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971.
In this review article, we discuss a class of biosensors that exploit the change in the colorimetric properties of noble metal nanoparticles in response to biomolecular binding at their surface. Several sensor fabrication techniques as well as sensor configurations are discussed with an emphasis on their strengths and limitations. We conclude by presenting the future prospects and challenges for the successful transition of this technology from the laboratory to a commercial product. 相似文献
972.
Chitta?Ranjan?Patra Yitzhak?Mastai Aharon?GedankenEmail author 《Journal of nanoparticle research》2004,6(5):509-518
Submicrometer sized gallium oxide hydroxide (GaO(OH)) and gallium oxide (Ga2O3) rods have been successfully fabricated on a large scale by refluxing an aqueous solution of Ga(NO3)3 and NH4OH in a simple domestic microwave oven (DMO). The structures, morphologies, compositions and physical properties of the as–synthesized and calcined products have been characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), selected area energy dispersive X-ray spectroscopy (SAEDS), thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), and energy dispersive X-ray (EDX) analysis. TEM images show that submicrometer sized as–synthesized Ga O(OH) rods have diameters of 0.3–0.5 m and lengths of 3.2–3.5 m. The calcined product consists of submicrometer rods with diameters of 0.4–0.5 m and lengths of 5–5.5 m. XRD, EDX and SAED analysis together indicate that the as–synthesized product has an orthorhombic gallium oxide hydroxide (GaO(OH)) crystal structure, and that the calcined product is rhombohedral Ga2O3. A possible mechanism for the formation of submicrometer sized GaO(OH) rods is discussed briefly. 相似文献
973.
Synthesis of nanometer-sized particles with new physical properties is an area of tremendous interest. In metal particles, the changes in size modify the electron density in the particles, which shifts the plasmon band. The most significant size effects occur when the particles are ultrafine (size is <10 nm). Thus the synthesis of ultrafine metal particles is enormously important to exploit their unique and selective application. Here we report a novel method for the synthesis of ultrafine gold particles in the size range of 0.5–3 nm using dopamine hydrochloride (dhc), an important neurotransmitter. This is the first time where such an important bioactive molecule like dhc has been used as a reagent for the transformation of Au(III) to Au(0). The synthesis is carried out, for the first time, either in simple aqueous or in a nonionic micellar (for example Triton X-100 (TX-100)) medium. The gold sol has a beautiful yellow–brown color showing max at 470 nm. The appearance of the absorption peak at substantially shorter wavelength (usually gold sol absorbs at 520 nm) indicates that the particles are very small. The method discussed here is very simple, reproducible and does not involve any reagent, which contains 'P' or 'S' atoms. Also in this case no polymer or dendrimer or thiol-related stabilizer is used. The effects of different parameters (such as the presence or absence of O2, temperature, TX-100 concentration and dhc concentration) on the formation of ultrafine gold particles are discussed. The effects of 3-mercapto propionic acid and pyridine on the ultrafine gold sol are also studied and compared with those on photochemically prepared gold sol. It is observed that 3-mercapto propionic acid dampens the plasmon absorption at 470 nm of ultrafine gold particles. Pyridine, on the other hand, has no effect on the particles. 相似文献
974.
V. V. Shvalagin A. L. Stroyuk S. Ya. Kuchmii 《Theoretical and Experimental Chemistry》2004,40(6):378-382
Cathodic photocorrosion occurs upon stationary photoirradiation of ethanolic ZnO sols. The photocorrosion rate increases with decreasing particle size. This effect due to the appearance of quantum-sized effects in ZnO nanocrystals results from an increase in the reduction potential of the semiconductor upon irradiation, which may exceed the Fermi level for cathodic decomposition of zinc oxide nanoparticles.Translated from Teoreticheskaya i Éksperimentalnaya Khimiya, Vol.40, No.6, pp. 363–367, November–December, 2004. 相似文献
975.
R.A. Ganeev A.I. Ryasnyansky A.L. Stepanov T Usmanov 《Optical and Quantum Electronics》2004,36(10):949-960
The nonlinear optical characteristics of silicate glasses doped with silver nanoparticles are investigated by Z-scan technique using second harmonic radiation of picosecond Nd:YAG laser (=532 nm, =55 ps). The real and imaginary parts of third-order nonlinear susceptibility of silver-contained glasses were measured. It was found that the sign of Im
(3)was negative due to saturated absorption and the sign of Re
(3) was changed from negative (self-defocusing) to positive (self-focusing) with growth of laser radiation intensity. The mechanisms responsible for saturated absorption and nonlinear refraction are discussed. 相似文献
976.
Monosized poly(styrene/N-[3-(dimethylamino)propyl]methacrylamide/poly(ethylene glycol) ethyl ether methacrylate) [poly(St/PEG-EEM/DMAPM)] cationic nanoparticles were synthesized by emulsifier-free emulsion polymerization conducted in the presence of a cationic initiator, 2,2-azobis(2-methylpropionamidine) dihydrochloride (APDH or V-50). Particle sizes and surface charge densities were measured with a Zeta Sizer. The structure of the terpolymers was determined by Fourier transform IR and 1H NMR spectroscopies. The amounts of the main monomer (St), cationic comonomer (DMAPM), stabilizer (PEG-EEM), and initiator (APDH), and the water-to-monomer phase ratio were all effective on both the average size and the surface charge of the nanoparicles. The average particle size was in the range 75–400 nm depending on the recipe applied; it decreased on increasing the amount of DMAP or PEG-EEM or the water-to-monomer phase ratio in the feed, while it increased with increasing St or APDH content. These nanoparticles were quite monodisperse with a polydispersity index of 1.008–1.14. 相似文献
977.
The present review surveys the results of X-ray diffraction studies of large stoichiometric transition metal clusters containing from 20 to 145 atoms in metal cores surrounded by ligand shells (72 compounds). Structures of such clusters have fragments of close packings (face-centered cubic (f.c.c.), hexagonal close (h.c.p.), and body-centered cubic (b.c.c.) packings) characteristic of crystalline bulk metals as well as mixed packings (f.c.c./h.c.p.), local close packings with pentagonal symmetry, and strongly distorted amorphous packings. The observed packing types, their distortions, and the relationship between the atomic structures of metal cores and the atomic radial distribution functions (RDF) are discussed. The structural principles established for the large clusters are applied to analysis of the experimental RDF for metal nanoparticles determined by X-ray diffraction and EXAFS spectroscopy. 相似文献
978.
Methods for the preparation of II-VI, III-V, and II-V as well as other compound semiconductor nanoparticles using main group single-molecular precursors have been developed. The work involves the design and synthesis of compounds containing all the elements required within the desired nanoparticulate material. Precursors are tailored to give reproducible, clean decomposition at moderate temperatures, leading to high quality, defect free, mono-dispersed nanoparticles. In this article we cover key aspects of precursor and nanoparticle synthesis. One of the more successful and reproducible series of single-source precursors used, and the one on which we have concentrated our research efforts, is the bis(dialkyldithio-/diseleno-carbamato)cadmium(II)/zinc(II) compounds, M(E(2)CNR(2))(2) (M = Zn or Cd, E = S or Se, and R = alkyl) for the preparation of chalcogenide nanoparticulate materials. Preliminary mechanistic studies suggest that the precursor to nanoparticle deposition route is strongly influenced by the alkyl substituent groups present, and may well determine the phase and quality of the final metal chalcogenide nanoparticles produced. Herein we discuss the synthesis of semiconductor nanoparticles using such single-molecular precursors. 相似文献
979.
O. N. Bakharev N. Zelders H. B. Brom A. Schnepf H. Schnöckel L. Jos de Jongh 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):101-104
We present
69,71Ga-NMR experiments on
microcrystalline samples of the recently discovered
supramolecular compound Ga
84
[
N
(
SiMe
3
)
2
]
20
Li
6
Br
2
(
thf
)
20
.
2
toluene, which is composed of
ligand-coordinated Ga84 metal clusters,
packed together in a fully ordered crystalline matrix. The
compound is highly conducting and even shows superconductivity
below T
c
~ 7.2 K. Our preliminary
results between 10-300 K show a metallic-like behavior: the
nuclear spin-lattice relaxation rate T
1
-1
follows the Korringa law
69
(
T
1
T
)
-1
= 0.36 s
-1
K
-1
, but with a relaxation rate approximately three
times smaller than in bulk -Ga
metal. No quantum-size effects are observed, the Korringa law
being followed down to 10 K, whereas the quantum-gaps for
individual clusters should amount to ~
10
3
K. These results therefore suggest a transport process based on
intermolecular charge transfer, similar as in alkali-doped
fullerenes and silicon-clathrates. 相似文献
980.
Structural change of mesoporous silica with sonochemically prepared gold nanoparticles in its pores 总被引:1,自引:0,他引:1
Ultrasonic irradiation of mesoporous silica soaked in a mixture of chloroauric acid and isopropanol for 120 min in Ar atmosphere at room temperature yielded Au/SiO2 mesoporous composite, which was characterized by high resolution transmission electron microscopy and optical absorption measurement. The structure of mesoporous silica after sonochemical preparation of gold (Au) nanoparticles within its pores was studied by nitrogen adsorption technique. It has been shown that the structural parameters, such as specific surface area (SSA), porosity (P), the mean pore diameter (lp) were increased significantly after ultrasonic irradiation. It is suggested that the collision of Au nanoparticles with pore walls and localized erosion induced by the asymmetric implosive collapse of cavities on the extensive liquid–solid interface that are responsible for the structural change in the mesoporous solid. 相似文献