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(a) Picture of the completely assembled far-UVC LED irradiation system where the radiation unit with the LEDs and the vertical and slanted reflectors are visible. (b) Half of a cross section schematic of the optical components of the far-UVC LED radiation unit. (c) Simulated (blue curve, solid line) and measured (red curve, dashed line) transmission spectra of the DBR filter under normal incidence. (d) Emission spectra measured at the maximum operation current of the LEDs (100 mA), at a distance of 25 mm from the lower edge of the vertical reflector and at five different positions (center (Pos. 1) and four corners of the LED array (Pos. 2–5)). (e) and (f) The irradiance distribution of the far-UVC LED irradiation system on a 70 mm × 70 mm target area measured (e) without and (f) with the DBR filter at the maximum operation current of the LEDs (100 mA) and at a distance of 25 mm from the lower edge of the system. In both cases the uniformity (defined as 100% − (standard deviation/mean value of the irradiance)) is > 90%.
Source publication
Multiresistant pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) cause serious postoperative infections. A skin tolerant far-UVC (< 240 nm) irradiation system for their inactivation is presented here. It uses UVC LEDs in combination with a spectral filter and provides a peak wavelength of 233 nm, with a full width at half maximum...
Citations
... It has great potential to replace harmful mercury-based lamps as the primary UV light source because aluminum gallium nitride (AlGaN)-based emitters are environmentally friendly, cost effective, highly robust, and energy efficient [13][14][15] . Recent studies have suggested that skin problems associated with UVLEDs should be avoided in the future 16,17 . At present, their optical performance is quite weak with the best external quantum efficiency (EQE) being only approximately 20% 18 , while that of commercially available materials is only 10% WPE 19 . ...
Deep ultraviolet light-emitting diodes (DUV LEDs) typically suffer from strong parasitic absorption in the p-epitaxial layer and rear metal contact/mirror. This problem is exacerbated by a substantial portion of the multiple quantum well (MQW) emissions having a strong out-of-plane dipole component, contributing to emission in widely oblique directions outside the exit cone of the front semiconductor emitting surface. To address this, we propose an architecture that leverages such a heavily oblique angular emission profile by utilizing spaced-apart or scattered volume emitter micropixels that are embedded in a low-index dielectric buffer film with a patterned top surface. This approach achieves high light extraction efficiency at the expense of enlarging the effective emission area, however, it does not require a high-index (e.g., sapphire) substrate or a lens or a nanotextured epi for outcoupling purposes. Hybrid wave and ray optical simulations demonstrated a remarkable larger than three to sixfold increase in light extraction efficiency as compared to that of a conventional planar LED design with a sapphire substrate depending on the assumed epi layer absorption, pixel size, and ratio of light emission area to the MQW active area. An extraction efficiency three times greater than that of a recent nanotextured DUV LED design was also demonstrated. This architecture paves the way for DUV LEDs to have a plug efficiency comparable to that of mercury lamps while being significantly smaller.
... AlGaN-based ultraviolet (UV) light emitting diodes (LEDs) have gained an increasing interest in the last years for their use in disinfection systems [1], [2], [3], [4]. In particular, it was demonstrated that by UV light it is possible to inactivate several viruses, including Sars-CoV-2 [5]. ...
We studied four AlGaN-based 265 nm LEDs with increasing QW thickness (1.4 nm, 3 nm, 6 nm, and 9 nm) during a constant current stress at 100 A cm-2. We focused our attention on the parasitic components of the emission spectra at low current levels, and on the optical power recovery observed at high current levels. We associated every parasitic peak or band to a region in the device where they can be generated, also demonstrating if they are related to band-to-band emission or radiative emission through defects. At high current levels, we showed the simultaneous effect of the decrease in injection efficiency in the active region and the increase in non-radiative recombination, by fitting the EQE curves with a mathematical model. Moreover, we associated the optical power recovery with a generation of negative charge near the active region, which led to an increase in injection efficiency in the QW.
... It has great potential to replace harmful mercury-based lamps as the primary UV light source because aluminum gallium nitride (AlGaN)-based emitters are environmentally friendly, cost effective, highly robust, and energy efficient [13][14][15] . Recent studies have suggested that skin problems associated with UVLEDs should be avoided in the future 16,17 . At present, their optical performance is quite weak with the best external quantum efficiency (EQE) being only approximately 20% 18, while that of commercially available materials is only 10% WPE 19 . ...
Deep ultraviolet light-emitting diodes (DUV LEDs) typically suffer from strong parasitic absorption in the p-epitaxial layer and rear metal contact/mirror. This problem is exacerbated by a significant portion of the multiquantum well (MQW) emissions having a strong out-of-plane dipole component, contributing to emission in widely oblique directions outside the exit cone of the emitting surface. Here, an architecture that exploits heavy oblique emission is proposed by using scattered volume emitter micropixels that are spaced apart and embedded in a low-index dielectric buffer film with a patterned top surface. This approach significantly increases the surface-to-volume ratio of the semiconductor and does not require a high-index (e.g., sapphire) substrate or a lens to achieve high extraction efficiency. Depending on the assumed epilayer absorption, the hybrid wave and ray optical simulations demonstrated a 3- to 6-fold increase in light extraction efficiency compared to that of a conventional planar design with a sapphire substrate reference. An extraction efficiency three times greater than that of a recent nanotextured DUV LED design was also demonstrated. This architecture paves the way for DUV LEDs to have a plug efficiency comparable to that of mercury lamps while still being significantly smaller.
... However, in the range of 222 nm, DNA exhibits an absorption minimum [17] that is, together with the higher adsorption of the radiation by proteins, limiting its antimicrobial use since bacteria might be shielded and the radiation is not reaching the bacteria to a sufficient extent [12,18]. To bypass the absorption of the radiation and simultaneously reduce the risk of DNA damage, far-UV-C radiation from light emitting diodes (LEDs) with a peak wavelength of 233 nm is a possible skin-tolerable alternative to conventional antisepsis [19,20]. ...
... Since the efficacy of UV-C radiation with a peak-wavelength of 233 nm was already confirmed in a former study to inactivate methicillin-sensitive and resistant S. aureus as well as S. epidermidis [19,20], the presented study is used to confirm the efficacy of UV-C radiation against other Staphylococcus spp. and to determine the efficacy against representatives of the Gram-negative genus Klebsiella and Pseudomonas in a quantitative carrier test. ...
... A far-UV-C LED irradiation module (Ferdinand-Braun-Institut, Berlin, Germany) was used for irradiation. The irradiation module uses a spectral filter and has a peak wavelength of 233 nm with an irradiance of 44 mW/cm 2 [19] over a target area of 70 mm  70 mm. ...
... Our results demonstrated that 0.5% Umonium 38 can effectively inactivate MRSA within 15 min, sustained for 14 days, and underscores its potential for safely and effectively disinfecting equipment surfaces and laboratory environments. MRSA inactivation currently focuses on light utilisation, such as far-UVC LEDs with a wavelength below 240 nm [20,21] and antimicrobial photodynamic therapy with a porphyrinic formulation [22] for antiseptic purposes on the skin. In addition, the efficacy of octenidine hydrochloride has been assessed for the inactivation of MRSA biofilm formation on medical implants and laboratory equipment within hospital settings [23]. ...
Aims
We investigated the antibacterial efficacy of Umonium³⁸ and Virkon® against Burkholderia pseudomallei, Escherichia coli, Pseudomonas aeruginosa and Methicillin-Resistant Staphylococcus aureus (MRSA) up to 14 days following treatment.
Methods and results
Umonium³⁸ was diluted to 0.5%, 1.0%, 1.5%, 2.0%, 2.5% and 3%, tested against the bacterial strains at various contact times (15 min to 24 h), and incubated for up to 14 days. A minimum concentration of 0.5% Umonium³⁸ with a contact time of 15 min effectively killed approximately 10⁸ CFU/ml of all four bacterial species. No growth was observed on agar plates from day 0 until day 14 for all six concentrations. The bacteria were also inactivated by a 30-minute treatment time using Virkon® 1% solution.
Conclusions
Umonium³⁸ effectively inactivates B. pseudomallei, E. coli, P. aeruginosa and MRSA at a concentration of ≥ 0.5% with a contact time of at least 15 min. The antimicrobial effect of Umonium³⁸ remained for 14 days.
... The biopsies were taken from each model, fixated in neutral buffered 4% formalin solution (Sigma # HT501128-4L, Merck KGaA, Darmstadt, Germany) and embedded in paraffin (paraffin blocks) (Histosec™, Merck Millipore GmbH, Darmstadt, Germany). DNA damage was assessed immediately and 24 h after (reculture of RHE at 37 °C and 5% CO 2 ) irradiation using the immunohistochemical approach described previously 45 www.nature.com/scientificreports/ ...
Melanin, the most abundant skin chromophore, is produced by melanocytes and is one of the key components responsible for mediating the skin’s response to ultraviolet radiation (UVR). Because of its antioxidant, radical scavenging, and broadband UV absorbing properties, melanin reduces the penetration of UVR into the nuclei of keratinocytes. Despite its long-established photoprotective role, there is evidence that melanin may also induce oxidative DNA damage in keratinocytes after UV exposure and therefore be involved in the development of melanoma. The present work aimed at evaluating the dependence of UV-induced DNA damage on melanin content and distribution, using reconstructed human epidermis (RHE) models. Tanned and light RHE were irradiated with a 233 nm UV-C LED source at 60 mJ/cm² and a UV lamp at 3 mJ/cm². Higher UV-mediated free radicals and DNA damage were detected in tanned RHE with significantly higher melanin content than in light RHE. The melanin distribution in the individual models can explain the lack of photoprotection. Fluorescence lifetime-based analysis and Fontana–Masson staining revealed a non-homogeneous distribution and absence of perinuclear melanin in the tanned RHE compared to the in vivo situation in humans. Extracellularly dispersed epidermal melanin interferes with photoprotection of the keratinocytes.
... The occurrence of parasitic emission bands therefore necessitates the use of filters. 9 Hence, it is important to understand from where exactly the parasitic luminescence of the heterostructure arises to target its suppression. ...
AlN layers annealed at high temperatures offer low threading dislocation densities of mid 108 cm−2 and are therefore increasingly used as base layers in ultraviolet (UV) light emitting diode (LED) heterostructure growth. These LEDs, just like those grown on conventional metalorganic vapor phase epitaxy (MOVPE) AlN templates, often suffer from long-wavelength parasitic luminescence. In this work, luminescence properties of far-UVC LED heterostructures grown on MOVPE-AlN/sapphire templates and high-temperature annealed AlN/sapphire templates are compared. To investigate the origin of parasitic emission with high spatial resolution, cross section scanning transmission electron microscopy was combined with cathodoluminescence measurements. As a result, the main origin of the parasitic luminescence band centered at 3.5 eV (354 nm) for the heterostructure grown on annealed AlN is assigned to point defects related to oxygen in the AlN template layer. The defect band centered at 3.0 eV (413 nm) for the heterostructure grown on MOVPE-AlN was found to be related to self-compensating VAl-Si point defect complexes in the n-AlGaN layer and oxygen incorporation close to the AlN/sapphire interface. The results also suggest that the type of AlN template determines the kind of parasitic luminescence from the n-AlGaN layer.
... The irradiation experiments were performed using a 233 nm far UV-C light source (12 nm FWHM), consisting of 120 LEDs and a distributed Bragg reflector short pass filter suppressing wavelengths > 240 nm (Ferdinand-Braun-Institut, Berlin, Germany) 51,52 . A homogenous irradiance of 0.13 mW/cm 2 was achieved on a 70 mm × 70 mm area. ...
... The punch biopsies of mucosa models and human oral mucosa were fixated in neutral buffered 4% formalin solution (Sigma #HT501128-4L, Saint Louis, MO) after irradiation. The fixated biopsies were dewatered and embedded in paraffin blocks (Histosec, Merck Millipore) 51 , sectioned to 1-2 µm and incubated with anti-6-4PP (clone 64 M-2, Cosmo Bio), anti-CPD (clone TDM-2, Cosmo Bio) or anti p53 (clone DO7, Novastra) and subsequently stained with Alkaline Phosphatase/RED, Rabbit/Mouse (Agilent Technologies) for the detection of 6-4PP, CPD and p53. ...
The inactivation of multi resistant pathogens is an important clinical need. One approach is UV-C irradiation, which was previously not possible in vivo due to cytotoxicity. Recently, far UV-C irradiation at λ < 240 nm was successfully used on skin with negligible damage. A potential application site is the nasal vestibule, where MRSA accumulates and cannot be treated using antiseptics. We irradiated 3D mucosa models and excised human mucosa with 222 and 233 nm far UV-C in comparison to 254 nm and broadband UV-B. Eradication efficiency was evaluated by counting colony forming units; irritation potential was evaluated by hen’s egg-chorioallantoic membrane assay and trans epithelial electrical resistance; cell viability was assessed by MTT. DNA damage and cell protective mechanisms were evaluated immunohistopathologically. On mucosa models, MRSA reduced by ≈ 5 log10 for 60 mJ/cm² irradiation at 233 nm. A slightly increased cell viability was observed after 24 h. Lower doses showed lower irritation potential than the positive controls or commercial mouthwash, while 80 mJ/cm² had strong irritation potential. DNA damage occurred only superficially and decreased after 24 h. On excised human mucosa, < 10% of keratinocytes were affected after 150 mJ/cm² 222 nm or 60 mJ/cm² 233 nm.
... 6 Additionally, AlGaN-based LEDs emitting in the far-ultraviolet-C (far-UVC) range have been created to meet the demand for skin-friendly UVC-antisepsis applications. 7 Very recently, the concept of polarization doping has been introduced to enhance the performance of far-UVC LEDs compared to those with conventional doping. 8 Understanding whether cations in the group III sublattice of Al x Ga 1Àx N are randomly distributed or exhibit some form of ordering (either long-range or short-range) is crucial for laying the foundation for the study of more complex doped materials. ...
In this study, we investigate the local structure of aluminum (Al) in a comprehensive series of AlxGa1−xN epilayers, where the Al concentration spans from the dilute limit to 100%. We analyze grazing incidence Al K-edge tender x-ray absorption spectroscopy data using both linear combination fitting based on reference limit spectra and full quantitative analysis. The results indicate deviations from random cation distribution with varying signs within the explored concentration range. Additionally, we observe a reduction in cationic interatomic distances over a wide concentration range, which contrasts with some previous studies conducted at hard x-ray absorption edges.
... Over the past decade, extensive research has substantiated the safety of human exposure to far-UVC light (wavelengths from 200 nm to 230 nm) and its effectiveness in inactivating diverse pathogens, including human coronaviruses [1][2][3][4][5][6][7][8][9][10] . These compelling findings underscore the immense potential of far-UVC sources in curtailing airborne viral transmission, thereby playing a crucial role in the containment of diseases like COVID-19 and averting future pandemics. ...
Far-UVC light in the wavelength range of 200-230 nm has attracted renewed interest because of its safety for human exposure and effectiveness in inactivating pathogens. Here we present a compact solid-state far-UVC laser source based on second-harmonic generation (SHG) using a low-cost commercially-available blue laser diode pump. Leveraging the high intensity of light in a nanophotonic waveguide and heterogeneous integration, our approach achieves Cherenkov phase-matching across a bonded interface consisting of a silicon nitride (SiN) waveguide and a beta barium borate (BBO) nonlinear crystal. Through systematic investigations of waveguide dimensions and pump power, we analyze the dependencies of Cherenkov emission angle, conversion efficiency, and output power. Experimental results confirm the feasibility of generating far-UVC, paving the way for mass production in a compact form factor. This solid-state far-UVC laser source shows significant potential for applications in human-safe disinfection, non-line-of-sight free-space communication, and deep-UV Raman spectroscopy.
