Comprehensive spectroscopy and photocatalytic activity analysis of TiO2-Pt systems under LED irradiation

This study presents a thorough spectroscopic analysis of TiO2-Pt systems under LED irradiation, with a focus on elucidating the photodeposition process of Pt nanoparticles onto TiO2 surfaces. The methodology leverages an innovative LED photoreactor tailored to a specific spectral range, enabling precise characterization of the excitation spectrum of TiO2-Pt composites. Through the identification of Pt precursor species and their excitation under LED-UV light, a photodeposition mechanism is proposed involving concurrent excitation of both the TiO2 semiconductor and the H2PtCl6 precursor. The LED photoreactors are employed to scrutinize the excitation profile of TiO2-Pt materials, revealing that the incorporation of Pt nanoparticles does not expand TiO2's absorption spectrum. Furthermore, UV-A exposure in the absence of Pt did not induce the formation of surface defects, underscoring the lack of visible light activity in TiO2-Pt systems. Spectroscopic analyses, complemented by naproxen photooxidation experiments, indicate the absence of a significant plasmonic effect in Pt nanoparticles within the experimental framework. Mass spectroscopy results corroborate the presence of distinct naproxen degradation pathways, suggesting minimal influence from photocatalyst properties. This research provides a detailed spectroscopic insight into TiO2-Pt photocatalysis, enriching the knowledge of photocatalytic materials in LED lighting.

Advances in Polyoxometalates as Electron Mediators for Photocatalytic Dye Degradation

The increasing concerns over the environment and the growing demand for sustainable water treatment technologies have sparked substantial interest in the field of photocatalytic dye removal. Polyoxometalates (POMs), known for their intricate metal-oxygen anion clusters, have received considerable attention due to their versatile structures, compositions, and efficient facilitation of photo-induced electron transfers. This paper provides an overview of the ongoing research progress in the realm of photocatalytic dye degradation utilizing POMs and their derivatives. The details encompass the compositions of catalysts, catalytic efficacy, and light absorption propensities, and the photocatalytic mechanisms inherent to POM-based materials for dye degradation are exhaustively expounded upon. This review not only contributes to a better understanding of the potential of POM-based materials in photocatalytic dye degradation, but also presents the advancements and future prospects in this domain of environmental remediation.

Boosted Photocatalytic Performance for Antibiotics Removal with Ag/PW12/TiO2 Composite: Degradation Pathways and Toxicity Assessment

Photocatalyst is the core of photocatalysis and directly determines photocatalytic performance. However, low quantum efficiency and low utilization of solar energy are important technical problems in the application of photocatalysis. In this work, a series of polyoxometalates (POMs) [H3PW12O40] (PW12)-doped titanium dioxide (TiO2) nanofibers modified with various amount of silver (Ag) nanoparticles (NPs) were prepared by utilizing electrospinning/photoreduction strategy, and were labelled as x wt% Ag/PW12/TiO2 (abbr. x% Ag/PT, x = 5, 10, and 15, respectively). The as-prepared materials were characterized with a series of techniques and exhibited remarkable catalytic activities for visible-light degradation tetracycline (TC), enrofloxacin (ENR), and methyl orange (MO). Particularly, the 10% Ag/PT catalyst with a specific surface area of 155.09 m2/g and an average aperture of 4.61 nm possessed the optimal photodegradation performance, with efficiencies reaching 78.19% for TC, 93.65% for ENR, and 99.29% for MO, which were significantly higher than those of PW12-free Ag/TiO2 and PT nanofibers. Additionally, various parameters (the pH of the solution, catalyst usage, and TC concentration) influencing the degradation process were investigated in detail. The optimal conditions are as follows: catalyst usage: 20 mg; TC: 20 mL of 20 ppm; pH = 7. Furthermore, the photodegradation intermediates and pathways were demonstrated by HPLC-MS measurement. We also investigated the toxicity of products generated during TC removal by employing quantitative structure-activity relationship (QSAR) prediction through a toxicity estimation software tool (T.E.S.T. Version 5.1.2.). The mechanism study showed that the doping of PW12 and the modification of Ag NPs on TiO2 broadened the visible-light absorption, accelerating the effective separation of photogenerated carriers, therefore resulting in an enhanced photocatalytic performance. The research provided some new thoughts for exploiting efficient and durable photocatalysts for environmental remediation.

Electrospun composite nanofibers as novel high-performance and visible-light photocatalysts for removal of environmental pollutants: A review

Environmental pollution caused by industries and human manipulations is coming a serious global challenge. On the other hand, the world is facing an energy crisis caused by population growth. Designing solar-driven photocatalysts which are inspired by the photosynthesis of plant leaves is a fantastic solution to use solar energy as green, available, and unlimited energy containing ∼50% visible light for the removal of environmental pollutants. The polymeric and non-polymeric-based electrospun composite nanofibers (NFs) are as innovative photocatalytic candidates which increase photocatalytic activity and transition from UV light to visible light and overcome the aggregation, photocorrosion, toxicity, and hard recycling and separation of the nanosized powder form of photocatalysts. The composite NFs are fabricated easily by either embedding the photocatalytic agents into the NFs during electrospinning or via their decorating on the surface of NFs post-electrospinning. Polyacrylonitrile-based, tungsten trioxide-based, zinc oxide-based, and titanium dioxide-based composite NFs were revealed as the most reported composite NFs. All the lately investigated electrospun composite NFs indicated long-term stability, high photocatalytic efficiency (∼> 80%) within a short time of light radiation (10-430 min), and high stability after several cycles of use. They were applied in various applications including degradation of dyes/antibiotics, water splitting, wastewater treatment, antibacterial usage, etc. The photogenerated species especially holes, O₂^∙-, and ^.OH were mostly responsible for the photocatalytic mechanism and pathway. The electrospun composite NFs have the potential to use in large-scale productions in condition that their thickness and recycling conditions are optimized, and their toxicity and detaching are resolved.

Preparation of a novel photocatalytic catalyst PW9@ZnO/Ag and the photocatalytic degradation of butyl xanthate under visible light

Photocatalytic technology is attracting considerable attention for the advantages of low cost and environmentally friendly properties. In this study, a novel photocatalyst PW₉@ZnO/Ag (PZA) was synthesized hydrothermally and characterized by a variety of means. The results indicated that ZnO and Ag NPs were successfully decorated and uniformly dispersed on PW₉ to form the composites. The prepared PZA was applied in the degradation of simulated butyl xanthate (BX) beneficiation wastewater both under the UV light and the xenon lamp, and a maximum degradation of 99.83% was obtained under the visible light with 10% ZnO loading, 1 g/L PZA, initial BX concentration of 20 mg/L, and pH 5.5. The PZA was recovered and reused for 5 times, and the degradation rates remained above 70%. Superoxide radical (·O₂^-) was the main active species for the photocatalytic degradation of BX. The experimental results demonstrate that PZA is a promising photocatalyst, making it a prospective strategy to overcome current challengers in the use of xanthate degradation and beneficiation wastewater treatment under visible light.

Recent Advances in Designing Fibrous Biomaterials for the Domain of Biomedical, Clinical, and Environmental Applications

Unique properties and potential applications of nanofibers have emerged as innovative approaches and opportunities in the biomedical, healthcare, environmental, and biosensor fields. Electrospinning and centrifugal spinning strategies have gained considerable attention among all kinds of strategies to produce nanofibers. These techniques produce nanofibers with high porosity and surface area, adequate pore architecture, and diverse chemical compositions. The extraordinary characteristics of nanofibers have unveiled new gates in nanomedicine to establish innovative fiber-based formulations for biomedical use, healthcare, and a wide range of other applications. The present review aims to provide a comprehensive overview of nanofibers and their broad range of applications, including drug delivery, biomedical scaffolds, tissue/bone-tissue engineering, dental applications, and environmental remediation in a single place. The review begins with a brief introduction followed by potential applications of nanofibers. Finally, the future perspectives and current challenges of nanofibers are demonstrated. This review will help researchers to engineer more efficient multifunctional nanofibers with improved characteristics for their effective use in broad areas. We strongly believe this review is a reader's delight and will help in dealing with the fundamental principles and applications of nanofiber-based scaffolds. This review will assist students and a broad range of scientific communities to understand the significance of nanofibers in several domains of nanotechnology, nanomedicine, biotechnology, and environmental remediation, which will set a benchmark for further research.

Exploring flowery MnO2/Ag nanocomposite as an efficient solar-light-driven photocatalyst

An efficient approach was developed to boost the solar light driven photocatalytic efficacy of pristine flowery MnO2 NCs through the immobilization of Ag NPs, which in turn produces MnO2/Ag NCs.

Heterogeneous UV-Switchable Au nanoparticles decorated tungstophosphoric acid/TiO2 for efficient photocatalytic degradation process

In the present study, gold nanoparticles were locally well-decorated on the surface of TiO₂ using the tungstophosphoric acid (HPW), as UV-switchable reducing intermediate linkers. The prepared Au NPs/HPW/TiO₂ nanostructure was characterized using FTIR, XRD, EDS, SEM and TEM, which confirmed the successful attachment of quasi-spherical Au NPs in the range of 20-30 nm on the surface of HPW modified TiO₂. Also, the FTIR results show that the Au NPs were binded to TiO₂ through the terminal the oxygen atoms HPW. The photocatalytic performance of prepared nanostructures was assessed in degradation of nitrobenzene. The nitrobenzene photodegradation kinetic study revealed that it well followed the Langmuir-Hinshelwood kinetic model with the apparent rate constant of 0.001 min^-1 using anatase TiO₂, 0.0004 min^-1 using HPW, 0.0014 using HPW/TiO₂, while it was obtained 0.0065 min^-1 using Au NPs@HPW/TiO₂ nanostructure. It shows that the photocatalytic rate of the prepared nanocomposites increased by 6.5- and 4.6-fold compared to photoactivity of anatase TiO₂ and HPW/TiO₂ respectively. Also, the photocatalytic mechanism of process was proposed. Moreover, the reusability study confirmed that its photocatalytic activity still remained high after three cycles.

Facile synthesis, characterization, mechanism and enhanced visible-light photocatalytic activity of SiW12/α-Fe2O3 nanocomposites

The photocatalytic mechanism of the SiW12/α-Fe2O3 nanohybrid.

Photocatalytic remediation of organic waste over Keggin-based polyoxometalate materials: A review

Photocatalytic remediation of industrial water pollution has courted intense attention lately due to its touted green approach. In this respect, Keggin-based polyoxometalates (POMs) as green solid acids in photocatalytic reaction possess superior qualities, viz. unique photoinduced charge-transfer properties, strong photooxidative-photoreductive ability, high chemical and thermal stability, and so forth. Unfortunately, it suffers from a large bandgap energy, low specific surface area, low recoverability, and scarce utilization in narrow absorption range. Therefore, the pollutant degradation performance is not satisfactory. Consequently, multifarious research to enhance the photocatalytic performance of Keggin-based POMs were reported, viz. via novel modifications and functionalizations through a variety of materials, inclusive of, inter alia, metal oxides, transition metals, noble metals, and others. In order to advocate this emerging technology, current review work provides a systematic overview on recent advancement, initiated from the strategized synthetic methods, followed by hierarchical enhancement and intensification process, at the same time emphasizes on the fundamental working principles of Keggin-based POM nanocomposites. By reviewing and summarizing the efforts adopted global-wide, this review is ended with providing useful outlooks for future studies. It is also anticipated to shed light on producing Keggin-based POM nanocomposites with breakthrough visible- and solar-light-driven photocatalytic performance against recalcitrant organic waste.

Multi-praseodymium-and-tungsten bridging octameric tellurotungstate and its 2D honeycomb composite film for detecting estrogen

Under coordination driving force of tungsten and rare-earth (RE) bridges, we synthesized a novel giant multi-tungsten-and-RE-bridging octameric tellurotungstate (TT) [H₂N(CH₃)₂]₁₆K₈Na₆H₁₀[Pr₈(H₂O)₂₀W₁₆O₄₈][B-α-TeW₉O₃₃]₈·70H₂O (1) in CH₃CN-H₂O mixed solvent. The cluster anion {[Pr₈(H₂O)₂₀W₁₆O₄₈][B-α-TeW₉O₃₃]₈}^40- features sixteen W^VI bridges, eight Pr^III bridges and eight trivacant Keggin [B-α-TeW₉O₃₃]^8- fragments, which the square {W₄O₁₂} cluster can be imagined as a seed to induce the aggregation of eight [B-α-TeW₉O₃₃]^8- fragments by coordination driving force of additional twelve W^VI bridges and eight Pr^III ions. Furthermore, the 2D 1@DODA (dimethyldioctadecyl ammonium bromide = DODA·Br) honeycomb composite material was prepared. The honeycomb morphology of the 1@DODA composite material provides rich binding sites for electrodepositing Au nanoparticles to make Au/1@DODA electrodes. The aptamer of 17β-estradiol (E2) hormone can be grafted to the Au/1@DODA electrodes via Au-S bonding interaction to construct the Au/1@DODA aptamer biosensors. By virtue of the specific recognition interaction of aptamer and the electrochemical signal amplification function of methylene blue and cDNA, the Au/1@DODA aptamer biosensors can realize the electrochemical detection of E2. This finding not only offers an electrochemical biosensing platform for detecting E2, but also expands POM-based composite materials in the applications of clinical detection and biological analysis.

Photo-reduction enables catalyst regeneration in Fenton reaction on an Fe2O3-decorated TiO2 nanotube-based photocatalyst

The Fenton reaction is regarded as an advanced oxidation process that can efficiently remediate environmental pollutants. However, the one-time irreversible consumption of its catalysts raises the cost in practical application. Herein, we report the generation of active Fe2+ sites via photo-reduction by photogenerated electrons on a TiO2 nanotube-based catalyst (TNT(Pd)/Fe2O3) with Fe2O3 decorated on the outside wall, while the inside cavity entrapped Pd nanoparticles. Fenton catalytic investigations under visible light show that TNT(Pd)/Fe2O3 displays superior methyl orange degradation activity with 90% removal in 10 minutes. The kinetic constant is 4.3 times as the sum of the pure photocatalysis and Fenton catalytic kinetic constants. The synergistic effect between the Fenton and photocatalytic reactions is further evidenced by the photocurrent and photodegradation tests. The TNT(Pd)/Fe2O3 catalyst showed no decay in the Fenton-photocatalytic performance over three successive cycles. XPS measurements after long-term stability tests revealed no loss, but a slight increase in the number of Fe2+ species. All of these results suggest that the most active Fe2+ species in the Fenton reaction can be regenerated via the reduction by photogenerated electrons. This work addressed the challenge in catalyst regeneration in the traditional Fenton reaction via photoreduction by rational combination with a photocatalyst and the realized synergistic effect between photocatalysis and the Fenton reaction.

Dual modification of TiO2 nanorod arrays with SiW11Co and Ag nanoparticles for enhanced photocatalytic activity under simulated sunlight

Well-organized TiO₂ nanorod arrays (TNRs) have increasingly attracted our attention in recent years due to their excellent photocatalytic properties. However, it is of great importance to prepare more efficient photocatalysts using a facile method towards their more widespread use. In this work, K₆SiW₁₁O₃₉Co(ii)(H₂O) (SiW₁₁Co) and Ag nanoparticles were introduced into TNRs using spin-coating and chemical bath deposition methods. It was found that TNRs/SiW₁₁Co/Ag composite films with an active area of only 1 cm² exhibit highly efficient and sustainable properties for the photodegradation of NO₂ and display a significant enhancement compared with P₂₅ and pure TNRs. Photocatalytic measurements demonstrated that both SiW₁₁Co and Ag synergistically improve the light absorption and charge separation efficiency, thus obtaining the most efficient photocatalytic performance. In addition, the probable photocatalytic mechanism and the dominating active species for NO₂ photodegradation were also proposed, in order to testify the effectively enhanced photocatalytic ability of the TNRs/SiW₁₁Co/Ag composite. Hence, the design of these polyoxometalate and metal particle co-modified TNRs may provide a new tactic for developing promising materials for photocatalytic degradation.