Titania Nanofibers Research Articles

Photo-reduction of heavy metal ions and photo-disinfection of pathogenic bacteria under simulated solar light using photosensitized TiO2 nanofibers.

We report the photosensitization of electrospun titania nanofibers, with a mean diameter of 195 nm, by low bandgap silver sulfide nanoparticles of 11–23 nm mean size with the aim of treating heavy metal ions and pathogenic bacteria simultaneously under simulated solar light irradiation. The 17 nm Ag2S/TiO2 nanofibers showed 90% photocatalytic reduction of Cr(vi) at pH of 3 with a pseudo-first order rate constant of 0.016 min−1 which is significantly better than the previously reported for Ag–Ag2S/TiO2 composite particles. The antibacterial capability of the Ag2S/TiO2 nanofibers was evaluated via photo-disinfection of the Gram-positive and Gram-negative bacterial strains. The smallest sized 11 nm Ag2S/TiO2 nanofiber showed the best bactericidal efficiency of 100% and 90.6% against Gram-negative E. coli and Gram-positive S. aureus after 1 h of irradiation, respectively, whereas, only 50% E. coli and 41% S. aureus were found to be inactivated in dark. Furthermore, a UV–O3 treatment of the 11 nm Ag2S/TiO2 nanofibers remarkably enhanced the antibacterial activity where 89% E. coli and 81% S. aureus were inactivated in just 10 min of the irradiation. Enhanced photocatalytic activity is attributed to the efficient charge separation and transfer and reduced electron–hole recombination induced by the effective heterojunction formation between TiO2 and the optimally sized Ag2S nanoparticles. The disinfection nature of the Ag2S nanoparticles, role of the generated hydroxyl species under irradiation, and the cell wall damage mechanism is also discussed. This study demonstrates the potential use of these multifunctional composite TiO2 nanofibers for water remediation.

Dispersive micro-solid phase extraction combined with dispersive liquid-liquid microextraction for speciation analysis of antimony by electrothermal vaporization inductively coupled plasma mass spectrometry

A method was developed for speciation analysis of antimony by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) after preconcentration/separation using dispersive micro-solid phase extraction (DMSPE) and dispersive liquid-liquid micro-extraction (DLLME). In DMSPE, titanium dioxide nanofibers were used for preconcentration and separation of analytes. The upper aqueous phase and elution solution from DMSPE were used for further preconcentration and separation of Sb(III) and Sb(V) by DLLME without any pre-oxidation or pre-reduction operation, respectively. The extracts from DLLME were used for ETV-ICP-MS determination with APDC as a chemical modifier. Under optimal conditions, the detection limits of this method were 0.019 and 0.025pgmL−1 with relative standard deviations of 5.7% and 6.9% for Sb(III) and Sb(V) (c=1.0ngmL−1, n=9), respectively. This method was applied for speciation analysis of Sb and its distribution in the tea leaves and the tea infusion, including total, suspended, soluble, organic and inorganic Sb as well as Sb(III) and Sb(V). The results showed that the contents of Sb are 62.7, 12.9 and 47.3ngg−1 in the tea leaves, tea residue and tea soup, respectively; those of soluble, organic, inorganic, Sb(III) and Sb(V) are 0.41, 0.11, 0.29, 0.21 and 0.07ngmL−1 in the tea soup, respectively. A certified reference material of tea leaves (GBW 07605) was analyzed by this method with satisfactory results.

Effects of heat treatment of TiO2 nanofibers on the morphological structure of PVDF nanocomposite membrane under UV irradiation

Nowadays, photocatalytic oxidation has been pledged as a valuable process for air and water purification due to its capability in degrading organic pollutants. In this study, polyvinylidene fluoride (PVDF) nanocomposite membrane consisted of electrospun titanium dioxide nanofibers (PVDF/TNF) was prepared by hot pressing TNF onto PVDF flat sheet membrane. Titanium dioxide nanofibers (TNF) were successfully fabricated through electrospinning technique, in which electrospun from a precursor solution consisted of polyvinylpyrrolidone (PVP)/titanium tetraisopropoxide (TTIP), ethanol and acetic acid. They were then heat-treated under different calcination temperatures ranging from 400 to 600°C. The morphological properties of TNF were characterized via scanning of electron microscope (SEM) and X-ray diffractometer (XRD). From the results collected, it is shown that the heat-treated TNF were consisted of anatase and rutile phases, whereas the un-treated TNF only possessed amorphous phase as analysed by XRD analysis. As a matter of fact, TNF-500 displayed satisfactory morphological structure, along with fiber diameter and crystalline structure compared to other TNF, thus TNF-500 was chosen for further testing. In addition, selected TNF have successfully deposited onto PVDF membrane as there is no visible lift-off. By introducing TNF into PVDF membrane matrix, said course of action resulted in a tremendously enhanced BPA photodegradation up to 85.88%. Even though the calcination process implemented on TNF has been reduced to about 4% in photocatalytic activity, further optimisation study on the loading of TNF-500 in PVDF membrane matrix could highlight favourable features of calcined TNF-500 for BPA degradation reaction.

Response Surface Modeling of Electrospinning Parameters on Titanium Oxide Nanofibers’ Diameter: A Box-Behnken Design (BBD)

Electrospinning has been employed to produce titanium oxide nanofibers from an ethanolic solution containing precursor titanium tetraisopropoxide and polymer polyvinylpyrrolidone with acetic acid as a stabilizer. Response surface methodology based on Box-Behnken Design was implemented to investigate the influence of applied voltage (10–25 kV), flow rate (1.0–3.0 ml/hr) and tip to collector distance (6–14 cm) on the electrospun nanofibers diameter. The fibers’ diameter was examined using scanning electron microscope. A second order polynomial was developed to predict the diameter of the fiber. The importance of each parameter was tested through analysis of variance with 95% of confidence level. From reduced response surface model, tip to collector distance was the most significance factor whereas applied voltage appeared to be the least significance factor in predicting fibers diameter. The decrement of 26.2% with an increase of tip to collector distance from 6 cm to 14 cm at constant flow rate and applied voltage. When the applied voltage increased from 10 kV to 25 kV, the fiber diameter decreased 10.96%.

Solution blow spun titania nanofibers from solutions of high inorganic/organic precursor ratio

In this work titania nanofibers were produced from different precursor solutions by solution blow spinning. Hydrophilic polyvinylpyrrolidone, hydrophobic poly(vinyl acetate) and amorphous and semi-crystalline poly(lactic acid) polymers were used with green-solvents and titanium isopropoxide as the inorganic precursor. Hybrid nanofibers with high inorganic loading content were successfully produced from all precursor solutions. The fibers were calcined at different annealing temperatures for evaluation of phase transitions. The minimum temperature to obtain pure titania fiber was found to be 500°C, as assessed by thermal characterization. Anatase was the unique polymorph formed at this annealing temperature. This is of paramount importance due to its photocatalytic character. Calcination at high temperatures showed that rutile slightly appeared at 600°C for the polyvinylpyrrolidone-based system and showed a strong peak at 700°C for all systems, co-existing with anatase as minor phase. The use of amorphous and semicrystalline poly(lactic acid) polymers did not influence the anatase crystal size and phase conversion. This was found to be dependent on the annealing temperature and medium acidity, as currently found in powder synthesis.

Extraction of microRNAs from biological matrices with titanium dioxide nanofibers.

MicroRNAs (miRNAs) are small RNAs that bind to mRNA targets and regulate their translation. A functional study of miRNAs and exploration of their utility as disease markers require miRNA extraction from biological samples, which contain large amounts of interfering compounds for downstream RNA identification and quantification. The most common extraction methods employ silica columns or the TRIzol reagent but give out low recovery for small RNAs probably due to their short strand lengths. Herein, we fabricated the titanium dioxide nanofibers using electrospinning to facilitate miRNA extraction and developed the optimal buffer conditions to improve miRNA recovery from biological matrices of cell lysate and serum. We found that our TiO2 fibers could obtain a recovery of 18.0±3.6% for miRNA fibers while carrying out the extraction in the more complex medium of cell lysate, much higher than the 0.02±0.0001% recovery from the commercial kit. The much improved extraction of miRNAs from our fibers could be originated from the strong coordination between TiO2 and RNA's phosphate backbone. In addition, the binding, washing, and elution buffers judiciously developed in the present study can achieve selective extraction of small RNA shorter than 500 nucleotides in length. Our results demonstrate that TiO2 nanofibers can work as a valuable tool for extraction of miRNAs from biological samples with high recovery. Graphical abstract Schematic for extraction of small RNAs using TiO2 nanofibers.

Immobilization of plasmonic Ag-Au NPs on the TiO2 nanofibers as an efficient visible-light photocatalyst

A heterostructure photocatalyst including metallic silver (Ag), gold (Au) in the form of nanoparticles (NPs) and titanium oxide (TiO2) nanofibers were fabricated using a combination of photodeposition and electrospinning techniques. In this procedure, electrospun TiO2 nanofibers were decorated by plasmonic Ag and Au NPs on the surface of nanofibers which were generated via photochemical reduction process. The synthesized Ag-Au/TiO2 nanocomposites which were considered as a favorable candidate for enabling the more access to visible-light in photocatalytic performance were subsequently characterized by field emission scanning electron spectroscopy (FESEM), transmission electron spectroscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and ultra-violet-visible (UV–vis) spectroscopy. UV–vis studies indicate the extension in the absorption region of composite toward the visible-light range have been occurred through the loading metallic nanoparticles into the TiO2 structure. Microscopic assessments in addition to EDS revealed that metallic NPs deposited on the surface of the fibers through photochemical reduction process. It was found that, the ratio of utilized Ag/Au in the final composite can significantly enhance the photocatalytic efficiency. It was suggested that introduction of the proper amount of noble metal NPs into the TiO2 matrix leads to the notable enhancement of visible-light decomposition of rhodamine B (Rh. B) as a model dye.

Heterostructure based on silver/silver chloride nanocubes loaded titanium dioxide nanofibers: A high-efficient and recyclable visible light-responsive photocatalyst

Abstract In this work, a new class of heterostructure photocatalyst has been fabricated, which silver/silver chloride nanocubes are well-dispersed on titanium dioxide nanofibers by means of a facile precipitation process combined with photoreduction method. This sort of heterostructure shows an excellent photocatalytic activity superior to the pure TO 2 nanofibers, Ag/AgCl powder and Ag/TiO 2 nanofibers for decomposing organic contaminants driven by visible light. The improved photocatalytic activity might be due to the surface plasmon resonance effect of Ag and the formation of heterojunction between Ag, AgCl and TiO 2 , which can effectively enhance visible light absorption and accelerate the charge separation and transfer. Significantly, the multiple cycle experiments for repeated use have proved that the catalyst is stable, segregative and recyclable. Finally, a possible mechanism related to the charge separation and the photocatalytic degradation of organics is also provided.

Study on Titanium Dioxide Nanofibers as New Solid Phase Extraction Adsorbent for Column Preconcentration and Separation of Trace Rare Earth Elements Prior to Their Determination by ICP-MS

Study on Titanium Dioxide Nanofibers as New Solid Phase Extraction Adsorbent for Column Preconcentration and Separation of Trace Rare Earth Elements Prior to Their Determination by ICP-MS

Fabrication of hierarchical TiO2 nanofibers by microemulsion electrospinning for photocatalysis applications

Abstract Hierarchical titanium dioxide (TiO2) nanofibers with distinctive microstructures were fabricated successfully via microemulsion electrospinning (ME-ES) followed by pyrolysis. The chemical composition, morphology and microstructure of hierarchical TiO2 nanofibers were characterized by Fourier transfer infrared (FT-IR), Energy dispersive X-ray (EDX) spectroscopy, Field emission-scanning electron microscopy (FE-SEM) and Transmission electron microscopy (TEM), respectively. The photocatalytic performances were evaluated by decomposing methylene blue (MB) aqueous solution with UV light embedded with 365 nm light filter as the light sources. The results indicated that multi-channel, hollow, irregular hollow and mesoporous TiO2 nanofibers with mixed crystalline were obtained only by adjusting the ratio of tetrabutyl titanate (TBT)/paraffin oil in the microemulsion system. In addition, the pores in the TiO2 nanofibers were axial-aligned for both the multi-channel and hollow nanofibers. All the TiO2 nanofibers prepared by microemulsion electrospinning displayed improved photocatalytic performances compared with the solid TiO2 nanofibers. The results has proved that microemulsion electrospinning is indeed a simple and convenient method for fabricating hierarchical TiO2 nanofibers with improved photocatalytic performances.

Photochemical Removal of SO2 over TiO2-Based Nanofibers by a Dry Photocatalytic Oxidation Process

Efficient and economical technologies are essential to the control of SO2, the emission of which poses serious health concerns and environmental risks. Photocatalysis is an attractive method for reducing SO2 emissions. To reduce energy consumption for excess moisture evaporation, a dry photocatalytic oxidation (DPCO) system was used instead of a traditional gas–liquid process in this study. Considering that TiO2 is a widely applied photocatalyst for the purification of gaseous pollutants, this study investigated the photocatalytic removal of SO2 over different TiO2-based nanofibers. Results show that the reduction of SO2 was mainly due to oxidation. Under ultraviolet irradiation, the removal of SO2 was enhanced by the presence of NO2, which was formed by the oxidation of NO. More interestingly, the SO2 removal efficiency remains 100% over cerium-based titania nanofibers with an increase in gas humidity, indicating that this sample has excellent resistance to H2O. This is very beneficial for application in...

Retraction: Gold Nanoparticles Immobilized on Electrospun Titanium Dioxide Nanofibers for Catalytic Reduction of 4-Nitrophenol.

The article, published as an Acceptd Article online on 13 February 2017 in Wiley Online Library (wileyonlinelibrary.com), has been withdrawn by agreement between the authors, the journal Editor in Chief, Greta Heydenrych, and Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. The retraction has been agreed on the basis of problems with the authorship.

Effect of calcination temperature on formaldehyde oxidation performance of Pt/TiO2 nanofiber composite at room temperature

Catalytic oxidation at room temperature over well-designed catalysts is an environmentally friendly method for the abatement of indoor formaldehyde (HCHO) pollution. Herein, nanocomposites of platinum (Pt) and titanium dioxide (TiO2) nanofibers with various phase compositions were prepared by calcining the electrospun TiO2 precursors at different temperatures and subsequently depositing Pt nanoparticles (NPs) on the TiO2 through a NaBH4-reduction process. The phase compositions and structures of Pt/TiO2 can be easily controlled by varying the calcination temperature. The Pt/TiO2 nanocomposites showed a phase-dependent activity towards the catalytic HCHO oxidation. Pt/TiO2 containing pure rutile phase showed enhanced activity with a turnover frequency (TOF) of 16.6min−1 (for a calcination temperature of 800°C) as compared to those containing the anatase phase or mixed phases. Density functional theory calculation shows that TiO2 nanofibers with pure rutile phase have stronger adsorption ability to Pt atoms than anatase phase, which favors the reduction of Pt over rutile phase TiO2, leading to higher contents of metallic Pt in the nanocomposite. In addition, the Pt/TiO2 with rutile phase possesses more abundant oxygen vacancies, which is conducive to the activation of adsorbed oxygen. Consequently, the Pt/rutile-TiO2 nanocomposite exhibited better catalytic activity towards HCHO oxidation at room temperature.

Synthesis of TiO2 nanofiber for photocatalytic and antibacterial applications

Titanium dioxide (TiO2) nanofiber was successfully synthesized by electrospinning method. The synthesized TiO2 powder was characterized by using advanced techniques such as X-ray diffraction analysis (XRD) and Scanning electron microscope (SEM). The XRD pattern shows the formation of the anatase structure of synthesized TiO2 and the crystallite size was calculated using Debye-Scherer equation. SEM image shows the nanofibrous morphology of synthesized TiO2 nanomaterials. In the present work, the synthesized TiO2 nanofiber successfully decomposed the methylene blue dye under UV-light irradiation. The higher colour removal efficiency of 87.36% was achieved for the sample calcinated at 450 °C. Moreover, the antibacterial effect of the synthesized TiO2 nanofiber was screened by disc diffusion method using gram positive bacteria Bacillus cereus and gram negative bacteria Klebsiella pneumoniae. The maximum zone of inhibition (25 mm) in millimeter was observed by K. pneumoniae. Thus, concluded that they could act as promising materials for efficient photocatalytic rate and good antibacterial agent.

Electrospinning of Photocatalytic Electrodes for Dye-sensitized Solar Cells

This work demonstrates a protocol to fabricate a fiber-based photoanode for dye-sensitized solar cells, consisting of a light-scattering layer made of electrospun titanium dioxide nanofibers (TiO2-NFs) on top of a blocking layer made of commercially available titanium dioxide nanoparticles (TiO2-NPs). This is achieved by first electrospinning a solution of titanium (IV) butoxide, polyvinylpyrrolidone (PVP), and glacial acetic acid in ethanol to obtain composite PVP/TiO2 nanofibers. These are then calcined at 500 °C to remove the PVP and to obtain pure anatase-phase titania nanofibers. This material is characterized using scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). The photoanode is prepared by first creating a blocking layer through the deposition of a TiO2-NPs/terpineol slurry on a fluorine-doped tin oxide (FTO) glass slide using doctor blading techniques. A subsequent thermal treatment is performed at 500 °C. Then, the light-scattering layer is formed by depositing a TiO2-NFs/terpineol slurry on the same slide, using the same technique, and calcinating again at 500 °C. The performance of the photoanode is tested by fabricating a dye-sensitized solar cell and measuring its efficiency through J-V curves under a range of incident light densities, from 0.25-1 Sun.

Electrospinning of Photocatalytic Electrodes for Dye-sensitized Solar Cells.

This work demonstrates a protocol to fabricate a fiber-based photoanode for dye-sensitized solar cells, consisting of a light-scattering layer made of electrospun titanium dioxide nanofibers (TiO2-NFs) on top of a blocking layer made of commercially available titanium dioxide nanoparticles (TiO2-NPs). This is achieved by first electrospinning a solution of titanium (IV) butoxide, polyvinylpyrrolidone (PVP), and glacial acetic acid in ethanol to obtain composite PVP/TiO2 nanofibers. These are then calcined at 500 °C to remove the PVP and to obtain pure anatase-phase titania nanofibers. This material is characterized using scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). The photoanode is prepared by first creating a blocking layer through the deposition of a TiO2-NPs/terpineol slurry on a fluorine-doped tin oxide (FTO) glass slide using doctor blading techniques. A subsequent thermal treatment is performed at 500 °C. Then, the light-scattering layer is formed by depositing a TiO2-NFs/terpineol slurry on the same slide, using the same technique, and calcinating again at 500 °C. The performance of the photoanode is tested by fabricating a dye-sensitized solar cell and measuring its efficiency through J-V curves under a range of incident light densities, from 0.25-1 Sun.

Fabrication of hierarchically porous TiO2 nanofibers by microemulsion electrospinning and their application as anode material for lithium-ion batteries.

Titanium dioxide (TiO2) nanofibers have been widely applied in various fields including photocatalysis, energy storage and solar cells due to the advantages of low cost, high abundance and nontoxicity. However, the low conductivity of ions and bulk electrons hinder its rapid development in lithium-ion batteries (LIB). In order to improve the electrochemical performances of TiO2 nanomaterials as anode for LIB, hierarchically porous TiO2 nanofibers with different tetrabutyl titanate (TBT)/paraffin oil ratios were prepared as anode for LIB via a versatile single-nozzle microemulsion electrospinning (ME-ES) method followed by calcining. The experimental results indicated that TiO2 nanofibers with the higher TBT/paraffin oil ratio demonstrated more axially aligned channels and a larger specific surface area. Furthermore, they presented superior lithium-ion storage properties in terms of specific capacity, rate capability and cycling performance compared with solid TiO2 nanofibers for LIB. The initial discharge and charge capacity of porous TiO2 nanofibers with a TBT/paraffin oil ratio of 2.25 reached up to 634.72 and 390.42 mAh·g−1, thus resulting in a coulombic efficiency of 61.51%; and the discharge capacity maintained 264.56 mAh·g−1 after 100 cycles, which was much higher than that of solid TiO2 nanofibers. TiO2 nanofibers with TBT/paraffin oil ratio of 2.25 still obtained a high reversible capacity of 204.53 mAh·g−1 when current density returned back to 40 mA·g−1 after 60 cycles at increasing stepwise current density from 40 mA·g−1 to 800 mA·g−1. Herein, hierarchically porous TiO2 nanofibers have the potential to be applied as anode for lithium-ion batteries in practical applications.

Well-dispersed Pd-Cu bimetals in TiO2 nanofiber matrix with enhanced activity and selectivity for nitrate catalytic reduction

The present development gives an insight into the effect of the distribution of bimetallic sites in denitrification. A highly-dispersed Pd-Cu bimetallic catalyst supported by titanium dioxide nanofibers (Pd-Cu/TiO2) was in situ fabricated by electrospinning and subsequent calcination and chemical reduction, and then applied in the catalytic reduction of water phase nitrate (NO3−) to nitrogen gas (N2). Compared with ex situ Pd-Cu impregnated catalyst, the in situ Pd-Cu/TiO2 nanofibers exhibited the high nitrate removal efficiency, selectivity and fast kinetics (about twice that of impregnated ones). These good catalytic performances are mainly benefited from increased active sites and raised ratio of nitrogen to hydrogen on them, which are brought about by the well-dispersed and closely connected Pd-Cu bimetallic nanoparticles in TiO2 nanofiber matrix. Moreover, the in situ nanofiber matrix provides a physical barrier to inhibit bimetallic nanoparticles movement, aggregation and leakage from the support into water, and hence significantly enhances the recyclability for nitrate reduction.

Solid phase extraction with titanium dioxide nanofibers combined with dispersive liquid-liquid microextraction for speciation of thallium prior to electrothermal vaporization ICP-MS

The authors describe a method for speciation of thallium that is based on solid phase extraction (SPE) combined with dispersive liquid-liquid microextraction (DLLME) prior to electrothermal vaporization ICP-MS determination. The method is shown to be applicable to the determination of total, suspended, soluble, organic and inorganic Tl, and of Tl(I) and Tl(III) in tea leaves and tea infusion. The SPE step involves the use of titanium dioxide nanofibers for preconcentration of the Tl analytes and simultaneous removal of the matrix components such as polyphenols, soluble sugars, catechin, caffeine and tea pigments. Following elution of Tl with dilute HNO3, the eluate was further preconcentrated and separation by DLLME. After optimization of the method, it has a detection limits of 0.015 pg mL−1 for Tl(I) and of 0.020 pg mL−1 for Tl(III), with relative standard deviations of 6.5% and 7.3% (at 0.10 ng mL−1; for n = 9), respectively. The technique has an enrichment factor of 450 and is highly selective. It was successfully applied to the speciation and distribution of thallium in tea leaves and tea infusions. A certified reference material of tea leaves was analyzed by this method, and the obtained values were in good agreement with the certified values.

Short-Term Effects of Titanium Dioxide Nanofiber on the Renal Function of Male Sprague Dawley Rats.

Titanium dioxide nanofiber (TDNF) is widely used in the manufacture of various household products, including cosmetics. As a result, the possibility exists for TDNFs to affect human health. Because the kidneys are responsible for filtering out waste from the blood, the goal of the present study was to investigate the short-term effects of TDNF on kidney function of male Sprague Dawley rats. To achieve study objectives, 6- to 7-wk-old male rats were exposed via oral gavage to a total of 0, 40, and 60 parts per million of TDNF for 2 wk. The TDNF was fabricated by electrospinning and then dissolved in water. We measured serum concentration of lactate dehydrogenase, renal histopathology, identification of TDNF in kidney tissue via scanning electron microscopy, and quantitative amounts of titanium-47 in kidney tissue. We also measured specific gene-expression analysis of transcripts involved in apoptosis, inflammation, cell-division regulation, cell structure, and motility. Results showed a slight dose-dependent reduction in renal weight. In contrast, a concentration-dependent elevation in titanium-47 amounts was noted in kidney tissue. We found no significant differences in histopathological patterns. Gnat3 and Hepacam3 were up-regulated in TDNF-treated groups. Up-regulation of NF-κB likely indicated the involvement of renal-tissue inflammation via an independent mechanism. Similarly, Gadd45-α was significantly overexpressed in kidney tissues. This transcript was previously increased following stressful growth-arrest conditions and treatment with DNA-damaging agents. Our overall results suggest marginal renal toxicity in Sprague Dawley rats after ingesting TDNF.