Qi Zhang

Exfoliated graphene-like carbon nitride in organic solvents: enhanced photocatalytic activity and highly selective and sensitive sensor for the detection of trace amounts of Cu2+

Due to their unprecedented electronic, surface and optical properties, the atomic-thick graphene-like materials have aroused great interest. Compared with the bulk counterparts, the graphene-like material can not only enhance the internal properties, but also gives rise to new promising properties. Herein, the graphene-like carbon nitride (graphene-like C3N4) was synthesized via liquid exfoliation from the bulk graphitic carbon nitride (g-C3N4) in 1,3-butanediol (1,3-BUT) for the first time. And the graphene-like C3N4 was characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM), thermogravimetric analysis (TG), and X-ray photoelectron spectroscopy (XPS). The obtained graphene-like C3N4 exhibited a two-dimensional thin-layer structure with about 3–6 atoms thickness, a high specific surface area of 32.54 m2 g−1, increased photocurrent responses, improved electron transport ability and enhanced photocatalytic activity. The photocatalytic reaction for the organic dye methylene blue (MB) by the graphene-like C3N4 followed first-order kinetics. Moreover, the graphene-like C3N4 exhibited a higher apparent rate of 0.1262 min−1, which was 3.1 times higher than that of the bulk g-C3N4 (0.0409 min−1). The enhanced photocatalytic reaction was due to a high specific surface area and a larger bandgap (by 0.14 eV). The yield of the graphene-like C3N4 was up to ∼0.35 mg mL−1. Moreover, the graphene-like C3N4 had a new property that it could be used as the sensor for trace amounts of Cu2+ determination, so the graphene-like C3N4 is a new but promising candidate for heavy metal ions (Cu2+) determination in water environment. Photoelectrochemical selective sensing of trace amounts of Cu2+ was also discussed.

Carbon Quantum Dots Modified BiOCl Ultrathin Nanosheets with Enhanced Molecular Oxygen Activation Ability for Broad Spectrum Photocatalytic Properties and Mechanism Insight

In this paper, carbon quantum dots (CQDs) modified BiOCl ultrathin nanosheets photocatalyst was synthesized via a facile solvothermal method. The structures, morphologies, optical properties, and photocatalytic properties were investigated in detail. The photocatalytic activity of the obtained CQDs modified BiOCl ultrathin nanosheets photocatalyst was evaluated by the degradation of bisphenol A (BPA) and rhodamine B (RhB) under ultraviolet, visible, and near-infrared light irradiation. The CQDs/BiOCl materials exhibited significantly enhanced photocatalytic performance as compared with pure BiOCl and the 5 wt % CQDs/BiOCl materials displayed the best performance, which showed a broad spectrum of photocatalytic degradation activity. The main active species were determined to be hole and O2•- under visible light irradiation by electron spin resonance (ESR) analysis, XPS valence spectra, and free radicals trapping experiments. The crucial role of CQDs for the improved photocatalytic activity was mainly attributed to the superior electron transfer ability, enhanced light harvesting, and boosted catalytic active sites.

Reactable ionic liquid-assisted rapid synthesis of BiOI hollow microspheres at room temperature with enhanced photocatalytic activity

BiOI hollow microspheres have been rapidly synthesized through a facile reactable ionic liquid 1-butyl-3-methylimidazolium iodine ([Bmim]I)-assisted microemulsion method at room temperature. The formation mechanism of the BiOI hollow microspheres has been investigated. The BiOI hollow microspheres were formed through self-assembly and inside-out Ostwald ripening growth mechanism. During the reactive process, the ionic liquid, which acts as the solvent, reactant and template at the same time, plays a crucial role on the formation of hollow microspheres. In addition, the influencing factors (such as the reactant, the concentration of ionic liquids and the amount of acetic acid) of the formation of BiOI hollow microsphere have also been explored. The photocatalytic ability of the as-prepared photocatalysts was evaluated using rhodamine B (RhB) as a target pollutant. After systematic characterizations, the relationship between the structure of the photocatalyst and the photocatalytic activities were also discussed in detail. It can be assumed that the enhancing photocatalytic activity of BiOI hollow microspheres could be attributed to the improved light harvesting, shortened diffusion pathways, high BET surface area and faster interfacial charge separation. O2˙− and h+ were the main active species for the photocatalytic degradation of RhB. It is hoped that this rapidly synthetic route at room temperature can be extended to the purposive preparation of other hollow microsphere materials.

Controllable synthesis of Bi4O5Br2 ultrathin nanosheets for photocatalytic removal of ciprofloxacin and mechanism insight

A novel Bi4O5Br2 photocatalyst was prepared via a reactable ionic liquids-assisted solvothermal method accompanied with facile pH control. A Bi4O5Br2 ultrathin nanosheets material with 8 nm thickness could be obtained. The photocatalytic activity of the Bi4O5Br2 ultrathin nanosheets was evaluated with respect to the photo-degradation of colourless antibiotic agent ciprofloxacin (CIP) under visible light irradiation. The results revealed that the Bi-rich Bi4O5Br2 ultrathin nanosheets exhibited higher photocatalytic activity than BiOBr ultrathin nanosheets for the photo-degradation of CIP. The O2˙− anion was determined to be the main active species for the photo-degradation process by ESR. After multiple characterizations, the variable energy band structure was confirmed to be responsible for the enhanced photocatalytic activity. The more negative conduction band (CB) value of Bi4O5Br2 facilitated the formation of more active species, O2˙−. The upshifting of the CB and the wider valence band favor the higher separation efficiency of electron–hole pairs. It was hoped that this architecture of ultrathin 2D inorganic materials with a suitable band gap can be extended to other systems for high-performance photocatalysis applications.

Effects of endogenous beta-amyloid overproduction on tau phosphorylation in cell culture.

Alzheimers disease is characterized by β‐amyloid (Aβ) overproduction and tau hyperphosphorylation. Recent studies have shown that synthetic Aβ promotes tau phosphorylation in vitro. However, whether endogenously overproduced Aβ promotes tau phosphorylation and the underlying mechanisms remain unknown. Here, we used mouse neuroblastoma N2a stably expressing wild‐type amyloid precursor protein (APPwt) or the Swedish mutant APP (APPswe) to determine the alterations of phosphorylated tau and the related protein kinases. We found that phosphorylation of tau at paired helical filament (PHF)‐1, pSer396 and pThr231 epitopes was significantly increased in cells transfected with APPwt and APPswe, which produced higher levels of Aβ than cells transfected with vector or amyloid precursor‐like protein 1. The activity of glycogen synthase kinase‐3 (GSK‐3) was up‐regulated with a concomitant reduction in the inhibitory phosphorylation of GSK‐3 at its N‐terminal Ser9 residue. In contrast, the activity of cyclin‐dependent kinase‐5 (CDK‐5) and protein kinase C (PKC) was down‐regulated. Inhibition of GSK‐3 by LiCl, but not inhibition of CDK‐5 by roscovitine, arrested Aβ secretion and tau phosphorylation. Inhibition of PKC by GF‐109203X activated GSK‐3, whereas activation of PKC by phorbol‐12,13‐dibutyrate inhibited GSK‐3. These results suggest that endogenously overproduced Aβ induces increased tau phosphorylation through activation of GSK‐3, and that inactivation of PKC is at least one of the mechanisms involved in GSK‐3 activation.

Sorption of heavy metal ions onto carboxylate chitosan derivatives--a mini-review.

Chitosan is of importance for the elimination of heavy metals due to their outstanding characteristics such as the presence of NH2 and -OH functional groups, non-toxicity, low cost and, large available quantities. Modifying a chitosan structure with -COOH group improves it in terms of solubility at pH ≤7 without affecting the aforementioned characteristics. Chitosan modified with a carboxylic group possess carboxyl, amino and hydroxyl multifunctional groups which are good for elimination of metal ions. The focal point of this mini-review will be on the preparation and characterization of some carboxylate chitosan derivatives as a sorbent for heavy metal sorption.

Atmospheric cold plasma jet for plant disease treatment

This study shows that the atmospheric cold plasma jet is capable of curing the fungus-infected plant leaves and controlling the spread of infection as an attractive tool for plant disease management. The healing effect was significantly dependent on the size of the black spots infected with fungal cells and the leaf age. The leaves with the diameter of black spots of <2u2009mm can completely recover from the fungus-infected state. The plasma-generated species passing through the microns-sized stomas in a leaf can weaken the function of the oil vacuoles and cell membrane of fungal cells, resulting in plasma-induced inactivation.

Removal of cadmium from aqueous solution using low molecular weight chitosan derivative

A 2(3) factorial design was used to examine the sorption of Cd(2+) onto cross-linked low molecular weight chitosan pyruvic acid derivative. Three factors and two levels of solution pH (A) (6.0 or 10.0), temperature (B) (45 or 70 °C) and Cd(II) concentration (C) (1 or 3 mg/L) were considered. Batch mode system was employed with 0.05 g of the sorbent and 25 mL of Cd(II) solution. The efficiency of cadmium removal during an exposition time of 4h was then evaluated. The factors and their interaction effect on the cadmium removal efficiency followed the order: Cd(II) concentration > solution pH > interaction between solution pH and Cd(II) concentration>interaction between solution pH, temperature and Cd(II) concentration. Langmuir isotherm model was the best isotherm model. The Pseudo second order fitted well the kinetic data. The thermodynamic studies revealed the nature of the cadmium sorption.

Erratum to: 17β-estradiol attenuates glycogen synthase kinase-3β activation and tau hyperphosphorylation in Akt-independent manner

Decline of estrogen is associated with high incidence of Alzheimer’s disease (AD) characterized pathologically with tau hyperphosphorylation, and glycogen synthase kinase-3β (GSK-3β) is a major tau kinase. However, the role of estrogen on GSK3β-induced tau hyperphosphorylation is elusive. Here, we treated N2a cells with wortmannin (Wort) and GF-109203X (GFX) or gene transfection to activate GSK-3β and to induce tau hyperphosphorylation and then the effects of 17β-estradiol (βE2) on tau phosphorylation and GSK-3β activity were studied. We found that βE2 could attenuate tau hyperphosphorylation at multiple AD-related sites, including Ser396/404, Thr231, Thr205, and Ser199/202, induced by Wort/GFX or transient overexpression of GSK-3β. Simultaneously, it increased the level of Ser9-phosphorylated (inactive) GSK-3β. To study whether the protective effect of βE2 on GSK-3β and tau phosphorylation involves protein kinase B (Akt), an upstream effector of GSK-3, we transiently expressed the dominant negative Akt (dnAkt) in the cells. We found that βE2 could attenuate Wort/GFX-induced GSK-3β activation and tau hyperphosphorylation with Akt-independent manner. It suggests that βE2 may arrest AD-like tau hyperphosphorylation by directly targeting GSK-3β.

Hyperphosphorylation of microtubule-associated tau protein plays dual role in neurodegeneration and neuroprotection.

The microtubule-associated protein tau plays a major role in maintaining the normal morphology of the neurons. The major biological activity of tau is to promote microtubule assembly and stabilize the microtubules. In the brain of Alzheimers disease (AD) patients, tau protein is abnormally hyperphosphorylated and thus become incompetent in promoting microtubule assemble and maintaining the stability of the microtubules. These detrimental effects of tau may lead the neurons to degeneration. Recent studies show that tau hyperphorylation may be neuroprotective in the early stages of the disease process. The primary aim of this review is to summarize the latest developments and perspectives in our understanding about the roles of tau hyperphosphorylation in neurodegeneration and neuroprotection.