Anatase TiO(2) nanosheets with highly reactive (001) facets exposed have been successfully synthesized by a facile hydrothermal route, taking advantage of a specific stabilization effect of fluorine ion on (001) facets. The percentage of highly reactive (001) facets in such TiO(2) nanosheets is very high (up to 89%). In addition, the as-prepared TiO(2) nanosheets exhibit excellent activity in the photocatalytic degradation of organic contaminants.

Nanowires (NWs) and nanobelts (NBs) are considered as ideal building blocks for constructing nanosized devices due to high surface to volume ratio and their special physical and chemical properties resulting from the reduced sizes. Until now, many semiconductor NWs/NBs have been successfully applied in nanodevices, including nanolasers, 1 nanogenerators, 2 and various chemical and biological nanosensors. 3,4 Well-known humidity control is very important for many fields in technology and our daily life. In the past years, many detection techniques have been explored from old wet and dry bulb thermometry to modern capacitive, resistive, and thermal conductive moisture detectors. In order to further promote the sensitivity, selectivity, chemical and thermal stability, intensive efforts have been put in the exploration of a humidity sensor based on nanostructured materials such as carbon nanotubes, 5 metal oxide nanoparticles, 6 and NW films. 7 Being an important n-type semiconductor with a wide band gap (E g ) 3.6 eV at 300 K), SnO 2 possesses many unique optical and electrical properties: remarkable receptivity variation in gaseous environment, high optical transparency in the visible range (up to 97%), low resistivity (10 -4 to 10 6 Ω‚cm -1 ), and excellent chemical stability. These properties make SnO 2 NWs/NBs well suited for chemical sensors and transparent conducting electrodes. To date, many nanodevices based on SnO 2 NWs/NBs have been fabricated, including field effect transistors (FET), 8 field emissions, 9 UV sensors, 10 and gas sensors. 3a,11 In this communication, we present a new type of SnO 2 nanodevice, a humidity detector using a single SnO 2 NW as the sensing unit. This new type of SnO 2 NW-based sensor has fast and sensitive response to relative humidity (RH) in air from a wide range of environments at room temperature (30°C). In addition, it has relatively good reproducibility, and its linear response to RH makes it to calibrate.Single-crystalline SnO 2 NWs to be used as humidity sensors were synthesized by chemical vapor deposition (CVD) using Au nanoparticles as catalysts in a homemade synthetic apparatus. 12 Experimental details are available in Supporting Information. Figure 1a is a typical SEM image of as-synthesized NWs with high yield. The XRD pattern indicates that the NWs are rutile structured SnO 2 with a good crystallinity ( Figure S1). The diameter of SnO 2 NWs ranges from 50 to 300 nm, and the length of SnO 2 NWs is up to tens of micrometers. Low-magnification TEM image (upper inset of Figure 1a) and corresponding EDS analysis ( Figure S2) show that a Au nanoparticle exists at the tip of the SnO 2 NW, which is the representative characteristic of the vapor-liquid-solid (VLS) growth mechanism. 13 The selective area electron diffraction (SAED, lower inset of Figure 1a) pattern taken from the body of the SnO 2 NW reveals that the as-synthesized SnO 2 NW is single crystalline and grows along the [001] direction.Cathodoluminescence (CL) analysis is a suitable technique to determine th...

Metal-organic frameworks (MOFs) and related material classes are attracting considerable attention for their applications in gas storage/separation as well as catalysis. In contrast, research concerning potential uses in electronic devices (such as sensors) is in its infancy, which might be due to a great challenge in the fabrication of MOFs and semiconductor composites with well-designed structures. In this paper, we proposed a simple self-template strategy to fabricate metal oxide semiconductor@MOF core-shell heterostructures, and successfully obtained freestanding ZnO@ZIF-8 nanorods as well as vertically standing arrays (including nanorod arrays and nanotube arrays). In this synthetic process, ZnO nanorods not only act as the template but also provide Zn(2+) ions for the formation of ZIF-8. In addition, we have demonstrated that solvent composition and reaction temperature are two crucial factors for successfully fabricating well-defined ZnO@ZIF-8 heterostructures. As we expect, the as-prepared ZnO@ZIF-8 nanorod arrays display distinct photoelectrochemical response to hole scavengers with different molecule sizes (e.g., H(2)O(2) and ascorbic acid) owing to the limitation of the aperture of the ZIF-8 shell. Excitingly, such ZnO@ZIF-8 nanorod arrays were successfully applied to the detection of H(2)O(2) in the presence of serous buffer solution. Therefore, it is reasonable to believe that the semiconductor@MOFs heterostructure potentially has promising applications in many electronic devices including sensors.

Crystal phase regulations may endow materials with enhanced or new functionalities. However, syntheses of noble metal-based allomorphic nanomaterials are extremely difficult, and only a few successful examples have been found. Herein, we report the discovery of hexagonal close-packed Pt–Ni alloy, despite the fact that Pt–Ni alloys are typically crystallized in face-centred cubic structures. The hexagonal close-packed Pt–Ni alloy nano-multipods are synthesized via a facile one-pot solvothermal route, where the branches of nano-multipods take the shape of excavated hexagonal prisms assembled by six nanosheets of 2.5 nm thickness. The hexagonal close-packed Pt–Ni excavated nano-multipods exhibit superior catalytic property towards the hydrogen evolution reaction in alkaline electrolyte. The overpotential is only 65 mV versus reversible hydrogen electrode at a current density of 10 mA cm−2, and the mass current density reaches 3.03 mA μgPt−1 at −70 mV versus reversible hydrogen electrode, which outperforms currently reported catalysts to the best of our knowledge.

A yellow luminescent thiolate-protected Ag(14)(SC(6)H(3)F(2))(12)(PPh(3))(8) cluster was synthesized and structurally characterized by single-crystal X-ray analysis. The cluster contains an octahedral Ag(6)(4+) unit encapsulated by eight cubically arranged [Ag(+)(SC(6)H(3)F(2)(-))(2)PPh(3)] tetrahedra that share one corner (i.e. SC(6)H(3)F(2)(-)) between them.

Tin dioxide (SnO 2 ), an n-type semiconductor with a wide band gap of 3.6 eV, has been widely used in photocatalytic degradation of organic dyes, [1] photovoltaic devices, [2] rechargeable lithium batteries, [3] and so on. In particular, remarkable receptivity to variations in gaseous environments and excellent chemical stability have made SnO 2 the bestknown gas-sensing material. [4][5][6][7][8][9] Over the past decades, considerable efforts have been made to improve the sensitivity and selectivity of SnO 2 -based solid-state gas sensors through modifying the sensing material itself and the fabrication technique, such as doping of catalytic metal particles, [4] hybridization of different sensing materials, [5, 6] and optimization of working temperature. [7] In principle, gas sensing by metal-oxide semiconductors like SnO 2 is based on the oxidation-reduction reaction of the detected gases occurring on the semiconductor surface, which leads to an abrupt change in conductance of the sensor. For this reason, the gas-sensing ability of metal oxide semiconductors is in theory very sensitive to the crystal faces of the sensing materials.[10] From the viewpoint of chemical activity, metaloxide nanocrystals with particular exposed crystal planes, such as high-index facets, may be good sensing materials, because high-index facets having high densities of atom steps, ledges, kinks, and dangling bonds usually exhibit much higher chemical activity. [11][12][13] However, such a strategy to improve sensitivity and selectivity of sensors has not attracted much attention up to now, possibly due to the difficulty of synthesizing metal-oxide nanocrystals with specific exposed crystal planes.Herein we report a simple method for the preparation of octahedron-shaped SnO 2 with exposed high-index {221} facets by exploiting the coordinative-adsorption effect of HCl and poly(vinyl pyrrolidone), PVP, in solution. The {221} facets of SnO 2 have a higher relative surface energy (2.28 J m À2 ) than common low-index facets such as {110} (1.401 J m À2 ), {101} (1.554 J m À2 ), and {100} (1.648 J m À2

National Natural Science Foundation of China [20725310, 20721001, 20673085, 20671079, J0630429]; National Basic Research Program of China [2007CB815303, 2009CB939804]; Fujian Province of China [2005HZ013

In this paper, we successfully synthesized three kinds of typical ZnO micro/nanocrystallites including flakes, columns, and pyramids by means of different facile wet chemical routes. The growth environment plays a crucial role in the morphologies of these ZnO micro/nanocrystallites. At the same time, we find that physical/chemical properties of these ZnO samples are dependent on their exposed surface, and the order of gas sensing and photocatalytic efficiency of the ZnO crystal planes is (0001) > {10 (1) over bar0} > {10 (1) over bar1} and (000 (1) over bar). On the basis of structural analyses of various exposed surfaces and related X-ray photoelectron spectroscopy, we deeply discussed the effect of definite surface structures on their gas sensing and photocatalytic properties.National Natural Science Foundation of China [20725310, 20721001, 20673085, 20801045]; National Basic Research Program of China [2007CB815303, 2009CB939804