Carbon dots decorated three-dimensionally ordered macroporous bismuth-doped titanium dioxide with efficient charge separation for high performance photocatalysis

Two-photon fluorescence-guided precise photothermal therapy located in a single cancer cell utilizing bifunctional N-doped carbon quantum dots

The utilization of carbon quantum dots (CQDs) for photothermal therapy has emerged as a hot research topic. However, there has been limited research on killing one single cancer cell which is critical in reducing unnecessary damage to the surrounding healthy tissues. In this work, we developed a two-photon fluorescence-guided precise photothermal therapy in a single human malignant melanoma (A375) cancer cell utilizing bifunctional N-doped CQDs. Resulting from the two-photon fluorescence of the CQDs, one single cancer cell can be located and simultaneously destroyed by the photothermal effect of the same CQDs. Specifically, the balanced two-photon absorption cross-section (7000 GM) and photoluminescence quantum yield (8.4%) of the CQDs enable the fluorescence-guided photothermal treatment to be achieved in only 5 s under the irradiation of 800 nm laser of 27.5 mW, much faster than the control experiment without the guidance of fluorescence. The heat generated by the aggregated CQDs is in sufficient amounts while being confined in a small area, as evidenced by the numerical simulations and photothermal experiments, to limit the range of thermal treatment in the cells. This work provides a new approach for realizing photothermal therapy with minimal damage and establishes a new application scenario of CQDs for precise tumor ablation.

Recent Progress of Three-dimensionally Ordered Macroporous (3DOM) Materials in Photocatalytic Applications: A Review

In recent years, three-dimensionally ordered macroporous (3DOM) materials have attracted tremendous interest in the field of photocatalysis due to the periodic spatial structure and unique physicochemical properties of 3DOM catalysts. In this review, the fundamentals and principles of 3DOM photocatalysts are briefly introduced, including the overview of 3DOM materials, the photocatalytic principles based on 3DOM materials, and the advantages of 3DOM materials in photocatalysis. The preparation methods of 3DOM materials are also presented. The structure and properties of 3DOM materials and their effects on photocatalytic performance are briefly summarized. More importantly, 3DOM materials, as a supported catalyst, are extensively employed to combine with various common materials, including metal nanoparticles, metal oxides, metal sulfides, and carbon materials, to enhance photocatalytic performance. Finally, the prospects and challenges for the development of 3DOM materials in the field of photocatalysis are presented.

Fabrication of Z-scheme Bi7O9I3/g-C3N4 heterojunction modified by carbon quantum dots for synchronous photocatalytic removal of Cr (Ⅵ) and organic pollutants

Chromium(VI) (Cr(VI)), a highly toxic metal ion, generally co-exists with organic pollutants in industrial effluents. The clean and effective technology for water purification is an imperative issue but still a challenging task. A series of Bi₇O₉I₃/g-C₃N₄ (BOI/CN) composites modified by lignin-derived carbon quantum dots (CQDs) were fabricated by hydrothermal method and applied for synchronous photocatalytic removal of Cr (Ⅵ) and levofloxacin (LEV). With the modification of CQDs in BOI/CN heterojunction, the 0.5-CQD/BOI/CN photocatalyst (0.5% content of CQDs) exhibited stronger light-harvesting capacity, more efficient charge separation, and faster electron transfer. Compared to those of BOI (51.2%), CN (36.8%), and BOI/CN (74.4%), the photoreduction efficiency of Cr(VI) reached up to 100% by 0.5-CQD/BOI/CN under 60 min of light irradiation, together with 94.8% degradation efficiency of LEV. The degradation of LEV was dominantly controlled by active species (•OH and •O₂^-) identified by electron paramagnetic resonance analysis and free radical trapping experiments. The intermediates of LEV were determined by LC-MS and the possible degradation pathway was speculated in combination with density functional theory calculation, involving defluorination, decarboxylation, quinolone rings opening, and piperazine moieties oxidation reactions. This work provides an advanced strategy for the fabrication of high-efficiency CQDs-based Z-scheme photocatalysts for environmental remediation.

Novel polypropylene-TiO2:Bi spherical floater for the efficient photocatalytic degradation of the recalcitrant 2,4,6-TCP herbicide

In this work, spherical photocatalytic floaters were fabricated by depositing TiO₂:Bi (TBi) particles on polypropylene (PP) spheres (recycled from beer cans). These particles were deposited on the sphere (TBi-sphere) by the spray coating technique and evaluated their performance for the photocatalytic degradation of 2,4,6-trichlorophenol (2,4,6-TCP) herbicide. SEM images demonstrated that the BTi powders consisted in conglomerated grains with sizes of 20-80 nm and the analysis by X-ray diffraction confirmed the presence of rutile and anatase phases in the BTi. The photocatalytic experiments showed that the TBi and TBi-sphere produced maximum degradation of 90 and 97% for 2,4,6-TCP, respectively, after 4 h under UV-Vis light. The photocatalytic powders/composites were reused 3 times and the loss of degradation efficiency was 3 and 16% for the TBi powder and TBi-sphere, respectively. This means that the TBi-sphere is more stable for the continuous degradation of the 2,4,6-TCP contaminant. The TiO₂:Bi powder was compared with the commercial TiO₂ (P25) and found that the TiO₂:Bi powder had higher light absorption (≈42%) and higher surface area (≈105%) than the P25. Therefore, the degradation percentage for the 2,4,6-TCP was 52% higher in the sample doped with Bi. Also, scavenger experiments were carried out and found that the main oxidizing agents produced for the degradation of 2,4,6-TCP were •OH^- radicals and •O₂^- anions. Other species such as h⁺ were also produced at lower amount. Hence, our results demonstrated that spherical/floatable photocatalytic composites are a viable option to remove herbicide residuals from the water, which is of interest in water-treatment-plants.

Recent Progress in Metal Oxide-Based Photocatalysts for CO2 Reduction to Solar Fuels: A Review

One of the challenges in developing practical CO₂ photoconversion catalysts is the design of materials with a low cost, high activity and good stability. In this paper, excellent photocatalysts based on TiO₂, WO₃, ZnO, Cu₂O and CeO₂ metal oxide materials, which are cost-effective, long-lasting, and easy to fabricate, are evaluated. The characteristics of the nanohybrid catalysts depend greatly on their architecture and design. Thus, we focus on outstanding materials that offer effective and practical solutions. Strategies to improve CO₂ conversion efficiency are summarized, including heterojunction, ion doping, defects, sensitization and morphology control, which can inspire the future improvement in photochemistry. The capacity of CO₂ adsorption is also pivotal, which varies with the morphological and electronic structures. Forms of 0D, 1D, 2D and 3DOM (zero/one/two-dimensional- and three-dimensional-ordered macroporous, respectively) are involved. Particularly, the several advantages of the 3DOM material make it an excellent candidate material for CO₂ conversion. Hence, we explain its preparation method. Based on the discussion, new insights and prospects for designing high-efficient metallic oxide photocatalysts to reduce CO₂ emissions are presented.

Enhanced Photo-Assisted Fenton Degradation of Antibiotics over Iron-Doped Bi-Rich Bismuth Oxybromide Photocatalyst

Herein, combining photocatalysis and Fenton oxidation, a photo-assisted Fenton system was conducted using Fe-doped Bi₄O₅Br₂ as a highly efficient photocatalyst to realize the complete degradation of Tetracycline antibiotics under visible light. It has been observed that the optimized photocatalyst 5%Fe-doped Bi₄O₅Br₂ exhibits a degradation efficiency of 100% for Tetracycline with H₂O₂ after 3 h visible-light irradiation, while a degradation percentage of 59.8% over the same photocatalyst and 46.6% over pure Bi₄O₅Br₂ were obtained without the addition of H₂O₂ (non-Fenton process). It is unambiguous that a boost photo-assisted Fenton system for the degradation of Tetracycline has been established. Based on structural analysis, it demonstrated that the Fe atoms in place of the Bi sites may result in the distortion of the local structure, which induced the occurrence of the spontaneous polarization and thus enhanced the built-in electric field. The charge separation efficiency is enhanced, and the recombination of electrons and holes is inhabited so that more charges are generated to reach the surface of the photocatalyst and therefore improve the photocatalytic degradation efficiency. Moreover, more Fe (II) sites formed on the 5%Fe-Bi₄O₅Br₂ photocatalyst and facilitated the activation of H₂O₂ to form oxidative species, which greatly enhanced the degradation efficiency of Tetracycline.

Fabrication and high photoelectrocatalytic activity of scaly BiOBr nanosheet arrays

Bismuth oxybromide (BiOBr) nanosheet arrays (NSAs) were successfully prepared on the surface of indium tin oxide glass (hydrophilic pretreated) by solvothermal method using [C₁₆mim]Br ionic liquid as bromine source and template. The effects of different reaction temperatures on array synthesis were investigated. BiOBr NSA-160 (NSAs prepared at 160 °C for 8 h) had the best photoelectrocatalytic (PEC) activity. The removal rate of ciprofloxacin hydrochloride by BiOBr NSA-160 was 91.4% by applying a bias voltage of 0.9 V and irradiating under visible light for 180 min. Results of the analyses of the morphology, photoelectric properties, energy band structure, and degradation active species show that BiOBr NSA-160 is a p-type photocatalyst with a thickness of approximately 500 nm, a light response range of less than 440 nm, and photocurrent density of 69 μA/cm² at the optimal bias voltage is 0.9 V. The high PEC activity of BiOBr NSA-160 was deduced from two aspects: one is that the bias potential effectively improves the separation efficiency of photogenerated carrier, and the other is that the structure of the nanoarray increases light absorption and active sites. BiOBr NSAs are promising PEC material for application in pollutant removal.

Effect of Ag loading position on the photocatalytic performance of TiO2 nanocolumn arrays

Plasmonic metal/semiconductor composites have attracted great attention for efficient solar energy harvesting in photovoltaic and photocatalytic applications owing to their extremely high visible-light absorption and tuned effective band gap. In this work, Ag-loaded TiO₂ nanocolumn (Ag-TNC) arrays were fabricated based on anodic aluminum oxide (AAO) template by combining atomic layer deposition (ALD) and vacuum evaporation. The effects of the Ag loading position and deposition thickness, and the morphology, structure and composition of Ag-deposited TNC arrays on its optical and photocatalytic properties were studied. The Ag-filled TiO₂ (AFT) nanocolumn arrays exhibited higher removal efficiency of methylene blue (MB) compared with Ag-coated TiO₂ (ACT) nanocolumn arrays and pure TiO₂ nanocolumns arrays. Both experimental and theoretical simulation results demonstrated that the enhanced photocatalytic performance of AFT nanocolumn arrays was attributed to the surface plasmon resonance (SPR) of Ag and the absorption of light by TiO₂. These results represent a promising step forward to the development of high-performance photocatalysts for energy conversion and storage.