Showing papers in "Nano Research in 2008"

Nano-Graphene Oxide for Cellular Imaging and Drug Delivery.

Abstract: Two-dimensional graphene offers interesting electronic, thermal, and mechanical properties that are currently being explored for advanced electronics, membranes, and composites. Here we synthesize and explore the biological applications of nano-graphene oxide (NGO), i.e., single-layer graphene oxide sheets down to a few nanometers in lateral width. We develop functionalization chemistry in order to impart solubility and compatibility of NGO in biological environments. We obtain size separated pegylated NGO sheets that are soluble in buffers and serum without agglomeration. The NGO sheets are found to be photoluminescent in the visible and infrared regions. The intrinsic photoluminescence (PL) of NGO is used for live cell imaging in the near-infrared (NIR) with little background. We found that simple physisorption via π-stacking can be used for loading doxorubicin, a widely used cancer drug onto NGO functionalized with antibody for selective killing of cancer cells in vitro. Owing to its small size, intrinsic optical properties, large specific surface area, low cost, and useful non-covalent interactions with aromatic drug molecules, NGO is a promising new material for biological and medical applications.

Raman spectroscopy and imaging of graphene

Abstract: Graphene has many unique properties that make it an ideal material for fundamental studies as well as for potential applications. Here we review recent results on the Raman spectroscopy and imaging of graphene. We show that Raman spectroscopy and imaging can be used as a quick and unambiguous method to determine the number of graphene layers. The strong Raman signal of single layer graphene compared to graphite is explained by an interference enhancement model. We have also studied the effect of substrates, the top layer deposition, the annealing process, as well as folding (stacking order) on the physical and electronic properties of graphene. Finally, Raman spectroscopy of epitaxial graphene grown on a SiC substrate is presented and strong compressive strain on epitaxial graphene is observed. The results presented here are highly relevant to the application of graphene in nano-electronic devices and help in developing a better understanding of the physical and electronic properties of graphene.

Controlled nanocutting of graphene

Abstract: Rapid pr ogress in graphene-based applications is calling for new processing techniques for creating graphene components with different shapes, sizes, and edge structures. Here we report a controlled cutting process for graphene sheets, using nickel nanoparticles as a knife that cuts with nanoscale precision. The cutting proceeds via catalytic hydrogenation of the graphene lattice, and can generate graphene pieces with specifi c zigzag or armchair edges. The size of the nanoparticle dictates the edge structure that is produced during the cutting. The cutting occurs along straight lines and along symmetry lines, defined by angles of 60o or 120o, and is defl ected at free edges or defects, allowing practical control of graphene nano-engineering.

A facile synthesis of monodisperse Au nanoparticles and their catalysis of CO oxidation

Abstract: Monodisperse Au nanoparticles (NPs) have been synthesized at room temperature via a burst nucleation of Au upon injection of the reducing agent t-butylamine-borane complex into a 1, 2, 3, 4-tetrahydronaphthalene solution of HAuCl4·3H2O in the presence of oleylamine. The as-synthesized Au NPs show size-dependent surface plasmonic properties between 520 and 530 nm. They adopt an icosahedral shape and are polycrystalline with multiple-twinned structures. When deposited on a graphitized porous carbon support, the NPs are highly active for CO oxidation, showing 100% CO conversion at −45 °C.

Bioconjugated silica nanoparticles: Development and applications

Abstract: Advanced bioanalysis, including accurate quantitation, has driven the need to understand biology and medicine at the molecular level. Bioconjugated silica nanoparticles have the potential to address this emerging challenge. Particularly intriguing diagnostic and therapeutic applications in cancer and infectious disease as well as uses in gene and drug delivery, have also been found for silica nanoparticles. In this review, we describe the synthesis, bioconjugation, and applications of silica nanoparticles in different bioanalysis formats, such as selective tagging, barcoding, and separation of a wide range of biomedically important targets. Overall, we envisage that further development of these nanoparticles will provide a variety of advanced tools for molecular biology, genomics, proteomics and medicine.

Charge transport in disordered graphene-based low dimensional materials

Abstract: Two-dimensional graphene, carbon nanotubes, and graphene nanoribbons represent a novel class of low dimensional materials that could serve as building blocks for future carbon-based nanoelectronics. Although these systems share a similar underlying electronic structure, whose exact details depend on confinement effects, crucial differences emerge when disorder comes into play. In this review, we consider the transport properties of these materials, with particular emphasis on the case of graphene nanoribbons. After summarizing the electronic and transport properties of defect-free systems, we focus on the effects of a model disorder potential (Anderson-type), and illustrate how transport properties are sensitive to the underlying symmetry. We provide analytical expressions for the elastic mean free path of carbon nanotubes and graphene nanoribbons, and discuss the onset of weak and strong localization regimes, which are genuinely dependent on the transport dimensionality. We also consider the effects of edge disorder and roughness for graphene nanoribbons in relation to their armchair or zigzag orientation.

Vertical nanowire array-based light emitting diodes

Abstract: Electroluminescence from a nanowire array-based light emitting diode is reported. The junction consists of a p-type GaN thin film grown by metal organic chemical vapor deposition (MOCVD) and a vertical n-type ZnO nanowire array grown epitaxially from the thin film through a simple low temperature solution method. The fabricated devices exhibit diode like current voltage behavior. Electroluminescence is visible to the human eye at a forward bias of 10 V and spectroscopy reveals that emission is dominated by acceptor to band transitions in the p-GaN thin film. It is suggested that the vertical nanowire architecture of the device leads to waveguided emission from the thin film through the nanowire array.

Two Distinct Fluorescent Quantum Clusters of Gold Starting from Metallic Nanoparticles by pH-Dependent Ligand Etching

Abstract: Two fluorescent quantum clusters of gold, namely Au25 and Au8, have been synthesized from mercaptosuccinic acid-protected gold nanoparticles of 4–5 nm core diameter by etching with excess glutathione. While etching at pH ∼3 yielded Au25, that at pH 7–8 yielded Au8. This is the first report of the synthesis of two quantum clusters starting from a single precursor. This simple method makes it possible to synthesize well-defined clusters in gram quantities. Since these clusters are highly fluorescent and are highly biocompatible due to their low metallic content, they can be used for diagnostic applications.

Energy harvesting for self-powered nanosystems

Abstract: In this article, an introduction is pr esented about the energy harvesting technologies that have potential for powering nanosystems. Our discussion mainly focuses on the approaches other than the well-known solar cell and thermoelectrics. We mainly introduce the piezoelectric nanogenerators developed using aligned ZnO nanowire arrays. This is a potential technology for converting mechanical movement energy (such as body movement, muscle stretching, blood pressure), vibration energy (such as acoustic/ultrasonic wave), and hydraulic energy (such as fl of body fl uid, blood fl ow, contraction of blood vessel, dynamic fl uid in nature) into electric energy for self-powered nanosystems.

A DNA-based approach to the carbon nanotube sorting problem

Abstract: Carbon nanotube sorting, i.e., the separation of a mixture of tubes into different electronic types and further into species with a specific chirality, is a fascinating problem of both scientific and technological importance. It is one of those problems that are easy to describe but difficult to solve. Single-stranded DNA forms stable complexes with carbon nanotubes and disperses them effectively in water. A particular DNA sequence of alternating guanine (G) and thymine (T) nucleotides ((GT) n , with n = 10 to 45) self-assembles into an ordered supramolecular structure around an individual nanotube, in such a way that the electrostatic properties of the DNA-carbon nanotube hybrid depend on tube structure, enabling nanotube separation by anion-exchange chromatography. This review provides a summary of the separation of metallic and semiconducting tubes, and purification of single (n, m) tubes using the DNA-wrapping approach. We will present our current understanding of the DNA-carbon nanotube hybrid structure and separation mechanisms, and predict future developments of the DNA-based approach.

Synthesis and Optical Properties of Cubic Gold Nanoframes.

Abstract: This paper describes a facile method of preparing cubic Au nanoframes with open structures via the galvanic replacement reaction between Ag nanocubes and AuCl2−. A mechanistic study of the reaction revealed that the formation of Au nanoframes relies on the diffusion of both Au and Ag atoms. The effect of the edge length and ridge thickness of the nanoframes on the localized surface plasmon resonance peak was explored by a combination of discrete dipole approximation calculations and single nanoparticle spectroscopy. With their hollow and open structures, the Au nanoframes represent a novel class of substrates for applications including surface plasmonics and surface-enhanced Raman scattering.

InAs/InP/ZnSe Core/Shell/Shell Quantum Dots as Near-Infrared Emitters: Bright, Narrow-Band, Non-Cadmium Containing, and Biocompatible.

Abstract: High quality InAs/InP/ZnSe core/shell/shell quantum dots have been grown by a one-pot approach. This engineered quantum dots with unique near-infrared (NIR) fluorescence, possessing outstanding optical properties, and the biocompatibility desired for in vivo applications. The resulting quantum dots have significantly lower intrinsic toxicity compared to NIR emissive dots containing elements such as cadmium, mercury, or lead. Also, these newly developed ultrasmall non-Cd containing and NIR-emitting quantum dots showed significantly improved circulation half-life and minimal reticuloendothelial system (RES) uptake.

Magnetic field-induced solvothermal synthesis of one-dimensional assemblies of Ni-Co alloy microstructures

Abstract: One-dimensional magnetic Ni-Co alloy microwires with different microstructures and differently shaped building blocks including spherical particles, multilayer stacked alloy plates, and alloy flowers, have been synthesized by an external magnetic field-assisted solvothermal reaction of mixtures of cobalt(II) chloride and nickel(II) chloride in 1, 2-propanediol with different NaOH concentrations. By adjusting the experimental parameters, such as precursor concentration and Ni/Co ratio, Ni-Co alloy chains with uniform diameters in the range 500 nm to 1.3 μm and lengths ranging from several micrometers to hundreds of micrometers can be obtained. A mechanism of formation of the one-dimensional assemblies of magnetic Ni-Co microparticles in a weak external magnetic field is proposed.

Random networks and aligned arrays of single-walled carbon nanotubes for electronic device applications

Abstract: Singled-walled carbon nanotubes (SWNTs), in the form of ultrathin films of random networks, aligned arrays, or anything in between, provide an unusual type of electronic material that can be integrated into circuits in a conventional, scalable fashion. The electrical, mechanical, and optical properties of such films can, in certain cases, approach the remarkable characteristics of the individual SWNTs, thereby making them attractive for applications in electronics, sensors, and other systems. This review discusses the synthesis and assembly of SWNTs into thin film architectures of various types and provides examples of their use in digital electronic circuits with levels of integration approaching 100 transistors and in analog radio frequency (RF) systems with operating frequencies up to several gigahertz, including transistor radios in which SWNT transistors provide all of the active functionality. The results represent important steps in the development of an SWNT-based electronics technology that could find utility in areas such as flexible electronics, RF analog devices and others that might complement the capabilities of established systems.

Wafer scale synthesis of dense aligned arrays of single-walled carbon nanotubes

Abstract: Here we present an easy one-step approach to pattern uniform catalyst lines for the growth of dense, aligned parallel arrays of single-walled carbon nanotubes (SWNTs) on quartz wafers by using photolithography or polydimethylsiloxane (PDMS) stamp microcontact printing (µCP). By directly doping an FeCl3/methanol solution into Shipley 1827 photoresist or polyvinylpyrrolidone (PVP), various catalyst lines can be well-patterned on a wafer scale. In addition, during the chemical vapor deposition (CVD) growth of SWNTs the polymer layers play a very important role in the formation of mono-dispersed nanoparticles. This universal and efficient method for the patterning growth of SWNTs arrays on a surface is compatible with the microelectronics industry, thus enabling of the fabrication highly integrated circuits of SWNTs.

Collective magnetic behavior of graphene nanohole superlattices

Abstract: We predict a new class of 2-D crystalline “bulk” magnets—the graphene nanohole (GNH) superlattices with each GNH acting like a “super” magnetic atom, using first principles calculations. We show that such superlattices can exhibit long-range magnetic order above room temperature, with a collective magnetic behavior governed by inter-NH spin spin interactions in additional to intra-NH spin ordering. Furthermore, magnetic semiconductors can be made by doping magnetic NHs into semiconducting NH superlattices. The possibility of engineering magnetic GNHs for storage media and spintronics applications is discussed.

Synthesis, Contact Printing, and Device Characterization of Ni-Catalyzed, Crystalline InAs Nanowires

Abstract: InAs nanowires have been actively explored as the channel material for high performance transistors owing to their high electron mobility and ease of ohmic metal contact formation. The catalytic growth of nonepitaxial InAs nanowires, however, has often relied on the use of Au colloids which is non-CMOS compatible. Here, we demonstrate the successful synthesis of crystalline InAs nanowires with high yield and tunable diameters by using Ni nanoparticles as the catalyst material on amorphous SiO2 substrates. The nanowires show superb electrical properties with field-effect electron mobility ~2700 cm2/Vs and ION/IOFF >103. The uniformity and purity of the grown InAs nanowires are further demonstrated by large-scale assembly of parallel arrays of nanowires on substrates via the contact printing process that enables high performance, “printable” transistors, capable of delivering 5 10 mA ON currents (~400 nanowires).

A unified geometric rule for designing nanomagnetism in graphene

Abstract: Based on the underlying graphene lattice symmetry and an itinerant magnetism model on a bipartite lattice, we propose a unified geometric rule for designing graphene-based magnetic nanostructures: spins are parallel (ferromagnetic (FM)) on all zigzag edges which are at angles of 0° and 120° to each other, and antiparallel (antiferromagnetic (AF)) at angles of 60° and 180°. The rule is found to be consistent with all the systems that have been studied so far. Applying the rule, we predict several novel graphene-based magnetic nanostructures: 0-D FM nanodots with the highest possible magnetic moments, 1-D FM nanoribbons, and 2-D magnetic superlattices.

Au/LaVO4 Nanocomposite: Preparation, characterization, and catalytic activity for CO oxidation

Abstract: The size of the gold particles is a very important parameter to get active catalysts. This paper reports a novel colloidal deposition method to prepare Au/LaVO4 nanocomposite catalyst with monodispersed Au colloids and uniform LaVO4 nanoplates in nonpolar solvent. Monodispersed Au colloids with tunable size (such as 2, 5, 7, 11, 13, and 16 nm) and LaVO4 nanocrystals with well-defi ned shapes were pre-synthesized assisted with oleic acid/amine. During the following immobilization process, the particle size and shape of Au and LaVO4 were nearly preserved. As-prepared Au/LaVO4 nanocomposite showed high catalytic activity for CO oxidation at room temperature. Since sizes of gold particles were well-defi ned before the immobilization process, size effect of gold particles was easy to be investigated and the results show that 5-nm Au/LaVO4 nanocomposite has the highest activity for CO oxidation. This synthetic method can be extended further for the preparation of other composite nanomaterials.

Concentration and preservation of very low abundance biomarkers in urine, such as human growth hormone (hGH), by Cibacron Blue F3G-A loaded hydrogel particles

Abstract: Urine is a potential source of diagnostic biomarkers for detection of diseases, and is a very attractive means of non-invasive biospecimen collection. Nonetheless, proteomic measurement in urine is very challenging because diagnostic biomarkers exist in very low concentration (usually below the sensitivity of common immunoassays) and may be subject to rapid degradation. Hydrogel nanoparticles functionalized with Cibacron Blue F3G-A (CB) have been applied to address these challenges for urine biomarker measurement. We chose one of the most difficult low abundance, but medically relevant, hormones in the urine: human growth hormone (hGH). The normal range of hGH in serum is 1 to 10 ng/mL but the urine concentration is suspected to be a thousand times less, well below the detection limit (50 pg/mL) of sensitive clinical hGH immunoassays. We demonstrate that CB particles can capture, preserve and concentrate hGH in urine at physiological salt and urea concentrations, so that hGH can be measured in the linear range of a clinical immunometric assay. Recombinant and cadaveric hGH were captured from synthetic and human urine, concentrated and measured with an Immulite chemiluminescent immunoassay. Values of hGH less than 0.05 ng/mL (the Immulite detection limit) were concentrated to 2 ng/mL, with a urine volume of 1 mL. Dose response studies using 10 mL of urine demonstrated that the concentration of hGH in the particle eluate was linearly dependent on the concentration of hGH in the starting solution, and that all hGH was removed from solution. Thus if the starting urine volume is 100 mL, the detection limit will be 0.1 pg/mL. Urine from a healthy donor whose serum hGH concentration was 1.34 ng/mL was studied in order detect endogenous hGH. Starting from a volume of 33 mL, the particle eluate had an hGH concentration of 58 pg/mL, giving an estimated initial concentration of hGH in urine of 0.175 pg/mL. The nanotechnology described here appears to have the desired precision, accuracy and sensitivity to support large scale clinical studies of urine hGH levels.

Demonstration of covalent sidewall functionalization of single wall carbon nanotubes by NMR spectroscopy: Side chain length dependence on the observation of the sidewall sp3 carbons

Abstract: Carboxylic acid-functionalized single walled carbon nanotubes (SWNTs) prepared via the reaction of an amino acid, NH2(CH2) n CO2H where n = 1 (glycine, GLY), 5 (6-aminohexanoic acid, AHA), 10 (11-aminoundecanoic acid, AUDA), with fluorinated single walled carbon nanotubes (F-SWNTs) have been characterized by MAS 13C NMR spectroscopy. The ease of observing the aliphatic CH2 groups and the resolution of the signal are dependent on the length of the amino acid’s aliphatic chain. We have proposed that where substituent chains are short (making NMR data collection difficult) chemical modification to extend the chain length should alleviate analysis problems. In this regard, we have investigated the esterification of the carboxylic acid termini. The amino acid-functionalized SWNTs were esterified with an appropriate alcohol to ensure parity of the overall substituent length, i.e., GLY-SWNT (C1) + 1-dodecanol (C12) = DOD-GLY-SWNT (1), AHA-SWNT (C5) + 1-octanol (C8) = OCT-AHA-SWNT (2), and AUDA-SWNT (C10) + 1-propanol (C3) = PRO-AUDA-SWNT (3). The 13C NMR shift for the sp3 nitrogen-substituted carbon atoms of the SWNT sidewall is observed at δ ≈ 75 ppm. Increasing the length of SWNT sidewall functional groups enhances the ability to observe the sidewall sp3 carbon. The methylene carbon signal intensity is less attenuated in the dipolar dephasing spectrum of the ester-functionalized SWNTs than their associated amino acid derivatives, suggesting more motional freedom of the side chain in the solid state. The confirmation of the dipolar dephasing spectral effects was assisted by the characterization of the ester of AUDA-SWNT with 1,3-propanediol: PPD-AUDA-SWNT (4).

Development of ultra-high density silicon nanowire arrays for electronics applications

Abstract: This article reviews our recent progress on ultra-high density nanowires (NWs) array-based electronics. The superlattice nanowire pattern transfer (SNAP) method is utilized to produce aligned, ultra-high density Si NW arrays. We fi rst cover processing and materials issues related to achieving bulk-like conductivity characteristics from 10 20 nm wide Si NWs. We then discuss Si NW-based fi eld-effect transistors (FETs). These NWs & NW FETs provide terrifi c building blocks for various electronic circuits with applications to memory, energy conversion, fundamental physics, logic, and others. We focus our discussion on complementary symmetry NW logic circuitry, since that provides the most demanding metrics for guiding nanofabrication. Issues such as controlling the density and spatial distribution of both p-and n-type dopants within NW arrays are discussed, as are general methods for achieving Ohmic contacts to both p-and n-type NWs. These various materials and nanofabrication advances are brought together to demonstrate energy effi cient, complementary symmetry NW logic circuits.

Computational Model of Edge Effects in Graphene Nanoribbon Transistors

Abstract: We present a semi-analytical model incorporating the effects of edge bond relaxation, the third nearest neighbor interactions, and edge scattering in graphene nanoribbon field-effect transistors (GNRFETs) with armchair-edge GNR (AGNR) channels. Unlike carbon nanotubes (CNTs) which do not have edges, the existence of edges in the AGNRs has a significant effect on the quantum capacitance and ballistic I-V characteristics of GNRFETs. For an AGNR with an index of m=3p, the band gap decreases and the ON current increases whereas for an AGNR with an index of m=3p+1, the quantum capacitance increases and the ON current decreases. The effect of edge scattering, which reduces the ON current, is also included in the model.

Bacteriophage M13 as a Scaffold for Preparing Conductive Polymeric Composite Fibers

Abstract: Using biological templates to build one-dimensional functional materials holds great pr omise in developing nanosized electrical devices, sensors, catalysts, and energy storage units. In this communication, we report a versatile assembly process for the preparation of water-soluble conductive polyaniline (PANi)/M13 composite nanowires by employing the bacteriophage M13 as a template. The surface lysine residues of M13 can be derivatized with carboxylic groups to improve its binding ability to the aniline; the resulting modifi ed M13 is denoted as m-M13. Highly negatively-charged poly(sulfonated styrene) was used both as a dopant acid and a stabilizing agent to enhance the stability of the composite fi bers in aqueous solution. A transparent solution of the conductive PANi/m-M13 composite fi bers can be readily obtained without any further purifi cation step. The fi bers can be easily fabricated into thin conductive fi lms due to their high aspect ratio and good solubility in aqueous solution. This synthesis discloses a unique and versatile way of using bionanorods to produce composite fi brillar materials with narrow dispersity, high aspect ratio, and high processibility, which may have many potential applications in electronics, optics, sensing, and biomedical engineering.

In situ TEM measurements of the mechanical properties and behavior of WS2 nanotubes

Abstract: The mechanical properties of individual WS2 nanotubes were investigated and directly related to their atomic structure details by in situ transmission electron microscope measurements. A brittle mode deformation was observed in bending tests of short (ca. 1 μm in length) multilayer nanotubes. This mode can be related to the atomic structure of their shells. In addition, longer nanotubes (6-7μm in length) were deformed in situ scanning electron microscope, but no plastic deformation was detected. A “sword-in-sheath” fracture mechanism was revealed in tensile loading of a nanotube, and the sliding of inner shells inside the outermost shell was imaged “on-line”. Furthermore, bending modulus of 217 GPa was obtained from measurements of the electric-fieldinduced resonance of these nanotubes.

Shape control of doped semiconductor nanocrystals (d-dots)

Abstract: Formation of Mn2+-doped ZnSe quantum dots (Mn:ZnSe d-dots) with both branched and nearly spherical shapes has been studied. Structure analysis indicates that the Mn2+ dopants were localized in the core of a branched nanocrystal. The growth of branched d-dots, rather than spherical ones, was achieved by simply varying the concentration of two organic additives, fatty acids, and fatty amines. The photoluminescence properties of the branched nanocrystals were explored and compared with those of the nearly spherical particles.

On the growth mechanism of nickel and cobalt nanowires and comparison of their magnetic properties

Abstract: Magnetic nanowires (NWs) are ideal materials for the fabrication of various multifunctional nanostructures which can be manipulated by an external magnetic field. Highly crystalline and textured nanowires of nickel (Ni NWs) and cobalt (Co NWs) with high aspect ratio (∼330) and high coercivity have been synthesized by electrodeposition using nickel sulphate hexahydrate (NiSO4·6H2O) and cobalt sulphate heptahydrate (CoSO4·7H2O) respectively on nanoporous alumina membranes. They exhibit a preferential growth along 〈110〉. A general mobility assisted growth mechanism for the formation of Ni and Co NWs is proposed. The role of the hydration layer on the resulting one-dimensional geometry in the case of potentiostatic electrodeposition is verified. A very high interwire interaction resulting from magnetostatic dipolar interactions between the nanowires is observed. An unusual low-temperature magnetisation switching for field parallel to the wire axis is evident from the peculiar high field M(T) curve.

A nano- and micro- integrated protein chip based on quantum dot probes and a microfluidic network

Abstract: A novel nano- and micro-integrated protein chip (NMIPC) that can detect proteins with ultrahigh sensitivity has been fabricated. A microfluidic network (mu FN) was used to construct the protein chips, which allowed facile patterning of proteins and subsequent biomolecular recognition. Aqueous phase-synthesized, water-soluble fluorescent CdTe/CdS core-shell quantum dots (aqQDs), having high quantum yield and high photostability, were used as the signaling probe. Importantly, it was found that aqQDs were compatible with microfluidic format assays, which afforded highly sensitive protein chips for cancer biomarker assays.

Elasticity, strength and resilience: A comparative study on mechanical signatures of α-Helix, β-sheet and tropocollagen domains

Abstract: In biology, structural design and materials engineering is unified through formation of hierarchical features with atomic resolution, from nano to macro. Three molecular building blocks are particularly prevalent in all structural protein materials: alpha helices (AHs), beta-sheets (BSs) and tropocollagen (TC). In this article we present a comparative study of these three key building blocks by focusing on their mechanical signatures, based on results from full-atomistic simulation studies. We find that each of the basic structures is associated with a characteristic material behavior: AH protein domains provide resilience at large deformation through energy dissipation at low force levels, BS protein domains provide great strength under shear loading, and tropocollagen molecules provide large elasticity for deformation recovery. This suggests that AHs, BSs, and TC molecules have mutually exclusive mechanical signatures. We correlate each of these basic properties with the molecule’s structure and the associated fundamental rupture mechanisms. Our study may enable the use of abundant protein building blocks in nanoengineered materials, and may provide critical insight into basic biological mechanisms for bio-inspired nanotechnologies. The transfer towards the design of novel nanostructures could lead to new multifunctional and mechanically active, tunable, and changeable materials.

Preparation of monodisperse Se colloid spheres and Se nanowires using Na2SeSO3 as precursor

Abstract: Nearly monodisperse spherical amorphous Se colloids are prepared by the dismutation of Na2SeSO3 solution at room temperature; by altering the pH of the solution, amorphous Se colloid spheres with sizes of about 120 nm, 200 nm, 300 nm, and 1 µm can be obtained. Se@Ag2Se core/shell spheres are successfully synthesized by using the obtained amorphous Se (a-Se) spheres as templates, indicating the potential applications of these Se nanomaterials in serving as soft templates for other selenides. Meanwhile, selenium nanowires are obtained through a “solid-solution-solid” growth process by dispersing the prepared Se spheres in ethanol. This simple and environmentally benign approach may offer more opportunities in the synthesis and applications of nanocrystal materials.