Mild Visible Light Research Articles

Light‐Activated Gene Expression System Using a Caging‐Group‐Free Photoactivatable Dye

AbstractOptical regulation of transcription using chemical compounds is an effective strategy to manipulate gene expression spatiotemporally. Conventional caging approaches with photoremovable protecting groups may require intense UV‐light exposure and release potentially toxic byproducts. To address these problems, here we developed a light‐mediated transcriptional regulation system by combining a caging‐group‐free photoactivatable dye PaX560 and a multidrug‐binding transcriptional regulator QacR. The cationic dye generated from PaX560 through traceless photoconversion bound QacR and reduced its repressor function, resulting in transcriptional activation. Importantly, this system allowed transcriptional activation with a large dynamic range under mild visible light exposure and simultaneous detection of the state of the photoactivated effector. This module was integrated into the T7 RNA polymerase expression system to demonstrate light‐activated transcription in vitro and in living cells.

Light-Activated Gene Expression System Using a Caging-Group-Free Photoactivatable Dye.

Optical regulation of transcription using chemical compounds is an effective strategy to manipulate gene expression spatiotemporally. Conventional caging approaches with photoremovable protecting groups may require intense UV-light exposure and release potentially toxic byproducts. To address these problems, here we developed a light-mediated transcriptional regulation system by combining a caging-group-free photoactivatable dye PaX560 and a multidrug-binding transcriptional regulator QacR. The cationic dye generated from PaX560 through traceless photoconversion bound QacR and reduced its repressor function, resulting in transcriptional activation. Importantly, this system allowed transcriptional activation with a large dynamic range under mild visible light exposure and simultaneous detection of the state of the photoactivated effector. This module was integrated into the T7 RNA polymerase expression system to demonstrate light-activated transcription in vitro and in living cells.

Double Layer SiO2-Coated Water-Stable Halide Perovskite as a Promising Antimicrobial Photocatalyst under Visible Light.

Halide perovskite nanocrystals (HPNCs) have emerged as promising materials for various light harvesting applications due to their exceptional optical and electronic properties. However, their inherent instability in water and biological fluids has limited their use as photocatalysts in the aqueous phase. In this study, we present highly water-stable SiO2-coated HPNCs as efficient photocatalysts for antimicrobial applications. The double SiO2 layer coating method confers long-term structural and optical stability to HPNCs in water, while the in situ synthesis of lead- and bismuth-based perovskite NCs into the SiO2 shell enhances their versatility and tunability. We demonstrate that the substantial generation of singlet oxygen via energy transfer from HPNCs enables efficient photoinduced antibacterial efficacy under aqueous conditions. More than 90% of Escherichia coli was inactivated under mild visible light irradiation for 6 h. The excellent photocatalytic antibacterial performance suggests that SiO2-coated HPNCs hold great potential for various aqueous phase photocatalytic applications.

Copper-catalyzed umpolung Sonogashira-type coupling of arene boronic acids under visible light.

We report herein that a copper catalyst catalyzed efficient cross-coupling of aryl and alkenyl boronic acids with alkynyl-1,2-benziodoxol-3(1H)-ones to afford diaryl alkynes and enynes under mild visible light irradiation conditions using a catalytic amount of base or even in the absence of base. The reaction applies copper as the catalyst and tolerates a variety of functional moieties including aryl bromide and iodide.

Implantable micro-scale LED device guided photodynamic therapy to potentiate antitumor immunity with mild visible light

BackgroundPhotodynamic therapy (PDT) is a promising strategy to promote antitumor immunity by inducing immunogenic cell death (ICD) in tumor cells. However, practical PDT uses an intense visible light owing to the shallow penetration depth of the light, resulting in immunosuppression at the tumor tissues.MethodsHerein, we propose an implantable micro-scale light-emitting diode device (micro-LED) guided PDT that enables the on-demand light activation of photosensitizers deep in the body to potentiate antitumor immunity with mild visible light.ResultsThe micro-LED is prepared by stacking one to four micro-scale LEDs (100 μm) on a needle-shape photonic device, which can be directly implanted into the core part of the tumor tissue. The photonic device with four LEDs efficiently elicits sufficient light output powers without thermal degradation and promotes reactive oxygen species (ROS) from a photosensitizer (verteporfin; VPF). After the intravenous injection of VPF in colon tumor-bearing mice, the tumor tissues are irradiated with optimal light intensity using an implanted micro-LED. While tumor tissues under intense visible light causes immunosuppression by severe inflammatory responses and regulatory T cell activation, mild visible light elicits potent ICD in tumor cells, which promotes dendritic cell (DC) maturation and T cell activation. The enhanced therapeutic efficacy and antitumor immunity by micro-LED guided PDT with mild visible light are assessed in colon tumor models. Finally, micro-LED guided PDT in combination with immune checkpoint blockade leads to 100% complete tumor regression and also establishes systemic immunological memory to prevent the recurrence of tumors.ConclusionCollectively, this study demonstrates that micro-LED guided PDT with mild visible light is a promising strategy for cancer immunotherapy.

Boryl Radical Activation of Benzylic C-OH Bond: Cross-Electrophile Coupling of Free Alcohols and CO2 via Photoredox Catalysis.

A new strategy for the direct cleavage of the C(sp3)-OH bond has been developed via activation of free alcohols with neutral diphenyl boryl radical generated from sodium tetraphenylborate under mild visible light photoredox conditions. This strategy has been verified by cross-electrophile coupling of free alcohols and carbon dioxide for the synthesis of carboxylic acids. Direct transformation of a range of primary, secondary, and tertiary benzyl alcohols to acids has been achieved. Control experiments and computational studies indicate that activation of alcohols with neutral boryl radical undergoes homolysis of the C(sp3)-OH bond, generating alkyl radicals. After reducing the alkyl radical into carbon anion under photoredox conditions, the following carboxylation with CO2 affords the coupling product.

A Polyimide-Based Photocatalyst for Continuous Hydrogen Peroxide Production Using Air and Water under Solar Light

A Polyimide-Based Photocatalyst for Continuous Hydrogen Peroxide Production Using Air and Water under Solar Light

Heterogeneous photoredox catalysis using fluorescein polymer brush functionalized glass beads

AbstractPhotocatalysis is a valuable and versatile method to perform a variety of chemical transformations under ambient temperatures and pressures using mild visible light. This work showcases an example of fluorescein‐functionalized polymers grafted to micro‐scale glass beads as heterogeneous photoredox catalysts. X‐ray photoelectron spectroscopy and thermogravimetric analysis were used to analyze the resulting functional glass beads. Model reactions that are demonstrated include a cyclic condensation and a radical dehalogenation that can both be performed to high yields. Successful recyclability of the fluorescein polymer brush beads is demonstrated with detailed characterization confirming that photocatalytic polymer brushes remain tethered to the surface. As such, this allows for purification and reuse of the heterogeneous photocatalyst beads after simple filtration.

New Hybrid Fe‐based MOFs/Polymer Composites for the Photodegradation of Organic Dyes

AbstractMetals Organic Frameworks (MOFs) are promising crystalline, embrittled materials generally produced in powdering form with varied remarkably functionalities. In contrary, polymers are flexible and processable materials. Therefore, obtaining shaped solids gathering polymer malleability and MOFs properties such as their photocatalytic activities, have attracted many researchers’ attention. This work, reports the successful fruitful incorporation of two different Fe‐based MOFs into a polymer matrix via a facile and cheap photopolymerization process upon mild visible light irradiation at 405 nm. The as‐prepared photocomposites display excellent stability and photocatalytic performance for several Acid Black degradation cycles. Hence, approximatively, 95 % of this model dye is decomposed by the two MIL‐100(Fe)/polymer and MIL‐88 A(Fe)/polymer composites under just 30 min of UV‐Visible lamp irradiation. Incorporation of the MOFs into the polymer is confirmed by several techniques including Scanning Electron Microscopy (SEM), Energy‐Dispersive X‐ray analysis (EDX), Transmission Electron Microscopy (TEM), X‐ Ray Diffraction analysis (DRX), Fourier‐Transform Infrared Spectroscopy (FTIR). Furthermore, these photocatalysts exhibit a high thermal stability, excellent rigidity and low band gap energy characterized by Thermogravimetric Analysis (TGA), Atomic Force Microscopy (AFM), Dynamic Mechanical Analysis (DMA) and UV‐Visible diffuse reflectance spectroscopy, respectively.

New hybrid perovskites/polymer composites for the photodegradation of organic dyes

Recently, many researchers have focused their attentions on associating perovskites with polymers in order to enhance their processability and rigidity while protecting their interesting environmental properties. Therefore, this work reports the successful development of two different Perovskites/polymer composites via a simple, rapid, low-cost and eco-friendly photopolymerization process under mild visible Light Emitting Diode LED@405 nm irradiation. The as-synthesized composites exhibit excellent photocatalytic activity towards the removal of the Acid Black dye from water, reaching approximately 95% under just 30 min of UV light irradiation. The fruitful hybridization between the perovskites and the acrylate monomer allowed the collect and reuse of this photocatalyst for several successive cycles without external usual time-consuming methods. Furthermore, the new as-fabricated shaped materials were fully characterized by numerous characterization techniques including, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-Ray Analysis (EDX), X-Ray Diffraction Analysis (XRD), Atomic Force Microscopy (AFM), Dynamic Mechanical Analysis (DMA) and Thermogravimetric Analysis (TGA), which have verified on one side the successful immobilization of the perovskites into the polymer and the structural stability of the photocatalysts after hybridization and in the other side the high rigidity and thermal stability of the obtained molded composites.

Polyoxometalates/polymer composites for the photodegradation of bisphenol‐A

AbstractNowadays water scarcity represents a threat for human and living beings. Therefore, to satisfy the demands of people for clean and safe water, new technologies for wastewater treatment have been developed. Thus, photocatalysis has emerged as a green chemical approach for such treatment. In this context, new polyoxometalate (POM)/polymer composites with relevant photocatalytic properties have been developed via an easy and cheap photopolymerization process upon mild visible light irradiation at 405 nm. This fruitful association between POM and polymer allowed the obtention of shaped materials facile to collect and reuse at the end of the photocatalytic treatment avoiding then the usual time‐consuming regeneration methods. The prepared photocomposites displayed excellent photocatalytic performance for the removal of bisphenol‐A from water under different sources of irradiation. Hence, 100%, 88%, and 50% of this model compound were decomposed by the phosphomolybdic composite under just 90 min of UV lamp, solar and LED@375 nm irradiations, respectively. The effectiveness of these developed photocatalysts towards the degradation of other organic compounds, as well as the degradation mechanism based on the generation of highly reactive chemicals such as •OH radicals promoting the degradation were already reported. Bisphenol‐A degradation pathway and the identification of the photoproducts were discussed using mass spectroscopy technique. Therefore, this paper highlighted the photocatalytic efficiency of the new manufactured materials for the photodegradation of the bisphenol‐A, thus expanding their application fields, under different sources of irradiation and under pure solar irradiation which make their applications more interesting and less energy consuming.

Photocatalyst-Free, Visible-Light-Mediated C(sp3)-H Arylation of Amides via a Solvent-Caged EDA Complex.

A photocatalyst-free and mild visible light photochemical procedure for C(sp3)-H arylation of amides is described. The reaction proceeds via an electron donor-acceptor (EDA) complex between an electron-rich arene substrate and electron-poor persulfate oxidant. C(sp3)-H arylation of the amide occurs selectively with the most electron-rich arene of the substrate. Mechanistic studies corroborate the reaction taking place in a solvent cage holding components in a close proximity.

Characterization of polyoxometalate/polymer photo‐composites: A toolbox for the photodegradation of organic pollutants

AbstractDifferent inorganic/organic photocomposites based on polyoxometalate (POM) nanoparticles have been developed for photocatalytic applications. Currently, polyoxometalate nanoparticles have been successfully in‐situ embedded into an acrylate polymer network by photopolymerization upon mild visible light irradiation at 405 nm. The proposed POM/polymer photocomposites have been characterized using complementary techniques for a better understanding of their photocatalytic activity. Interestingly, the obtained photocomposites exhibit high rigidity, excellent thermal stability, a non‐negligible porosity and new functionalities such as light reactivity and redox properties. Moreover, developed composites showed efficient catalytic activity for the color removal of aqueous solutions of erythrosine and rose Bengal under Light Emitting Diodes LED@375 nm irradiation reaching 80 and 90% as a final color removal, respectively.

Additive‐Free Green Light‐Induced Ligation Using BODIPY Triggers

AbstractPhotochemical ligation is important in biomaterials engineering for spatiotemporal control of biochemical processes. Such reactions however generally require activation by high energy UV or short wavelength blue light, which can limit their use as a consequence of the potential of these high energy light sources to damage living cells. Herein, we present an additive‐free, biocompatible, chemical ligation triggered by mild visible light. BODIPY dyes with a pendant thioether attached at the meso‐position undergo photolysis of the [C−S] bond under green light (λ=530 nm) excitation, producing an ion pair intermediate that can react specifically with a propiolate group. The utility of this photochemical ligation in materials science is demonstrated by the fabrication of hydrogels with specific architectures, photo‐immobilization of biomacromolecules, and live cell encapsulation within a hydrogel scaffold.

Additive-Free Green Light-Induced Ligation Using BODIPY Triggers.

Photochemical ligation is important in biomaterials engineering for spatiotemporal control of biochemical processes. Such reactions however generally require activation by high energy UV or short wavelength blue light, which can limit their use as a consequence of the potential of these high energy light sources to damage living cells. Herein, we present an additive-free, biocompatible, chemical ligation triggered by mild visible light. BODIPY dyes with a pendant thioether attached at the meso-position undergo photolysis of the [C-S] bond under green light (λ=530 nm) excitation, producing an ion pair intermediate that can react specifically with a propiolate group. The utility of this photochemical ligation in materials science is demonstrated by the fabrication of hydrogels with specific architectures, photo-immobilization of biomacromolecules, and live cell encapsulation within a hydrogel scaffold.

Time-Dependent Differential and Integral Quantum Yields for Wavelength-Dependent [4+4] Photocycloadditions.

The [4+4] photocycloaddition of anthracene is one of most relevant photoreactions and is widely applied in materials science, as it allows to remote-control soft matter material properties by irradiation. However, highly energetic UV irradiation is commonly applied, which limits its application. Herein, the wavelength dependence of the photodimerization of anthracene is assessed for the first time, revealing that the reaction is induced just as effectively with mild visible light (410 nm). To fully establish [4+4] cycloadditions within defined chemical environments, a conceptual framework for the solution kinetics of the photo-dimerization up to long reaction times is established by developing a novel photoreaction rate law that is dependent on individual rate coefficients of the key reaction steps. These coefficients can be determined based on low conversion photochemical experiments. Both differential and integral quantum yields can subsequently be predicted that are strongly time-dependent, highlighting the need for a detailed reaction pathway analysis. The presented approach simplifies a complex photochemical scenario, making the photochemical anthracene dimerization, or potentially any other photochemical dimerization, amenable to a time-dependent understanding at the elementary reaction level.

Characteristics, mechanisms and bacteria behavior of photocatalysis with a solid Z-scheme Ag/AgBr/g-C3N4 nanosheet in water disinfection

In this study, a series of Ag/AgBr/g-C3N4 nanosheet (CNNS) photocatalysts were prepared by a more environmental-friendly method. The prepared material was characterized and then applied in photocatalytic disinfection of Escherichia coli (E. coli) under mild visible light for the first time. Results showed that all E. coli (108 CFU/mL) could be eliminated under irradiation at 20 mW·cm−2 within 120 min. Based on the energy band determination and electron spin resonance analysis, the Z-scheme in the photocatalyst was responsible for the enhanced disinfection effects where Ag nanoparticles acting as the electron mediator. Scavenger experiments demonstrated that photogenerated holes and superoxide radicals were the main reactive species. The variations in cell membrane permeability, cell membrane structure, enzyme activities and ATP concentration were monitored, and results indicated that the reactive species overwhelmed the bacterial defense mechanism, leading to the penetration of bacterial membranes, release of ions, protein fragmentation, and eventually, inactivation.

Visible-Light-Induced Passerini Multicomponent Polymerization.

Herein, we introduce an additive-free visible-light-induced Passerini multicomponent polymerization (MCP) for the generation of high molar mass chains. In place of classical aldehydes (or ketones), highly reactive, in situ photogenerated thioaldehydes are exploited along with isocyanides and carboxylic acids. Prone to side reactions, the thioaldehyde moieties create a complex reaction environment which can be tamed by optimizing the synthetic conditions utilizing stochastic reaction path analysis, highlighting the potential of semi-batch procedures. Once the complex MCP environment is understood, step-growth polymers can be synthesized under mild reaction conditions which-after a Mumm rearrangement-result in the incorporation of thioester moieties directly into the polymer backbone, leading to soft matter materials that can be degraded by straightforward aminolysis or chain expanded by thiirane insertion.

Nanocomposites based on 3D macroporous biomass carbon with SnS2 nanosheets hierarchical structure for efficient removal of hexavalent chromium

In this study, a novel nanocomposite, carbon/SnS2 with 3D hierarchical macroporous (MCS), was successfully prepared for rapid photocatalytic treatment of hexavalent chromium (Cr(VI)). The 3D macroporous carbon (MC) can be obtained through a simple carbonization process of loofah. Since the MCS has a large specific surface area, it can provide numerous photocatalytic active sites and has excellent adsorption properties for the Cr(VI). In addition, the excellent electrical conductivity and unique hierarchical nanoarchitecture of macroporous biomass carbon could rapidly absorb the Cr(VI) from wastewater and provide electron transport tunnel for rapid charge separation/transport to suppress hole electron recombination. It is confirmed that such three dimensional photocatalytic material can quickly purify Cr(VI)-containing wastewater under mild visible light irradiation, with a efficiency of 63.2% Cr(VI) reduction within 120 mins. Besides the high visible light-driven photocatalytic activity, MCS also exhibits excellent cycling stability. In addition, the SEM images of MCS before and after photocatalytic removal of Cr(VI) indicate that the morphology of composite was perfectly maintained and no peeling-off of SnS2 was observed. More importantly, this study demonstrated that MCS can be used for practical applications due to its stability and economic availability.

Contemporary Photoligation Chemistry: The Visible Light Challenge.

Catalyst-free and bond-forming light-induced reactions have seen an unprecedented renaissance in the realm of soft matter materials science due to their efficiency, spatio-temporal controllability and, sometimes, photoreversible nature. However, many of these reactions rely on the application of high energy UV light that can cause photo-degradation and is inapplicable in biological environments. If up-conversion systems or two-photon processes are to be avoided, strategies for red-shifting catalyst-free ligation technology are critically required. This Concept article introduces the reader to recent methods that lead to efficient, catalyst-free visible-light-induced ligation chemistry based on polyaromatic substituted photoreactive compounds-pyrene and anthracene-and, furthermore, emphasizes the broad and facile applicability of these molecules in polymeric material design. Concomitantly, we highlight that a careful action plot analysis of photochemical reactivity can provide deep insights into reactivity patterns, far beyond those suggested by the absorption spectrum. Indeed, we suggest that an action plot analysis is necessary for the evaluation of any photochemical system and its response to structural chemical changes.