RSC Advances

Wu, Hung-Yu; Nguyen, Nhat Huy; Bai, Hsunling; Chang, Sue-min; Wu, Jeffrey C. S.

doi: 10.1039/c5ra10408dpmid: N/A

In this study, the photocatalytic reduction of CO2 in a monoethanolamine solution to form valuable energy sources was investigated using Mo-doped TNTs photocatalysts for the first time. The results revealed that the structure of Mo-doped TNTs changed with the increase of calcination temperature. For Mo-doped TNTs calcined at 500 °C, the partial corruption of titanate nanotubes into anatase particles caused the reduction of Mo species from Mo6+ to Mo5+ and produced oxygen vacancies, which resulted in the highest CO2 reduction ability. The yield rates of CH4, CO and total combustible organic compounds were 0.52, 10.41 and 13.53 μmol gcat−1, respectively, under UVA (8 W, 63 μW cm−2) irradiation. The photoreduction quantum efficiencies of CH4 and CO were achieved at 0.036% and 0.180%, respectively. It was found that the molybdenum structure and oxygen vacancies could be the key factors controlling the photocatalytic reduction efficiency of CO2. A possible structure transformation of Mo-doped TNTs at different calcination temperatures was inferred and the reaction mechanism for photocatalytic CO2 reduction with oxygen vacancy sites of Mo-doped TNTs was proposed.

Chen, Fei; Yang, Qi; Niu, Chenggang; Li, Xiaoming; Zhang, Chang; Zeng, Guangming

doi: 10.1039/c5ra10480gpmid: N/A

An efficient visible-light-driven photocatalyst Ag@AgCl/ZnSn(OH)6 (Ag@AgCl/ZSH) was successfully fabricated by an ultrasonic assisted precipitation-photoreduction method at room temperature. The photophysical properties of the as-prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), UV-vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and photoluminescence emission spectra (PL) analysis. The photocatalytic activities of the as-prepared samples were evaluated by the photodegradation of rhodamine B (RhB), crystal violet (CV) and phenol aqueous solution. The Ag@AgCl (8 wt%)/ZSH-20 composite exhibited the optimal photocatalytic performance, and the corresponding degradation rates for RhB, CV and phenol solution were as high as 22/3.6, 15/4 and 16/3.6 times those of pure ZSH and the conventional visible-light photocatalyst N–TiO2, respectively. The effect of photo-reduction time on the photocatalytic properties of the Ag@AgCl/ZSH composites was systematically investigated. Moreover, a possible degradation mechanism was proposed based on reaction equations and a simulated scheme on the basis of active species trapping experiments and band energy analysis. The dramatically enhanced photocatalytic performance of Ag@AgCl/ZSH should be ascribed to the surface plasmon resonance (SPR) effect from Ag@AgCl nanoparticles and high separation of photogenerated electron–hole pairs in the photocatalytic process, leading to low recombination rates of the photoinduced electron–hole pairs. High degradation efficiencies and physicochemical features were maintained after five recycling experiments, indicating that the photocatalysts were relatively durable and stable. It is expected that the plasmonic photocatalyst Ag@AgCl/ZSH is a promising candidate material for the photodegradation of organic pollutants in wastewater.

Gong, Sai; Guo, San-Dong; Chen, Peng; Liu, Bang-Gui

doi: 10.1039/c5ra09921hpmid: N/A

Motivated by experimental nonmetallic features and high magnetic Curie temperatures of 360 and 522 K in double perovskite Ca2CrReO6 and Ca2FeReO6, we systematically investigate the structural, electronic, and magnetic properties of Ca2MReO6 (M = Cr, Fe) by combining the modified Becke–Johnson (mBJ) exchange potential with usual generalized gradient approximation (GGA). Our full optimization leads to stable ground-state structures with monoclinic symmetry (P21/n) consistent with experiment. The mBJ calculation successfully produces ferrimagnetic phase with semiconductor gaps of 0.38 eV and 0.05 eV, respectively, in contrast with wrong metallic phases from GGA calculations. With the spin–orbit coupling (SOC) taken into account, the Ca2MReO6 (M = Cr, Fe) shows high magneto-crystalline anisotropy (MCA) with the magnetic easy axis along the [010] direction. Although reducing to 0.31 and 0.03 eV, the semiconductor gaps remain open in spite of the SOC broadening of the Re t2g bands. Therefore, our DFT investigation has established the correct ferrimagnetic semiconductor ground states for the double perovskite Ca2MReO6 (M = Cr, Fe) materials. Our analysis shows that the semiconductor gaps are due to orbital-selective splitting on Re t2g bands in the minority-spin channel, originated from the O-octahedral distortion and Coulomb correlation effect. This mechanism, different from that in other double perovskite materials such as Sr2CrOsO6, Ca2CrOsO6 and Sr2FeOsO6, can be useful to fully understand chemical and physical properties of double perovskite compounds.

Selim, Mohamed S.; El-Safty, Sherif A.; El-Sockary, Maher A.; Hashem, Ahmed I.; Abo Elenien, Ossama M.; EL-Saeed, Ashraf M.; Fatthallah, Nesreen A.

doi: 10.1039/c5ra07400bpmid: N/A

Since the use of organotin antifouling paints was prohibited in 2003, researchers have endeavored to develop novel environment-friendly marine antifouling coatings. We report the successful fabrication of model silicone foul-release (FR) coatings with elastomeric polydimethylsiloxane (PDMS)/spherical silver (Ag) nanocomposites. This design integrates two inhibition modes of (1) chemical inertness and (2) the physical repelling force of microfouling. The antifouling nanocomposite models were successfully synthesized via the solution casting technique. In this approach, a series of filler concentrations of Ag nanoparticles (NPs) with a particle size of <10 nm and spherical morphology facet dominantly controlled on the {111} lattice plane was used to control the antifouling models. The surface hydrophobicity, roughness, and free energy properties of the nanocomposites were systematically studied as fouling non-stick factors. The physicomechanical properties were also assessed. Selected bacterial strains were used as microfoulants for a laboratory assay investigation for 30 days. Our findings provide important insights into how subtle structural changes in polymer nanocomposites can considerably improve biological activity and simplify surface cleaning. Hydrophobicity, surface inertness, fouling resistance, and surface easy-cleaning properties significantly improved in the nanocomposite design models fabricated with nanofiller loadings of up to 0.1% spherical Ag NPs without changes in the bulk mechanical properties. The fabricated models were subjected to a rigorous test in a field trial in Red Sea water. The results show the potential of our models based on Ag nanofillers up to 0.1% for ecologically friendly antifouling coatings as an alternative to traditional systems. The PDMS/Ag composite models have a long-term durability and antifouling performance, which are important factors for developing effective, stable, and eco-friendly nanocomposites.

Liu, Cai-Ming; Zhang, De-Qing; Zhu, Dao-Ben

doi: 10.1039/c5ra11621jpmid: N/A

A novel lanthanide metal–organic framework was yielded by a hydrothermal reaction of 5-chloro-6-hydroxypyridine-3-carboxylic acid (5-Cl-6-HOPy-3-CO2H) and Dy2O3 in the presence of oxalic acid [H2(OX)], namely, {[Dy2(1H-5-Cl-6-Opy-3-CO2)2(OX)2(H2O)]·2H2O}∞ (1, 1H-5-Cl-6-Opy-3-CO2− = 1-hydro-5-chloro-6-oxopyridine-3-carboxylate, which was formed by the autoisomerization of single deprotonated 1H-5-Cl-6-HOpy-3-CO2− anion). The dysprosium(iii) ions are bridged by oxalate anions to construct an interesting 4-connected layer network with a Schälfli topology symbol of (32·52) (3·53), such layers are connected with each other by the 1H-5-Cl-6-HOpy-3-CO2− anions to form a three-dimensional framework. Magnetic investigations indicated that 1 is a field-induced single-molecule magnet, displaying two-step thermal magnetic relaxation, with an effective thermal barrier of 37.6 K. Surprisingly, a zigzag chain-like gadolinium(iii) complex, {[Gd(1H-5-Cl-6-Opy-3-CO2)2(OX)0.5(H2O)3]·6H2O}∞ (2), was isolated using Gd2O3 instead of Dy2O3 owing to the lanthanide contraction effect. Notebaly, a unique F-shaped (H2O)6 supramolecular aggregate exists in the crystal structure of 2.

Hu, Jing; Li, Hao; Yang, Yumeng; Wang, Shizeng; Tang, Pingwah; Li, Chunfang; Tian, Guifang; Yuan, Qipeng

doi: 10.1039/c5ra08748apmid: N/A

Alpha-linolenic acid (ALA) is known for its ability to promote the production of β-carotene in Blakeslea trispora. However, the mechanism is still poorly understood. In this study, gas chromatography-mass spectrometry (GC-MS)-based metabolomic approach and multivariate analysis were used to study mechanisms underlying the regulation effects of ALA on β-carotene synthesis in B. trispora. ALA treatment promoted the biomass of B. trispora and β-carotene production. The maximum β-carotene production 5.344 mg L−1 was realized after 72 h of cultivation in the presence of 50 μL ALA. The intracellular metabolite profiles found upon treatment of the cells with different addition time points of ALA were unique and could be distinguished from the aid of principal component analysis (PCA). Furthermore, partial least-squares-discriminant analysis (PLS-DA) revealed a group classification and pairwise discrimination between the control and ALA treated groups, and 28 differential metabolites with variable importance in the projection (VIP) value greater than 1. The addition of ALA decreased the glycolysis, TCA cycle and fatty acid synthesis. The accumulation of linolenic acid and linoleic acid indicated that ALA was directly absorbed by the fungus and transformed into its own linolenic acid. As a result, the flux from acetyl-CoA to β-carotene synthesis increased. Besides, the addition of ALA increased the level of dissolved oxygen and the production of β-carotene.

Tan, Yajun; Mao, Qifeng; Su, Wei; Zhu, Yunfeng; Li, Liquan

doi: 10.1039/c5ra09754apmid: N/A

Mg100−xNix (x = 0, 5, 10 and 20) composites with the main particle size below 400 nm were synthesized by hydriding combustion synthesis followed by mechanical milling (HCS + MM). XRD and TEM results of Mg100−xNix revealed that the products had the phases of MgH2, Mg2NiH4, Mg2NiH0.3 and Mg (Mg just for x = 0 and 5), with Mg–Ni hydrides distributing uniformly in the composites. DSC results of Mg100−xNix composites demonstrated that the hydrogen desorption peak for MgH2 in the Mg80Ni20 composite was decreased to 223.9/247.3 °C. With 5 at% Ni added, the Mg95Ni5 reached its saturated hydrogen absorption capacity of 5.80 wt% within 100 s at 473 K. As for Mg80Ni20, a hydrogen absorption of 3.70 wt% at 313 K and a desorption capacity of 1.84 wt% at 473 K could be obtained. The Mg2Ni distributing uniformly in Mg–Ni composites significantly facilitates hydrogen diffusion and improves the hydriding/dehydriding kinetics and hydrogen storage capacity at low temperature. The amount of Ni is related greatly to the hydriding/dehydriding properties of Mg100−xNix, which makes the hydrogen storage capacity and hydriding/dehydriding kinetics remarkable. Besides, the excellent cycling stability was also obtained through the isothermal de/hydrogenation cycling kinetics measurement.

Qian, Kun; Wang, Yilin; Liang, Zhiqiang; Li, Jiyang

doi: 10.1039/c5ra09942kpmid: N/A

Germanosilicate zeolite ITQ-44 with extra-large 18-rings has been hydrothermally synthesized by using a commercial benzyltriethylammonium bromide (denoted as SDA-1) as structure-directing agent (SDA). The crystallization field and the influence of various synthetic factors on the synthesis of ITQ-44, such as the crystallization temperature, the crystallization time, the Si/Ge ratio, and the amount of the F− and water have been studied. The as-synthesized ITQ-44 has been characterized by XRD, ICP, CHN, TG, SEM, NMR, N2 adsorption and NH3-TPD. The results indicate that use of SDA-1 cations could lead to a pure phase of ITQ-44 in a wide synthetic range and remain intact in the final product. The framework structure of ITQ-44 is maintained at 500 °C. B, Al and Ga atoms can be introduced into the framework of germanosilicate ITQ-44, which produces Lewis acid sites in the framework. This work offers the possibility to synthesize extra-large pore germanosilicate zeolites with simple and commercial SDAs, which is important for the practical applications of germanosilicate zeolites.

He, Xiaohui; Liu, Jingyin; Zhu, Hongyu; Zheng, Yan; Chen, Defu

doi: 10.1039/c5ra09393gpmid: N/A

Novel quaternary ammonium functional addition-type norbornene copolymers (QCnP(BN/PhBN), n = 1, 6, 10, 12) with different alkyl side chain length comb-shaped structures or different contents of 2-(4-phenyl-butoxymethy-lene)-5-norbornene (PhBN) (22–77%) are synthesized via copolymerization of functionalized norbornenes, and their corresponding hydroxide-conductive anion exchange membranes (AEMs) with effective hydrophilic–hydrophobic separation are prepared and confirmed by TEM or SEM. The achieved AEMs show high ion exchange capacity (1.83 mmol g−1), as well as low methanol permeability (1.97–20.4 × 10−7 cm2 s−1), which are lower than that of Nafion®. The ionic conductivity increases with the operation temperature increasing and is observed up to 4.14 × 10−3 S cm−1. The AEMs exhibit excellent dimensional stability with a swelling degree in plane between 0.9–3.3% and good chemical stability under 6 M NaOH solution even after a month. Membrane electrode assembly (MEA) is fabricated by using the alkalized QC12P(BN/PhBN)-77 as the AEM and tested in an alkaline direct methanol fuel cell. The open circuit voltage (OVC) of 0.54 V and the maximum current density of 66 mW cm−2 are achieved at 80 °C, respectively.

Shen, Youming; Zhang, Xiangyang; Huang, Xi; Zhang, Youyu; Zhang, Chunxiang; Jin, Junling; Liu, Xuewen; Li, Haitao; Yao, Shouzhuo

doi: 10.1039/c5ra11116apmid: N/A

A new naphthalimide derivative containing hexanoic acid and boronate groups was designed and synthesized. The compound displays off/on ratio singles, highly selective and sensitive towards glucose based on a naphthalimide derivative reacting with enzyme generated H2O2 in 100% water. The fluorescence intensity is proportional to the concentration of glucose over a range of 0–120 μM (R2 = 0.9912), with a limit of detection of 0.3 μM (S/N = 3). Moreover, the fluorescent sensor has been used for determination of glucose in serum with satisfactory results, which further demonstrates its value in practical applications.