RSC Advances

Zhou, Wei-Fang; Chen, Lang; Xie, Jun; Au, Chak-Tong; Yin, Shuang-Feng

doi: 10.1039/c5ra16206hpmid: N/A

Manganese-containing MFI-type Mn–ZSM-5 zeolites were prepared and characterized by XRD, UV-vis DRS, SEM, XPS, N2 adsorption–desorption, NH3-TPD and ICP-AES techniques. The zeolites show high catalytic activity and selectivity in the heterogeneous oxidation of p-chlorotoluene to p-chlorobenzaldehyde. The effects of catalyst concentration, water addition, HBr amount, as well as reaction time and temperature on product yield were investigated. Under the optimized conditions (catalyst 20 mg, p-chlorotoluene 1 mL, solvent (acetic acid) 10 mL, HBr (40 wt%) 30 mg, H2O 3 g, oxygen flow rate 50 mL min−1, time 8 h, temperature 100 °C), the Mn–ZSM-5 (Si/Mn = 48, Mn 1.7 wt%) catalyst shows p-chlorotoluene conversion of 93.8% and p-chlorobenzaldehyde selectivity of 90.5%. The excellent catalytic activity can be attributed to the distribution of Mn species and the mild acid sites.

Kang, Tian-Chen; Zhao, Xuan; Sha, Feng; Wu, Xin-Yan

doi: 10.1039/c5ra14667dpmid: N/A

An efficient asymmetric vinylogous allylic alkylation of β,γ-butenolides with Morita–Baylis–Hillman carbonates has been developed. With a chiral cyclohexane-based squaramide-phosphine catalyst 5e, optically active γ,γ-disubstituted butenolides containing adjacent quaternary and tertiary chiral centers have been constructed in good-to-excellent yields (up to 98%) and excellent stereoselectivities (87 : 13–99 : 1 dr, 96–99% ee).

Yu, Yaoguang; Chen, Gang; Wang, Xu; Jia, Dechang; Tang, Pengxiao; Lv, Chade

doi: 10.1039/c5ra13755apmid: N/A

A series of BiOI/Bi5O7I composite photocatalysts with heterostructures was successfully synthetized through a facile hydrothermal method. Attributed to the heterostructure between BiOI and Bi5O7I, photogenerated electrons and holes can be separated efficiently. The photocatalytic activity of the as-prepared samples was evaluated through the MO degradation reaction. The removal rate of MO was up to 93% after 40 min under visible light (λ ≥ 400 nm) irradiation, while the photocatalytic activity showed no decay after 3 cycles. Furthermore, the photocatalytic mechanism of MO degradation over the BiOI/Bi5O7I composite photocatalyst was investigated by taking TA, H2O2 and EDTA as probes. The experimental results indicate that the enhanced photocatalytic performance is attributed to the synergistic effect of photogenerated holes and superoxide radicals. The excellent activity and photostability reveal that the BiOI/Bi5O7I composite photocatalyst is a promising visible-light-response photocatalyst with potential applications in the field of water treatment.

Chen, Yi-An; Liu, Ching-Yuan

doi: 10.1039/c5ra13517fpmid: N/A

We report herein an operationally simple homocoupling reaction that targets the convenient synthesis of organic-electronically important building blocks. A variety of synthetically useful bithiophene derivatives and functionalized biphenyls are efficiently prepared by an on-water and under-air protocol using Pd/C as catalyst. We find that Pd/C gives generally higher and cleaner homocoupling conversions than using Pd(OAc)2 in the cases of (hetero)aryl iodides since Pd(OAc)2 triggers more side reactions including dehalogenations and oligomerizations. Under the optimum conditions, a broad range of functional groups such as ester, ketone, aldehyde, nitrile, nitro, chloride, and bromide are well tolerated. We expect the present methodology would make a valuable synthetic contribution towards bridging green chemistry with thiophene-based organic materials.

Larrude, Dunieskys Gonzalez; Garcia-Basabe, Yunier; Freire Junior, Fernando Lázaro; Rocco, Maria Luiza M.

doi: 10.1039/c5ra12799hpmid: N/A

Graphene sheet layers were grown by chemical vapor deposition (CVD) under a polycrystalline copper substrate using methane (CH4) and triphenylphosphine (P(C6H5)3) as carbon and phosphorous precursors, respectively. The films obtained from the CH4 and P(C6H5)3 chemical precursors were labeled as G/Cu and GP/Cu, respectively. Electronic structure investigation was performed on these two graphene samples combining different spectroscopic techniques. Raman spectroscopy shows the presence of single and multilayers in G/Cu and GP/Cu, respectively. A blue shift of 30 cm−1 of the 2D band in the GP/Cu film with respect to G/Cu is evidence of the p-type doping of GP/Cu. X-ray photoelectron and reflection electron energy loss spectroscopy (REELS) confirm the bilayer formation in the GP/Cu film. REELS also shows that the presence of phosphorous does not open the electronic band gap of the graphene film. The work function of 4.3 eV for G/Cu and 4.8 eV for GP/Cu films were determined by ultraviolet photoelectron spectroscopy. The increase of the work function is attributed to the electron transfer to the Cu substrate. The partially unoccupied densities of states in phosphorous doped graphene (GP/Cu) were evaluated by X-ray photoabsorption spectroscopy. The core-hole clock approach using resonant Auger spectroscopy was employed for investigating the charge transfer dynamics around the P K-edge in GP/Cu. Ultrafast charge transfer delocalization on a time scale of femtoseconds was observed, demonstrating a strong electronic coupling between unoccupied states of the phosphorous and the conduction band of the copper substrate. The combined spectroscopic results suggest p-type doping in GP/Cu by the electron transfer mechanism.

Liu, Shan; Liu, Yan-Jun; Deng, Fu; Ma, Ming-Guo; Bian, Jing

doi: 10.1039/c5ra12440apmid: N/A

Fe3O4/C nanocomposites have been successfully synthesized by calcination ferrous precursors, which were obtained with microcrystalline cellulose (MCC) or cellulose nanocrystals (CNC) by an environmentally-friendly ultrasound method in ethylene glycol (EG). The effects of different cellulose types on the Fe3O4/C nanocomposites were investigated by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetry analysis (TG), and derivative thermogravimetry (DTG). The experimental results revealed that the different cellulose types played an important role in the phases, crystallinities, and morphologies of the Fe3O4/C nanocomposites. Moreover, the magnetic performance revealed that Fe3O4/C nanocomposites had relatively high superparamagnetic and ferromagnetic performances, which provided promising applications for the dye removal and wastewater treatment fields.

Srivastava, Ambrish Kumar; Misra, Neeraj

doi: 10.1039/c5ra14735bpmid: N/A

Superalkalies, due to lower ionization potentials than alkalies, possess potential reducing capability and can be used in the synthesis of a variety of charge transfer salts. In order to check whether superalkali hydroxides are as basic as a typical alkali hydroxide, we have performed a systematic investigation on the hydroxides of small FLin (n = 2–5) superalkali clusters. The equilibrium structures are identified and their stability is analyzed against the elimination of LiOH and LiF molecules. Our MP2 calculations show that the proton affinity and gas phase basicity of the FLinOH species are lower than that of LiOH by 50–100 kJ mol−1. The trend of basicity of FLinOH is in accordance with their HOMO–LUMO energy gap as well as the LiOH and LiF elimination energies. Considering the fact that charge transfer salts possess significant nonlinear optical (NLO) responses, we have also calculated NLO parameters such as the total static dipole moment, the mean polarizability and the first static mean hyperpolarizability of the FLinOH species. The dipole moment and the polarizability values increase successively from FLi2OH to FLi5OH. On the contrary, the hyperpolarizability only increases for FLi3OH (2.7 × 103 a.u) and FLi5OH (2.6 × 105 a.u.). The dramatically large hyperpolarizability of FLi5OH is due to anionic Li possessing an excess electron, thus resembling the feature of an “alkalide”. The present work should provide new insights into the design of strong inorganic bases for chemical synthesis as well as potential NLO species for electro-optical applications.

Maniruzzaman, M.; Snowden, Martin J.; Bradely, Mike S.; Douroumis, D.

doi: 10.1039/c5ra13176fpmid: N/A

The aim of this study is to utilise an advanced surface chemical analysis based on X-ray photoelectron spectroscopy (XPS) to determine and characterise drug/polymer interactions in solid dispersions manufactured via hot melt extrusion (HME). Cetirizine HCl (CTZ) and verapamil HCl (VRP) were used as model cationic drugs while Eudragit® grade L100 and L100-55 polymers were used as anionic carriers. A molecular dynamics (MD) based simulation approach predicted drug/polymer interactions while scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) mapping showed homogenous distribution of the drug particles onto the polymer matrices. Hot stage microscopy (HSM) characterised the solid state of the drugs in extruded formulations. XPS analysis revealed the strength and nature of interaction between the –NH3 groups of the APIs with the –COOH groups of the polymers. The results obtained from XPS were supported by XRD and NMR studies. The estimation of non-protonated/protonated N atom (N/N′) ratios using XPS revealed the strength of the intermolecular interaction in drug/polymer extrudates which can be used as an efficient tool to study the drug/polymer interaction.

Abdeen, Z.; Akl, Z. F.

doi: 10.1039/c5ra10264bpmid: N/A

Poly(vinyl alcohol)/multiwalled carbon nanotubes (PVA/MWCNTs) composite hydrogels were prepared by a dispersion method and their ability to adsorb and remove uranyl ions from aqueous solutions was investigated. The prepared composites were characterized by XRD, TEM, SEM and FTIR. The effect of contact time, solution pH, initial UO22+ ion concentration and temperature on UO22+ ion adsorption from aqueous solution onto the prepared hydrogels was studied. The obtained results illustrated that, dispersion of MWCNTs into the PVA matrix enhanced the removal efficiency of UO22+ ions compared to PVA only. The Langmuir and Freundlich adsorption models have been applied to evaluate the adsorption efficiency and the data correlated well with the Langmuir model. Thermodynamic parameters (ΔH°, ΔS°, ΔG°) were determined which indicated that the UO22+ ion adsorption process onto the prepared hydrogels was exothermic and spontaneous. The adsorbed UO22+ can be desorbed effectively by 0.1 M EDTA.

Guo, Zhiqiang; Li, Chao; Lu, Shuanglong; Pan, Yue; Gu, Hongwei

doi: 10.1039/c5ra08816jpmid: N/A

A novel and controlled sol-hydrothermal synthesis of nano-TiO2 assisted by citrate/F− has been developed. We studied factors that influence its size and morphology, such as citrate, Cl−, F− and so on. Different ratios of citrate to TiCl4 gave different sizes and morphologies. Cl− preferentially formed a rutile phase, while citrate preferentially formed an anatase phase, and F− gave a dominant {001} facet. Additionally, we found that the photocatalytic activity of the TiO2 synthesised with the assistance of citrate was superior to the commercially available TiO2.