TiO2 Spheres Research Articles

Surface properties, adherence, and photocatalytic activity of sol–gel dip-coated TiO2–ZnO films on glass plates

In this study, TiO 2 –ZnO nanostructured films prepared from different Ti/water mole ratios were deposited on glass plates by a sol–gel dip-coating method. The structural and surface properties, adherence, and photoactivity of synthesized TiO 2 –ZnO coatings in methylene blue degradation were investigated. Among the as-prepared TiO 2 –ZnO coatings from sols with different Ti/water mole ratios (1, 0.66, 0.5, and 0.4), the highest sol concentration (Ti/water mole ratio of 1) showed the highest methylene blue photodegradation of almost 80% after 400 min of UV irradiation. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), Energy-dispersive X-ray (EDX), and UV-vis diffuse reflectance spectra (DRS) confirmed that at high sol concentrations (Ti/water mole ratios of 1 and 0.66), a mixed phase of anatase and rutile is formed, whereas at a Ti/water mole ratio of 0.5, just pure rutile is formed. In detail, decreasing the sol concentration increases the cracks, degree of agglomeration, and the thickness of coatings. UV-vis DRS studies also confirm that decreasing the sol concentration in synthesized TiO 2 –ZnO films leads to a shift in the absorption region of the coating to the UV region. Moreover, decreasing the sol concentration declines the coating adherence onto glass plates. TEM images of the TiO 2 –ZnO coating synthesized from sol with a Ti/water mole ratio of 1 revealed the formation of ZnO nanorods around a spherical TiO 2 , which indicates the presence of strong interaction between TiO 2 and ZnO nanoparticles. The TiO 2 –ZnO coating synthesized from sol with a Ti/water mole ratio of 1 was then evaluated at different methylene blue concentrations, pH values, and number of coatings. After five consecutive runs, no significant decrease in the photodegradation efficiency was observed. Scanning electron microscopy (SEM) picture of used coating showed a smooth and stable layer without any detachment. Thermogravimetric analysis (TG) and sonication test confirmed thermal and mechanical stabilities of this coating as well.

Non-thermal Plasma Technology for the Effective Regeneration of Macroscopic Adsorbent Materials Used in the Removal of Patent Blue V Dye from Aqueous Solutions

In this work, two different commercial macroscopic adsorbent materials (Na-ZSM5 zeolite in spherical pellets and TiO2 cylindrical pellets) has been tested in the removal of model organic food dyes (Patent blue V, E131) and they were regenerated using an innovative techniques based on non-thermal plasma process. The adsorption experiments were carried out using a pyrex cylindrical reactor and liquid samples were analyzed in continuous mode by spectrophotometric measurement at ? = 636 nm. The results demonstrated that these materials were able to remove Patent blue V dye, with removal efficiency equal to 80% for the zeolite and 95% for TiO2 pellets after 400 min of treatment time. The adsorbent materials have been used for several cycles until their saturation. In particular, after seven adsorption cycles, the adsorbing capacity was reduced of about 60 and 20% for zeolite and TiO2 pellets, respectively. Subsequently, the materials were regenerated by non-thermal plasma and reused in the adsorption system. The results evidenced that the regeneration by non-thermal plasma was able to induce the complete degradation of the absorbed organic substance and consequently restoring the initial adsorption capacity of both macroscopic adsorbent materials

Nitrogen-doped black TiO2 spheres with enhanced visible light photocatalytic performance

N-doped black TiO2 spheres (N2–b-TiO2) were prepared by solvothermal reaction and calcination under a nitrogen atmosphere. N-doping introduces new impurity levels above the TiO2 valence band, enhancing the effective absorption of visible light. The presence of OV and Ti3+ in the disordered outer layer inhibits electron–hole pair recombination, and the spherical structure provides many active sites. Those were confirmed by X-ray diffraction, Fourier transform IR, X-ray photoelectron spectroscopy and High-resolution transmission electron microscopy. UV–visible absorption indicates that the nitrogen-doped black TiO2 samples has a reduced band gap and a strong visible light absorption, which is attributed to the doping of OV, Ti3+ and N. The photocatalytic efficiency of the best sample (N2–b-TiO2) for potassium dichromate and rhodamine B was 96.2% and 99.5%, respectively. The superoxide radical (•O2−) played a dominant role in photocatalysis by scavenging experiments. Thus, a photocatalytic mechanism with reduced band gap has been proposed. This study provides a simple and practical method for non-metallic doping to control the photocatalytic performance of semiconductors.

Simple-Structured Micromotors Based on Inherent Asymmetry in Crystalline Phases: Design, Large-Scale Preparation, and Environmental Application.

The key principle of designing a micro/nanomotor is to introduce asymmetry to a micro/nanoparticle. However, micro/nanomotors designed based on external asymmetry and inherent chemical and geometrical asymmetry usually suffer from tedious small-scale preparation, high cost, and/or complexity of external power and control devices, making them face insurmountable hurdles in practical applications. Herein, considering the possible distinct properties of different polymorphs, we propose a novel design strategy of simple-structured micromotors by introducing inherent asymmetry in crystalline phases. The inherent phase asymmetry can be easily introduced in spherical TiO2 particles by adjusting the calcination temperature to control the phase transition and growth of primary grains. The as-designed anatase/rutile TiO2 micromotors not only show efficient autonomous motions controlled by light in liquid media stemming from the asymmetric surface photocatalytic redox reactions but also have a promising application in environmental remediation due to their high photocatalytic activity in "on-the-fly" degradation of organic pollutants, facile large-scale fabrication, and low cost. The proposed design strategy may pave the way for the large-scale productions and applications of micro/nanomotors.

Multi-dimensional anatase TiO2 materials: Synthesis and their application as efficient charge transporter in perovskite solar cells

Recently, organo-metal halide perovskite (e.g., CH3NH3PbI3) solar cells have shown a significant surge in progress and efficiency. The photovoltaic performance of perovskite solar cells (PSC) extensively depends on the morphology of the materials at nano-level, because the intrinsic electrical, optical and electrochemical properties also change with a change in morphology. Different TiO2 nanostructures with diverse dimensionalities, 0D hollow TiO2 nanoparticles (HTNPs), 3D hollow TiO2 mesospheres (HTMSs) and 3D hierarchical TiO2 spheres (HTSs) were synthesized hydrothermally. The PSCs based on 3D HTSs or 3D HTMSs as electron transport layers (ETLs) shows better performance than the PSCs fabricated with 0D HTNPs as ETL. The enhanced results can be attributed to the better penetration of the perovskite materials in the porous network of the HTSs or HTMSs and decreased interfacial recombination due to superior charge extraction and electron transport at the HTSs/CH3NH3PbI or HTMSs/CH3NH3Pb interfaces. By using a self-assembled TiO2 compact layer (c-TiO2), followed by a mesoporous layer of HTSs, produces PSCs with an excellent efficiency of 15.08%. Such c-TiO2-ETL films may improve PSCs performance by enhancing electron extraction and block the photogenerated holes.

In-situ constructing of hollow TiO2@rGO hybrid spheres as high-rate and long-life anode materials for lithium-ion batteries

Abstract The hollow TiO2@rGO hybrid spheres are in-situ synthesized by using TiO2 spheres as a precursor and a simple hydrothermal route with subsequent annealing. The unique hollow structure has large special surface areas, and the reduced graphene oxide (rGO) layer can accelerate transfer of lithium ions and electrons and efficiently enhance the structural stability. The prepared hollow TiO2@rGO hybrid spheres exhibit better electrochemical performance than pure TiO2 hollow microspheres. It exhibits a high special capacity of 254.3 mA h g−1 at 1C after 600 cycles and highly stable capacity retention, and superior rate capacity of 159.1 mAh g−1 at 10C after 3000 cycles. Moreover, the hollow TiO2@rGO hybrid spheres have high surface area, superior structural stability, and excellent high-rate and long-life cycle property as anode material for LIBs.

Novel thermal decomposition approach for the synthesis of TiO2@Ag core-shell nanocomposites and their application for catalytic reduction of 4-nitrophenol

Metal-semiconductor core-shell nanocomposites with TiO2 as core and Ag nanoparticles as shell (TiO2@Ag) have been synthesized by a novel thermal decomposition approach. The size of Ag nanoparticles in TiO2@Ag can be controlled by varying the amount of silver acetate used during the synthesis. The synthesized TiO2@Ag core-shell nanocomposites were characterized using various state-of-art analytical techniques. XRD analysis confirms the formation of anatase and metallic silver in the core-shell nanocomposites and FT-IR studies prove purity of the TiO2@Ag core-shell nanocomposites. XPS studies confirm the presence of Ti4+ and metallic silver in the nanocomposites, and FESEM and TEM studies prove the coating of Ag nanoparticles on the surface of TiO2 spheres. The TiO2@Ag core-shell nanocomposites were explored as catalyst for the reduction of 4-nitrophenol in an aqueous solution at room temperature. In terms of catalytic performance, the TiO2@Ag core-shell nanocomposites are better compared to pure TiO2 as well as Ag nanoparticles.

Synthesis of nanodispersed titanium dioxide via pH-controlled polymerization of titanium acid

The possibility of synthesis of highly photoactive nanosized titania employing ion exchange to exert control over polycondensation of titanium acid in aqueous medium has been demonstrated. The resultant spherical TiO2 nanoparticles exhibits extra high light-induced oxidation activity remaining for some time even after termination of UV illumination. The nanodispersed titania readily penetrate into the surface pores and can be used for deposition of photocatalytic coatings by impregnation technique.

Facile template-free route to synthesis visible light respensive hollow TiO2 spheres

The monodisperse hollow TiO2 spheres (HTS) were fabricated by facile template-free route involving direct precipitation and etching reaction. Tetrabutyl titanate was used as titanium precursor to form amorphous TiO2 spheres (ATS) directly in ethanol-acetonitrile mixed solution. Then, the ATS were etched by F− with the protection of PVP to form HTS under hydrothermal reaction conditions. The physical and chemical characterizations of synthesized samples were conducted by SEM, TEM, XRD and UV–vis diffuse reflectance spectroscopy. Result showed that morphology and structure of HTS can be easily controlled by adjusting time of etching reaction. The HTS obtained by etching for 4 h exhibited good hollow structure with unique shell assembled with enriched nanothorns, and it possessed good photocatalytic activity under visible light irradiation.

Effect of dysprosium ion (Dy3+) doping on morphological, crystal growth and optical properties of TiO2 particles and thin films

Dy3+ doped (0.5, 2.5, 5 and 7.5 wt %) TiO2 particles and thin films were obtained by modified alcoholysis-sol-gel route using tetrabutyl orthotitanate as a precurspor. By controlling the hydrolysis of this precursor through alcoholysis reaction, monodisperse and spherical TiO2 particles were obtained. X-ray diffraction and Raman results confirmed that the Dy3+ doped TiO2 particles are composed of only anatase phase. The Dy3+ doping inhibited any phase transformation and slowed down the particle growth of anatase TiO2. Scanning electron microscopy of bare TiO2 showed monodisperse, spherical and non-aggregated particles. In contrast, the Dy3+doped TiO2 samples exhibited poor dispersity. The luminescence spectra show three characteristic bands at 481, 577 and 683 nm, which are due to 4F9/2 → 6H15/2 (blue), 4F9/2 → 6H13/2 (yellow), and 4F9/2 → 6H11/2 (red) transitions of trivalent Dy3+ ions. The photoluminescence study revealed the dependence of the luminescent intensity on dopant concentration in TiO2 particles.

Tunable high-index photonic glasses

Materials with extreme photonic properties such as maximum diffuse reflectance, high albedo, or tunable band gaps are essential in many current and future photonic devices and coatings. While photonic crystals, periodic anisotropic structures, are well established, their disordered counterparts, photonic glasses (PGs), are less understood despite their most interesting isotropic photonic properties. Here, we introduce a controlled high index model PG system. It is made of monodisperse spherical TiO$_2$ colloids to exploit strongly resonant Mie scattering for optimal turbidity. We report spectrally resolved combined measurements of turbidity and light energy velocity from large monolithic crack-free samples. This material class reveals pronounced resonances enabled by the possibility to tune both the refractive index of the extremely low polydisperse constituents and their radius. All our results are rationalized by a model based on the energy coherent potential approximation, which is free of any fitting parameter. Surprisingly good quantitative agreement is found even at high index and elevated packing fraction. This class of PGs may be the key to optimized tunable photonic materials and also central to understand fundamental questions such as isotropic structural colors, random lasing or strong light localization in 3D.

Synthesis and characterization of poly-urethane foam doped with different nano-fillers

Abstract A detailed experimental study is performed to study the deformation behaviour and thermal stability of TiO2 and ZnO reinforced PU foams. Uniform dispersion of nano-fillers in PU foams is ensured by introducing water based slurry of nano-particles in polyol. The bulk density of the foam samples observed to be in the range of 0.02-0.05 g/cc with neat PU foam sample having maximum density. The SEM analysis revealed that pores size is about 570 μm for neat PU foams and decreases after addition of nanofiller in PU foam. SEM micrographs reveal that nanoparticles accumulate at cell walls and thus having adverse effect on the mechanical properties of foams. Moreover, the spherical morphology TiO2 nanoparticle found to substantially enhance the densification modulus but shows a marginal increase with the addition of rod like ZnO nanoparticles. On the other hand, the value of elastic modulus and plateau modulus decreases with the addition of either of the nanoparticles. The quasistatic cyclic compression tests reveal that the energy loss coefficient (ELC) increases after addition of both types of fillers but ELC found to be maximum with ZnO addition due to the frictional losses between ZnO nanoparticles. The specific energy absorbed by nanoparticles infused PU foam during compression is (7MJ/m3/g cc-1) which is higher than expanded polystyrene foam (4MJ/m3/g cc-1), which are used as inner lining of helmets. The thermogravimetric analysis of neat and modified PU foams samples shows that even though thermal stability of neat PU foam is substantially increased by adding ZnO as nanofiller, it tends to decrease for TiO2 reinforced PU foams.

Mesoporous hollow black TiO2 with controlled lattice disorder degrees for highly efficient visible-light-driven photocatalysis.

Black TiO2 has received tremendous attention because of its lattice disorder-induced reduction in the TiO2 bandgap, which yields excellent light absorption and photocatalytic ability. In this report, a highly efficient visible-light-driven black TiO2 photocatalyst was synthesized with a mesoporous hollow shell structure. It provided a higher specific surface area, more reaction sites and enhanced visible light absorption capability, which significantly promoted the photocatalytic reaction. Subsequently, the mesoporous hollow black TiO2 with different lattice disorder-engineering degrees were designed. The structure disorder in the black TiO2 obviously increased with reduction temperature, leading to improved visible light absorption. However, their visible-light-driven photocatalytic efficiency increased first and then decreased. The highest value can be observed for the sample reduced at 350 °C, which was 2-, 1.4- and 5-fold that of the samples reduced at 320 °C, 380 °C and 400 °C, respectively. This contradiction can be ascribed to the varied functions of the surface defects with different concentrations in the black TiO2 during the catalytic process. In particular, the defects at low concentrations boost photocatalysis but reverse photocatalysis at high concentrations when they act as charge recombination centers. This study provides significant insight for the fabrication of high-efficiency visible-light-driven catalytic black TiO2 and the understanding of its catalysis mechanism.

Bio-derived 3D TiO2 hollow spheres with a mesocrystal nanostructure to achieve improved electrochemical performance of Na-ion batteries in ether-based electrolytes

Novel hollow TiO2 spheres with mesocrystal shells were fabricated via sacrificial bio-templates, exhibiting enhanced Na+ ion storage in ether-based electrolyte.

Local temperature control of hybrid plasmonic nano-antennas

Local enhanced heat generation in plasmonic nano-antennas caused by the finite conductivity of metals can cause local super-heating areas, a disadvantage to the normal work of nano-antennas. In this work, an approach to simultaneously enabling near-field intensity enhancement at the operating wavelength in the visible and local operating temperature control of hybrid plasmonic antennas is studied. Results show that the operating temperature for the pure Au or Ag nanoparticles (NP) is very high at a low intensity of incident light in vacuum, owing to a negligible thermal radiation dissipation in the infrared region. Thus, different dielectric spheres (i.e., Al2O3, SiO2, and TiO2) were introduced to enhance the thermal radiation dissipation of the hybrid plasmonic antennas. The hybrid antennas obtained greater absorption ability and near-field enhancement compared to pure plasmonic NPs. Additionally, the hybrid antennas showed great thermal emittance capability compared to pure plasmonic NPs. The Ag–TiO2 hybrid antenna obtained the lowest temperature increase among the three hybrid systems while maintaining the highest near-field enhancement. The sharp absorption peaks or near-field enhancement spectra of the Ag–TiO2 hybrid antennas can be attributed to the excitation of the whispering gallery mode coupled with the surface plasmon mode, resulting in an enhanced absorption or near-field enhancement. The absorption cross section, the near-field intensity enhancement, and the thermal emittance of the Ag–TiO2 hybrid antennas increase with the size of the TiO2 sphere. A saturation value exists for the TiO2 sphere size to reduce the temperature increase at a specific intensity of incident light. In addition, air convection with the consideration of size effect also can further reduce the operating temperature of the hybrid antenna.

Preparation and characterization of spherical titania and their influence on self-cleaning and anticorrosion properties of acrylic resin

Firstly, spherical TiO2 particles of micro-nano size were prepared by using the inclusion reaction product which resulted from the chemical reaction between urea and EtOH and the inclusion reaction product served as a template. The size of spherical TiO2 can be regulated by the ratio of urea solution. The spherical TiO2 particles are mainly composed of anatase. Then the above spherical TiO2 particles were used to enhance the properties of acrylic resin. With the increase of TiO2, the microstructure surface of TiO2/acrylic resin coating was in the uneven shape of lotus leaf. When the addition of TiO2 reaches up to 30 wt.%, it can enhance the anti-corrosion properties of the acrylic resin coating brushed on Q235 steel plate, the water contact angle on the surface of TiO2/acrylic resin coating is 121.5° and displays good self-cleaning properties in the water with sand whose concentration reaches 20 wt.%. The composite coatings exhibited the highest 5B rating determined by adhesion test ASTM D-3359-02 (American Society for Testing and Materials).

Porous spheres of TiO2 (B)/anatase entwined by graphene nanoribbons for high Li+ rate performance

A porous spherical hybrid of TiO2 (B)/anatase entwined by graphene nanoribbons (GNRs) was synthesized by a facile and scalable method. The entwining of GNRs can adhere on the surface of TiO2 by electrostatic interactions and prevent TiO2 nanoribbons from self-scrolling to nanotubes, facilitating large lithium storage and high rate capability. The TiO2/GNRs nanocomposite exhibited high rate capability in galvanostatic charge-discharge experiments, providing a capacity of 131 mAh g−1 with a coulombic efficiency of 99.2% at a charge rate of 10C (1 C = 335 mA g−1) over 1400 cycles. The appealing electrochemical performance can be attributed to the synergistic effect of TiO2 nanoribbons entwined by GNRs.

Spray pyrolysis synthesis of mesoporous TiO2 microspheres and their post modification for improved photocatalytic activity

Mesoporous TiO2 microspheres were prepared by spray pyrolysis for photocatalysis. Post modification of TiO2 by heat treatment was performed to optimize its photocatalytic performance. First, spherical TiO2 particles with mesoporous structure were synthesized at pyrolysis temperatures of 500, 600, and 700 °C. After characterization by XRD, SEM, and N2 adsorption, a sample prepared at 500 °C was found to possess desirable properties for photocatalytic performance through post-modification. In methylene blue degradation, mesoporous TiO2 microspheres synthesized at 500 °C outperformed other microspheres. Furthermore, samples obtained by spray pyrolysis at 500 °C were calcined at various temperatures as a post-modification process. The sample calcined at 350 °C showed improved photocatalytic activity due to optimal anatase crystallinity and surface area.

Facile synthesis of spherical Au/TiO2 nanoparticles by sol-gel method using Tween 80 for photocatalytic decolourization of Malachite Green dye

The current study demonstrated the successful photocatalytic decolourization of malachite green (MG) dye over novel spherical TiO2 nanocomposites embedding with 0–1 wt% of Au nanoparticles. Au/TiO2 nanocomposites were prepared by using sol-gel method and Tween 80 as a template. A shift in solution color from yellow to dark purple color was spontaneously detected after addition of Tween 80 revealing the reduction of Au ions into metallic Au nanoparticles. The structural, crystalline and morphological features of the samples were characterized using X-ray diffraction, XRD, Field emission scanning electron microscopy, FESEM, together with energy-dispersive X-ray spectroscopy, EDX, and Fourier transform infra-red spectroscopy, FTIR,. The obtained characterization results indicate that the existence of Au nanoparticles control the growth of titania crystallites and reduce the crystallite size to nano dimensions. The photocatalytic reactivity of Au/TiO2 was found to be highly effected in the presence SnO2 as a co-dopant with Au. DR UV-Vis study showed the disappearance of surface plasmon absorption in the presence of SnO2.

Interfacing CRYSTAL/AMBER to Optimize QM/MM Lennard⁻Jones Parameters for Water and to Study Solvation of TiO₂ Nanoparticles.

Metal oxide nanoparticles (NPs) are regarded as good candidates for many technological applications, where their functional environment is often an aqueous solution. The correct description of metal oxide electronic structure is still a challenge for local and semilocal density functionals, whereas hybrid functional methods provide an improved description, and local atomic function-based codes such as CRYSTAL17 outperform plane wave codes when it comes to hybrid functional calculations. However, the computational cost of hybrids are still prohibitive for systems of real sizes, in a real environment. Therefore, we here present and critically assess the accuracy of our electrostatic embedding quantum mechanical/molecular mechanical (QM/MM) coupling between CRYSTAL17 and AMBER16, and demonstrate some of its capabilities via the case study of TiO2 NPs in water. First, we produced new Lennard–Jones (LJ) parameters that improve the accuracy of water–water interactions in the B3LYP/TIP3P coupling. We found that optimizing LJ parameters based on water tri- to deca-mer clusters provides a less overstructured QM/MM liquid water description than when fitting LJ parameters only based on the water dimer. Then, we applied our QM/MM coupling methodology to describe the interaction of a 1 nm wide multilayer of water surrounding a spherical TiO2 nanoparticle (NP). Optimizing the QM/MM water–water parameters was found to have little to no effect on the local NP properties, which provide insights into the range of influence that can be attributed to the LJ term in the QM/MM coupling. The effect of adding additional water in an MM fashion on the geometry optimized nanoparticle structure is small, but more evident effects are seen in its electronic properties. We also show that there is good transferability of existing QM/MM LJ parameters for organic molecules–water interactions to our QM/MM implementation, even though these parameters were obtained with a different QM code and QM/MM implementation, but with the same functional.