Assistance Of UV Light Research Articles

Engineering of self-assembled silver-peptide colloidal nanohybrids with enhanced biocompatibility and antibacterial activity

Several bacterial strains have developed resistance against commercial antibiotics, and interestingly, supramolecular nanomaterials have shown considerable advantages for antibacterial applications. However, the main challenges in adopting nanotechnology for antibacterial studies are random aggregation, compromised toxicity, multi-step preparation approaches, and unclear structure-function properties. Herein, we designed the amphiphilic tripeptide that acts as a reducing and capping agent for silver metal to form silver-peptide colloidal nanohybrids with the mild assistance of UV light (254 nm) through the photochemical reduction method. The nanohybrids are characterized by different spectroscopic and microscopic techniques, and non-covalent molecular interactions between metal and peptide building blocks confirm their central role in the formation of nanohybrids. The tripeptide is biocompatible and can reduce the toxicity of silver ions (Ag+) by reducing to Ag0. These colloidal nanohybrids showed antibacterial activity against gram-negative and gram-positive bacterial strains, and the possible mechanism of killing bacterial cells could be membrane disruption. This synthetic strategy is facile and green, which helps avoid using toxic chemicals or reagents and complicated methods for colloidal nanohybrid preparation for biomedical applications.

UV-assisted fluctuation-enhanced gas sensing by ink-printed MoS2 devices

In this work, MoS2 flakes were printed on ceramic substrates and investigated toward 1–10 ppm of nitrogen dioxide (NO2), 2–12 ppm of ammonia (NH3), and 2–12 ppm acetone (C3H6O) under UV light (275 nm). The structure of overlapping MoS2 flakes and UV light assistance affected high responsivity to NO2 when DC resistance was monitored, and superior sensitivity to NH3 was obtained from the low-frequency noise spectra. MoS2 exhibited response and recovery times in hundreds of seconds and stability throughout the experiments conducted within a few months. MoS2 sensor exhibited a resistance drift during the detection of a specific relaxation time. Subtracting the baseline burden with exponential drift exposed the direction of changes induced by oxidizing and reducing gases and reduced DL to 80 ppb, 130 ppb, and 360 ppb for NO2, NH3, and C3H6O, respectively. The fluctuation-enhanced sensing (FES) revealed that the adsorption of NO2 on MoS2 decreases the noise intensity, whereas adsorbed NH3 increases the fluctuations of current flowing through the sensor, and these changes are proportional to the concentration of gases. The noise responses for NO2 and NH3 were opposite and higher than DC resistance responses with subtracted baseline (an increase of 50% for 10 ppm of NO2 and an increase of more than 600% for 12 ppm of NH3), showing that FES is a highly sensitive tool to detect and distinguish between these two gases. This way, we introduce a simple and low-cost method of gas sensor fabrication using ink-printed MoS2 and the possibility of enhancing its sensitivity through data processing and the FES method.

UV-assisted robotic arm freeforming of SiOC ceramics from a preceramic polymer

Material extrusion is a very common and facile additive manufacturing technique for ceramic materials, allowing for rapid design and fabrication of 3D structures without expensive tools. However, fabricating sophisticated structures with large spanning parts and overhanging features using this technology is still a challenge. Here, UV-assisted additive manufacturing is enabled by performing material extrusion with the assistance of UV light using mixture of a preceramic polymer and a photopolymer. The rheological properties of the ink were investigated under UV light radiation to optimize the printing parameters to achieve excellent printability. Complex ceramic structures were fabricated with this method, such as spiral and truss structures, which would be very difficult to obtain using traditional material extrusion without sacrificial supports. These structures have potential application in lightweight ceramic components, such as sandwich structures.

Instant‐in‐Air Liquid Metal Printed Ultrathin Tin Oxide for High‐Performance Ammonia Sensors

AbstractLiquid metal‐based printing techniques are emerging as an exemplary platform for harvesting non‐layered 2D materials with a thickness down to a few nanometres, leading to an ultra‐large surface‐area‐to‐volume ratio that is ideal for sensing applications. In this work, the synthesis of 2D tin dioxide (SnO2) by exfoliating the surface oxide of molten tin is reported which highlights the enhanced sensing capability of the obtained materials to ammonia (NH3) gas is reported. It is demonstrated that amperometric gas sensors based on liquid metal‐derived 2D SnO2 nanosheets can achieve excellent NH3 sensing performance at low temperature (150 °C) with and without UV light assistance. Detection over a wide range of NH3 concentrations (5–500 ppm) is observed, revealing a limit of detection at the parts per billion (ppb) level. The 2D SnO2 nanosheets also feature excellent cross‐interference performance toward different organic and inorganic gas species, showcasing a high selectivity. Further, ab initio DFT calculations reveal the NH3 adsorption mechanism is dominated by chemisorption with a charge transfer into 2D SnO2 nanosheets. In addition, a proof of concept for prototype flexible ammonia sensors is demonstrated by depositing 2D SnO2 on a polyimide substrate, signifying the high potential of employing liquid metal printed SnO2 for realizing wearable gas sensors.

Highly response and humidity-resistant gas sensor based on polyaniline-functionalized Bi2MoO6 with UV activation

The bismuth molybdate (Bi2MoO6) has shown great application potential in the field of gas sensing owing to its abundant Lewis acid sites, suitable energy band and unique layered structure. In this work, a room temperature, highly response, selectivity and humidity-resistant NH3 gas sensor based on the Bi2MoO6/Polyaniline (BMO/PANI) nanocomposite was successfully developed by an in-situ chemical oxidative polymerization process. The obtained samples were characterized by X-ray diffractometer, UV–vis diffuse reflectance spectra, Transmission electron microscopy, X-ray photoelectron spectroscopy, etc. A series of gas-sensing properties studies were conducted with the assistance of UV light, which indicate that UV light illumination could significantly enhance the response of the prepared BMO/PANI sensor and short recovery time (71s). Additionally, the sensor also demonstrated excellent selectivity, repeatability, long-term stability, and moisture resistance. These outstanding characteristics of the sensor are attributed to the dramatic increase of surface state density upon activation by the UV light and the distinctive heterogeneous interface strengthens the interfacial charge transfer.

UV-light-assisted NO2 gas sensor based on WS2/PbS heterostructures with full recoverability and reliable anti-humidity ability

Abstract Transition metal dichalcogenides (TMDs) have blazed a novel trail in the field of NO2 gas detection owing to the unique photoelectric properties and prospective gas sensing performance especially working at low operating temperature. However, the incomplete recoverability and susceptibility to humidity at room temperature restrict the practical applications of TMDs-based gas sensors. Herein, we demonstrate a fully recoverable WS2 based gas sensor with enhanced anti-humidity ability by combining the decoration of zero-dimensional PbS nanoparticles and the assistance of UV light. Through the control over the molar ratio of WS2/PbS, the optimized WS2/PbS (the molar is 10:1) gas sensor exhibits a remarkable elevated recovery rate from 33.4% to 99.8% with almost no baseline drift as compared to that in the pure WS2 gas sensor. More importantly, attributing to the irradiation of UV can accelerate the desorption of water molecules, WS2/PbS heterostructure based gas sensor manifests more stabilized anti-humidity performance with stable initial resistance and negligible response value drift (8.8%) in the range of 10%–90% relative humidity. Furthermore, UV-assisted WS2/PbS gas sensor also possesses prominent sensing performances including high sensitivity, low detection limit (∼20 ppb), favorable selectivity and outstanding long-term stability. This research will pave the way on designing high-performance TMDs-based gas sensors operating at room temperature.

GaN nanowires decorated with Pd for methane gas sensor

In this study, palladium (Pd)-decorated gallium nitride (GaN) nanowire have been prepared for room-temperature methane (CH4) gas sensors. The material was fabricated via MOCVD method combined with subsequent magnetron sputtering process and characterized by SEM technique. The SEM images indicate that the presence of different thickness of Pd film on the surface of the nanowires. When used for methane gas sensing, with the assistance of UV light, the 10nm Pd-decorated GaN nanowire sensor has the highest response to 200ppm methane, which were about 2 times higher than that of pure GaN samples. What’s more, 10nm Pd-decorated GaN sensor also has the lowest detection limit (20ppm) and the shortest response time (<10s). Thus, the application of Pd-GaN nanowire as methane gas sensor will have board prospects.

Enhanced activation of peroxymonosulfate by CNT-TiO2 under UV-light assistance for efficient degradation of organic pollutants

In this work, a UV-light assisted peroxymonosulfate (PMS) activation system was constructed with the composite catalyst of multi-walled carbon nanotubes (CNT) — titanium dioxide (TiO2). Under the UV light irradiation, the photoinduced electrons generated from TiO2 could be continuously transferred to CNT for the activation of PMS to improve the catalytic performance of organic pollutant degradation. Meanwhile, the separation of photoinduced electron-hole pairs could enhance the photocatalysis efficiency. The electron spin resonance spectroscopy (EPR) and quenching experiments confirmed the generation of sulfate radical (SO4•−), hydroxyl radical (•OH) and singlet oxygen (1O2) in the UV/PMS/20%CNT-TiO2 system. Almost 100% phenol degradation was observed within 20 min UV-light irradiation. The kinetic reaction rate constant of the UV/PMS/20%CNT-TiO2 system (0.18 min−1) was 23.7 times higher than that of the PMS/Co3O4 system (0.0076 min−1). This higher catalytic performance was ascribed to the introduction of photoinduced electrons, which could enhance the activation of PMS by the transfer of electrons in the UV/PMS/CNT-TiO2 system.

In Situ Growth of Leakage-Free Direct-Bridging GaN Nanowires: Application to Gas Sensors for Long-Term Stability, Low Power Consumption, and Sub-ppb Detection Limit.

Direct-bridge growth of aligned GaN nanowires (NWs) over the trench of GaN-coated sapphire substrate was realized in which the issues of parasitic deposition and resultant bypass current were resolved by combining the novel shadowing effect of the deep trench with the surface-passivation effect of the SiO2 coating. Due to the robust connection and the absence of a contact barrier in bridging NWs, the intrinsic sensing properties of the NW itself can be obtained. For the first time, the gas-sensing properties (e.g., NO2) of the bridging GaN NWs were studied. With the assistance of UV light, the detection limit was improved from 4.5 to 0.5 ppb at room temperature, and the corresponding response time was reduced from 518 to 18 s. This kind of sensor is promising for high sensitivity (detection of less than parts per billion), low power consumption (capable of room-temperature operation), high stability (variation in resistance of <0.8% during 240 days), and in situ monolithic integration.

Template-free growth of coral-like Ge nanorod bundles via UV-assisted ionic liquid electrodeposition

Germanium (Ge) is an important semiconductor material in optoelectronic devices and is being researched in energy storage fields. Ge nanostructure materials with different morphologies may lead to distinctly different application performances. In this work, Ge nanorod architectures were successfully template-free electrodeposited on ITO substrate from the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([Emim]Tf2N) containing dissolved GeCl4 with the assistance of UV light. The UV irradiation influences the conformation of imidazolium rings of [Emim]+ adsorbed during the deposition process. A solution template has been formed on the surface of the electrode which inhibited the lateral growth of Ge nuclei and promoted the growth of Ge nanorod structures. Consequently, the coral-like Ge nanorod bundles (NRBs) has been obtained. This method provides attractive prospects for the other semiconductor nanorod structures.

SnO2-montmorillonite composite for removal and inhibition Microcystis aeruginosa assisted by UV-light

Cyanobacterial blooms have become a serious pollution problem, in particular, for water resources. Microcystis aeruginosa (M. aeruginosa) is most common toxic cyanobacterial bloom in fresh waters. In this paper, SnO2-montmorillonite composite was prepared by ion exchange method and applied to remove M. aeruginosa with the assistance of UV-light. The structure of the resulting composite was identified by XRD, IR and TEM. It was determined that some SnO2 nanoparticles were inserted into the interlayer of montmorillonite and some were dispersed on the surface of montmorillonite. M. aeruginosa removal efficiency was judged by the rate of 95% after treatment with 0.3 g/L SnO2-montmorillonite for 1 h. SnO2-montmorillonite composite absorbed M. aeruginosa and promoted M. aeruginosa lysis by damaging cell wall and membrane. The cellular contents, including protein and chlorophyll a, were then degraded with the assistance of UV-light, which inhibited the biological activity of M. aeruginosa. In fact, SnO2-montmorillonite composite removed M. aeruginosa by combination of adsorption flocculation and UV-induced catalytic degradation. SnO2-montmorillonite shows promise to become an effective material for the removal of algae and the cyanobacteria bloom.

Photo-oxidative doping in π-conjugated zig-zag chain of carbon atoms with sulfur-functional group

Photo-oxidative doping processes were studied for the trans-polyacetylene backbone with the –SCH3 side group as a chemically representative of the precisely controlled S-functionalized zig-zag graphene nanoribbon edge. Sulfur K-edge X-ray absorption near edge structure (XANES) spectroscopy indicates that photochemical reaction of S–CH3 with atmospheric O2 forms selectively oxidized products such as –S(O)CH3 and –SO3– bound to the polyacetylene (PA) backbone. Using the correlation between the oxidation states of sulfur and the XANES peak positions, the partial charge distribution of CH3Sδ+–PAδ– has been estimated. Such positively charged sulfur atoms can attract higher electronegative oxygen atoms and expect to enhance the photooxidization capabilities. The formation of the –SO3– side group is evidently responsible for hole doping into the PA backbone. The results can provide some strategy for area-selective and controllable doping processes of atomic-scale molecular systems with the assistance of UV light.

Assessing the use of zero-valent iron microspheres to catalyze Fenton treatment processes

The application of Fenton processes is limited by the production of iron sludge and its pH-dependence efficiency. UV-light assistance and the use of alternative catalysts as zero-valent iron (ZVI) may avoid both drawbacks favoring its potential industrial application. The use of ZVI microspheres as the catalyst of Fenton processes is herein assessed and optimized in terms of reagents dosage, particle size and surface area. Microspheres providing a surface area of 0.8m2/g showed the best performance and the lowest tendency to be dissolved under acidic conditions, resulting a concentration ratio of [H2O2]/[Fe0]=60 under optimal reaction conditions. The optimized 450W UV-radiation photo-Fenton treatment addressed the almost complete mineralization of phenol (COD and TOC removal≈98–99%) at both acidic and neutral initial pH values; whereas good mineralization results of oxalic acid were only achieved under acidic conditions (COD removal≈100%; TOC removal≈83%). Only initial neutral pH conditions enabled the recovery of the catalyst. Although a more powerful oxidation treatment was performed under acidic conditions, it also implied a higher dissolution of the microspheres. The application of less powerful radiation (100W) limited catalyst losses under acidic conditions, but longer treatment time is required aiming to address similar degradation results.

Dry De-NOx Process via Gas-Phase Photochemical Oxidation Using an Ultraviolet and Aerosolized H2O/H2O2 Hybrid System

A dry de-NOx technique based on a highly efficient photochemical oxidation process was demonstrated for a simulated flue gas of a diesel engine using a lab-scale reaction chamber. A hybrid system of an ultraviolet (UV185, 254 nm) lamp and aerosolized H2O/hydrogen peroxide (H2O2) was employed. De-NOx characteristics when using an UV lamp, an aerosolized H2O/H2O2 solution, and a hybrid system of both components were investigated individually. The UV lamp treatment had a significant impact on the de-NOx process by generating ozone, while the aerosolized H2O/H2O2 solution showed less effect because of the ambient temperature when the system was operated separately. With the assistance of UV light, however, aerosolized H2O/H2O2 contributed to the oxidation reaction and NO and NO2 removal efficiencies of up to 100 and 97.8%, respectively, were achieved. Ammonia was introduced into the reaction chamber to solidify and remove the oxidized nitric oxide (NO) through the formation of ammonium nitrate aerosols. Scanning electron microscopy and energy-dispersive spectroscopy analysis were used to identify and interpret the particulate byproducts after the reaction.

UV light assisted synthesis of ternary reduced graphene oxide hybrid materials and their photocatalytic performance

Freely-assembled ternary hybrids consisting of Pt, reduced graphene oxide (RGO) and P25 were synthesized by a direct solution process with the assistance of UV light. The Pt-RGO/P25 hybrids were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet visible (UV-vis) diffuse reflectance spectroscopy (DRS) and photoluminescence spectra (PL). Importantly, when Pt-RGO/P25 hybrids were used as photocatalysts, they could show a superior photocatalytic performance when compared to commercial P25 and RGO/P25 hybrids under UV, solar light and λ > 600 nm visible light irradiation, which could be explained on the basis of the plasmonic response and the formation of Pt Schottky barrier at the interface between TiO2 and graphene. This work could provide new insight for enhancing graphene/TiO2 photocatalytic performance and facilitate their application in environmental protection.

Systematic Study of Anodic Etching of Highly Doped N-type 4H-SiC in Various HF Based Electrolytes

In this paper, we study the electrochemical anodization of n-type heavily doped 4H-SiC wafers in HF based electrolytes without any UV light assistance. We present, in particular, the differences observed when varying the process conditions such as the HF concentration, the type of additive and the applied current regime. The use of a solvent such as acetic acid seems to be more suitable to produce homogeneous morphologies compared with Cetyltrimethylammonium chloride (CTAC), Ammonium dodecylsulfate (ADS), Triton X-100 surfactants. In addition, the use of pulsed current regimes improves the global homogeneity of the porous layers. Nevertheless, for some unexplained reasons, at specific concentrations of 15 and 50%, this homogeneity cannot be ensured and the observed morphology mixes mesopores and macropores with random orientations.

Room light anodic etching of highly doped n-type 4 H-SiC in high-concentration HF electrolytes: Difference between C and Si crystalline faces

In this paper, we study the electrochemical anodization of n-type heavily doped 4 H-SiC wafers in a HF-based electrolyte without any UV light assistance. We present, in particular, the differences observed between the etching of Si and C faces. In the case of the Si face, the resulting material is mesoporous (diameters in the range of 5 to 50 nm) with an increase of the ‘chevron shaped’ pore density with depth. In the case of the C face, a columnar morphology is observed, and the etch rate is twice greater than for the one for the Si face. We've also observed the evolution of the potential for a fixed applied current density. Finally, some wafer defects induced by polishing are clearly revealed at the sample surfaces even for very short etching times.

Ultra-violet light assisted reactive RF magnetron sputtering deposition of AlN thin films at room temperature

An ultra-violet (UV) assisted reactive RF magnetron sputtering deposition method for AlN thin film on Si (100) substrate is proposed and developed. The experiments are conducted at room temperature and the highest substrate temperature is below 86°C. AlN thin films are amorphous-like crystal structure if deposited without UV light exposure, and become either (002) or (100) orientation dominated crystals with large grain sizes with the UV-light assistance if deposited either at high RF power or high N2/Ar flow ratio. UV-light enhanced Al ionization is believed to be responsible for the increased deposition rate and well-aligned crystal orientation of the AlN at room temperature.

Silver nanoparticles and silver molybdate nanowires complex for surface-enhanced Raman scattering substrate

Selective synthesis of silver and uniform single crystalline silver molybdate nanowires in large scale can be easily realized by a facile soft template approach. Ag6Mo10O33 nanowires with a uniform diameter of about 50 nm and the length up to several hundred micrometers were synthesized in large scale for the first time at room temperature using 12-silicotungstic acid system. The silver nanoparticles can be easily synthesized with the assistance of UV-light. Sensitive surfaceenhanced Raman scattering signals of p-aminothiophenol were observed on Ag nanoparticles and silver molybdate nanowires complex. The results demonstrated that synthetic method could be a potential mild way to selectively synthesize various molybdate nanowires with various phases in large scale. The silver nanoparticles and silver molybdate nanowires complex would be proposed for surface-enhanced Raman scattering substrate.

Modeling of iron activated persulfate oxidation treating reactive azo dye in water matrix

Advanced oxidation processes (AOPs) offer effective solutions for the treatment of wastewaters containing hazardous and refractory organic pollutants. However, their efficiency is strongly influenced by varying process conditions thus the prediction of the system behavior is of an unappreciable interest. In this study iron activated persulfate oxidation was applied for degradation of reactive azo dye, C.I. Reactive Red 45 (RR45), in water matrix. Fe 2+/S 2O 8 2− and Fe 0/S 2O 8 2− processes were maintained in a dark as well as with UV light assistance. The main purpose was to develop the flexible mathematical/mechanistic model ( MM) which would (i) predict not only the conversion of parent pollutant, i.e. decolorization of model dye solution, but also the mineralization of model pollutant, and (ii) could keep the predictive power regardless the process operating conditions. Hence, the pH dependent mechanism describing both organic and inorganic ferric complexes formation as one of the major limitations of iron activated processes, as well as iron activated persulfate oxidation, was built in the model. Developed MM showed a high accuracy in predicting the degradation of RR45 considering both decolorization and mineralization, as well as the profiles of iron species, persulfate decomposition, the subsequent formation of sulfates and pH changes during the treatment. Good agreement of the data predicted and the empirically obtained was confirmed by calculated root mean square deviation (RMSD) values.