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

In the last decade, the field of stimuli-responsive luminescent materials have been intensely emerged because of the high potential application to functional sensors or photoelectronic devices. In particular, luminescent molecular crystals constructed from Au(I) complexes have produced a wide range of examples of luminescent alterations when some external stimulations, such as heat, mechanical stress, vapor (or solvents), were applied to the solid samples. In this review, we describe the recent progress through a summary of the reported Au(I) complexes based on their utilized stimuli-responsive mechanisms, which are categorized in crystal phase transitions (“crystal-to-amorphous”, “crystal-to-crystal” and “single-crystal-to-single-crystal” transitions) and molecular rotation in crystalline media, respectively.

Energy production and environmental pollution are the two major problems the world is facing today. The depletion of fossil fuels and the emission of harmful gases into the atmosphere leads to the research on clean and renewable energy sources. In this context, hydrogen is considered an ideal fuel to meet global energy needs. Presently, hydrogen is produced from fossil fuels. However, the most desirable way is from clean and renewable energy sources, like water and sunlight. Sunlight is an abundant energy source for energy harvesting and utilization. Recent studies reveal that photoelectrochemical (PEC) water splitting has promise for solar to hydrogen (STH) conversion over the widely tested photocatalytic approach since hydrogen and oxygen gases can be quantified easily in PEC. For designing light-absorbing materials, semiconductors are the primary choice that undergoes excitation upon solar light irradiation to produce excitons (electron-hole pairs) to drive the electrolysis. Visible light active semiconductors are attractive to achieve high solar to chemical fuel conversion. However, pure semiconductor materials are far from practical applications because of charge carrier recombination, poor light-harvesting, and electrode degradation. Various heteronanostructures by the integration of metal plasmons overcome these issues. The incorporation of metal plasmons gained significance for improving the PEC water splitting performance. This review summarizes the possible main mechanisms such as plasmon-induced resonance energy transfer (PIRET), hot electron injection (HEI), and light scatting/trapping. It also deliberates the rational design of plasmonic structures for PEC water splitting. Furthermore, this review highlights the advantages of plasmonic metal-supported photoelectrodes for PEC water splitting.

This review summarizes several aspects of type II photoactive organic-inorganic hybrid materials prepared from silylated fluorophores, including their photophysical properties and uses. In this sense, several examples are presented and discussed taking the nature of the silyl derivative into account. Applications as latent fingerprints detection, chemosensors for metal cations, anions, pH, heavy metals, and small organic molecules, as well as recent use as drug delivery systems, bioimaging, organic solar cells, aerogels, and highly fluorescent hybrid materials, are reported and compared to the literature. Also, fluorescent type II organic-inorganic hybrid materials from non-silylated fluorophores, prepared with binding agents, such as 3-(triethoxysilyl)propyl isocyanate (TESPIC), 3-mercaptopropyltriethoxysilane (TMMPS), or 3-isocyanato propyltrimethoxysilane (ICPTES) are also covered in this review.

Photochromic compounds are of great interest currently owing to their potential applications. Their three-dimensional structure must be clarified to understand the photochromism mechanism. In-situ X-ray crystal structure analysis is a powerful tool for determining the structure directly after the photochromic reaction. In this review, I discuss about solid-state photochromic compounds, their direct X-ray observation in the crystal form, and in-situ control of photochromism in “dual photoreactive soft crystals”, which is a novel approach.

Functionalized fullerenes have shown interesting biomedical applications as potential phototherapeutic agents. The hydrophobic carbon sphere of fullerene C₆₀ can be substituted by cationic groups to obtain amphiphilic structures. These compounds absorb mainly UV light, but absorption in the visible region can be enhanced by anchoring light-harvesting antennas to the C₆₀ core. Upon photoexcitation, fullerenes act as spin converters by effective intersystem crossing. From this excited state, they can react with ground state molecular oxygen and other substrates to form reactive oxygen species. This process leads to the formation of singlet molecular oxygen by energy transfer or superoxide anion radical by electron transfer. Photodynamic inactivation experiments indicate that cationic fullerenes are highly effective photosensitizers with applications as broad-spectrum antimicrobial agents. In these structures, the hydrophobic character of C₆₀ improves membrane penetration, while the presence of positive charges increases the binding of the fullerene derivatives with microbial cells. Herein, we summarize the progress of antimicrobial photodynamic inactivation based on substituted fullerenes specially designed to improve the photodynamic activity.

Converting methane and carbon dioxide into hydrogen and carbon monoxide is significant and attractive because it can mitigate the greenhouse effect and produce useful chemical intermediate. However, these two greenhouse gases are challenging to convert due to their high bond energy and chemically inert. Although thermocatalytic dry reforming of methane (DRM) achieves high efficiency, it requires high energy and often causes deactivation due to carbon deposition. Recently, a lot of research results show that photo-enhanced DRM is a promising and green route for this reaction under relatively mild conditions. This review first introduces the importance and challenge of CH₄ and CO₂ conversion. Then, we summarize the related reports of photo-enhanced dry reforming of methane in detail, including material preparation, experimental conditions and results, and mechanism study. In particular, the related studies have been classified according to types of input energy and the types of catalyst. Finally, we provide insightful perspectives and prospects for the future development of this field.

Supramolecular optical chemosensors are useful tools in analytical chemistry for the visualization of molecular recognition information. One advantage is that they can be utilized for array systems to detect multiple analytes. However, chemosensor arrays have been evaluated mainly in the solution phase, which limits a wide range of practical applications. Thus, appropriate solid support materials such as polymer gels and papers are required to broaden the scope of the application of chemosensors as on-site analytical tools. In this review, we summarize the actual approaches for the fabrication of solid-state chemosensor arrays combined with powerful data processing techniques and portable digital recorders for real-world applications.

Mechano-responsive luminescence, or mechanochromic luminescence (MCL), is a type of luminescence that can be reversibly controlled by the addition of mechanical stimuli. Organic materials exhibiting MCL have been an ongoing area of development since the early 2000s, and the number of reports into such materials has been steadily increasing. While the majority of MCL systems rely on the brittle nature of organic crystalline solids, there is a growing interest in "flexible" organic crystals that exhibit mechanical bending or shape deformation owing to their elasticity/plasticity. Such non-destructive deformed crystals may exhibit a new type of MCL that can be controlled by the magnitude of the force stress. In this review, we describe MCL systems capable of the spontaneous recovery of changes in their luminescent properties in response to the loading/unloading of mechanical stress. We particularly focus on the MCL of flexible crystals based on the density gradient of molecular packing (i.e., elastic and plastic crystals) and an emerging system known as "superelastochromism,” which is based on spontaneously reversible crystal polymorphism. This emerging research area has the potential to play an important role in the promotion of next-generation soft crystals.

Luminescent lanthanide (Ln) complexes are attracted much attention because of their stable emission colors induced by the photo-antenna effect through the photo-excited energy transfer from aromatic ligands to Ln ions. Here, we will introduce some systems of luminescent Ln complexes with metastable states with the phase transition induced by water and other small molecules, the relative arrangement of hydrogel formation and Ln luminescence enhancement, and the diversity of the thin air-water interface. The energy donor levels in each system should be designed to sensitize Ln-luminescence with the consideration of media, interaction and assembling. Luminescence quenching of Ln complexes in water is a point that should be considered for the development of materials and for the purpose of bio-related materials. Then, the principle of the change in luminescence intensity by the effect of water molecules is described, and the estimation of a hydrated structure of the complex is estimated using the luminescence lifetimes in H₂O and D₂O. The molecular arrangement of these crystals changes under the vapor-stimuli, and the coloration and luminescence may be enhanced. Some interesting cases of luminescent Ln complexes with the crystal-to-crystal phase transitions will be introduced with the vapor adsorption. Hydrogels are mostly water by volume; a system in which Ln luminescence is maintained implies that Ln ions are placed in hydrophobic positions in self-assemblies with strong luminescence. The formation of thin films at the molecular level and their Ln luminescence properties are introduced. For example, when a monolayer of a surface-active Ln complex is formed at the air-water interface, the repeated accumulation of the flexible film forms a metastable structure with a regular structure different from that of a crystal, and no water is incorporated into the film. These can not only derive circularly or linearly polarized light, but also take in other molecules and change the emission. Finally, we will suggest the prospects for the development of Ln complexes.