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1.  Nanoscaled alloy formation from self-assembled elemental Co nanoparticles on top of Pt films 
Summary
The thermally activated formation of nanoscale CoPt alloys was investigated, after deposition of self-assembled Co nanoparticles on textured Pt(111) and epitaxial Pt(100) films on MgO(100) and SrTiO3(100) substrates, respectively. For this purpose, metallic Co nanoparticles (diameter 7 nm) were prepared with a spacing of 100 nm by deposition of precursor-loaded reverse micelles, subsequent plasma etching and reduction on flat Pt surfaces. The samples were then annealed at successively higher temperatures under a H2 atmosphere, and the resulting variations of their structure, morphology and magnetic properties were characterized. We observed pronounced differences in the diffusion and alloying of Co nanoparticles on Pt films with different orientations and microstructures. On textured Pt(111) films exhibiting grain sizes (20–30 nm) smaller than the particle spacing (100 nm), the formation of local nanoalloys at the surface is strongly suppressed and Co incorporation into the film via grain boundaries is favoured. In contrast, due to the absence of grain boundaries on high quality epitaxial Pt(100) films with micron-sized grains, local alloying at the film surface was established. Signatures of alloy formation were evident from magnetic investigations. Upon annealing to temperatures up to 380 °C, we found an increase both of the coercive field and of the Co orbital magnetic moment, indicating the formation of a CoPt phase with strongly increased magnetic anisotropy compared to pure Co. At higher temperatures, however, the Co atoms diffuse into a nearby surface region where Pt-rich compounds are formed, as shown by element-specific microscopy.
doi:10.3762/bjnano.2.51
PMCID: PMC3190617  PMID: 22003453
alloy; Co; CoPt; epitaxy; HRTEM; magnetometry; nanoparticles; Pt; XMCD
2.  Engineering Au Nanoparticle Arrays on SiO2 Glass by Pulsed UV Laser Irradiation 
Plasmonics (Norwell, Mass.)  2012;8(1):105-113.
We study semi-regular arrays of Au nanoparticles (NP) obtained via UV laser irradiation of thin Au films on glass substrate. The NP structures are prepared from films of a thickness up to 60 nm produced by discharge sputtering or pulsed laser deposition, and annealed by nanosecond laser pulses at 266 or 308 nm, respectively, at fluencies in the range of 60–410 mJ/cm2. For the rare- and close-packed NP structures, consistent description of optical properties is derived from microscopic observation, measurements of the absorption, and Raman spectra, and modeling of the near-field intensity distributions. The absorption bands centered at 540–570 nm are ascribed to resonant absorption of the surface plasmons. For the band positions, half widths, and intensities, the dependence on the NP shape (partial spheres), size, size distribution, and also excitation energy is observed. The structures are characterized by markedly reduced dephasing times of ∼3 fs. It is shown, that laser annealing of thin Au films provides reliable and cost effective method for controlled preparation of semi-regular NP arrays favorable for photonic applications.
doi:10.1007/s11468-012-9428-3
PMCID: PMC3597268  PMID: 23503766
Au nanoparticles; Laser annealing; Semi-regular nanostructures; Surface plasmon resonance
3.  Nanoparticle Thin Films for Gas Sensors Prepared by Matrix Assisted Pulsed Laser Evaporation 
Sensors (Basel, Switzerland)  2009;9(4):2682-2696.
The matrix assisted pulsed laser evaporation (MAPLE) technique has been used for the deposition of metal dioxide (TiO2, SnO2) nanoparticle thin films for gas sensor applications. For this purpose, colloidal metal dioxide nanoparticles were diluted in volatile solvents, the solution was frozen at the liquid nitrogen temperature and irradiated with a pulsed excimer laser. The dioxide nanoparticles were deposited on Si and Al2O3 substrates. A rather uniform distribution of TiO2 nanoparticles with an average size of about 10 nm and of SnO2 nanoparticles with an average size of about 3 nm was obtained, as demonstrated by high resolution scanning electron microscopy (SEM-FEG) inspections. Gas-sensing devices based on the resistive transduction mechanism were fabricated by depositing the nanoparticle thin films onto suitable rough alumina substrates equipped with interdigitated electrical contacts and heating elements. Electrical characterization measurements were carried out in controlled environment. The results of the gas-sensing tests towards low concentrations of ethanol and acetone vapors are reported. Typical gas sensor parameters (gas responses, response/recovery time, sensitivity, and low detection limit) towards ethanol and acetone are presented.
doi:10.3390/s90402682
PMCID: PMC3348821  PMID: 22574039
Nanoparticles; thin films; MAPLE; gas sensors
4.  Three strategies to stabilise nearly monodispersed silver nanoparticles in aqueous solution 
Nanoscale Research Letters  2012;7(1):151.
Silver nanoparticles are extensively used due to their chemical and physical properties and promising applications in areas such as medicine and electronics. Controlled synthesis of silver nanoparticles remains a major challenge due to the difficulty in producing long-term stable particles of the same size and shape in aqueous solution. To address this problem, we examine three strategies to stabilise aqueous solutions of 15 nm citrate-reduced silver nanoparticles using organic polymeric capping, bimetallic core-shell and bimetallic alloying. Our results show that these strategies drastically improve nanoparticle stability by distinct mechanisms. Additionally, we report a new role of polymer functionalisation in preventing further uncontrolled nanoparticle growth. For bimetallic nanoparticles, we attribute the presence of a higher valence metal on the surface of the nanoparticle as one of the key factors for improving their long-term stability. Stable silver-based nanoparticles, free of organic solvents, will have great potential for accelerating further environmental and nanotoxicity studies.
PACS: 81.07.-b; 81.16.Be; 82.70.Dd.
doi:10.1186/1556-276X-7-151
PMCID: PMC3351018  PMID: 22356679
silver nanoparticles; stability; functionalisation; monodispersed; aging; toxicity.
5.  Directed deposition of silicon nanowires using neopentasilane as precursor and gold as catalyst 
Summary
In this work the applicability of neopentasilane (Si(SiH3)4) as a precursor for the formation of silicon nanowires by using gold nanoparticles as a catalyst has been explored. The growth proceeds via the formation of liquid gold/silicon alloy droplets, which excrete the silicon nanowires upon continued decomposition of the precursor. This mechanism determines the diameter of the Si nanowires. Different sources for the gold nanoparticles have been tested: the spontaneous dewetting of gold films, thermally annealed gold films, deposition of preformed gold nanoparticles, and the use of “liquid bright gold”, a material historically used for the gilding of porcelain and glass. The latter does not only form gold nanoparticles when deposited as a thin film and thermally annealed, but can also be patterned by using UV irradiation, providing access to laterally structured layers of silicon nanowires.
doi:10.3762/bjnano.3.62
PMCID: PMC3458599  PMID: 23019549
chemical vapor deposition; gold; nanoparticle; patterning; radiation-induced nanostructures; vapor-liquid-solid mechanism
6.  Effects of crystallization and dopant concentration on the emission behavior of TiO2:Eu nanophosphors 
Uniform, spherical-shaped TiO2:Eu nanoparticles with different doping concentrations have been synthesized through controlled hydrolysis of titanium tetrabutoxide under appropriate pH and temperature in the presence of EuCl3·6H2O. Through air annealing at 500°C for 2 h, the amorphous, as-grown nanoparticles could be converted to a pure anatase phase. The morphology, structural, and optical properties of the annealed nanostructures were studied using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy [EDS], and UV-Visible diffuse reflectance spectroscopy techniques. Optoelectronic behaviors of the nanostructures were studied using micro-Raman and photoluminescence [PL] spectroscopies at room temperature. EDS results confirmed a systematic increase of Eu content in the as-prepared samples with the increase of nominal europium content in the reaction solution. With the increasing dopant concentration, crystallinity and crystallite size of the titania particles decreased gradually. Incorporation of europium in the titania particles induced a structural deformation and a blueshift of their absorption edge. While the room-temperature PL emission of the as-grown samples is dominated by the 5D0 - 7Fj transition of Eu+3 ions, the emission intensity reduced drastically after thermal annealing due to outwards segregation of dopant ions.
doi:10.1186/1556-276X-7-1
PMCID: PMC3260088  PMID: 22214494
titania nanoparticles; europium doping; optical properties; photoluminescence
7.  Laser-Induced, Polarization Dependent Shape Transformation of Au/Ag Nanoparticles in Glass 
Nanoscale Research Letters  2009;4(11):1380-1383.
Bimetallic, initially spherical Ag/Au nanoparticles in glass prepared by ion implantation have been irradiated with intense femtosecond laser pulses at intensities still below the damage threshold of the material surface. This high-intensity laser processing produces dichroism in the irradiated region, which can be assigned to the observed anisotropic nanoparticle shapes with preferential orientation of the longer particle axis along the direction of laser polarization. In addition, the particle sizes have considerably been increased upon processing.
doi:10.1007/s11671-009-9408-5
PMCID: PMC2893753  PMID: 20628450
Alloy nanoparticles; Glass; Laser irradiation; Femtosecond laser processing; Dichroism
8.  Laser-Induced, Polarization Dependent Shape Transformation of Au/Ag Nanoparticles in Glass 
Nanoscale Research Letters  2009;4(11):1380-1383.
Bimetallic, initially spherical Ag/Au nanoparticles in glass prepared by ion implantation have been irradiated with intense femtosecond laser pulses at intensities still below the damage threshold of the material surface. This high-intensity laser processing produces dichroism in the irradiated region, which can be assigned to the observed anisotropic nanoparticle shapes with preferential orientation of the longer particle axis along the direction of laser polarization. In addition, the particle sizes have considerably been increased upon processing.
doi:10.1007/s11671-009-9408-5
PMCID: PMC2893753  PMID: 20628450
Alloy nanoparticles; Glass; Laser irradiation; Femtosecond laser processing; Dichroism
9.  Synthesis of 3D nanostructured metal alloy of immiscible materials induced by megahertz-repetition femtosecond laser pulses 
Nanoscale Research Letters  2012;7(1):518.
In this work, we have proposed a concept for the generation of three-dimensional (3D) nanostructured metal alloys of immiscible materials induced by megahertz-frequency ultrafast laser pulses. A mixture of two microparticle materials (aluminum and nickel oxide) and nickel oxide microparticles coated onto an aluminum foil have been used in this study. After laser irradiation, three different types of nanostructure composites have been observed: aluminum embedded in nickel nuclei, agglomerated chain of aluminum and nickel nanoparticles, and finally, aluminum nanoparticles grown on nickel microparticles. In comparison with current nanofabrication methods which are used only for one-dimensional nanofabrication, this technique enables us to fabricate 3D nanostructured metal alloys of two or more nanoparticle materials with varied composite concentrations under various predetermined conditions. This technique can lead to promising solutions for the fabrication of 3D nanostructured metal alloys in applications such as fuel-cell energy generation and development of custom-designed, functionally graded biomaterials and biocomposites.
doi:10.1186/1556-276X-7-518
PMCID: PMC3599459  PMID: 22999219
3D nanostructured metal alloy; Femtosecond laser pulses; Aluminum and nickel oxide; Ultrafast laser thermal effects
10.  Gold-Coated Iron Composite Nanospheres Targeted the Detection of Escherichia coli 
We report the preparation and characterization of spherical core-shell structured Fe3O4–Au magnetic nanoparticles, modified with two component self-assembled monolayers (SAMs) consisting of 3–mercaptophenylboronic acid (3–MBA) and 1–decanethiol (1–DT). The rapid and room temperature synthesis of magnetic nanoparticles was achieved using the hydroxylamine reduction of HAuCl4 on the surface of ethylenediaminetetraacetic acid (EDTA)-immobilized iron (magnetite Fe3O4) nanoparticles in the presence of an aqueous solution of hexadecyltrimetylammonium bromide (CTAB) as a dispersant. The reduction of gold on the surface of Fe3O4 nanoparticles exhibits a uniform, highly stable, and narrow particle size distribution of Fe3O4–Au nanoparticles with an average diameter of 9 ± 2 nm. The saturation magnetization value for the resulting nanoparticles was found to be 15 emu/g at 298 K. Subsequent surface modification with SAMs against glucoside moieties on the surface of bacteria provided effective magnetic separation. Comparison of the bacteria capturing efficiency, by means of different molecular recognition agents 3–MBA, 1–DT and the mixed monolayer of 3–MBA and 1–DT was presented. The best capturing efficiency of E. coli was achieved with the mixed monolayer of 3–MBA and 1–DT-modified nanoparticles. Molecular specificity and selectivity were also demonstrated by comparing the surface-enhanced Raman scattering (SERS) spectrum of E. coli-nanoparticle conjugates with bacterial growth media.
doi:10.3390/ijms14036223
PMCID: PMC3634437  PMID: 23507756
magnetic gold nanoparticle; SERS; immunomagnetic separation; E. coli; surface functionalisation of particles
11.  Atomic-scale engineering of magnetic anisotropy of nanostructures through interfaces and interlines 
Nature Communications  2012;3:1313-.
The central goals of nanoscale magnetic materials science are the self-assembly of the smallest structure exhibiting ferromagnetic hysteresis at room temperature, and the assembly of these structures into the highest density patterns. The focus has been on chemically ordered alloys combining magnetic 3d elements with polarizable 5d elements having high spin–orbit coupling and thus yielding the desired large magneto-crystalline anisotropy. The chemical synthesis of nanoparticles of these alloys yields disordered phases requiring annealing to transform them to the high-anisotropy L10 structure. Despite considerable efforts, so far only part of the nanoparticles can be transformed without coalescence. Here we present an alternative approach to homogeneous alloys, namely the creation of nanostructures with atomically sharp bimetallic interfaces and interlines. They exhibit unexpectedly high magnetization reversal energy with values and directions of the easy magnetization axes strongly depending on chemistry and texture. We find significant deviations from the expected behaviour for commonly used element combinations. Ab-initio calculations reproduce these results and unravel their origin.
The design and assembly of nanostructures exhibiting ferromagnetic hysteresis at room temperature are recognized goals for high-density data storage. Here, the authors engineer nanostructures with atomically sharp bimetallic interfaces and interlines, which exhibit large magnetic anisotropy and high temperature hysteresis.
doi:10.1038/ncomms2316
PMCID: PMC3535417  PMID: 23271648
12.  Synthesis and characterization of potential iron–platinum drugs and supplements by laser liquid photolysis 
Highly crystalline nanospherical iron–platinum systems were produced by 248 nm laser irradiation of a liquid precursor at different laser fluences, ranging from 100–375 mJ/cm2. The influence of laser intensity on particle size, iron composition, and structure was systematically investigated. Different nanostructures of iron–platinum alloy and chemically disordered iron–platinum L10 phase were obtained without annealing. The prepared precursor solution underwent deep photolysis to polycrystalline iron–platinum nanoalloys through Fe(III) acetylacetonate and Pt(II) acetylacetonate. Fe(II) and Pt(I) acetylacetone decomposed into Fe0 and Pt0 nanoparticles. We found that the (001) diffraction peak shifted linearly to a lower angle, with the last peak shifting in opposition to the others. This caused the face-centered cubic L10 structure to change its composition according to laser fluence. The nanostructures were shown to contain iron and platinum only by energy-dispersive spectroscopy at several spots. The response of these iron–platinum nanoparticles to infrared depends on their stoichiometric composition, which is controlled by laser fluence.
doi:10.2147/NSA.S24419
PMCID: PMC3781719  PMID: 24198494
nanostructures; iron; platinum; nanoparticles; laser liquid photolysis; composition
13.  Electrochemical and Structural Study of a Chemically Dealloyed PtCu Oxygen Reduction Catalyst 
A carbon-supported, dealloyed platinum-copper (Pt-Cu) oxygen reduction catalyst was prepared using a multi-step synthetic procedure. Material produced at each step was characterized using high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), electron energy loss spectroscopy (EELS) mapping, x-ray absorption spectroscopy (XAS), x-ray diffraction (XRD), and cyclic voltammetry (CV), and its oxygen reduction reaction (ORR) activity was measured by a thin-film rotating disk electrode (TF-RDE) technique. The initial synthetic step, a co-reduction of metal salts, produced a range of poorly crystalline Pt, Cu, and Pt-Cu alloy nanoparticles that nevertheless exhibited good ORR activity. Annealing this material alloyed the metals and increased particle size and crystallinity. TEM shows the annealed catalyst to include particles of various sizes, large (>25 nm), medium (12–25 nm), and small (<12 nm). Most of the small and medium-sized particles exhibited a partial or complete coreshell (Cu-rich core and Pt shell) structure with the smaller particles typically having more complete shells. The appearance of Pt shells after annealing indicates that they are formed by a thermal diffusion mechanism. Although the specific activity of the catalyst material was more than doubled by annealing, the concomitant decrease in Pt surface area resulted in a drop in its mass activity. Subsequent dealloying of the catalyst by acid treatment to partially remove the copper increased the Pt surface area by changing the morphology of the large and some medium particles to a “Swiss cheese” type structure having many voids. The smaller particles retained their core-shell structure. The specific activity of the catalyst material was little reduced by dealloying, but its mass activity was more than doubled due to the increase in surface area. The possible origins of these results are discussed in this report.
doi:10.1021/jp106042z
PMCID: PMC3691677  PMID: 23807900
Dealloyed catalyst; fuel cell; PtCu catalyst; HAADF STEM; EELS; TEM
14.  Preparation and characterization of supported magnetic nanoparticles prepared by reverse micelles 
Summary
Monatomic (Fe, Co) and bimetallic (FePt and CoPt) nanoparticles were prepared by exploiting the self-organization of precursor loaded reverse micelles. Achievements and limitations of the preparation approach are critically discussed. We show that self-assembled metallic nanoparticles can be prepared with diameters d = 2–12 nm and interparticle distances D = 20–140 nm on various substrates. Structural, electronic and magnetic properties of the particle arrays were characterized by several techniques to give a comprehensive view of the high quality of the method. For Co nanoparticles, it is demonstrated that magnetostatic interactions can be neglected for distances which are at least 6 times larger than the particle diameter. Focus is placed on FePt alloy nanoparticles which show a huge magnetic anisotropy in the L10 phase, however, this is still less by a factor of 3–4 when compared to the anisotropy of the bulk counterpart. A similar observation was also found for CoPt nanoparticles (NPs). These results are related to imperfect crystal structures as revealed by HRTEM as well as to compositional distributions of the prepared particles. Interestingly, the results demonstrate that the averaged effective magnetic anisotropy of FePt nanoparticles does not strongly depend on size. Consequently, magnetization stability should scale linearly with the volume of the NPs and give rise to a critical value for stability at ambient temperature. Indeed, for diameters above 6 nm such stability is observed for the current FePt and CoPt NPs. Finally, the long-term conservation of nanoparticles by Au photoseeding is presented.
doi:10.3762/bjnano.1.5
PMCID: PMC3045932  PMID: 21977392
Co; CoPt; core–shell particles; FePt; magnetic anisotropy; magnetic particles; plasma etching; reverse micelles; self-assembly
15.  Mechanisms of nanoparticle-mediated photomechanical cell damage 
Biomedical Optics Express  2012;3(3):435-446.
Laser-assisted killing of gold nanoparticle targeted macrophages was investigated. Using pressure transient detection, flash photography and transmission electron microscopy (TEM) imaging, we studied the mechanism of single cell damage by vapor bubble formation around gold nanospheres induced by nanosecond laser pulses. The influence of the number of irradiating laser pulses and of particle size and concentration on the threshold for acute cell damage was determined. While the single pulse damage threshold is independent of the particle size, the threshold decreases with increasing particle size when using trains of pulses. The dependence of the cell damage threshold on the nanoparticle concentration during incubation reveals that particle accumulation and distribution inside the cell plays a key role in tissue imaging or cell damaging.
doi:10.1364/BOE.3.000435
PMCID: PMC3296532  PMID: 22435092
(170.0170) Medical optics and biotechnology; (170.5180) Photodynamic therapy; (170.5120) Photoacoustic imaging
16.  Direct-writing of PbS nanoparticles inside transparent porous silica monoliths using pulsed femtosecond laser irradiation 
Nanoscale Research Letters  2011;6(1):542.
Pulsed femtosecond laser irradiation at low repetition rate, without any annealing, has been used to localize the growth of PbS nanoparticles, for the first time, inside a transparent porous silica matrix prepared by a sol-gel route. Before the irradiation, the porous silica host has been soaked within a solution containing PbS precursors. The effect of the incident laser power on the particle size was studied. X-ray diffraction was used to identify the PbS crystallites inside the irradiated areas and to estimate the average particle size. The localized laser irradiation led to PbS crystallite size ranging between 4 and 8 nm, depending on the incident femtosecond laser power. The optical properties of the obtained PbS-silica nanocomposites have been investigated using absorption and photoluminescence spectroscopies. Finally, the stability of PbS nanoparticles embedded inside the host matrices has been followed as a function of time, and it has been shown that this stability depends on the nanoparticle mean size.
doi:10.1186/1556-276X-6-542
PMCID: PMC3224756  PMID: 21970510
17.  A Novel Preparation Method for 5-Aminosalicylic Acid Loaded Eudragit S100 Nanoparticles 
In this study, solution enhanced dispersion by supercritical fluids (SEDS) technique was applied for the preparation of 5-aminosalicylic acid (5-ASA) loaded Eudragit S100 (EU S100) nanoparticles. The effects of various process variables including pressure, temperature, 5-ASA concentration and solution flow rate on morphology, particle size, 5-ASA loading and entrapment efficiency of nanoparticles were investigated. Under the appropriate conditions, drug-loaded nanoparticles exhibited a spherical shape and small particle size with narrow particle size distribution. In addition, the nanoparticles prepared were characterized by X-ray diffraction, Differential scanning calorimetry and Fourier transform infrared spectroscopy analyses. The results showed that 5-ASA was imbedded into EU S100 in an amorphous state after SEDS processing and the SEDS process did not induce degradation of 5-ASA.
doi:10.3390/ijms13056454
PMCID: PMC3382771  PMID: 22754377
supercritical antisolvent; solution enhanced dispersion by supercritical fluids; Eudragit S100; 5-ASA; nanoparticles; colon-specific
18.  Synthesis and characterization of hybrid nanostructures 
Nano Reviews  2011;2:10.3402/nano.v2i0.5983.
There has been significant interest in the development of multicomponent nanocrystals formed by the assembly of two or more different materials with control over size, shape, composition, and spatial orientation. In particular, the selective growth of metals on the tips of semiconductor nanorods and wires can act to couple the electrical and optical properties of semiconductors with the unique properties of various metals. Here, we outline our progress on the solution-phase synthesis of metal-semiconductor heterojunctions formed by the growth of Au, Pt, or other binary catalytic metal systems on metal (Cd, Pb, Cu)-chalcogenide nanostructures. We show the ability to grow the metal on various shapes (spherical, rods, hexagonal prisms, and wires). Furthermore, manipulating the composition of the metal nanoparticles is also shown, where PtNi and PtCo alloys are our main focus. The magnetic and electrical properties of the developed hybrid nanostructures are shown.
doi:10.3402/nano.v2i0.5983
PMCID: PMC3215196  PMID: 22110873
synthesis; Hybrid Nanocrystals; Nanowires; Electrical and magnetic properties; MOCVD
19.  Enhanced optical output power of blue light-emitting diodes with quasi-aligned gold nanoparticles 
The output power of the light from GaN-based light-emitting diodes (LEDs) was enhanced by fabricating gold (Au) nanoparticles on the surface of p-GaN. Quasi-aligned Au nanoparticle arrays were prepared by depositing Au thin film on an aligned suspended carbon nanotube thin film surface and then putting the Au-CNT system on the surface of p-GaN and thermally annealing the sample. The size and position of the Au nanoparticles were confined by the carbon nanotube framework, and no other additional residual Au was distributed on the surface of the p-GaN substrate. The output power of the light from the LEDs with Au nanoparticles was enhanced by 55.3% for an injected current of 100 mA with the electrical property unchanged compared with the conventional planar LEDs. The enhancement may originate from the surface plasmon effect and scattering effect of the Au nanoparticles.
doi:10.1186/1556-276X-9-7
PMCID: PMC3882480  PMID: 24393473
GaN; Light-emitting diodes (LEDs); Au nanoparticles; Carbon nanotube
20.  In Situ Mineralization of Magnetite Nanoparticles in Chitosan Hydrogel 
Nanoscale Research Letters  2009;4(9):1041-1046.
Based on chelation effect between iron ions and amino groups of chitosan, in situ mineralization of magnetite nanoparticles in chitosan hydrogel under ambient conditions was proposed. The chelation effect between iron ions and amino groups in CS–Fe complex, which led to that chitosan hydrogel exerted a crucial control on the magnetite mineralization, was proved by X-ray photoelectron spectrum. The composition, morphology and size of the mineralized magnetite nanoparticles were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy and thermal gravity. The mineralized nanoparticles were nonstoichiometric magnetite with a unit formula of Fe2.85O4 and coated by a thin layer of chitosan. The mineralized magnetite nanoparticles with mean diameter of 13 nm dispersed in chitosan hydrogel uniformly. Magnetization measurement indicated that superparamagnetism behavior was exhibited. These magnetite nanoparticles mineralized in chitosan hydrogel have potential applications in the field of biotechnology. Moreover, this method can also be used to synthesize other kinds of inorganic nanoparticles, such as ZnO, Fe2O3 and hydroxyapatite.
doi:10.1007/s11671-009-9355-1
PMCID: PMC2894183  PMID: 20596346
Chitosan hydrogel; Magnetite; Mineralization; Chelation
21.  In Situ Mineralization of Magnetite Nanoparticles in Chitosan Hydrogel 
Nanoscale Research Letters  2009;4(9):1041-1046.
Based on chelation effect between iron ions and amino groups of chitosan, in situ mineralization of magnetite nanoparticles in chitosan hydrogel under ambient conditions was proposed. The chelation effect between iron ions and amino groups in CS–Fe complex, which led to that chitosan hydrogel exerted a crucial control on the magnetite mineralization, was proved by X-ray photoelectron spectrum. The composition, morphology and size of the mineralized magnetite nanoparticles were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy and thermal gravity. The mineralized nanoparticles were nonstoichiometric magnetite with a unit formula of Fe2.85O4and coated by a thin layer of chitosan. The mineralized magnetite nanoparticles with mean diameter of 13 nm dispersed in chitosan hydrogel uniformly. Magnetization measurement indicated that superparamagnetism behavior was exhibited. These magnetite nanoparticles mineralized in chitosan hydrogel have potential applications in the field of biotechnology. Moreover, this method can also be used to synthesize other kinds of inorganic nanoparticles, such as ZnO, Fe2O3and hydroxyapatite.
doi:10.1007/s11671-009-9355-1
PMCID: PMC2894183  PMID: 20596346
Chitosan hydrogel; Magnetite; Mineralization; Chelation
22.  Composition tunable cobalt–nickel and cobalt–iron alloy nanoparticles below 10 nm synthesized using acetonated cobalt carbonyl 
A general organometallic route has been developed to synthesize CoxNi1−x and CoxFe1−x alloy nanoparticles with a fully tunable composition and a size of 4–10 nm with high yield. In contrast to previously reported synthesis methods using dicobalt octacarbonyl (Co2(CO)8), here the cobalt–cobalt bond in the carbonyl complex is first broken with anhydrous acetone. The acetonated compound, in the presence of iron carbonyl or nickel acetylacetonate, is necessary to obtain small composition tunable alloys. This new route and insights will provide guidelines for the wet-chemical synthesis of yet unmade bimetallic alloy nanoparticles.
Electronic supplementary material
The online version of this article (doi:10.1007/s11051-012-0991-5) contains supplementary material, which is available to authorized users.
doi:10.1007/s11051-012-0991-5
PMCID: PMC3422617  PMID: 22924022
Synthesis; Nanoparticles; Cobalt alloy; Carbonyl disproportionation; Acetone
23.  Pd Nanoparticles and Thin Films for Room Temperature Hydrogen Sensor 
Nanoscale Research Letters  2009;4(10):1191-1196.
We report the application of palladium nanoparticles and thin films for hydrogen sensor. Electrochemically grown palladium particles with spherical shapes deposited on Si substrate and sputter deposited Pd thin films were used to detect hydrogen at room temperature. Grain size dependence of H2 sensing behavior has been discussed for both types of Pd films. The electrochemically grown Pd nanoparticles were observed to show better hydrogen sensing response than the sputtered palladium thin films. The demonstration of size dependent room temperature H2 sensing paves the ways to fabricate the room temperature metallic and metal–metal oxide semiconductor sensor by tuning the size of metal catalyst in mixed systems. H2 sensing by the Pd nanostructures is attributed to the chemical and electronic sensitization mechanisms.
doi:10.1007/s11671-009-9379-6
PMCID: PMC2894097  PMID: 20596429
Palladium; Hydrogen sensors
24.  Pd Nanoparticles and Thin Films for Room Temperature Hydrogen Sensor 
Nanoscale Research Letters  2009;4(10):1191-1196.
We report the application of palladium nanoparticles and thin films for hydrogen sensor. Electrochemically grown palladium particles with spherical shapes deposited on Si substrate and sputter deposited Pd thin films were used to detect hydrogen at room temperature. Grain size dependence of H2sensing behavior has been discussed for both types of Pd films. The electrochemically grown Pd nanoparticles were observed to show better hydrogen sensing response than the sputtered palladium thin films. The demonstration of size dependent room temperature H2sensing paves the ways to fabricate the room temperature metallic and metal–metal oxide semiconductor sensor by tuning the size of metal catalyst in mixed systems. H2sensing by the Pd nanostructures is attributed to the chemical and electronic sensitization mechanisms.
doi:10.1007/s11671-009-9379-6
PMCID: PMC2894097  PMID: 20596429
Palladium; Hydrogen sensors
25.  Preparation of Ultrafine Fe–Pt Alloy and Au Nanoparticle Colloids by KrF Excimer Laser Solution Photolysis 
Nanoscale Research Letters  2009;4(6):565-573.
We prepared ultrafine Fe–Pt alloy nanoparticle colloids by UV laser solution photolysis (KrF excimer laser of 248 nm wavelength) using precursors of methanol solutions into which iron and platinum complexes were dissolved together with PVP dispersant to prevent aggregations. From TEM observations, the Fe–Pt nanoparticles were found to be composed of disordered FCC A1 phase with average diameters of 0.5–3 nm regardless of the preparation conditions. Higher iron compositions of nanoparticles require irradiations of higher laser pulse energies typically more than 350 mJ, which is considered to be due to the difficulty in dissociation of Fe(III) acetylacetonate compared with Pt(II) acetylacetonate. Au colloid preparation by the same method was also attempted, resulting in Au nanoparticle colloids with over 10 times larger diameters than the Fe–Pt nanoparticles and UV–visible absorption peaks around 530 nm that originate from the surface plasmon resonance. Differences between the Fe–Pt and Au nanoparticles prepared by the KrF excimer laser solution photolysis are also discussed.
doi:10.1007/s11671-009-9281-2
PMCID: PMC2894087  PMID: 20596425
Nanoparticle; Excimer laser; Laser solution photolysis; Precursor; Fe–Pt alloy; Au

Results 1-25 (405410)