Micro & Nano Letters
Volume 9, Issue 12, December 2014
Volumes & issues:
Volume 9, Issue 12
December 2014
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- Source: Micro & Nano Letters, Volume 9, Issue 12, page: 829 –829
- DOI: 10.1049/mnl.2014.0652
- Type: Article
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- Author(s): Akarapu Ashok and Prem Pal
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 830 –834
- DOI: 10.1049/mnl.2014.0360
- Type: Article
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p.
830
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In this reported work, silicon dioxide (SiO2) thin films have been developed at room temperature using anodic oxidation of silicon. The effect of various process parameters on oxide properties including thickness, surface morphology, roughness and so on are investigated to determine the optimal conditions for the growth of SiO2 for applications in microelectromechanical systems (MEMS). A spectroscopic ellipsometry was used to characterise the refractive index and thickness of the as-deposited films. Atomic force microscopy was employed to measure the surface roughness of the oxide films. To fabricate the overhanging micromechanical structures, the etch rate of the as-grown oxide film was studied in 25 wt% tetramethylammonium hydroxide and 10 wt% potassium hydroxide solutions at different temperatures. Finally, the as-grown oxide film is demonstrated for the fabrication of differently shaped MEMS components using an etchant showing minimum oxide etch rate.
- Author(s): Ho Jung ; Tae Hyun Kim ; Kyung Tae Kim ; Jae Hong Park ; Hee Yeoun Kim
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 835 –840
- DOI: 10.1049/mnl.2014.0378
- Type: Article
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The fabrication and evaluation of a wide-range vacuum gauge for monitoring the pressure level inside an infrared focal plane array and a wafer-level packaging (WLP) are reported. The proposed vacuum gauge has a microbolometer structure produced using the conventional surface micromachining process to achieve thermal isolation and high sensitivity. This structure has other advantages such as fast response time, a wider measurement range and easier integration to a Si substrate compared with other pressure sensors. The evaluation results show that the fabricated vacuum gauge has a linear dynamic range and a sensitivity of 10−3 to 105 K/W/torr for vacuum pressures ranging from 10−6 to 760 torr. Also, the response time to vacuum change is reduced from 0.11 s at 10−5 torr to 15 ms at 100 torr. Therefore, the microbolometer-based vacuum gauge has good potential for application in WLP, and it is possible to hermetically seal it with various read-out integrated circuit substrates.
- Author(s): Hao Cui and Si-Hyun Park
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 841 –844
- DOI: 10.1049/mnl.2014.0373
- Type: Article
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841
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Numerical simulations are performed to investigate the light-extraction efficiencies (LEEs) of gallium nitride-based light-emitting diodes (LEDs) on patterned sapphire substrates (PSSs), using the three-dimensional finite-difference time-domain method. PSSs with hexagonal arrays of cone-shaped patterns were used, and the pitch of the pattern array, pattern fill factor and pattern height were varied from nanoscale to microscale. The relative LEE for each PSS-LED was calculated, and the geometrical parameters were analysed for optimised light extraction enhancement of the PSS-LEDs.
- Author(s): Jaewoo Lee ; Changhan Je ; Yi-Gyeong Kim ; Sung Q Lee ; Woo-Seok Yang ; Sang-Gug Lee
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 845 –849
- DOI: 10.1049/mnl.2014.0381
- Type: Article
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A bottom-inlet-type micro-electro-mechanical system acoustic sensor based on two polyimide/a-Si sacrificial layers is presented. A diaphragm was adapted to be on the top side of the sacrificial layers, showing the bottom-inlet structure for the package, which has the sensitivity of more than 3 dB compared with that of the top-inlet type. Also, the fundamental CMOS process implemented with Al electrodes was applied to have simple releasing steps by O2 ashing and XeF2 isotropic etching because of their material etching selectivity. The sensor module had a sensitivity of −38.9 dBV/Pa at 1 kHz with a bias of 9.2 V in the sweep range from 100 Hz to 16 kHz. In addition, to evaluate the open-circuit sensitivity, structure-based equivalent circuit modelling was performed with lumped parameters. The modelled sensitivity was in good agreement with the measured sensitivity in the error rate of 4.3% under 8 kHz, demonstrating the validity of the modelling. The modelled open-circuit sensitivity was determined to be −37.2 dBV/Pa at 1 kHz using the proposed lumped model.
- Author(s): Norhafizah Burham ; Azrul Azlan Hamzah ; Burhanuddin Yeop Majlis
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 850 –853
- DOI: 10.1049/mnl.2014.0382
- Type: Article
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850
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A simple and reliable fabrication technique for producing nanoporous filters is presented. The nanoporous filter plays an important role in biomedical microelectromechanical systems applications, especially in filtering out waste and solute from inside human blood. Nanosized components in the biological fluid are filtered using silicon membranes that are controlled by nanosized pores. The technique explored was the electrochemical etching (ECE) process of silicon. This approach starts with thinning the bulk silicon until only several micrometres thick using the KOH process and then carry out ECE to produce pores. The yield of the process was a 3 µm thick nanoporous silicon membrane with pore sizes of less than 100 nm. This physical characteristic enables the membrane to filter all the waste and solute particles of less than 100 nm. Owing to this simple and reliable method, the development of nanoporous silicon membrane can be used in nanofiltration applications especially in an artificial kidney.
- Author(s): Umar Sidik ; Jung Hee Kim ; Hae-Kyoung Kim ; Hee Young Lee ; Jai-Yeoul Lee
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 854 –857
- DOI: 10.1049/mnl.2014.0385
- Type: Article
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854
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The effects of Cr-stoichiometry on the structural, electrical and optical properties of delafossite-type CuCrO2 thin films are reported. Thin films were grown by pulsed laser deposition on glass and c-sapphire single-crystal substrates, and the effects of increased temperature on the thin film properties were examined. The substrate temperature and oxygen partial pressure were found to be important processing parameters for fabricating delafossite thin films. The electrical properties of the thin films generally improved with increasing substrate temperature. The properties of the thin films depend on the crystallinity. The improvements in crystallinity and electrical conductivity were made by increasing the Cr-deficiency in the CuCr1 − x O2 system. By optimising processing parameters, the electrical conductivity of a CuCr1 − x O2 thin film was 8.30 S/cm (x = 0.00) and this increased with the introduction of Cr-deficiency to 21.03 S/cm (x = 0.03) with a mean optical transmittance of 60%. The bandgaps of the thin films ranged from approximately 3.00 to 3.22 eV.
- Author(s): Songhyun Jo ; Kyoungsoo Park ; Yong Wook Lee
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 858 –861
- DOI: 10.1049/mnl.2014.0386
- Type: Article
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Proposed is a Lyot-type flat-top fibre multiwavelength filter based on a polarisation-diversity loop structure, which has flat-top and lossy flat-top passbands and multiwavelength switching capability. The proposed filter is composed of a polarisation beam splitter, two half-wave plates (HWPs) and two polarisation-maintaining fibre (PMF) loops concatenated with a 60° offset between their principal axes. One of the two PMF loops is two times longer than the other. It is able to operate in a flat-top or a lossy flat-top band mode at the selected combination of the azimuthal orientation angles of two HWPs. In particular, through the adjustment of the orientation angles of the two HWPs, its multiwavelength channels can be interleaved in each mode, which cannot be realised in a previously reported Lyot-Sagnac comb filter based on a fibre coupler. In addition to the channel interleaving capability, it provides narrower passbands compared with previous fibre multiwavelength filters with the same order. To make a quantitative comparison between the passband bandwidths of the proposed filter and other filters, both −1 and −3 dB passband bandwidths of a conventional zeroth-order, a Solc-type first-order and the proposed multiwavelength filters were considered and compared with each other.
- Author(s): Yin Bai ; Jianhua Tong ; Jizhou Sun ; Yang Li ; Chao Bian ; Shanhong Xia
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 862 –865
- DOI: 10.1049/mnl.2014.0391
- Type: Article
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The fabrication and characterisation of an integrated microfluidic chip for phosphate detection are described. A micro three-electrode-system embedded in a microfluidic channel was used for the analysis of samples. Working electrodes and counter electrodes were arranged as an interdigitated array to increase the current response. Owing to the nonlinear diffusion effect of ultra-microelectrodes and the high generation-collection mode of interdigitated electrode arrays, the current density and sensitivity of phosphate detection were improved effectively compared with normal disk microelectrodes. The current density sensitivity for phosphate detection is −0.00537 μA/mm2·(μmol/l)−1, which is three times that of the disk microelectrode. The current density was averagely 6.5 times that of the disk microelectrode. The microfluidic chip was then used for total phosphorus (TP) detection. The TP detection results showed good consistency with nominal values of standard solutions.
- Author(s): Eun-Wook Jeong ; Dong-Yong Kim ; In-Kyun Choi ; Hong-Seok Park ; Kwun Nam Hui ; Young-Rae Cho
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 866 –868
- DOI: 10.1049/mnl.2014.0397
- Type: Article
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p.
866
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Evaluation of gas permeation properties through barrier layers is important for the development of flexible organic light-emitting devices (FOLEDs). In this reported work, an helium (He) leak detector was used in a novel permeation test for metallic barrier layers. Aluminium (Al) or chromium (Cr) film was deposited as a barrier layer onto a polyethylene terephthalate (PET) substrate using a magnetron sputtering system. For the samples of PET substrates with Al and Cr films at thicknesses of 200 nm, the He pressures were 3.1 × 10−6 and 1.3 × 10−5 Torr, respectively, as measured via He detector testing. The poor permeation blocking by the Cr film was because of microcracks. The He pressure for samples with 1 000 nm thick Al coating and for Al foil (30 μm) showed different values of 3.2 × 10−8 and 1.1 × 10−10 Torr, respectively, which indicated high sensitivity in a low permeation range. The high sensitivity in permeation properties measured by He detector testing reflected the qualities of He that include one of the lightest weights known to science and a very small size. This He detector test will be useful in the development of long-life FOLEDs, as it will aid the measuring of the gas permeation properties of barrier layers that are highly effective in blocking water vapour.
- Author(s): Dao Liang ; Zi-Fang Lin ; Cheng-Chun Huang ; Wen-Pin Shih
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 869 –873
- DOI: 10.1049/mnl.2014.0401
- Type: Article
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869
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A tunable lens driven by a dielectric elastomer actuator is developed. A solution of NaCl was used as the deformable lens and one of the electrodes for applying a bias voltage across the actuator. The dielectric elastomer actuator was made of a curved polydimethylsiloxane (PDMS) thin film sandwiched between a gold electrode and the NaCl solution. When a bias voltage was applied, the electrostatic force induced a radial compression, causing a lateral deflection of the PDMS. The radius of the curvature of the NaCl lens was consequently changed. The variation of the focal length under different bias voltages was characterised separately using two different approaches, and consistent results were obtained. The lens diameter was 4 mm. The focus lens can be tuned from 16.1 to 13.1 mm when the bias voltage is increased from 0 to 900 V.
- Author(s): Yeong-Tai Seo ; Kuk Jin Jang ; Min-Ho Lee ; Woo-Kyeong Seong ; Kook-Nyung Lee ; Yong-Kweon Kim
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 874 –876
- DOI: 10.1049/mnl.2014.0405
- Type: Article
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874
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The reference electrode in an electrolyte solution affects the surface potential of the nanoFET (field-effect transistor) channel which can result in a false signal to be measured in the FET channel during bio- and chemical sensing experiments. In this reported work, it was demonstrated that different sensing results that were obtained were affected by the choice of the reference electrode through a pH and ion concentration sensing experiment. Three types of reference electrodes were compared: the SCE (saturated calomel reference electrode), the Ag/AgCl tube and the integrated Ag/AgCl electrode. The pH sensitivity equivalent to the surface potential was evaluated: 32.3, 34.6 and 16.3 mV/pH in the case of the SCE, the refillable tube type Ag/AgCl and the integrated Ag/AgCl, respectively.
- Author(s): Mantana Suwan and Sitthisuntorn Supothina
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 877 –880
- DOI: 10.1049/mnl.2014.0418
- Type: Article
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p.
877
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One-dimensional nanostructured oxides are typically synthesised by the hydrothermal method in a small pressurised reactor under static conditions that usually results in a low synthesis yield. In this reported work, K-doped tungsten oxide (K2W4O13) nanowires were synthesised under stirred hydrothermal treatment of hydrous K2W4O13 precursor in the presence of K2SO4 employed as the shape-directing agent to promote the formation of nanowires. Under static conditions (0 rpm), only 24.6% yield was obtained. The yield was significantly increased with the increase of stirring speed. The yield of 90.3%, almost four times the static condition, was obtained when synthesised under continuous stirring at 500 rpm. The samples synthesised from both the conditions have the same crystal structure, which is K2W4O13. However, the difference in particle morphology was observed; the average diameter of 11.4 ± 0.3 nm and the length up to several hundred micrometres were obtained from the stirred condition, while more irregularities of the nanowires (average diameter of 7.1 ± 1.1 nm and very diverse length) were obtained under static conditions. The more uniformity observed under stirred hydrothermal conditions is attributed to the more uniform crystallisation process attained under the stirring condition. A high near-infrared (NIR) reflectance of 91.3% suggests its NIR shielding ability.
- Author(s): Hyeok Kim ; Jae-Hyun Kim ; Taehee Kim ; Hee-Suk Jung ; Bonkee Koo ; Dong-Seok Song ; SeongMin Kim ; Min Jae Ko ; Doh-Kwon Lee ; Do-Kyung Kim ; Shin-Won Kang ; Jin-Hyuk Bae
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 881 –883
- DOI: 10.1049/mnl.2014.0420
- Type: Article
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p.
881
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Thin-film solar cells based on hydrogenated amorphous silicon (a-Si:H) and conjugated polymers have been studied extensively. However, organic–inorganic hybrid tandem solar cells incorporating the two materials as subcells are yet to be extensively studied. Here, a computational study on the optimal design of organic–inorganic hybrid tandem solar cells to achieve the maximum possible efficiency is presented. The optical simulations predict the optimal design of an organic–inorganic hybrid tandem solar cell, desirable for a wide range of spectral response and high efficiency. The optimum combination of thicknesses of a-Si:H and organic photovoltaic (OPV) subcells to achieve the highest possible efficiency in terms of short circuit current (J sc) is determined. Thicknesses of 400 and 140 nm for a-Si:H and OPV subcells, respectively, are suggested for the optimised tandem solar cell to achieve current matching and a maximum power conversion efficiency of 11.57%.
- Author(s): Po-Fat Chong ; Xiaomei Shi ; Ching-Hsiang Cheng
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 884 –886
- DOI: 10.1049/mnl.2014.0421
- Type: Article
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884
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A capacitive micromachined ultrasonic transducer (CMUT) with a graphene membrane is reported. The CMUT membranes were commonly made from very thin silicon nitride or metal material. To date, no graphene CMUT has been successfully used. In this reported work, a photomask were used for the cavity pattern to make a 1μm layer EPON SU-8 photoresist on the silicon substrate. Then a single-layer graphene were tranferred directly to be attached to the EPON SU-8 cavity layer to form the CMUT with a graphene membrane. The resonance frequency was measured to be 95 MHz in air.
- Author(s): Hyeok Kim ; Dong-Seok Song ; SeongMin Kim ; Nicolas Battaglini ; Philippe Lang ; Gilles Horowitz ; Do-Kyung Kim ; In Man Kang ; Jin-Hyuk Bae
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 887 –890
- DOI: 10.1049/mnl.2014.0422
- Type: Article
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The gap-type diode is a basic component of organic field-effect transistors. In the critical voltage range above 10 V, the gap-type diode works in the same way as a sandwich-type diode adapted for organic light-emitting diodes and organic photovoltaic cells. However, the gap-type diode is rarely studied, and compact modelling is not often found in previous reports that deal with this type of an organic diode. Enhanced bulk transport is exhibited using the one-pot treatment of self-assembled monolayers (SAMs) for an SiO2 surface and an Au contact metal in the gap-type organic diode. Charge-injection improvement via the SAM treatment on Au induces higher bulk transport. This phenomenon is analysed mainly through compact modelling.
- Author(s): Hiroaki Honma ; Kazuhiro Takahashi ; Masashi Fukuhara ; Makoto Ishida ; Kazuaki Sawada
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 891 –895
- DOI: 10.1049/mnl.2014.0423
- Type: Article
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Presented is a fabrication process for the transmission of red–green–blue (RGB) colour filters based on surface plasmons (SPs) using aluminium (Al) nanowire arrays patterned through electron-beam lithography and the lift-off technique. An array of Al nanowires was deployed over a through hole formed by sacrificial silicon etching. The period of the Al nanowire arrays is the dominant structural parameter in determining the transmission peak position of SPs for a given material configuration. The Al nanowire arrays are designed with the same Al wire width under the assumption of operation using a microelectromechanical systems (MEMS) comb-drive actuator for the realisation of an RGB tunable colour filter. The peak wavelength of the transmitted light was red-shifted by increasing the period of the Al nanowire arrays from 450 to 600 nm, and RGB colours were demonstrated. A black pixel was produced using the 400 nm pitch Al nanowire array. The maximum measured transmittance of the peak wavelength was 56%. In addition, the number of nanowires sufficient for low-power operation by a MEMS comb-drive actuator was investigated and sufficient transmission light intensity was obtained from the pixel size of 10 µm2, including 20 Al nanowires.
- Author(s): Se Bin Choi ; Jung Shin Lee ; Seung Joo Baik ; Joon Sang Lee
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 896 –900
- DOI: 10.1049/mnl.2014.0426
- Type: Article
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An emulsion system was simulated under simple shear rates to analyse its rheological characteristics using the lattice Boltzmann method. The relative viscosity of an emulsion under a simple shear flow along with changes in temperature, shear rate, surfactant concentration and droplet size was calculated. The relative viscosity of emulsions decreased with increase in temperature. The shear thinning phenomena explaining the inverse proportion between shear rate and viscosity were observed. An increase in the surfactant concentration caused an increase in the relative viscosity for a decane-in-water emulsion, because the increased deformation caused by the decreased interfacial tension significantly influenced the wall shear stress. An increase in droplet size caused a decrease in the relative viscosity and smaller shear thinning behaviour because of decreased aggregational and repulsive forces within the emulsion system.
- Author(s): Yu-Yen Chen ; Bo-An Chen ; Daniel Tsai ; Cheng-Chun Huang ; Jiashing Yu ; Wen-Pin Shih ; Chii-Wann Lin
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 901 –905
- DOI: 10.1049/mnl.2014.0447
- Type: Article
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A bipolar electrode probe used for implantable nerve stimulation treatments in minimally invasive surgeries is presented. The probe is composed of a flexible printed circuit substrate and a patterned SU-8 film. This probe features a three-dimensional (3D) tweezer-like mechanism opened by residual stress from the SU-8 film, designed to fix the probe in the tissue surrounding a target nerve. Stripes on the SU-8 film direct the net residual stress in a single direction to form a curve. The holding strengths of the probes with different deformations are defined and measured by a tensile test. Results show that the fixing ability of a 3D probe is better than a plane probe. The probes with curvature heights between 13 and 14 mm have a maximum average breaking force of 0.258 N, which is 16.3 and 13.1% higher than the probes with curvature heights between 9 and 10 mm and between 10 and 11 mm, respectively. In addition, a film of gelatin fibrous membrane, produced by electrospinning, covers the fixed ends of the probe's anchors and acts as cell scaffolds to induce cell growth, which help to ensure long-term fixation in the body. 3T3 fibroblast cells are grown to verify the scaffold effect of the fibrous membrane.
Editorial: APCOT 2014 special issue
Investigation of anodic silicon dioxide thin films for microelectromechanical systems applications
Fabrication of thermal-based vacuum gauge
Numerical simulations of light-extraction efficiencies of light-emitting diodes on micro and nanopatterned sapphire substrates
Bottom-inlet-type micro-electro-mechanical system acoustic sensors based on two polyimide/amorphous-Si sacrificial layers
Effect of current density on silicon surface in electrochemical etching
Structures and characteristics of delafossite CuCr1−x O2 thin films prepared by pulsed laser deposition
Lyot-type flat-top fibre multiwavelength filter based on polarisation-diversity loop structure
Microfluidic chip with interdigitated ultra-microelectrode array for total phosphorus detection
Evaluation of gas permeation through barrier layers for organic electronic devices by helium detector method
Tunable lens driven by dielectric elastomer actuator with ionic electrodes
Effect of reference electrode in the nanoFET (field-effect transistor)-based biosensor experiment
Increasing synthesis yield of K-doped tungsten oxide nanowire using stirred hydrothermal reactor and its near-infrared reflectance property
Optimal design of organic–inorganic hybrid tandem solar cell based on a-Si:H and organic photovoltaics for high efficiency
Capacitive micromachined ultrasonic transducer (CMUT) array with single-layer graphene membrane
Highly enhanced charge injection and bulk transport in organic gap-type diodes via one-pot treatment process: experiment and simulation
Free-standing aluminium nanowire arrays for high-transmission plasmonic colour filters
Numerical simulations for the rheological characteristics of emulsions under several conditions including temperature, shear rate, surfactant concentration and droplet size
Implantable probe with split anchors via residual stress and induced cell growth with gelatin nanofibres
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- Author(s): Golnoush Zamiri ; A. Zakaria ; M.Z.B. Hussein ; R. Zamiri ; A. Rebelo ; H. Abbastabar Ahangar
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 906 –908
- DOI: 10.1049/mnl.2014.0120
- Type: Article
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Manganese (Mn)-doped titanium dioxide (TiO2) nanostructures were synthesised by hydrothermal reaction of TiO2 and Mn acetate with ethylenediamine and thiourea. The prepared samples were characterised by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. Characterisation of samples confirmed the formation of pure and crystalline nanostructures. Photoluminescence spectroscopy was carried out to study the optical properties of the pure and Mn-doped TiO2 nanostructures. A vibrating sample magnetometer was used to study the magnetic properties of the prepared Mn-doped TiO2 nanostructures.
- Author(s): Tiantian Tao ; Xiaobo Zhang ; Lin Liu ; Juanjuan Ma ; Dongen Zhang ; Binbin Pan ; Zhiwei Tong
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 909 –912
- DOI: 10.1049/mnl.2014.0496
- Type: Article
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Layered Bi2SrTa2O9 was achieved by solid-phase synthesis and then cationic metalloporphyrin 5,10,15,20-tetrakis(N-methylpyridinium-4-yl) porphyrinato manganese (MnTMPyP), was intercalated into layered material Bi2SrTa2O9 by a guest-exchange method using n-PrNH3 +-SrTa2O7 as a precursor. The new intercalation multicomposite MnTMPyP-SrTa2O7 was characterised using X-ray diffraction, infrared and scanning electron micrograph images. Moreover, the MnTMPyP-SrTa2O7 nanocomposite exhibited fine electrocatalytic activity towards oxygen reduction.
- Author(s): Chun-Mei Li ; Bai-Ge Li ; Jian-Ping Yu
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 913 –916
- DOI: 10.1049/mnl.2014.0393
- Type: Article
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An effective method for Agrobacterium tumefaciens inhibition using silica nanoparticles (NPs) as the carrier and melittin as the antibacterial drug is developed. The diameters of the inhibition zones of A. tumefaciens treated with different concentrations of melittin-conjugated silica NPs, pure silica NPs, gentamicin and free melittin are determined. The results indicate that the pure silica NPs have no impact on A. tumefaciens. The melittin-conjugated silica NPs have strong antibacterial activity against A. tumefaciens. In addition, the antibacterial activity of the melittin-conjugated silica NPs is dose dependent. The diameter of the inhibition zone caused by the melittin-conjugated silica NPs is almost the same as the positive control. Compared with the free drug molecules, silica NPs as an ideal carrier can gather a large number of drug molecules on their surface so as to greatly enhance the antibacterial activity.
- Author(s): Anousheh Kazemeini-Asl ; Majdid M. Larijani ; Vahid Fathollahi
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 917 –921
- DOI: 10.1049/mnl.2014.0287
- Type: Article
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Cu thin films sputter-coated on single crystals of silicon were implanted with 30 keV nitrogen ions under various doses from 1.9 × 1017 to 5.7 × 1017 ions/cm2. The prepared samples were subsequently annealed in nitrogen atmosphere. The grazing incidence X-ray diffraction analysis revealed that in addition to the crystalline copper nitride phase, copper azides were developed by nitrogen ion implantation. With an increase of the implantation dose to 2.3 × 1018 ions/cm2, much of the Cu film was transformed to the crystalline Cu3N phase. Furthermore, the effect of nitrogen ion implantation on Cu thin films under various doses was investigated. The structural properties, morphology and sheet resistance of samples were investigated by grazing incidence X-ray diffraction, atomic force microscopy, field emission scanning electron microscopy and four-point probe techniques, respectively. In addition, the dependence of resistivity of the implanted samples on the implantation dose as well as structural properties is discussed.
- Author(s): Ping-Cheng Hsu ; Ting-An Lin ; I-Shou Tsai
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 922 –926
- DOI: 10.1049/mnl.2014.0415
- Type: Article
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A simple method was used to produce a high concentration of single-layer graphene sheets in a single organic solvent system, without using any surfactants. In this experiment, the concentration of single-layer graphene sheets dispersed in solution increased as the sonication time increased, but damage occurred after performing sonication for 120 min. The concentration of single-layer graphene sheets was 0.915 mg/ml after sonication for 60 min. According to a transmission electron microscope image, the length of the single-layer graphene sheets was ∼2–3 μm, and the width was 0.5–1 μm. The perfect single-layer graphene sheets and the defective single-layer graphene sheets were distinguished using selected-area electron diffraction. X-ray diffraction determined that the two-theta angle of the numerous single-layer graphene sheets on a (002) plane was 25.57°, but the ‘one layer’ graphene sheets produced no peak along the (002) plane. According to the Raman spectra, the ratio of ID /IG was 0.3, which indicated that the graphene sheets contained few defects.
- Author(s): Cungui Zhong ; Qing Cao ; Xiaoling Xie ; Shilei Gong ; Chunmin Zhou ; Ying Wang
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 927 –931
- DOI: 10.1049/mnl.2014.0493
- Type: Article
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Coal tar pitches (CTPs) are used as a supercapacitor precursor because they are of low cost and produce high carbon yields. In this reported work, a simple and feasible method for the fabrication of pitch-based carbon electrode materials with high capacitance was established using nanosized oxides as a template and the potassium hydroxide (KOH) activation method. The preparation conditions were optimised using an orthogonal array design. The electrochemical performance of the electrode materials was examined by constructing a single electrode capacitor in 6 mol l−1 KOH electrolyte; specific surface area was determined by N2 adsorption–desorption analysis and textural characterisation was conducted by transmission electron microscopy. Results showed that the synthetic carbon material possessed the highest iodine adsorption value of 2238 mg g−1 under optimum conditions (Al2O3 used as the template, an activation temperature of 700°C and a CTP/template mass ratio of 1:1), a high capacitance of 258 F g−1 at a current density of 0.5 A g−1 and good cycle stability.
- Author(s): Guoe Cheng ; Yu Zhang ; Hanzhong Ke ; Tingting Hao ; Youzhi Wang
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 932 –934
- DOI: 10.1049/mnl.2014.0238
- Type: Article
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The composite of peanut-like TiO2 nanoparticles and reduced graphene oxide (rGO) was successfully synthesised via a facile one-step hydrothermal method in mixed solvents of diethanol amine and distilled water. The crystallite, morphology and structure features of the composite were characterised by X-ray diffraction, Brunauer-Emmett-Teller specific area analysis, transmission electron microscopy and high-resolution transmission electron microscopy. The results indicated that the as-synthesised TiO2 was of peanut-like shape with about 21–32 nm in length and was anchored on the surface of the rGO sheet. In addition, the TiO2/rGO composite presented excellent photocatalytic activity of rhodamine B under visible light irradiation compared with commercial Degussa P25. A proposed mechanism for the photocatalytic process is also discussed.
- Author(s): Raid A. Ismail ; Hani H. Ahmed ; Abdul-Majeed E. Al-Samarai ; Sabre J. Mohmed
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 935 –939
- DOI: 10.1049/mnl.2014.0149
- Type: Article
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Nanostructured cadmium oxide (CdO) thin films have been deposited on glass substrates using the chemical bath deposition (CBD) technique at different pH values. To obtain good film stoichiometry, the heating of films in static air at a temperature of 573 K for 3 h was carried out. X-ray diffraction and atomic force microscope investigations confirmed the cubic structure of the deposited CdO films. Films prepared with pH = 12.4 are almost homogeneous and consisted of nanowires with diameters of less than 100 nm. The optical properties showed that the CdO films prepared have an average optical transmittance of ∼86% and the optical bandgap varied from 2.38 to 2.57 eV for pH solutions of 10.2 and 12.4, respectively. The effect of pH on the film thickness, grain size and root-mean square of roughness was investigated and analysed.
- Author(s): Shi-Zhao Kang ; Dieer Yin ; Xiangqing Li ; Qiang Zhang ; Jin Mu
- Source: Micro & Nano Letters, Volume 9, Issue 12, p. 940 –943
- DOI: 10.1049/mnl.2014.0305
- Type: Article
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p.
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–943
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Water-dispersible TiO2 nanoparticles with narrow size distribution and good crystallinity were synthesised in a solvothermal process using lactic acid as the capping agent. X-ray diffraction, transmission electron microscopy and nitrogen adsorption–desorption isotherm were used to characterise the products. Meanwhile, the dispersion behaviour of the as-prepared TiO2 nanoparticles was investigated. The as-prepared powder can be easily redispersed in water to form a stable solution-like suspension with a concentration of 60 mg·ml−1. Moreover, the dispersion mechanism was also preliminarily discussed, suggesting that the excellent dispersibility of the as-prepared TiO2 nanoparticles is probably because of electrostatic repulsion from lactic acid molecules covalently linked to TiO2 nanoparticles.
- Source: Micro & Nano Letters, Volume 9, Issue 12, page: 944 –944
- DOI: 10.1049/mnl.2014.0599
- Type: Article
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Effect of manganese doping on optical and magnetic properties of titanium dioxide nanostructures prepared by hydrothermal technique in the presence of thiourea
Preparation and electrochemical behaviour study of layered Bi2SrTa2O9 with a cationic manganese porphyrin
Melittin based on silica nanoparticles for Agrobacterium tumefaciens inhibition
Influence of ion dose on nanostructure morphology and electrical properties of nitrogen implanted-annealed copper
Numerous single-layer graphene sheets prepared from natural graphite by non-chemical liquid-phase exfoliation
Preparation of pitch-based carbon materials using a template and an orthogonal array design for super capacitors
Hydrothermal synthesis of TiO2/reduced graphene oxide nanocomposite with enhanced photocatalytic activity
Effect of pH on the structural and optical properties of nanostructured CdO films grown by chemical bath deposition technique
Preparation of water-dispersible TiO2 nanoparticles
Erratum: ‘Use of ZnO nanorods grown atomic force microscope tip in the architecture of a piezoelectric nanogenerator’
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