A simple and cost-effective one-step hydrothermal method, which was based on the reactions of tin(IV) chloride pentahydrate and different dosages of thioacetamide in water at 190 °C for 6 h, was employed for the synthesis of composition-tunable SnS 2 /SnO 2 nanoheterojunctions (e.g., SnS 2 /SnO 2 -A, SnS 2 /SnO 2 -B and SnS 2 /SnO 2 -C). The photocatalytic properties of the as-synthesized SnS 2 /SnO 2 nanoheterojunctions were tested by the reduction of aqueous Cr(VI) under visible-light ( λ  > 420 nm) irradiation. Furthermore, the photocatalytic efficiency of SnS 2 /SnO 2 -B was compared with those of PM-SnS 2 /SnO 2 (which denotes the physically mixed SnS 2 /SnO 2 nanocomposite with the same composition as SnS 2 /SnO 2 -B) and SnS 2 nanoflakes at different dosages of photocatalysts. It was observed that (i) the photocatalytic activities of the as-synthesized SnS 2 /SnO 2 nanoheterojunctions depended on their compositions, and SnS 2 /SnO 2 -B with 70 mol% SnS 2 displayed the highest photocatalytic activity; (ii) SnS 2 /SnO 2 -B invariably exhibited higher photocatalytic efficiencies than PM-SnS 2 /SnO 2 and SnS 2 nanoflakes at different dosages of photocatalysts; (iii) the washing with 1 mol/L HNO 3 can effectively regenerate the used photocatalyst; (iv) SnS 2 /SnO 2 -B exhibited good photocatalytic stability in reuses, with regeneration by 1 mol/L HNO 3 -washing after each cycle of photocatalytic use; and (v) Cr(VI) was reduced to Cr(III). The possible formation mechanism of SnS 2 /SnO 2 nanoheterojunctions and the reasons accounting for the photocatalytic results were also discussed.

One-step hydrothermal synthesis of high-performance visible-light-driven SnS2/SnO2 nanoheterojunction photocatalyst for the reduction of aqueous Cr(VI)

Although there has been significant progress in the fabrication and performance optimization of one-dimensional nanostructure-based photodetectors, it is still a challenge to develop an effective and low-cost device with high performance characteristics, such as a high photocurrent/ dark-current ratio, photocurrent stability, and fast time response. Herein an efficient and low-cost method to achieve high-performance 'visible-blind' microscale ZnS nanobelt-based ultraviolet (UV)-light sensors without using a lithography technique, by increasing the nanobelt surface areas exposed to light, is reported. The devices exhibit about 750 times enhancement of a photocurrent compared with individual nanobelt-based sensors and an ultrafast time response. The photocurrent stability and time response to UV-light do not change significantly when a channel distance is altered from 2 to 100 μm or the sensor environment changes from air to vacuum and different measurement temperatures (60 and 150°C). The photoelectrical behaviors can be recovered well after returning the measurement conditions to air and room temperature again. The low cost and high performance of the resultant ZnS nanobelt photodetectors guarantee their highest potential for visible-blind UV-light sensors working in the UV-A band.

An Efficient Way to Assemble ZnS Nanobelts as Ultraviolet-Light Sensors with Enhanced Photocurrent and Stability

1D nanostructures, such as nanotubes, nanowires, and nanobelts, have become of interest because of their potential value for leading to an understanding of fundamental physical concepts and constructing nanoscale electric and optoelectronic devices. ZnS, an important semiconductor compound of the II–VI group, has a wide band gap energy of 3.7 eV (1 eV = 1.602 × 10 J) at 300 K. ZnS is one of the first semiconductors discovered and probably one of the most important materials in the electronics industry. Recently, various ZnS 1D nanostructures have successfully been synthesized. Among them, ZnS nanobelts are one of the most interesting objects. Nanobelts of different widths, ranging from tens of nanometer to several micrometers, have been prepared and studied in detail. Ultrafine ZnO nanobelts proved to be of particular interest for the general study of size-induced electrical and optical properties of functional oxides. Thus the synthesis and novel property exploration of ultrafine ZnS nanobelts are indispensable. However, largescale ZnS nanobelt synthesis, especially for small (width < 20 nm) belts, is still a challenge. In this communication, we describe the synthesis of ultrafine ZnS nanobelts by controlling evaporation and agglomeration rates. The range of the belt widths was 5–30 nm, and peaked at 10–20 nm. The belt thickness varied with width and was typically of only several nanometers. The regarded ultrafine ZnS nanobelts not only showed a pronounced quantumconfinement effect (a blue-shift of ca. 0.45 eV compared to bulk ZnS materials), but also possessed good field-emitting characteristics: a low turn-on field of 3.47 V lm and a high field-enhancement factor (over 2000). Although the work function of ZnS (7.0 eV) is larger than that of Si (3.6 eV), AlN (3.7 eV), SiC (4.0 eV), C nanotubes (5 eV) or ZnO (5.3 eV), the field-emission (FE) properties of the present tiny ZnS nanobelts are comparable or even better than those of many other 1D nanostructures because of a characteristically high aspect ratio. Therefore, ultrafine ZnS nanobelts may be attractive as field emitters and highly useful in novel nanoscale electric and optoelectronic devices. Figure 1 shows FE scanning electron microscopy (SEM) images of the as-grown nanobelts. A low-magnification SEM image in Figure 1a reveals that the nanobelts are several to tens of micrometers in length. The corresponding high-magnification SEM image in Figure 1b shows that each nanobelt has a uniform width over its entire length. The typical belt width is in the range of 10–20 nm. A high-magnification SEM image in Figure 1c clearly indicates that a product exhibits numerous beltlike structures. Figure 1d and e shows typical high-magnification SEM images of individual nanobelts. An X-ray diffraction (XRD) pattern from the product is shown in Figure 1f, where all the diffraction peaks can be indexed to wurtzite-type ZnS with lattice constants of a = 0.382 nm and c = 0.626 nm (Joint Committee for Powder Diffraction Studies (JCPDS) Card: 36-1450). By using electron-beam irradiation in SEM, we found that the nanobelts were very sensitive to an electron beam. Figure 1S, Supporting Information, depicts nanobelt SEM images after electron-beam irradiation. Clearly, the nanobelt width increased with an increase in irradiation time. High-resolution transmission electron microscopy (HRTEM; using a JEM-3000F high-resolution transmission electron microscope) was used to further characterize the beltlike product. By measuring over 100 nanobelts, we confirmed that the typical width of the belts is in the range of 5–30 nm and peaked at 10–20 nm. Figure 2a and b show typical belt TEM images. Very narrow nanostructures were observed, less than 20 nm in width. It can also be seen that a thin amorphous carbon layer coats the side belt surfaces, as marked in Figure 2d and e. Figure 2c is an enlarged image from the area c marked in Figure 2b. All nanobelts are singlecrystalline. The smallest width of ZnS nanobelts was measured as 7.5 nm (Fig. 2c). This particular nanobelt is likely to be very thin (ca. 1–2 nm). In fact, we could easily see the lattice fringes for the nanobelt laid behind, as shown in Figure 2c. The nanobelt thickness (Fig. 2d) is likely to be only four atomic layers, as indicated by the arrows in Figure 2c. The nanobelts are easily curled. Figure 2d and e are lattice-resolved HRTEM images taken from individual nanobelts of 9 and 10 nm width, respectively. The marked interplanar d-spacings of 0.31 and 0.33 nm correspond to the (002) and (010) lattice planes of wurtzite ZnS. From Figure 2c–e, it is C O M M U N IC A IO N

Ultrafine ZnS Nanobelts as Field Emitters

Synthesis of wurtzite ZnS nanoparticles using the microwave assisted solvothermal method

Hierarchically nanosized hydroxyapatite (HA) with flower-like structure assembled from nanosheets consisting of nanorod building blocks was successfully synthesized by using CaCl2, NaH2PO4, and potassium sodium tartrate via a hydrothermal method at 200°C for 24 hours. The effects of heating time and heating temperature on the products were investigated. As a chelating ligand and template molecule, the potassium sodium tartrate plays a key role in the formation of hierarchically nanostructured HA. On the basis of experimental results, a possible mechanism based on soft-template and self-assembly was proposed for the formation and growth of the hierarchically nanostructured HA. Cytotoxicity experiments indicated that the hierarchically nanostructured HA had good biocompatibility. It was shown by in-vitro experiments that mesenchymal stem cells could attach to the hierarchically nanostructured HA after being cultured for 48 hours.

Objective
The purpose of this study was to develop facile and effective methods for the synthesis of novel hydroxyapatite (HA) with hierarchical nanostructures assembled from independent and discrete nanobuilding blocks.

/pdf/hierarchically-nanostructured-hydroxyapatite-hydrothermal-2y2fzk1p4s.pdf

Hierarchically nanostructured hydroxyapatite: hydrothermal synthesis, morphology control, growth mechanism, and biological activity

Highly ordered hierarchical calcium carbonate is an important phase involved in calcification by a wide variety of invertebrate organisms, and its formation is of technological interest in the development of functional materials. In this article, porous CaCO3 hierarchical microspheres with a hedgehoglike appearance have been fabricated on the flexible substrate under mild conditions. There are two points that play important roles in the regular organization of the terminal products: one is the biphase interfaces, which are generated by organic solvent n-hexane and an aqueous saturated solution of Ca(OH)2, and the other is hydroxyl-terminated monolayers assembled on the flexible PET (poly(ethylene terephthalate)) substrate. The SEM images show that novel CaCO3 hierarchical microspheres consist of densely stacked “shuttles” by the oriented self-organization of CaCO3 nanoparticles. The IR and XRD spectra indicate that the as-synthesized products are composed of a calcite phase obtained by an ACC (amorphous c...

Fabrication of hierarchical CaCO3 mesoporous spheres: particle-mediated self-organization induced by biphase interfaces and SAMs.

In this research, the role that the organic–inorganic liquid interface plays in the synthesis of nonequilibrium crystalline materials is investigated. A hierarchical nanocrystalline film of wurtzite ZnS, the high-temperature stable phase, is successfully prepared at room temperature by an interfacial in situ fabrication process. The organic–inorganic liquid interface constructed by n-hexane and water acts as the reaction zone for the synthesis of ZnS nanocrystalline film. A series of experimental results have proved that the liquid–liquid interface is the key factor for wurtzite ZnS formation at room temperature without any additive. The ZnS film consists of core–shell subunits characterized by ZnS nanoparticles around an organic core. Between the liquid–liquid interface, the core–shell subunits are coupled onto the surface of a SAM-modified substrate by terminal amino groups, so that the ZnS nanocrystalline film is formed by a layer-by-layer mode. This research brings forward a feasible route for synthes...

The Role of the Liquid–Liquid Interface in the Synthesis of Nonequilibrium Crystalline Wurtzite ZnS at Room Temperature

The invention discloses a method for realizing self-cleaning by performing superhydrophobic modification treatment on the surface of a substrate, which comprises the following steps: 1) cleaning and drying an inorganic substrate, and placing the inorganic substrate at room temperature; 2) radiating the inorganic substrate treated by the step 1 with ultraviolet; and 3) preparing a superhydrophobic coating on the inorganic substrate to obtain a self-cleaning surface with superhydrophobic performance. When the substrate is a polymer substrate, a silane buffering layer is formed on the polymer substrate first before the step 2 and the step 3 are executed. The contact angle of water subjected to distillation for three times with the substrate surface prepared by the invention can reach 150 DEG, and the superhydrophobic coating can prevent pollution of impurities effectively and thus realize self-cleaning. The superhydrophobic coating has high stability.

Method for realizing self-cleaning by performing superhydrophobic modification treatment on surface of substrate

The invention discloses a preparation method for a hexagonal phase zinc sulfate nano-crystal coating. The method comprises the following steps: A) providing a substrate; B) forming a hydrophilic self-assembled silicane molecule layer on the substrate; C) adding a inorganic zinc salt and a water-soluble organic amine to water to prepare a zinc salt aqueous solution, then adding a carbon-sulfur double bond-containing compound to an organic solvent to prepare an organic solvent of the carbon-sulfur double bond-containing compound, wherein the organic solvent is insoluble in the water; D) mixing the organic solvent of the carbon-sulfur double bond-containing compound and the zinc salt aqueous solution to form a different-phase interface between the organic solvent of the carbon-sulfur double bond-containing compound and the zinc salt aqueous solution; and E) placing the substrate on the different-phase interface, and making the hydrophilic self-assembled silicane molecule layer toward to the zinc salt aqueous solution to form the hexagonal phase zinc sulfate nano-crystal coating on the substrate through the hydrophilic self-assembled silicane molecule layer. With the method provided by the present invention, the hexagonal phase zinc sulfate nano-crystal coating can be prepared at a room temperature, the production cost can be reduced, and pollution is decreased.

Preparation method for hexagonal phase zinc sulfate nano-crystal coating

Patterned ultraviolet screening film preparation method

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