Advanced Materials Research Vol. 802

Abstract: TiO₂ nanofibers were fabricated via an electrospinning method. Titanium (IV) isopropoxide (TIP) and poly (viny pyrrolidone) (PVP) were used as a starting precursor. The electrospun TiO₂ nanofibers were obtained by injecting the precursor through a needle under a strong electrical field. As-spun fibers were calcined at 500, 600, 700, 800 and 900 °C for 2 h. The structural of properties of the nanofibers were characterized using X-ray diffraction (XRD) and Scanning electron microscope (SEM). XRD results indicated that the crystallinity of TiO₂ nanofibers corresponds to rutile and anatase phase of TiO₂ depending on calcinations temperature. SEM results indicated that the surface morphology and size TiO₂ nanofibers. The photocatalytic degradation of RhB may be attributed to significant absorption enhancement in visible region by phase transformation of TiO₂ nanofibers and fiber size dependence active surface areas.

Abstract: Titanium dioxide nanoparticles (TiO₂) were successfully synthesized via a sonochemical-assisted process using titanium isopropoxide as the titanium sources and calcination process at 300-500 °C. The effect of sonication time and heat treatment temperature on structural and nanostructure properties of the nanoparticles were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM) and transmission electron microscope (TEM). The XRD and Raman results indicated that the crystalline of as-sonochemically synthesized TiO₂ nanoparticles corresponded to anatase phase of TiO₂ after sonication for 30 mim. The high quality crystalline anatase phase and increasing of crystalline size can be obtained after calcinations process.

Abstract: Triphenylamine-base organic dyes were designed and investigated for dye-sensitized solar cells (DSSCs). The dye molecules consist of three parts, an electron-donor connected by the π-conjugated linker (benzene and thiophene) as an electron spacer and an acceptor/anchoring (cyanoacrylic acid). In this study, quantum chemical calculations were used to study the electronic properties, optical properties and density of electron in the linker of dye molecule by using the density functional theory. The results present that thiophene is the most appropriate to use as electron linker between triphenylamine donor and acrylic acceptor due to the wide of absorption band and π-conjugate bond effect on exhibiting red-shifted absorption spectra.

Abstract: This paper describes metallization of PET surface by Sn-free electroless deposition (ELD) of thin copper layer. Prior to introduction to ELD process, the PET surface was plasma-pretreated in argon atmosphere. ELD is a multi-step process involving silanization with TMS, activation with PdCl₂ and copper deposition. Contact angle measurement and XPS analysis were carried out at each stage in order to confirm the chemical change of the PET surface after modification. XPS analysis revealed that the copper surface consisted mainly of Cu₂O, combined with Cu⁰, making Cu-coated PET sheet suitable for the use as substrate for electropolymerization of pyrrole. This study offers an alternative to preparing flexible sensors. This process could be further applied to micro-contact printing technique to fabricate flexible patterned electrodes.

Abstract: Sensor response and pattern recognition of polymer-coated single-walled carbon nanotubes (SWNTs) were investigated. Printed circuit board (PCB) with Cu/Au interdigitated electrode was used as sensor platform. SWNTs network was firstly formed on PCB by drop-casting. For polymer-coated SWNTs preparation, poly(methyl methacrylate) (PMMA) and thiophene were employed as polymers to coat on SWNTs by spin coating; PMMA/SWNTs and thiophene/SWNTs. Raman spectra showed no obvious structure changes of SWNTs after polymer coating. Next, gas sensing test was conducted. Pristine SWNTs, PMMA/SWNTs and thiophene/SWNTs were exposed to vapors of ethanol and dichloromethane at room temperature. From normalized sensor response results, it was found that pristine SWNTs and PMMA/SWNTs showed the highest response to ethanol and dichloromethane vapors, respectively. In order to discriminate vapors between ethanol and dichloromethane, pattern recognition technique was utilized. Principal component analysis (PCA) results showed that pattern recognition of ethanol and dichloromethane vapors can be discriminated by using pristine SWNTs and polymer-coated SWNTs sensors.

Abstract: A blend of molecular acceptor and molecular donor made of Copper Phthalocyanine (CuPc) and Indium in various ratios were evaporated in high vacuum on to intrinsic silicon substrates by using vacuum thermal co-evaporation technique. Electronic properties of In-doped CuPc thin films have been examined by X-ray photoelectron spectroscopy (XPS). The results obtained by XPS suggests that In-doped CuPc is a hole transport material.

Abstract: We investigate the increase of C-H vibration in benzene rings of pentacene molecule upon doping with indium by the X-ray photoelectron spectroscopy (XPS) characterization technique. The risen of C-H vibration spectral component is employed to demonstrate the charge transfer between In dopant atoms and C atoms in benzene rings of pentacene molecule. This experiment can be used to explain the same mechanism of charge transfer between In dopant atoms and C atoms in In-doped nickel-phthalocyanine(NiPc).

Abstract: The authors examined the thermal and electrical transport properties of Tl₇Sb₂ at temperatures ranging from room temperature to 400 K. The crystal system of Tl₇Sb₂ is cubic with the lattice parameter a = 1.16053 nm and the space group is Im3m. The polycrystalline samples were prepared by melting stoichiometric amounts of thallium and antimony. Although, usually the thermal conductivity of thallium compounds is very low (<1 Wm^-1K^-1), that of Tl₇Sb₂ was relatively high (~13 Wm^-1K^-1 at room temperature). This is because of the large electronic contribution to the thermal conductivity.