Chemphyschem最新文献

Herein, we employed a combination of static electronic structure calculations and nonadiabatic dynamics simulations at linear-response time dependent density functional theory (LR-TDDFT) level with the optimally tuned range-separated hybrid (OT-RSH) functional to explore the ultrafast photoinduced dynamics of a zinc phthalocyanine-benzoperylenetriimide (ZnPc-BPTI) conjugate. Due to the flexibility of the linker, we identified two major conformations: the stacked conformation (ZnPc-BPTI-1) and the extended conformation (ZnPc-BPTI-2). Since the charge transfer states are much lower than the lowest local excitation in ZnPc-BPTI-1, which is contrary to ZnPc-BPTI-2, the ultrafast electron transfer (~3.6 ps) is only observed in the nonadiabatic simulations of ZnPc-BPTI-1 upon local excitation around the absorption maximum of ZnPc. However, when considering the solvent effects in benzonitrile: the lowest S₁ states are both charge transfer states from ZnPc to BPTI for different conformers. Subsequent nonadiabatic dynamics simulations indicate that both conformers experience ultrafast electron transfer in benzonitrile with two time constants of 90 [100] fs and 1.40 [1.43] ps. Our present work not only agrees well with previous experimental study, but also points out the important role of conformational changes and solvent effects in regulating the photodynamics of organic donor-acceptor conjugates.

The utilization of liquid crystals (LC) as materials has enabled the enlargement of lenses with the potential to alter their focus. Tunable LC lenses with adjustable focus are essential for optical imaging, sensing, and detection devices. This technology offers many benefits, such as the ability to adjust focus, operate with low power, and be easily made. Its compact structure and stability are also advantages. Adding polymer additives to pure LC systems enhances their capabilities and provides more flexibility and functionality. This review explores ways to enhance the performance of tunable LC lenses, including image quality, speed, optical power, and device fabrication. Especially, enhancements include a switchable focus range, wider viewing angles, and a flexible lens. The challenges in fabricating and controlling LC methods have significant implications for many potential applications. The discovery of new LC materials and lens designs will further highlight these implications.

Catalytic NO reduction by CO is imperative to satisfy the increasingly rigorous emission regulations. Identifying the structural characteristic of crucial intermediate that governs the selectivity of NO reduction is pivotal to having a fundamental understanding on real-life catalysis. Herein, benefiting from the state-of-the-art mass spectrometry, we demonstrated experimentally that the Cu₂VO_3-5 ^- clusters can mediate the catalysis of NO reduction by CO, and two competitive channels to generate N₂O and N₂ can co-exist. Quantum-chemical calculations were performed to rationalize this selectivity. The formation of the ONNO unit on the Cu₂ dimer was demonstrated to be a precursor from which two pathways of NO reduction start to emerge. In the pathway of N₂O generation, only the Cu₂ dimer was oxidized and the VO₃ moiety functions as a "support", while both moieties have to contribute to anchor oxygen atoms from the ONNO unit and then N₂ can be generated. This finding displays a clear picture to elucidate how and why the involvement of VO₃ "support" can regulate the selectivity of NO reduction.

Both, molecular chemical reactions and transport of atoms in solid media are determined by the energy landscape in which the seemingly different processes take place. Chemical reactions can be described as cooperative translocation of two chemical entities on a common potential energy surface. Transport of atoms in a solid can be envisaged as the translocation of a single particle in the potential energy landscape of all other particles constituting the solid. The goal of this manuscript is to demonstrate common grounds but also distinct differences in the physico-chemical processes, their experimental quantification and their theoretical modelling. This work will span the range from the historical foundations all the way to the current challenges. While scientists at the beginning of the 20^th century where commonly active in both fields, e. g., Wilhelm Jost has pioneered and shaped the field of transport in solids and reaction kinetics in Germany, the fields have drifted apart for the last 50 decades. It is now time to bring the fields together again. Ultimately, it is suggested that knowledge gained in the field of transport may in fact stimulate advancement in the field of molecular reactivity and vice versa. Here, the energy landscapes are pivotal for knowledge-based advancement.

Scanning Transmission X-ray microscopy (STXM) is a sensitive and selective probe for the penetration of rapamycin which is topically applied to human skin ex vivo and is facilitated by skin treatment with microneedles puncturing the skin. Inner-shell excitation serves as a selective probe for detecting rapamycin by changes in optical density as well as linear combination modeling using reference spectra of the most abundant species. The results indicate that mechanical damage induced by microneedles allows this drug to accumulate in the stratum corneum without reaching the viable skin layers. This is unlike intact skin which shows no drug penetration at all and underscores the mechanical impact of microneedle skin treatment. These results are compared to drug penetration profiles of other drugs highlighting the importance of skin barriers. High spatial resolution studies also indicate that the lipophilic drug rapamycin is observed in corneocytes. Attempts in data evaluation are reported to probe rapamycin also in the lipid layers between the corneocytes, which was not accomplished before. These results are compared to recent results on rapamycin uptake in skin where barrier impairment was induced by pre-treatment with the enzyme trypsin and drug formulations leading to occlusion.

The reaction mechanisms and corresponding structure-activity relationships of tertiary amines with respect to CO₂ capture have been investigated using density functional theory (DFT) calculations. The reaction mechanism for CO₂ capture via base-catalyzed hydration to form bicarbonate is proposed to proceed in a single step involving proton transfer and the formation of a carbon-oxygen bond. Based on the height of the reaction barriers, we suggest that amines containing side chains with the ethyl group, along with a single hydroxyl group, and cyclic structures, are especially active for CO₂ capture. The activation barrier is shown to be a descriptor for predicting the experimental CO₂ loading values. To enhance the prediction accuracy for CO₂ loading, we employ the sure-independence screening and sparsifying operator (SISSO) method, which can scan a large pool of mathematical terms stemming from combining DFT-derived descriptors to select the superior ones. Thus, we can predict the CO₂ loading with acceptable accuracy from the obtained mathematical expression. Since the computational workload of applying this expression is negligible, this facilitates high-throughput screening and accelerates the design of tertiary amines for CO₂ capture.

Herein, we synthesized a series of catalysts comprising iron (Fe), and nickel (Ni) supported on γ-Al₂O₃ nano-powder (Fe-Ni/γ-Al₂O₃) by controlling the stoichiometric ratio of the metals through the facile co-precipitation method. The ratio of Fe and Ni on the γ-Al₂O₃ support varied from 0 to 70 weight percent (wt %). The freshly prepared catalysts phase, structure, and crystallinity exhibited variability as the Fe and Ni stoichiometric ratios were altered. The catalyst demonstrated effective performance in methane cracking, producing turquoise hydrogen and carbon nanotubes (CNTs) using a temperature-programmed reactor coupled with mass spectrometry. It was observed that the Fe3Ni4 catalyst, comprising 30 % Fe and 40 % Ni, exhibited a maximum methane conversion rate of 85 % and a hydrogen yield of 72.55 %. Moreover, the values of turnover frequency (2.38 min^-1) indicated that the Fe3Ni4 had a better production rate and was consistent with the conversion process throughout the reaction. The structural attributes of the spent catalysts were examined, revealing variations in the lateral length, uniformity, and diameters (~33 to 56 nm) of the produced Carbon Nanotubes (CNTs) when transitioning from catalyst Fe0Ni7 to Fe7Ni0. The investigation underscored the significance of metal stoichiometrically controlled catalysts and their catalytic efficacy in methane cracking applications.

Molecular ferroelectrics are emerging as a robust family of electric-ordered materials due to their distinct structural flexibility, molecular tunability, and versatility. In recent years, diverse chemical design approaches have significantly contributed to discovering and optimizing ferroelectric performances of molecule-based ferroelectric systems. Notably, halogen substitution is one of the most effective strategies for inducing symmetry breaking and optimizing the dipole moments and potential energy barriers. In this minireview, we have summarized recent significant advances of halogen substitution strategy in molecule-based ferroelectrics, including organic-inorganic hybrids and metal-free molecular systems. Subsequently, we discuss the underlying mechanism of halogen substitution to improve ferroelectric performances, including the generation of spontaneous polarization, enhancement of Curie temperature, and bandgap engineering. Finally, the future directions in designing and modulating molecular ferroelectrics by halogen substitution strategy are also highlighted.

Recent advancements in signal amplifiers, such as biofunctionalized gold nanoparticles (AuNPs) have improved the surface plasmon resonance (SPR) performance. However, the correlation between the sizes of DNA-Au conjugates and the SPR chips remains elusive. We investigated how the size of AuNPs functioned with DNA detection probes (D-AuNPs) affect SPR signals in sandwich DNA hybridization assays. The effects of three sizes (5, 13, and 29 nm) of D-AuNPs with an equal surface probe density were systematically compared to delineate the relationship between signal amplification and steric hindrance. Sporadically adsorbed target DNA on sparse capture probe-coated chips led to a growth of signal amplification with larger D-AuNPs. In contrast, on dense capture probe-coated SPR chips, when the target DNA concentration was above 1.5 nM, the medium-sized 13 nm AuNPs displayed 1.7- and 1.3-fold enhancement factors than 5 nm and 29 nm ones, respectively. Our results indicate the steric hindrance disturbs the capture of D-AuNPs on dense target DNA-modified chips, rendering the surface density of captured D-AuNPs a determining factor of the sensor response. Alternatively, the sensor sensitivity to D-AuNP surface density is crucial on chips with sparse target DNA. These insights should stimulate and guide future research on surface functionalization toward SPR sensors and AuNPs.

Organic field-effect transistors (OFETs) with good flexibility and low operating voltage, are of great meaning for the low power stretchable and wearable electronic devices. The operating voltage and flexibility are easily affected by the dielectric layers in the OFETs. Bilayer dielectrics comprising both high- and low-permittivity (k) insulating polymers, have been reported. The flexible bilayer dielectrics can combine the advantages of both insulating polymers, which are high charge carriers from low-k polymers and low operating voltage from high-k polymers. However, the effect of film thicknesses in the bilayer dielectrics on the OFET performance is seldom investigated. Here, bilayer dielectrics comprising high-k polyvinyl alcohol (PVA) and low-k polymethylmethacrylate (PMMA) were fabricated. And PVA/PMMA bilayers with three different PVA film thicknesses are carefully investigated. The 300 nm PVA/100 nm PMMA bilayer dielectric makes the pentacene OFETs show the highest hole mobility of 1.24 cm² V^-1s^-1 and the corresponding inverters give a high voltage gain of 40 and a noise margin of 2.3 V (77 % of 1/2 V_DD) at low operating voltage of 6 V. Both the pentacene transistors and the inverters still work properly under bending radium of 5.85 mm, proving the good prospects of the PVA/PMMA bilayer dielectric in practical applications.