201
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Pol SV, Pol VG, Gedanken A, Sung MG, Asai S. Effects of a 10 T external magnetic field on the thermal decomposition of Fe, Ni, and Co acetyl acetonates. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:7532-7537. [PMID: 18540641 DOI: 10.1021/la800683m] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The current investigation is centered on the thermal decomposition (700 degrees C) of acetyl acetonates of Ni, Co, and Fe in a closed reactor that was conducted by employing an external magnetic field (MF) of 10T. Interestingly, reactions of Co and Ni acetyl acetonates under a 10T MF produce Co and Ni nanoparticles (NPs) coated with carbon, while Fe acetyl acetonate produces Fe3O4 uncoated with carbon. Additionally, it is observed that all the as-formed magnetic particles tend to align in one dimension along applied MF; thus, this process can be used to fabricate large arrays of magnetic nanoparticles. The effect of an applied MF to synthesize morphologically and compositionally different products from corresponding precursors with their mesoscopic organization is the key theme of the present paper, explained with a plausible mechanism.
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Affiliation(s)
- S V Pol
- Center for Advanced Materials and Nanotechnology, Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
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202
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Nanocrystal conversion chemistry: A unified and materials-general strategy for the template-based synthesis of nanocrystalline solids. J SOLID STATE CHEM 2008. [DOI: 10.1016/j.jssc.2008.04.007] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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203
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Yoon KY, Jang Y, Park J, Hwang Y, Koo B, Park JG, Hyeon T. Synthesis of uniform-sized bimetallic iron–nickel phosphide nanorods. J SOLID STATE CHEM 2008. [DOI: 10.1016/j.jssc.2008.05.022] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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204
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Zhou HP, Zhang YW, Mai HX, Sun X, Liu Q, Song WG, Yan CH. Spontaneous organization of uniform CeO2 nanoflowers by 3D oriented attachment in hot surfactant solutions monitored with an in situ electrical conductance technique. Chemistry 2008; 14:3380-90. [PMID: 18260069 DOI: 10.1002/chem.200701348] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Uniform CeO(2) nanoflowers were synthesized by rapid thermolysis of (NH(4))(2)Ce(NO(3))(6) in oleic acid (OA)/oleylamine (OM), by a unique 3D oriented-attachment mechanism. CeO(2) nanoflowers with controlled shape (cubic, four-petaled, and starlike) and tunable size (10-40 nm) were obtained by adjusting the reaction conditions including solvent composition, precursor concentration, reaction temperature, and reaction time. The nanoflower growth mechanism was investigated by in situ electrical conductance measurements, transmission electron microscopy, and UV/Vis spectroscopy. The CeO(2) nanoflowers are likely formed in two major steps, that is, initial formation of ceria cluster particles capped with various ligands (e.g., OA, OM, and NO(3) (-)) via hydrolysis of (NH(4))(2)Ce(NO(3))(6) at temperatures in the range 140-220 degrees C, and subsequent spontaneous organization of the primary particles into nanoflowers by 3D oriented attachment, due to a rapid decrease in surface ligand coverage caused by sudden decomposition of the precursor at temperatures above 220 degrees C in a strong redox reaction. After calcination at 400 degrees C for 4 h the 33.8 nm CeO(2) nanoflowers have a specific surface area as large as 156 m(2) g(-1) with high porosity, and they are highly active for conversion of CO to CO(2) in the low temperature range of 200-400 degrees C. The present approach has also been extended to the preparation of other transition metal oxide (CoO, NiO, and CuO(x)) nanoflowers.
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Affiliation(s)
- Huan-Ping Zhou
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, PKU-HKU Joint Laboratory in Rare Earth Materials and Bioinorganic Chemistry, Peking University, Beijing, China
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205
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Saunders AE, Koo B, Wang X, Shih CK, Korgel BA. Structural Characterization and Temperature-Dependent Photoluminescence of Linear CdTe/CdSe/CdTe Heterostructure Nanorods. Chemphyschem 2008; 9:1158-63. [DOI: 10.1002/cphc.200800008] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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206
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Kilin DS, Prezhdo OV, Xia Y. Shape-controlled synthesis of silver nanoparticles: Ab initio study of preferential surface coordination with citric acid. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.04.046] [Citation(s) in RCA: 184] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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207
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Zhang YJ, Zhang Y, Wang ZH, Li D, Cui TY, Liu W, Zhang ZD. Controlled Synthesis of Cobalt Flowerlike Architectures by a Facile Hydrothermal Route. Eur J Inorg Chem 2008. [DOI: 10.1002/ejic.200800137] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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208
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Michalek F, Lagunas A, Jimeno C, Pericàs MA. Synthesis of functional cobalt nanoparticles for catalytic applications. Use in asymmetric transfer hydrogenation of ketones. ACTA ACUST UNITED AC 2008. [DOI: 10.1039/b808383e] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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209
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Soumare Y, Piquemal JY, Maurer T, Ott F, Chaboussant G, Falqui A, Viau G. Oriented magnetic nanowires with high coercivity. ACTA ACUST UNITED AC 2008. [DOI: 10.1039/b810943e] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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210
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Su Y, Li L, Li G. Self-assembly and multicolor emission of core/shell structured CaWO4:Na+/Ln3+ spheres. Chem Commun (Camb) 2008:4004-6. [DOI: 10.1039/b810648g] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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211
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Gaikwad AV, Verschuren P, Kinge S, Rothenberg G, Eiser E. Matter of age: growing anisotropic gold nanocrystals in organic media. Phys Chem Chem Phys 2008; 10:951-6. [DOI: 10.1039/b715112h] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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212
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Du J, Chai L, Wang G, Li K, Qian Y. Controlled Synthesis of One-Dimensional Single-Crystal Co3O4 Nanowires. Aust J Chem 2008. [DOI: 10.1071/ch07186] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Uniform Co3O4 nanowires with diameters of ~80 nm and lengths of 10–20 μm have been prepared by a hydrothermal reaction and sequential decomposition of the intermediate product. Transmission electron microscopy characterization and selected-area electron diffraction patterns show that the nanowires elongate along the [110] direction. The amount of CO(NH2)2 employed and the heating rate of calcination have a key effect on the morphology of the product. In addition, analysis of the optical properties indicates a blue shift of the bandgaps and reveals the semiconductive nature of the products.
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213
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de Silva RM, Palshin V, de Silva KMN, Henry LL, Kumar CSSR. A new role for surfactants in the formation of cobalt nanoparticles. ACTA ACUST UNITED AC 2008. [DOI: 10.1039/b714456c] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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214
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Jiang C, Wang L, Kuwabara K. Selective-precursor reducing route to cobalt nanocrystals and ferromagnetic property. J SOLID STATE CHEM 2007. [DOI: 10.1016/j.jssc.2007.09.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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215
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Keng PY, Shim I, Korth BD, Douglas JF, Pyun J. Synthesis and self-assembly of polymer-coated ferromagnetic nanoparticles. ACS NANO 2007; 1:279-292. [PMID: 19206678 DOI: 10.1021/nn7001213] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We describe the synthesis and characterization of polymer-coated ferromagnetic cobalt nanoparticles (CoNPs). The synthesis of end-functionalized polystyrene surfactants possessing amine, carboxylic acid, or phosphine oxide end-groups was accomplished using atom-transfer radical polymerization. This versatile synthetic method enabled the production of multigram quantities of these polymeric surfactants that stabilized ferromagnetic CoNPs when dispersed in organic media. An in-depth investigation into the synthesis of polystyrene-coated ferromagnetic CoNPs was also conducted using various combinations of these polymeric surfactants in the thermolysis of dicobaltoctacarbonyl (Co(2)(CO)(8)). Moreover, the application of a dual-stage thermolysis with Co(2)(CO)(8) allowed for the preparation of large samples (200-820 mg) per batch of well-defined and dispersable ferromagnetic nanoparticles. Characterization of these functionalized nanoparticle materials was then done using transmission electron microscopy, X-ray diffraction, vibrating sample magnetometry, and thermogravimetric analysis. Self-assembly of these dipolar nanoparticles was investigated in solutions cast onto supporting substrates, where local nematic-like ordering of nanoparticle chains was observed along with a tendency of adjacent chains to form "zippering" configurations, both phenomena having been predicted by recent simulations of dipolar fluids in conjunction with van der Waals interactions.
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Affiliation(s)
- Pei Yuin Keng
- Department of Chemistry, University of Arizona, Tucson, AZ 85721, USA
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216
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Sun Y, Wiederrecht GP. Surfactantless synthesis of silver nanoplates and their application in SERS. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2007; 3:1964-1975. [PMID: 17935082 DOI: 10.1002/smll.200700484] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Silver nanoplates with thicknesses of 50-70 nm and edge lengths ranging from 200 nm to 1 mum have been grown on semiconductor wafers at room temperature through a simple galvanic reaction between an aqueous solution of AgNO(3) and n-type GaAs. The as-grown Ag structures have chemically clean surfaces due to no surfactant or coordinating molecules being involved in the synthesis. Electron microscopy characterizations indicate that each Ag plate has rough surfaces and a half-moon morphology with one straight edge and one arclike edge. Systematic studies on varying reaction conditions reveal that the oxide (i.e., Ga(2)O(3) and As(2)O(3)) layers of GaAs, generated in situ in the reactions, play an important role in assisting the growth of anisotropic nanoplates. The cleanliness of the surfaces of the Ag nanoplates is beneficial to attachment of interesting molecules on their surfaces for various applications, such as plasmonic-enhanced photophysical and photochemical processes and surface-enhanced spectroscopies.
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Affiliation(s)
- Yugang Sun
- Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA.
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217
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Lou TJ, Zeng JH, Lou XD, Fu HL, Wang YF, Ma RL, Tong LJ, Chen YL. A facile synthesis to Zn2SiO4:Mn2+ phosphor with controllable size and morphology at low temperature. J Colloid Interface Sci 2007; 314:510-3. [PMID: 17618644 DOI: 10.1016/j.jcis.2007.06.026] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2007] [Revised: 05/08/2007] [Accepted: 06/04/2007] [Indexed: 11/28/2022]
Abstract
Sphere- and rod-shaped Zn(2)SiO(4):Mn(2+) phosphor nanocrystals were synthesized at 230 degrees C. The process consists of tuning the surfactant concentration in the oil/surfactant/ethanol system. Powder X-ray (XRD) and transmission electron microscopy (TEM) were used to characterize the phase purity, size and morphology. Photoluminescent (PL) spectra were collected and analyzed. Fourier transform infrared (FT-IR) spectra of the samples indicate the removal of surfactant in the phosphor nanoparticles. As a result, the sphere-shaped phosphor nanoparticles of 100 nm in size can be redispersed in ethanol ultrasonically. The suspension maintain stable for over 48 h.
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Affiliation(s)
- Tian Jun Lou
- College of Chemistry and Chemical Engineering, Henan Institute of Science and Technology, Xinxiang 453003, China.
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218
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Xia A, Hu J, Wang C, Jiang D. Synthesis of magnetic microspheres with controllable structure via polymerization-triggered self-positioning of nanocrystals. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2007; 3:1811-7. [PMID: 17853495 DOI: 10.1002/smll.200700117] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
A facile and novel method for the synthesis of magnetite-polymer hybrid microspheres with controllable structure is reported. On the basis of the interactions between polymers and magnetic nanocrytals, which are coated with a primary oleic acid layer, a variety of magnetic microspheres with well-tailored structure are fabricated by carefully modulating polymerization and selecting components of composite microspheres; the evolvement of hierarchical structure, and the magnetic properties of microspheres were systematically studied. Importantly, the mechanism of polymerization-triggered self-positioning of magnetic nanocrystals is investigated.
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Affiliation(s)
- Ao Xia
- Key Laboratory of Molecular Engineering of Polymers & Department of Macromolecular Science, Advanced Materials Laboratory, Fudan University, 200433 Shanghai, PR China
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219
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Geng J, Lu D, Zhu JJ, Chen HY. Antimony(III)-doped PbWO4 crystals with enhanced photoluminescence via a shape-controlled sonochemical route. J Phys Chem B 2007; 110:13777-85. [PMID: 16836323 DOI: 10.1021/jp057562v] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Sb(III)-doped lead tungstate single crystals with controlled shapes and enhanced green emission have been synthesized via a facile, Pluronic P123 (EO(20)PO(70)EO(20))-assisted, sonochemical method. The surfactant Pluronic P123 was found to play a crucial role in the morphology control of the final products. The growth process was investigated by carefully following time-dependent experiments, and the oriented attachment process accompanying Ostwald ripening was proposed for the possible formation mechanism. The optical properties, such as the Raman spectra and PL spectra, of doped PbWO(4) were studied. Room-temperature photoluminescence of doped PbWO(4) samples with different morphologies at desired Sb doping concentrations showed greatly enhanced luminescence intensity compared to the undoped PbWO(4).
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Affiliation(s)
- Jun Geng
- Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, P. R. China
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220
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Du YP, Zhang YW, Yan ZG, Sun LD, Gao S, Yan CH. Single-crystalline and near-monodispersed NaMF3 (M = Mn, Co, Ni, Mg) and LiMAlF6 (M = Ca, Sr) nanocrystals from cothermolysis of multiple trifluoroacetates in solution. Chem Asian J 2007; 2:965-74. [PMID: 17534994 DOI: 10.1002/asia.200700054] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We report the synthesis of single-crystalline and near-monodispersed NaMF3 (M = Mn, Co, Ni, Mg), LiMAlF6 (M = Ca, Sr), and NaMgF3:Yb,Er nanocrystals (quasisquare nanoplates, nanorods, and nanopolygons) by the cothermolysis of multiple trifluoroacetates in hot combined organic solvents (oleic acid, oleylamine, and 1-octadecene). The nanocrystals were characterized by XRD, TEM, superconductive quantum interference device (SQUID), and upconversion luminescence spectroscopy. By regulating the polarity of the dispersant, the NaMF3 (M = Mn, Co, Ni) nanoplates were partially aligned to form nanoarrays on copper TEM grids. The sizes of the NaMF3 nanocrystals were easily tuned by the use of proper synthetic conditions such as reaction temperature and time and solvent composition. On the basis of a series of experiments in which the reaction conditions were varied, together with GC-MS and FTIR analysis, the reaction pathways for the formation of these nanocrystals from trifluoroacetate precursors were proposed. The magnetic measurements showed that the differently sized NaMnF3 square plates displayed interesting weak ferromagnetic behavior on the nanometer scale. The strong red upconversion luminescence emitted from the NaMgF3:Yb,Er nanorods under 980-nm near-IR laser excitation suggests that NaMgF3 may be a good candidate host material for red upconversion luminescence.
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Affiliation(s)
- Ya-Ping Du
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, Peking University, Beijing 100871, China
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221
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Ng CHB, Fan WY. Shape evolution of Cu2O nanostructures via kinetic and thermodynamic controlled growth. J Phys Chem B 2007; 110:20801-7. [PMID: 17048890 DOI: 10.1021/jp061835k] [Citation(s) in RCA: 201] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report the shape evolution process of Cu(2)O nanocrystals upon slow oxidation of Cu under ambient conditions, yielding novel hexagonal and triangular platelike morphologies. The shape of the obtained nanocrystals evolves from hexagonal to triangular to octahedral; the growth patterns are governed by kinetically and thermodynamically controlled growth. Preferential adsorption of I(-) on {111} planes of Cu(2)O nanoparticles induced the selective crystal growth of metastable platelike structures with {111} faces as the basal planes. On aging, the growth process appeared to shift into the thermodynamic regime and the thermodynamically stable octahedral shape is obtained. The possible growth mechanisms were investigated by varying the synthetic conditions. The band gap of Cu(2)O nanooctahedrons was determined by the classical Tauc approach to be 2.24 eV, which is blue shifted with respect to the bulk Cu(2)O value (2.17 eV). Results suggest that the slow oxidation process and use of crystallographic selective surfactants are essential for the appearance of anisotropic metastable shapes. In general, surface energy control by surfactant molecules might provide a convenient channel for tailoring nanocrystal shapes of metal oxides.
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Affiliation(s)
- Choon Hwee Bernard Ng
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
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222
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Shanbhag S, Tang Z, Kotov NA. Self-organization of Te nanorods into V-shaped assemblies: a Brownian dynamics study and experimental insights. ACS NANO 2007; 1:126-32. [PMID: 19206528 DOI: 10.1021/nn7000905] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Computer modeling of nanoscale processes provides critical quantitative insights into nanoscale self-organization, which is hard to achieve by other means. Starting from a suspension of Te nanorods, it was recently found that short nanorods (50 nm) self-organized into checkmark-like V-shaped assemblies over a period of a few days, whereas long nanorods (2200 nm) did not. This experimental fact was difficult to explain, and so here we use Brownian dynamics simulations of a dilute suspension of hard spherocylinders to better understand the process of self-organization. With the assumption that close encounters between nanorod tips result in their merger into V-particles, it was found that the ratio of the initial rate of nanorod formation for the short and long rods was 3760. By systematically varying the length and the concentration, we found that the concentration of the nanorods, rather their length, was primarily instrumental in setting the initial rate of checkmark formation. Using a simple kinetic model in conjunction with experimental data, we find that approximately 30,000 close encounters are required on average for a single successful merger. This study gives an important reference point for understanding the mechanism of the formation of complex nanostructured system by oriented attachment; it also can be extended to and provides conceptual leads for other self-organized systems.
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Affiliation(s)
- Sachin Shanbhag
- Department of Chemical and Biomedical Engineering, FAMU-FSU College of Engineering, Tallahassee, Florida 32310, USA
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223
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Bastus NG, Kogan MJ, Amigo R, Grillo-Bosch D, Araya E, Turiel A, Labarta A, Giralt E, Puntes VF. Gold nanoparticles for selective and remote heating of β-amyloid protein aggregates. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2007. [DOI: 10.1016/j.msec.2006.08.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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224
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Kinge SS, Crego-Calama M, Reinhoudt DN. Gold nanoparticle assemblies through hydrogen-bonded supramolecular mediators. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:8772-7. [PMID: 17630787 DOI: 10.1021/la700514u] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The synthesis of spherical gold nanoparticle assemblies with multicomponent double rosette molecular boxes as mediators is presented. These nine-component hydrogen-bonded supramolecular structures held together by 36 hydrogen bonds induce gold nanoparticle assembly. The morphologies of the nanoparticle assemblies can be tuned easily by changing the quantity of the building block chemisorbed on the nanoparticle surface.
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Affiliation(s)
- Sachin S Kinge
- Laboratory of Supramolecular Chemistry and Technology, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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225
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Ni X, Li D, Zhang Y, Zheng H. Complexant-assisted Fabrication of Flowery Assembly of Hexagonal Close-packed Cobalt Nanoplatelets. CHEM LETT 2007. [DOI: 10.1246/cl.2007.908] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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226
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Jun YW, Choi JS, Cheon J. Shape control of semiconductor and metal oxide nanocrystals through nonhydrolytic colloidal routes. Angew Chem Int Ed Engl 2007; 45:3414-39. [PMID: 16642516 DOI: 10.1002/anie.200503821] [Citation(s) in RCA: 1006] [Impact Index Per Article: 59.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Inorganic nanocrystals with tailored geometries exhibit unique shape-dependent phenomena and subsequent utilization of them as building blocks for the fabrication of nanodevices is of significant interest. Herein, we review the recent developments in the shape control of colloidal nanocrystals with a focus on the scientifically and technologically important semiconductor and metal oxide nanocrystals obtained by nonhydrolytic synthetic methods. Many structurally unprecedented motifs have been discovered including polyhedrons, rods and wires, plates and prisms, and other advanced shapes such as branched rods, stars, inorganic dendrites, and dumbbells. The currently proposed shape-guiding mechanisms are presented and the important pioneering studies on the assembly of shape-controlled nanocrystals into ordered superlattices and the fabrication of prototype advanced nanodevices are discussed.
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Affiliation(s)
- Young-wook Jun
- Department of Chemistry, Yonsei University, Seoul 120-749, Korea
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227
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Bose PP, Drew MGB, Banerjee A. Decoration of Au and Ag Nanoparticles on Self-Assembling Pseudopeptide-Based Nanofiber by Using a Short Peptide as Capping Agent for Metal Nanoparticles. Org Lett 2007; 9:2489-92. [PMID: 17542598 DOI: 10.1021/ol0708471] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The surface of a nanofiber that is formed from a self-assembling pseudopeptide has been decorated by gold and silver nanoparticles that are stabilized by a dipeptide. Transmission electron microscopic images make the decoration visible. In this paper, a new strategy of mineralizing a pseudopeptide based nanofiber by gold and silver nanoparticles with use of a two-component nanografting method is described.
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Affiliation(s)
- Partha Pratim Bose
- Department of Biological Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
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228
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Du W, Qian X, Ma X, Gong Q, Cao H, Yin J. Shape-controlled synthesis and self-assembly of hexagonal covellite (CuS) nanoplatelets. Chemistry 2007; 13:3241-7. [PMID: 17200918 DOI: 10.1002/chem.200601368] [Citation(s) in RCA: 145] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Single-crystalline, hexagonal covellite (CuS) nanoplatelets were successfully synthesized through a facile, inexpensive, reproducible, and improved solvothermal process in toluene at 120 degrees C for 24 h with hexadecylamine as a capping agent and copper acetate and carbon disulfide as precursors. These nanoplatelets are about 26+/-1.5 nm in diameter and 8+/-1.2 nm thick, and have a tendency to self-assemble into pillarlike nanostructures with face-to-face stacks, raftlike nanostructures with side-by-side arrays, and stratiform nanostructures with layer-by-layer self-assembly. The crystal shape, morphology, and crystallographic orientation of the covellite obtained were investigated by means of XRD, TEM, and high-resolution TEM, and a potential self-assembly mechanism was proposed.
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Affiliation(s)
- Weimin Du
- School of Chemistry and Chemical Technology, Shanghai Jiao Tong University, Shanghai 200240, P.R. China
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229
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Nanoparticles in Liquid Crystals: Synthesis, Self-Assembly, Defect Formation and Potential Applications. J Inorg Organomet Polym Mater 2007. [DOI: 10.1007/s10904-007-9140-5] [Citation(s) in RCA: 281] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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230
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Pol SV, Pol VG, Gedanken A, Felner I, Sung MG, Asai S. External Magnetic Field-Induced Mesoscopic Organization of Fe3O4 Pyramids and Carbon Sheets. Inorg Chem 2007; 46:4951-9. [PMID: 17487966 DOI: 10.1021/ic070108g] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The current investigation is centered on the thermal decomposition of iron(II) acetyl acetonate, Fe(C5H7O2)2, in a closed cell at 700 degrees C, which is conducted under a magnetic field (MF) of 10 T. The product is compared with a similar reaction that was carried out without a MF. This article shows how the reaction without a MF produces spherical Fe3O4 particles coated with carbon. The same reaction in the presence of a 10 T MF causes the rejection of the carbon from the surface of pyramid-shaped Fe3O4 particles, increases the Fe3O4 particle diameter, forms separate carbon particles, and leads to the formation of an anisotropic (long cigarlike) orientation of Fe3O4 pyramids and C sheets. The macroscopic orientation of Fe3O4 pyramids+C sheets is stable even after the removal of an external MF. The suggested process can be used to fabricate large arrays of uniform wires comprised of some magnetic nanoparticles, and to improve the magnetic properties of nanoscale magnetic materials. The probable mechanism is developed for the growth and assembly behavior of magnetic Fe3O4 pyramids+C sheets under an external MF. The effect of an applied MF to synthesize morphologically different, but structurally the same, products with mesoscopic organization is the key theme of the present paper.
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Affiliation(s)
- S V Pol
- Department of Chemistry and Kanbar Laboratory for Nanomaterials at the Bar-Ilan University Center for Advanced Materials and Nanotechnology, Bar-Ilan University, Ramat-Gan 52900, Israel
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231
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Sun X, Zhang YW, Du YP, Yan ZG, Si R, You LP, Yan CH. From trifluoroacetate complex precursors to monodisperse rare-earth fluoride and oxyfluoride nanocrystals with diverse shapes through controlled fluorination in solution phase. Chemistry 2007; 13:2320-32. [PMID: 17163562 DOI: 10.1002/chem.200601072] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We report the first systematic synthesis of monodisperse rare-earth (RE=La to Lu, Y) fluoride and oxyfluoride nanocrystals with diverse shapes (trigonal REF3 triangular, truncated-triangular, hexagonal, and polygonal nanoplates; orthorhombic REF3 quadrilateral and zigzag-shaped nanoplates; cubic REOF nanopolyhedra and nanorods) from single-source precursors (SSP) of [RE(CF(3)COO)(3)] through controlled fluorination in oleic acid (OA)/oleylamine (OM)/1-octadecene (ODE). To selectively obtain REF3 or REOF nanocrystals, the fluorination of the RE-O bond to the RE-F bond at the nucleation stage was controlled by finely tuning the ratio of OA/ODE or OA/OM, and the reaction temperature. For phase-pure REF3 or REOF naocrystals, their shape-selective syntheses could be realized by further modifying the reaction conditions. The two-dimensional growth of the REF3 nanoplates and the one-dimensional growth of the REOF nanorods were likely due to the selective adsorption of the capping ligands on specific crystal planes of the nanocrystals. Those well-shaped nanocrystals with diverse geometric symmetries (such as D(3h), D(6h), C(2h), O(h), and D(nh)) displayed a remarkable capability to form self-assembled superlattices. By manipulating the solvent-substrate combination, the plate-shaped REF3 nanocrystals could form highly ordered nanoarrays by means of either the face-to-face formation or the edge-to-edge formation. By using this SSP strategy, we also obtained high-quality LaF3:Eu and LaF3:Eu/LaF3 triangular nanoplates that showed photoluminescent red emissions of Eu3+ ions sensitive to the surface effect.
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Affiliation(s)
- Xiao Sun
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, PKU-HKU Joint Laboratory in Rare Earth Materials and Bioinorganic Chemistry, Peking University, Beijing 100871, P.R. China
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232
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Lu AH, Salabas EL, Schüth F. Magnetic nanoparticles: synthesis, protection, functionalization, and application. Angew Chem Int Ed Engl 2007; 46:1222-44. [PMID: 17278160 DOI: 10.1002/anie.200602866] [Citation(s) in RCA: 3273] [Impact Index Per Article: 192.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
This review focuses on the synthesis, protection, functionalization, and application of magnetic nanoparticles, as well as the magnetic properties of nanostructured systems. Substantial progress in the size and shape control of magnetic nanoparticles has been made by developing methods such as co-precipitation, thermal decomposition and/or reduction, micelle synthesis, and hydrothermal synthesis. A major challenge still is protection against corrosion, and therefore suitable protection strategies will be emphasized, for example, surfactant/polymer coating, silica coating and carbon coating of magnetic nanoparticles or embedding them in a matrix/support. Properly protected magnetic nanoparticles can be used as building blocks for the fabrication of various functional systems, and their application in catalysis and biotechnology will be briefly reviewed. Finally, some future trends and perspectives in these research areas will be outlined.
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Affiliation(s)
- An-Hui Lu
- Max-Planck-Institut für Kohlenforschung, 45470 Mülheim an der Ruhr, Germany
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233
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Teranishi T, Inoue Y, Saruyama M, Nakaya M, Kanehara M. Anisotropically Phase-segregated Co9S8/PdSxNanoacorns: Stability Improvement and New Heterostructures. CHEM LETT 2007. [DOI: 10.1246/cl.2007.490] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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234
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235
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Wu Z, Yu K, Huang Y, Pan C, Xie Y. Facile solution-phase synthesis of gamma-Mn3O4 hierarchical structures. Chem Cent J 2007; 1:8. [PMID: 17880738 PMCID: PMC1994067 DOI: 10.1186/1752-153x-1-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2007] [Accepted: 03/17/2007] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND A lot of effort has been focused on the integration of nanorods/nanowire as building blocks into three-dimensional (3D) complex superstructures. But, the development of simple and effective methods for creating novel assemblies of self-supported patterns of hierarchical architectures to designed materials using a suitable chemical method is important to technology and remains an attractive, but elusive goal. RESULTS The hierarchical structure of Mn3O4 with radiated spherulitic nanorods was prepared via a simple solution-based coordinated route in the presence of macrocycle polyamine, hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene (CT) with the assistance of thiourea as an additive. CONCLUSION This approach opens a new and facile route for the morphogenesis of Mn3O4 material and it might be extended as a novel synthetic method for the synthesis of other inorganic semiconducting nanomaterials such as metal chalcogenide semiconductors with novel morphology and complex form, since it has been shown that thiourea can be used as an effective additive and the number of such water-soluble macrocyclic polyamines also makes it possible to provide various kinds of ligands for different metals in homogeneous water system.
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Affiliation(s)
- Zhengcui Wu
- Department of Nanomaterials and Nanochemistry, Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, P. R. China
- Anhui Key Laboratory of Functional Molecular Solids, College of Chemistry and Materials Science, Anhui Normal University, Wuhu 241000, P. R. China
| | - Kuai Yu
- Department of Nanomaterials and Nanochemistry, Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Yaobin Huang
- Department of Nanomaterials and Nanochemistry, Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Cheng Pan
- Department of Nanomaterials and Nanochemistry, Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Yi Xie
- Department of Nanomaterials and Nanochemistry, Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, P. R. China
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236
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Song Q, Ding Y, Wang ZL, Zhang ZJ. Formation of orientation-ordered superlattices of magnetite magnetic nanocrystals from shape-segregated self-assemblies. J Phys Chem B 2007; 110:25547-50. [PMID: 17166006 DOI: 10.1021/jp0652695] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Magnetic magnetite (Fe3O4) nanocrystals have been synthesized by combining nonhydrolytic reaction with seed-mediated growth. The shape of these magnetite nanocrystals can be controlled either as pure spheres or a mixture of mainly faceted nanocrystals. Faceted magnetite nanocrystals consist of truncated tetrahedral platelets (TTPs), truncated octahedrons (TOs), and octahedrons (OTs). Transmission electron microscopy analysis indicates that the faceted nanocrystal mixture tends to self-segregate based upon the shape in a self-assembly process, and each shape forms its own distinct crystallographic orientation-ordered superlattice assemblies. Self-assemblies of the Fe3O4 nanocrystals in the shapes of TTP, TO, and OT show hexagonal, primitive cubic, and distorted body-centered cubic (bcc) superlattice structures, respectively. The possible mechanism for the formation of different superstructures is attributed to van der Waals interactions. Nanocrystals with different shapes provide diverse building blocks for bottom-up approaches in building nano- and mesosystems. Furthermore, the self-segregation phenomenon of different shaped nanocrystals in self-assembly processes could be very important in envisioning efficient assembly strategies for nanoscience- and nanotechnology-based devices.
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Affiliation(s)
- Qing Song
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA
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237
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Lu AH, Salabas E, Schüth F. Magnetische Nanopartikel: Synthese, Stabilisierung, Funktionalisierung und Anwendung. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200602866] [Citation(s) in RCA: 258] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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238
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Lu AH, Salabas E, Schüth F. Magnetic Nanoparticles: Synthesis, Protection, Functionalization, and Application. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/anie.200602866 pmid: 17278160] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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239
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Density-functional study of Au–Cu binary clusters of small size (n=6): Effect of structure on electronic properties. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/j.theochem.2006.09.034] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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240
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Synthetic Strategies to Size and Shape Controlled Nanocrystals and Nanocrystal Heterostructures. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 620:1-17. [DOI: 10.1007/978-0-387-76713-0_1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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241
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Zhang J, Dai Z, Bao J, Zhang N, López-Quintela MA. Self-assembly of Co-based nanosheets into novel nest-shaped nanostructures: Synthesis and characterization. J Colloid Interface Sci 2007; 305:339-44. [PMID: 17049548 DOI: 10.1016/j.jcis.2006.09.073] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2006] [Revised: 09/27/2006] [Accepted: 09/27/2006] [Indexed: 10/24/2022]
Abstract
We report the first observation of the formation of novel Co-based three-dimensional (3D) self-assembly hollow nanostructures, i.e., nest-shaped nanospheres composed of sheet-like particles, via reduction of cobalt salt with sodium tetrahydroboride in cetyltrimethylammonium bromide (CTAB)-cyclohexane-NH4F aqueous solutions. It was found that the cyclohexane has a significant influence on the formation of the nest-shaped Co-based nanospheres, because when the experiments are carried out in the absence of cyclohexane, only sheet-like particles are formed. NH4F plays also an important role in the formation of the hollow nanostructures because without this salt mainly solid spherical structures, composed of sheet-like particles, instead of nest-shaped structures are obtained. The nanostructures are mainly formed by Co, but also a minor amount (17%) of Co2B is present in the final compounds. The structures are characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), and field-emission scanning electron microscopy (FESEM). A possible mechanism for the formation of the novel Co-based nanostructures is proposed.
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Affiliation(s)
- Jie Zhang
- Department of Chemistry, Laboratory of Materials Science, Nanjing Normal University, Nanjing 210097, PR China
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242
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Zhu P, Wu W, Zhou J, Zhang W. Preparation of size-controlled In2O3 nanoparticles. Appl Organomet Chem 2007. [DOI: 10.1002/aoc.1300] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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243
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Lee DC, Smith DK, Heitsch AT, Korgel BA. Colloidal magnetic nanocrystals: synthesis, properties and applications. ACTA ACUST UNITED AC 2007. [DOI: 10.1039/b605630j] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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244
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Saunders AE, Ghezelbash A, Smilgies DM, Sigman MB, Korgel BA. Columnar self-assembly of colloidal nanodisks. NANO LETTERS 2006; 6:2959-63. [PMID: 17163739 DOI: 10.1021/nl062419e] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The self-assembly of sterically stabilized colloidal copper sulfide nanodisks, 14-20 nm in diameter and 5-7 nm thick, was studied. The nanodisks were observed by electron microscopy and small-angle X-ray scattering to form columnar arrays when evaporated as thin films from concentrated dispersions. These superstructured nanomaterials might give rise to technologically useful properties, such as anisotropic electrical transport and electrorheological and optical properties.
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Affiliation(s)
- Aaron E Saunders
- Department of Chemical Engineering, Texas Materials Institute, Center for Nano- and Molecular Science and Technology, The University of Texas at Austin, Austin, Texas 78712, USA
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245
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Kim CW, Kim YH, Cha HG, Kwon HW, Kang YS. Synthesis and Characterization of Highly Magnetized Nanocrystalline Co30Fe70Alloy by Chemical Reduction. J Phys Chem B 2006; 110:24418-23. [PMID: 17134196 DOI: 10.1021/jp064440+] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Co(30)Fe(70) nanoparticles with mean particle size of about 8 nm were successfully synthesized by the chemical reduction of cobalt chloride and iron chloride with borohydride as a reducing agent in aqueous solution. The composition and size of the Co(30)Fe(70) nanoparticles were optimized by controlling the molar ratio of starting materials, reaction time, and dropping rate of aqueous reducing agent. As alloy powders prepared by chemical reduction tend to be amorphous in the as-synthesized state, the as-precipitated Co(30)Fe(70) nanoparticles were heat-treated to achieve crystallinity at the different temperatures for 1 h. The Co(30)Fe(70) nanocrystallite by chemical reduction shows excellent soft magnetic behavior, such as high permeability, negligible coercivity, and high saturation magnetization like that of Co(30)Fe(70) bulk.
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Affiliation(s)
- Chang Woo Kim
- Department of Chemistry, Pukyong National University, Busan 608-737, Korea
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246
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Hydrogel-assisted synthesis of nanotubes and nanorods of CdS, ZnS and CuS, showing some evidence for oriented attachment. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.10.032] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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247
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Seo WS, Lee JH, Sun X, Suzuki Y, Mann D, Liu Z, Terashima M, Yang PC, McConnell MV, Nishimura DG, Dai H. FeCo/graphitic-shell nanocrystals as advanced magnetic-resonance-imaging and near-infrared agents. NATURE MATERIALS 2006; 5:971-6. [PMID: 17115025 DOI: 10.1038/nmat1775] [Citation(s) in RCA: 457] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2006] [Accepted: 09/27/2006] [Indexed: 05/12/2023]
Abstract
Nanocrystals with advanced magnetic or optical properties have been actively pursued for potential biological applications, including integrated imaging, diagnosis and therapy. Among various magnetic nanocrystals, FeCo has superior magnetic properties, but it has yet to be explored owing to the problems of easy oxidation and potential toxicity. Previously, FeCo nanocrystals with multilayered graphitic carbon, pyrolytic carbon or inert metals have been obtained, but not in the single-shelled, discrete, chemically functionalized and water-soluble forms desired for biological applications. Here, we present a scalable chemical vapour deposition method to synthesize FeCo/single-graphitic-shell nanocrystals that are soluble and stable in water solutions. We explore the multiple functionalities of these core-shell materials by characterizing the magnetic properties of the FeCo core and near-infrared optical absorbance of the single-layered graphitic shell. The nanocrystals exhibit ultra-high saturation magnetization, r1 and r2 relaxivities and high optical absorbance in the near-infrared region. Mesenchymal stem cells are able to internalize these nanoparticles, showing high negative-contrast enhancement in magnetic-resonance imaging (MRI). Preliminary in vivo experiments achieve long-lasting positive-contrast enhancement for vascular MRI in rabbits. These results point to the potential of using these nanocrystals for integrated diagnosis and therapeutic (photothermal-ablation) applications.
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Affiliation(s)
- Won Seok Seo
- Department of Chemistry and Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
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248
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Wolcott A, Kuykendall TR, Chen W, Chen S, Zhang JZ. Synthesis and Characterization of Ultrathin WO3 Nanodisks Utilizing Long-Chain Poly(ethylene glycol). J Phys Chem B 2006; 110:25288-96. [PMID: 17165974 DOI: 10.1021/jp064777b] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Metal oxide nanostructures hold great potential for photovoltaic (PV), photoelectrochemical (PEC), and photocatalytic applications. Whereas thin films of various materials of both nanoparticle and nanorod morphologies have been widely investigated, there have been few inquiries into nanodisk structures. Here, we report the synthesis of ultrathin WO3 nanodisks using a wet chemical route with poly(ethylene glycol) (PEG) as a surface modulator. The reported nanodisk structure is based on the interaction of the nonionic 10000 g/mol PEG molecules with tungsten oxoanion precursors. The WO3 nanostructures formed are dominated by very thin disks with dimensions on the nanometer to micrometer scale. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images reveal the structures to have dimensions on the order of 350-1000 nm in length, 200-750 nm in width, and 7-18 nm in thickness and possessing textured single-crystalline features. A number of analytical techniques were used to characterize the WO3 nanodisks, including selected-area electron diffraction (SAED), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), Raman scattering spectroscopy, UV-visible spectrophotometry, and cyclic voltammetry (CV). The growth of the WO3 nanodisks was inhibited in the [010] crystal direction, leading to ultrathin morphologies in the monoclinic crystal phase. The large flat surface area and high aspect ratio of the WO3 nanodisks are potentially useful in PEC cells for hydrogen production via direct water splitting, as has been demonstrated in a preliminary experiment with external bias.
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Affiliation(s)
- Abraham Wolcott
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, USA
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249
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Koo B, Park J, Kim Y, Choi SH, Sung YE, Hyeon T. Simultaneous Phase- and Size-Controlled Synthesis of TiO2 Nanorods via Non-Hydrolytic Sol−Gel Reaction of Syringe Pump Delivered Precursors. J Phys Chem B 2006; 110:24318-23. [PMID: 17134182 DOI: 10.1021/jp065372u] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The simultaneous phase- and size-controlled synthesis of TiO(2) nanorods was achieved via the non-hydrolytic sol-gel reaction of continuously delivered two titanium precursors using two separate syringe pumps. As the injection rate was decreased, the length of the TiO(2) nanorods was increased and their crystalline phase was simultaneously transformed from anatase to rutile. When the reaction was performed by injecting titanium precursors contained in two separate syringes into a hot oleylamine surfactant solution with an injection rate of 30 mL/h, anatase TiO(2) nanorods with dimensions of 6 nm (thickness) x 50 nm (length) were produced. When the injection rate was decreased to 2.5 mL/h, star-shaped rutile TiO(2) nanorods with dimensions of 25 nm x 200 nm and a small fraction of rod-shaped anatase TiO(2) nanorods with dimensions of 9 nm x 100 nm were synthesized. Pure star-shaped rutile TiO(2) nanorods with dimensions of 25 nm x 450 nm were synthesized when the injection rate was further decreased to 1.25 mL/h. The simultaneous phase transformation and length elongation of the TiO(2) nanorods were achieved. Under optimized reaction conditions, as much as 3.5 g of TiO(2) nanorods were produced. The TiO(2) nanorods were used to produce dye-sensitized solar cells, and the photoconversion efficiency of the mixture composed of star-shaped rutile TiO(2) nanorods and a small fraction of anatase nanorods were comparable to that of Degussa P-25.
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Affiliation(s)
- Bonil Koo
- National Creative Research Center for Oxide Nanocrystalline Materials and School of Chemical and Biological Engineering, Seoul National University, Seoul 151-744, Korea
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250
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Abstract
We explore the growth mechanism of gold nanocrystals onto preformed cadmium sulfide nanorods to form hybrid metal nanocrystal/semiconductor nanorod colloids. By manipulating the growth conditions, it is possible to obtain nanostructures exhibiting Au nanocrystal growth at only one nanorod tip, at both tips, or at multiple locations along the nanorod surface. Under anaerobic conditions, Au growth occurs only at one tip of the nanorods, producing asymmetric structures. In contrast, the presence of oxygen and trace amounts of water during the reaction promotes etching of the nanorod surface, providing additional sites for metal deposition. Three growth stages are observed when Au growth is performed under air: (1) Au nanocrystal formation at both nanorod tips, (2) growth onto defect sites on the nanorod surface, and finally (3) a ripening process in which one nanocrystal tip grows at the expense of the other particles present on the nanorod. Analysis of the hybrid nanostructures by high-resolution TEM shows that there is no preferred orientation between the Au nanocrystal and the CdS nanorod, indicating that growth is nonepitaxial. The optical signatures of the nanocrystals and the nanorods (i.e., the surface plasmon and first exciton transition peaks, respectively) are spectrally distinct, allowing the different stages of the growth process to be easily monitored. The initial CdS nanorods exhibit band gap and trap state emission, both of which are quenched during Au growth.
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Affiliation(s)
- Aaron E Saunders
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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