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At least 217 records · Page 12Linked to original sources
PubMed2006

Wing scale microstructures and nanostructures in butterflies--natural photonic crystals.

The aim of our study was to investigate the correlation between structural colour and scale morphology in butterflies. Detailed correlations between blue colour and structure were investigated in three lycaenid subfamilies, which represent a monophylum in the butterfly family Lycaenidae (Lepidoptera): the Coppers (Lycaeninae), the Hairstreaks (Theclinae) and the Blues (Polyommatinae). Complex investigations such as spectral measurements and characterization by means of light microscopy, scanning electron microscopy and transmission electron microscopy enabled us to demonstrate that: (i) a wide array of nanostructures generate blue colours; (ii) monophyletic groups use qualitatively similar structures; and (iii) the hue of the blue colour is characteristic for the microstructure and nanostructure of the body of the scales.

Animals↗
PubMed2006

The effects of fluoride on the nanostructure and surface pK of enamel crystals: an atomic force microscopy study of human and rat enamel.

Atomic force microscopy (AFM) studies have revealed 30-40 nm-wide regular positively charged bands across maturation-stage rat enamel crystals. Low pH resolved these into positively charged spherical domains of approximately 30 nm diameter. Crystal surface pK values from adhesion force titrations were approximately 6.5. The effect of fluoride on this pK value and on the nanostructure of fluorosed human enamel crystals has not been reported. The nanostructure and surface chemistry (pK) of normal and fluorotic human and of fluoride-treated rat maturing enamel crystals was examined. Enamel was sectioned and polished, prior to examination, using AFM in height and friction modes. High-resolution height images revealed 30 nm-diameter spherical domains within crystals, arranged as layers of hexagons or as a shallow spiral. Fluorotic enamel showed similar, but less well ordered, nanodomains. These could represent an arrangement of original initiation sites or binding sites for modulating matrix proteins. Surface pK was derived from adhesion-force measurements between functionalized tips (OH or COOH) and crystal surfaces between pH 2 and pH 10. pK values of approximately 6.5 for normal crystals were reduced to approximately 5.5 after fluoride treatment. Reduction in surface pK by fluoride might indicate lowered protonation with possible effects on matrix protein binding.

Amelogenesis↗
PubMed2006

In vivo efficacy of aerosolized nanostructured itraconazole formulations for prevention of invasive pulmonary aspergillosis.

Aerosolized evaporative precipitation into aqueous solution and spray freezing into liquid nanostructured formulations of itraconazole as prophylaxis significantly improved survival relative to commercial itraconazole oral solution and the control in a murine model of invasive pulmonary aspergillosis. Aerosolized administration of nanostructured formulations also achieved high lung tissue concentrations while limiting systemic exposure.

Aerosols↗
PubMed2005

Transport spectroscopy of chemical nanostructures: the case of metallic single-walled carbon nanotubes.

Transport spectroscopy, a technique based on current-voltage measurements of individual nanostructures in a three-terminal transistor geometry, has emerged as a powerful new tool to investigate the electronic properties of chemically derived nanostructures. In this review, we discuss the utility of this approach using the recent studies of single-nanotube transistors as an example. Specifically, we discuss how transport measurements can be used to gain detailed insight into the electronic motion in metallic single-walled carbon nanotubes in several distinct regimes, depending on the coupling strength of the contacts to the nanotubes. Measurements of nanotube devices in these different conductance regimes have enabled a detailed analysis of the transport properties, including the experimental determination of all Hartree-Fock parameters that govern the electronic structure of metallic nanotubes and the demonstration of Fabry-Perot resonators based on the interference of electron waves.

Biological Transport↗
PubMed2006

Synthesis of nanostructured bio-related materials by hybridization of synthetic polymers with polysaccharides or saccharide residues.

In the first part of this review, we describe the synthesis of nanostructured hybrid materials composed of polysaccharides and synthetic polymers. Amylose-synthetic polymer inclusion complexes were synthesized by amylose-forming polymerization using phosphorylase enzyme in the presence of synthetic polymers such as polyethers and polyesters. Alginate-polymethacrylate hybrid materials were prepared by free-radical polymerization of cationic methacrylate in the presence of sodium alginate. These methods allow the simultaneous control of the nanostructure with polymerization, giving well-defined hybrid materials. In the second part of this review, we describe the synthesis of novel glycopolymers with rigid structures. Polyaniline-based glycopolymers were synthesized by means of oxidative polymerization of N-glycosylaniline. Polysiloxane-based glycopolymers were prepared by means of introduction of sugar-lactone to the rodlike polysiloxane. These glycopolymers had regular higher-ordered structures due to their rigid polymer backbones, resulting in control of the three-dimensional array of sugar-residues.

Carbohydrate Conformation↗
PubMed2004

New hetero silicon-carbon nanostructure formation mechanism.

We report the formation of silicon and carbon hetero-nanostructures in an inductively coupled plasma system by a simultaneous growth/etching mechanism. Multi-walled carbon nanotubes were grown during one, three and five hour depositions, while tapered silicon nanowires were progressively etched. The carbon and silicon nanostructures and the interfaces between them were studied by electron microscopies and micro Raman spectroscopies. The potential of this method for large-scale controlled production of nano heterostructures without the requirement of a common catalyst is explored.

Carbon↗
PubMed2004

Shape and size control of ZnO nanostructures via a simple solution route.

ZnO nanostructures with different morphologies were synthesized by condensing the Zn(OH)4(2-) precursors under hydrothermal conditions in the presence of a surfactant, cetyltrimethylammonium bromide (CTAB). Shape and size control of ZnO nanostructures was achieved by relatively simple variations of molar ratio of CTAB to Zn(OH)4(2-). With a higher molar ratio, ZnO nanotubes were obtained, whereas with a lower molar ratio, ZnO nanorods were formed; furthermore, with a moderate w value, the coexistence of ZnO nanorods and nanotubes was also observed. The photoluminescence of ZnO nanorods and nanotubes was also investigated.

Cetrimonium↗
PubMed2005

Nanostructures in diatom frustules: functional morphology of valvocopulae in Cocconeidacean monoraphid taxa.

Nanopositioning is one of the most intriguing challenges in nanoelectronics and photonics. As the optoelectronic circuit components become more and more complex, the importance of nanopositioning becomes critical. For example, in single-mode fiber telecommunications it is easy to show that an alignment deviation as small as a few tens of nanometers can yield to 50 percent of loss performance. Diatoms are unicellular plants occurring in almost every aquatic environment. Their main morphological character is the frustule, a silica cell wall that consists of two valves, encasing the protoplasm, joined together by a girdle. The girdle is composed of a series of silica bands (copulae) linked together along their margins. In several diatom species, the first girdle bands (valvocopulae), which associate the valves with the rest of the girdle, appear different in shape and bring specific nanostructures devoted to facilitate this linkage. The species of the diatom family Cocconeidaceae show elaborate linkage systems between the valves in which functionally complex valvocopulae are involved. Different levels of complexity and functional efficiency are recognizable in the valve-valvocopula and valvocopula-valvocopula linkages of different cocconeidacean taxa. This work briefly reviews the morphological characteristics and the functional role of the nanostructures involved in the linkages; in fact, we firmly believe that they are stimulating models for design and manufacturing engineers working in the technological nanoworld.

Diatoms↗
PubMed2005

Nanophononics: phonon engineering in nanostructures and nanodevices.

Phonons, i.e., quanta of lattice vibrations, manifest themselves practically in all electrical, thermal and optical phenomena in semiconductors and other material systems. Reduction of the size of electronic devices below the acoustic phonon mean free path creates a new situation for phonon propagation and interaction. From one side, it complicates heat removal from the downscaled devices. From the other side, it opens up an exciting opportunity for engineering phonon spectrum in nanostructured materials and achieving enhanced operation of nanodevices. This paper reviews the development of the phonon engineering concept and discusses its device applications. The review focuses on methods of tuning the phonon spectrum in acoustically mismatched nano- and heterostructures in order to change the phonon thermal conductivity and electron mobility. New approaches for the electron-phonon scattering rates suppression, formation of the phonon stopbands and phonon focusing are also discussed. The last section addresses the phonon engineering issues in biological and hybrid bio-inorganic nanostructures.

Acoustics↗
PubMed2005

Nanostructured electrochemical sensors based on functionalized nanoporous silica for voltammetric analysis of lead, mercury, and copper.

We have successfully developed electrochemical sensors based on functionalized nanostructured materials for voltammetric analysis of toxic metal ions. Glycinylurea self-assembled monolayers on mesoporous silica (Gly-UR SAMMS) were incorporated in carbon paste electrodes for the detection of toxic metal ions such as lead, copper, and mercury based on adsorptive stripping voltammetry (AdSV). The electrochemical sensor yields a linear response at a low ppb level of Pb2+ (i.e., 2.5-50 ppb) after a 2-min preconcentration period, with reproducible measurements (%RSD = 3.5, N = 6) and an excellent detection limit (1 ppb). By exploiting the interfacial functionality of Gly-UR SAMMS, the sensor is selective for the target species, does not require the use of a mercury film, and can be easily regenerated in dilute acid solution. The rigid, open, parallel pore structure, combined with suitable interfacial chemistry of SAMMS, also results in fast analysis times (2-3 min). The nanostructured SAMMS materials enable the development of miniature sensing devices that are compact and low cost, have low energy consumption, and are easily integrated into field-deployable units.

Copper↗
PubMed2006

Measurement of light wavelength based on nanostructured ordered pore arrays.

A new method of light wavelength measurement is presented based on the nanostructured ordered pore arrays with multi-domains and centimeter square size formed by solution dipping-colloidal monolayer. Because of periodicity of the ordered pore arrays, perpendicular incidence of a parallel beam light on the array will lead to the diffraction spots or ring, depending on relative sizes of the beam and the domain in the arrays. The diffraction angle corresponds to wavelength of the incident light. On this basis, one can measure the wavelength of an incident light in transmission mode using such nanostructured ordered pore arrays, which is different from the conventional one fabricated from Michelson interference principle. Both the resolution and measurement precision can reach < 1 nm in such a simple method. Comparatively, this new measurement setup is simple in structure, low in cost, convenient in measurement, and especially, small in size. It could be used for online demarcation and real-time measurement of light wavelength in such as, mine operation, seabed exploration, and even space exploration due to its miniature.

Biophysics↗
PubMed2006

Multilayer enhanced gold film over nanostructure surface-enhanced Raman substrates.

We have developed a novel class of gold multilayer, surface-enhanced Raman scattering (SERS) substrates that are capable of enhancing SERS signals by 15.3-fold over conventional gold film over nanostructure (GFON) SERS substrates, making them comparable in sensitivity to optimized silver film over nanostructure (SFON) substrates, while providing the long-term stability obtained from gold. They are fabricated by depositing 10 A thick silver oxide islands on conventional GFON substrates, followed by deposition of a second continuous gold layer. The silver oxide layer acts as a dielectric spacer between the two continuous gold films and produces significantly enhanced SERS signals, as compared to optimized single layer substrates of the same geometry or comparable substrates prepared by deposition of silver islands that are not oxidized. In addition to the enhanced sensitivity of these multilayer substrates, they also exhibit long SERS active shelf-lives (i.e., months), with no measurable degradation in SERS enhancement, and relative standard deviations in SERS enhancement of less than 5.2% across the substrate's surface.

Coated Materials, Biocompatible↗
PubMed2005

Plasmonics-based nanostructures for surface-enhanced Raman scattering bioanalysis.

Surface-enhanced Raman scattering (SERS) spectroscopy is a plasmonics-based spectroscopic technique that combines modern laser spectroscopy with unique optical properties of metallic nanostructures, resulting in strongly increased Raman signals when molecules are adsorbed on or near nanometer-size structures of special metals such as gold, silver, and transition metals. This chapter provides a synopsis of the development and application of SERS-active metallic nanostructures, especially for the analysis of biologically relevant compounds. Some highlights of this chapter include reports of SERS as an immunoassay readout method, SERS gene nanoprobes, near-field scanning optical microscopy SERS probes, SERS as a tool for single-molecule detection, and SERS nanoprobes for cellular studies.

DNA↗
PubMed2006

Multiple diffusion mechanisms due to nanostructuring in crowded environments.

One of the key questions regarding intracellular diffusion is how the environment affects molecular mobility. Mostly, intracellular diffusion has been described as hindered, and the physical reasons for this behavior are: immobile barriers, molecular crowding, and binding interactions with immobile or mobile molecules. Using results from multi-photon fluorescence correlation spectroscopy, we describe how immobile barriers and crowding agents affect translational mobility. To study the hindrance produced by immobile barriers, we used sol-gels (silica nanostructures) that consist of a continuous solid phase and aqueous phase in which fluorescently tagged molecules diffuse. In the case of molecular crowding, translational mobility was assessed in increasing concentrations of 500 kDa dextran solutions. Diffusion of fluorescent tracers in both sol-gels and dextran solutions shows clear evidence of anomalous subdiffusion. In addition, data from the autocorrelation function were analyzed using the maximum entropy method as adapted to fluorescence correlation spectroscopy data and compared with the standard model that incorporates anomalous diffusion. The maximum entropy method revealed evidence of different diffusion mechanisms that had not been revealed using the anomalous diffusion model. These mechanisms likely correspond to nanostructuring in crowded environments and to the relative dimensions of the crowding agent with respect to the tracer molecule. Analysis with the maximum entropy method also revealed information about the degree of heterogeneity in the environment as reported by the behavior of diffusive molecules.

Biophysics↗
PubMed2006

Preparation, characterization and physico-chemical properties of solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC): their benefits as colloidal drug carrier systems.

Solid lipid nanoparticles (SLN) have attracted increasing attention by various research groups and companies since the early 1990s. Their advantages over existing traditional carriers have been clearly documented. In addition, modified SLN have been described which are nanostructured lipid carriers (NLC) composed of liquid lipid blended with a solid lipid to form a nanostructured solid particle matrix. NLC combine controlled release characteristics with some advantages over SLN. This paper reviews the production techniques, characterization and physical stability of these systems including destabilizing factors and principles of drug loading, then considers aspects and benefits of SLN and NLC as colloidal drug carriers.

Chemical Phenomena↗
PubMed2003

Higher-order organization by mesoscale self-assembly and transformation of hybrid nanostructures.

The organization of nanostructures across extended length scales is a key challenge in the design of integrated materials with advanced functions. Current approaches tend to be based on physical methods, such as patterning, rather than the spontaneous chemical assembly and transformation of building blocks across multiple length scales. It should be possible to develop a chemistry of organized matter based on emergent processes in which time- and scale-dependent coupling of interactive components generate higher-order architectures with embedded structure. Herein we highlight how the interplay between aggregation and crystallization can give rise to mesoscale self-assembly and cooperative transformation and reorganization of hybrid inorganic-organic building blocks to produce single-crystal mosaics, nanoparticle arrays, and emergent nanostructures with complex form and hierarchy. We propose that similar mesoscale processes are also relevant to models of matrix-mediated nucleation in biomineralization.

Journal Article↗
PubMed2003

Templateless assembly of molecularly aligned conductive polymer nanowires: a new approach for oriented nanostructures.

Although oriented carbon nanotubes, oriented nanowires of metals, semiconductors and oxides have attracted wide attention, there have been few reports on oriented polymer nanostructures such as nanowires. In this paper we report the assembly of large arrays of oriented nanowires containing molecularly aligned conducting polymers (polyaniline) without using a porous membrane template to support the polymer. The uniform oriented nanowires were prepared through controlled nucleation and growth during a stepwise electrochemical deposition process in which a large number of nuclei were first deposited on the substrate using a large current density. After the initial nucleation, the current density was reduced stepwise in order to grow the oriented nanowires from the nucleation sites created in the first step. The usefulness of these new polymer structures is demonstrated with a chemical sensor device for H(2)O(2), the detection of which is widely investigated for biosensors. Finally, we demonstrated that controlled nucleation and growth is a general approach and has potential for growing oriented nanostructures of other materials.

Journal Article↗
PubMed2004

A general atmospheric pressure chemical vapor deposition synthesis and crystallographic study of transition-metal sulfide one-dimensional nanostructures.

A series of transition-metal sulfide one-dimensional (1D) nanostructures have been synthesized by means of a general atmospheric pressure, chemical vapor deposition (APCVD) strategy. Vapour-liquid-solid (VLS) and vapour-solid (VS) mechanisms, along with the results of SEM and TEM observations, were used to explain the formation of these nanostructures. The regularity of the growth in the direction of the hexagonal nanowire is explored; we find that it prefers to grow along (1 0 0), (1 1 0), or (0 0 x) directions owing to particular crystal structures. The adopted synthetic route was expected to provide abundant useful 1D building blocks for the research of mesoscopic physics and fabrication of nanoscale devices.

Journal Article↗