Synergism of oxygen vacancies, Ti3+ and N dopants on the visible-light photocatalytic activity of N-doped TiO2

MOF-Derived Oxygen-Deficient Titania-Mediated Photodynamic/Photothermal-Enhanced Immunotherapy for Tumor Treatment

Immunotherapy has emerged as a revolutionizing therapeutic modality for cancer. However, its efficacy has been largely limited by a weak immune response and an immunosuppressive tumor microenvironment. Herein, we report a metal-organic framework (MOF)-derived titanium oxide nanoparticle (MCTx NP) as an immune booster that can greatly improve the immunotherapy efficacy by inducing "immunogenic cell death" (ICD) and remodeling the tumor microenvironment. The NPs, inheriting the characteristic structure of MIL-125 and enriched with oxygen vacancies (OVs), demonstrate both high photothermal conversion efficiency and a reactive oxygen species (ROS) generation yield upon near-infrared (NIR) activation. Moreover, the NPs can release O2 and reduce glutathione (GSH) in the tumor environment, showcasing their potential to reverse the immunosuppressive microenvironment. In vitro/vivo results demonstrate that MCTx NPs directly kill tumor cells and effectively eliminate primary tumors by exerting dual photodynamic/photothermal therapy under a single NIR irritation. At the same time, MCTx NPs augment the PD-L1 blockade efficacy by potently inducing ICDs and reversing the immunosuppressive tumor microenvironment, including promoting dendritic cell (DC) maturation, decreasing regulatory T cells (Tregs)' infiltration, and increasing cytotoxic T lymphocytes (CTLs) and helper T cells (Ths), resulting in effective distant tumor suppression. This work highlights MCTx NP-mediated photodynamic- and photothermal-enhanced immunotherapy as an effective strategy for tumor treatment.

Solar-powered detection of organic dyes using nitrogen-doped N-TiO2/Ag2O nanorod arrays

Organic pollutant detection has caused widespread concern regarding due to their potential environmental and human health risks. In this work, a nitrogen-doped titanium dioxide/silver oxide (N-TiO2/Ag2O) composite has been designed as a sensitive photoelectrochemical (PEC) monitoring platform of organic dyes. Sensitive determination relies on the outstanding PEC performance of N-TiO2/Ag2O. The improved PEC performance stems from the effective separation of photocarriers and the extended light response range provided by the narrowing bandgap and a p-n junction with N-TiO2/Ag2O. The N-TiO2/Ag2O electrode exhibits a photocurrent density of up to 2.2 mA/cm2, demonstrating three times increase compared with the photocurrent density observed with the pure TiO2 film. The linear detection range for rhodamine B (RhB), methylene blue (MB), and methyl orange (MO) is 0.2 ng/mL to 10 μg/mL with an ultrasensitive detection limit of 0.2 ng/mL without bias voltage. Due to the outstanding photocurrent density and sensitive response to organic pollutants, the N-TiO2/Ag2O PEC sensor provided a promising analytical method to detect environmental organic dyes.

Activation of 2D titanate nanosheet photocatalysts by nitrogen doping and solution plasma processing

Novel two-dimensional (2D) oxides are of great interest for photocatalysis because of their superlative physical features, namely, large surface areas, short charge diffusion pathways, high crystallinity and easy surface modification. However, most 2D oxides suffer from weak visible light absorption and severe photogenerated carrier recombination. Nitrogen doping can successfully narrow the bandgap of 2D oxides but can hardly improve the charge separation. In this work, we pre-dope nitrogen into 2D titanate nanosheets (HTiO), followed by surface processing with solution plasma. By dual modification of nitrogen doping and solution plasma processing (SPP), the modified 2D titanate nanosheets (N-HTiO-SPP) display broad absorption extending to the visible light region and the healing of oxygen vacancies brought about by nitrogen doping. Compared with HTiO and nitrogen doped titanate (N-HTiO), a higher removal rate and mineralization rate towards the photocatalytic degradation of acetaldehyde were achieved over N-HTiO-SPP under solar light. This work provides a powerful way to activate 2D wide bandgap semiconductors for enhanced photocatalytic activity.

Synthesis of Cu-Doped TiO2 on Wood Substrate with Highly Efficient Photocatalytic Performance and Outstanding Recyclability for Formaldehyde Degradation

Photocatalytic oxidation is considered one of the most effective ways to remove formaldehyde from indoor air. However, the use of powder photocatalysts is limited by their low adsorption capacity and strong aggregation tendency. Hence, there is a need for a composite material with good cycling stability and high degradation efficiency. In the present study, a unique wood-based composite is produced by arranging Cu-TiO₂ nanoparticles on porous structured wood. The porous structure of wood can adsorb formaldehyde, and the abundant functional groups on the surface can act as a reaction platform for anchoring the Cu-TiO₂ nanoparticles. Cu doping facilitates electron interaction between TiO₂ and Cu, promotes the transfer of charge carriers, lowers the electron-hole recombination rate, and improves the photocatalytic degradation efficiency of formaldehyde. The photocatalytic efficiency of the wood-based composites was highest (85.59%) when the n(Cu)/n(Ti) ratio was 7%. After nine cycles, the wood composites still had a high degradation rate, indicating good recyclability. Overall, this wood composite is an eco-friendly and promising material for indoor air filtration.

Laser-Based Synthesis of TiO2-Pt Photocatalysts for Hydrogen Generation

The development of visible-light active titanium dioxide is one of the key challenges in photocatalysis that stimulates the development of TiO₂-based composite materials and methods for their synthesis. Here, we report the use of pristine and Pt-modified dark titanium dioxide prepared via pulsed laser ablation in liquid (Nd:YAG laser, 1064 nm, 7 ns) for photocatalytic hydrogen evolution from alcohol aqueous solutions. The structure, textural, optical, photoelectrochemical, and electrochemical properties of the materials are studied by a complex of methods including X-ray diffraction, low-temperature nitrogen adsorption, electrophoretic light scattering, diffuse reflection spectroscopy, photoelectrochemical testing, and electrochemical impedance spectroscopy. Both the thermal treatment effect and the effect of modification with platinum on photocatalytic properties of dark titania materials are studied. Optimal compositions and experimental conditions are selected, and high photocatalytic efficiency of the samples in the hydrogen evolution reaction (apparent quantum yield of H₂ up to 0.38) is demonstrated when irradiated with soft UV and blue LED, i.e., 375 and 410 nm. The positive effect of low platinum concentrations on the increase in the catalytic activity of dark titania is explained.

Excellent visible light responsive photocatalytic behavior of N-doped TiO2 toward decontamination of organic pollutants

In this work, N-doped TiO₂ (N-TiO₂) with ample and tunable OVs was successfully synthesized, deriving from facile hydrothermal method and baked in the NH₃ atmosphere. N-doping boosts the amount of surface hydroxyl and superoxide (O₂^-) of TiO₂, demonstrated by XPS and nitroblue tetrazolium (NBT)-O₂^- quantitative reaction. Rich and tunable OVs were confirmed by low temperature electron spin resonance (ESR) results, demonstrating that doping of N into TiO₂ can definitely construct higher OVs than the reference TiO₂. Surface photovoltage spectrum (SPS) test, fluorescence experiments and electrochemical measurements all display that N-TiO₂ photocatalysts with OVs have a higher severance efficiency of photogenerated e-/h⁺ pairs than the pristine TiO₂. Photocatalytic evaluation results exhibit that N-TiO₂ photocatalysts demonstrate better performance than the reference TiO₂ toward decontamination of rhodamine B and tetracycline. TiO₂ treated in ammonia atmosphere for 1 h shows the highest photocatalytic property. The visible light responsive catalytic behavior of TiO₂ treated in ammonia atmosphere for 1 h is much higher than that of commercial TiO₂ (P25) and the pristine TiO₂, separately. The ameliorated visible light behavior of N-TiO₂ photocatalysts is attributable to rich oxygen vacancies produced through introducing N into TiO₂ and the boosted severance of photoactivated e-/h⁺.

C-,N- and S-Doped TiO2 Photocatalysts: A Review

This article presents an overview of the reports on the doping of TiO2 with carbon, nitrogen, and sulfur, including single, co-, and tri-doping. A comparison of the properties of the photocatalysts synthesized from various precursors of TiO2 and C, N, or S dopants is summarized. Selected methods of synthesis of the non-metal doped TiO2 are also described. Furthermore, the influence of the preparation conditions on the doping mode (interstitial or substitutional) with reference to various types of the modified TiO2 is summarized. The mechanisms of photocatalysis for the different modes of the non-metal doping are also discussed. Moreover, selected applications of the non-metal doped TiO2 photocatalysts are shown, including the removal of organic compounds from water/wastewater, air purification, production of hydrogen, lithium storage, inactivation of bacteria, or carbon dioxide reduction.