Low UV Irradiation Research Articles

Nitric oxide/PDT combination therapy by the fluorescent self-reporting Co-delivery platforms

Nitric oxide (NO) combined with photodynamic therapy (PDT) is a promising tumor treatment method. Herein, the cationic lipid DPNO(Zn) was developed as co-delivery carrier of NO and photosensitizer Chlorin e6 (Ce6). The target CNO lipid nanoparticles (LNPs) were obtained by solvent exchange method as a NO/PDT combination therapy platform, and biocompatible polymer γPGA could be easily coated to form PCNO for in vivo applications. Fluorescence spectra and confocal imaging experiments showed that the Ce6-loaded LNPs could release NO rapidly under low power UV irradiation with fluorescence self-reporting ability. On the other hand, under the irradiation of 660 nm laser, the LNPs could effectively produce singlet oxygen (1O2). In vitro and in vivo antitumor assays showed that the combination treatment of NO/PDT was more effective in tumor growth inhibition compared with individual NO or PDT treatment. Mechanism studies of NO/PDT combined therapy revealed that 1O2 could increase the level of p53 protein, thus activating the caspase 3 apoptosis pathway. And the rapid release of NO could amplify the effect of this pathway by reducing the level of HIF-1α. The NO and 1O2 released under laser irradiation could not only directly damage DNA and mitochondria, resulting in tumor cell dysfunction, but also induce the upregulation of iNOS to further enhance the gas therapy efficiency. This study proved that the light-triggered NO/1O2 generation system can be used as an effective NO/PDT synergistic therapy platform for cancer treatment.

Radiation Curing of Phosphorus Telomer-Based Coatings Using UV LEDs or Medium-Pressure Mercury Lamp

In the presented study, UV LEDs (365 nm) or a medium-pressure mercury lamp (UV-ABC) were verified as UV radiation sources initiating the photocrosslinking process of varnishes based on novel photopolymerizable phosphorus (meth)acrylate oligomers. Coating formulations were composed of (meth)acrylic/styrene telomers with terminal P-atoms (prepared via a UV phototelomerization process) and different photoinitiators (HAPs, APOs, or APO blends). The kinetics of the UV crosslinking process of the coating formulations depending on UV irradiation and the UV range was investigated by the photo-DSC method. Moreover, the hardness of the varnishes and the conversion of double bonds using the FTIR method were tested. The photopolymerization rate and the photoinitiation index, depending on the type of photoinitiator, were as follows: APOs < APO blends < HAPs. However, the highest coating hardness results were obtained using the least reactive photoinitiator from the APO group, i.e., Omnirad TPOL, or a mixture of three different types of acylphosphine (Omnirad BL 750). The greater effectiveness of the above-mentioned APOs over HAP was also demonstrated when using a UV LED lamp at 365 nm with a low UV dose and UV irradiance, thanks to the presence of phosphoric acid diester in the coating composition, acting as both a telogen and an antioxidant.

Synergistic effects in ZnO nanorod films by pulsed electrodeposition on graphene oxide towards enhanced photocatalytic degradation

In this work the synthesis, characterization and photocatalytic activity of novel graphene oxide-supported ZnO nanostructured film are reported. The ZnO film was deposited onto GO layer in a two-step procedure varying the deposition mode. The electrodeposited ZnO films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform Infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The effect of the electrodeposition mode and GO presence on the properties of the ZnO nanostructured film was assessed. The applicability towards the adsorption, photodegradation of methylene blue (MB) for the obtained films was analyzed. The results indicated the electrodeposition pulses result in a strong interaction between ZnO and GO results, lower c-axis strain of the deposited ZnO and higher oxygen vacancies. Synergistic effect of oxygen vacancies and morphology towards degradation performance was indicated. Both adsorption and photocatalysis towards the degradation of MB on the modified ZnO films were observed, 52 % degradation efficiency being recorded in 90 min with a rate constant of 0.00171 min−1 under low UV irradiation, with respect to 5 % corresponding to ZnO film obtained in single step by direct mode and in absence of GO layer. A recycling experiment indicated excellent stability of the photocatalyst, the degradation efficiency reaching 98 % after 3 successive runs.

Nanoscale Synergetic Effects on Ag-TiO2 Hybrid Substrate for Photoinduced Enhanced Raman Spectroscopy (PIERS) with Ultra-Sensitivity and Reusability.

Here, a 4N-in-1 hybrid substrate concept (nanocolumnar structures, nanocrack network, nanoscale mixed oxide phases, and nanometallic structures) for ultra-sensitive and reliable photo-induced-enhanced Raman spectroscopy (PIERS), is proposed. The use of the 4N-in-1 hybrid substrate leads to an ≈50-fold enhancement over the normal surface-enhanced Raman spectroscopy, which is recorded as the highest PIERS enhancement to date. In addition to an improved Raman signal, the 4N-in-1 hybrid substrate provides a high detection sensitivity which may be attributed to the activation possibility at extremely low UV irradiation dosage and prolonged relaxation time (long measurement time). Moreover, the 4N-in-1 hybrid substrate exhibits a superior photocatalytic degradation performance of analytes, allowing its reuse at least 18 times without any loss of PIERS activity. The use of the 4N-in-1 concept can be adapted to biomedicine, forensic, and security fields easily.

Flexible, disposable photocatalytic plastic films for the destruction of viruses.

A thin, 30 μm, flexible, robust low-density polyethylene, LDPE, film, loaded with 30 wt% P25 TiO2, is extruded and subsequently rendered highly active photocatalytically by exposing it to UVA (352 nm, 1.5 mW cm−2) for 144 h. The film was tested for anti-viral activity using four different viruses, namely, two strains of Influenza A Virus (IAV), WSN, and a recombinant PR8, encephalomyocarditis virus (EMCV), and SARS-CoV-2 (SARS2). The film was irradiated with either UVA radiation (352 nm, 1.5 mW cm−2; although only 0.25 mW cm−2 for SARS2) or with light from a cool white fluorescent lamp (UVA irradiance: 365 nm, 0.047 mW cm−2). In all cases the films exhibited an average virus inactivation rate of >1.5log/h. In the case of SARS2, the rates were > 2log/h, with the rate determined using a dedicated, low intensity UVA source (0.25 mW cm−2) only 1.3 x's faster than that for a cool white lamp (UVA irradiance = 0.047 mW cm−2), which suggests that SARS2 is particularly prone to photocatalytic inactivation even under low UV irradiation conditions, such as found in a room lit with just white fluorescent tubes. This is the first example of a flexible, very thin, photocatalytic plastic film, produced by a scalable process (extrusion), for virus inactivation. The potential of such a film for use as a disposable, self-sterilising thin plastic material alternative to the common, non-photocatalytic, inert equivalent used currently for curtains, aprons and table coverings in healthcare is discussed briefly.

Water Clusters in Interaction with Corannulene in a Rare Gas Matrix: Structures, Stability and IR Spectra

The interaction of polycyclic aromatic hydrocarbons (PAHs) with water is of paramount importance in atmospheric and astrophysical contexts. We report here a combined theoretical and experimental study of corannulene-water interactions in low temperature matrices and of the matrix’s influence on the photoreactivity of corannulene with water. The theoretical study was performed using a mixed density functional based tight binding/force field approach to describe the corannulene-water clusters trapped in an argon matrix, together with Born-Oppenheimer molecular dynamics to determine finite-temperature IR spectra. The results are discussed in the light of experimental matrix isolation FTIR spectroscopic data. We show that in the solid phase, π isomers of (C20H10)(H2O)n, with n = 2 or 3, are energetically favored. These π complexes are characterized by small shifts in corannulene vibrational modes and large shifts in water bands. These π structures, particularly stable in the case of the water trimer where the water cluster is trapped “inside” the corannulene bowl, may account for the difference in photoreactivity of non-planar–compared to planar–PAHs with water. Indeed, planar PAHs such as pyrene and coronene embedded in H2O:Ar matrices form σ isomers and react with water to form alcohols and quinones under low energy UV irradiation, whereas no photoreactivity was observed for corannulene under the same experimental conditions.

Solar disinfection – An appropriate water treatment method to inactivate faecal bacteria in cold climates

Solar disinfection (SODIS) is an inexpensive drinking water treatment method applied in tropical and sub-tropical low-income countries. However, it has been unclear whether it functions adequately also in colder climates. To investigate this issue, SODIS experiments were performed in the humid continental climate of Finland by exposing faecally contaminated drinking water to natural solar radiation at different water temperatures (8–23 °C) and UV intensities (12–19 W/m2) in polyethylene (PE) bags. To establish an adequate benchmark, SODIS experiments with the same experimental design were additionally conducted in the Mediterranean climate of Spain in typical conditions of SODIS application (~39 °C and 42 W/m2).Out of all experiments, the highest coliform and enterococci inactivation efficiencies in terms of lowest required doses for 4-log disinfection (25 Wh/m2 and 60 Wh/m2, respectively) were obtained in humid continental climate at the lowest studied mean water temperature (8–11 °C). Despite the low mean UV irradiance (~19 Wh/m2), 4-log disinfection of coliforms and enterococci were also reached fast in these conditions (1 h 27 min and 3 h 18 min, respectively). Overall, the doses required for disinfection increased as the water temperatures and UV intensities of the experiments rose. Disinfection of 4-logs (> 99.99%) of both bacteria was reached in all SODIS experiments within 6 h, suggesting SODIS could be a sufficient household water treatment method also in colder climates, unlike previously thought.The effects of different water temperatures on bacterial inactivation were also tested in the absence of sunlight. Together the obtained results indicate that while water temperatures below or close to the optima of coliforms and enterococci (~10 °C) alone do not cause inactivation, these temperatures may enhance SODIS performance. This phenomenon is attributed to slower bacterial metabolism and hence slower photorepair induced by the low water temperature.

Low-temperature UV irradiation of carbon/AgNWs counter electrodes for inexpensive flexible dye-sensitized solar cells

Here, we report an inexpensive and highly catalytic carbon/AgNWs counter electrode for flexible dye-sensitized solar cells (DSSCs). In order to reduce the process time, an organic surfactant is added to disperse the carbon composites. Then, a uniform catalytic layer can deposit on the silver nanowire (AgNW) transparent conductive electrode. Ultimately, a low temperature UV irradiation post-treatment is proposed to clean the surface of the catalytic layer. Through the electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) curve and Tafel curve, it can be established that this carbon/AgNWs counter electrode exhibits high catalytic activity than that of Pt/ tin-doped indium oxide (ITO) electrode. In addition, the current density–voltage characteristic curves also prove that the as-assembled DSSC has a superior photoelectrical conversion efficiency.

Ultrasound-assisted decoration of CuOx nanoclusters on TiO2 nanoparticles for additives free photocatalytic hydrogen production and biomass valorization by selective oxidation

• Ultrasound-assisted ultra-wet (US-UWet) impregnation synthetic method is presented. • Mixed cupric and cuprous oxides nanoclusters (< 4 nm) were decorated on TiO 2 P25. • The nanocomposite showed H 2 formation capability under low power UV irradiation. • The additive free oxidation of biomass derived model platform chemicals was studied. • Nanocomposite revealed higher selectivity comparing to P25 for HMF and BnOH oxidation. The herein presented ultrasound-assisted ultra-wet (US-UWet) impregnation synthetic approach was followed in order to avoid the drawbacks of the conventional wet impregnation synthesis. The goal was to homogeneously decorate the surface of the TiO 2 nanoparticles with nanometric sized (< 4 nm) clusters of mixed cupric and cuprous oxides. The physicochemical features of the nanocomposite (TiO 2 CuO x ) were determined by high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM), high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), and Diffuse reflectance (DR) spectroscopy. TiO 2 CuO x showed an enhanced and continuous capability to generate molecular hydrogen upon low power ultraviolet irradiation. The benchmark commercial TiO 2 P25 did not reveal any H 2 formation under these conditions. TiO 2 CuO x presented also a high efficiency for the additives-free selective partial oxidation of two well established biomass derived model platform chemicals/building blocks, 5-hydroxymethylfurfural (HMF) and benzyl alcohol (BnOH) to the value-added chemicals 2,5-diformylfuran (DFF) and benzyl aldehyde (PhCHO), respectively. The nanocomposite showed higher DFF and PhCHO yield compared to P25.

Facile Controlling of the Physical Properties of Zinc Oxide and Its Application to Enhanced Photocatalysis.

In this study, the physical properties of ZnO were facile controlled by the synthesis method with the addition of capping and precipitation agents. As-prepared ZnO samples had different morphologies such as carnation flower-like ZnO (CF-ZnO), rose-flower-like ZnO (RF-ZnO), rod-like ZnO (R-ZnO), and nanoparticle ZnO (N-ZnO) and were characterized by SEM, XRD, N2 adsorption/desorption isotherms, FT-IR, and DR/UV-vis. All samples had a crystallite structure of hexagonal wurtzite type. The CF-ZnO and RF-ZnO samples had the hierarchical structure like a carnation flower and a beautiful rose, respectively. R-ZnO was composed of many hexagonal rods and few spherical particles, while N-ZnO microstructures were made up of nanoparticles with approximately 20–30 nm, exhibiting the largest surface area, pore volume, and pore width among as-prepared samples, and their crystal size and bandgap energy were 17.8 nm and 3.207 eV, respectively. The catalytic performances of ZnO samples were evaluated by degradation of Tartrazine (TA) and Caffeine (CAF) under low UV irradiation (15 W). N-ZnO showed a high photocatalytic activity compared to other samples. Besides, the reaction kinetics was investigated by the first-order kinetic model, and the catalytic performance of ZnO was evaluated through several organic pollutants.

Suspended graphene arrays for gas sensing applications

Suspended graphene (SUS-G) has long been hailed as a potential ‘true graphene’ as its conductive properties are much closer to those of theoretical graphene. However, substantial issues with yield during any device fabrication process have severely limited its use to date. We report the successful fabrication of a fully operational prototype of a miniature 9 mm2 suspended graphene array sensor chip, incorporating 64 graphene sensor devices, each comprising of 180 SUS-G membranes with ever reported 56% fully intact graphene membranes for sensitive and selective gas sensing applications. While a bare sensor chip can operate as a sensitive gas sensor for a variety of gasses such as ammonia, nitrogen dioxide and carbon monoxide, down to ppm/ppb concentrations, a tetrafluorohydroquinone functionalized sensor acquires specificity to formaldehyde gas molecules with limited cross-sensitivity for ethanol, toluene and humidity. Unlike an equivalent device with fully supported functionalized graphene sensor, a functionalized SUS-G sensor can be furthermore reset to its baseline by using UV assisted desorption instead of substrate heating. The low power UV irradiation does not show severe damage to the SUS-G structures and loss of functional probes for the formaldehyde gas—a previously unreported feature. A resettable and selective formaldehyde gas sensor array with mass manufacturability, low power consumption and overall dimensions down to 1 mm2, would represent a significant technological step forward in the development of an electronic nose, for the simultaneous detection of multiple-target gases, with potential for integration in portable electronic devices and the internet of things.

Electrochemically assisted photocatalysis for the disinfection of rainwater under solar irradiation

In this work a photo electrochemical reactor (PEC) with a compound parabolic collector (CPC) has been designed and tested for the electrochemically assisted photocatalytic (EAP) disinfection of rainwater under real sun conditions in South Africa. The reactor consisted of a Ti mesh coated with aligned titania nanotubes with a carbon counter electrode in a concentric tubular configuration, within a borosilicate glass tube with a CPC. Environmental strains of Escherichia coli and Pseudomonas aeruginosa were used. The viability of the microorganisms was analysed by culture-based and by EMA-qPCR methods. The reactor was tested under real sun during the winter in South Africa with a relatively low UV irradiance (max: 13 Wm-2). Under real sun irradiation, EAP yielded a 5.5-log10 reduction for E. coli and a 5.8-log10 reduction for P. aeruginosa for culture-based analysis. The EAP treatment also showed improved results by EMA-qPCR analysis with a 2.4-log10 reduction in gene copies for E. coli and 3.0-log10 for P. aeruginosa.

Algae removal performance of UV-radiation-enhanced coagulation for two representative algal species

Algal blooms severely impact the ecological environment and human health, as well as drinking water supplies and treatment systems. This study investigated UV-radiation-enhanced aluminum (Al)-based coagulation for the removal of two representative algal species (Microcystis aeruginosa and Cyclotella sp.) which are responsible for most fresh water algal bloom in different seasons. The results demonstrated that the UV-Al process can enhance algae removal, and simultaneously control algal organic matter (AOM) release. Comparing with Microcystis aeruginosa, Cyclotella sp. was more sensitive to UV irradiation and its activity was severely inhibited by 240 s of UV irradiation; intracellular reactive oxygen species (ROS) increased sharply then decreased rapidly, and SEM images showed cell walls exhibited substantial compression. UV irradiation decreased the zeta potential, which might have contributed to algae removal. Approximately 93.5% of Microcystis aeruginosa cells and 91.4% of Cyclotella sp. cells were removed after 240 s of UV irradiation with 0.4 mmol/L Al. The MCs concentrations after Al coagulation were low (<100 ng/L). The DOC of Microcystis aeruginosa and Cyclotella sp. was also lower (1.2 and 1.6 mg/L, respectively) than the national standard level after UV-Al process. This study highlights the practical application of UV irradiation for enhancing algae removal and simultaneously controlling AOM release in water treatment plants, which is a simple and promising technology. This result also indicates that the water treatment parameters should be adjusted according to the algae species present in different seasons, especially for diatom which needs low UV irradiation and Al dosage.

Intelligent magnetic imprinted nanoparticles for efficient lysozyme separation from egg whites and sustained antibacterial activity

Intelligent magnetic materials are capable of responding to environmental stimuli in an on/off manner. The photo- and thermal-responsive nanogel layer was surface-grafted onto several magnetic nanoparticles to prepare the magnetic imprinted nanoparticles (Fe3O4 MIPs). The Fe3O4 MIPs show dramatic temperature and light, dual-dependent rebinding and release characteristics for lysozyme. Above the volume phase transition temperature of the PNIPAAm, the imprinted protein (lysozyme) can be selectively separated from egg whites and the activity remained unchanged. By combining low temperature and UV irradiation, a more finely tuned release of the binding protein can be achieved. Time-dependent antibacterial activity was observed, and it was found that Fe3O4 MIPs-loaded lysozyme almost completely suppressed the growth of E. coli with the continuous lysozyme release. More importantly, the Fe3O4 MIPs could easily be separated by an external magnetic field and can be recycled. The photo- and thermal-responsive Fe3O4 MIPs pave a new way for the development of an advanced, sustainable material for use in bioseparation, drug delivery, and antibacterial materials.

Photocatalytic reforming of glycerol to H2 in a thin film Pt‐TiO2 recirculating photoreactor

AbstractBACKGROUNDWith an increase in global bioenergy production, the ‘biorefinery concept’ has now become a significant focus of research. The desire to achieve efficient conversion of biomass material into both energy and value‐added products requires a combination of technologies and processes. As such, the photocatalytic reforming of feedstocks such as glycerol to hydrogen (H2) has a lot of potential.RESULTSReported here is the first example of a thin film‐based photocatalytic system capable of achieving H2 evolution using a glycerol feedstock. Using a titania (TiO2) sol–gel, glass columns were coated with a thin TiO2 layer before using photodeposition to add platinum (Pt) as a co‐catalyst. The coated columns were assembled into a simple yet effective recirculating system which used low power UV irradiation. Under optimum conditions (two coated columns and a 40 mL min−1 flow rate), a steady state of 0.9 μmol min−1 H2 with a photonic efficiency [ηphoton (%)] of 10.22 % was achieved. Furthermore, only one column showed flaking and loss of coating whereas the remaining columns were stable for the duration of the study, which equated to &gt; 100 h of experimental testing including replicates and determining optimal parameters.CONCLUSIONH2 evolution via photocatalytic glycerol reforming in a Pt‐TiO2 thin film catalyst recirculating system has been demonstrated under UV irradiation and ambient conditions. The system developed highlights that it is both catalyst development and reactor engineering that are required to continue to advance the field of photocatalysis. © 2020 The Authors. Journal of Chemical Technology &amp; Biotechnology published by John Wiley &amp; Sons Ltd on behalf of Society of Chemical Industry.

A novel ultraviolet illumination used in riboflavin photochemical method to inactivate drug-resistant bacteria in blood components

BackgroundUltraviolet (UV) fluorescent lamp (FL) was applied in mainstream riboflavin photochemical method (RPM) to inactivate pathogens in blood components. Low UV irradiance emitted by UV-FL resulted in more time to achieve effective inactivation. Materials and methodsA novel light emitting diode (LED) UV illumination with adjustable irradiance was developed by us. Two strains of drug-resistant bacteria (DRB), pan-drug resistant Acinetobacter baumannii (PDRAB) and methicillin-resistant Staphylococcus aureus (MRSA) were cultured and used for evaluating the inactivation effectiveness of RPM using UV-LED or UV-FL against DRB in plasma or platelets. Three plasma factors and four platelet parameters were measured after treatments. ResultsThere was a linear relationship between UV-LED irradiance and electric current, the minimum UV irradiance was 24 mW/cm2, and the maximum was 258 mW/cm2. At the same UV dose of 15 J/cm2, inactivation effectiveness of UV-LED with 258 mW/cm2 against PDRAB in plasma or platelets were comparable to that of UV-FL with 16 mW/cm2, both above 98%. UV-FL treatment required 10–15 min, but UV-LED only required 1–2 min. However, MRSA showed a resistance to UV-LED (inactivation effectiveness was around 40%) compared with UV-FL (inactivation effectiveness was above 98%). The retention of fibrinogen, factor V, factor VII in plasma and platelet counts in platelets with UV-LED treatment were significantly higher than UV-FL at the same UV dose. ConclusionThe treatment of RPM using UV-LED with high UV irradiance was able to dramatically shorten inactivation time against PDRAB in plasma or platelets and improve retention of blood components compared with UV-FL.

Core–Shell Nanocatalysts of Co3O4 and NiO Shells from New (Discarded) Resources: Sustainable Recovery of Cobalt and Nickel from Spent Lithium-Ion Batteries, Ni–Cd Batteries, and LCD Panel

This work focuses on end-of-life Ni-Cd and Li-ion batteries and introduces a novel approach to prepare two types of core-shell nanocatalysts consisting of NiO and CoO as the shells, respectively. Using a hydrometallurgical technique, we are able to successfully recover metals such as Co and Ni, and then use the recovered metals as precursors in preparation of catalysts via a precipitation technique using an alumina-borosilicate substrate which has been fabricated from scrap LCDs. The structures of the obtained nanocatalysts are carefully investigated by electron microscopes. It is revealed that the NiO show nanowire structure, while the CoO has nanobelt structure shells over the core of the substrates. The synthesized nanomaterials are used as photocatalysts to decompose methylene blue as an organic pollution model available in wastewater. Our nanocatalysts exhibit high photocatalytic performance with four times the reusability under a very low power UV (9 W) irradiation.

Erratum: “Theoretical Transmission Spectra of Exoplanet Atmospheres with Hydrocarbon Haze: Effect of Creation, Growth, and Settling of Haze Particles. II. Dependence on UV Irradiation Intensity, Metallicity, C/O Ratio, Eddy Diffusion Coefficient, and Temperature” (2019, ApJ, 877, 109)

Recent transmission spectroscopy has revealed that clouds and hazes are common in the atmospheres of close-in exoplanets. In this study, using the photochemical, microphysical, and transmission spectrum models for close-in warm ($\lesssim$ 1000 K) exoplanet atmospheres that we newly developed in our preceding paper (Kawashima & Ikoma 2018), we investigate the vertical distributions of haze particles and gaseous species and the resultant transmission spectra over wide ranges of the model parameters including UV irradiation intensity, metallicity, carbon-to-oxygen ratio (C/O), eddy diffusion coefficient, and temperature. The sensitivity to metallicity is of particular interest. We find that a rise in metallicity leads basically to reducing the photodissociation rates of the hydrocarbons and therefore the haze monomer production rates. This is due to an enhanced photon-shielding effect by the major photon absorbers such as $\mathrm{H_2O}$, $\mathrm{CO}$, $\mathrm{CO_2}$, and $\mathrm{O_2}$, existing at higher altitudes than the hydrocarbons. We also find that at relatively short wavelengths ($\lesssim$ 2-3 $\mu$m), the absorption features in transmission spectra are most pronounced for moderate metallicities such as 100 times the solar metallicity, whereas the lower the metallicity the stronger the absorption features at relatively long wavelengths ($\gtrsim$ 2-3 $\mu$m), where the contribution of haze is small. These are because of the two competing effects of reduced haze production rate and atmospheric scale height for higher metallicities. For the other model parameters, we show that stronger absorption features appear in transmission spectra of the atmospheres with lower UV irradiation, lower C/O ratio, higher eddy diffusion coefficient, and higher temperature.

Improvement of performance and fouling resistance of polyamide reverse osmosis membranes using acrylamide and TiO2 nanoparticles under UV irradiation for water desalination

ABSTRACTThe purpose of this research is to explain the surface modification of fabricated polyamide reverse osmosis (RO) membranes using UV‐initiated graft polymerization at different irradiation times (15, 30, 60, and 90 s) and various acrylamide concentrations (10, 20, and 30 g L−1). Also, coating of membranes surface with various concentrations of TiO2 nanoparticles (10, 20, 30, and 50 ppm) followed by the same UV irradiation times was investigated. After that, the membranes modification was done by grafting of acrylamide blended with TiO2 nanoparticles via UV irradiation. The characterization of membranes surface properties and their performance were systematically carried out. The results demonstrated the enhanced hydrophilicity of modified membranes and confirmed the presence of acrylamide and nanoparticles on the membranes surface. Acrylamide‐grafted membranes could reach to higher water flux than pristine membrane with little reduction in salt rejection. Moreover, TiO2‐coated membranes indicated enhancement of water flux continuously with increase in nanoparticles concentration and irradiation time and rejection of membranes was slightly decreased at low irradiation times. Also, RO membranes modified simultaneously with acrylamide and TiO2 nanoparticles under UV irradiation exhibited improved water flux up to 18%, slightly higher rejection, and considerable better fouling resistance compared with pristine one. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48461.RESEARCH HIGHLIGHTS Aromatic polyamide thin film composite reverse osmosis (RO) membranes fabricated through interfacial polymerization process between m‐phenylenediamine and trimesoyl chloride on the porous polysulfone support. The desirable UV irradiation time for surface modification of RO membranes was up to 90 s. Modification of RO membranes surface was carried out by UV‐initiated grafting of acrylamide, coating of membranes surface with TiO2 nanoparticles followed by the UV irradiation, and grafting of acrylamide blended with TiO2 nanoparticles via UV irradiation. ATR‐FTIR, SEM, EDX, and AFM confirmed modification of membranes surface with acrylamide, TiO2 nanoparticles, and both of them. All modified membranes had lower contact angle than unmodified one indicating enhanced surface hydrophilicity. Acrylamide‐grafted membranes could result in higher water flux than unmodified membrane with little reduction in salt rejection. TiO2‐coated membranes indicated improvement of water flux with increase in nanoparticles concentration and irradiation time and rejection of membranes was decreased slightly at low UV irradiation times. RO membranes modified simultaneously with acrylamide and TiO2 nanoparticles under UV irradiation had improved water flux, slightly higher rejection, and considerable enhanced antifouling property compared with unmodified one.

QUV Accelerated Aging Effects on the Structure and Properties of Polyether Polyurethane Fibers

This paper presents an experimental study about the effects of UV irradiation on polyether polyurethane (PU) fibers investigated by FTIR, SAXS and AFM, and the multiple mechanism is finally proposed.The results show that, at low UV irradiation (0.6W/m2, 0.9W/m2), the mechanism responsible for UV degradation of polyether PU fibers could be described as a primary reaction causing the break up of chemical bonds and forming the new quinone structure, along with a secondary reaction to explain hydrogen peroxide formed in the presence of UV irradiation, water and oxygen environment which promotes QUV aging by providing loose structure of polyether PU fibers. Moreover, the micro phase separation is promoted for a parallel reaction occurred to produce new polyether PUs and more compact micro domains by the residual isocyanate in pre-polymerization stage and alcohols formed under QUV aging. Under higher UV irradiation (1.2W/m2, 1.5W/m2), in addition to the primary reaction, a tertiary reaction showing the re-polymerization occurred under accumulation of aging products (carboxylic acids and alcohols) is also considered as the mechanism, while the secondary reaction would be inhibited for the peak assigned to H2O2 is not observed. Also, this decreases micro phase separation of polyether PU fibers for the primary reaction is dominant.