Resolving the overlooked photochemical nitrophenol transformation mechanism induced by nonradical species under visible light.

Nitrophenols present on the surface of particulates are ubiquitous in the atmosphere. However, its atmospheric photochemical transformation pathway remains unknown, for which the crucial effect of visible light is largely overlooked, resulting in an incomplete understanding of the effects of nitrophenols in the atmospheric environment. This study delves into the photolysis mechanism of 4-nitrophenol (4NP), one of the most abundant atmospheric nitrophenol compounds, on the surface of photoactive particulates under visible light irradiation. Unexpectedly, the nonradical species (singlet oxygen, 1O2) was identified as a dominant factor in driving the visible photolysis of 4NP. The pathways of HONO and p-benzoquinone (C6H4O2) generation were clarified by acquiring direct evidence of C-N and O-H bond breakage in the nitro (-NO2) and hydroxyl (-OH) groups of 4NP. The further decomposition of HONO results in the generation of NO and hydroxyl radicals, which could directly contribute to atmospheric oxidizing capacity and complicate the PM2.5 composition. Significantly, the behavior of 1O2-induced visible photolysis of 4NP was universal on the surface of common particulates in the atmosphere, such as A1 dust and Fe2O3. This work advances the understanding of the photochemical transformation mechanism of particulate-phase atmospheric nitrophenols, which is indispensable in elucidating the role of nitrophenols in atmospheric chemistry.

Photocatalytic Optical Hollow Fiber with Enhanced Visible-light-driven CO2 Reduction.

A visible-light-driven CO2 reduction optical fiber is fabricated using graphene-like nitrogen-doped composites and hollow quartz optical fibers to achieve enhanced activity, selectivity, and light utilization for CO2 photoreduction. The composites are synthesized from a lead-based metal-organic framework (TMOF-10-NH2 ) and g-C3 N4 nanosheet (CNNS) via electrostatic self-assembly. The TMOF-10-NH2 /g-C3 N4 (TMOF/CNNS) photocatalyst with an S-type heterojunction is coated on optical fiber. The TMOF/CNNS coating, which has a bandgap energy of 2.15 eV, has good photoinduced capability at the coating interfaces, high photogenerated electron-hole pair yield, and high charge transfer rate. The conduction band potential of the TMOF/CNNS coating is more negative than that for CO2 reduction. Moreover, TMOF facilitates the CO desorption on its surface, thereby improving the selectivity for CO production. High CO2 photoreduction and selectivity for CO production is demonstrated by the TMOF/CNNS-coated optical fiber with the cladding/core diameter of 2000/1000 µm, 10 wt% TMOF in CNNS, coating thickness of 25 µm, initial CO2 concentration of 90 vol%, and relative humidity of 88% RH under the excitation wavelength of 380-780 nm. Overall, the photocatalytic hollow optical fiber developed herein provides an effective and efficient approach for the enhancement of light utilization efficiency of photocatalysts and selective CO2 reduction.

A Novel Perspective on Enhancing Photocatalytic Performance through the Synergistic Effect of Nd Single Atoms and Heterostructures.

There are few reports on lanthanide single atom modified catalysts, as the role of the 4f levels in photocatalysis is difficult to explain clearly. Here, the synergistic effect of 4f levels of Nd and heterostructures is studied by combining steady-state, transient, and ultrafast spectral analysis techniques with DFT theoretical calculations based on the construction of Nd single atom modified black phosphorus/g-C3N4 (BP/CN) heterojunctions. As expected, the generation rates of CO and CH4 of the optimized heterostructure are 7.44 and 6.85 times higher than those of CN, and 8.43 and 9.65 times higher than those of BP, respectively. The Nd single atoms can not only cause surface reconstruction and regulate the active sites of BP, but also accelerate charge separation and transfer, further suppressing the recombination of electron-hole pairs. The electrons can transfer from g-C3N4:Nd to BP:Nd, with a transfer time of ≈11.4 ps, while the radiation recombination time of electron-hole pairs of g-C3N4 is ≈26.13 µs, indicating that the construction of heterojunctions promotes charge transfer. The 2P1/2/2G9/2/4G7/2/2H11/2/4F7/2→4I9/2 emissions from Nd3+ can also be absorbed by heterostructures, which improves the utilization of light. The energy change of the key rate measurement step CO2 *→COOH* decreases through Nd single atom modification.

Nanoparticulate TiN Loading to Promote Z-Scheme Water Splitting Using a Narrow-Bandgap Nonoxide-Based Photocatalyst Sheet.

Some oxide-based particulate photocatalyst sheets exhibit excellent activity during the water-splitting reaction. The replacement of oxide photocatalysts with narrow-bandgap photocatalysts based on nonoxides could provide the higher solar-to-hydrogen energy conversion efficiencies that are required for practical implementation. Unfortunately, the activity of nonoxide-based photocatalyst sheets is low in many cases, indicating the need for strategies to improve the quality of nonoxide photocatalysts and the charge transfer process. In this work, single-crystalline particulate SrTaO2N is studied as an oxygen evolution photocatalyst for photocatalyst sheets applied to Z-scheme water splitting, in combination with La5Ti2Cu0.9Ag0.1O7S5 and Au as the hydrogen evolution photocatalyst and conductive layer, respectively. The loading of SrTaO2N with CoOx provided increases activity during photocatalytic water oxidation, giving an apparent quantum yield of 15.7% at 420 nm. A photocatalyst sheet incorporating CoOx-loaded SrTaO2N is also found to promote Z-scheme water splitting under visible light. Notably, the additional loading of nanoparticulate TiN on the CoOx-loaded SrTaO2N improves the water splitting activity by six times because the TiN promotes electron transfer from the SrTaO2N particles to the Au layer. This work demonstrates key concepts related to the improvement of nonoxide-based photocatalyst sheets based on facilitating the charge transfer process through appropriate surface modifications.

Effective Interfacing of Surface Homojunctions on Chemically Identical g-C3N4 for Efficient Visible-Light Photocatalysis without Sacrificial Agents.

Developing efficient homojunctions on g-C3N4 promises metal-free photocatalysis to realize truly sustainable artificial photosynthesis. However, current designs are limited by hindered charge separation due to inevitable grain boundaries and random formation of ineffective homojunctions embedded within the photocatalyst. Here, efficient photocatalysis is driven by introducing effective surface homojunctions on chemically and structurally identical g-C3N4 through leveraging its size-dependent electronic properties. Using a top-down approach, the surface layer of bulk g-C3N4 is partially exfoliated to create sheet-like g-C3N4 nanostructures on the bulk material. This hierarchical design establishes a subtle band energy offset between the macroscopic and nanoscopic g-C3N4, generating homojunctions while maintaining the chemical and structural integrities of the original g-C3N4. The optimized g-C3N4 homojunction demonstrates superior photocatalytic degradation of antibiotic pollutants at >96% efficiency in 2 h, even in different real water samples. It achieves reaction kinetics (≈0.041 min-1) up to fourfold better than standalone materials and their physical mixture. Mechanistic studies highlight the importance of the unique design in boosting photocatalysis by effectively promoting interfacial photocarrier manipulation and utilization directly at the point-of-catalysis, without needing co-catalysts or sacrificial agents. This work presents enormous opportunities for developing advanced and green photocatalytic platforms for sustainable light-driven environmental, energy, and chemical applications.

Dual-Atom P-Co-Dy Charge-Transfer Bridge on Black Phosphorus for Enhanced Photocatalytic CO2 Reduction.

The synergistic effect of rare earth single-atoms and transition metal single-atoms may enable us to achieve some unprecedented performance and characteristics. Here, Co-Dy dual-atoms on black phosphorus with a P-Co-Dy charge-transfer bridge are designed and fabricated as the active center for the CO2 photoreduction reaction. The synergistic effect of Co-Dy on the performance of black phosphorus is studied by combining X-ray absorption spectroscopy, ultrafast spectral analysis, and in situ technology with DFT calculations. The results show that the Co and Dy bimetallic active site can promote charge transfer by the charge transfer bridge from P to Dy, and then to Co, thereby improving the photocatalytic activity of black phosphorus. The performance of catalysts excited at different wavelength light indicates that the 4G11/2/2I15/2/4F9/2→6H15/2 and 4F9/2→6H13/2 emissions of Dy can be absorbed by black phosphorus to improve the utilization of sunlight. The in situ DRIFTS and density functional theory (DFT) calculations are used to investigate the CO2 photoreduction pathway. This work provides an depth insight into the mechanism of dual-atom catalysts with enhanced photocatalytic performance, which helps to design novel atomic photocatalysts with excellent activity for CO2 reduction reactions.

Rapid Preparation Triggered by Visible Light for Tough Hydrogel Sensors with Low Hysteresis and High Elasticity: Mechanism, Use and Recycle-by-Design.

Hydrogels have emerged as promising candidates for flexible devices and water resource management. However, further applications of conventional hydrogels are restricted due to their limited performance and lack of a recycling strategy. Herein, a tough, flexible, and recyclable hydrogel sensor via a visible-light-triggered polymerization is rapidly created. The Zn2+ crosslinked terpolymer is in situ polymerized using g-C3N4 as the sole initiator to form in situ chain entanglements, endowing the hydrogels with low hysteresis and high elasticity. In the use phase, the hydrogel sensor exhibited high ion conductivity, excellent mechanical properties, fast responsiveness, high sensitivity, and remarkable anti-fatigue ability, making it exceptionally effective in accurately monitoring complex human movements. At the end-of-life (EOL), leveraging the synergy between the photodegradation capacity of g-C3N4 and the adsorption function of the hydrogel matrix, the post-consumer hydrogel is converted into water remediation materials, which not only promoted the rapid degradation of organic pollutants, but also facilitated collection and reuse. This innovative strategy combined in situ entangling reinforcement and tailored recycle-by-design that employed g-C3N4 as key blocks in the hydrogel to achieve high performance in the use phase and close the loop through the reutilization at EOL, highlighting the cost-effective synthesis, specialized structure, and life cycle management.

Visible-Light-Driven NO Release from Postmodified MOFs via Photoinduced Electron Transfer for Antibacterial Application.

Photoresponsive nitric oxide (NO)-releasing materials (NORMs) enable the spatiotemporal delivery of NO to facilitate their potential applications in physiological conditions. Here two novel metal-organic frameworks (MOFs)-based photoactive NORMs achieved by the incorporation of prefunctionalized NO donors into the photosensitive Fe-MOFs via a postmodification strategy is reported. The modified Fe-MOFs display superior photoactivity of NO release when exposed to visible light (up to 720 nm). Significantly, the visible-light-driven NO release properties are further corroborated by their efficient antibacterial performance.

Defects Healing of the ZnO Surface by Filling with Au Atom Catalysts for Efficient Photocatalytic H2 Production.

Healed defects on photocatalysts surface and their interaction with plasmonic nanoparticles (NPs) have attracted attention in H2 production process. In this study, surface oxygen vacancy (Vo ) defects are created on ZnO (Vo -ZnO) NPs by directly pyrolyzing zeolitic imidazolate framework. The surface defects on Vo -ZnO provide active sites for the diffusion of single Au atoms and as nucleation sites for the formation of Au NPs by the in situ photodeposition process. The electronically healed surface defects by single Au atoms help in the formation of a heterojunction between the ZnO and plasmonic Au NPs. The formed Au/Vo -Au:ZnO-4 heterojunction prolongs photoelectron lifetimes and increases donor charge density. Therefore, the optimized photocatalysts of Au/Vo -Au:ZnO-4 has 21.28 times higher H2 production rate than the pristine Vo -ZnO under UV-visible light in 0.35 m Na2 SO4 and 0.25 m Na2 SO3 . However in 0.35 m Na2 S and 0.25 m Na2 SO3 , the H2 production rate is 25.84 mmole h-1 g-1 . Furthermore, Au/Vo -Au:ZnO-4 shows visible light activity by generating hot carries via induced surface plasmonic effects. It has 48.58 times higher H2 production rate than pristine Vo -ZnO. Therefore, this study infers new insight for defect healing mediated preparation of Au/Vo -Au:ZnO heterojunction for efficient photocatalytic H2 production.

A Dual-Active Covalent Triazine Framework Film for Efficient Visible-Light-Driven Hydrogen Peroxide Production.

Photocatalytic hydrogen peroxide production from water and oxygen offers a clean and sustainable alternative to the conventional energy-intensive anthraquinone oxidation method. Compared to powdered covalent triazine frameworks (CTFs), the film morphology of CTFs provides better connectivity in 2D, yielding several advantages: more efficient connections between active sites, reduced electron-hole pair recombination, increased resistance to superoxide radical induced corrosion, and decreased light scattering. Leveraging these benefits, it has incorporated dual active sites for both the oxygen reduction reaction (ORR) and the water oxidation reaction (WOR) into a CTF film system. This dual-active CTF film demonstrated an exceptional hydrogen peroxide production rate of 19 460 µmol h⁻¹ m⁻2 after 1 h and 17 830 µmol h⁻¹ m⁻2 after 5 h under visible light irradiation (≥420 nm) without the need for sacrificial agents.

Visible-Light-Responsive Photoreversible Multi-Color Switching for Rewritable Light-Printing and Information Display.

Photoreversible color switching systems (PCSSs) exhibiting multi-color responses to visible light are favored for sustainable societal development over those relying on ultraviolet light due to safer operation and better penetration depth. Here, a PCSS capable of multi-color switching responsive to visible light based on highly photoreductive rutile-phase Sn-doped TiO2-x nanoparticles is reported. The Sn-doping significantly red-shifts the absorption band of the nanoparticles to the visible region, improving charge separation and transfer efficiencies and introducing Ti3+ species and oxygen vacancies as internal sacrificial electron donors for scavenging photogenerated holes. The resulting Sn-doped TiO2-x nanoparticles feature exceptional photoreduction ability and activity, thereby enabling photoreversible color switching of various redox dyes operational under visible light illumination. Furthermore, multi-color switching can be achieved via the color overlay effect by combining different redox dyes in one system, opening the door to many advanced applications, as demonstrated in their successful uses for developing visible-light-driven rewritable multi-color light-printing systems and visual information displays.

Solvated Electrons Generated on the Surface of Na-SPHI for Boosting Visible Light Photocatalytic Hydrogen Evolution with Ultra-High AQE.

Enhancing the utilization of visible-light-active semiconductors with an excellent apparent quantum efficiency (AQE) remains a significant and challenging goal in the realm of photocatalytic water splitting. In this study, a fully condensed sulfur-doped poly(heptazine imide) metalized with Na (Na-SPHI) is synthesized by an ionothermal method by using eutectic NaCl/LiCl mixture as the ionic solvent. Comprehensive characterizations of the obtained Na-SPHI reveal several advantageous features, including heightened light absorption, facilitated exciton dissociation, and expedited charge transfer. More importantly, solvated electron, powerful reducing agents, can be generated on the surface of Na-SPHI upon irradiation with visible light. Benefiting from above advantage, the Na-SPHI exhibits an excellent H2 evolution rate of 571.8 µmol·h-1 under visible light illumination and a super-high AQE of 61.7% at 420 nm. This research emphasizes the significance of the solvated electron on the surface of photocatalyst in overcoming the challenges associated with visible light-driven photocatalysis, showcasing its potential application in photocatalytic water splitting.

Single Atom Ag Bonding Between PF3T Nanocluster and TiO2 Leads the Ultra-Stable Visible-Light-Driven Photocatalytic H2 Production.

Atomic Ag cluster bonding is employed to reinforce the interface between PF3T nano-cluster and TiO2 nanoparticle. With an optimized Ag loading (Ag/TiO2 = 0.5 wt%), the Ag atoms will uniformly disperse on TiO2 thus generating a high density of intermediate states in the band gap to form the electron channel between the terthiophene group of PF3T and the TiO2 in the hybrid composite (denoted as T@Ag05-P). The former expands the photon absorption band width and the latter facilitates the core-hole splitting by injecting the photon excited electron (from the excitons in PF3T) into the conduction band (CB) of TiO2. These characteristics enable the high efficiency of H2 production to 16 580 µmol h-1 g-1 and photocatalysis stability without degradation under visible light exposure for 96 h. Compared to that of hybrid material without Ag bonding (TiO2@PF3T), the H2 production yield and stability are improved by 4.1 and 18.2-fold which shows the best performance among existing materials in similar component combination and interfacial reinforcement. The unique bonding method offers a new prospect to accelerate the development of photocatalytic hydrogen production technologies.

Rational Design of Hydroxylated Thiazole Orange Photocages for Green Light-Triggered DNA Recombination.

The precise control of DNA recombination enables the cell- or time-dependent regulation of gene expression in studies of gene function. Caged estrogen receptor ligands combined with a Cre-ERT2/loxP system are useful tools for light-triggered DNA recombination. However, the photolysis of most caged compounds requires ultraviolet or blue light, which is toxic and displays low tissue penetration. Although a cyanine-based photo-responsive protecting group (PPG) can release estrogen receptor ligands with longer-wavelength light, its low photolytic efficiency requires long illumination times. We developed a caged estrogen receptor ligand with improved green light-responsive PPGs. The rational modification of Hydroxylated Thiazole Orange (HTO) photocages using electron-donating groups (EDGs), such as dimethoxy (DiMeO)-substituted HTO, resulted in high photolytic efficiency (up to ÏµΦ ≈320 M-1  cm-1 ). Theoretical calculations demonstrated that the enhanced photolytic efficiencies were derived from the increased intramolecular charge transfer by EDGs upon excitation. The efficient uncaging of estrogen receptor ligands enabled the control of gene recombination in a ligand-dependent Cre-ERT2/loxP system in live cells.

Scattered high-energy synchrotron radiation at the KARA visible-light diagnostic beamline.

To characterize an electron beam, visible synchrotron light is often used and dedicated beamlines at synchrotron sources are becoming a more common feature as instruments and methods for the diagnostics are, along with the accelerators, further developed. At KARA (Karlsruhe Research Accelerator), such a beamline exists and is based on a typical infrared/visible-light configuration. From experience at such beamlines no significant radiation was expected (dose rates larger than 0.5 µSv h-1). This was found not to be the case and a higher dose was measured which fortunately could be shielded to an acceptable level with 0.3 mm of aluminium foil or 2.0 mm of Pyrex glass. The presence of this radiation led to further investigation by both experiment and calculation. A custom setup using a silicon drift detector for energy-dispersive spectroscopy (Ketek GmbH) and attenuation experiments showed the radiation to be predominantly copper K-shell fluorescence and is confirmed by calculation. The measurement of secondary radiation from scattering of synchrotron and other radiation, and its calculation, is important for radiation protection, and, although a lot of experience exists and methods for radiation protection are well established, changes in machine, beamlines and experiments mean a constant appraisal is needed.

Benzothiadiazole-Based Ordered Mesoporous Polymer as a Versatile, Metal-Free Heterogeneous Photocatalyst.

Visible-light active heterogeneous organophotocatalysts have recently gained considerable interest in organic synthetic community. Ordered mesoporous polymers (OMPs) are highly promising as heterogeneous alternative to traditional precious metal/organic dyes-based photocatalysts. Herein, we report the preparation of a benzothiadiazole functionalized OMPs (BT-MPs) through a "bottom-up" strategy. High ordered periodic porosity, large surface area, excellent stability and rational energy-band structures guarantee the high catalytic activity of BT-MPs. As a result, at least six conversions, e.g., the [3+2] cycloaddition of phenols with olefins, the selective oxidation of sulfides, the C-3 thiocyanation of indole and the aminothiocyanation of ß-keto ester, could be promoted smoothly by BT-MPs. In addition, BT-MPs was readily recovered with well maintaining its photocatalytic activity and could be reused for at least eight times. This study highlights the potential of exploiting photoactive OMPs as recyclable, robust and metal-free heterogeneous photocatalysts.

Dual Role of a Novel Heteroleptic Cu(I) Complex in Visible-Light-Driven CO2 Reduction.

A novel mononuclear Cu(I) complex was synthesized via coordination with a benzoquinoxalin-2'-one-1,2,3-triazole chelating diimine and the bis[(2-diphenylphosphino)phenyl] ether (DPEPhos), to target a new and efficient photosensitizer for photocatalytic CO2 reduction. The Cu(I) complex absorbs in the blue-green region of the visible spectrum, with a broad band having a maximum at 475 nm (ϵ =4500 M-1 cm-1), which is assigned to the metal-to-ligand charge transfer (MLCT) transition from the Cu(I) to the benzoquinoxalin-2'-one moiety of the diimine. Surprisingly, photo-driven experiments for the CO2 reduction showed that this complex can undergo a photoinduced electron transfer with a sacrificial electron donor and accumulate electrons on the diimine backbone. Photo-driven experiments in a CO2 atmosphere revealed that this complex can not only act as a photosensitizer, when combined with an Fe(III)-porphyrin, but can also selectively produce CO from CO2. Thus, owing to its charge-accumulation properties, the non-innocent benzoquinoxalin-2-one based ligand enabled the development of the first copper(I)-based photocatalyst for CO2 reduction.

Visible-Light-Induced Multi-Component Nitrooxylation Reactions of α-Diazoesters, Cyclic Ethers, and tert-Butyl nitrite Leading to Organic Nitrate Esters.

A simple and efficient strategy has been developed for the synthesis of organic nitrate esters via visible-light-induced multi-component nitrooxylation reactions of α-diazoesters, cyclic ethers, and tert-butyl nitrite under open air atmosphere. This transformation could be conducted under mild and metal-free conditions to provide a number of organic nitrate esters in moderate to good yields using air as the green oxidant.

Visible-Light-Promoted Cascade Coupling of 2-Isocyanonaphthalenes with Elemental Sulfur and Amines to Construct Naphtho[2,1-d]thiazol-2-Amines.

A visible-light-induced strategy has been explored for the synthesis of naphtho[2,1-d]thiazol-2-amines through ortho-C-H sulfuration of 2-isocyanonaphthalenes with elemental sulfur and amines under external photocatalyst-free conditions. This three-component reaction, which utilizes elemental sulfur as the odorless sulfur source, molecular oxygen as the clean oxidant, and visible light as the clean energy source, provides a mild and efficient approach to construct a series of naphtho[2,1-d]thiazol-2-amines. Preliminary mechanistic studies indicated that visible-light-promoted photoexcitation of reaction intermediates consisting of thioureas and DBU might be involved in this transformation.

Visible-Light-Mediated [2+2] Photocycloadditions of Alkynes.

Visible-light-mediated [2+2] photocycloaddition reaction can be considered an ideal solution due to its green and sustainable properties, and is one of the most efficient methods to synthesize four-membered ring motifs. Although research on the [2+2] photocycloaddition of alkynes is challenging because of the diminished reactivity of alkynes, and the more significant ring strain of the products, remarkable achievements have been made in this field. In this article, we highlight the recent advances in visible-light-mediated [2+2] photocycloaddition reactions of alkynes, with focus on the reaction mechanism and the late-stage synthetic applications. Advances in obtaining cyclobutenes, azetines, and oxetene active intermediates continue to be breakthroughs in this fascinating field of research.