RSC Advances

Larsen, George K.; Stom, Nicholas; Zhao, Yiping

doi: 10.1039/c5ra16939apmid: N/A

We demonstrate the continuous tuning of the circular dichroism spectra of chiral patchy particle structures fabricated by dynamic shadowing growth (DSG) using the galvanic replacement reaction (GRR), which is a wet chemical process where Au ions in solution are gradually replaced by Ag atoms in a support. It is found that the unpolarized and circular polarization optical responses generally shift to longer wavelengths as a function of reaction time. The red-shifts in the spectra are attributed to changes in the ambient refractive index, chiral patch morphology, and material composition. For reaction times less than 4 minutes, the circular dichroism spectra can be adjusted over a wide range of wavelengths in the visible and near-infrared region with only slight reductions in magnitude. Thus, the combination of dry (DSG) and wet (GRR) nanofabrication techniques offers a route to dynamically tune the spectral response of chiral plasmonic thin films.

Share, Keith; Lewis, John; Oakes, Landon; Carter, Rachel E.; Cohn, Adam P.; Pint, Cary L.

doi: 10.1039/c5ra19717apmid: N/A

Tungsten diselenide (WSe2) is demonstrated as an efficient electrode for sodium ion batteries for the first time. A high reversible capacity above 200 mA h g−1 is observed at 20 mA g−1 rate, with over 250 mA h g−1 capacity measured in the first sodium extraction. Assessment of electrolyte and binder materials on performance was examined and an EC/DEC electrolyte with CMC binder emerges to yield the highest capacity and cycling retention. Comparison between WS2 and WSe2 distinguishes WSe2 to exhibit superior performance due to more efficient energetics bearing a small overpotential <0.30 V. Ex situ analysis and imaging after cycling confirms a sodium-mediated conversion reaction that yields isolated domains of W metal or NaxSe and reformation of WSe2 upon sodium extraction, enabling insight into the chemical storage pathway. This work highlights the promise of WSe2 compared to other conversion-based transition metal dichalcogenides as a practical material for sodium ion batteries.

Khazaei, Ardeshir; Sarmasti, Negin; Seyf, Jaber Yousefi; Tavasoli, Mahsa

doi: 10.1039/c5ra16102apmid: N/A

In this investigation, hexahydroquinoline (HHQ) derivatives were synthesized via a one-pot reaction using dimedone, β-ketoester, ammonium acetate, and different aryl aldehydes. ZrOCl2·8H2O was used as a potential green catalyst, it is a commercially available solid material, with low toxicity, low cost and high activity, and it is easy to handle. The reaction conditions were optimized using response surface methodology (Central Composite Design (CCD)) with three replicates at a central point. Optimization showed that the optimum reaction temperature and amount of catalyst are 83.75 °C and 0.15 mol%, respectively. The lower reaction yields at temperatures higher than 83.75 °C are related to the formation of a new crystalline phase of ZrOCl2·8H2O. The fitted quadratic polynomial model applied to the experimental yield could well predict the experimental reaction yield. Ecofriendly reaction conditions, easy workup procedure, the reusability of the catalyst, short reaction times and high yields are some of the advantages of this work.

Kohlrausch, Emerson C.; Zapata, Maximiliano J. M.; Gonçalves, Renato V.; Khan, Sherdil; Vaz, Mauricio de O.; Dupont, Jairton; Teixeira, Sérgio R.; Leite Santos, Marcos J.

doi: 10.1039/c5ra17225jpmid: N/A

In this work we show that phase formation and oxygen substitution can be controlled by the source of nitrogen used during the synthesis of TiO2 nanoparticles. By performing a thorough study on the structure of the nanoparticles, the use of NH4+ or NO3− was found to influence not only the N-doping level but also the formation of the polymorphic phase. Structural and microstructural refinement obtained by XRD pattern and data processing performed by the Rietveld refinement revealed that TiO2 obtained with HNO3 presents ca. 98% of anatase and ca. 2% for rutile. Meanwhile TiO2 nanoparticles synthesized with NH4F and NH4Cl presents a single anatase phase with ca. 7.0% and 4.4% of nitrogen substitutional oxygen sites, respectively. The local structure of N-doped TiO2 around the Ti atoms was investigated by X-ray absorption spectroscopy. The XANES spectra show that N-doped TiO2 possesses a characteristic pre-edge of a single anatase structure. The coordination number decreased and the shrinking Ti–O bond distances are due to the N-doping in the TiO2 structure. The most efficient dye sensitized solar cell and the higher hydrogen production was obtained from the TiO2/NH4Cl, which was obtained as a single anatase phase with intermediary concentration of N substitutional oxygen sites.

Zhao, Hailei; Cui, Bo; Chen, Zhenhua; Wang, Hongzhi; Zhang, Qinghong; Li, Yaogang

doi: 10.1039/c5ra18549apmid: N/A

Pure inorganic materials are expected to find applications in various fields including energy-efficient and environmental-friendly soft display technologies, thereby requiring them to operate effectively while being bent or stretched. In the present study, excellent mechanical flexibility properties were successfully imparted into conventionally fragile inorganic materials using a nanobelt network design. Specifically, organic–inorganic composite materials were engineered into considerably long and continuous nanobelts using a simple electrospinning process. The composites were then subjected to calcination and nitridation processes to produce highly fluorescent inorganic (Si-based) membranes with high flexibility. The synthesized nanobelts exhibit high aspect ratios and well-defined rectangular cross-sections, and display excellent mechanical flexibility. The nanobelts could be bent to a minimum curvature radius down to 1 mm. Furthermore, the nanobelts incur no visible damage after 500 cycles of bending to a radius of 1 cm. Under an applied strain of 6% for 500 cycles, the flexible SiO2-based fluorescent nanobelt membrane maintained a high strength of 6.0 MPa. Moreover, the photoluminescence intensity of the free-standing fluorescent nanofibrous inorganic membranes featured excellent environmental, thermal and mechanical cyclic stability. The current findings strongly indicate the great potential of the engineered fluorescent inorganic membranes as fluorescent materials in flexible display technologies and the remote packaging of LED.

Chulkaivalsucharit, Poommarat; Wu, Xiaoling; Ge, Jun

doi: 10.1039/c5ra21069kpmid: N/A

By co-precipitation with metal ions and organic ligands in water droplets of reverse micelles, the enzyme horseradish peroxidase (HRP) was encapsulated in metal–organic framework (MOF) nanocrystals. The HRP embedded in MOF with an average size around 30 nm showed an increased activity compared to the native enzyme.

Shee, Sujit Kumar; Reddy, Sreekantha T.; Athar, Javaid; Sikder, Arun Kanti; Talawar, M. B.; Banerjee, Shaibal; Shafeeuulla Khan, Md Abdul

doi: 10.1039/c5ra16476apmid: N/A

The essential idea of developing energetic binders and plasticizers is to enhance the thermal stability and energy content, improve the oxygen balance and burning behaviour of moulds, reduce the glass transition temperature and improve other mechanical properties of propellant and explosives formulations. The compatibility of energetic binder poly-glycidyl nitrate (PGN) with some energetic plasticizers of solid propellants was studied using differential scanning calorimetry (DSC), rheology and DFT methods in relation to the effect of the addition of five different energetic plasticizers, i.e. bis(2,2-dinitro propyl) acetal (BDNPA), dinitro-diaza-alkanes (DNDA-57), 1,2,4-butanetriol trinitrate (BTTN), N-N-butyl-N′(2-nitroxy-ethyl) nitramine (BuNENA) and diethyleneglycol dinitrate (DEGDN), on the rheological and thermal properties of the energetic binder PGN. The results obtained for the mixture of plasticizer and binder with respect to decomposition temperature (Tmax) and the format of the peak are compared with the results obtained for the pure binder, indicating the compatibility of these plasticizers with PGN. The glass transition temperatures (Tg) of all these mixes were determined by low-temperature DSC, which showed a lowering of Tg with a single peak. Rheological evaluation revealed that the viscosity of the binder is sufficiently lowered with an increase in flow behaviour on addition of 20% (w/w) plasticizer. The addition of 20% DEGDN has the maximum effect on the lowering of the viscosity of PGN. Quantum chemically derived molecular electrostatic potential (MESP) shows the possible sites of interaction of plasticizers and binder with the estimated lowest Vmin values and their magnitudes provide an insight into their mutual interactions. The relative trend in interaction energies between plasticizer and binder, PGN, is well correlated with a corresponding trend in the ability of plasticizers towards reducing the viscosity of PGN. The information gathered in the present study would in general be valuable with respect to designing new plasticizers.

Ren, X. Y.; Bai, X. Q.; Yuan, C. Q.; Yang, Y.; Xie, H.; Cao, P.; Ma, C. Y.; Wang, X. J.; Yan, X. P.

doi: 10.1039/c5ra13855hpmid: N/A

Biofouling seriously affects the properties and service life of metal materials. A number of studies have shown that the initial bacterial attachment to the metal surface and the subsequent formation of biofilm are dependent on the surface characteristics of the substratum, including metal surface free energy, roughness and metallurgical features. In this study, a novel recombinant fusion protein, which consists of receptor binding domain protein (RBD), truncated protein fragment of MrpF and alkaline phosphatase (PhoA) domains, has been constructed in an attempt to increase the surface contact angle of stainless steel. It has been confirmed that RBD has a strong affinity to 304 stainless steel; the truncated protein fragment of MrpF has high hydrophobicity and anchoring features, which can improve the contact angle of the material surface, whilst PhoA is an effective detection tool to monitor the expression and secretion of fusion protein. Multiple assays including FTIR, XPS, SEM-EDS and contact angle measurement revealed the existence of nitrogen and sulfur elements, binding energy shifts of nitrogen, carbon and oxygen atoms, and new FTIR peaks in treated stainless steel samples with increased contact angles at about 50°, confirming that a new organic steel material has been produced responding to these surface property changes. Using novel recombinant peptides to react with steel could become a new technique to increase the surface contact angle of the stainless steel for diverse applications.

Kuo, Feng-Jia; Ho, Mon-Shu; Dai, Jane; Fan, Ming-Huisung

doi: 10.1039/c5ra17864apmid: N/A

This study investigated the possibility of using atomic force microscopy (AFM) as a drug delivery system as well as a means to manipulate individual cells in an open microfluidic system for the rapid evaluation of human erythrocyte pathology in situ. We also examined the stability and biocompatibility of a patterned polydimethylsiloxane (PDMS) platform for use in conjunction with AFM. Our results demonstrate the effectiveness of integrating a microfluidic actuator with AFM technology to conduct in vitro medical analysis using only a miniscule quantity of human tissue.

He, Yue; Jiao, Bi-ning

doi: 10.1039/c5ra21116fpmid: N/A

In this work, a novel fluorescent method for protein detection has been developed based on terminal protection of small molecule-linked DNA by target protein and the difference in affinity of graphene oxide (GO) for single-stranded DNA (ssDNA) containing different numbers of bases in length. A probe ssDNA, which is labeled carboxyfluorescein (FAM) at the 5′ end and a small molecule at the 3′ end, is designed for the detection of target protein. In the absence of target protein, the probe ssDNA can be hydrolyzed into mononucleotides by Exo I. The introduction of GO into the sensing solution results in weak quenching of the fluorescence of FAM due to the weak affinity of the short FAM-labeled oligonucleotide fragment to GO. Conversely, and very importantly, in the presence of target protein, the specifically binding of target protein to the small molecule of probe ssDNA can protect probe ssDNA from the Exo I-catalyzed digestion. Then the adsorption of the probe ssDNA on GO makes FAM close proximity to GO surface resulting in high efficiency quenching of fluorescence of FAM, and the fluorescence intensity gradually decreases with increasing concentration of target protein. Taking folate receptor (FR) as an example in this work, we can determine the protein in a linear range from 1 to 80 ng mL−1 with a detection limit of 0.81 ng mL−1. Besides satisfactory sensitivity, the developed strategy also shows high selectivity, excellent reproducibility, and low cost, implying that this technique may have great potential applications in the future.