Nano

Nanoparticles (NPs) with high uniformity have been extensively investigated for their excellent chemical stability. Near-monodisperse globular MoS₂ NPs were prepared with sulphur powders (SPs) as a sulphur source by a one-pot polyol-mediated process without surfactants, transfer agents and toxic agents at 170–190${}^{\circ }$C. The as-processed SPs greatly affected the formation of the MoS₂ NPs after low-activity sulphur (S₈)_n was reassembled from common SPs (S${}_8)$. The average size of MoS₂ NPs can be reduced remarkably from 100–200nm to 50nm by introducing low amounts of MnCl₂. A preliminary four-step growth mechanism based on the aggregation-coalescence model was also proposed. This green and simple method may be an alternative to the common hot-injection and heating-up methods for the preparation of monodisperse NPs, particularly transition metal dichalogenides.

The sandwich-type immunoassays have been developed by using electrochemical and surface-enhanced Raman scattering (SERS) techniques for the detection of carcinoembryonic antigen (CEA). Nile blue as a kind of Raman dye has been decorated on nanospheres with polydopamine resin (PDR) via $\pi$-stacking interaction. The Nile blue displays the strong SERS signals as well as a characteristic electrochemical reduction peak at $-$0.33V (versus Ag/AgCl). The implementation of the PDR nanospheres mixing with Au nanoparticles (AuNPs/PDR) exhibits a better electrical conductivity and large SERS enhancement. The immunoassays based on Nile blue-labeled AuNPs/PDR nanospheres have been fabricated by using electrochemical and SERS techniques for the detection of CEA. The proposed immunoassay shows higher sensitivity, high selectivity, lower detection limit and long-term stability. The performances of the electrochemical immunoassay are better than that of SERS immunoassay. For the electrochemical immunoassay, the linear range occurs from 1pg/mL to 100ng/mL ($R=0.995$) with a detection limit of 0.68pg/mL and signal-to-noise ratio of 3 in the detection of CEA. The data for the analysis of human serum samples by using the electrochemical method are acceptably consistent with those obtained from the enzyme-linked immunosorbent assay (ELISA). The proposed immunoassay exhibits a promising potential for application in clinical diagnosis.

This article has been retracted at the request of the Editors. It was submitted while a practically identical article was under review by another journal. The duplicated article is "Self-assembly of N-doped 3D porous carbon frameworks from carbon quantum dots and its application for oxygen reduction reaction", Journal of Materials Science: Materials in Electronics, 2017, 28(17), 12660-12669. It is inappropriate and violates the Scientific rule of anti-plagiarism. We regret that this was not detected before the article was accepted for publication in the journal.

ZrNi metallic glass alloy nanowires (NWs) under torsion are studied using molecular dynamics simulations based on the many-body embedded-atom potential. The effect of cooling rate on the deformation mechanism and mechanical properties of ZrNi NWs is evaluated in terms of shear strain, torque, potential energy and radial distribution function. Simulation results show that for slower cooling rates, the NWs have larger packing density, whereas for faster cooling rates, the packing density of atoms decreases. The amount of deformation increases with increasing torsional angle before it reaches a critical torsional angle (${\theta }_c)$. The torque required for deformation and the ${\theta }_c$ value increase with decreasing cooling rate, indicating a larger mechanical strength. Localized shear bands concentrate at regions with high shear strains, leading to the formation of torsional buckling.

Superconductors in proximity to topological insulators (TIs) have the potential to unlock exotic quantum phenomena, such as Majorana fermions. Quasi-one-dimensional structures are particularly suited to host these quantum states. Despite the growth of TI nanostructures being relatively straightforward, the in situ synthesis of superconductor-TI structures has been challenging. Here, we present a systematic study of the growth of the s-wave superconductor Sn on the TI Bi₂Te₃ by physical vapor transport. If Sn does not enter the Bi₂Te₃ lattice as a dopant, two types of structures are formed: Sn nanoparticles, that cover Bi₂Te₃ plates and belts in a cloud-like shape, and thin Sn layers on Bi₂Te₃ plates, that appear in puddle-like recessions. These heterostructures have potential applications as novel quantum devices.

In this study, two hydrogen sensors with Pd/SiO₂/Si and Ni/SiO₂/Si structures have been fabricated. Palladium nanoparticles are synthesized and then deposited on the oxide surface using spin coating. Capacitance–voltage curves for the Pd/SiO₂/Si sensor at room temperature and for the Ni/SiO₂/Si sensor at 140${}^{\circ }$C in pure nitrogen and 1% H₂–N₂ mixture are described. The time required for reaching 90% of the steady-state signal magnitude ($t_{90\%}$) for Pd/SiO₂/Si capacitor was 1.4s and for Ni/SiO₂/Si capacitor was 90 s. The time interval for recovery from 90% to 10% of steady-state signal magnitude ($t_{10\%})$ for Pd/SiO₂/Si capacitor was 14s and for Ni/SiO₂/Si capacitor was 40min. For the Pd/SiO₂/Si capacitor, the response is 88% and for Ni/SiO₂/Si capacitor the response is 29%. Comparison of Pd nanoparticles capacitive- and resistance-based sensors shows that the metal-oxide-semiconductor capacitive is faster and more sensitive than the resistance-based hydrogen gas sensors.

First-principles plane-wave pseudopotential calculations were performed to study the energetics and electronic structures of oxygen defects on rutile TiO₂(0 0 1). The influence of the material thickness on non-linearity (NL) was studied. With the increase in the thickness, the NL became stronger. Calculating the site-projected density of states by applying an external electric field showed that the NL of the bulk is due to the exchange of electrons between O 2p orbitals and Ti 3d orbitals. Finally, the influence of oxygen defects — oxygen vacancies (Vo), oxygen interstitials (Oi), and oxygen vacancies/oxygen interstitial (Vo$+$Oi) pairs (Frenkel pair defects) — on the NL of TiO₂ was studied. These results demonstrate that the band gap ($E_g)$ of TiO₂ became gradually narrower as the electric field increased. The Stark effect and defects can lead to the splitting of degenerate energy levels. Stronger electric fields increase the band splitting and reduce $E_g$. With the increase in the Vo concentration, the decrease in the splitting amplitude and width of the energy level lead to weakening of the transfer of electrons between O and Ti atoms and optimizing the NL of TiO₂. Therefore, the incorporation of Vo plays a significant role in improving the NL of TiO₂.

Hydroxyapatite (HAP) with multiform morphologies, such as hollow dandelion-like bundles and nanoparticles with a diameter of 50nm, was prepared using natural rosin-based surfactant dehydroabietyl phosphate diester (DDPD) as phosphorus source, crystal growth control agent, and template simultaneously by a facile hydrothermal method. Samples were obtained and characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Results showed that DDPD and pH value of solution were the key factors for the morphology of HAP. Hollow dandelion-like bundles HAP, containing the Ca-monodehydroabietyl phosphate (PM-Ca) organic metal compounds, were formed at pH$=$3 without acid-base regulation, and nanoparticles were obtained at pH$=$12. SEM exhibited that the hollow dandelion-like bundles HAP are of 10$\mu$m (outer) and 1$\mu$m (inner) diameter, respectively. Cell viabilities are above 95% when the cells are co-cultured with all HAP samples at concentrations in the range of 250–1000$\mu$g/ml. It indicated that the prepared HAP with PM-Ca has a good cytocompatibility without apparent toxicity. Finally, the possible formation mechanism of the HAP microstructures was discussed in detail.

During plasma etching for fin patterning in the three-dimensional (3D) FinFET structure, the exposure of the Si surface to plasma with reactive ions can induce physical damages, resulting in the degradation of electrical properties of the device. In this study, we evaluated the damage with a measurable value by simulation and surface damage analyses using HR-TEM and RBS. As a result, the degree of the damaged layer was strongly dependent on the energy of the ions bombarding the Si substrate during plasma etching. The damage was quantified with the interface defect density measured by the charge pumping method. Plasma etching with high ion energy showed approximately one order of magnitude higher defect density than that with low ion energy and/or wet etching with no ion bombardment. We introduced Si soft treatment (with very low ion energy) to remove the damaged layer. The Si soft treatment was very effective to remove the damage on a highly damaged silicon surface. However, the Si soft treatment itself increased the number of defects for a low damage silicon surface.

The novel Cu₂O/$e$-HTi₂NbO₇ heterojunction nanocomposite was assembled through a facile exfoliation-restacking route. The as-prepared nanocomposite and its precursors, Cu₂O and $e$-HTi₂NbO₇, were characterized by means of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), N₂ adsorption–desorption measurements, laser Raman spectroscopy (LRS) and UV–Vis diffuse reflection spectroscopy (UV–Vis DRS). The photocatalytic performance was evaluated by photocatalytic oxidation of ethyl mercaptan (EM) and photocatalytic degradation of methylene blue (MB) dyes under sunlight irradiation. The results showed that Cu₂O nanoparticles were successfully distributed on the surface of $e$-HTi₂NbO₇ nanosheets, and the intensity of spectral absorption of the as-prepared nanocomposite in the visible-light region was significantly enhanced. The as-prepared nanocomposite displayed the enhanced photocatalytic activity than the Cu₂O nanoparticles and HTi₂NbO₇ nanosheets due to the formation of a heterojunction structure between Cu₂O nanoparticles and HTi₂NbO₇ nanosheet and a possible photocatalytic mechanism was suggested.

Metal-free photocatalysts trithiocyanuric acid (C₃N₃S${}_3)$ and its polymers were one-step synthesized and used for selective aerobic oxidation of benzyl alcohol under visible light. The S–S bridged C₃N₃S₃ polymers showed higher oxidation activity with increasing polymerization time and reached a maximum at 40h. As a major factor, catalysts’ solubility in water at different temperatures (from 298.15K to 368.15K) was measured at atmospheric pressure. The obtained data were correlated by polynomial empirical equation and modified Apelblat equation, respectively. Experimental results proved that the solubility of C₃N₃S₃ and its polymers increased with increasing temperature. The solubility of C₃N₃S₃ polymers with lower polymerization degree (DP) were better than that of parent C₃N₃S₃ owing to the hydrophilicity caused by a low symmetry and disorder structure, whereas the higher DP could lead to the decrease of polymer solubility and further affect the photocatalytic activity. Thermodynamic properties of the solution system including the enthalpy ($\mathrm{\Delta }{H}_S^0)$ and heat capacity ($c_p^0$) were calculated by the modified Apelblat equation.

As one of the electrode materials for supercapacitor, Co₃O₄/graphene composite was mainly synthesized via two-steps method. Here, a facile one-pot method was used for Co₃O₄/graphene composite, and the performances of one-pot-synthesized Co₃O₄/graphene composite were carefully investigated. Liquid-phase exfoliation was used for graphene and the $D$-band/$G$-band ratio of liquid-phase exfoliated graphene was only 0.094, which indicated that the graphene had low defect density and enhanced electrical conductivity. Morphologies investigation of Co₃O₄/graphene composites indicated that Co₃O₄ nanoparticles with mean diameter of 14nm were uniformly anchored on graphene sheets. The facile one-pot method associated with liquid-phase exfoliated graphene induced Co₃O₄/graphene composite with enhanced specific capacitance of 392 F$\cdot$g${}^{-1}$ at a current density of 1 A$\cdot$g${}^{-1}$. The Co₃O₄/graphene composite also expressed relatively small internal resistance and diffusion resistance (0.36$\mathrm{\Omega }$ and 0.45$\mathrm{\Omega }$, respectively). Moreover, the synthesized Co₃O₄/graphene composite yielded excellent rate performances with only 9.5% capacitance loss when current density was increased by a factor of 10.

Coprinus comatus-based nitrogen-doped activated carbon (N-ACC) is prepared by chemical activation and nitrogen-doped methods. The N-ACC possesses large specific surface areas (976.96m²g${}^{-1}$), high nitrogen contents (11.53wt.%), and super hydrophilicity. As electrode material for supercapacitors, the N-ACC shows remarkable electrochemical performance, such as 346Fg${}^{-1}$ maximum specific capacitance at a current density of 1Ag${}^{-1}$, which retains 260Fg${}^{-1}$ even at a high current density of 10Ag${}^{-1}$ (about 75% capacitance retention) in 2M KOH aqueous electrolyte. The assembled N-ACC//N-ACC symmetric supercapacitor exhibits energy density of 14.63Whkg${}^{-1}$ at power density of 810W kg${}^{-1}$, and excellent cycling stability with 92% specific capacitance retention after 10000 cycles in the voltage range 0–1.8V in 0.5M Na₂SO₄ aqueous solution. These results indicate that the N-ACC as electrode materials can be used for high performance supercapacitors.