Dioxide Hollow Research Articles

Foldable paper-based photoelectrochemical biosensor based on etching reaction of CoOOH nanosheets-coated laser-induced PbS/CdS/graphene for sensitive detection of ampicillin

Timely and rapid detection of antibiotic residues in the environment is conducive to safeguarding human health and promoting an ecological virtuous cycle. A foldable paper-based photoelectrochemical (PEC) sensor was successfully developed for the detection of ampicillin (AMP) based on glutathione/zirconium dioxide hollow nanorods/aptamer (GSH@ZrO2 HS@apt) modified cellulose paper as a reactive zone with laser direct-writing lead sulfide/cadmium sulfide/graphene (PbS/CdS/LIG) as photoelectrode and cobalt hydroxide (CoOOH) as a photoresist material. Initially, AMP was introduced into the paper-based reaction zone as a biogate aptamer, which specifically recognized the target and then left the ZrO2 HS surface, releasing glutathione (GSH) encapsulated inside. Subsequently, the introduction of GSH into the reaction region and etching of CoOOH nanosheets to expose the PbS/CdS/LIG photosensitive material increased photocurrent. Under optimal conditions, the paper-based PEC biosensor showed a linear response to AMP in the range of 5.0 - 2 × 104 pM with a detection limit of 1.36 pM (S/N = 3). In addition, the constructed PEC sensing platform has excellent selectivity, high stability and favorable reproducibility, and can be used to assess AMP residue levels in various real water samples (milk, tap water, river water), indicating its promising application in environmental antibiotic detection.

Template-Assisted Synthesis of Porous Manganese Dioxide Hollow Rods as Supercapacitor Electrode Material

Template-Assisted Synthesis of Porous Manganese Dioxide Hollow Rods as Supercapacitor Electrode Material

Synthesis of novel Fe0-Fe3O4/CeO2/C composite cathode for efficient heterogeneous electro-Fenton degradation of ceftriaxone sodium

Fe0-Fe3O4 nanoparticles and cerium dioxide hollow spheres as efficient heterogeneous electro-Fenton reagents were rationally designed to be embedded in porous carbon derived from skimmed cotton for the electrocatalytic degradation of ceftriaxone sodium. Skimmed cotton porous carbon material has a hollow tubular structure, and cerium dioxide is dispersed on the surface of the carbon material in a hollow sphere structure of uniform size. Fe0-Fe3O4 nanoparticles were wrapped in irregular particle shapes on the surface of cerium dioxide hollow spheres, and the remaining part was laid flat on the surface of porous carbon material. The as-synthesized Fe0-Fe3O4/CeO2/C showed excellent degradation efficiency of 95.59 % for ceftriaxone sodium within 120 mins and obtained a COD removal rate of 95.21 % at 240 mins. The zero-valent iron as a reducing agent effectively accelerated the Fe3+/Fe2+ cycle, allowing the composites to exhibit higher catalytic activity and further reducing the possibility of secondary contamination. Moreover, the existence of cerium dioxide further promoted the redox cycle of Ce4+/Ce3+ and accelerated the electron transfer in the interface of the catalyst. The synergistic effect of iron and cerium greatly facilitated the production of hydroxyl radicals and increased the yield of hydroxyl radicals in the reaction system.

Development of Free-Standing Titanium Dioxide Hollow Nanofibers Photocatalyst with Enhanced Recyclability.

Titanium dioxide hollow nanofibers (THN) are excellent photocatalysts for the photodegradation of Bisphenol A (BPA) due to their extensive surface area and good optical properties. A template synthesis technique is typically employed to produce titanium dioxide hollow nanofibers. This process, however, involves a calcination procedure at high temperatures that yields powder-form photocatalysts that require post-recovery treatment before recycling. Meanwhile, the immobilization of photocatalysts on/into a membrane has been reported to reduce the active surface area. Novel free-standing TiO2 hollow nanofibers were developed to overcome those shortcomings. The free-standing photocatalyst containing 0.75 g of THN (FS-THN-75) exhibited good adherence and connectivity between the nanofibers. The recyclability of FS-THN-75 outperformed the THN calcined at 600 °C (THN-600), which retained 80% of its original weight while maintaining excellent degradation performance. This study recommends the potential application of free-standing TiO2 hollow nanofibers as high potential novel photocatalysts for the treatment of BPA in wastewater.

Synthesis and Characterization of Titanium Dioxide Hollow Nanofiber for Photocatalytic Degradation of Methylene Blue Dye.

Environmental crisis and water contamination have led to worldwide exploration for advanced technologies for wastewater treatment, and one of them is photocatalytic degradation. A one-dimensional hollow nanofiber with enhanced photocatalytic properties is considered a promising material to be applied in the field. Therefore, we synthesized titanium dioxide hollow nanofibers (THNF) with extended surface area, light-harvesting properties and an anatase–rutile heterojunction via a template synthesis method and followed by a calcination process. The effect of calcination temperature on the formation and properties of THNF were determined and the possible mechanism of THNF formation was proposed. THNF nanofibers produced at 600 °C consisted of a mixture of 24.2% anatase and 75.8% rutile, with a specific surface area of 81.2776 m2/g. The hollow nanofibers also outperformed the other catalysts in terms of photocatalytic degradation of MB dye, at 85.5%. The optimum catalyst loading, dye concentration, pH, and H2O2 concentration were determined at 0.75 g/L, 10 ppm, pH 11, and 10 mM, respectively. The highest degradation of methylene blue dye achieved was 95.2% after 4 h of UV irradiation.

Improved charge separation and carbon dioxide photoreduction performance of surface oxygen vacancy-enriched zinc ferrite@titanium dioxide hollow nanospheres with spatially separated cocatalysts

Here, we describe the fabrication of surface oxygen vacancy-enriched ZnFe2O4@TiO2 double-shell hollow heterostructure nanospheres (ZnFe2O4@H-TiO2-x) coupled with spatially separated CoOx and Au-Cu bimetallic cocatalysts. The ZnFe2O4@TiO2 heterojunction and spatially separated dual cocatalysts can significantly promote the separation of photoinduced charge carriers. Combined with the unique hollow double-shell heterostructure characteristics and improved surface state properties, the hybrid nanospheres can efficiently adsorb and activate CO2 molecules. These advantages cause the optimized catalyst to exhibit remarkably higher gas-phase photocatalytic CO2 reduction activity than the control CoOx/ZnFe2O4/Au-Cu and ZnFe2O4@H-TiO2-x double-shell hollow nanospheres loaded with a single cocatalyst. Meanwhile, the Au-Cu bimetal effect boosts the CO2 conversion rate and CH4 selectivity. The optimized hybrid catalyst with a Au/Cu ratio of 1:1 provides a CH4 yield of 21.39 μmol g−1 h−1 with 93.8% selectivity. This work provides a rational photocatalyst design to improve CO2 conversion and CH4 selectivity.

Preparation and Photocatalytic Activity of Fe/Yb Co-doped Titanium Dioxide Hollow Sphere

Preparation and Photocatalytic Activity of Fe/Yb Co-doped Titanium Dioxide Hollow Sphere

Unexpected Link between the Template Purification Solvent and the Structure of Titanium Dioxide Hollow Spheres

Carbon spheres were applied as templates to synthesize titanium dioxide hollow spheres. The templates were purified with either ethanol or acetone, and the effects of this treatment on the properties of the resulting titania were investigated. The photocatalytic activity of the catalysts was measured via the decomposition of phenol model pollutant under visible light irradiation. It was found that the solvent used for the purification of the carbon spheres had a surprisingly large impact on the crystal phase composition, morphology, and photocatalytic activity. Using ethanol resulted in a predominantly rutile phase titanium dioxide with regular morphology and higher photocatalytic activity (r0,phenol = 3.9 × 10−9 M∙s−1) than that containing mainly anatase phase prepared using acetone (r0,phenol = 1.2 × 10−9 M∙s−1), surpassing the photocatalytic activity of all investigated references. Based on infrared spectroscopy measurements, it was found that the carbon sphere templates had different surface properties that could result in the appearance of carbonate species in the titania lattice. The presence or absence of these species was found to be the determining factor in the development of the titania’s properties.

Iron-doped titanium dioxide hollow nanospheres for efficient nitrogen fixation and Zn–N2 aqueous batteries

A shell-engineering strategy is proposed for the design of vacancy-laden Fe-doped TiO2 hollow nanospheres, such as “breathing alveolus”, enabling highly efficient and sustainable electrocatalytic N2 reduction and realizing Zn–N2 aqueous batteries.

Titanium dioxide hollow nanofibers for enhanced photocatalytic activities

One-dimensional photocatalysts with enhanced properties are desirable for photocatalytic degradation of organic pollutants. In this work, hollow titanium dioxide nanofibers (HTNF) were successfully prepared via template synthesis technique. Firstly, polyacrylonitrile (PAN) nanofibers were synthesized by electrospinning and oxidized for further use. By dip-coating the electrospun nanofibers in TiO2 sol–gel, TiO2/PAN nanofibers composite was obtained. Subsequently, the nanocomposite was calcined. The decomposition of PAN during calcination resulted in the formation of HTNF. The nanofibers were characterized by FESEM, TGA and XRD. The characterization revealed hollow nanofibers structure with diameter of 200–250 nm. XRD analysis showed that the nanofibers had mixed crystalline phase, with 24.2% anatase and 75.8% rutile. The photocatalytic performance of HTNF were studied by evaluating the degradation of Bisphenol A (BPA) under UV light irradiation. In the photodegradation process, the effect of several parameters such as the initial concentration of BPA, pH of the solution and photocatalyst dosage were investigated. The optimum photocatalyst dosage, pH and initial BPA concentration were 0.75 g/L, pH 4.1 and 10 ppm BPA, respectively. Under these conditions, the photocatalytic performance of HTNF were found to be 97.3%, which was 12.6% higher than those of Degussa P25 TiO2. The degradation of BPA followed the pseudo-first-order kinetic model.

Effective electro-Fenton-like process for phenol degradation on cerium oxide hollow spheres encapsulated in porous carbon cathode derived from skimmed cotton

The uniform size cerium dioxide hollow spheres which were prepared by the SiO2 hard template method were loaded on microporous porous carbon obtained by carbonization derived from skimmed cotton (CSC) for electro-Fenton-like degradation of phenol. The microstructures of CSC/CeO2 composite materials were characterized utilizing XRD, BET, XPS, SEM, and TEM. The electrochemical performance of the CSC/CeO2 cathodes was studied through cyclic voltammetry and electrochemical impedance spectroscopy. The prepared CSC has a hollow tubular structure, and cerium dioxide is evenly loaded on the surface of the CSC in the form of uniform-sized hollow spheres. The CSC/CeO2 materials have a great specific surface area (287.73 m2 g−1) and a uniform poresize. The electrochemical performance analysis demonstrated that the redox ability of the material greatly was improved by loading CeO2 on the porous carbon surface of the skimmed cotton. The load ratio of cerium dioxide hollow spheres affects the structure and properties of CSC/CeO2 materials. Ce3+ and Ce4+ were co-existed in CSC/CeO2, which promoted the generation of H2O2 and .OH, and improved the catalytic activity of composite materials. The degradation efficiency of phenol reached 97.6% in 120 min, and the CSC/CeO2 cathode manifested excellent stability after being experimented 20 times. CSC/CeO2 composite material has great practical value in the treatment of phenolic wastewater and has promise for further application.

Preparation and characterization of noble metal modified titanium dioxide hollow spheres – new insights concerning the light trapping efficiency

Titanium dioxide hollow spheres (TiO2-HSs) were fabricated by applying carbon spheres (CSs) as templates, which were eliminated by calcination. The most suitable TiO2 was selected and an attempt was made to further increase its photocatalytic activity via noble metal (Au and Pt, at 0.25 wt%) deposition. The photocatalytic efficiency was determined by the decomposition of phenol and oxalic acid under both UV-A and visible light irradiation. It was established, that both the unique morphology and the presence of noble metals contributed to the photocatalytic activity gain compared to the solid spherical reference. For the elucidation of the observed phenol degradation performance under UV-A light irradiation, new insights were proposed: within the TiO2 samples the ratio of HSs with enhanced light trapping properties were demonstrated, and the data was compared to the observed photocatalytic activities and a direct correlation was found.

Novel selective adsorption and photodegradation of BPA by molecularly imprinted sulfur doped nano-titanium dioxide

To achieve selective adsorption of bisphenol A (BPA) and synergy between photocatalysis and adsorption, a molecular imprinting surface-polymerized nanoparticles loaded on sulfur-doped titanium dioxide hollow spheres (MICST) with the large specific surface area was composed by a chemical method. Firstly, with the aid of surfactants CTAB and SDS, uniform sulfur doped titanium dioxide particles (CST) was synthesized, then the molecularly imprinted polymer layers loaded on the surface, and finally molecular imprinted sulfur-doped titanium dioxide was got after the template molecular were removed. TEM, SEM, EDS, FTIR, BET, and XRD were employed to characterize materials. The specific area measured by BET test was 160 m2/g. The parameters including contact time, pH and selectivity were evaluated and optimized systematically. Additionally, the adsorption capacity and selectivity as well as the photodegradation activity were investigated. The maximum adsorption capacity of BPA was 191 mg/g which could be proved by the Langmuir adsorption model. It is superior to most of the reported imprinted photocatalysts in literature. Moreover, the effect of the amount of imprinted polymers was studied for the photodegradation effect. The prepared materials can be a significant candidate for the treatment of recalcitrant organic pollutants in wastewater.

Ag2O/TiO2 hollow microsphere heterostructures with exposed high-energy {001} crystal facets and high photocatalytic activities

In this paper, one-step hydrothermal method was used to prepare the graded titanium dioxide hollow microspheres, and the {001} crystal plane was exposed. The silver oxide nanoparticles were deposited on the exposed crystal face of titanium dioxide by wet chemical coprecipitation to form Ag2O/TiO2 composite material. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption–desorption (BET), and so on. The degradation abilities of Ag2O/TiO2 composite materials with different molar ratios to rhodamine B were studied under UV–Vis irradiation. And then the mechanism of photocatalytic degradation was analyzed. The experimental results showed that when the molar ratio of titanium dioxide to silver nitrate was 4:1, the degradation effect was best, and the degradation rate reached 95.4% in 80 min. This outstanding photochemical catalysis performance was mainly due to good cooperation, including exposure of specific crystal planes of TiO2 hollow microspheres and highly scattered Ag2O nanoparticles, and the p–n heterostructure between Ag2O and TiO2 will induce efficient charge separation efficiency.

Efficient enhancement of electrochemiluminescence from tin disulfide quantum dots by hollow titanium dioxide spherical shell for highly sensitive detection of chloramphenicol

In this study, modified hollow titanium dioxide and SnS2 quantum dots (SnS2 QDs) were used to build a novel electrochemiluminescence immunoassay (ECLIA) for ultrasensitive detection of chloramphenicol (CAP). The titanium dioxide hollow spheres (THS) modified with polyethyleneimine (PEI) and gold nanoparticles (Au NPs) was synthesized as a probe material for the novel ECLIA, meanwhile it also could be a coreaction accelerator which could greatly improve the interaction efficiency between SnS2 QDs and S2O82-. Then the modified THS was combined with chloramphenicol antibody to form ECLIA probes, and colloidal gold synthesized as a platform for an ECLIA by ascorbic acid (AA) reduction. A competitive immunoassay strategy was used for the detection of CAP, where CAP in the sample would compete with the coating antigen for the limited antibodies. The proposed ECLIA for CAP detection exhibited high sensitivity with a wide linear range from 0.01 ng mL-1 to 100 ng mL-1 and a low detection limit at 3.1 pg mL-1. Furthermore, it could be seen from electrochemical analysis that the effect of THS on the enhancement of ECL signal is about twice as high as that of ordinary titanium dioxide. Importantly, this work not only successfully applied THS to amplify electrochemical-luminescence signal in the ECLIA, but also successfully prepared a stable and highly selective sensor for ultrasensitive detection of CAP.

A novel strategy for tailoring Cobalt/Titanium Dioxide Hollow Spheres for hydrogen production

A novel strategy for tailoring Cobalt/Titanium Dioxide Hollow Spheres for hydrogen production

Self-template synthesis of double-shell TiO2@ZIF-8 hollow nanospheres via sonocrystallization with enhanced photocatalytic activities in hydrogen generation

The photocatalytic hydrogen evolution on inorganic semiconductors has been studied for several decades. However, the conversion efficiency of solar energy is still poor caused by the recombination of photo-generated electron-hole pairs. Semiconductors - metal organic frameworks (MOFs) hybrid photocatalysts are being regarded as promising candidates due to large surface area and porosity. Here we reported the coordinative integration of a composite material with efficient capacity of H2 evolution driven by solar light, namely TiO2@ZIF-8, made up of titanium dioxide hollow nanospheres (TiO2 HNPs) externally decorated with zeolitic imidazolate framework-8 (ZIF-8) via a facile sonochemical route. The resulting composite demonstrates the high dispersion of ZIF-8 on the surface of TiO2 HNPs and this kind of close connection makes for an efficient photocatalyst through the synergistic effect. Up to 50.89% of apparent quantum efficiency (AQE), the hybrid double-shell HNPs exhibits 3.5 times higher H2 evolution rate (HER) than the bare TiO2 HNPs under solar light and shows good stability and recyclability. It is further proposed by photoluminescence spectra and optoelectronic measurement that the remarkably enhanced photocatalytic activity of TiO2@ZIF-8 is not only attributed to the efficient charge separation with electron injection from ZIF-8 to TiO2 HNPs, but also more active reaction sites provided by cavity structure of ZIF-8. Overall, this work exemplifies that surface engineering of semiconductors with MOFs is a great strategy to achieve advanced photocatalytic performance for solar energy conversion.

One-step fabrication of g-C3N4 nanosheets/TiO2 hollow microspheres heterojunctions with atomic level hybridization and their application in the multi-component synergistic photocatalytic systems

In this paper, graphitic carbon nitride nanosheets/titanium dioxide hollow microspheres heterojunctions (g-C3N4 NSs/TiO2 HMSs) with excellent photocatalytic activity were successfully fabricated by a simple one-step synthesis strategy in the assistance of hydrothermal carbon microspheres. Hydrothermal carbon microspheres act as both dispersant and structure-directing agent for the simultaneous construction of graphitic carbon nitride nanosheets and titanium dioxide hollow microspheres. The synergistic photocatalytic effects in the 4-fluorophenol/hexavalent chromium [4-FP/Cr(VI)] and hexavalent chromium/trivalent arsenic [Cr(VI)/As(III)] multi-component composite pollution systems were studied by using as-prepared g-C3N4 NSs/TiO2 HMSs under different pH conditions. Interestingly, the efficiencies of 4-FP degradation, Cr(VI) reduction, and As(III) oxidation were simultaneously improved in the 4-FP/Cr(VI) and Cr(VI)/As(III) multi-component synergistic photocatalytic systems relative to the single-component photocatalytic systems. The synergistic photocatalytic mechanisms in the 4-FP/Cr(VI) and Cr(VI)/As(III) multi-component synergistic photocatalytic systems were systematically discussed.

Single-crystalline titanium dioxide hollow tetragonal nanocones with large exposed (1 0 1) facets for excellent photocatalysis

Crystal facet engineering and surface modification of semiconductor have become important strategies to improve photocatalytic activity by optimizing surface charge carrier separation/transfer and extending solar spectrum utilization. In this work, we report anatase single-crystalline TiO2 hollow tetragonal nanocones with large exposed (101) facets by a facile liquid-phase interfacial synthetic strategy, using the hydrolysis of tetrabutyltitanate with adscititious water in the organic solvent of cyclohexane and a capping agent of 1, 6-hexanediamine. The specific surface area of these TiO2 hollow tetragonal nanocones is as high as 331.3m2/g. Thanks to large exposed (101) facets and high surface area, these TiO2 hollow tetragonal nanocones exhibited excellent full-arc photocatalytic activities for the degradation of organic pollutants. Remarkably, the butoxy group could be modified onto TiO2 hollow tetragonal nanocones through post-synthesis treatment in tetrabutyltitanate glycol solution, which brought about eximious visible light photocatalytic activities for the degradation of colored dyes of RhB and MO, especially for RhB, by virtue of much improved electron trapping ability of the Ti-O group from the excited dye due to the strong electronegativity of the oxygen atom in the butoxy group. This work advances us to rationally tailor the atomic and electronic structure of the photocatalyst for outstanding photocatalytic properties in various environmental and energy-related applications.

Controllable in situ synthesis of epsilon manganese dioxide hollow structure/RGO nanocomposites for high-performance supercapacitors.

Well-organized epsilon-MnO2 hollow spheres/reduced graphene oxide (MnO2HS/RGO) composites have been successfully constructed via a facile and one-pot synthetic route. The ε-MnO2 hollow spheres with the diameter of ∼500 nm were grown in situ with homogeneous distribution on both sides of graphene oxide (GO) sheets in aqueous suspensions. The formation mechanism of the MnO2HS/RGO composites has been systematically investigated, and a high specific capacitance and good cycling capability were achieved on using the composites as supercapacitors. The galvanostatic charge/discharge curves show a specific capacitance of 471.5 F g(-1) at 0.8 A g(-1). The hollow structures of ε-MnO2 and the crumpled RGO sheets can enhance the electroactive surface area and improve the electrical conductivity, thus further facilitating the charge transport. The MnO2HS/RGO composite exhibits a high capacitance of 272 F g(-1) at 3 A g(-1) (92% retention) even after 1000 cycles. The prominent electrochemical performance might be attributed to the combination of the pseudo-capacitance of the MnO2 nanospheres with a hollow structure and to the good electrical conductivity of the RGO sheets. This work explores a new concept in designing metal oxides/RGO composites as electrode materials.