Nano

Fe₃O₄–SiO₂ core–shell structure nanoparticles containing magnetic properties were investigated for their potential use in drug delivery. The Fe₃O₄–SiO₂ core–shell structure nanoparticles were successfully synthesized by a simple and convenient way. The Fe₃O₄–SiO₂ nanoparticles showed superparamagnetic behavior, indicating a great application potential in separation technologies. From the application point of view, the prepared nanoparticles were found to act as an efficient drug carrier. Specifically, the surface of the core–shell nanoparticles was modified with amino groups by use of silane coupling agent 3-aminopropyltriethoxysilane (APTS). Doxorubicin (DOX) was successfully grafted to the surface of the core–shell nanoparticles after the decoration with the carboxyl acid groups on the surface of amino-modified core–shell structure nanoparticles. Moreover, the nanocomposite showed a good drug delivery performance in the DOX-loading efficiency and drug release experiments, confirming that the materials had a great application potential in drug delivery. It is envisioned that the prepared materials are the ideal agent for application in medical diagnosis and therapy.

This paper investigates the mechanical properties of hydrogenated silicon carbide nanotubes (H-SiCNTs) using a molecular mechanics model in conjunction with the density functional theory (DFT). Analytical expressions presented in this study can be employed for nanotubes with different chiralities. Four different positions of adsorptions are considered in this paper and it is shown that the most stable state happens when hydrogen atoms are adsorbed on silicon and carbon atoms at the two opposite sides of hexagonal phase of silicon carbide. This paper will contribute to future research on similar studies of H-SiCNTs in the specific area as the force constants used in the molecular mechanics models regarding the hydrogen adsorption are proposed. Also, the mechanical properties and atomic structure of hydrogenated silicon carbide (H-SiC) sheet for different states of adsorption are determined using the DFT. The results for bending stiffness of H-SiC sheets indicate the isotropic behavior of these materials.

The Eu³⁺-doped CdTe quantum dots (QDs) have been successfully synthesized in aqueous phase through microwave-assisted hydrothermal method. The as-prepared products were characterized by X-ray diffraction (XRD) technique, high-resolution transmission electron microscope (HRTEM), energy dispersive spectrum (EDS), X-ray photoclectron spectrum (XPS), UV-visble (UV-Vis) absorption spectrum and photoluminescence (PL). As the results show, the average sizes of the cubic phase CdTe and CdTe:1%Eu³⁺ are an average size of 3.7 nm and 3.5 nm, respectively. The average lattice parameter of CdTe:Eu³⁺ decreases with increasing Eu³⁺ ions concentration. Furthermore, compared to green emission of the host CdTe, the CdTe:1%Eu³⁺ presents additional orange fluorescence emission of Eu³⁺ ions. Recombination luminescence color is almost located in the yellow region of the CIE 1931, and the CIE 1931 coordinate is (0.448, 0.513). The effect of different Eu³⁺ doping concentration on the luminescence of CdTe:Eu³⁺ QDs was discussed in detail. It suggests that CdTe:Eu³⁺ QDs are potential phosphors for white light-emitting materials.

The degeneracy of the two fundamental modes HE₁₁ of the nanowire (NW) is removed due to the coupling of surface plasmon (SP). For the coupled mode 1 of HE₁₁ the electric field is concentrated between the metal sphere and the NW because of the coupling of the metal sphere. The coupling intensity depends on the relative position of the metal sphere. There is no field concentration phenomenon for the coupled mode 2 of HE₁₁, and the coupling only affects the distribution of the local field in the NW. For the coupled mode 2 of HE₁₁, both the mode volume and the Purcell factor do not have obvious change. However, for the coupled mode 1 of HE₁₁ both the mode volume and the Purcell factor have a fundamental change. The mode volume increases with the increase of the metal sphere distance from the point of maximum field intensity of the Fabry–Perot standing wave. The Purcell factor decreases with the increase of the metal sphere distance from the point of maximum field intensity of the Fabry–Perot standing wave.

Nickel oxide (NiO) nanoparticles were synthesized by calcination at 400°C to 700°C for 8 h of the precursor obtained via mechanochemical reaction of Ni(NO₃)₂ ⋅ 6H₂O with citric acid as a dispersant. The nanoparticles were characterized by thermogravimetric-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The kinetics of different surfaces of the nanocrystals under nonisothermal conditions was investigated. The activation energies for different lattice planes of NiO nanoparticles were determined using the Arrhenius equation, revealing their preferred orientation. The growth of NiO obeyed the general theory that nanoparticles with the largest surface energy tend to form. XRD data reveal that the NiO nanoparticles possess preferred (111) or (200) orientations that reflect their complex activity. The nature of preferred growth orientation was found to be negative diffusion activity among different lattice surfaces, which indicates that oxygen atoms diffuse from low oxygen concentration on the lattice surface to high concentration on the lattice surface.

The nanoporous Co₃O₄ thin films were prepared on indium tin oxide (ITO) glasses by an electrodeposition method. The surface morphology and composition of the nanoporous Co₃O₄ films were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDS) and X-ray photoelectron spectroscopy (XPS). The results show that the as-deposited nanoporous Co₃O₄ film is constructed by many interconnected nanoflakes with thickness of about 40 nm. The cyclic voltammetry (CV) measurement indicates that the nanoporous Co₃O₄ films exhibit remarkable electrocatalytic activities for the hydrogen peroxide (H₂O₂) reduction which shows that it is a good candidate to be employed as electrode materials for electrochemical sensing of H₂O₂. Further analysis indicated that the detection sensitivity of the sensor was 1.357 mA mM^-1 cm^-2 and the detection limit was estimated to be about 0.2 mM.

In this paper, a facile two-step synthesis route combining an electrospinning technique and vapor transport deposition method has been accepted as a straightforward protocol for the exploitation of ZnO/carbon nanofibers (CNFs) hierarchical heterostructures which are composed of ZnO nanorods on the surface of CNFs. Photocatalytic tests display that the ZnO/CNFs heterostructures possess degrading Rhodamine B (RB) at a much higher rate than pure ZnO. The enhanced photocatalytic activity could be attributed to the effective separation of photogenerated carriers driven by the photoinduced potential difference, which is generated at the ZnO/CNFs heterojunction interface. Moreover, the heterostructures could be reclaimed easily by sedimentation without a decrease of the photocatalytic activity. Such simple and versatile strategy can provide a general way to fabricate other heterostructures, such as TiO₂/CNFs.

Solvent vapor atmosphere is introduced for solution-evaporated poly(3-hexylthiophene) (P3HT) formation in fabricating organic field-effect transistors (OFETs). As changing the solvent vapor atmosphere, prominent influences on the assemblies of P3HT nanowires during solidification were represented, leading to the difference in nanostructure morphologies. We demonstrated that the device fabricated under anisole solvent vapor atmosphere is superior in electrical performance to that of the devices fabricated under other conditions. In this process, anisole solvent vapor atmosphere transparently facilitated one-dimensional (1D) self-assembly through π–π stacking interaction among the P3HT units during solidification.

High-ordered particle-in-bowl (PIB) arrays are developed in this paper for surface enhanced Raman spectroscopy (SERS). A heterogeneous shadow mask, composing of the chrome (Cr) layer and colloid residues, is used to fabricate the silicon (Si) template from where the PIB arrays finally lift-off. The finite difference time domain (FDTD) method is employed to investigate the Raman enhancement mechanism of this PIB architecture. The electromagnetic (EM) field tends to concentrate in the gap between the bowl and the particle forming the "hot spots". The enhancement factor (EF) of the EM field is about 70 with an excitation wavelength of 785 nm. The Raman measurements validate the EM calculation of the PIB arrays. The EF is about 1.12 × 10⁷ using Rodamine 6G (R6G) as probe molecule. The proposed PIB array is high-ordered in morphology and ultra-sensitive in Raman measurement, providing an ideal substrate for SERS-based bio-chemical sensing, disease diagnosis and analytical chemistry.

In this paper, we have used semiclassical Monte Carlo method to show the dependence of spin relaxation length in III–V compound semiconductor core–shell nanowires on different parameters such as lateral electric field, temperature and core dimensions. We have reported the simulation results for electric field in the range of 0.5–10 kV/cm, temperature in the range of 77–300 K and core length ranging from 2 nm to 8 nm. The spin relaxation mechanisms used in III–V compound semiconductor core–shell nanowire are D'yakonov–Perel (DP) relaxation and Elliott–Yafet (EY) relaxation. Depending upon the choice of materials for core and shell, nanowire forms two types of band structures. We have used InSb–GaSb core–shell nanowire and InSb–GaAs core–shell nanowire and nanowire formed by swapping the core and shell materials to show all the results.

A strong electrochemiluminescence (ECL) emission from ZnO nanoparticles (NPs) suspended in aqueous solution at a Pt electrode or in NPs layers modified on a Pt or graphite electrode, which occurred between -1.0 V(versus Ag/AgCl, Sat. KCl) and -2.0 V, was observed in 0.25 M NaOH in the presence of peroxydisulfate. The ECL intensity was linear to the concentration of suspended ZnO NPs in the range from 1.0 × 10^-5 to 1.0 × 10^-3 g/mL. The ECL spectrum of ZnO NPs revealed that both ZnO and peroxydisulfate-dissolved oxygen have been involved in the ECL process, and ECL spectrum has a red shift compared with photoluminescence (PL). The electrochemical redox behavior of ZnO NPs was also studied at a ZnO NPs modified carbon paste electrode by entrapping ZnO NPs in carbon paste, which reveals that the alkaline medium changed the surface state of ZnO NPs. The surface passivation has a significant effect on the ZnO NPs'electrochemical behaviors.

Uniform CoFe₂O₄ hollow spheres with diameter of about 300 nm and a shell thickness of approximately 60 nm were synthesized by a easy vapor diffusion method in the presence of polyvinyl pyrrolidone (PVP), in combination with calcination at 550°C. The structure and morphology of as-prepared samples were characterized by electron microscopy and X-ray diffractometry (XRD). The hollow spheres exhibited a high saturation magnetization value of 66.4 emu/g and coercivity of 417 Oe at room temperature. A possible formation mechanism for the CoFe₂O₄ hollow spheres was proposed.

We report a novel solid-phase extraction adsorbent for the preconcentration of three phthalate esters (PAEs) from aqueous samples. The material was obtained by modifying multiwalled carbon nanotubes (MWCNTs) with mesoporous silica. The structural characterization of the adsorbent was conducted by Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM) and N₂ adsorption–desorption measurement, which confirmed the successful coating of mesoporous silica on MWCNTs and the adsorbent possessing large surface and porous structure. The effects of adsorbent amount, type and volume of eluent and sample pH on extraction efficiency were optimized. Following extraction, the PAEs were quantified by high performance liquid chromatography (HPLC). Under optimal conditions, the recoveries ranged from 89.8% to 96.3%. The calibration plot was linear in the 3–1000 ng⋅mL^-1 concentration range, with correlation coefficients ranging from 0.9993 to 0.9995. The repeatability of the method, expressed as relative standard deviation (RSD), ranged from 3.8% to 7.7% (for n = 5). Limits of detection (LODs) were between 0.28 ng mL^-1 and 0.53 ng⋅mL^-1. The relative recoveries (RR) for spiked river water, pond water and tap water samples were in the ranges of 80.9–98.0%, 82.7–96.1% and 88.3–95.5%, respectively. The results showed that the method obviously had a large potential for preconcentration and determination of PAEs in environmental samples.

Single-walled carbon nanotubes (SWCNTs) with incovalently attached iodine, were obtained by physical absorption. The different diameter sizes of SWCNTs, with different numbers of iodine molecule, enhance the density contrast between them which becomes evident in density gradient ultracentrifugation (DGU) targeted to sort certain species of SWCNTs. The results of optical absorbance and photoluminescence emission showed that iodine-assisted DGU preferentially separates semiconducting nanotubes with certain diameters [(6, 5), (7, 5), (8, 4), and (7, 6)].We have applied these semiconducting, species enriched SWCNTs to prepare solution-processed field effect transistor (FET) devices with random nanotube network active channels. The devices exhibit stable p-type semiconductor behavior in air with very promising characteristics. The on-off current ratio reaches up to 2 × 10⁴ within a narrow window of voltage (-10 V to 10 V), and estimated hole mobility of 21.7 cm² V^-1 s^-1.