bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of magnetic spinel ferrite CoFe2O4 nanoparticles from ferric salt and characterization of the size-dependent superparamagnetic properties
Authors: Liu Chao , Rondinone Adam J. , Zhang Z. John 
Published: October 2007

Abstract
The CoFe2O4 nanoparticles have been synthesized by using a stable ferric salt of FeCl3 with a micellar microemulsion method. The normal micelles are formed by sodium dodecyl sulfate (NaDS) in aqueous solutions. The mean size of the nanoparticles can be controlled from less than 4 nm to about 10 nm through controlling the concentrations of the reagents. The neutron diffraction in combination with the Rietveld refinement shows that these CoFe2O4 nanoparticles have a high degree of inversion with 66% of the tetrahedral sublattice occupied by Fe3+. Magnetic measurements and neutron diffraction studies demonstrate the superparamagnetic nature of these CoFe2O4 nanoparticles. The size-dependent superparamagnetic properties of CoFe2O4 nanoparticles have also been systematically studied. The blocking temperature and coercive field of the nanoparticles increase with increasing size of the nanoparticles. The superparamagnetic behaviors of CoFe2O4 nanoparticles are consistent with the Stoner-Wohlfarth theory of single domain particles.
Fabrication and physical properties of self-organized silver nanocrystals
Authors: Pileni M. P. 
Published: October 2007

Abstract
A simple method is used to prepare highly monodispersed silver nanoparticles in the liquid phase, which starts from an initial synthesis in functionalized AOT reverse micelles. To narrow the particle size distribution from 43 to 12.5% in dispersion, the particles are extracted from the micellar solution. The size-selected precipitation method is used. The nanocrystallites dispersed in hexane are deposited on a support. A monolayer made of nanoparticles with spontaneous compact hexagonal organization is observed. The immersion of the support on the solution yields to the formation of organized multilayers arranged as microcrystal in a face-centered-cubic structure.
We compare the optical properties of spherical particles organized in a two- and three-dimensional structure with isolated and disordered particles. When particles, deposited on cleaved graphite, are arranged in a hexagonal array, the optical measurements under p-polarization show a new high-energy resonance, which is interpreted as a collective effect, resulting from optical anisotropy due to the mutual interactions between particles. We support this interpretation by numerical calculations performed for finite-size clusters of silver spheres. For disordered particles, a low-energy resonance appears instead of the high-energy resonance observed for spherical and organized particles. This is interpreted as optical shape anisotropy due to the asymmetrical arrangement of particles.
The tip of a scanning tunneling microscope (STM) may be used as an extremely localized source of low-energy electrons to locally excite photon emission from a variety of metal films. The detection of locally excited luminescence at the junction of an STM tip provides access to electron dynamic properties at the surface, which makes it possible to study luminescence phenomena of nanometer-sized structures.
The photon intensity emitted from electrically isolated silver nanoparticles self-organized as a 2D network on a gold (111) substrate is analyzed. We observed unexpectedly strong variations of photon-emission efficiency from isolated nanoparticles, depending on how tightly they are embedded within the network site. The quenching site observed in the STM photon emission map is interpreted as an enhanced interaction of electrons with surface photon modes.
Redox-active polymer-nanoparticle hybrid materials
Authors: Watson Keith J. , Zhu Jin , Nguyen SonBinh T. , Mirkin Chad A. 
Published: October 2007

Abstract
Ring-opening metathesis polymerization was used to modify organic soluble gold nanoparticles with redox-active polymers. A gel-permeation chromatography study revealed that each nanoparticle is modified with approximately 11 polymer chains. Electrochemical studies of nanoparticles modified with block copolymers of two different redox-active groups revealed that each monomer is electrochemically accessible, while no current rectification was observed.
Binary cooperative complementary nanoscale interfacial materials
Authors: Jiang L. , Wang R. , Yang B. , Li T. J. , Tryk D. A. , Fujishima A. , Hashimoto K. , Zhu D. B. 
Published: October 2007

Abstract
Binary cooperative complementary nanoscale interfacial materials, i.e, materials with two complementary properties on the nanoscale, are introduced as a new concept for the design of functional materials. The concept is based on the generation of nanostructures with mutually compensating properties on the surface of a solid. Under certain coordinating conditions, unexpected properties may often appear at these kinds of interfaces, creating a huge potential for applications and theoretical research. Recent research indicates that the binary cooperative complementary concept is extremely useful for the design and creation of nanoscale functional materials.
Phototransformation of Alkanethiol-derivatized Noble Metal Nanoparticle
Authors: Ah Chil Seong , Han Hyouk Soo , Kim Kwan , Jang Du-Jeon 
Published: October 2007

Abstract
Photon-initiated shape transformation of n-alkanethiol-derivatized noble metal nanoparticles has been studied with variations of metal, alkanethiol, and solvent. Silver nanoparticles undergo fragmentation upon irradiation while gold ones barely do. Silver/gold composite particles follow the case of silver with a reduced efficiency. The efficiency decreases as alkanethiol length or solvent dipole moment increases. Following the conduction of thermalized photon energy, alkanethiol can dissociate in a period of heat dissipation, and some of dethiolated particles fragment within the recombination time. Prior to the thermal conduction, shape transformation via melt and vaporization also occurs for both metals but this effect is less apparent for silver because of more notable fragmentation followed. The difference in the transformation of two metals is ascribed to the differences in work function, oxidation potential, atomization enthalpy, and particle size. Smaller fragmentation efficiency with more polar solvent or longer alkanethiol is attributed mainly to relatively smaller dissociation rate compared with heat dissipation rate.
Synthesis and characterization of Cu x S nanoparticles. Nature of the infrared band and charge-carrier dynamics
Authors: Brelle M. C. , Torres-Martinez C. L. , McNulty J. C. , Mehra R. K. , Zhang J. Z. 
Published: October 2007

Abstract
CuxS (x = 1,2) nanoparticles have been synthesized utilizing different capping molecules including polyethyleneglycol (PEG), polyvinylpyrrolidone (PVP), casein hydrolysate-enzymatic (CAS), and bovine serum albumin (BSA). The ground-state electronic absorption spectra of the CuxS nanoparticles show three distinct types of CuxS formed: a green type assigned as crystalline CuS, and two brown types assigned as crystalline Cu2S and amorphous Cu2S. The brown types exhibit a steady increase in absorption toward shorter wavelengths starting at around 650 nm, while the green type shows the same steady increase in absorption, but with an additional absorption band in the infrared (IR). The IR band is attributed to an electron-acceptor state lying within the bandgap. ESR measurements of free Cu(II) ions in solution for all samples show the presence of Cu(II) in the brown amorphous samples, but not in the green or brown crystalline samples. Ultrafast dynamics of photoinduced electrons have been measured for all samples using femtosecond-transient absorption/bleach spectroscopy. In all brown Cu2S samples studied, the early time-transient profiles feature a pulse-width-limited (<150 fs) rise followed by a fast decay (1.1 ps) and a slow decay (>80 ps). These decay dynamics were found to be independent of pump power and stabilizing agent. The fast 1.1 ps decay is attributed to charge carrier trapping, while the long decay may be due to either recombination or deep trapping of the charge carriers. The green CuxS samples studied showed interesting power-dependent behavior. At low excitation intensities, the green CuxS samples showed a transient bleach signal, while at high intensities, a transient absorption signal has been observed. The increased transient absorption over bleach at high intensities is attributed to trap-state saturation. A kinetic model has been developed to account for the main features of the electronic relaxation dynamics.
One-dimensional growth of rock-salt PbS nanocrystals mediated by surfactant/polymer templates
Authors: Yang Shihe , Wang Suhua , Fung K. K. 
Published: October 2007

Abstract
A novel method has been developed for the synthesis of compound semiconductor nanorods (PbS). This method consists of using a functionalized lead(II) salt Pb(AOT)2 as the precursor and a polymer (PVB) as both a matrix and a stabilizer. The PbS nanocrystallites prepared using this method are all oriented with their (100) lattice planes parallel to the substrate surface. Possible mechanisms are briefly discussed for the growth of the rod-shaped PbS nanocrystals with the preferred orientation in the polymer film.
Preparation of II-VI group semiconductor nanowire arrays by dc electrochemical deposition in porous aluminum oxide templates
Authors: Xu Dongsheng , Chen Dapeng , Xu Yajie , Shi Xuesong , Guo Guolin , Gui Linlin , Tang Youqi 
Published: October 2007

Abstract
II-VI group compound semiconductors such as CdS, CdSe, and CdTe nanowire arrays have been prepared by direct current electrodeposition in porous anodic aluminum oxide template from nonaqueous electrolyte. SEM and TEM results show that these nanowires have a highly anisotropic structure of aligned nanowires with diameters of 15-200 nm, which are consistent with the diameters of the templates used. Electron diffraction and HREM investigations demonstrate that the crystalline structures of these nanowires are uniform hexagonal single crystal. This approach can be used to fabricate single crystal nanowire arrays of a wide range of semiconductors and other materials.
Control of morphology in synthesizing mesoporous silica
Authors: Mou Chung-Yuan , Lin Hong-Ping 
Published: October 2007

Abstract
Mesoporous silica can be synthesized by either the alkaline route or the acidic route, both using surfactants as templates. Morphological transformations of mesoporous silica can produce various hierarchical orders. Different morphologies are produced under different synthetic conditions. In the alkaline route, the surfactant/silicate liquid crystal system undergoes phase transformation to form vesicles and further transforms to the hexagonal phase. The results are tubule-within-tubule and hollow pillar-within-sphere structures depending on cosurfactant/surfactant composition. Using nitric acid in the acidic route, one can obtain hierarchical ropes or gyroids depending on stirring conditions. Ammonia hydrothermal treatment can induce further morphological transformation to nanotubes of mesoporous silica.
Polymeric nanostructured composite films
Authors: Shen Jiacong , Sun Junqi , Zhang Xi 
Published: October 2007

Abstract
This research news describes the construction of polymeric nanostructured composite film based on a variety of interactions, such as hydrophobic–hydrophilic effect, electrostatic interaction, hydrogen bonding, etc. The work focused on developing strategies to solve the basic problems in the area of ultrathin film research, such as stability, improving the interface quality, creating patterned interface, and techniques to construct nanolayered structure. With in-depth study of the relationship between the microscopic layered architecture and macroscopic function of supramolecular assemblies, it is anticipated that one could obtain miniature devices or machines of high efficiency through integration of the assembling process and device fabrication.
Processible nanomaterials with high conductivity and magnetizability. Preparation and properties of maghemite/polyaniline nanocomposite films
Authors: Tang Ben Zhong , Geng Yanhou , Sun Qunhui , Zhang Xi Xiang , Jing Xiabin 
Published: October 2007

Abstract
A versatile process employing anionic surfactants has been developed for the preparation of processible nanocomposite films with electrical conductivity and magnetic susceptibility. Maghemite (γFe2O3) nanoclusters (~10 nm in size) are coated with 4-dodecyl-benzenesulfonic acid, and polyaniline (PAn) chains are doped with 10-camphorsulfonic acid. The coated nanoclusters and doped polymers are soluble in common solvents, and casting the solutions readily gives free-standing nanocomposite films with nanocluster contents as high as ~50 wt %. The γFe2O3/PAn nanocomposites show high conductivity (82–237 S cm -1 ) and magnetizability (up to ~35 emu/g γFe2O3).
High-density femtosecond transient absorption spectroscopy of semiconductor nanoparticles. A tool to investigate surface quality
Authors: Burda C. , El-Sayed Mostafa A. 
Published: October 2007

Abstract
At the high laser excitation intensities used in our experiments, more than 50 electron-hole pairs are formed in colloidal semiconductor nanoparticles used in our studies. At this density of charge carriers, new transient absorptions are observed in the femtosecond transient spectra in the 450 to 700 nm region with unresolved fast rise (<100 fs) and two decay components of 660 fs and >150 ps. The absorption at 510 nm could be quenched with the adsorption of electron acceptors (e.g., benzoquinone, 1,2-naphthoquinone), whereas the low-energy transient absorption was not affected. For CdS NPs, we found that passivation eliminated most of the transient absorption. The transient absorptions are thus proposed to result from either trap-state absorption, trapped dimers (or complexes) and/or Stark-shifted exciton absorption resulting from surface electric field of the uncompensated trapped electron-hole pairs. All these possibilities require effective surface trapping at these high levels of excitation.
Chemistry and photophysics of thiol-stabilized II-VI semiconductor nanocrystals
Authors: Eychmüller Alexander , Rogach Andrey L. 
Published: October 2007

Abstract
The chemical and physical properties of thiol-stabilized semiconductor nanocrystals are reviewed. The materials prepared include cadmium and mercury chalcogenides with sizes ranging between 1.4 and about 8 nm. In this size regime, the optical properties of the particles are governed by the size-quantization effect. All nanocrystals synthesized belong to the cubic crystal structure. Some applications of this class of materials are outlined.
Distribution and shape of self-assembled InAs quantum dots grown on GaAs (001)
Authors: Zhang K. , Falta J. , Schmidt Th. , Heyn Ch. , Materlik G. , Hansen W. 
Published: October 2007

Abstract
Grazing incidence small angle X-ray scattering (GISAXS) and atomic force microscopy (AFM) experiments are employed to study self-assembled InAs quantum dots (QDs) grown by molecular beam epitaxy (MBE) on GaAs (001). The GISAXS spectra show pronounced non-specular diffuse scattering satellite peaks with high diffraction orders up to ±3 along [110], [1-10], and [100] sample azimuthal orientations with respect to the incoming beam, indicating a lateral ordering of the InAs QDs. The correlation lengths of the lateral dot distribution are found to be identical along [110] and [1-10] but smaller along [100] direction. The ratio of the mean dot-dot distances along [100] and [1-10] azimuths is determined to be 1.13, indicating the anisotropic ordering of QD distribution. Broad diffraction peaks are observed at larger scattering angles and associated to dot facet crystal truncation rods (CTR). We determine {111}-like facets along [110] and [1-10] sample azimuths, and {101}-like facets along [100] azimuth.
A complementary study of surface-enhanced Raman scattering and metal nanorod arrays
Authors: Yao J. L. , Pan G. P. , Xue K. H. , Wu D. Y. , Ren B. , Sun D. M. , Tang J. , Xu X. , Tian Z. Q. 
Published: October 2007

Abstract
The two-dimensional arrays of various metal nanowires with diameters ranging from 15 to 70 nm have been fabricated by electrodepositing metals of Cu, Ag, Au, Ni, and Co into the nanoholes of the anodic aluminum oxide (AAO) films, followed by partial removal of the film. The strong surface-enhanced Raman scattering (SERS) effects were observed from the metal nanowire arrays including Ni, Co metals that were normally considered to be non-SERS active substrates. It has been shown that metal nanowire arrays can serve as very good SERS active substrates, especially for transition metals. The SERS intensity of the probe molecule adsorbed at the nanowires depends critically on the length of the nanowires explored at the surface. And the band frequency is very sensitive to the diameter, which reflects the change in the electronic property of metal nanowires. Applying this probe molecule strategy, SERS could develop into a diagnostic tool of metal nanowires (nanorods).
A gold nanoparticle/latex microsphere-based colorimetric oligonucleotide detection method
Authors: Reynolds Robert A. , Mirkin Chad A. , Letsinger Robert L. 
Published: October 2007

Abstract
An exceptionally simple and effective DNA detection methodology based on latex microsphere and gold nanoparticle probes has been developed. The latex and gold particle probes, which were functionalized with separate oligonucleotide sequences, undergo hybridization in the presence of target strands that are complementary to both of the probes. Duplex formation thus results in linking of gold nanoparticles to the latex microspheres and a corresponding white-to-red color change, which, because of the particularly large extinction coefficient of the gold nanoparticles, is clearly visible to the naked eye. Background signal caused by unbound gold nanoparticles is significantly reduced by filtering the solution containing the sample and probes through a size-selective cellulose acetate membrane. The unbound gold probes move freely through this membrane while the larger latex particles are trapped. Therefore, if the latex and gold nanoparticles are joined together via the target oligonucleotides, the membrane appears red, indicating a positive test result. If no hybridization takes place, the membrane appears white, indicating a negative result. The lower detection limits for this system are 500 pM for a 24 base single-stranded target and 2.5 nM for a duplex target oligonucleotide.
Colloidal nanocrystals for telecommunications. Complete coverage of the low-loss fiber windows by mercury telluride quantum dot
Authors: Harrison M. T. , Kershaw S. V. , Burt M. G. , Rogach A. L. , Kornowski A. , Eychmüller Alexander , Weller H. 
Published: October 2007

Abstract
Optical fibers have revolutionized the telecommunications industry to such an extent that the network capacity available today was unthinkable 20 years ago. Even so, with the advent of the datawave, and the exponential increase of network traffic predicted to continue indefinitely, the generation of bandwidth remains a challenge. One of the major limitations to the implementation of future high-capacity, ultra-broadband optical networks is the expansion of the fiber bandwidth beyond that available from the current state-of-the-art signal amplification device--the erbium-doped fiber amplifier (EDFA). Although there is currently a large effort to expand the flat-gain bandwidth of the EDFA, most of these efforts involve sophisticated engineering, exotic glass fibers, or multicomponent cascaded systems. In a radically different approach, we are attempting to use the unique properties of semiconductor nanocrystals, or quantum dots, as "designer atoms" in order to produce an ultra-broadband optical amplifier with complete coverage of the telecommunications wavelengths. In this paper we review the synthesis of thiol-stabilized mercury chalcogenide nanocrystals via an aqueous colloidal route, which demonstrate extremely intense photoluminescence all the way across the spectral region of interest, i.e., from 1000 to over 1700 nm.
Multiply coated microspheres. A platform for realizing fields-induced structural transition and photonic bandgap
Authors: Sheng Ping , Wen Weijia , Wang Ning , Ma Hongru , Lin Zhifang , Zhang W. Y. , Lei X. Y. , Wang Z. L. , Zheng D. G. , Tam Wing Yim , Chan C. T. 
Published: October 2007

Abstract
Under crossed electric and magnetic fields, multiply coated microspheres form columnar crystallites with an internal structure that transforms from body-centered-tetragonal to face-centered-cubic as the ratio between the magnetic and the electric fields exceeds a minimum value. The observed transition scenario is in excellent agreement with calculations. These multiply coated microspheres also serve as building blocks for photonic crystals. Robust photonic gaps exist in any periodic structure built from such spheres when the filling ratio of the spheres exceeds a threshold.
Effect of nanostructured supports on catalytic methane decomposition
Authors: Ji L. , Tang S. , Chen P. , Zeng H. C. , Lin J. , Tan K. L. 
Published: October 2007

Abstract
Carbon deposition from catalytic methane decomposition has drawn increasing interest recently. Previously, we have found the carbon formation depends on the crystalline structure of the support, following the trend of Ni/CeO2 > Ni/CaO > Ni/MgO, because Ni supported on MgO is uniformly dispersed and can stabilize high-x CH x intermediates. We have also found that the addition of Pt can inhibit the carbon deposition on Co/Al2O3 because the alloying between Pt and Co results in the better dispersion of Co on the support. Furthermore, it was revealed that by judging the Ni/Mg molar ratio from 1 to 0.25 we could reduce the diameter of deposited carbon nanotubes from 20 to 12 nm, with substantially smaller production rate. All of these previous studies indicated that better dispersion of the supported metal would benefit the decreasing of carbon deposition. Here we present our recent investigation of the effect of support particle size on the carbon deposition. Three different types of 10 wt% Co/Al2O3 catalysts were prepared: Co on commercial Al2O3 (Cat 1), Co on sol-gel-processed Al2O3 (Cat 2), and sol-gel-made homogeneous Co-in-Al2O3 (Cat 3). TEM showed that the diameter of the Co3O4 particles in sol-gel Al2O3 is only around 6 nm, while it is 20-40 nm in the commercial catalyst. By using XRD and FTIR, Co was identified as crystalline Co3O4 in the as-prepared Cat 1 sample, CoAl2O4 in Cat 2, and amorphous Al2O3 in Cat 3, indicating the best dispersion in Cat 3. Methane CO2 reforming was studied on the three catalysts. Longer lifetime was measured for Cat 3 as compared to those on Cat 1 and Cat 2 (>20 h vs. 1 h). The support size effect is discussed.
The chelate effect in binding, catalysis, and chemotherapy
Authors: Breslow Ronald , Belvedere Sandro , Gershell Leland , Leung David 
Published: October 2007

Abstract
Cyclodextrin (CD) dimers bind amino acid side chains, and such binding can dissociate aggregated proteins, including citrate synthase (dimer) and lactic dehydrogenase (tetramer). A CD dimer can bind a hydrophobic photosensitizer that, upon irradiation, generates singlet oxygen. This cleaves the dimer and releases the photosensitizer. CD dimers in a cytochrome P-450 mimic steer catalyzed hydroxylation to a bound steroid with geometric control. Chelate binding has also led to a group of cytodifferentiating agents whose mechanism has been recently established. They have promising anticancer properties, and are currently entering human trials as therapeutic agents.