Nano

In this paper, for the aim of increasing the production rate of highly aligned nanofibers, electrocentrifuge spinning (ECS) technique was modified by equipping it with two nozzles as the spinneret. This new setup obviously doubles the production rate of nanofibers relative to the conventional ECS. To investigate the effect of this modification on the degree of nanofibers alignment (DeNA), the values of DeNA were measured for 30 distinctive experiments and the results were compared with that of ECS setup with a single nozzle. The originality of this work has lain in the fact that for these 30 experiments, which were designed by Design Expert Software (DES), the DeNA of the new ECS was the same as the conventional setup. Additionally, a spinneret with four nozzles was employed to evaluate the influence of number of nozzles on the DeNA. Lastly, the optimum values of voltage, polymer concentration, spinneret rotational speed and collector diameter were determined in order to maximize the DeNA of the modified ECS setup.

Carbon nanofibers (CNFs) were synthesized by using a safe and less hazardous method, compared to using floating catalysts in chemical vapor deposition (CVD) process. This process used C₂H₂ as carbon source and oil palm kernel shell-based powdered activated carbon (PAC) as cheap solid substrate. Use of nickel (Ni²⁺) impregnated PAC as fixed substrate for the synthesis of CNF is one of the novelties of the research work accomplished by the authors. The PAC–CNFs porous nanocomposite product was used for the sorption of lead ions (Pb²⁺) from synthetic aqueous solution. Kinetics of Pb²⁺ adsorption and isotherms were investigated by varying initial concentration of lead and contact time. PAC–CNFs were found to remove Pb²⁺ better at acidic pH of about 5.5. Langmuir and Freundlich isotherms were applied to the sorption equilibrium data to find the best fitted model. Langmuir isotherm model with R² = 0.965 fitted the adsorption data better than the Freundlich isotherm. The kinetic processes of Pb²⁺ adsorption on CNFs were investigated by applying different kinetic models, namely zero-order, pseudo-first-order and pseudo-second-order. The pseudo-second-order rate equation exhibited the best results with R² = 0.999, q_e = 74.79 (mg/g) and K₂ = 0.029 (min ⋅ g/mg). The novel nanocomposite product seemed to have the potential to remove Pb²⁺ ions from aqueous solution.

The present work aims at the synthesis of Zinc-doped CdSe(Zn:CdSe) nanoparticles with average size near the Bohr radius by wet chemical method. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), UV-Vis spectrometer is used for the determination of bandgap and crystallite size is estimated using Debye–Scherrer formula and Brus equation. The nonlinear optical property that is excitonic nonlinear absorption and the wavelength dependence of nonlinear absorption has also been measured near the excitonic transitions involving the lowest electron state (1S) and one of the hole states 1S_3/2(h). We observe the saturable absorption (SA), which can be described by a third-order and a fifth-order nonlinear process for Zn:CdSe nanocrystals. The irradiance and wavelength dependence of the excitonic nonlinearity are explained by two-level model. The calculations have been performed with the help of Z-scan experimental setup using Handy Compact Q-switched pulsed Nd:YAG laser (HYL-101 Quanta System).

We report an efficient and green approach for mass production of few layered graphene nanosheets (FLGNSs) by intercalation and exfoliation of pyrolytic graphite sheet in a simple protic, H₂SO₄ electrolyte. The as-prepared FLGNSs at the optimum intercalate concentration of 0.5 M H₂SO₄ is able to produce large domain of lateral dimension of 11–26 μm consisting of 4–6 stacked graphene layers, as confirmed by field emission scanning electron microscopy and atomic force microscopy, respectively. Surface oxygenation and a characteristic absorbance peak at 228 nm are well observed for electrochemical exfoliated FLGNSs from Fourier transform infrared spectroscopy and UV–Vis spectra respectively. (002) planes of the obtained graphene sheets have been confirmed from X-ray diffraction pattern. The characteristic Raman bands have been observed at 1354 cm^-1 and 1590 cm^-1 in the exfoliated FLGNSs.

Ag/Bi₄Ti₃O₁₂ heterostructure with high photocatalytic activity was synthesized via a simple and practical hydrothermal method by using Bi₄Ti₃O₁₂ nanobelts as substrate materials. The as-prepared Ag/Bi₄Ti₃O₁₂ heterostructure included Ag quantum dots assembling uniformly on the surface of Bi₄Ti₃O₁₂ nanobelts. Comparing with pure Bi₄Ti₃O₁₂ nanobelts, the composite photocatalyst exhibited enhanced photocatalytic activity under visible light irradiation in the decomposition of rhodamine B aqueous solution. The enhancement performance is believed to be induced by the intimate contact interface, where silver quantum dots serve as good electron acceptor for facilitating quick photoexcited electron transfer and thus decreasing electron-hole recombination. It was also found that the photodegradation of rhodamine B molecules is mainly attributed to the oxidation action of the generated radicals.

Spherical Bi₂S₃ nanoparticles (NPs) were prepared by a facile in situ thermal sulfuration method. Different Bi₂S₃ samples were obtained by controlling the sulfuration time. The products were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), Raman and Fourier-transform infrared (FT-IR) methods. The optical properties were examined by UV-visible-near-infrared (UV-Vis–NIR) and photoluminescence (PL) techniques. The results show that the phase of the products after sulfuration is pure and the spherical shape of Bi NPs has been successfully transmitted to Bi₂S₃ samples. The light absorption edges exhibit red shift to 1060 nm while the light emission displays blue shift to 868 nm, compared with the energy bandgap of bulk Bi₂S₃. The reason for the special optical properties of Bi₂S₃ NPs by this in situ sulfuration route is considered to associate with the defects and quantum size effect of NPs.

In this study, silver orthophosphate@carbon layer (Ag₃PO₄@C) core/shell heterostructure photocatalyst was prepared for the first time. The results showed that a uniform carbon layer was formed around the Ag₃PO₄. By adjusting the hydrothermal fabrication parameters, the thickness of carbon layer could be easily controlled. Furthermore, the Ag₃PO₄@C had remarkable light absorption in the visible region. Photocatalytic tests displayed that the Ag₃PO₄@C heterostructures possessed a much higher degradation rate of phenol than pure Ag₃PO₄ under visible light. The enhanced photocatalytic activity could be attributed to high separation efficiency of photogenerated electrons and holes based on the synergistic effect between carbon as a sensitizer and Ag₃PO₄. Recycle tests showed that the Ag₃PO₄@C core/shell heterostructures maintained high stability over several cycles. The good stability could be attributed to the protection of insoluble carbon layer on the surfaces of Ag₃PO₄ crystals in aqueous solution.

This paper reports a new graphene oxide (GO)/acenaphthenequinone composite as efficient electrode in electrochemical supercapacitors. The nanosheets of GO provide high surface area and conductivity. The microneedle-like acenaphthenequinone contributes convincible specific capacitance. The structure and morphology of GO/acenaphthenequinone composite have been characterized by field-emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR) spectra and Raman spectra. According to the cyclic voltammetry (CV), galvanostatic charge/discharge, impedance spectra and cycling life analyses, the GO/acenaphthenequinone composite exhibits brilliant supercapacitors performance with a specific capacitance of 248.7 F g^-1 at a scan rate of 1 mV s^-1 and enhanced stability of about 82% (147.5 F g^-1) of initial capacitance (179.8 F g^-1) after 500 cycles at a current density of 1 A g^-1.

Application of single layered graphene sheets (SLGSs) as resonant sensors in detection of ultra-fine nanoparticles (NPs) is investigated via molecular dynamics (MD) and nonlocal elasticity approaches. To take into consideration the effect of geometric nonlinearity, nonlocality and atomic interactions between SLGSs and NPs, a nonlinear nonlocal plate model carrying an attached mass-spring system is introduced and a combination of pseudo-spectral (PS) and integral quadrature (IQ) methods is proposed to numerically determine the frequency shifts caused by the attached metal NPs. In MD simulations, interactions between carbon–carbon, metal–metal and metal–carbon atoms are described by adaptive intermolecular reactive empirical bond order (AIREBO) potential, embedded atom method (EAM), and Lennard–Jones (L–J) potential, respectively. Nonlocal small-scale parameter is calibrated by matching frequency shifts obtained by nonlocal and MD simulation approaches with same vibration amplitude. The influence of nonlinearity, nonlocality and distribution of attached NPs on frequency shifts and sensitivity of the SLGS sensors are discussed in detail.

Determination of an injection condition which is minimally invasive to the cell membrane is of great importance in drug and gene delivery. For this purpose, a series of molecular dynamics (MD) simulations are conducted to study the penetration of a carbon nanotube (CNT) into a pure POPC cell membrane under various injection velocities, CNT tilt angles and chirality parameters. The simulations are nonequilibrium and all-atom. The force and stress exerted on the nanotube, deformation of the lipid bilayer, and strain of the CNT atoms are inspected during the simulations. We found that a lower nanotube velocity results in successfully entering the membrane with minimum disruption in the CNT and the lipid bilayer, and CNT's chirality distinctly affects the results. Moreover, it is shown that the tilt angle of the CNT influences the nanotube's buckling and may result in destroying the membrane structure during the injection process.

We reported a sensitive voltammetric sensor for Sudan I determination by modifying glassy carbon electrode (GCE) with single-walled carbon nanotubes (SWCNTs)/β-cyclodextrin conjugate. The cyclic voltammetry results showed that the modified GCE exhibited strong catalytic activity toward the electro-reduction of Sudan I with a well-defined cyclic voltammetric peak at -673 mV. Differential pulse voltammetry measurement showed that the response current exhibited a linear range between 50 nM and 5 μM, and the detection limit was as low as 2.22 nM (S/N = 3). The enhanced electrochemical performance of the fabricated sensor was attributed to the combination of the excellent electrocatalytic properties of SWCNTs and the molecular recognition ability of β-cyclodextrin to Sudan I. The sensor was successfully applied to determine Sudan I in real food samples with satisfactory results.

This paper presents the analog/RF performance for an III–V semiconductor-based staggered hetero-tunnel-junction n-type nanowire (NW) tunneling field effect transistor (n-TFET), for the first time. The device parameters for analog/mixed-signaling applications, such as transconductance (g_m), transconductance-to-drive current ratio (g_m/I_DS), output resistance (R_out), intrinsic gain and unity-gain cutoff frequency (f_T) are studied for III–V based NW n-TFET, with the help of device simulator and compared with those for a similarly sized homojunction (HJ) NW n-TFET. The result reveals that the hetero-tunnel-junction n-TFETs outperform their HJ counterparts for analog/mixed-signal system-on-chip (SoC) applications.

The fabrication of gallium, zinc and nickel oxide nanodots for application of resistive random access memory (RRAM) was demonstrated using the atomic force microscopy (AFM) local anodic oxidation technique. Thin metal films were deposited on indium tin oxide conductive glass substrates. In the atmospheric environment, using AFM equipped with an Ag-coated probe can generate metal oxide nanodots locally on the metal films. These nanodots act as an insulator layer in a single unit cell of the RRAM. The voltage-biased method allows devices to reset from a low-resistance state (LRS) to a high-resistance state (HRS) at 0.9 V. These results show the ability of the AFM local anodic oxidation to produce 50 nm NiO nanodots on glass substrates for potentially high-density RRAMs. As we developed the characteristics of the structure, we found that a lateral NiO nanobelt RRAM performs very low power operation from such experimental manufacturing process. Using a current-biased method, the lateral device switches from a HRS to a LRS with a low writing voltage of 0.64 V.

Hexavalent chromium (Cr (VI)) is a highly toxic pollutant which is harmful to marine organisms as well as humanity. Removing Cr (VI) from water is a hot-spot in environmental remediation. In this work, a novel kind of composite nanofibers membrane (thermal plastic elastomer ester (TPEE)@AlOOH) was first proposed by a simple method, based on a hybrid strategy composed of electrospinning and hydrothermal method. The obtained nanofibrous membrane was turned out to be a petaloid structure, which can enlarge the specific surface area of electrospun fibers. Furthermore, the Cr (VI) removal experiments suggested that the obtained nanofibrous membrane showed a high and fast efficiency, a stable recyclable property for the Cr (VI) removal. Therefore, such a novel nanofibrous membrane can be potentially widely used in Cr (VI) removal.

In this paper, a multiscale modeling approach is proposed for studying the pinhole defects in double wall carbon nanotube (DWNT) reinforced polymer composites. Two configurations of DWNT i.e., armchair (5,5), (10,10) and zigzag (9,0), (16,0) are selected for the analyses wherein C–C bonds at atomic scale are modeled as Euler beam. The three-dimensional (3D) solid elements are used for matrix material and square representative volume element (RVE) is constructed for the nanocomposite. These composite materials consist of aligned carbon nanotubes (CNTs) that are uniformly distributed within the matrix. The presence of chemical covalent bonding between functionalized CNT and matrix are modeled as elastic crosslinks. The nonbonded van der Waals interactions between inner and outer wall are modeled as cohesive interaction elements. The influence of the pinhole defects on the nanocomposite are studied under axial load condition. It has been observed that with the increase in the number of atomic vacancies, the elastic modulus of the composite are reduced significantly. The effects of nanotube chirality and composite stiffness ratio on the elastic properties are also analyzed in the presence of pinhole defects.

Ag pillared interlayered clays (Ag-PILCs) were synthesized through a novel method, in which Ag nanoparticles were formed in montmorillonite interlayers. In this method, silver ions were first exchanged into montmorillonite interlayers, and then reduced into Ag nanoparticles by trisodium citrate at 100°C in aqueous solutions. The synthesized Ag@montmorillonite nanocomposite was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and its surface area was evaluated by using Brunauer–Emmet–Teller (BET) method. Compared to traditional PILCs synthesized through ion exchange method, the formed Ag-PILCs had better thermal stability and stronger structure because their pillars are nanoparticles. Furthermore, this method introduces a possibility to control the size of the pillars and thus the pore size of the PILCs, due to that the nanoparticle pillars can be modified on their forms and diameters in the synthesizing process. Also, it was found that the intercalating Ag nanoparticle pillars were formed at restricted pH values and silver ion concentrations.