Small-Angle Neutron Scattering Studies of Hemoglobin Confined Inside Silica Tubes of Varying Sizes

In addition to the chemical nature of the surface, the dimensions of the confining host exert a significant influence on confined protein structures; this results in immense biological implications, especially those concerning the enzymatic activities of the protein. This study probes the structure of hemoglobin (Hb), a model protein, confined inside silica tubes with pore diameters that vary by one order of magnitude (approximate to 20-200 nm). The effect of confinement on the protein structure is probed by comparison with the structure of the protein in solution. Small-angle neutron scattering (SANS), which provides information on protein tertiary and quaternary structures, is employed to study the influence of the tube pore diameter on the structure and configuration of the confined protein in detail. Confinement significantly influences the structural stability of Hb and the structure depends on the Si-tube pore diameter. The high radius of gyration (R-g) and polydispersity of Hb in the 20 nm diameter Si-tube indicates that Hb undergoes a significant amount of aggregation. However, for Si-tube diameters greater or equal to 100 nm, the R-g of Hb is found to be in very close proximity to that obtained from the protein data bank (PDB) reported structure (R-g of native Hb=23.8 angstrom). This strongly indicates that the protein has a preference for the more native-like non-aggregated state if confined inside tubes of diameter greater or equal to 100 nm. Further insight into the Hb structure is obtained from the distance distribution function, p(r), and ab initio models calculated from the SANS patterns. These also suggest that the Si-tube size is a key parameter for protein stability and structure.

A room temperature, templated synthesis of lanthanide trifluoride nanoparticles and their unusual self-assembly

A new methodology has been developed for synthesizing lanthanide trifluoride (LnF(3)) nanoparticles using a simple diffusion technique. The approach uses a lanthanide based hydrogel matrix to control the kinetics of the reaction, which also acts as a stabilizing platform, thus enabling the room temperature, in situ synthesis of finely sized (3-5 nm), monodisperse nanoparticles that were found to form in an ordered pattern on the gel fibers.

Alumina and Silica based Epoxy Nano-composites for Electrical Insulation

Plain epoxy resins or resin impregnated cellulose have found application as electrical insulation in power equipment. In the past, their performance was improved by the use of inorganic oxide fillers of microscopic dimensions. In the recent past nano-particle doped epoxy insulation came into use with a view to further enhance the dielectric properties. This paper reports dielectric investigations into epoxy nano-composites based on a class of metal oxides, Al2O3 and SiO2. In particular, consideration has been given to the partial discharge performance and electrical breakdown under different voltage profiles as a function of the volumetric composition of the nano-particles in epoxy resin.

Size Control and Magnetic Property Trends in Cobalt Ferrite Nanoparticles Synthesized Using an Aqueous Chemical Route

Cobalt ferrite (CoFe2O4) is an engineering material which is used for applications such as magnetic cores, magnetic switches, hyperthermia based tumor treatment, and as contrast agents for magnetic resonance imaging. Utility of ferrites nanoparticles hinges on its size, dispersibility in solutions, and synthetic control over its coercivity. In this work, we establish correlations between room temperature co-precipitation conditions, and these crucial materials parameters. Furthermore, post-synthesis annealing conditions are correlated with morphology, changes in crystal structure and magnetic properties. We disclose the synthesis and process conditions helpful in obtaining easily sinterable CoFe2O4 nanoparticles with coercive magnetic flux density (H-c) in the range 5.5-31.9 kA/m and M-s in the range 47.9-84.9 A.m(2)Kg(-1). At a grain size of similar to 54 +/- 2 nm (corresponding to 1073 K sintering temperature), multi-domain behavior sets in, which is indicated by a decrease in H-c. In addition, we observe an increase in lattice constant with respect to grain size, which is the inverse of what is expected of in ferrites. Our results suggest that oxygen deficiency plays a crucial role in explaining this inverse trend. We expect the method disclosed here to be a viable and scalable alternative to thermal decomposition based CoFe2O4 synthesis. The magnetic trends reported will aid in the optimization of functional CoFe2O4 nanoparticles

Facile hydrothermal synthesis of carbon nanoparticles and possible application as white light phosphors and catalysts for the reduction of nitrophenol

We report a simple hydrothermal synthesis of highly reproducible carbon nanoparticles in a size range between 2 and 7 nmfroma single precursor sucrose without either surface passivating agents or acids and bases. The carbon nanoparticles can be used as white light phosphors, especially for ultraviolet light emitting diodes and metal-free catalyst for the reduction of nitrophenol.

Tailor-Made Hollow Silver Nanoparticle Cages Assembled with Silver Nanoparticles: An Efficient Catalyst for Epoxidation

A novel approach toward the synthesis of hollow silver nanoparticle (NP) cages built with building blocks of silver NPs by layer-by-layer (LbL) assembly is demonstrated. The size of the NP cage depends on the size of template used for the LbL assembly. The microcages showed a uniform distribution of spherical silver nanoparticles with an average diameter of 20 +/- 5 nm, which increased to 40 +/- S nm when the AgNO3 concentration was increased from 25 to 50 mM. Heat treatment of the polyelectrolyte capsules at 80 degrees C near their pK(a) values yielded intact nano/micro cages. These cages produced a higher conversion for the epoxidation of olefins and maintained their catalytic activity even after four successive uses. The nanocages exhibited unique and attractive characteristics for metal catalytic systems, thus offering the scope for further development as heterogeneous catalysts.

Multivalent Cu-Doped ZnO Nanoparticles with Full Solar Spectrum Absorbance and Enhanced Photoactivity

Full solar spectrum absorbers are widely pursued for applications related to photocatalysis and photovoltaics. Here we report multivalent Cu-doped ZnO nanoparticles which exhibit full solar spectrum absorbance and high photoactivity. Metathesis-based, green-chemical approaches with synthesis yield of similar to 100% are used. Cu incorporation in ZnO results in an increase of average solar spectrum absorbance from a mere 0.4% to 34%. On the other hand, (Zn, Cu)0 composites result in materials with up to 64% average solar spectrum absorbance. Doped systems operate well under both visible and UV illumination. The nanomaterials prepared are characterized by using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, and X-ray photoelectron spectroscopy (XPS). Photocatalysts explored have particle sizes >= 50 nm. This is deliberately done in order to avoid the nanotoxic size regime of ZnO. Despite the large particle size and low specific surface area (<20 m(2).g(-1)), the best catalyst reported here compare favorably with recent reports on ZnO based systems. Using X-photoelectron spectroscopy and synthesis property correlations, we infer that the presence of multivalent Cu (most likely in the form of Cu1+delta) on ZnO surface is responsible for the observed photoactivity enhancement.

Density Functional Theoretical Modeling, Electrostatic Surface Potential and Surface Enhanced Raman Spectroscopic Studies on Biosynthesized Silver Nanoparticles: Observation of 400 pM Sensitivity to Explosives

Interaction of adsorbate on charged surfaces, orientation of the analyte on the surface, and surface enhancement aspects have been studied. These aspects have been explored in details to explain the surface-enhanced Raman spectroscopic (SERS) spectra of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (HNIW or CL-20), a well-known explosive, and 2,4,6-trinitrotoluene (TNT) using one-pot synthesis of silver nanoparticles via biosynthetic route using natural precursor extracts of clove and pepper. The biosynthesized silver nanoparticles (bio Ag Nps) have been characterized using UV-vis spectroscopy, scanning electron microscopy and atomic force microscopy. SERS studies conducted using bio Ag Nps on different water insoluble analytes, such as CL-20 and TNT, lead to SERS signals at concentration levels of 400 pM. The experimental findings have been corroborated with density functional computational results, electrostatic surface potential calculations, Fukui functions and potential measurements.

The influence of mesoporous silica in low T-g cyclic olefin copolymer nanocomposite films: Mechanical and moisture barrier studies

In this study, mesoporous silica-cyclic olefin copolymer nanocomposite films were fabricated by solution casting. With an increase in silica loading, the stiffness of the matrix increased. The nanocomposite film shows increased strain to failure with moisture after aging by matrix plasticization. The storage modulus and loss factor for samples with silica content show better results compared with pristine polymer, as indicated by dynamic mechanical analysis. The interaction between filler-polymer chain exhibit hydrophobicity compared to the neat polymer. Water absorption studies at room temperature and near the T-g of the polymer (similar to 64 degrees C) were carried out. The nanocomposites up to 4 wt% filler reduces the water diffusion by forming hydrogen and chemical bonding. The result by calcium degradation test method for moisture permeability and Schottky structured organic device encapsulation under weathering condition confirms the effective reinforcement effect of silica particles in the matrix. (C) 2014 Elsevier Ltd. All rights reserved.

Metallic Nanoparticles Arranged in a Helical Geometry: Route Towards Strong and Broadband Chiro-optical Response

Recent advances in nanotechnology have paved ways to various techniques for designing and fabricating novel nanostructures incorporating noble metal nanoparticles, for a wide range of applications. The interaction of light with metal nanoparticles (NPs) can generate strongly localized electromagnetic fields (Localized Surface Plasmon Resonance, LSPR) at certain wavelengths of the incident beam. In assemblies or structures where the nanoparticles are placed in close proximity, the plasmons of individual metallic NPs can be strongly coupled to each other via Coulomb interactions. By arranging the metallic NPs in a chiral (e.g. helical) geometry, it is possible to induce collective excitations, which lead to differential optical response of the structures to right-and left circularly polarized light (e.g. Circular Dichroism - CD). Earlier reports in this field include novel techniques of synthesizing metallic nanoparticles on biological helical templates made from DNA, proteins etc. In the present work, we have developed new ways of fabricating chiral complexes made of metallic NPs, which demonstrate a very strong chiro-optical response in the visible region of the electromagnetic spectrum. Using DDA (Discrete Dipole Approximation) simulations, we theoretically studied the conditions responsible for large and broadband chiro-optical response. This system may be used for various applications, for example those related to polarization control of visible light, sensing of proteins and other chiral bio-molecules, and many more.

In-situ Stabilization of Tin Nanoparticles in Porous Carbon Matrix derived from Metal Organic Framework: High Capacity and High Rate Capability Anodes for Lithium-ion Batteries

It is a formidable challenge to arrange tin nanoparticles in a porous matrix for the achievement of high specific capacity and current rate capability anode for lithium-ion batteries. This article discusses a simple and novel synthesis of arranging tin nanoparticles with carbon in a porous configuration for application as anode in lithium-ion batteries. Direct carbonization of synthesized three-dimensional Sn-based MOF: K2Sn2(1,4-bdc)(3)](H2O) (1) (bdc = benzenedicarboxylate) resulted in stabilization of tin nanoparticles in a porous carbon matrix (abbreviated as Sn@C). Sn@C exhibited remarkably high electrochemical lithium stability (tested over 100 charge and discharge cycles) and high specific capacities over a wide range of operating currents (0.2-5 Ag-1). The novel synthesis strategy to obtain Sn@C from a single precursor as discussed herein provides an optimal combination of particle size and dispersion for buffering severe volume changes due to Li-Sn alloying reaction and provides fast pathways for lithium and electron transport.

Antimicrobial and conducting polymer substrate derived from hybrid structures of silver nanoparticles and multiwall carbon nanotubes

Hybrid nanocomposites of polycaprolactone (PCL) with multiwall carbon nanotubes (MWNTs) and silver nanoparticles (nAg) were prepared by melt mixing. Synergetic effect of the two nanofillers (MWNT and nAg) in PCL matrix was evaluated for dielectric and antibacterial properties. Dielectric results showed that the addition of nAg as filler in PCL matrix (PCL/nAg) had no effect on conductivity, whereas addition of MWNT in PCL matrix (PCL/MWNT) caused a sharp increase in conductivity of PCL. Interestingly, the hybrid nanocomposite (PCL/MWNT/nAg) incorporating MWNT and nAg also exhibited high electrical conductivity. The hybrid composite was found to have antibacterial property similar to that of PCL/nAg composite for lower loading of nAg. This study demonstrates that the synergetic interaction of the nanofillers in the hybrid nanocomposite improves both electrical conductivity and antibacterial properties of PCL.

Synthesis and Mechanism of Composition and Size Dependent Morphology Selection in Nanoparticles of Ag-Cu Alloys Processed by Laser Ablation Under Liquid Medium

We have synthesized Ag-Cu alloy nanoparticles of four different compositions by using the laser ablation technique with the target under aqueous medium. Following this, we report a morphological transition in the nanoparticles from a normal two-phase microstructure to a structure with random segregation and finally a core shell structure at small sizes as a function of Cu concentration. To illustrate the composition dependence of morphology, we report observations carried out on nanoparticles of two different sizes: similar to 5 and similar to 20 nm. The results could be rationalized through the thermodynamic modeling of free energy of phase mixing and wettability of the alloying phases.

Digestive ripening facilitated atomic diffusion at nanosize regime: Case of AuIn2 and Ag3In intermetallic nanoparticles

Monodisperse colloidal gold-indium (AuIn2) intermetallic nanoparticles have been synthesized from Au and In colloids using the digestive ripening process. Formation of the intermetallic proceeds via digestive ripening facilitated atomic diffusion of Au and In atoms from the Au and In nanoparticles followed simultaneously by their growth in the solution. Optimization of the reaction temperature was found to be crucial for the formation of AuIn2 intermetallic from gold and indium nanoparticles. Transmission electron microscopy revealed the presence of nearly monodisperse nanoparticles of Au and AuIn2 with particle size distribution of 3.7 +/- 1.0 nm and 5.0 +/- 1.6 nm, respectively. UV-visible spectral studies brought out the absence of SPR band in pure AuIn2 intermetallic nanoparticles. Optical study and electron microscopy, in combination with powder X-ray diffraction established phase pure AuIn2 intermetallic nanoparticles unambiguously. The potential of such an unprecedented approach has been further exploited in the synthesis of Ag3In intermetallic nanoparticles with the dimension of less than 10 nm. (C) 2014 Elsevier B.V. All rights reserved.