Photocatalytic Effect Research Articles

Decoration of viscose fibers with silver nanoparticle-based titanium-organic framework for use in environmental applications.

To effectively remove pharmaceuticals, nitroaromatic compounds, and dyes from wastewater, an efficient multifunctional material was created based on silver nanoparticles (Ag) and MIL-125-NH2 (MOF) immobilized on viscose fibers (VF) as a support substrate. Firstly, silver nanoparticles (Ag) were immobilized on the surface of viscose fibers (VF) via in situ synthesis using trisodium citrate (TSC) as a reducing agent to create (VF-Ag). Then, VF and VF-Ag were decorated with the titanium metal-organic framework MIL-125-NH2 (MOF) to create VF-MOF and VF-Ag-MOF. The influence of VF-Ag, VF-MOF, and VF-Ag-MOF on the sonocatalytic or sonophotocatalytic degradation of sulfa drugs was investigated. The results show that VF-Ag-MOF showed excellent sonocatalytic and sonophotocatalytic activity towards the degradation of sulfa drugs compared to VF-Ag and VF-MOF. Furthermore, sonophotodegradation showed a dramatic enhancement in the efficiency of degradation of sulfa drugs compared to sonodegradation. The sonophotodegradation degradation percentage of sulfanilamide, sulfadiazine, and sulfamethazine drugs in the presence of VF-Ag-MOF was 65, 90, and 95 after 45min of ultrasonic and visible light irradiation. The catalytic activity of VF-Ag, VF-MOF, and VF-Ag-MOF was evaluated through the conversion of p-nitrophenol (4-NP) to p-aminophenol (4-AP). The results demonstrate that VF-Ag-MOF had the highest catalytic activity, followed by VF-Ag and VF-MOF. The conversion percentage of 4-NP to 4-AP was 69%. The catalytic or photocatalytic effects of VF-Ag, VF-MOF, and VF-Ag-MOF on the elimination of methylene blue (MB) dye were investigated. The results demonstrate that VF-Ag-MOF showed high efficiency in removing the MB dye through the reduction (65%) or photodegradation (71%) after 60min. VF-Ag-MOF composites structure-activity relationships represent that doping within silver NPs enhanced the photocatalytic activity of MIL-125-NH2, which could be explained as follows: (i) Due to the formation of a Schottky barrier at the junction between MIL-125-NH2 and Ag NPs, the photogenerated electrons in the conduction band of MIL-125-NH2 were supposed to be quickly transferred to the valence band of the Ag NPs, and subsequently, the electrons were transferred to the conduction band of Ag NPs. This considerable electron transferring process, which is reported as Z scheme heterojunction, can efficiently suppress the recombination of electron/hole pairs in VF-Ag-MIL-125-NH2 composites. (ii) Sufficient separation between the photogenerated charge carriers (holes and electrons) and avoiding their recombination enhanced the photocatalytic activity of composites.

Anatase-Rutile phase transition of Ca@TiO2 nanostructures for the removal of environmental pollutants under visible photon illumination

Regulating the crystalline structure of titanium dioxide is essential granting the potential purposes for oxide. In the present investigation, we employed X-ray diffraction to investigate the significance of calcium doping on the anatase–rutile transition of phase. Preparation of Calcium-doped TiO2 by sonochemical approach, followed by sintering at 700 °C temperatureencompasses a phase transition. The inclusion of calcium into the TiO2 lattice was hampered by the calcium ion's greater radius when contrasted to the titanium ion. Ca@TiO2 nanostructures exhibited a reduced estimated band gap energy compared to pristine TiO2. The Ca2+ substitutesinto the TiO2 surface were demonstrated by the Fourier transform infrared (FT-IR) spectral investigation. By conducting photocatalytic decomposition of persisting Congo red (CR) dye during visible photonradiation exposure, the photocatalytic effectiveness of the produced Ca@TiO2 nanostructures was examined. Ca@TiO2 nanostructures have been discovered to have more catalytic capability than pristine TiO2 nanoparticles. In 4 h of exposure duration with the Ca@TiO2 nanostructures, the maximal degradation of the CR dye, or 88 %, was accomplished with efficient regeneration.

Dye-augmented bandgap engineering of a degradable cascade nanoreactor for tumor immune microenvironment-enhanced dynamic phototherapy of breast cancer

Non-invasive precision tumor dynamic phototherapy has broad application prospects. Traditional semiconductor materials have low photocatalytic activity and low reactive oxygen species (ROS) production rate due to their wide band gap, resulting in unsatisfactory phototherapy efficacy for tumor treatment. Employing the dye-sensitization mechanism can significantly enhance the catalytic activity of the materials. We develop a multifunctional nanoplatform (BZP) by leveraging the benefits of bismuth-based semiconductor nanomaterials. BZP possesses robust ROS generation and remarkable near-infrared photothermal conversion capabilities for improving tumor immune microenvironment and achieving superior phototherapy sensitization. BZP produces highly cytotoxic ROS species via the photocatalytic process and cascade reaction, amplifying the photocatalytic therapy effect. Moreover, the simultaneous photothermal effect during the photocatalytic process facilitates the improvement of therapeutic efficacy. Additionally, BZP-mediated phototherapy can trigger the programmed death of tumor cells, stimulate dendritic cell maturation and T cell activation, modulate the tumor immune microenvironment, and augment the therapeutic effect. Hence, this study demonstrates a promising research paradigm for tumor immune microenvironment-improved phototherapy. Statement of significanceThrough the utilization of dye sensitization and rare earth doping techniques, we have successfully developed a biodegradable bismuth-based semiconductor nanocatalyst (BZP). Upon optical excitation, the near-infrared dye incorporated within BZP promptly generates free electrons, which, under the influence of the Fermi energy level, undergo transfer to BiF3 within BZP, thereby facilitating the effective separation of electron–hole pairs and augmenting the catalytic capability for reactive oxygen species (ROS) generation. Furthermore, a cascade reaction mechanism generates highly cytotoxic ROS, which synergistically depletes intracellular glutathione, thereby intensifying oxidative stress. Ultimately, this dual activation strategy, combining oxidative and thermal damage, holds significant potential for tumor immunotherapy.

Photogenerated electron- and hole-trap distributions in Al-doped anatase TiO2 crystals measured by cryogenic EPR imaging

Electron paramagnetic resonance (EPR) imaging was performed on aluminium-doped anatase titanium dioxide (TiO2) crystals to demonstrate the distributions of photogenerated trapped electrons and holes at cryogenic temperatures. Complementary distributions of trapped electrons and holes were observed at 25 K; trapped electrons were predominant on the {101} planes, whereas trapped holes were predominant on the (001) and {110} planes in the tetragonal crystal structure. These separate distributions are consistent with the reported facet-dependent photocatalytic efficiency of photoreduction and photooxidation in anatase crystals, resulting from crystal plane-dependent carrier transfer. By this extrinsic trap system, the carrier transport properties were derivatively extracted through electron and hole traps. This report provides insight into the fundamental physics governing the facet dependence of photocatalytic effects.

Design of highly selective and stable CsPbI3 perovskite catalyst for photocatalytic reduction of CO2 to C1 products

Finding efficient photocatalytic carbon dioxide reduction catalysts is one of the core issues in addressing global climate change. Herein, the pristine CsPbI3 perovskite and doped CsPbI3 perovskite were evaluated in carbon dioxide reduction reaction (CO2RR) to C1 products by using density functional theory. Free energy testing and electronic structure analysis methods have shown that doped CsPbI3 exhibits more effective catalytic performance, higher selectivity, and stability than undoped CsPbI3. Additionally, it is discovered that CsPbI3 (100) and (110) crystal surfaces have varied product selectivity. The photo-catalytic effectiveness is increased by the narrower band gap of Bi and Sn doped CsPbI3, which broadens the absorption spectrum of visible light and makes electron transport easier. The calculation results indicate that Bi doped CsPbI3 (100) and CsPbI3 (110) crystal faces exhibit good selectivity towards CH4, with free energy barriers as low as 0.55 eV and 0.58 eV, respectively. Sn doped CsPbI3 (100) and CsPbI3 (110) crystal planes exhibit good selectivity for HCOOH and CH3OH, respectively. The results indicate that the Bi and Sn doped CsPbI3 perovskite catalyst can further improve the CO2 photocatalytic activity and high selectivity for C1 products, making it a suitable substrate material for high-performance CO2RR.

Overcoming the Interfacial Photocatalytic Degradation of Nonfullerene Acceptor-Based Organic Photovoltaics by Introducing a UV-A-Insensitive Titanium Suboxide Layer.

Although recent dramatic advances in power conversion efficiencies (PCEs) have resulted in values over 19%, the poor photostability of organic photovoltaics (OPVs) has been a serious bottleneck to their commercialization. The photocatalytic effect, which is caused by incident ultraviolet-A (UV-A, 320-400 nm) light in the most commonly used zinc oxide (ZnOX) electron transport layer (ETL), significantly deteriorates the photostability of OPVs. In this work, we develop a new and facile method to enhance the photostability of nonfullerene acceptor-based OPVs by introducing UV-A-insensitive titanium suboxide (TiOX) ETL. Through an in-depth analysis of mass information at the interface between the ETL and photoactive layer, we confirm that the UV-A-insensitive TiOX suppresses the photocatalytic effect. The resulting device employing the TiOX ETL shows excellent photostability, obtaining 80% of the initial PCE for up to 200 h under 1 sun illumination, which is 10 times longer than that of the conventional ZnOX system (19 h).

Enhanced photocatalytic antibacterial activity of Au-coated Ni–Ti–O nanotubes for biomedical applications

Nickel-titanium (NiTi) alloy is a smart material exhibiting superelasticity, contributing to low stiffness and facilitating integration with bone structures. However, NiTi alloy's bioactivity and antibacterial activity limit its dental applications. In this study, we fabricated nickel titanium oxide (Ni–Ti–O) nanotubes with the potential for bioactivity and photocatalytic properties on the surface of NiTi alloy. Specifically, we applied a coating of gold (Au) nanoparticles to the surface of Ni–Ti–O nanotubes, in order to leverage the antibacterial activity through the photocatalytic effect under 470 nm visible light. Field-emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) observations revealed that Au was deposited mainly at the top surface of Ni–Ti–O nanotubes (diameter: 12.76 ± 2.91 nm, height: 721.12 ± 50.25 nm). X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and diffuse reflectance spectroscopy (DRS) analyses revealed that the Ni–Ti–O nanotubes were NiTiO3 crystalline phases with low crystallinity. Therefore, based on the methylene blue (MB) degradation test, the photocatalytic effect was only achieved under visible light at 470 nm, facilitated by the presence of Au. The antibacterial colony forming unit test and enzymatic activity tests demonstrated that Au-coated Ni–Ti–O nanotubes displayed excellent antibacterial activity under 470 nm visible light irradiation, which was also attributed to photocatalytic effect. Consequently, the combination of Au-coated Ni–Ti–O nanotubes and visible light-based photofunctionalization holds promise for expressing antibacterial properties in dental applications.

A comprehensive study on the co-removal of Cr (VI) and ciprofloxacin via microbial-photocatalytic coupling: Mechanistic insights and performance evaluation

The increasing contamination of water systems by antibiotics and heavy metals has become a growing concern. The intimately coupled photocatalysis and biodegradation (ICPB) approach offers a promising strategy for the effective removal of mixed pollutants. Despite some prior research on ICPB applications, the mechanism by which ICPB eliminates mixed pollutants remains unclear. In our current study, the ICPB approach achieved approximately 1.53 times the degradation rate of ciprofloxacin (CIP) and roughly 1.82 times the reduction rate of Cr (VI) compared to photocatalysis. Remarkably, after 30 days, the ICPB achieved a 96.1% CIP removal rate, and a 97.8% reduction in Cr (VI). Our investigation utilized three-dimensional fluorescence analysis and photo-electrochemical characterization to unveil the synergistic effects of photocatalysis and biodegradation in removal of CIP and Cr (VI). Incorporation of B–Bi3O4Cl (B-BOC) photocatalyst facilitated electron-hole separation, leading to production of ·O2−, ·OH, and h+ species which interacted with CIP, while electrons reduced Cr (VI). Subsequently, the photocatalytic products were biodegraded by a protective biofilm. Furthermore, we observed that CIP, acting as an electron donor, promoted the reduction of Cr (VI). The microbial communities revealed that the number of bacteria favoring pollutant removal increased during ICPB operation, leading to a significant enhancement in performance.

Tailoring visible-light active TiO2/cellulose nanocomposites with controlled crystalline structure for enhanced photocatalytic performance.

This work involves a green and simple synthesis of TiO2 nanoparticles on cellulose under mild conditions without the need for calcination via hydrolysis of titanium oxysulfate (TiOSO4). The synthesis conditions, such as sulfuric acid concentration (0-10%wt), temperature (70-90℃), and time (4-8h), focused on precisely controlling the structure of TiO2 to enhance its photocatalytic effectiveness under visible light. At a lower 2.5wt% sulfuric acid concentration, pure anatase was formed on the cellulose, while an increase in the range of 5.0-7.5wt% sulfuric acid concentration yielded a rutile phase, resulting in a mixed phase of anatase and rutile on the cellulose. The pure rutile phase was found at a low temperature (70℃), while increased temperature led to the formation of the anatase phase. These results confirmed that the formation of crystalline TiO2 phase on the cellulose depended on sulfuric acid concentration and temperature for hydrolysis. Additionally, the photocatalytic properties of the obtained materials were evaluated by degradationvisible of Rhodamine B (RhB) under UV and visible light. The findings revealed that the mixed phase (anatase/rutile) of TiO2 on the cellulose demonstrated a superior photocatalytic efficiency (99.2%) compared to pure anatase (85.75%) and rutile (75.08%) when exposed to visible light.

Understanding the light induced hydrophilicity of metal-oxide thin films

Photocatalytic effects resulting in water splitting, reduction of carbon dioxide to fuels using solar energy, decomposition of organic compounds, and light-induced hydrophilicity observed on surfaces of various metal oxides (MOx), all rely on the same basic physical mechanisms, and have attracted considerable interest over the past decades. TiO2 and ZnO, two natively n-type doped wide bandgap semiconductors exhibit the effects mentioned above. In this study we propose a model for the photo-induced hydrophilicity in MOx films, and we test the model for TiO2/Si and ZnO/Si heterojunctions. Experimentally, we employ a wet exposure technique whereby the MOx surface is exposed to UV light while a water droplet is sitting on the surface, which allows for a continuous recording of contact angles during illumination. The proposed model and the experimental techniques allow a determination of minority carrier diffusion lengths by contact angle measurements and suggest design rules for materials exhibiting photocatalytic hydrophilicity. We expect that this methodology can be extended to improve our physical understanding of other photocatalytic surface effects.

Photocatalytic degradation of Orange-II by surfactant assisted Mn/Mg co-doped TiO2 nanoparticles under visible light irradiation

In this research, the photocatalytic effect was studied for sol-gel synthesized Mn/Mg co-doped metal oxide (TiO2) nanoparticles (NPs), which are encapsulated with anionic Gemini surfactant. The physicochemical properties of Mn/Mg co-doped TiO2 were investigated using a variety of characterization techniques, FT-IR, UV Vis-DRS, XRD, SEM, EDX, TEM, BET and PL. Characterization results reveal that Mn/Mg dopants stabilize TiO2 in the form of anatase phase and reduce the bandgap energy. Presence of strong chemical bonding and functional groups at the interface of dopant and TiO2 NPs was confirmed with FT-IR. The photocatalytic activity of these catalysts was assessed by the degradation of Orange II (AO7) using visible light irradiation. Of the variable nanomaterials MMT5-GS2 showed remarkable results. The photoluminescence studies revealed that OH radicals are the reactive species and responsible for oxidative photocatalytic degradation of Orange II.

A novel dual S-scheme Co9S8/MnCdS/Co3O4 heterojunction for photocatalytic hydrogen evolution under visible light irradiation.

Rational design and synthesis of a unique heterojunction photocatalyst structure is an important strategy to enhance its performance and structural stability. Herein, Co9S8/MnCdS/Co3O4 photocatalysts with double S-scheme heterojunctions were successfully prepared by coupling Co9S8 and Co3O4 sheet structures with n-type MnCdS nanoparticles through a simple solvothermal and mechanical mixing method. The construction of the dual S-scheme heterostructure offers the possibility to expand the light absorption range, extend the carrier lifetime and maximise the redox capacity. In addition, the mechanism of charge transfer and the reason for the improvement of photocatalytic activity were explored through photoelectrochemical characterization. The lamellar structures of Co9S8 and Co3O4 not only provide excellent dispersion and slow down the agglomeration of MnCdS nanoparticles, but also promote charge transfer, which improves the photocatalytic hydrogen production effect. Under simulated solar irradiation, the evolution rate of H2 after 5 h was as high as 46.44 μmol, which was 3.49 and 1.49 times higher than those of pristine MnCdS and MnCdS/Co3O4, respectively. Meanwhile, it has good stability under 20 h irradiation. This work demonstrates a novel idea for the rational design of double S-scheme photocatalysts with efficient space separation.

Performance of PVDF-La dope TiO2 Membrane Photocatalytic Under Visible Light Irradiation for Produced Water Treatment

Membrane technology has been widely applied in water management systems for production, but is still hindered by fouling phenomena and low selectivity. Improving membrane performance through modification, such as the addition of photocatalytic materials, has been explored. In this research, La@TiO2 composite was incorporated into PVDF membranes for the treatment of produced water. Lanthanum doping on TiO2 effectively inhibits carrier recombination and enhances photocatalytic activity. According to the research results, adding the La@TiO2 composite to the membrane matrix increased the porosity value and membrane pore size. The PVDF-La@TiO2 1.5%wt membrane exhibited the highest flux values, specifically 20.59 L.m-2.h-1 and 40 L.m-2.h-1 in dark conditions and visible light irradiation. The rejection rates for COD, TDS, and ammonia were 69.89%, 57.77%, and 69.65%. The photocatalytic degradation effect of PVDF-La@TiO2 is proven by a significant difference in the filtration results under vis-light irradiation. The kinetics of COD removal are better described by a pseudo-first-order model. The degradation of PVDF-La@TiO2 1.5% pollutant demonstrated significant results, confirming its photocatalytic activity under irradiation. Overall, the membrane exhibited good performance and proved to be reusable after 6 hours of photofiltration. This research holds promise for enhancing the use of membrane photocatalytics in the treatment of produced water.

Conformational control of antimicrobial peptide amphiphilicity: consequences for boosting membrane interactions and antimicrobial effects of photocatalytic TiO2 nanoparticles.

This study reports on the effects of conformationally controlled amphiphilicity of antimicrobial peptides (AMPs) on their ability to coat TiO2 nanoparticles (NPs) and boost the photocatalytic antimicrobial effects of such NPs. For this, TiO2 NPs were combined with AMP EFK17 (EFKRIVQRIKDFLRNLV), displaying a disordered conformation in aqueous solution but helix formation on interaction with bacterial membranes. The membrane-bound helix is amphiphilic, with all polar and charged amino acid residues located at one side and all non-polar and hydrophobic residues on the other. In contrast, the d-enantiomer variant EFK17-d (E(dF)KR(dI)VQR(dI)KD(dF)LRNLV) is unable to form the amphiphilic helix on bacterial membrane interaction, whereas the W-residues in EFK17-W (EWKRWVQRWKDFLRNLV) boost hydrophobic interactions of the amphiphilic helix. Circular dichroism results showed the effects displayed for the free peptide, to also be present for peptide-coated TiO2 NPs, causing peptide binding to decrease in the order EFK17-W > EFK17 > EFK17-d. Notably, the formation of reactive oxygen species (ROS) by the TiO2 NPs was essentially unaffected by the presence of peptide coating, for all the peptides investigated, and the coatings stabilized over hours of UV exposure. Photocatalytic membrane degradation from TiO2 NPs coated with EFK17-W and EFK17 was promoted for bacteria-like model bilayers containing anionic phosphatidylglycerol but suppressed in mammalian-like bilayers formed by zwitterionic phosphatidylcholine and cholesterol. Structural aspects of these effects were further investigated by neutron reflectometry with clear variations observed between the bacteria- and mammalian-like model bilayers for the three peptides. Mirroring these results in bacteria-like model membranes, combining TiO2 NPs with EFK17-W and EFK17, but not with non-adsorbing EFK17-d, resulted in boosted antimicrobial effects of the resulting cationic composite NPs already in darkness, effects enhanced further on UV illumination.

Enhanced sequestration of Pb2+ and Cu2+ by Artemia cyst shell supported nano-Mg composite and the potential photocatalytic performance of carbonized exhausted-adsorbent

This study reported a new strategy for enhanced Pb2+ and Cu2+ sequestration by Artemia cyst shell (shell) supported nano-Mg from aqueous solutions and the carbonated exhausted-adsorbents sequenced potential application in photo-catalyst, which obtained two expected results. One is that the immobilization of nano-Mg onto Artemia cyst shell (shell-Mg) can greatly strengthen the adsorption effect of the neat cyst shell on Pb2+ and Cu2+. The adsorption capacities of shell-Mg for both metal ions reached to 622.01 and 313.91 mg/g, which was 10–15 and 30–50 times that of the neat shell respectively. And shell-Mg has strong selectivity, which was approximately 2–4 times that of shell. The shell-Mg can be used to retrieve Pb2+ and Cu2+ from aqueous solutions efficiently. Another is that the carbonated exhausted-adsorbents (C-shell-Mg-Pb and C-shell-Mg-Cu) showed their potential photocatalytic degradation effects on congo red under pH = 4 condition, the decolorization rate reached to 61.19% and 80.39% respectively. Reuse of exhausted adsorbents can avoid the secondary pollution caused by the regeneration, extend the utilization value of exhausted adsorbents, and provide a new viewpoint for the reuse of spent bio-nanomaterial adsorbents.

Facile construction of metal–organic frameworks/topological insulator heterostructure for photothermal catalytic CO2 reduction

MOF/topological insulator-based heterostructure, namely ZIF-8/Bi2Se3 NSs, exhibits excellent photo-to-heat conversion ability and remarkable photothermal catalytic activity with CO evolution rate of 22.65 μmol g−1 h−1.

A cryptand-like Ti-coordination compound with visible-light photocatalytic activity in CO2 storage.

A cryptand-like Ti-coordination compound, namely Ti12Cs, comprising two Ti6-salicylate cages and hosting two Cs+ ions, was synthesized by the solvothermal method. It exhibits strong visible-light absorption with an absorption band edge of 652 nm, attributed to the electron transition from salicylate ligands to Ti ions. Electrochemical impedance, visible-light transient photocurrent response, and photoluminescence spectra confirm that Ti12Cs has excellent visible-light response and charge-separation properties. Ti12Cs can be used as a heterogeneous and recyclable photocatalyst for CO2/epoxide cycloaddition, with high utilization efficiency of visible-light under mild conditions. The mechanism investigation points to a synergistic effect of photocatalysis and Lewis acid catalysis.

Study on the photo-assisted activation of PMS by CuMo1−xWxO4 for degradation of tetracycline

This study synthesizes CuMo1−xWxO4 solid solutions with tunable Mo/W ratios, enhancing electron–hole separation and PMS activation for tetracycline degradation, while demonstrating excellent stability and a synergistic effect of photocatalysis.

High-efficiency and conveniently recyclable g-C3N4/diatomite/calcium alginate composite gel bead photocatalysts

Graphitic carbon nitride (g-C3N4) is considered an encouraging photocatalyst with visible light activity. However, the utilization of g-C3N4 nanosheets in powdered form in wastewater treatment presents difficulties in the recovery and recycling of photocatalysts. Consequently, supported g-C3N4 photocatalysts have been developed for practical applications. In the present work, a novel, conveniently recyclable composite gel bead photocatalyst, comprised of g-C3N4/diatomite/calcium alginate, has been fabricated using a dropwise addition strategy. The systematic investigation of photocatalytic activity and photochemical stability of the composite gel beads was conducted through the degradation of methylene blue (MB) under visible light exposure (λ > 420 nm). As a result, g-C3N4/diatomite/calcium alginate gel beads show a high photocatalytic effectiveness of 95% when MB solution is disintegrated at 120 minutes.

A pyrenetetrayl/phenanthroline-based one-dimensional covalent organic framework for metal-free photocatalytic organic conversion

A 1D COF, termed PP-COF, was reported with optimized eclipsed packing (AA) and excellent optoelectronic performance. Compared with 2D COF, PP-COF exhibited more efficient photocatalytic effects in bisarylation and oxidative coupling reactions.