Journal of Photochemistry and Photobiology最新文献

Fluorescence quenching of an excited guest encapsulated within a cationic host by a cationic molecule was examined on an anionic inorganic surface. Repulsion between the host and the quencher was overcome by adsorbing both an anionic surface. Dimethyl stilbene (DMS), octa amine (OAm₂¹⁶⁺), viologen derivatives (VD²⁺) and saponite are used as guest, cationic capsule, cationic electron acceptor and anionic inorganic surface, respectively. The fluorescence behavior of DMS within OAm₂¹⁶⁺ (denoted as DMS@OAm₂¹⁶⁺) was observed by steady-state and time-resolved fluorescence measurements. As a result of electron transfer the fluorescence of DMS@OAm₂¹⁶⁺ was quenched by VD²⁺ under the presence of saponite, while no quenching was observed in the absence of saponite. Those results indicate that the dynamic electron transfer between DMS@OAm₂¹⁶⁺ and VD²⁺ which are electrostatically repulsive, can be observed in the (DMS@OAm₂¹⁶⁺)-VD²⁺-saponite triad supramolecular system where the two cationic systems are brought closer by the anionic clay sheet.

Open-shell species are attracting significant attention owing to their unique physicochemical properties and highly reactive characteristics. Over the past decade, photoredox catalysis (PRC) has emerged as a powerful strategy for radical reactions. Recently, photocatalysis involving the excitation of open-shell catalytic species generated from in situ photo- or electrochemical electron transfer has also attracted significant attention in synthetic organic chemistry. These systems can achieve redox potentials that are difficult to achieve in the ground state of the photocatalyst or by simple excitation of the photocatalyst. In this review article, we discuss recent advancements in highly reducing organic photocatalyst (OPC) systems involving the photoexcitation of electron-primed catalytic species, which can be engaged in photochemically (conPET: consecutive photoinduced electron transfer) or electrochemically (e-PRC: electrochemically mediated photoredox catalysis). We believe that expanding the redox windows of catalysts to activate inert substrates from the viewpoint of redox potential will improve rational reaction design, and the use of sophisticated OPC systems will be promising for achieving elusive molecular transformations.

The Feature highlights Electron Paramagnetic Resonance (EPR) spectroscopy as an indispensable tool to understand the excited state reactivity of organic molecules.

The photoreaction of an N-Boc secondary amine and N-Boc N-methyl α-amino acid ester with acrylonitrile using inexpensive two-molecule photoredox catalysts results in the production of α-alkylated amine through the generation of an α-carbamy radical under mild conditions. In particular, this mothed leads to a regioselective modification of N-Boc N-methyl α-amino acid ester with the retention of α-chirality through the generation of the less stable primary α-carbamyl radical.

The photophysical properties and photocatalysis of tris(pentafluorophenyl)borane [B(C₆F₅)₃], known as a strong Lewis acid, were revealed. The excited-state B(C₆F₅)₃ exerts single-electron oxidation capability with an oxidation potential (E_red* = 2.02 V vs SCE) close to those of electronically unbiased toluene derivatives (E_ox = 2.01 to 2.29 V). This property was experimentally proven by the direct observation of the radical cation of the toluene dimer by the transient absorption spectroscopy of a mixture of B(C₆F₅)₃ and toluene. In cooperation with a suitable Brønsted base catalyst, B(C₆F₅)₃ catalytically generated benzylic radicals from toluene derivatives under photoirradiation for subsequent carbon-carbon bond-forming reactions.

Presently we report a second example of a biochemical reaction sensitized remotely by excitons (electronic excited states) efficiently transferred along intermediate filaments (IFs) over macroscopic distances. IFs are excellent conductors of energy in the form of excitons, with the efficiency of ca. 0.53 reported in vitro. Excitons were generated by visible light and propagated along Müller cell (MC) intermediate filaments, about 100 μm long. These experiments used a capillary matrix filled by MC IFs extracted from porcine retina. Excitons induced efficient isomerization of 11-cis- to all-trans-retinal, with the reaction quantum yield φ_cis/trans = 0.347 obtained for 11-cis-retinal concentration of 1.0 × 10⁻³ M (0.284 g/L) using 546 nm light at 6.87 mW/cm² power density. Exciton quantum yield φ_exc at 546 nm was also measured in function of radiation power density, with nonlinearity indicative of biphotonic processes. This is the first case of biphotonic processes occurring at such low light intensities with steady-state illumination. The present results support quantum mechanism of high-contrast vision of vertebrate eyes.

Visible light (VL) has been shown to promote genotoxicity through free radical generation and structural protein degradation. These stressful events promote cellular vulnerability, which manifests clinically as erythema, hyperpigmentation, and photoaging. Having established biologic impacts of VL, development of photoprotection strategies against this part of the solar spectra are warranted. This invited review presents advances in the VL literature and discusses available and potential means of VL photoprotection.

The present work investigates the disinfection of dialysate water used in hemodialysis through the application of bioinspired W/WO₃ electrodes constructed on microbial biofilm from C. parapsilosis by electrochemical anodization. The bioinspired electrode was photoactivated by UV/Vis or visible irradiation, and the photocurrent was found to be at least twice higher than that obtained for nanoporous W/WO₃ electrode in the dialysate water. Under optimized conditions, the photo-electrocatalytic analysis conducted on the bioinspired electrode at E_app = 1.5 V and under UV/Vis irradiation led to complete fungi inactivation (5 min) and up to 70% of total organic carbon removal monitored during cell lysis after 120 min of treatment. The results show the bioinspired electrode maintains the structural print of the fungi and works as fungus recognition material. The proposed electrode is also found to exhibit higher surface area, which improves adsorption of microorganisms, leading to faster and more efficient degradation compared to nanoporous W/WO₃ electrode, with a 30% increase in the degradation of organic matter present in the medium. The findings show that the bioinspired electrode has outstanding advantages when compared with other materials investigated; these advantages include controlled morphology, good reproducibility, higher adsorption on the electrode surface, and higher efficiency in the disinfection of C. parapsilosis, an agent of several cases of contamination in dialysate.

Hole-transport materials (HTMs) contribute an important function in perovskite solar cells (PSCs) for achieving favourable photovoltaic performance with durability. In this work, we designed and synthesized a series of porphyrin based hydrophobic HTMs based on donor-π-donor (D-π-D) tactic in which triphenylimidazole as donor and either free-base porphyrin (H2LD) or metalloporphyrin (Cu, CuLD or Zn, ZnLD) as π-spacer for PSCs. All three HTMs were characterized by a variety of spectroscopic and electrochemical methods. Optical and electrochemical properties propose that the highest occupied molecular orbital (HOMO) energy levels were healthily aligned with the valence band of MAPbI₃ perovskite. Among these HTMs, CuLD exhibited higher hole mobility of 7.39 × 10^-5 cm²V^-1s^-1, when compared to ZnLD 5.77 × 10^-5 cm²V^-1s^-1, and H2LD 2.7 × 10^-5 cm²V^-1s^-1. We fabricated PSCs with these HTMs and among them the CuLD based PSCs showed highest power conversion efficiency of 12.44%. The better PCE for the PSCs fabricated with CuLD could be attributed to the higher conductivity and better hole mobility which could be correlated to the better film formation.

Photoelectrochemical (PEC) water splitting is an emerging technology to store the solar energy in the chemical bonds of molecular hydrogen. Among several photo electrodes used for PEC water splitting, α-Fe₂O₃ is a promising material due to its suitable bandgap, chemical stability, and abundance. Despite these, the position of its conduction band does not allow spontaneous movement of photo-generated electrons to cause the water reduction. This demands the application of a minimum electrical bias of ∼1.5 V vs. SHE to increase the energy of the conduction band such that it will be energetically above the H₂O/H₂ redox level. We show that by utilizing the energy of neutralization, the minimum electrical voltage required for PEC water splitting can be brought down to ∼0.8 V. By employing an OH⁻/H⁺dual-ion configuration. OH⁻/H⁺dual-ion assisted PEC water splitting required only 0.95 V to produce a current density of 10 mA/cm², and for achieving the same rate in a conventional symmetric ion configuration, at least a doubling of the applied electrical bias (∼1.8 V) is required.