Direct Z-scheme MoSe2 decorating TiO2 nanotube arrays photocatalyst for water decontamination

Electrochemical Sensor Based on Multi-Walled Carbon Nanotubes and N-Doped TiO2 Nanoparticles for Voltametric Simultaneous Determination of Benserazide and Levodopa

An electrochemical sensor for simultaneous determination of Benserazide (BEZ) and levodopa (L-dopa) was successfully developed using a glassy carbon electrode (GCE) modified with multi-walled carbon nanotube and nitrogen-doped titanium dioxide nanoparticles (GCE/MWCNT/N-TiO₂). Cyclic voltammetry and square wave voltammetry were employed to investigate the electrochemical behavior of different working electrodes and analytes. In comparison with unmodified GCE, the modified electrode exhibited better electrocatalytic activity towards BEZ and L-dopa and was efficient in providing a satisfactory separation for oxidation peaks, with a potential difference of 140 mV clearly allows the simultaneous determination of these compounds. Under the optimized conditions, linear ranges of 2.0-20.0 and 2.0-70.0 μmol L^-1 were obtained for BEZ and L-dopa, respectively, with a limit of detection of 1.6 µmol L^-1 for BEZ and 2.0 µmol L^-1 for L-dopa. The method was applied in simultaneous determination of the analytes in pharmaceutical samples, and the accuracy was attested by comparison with HPLC-DAD as the reference method, with a relative error lower than 4.0%.

Ternary Z-Scheme Ag-Embedded TiO2-Ag2S Nanojunction as a Novel Photoelectrochemical Converter for CD44 Detection

Nanoarrays (NAs) with stable signal output have become the most promising photoelectrochemical (PEC) biosensing substrate. However, a general issue is that interfacial charge-carrier recombination in a single-component semiconductor cannot be easily prevented, resulting in a low photocurrent density. Herein, a biosensor utilizing a Ag-embedded TiO₂-Ag₂S nanojunction (TiO₂-Ag-Ag₂S) as a signal converter was developed for the detection of CD44 protein─a transmembrane glycoprotein highly expressed in breast cancer cells. The ternary Z-scheme heterojunction was prepared by a distinctive scheme in which the Ag layer is introduced onto the surface of rutile TiO₂ NAs by magnetron sputtering, whereas the Ag₂S is rooted in the local sulfuration of Ag. With a sufficient density of oriented nanorods, TiO₂-Ag-Ag₂S exhibits a smooth photocurrent output and minimal variation among different batches; it is undoubtedly a satisfactory PEC sensing carrier, which enables highly specific identification of target CD44 on the surface of MDA-MB-231 cells due to DNA strand displacement reactions (SDRs) and host-guest recognition between hyaluronic acid (HA) and CD44. The biosensor shows a sensitive PEC response to CD44 over a wide range of 37 to 5.0 × 10⁵ cells/mL. We can conclude that this approach will provide an alternative solution to breast cancer diagnosis.

S-Scheme BiOCl/MoSe2 Heterostructure with Enhanced Photocatalytic Activity for Dyes and Antibiotics Degradation under Sunlight Irradiation

Semiconductor photocatalysis is considered to be a promising technique to completely eliminate the organic pollutants in wastewater. Recently, S-scheme heterojunction photocatalysts have received much attention due to their high solar efficiency, superior transfer efficiency of charge carriers, and strong redox ability. Herein, we fabricated an S-scheme heterostructure BiOCl/MoSe₂ by loading MoSe₂ nanosheets on the surface of BiOCl microcrystals, using a solvothermal method. The microstructures, light absorption, and photoelectrochemical performances of the samples were characterized by the means of SEM, TEM, XRD, transient photocurrents, electrochemical impedance, and photoluminescence (PL) spectra. The photocatalytic activities of BiOCl, MoSe₂, and the BiOCl/MoSe₂ samples with different MoSe₂ contents were evaluated by the degradation of methyl orange (MO) and antibiotic sulfadiazine (SD) under simulated sunlight irradiation. It was found that BiOCl/MoSe₂ displayed an evidently enhanced photocatalytic activity compared to single BiOCl and MoSe₂, and 30 wt.% was an optimal loading amount for obtaining the highest photocatalytic activity. On the basis of radical trapping experiments and energy level analyses, it was deduced that BiOCl/MoSe₂ follows an S-scheme charge transfer pathway and •O₂⁻, •OH, and h⁺ all take part in the degradation of organic pollutants.

Construction of an α-Fe2O3/Bi2O3 p–n heterojunction with exceptional visible-light photocatalytic performance for dye removal

α-Fe2O3/Bi2O3 nanocomposites with a p–n heterojunction were synthesized via an anodization strategy and the hydrothermal method for photocatalytic applications.

Preparation and application of BiOBr-Bi2S3 heterojunctions for efficient photocatalytic removal of Cr(VI)

Recently, the photocatalytic reduction of Cr(VI) has been extensively studied. Herein, we successfully prepared the BiOBr-Bi₂S₃ heterojunctions with high photocatalytic Cr(VI) reduction performance using an ion exchange method. The optimal BiOBr-Bi₂S₃ heterojunction (prepared with BiOBr, pH of 6.0, 2 mmol Na₂S₂O₃·5H₂O,) achieved 100% removal of Cr(VI) within 12 min. The performance of photo-reduced Cr(VI) was about 28.9 and 184.6 times higher than that of pure Bi₂S₃ and BiOBr, respectively. Besides, BiOBr-Bi₂S₃ heterojunctions had a good adsorption efficiency for Cr(III), suggesting that they could be applied as bifunctional photocatalyst. The formation process and photoelectric properties of the BiOBr-Bi₂S₃ heterojunctions were revealed by a series of characterizations. In conclusion, this work reported the synergistic effect of adsorption and photocatalysis of the BiOBr-Bi₂S₃ heterojunctions for Cr removal for the first time, suggesting that the BiOBr-Bi₂S₃ heterojunctions could act as a novel photocatalytic adsorbent to treat the Cr(VI)-containing wastewater.

In-situ synthesized porphyrin polymer/TiO2 composites as high-performance Z-scheme photocatalysts for CO2 conversion

The promising photocatalytic conversion of CO₂ into valuable fuel promotes the development of photocatalyst through various methods. In this work, TiO₂ nanoparticle was composited with covalent porphyrin polymers (COP-Ps) to fabricate composite photocatalysts. The resultant COP-Ps/TiO₂ composites by in situ hydrothermal method exhibit much improved photocatalytic activity for the conversion of CO₂ into CO relative to two components, and it is attributable to improved charge transfer between two moieties led by strong interaction. Especially, TiO₂ is composited more evenly with the sulfonated hollow COP-P (sh-COP-P). The resultant composite sh-COP-P/TiO₂ performs best with a CO production rate of 5.70 μmol·g^-1·h^-1, which is approximately 20.4 times as high as that of pure TiO₂ and 2.3 times of sh-COP-P polymer. For comparison, the simple physical mixture of sh-COP-P and TiO₂ (sm-sh-COP-P/TiO₂) was fabricated, and it performs more badly due to poor mixing uniformity. A Z-scheme photocatalytic mechanism was proposed for sh-COP-P/TiO₂ composite on the basis of energy band analysis and hydroxyl radical test. This study provides a new in situ strategy to fabricate organic polymer/metal oxide composites of high photocatalytic activity for CO₂ reduction.

An effective non-equivalent ion exchange method for building an advanced Z-scheme WO3/Bi2WO6 photocatalyst

X-ray diffraction (XRD) patterns of (a) WO3, Bi2WO6 and (b) WBs composites.

Facile fabrication of BiOCl nanoplates with high exposure {001} facets for efficient photocatalytic degradation of nitro explosives

BiOCl nanoplates with highly exposed {001} facets displayed excellent photocatalytic activity on the degradation of nitro explosives.

Design of charge transfer channels: defective TiO2/MoP supported on carbon cloth for solar-light-driven hydrogen generation

We successfully integrated MoP and TiO₂ on flexible carbon cloth (CC) to construct a panel photoreactor with efficient charge transfer channels, where CC acts as an electron collector and guides directional migration of electrons (TiO₂ → MoP → CC).

Design and synthesis of robust Z-scheme ZnS-SnS2 n-n heterojunctions for highly efficient degradation of pharmaceutical pollutants: Performance, valence/conduction band offset photocatalytic mechanisms and toxicity evaluation

Petal-like ZnS-SnS₂ heterojunctions with Z-scheme band alignment were prepared by one-pot solvothermal strategy. The optimal (1:1) ZnS-SnS₂ can degrade 93.46 % of tetracycline and remove 73.9 % COD of pharmaceutical wastewater under visible-light irradiation due to the efficient production of H, O₂^-, h⁺ and OH. The toxicity evaluation by ECOSAR prediction and the growth of E. coli indicates efficient toxicity reduction of tetracycline by photocatalysis and the non-toxicity of ZnS-SnS₂. The attacked sites on tetracycline by reactive species were analyzed according to Fukui index, and two degradation pathways of tetracycline were inferred via the identification of intermediate products. Tetracycline degradation efficiency and the energy consumption in different water bodies were compared, and it was found that the electrical energy per order (EE/O) was the lowest in Ganjiang River. The valence band offset (ΔE_VBO) and conduction band offset (ΔE_CBO) of ZnS-SnS₂ were 1.02 eV and 0.22 eV, respectively. The probable photocatalytic mechanism of ZnS/SnS₂ heterojunctions with Z-scheme band alignment based on ΔE_VBO and ΔE_CBO was first presented.

Cyclic Silylselenides: Convenient Selenium Precursors for Atomic Layer Deposition

Three cyclic silylselenides were prepared in a straightforward manner. Property tuning has been achieved by varying the ring size and the number of embedded selenium atoms. All silylselenides possess improved resistance towards moisture and oxidation as well as high thermal robustness and sufficient volatility with almost zero residues. The six-membered diselenide proved to be particularly superior Se precursors for atomic layer deposition and allowed facile preparation of MoSe₂ layers. Their structure and composition have been investigated by Raman and X-ray photoelectron spectroscopy as well as scanning electron microscopy revealing vertically aligned flaky shaped nanosheets.

TiO2-based catalysts for photocatalytic reduction of aqueous oxyanions: State-of-the-art and future prospects

Nowadays, an increasing discharge of oxyanions to the natural environment has been attracting worldwide attention. TiO₂-based photocatalysis is regarded as one of the most promising technologies for the conversion of toxic oxyanions (such as chromate, nitrate, nitrite, bromate, perchlorate and selenate) to harmless and/or less toxic substances in contaminated waters. Various types of TiO₂-based catalysts have been developed, and each of them exhibits its own advantages in catalytic reduction of oxyanions. However, the application of these nanostructured TiO₂ in real water bodies remains a challenge, with limitations associated with sunlight harvesting abilities, production costs, reuse stability and exposure risks. Herein, we aim to present a critical review on reported TiO₂-based photocatalytic reduction of aqueous oxyanions, provide a comprehensive understanding of the possible reaction pathways of formed active species, and evaluate the reduction performance of different types of TiO₂-based catalysts. In addition, the impact of operating parameters (such as solution pH, temperature, dissolved oxygen and coexisting substances) on catalytic reduction performance is discussed. Furthermore, the perspectives of TiO₂-based photocatalytic reduction of oxyanions are also proposed.

Insights into the TiO2-Based Photocatalytic Systems and Their Mechanisms

Photocatalysis is a multifunctional phenomenon that can be employed for energy applications such as H2 production, CO2 reduction into fuels, and environmental applications such as pollutant degradations, antibacterial disinfection, etc. In this direction, it is not an exaggerated fact that TiO2 is blooming in the field of photocatalysis, which is largely explored for various photocatalytic applications. The deeper understanding of TiO2 photocatalysis has led to the design of new photocatalytic materials with multiple functionalities. Accordingly, this paper exclusively reviews the recent developments in the modification of TiO2 photocatalyst towards the understanding of its photocatalytic mechanisms. These modifications generally involve the physical and chemical changes in TiO2 such as anisotropic structuring and integration with other metal oxides, plasmonic materials, carbon-based materials, etc. Such modifications essentially lead to the changes in the energy structure of TiO2 that largely boosts up the photocatalytic process via enhancing the band structure alignments, visible light absorption, carrier separation, and transportation in the system. For instance, the ability to align the band structure in TiO2 makes it suitable for multiple photocatalytic processes such as degradation of various pollutants, H2 production, CO2 conversion, etc. For these reasons, TiO2 can be realized as a prototypical photocatalyst, which paves ways to develop new photocatalytic materials in the field. In this context, this review paper sheds light into the emerging trends in TiO2 in terms of its modifications towards multifunctional photocatalytic applications.