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ABSTRACT: Nanosized Co spinel ferrite was prepared by a combustion method. The grain size of resultant ferrite can be controlled by
the reaction conditions. Magnetic investigation revealed that the products with an average grain size of 4 nm behave as superparamagnetic
materials and have zero coercive force; whereas the samples with an average grain size of 85 nm (near the size of critical
single domain) have the maximal coercive force. There were the negative magnetic intergrain interactions which became stronger
when the grain size neared that of the single domain.
Keywordscombustion method-Co spinel ferrite-magnetic interaction-nanometer materials
Chinese Science Bulletin 04/2012; 46(5):384-387. · 1.32 Impact Factor
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ABSTRACT: Quaternary water-in-oil reverse micelles consisting of cetyltrimethylammonium bromide (CTAB), nhexanol, n-heptane and water
were prepared and characterized. The optimized reaction conditions were determined, and monodispersed droplets of the reverse
micelles were used as microreactors to synthesize CdS nanoparticles. By using transmission electron microscopy (TEM), UV-Vis
spectroscopy and fluorescence spectroscopy, the influences of the reverse micelle components on the size, size distribution,
morphology, stability and optical properties of CdS nanoparticles were investigated. CdS nanoparticles with narrow size distribution
were obtained and the size range is 6–8 nm whenW=24 (W=[water]/[CTAB]), P=5.27 (P=[n-hexanol]/ [CTAB]), [CTAB]=0.2 mol/L, [Cd2+] and [S2-] are 8.45×10−4 mol/L.
Chinese Science Bulletin 04/2012; 46(22):1873-1877. · 1.32 Impact Factor
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ABSTRACT: Owing to their direct toxic effects on human beings, animals, and plants, chemical warfare agents (CWAs) and their mimics
have become widespread in chemical warfare and agriculture. The considerable concerns about their entry into biological systems
and the residues in environment stimulate the development of rapid and sensitive methods for the detection and analysis of
this family of compounds. In the progress of sensitive, selective, and fast responsive detection, fluorescent molecular probes
have been widely used in the detection of CWAs in recent years. Here the recent reports on the design of fluorescent molecular
probes and their advantages in the detection of CWAs were reviewed. Furthermore, the extensive interests accelerate the development
of novel fluorescent molecular probes and detection techniques in this field.
Keywordschemical warfare agents-detection-fluorescent-molecular probes
Frontiers of Chemistry in China 04/2012; 5(2):123-133.
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ABSTRACT: The progress of the design, synthesis, fluorescence properties and application of a new family of fluorescent molecular switches
towards information processing at the molecular level was reviewed. On the basis of the high fluorescence quantum yields and
surroundings-sensitive fluorescent properties of the 5-methoxy-2-(2-pyridyl)-thiazole (2-MPT, 1) and a series of its derivatives
as prepared, multiple binary logic and arithmetic functionalities were realized through encoding the controllable fluorescence
switching properties with binary digit. Combined with the microfluidic platform, the fabrication of the molecular logic devices
was attempted.
Science in China Series B Chemistry 04/2012; 52(6):700-714. · 1.20 Impact Factor
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ABSTRACT: β-NaYF4:Yb,Er nanoparticles (NPs) are one of the most efficient upconversion materials, which can convert near-infrared light to
higher-energy light through multiple photon absorptions or energy transfer. In addition, they may be attractive alternative
donors for luminescence resonance energy transfer (LRET) studies, because of their sharp absorption and emission profiles,
high quantum yields, large anti-stokes shifts, long lifetime, low toxicity, and superior photo-stability. In principle, many
problems of fluorescence resonance energy transfer (FRET), such as excitation of acceptors, emission overlaps between donors
and acceptors, high background noise, potential toxicity, and instability, can be overcome using β-NaYF4:Yb,Er NPs as energy donors. Because the organic coating induced separation can significantly reduce the energy transfer efficiency
and aqueous FRET system is difficult to be applied in devices, we demonstrate a novel NP-dye LRET system in solid state. The
emission of the β-NaYF4:Yb,Er NPs at 539 nm overlaps with the absorption of the tetrametrylrhodarnine isothiocyante (TRITC), satisfying the requirement
of LRET process. Since TRITC molecules are adsorbed on the β-NaYF4:Yb,Er NPs by an electrostatic interaction, the interaction distance is suitable for LRET without any further modulation.
The resultant solid LRET system is ready for the further applications for devices.
Keywordsupconversion emission-β-NaYF4:Yb,Er-nanoparticles-TRITC-assembly-luminescence resonance energy transfer (LRET)
Science in China Series B Chemistry 04/2012; 52(10):1590-1595. · 1.20 Impact Factor
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ABSTRACT: Since the discovery of a surfactant directed self-assembly approach for the fabrication of mesoporous silica in 1992, increasing
attention has been focused on the design and synthesis of mesostructured functional materials. Organic functionalization is
becoming a major topic in this research field, since highly ordered mesostructured organic-inorganic hybrids offer novel functionalities
and enhanced performance over their individual components. We begin with a brief overview of the three fundamental methods
(post-synthetic grafting technique, co-condensation method, and preparation of periodic mesoporous organosilicas) for the
preparation of organically functionalized mesostructured silica, and focus on one of the most promising approaches, which
herein was named as functional-template directed self-assembly (FTDSA) approach, and in the eyes of the authors it has a special
position in the preparation of this class of hybrid materials. A comprehensive overview of the state of research in the area
of FTDSA and its potential applications will be given.
Science in China Series B Chemistry 04/2012; 52(11):1759-1768. · 1.20 Impact Factor
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Berichte der deutschen chemischen Gesellschaft 08/2010; 2010(27):4357 - 4362. · 2.94 Impact Factor
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ABSTRACT: Monodisperse beta-NaYF4:Yb,Tm nanocrystals with controlled size (25-150 nm), shape (sphere, hexagonal prism, and hexagonal plate), and composition (Yb: 20-40%, Tm: 0.2-5%) were synthesized from the thermolysis of metal trifluoroacetates in hot surfactant solutions. The upconversion (UC) of near-infrared light (980 nm) to ultra-violet (360 nm), blue (450 and 475 nm), red (650 and 695 nm) and infrared (800 nm) light in the beta-NaYF4:Yb,Tm nanocrystals has been studied by UC spectroscopy. Both the total intensity of UC emissions and the relative intensities of emissions at different wavelengths have shown a strong dependence on different particle sizes and different Tm3+ and Yb3+ concentrations. As a result, different overall output colors of UC emissions can be achieved by altering sizes and Yb3+/Tm3+ doping concentrations of the beta-NaYF4:Yb,Tm nanocrystals. The intensity-power curves of a series of samples have proved that emissions at 360 and 450 nm can be ascribed to four-photon process (1D2 to 3H6 and 1D2 to 3H4, respectively), while emissions at 475 and 650 nm are three-photon processes (1G4 to 3H6 and 1G4 to 3H4, respectively) and emissions at 695 and 800 nm are two-photon ones (3F2 to 3H6 and 3F4 to 3H6, respectively). A UC saturation effect would occur under a certain excitation intensity of the 980 nm CW diode laser for the as-obtained beta-NaYF4:Yb,Tm nanocrystals, leading to the decrease of the slopes of the I-P curves. The results of our study also revealed that the successive transfer model instead of the cooperative sensitization model can be applied to explain the UC behaviors of the beta-NaYF4:Yb,Tm nanocrystals. Further, an unexpected stronger emissions of four-photon process at 360 and 450 nm for approximately 50 nm beta-NaYF4:Yb,Tm nanocrystals than those for the bigger (approximately 150 nm) nanocrystals was observed and explained in terms of the effects of crystallite size, surface-to-volume ratio and homogeneity of the doping cations.
Nanoscale 06/2010; 2(6):953-9. · 5.91 Impact Factor
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ABSTRACT: Elongated tetrahexahedral Au nanocrystals have been grown in high yields using a seed-mediated growth method. Morphological and structural characterizations show that these Au nanocrystals are single-crystalline and enclosed by 24 high-index {037} facets. They are more electrochemically active than octahedral Au nanocrystals that are enclosed by 8 low-index {111} facets. To date, there have been only a few reports of metal nanocrystals that are enclosed exclusively by high-index facets, including trisoctahedral Au nanocrystals enclosed by 24 {122} facets and tetrahexahedral Pt nanocrystals enclosed by 24 {037} facets. Our tetrahexahedral Au nanocrystals will be an important addition to the family of metal nanocrystals that are enclosed exclusively by high-index facets and will also be useful for fundamental catalytic studies on metal nanocrystals.
Journal of the American Chemical Society 11/2009; 131(45):16350-1. · 9.91 Impact Factor
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ABSTRACT: We report on the strong polarization dependence of the plasmon-enhanced fluorescence on single gold nanorods. The fluorescence from the organic fluorophores that are embedded in a mesostructured silica shell around individual gold nanorods is enhanced by the longitudinal plasmon resonance of the nanorods. Our electrostatic calculations show that under an off-resonance excitation, the electric field intensity contour around a nanorod rotates away from the length axis as the excitation polarization is varied. The polarization dependence of the plasmon-enhanced fluorescence is ascribed to the dependence of the averaged electric field intensity enhancement within the silica shell on the excitation polarization. The measured fluorescence enhancement factor is in very good agreement with that obtained from the electrostatic calculations. The fluorescence enhancement factor increases as the longitudinal plasmon wavelength is synthetically tuned close to the excitation wavelength. In addition, the polarization dependence is used to determine the orientation angle of the gold nanorods. The results are in excellent agreement with the actual measurements. Furthermore, the emission spectrum of the fluorophore is modified by the longitudinal plasmon resonance of the gold nanorods. A linear correlation between the emission peak wavelength and the longitudinal plasmon wavelength is obtained.
Nano Letters 09/2009; 9(11):3896-903. · 13.20 Impact Factor
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ABSTRACT: Gold nanocubes are assembled into clusters of varying numbers and ordering on indium tin oxide substrates. The plasmon coupling in the clusters is studied with both dark-field imaging and finite-difference time-domain calculations. Generally, as a cluster becomes larger and more asymmetric, it exhibits more scattering peaks towards longer wavelengths. The coupling of the vertically oriented dipole in the nanocube with its image dipole in the substrate generates two scattering peaks. One is fixed in energy and the other red-shifts with increasing cluster size. The coupling of horizontally oriented dipoles among different nanocubes produces multiple scattering peaks at lower energies. Their positions and intensities are highly dependent on the number and ordering of nanocubes in the cluster. Au nanocubes in the clusters are further welded together by thermal treatment. The scattering peaks of the thermally treated clusters generally become sharper. The lower-energy scattering peaks arising from dipolar oscillations are red-shifted.
Small 07/2009; 5(18):2111-9. · 8.35 Impact Factor
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ABSTRACT: Two new atisane-type diterpenoid glucosides, spiraeosides A (1) and B (2), were isolated from the aerial parts of Spiraea japonica L. f. var. ovalifolia. Their structures were characterized based on spectral analysis, and the structure of 1 was further confirmed by single-crystal X-ray diffraction.
Planta Medica 05/2009; 75(12):1349-51. · 2.15 Impact Factor
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Angewandte Chemie International Edition 02/2008; 47(5):877-81. · 13.45 Impact Factor
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ABSTRACT: It has long been known that metal ions and saccharides are involved in many biochemical processes. In this paper, metal nitrates were used as reactants to detect the coordination structures of the hydroxyl groups of galactitol in different environments. Three novel crystal structures and FT-IR spectra of metal nitrate-galactitol complexes of La(NO3)3.C6H14O6.(4)H2O, 2Ca(NO3)2.C6H14O6.H2O, and Sr(NO3)2.C6H14O6 were examined in an effort to clarify the structural factors that control metal ion interactions with saccharides in aqueous and biological systems. The coordination structures of galactitol with alkaline earth and lanthanide nitrates in the solid state were compared using FT-IR, Raman, and X-ray diffraction techniques to extensively discuss the coordination rules of different kinds of metal ions. Results provided a model of the coordination sites found in sugars and showed that the introduction of NO3- made the coordination modes of galactitol more diverse and complex than those of the corresponding chloride complexes. Specifically, new coordination modes of galactitol and complicated topology networks were found in 2Ca(NO3)2.C6H14O6.H2O and Sr(NO3)2.C6H14O6. FT-IR results are consistent with the crystal structures and thus provide the possibility of using the similarity of IR spectra to speculate about unknown structures when the compounds are difficult to prepare as single crystals.
Inorganic Chemistry 08/2007; 46(14):5508-17. · 4.60 Impact Factor
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ABSTRACT: Gold nanorods, nanospheres, and bipyramids have been assembled using glutathione and cysteine into three types of necklace structures, which might be useful for the fabrication of nanoscale photonic, electronic, and optoelectronic devices.
Chemical Communications 06/2007; · 6.17 Impact Factor
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ABSTRACT: We have demonstrated glutathione- and cysteine-induced transverse overgrowth on gold nanorods. In aqueous solutions, glutathione and cysteine are preferentially bound to the ends of gold nanorods that are stabilized by a cationic surfactant bilayer. This preferential end binding blocks the growth of the nanorods in the longitudinal direction completely and allows for the growth only in the transverse direction. As a result, the diameters of the nanorods become larger and larger while their lengths remain unchanged, as more and more gold precursor is supplied. In addition, the shape of the nanorods undergoes a gradual change from rods, peanuts, and truncated octahedra to faceted spheres during overgrowth. We believe that this transverse overgrowth provides an alternative means for tailoring the longitudinal plasmon wavelengths and extinction cross sections of gold nanoparticles and will therefore facilitate their use in optics, optoelectronics, and biotechnology.
Journal of the American Chemical Society 06/2007; 129(20):6402-4. · 9.91 Impact Factor
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ABSTRACT: Gold nanorods were prepared in high yields by using a one-step seed-mediated process in aqueous cetyltripropylammonium bromide (CTPAB) and cetyltributylammonium bromide (CTBAB) solutions in the presence of silver nitrate. The diameters of the nanorods range from 3 to 11 nm, their lengths are in the range of 15 to 350 nm, and their aspect ratios are in the range of 2 to 70. The diameters of the Au nanorods obtained from one growth batch in CTPAB solutions decrease as their lengths increase, and their volumes decrease as the aspect ratios increase. The diameters of the Au nanorods obtained from one growth batch in CTBAB solutions first decrease and then slightly increase as their lengths increase, and their volumes increase as the aspect ratios increase. These Au nanorods are single-crystalline and are seen to be oriented in either the [100] or [110] direction under transmission electron microscopy imaging, irrespective of their sizes. To the best of our knowledge, this is the first report of the preparation by using wet-chemistry methods of single-crystalline Au nanorods with aspect ratios larger than 15.
Chemistry 02/2007; 13(10):2929-36. · 5.93 Impact Factor
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ABSTRACT: Metallic copper, which is normally considered as a contaminant in the growth of single-walled carbon nanotubes (SWNTs), was found to be an efficient catalyst to grow SWNTs under suitable conditions. It showed very high catalytic activity for the growth of both random SWNT networks and horizontally aligned SWNT arrays. Especially, high-quality SWNT arrays were obtained when monodispersed copper nanoparticles were used. The catalytic behavior of copper for the growth of SWNTs was discussed. The weaker interaction between the copper and silica surfaces plays an important role in the growth of high-quality horizontally aligned SWNT arrays. This new synthesis process of SWNTs with a non-ferromagnetic catalyst brings more convenience to the study of magnetic properties of SWNTs and gives more insight in structure-controlled synthesis of SWNTs.
Nano Letters 01/2007; 6(12):2987-90. · 13.20 Impact Factor
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ABSTRACT: Flaky monoclinic La2Ti2O7 was prepared via a hydrothermal method based on the reaction of Ti(SO4)2 and La(NO3)3. Relative to the solid-state reaction sample, the flaky La2Ti2O7 showed higher surface areas, much smaller crystal size and more efficient light absorption. All these factors led to the
higher photoactivity to produce H2 from water splitting under UV irradiation.
Catalysis Letters 12/2006; 113(1):54-58. · 2.24 Impact Factor
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ABSTRACT: Gold nanorods and bipyramids have been synthesized using the seed-mediated approach in aqueous cetyltriethylammonium bromide (CTEAB) solutions in the presence of silver nitrate. Gold nanoparticle seeds that are stabilized with either CTEAB or sodium citrate have been used. The use of the CTEAB-stabilized seeds gives gold nanorods in high yield in one step with the longitudinal plasmon wavelength ranging from 750 to 1030 nm, depending on the amount of the seeds. The longitudinal plasmon wavelength can be extended to 1100 nm by the use of a two-step growth method. The growth of gold nanorods in CTEAB solutions takes 5-10 h, more than 5 times slower than that in cetyltrimethylammonium bromide solutions at the same concentration of surfactants. The use of the citrate-stabilized seeds gives both gold bipyramids and a small percentage of gold nanorods. The longitudinal plasmon wavelength of the bipyramids is tunable from 700 to 1100 nm by varying the amount of the citrate-stabilized seeds. The growth of gold bipyramids takes more than 1 day. Transmission electron microscopy characterizations reveal that the gold nanorods grown from both types of gold nanoparticle seeds are single-crystalline and that the gold bipyramids are penta-twinned.
The Journal of Physical Chemistry B 09/2006; 110(33):16377-83. · 3.70 Impact Factor
