Showing papers in "Nanotechnology in 2010"
TL;DR: “Gene Chip” is used as an example that is still object of research in basic nanoscience, but at the same time is already of interest in the nanoengineering step and has partially even reached the technology status.
Abstract: Chapter 2 defines the expressions “Nanoscience” and “Nanotechnology” on a strictly scientific base. Various examples are used to illustrate the development from a scientific discovery via an engineering step to a final technology. “Molecular Motors and Machines”, “Molecular Switches” as well as “Single Electron Memories” are examples that are still exclusively objects of basic research, whereas “Drug Delivery” already reached the status of Nanoengineering. The “Gene Chip” is used as an example that is still object of research in basic nanoscience, but at the same time is already of interest in the nanoengineering step and has partially even reached the technology status. “Hyperthermia” and “Gas Sensors” have left the field of fundamental research and have developed to engineering as well as to technology. Chapter 2 closes with some examples belonging to the field of “Technology on the Nanoscale” which is, however, often but wrongly called “Nanotechnology”.
Keywords:
molecular motors and switches;
singleelectron memories;
drug delivery;
gene chips;
gas sensors
666 citations
TL;DR: The p-type doping behavior was confirmed by characterizing the Raman G-band of the doped graphene film and the doping effect was manifested only with 1-2 layer graphene but not with multi-layer graphene, advancing the numerous applications of graphene films as transparent conducting electrodes.
Abstract: We report chemical doping (p-type) to reduce the sheet resistance of graphene films for the application of high-performance transparent conducting films. The graphene film synthesized by chemical vapor deposition was transferred to silicon oxide and quartz substrates using poly(methyl methacrylate). AuCl(3) in nitromethane was used to dope the graphene films and the sheet resistance was reduced by up to 77% depending on the doping concentration. The p-type doping behavior was confirmed by characterizing the Raman G-band of the doped graphene film. Atomic force microscope and scanning electron microscope images reveal the deposition of Au particles on the film. The sizes of the Au particles are 10-100 nm. The effect of doping was also investigated by transferring the graphene films onto quartz and poly(ethylene terephthalate) substrates. The sheet resistance reached 150 Omega/sq at 87% transmittance, which is comparable to those of indium tin oxide conducting film. The doping effect was manifested only with 1-2 layer graphene but not with multi-layer graphene. This approach advances the numerous applications of graphene films as transparent conducting electrodes.
381 citations
TL;DR: It is shown that the sensitization in nanoparticles is enhanced due to auto-amplified electronic cascades inside the nanoparticles, which reinforces the energy deposition in the close vicinity of the metal.
Abstract: Recently, the use of gold nanoparticles as potential tumor selective radiosensitizers has been proposed as a breakthrough in radiotherapy. Experiments in living cells and in vivo have demonstrated the efficiency of the metal nanoparticles when combined with low energy x-ray radiations (below conventional 1 MeV Linac radiation). Further studies on DNA have been performed in order to better understand the fundamental processes of sensitization and to further improve the method. In this work, we propose a new strategy based on the combination of platinum nanoparticles with irradiation by fast ions effectively used in hadron therapy. It is observed in particular that nanoparticles enhance strongly lethal damage in DNA, with an efficiency factor close to 2 for double strand breaks. In order to disentangle the effect of the nano-design architecture, a comparison with the effects of dispersed metal atoms at the same concentration has been performed. It is thus shown that the sensitization in nanoparticles is enhanced due to auto-amplified electronic cascades inside the nanoparticles, which reinforces the energy deposition in the close vicinity of the metal. Finally, the combination of fast ion radiation (hadron therapy) with platinum nanoparticles should strongly improve cancer therapy protocols.
368 citations
TL;DR: The opening of a bandgap in graphene is explained in terms of functionalization of its pristine lattice with oxygen atoms, that is, on the extent of the bandgap opening upon increased functionalisation density.
Abstract: We report a change in the semimetallic nature of single-layer graphene after exposure to oxygen plasma. The resulting transition from semimetallic to semiconducting behavior appears to depend on the duration of the exposure to the plasma treatment. The observation is confirmed by electrical, photoluminescence and Raman spectroscopy measurements. We explain the opening of a bandgap in graphene in terms of functionalization of its pristine lattice with oxygen atoms. Ab initio calculations show more details about the interaction between carbon and oxygen atoms and the consequences on the optoelectronic properties, that is, on the extent of the bandgap opening upon increased functionalisation density.
311 citations
TL;DR: Receptor-targeted cancer detection using Au clusters is demonstrated on FR(+ve) oral squamous cell carcinoma (KB) and breast adenocarcinoma cell MCF-7, where the FA-conjugated Au(25) clusters were found internalized in significantly higher concentrations compared to the negative control cell lines.
Abstract: Molecular-receptor-targeted imaging of folate receptor positive oral carcinoma cells using folic-acid-conjugated fluorescent Au(25) nanoclusters (Au NCs) is reported. Highly fluorescent Au(25) clusters were synthesized by controlled reduction of Au(+) ions, stabilized in bovine serum albumin (BSA), using a green-chemical reducing agent, ascorbic acid (vitamin-C). For targeted-imaging-based detection of cancer cells, the clusters were conjugated with folic acid (FA) through amide linkage with the BSA shell. The bioconjugated clusters show excellent stability over a wide range of pH from 4 to 14 and fluorescence efficiency of approximately 5.7% at pH 7.4 in phosphate buffer saline (PBS), indicating effective protection of nanoclusters by serum albumin during the bioconjugation reaction and cell-cluster interaction. The nanoclusters were characterized for their physico-chemical properties, toxicity and cancer targeting efficacy in vitro. X-ray photoelectron spectroscopy (XPS) suggests binding energies correlating to metal Au 4f(7/2) approximately 83.97 eV and Au 4f(5/2) approximately 87.768 eV. Transmission electron microscopy and atomic force microscopy revealed the formation of individual nanoclusters of size approximately 1 nm and protein cluster aggregates of size approximately 8 nm. Photoluminescence studies show bright fluorescence with peak maximum at approximately 674 nm with the spectral profile covering the near-infrared (NIR) region, making it possible to image clusters at the 700-800 nm emission window where the tissue absorption of light is minimum. The cell viability and reactive oxygen toxicity studies indicate the non-toxic nature of the Au clusters up to relatively higher concentrations of 500 microg ml(-1). Receptor-targeted cancer detection using Au clusters is demonstrated on FR(+ve) oral squamous cell carcinoma (KB) and breast adenocarcinoma cell MCF-7, where the FA-conjugated Au(25) clusters were found internalized in significantly higher concentrations compared to the negative control cell lines. This study demonstrates the potential of using non-toxic fluorescent Au nanoclusters for the targeted imaging of cancer.
298 citations
TL;DR: This work demonstrates a large-scale batch fabrication of GaN light-emitting diodes (LEDs) with patterned multi-layer graphene (MLG) as transparent conducting electrodes as a potential development toward future practical application of graphene electrodes in optoelectronic devices.
Abstract: This work demonstrates a large-scale batch fabrication of GaN light-emitting diodes (LEDs) with patterned multi-layer graphene (MLG) as transparent conducting electrodes. MLG films were synthesized using a chemical vapor deposition (CVD) technique on nickel films and showed typical CVD-synthesized MLG film properties, possessing a sheet resistance of [Formula: see text] with a transparency of more than 85% in the 400-800 nm wavelength range. The MLG was applied as the transparent conducting electrodes of GaN-based blue LEDs, and the light output performance was compared to that of conventional GaN LEDs with indium tin oxide electrodes. Our results present a potential development toward future practical application of graphene electrodes in optoelectronic devices.
293 citations
TL;DR: This paper investigates the resistive switching characteristics in a Cu/HfO(2):Cu/Pt sandwiched structure for multilevel non-volatile memory applications and finds different resistance values are achieved using different compliance currents in the program process.
Abstract: In this paper, the resistive switching characteristics in a Cu/HfO(2):Cu/Pt sandwiched structure is investigated for multilevel non-volatile memory applications. The device shows excellent resistive switching performance, including good endurance, long retention time, fast operation speed and a large storage window (R(OFF)/R(ON)>10(7)). Based on the temperature-dependent test results, the formation of Cu conducting filaments is believed to be the reason for the resistance switching from the OFF state to the ON state. By integrating the resistive switching mechanism study and the device fabrication, different resistance values are achieved using different compliance currents in the program process. These resistance values can be easily distinguished in a large temperature range, and can be maintained over 10 years by extrapolating retention data at room temperature. The integrated experiment and mechanism studies set up the foundation for the development of high-performance multilevel RRAM.
279 citations
TL;DR: In this method, a yarn freshly spun from a super-aligned carbon nanotube array is first twisted and then passes through a volatile solvent for shrinking, and thus has a tensile strength up to about 1 GPa.
Abstract: We report a simple and continuous spinning method that combines twisting and shrinking processes to produce carbon nanotube yarns. In this method, a yarn freshly spun from a super-aligned carbon nanotube array is first twisted and then passes through a volatile solvent for shrinking. The as-produced yarn consists of densely packed carbon nanotubes, and thus has a tensile strength up to about 1 GPa. The tensile strength depends on the diameter and the twisting angle of the yarn. Different kinds of solvents, such as water, ethanol, and acetone, are used to shrink the twisted yarns, and acetone shows the best shrinking effect. The origin of the solvent shrinking effect is investigated. Our method is favorable for continuous mass production of high strength carbon nanotube yarns with a wide range of diameters, especially ultra-thin yarns.
272 citations
TL;DR: It was found that AuCl(3) doping on graphene can alter the graphene surface wetting properties such that a uniform coating of the hole-transporting layer can be achieved and device success rate can be increased, resulting in improved overall PCE performance of the OPV devices.
Abstract: In this work graphene sheets grown by chemical vapor deposition (CVD) with controlled numbers of layers were used as transparent electrodes in organic photovoltaic (OPV) devices. It was found that for devices with pristine graphene electrodes, the power conversion efficiency (PCE) is comparable to their counterparts with indium tin oxide (ITO) electrodes. Nevertheless, the chances for failure in OPVs with pristine graphene electrodes are higher than for those with ITO electrodes, due to the surface wetting challenge between the hole-transporting layer and the graphene electrodes. Various alternative routes were investigated and it was found that AuCl3 doping on graphene can alter the graphene surface wetting properties such that a uniform coating of the hole-transporting layer can be achieved and device success rate can be increased. Furthermore, the doping both improves the conductivity and shifts the work function of the graphene electrode, resulting in improved overall PCE performance of the OPV devices. This work brings us one step further toward the future use of graphene transparent electrodes as a replacement for ITO. (Some figures in this article are in colour only in the electronic version)
271 citations
TL;DR: Detailed current-voltage and current-time measurements are reported to reveal the forming and switching behaviors of Cu/Ta(2)O(5)/Pt nonvolatile resistive memory devices and concluded that the RESET process consists of the Joule-heating-assisted oxidation of Cu atoms at the thinnest part of the metal filament followed by diffusion and drift of the Cu ions under their own concentration gradient and the applied electric field.
Abstract: We report detailed current-voltage and current-time measurements to reveal the forming and switching behaviors of Cu/Ta(2)O(5)/Pt nonvolatile resistive memory devices. The devices can be initially SET (from the OFF state to the ON state) when a low positive bias voltage is applied to the Cu electrode. This first SET operation corresponds to the first formation of a metal filament by inhomogeneous nucleation and subsequent growth of Cu on the Pt electrode, based on the migration of Cu ions in the stable Ta(2)O(5) matrix. After the forming, the device exhibits bipolar switching behavior (SET at positive bias and RESET (from the ON state to the OFF state) at negative bias) with increasing the ON resistance from a few hundred Ω to a few kΩ. From the measurements of the temperature stability of the ON states, we concluded that the RESET process consists of the Joule-heating-assisted oxidation of Cu atoms at the thinnest part of the metal filament followed by diffusion and drift of the Cu ions under their own concentration gradient and the applied electric field, disconnecting the metal filament. With ON resistances of the order of a few kΩ, the SET and RESET operations are repeated by the inhomogeneous nucleation and the Joule-heating-assisted dissolution of a small filament on a remaining filament. This switching model is applicable to the operation of cation-migration-based resistive memories using other oxide materials.
270 citations
TL;DR: The enhanced microwave absorption of Fe/SiO(2) nanoflakes can be attributed to the combination of the proper electromagnetic impedance match due to the decrease of permittivity and large magnetic loss due to strong and broadband natural resonance.
Abstract: Fe nanoflakes were prepared by the ball-milling technique, and then were coated with 20 nm-thick SiO2 to prepare Fe/SiO2 core–shell nanoflakes. Compared with the uncoated Fe nanoflakes, the permittivity of Fe/SiO2 nanoflakes decreases dramatically, while the permeability decreases slightly. Consequently, reflection losses exceeding − 20 dB of Fe/SiO2 nanoflakes are obtained in the frequency range of 3.8–7.3 GHz for absorber thicknesses of 2.2–3.6 mm, while the reflection loss of uncoated Fe nanoflakes almost cannot reach − 10 dB in the same thickness range. The enhanced microwave absorption of Fe/SiO2 nanoflakes can be attributed to the combination of the proper electromagnetic impedance match due to the decrease of permittivity and large magnetic loss due to strong and broadband natural resonance. The key to the combination is the coexistence of the nanoshell microstructure and the nanoflake morphology.
TL;DR: It is found that thermal expansion of graphene is negative for all temperatures between 300 and 30 K, and with a lowering of temperature, the positively dispersing electromechanical modes evolve into negatively dispersing ones.
Abstract: We use suspended graphene electromechanical resonators to study the variation of resonant frequency as a function of temperature. Measuring the change in frequency resulting from a change in tension, from 300 to 30 K, allows us to extract information about the thermal expansion of monolayer graphene as a function of temperature, which is critical for strain engineering applications. We find that thermal expansion of graphene is negative for all temperatures between 300 and 30 K. We also study the dispersion, the variation of resonant frequency with DC gate voltage, of the electromechanical modes and find considerable tunability of resonant frequency, desirable for applications like mass sensing and RF signal processing at room temperature. With a lowering of temperature, we find that the positively dispersing electromechanical modes evolve into negatively dispersing ones. We quantitatively explain this crossover and discuss optimal electromechanical properties that are desirable for temperature-compensated sensors.
TL;DR: The mechanical robustness of superhydrophobic surfaces was evaluated on hierarchically structured silicon surfaces and the effect of two-scale hierarchical structures on robustness was investigated using an abrasion test and the results compared to those of superHydrophilic surfaces fabricated from polymeric materials and from silicon that contains only nanostructures.
Abstract: Improvement of the robustness of superhydrophobic surfaces is critical in order to achieve commercial applications of these surfaces in such diverse areas as self-cleaning, water repellency and corrosion resistance. In this study, the mechanical robustness of superhydrophobic surfaces was evaluated on hierarchically structured silicon surfaces. The effect of two-scale hierarchical structures on robustness was investigated using an abrasion test and the results compared to those of superhydrophobic surfaces fabricated from polymeric materials and from silicon that contains only nanostructures. Unlike the polymeric and nanostructure-only surfaces, the hierarchical structures retained superhydrophobic behavior after mechanical abrasion.
TL;DR: It is shown that, even for infinitely long and perfect nanotubes with well-designed tube-electrode interfaces, excessive radial heat radiation from nanotube surfaces and quenching of phonon modes in large bundles are additional processes that substantially reduce thermal transport along nanot tubes.
Abstract: The extremely high thermal conductivity of individual carbon nanotubes, predicted theoretically and observed experimentally, has not yet been achieved for large nanotube assemblies. Resistances at tube–tube interconnections and tube–electrode interfaces have been considered the main obstacles for effective electronic and heat transport. Here we show that, even for infinitely long and perfect nanotubes with well-designed tube–electrode interfaces, excessive radial heat radiation from nanotube surfaces and quenching of phonon modes in large bundles are additional processes that substantially reduce thermal transport along nanotubes. Equivalent circuit simulations and an experimental self-heating 3ω technique were used to determine the peculiarities of anisotropic heat flow and thermal conductivity of single MWNTs, bundled MWNTs and aligned, free-standing MWNT sheets. The thermal conductivity of individual MWNTs grown by chemical vapor deposition and normalized to the density of graphite is much lower (κMWNT = 600 ± 100 W m−1 K−1) than theoretically predicted. Coupling within MWNT bundles decreases this thermal conductivity to 150 W m−1 K−1. Further decrease of the effective thermal conductivity in MWNT sheets to 50 W m−1 K−1 comes from tube–tube interconnections and sheet imperfections like dangling fiber ends, loops and misalignment of nanotubes. Optimal structures for enhancing thermal conductivity are discussed.
TL;DR: It was demonstrated that the viscosity of water-based nanofluids can be significantly decreased by pH of the suspension independently from the thermal conductivity, and optimum directions in nan ofluid development are suggested.
Abstract: The effect of average particle sizes on basic macroscopic properties and heat transfer performance of alpha-SiC/water nanofluids was investigated. The average particle sizes, calculated from the specific surface area of nanoparticles, were varied from 16 to 90 nm. Nanofluids with larger particles of the same material and volume concentration provide higher thermal conductivity and lower viscosity increases than those with smaller particles because of the smaller solid/liquid interfacial area of larger particles. It was also demonstrated that the viscosity of water-based nanofluids can be significantly decreased by pH of the suspension independently from the thermal conductivity. Heat transfer coefficients were measured and compared to the performance of base fluids as well as to nanofluids reported in the literature. Criteria for evaluation of the heat transfer performance of nanofluids are discussed and optimum directions in nanofluid development are suggested.
TL;DR: Fe(3)O(4) nanoparticles coated with bipolar surfactant tetramethylammonium 11-aminoundecanoate are biocompatible and promising for bio-applications such as drug delivery, magnetic resonance imaging and magnetic hyperthermia.
Abstract: In order to reveal the biocompatibility of Fe(3)O(4) nanoparticles and bipolar surfactant tetramethylammonium 11-aminoundecanoate cytotoxicity tests were performed as a function of concentration from low (0.1 microg ml(-1)) to higher concentration (100 microg ml(-1)) using various human glia, human breast cancer and normal cell lines. Cytotoxicity tests for human glia (D54MG, G9T, SF126, U87, U251, U373), human breast cancer (MB157, SKBR3, T47D) and normal (H184B5F5/M10, WI-38, SVGp12) cell lines exhibited almost nontoxicity and reveal biocompatibility of Fe(3)O(4) nanoparticles in the concentration range of 0.1-10 microg ml(-1), while accountable cytotoxicity can be seen at 100 microg ml(-1). The results of our studies suggest that Fe(3)O(4) nanoparticles coated with bipolar surfactant tetramethylammonium 11-aminoundecanoate are biocompatible and promising for bio-applications such as drug delivery, magnetic resonance imaging and magnetic hyperthermia.
TL;DR: A prototype carbon nanotube (CNT) yarn strain sensor with excellent repeatability and stability for in situ structural health monitoring was developed and showed consistent piezoresistive behavior under repetitive straining and unloading.
Abstract: Carbon nanotube (CNT) based sensors are often fabricated by dispersing CNTs into different types of polymer. In this paper, a prototype carbon nanotube (CNT) yarn strain sensor with excellent repeatability and stability for in situ structural health monitoring was developed. The CNT yarn was spun directly from CNT arrays, and its electrical resistance increased linearly with tensile strain, making it an ideal strain sensor. It showed consistent piezoresistive behavior under repetitive straining and unloading, and good resistance stability at temperatures ranging from 77 to 373 K. The sensors can be easily embedded into composite structures with minimal invasiveness and weight penalty. We have also demonstrated their ability to monitor crack initiation and propagation.
TL;DR: This is the first study involving 1.9 nm nanometre sized particles to report multiple cellular responses which impact on the radiation dose modifying effect, and highlights the need for extensive characterization of responses to gold nanoparticles when assessing dose enhancing potential in cancer therapy.
Abstract: High atomic number (Z) materials such as gold preferentially absorb kilovoltage x-rays compared to soft tissue and may be used to achieve local dose enhancement in tumours during treatment with ionizing radiation. Gold nanoparticles have been demonstrated as radiation dose enhancing agents in vivo and in vitro. In the present study, we used multiple endpoints to characterize the cellular cytotoxic response of a range of cell lines to 1.9 nm gold particles and measured dose modifying effects following transient exposure at low concentrations. Gold nanoparticles caused significant levels of cell type specific cytotoxicity, apoptosis and increased oxidative stress. When used as dose modifying agents, dose enhancement factors varied between the cell lines investigated with the highest enhancement being 1.9 in AGO-1522B cells at a nanoparticle concentration of 100 microg ml(-1). This study shows exposure to 1.9 nm gold particles to induce a range of cell line specific responses including decreased clonogenic survival, increased apoptosis and induction of DNA damage which may be mediated through the production of reactive oxygen species. This is the first study involving 1.9 nm nanometre sized particles to report multiple cellular responses which impact on the radiation dose modifying effect. The findings highlight the need for extensive characterization of responses to gold nanoparticles when assessing dose enhancing potential in cancer therapy.
TL;DR: First-principles calculations are performed to study the geometry, electronic structure and magnetic properties of light non-metallic atom-doped graphene (B, N, O and F).
Abstract: First-principles calculations are performed to study the geometry, electronic structure and magnetic properties of light non-metallic atom-doped graphene (B, N, O and F). The planar structure and the quasi-linear energy dispersion near the Dirac point remain through doping with B and N atoms, by which p-type doping and n-type doping graphene are respectively induced. A bandgap of about 0.5 eV is generated through O doping, and geometrically the O atom is also in the graphene plane. No magnetic moment is detected in B- , N- and O-doped graphene. For F doping, the F atom bonds with one of the carbon atoms close to the vacancy, with the other two carbon atoms undergoing a Jahn-Teller distortion. A weak polarized magnetic moment of 0.71 µ(B) is detected through F doping.
TL;DR: The thermal transport properties of hexagonal boron nitride nanoribbons (BNNRs) are investigated and a critical role of the T(1.5) dependence is revealed in determining the thermal transport.
Abstract: The thermal transport properties of hexagonal boron nitride nanoribbons (BNNRs) are investigated. By calculating the phonon spectrum and thermal conductance, it is found that the BNNRs possess excellent thermal transport properties. The thermal conductance of BNNRs can be comparable to that of graphene nanoribbons (GNRs) and even exceed the latter below room temperature. A fitting formula is obtained to describe the features of thermal conductance in BNNRs, which reveals a critical role of the T1.5 dependence in determining the thermal transport. In addition, an obviously anisotropic thermal transport phenomenon is observed in the nanoribbons. The thermal conductivity of zigzag-edged BNNRs is shown to be about 20% larger than that of armchair-edged nanoribbons at room temperature. The findings indicate that the BNNRs can be applied as important components of excellent thermal devices.
TL;DR: The measurements of thermal conductivity indicate that the stable ethylene-glycol-based nanofluids containing graphene oxide nanosheets have substantially higher thermal conductivities than the base fluid.
Abstract: Stable ethylene-glycol-based nanofluids containing graphene oxide nanosheets have been prepared. The measurements of thermal conductivity indicate that the nanofluids have substantially higher thermal conductivities than the base fluid. The thermal conductivity enhancement depends strongly on the volume fraction of graphene oxide nanosheets and increases with the increasing loading. When the nanosheet loading is 5.0 vol%, the enhancement ratio is up to 61.0%. The thermal conductivity of the fluids remains almost constant for seven days, indicating their high stability. The level of enhancement is independent of temperature in the measured temperature range.
TL;DR: A catalyst-free method for growing self-assembled GaN wires on c-plane sapphire substrates by metal-organic vapour phase epitaxy is developed, and detailed study of the growth mechanisms shows that a combination of key parameters is necessary to obtain vertical growth.
Abstract: A new catalyst-free method has been developed to grow self-assembled GaN wires on c-plane sapphire substrates by metal-organic vapour phase epitaxy. This approach, based on in situ deposition of thin SiNx layer (~2 nm), enables epitaxial growth of c-oriented wires with 200-1500 nm diameters and a large length/diameter ratio (>100) on c-plane sapphire substrate. The detailed study of the growth mechanisms shows that a combination of key parameters is necessary to obtain vertical growth. In particular, the duration of SiNx deposition prior to the wire growth is critical for controlling the epitaxy with the substrate. The GaN seed nucleation time determines the mean-size diameter and structural quality and a high Si-dopant concentration promotes the vertical growth. Such GaN wires exhibit UV-light emission centered at about 350 nm and a weak yellow band (~550 nm) at low temperature. This approach may be viewed as a fast and reproducible technique to grow GaN wires by MOVPE. Compared to other techniques, it allows studying quite systematically the influence of the growth parameters without being dependent on time consuming ex situ surface preparations like surface patterning used in selective area growth (SAG). The growth of heterostructures, as longitudinal n-u and n-p wires (using Si and Mg dopants) as well as a core-shell InGaN/GaN MQW using the wires as templates has been demonstrated. The growth occurs on the non-polar m-plane facets of the wire and not on c-plane as it is the case on 2D materials with the same sapphire substrate. It gives different piezoelectric contributions to the wires optical properties, which have been studied by cathodo- and photo-luminescence. The fundamental building blocks of wire-based blue LED were demonstrated during this thesis. The realisation of an efficient device still requires a deeper understanding and optimization of the parameters controlling the material growth and an optimization of the electrical contacts.
TL;DR: Using a tailor-made polymer and by controlling the nanofabrication conditions, defect-free ultra-thin film membranes with unmatched carbon dioxide permeances are developed and manufactured, i.e. > 5 m(3) (STP) m(-2) h(-1) bar(-1).
Abstract: Miniaturization and manipulation of materials at nanometer scale are key challenges in nanoscience and nanotechnology. In membrane science and technology, the fabrication of ultra-thin polymer films (defect-free) on square meter scale with uniform thickness ( 5 m3 (STP) m − 2 h − 1 bar − 1. The permeances are extremely high, because the membranes are made from a CO2 philic polymer material and they are only a few tens of nanometers thin. Thus, these thin film membranes have potential application in the treatment of large gas streams under low pressure like, e.g., carbon dioxide separation from flue gas.
TL;DR: The derivation of the optimum mean diameter of magnetic nanoparticles (MNP) for hyperthermia as a tumour therapy in the literature is commonly reduced to application of the Neel relaxation model as mentioned in this paper.
Abstract: The derivation of the optimum mean diameter of magnetic nanoparticles (MNP) for hyperthermia as a tumour therapy in the literature is commonly reduced to application of the Neel relaxation model. Serious restrictions of this model for MNP for hyperthermia are discussed and a way is outlined to a more comprehensive model including hysteresis.
TL;DR: Together, these results provide a functional covalent conjugation of ND-paclitaxel, which can be delivered into lung carcinoma cells and preserves the anticancer activities on the induction of mitotic blockage, apoptosis and anti-tumorigenesis.
Abstract: A nanoparticle-conjugated cancer drug provides a novel strategy for cancer therapy. In this study, we manipulated nanodiamond (ND), a carbon nanomaterial, to covalently link paclitaxel for cancer drug delivery and therapy. Paclitaxel was bound to the surface of 3‐5 nm sized ND through a succession of chemical modifications. The ND-paclitaxel conjugation was measured by atomic force microscope and nuclear magnetic resonance spectroscopy, and confirmed with infrared spectroscopy by the detection of deuterated paclitaxel. Treatment with 0.1‐50 μ gm l −1 ND-paclitaxel for 48 h significantly reduced the cell viability in the A549 human lung carcinoma cells. ND-paclitaxel induced both mitotic arrest and apoptosis in A549 cells. However, ND alone or denatured ND-paclitaxel (after treatment with strong alkaline solution, 1 M NaOH) did not induce the damage effects on A549 cells. ND-paclitaxel was taken into lung cancer cells in a concentration-dependent manner using flow cytometer analysis. The ND-paclitaxel particles were located in the microtubules and cytoplasm of A549 cells observed by confocal microscopy. Furthermore, ND-paclitaxel markedly blocked the tumor growth and formation of lung cancer cells in xenograft SCID mice. Together, we provide a functional covalent conjugation of ND-paclitaxel, which can be delivered into lung carcinoma cells and preserves the anticancer activities on the induction of mitotic blockage, apoptosis and anti-tumorigenesis. (Some figures in this article are in colour only in the electronic version)
TL;DR: Growth by molecular beam epitaxy and structural characterization of gallium-nucleated GaAs nanowires on silicon and a precise positioning process using a hole array in a dielectric layer thermally grown on silicon are demonstrated.
Abstract: We report growth by molecular beam epitaxy and structural characterization of gallium-nucleated GaAs nanowires on silicon. The influences of growth temperature and V/III ratio are investigated and compared in the case of oxide-covered and oxide-free substrates. We demonstrate a precise positioning process for Ga-nucleated GaAs nanowires using a hole array in a dielectric layer thermally grown on silicon. Crystal quality is analyzed by high resolution transmission electron microscopy. Crystal structure evolves from pure zinc blende to pure wurtzite along a single nanowire, with a transition region.
TL;DR: It is demonstrated that nonresonant coupling of the incident sunlight with aluminum nanoparticles results in higher optical absorption in the photoactive region than resonant coupling with silver nanoparticle arrays.
Abstract: This paper investigates the influence of resonant and nonresonant plasmonic nanostructures, such as arrays of silver and aluminum nanoparticles in the forward scattering configuration, on the optical absorption in a thin-film amorphous silicon solar cell. It is demonstrated that nonresonant coupling of the incident sunlight with aluminum nanoparticles results in higher optical absorption in the photoactive region than resonant coupling with silver nanoparticle arrays. In addition, aluminum nanoparticles are shown to maintain a net positive enhancement of the optical absorption in amorphous silicon, as compared to a negative effect by silver nanoparticles, when the nanoparticles are oxidized.
TL;DR: At low temperature, nitrogen-vacancy centers in bulk diamond are spectrally more stable, and it is expected that in the long term the bulk diamond approach will be better suited for on-chip integration of a photonic network.
Abstract: Optical microcavities and waveguides coupled to diamond are needed to enable efficient communication between quantum systems such as nitrogen-vacancy centers which are known already to have long electron spin coherence lifetimes. This paper describes recent progress in realizing microcavities with low loss and small mode volume in two hybrid systems: silica microdisks coupled to diamond nanoparticles, and gallium phosphide microdisks coupled to single-crystal diamond. A theoretical proposal for a gallium phosphide nanowire photonic crystal cavity coupled to diamond is also discussed. Comparing the two material systems, silica microdisks are easier to fabricate and test. However, at low temperature, nitrogen-vacancy centers in bulk diamond are spectrally more stable, and we expect that in the long term the bulk diamond approach will be better suited for on-chip integration of a photonic network.
TL;DR: Silicon nanowire sensors developed by using top-down fabrication that is CMOS (complementary metal-oxide-semiconductor) compatible for resistive chemical detection with fast response and high sensitivity for pH detection and the long term drifting effects were investigated.
Abstract: Silicon nanowire (SiNW) sensors have been developed by using top-down fabrication that is CMOS (complementary metal‐oxide‐semiconductor) compatible for resistive chemical detection with fast response and high sensitivity. Top-down fabrication by electron beam lithography and reactive ion etching of a silicon on insulator (SOI) substrate enables compatibility with the CMOS fabrication process, accurate alignment with other electrical components, flexible design of the nanowire geometry and good control of the electrical characteristics. The SiNW sensors showed a large operation range for pH detection (pH = 4‐10) with an average sensitivity of (� R/R)/pH = 2.6%/pH and a rise time of 8 s. A small pH level difference (� pH = 0.2) near neutral pH conditions (pH = 7) could be resolved with the SiNW sensors. The sensor response to the presence of alkali metal ions and the long term drifting effects were also investigated. (Some figures in this article are in colour only in the electronic version)