Topics in Current Chemistry最新文献

Organic mechanofluorochromic (MFC)?materials (that change their emission under anisotropic and isotropic pressure) have attracted a?great attention in recent years due to their promising applications in sensing pressure, storage devices, security inks, three-dimensional (3D) printing, etc. Stimuli-responsive organic materials with aggregation-induced emission (AIE) characteristics would be an interesting class of materials to enrich the chemistry of MFC compounds. A diamond anvil cell (DAC) is a small tool that is employed to generate high and uniform pressure on materials over a small area. This article discusses the relationship between the chemical structure of AIE compounds and the change in emission properties under anisotropic (mechanical grinding) and isotropic (hydrostatic) pressure. The luminescent properties of such materials depend on the molecular rearrangement in the lattice, conformational changes, excited state transitions and weak intermolecular interactions. Hence, studying the change in luminescent property of these compounds under varying pressure will provide a deeper understanding of the excited-state properties of various emissive compounds with stress. The development of such materials and studies into the effect of pressure on their luminescence properties are summarized.

Atomistic machine learning (AML) simulations are used in chemistry at an ever-increasing pace. A large number of AML models has been developed, but their implementations are scattered among different packages, each with its own conventions for input and output. Thus, here we give an overview of our MLatom 2 software package, which provides an integrative platform for a wide variety of AML simulations by implementing from scratch and interfacing existing software for a range of state-of-the-art models. These include kernel method-based model types such as KREG (native implementation), sGDML, and GAP-SOAP as well as neural-network-based model types such as ANI, DeepPot-SE, and PhysNet. The theoretical foundations behind these methods are overviewed too. The modular structure of MLatom allows for easy extension to more AML model types. MLatom 2 also has many other capabilities useful for AML simulations, such as the support of custom descriptors, farthest-point and structure-based sampling, hyperparameter optimization, model evaluation, and automatic learning curve generation. It can also be used for such multi-step tasks as Δ-learning, self-correction approaches, and absorption spectrum simulation within the machine-learning nuclear-ensemble approach. Several of these MLatom 2 capabilities are showcased in application examples.

As proficient photovoltaic devices, dye-sensitized solar cells (DSSCs) have received considerable consideration in recent years. In order to accomplish advanced solar-to-electricity efficiency and increase long-term functioning stability, improvements in the configuration structure of DSSCs are essential, as is an understanding of their elementary principles. This work discusses the application of different semiconductor constituents designed for effective DSSCs. The main parameters crucial to fabrication of DSSC electrodes in nano-porous semiconductor structures are high surface area and large pore size. Different inorganic semiconductor materials are used to load sensitizer dyes, which absorb a lot of light and induce high photocurrent for efficient DSSCs. The first section of the review covers energy sources, photovoltaics, and the benefits of solar cells in daily life, while the second part includes the various types of semiconductors applied in DSSC applications. The final section provides a brief review of future perspectives for DSSCs and a survey of semiconductor materials proposed for solar cell applications.

Chitosan is a very well-known biocompatible and biodegradable polysaccharide consisting of β-(1–4)-linked glucosamine units, derived from the deacetylation of chitin. This unique biopolymer consists of primary amines as well as hydrophilic hydroxyl groups along with the chitosan backbone and has exceptional properties and wide applications. Numerous articles have been devoted to the preparation and properties of chitosan-based biomaterials, which have been demonstrated as beads, films, fibers (2D-scaffolds), gels, sponges (3D-scaffolds), and wound-healing materials. The unusual adsorption capacity of chitosan cross-linked polymer is demonstrated by trapping cations, anions, organic dyes, and pharmaceutical ingredients from wastewater. The most striking manifestations of flexibility in the preparation of these adsorbents have been critically reviewed, and their sorption efficiencies compared. Notably, these materials are also used as drug delivery carriers. Further, various metal-loaded chitosan-based nanocomposite materials have been used efficiently in organic catalytic reactions. As per the rich literature survey, such chitosan-based materials warrant further research due to their abundance, eco-friendliness, and effectiveness towards commercialization. The biotechnological aspects of chitosan may lead to promising low-cost materials and by-products of industrial and agricultural significance. The constant demand for potential adsorbents for the removal of pollutants, can be met by fine-tuning the structural properties of chitosan with appropriate cross-linkers or additives.

Excitation energy transfer (EET) as a fundamental photophysical process is well-explored for developing functional materials with tunable photophysical properties. Compared to traditional fluorophores, aggregation-induced emission luminogens (AIEgens) exhibit unique advantages for building EET systems, especially serving as energy donors, due to their outstanding photophysical properties such as bright fluorescence in aggregation state, broad absorption and emission spectra, large Stokes shift, and high photobleaching resistance. In addition, the photophysical properties of AIEgens can be modulated by energy transfer for improved luminescence performance. Therefore, a variety of EET systems based on AIEgens have been constructed and their applications in different areas have been explored. In this review, we summarize recent progress in the design strategy of AIE-based energy transfer systems for light-harvesting, fluorescent probes and theranostic systems, with an emphasis on design strategies to achieve desirable properties. The limitations, challenges and future opportunities of AIE–EET systems are briefly outlined.

Design strategies and applications (light-harvesting, fluorescent probe and theranostics) of AIEgen-based excitation energy systems are discussed in this review.

Aggregation induced emission (AIE) luminogens (AIEgens) have great potential in the field of organic optoelectronic devices because of their highly efficient emission property in solid state. For example, high efficiency organic light-emitting diodes (OLEDs) based on AIEgens have been developed successfully. Some AIEgens also show good photovoltaic response properties for organic solar cells (OSCs) and organic photodetectors (OPDs), and lasing properties for optically pumping organic lasers (OLs). The review will cover the status and prospects of AIEgens in OLEDs, OLs, OSCs and OPDs. It is expected that AIEgens will become an important organic optoelectronic material system in the future.

The enhancement of photoluminescence through formation of molecular aggregates in organic oligomers and conjugated organic polymers is reviewed. A historical contextualization of aggregation-induced emission (AIE) phenomena is presented. This includes the loose bolt or free rotor effect and J-aggregation phenomena, and discusses their characteristic features, including structures and mechanisms. The basis of both effects is examined in key molecules, with a particular emphasis on the AIE effect occurring in conjugated organic polymers with a polythiophene (PT) skeleton with triphenylethylene (TPE) units. Rigidification of the excited state structure is one of the defining conditions required to obtain AIE, and thus, by changing from a flexible ground state to rigid (quinoidal-like) structures, oligo and PTs are among the most promising emerging molecules alongside?with the more extensively used TPE derivatives. Molecular structures moving away from the domination of aggregation-caused quenching to AIE are presented. Future perspectives for the rational design of AIEgen structures are discussed.

The development of multimodal nanoprobes has been growing?in recent years. Among these novel nanostructures are bimodal systems based on quantum dots (QDs) and low molecular weight Gd³⁺ chelates, prepared for magnetic resonance imaging (MRI) and optical analyses. MRI is a technique used worldwide that provides anatomic resolution and allows distinguishing of physiological differences at tissue and organ level. On the other hand, optical techniques are very sensitive and allow events to be followed at the cellular or molecular level. Thus, the association of these two techniques has the potential to achieve a more complete comprehension of biological processes. In this review, we present state-of-the-art research concerning the development of potential multimodal optical/paramagnetic nanoprobes based on Gd³⁺ chelates and QDs, highlighting their preparation strategies and overall properties.

Fluorescence imaging is an important method in the field of biomedicine. Fluorescence imaging is nondestructive, has high efficiency and sensitivity, high resolution and allows real-time dynamic monitoring of living cells. However, it also has some disadvantages, such as high background signals and low selectivity. Bioorthogonal reactions, with the advantages of being both nondestructive and effective, are used to trace and analyze biological interactions in vivo. This review focuses on recent progress in understanding the mechanism of action of fluorescence probes.