials. Thus, the Nb and Ta doped TiO2-supported Pt catalysts were found to be promising methanol oxidation catalysts in terms of their catalytic activity and stability.

Preparation, optical property, and photocatalytic activity of cubic Cu2O/amorphous TiO2 and spheric CuO/TiO2 core–shell nanocomposites

Cu2O/amorphous TiO2 core–shell nanocomposites with uniform cubic structure were prepared by a hydrolysis method and CuO/TiO2 core–shell nanocomposites were obtained by a post-calcination process. The structure and morphology of the products were characterized by powder X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. The results showed that the cubic Cu2O/TiO2 core–shell nanocomposites were of 110–140nm in side length and the as-hydrolyzed TiO2 shell layer was amorphous. The products transformed to quasi-spheric CuO/TiO2 (anatase) nanocomposites after calcination. The visible-light photocatalytic properties of different products towards methyl orange (MO) were investigated. The results showed that the photocatalytic activity of the cubic Cu2O/amorphous TiO2 core–shell nanocomposites was higher than that of pure Cu2O nanocubes, pure TiO2 nanoparticles, and the spheric CuO/TiO2 core–shell nanocomposites.

Anatase-TiO2/CNTs nanocomposite as a superior high-rate anode material for lithium-ion batteries

Anatase-TiO2/carbon nanotubes (CNTs) with robust nanostructure is fabricated via a facile two-step synthesis by ammonia water assisted hydrolysis and subsequent calcination. The as-synthesized nanocomposite was characterized employing X-ray powder diffraction, Fourier transform infrared spectrophotometry, Raman spectrophotometry, thermal gravimetric analysis, transmission electron microscopy, high-resolution transmission electron microscopy and selected area electronic diffraction, and its electrochemical properties as an anode material for lithium-ion batteries (LIBs) were investigated by cyclic voltammetry, galvanostatic discharge/charge test and electrochemical impendence spectroscopy. The results show that the pure anatase TiO2 nanoparticles with diameters of about 10nm are uniformly distributed on/among the CNTs conducting network. The as-synthesized nanocomposite exhibits remarkably improved performances in LIBs, especially super-high rate capability and excellent cycling stability. Specifically, a reversible capacity as high as 92mAhg−1 is achieved even at a current density of 10Ag−1 (60C). After 100 cycles at 0.1Ag−1, it shows good capacity retention of 185mAhg−1 with an outstanding coulombic efficiency up to 99%. Such superior Li+ storage properties demonstrate the reinforced synergistic effects between the nano-sized TiO2 and the interweaved CNTs network, endowing the nanocomposite with great application potential in high-power LIBs.

Synthesis based structural and optical behavior of anatase TiO2 nanoparticles

The effect of synthesis method on optical and photoconducting properties of titanium dioxide (TiO2) nanoparticles has been investigated. Sol–gel and co-precipitation methods have been employed to prepare pure anatase phased TiO2 nanoparticles calcinated at different temperatures below 500°C. The optimized value of average crystallite size is within the range of 19−21nm for a common calcination temperature of 400°C for both the methods. The redshift in optical band gap of 0.9eV has been observed for the sample synthesized by co-precipitation method with respect to the sol–gel method. The photoluminescence spectrum exhibits broad visible emission in both routes of synthesis while photoconductivity shows fast growth and decay of photocurrent in TiO2 prepared by co-precipitation method as compared to TiO2 prepared by the sol–gel method under visible illumination. Crystal structure based Rietveld refinement of X-ray diffraction data, scanning electron microscopy as well as photoluminescence and photoconductivity measurements were performed to characterize nanocrystalline anatase TiO2.

Natural dye extract of lawsonia inermis seed as photo sensitizer for titanium dioxide based dye sensitized solar cells

Natural dye extract of lawsonia inermis seed were used as photo sensitizer to fabricate titanium dioxide nanoparticles based dye sensitized solar cells. Pure titanium dioxide (TiO2) nanoparticles in anatase phase were synthesized by sol–gel technique and pre dye treated TiO2 nanoparticles were synthesized using modified sol–gel technique by mixing lawsone pigment rich natural dye during the synthesis itself. This pre dye treatment with natural dye has yielded colored TiO2 nanoparticles with uniform adsorption of natural dye, reduced agglomeration, less dye aggregation and improved morphology. The pure and pre dye treated TiO2 nanoparticles were subjected to structural, optical, spectral and morphological studies. Dye sensitized solar cells (DSSC) fabricated using the pre dye treated and pure TiO2 nanoparticles sensitized by natural dye extract of lawsonia inermis seed showed a promising solar light to electron conversion efficiency of 1.47% and 1% respectively. The pre dye treated TiO2 based DSSC showed an improved efficiency of 47% when compared to that of conventional DSSC.

Synthesis of TiO2/WO3 nanoparticles via sonochemical approach for the photocatalytic degradation of methylene blue under visible light illumination

Through an ultrasound assisted method, TiO2/WO3 nanoparticles were synthesized at room temperature. The XRD pattern of as-prepared TiO2/WO3 nanoparticles matches well with that of pure monoclinic WO3 and rutile TiO2 nanoparticles. TEM images show that the prepared TiO2/WO3 nanoparticles consist of mixed square and hexagonal shape particles about 8–12nm in diameter. The photocatalytic activity of TiO2/WO3 nanoparticles was tested for the degradation of a wastewater containing methylene blue (MB) under visible light illumination. The TiO2/WO3 nanoparticles exhibits a higher degradation rate constant (6.72×10−4s−1) than bare TiO2 nanoparticles (1.72×10−4s−1) under similar experimental conditions.

The effect of the presence of Ag nanoparticles on the photocatalytic degradation of oxalic acid adsorbed on TiO2 nanoparticles monitored by ATR-FTIR

Photocatalytic degradation of oxalic acid adsorbed on the Ag/P25 TiO2 composite nanoparticle films were investigated using ATR-FTIR technique under UV irradiation. Ag/P25 TiO2 composite nanoparticle films with various Ag content were tested. Topography and chemical structure/composition of the composite nanoparticle films were analyzed by AFM and XPS respectively. It was found that in the degradation reaction of the oxalic acid, the presence of only 2% Ag nanoparticles leads to six times more oxalic acid degradation compared to that degraded in the presence of pure P25 TiO2 nanoparticles. The degradation rate of the oxalic acid is three times higher in the case of Ag/TiO2 composite nanoparticle film than in the case of pure TiO2 nanoparticles. It was observed that both the rate of oxalic acid degradation and the degraded amount of the oxalic acid were significantly affected by Ag incorporation.

Novel synthesis of rutile titanium dioxide–polypyrrole nano composites and their application in hydrogen generation

This work presents the first report of rutile titanium dioxide (TiO2)–polypyrrole (PPy) nanocomposites prepared by chemical polymerization of pyrrole in situ in the presence of pure rutile phase TiO2 nanoparticles. The TiO2 rutile nanoparticles were made in water while the composite was made in a biphasic ionic liquid–water system. We attempted for the first time to split water under sunlight with this recoverable photocatalyst.

Study of the role of metal core on the thermal behavior of Ag@TiO2 core–shell nanoparticles

Thermal behavior of the TiO2 shell in the core–shell Ag@TiO2 system has been investigated by the time differential perturbed angular correlation (TDPAC), transmission electron microscope and X-ray diffraction measurements in the temperature range from 473 to 1073 K. Although the thickness of the TiO2 shell increases on annealing, the TDPAC results show that the anatase phase persists till 1073 K. This is in contrast with the results for the pure TiO2 nanoparticles. These observations suggest that the phase transformation from anatase to rutile is hindered in case of core–shell nanoparticles possibly because the growth of the shell thickness in case of Ag@TiO2 nanoparticles is not effective for rutile formation due to the presence of Ag-core.

Modification and Dyeing of Silk Fabric Treated with Tetrabutyl Titanate by Hydrothermal Method

Nano-structured TiO2 particles prepared by hydrothermal method are first immobilized on the surface of silk fiber using tetrabutyl titanate, which is dyed with C.I. Reactive Blue 19. The morphology, crystalline phase, chemical structure, thermal, and optical properties of silk fabric before and after treatment are determined by means of scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, thermal gravimetric, and diffuse reflectance spectrum techniques. The UV protection, percentage of exhaustion, percentage of fixation, K/S value, and color fastness are investigated. The results indicate that when silk fabric is treated with tetrabutyl titanate aqueous solution at 110 °C for 2 h, pure anatase phase TiO2 nanoparticles of size less than 10 nm are synthesized, and then simultaneously grafted onto fiber surface. Compared with the original fabric, the thermal stability of the TiO2-coated fabric changes little. The protection against ultraviolet radiation is distinctly improved. The yellowness and whiteness values change a little. The percentage of exhaustion, fixation and K/S value are reduced to some extent due to the existence of TiO2 film. The color fastness to wet rubbing decreases slightly. The K/S value of the TiO2-coated fabric increases after being scrubbed. The color fastness to light of silk fabric after treatment is enhanced.

Mesoporous anatase TiO2/reduced graphene oxide nanocomposites: A simple template-free synthesis and their high photocatalytic performance

Mesoporous anatase phase TiO2 was assembled on reduced graphene oxide (rGO) using a template-free one-step hydrothermal process. The nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Brunauer–Emmett–Teller (BET) surface area. Morphology of TiO2 was related to the content of graphene oxide. TiO2/rGO nanocomposites exhibited excellent photocatalytic activity for the photo-degradation of methyl orange. The degradation rate was 4.5 times greater than that of pure TiO2 nanoparticles. This difference was attributed to the thin two-dimensional graphene sheet. The graphene sheet had a large surface area, high adsorption capacity, and acted as a good electron acceptor for the transfer of photo-generated electrons from the conduction band of TiO2. The enhanced surface adsorption characteristics and excellent charge transport separation were independent properties of the photocatalytic degradation process.

Sol–gel synthesis and characterization of pure and manganese doped TiO2 nanoparticles – A new NLO active material

Pure and Manganese (4%, 8%, 12% and 16%) doped titanium di-oxide (Mn–TiO2) nanoparticles were synthesized by sol–gel technique. The preparation of pure and Mn doped TiO2 nanoparticles were achieved by tetra-isopropyl orthotitanate and 2-propanol as common starting materials and the products were annealed at 450°C and 750°C to get anatase and rutile phases, respectively. The prepared materials were characterized by X-ray diffraction analysis (XRD), Fourier transform infra-red spectroscopy (FT-IR), UV–VIS-Diffuse reflectance spectroscopy (DRS), Photoluminescence (PL) spectroscopy, Scanning electron microscopy (SEM) with Energy dispersive X-ray analysis (EDX) and Kurtz powder second harmonic generation (SHG) test. XRD patterns confirmed the crystalline nature and tetragonal structure of synthesized materials. The functional groups present in the samples were identified by FTIR study. The allowed direct and indirect band gap energies, as well as the crystallite sizes of obtained nanoparticles were calculated from DRS analysis. Microstructures and elemental identification were done by SEM with EDX analysis. The existence of SHG signals was observed using Nd: YAG laser with fundamental wavelength of 1064nm. The products were found to be transparent in the entire visible region with cut-off wavelengths within the UV region confirms its suitability for device fabrications.

CNT@TiO2 nanohybrids for high-performance anode of lithium-ion batteries

This work describes a potential anode material for lithium-ion batteries (LIBs), namely, anatase TiO2 nanoparticle-decorated carbon nanotubes (CNTs@TiO2). The electrochemical properties of CNTs@TiO2 were thoroughly investigated using various electrochemical techniques, including cyclic voltammetry, electrochemical impedance spectroscopy, galvanostatic cycling, and rate experiments. It was revealed that compared with pure TiO2 nanoparticles and CNTs alone, the CNT@TiO2 nanohybrids offered superior rate capability and achieved better cycling performance when used as anodes of LIBs. The CNT@TiO2 nanohybrids exhibited a cycling stability with high reversible capacity of about 190 mAh g-1 after 120 cycles at a current density of 100 mA g-1 and an excellent rate capability (up to 100 mAh g-1 at a current density of 1,000 mA g-1).