UV-C LEDs Research Articles

Multi-Disciplinary Optimization of UV-C Filter for Air Disinfection

Because of the recent COVID-19 pandemic, the problem of preventing and containing the diffusion of pathogens spread through air has become a main topic of research. The problem is particularly important for specific environments, such as dental or other medical practices, where the aerosol treatments in open-mouth patients, combined with closed and crowded rooms, raise the risk of infection. As an efficient countermeasure, in this study we propose a solution that is able to remove the risk at the source, through the aspiration of the aerosol and the neutralization of the bacterial load by means of a UV-C LED filter, which releases the sterilized air in the environment. To maximize the efficiency of the solution, in this study we performed a numerical multi-disciplinary optimization (MDO) of the filter, coupling numerical simulations of multiple disciplines (CFD and electromagnetics) by the process automation and optimization environment modeFRONTIER of ESTECO. Geometrical parameters of the filter are updated for each candidate solution proposed by the optimization algorithm, and their performance in terms of viral neutralization efficiency and air mass flow rate are evaluated by the simulations, until the optimal solution is found. The methodology and results of the study are presented.

Decontamination of Fused-Silica Surfaces by UVC Irradiation as Potential Application on Touchscreens.

The contamination of surfaces by antibiotic-resistant pathogens presents an escalating challenge, especially on touchscreens in public settings such as hospitals, airports, and means of transport. Traditional chemical cleaning agents are often ineffective and leave behind harmful residues. Thus, the application of optical radiation is gaining relevance as a rapid, effective, and environmentally friendly disinfection method. This study examines the contamination of publicly accessible touchscreens and the efficacy of an irradiation approach for the radiation disinfection of microorganisms on quartz surfaces with UVC LEDs. In this setup, the LED radiation is laterally coupled into a quartz plate that serves as cover glass of a simplified touchscreen model. The process allows for the irradiation of microorganisms on the surface, without the user being exposed to hazardous radiation. To assess the efficacy of the disinfection process, a range of bacteria, mostly ESKAPE surrogates, such as Staphylococcus carnosus, Acinetobacter kookii, Escherichia coli, Enterococcus mundtii, and additionally Micrococcus luteus, were spread over a quartz plate with a homebuilt nebulization system. After operating the side-mounted LEDs for 30 s, a reduction in all bacteria except M. luteus by more than three orders of magnitude was observed. In the case of M. luteus, a significant reduction was achieved after 60 s (p < 0.05). This result demonstrates the potential of side-mounted UVC LEDs for rapid disinfection of touchscreens between two users and thus for reducing the spread of pathogens without irradiating humans.

Tuneable Red and Blue Emission of Bi3+-Co-Doped SrF2:Eu3+ Nanophosphors for LEDs in Agricultural Applications.

Tunable blue/red dual-emitting Eu3+-doped, Bi3+-sensitized SrF2 phosphors were synthesized utilizing a solvothermal-microwave method. All phosphors have cubic structure (Fm-3m (225) space group) and well-distinct sphere-like particles with a size of ~20 nm, as examined by X-ray diffraction and transmission electron microscopy. The diffuse reflectance spectra reveal a redshift of the absorption band in the UV region as the Bi3+ concentration in SrF2: Eu3+ phosphor increases. Under the 265 nm excitation, photoluminescence spectra show emission at around 400 nm from the host matrix and characteristic orange 5D0 → 7F1,2 and deep red 5D0 → 7F4 Eu3+ emissions. The red emission intensity increases with an increase in Bi3+ concentration up to 20 mol%, after which it decreases. The integrated intensity of Eu3+ red emission in the representative 20 mol% Bi3+ co-doped SrF2:10 mol% Eu3+ shows twice as bright emission compared to the Bi3+-free sample. To demonstrate the potential application in LEDs for artificial light-based plant factories, the powder with the highest emission intensity, SrF2: 10Eu, 20 Bi, was mixed with a ceramic binder and placed on top of a 275 nm UVC LED chip, showing pinkish violet light corresponding to blue (409 nm) and red (592, 614, and 700 nm) phosphors' emission.

Enhancing food safety: Employing ultraviolet-C light emitting diodes for water, leaf, and surface disinfection

This study aimed to explore the use of ultraviolet-C light emitting diodes that emit light at 255 nm and 265 nm, to disinfect bacteria present at occurrence levels and spiked in water matrices, salads and stainless-steel surfaces. The UV-C LEDs effectively inactivated bacteria associated with food outbreaks (Salmonella enterica, Listeria monocytogenes and Escherichia coli) as well as a cocktail of bacteria isolated from packaged salads. Combining the wavelengths did not enhance disinfection. Even low UV fluences of 4 mJ/cm2 achieved a significant 6-log reduction of bacteria spiked in water at high initial concentrations of approximately 108 CFU/mL. Exposure of salad (lettuce and arugula) leaves (110 mJ/cm2) and contaminated stainless-steel surfaces (11 mJ/cm2) to three small LEDs that emitted light at 265 nm reduced the pathogenic bacteria by 3 and 2-logs, respectively. The results obtained show that this disinfection technology could be promising for the food industry to guarantee effective inactivation of bacteria associated with foodborne diseases present in water, food and surfaces. Industrial relevanceThis study demonstrated the potential of ultraviolet-C light emitting diodes, emitting at 255 nm and 265 nm, to provide an effective and sustainable disinfection solution for the food industry, ensuring the inactivation of bacteria associated with foodborne diseases on water, food, and surfaces, thereby enhancing food safety. Additionally, this technology holds potential for extending product shelf-life, further benefiting the food industry. The results highlighted the effectiveness of UV-C LEDs even at low fluences, making them a practical choice for modern disinfection needs.

Comparative Efficacy Assessment of Solitary SMD Beaded Ultraviolet-C Light Emitting Diodes for Enhanced Disinfection of High-Touch Surfaces (Optimization of Surface Disinfection utilizing SMD beaded UV-C LEDs)

Comparative Efficacy Assessment of Solitary SMD Beaded Ultraviolet-C Light Emitting Diodes for Enhanced Disinfection of High-Touch Surfaces (Optimization of Surface Disinfection utilizing SMD beaded UV-C LEDs)

Innovative microbial water quality management in water distribution systems using in-pipe hydropowered UV disinfection: envisioning futuristic water-energy systems

ABSTRACT Hydropower UV disinfection has not been explored as a possible alternative for off-grid disinfection. Hydropowered UV LED technology was developed using off-the-shelf UV-C LEDs and pico – and femto-scale hydro turbine generators and evaluated across point-of-use relevant flow rates. Commercially available UV LED flow through reactors were subjected to microorganism challenge testing with 3 power schemes: wall-plug, hydropower, and hydropower-charged battery. UV LEDs powered by hydropower-charged battery demonstrated similar disinfection as wall-plug powered UV LEDs, achieving 0.5-1.8 MS2 log10 reduction at flow rates 0.5-2.3 L min−1, corresponding to reduction equivalent doses (RED) up to 16 or 30 mJ/cm2 for 254 and 285 nm, respectively. With hydropowered UV LEDs alone, MS2 log10 reduction decreased to <0.3 log10 reduction due to an underperforming and grossly inefficient turbine, with RED of 8 or 18 mJ/cm2 for 254 and 285 nm, respectively. Assessment of existing markets of UV disinfection systems and pico-hydro turbines demonstrated that hydropowered UV systems are already theoretically feasible for scales at point-of-entry (POE) and above. Economic feasibility will improve if turbines and/or UV system efficiencies improve. Prototype hydropower UV LED systems ranged from $145 to 220 depending on the UV LED reactor, and the battery system added $81. This study demonstrates the practicality of sustainable, renewable energy POU UV disinfection technology that can benefit decentralised, off-grid, rural and remote communities. The system may also scale up to provide renewable energy disinfection at larger scales, such as buildings and water distribution systems, for protecting human health in highly populated areas.

Ultraviolet (Spot)light on Water Treatment: Targeting Inactivation Efficiency and Stress Responses of Gram-Positive and Gram-Negative Bacteria Using UV-B and UV-C LEDs

This study examines the inactivation kinetics and stress responses of Gram-positive and Gram-negative waterborne bacteria using ultraviolet (UV)-B and UV-C LEDs at varying fluences. Our findings show that UV-light-emitting diodes (LED) treatment effectively inactivates both bacterial types, achieving over 4-log reductions at 255 nm and 285 nm wavelengths. Notably, inactivation rates at 285 nm, especially at higher fluences, are comparable to or exceed those at 255 nm. Additionally, UV-B treatment at 285 nm requires shorter exposure times for the same UV dose due to its deeper penetration into water and higher radiant flux. Stress responses varied between species: 255 nm exposure caused more direct DNA damage, triggering the SOS response with recA upregulation, particularly in Gram-positive L. innocua; while 285 nm exposure primarily induced oxidative stress, leading to soxS upregulation, especially in Gram-negative bacteria. These results suggest that UV-B complements UV-C effects by causing reactive oxygen species (ROS) formation in addition to DNA damage, challenging DNA repair. Given the higher cost of UV-C LEDs, our results support the optimization of water treatment systems using UV-B LEDs, which is a promising approach for improving bacterial inactivation while reducing exposure time and energy use.

Fabrication and Control of a Decontamination System with UV-C LED for Garlic (Allium sativum L.) Used in Planting

El proceso de desinfección es esencial para prevenir proliferación de bacterias que pueden contaminar los alimentos causando pérdida dentro de la cadena de suministro. Por lo tanto, el objetivo de la propuesta tuvo como finalidad la fabricación y control de un sistema de desinfección integrando una banda transportadora multinivel y luz UV-C LED. La metodología consistió en adaptar la automatización al mecanismo, mediante la programación con base en GEMMA y GRAFCET. Se integró un Controlador Lógico Programable (PLC, por sus siglas en inglés) e Interfaz Hombre Máquina (HMI, por sus siglas en inglés) como elementos de control. Adicionalmente, se configuraron diferentes rutinas como la velocidad de la banda, altura de las lámparas, el tiempo de exposición, paro de emergencia y emisión de la luz UV-C LED en cada zona de radiación. Se realizó un conteo microbiológico para evaluar el proceso de desinfección de la semilla de ajo (Allium sativum L.), utilizando dosis reportadas en la literatura. Los resultados demostraron que la propuesta es un producto científico tecnológico semi-industrial. Los niveles de la banda transportadora permiten que la semilla de ajo rote durante el proceso de desinfección. Con un efecto germicida del 92.30 % en mesófilos aerobios, se atiende adecuadamente el funcionamiento de los mecanismos de transporte y emisión de luz UV-C LED. Se puede concluir que el sistema puede adaptarse a cualquier producto del sector agroindustrial, además la automatización se puede extender con la inclusión de mayores parámetros. Para trabajo futuro queda determinar la mejor dosis, manejo de otros productos y combinaciones de radiación UV LED, así como un conteo microbiológico más exhaustivo.

Performance of high-efficiency UV-C LEDs in water disinfection: Experimental, life cycle assessment, and economic analysis of different operational scenarios

The widespread use of low or medium pressure mercury lamps in UV-C water disinfection should consider recent advances in UV-C LED lamps that offer a more sustainable approach and avoid its main drawbacks. The type of water and the mode of operation are critical when deciding on the treatment technology to be used. Therefore, this study investigates the potential application of UV-C LED disinfection technology in terms of kinetics, environmental assessment, and economic analysis for two scenarios: the continuous disinfection of a wastewater treatment plant (WWTP), and disinfection of harvested rainwater (RWH) in a residential household that operates intermittently. Experiments are conducted using both the new UV-C LED system and the conventional mercury lamp to disinfect real wastewater. Removal of total coliforms and Escherichia coli bacteria, with concentrations of approximately 105 and 104 CFU per 100 mL has been followed to assess the performance of both types of UV-C lamps. The experimental study provides kinetic parameters that have been further used in the environmental assessment conducted from a life cycle perspective. Additionally, considering the significant role of electricity consumption, a preliminary economic analysis has been conducted. The results indicate that first-order kinetic constants of pathogens removal with UV-C LEDs achieve 1.4 times higher values than Hg lamp. Regarding the environmental and economic assessment, for disinfection systems operating continuously, LEDs result in environmental impacts 5 times higher than Hg lamp in most categories, indicating that Hg lamps offer a viable option both from economic and environmental point of view. However, for installations with intermittent operation, LEDs emerge as the most competitive alternative, due to their ability to be turned on and off without affecting their lifespan. This study shows that UV-C LED lamps hold promise to replace conventional mercury lamps in a near future.

Graphene-Enhanced UV-C LEDs.

Light-emitting diodes in the UV-C spectral range (UV-C LEDs) can potentially replace bulky and toxic mercury lamps in a wide range of applications including sterilization and water purification. Several obstacles still limit the efficiencies of UV-C LEDs. Devices in flip-chip geometry suffer from a huge difference in the work functions between the p-AlGaN and high-reflective Al mirrors, whereas the absence of UV-C transparent current spreading layers limits the development of UV-C LEDs in standard geometry. Here it is demonstrated that transfer-free graphene implemented directly onto the p-AlGaN top layer by a plasma enhanced chemical vapor deposition approach enables highly efficient 275nm UV-C LEDs in both, flip-chip and standard geometry. In flip-chip geometry, the graphene acts as a contact interlayer between the Al-mirror and the p-AlGaN enabling an external quantum efficiency (EQE) of 9.5% and a wall-plug efficiency (WPE) of 5.5% at 8V. Graphene combined with a ≈1nm NiOx support layer allows a turn-on voltage <5V. In standard geometry graphene acts as a current spreading layer on a length scale up to 1mm. These top-emitting devices exhibit a EQE of 2.1% at 8.7V and a WPE of 1.1%.

Enhancement of Light Efficiency of Deep-Ultraviolet Light-Emitting Diodes by Encapsulation with a 3D Photonic Crystal Reflecting Layer.

Recently, UVC LEDs, which emit deep ultraviolet light, have found extensive applications across various fields. This study demonstrates the design and implementation of thin films of three-dimensional photonic crystals (3D PhCs) as reflectors to enhance the light output power (LOP) of UVC LEDs. The 3D PhC reflectors were prepared using the self-assembly of silica nanospheres on a UVC LED lead frame substrate via the evaporation-induced method (side) and the gravitational sedimentation method (bottom), respectively. These PhCs with the (111) crystallographic plane were deposited on the side wall and bottom of the UVC LED lead frame, acting as functional materials to reflect UVC light. The LOP of UVC LEDs with 3D PhC reflectors at a driving current of 100 mA reached 19.6 mW. This represented a 30% enhancement compared to commercial UVC LEDs with Au-plated reflectors, due to the UVC light reflection by the photonic band gaps of 3D PhCs in the (111) crystallographic plane. Furthermore, after aging tests at 60 °C and 60% relative humidity for 1000 h, the relative LOP of UVC LEDs with 3D PhC reflectors decreased by 7%, which is better than that of commercial UVC LEDs. Thus, this study offers potential methods for enhancing the light output efficiency of commercial UVC light-emitting devices.

Environmental life cycle assessment of UV-C LEDs vs. mercury lamps and oxidant selection for diclofenac degradation

This study is the first environmental comparison between a UV-C LED lamp (emitting at 265 nm) and mercury lamps employed in a lab-scale photoreactor for water treatment purification purposes, using the removal of diclofenac as a case study. Ex-ante life cycle assessment (LCA) methodology was used as a robust method to identify hotspots and recommendations at the early stage of the UV-C LEDs technology. The functional unit was defined as “the treatment of 1 L of polluted water with 20 mg L−1 of diclofenac to achieve a 90% removal of the contaminant”, while the system boundaries include the production and the operation of the photoreactors, following a cradle-to-gate approach. Several scenarios were explored, and overall, the UV-C LED lamp shows a promising environmental performance, with less or similar potential impacts than the mercury lamps in the 16 categories selected from the Environmental Footprint (EF) method. In particular, it reveals less impact in “human toxicity non-cancer” and “resource use minerals and metals” and presents electricity as the main source of impact. Given the higher efficacy of the UV-driven advanced oxidation processes compared to the UV irradiation alone, and since no studies have previously been conducted on the sustainability of free chlorine (FC) as an oxidant in water treatment, a comparison between UV-C, UV-C/H2O2, and UV-C/FC while employing the 265 nm UV-C LED lamp was also assessed. UV-C/H2O2 was more sustainable than UV-C/FC for the same treatment time, but both led to an overall impact reduction of 35% and 30%, respectively. To increase sustainability, employing cleaner energy sources such as photovoltaic or wind energy also resulted in an 80% and 93% reduction in the “climate change” category. Overall, this study demonstrates that using UV-C LEDs and the selected oxidants for water purification is beneficial and encourages the scale-up of the system.

Characterization and Optimization of a Novel UV-C LED Aerodynamic Device for Airborne Microbe Viability Abatement

Characterization and Optimization of a Novel UV-C LED Aerodynamic Device for Airborne Microbe Viability Abatement

Design strategies based on UV-C LED characterization to enhance Escherichia coli inactivation

This research is focused on the development of a UV-C LED lamp designed for effective water disinfection, tackling as a primary issue the low quantum efficiency and significant self-heating due to elevated operating currents which reduce the LED performance. By conducting thorough characterization and employing strategies including aluminum heat sinks and varied electrical biasing methods such as constant current, PWM, and high-current short-time pulses. The study assesses the disinfection potential against pathogenic bacteria such as Escherichia coli and Salmonella. Results indicate successful E. coli inactivation within agar mediums and notable growth suppression in Mueller-Hinton culture mediums, as confirmed through optical density measurements. Therefore, this investigation underlines the importance of optimized operational strategies to enhance UV-C LED lamps' disinfection capabilities.

SIMULARE NUMERICĂ A INFLUENȚEI UNOR PARAMETRI GEOMETRICI ASUPRA CALITATII DECONTAMINARII UNUI RECEPTOR DE TIP NON-LAMBERTIAN, UTILIZAND O MATRICE DE LED-uri UV-C

The ultraviolet (UV) irradiation has been studied and used in the recent decades as a mean to inactivate various potentially harmful microorganisms, being considered an effective treatment that could limit or even avoid the use of chemical disinfectants. Within the wavelength spectrum of UV radiation, the UV-C radiation wavelength ranging between 200 and 280 nm is considered lethal to most types of microorganisms. In this paper it was studied the variation of the distribution of radiation's intensity generated by a matrix of 25 UV-C LEDs (5 x 5), (assimilated to the LED panel above a stationary conveyor), on a spherical surface (assimilated to a berry) positioned in reprezentative locations below the matrix. A fruit located under the irradiation matrix receives the strongest radiation from the LED located at the smallest distance from it, but is influenced, as a result of the superposition principle, to a lesser extent by the other LEDs within the network. It has been found that for a too small distance between the matrix of LEDs and the conveyor, the radiation dose is uneven on the surface of fruit, and by increasing this distance a radiation distribution much more uniform is obtained, but at the expense of a decrease in its intensity and an increase in the time required for irradiation, implicitly leading to an increase in operating costs. In conclusion, for the most efficient operation of the equipment, a compromise solution must be chosen.

Inactivation kinetics of polyphenol oxidase and peroxidase enzymes in buffer solutions by ultraviolet light sources at multiple UV-C wavelengths

This study aimed to evaluate the effect of multiple wavelengths of UV-C light sources on the inactivation of polyphenol oxidase (PPO) and peroxidase (POD) in buffer solutions. Enzyme solutions were treated with a UV-C excimer lamp (EL) emitting at 222 nm, low-pressure mercury (LPM) lamp at 253.7 nm, four UV-LEDs sources emitting at 255, 265, 275 and 285 nm, and a novel pulsed UV-C lamp (PL) emitting at 232, 242, 261 and 272 nm. Three kinetic models were used to compare UV-C wavelengths enzymatic inactivation efficacy considering the volume average fluence for 90% reduction (HD). Validation of kinetic parameters was performed under continuous-flow treatment in a UV-C LED and EL system. EL treatment resulted in the highest inactivation efficacy of PPO and POD enzymes with HD of 52.8 and 74.8 mJ/cm2, respectively. PL inactivation efficacy for both enzymes was higher than with LPM lamp or UV-LEDs. The two-component first-order model best described the inactivation of PPO and POD in a buffer solution. The adjusted kinetic parameters for this model were validated under UV-C light continuous flow processing. This study contributes to the development of liquid food treatment by ultraviolet technology.

Cell density and extracellular matrix composition mitigate bacterial biofilm sensitivity to UV-C LED irradiation

Ultraviolet-C light-emitting diodes (UV-C LEDs) are an emerging technology for decontamination applications in different sectors. In this study, the inactivation of bacterial biofilms was investigated by applying an UV-C LED emitting at 280 nm and by measuring both the influence of the initial cell density (load) and presence of an extracellular matrix (biofilm). Two bacterial strains exposing diverging matrix structures and biochemical compositions were used: Pseudomonas aeruginosa and Leuconostoc citreum. UV-C LED irradiation was applied at three UV doses (171 to 684 mJ/cm2) on both surface-spread cells and on 24-h biofilms and under controlled cell loads, and bacterial survival was determined. All surface-spread bacteria, between 105 and 109 CFU/cm2, and biofilms at 108 CFU/cm2 showed that bacterial response to irradiation was dose-dependent. The treatment efficacy decreased significantly for L. citreum surface-spread cells when the initial cell load was high, while no load effect was observed for P. aeruginosa. Inactivation was also reduced when bacteria were grown under a biofilm form, especially for P. aeruginosa: a protective effect could be attributed to abundant extracellular DNA and proteins in the matrix of P. aeruginosa biofilms, as revealed by Confocal Laser Scanning Microscopy observations. This study showed that initial cell load and exopolymeric substances are major factors influencing UV-C LED antibiofilm treatment efficacy.Key points• Bacterial cell load (CFU/cm2) could impact UV-C LED irradiation efficiency• Characteristics of the biofilm matrix have a paramount importance on inactivation• The dose to be applied can be predicted based on biofilm propertiesGraphical

Design optimization of a cylindrical UV-C LED reactor for effective water disinfection with numerical simulations and test reactor fabrication

Ultraviolet C-band light-emitting diodes (UV-C LEDs) provide effective water disinfection and flexible reactor design. In this study, the disinfection performance of the cylindrical UV-C LED reactor was optimized using a new computational fluid dynamics (CFD) technique and validated experimentally with test reactors. The CFD technique provided UV doses for individual particles representing microorganisms, which were integrated along their trajectories using the discrete phase method within the radiation field acquired through the Monte Carlo method. Utilizing the minimum UV dose as a criterion, four key design parameters were evaluated: reactor aspect ratio (L/D) (in the range of 2.5−6), LED power angle (15−55°), wall reflectivity (0.6−0.94), and water flow rate (1−4 l/min). The optimal L/D of 4.2 was determined and subsequently applied to fabricate the test reactors. The polytetrafluoroethylene (PTFE) test reactor exhibited superior disinfection performance for E. coli O157:H7 compared to the one made of SUS304, due to its high wall reflectivity. Furthermore, a lower water flow rate enhanced disinfection performance by extending the residence time. The predicted log reductions exhibited a consistent trend with the measured values, confirming the efficacy of the CFD methodology applicable to various reactor designs and LED configurations.

Effect of Trap Behavior on Recombination in AlGaN-Based UV-C LEDs Degradation

Effect of Trap Behavior on Recombination in AlGaN-Based UV-C LEDs Degradation

The Mapping of Alpha-Emitting Radionuclides in the Environment Using an Unmanned Aircraft System

The protection of first responders from radioactive contamination with alpha emitters that may result from a radiological accident is of great complexity due to the short range of alpha particles in the air of a few centimeters. To overcome this issue, for the first time, a system mounted on a UAS for the near-real-time remote measurement of alpha particles has been developed, tested, and calibrated. The new system, based on an optical system adapted to be installed on a UAS in order to measure the UV-C fluorescence emitted by alpha particles in the air, has been tested and calibrated, carried out in the laboratory and in field experiments using UV-C LEDs and 241Am sources. In experimental flights, the probability of detecting a point source was determined to be approximately 60%. In the case of a surface extended source, a detection efficiency per unit surface activity of 10 counts per second per MBq cm−2 was calculated. A background count rate of UV-C of around 26 ± 28 s−1 for an integration time of 0.1 s was measured during flights, which led to a decision threshold surface activity of 5 MBq cm−2.