UVA Light Irradiation Research Articles

Enhancing antimicrobial efficacy against Pseudomonas aeruginosa biofilm through carbon dot-mediated photodynamic inactivation

Pseudomonas aeruginosa biofilms shield the bacteria from antibiotics and the body’s defenses, often leading to chronic infections that are challenging to treat. This study aimed to assess the impact of sub-lethal doses of antimicrobial photodynamic inactivation (sAPDI) utilizing carbon dots (CDs) derived from gentamicin and imipenem on biofilm formation and the expression of genes (pelA and pslA) associated with P. aeruginosa biofilm formation.The anti-biofilm effects of sAPDI were evaluated by exposing P. aeruginosa to sub-minimum biofilm inhibitory concentrations (sub-MBIC) of CDsGEN-NH2, CDsIMP-NH2, CDsGEN-IMP, and CDsIMP-GEN, combined with sub-lethal UVA light irradiation. Biofilm formation ability was assessed by crystal violet (CV) assay and enumeration method. Additionally, the impact of sAPDI on the expression of pelF and pslA genes was evaluated using real-time quantitative polymerase chain reaction (RT-qPCR).Compared to the control group, the sAPDI treatment with CDsGEN-NH2, CDsIMP-NH2, CDsGEN-IMP, and CDsIMP-GEN resulted in a significant reduction in biofilm activity of P. aeruginosa ATCC 27853 (P < 0.0001). The CV assay method demonstrated reductions in optical density of 83.70%, 81.08%, 89.33%, and 75.71%, while the CFU counting method showed reductions of 4.03, 3.76, 4.39, and 3.21 Log10 CFU/mL. qRT-PCR analysis revealed decreased expression of the pelA and pslA genes in P. aeruginosa ATCC 27853 following sAPDI treatment compared to the control group (P < 0.05).The results indicate that sAPDI using CDs derived from gentamicin and imipenem can decrease the biofilm formation of P. aeruginosa and the expression of the pelA and pslA genes associated with its biofilm formation.

High‐Performance Dynamic Photo‐Responsive Polymers With Superior Closed‐Loop Recyclability

AbstractChemical recycling to monomer (CRM) provides an ideal solution for reducing plastic waste and achieving a circular polymer economy. Cyclopentene (CP) and its derivatives are representative molecules that exemplify an efficient CRM process under mild conditions. However, most CP‐based polymers possess limited thermal and mechanical properties, constraining their potential applications. Herein, new CP‐based polymers with superior thermo‐mechanical properties and autonomous functions are proposed by integrating anthracene as a dynamic functional motif. Anthracenes not only serve as supramolecular cross‐linkages through strong π–π interactions but also form stronger chemical ones under UVA light irradiation, enhancing thermo‐mechanical properties. Furthermore, damage‐reporting, self‐healing, and local shape reprogramming capabilities are accomplished by utilizing the reversible nature of photodimerized anthracene. A mild and orthogonal depolymerization condition for the CP‐based polymers facilitates efficient monomer recovery even from mixed plastic wastes. This work presents a simple yet effective strategy to expand the usability of chemically recyclable polymers and contribute to a closed‐loop polymer economy.

Photoinduced Intermolecular Radical Hydroalkylation of Olefins via Ligated Boryl Radicals-Mediated Halogen Atom Transfer.

Light-mediated Halogen-Atom Transfer (XAT) has become a significant methodology in contemporary synthesis. Unlike α-aminoalkyl and silyl radicals, ligated boryl radicals (LBRs) have not been extensively explored as halogen atom abstractors. In this study, we introduce NHC-ligated boranes as optimal radical chain carriers for the intermolecular reductive radical hydroalkylation and hydroarylation of electron-deficient olefins by using direct UV-A light irradiation. DFT analysis allowed us to rationalize the critical role of the NHC ligand in facilitating efficient chain propagation.

UiO-66-NDC (1,4-naphthalenedicarboxylic acid): A versatile metal-organic framework-based catalyst for photocatalytic degradation of dye chemicals

Metal-organic frameworks (MOFs) have received significant attention for their use as photocatalysts and photocatalyst supports. These materials have several benefits, including stability, catalyst reusability, tunability, and the capacity for post-reaction separation. Here, the potential applications of UiO-66-NDC as a photocatalyst for the degradation of reactive orange 16 (RO16), methyl orange (MO), and rhodamine B (RhB) were investigated. UiO-66-NDC was chosen for photocatalytic dye degradation due to its large surface area, adjustable characteristics, stability, effective light absorption, capacity for charge separation, and adaptability in design. UiO-66-NDC was synthesized the solvothermal process and its solid-state structure was characterized by solid-state methods, including UV-DRS, FTIR, zeta potential, PXRD and SEM measurements. The photocatalytic studies were performed by subjecting dye solutions with certain concentrations to UVA light irradiation in the presence of UiO-66-NDC. UV–Vis. spectroscopy was used to monitor the degradation process, which made it possible to calculate the degradation rate constants and the percentage of dye removal. The removal efficiency of adsorption, which was also examined, was at a minimum (17 % for RO16, 48 % for MO, and 25 % for RhB). The degradation of the dyes by UiO-66-NDC showed excellent photocatalytic activity, with degradation rates for RO16, MO, and RhB of 91 %, 93 %, and 81 %, respectively (300 mg/L catalyt; 20 ppm dye conc.). It was determined that the optimal concentration of catalyst was 300 mg/L. The reusability of UiO-66-NDC was successfully demonstrated through five successive cycles. The •OH radical was identified as the active species in photocatalysis. It was possible to remove 97 % of RO16, 99 % of MO, and 95 % of RhB at a high starting dye concentration (15 mg/L).

Spatial targeted delivery of riboflavin with a controlled corneal iontophoresis delivery system in theranostic-guided UV-A light photo-therapy.

Seven human donor eye globes underwent corneal cross-linking using theranostic UV-A device with accessory corneal iontophoresis system for patterned delivery of a 0.22% riboflavin solution. Theranostic-guided UV-A light illumination assessed riboflavin distribution and treated corneas at 10 mW/cm2 for 9 min with a 5.0-mm beam size. Corneal topography maps were taken at baseline and 2-h post-treatment. Analysis utilized corneal topography elevation data, with results showing controlled riboflavin delivery led to a consistent gradient, with 40% higher levels centrally (248 ± 79 μg/cm3) than peripherally (180 ± 72 μg/cm3 at ±2.5 mm from the center). Theranostic-guided UV-A light irradiation resulted in significant changes in corneal topography, with a decrease in best-fit sphere value (-0.7 ± 0.2 D; p < 0.001) and consistent downward shift in corneal elevation map (-11.7 ± 3.7 μm). The coefficient of variation was 2.5%, indicating high procedure performance in achieving significant and reliable corneal flattening.

SiO2/WO3/ZnO based self-cleaning coatings for solar cells

The accumulation of pollution and any kinds of contamination on the glass cover of the solar cell affects the efficiency of the photovoltaic (PV) systems. The contamination on the glass cover can absorb and reflect a certain part of the sunlight irradiation, which can decrease the intensity of the light coming in through the glass cover. With the study, it was planned to develop self-cleaning coatings for the PV systems. It was aimed to prevent or reduce the contamination-induced efficiency loss of the existing PV systems. In the scope of the project, SiO2/WO3 and SiO2/WO3/ZnO composites were coated from their solutions on the glass substrates using a dip-coating technique. WO3 was selected as a photocatalyst semiconductor. Under the UV light irradiation, WO3 could absorb the photons of the UV light, generating the photoinduced charge carriers. The photoexcited charge carriers provide both the photoinduced hydrophilicity on the surface of the coating and the photocatalytic degradation of the organic contaminants accumulated on the surface of the coating, which allows water droplets to spread and flow on the surface of the cover glass to remove the contaminations. However, the recombination rate of the photoexcited charge carriers on the WO3 film was high. In order to suppress the recombination of the photoinduced charge carriers, WO3 was coupled with SiO2 and ZnO. Both of these semiconductors improved the photocatalytic activity of the WO3 film. Although SiO2 has superior features in terms of the light transmission, it was not very effective under UV light as a photocatalyst alone. The widely preferred photocatalyst ZnO was added into the composite film structure to enhance the photocatalytic activity. The self-cleaning mechanism of the film coatings on a solar cell was investigated through the photocatalytic dye removal efficiency on the as-prepared film samples. There was a slight decrease in the light transparency and the solar cell efficiency because of the WO3 content of the composite film. On the other hand, coupling the SiO2/WO3 film with ZnO enhanced the photocatalytic activity, and it suppressed the reduction effect of the WO3 phase on both the light transparency and the solar cell efficiency. The photocatalytic dye removal efficiency was increased to over 90% after 240 min of UVA light irradiation. In addition, the solar cell coated with the SiO2/WO3/ZnO film provided almost the same solar cell efficiency as the uncoated solar cell. The water contact angle measurement also exhibited the photocatalytic degradation of the model contamination on the glass cover of the solar cell under the UVA light irradiation.Graphical

Photocatalytic degradation of ciprofloxacin by using tannin-doped BaTiO3 catalyst

The aim of this study is to highlight the significance of ciprofloxacin degradation, a commonly used antibiotic in healthcare and agriculture, by synthesizing tannin-doped BaTiO3 (T-Ba) photocatalysts at various tannin amounts (0–50 wt%) and investigating their photocatalytic activity under both UV-A light and visible light irradiation. The impact of several parameters, including the initial concentration of ciprofloxacin, photocatalyst dosage, initial solution pH, and scavengers effect, on the photocatalytic activity was explored. The photocatalysts were characterized by FTIR, SEM, XRD, XPS, TEM, BET, PL and UV-DRS analysis. In the conducted studies, it was observed that the highest efficiency was achieved at 96 % under appropriate parameters. The kinetic study was conducted based on the Langmuir-Hinshelwood equations. According to stability tests, ciprofloxacin degradation was found as 92 % after the second cycle, while it was 50 % after the fifth cycle.

Uncovering the potential of yttrium doped zinc oxide nanoparticles as an efficient catalyst for photodegradation of recalcitrant pollutant and a contributor antibacterial property

This work focused on the development of photocatalytic and antibacterial ZnO doped nanoparticles for wastewater treatment application. ZnO nanoparticle was successfully doped via a sol-gel method with different concentration of yttrium (Y), a rare-earth element. The improved properties of the structural, optical, photocatalytic and antibacterial after the nanoparticles doping modification were analyzed. XRD analysis confirmed the hexagonal (wurtzite) structure with average crystalline size between 10 and 22.7 nm. The exhibited XRD peaks that shifted towards lower angles after doping confirmed the Y3+ substitution in the ZnO structures. High-resolution transmission electron microscopy (HRTEM) showed an increase in grain size as the concentration of Y3+ ions inside the ZnO matrix increased. Ultraviolet-visible-near-infrared spectroscopic measurement revealed a red shift of the bandgap energy of 0.128 eV, which confirmed the substitution process. It was observed that the Y-dopant significantly improved the photocatalytic activity of the ZnO nanoparticles; 91.8 %, 72.9 %, 29.2 % and 85.0 % of 20 ppm of humic acid, 20 ppm of BPA, 20 ppm of phenol and 20 ppm of caffeine respectively under UVA light irradiation. In addition, Y-doped ZnO nanoparticle was found to be highly effective against S. aureus as compared to E. coli. The 9 wt% Y-doped ZnO (9YZnO) nanoparticles have shown no bacterial growth at both minimum inhibitory concentration/minimum bacterial concentration MIC/MBC concentration which served as evidence of the improved antibacterial properties of the modified ZnO nanoparticles. Overall, in this study Y-doped ZnO nanoparticle had shown good performance as photocatalysis material in degrading organic compounds (natural, industrial and consumable organic compounds) and antibacterial material against germ positive microorganism. Considering the developed nanoparticle's performance, its application could be an efficient alternative for water and wastewater treatment applications.

Engineered protein-iron and/or gold-protein-iron nanocomposites in aqueous solutions upon UVA light: Photo-induced electron transfer possibilities and limitations

Occurrence/suppression of photo-induced electron transfer (PI-ET) process in solutions of nanocomposites represents a very hot topic in several photo-related research domains. In this work, this phenomenon is investigated in aqueous solutions using iron-containing mono-/bi-metallic nanocomposites that have been engineered through protein-templated syntheses, with the aim to potentially create new biocompatible imaging contrast agents for medical diagnostics. Two types of iron-containing nanocomposites, mono-metallic (protein-Fe) and bi-metallic (Au-protein-Fe), have been synthesized and characterized with the aid of several experimental techniques, such as high-resolution transmission electron microscopy (HR-TEM), steady-state fluorescence, electron paramagnetic resonance (EPR) and light-induced EPR (LEPR). Theoretical model of the N-terminal region of the bovine serum albumin protein interacting with Fe cations and simulations of the EPR spectral features upon UVA light irradiation complemented the material’s analysis. Two iron forms within the mono-/bi-metallic nanocomposites have been detected experimentally: (i)complexed iron cations (giving EPR signal at g = 4.29) and (ii)superparamagnetic iron oxide nanoparticles (SPIONs; expressing EPR resonances at g// = 2.21 and g⊥ = 2.09). Upon UVA-light irradiation (325 nm), PI-ET between the two iron forms have been observed in the protein-Fe nanocomposite; however, this electronic communication is suppressed in the Au-protein-Fe system. The presence of luminescent Au nanoclusters and dissimilar sizes of SPIONs in bi-metallic nanocomposites (around 5 nm vs. approx. 2 nm in the monometallic protein-Fe system) represent the two possible reasons underneath suppression of the PI-ET process in the former. Moreover, OH radicals were detected in aqueous solutions in both iron-containing nanocomposites (Fe and Au/Fe systems) when irradiated at 325 nm for 5 min at r.t. The reported evidence of PI-ET in iron-containing nanocomposite aqueous solutions can thus have a large impact on their potential medical and/or environmental applications.

Ultrasonically functionalized chitosan-gallic acid films inactivate Staphylococcus aureus through envelope-disruption under UVA light exposure

The significant threat of foodborne pathogens contamination has continuously promoted the development of efficient antimicrobial food packaging materials. Here, an antimicrobial film was prepared with gallic acid-grafted-chitosan (CS/GA) that obtained by a two-step ultrasound method. The resultant films exhibited good transparency, improved UV barrier performance, and enhanced mechanical strength. Specifically, with the grafting of 1.2 % GA, the UV blocking ability of CS/GA film at 400 nm was significantly increased by 19.7 % and the tensile strength was nearly two times higher than that of CS film. Moreover, the CS/GA films exhibited an inspiring photoactivated bactericidal ability under 400 nm UVA light irradiation that eradicated almost 99.9 % of Staphylococcus aureus (S. aureus) cells within 60 min. To gain more insights into the antibacterial mechanism, the treated S. aureus cells were further investigated by visualizing bacterial ultrastructure and analyzing membrane properties. The results pointed to the peptidoglycan layer as the primary action target when bacteria come into contact with CS/GA films. Afterward, the intracellular oxidative lesions, disrupted bacterial integrity, and disordered membrane functional properties collectively resulted in eventual cell death. The findings revealed the unique peptidoglycan targeting and membrane disruptive mechanisms of CS/GA films, confirming the application values in controlling foodborne pathogens.

Magnetically Recyclable Nanoscale Zero-Valent Iron-Mediated PhotoRDRP in Ionic Liquid toward Smart, Functional Polymers.

A facile method based on recyclable nanoscale zero-valent iron (nZVI)-mediated photoinduced reversible deactivation radical polymerization in ionic liquid (IL) leads to the synthesis of narrow disperse poly(tert-butyl methacrylate) (PTBMA), amphiphilic PTBMA-block-poly(poly(ethylene glycol)methacrylate) diblock copolymer and double hydrophilic poly(methacrylic acid)-block-poly(poly(ethylene glycol)methacrylate) (PMAA-b-PPEGMA) diblock copolymers thereof. Stimuli response of the synthesized PMAA-b-PPEGMA diblock copolymer against variation in pH and temperature is assessed. Recyclability of the nZVI (catalyst) and IL (solvent) is established. Polymerization may be switched ON or OFF, simply by turning the UVA light irradiation ON or OFF, offering temporal control. The diblock copolymer self-aggregates into spherical nanoaggregates which are employed for encapsulation of coumarin 102 (C102, a typical hydrophobic dye), describing their potential application in drug delivery applications. The facile synthesis strategy may open up new avenues for the preparation of intelligent functional polymers for engineering and biomedical applications.

High-Fluence Accelerated PACK-CXL for Bacterial Keratitis Using Riboflavin/UV-A or Rose Bengal/Green in the Ex Vivo Porcine Cornea.

To investigate and compare the efficacy of high-fluence accelerated photoactivated chromophore for keratitis-corneal cross-linking (PACK-CXL) using either riboflavin/ultraviolet (UV)-A light or rose bengal/green light to treat Staphylococcus aureus or Pseudomonas aeruginosa infections in an ex vivo porcine cornea model. One hundred and seventeen ex vivo porcine corneas were injected with clinical isolates of S. aureus or P. aeruginosa, divided into eight groups, and cultured for24 hours. Then, either riboflavin with UV-A light irradiation (30 mW/cm2; 8 minutes, 20seconds; 15 J/cm2) or rose bengal with green light irradiation (15 mW/cm2, 16minutes, 40 seconds; 15 J/cm2) was applied; unirradiated infected groups served as controls. All corneas were incubated for another 24 hours. Next, corneal buttons were obtained and vortexed to release the bacterial cells. The irradiated and unirradiated solutions were then plated and incubated on agar plates. The amount of colony-forming units was quantified and the bacterial killing ratios (BKRs) resulting from different PACK-CXL protocols relative to non-treated controls were calculated. Riboflavin/UV-A light PACK-CXL resulted in median BKRs of 52.8% and 45.8% in S. aureus and P. aeruginosa, respectively, whereas rose bengal/green light PACK-CXL resulted in significantly greater BKRs of 76.7% and 81.0%, respectively (both P < 0.01). Both accelerated PACK-CXL protocols significantly decreased S. aureus and P. aeruginosa bacterial loads. Comparing the riboflavin/UV-A light and rose bengal/green light PACK-CXL approaches in the same experimental setup may help develop strain-specific and depth-dependent PACK-CXL approaches that could be used alongside the current standard of care. Our study used an animal model to gain insight into the efficacy of high-fluence accelerated PACK-CXL using either riboflavin/UV-A light or rose bengal/green light to treat Staphylococcus aureus or Pseudomonas aeruginosa infections.

Hetero-Structured Palladium-Coated Zinc Oxide Photocatalysts for Sustainable Water Treatment

Hetero-structured catalysts have recently attracted considerable interest from researchers in various fields, including electronics, sensing, energy, and photocatalysis. Treated water contains many harmful microorganisms and organic contaminants, which can be effectively removed through an advanced photocatalytic oxidation process. Photocatalysts with wide band gaps, such as semiconductor oxides like titanium dioxide (TiO2) and zinc oxide (ZnO), are typically utilized to decompose these organic pollutants. These generate a charge when exposed to UV-A light irradiation and produce oxidation radicals that cause the decomposition of the organic matter present in water. Metals such as Pd, Ag, Au, Cu, and Ni are being studied as photocatalysts. Semiconducting oxides and metals with appropriate band gaps and Fermi levels can effectively capture the charge generated by the oxide owing to the Moss–Burstein effect. These reactions can enhance the photocatalytic effect by hindering the recombination of the generated holes and electrons, thereby increasing the probability of charge survival.In this study, the performance of zinc oxide nanowires (ZnO NWs) decorated with Pd nanoparticles was evaluated as photocatalysts for sustainable water treatment. To maximize the number of active sites on the surface of the ZnO nanowires, Pd nanoparticles were uniformly deposited via atomic layer deposition (ALD). In ALD, a very thin film that can be deposited in one cycle is created with less than one atomic layer owing to the precursor oxidation reaction. Additionally, the ALD process provides all the surfaces with sufficient time and chemical sources to react, resulting in a uniform amount of deposited material. This unique technology is suitable for the large-area deposition of atomic-level thickness surface materials. Therefore, ALD was used to deposit Pd onto the catalyst surface. The ZnO nanowires were initially fabricated in the form of seeds by ALD and grown via a hydrothermal method. Subsequently, ALD Pd nanoparticles with an average particle size of 3.75 nm were deposited on the enlarged ZnO nanowires. The prepared hetero-structured ALD Pd-deposited ZnO nanowires were analyzed using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and valence band X-ray photoelectron spectroscopy. A new Fermi level of the Pd-ZnO hetero-structure was formed, which was lower than the conduction band energy level of ZnO. The new Fermi level suppresses the recombination of the conduction band and valence band electron holes under UV-A irradiation. The enhanced charge separation enhances the photocatalytic activity. In addition, compared to ZnO NWs, ALD Pd-deposited ZnO NWs produced higher amounts of reactive oxygen species and improved the decomposition rate of organic pollutants in water. To evaluate the performance of the prepared photocatalyst, the decomposition rates of 4-chlorophenol (4-CP), 4-chlorobenzoic acid, and furfuryl alcohol were measured. Regarding the decomposition rate of 4-CP, the photocatalytic performance increased significantly from 42.5 % to 62.8 % when the ZnO nanowires were decorated with Pd nanoparticles. Figure 1

Boosting Tetracycline Degradation with an S-Scheme Heterojunction of N-Doped Carbon Quantum Dots-Decorated TiO2.

N-doped carbon quantum dots (N-CQDs) derived from the Rumex crispus L. plant were incorporated into TiO2 via a facile hydrothermal method. As-prepared materials were characterized and used in the photocatalytic tetracycline (TC) degradation under UVA light irradiation by examining several operational parameters involving the N-CQDs amount, initial TC concentration, pH, and photocatalytic reaction time. XRD analysis revealed the conversion of the rutile phase to the anatase phase after the incorporation of N-CQDs into the TiO2 structure. The results revealed that the N-CQDs/TiO2 photocatalysts demonstrated the highest efficiency in TC degradation compared to other processes of adsorption, photolysis (UVA), and photocatalysis with TiO2 (TiO2/UVA). Under optimized conditions, 10 mg/L TC at pH 5.15 with 0.2 g/L N-CQDs/TiO2 catalyst showed 97.7% photocatalytic degradation for 120 min under UVA irradiation. The formation of an S-scheme heterojunction between N-CQDs and TiO2 provided enhanced charge separation and strong redox capability, causing significant improvement in the photocatalytic performance of N-CQDs/TiO2. Trapping experiments showed that O2•- and h+ are the predominant reactive species for the TC elimination in an aqueous solution.

Photocatalytic degradation of ethylene in tubular microreactor coated with thin-film of TiO2: Mathematical modeling with experimental validation and geometry analysis using computational fluid dynamics simulations

The study aimed to establish a comprehensive understanding of the photocatalytic process and optimize the reactor design for efficient ethylene regulation to improve the shelf-life of fruits and vegetables. For this, it was performed 2D computational fluid dynamics modeling at two different reactor geometry (conventional cylindric reactor and annular cylindric reactor) using the conservation equations combined with Langmuir-Hinshelwood mechanism. A continuous single-phase multicomponent fluid flow with the reactor surface supported with a thin-film catalyst under UV-A light irradiation was simulated for initial ethylene concentration at 0.479–4.234 × 10−3 molC2H4 m−3 and inlet axial velocity at 0.0085–0.1019 m s−1. In the 2D CFD results, it was observed that the difference in ethylene concentration between the microreactor bulk and surface is only significant for high initial concentrations and axial velocities. Furthermore, it was found that the parabolic conversion profile remains unchanged for lengths greater than 10% of the reactor length across all geometries studied. The variation in reactor diameters resulted in a substantial reduction in ethylene conversion; however, the incorporation of an annular cylinder coated with a catalyst led to an enhancement in conversion rates, with improvements of approximately 28%, 17%, and 6% observed for diameters of 5 mm, 10 mm, and 20 mm, respectively. This reduction in improvement as diameter increase can be attributed to the laminar flow dynamics that impede the diffusion of ethylene molecules from the bulk to the catalytic surface. Consequently, the simulated data highlight the potential of employing a catalyst-doped annular cylinder as a promising strategy to increase ethylene conversion and extend the shelf life of fruits. However, it should be noted that the addition of an annular cylinder, while enhancing conversion, also introduces operational complexities and cost implications due to the significant increase in pressure drop associated with lower diameters.

Improving the Photo Electro Catalytic Degradation of Methylene Blue by Modified TiO2/ITO Photo Anodes

TiO2 photoanodes have gained significant attention for the removal of organic pollutants through photoelectrocatalytic processes, with the aim of developing a cost-effective and efficient method for improving the degradation of pollutants in surface water. This study investigated the effects of adding titanium nanooxide (Degussa P25) containing 70% anatase and 30% rutile phases on the properties of nanostructured TiO2 photoanodes prepared on glass substrates (indium tin oxide (ITO)) using sol–gel/dip coating techniques The results obtained from ultraviolet–visible transmittance spectroscopy, electrochemical (EC) impedance spectroscopy, photocurrent, and atomic force microscopy analyses revealed that the addition of Degussa P25 improved the electrical conductivity of the TiO2/ITO anode and reduced the optical bandgap from 3.50 to 3.35 eV, while the size of the titanium oxide particles decreased to about 75 nm. The EC impedance spectra measurement confirms that the addition of titanium nanooxide Degussa P25 improved the electrical conductivity for TiO2/ITO anode. The photoelectrocatalysis (PEC) performance of the TiO2 photoanodes was investigated via the degradation of methylene blue (MB) under UVA light irradiation. The AB photoanode (with the addition of Degussa P25) exhibited excellent PEC performance, with 95.9% color removal efficiency and 63% total organic carbon (TOC) removal efficiency, compared to 92% color removal efficiency and 56% TOC removal efficiency for the A photoanode (without the addition of Degussa P25). The kinetic constants (k) were 134 × 10−4, 110 × 10−4 (min−1) for A and AB anodes, respectively, and the degradation of MB followed first-order kinetics for all anodes. The A and AB anodes were compared as electrodes for the degradation of MB using PEC, photocatalysis (PC), and EC technologies. Subsequently, The A and AB anodes were utilized as electrodes to compare the performance of PEC, PC, and EC technologies for the degradation of MB. The results showed that the AB anode exhibited higher efficiency in all PC technologies, with color removal (%) efficiencies of 95.9% (PEC), 33% (PC), and 21% (EC) compared to 92% (PEC), 28% (PC), and 19% (EC) for the A anode. Additionally, the photooxidation process had a 2.1% effect on the degradation of the initial MB concentration.

A comparison of endosulfan removal by photocatalysis process under UV-A and visible light irradiation: optimization, degradation byproducts and reuse.

The online version contains supplementary material available at 10.1007/s40201-023-00864-z.

Predicting corneal cross-linking treatment efficacy with real-time assessment of corneal riboflavin concentration.

To assess predictability of tissue biomechanical stiffening induced by UV-A light-mediated real-time assessment of riboflavin concentration during corneal crosslinking (CXL) of human donor tissues. Studio Italiano di Oftalmologia, Rome, Italy. Laboratory study. 20 sclerocorneal tissues were randomly stratified to undergo CXL with either the epithelium intact (n = 12) or removed (n = 8). Samples underwent corneal soaking with 0.22% riboflavin formulation (RitSight) with dosing time of t = 10 minutes and t = 20 minutes in epithelium-off and epithelium-on protocols, respectively. All tissues underwent 9-minute UV-A irradiance at 10 mW/cm 2 using theranostic device (C4V CHROMO4VIS). The device used controlled UV-A light irradiation to induce both imaging and treatment of the cornea, providing a real-time measure of corneal riboflavin concentration and treatment efficacy (ie, theranostic score) during surgery. Tissue biomechanics were assessed with an air-puff device (Corvis), which was performed before and after treatment. A 3-element viscoelastic model was developed to fit the corneal deformation response to air-puff excitation and to calculate the mean corneal stiffness parameter (k c ). Significant corneal tissue stiffening ( P < .05) was induced by the theranostic UV-A device in either CXL treatment protocol. Significant correlation was found between the theranostic score and the increase in k c ( R = 0.75; P = .003). The score showed high accuracy (94%) and precision (94%) to predict correctly samples that had improved tissue biomechanical strengthening. Real-time assessment of corneal riboflavin concentration provided a predictive and precise approach for significant improvement of tissue strength on individual corneas, regardless of CXL treatment protocol.

Photocatalytic degradation of organic micropollutants under UV-A and visible light irradiation by exfoliated g-C3N4 catalysts

In the present study, the photocatalytic performance of exfoliated graphitic carbon nitride (g-C3N4) catalysts, with enhanced properties and response in UV and visible light irradiation, was evaluated for the removal of selected contaminants i.e., diuron, bisphenol A and ethyl paraben. Commercial TiO2 Degussa P25 was also used as a reference photocatalyst. The g-C3N4 catalysts demonstrated good photocatalytic activity which in some cases is comparable to TiO2 Degussa P25 leading to high removal percentages of the studied micropollutants under UV-A light irradiation. In contrast to TiO2 Degussa P25, g-C3N4 catalysts were also able to degrade the studied micropollutants under visible light irradiation. For all the studied g-C3N4 catalysts under both UV-A and visible light irradiation, the overall degradation rate decreases in the order of bisphenol A > diuron > ethyl paraben. Among the studied g-C3N4, the chemically exfoliated catalyst (g-C3N4-CHEM) showed superior photocatalytic activity under UV-A light irradiation due to its enhanced characteristics, such as pore volume and specific surface area and ~ 82.0 % in 6 min, ~75.7 % in 15 min and ~ 96.3 % in 40 min removals were achieved for BPA, DIU and EP, respectively. Under visible light irradiation, the thermally exfoliated catalyst (g-C3N4-THERM) demonstrated the best photocatalytic performance and the degradation ranged from ~29.5 to 59.4 % after 120 min. EPR data revealed that the three g-C3N4 semiconductors generate mainly O2•−, whereas TiO2 Degussa P25 generates both HO• and O2•−, the latter only under UV-A light irradiation. Nevertheless, the indirect formation of HO• in the case of g-C3N4 should also be considered. Hydroxylation, oxidation, dealkylation, dechlorination and ring opening were the main degradation pathways. The process proceeded without significant alterations in toxicity levels. Based on the results, heterogeneous photocatalysis using g-C3N4 catalysts is a promising method for the removal of organic micropollutants without the formation of harmful transformation products.

ZnO Nanorods Grown on Flexible Polyurethane Foam Surfaces for Photocatalytic Azo Dye Treatment

A flexible photocatalyst hybrid structure made up of aligned ZnO nanorods and three-dimensional networks of polyurethane (PU) foam struts was fabricated. The surfaces of the PU struts were first functionalized by the two-step chemical solution treatment method. The functional groups of the PU foam and the nanohybrid structure were characterized using Fourier transmission infrared spectroscopy (FTIR). Their crystal structures and morphologies were examined by using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The adequacy of the chemical surface modification process was examined by analyzing the differences in the −N ═ C ═ O and O–H regions of the FTIR spectrum. The hybrid photocatalyst samples were also tested in terms of their structural integrities under ultrasonic irradiation. It was observed that the ZnO layers remained intact and adherent on the surfaces even after 1 h of sonication. The optical properties of the samples were also characterized by ultraviolet–visible (UV–vis) and photoluminescence (PL) spectroscopies. Aqueous Acid Red 88 (AR88) azo dye solutions were prepared and used to assess both the color and the total organic carbon (TOC) removal efficiencies of the samples utilizing the laboratory-scale photoreactor. The maximum color removal of 97% was reached in 180 min under UVA light irradiation as a consequence of simultaneous adsorption and photocatalysis mechanisms.