Simple Vapor Deposition Method Research Articles

Array-based titanium dioxide biosensors for ratiometric determination of glucose, glutamate and urea

A novel optical array-based titanium dioxide (TiO 2) biosensor combining with simple vapor deposition method was developed to simultaneously determine multianlaytes including glucose, urea and glutamate in serum samples. Carboxy seminaphthorhodamine-1-dextran (SNARF-1-dextran), serving as a single-molecule fluorescent probe, was co-immobilized with different enzymes including urease, glucose dehydrogenase (GDH), and glutamate dehydrogenase (GLDH) for determination of urea, glucose and glutamate simultaneously. The SNARF-1-dextran was a useful pH sensitive dye and the fluorescence ratio at 585 and 630 nm was used to characterize the change in solution pH. Atomic force microscopic (AFM) and scanning electron microscopy (SEM) images showed that TiO 2 is a crack-free stable sol–gel material, which can effectively trap enzymes in the sol–gel-derived matrices prepared by vapor deposition method. The surface morphology of the sol–gel-derived TiO 2 films changed significantly after the immobilization of macromolecules and enzymes. The array-based TiO 2 biosensors show good analytical performance on the simultaneous determination of multiple samples for multianalytes without obvious cross-interference. The analytical ranges of the three analytes in water samples were between 0.01 and 10 mM and limit of detections (LODs) were in the range 2.4–5.5 μM. In addition, satisfactory dynamic ranges of 2–3 orders of magnitude with LODs of 3.1–7.8 μM in serum samples were obtained. These results demonstrate the first report of combining a sol–gel-derived TiO 2 array biosensor with SNARF-1-dextran for ratiometric determination of multianalytes simultaneously and provide a viable alternative to current silica technology for the fabrication of array-based optical biosensors.

Growth and photoluminescence of vertically aligned ZnO nanowires/nanowalls

By controlling the incoming gas flow, vertically aligned ZnO nanowires and nanowalls have been successfully synthesized on a Si (1 0 0) substrate by the simple physical vapour deposition method. The growth process of the ZnO nanowalls was observed by adjusting the growth time. The probable growth mechanisms of the ZnO nanowires and nanowalls were discussed in detail. In contrast to the photoluminescence results of nanowires, an enhancement of the LO phonon signal was observed in ZnO nanowalls, which was attributed to an additional channel of electron–phonon coupling induced by the residual strains in the ZnO nanowalls during the coalescence growth process.

Evidence of hexagonal WO 3 structure stabilization on mica substrate

WO 3 nanorods are grown by a simple vapor deposition method on a mica substrate and characterized by Selected Area Electron Diffraction and Energy Dispersive X-rays Spectroscopy. Experimental results show the clear evidence of an unexpected WO 3 hexagonal structure as well as an epitaxial growth on the mica substrate. Besides, potassium is evidenced inside the nanorods. It is thus deduced that a metastable WO 3 hexagonal phase is stabilized by epitaxy through a tungsten bronze interlayer having same hexagonal structure.

Controllable Morphology Evolution and Photoluminescence of ZnSe Hollow Microspheres

Hollow ZnSe microspheres were successfully synthesized by a simple chemistry vapor deposition method in a horizontal tube furnace. The as-obtained samples were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectrometry. The growth mechanism of the ZnSe microspheres was discussed in detail, which can be addressed as the SO 2 gas trap, expand, and burst during the deposition process. The morphology evolutions of the microspheres were observed. The size, open mouth, surface state, and morphology of the hollow ZnSe microspheres could be adjusted through changing the experimental conditions. Photoluminescence measurements show that the as-synthesized hollow ZnSe microspheres exhibit strong blue emissions with the intensities being adjustable. These hollow ZnSe microspheres may have promising applications in blue emitters, gas sensors, microreactors, and catalyst carriers.

MnS doped mesoporous silica catalysts for the generation of novel carbon nanocages

Novel MnS impregnated mesoporous silica systems have been originated for the generation of carbon nanocages. The procedure involves a simple catalytic vapour deposition (CVD) method. This is the first time that a transition metal sulfide has been used for the synthesis of carbon nanostructures.

TiS 2 whisker growth by a simple vapor-deposition method

We reported the synthesis of titanium disulfide (TiS 2) whiskers on Ni-coated Si wafer via a simple vapor transport deposition method at 630 °C. To our knowledge, this is the first time to report the synthesis of TiS 2 whiskers with exact stoichiometric composition. By gently controlling the configuration of S and Ti sources and Si substrate during vapor reaction, TiS 2 whiskers could be successfully acquired. TiS 2 whiskers are single crystalline with exact stoichiometric composition. This kind of solid sulfide source method also can be used for synthesis of other transitional metal dichalcogenide whiskers. We believe that the successful growth of TiS 2 whiskers would provide significant theoretical and experimental opportunities for researchers.

ZnO nanorod arrays grown under different pressures and their photoluminescence properties

The ZnO nanorod arrays were synthesized via a simple vapor deposition method on Si (1 1 1) substrates at a low growth temperature of 520 °C. By selecting different source materials under different growth pressures, well-aligned hexagonal-shaped ZnO nanorod arrays were obtained under both conditions. X-ray diffraction (XRD) analysis confirmed the nanorods are c-axis orientated. Selected area electron diffraction (SAED) and transmission electron microscopy (TEM) analysis demonstrated the individual nanorod is single crystal. Photoluminescence (PL) analyses show the superior optical properties of the nanorod arrays.

Glutamate optical biosensor based on the immobilization of glutamate dehydrogenase in titanium dioxide sol–gel matrix

A simple and novel titania sol-gel derived optical biosensor coupled with carboxy seminaphthorhodamine-1-dextran (SNARF-1-dextran) as the fluorescent dye was fabricated for the determination of glutamate in water and biological samples. The NADH-dependent glutamate dehydrogenase (GLDH) was trapped in titania sol-gel derived matrix prepared by vapor deposition method. In addition, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize the surface morphology of the spots. SEM and AFM images showed that the deposition of titania precursor at 27 degrees C for 6.5h was found to be suitable to form transparent titania sol-gel matrix to encapsulate GLDH and fluorescent probe. AFM images showed that the roughness of TiO(2) surface increased from 2.16 nm in the absence of GLDH and SNARF to 37.8 nm after the immobilization. The developed titania biosensor has good analytical performance with water samples. A dynamic range between 0.04 and 10mM with the detection limit of 5.5 microM were observed. The responses to glutamate in biological samples also showed good performances, and the dynamic range and detection limit were 0.02-10mM and 6.7 microM, respectively. High precision with relative standard deviations of 4.2 and 10.7% in water and biological samples, respectively, were also demonstrated. In addition, the biosensor showed a relatively high storage stability over more than 1 month. Results obtained in this study clearly demonstrate that this simple vapor deposition method can be successfully used to form transparent titania sol-gel film for the fabrication of glutamate biosensors that are suitable for optical detection of glutamate in water and biological samples.

Synthesis and characterization of In 2O 3/SnO 2 hetero-junction beaded nanowires

Hetero-junction beaded nanowires were synthesized via a simple thermal vapor deposition method. These nanowires were characterized with XRD, Raman, SEM, TEM, HRTEM, SAED and PL spectroscopy. Many single-crystal In 2O 3 beads epitaxially grown along the axis of the single-crystal core SnO 2 nanowires form the beaded nanowires. The In 2O 3 beads have definite orientations along the [2 0 0] direction of the core SnO 2 nanowires and show regular rhombohedral morphology. A possible growth mechanism for the beaded nanowires is proposed.

Field emission from AlN nanoneedle arrays

AlN nanoneedles with an average tip dimension of ∼15nm were synthesized via a simple vapor deposition method. The AlN nanoneedles exhibit excellent field-emission properties with a low turn-on field of 3.1V∕μm and a high current density of 4.7mA∕cm2 at the field of 9.9V∕μm. The field enhancement factor for a single nanoneedle is estimated to be as high as 30 000 due to its small tip radius. These features make the AlN nanoneedles a competitive candidate for field-emission-based displays.

Preparation of silver thin films using liquid-phase precursors by metal organic chemical vapor deposition and their conversion to silver selenide films by selenium vapor deposition

A series of new Ag precursors containing β-diketonate and neutral phosphite ligands were synthesized and characterized by various spectroscopic methods. These volatile precursors in liquid phase were thermally stable and quite useful in the preparation of silver thin films through bubbler-type chemical vapor deposition (CVD). In a typical case of silver (I) 1,1,1-trifluoro-2,4-pentanedionate triethyl phosphite adduct ((tfac)AgP(OEt)3) precursor, very pure silver thin films were obtained under relatively mild conditions without any appreciable amount of F, O, and P impurities. These thin films were easily converted to β-orthorhombic silver selenide by simple selenium vapor deposition method. In scanning electron microscopic analyses, the average particle size of the latter was found to increase to about 1.26 μm after gas-phase selenization reaction.

Electrical properties of individual single-crystalline gallium phosphide nanowires with anouter oxide shell

High-quality single-crystalline GaP nanowires were grown by a simple vapourdeposition method and their electrical and opto-electric transport properties werestudied. Structural studies showed that the GaP nanowires consisted of acore–shell structure with a single-crystalline GaP core and an outer gallium oxide(GaOx) layer of thickness nm. The individual GaP nanowires exhibited n-type field effects with an on/off ratio as high as105 and their carrier mobilities are in the range of about10–22 cm2 V−1 s−1 at room temperature. When the devices were exposed to an ultraviolet (UV)light source, the current in the nanowires increased abruptly to more than103 times, and this was possibly due to carrier generation in the nanowires and de-adsorption of adsorbedO2− ionson the GaOx surface shell. The nanowires also showed good reversible switching actions between thehigh- and low-resistance states.

Synthesis of high-purity GaP nanowires using a vapor deposition method

High-purity gallium phosphide (GaP) nanowires were successfully synthesized on the nickel monoxide (NiO) or the cobalt monoxide (CoO) catalyzed alumina substrate by a simple vapor deposition method. To synthesize the high-purity GaP nanowires, the mixture source of gallium (Ga) and GaP powder was directly vaporized in the range of 850–1000 °C for 60 min under argon ambient. The diameter of GaP nanowires was about 38–105 nm and the length was up to several hundreds of micrometers. The GaP nanowires have a single-crystalline zinc blend structure and reveal the core-shell structure, which consists of the GaP core and the GaPO 4/Ga 2O 3 outer layers. We demonstrate that the mixture of Ga/GaP is an ideal source for the high-yield GaP nanowires.