UV Light Sensitivity Research Articles

Conjugated Polymer-Based Photo-Crosslinker for Efficient Photo-Patterning of Polymer Semiconductors.

Photo-patterning of polymer semiconductors using photo-crosslinkers has shown potential for organic circuit fabrication via solution processing techniques. However, the performance of patterning, including resolution (R), UV light exposure dose, sensitivity (S), and contrast (γ), remains unsatisfactory. In this study, a novel conjugated polymer based photo-crosslinker (PN3, Figure 1a) is reported for the first time, which entails phenyl-substituted azide groups in its side chains. Due to the potential π-π interactions between the conjugated backbone of PN3 and those of polymer semiconductors, PN3 exhibits superior miscibility with polymer semiconductors compared to the commonly used small molecule photo-crosslinker 4Bx (Figure 1a). Consequently, photo-patterning of polymer semiconductors with PN3 demonstrates improved performance with much lower UV light exposure dose, higher S and higher γ compared to 4Bx. By utilizing electron beam lithography, patterned arrays of polymer semiconductors with resolutions down to 500nm and clearer edges are successfully fabricated using PN3. Furthermore, patterned arrays of PDPP4T, the p-type semiconductor (Figure 1b), after being doped, can function as source-drain electrodes for fabricating field-effect transistors (FETs) with comparable charge mobility and significantly lower sub-threshold swing value compared to those with gold electrodes.

Enhancing UV light sensitivity of PVP polymer by doping chromium trioxide via the electrospun solutions

Herein, chromium trioxide (Cr2O3) doped Polyvinylpyrrolidone(PVP) nanofibers with high crystallinity and UV light sensitivity are successfully grown onto the glass substrates by electrospun deposition at room temperature. The effect of Cr2O3 concentration on the morphology, structure, and photoluminescence properties of the as-fabricated PVP nanofibers is examined. With the increase in doping concentration of Cr2O3 (i.e., 1, 2 and 3 %), the direct band gap of PVP nanofibers is reduced to 4.05, 4.01, and 3.85 eV, respectively. XRD and FE-SEM results manifest that the crystallinity and diameter of the nanofibers are dependent upon Cr2O3 concentration, i.e., the mean diameter decreases from 600 to 200 nm. Photoluminescence spectra indicate higher UV emission upon the addition of Cr2O3, with greater emission near the band edge for thinner nanofibers. A possible mechanism for the formation of PVP/Cr2O3 nanofibers is addressed in detail. Furthermore, it is found that the sensitivity of the as-fabricated PVP/Cr2O3 detector to UV-light emission strongly depends on Cr2O3 concentration, i.e., good responsivity (2.257 A/W) and specific detectives (9.8 × 1012 cm Hz1/2/W) at a Cr2O3 concentration of 2 % are achieved at a wavelength of 454.1 nm, besides recording the lowest rise and fall times.

Enhanced UV photodetector performance using sputtered Mg-doped ZnO thin film

In this article, we demonstrate UV photodetector synthesized using Mg-doped ZnO thin film (TF) (10 % Mg) grown on a p-Si substrate using the radio frequency (RF) magnetron sputtering system. The fabricated MgZnO TF was annealed at 500 °C in air resulting in notable changes in morphology, optical band gap and crystallinity that significantly improved the UV light sensitivity. The annealed device (MgZnO TF/p-Si) exhibited a remarkable 155-fold increase in photocurrent density compared to the as-deposited device at + 2 V bias. Also, at the same bias the annealed device (500 °C) exhibited high photosensitivity (up to 1262 times), responsivity (20.32 A/W), specific detectivity (1.82 × 1013 Jones) and external quantum efficiency (EQE) (7745 %) in comparison to the as-deposited device. Additionally, the 500 °C device achieved a low noise equivalent power (NEP) of 0.07 × 10−12 W which is about 262 times lower than that of the as-deposited device (18.4 × 10−12 W). Furthermore, on UV illumination (λ = 325 nm) the MgZnO TF/p-Si (500 °C) detector showed fast device response with rise time/fall time values of 0.26 s/0.25 s respectively at + 2 V applied bias.

Numerical simulation of one-dimensional perovskite solar cell model

Perovskite solar cell (PSC) is one of the advanced third-generation solar cells that have rapid efficiencies but instability issues in terms of air, moisture, and UV light sensitivity becomes a barrier to commercialization. The instability issue is due to the charge accumulation at the interface of the PSC reducing its efficiency. This research focuses on the operation of PSCs through a one-dimensional (1D) drift-diffusion model for planar heterojunction PSCs. The model also accounts for the electric potential by Poisson’s equation, the ion generation, and the recombination rate. The method of lines technique is applied to solve the model for the perovskite layer numerically using the finite difference method which is then solved forward in time using the ‘ode15s’ solver in MATLAB. It is highlighted that the comparison with the experimental data from the reference shows good agreement. The effect of parameter thickness variation of the perovskite layer upon the efficiency of PSCs is analyzed. The result shows that the best efficiency obtained is 19.77% obtained at thickness 0.25 𝜇𝑚. The results may prove useful for a guideline of the cell thickness that predicts the perovskites cell performance.

Lifetime considerations of geotextile UV exposure before installation

Geotextile are in most case intended for buried application, without exposure to sunlight. However, a short exposure to sunlight may occur before installation. Because of potential delay of installation and soil burying, the material is required to meet UV resistance. Artificial UV weathering will assess the potential risk of unintended exposure to sunlight. Photodegradation reactions consider the interactions with exposure conditions as well as polymer sensitivity to sunlight. Based on both laboratory measurements and field data, this paper evaluates the effect of light intensity, temperature and humidity with climates. Using polymer relation of its UV light sensitivity with the effective irradiance, a cumulative index is calculated for the reduction of geotextile service life from exposure to sunlight. Artificial weathering cycles for geotextiles are compared and related to the specific degradation mechanisms of polypropylene and polyethylene terephthalate. The reaction rate is correlated with temperature, respectively for each polymer. A model using radiant energy and temperature is proposed for guidance to service life prediction of partly UV-exposed geotextiles.

Preservation of conditioned behavior based on UV light sensitivity in dissected tail halves of planarians – a proof by DNN

Preservation of conditioned behavior based on UV light sensitivity in dissected tail halves of planarians – a proof by DNN

Wearable Triboelectric Nanogenerators Based on Polyamide Composites Doped with 2D Graphitic Carbon Nitride.

Triboelectric nanogenerators (TENGs) have attracted many researchers’ attention with their remarkable potential despite the fact that the practical implementation requires further improvement in their electric performance. In this work, a novel graphene phase two-dimension material, graphitic carbon nitride (g-C3N4), was employed for the development of a TENG material with enhanced features. An electrospun nanofibrous PA66 membrane doped with g-C3N4 was fabricated as a multifunctional TENG for harvesting different kinds of mechanical energy and detecting human motions. By utilizing the innovative 2D material in PA66 solution for electrospinning, the as-made TENG showed a two times enhancement in electrical performance as compared to the control device, and also had the advantages of lightweight, softness, high porosity, and rugged interface properties. The assembled TENG with 4 cm2 could light up 40 light-emitting diodes by gentle hand clapping and power electronic watches or calculators with charging capacitors. At a given impact force of 40 N and 3 Hz, the as-made TENG can generate an open-circuit voltage of 80 V, short current of ±3 µA, charge transfer of 50 nC, and a maximum power density of 45 mW/m2 at a load resistance of 500 MΩ. The UV light sensitivity of TENG was also improved via g-C3N4 doping, showing that charge transfer is very sensitive with a two times enhancement with dopant. For the demonstration of applications, the g-C3N4 doped TENG was fabricated into an energy flag to scavenge wind energy and sensor devices for detecting human motions.

A green way to simultaneously enhance the mechanical, flame retardant and anti-ultraviolet aging properties of polylactide composites by the incorporation of tannic acid derivatives

Polylactic acid (PLA), characterized by its biodegradability, easy processing, and environmental friendliness, is regarded as one of the ideal substitutes for petroleum-based polymers. But, the flammability and UV light sensitivity of PLA often impact the safety and service life of its products. In this study, a bio-based additive (BA-TA-MEL) is synthesized via a one-pot method and used as a flame-retardant and anti-UV agent for PLA. The results show that PLA/5%BA-TA-MEL can achieve the desired V-0 degrade in the UL-94 test and an LOI value of 27.1%. Moreover, the PLA/5%BA-TA-MEL exhibits brilliant UV resistance, which increases the UPF to 290.4 from 0.4 of pure PLA. The BA-TA-MEL acts as a rigid particle in the matrix, effectively enhancing the tensile strength of materials. The current work develops a new approach to preparing biodegradable material with excellent performance and extended life to reduce the environmental pressure and pollution caused by petroleum-based plastics.

Rapid organic dye degradation and wavelength dependent sensing study in Cu1-xFexO

Cu1-xFexO (x = 0, 0.0156, 0.0234 and 0.0312) nanoparticles have been synthesized by using a simple sol-gel route. A pure monoclinic phase (space group c2/c) was observed from XRD studies. A Rietveld analysis of the XRD spectra using GSAS software helped evaluate the variations of lattice constant, lattice strain and bond length/angles. With Fe doping, while the indirect bandgap could be nominally tuned from ∼1.40 eV to ∼1.46 eV, the Fe-doping seems to improve carrier concentration, mobility, and lattice regularity than pure CuO. The photocatalytic degradation of toxic methylene blue (MB) dye could be enhanced from 0.91%/min for the pure CuO to 1.48%/min for 3.125%-Fe-doped CuO. This property has been correlated to the carrier properties of the materials. The UV and visible photoresponse of Cu1-xFexO nanoparticles was investigated. A drastic reduction in both UV and visible light-sensitivity with Fe-doping was observed and correlated with carrier properties.

New evidence for preservation of conditioned behavior based on UV light sensitivity in dissected tail halves of planarians

New evidence for preservation of conditioned behavior based on UV light sensitivity in dissected tail halves of planarians

A universal, multifunctional, high-practicability superhydrophobic paint for waterproofing grass houses

Roof leakage is a common phenomenon on rainy days and makes residents uncomfortable. Superhydrophobic materials are promising candidates to protect grass houses from rainwater. However, mechanical weakness, chemical corrosion, and UV light sensitivity are the three main challenges restricting these nonwetting materials from wider application in real life. Herein, we developed an inorganic–organic superhydrophobic paint (IOS-PA) for preparing a waterproof grass house. IOS-PA not only showed mechanical robustness and chemical anticorrosion but also displayed self-healing properties, anti-icing properties, and high and low temperature (150 °C and −196 °C) resistance. Photocatalysis was also achieved with IOS-PA, as demonstrated by organic matter (Nile red, methyl blue, and methyl orange) degradation. Moreover, extremely long-term UV resistance, i.e., resistance to UV irradiation (365 nm, 5.0 ± 0.6 mW/cm2) for 100 h and ambient sunlight for 8640 h (1 year), caused the conflicting properties of superhydrophobicity and photocatalysis to coexist in IOS-PA, further accomplishing self-cleaning for the removal of both dirt particles and organic contamination. Specifically, a grass house coated with IOS-PA exhibited favorable waterproof properties, indicating the potential to ensure comfortable living conditions for people living in undeveloped areas, even on rainy days. With a variety of excellent characteristics, IOS-PA, we believe, is advantageous for scalable production and practical application in reality.

Tuning the sensitivity of polydiacetylene-based colorimetric sensors to UV light and cationic surfactant by co-assembling with various polymers

This study introduces a simple approach for fine-tuning the sensitivity of polydiacetylene(PDA)-based colorimetric sensors to UV light and cationic surfactant. The PDA assemblies were prepared by co-assembling of 10,12-pentacosadiynoic acid (PCDA) monomer and 3 types of water-soluble polymers, including poly(vinylpyrrolidone) (PVP), poly(N-vinyl formamide) (PNVF) and poly(N,N-dimethyl acrylamide) (PDMA). X-ray diffraction reveals the intercalation of these polymers with PDA bilayers. Infrared spectroscopy also observes the variation of local interactions within PDA/polymers assemblies, depending on the structure of polymeric side chain. The incorporation of these polymers strongly affects the color-transition behaviors of PDA upon exposure to UV light and cationic surfactant. The PDA/polymer assemblies show significant improvement in UV light sensitivity. The color transition upon prolonged exposure to UV light can also be controlled. The addition of PVP and PNVF chains provides the sensors that change color at relatively long UV light irradiation time. The use of PDMA, however, causes the opposite result. The same approach is utilized for preparing quantitative-colorimetric sensors of cationic surfactant. The variation of polymeric side chain or molecular weight provides the PDA/polymer assemblies that change color at different concentration of the cationic surfactant.

Free carrier enhanced depletion in ZnO nanorods decorated with bimetallic AuPt nanoclusters.

The decoration of semiconductor nanostructures with small metallic clusters usually leads to an improvement of their properties in sensing or catalysis. Bimetallic cluster decoration typically is claimed to be even more effective. Here, we report a detailed investigation of the effects of Au, Pt or AuPt nanocluster decoration of ZnO nanorods on charge transport, photoluminescence and UV sensitivity. ZnO nanorods were synthesized by chemical bath deposition while decoration with small nanoclusters (2-3 nm in size) was achieved by a laser-ablation based cluster beam deposition technology. The structural properties were investigated by scanning electron microscopy, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry, and the optoelectronic properties by current-voltage and photoluminescence measurements. The extent of band bending at the cluster-ZnO interface was quantitatively modeled through numerical simulations. The decoration of ZnO nanorods with monometallic Au or Pt nanoclusters causes a significant depletion of free electrons below the surface, leading to a reduction of UV photoluminescence, an increase of ZnO nanorod dark resistance (up to 200 times) and, as a consequence, an improved sensitivity (up to 6 times) to UV light. These effects are strongly enhanced (up to 450 and 10 times, respectively) when ZnO nanorods are decorated with bimetallic AuPt nanoclusters that substantially augment the depletion of free carriers likely due to a more efficient absorption of the gas molecules on the surface of the bimetallic AuPt nanoclusters than on that of their monometallic counterparts. The depletion of free carriers in cluster decorated ZnO nanorods is quantitatively investigated and modelled, allowing the application of these composite materials in UV sensing and light induced catalysis.

Dielectrophoretic Assembly of Aluminum Nitride (AlN) Single Nanowire Deep Ultraviolet Photodetector

High UV-light sensitivity, fast response, and low power consumption are the most important features of nanowire-based devices for new applications in photodetectors, optical switches, and image sensors. Single AlN nanowire deep ultraviolet (UV) photodetector has been fabricated utilizing very high-quality AlN nanowires through a very practical dielectrophoretic assembly scheme. The low-voltage (≤ 3 V) operating UV photodetector has selectively shown a high photocurrent response to the 254 nm UV light. Furthermore, the photocurrent transients have been modelled to determine the rise and decay time constants as 7.7 s and 11.5 s, respectively. In consequence, combination of deep UV light selectivity and low voltage operation make AlN nanowires great candidates for the development of compact deep UV photodetectors.

UV-induced photosensing characteristics of SiC and GaN nanowires

PurposeThis study aims to investigate photosensing characteristics of SiC and GaN nanowire-based devices through exposure to UV light. The photocurrent transients have been modeled to determine rise and decay process time constants. The 1D-semiconductor nanowires can exhibit higher light sensitivity compared to bulk materials because of their large surface area to volume ratio and the quantum size effects.Design/methodology/approachNanowire devices have been fabricated through dielectrophoresis for integrating nanowires onto pre-patterned electrodes (10 nm Ti/ 90 nm Au) with a spacing about 3 µm onto SiO2/Si (doped) substrate. The photocurrent measurements were carried out under room temperature conditions with UV light of 254 nm wavelength.FindingsSiCNWs yield very short rise and decay time constants of 1.3 and 2.35 s, respectively. This fast response indicates an enhanced surface recombination of photoexcited electron-hole pairs. Conversely, GaNNWs yield longer rise and decay time constants of 10.3 and 15.4 s, respectively. This persistent photocurrent suggests a reduced surface recombination process for the GaNNWs.Originality/valueHigh selective UV light sensitivity, small size, very short response time, low power consumption and high efficiency are the most important features of nanowire-based devices for new and superior applications in photodetectors, photovoltaics, optical switches, image sensors and biological and chemical sensing.

Improvement of bioavailability for resveratrol through encapsulation in zein using electrospraying technique

Abstract Resveratrol has proven antioxidant, anticancer, anti-inflammatory and cardioprotective effects. However, poor water solubility, low bioavailability and UV light sensitivity hinder its usage in food applications. Encapsulation of resveratrol can help to overcome these problems. In this work, encapsulation by electrospraying was adopted, owing to the possibility of obtaining spherical and nano-sized particles at room temperature. This study proved that resveratrol can be efficiently encapsulated with zein without modifying its native form. Size of nanoencapsulated particles obtained ranged from 230 to 330 nm. Nanoencapsulation through electrospraying process yielded 68.49% encapsulation efficiency at 1:50 resveratrol to zein w/w%. Further, nanoencapsulated resveratrol showed better stability and sustained release profiles as compared to the unencapsulated form. Nanoencapsulation with zein protected resveratrol in simulated stomach conditions and released resveratrol in the intestinal condition. Additionally, nanoencapsulated resveratrol showed increased permeability of 1.15 fold in ex-vivo dynamic engineered small intestinal system which in turn relates to improved bioavailability. Prepared nanoparticles can be used for oral administration by incorporation into food products or in tablet form.

Fabrication of Zinc Oxide-Based Thin-Film Transistors by Radio Frequency Sputtering for Ultraviolet Sensing Applications.

In this study, zinc indium tin oxide thin-film transistors (ZITO TFTs) were fabricated by the radio frequency (RF) sputtering deposition method. Adding indium cations to ZnO by co-sputtering allows the development of ZITO TFTs with improved performance. Material characterization revealed that ZITO TFTs have a threshold voltage of 0.9 V, a subthreshold swing of 0.294 V/decade, a field-effect mobility of 5.32 cm2/Vs, and an on-off ratio of 4.7 × 105. Furthermore, an investigation of the photosensitivity of the fabricated devices was conducted by an illumination test. The responsivity of ZITO TFTs was 26 mA/W, with 330-nm illumination and a gate bias of -1 V. The UV-to-visible rejection ratio for ZITO TFTs was 2706. ZITO TFTs were observed to have greater UV light sensitivity than that of ZnO TFTs. We believe that these results suggest a significant step toward achieving high photosensitivity. In addition, the ZITO semiconductor system could be a promising candidate for use in high performance transparent TFTs, as well as further sensing applications.

Two UV-Sensitive Photoreceptor Proteins, Opn5m and Opn5m2 in Ray-Finned Fish with Distinct Molecular Properties and Broad Distribution in the Retina and Brain.

Opn5 is a group within the opsin family of proteins that is responsible for visual and non-visual photoreception in animals. It consists of several subgroups, including Opn5m, the only subgroup containing members found in most vertebrates, including mammals. In addition, recent genomic information has revealed that some ray-finned fishes carry paralogous genes of Opn5m while other fishes have no such genes. Here, we report the molecular properties of the opsin now called Opn5m2 and its distributions in both the retina and brain. Like Opn5m, Opn5m2 exhibits UV light-sensitivity when binding to 11-cis-retinal and forms a stable active state that couples with Gi subtype of G protein. However, Opn5m2 does not bind all-trans-retinal and exhibits exclusive binding to 11-cis-retinal, whereas many bistable opsins, including fish Opn5m, can bind directly to all-trans-retinal as well as 11-cis-retinal. Because medaka fish has lost the Opn5m2 gene from its genome, we compared the tissue distribution patterns of Opn5m in medaka fish, zebrafish, and spotted gar, in addition to the distribution patterns of Opn5m2 in zebrafish and spotted gar. Opn5m expression levels showed a gradient along the dorsal–ventral axis of the retina, and preferential expression was observed in the ventral retina in the three fishes. The levels of Opn5m2 showed a similar gradient with preferential expression observed in the dorsal retina. Opn5m expression was relatively abundant in the inner region of the inner nuclear layer, while Opn5m2 was expressed in the outer edge of the inner nuclear layer. Additionally, we could detect Opn5m expression in several brain regions, including the hypothalamus, of these fish species. Opn5m2 expression could not be detected in zebrafish brain, but was clearly observed in limited brain regions of spotted gar. These results suggest that ray-finned fishes can generally utilize UV light information for non-image-forming photoreception in a wide range of cells in the retina and brain.

129-Derived Mouse Strains Express an Unstable but Catalytically Active DNA Polymerase Iota Variant.

Mice derived from the 129 strain have a nonsense codon mutation in exon 2 of the polymerase iota (Polι) gene and are therefore considered Polι deficient. When we amplified Polι mRNA from 129/SvJ or 129/Ola testes, only a small fraction of the full-length cDNA contained the nonsense mutation; the major fraction corresponded to a variant Polι isoform lacking exon 2. Polι mRNA lacking exon 2 contains an open reading frame, and the corresponding protein was detected using a polyclonal antibody raised against the C terminus of the murine Polι protein. The identity of the corresponding protein was further confirmed by mass spectrometry. Although the variant protein was expressed at only 5 to 10% of the level of wild-type Polι, it retained de novo DNA synthesis activity, the capacity to form replication foci following UV irradiation, and the ability to rescue UV light sensitivity in Polι(-/-) embryonic fibroblasts derived from a new, fully deficient Polι knockout (KO) mouse line. Furthermore, in vivo treatment of 129-derived male mice with Velcade, a drug that inhibits proteasome function, stabilized and restored a substantial amount of the variant Polι in these animals, indicating that its turnover is controlled by the proteasome. An analysis of two xeroderma pigmentosum-variant (XPV) cases corresponding to missense mutants of Polη, a related translesion synthesis (TLS) polymerase in the same family, similarly showed a destabilization of the catalytically active mutant protein by the proteasome. Collectively, these data challenge the prevailing hypothesis that 129-derived strains of mice are completely deficient in Polι activity. The data also document, both for 129-derived mouse strains and for some XPV patients, new cases of genetic defects corresponding to the destabilization of an otherwise functional protein, the phenotype of which is reversible by proteasome inhibition.

Transparent ZnO/glass surface acoustic wave based high performance ultraviolet light sensors**Project supported by the National Natural Science Foundation of China (Grant Nos. 61274037 and 61301046) and the Research Fund for the Doctoral Program of Higher Education of China (Grant Nos. 20120101110031 and 20120101110054).

Surface acoustic wave (SAW) resonators are a type of ultraviolet (UV) light sensors with high sensitivity, and they have been extensively studied. Transparent SAW devices are very useful and can be developed into various sensors and microfluidics for sensing/monitoring and lab-on-chip applications. We report the fabrication of high sensitivity SAW UV sensors based on piezoelectric (PE) ZnO thin films deposited on glass substrates. The sensors were fabricated and their performances against the post-deposition annealing condition were investigated. It was found that the UV-light sensitivity is improved by more than one order of magnitude after annealing. The frequency response increases significantly and the response becomes much faster. The optimized devices also show a small temperature coefficient of frequency and excellent repeatability and stability, demonstrating its potential for UV-light sensing application.