Materials Literature
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The electronic properties of single-walled carbon nanotubes (SWNTs) are altered by intertube coupling whenever bundles are formed. These effects are examined experimentally by applying Rayleigh scattering spectroscopy to probe the optical transitions of given individual SWNTs in their isolated and bundled forms. The t…
Light-emitting Si-rich silicon nitride (SRN) films were fabricated by plasma enhanced chemical vapor deposition followed by low temperature (500–900°C) annealing. The optical properties of SRN films were studied by micro-Raman and photoluminescence spectroscopy and indicate the presence of small Si clusters characteri…
Nonaqueous sol–gel routes to metal oxide nanoparticles have become a promising alternative to aqueous methods, allowing the controlled synthesis of a variety of metal oxides as highly crystalline products at comparably low temperatures. The use of solvents like benzyl alcohol that also function as surface modifiers ma…
By using nanosecond laser pulses at 532-nm wavelength, we have intensively studied the optical limiting and nonlinear optical properties of some new composites which consist of mono-functional 1,2-dihydro-1,2-methanofullerene[60]-61-carboxylic acid (FCA), multifunctional fullerenol, and supramolecular C60(HNC4H8NCH3)9…
The photoluminescence decay characteristics of silicon nanocrystals in dense ensembles fabricated by ion implantation into silicon dioxide are observed to vary in proportion to the calculated local density of optical states. A comparison of the experimental $1∕e$ photoluminescence decay rates to the expected spontaneo…
Eight crystalline dipeptides were studied: AV (Ala-Val), VA (Val-Ala), AI (Ala-Ile), VV (Val-Val), IA (Ile-Ala), IV (Ile-Val), VI (Val-Ile), and LS (Leu-Ser) (all LL isomers). The first seven form an isostructural series (space group P6(1)), whereas LS has a different structure (P6(5)). All structures display H-bonded…
Abstract In this work, CNTs have been bombarded with low energy N ions. X‐ray photoelectron spectroscopy have been used to determine the binding configuration of the N‐doped CNTs. AFM was also used to determine their morphology and mechanical properties. The same morphology is maintained after the N 2 + bombardment. X…
An optical biosensor for protease activity, capable of detecting picomole quantities of protease, is constructed from a 1D photonic crystal of porous Si. The porous Si layer is coated with a thin film of zein, a natural hydrophobic protein. Proteolytic cleavage produces small fragments that infiltrate the pores of the…
We present a time-reversible Born-Oppenheimer molecular dynamics scheme, based on self-consistent Hartree-Fock or density functional theory, where both the nuclear and the electronic degrees of freedom are propagated in time. We show how a time-reversible adiabatic propagation of the electronic degrees of freedom is p…
Saturable and reverse saturable absorption at longitudinal surface plasmon resonance (SPR) in gold nanorods (Au NRs) have been observed using Z-scan and transient absorption techniques with femtosecond laser pulses. At lower excitation irradiances, the wavelength dispersion of saturable absorption has been determined…
Optical Kerr nonlinearity (n2) in n-type indium tin oxide (ITO) films coated on glass substrates has been measured using Z-scans with 200-fs laser pulses at wavelengths ranging from 720 to 780 nm. The magnitudes of the measured nonlinearity in the ITO films were found to be dependent on the carrier concentration with…
Abstract The electronic structure and equilibrium geometry of La 2/3 Sr 1/3 MnO 3 are studied theoretically by means of density functional calculations. The doping is treated by introducing holes and a compensating jellium background. The results for the local density approximation (LDA) agree with previous LDA calcul…
Uniform V(2)O(5)· xH(2)O nanobelts with high aspect ratios and ultra-long V(2)O(5)· xH(2)O nanorolls with novel scroll-like structures were synthesized on a large scale by a simple hydrothermal growth route using NH(4)VO(3) as the raw material in the presence of different acids at 180 °C for 24 h. Their morphologies w…
Cubic boron nitride ($c$-BN) is the second (only to diamond) hardest material with superior thermal stability. Despite its wide range of applications as a superhard material, the structural deformation modes of $c$-BN at the atomistic level are still not well understood. In this paper, we report first-principles calcu…
Molecular self-assembly offers unique directions for the fabrication of novel supramolecular structures and advanced materials. The inspiration for the development of such structures is often derived from self-assembling modules in biology, as natural systems form complex structures from simple building blocks such as…
We present a new class of artificial materials which exhibit a tailored response to the electrical component of electromagnetic radiation. These electric metamaterials (EM-MMs) are investigated theoretically, computationally, and experimentally using terahertz time-domain spectroscopy. These structures display a reson…
The crystal and magnetic structures of the orthorhombic e-Fe2O3 have been studied by simultaneous Rietveld refinement of X-ray and neutron powder diffraction data in combination with Mossbauer spectroscopy, as well as magnetisation and heat capacity measurements. It has been found that above 150 K the e-Fe2O3 polymorp…
A quantum leap in glucose sensing: Commercially available fluorescent quantum dots are used in combination with boronic acid modified viologens to sense glucose in aqueous solution. The signal response is optimized by adjusting the ratio of quantum dots to viologen quencher.
Abstract Summary: Dispersing surface‐modified zinc oxide nanoparticles (ZnO) in methyl methacrylate (MMA) improves the free radical bulk polymerization process as well as the thermal stability of the formed polymer. Hydroxy groups available on the ZnO surface may induce a degenerative transfer. This suppresses the gel…
Abstract Highly uniform single‐crystal Na‐OMS‐2 (OMS: octahedral molecular sieve), pyrolusite, and γ‐MnO 2 nanostructures with an interesting 3D urchinlike morphology have been successfully prepared using a hydrothermal method based on a mild and direct reaction between sodium dichromate and manganese sulfate. The cry…