Shaoyun Shan

Microwave-hydrothermal preparation of flower-like ZnO microstructure and its photocatalytic activity

Abstract The flower-like ZnO microstructure was prepared by a straightforward microwave-hydrothermal technique using zinc chloride and arginine solution as reactants. The as-synthesized crystal structure and morphology were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and the optical properties of the ZnO nanostructure were studied by Raman and photoluminescence (PL) spectra, which confirms the high crystal quality of ZnO microstructure. The as-synthesized ZnO flowers exhibit a significant enhancement of photocatalytic capability toward degrading methyl blue (MB) under UV light, the photodegradation of MB reaches 95.60%, only within 2 h of adding the as-synthesized ZnO in the MB solution under UV irradiation. Furthermore, the photodegradation could be described as the pseudo-first-order kinetics with degradation rate constant of 1.0675-1.6275 h −1 , which is relative to the morphology of the structures.

Development of sintering-resistant CaO-based sorbent derived from eggshells and bauxite tailings for cyclic CO2 capture

Carbon dioxide, one of the major greenhouse gases, are believed to be a major contributor to global warming. As a consequence, it is imperative for us to control and remove CO2 emissions. The CaO, a kind of effective CO2 sorbent at high temperature, has attracted increasing attention due to some potential advantages. The main drawback in practical application is the deterioration of CO2 capture capacity following multiples cycles. In the present study, novel low-cost porous CaO-based sorbents with excellent CO2 absorption-desorption performance were synthesized using bauxite tailings (BTs) and eggshells as raw materials via solid-phase method. Effect of different BTs content on CO2 absorption-desorption properties was investigated. Phase composition and morphologies were analyzed by XRD and SEM, and CO2 absorption properties were investigated by the simultaneous thermogravimetric analyzer. The as-prepared CaO-based sorbent doped with 10 wt% BTs showed superior CO2 absorption stability during multiple absorption-desorption cycles, with being >55% conversion after 40 cycles. This improved CO2 absorption performance was attributed to the particular morphologies of the CaO-based sorbents. Additionally, during absorption-desorption cycles the occurrence of Ca12Al14O33 phase is considered to be responsible for the excellent CO2 absorption performance of CaO-based sorbents. In the meanwhile, the use of solid waste eggshell and BTs not only decreases the release of solid waste, but also moderates the greenhouse effect resulted from CO2.

Polypyrrole Nanofibers Supported Cr(III)(salen)Cl Catalyst: A Novel Polymer Supported Catalyst for Alternating Copolymerization of Cyclohexene Oxide with Carbon dioxide

Polypyrrole(PPy) supported Cr(III)(salen)Cl catalyst was prepared for alternating copolymerization of cyclohexene oxide and carbon dioxide. The supported catalyst and the copolymerization products were characterized by FTIR, XRD, XPS, ICP-MS, SEM, TEM, NMR, gel permeation chromatography, thermogravimetric analysis and differential scanning calorimetry. After the study, we concluded that the homogeneous Cr(III)(salen)Cl is successfully supported on the PPy, and its catalytic performance is much better than the homogeneous one. Moreover, the copolymerization product catalyzed by PPy-Cr(III)(salen)Cl exhibits higher molecular weight, narrower molecular weight distribution, superior thermal stability and selectivity.Graphical Abstract

Porous structured MIL-101 synthesized with different mineralizers for adsorptive removal of oxytetracycline from aqueous solution

In this work, highly porous MIL-101 materials using hydrochloric acid (HCl) or hydrofluoric acid (HF) as a mineralizer were synthesized. The products were characterized with X-ray diffraction, scanning electron microscopy, thermal gravimetric analysis, and N2 sorption analysis. The results proved that the mineralizers had an obvious effect on the microstructures and morphologies of MIL-101, and MIL-101(HCl) showed remarkable superiority in a higher specific surface area, smaller particle size and higher crystallinity to the HF counterpart. These materials were then used to adsorb and remove the oxytetracycline (OTC) antibiotics from a water solution and an effective fast adsorption of OTC in aqueous solution was observed in the adsorptive kinetics. Compared with MIL-101(HF), a higher adsorption capacity on the MIL-101(HCl) was obtained, which was probably attributed to the higher specific surface area for the MIL-101(HCl). The adsorption mechanism might be greatly ascribed to π–π interaction, and acid–alkaline interaction between the oxytetracycline molecule and the adsorbent.

Synthesis and characterization of Schiff base contained dextran microgels in water-in-oil inverse microemulsion.

Polysaccharide-based microgels with high water content, excellent biocompatibility and controllable particle size have been widely studied as ideal candidates for drug release and delivery. In this study, microgels based on dextran were developed via the Schiff base formation between aldehyded dextran and ethylenediamine in a water-in-oil (W/O) microemulsion. Particle size of the resulted microgel was controllable between 800 and 1100nm by modulating the amount of the employed co-surfactants (Span 80/Tween 80). Furthermore, fluoresceins (e.g., aminofluorescein) and drugs (e.g., doxorubicin) with free amino groups can be conjugated onto the network of the dextran-based microgel via Schiff base linkages. Since the Schiff base linkages are degradable via hydrolysis and their stability decreases with the environmental pH decreases, the resulted Schiff bases contained microgel showed a pH dependent degradation profile. These results indicated that the pH-sensitive microgel based on dextran could be used as promising drug delivery systems for biomedical applications.

Efficient alternating copolymerization of sulfur dioxide with cyclohexene oxide and a mechanistic understanding

The alternating copolymerization of sulfur dioxide with epoxides is rarely reported because of the low reactivity and polysulfite selectivity of the process. This work describes an efficient alternating copolymerization of sulfur dioxide with cyclohexene oxide using salenCrIIICl as the catalyst. The effect of temperature, time, and type of catalyst on the overall activity and selectivity was investigated in detail. The results proved that the reactivity and polysulfite selectivity of salenCrIIICl are better than those of amines and inorganic salts. The copolymer product poly(cyclohexene sulfite) was characterized by nuclear magnetic resonance spectroscopy, infrared spectroscopy, thermogravimetric analysis and gel permeation chromatography. We found that SO2 not only acts as reactant, but also acts as a co-catalyst to promote the copolymerization reaction in the presence of salenCrIIICl. On the basis of the copolymerization mechanism of CO2 and epoxide using a salen catalyst, and spectroscopic evidence, a mechanism to account for the results is proposed.

Effective and reusable microcrystalline cellulosic Salen complexes for epoxidation of alpha-pinene

Abstract 2,3-Epoxypinane, one of the alpha-pinene derivatives, has great economic value. Among the catalyst systems for the epoxidation of alpha-pinene, Salen transition metal complexes have shown exceptional catalytic activities, yet their reusability was a major problem. Herein, for the first time, we developed a heterogeneous microcrystalline cellulosic Salen complex using a facile method. Compared with some catalytic systems, the complex displayed superior catalytic activities in the epoxidation of alpha-pinene. Moreover, the key advantage is cellulose, the most abundant regenerable biopolymer in accordance with the requirements of green chemistry, which has been employed to synthesize a Salen complex. The reusability of the catalyst and different oxidant systems were also investigated in detail. The results demonstrated that the catalyst maintains excellent catalytic activity and selectivity after being used six times when using O2 and the co-oxidant. These interesting results unveil the potential of the cellulosic Salen complex for heterogeneous catalytic reactions.

Microwave-Solvothermal synthesis of nanostructured BiOBr with excellent visible-light photocatalytic properties

Novel BiOBr hierarchical microspheres have been successfully prepared via a facile microwave-assisted solvothermal route and used for visible-light photocatalytic degradation of RhB. The phase and morphology of the products were characterized by powder X-ray diffraction (XRD), thermogravimetric analysis (TG), scanning electron microscopy (SEM), BET, and UV-vis diffuse reflectance spectra. The SEM observations displayed that BiOBr flower-like nanostructure assembled from nanosheets. The BiOBr flowerlike nanostructure, with a narrow band gap (2.63 eV), shows excellent photocatalytic activity in the degradation of RhB dye under visible-light, much higher than those of BiOBr nanosheet and P25 photocatalysts.

A novel magnetic MIL-101(Fe)/TiO2 composite for photo degradation of tetracycline under solar light

A novel magnetic MIL-101(Fe)/TiO2 composite was synthesized for photo degradation of tetracycline (TC) under solar light. The composite was characterized by XRD, TGA, SEM, TEM, EDS, BET, FTIR, XPS, VSM, ESR, and PL. The resultant composite was environment friendly material, which exhibited high TC degradation efficiency and excellent reusability. In the meantime, it could be separated easily from TC solution by using magnet, which would save significant time and cost of preparation and degradation, having broad prospect in application. Using 1 g L-1 magnetic MIL-101(Fe)/TiO2 at pH = 7, 92.76% degradation efficiency was achieved under solar light irradiation in 10 min for 20 mg L-1 TC. Further experiments indicated that TiO2 introduced in the composite played an important role in the degradation process, which could be activated by the UV light in solar light to generate large amount of O2- and OH radicals. The degradation efficiency of TC in this paper was significantly higher than other research papers reported in last three years. This study put forward new magnetic Fe-based metal-organic frameworks (MOFs)/TiO2 composite for degrading pharmaceutical wastewater.

Schiff base-containing dextran nanogel as pH-sensitive drug delivery system of doxorubicin: Synthesis and characterization

Stimuli-responsive hydrogels have been widely researched as carrier systems, due to their excellent biocompatibility and responsiveness to external physiologic environment factors. In this study, dextran-based nanogel with covalently conjugated doxorubicin (DOX) was developed via Schiff base formation using the inverse microemulsion technique. Since the Schiff base linkages are acid-sensitive, drug release profile of the DOX-loaded nanogel would be pH-dependent. In vitro drug release studies confirmed that DOX was released much faster under acidic condition (pH 2.0, 5.0) than that at pH 7.4. Approximately 66, 28, and 9% of drug was released in 72 h at pH 2.0, 5.0, and 7.4, respectively. Cell uptake by the human breast cancer cell (MCF-7) demonstrated that the DOX-loaded dextran nanogel could be internalized through endocytosis and distributed in endocytic compartments inside tumor cells. These results indicated that the Schiff base-containing nanogel can serve as a pH-sensitive drug delivery system. And the presence of multiple aldehyde groups on the nanogel are available for further conjugations of targeting ligands or imaging probes.