Excimer Lamp Research Articles

Different biological effects of exposure to far-UVC (222nm) and near-UVC (254nm) irradiation.

Ultraviolet C (UVC) light has long been used as a sterilizing agent, primarily through devices that emit at 254nm. Depending on the dose and duration of exposure, UV 254nm can cause erythema and photokeratitis and potentially cause skin cancer since it directly modifies nitrogenated nucleic acid bases. Filtered KrCl excimer lamps (emitting mainly at 222nm) have emerged as safer germicidal tools and have even been proposed as devices to sterilize surgical wounds. All the studies that showed the safety of 222nm analyzed cell number and viability, erythema generation, epidermal thickening, the formation of genetic lesions such as cyclobutane pyrimidine dimers (CPDs) and pyrimidine-(6-4)-pyrimidone photoproducts (6-4PPs) and cancer-inducing potential. Although nucleic acids can absorb and be modified by both UV 254nm and UV 222nm equally, compared to UV 254nm, UV 222nm is more intensely absorbed by proteins (especially aromatic side chains), causing photooxidation and cross-linking. Here, in addition to analyzing DNA lesion formation, for the first time, we evaluated changes in the proteome and cellular pathways, reactive oxygen species formation, and metalloproteinase (MMP) levels and activity in full-thickness in vitro reconstructed human skin (RHS) exposed to UV 222nm. We also performed the longest (40days) in vivo study of UV 222nm exposure in the HRS/J mouse model at the occupational threshold limit value (TLV) for indirect exposure (25mJ/cm2) and evaluated overall skin morphology, cellular pathological alterations, CPD and 6-4PP formation and MMP-9 activity. Our study showed that processes related to reactive oxygen species and inflammatory responses were more altered by UV 254nm than by UV 222nm. Our chronic in vivo exposure assay using the TLV confirmed that UV 222nm causes minor damage to the skin. However, alterations in pathways related to skin regeneration raise concerns about direct exposure to UV 222nm.

Biomimetic high water adhesion superhydrophobic surface via UV nanoimprint lithography

Imitating nature and comprehending its workings is a means for human beings to advance the development of functional materials. In this study, UV nanoimprint lithography technology was utilized to successfully replicate the micro-nano hierarchical structure (micro-papillae and nano-wax tube crystals) present on the surface of the natural fresh lotus leaf. A series of UV-curable waterborne polyurethane acrylate (UV-WPUA) surfaces with special wetting and superhydrophobic properties were obtained. The polydimethylsiloxane negative stamp with lotus leaf’s structure was obtained through a stamp replica molding method, and then the UV-WPUA resin covered with the negative stamp was exposed to 172 nm Xe2* excimer and medium-pressure mercury lamps to mimic the micro-nano hierarchical structure of the lotus leaf. The UV-WPUA surfaces displayed high water adhesion superhydrophobic properties, with a water contact angle reaching 160.8° and water adhesive force of 140.0 μN, and exhibiting excellent self-cleaning performance. The results indicate that higher the UV intensity, the more accurately the surface replicates the micro-nano hierarchical structure of the lotus leaf, resulting in larger water contact angle and higher adhesive force. This study paves the way for the advancement of functional surfaces through the simulation of natural materials.

High-Strength Epoxy Nanocomposites Reinforced with Photochemically Treated CNTs.

A carbon nanotube (CNT)/epoxy nanocomposite was prepared using a photochemical surface modification process of CNTs. The vacuum ultraviolet (VUV)-excimer lamp treatment created reactive sites on the CNT surface. Increasing the irradiation time increased the oxygen functional groups and changed the oxygen bonding state such as C=O, C-O, and -COOH. By the VUV-excimer irradiation on CNTs, the epoxy infiltrated well between the CNT bundles and formed a strong chemical bond between CNT and epoxy. The tensile strength and elastic modulus of the nanocomposites with VUV-excimer irradiated sample during 30 min (R30) were found to increase by 30 and 68% compared to using pristine CNT, respectively. R30 was not pulled out and remained embedded in the matrix until the fracture occurred. The VUV-excimer irradiation is an effective surface modification and functionalization method for improving the mechanical properties of CNT nanocomposite materials.

Accelerated Ultraviolet Treatment of Carbamazepine and NDMA in Water under 222 nm Irradiation.

Krypton chloride (KrCl*) excimer ultraviolet (UV) light may provide advantages for contaminant degradation compared to conventional low-pressure (LP) UV. Direct and indirect photolysis as well as UV/hydrogen peroxide-driven advanced oxidation (AOP) of two chemical contaminants were investigated in laboratory grade water (LGW) and treated secondary effluent (SE) for LPUV and filtered KrCl* excimer lamps emitting at 254 and 222 nm, respectively. Carbamazepine (CBZ) and N-nitrosodimethylamine (NDMA) were chosen because of their unique molar absorption coefficient profiles, quantum yields (QYs) at 254 nm, and reaction rate constants with hydroxyl radical. Quantum yields and molar absorption coefficients at 222 nm for both CBZ and NDMA were determined, with measured molar absorption coefficients of 26 422 and 8170 M-1 cm-1, respectively, and QYs of 1.95 × 10-2 and 6.68 × 10-1 mol Einstein-1, respectively. The 222 nm irradiation of CBZ in SE improved degradation compared to that in LGW, likely through promotion of in situ radical formation. AOP conditions improved degradation of CBZ in LGW for both UV LP and KrCl* sources but did not improve NDMA decay. In SE, photolysis of CBZ resulted in decay similar to that of AOP, likely due to the in situ generation of radicals. Overall, the KrCl* 222 nm source significantly improves contaminant degradation compared to that of 254 nm LPUV.

Novel bandpass filter for far UV-C emitting radiation sources

Disinfection with far UV-C radiation (<230 nm) is an effective method to inactivate harmful microorganisms like the SARS-CoV2 virus. Due to the stronger absorption than regular UV-C radiation (254 nm) and hence limited penetration into human tissues, it has the promise of enabling disinfection in occupied spaces. The best far-UV sources so far are discharge lamps based on the KrCl* excimer discharge peaking at 222 nm, however they produce longer wavelength radiation as a by-product. In current KrCl* excimer lamps usually a dichroic filter is used to suppress these undesired longer wavelengths. A phosphor-based filter is an alternative which is cheaper and easier to apply. This paper describes the results of our exploration of this opportunity. Various compounds were synthesized and characterized to find a replacement for the dichroic filter. It was found that Bi3+-doped ortho-borates with the pseudo-vaterite crystal structure exhibit the best absorption spectrum i.e. high transmission around 222 nm and strong absorption in the 235–280 nm range. Y0.24Lu0.75Bi0.01BO3 showed the best absorption spectrum in the UV-C. To suppress the unwanted Bi3+ emission (UV–B), the excitation energy can be transferred to a co-dopant. Ho3+ turned out to be the best co-dopant, and Ho0.24Lu0.75Bi0.01BO3 appeared to be the best overall candidate for the phosphor filter material. A suitable formulation for a coating suspension containing this material was found, and quite homogeneous coatings were achieved. The efficiency of these filter layers was investigated and the results in terms of exposure limit increase i.e. gain factor vs. no filter were compared with the dichroic filter. We achieved a gain factor for the Ho3+ containing sample of up to 2.33, i.e. not as good as that of the dichroic filter (∼4.6), but a very relevant improvement, making Ho0.24Lu0.75Bi0.01BO3 an interesting material for a cost-effective filter for KrCl* far UV-C lamps.

Retrospective analysis of ultrathin skin grafting over carbon dioxide ablated lesions supplemented with excimer lamp (308 nm) therapy in stable vitiligo.

Background Of all the tissue or cellular grafting techniques used in the treatment of vitiligo, melanocyte transplant/transfer through ultrathin skin grafting (UTSG) provides rapid onset of regimentation. The regimentation process is further accelerated with a combination of psoralen and ultraviolet A radiation, or psoralen and ultraviolet A obtained by sunlight or narrowband ultraviolet light B, or excimer laser/lamp (308 nm). Aims We assessed the efficacy of carbon dioxide laser ablation followed by melanocyte transplant/transfer through ultrathin skin graft sheet/sheets and further treated by excimer lamp therapy in patients with stable vitiligo. Methods One hundred ninety-two patients with stable vitiligo were treated with UTSG following carbon dioxide laser ablation and patients were then put on excimer lamp therapy. Primary efficacy was determined in terms of grades of regimentation and colour match at the end of 1-year. Results A total of 192 stable vitiligo patients with a mean age of 32.71 ± 8.55 years were recruited. Of the total 410 lesions, 394 showed excellent regimentation indicating a success rate of 96.1% at 1-year follow-up, whereas 16 (3.9%) lesions present on fingertips and toe tips showed poor or no regimentation at 3-month and 1-year follow-up. With regards to colour match, 394 (96.1%) lesions had achieved excellent colour match, and 16 lesions (3.9%) had poor or no colour match at 1-year follow-up. Limitations This was a single-center study with a small sample size. Conclusion The effectiveness of carbon dioxide laser ablation followed by melanocyte transfer/transplant through ultra-thin skin graft sheet/sheets when combined with excimer lamp therapy provides favourable cosmetic outcomes with rapid onset of regimentation in stable vitiligo.

Analysis and Experimental Validation of an Integrated Current-Source Power Supply With High Power Factor for DBD Applications

An integrated current-source high-frequency pulse excitation power supply with high power factor (PF), low total harmonic distortion (THD) of the input current, and high efficiency for dielectric barrier discharge (DBD) loads is proposed in this article. The proposed power supply consists of a current source unit and a bipolar pulse excitation voltage generation unit. The current source unit is used to generate a current source for the excitation voltage generation unit and achieve a high PF and a low current harmonic distortion in the ac side of the proposed power supply. By planning the modes of the excitation voltage generation unit, not only a bipolar pulse excitation voltage with high rising and falling rates on the DBD loads is generated, but also the soft-switching of all power switches is achieved. The experimental results show that not only a unity PF ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;$</tex-math> </inline-formula> 0.99) and a low THD ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&lt;$</tex-math> </inline-formula> 10%) are achieved, but also a bipolar high-frequency (hundreds of kilohertz) pulse excitation voltage with high average rising and falling rates (7.227 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 109 V/s) for a DBD excimer lamp is generated. Finally, in comparison with different power supplies, the proposed power supply can not only fully take advantage of the potential of the DBD excimer lamp but also has many advantages of high efficiency (92%), integrated structure, and simple driver.

222 nm Far-UVC from filtered Krypton-Chloride excimer lamps does not cause eye irritation when deployed in a simulated office environment.

Far-UVC, from filtered Krypton-Chloride lamps, is promising for reducing airborne transmission of disease. While significant research has been undertaken to investigate skin safety of these lamps, less work has been undertaken on eye safety. There is limited data on human eye safety or discomfort from the deployment of this germicidal technology. In this pilot study, immediate and delayed eye discomfort were assessed in a simulated office environment with deployment of Krypton-Chloride lamps, located on the ceiling and directed downwards into the occupied room. Discomfort was assessed immediately postexposure and several days after exposure using validated, Standard Patient Evaluation Eye Dryness (SPEED) and Ocular Surface Disease Index (OSDI) questionnaires. Our results show no significant eye discomfort or adverse effects from the deployment of Far-UVC in this simulated office environment, even when lamps were operated continuously with participants receiving head exposures of up to 50 mJ cm-2 . In addition, a statistically significant reduction in bacteria and fungi of 52% was observed. Far-UVC in this simulated office environment did not cause any clinically significant eye discomfort and was effective at reducing pathogens in the room. These results contribute an important step to further investigation of the interaction of Far-UVC with the human eye.

Inactivation of Coronavirus OC43 by Excimer Lamp, UV Lamp, and Deep UV-LED at Irradiation Wavelengths of 222 nm, 254 nm, and 275 nm

Inactivation of Coronavirus OC43 by Excimer Lamp, UV Lamp, and Deep UV-LED at Irradiation Wavelengths of 222 nm, 254 nm, and 275 nm

A novel LC‐based bipolar pulsed power supply for dielectric barrier discharge excimer lamps

SummaryAn excitation voltage with a high rising rate, falling rate, and idle time simultaneously is beneficial to taking advantage of the potential of dielectric barrier discharge (DBD) loads. However, how to generate this kind of excitation voltage with a simple structure is rarely researched. To address the issue, a novel LC‐based bipolar high‐voltage pulsed power supply is proposed in this paper. The proposed power supply is comprised of an inductance, two capacitances, a step‐up transformer, and two power switches sharing the same ground. By planning the switch sequence of the two power switches, a resonant stage and an idle stage are formed. The resonant stage is used to generate a bipolar pulse excitation voltage on DBD excimer lamps and an idle time in the excitation voltage is generated in the idle stage. The characteristics and the parameters design of the proposed power supply are studied by theoretical analysis. To verify the feasibility of the proposed power supply, an experimental setup is built with a DBD‐type excimer lamp. The experimental results show that the power supply not only better takes advantage of the potential of DBD excimer lamps, but also there is a fine luminous regulation feature for the excimer lamp. Besides these characteristics, the proposed power supply has several other benefits, such as good adaptability to different DBD‐type excimer lamps, a small number of components, and high efficiency.

Ozone catalytic oxidation of dimethyl sulfide and surface analysis of iodine catalyst

This study reports on the ozone catalytic oxidation of dimethyl sulfide; a major odor material in wastewater facilities. A xenon excimer lamp (XEL) was used for ozone generation, and iodine compounds (I− and IO3 −) were utilized as a catalyst. The three types of activated carbon tested as catalysts were: activated carbon impregnated with iodine compounds and sulfate (AC-I/S), activated carbon impregnated with iodine (AC-I) and activated carbon without impregnation (AC). Only AC-I/S had catalytic activity in the dynamic adsorption experiment. The breakthrough time of dimethyl sulfide increased by 10 times upon adding ozone to the AC-I/S. Catalyst characterization by pH measurement and XPS analysis suggested that the catalytic activity of iodine compounds was influenced by the surface acidity. These results suggest that the XEL and AC-I/S are applicable for ozone catalytic oxidation in gas treatments.

Theoretical Investigation of DBD Discharge Development for VUV Emission in Excimer Lamp

Theoretical Investigation of DBD Discharge Development for VUV Emission in Excimer Lamp

Sensitive Detection of Nitrite and Nitrate in Seawater by 222 nm UV-Irradiated Photochemical Conversion to Peroxynitrite and Ion Chromatography-Luminol Chemiluminescence System

Sensitive detection methods for nitrite (NO2-) and nitrate (NO3-) ions are essential to understand the nitrogen cycle and for environmental protection and public health. Herein, we report a detection method that combines ion-chromatographic separation of NO2- and NO3-, on-line photochemical conversion of these ions to peroxynitrite (ONOO-) by irradiation with a 222 nm excimer lamp, and chemiluminescence from the reaction between luminol and ONOO-. The detection limits for NO2- and NO3- were 0.01 and 0.03 μM, respectively, with linear ranges of 0.010-2.0 and 0.10-3.0 μM, respectively, at an injection volume of 1 μL. The results obtained by the proposed method for seawater analysis corresponded with those of a reference method (AutoAnalyzer based on the Griess reaction). As luminol chemiluminescence can measure ONOO- at picomolar concentrations, our method is expected to be able to detect NO2- and NO3- at picomolar concentrations owing to the high conversion ratio to ONOO- (>60%), assuming that contamination and background chemiluminescence issues can be resolved. This method has the potential to emerge as an innovative technology for NO2- and NO3- detection in various samples.

Oxygen Effect on the Ultraviolet-C Photochemistry of Lactic Acid.

Lactic acid, a small α-hydroxyacid, is ubiquitous in both indoor and outdoor environments. Recently, the photochemistry of lactic acid has garnered interest among the abiotic organic chemistry community as it would have been present in abiotic settings and photoactive with the high-energy solar radiation that would have been available in the low oxygen early Earth environment. Additionally, we propose that the photochemistry of lactic acid is relevant to modern Earth during indoor ultraviolet-C (UVC) sterilization procedures as lactic acid is emitted by humans and is thus prevalent in indoor environments where UVC sterilization is increasingly being used. Here, we study the oxygen effect on the gas phase photolysis of lactic acid using Fourier-transform infrared (FTIR) spectroscopy and isotopically labeled oxygen (18O2). We find that the major products of gas phase lactic acid photolysis are CO2, CO, acetaldehyde, and acetic acid. Furthermore, these products are the same with or without added oxygen, but the partial pressures of produced CO2, CO, and acetaldehyde increase with the amount of added oxygen. Notably, the added oxygen is primarily incorporated into produced CO2 and CO, while little or none is incorporated into acetaldehyde. We combine the results presented here with those in the literature to propose a mechanism for the gas phase photolysis of lactic acid and the role of oxygen in this mechanism. Finally, we compare the output of a krypton-chloride excimer lamp (λ = 222 nm), one of the lamps proposed for UVC sterilization procedures, to the absorption of lactic acid. We show that lactic acid would be photoactive during UVC sterilization procedures, and we use the gas phase results presented here and aqueous lactic acid photolysis results previously published to assess potential byproducts from lactic acid reactions during UVC sterilization procedures.

The Dielectric Barrier Discharge and the Start of a Beautiful Friendship: Personal Remembrance of Dr. Ulrich Kogelschatz

One can safely say that the pioneering work of Dr. Ulrich Kogelschatz and his team on the physics and chemistry of the dielectric barrier discharge was foundational and remain of great relevance to the present day. Kogelschatz and his team made some of the early high-resolution measurements of the current pulses associated with filaments and conducted simulations to elucidate the chemical processes taking place in DBD plasmas. On the engineering/technology side, he contributed to the development of DBD-based excimer lamps, to the optimization of DBD-based ozone generators and to many other advancements. His numerous papers on the physics and applications of DBD have educated a generation of researchers involved with such devices. I consider myself one of those students who learned a lot from him, both from his writings and from personal interaction. In this perspective, I first briefly summarize the working of barrier discharges and some of Kogelschatz’s contributions to this field. Then, I highlight some of the most valuable interactions I had the privilege to have with him, who I considered to be a mentor and a dear friend for many years. Please note that I use the formal title “Dr. Kogelschatz” in the title and sub-titles but in the text, I use Ulrich (or Uli) as that is how I addressed him in person.

Effect of fractional laser alone or in combination on alopecia areata: A systematic review and meta-analysis.

Alopecia areata (AA) is characterized by limited non-scarring patchy alopecia, which appears as round or oval patches and is prone to recurrence, causing severe psychological burdens to patients. No specific device has been approved by the FDA for the treatment of baldness, but new treatments are being investigated and treatments such as the excimer laser, He- Ne laser, and excimer lamp have been proposed. A growing number of studies have found that fractional lasers also have great potential in the treatment of AA. A literature search and meta-analysis using Review Manager 5.4 software to investigate the efficacy of fractional laser treatment for AA. Fractional laser combined with minoxidil (RR 1.32, 95% CI 1.17-1.49, p < 0.00001) or cortisol (RR 1.39, 95% CI 1.15-1.67, p=0.00006) was more effective than either drug alone in the treatment of AA. Of course, the fractional laser alone was also effective in the treatment of AA (RR 10.33, 95% CI 2.07-51.36, p=0.004) and more effective than cortisol alone (RR 1.86, 95% CI 1.36-2.52, p < 0.00001), and there was no effect on the occurrence of adverse effects (p=0.49 > 0.05). When compared to other physical treatments of a comparable kind, fractional laser therapy's effectiveness was not significantly different (p=0.15 > 0.05). Our results show that the use of fractional lasers can effectively treat alopecia areata.

Field Study and Evaluation of KrCl* Far UV-C Device Capability for Inactivation of Phi6 Bacteriophage.

"Far UV-C" is an effective disinfection method that can be deployed in occupied areas. Commercially available Krypton Chloride (KrCl*) excimer lamps filtered to emit at 222 nm are effective in disinfecting pathogens and safe for human exposure up to an allowable threshold exposure, which is much longer than for conventional UV lamps emitting at 254 nm. Laboratory and controlled field testing of a filtered KrCl* excimer lamp for disinfection of a virus suspended in a thin film aqueous solution in an occupied office setting was conducted. Complete inactivation of almost 6 log (99.9999%) of Phi6 bacteriophage virus was achieved in ~20 min of exposure time in a field setting, equivalent to a dose of about 10 mJ cm-2 . The Phi6 inactivation rate constant for the field test results were not statistically different from laboratory values (P > 0.05, paired t-test). When positioned at 1 m distance from possible human exposure, this device can be used safely for almost 4.5 h of continuous direct exposure without any acute or long-term adverse health effects. This study illustrates the applicability and deployment of Far UV-C for pathogen reduction and can help in decision making for implementation of Far UV-C for disinfection in human-occupied environments.

An excimer lamp to provide far-ultraviolet C irradiation for dining-table disinfection

Dining tables may present a risk to diners by transmitting bacteria and/or viruses. Currently, there is a lack of an environmental-friendly and convenient means to protect diners when they are sitting together. This investigation constructed far-UVC excimer lamps to disinfect dining-table surfaces. The lamps were mounted at different heights and orientations, and the irradiance on table surfaces was measured. The irradiation doses to obtain different inactivation efficiencies for Escherichia coli (E. coli) were provided. In addition, numerical modeling was conducted for irradiance and the resulting inactivation efficiency. The surface-to-surface (S2S) model was validated with the measured irradiance. The germicidal performance of far-UVC irradiation, the far-UVC doses to which diners were exposed, and the risk of exposure to the generated ozone were evaluated. The results revealed that an irradiation dose of 12.8 mJ/cm2 can disinfect 99.9% of E. coli on surfaces. By varying the lamp irradiance output, the number and positions of the lamps, the far-UVC irradiation can achieve a 3-log reduction for a dining duration of 5 min. Besides, the far-UVC lamp has a low damage risk to diners when achieving an effective inactivation rate. Moreover, there is virtually no ozone exposure risk in a mechanically ventilated dining hall.

A novel self-wrinkled polyurethane-acrylate wood coating with self-matting, anti-fingerprint performance and skin-tactile feeling via excimer lamp/UV curing.

Wrinkled surfaces exist widely in nature and organic living world, such as plants, insects, and skin. The optical, wettability and mechanical properties of materials can be enhanced by artificially preparing regular microstructure on the surface of materials. In this study, a novel self-wrinkled polyurethane-acrylate (PUA) wood coating with self-matting, anti-fingerprint performance and skin-tactile feeling curing by excimer lamp (EX) and ultraviolet (UV) was prepared. The wrinkles were formed on the surface of PUA coating at microscopic level after excimer and UV mercury lamp irradiation. The width and height of the wrinkles on the coating surface can be controlled to adjust the coating performance by changing the curing energy. When the PUA coating samples were cured by excimer lamp and UV mercury lamp with curing energy of 25-40 mJ cm-2 and 250-350 mJ cm-2, the excellent coating performances were observed. The gloss value of self-wrinkled PUA coating at 20° and 60° were less than 3 GU, while at 85° was 6.5 GU, which satisfied the demanding of matting coating. Besides, the fingerprints on the coating samples could disappear in 30 s and could still have anti-fingerprint performance after 150 times of anti-fingerprint tests. Furthermore, the pencil hardness, abrasion quantity and adhesion of self-wrinkled PUA coating were 3H, 0.045 g and 0 grade respectively. Finally, the self-wrinkled PUA coating has excellent skin-tactile feeling for touching. The coating can be applied to wood substrates, and has potential application in the field of wood-based panels, furniture and leather.

Study of Color Change Characteristics of Plasma Indicators by Vacuum Ultraviolet Light from Excimer Lamps

We examined the color change characteristics of two types of "Plasma Indicators" (referred to as Indicators hereinafter) irradiated by vacuum ultraviolet (VUV) light from excimer lamps. We found that the colors of both Indicators change in accordance with the sensitivity of the VUV irradiation dose when the oxygen concentration is constant. We concluded that an appropriate Indicator must be selected according to the required VUV irradiation dose of each excimer lamp application. Moreover, we demonstrated that both Indicators were useful, and the reproducibility of VUV irradiation was confirmed only under the same VUV irradiation conditions.