The influence of incorporating organic molecules or inorganic nanoparticles on the optical and electrical properties of carbon nanotube films

Organic molecules and inorganic nanoparticles were incorporated into transparent and conductive single- or double-wall carbon nanotube (SWNT or DWNT) films, and their electrical and optical properties were measured. When organic tetrafluoro-tetracyanoquinodimethane (F₄TCNQ) molecules were incorporated into the nanotube films, sheet resistance was reduced to ∼50% of those from the pristine SWNT and DWNT films. Larger improvements were observed with Au nanoparticle decoration or HNO₃/SOCl₂ dipping processes. The sheet resistances were measured to be at 75% of transmittance for HNO₃/SOCl₂-treated DWNT films and at 77% for Au-incorporated DWNT films, making their electrical conductivities 200%-300% better than those of the pristine DWNT films. It was observed that DWNTs have better electrical/optical performance than SWNTs. The relative influence of various dopants, F₄TCNQ, Au, and HNO₃/SOCl₂ as well as microwave irradiation on the optical and electrical properties was identified by using Raman and UV-vis-NIR spectra.     

Trap-state-assisted white light emission from a CdSe nanocrystal integrated hybrid light-emitting diode

This Letter reports on the fabrication of hybrid white-light-emitting diodes made of semiconductor nanocrystals (NCs) integrated on InGaN/GaN LEDs. Using core type and core/shell type CdSe NCs, the white light properties are systematically engineered for white light generation with high color rendering index (CRI). Unlike CdSe/ZnS core/shell NCs, which exhibited a unique narrowband edge emission, core type CdSe NCs offered extended broad emission toward orange/red wavelengths associated with deep trap states. Consequently, the light-emitting properties of the devices showed strong dependence on the type of NCs used, and devices with CdSe NCs offered admirable characteristics, such as Commission Internationale d'Eclairage coordinates of (0.356, 0.330) and a CRI as high as 87.4.     

Optical fiber-coupled InGaAs-based terahertz time-domain spectroscopy system

The successful demonstration of an optical fiber-coupled terahertz time-domain spectroscopy (THz-TDS) system is described in this study. The terahertz output power of the emitter with two optical band rejection filters was 132 nW, which is an improvement of 70% over the output power without any filters. This improvement is due to the suppression of an optical modulated signal that is reverse-generated when an alternating current bias exceeding a certain threshold is applied to the emitter. Under the optimal alignment conditions, the terahertz detector in a fiber-coupled THz-TDS system clearly measured water vapor dips in the free space.     

Micellar ordered structure effects on high‐resolution CE‐SSCP using Pluronic triblock copolymer blends

Pluronic F108 block copolymers have shown a great promise to achieve the desirable high resolution in the conformation‐sensitive separation of ssDNA using CE‐SSCP. However, fundamental understanding of the structures and properties of Pluronic matrix affecting the resolution is still limited. Unlike conventional gel‐forming homopolymers, Pluronic F108 block copolymers are amphiphilic macromolecules consisting of poly(ethylene oxide)‐b‐poly(propylene oxide)‐b‐poly(ethylene oxide) triblock copolymers, which are capable of forming a highly ordered micellar structure in aqueous solution. In this study, we have performed a series of experiments by blending different types of Pluronic polymers to control the formation of micelles and to study the correlation between separation and rheological characteristics of Pluronic gels affecting the resolution of CE‐SSCP. Our experiments have been specifically designed to elucidate how the micellar structure affects the resolution of CE‐SSCP upon altering the size uniformity and constituent homogeneity of the micelles. Our results suggest that uniformly sized micelle packing is the primary structural feature of Pluronic gel matrix for the high‐resolution separation, while the size and constituent of the micelle themselves need to be considered as secondary factors.     

REDUCTION OF NITROGEN FUNCTIONAL GROUPS WITH ELEMENTAL SULFUR IN LIQUID AMMONIA AND AMINES

Abstract

Nitrosobenzene and phenylhydroxylamine were reduced with elemental sulfur in liquid ammonia and amines to give aniline as the major product. Although hydrazobenzene was obtained by the reactions of azoxybenzene and azobenzene with elemental sulfur in liquid ammonia and amines, the expected aniline was not obtained. The utilities of elemental sulfur in liquid ammonia and amines as reductant is discussed.     

Reaction of 4-Nitrobenzenesulfenamide with Liquid Ammonia

Abstract

Although numerous investigations on the chemistry of organic sulfenamides, for example, studies on the S–N torsional barrier,¹ the electronic nature of the S–N bond² and some nucleophilic substitutions on sulfur or nitrogen atom³ have been known, no example of nucleophilic substitution on arylcarbon of aromatic sulfenamides has been reported.     

REACTION OF α-CHLOROTOLUENE WITH ELEMENTAL SULFUR IN LIQUID AMMONIA

Abstract

α-Chlorotoluene (1) reacts with elemental sulfur in liquid ammonia affording dibenzyl disulfide (2), dibenzyl trisulfide (3), dibenzyl tetrasulfide (4), dibenzyl pentasulfide (5) and benzylidene benzylimide (6) at a low temperature such as 20°C. This reaction is presumed to be initiated by the nucleophilic attack of ammonium thioaminohydroxylate, “H₂NS^-NH₄ ⁺,” or dithioaminohydroxylate, “H₂NSS^-NH₄,” formed upon treating elemental sulfur in liquid ammonia, on α-chlorotoluene (1). Benzylidene benzylimide (6) is presumed to be formed from benzylamine, which can be formed by treatment of α-chlorotoluene (1) with ammonia.     

Coarsening Nature of Liquid-Ordered Domain in Model Membrane

We present the coarsening dynamics of a liquid-ordered (Lo) domain in a supported lipid membrane under an electric field. In a relatively small nanosmooth region surrounded by geometrical walls of nanocorrugated regions, full coarsening of the Lo domain was produced while in a large nanosmooth region, an intermediate, less-ordered Lo domain was developed so that the diffusion of charged phospholipids in the liquid-disordered (Ld) domain was allowed across the geometrical walls in the presence of an electric field. No appreciable diffusion of the charged lipids into a fully coarsened Lo domain by the electric field implies that the structural ordering of the membrane components plays a significant role on the formation of lipid rafts for biological processes.     

Tip-based nanoscale selective growth of discrete silicon nanowires by near-field laser illumination

Growth of discrete silicon nanowires is reported with nanoscale location selectivity by employing near-field laser illumination. An uncoated dielectric atomic force microscope (AFM) tip provides a nanometer-scale light source that is sufficiently localized to induce nucleation and subsequent growth of a single nanowire under its optical near-field. Far-field laser-induced heating is additionally supplied to the substrate to both relieve the required near-field light budget and also assist stable epitaxial growth. Specific catalysts are selected for the nanowire growth by non-contact mode AFM imaging. Through real-time monitoring of the deflection of the AFM cantilever during the growth process, the gap between the tip and the sample and hence truly near-field illumination are maintained throughout the growth process. The study shows that tip-based near-field laser illumination could be an effective tool for the direct integration of semiconductor nanowires.