The effect of morphology on the plasmonic sensing of the presence of formaldehyde in water by gold nanostructures has been investigated. The gold nanostructures with two different morphologies, namely spherical and rod, were prepared using a seed-mediated method. In typical results, it was found that the plasmonic properties of gold nanostructures were very sensitive to the presence of formaldehyde in their surrounding medium by showing the change in both the plasmonic peaks position and the intensity. Spherical nanoparticles (GNS), for example, indicated an increase in the sensitivity when the size was increased from 25 to 35 nm and dramatically decreased when the size was further increased. An m value, the ratio between plasmonic peak shift and refractive index change, as high as 36.5 nm/RIU (refractive index unit) was obtained so far. An expanded sensing mode to FD was obtained when gold nanostructures with nanorods morphology (GNR) were used because of the presence of two plasmonic modes for response probing. However, in the present study, effective plasmonic peak shift was not observed due to the intense plasmonic coupling of closely packed nanorod structures on the surface. Nevertheless, the present results at least provide a potential strategy for response enhancement via shape-effects. High performance plasmonic sensors could be obtained if controlled arrays of nanorods can be prepared on the surface.
A network of gold nanostructures exhibiting one-dimensional gold nanostructure properties may become a prospective novel structure for optical, electrical and catalytic applications benefited by its unusual characteristics resulting from the collective properties of individual nanostructures in the network. In this paper, we demonstrate a facile method for the formation of high-density gold nanonetwork film on the substrate surface composed of quasi-1D nanoparticles (typically fusiform) with length ca. 10 nm - via reduction of gold ions in the presence of nanoseeds attached surface, binary surfactants of cetyltrimethylammonium bromide and hexamethyleneteramine and Ag+ ions. The length of the nanonetworks can be up to ca. 100 nm, which corresponds to the aspect ratio of ca. 10. The quasi-1D gold nanostructures as well as the nanonetworks were found to be sensitive to the binary surfactants system and the Ag+ ions as they can only be formed if all the chemicals are available in the reaction. The nanonetworks exhibit unique 1D optical properties with the presence of transverse and longitudinal surface plasmon resonance absorption. Owing to their peculiar structures that are composed of small quasi-1D nanoparticles, the nanonetworks may produce unusual optical and catalytic properties, which are potentially used in surface-enhanced Raman scattering, catalysis and optical and non-linear optical applications.
We found that the gold nanoparticles with high-density and crystalline-shape, such as nanocubes, nanobricks, pentahedral nanorods, etc., can be realized on the surface by using a seed-mediated growth method with a unique seeding process, namely alcohothermal. By using a conventional growth solution that contains HAuCl4, cetyltrimethylammonium bromide, NaOH and ascorbic acid, gold nanoparticles with crystalline-morphology (gold nanocrystals) of yield up to ca. 95%, can be prepared. An alcohothermal seeding was carried out by a thermal reduction of gold ions from an alcoholic solution of gold salt on the surface through an annealing process at a moderate temperature, namely 250 degrees C. It is believed that the unique initial characteristic (presumably the structures) of the gold nanoseeds particles as the result of peculiar nanoseeds formation process, prepared using this approach, instead of a simple thermal restructuring of the as prepared nanoseeds as confirmed by the results of annealing treatment on the nanoseed prepared using the normal and in-situ reduction seeding, was as the driving factor for the projected growth of crystalline-shape gold nanoparticles on the surface. The crystalline-shape gold nanoparticles modified-surface should find a potential application in catalysis, sensors and SERS.
Highly efficient and remarkable selective acetone conversion to isopropanol has been achieved via a heterogeneous catalytic hydrogenation of acetone by NaBH4 in the presence of semihollow palladium nanoparticles (PdNPs) grown on ITO substrate. PdNPs with high surface defect grown on an indium tin oxide (ITO) surface were prepared via a simple immersion of the substrate into a solution containing K2PdCl6, sodium dodecyl sulphate (SDS), and formic acid for 2 h at room temperature. The sample showed remarkably high heterogeneous catalytic efficiency by producing 99.8% of isopropanol within 6 min using only 0.28 μg of PdNPs on the ITO surface. The present system exhibits heterogenenous catalytic hydrogenation efficiency 1 × 10(6) time higher than using the conventional Raney Ni system.
The crystallographic plane of the ZnO nanocrystals photocatalyst is considered as a key parameter for an effective photocatalysis, photoelectrochemical reaction and photosensitivity. In this paper, we report a simple method for the synthesis of a new (101) high-energy plane bounded ZnO nanocubes photocatalyst directly on the FTO surface, using a seed-mediated ultrasonic assisted hydrolysis process. In the typical procedure, high-density nanocubes and quasi-nanocubes can be grown on the substrate surface from a solution containing equimolar (0.04 M) zinc nitrate hydrate and hexamine. ZnO nanocubes, with average edge-length of ca. 50 nm, can be obtained on the surface in as quickly as 10 min. The heterogeneous photocatalytic property of the sample has been examined in the photodegradation of methyl orange (MO) by UV light irradiation. It was found that the ZnO nanocubes exhibit excellent catalytic and photocatalytic properties and demonstrate the photodegradation efficiency as high as 5.7 percent/μg mW. This is 200 times higher than those reported results using a relatively low-powered polychromatic UV light source (4 mW). The mechanism of ZnO nanocube formation using the present approach is discussed. The new-synthesized ZnO nanocubes with a unique (101) basal plane also find potential application in photoelectrochemical devices and sensing.
A simple method for the synthesis of ZnO nanofilms composed of vertical array of quasi-1D ZnO nanostructures (quasi-NRs) on the surface was demonstrated via a 1D crystal growth of the attached nanoseeds under a rapid hydrolysis process of zinc salts in the presence of ammonia at room temperature. In a typical procedure, by simply controlling the concentration of zinc acetate and ammonia in the reaction, a high density of vertically oriented nanorod-like morphology could be successfully obtained in a relatively short growth period (approximately 4 to 5 min) and at a room-temperature process. The average diameter and the length of the nanostructures are approximately 30 and 110 nm, respectively. The as-prepared quasi-NRs products were pure ZnO phase in nature without the presence of any zinc complexes as confirmed by the XRD characterisation. Room-temperature optical absorption spectroscopy exhibits the presence of two separate excitonic characters inferring that the as-prepared ZnO quasi-NRs are high-crystallinity properties in nature. The mechanism of growth for the ZnO quasi-NRs will be proposed. Due to their simplicity, the method should become a potential alternative for a rapid and cost-effective preparation of high-quality ZnO quasi-NRs nanofilms for use in photovoltaic or photocatalytics applications.PACS: 81.07.Bc; 81.16.-c; 81.07.Gf.
Five new stilbenoids, vatalbinosides A-E (1-5), and 13 known compounds (6-18) were isolated from the stem of Vatica albiramis. The effects of these new compounds on interleukin-1β-induced production of matrix metalloproteinase-1 (MMP-1) in human dermal fibroblasts were examined. Three resveratrol tetramers, (-)-hopeaphenol (6), vaticanol C (13), and stenophyllol C (14), were identified as strong inhibitors of MMP-1 production.
A combinative effect of two or more individual material properties, such as lattice parameters and chemical properties, has been well-known to generate novel nanomaterials with special crystal growth behavior and physico-chemical performance. This paper reports unusually high catalytic performance of AgPt nanoferns in the hydrogenation reaction of acetone conversion to isopropanol, which is several orders higher compared to the performance shown by pristine Pt nanocatalysts or other metals and metal-metal oxide hybrid catalyst systems. It has been demonstrated that the combinative effect during the bimetallisation of Ag and Pt produced nanostructures with a highly anisotropic morphology, i.e., hierarchical nanofern structures, which provide high-density active sites on the catalyst surface for an efficient catalytic reaction. The extent of the effect of structural growth on the catalytic performance of hierarchical AgPt nanoferns is discussed.
This Research Article reports an unusually high efficiency heterogeneous photodegradation of methyl orange (MO) in the presence of Ag nanoparticle-loaded ZnO quasi-nanotube or nanoreactor (A-ZNRs) nanocatalyst grown on FTO substrate. In typical process, photodegradation efficiency of as high as 21.6% per μg per Watts of used catalyst and UV power can be normally obtained within only a 60-min reaction time from this system, which is 10(3) order higher than the reported results. This is equivalent to the turnover frequency of 360 mol mol(-1) h(-1). High-density hexagonal A-ZNRs catalysts were grown directly on FTO substrate via a seed-mediated microwave-assisted hydrolysis growth process utilizing Ag nanoparticle of approximately 3 nm in size as nanoseed and mixture aqueous solution of Zn(NO3)·6H2O, hexamethylenetetramine (HMT), and AgNO3 as the growth solution. A-ZNRs adopts hexagonal cross-section morphology with the inner surface of the reactor characterized by a rough and rugged structure. Transmission electron microscopy imaging shows the Ag nanoparticle grows interstitially in the ZnO nanoreactor structure. The high photocatalytic property of the A-ZNRs is associated with the highly active of inner side's surface of A-ZNRs and the oxidizing effect of Ag nanoparticle. The growth mechanism as well as the mechanism of the enhanced-photocatalytic performance of the A-ZNRs will be discussed.
This paper reports a facile, solution-phase approach to synthesizing a one-dimensional amorphous face-centered-cubic (fcc) platinum (a-Pt) nanostructure (nanofibers) directly on an indium-tin oxide (ITO) substrate. The electron microscopy analysis result shows that the a-Pt nanofiber has a diameter and length of approximately 50 nm and 1 μm, respectively, and is grown in high density on the entire surface of the ITO substrate. The X-ray photoelectron spectroscopy analysis result further reveals that the a-Pt nanofibers feature metallic properties with highly reactive surface chemistry, promising novel performance in electrochemistry, catalysis, and sensors. A synergetic interplay between the formic acid reducing agent and the hexamethylenetetramine surfactant in the reduction of Pt ions is assumed as the driving force for the formation of the amorphous phase in the Pt nanostructure. The catalytic properties of a-Pt were examined in the acetone hydrogenation reaction under microwave irradiation. a-Pt shows excellent heterogeneous catalytic properties for converting acetone to isopropyl alcohol with turnover number and frequency as high as 400 and 140 min(-1), respectively. The preparation and formation mechanism of the a-Pt nanofibers will be discussed in detail in this paper.
This paper reports the synthesis of two-dimensional, hierarchical, porous, and (001)-faceted metal (Ag, Zn, and Al)-doped TiO2 nanostructures (TNSs) and the study of their photocatalytic activity. Two-dimensional metal-doped TNSs were synthesized using the hydrolysis of ammonium hexafluorotitanate in the presence of hexamethylenetetramine and metal precursors. Typical morphology of metal-doped TNSs is a hierarchical nanosheet that is composed of randomly stacked nanocubes (dimensions of up to 5 μm and 200 nm in edge length and thickness, respectively) and has dominant (001) facets exposed. Raman analysis and X-ray photoelectron spectroscopy results indicated that the Ag doping, compared to Zn and Al, much improves the crystallinity degree and at the same time dramatically lowers the valence state binding energy of the TNS and provides an additional dopant oxidation state into the system for an enhanced electron-transfer process and surface reaction. These are assumed to enhance the photocatalytic of the TNS. In a model of photocatalytic reaction, that is, rhodamine B degradation, the AgTNS demonstrates a high photocatalytic activity by converting approximately 91% of rhodamine B within only 120 min, equivalent to a rate constant of 0.018 m-1 and ToN and ToF of 94 and 1.57 min-1, respectively, or 91.1 mmol mg-1 W-1 degradation when normalized to used light source intensity, which is approximately 2 times higher than the pristine TNS and several order higher when compared to Zn- and Al-doped TNSs. Improvement of the crystallinity degree, decrease in the defect density and the photogenerated electron and hole recombination, and increase of the oxygen vacancy in the AgTNS are found to be the key factors for the enhancement of the photocatalytic properties. This work provides a straightforward strategy for the preparation of high-energy (001) faceted, two-dimensional, hierarchical, and porous Ag-doped TNSs for potential use in photocatalysis and photoelectrochemical application.