RSC Advances

Wang, Yituo; Han, Guimei; Tian, Zhe; Wang, Meng; Li, Jianling; Wang, Xindong

doi: 10.1039/c4ra06365apmid: N/A

Bentonite (BOT) has excellent hygroscopicity and large specific surface, so it is chosen as a dopant of Nafion® membranes in this paper. By using the sol–gel method, bentonite has been modified by dodecylamine and fixed to the Nafion 212 membrane to prepare a Nafion/SiO2/m-BOT composite membrane. The results of SEM and FT-IR shows that m-BOT is successfully synthesized and bound well with the Nafion 212 membrane. The limiting current density of cathode methanol oxidation indicates that the methanol permeability of the composite membrane is 20.40% lower than that of the Nafion 212 membrane. Although the conductivity of the composite membrane (6.67 × 10−2 S cm−1) declines slightly compared with that of Nafion 212 (9.91 × 10−2 S cm−1), the performance of the cell using the composite membrane (135.17 mW cm−2) is better than the Nafion 212 membrane (118.7 mW cm−2) at 55 °C. Besides, as the anode methanol concentration increases, higher performance is obtained, which indicates that the composite membrane is more suitable for cells running with a high concentration of methanol.

Sun, Songmei; Wang, Wenzhong

doi: 10.1039/c4ra06419dpmid: N/A

Bismuth based complex oxides have attracted considerable interest due to their great potential to harvest solar light to solve the current environmental and energy crisis. Bismuth based complex oxides have excellent photo-oxidation ability for organic contaminant degradation and water oxidation via a photocatalytic process. Many efforts have been made to improve their photocatalytic performance, especially on the BiVO4, Bi2WO6 and Bi2MoO6 materials, which have been mostly studied in the past few years. Significant progress in understanding the fundamentals and improving the photocatalytic performance has been made due to the various new developed concepts and approaches in recent years. In this review, we present a comprehensive overview on the fundamentals and recent advances of BiVO4, Bi2WO6 and Bi2MoO6 photocatalysts. After the analysis of the structure–property relationships, the strategies that have been employed to enhance their photocatalytic performance are discussed in detail, including morphology control, surface modification, doping and construction of composite material. Furthermore, remarks on the challenges and perspectives of research directions are proposed for further development of the highly efficient bismuth based complex oxide photocatalysts.

Riaz, Ufana; Ashraf, S. M.

doi: 10.1039/c4ra06698gpmid: N/A

Microwave-enhanced photodegradation of dyes is one of the emerging and promising technologies for waste water remediation. Microwaves effectively accelerate photocatalytic degradation, but only in the presence of a suitable photocatalyst such as TiO2, ZnO and also when a microwave electrodeless lamp (MEL) substitutes a traditional lamp as a light source. As the existing inorganic photocatalysts have been proven to be potentially toxic to the aquatic environment, this remediation technique can be extremely simplified if the photocatalyst can be replaced by a benign catalyst which can work under microwave irradiation in the absence of any external light source. In the present study, an attempt is made for the first time to degrade and mineralize Orange G (OG) dye in a laboratory microwave oven at 30 °C, using an organic catalyst, poly(1-naphthylamine) (PNA), a conjugated polymer synthesized by an enzymatic method. PNA was characterized by relevant experimental techniques. The degradation was carried out by exposing the OG dye solutions to microwave irradiation for different time intervals in the absence of UV-vis radiation and TiO2. PNA as a catalyst was found to enhance the dye degradation under microwave irradiation by almost two times as compared to its degradation under microwave irradiation alone. 100 ppm of OG dye solution was found to degrade up to 90% in 20 min at 30 °C in the presence of PNA. The same solution revealed mineralization up to 85% in 40 min as confirmed by the total organic content (TOC) analysis. With the help of LC-MS, seven intermediates were identified ranging between m/z 227 and m/z 97, on the basis of which a tentative degradation pathway for the dye has been proposed. Dye degradation in the presence of PNA as a microwave catalyst under the present experimental setup was found to yield results better than other photocatalytic or microwave-assisted photocatalytic degradation methods.

Hao, Yanjun; Xie, Yaoming; Schaefer III, Henry F.

doi: 10.1039/c4ra09829cpmid: N/A

The SiOOH potential energy surface has become central to the understanding of recent experiments (Science 2013, 342, 463) by Chakraborty associated with nebular meteorite formation. The entrance complex, transition states, and exit complex for the title reaction SiO + OH→ SiO2 + H have been studied using the CCSD(T) method with correlation consistent basis sets as large as cc-pV(Q+d)Z. Reported here are characteristics of the reactants, products, six transition states, and four intermediate complexes for this reaction. These show four previously undiscovered stationary point geometries. The entrance complex OH⋯OSi is predicted to lie 28.6 kJ mol−1 below the separated reactants. The classical barriers cis-TS1 and trans-TS1 are predicted to lie 21.8 kJ mol−1 and 6.8 kJ mol−1, respectively, below the reactants. The exit complex HSiO2 is bound by 115.3 kJ mol−1 relative to the separated products. After zero-point vibrational energy corrections, the reaction energy is predicted to be −1.4 kJ mol−1. Vibrational frequencies of the stationary points are reported and compared with the limited available experimental results. The SiOOH potential surface is found to be very different from that for COOH, contrary to the analogy drawn by Chakraborty. Notwithstanding, the assumption of Chakraborty appears justified, because all the stationary points for the SiO + OH reaction have lower relative energies than known for the analogous carbon system.

Hu, Yaoping; Yang, Jing; Tian, Jiangwei; Jia, Li; Yu, Jun-Sheng

doi: 10.1039/c4ra08306gpmid: N/A

We have developed a facile approach for green and size-controllable synthesis of photoluminescent carbon nanoparticles (CNPs) by hydrothermal treatment of various waste plastic bags (WPBs) in low-concentration H2O2 solutions (≤5.0 wt%). This approach requires no toxic regents, severe synthetic conditions, or complicated procedures. Fine control over the particle size of the CNPs is achieved by simply changing the H2O2 concentration, and higher H2O2 concentration leads to smaller particle size of the CNPs. An interesting formation mechanism of the CNPs derived from WPBs has been proposed including thermo-oxidative degradation, polymerization, carbonization, and passivation. It is found that the CNPs can selectively quantify the concentration of Fe3+ from 10 to 400 μM with a detection limit as low as 2.8 μM. Moreover, the strong photoluminescence, excellent optical stability, low cytotoxicity, and good water-dispersibility of the CNPs make them suitable candidates for cellular imaging. The simple method developed here presents a new way for effective reuse of WPBs and realizes the encouraging “waste-to-treasure” conversion.

Sinha, Soumyadeep; Sarkar, Shaibal K.

doi: 10.1039/c4ra06308bpmid: N/A

Zinc nitride films are deposited by Atomic Layer Deposition (ALD) within a temperature range of 150–315 °C using diethylzinc (DEZ) and ammonia (NH3). Self-limiting growth characteristics are examined by an in situ Quartz crystal microbalance (QCM) that is subsequently verified and complemented by ex situ X-ray reflectivity (XRR) measurements. A saturated growth rate of ca. 1.4 Å per ALD cycle is obtained within the ALD temperature window of 175–215 °C. In situ Fourier transform infrared (FTIR) spectroscopy is employed to study the reaction mechanism during each ALD half cycle. As deposited films on microscope glass substrates have strong orientation in the {321} direction. Films are found to be optically transparent with band-edge photoluminescence.

Liu, Lizhu; Li, Jinfeng; Zhang, Xiaorui; Jin, Ke

doi: 10.1039/c4ra06705cpmid: N/A

“Core–shell” structured epoxy-acrylate emulsions with different contents of epoxy resins were synthesized. Styrene (St), butyl acrylic (BA), methyl methacrylate (MMA) and epoxy resin (E-51) were used as the main raw materials. The fine control of the epoxy content was the key approach to design the morphologies of the emulsion. Due to the different epoxy contents, there was a transition of the particle morphologies from irregular structure, to two-layer core–shell structure to three-layer core–shell structure. The particle size became larger and then smaller again, and the thermal stability of the emulsion decreased with the increase of the epoxy content. The emulsion with clear three-layer “core–shell” structures and uniform particle size distribution could be prepared when the content of epoxy resin was 30 wt%. The corresponding film prepared by the emulsion had the characteristic of self-stratification.

Gu, Zhenhua; Li, Kongzhai; Qing, Shan; Zhu, Xing; Wei, Yonggang; Li, Yongtao; Wang, Hua

doi: 10.1039/c4ra06715kpmid: N/A

CeO2, Fe2O3 and a series of CeO2-modified Fe2O3 oxides with Ce/Fe molar ratios ranging from 5 : 95 to 50 : 50 were prepared by a co-precipitation method and thermally aged at different temperatures, which were compared with corresponding samples prepared by physically mixing CeO2 and Fe2O3. The structural/textural feature, reduction behavior, oxygen storage capacity (OSC), and redox performance of the prepared materials were investigated via XRD, Raman, TEM, BET surface area, XPS, H2-TPR and oxygen pulse techniques. It was found that CeO2 particles were very small (<10 nm) and highly dispersed on the surface of Fe2O3 rods even after calcination at 800 °C. The nano-size effects resulted in strong chemical interaction in the Fe2O3–CeO2 interfaces, which significantly improved Fe2O3 reducibility in the reducing atmosphere. Hematite-like solid solutions were also observed in the mixed oxides, but it only existed on the materials with relatively low CeO2 content (Ce/Fe < 20 : 80). The formation of hematite-like solid solution could improve the surface reduction of Fe2O3, while the deep reduction of Fe2O3 depended mainly on the crystal size of Fe2O3 particles. The size effect played a more important role than solid solution on the reduction behavior of CeO2-modified Fe2O3 oxides. In addition, the presence of CeO2 on Fe2O3 also strongly improved the oxygen storage capacity and redox stability of Fe2O3, which can be attributed to the chemical interaction between cerium and iron oxides, involving the formation of a complex oxide (CeFeO3) after the TPR/OSC redox testing. These data provide useful references to design novel OSC materials for chemical looping technologies.

Jiang, Shengjuan; Wang, Songhua; Sun, Yujun; Ma, Yuhan

doi: 10.1039/c4ra07313dpmid: N/A

To improve the understanding of changes happening with nutrients in Pleurotus ostreatus during slow frozen storage in the short term, the metabolite contents of the fruiting body were evaluated. The effects of slow freezing and short-term storage on the variations of nutrients were studied at two temperatures, −20 and −30 °C, at various time points during storage. The contents of reducing sugars and vitamin C at all the treatments showed sustained downward trends. In the pileus, the contents of polysaccharide, proteins, and amino acids increased at first, and then decreased. In the stipe, the contents of all the measured substances maintained a slow decline. The variations of α-amylase showed a general downward trend with the freezing time. The fluctuation of the activity of POD implied reactive oxygen species production. Significant differences between the freezing/storage at −20 °C and −30 °C were observed in the contents of polysaccharides, reducing sugars, proteins, amino acids and vitamin C. In brief, when 30 min slow freezing was applied, the contents of most of the compounds showed a downward tendency or “up-down” trend because of ice damage.

Mei, Wenhai; Lü, Changli; Yan, Jingling; Wang, Zhen

doi: 10.1039/c4ra90021apmid: N/A

Correction for ‘Anion exchange membranes by bromination of benzylmethyl-containing poly(fluorene ether sulfone)s' by Wenhai Mei et al., RSC Adv., 2014, 4, 27502–27509.