UV Light Irradiation Research Articles

Tuning up of chromism, luminescence in cadmium-viologen complexes through polymorphism strategy: Inkless erasable printing application

In our work, polymorphism strategy has been successfully applied to tune up chromism and luminescence properties of viologen-based materials. Two polymorphs of viologen-based complexes of α-CdBr2(PHSQ)2(H2O)2 (1) and β-CdBr2(PHSQ)2(H2O)2 (2) (PHSQ = N-(4-sulfophenyl)-4,4′-bipyridinium) were synthesized by changing the solvent. They can both respond to UV light and electricity in the manner of chromism visible to the naked eye and the coloration states have good reversibility, through which an inkless erasable printing model has been established. But the coloration contrast of 1 is higher compared to 2. Meanwhile, they both exhibit photoluminescence properties and the intensity of 1 is twice that of 2, which is accompanied by photoquenching upon continuous UV light irradiation. The only divergence of disordered/ordered O atoms in the two crystalline compounds leads to significantly different chromic and luminescent properties. Further explorations simultaneously demonstrate that the different chromic performance between 1 and 2 should attribute to the alteration of stimulus-induced (light/ electricity) electron transfer channels caused by the ordered/disordered O atoms in the complexes, which is achieved through CH···O and OH···O interactions to change crystal arrangement and structural rigidity, thus affect luminescent properties.

UV-enhanced photorefractive response rate in a thin-film lithium niobate microdisk.

The photorefractive (PR) effect plays a critical role in emerging photonic technologies, including dynamic volume holography and on-chip all-optical functionalities. Nevertheless, its slow response rate has posed a significant obstacle to its practical application. Here, we experimentally demonstrate the enhancement of the PR response rate in a high-Q thin-film lithium niobate (TFLN) microdisk under UV light irradiation. At an irradiation intensity of 30 mW/cm2, the PR effect achieves a high response bandwidth of approximately 256 kHz. By employing this UV-assisted PR effect, we have achieved rapid laser-cavity locking and self-stabilization, where perturbations are automatically compensated. This technique paves the way toward real-time dynamic holography, editable photonic devices on a lithium niobate platform, and high-speed all-optical information processing.

Bigger is not Better for Indolino‐Oxazoline Photochemical Properties

AbstractIndolino‐oxazolidine derivatives are a new and pretty confidential family of multimodal molecular switches. Indeed, acid, electrochemical potential, and UV light irradiation can be used to convert these compounds form their colorless closed form to a colorful open form. In this publication, we have investigated the influence of the extension of the π‐conjugated system beared by the indolino moiety on their halo‐, electro‐ and photochromic properties. In this context, we have demonstrated that only their photochemical properties are strongly affected by this structural modification. Moreover, quantum chemistry calculations have allowed to rationalize our experimental observations and, noticeably, evidenced an oxidative quenching process in presence of chlorobenzene, which enhances their photoreactivity.

Enhanced photocatalytic activity of (In–Sr–P) tridoped TiO2/Bi2O3 composite loaded on mesoporous carbon: A facile sol-hydrothermal synthesis approach

Photocatalysis attracted attention as a promising technique for wastewater treatment, especially for water contaminated with organic pollutants such as dyes. However, designing a suitable photocatalyst with a simple procedure and high catalytic performance is still a big challenge for large-scale production. Here, indium-strantiom and phosphorous tridoped Bi2O3–TiO2 composite loaded on mesoporous carbon (ISP–TiO2/Bi2O3@C) was prepared via the sol-hydrothermal method. The as-prepared ISP-TiO2/Bi2O3@C displayed a mesoporous structure with a BET surface area of 84.804 m2 g−1. The photocatalytic activity of the ISP-TiO2/Bi2O3@C composite was investigated toward the degradation of rhodamine B (RB) under exposure to UV, and sunlight. It was found that ISP-TiO2/Bi2O3@C photocatalyst exhibited superior photocatalytic activity against photodegradation of RB under UV light and sunlight irradiation with a degradation percentage of 99.12, and 95.71 %, respectively. In addition, ISP-TiO2/Bi2O3@C composite displayed a distinguished recycling ability after the fifth recovery cycle, indicating a promising candidate for photocatalytic applications under UV light and sunlight. Consequentially, the higher photocatalytic activity of ISP-TiO2/Bi2O3@C under sunlight irradiation implies that the sol-hydrothermal method is promising for the preparation of efficient and low-cost TiO2-based photocatalysts for the photodegradation of various environmental pollutants.

Photocatalytic, antimicrobial and antibiofilm activities of MgFe2O4 magnetic nanoparticles

This study reports the antibacterial and antibiofilm activities of Magnesium ferrite nanoparticles (MgFe2O4) against gram-positive and gram-negative bacteria. The photocatalytic degradation of Carbol Fuchsin (CF) dye (a class of dyestuffs that are resistant to biodegradation) under the influence of UV-light irradiation is also studied. The crystalline magnesium ferrite (MgFe2O4) nanoparticles were synthesized using the co-precipitation method. The morphology of the resulting nanocomposite was examined using scanning electron microscopy (SEM), while transmission electron microscopy (TEM) was employed for further characterization of particle morphology and size. Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) were utilized to analyze the crystalline structure, chemical composition, and surface area, respectively. Optical properties were evaluated using UV–Vis spectroscopy. The UV-assisted photocatalytic performance of MgFe2O4 nanoparticles was assessed by studying the decolorization of Carbol fuchsin (CF) azo dye. The crystallite size of the MgFe2O4 nanoparticles at the (311) plane, the most prominent peak, was determined to be 28.5 nm. The photocatalytic degradation of 10 ppm CF using 15 mg of MgFe2O4 nanoparticles resulted in a significant 96% reduction after 135 min at ambient temperature (25 °C) and a pH value of 9. Additionally, MgFe2O4 nanoparticles exhibited potent antibacterial activity against E. coli and S. aureus in a dose dependent manner with maximum utilized concentration of 30 µg/ml. Specifically, MgFe2O4 nanoparticles demonstrated substantial antibacterial activity via disk diffusion and microbroth dilution tests with zones of inhibition and minimum inhibitory concentrations (MIC) for E. coli (26.0 mm, 1.25 µg/ml) and S. aureus (23.0 mm, 2.5 µg/ml), respectively. Moreover, 10.0 µg/ml of MgFe2O4 nanoparticles elicited marked percent reduction in biofilm formation by E. coli (89%) followed by S. aureus (78.5%) after treatment. In conclusion, MgFe2O4 nanoparticles demonstrated efficient dye removal capabilities along with significant antimicrobial and antibiofilm activity against gram-positive and gram-negative bacterial strains suggesting their potential as promising antimicrobial and detoxifying agents.

UV photodegradation of methylene blue using microstructural carbon materials derived from citrullus colocynthis

A low temperature aqueous growth followed by mild pyrolysis was used in this study to synthesize high-quality carbonized materials from the deserted plant Citrullus Colocynthis. It was found that the carbon material prepared for this study contained an abundance of functional groups and surface active sites. A few microns were evidently the size of the carbon material. This study investigated a variety of photocatalytic performance evaluation parameters, including initial dye concentration of methylene blue, pH effect on dye solution, scavenger stability, and recycle stability via irradiating UV light. Methylene blue degradation was found to be significantly affected by pH and concentration of the dye solution. It has been found that pH five is the most effective pH for the removal of dyes. As a result of the study, we found that methylene blue decays according to pseudo first order kinetics and is estimated to remove dye at an almost 100% rate.

Microwave-assisted synthesis of Ni-doped europium hydroxide for photocatalytic degradation of 4-nitrophenol

Microwave-assisted synthesis method was used to prepare europium hydroxide (Eu(OH)3) and different percentages of 1, 5, and 10 % nickel-doped Eu(OH)3 (Ni–Eu(OH)3) nanorods (NRs). X-ray diffraction study showed a hexagonal phase with an average crystallite size in the range of 21 – 35 nm for Eu(OH)3 and Ni–Eu(OH)3 NRs. FT-IR and Raman studies also confirmed the synthesis of Eu(OH)3 and Ni–Eu(OH)3. The synthesized materials showed rod-like morphology with an average length and diameter between 27 – 50 nm and 8 – 13 nm, respectively. The band gap energies of Ni–Eu(OH)3 NRs were reduced (4.06 – 3.50 eV), which indicates that the doping of Ni2+ ions has influenced the band gap energy of Eu(OH)3. The PL study exhibited PL quenching with Ni doping. The photocatalytic degradation of 4-nitrophenol (4-NP) by the synthesized materials under UV light irradiation was investigated, in which 10 % Ni–Eu(OH)3 NRs showed the best response. A kinetic study was also conducted which shows pseudo-first-order kinetics. Based on this, Ni–Eu(OH)3 NRs have shown a potential to be a UV-light active material for photocatalysis.

P‐253: Late‐News Poster: The Evaluation on the Stability of Electroluminescent Materials Using Polaron Pair Formation Kinetics

We developed the method for evaluation of the stability of electroluminescent materials by using QEMS (quantum efficiency measurement system). Relative PL (photoluminescence) intensity decay of BDs (blue dopants) with BHs (blue hosts) in solution under UV light irradiation were measured and the rate constants for polaron pair formation by electron transfer were determined through first‐order kinetics analyses. The rate constants of polaron pair formation (6.487E‐04 –1.805E‐03 min‐1 ) were inversely proportional to the lifetime of OLED (organic light‐emitting diode) devices. We expect that this evaluation method can be applied to the development of new OLED materials and longer lifetime OLED devices.

Aptamer-carbon quantum dots and silver nanoparticles construct a FRET sensor for sensitive detection of E. coli

E. coli is considered to be one of the most dangerous foodborne pathogens and precise detection of E. coli in food is required to ensure the quality and safety of food. In this work, carbon quantum dots (CQDs) were prepared from grapefruit peel as a carbon source by microwave heating method. A fluorescent resonance energy transfer (FRET)-based fluorescent biosensor was constructed by combining CQDs with silver nanoparticles (Ag NPs) for rapid detection of E. coli (BL21). The prepared CQDs showed good dispersion under transmission electron microscopy (TEM), with a spherical shape and an average particle size of 7.4 nm. The CQDs showed bright green fluorescence under UV light irradiation, which was strongly fluorescent (> 1.0 × 103 a.u.) and there was no change in fluorescence intensity over 150 days. Its fluorescence transduction is based on the spectral overlap between the donor (CQDs) emission and the acceptor (nanoparticles) absorbance. The fluorescence of CQDs attached to the aptamer is burst in the presence of Ag NPs. Upon addition of a specific E. coli (BL21) solution, an aptamer-target complex is formed and the preferential interaction of the aptamer with the specific bacteria leads to the release of CQDs and Ag NPs. After a period of incubation, the bacteria are centrifuged, resulting in the precipitation of E. coli aptamer couples and Ag NPs, and therefore the recovery of CQDs fluorescence. This method allows specific detection of E. coli (BL21) in a wide range of pathogenic bacteria. The final results show that the sensor has a linear range of 2×103 ∼ 2×108 CFU·mL−1 and a low detection limit of 77 CFU·mL−1 for E. coli.

A short-circuited photo-assisted electrochemical cell for wastewater treatment

An economically attractive and highly efficient electrochemical cell is fabricated by connecting a carbon felt (CF) and a steel plate (S). Using this configuration, a photo-stimulated (CF/S) arrangement promotes photo-assisted Fenton reactions that result in the degradation of recalcitrant pollutants in water. As opposed to electro-Fenton reports that describe systems with externally polarized electrodes or photo-Fenton systems that utilize iron modified carbon substrates, this work proposes a short-circuited CF/S arrangement that does not require an external potential source. By following the color removal of a dye solution and the chromatography analysis of an emergent contaminant (sulfamethoxazole (SMX)), it was found that the highest efficiencies for the production of oxidative species are observed for tests performed under O2 saturation and UV light irradiation. Under these conditions, the CF/S arrangement achieves 97 % degradation of SMX (after 60 min) and 40 % of total organic carbon (TOC) removal after 240 min. Interestingly however, the CF/S arrangement also revealed a notable efficiency when anoxic and dark conditions were employed. We postulate that in this case, •OH radicals are produced by means of Fenton-like reactions and in order to support this interpretation, cyclic voltammetry and scanning electronic microscopy (SEM) and X-ray diffraction spectroscopy (XRD) measurements were carried out. The resulting data confirmed a Fenton-like mechanism that was further supported by the detection of •OH radical species that was assessed using coumarin absorption data. This study demonstrates that the CF/S cell is a promising approach for a novel photo-assisted Fenton wastewater treatment.

Photocatalytic water splitting over K6M10.8O30 (M = Ta, Nb) with a partially filled tetragonal tungsten bronze structure

Abstract K6M10.8O30 (M = Ta, Nb) with partially filled C sites in a tetragonal tungsten bronze structure represented as the general formula (A1)4(A2)2C4M10O30 shows photocatalytic activity for water splitting under UV light irradiation upon loading with suitable cocatalysts. An apparent quantum yield of the optimized NiO(0.2 wt%)-loaded K6Ta10.8O30 for water splitting is 13% at 248 nm.

Hydrothermally synthesized ZnFe2O4/ZnO heterojunction nanocomposites for enhanced RB dye degradation via Z-scheme photocatalysis

ZnFe2O4/ZnO nanocomposites with 1:1, 1:2, 1:3 and 1:4 wt ratios synthesized by hydrothermal method are used as a photocatalyst to degrade Rose Bengal (RB) dye. For structural investigation X-ray diffraction (XRD) and Fourier transform Infrared (FTIR) was performed. The presence of both phases corresponding to ZnFe2O4 and ZnO in XRD suggests the successful formation of a nanocomposite. Value of crystallite size varies from 25.01 nm to 18.61 nm for 1:1 to 1:4 nanocomposite. Almost spherical morphology of nanocomposite obtained through High-resolution transmission electron microscopy (HRTEM). FTIR demonstrated Zn–O and Fe–O bonds in as synthesized samples. Also, X-ray photoelectron spectroscopy (XPS) is used to detect the presence of Fe2+, Zn2+ and O2− ions in synthesized nanocomposites. In UV-DRS, values of band gap vary from 1.73 to 1.88 eV in nanocomposite as the weight ratio of ZnO increases. The formation of heterojunction is responsible for enhancing electron hole mobility. Due to this enhancement, degradation efficiency of 88% is achieved in 90 min irradiation of UV light by ZnFe2O4/ZnO (1:4) nanocomposites for RB dye followed Z-scheme mechanism. Also, the magnetization value of different nanocomposites changes from 0.9 to 0.1 emu/g. Magnetization nature is responsible for separating the catalyst from the reaction mixture after use. So, the nanocomposite can be reused which maintains the green protocol in the environment. ZnFe2O4/ZnO nanocomposite with 1:4 wt ratio can be reused up to 5 cycles. The formation of such nanocomposites can offer unique properties and advantages by combining the characteristics of both materials can lead to enhanced functionalities suitable for various applications such as catalysis, sensors, and magnetic devices.

Hot injection synthesis of CuS decorated CdS and ZnS nanomaterials from metal thiosemicarbazone complexes as single source precursors: Application in the photocatalytic degradation of methylene blue

CdS and ZnS are considered excellent semiconductors for photocatalysis, but photocorrosion and low photocatalytic activity limit their practical application. In order to improve on their photocatalytic activities, Copper sulfide-decorated CdS and ZnS (CuS@CdS and CuS@ZnS) nanocomposites were synthesized from Cu(II), Zn(II) and Cd(II) complexes of 2–(phenyl(pyridin–2–yl)methylene)hydrazine–1–carbothioamide, as single source precursors using a facile hot injection method at 250 °C, employing olive oil as capping agent. The structure, morphology, and optical properties of the as-prepared nanocomposites were determined using various analytical techniques. The results of powder X-ray diffraction (p-XRD), energy dispersive X-ray spectroscopy (EDX) and elemental mapping showed the presence of CuS, CdS and ZnS in CuS@CdS and CuS@ZnS, confirming the formation of nanocomposites. Transmission Electron Microscopy (TEM) images show agglomeration of CuS nanoparticles on the surface of CdS and ZnS nanoparticles. Scanning electron microscopy (SEM) images of CuS@CdS and CuS@ZnS nanocomposites revealed an agglomerated flower-like structure with porous surface. The band gap energies of 2.84 eV and 3.12 eV for CuS@CdS and CuS@ZnS, respectively, obtained from Tauc plots, demonstrate that combining CuS with single CdS and ZnS has an effect on their optical properties which probably account for the improved photocatalytic responses. The photocatalytic performance of the as-prepared materials was evaluated using the photodegradation of methylene blue (MB) dye under UV light irradiation. Results show that the degradation efficiencies for CuS@CdS (57 %) and CuS@ZnS (65 %) nanocomposites exhibited higher photocatalytic activity compared to those of pure CuS (42.0 %), CdS (35.1 %) and ZnS (57 %), suggesting that thiosemicarbazone complexes can be used as precursors for the development of metal sulphide nanocomposites as useful photocatalysts for the degradation of organic pollutants.

Effect of mass ratio on rGO/TiO2 composite as catalyst for methylene blue degradation under UV irradiation

Adsorption and photocatalytic are commonly used methods for the removal of dye contained in industrial wastewater. Therefore, this study aimed to combine reduced Graphene Oxide (rGO) with Titanium Oxide (TiO2) through various compositions using the hydrothermal method to obtain a catalyst of rGO/TiO2 nanocomposites for the removal of contaminants from wastewater. The synthesized rGO/TiO2 nanocomposites were mixed with methylene blue (MB) to reduce their content in water under dark conditions and UV light irradiation. The change of the optical properties of MB under both conditions was also examined, where a decrease in absorbance was observed. Under UV light irradiation, the maximum wavelength [Formula: see text] of MB shifted from 664[Formula: see text]nm to 649[Formula: see text]nm but remained constant at 664[Formula: see text]nm in dark conditions. The results of optical characterizations confirmed that the adsorption of MB by rGO/TiO2 nanocomposites under dark conditions did not change the MB structure. However, a significant degradation was observed with photocatalytic process under UV light irradiation. Nanocomposites rGO/TiO2 with rGO 60% and TiO2 40% (GT40) have better performance in reducing MB under UV light irradiation.

Fluorescent modification and performance study of carbon quantum dots on twisted bamboo fiber bundles

ABSTRACT In recent years, carbon quantum dots (CQDs) have been employed in the functionalization research of fiber-based materials due to their distinctive physicochemical properties. We used citric acid and urea as precursors and combined with hydrothermal method to prepare green and non-toxic carbon quantum dots (NCQDs), which were loaded into four-color twisted bamboo fiber bundles and possessed photoluminescence effect by simple impregnation method. Based on the verification of the structure and fluorescence properties of NCQDs, the fluorescent twisted bamboo fiber tows were comparatively analyzed for their chemical composition, microscopic morphology, mechanical properties, color difference, and thermal stability. The results showed that the four groups of fluorescent twisted bamboo fiber tows emitted uniform and bright blue fluorescent effects under UV light irradiation, and increased the tensile strength by 19.77% ~ 39.27% and the sexual modulus by 66.11% ~ 88.78% compared with the original twisted bamboo fiber tows. The impregnated carbon quantum dot solution enhances the functionality of the fiber bundle while enriching the color expression. It is expected to be a potential application material in the fields of smart marking, fluorescent anti-counterfeiting, interior decoration, and home textile industry.

Facile Synthesis to Porous TiO2 Nanostructures at Low Temperature for Efficient Visible-Light Degradation of Tetracycline.

In this study, nanoporous TiO2 with hierarchical micro/nanostructures was synthesized on a large scale by a facile one-step solvothermal method at a low temperature. A series of characterizations was performed and carried out on the as-prepared photocatalysts, which were applied to the degradation of the antibiotic tetracycline (TC). The results demonstrated that nanoporous TiO2 obtained at a solvothermal temperature of 100 °C had a spherical morphology with high crystallinity and a relatively large specific surface area, composed of a large number of nanospheres. The nanoporous TiO2 with hierarchical micro/nanostructures exhibited excellent photocatalytic degradation activity for TC under simulated sunlight. The degradation rate was close to 100% after 30 min of UV light irradiation, and reached 79% only after 60 min of visible light irradiation, which was much better than the photodegradation performance of commercial TiO2 (only 29%). Moreover, the possible intermediates formed during the photocatalytic degradation of TC were explored by the density functional theory calculations and HPLC-MS spectra. Furthermore, two possible degradation routes were proposed, which provided experimental and theoretical support for the photocatalytic degradation of TC. In this study, we provide a new approach for the hierarchical micro/nanostructure of nanoporous TiO2, which can be applied in industrial manufacturing fields.

A joint experimental and theoretical investigation of the binding mechanism between zein and folic acid in an ethanol–water solution

ABSTRACT The aim of the present study was to determine the binding mechanisms between zein and folic acid in an ethanol – water solution. Fluorescence spectroscopy demonstrated that folic acid quenched the fluorescence intensity of zein by both dynamic and static fluorescence quenching mechanisms, with static quenching playing a prominent role. The binding constants (Ka) of the zein-folic acid complex at 292, 302, and 312 K were evaluated to be 5.97 × 105, 3.00 × 105 and 1.54 × 105 L/mol, respectively. The process of folic acid binding zein was driven by ∆H0 = –51.24 kJ/mol, ∆S0 = –64.90 J/mol•K. Van der Waals forces and hydrogen bonding primarily governed the formation of the zein-folic acid complex. Confirmation of the complex formation was obtained via UV-visible absorption spectroscopy, Fourier transform infrared spectroscopy, and circular dichroism spectroscopy, which also revealed alterations in the secondary structure of zein upon binding to folic acid. Measurements of particle size and zeta potential demonstrated an enhancement in the stability of the complex system. Scanning electron microscopy and transmission electron microscopy showed the complex to possess a spherical morphology, with significant changes in the zein’s morphology following its binding to folic acid. Additionally, zein increased the photostability of folic acid against UV light radiation. Molecular docking and molecular dynamics simulations were used to investigate the binding mechanisms involved further, and the results effectively elucidated the observed experimental phenomena. This research establishes a significant theoretical foundation for the utilization of zein as a system for delivering and safeguarding folic acid.

Photocatalytic activity of BaTi5O11 nanocrystals synthesized by hydrothermal method

[Formula: see text] nanocrystals were synthesized by a hydrothermal method, and their photocatalytic performance was investigated by degradation of methylene blue (MB) under UV-light irradiation. About 82% MB was photodegraded after 30 min irradiation, which indicated that the [Formula: see text] nanocrystals had good photocatalytic performance due to the distorted [Formula: see text] octahedra in the monoclinic [Formula: see text] crystal structure and nano-size [Formula: see text] particles. It indicated that the [Formula: see text] nanocrystals were promising candidates as UV-light photocatalysts.

A pure pyrochlore phase ferroelectric thin film diode for optoelectric artificial synapse

In this work, Au/Bi2Ti2O7/ITO ferroelectric diodes based on Schottky barrier were fabricated on ITO substrates by the sol-gel method. The device has a simple structure and good diode performance. Under UV light irradiation at 23.5 mW/cm2, the device exhibits an open-circuit voltage of 0.31 V and a short-circuit current of −0.0425 μA. It shows that the device has good optoelectronic properties. Au/Bi2Ti2O7/ITO ferroelectric diodes also exhibited behaviors similar to biological synapses, including long-term plasticity, short-term plasticity, paired-pulse facilitation, and spike-timing-dependent plasticity when stimulated by pulses. We also build convolutional neural networks and use the MNIST dataset for handwritten digit recognition.

Elimination of synthetic dyes by clamshell derived photo-active hydroxyapatite

Herein, a novel designed hydroxyapatite (HAp) derived from freshly calcined clamshell waste through the wet precipitation method was synthesized. HAp has been developed as a heterogeneous photocatalyst for the anionic dye methyl orange (MO) degradation. The pH on synthesizing HAp was varied in basic conditions. The results show HAp formed at pH more than 10. The MO photodegradation was done under UV-light irradiation for 120 min. HAp catalyst showed the optimum MO degradation efficiency using rod-like structure HAp synthesized at pH 12. HAp with optimum photodegradation efficiency was optimized for the catalyst loading and the pH of the MO solution. MO at pH 6 with 0.05 g catalyst loading showed the highest degradation efficiency around 97 % using HAp prepared at pH 12 with band gap at 4.990 eV. This finding brings a new insight on natural sources materials as photo-active in sustainable of persistent water pollutants.