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

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.

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.

Triplet-triplet annihilation photon up-conversion (TTA-PUC) has gained immense attention among the scientific community in the last decade due to its application in the fields of energy, biology, and photocatalytic organic synthesis. One of the main aims to improve the efficiency of these low-to-high photon-energy conversion is to reduce energy losses during the intersystem crossing (ISC). Since 2015, many strategies have been reported to address this challenge and a significant update has been noticed in this field. This review is aimed to critically analyze these updates and provide an outlook for the future. A detailed mechanism of ISC in thermally activated delayed-fluorescence (TADF) molecules that possess a small singlet−triplet energy gap, is discussed with a focus on its deeper understanding and the impact of molecular design. In this context, a range of selected organic and inorganic TADF molecules are thoroughly evaluated. Osmium(II) complexes that exhibit a spin-forbidden metal-to-ligand charge-transfer (³MLCT) transition in their Vis-NIR-IR absorption spectra and can be excited directly into their triplet state, thereby bypassing the energy loss during ISC, are also debated in sufficient detail for their advantages as well as shortcomings in being used in TTA-PUC. This work aims at reviewing the latest progress in this field, understanding the fundamental ISC mechanism of these photosensitizers, and critically addressing the challenges that are faced in this field. This review is anticipated to serve as a helpful script for identifying future directions and designing molecular sensitizers for TTA-PUC, which can sensitize the triplet state with minimum energy loss during ISC and can be helpful for increasing the anti-Stokes shift in TTA-PUC.

Mitochondria is the cell's energy powerhouse and regulate most of the metabolism process through the inherent mitochondrial genes (mtDNA). The control of mtDNA replication and transcription is known to be mediated by noncanonical forms of guanine-rich nucleotides G-quadruplexes (G4s). These putative and transient guanine-based structures and their dynamics are closely associated with mtDNA deletion breakpoints pertaining to fatal diseases such as cancers, hypertension, diabetes, etc. The precise reason for the origin of G4s at deletion breakpoints in the heavy strand and during the replication process has not yet been identified, owing to its complex biochemical phenomenon. Biomolecular structure, typically having a size of 5–10 nm with an average life span of seconds, strongly demands high-end instruments to explore the precise biochemical mechanism and dynamics (folding or unfolding) in biological systems. In that sense, since the last decade, tremendous efforts have been kept in X-ray crystallography, circular dichroism spectroscopy (CD), nuclear magnetic resonance spectroscopy (NMR), immunofluorescence, and the mtG4-ChIP methods to recognize and characterize the G4s structures in physiological conditions. Owing to their non-invasiveness, robustness, and high spatio-temporal resolution at the molecular level, fluorescence methods have been exploited to recognize noncanonical forms of nucleic acids even at the subcellular level. In light of this, from 2015 until today, the documentation of photophysical and bioanalytical capabilities of mtG4s recognizing small and quencher-free fluorescent probes has not yet been reported. Considering the plethora of G4s propensity with mtDNA replication, transcription, oxidative phosphorylation, glycolysis etc. In the current article, we have systematically documented small fluorescent probes that have been exclusively used to recognize mtG4 in cellular conditions with photophysical and biophysical properties. Furthermore, the probe's designing rationale binding mechanism, readout system, cellular localization, and cytotoxicity were tabulated.

Bottom-up strategies have allowed the synthesis of “molecular” nanographenes with full control over size, shape and functionality. In recent years, the progress on wet chemical approaches, oxidative cyclodehydrogenation amongst all, has been the foundation to the synthesis of an impressive number of soluble and well-defined molecular nanographenes. The level of control over nanographene syntheses has allowed a fine-tuning of the photophysical and electrochemical properties and, in turn, has a compelling potential in the field of material science. In this regard, understanding and harnessing the competition between electron transfer and energy transfer in nanographenic systems is of utmost importance. However, a comprehensive structure-property relationship remains still an open aspect. In the present review we describe a large variety of hexa-peri-hexabenzocoronene (HBC)-based nanographenes obtained through wet chemical strategies and linked – either covalently or non-covalently – to porphyrins, rylenes, fullerenes, etc. Particular attention was placed on the optical, electrochemical and excited-state properties.

Spectral microscopy provides information about the spatial distribution and physiological functional states of pigment-protein complexes in photosynthetic organisms. This can be used to complement the newly developed techniques, such as cryogenic electron microscopy and atomic force microscopy, which are less effective in functional analysis of photosynthesis, despite having an excellent spatial resolution. The combination of optical microscopies with various spectroscopic techniques has extended the possibility of a multi-perspective investigation in photosynthesis research. Some of these spectroscopic techniques include fluorescence and absorption spectra, excitation spectra, time-resolved fluorescence measurement, Raman scattering spectroscopy, etc. These techniques can be applied to in vivo investigations of photosynthetic activity without introducing any artificial fluorophore since the photosynthetic pigments are informative probes. In particular, the technique has been effective in clarifying the dynamic physiological responses of photosynthetic organisms to variable environments. In this paper, we review the recent progress in spectral microscopy in the field of in vivo photosynthesis research. We have also introduced and discussed some distinctive spectral microscopies such as anti-Stokes fluorescence spectral microscopy, excitation spectral microscopy, cryo-microscopy, and Raman spectral microscopy.

A review regarding the studies of light-sensitive systems based on bacteriorhodopsin is presented. Briefly given are modern ideas about bacteriorhodopsin and its molecular properties, about the photocycle of its transformation. The possibilities and ways of bacteriorhodopsin modifications are shown, in particular, such as dehydration, modification using chemical additives, changing the primary protein sequence by use of genetic mutants of bacteriorhodopsin, replacing the chromophore with its synthesized analogues. Such modifications can optimize the use of bacteriorhodopsin to create photosensitive recording media. Particular attention is paid to various areas of possible applications of light-sensitive materials of this type, in particular, polymer films based on bacteriorhodopsin and its derivatives, the so-called Biochrome films. The possibilities of using BR-based polymer films not only as a photochromic material for multiple recording, but also as a material for write-once recording and permanent memory (the so-called material for write-once recording of optical information) are also considered.

In the past three decades, dye-sensitized solar cells (DSSCs) have gained increased recognition as a potential substitute for inexpensive photovoltaic (PV) devices, and their maximum efficiency has grown from 7% to 14.3%. Recent developments in DSSCs have attracted a plethora of research activities geared at realizing their full potential. DSSCs have seen a revival as the finest technology for specific applications with unique features such as low-cost, non-toxic, colourful, transparent, ease of fabrication, flexibility, and efficient indoor light operation. Several organic materials are being explored and employed in DSSCs to enhance their performance, robustness, and lower production costs to be viable alternatives in the solar cell markets. This review provides a concise summary of the developments in the field over the past decade, with a special focus on the incorporation of organic materials into DSSCs. It covers all elements of the DSSC technology, including practical approaches and novel materials. Finally, the emerging applications of DSSCs, and their future promise are also discussed.