UVC Light-emitting Diodes Research Articles

Ultraviolet (UV-C) Light Systems for the Inactivation of Feline Calicivirus and Tulane Virus in Model Fluid Foods.

Conventional UV-C (254nm) inactivation technologies have limitations and potential operator-safety risk. To overcome these disadvantages, novel UV-C light-emitting diodes (LED) are developed and investigated for their performance. This study aimed to determine the inactivation of human norovirus (HuNoV) surrogates, Tulane virus (TV), and feline calicivirus (FCV-F9), by UV-C (254nm) in comparison to UV-C LED (279nm) in phosphate-buffered saline (PBS) and coconut water (CW). Five-hundred microliters of FCV-F9 (~ 5 log plaque forming units (PFU)/mL) or TV (~ 6 log PFU/mL) were added to 4.5mL PBS or CW in continuously stirred glass beakers and exposed to 254nm UV-C for 0 up to 15min (maximum dosage of 33.89mJ/cm2) or 279nm UV-C LED for 0 up to 2.5min (maximum dosage of 7.03mJ/cm2). Recovered viruses were assayed in duplicate from each treatment replicated thrice. Mixed model analysis of variance was used for data analysis. Significantly lower D10 values were obtained in PBS and CW (p ≤ 0.05) for both tested viruses using UV-C LED (279nm) where FCV-F9 showed D10 values of 7.08 ± 1.75mJ/cm2 and 3.75 ± 0.11mJ/cm2, while using UV-C (254nm) showed D10 values of 13.81 ± 0.40mJ/cm2 and 6.43 ± 0.44mJ/cm2 in PBS and CW, respectively. Similarly, lower D10 values were obtained for TV of 3.91 ± 1.03mJ/cm2 and 4.26 ± 1.02mJ/cm2 with 279 nmUV-C LED and were 18.76 ± 3.16mJ/cm2 and 10.21 ± 1.48mJ/cm2 with 254nm UV-C in PBS and CW, respectively. Viral resistance to these treatments was fluid-matrix dependent. These findings indicate that use of 279nm UV-C LED is more effective in inactivating HuNoV surrogates than conventional 254nm UV-C in the tested fluids.

Spectral Dependence of Bovine Coronavirus Photoinactivation under Irradiation by UV-A, UV-B, and UV-C Light-Emitting Diodes

Spectral Dependence of Bovine Coronavirus Photoinactivation under Irradiation by UV-A, UV-B, and UV-C Light-Emitting Diodes

Examining Degradation Mechanisms in Strain-Relaxed AlGaN-Based UV-C Light-Emitting Diodes Using Raman Spectroscopy

Examining Degradation Mechanisms in Strain-Relaxed AlGaN-Based UV-C Light-Emitting Diodes Using Raman Spectroscopy

Progress and Outlook of 10% Efficient AlGaN‐Based (290–310 nm) Band UVB LEDs

Eco‐friendly and low‐cost aluminum gallium nitride (AlGaN) for the epitaxial growth of ultraviolet‐B (UVB) light‐emitting diodes (LEDs) on c‐Sapphire has the possibility of high external‐quantum efficiency (EQE). In this review paper a special growth techniques for 50% relaxed and 4 μm thick AlGaN buffer layer underneath the multi‐quantum wells (MQWs) are challenged to achieve a maximum internal‐quantum efficiency of 50–57% in 310–290 nm band UVB LEDs. The influence of a thin “Valley” layer in p‐type multi‐quantum barrier electron‐blocking layer on 2D hole generation and injection via intraband tunneling was attempted. Finally, the influence of soft polarized Mg‐doped p‐type Al‐graded AlGaN hole injection layer assisted by excimer laser annealing for better hole injection toward the MQWs was investigated and quite high hole concentration of 2 × 1016 cm−3 and resistivity of 24 Ω‐cm at room temperature was achieved. Consequently, the EQE of transparent 310 and 304 nm UVB LEDs, respectively, reached to a confirmed world record values of ≈5% and ≈10% with light powers of 29 and 40 mW on wafer. This EQE value can surpass 21% if flip‐chip, nanoPSS, photonic crystal, and lens with highly reflective p‐electrodes are incorporated in LED.

Development and application of the UVC LED-based spectrophotometer for high frequency online monitoring of nitrate concentration in municipal wastewater

Developing a fast, sensitive and stable sensor for online monitoring nitrate concentration is an urgent need for the optimization of denitrification processes in wastewater treatment plants (WWTPs). In this study, the miniaturized spectrophotometric nitrate sensor was developed using UVC light-emitting diodes (LEDs) coupled with AlGaN or SiC-based photodiodes. The use of novel SiC photodiodes could effectively eliminate UVB and UVA light in the 230 nm LED emission spectra. Replacing 235 nm UVC-LED with 230 nm UVC-LED could effectively increase the detection sensitivity but not the linear range that follows the Lambert-Beer's law. The influences of dissolved organic matter (DOM) on nitrate analysis could be corrected by a unified coefficient α across the NO3--N concentration ranging in 0–50 mg/L. Across the investigated WWTP samples, the correction coefficient α was mainly determined by the fractions of humic substances with apparent molecular weight (MW) of 1.5–9.0 kDa, while the degradation of the large MW proteinaceous biopolymer resulted in dramatic variations of correction coefficient α along the WWTP A/A/O process. Microfiltration membranes with pore sizes ≤ 30 µm could sufficiently eliminate the influences of particles in effluents on photometric nitrate analysis. The ultrafiltration and enhanced coagulation treatment could effectively remove the biopolymer fractions of DOM in wastewater, and thus alleviate its influences on sensitivity and accuracy of nitrate analysis. The spectrophotometric nitrate sensors were successfully applied for on-line monitoring NO3--N concentrations in the influent and effluent of denitrifying biofilter in a municipal WWTP, providing high-frequency feedback signals to precise control of feeding external carbon source.

Using low-temperature growth to resolve the composition pulling effect of UV-C LEDs

One approach to improving the output power of ultraviolet (UV-C) light-emitting diodes (LEDs) is to adopt an electron-blocking layer (EBL) with a high barrier. However, the intended effect may not be realized because of the composition pulling effect, which is the unintended occurrence of a gradient layer at an AlGaN/AlGaN hetero-interface with substantial differences in the Al composition. Here, we demonstrate that low-temperature growth (i.e., <1000 °C) can be used to control the unintentional gradient layer at an AlN/AlGaN hetero-interface between a barrier layer and AlN-EBL with a difference in Al compositions of more than 30%. LEDs with an emission wavelength of 265 nm were fabricated, and an AlN-EBL was grown at low temperature to realize an abrupt interface. At an applied current of 100 mA, growing the EBL under low-temperature conditions improved the forward voltage by 0.5 V and remarkably improved the peak luminous intensity by 1.4–1.6 times. Our results can be used to realize UV-C LEDs with a steep EBL and further improve their device characteristics.

Effect of channel configuration on the water sterilization efficiency of a photoreactor with ultraviolet C light-emitting diodes

This study investigated the effect of flow channel configuration on the water disinfection efficiency of a photoreactor with ultraviolet (UV) C light-emitting diodes (LEDs). The synergistic effect of UV radiation and hydrodynamics on microbial inactivation was analyzed to obtain the UV fluence distribution for five channel configurations. Simulations revealed that the serpentine and spiral configurations led to similar microbial residence times. However, the high mixing efficiency in the serpentine configuration resulted in the efficiency of Escherichia coli inactivation being higher in this configuration than in the spiral configuration. Although the pin configuration achieved the highest average UV fluence of the five channel configurations, the E. coli inactivation value in this configuration was low because approximately 25 % of the microbes received UV fluence of less than 5 mJ/cm2. This study modified the pin configuration, and the results revealed that this configuration effectively increased the UV fluence received by microbes and eliminated low-fluence particles. At a flow rate of 120 mL/min, the average UV fluence in the modified pin configuration was 43 %, 52 %, and 72 % higher than those in the serpentine, spiral, and bioinspired configurations, respectively. Experimental findings indicated that at a maximum flow rate of 160 mL/min, the E. coli inactivation value achieved in the modified pin configuration was 3.3 log, which was approximately 0.4, 1.2, 1.5, and 1.8 log higher than those achieved in the serpentine, spiral, pin, and bioinspired configurations, respectively. The results of this study provide insights regarding enhancement of the UV exposure of microorganisms and can be used as a guideline in flow channel design for water disinfection reactors with UV-C LEDs.

APPLICATION OF ULTRAVIOLET LED SYSTEMS IN THE GRAIN PROCESSING AND COMPOUND FEED INDUSTRIES

The materials of the article outline the features of the use of ultraviolet LED systems in industry, and propose a solution for their use in the grain processing and compound feed industry. Ultraviolet light (UV) is a well-researched and widely used means of decontamination and disinfection of surfaces, air, water, and food. Usually, far ultraviolet radiation (or ultraviolet C, UVC) with a wavelength of 254 nm is used, which corresponds to the peak absorption of wave energy by the DNA of a living cell. There is a mathematical mechanism for calculating the parameters of radiation in relation to its effect on microorganisms: a curve describing the microbial death depending on the increase in the radiation dose received by the bacteria and formulae for the relationship between the three main parameters (dose, radiation flux and exposure duration). Ultraviolet lamps (tubes) are commonly used, on the basis of which a large number of emitters have been developed for different needs. There are also emitters for grain and feed disinfection in use, but only outside of industrial production lines. Ultraviolet irradiation is not used directly on manufacturing lines so far. However, it can be used to reduce the microbial burden of a feed or food product prior to packaging the finished product. For this purpose, ultraviolet light-emitting diodes (LEDs) available on the world market today can be used. However, their use faces difficulties: ultraviolet LEDs emit wavelengths longer than lamps (at about 275 nm or more), which requires an increase in the duration of irradiation, which is undesirable for industrial processing of products directly on the line. However, the small size of the UVC LEDs will allow them to be installed in grain processing and feed mills inside equipment (magnetic separators, gravity feeders, etc.) with appropriate protection against damage by moving material. In addition, suspended emitters of any configuration can be placed above belt conveyors that move material at a certain speed. This approach will require certain measures to control the efficiency of irradiation (requires microbiological studies) and to protect personnel from the harmful effects of ultraviolet rays (means of personal and collective protection, measurement of radiation intensity).

The application of UVC light-emitting diodes irradiation for decontamination in fresh Tartary buckwheat noodles

Abstract Fresh noodles are easily to deterioration and contamination by microorganisms, improving its quality retention remains challenging. This study shows the potential of Ultraviolet C light-emitting diodes (UVC-LEDs, 275 nm) for the inactivation of Bacillus subtilis or Staphylococcus aureus inoculated on Tartary buckwheat fresh Tartary buckwheat noodles (FTBN) and as well as the inactivation of natural microbiota and quality of FTBN treated with UVC-LEDs during storage at 25 °C. The results showed that within a certain irradiation range of UVC-LEDs (0–1200 mJ/cm2), B. subtilis and S. aureus inoculated with FTBN would have deactivation and the dosage-dependent manner (P < 0.05). The initial total plate count of FTBN treated with UVC-LEDs was significantly reduced (P < 0.05) and shelf life was extended to 3 days. Changes of the pH, color, water distribution, cooking characterisitcs, and texture properties of FTBN treated with UVC-LEDs were delayed during storage. Based on these advantages, UVC-LEDs has good sterilization performance and improves the shelf life of noodles.

Design, Realization, and Test of Ultraviolet-C LED Arrays Suitable for Long-Lasting Irradiation of Biological Samples

We present the electrical and optical design, assembling, and thorough experimental characterization of two compact arrays of short-wavelength ultraviolet (UV-C) light-emitting diodes (LEDs) suitable for near-field irradiation. Through a combination of technical expedients, we have achieved effective thermal management such that long-lasting irradiations are possible without appreciable deterioration of UV-C emission. We successfully used these compact UV-C LED arrays for long lasting irradiation tests aimed at generating the biosynthesis of defensive metabolites that enhance the resistance of plants and fruits to pathogen attacks. Finally, we comment on the possibility of implementing these compact UV-C sources on robotic systems to make an automated device suitable to reduce pesticide use in agricultural crops.

High performance and high yield sub-240 nm AlN:GaN short period superlattice LEDs grown by MBE on 6 in. sapphire substrates

We develop ultraviolet (UV) light emitting diodes (LEDs) that operate in the sub-240 nm (far UVC) regime. The traditional limitations of high Al content AlGaN—the low light extraction efficiency due to transverse magnetic polarization and the poor doping efficiency—were overcome by using AlN:GaN short period superlattices (SPSLs) of varying compositions throughout almost the entire device structure. The quality of our molecular beam epitaxy process for growing SPSL devices was verified via transmission electron microscopy and x-ray diffraction—together, these demonstrate our capacity for growing high quality interfaces with a great deal of control over the thicknesses of each individual layer. Resistivity measurements of our SPSL were three times smaller than bulk AlGaN of similar composition due to the improved doping efficiency. Devices fabricated on 6 in. sapphire substrates showed uniform performance, leading to over 10 000 functional devices per wafer. Packaged diodes exhibited a peak wall plug efficiency of 0.55% and an output power of 1.7 mW when operated at peak efficiency. The devices had an operating life (70% initial power) of 2800 h (at 20 mA continuous wave). Additionally, they could be driven as high as 1 A, which resulted in a record for radiant flux of a far UVC LED grown on sapphire (17.4 mW).

Removal of diclofenac by UV-B and UV-C light-emitting diodes (LEDs) driven advanced oxidation processes (AOPs): Wavelength dependence, kinetic modelling and energy consumption

In this study, the degradation of diclofenac (DCF), a frequently detected non-steroidal pharmaceutical, was evaluated by using UV-B and UV-C (265, 285, and 310 nm) light-emitting diodes (LEDs) alone and in combination with hydrogen peroxide (UV/H2O2) and free chlorine (UV/FC). The degradation of DCF followed a pseudo first-order kinetic, and their trend reflected the pattern of the molar absorption coefficients of the DCF and the oxidants. A positive synergistic factor was found for the UV-LED driven advanced oxidation processes in almost all cases, but despite the higher degradation rates, the overall electricity demand is similar to UV alone due to the oxidants’ energy cost. The rigorous kinetic degradation mechanisms at different wavelengths were proposed for the two processes, UV/H2O2 and UV/FC, where the predicted values were respectively kHO = 9.12 · 109 M−1 s−1 and kCl = 1.30 · 1010 M−1 s−1. No significant synergy (p > 0.05) was found for the dual-wavelength system (265 + 285 nm), and the time-based constants in all cases changed linearly with lamp intensity. Finally, dissolved organic carbon and phytotoxicity analysis revealed low mineralisation (around 20–30%) associated with the formation of stable dimers and a decrease in toxicity towards tomato and radish seeds. In the main, this work shows the great potential of implementing wavelength-specific LEDs in water treatments and effectively designing the reactor playing with adjustable intensities and kinetic degradation rates.

60Co γ-irradiation of AlGaN UVC light-emitting diodes

270 nm AlGaN UV Light-Emitting Diodes (LEDs) were exposed to 1–5 Mrad fluences of Co-60 γ-rays. The effect of the exposure to radiation was a ∼40% reduction in optical output after the highest fluence. No significant midgap emission was induced in the electro-luminescence spectra of the irradiated LEDs. We ascribe the decrease in optical output to creation of non-radiative states within the active regions. There were small (5–10%) increases in forward and reverse current as a result of irradiation with an effective carrier removal rate of <1 cm−1. The irradiation did not produce any increase in degradation rate of the LEDs output power under high drive current (95 mA) compared to unirradiated devices, which is consistent with the lack of midgap emission. The relatively small changes in electrical and optical properties, along with the resistance of the AlxGa1-xN/AlN to displacement damage effects indicate these devices may be well-suited to harsh terrestrial and space radiation applications.

Hillock Related Degradation Mechanism for AlGaN-Based UVC LEDs.

Heteroepitaxial growth of high Al-content AlGaN often results in a high density of threading dislocations and surface hexagonal hillocks, which degrade the performance and reliability of AlGaN-based UVC light emitting diodes (LEDs). In this study, the degradation mechanism and impurity/defect behavior of UVC LEDs in relation to the hexagonal hillocks have been studied in detail. It was found that the early degradation of UVC LEDs is primarily caused by electron leakage. The prominent contribution of the hillock edges to the electron leakage is unambiguously evidenced by the transmission electron microscopy measurements, time-of-flight secondary ion mass spectrometry, and conductive atomic force microscopy. Dislocations bunching and segregation of impurities, including C, O, and Si, at the hillock edges are clearly observed, which facilitate the trap-assisted carrier tunneling in the multiple quantum wells and subsequent recombination in the p-AlGaN. This work sheds light on one possible degradation mechanism of AlGaN-based UVC LEDs.

Modeling the electrical degradation of AlGaN-based UV-C LEDs by combined deep-level optical spectroscopy and TCAD simulations

The long-term stability of ultraviolet (UV)-C light-emitting diodes (LEDs) is of major importance for many applications. To improve the understanding in this field, we analyzed the degradation of AlGaN-based UVC LEDs and modeled the variation of electrical characteristics by 2D simulations based on the results of deep-level optical spectroscopy (DLOS). The increase in the forward leakage current observed during ageing was ascribed an increase in trap-assisted tunneling. The analysis of the degradation kinetics suggests the role of a defect diffusion process, possibly involving impurities coming from the p-type layers.

Impact of Mg-doping on the performance and degradation of AlGaN-based UV-C LEDs

We investigate the impact of Mg-doping on the performance and degradation kinetics of AlGaN-based UV-C light-emitting diodes (LEDs). By comparing LEDs from three wafers with different nominal doping levels [Mg/(Al+Ga) ratio: 0.15%, 0.5%, and 1% in the gas phase during epitaxy] in the AlGaN:Mg electron-blocking layer (EBL), we demonstrate the following results: (i) A higher Mg-doping in the EBL results in a higher optical power at low current levels, which is ascribed to an increased hole injection efficiency. (ii) The reduction of the optical power follows a non-exponential trend, which can be reproduced by using the Hill's formula and is ascribed to the generation/activation of defects within the quantum wells. (iii) A higher Mg-doping in the EBL mitigates the degradation rate. An interpretation of the experimental data is proposed, assuming that hydrogen, which is present in and moving from the EBL, can reduce the rate of de-hydrogenation of point defects in the active region, which is responsible for degradation.

Short-Wave Ultraviolet-Light-Based Disinfection of Surface Environment Using Light-Emitting Diodes: A New Approach to Prevent Health-Care-Associated Infections.

Ultraviolet (UV)-C irradiation is a promising method for microbial eradication on surfaces. Major developments have taken place in UV-C light-emitting diodes (LEDs) technology. In this study, we examined the suitability of UV-C LED-based surface disinfection in hospitals. We tested the efficacy of UV-C LED surface treatment on different microorganisms dried on a carrier surface or in a liquid solution. The influences of soiling, shading, surface material, radiation wavelength, microbial load and species on the disinfection performance were investigated. UV-C LED caused a reduction of >5 log10 levels of E. coli, S. aureus and C. albicans, whereas 3 log10 reduction was observed for G. stearothermophilus spores. The components of the medium led to a reduced UV-C LED efficiency compared to buffered solutions. We observed that the microbial load and the roughness of the carrier surface had a major influence on the UV-C LED disinfection efficiencies, whereas shading had no impact on inactivation. This study showed that UV-C is suitable for surface disinfection, but only under certain conditions. We showed that the main factors influencing microbial inactivation through UV-C light (e.g., intrinsic and extrinsic factors) had a similar impact when using a UV-C LED radiation source compared to a conventional UV-C lamp. However, the potential of LEDs is contributed by their adjustable wavelength and customizable geometry for the decontamination of medical devices and surfaces, and thereby their ability to overcome shading effects.

Antibacterial effects of vinegar N6 and UV-C light-emitting diodes against Shiga toxin-producing and enterohemorrhagic Escherichia coli in fresh beef.

The online version contains supplementary material available at 10.1007/s10068-023-01260-x.

Inactivation of the waterborne marine pathogen Vibrio alginolyticus by photo-chemical processes driven by UV-A, UV-B, or UV-C LED combined with H2O2 or HSO5−

Ultraviolet (UV) radiation is a well-implemented process for water disinfection. The development of emergent UV sources, such as light-emitting diodes (LEDs), has afforded new possibilities for advanced oxidation processes. The emission wavelength is considered to be an important factor for photo-chemical processes in terms of both biological damage and energetic efficiency, as the inactivation mechanisms and mode-of-action may differ according to the wavelength that is applied. In addition, these processes merit exploration for inactivating emerging pathogens, such as marine vibrios, that are important bacteria to control in maritime activities. The main goal of this study was to compare the disinfection efficacy of several UV-LED driven processes with different modes of action. First, the effect of UV-LEDs was assessed at different UV ranges (UV-A, UV-B, or UV-C). Second, the possible enhancement of a combination with hydrogen peroxide (H2O2) or peroxymonosulfate salt (HSO5−) was investigated under two different application strategies, i.e. simultaneous or sequential. The results obtained indicate a high sensitivity of Vibrio alginolyticus to UV radiation, especially under UV-B (kobs = 0.24 cm2/mJ) and UV-C (kobs = 1.47 cm2/mJ) irradiation. The highest inactivation rate constants were obtained for UV/HSO5− (kobs (cm2/mJ)=0.0007 (UV-A); 0.39 (UV-B); 1.79 (UV-C)) with respect to UV/H2O2 (kobs (cm2/mJ)=0.0006 (UV-A); 0.26 (UV-B); and 1.54 (UV-C)) processes, however, regrowth was avoided only with UV/H2O2. Additionally, the disinfection enhancement caused by a chemical addition was more evident in the order UV-A > UV-B > UV-C. By applying H2O2 (10 mg/L) or HSO5− (2.5 mg/L) in a sequential mode before the UV, negligible effects were obtained in comparison with the simultaneous application. Finally, promising electrical energy per order (EEO) values were obtained as follows: UV/HSO5− (EEO (kWh/m3)=1.68 (UV-A); 0.20 (UV-B); 0.04 (UV-C)) and UV/H2O2 (EEO (kWh/m3)=2.15 (UV-A); 0.32 (UV-B); 0.04 (UV-C)), demonstrating the potential of UV-LEDs for disinfection in particular activities such as the aquaculture industry or maritime transport.

Quantifying the effectiveness of ultraviolet-C light at inactivating airborne Mycobacterium abscessus

Mycobacterium abscessus (MABS) group are environmental organisms that can cause infection in people with cystic fibrosis (CF) and other suppurative lung diseases. There is potential for person-to-person airborne transmission of MABS among people with CF attending the same care centre. Ultraviolet light (band C, UV-C) is used for Mycobacterium tuberculosis control indoors; however, no studies have assessed UV-C for airborne MABS. To determine whether a range of UV-C doses increased the inactivation of airborne MABS, compared with no-UVC conditions. MABS was generated by a vibrating mesh nebulizer located within a 400L rotating drum sampler, and then exposed to an array of 265nm UV-C light-emitting diodes (LED). A six-stage Andersen Cascade Impactor was used to collect aerosols. Standard microbiological protocols were used for enumerating MABS, and these quantified the effectiveness of UV-C doses (in triplicate). UV-C effectiveness was estimated using the difference between inactivation with and without UV-C. Sixteen tests were performed, with UV-C doses ranging from 276 to 1104μWs/cm2. Mean (±SD) UV-C effectiveness ranged from 47.1% (±13.4) to 83.6% (±3.3). UV-C led to significantly greater inactivation of MABS (all P-values ≤0.045) than natural decay at all doses assessed. Using an indoor model of the hospital environment, it was estimated that UV-C doses in the range studied here could be safely delivered in clinical settings where patients and staff are present. This study provides empirical in-vitro evidence that nebulized MABS are susceptible to UV-C inactivation.