Latest ArticlesSurface fluorination of conventional polymers can give them desirable surface properties similar to the expensive and difficult-to-process fluoropolymers. However, traditional surface fluorination techniques often require toxic reagents and special equipment. Here, we report a simple and effective polymer surface fluorination method by using safe and inexpensive perfluoro-2-methyl-3-pentanone (PFMP, C2F5C(O)CF(CF3)2) and UV irradiation. This method is applicable to various polymer materials, and generates nanometer-thick fluorinated layer on the outermost surface, significantly changing their surface properties without changing the surface morphology.
Developing platinum-group-metal (PGM) catalysts possessing strong metal-support interaction and controllable PGM size is urgent for the sluggish oxygen reduction reaction (ORR) in proton-exchange membrane fuel cells. Herein, we propose an in-situ self-assembled reduction strategy to successfully induce highly-dispersed sub-3 nm platinum nanoparticles (Pt NPs) to attach on resin-derived atomic Co coordinated by N-doped carbon substrate (Pt/CoSA-N-C) for ORR. To be specific, the interfacial electron interaction effect, along with a highly robust CoSA-N-C support endow the as-fabricated Pt/CoSA-N-C catalyst with significantly enhanced catalytic properties, i.e., a mass activity (MA) of 0.719 A/mgPt at 0.9 ViR‑free and a reduction of 24.2% in MA after a 20,000-cycles test. Density functional theory (DFT) calculations demonstrate that the enhanced electron interaction between Pt and CoSA-N-C support decreases the d-band center of Pt, which is in favor of lowering the desorption energy of *OH on Pt/CoSA-N-C surface and accelerating the formation of H2O, thus enhance the instinct activity of ORR. Furthermore, the higher binding energy between Pt and CoSA-N-C compared to Pt and C indicates that the migration of Pt has been suppressed, which theoretically explains the improved durability of Pt/CoSA-N-C. Our work offers an enlightenment on constructing composite Pt-based catalysts with multiple active sites.
A new bismuth-based halide double perovskite Cs2KBiCl6 was isolated successfully through solid-state reactions and investigated using X-ray and neutron diffraction. Rather than an ordered structure, the crystal structure consists of shifted Cs, K, Bi, and Cl sites from the ideal positions with fractional occupancy in compensation, leading to variable local coordination of Cs+ ions, as revealed by 133Cs solid-state nuclear magnetic resonance spectroscopy. Cs2KBiCl6 displays volume hysteresis at 5–298 K range upon heating and cooling. The Cs2KBiCl6 has a direct bandgap of 3.35(2) eV and red-shift luminescence of around 600 nm upon Mn doping compared with the Na analogue. The stabilization of disordered structure in Cs2KBiCl6 is related to two factors including the large-sized K+ cation which prefers to coordinate with more than six Cl−, and the Bi3+ with 6s2 lone pair which has a preference for a local asymmetric environment. These findings could have general application and help to understand the structure and property of halide perovskites.
Ferroelastic hybrid perovskite materials have been revealed the significance in the applications of switches, sensors, actuators, etc. However, it remains a challenge to design high-temperature ferroelastic to meet the requirements for the practical applications. Herein, we reported an one-dimensional organic-inorganic hybrid perovskites (OIHP) (3-methylpyrazolium)CdCl3 (3-MBCC), which possesses a mmmF2/m ferroelastic phase transition at 263 K. Moreover, utilizing crystal engineering, we replace –CH3 with –NH2 and –H, which increases the intermolecular force between organic cations and inorganic frameworks. The phase transition temperature of (3-aminopyrazolium)CdCl3 (3-ABCC), and (pyrazolium)CdCl3 (BCC) increased by 73 K and 10 K, respectively. Particularly, BCC undergoes an unconventional inverse temperature symmetry breaking (ISTB) ferroelastic phase transition around 273 K. Differently, it transforms from a high symmetry low-temperature paraelastic phase (point group 2/m) to a low symmetry high-temperature ferroelastic phase (point group 1) originating from the rare mechanism of displacement of organic cations phase transition. It means that crystal BCC retains in ferroelastic phase above 273 K until melting point (446 K). Furthermore, characteristic ferroelastic domain patterns on crystal BCC are confirmed with polarized optical microscopy. Our study enriches the molecular mechanism of ferroelastics in the family of organic-inorganic hybrids and opens up a new avenue for exploring high-temperature ferroic materials.
Nonradical oxidation has received wide attention in advanced oxidation processes for environmental remediation. Understanding the relationship between material characteristics and their ability to initiate nonradical oxidation processes is the key to better material design and performance. Herein, a novel titanium-based metal-organic framework MIL-125-Ti/H2O2 system was established to show a highly selective degradation efficacy toward tetracycline antibiotics. MIL-125-Ti with the abundance of TiO6 octahedra units was found to effectively activate H2O2 under dark conditions by forming an oxidative Ti-peroxo complex. The presence of the Ti-peroxo complex, confirmed by UV-visible spectrophotometer, fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy characterizations, showed superior degradation (> 95% removal rate) of oxytetracycline hydrochloride (OTC), doxycycline hydrochloride, chlortetracycline hydrochloride, and tetracycline. Density functional theory calculations were performed to assist the elucidation on the mechanism of H2O2 activation and antibiotics degradation. The MIL-125-Ti/H2O2 system was highly resistant to halogens and background organics, and could well maintain its original catalytic activity in actual water matrices. It retained the ability to degrade 75% of OTC within ten test cycles. This study provides new insight into the nonradical oxidation process initiated by the unique Ti-peroxo complex of Ti-based MOF.
A novel cationic Pt(Ⅱ) complex 2 with 2-(2,4-difluorophenyl)pyridine as the cyclometalating ligand and 1,10-phenanthroline as the auxiliary ligand has been synthesized and fully characterized. This complex exhibits much higher aggregation-induced phosphorescent emission activity than that of a non-fluorinated complex 1 in CH3CN/H2O. The complex 2 demonstrates efficient detection on picric acid (PA) in CH3CN/H2O, providing a high quenching constant (KSV = 2.3 × 104 L/mol) and a low limit of detection (LOD = 0.26 µmol/L). In addition, complex 2 shows high selectivity for detection of PA in real water samples. Density functional theory calculations and proton nuclear magnetic resonance spectra suggest that the detection mechanism is attributed to the photo-induced electron transfer.
Ultra-high nickel material is considered to be a promising cathode material. However, with the increase of nickel content, the interfacial side reactions between the cathode and electrolyte become increasingly serious. Herein, an atomically controllable ionic conductor Li3PO4 (LPO) coating is deposited on the LiNi0.90Co0.06Mn0.04O2 (NCM9064) based electrode by the atomic layer deposition method. The results shows that the LPO coating is uniformly and densely covered on the surface of secondary particles of NCM9064, helping to prevent the direct contact between the electrolyte and cathode during the charging-discharging process. In addition, the coating layer is electrochemically stable. As a result, the interfacial side reactions during the long cycle are effectively suppressed, and the solid electrolyte interphase layer at the interface is stabilized. The electrode with 20 layers of LPO deposition (ALD-LPO-20) exhibits an excellent capacity retention of 81% after 200 cycles in 2.8-4.3 V at 25 ℃, which is 18% higher than the unmodified material (ALD-LPO-0). Besides, the moderate LPO coating improves the rate capability and high temperature cycling performance of NCM9064. This study provides a method for the modification of ultra-high nickel cathode materials and corresponding electrodes.
In persulfate-based advanced oxidation process (PS-AOPs), fixing nanosized metal oxide on processable substrates is highly desirable to avoid the aggregation and loss of nanocatalysts during the practical application. However, it is still challenging to develop a versatile strategy for the deposition of metal oxide nanocatalysts on various substrates with different physicochemical properties. Herein, polyphenols are utilized as a "molecular glue" and reductant to mediate the interfacial deposition of MnO2 nanocatalysts on different substrates. MnO2 nanocatalysts were in-situ grown on macroscope mineral substrates (e.g., airstone) via an interfacial redox strategy between tannic acid (TA) and oxidized KMnO4, and then employed as a fixed catalyst of peroxymonosulfate (PMS) activation for treating pharmaceutical and personal care products (PPCPs) in water. The fixed MnO2 exhibited superior catalytic performance toward different PPCPS via a singlet oxygen (1O2)-dominated nonradical oxidation pathway. PPCPs in the secondary effluent of wastewater treatment plants could be effectively removed by a fixed-bed column of the fixed MnO2 with long term stability. Redox cycle of Mn4+/Mn3+ and surface hydroxyl group of the fixed MnO2 was proved to be responsible for the activation of PMS. This work provides a new avenue for developing fixed metal oxides for sustainable water treatment.
Metal–organic framework (MOF) is a periodic sexual network structure with large surface area and high porosity, which is assembled by inorganic nodes and organic ligands through coordinate covalent bond. MOFs have the advantages of controllable pore size and shape, large specific surface area, easy modification and more active sites. In addition, MOF based nanoenzymes display excellent enzyme catalytic activity due to their special structure and multiple exposed metal active sites, controlling the production of reactive oxygen species (ROS) in cells or the body, and thus regulating the polarization of macrophage. This article reviews the mechanism of MOF material regulating macrophage polarization and the function of macrophages with different phenotypes. By utilizing the excellent properties of MOFs and the advantages of combining them with bioactive materials, we have discovered their excellent applications in the treatment of inflammatory diseases. Finally, we discussed the current challenges and prospects faced by MOF based composite materials. We expect that the research in this developing field will play a more important role in combating inflammatory diseases in the field of nanomedicine.
Ursolic acid (UA) is a naturally occurring ursane triterpenoid, which exhibits a wide range of unique biological activities. To clarify its mechanism of action (MOA), a series of fluorescent derivatives of UA (5a–c) were designed and synthesized by conjugation with 7-nitrobenzo-2-oxa-1,3-diazole (NBD) fluorophore. Among them, 5c exhibited similar anti-proliferative activity with UA against HCT116 cells (half maximal inhibitory concentration (IC50) = 9.21 ± 0.50 µmol/L). Cell imaging experiment indicated that 5c was rapidly taken up in HCT116 cells in a dose and time-dependent manner. Then, 5c was found to localize in endoplasmic reticulum (ER), lysosomes, and mitochondria, but not in nucleus of HCT116 cells by confocal microscopy studies. Preliminary MOA proved that UA induced autophagy with a unique intracellular distribution mechanism involving ER and lysosome. In all, our work provides new clues for revealing the molecular mechanism of UA as an antitumor agent.
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