Fabrication of Transparent and Conductive SWCNT/SiO2 Composite Thin-Film by Photo-Irradiation of Molecular Precursor Films

A single-walled carbon nanotube (SWCNT)-silica composite thin film on a quartz glass was formed by ultraviolet irradiation (20–40 °C) onto a spin-coated precursor film. With 7.4 mass% SWCNTs, the electrical resistivity reached 7.7 × 10−3 Ω·cm after UV-irradiation. The transmittance was >80% at 178–2600 nm, and 79%–73% at 220–352 nm. Heat treatment increased the transparency and pencil hardness, without affecting the low electrical resistivity. Raman spectroscopy and microscopic analyses revealed the excellent film morphology with good SWCNT dispersal. The low refractive index (1.49) and haze value (<1.5%) are invaluable for transparent windows for novel optoelectronic devices.

A DFT Analysis of Electronic, Reactivity, and NLO responses of a Reactive Orange Dye: the Role of Hartree-fock Exchange Corrections

An experimental and theoretical study based on DFT/TD-DFT approximations is presented to understand the nature of electronic excitations, reactivity, and NLO properties of reactive orange 16 dye (RO16), an azo chromophore widely used in textile and pharmacological industries. The results show that the solvent has a considerable influence on the electronic properties of the material. According to experimental results, the absorption spectrum is noticed by four intense transitions, which have been identified as $\pi\rightarrow\pi^*$ states using TD-DFT calculations. However, the TD-DFT results reveal a weak $n\rightarrow\pi^*$ in the low-lying spectral region. Continuum models of solvation indicate that these states suffer bathochromic and hypsochromic shifts, respectively. However, the expected blue shift for the absorption $n\rightarrow\pi^*$ is only described using long-range or dispersion-corrected DFT methods. RO16 is classified as a strong electrophilic system ($\omega > 1.5$ eV). From vacuum to solvent, the environment is active and changes the nucleophilic status from strong to moderate nucleophile ($2.0 \leq N \leq 3.0$ eV). The results also suggest that all electrical constants are strongly dependent on long-rang and Hartree-Fock exchange contributions, and the absence of these interactions gives results far from reality. In particular, the results for the NLO response show that the chromophore presents a potential application in this field, with a low refractive index, and first-hyperpolarizability ca. 214 times bigger than the value usually reported for urea ($\beta = 0.34 \times 10^{-30}$ esu), which is a standard NLO material. Concerning the solvent effects, the results indicate that $\beta_\textrm{total}$ increases ca. 180\% regarding the gas-phase value. The results suggest RO16 is a potential compound in NLO applications.

Ultrahigh Sensitivity Mach−Zehnder Interferometer Sensor Based on a Weak One-Dimensional Field Confinement Silica Waveguide

We report a novel Mach−Zehnder interferometer (MZI) sensor that utilizes a weak one-dimensional field confinement silica waveguide (WCSW). The WCSW has a large horizontal and vertical aspect ratio and low refractive index difference, which features easy preparation and a large evanescent field for achieving high waveguide sensitivity. We experimentally achieved WCSW ultrahigh waveguide sensitivity of 0.94, MZI sensitivity of 44,364 π/RIU and a low limit of detection (LOD) of 6.1 × 10−7 RIU.

Manipulation of thermal radiation by using photonic crystals

This paper focuses on manipulating thermal emission and radiation loss of heat energy in a heat waveguide. A One-Dimensional Photonic Crystal is used as a waveguide clad to prohibit the thermal emission from escaping. The model may reduce the radiation loss of heat energy in the waveguide core, and heat energy can be confined to propagate along the waveguide’s longitude axis. The waveguide clad comprises alternative layers of high and low refractive index materials containing sufficient electromagnetic stop bands to trap the thermal emission from escaping out of the waveguide. The numerical simulation of the model shows that the forbidden bandgap of photonic crystal structures with alternative layers of silica and silicon has width enough to make heat energy be confined within the waveguide core so that efficient heat energy transmission can be achieved along the longitude axis of the waveguide.