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Applied Nanoscience (v.1, #1)

Introducing the editors (pp. 1-5).

Mesoporous carbon-coated Li₄Ti₅O₁₂ spheres for fast Li⁺ ion insertion/deinsertion in lithium battery anodes by N. Jayaprakash; Surya S. Moganty; Xiong Wen Lou; Lynden A. Archer (pp. 7-11).

We report on synthesis and electrochemical properties of a family of carbon-coated, mesoporous lithium titanate nanostructures (C@Li₄Ti₅O₁₂). Synthesized using a scalable solvothermal approach employing low-cost petroleum pitch as the carbon source, the nanostructured C@Li₄Ti₅O₁₂ materials manifest exceptional capacity to reversibly intercalate/de-intercalate lithium at both low and high charge rates. The combination of fast electrolyte and ion transport made possible in the inherently zero-strain material, Li₄Ti₅O₁₂, is thought to be responsible for our observations.

Keywords: C@Li₄Ti₅O₁₂ ; Pitch; Electrochemical study; Lithium battery anode

Nanoscale microwave microscopy using shielded cantilever probes by Keji Lai; Worasom Kundhikanjana; Michael A. Kelly; Zhi-Xun Shen (pp. 13-18).

Quantitative dielectric and conductivity mapping in the nanoscale is highly desirable for many research disciplines, but difficult to achieve through conventional transport or established microscopy techniques. Taking advantage of the micro-fabrication technology, we have developed cantilever-based near-field microwave probes with shielded structures. Sensitive microwave electronics and finite-element analysis modeling are also utilized for quantitative electrical imaging. The system is fully compatible with atomic force microscope platforms for convenient operation and easy integration of other modes and functions. The microscope is ideal for interdisciplinary research, with demonstrated examples in nano electronics, physics, material science, and biology.

Keywords: Nanoscale imaging; Microwave microscopy; Quantitative dielectric mapping; MEMS cantilevers; Non-destructive sensing

Fabrication and characterization of electroless Ni–P–ZrO₂ nano-composite coatings by Yongjian Yang; Weiwei Chen; Chungen Zhou; Huibin Xu; Wei Gao (pp. 19-26).

A novel technique has been developed to produce nano-particle oxide reinforced metal coatings. This method is based on electroless deposition process by adding ZrO₂ sol into conventional electroless Ni–P plating bath. Ni–P–ZrO₂ nano-composite coatings have been produced with highly dispersive ZrO₂ nano-particles inside the alloy coating matrix. The as plated nano-composite coating exhibits much increased microhardness up to 1045 HV₂₀₀ and remarkably improved wear resistance. X-ray and electron diffraction patterns show a phase transformation in the Ni matrix of the coating from amorphous to nanocrystalline when ZrO₂ sol is introduced into the coating. By comparison with the plain Ni–P coating and conventional Ni–P–ZrO₂ composite coating incorporated with solid ZrO₂ powders, two mechanisms for the increased mechanical properties are proposed based on nano-particle dispersion strengthening and phase transformation strengthening. The formation mechanism of ZrO₂ nano-particle is also discussed.

Keywords: Electroless plating; Ni–P–ZrO₂ nano-composite coatings; ZrO₂ sol; Oxide nano-particle dispersion; Microhardness; Wear resistance

Shape-controlled synthesis of silver particles by surfactant self-assembly under ultrasound radiation by Jafar Moghimi-Rad; Taghi Dallali Isfahani; Iraj Hadi; Sousan Ghalamdaran; Jamshid Sabbaghzadeh; Mohammad Sharif (pp. 27-35).

Several methods have been offered for silver nanoparticles production. A new method has been developed including shape-controlled synthesis of silver nanoparticles in different shapes. Dendrite, cubic, spherical and porous structures were formed by self-arrangement of the surfactant as a template under ultrasound radiation. In order to produce silver particles, ascorbic acid has been used to reduce an aqueous solution of silver nitrate in the presence of dodecylbenzenesulfonic acid sodium salt, poly (vinyl pyrrolidinone), and a mixture of organic and aqueous solutions. Scanning electron microscopy and transmission electron microscopy analysis revealed that the morphology and the size of produced particles were influenced by the type of capping agent, presence of ultrasound radiation, and crystallization time. In order to measure the surface roughness of dendrite and porous particles, an optical reflectometer was used. Surfactant molecules in an aqueous solution can aggregate in different shapes depending on temperature, ionic property of solution, time, and aprotic solvent content.

Keywords: Silver particles; Self-assembly; Dendrite; Nanoparticles; Ultrasound radiation; Shape-controlled synthesis

Photocatalytic activities of wet oxidation synthesized ZnO and ZnO–TiO₂ thick porous films by Ruiqun Chen; Jie Han; Xiaodong Yan; Chongwen Zou; Jiming Bian; Ahmed Alyamani; Wei Gao (pp. 37-44).

Highly porous zinc oxide (ZnO) film was produced by using reactive magnetron sputtering zinc target followed by wet oxidation. Titanium dioxide (TiO₂) was mixed to the porous films by using either TiO₂ target magnetron sputter deposition or sol-spin method. The film thickness could reach 50 μm with uniform porosity. On the sputtering prepared ZnO–TiO₂ film surface, fine nanorods with small anatase TiO₂ nano-clusters on the tips were observed by SEM and TEM, and the titanium (Ti) composition was determined by XPS as 0.37%. The sol-spin treatment could increase the Ti composition to 4.9%, with reduced pore size compared to the untreated ZnO porous film. Photoluminescence measurements showed that the Ti containing porous film has strong ultraviolet-visible light emission. In the photo-catalysis testing, ZnO and ZnO–TiO₂ have similar photo-catalysis activity under 365 nm UV irradiation, but under visible light, the photocatalysis activities of ZnO–TiO₂ films were twice higher than that of ZnO porous film, implying promising applications of this porous oxide composite for industrial and dairy farm wastewater treatment.

Keywords: Zinc oxide; Titanium dioxide; Porous film; Reaction with estrone; Photocatalysis with visible light

Preparation and characterization of colloidal ZnO nanoparticles using nanosecond laser ablation in water by Raid A. Ismail; Abdulrahman K. Ali; Mukhlis M. Ismail; Khaleel I. Hassoon (pp. 45-49).

Pulsed laser ablation in liquid was employed to synthesize zinc oxide (ZnO) nanocolloidal suspension. Colloidal ZnO nanocrystals are synthesized by pulsed laser ablation of high purity zinc target in double distilled water with various laser fluences at RT. UV–visible absorption and transmission electron microscope are used for the characterization of colloidal ZnO nanoparticles (NPs). The optical properties, size, and the morphology of the synthesized ZnO were influenced strongly by laser fluence and wavelength. The use of water gave spherical ZnO NPs with average size 35 nm. The optical band gaps of the ZnO NPs are increased with laser fluence up to 22.3 J/cm².

Keywords: Laser ablation; Zinc oxide; Nanocolloidal; TEM

Magnetic entropy change in bulk nanocrystalline Gd metals by Hong Zeng; Jiuxing Zhang; Chunjiang Kuang; Ming Yue (pp. 51-57).

The magnetocaloric properties of the as-consolidated nanocrystalline and coarse-grained gadolinium metals were studied in the present work. With the decrease of Gd grains from micrometer to nanometer range, magnetic entropy change drops surprising from 10.07 to 4.47 J kg⁻¹ K⁻¹ at a magnetic-field change of 5 T, and their resultant magnetic entropy change uniformly peaks at 294, 290, and 288 K, respectively, corresponding to the magnetic transition temperature of the three samples. The Curie temperature T _C of the nanocrystalline Gd shifts by more than 6 K below that of coarse-grained Gd sample. However, the values of magnetic entropy change of the nanocrystalline metals exhibit a more constant tendency compared with the coarse-grained sample. The Arrott plots indicate the second-order character of magnetic phase transition still in the nanocrystalline Gd metals. The refrigerant capacity calculated is also used to evaluate material refrigeration capacity.

Keywords: Magnetocaloric effect; Magnetic entropy changes (∆S); Nanocrystalline metals

A Monte Carlo investigation of Gallium and Arsenic migration on GaAs(100) surface by A. Amrani; M. Djafari Rouhani; A. Mraoufel (pp. 59-65).

We perform an atomic scale simulation of GaAs/GaAs(100) growth, using the Kinetic Monte Carlo (KMC) technique, to investigate some aspects of Gallium and Arsenic surface migration. We show that the interlayer migration rate is smaller for Arsenic than for Gallium. Results suggest that upward diffusion is thermally activated while downward diffusion is kinetically controlled. We also find an oscillatory behavior of the surface diffusion rates during the growth, in close relation to the roughening of the substrate. The surface migration rates are governed by the temperature, but mostly by the Arsenic to Gallium flux ratio. The Gallium average diffusion lengths are estimated to be ~440 nm at 620°C and ~130 nm at 530°C, in agreement with experimental data.

Keywords: KMC; MBE; Monte Carlo method; Simulation; GaAs; Diffusion length

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Applied Nanoscience (v.1, #1)

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Applied Nanoscience (v.1, #1)