Visible Light Stimulation Research Articles

Mesoporous Vinylene-Linked Covalent Organic Frameworks with Heteroatom-Tuned Crystallinity and Photocatalytic Behaviors.

Owing to its prominent π-delocalization and stability, vinylene linkage holds great merits in the construction of covalent organic frameworks (COFs) with promising semiconducting properties. However, carbon-carbon double bond formation reaction always exhibits relatively low reversibility, unfavorable for the formation of high crystalline frameworks through self-error correction and assembling processes. In this work, we report a heteroatom-tuned strategy to build up a series of two-dimensional (2D) vinylene-linked COFs by Knoevenagel condensation of an electron-deficient methylthiazolyl-based monomer with different triformyl substituted (hetero-)aromatic derivatives. The resulting COFs show high-quality periodic mesoporous structures with high surface areas. Embedding heteroatoms into the backbones enables significantly improving their crystallinity, and finely tailoring their semiconducting structures. Upon visible light stimulation, one of the as-prepared COFs with donor-π-acceptor structure could deliver a nearly seven-fold increase in the catalytic activity of hydrogen generation as compared with the other two. Meanwhile, in combination with high crystallinity and the matched conduction band energy level, such kind of COFs can be able to selectively generate singlet oxygen and superoxide radicals in a high ratio of up to 30:1, allowing for catalyzing aerobic thioanisole oxidation in distinctly tunable activities through the substituent electronic effect of the substrates.

Mesoporous Vinylene‐Linked Covalent Organic Frameworks with Heteroatom‐Tuned Crystallinity and Photocatalytic Behaviors

AbstractOwing to its prominent π‐delocalization and stability, vinylene linkage holds great merits in the construction of covalent organic frameworks (COFs) with promising semiconducting properties. However, carbon‐carbon double bond formation reaction always exhibits relatively low reversibility, unfavorable for the formation of high crystalline frameworks through self‐error correction and assembling processes. In this work, we report a heteroatom‐tuned strategy to build up a series of two‐dimensional (2D) vinylene‐linked COFs by Knoevenagel condensation of an electron‐deficient methylthiazolyl‐based monomer with different triformyl substituted (hetero−)aromatic derivatives. The resulting COFs show high‐quality periodic mesoporous structures with high surface areas. Embedding heteroatoms into the backbones enables significantly improving their crystallinity, and finely tailoring their semiconducting structures. Upon visible light stimulation, one of the as‐prepared COFs with donor‐π‐acceptor structure could deliver a nearly seven‐fold increase in the catalytic activity of hydrogen generation as compared with the other two. Meanwhile, in combination with high crystallinity and the matched conduction band energy level, such kind of COFs can be able to selectively generate singlet oxygen and superoxide radicals in a high ratio of up to 30 : 1, allowing for catalyzing aerobic thioanisole oxidation in distinctly tunable activities through the substituent electronic effect of the substrates.

Ectopically expressed rhodopsin is not sensitive to X-rays

Visual perception of X-radiation is a well-documented, but poorly understood phenomenon. Scotopic rod cells and rhodopsin have been implicated in visual responses to X-rays, however, some evidence suggests that X-rays excite the retina via a different mechanism than visible light. While rhodopsin’s role in X-ray perception is unclear, the possibility that it could function as an X-ray receptor has led to speculation that it could act as a transgenically expressed X-ray receptor. If so, it could be used to transduce transcranial X-ray signals and control the activity of genetically targeted populations of neurons in a less invasive version of optogenetics, X-genetics. Here we investigate whether human rhodopsin (hRho) is capable of transducing X-ray signals when expressed outside of the retinal environment. We use a live-cell cAMP GloSensor luminescence assay to measure cAMP decreases in hRho-expressing HEK293 cells in response to visible light and X-ray stimulation. We show that cAMP GloSensor luminescence decreases are not observed in hRho-expressing HEK293 cells in response to X-ray stimulation, despite the presence of robust responses to visible light. Additionally, irradiation had no significant effect on cAMP GloSensor responses to subsequent visible light stimulation. These results suggest that ectopically expressed rhodopsin does not function as an X-ray receptor and is not capable of transducing transcranial X-ray signals into neural activity for X-ray mediated, genetically targeted neuromodulation.

Synergistic effect of Sonophotocatalytic degradation of crystal violet and alizarin red S dyes using Ag-doped ZnSnO3 nanoparticles

This study proposes an environmentally conventional sonophotocatalytic method that uses silver (Ag)-doped ZnSnO3 nanoparticles (NPs) to effectively eliminate industrial dye-polluted wastewater. This study was conducted to investigate the effect of the Ag doping ratio of the synthesized ZnSnO3 NPs on the removal of dye molecules. We used crystal violet (CV) and alizarin red S (AR) dyes as test pollutants to examine the catalytic activity of the synthesized Ag-doped ZnSnO3 NPs in response to the ultrasound and visible light stimulation. The most effective photocatalytic performance was exhibited by 4 % Ag-ZnSnO3 NPs, which degraded 95 % of the CV and 52 % of the AR dye in 100 min. Surprisingly, using sonophotodegradation to combine ultrasound with visible-light irradiation has resulted in almost complete degradation of the CV dye in 100 min, demonstrating a strong beneficial synergy between the sonocatalytic and photocatalytic processes. Additionally, the sonophotocatalytic degradation of the CV and AR dyes was examined at various pH values. It shows to have high stability across several cycles of dye treatment, indicating that this method can be used for industrial effluents. Scavenger tests demonstrated that the primary active species in the dye degradation is O2•−. Ultimately, the prepared Ag-ZnSnO3 NPs and sonophotocatalytic processes may offer a promising path toward a variety of environmental uses, including the remediation of water and the removal of other organic contaminants.

Visible-light-promoted catalytic epoxidation of alkenes under metal-free conditions

In this work, we report a method for the synthesis of functionalized epoxy analogues using the synergistic interaction of 4CzIPN and oxygen under visible light stimulation.

A plant leaf-mimicking film with tailored photodynamic antibacterial behavior for efficient preservation of perishable products

This work unveiled a novel biomimic visible light-harvesting film (NHC-Cur-CS) with exceptional photodynamic bactericidal activity to address the microbial spoilage of perishable products. This film was designed through a demand-oriented tailoring process that involved the integration of curcumin-loaded nitrogen-rich hollow/porous carbon fillers (NHC-Cur) and the skillful selection of chitosan (CS) matrix. The NHC-Cur-CS film boasts an impressive array of antibacterial features, including high killing rates (≥ 99.27%) and short processing times (20 min) upon visible light stimulation. The NHC-Cur-CS film has demonstrated commendable preservation performance, extending the shelf-life of citrus by up to 2.2 times. These desirable outcomes stem from the innovative designs: (i) the formation of Z-type heterojunction and hollow/porous structure bestow NHC-Cur with superior photodynamic activity, and (ii) the meticulous matching of NHC-Cur with CS mitigates the shortcomings of both materials in antibacterial process. These remarkable features highlight the potential of NHC-Cur-CS film for safeguarding perishable products effectively.

Improved separation of quartz optically stimulated luminescence from a mixed sample using pulsed green light

In the luminescence dating of samples containing both quartz and feldspar (e.g. fine silt, or unseparated rock), the infra-red stimulated luminescence (IRSL) from feldspar is most often used, even though the luminescence characteristics of the OSL from quartz are better understood, and quartz OSL is known to be more stable than feldspar IRSL and more readily reset when exposed to daylight. Unfortunately, in almost all unseparated samples giving both quartz and feldspar luminescence signals, the feldspar OSL (stimulated by blue or green wavelengths) intensity is similar to, or greater than, that from quartz. Separation of quartz and feldspar signals has been achieved before using prior IR and/or pulsed visible light stimulation. This study investigates whether using pulsed green stimulation after IR stimulation gives better discrimination in favour of quartz optically stimulated luminescence (OSL) than using post-IR pulsed blue stimulation, by using the luminescence response of single mineral rocks (quartzite, potassium feldspar) at various temperatures. The results presented here support the view that pulsed blue and pulsed green stimulation of quartz (quartzite or calibration quartz grains) both excite charge to the conduction band, resulting in only a minor dependence on the temperature of the blue or green stimulation. We also confirm that IR depletes the quartz OSL signal only if undertaken at elevated temperature (>125 °C). In contrast, all 3 light sources can result in luminescence from potassium-rich feldspar, but the post-infrared pulsed blue light stimulated luminescence (post-IR PBSL) signal is significantly less dependent on the prior IR stimulation temperature than the post-infrared pulsed green light stimulated luminescence (post-IR PGSL) signal. This is presumably because green stimulation excites mainly into the band-tails. As a consequence, it is shown that the contribution of feldspar OSL to pulsed-green light stimulated luminescence (PGSL) is reduced more by a prior IR stimulation at elevated temperature, than the corresponding pulsed-blue light stimulated luminescence (PBSL). These results are consistent with the band models used to describe the origins of quartz and feldspar luminescence proposed by previous studies. We conclude that the post-IR PGSL provide better discrimination in favour of quartz OSL than does the corresponding post-IR PBSL, and that this should be taken advantage of in future studies on samples with mixed sources of luminescence.

Mutually supportive growth strategy to engineer a hollow biochar sphere-supported TiO2 composite with improved interfacial compatibility for efficient visible light-driven photocatalysis

Improving the interfacial compatibility between active components and support is significant and challenging. Herein, a mutually supportive growth strategy was created to engineer a Fe-Cu-doped hollow biochar sphere (HBS)-supported TiO2 (TiO2/Fe-Cu-HBS) composite with strong interfacial interaction via simultaneous growth of crystalline TiO2 and epitaxial carbonization of mechanical activation-treated starch-FeCl3-CuCl2. The TiO2/Fe-Cu-HBS composite with highly dispersed distribution and embedding of spherical TiO2 particles on the Fe-Cu-HBS shell had a narrow bandgap, favorable visible light capture and absorption capability, high separation efficiency of electron–hole pairs, and high transfer efficiency of photogenerated carriers. The superior photogenerated electron transport, high specific surface area, and enriched surface oxygen vacancies led to the generation of abundant reactive radicals on TiO2/Fe-Cu-HBS under visible light stimulation, contributing to efficient photocatalytic degradation of tetracycline hydrochloride (removal rate of 95.4% within 120 min; mineralization rate of 75.3% within 180 min), rhodamine B (removal rate of 99.2% within 100 min), and carbamazepine (removal rate of 67.5% within 120 min). Moreover, TiO2/Fe-Cu-HBS maintained high photocatalytic degradation efficiency after five cycles ascribed to its favorable structural stability. A mechanism of photocatalytic degradation of tetracycline hydrochloride and possible degradation pathways were proposed. This work provides a new growth strategy for constructing highly active and stable visible light-driven TiO2-based composite photocatalysts for effectively treating organic pollutants.

An Image Detection–Memory–Recognition Artificial Visual Unit Based on Dual‐Gate Phototransistors

Optoelectronic synapses integrating sensing–memory–processing functions have great advantages in neuromorphic computing for visual information processing and complex learning, recognition, and memory in an energy‐efficient manner. Herein, a light‐induced bidirectional response is demonstrated in the proposed WSe2/MoS2 junction field‐effect transistor (JFET) with an extra Ge back gate. The WSe2/MoS2 JFET exhibits high responsivity and detectivity owing to effective modulation by the top junction and back dielectric gates. The unique bidirectional photoresponse and interfacial state storage properties of the device result in significant synaptic excitatory effects under visible light stimulation and remarkable synaptic inhibitory effects under infrared illumination. Optical storage with visible light and optical erasure with infrared light can be achieved in the device based on its synaptic behavior. The conductance changes under different types of illumination can be used to mimic the weight update in a neural network for image recognition. A high accuracy exceeding 98% was achieved in handwritten digit recognition. This visible and infrared dual‐band phototransistor, which integrates image perception, memory, and recognition functionalities, provides a promising solution for self‐driving, surveillance, computer vision, and biomedical imaging applications.

Photocatalytic dehydrogenative oxidation/amination of 2-alkyl benzamides under transition-metal-free conditions

In this work, we report a method for the synthesis of functionalized hydroxyisoindolines under visible light stimulation with synergistic interactions of eosin Y, nBu4NBr and oxygen.

Visible-light responsive photocatalytic fuel cell with double Z-scheme heterojunction PTh/Ag3PO4/BiOI/Ti photoanode for efficient rhodamine B degradation and stable electricity generation

The development of photocatalytic fuel cell (PFC) with visible-light response is usually limited by the low efficiency of electron-hole separation in photoanode. In this work, 20%-PTh/Ag3PO4/BiOI/Ti photoanode was prepared for the first time to construct a PFC with Cu2O/Cu cathode to degrade rhodamine B. With visible-light stimulation, the rhodamine B degradation rate, maximum photocurrent density and maximum power density of the PFC were respectively 96.33% (2 h), 0.39 mA cm−2 and 82.20 μW cm−2. The main active species in the PFC were proved by quenching experiments to be h+, ∙OH and ∙O−2. The satisfactory performance of the PFC was due to that a double Z-scheme heterojunction was formed in the photocatalyst of 20%-PTh/Ag3PO4/BiOI/Ti photoanode, which made the photogenerated electrons of Ag3PO4 and BiOI directly combine with the photogenerated holes of PTh, so that the photogenerated holes of Ag3PO4 and BiOI and the photogenerated electrons of PTh directly or indirectly participated in the degradation reaction of RhB. In this way, the separation efficiency of electron-hole pairs in the photoanode was improved, and the performance of the PFC was significantly enhanced.

Effect of azobenzene composition ratio on the degree of photosoftening: Experimental and molecular dynamics simulation studies

Azobenzene-incorporated liquid crystalline polymer (azo-LCP), which undergo property change and deformation upon Ultra violet and visible light stimulation, are promising materials in various fields. This study investigated the effect of azobenzene concentration on photosoftening based on the photoisomerization of an azo-LCP. The experimental results confirmed that as the azobenzene concentration increased, the order parameter decreased and mechanical properties deteriorated. Photoisomerization and photosoftening was also conducted on an azo-LCP unit cell constructed by molecular dynamics simulation. The simulation results showed that changes in the order parameter, length contraction and elastic modulus due to the photosoftening, in alignment with the experimental results.

Ultraviolet-magnetic response multicolored janus colloidal photonic crystal beads for information coding

We report a new kind of ultraviolet (UV)-magnetic response Janus colloidal photonic crystal (CPC) beads for information coding. The Janus beads made up of fluorescent CPCs and Fe3O4 nanoparticles show different colors under visible light, UV light and magnetic stimulation. In the concrete scheme, monodisperse colloidal particles with and without fluorescent molecule SPMA were prepared by semi-continuous emulsion polymerization. Then colloidal particles and Fe3O4 nanoparticles were paired as precursors to prepare Janus beads by the droplet template method. During the slow self-assembly process, Fe3O4 nanoparticles were deposited on the bottom and colloidal particles filled the other parts of the beads so that a Janus structure formed. Therefore, the upper surface of Janus beads appears structural color and the lower surface appears black. The variation of Fe content in different hemispheres allows the controllable magnetic response to reverse the beads. The presence of fluorescent molecule SPMA makes fluorescent Janus beads (FJBs) emit fluorescence under UV light. According to design, an array in a particular arrangement of Janus beads can realize reversible changes between three different optical information. Furthermore, the binary cipher was combined with Janus beads to design and fabricate an optical encoding array, revealing an important application in information coding.

Synthesis of Coumarin 3‐aldehyde Derivatives via Photocatalytic Cascade Radical Cyclization‐Hydrolysis

AbstractNew synthetic method of coumarins 3‐aldehyde via visible light stimulation and oxidation promotion cascade radical cyclization/hydrolysis process is reported. this reaction involves a two‐step procedure, the 1,3‐dioxolane radical is initiated in situ from 1,3‐dioxolane via the excited Ru(bpy)3Cl2 and oxidant TBHP, subsequently an addition to triple bond of various alkynes produces vinyl radicals, the radical intermediates can smoothly convert to coumarin 3‐aldehyde via tandem cyclization/acidic hydrolysis process in good to excellent yields. Furthermore, the synthetic application valuable of coumarin 3‐aldehyde is also evaluated in this work.

Development of Efficient Photocatalyst MIL-68(Ga)_NH2 Metal-Organic Framework for the Removal of Cr(VI) and Cr(VI)/RhB from Wastewater under Visible Light

Severe environmental pollution is caused by the massive discharge of complex industrial wastewater. The photocatalytic technology has been proved as an effective way to solve the problem, while an efficient photocatalyst is the most critical factor. Herein, a new photocatalyst MIL-68(Ga)_NH2 was obtained by hydrothermal synthesis and were characterized by PXRD, FTIR, 1H NMR, and TGA systematically. The result demonstrates that MIL-68(Ga)_NH2 crystallized in orthorhombic system and Cmcm space group with the unit cell parameters: a = 36.699 Å, b = 21.223 Å, c = 6.75 Å, V = 5257.6 Å3, which sheds light on the maintenance of the crystal structure of the prototype material after amino modification. The conversion of Cr(VI) and binary pollutant Cr(VI)/RhB in wastewater under visible light stimulation was characterized by the UV-vis DRS. Complementary experimental results indicate that MIL-68(Ga)_NH2 exhibits remarkable photocatalytic activity for Cr(VI) and the degradation rate reaches as high as 98.5% when pH = 2 and ethanol as hole-trapping agent under visible light irradiation with good reusability and stability. Owing to the synergistic effect between Cr(VI) and RhB in the binary pollutant system, MIL-68(Ga)_NH2 exhibits excellent catalytic activity for both the pollutants, the degradation efficiency of Cr(VI) and RhB was up to 95.7% and 94.6% under visible light irradiation for 120 min, respectively. The possible removal mechanism of Cr(VI)/RhB based on MIL-68(Ga)_NH2 was explored. In addition, Ga-based MOF was applied in the field of photocatalytic treatment of wastewater for the first time, which broadened the application of MOF materials in the field of photocatalysis.

Boosting the Visible Light Photocatalytic Activity of ZnO through the Incorporation of N-Doped for Wastewater Treatment

In the present work, we prepared N-doped ZnO by a facile chemical vapor deposition method and used it for the degradation of wastewater containing noxious rose bengal (RB) dye under visible-light stimulation. The as-prepared N-doped ZnO and the undoped ZnO (used as a control sample) were characterized by numerous spectroscopic and microscopic methods. These analyzing results confirmed the successful formation of the N-doped ZnO compound and it could be implemented for wastewater treatment. Interestingly, the N-doped ZnO material confirmed the maximum RB dye degradation efficiency (96.90%) and was shown to be 154% more efficient than undoped ZnO (62.95%) within 100 min of visible-light irradiation. The bandgap energy was considerably decreased after the incorporation of N onto the ZnO matrix compared to undoped ZnO. The improved photocatalytic performance is because of the reduction of bandgap energy, which suppressed the electron–hole pair recombination. In addition, a plausible photodegradation mechanism of RB dye was discussed employing N-doped ZnO under visible light. The findings show that our as-synthesized product can be used to eliminate contaminants, which provides a new avenue for effective implications.

Phosphor-Enhanced, Visible-Light-Storing g-C3N4/Ag3PO4/SrAl2O4:Eu2+,Dy3+ Photocatalyst Immobilized on Fractal 3D-Printed Supports.

The combination of a phosphor with semiconductor photocatalysts can provide photoactivity in the dark. Indeed, the phosphor acts as a "light battery", harvesting photons during irradiation and later re-emitting light that can be used by the catalytic phase when in conditions of total darkness. This allows for continued activity of the composite catalyst, even in conditions of unstable light stimulation. In this study, we assess the use of a heterojunction, namely graphitic-C3N4/Ag3PO4, that enables efficient photoactivity specifically under visible light stimulation, in combination with a phosphor that exhibits green-blue phosphorescence (510 nm), that is SrAl2O4:Eu2+,Dy3+. Our findings showed that this combination was particularly interesting, noticeably displaying significant photoactivity in darkness, after short periods of activation by visible light. After finding the right combination and optimal ratios for maximum efficiency, the resulting catalyst composite was immobilized on resin supports with a fractal surface, printed by LCD-SLA 3D printing. The immobilization was effectuated via an aqueous-phase plasma-aided grafting (APPAG) process, using cold plasma discharge (CPD) and using vinylphosphonic acid (VPA) as a coupling agent. Whereas the colloidal photocatalyst displayed a serious problem of partial physical separation between the catalytic phase, g-C3N4/Ag3PO4, and the phosphor, the immobilization of the composite catalyst on polymer supports allowed solving this issue. Photodegradation assessments confirmed that the hybrid supported phosphor-enhanced catalyst was active, notably in dark conditions, as well as fairly photostable. This study offers new prospects for the fabrication of polymer-based panels for water purification, with round-the-clock activity and that are, in addition, extremely easy to recover and reuse, by comparison with colloidal catalysts.

Near‐Infrared Persistent Luminescence and Trap Reshuffling in Mn4+ Doped Alkali‐Earth Metal Tungstates

AbstractNear‐infrared persistent luminescent materials have great potential for in vivo bioimaging and night‐vision surveillance due to their long‐lasting autofluorescence‐free emission through deep tissues and multicycle photostimulated luminescence by releasing energy from captured traps using high‐intensity 808 or 980 nm lasers. However, phosphors combining both near‐infrared persistent luminescence and photostimulated luminescence are found mostly in chromium doped gallates hosts, other emitters are rarely reported. Herein, a new material system with near‐infrared persistent luminescence is achieved in tetravalent manganese doped double‐perovskite alkali‐earth metal tungstates via the aliovalent substitution of calcium ions with lanthanum ions. Persistent luminescence can be generated via X‐ray irradiation, providing great promise in long‐term deep‐tissue ultrasensitive imaging, information storage, and X‐ray detection. Photostimulated detrapping is successfully demonstrated using a common 420 nm light emitting diode instead of a high‐intensity 808 or 980 nm laser. The traps distribution is proved to be reshuffled upon this laser‐free visible light stimulation. Reshuffling of trap distributions upon visible light stimulation may be promising for optical information storage applications. This work is expected to broaden the range of near‐infrared persistent material systems and provides new insights into manipulating photostimulated traps via laser‐free light stimulation.

311 Effects of visible light in different skin phototypes pigmentation

Melanin is synthesized in the human epidermis within melanocytes and transferred to keratinocytes to regulate skin colour, where it provides protection against ultraviolet radiation (UVR)-induced damage. The Fitzpatrick scale stratifies our skin’s tanning response to UVR into six skin phototypes (SPT), SPT-I lightest to SPT-VI darkest. This study investigated the impact of UVR and visible light stimulation on Caucasian skin ex vivo. We treated skin obtained from SPT-I, -II and -III healthy donors with one daily doses of 6 J/cm2 (UVR) and 140 J/cm2 (blue or green light) for a period of three days, and assessed their influence on observable surface tanning response, histological melanin content, DNA damage, and cell apoptosis.

Enhancement of photocatalytic disinfection performance of the Bi4O5Br2 with the modification of silver quantum dots

Here, a novel Ag quantum dots (Ag QDs) with diameter 3.1–10 nm modified Bi4O5Br2 composite system was firstly fabricated via the facile mechanical agitation method and the photocatalytic ability of Ag QDs/Bi4O5Br2 was evaluated by disinfection towards Escherichia coli (E.coli) under visible light stimulation (λ > 420 nm). The Ag QDs/Bi4O5Br2 composites displayed the superior photocatalytic disinfection ability to the pure Bi4O5Br2. Especially, the 1000 Ag QDs/Bi4O5Br2 composite exhibited the strongest photocatalytic ability with disinfecting all bacteria (1 × 107 cfu/mL) after 180 min visible light irradiation. The promoted photocatalytic ability of 1000 Ag QDs/Bi4O5Br2 mainly be attributed to the synergistic effect of SPR produced by Ag and the formation of Schottky barrier which facilitate the separation efficiency of charge carrier and light utilization. The mechanism of photocatalytic disinfection over the Ag QDs/Bi4O5Br2 composite was that the generated active species h+ (hole) and ·O2− (superoxide radical) disrupted the cell envelop to induce the leakage and decomposition of the cellular substances (e.g. protein, deoxyribonucleic acid (DNA) and potassium ion (K+)) as validated with the multiple techniques. This work open a new horizon to develop high-efficient BimOyXn-based photocatalytic disinfection materials.