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Ultrathin semiconductor nanowires are promising alternatives to nanoparticle or bulk counterparts for the construction of photoanodes for solar energy conversion, because of their profuse surface reactive sites and excellent charge transport properties. Herein, well-aligned ultrathin corrugated nanowire TiO2 (UCW-TiO2) thin films with a diameter of 10 nm grown on fluorine-doped tin oxide (FTO) substrates by a unique monomicelle-directed assembly method are applied as a versatile photoanode platform. On this platform, photoanodes were used for direct photoelectrochemical (PEC) benzyl alcohol oxidation and can also be dye-sensitized for visible-light driven water oxidation. The conversion of benzyl alcohol (BA) over the pristine UCW-TiO2 photoanode is close to 100%, and the selectivity can reach 90.2% with a faradaic efficiency of 93% after 15 h. With surface anchoring of a suitable chromophore and oxygen evolution catalysts (OECs), the dye-sensitized UCW-TiO2 photoanode achieves 5-fold larger faradaic efficiency for water oxidation than that of a spherically structured TiO2 assembled photoanode. Electrochemical and spectroscopic measurements demonstrate that the ultrathin corrugated nanowire structured TiO2 accelerates electron transport kinetics and suppresses recombination of surface accumulated holes and electrons compared with spherically structured TiO2. Both BA oxidation and water oxidation studies show that the UCW-TiO2 is a versatile photoanode platform for a variety of highly efficient solar energy conversion applications. [ABSTRACT FROM AUTHOR]

Photocatalytic lignin valorization has caught widespread attention; yet the reaction systems often employ noble metal complexes, hydrogen atom transfer (HAT) agents, and/or sacrificial electron donors/acceptors that do not comply with atom economy or environmental friendliness. Herein, we discovered that N-phenylphenothiazine (PTH) as a metal-free photocatalyst induced the cleavage of the lignin Cα–Cβ bond under ambient conditions free of those additional agents with a high yield and selectivity toward benzoic acid. Transient spectroscopic investigations revealed that the energy-demanding Cα–Cβ bond cleavage was induced by the potent oxidant, 2PTH˙+*, that was derived from consecutive two-photon excitation of PTH. [ABSTRACT FROM AUTHOR]

Solar‐to‐hydrogen conversion is a sustainable way of producing renewable fuels, yet the efficiency is limited by the poor photo‐induced charge‐carrier separation on electrode surface. Developing active and stable hydrogen evolution photocatalysts is challenging and entails intelligent material structure design and tailoring. Here, a novel water dispersible supramolecular metal organic framework (SMOF) is employed as a general and high‐performance platform to encapsulate CdS quantum dots (QDs) for achieving highly improved solar‐induced H2‐production activity. Particularly, the CdS QDs@SMOF heterostructure exhibits an excellent H2 generation activity of 49.4 µmol h−1 (TOF = 47.0/h), exceeding those of most reported heterogeneous metal organic frameworks‐based photocatalytic systems. Advanced characterizations disclose that the strong electrostatic interaction and light‐induced charge transfer between SMOF and CdS QDs, combined with the high surface area, water dispersible nature, and abundant reactive centers synergistically contribute to this distinguished photocatalytic performance. The work not only demonstrates the water dispersible SMOF can serve as a versatile and effective platform supporting semiconductor to boost the photocatalytic H2‐production performance without co‐catalysts, but also paves avenues to the design and synthesis of SMOF‐based heterostructures for general catalysis applications. [ABSTRACT FROM AUTHOR]

Photocatalytic activation of prodrugs for killing cancer cells is an attractive alternative phototherapy to photodynamic therapy that typically relies on the supply of oxygen. Although prodrugs are widely developed, few other than Pt-(IV) complexes are studied for photocatalytic activation. Herein, we report the photocatalytic reduction of nitrobenzene to aniline, an important chemical conversion for a large class of nitroaromatic prodrugs in cancer therapy that was previously limited to only enzyme-catalyzed activation. The carefully designed photocatalyst is a photosensitizer (PS)-functionalized gold nanocluster (Au NC) (abbreviated as Au-PS) in which a ruthenium coordination compound as the PS is covalently linked to the glutathione-ligated Au NC surface. Visible light excitation of the photocatalyst reduces nitrobenzene to aniline with 100% selectivity. The remarkably high selectivity is attributed to the specific catalytic nature of the reduced Au NC from photoinduced charge separation within the Au-PS analyzed by time-resolved absorption spectroscopy. In vitro experiments show that the nitroaromatic prodrug 5-(aziridin-1-yl)-2,4-dinitrobenzamide (CB1954) induces significant cytotoxicity in the presence of the Au-PS and light under hypoxia. The photocatalytic nitroaromatic prodrug activation by the Au-PS provides an alternative approach in the category of photochemotherapy to confront hypoxic cancer cells. [ABSTRACT FROM AUTHOR]

Pure organic dye QAP-C8 based on quinacridone (QA) with octyl side chains as the donor and pyridine dicarboxylic acid (PDA) as the acceptor was first used in both the photoanode and the photocathode of photoelectrochemical cells. A tandem device with QAP-C8 as the photosensitizer realized overall water splitting and showed a STH of 0.11% under neutral pH conditions without an external bias. [ABSTRACT FROM AUTHOR]

Herein, green-fluorescent N-doped carbon quantum dots (N-CQDs) with quantum yield of 30.6% were prepared via a simple bottom-up electrochemical (EC) method using the mixtures of pyrocatechol and ethylenediamine as both precursors and electrolytes. The ON-OFF fluorescence (FL) principle that the FL intensity of the N-CQDs was quenched in the presence of Fe 3+ was further extended to the ON-OFF-ON and ON-OFF-ON-OFF ones for pyrophosphate anions (PPi) and alkaline phosphatase (ALP) detection, respectively, based on the specific competitive interaction of N-CQDs with Fe 3+ and PPi and the hydrolysis of PPi in the presence ALP. Under the optimized conditions, limit of detection (LOD) of 1.2 μM and 0.5 μM were achieved for assays of Fe 3+ and PPi, respectively. Meanwhile, measurable evaluation of ALP activity was reached in a wide range from 5 to 360 U/L with a LOD of 1.1 U/L. The as-proposed sensors showed many advantages including label free, rapid, simple, low-cost, high sensitive, which has great promising application potential in vivo and in vitro clinical diagnosis and will promote the application of EC derived carbon nanomaterials. [ABSTRACT FROM AUTHOR]

Herein, a uniform porous highly oriented pyrolytic graphite (HOPG) electrode was prepared via diazonium salt assisted electrochemical etching method and firstly utilized to immobilize enzymes for the construction of a high-performance glucose biosensor. The formation mechanism and morphology structure of the porous HOPG electrode were investigated using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) characterizations. The glucose oxidase (GOx) was functionalized with pyrene groups and then immobilized on the porous HOPG substrate through π-π stacking interactions and hydrogen bonding. As a result, eight times higher oxidation current density can be obtained for a given glucose concentration for the porous HOPG electrode than the pristine one. Detection limit of 5 μM for glucose was achieved for the as-fabricated biosensor. It was obtained that 78 % biocatalytical activity of GOx can be retained after the pyrene functionalization and 65.7 % one can even be maintained after four weeks, which confirmed the high efficiency and good stability of the as-prepared biosensor. What's more, it can be anticipated that various other enzymes can be loaded into this porous HOPG platform using the same enzyme modification methodology for the construction of efficient biosensors. [ABSTRACT FROM AUTHOR]

To achieve high catalytic activity and stability with low noble-metal loadings on special supports has triggered much research interest in the past few years. Herein, a mild co-reduction strategy was exploited to fabricate glutathione decorated Au clusters (with a size of ∼1.4 nm) on reduced graphene oxide (Au@HSG-rGO) with low Au loadings and high catalytic activity in an aqueous medium. The resultant Au@HSG-rGO complex exhibited 20.8 times higher catalytic activity than Au nanoparticle supported graphene for catalysis of the reduction of 4-nitrophenol (4-NP). The Au@HSG-rGO was packed in a filtering platform to afford a fixed-bed system, with which the catalytic conversion reached 96.03% for 0.2 mM 4-NP solution at a flow rate of 1 mL min−1. In addition, the poly(2-(dimethylamino) ethyl acrylate) modified Au@HSG-rGO (Au@HSG-rGO-PDMAEA) viaπ–π stacking interactions exhibited good recyclability and tunable catalytic activity and only showed slight loss of activity after recycling five times. The PDMAEA served as forest-like shelters to efficiently protect the Au@HSG clusters from aggregation and also endowed the system with enhanced stability and temperature-controlled catalytic activity. Meanwhile, the Au@HSG-rGO showed excellent electrocatalytic activity for the oxygen reduction reaction in alkaline electrolytes. This simple, economical and mild strategy could be generalized to the preparation of other metal cluster complexes for broad catalytic and analytical applications. [ABSTRACT FROM AUTHOR]

Carbon quantum dots (CQDs) are attracting tremendous interest owing to their low toxicity, water dispersibility, biocompatibility, optical properties and wide applicability. Herein, CQDs with an average diameter of (4.0 ± 0.2) nm and high crystallinity were produced simply from the electrochemical oxidation of a graphite electrode in alkaline alcohols. The as-formed CQDs dispersion was colourless but the dispersion gradually changed to bright yellow when stored in ambient conditions. Based on UV-Vis absorption, fluorescence spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and high-resolution transmission electron microscopy (HRTEM), this colour change appeared to be due to oxygenation of surface species over time. Furthermore, the CQDs were used in specific and sensitive detection of ferric ion (Fe3+) with broad linear ranges of 10–200 μM with a low limit of detection of 1.8 μM (S/N = 3). The application of the CQDs for Fe3+ detection in tap water was demonstrated and the possible mechanism was also discussed. Finally, based on their good characteristics of low cytotoxicity and excellent biocompatibility, the CQDs were successfully applied to cell imaging. [ABSTRACT FROM AUTHOR]

Herein, a facile and efficient method was developed for fabrication of solid-state electrochemiluminescence (ECL) sensor via non-covalent π-π stacking and covalent bonding on the graphite electrode (GE) surface. The electrode was firstly modified with 1-aminopyrene via π-π stacking between GE surface and the pyrene moiety. Thereafter a stable and efficient solid-state ECL sensor was fabricated by covalent immobilization of ruthenium(II) onto the GE surface via amidation reaction between the 1-aminopyrene and bis(2,2′-bipyridyl)(4-methyl-4′-carboxypropyl-2,2′-bipyridyl) ruthenium(II) bishexafluorophosphate. The sensor has been investigated using tripropylamine and tetracycline as representative analytes, and low detection limits of 0.7 nM and 3.5 nM (S/N=3) were reached, respectively. [ABSTRACT FROM AUTHOR]

Photoexcitation of keto-enamine allows intramolecular proton transfer from C-NH to C=O, leading to tautomerization, while the photogenerated isomers are excluded from the study of photocatalytic applications. Herein, we demonstrate the photoisomerization of keto-enamine linkages on covalent organic frameworks (COFs) induced by excited-state intramolecular proton transfer (ESIPT). Partial enolization generates partially enolized photoisomers with a mixture of keto (C=O) and enol (OH) forms, conferring extended π-conjugation with an increase in electron density. The spatially separated D-A configuration is thus rebuilt with the enol-imine-linked branch as a donor and the keto-enamine-linked branch as an acceptor, and in turn, the photoinduced charges transfer between the two adjacent branches with a long lifetime. We further prove that the partially enolized photoisomer is a key transition instead of the keto-enamine form as an excited-state model to understand the photocatalytic behaviors. Therefore, ESIPT-induced photoisomerization must be considered for rationally designing keto-enamine-linked COFs with enhanced photocatalytic activity. Also, our study points toward the importance of controlling excited-state structures for long-lived separated charges, which is of particular interest for optoelectronic applications., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

The integration of the glycerol oxidation reaction (GOR) with the hydrogen evolution reaction in photoelectrochemical (PEC) cells is a desirable alternative to PEC water splitting since a large quantity of glycerol is easily accessible as the byproduct from the biodiesel industry. However, the PEC valorization of glycerol to the value-added products suffers from low Faradaic efficiency and selectivity, especially in acidic conditions, which is beneficial for hydrogen production. Herein, by loading bismuth vanadate (BVO) with a robust catalyst composed of phenolic ligands (tannic acid) coordinated with Ni and Fe ions (TANF), we demonstrate a modified BVO/TANF photoanode for the GOR with a remarkable Faradaic efficiency of over 94% to value-added molecules in a 0.1 M Na 2 SO 4 /H 2 SO 4 (pH = 2) electrolyte. The BVO/TANF photoanode achieved a high photocurrent of 5.26 mA·cm -2 at 1.23 V versus reversible hydrogen electrode under 100 mW/cm 2 white light irradiation for formic acid production with 85% selectivity, equivalent to 573 mmol/(m 2 ·h). Transient photocurrent and transient photovoltage techniques and electrochemical impedance spectroscopy along with intensity-modulated photocurrent spectroscopy indicated that the TANF catalyst could accelerate hole transfer kinetics and suppress charge recombination. Comprehensive mechanistic investigations reveal that the GOR is initiated by the photogenerated holes of BVO, while the high selectivity to formic acid is attributed to the selective adsorption of primary hydroxyl groups in glycerol on TANF. This study provides a promising avenue for highly efficient and selective formic acid generation from biomass in acid media via PEC cells.

Enteromorpha prolifera (E. prolifera), one of the main algae genera for green tide, significantly influences both the coastal ecological environment and seawater quality. How to effectively utilize this waste as reproducible raw resource with credible application mechanism are urgent environmental issues to be solved. Herein, E. prolifera was converted to attractive fluorescent carbon nanodots (CNDs) by one-pot green hydrothermal process. The purity and quantum yields for the as-prepared CNDs can be enhanced upon the post-treatment of ethanol sedimentation. The CNDs can be well dispersed in aqueous medium with uniform spherical morphology, narrow size distribution and average size of 2.75 ± 0.12 nm. The ease synthesis and relatively high quantum yields of the CNDs make E. prolifera inexpensive benefit to the human and nature, such as applications in efficient cell imaging and fiber staining. Furthermore, it was discovered that the fluorescence intensity of the CNDs can be selectively quenched upon Fe 3+ addition, which can be used for specific sensitive assay and removal of Fe 3+ in aqueous medium. More importantly, it was reasonably proposed that the quenching was resulted from the synergistic effects of CNDs aggregation and Fe 3+ -CNDs charge-transfer transitions due to the coordination interactions between Fe 3+ and the oxygenous groups on the CNDs.

Tungsten oxide (WO 3- x ), a new alternative to conventional semiconductor material, has attracted numerous attentions owning to its widespread potential applications. Various methods have been reported for the synthesis of WO 3- x nanostructures such as nanowires or nanodots. However, templates or surfactants are often required for the synthesis, which significantly complicate the process and hinder the broad applications. Herein, one-pot template/surfactant-free solvothermal method is proposed to synthesize the WO 3- x nanostructures including fluorescent quantum dots (QDs) and bundle-like nanowires simultaneously. The as-prepared WO 3- x QDs can be well dispersed in aqueous medium, exhibit excellent photoluminescent properties, and show an average size of 3.25 ± 0.25 nm as evidenced by transmission electron microscopy. Meanwhile, the diameter of the WO 3- x nanowires is found to be about 27.5 nm as manifested by the scanning electron microscope images. The generation mechanism for these two WO 3- x nanostructures are systematically studied and proposed. The WO 3- x QDs have been successfully applied in efficient fluorescent staining and specific ferric ion detection. Moreover, the WO 3- x nanowires can be utilized as effective dielectric materials for electromagnetic wave absorption., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)