RSC Advances

Zhou, Xun; Meng, Weili; Dong, Chao; Liu, Changwen; Qiu, Zeliang; Qi, Juanjuan; Chen, Junwei; Wang, Mingtai

doi: 10.1039/c5ra16898hpmid: N/A

High-purity Cu2ZnSnS4 quantum dots (CZTS-QDs) with a size of 3–5 nm and a band gap of 1.67 eV are synthesized by a facile solvothermal method using simple chemicals in ethanol solvent. The CZTS-QDs have an ionization potential (IP) of −5.96 eV and an electron affinity (EA) of −4.33 eV, which are almost not changed after removal of capping molecules on them. Due to the favorable IP and EA positions with respect to those of poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV), the CZTS-QDs act as effective electron acceptors for hybrid solar cells based on polymer/CZTS blends with MEH-PPV as the polymer. CZTS-QDs and MEH-PPV form type-II heterojunctions to enable the solar cells to have a promising open-circuit voltage of 0.63 V, and the efficient charge separation for neutral excited states produced either on the polymer or on the CZTS-QDs makes the solar cells have a wide spectral response extending to 900 nm. It is revealed that removal of capping molecules on the quantum dots mainly leads to a reduced polymer exciton diffusion effect on the electron transport dynamics due to the formation of wider CZTS charge transport channels and an increased short-circuit current (Jsc) in the solar cells, where the enhanced Jsc dominantly correlates with the increased charge transfer and collection efficiencies due to the improved charge transport property in CZTS channels.

Gabr, Moustafa T.; Pigge, F. Christopher

doi: 10.1039/c5ra18724apmid: N/A

Aggregation-induced emission (AIE) is emerging as an important design element in a variety of new fluorescent-based chemical sensors and bio-imaging agents. In particular, derivatives of tetraphenylethylene (TPE) have been widely utilized in this regard as the TPE framework is a reliable AIE-luminogen. To expand the library of AIE active tetraarylethylenes, we have explored the effects of replacing one or two of the phenyl rings in TPE with pyridine. Efficient synthetic routes that deliver mono- and bis-pyridyl tetraarylethylenes have been developed and the luminescent properties of these heterocyclic TPE analogues, along with their corresponding N-methylated pyridinium salts, have been examined.

Lai, Shuangshuang; Meng, Dongmei; Zhan, Wangcheng; Guo, Yun; Guo, Yanglong; Zhang, Zhigang; Lu, Guanzhong

doi: 10.1039/c5ra12505gpmid: N/A

Cu/ZSM-5 and Ce doped Cu/ZSM-5 catalysts were prepared by the incipient-wetness-impregnation method, and the effect of Ce doping on the structure and the catalytic performance of the Cu/ZSM-5 catalyst was investigated in detail for the selective catalytic reduction (SCR) of NO with NH3. The results showed that the addition of Ce can markedly broaden the operation temperature window of the Cu/ZSM-5 catalyst for NH3-SCR and enhance its H2O and SO2 resistance. The presence of Ce promoted an enrichment of copper species (isolated Cu2+ ions and CuO nanoparticles) on the catalyst surface and the increase in the Lewis acid sites on the surface of the Cu/ZSM-5 catalyst, and strengthened the redox property of the Cu/ZSM-5 catalyst. As a result, Ce-doped Cu/ZSM-5 catalyst possessed the high adsorption ability of NH3 and nitrite/nitrate, which is propitious to the increase in the reactivity of the Ce-doped Cu/ZSM-5 catalyst. In situ DRIFTS results indicated that the NH3-SCR reaction on the Cu/ZSM-5 catalyst and Ce1–Cu4/ZSM-5 catalysts definitely followed Langmuir–Hinshelwood mechanisms, and bridged nitrates and bidentate nitrates were the active intermediate. However, Eley–Rideal mechanism can't be confirmed over the Cu/ZSM-5 and Ce1–Cu4/ZSM-5 catalysts.

Zheng, Yawen; Yang, Dan; Wu, Xin; Yan, Haoran; Zhao, Yuancong; Feng, Bo; Duan, Ke; Weng, Jie; Wang, Jianxin

doi: 10.1039/c5ra14720dpmid: N/A

In this study, vitamin-based small organic molecules were used as precursors to synthesize carbon dots by means of a hydrothermal approach. The obtained carbon dots presented high luminescence and good cellar-imaging properties when folic acid was used as a precursor and the quantum yield of the carbon dots obtained using the present method was more than 30%. Moreover, green and yellow-green photoluminescence was also successfully achieved by adding the reagents H3PO4 and H2C2O4, respectively. The related formation mechanism and photoluminescence emission mechanism of carbon quantum dots were discussed. The present study will open a new possible route for the synthesis of carbon dots with high quality using small organic molecules as precursors.

Yan, Ming; Yan, Yan; Wu, Yilin; Shi, Weidong; Hua, Yinqun

doi: 10.1039/c5ra13684apmid: N/A

Recently, the controlled synthesis of semiconductor photocatalysts has received much attention in the field of pollutant degradation. In this study, BiVO4 photocatalysts of different crystalline phases (monoclinic scheelite (M-phase), tetragonal zircon (T-phase) and monoclinic–tetragonal heterojunction (M–T)) have been successfully synthesized via a facile microwave-assisted method. The crystalline phases of the products were controlled by switching the organic additives. The photocatalytic activities of the as-prepared samples were evaluated by the degradation of tetracycline (TC) under visible light irradiation. The obtained results clearly showed that the M–T BiVO4 exhibited the highest photodegradation ratio of the three samples of 80.5% in 1 h, which can be attributed to the heterojunction structure between different phases.

Li, Lili; Li, Xingyue; Ai, Lunhong; Jiang, Jing

doi: 10.1039/c5ra17427apmid: N/A

The earth-abundant metal phosphides have emerged as new and active alternatives for the precious metal platinum to electrocatalyze the hydrogen evolution reaction (HER) via water splitting. In this study, we report on the straightforward and controllable synthesis of various nanostructured cobalt phosphide assemblies through the direct chemical transformation of a Co-containing metal–organic framework (ZIF-67-Co) under mild phosphorization conditions. The resulting CoP nanoparticle assemblies (NPAs) and nanorod assemblies (NRAs) can be selectively produced by rationally tuning the calcination atmosphere. The CoP NRAs were found to be highly active for electrocatalytic hydrogen generation, which exhibited better performance than that of the CoP NPAs, as evidenced by their relatively low onset overpotential (∼86 mV), small Tafel slope (∼69 mV dec−1) and long-term stability in acidic media.

Horikoshi, Satoshi; Watanabe, Tomoki; Kamata, Momoko; Suzuki, Yumiko; Serpone, Nick

doi: 10.1039/c5ra18039bpmid: N/A

This article examined how and the possible effect microwaves may have on intramolecular reactions such as those of the Claisen-type rearrangement carried out in dimethyl sulfoxide (DMSO) solvent and in solvent-free, microwave irradiation conditions. For comparison, the reaction was also performed by conventional heating using an oil bath. 2-Allylphenol was synthesized from allylphenyl ether in DMSO solvent under stirring conditions as a model intramolecular reaction taking place via the Claisen rearrangement using a commercial microwave chemical apparatus together with conventional heating; no enhancement of the reaction occurred. To further examine the influence of microwave irradiation on Claisen rearrangement reactions, we also investigated the transformation of 1-allyloxy-4-methoxybenzene to 2-allyl-4-methoxyphenol under both solvent-free conditions (no stirring) and in DMSO medium; here also no reaction enhancement was observed. This notwithstanding, microwaves did impact the formation of a by-product formed in the latter reaction, which was identified by GC and GC/MS as 4-methoxyphenol, the yield of which was nearly fourfold greater (ca. 6%) under microwave irradiation than under oil-bath heating (ca. 1.5%). The latter suggests that under solvent-free conditions a microwave non-thermal effect influenced the formation of this by-product during the Claisen rearrangement process, contrary to the case where the reaction was performed in DMSO medium for which the yields were identical (ca. 2.5%), regardless of whether the reactant was microwave or oil-bath heated.

Zhou, Daojin; Zhang, Zepeng; Tang, Jialun; Zhang, Xiangming; Wang, Qiang; Liao, Libing

doi: 10.1039/c5ra14196fpmid: N/A

Montmorillonite with different exchangeable cations (Li+, Na+ and Ca2+) in the inter spaces were modified using a combination of cationic and anionic surfactants, to prepare cationic–anionic organomontmorillonites (Li-organomontmorillonite, Na-organomontmorillonite and Ca-organomontmorillonite). The prepared organomontmorillonites were used in oil-based drilling fluids. Structure and properties of the cationic–anionic organomontmorillonites were studied using X-ray diffraction, thermogravimetry and contact angles. The properties of different oil–water ratios of oil-based drilling fluids/muds with added organomontmorillonite at room and high temperatures were studied using a rotary viscometer, filtration loss apparatus and a six-speed viscometer. The results showed that exchangeable cations in the inter-spaces of montmorillonite had an obvious impact on the structure and properties of the cationic–anionic organomontmorillonites. Of the three kinds of cationic–anionic organomontmorillonite, the cationic–anionic organomontmorillonite prepared from Li-montmorillonite had the largest basal spacing, best thermal stability and highest surface polarity which was followed by Na-montmorillonite and Ca-montmorillonite successively. Application of the research to oil-based drilling fluids/muds through adding different organomontmorillonites showed that Li-organomontmorillonite showed the best applied properties in full oil-based drilling fluids/muds at 180 °C. Na-organomontmorillonite showed the best applied properties in 80 : 20/90 : 10 oil–water ratio oil-based drilling fluids/muds at 180 °C. The oil-based drilling fluids/muds with added Ca-organomontmorillonite had the worst applied properties at 180 °C.

Chen, Yao; Xu, Xiaoli; Fu, Tingming; Li, Wei; Liu, Zongliang; Sun, Haopeng

doi: 10.1039/c5ra19551apmid: N/A

Acetylcholinesterase inhibitors (AChEIs) are considered to be one of the most successful therapeutic strategies in the treatment of Alzheimer's disease (AD). To enlarge the scale of chemical scaffolds served as AChEIs, a compound collection containing 1280 approved drugs by the U. S. food and drug administration (FDA) was screened. Six drugs, including Alfuzosin, Tandutinib, Dyclonine, Nefazodone, Miconazole and Mesoridazine exhibited potent inhibitory effects on acetylcholinesterase (AChE). The binding mode indicated their “dual site binding” manner, which targeted the catalytic site (CAS) and peripheral anionic site (PAS) simultaneously. Considering that approved drugs have proper physicochemical properties and good safety, these drugs provided us with good starting point to further design selective and potent AChEIs with novel scaffold and good drug-like ability.

Dhumal, Dinesh M.; Kothari, Priya R.; Kalhapure, Rahul S.; Akamanchi, Krishnacharya G.

doi: 10.1039/c5ra18112gpmid: N/A

Despite the various therapeutic actions displayed by curcumin, its poor aqueous solubility and bioavailability restricts its biological applications. This problem can be addressed by its efficient loading into a nano formulation. The present paper reports the utilization of a new semi-synthetic oleic acid derived bicephalous heterolipid, E1E, as an oil phase in the formulation development of a self-microemulsifying drug delivery system (SMEDDS) of curcumin to enhance its solubility and bioavailability. The solubility of curcumin in E1E was found to be 14 and 2.6-fold greater than oleic acid and ethyl oleate respectively. The SMEDDS developed from E1E (Curcumin-E1E_SMEDDS5e) had high curcumin loading efficiency of 70.52 ± 2.46 mg g−1, and was able to form spontaneous microemulsion on addition to aqueous phase with mean globule diameter of 22.39 ± 0.2 nm and polydispersity index of 0.243 ± 0.010. In vivo oral bioavailability studies in male Wistar rats revealed that the maximum serum concentration (Cmax) and time taken to reach maximum serum concentration (Tmax) were 4.921 ± 0.42 μg mL−1 and 60 min respectively. The absorption of curcumin increased 26-folds via its delivery through Curcumin-E1E_SMEDDS5e. The cytostatic and total growth inhibition concentrations of Curcumin-E1E_SMEDDS5e against HeLa cell line were almost comparable to doxorubicin (GI50 and TGI < 10 μg mL−1) whereas lethal concentration (LC50) was 71.8 μg mL−1. Further, the minimum inhibitory concentrations against E. coli and S. aureus were 48.62 and 97.65 μg mL−1 respectively. These results suggested potent anticancer, antibacterial activity and non-cytotoxicity of developed Curcumin-E1E_SMEDDS5e. The heterolipid, E1E, proved to be an efficient solubility and bioavailability enhancer for curcumin for formulation development of its SMEDDS.