Ying Jiang

Controlled synthesis of single-crystal SnSe nanoplates

AbstractTwo-dimensional layered IV–VI chalcogenides are attracting great interest for applications in next-generation optoelectronic, photovoltaic, and thermoelectric devices. However, great challenges in the controllable synthesis of high-quality IV–VI chalcogenide nanostructures have hindered their in-depth studies and practical applications to date. Here we report, for the first time, a feasible synthesis of single-crystal IV–VI SnSe nanoplates in a controlled manner on mica substrates by vapor transport deposition. The as-grown SnSe nanoplates have approximately square shapes with controllable side lengths varying from 1 to 6 μm. Electrical transport and optoelectronic measurements show that as-obtained SnSe nanoplates display p-type conductivity and high photoresponsivity.n

Shaped Pd–Ni–Pt Core-Sandwich-Shell Nanoparticles: Influence of Ni Sandwich Layers on Catalytic Electrooxidations

Shape-controlled metal nanoparticles (NPs) interfacing Pt and nonprecious metals (M) are highly active energy conversion electrocatalysts; however, there are still few routes to shaped M-Pt core-shell NPs and fewer studies on the geometric effects of shape and strain on catalysis by such structures. Here, well-defined cubic multilayered Pd-Ni-Pt sandwich NPs are synthesized as a model platform to study the effects of the nonprecious metal below the shaped Pt surface. The combination of shaped Pd substrates and mild reduction conditions directs the Ni and Pt overgrowth in an oriented, layer-by-layer fashion. Exposing a majority of Pt(100) facets, the catalytic performance in formic acid and methanol electro-oxidations (FOR and MOR) is assessed for two different Ni layer thicknesses and two different particle sizes of the ternary sandwich NPs. The strain imparted to the Pt shell layer by the introduction of the Ni sandwich layer (Ni-Pt lattice mismatch of ∼11%) results in higher specific initial activities compared to core-shell Pd-Pt bimetallic NPs in alkaline MOR. The trends in activity are the same for FOR and MOR electrocatalysis in acidic electrolyte. However, restructuring in acidic conditions suggests a more complex catalytic behavior from changes in composition. Notably, we also show that cubic quaternary Au-Pd-Ni-Pt multishelled NPs, and Pd-Ni-Pt nanooctahedra can be generated by the method, the latter of which hold promise as potentially highly active oxygen reduction catalysts.

Rational Design of Sub-Parts per Million Specific Gas Sensors Array Based on Metal Nanoparticles Decorated Nanowire Enhancement-Mode Transistors

One key to one lock hybrid sensor configuration is rationally designed and demonstrated as a direct effective route for the target-gas-specific, highly sensitive, and promptly responsive chemical gas sensing for room temperature operation in a complex ambient background. The design concept is based on three criteria: (i) quasi-one-dimensional metal oxide nanostructures as the sensing platform which exhibits good electron mobility and chemical and thermal stability; (ii) deep enhancement-mode field-effect transistors (E-mode FETs) with appropriate threshold voltages to suppress the nonspecific sensitivity to all gases (decouple the selectivity and sensitivity away from nanowires); (iii) metal nanoparticle decoration onto the nanostructure surface to introduce the gas specific selectivity and sensitivity to the sensing platform. In this work, using Mg-doped In2O3 nanowire E-mode FET sensor arrays decorated with various discrete metal nanoparticles (i.e., Au, Ag, and Pt) as illustrative prototypes here further confirms the feasibility of this design. Particularly, the Au decorated sensor arrays exhibit more than 3 orders of magnitude response to the exposure of 100 ppm CO among a mixture of gases at room temperature. The corresponding response time and detection limit are as low as ∼4 s and ∼500 ppb, respectively. All of these could have important implications for this one key to one lock hybrid sensor configuration which potentially open up a rational avenue to the design of advanced-generation chemical sensors with unprecedented selectivity and sensitivity.

Nanoscale-Phase-Separated Pd–Rh Boxes Synthesized via Metal Migration: An Archetype for Studying Lattice Strain and Composition Effects in Electrocatalysis

Developing syntheses of more sophisticated nanostructures comprising late transition metals broadens the tools to rationally design suitable heterogeneous catalysts for chemical transformations. Herein, we report a synthesis of Pd-Rh nanoboxes by controlling the migration of metals in a core-shell nanoparticle. The Pd-Rh nanobox structure is a grid-like arrangement of two distinct metal phases, and the surfaces of these boxes are {100} dominant Pd and Rh. The catalytic behaviors of the particles were examined in electrochemistry to investigate strain effects arising from this structure. It was found that the trends in activity of model fuel cell reactions cannot be explained solely by the surface composition. The lattice strain emerging from the nanoscale separation of metal phases at the surface also plays an important role.

Controllable Electrical Properties of Metal-Doped In2O3 Nanowires for High-Performance Enhancement-Mode Transistors

In recent years, In(2)O(3) nanowires (NWs) have been widely explored in many technological areas due to their excellent electrical and optical properties; however, most of these devices are based on In(2)O(3) NW field-effect transistors (FETs) operating in the depletion mode, which induces relatively higher power consumption and fancier circuit integration design. Here, n-type enhancement-mode In(2)O(3) NW FETs are successfully fabricated by doping different metal elements (Mg, Al, and Ga) in the NW channels. Importantly, the resulting threshold voltage can be effectively modulated through varying the metal (Mg, Ga, and Al) content in the NWs. A series of scaling effects in the mobility, transconductance, threshold voltage, and source-drain current with respect to the device channel length are also observed. Specifically, a small gate delay time (0.01 ns) and high on-current density (0.9 mA/μm) are obtained at 300 nm channel length. Furthermore, Mg-doped In(2)O(3) NWs are then employed to fabricate NW parallel array FETs with a high saturation current (0.5 mA), on/off ratio (>10(9)), and field-effect mobility (110 cm(2)/V·s), while the subthreshold slope and threshold voltage do not show any significant changes. All of these results indicate the great potency for metal-doped In(2)O(3) NWs used in the low-power, high-performance thin-film transistors.

In Situ Observation of Hydrogen‐Induced Surface Faceting for Palladium–Copper Nanocrystals at Atmospheric Pressure

Nanocrystal (NC) morphology, which decides the number of active sites and catalytic efficiency, is strongly determined by the gases involved in synthesis, treatment, and reaction. Myriad investigations have been performed to understand the morphological response to the involved gases. However, most prior work is limited to low pressures, which is far beyond realistic conditions. A dynamic morphological evolution of palladium-copper (PdCu) NC within a nanoreactor is reported, with atmospheric pressure hydrogen at the atomic scale. Inu2005situ transmission electron microscopy (TEM) videos reveal that spherical PdCu particles transform into truncated cubes at high hydrogen pressure. First principles calculations demonstrate that the surface energies decline with hydrogen pressure, with a new order of γH-001 <γH-110 <γH-111 at 1u2005bar. A comprehensive Wulff construction based on the corrected surface energies is perfectly consistent with the experiments. The work provides a microscopic insight into NC behaviors at realistic gas pressure and is promising for the shaping of nanocatalysts by gas-assisted treatments.

Vertical/Planar Growth and Surface Orientation of Bi2Te3 and Bi2Se3 Topological Insulator Nanoplates

Nanostructures are not only attractive for fundamental research but also offer great promise for bottom-up nanofabrications. In the past, the growth of one-dimensional vertical/planar nanomaterials such as nanowires has made significant progresses. However, works on two-dimensional nanomaterials are still lacking, especially for those grown out of a substrate. We report here a vertical growth of topological insulator, Bi2Se3 and Bi2Te3, nanoplates on mica. In stark contrast to the general belief, these nanoplates are not prisms exposing (100) lateral surfaces, which are expected to minimize the surface area. Instead, they are frustums, enclosed by (01-4), (015), and (001) facets. First-principles calculations, combined with experiments, suggest the importance of surface oxidation in forming these unexpected surfaces.

Effects of in ovo feeding of carbohydrates on hatchability, body weight, and energy status in domestic pigeons (Columba livia)

The effects of in ovo feeding of carbohydrates on hatchability, BW, yolk sac weights (YSW), pectoral muscle weights (PMW), liver and pectoral muscle glycogen concentration, serum glucose level, and hepatic glucose-6-phosphatase activity of domestic pigeons, hatched from eggs laid by a 40-wk-old breeder flock, were investigated. At 14.5 of incubation, fertile eggs were injected with 200 μL of 1.5% maltose (M) + 1.5% sucrose (S), 2.5% M + 2.5% S, 3.5% M + 3.5% S, or 4.5% M + 4.5% S in 0.75% saline, with controls not injected. Results showed that in ovo injection with 1.5% M + 1.5% S or 2.5% M + 2.5% S increased the hatchability compared with the control, whereas injection of 4.5% M + 4.5% S decreased the hatchability. The BW at hatch was quadratic, and BW was maximized by injecting 2.5% M + 2.5% S. The YSW at hatch decreased linearly by the injection with 3.5% M + 3.5% S compared with the control group. In ovo injection of 2.5% M + 2.5% S increased the PMW at hatch. There were no significant differences between any of the treatment groups for liver glycogen reserves. Serum glucose level at hatch was quadratic, and the glucose level was maximized between supplemental 2.5% M + 2.5% S and supplemental 3.5% M + 3.5% S. The pectoral muscle glycogen reserves increased quadratically as supplemental carbohydrates increased, and the response was maximized by injecting 2.5% M + 2.5% S. In conclusion, the present results demonstrate that the injected carbohydrates are available for use and storage. In ovo feeding of carbohydrates, especially at the level of 2.5% M + 2.5% S, on 14.5 d of incubation can improve the hatchability, BW, and PMW by elevating the pectoral muscle glycogen reserves in domestic pigeons at hatch. Results also suggested that in ovo injection of carbohydrates could increase the yolk sac nutrient utilization and hence might enhance the pigeon enteric development.

Direct observation of Pt nanocrystal coalescence induced by electron-excitation-enhanced van der Waals interactions

AbstractNanocrystal coalescence has attracted paramount attention in nanostructure fabrication in the past decades. Tremendous endeavor and progress have been made in understanding its mechanisms, benefiting from the development of transmission electron microscopy. However, many mechanisms still remain unclear, especially for nanocrystals that lack a permanent dipole moment standing on a solid substrate. Here, we report an in situ coalescence of Pt nanocrystals on an amorphous carbon substrate induced by electron-excitationenhanced van der Waals interactions studied by transmission electron microscopy and first principles calculations. It is found that the electron-beam-induced excitation can significantly enhance the van der Waals interaction between Pt nanocrystals and reduce the binding energy between Pt nanocrystals and the carbon substrate, both of which promote the coalescence. This work extends our understanding of the nanocrystal coalescence observed in a transmission electron microscope and sheds light on a potential pathway toward practical electronbeam-controlled nanofabrication.n

Recent advances in gas-involved in situ studies via transmission electron microscopy

Gases that are widely used in research and industry have a significant effect on both the configuration of solid materials and the evolution of reactive systems. Traditional studies on gas–solid interactions have mostly been static and post-mortem and unsatisfactory for elucidating the real active states during the reactions. Recent developments of controlled-atmosphere transmission electron microscopy (TEM) have led to impressive progress towards the simulation of real-world reaction environments, allowing the atomic-scale recording of dynamic events. In this review, on the basis of the in situ research of our group, we outline the principles and features of the controlled-atmosphere TEM techniques and summarize the significant recent progress in the research activities on gas–solid interactions, including nanowire growth, catalysis, and metal failure. Additionally, the challenges and opportunities in the real-time observations on such platform are discussed.