Nano

To repair bone defects, an important approach is to fabricate tissue engineering scaffolds as substitutions to replace auto-/allologous bones. Currently, processing a biomaterial into three-dimensional porous scaffolds and incorporating the calcium phosphate (Ca–P) nanoparticles into scaffolds profile two main characteristics of bone tissue engineering scaffolds. Based on this fact, in this paper we describe the design principles of the Ca–P nanoparticle-based and porous bone tissue engineering scaffolds. Then we summarize a variety of the Ca–P nanoparticle-based scaffolds, including discussion of the integration of the Ca–P nanoparticles with ceramics and polymers, followed by introduction of safety of the Ca–P nanoparticles in scaffolds.

Designing self-assembling peptides as nanomaterials has been an attractive strategy in recent years, however, these peptides were usually studied in aqueous solutions for their self-assembling behaviors and applications. In this study, we have designed a surfactant-like peptide AGD with a wedge-like shape and studied its self-assembling behaviors in aqueous solution or nonpolar system. By analyzing the intermolecular hydrogen bond using FT-IR and characterizing the nanostructures with DLS, AFM and TEM, it was confirmed that AGD could not undergo self-assembly in aqueous solution while could self-assemble into well-ordered nanorings in nonpolar system. A molecular model has been proposed to explain how the nanorings were formed in the manner of reversed micelle. These results suggested a novel strategy to fabricate self-assembling peptide nanomaterials in nonpolar system, which could have potential applications in many fields.

In this work, stable and well dispersed colloidal Au/TiO₂ binary nanoparticles (NPs) were synthesized initially. Meanwhile, they were immobilized simultaneously on colloidal carbon spheres (CSs), one of popular hard templates, to prepare hybrid self-assembly nanostructures. The morphology and crystal structure of these nanocomposites (NCs) were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), thermogravimetric (TGA) and N₂ sorption analysis. By controlling the NPs size, ratio of Au/TiO₂ NPs, process temperature and time, and concentration of surfactants (e.g., MPA), Au/TiO₂@CSs NCs could be tailored into core-shell nanostructures with various surface coverages of Au NPs and/or TiO₂NPs. Interestingly, hollow spheres with a binary-nanoparticle monoshell could be achieved by calcinations of typical Au/TiO₂@CSs NCs. In principle, these novel hybrid nanostructures with controllable functionality and high-surface-area traits could be very promising photocatalysts for waste water treatment.

Time-dependent wet-processing of HiPCo nanotubes in ~ 0.5 M phosphoric acid and its effect on the structural, transport, infrared light absorption and photoconduction characteristics have been studied. Nanotubes were treated for nominal time intervals of 1, 2 and 3 h. The treatment is found to be a two-step process that initially results in the removal/partial replacement of most pre-existing C-O, O–H and CH_x groups with phosphorous oxy and carbonyl groups. According to T-dependent current–voltage measurements, the differential conductance, G of nanotube network varies with temperature as ~ T^a, with a exhibiting a slight increase as a result of the treatment, attributed to a slight increase in disorder and not doping effects. The nanotubes processed for three hours also show an order of magnitude improvement in photoconduction response time compared to that of untreated tubes, with growth/decay characteristic time constants approaching a sub-second range.

The magnetic control on scattering of light by ultrafine iron oxide (γ-Fe₂O₃) nanoparticles suspended in a carrier liquid was investigated. The light scattering behavior was studied using laser light under the influence of a permanent magnet over a rotating frame of reference. When the magnet is rotated continuously from 0° to 360° with respect to the direction of the incident laser beam, the scattered light pattern from the sample has the same angular displacement but in counter direction to the magnetic field rotation. When external field is not applied to the ferrofluid, no other preferred directional scattering of light is observed. The applied magnetic field induces directional self assembly of magnetic nanoparticles through dipole–dipole interactions. This finally leads to the formation of "nanoparticle grating" and the optical geometry of diffraction grating clearly describes the anomalous scattering behavior of the ferrofluid. Most interestingly, for each complete orientation of the field from 0° to 360°, the transmitted light intensity switches between maxima and minima for longitudinal and transverse applied magnetic fields.

We report on the growth of Co-doped ZnO nanowires (NWs) on Si substrate using a self-catalytic vapor deposition method from a Co-doped ZnO nanopowder source and study its structural, optical and magnetic properties for the as-grown and rapid thermal annealed samples. Co (5%)-doped ZnO (ZnCoO) nanoparticles (NPs) are used as source material for the growth process. Electron microscopy imaging clearly reveals the formation of long ZnO NWs with uniform diameter. X-ray diffraction analysis confirms the single crystalline hexagonal structure of Co-doped ZnO NWs without impurities of metallic cobalt or other phases. Micro-Raman studies of doped samples show doping/disorder induced additional modes as compared to the undoped ZnO. Room temperature photoluminescence spectra of the doped ZnO NWs show strong emission band at ~380 nm and no significant emission was observed in the visible region indicating low defect content in the NWs. The field dependent magnetization (M–H curve) measured at room temperature exhibits paramagnetic nature for the NWs with the magnetic moment in the range 2–3.7 milli-emu/cm² for the applied field of 2 Tesla, while the source ZnCoO NPs exhibit room temperature ferromagnetism with saturation magnetization ~6 emu/g. Possible mechanism of alteration in magnetic behavior in doped NWs are discussed based on the growth conditions and role of defects.

The feasibility of the Boron Nitride Nanotubes (BNNTs) as nanomechanical resonators, using continuum mechanics based approach and finite element method (FEM) is illustrated in this paper. Two types of end constraints of single walled boron nitride nanotubes (SWBNNTs), namely cantilevered and bridged are assumed. Analytical formulas based on continuum mechanics are used to examine the mass sensitivity of SWBNNTs considering as a thin wall tubes for both types of end constraints for different lengths and different diameters. The FEM analysis, considering SWBNNT as a transversely anisotropic material is performed and results are compared with the continuum mechanics based approach. The results indicated that the mass sensitivity of SWBNNT-based nanomechanical resonators can reach 10^-8 fg and a logarithmically linear relationship exists between the resonant frequency and the attached mass, when mass is larger than 10^-7 fg. The sensitivity of resonant frequency shift to both tube length and diameter has also been demonstrated. It is clear that the change in resonant frequency shift to tube length is more significant than that with the tube diameter and mass sensitivity increases when smaller size nanotube resonators are used in mass sensors. The simulation results based on present FEM found in good agreement with the analytical approach.

In this work manganese dioxide (Ramsdellite-MnO₂) was synthesized at room temperature using a facile electrochemical method. X-ray diffraction (XRD) was used to identify the type and the size of the crystal particle, while field emission scanning electron microscopy (FESEM) and energy filtered transmission electron microscopy (EFTEM) were used to show and identify the morphology of the particles and changes of their morphologies with the increase of reaction times. Fourier transform infrared (FTIR) spectroscopy confirmed the Mn–O bond. Results from XRD showed that optimum time for synthesis Ramsdellite-MnO₂ was 9 h. The results of EFTEM showed a mixture of nanospheres and nanorods after 9 h reaction time while a homogenous morphology of nanospheres was detected at 12 h reaction time. Results confirmed on the existence of a correlation between the reaction time and the resulting nanostructures. Moreover, the EFTEM result showed that average particle size for 12 h was (25 ± 7 nm). The variation of calculated specific capacitance (F/g) versus the different scan rate has indicated that the efficiency of synthesized Ramsdellite-MnO₂ nanostructures in 12 h reaction time was superior to 9 h.

This paper presents a detailed investigation of the effects of piezoelectricity, spontaneous polarization and charge density on the electronic states and the quasi-Fermi level energy in wurtzite-type semiconductor heterojunctions. This has required a full solution to the coupled Schrödinger–Poisson–Navier model, as a generalization of earlier work on the Schrödinger–Poisson problem. Finite-element-based simulations have been performed on a AlN/GaN quantum well by using both one-step calculation as well as the self-consistent iterative scheme. Results have been provided for field distributions corresponding to cases with zero-displacement boundary conditions and also stress-free boundary conditions. It has been further demonstrated by using four case study examples that a complete self-consistent coupling of electromechanical fields is essential to accurately capture the electromechanical fields and electronic wavefunctions. We have demonstrated that electronic energies can change up to approximately 0.5 eV when comparing partial and complete coupling of electromechanical fields. Similarly, wavefunctions are significantly altered when following a self-consistent procedure as opposed to the partial-coupling case usually considered in literature. Hence, a complete self-consistent procedure is necessary when addressing problems requiring more accurate results on optoelectronic properties of low-dimensional nanostructures compared to those obtainable with conventional methodologies.

The composites of graphene oxide/Fe₂O₃-nanotubes (GO/Fe₂O₃-NTs) have been fabricated through a facile one-step hydrothermal method. Fe₂O₃-NTs crystallines were homogeneously distributed on GO, which have been confirmed by transmission electron microscopy analysis (TEM). The structure, composition and electrochemical properties of GO/Fe₂O₃-NTs composites were investigated by means of selective-area electron diffraction (SAED), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Raman spectra, cyclic voltammogram (CV) curves and galvanostatic charge–discharge curves. GO/Fe₂O₃-NTs composites exhibit a high specific capacitance of 133.2 Fg^-1 in 1 M Li₂SO₄ electrolyte. In addition, the GO/Fe₂O₃-NTs composites electrode shows good long-term cycle stability (only 9% decrease of the specific capacitance is observed after 1000 charge–discharge cycles).