Journal of Nano Research Vol. 57

Abstract: The effect of recyclability on the catalytic activity of supported Au₁₀₁(PPh₃)₂₁Cl₅ nanoparticles (1.0 wt% Au₁₀₁/AC) was investigated for benzyl alcohol oxidation under mild conditions. The influence of recyclability on the catalytic activity of activated Au₁₀₁/AC nanocatalysts was studied trough a comparison of gold particle diameter and also catalysts conversion between the fresh (as synthesized) and recycled gold catalysts. The monitoring of gold particle diameters by transmission electron microscopy (TEM) showed that the gold particles size gradually increased during the catalytic reaction. The mean diameter of the fresh gold catalysts increased from approximately 3 to 3.2, 5.1 and 5.3 nm after 1, 2 and 3 h reaction time, respectively. Whereas the average gold particle diameter of the recycled samples were slightly enlarged from approximately 5.3 (the sample recycled after 3 h of the first catalytic test) to 5.7, 5.9 and 6.2 nm with durations of 1, 2 and 3 h reaction time, respectively. Therefore, larger gold particles gradually formed for fresh and also recycled gold catalysts during reaction tests. Meanwhile, the catalytic activity of activated 1.0 wt% Au₁₀₁/AC catalysts jumped to full conversion when the recycled gold catalysts were utilized due to removing ligand stabilizer from gold particles and so bigger particles had formed.

Abstract: Metallic nanoparticles have various potential applications. Recent studies have showed that their morphology had a strong influence on their optical and electrical properties. In this work, rapid thermal annealing was used to produce gold nanoparticles on silicon substrates. Morphology control of the gold nanoparticles was made by changing inert annealing gases. Spherical gold nanoparticles were obtained with nitrogen while hemispherical gold nanoparticles were formed with argon.

Abstract: In this research, unzipped sulfanilic acid inspired hydrophobic peptide tube was synthesis by increasing the polarity of sulfanilic acid through nucleophilic attachment of aniline which then provided two reactive sites at the S-terminus. These two sites were then attached with the N-terminal of valine and alanine respectively at an intensity of 1000-1600 of 11 2θ (°). Through π- π stacking at the side chains, the opened ended peptide was linearly arranged to form the unzipped tube. Fourier transform infrared spectroscopy (FTIR) confirm the amine bond formation whiles X-ray diffraction test results confirmed D-spacing 7.36 and 4.44 corresponding 2θ (°)12 and 19.97 respectively whiles the torsion angles (Ø₂₎ conformations was between-150.5°and-169.2° and-2 between-129.0° and-150.6°. The Thermogravimetric analysis result showed an increase in the rigidity of the bond with an increasing intensity. Finally, Differential scanning calorimetry (DSC) test was carried out to confirm the crystallinity of the structure. Keywords: Sulfanilic acid, hydrophobic Peptide, Unzipped tubes, Nanomaterial

Abstract: The effect of sulfating agent concentration, calcination temperature, and Ni incorporation on commercial zirconia have been evaluated. Sulfation of commercial zirconia was prepared by wet impregnation with different amounts of sulfuric acid (0.2, 0.5 and 0.8 M) then calcined at 400, 500, 600, 700, 800 and 900°C for 4 h. Ni was incorporated by refluxing over sulfated zirconia, followed by calcination-reduction process. All samples were characterized by XRD, FTIR, ammonia sorption, SEM-EDX, TEM, and AAS. The presence of sulfate has been added to acidic strength of the sulfated zirconia, the more sulfuric acid were used the stronger the acidic property. There has been degradation of sulfate groups that was adrift in sulfated zirconia by calcination treatment above 600°C. The best physicochemical properties of sulfated zirconia were modification with 0.8 M sulfuric acid and on calcination at 400°C. The 0.8SZ-400 has exhibited the highest Brønsted acidic sites with total acidity of 1.71 mmol/g. The impregnation of Ni enhanced the Lewis acidic sites on the surface of the 0.8SZ-400 which NiSZ gave 2.71 mmol/g of total acidity. All prepared materials consisted of nearly spherical shape of nanocrystal with mostly aggregated particles.

Abstract: The non-linear diffusion-deformation theory of self-organization of nanoclusters of dot defects in semiconductor exposed to ultrasound treatment that considers the interaction of defects among themselves and with atoms of a matrix via the elastic field created by dot defects and an acoustic wave is developed. Within this theory the influence of ultrasound on the conditions of formation of spherical nanoclusters and their radius is investigated. The nanocluster size depending on average concentration of defects and amplitude of an acoustic wave is determined. It is established that ultrasonic treatment of the semiconductor in the process of formation of an ensemble of nanoclusters leads to reduction of dispersion of their sizes. In the framework of this model, a possibility of the ultrasound-stimulated the size dispersion reduction of strained InAs/GaAs quantum dots doped with an isovalent impurity are analyzed.

Abstract: We have observed surface plasmon resonances (SPR) in Au thin films between 18 nm to 27 nm thick deposited onto glass substrates. The observed resonance angles are between 15.5 to 18.75 degrees, which are lower than predicted theoretical values for thicker films. The shift of resonances with the change of refractive index of surrounding confirms its application for nanobio-sensing. A thorough topological surface analysis and transmitted spectra were performed. Au thin films were annealed in Argon and the analysis repeated and compared with those from pre-annealing. The annealing process will cause a sharper appearance of surface plasmon resonances which will make these thin film devices a more suitable candidate for nanobio-sensing applications.

Abstract: We have investigated the surface effect of colloidally prepared CdSe nanocrystals (NCs) with the size range of 23-40 Å on their structural properties by changing the organic capping ligands. The TOPO/HDA-passivated NCs reveal a size-dependent behavior involving an elongated axial bond R⁽¹⁾ of an atomic tetrahedron and a shrunken equatorial bonds R⁽²⁾. After treatment of the NCs with pyridine, the bond length R⁽¹⁾ decreases significantly whereas R⁽²⁾ remains unchanged relative to the TOPO/HDA-passivated NCs, suggesting that a tensile stress along the [001] direction is contributed from the surface modification. In addition, we find that the expansion ratio of the pyridine-treated NCs along the c axis depends strongly on the density of stacking faults, which provides an evidence for the relaxation of atomic positions near the interface of stacking faults.

Abstract: In this paper, an analytical model for modified Surrounding Gate Tunnel FET with gate stack engineering and different gate metals has been developed. Further, considering the scaling advantageous of Gate stack engineering and high degree performance of dual material engineering, the both has been integrated into a novel structure known as Surrounding Gate (SG) Tunnel FET with stacked oxide SiO₂/high-k and dual material (DM) has been proposed. The two dimensional (2D) potential at the surface and electric field mathematical models for the DMSG TFET are developed by solving 2D Poisson's equation with matching device boundary conditions. Based on the Kane's formula, mathematical expression for the band-to-band (BTB) tunneling generation rate is derived and then used to calculate the drain current. The impact on the proposed device performance due to the variation of different device parameters has also been studied. It has been found from the presented results that the ON current of the DMSG TFET with stack is 10^-6A, OFF current is 10^-13A and ON/OFF ratio is 10⁷. The mathematical results have been verified using the simulated results obtained from TCAD, a 3-D device simulator from ATLAS.

Abstract: ZnO NWFETs were fabricated with and without Al₂O₃ passivation. This was done by developing a new recipe for depositing the thin film of ZnO. By using a high donor concentration of 1.7 x 10¹⁸ cm^-3 for the thin film, contact resistance values were lowered (passivated device had R_con = 2.5 x 10⁴ Ω; unpassivated device had R_con = 3.0 x 10⁵ Ω). By depositing Zn first instead of O₂, steep subthreshold slopes were obtained. The passivated device had a subthreshold slope of 225 mV/decade and the unpassivated device had a slope of 125 mV/decade. Well-behaved electrical characteristics have been obtained and the passivated device shows field effect mobility of 10.9 cm²/Vs and the un-passivated device shows a value of 31.4 cm²/Vs. To verify the results, 3D simulation was also carried out which shows that the obtained values of sub-threshold slope translate into interface state number densities of-1.86 x 10¹³ cm^-2 for the unpassivated device and 3.35 x 10¹⁴ cm^-2 for the passivated device. The passivated device is suitable for biosensing applications.

Abstract: In the current scenario nanotechnology and nanomaterials are emerging as key role in engineering and medical industries. The objective of this research is to increase the usage of fly ash in concrete to enhance the strength properties of concrete mixed with nano silica and to reduce the emission control caused by CO₂ discharged from cement manufacturing industries. The strength properties of concrete mixture is enhanced with nano size particles filled the voids amoung micron size cement particle, and hence a denser concrete mixture was being attained. Fly ash is used for partial replacement of cement to enhance the environmental sustainability and to reduce the cost. This research work focussed on preparation of nano silica mixed concrete with replacement of fly ash in concrete mixture. Nano silica was added in addition to the above by 1% and 2% to improve the overall strength properties. Different experimental analysis were carried out to obtained the results such as compression strength, ultimate divide tensile strength and elastic modulus of the enriched concrete mixture. From the observed results it was found that, compression strength was increased by adding 1% nano silica and 25% of fly ash and also increased the ultimate tensile strength by 28%. Scanning Electrom Microscope (SEM) results reveal that, the incorporation of the nano silica in concrete increases the mechanical properties and porosity was successfully minimized with enhancement of pore size distribution.