TiO2 Nanoflowers Research Articles

Direct Blue Dye Degradation Using Titanium Nanostructures Under Energy-Efficient UV-LED Irradiation

The present study describes the effect of titanium dioxide (TiO2) morphology on the photocatalytic activity under irradiation of ultraviolet light-emitting diode (UV-LED). Different TiO2 nanostructures were synthesized using hydrothermal (nanotubes and nanospheres) and solvothermal (nanoflowers) methods. The morphology, phase composition, bandgap, and chemical properties of the synthesized different TiO2 nanostructures were characterized using x-ray diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet visible diffuse reflectance spectroscopy (UV-Vis DRS), and Brunauer-Emmett-Teller (BET) analysis. The surface area of the nanotubes was larger than that of the nanospheres and nanoflowers by four- and three-fold, respectively. The photocatalytic activity of the photocatalysts was evaluated by degradation of direct blue-15 dye under UV-LED irradiation in a slurry-type reactor. The photocatalytic activity of the TiO2 nanoflowers was higher than that of TiO2 nanotubes or nanospheres, suggesting that nanoflowers can serve as efficient photocatalysts for dye degradation.

Effects of growth substrate on the morphologies of TiO2 hierarchical nanoarrays and their optical and photocatalytic properties

TiO2 nanorods (NRs) and nanoflowers (NFs) were synthesized on conductive and nonconductive sides of fluorine doped tin oxide (FTO-glass) substrate using a facile hydrothermal method. The effects of growth substrates on the various TiO2 morphologies and the optical performance of the different morphologies were also investigated. The average length of the TiO2 NRs was approximately 4.5 µm with a diameter of 175–215 nm. The average diameter of the TiO2 NFs was ca. 7.2 µm. The band gap values of the NRs and NFs were calculated to be 2.86 and 2.93 eV, respectively. Under illumination of UV-light, the prepared TiO2 NRs photocatalyzed the degradation of methyl orange at a higher rate than that of the TiO2 NFs, which can be attributed to the larger specific surface area of the TiO2 NRs.

Branched hierarchical titanium dioxide nanoflower on carbon nanofiber with efficient scattering layer for high performance dye-sensitized solar cells

A new bilayered photoanode is fabricated for dye-sensitized solar cells (DSSCs) composed of the carbon nanofiber coated by hierarchical TiO2 nanoflower (CNF-TNF) as underlayer and the urchin-like TiO2 hollow sphere (UTHS) as light-scattering layer. The CNF-TNF with a large specific surface area of 336.5m2g−1 provides dual-functions of more dye loading and efficient charge transport, leading to the enhanced short-circuit photocurrent density of 21.40mA cm−2 and prolonged electron lifetime of 189.2ms. The incorporated carbon nanofiber not only reduces the interfacial resistance and the charge recombination rate, but also improves the light harvesting, resulting in a high photoelectric conversion efficiency (PCE) up to 8.57% for the single-layered CNF-TNF based DSSC. In addition, by optimizing the surface morphology of TiO2 hollow sphere, we obtain the unique 3D UTHS, exhibiting strong light-scattering effect and low charge recombination due to the favorable connection among spheres provided by modified porous shell. As a consequence, an overall PCE of 9.21% is achieved for CNF-TNF+UTHS based DSSC, which is far superior to that of P25 based DSSC (5.10%). To the best of our knowledge, it is the first time that the hierarchically CNF-TNF composite is synthesized and utilized for enhanced efficiency DSSCs.

Rutile-Phased TiO Nanorods/Nanoflowers Based Dye-Sensitized Solar Cell

Aligned Rutile TiO2 nanorods (r-TNRs) and TiO2 nanoflowers (r-TNFs) were successfully prepared by hydrothermal method. Using hydrochloric acid (HCl) as chelating agent and titanium butoxide (TBOT) as precursor, aligned r-TNRs with r-TNFs were successfully growth onto fluorine-doped tin oxide (FTO) with different morphologies. The influences of surface morphologies to the rutile based Dye-sensitized solar cell (DSC) efficiency are discussed. The highest light-to-electric energy conversion efficiency, 1.80% is achieved using different concentration under simulated solar light illumination of 100 mWcm-2 (1.5 AM).

High-efficiency dye-sensitized solar cells with hierarchical structures titanium dioxide to transfer photogenerated charge

Hierarchical TiO2 nanorod-sheet-flowers (TNRSFs) consisting of one dimensional (1D) vertically aligned rutile TiO2 nanorods array (TNRA), 2D TiO2 nanosheets (TNSs) and 3D TiO2 nanoflowers (TNFs) have been synthesized via a simple NaOH-assisted hydrothermal method and employed as an photoanode for high-efficiency dye-sensitized solar cells (DSSCs). In our strategy, The TNFs layer with large thickness can potentially enable a great amount of dye adsorption and significantly strengthen the light-harvesting ability, which is beneficial for generating more charge. In addition, The TNRA and TNSs act like charge collectors, providing efficient transport pathways for electrons, which means the photogenerated charge can be collected efficiently through this conducting network. The electrochemical impedance spectroscopy (EIS) measurement shows that the TNRSF film possesses better electron transport ability and longer electron lifetime (28.4ms) compared with the TiO2 nanoparticals (TNPs) film. Furthermore, an overall power conversion efficiency of 8.41% (with a Jsc of 16.95mAcm−2, Voc of 0.73V and FF of 68%) is achieved for the DSSC based on the TNRSF photoanode, indicating a 51.8% enhancement compared with that of the TNPs photoanode (5.54%). The discoveries from this work highlight the significance of designing photoanode materials with hierarchical structures for enhanced photovoltaic performance.

Monodispersed 3D MnWO4–TiO2 composite nanoflowers photocatalysts for environmental remediation

Pollutants from textile industries into water-bodies have caused huge environmental hazards. The semiconductor mediated photocatalytic purification of polluted water is a promising environmental remediation technology. In the present study MnWO4–TiO2 composite nanoflowers endowed with efficient photocatalytic activity have been successfully synthesized by facile hydrothermal approach. XRD, SEM, TEM, EDX spectroscopy and UV-DRS were used to characterize the as-synthesized samples. The average size of composite nanoflower is ∼2 μm while the nanorods constructing the nanoflowers had the average diameters of 90 nm. The photocatalytic activity of the MnWO4–TiO2 nanoflowers for the degradation of methyl orange (MO) in visible light was much higher than of pristine TiO2 nanorods and MnWO4 nanoflowers respectively. The superior photocatalytic activity could be attributed to the formation of a MnWO4–TiO2 heterojunction in the MnWO4–TiO2 nanoflowers.

A facile strategy to fabricate plasmonic Cu modified TiO2 nano-flower films for photocatalytic reduction of CO2 to methanol

Cu nanoparticles (NPs) deposited TiO2 nano-flower films were fabricated using a combination of a hydrothermal method and a microwave-assisted reduction process. The investigations indicated that Cu NPs and TiO2 film both exhibit visible light harvesting properties based on localized surface plasmon resonance (LSPR) of Cu NPs and unique nanostructures of TiO2 film. Fluorescence quenching was observed because the recombination of charge carriers was effectively suppressed by Cu NPs deposition. The experimental results indicate that Cu/TiO2 films exhibit better activity for the photocatalytic reduction of CO2 due to the charge transfer property and LSPR effect of Cu NPs. The CH3OH production rate reached 1.8μmolcm−2h−1 (energy efficiency was 0.8%) over 0.5 Cu/TiO2 film under UV and visible light irradiation, which was 6.0 times higher than that observed over pure TiO2 film. In addition, a tentative photocatalytic mechanism is proposed to understand the experimental results over the Cu modified TiO2 nano-flower films.

Initial reactant controlled synthesis of double layered TiO2 nanostructures and characterization of its spectra of absorption and photoluminescence

Double layered titanium dioxide (TiO2) nanostructures were synthesized on fluorine-doped tin oxide (FTO) substrates using a low-cost and convenient hydrothermal method. The prepared TiO2 nanostructures were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). The SEM images showed that the double layered TiO2 nanostructure composed of one layer of TiO2 nanorods film on FTO and one layer of TiO2 nanoflowers on the TiO2 nanorods film. The results of XRD indicated that the prepared TiO2 nanostructures were rutile TiO2. The band gap of the prepared TiO2 nanostructures was calculated by ultraviolet–visible (UV–vis) absorption spectrum. Optical properties of the samples were investigated by photoluminescence (PL) spectroscopy. The results indicated that all of the prepared samples had the same luminescence center. And the luminescence intensity of double layered TiO2 increased with increasing the excitation wavelength.

Enhanced photocatalytic degradation of rutile/anatase TiO2 heterojunction nanoflowers

Rutile/anatase TiO2 heterojunction nanoflowers were prepared via a facile one-step hydrothermal approach using titanium tetrachloride and urea as the raw materials, cetyl trimethyl ammonium bromide (CTAB) as the template. The prepared TiO2 nanoflowers were characterized by XRD, SEM, TEM and BET analyses. The photocatalytic performance of the as-prepared TiO2 samples for methyl blue degradation under simulated solar light was investigated. TiO2 heterojunction nanoflowers with mixed rutile/anatase phase (prepared with 3mmol CTAB) give the highest photocatalytic activity. In addition, TiO2 nanoflowers show excellent stability after 9cycles under the same conditions. These results suggested that the mixed phase anatase/rutile TiO2 heterojunction nanoflowers have great potential for the future photodegradation of real dye waste water.

Evaluation of a metal free dye for efficient dye sensitized solar cells based on hydrothermally synthesized TiO2 nanoflowers

Hierarchical TiO2 nanoflowers for DN350 organic dye sensitized solar cells.

Single-crystalline rutile TiO2 nano-flower hierarchical structures for enhanced photocatalytic selective oxidation from amine to imine

One-pot synthesized single-crystalline 3D rutile TiO2 nano-flower hierarchical structures exhibited superior reactivity toward photocatalytic selective oxidation from amine to imine.

Bilayered photoanode from rutile TiO2nanorods and hierarchical anatase TiO2hollow spheres: a candidate for enhanced efficiency dye sensitized solar cells

A bilayered photoanode for dye-sensitized solar cells (DSSCs) was constructed with the top layer using TiO2 hierarchical hollow spheres (THS) and the second layer based on 3D TiO2 nanorods. The anatase THS with diameters of 400–600 nm and with a specific surface area of 100.3 m2 g−1 were synthesized via a simple hydrothermal method. As a light scattering layer, the THS could provide dual-functions of adsorbing dye molecules and strong light-harvesting efficiency. The 3D TiO2 nanorods consisting of 1D vertically aligned rutile TiO2 nanorods (TNR) and 3D TiO2 nanoflowers (TNF) were synthesized by a one-step hydrothermal method. The unique 3D nanostructure could offer a better light scattering capability, faster electron transport and lower electron recombination. Consequentially, the bilayered cell exhibited a much higher short-circuit photocurrent density of 15.60 mA cm−2 and energy conversion efficiency of 7.50%, which indicated a 108.6% and a 36.8% increment of cell efficiency compared to the TNR-F electrode (7.36 mA cm−2, 3.60%) and THS electrode (13.20 mA cm−2, 5.48%), respectively.

Synthesis and characteristics study of TiO2 nanowires and nanoflowers on FTO/glass and glass substrates via hydrothermal technique

In this work, a typical hydrothermal synthesis to grow long, high density, vertically aligned, well oriented and homogenous TiO2 nanowires arrays and flower-like film on conductive and nonconductive (glass) sides of fluorine doped tin oxide (FTO-glass) substrate are presented. Under the same conditions, the TiO2 nanowires arrays were directly grown on the FTO coated side. While the flower-like nanostructures were grown on the glass side. Two cleaned FTO-glass samples were placed inside the autoclave cylinder. The samples were placed at horizontal and inclined at 45° respectively. The average diameter and length of nanowires are 150 nm and 7.0 μm respectively. Also the average diameter of the prepared flower-like nanostructure of TiO2 is ≈5–10 µm. The flower-like nanostructure growth was confirmed in the absence of FTO by scratched line made on conductive side. The optical propertied of the TiO2 flower-like nanostructures was also investigated. The synthesized products were characterized by SEM equipped with EDS, XRD and UV–VIS NIR spectrophotometer.

Morphological, optical, structural and photoelectrochemical properties of TiO2 nanoflower prepared via PVP surfactant assisted liquid phase deposition technique

This paper reports the synthesis of TiO2 nanoflowers as photovoltaic materials of the photoelectrochemical cell (PEC) via the phase liquid deposition technique assisted with a polyvinylpyrrolidone (PVP) surfactant. This work investigates the influence of the surfactant concentration on the morphological, optical, phase structure and PEC properties of the TiO2 PEC cell. The grain size of the TiO2 sample decreases with increase in PVP concentration. The smallest grain size of 16 ± 2 nm is obtained at 8 mM PVP. The thickness of the sample increases with PVP concentration. The concentration of PVP does not influence the optical absorption and band gap of the sample. The phase structure and crystallinity degree of the sample are not influenced by PVP concentration. The crystallite size is around 20 nm. The short-circuit current density, Jsc, of the PEC cell utilising these TiO2 samples increases with decrease in grain size which is due to the increase in PVP concentration. The best Jsc was 0.068 mA cm−2 obtained at 8 mM PVP.

A novel fabrication of silver-modified 3D singlecrystal nanowires-assembled rutile TiO2 nanoflowers with enhanced visible photocatalytic activities

Silver-modified 3D singlecrystal nanowires-assembled rutile TiO2 nanoflowers (SMTNs) have been synthesized via a facile surfactant-assisted hydrothermal and followed by photo-reduction Ag-loading method, in which controlled hydrolysis of titanium isopropoxide (TTIP) in a mixed solution of hydrochloric acid (HCl) and cetyltrimethyl ammonium bromide (CTAB) with using AgNO3 as silver source. The physical and chemical properties of SMTNs were studied by XRD, FESEM, HRTEM and UV–vis diffuse reflectance spectra (DRS) techniques. The photocatalytic activity of the SMTNs was evaluated by photocatalytic degradation of Rhodamine B (Rh B) aqueous solution under visible light irradiation. The experimental results showed that the SMTNs exhibited a much better photocatalytic activity than that of TNs (TiO2 nanoflowers) and P25 (commercial TiO2).

Morphology, structure, optical property and photoelectrochemical property of TiO 2 nanoflower films synthesised via liquid phase deposition technique

This reported study was concerned with the synthesis of TiO2 nanoflowers as a photovoltaic material of the photoelectrochemical cell (PEC) via the phase liquid deposition technique. It highlighted the effect of the growth time on the morphology of TiO2 samples. Three growth times were chosen, namely 2, 4 and 6 h. The morphology was examined by scanning electron microscopy (SEM). The nanoflowers' morphology of the TiO2 sample grown for 4 h was then chosen to be characterised by cross-sectional SEM, X-ray diffraction, ultraviolet–visible and photoelectrochemical measurement. The sample was crystalline with anatase phase. The sample showed the strongest absorption at 330 nm. The TiO2 nanoflowers PEC demonstrated the J sc and V oc of 0.046 mAcm−2 and 0.26 V, respectively.

One-step formation and photocatalytic performance of spindle-like TiO2 nanorods synthesized by dealloying amorphous Cu50Ti50 alloy

The dealloying process of amorphous Cu50Ti50 powders and the formation of spindle-like rutile TiO2 nanorods have been investigated. The amorphous Cu50Ti50 powders were prepared by a mechanical alloying method. The results show that the rutile TiO2 nanostructures can be facilely obtained through the one-step dealloying of amorphous Cu50Ti50 powders in a concentrated HNO3 solution. The as-dealloyed powders exhibit a “core–shell” structure after the short-term dealloying treatment. Both discrete TiO2 nanorod shells and nanoflower clusters are formed after the long-term dealloying. In addition, the as-obtained TiO2 nanorods exhibit a good photocatalytic performance for the degradation of methyl orange.

Ti thin film towards the growth of crystalline-TiO2 nanostructures: stepped light-induced transient measurements of photocurrent and photovoltage in dye sensitized solar cell

Highly dense and well-defined TiO2 nanoflowers (NFs) were grown by the hydrothermal process on a titanium (Ti) coated FTO substrate. The Ti layer with a thickness of ~500–600 nm was deposited on FTO at room temperature with a pressure of ~5 mTorr using a Ti-source through RF magnetic sputtering. The unique TiO2 NF thin film substrate was applied as a photoanode for the fabrication of a dye sensitized solar cell (DSSCs). Each NF was made of uniform clover leaf-like petals of an average diameter of ~80–100 nm. The synthesized TiO2 NFs possessed a pure anatase phase with good crystal quality. The fabricated DSSC with TiO2 NF thin film photoanode accomplished a reasonably good overall solar-to-electricity conversion efficiency (η) of ~3.64% with a high short circuit photocurrent density (JSC) of ~9.6 mA cm−2. The improved performance and photocurrent density were explained by the charge transport time, diffusion coefficient, diffusion length and charge collection efficiency of the fabricated DSSC.

Influences of Surface Morphology of Nanostructured Rutile TiO2 Nanorods/Nanoflowers as Photoelectrode on the Performance of Dye-sensitized Solar Cell

Aligned Rutile TiO2 nanorods (r-TNRs) and TiO2 nanoflowers (r-TNFs) were successfully prepared by hydrothermal method. Using hydrochloric acid (HCl) as chelating agent and titanium butoxide (TBOT) as precursor, aligned r-TNRs with r-TNFs were successfully growth onto fluorine-doped tin oxide (FTO) with different morphologies. The influences of surface morphologies to the rutile based Dye-sensitized solar cell (DSC) efficiency are discussed. The highest light-to-electric energy conversion efficiency, 1.80% is achieved using different concentration under simulated solar light illumination of 100 mWcm-2 (1.5 AM).

Low temperature fabrication of nanoflower arrays of rutile TiO2 on mica particles with enhanced photocatalytic activity

Abstract In this work, nanoflower arrays of rutile TiO2 composed of nanorods were directly grown onto mica substrates through hydrolysis of TiCl4 ethanolic solution in water at 70 °C without calcination. SnO2 as a rutile promoting additive was deposited onto mica prior to TiO2. The rutile promoting effects of SnO2 could be ascribed to the structural similarity of rutile and cassiterite. The nanorod crystals grew along the [0 0 1] direction, forming predominantly exposed {1 1 0} side-facets and {0 1 1} top-facets. A reasonable growth mechanism for elucidating the formation of rutile TiO2 nanoflower arrays was proposed. The obtained nanoflower arrays of rutile TiO2 coated mica particles show excellent photocatalytic activity towards degradation of rhodamine B (RhB) under UV illumination, which is almost 1.9 times as high as that of Degussa P25. The enhanced photocatalytic activity of rutile TiO2 superstructures can be ascribed to the combined contribution of high crystallinity, low band gap, and effective separation of electrons and holes by the synergistic effect between the exposed {1 1 0} and {0 1 1} facets of the rutile nanorods. Furthermore, we demonstrated that these rutile TiO2 coated mica particles can be easily recycled without decrease of the photocatalytic activity, which provide possibility to future industrial applications in environmental pollutants cleaning up.