Nanostructure Sample Research Articles

High-performance electrode materials for supercapacitor applications using Ni-catalyzed carbon nanostructures derived from biomass waste materials

Herein, nanostructured nickel metal, oxide, and oxyhydroxides have been successfully grown on various types of carbon nanostructures (CNS) via a simple, low cost and eco-friendly route derived from biomass waste materials. Nickel oxide and oxyhydroxide phases could be detected in the roasted precursor materials before pyrolysis as confirmed by X-ray diffraction (XRD) analysis. Transmission electron microscopy (TEM) images showed that these samples were composed mainly of porous amorphous carbon nanostructures. Whereas nickel-metal and nickel oxyhydroxide were the predominant detected phases after pyrolysis in addition to the graphite and carbon phases in the form of carbon nanotubes as confirmed by XRD analysis and TEM investigation, respectively. These composites were explored as potential electrodes for supercapacitor application delivering satisfactory specific capacitance values beside its remarkable charge/discharge reversibility. Among them, the formed porous amorphous carbon nanostructure sample decorated with NiO species displayed the highest capacitive performance. This sample delivered a specific capacitance of 508 F g−1 at 1 A g−1. Moreover, the cycling stability behavior of this sample at 5 A g−1 delivered 78% of its initial capacity after 3000 GCD cycles. The obtained results suggested that the prepared materials are a promising candidate as electrode material for energy storage applications.

Super-resolution imaging of plasmonic nanostructures by microsphere-assisted microscopy.

We fabricate both triangularly and circularly shaped Au, Ag, and Cr nanoparticle arrays and observe the imaging properties of these plasmonic nanostructures by BaTiO3 glass (BTG) microsphere-assisted microscopy. We experimentally find that the resolution of triangularly shaped Ag nanoparticle arrays is higher than that of Au and Cr ones, and a gap resolution of ∼λ/7.7 is demonstrated for the circularly shaped Au, Ag, and Cr nanostructures. Numerical simulations show that when a fully immersed BTG microsphere is dispersed on the surface of a plasmonic nanostructure sample, an enhanced electric field is generated in the vicinity of the sample, especially at the gap of the microsphere and the sample, due to the focusing effect of the microsphere and the excitation of localized surface plasmon resonance in the plasmonic nanostructure. The enhanced electric field in Ag nanostructures is significantly stronger than that in Au and Cr ones. Besides, the microsphere collects, amplifies, and propagates the enhanced near-field information to the far field, resulting in the improvement of imaging resolution.

A comparative dosimetric study between silicon activated aluminum-based nanocrystal and its corresponding glass system structure

Si-doped Na5Ca2AlP4O16 nanophosphor was prepared using sol-gel method and then characterized by both X-ray diffraction (XRD) and transmission electron microscope (TEM). The distribution uniformity of the associate elements was confirmed using SEM-EDX mapping. A comparative dosimetric study between this prepared sample and a glass system based on aluminum oxide with the same constituents [(500 ppm Si-doped 15Al2O3-35 P2O5–25CaO–25Na2CO3, in mol. % (abbreviated by APCNSi5)] was achieved. The effective atomic number (Zeff) of both matrices were calculated and found to be 10.6 and 11 for nanophosphor and APCNSi5 samples, respectively. Both values approached that of natural bone. The Energy Dependence (ED) of the two samples was calculated and the nanophosphor sample behaved much better, specially in the energy range 0.1–20 MeV. Thermoluminescent (TL) response of the Na5Ca2AlP4O16: Si4+ nanophosphor is found to be 2.52 times that of glass system APCNSi5. TL property study of prepared samples showed that nanostructure sample had an excellent dose-response linearity up to 40 Gy γ-doses, while linearity up to only 20 Gy was recorded with APCNSi5 sample. In addition, the minimum detectable dose values (MDDs) were found to be 0.05 and 6 mGy for Na5Ca2AlP4O16: Si4+ and APCNSi5 samples, respectively. The important features of the work presented herein are that an efficient good dosimeter depends mainly on: (a) careful choice of its constituents (b) the recognition of the processes that underlie the formation of its particular structures.

Synthesis and characterization of novel ferrite–piezoelectric multiferroic core–shell-type structure

Hybrid ferromagnetic/piezoelectric core–shell nanoparticles and ceramics have potential for a wide range of applications due to their tunability, electronic and magnetic properties. In this study, we designed a core–shell-type nanostructure of composition CoFe2O4/BNT-BT0.08, where BNT-BT0.08 is the abbreviation of bismuth, sodium titanate (Bi0.5Na0.5TiO3, BNT) doped with 8 mol% barium titanate (BaTiO3, BT). This multiferroic composite was prepared by covering CoFe2O4 nanoparticles with a shell of BNT-BT0.08 using the sol–gel technique. Scanning and transmission electron microscopy confirmed formation of a core–shell structure. The results of microstructure, dielectric, piezoelectric and magnetic investigations demonstrated that this heterostructure shows simultaneously electrical and magnetic behavior, at room temperature. XRD pattern of core–shell composite CoFe2O4/BNT-BT0.08 powder reveals only cubic CoFe2O4 and rhombohedral Bi0.5Na0.5TiO3 phases. CoFe2O4/BNT-BT0.08 core–shell nanostructure sample shows high values of permittivity (e ≥ 600) together with high dielectric losses (tan δ ≥ 1) in the low-frequency range (ν ≤ 104 Hz). PFM and polarization hysteresis indicated a ferroelectric domains structure and remnant polarization of ~ 2.6 µC/cm2 for the ceramics pellets samples of CoFe2O4/BNT-BT0.08. The present study reveals the possibility of coating nanoparticles onto nanometer-sized core particles, using controlled sol–gel process, in order to prepare multifunctional core–shell composites for piezoelectric and magnetoelectronic sensors.

Thermoluminescence properties of micro and nano structure hydroxyapatite after gamma irradiation

Abstract The goal of this study is to compare the thermoluminescence properties of nano and micro structure hydroxyapatite. Nano structure hydroxyapatite was synthesized via hydrolysis method, while the micro structure one was from Merck Company. X-ray diffraction and fourier transform infrared spectroscopy were used to determine the crystal structure and chemical composition of the hydroxyapatite samples. Particles sizes of each sample were estimated using Scherer equation and transmission electron microscopy system. Thermoluminescence properties of the samples were investigated under gamma irradiation. The glow curves of micro and nano structure samples show a peak at 150 °C and 200 °C, respectively. Thermoluminescence responses of both the samples were linear in the range of 25 – 1 000 Gy where, nano structure sample show a greater slope and stronger linearity in comparison to the micro sample. The results show that the thermoluminescence response of micro sample faded rapidly in comparison to the nano sample due to the existence of the peak at higher temperature.

A four-probe thermal transport measurement method for nanostructures.

Several experimental techniques reported in recent years have enabled the measurement of thermal transport properties of nanostructures. However, eliminating the contact thermal resistance error from the measurement results has remained a critical challenge. Here, we report a different four-probe measurement method that can separately obtain both the intrinsic thermal conductance and the contact thermal resistance of individual nanostructures. The measurement device consists of four microfabricated, suspended metal lines that act as resistive heaters and thermometers, across which the nanostructure sample is assembled. The method takes advantage of the variation in the heat flow along the suspended nanostructure and across its contacts to the four suspended heater and thermometer lines, and uses sixteen sets of temperature and heat flow measurements to obtain nine of the thermal resistances in the measurement device and the nanostructure sample, including the intrinsic thermal resistance and the two contact thermal resistances to the middle suspended segment of the nanostructure. Two single crystalline Si nanowires with different cross sections are measured in this work to demonstrate the effectiveness of the method. This four-probe thermal transport measurement method can lead to future discoveries of unique size-dependent thermal transport phenomena in nanostructures and low-dimensional materials, in addition to providing reliable experimental data for calibrating theoretical models.

Fabrication, structure and hydrogen-gas-sensing properties of multiple networked GaN nanostructure gas sensors

The controlled synthesis of nanostructures with different shapes and morphologies has attracted considerable interest because the sensing properties of nanostructures depend on their structure, shape, phase, size, and size distribution, as well as their composition. This paper compares the responses of GaN nanostructures with different morphologies to hydrogen. The underlying mechanism for the hydrogen gas sensing of the multiple networked GaN nanowire sensor can be explained based on the well-established surface depletion model. On the other hand, the difference between two different samples, the GaN nanostructure sample synthesized at 1,100 °C and that synthesized at 1,000 °C, could be explained as follows: The major process behind the interaction between the nanostructures and hydrogen is the chemisorption of the dissociated hydrogen on the GaN surface. The chemisorption creates an electron accumulation layer on the GaN surface that enhances its electrical conductance. The GaN nanostructure sample synthesized at 1,100 °C with a higher ammonia flow rate showed a higher response to H2 gas than that synthesized at 1,000 °C with a lower ammonia flow rate, which might be attributed to the higher surface-to-volume ratio of the former.

Superior sensor performance from Ag@WO3 core–shell nanostructure

WO3, Ag–WO3 mixture and Ag@WO3 core–shell nanostructure materials were prepared by a hydrothermal process. Material characterization included UV–Vis spectroscopy, XRD, XPS, and TEM imaging. Gas sensors fabricated using the samples were mainly characterized by the response to alcohol vapor. It was found that the Ag@WO3 core–shell nanostructure provides greatly enhanced chemical sensor performance. Specifically, the sensor response towards 500ppm alcohol vapor increases from 44 for pure WO3 and 52 for Ag–WO3 mixture to 154 for the Ag@WO3 core–shell structure; response and recovery time are shortened considerably from 3 and 15s for pure WO3, 12 and 7s for the Ag–WO3 mixture to 2 and 4s for the Ag@WO3 core–shell nanostructure. Moreover, optimum sensor working temperature lowered from 370°C to 340°C. It appears that the Ag@WO3 core–shell nanostructure results in an effective Schottky junction enhanced sensor while the Ag–WO3 mixture does not. The significant downshift in the Ag 3d XPS chemical shift for the Ag@WO3 core–shell nanostructure sample confirms that the sensor performance improvement is due to Schottky junction formation at the Ag/WO3 interface.

Local Optical Activity in Achiral Two-Dimensional Gold Nanostructures

Since Pasteur’s discovery of molecular chirality, which means that the molecule has a nonsuperposable mirror image, the geometrical chirality of a material has been considered the prerequisite for exhibiting circular dichroism (CD, defined as the differential absorption of left and right circularly polarized light) of the structural origin. Here, we report an experimental demonstration of nanoscale local CD activities for achiral (nonchiral) rectangular gold nanostructures. Macroscopic CD spectral measurements of the nanostructure sample did not show any CD activity over the entire range of measured wavelengths, as expected from the achiral shape of the rectangle. In contrast, we found both locally positive and negative CD signals in a single rectangular nanostructure, whose distribution was symmetric about the center of the rectangle, with large CD signals at the corners. The results demonstrate that the established selection rule of optical activity is not valid for local microscopic measurements.

Hydrothermal synthesized nanostructure Bi–Sb–Te thermoelectric materials

Nanostructure p-type Bi0.4Sb1.6Te3 was successfully prepared by adopting a feasible hydrothermal synthesis method. The crystallinity, particle size, morphology and chemical composition were characterized by XRD, FE-SEM, EDS respectively. Thermoelectric properties were also measured and a maximum ZT value up to 1.26 has been obtained at 398K in prepared nanostructure sample. The achieved higher ZT value is attributed to the unique nanostructures which increase phonon scattering in the nanostructured materials to effectively reduce thermal conductivity. It is suggested that the as-prepared nanostructure Bi0.4Sb1.6Te3 has high potential for thermoelectric energy conversion application.

Preparation of Zn3B10O18·14H2O nanomaterials and their thermochemical properties

Two kinds of Zn3B10O18·14H2O morphologies, a cabbage-like micro-/nanostructure and a nanobelt, have been prepared by solution method. All the samples were characterized by XRD, IR, EDS, TG–DTA techniques, chemical analysis and SEM. The flame retardant properties of the prepared Zn3B10O18·14H2O nanomaterials were investigated by the thermal analysis method and limited oxygen index method, showing that the nanobelt sample with the smaller size had the better behavior than the cabbage-like micro-/nanostructure sample. Through an appropriate thermochemical cycle, the standard molar enthalpies of formation of −(11803.1±8.0)kJmol−1 for cabbage-like Zn3B10O18·14H2O micro-/nanostructure and −(11791.2±8.0)kJmol−1 for Zn3B10O18·14H2O nanobelt have been obtained from measured different enthalpies of solution, together with the standard molar enthalpies of formation of ZnO(s), H3BO3(s), and H2O(l), which shows that their stabilities decrease gradually with the decrease of Zn3B10O18·14H2O sizes.

Growth and optical properties of tetrapod-like indium-doped ZnO nanorods with a layer-structured surface

We report tetrapod-like indium-doped ZnO nanorods with a layer-structured surface, synthesized by a thermal vapor transport method. The high crystalline quality of the nanostructure sample obtained was confirmed by using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. We carried out photoluminescence and photoluminescence excitation measurements to investigate the possible application of this indium-doped ZnO nanostructure in the field of optical devices. The photoluminescence exhibited an ultra strong visible wavelength emission with a peak intensity 300 times stronger than the band edge ultraviolet emission. In addition, a very slow decay of visible wavelength emission was revealed by time-resolved photoluminescence spectroscopy.

Synthesis, structure characterization and magnetic properties of nanosize LiCo1 − y Ni y O2 prepared by sol–gel citric acid route

Single phase LiCo1 − yNiyO2 (y = 0.4 and 0.5) with fine particles and high homogeneity was synthesized by “chimie douce” assisted by citric acid as the polymeric agent and investigated as positive electrodes in rechargeable lithium batteries. The long-range and short-range structural properties are investigated with experiments including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and superconducting quantum interference device magnetometry. The physicochemical properties of the powders (crystallinity, lattice constants, grain size) have been investigated in this composition. The powders adopted the α-NaFeO2 structure as it appeared from XRD and FTIR results. Magnetic measurements shows signal at low temperature attributed to the magnetic domains in the nanostructure sample from which we estimated that the cation mixing are 3.35 and 4.74% for y = 0.4 and 0.5 in LiCo1 − yNiyO2, respectively. LiCo0.5Ni0.5O2 cathode yields capacity (135 mAh g−1) compared to LiCo0.6Ni0.4O2 cathode (147 mAh g−1) when discharged to a cutoff voltage of 2.9 V vs. Li/Li+. Lower capacity loss and higher discharge efficiency percentage are observed for the cell of LiCo0.6Ni0.4O2 cathode.

Transient subpicosecond Raman studies of electron velocity overshoot in an InP p-i-n nanostructure semiconductor

Transient electron transport in an InP p-i-n nanostructure semiconductor has been studied by subpicosecond Raman spectroscopy at T=300 K. Both the nonequilibrium electron distribution and electron drift velocity in the regime of electron velocity overshoot have been directly measured. It is demonstrated that electron drift velocity in an InP p-i-n nanostructure is significantly larger than that in a GaAs p-i-n nanostructure sample, as a result of the larger central to satellite valley energy separation in InP.