Advanced Materials Research Vol. 1024

Abstract: Fe-TiO₂ nanoparticles with 5-9 nm sizes were prepared by sol gel method subsequently subjected to hydrothermal treatment at 150°C for 6 h. Titanium (IV) isopropoxide and iron (III) nitrate nonahydrate were used as precursor. The morphology, structure and composition of the Fe-TiO₂ were investigated by X-ray diffraction (XRD), Transmission emission microscopy (TEM) and UV-vis spectroscopy (UV-vis). XRD analysis revealed the prepared samples was dominated with anatase phase and a trace of brookite phase. The TiO₂ crystallite size was reduced as Fe content was increased. Compared with the pure TiO₂ nanoparticles, the Fe-TiO₂ nanoparticles exhibited higher photocatalytic activity in decolorizing methyl orange into non-toxic inorganic products under UV irradiation.

Abstract: This work describes the formation of platinum nanodendrites (PtNDs) using the chemical reduction method. The PtNDs were formed with varying concentration of K₂PtCl₄ precursor (5-20 mM) and growth duration (8-16 min). The optimum concentration of K₂PtCl₄ was 15 mM whereby high crystalline nanodendrites with an average size of 118 nm were produced. Aggregation of nanodendrites occurred when the growth duration was prolonged to more than 12 minutes. The morphology and size of PtNDs were characterized by using a transmission electron microscope (TEM), high resolution transmission electron microscope (HRTEM) and X-ray diffractometer (XRD). Additionally, the memory characteristics of PtNDs embedded in polymethylsilsesquioxanes (PMSSQ)/Si with gold electrodes were studied in this work. PtNDs played a role as charge-trapped sites and showed good memory effect when embedded in PMSSQ. Optimum memory properties of PMSSQ-embedded PtNDs were obtained for PtNDs synthesized with 15 mM K₂PtCl₄ concentration at 12 min of growth duration with 170 electrons trapped per PtNDs and V_th of 2.8 V.

Abstract: We report on the simulation and fabrication of nanostructured silicon surfaces for field emission (FE) applications, e.g. ionization sensors and x-ray tubes. For the design and optimization of field-emitting silicon structures, the influence of the geometric parameters like tip height, apex radius, aperture angle and curvature shape on the field enhancement factor was investigated by simulation using finite element method. A universal geometric model which describes the real geometry of our silicon structures sufficiently accurate was taken for modeling a variety of different silicon tip structures as well as ridge structures. While a high dependency of the field enhancement on the aspect ratio and the aperture angle was found, the simulations show that the elliptic curvature affects the field enhancement only marginally. Finally, an improved process for fabrication of such silicon structures on n-type as well as p-type substrate is described, using reactive ion etching with adjustable anisotropy, wet thermal oxidation and wet etching.

Abstract: The co-precipitation method was employed to fabricate Zn/AlNO₃LDH in molar ratio, Zn²⁺/Al³⁺= 2 at PH=7. The sodium dodecyl sulfate (SDS) was intercalated to Zn/Al-LDH using coprecipitation method to form a new organicinorganic nanocomposite (LDH-SDS) with different concentration of SDS solution (0.2M, 0.4M and 0.8M). The structural properties of the resultant nanocomposites were perused using powder X-ray diffraction (PXRD). The shifting in the basal spacing for LDHSDS samples (2.562.60nm) with respect to Zn/AlNO₃ (0.890 nm) indicated SDS intercalation within the galleries. The UVVIS NIR Diffuse reflectance spectroscopy were applied to evaluate the optical band gap energy of LDH and LDHSDS samples. Due to the presence of different phases in LDH, more than one energy gap was shown in diffuse reflectance spectroscopy of the Zn/AlLDH sample and LDHSDS nanocomposites. For LDHSDS samples the values of Eg1 and Eg2 were observed to increase to around 5.2 eV and 4.1 eV. The electron spin resonance (ESR) spectra of Zn/Al-LDH are comprised of a broad signal with g-factor=2.11875 which can be caused by the existence of nitrate radicals within LDH interlayer, it was obtained up to around g=1.98639 for LDH-SDS samples which can be attributed to the interaction between SO₄^2- from DS anion and Al nuclei (5/2) from the layers.

Abstract: Application of nanotechnology in enhanced oil recovery (EOR) has been increasing in the recent years. After secondary flooding, more than 60% of the original oil in place (OOIP) remains in the reservoir due to trapping of oil in the reservoir rock pores. One of the promising EOR methods is surfactant flooding, where substantial reduction in interfacial tension between oil and water could sufficiently displace oil from reservoir. The emulsion that is created between the two interfaces has a higher viscosity than its original components, providing more force to push the trapped oil. In this paper, the recovery mechanism of the enhanced oil recovery was determined by measuring oil-nanofluid interfacial tension and the viscosity of the nanofluid. Series of core flooding experiments were conducted using packed silica beads whichreplicate core rocks to evaluate the oil recovery efficiency of the nanofluid in comparison to that using an aqueous commercial surfactant, 0.3wt% sodium dodecyl sulfate (SDS). 117 % increase in the recovery of the residual oil in place (ROIP) was observed by the 2 pore volume (PV) injection of aluminium oxide nanofluid in comparison with 0.3wt% SDS. In comparison to the type of material, 5.12% more oil has been recovered by aluminium oxide compared to zinc oxide nanofluid in the presence of EM wave. The effect of the EM wave on the recoverywas also studied by and it was proven that electric field component of the EM waves has been stimulating the nanofluid to be more viscous by the increment of 54.2% in the oil recovery when aluminium oxide nanofluid was subjected to 50MHz EM waves irradiation.

Abstract: This paper reports the results of zinc oxide (ZnO) nanostructure growth on different types of metal catalysts, namely gold and platinum, and also the effect of annealing time of the metal catalysts prior to the deposition of ZnO nanostructures. The metal catalysts layers with 15 nm thickness were deposited on glass substrates by sputter coater and then annealed in air ambient for 15 and 30 min at 500 °C. ZnO nanostructure was then deposited on the metal catalysts by thermal chemical vapour deposition (TCVD) method. We found that the Au catalyst morphologies varied with the annealing time, and the growth morphology of the ZnO followed the morphology of the Au catalyst. The morphology of the metal catalysts and ZnO nanostructures were characterized using field emission scanning electron microscopy (FESEM). The grown ZnO nanostructures were tested for their ability for extended gate field effect transistor (EGFET) sensor application. The samples were attached to the gate of an NFET and were dipped in acid and alkali buffer solutions while the gate voltage was measured. We found that the extended gate gave different voltage in buffer solutions with different pH which indicated that the samples can act as the extended gate of an EGFET sensor.

Abstract: The paper presents the memristive behavior of sputtered titania thin films on ITO substrate. Titania thin films were deposited by RF magnetron sputtering method while varying the oxygen flow rate of (O₂/ (O₂ + Ar) x100 = 10, 20 and 30 %) during deposition process. The effect of oxygen flow rate to the structural properties was studied including the physical thickness, and also the effect towards switching behavior. It was found that sample deposited at 20 % oxygen flow rate gave better memristive behavior compared to other samples, with larger R_OFF/R_ON ratio of 9. The characterization of memristive behavior includes the effect of electroforming process and successive of I-V measurements are discussed.

Abstract: Nanoparticles such as cadmium selenide (CdSe) have unique optical properties in term of band gap. These properties can be adjusted by controlling the size of nanoparticles. In this research we have synthesized different sizes of CdSe nanoparticles by controlling the reaction temperatures at 260 ^oC and 300 ^oC using a hot injection method. The as-synthesized CdSe nanoparticles were characterized using UV-visible spectroscopy and high resolution transmission electron microscope. From the UV-visible absorption spectra, the absorption peak of CdSe nanoparticles synthesis at growth temperature of 260 ^oC was 521 nm with estimated particle diameter of 2.57 nm, and for 300 ^oC the absorption peak was at 601 nm with estimated particle diameter of 4.63 nm. This indicates that the size of CdSe nanoparticles can be controlled by controlling the reaction temperature.

Abstract: This work describes the formation of gold nanoparticles (AuNPs) by using the sacrificial template growth hydrothermal method. AuNPs was grown on Aluminum/ polymethylsilsesquioxanes (PMSSQ) /Silicon substrates. Sputtered Al was used as a sacrificial template. The effect of hydrothermal reaction time on AuNPs properties was investigated for 1, 2, 3 and 4 hours. Properties of AuNPs were studied by using Field-Emission Scanning Electron Microscope (FESEM), X-ray Diffraction (XRD) and Semiconductor Characterization System (SCS). This approach allows the formation of AuNPs directly on the substrates. XRD analysis proved that Al template was removed during hydrothermal reaction. This approach allows the formation of AuNPs directly on the substrates. The number of AuNPs increased with increasing hydrothermal reaction time. However, longer than 1 hour reaction time, AuNPs tend to grow in clusters that could be due to unintended aggregation and agglomeration caused by self-association of the AuNPs. I-V characteristics showed hysteresis properties that indicated charge storage capability of AuNPs embedded in PMSSQ. AuNPs grown in 1 hour hydrothermal reaction produced the best memory properties due to well distribution of isolated AuNPs as observed in SEM image with the lowest abrupt current of 2.4 V.

Abstract: This paper reports on ITO/Ag and ITO/Ni thin transparent conductive electrodes (TCE) for optoelectronics device applications. The ITO/Ag and ITO/Ni bi-layer TCE were deposited on Si and glass substrates by thermal evaporator and radio frequency (RF) magnetron sputtering. Post-annealing was performed on the samples at 600°C in air. Electrical, optical and morphological characteristics were investigated by means of Hall Effect measurement system, UV-Vis spectrophotometer and atomic force microscope (AFM). The measured electrical resistivity of ITO/Ag (0.5 × 10^-4 Ωcm) is lower than ITO/Ni (1.2 × 10^-4 Ωcm) due to the high carrier concentration of ITO/Ag of 12.0 × 10²¹ cm^-3. Optical transmittance at visible ranges of ITO/Ag (70%) is higher than the ITO/Ni (44%). Higher surface roughness and smaller grain sizes of ITO/Ag as compared to the ITO/Ni are factors that contribute to the good quality of TCE characteristics.