Search Results (102)

The study concerns the simulation of an active personal protective mask that performs air purification of incoming and outgoing air to and from the user using ultraviolet germicidal irradiation (UVGI). The specific method for determining the radiation dose is done using a CFD simulation of the process of breathing to determine the duration of the irradiation of the air. Additionally, an optical simulation is performed in order to determine the average irradiance in the illuminated zone. For the purposes of the UVGI, a radiation dose of 20–40 J/m² is sufficient to achieve LD90 when applied to most Flu and Corona viruses. Full article

Developing advanced bioinspired photoprotective barrier from marine resources represents a critical frontier of bioprocessing. This study established a rational design and implementation of effective photoprotective surface-coating eumelanin from ink of an Indian squid (Uroteuthis duvaucelii). The Central Composite Design was developed to optimize extraction and functionalization parameters of eumelanin on quartz substrates, strategically developing the matrix for peak optical attenuation within the potential Far-UVC window (220 nm). Translational photoprotective efficacy of the surface, as well as finished eumelanin on quartz surface, was validated by subjecting them to a challenging macro-level biological assay using a hospital-grade 254 nm ultraviolet germicidal source (125 µWcm⁻²). Quantitative physical dosimetry established that the squid eumelanin coating (A254 = 1.00) reduced internal transmittance to approximately 10%, successfully dampening the incident fluence from 0.225 J cm⁻² down to a heavily attenuated 0.0225 J cm⁻² at the biological sample plane. While unshielded control indicator microbial strains suffered complete lethal inactivation, the eumelanin barrier maintained exceptional cell viability, yielding biological shielding efficiencies of 98% for Bacillus subtilis, 96% for Staphylococcus aureus, and 92% for Escherichia coli. Characteristic features from FE-SEM, FTIR, and XRD analysis established that this superior photoprotective property is governed by the extensively conjugated, π-π-stacked indolic architecture possessing a characteristic 3.4 Å interlayer d-spacing, which facilitates rapid, non-radiative energy dissipation. This work establishes an effective framework for translating squid biomass into high-value, transparent optical barriers, providing a potential sustainable alternative to synthetic ultraviolet absorbers. Full article

Germicidal UV (GUV) technology, which utilizes light in the UV-C portion of the electromagnetic spectrum, has become a viable alternative to traditional chemical disinfectants to sanitize surfaces in the built environment. However, the degradation of polymers that have been exposed to UV-C light is a concern due to the potential change in structural integrity and visual appearance. The resistance to UV-C degradation is often tabulated in relative qualitative terms, making it rather difficult for designers to understand the implications of the choice of a material of construction. This study was initiated to develop a systematic, standardized method of exposing polymeric materials to UV-C light to ensure that the subsequent property measurements can be compared quantitatively. The exposure method is based on an apparatus that can be readily duplicated using commercially available materials and equipment. To demonstrate the proposed exposure framework, samples of six formulated polymer resins were exposed to three UV-C light sources with different peak wavelengths (KrCl excimer lamp [222 nm], low-pressure mercury lamp [254 nm], and LED lamp [280 nm]). Exposures were conducted at five independent laboratories, and subsequent property testing was performed at multiple facilities using established materials-characterization methods. This coordinated approach enables comparative evaluation of material responses across UV-C source types, wavelengths, and dose levels, providing a practical foundation for developing standardized exposure methodologies and informing future formulation development efforts. Post-exposure testing included quantifying changes in optical, mechanical, and physical properties, including color, gloss, reflectivity, spectral transmittance (haze), flammability, tensile strength, and elastic modulus. These measurements were conducted using established laboratory methods commonly employed throughout the polymer and materials industries. Together, these results provide a comparative dataset illustrating how polymer properties respond to coordinated UV-C exposure conditions, supporting the development of standardized approaches for evaluating material durability in germicidal UV applications. Full article

Background/Objectives: The increased prevalence of multidrug-resistant Escherichia coli and carbapenemase-producing Enterobacteriaceae poses a critical threat to global health and food safety. Antimicrobial Blue Light (aBL) in the 400–470 nm spectrum has emerged as a promising, chemical-free disinfection strategy that targets intracellular porphyrins and flavins to induce oxidative stress. However, the influence of wavelength, dosimetry, and environmental stressors on endogenous photoinactivation remains poorly standardized regarding optical parameters and biological exposure protocols. This systematic review aimed to evaluate the antimicrobial efficacy of pure blue light (400–470 nm) against E. coli across various phenotypes and environmental conditions, excluding the use of exogenous photosensitizers. Methods: PubMed, Scopus, and Web of Science were searched for studies that utilized 400–470 nm light as an antimicrobial agent against E. coli. Data extraction focused on spectral efficiency, total fluence (J/cm²), and log₁₀ reduction. The Risk of Bias was assessed using an adapted Office of Health Assessment and Translation tool for in vitro studies. Results: Synthesis of 11 high-quality studies indicated that wavelengths near 405 nm have the highest germicidal efficiency due to the Soret band absorption of endogenous porphyrins. Efficacy is highly dose-dependent: significant log₁₀ reductions were achieved in planktonic cells, although biofilms required substantially higher fluences. Sub-lethal environmental stressors such as acidic pH, high salinity, and thermal fluctuations demonstrated a synergistic effect, which significantly enhanced the rate of photoinactivation. Multidrug-resistant and carbapenemase-producing Enterobacteriaceae strains showed similar susceptibility to aBL relative to antibiotic-sensitive strains, suggesting no cross-resistance between light and traditional drugs. Conclusions: Endogenous blue light is a highly effective, non-thermal technology for E. coli decontamination. Its efficacy is modulated by the interplay between optical parameters and environmental conditions. These findings provide a framework for the development of standardized protocols for applying aBL to clinical wound care and food industry use cases. They also highlight the potential of aBL as a critical tool in the post-antibiotic era. This systematic review was registered in the International prospective register of systematic reviews (PROSPERO) under protocol CRD420261331871. Full article

Background: A compact, in-house-developed ultraviolet germicidal irradiation (UVGI) system using eight 36 W Philips low-pressure mercury UV-C lamps with a peak emission at 253.7 nm was developed for effective sterilization of bacteria and fungi using a wireless mode of operation. Methods: Under controlled laboratory conditions, the system was tested against representative biofilm-forming microorganisms, including Bacillus subtilis, Escherichia coli K12, and a multidrug-resistant Candida albicans M-207 isolate. Microbial viability was assessed using colony-forming unit (CFU) enumeration and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, with structural changes analyzed by scanning electron microscopy (SEM). Cultures were exposed to 253.7 nm UV-C radiation at distances of 1–5 m for 15–90 min. Results: UV-C exposure resulted in time- and distance-dependent reductions in viable counts for all tested organisms, as determined by CFU analysis. At 1 m and 15 min exposure, viable counts for all tested organisms were reduced below the limit of detection (LOD) of the CFU assay, indicating substantial microbial inactivation under the tested conditions. Reduced efficacy was observed at increased distances (3 m and 5 m), with log₁₀ reductions varying depending on organism and exposure conditions. Residual metabolic activity detected by the MTT assay suggests the presence of non-proliferating or damaged cells, consistent with the different endpoints measured by the two assays. The SEM analysis further revealed disruption of biofilm architecture and reduction in cell density with increasing UV dose. Conclusions: The UVGI system demonstrated dose-dependent inactivation of biofilm-forming microorganisms under controlled conditions, supporting its proof-of-concept efficacy. Further studies are required to evaluate performance under real-world conditions. Full article

We evaluated the indoor environmental quality of the administrative office at University Medical Center Ho Chi Minh City branch 2 and implemented a multi-stage engineering control strategy to optimize occupational health conditions. A cross-sectional assessment monitored important air quality parameters, including carbon dioxide (CO₂), fine particulate matter (PM2.5 and PM10), humidity, and illumination. Following baseline measurements, an integrated system was deployed to address pollutant mass balance, consisting of High-Efficiency Particulate Air (HEPA) filtration units for mechanical particle scrubbing, ceiling-mounted axial fans to induce forced convection, and ultraviolet-C germicidal lamps for photochemical disinfection. Post-intervention results demonstrated significant gains in system removal efficiency. CO₂ concentrations decreased by over 60% due to enhanced volumetric air exchange, while PM2.5 levels decreased by more than 40% through interception and diffusion mechanisms within the HEPA media. Furthermore, UVC irradiation achieved a 90% reduction in viable airborne microbial colonies. The results of this study show that low-cost, scalable environmental engineering controls and fluid dynamic optimizations effectively mitigate indoor air pollution and enhance workplace stability in healthcare administrative settings. Full article

To map and describe the scientific evidence on germicidal ultraviolet C (UV-C) light for hospital surface disinfection, this scoping review examined device types, reported operational parameters, microbiological and clinical outcomes, and implementation aspects. Primary studies conducted in hospital settings and evaluating UV-C or ultraviolet germicidal irradiation on environmental surfaces were searched in four databases without date restrictions. Data were synthesized descriptively in tables and narrative form following JBI and PRISMA-ScR guidance. Eleven studies (2007–2025) met the inclusion criteria. Reported microbial reductions ranged from 1 to ≥5 log₁₀. Higher and more consistent reductions were predominantly observed under laboratory or controlled experimental conditions, whereas reductions in real-world hospital surface sampling were more variable and influenced by pathogen type, surface material, room geometry, and shadowing. Integration of UV-C with manual cleaning and multi-position irradiation cycles was associated with greater effectiveness. Reporting of key radiometric parameters (dose, exposure time, and distance) was frequently incomplete, limiting reproducibility and cross-study comparability. Clinical findings were heterogeneous: some interrupted time-series analyses suggested reductions in healthcare-associated infections, although effects were not uniform across microorganisms. Implementation reports described room-level cycle times compatible with turnover, variable staffing requirements, and limited economic evaluation. Overall, UV-C appears to be a promising adjunct to standard cleaning practices in hospital environments. However, standardized radiometric reporting, multicenter studies, and robust clinical and economic evaluations are necessary to support safe, reproducible, and sustainable large-scale implementation. Full article

The need for contrasting Healthcare-Associated Infections requires the promotion and support of alternative disinfection techniques. Due to the antimicrobial potential of UV, devices equipped with UVC, UVB and UVA lamps or LEDs have been developed in recent years for domestic, everyday use. In this study, four bacterial strains (S. aureus, E. faecalis, E. coli, and P. aeruginosa) were exposed to different doses of near-UVA radiation at 405 nm, with an average irradiance of 21 mW/cm², using an experimental multi-LED device. Bacterial suspensions were irradiated under both sub-lethal and non-sub-lethal stress conditions. When using only near-UVA light, the highest abatement effect was observed on P. aeruginosa (2.4 log₁₀). Treatment with osmotic stress, in combination with light irradiation, was effective on all bacterial strains (mean abatement of 2.76, 5.46, 5.31, and 1.5 log₁₀ on E. coli, E. faecalis, P. aeruginosa, and S. aureus, respectively). In heat stress conditions at 4 °C, P. aeruginosa and S. aureus species were the most susceptible (2.76 and 5.5 log₁₀), whereas at 45 °C all species, except E. faecalis (0.58 log₁₀), achieved significant reduction. The addition of exogenous photosensitive porphyrins produced a reduction in total concentrations from the lowest doses for S. aureus and P. aeruginosa, while for E. coli and E. faecalis, the reductions did not exceed 1 log₁₀ abatement. Near-UVA radiation at 405 nm has a high disinfectant potential when combined with certain sub-lethal stress conditions. The most significant germicidal effect was achieved with the use of exogenous porphyrins in S. aureus and P. aeruginosa species. This study opens perspectives on the possible future application of near-UVA radiation in disinfection in order to limit the spread of healthcare-related infections. Full article

This investigation examines the optical degradation of 260 nm and 265 nm UVC LEDs subjected to varying drive current conditions, simulating real-world deployment in consumer and professional disinfection systems. The primary aim was to assess lifetime trends and degradation behaviour based exclusively on radiometric and spectral data. A total of 24 devices (12 per wavelength group) were operated for 2000 h under a broad range of thermally stabilised current levels, from low-standby to maximum-rated operation. The results demonstrated distinct current-dependent ageing characteristics, wherein, for the tested device sets and operating conditions, 260 nm LEDs exhibited faster optical power degradation than the investigated 265 nm LEDs under nominal drive conditions. Notably, a moderate current derating of approximately 20% resulted in a more than fourfold increase in L70 lifetime and over a threefold extension in the number of effective disinfection cycles. Despite a stable spectral power distribution throughout ageing, significant statistical variation in lifetime metrics (L90, L80, L70, L50) was observed even among identically operated devices, underscoring the need for population-level reliability qualification. Optical lifetime estimates based on empirical model fitting indicated that the Ruschel logarithmic function most accurately captured the long-term degradation trends for the analysed datasets. These findings provide practical guidance for the design of durable and efficient UVC LED systems within the investigated device class and operating regimes, supporting sustained germicidal performance and long-term operational reliability across diverse use cases. Full article

This study evaluates energy conversion and heat transfer in a germicidal chamber employing gold nanorods (AuNRs) irradiated with an infrared laser (808 nm, 0.8 W) to generate heat via localized surface plasmon resonance. The investigation focused on the preliminary selection of chamber materials and the geometry of the bottom surface supporting the AuNRs as the heat source in a photothermoablation application. A one-way multiphysics and multiscale approach was applied, integrating nanoscale heating phenomena with a macroscale fluid and heat flow. The validated 2D numerical model shows satisfactory agreement with experimental data and is suitable for further design analyses. Computational Fluid Dynamics (CFD) simulations were conducted to determine temperature and entropy distributions, mean and maximum temperatures, and Nusselt numbers, allowing the assessment of the energy conversion process under different configurations and AuNR dimensions. The results indicate that a configuration with a gradually descending stepped structure enhances interactions between nanoparticles and the fluid, increasing the internal energy and producing elevated temperatures. Under optimal conditions, a temperature rise of approximately 75 °C was achieved. These findings demonstrate that integrating material selection, surface geometry, and nanoparticle absorbance optimization can significantly improve the efficiency of bacterial inactivation in germicidal chambers. This study provides a framework for future investigations on fully three-dimensional multiscale and multiphysical modeling, as well as a targeted AuNR design to maximize the thermal performance. Full article

Background/Objectives: Environmental contamination of dental surfaces is a major vector for cross-infection. Ultraviolet-C (UVC) irradiation provides rapid, chemical-free decontamination; however, depending on wavelength and ventilation conditions, ozone generation may occur. This study evaluated the germicidal efficacy of UVC on three high-touch surfaces: a wooden work table, a stainless-steel consumables table, and a dental unit table. Methods: Surfaces were sampled at baseline, after 5 min (27 mJ/cm²), and after 10 min (54 mJ/cm²) of UVC exposure at 90 µW/cm². Colony-forming units (CFU/cm²) were enumerated using Mueller–Hinton agar. Results: UVC achieved >99% reduction after 5 min and complete elimination after 10 min. Material properties (porosity, reflectivity, and grooves), along with quantified parameters like surface roughness (Ra) and contact angle, influenced minor differences in decontamination. Conclusions: Used with appropriate safety protocols, short-duration UVC irradiation effectively decontaminates dental surfaces and can complement chemical disinfection. Future studies must incorporate artificially soiled surfaces, biofilms, and emerging far-UVC/UV-LED technologies. Full article

UV-C radiation has emerged as a germicidal agent against pathogens, particularly following the COVID-19 pandemic. While UV-C effectively reduces cross-contamination in hospitals, it induces photodegradation in polymer devices, potentially damaging and posing risks to patient safety. Therefore, it is crucial to detect the effects of UV-C photodegradation on early stages, as well as the effects of prolonged UV-C exposure. In this study, we investigated the UV-C photodegradation (254 nm, 471 kJ/mol) of isotactic polypropylene homopolymer (PP), commonly used in medication packaging. The impact of UV-C on PP was evaluated through rheology and infrared spectroscopy. Surface energy was measured by the contact angles formed by drops of water and diiodomethane. The effects of photodegradation on the polymer’s morphology were examined using scanning electron microscopy, and the melting temperature and crystallinity by differential scanning calorimetry. Lastly, the effect of UV-C on molecular mobility was studied using ¹H Time Domain Nuclear Magnetic Resonance (¹H TD-NMR). These techniques proved to be valuable tools for identifying the early stages of UV-C photodegradation, and ¹H TD-NMR was a sensitive method to identify the chain branching as a photodegradation product. This study highlights the impact of UV-C on PP photodegradation and hence the importance of understanding UV-C-induced degradation. Full article

The rapid and accurate identification of pathogenic spores is essential for the early diagnosis of diseases in modern agriculture. Gray mold disease, caused by Botrytis cinerea, is a significant threat to several crops and is traditionally controlled using fungicides or, alternatively, by UV-C radiation. Classically, the determination of conidial germination percentage, a key indicator for assessing pathogen viability, has been a manual, time-consuming, and error-prone process. This study proposes an approach based on deep learning, using one-stage detectors to automate the detection and counting of germinated and non-germinated conidia in microscopy images. We trained and assessed the performance of three models under several metrics: YOLOv8, YOLOv11, and RetinaNET. The results show that these three architectures provide an efficient and accurate solution for the recognition of gray mold conidia viability. Selecting the best model, we performed the task of detecting and counting conidia for determining the germination percentage on samples treated with different UV-C radiation dosages. The results show that these deep-learning models achieved counting accuracies that closely matched those obtained with conventional manual methods, yet they delivered results far more rapidly. Because they operate continuously without fatigue or operator bias, these models begin to open possibilities, after widening field tests and datasets, for efficient and fully automated monitoring pipelines for disease management in the agro-industry. Full article

This study is the first to investigate the performance of ultraviolet germicidal irradiation (UVGI) in underfloor air distribution (UFAD) systems. A simplified mathematical model is developed to predict airborne pathogen transport and inactivation by upper room UVGI in UFAD spaces. The proposed model is substantiated for the SARS-CoV-2 virus as a simulated pathogen through a comprehensive computational fluid dynamics methodology validated against published experimental data of upper room UVGI and UFAD flows. Simulations show an 11% decrease in viral concentration within the upper irradiated zone when a 15 W louvered germicidal lamp is utilized. Finally, a case study on Mycobacterium tuberculosis (M. tuberculosis) bacteria is carried out using the validated simplified model to optimize the use of return air and UVGI implementation, ensuring acceptable indoor air quality and enhanced energy efficiency. Results reveal that the UFAD-UVGI system may consume up to 13.6% less energy while keeping the occupants at acceptable levels of M. tuberculosis concentration and UV irradiance when operated with 26% return air and a UVGI output of 72 W. Full article