Black TiO2 Research Articles

Analysis of the Inhomogeneous Growth of Sputtered Black TiO2 Thin Films.

Black titanium dioxide (B-TiO2) is a highly active photoelectrochemical material compared to pure titanium dioxide due to its increased light absorption properties. Recently, we presented the deposition of thin-film B-TiO2 using an asymmetric bipolar reactive magnetron sputter process. The resulting samples exhibit excellent photoelectrochemical properties, which can be fine-tuned by varying the process parameters. In this article, results of morphological, electrical, and photoelectrochemical measurements are discussed to better understand the surprisingly high electrochemical activity of the films. In order to study the influence of the dynamic process on film formation, we use static sputtering with a fixed substrate covering the entire chamber area in front of the two targets. This allows the material composition of the sputtered film to be analyzed depending on its relative position to the targets. The results lead to the conclusion that the asymmetric bipolar sputtering mainly produces two phases, a transparent, nonconductive crystalline phase and a black, conductive amorphous phase. As a consequence, the dynamically sputtered samples are multilayers of these two materials. We discuss that the significantly better electrical and photoelectrochemical properties emerge from the inhomogeneous nature of the laminates, like also found in core-shell nanoparticles of B-TiO2.

Urease-Powered Black TiO2 Micromotors for Photothermal Therapy of Bladder Cancer.

Urease-powered nano/micromotors can move at physiological urea concentrations, making them useful for biomedical applications, such as treating bladder cancer. However, their movement in biological environments is still challenging. Herein, Janus micromotors based on black TiO2 with urease asymmetric catalytic coating were designed to take benefit of the optical properties of black TiO2 under near-infrared light and the movement capability in simulated bladder environments (urea). The black TiO2 microspheres were half-coated with a thin layer of Au, and l-Cysteine was utilized to attach the urease enzyme to the Au surface using its thiol group. Biocatalytic hydrolysis of urea through urease at biologically relevant concentrations provided the driving force for micromotors. A variety of parameters, such as urea fuel concentration, viscosity, and ionic character of the environment, were used to investigate how micromotors moved in different concentrations of urea in water, PBS, NaCl, and urine. The results indicate that micromotors are propelled through ionic self-diffusiophoresis caused by urea enzymatic catalysis. Due to their low toxicity and in vitro anticancer effect, micromotors are effective agents for photothermal therapy, which can help kill bladder cancer cells. These promising results suggest that biocompatible micromotors hold great potential for improving cancer treatment and facilitating diagnosis.

Three-in-one: Saturated, UV-protective and anti-bacterial structural colored textiles

Structural color based textiles have attracted significant attention owing to their potential in facilitating environmentally-friendly and durable coloration processes. However, the improvement of color saturation in textiles based on structural color is still under continuous investigation. Additionally, there is a rising demand for textiles featuring specialized functionalities such as anti-bacteria and anti-ultraviolet properties in daily life. In this study, a “three-in-one” amorphous photonic structure (APS) and multi-functional textile design is performed to achieve high structural color saturation, UV protection, and anti-bacteria properties. In this system, poly(styrene-butyl acrylate-methacrylate) (P(St-BA-MAA)) colloidal particles are used as building blocks, black titanium dioxide (TiO2) is used as black dopant, and water-soluble polyurethane (WPU) is used as the binder. The WPU demonstrates a significant capability to enhance the color fastness of APS/TiO2 textiles. The strong absorption of incoherent scattered light by black TiO2 in the visible range plays a crucial role in achieving a highly saturated APS-based textile. In addition, the doped black TiO2 possesses strong UV–visible light absorption and anti-bacterial capabilities, thereby supporting the development of textiles functionalized with UV protection and anti-bacteria. Our proposed simplified approach to fabricating high color saturation and functionalized APS/TiO2 textiles demonstrates significant potential for eco-textile coloring in line with market demands.

Synergistic modulation of oxygen vacancies and heterojunction structure in Pd@CN@TiO2 promotes efficient photocatalytic Suzuki–Miyaura CC coupling reactions

This paper reports a concise strategy for the controlled preparation of Pd@g‐C3N4/TiO2 photocatalysts rich in oxygen vacancies. The scheme forms black TiO2 with oxygen vacancies on a carbon nitride material by in‐situ growth and heat treatment, and then utilizes solvothermal reduction to load metallic palladium into the material. The composites were structurally analyzed using Fourier transform infrared (FT‐IR), X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction analysis (XRD), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR), scanning electron microscopy (SEM), elemental mapping, diffuse reflectance spectroscopy (DRS), and inductively coupled plasma (ICP) analysis. The results show that the oxygen vacancies in the black TiO2 materials prepared by the method reported in this paper can effectively improve the separation efficiency of the photogenerated electron–hole pairs and prolong the lifetime of the charge carriers by inhibiting charge recombination. In addition, the heterojunction structure formed between TiO2 and g‐C3N4 materials also enhances the photocatalytic performance of the materials to some extent. After a simple optimization of the conditions, the Pd@g‐C3N4/TiO2 photocatalyst could promote the Suzuki–Miyaura CC coupling reactions under mild conditions (room temperature, 30 W LED lamp, λ = 455 nm), and good biaryl yields were obtained (optimum yield = 99%). It is very noteworthy that the photogenerated electrons and holes generated by the photoexcited catalyst were confirmed to be the main active species in the photocatalytic process of the catalyst by radical trapping assay and EPR test. The Pd@g‐C3N4/TiO2 material reported in this paper has excellent photocatalytic activity and stability in use, which provides a new reference scheme for wider green synthesis and catalysis.

Red mud accommodated mesoporous black TiO2 framework with enhanced organic pollutant photodegradation.

In this work, black TiO2 (BTiO2) loaded on black red mud (BRM) was successfully prepared with the conversion of Fe2O3 into magnetic Fe3O4 in red mud and the reduction of partial Ti4+ to Ti3+ in TiO2 via the facile sol-gel method and H2 reduction treatment. The obtained low-cost BRM/BTiO2 composites exhibit remarkable photocatalytic degradation toward rhodamine B (91.2%) and tetracycline (83.6%) under visible light irradiation, much better than pristine TiO2. This enhancement is attributed to the narrow bandgap with the desired solar-light excitation, the black color with good solar-light absorption, and the heterojunctions with the efficient separation of photogenerated electron-hole pairs. Moreover, the desired magnetic separation of BRM/BTiO2 composites realizes the recycle and recovery of photocatalysts, favoring practical applications in environment. This work provides a cost-efficiency way to prepare RM-supported TiO2 composites for treating organic pollutants in the wastewater, which is of great significance to the comprehensive utilization of RM waste, the cost saving of the photocatalyst, and the visible-light active enhancement of TiO2.

Fabrication of black TiO2 through microwave heating for visible light-driven photocatalytic degradation of rhodamine 6G

This study shows that a narrower band gap TiO2, namely black TiO2, can be prepared using NaBH4 as a reducing material and microwave heating, which is a faster, greener, and simpler method than the existing method using furnace heating.

Enhanced activity of highly ordered pristine and black anodic TiO2 nanotubes for high performance supercapacitors

This study reports on the effects of tube ordering and electrolytic surface reduction of TiO2 nanotubes on supercapacitor performance and reveals the feasibility of TiO2 nanotubes as efficient nanoporous electrodes for supercapacitors.

Low-content Ru–Pt supported on oxygen vacancy enriched black TiO2 with strong electronic interactions as efficient hydrogen generation electrocatalysts

Ultrafast quasi-solid microwave (60 s) is employed to achieve phosphorus-doped black TiO2 supported Ru and Pt (Ru–Pt/P–TiO2−x) for the HER with an overpotential of 14 mV at 10 mA cm−2 in an acidic electrolyte.

Improved efficiency of quantum dot-sensitized solar cells based on transparent black TiO2 modified photoanodes

This research utilized n-butyl titanate and B-P25 to construct transparent TiO2 photoanodes for QDSSCs. The B-P25 presents rich oxygen vacancies after reduction, facilitate the transport of photogenerated charge carriers in the photoanode films.

Exploiting Laser‐Induced Oxidation Phase Diagrams for Multifunctional Titania Thin Films

AbstractLocal laser‐induced oxidation is an extremely valuable technique to perform high‐throughput optimization across multidimensional parameter sets. In this work, a versatile method is presented for the synthesis of titanium dioxide (TiO2) thin‐films with varying crystalline structures through the use of localized, visible, continuous‐wave laser‐processing. By controlling the laser intensity and the exposure time, the conversion of amorphous titanium disulfide (a‐TiS2) precursor films into distinct phases of TiO2 is achieved and a laser‐induced oxidation phase diagram is constructed with the resulting material phases, including anatase, rutile, and black TiO2. By utilizing the dependence of phase formation on the rate and duration of laser energy input, mixtures of anatase and rutile phases are fabricated with controlled spatial arrangements. Photocatalytic properties of the synthesized films are evaluated using the degradation of nitrogen oxide (NOx) gas under UV illumination and an organic dye under white‐light illumination, revealing that mixtures of anatase and rutile phases demonstrate superior photocatalytic activity. The laser‐induced oxidation method highlighted showcases a strategy for precisely tailored phase composition for directly tunable properties, paving the way for in‐depth studies into structure‐property relationships in photocatalysis and other applications of metal oxide films.

Black brookite rich in oxygen vacancies as an active photocatalyst for CO2 conversion: Experiments and first-principles calculations

Photocatalytic CO2 conversion is a clean technology to deal with CO2 emissions, and titanium oxide (TiO2) polymorphs are the most investigated photocatalysts for such an application. In this study, black TiO2 brookite is produced by a high-pressure torsion (HPT) method and employed as an active photocatalyst for CO2 conversion. Black brookite with a large concentration of lattice defects (vacancies, dislocations and grain boundaries) showed enhanced light absorbance, narrowed optical bandgap and diminished recombination rate of electrons and holes. The photocatalytic activity of the black oxide for CO2 conversion was higher compared to commercial brookite and benchmark P25 catalyst powders. First-principles calculations suggested that the presence of oxygen vacancies in black brookite is effective not only for reducing optical bandgap but also for providing active sites for the adsorption of CO2 on the surface of TiO2.

Synthesis of black TiO2 nanotubes decorated biomass-derived spongy carbon as an electrode material for producing deionized water through capacitive deionization technology

The capacitive deionization (CDI) technique is considered a promising eco-friendly desalination method due to its high energy efficiency, ease of operation, and simplistic electrode regeneration capability. Thus, significant research is focused on developing highly efficient electrode materials with high electrochemical stability and salt electro-adsorption capacity (Sc) behavior during operation because these are the governing factors in examining the measured activity of fabricated CDI cells. In this manuscript, we report the synthesis of hydrogenated titanium nanotubes@spongy activated carbon (HTiO2 NTs@SAC) using pyrolysis and hydrothermal processes. The SAC is synthesized by the pyrolysis of spongy loofa in an inert atmosphere and further hydrothermally activating it in an aqueous potassium hydroxide solution. The hydrothermal process activates and enhances the hydrophilicity of SAC. HTiO2 is synthesized electrochemically at 20 V in 0.1 M perchloric acid. Such HTiO2 NTs@SAC configuration can provide excellent pathways to increase ion adsorption and improve the kinetics of charge transfer by enhancing the contact between the electrolyte and electrode at the interface. It is found that HTiO2 NTs@SAC has a specific capacitance (Cs) of 385.7 F g−1 compared with 332.7 F g−1 for SAC. The salt electrosorption capacity (Sc) of HTiO2 NTs@SAC electrode material is found to be 24.90 mg g−1 in 250 μS cm−1 saline solution at 1.2 V, which is much higher than the values obtained for SAC (9.8 mg g−1). HTiO2 NTs@SAC has also shown an antimicrobial effect toward gram-negative bacteria and exhibited good performance in the supercapacitor application, wherein HTiO2 NTs@SAC showed a higher Cs (505.55 F g−1) than SAC (380 F g−1) at 1 A g−1. Thus, we demonstrate that the prepared composite can be used as an energy storage material, an antibacterial material, and a CDI electrode in the CDI technology.

Fabrication of 5-fluorouracil loaded multi-responsive molecularly imprinted poly (NVCL-co-MAA) coated black titanium dioxide nanocomposite as a chemo-photodynamic therapy agent

TiO2 nanoparticles (NPs) are commonly used in cancer photodynamic therapy due to their ultraviolet light–triggered properties. In this study, a molecularly imprinted polymer (MIP)-coated black TiO2 (b-TiO2) nanocomposites (NCs) were synthesized using free radical polymerization of thermosensitive N-vinyl caprolactam and pH-sensitive methacrylic acid functional monomers on the surface of b-TiO2 NPs. B-TiO2 NPs were prepared using calcination of as-synthesized white TiO2 NPs (w-TiO2) at high temperatures. The MIP layer was in-situ deposited on surface-activated b-TiO2 NPs with azobisisobutyronitrile as an initiator and uracil as a pseudo-template molecule of 5-Fluorouracil (5-FU). The samples were characterized using FTIR, NIR, XRD, DLS, TEM, BET and TGA analyses. The average crystallite sizes of w-TiO2, b-TiO2 NPs and the NCs were determined through Sharer's equation as 6.8, 10.36 and 12.61 nm, respectively, which were smaller than those obtained by DLS (7.5, 115 and 130.6 nm, respectively), indicating the aggregation of small particles during calcination at high temperatures. The equilibrium adsorption capacity of NCs and non-imprinted NCs with specific areas of 14.80 m2.g−1 and 7.611 m2.g−1, respectively, toward 5-FU was determined to be 80 and 25 mg.g−1, respectively, indicating that the imprinting process is highly efficient. Higher cumulative drug released in pH 5.5 and 41 ºC confirmed the remarkable potential of NCs as a pH/temperature-responsive delivery vehicle. Moreover, the NCs demonstrated enhanced photothermal/photodynamic and low hemolytic activity (< 5%) compared to b-TiO2 NPs. The findings indicate that NCs showed excellent potential for combining stimuli-responsive chemotherapy with photothermal/photodynamic therapy for melanoma treatment.

Photocatalytic degradation of tetracycline using surface defective black TiO2–ZnO heterojunction photocatalyst under visible light

Fabrication of heterojunction and surface defective engineering, through the formation of oxygen vacancies, are among the various photocatalytic enhancement techniques. A combination of these techniques has the prospect of enhancing photocatalytic activities through improved light absorption capabilities and charge separation process of the photocatalysts. In this study, a heterojunction of black titanium oxide-zinc oxide (BTiO2–ZnO) nanocomposite was synthesized using the conventional sol-gel approach, coupled with aluminum foil-assisted NaBH4 reduction. The structure, morphology, surface properties, and optical characteristics of the synthesized material were studied using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), UV–vis absorption spectra, scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscope (TEM). The XRD confirmed the successful formation of BTiO2–ZnO heterostructure, while SEM revealed the structural morphology as pseudo-spherical with slight agglomeration. BTiO2–ZnO was found to be more efficient than BTiO2 and BZnO for the removal of tetracycline with degradation efficiencies of 63, 58, and 56 % respectively. The effects of process parameters such as the amount of photocatalyst, pollutant's concentration, and the initial solution pH on photocatalytic degradation study were systematically explored. The results confirm that the formation of the heterostructure from BTiO2 and BZnO could offer a facile route to improving the catalytic degradation of tetracycline. Therefore, this study offers a novel perspective on the design of efficient metal oxide photocatalyst systems that rely on the integration of defect engineering and heterojunction for the removal of organic contaminants.

Flame-assisted combustion preparation of highly efficient black TiO2 microspheres photocatalysts under visible light

Black TiO2 microspheres photocatalysts with high light absorption intensity and photosensitive activity were prepared by a simple two-step method of flame-assisted combustion hydrolysis of tetrabutylorthotitanate (TBOT) and NaBH4 reduction. The black TiO2 microspheres photocatalysts were characterized by XRD, TEM, XPS, EELS, and UV-Vis absorption spectroscopy. The results show that the reduced TiO2 exhibits a unique core-shell composite structure with a large number of oxygen vacancies and defects in the outer layer due to Ti3+, which effectively reduces the band gap of the photocatalyst. Compared with the commercial P25 catalyst, B-TiO2 (1:7) showed higher removal of carbamazepine (CBZ) under visible light and its photocatalytic activity was 1.7 times higher than that of P25. This high photocatalytic activity is due to the efficient separation of electron-hole pairs, creating a greater number of active species. B-TiO2 (1:7) maintained high activity after five repeated cycles and achieved 89.7 % removal of CBZ.

Boosting-photothermal properties of Cu/ Black TiO2 nanoparticles on biomimetics texture structure as high‐performance and self‐regenerating solar-evaporator

To address the global water crisis, solar vapor generation emerged as a promising technology for clean-water uptake from seawater. Black TiO2 with wide-spectrum absorbancy, non-toxicity, cost-effectively, and chemical stability has attracted great interest in efficient solar-driven evaporators. Herein, the black TiO2 nanoparticles were synthesized through one step and facile reduction process of white oxide powder squeezed between two layers of NaCl. The prepared powder was deposited on the bare and copper-treated cotton fabrics as light absorbers in the proposed solar steam generation (SSG) systems. Various structural and morphology characterization methods have been utilized to verify of synthesis procedure. Heat localization was performed by the floated yarn-stitched polyurethane (PU) foam as a holder for the fabrics. Continuous water transmission from the saline water container to the evaporation surface was done via capillary forces in the yarns. The hybrid absorber introduced a superior solar-thermal conversion efficiency of about 98.56 % and 1.94 kg.m−2 h−1 evaporation rate which was 3.13 times larger than the control one. Antifouling and recyclability properties of the samples were studied in outdoor conditions. The suggested hybrid-based (Cu/black TiO2) SSG with significant properties of simplicity, non-toxicity, and high evaporating activity opens new shortcuts toward green water desalination and also salt extraction demands.

Development of SDS-Modified PbO2 Anode Material Based on Ti3+ Self-Doping Black TiO2NTs Substrate as a Conductive Interlayer for Enhanced Electrocatalytic Oxidation of Methylene Blue.

Efficient and stable electrode materials are urgently required for wastewater treatment in the electrocatalytic degradation of toxic and refractory organic pollutants. Ti3+ self-doping black TiO2 nanotube arrays (Ti/B-TiO2-NTs) as an interlayer were used for preparing a novel PbO2 electrode via an electrochemical reduction technology, and a sodium dodecyl sulfate (SDS)-modified PbO2 catalytic layer was successfully achieved via an electrochemical deposition technology. The physicochemical characterization tests showed that the Ti/B-TiO2-NTs/PbO2-SDS electrodes have a denser surface and finer grain size with the introduction of Ti3+ in the interlayer of Ti/TiO2-NTs and the addition of SDS in the active layer of PbO2. The electrochemical characterization results showed that the Ti3+ self-doping black Ti/TiO2-NTs/PbO2-SDS electrode had higher oxygen evolution potential (2.11 V vs. SCE), higher electrode stability, smaller charge-transfer resistance (6.74 Ω cm-2), and higher hydroxyl radical production activity, leading to it possessing better electrocatalytic properties. The above results indicated that the physicochemical and electrochemical characterization of the PbO2 electrode were all enhanced significantly with the introduction of Ti3+ and SDS. Furthermore, the Ti/B-TiO2-NTs/PbO2-SDS electrodes displayed the best performance on the degradation of methylene blue (MB) in simulated wastewater via bulk electrolysis. The removal efficiency of MB and the chemical oxygen demand (COD) could reach about 99.7% and 80.6% under the optimal conditions after 120 min, respectively. The pseudo-first-order kinetic constant of the Ti/B-TiO2-NTs/PbO2-SDS electrode was 0.03956 min-1, which was approximately 3.18 times faster than that of the Ti/TiO2-NTs/PbO2 electrode (0.01254 min-1). In addition, the Ti/B-TiO2-NTs/PbO2-SDS electrodes showed excellent stability and reusability. The degradation mechanism of MB was explored via the experimental identification of intermediates. In summary, the Ti3+ self-doping black Ti/TiO2-NTs/PbO2-SDS electrode is a promising electrode in treating wastewater.

Investigation on swelling behavior of sodium alginate/black titania nanocomposite hydrogels and effect of synthesis conditions on water uptake

Polymeric nanocomposite hydrogels were developed from a hydrophilic natural polymer, sodium alginate (SA) with black nano crystalline titania (black TiO2) by using ionic cross linker CaCl2, in view of the possible enhancement in properties of SA towards water treatment application. The optimum conditions for the preparation of films were done by varying the amount of cross-linking agent, cross-linking time and the amount of black nano crystalline TiO2. The nanocomposite hydrogels were then characterized by X-ray diffraction studies (XRD), fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The surface morphologies of the nanocomposite have been examined by using scanning electron microscopy (SEM). The swelling studies and its kinetics have been investigated under diverse PH conditions. Permeability of the gels were assessed in terms of film characteristics and PH. The results proved that the gels exhibit PH sensitivity. Based on the results, we have proposed a possible mechanism of water transport through the gels. The developed SA/black TiO2 nanocomposite hydrogels have been successfully employed for the efficient degradation organic dyes such as methylene blue and malachite green. The experimental results of dye degradation studies have been compared with theoretical models and it has been observed that the dye degradation follows pseudo second order kinetics for both methylene blue and malachite green. By altering the PH, the nanocomposite hydrogels can be broken and spent TiO2 can be recovered.

Mesoporous black TiO2 hollow shells with controlled cavity size for enhanced visible light photocatalysis.

Black TiO2 formed by introducing lattice disorder into pristine TiO2 has a narrowed band gap and suppresses the recombination of charge carriers. This provides a potential strategy for visible light photocatalysis. However, the microstructural design of black TiO2 for a higher optimization of visible light is still in high demand. In this work, we proposed the preparation of black TiO2 hollow shells with controllable cavity diameters using silica spheres as templates for the cavities and the NaBH4 reduction method. The decreased cavity size resulted in a hollow shell with an enhanced visible-light absorption and improved photocatalytic performance. Moreover, we demonstrated that this cavity can be combined with gold nanoparticles (AuNPs) to form AuNPs@black TiO2 yolk-shells. The AuNPs provided additional visible light absorption and promoted the separation of photogenerated carriers in the yolk-shell structures. This further improved the photocatalysis, the degradation rate of Cr(VI) can reach 0.066 min-1. Our work evaluated the effect of the cavity size on the photocatalytic performance of hollow and yolk-shell structures and provided concepts for the further enhancement of visible-light photocatalysis.

Green Synthesis of ZnO and Black TiO2 Materials and Their Application in Photodegradation of Organic Pollutants.

ZnO and black TiO2 have been selected as the most efficient materials for organic pollution abatement due to their increased efficiency when compared to other materials. However, the concept of green chemistry makes it desirable to design green synthesis approaches for their production. In this study, black TiO2 was synthesized using an environmentally safe synthetic technique with glycerol as a reductant. ZnO was prepared by using ionic-liquid-based microwave-assisted extracts of Polygonum minus. To investigate the materials' potential to photodegrade organic pollutants, methylene blue (MB) and phenol were chosen as model organic pollutants. Both materials were found to exhibit spherical morphologies and a mesoporous structure and were efficient absorbers of visible light. ZnO exhibited electron-hole pair recombination lower than that of black TiO2. Black TiO2 was discovered to be an anatase phase, whereas ZnO was found to have a hexagonal wurtzite structure. In contrast to black TiO2, which had a surface area of 239.99 m2/g and a particle size of 28 nm, ZnO had a surface area of 353.11 m2/g and a particle size of 32 nm. With a degradation time of 60 min, ZnO was able to eliminate 97.50% of the 40 mg/L MB. Black TiO2, on the other hand, could reduce 90.0% of the same amount of MB in 60 min. When tested for phenol degradation, ZnO and black TiO2 activities were reduced by nearly 15 and 25%, respectively. A detailed examination of both ZnO and black TiO2 materials revealed that ZnO has more potential and versatility for the degradation of organic pollutants under visible light irradiation.