Yellow Carbon Dots for Fluorescent Water Sensing, Relative Humidity Sensing, and Anticounterfeiting Applications.

Most fluorescent probes based on carbon dots (CDs) fluorescence color or intensity change are still used for detection in solution, but in practical fluorescence detection applications, detection in the solid state is necessary. Therefore, a CDs-based fluorescence sensing device is designed in this paper, which can be used for water detection in liquid and solid states. Using oPD as a single precursor, yellow fluorescent CDs (y-CDs) were prepared by hydrothermal method, which can be used in the field of water detection and anti-counterfeiting by using its solvent-sensitive properties. First, y-CDs can be used to visually and intelligently detect the water content in ethanol. Secondly, it can be used to detect the Relative Humidity (RH) of the environment by combining it with cellulose to form a fluorescent film. Finally, y-CDs can also be used as a fluorescent material for fluorescence anti-counterfeiting.

Fabrication and characterization of InSb nanosheet/hBN/graphite heterostructure devices.

Semiconductor InSb nanosheet/hexagonal boron nitride (hBN)/graphite trilayers are fabricated, and single- and double-gate devices made from the trilayers are realized and characterized. The InSb nanosheets employed in the trilayer devices are epitaxially grown, free-standing, zincblende crystals and are in micrometer lateral sizes. The hBN and graphite flakes are obtained by exfoliation. Each trilayer is made by successively stacking an InSb nanosheet on an hBN flake and on a graphite flake using a home-made alignment stacking/transfer setup. The fabricated single- and double-gate devices are characterized by electrical and/or magnetotransport measurements. In all these devices, the graphite and hBN flakes are employed as the bottom gates and the gate dielectrics. The measurements of a fabricated single bottom-gate field-effect device show that the InSb nanosheet in the device has an electron field-effect mobility of âˆ¼7300 cm2V-1s-1and a low gate hysteresis of âˆ¼0.05 V at 1.9 K. The measurements of a double-gate Hall-bar device show that both the top and the bottom gate exhibit strong capacitive couplings to the InSb nanosheet channel and can thus tune the nanosheet channel conduction effectively. The electron Hall mobility in the InSb nanosheet of the Hall-bar device is extracted to be larger than 1.1 × 104cm2V-1s-1at a sheet electron density of âˆ¼6.1 × 1011cm-2and 1.9 K and, thus, the device exhibits well-defined Shubnikov-de Haas oscillations.

Measurements of anisotropic g-factors for electrons in InSb nanowire quantum dots.

We have measured the Zeeman splitting of quantum levels in few-electron quantum dots (QDs) formed in narrow bandgap InSb nanowires via the Schottky barriers at the contacts under application of different spatially orientated magnetic fields. The effective g-factor tensor extracted from the measurements is strongly anisotropic and level-dependent, which can be attributed to the presence of strong spin-orbit interaction (SOI) and asymmetric quantum confinement potentials in the QDs. We have demonstrated a successful determination of the principal values and the principal axis orientations of the g-factor tensors in an InSb nanowire QD by the measurements under rotations of a magnetic field in the three orthogonal planes. We also examine the magnetic field evolution of the excitation spectra in an InSb nanowire QD and extract a SOI strength of [Formula: see text] ∼ 180 µeV from an avoided level crossing between a ground state and its neighboring first excited state in the QD.

Dimension Engineering of High-Quality InAs Nanostructures on a Wafer Scale.

Low-dimensional narrow-band-gap III-V semiconductors are key building blocks for the next generation of high-performance nanoelectronics, nanophotonics, and quantum devices. Realizing these various applications requires an efficient methodology that enables the material dimensional control during the synthesis process and the mass production of these materials with perfect crystallinity, reproducibility, low cost, and outstanding electronic and optoelectronic properties. Although advances in one- and two-dimensional narrow-band-gap III-V semiconductors synthesis, the progress toward reliable methods that can satisfy all of these requirements has been limited. Here, we demonstrate an approach that provides a precise control of the dimension of InAs from one-dimensional nanowires to wafer-scale free-standing two-dimensional nanosheets, which have a high degree of crystallinity and outstanding electrical and optical properties, using molecular-beam epitaxy by controlling catalyst alloy segregation. In our approach, two-dimensional InAs nanosheets can be obtained directly from one-dimensional InAs nanowires by silver-indium alloy segregation, which is much easier than the previously reported methods, such as the traditional buffering technique and select-area epitaxial growth. Detailed transmission electron microscopy investigations provide solid evidence that the catalyst alloy segregation is the origination of the InAs dimensional transformation from one-dimensional nanowires to two-dimensional nanosheets and even to three-dimensional complex crosses. Using this method, we find that the wafer-scale free-standing InAs nanosheets can be grown on various substrates including Si, MgO, sapphire, GaAs, etc. The InAs nanosheets grown at high temperature are pure-phase single crystals and have a high electron mobility and a long time-resolved terahertz kinetics lifetime. Our work will open up a conceptually new and general technology route toward the effective controlling of the dimension of the low-dimensional III-V semiconductors. It may also enable the low-cost fabrication of free-standing nanosheet-based devices on an industrial scale.

Anisotropic Pauli Spin-Blockade Effect and Spin-Orbit Interaction Field in an InAs Nanowire Double Quantum Dot.

We report on experimental detection of the spin-orbit interaction field in an InAs nanowire double quantum dot device. In the spin blockade regime, leakage current through the double quantum dot is measured and is used to extract the effects of spin-orbit interaction and hyperfine interaction on spin state mixing. At finite magnetic fields, the leakage current arising from the hyperfine interaction can be suppressed, and the spin-orbit interaction dominates spin state mixing. We observe dependence of the leakage current on the applied magnetic field direction and determine the direction of the spin-orbit interaction field. We show that the spin-orbit field lies in a direction perpendicular to the nanowire axis but with a pronounced off-substrate-plane angle. The results are expected to have an important implication in employing InAs nanowires to construct spin-orbit qubits and topological quantum devices.

Coherent Transport in a Linear Triple Quantum Dot Made from a Pure-Phase InAs Nanowire.

A highly tunable linear triple quantum dot (TQD) device is realized in a single-crystalline pure-phase InAs nanowire using a local finger gate technique. The electrical measurements show that the charge stability diagram of the TQD can be represented by three kinds of current lines of different slopes and a simulation performed based on a capacitance matrix model confirms the experiment. We show that each current line observable in the charge stability diagram is associated with a case where a QD is on resonance with the Fermi level of the source and drain reservoirs. At a triple point where two current lines of different slopes move together but show anticrossing, two QDs are on resonance with the Fermi level of the reservoirs. We demonstrate that an energetically degenerated quadruple point at which all three QDs are on resonance with the Fermi level of the reservoirs can be built by moving two separated triple points together via sophistically tuning of energy levels in the three QDs. We also demonstrate the achievement of direct coherent electron transfer between the two remote QDs in the TQD, realizing a long-distance coherent quantum bus operation. Such a long-distance coherent coupling could be used to investigate coherent spin teleportation and superexchange effects and to construct a spin qubit with an improved long coherent time and with spin state detection solely by sensing the charge states.

Epitaxial Growth of Ternary Topological Insulator Bi2 Te2 Se 2D Crystals on Mica.

Nanostructures of ternary topological insulator (TI) Bi2 Te2 Se are, in principle, advantageous to the manifestation of topologically nontrivial surface states, due to significantly enhanced surface-to-volume ratio compared with its bulk crystals counterparts. Herein, the synthesis of 2D Bi2 Te2 Se crystals on mica via the van der Waals epitaxy method is explored and systematically the growth behaviors during the synthesis process are investigated. Accordingly, 2D Bi2 Te2 Se crystals with domain size up to 50 µm large and thickness down to 2 nm are obtained. A pronounced weak antilocalization effect is clearly observed in the 2D Bi2 Te2 Se crystals at 2 K. The method for epitaxial growth of 2D ternary Bi2 Te2 Se crystals may inspire materials engineering toward enhanced manifestation of the subtle surface states of TIs and thereby facilitate their potential applications in next-generation spintronics.

Synthesis of Bi2Te3 Nanotubes Using Te Nanotubes as a Template.

Bi2Te3 nanotubes are synthesized by a facile two-step hydrothermal method. Te nanotubes are prepared firstly and then used as a template to produce Bi2Te3 nanotubes. The structure and morphology of the synthesized nanotubes are characterized by X-ray diffraction, field emission scanning electron microscope, and transmission electron microscope. The synthesized Bi2Te3 nanotubes are several microns in length and about 400 nm in diameter. The growth process is investigated in detail under different experimental conditions. The formation mechanism of Bi2Te3 nanotubes from the Te nanotube template is proposed and discussed. Electrical property of single Bi2Te3 nanotube is investigated. The synthesis of smooth Bi2Te3 nanotubes opens up the opportunities of investigating novel physical phenomena of topological insulators with two independent surfaces.

Enhanced anisotropic effective g factors of an Al0.25Ga0.75N/GaN heterostructure based quantum point contact.

Gate-defined quantum point contacts (QPCs) were fabricated with Al0.25Ga0.75N/GaN heterostructures grown by metal-organic chemical vapor deposition (MOCVD). In the transport study of the Zeeman effect, greatly enhanced effective g factors (g*) were obtained. The in-plane g* is found to be 5.5 ± 0.6, 4.8 ± 0.4, and 4.2 ± 0.4 for the first to the third subband, respectively. Similarly, the out-of-plane g* is 8.3 ± 0.6, 6.7 ± 0.7, and 5.1 ± 0.7. Increasing g* with the population of odd-numbered spin-splitted subbands are obtained at 14 T. This portion of increase is assumed to arise from the exchange interaction in one-dimensional systems. A careful analysis shows that not only the exchange interaction but the spin-orbit interaction (SOI) in the strongly confined QPC contributes to the enhancement and anisotropy of g* in different subbands. An approach to distinguish the respective contributions from the SOI and exchange interaction is therefore proposed.

Surface-bulk coupling in a Bi2Te3 nanoplate grown by van der Waals epitaxy.

We report an experimental study of the effect of coherent surface-bulk electron scattering on quantum transport in a three-dimensional topological insulator Bi2Te3 nanoplate. The nanoplate is grown via van der Waals epitaxy on a mica substrate and a top-gated Hall-bar device is fabricated from the nanoplate directly on the growth substrate. Top-gate voltage dependent measurements of the sheet resistance of the device reveal that the transport carriers in the nanoplate are of n-type and that, with decreasing top gate voltage, the carrier density in the nanoplate is decreased. However, the mobility is increased with decreasing top-gate voltage. This mobility increase with decreasing carrier density in the nanoplate is demonstrated to arise from a decrease in bulk-to-surface electron scattering rate. Low-field magnetotransport measurements are performed at low temperatures. The measured magnetoconductivity of the nanoplate shows typical weak anti-localization (WAL) characteristics. We analyze the measurements by taking surface-bulk inter-channel electron scattering into account and extract dephasing times τφ, diffusion coefficients D of electrons at the top surface and in the bulk, and the surface-bulk scattering times τSB as a function of top-gate voltage and temperature. It is found that the dephasing in the nanoplate arises dominantly from electron-electron scattering with small energy transfers. It is also found that the ratio of τφ/τSB (a measure of the surface-bulk electron coherent coupling) is decreased with decreasing gate voltage or increasing temperature. We demonstrate that taking the surface-bulk coherent electron scattering in our Bi2Te3 nanoplate into account is essential to understand quantum transport measurements at low temperatures.

Factors influencing prolactin levels in chronic long-term hospitalized schizophrenic patients with co-morbid type 2 diabetes mellitus.

Background: For long-term hospitalized patients suffering from schizophrenia, metabolic disease and hyperprolactinemia (HPRL) are common comorbidities. This article is aimed at analyzing the factors influencing comorbid type 2 diabetes mellitus (T2DM) on prolactin (PRL) levels in long-term hospitalized patients suffering from schizophrenia. Methods: This study included 378 long-term hospitalized patients with schizophrenia. Common metabolic markers and PRL levels of included samples were collected, and the severity of psychopathology was assessed using the Positive and Negative Symptoms Scale (PANSS). Based on the patients with or without T2DM, the samples were divided into two groups. The differences in clinical parameters between the two groups were compared, and the effects of the parameters on the PRL levels were analyzed. Results: Compared with non-DM patients, the patients in the DM subgroup had lower PRL levels (P < 0.0001) and rather severe psychiatric symptoms (P = 0.016). Female, treated by risperidone, and high levels of triglyceride (TG) were faced with risk for HPRL (B = 26.31, t = 5.39, P < 0.0001; B = 19.52, t = 4.00, P < 0.0001; B = 2.71, t = 2.31, P = 0.022, respectively). Meanwhile, co-morbid DM and aripiprazole treatment were protective factors (B = 15.47, t = 3.05, P = 0.002; B = -23.77, t = -2.47, P = 0.014; respectively). Ultimately, in the DM subgroup, the dose of metformin was found to be a protective factor for HPRL (B = -0.01, t = -1.46, P = 0.047), while female and aripiprazole were risk factors (B = 16.06, t = 3.26, P = 0.001; B = 20.13, t = 2.57, P = 0.011; respectively). Conclusion: Aripiprazole is a protective factor for HPRL in long-term hospitalized patients, whereas the female is a risk factor. Metformin is beneficial in reducing PRL levels in patients with co-morbid DM. More aggressive and effective interventions are required for preventing adverse drug reactions in women and patients with co-DM.

Fabrication of a "progress bar" colorimetric strip sensor array by dye-mixing method as a potential food freshness indicator.

Colorimetric sensing is a low-cost, intuitive method for monitoring the freshness of food. We prepared a colorimetric strip sensor array by mixing different amounts of bromophenol blue (BPB) and bromocresol green (BCG). As results of NH3 simulation, the array strip turned from yellow to blue, and the number of blue spots increased with the increasing NH3, like a progress bar. Although the actual color is quite different, the color-changing trend was consistent with the simulated model calculated by a computer. The progress bar results remained stable under three lighting conditions. Furthermore, in the Cod preservation experiment, the color-changing progress of the strip sensor array is consistent with the simulation and can indicate Cod freshness while providing more distinguish levels. Therefore, a "progress bar" indicator built by this strategy possess the potential of realizing nondestructive, more accurate, and commercially available food quality monitoring through the naked eye and smart equipment recognition.

Charge detection of a quantum dot under different tunneling barrier symmetries and bias voltages.

We report the realization of a coupled quantum dot (QD) system containing two single QDs made in two adjacent InAs nanowires. One QD (sensor QD) was used as a charge sensor to detect the charge state transitions in the other QD (target QD). We investigated the effect of the tunneling barrier asymmetry of the target QD on the detection visibility of the charge state transitions in the target QD. The charge stability diagrams of the target QD under different configurations of barrier-gate voltages were simultaneously measured via the direct signals of electron transport through the target QD and via the detection signals of the charge state transitions in the target QD revealed by the sensor QD. We find that the complete Coulomb diamond boundaries of the target QD and the transport processes involving the excited states in the target QD can be observed in the transconductance signals of the sensor QD only when the tunneling barriers of the target QD are nearly symmetric. These observations were explained by analyzing the effect of the ratio of the two tunneling rates on the electron transport processes through the target QD. Our results imply that it is important to consider the symmetry of the tunnel couplings when constructing a charge sensor integrated QD device.

Classifiers in Mandarin Chinese: Behavioral and electrophysiological evidence regarding their representation and processing.

In Chinese, when objects are named with their quantity, a numeral classifier must be inserted between the quantifier and the noun to produce a grammatically correct quantifier + classifier + noun phrase. In this study, we adopted the picture-word interference paradigm to examine participants' naming latencies for multiple objects and their electroencephalogram in four conditions by manipulating two factors, i.e. semantic relatedness and classifier congruency. Results show that in noun phrase production, naming latencies are significantly longer in classifier-incongruent and semantically related conditions than in classifier-congruent and semantically unrelated conditions. Also, an N400-like effect was observed and found to be stronger in classifier-incongruent and semantically unrelated conditions. Together, the behavioral data and event-related potential analyses suggest that the use of classifiers as lexico-syntactic features in Mandarin Chinese takes place via a competitive selection process in noun phrase production.

A charge sensor integration to tunable double quantum dots on two neighboring InAs nanowires.

A single quantum dot serving as a charge sensor is integrated to scalable double quantum dots using local top finger-gate techniques on two neighboring pure-phase InAs nanowires. The single dot built on one nanowire capacitively couples one of the double dots constructed on another nanowire via a metal bridge gate. The charge occupation states of double quantum dots can be accurately monitored by the sensor even in a few-electron regime in which transport tunneling current through the double dots vanishes. In the tunneling spectroscopy of double dots, electron inter dot tunneling process is absent; however, it can be illustrated by the sensor in terms of a transconductance line between the two closest triple points. Thus, tunnel coupling strength between the double dots is quantitatively extracted from the detectable charge transition. The highly tunable multiple quantum dots with integrated charge sensors on InAs nanowires could be an essential building block for quantum information processing technology.

Anisotropic magnetoresistance as evidence of spin-momentum inter-locking in topological Kondo insulator SmB6 nanowires.

SmB6, which opens up an insulating bulk gap due to hybridization between itinerant d-electrons and localized f-electrons below a critical temperature, turns out to be a topological Kondo insulator possessing exotic conducting states on its surface. However, measurement of the surface-states in SmB6 draws controversial conclusions, depending on the growth methods and experimental techniques used. Herein, we report anisotropic magnetoresistance (AMR) observed in the Kondo energy gap of a single SmB6 nanowire that is immune to magnetic dopant pollution and features a square cross-section to show high-symmetry crystal facets. The AMR clearly shows a cosine function of included angle θ between magnetic field and measuring current with a period of π. The positive AMR is interpreted by anisotropically lifting the topological protection of spin-momentum inter-locking surface-states by rotating the in-plane magnetic field, which, therefore, provides the transport evidence that supports the topologically nontrivial nature of the SmB6 surface-states.

A highly tunable quadruple quantum dot in a narrow bandgap semiconductor InAs nanowire.

Quantum dots (QDs) made from semiconductors are among the most promising platforms for the development of quantum computing and simulation chips, and they have the advantages of high density integration and compatibility with the standard semiconductor chip fabrication technology compared to other platforms. However, the development of a highly tunable semiconductor multiple QD system still remains a major challenge. Here, we demonstrate the realization of a highly tunable linear quadruple QD (QQD) in a narrow bandgap semiconductor InAs nanowire via a fine finger gate technique. The QQD is studied by electron transport measurements in the linear response regime. Characteristic two-dimensional charge stability diagrams containing four groups of resonant current lines of different slopes are obtained for the QQD. It is shown that these current lines arise from and can be individually assigned to resonant electron transport through the energy levels of different QDs. Benefitting from the excellent gate tunability, we also demonstrate the tuning of the QQD to regimes where the energy levels of two QDs, three QDs and all four QDs are energetically in resonance, respectively, with the Fermi level of the source and drain contacts. A capacitance network model is developed for the linear QQD and the simulated charge stability diagrams based on this model show good agreement with the experiments. Our work provides solid experimental evidence that narrow bandgap semiconductor nanowire multiple QDs could be used as a versatile platform to achieve integrated qubits for quantum computing and to perform quantum simulations of complex many-body systems.

Mott variable-range hopping transport in a MoS2 nanoflake.

The transport characteristics of a disordered, multilayered MoS2 nanoflake in the insulator regime are studied by electrical and magnetotransport measurements. The MoS2 nanoflake is exfoliated from a bulk MoS2 crystal and the conductance G and magnetoresistance are measured in a four-probe setup over a wide range of temperatures. At high temperatures, we observe that ln G exhibits a -T -1 temperature dependence and the transport in the nanoflake dominantly arises from thermal activation. At low temperatures, where the transport in the nanoflake dominantly takes place via variable-range hopping (VRH) processes, we observe that ln G exhibits a -T -1/3 temperature dependence, an evidence for the two-dimensional (2D) Mott VRH transport. Furthermore, we observe that the measured low-field magnetoresistance of the nanoflake in the insulator regime exhibits a quadratic magnetic field dependence ∼ αB 2 with α ∼ T -1, fully consistent with the 2D Mott VRH transport in the nanoflake.

Growth Mechanism of SmB6 Nanowires Synthesized by Chemical Vapor Deposition: Catalyst-Assisted and Catalyst-Free.

SmB6 nanowires, as a prototype of nanostructured topological Kondo insulator, have shown rich novel physical phenomena relating to their surface. Catalyst-assisted chemical vapor deposition (CVD) is a common approach to prepare SmB6 nanowires and Ni is the most popular catalyst used to initiate the growth of SmB6 nanowires. Here, we study the effect of growth mechanism on the surface of SmB6 nanowires synthesized by CVD. Two types of SmB6 nanowires are obtained when using Ni as the catalyst. In addition to pure SmB6 nanowires without Ni impurity, a small amount of Ni is detected on the surface of some SmB6 nanowires by element analysis with transmission electron microscopy. In order to eliminate the possible distribution of Ni on nanowire surface, we synthesize single crystalline SmB6 nanowires by CVD without using catalyst. The difference between catalyst-assisted and catalyst-free growth mechanism is discussed.