ChemPhotoChem最新文献

Cover image provided courtesy of Tomohiro Higashi and co-workers from University of Miyazaki, Japan.

The Front Cover illustrates the micro-environments associated with photocatalytic cross-dehydrogenative coupling (CDC) reactions, wherein covalent organic frameworks (COFs) function as heterogeneous catalysts. COFs exhibit favorable photocatalytic activity in diverse chemical transformations, owing to their remarkable high crystallinity, excellent stability, and convenient recyclability. The CDC reactions represent an efficient and clean methodology for the formation of C-Nu (Nu = nucleophilic reagent) bonds through activation of C-H and Nu-H bonds, respectively. As expected, the robust COFs offer a highly versatile platform for heterogeneous photocatalytic CDC reactions. More information can be found in the Concept article by Bin Guo, David J. Young, Hong-Xi Li, and co-workers (DOI: 10.1002/cptc.202400274).

The Front Cover illustrates organohalogenochromism (OHC) which induces a significant hypsochromic or bathochromic shift of photoabsorption band of dye in halogenated solvents. The expression of OHC would be ascribable to the specific intermolecular interaction between the organohalogen and the dye molecules, including halogen−anion interaction (i.e. halogen bond) and halogen/π interaction. The insight into the OHC allows us to create an optical spectroscopic method and functional dye material for detection and visualization of toxic volatile organohalogen compounds. More information can be found in the Concept article by Yousuke Ooyama and co-workers (DOI: 10.1002/cptc.202400187).

A novel solid state bio-solar cell is demonstrated based on a purple bacterial reaction center-light harvesting 1 complex (RC-LH1) that exhibits high quantum efficiency and long carrier lifetimes. We demonstrate that careful choice of transport layers enables a high open circuit voltage of up to 0.3 V in these solid state biophotovoltaic devices. Electronic processes were investigated with impedance spectroscopy. Equivalent circuit modelling of impedance spectra obtained under illumination at DC offset voltages between open circuit and short circuit conditions revealed two relaxations on microsecond and millisecond time scales that are attributed to the charge transit time and carrier recombination processes, respectively. The operational stability of the solar cells was examined under constant illumination for over 3 hours and a burn-in time of several minutes was observed, after which operational parameters stabilized. This work is the largest voltage reported for RC-LH1 based solid state biophotovoltaic devices to date.

In photocatalysis, the photoabsorber plays a crucial role in the reaction. The most important parameters are stability, cost and optical band gap. In this work, a prominent class of absorbers, namely carbon nitrides (CN), has been investigated. In the literature, CN is most often described as stable, although photodegradation has been observed. In order to retain the beneficial properties of CN while improving stability, a crystalline phase poly(triazine imide) (PTI) of carbon nitride was investigated and compared to polymeric CN in photocatalytic hydrogen generation experiments. In order to improve the charge separation for the photoinduced hydrogen evolution reaction, pyrite (FeS₂) was used as a surface co-catalyst with a loading of 1, 5 and 10 wt %. At the same time, any photodegradation products in solution were investigated by ion chromatography. Interestingly, PTI shows hardly any photocorrosion compared to defective carbon nitride, indicating its higher photostability in hydrogen evolution experiments. However, FeS₂ produces ammonium as a degradation product when synthesised from nitrogen-containing precursors. When made from nitrogen-free precursors, FeS₂ together with photostable PTI releases little ammonia, making it a photostable, earth-abundant composite for photocatalytic hydrogen generation.

Advances in bioimaging technologies capable of visualizing physiological and pathological processes are of great significance for revealing diseases development and promoting clinical diagnosis and treatment. Photoacoustic (PA) imaging, utilizing small-molecule probes, offers a promising approach for achieving high-spatiotemporal-imaging of dynamic biological process. The development of near-infrared absorbing dyes has significantly contributed to the research of small-molecule PA probes, particularly boron-dipyrromethene derivatives (BODIPYs) known for their simple synthesis, tunable NIR photophysical properties and superior PA imaging abilities. This review highlights recent advances in biomedical applications of BODIPY-based PA probes, including the design strategies, spectral characteristics, response mechanisms and applications for imaging biomarkers such as reactive oxygen/nitrogen species, gaseous signaling molecules and metal ions. Moreover, their challenges and future prospects are elucidated. The insights provided in this review are expected to guide future studies on small-molecule PA probes for bioimaging and biosensing.

Hole-scavengers are a crucial part of particulate photocatalytic systems. The use of hole-scavengers increases the photocatalytic activity by preventing electron-hole recombination. The holes are used in photo-oxidation of the hole-scavenger molecules increasing the probability of electrons involved in photoreduction of water. In this study, different hole-scavengers utilized in photocatalytic water splitting reaction were tested. The impact of different hole scavengers on photocatalytic reactions were investigated on [Ca₂Nb₃O₁₀]⁻ 2D nanosheets mechanistically. Cyclic voltammetry and chronoamperometry tests were employed to assess the impact of hole scavengers on photocatalytic efficiency. The photoelectrochemical tests agree with the results of the photocatalytic reactions. Methanol and EDTA give the largest oxidation photocurrent and the best photocatalytic activity.

Artificial photosynthesis, encompassing the photocatalytic generation of H₂ and CO₂ reduction innovations, seems to be a highly promising approach. This is due to its ability to efficiently transform CO₂ into hydrocarbon fuel and valuable chemical products using solar energy as a direct energy source. This will simultaneously help to mitigate global warming and energy shortage issues. Chalcogenide-based semiconductors have recently gotten a lot of attention as an important area of research for photocatalytic H₂ production and CO₂ conversion, owing to their low band gap energy, suitable band structures, and a great photoresponsivity spectrum. Modifying chalcogenides into their heterostructures could be a great way to solve problems like photo corrosion and carrier recombination. Therefore, this review summarized a series of different modifications of chalcogenides and recent developments in their photocatalytic and photo electrocatalytic performance, particularly in H₂ production and CO₂ conversion. Lastly, we discussed the challenges, limitations, areas for development, and future prospects of chalcogenides and their heterostructures capable of utilizing visible light to produce H₂ gas and reduce CO₂.

The photolysis of the gold nanoclusters Au₂₅(SR)₁₈^z (R=C₂H₄Ph and C₁₂H₂₅, z=1−, 0 and 1+) NCs in halogenated solvents such as dichloromethane leads to changes in the charged states of the Au₂₅(SR)₁₈^z observed using UV-Visible and ¹H NMR spectroscopic techniques. Matrix-assisted laser desorption/ionization mass spectrometry results proved that during charge transformation from anion to neutral and eventually cation forms, the size of nanoclusters remains intact. Electrochemistry of Au₂₅(SR)₁₈ has enabled the monitoring of these changes by cyclic voltammetry, indicating decay in the redox peak current upon irradiation. In the absence of light and/or in a non-halogenated solvent, e. g., tetrahydrofuran, no substantial change in the photophysical signatures of Au₂₅ nanoclusters was observed. These observations highlight the importance of selecting appropriate solvent(s) in the synthesis and photochemical studies of atomically precise metal nanoclusters and the possibility of using photochemistry in halogenated solvents to synthesize different charge states of atomically precise metal nanoclusters. Thus, other monodispersed molecule-like nanoclusters, with various sizes and charges, can be achieved via this photosynthetic protocol under controlled conditions, e. g., solvent, light, and photolysis duration.

The Front Cover illustrates the improvement on stability as well as on thermally activated delayed fluorescence (TADF) characteristics, such as lifetime and efficiency, obtained by modifying the core of the organic emitters. The properties of TADF dyes are enhanced going from 9,9-dimethyl-fluorene to the more bulky 9,9’-spirobifluorene. Very long delayed fluorescence has been detected in both dyes as thin films and crystals, where the bulky core is pivotal to reduce deactivating intermolecular pathways. More information can be found in the Research Article by Fabio Rizzo and co-workers (DOI: 10.1002/cptc.202400235).