Electronic structure and hydrogen bond in the crystal of paracetamol drugs

We study the density of state (DOS), band structure (BS), and atomic orbit projected density of state (PDOS) of paracetamol crystal adopting the density functional theory (DFT) technique in the local density approximation (LDA). The band structure around the Fermi level and the contributions from p-type orbit of C, N, O, and s-type orbit of H to the total density of state (TDOS) are addressed, and we find that the electronic characteristic is the key to form the hydrogen bond between O and H atoms. We show that the structure of paracetamol crystal consists of the –OH···O=C and –NH···OH hydrogen-bonding cycle by studying a single paracetamol molecule as well as the PDOS graph of O and H atoms in the crystal.     

Theoretical investigation of nitration and nitrosation of dimethylamine by N2O4

Reactive nitrogen oxygen species (RNOS) contribute to the deleterious effects attributed to reacting with biomolecules. The mechanisms of the nitration and nitrosation of dimethylamine (DMA), which is the simplest secondary amine by N2O4, a member of RNOS, have been investigated at the CBS-QB3 level of theory. The nitration and nitrosation proceed via different pathways. The nitration of DMA follows three pathways. The first is the abstraction of the hydrogen atom of the amino group of DMA by the NO2 radical followed by a recombination reaction of the resulting aminyl radical with another NO2 radical. The second is DMA directly reacting with symmetrical O2NNO2 leading to dimethylnitramine via a concerted and a stepwise mechanism. The third is the reaction of DMA with asymmetrical ONONO2. By computation, the main pathway for the formation of dimethylnitramine in the gas phase is by DMA directly reacting with asymmetrical ONONO2. As to the nitrosation, a concerted mechanism for the reaction of DMA with asymmetrical ONONO2 plays a major role in nitrosodimethylamine (NDMA) formation. In addition, the solvent effect on these nitration and nitrosation reactions has been also studied by using the implicit polarizable continuum model. Two major pathways of the formation of dimethylnitramine in water were found, and they are the radical process involving NO2 and the concerted mechanism starting from symmetrical O2NNO2. The result of the nitrosation of DMA in water is consistent with that in the gas phase. Comparison of the energy barriers of each mechanism leads to the conclusion that the nitrosation is more favorable than the nitration in the reaction of DMA with N2O4. This conclusion is in good agreement with the experimental results. The results obtained here will help elucidate the mechanism of the lesions of biomolecules by RNOS.     

Methylene Blue/Carbon Dots Composite with Photothermal and Photodynamic Properties: Synthesis,Characterization, and Antibacterial Application

Photodynamic therapy and photothermal therapy provide new ways to combat antibiotic resistance. In this research, methylene blue (MB) as an effective photosensitizer was conjugated with carbon quantum dots (CQDs), the composite product not only possessed good antibacterial properties against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) due to excellent singlet oxygen (¹O₂) production rate and light heat transfer performance, but also showed good biocompatibility. Combined with 808 nm and 660 nm laser irradiation, the minimum bactericidal concentration of CQDs-MB towards S. aureus and E. coli was 5 μm . Therefore, this study provides a potential candidate material based on CQDs for clinical applications.     

Observation of Asymmetric Oxidation Catalysis with B20 Chiral Crystals**

The study of heterogeneous reactions for enantiomeric processes based on inorganic crystals has been resurgent in recent years. However, the question remains how homochirality develops in nature and chemical reactions. Here, the successful growth of B20 group PdGa single crystals with different chiral lattices enabled us to achieve enantioselective recognition of 3,4-dihydroxyphenylalanine (DOPA) based on a new mechanism, namely orbital angular momentum (OAM) polarization. The orbital textures of PdGa crystals indicate large OAM polarization near the Fermi level and carrying opposite signs. A positive or negative magnetization in the [111] direction is expected depending on the chiral lattice of PdGa crystals. Due to this, the adsorption energies of PdGa crystals and DOPA molecules differ depending on how well the O-2p orbital of DOPA pairs with the Pd-4d orbital of PdGa. The results provide one possible explanation for how chirality arises in nature by providing an enantioselective route with pure inorganic crystals.     

Amplification of Dissymmetry for Circularly Polarized Photodetection by Cooperative Supramolecular Polymerization

Circularly polarized photodetectors require chiral light absorption materials with high sensing efficiency and low costs. Here readily accessible point chirality has been introduced to dicyanostilbenes as the chiral source, facilitating remote chirality transfer to the π-aromatic core by cooperative supramolecular polymerization. The single-handed supramolecular polymers display powerful circularly polarized photodetection capability with a dissymmetry factor value as high as 0.83, superior to those of π-conjugated small molecules and oligomers. Strong chiral amplification occurs between the enantiopure sergeants and the achiral soldiers. The resulting supramolecular copolymers exhibit comparable photodetection efficiency to those of the homopolymeric ones, with a 90 % decrease in the enantiopure compound consumption. Therefore, cooperative supramolecular polymerization provides an effective yet economical avenue toward circularly polarized photodetection applications.     

Flexible Conductive Decellularized Fish Skin Matrix as a Functional Scaffold for Myocardial Infarction Repair

Engineering cardiac patches are proven to be effective in myocardial infarction (MI) repair, but it is still a tricky problem in tissue engineering to construct a scaffold with good biocompatibility, suitable mechanical properties, and solid structure. Herein, decellularized fish skin matrix is utilized with good biocompatibility to prepare a flexible conductive cardiac patch through polymerization of polydopamine (PDA) and polypyrrole (PPy). Compared with single modification, the double modification strategy facilitated the efficiency of pyrrole polymerization, so that the patch conductivity is improved. According to the results of experiments in vivo and in vitro, the scaffold can promote the maturation and functionalization of cardiomyocytes (CMs). It can also reduce the inflammatory response, increase local microcirculation, and reconstruct the conductive microenvironment in infarcted myocardia, thus improving the cardiac function of MI rats. In addition, the excellent flexibility of the scaffold, which enables it to be implanted in vivo through “folding-delivering-re-stretehing” pathway, provides the possibility of microoperation under endoscope, which avoids the secondary damage to myocardium by traditional thoracotomy for implantation surgery.     

储能薄膜电容器介电高分子材料

高功率密度、高充放电效率以及超长使用寿命等特点是聚合物薄膜电容器能够广泛应用于电动汽车、智能电网等各类电子电气领域中的重要原因。其中,介电高分子材料因其质轻、击穿强度高、易大规模加工等优点赋予了薄膜电容器更多的可能性。但同时,介电高分子的介电常数普遍较低,导致所制备的电容器能量密度偏低因而不能更好地适应设备小型化轻型化的要求。本文概述了电介质以及薄膜电容器的基本原理以及性能参数,着重介绍了以储能为主要研究方向的介电高分子材料,主要包括聚合物基纳米复合介电高分子、偶极玻璃聚合物、交联型介电高分子以及多组分全有机介电高分子。最后对介电高分子在制备性能优异的储能电容器过程中面临的多重挑战和潜在机遇进行了总结。     

Ordered Mesoporous Intermetallic Ga-Pt Nanoparticles: Phase-Controlled Synthesis and Performance in Oxygen Reduction Electrocatalysis

The intermetallic phase control is a promising strategy to optimize the physicochemical properties of ordered intermetallic compounds and engineer their performance in various (electro)catalytic reactions. However, the intermetallic phase-dependent catalytic performance is still rarely reported because of the difficulty in synthesizing ordered intermetallics with precisely controlled phase structures at atomic level, especially having ordered mesoscopic structure/morphology. Here, we successfully reported a precise synthesis of two phase-pure mesoporous intermetallic gallium-platinum (meso-i-Ga-Pt) nanoparticles, including meso-i-Ga₃Pt₅ with an orthorhombic space group and meso-i-Ga₁Pt₁ with a non-symmorphic chiral cubic space group. The intermetallic phase control of ordered meso-i-Ga-Pt nanoparticles was realized by carefully tuning the induced Ga salts with different anions that optimized the free energies during the synthesis. The intermetallic phase-dependent catalytic performance of ordered meso-i-Ga-Pt was systematically evaluated for oxygen reduction reaction (ORR) electrocatalysis, with completely opposite catalytic performance in alkaline media. Interestingly, ordered meso-i-Ga₁Pt₁ catalyst with chiral atomic arrangements disclosed unexpected high ORR activity and stability with 5.9 and 3.2 enhancement factors in mass activity compared to those of meso-i-Ga₃Pt₅ and commercial Pt/C.     

Back Cover: Illustrating the Fate of Methyl Radical in Photocatalytic Methane Oxidation over Ag−ZnO by in situ Synchrotron Radiation Photoionization Mass Spectrometry (Angew. Chem. Int. Ed. 32/2023)

Photocatalysis has emerged as an ideal method for the direct activation and conversion of methane under mild conditions. In this reaction, methyl radical (⋅CH₃) was deemed a key intermediate that affected the yields and selectivity of the products. However, direct observation of ⋅CH₃ and other intermediates is still challenging. Here, a rectangular photocatalytic reactor coupled with in situ synchrotron radiation photoionization mass spectrometry (SR-PIMS) was developed to detect reactive intermediates within several hundred microseconds during photocatalytic methane oxidation over Ag−ZnO. Gas phase ⋅CH₃ generated by photogenerated holes (O⁻) was directly observed, and its formation was demonstrated to be significantly enhanced by coadsorbed oxygen molecules. Methoxy radical (CH₃O⋅) and formaldehyde (HCHO) were confirmed to be key C1 intermediates in photocatalytic methane overoxidation to CO₂. The gas-phase self-coupling reaction of ⋅CH₃ contributes to the formation of ethane, which indicates the key role of ⋅CH₃ desorption in the highly selective synthesis of ethane. Based on the observed intermediates, the reaction network initiated from ⋅CH₃ of photocatalytic methane oxidation could be clearly illustrated, which is helpful for studying the photocatalytic methane conversion processes.