UVC Range Research Articles

Surface Disinfection Systems with UV-C Lamps – Verification Measurements and Design Procedure Proposal

ABSTRACT Ultraviolet radiation in the UV-C range is widely applied to disinfect surfaces, air, and water. UV-C (germicidal) lamps are commonly used, and their application is reliable, scientifically proven, and efficient to inactivate various types of bacteria, viruses, and fungal spores, including the SARS-CoV-2 virus. This research aims to develop a UV-C irradiance design procedure for germicidal devices disinfecting surfaces in rooms. This procedure considers the required values of UV-C radiation doses that disinfect rooms efficiently. For this purpose, it has been proposed to apply the DIALux evo software to design the appropriate UV-C irradiance on disinfected room surfaces using different germicidal devices. The measurements verified the accuracy of the simulation performed in the DIALux evo software, which also considered the reflection of the ultraviolet radiation from the principal planes of the room. Two rooms with different dimensions were selected to verify the computational accuracy of the developed design procedure for the disinfection system. Ultraviolet lamps were placed in the rooms, and irradiance measurements were taken at the selected measuring points. The results of the irradiance measurements were compared. The comparative analysis of the disinfection device proved that it was possible to adapt the DIALux evo software to make the calculations for designing room disinfection systems. The research made it possible to determine a suitable design procedure for surface disinfection systems, which prevents errors in proper surface disinfection after implementing UV-C lamps in the room.

The Impact of Time and Temperature of Operation on the Characteristics of High-Power UVC LEDs and Their Disinfection Efficiency

Disinfection and sterilization based on the use of UVC radiation are the key technologies ensuring health and safety. Their reliability depends on assuring the effectiveness of the performed process. In recent years, the rapid development of LED sources emitting high-power radiation in the UVC range has been observed, and there is a growing interest in using them in a variety of smart applications, mostly because they are easy to control, do not contain hazardous substances, and there are prospects to increase their energy efficiency. However, the literature does not provide enough knowledge on the reliability of disinfection with high-power UVC LEDs. This research aims to present a methodology of linking the performance characteristics with assessing the forecasted changes in the disinfection efficiency of exemplary UVC high-power LEDs caused by thermal and temporal changes in their characteristics. Based on the performed degradation test, the impact of the temperature and time of operation of the high-power UVC LEDs on the effectiveness of disinfection was evaluated, and the required disinfection times for exemplary pathogens were calculated. The results reveal a strong influence of the time of operation of high-power UVC LEDs on the disinfection reliability caused by the degradation of their optical power but with a low significance of wavelength shift.

Degradation- and Thermal-Related Changes in Selected Electro-Optical Parameters of High-Power 270–280 nm LEDs

Recently, the rapid development of LED sources emitting high-power radiation in the UVC range has been observed, and there is a growing interest in using these LED sources in practical solutions. The innovative constructions of disinfection and sterilization devices depend on the effectiveness and reliability of UVC radiation sources. At the same time, the literature reports that deep experimental analysis of degradation of high-power LEDs is limited. The aim of this research is to contribute to existing knowledge through a comparative assessment of the changes in optical power, spectral power distribution, and forward voltage drop in time and temperature of exemplary high-power UVC LEDs. For this purpose, a controlled 1500 h degradation of six different high-power UVC LEDs was performed, based on which we determined their expected lifetimes L70, L80, and L90. According to our results, the L80 varies from 180 h to 1500 h. Stronger degradation of optical power was observed with lower current. No significant impact on the spectral parameters was observed. The results also indicate the low influence of temperature on the voltage (<0.12%/°C), optical power (<0.22%/°C), and spectral parameters (peak wavelength Δλ and full width at half maximum ΔFWHM < 0.025 nm/°C).

Comprehensive Electro-Optical Investigation of a Ga-Doped AlN Nanowire LED for Applications in the UV-C Range

Comprehensive Electro-Optical Investigation of a Ga-Doped AlN Nanowire LED for Applications in the UV-C Range

Dependence of persistent photoconductivity on the thickness of β-Ga2O3 thin film photodetectors on c-plane sapphire via magnetron sputtering

β-Ga2O3 is a next-generation, ultra-wide bandgap semiconductor with intrinsic solar-blindness having the potential to replace Si for photodetection applications especially for the UV-C range. The material itself shows excellent photoconductive gain but is quite prone to the menace of the persistent photoconductivity, or the PPC. The fabricated devices become slower because of PPC and it also leads to reliability issues for photodetection logic. Herein, we report the dependence of the PPC effect on the different thickness of β-Ga2O3 thin film based solar-blind photodetectors. The polycrystalline films are grown on c-plane sapphire via RF magnetron sputtering at an elevated temperature of 500 °C. Optical bandgap of the films decreases with increasing thickness while their grain size increases. The oxygen-related defects studied using x-ray photoelectron spectroscopy are responsible for the observation of the enhanced PPC effect for the thinner films. The device performance is intimately connected with the quality of the thin film, its stoichiometry and the amount of oxygen defects present in the system. Better quality films with lower amount of oxygen vacancies show an improved performance with the least amount of PPC. This work shows that oxygen vacancies play an important role in determining the ultimate device performance and need to be engineered for high performance photodetectors.

Designing, Modeling, and Fabrication of a Novel Solar-Concentrating Spittoon against COVID-19 for Antibacterial Sustainable Atmosphere

Spreading infectious illnesses such as viral meningitis, hepatitis, and cytomegalovirus among people is facilitated by spitting in public. India is more prone to transferring infectious illnesses. Recent research discovered that the new Coronavirus may also be transmitted via an infected person’s saliva. Self-collected saliva from 91.7% of patients contains COVID-19. Numerous nations have prioritized preventing individuals from spitting in open or public areas such as hospitals, parks, airports, train stations, etc. The UVC range has a greater damaging effect on microbial cells because microorganisms’ intracellular components, such as RNA, DNA, and proteins, are sensitive to UVC photon absorption. In this article, the design and construction of a solar-concentrating spittoon is attempted. At its receiver, it can create a temperature of 390 K and 176 W of heat. At this temperature, most viruses (including Coronavirus), bacteria, and pathogens are inactivated. Daily, from 8:00 a.m. until 5:00 p.m., the solar-concentrating spittoon is functional. The solar-concentrating spittoon performance was best for nine hours. The receiver thermal efficiency was 80% and 20% of heat was lost to the surroundings. The overall efficiency was found to be 70%. During this time, most people spend their time outside, where this solar-powered spittoon can incinerate human cough and spit within one minute. The installation of this solar-concentrated spittoon will aid in preventing the spread of fatal dangerous diseases and cleaning the city.

ANALYSIS OF EXISTING ENERGY INSTALLATIONS FOR ULTRAVIOLET DISINFECTION OF RECIRCULATING NUTRIENT SOLUTION IN SYSTEMS OF CROPS AUTOMATIC HYDROPONIC IRRIGATION IN PROTECTED GROUND

Decisive for solving food security problems in Ukraine while preserving and restoring the ecology of the environment should be an intensive method of management, i.e. the orientation of economic entities of their own activities on the innovative type of development, active use of scientific and technical developments and implementation of modern agricultural innovations. In its turn, the qualitative and quantitative indicators of crop production of protected soil depend on the technical condition of technological equipment.
 The purpose of the work is research and analysis of existing power plants for ultraviolet disinfection of recirculating nutrient solution in systems of automatic hydroponic irrigation of crops in a protected soil, as well as elucidation of the impact of filtration and disinfection of nutrient solution on the presence of microorganisms when reusing plants in systems. The paper investigates the ways to improve the operation of power plants for ultraviolet disinfection of recirculating nutrient solution in the cultivation of crop products of protected soil. It provides the value of the required radiation dose for 90% disinfection of the recirculation solution from various bacteria, viruses and fungal spores and the dependence of bactericidal efficiency on the wavelength of light. Ultraviolet rays with a length from 200 to 280 nm (UV-C range) have the most pronounced bactericidal effect. Research in this area has shown that the optimal wavelength for irradiation is 253.7 nm. As a result of such irradiation, microorganisms die or lose their ability to reproduce. It has been proven that the classical layout scheme of power plants for ultraviolet disinfection of the recirculation solution is inefficient, because it does not rid the recirculation solution of turbidity and the presence of iron and does not guarantee high efficiency of the ultraviolet disinfection plants. The paper describes the method of carbonate precipitation of metal ions, which is based on the formation of insoluble metal compounds as a result of treatment of an aqueous solution with carbonates or bicarbonates of alkali metals. Prospects for further research are the development of methods and tools to improve the operation of power plants for ultraviolet disinfection of recirculating nutrient solution in the cultivation of crop products of protected soil.

A New Drug-Free Cancer Therapy Using Ultraviolet Pulsed Irradiation. PDT (PhotoDynamic Therapy) to PPT (Pulsed Photon Therapy)

Pulsed ultraviolet (UV) irradiation can be used to generate a broad UV-C spectrum. The pulsing nature of such a spectrum helps increase the damage to cancer cells, leading to their injury and death. In contrast, non-tumor cells repair the damage and survive the same pulsed UV irradiation energy. Herein, we describe the development of a pulsed UV irradiation method for cancer cell dysfunction that irradiates cells with pulsed light by generating tremendous instantaneous UV energy-tens of thousands of times greater than that generated by UV lamps-to cause specific cell injury and dysfunction of cancer cells. A newly developed pulsed ultraviolet irradiation device was used. Features of the device used in this study. This device employs a quartz discharge xenon lamp. Cultured tumor cells and non-tumor cells were irradiated with pulsed light at different irradiation doses, and their reactions were observed using optical, electron, and laser microscopes. Cancer cells have more FAS (CD95) receptor domains than non-cancer cells, and pulsed UV irradiation stimulates the production of reactive oxygen species (ROS) and OH, which exceeds the oxidative stress removal function, resulting in cell injury and death. That is, at low UV doses, only cancer cells underwent cell death, whereas non-cancer cells did not. The pulsed UV irradiation technique directly destroys cancer cells and minimizes the number of residual cancer cells while allowing minimum invasion into non-tumor cells, thereby improving their survival. This suggests the possibility of activating the host's local immune response to eliminate residual cancer cells. A newly developed pulsed UV radiation system shows potential for use in the development of a drug-free cancer treatment system that selectively kills tumor cells by irradiating them with high-intensity pulsed UV rays over a broad UV-C range of 230-280 nm.

Development of a geometrical model for the determination of the average intensity in a flow-through UV-LED reactor and validation with biodosimetry and actinometry

Ultraviolet (UV) treatment is widely used for water disinfection. The recent development and improvement of the light emitting diodes (LEDs) in the UVC range makes them an alternative to the traditional mercury vapor UV lamps in the middle or long term. Determining the UV intensity applied by a reactor is essential for evaluating its efficacy. Although doing so is relatively straightforward in simple laboratory reactors, such as a collimated beam reactor (CBR), its calculation for more complex devices, such as a flow-through reactor (FTR), requires indirect approaches. The objective in this study is determining the UV intensity in FTRs equipped with UV-C LEDs by utilizing indirect approaches such as the geometrical modeling of the intensity distribution, chemical actinometry, and biodosimetry using a CBR as a reference. With this method, the inactivation of four bacterial indicators in both the CBR and FTR have also been addressed. The three approaches that were used reported similar values of mean intensity with an average value of 0.86 mW cm−2. Determining the mean intensity enabled calculating the UV doses that were applied to the target water and then determining the inactivation kinetics parameters. The UV dose that was necessary to achieve four-log reductions from the initial bacterial concentration ranged from 5.8 to 17.5 mJ cm−2 depending on the target species. Additionally, the geometrical model developed in this study introduces new possibilities into the optimization of the reactor design.

Design and Analysis of a Novel Ultraviolet-C Device for Surgical Face Mask Disinfection.

This paper deals with the design of a compact sanitization device and the definition of a specific protocol for UV-C disinfection of a surgical face mask. The system was designed considering the material properties, face mask shape, and UV-C light distribution. DIALux software was used to evaluate the irradiance distribution provided by the lamps emitting in the UV-C range. The irradiance needed for UV-C-decontaminated bacteria and virus, and other contaminating pathogens, without compromising their integrity and guaranteeing inactivation of the bacteria, was evaluated. The face mask’s material properties were analyzed with respect to UV-C exposure in terms of physicochemical properties, breathability, and bacterial filtration performance. Information on the effect of time-dependent passive decontamination at room temperature storage was provided. Single and multiple cycles of UV-C sanitization did not adversely affect respirator breathability and bacterial filtration efficiency. This multidisciplinal approach may provide important information on how it is possible to correctly sanitize a face mask and, in case of shortage, safely reuse the face mask.

Emerging Ultraviolet Persistent Luminescent Materials

AbstractUltraviolet (UV, 200–400 nm) persistent luminescence (PersL) is an emerging topic of luminescent materials due to their “self‐sustainable” high‐photon‐energy characteristics. Although the family of UV PersL materials is fast‐growing, especially in the past few years, an overview on the current status in terms of material development, mechanism investigation, promising applications, research challenges, future directions, and the correlations of these aspects is absent. Many potential applications of UV PersL have recently been demonstrated and proposed depending on where UV PersL falls in the UVA (315–400 nm), UVB (280–315 nm), or UVC (200–280 nm) range. Hence, here the state‐of‐the‐art UV PersL materials, the theoretical and experimental attempts and explanations of UV PersL mechanisms, and strategies utilized to improve UV PersL performance are summarized. Also their unprecedented application promises spanning “solar‐blind” tagging (“glow‐in‐the‐bright” tagging), persistent disinfection, persistent photocatalysis, and “device‐free” skin phototherapy that are beyond the capabilities of the “glow‐in‐the‐dark” visible and infrared PersL are discussed. Facing challenges in understanding their complicated mechanisms, meeting their high charging requirement, and easing the public concerns, a bright future for UV PersL materials from lab to market is envisaged.

Solid–Liquid Hybrid‐State Organic Lens for Highly Efficient Deep Ultraviolet Light‐Emitting Diodes

Deep ultraviolet light‐emitting diodes (DUV‐LEDs) are considered to be the most promising ultraviolet light sources for effective and fast sterilization under the worldwide spread of the coronavirus disease (COVID‐19). However, it reminds challenging to promote the light extraction of DUV‐LEDs owing to the strong DUV light absorption of conventional encapsulation materials. Herein, solid–liquid hybrid‐state gels (SLHGs) to fabricate organic lenses for DUV‐LEDs, which largely enhance the light extraction efficiency without sacrificing the working stability, are proposed. Solid‐state cross‐linked networks of polydimethylsiloxane are used in the SLHG structure to maintain the liquid components of silicone oil and demonstrate excellent formability, DUV transparency (over 90% transmittance in the UVC range), and thermal stability. The radiant power of DUV‐LEDs (275 nm) with the optimized SLHG organic lens is enhanced by 52.5% compared to a commercial quartz lens, achieving a record packaging optical effiency of 1.31 among solid‐state packaging DUV‐LEDs. A sterilization evaluation for SARS‐CoV‐2 demonstrates that the inactivation time can be reduced by ≈25% using the SLHG organic lens. Consequently, herein, a feasible and effective method to enhance the optical performance of DUV‐LEDs and advance their promising potential for disinfection applications is provided.

Embedded UV Sensors in CMOS SOI Technology.

We report on ultraviolet (UV) sensors employing high voltage PIN lateral photodiode strings integrated into the production RF SOI (silicon on isolator) CMOS platform. The sensors were optimized for applications that require measurements of short wavelength ultraviolet (UVC) radiation under strong visible and near-infrared lights, such as UV used for sterilization purposes, e.g., COVID-19 disinfection. Responsivity above 0.1 A/W in the UVC range was achieved, and improved blindness to visible and infrared (IR) light demonstrated by implementing back-end dielectric layers transparent to the UV, in combination with differential sensing circuits with polysilicon UV filters. Degradation of the developed sensors under short wavelength UV was investigated and design and operation regimes allowing decreased degradation were discussed. Compared with other embedded solutions, the current design is implemented in a mass-production CMOS SOI technology, without additional masks, and has high sensitivity in UVC.

Photoactive Cu-Containing ZnO-ZnAl-=SUB=-2-=/SUB=-O-=SUB=-4-=/SUB=- nanocomposites

Photoactive Cu-containing ZnO-ZnAl2O3 nanocomposites were synthesized by the polymer-salt method. To study the structure and properties of materials, the methods of luminescent spectroscopy and X-ray phase analysis were used. It has been shown that the resulting nanocomposites are capable of photogeneration of singlet oxygen under the action of UV and blue light. The synthesized materials consist of nanosized hexagonal ZnO crystals and cubic ZnAl2O4 crystals doped with Cu. The study of luminescent properties showed that nanocomposites can be used as down-converters of light that convert radiation from the UV-C range to UV-A and the visible spectral range. Keywords: singlet oxygen, nanoparticle, luminescence, ZnO, ZnAl2O4.

Фотоактивные Cu-содержащие нанокомпозиты ZnO-ZnAl-=SUB=-2-=/SUB=-O-=SUB=-4-=/SUB=-

Photoactive Cu-containing ZnO-ZnAl2O3 nanocomposites were synthesized by the polymer-salt method. To study the structure and properties of materials, the methods of luminescent spectroscopy and X-ray phase analysis were used. It has been shown that the resulting nanocomposites are capable of photogeneration of singlet oxygen under the action of UV and blue light. The synthesized materials consist of nanosized hexagonal ZnO crystals and cubic ZnAl2O4 crystals doped with Cu. The study of luminescent properties showed that nanocomposites can be used as down-converters of light that convert radiation from the UV-C range to UV-A and the visible spectral range.

Preparation and Characterization of Acrylic Pressure-Sensitive Adhesives Crosslinked with UV Radiation-Influence of Monomer Composition on Adhesive Properties.

In this study, syntheses of acrylate copolymers were performed based on the monomers butyl acrylate (BA), 2-ethylhexyl acrylate (2-EHA), and acrylic acid (AA) and the second-type unsaturated photoinitiator 4-acryloyloxybenzophenone (ABP). The structure of the obtained copolymers was confirmed via FT-IR spectroscopic analysis, and the viscosity and the content of non-volatile substances were determined. The adhesive films were then coated and cross-linked using ultraviolet radiation in the UV-C range at various doses (5–50 mJ/cm2). Due to the dependence of the self-adhesive properties of the adhesive layer on the basis weight, various basis weights of the layer in the range of 30–120 g/m2 were tested. Finally, the self-adhesive properties were assessed: tack, peel adhesion, shear strength (cohesion) at 20 °C and 70 °C, as well as the SAFT test and shrinkage. The aim of the study was to determine the effect of the type of monomer used, the dose of ultraviolet radiation, and the basis weight on the self-adhesive and usable properties of the obtained self-adhesive tapes.

Synthesis and characterization of ZnO nanorods-Zn2SiO4 nanoparticles-PMMA nanocomposites for UV-C protection

Nowadays, UV-C is used in a variety of applications, such as disinfection and sterilization of air, surface, and liquids. In particular, its application against the pandemic COVID-19 virus is of great interest. On the other hand, it must be remarked that UV-C is harmful to the eyes, face, head, ears, and skin of engaged employees or personnel but studies on the UV-C range are rare. To the best of our knowledge, studies on zinc silicate as UV-absorber are very rare. In this research, flexible and transparent ZnO nanorods-Zn2SiO4 nanoparticles-PMMA nanocomposite thin films were made for protecting against UV-C radiation. To find the most suitable morphology, the effect of pH variation on the morphology and structural properties of the prepared ZnO–Zn2SiO4 composites were studied. Here we show that the most regular morphology of composites consisting of ZnO nanorods decorated with Zn2SiO4 nanoparticles was obtained at pH 12.5. The UV–vis spectra show that ZnO–Zn2SiO4-PMMA nanocomposite thin films prepared at pH 12.5 exhibit optical transparency in the visible-wavelength region and a prominent UV-C absorbing capability.

GAS BURNER AND QUARTZ BLOWING TABLE

The technology of ultraviolet (UV) disinfection of water, air and surface is based on the bactericidal action of UV radiation. There are several sections of the UV radiation spectrum that have different biological effects: UV-A – 315…400 nm; UV-B – 280…315 nm; UV-C – 200…280 nm; vaccum UV – 100…200 nm. The UV-C range is often called bactericidal because of its high decontamination efficiency against bacteria and varus. The greatest bactericidal effect has radiation in the wavelength range from 205 to 280 nm, and the maximum bactericidal sensitivity of microorganisms is at a wavelength of 265 nm. Therefore, the production of equipment and installations for the manufacture of UV light sources is reaching a new level. One of the most basic equipment for the production of UV lamps is a quartz blowing table and gas burners. The article describes the Assembly of a quartz blowing table and a gas burner. Standard methods of production and testing of quartz blowing tables and gas burners were analyzed. In the course of work and on the basis of the conducted researches technical characteristics and a complete set of the equipment were fulfilled.

Lattice and electronic structures of BAlN in the deep ultraviolet spectral region

BAlN exhibit intriguing properties for both fundamental research and potential application in optoelectronic devices operating in the deep ultraviolet spectral ranges. For BxAl1-xN, the crystal lattice constant derived for the whole range of the alloy composition closely follows Vegard's law. The mechanical stability is represented by elastic constants. The fundamental bandgap is converted from direct in AlN to indirect in BN. The orbital projected band structure of BAlN is obtained to gain insight into the electronic structure and the optical anisotropy with favorable light polarization is understood in terms of the crystal field split-off energy. The band structure parameters including the band gap, the effective masses of electrons and holes are presented and the corresponding electron mobility of BAlN with the direct band gap are predicted to be larger than that of AlN. It is worth noting that BAlN with the direct band gap are quite promising for application in electronic and optoelectronic devices operating in the UVC range.

Inactivation of Coronaviruses and Phage Phi6 from Irradiation across UVC Wavelengths.

Ultraviolet (UV) devices emitting UVC irradiation (200–280 nm) have proven to be effective for virus disinfection, especially on surfaces and in air, due to their rapid effectiveness and limited to no material corrosion. Numerous studies of UV-induced inactivation focused on nonenveloped viruses. Little is known about UVC action on enveloped viruses across UVC wavelengths. In this study, we determined inactivation efficiencies of two coronaviruses (ssRNA) and an enveloped dsRNA bacteriophage surrogate in buffered aqueous solution (pH 7.4) using five commonly available UVC devices that uniquely emit light at different wavelengths spanning 222 nm emitting krypton chloride (KrCl*) excimers to 282 nm emitting UVC LEDs. Our results show that enveloped viruses can be effectively inactivated using UVC devices, among which the KrCl* excimer had the best disinfection performance (i.e., highest inactivation rate) for all three enveloped viruses. The coronaviruses exhibited similar sensitivities to UV irradiation across the UVC range, whereas the bacteriophage surrogate was much more resistant and exhibited significantly higher sensitivity to the Far UVC (<230 nm) irradiation. This study provides necessary information and guidance for using UVC devices for enveloped virus disinfection, which may help control virus transmission in public spaces during the ongoing COVID-19 pandemic and beyond.