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To optimize the working efficiency of the novel UV-LED system based on TiO2 photocatalyst, the influence mechanism of LED lamp arrangement, light source wavelength and working voltage on photocatalytic efficiency was investigated. Acid red 26 (AR 26), acetaminophen (ACT) and diclofenac (DCF) were used as contaminant targets of the photocatalytic system. LED lamp arrangement had almost no effect on the degradation of AR26. However, the degradation efficiency of ACT and DCF was improved under a higher light uniformity. The ACT concentration and DCF concentration at 360 min decreased by 14% and 15%, respectively, with increasing light distribution from 45% to 66.5%. The main reason for this discrepancy in effect was whether the rate-determining step of the degradation mechanism was affected by the light uniformity. The short wavelength and high working voltage of LEDs were conducive to the photocatalytic degradation of contaminants to a different degree. When the wavelength was reduced from 405nm to 365nm, the conversion of AR26, ACT, and DCF increased by 77%, 227%, and 106%, respectively. The conversion rates of AR26, ACT, and DCF increased by 28%, 54%, and 32%, respectively, with voltage increasing from 3 V to 4 V. The data of this work will provide support for optimizing the working efficiency of UV-LED systems based on TiO2 photocatalysts. [ABSTRACT FROM AUTHOR]

Ozone (O3) is a critical gas in various industrial applications, particularly in semiconductor manufacturing, where it is used for wafer cleaning and oxidation processes. Accurate and reliable detection of ozone concentration is essential for process control, ensuring product quality, and safeguarding workplace safety. By studying the UV absorption characteristics of O3 and combining the specific operational needs of semiconductor process gas analysis, a pressure-insensitive ozone gas sensor has been developed. In its optical structure, a straight-through design without corners was adopted, achieving a coupling efficiency of 52% in the gas chamber. This device can operate reliably in a temperature range from 0 °C to 50 °C, with only ±0.3% full-scale error across the entire temperature range. The sensor consists of a deep ultraviolet light-emitting diode in a narrow spectrum centered at 254 nm, a photodetector, and a gas chamber, with dimensions of 85 mm × 25 mm × 35 mm. The performance of the sensor has been meticulously evaluated through simulation and experimental analysis. The sensor's gas detection accuracy is 750 ppb, with a rapid response time (t90) of 7 s, and a limit of detection of 2.26 ppm. It has the potential to be applied in various fields for ozone monitoring, including the semiconductor industry, water treatment facilities, and environmental research. [ABSTRACT FROM AUTHOR]

In this research we present a low-cost system for breath acetone analysis based on UV-LED photoacoustic spectroscopy. We considered the end-tidal phase of exhalation, which represents the systemic concentrations of volatile organic compounds (VOCs) – providing clinically relevant information about the human health. This is achieved via the development of a CO2-triggered breath sampling system, which collected alveolar breath over several minutes in sterile and inert containers. A real-time mass spectrometer is coupled to serve as a reference device for calibration measurements and subsequent breath analysis. The new sensor system provided a 3σ detection limit of 8.3 ppbV and an NNEA of 1.4E-9 Wcm−1Hz−0.5. In terms of the performed breath analysis measurements, 12 out of 13 fell within the error margin of the photoacoustic measurement system, demonstrating the reliability of the measurements in the field.

The COVID-19 pandemic highlighted public awareness of airborne disease transmission in indoor settings and emphasized the need for reliable air disinfection technologies. This increased awareness will carry in the post-pandemic era along with the ever-emerging SARS-CoV variants, necessitating effective and well-defined protocols, methods, and devices for air disinfection. Ultraviolet (UV)-based air disinfection demonstrated promising results in inactivating viral bioaerosols. However, the reported data diversity on the required UVC doses has hindered determining the best UVC practices and led to confusion among the public and regulators. This article reviews available information on critical parameters influencing the efficacy of a UVC air disinfection system and, consequently, the required dose including the systems components as well as operational and environmental factors. There is a consensus in the literature that the interrelation of humidity and air temperature has a significant impact on the UVC susceptibility, which translate to changing the UVC efficacy of commercialized devices in indoor settings under varying conditions. Sampling and aerosolization techniques reported to have major influence on the result interpretation and it is recommended to use several sampling methods simultaneously to generate comparable and conclusive data. We also considered the safety concerns and the potential safe alternative of UVC, far-UVC. Finally, the gaps in each critical parameter and the future research needs of the field are represented. This paper is the first step to consolidating literature towards developing a standard validation protocol for UVC air disinfection devices which is determined as the one of the research needs.

UV-LEDs are a promising technology to degrade pharmaceuticals in water. However, to consider the installation of a UV-LED system to actual treatment systems, the degradation by-products of pharmaceuticals, their toxicities, and their degradation pathways should be better understood to determine optimal UV irradiation conditions. In addition, it is necessary to estimate the impact of co-existing substances such as nitrate ion (NO3∁E and dissolved organic matter (DOM). We analyzed degradation by-products of five common pharmaceuticals by high resolution mass spectrometry, and ion chromatography to understand the decomposition mechanisms of pharmaceuticals in Milli-Q water and evaluated the influence of NO3∁Eand DOM in environmental water in UV-LED degradation experiments. The results showed that pharmaceutical degradation percentage was nearly 100% for most of the target compounds (except ibuprofen) in Milli-Q water. Additionally, a part of the degradation mechanism of sulfamethoxazole was clarified. It is suggested that UV absorption occurred at the benzene ring and transfer energy resulted in S-N bond cleavage via homolysis. UV irradiation in the presence of DOM or NO3∁Epromoted the dichlorination reaction by the photosensitizing effect of chlorinated organic compounds such as diclofenac and triclosan, suggesting that 280 Em irradiation is effective for the degradation of pharmaceuticals in water treatment.

Cyanide and heavy metals pose significant risks as contaminants in certain industrial effluents. This study aims to concurrently eliminate cyanide and specific heavy metals from synthetic wastewater resembling gold processing effluent, employing an improved electrocoagulation method incorporating ozone and UV-LED. The investigation delves into the effects of pH, electrode type, current density, reaction time, and ozonation. The findings revealed notable removal efficiencies: 98% for cyanide, 76% for nickel, 85% for copper, and 84% for zinc when utilizing a stainless steel electrode as the cathode. Optimal removal rates were achieved at 94% for cyanide, 93% for copper, 92% for zinc, and 83% for nickel, employing the UV-LED-ozone technique with an ozonation flow rate of 4 mg/s at pH = 10. Notably, when Al-Gr-SS-Fe electrodes and a current of 15 mA/cm2 were applied, these removal efficiencies were observed. Therefore, the most favorable conditions for the concurrent removal of pollutants from synthetic wastewater involved maintaining a pH of 10, utilizing SS-Fe as anode and Al-Gr as cathode electrodes, and employing a current density of 15 mA/cm2. The addition of ozonation with a flow rate of 4 mg/s, along with UV-LED, further enhanced the removal process. In summary, it can be inferred that the enhanced electrocoagulation method outperformed conventional electrocoagulation, leading to increased elimination of cyanide and selected heavy metals. [ABSTRACT FROM AUTHOR]

Controlling the microbial load in the environment is crucial to prevent the spread of organisms. The continuous spread of nosocomial infections in hospital facilities and the emergence of the coronavirus (COVID-19) highlighted the importance of disinfection processes in health safety. This work aimed to evaluate the effectiveness of LED-based disinfection lamps on bacteria from the ESKAPEE group and virus phage in vitro inactivation to be applied in hospital environments and health facilities disinfection.This study evaluated the effect of different UV wavelengths (275 nm, 280 nm (UVC), 310 nm (UVB) and 340 nm (UVA)) on the disinfection process of various microbial indicators including E. coli, S. aureus, P. aeruginosa, B. subtilis and Bacteriophage lambda DSM 4499. Exposure time (5 min–30 min), exposure distance (0.25 m and 0.5 m) and surface materials (glass, steel, and polished wood) were evaluated on the disinfection efficiency. Furthermore, the study determined the recovery capacity of each species after UV damage.UVC-LED lamps could inactivate 99.99 % of microbial indicators after 20 min exposures at a 0.5 m distance. The exposure time needed to completely inactivate E. coli, S. aureus, P. aeruginosa, B. subtilis and Bacteriophage lambda DSM 4499 can be decreased by reducing the exposure distance. UVB-LED and UVA-LED lamps were not able to promote a log reduction of 4 and were not effective on B. subtilis or bacteriophage lambda DSM 4499 inactivation. Thus, only UVC-LED lamps were tested on the decontamination of different surface materials, which was successful. P. aeruginosa showed the ability to recover from UV damage, but its inactivation rate remains 99.99 %, and spores from B. subtilis were not completely inactivated. Nevertheless, the inactivation rate of these indicators remained at 99.99 % with 24 h incubation after UVC irradiation. UVC-LED lamps emitting 280 nm were the most indicated to disinfect surfaces from microorganisms usually found in hospital environments.

In the presented studies, a system for the characterization of planar photocatalysts was developed and tested. In the system, reference substances can be studied online with regard to their degradability and adsorption on photocatalytic materials. In order to perform accurate calculations of the quantum and photon efficiency of the catalysts, the LED arrays used were adjusted in their spacing by simulations so that a homogeneous light field is imaged on the catalysts. The system was tested with respect to measurement accuracy and reproducibility and the photocatalytic degradation of methylene blue, methyl orange and rhodamine B was investigated. Exemplarily, the reaction kinetics, photolysis and adsorption on the tested photocatalysts were determined for these compounds and the calculation was presented in detail. The exact construction plans and circuits as well as the sensors and their programming are presented in detail and should encourage other scientists to replicate the experimental setup, since especially in the field of photocatalysis research, often the results of publications cannot be compared with each other.

LEDs development has attracted attention over conventional mercury lamps for the tiny size, high efficiency, long lifetime, low operating temperature. The antimicrobial effectiveness of traditional UV-lamps radiation (wavelength of 254 nm) compared to UV-C LEDs (LED1 wavelength range 275–286 nm and LED2 range 260–270 nm) was carried out, for possible applications to automated sterile drug compounding. The UV lamp and the tested UV-LED devices remarkably reduced microbial load, following a time-dose response, but the best performance was evidenced by LED1, which guaranteed the complete inactivation of high concentrations of bacteria, yeasts, and spores at doses between 200 and 2000 J/m2. [ABSTRACT FROM AUTHOR]

When ultraviolet light-emitting diodes (UV-LEDs) are used for surface disinfection, the UV dose in some areas may exceed the required level but be insufficient in other areas. The most ideal radiation field is that with the same irradiance level at each point. In this study, a universal formula for determining the radiation field was derived, and a corresponding VBA program was coded for the mathematical simulation, analysis, and optimization of the radiation field. The radiation fields of nine UV-LED radiation patterns were simulated and analyzed. The results indicate that for a board with multiple UV-LEDs, the ratio of the radiation distance to the UV-LED spacing and the radiation patterns of the UV-LEDs are the key factors that influence the uniformity of the radiation field. Because of edge effects, a uniform radiation field can be reached only within 80% of the edge length projected directly below the UV-LED board. When the ratio of the radiation distance to the UV-LED spacing is within the range of 3 to 15, the uniformity is good (the ratio of the minimum to maximum values ≥ 81.8%). The radiation pattern with a smaller maximum emission angle is good for a relatively higher ratio of the irradiation distance to UV-LED spacing, and vice versa.

Ozone (O3) is a critical gas in various industrial applications, particularly in semiconductor manufacturing, where it is used for wafer cleaning and oxidation processes. Accurate and reliable detection of ozone concentration is essential for process control, ensuring product quality, and safeguarding workplace safety. By studying the UV absorption characteristics of O3 and combining the specific operational needs of semiconductor process gas analysis, a pressure-insensitive ozone gas sensor has been developed. In its optical structure, a straight-through design without corners was adopted, achieving a coupling efficiency of 52% in the gas chamber. This device can operate reliably in a temperature range from 0 °C to 50 °C, with only ±0.3% full-scale error across the entire temperature range. The sensor consists of a deep ultraviolet light-emitting diode in a narrow spectrum centered at 254 nm, a photodetector, and a gas chamber, with dimensions of 85 mm × 25 mm × 35 mm. The performance of the sensor has been meticulously evaluated through simulation and experimental analysis. The sensor’s gas detection accuracy is 750 ppb, with a rapid response time (t90) of 7 s, and a limit of detection of 2.26 ppm. It has the potential to be applied in various fields for ozone monitoring, including the semiconductor industry, water treatment facilities, and environmental research.

A homogeneous persulfate (PS) activation under low energy consumption ultraviolet light-emitting diodes (UV-LEDs) was established in order to degrade the resistive fluoxetine-hydrochloride drug in aqueous media. For this aim, a falling film photo-reactor, equipped with four arrays of six UV-LEDs (395 nm, 1 W each), was utilized. Trace concentrations of ferrous sulfate and heating the media could significantly improve the degradation efficiency. Under the established optimal conditions of 100 mg/L of persulfate, 1 mg/L of ferrous sulfate, natural pH of 6.4 and temperature of 40 °C, a 71.1% degradation efficiency was achieved for 40 mg/L fluoxetine initial concentration after 50 min. The kinetic study revealed a pseudo-first order overall degradation rate. Based on scavenger quenching results, it was revealed that the hydroxyl radical and sulfate anion radical had, respectively, 52.3 and 31.4% contribution in degradation. To extend results to real conditions, the influence of inorganic cations/anions and also humic acid was investigated. From LC-MS analysis results, the transformation products were identified and three degradation pathways were proposed. Interestingly, a cost evaluation indicated electrical energy consumption of 16.7 kWh/m3 and operating cost of only $1.71 per each cubic meter. Consistently, the profound UV-LED/PS/Fe2+/heat process exhibited desired capabilities in scenarios for treating resistive drug wastewaters.

Fiber-reinforced concrete (FRC) is a cementitious composite material that is gaining interest in the construction field to limit crack propagation and increase toughness. Polypropylene (PP) fibers are promising alternatives to steel fibers, primarily used in FRC, as they reduce weight and cost and are resistant to corrosion. However, the hydrophobic surface of PP inhibits a good adhesion with the surrounding cementitious matrix and so the exploitation of optimized mechanical performance. Though several chemical treatments have been studied, this work suggests more sustainable, cost-efficient, and fast surface treatments for the first time to increase the hydrophilicity of PP: UV-LED, picosecond UV-LASER, and corona discharge treatment. The treatments mainly provided a chemical functionalization without altering the surface morphology of PP, and their effectiveness in increasing PP hydrophilicity was confirmed by ATR-FTIR spectroscopy and optical contact angle measurements. The improved adhesion with the matrix was assessed by the pullout test of treated PP specimens from lime-based and cement-based matrices and by detecting the failure mode in the interphase zone through scanning electron microscopy. [ABSTRACT FROM AUTHOR]

The objective of this study was to examine the impact of unfiltered water conditions on UV disinfection. UV biodosimetry tests were conducted over a year using water samples from two treatment plants that apply UV without filtration. The influence of turbidity, absorbance, and zeta potential on UV dose–response curves was analyzed to evaluate relationships between unfiltered water quality and log-inactivation of surrogate organisms. It was observed that diminishing inactivation with increasing UV dose (tailing effect) was governed principally by the surface charge of particulate matter. The increased tailing level observed in raw waters was postulated to be due to having more neutral surface charges, resulting in elevated electrostatic attraction between particles and microorganisms that increased UV resistance. Inactivation at a dose of 35 mJ/cm2 in water samples with low turbidity levels (0.38 NTU) and relatively negative surface charge resulted in 3.0 log-removal in comparison with 2.2 and 2.0 log-removal for samples with turbidity levels of 1.57 and 0.61 NTU, respectively. The results of this study highlight the risks of UV disinfection of unfiltered supplies with respect to the effects of water quality characteristics on UV effectiveness and could be employed to optimize the estimation of UV disinfection potential. HIGHLIGHTS Convectional treatment indicators such as turbidity and UV absorbance (UVA) could not sufficiently interpret the UV disinfection potential in unfiltered drinking water treatment systems.; Particle surface charge has a more significant impact on UV efficiency than turbidity and UVA.; Pre-treatments that affect particle surface charge could be used to improve UV disinfection potential of unfiltered sources.;

Ultraviolet (UV)-light-emitting diodes (UV-LEDs) are energy efficient and of special interest for the inactivation of micro-organisms. In the context of the coronavirus disease 2019 pandemic, novel UV technologies can offer a powerful alternative for effective infection prevention and control. This study assessed the antimicrobial efficacy of UV-C LEDs on Escherichia coli, Pseudomonas fluorescens and Listeria innocua, as well as severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), human immunodeficiency virus-1 (HIV-1) and murine norovirus (MNV), dried on inanimate surfaces, based on European Standard EN 17272. This study found 90% inactivation rates for the tested bacteria at mean UV-C doses, averaged over all three investigated UV-C wavelengths, of 1.7 mJ/cm2 for E. coli , 1.9 mJ/cm2 for P. fluorescens and 1.5 mJ/cm2 for L. innocua. For the tested viruses, UV doses <15 mJ/cm2 resulted in 90% inactivation at wavelengths of 255 and 265 nm. Exposure of viruses to longer UV wavelengths, such as 275 and 285 nm, required much higher doses (up to 120 mJ/cm2) for inactivation. Regarding inactivation, non-enveloped MNV required much higher UV doses for all tested wavelengths compared with SARS-CoV-2 or HIV-1. Overall, the results support the use of LEDs emitting at shorter wavelengths of the UV-C spectrum to inactivate bacteria as well as enveloped and non-enveloped viruses by exposure to the appropriate UV dose. However, low availability and excessive production costs of shortwave UV-C LEDs restricts implementation at present, and supports the use of longwave UV-C LEDs in combination with higher irradiation doses. [ABSTRACT FROM AUTHOR]

In this study, electrochemically generated free chlorine (EC/Cl2) was activated by UV irradiation with a light emitting diode (LED) lamp at 275 nm to degrade acetaminophen (AAP, 2 μM) in aqueous solution. The potential at a RuO2-IrO2/Ti plate anode was set at 1.5 V vs. the Ag/AgCl electrode. Chlorine was in situ generated in the presence of Cl杴 at the anode and then it was transformed into various active species such as 晑OH and reactive chlorine species (RCS) under UV-LED irradiation. The degradation of AAP was investigated using batch tests, evaluating the influence of different experimental conditions such as NaCl concentration, phosphate buffer saline concentration, irradiation time and solution pH, keeping constant the UV-LED power and temperature. Results show that AAP could be completely degraded by the hybrid process with a high mineralization ratio (73%), and the degradation process followed a pseudo-first-order kinetics. The value of the Electric Energy per Order (EEO) = 1.272 kWh m杴3 order?, which is lower than the energy consumption of some other UV-based processes for AAP degradation. Adding 1 mM HCO3杴 ions slightly decreased the rate of AAP degradation. Luminescent bacteria experiment revealed that the acute toxicity of the reacted solution could be greatly reduced and the ecological risk was effectively abated. The scavenging assay shows that RCS plays a key role in the AAP degradation. The intermediate products were identified, and possible degradation routes were proposed. The system can advantageously replace conventional UV mercury lamp based ones in the degradation of microorganic pollutants. [ABSTRACT FROM AUTHOR]

In this paper, a method of indium-tin oxide /Graphene /Indium-tin oxide (ITO/Gr/ITO) structure as transparent conductive layer (TCL) to improve the current spreading of ultraviolet light-emitting diodes (UV-LEDs) is reported. The ITO/Gr/ITO structure is obtained by RF magnetron sputtering and wet-transferred. Raman spectroscopy measurement further reveal that the number of inserted graphene in the structure are single layer and few layers. It can be found that the forward voltage of optimized LEDs with ITO/Gr/ITO TCL is significantly reduced. Furthermore, the light output power (LOP) and the wall plug efficiency (WPE) of the LEDs with ITO/Gr/ITO structure have also been improved significantly compared with that of the conventional LED with ITO TCL. Light distribution analysis shows that the introduction of ITO/Gr/ITO structure as TCL in UV-LEDs is an effective method to improve the current spreading. As a result, an LED with a 45.7% increase in LOP at 100 mA, and a 52% increase in maximum WPE is obtained by the use of ITO/Gr/ITO with a single graphene interlayer.

Ultraviolet-C (UV-C) irradiation is a well-recognized technology for improving blueberry postharvest quality, and previous literature indicates that it has the potential for dual-use as an antimicrobial intervention for this industry. However, the practicality and feasibility of deploying this technology in fresh blueberry fruit are significantly hindered by the shadowing effect occurring at the blossom-end scar of the fruit. The purpose of this study was to determine if treating the blueberry fruit within a chamber fitted with UV-Light Emitting Diodes (LEDs) emitting a peak UV-C at 275 nm could minimize this shadowing and result in improved treatment efficacy. Ten blueberry fruits were dip-inoculated with E. coli at a concentration of 105 CFU/mL and irradiated within the system at doses of 0, 1.617, 3.234, 9.702, and 16.17 mJ/cm2 (0, 30, 60, 180, and 300 s). Statistical analysis was performed to characterize the extent of microbial survival as well as the UV-C inactivation kinetics. A maximum of 0.91–0.95 log reduction was observed, which attenuated after 60 s of treatment. The microbial inactivation and survival were thus modeled using the Geeraerd-tail model in Microsoft Excel with the GInaFIt add-in (RMSE = 0.2862). Temperatures fluctuated between 23 ± 0.5°C and 39.5°C ± 0.5°C during treatment but did not statistically impact the treatment efficacy (P = 0.0823). The data indicate that the design of a UV-LED system may improve the antimicrobial efficacy of UV-C technology for the surface decontamination of irregularly shaped fruits, and that further optimization could facilitate its use in the industry.

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Photo-activated chemiresistive sensors have introduced a considerable improvement among all gas sensor technologies. However, the major drawback of these gas sensors is the long response time, which limits the potential of such sensors in many applications where rapid measurement is required. In this work, we investigated the response curve slope for gas concentration measurement. Our aim was to significantly reduce the response time of the ultraviolet light-emitting diodes (UV-LED)-activated chemiresistive metal oxide semiconductor (MOS) gas sensors so that steady-state response times are no longer needed. As a model semiconductor, zinc oxide (ZnO) nanowires (NWs) were fabricated to detect different concentrations of nitrogen dioxide (NO 2) at room temperature under UV radiation with a wavelength of 275 nm. The consistent slope measurement results and the reproducible correlation between the response curve slope and the NO 2 concentration represented the slope as an indicator of the gas concentration. The results indicated relatively high steady-state responses of 0.36, 0.65, 1.15, and 1.51 to the 5, 10, 25, and 50 ppm concentrations of NO 2 , respectively. [Display omitted] • UV-LED-activated ZnO semiconductor is a promising gas-sensing material. • The initial response curve slope (IRCS) is a reliable indicator of the NO 2 concentration. • The IRCS indicates the changes in concentration in the presence of a background gas. [ABSTRACT FROM AUTHOR]

With the recent development of ultraviolet light emitting diodes (UV-LEDs), it is now possible to apply UV disinfection, previously used only for medium-to-large sized sewage treatment plants, to Johkasou wastewater, a household wastewater treatment system. However, it is known that coliforms that have been inactivated by UV irradiation regain their activity after of sunlight irradiation, etc. Therefore, in small Johkasou, where discharge channels are often open, photorecovery may occur immediately after UV disinfection. However, no studies have been conducted to investigate photorecovery by sunlight after UV disinfection of wastewater from small Johkasou. In this study, the relationship between the photorecovery of coliforms and the dose of sunlight after UV-LED irradiation of effluent in Johkasou was investigated. As a result, we identified the amount of sunlight that will maximize photoreactivation effect. We also clarified the suppressing effect of an excessive amount of sunlight on the photoreactivation phenomenon. Additionally, since it was confirmed that the photoreactivation effect was suppressed by a certain period of darkness following UV-LED irradiation, it was considered that the photoreactivation effect can also be suppressed by allowing wastewater to reside in darkness for the currently estimated residence time in a disinfection tank.

2,4-Dichlorophenol (2,4-DCP) one of the most common and abundant pollutants, is widely found in various industrial effluents such as resin and plastic products in the petrochemical industry. The apparent effect of this recalcitrance compound on the health and environment is enhancing its efficient degradation before wastewater discharged into the receiving water. Hence, the removal of 2,4-DCP from aqueous solutions using the photocatalytic UV-LED/ZnO process was investigated. In this experimental study, the removal of 2,4-DCP using UV-LED in the presence of ZnO in the bench scale reactor was examined. The effects of operational parameters such as the pH of the solution (3-11), initial concentration of 2,4-DCP (50-200 mg/L), the amount of ZnO dose (0.003-0.025 mol/L) and different ionic strengths were evaluated. The experimental results indicated that different operational parameters influenced the removal of 2,4-DCP. The highest 2,4-DCP removal rate was obtained at pH = 11 by adding 0.006 mol/L ZnO into the solution with an initial concentration of 50 mg/L 2,4-DCP, removing more than 98.2% of 2,4-DCP. When UV-LED and ZnO were used alone, the removal efficiencies were 32.11% and 30.93%, respectively. Also, the maximum chemical oxygen demand removal rate was 64.45% in optimum conditions and ionic strength was reported to be ineffective. The results indicated that combined ZnO and UV-LED processes in optimal conditions could be used as an alternative technology for the treatment of various industrial wastewater containing 2,4-DCP. [ABSTRACT FROM AUTHOR]

AlGaN-based materials have exhibited considerable potential for fabricating ultraviolet (UV) light-emitting diodes (LEDs) owing to their direct, wide, and adjustable energy bandgap. AlGaN-based devices have extensive applicability owing to their stable physico-chemical properties. With decades of research effort, significant progress has been achieved in enhancing the working efficiency of AlGaN-based LEDs by optimizing the crystalline quality, doping efficiency, and device design. In this review, methods to obtain high-quality AlGaN-based materials, achieve high doping efficiency, and design UV-LED structures are summarized and discussed. Finally, the issues that need to be addressed in AlGaN-based UV-LED devices are highlighted.

This work provides new insight into the development of the TiO2/Oxone/UV-LED process for organic contaminant degradation as well as hospital waste management. The Moxifloxacin (MOX) degradation using Oxone activated TiO2 under UV-LED was studied. The TiO2/Oxone/UV LED process was carried out by the addition of Oxone (0.025, 0.05, 0.1 and 0.2 mM) activated by TiO2 different concentrations 0.0125, 0.025, 0.05, 0.1 and 0.5 g/L. The degradation efficiency was studied by HPLC having UV/Vis detector, C18 column (5µ, 4.6 × 250 mm2). The complete removal of 10 ppm of MOX occurred at 0.1 g/L TiO2 and 0.1 mM Oxone with UV-LED exposure time of 12 min. The TOC analysis was performed and 55% TOC reduction was observed at described procedure. The parameters such as drug initial concentration, Oxone, TiO2 dosages and pH were optimized and their effects on degradation were noted. The pseudo-first order reaction kinetics was observed for MOX degradation. It was revealed from the mechanism of activation that SO4-. and OH. have played a key role in the degradation. The effect of pH (3.6–11) was observed to evaluate the degradation rate of Moxifloxacin. The pH 9.4 achieved the maximum degradation. The UPLC-ESI-MS analysis was performed to identify the intermediates and degraded end-products.

Large scale outbreaks of infectious respiratory disease have repeatedly plagued the globe over the last 100 years. The scope and strength of the outbreaks are getting worse as pathogenic RNA viruses are rapidly evolving and highly evasive to vaccines and anti-viral drugs. Germicidal UV-C is considered as a robust agent to disinfect RNA viruses regardless of their evolution. While genomic damage by UV-C has been known to be associated with viral inactivation, the precise relationship between the damage and inactivation remains unsettled as genomic damage has been analyzed in small areas, typically under 0.5 kb. In this study, we assessed genomic damage by the reduced efficiency of reverse transcription of regions of up to 7.2 kb. Our data seem to indicate that genomic damage was directly proportional to the size of the genome, and a single hit of damage was sufficient for inactivation of RNA viruses. The high efficacy of UV-C is already effectively adopted to inactivate airborne RNA viruses. • RNA viruses are highly sensitive to UV-C as they are inactivated by a single hit of genomic damage. • Viral inactivation rate of RNA viruses seems directly proportional to their genome size. [ABSTRACT FROM AUTHOR]

This paper proposes a lens design method for effectively collimating the light emitting from a light-emitting diode (LED). This collimating lens contains two aspherical lens surfaces which can be mathematically characterized using a few designing parameters, and hence is called an analytic collimating lens. An optical ray-tracing algorithm has been developed for these analytic collimating lenses to analyze their optical performance and to optimize their designs. Six high-power and commercially available ultraviolet (UV) LEDs are chosen as examples for demonstrating the optimal collimating lens design. For each UV-LED, the corresponding optical collimating lens is determined by inputting the ray data file provided by the manufacture over a finite-size emitting area. The divergent angles of the six UV-LEDs have been successfully collimated to a narrow range in between 1.56° to 2.84° from their original radiation angle around 46° to 120°. Furthermore, the proposed analytical collimating lenses are suitable for mass-production using standard mold injection methods, and hence possess great potentials for industry applications of LEDs. [ABSTRACT FROM AUTHOR]

The congener polychlorinated biphenyls (PCBs) are one of the of persistent organic pollutant compounds that increase lifestyle-related diseases, such as diabetes, obesity, and cancer. So, 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB153), which is one of the most common PCB contaminants in nature, was selected as a model compound to study the photocatalytic degradation of Fe3O4@SiO2@TiO2 core-shell structure. In this work, Fe3O4@SiO2@TiO2 nanocomposite was synthesized and characterized using transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), energy-dispersive X-ray (EDS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM) techniques. Then, the effect of parameters such as catalyst dosage, initial concentration of PCB 153, solution pH, amount of H2O2, and kind of co-solvent on photocatalytic degradation of PCB 153 by the synthesized nanocomposite was investigated. The high degradation efficiency of Fe3O4@SiO2@TiO2 nanocomposite, which was 96.5%, was obtained at 4 g/l of the catalysts, 4 ppm of PCB 153, pH 5, 20 mM H2O2, 2 h of reaction time, and acetone as a cosolvent. Also, the rate of mineralization for Fe3O4@SiO2@TiO2 nanocomposite with H2O2 and UV-LED irradiation was 75.3% which had a significant efficiency compared to control experiments. Moreover, the mentioned photocatalysts are possible to be reused through exposing to external magnetic field, with insignificant decrease in the catalytic activity even after 6 cycles. The photocatalytic degradation process has an effective and environmental friendly effect on the degradation of organic pollutants. [ABSTRACT FROM AUTHOR]

• Degradation of AR14 in water was accomplished using UV-LED/PS system. • Pulsed and continuous UV-LED illuminations were compared for AR14 degradation. • Impact of pulse irradiation parameters on photooxidative removal of AR14 was conducted. • Pulsed irradiation resulted in comparable degradation as continuous illumination. • Results demonstrated the higher quantum efficiency by lower pulse period and higher duty cycle. Removal of organic contaminants by UV-based advanced oxidation processes (AOPs) has been considered as one of the most effective procedures among environmental remediation methods. Ultraviolet light-emitting diodes (UV-LEDs) have possessed a unique place as an emerging technology in AOPs. In the present research, the impact of pulsed illumination on the overall efficiency of AR14 degradation by UV-LEDs and persulfate (PS) was considered. In comparison with continuous illumination, pulsed irradiation of UV-LEDs gifts the radiation of light in a programmed order to benefit its flexible pulse pattern, high-frequency utilization, and lower energy consumption attitudes. Duty cycles, pulse periods/frequencies, oxidant, and also removal kinetics were considered as operational parameters. Outcomes showed the efficacy of UV-LED and PS processes were both quite slow, while the hybrid route, UV-LED/PS showed great ability in degradation of AR14. Results depicted removal efficiency of (~93%) in UV-LED/PS system. Pulsed illumination has shown to be a beneficial technique providing higher output power and improved thermal management. 80% of the Duty cycle and 30 ms of the pulsed period was considered as optimized destruction state. Furthermore, results demonstrated that PS addition to the system significantly enhances the AR14 destruction efficiency by a pseudo-first-order rate constant (k) by 44 times. [Display omitted] [ABSTRACT FROM AUTHOR]

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• Direct photolysis of iohexol had significant dependence of UV wavelength spectral. • Distinctive photogenerated intermediates were observed with different photosensitizers. • Reactive sites and transformation pathways of iohexol were proposed. • Iohexol elimination and DBP yields by UV-LED irradiation followed the order of 255 > 265 > 275 > 285 nm. Iodinated X-ray contrast media (ICM) are ubiquitously present in water sources and challenging to eliminate using conventional processes, posing a significant risk to aquatic ecosystems. Ultraviolet light-emitting diodes (UV-LED) emerge as a promising technology for transforming micropollutants in water, boasting advantages such as diverse wavelengths, elimination of chemical additives, and no induction of microorganisms' resistance to disinfectants. The research reveals that iohexol (IOX) degradation escalates as UV wavelength decreases, attributed to enhanced photon utilization efficiency. Pseudo-first-order rate constants (k obs) were determined as 3.70, 2.60, 1.31 and 0.65 cm2 J−1 at UV-LED wavelengths of 255, 265, 275 and 285 nm, respectively. The optical properties of dissolved organic matter (DOM) and anions undeniably influence the UV-LED photolysis process through photon competition and the generation of reactive substances. The influence of Cl− on IOX degradation was insignificant at UV-LED 255, but it promoted IOX degradation at 265, 275 and 285 nm. IOX degradation was accelerated by ClO 2 −, NO 3 −and HA due to the formation of various reactive species. In the presence of NO 3 −, the k obs of IOX followed the order: 265 > 255 > 275 > 285 nm. Photosensitizers altered the spectral dependence of IOX, and the intermediate photoactivity products were detected using electron spin resonance. The transformation pathways of IOX were determined through density functional theory calculations and experiments. Disinfection by-products (DBPs) yields of IOX during UV-LED irradiation decreased as the wavelength increased: 255 > 265 > 275 > 285 nm. The cytotoxicity index value decreased as the UV-LED wavelength increased from 255 to 285 nm. These findings are crucial for selecting the most efficient wavelength for UV-LED degradation of ICM and will benefit future water purification design. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, the influences of thermal annealing and chemical passivation on the optical and electrical properties of ultraviolet light-emitting-diode (UV-LED) were investigated. The electroluminescence (EL) intensities of the LEDs under KOH treatment and thermal annealing increased by 48% and 81%, respectively compared to as-fabricated LED under current level of 10 mA. Cathodoluminescence (CL) mapping of UV-LEDs confirmed no variation of the density of the non-radiative recombination centers after surface treatments, and no obvious change in surface morphology was identified due to lacking of energy for surface atom migration. However, Raman spectroscopy indicates a relaxation of compressive strains inside the thin film after both thermal and chemical treatments, and conductive atomic force microscopy (c-AFM) also illustrated reduced leakage current after KOH passivation, which are responsible for the improved luminescence properties of UV-LEDs.

Puffball-like γ–MnO2 nanoparticles of about 40 ± 1 nm size, having a unique morphology and high BET surface area were synthesized under reflux conditions and subsequently modified with Cu2+. The as-synthesized nanoparticles were systematically characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT–IR), N2 adsorption–desorption isotherms (BET) and energy dispersive X-ray analysis (EDX). The puffball–γ–MnO2 nanoparticles showed remarkable photocatalytic activity in treatment of wastewater and decolorization of dyes, especially Rhodamine 6G in presence of ultraviolet light–emitting diodes (UV–LEDs) irradiation. Under the optimized conditions, 91.5% decolorization was obtained for 200 mL of a 5 ppm solution of Rhodamine 6G within 40 min. It was also found that inclusion of Cu2+ has a significant positive effect (up to 17%) on the performance of these newly devised nanoparticles. [ABSTRACT FROM AUTHOR]

Limited sources exist for the application of germicidal ultraviolet (GUV) radiation. Ultraviolet light-emitting diodes (UV-LEDs) have significantly improved in efficiency and are becoming another viable source for GUV. We have developed a mean differential continuous pulse method (M-DCP method) for optical measurements of light-emitting diodes (LEDs) and laser diodes (LDs). The new M-DCP method provides an improvement on measurement uncertainty by one order of magnitude compared to the unpublished differential continuous pulse method (DCP method). The DCP method was already a significant improvement of the continuous pulse method (CP method) commonly used in the LED industry. The new M-DCP method also makes it possible to measure UV-LEDs with high accuracy. Here, we present the DCP method, discuss the potential systematic error sources in it, and present the M-DCP method along with its reduced systematic errors. This paper also presents the results of validation measurement of LEDs using the M-DCP method and common test instruments. [ABSTRACT FROM AUTHOR]

Controlling the microbial load in the environment is crucial to prevent the spread of organisms. The continuous spread of nosocomial infections in hospital facilities and the emergence of the coronavirus (COVID-19) highlighted the importance of disinfection processes in health safety. This work aimed to evaluate the effectiveness of LED-based disinfection lamps on bacteria from the ESKAPEE group and virus phage in vitro inactivation to be applied in hospital environments and health facilities disinfection. This study evaluated the effect of different UV wavelengths (275 nm, 280 nm (UVC), 310 nm (UVB) and 340 nm (UVA)) on the disinfection process of various microbial indicators including E. coli , S. aureus , P. aeruginosa , B. subtilis and Bacteriophage lambda DSM 4499. Exposure time (5 min-30 min), exposure distance (0.25 m and 0.5 m) and surface materials (glass, steel, and polished wood) were evaluated on the disinfection efficiency. Furthermore, the study determined the recovery capacity of each species after UV damage. UVC-LED lamps could inactivate 99.99 % of microbial indicators after 20 min exposures at a 0.5 m distance. The exposure time needed to completely inactivate E. coli , S. aureus , P. aeruginosa , B. subtilis and Bacteriophage lambda DSM 4499 can be decreased by reducing the exposure distance. UVB-LED and UVA-LED lamps were not able to promote a log reduction of 4 and were not effective on B. subtilis or bacteriophage lambda DSM 4499 inactivation. Thus, only UVC-LED lamps were tested on the decontamination of different surface materials, which was successful. P. aeruginosa showed the ability to recover from UV damage, but its inactivation rate remains 99.99 %, and spores from B. subtilis were not completely inactivated. Nevertheless, the inactivation rate of these indicators remained at 99.99 % with 24 h incubation after UVC irradiation. UVC-LED lamps emitting 280 nm were the most indicated to disinfect surfaces from microorganisms usually found in hospital environments., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Paula V. Morais reports financial support was provided by Foundation for Science and Technology. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

In this research we present a low-cost system for breath acetone analysis based on UV-LED photoacoustic spectroscopy. We considered the end-tidal phase of exhalation, which represents the systemic concentrations of volatile organic compounds (VOCs) - providing clinically relevant information about the human health. This is achieved via the development of a CO 2 -triggered breath sampling system, which collected alveolar breath over several minutes in sterile and inert containers. A real-time mass spectrometer is coupled to serve as a reference device for calibration measurements and subsequent breath analysis. The new sensor system provided a 3σ detection limit of 8.3 ppbV and an NNEA of 1.4E-9 Wcm -1 Hz -0.5 . In terms of the performed breath analysis measurements, 12 out of 13 fell within the error margin of the photoacoustic measurement system, demonstrating the reliability of the measurements in the field., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper, (© 2024 The Authors.)

This paper proposes a lens design method for effectively collimating the light emitting from a light-emitting diode (LED). This collimating lens contains two aspherical lens surfaces which can be mathematically characterized using a few designing parameters, and hence is called an analytic collimating lens. An optical ray-tracing algorithm has been developed for these analytic collimating lenses to analyze their optical performance and to optimize their designs. Six high-power and commercially available ultraviolet (UV) LEDs are chosen as examples for demonstrating the optimal collimating lens design. For each UV-LED, the corresponding optical collimating lens is determined by inputting the ray data file provided by the manufacture over a finite-size emitting area. The divergent angles of the six UV-LEDs have been successfully collimated to a narrow range in between 1.56° to 2.84° from their original radiation angle around 46° to 120°. Furthermore, the proposed analytical collimating lenses are suitable for mass-production using standard mold injection methods, and hence possess great potentials for industry applications of LEDs.

Three-dimensional (3D) printing has become a popular technique in many areas. One emerging field is the use of 3D printing for the development of 3D drug delivery systems (DDS) and drug-loaded medical devices. This article describes a novel concept for the fabrication of timecontrolled drug delivery systems based on stereolithography combined with inkjet printing. An inkjet printhead and an UV-LED light source have been integrated into an existing stereolithography system. Inkjet printing is used to selectively incorporate active pharmaceutical ingredients (API) during a stereolithographic 3D printing process. In an initial experimental study, poly (ethylene glycol) diacrylate (PEGDA) was used as polymer whereas 2-Hydroxy-4´-(2- hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959) and Lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) were used as photoinitiators. Basic structures could be manufactured successfully by the new hybrid 3D printing system.

2, 4-Dichlorophenol is one of the most common and abundant pollutants widely found in various industrial effluent. The obvious effect of this organic compound on health and environment depends on enhancing the degradation efficiency of this aqueous pollutant before wastewater being discharged into the receiving water. Therefore, in this study, removal of 2, 4-dichlorophenol from aqueous solution was investigated through using UV-LED/TiO2 process. In this experimental study, removal of 2, 4-DCP in the presence of TiO2 by using UV-LED in a bench scale reactor was examined. The effects of operational parameters such as pH (3-11), initial concentration of 2, 4-DCP (50-200mg/L), TiO2 concentration (0.003-0.025mol/L) and ionic strength were evaluated. The results indicated that removal of 2, 4-DCP was influenced by different operational parameters. The highest 2, 4-DCP removal rate were obtained at pH=3 by adding 0.012 mol/L of TiO2 to solution with an initial concentration of 50mg/L of 2, 4-DCP which more than 95.82% of 2, 4-DCP was removed. While UV-LED and TiO2 were used separately, the 2, 4-DCP removal efficiency was 32.11% and 36.56%, respectively. Also, the results indicated that maximum COD removal rate was 71.5% in optimum condition and also indicated lack of impact on ionic strength changes for removal of organic material. The results indicated that combined TiO2/UV-LED process in optimal conditions can be used as a new technology for treatment of various industrial wastewater containing 2, 4-DCP.

In the face of the water scarcity problem, the use of treated wastewater emerges as a viable alternative to meet the demand of the agricultural sector, the main consumer of available water in the world. Thus, the development of technologies to provide safe wastewater reuse is a priority. We evaluated the reduction rate of the fecal indicator Escherichia coli naturally present in effluent from an urban wastewater treatment plant (WWTP) submitted to UV-LED (Ultraviolet-Light-Emitting Diodes) radiation, emitting UVA (365 and 405 nm) or UVC (255 and 280 nm), used alone or coupled. The 280-nm wavelength seems to be crucial to the success of the disinfection systems, as all the programs that used this wavelength reached a 4-log reduction of E. coli. [ABSTRACT FROM AUTHOR]

Effective and reliable interconnections are crucial for microfluidics to connect with the macro world. Current microfluidic interfaces are still bulky, expensive, or with issues of clogging and material limitation. In this study, a novel ultraviolet (UV)-assisted coaxial three-dimensional (3D) printing approach was proposed to fabricate hollow microfluidic connectors with advantages of rapid prototyping, fixture-free, and materials compatible. An assembled coaxial nozzle was designed to enable co-flow extrusion, where the inner flow (water) served as the sacrificial layer and the outer flow (adhesive) was cured for shell formation. Furthermore, a converged UV-LED light source was attached to the coaxial nozzle for UV curing of adhesives. UV rheological characterizations were performed to study the UV curing kinematics, and the gelation time was employed to describe the state transition behaviors of UV curable adhesives used in the study. To explore requirements for successful hollow connectors direct printing, processing criteria such as co-flow regime and pre-cure time were investigated. The hollow connectors with an inner channel diameter of ~150 μ m and a height of 5 mm were successfully printed on polymethyl methacrylate (PMMA) and glass substrate. The integration feasibility of the proposed method was also demonstrated by the presented microfluidic device with printed hollow connectors. [ABSTRACT FROM AUTHOR]

Copyright of Imaging Science & Photochemistry is the property of Imaging Science & Photochemistry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Imaging Science & Photochemistry is the property of Imaging Science & Photochemistry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)