Copper Azide Confined Inside Templated Carbon Nanotubes

The currently used primary explosives, such as lead azide and lead styphnate, present serious health hazards due to the toxicity of lead. There is a need to replace them with equally energetic but safer‐to‐handle and more environmentally friendly materials. Copper azide is more environmentally acceptable, but very sensitive and detonates easily from electrostatic charges during handling. If the highly sensitive copper azide is encapsulated within conducting containers, such as anodic aluminum oxide (AAO)‐templated carbon nanotubes (CNTs), its sensitivity can be tamed. This work describes a technique for confining energetic copper azide within CNTs. ～5 nm colloidal copper oxide nanoparticles are synthesized and filled into the 200 nm diameter CNTs, produced by template synthesis. The Cu‐O inside the CNTs is reduced in hydrogen to copper, and reacted with hydrazoic acid gas to produce copper azide. Upon initiation, the 60 μm long straight, open‐ended CNTs guide decomposition gases along the tube channel without fracturing the nanotube walls. These novel materials have potential for applications as nano‐detonators and green primary explosives; they also offer new opportunities for understanding the physics of detonation at the nanoscale.     

A functional hybrid memristor crossbar-array/CMOS system for data storage and neuromorphic applications

Crossbar arrays based on two-terminal resistive switches have been proposed as a leading candidate for future memory and logic applications. Here we demonstrate a high-density, fully operational hybrid crossbar/CMOS system composed of a transistor- and diode-less memristor crossbar array vertically integrated on top of a CMOS chip by taking advantage of the intrinsic nonlinear characteristics of the memristor element. The hybrid crossbar/CMOS system can reliably store complex binary and multilevel 1600 pixel bitmap images using a new programming scheme.     

Shape effect on electronic and photovoltaic properties of CdS nanocrystals

Changes in electronic and photovoltaic properties of semiconductor nanocrystals predominantly due to changes in shape are discussed here. Cadmium sulfide (CdS) semiconductor nanocrystals of various shapes (tetrapod, tetrahedron, sphere and rod) obtained using an optimized solvothermal process exhibited a mixed cubic (zinc blende) and hexagonal (wurtzite) crystal structure. The simultaneous presence of the two crystal phases in varying amounts is observed to play a pivotal role in determining both the electronic and photovoltaic properties of the CdS nanocrystals. Light to electrical energy conversion efficiencies (measured in two-electrode configuration laboratory solar cells) remarkably decreased by one order in magnitude from tetrapod --> tetrahedron --> sphere --> rod. The tetrapod-CdS nanocrystals, which displayed the highest light to electrical energy conversion efficiency, showed a favorable shift in position of the conduction band edge leading to highest rate of electron injection (from CdS nanocrystal to the wide band gap semiconductor viz. titanium dioxide, TiO2) and lowest rate of electron-hole recombination (higher free electron lifetimes).     

Different hierarchical nanostructured carbons as counter electrodes for CdS quantum dot solar cells

CdS quantum dot sensitized solar cells based on TiO(2) photoanode and nanostructured carbon as well as Pt as counter electrodes using iodide/triiodide and polysulfide electrolytes were fabricated to improve the efficiency and reduce the cost of solar cells. Compared with conventional Pt (η = 1.05%) and CMK-3 (η = 0.67%) counter electrodes, hollow core-mesoporous shell carbon (HCMSC) counter electrode using polysulfide electrolyte exhibits much larger incident photon to current conversion efficiency (IPCE = 27%), photocurrent density (J(sc) = 4.31 mA.cm(-2)) and power conversion efficiency (η = 1.08%), which is basically due to superb structural characters of HCMSC such as large specific surface area, high mesoporous volume, and 3D interconnected well-developed hierarchical porosity network, which facilitate fast mass transfer with less resistance and enable HCMSC to have highly enhanced catalytic activity toward the reduction of electrolyte shuttle.     

Investigation on the competing effects of clay dispersion and matrix plasticisation for polypropylene/clay nanocomposites. Part II: crystalline structure and thermo-mechanical behaviour

In view of the structure–property relationship, the mechanical property enhancement of polypropylene (PP)/clay nanocomposites can also be associated with the alterations of their crystalline structures and behaviour in addition to the general interpretation of intercalation/exfoliation level and uniform dispersion of more rigid clay platelets with higher aspect ratios in the PP matrix. Wide-angle X-ray diffraction (WAXD) was utilised to evaluate the effects of clay content, maleated PP (MAPP) content (MAPP as the compatibiliser) on PP crystalline structures of nanocomposites. Furthermore, the melting and crystallisation behaviour of PP/clay nanocomposites was also investigated by conducting differential scanning calorimetry (DSC). The thermo-mechanical properties were characterised via dynamic mechanical thermal analysis (DMTA). It is observed that enhancement of mechanical properties are mainly affected by the preferred orientation of PP crystals, the growth of α-PP phase and effective nucleating agent role of additional clay while the excessive amount of MAPP becomes detrimental to these crucial aspects, which is also evidently revealed in DMTA measurements.     

Molecular discriminators using single wall carbon nanotubes

The interaction between single wall carbon nanotubes (SWNTs) and amphiphilic molecules has been studied in a solid phase. SWNTs are allowed to interact with different amphiphilic probes (e.g.?lipids) in a narrow capillary interface. Contact between strong hydrophobic and amphiphilic interfaces leads to a molecular restructuring of the lipids at the interface. The geometry of the diffusion front and the rate and the extent of diffusion of the interface are dependent on the structure of the lipid at the interface. Lecithin having a linear tail showed greater mobility of the interface as compared to a branched tail lipid like dipalmitoyl phosphatidylcholine, indicating the hydrophobic interaction between single wall carbon nanotube core and the hydrophobic tail of the lipid. Solid phase interactions between SWNT and lipids can thus become a very simple but efficient means of discriminating amphiphilic molecules in general and lipids in particular.     

Realization of thermally durable close-packed 2D gold nanoparticle arrays using self-assembly and plasma etching

Realization of thermally and chemically durable, ordered gold nanostructures using bottom-up self-assembly techniques are essential for applications in a wide range of areas including catalysis, energy generation, and sensing. Herein, we describe a modular process for realizing uniform arrays of gold nanoparticles, with interparticle spacings of 2?nm and above, by using RF plasma etching to remove ligands from self-assembled arrays of ligand-coated gold nanoparticles. Both nanoscale imaging and macroscale spectroscopic characterization techniques were used to determine the optimal conditions for plasma etching, namely RF power, operating pressure, duration of treatment, and type of gas. We then studied the effect of nanoparticle size, interparticle spacing, and type of substrate on the thermal durability of plasma-treated and untreated nanoparticle arrays. Plasma-treated arrays showed enhanced chemical and thermal durability, on account of the removal of ligands. To illustrate the application potential of the developed process, robust SERS (surface-enhanced Raman scattering) substrates were formed using plasma-treated arrays of silver-coated gold nanoparticles that had a silicon wafer or photopaper as the underlying support. The measured value of the average SERS enhancement factor (2?×?10(5)) was quantitatively reproducible on both silicon and paper substrates. The silicon substrates gave quantitatively reproducible results even after thermal annealing. The paper-based SERS substrate was also used to swab and detect probe molecules deposited on a solid surface.     

Microfibril reinforced polymer–polymer composites: Application of Tsai-Hill equation to PP/PET composites

In this paper an attempt has been made to check the extent of validity of the Tsai-Hill equation applied to polymer–polymer microfibril reinforced composites (MFCs), in which the reinforcing elements represent microfibrils with diameters around 1 μm and aspect ratios of approximately 100. For this purpose compression moulded plates of polypropylene/poly(ethylene terephthalate: 70/30 by wt%) composites have been prepared and their structures are established by wide angle X-ray scattering and scanning electron microscope (SEM) analysis. The tensile tests of cut specimens at various angles ( with respect to the uniaxially aligned microfibrils) show the degree of agreement with Tsai-Hill predictions. The measured values are slightly higher than the calculated ones and this finding is explained by the higher aspect ratios of microfibrils, their more homogenous distribution and most importantly, by the better matrix/reinforcement adhesion in the case of MFCs as compared to the common composites. The fracture mechanism as determined from the SEM observations on the fracture surfaces is also discussed and a good agreement with the mechanical behaviour is found.     

Soft matter electrolytes based on polymethylmetacrylate dispersions in lithium bis(trifluoromethanesulfonyl)imide/1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquids

Ion transport in a polymer-ionic liquid (IL) soft matter composite electrolyte is discussed here in detail in the context of polymer-ionic liquid interaction and glass transition temperature. The dispersion of polymethylmetacrylate (PMMA) in 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF₆) and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMITFSI) resulted in transparent composite electrolytes with a “jelly-like” consistency. The composite ionic conductivity measured over the range −30 °C to 60 °C was always lower than that of the neat BMITFSI/BMIPF₆ and LiTFSI-BMITFSI/LiTFSI-BMIPF₆ electrolytes but still very high (>1 mS/cm at 25 °C up to 50 wt% PMMA). While addition of LiTFSI to IL does not influence the glass T_g and T_m melting temperature significantly, dispersion of PMMA (especially at higher contents) resulted in increase in T_g and disappearance of T_m. In general, the profile of temperature-dependent ionic conductivity could be fitted to Vogel-Tamman-Fulcher (VTF) suggesting a solvent assisted ion transport. However, for higher PMMA concentration sharp demarcation of temperature regimes between thermally activated and solvent assisted ion transport were observed with the glass transition temperature acting as the reference point for transformation from one form of transport mechanism to the other. Because of the beneficial physico-chemical properties and interesting ion transport mechanism, we envisage the present soft matter electrolytes to be promising for application in electrochromic devices.