UV Light Utilization Research Articles

Enhanced photovoltaic performance of silicon solar cells using a down-shift KCa2Mg2(VO4)3 phosphor.

The efficiency of silicon solar cells is still lower than theoretical values, partly due to their inability to utilize the ultraviolet and infrared portions of the solar spectrum. Herein, a novel method using a KCa2Mg2(VO4)3 phosphor with a down-shift effect to improve the photovoltaic performance of silicon solar cells and enhance the utilization of UV light in standard p-type silicon solar cells is proposed. The synthesized phosphors were mixed with an ethylene vinyl acetate (EVA) copolymer and pressed into a film, which was subsequently encapsulated in monocrystalline silicon solar cells. The results show that the addition of this film notably enhanced the photovoltaic performance of the silicon solar cells; the current density was increased by 2.89% (from 33.20 to 34.16 mA cm-2), and the photovoltaic conversion efficiency was improved by 5.69% (from 15.11% to 15.97%) at the optimal concentration compared to bare cells.

Preparation and Photovoltaic Performance of a Composite TiO2 Nanotube Array/Polyaniline UV Photodetector.

TiO2 has great potential for application in UV photodetectors due to its excellent photoelectric response. In this work, composite nanomaterials of TiO2 nanotube arrays (TiO2 NTAs) and polyaniline (PANI) were successfully prepared on titanium sheets using an anodic oxidation electrochemical method. The results showed that the TiO2 NTA/PANI composite materials had excellent UV photosensitivity and responsiveness and good stability and reproducibility. This was mainly attributed to the p-n heterostructure formed inside the TiO2 NTA/PANI composites that hindered the recombination of photogenerated electron-hole pairs and improved their utilization of UV light. This work provides a theoretical basis for the application of metal oxides in UV photodetectors, which is important for the development of UV photodetectors.

Photoelectrochemical UV Detector Based on High-Temperature Resistant ITO Nanowire Network Transparent Conductive Electrodes: Both the Response Range and Responsivity Are Improved.

UV transparent conductive electrodes based on transferable ITO nanowire networks were prepared to solve the problem of low UV light utilization in conventional photoelectrochemical UV detectors. The mutually cross-linked ITO nanowire network achieved good electrical conductivity and light transmission, and the novel electrode had a transmission rate of more than 80% throughout the near-UV and visible regions. Compared to Ag nanowire electrodes with similar functionality, the chemical stability of the ITO nanowire transparent conductive electrode ensured that the device worked stably in iodine-based electrolytes. More importantly, ITO electrodes composed of oxides could withstand temperatures above 800 °C, which is extremely critical for photoelectrochemical devices. After the deposition of a TiO2 active layer using the high-temperature method, the response range of the photoelectrochemical UV detector was extended from a peak-like response between 300-400 nm to a plateau-like response between 200-400 nm. The responsivity was significantly increased to 56.1 mA/W. The relationship between ITO nanowire properties and device performance, as well as the reasons for device performance enhancement, were intensively investigated.

Photooxidation potential of fine particles from desulfurization flue gas aerosol

In China, desulfurization flue gas from coal-fired power plants (CFPPs) has been the focus of research for many years. In this study, for the first time, we simulated the emission process of flue gas and prepared photocatalysts by deposition. An innovative photocatalytic perspective was applied to study the composition, photocatalytic properties, hygroscopicity, and redox properties of the fine particles from flue gas aerosols. The characterization results of XRD, HRTEM, and XPS of freeze-dried desulfurized flue gas samples indicated that aerosol condensation occurred during the smoke plume transportation process, resulting in the formation of well-crystallized fine particles primarily consisting of soluble salts and metal oxides. The UV–vis and ESR results confirmed that desulfurized flue gas has UV light utilization and photocatalytic potential for producing oxidation groups such as hydroxyl radicals and superoxide radicals in light. The subsequent photocatalyst experiments revealed an 85.4 % reduction of 7 ppm isoprene in 30 min; ozone production (373 μg/m3) was observed under more complicated conditions (NO2 = 80 ppb, VOCs = 7 ppm). As a result of the study, a new research approach was proposed for exploring the photoactive potential of flue gas aerosol produced by CFPPs, as well as its impact on the concentration of VOCs and ozone. The finding provided a new possible pathway for desulfurization flue gas emissions and a reference for futureresearch on the observation and control of atmospheric pollution.

Patterned Ga2O3 nanowires synthesized by CVD method for High-performance self-powered ultraviolet photodetector

High-performance and energy-efficient ultraviolet photodetectors play a critical role in civilian and military fields. Here, patterned growth of highly crystalline straight Ga2O3 nanowires on p-type GaN epitaxial film wafer substrate is achieved by bottom-up technology using an economical chemical vapor deposition method. A self-powered ultraviolet photodetector based on GaN/Ga2O3 nanowires p-n junction for broadband UV detection is constructed by combining spin coating Poly(methyl methacrylate) as an insulating layer and magnetic sputtering an Au thin film as top transparent conductive electrode. This nanowires-film structure device exhibits excellent performance under zero bias voltage, including considerable responsivity of 960 mA W−1, high detectability of 3.82 × 1013 Jones, ultrahigh ultraviolet/visible inhibition ratio (R254 nm/R400 nm) of 7.92 × 103, fast rise/decay time of 4/12 ms and a high photo-to-dark current ratio greater than 104. The self-powered property under zero bias is attributed to the built-in electric field formed between the p-GaN film and the n-Ga2O3 nanowires, which creates a driving force for the rapid separation of photo-generated carriers. The high-performance mainly credits to the device's excellent UV light utilization efficiency and unique interfacial engineering of the p-n junction. This work provides a new avenue for the application of Ga2O3 nanowires in high-performance p-n junction self-powered photodetectors that can operate in harsh environments where it is inconvenient to transmit electric power.

Enhancement of UV-light harvesting in perovskite solar cells by internal down-conversion with Eu-complex hole transport layer

Recently, based on a lot of advantages of organic–inorganic lead halide perovskites, they have been applied in many ways, among which it exhibited outstanding characteristic for photovoltaic performance in application to solar cells. The CH3MH3PbI3 (MAPbI3)-perovskite solar cells (PSCs) show high solar energy conversion efficiency compared to conventional solar cells, but because they are greatly affected by external environments (such as temperature, moisture, light, etc.). For this reason, detailed researches are needed to improve the performances of the perovskite materials and prevent the degradation of the PSCs. Since less than 50% of sunlight contains the visible light and most of its energy can be used, the converting incident light from UV and IR regions into visible light for more productive and efficient solar cells must also be studied as well as the stability improvement. The main purpose of this study is to enhance the availability of UV-light used in the PSCs. Ultimately, we tried to increase the utilization of UV-light in sunlight and consequently improve the performance of the PSCs. Therefore, PSCs to be used were synthesized by controlling amounts of Eu-complex and injecting them into PEDOT:PSS to give a change in the hole transport layers (HTLs). By introducing Eu-complex, a down-conversion material, that absorbs light in UV range and re-emits the light in visible range into PEDOT:PSS, which has a great advantage as HTL with stability against UV-light and generation of more photon increase light-harvesting. As a result, the Eu-complex was shown to enhance the energy conversion efficiency of the PSCs as much as 25% and to raise the light-harvesting of the UV region through the internal down-conversion process.

Pollution free UV-C radiation to mitigate COVID-19 transmission

The high rate of transmission of the COVID-19 virus has brought various types of disinfection techniques, for instance, hydrogen peroxide vaporization, microwave generating steam, UV radiation, and dry heating, etc. to prevent the further transmission of the virus. The chemical-based techniques are predominantly used for sanitization of hands, buildings, hospitals, etc. However, these chemicals may affect the health of humans and the environment in unexplored aspects. Furthermore, the UV lamp-based radiation sanitization technique had been applied but has not gained larger acceptability owing to its limitation to penetrate different materials. Therefore, the optical properties of materials are especially important for the utilization of UV light on such disinfection applications. The germicidal or microorganism inactivation application of UV-C has only been in-use in a closed chamber, due to its harmful effect on human skin and the eye. However, it is essential to optimize UV for its use in an open environment for a larger benefit to mitigate the virus spread. In view of this, far UV-C (222 nm) based technology has emerged as a potential option for the sanitization in open areas and degradation of microorganisms present in aerosol during the working conditions. Hence, in the present review article, efforts have been made to evaluate the technical aspects of UV (under the different spectrum and wavelength ranges) and the control of COVID 19 virus spread in the atmosphere including the possibilities of the human body sanitization in working condition.

Endogenous Synergistic Enhanced Self‐Powered Photodetector via Multi‐Effect Coupling Strategy toward High‐Efficiency Ultraviolet Communication

AbstractUltraviolet (UV) communication is a promising security optical wireless communication technology, and self‐powered photodetectors as their optical receivers offer formidable evolution opportunities. However, insufficient light harvesting and carrier separation of self‐powered photodetectors hinder them from achieving high‐efficiency UV communication. Herein, a multi‐effect coupling strategy is proposed to design an enhanced self‐powered Ag NPs@ZnO nanowires/PEDOT:PSS (AZP) UV photodetector. Taking full advantage of the plasmonic and pyro‐phototronic coupling effect, the endogenous synergistic enhancement of UV light utilization and charge separation efficiency is realized without external field. The responsivity and detectivity of the AZP photodetector are significantly increased more than two and three times respectively, and the response time is less than 0.1 ms. Furthermore, a UV communication system is integrated based on the self‐powered AZP photodetector that conducts synchronous, accurate, and rapid wireless data transmission. Notably, the integrated UV communication system presenting large communication bandwidth with 4800 baud exhibits desirable efficient information transmission potential. This work provides design strategies for the advanced self‐powered UV photodetector toward future energy‐saving and high‐efficiency optical wireless communication.

CDIFFerently: A Bundled Approach to Clostridium difficile Reduction

Background: Since 2015 the rate of healthcare facility-onset Clostridium difficile infections (HO CDI) at Faxton-St Luke’s Healthcare (FSLH) has remained higher than both New York state and federal benchmarks, despite the use of traditional prevention efforts. Methods: We used the define-measure-analyze-improve-control (DMAIC) process improvement model to better understand the reasons that our rates remained high and to develop a comprehensive reduction strategy.•Define: High HO CDI rates. NHSN SIR consistently above 1.0•Measure•Diagnostic stewardship. Are patients being tested appropriately?•Antibiotic stewardship: Do prescribing practices follow best-practice recommendations?•Environmental cleanliness: Are staff following standard and transmission based precautions? How effective are current cleaning practices? What is being done to limit contamination of the environment of care?•Perform a gap analysis of CDI prevention strategies at FSLH vs current best practice recommendations, emerging strategies in scientific literature and successful approaches at other health-care facilities.•Analyze•Staff do not have a clear understanding of symptoms and risk factors of CDI and often initiate testing inappropriately.•Overuse of broad spectrum antimicrobial agents. No antibiotic time outs. Limited Pharmacy staff available for auditing and feedback regarding prescribing practices.•UV disinfection system under-utilized. Shared patient care equipment not cleaned between uses. Delay in implementation of contact precautions. Lack of opportunities for patient hand hygiene.•Improve•Algorithms for screening and testing built into Electronic Medical Record Orders for testing coupled with orders for contact precautions•Align antimicrobial prescribing with best practice•Audit and reward compliance with UV light utilization, environmental cleaning Reduce shared patient care equipment, replace with disposable items•Provide products for patient hand hygiene•Implement marketing campaign to tie elements together•Control•Audit compliance with testing and isolation policies•Laboratory rejection of formed stools•Audit cleaning processes with adenosine triphosphate (ATP) monitor•Track ultraviolet light usageFunding: NoneDisclosures: None

Two Hybrid Au-ZnO Heterostructures with Different Hierarchical Structures: Towards Highly Efficient Photocatalysts

A new paradigm for photocatalysts based on two different hierarchically structured honeycomb and porous cylindrical Au-ZnO heterostructures was successfully developed via a straightforward and cost-effective hydrothermal method under different preparation conditions, which can be promising for industrial applications. The photocatalytic performance of all as-prepared samples under the illumination of sunlight was evaluated by the photocatalytic degradation of rhodamine B (RhB) and malachite green (MG) aqueous solutions. The results show that the photocatalytic degradation efficiency of RhB and MG was 55.3% and 40.7% for ZnO, 95.3% and 93.4% for the porous cylindrical Au-ZnO heterostructure, and 98.6% and 99.5% for the honeycomb Au-ZnO heterostructure, respectively. Compared with those from the ZnO, the results herein demonstrate an excellent reduction in the photoluminescence and improvement in the photocatalysis for the Au-ZnO hybrids with different morphologies. These results were attributed not only to the greatly improved sunlight utilization efficiency due to the surface plasmon resonance (SPR) absorption of Au nanoparticles in the visible region coupled with the UV light utilization by the ZnO nanostructures and multi-reflections of the incident light in the pore structures of their interior cavities but also to the high charge separation efficiency and low Schottky barrier generated by the combination of Au nanoparticles and ZnO micromaterials. Moreover, the honeycomb Au-ZnO heterostructure had a high Au content, surface area and surface oxygen vacancy (OV), which enabled photocatalytic properties that were higher than those of the porous cylindrical Au-ZnO heterostructures. In addition, two different formation mechanisms for the morphology and possible photocatalytic mechanisms are proposed in this paper.

High‐Performance All‐Inorganic Perovskite‐Quantum‐Dot‐Based Flexible Organic Phototransistor Memory with Architecture Design

AbstractA novel organic phototransistor memory (OPTM) with architecture design is fabricated with all‐inorganic perovskite quantum dots (QDs) as charge trapping layer. The novel architecture enables ultrashort channel length and vertical the charge transfer to effectively suppress both trapped carriers effect and interface effect, two key factors which impact photonic memory performance. Additionally, perovskite QDs are introduced to function as both the charge trapping layer and a UV‐light‐responsive material that emits visible light that can be subsequently absorbed by the active layer, leading to efficient utilization of UV light to generate trapped charges. OPTM exhibits excellent memory properties under significantly improved light conditions, which is superior to previous reports. Moreover, flexible OPTM exhibits excellent mechanical stability, which is associated with vertical charge transport that eliminates the effect of cracks and dislocations formed during bending. Furthermore, an OPTM array is fabricated, which can realize imaging and memory capability with long‐term retention performance and shows reproducibility under the electric erasing and reprogramming process. Hence, with this novel architecture, OPTM realizes light programming with a short time, low light intensity, and broadband photoresponse along with excellent memory performance, which has great potential for practical application, especially in the flexible electronics market.

Nontoxic fluorescent carbon nanodot serving as a light conversion material in plant for UV light utilization.

In this study, water-soluble fluorescent carbon nanodots (CNDs) were directly injected into the leaf of nicotiana tabacum. With the help of UV-to-blue light conversion nanomaterial, the photosynthetic rate of the leaf was improved 18% upon additional 6 W UV irradiation. The photostability and toxicity of different kinds of CNDs were discussed. The results showed that CNDs functionalized with NH2-groups on their surfaces could maintain good fluorescence in plant leaf, and CNDs with complex surface groups tended to have high toxicity to the plant. The NH2-functionalized CNDs with non-toxicity and good photostability were used as in vivo light conversion material for direct utilization of UV light in the solar energy.

High-Performance Perovskite Solar Cells with a Weak Covalent TiO2:Eu3+ Mesoporous Structure

Mesoporous TiO2 nanocrystals with attached Eu3+ ions in an amorphous state are employed as structures for highly efficient perovskite solar cells. The down-conversion TiO2:Eu3+ nanocrystal shows a good photoluminescence characteristic to convert the incident high-energy photon into a lower-energy photon, which improves the UV light utilization capability of perovskite solar cells (PSCs). The device within 1.0 wt % Eu3+ ions shows an improvement of 29.2% from 12.22% to 15.79% in PCE compared with the typical devices without Eu3+ in TiO2, which is attributed to the increased utilization of incident UV light and the dramatically suppressed electron recombination process. To summarize, the combination of a high UV light-harvesting capability and a slow electron recombination process with TiO2:Eu3+ mesoporous structure could successfully develop more efficient and stable PSCs.

Kelp-inspired N–I-doped ZnO photocatalysts with highly efficient catalytic activity

Efficient N–I-doped ZnO photocatalysts with hierarchical structures are fabricated with kelp as the template. Abundant nitrogen and iodine are successfully simultaneously introduced into the bulk ZnO crystals though calcination under high temperature (600°C). The morphology, structure, composition, and optical absorption properties of the kelp-templated ZnO are characterized by X-ray diffraction (XRD), field-emission scanning microscopy (FESEM), transmission electron microscopy (TEM), and diffuse reflectance spectra (DRS), respectively. The band gap of the kelp-templated ZnO is narrowed by the N–I coping. The photocatalytic activity under UV-irradiation of the kelp-templated ZnO is about 23.1 times and 1.1 times that of common ZnO and P25, respectively. In addition, no obvious activity of the kelp-templated ZnO is decreased, during five cycle runs. The efficient photocatalytic activity of the kelp-templated ZnO is attributed to the sufficient UV-light utilization and efficient separation of electron–hole pairs.

Structure–activity relationship of nanosized porous PEG-modified TiO2 powders in degradation of organic pollutants

This study aims to gain insights in structure–activity relationship of TiO2 photocatalysts. For this purpose photocatalysts were synthesized via classical sol–gel method using titanium isopropoxide as a precursor and polyethylene glycols (PEGs) of different molecular mass (Mn=200, 600, 2000, 10,000) as a template agents. Incorporating PEG into TiO2 network enhanced not only catalyst porous structure, but also increased the fraction of anatase phase. The use of low-molecular-weight PEGs resulted in catalysts with increased anatase content and enlarged specific surface area. The catalyst photoactivity was estimated through degradation of organic pollutants: Reactive Black 5, arylazo pyridone dye and phenol. The results revealed that the photoactivity was following the same order independently of target pollutant: TiO2/P600>TiO2/P200>TiO2/P2000>TiO2/P10000>TiO2. BET surface area and anatase fraction, rather than pore diameter or pore volume, were found to be predominant catalyst property determining the activity for particular reaction system. The existence of synergistic effect between anatase and rutile phases was confirmed for the most active catalysts TiO2/P200 and TiO2/P600. These catalysts showed similar activity in dye degradation, while TiO2/P200 displayed significantly lower activity in phenol degradation, which was attributed to its lower sorption capacity and lower UV light utilization. The difference in the reactivity between investigated pollutants was discussed in relationship with their size, structure and sorption ability.

New insights into how RGO influences the photocatalytic performance of BiOIO3/RGO nanocomposites under visible and UV irradiation

Reduced graphene oxide (RGO) has been demonstrated to be effective in enhancing the photocatalytic activity of various semiconductors. However, an important issue that has been overlooked is the role of RGO in UV-induced photocatalysis of RGO-based nanocomposites. In the present work, novel BiOIO3/RGO nanocomposites were prepared by a simple one-pot hydrothermal method, during which BiOIO3 nanoplates were formed in situ on RGO sheets resulting from partial reduction of RGO. The two components of the composite displayed intimate interfacial contact. The as-prepared BiOIO3/RGO nanocomposites exhibited highly enhanced visible photocatalytic activity, relative to that of pure BiOIO3, toward removal of NO from air. However, the BiOIO3/RGO nanocomposites showed only slightly increased photocatalytic activity, relative to pure, under UV irradiation. The limited enhancement of UV activity can be ascribed to the fact that BiOIO3 would be expected to compete with RGO with regard to absorption and utilization of UV light. Evidence shows that RGO can act as a semiconductor rather than a photosensitizer or electron reservoir in BiOIO3/RGO nano-composites. In addition, the active species responsible for photoactivity have been investigated by a DMPO spin-trapping electron spin resonance technique. Photo-generated holes were found to be the main active species inducing the photo-oxidation of NO under visible light, whereas holes and OH radicals are considered to be responsible for photo-activity under UV light. This work points to BiOIO3/RGO nano-composites as new and efficient visible light photocatalysts for environmental remediation applications, and also as a source of new insights into the pivotal role of RGO in photocatalysis of RGO-based nanocomposites under visible as well as UV light.

Photocatalytic packed bed reactor design for efficient UV light utilization

In this study, TiO2/SiO2 beads packed bed reactor system in which black light was placed at the center of the reactor was developed for a low cost and environmentally–friendly water treatment process. The reactor was designed to achieve efficient utilization of UV light, large contact area with pollutants as well as easier post separation at the same time. As model pollutants, PNP and DNP were used in this study, and the effects of the initial concentration of those substrates and radial thickness of the packed bed for the decomposition properties were examined. The results showed that the decomposition ratio decreased with the increase of the initial concentration and the packed bed radial thickness. The result suggested that the UV light was absorbed by the solution and TiO2/SiO2 beads. To take into consideration the effect of light absorption toward radial direction of the reactor on the decomposition ratio, simple model called “2-boxes model” was developed. The result of reaction kinetics analysis showed that the 2-boxes model could reasonably explain the experimental data. Finally, by using 2-boxes model, the effective diameter of penetrated UV light was examined. The result confirmed that it decreased with the increase of UV absorption caused by the increase of initial inlet concentration and the increase of the radial thickness of the packed bed. This indicates that the simple 2-boxes model can approximately estimate the effective diameter of packed bed for PNP or DNP decomposition, and it will give a design guideline for an efficient TiO2/SiO2 beads packed bed reactor system for water treatment.

Hydrogen peroxide generation and photocatalytic degradation of estrone by microstructural controlled ZnO nanorod arrays

The strong oxidant, hydrogen peroxide (H2O2), generated by ZnO nanorod arrays under UV light irradiation was monitored by fluorescence analysis. The ZnO nanorod arrays were synthesized via a low temperature hydrothermal method and their dimensions, i.e., diameter and height, can be controlled by adjusting the concentration of zinc nitrate (Zn(NO3)2·6H2O) and hexamethylenetetramine (HMT). The morphology, nanostructure, surface roughness and optical property were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmittance spectra, respectively. The ZnO nanorod arrays were applied in the degradation of estrone, which is an emerging steroid estrogen contaminant. The results revealed that the ZnO nanorod array produced from 25mM Zn2+ and HMT had the highest aspect ratio, the largest surface roughness and the lowest band gap energy, which was beneficial to the efficiency of UV light utilization, photocatalytic degradation of estrone and H2O2 generation.

Covalent-Bond-Based Immobilization Approaches for Single-Molecule Fluorescence

The streptavidin-biotin bridge is commonly used in single-molecule studies to surface immobilize biomolecules onto microscope slides. However, the presence of tryptophanes impedes utilization of UV light and numerous fluorescent nucleotide analogs, such as 2-aminopurine. We present two new approaches to surface-immobilize nucleic acids for single molecule fluorescence experiments using covalent bonds and self-assembled monolayers instead of the traditional avidin-biotin linkage. The first approach takes advantage of a click-chemistry reaction between an azide and an alkyne to surface-immobilize nucleic acids through the resulting triazole linkage. The second approach uses disulfide bond bridges for immobilization. We have characterized the properties of the resulting surface-immobilized fluorophore-labeled DNA molecules and single-molecule fluorescence detection. We find that both approaches are specific and yield comparable surface densities and low fluorescence background to the avidin-biotin linkage, but offer new surface chemical properties that might be advantageous to prevent non-specific binding of biopolymers to the surface and to expand the range of fluorescent probes that can be employed in single molecule studies.

Immobilization of Single Biomolecules Using Covalent-Bond Linkages for Fluorescence Single-Molecule Experiments

The streptavidin-biotin bridge is commonly used in single-molecule studies to surface immobilize biomolecules onto microscope slides. However, the presence of tryptophanes impedes utilization of UV light and numerous fluorescent nucleotide analogs, such as 2-aminopurine. We are developing new approaches to immobilize DNA/RNA molecules without use of streptavidin and biotin. One approach consists of using the Huisgen cycloaddition reaction between an alkyne and an azide, which is an example of “click” chemistry reaction. In this “click” chemistry approach, 3′-azide modified oligos are immobilized to an alkyne-modified microscope slide surface through a triazole linkage. This cycloaddition reaction is very stable in many physiologically relevant buffers, and has been shown to occur without the need of a catalyst. In another approach, we take advantage of the efficient coupling between thiol groups to immobilize biomolecules by forming disulfide bridges. 3′-thiol modified oligos are surface immobilized on a thiol-modified microscope slide by forming disulfide bonds. We are currently improving the immobilization efficiency by optimizing the reaction parameters and conditions. We anticipate that these approaches will allow us to investigate local conformational changes in biomolecular systems at the single molecule level.