Latest ArticlesNonradical 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.
An approach for distinguishing two types of positional isomers of dimeric shikonin and its analogs was explored with 4JC, H long-range correlation by prolonging the acquisition time at 2,3JC, H values of 2.0 and 8.0 Hz. Furthermore, the 1H (proton) nuclear magnetic resonance (NMR) pattern of phenolic hydroxyl protons was developed as a "diagnosis signal" to ascertain the relative location of each side chain in DMSO–d6 at sample concentrations of 0.022–0.034 mol/L. The chemical shift differences of 0.6 ppm between OH-5′ and OH-1 and between OH-8′ and OH-4 are assigned to Type A and Type B, respectively. All reported ambiguous structures were corrected by this pattern. Additionally, the steric structures of isolated compounds were elucidated by quantum chemical calculations of electronic circular dichroism (ECD) spectra.
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.
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.
The interaction among type Ⅱ collagen (CII), human DR4 major histocompatibility complex type Ⅱ molecule (MHC Ⅱ) and T-cell receptor (TCR) is associated with the development of rheumatoid arthritis (RA). The activation of T cells can be reduced through exposure to modified CII(263–272) glycopeptide fragment via competitive inhibition with self-antigen. In this work, 30 peptides based on the sequence of CII(263–272) were prepared and evaluated for their binding to DR4 protein by surface plasmon resonance (SPR) assay. The effect on the secretion of pro-inflammatory factors by the spleen cells in collagen induced rheumatoid arthritis (CIA) mouse was also investigated. Two N-glycosylated CII peptides were identified to have strong binding to the human recombinant DR4 protein and weak proinflammatory effect. These glycopeptides could be developed as therapeutic saccharide vaccines for the treatment of rheumatoid arthritis (RA).
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.
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.
Alginate is a natural polysaccharide polymer. Hydrogel filtration membranes prepared from alginate show excellent fouling resistance and controllable separation performance, but poor mechanical properties limit the use of algae hydrogels. In this study, Ba2+/Ca2+ co-crosslinked alginate (Ba/CaAlg) hydrogel membrane was prepared by cross-linking sodium alginate with a blend aqueous solution of barium ions and calcium ions, and the membrane was applied to the separation of dyes/salts from dyeing wastewater. Compared with the CaAlg membrane, the Ba/CaAlg hydrogel membrane exhibited more stable structure, and the mechanical properties and salt tolerance of the membrane were significantly improved. The flux of Ba/CaAlg membrane for methyl blue/sodium chloride mixed solution reached 43.5 L m−2 h−1, which was significantly higher than that of CaAlg membrane. Besides, the Ba/CaAlg membrane showed higher dye rejection (>99.6%) and lower salt rejection (<8.2%). The structure of Ba/CaAlg membrane was preliminarily simulated by molecular dynamics, and the pore size and distribution of the membrane were calculated. The Ba/CaAlg membrane has a broad application prospect in dyes/salts separation.
Due to its high operational voltage and energy density, P2-type Na0.67Ni0.3Mn0.7O2 has become a leading cathode material for sodium-ion batteries (SIBs), which is an ideal option for large-scale energy storage. However, the practical application of P2-type Na0.67Ni0.3Mn0.7O2 is limited by the capacity constraints and unwanted phase transitions, presenting significant challenges to the widespread application of SIBs. To address these challenges and optimize the electrochemical properties of the P2 phase cathode material, this study proposes a Cu and Zn co-doped strategy to improve the electrochemical performance. The incorporation of Cu/Zn can stabilize the P2-phase structure against P2-O2 phase transitions, thus enhancing its electrochemical properties. The as-obtained P2-type Na0.67[Ni0.3Mn0.58Cu0.09Zn0.03]O2 cathode material shows an impressive cycling stability, maintaining 80% capacity retention after 1000 cycles at 2 C. The cyclic voltammetry (CV) tests show that the Cu2+/Cu3+ redox reaction is also involved in charge compensation during the charge/discharge process.
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.
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