Wavelength UV Light Research Articles

Impacts of Mixing Mode on Photocatalytic Reduction of Hexavalent Chromium over Titanium Dioxide Nanomaterial under Various Environmental Conditions

This study explores the effects of initial Cr(VI) concentration, wavelength, hole-scavenger (absence and presence of salicylic acid), and oxygen conditions (aeration by air, nitrogen gas, and mechanical stir only) on photocatalytic reduction of hexavalent chromium over titanium dioxide photocatalyst and the chromic species distribution after photocatalysis. The experimental results show the existence of strong interactions between these factors. The factor of hole-scavenger was more important than the UV light wavelength condition for a reduction of 3 mg Cr(VI) L−1, whereas both factors became important when Cr(VI) concentration increased to 20 mgL−1. The higher the UV wavelength was, the less the amount of chromium retained on the TiO2 surface. The influence of oxygen-containing conditions in the solution on the reduction of 3 mgL−1 Cr(VI) was unobvious, whereas its influence became remarkable for the reduction of 20 mgL−1 Cr(VI) in the presence of SA. The interaction between oxygen-containing factor and other environmental factors, such as Cr(VI) concentration and scavenger presence (SA in this study), is a key factor about the degree of oxygen effect on Cr(VI) photo-reduction and the chromic species distribution. Simple stirring obtained better photocatalytic efficiency than aeration by air or nitrogen gas.

Ultrahigh stable lead halide perovskite nanocrystals as bright fluorescent label for the visualization of latent fingerprints

Fingerprints formed by the raised papillary ridges are one of the most important markers for individual identification. However, the current visualization methods for latent fingerprints (LFPs) suffer from poor resolution, low contrast, and high toxicity. In this work, the CsPbBr3/Cs4PbBr6 nanostructured composite crystal (CsPbBr3/Cs4PbBr6 NCC) were synthesized via a simple chemical solvent-assisted method. Compared with conventional perovskites, the as-prepared CsPbBr3/Cs4PbBr6 NCC present an outstanding long-term environmental and water stability with 42% and 80% photoluminescence intensity remaining after 28 d under water and air conditions, respectively. Moreover, a special response to biomolecules from fingerprints was observed due to the hydrophobic interactions between the CsPbBr3/Cs4PbBr6 NCC surface hydrophobic ligands (oleyl amine and oleic acid) and the hydrophobic groups in the biomolecules from the human fingers. Clear LFPs images were visualized in a bright environment illuminating the prepared CsPbBr3/Cs4PbBr6 NCC powder under UV light of wavelength 365 nm. The images were also obtained on porous and non-porous surfaces such as metal, plastic, wood, glass, and paper products. These perovskite nanocrystals are expected a stable and bright luminescent labeling agent for LFPs visualization and have potential application in crime scene and personal identifications.

Synthesis of Gd2O3 Nanoparticles and Their Photocatalytic Activity for Degradation of Azo Dyes

Gadolinium oxide (Gd2O3) nanoparticles were prepared via the reaction of gadolinium nitrate hexahydrate (Gd (NO3)3·6H2O) and ethylamine (C2H5NH2), and their surface morphology, particle size, and properties were examined by using scanning electron microscopy, X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and ultraviolet visible (UV-vis) spectroscopy. The Gd2O3 nanoparticles were used as the photocatalyst for the degradation of various azo dyes, such as methyl orange (MO), acid orange 7 (AO7), and acid yellow 23 (AY23) under irradiation with UV light. The effect of the experimental parameters (initial concentration of azo dyes, dosage of catalyst, and wavelength of UV light) on the photocatalytic properties of the Gd2O3 nanoparticles were investigated. At a constant H2O2 concentration, the photocatalytic degradation efficiency of the Gd2O3 nanoparticles for various azo dyes was in the order: methyl orange > acid orange 7 > acid yellow 23. The kinetics study showed that the photocatalytic degradation of azo dyes was followed by a pseudo first-order reaction rate law.

Determination of sun protection factor and physical remanence of dermocosmetic emulgels formulated with Manilkara zapota (L.) fruit extract

Purpose: To develop a stable emulgel formulation from Manilkara zapota fruit extract (MZFE) and evaluate its sun-protective factor (SPF) and its physical retention on facial skin.
 Methods: Active test formulations containing MZFE and placebo (containing no active ingredients) were prepared by dispersing the primary emulsion into a gel phase. Both test and placebo emulgel formulations were subjected to physicochemical evaluation, stability studies, and assessment of possible photo-protective properties. The sun-protective factor (SPF) was determined in vitro by spectrophotometric analysis. Non-invasive in vivo skin bioengineering technique was used to assess the UV-quenching effects of the test and placebo emulgel formulations.
 Results: A stable and cosmetically acceptable emulgel formulation loaded with MZFE was obtained. The formulation and control exhibited optimum physicochemical stability in stress stability tests. The formulation exhibited promising photo-protective effects both in vitro (SPF = 14.215 ± 0.140) and in vivo (lasted for approximately 120 min).
 Conclusion: The developed MZFE-loaded test emulgel formulation possesses suitable photoprotection capability in vitro, and displays quenching effects against specific wavelengths of UV light, indicating a UV-filtering property

Magnetic Fe3O4@TiO2 nanocomposites to degrade bisphenol A, one emerging contaminant, under visible and long wavelength UV light irradiation

The environmentally benign Fe3O4@TiO2 heterojunction photocatalysts were fabricated to remove Bisphenol A (BPA) under visible and long wavelength UV light irradiation. To reveal the incorporation of Fe3O4 and TiO2 nanoparticles, Fe3O4@TiO2 composite was systematically characterized by XRD, Raman, FTIR, XANES and UV-Vis. Both titanium and iron were close to their highest oxidation state, and retained the magnetic properties of Fe3O4 under the high temperature calcination. Superior photocatalytic BPA degradation rate (kobs=0.0152 min−1) was recorded with 500FT, under long wavelength UV light for first 30 min. The enhanced photocatalytic activity was recorded due to the moderate iron loading, which reduced the hole-pair separation effectively, and shifted the band-gap in the visible range. In addition, the magnetic properties of Fe3O4 in 500FT, which play a crucial role in recollecting the used catalyst from environment, greatly promotes the practical applications of Fe3O4@TiO2 photocatalyst. This study provides an understanding of facile synthesis and characteristics of low-cost materials for wastewater treatment.

Effects of UV Light Path Length and Wavelength on UV/Chlorine versus UV/H2O2 Efficacy

Inconsistent trends have been reported in the relative competitiveness of UV/chlorine and UV/H2O2 advanced oxidation processes for micropollutant degradation during drinking water treatment at benc...

Application of a LED-UV based light technology for decontamination of chicken breast fillets: Impact on microbiota and quality attributes

Light-emitting diode (LED) technologies are economical and efficient devices that could be considered in poultry processing as disinfection strategies. This study evaluated the efficacy of a LED-based device to reduce the microbial load on chicken meat and investigated it's impact on selected quality parameters. Quality parameters including pH, texture and color after LED-UV exposure and during subsequent storage for 7 days at 4 ̊C were investigated. Diced chicken breast fillets were exposed to UV light wavelengths of 255, 280, 300 and 365 nm for 2, 4, 6, 8 and 10 min. A microbiological analysis was conducted on chicken samples to enumerate bacterial counts. Reductions between 1.17 and 1.67 log CFU/g for total viable counts of mesophilic, psychrophilic bacteria and total Enterobacteriaceae counts were observed, whereas, up to 2 log CFU/g was obtained for Pseudomonas and lactic acid bacteria groups after treatment with wavelengths of 280, 300 and 365 nm. Furthermore, color, texture and pH were not affected by exposure to UV light at 280 nm even following 7 days storage. Thus, LED-based technologies could be applied on poultry meat to reduce the levels of spoilage bacteria while maintaining quality attributes.

Photosynthesis of polymer networks with controlled properties by dimerization of cinnamoyl groups

AbstractPhotosensitive monomers/polymers/copolymers containing a variable amount of cinnamoyl (Ci) groups ranging from 3 up to 480 per molecule were synthesized. These precursors were photocrosslinked by irradiation with UV light of wavelength 320–380 nm via the photodimerization of the Ci units. The evolution of conversion, gel fraction, modulus and Tg during irradiation was followed. Two types of photosensitive systems were studied: (i) a blend of photosensitive precursors of different functionality fCi and (ii) copolymers with a different content of Ci units and Tg. The control of the precursors' structure and composition as well as photocuring time period make it possible to finely tune the properties of the formed polymer network films. The prepared photocrosslinked networks show a very broad range of thermomechanical properties with Tg from −25 °C up to 135 °C and moduli over a range of three orders of magnitude. © 2021 Society of Chemical Industry

Coumarin derivative trigger controlled photo-healing of ion gels and photo-controlled reversible adhesiveness

Fabrication strategies for photo-responsive ion gels have attracted attention owing to their precise spatial and temporal control with predetermined responses to light stimuli. In this work, a reversible light-driven method was introduced to devise photo-responsive ion gels by harnessing coumarin-based building blocks under 365 nm irradiation. A series of random copolymers composed of N, N-dimethylacrylamide (DMA) and 7-(2′-methacryloyloxyethoxy)–4-methylcoumarin (MAOEMC), namely P(DMA-r-MAOEMC), were synthesized through reversible addition-fragmentation chain transfer (RAFT) polymerization with sufficient molecular weight (≈100 kDa). The coumarin moieties in those polymers exhibited a reversible photo-induced dimerization and photocleavage behavior in 1-ethyl-3-methylimidazolium bis (trifluoromethylsufonyl) imide ([C2mim][NTf2]). Those polymers - ionic liquid system at high polymer concentration (20 wt%) under suitable wavelength UV light irradiation led to sol–gel transition, which could be functionalized as photo-healable material and photo-controlled adhesion agents. Notably, the photo-controlled adhesiveness was reversible and can be mediated from 1.2 MPa to 0.2 MPa. This work opens new avenues to develop multifunctional ion gels using dynamic covalent bonds.

Red-Light Driven Photocatalytic Oxime Ligation for Bioorthogonal Hydrogel Design.

Light-mediated polymer cross-linking is frequently employed for the preparation of hydrogels for biomedical applications. However, most photopolymerization processes require activation by UV light or short wavelength visible light, which are highly absorbed by skin and tissue, limiting their uses in transdermal initiation. Herein, we introduce red light-enabled oxime ligation by the in situ photogeneration of aldehydes, which rapidly react with hydroxylamines. We demonstrate efficient polymer cross-linking behind a dermal tissue model by red light initiation. Optimization of the photopolymerization conditions allows for 3D encapsulation of human foreskin fibroblasts with good cell viability postencapsulation.

Mussel-inspired adhesive and conductive hydrogel with tunable mechanical properties for wearable strain sensors

HypothesisFlexible and wearable hydrogel strain sensors have attracted significant attention for human activity monitoring and electronic skins. However, it remains a great challenge to develop an integrated hydrogel strain sensor showing intrinsic adhesive performances, tunable mechanical and high strain-sensitive properties. Marine mussels show a superior capacity to adhere to various substrates (including organic and inorganic), while polycaprolactone (PCL) can be easily modified into crosslinkers with different degrees of functionality (bi-, tri-, and quadri-functional groups) to control the crosslinking density. Therefore, the developed mussel-inspired 3,4-dihydroxyphenyl-l-alanine acrylamide–polycaprolactone (l-DMA–PCL) hydrogels could address these issues and serve as the potential wearable strain sensors for biomaterials and healthcare monitoring. Experimentsl-DMA monomers were successfully crosslinked by functionalized PCL (bi-, tri-, and quadri-functional) using UV light (wavelength ~ 365 nm) to prepare the l-DMA–PCL hydrogel. Adhesive behaviors, tunable mechanical properties and strain sensing performances of the l-DMA–PCL hydrogels were systematically studied. FindingsThe l-DMA–PCL hydrogel exhibited reversible adhesion to various material substrates (including steel, aluminum, ceramics, poly(ethylene terephthalate) (PET), wood, rubber, even for polypropylene (PP) and polytetrafluoroethylene (PTFE)) as well as skin. Moreover, the mechanical properties (stress: 50.2–72.4 KPa, strain: 700–1140%, Young’s modulus: 8.6–14.8 KPa, and toughness: 16.4–53.6 KJ/m3) of the hydrogels could be readily tuned by the modulation of functionality degree (bi-, tri-, and quadri-functional) of PCL. Intriguingly, the hydrogel-based wearable strain sensor showing high conductivity (0.0550 S/cm) and sensitive responses to both large (e.g., joint bending) and subtle human motions (e.g., frowning and speaking). Based on these achievements, this work provides new insights into the development of hydrogel with adhesiveness, controllable mechanical performance and high strain sensitivity as a flexible and wearable hydrogel strain sensors.

Degradation of Linear Alkylbenzene Sulfonate by UV/H2O2 Process

ABSTRACT In this study, we investigated the degradation of linear alkylbenzene sulfonate (LAS) by an ultraviolet/hydrogen peroxide (UV/H2O2) process. In a collimated beam experiment with UV light of wavelength 222 or 254 nm, faster LAS degradation rates occurred at elevated H2O2 concentrations. The degradation behavior varied with the wavelength of the light source. Furthermore, according to the results of a degradation experiment in a tubular reactor, the reaction rate was faster in the UV/H2O2 process than in the UV-only process.

Real-Time Estimation of Disinfection By-Products through Differential UV Absorbance

Efforts to control of unwanted disinfection by-products (DBPs) can be hindered by the relatively low-frequency data that is generated from DBP monitoring for regulatory purposes. Differential UV absorbance (DUVA) has the potential to overcome some of these difficulties as a relatively simple and low-cost technique for the estimation of regulated DBPs (i.e., trihalomethanes, THMs, and haloacetic acids, HAAs). DUVA is based on the principle that differences in UV absorbance at specific wavelengths before and after chlorination can be correlated to DBP occurrence. This project sought to assess a lab-based protocol for the determination of a site-specific linear calibration curve for in situ real-time estimations of DBPs from DUVA measurement in water treatment plants (WTPs). A field spectrophotometer probe capable of high frequency scans within the UV light wavelength spectra with light paths of 100 mm was used. Models were developed to estimate DBP levels, at a scale representative of DUVA and DBP levels that actually occur in the WTP under study. Results showed that level of uncertainty on DBP levels estimation is relatively low (23% for HAAs and 32% for THMs). Although DBP estimations through DUVA are not of regulatory value, they can be used for real-time estimation of DBP levels to better inform operational decision making in water treatment plants and management of DBPs in distribution systems.

Synthesis of Carbon Dots via Hydrothermal Reaction for Selective Detection of Serotonin.

Serotonin (5-HT) is a significant neurotransmitter involved in the regulation of mood, social behavior, depression, and other neurological activities. In this work, we synthesized nitrogen-doped carbon dots using naturally occurring amino acids such as L-aspartic acid and L-cysteine by employing a one-step hydrothermal reaction. The amino acid-derived carbon dots (CDs) are called AACDs. The as-synthesized AACDs showed strong blue-color emission under UV light and photoluminescence (PL) emission maximum wavelength at 457 nm with an excitation wavelength of 344 nm. The AACDs had superior aqueous solubility due to the carboxyl (-COOH) and amine (-NH₂) functional groups on their surface. 5-HT could be detected by adding cobalt ions (Co2+) to the AACDs. The Co2+ ions facilitate cross-linking between free amino and carboxylate groups. Fluorescence quenching by AACDs incorporating Co2+ ion was observed to be dependent on the concentration of serotonin. The limit of detection (LOD) of AACDs for 5-HT was 2.24 μM.

Water-mediated through-space-conjugation of aromatic groups for stimuli-responsive photoluminescence

Aqueous media acts as a functional component for the metal carbonyl vesicles (MCsome) assembled from FpC3Bithiophene (Fp: (Cp)Fe(CO)2(PPh3), C3: propyl) molecules. The MCsome in THF/water (with the ratio up to 0.30) have an aqueous vesicular membrane, which integrates the assembling blocks and restricts the intramolecular rotation of bithiophene groups. The restriction fixed the relative position of the aromatic groups giving rise to a through-space conjugation (TSC), which is responsible for the fluorescence with the wavelengths and intensities depending on the twisting angle of bithiophene groups. A dialysis process to remove THF trigged a torsional-to-planar rotation switching off the fluorescence, while the irradiation of UV light (wavelength 365 nm) stimulated a planar-to-torsional rotation for the solutions in THF/water mixed solvents, which turned on the fluorescence. This aqueous-mediated TSC-caused fluorescence signifies that water, as in natural systems, can act as a structural and functional component for material innovation.

UV Light-Modulated Fluctuation-Enhanced Gas Sensing by Layers of Graphene Flakes/TiO2 Nanoparticles

We present experimental results of fluctuation-enhanced gas sensing by low-cost resistive sensors made of a mixture of graphene flakes and TiO2 nanoparticles. Both components are photocatalytic and activated by UV light. Two UV LEDs of different wavelengths (362 and 394 nm) were applied to modulate the gas sensing of the layers. Resistance noise was recorded at low frequencies, between 8 Hz and 10 kHz. The sensors’ response was observed in an ambient atmosphere of synthetic air and toxic NO2 at selected concentrations (5, 10, and 15 ppm). We observed that flicker noise changed its frequency dependence at different UV light wavelengths, thereby providing additional information about the ambient atmosphere. The power spectral density changed by a few times as a result of UV light irradiation. The sensors were operated at 60 and 120°C, and the effect of UV light on gas sensing was most apparent at low operating temperature. We conclude that UV light activates the gas-sensing layer and improves gas detection at low concentrations of NO2. This result is desirable for the detection of the components of gas mixtures, and the modulated sensor can replace an array of independent resistive sensors which would consume much more energy for heating. We also suggest that a more advanced technology for preparing the gas-sensing layer, by use of spin coating, will produce corresponding layers with thickness of about a few μm, which is about ten times less than that for the tested samples. The effects induced by the applied UV light, having a penetration depth of only a few μm, would then be amplified.

Synthesis of bovine serum albumin capped boron-doped carbon dots for sensitive and selective detection of Pb(II) ion

Carbon dots have tremendous potential to be used for biochemical sensing and environmental testing due to its superior optical properties and excellent biocompatibility. The surface of carbon dots can be easily functionalized. In the present study boron doped carbon dots have been synthesized using one pot approach by microwave treatment method. The surface of boron doped carbon dots is capped with bovine serum albumin. The maximum fluorescence emission observed at 444 nm when excited upon 345 nm of wavelength. In the normal light, it is light green in colour but when exposed in long wavelength UV light it exhibited blue fluorescence. The carbon dots have an irregular shape with a diameter below 5 nm. The applicability of synthesized carbon dots as the fluorescent sensor has been checked using different metal ions. It is observed that Pb(II) ion shows appreciable and selective quenching. Linear relationship is exist between the decrease in fluorescence intensity and the concentrations of Pb(II) ion in the range from 1 ppb to 10 ppb concentration. Limit of detection is found to be 0.08 ppb. This study will be helpful in the development of new fluorescent nano-biosensors.

Azomethine phthalimides fluorescent E→Z photoswitches

Herein, we report the synthesis and E→Z photoswitching behavior of two 4-substituted azomethine phthalimides containing anthracenyl and 4-(dimethylamino)phenyl moieties (EAMP1 and EAMP2). These compounds represent newly synthesized and unstudied photoswitches with dual fluorescence properties as E-isomers and at photostationary state (PSS) depending on the solvent polarity. Steady-state fluorescence measurements were performed in various solvents and the results show strong sensitivity on the environmental polarity. The kinetics of E→Z photoswitching to PSS was studied in AcCN by visible light activation at 410 nm (EAMP1) and long wavelength UV-light activation at 350 nm (EAMP2). The quantitative and qualitative performance of the switching behavior was evaluated by the degree of photoisomerization (R) and the rate constant (k). It was found for EAMP1 R = 6.95 %, k = 8.87 × 10−4 s−1 and EAMP2 R = 88.72 %, k = 4.00 × 10−4 s−1, respectively. The reason for the lower photoconversion of EAMP1 compared to the EAMP2 was analyzed through optimization of the molecular geometry of E- and Z-isomers in the ground state (S0) and first excited state (S1) by DFT/TD-DFT calculations with B3LYP/6-31+G(d,p) level of theory using IEFPCM in AcCN. It was found that E-isomers in the S0 have nonplanar conformation, while the Z-isomer of EAMP1 prefers twisted conformation and the Z-isomer of EAMP2 T-shaped conformation is energetically advantageous compared to the twisted one. The reason is the weak H…..π noncovalent interaction (NCI) between 4-(dimethylamino)phenyl moiety and phthalimide ring. Moreover, the Z-isomer of EAMP2 is unusual stable up to 600 min at room temperature in dark compared to the EAMP1, which undergoes full Z→E relaxation for less than 60 min at the same conditions. The Z→E relaxation of EAMP2 is achieved for 90 min at 60 °C. The fluorescence E→Z switching behavior was studied by emission measurements in AcCN and 1,4-DOX as E-isomers and at PSS in room and liquid nitrogen (77 K) temperatures. In the polar and nonpolar solvents, red-shifted emissions with increased fluorescence quantum (Φfl) yields have been observed at PSS compared to the E-isomers. The molecular rotor behavior was studied in the binary mixture of glycerol:ethanol and the results show a sensitivity of the emission bands depending on the environmental viscosity. Time-resolved fluorescence decay measurements were performed in AcCN and 1,4-DOX as E-isomers and at PSS to estimate the mechanism of fundamental fluorescence bands. We found that dyes at PSS have longer lifetime (τ) compared to the E-isomers, especially in less polar 1,4-DOX.

Synthesis of novel cellulose mixesters for transparent responsive films with switchable mechanical properties

Soft actuators have attracted much attention during the last decades due to their potentially broad applications ranging from sensors to artificial muscles. Up to now, most of such soft actuators are still based on synthetic polymers. Herein, we described a novel group of materials derived from sustainable cellulose as potential starting materials for the preparation of soft actuators. To be precisely, cellulose mixesters with acyl esters of distinct chain lengths and cinnamic ester were synthesized through a two-step synthesis and used for the preparation of responsive thin film actuators. These cellulose mixesters have degree of substitution ascribed to stearoyl groups (DSSt) of 1.51 or lauroyl groups (DSLa) of 1.48 and degree of substitution ascribed to cinnamoyl groups (DSCi) around 1.35. Furthermore, the influence of the chain lengths of the two different aliphatic esters as well as the switchable crosslinking of cinnamoyl moieties on the materials properties was further shown. Using these cellulose mixesters, transparent thin films with thickness of 4−15 μm were prepared via facile solvent casting. These films had light-responsive mechanical properties from rigid to elastic after illumination with UV light of distinct wavelengths (254 nm and 310−400 nm). Moreover, the thin films showed shape memory effect and the ability of self-healing.

Eu(O2C‐C≡C‐CO2): An EuII Containing Anhydrous Coordination Polymer with High Stability and Negative Thermal Expansion

Anhydrous EuII–acetylenedicarboxylate (EuADC; ADC2− = −O2C‐C≡C‐CO2 −) was synthesized by reaction of EuBr2 with K2ADC or H2ADC in degassed water under oxygen‐free conditions. EuADC crystallizes in the SrADC type structure (I41/amd, Z=4) forming a 3D coordination polymer with a diamond‐like arrangement of Eu2+ nodes (msw topology including the connecting ADC2− linkers). Deep orange coloured EuADC is stable in air and starts decomposing upon heating in an argon atmosphere only at 440 °C. Measurements of the magnetic susceptibilities (μ eff=7.76 μB) and 151Eu Mössbauer spectra (δ=−13.25 mm s−1 at 78 K) confirm the existence of Eu2+ cations. Diffuse reflectance spectra indicate a direct optical band gap of E g=2.64 eV (470 nm), which is in accordance with the orange colour of the material. Surprisingly, EuADC does not show any photoluminescence under irradiation with UV light of different wavelengths. Similar to SrADC, EuADC exhibits a negative thermal volume expansion below room temperature with a volume expansion coefficient α V=−9.4(12)×10−6 K−1.