International Journal of Nanotechnology (13 papers in press)
Fabrication of super hydrophobic duo-structures
by X.Y. Zhang
Synthesis of zinc oxide/graphene oxide nanocomposite material for antibacterial application
by Le Thanh Trinh, Le Anh Bao Quynh, Nguyen Huu Hieu
Abstract: In this study, graphene oxide (GO) was prepared by a modified Hummers method and ZnO/GO was synthesised by coprecipitation. The structural and morphological properties of ZnO/GO nanocomposite were characterised by using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), BrunauerEmmettTeller (BET) method, and Raman spectroscopy. The characterisation results show that ZnO nanoparticles with a mean size of 1426 nm were synthesised and randomly decorated on the surfaces and edges of GO sheets. In addition, the antimicrobial activities of GO and ZnO/GO were tested against bacteria Escherichia coli (E. coli). The test results reveal that the antibacterial activity at low loading of the ZnO/GO nanocomposite was higher than that of GO on E. coli.
Keywords: zinc oxide; graphene oxide; nanocomposite; antibacterial; E. coli.
Fluidic platform with embedded differential capacitively coupled contactless conductivity detector for micro-object sensing
by Loc Quang Do, Tung Thanh Bui, Ha Thuy Thi Tran, Katsuya Kikuchi, Masahiro Aoyagi, Trinh Chu Duc
Abstract: In this paper, we present a microfluidic platform with differential capacitively coupled contactless conductivity detection (DC4D) technique for microparticle detection. The microfluidic platform is formed by bonding PDMS channel to glass substrate. The proposed microfluidic sensor embedded in the microchannel consists of three adjacent electrodes. These electrodes are arranged to form differential coplanar capacitor structures to provide high sensitivity. The differential capacitance is changed when a microsized object crosses the sensing area in the microfluidic channel. This microfluidic
system with the novel sensing design based on DC4D technique provides a platform for detection the presence of an object as well as its electrical property.
Keywords: microfluidic platform; cell detection; capacitive sensing.
One-step hydrothermal synthesis of titanium dioxide-decorated on reduced graphene oxide for dye-sensitised solar cells application
by Foo Wah Low, Chin Wei Lai, Sharifah Bee Abd Hamid
Abstract: Dye-sensitised solar cells (DSSCs) are one of the promising prospects for efficient renewable resources. To bring DSSCs to the point of commercial readiness and viability in terms of performance and cost, substantial research on the development of high efficient DSSCs system is necessary. Our recent studies have indicated that a maximum conductivity of 29.1 μS/cm and conversion efficiency of 4.76% under 1.5 AM condition was successfully achieved from 0.2 wt% TiO2 loaded on reduced graphene oxide (rGO) forming a nanocomposite film, which is approximately twice or triple times higher than that of pure rGO nanosheets and anatase TiO2 film. The findings were mainly attributed to the fact that rGO nanosheets could further increase the photo-induced electrons transportation rate and minimise the recombination losses within the TiO2 lattice in this binary hybrid photoelectrode.
Keywords: reduced graphene oxide; rGO; titanium dioxide (TiO2); rGO-TiO2 nanocomposite; dye-sensitised solar cells; DSSCs.
3D laser lithographic fabrication of hollow microneedle mimicking mosquito and its characterization
by Masato Suzuki, Tomokazu Takahashi, Seiji Aoyagi
Abstract: Microneedles mimicking mosquito were fabricated by employing a three-dimensional laser lithography. An ultra-precision three-dimensional laser lithography system Nanoscribe GT is employed. Based on two-photon absorption phenomenon, an extremely small space of less than 200 nm in the photocurable polymer material is cross-linked, where a laser beam is focused on. The total cross-linked space finally emerges after development process. First a bundled needle comprising three parts was fabricated, which imitates central hollow labrum of sucking blood, and two side solid maxillae having jagged edges. Second, a practical needle of comprising two parts was proposed and fabricated. The functions of three-piece mosquitos proboscis (one labrum and two maxillae) are integrated to two parts. Each half-needle has semi-circular channel and jagged edges. By combining the two-halves, one hollow microneedle is realized. Alternative motion like mosquito maxillae is possible. Fluid is introduced into the channel through small holes in the wall, and is drawn up by capillary force. Reduction in number of microneedles simplifies both fabrication process and drive system for puncturing. It was experimentally confirmed that the needle successfully penetrates PDMS skin. The effectiveness of alternative motion of two parts with 90 deg phase to each other was also investigated.
Keywords: Microfabrication; three-dimensional fabrication; rapid prototyping; microneedle; low invasive treatment; stiffness test; insertion test; blood sampling test.
Plasma polymerised poly(methyl methacrylate) and cyclopropylamine films on polylactic acid nanofibres by electrospinning
by Chuan Li, J.H. Hsieh, H.Y. Wang
Abstract: Polylactic acid (PLA) is a thermoplastic, biodegradable polyester. It can be derived from natural resources such as corn starch, cassava starch or sugarcane. PLA can also be classified as a bioplastic. To produce PLA in the industrial scale, the most common ways are to polymerise two monomers: lactic acid and cyclic di-ester (lactide) with various metal catalysts in solution or suspension. PLA can be manufactured by injection moulding, extrusion, casting, and in most recent techniques such as electrospinning and three dimensional printing. The variety of different processes makes PLA available to a wide range of applications. PLA is soluble in tetrahydrofuran, dioxane, chlorinated solvents and heated benzene. The selected solubility provides limited choices for dissolving PLA into solution for electrospinning process to fabricate nanofibres. One advantage of using electrospinning is to create materials with very high porosities with complex geometry, maintaining its biodegradability, enhancing bio-adhesion and extracellular chemical signal transduction for cell culture. In this study, we fabricate PLA nanofibres by electrospinning and then coat these fibres with poly(methyl methacrylate) (PMMA) and cyclopropylamine (CPA) using plasma polymerisation. PMMA is a transparent, nontoxic thermoplastic polymer with highly stable physical and chemical properties whilst CPA is a volatile and chemically active molecule with a primary amine. In addition to fabrication, we also investigated the structure and morphology of the PLA fibres with/without PMMA/CPA coatings by SEM, EDS, FTIR and AFM. These fibres are tested for their biocompatibility via cell culture of 3T3 fibroblasts (mouse embryonic). The 3T3 cell line is the standard fibroblast commonly used for DNA transfection studies. The culture is assessed by MTT assays and cell proliferation to evaluated cellular activities on the PLA nanofibres.
Keywords: polylactic acid; PLA; poly(methyl methacrylate); cyclopropylamine; electrospinning; plasma polymerisation.
Effects of growth temperature on Mg-doped ZnO films fabricated by pulsed-laser deposition
by Hau-Wei Fang, Jenh-Yih Juang, Shiu-Jen Liu
Abstract: Magnesium-doped zinc oxide (MZO) films were fabricated by pulsed-laser deposition (PLD) at various substrate temperatures (Ts). The substitution of Mg for Zn sites (MgZn) in the films was confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and room-temperature photoluminescence (RTPL) measurements. Characteristic deep-level emissions (DLE) observed in the RTPL spectra further indicate the presence of Zn vacancies (VZn) in the MZO films. Moreover, it was found that the intensity of the blue emission corresponding to VZn increases with increasing Ts, indicating the important role played by Ts on the incorporation of Mg into ZnO matrix. Hall effect measurements reveal the p-type conduction of the MZO films grown at 400°C. The p-type characteristic is attributed to the formation of nMgZn - VZn complex which could act as acceptor for MZO films.
Keywords: p-type; ZnO films; photoluminescence; X-ray photoelectron spectroscopy; XPS; pulsed-laser deposition; PLD; Mg doping.
Plasmonic optical enhancement of solar module
by Hsin-Hsin Hsieh, Chia-Yu Lin, Chi-Shiung Hsi
Abstract: An advanced solar module of light enhancement is presented in this paper. The light enhancement was dominated by a layer of sputtered-deposited Ag nanoparticles (NPs) on the encapsulant material (ethylene vinyl acetate, EVA). It was found that surface plasmonic resonance effects of Ag NPs increase the transmittance at the wavelength of (500~800) nm by around 2% as detected by IPCE profile. The photovoltaic performance of solar modules showed a current enhancement with Ag-EVA sample, and a high power output around 0.250 W was observed compared to the conventional solar module. A high fill factor of 73.63% also implied a high performance in series and shunt resistance. This paper not only illustrated the performance of the surface plasmonic resonance of a solar device but also verified the application in the industrial production.
Keywords: plasmonic resonance; Ag nanoparticles; ethylene vinyl acetate; EVA; solar; transmittance.
Oxidation behaviours of Ti(C, N, O) nanocomposite coatingsLin
by J.H. Hsieh, Y.J. Cho, C. Li
Abstract: It is known that the lifetime of Ti-based hard coatings is dependent on the oxidation rate of Ti. Ti(C,N,O) coatings prepared by an unbalanced magnetron sputtering process had been shown to have improved tribological properties. The present studies applied a static oxidation approach to explain that the oxidation activation energy could be correlated to wear rate. The properties of the oxidised films were analysed by Raman spectroscopy and scanning electron microscopy (SEM). In static oxidation, the formed titanium oxide (TiO2) layer was found to have mainly anatase structure at temperatures between 500°C to 600°C and transformed to rutile structure at temperature higher than 600°C. Through this study, oxidation rate and activation energy of oxidation for each sample were evaluated. It was found the samples exhibited a higher activation energy of oxidation could have a higher wear resistance. The role of oxidation mechanism was proved to be critical to the wear of Ti(C, N, O) thin films
Keywords: Ti(C; N; O) thin films; unbalance magnetron sputtering; oxidation; wear resistance.
PMMA and PMMA-Ag thin films deposited by a system combining inductively coupled plasma polymerisation and RF sputtering
by S.T.C. Hsieh, J.H. Hsieh, Y. Li
Abstract: A plasma system, combining inductively coupled plasma (ICP) polymerisation and RF sputtering, was used to deposit poly(methyl methacrylate) (PMMA) thin films with or without embedding Ag nanoparticles (NPs), aiming at improved biocompatibility and anti-bacterial behaviours. Fourier transform infrared spectrometry (FTIR) was used to determine the vibrational modes of bonding in the deposited PMMA films. The films' cross-sectional morphologies were examined by FESEM. Ultraviolet-Visible (UV-Vis) photospectrometry was used to examine the optical properties. Eventually, the film structure and the embedment of Ag NPs were confirmed. The biocompatibility of the PMMA and PMMA/Ag films were shown to be desirable. Ag NPs did not show negative effect on the biocompatibility. In addition, the PMMA-Ag films show expected antibacterial behaviour.
Keywords: PMMA thin films; RF sputtering; plasma polymerisation; plasmonic behaviour; Ag nanoparticles.
In situ transfection using layer-by-layer assembled chitosan/DNA multilayers
by Wei-Wen Hu, Yung-Jen Chen
Abstract: For tissue engineering concerns, gene delivery can introduce therapeutic genes to promote tissue regeneration. However, how to spatially control transfection and elongate the duration of transgene expression is a critical issue. Therefore, in this study, we applied chitosan to adsorb DNA on substrate surfaces for in situ gene delivery because chitosan is a biocompatible polycations which can be used to immobilise DNA using layer-by-layer (LbL) assembly to prepared polyelectrolyte multilayers (PEMs). DNA immobilisation can be simply controlled by bilayer numbers of PEMs so that more bilayers can deliver more DNA, which promotes not only gene delivery efficiency but also the duration of transgene expression. Chitosan solutions with different pH values were investigated for their effects on PEM constructions. The infrared spectroscopy, UV-Visible spectrometry, and quartz crystal microbalance assay demonstrated that acidic chitosan solutions reduced the ratios of chitosan adsorption but did not have significant effects on DNA deposition. The DNA release experiments suggested that PEMs with lower chitosan ratios exhibited more DNA delivery in neutral environment, however, this trend was inconsistent to the transfections results that PEMs prepared using chitosan solutions with higher pH demonstrated better transfection behaviours. To explain this contradiction, free chitosan molecules were spiked before cell seeding, by which the transfection efficiencies of the PEMs prepared by acidic chitosan solutions were highly improved, suggesting that in situ gene delivery from PEM depends not only on DNA but also on polycation release.
Keywords: chitosan; gene delivery; in situ tranfection; layer-by-layer assembly; polyelectrolyte multilayers; PEMs.
Cyclopropylamine modified plasma polymerised poly(methyl methacrylate) thin films for cell culture
by Vincent Chan, Chuan Li, Ya-Hui Tsai, Y.H. Tseng, Yun Chen
Abstract: Cyclopropylamine (CPA) is a biochemical active, volatile low carbon polymer. It usually is rendered as a compound, for instance the N-substituted cyclopropylamine, to synthesise many antidepressants or anticancer pharmaceuticals. On the other hand, poly(methyl methacrylate) (PMMA) commonly known as acrylic is a transparent thermoplastic polymer. Because of its nontoxic, stable physical and chemical properties, and because it is inexpensive and easy to processed, PMMA is widely used as structural and adhesive material. In this study, we fabricated CPA-PMMA thin films by plasma polymerisation and investigated the microstructure, surface morphology, optical properties and wettability of films. The plasma polymerisation was conducted in a vacuum chamber powered by a radio frequency supply. The composition of mixed monomers was controlled by the ratio of partial pressure of monomer gases. The deposited films were subjected to the following measurements: surface profiler for the average thickness and deposition rate, Fourier transform infrared (FTIR) spectrometer for the vibrational modes of microstructures; contact angle for the wettability, and UV-Vis-NIR spectrometer for the optical transparency and absorption. Finally these films were prepared for cell culture and the host was chosen to be 3T3 fibroblasts. The culture was assessed by MTT assays to evaluate the cellular viability in culture media and directly on films. Results from cell culture showed that all films are nontoxic and capable of supporting the growth of 3T3 fibroblasts.
Keywords: poly(methyl methacrylate); PMMA; cyclopropylamine; plasma polymerisation; 3T3 fibroblast; MTT assay.
Effect of dose loss of phosphorus on capacitance-voltage characteristics of n-type poly-Si junctionless thin-film transistors
by Jung-Ruey Tsai, Ting-Ting Wen, Horng-Chih Lin
Abstract: This study examines the effects of the dose loss of phosphorus on the capacitance-voltage characteristics of an n-type polycrystalline silicon junctionless (JL) transistor using experimental, analytical and simulated analyses. It clearly demonstrates that the gate voltage increases as the doping concentration in the channel of the JL transistor decreases, maintaining constant capacitance because the depletion region is easily formed at the surface of the channel with a low doping concentration. The critical gate voltage (VGC) is defined as the applied gate voltage that induces the gate capacitance at the kink of the C-V curve. The simulated results clearly suggest that the critical gate voltage increases linearly with the percentage of dose loss of phosphorus.
Keywords: dose loss; phosphorus; interface segregation; interface trap; junctionless transistor; capacitance-voltage.