Thermally stable imidazoline-based sulfonate copolymers for enhanced oil recoveryGou, Shaohua; Luo, Shan; Liu, Tongyi; Xia, Hong; Jing, Dong; Zhang, Qin; Li, Shiwei; Li, Zhonghui; Guo, Qipeng
doi: 10.1039/c5ra15434kpmid: N/A
Novel imidazoline-based sulfonate copolymers (noted PAMDSCM and PAMPSCM) were successfully prepared by copolymerization of acrylamide (AM), acrylic acid (AA), 1-acrylamido ethyl-2-oleic imidazoline (ACEIM) with the sodium salts of 3-(diallyl-amino)-2-hydroxypropyl (NDS) or 2-acrylamido-2-methylpropane sulfonic acid (AMPS), respectively. The copolymers were characterized by infrared (IR) spectroscopy, 1H nuclear magnetic resonance (1H NMR) spectroscopy, pyrene fluorescence probe spectroscopy, viscosimetry and thermogravimetry (TG). Both PAMDSCM and PAMPSCM copolymers had excellent high-temperature tolerance in comparison with the same concentration of HPAM, and the residual viscosities were 32.0 mPa s and 31.3 mPa s (viscosity retention rates were 38.8% and 37.1%) at 140 °C, respectively. The copolymers possessed superior long-term thermal stability and their residual viscosity rates were up to 81.8% and 63.8% (52.9 mPa s and 47.1 mPa s) lasting 1.5 hours at 100 °C and 170 s−1, respectively.
Unexpected efficiency enhancement of flexible dye-sensitized solar cells by repeated outward bendingHe, Xue-Long; Liu, Mei; Yang, Guan-Jun; Fang, Baizeng; Li, Chang-Jiu
doi: 10.1039/c5ra19365fpmid: N/A
The photovoltaic performance of flexible dye-sensitized solar cells (DSCs) is generally degraded during bending activity which presents a typical flexible service condition. In this study, however, we report an unexpected efficiency enhancement of ca. 19% (i.e., from 3.88% to 4.62%) of flexible DSCs after repeated outward bending. The photovoltaic performance, electrochemical properties, mechanical properties and electrical properties were examined to understand the efficiency enhancement mechanism. It was found that the anisotropic evolution of particle–particle connection in the nanostructured TiO2 film, strengthening the electron transport in the out-plane (vertical to the TiO2 film surface) direction and weakening the electron transport in the in-plane (parallel to the TiO2 film surface) direction, is responsible for such an abnormal efficiency enhancement. Based on the results, an efficiency enhancement model for the flexible DSCs under repeated outward bending is proposed.
Carbonate-assisted hydrothermal synthesis of porous, hierarchical CuO microspheres and CuO/GO for high-performance lithium-ion battery anodesShi, Lin; Fu, Xinxin; Fan, Chenyao; Yu, Siqi; Qian, Guodong; Wang, Zhiyu
doi: 10.1039/c5ra16128bpmid: N/A
Porous, hierarchical CuO microspheres (MSs) have been successfully synthesized through a facile, surfactant-free carbonate-assisted hydrothermal method. A growth mechanism based on self-aggregation and decomposition of precursor Cu2(OH)2CO3 nanoparticles and Ostwald ripening under hydrothermal conditions is proposed to explain the formation of CuO MSs. Then the CuO MSs are encapsulated with GO through engineering the ionic strength in solution and applied as anode materials for lithium ion batteries, which demonstrates that CuO/GO exhibits significant improvements over the bare CuO MSs. It can deliver a high reversible capacity of 500 mA h g−1 after 500 cycles, with 80% capacity retention of the second reversible capacity (625.8 mA h g−1) at a current density of 0.5C. This is much higher than 233.5 mA h g−1 of the bare CuO MSs at the same rate. Such significantly enhanced electrochemical performance of the CuO/GO hybrid can be attributed to the synergistic effect of successful integration of the CuO MSs with the highly conductive and flexible GO sheets. This study demonstrates that facile structural tuning of the metal oxide in combination with advantageous carbon materials is a promising way to fabricate anodes for high-performance lithium-ion batteries.
Effect on physical and chemical characteristics of activated carbon on adsorption of trimethoprim: mechanisms studyLiu, Hai; Zhang, Jian; Ngo, Huu Hao; Guo, Wenshan; Wu, Haiming; Guo, Zizhang; Cheng, Cheng; Zhang, Chenglu
doi: 10.1039/c5ra17968hpmid: N/A
Five different types of activated carbon varying in porosity, structure, and functional groups were prepared and used as adsorbents. The effect of the key properties of each activated carbon on its adsorption capacity, rate and mechanisms on trimethoprim (TMP) removal were evaluated. The kinetics results suggested that chemical adsorption interactions and particle diffusion into micropores were the main rate-control steps for TMP adsorption, and the existence of mesopores promoted the diffusion of TMP into internal pores. The adsorption of TMP onto activated carbon can be attributed to the pore-filling effect (micropores and some narrow mesopores) and strong adsorptive interactions with the graphene surface or oxygenated groups. Regarding the surface area-normalized adsorption of TMP, porous activated carbon exhibited 50–500 times lower adsorption than nonporous carbon adsorbent due to the size-exclusion effect, especially when oxygen complexes presented on the edges of the pores of the activated carbon. From a system design point of view, a fast adsorption rate and high adsorption capacity are normally required, and these findings imply that activated carbon with high microporosity, a certain mesoporosity and approachable surface groups can have great application potential for TMP removal.
Effect of size and oxidation state of platinum nanoparticles on the electrocatalytic performance of graphene-nanoparticle compositesMondal, Avijit; Jana, Nikhil R.
doi: 10.1039/c5ra17087gpmid: N/A
A surfactant and stabilizer free graphene-based composite with Pt nanoparticles is considered to be a promising electrocatalyst with greatly improved performance. Here we show that both the size and oxidation state of Pt nanoparticles can significantly influence the electrocatalytic performance of the nanocomposite. We have synthesized Pt–graphene nanocomposites with varied sizes and oxidation states of Pt nanoparticles and test their catalytic activity towards methanol electro-oxidation. We found that the size <1.5 nm with mixed oxidation offers methanol oxidation at lower onset potential and with better tolerance to CO poisoning. However, these benefits are lost due to catalyst durability and thus catalytic current decays rapidly with time. As the nanoparticle size increases in the range of 2–5 nm this onset potential increases, CO tolerance decreases but the catalytic current becomes more stable with time. Thus an optimum nanoparticle size of 2.2 nm shows the best catalytic activity and durability. The oxygenic platinum with variable oxidation states offers stable grafting with the graphene surface, prevents active Pt (0) sites and assists for better CO tolerance. This result would be useful in the design and development of electrocatalysts with better performances.
ZrO2 nanoparticles as a reusable solid dual acid–base catalyst for facile one-pot synthesis of multi-functionalized spirooxindole derivatives under solvent free conditionBodhak, Chandan; Kundu, Ashis; Pramanik, Animesh
doi: 10.1039/c5ra16259apmid: N/A
A two-step one-pot protocol for the facile synthesis of biologically important spirooxindole derivatives such as spiro[4H-pyran-3,3′-oxindoles] and spiro[indoline-3,4′(1H′)-pyrano-[2,3-c]pyrazol-2-ones has been developed. In this method ZrO2 nanoparticles have been utilized as a reusable solid dual acid–base catalyst to get quick access to the multi-functionalized spirooxindole derivatives under solvent free condition at room temperature. The main advantages of this method are the operational simplicity, reduced reaction time, elimination of solvents, high yield of the products, convenient work up procedure and employment of nontoxic and recyclable ZrO2 nano catalyst. All these factors make the present method economical, green and sustainable.
Photoinduced curcumin derivative-coatings with antibacterial propertiesCondat, M.; Mazeran, P.-E.; Malval, J.-P.; Lalevée, J.; Morlet-Savary, F.; Renard, E.; Langlois, V.; Abbad Andalloussi, S.; Versace, D.-L.
doi: 10.1039/c5ra19499gpmid: N/A
The development of new antibacterial coating (against Escherichia coli and Staphylococcus aureus) with the use of a natural dye (curcumin) and epoxidized soybean oil, according to a photochemistry process has been investigated. Curcumin has been used both as a photosensitizer and an antibacterial agent under visible light illumination. The photoinduced coatings show good adherence properties on an inox substrate and a high thermal stability to 375 °C. Under visible light activation, singlet oxygen (1O2) could be generated from the curcumin derivative-coatings, thus inhibiting by 99% and 95% the growth of Staphylococcus aureus and Escherichia coli, respectively, even after 48 h of incubation.
Anti-site disorder and physical properties in microwave synthesized RE2Ti2O7 (RE = Gd, Ho) pyrochloresGómez-Pérez, Alejandro; Prado-Gonjal, Jesús; Muñoz-Gil, Daniel; Andrada-Chacón, Adrián; Sánchez-Benítez, Javier; Morán, Emilio; Azcondo, María Teresa; Amador, Ulises; Schmidt, Rainer
doi: 10.1039/c5ra07796fpmid: N/A
In this work we report on the microwave assisted synthesis of nano-sized Gd2Ti2O7 (GTO) and Ho2Ti2O7 (HTO) powders from the RE2Ti2O7 pyrochlore family (RE = rare earth). Synchrotron X-ray powder diffraction was used to study RE–Ti cationic anti-site defects with concentrations that decrease in both samples with increasing temperature starting from 1100 °C, and the defects disappear at 1400 °C. SQUID magnetometry measurements revealed that GTO shows a predominantly anti-ferromagnetic structure, whereas HTO exhibits magnetic saturation and a ferromagnetic component at low temperature. Impedance spectroscopy data revealed strongly increased ionic oxygen vacancy conduction in HTO ceramic pellets as compared to GTO, which may be associated with a higher degree of oxygen vacancy disorder. This argument was supported by Raman spectroscopy data.