http://www.nanoscalereslett.com The latest research articles published by Nanoscale Research Letters 2012-05-17T00:00:00Z A vacuum-sealed miniature X-ray tube based on a carbon nanotube field-emission electron source has been demonstrated. The diameter of the X-ray tube is 10 mm; the total length of the tube is 50 mm, and no external vacuum pump is required for the operation. The maximum tube voltage reaches up to 70 kV, and the X-ray tube generates intense X-rays with the air kerma strength of 108 Gy * cm2 min1. In addition, X-rays produced from the miniature X-ray tube have a comparatively uniform spatial dose distribution http://www.nanoscalereslett.com/content/7/1/258 Sung Hwan Heo Hyun Jin Kim Jun Mok Ha Sung Oh Cho Nanoscale Research Letters 2012, null:258 2012-05-17T00:00:00Z doi:10.1186/1556-276X-7-258 /content/figures/1556-276X-7-258-toc.gif Nanoscale Research Letters 1556-276X ${item.volume} 258 2012-05-17T00:00:00Z PDF We have theoretically studied the thermoelectric properties ofserially coupled quantum dots (SCQDs) embedded in an insulatorconnected to metallic electrodes. In the framework of KeldyshGreen's function technique, the Landauer formula of transmissionfactor is obtained by using the equation of motion method. Based onsuch analytical expressions of charge and heat currents, wecalculate the electrical conductance, Seebeck coefficient, electron thermal conductance and figure of merit (ZT) of SCQDs. The effects of interdot hopping and electron Coulomb interactions on ZT are analyzed. We demonstrate that ZT is not a monotonic increasing function of interdot electron hopping strength (t_c). We also show that in the absence of phonon thermal conductance, SCQD can reach theCarnot efficiency as t_c approaches zero. http://www.nanoscalereslett.com/content/7/1/257 David Kuo Yia-Chung Chang Nanoscale Research Letters 2012, null:257 2012-05-16T00:00:00Z doi:10.1186/1556-276X-7-257 /content/figures/1556-276X-7-257-toc.gif Nanoscale Research Letters 1556-276X ${item.volume} 257 2012-05-16T00:00:00Z PDF The enhancement of bendability for flexible nanoelectronics is critically important to realize future portable and wearable nanoelectronics for personal and military purposes. Because there is an enormous variety of materials and structures that are used for flexible nanoelectronic devices, a governing design rule for optimizing the bendability of these nanodevices is required. In this article, we suggest a design rule to optimize the bendability of flexible nanoelectronics through neutral axis (NA) engineering. In flexible optical nanoelectronics, transparent electrodes such as indium-tin-oxide (ITO) are usually the most fragile under an external load because of its brittle property. Therefore, we representatively focus on the bendability of the ITO which has been widely used as transparent electrodes, and the NA is controlled by employing a buffer layer on the ITO layer. First, we independently investigate the effect of the thickness and elastic modulus of a buffer layer on the bendability of an ITO film. Then, we develop a design rule for the bendability optimization of flexible optical nanoelectronics. Because NA is determined by considering both the thickness and elastic modulus of a buffer layer, the design rule is conceived to be applicable regardless of the material and thickness that are used for the buffer layer. Finally, our design rule is applied to optimize the bendability of an organic solar cell, which allows the bending radius to reach about 1 mm. Our design rule is thus expected to provide a great strategy to enhance the bending performance of a variety of flexible nanoelectronics. http://www.nanoscalereslett.com/content/7/1/256 Sangmin Lee Jang-Yeon Kwon Daesung Yoon Handong Cho Jinho You Yongtae Kang Dukhyun Choi Woonbong Hwang Nanoscale Research Letters 2012, null:256 2012-05-15T00:00:00Z doi:10.1186/1556-276X-7-256 /content/figures/1556-276X-7-256-toc.gif Nanoscale Research Letters 1556-276X ${item.volume} 256 2012-05-15T00:00:00Z PDF Scanning tunneling spectroscopy (STS) was used to measure local differential conductance (d http://www.nanoscalereslett.com/content/7/1/255 Soo-hyon Phark Jérôme Borme Augusto León Vanegas Marco Corbetta Dirk Sander Jürgen Kirschner Nanoscale Research Letters 2012, null:255 2012-05-15T00:00:00Z doi:10.1186/1556-276X-7-255 /content/figures/1556-276X-7-255-toc.gif Nanoscale Research Letters 1556-276X ${item.volume} 255 2012-05-15T00:00:00Z PDF We fabricate and characterize carbon fibre tips for their use in combined scanning tunnelling and force microscopy based on piezoelectric quartz tuning fork force sensors. An electrochemical fabrication procedure to etch the tips is used to yield reproducible sub-100 nm apex. We also study electron transport through single-molecule junctions formed by a single octanethiol molecule bonded by the thiol anchoring group to a gold electrode and linked to a carbon tip by the methyl group. We observe the presence of conductance plateaus during the stretching of the molecular bridge, which is the signature of the formation of a molecular junction. http://www.nanoscalereslett.com/content/7/1/254 Gabino Rubio-Bollinger Andres Castellanos-Gomez Stefan Bilan Linda Zotti Carlos Arroyo Nicolas Agrait Juan Carlos Cuevas Nanoscale Research Letters 2012, null:254 2012-05-15T00:00:00Z doi:10.1186/1556-276X-7-254 /content/figures/1556-276X-7-254-toc.gif Nanoscale Research Letters 1556-276X ${item.volume} 254 2012-05-15T00:00:00Z PDF The dielectric/metal/dielectric (DMD) multilayer is suitable for a transparent electrode because of its high optical and high electrical properties; however, it is fabricated by an expensive and inefficient multistep vacuum process. We present a WO3/Ag/WO3 (WAW) multilayer transparent anode with solution-processed WO3 for polymer light-emitting diodes (PLEDs). This WAW multilayer not only has high transmittance and low resistance but also can be easily and rapidly fabricated. We devised a novel method to deposit a thin WO3 layer by a solution process in an air environment. A tungstic acid solution was prepared from an aqueous solution of Na2WO4 and then converted to WO3 nanoparticles (NPs) by a thermal treatment. Thin WO3 NP layers form WAW multilayer with a thermal evaporated Ag layer, and they improve the transmittance of the WAW multilayer because of its high transmittance and refractive index. Moreover, the surface of the WO3 layer is homogeneous and flat with low roughness because of the WO3 NP generation from the tungstic acid solution without aggregation. We performed optical simulation and experiments, and the optimized WAW multilayer had a high transmittance of 85% with a sheet resistance of 4 /sq. Finally, PLEDs based on the WAW multilayer anode achieved a maximum luminance of 35550 cd/m2 at 8 V, and this result implies that the solution-processed WAW multilayer is appropriate for use as a transparent anode in PLEDs. http://www.nanoscalereslett.com/content/7/1/253 Kang-Min Jeon Hong-Seok Youn Seong-Beom Kim Seong-Beom Shin Min-Yang Yang Nanoscale Research Letters 2012, null:253 2012-05-15T00:00:00Z doi:10.1186/1556-276X-7-253 /content/figures/1556-276X-7-253-toc.gif Nanoscale Research Letters 1556-276X ${item.volume} 253 2012-05-15T00:00:00Z PDF A network of gold nanostructures exhibiting one-dimensional gold nanostructure properties may become a prospective novel structure for optical, electrical and catalytic applications benefited by its unusual characteristics resulting from the collective properties of individual nanostructures in the network. In this paper, we demonstrate a facile method for the formation of high-density gold nanonetworks film on the substrate surface composed by quasi-1D nanoparticles (typically fusiform) of length ca. 10 nm - via reduction of gold ions in the presence of nanoseeds attached-surface, binary surfactants of cetyltrimethylammonium bromide (CTAB) and hexamethyleneteramine (HMT) and Ag+ ions. The length of the nanonetworks can be up to ca. 100 nm, which corresponds to aspect ratio of ca. 10. The quasi-1D gold nanostructures as well as the nanonetworks were found to be sensitive to the binary surfactants system and the Ag+ ions as they can only be formed if all the chemicals are available in the reaction. The nanonetworks exhibit unique 1D optical properties with the presence of transverse and longitudinal surface Plasmon resonance absorption. Owing to their peculiar structures that are composed of small quasi-1D nanoparticles, the nanonetworks may produce unusual optical and catalytic properties, which are potentially used in SERS, catalysis and optical and non-linear optical applications. http://www.nanoscalereslett.com/content/7/1/252 Akrajas Ali Umar Iwantono Iwantono Ariyanto Abdullah Muhamad Mat Salleh Munetaka Oyama Nanoscale Research Letters 2012, null:252 2012-05-15T00:00:00Z doi:10.1186/1556-276X-7-252 /content/figures/1556-276X-7-252-toc.gif Nanoscale Research Letters 1556-276X ${item.volume} 252 2012-05-15T00:00:00Z PDF The aim of the present study was to develop a transdermal system for controlled delivery of melatonin combining three strategies: nanoencapsulation of melatonin, drying of melatonin-loaded nanocapsules and incorporation in a hydrophilic gel. Nanocapsules were prepared by interfacial deposition of the polymer and were spray-dried using water-soluble excipients. In vitro drug release profiles were evaluated by the dialysis bag method and skin permeation studies were carried out using Franz cells with porcine skin as the membrane. The use of 10% (w/v) water-soluble excipients (lactose or maltodextrin) as spray-drying adjuvants furnished redispersible powders (redispersibility index ~ 1.0) suitable for incorporation into hydrogels. All formulations showed better controlled in vitro release of melatonin compared to the melatonin solution. The best controlled release results were achieved with the hydrogels prepared with dried nanocapsules (hydrogels>redispersed dried nanocapsules>nanocapsule suspension>melatonin solution). The skin permeation studies demonstrated a significant modulation of the transdermal melatonin permeation for hydrogels prepared with redispersible nanocapsules. In this way, the additive effect of the different approaches used in this study (nanoencapsulation, spray-drying and preparation of semisolid dosage forms) allows not only the control o melatonin release, but also transdermal permeation. http://www.nanoscalereslett.com/content/7/1/251 Cristiane Hoffmeister Tais Durli Scheila Schaffazick Renata Raffin Eduardo Bender Ruy Beck Adriana Pohlmann Silvia Stanisçuaski Nanoscale Research Letters 2012, null:251 2012-05-15T00:00:00Z doi:10.1186/1556-276X-7-251 /content/figures/1556-276X-7-251-toc.gif Nanoscale Research Letters 1556-276X ${item.volume} 251 2012-05-15T00:00:00Z PDF The use of electrostatic force microscopy (EFM) to characterize and manipulate surfaces at the nanoscale usually faces the problem of dealing with systems where several parameters are not known. Artificial neural networks (ANNs) have demonstrated to be a very useful tool to tackle this type of problems. Here we show that the use of ANNs allows us to quantitatively estimate magnitudes such as the dielectric constant of thin films. To improve thin film dielectric constant estimations in EFM, we first increase the accuracy of numerical simulations by replacing the standard minimization technique by a method based on ANN learning algorithms. Second, we use the improved numerical results to build a complete training set for a new ANN. The results obtained by the ANN suggest that accurate values for the thin film dielectric constant can be only estimated if the thin film thickness and sample dielectric constant are known. http://www.nanoscalereslett.com/content/7/1/250 Elena Castellano-Hernandez Francisco Rodríguez Eduardo Serrano Pablo Varona Sacha Gomez-monivas Nanoscale Research Letters 2012, null:250 2012-05-15T00:00:00Z doi:10.1186/1556-276X-7-250 /content/figures/1556-276X-7-250-toc.gif Nanoscale Research Letters 1556-276X ${item.volume} 250 2012-05-15T00:00:00Z PDF A kind of ferronematic materials composed of 4-cyano-4'-pentylbiphenyl nematic liquid crystal and oil-based Fe3O4 magnetic fluid was prepared by using ultrasonic agitation. The birefringence and figure of merit of optical properties of pure magnetic fluids and the as-prepared ferronematic materials were examined and compared. The figure of merit of optical properties weighs the birefringence and extinction of the materials and is more appropriate to evaluate their optical properties. Similar magnetic-field- and magnetic-particle-concentration-dependent properties of birefringence and figure of merit of optical properties were obtained for the pure magnetic fluids and the ferronematic materials. For the ferronematic materials, the values of Q increase with the volume fractions of nematic liquid crystal under certain fixed field strength and are larger than those of their corresponding pure magnetic fluids at high field region. In addition, the enhancement of Q value increases monotonously with the magnetic field and becomes remarkable when the applied magnetic field is beyond 50 mT. The maximum relative enhanced value of QR exceeds 6.8% in our experiments. The results of this work may conduce to extend the pragmatic applications of nanostructured magnetic fluids in optical field. http://www.nanoscalereslett.com/content/7/1/249 Xiang Wang Shengli Pu Hongzhu Ji Guojun Yu Nanoscale Research Letters 2012, null:249 2012-05-15T00:00:00Z doi:10.1186/1556-276X-7-249 /content/figures/1556-276X-7-249-toc.gif Nanoscale Research Letters 1556-276X ${item.volume} 249 2012-05-15T00:00:00Z PDF