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Online ISSN 1750-0443

Micro & Nano Letters

Volume 5, Issue 4, August 2010

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Volume 5, Issue 4

August 2010

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    • Influence of different preparation methods on crystallisation and morphology of Fe2O3 nanoparticles
      • Author(s): Ting Wang ; Xin Jiang ; Huan-cong Huang
      • Source: Micro & Nano Letters, Volume 5, Issue 4, p. 196 –199
      • DOI:  10.1049/mnl.2010.0045
      • Type: Article
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      • p. 196 –199 (4)
        Iron oxide nanoparticles were prepared by adsorption phase synthesis (APS), impregnation method (IM) and precipitation synthesis (PS). The grain sizes of Fe2O3 prepared by APS and IM were much smaller than that by PS. In the APS process, when the reaction took place in the adsorption layer, strong chemical bonds between Fe2O3 particles and silica could be built, which inhibited the phase transformation from γ-Fe2O3 to α-Fe2O3 during the calcination process. The physical interaction did not restrain the crystal transformation although the restriction on the aggregation of Fe2O3 particles was obvious.
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      Template-free synthesis of α-Fe2O3 microcubes and their magnetic property
      • Author(s): Haojie Song ; Na Li ; Shilong Yu
      • Source: Micro & Nano Letters, Volume 5, Issue 4, p. 200 –202
      • DOI:  10.1049/mnl.2010.0049
      • Type: Article
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      • p. 200 –202 (3)
        Micro/nanostructured α-Fe2O3 microcubes were obtained by a facile template-free hydrothermal route. The as-obtained products were characterised by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and vibrating sample magnetometry. It is shown that the cubic structures are consisted of well-aligned α-Fe2O3 nanoparticles with a mean diameter of about 15 nm. Magnetic hysteresis measurement reveals that the α-Fe2O3 cubic structures display weak ferromagnetic behaviour with a remanence of 0.1164 emu/g and a coercivity of 1828.7710 Oe at room temperature. The formation mechanism of the α-Fe2O3 microcubes was also discussed.
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      Compact nanostructure integrated pool boiler for microscale cooling applications
      • Author(s): M. Şeşen ; W. Khudhayer ; T. Karabacak ; A. Koşar
      • Source: Micro & Nano Letters, Volume 5, Issue 4, p. 203 –206
      • DOI:  10.1049/mnl.2010.0070
      • Type: Article
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      • p. 203 –206 (4)
        An efficient cooling system without any external energy consumption that consists of a plate, on which an array of copper nanorods with an average diameter ∼100 nm and length ∼500 nm is integrated to a planar copper thin film coated silicon wafer surface, a heater, an aluminium base and a pool was developed. Heat is efficiently transferred from the nanostructure coated base plate to the liquid in the pool through boiling heat transfer mechanism. Phase change took place near the nanostructured plate, where the bubbles started to emerge because of the existing wall superheat. Bubble formation and bubble motion inside the pool resulted in effective heat transfer from the plate surface to the pool. Surface temperatures were measured and heat transfer coefficients were calculated for two working fluids; namely, water and ethanol. In this study, it was shown that using nanostructured surfaces can have the potential to be an effective method of device cooling for small and excessive heat generating microsystem applications, such as microelectromechanical systems, or microprocessors.
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      Investigation of electrocatalytic function of Co3O4 flower-like structures and application as uric acid sensor
      • Author(s): Mingyan Wang ; Dongen Zhang ; Zhiwei Tong ; Weixing Ma ; Xingyou Xu
      • Source: Micro & Nano Letters, Volume 5, Issue 4, p. 207 –210
      • DOI:  10.1049/mnl.2010.0060
      • Type: Article
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      • p. 207 –210 (4)
        This investigation evaluates the electrocatalytic property of Co3O4 flower-like structures (CoFS) and its potential application as an amperometric sensor in uric acid (UA) detection. By simple dropcoating method, CoFS were used as a modifier on the glassy carbon electrode (GCE) to fabricate an amperometric sensor. The morphology of the sensor surface was characterised by scanning electron microscope (SEM). The effective surface area of the sensor was calculated by chronocoulometry (CC). The electrocatalytic ability of the sensor to UA oxidation reaction in phosphate buffer solution (pH 7.4) was investigated by cyclic voltammetry (CV) and chronoamperometry. Results suggested that the surface area of the sensor was almost two times larger than that of bare GCE and the CoFS exhibited a strong electrocatalytic activity to the redox reaction of UA. The catalytic peak currents of UA were linearly dependent on the concentrations of UA in the range from 1.0×10−6 to 2.7×10−4 M, with a detection limit of 5.0×10−7 M. The sensor displayed good stability and reproducibility, and it was successfully applied to determine the UA concentrations in human urine samples.
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      Fabric tactile sensor composed of ball-shaped umbonal fibre for detecting normal and lateral force
      • Author(s): G. Kita ; Y. Suzuki ; M. Shikida ; K. Sato
      • Source: Micro & Nano Letters, Volume 5, Issue 4, p. 211 –214
      • DOI:  10.1049/mnl.2010.0030
      • Type: Article
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      • p. 211 –214 (4)
        The authors previously proposed an artificial hollow fibre for use as a microelectromechanical systems (MEMS) material to produce a wearable sensing system and developed a fabric tactile sensor to apply to it. In this Letter, the authors developed a ball-shaped projection for producing the umbonal fibre to improve sensing performance for normal- and lateral-forces detection. An adhesive was manually dropped on the fibre to form the ball-shaped projection structure by surface tension. Its typical diameter was 1.0 mm. The entire surface of the umbonal fibre was then coated with metal and insulation layers. Finally, the umbonal hollow fibre, two weft hollow fibres, a brass wire and cotton yarn were woven together to produce the fabric tactile sensor. The sensor output linearly increased with the increase in applied normal force because of the ball-shaped projection. The sensor output obtained from the two weft fibres increased with the increase of the applied lateral force. It also demonstrated excellent repeatability.
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      Solution of Euler–Bernoulli equation using a semi-analytical technique for steady-state deflection of microelectromechanical cantilever under electrostatic actuation
      • Author(s): S. Chakraborty  and  T.K. Bhattacharyya
      • Source: Micro & Nano Letters, Volume 5, Issue 4, p. 215 –218
      • DOI:  10.1049/mnl.2010.0043
      • Type: Article
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      • p. 215 –218 (4)
        A technique to solve Euler–Bernoulli equation for microcantilever beams under electrostatic actuation to find its static deflection is presented. Euler–Bernoulli equation contains fourth-order derivative of deflection with respect to position. Owing to the nonlinearities imposed by the electrostatic force, this cannot be solved analytically. The authors double integrate it using Leibniz integration rule to reduce it to a second-order integro–differential equation, which has then been numerically solved to find the deflection of the beam. This reduces the computational complexities of finite-difference analysis. The results have been compared with finite difference analysis and also verified with the experimental results.
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      On the thermally conductive behaviour of compacted graphite nanosheets
      • Author(s): Wen-Shyong Kuo ; Tse-Hao Ko ; Hsin-Fang Lu
      • Source: Micro & Nano Letters, Volume 5, Issue 4, p. 219 –221
      • DOI:  10.1049/mnl.2010.0053
      • Type: Article
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      • p. 219 –221 (3)
        Thermally conductive properties of compacts composed of graphite nanosheets (GNSs) are studied. The GNSs were made by the intercalation and exfoliation of natural graphite (NG) flakes. The GNSs were then compressed to make graphite compacts. Thermal diffusivities along the in-plane and transverse directions are measured using a laser flash method. The anisotropic ratio of the thermal conductivities ranges between 20 and 25. The properties of graphite compacts based on NG flakes are also studied. The results reveal that the GNS-based compact can be consolidated at a lower density, whereas the NG-based counterpart is denser and has a higher thermal conductivity. To protect the graphite compact, a method for coating a copper layer on the graphite compact was developed. The results also indicate the copper coating enhances heat transfer into the graphite compact.
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      Preparation and size control of cerium(IV) oxide ultrafine nanoparticles
      • Author(s): V. Bartůněk  and  O. Smrčková
      • Source: Micro & Nano Letters, Volume 5, Issue 4, p. 222 –224
      • DOI:  10.1049/mnl.2010.0059
      • Type: Article
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      • p. 222 –224 (3)
        CeO2 ultrafine nanoparticles (made by reaction of cerium(IV) sulphate with ammonia solution) have been treated in suspension in boiling water, N,N-dimethylformamide and dimethylsulfoxide (DMSO) for various times. Prepared nanoparticles were analysed by X-ray diffraction (XRD), X-ray fluorescence, infrared spectroscopy and high-resolution transmission electron microscopy (HRTEM). Sizes of nanoparticles were calculated by using Scherrer formula. Validation of nanoparticles sizes, shapes and ordering was determined from HRTEM images. It has been discovered that sizes of nanoparticles increase with increasing boiling point of the solvent and with increasing time. Maximal sizes of nanoparticles were 8.9 nm and were obtained by treatment in boiling DMSO. Obtained nanoparticles were high quality, separable and had cubical-like (smaller ones) and spherical-like (bigger ones) shapes. The main advantage of this method is simply enabling its use in almost all chemical laboratories and high quality characterisation of nanoparticles sizes by HRTEM and XRD.
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      Numerical studies on deformation and adhesion behaviour of substrate during nanoindentation
      • Author(s): Xuesong Han ; Shuxin Wang ; Lianhong Zhang ; Bin Lin ; Siyuan Yu
      • Source: Micro & Nano Letters, Volume 5, Issue 4, p. 225 –229
      • DOI:  10.1049/mnl.2010.0052
      • Type: Article
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      • p. 225 –229 (5)
        The behaviour of micro/nanosurface adhesive contacts and adhesive characteristics are important for micro/nanomechanical design and a material's mechanical property. The objective of this Letter is to study a material's deformation and adhesion behaviour during the nanoindentation process using the numerical analysis method. The results show that nanoindentation has a great influence upon the whole surface structure of a material and thus influences the material's microhardness. Single crystal copper under low indentation speed can induce more dislocation and is inclined to generate elastic-plastic deformation, whereas rigid-plastic deformation is induced at high indentation speed. These phenomena support that a material's mechanical property may not be its inherent property as the mechanical property can be changed under different dynamic external load conditions. The speed dependence of adhesion behaviour supports that the thermodynamic diffusion may be one of the inherent key factors that influence adhesion behaviour in the case of the nanoindentation process. Both the dislocation and deformation of the material greatly decreased with increasing indentation speed, which indicates that a material's mechanical property may not be its inherent property but a relative length scale dependent property.
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      Template-free hydrothermal synthesis and characterisation of single crystalline Ce(OH)CO3 and CeO2 with spindle-like structures
      • Author(s): Tao Fan ; Lixin Zhang ; Hongfang Jiu ; Yixn Sun ; Guode Liu ; Youyi Sun ; Qinglin Su
      • Source: Micro & Nano Letters, Volume 5, Issue 4, p. 230 –233
      • DOI:  10.1049/mnl.2010.0063
      • Type: Article
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      • p. 230 –233 (4)
        Single crystalline Ce(OH)CO3 and CeO2 with spindle-like structures were synthesised by a facile hydrothermal synthesis method. Then the effect of reaction time and concentration of cerium precursor on the formation and morphologies of Ce(OH)CO3 and CeO2 were further investigated. The products were characterised by X-ray powder diffraction, transmission electron microscopy and scanning electron microscopy. The results show that the single crystalline Ce(OH)CO3 with spindle-like structures could be obtained at 120°C for 8 h. The present method shows an easy process without high reaction temperature, long reaction time, surfactant and template to attain final Ce(OH)CO3 products. Furthermore, single crystalline CeO2 with spindle-like structures had been fabricated by a oxidation process at 600°C for 2 h using Ce(OH)CO3, with spindle-like structures as the precursor. Meanwhile, the single crystalline spindle-like CeO2 shows a high catalytic activity on CO conversion.
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      Simple approach to fabricate AgBr nanoparticles/polyvinylpyrrolidone microspheres
      • Author(s): Jie Bai  and  Wen-bin Li
      • Source: Micro & Nano Letters, Volume 5, Issue 4, p. 234 –236
      • DOI:  10.1049/mnl.2010.0062
      • Type: Article
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      • p. 234 –236 (3)
        A general synthetic method for preparing AgBr nanoparticles/polyvinylpyrrolidone composite microspheres has been developed. The authors have successfully prepared composite microspheres containing AgBr nanoparticles by employing the sol–gel technique and electrospinning technique. The composite micro- and nanospheres have much enhanced properties than the polymer microspheres. The method is simple and effective. The structures and components of composites that the authors obtained are established by field-emission scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The composite microspheres have extensive foreground as catalyst materials, photochromic materials and antibacterial materials.
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      Swelling properties of nano-hydroxyapatite reinforced poly(vinyl alcohol) gel biocomposites
      • Author(s): Yusong Pan
      • Source: Micro & Nano Letters, Volume 5, Issue 4, p. 237 –240
      • DOI:  10.1049/mnl.2010.0061
      • Type: Article
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      • p. 237 –240 (4)
        Nano-hydroxyapatite reinforced poly(vinyl alcohol) (nano-HA/PVA) gel composites is proposed as a promising biomaterial to replace diseased or damaged articular cartilage. Nano-HA/PVA gel composites were prepared by in situ synthesis of nano-HA particles in PVA solution and accompanied by freeze/thaw method. The influences of freeze/thaw cycle times, nano-HA content, PVA concentration and swelling media on the swelling characteristics of the gel composites were investigated. The results showed that the swelling ratio of the gel composites increased, but its swelling rate decreased with the rise of swelling time. Both the swelling ratio and equilibrium swelling ratio of the gel composites in the different swelling media presented an increasing trend with the rise of freeze/thaw cycle times. Contrarily, the equilibrium swelling ratio of the gel composites decreased with the rise of nano-HA and PVA concentration. Swelling media have significant influence on the swelling behaviour of the gel composites. The equilibrium swelling ratio of the gel composites in distilled water was the largest and it reached the lowest in bovine serum. Simultaneously, the equilibrium swelling ratio in bovine serum was far lower than that in inorganic swelling media, such as distilled water and physiological saline.
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      Synthesis and characterisations of poly(aniline-co-o/m-toluidine)/Sb2O3 nanocomposites
      • Author(s): J. Juliet Latha Jeyakumari ; A. Yelilarasi ; B. Sundaresan ; V. Dhanalakshmi ; R. Anbarasan
      • Source: Micro & Nano Letters, Volume 5, Issue 4, p. 241 –246
      • DOI:  10.1049/mnl.2010.0065
      • Type: Article
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      • p. 241 –246 (6)
        This study is focused on the preparation and characterisation of conducting poly(aniline-co-o/m-toluidine)/Sb2O3 nanocomposites. These nanocomposites were synthesised by the oxidative chemical polymerisation with peroxydisulphate as an oxidant in aqueous hydrochloric acid (HCl) medium and Sb2O3 as a nanomaterial under different experimental conditions. The nanocomposites were characterised by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis, high-resolution transmission electron microscopy and conductivity measurements. FTIR-based kinetics was proposed based on the relative intensities of FTIR peaks.
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