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Applied Nanoscience (v.1, #2)
Nitrogen-doped carbon nanotubes as a metal catalyst support by Letlhogonolo F. Mabena; Suprakas Sinha Ray; Sabelo D. Mhlanga; Neil J. Coville (pp. 67-77).
The science and technology of catalysis is of fundamental importance to a national economy. Today about 90% of all technical chemicals are manufactured by the use of catalysts. Nanoparticles of noble metals are extremely important materials in the catalysis industry due to cost issues and properties that are not found in their bulk state. An efficient way to produce and stabilise noble metal nanoparticles is by dispersion on a suitable support. Carbon-based supports, such as carbon nanotubes, carbon spheres, carbon fibres, etc., have been found to be good supports for metal nanoparticles. However, to be used effectively, the carbon surface must be modified either by functionalisation or doping. This review discusses the synthesis and the possible applications of nitrogen-doped carbon nanotubes as supports for metal nanoparticles in heterogeneous catalysis.
Keywords: Nitrogen-doped carbon nanotubes; Metal nanoparticles; Synthesis; Catalysis support
Multicolor microcontact printing of proteins on nanoporous surface for patterned immunoassay by Elaine Ng; Ashwini Gopal; Kazunori Hoshino; Xiaojing Zhang (pp. 79-85).
The large scale patterning of therapeutic proteins is a key to the efficient design, characterization, and production of biologics for cost effective, high throughput, and point-of-care detection and analysis system. We demonstrate an efficient method for protein deposition and adsorption on nanoporous silica substrates in specific patterns using a method called “micro-contact printing”. Multiple color-tagged proteins can be printed through sequential application of such micro-patterning technique. Two groups of experiments were performed. In the first group, the protein stamp was aligned precisely with the printing sites, where the stamp was applied multiple times. Optimal conditions were identified for protein transfer and adsorption using the pore size of 4 nm and thickness of 30 nm porous silica thin film. In the second group, we demonstrate the patterning of two-color rabbit immunoglobin labeled with fluorescein isothiocyanate and tetramethyl rhodamine iso-thiocyanate on porous silica substrates that have a pore size 4 nm, porosity 57% and thickness of the porous layer 30 nm. A pair of protein stamps, with corresponding alignment markings and coupled patterns, were aligned and used to produce a two-colored stamp pattern of proteins on porous silica. Different colored proteins can be applied to exemplify the diverse protein composition within a sample. This method of multicolor microcontact printing can be used to perform a fluorescence-based patterned enzyme-linked immunosorbent assay to detect the presence of various proteins within a sample.
Keywords: Multicolor; Microcontact printing; Patterned immunoassay; Nanoporous
On the optical and thermal properties of in situ/ex situ reduced Ag NP’s/PVA composites and its role as a simple SPR-based protein sensor by A. Nimrodh Ananth; S. Umapathy; J. Sophia; T. Mathavan; D. Mangalaraj (pp. 87-96).
Silver/polyvinyl alcohol (Ag-PVA) nanocomposite films have been prepared via in situ generation of silver nanoparticles (Ag NPs) by the respective metallic salts and dispersion of preformed Ag NPs (ex situ synthesis) inside polyvinyl alcohol (PVA) and its effect of sensing towards a model protein (bovine serum albumin—BSA) was investigated. The influence of Ag NPs, irrespective of their reduction methodology on the optical and the thermal properties of the PVA, had been investigated using UV–Vis spectrophotometer and differential scanning calorimetry. The absorption peak around 400 nm indicates the surface plasmon resonance response of Ag NPs. The interaction of the dispersed and preformed Ag NPs with the PVA chains is confirmed by the corresponding vibrational signatures of the PVA through Fourier transform infrared spectroscopy (FTIR). The changes in the glass transition and melting temperatures (T g and T m) of the pure PVA upon the presence of Ag NPs are reported using differential scanning calorimeter (DSC). The sizes of the synthesized Ag NPs are found to be in the range of 200 ± 10 nm for in situ reduction of silver nitrate (AgNO3) and 100 ± 10 nm for the external addition of preformed Ag NPs by sodium borohydride (NaBH4) reduction using scanning electron microscopy (SEM).
Keywords: Surface plasmon resonance; In situ generation; Ag-PVA; BSA
Microwave-assisted chemical reduction routes for direct synthesis of Fe–Pt nanoparticles in ordered face centered tetragonal L10 phase by S. Acharya; K. Singh (pp. 97-101).
In the present work, microwave-assisted chemical reduction route has been explored for the direct synthesis of face centered tetragonal (fct) L10 phase of Fe–Pt nanoparticles. Effects of microwave power and irradiation time on the growth process were investigated. Using this facile and high yield technique we could tune particle size from 7 to 17 nm. The as-prepared Fe–Pt NPs were observed in ordered fct L10 phase without any post-synthesis treatment. The particle size and magnetic properties of the as-prepared Fe–Pt were found to be very sensitive to the microwave irradiation power, while influence of exposure time was insignificant. The hysteresis measurements were performed at room temperature (300 K) to study magnetic properties of as-synthesized Fe–Pt as a function of crystallite size. All specimens of Fe–Pt were found to exhibit ferromagnetic behavior at room temperature. Coercivity and saturation magnetization were observed to be decreasing with diminishing particle size. The microwave-assisted route is found to be a simple technique for direct synthesis of metal alloys and may prove to be a potential tool of high density data storage materials such as Fe–Pt.
Keywords: Fe–Pt nanoparticles; Direct synthesis L10 phase; Microwave-assisted synthesis; Chemical reduction
High yield synthesis of carbon nanofibers in an environmental friendly route by R. Ravindra; Bhat Badekai Ramachandra (pp. 103-108).
An environmental friendly route for the high yield synthesis of carbon nanofibers (CNFs) has been developed. CNFs have been synthesized using nickel formate as catalyst precursor at 680°C using chemical vapor deposition method. Upon pyrolysis this catalyst precursor yields metal catalyst nanoparticles directly. The sodium chloride and potassium chloride was used as catalyst support, it was chosen because of its non-toxic and water soluble nature. The problems such as detrimental effect, environment and even cost has been avoided by using water soluble supports. The structure of the products was characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and X-ray diffraction method. The purity of as grown products and purified products was determined by thermal analysis. Here, we report the 7,800 and 7,200 wt% yield of CNFs synthesized over NaCl and KCl support. This synthetic route can be used for the large scale synthesis in industries.
Keywords: Carbon nanofibers; Water soluble substrates; Chemical vapor deposition; Environmental friendly method
Development and study of the thermal and electrical behaviour of TGDDS epoxy nanocomposites for high-performance applications by K. Shree Meenakshi; E. Pradeep Jaya Sudhan (pp. 109-115).
The present work focuses on a comparative study of the thermal and electrical behaviour of N,N′-tetraglycidyl diaminodiphenylsulphone (TGDDS) denoted as ‘B’ to find the suitability for its use in high-performance applications. The synthesis of the tetraglycidyl epoxy was done and they were characterized by FT-IR (Fourier transform infrared spectra) and nuclear magnetic resonance spectra (1H-NMR and 13C-NMR). Nanoclay and POSS-amine nanoreinforcements denoted as N1 and N2 were incorporated into the synthesized epoxy resins. Curing was done using diaminodiphenylmethane (DDM) and bis(3-aminophenyl)phenylphosphine oxide (BAPPO) curing agents denoted as X and Y, respectively. The thermal behaviour of the tetraglycidyl resins and their corresponding nanocomposites was studied by thermogravimetric analysis (TGA). The electrical behaviour, namely dielectric strength, comparative tracking index (CTI), volume resistivity, surface resistivity and arc resistance of the nanocomposites were also studied and the interesting results obtained are discussed.
Keywords: Epoxy resin; Thermal stability; Electrical behaviour; Thermogravimetric analysis