Energy-loss function of TTF-TCNQ

We investigate the energy-loss function for a previously developed model of quasi-one-dimensional metals with two one-dimensional electron bands per donor and acceptor chains and the three-dimensional long-range Coulomb electron-electron interaction within the random phase approximation. It is essentially influenced by two hybridized collective modes which result from the strong coupling of the intraband plasmon and the interband dipolar modes. Our calculations show that the spectral weights of the renormalized plasmon and the dipolar mode dominate within the long wavelength limit, while for large longitudinal wave vectors the intraband electron-hole quasi-continuumgains some experimentally observable spectral weight as the second mode approaches it. The function obtained is brought into correspondence with the data of the quasi-one-dimensional organic conductor tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) obtained from electron energy-loss spectroscopy (EELS) measurements.     

Self-aggregated Si quantum dots in amorphous Si-rich SiC

Amorphous silicon quantum dots (Si-QDs) self-aggregated in silicon-rich silicon carbide are synthesized by growing with plasma-enhanced chemical vapor deposition on (100)-oriented Si substrate. Under the environment of Argon (Ar)-diluted Silane (SiH₄) and pure methane (CH₄), the substrate temperature and RF power are set as 350 °C and 120 W, respectively, to provide the Si-rich SiC with changing fluence ratio (R = [CH₄ ]/[SiH₄] + [CH₄]). By tuning the fluence ratio from 50% to 70%, the composition ratio x of Si-rich Si_1 ? xC_x film is varied from 0.27 to 0.34 as characterized by X-ray photoelectron spectroscopy (XPS), which reveals the component of Si_2p decreasing from 66.3 to 59.5%, and the component of C_1s increasing from 23.9% to 31% to confirm the formation of Si-rich SiC matrix. Annealing of the SiC sample from 650 °C to 1050 °C at 200 °C increment for 30 min induces the very tiny shift on the wavenumber of the crystalline Si (c-Si) related peak due to the precipitation of Si-QDs within the SiC matrix, and the Raman scattering spectra indicate a broadened Raman peak ranging from 410 to 520 cm^? 1 related to the amorphous Si accompanied with the significant enhancement for SiC bond related peak at 980 cm^? 1. From the high resolution transmission electron microscopy images, the critical temperature for Si-QD precipitation is found to be 850 °C. The self-assembly of the crystallized Si-QDs with the size of 3 ± 0.5 nm and the volume density of (3 ± 1) × 10¹⁸ (#/cm³) in Si-rich SiC film with R = 70% are observed after annealing at higher temperature.     

Evidence for the assembly of carboxyphenylethynyl zinc porphyrins on nanocrystalline TiO2 surfaces

UV-visible absorption and AFM studies suggest that carboxyphenylethynyl zinc porphyrins aggregate on nanocrystalline TiO2 surfaces in an H-type fashion.     

Calcium copper-titanate thin film growth: tailoring of the operational conditions through nanocharacterization and substrate nature effects

A novel approach based on a molten multicomponent precursor source has been applied for the MOCVD fabrication of high-quality CaCu(3)Ti(4)O(12) (CCTO) thin films on various substrates. The adopted in situ strategy involves a molten mixture consisting of Ca(hfa)(2).tetraglyme, Ti(tmhd)(2)(O-iPr)(2), and Cu(tmhd)(2) [Hhfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; tetraglyme = 2,5,8,11,14-pentaoxapentadecane; Htmhd = 2,2,6,6-tetramethyl-3,5-heptandione; O-iPr = isopropoxide] precursors. Film structural and morphological characterizations have been carried out by several techniques [X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM)], and in particular the energy filtered TEM mapping and X-ray energy dispersive (EDX) analysis in TEM mode provided a suitable correlation between nanostructural properties of CCTO films and deposition conditions and/or the substrate nature. Correlation between the nanostructure and optical/dielectric properties has been investigated exploiting spectroscopic ellipsometry.     

Solid-state 139La and 15N NMR spectroscopy of lanthanum-containing metallocenes

A preliminary set of solid-state 139La and 15N NMR data for lanthanum-containing metallocenes is presented, including (C5H5)3La, (C5Me4H)3La, [(C5Me5)2La]+[BPh4]-, and 15N-enriched [(C5Me4H)2La(THF)]215N2. Broad 139La NMR spectra, with breadths ranging from 600 kHz to 2.5 MHz, were acquired with piecewise QCPMG techniques at 9.4 T. Simulations of the spectra reveal 139La quadrupolar coupling constants (CQ) between 44 and 105 MHz. In addition, the first NMR measurement of a nitrogen chemical shift (CS) tensor for dinitrogen bound side-on to a metal atom is reported for [(C5Me4H)2La(THF)]215N2. The 139La NMR parameters show remarkable sensitivity to changes in metallocene structure and can be interpreted in an intuitive manner. Preliminary RHF and DFT calculations of 139La electric field gradient (EFG) and nitrogen CS tensors are used to provide tensor orientations and to rationalize the origin of the NMR parameters in terms of molecular structure and symmetry. The sensitivity of 139La and 15N NMR tensor parameters to changes in structure and bonding should prove invaluable in future studies of noncrystalline and disordered systems.     

Experimental quantum key distribution with decoy states

To increase dramatically the distance and the secure key generation rate of quantum key distribution (QKD), the idea of quantum decoys--signals of different intensities--has recently been proposed. Here, we present the first experimental implementation of decoy state QKD. By making simple modifications to a commercial quantum key distribution system, we show that a secure key generation rate of 165 bit/s, which is 1/4 of the theoretical limit, can be obtained over 15 km of a telecommunication fiber. We also show that with the same experimental parameters, not even a single bit of secure key can be extracted with a non-decoy-state protocol. Compared to building single photon sources, decoy state QKD is a much simpler method for increasing the distance and key generation rate of unconditionally secure QKD.     

Temperature effect on water intrusion/expulsion in grafted silica gels

Water intrusion-expulsion cycles within a hydrophobic silica gel system were observed at various temperatures. The hysteresis phenomenon revealed an attenuation effect growing with temperature. A simple model derived from the Laplace-Washburn equation made it possible to characterize the observed phenomena both qualitatively and quantitatively. The model involves advancing and receding contact angles increasing with temperature, which influence the hysteresis phenomenon very differently, depending on their value.     

Characterization of volatile organic compounds and odorants associated with swine barn particulate matter using solid-phase microextraction and gas chromatography-mass spectrometry-olfactometry

Swine operations can affect air quality by emissions of odor, volatile organic compounds (VOCs) and other gases, and particulate matter (PM). Particulate matter has been proposed to be an important pathway for carrying odor. However, little is known about the odor-VOCs-PM interactions. In this research, continuous PM sampling was conducted simultaneously with three collocated TEOM 1400a analyzers inside a 1000-head swine finish barn located in central Iowa. Each TEOM was fitted with total suspended particulate (TSP), PM-10, PM-2.5 and PM-1 preseparators. Used filters were stored in 40 mL vials and transported to the laboratory. VOCs adsorbed/absorbed to dust were allowed to equilibrate with vial headspace. Solid-phase microextraction (SPME) Carboxen/polydimethylsiloxane (PDMS) 85 microm fibers were used to extract VOCs. Simultaneous chemical and olfactometry analyses of VOCs and odor associated with swine PM were completed using a gas chromatography-mass spectrometry-olfactometry (GC-MS-O) system. Fifty VOCs categorized into nine chemical function groups were identified and confirmed with standards. Five of them are classified as hazardous air pollutants. VOCs were characterized with a wide range of molecular weight, boiling points, vapor pressures, water solubilities, odor detection thresholds, and atmospheric reactivities. All characteristic swine VOCs and odorants were present in PM and their abundance was proportional to PM size. However, the majority of VOCs and characteristic swine odorants were preferentially bound to smaller-size PM. The findings indicate that a significant fraction of swine odor can be carried by PM. Research of the effects of PM control on swine odor mitigation is warranted.