Properties Of Nanoscale Materials Research Articles

Functional nanoscale biomolecular materials

Various approaches have been developed to exploit the functional properties of proteins and the structural properties of nanoscale materials. These range from biomolecule-nanomaterial hybrids and biocatalytically-generated self-assembled amphiphiles to protein-based structural templates. This commentary by Jonathan Dordick, discusses the article by Douglas Clark and colleagues, in which the authors report a study on the extremophilic protein γ-prefoldin (γPFD).

A superbright X-ray laboratory microsource empowered by a novel restoration algorithm

The properties of nanoscale materials vary with the size and shape of the building blocks, which can be measured by (grazing-incidence) small-angle X-ray scattering along with the mutual positions of the nanoparticles. The accuracy in the determination of such parameters is dependent on the signal-to-noise ratio of the X-ray scattering pattern and on the visibility of the interference fringes. Here, a first-generation-synchrotron-class X-ray laboratory microsource was used in combination with a new restoration algorithm to probe nanoscale-assembled superstructures. The proposed algorithm, based on a maximum likelihood approach, allows one to deconvolve the beam-divergence effects from data and to restore, at least partially, missing data cut away by the beam stopper. It is shown that the combination of a superbright X-ray laboratory microsource with the data-restoring method allows a virtual enhancement of the instrument brilliance, improving signal-to-noise ratio and fringe visibility and reaching levels of performance comparable to third-generation synchrotron radiation beamlines.

Quartz tuning fork-based frequency modulation atomic force spectroscopy and microscopy with all digital phase-locked loop

We present a platform for the quartz tuning fork (QTF)-based, frequency modulation atomic force microscopy (FM-AFM) system for quantitative study of the mechanical or topographical properties of nanoscale materials, such as the nano-sized water bridge formed between the quartz tip (~100 nm curvature) and the mica substrate. A thermally stable, all digital phase-locked loop is used to detect the small frequency shift of the QTF signal resulting from the nanomaterial-mediated interactions. The proposed and demonstrated novel FM-AFM technique provides high experimental sensitivity in the measurement of the viscoelastic forces associated with the confined nano-water meniscus, short response time, and insensitivity to amplitude noise, which are essential for precision dynamic force spectroscopy and microscopy.

The Use of Plasmon Spectroscopy and Imaging in a Transmission Electron Microscope to Probe Physical Properties at the Nanoscale

Valence EELS and energy-filtering TEM appear to be powerful tools to explore diverse nanoscale phenomena. The techniques enable real-time information on the band structure, bonding, dielectric and optical response and phase compositions of nanostructured materials. Furthermore, electron beam-induced excitations in the 0 to 50 eV energy loss range dominated by plasmons are sensitive to valence electron states primarily responsible for intrinsic materials properties. We used universality and scaling in relationships between the volume plasmon energy and cohesive energy, elastic moduli and hardness to derive analytical expressions for quantitative determination of the properties. Based on this approach, cohesive and elastic properties of metastable nanoprecipitates in structural alloys and hardness of diesel engine soot nanoparticles have been evaluated. Spatially-resolved plasmon spectroscopic imaging techniques offer possibilities to determine and image in situ multiple physical properties of nanoscale materials and to monitor their changes during dynamic transformations, thus establishing new capabilities for material research.

Generalized interface models for transport phenomena: Unusual scale effects in composite nanomaterials

The effective transport properties of heterogeneous nanoscale materials and structures are affected by several geometrical and physical factors. Among them, the presence of imperfect interfaces plays a central role being often at the origin of the scale effects. To describe real contacts between different phases, some classical schemes have been introduced in literature, namely the low and the high conducting interface models. Here, we introduce a generalized formalism, which is able to take into account the properties of both previous schemes and, at the same time, it implements more complex behaviors, already observed in recent investigations. We apply our models to the calculation of the effective conductivity in a paradigmatic structure composed of a dispersion of particles. In particular, we describe the conductivity dependence upon the size of the inclusions finding an unusual non-monotone scale effect with a pronounced peak at a given particle size. We introduce some intrinsic length scales governing the universal scaling laws.

Quantitative Determination of the Band Gap of WS2 with Ambipolar Ionic Liquid-Gated Transistors

We realized ambipolar field-effect transistors by coupling exfoliated thin flakes of tungsten disulfide (WS(2)) with an ionic liquid dielectric. The devices show ideal electrical characteristics, including very steep subthreshold slopes for both electrons and holes and extremely low OFF-state currents. Thanks to these ideal characteristics, we determine with high precision the size of the band gap of WS(2) directly from the gate-voltage dependence of the source-drain current. Our results demonstrate how a careful use of ionic liquid dielectrics offers a powerful strategy to study quantitatively the electronic properties of nanoscale materials.

Nonequilibrium Green’s function techniques in current–voltage calculations of nanoscale materials

Nonequilibrium Green’s function techniques are today a vital tool for investigating electrical properties of nanoscale materials. In this review paper, recent works addressed on comprehend nanomaterials have been reviewed. A brief description of the theoretical basis of nonequilibrium Green’s function and its application in deducing the current formula for a two probe model are given. Applications of nonequilibrium Green’s functions in hunting electronic transport properties of nanoscale materials have been presented. A short conclusion and prospects on two probe model calculations are discussed.

Quantum mechanics for nanostructures

The properties of new nanoscale materials, their fabrication and applications, as well as the operational principles of nanodevices and systems, are solely determined by quantum-mechanical laws and principles. This textbook introduces engineers to quantum mechanics and the world of nanostructures, enabling them to apply the theories to numerous nanostructure problems. The textbook covers the fundamentals of quantum mechanics, including uncertainty relations, the Schrodinger equation, perturbation theory, and tunneling. These are then applied to a quantum dot, the smallest artificial atom, and compared to hydrogen, the smallest atom in nature. Nanoscale objects with higher dimensionality, such as quantum wires and quantum wells, are introduced, as well as nanoscale materials and nanodevices. Numerous examples throughout the text help students to understand the material.

Tracer design for magnetic particle imaging (invited)

Magnetic particle imaging (MPI) uses safe iron oxide nanoparticle tracers to offer fundamentally new capabilities for medical imaging, in applications as vascular imaging and ultra-sensitive cancer therapeutics. MPI is perhaps the first medical imaging platform to intrinsically exploit nanoscale material properties. MPI tracers contain magnetic nanoparticles whose tunable, size-dependent magnetic properties can be optimized by selecting a particular particle size and narrow size-distribution. In this paper we present experimental MPI measurements acquired using a homemade MPI magnetometer: a zero-dimensional MPI imaging system designed to characterize tracer performance by measuring the derivative of the time-varying tracer magnetization, M'(H(t)), at a driving frequency of 25 kHz. We show that MPI performance is optimized by selecting phase-pure magnetite tracers of a particular size and narrow size distribution; in this work, tracers with 20 nm median diameter, log-normal distribution shape parameter, σ(v), equal to 0.26, and hydrodynamic diameter equal to 30 nm showed the best performance. Furthermore, these optimized MPI tracers show 4 × greater signal intensity (measured at the third harmonic) and 20% better spatial resolution compared with commercial nanoparticles developed for MRI.

Nanoscale materials for organohalide degradation via reduction pathways

AbstractThe unique chemical and physical properties of nanoscale materials have led to important roles in several scientific and technological fields. Environmental chemistry processes have benefited from the enhanced reactivity of nanoscale particles relative to their bulk counterparts with contaminants. Here, we describe recent advances in the synthesis and characterization of metallic and bimetallic nanoparticles that have been effective toward degrading toxic organohalide contaminants. We then review the degradation mechanisms involved in the reactions of nanoscale particles with organohalides via reduction pathways. We also discuss an emerging area – the degradation of organohalides via multi-electron transfer pathways.

BIOPHYSICAL APPLICATIONS OF SCANNING ION CONDUCTANCE MICROSCOPY (SICM)

Scanning probe microscopy (SPM) techniques represent one of the most promising approaches to probe the physical and chemical properties of nanoscale materials. The growing convergence of physics and biology has demanded nanotechnology tools to understand the fundamental physics of biological systems. Despite the advantages of SPM techniques, there have been challenges with its application to characterization of biological specimens. In recent times, the development of one class of SPM technique, scanning ion conductance microscopy (SICM), has overcome these limitations and enabled noninvasive, nanoscale investigation of live cells. In this review article, we present the theory behind the SICM operating principles and data modeling. Based on this framework, we discuss recent research advances where the SICM technique has proven technically superior. SICM applications discussed herein include imaging of cell topography, monitoring of live cell dynamics, mechanical stimulation of live cells, and surface patterning. Additional findings on the combination of SICM with other SPM techniques as well as patch clamp electrophysiology are presented in the context of building integrated knowledge on the structure and function of live cells. In summary, SICM bridges physics and biology to enable a range of important biomedical applications.

Femtosecond electron diffraction: Preparation and characterization of (110)-oriented bismuth films

Here, we present a new approach to synthesize (110)-oriented ultrathin membranes of bismuth (Bi). This rather exotic orientation was achieved by directing the growth through rationale control of lattice matching. Bi films were hetero-epitaxially grown on the (100)-surface of freshly cleaved potassium chloride crystals. The sample orientation was characterized by x-ray and electron diffraction. In addition, high quality free-standing films were obtained after dissolution of the substrate in water and controlled evaporation. Femtosecond electron diffraction (FED) was, therefore, used to monitor the coherent shear acoustic phonons in (110)-oriented free-standing Bi films produced by impulsive femtosecond optical excitation. The small de Broglie wavelength (flat Ewald sphere) of keV-electrons combined with an off-Bragg detection scheme provided a magnified view of shear atomic motions, i.e., lattice distortions in the transverse direction. All-optical pump-probe experiments are usually insensitive to shear displacements, a fact that makes FED a unique non-contact method to achieve the complete characterization of elastic properties of nanoscale materials.

Carbon nanohorn-based nanofluids: characterization of the spectral scattering albedo

The full characterization of the optical properties of nanofluids consisting of single-wall carbon nanohorns of different morphologies in aqueous suspensions is carried out using a novel spectrophotometric technique. Information on the nanofluid scattering and absorption spectral characteristics is obtained by analyzing the data within the single scattering theory and validating the method by comparison with previous monochromatic measurements performed with a different technique. The high absorption coefficient measured joint to the very low scattering albedo opens promising application perspectives for single-wall carbon nanohorn-based fluid or solid suspensions. The proposed approximate approach can be extended also to other low-scattering turbid media.PACS: 78.35.+c Brillouin and Rayleigh scattering, other light scattering; 78.40.Ri absorption and reflection spectra, fullerenes and related materials; 81.05.U- carbon/carbon-based materials; 78.67.Bf optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures, nanocrystals, nanoparticles, and nanoclusters.

The future of nanomedicine: Promises and limitations

The nascent field of nanomedicine has evoked enormous interest among physical and biological scientists and has already attracted hundreds of millions of dollars of research funding. The great appeal of nanomedicine lies in its promise of using the unique properties of nanoscale materials to address some of the most challenging problems of medical diagnosis and therapy. While some questions have been raised about the possible toxicities of nanomaterials, and about the ethical implications of applying these advanced, but undoubtedly expensive, technologies to medical practice, for the most part nanomedicine has enjoyed unalloyed enthusiasm from both its proponents in the research community and from policy makers. However, will the promise of nanomedicine actually be fulfilled? This paper discusses the internal intellectual culture of nanomedicine and how that gives rise to problems and contradictions that may slow its evolution and introduction into clinical practice.

Pine cone-mediated green synthesis of silver nanoparticles and their antibacterial activity against agricultural pathogens

The medicinal and physicochemical properties of nanoscale materials are strong functions of the particle size and the materials used in their synthesis. The nanoparticle shape also contributes significantly to their medicinal properties. Several shapes ranging from oval, spherical, rods, to teardrop structures may be obtained by chemical methods. Triangular and hexagonal nanoparticles have been synthesized by using a pine cone extract (PCE). Here, we report the discovery that PCE, when reacted with silver nitrate ions, yields a high percentage of thin, flat, single-crystalline nanohexagonal and nanotriangular silver nanoparticles. The nanohexagonal and nanotriangular nanoparticles appear to grow by a process involving rapid reduction with assembly at room temperature at a high pH. The nanoparticles were characterized by UV–Vis absorption spectroscopy, SEM-EDS, TEM, FTIR, and X-ray diffraction analyses. The anisotropy of the nanoparticle shape results in large near-infrared absorption by the particles. Highly anisotropic particles are applicable in various fields, including agriculture and medicine. The obtained silver nanoparticles (Ag NPs) had significant antibacterial action on both Gram classes of bacteria associated with agriculture. Because the Ag NPs are encapsulated with functional group-rich PCE, they can be easily integrated in various applications.

Structure and properties of nanoscale materials: theory and atomistic computer simulation

We present a review of a few research topics developed within the Theory and Atomistic Computer Simulation Department at CINaM. The bottom line of the scientific activity is to use up–to–date theoretical and computer simulation techniques to address physics and materials science problems, often at the nanometric scale, in close contact with experimental groups. It ranges from the study of the structure and properties of molecular systems for organic electronics to metallic clusters and alloys, magnetic oxides, nuclear fuels and carbon–based nanostructures. These studies are motivated by fundamental research questions as well as more applied goals including environmental and energy issues, or information technologies. This broad spectrum of activities requires a large range of techniques, from theory and ab initio calculations to semi–empirical models incorporated in Monte Carlo or molecular dynamics simulations.

Conformational changes of fibrinogen in dispersed carbon nanotubes

The conformational changes of plasma protein structures in response to carbon nanotubes are critical for determining the nanotoxicity and blood coagulation effects of carbon nanotubes. In this study, we identified that the functional intensity of carboxyl groups on carbon nanotubes, which correspond to the water dispersity or hydrophilicity of carbon nanotubes, can induce conformational changes in the fibrinogen domains. Also, elevation of carbon nanotube density can alter the secondary structures (ie, helices and beta sheets) of fibrinogen. Furthermore, fibrinogen that had been in contact with the nanoparticle material demonstrated a different pattern of heat denaturation compared with free fibrinogen as a result of a variation in hydrophilicity and concentration of carbon nanotubes. Considering the importance of interactions between carbon nanotubes and plasma proteins in the drug delivery system, this study elucidated the correlation between nanoscale physiochemical material properties of carbon nanotubes and associated structural changes in fibrinogen.

Quantum dots as liquid crystal dopants

Liquid crystal nanoscience, a field exploring the mutually beneficial combination of the unique properties of nanoscale materials and fluid, yet ordered liquid crystalline phases, is increasingly focusing on semiconductor quantum dots. In one major research thrust, the anisotropic properties of the liquid crystal host are sought to facilitate the assembly of quantum dots into arrays, in another, both size- and shape-dependent optical and electronic properties of quantum dots are used to manipulate optical, electro-optical and alignment properties of liquid crystalline materials. This feature article reviews recent accomplishments and new insights in this fascinating area of soft matter nanocomposites including work from our laboratory on a series of CdSe and CdTe quantum dots as additives in nematic liquid crystal hosts.

Determination of curcumin in turmeric using magnetic iron oxide nanoparticles as solid phase extractor and HPLC

Curcumin, a derivative of Curcuma longa L., is used extensively in the food industry and researches have shown the health benefits of this compound [1]. In this work, a novel, simple and rapid method for extraction and determination of curcumin in turmeric was performed using magnetic iron oxide nanopaticles (MIONs) as solid phase extractor and HPLC. The unique properties of nanoscale materials offer excellent prospects for designing new methods and instrumentation for chemical analysis [2]. The MIONs were synthesized according to the method proposed by Laurent et al. [3]. The average size of nanoparticles was in the range of 90nm which was determined by using atomic force microscopy (AFM) (Fig.1). Extraction of curcumin is based on adsorptionof Fe (3+)-curcumin complex on MIONs. Desorption of analyte was performed by NaOH solution containing methanol in order to dissolve the desorbed analyte. Various parameters affecting the extraction recovery such as: pH, volume and concentration of NaOH as desorbing reagent, and concentration of Fe (+3) and percentage of methanol were investigated and optimized. These optimized parameters were: pH=2.0, 1.5 mL of 0.2M NaOH containing 30% methanol and 0.1M of Fe (3+), respectively. The intra-day precision (R.S.D.) was 4.0% and inter-day R.S.D. was less than 7.0%. The preconcentration factor of 100 was achieved in this method. The proposed procedure has been successfully applied to the determination of curcumin in turmeric. Keywords: Curcumin, turmeric, Magnetic iron oxide nanoparticles, Solid phase extraction, Determination, HPLC

Simultaneous measurement of normal and friction forces using a cantilever-based optical interfacial force microscope

We measured normal and friction forces simultaneously using a recently developed cantilever-based optical interfacial force microscope technique for studies of interfacial structures and mechanical properties of nanoscale materials. We derived how the forces can be incorporated into the detection signal using the classical Euler equation for beams. A lateral modulation with the amplitude of nanometers was applied to create the friction forces between tip and sample. We demonstrated its capability by measuring normal and friction forces of interfacial water at the molecular scale over all distance ranges.