UV Irradiation Period Research Articles

UV-Radiation and TiO2 Nanoparticles Effects on Physical Properties of PVA/CMC/TiO2 Nanocomposite Films

Fabrication of nanocomposite films of polyvinyl alcohol/carboxymethyl cellulose (PVA/CMC) blended with Titanium dioxide nanoparticles (TiO2 NPs) by a modest solution casting technique is investigated. Also, TiO2 NPs and UV-irradiation effects for different intervals (12, 26, 40, and 48 hours) on the morphology (FESEM), structure (XRD), composition (FTIR) and optical properties (UV-Vis) of as-prepared films are inspected. FESEM images display that the morphology of PVA/CMC/TiO2 nanocomposite films is altered due to the strong influence of TiO2 NPs and UV exposure. The XRD spectra indicate that the amorphous phase of the samples has changed (decline or enhancement) due to UV exposure. The FTIR spectra demonstrate that the UV-irradiation period had a favourable impact on polymer structure by exhibiting some interesting IR peaks. Furthermore, the UV-Vis examination illustrates that the increased UV-irradiation times (12 h to 40 h) and TiO2 NPs addition improved the absorption intensity of the as-prepared films. Interestingly, the Energy gap Eg of the nanocomposite films was tuned from 4.47 eV to 5.01 eV with increased irradiation time (12 h to 40 h). In contrast, due to a higher increased UV-irradiation time of 48 h, the Energy gap Eg value of nanocomposite film was decreased to 4.62 eV. That can be attributed to the strong effect of UV exposure, which influenced the creation of structural defects. Finally, these findings prove that the PVA/CMC/TiO2 nanocomposite films have an amazing chance to be used in important optoelectronic applications.

Inglet oxygen generaion via silver nanoparticles UV-photoexcitation

The NIR-luminescence of suspension of silver nanoparticles stabilized in distilled water has been investigated by photoexcitation of surface plasmon resonance (SPR). The observed short-living luminescence with the spectral maximum at 1300 nm is attributed to the singlet oxugen molecules luminescence. The singlet oxygen generation is assumed to pass in two stages as a result of three-photon process. First the one-photon SPR excitation of silver nanoparticle is occurred and leads to superoxide oxygen generation on the nanoparticle surface. Next the superoxide anion absorbs two more photons of the same laser pulse resulting in electron photodetachment with singlet oxygen formation. During a long period of UV-irradiation the studying suspension ceases to be photostable and sedimentation occurs. The sedimentation may be related to disturbance of nanoparticles steric stability resulting in more efficient superoxide anion adsorption on nanoparticles surface with silver oxide formation.

Modified matrix of ZnO prismoid structures for improved photocatalytic activity: A theoretical and experimental insight

Currently, the world needs low-cost and high-performance photocatalysts to degrade the carcinogenic pollutant from water. In the present work, a modified ZnO matrix using Mg as a dopant has been reported with theoretical and experimental results to highlight its structure and functions on photocatalytic activity. A versatile chemical co-precipitation technique was employed to get the Mg-ZnO nanostructures. Structural characterization by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) studies show the formation of hexagonal wurtzite structures with no impurity phases. Optical studies confirm the formation of ZnO with intrinsic defects after modifying the matrix, which agrees with the band structure calculations computed using density functional theory (DFT). Mg-modified ZnO introduced intrinsic defects like vacancies and interstitials that have a great impact on applications like photocatalysis. Based on these supporting results we employed prepared samples for dye degradation, which performed well (80% degradation efficiency) in a short period of UV irradiation. This could be a promising technology for environmental remediation.

Photoswitchable and reusable superhydrophobic/hydrophilic TiO2-coated stainless-steel mesh as oil–water separator

This study fabricated a superhydrophobic/hydrophilic stainless-steel mesh with a TiO2-coated surface for efficient oil–water separation. The mesh manifested both hydrophobic and hydrophilic properties upon incorporating fluorine- and amine-containing silanes, respectively. The photoswitching speed and recovery of surface properties were evaluated by adjusting the UV irradiation period. Additionally, the mesh was subjected to ultrasonic treatment to enhance the photoswitching speed. After alternating UV irradiation and ultrasonification treatments, the variations in contact angle confirmed the feasibility of reversible surface conversion: 158° → 15° → 149.4° → 9.1° → 146.8° → 8.4° → 147.3°. Furthermore, the oil–water separation efficiency of the fluorine-modified mesh was assessed using water and n-hexane solutions. Over eight cycles, the hydrophobic/hydrophilic mesh achieved an average separation efficiency of 95.3% and 96.7%, respectively. The separation process occurred within approximately 5 s. Thus, this study proposed a comprehensive approach for developing a single superhydrophobic mesh capable of facile and rapid photoswitching between hydrophilic and hydrophobic properties. The developed mesh offers precise filtration, durability, and reusability, contributing to sustainable oil–water separation processes.

Long‐Lived Luminescence Emitted from Imide Compounds Dispersed in Polymer Matrices after Continuous Ultraviolet Irradiation and its Relation to Oxygen Quenching

AbstractLong‐lived room‐temperature delayed phosphorescence, called prolonged irradiation‐induced delayed luminescence (PIDL), was observed in air for three imide compounds (ICs) dispersed in polymethyl methacrylate under UV irradiation after an induction time of 1.60–6.78 min, whereas the ICs alone showed only fluorescence after a short period of UV irradiation. The PIDL emission continued as an afterglow for several seconds (0.36–1.30 s) after the irradiation was stopped. In the initial stage of irradiation, the ICs in the excited triplet state (T1) generated via intersystem crossing were immediately quenched by ground state triplet molecular oxygen (3O2), and the excited state energy of ICs was transferred by photosensitization to 3O2, generating singlet oxygen (1O2), causing a gradual depletion of the concentration of 3O2 in the host matrix. When most of the 3O2 adjacent to the ICs had been consumed, the ICs started to emit a PIDL. The induction time until the appearance of PIDL was linearly proportional to the 3O2 concentration. Optical measurements and numerical simulations based on the Jablonski diagram support the PIDL generation mechanism and reveal the relationships between the rate constants and oxygen permeabilities of the host matrices.

Synthesis of Acrylate‐Functionalized Polyglycerols and an Investigation of their UV Curing Behaviors

AbstractIn this study, hyperbranched polyglycerol (HPG) is synthesized via ring‐opening polymerization of a glycidol monomer. An epoxy group is introduced at the end of HPG through a reaction with epichlorohydrin in a one‐pot process. The number of epoxy groups introduced increase proportional to the amount of boron‐trifluoride‐tetrahydrofuran catalyst used. In addition, acrylate‐functionalized polyglycerol (AG) is synthesized via a reaction of the epoxy group with an acrylic acid, and a maximum of 5.7 acrylate groups are introduced per molecule. AG shows photocuring behavior with the photoinitiator Irgacure 819, while viscosity is adjusted from 18 to 2947 cPs by introducing up to 80 wt% 2‐hydroxyethyl acrylate (2‐HEA). Diluted resin can cure over 97 wt% even with a short UV irradiation period of 20 s. Furthermore, hydrophilicity increases proportional to the amount of 2‐HEA added, and water absorption can be controlled in the range of 30–124 wt%.

UV irradiation of PVA-3%M, (M=NiO, MgO, Al2O3) nanoparticles for medical applications

Polyvinyl Alcohol (PVA) of PVA-3%M, where M stands for NiO, MgO, and Al2O3, has been created. Characterization was done using X-ray diffraction (XRD). This characteristic verified the production of the generated oxide NPs during chemical precipitation in PVA. The PVA-3% M nanoparticles (M=NiO, MgO, and Al2O3) were examined for their optical characteristics. After 60 minutes, the PVA-3% M nanoparticles (M=NiO, MgO, and Al2O3) were subjected to UV light irradiation to examine its effects. The optical properties have been studied in UVA (315–400 nm) area, or long-wave UV, in energy of (3.9–3.1) eV. Time under UV light has an impact on the optical energy gap of PVA-3% M. As a function of the UV exposure time, the optical characteristics of PVA3% M nanoparticles (M=NiO, MgO, and Al2O3) were evaluated. Calculated optical constants for PVA-3% M (M=NiO, MgO, Al2O3) NPs as-prepared and after UV irradiation illustrate the impact of UV irradiation period. These data demonstrate that a highly forced for medical applications.

Efficient utilization of peach gum to prepare UV-responsive peelable pressure-sensitive adhesives for non-destructive fabrication of ultrathin electronics

Restricted by the poor solubility and complex structure, it remains a significant challenge to efficiently convert raw peach gum (RPG), a natural plant gum comprised of polysaccharides, into usable polymer materials. Herein, a novel approach is reported to prepare UV-responsive peelable pressure-sensitive adhesives (PSAs), which are mainly applied in the manufacturing of ultrathin electronics, through efficient utilization of RPG via prior dissolution using the N,N-dimethylacetamide/lithium chloride (DMAc/LiCl) solvent system and later degradation using H2O2 under UV light at room temperature. With sorbitol-based polyurethane acrylate (SPUA) as a UV-curable oligomer, rosin as a tackifier, and epoxidized soybean oil (ESO) as a plasticizer, before UV irradiation, the 180° peel strength of the prepared PSAs reached 244.4 N/m. A short period of UV irradiation caused a formed cross-linked network structure inside the PSA and a disruption of the adhesive interface, resulting in a sharp decrease of 180° peel strength to 7.3 N/m to achieve a non-destructive peeling of the adherend electronics from the carrier. This work provides a feasible strategy for efficiently utilizing natural peach gum to prepare bio-based UV-responsive peelable PSAs.

Photochemically Enhanced Emission by Introducing Rational Photoactive Subunits into an Aggregation-Induced Emission Luminogen.

Herein, we propose a rational design strategy by introducing photoactive thienyl and pyridyl groups into an AIE-active tetraarylethene skeleton to achieve highly efficient photochemistry-activated fluorescence enhancement from dominantly photo-physical aggregation-induced emission behavior, and prove that such photoactivated fluorescence enhancement is perfectly suited for superstable photocontrollable dual-mode patterning applications in both solution and solid matrix. It is found that the photoactivated fluorescence of designed AIEgen is attributed to the irreversible cyclized-dehydrogenation reaction under UV irradiation, and the oxidation product has a brighter fluorescence in both solution and solid states owning to its rigid and planar structure. The overall transformation rate of the AIEgen from its opened form to dehydrogenated form is up to nearly 100 % in a short period of UV irradiation, and the fast transformation and the stable product of this photochemical reaction guarantees super stability of photocontrolled patterning, which can be applied in photoactivated dual-mode patterning and advanced anti-counterfeiting.

Major target for UV-induced complete loss of HIV-1 infectivity: A model study of single-stranded RNA enveloped viruses

Deep ultraviolet light (UV) is useful for the disinfection of microorganisms, including bacteria and viruses. Although genome damage by UV has been widely accepted, the adverse effects of UV on the activity and/or function of viral proteins including the envelope components are poorly documented. Worthy of note, the observed unfavorable UV-effects for viruses are only insufficiently analyzed in association with the reduction in viral infectivity. In this study, we aimed to clarify which component of virions affected by UV significantly correlates with the loss of viral infectivity using HIV-1 as a model for single-stranded RNA enveloped viruses. Using our UV irradiation apparatus at three wavelengths (265, 280, and 300 nm), we first quantitatively determined the UV power density and irradiation period of each wavelength required for a reduction in infectivity. A heat-treated sample as a control drastically reduced the virion-associated reverse transcriptase (RT) activity and Gag-p24 level. The UV-irradiated samples at the three wavelengths, completely lacking viral infectivity, showed p24 levels similar to those without irradiation. While the virion-associated RT activity was gradually decreased in a wavelength and power density dependent manner, this reduction did not explain the loss of viral infectivity by UV. Remarkably, virological assays revealed that the entry efficiency of the UV-irradiated virus samples at the three wavelengths is comparable to those without irradiation. Importantly, this result shows that, even the virions exposed to UV of various wavelengths at the lethal level, still maintain the function of their envelope composed of a host lipid bilayer and viral proteins. In sharp contrast, UV-induced genome damage shown by semiquantitative RT-PCR correlated well with the reduction in viral infectivity, indicating that it is a major determinant for virus inactivation by UV. The degree of damage was found to be distinct among the regions analyzed. This was probably due to the different nucleotide sequences in those genomic regions amplified by PCR. Our data clearly demonstrate a principal mechanism for viral inactivation by UV and provide information contributing to the improvement of UV-based disinfection technology for microorganisms.

Photoprotective activity of zirconia nanoparticles

The increasing incidence of diseases caused by the harmful effects of UV radiation in skin, predominantly skin cancer, induce the search for more efficient photoprotector agents. Nowadays, titanium dioxide (TiO2) and zinc oxide (ZnO) are the most widely used photoprotectors and therefore form the main components of commercially available sunscreens. Although the outstanding efficiency in absorbing and scattering UV radiation, mainly as nanoparticles, recent studies have raised concerns regarding the safe use of these nanoparticles, especially due to their high generation of reactive oxygen species (ROS). Thereby, this work focus on the evaluation of the photoprotective activity of zirconia nanoparticles (ZrO2 NPs) and their cytotoxicity study in the presence and absence of UV irradiation. The ZrO2 NPs were synthesized by hydrothermal method and their hydrodynamic diameter, Zeta potential and colloidal stability were characterized by dynamic light scattering. The morphology and size were observed by transmission electron microscopy. The synthesis resulted in ZrO2 NPs with 50 nm of diameter and 56 nm of hydrodynamic diameter. The high colloidal stability was evidenced by the high value of Zeta potential (+48 mV) and low polydispersity index (0.09). The UV–vis spectrum of the ZrO2 NPs in aqueous suspension showed an intense light scattering below 250 and a wide absorption band at 285 nm. The poor generation of ROS by ZrO2 NPs was confirmed by the absence of photodegradation of methylene blue after long periods of irradiation. The in vitro assays performed with HaCaT cell line showed that the cell viability did not decrease in the absence of irradiation. However, after 24 h of incubation, the cell viability decreased under UV-irradiation in comparison with irradiated cells that were not incubated with ZrO2 NPs. Notably, in these assays, the cells were incubated with the ZrO2 NPs and after 24 h, they were replaced by fresh culture medium before the cell viability assay. Nevertheless, another in vitro assay was performed in order to evaluate the photoprotective activity of ZrO2 NPs. The cells were irradiated in the presence of ZrO2 NPs suspension. In this case, cell viability did not decrease even after long period of UV-irradiation and at higher concentration of ZrO2 NPs. The present results showed that ZrO2 NPs could be an interesting material to be used for skin photoprotection since they showed low cytotoxicity, absence of ROS generation and protection under UV irradiation. Additionally, the ZrO2 NPs suspension was transparent as usually required for applications in sunscreens.

Influences of merbau heartwood extracts and their metal complexes on wood photodegradation

Merbau (Intsia spp.) heartwood is a highly valued commercial wood but has problems with extractive bleeding when used as a construction material outdoors. The metal complexation method is one solution to resolve this problem. However, properties of merbau heartwood extracts would be modified and the anti-weathering ability changed. This study investigates the wood photo-protection ability of the merbau heartwood extract and its metal complexes. The results reveal that merbau heartwood extract has good free radical scavenging ability and UV absorptivity, which could inhibit wood photodegradation. After metal complexation, the extract-metal complexes also have wood photo-protection ability that inhibits wood photodegradation. Furthermore, since catecholic phenols were chelated by iron(II)/copper(II), the oxidative derivatives were consequently inhibited. Accordingly, these findings show that both merbau heartwood extract and its metal complexes have the ability to remove photo-induced hazards and enhance wood photostability for short periods of UV irradiation. Additionally, these results can be a reference for the environmentally benign utilization of merbau heartwood.

Analysis of Adsorption and Decomposition of Odour and Tar Components in Tobacco Smoke on Non-Woven Fabric-Supported Photocatalysts

The release of substantial amounts of toxicologically significant, irritant, and malodourous compounds during the complete combustion of tobacco can generate an unpleasant environment, especially indoors. Herein, we developed non-woven fabric-supported UV- and visible-light-responsive photocatalysts capable of adsorbing and decomposing the odour and tar components of tobacco smoke under irradiation with UV or visible light. The processes of odour component adsorption and subsequent decomposition under irradiation were evaluated in terms of colour changes in the catalytic system and by gas chromatography–mass spectrometry. By considering three different photocatalysts, namely TiO2, Fe(III)-grafted TiO2, and Cu(II)-grafted WO3, we assessed the magnitude of odour and tar component adsorption on the fabric fibres, as well as the decomposition of these species after specific visible light or UV irradiation periods. Considering the expansion of our technology for practical applications, the best results among the three tested materials were obtained for non-woven fabric-supported Fe/TiO2. We believe that our technology can be implemented in the design of interior decoration materials for creating a comfortable environment.

Multiple Anti‐Counterfeiting Guarantees from a Simple Tetraphenylethylene Derivative – High‐Contrasted and Multi‐State Mechanochromism and Photochromism

AbstractHerein the novel tetraphenylethylene (TPE) derivative 1 was designed with an integration of aggregation‐induced emission (AIE), multi‐state mechanochromism and self‐recovery photochromism. The molecule was susceptible to grinding, heating and vapor fuming and showed corresponding transition of its emission colors. The heated powder or single crystal of 1 exhibited reversible photochromism. After a short period of UV irradiation, it showed a bright red color, but recovered to its original white appearance within 1 min. The photochromism is due to the formation of photocyclization intermediates upon UV irradiation, while the eversible mechanochromism is attributed to the weak molecular interactions derived from head‐to‐tail stacking of the molecules. This reversible multi‐state, high‐contrasted and rapid responsive mechanochromic and photochromic property cooperatively provide double enhancement of a multimode guarantee in advanced anti‐counterfeiting.

Multiple Anti-Counterfeiting Guarantees from a Simple Tetraphenylethylene Derivative - High-Contrasted and Multi-State Mechanochromism and Photochromism.

Herein the novel tetraphenylethylene (TPE) derivative 1 was designed with an integration of aggregation-induced emission (AIE), multi-state mechanochromism and self-recovery photochromism. The molecule was susceptible to grinding, heating and vapor fuming and showed corresponding transition of its emission colors. The heated powder or single crystal of 1 exhibited reversible photochromism. After a short period of UV irradiation, it showed a bright red color, but recovered to its original white appearance within 1 min. The photochromism is due to the formation of photocyclization intermediates upon UV irradiation, while the eversible mechanochromism is attributed to the weak molecular interactions derived from head-to-tail stacking of the molecules. This reversible multi-state, high-contrasted and rapid responsive mechanochromic and photochromic property cooperatively provide double enhancement of a multimode guarantee in advanced anti-counterfeiting.

Accurate, sensitive, and precise determination of cobalt in soil matrices by the combination of batch type gas-liquid separator-assisted photochemical vapor generation and atomic absorption spectrophotometry.

Determination of cobalt at low concentrations is an important issue because of its potential harmful effects on human health. Although flame atomic absorbance spectrometry (FAAS) is a fast and cheap method, it has high detection limits compared to other methods due to low nebulizer efficiency. In this study, the sensitivity, accuracy, and precision of the conventional FAAS were tried to be improved for cobalt determination using a photochemical vapor generation (PVG) system equipped with a batch type gas-liquid separator (BTGLS). The system parameters including organic acid type and concentration, UV irradiation period, mixing type, atomizer temperature, carrier gas flow rate, and sample volume were optimized to improve the detection power. The limits of detection and quantification were found to be 8.7 and 28.9μgL-1, respectively. The low relative standard deviation results indicated high precision. Applicability and accuracy of the method to soil samples was determined by recovery studies and percent recoveries were obtained between 98.9-107.0%. Graphical abstract Please provide caption for the graphical abstract.PVG-BT-GLS-AAS system .

Degradation of acetaminophen in aqueous solution by UV and UV-activated sludge processes.

Acetaminophen (N-acetyl-p-aminophenol, APAP) is one of the most common antipyretic analgesics used to treat common ailments throughout the world. Recently, APAP has been frequently detected in wastewater effluent and groundwater, resulting in potential risks to the environment. Current methods for eliminating APAP are complicated and cost-prohibitive. This study examined APAP degradation by ultraviolet-C (UV-C) and UV-C irradiation combined with activated sludge (UV/AS) to evaluate potential applications in wastewater treatment. The results of this study indicate that UV-C irradiation reached an APAP degradation efficiency of more than 52% and a degradation rate of 0.0012-0.0013 min-1 during 720 min of exposure, while the initial APAP concentration exhibited only a nominal effect on the degradation rate. However, the UV/AS treatment demonstrated an APAP degradation rate that was 9.6 times the rate of the UV-C-only treatment, with a degradation efficiency of 99% over the same UV irradiation period. The results further indicated that APAP photolysis efficiency was more effective when applied to sterilized AS than when applied to unsterilized AS. Finally, excessive dosage of both AS and humic acid inhibited APAP photolysis efficiency.

Mycosporine-like amino acids (MAAs)—producing Microcystis in Lake Erie: Development of a qPCR assay and insight into its ecology

Mycosporine-like amino acids (MAAs) are UV-absorbing metabolites found in cyanobacteria. While their protective role from UV in Microcystis has been studied in a laboratory setting, a full understanding of the ecology of MAA-producing versus non-MAA-producing Microcystis in natural environments is lacking. This study presents a new tool for quantifying MAA-producing Microcystis and applies it to obtain insight into the dynamics of MAA-producing and non-MAA-producing Microcystis in Lake Erie. This study first developed a sensitive, specific TaqMan real-time PCR assay that targets MAA synthetase gene C (mysC) of Microcystis (quantitative range: 1.7 × 101 to 1.7 × 107 copies/assay). Using this assay, Microcystis was quantified with a MAA-producing genotype (mysC+) in water samples (n = 96) collected during March-November 2013 from 21 Lake Erie sites (undetectable − 8.4 × 106 copies/ml). The mysC+ genotype comprised 0.3–37.8% of the Microcystis population in Lake Erie during the study period. The proportion of the mysC+ genotype during high solar UV irradiation periods (mean = 18.8%) was significantly higher than that during lower UV periods (mean = 9.7%). Among the MAAs, shinorine (major) and porphyra (minor) were detected with HPLC-PDA-MS/MS from the Microcystis isolates and water samples. However, no significant difference in the MAA concentrations existed between higher and lower solar UV periods when the MAA concentrations were normalized with Microcystis mysC abundance. Collectively, this study’s findings suggest that the MAA-producing Microcystis are present in Lake Erie, and they may be ecologically advantageous under high UV conditions, but not to the point that they exclusively predominate over the non-MAA-producers.

Polymerization-Induced Phase Separation Formation of Structured Hydrogel Particles via Microfluidics for Scar Therapeutics

Excessive scar formation can form disabling contractures that result in a debilitating psychological outcome. Sustainable hydrophobic corticosteroid release in vivo is essential to regulate the wound healing process. Functional hydrogel particles are widely applied for sustainable release. However, due to the limited aqueous solubility of hydrophobic compounds, most of the corticosteroid is released from the hydrogels within seconds, causing undesirable scar formation and recurrence. In this study, a novel polymerization-induced phase separation is investigated to form well-defined polyethylene glycol diacrylate (PEGDA) core/alginate shell structured hydrogel particles using microfluidics without toxic organic solvents. Based on their wettability preference, hydrophobic corticosteroid-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles are compartmentalized in the PEGDA core during polymerization to control the corticosteroid release. The distribution of the PLGA nanoparticles is precisely regulated by the phase separation boundary and characterized using a fluorescent dye. The thickness of the shell and partition coefficients are determined using the UV intensity and irradiation period. Upon encapsulation of the PLGA nanoparticles within the poly(PEGDA) core, a long-term corticosteroid treatment is developed and effective scar therapeutic outcomes are evaluated using both in vitro and in vivo models.

New allyl-functional catalytic comonomers for sequential thiol-Michael and radical thiol-ene reactions

Soft poly(thioether) thermosets have been synthesized by employing a two-step curing procedure based on click chemistry. The first stage of curing is a thiol-Michael addition between acrylates (or methacrylates) and thiols in excess, catalyzed by a set of novel tertiary amine catalyst comonomers with allyl functionality. Subsequently, the pendant allyl groups of the comonomer get incorporated into the polymer network by undergoing thiol-ene UV photopolymerization with the remaining thiols. The strong catalysis by the high concentration of tertiary amine groups facilitates quantitative conversions at the end of the first stage. All remaining functional groups are depleted after a short period of UV irradiation. Final materials are clear, transparent, and exhibit homogeneous network structures with alpha relaxation temperatures in the range 3–25 °C. This sub-ambient relaxation temperature range suggests these materials may be suitable for coating applications where delicate substrates are involved such as plastic, wood and paper.