Journal of Photochemistry and Photobiology C: Photochemistry Reviews最新文献

Symmetry breaking charge transfer (SBCT) in excited molecules plays a central role in photochemical energy conversion in both artificial and biological systems. The photophysical properties of chromophore aggregates can be tuned over a wide range, which opens up prospects for their application in optoelectronic devices, as well as photosensitizers-catalysts. SBCT occurs at a high rate, so its use at the stage of primary charge separation can be effective in the development of organic photovoltaic devices. The processes of symmetry breaking in quadrupolar and octupolar molecules and symmetrical dimers are analyzed from a unified standpoint. The manifestations of symmetry breaking in the IR and optical spectra are described. The most important experimental results and their theoretical description within simple models are discussed. Particular attention is paid to the physical interpretation of regularities observed in experiments.

During the past two decades, there is an explosive growth of numerous scientific researches on dual-emitting fluorescence ratiometric nanoprobes (FRNPs). FRNPs adopt dual-signal ratiometry as signal output toward specific targets, and exhibit unique in-built signal self-calibration function and high accuracy for target detection. Especially, FRNPs can perform high-performance detection of in-vitro/in-vivo pH. These explored FRNPs-pH systems were extensively applied to pH-sensing, imaging and therapeutic applications at the levels of living cells and small animals. Thereby, this review has systematically summarized the promising FRNPs-pH systems reported in recent years. The first section has clearly introduced dual-emission fluorescence (FL) ratiometric modes and FL sensing mechanisms during the construction and application processes. The second section wholly summarizes various construction methods of FRNPs-pH systems based on different compositions and structures. The third section rationally discusses potential applications of FRNPs-pH systems, referring to FL bioimaging at the levels of living cells and small animals, pH-sensing and imaging detection at the levels of whole cells, organelles, tissues and organs, as well as FL imaging-guided tumor therapy. Furthermore, the current status, potential challenges and development perspectives in following researches are analyzed reasonably. This comprehensive and timely review promotes further explorations of multifunctional luminescent nanoprobes and versatile sensing materials for highly efficient biomedical applications.

The increasing number of infectious and chronic diseases, along with the rising healthcare demand caused by an aging population, has led the scientific community to seek novel diagnostic and therapeutic techniques that reduce both mortality rates and healthcare costs. Fluorescence-emission techniques, known for their high sensitivity, rapid response, real-time spatial-temporal resolution, and on-site capabilities, are emerging as key technologies in early diagnosis. However, the biocompatibility of fluorescence probes and their brightness in biological systems continue to be a bottleneck in realizing the full potential of this technique. To address this issue, researchers are turning to efficient luminescence based on through-space conjugation, which is achieved through the clustering of non-conventional chromophores. This review discusses the main recent findings on this phenomenon, analysing its emissive mechanism and how its characteristics can be applied in fields such as sensing, imaging, and various therapies, with a focus on its potential applications in biomedicine.

More than 125 known species of fungi, all part of the Agaricales order, can spontaneously emit light. This bioluminescence results from the oxidation of a luciferin derived from caffeic acid by oxygen under the action of the enzyme luciferase. The production and regeneration of caffeic acid tie together the Krebs cycle and the Shikimic Acid pathway in both fungi and plants. Therefore, successful genetic manipulation of luciferase has led to the development of bioluminescent reporters and eukaryotic organisms that exhibit self-sustained glow. This review aims to discuss the underlying mechanisms of fungal bioluminescence, with a focus on the biochemical and chemical processes that lead to light emission, along with an elaboration on its extensive biotechnological applications.

Photodynamic therapy (PDT) of cancer is a clinically approved, minimally invasive therapeutic approach, combining PDT drug (photosensitizer, PS), molecular oxygen and light to induce cytotoxicity via reactive oxygen species (ROS), which are generated by the light excited PS. Most of the PS molecules fluoresce under excitation with light and fluorescence imaging (FLI) can be employed to evaluate their biodistribution and assess the intratumoral delivery before the therapeutic light application. Light absorption can also be utilized to track a PS by photoacoustic imaging (PAI). However, an excitation of the PS during assessment of its biodistribution through FLI or PAI results in premature photobleaching and causes toxicity. An involvement of a separate fluorescent (luminescent) or photoacoustic imaging probe, which provides imaging contrast in combination with PS without excitation of the latter, can allow for “see-and-treat” approach with FLI/PAI guided PDT. On the other hand, it is well-known that near-infrared (NIR) light is able to penetrate relatively deeper in comparison with visible light, due to reduced absorption and scattering. In addition to the conventional NIR window (NIR-I, ∼700–950 nm), other transparency windows for biological tissues have recently been identified at ∼1000–1700 nm (NIR-II), benefiting optical bioimaging due to the reduced tissue scattering and autofluorescence. Multiple NIR-II imaging probes are currently introduced both for luminescence and photoacoustic bioimaging, providing the significantly improved signal to noise ratio (SNR), imaging depth and resolution. Their combinations with PS are also being increasingly reported, though no review on this hot topic currently exists. Herein, a state-of-the-art in NIR photoluminescence (including fluorescence) and photoacoustic imaging guided PDT is presented. NIR-I and NIR-II spectral ranges are considered, along with both molecular and nanoparticle formulations for imaging guided PDT. It is expected that this review will provide a solid foundation for future translational studies in the domain of NIR imaging guided photodynamic therapy and drug delivery.

Mechanochemistry, a burgeoning field in green chemistry, has been utilized frequently to synthesize various organic molecules, metal complexes, coordination polymers (CPs) and metal-organic frameworks (MOFs) in the solid state from the reactants with very little or no solvent. These mechanical grinding reactions also resulted in successful isolation of materials that are inaccessible otherwise from solution. On the contrary, single crystal X-ray crystallographic technique is routinely used to study the solid-state structural transformations driven by thermal and photochemical methods. In the absence of single crystals, [2 + 2] photocycloaddition reactions can easily be monitored by NMR spectroscopy along with other suitable physical and analytical techniques. During mechanical grinding, several structural changes have been found to take place with the loss of single crystalline nature. Here from our personal perspective, we reviewed how this [2 + 2] cycloaddition reactions have been used effectively to monitor the structural changes induced by mechanochemical grinding. These structural transformations are caused by the pedal motion of olefin bonds, conformational changes of molecular fragments, movements of molecules, change in the composition by absorbing water from the atmosphere, anisotropic expansion of volume, rotation of helical coordination polymers, dimensionality change, loss of coordinating and lattice solvents and catalytic role of template molecules on the [2 + 2] photocycloaddition reactivity.

This review focuses on the many research that have been undertaken in visible-light driven environmental photocatalysis field employing Metal-Organic Framework (MOF) materials for the removal of aqueous pollutants. Correlations between their structural and functional features, and the reactional pathways for pollutant degradation were also addressed, with a particular emphasis on the syntheses and on the charge transfer complexes occurring in the MOF compounds. The extensive possibilities for modifying the properties of MOFs in diverse applications were critical while dealing with a variety of contaminants with different properties. Indeed, because of the infinite number of combinations of different inorganic poly-oxo clusters and organic linkers, and to the possibility of tailoring other variables such as functional groups, pore size, defects, and incorporation of other materials (dyes, semiconductors, metal nanoparticles, covalent organic frameworks, carbon-based materials, magnetic compounds, and inert carriers), MOFs have a high potential to lead the photocatalytic field. Furthermore, the use of mixed methods has shown to be a legitimate and fascinating technique for further developing these systems while considering their strengths and weaknesses. Despite considerable advancements in MOF-based photocatalysts, significant obstacles remain. However, the research of heterogeneous photocatalysis dates back to the 1970 s, but the discussion of MOF materials is even more recent, with just a few decades spent investigating these systems. Nonetheless, tremendous breakthroughs in this area have been made, from structural design to computer simulations, and reports of various MOF materials have constantly increased in the previous several years. As a result, combining the collaborative efforts of researchers from many domains, the future appears to hold promising prospects for MOF-based photocatalysts.

Although numerous photocatalysts, such as organic compounds and metallic complexes, have been systematically designed and synthesized for visible light-induced photopolymerization, their disadvantages, such as toxicity and poor water dispersibility, cannot be neglected in practical production. Hence, high-performance photoinitiators based on nanomaterials, such as carbon dots and carbon nitrides, have recently been reported due to their favorable characteristics of eco-friendliness, high biocompatibility, etc. In this review, carbon-family-based photocatalysts reported in the last five years are thoroughly discussed by the classifications in terms of their photoinitiation mechanisms, such as photoinduced electron transfer-reversible addition-fragmentation chain-transfer polymerization (PET-RAFT), atom transfer radical polymerization (ATRP), cationic polymerization (CP) and free radical polymerization (FRP). Carbon family materials play significant roles in the applications of visible light-induced photopolymerization, such as 3D printing and hydrogel materials fabrication. Specifically, they can not only initiate photopolymerization but also endow products with specific chemical or physical properties, e.g., nontoxic, economical, and facile synthesis routes. Finally, reports on newly developed carbon-family nanomaterials, such as silicon quantum dots, are introduced and discussed as perspectives for photopolymerization, which could inspire researchers in the relevant fields.

Research over dye-sensitized hydrogen generation using TiO₂ semiconductor photocatalysts has gained abiding importance over the past three decades due to its manifold advantages over other photocatalytic systems for the production of clean energy fuels. The single-step excitation of the electrons over the sensitizer molecules anchored at the TiO₂ semiconductor serves as a driving source to facilitate the electron effect transfers, thus prompting the visible-light driven photocatalytic hydrogen generation activities. Though many review articles that evaluate the performance of such dye-sensitized semiconductor particulate systems are available in the literature, research progress made in the last few years since 2016 is not yet systematically reviewed. In this article, we therefore, systematically review the development of new dye-sensitizers that include metal-free organic dyes, metal-based sensitizers, and donor-bridged-acceptor (D-π-A) type dye-sensitizers, and their performances in sensitization of the TiO₂ semiconductor photocatalyst towards visible light driven hydrogen generation through water splitting. It has been chronicled that the aforesaid sensitizers are capable of harvesting a broader part of the solar spectrum, and could achieve photocatalytic H₂ production with varying degrees of success. The results discussed in this review afford a significant scope of rationalizating the factors that govern the H₂ production activity over the dye-modified TiO₂ photocatalyst, and provide a basis for further research towards the realization of high-performing dye-sensitized H₂ production photocatalytic system. The prospect of artificial intelligence (AI)-machine learning (ML) based modeling for quicker design and development of dye-sensitized TiO₂ based photocatalytic solar to fuel conversion system has been briefly discussed in the article.