Showing papers in "Nanotechnology in 2005"

The bactericidal effect of silver nanoparticles

Abstract: Nanotechnology is expected to open new avenues to fight and prevent disease using atomic scale tailoring of materials. Among the most promising nanomaterials with antibacterial properties are metallic nanoparticles, which exhibit increased chemical activity due to their large surface to volume ratios and crystallographic surface structure. The study of bactericidal nanomaterials is particularly timely considering the recent increase of new resistant strains of bacteria to the most potent antibiotics. This has promoted research in the well known activity of silver ions and silver-based compounds, including silver nanoparticles. The present work studies the effect of silver nanoparticles in the range of 1-100 nm on Gram-negative bacteria using high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). Our results indicate that the bactericidal properties of the nanoparticles are size dependent, since the only nanoparticles that present a direct interaction with the bacteria preferentially have a diameter of approximately 1-10 nm.

Inkjet printing of nanosized silver colloids

Abstract: A water-based conducting ink, composed of well dispersed nano-silver particles, has been successfully inkjet printed using an ordinary commercial printer. The silver colloids with diameter around 50 nm were dispersed in a water and diethylene glycol cosolvent system. The 25 wt% silver ink had a viscosity of about 7.4 cP and surface tension of 33.5 dyn cm(-1) at 20 degrees C, which is appropriate for printing jobs. Continuous and smooth lines of 130 microm width could be printed on ordinary glass substrates using an Epson R210 printer. After baking at 260 degrees C for 3 min, these lines exhibited a resistivity of 1.6 x 10(-5) Omega cm, which could serve as conducting lines for electronic applications.

CMOL FPGA: a reconfigurable architecture for hybrid digital circuits with two-terminal nanodevices

Abstract: This paper describes a digital logic architecture for ‘CMOL’ hybrid circuits which combine a semiconductor–transistor (CMOS) stack and two levels of parallel nanowires, with molecular-scale nanodevices formed between the nanowires at every crosspoint. This cell-based, field-programmable gate array (FPGA)-like architecture is based on a uniform, reconfigurable CMOL fabric, with four-transistor CMOS cells and two-terminal nanodevices (‘latching switches’). The switches play two roles: they provide diode-like I –V curves for logic circuit operation, and allow circuit mapping on CMOL fabric and its reconfiguration around defective nanodevices. Monte Carlo simulations of two simple circuits (a 32-bit integer adder and a 64-bit full crossbar switch) have shown that the reconfiguration allows one to increase the circuit yield above 99% at the fraction of bad nanodevices above 20%. Estimates have shown that at the same time the circuits may have extremely high density (approximately 500 times higher than that of the usual CMOS FPGAs with the same design rules), while operating at higher speed at acceptable power consumption. (Some figures in this article are in colour only in the electronic version)

Synergistic antibacterial effects of β-lactam antibiotic combined with silver nanoparticles

Abstract: The bactericidal action of silver (0) nanoparticles and amoxicillin on Escherichia coli is studied, respectively Increasing concentration of both amoxicillin (0–0525 mg ml−1) and silver nanoparticles (0–40 µg ml−1) showed a higher antibacterial effect in Luria–Bertani (LB) medium Escherichia coli cells have different bactericidal sensitivity to them When amoxicillin and silver nanoparticles are combined, it results in greater bactericidal efficiency on Escherichia coli cells than when they were applied separately Dynamic tests on bacterial growth indicated that exponential and stationary phases are greatly decreased and delayed in the synergistic effect of amoxicillin and silver nanoparticles In addition, the effect induced by a preincubation with silver nanoparticles is examined The results show that solutions with more silver nanoparticles have better antimicrobial effects One hypothesized mechanism is proposed to explain this phenomenon

Labelling of cells with quantum dots

Abstract: Colloidal quantum dots are semiconductor nanocrystals well dispersed in a solvent The optical properties of quantum dots, in particular the wavelength of their fluorescence, depend strongly on their size Because of their reduced tendency to photobleach, colloidal quantum dots are interesting fluorescence probes for all types of labelling studies In this review we will give an overview on how quantum dots have been used so far in cell biology In particular we will discuss the biologically relevant properties of quantum dots and focus on four topics: labelling of cellular structures and receptors with quantum dots, incorporation of quantum dots by living cells, tracking the path and the fate of individual cells using quantum dot labels, and quantum dots as contrast agents

Fabrication of a 50 nm half-pitch wire grid polarizer using nanoimprint lithography

Abstract: We report the fabrication of a 50 nm half-pitch wire grid polarizer with high performance using nanoimprint lithography. The device is a form of aluminium gratings on a glass substrate whose size of 5.5 cm × 5.5 cm is compatible with a microdisplay panel. A stamp with a pitch of 100 nm was fabricated on a silicon substrate using laser interference lithography and sidewall patterning. The imprint and the aluminium etching processes are optimized to realize uniform aluminium gratings with aspect ratio of 4. The polarization extinction ratio of the fabricated device is over 2000, with transmission of 85% at a wavelength of 450 nm, which is the highest value ever reported. This work demonstrates that nanoimprint lithography is a unique cost-effective solution for nanopatterning requirements in consumer electronics components.

Large-scale synthesis and field emission properties of vertically oriented CuO nanowire films

Abstract: Using a simple method of direct heating of bulk copper plates in air, oriented CuO nanowire films were synthesized on a large scale. The length and density of nanowires could be controlled by growth temperature and growth time. Field emission (FE) measurements of CuO nanowire films show that they have a low turn-on field of 3.5–4.5 V µm−1 and a large current density of 0.45 mA cm−2 under an applied field of about 7 V µm−1. By comparing the FE properties of two types of samples with different average lengths and densities (30 µm, 108 cm−2 and 4 µm, 4 × 107 cm−2, respectively), we found that the large length–radius ratio of CuO nanowires effectively improved the local field, which was beneficial to field emission. Verified with finite element calculation, the work function of oriented CuO nanowire films was estimated to be 2.5–2.8 eV.

Conducting polymer-based nanostructurized materials: electrochemical aspects.

Abstract: New modern technologies require new materials. During the past decade, the movement towards nanodimensions in many areas of technology aroused a huge interest in nanostructurized materials. The present article reviews recent works dealing with electrochemistry-related aspects of nanostructurized conducting polymers. Electrochemical synthesis and some properties of nanostructurized conducting polymers, and nanocomposites derived from conducting polymers and metals, carbon, and inorganic and organic materials are considered. Some potential areas for electrochemistry-related applications of nanocomposites are highlighted, including batteries, supercapacitors, energy conversion systems, corrosion protection, and sensors.

Controlled synthesis of CeO2 nanorods by a solvothermal method

Abstract: Pure phase CeO2 nanorods (about 40?50?nm in diameter and 03?2??m in length) were synthesized through a solvothermal synthesis method The addition of ethylenediamine is critical to obtain CeO2 nanorods Other experimental conditions, such as the solvent composition, surfactant and the cerium source precursor were of importance in the final product morphology The reaction temperature and reaction time also had significant influence on the yield of CeO2 nanorods A possible formation mechanism of CeO2 nanorods was discussed mainly based on the dependences of controlling parameters on the final morphologies In addition, the optical properties of CeO2 nanorods were investigated The UV?visible adsorption spectrum and photoluminescence spectrum of the CeO2 nanorods showed unusual red-shift and enhanced light emission, respectively

Two-photon lithography of nanorods in SU-8 photoresist

Abstract: Studies on two-photon lithography in negative SU-8 photoresist demonstrate the possibility of obtaining mechanically stable, stress-free, extended nanorods having lateral sizes of about 30 nm (corresponding to λ/25 resolution). The high resolution achievable with the given combination of materials and fabrication techniques demonstrates its potential for the fabrication of large-scale nanostructures, such as photonic crystals with photonic stop gaps at visible wavelengths.

High power density supercapacitors using locally aligned carbon nanotube electrodes

Abstract: An ew form of thin films formed by multi-walled carbon nanotubes exhibiting high packing density and local alignment were fabricated using a highly concentrated colloidal suspension of carbon nanotubes. Electrical double layer capacitors built from these film electrodes exhibited a close to rectangular cyclic voltammogram even at a high scan rate of 1000 mV s −1 , an dp roduced very high specific power density of about 30 kW kg −1 ,i deal for surge-power delivery applications. The preparation procedure is very simple, and does not require any binders. It has potential for highly efficient manufacturing of high power density supercapacitors and other similar electronic devices.

Structure and properties of electrospun PLLA single nanofibres.

Abstract: An electrospinning method was used to spin semi-crystalline poly(L-lactide) (PLLA) nanofibres. Processing parameter effects on the internal molecular structure of electrospun PLLA fibres were investigated by x-ray diffraction (XRD) and differential scanning calorimetry (DSC). Take-up velocity was found as a dominant parameter to induce a highly ordered molecular structure in the electrospun PLLA fibres compared to solution conductivity and polymer concentration, although these two parameters played an important role in controlling the fibre diameter. A collecting method of a single nanofibre by an electrospinning process was developed for the tensile tests to investigate structure-property relationships of the polymer nanofibres. The tensile test results indicated that higher take-up velocity caused higher tensile modulus and strength due to the ordered structure developed through the process.

A batch fabricated biomimetic dry adhesive

Abstract: The fine hair adhesive system found in nature is capable of reversibly adhering to just about an ys urface. This dry adhesive, best demonstrated in the pad of the gecko, makes use of a multilevel conformal structure to greatly increase inelastic surface contact, enhancing short range interactions and producing significant amounts of attractiv ef orces. Recent work has attempted to reproduce and test the terminal submicrometre 'hairs' of the system. Here we report the first batch fabricated multi-scale conformal system to mimic nature's dry adhesive. The approach makes use of massively parallel MEMS processing technology to produce 20-150 µm platforms, supported by single slender pillars, and coated with ∼2 µ ml ong, ∼200 nm diameter, organic looking polymer nanorods, or 'organorods'. To characterize the structures a new mesoscale nanoindenter adhesion test technique has been developed. Experiments indicate significantly improved adhesion with the multiscale system. Additional processing caused a hydrophilic to hydrophobic transformation of the surface and testing indicated further improvement in adhesion. (Some figures in this article are in colour only in the electronic version)

Controlled growth of highly uniform, axial/radial direction-defined, individually addressable InP nanowire arrays

Abstract: We report on the systematically controlled growth of InP nanowire arrays by catalyst-free selective area metalorganic vapour phase epitaxy on partially masked InP(111)A substrates. The length, diameter, shape and position of the nanowires were precisely controlled by careful choice of the growth conditions and mask patterning. Manipulation of the growth conditions also enabled us to deliberately define the nanowire growth along either the axial or the radial direction, which has significant potential for the realization of novel nanostructures. Transmission electron microscopy studies revealed that the InP nanowires grown were single-crystalline with wurtzite crystal structure and the photoluminescence studies carried out at 4 K on InP nanowire arrays revealed a single intense emission peak with a significant blueshift. The controlled fabrication thus enabled the nanowires to be realized in a highly uniform manner as reproducibly identical structures and with perfect positioning in predetermined configurations, making them highly suitable for practical integration into nanodevices.

Orientation and size dependence of the elastic properties of zinc oxide nanobelts

Abstract: Molecular dynamics simulations are performed to characterize the response of zinc oxide (ZnO) nanobelts to tensile loading. The ultimate tensile strength (UTS) and Young's modulus are obtained as functions of size and growth orientation. Nanobelts in three growth orientations are generated by assembling the unit wurtzite cell along the [0001], , and crystalline axes. Following the geometric construction, dynamic relaxation is carried out to yield free-standing nanobelts at 300 K. Two distinct configurations are observed in the [0001] and orientations. When the lateral dimensions are above 10 A, nanobelts with rectangular cross-sections are seen. Below this critical size, tubular structures involving two concentric shells similar to double-walled carbon nanotubes are obtained. Quasi-static deformations of belts with and orientations consist of three stages, including initial elastic stretching, wurtzite-ZnO to graphitic-ZnO structural transformation, and cleavage fracture. On the other hand, [0001] belts do not undergo any structural transformation and fail through cleavage along (0001) planes. Calculations show that the UTS and Young's modulus of the belts are size dependent and are higher than the corresponding values for bulk ZnO. Specifically, as the lateral dimensions increase from 10 to 40 A, decreases between 38–76% and 24–63% are observed for the UTS and Young's modulus, respectively. This effect is attributed to the size-dependent compressive stress induced by tensile surface stress in the nanobelts. and nanobelts with multi-walled tubular structures are seen to have higher values of elastic moduli (~340 GPa) and UTS (~36 GPa) compared to their wurtzite counterparts, echoing a similar trend in multi-walled carbon nanotubes.

Graphoepitaxy of cylinder-forming block copolymers for use as templates to pattern magnetic metal dot arrays

Abstract: We report a method to fabricate high-quality patterned magnetic dot arrays using block copolymer lithography, metal deposition, and a dry lift-off technique. Long-range order of cylindrical domains oriented perpendicular to the substrate and in hexagonal arrays was induced in the block copolymer films by prepatterning the substrate with topographic features and chemically modifying the surface to exhibit neutral wetting behaviour towards the blocks of the copolymer. The uniformity of the domain size and row spacing of block copolymer templates created in this way was improved compared to those reported in previous studies that used graphoepitaxy of sphere-forming block copolymers. The pattern of block copolymer domains was transferred to a pattern of magnetic metal dots, demonstrating the potential of this technology for the fabrication of patterned magnetic recording media.

Influence of nanoparticle surface modification on the electrical behaviour of polyethylene nanocomposites

Abstract: In this study, we present the results of the influence of surface modification of TiO2 nanoparticles on the short-term breakdown strength and space charge distribution of low-density polyethylene (LDPE). A polar silane coupling agent N-(2-aminoethyl) 3-aminopropyl-trimethoxysilane (AEAPS) was used for the nanoparticle surface modification. Despite agglomeration and a poor interface compared to untreated nanoparticles, it was found that the incorporation of polar groups onto the nanoparticle surface improved both the dielectric breakdown strength and space charge distribution as compared to samples filled with untreated nanoparticles. Microstructure studies showed that the presence of polar groups on the TiO2 nanoparticle surface did not evidently affect the degree of crystallinity, crystalline morphology (except for internal spherulitic order), and chemical structure of the polymer matrix. The improved dielectric breakdown strength was therefore concluded to be directly due to beneficial effects related to the variation of the electrical features at the particle surface due to introduction of polar groups. For the same reason, with the use of surface modified nanoparticles, formation of space charge was suppressed.

Electrospun fibre bundle made of aligned nanofibres over two fixed points

Abstract: Despite recent advances in electrospinning, creating highly ordered structure through the use of electrospun fibres is not possible. This is due to the chaotic motion of the electrospinning jet which means that the deposition location of the fibres covers a few centimetres radius. As a result, applications for electrospun fibres are restricted to applications where precise positioning is not required. However, through the use of steel blades to control the electric field, it is now possible to create a fibre bundle made of highly aligned nanofibres where the ends of the fibre bundle are fixed during electrospinning. The creation of highly ordered structures made of electrospun fibre bundles is now possible since the fibre bundle is robust enough to be handled, and it is also easy to transfer the fibre bundle onto a substrate. More importantly, with the two ends of the fibre bundle known, automating the transfer of the fibre bundle onto a substrate is a possibility.

Mimicking the nanofeatures of bone increases bone-forming cell adhesion and proliferation

Abstract: There is a great need to design better orthopaedic implant devices by modifying their surface properties. In this respect, one approach that has received much attention of late is the simulation of the surface roughness of bone in synthetic orthopaedic implant materials. Bone has numerous nanometre features due to the presence of nanostructured entities such as collagen and hydroxyapatite. Despite this fact, current orthopaedic implant materials are smooth at the nanoscale. Previous studies have measured increased osteoblast (bone-forming cell) functions on biologically inspired nanophase titania compared to conventional titania formulations. In fact, in vitro calcium deposition by osteoblasts was up to three times higher on nanostructured compared to conventional titania. However, it was unclear in those studies what underlying surface properties (roughness, crystallinity, crystal phase, chemistry, etc) promoted enhanced functions of osteoblasts on nanophase titania. For that reason, the objective of the present in vitro study was to specifically determine the role nanostructured surface roughness of titania had on increasing functions of osteoblasts. To achieve this, the surface roughness of nanophase and conventional titania was transferred to a model tissue engineering polymer: poly-lactic-co-glycolic acid (PLGA). Results of the present study demonstrated greater osteoblast adhesion and proliferation for up to 5 days of culture on PLGA moulds of nanophase compared to conventional titania. In this manner, this study elucidated that the property of nanophase titania which increased osteoblast function was a large degree of nanometre surface features that mimicked bone. For this reason, nanophase materials deserve more attention in improving orthopaedic implant applications.

Porous tubular structures with controlled fibre orientation using a modified electrospinning method

Abstract: Electrospinning offers an avenue to produce small diameter tubes made out of nanofibres. However, to date, most tubes from electrospun fibres have been either random fibres or from sheets that were rolled into tubes. Although there have been suggestions of getting tubes made of circumferentially aligned fibres, this is the first time that a method used to create a tube made of diagonally aligned electrospun fibres has been described. This tube was formed by depositing fibres on a rotating tube during electrospinning to give a resultant tube with uniform thickness and superior all round mechanical strength without any line of weakness. A knife-edged auxiliary electrode was given a charge that was opposite to that of the charge given to the needle to create an electrostatic field that encouraged fibre alignment on a rotating tube collector. A tubular structure made of nanofibres aligned in a diagonal direction was produced through electrospinning.

Anti-reflective optical coatings incorporating nanoparticles

Abstract: This paper presents a simple approach for forming anti-reflective film stacks on plastic substrates employing aqueous colloidal dispersions of metal oxide nanoparticles. Results demonstrate that it is possible to fabricate a polymeric thin film of continuously tunable refractive index over a wide range by loading the film with varying concentrations of metal oxide nanoparticles. Specifically, the refractive index for the polymer film was tuned from 1.46 to 1.54 using silica nanoparticle loadings from 50 to 0 wt% and from 1.54 to 1.95 using ceria nanoparticle loadings from 0 to 90 wt%, respectively. The low and high refractive index layer sa re thencombined to create an anti-reflective coating which exhibits a reflectance spectrum, abrasion resistance, haze and transmission values that compare well with those produced using state-of-the-art vacuum based techniques. Furthermore, the results show that it is possible to begin with aqueous dispersions and then dilute them with organic solvents for use in a spin coating method to prepare the polymer–metal oxide nanoparticle composite films. (Some figures in this article are in colour only in the electronic version)

Polymeric worm micelles as nano-carriers for drug delivery.

Abstract: Nanoscale carriers of active compounds, especially drugs, need not be spherical in shape. Worm micelles as blends of degradable polylactic acid (PLA) and inert block copolymer amphiphiles were prepared for controlled release and initial study of carrier transport through nano-porous media. The loading capacity of a typical hydrophobic drug, Triamterene, and the release of hydrophobic dyes were evaluated together with morphological changes of the micelles. Degradation of PLA by hydrolysis led to the self-shortening of worms and a clear transition towards spherical micelles, correlating with the release of hydrophobic dyes. Perhaps equally important for application is the flexibility of worm micelles, which we show allows them to penetrate nanoporous gels where 100 nm sized vesicles cannot enter. Such gels have served as tissue models, and so the results here collectively suggest a new class of hydrophobic drug nano-carriers that are capable of tissue permeation as well as controlled release.

A low temperature combination method for the production of ZnO nanowires.

Abstract: The growth of large-area, patterned and oriented ZnO nanowires on silicon using a low temperature silicon?CMOS compatible process is demonstrated. Nanowire synthesis takes place using a thin nucleation layer of ZnO deposited by radiofrequency magnetron sputtering, followed by a hydrothermal growth step. No metal catalysts are used in the growth process. The ZnO nanowires have a wurtzite structure, grow along the c-axis direction and are distributed on the silicon substrate according to the pre-patterned nucleation layer. Room temperature PL measurements of the as-grown nanowires exhibit strong yellow?red emission under 325?nm excitation that is replaced by ultraviolet emission after annealing. This method can be used to integrate patterned 1D nanostructures in optoelectronic and sensing applications on standard silicon CMOS wafers.

Resonance analysis of multi-layered graphene sheets used as nanoscale resonators

Abstract: A stacked plate model for the vibration of multi-layered graphene sheets (MLGSs), in which the van der Waals (vdW) interaction between layers is described by an explicit formula, is presented. Explicit formulae are derived for predicting the natural frequencies of double- and triple-layered graphene sheets, and they clearly indicate the effect of vdW interaction on the natural frequencies. The natural frequencies are calculated for various numbers of layered graphene sheets, and the results show that the vdW interaction has no influence on the lowest natural frequency (classical frequency) of an MLGS but plays a significant role in all higher natural frequencies (resonant frequencies) for a given combination of m and n. The vibration modes that are associated with the classical frequencies for each sheet of an MLGS are identical. In contrast, the vibration modes that are associated with the resonant frequencies are non-identical and give various vibration patterns, which indicates that MLGSs are highly suited to use as high frequency resonators.

The determination of atomic force microscope cantilever spring constants via dimensional methods for nanomechanical analysis

Abstract: Many papers have been published on methods to determine the normal spring constant, kz, of atomic force microscope (AFM) cantilevers. This is necessary to calibrate force measurements in the AFM, which then lead to a wide variety of applications from measuring the rupture force of protein bonds to determining the Young's modulus of materials such as polymers at surfaces. Manufacturers' nominal values of kz have been found to be up a factor of two in error, therefore practical methods to calibrate kz are required. There are three main categories of methods, with some overlap, which we call: (1) dimensional, (2) static experimental and (3) dynamic experimental. Here, we consider the dimensional aspects of these methods involving the cantilever material properties and geometry. We do this via reviewing the analytical equations of seven publications and comparing them with finite element analysis (FEA) calculations. It is shown that the best analytical equations are those of Neumeister and Ducker but that these need a revision for the bending of the triangular portion of the V-shaped cantilever. This is done and the correlation with FEA is then excellent. Equations are also provided for the effect of a metallized layer and the imaging tip not being at the cantilever apex; these also agree with FEA. We evaluate the relevant uncertainties and provide recommendations as to the best equations to use together with relevant correction parameters based on the assumption that the FEA calculations are valid. We test this assumption elsewhere.

In vitro characterization of movement, heating and visualization of magnetic nanoparticles for biomedical applications

Abstract: Magnetic nanoparticles can be used for a variety of biomedical applications. They can be used in the targeted delivery of therapeutic agents in vivo, in the hyperthermic treatment of cancers, in magnetic resonance (MR) imaging as contrast agents and in the biomagnetic separations of biomolecules. In this study, a characterization of the movement and heating of three different types of magnetic nanoparticles in physiological systems in vitro is made in a known external magnetic field and alternating field respectively. Infra-red (IR) imaging and MR imaging were used to visualize these nanoparticles in vitro. A strong dependence on the size and the suspending medium is observed on the movement and heating of these nanoparticles. First, two of the particles (mean diameter d = 10 nm, uncoated Fe3O4 and d = 2.8 µm, polystyrene coated Fe3O4+γ-Fe2O3) did not move while only a dextran coated nanoparticle (d = 50 nm, γ-Fe2O3) moved in type 1 collagen used as an in vitro model system. It is also observed that the time taken by a collection of these nanoparticles to move even a smaller distance (5 mm) in collagen (~100 min) is almost ten times higher when compared to the time taken to move twice the distance (10 mm) in glycerol (~10 min) under the same external field. Second, the amount of temperature rise increases with the concentration of nanoparticles regardless of the microenvironments in the heating studies. However, the amount of heating in collagen (maximum change in temperature ΔTmax~9 °C at 1.9 mg Fe ml−1 and 19 °C at 3.7 mg Fe ml−1) is significantly less than that in water (ΔTmax~15 °C at 1.9 mg Fe ml−1 and 33 °C at 3.7 mg Fe ml−1) and glycerol (ΔTmax~13.5 °C at 1.9 mg Fe ml−1 and 30 °C at 3.7 mg Fe ml−1). Further, IR imaging provides at least a ten times improvement in the range of imaging magnetic nanoparticles, whereby a concentration of (0–4 mg Fe ml−1) could bevisualized as compared to (0–0.4 mg Fe ml−1) by MR imaging. Based on these in vitro studies, important issues and parameters that require further understanding and characterization of these nanoparticles in vivo are discussed.

Fabrication of nanostructures of polyethylene glycol for applications to protein adsorption and cell adhesion.

Abstract: A simple method was developed to fabricate polyethylene glycol (PEG) nanostructures using capillary lithography mediated by ultraviolet (UV) exposure Acrylate-containing PEG monomers, such as PEG dimethacrylate (PEG-DMA, MW = 330), were photo-cross-linked under UV exposure to generate patterned structures In comparison to unpatterned PEG films, hydrophobicity of PEG nanostructure modified surfaces was significantly enhanced This could be attributed to trapped air in the nanostructures as supported by water contact angle measurements Proteins (fibronectin, immunoglobulin, and albumin) and cells (fibroblasts and P19 EC cells) were examined on the modified surfaces to test for the level of protein adsorption and cell adhesion It was found that proteins and cells preferred to adhere on nanostructured PEG surfaces in comparison to unpatterned PEG films; however, this level of adhesion was significantly lower than that of glass controls These results suggest that capillary lithography can be used to fabricate PEG nanostructures capable of modifying protein and cell adhesive properties of surfaces

Preparation and characterization of γ-AlOOH nanotubes and nanorods

Abstract: A solution-phase reaction under hydrothermal conditions at relatively low temperature is first put forward for the preparation of ?-AlOOH nanotubes and nanorods, on the basis of the possible strategy that the 2D framework structure of ?-AlOOH containing lamellae could provide orientation for the growth of 1D nanostructures. X-ray diffraction?(XRD) patterns, transmission electronic microscope?(TEM) images, Fourier transform infrared?(FTIR) spectra, and photoluminescence?(PL) spectra were used to characterize the products. A possible formation mechanism of nanotubes and nanorods from lamellar precursor is proposed.

Preparation of biocatalytic nanofibres with high activity and stability via enzyme aggregate coating on polymer nanofibres

Abstract: We have developed a unique approach for the fabrication of enzyme aggregate coatings on the surfaces of electrospun polymer nanofibres. This approach employs covalent attachment of seed enzymes onto nanofibres consisting of a mixture of polystyrene and poly(styrene-co-maleic anhydride), followed by a glutaraldehyde (GA) treatment that cross-links additional enzyme molecules and aggregates from the solution onto the covalently attached seed enzyme molecules. These cross-linked enzyme aggregates, covalently attached to the nanofibres via the linkers of seed enzyme molecules, are expected to improve the enzyme activity due to increased enzyme loading, and also the enzyme stability. To demonstrate the principle, we coated α-chymotrypsin (CT) on nanofibres electrospun from a mixture of polystyrene and poly(styrene-co-maleic anhydride). The initial activity of CT-aggregate-coated nanofibres was nine times higher than nanofibres with just a layer of covalently attached CT molecules. The enzyme stability of CT-aggregate-coated nanofibres was greatly improved with essentially no measurable loss of activity over a month of observation under rigorous shaking conditions. This new approach of enzyme coating on nanofibres, yielding high activity and stability, creates a useful new biocatalytic immobilized enzyme system with potential applications in bioconversion, bioremediation, and biosensors.

Optical and electrochemical properties of nanosized NiO via thermal decomposition of nickel oxalate nanofibres

Abstract: Nickel oxide nanoparticles with an average diameter of about 9 nm were synthesized via thermal decomposition of NiC2O4 precursor at 450 °C. The nanoparticles were investigated using XRD, TEM, TGA, and UV–vis spectrophotometry. The optical absorption spectrum indicates that the NiO nanoparticles have a direct band gap of 3.56 eV. The electrochemical tests show that the ultrafine NiO nanoparticles, as a promising electrode material, can deliver a large reversible discharge capacity of about 610 mA h g−1.