共查询到20条相似文献,搜索用时 15 毫秒
1.
A novel conjugate of water-soluble CdTe quantum dots to a small biomolecule guanine has been obtained in aqueous phase. The photoluminescence property and the stability of the conjugate increased comparing to CdTe QDs. The interaction between CdTe QDs and guanine was studied by TEM, fluorescence microscope and photoluminescence (PL), IR, UV-Vis spectra. The effects of reflux time, pH value, ionic strength, and the ratio of CdTe QDs to guanine on the photoluminescence properties of conjugate were investigated in detail. The results show that guanine has a great influence on both the photoluminescence property and stability of thioglycolic acid-stabilized CdTe QDs. The formation of coordination and hydrogen bond between guanine molecules and CdTe including thioglycolic acid on its surface may effectively enhance the PL intensity and stability of CdTe QDs. The maximum PL intensity of the conjugate was obtained on the condition with lower ionic strength, less than 30 min reflux time, neutral pH value and 6/1 as molar ratio of guanine to CdTe. 相似文献
2.
Syntheses, structures, and properties of novel molybdenum and tungsten complexes of fullerenes 总被引:1,自引:0,他引:1
The synthesis and characterization of several fullerene-based organometallic complexes containing Mo and W is reported. 相似文献
3.
4.
Leyong Zeng Wenzhi RenJianjun Zheng Aiguo Wu Ping Cui 《Applied Surface Science》2012,258(7):2570-2575
Water soluble FeOOH nanospindles with small size were synthesized by a simple hydrolysis method of inorganic salts and water bath treatment with different incubation time. The morphology, microstructure, magnetic resonance imaging (MRI) performance and cytotoxicity of the as-prepared FeOOH nanospindles were investigated, respectively. The results showed that the longitudinal length of FeOOH nanospindles was about 40-50 nm, and the incubation time had important effect for the morphology and production rate of FeOOH nanospindles. MRI test showed that the longitudinal and transverse relaxivities (r1 and r2 values) of FeOOH nanospindles were about 3.06 mM−1 s−1 and 5.06 mM−1 s−1, respectively. Furthermore, the experimental results of the Prussian Blue staining showed the clusters of FeOOH nanospindles in the cytoplasm of the labeled cells, and the cytotoxicity characterization indicated that FeOOH nanospindles have low cytotoxicity. Therefore, the as-prepared FeOOH nanospindles will have potential applications as T1- and T2-weighted MRI contrast agents. 相似文献
5.
N. V. Bulina É. A. Petrakovskaya A. S. Fedorov G. N. Churilov 《Physics of the Solid State》2007,49(3):599-602
Fullerenes containing manganese and iron atoms are synthesized in a high-frequency carbonhelium plasma at atmospheric pressure. The electron paramagnetic resonance (EPR) spectrum of the synthesized compound contains not only lines attributed to iron atoms but also the lines of a manganese ion pair with an additional hyperfine structure. The latter lines are assigned to the endohedral complex Mn2@Cn (n > 70). The possible existence of these structures is evaluated from quantum-chemical calculations of the optimum geometry of the endothedral fullerene Mn2@C84 with C 2v symmetry. It is found that the manganese atoms are spaced ~2.72 Å apart at the center of the molecule. 相似文献
6.
ZnS nanoparticles with Mn2+ doping (0.5-20%) have been prepared through a simple chemical method, namely the chemical precipitation method. The structure of the nanoparticles has been analyzed using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and UV-vis spectrometer. The size of the particles is found to be 3-5 nm range. Photoluminescence spectra were recorded for undoped ZnS nanoparticles using an excitation wavelength of 320 nm, exhibiting an emission peak centered at around 445 nm. However, from the Mn2+-doped samples, a yellow-orange emission from the Mn2+4T1-6A1 transition is observed along with the blue emission. The prepared Mn2+-doped sample shows efficient emission of yellow-orange light with the peak emission 580 nm with the blue emission suppressed. The maximum PL intensity is observed only at the excitation energy of 3.88 eV (320 nm). Increase in stabilizing time up to 48 h in de-ionized water yields the enhancement of emission intensity of doped (4% Mn2+) ZnS. The correlation made through the concentration of Mn2+ versus PL intensity resulted in opposite trend (mirror image) of blue and yellow emissions. 相似文献
7.
We describe the synthesis of nano-structured materials of ZnO and Pd by laser ablation and their applications to sensors. The synthesis of ZnO nano-wires was performed by nano-particle assisted deposition (NPAD) where nano-crystals were grown with nano-particles generated by laser-ablating a ZnO sintered target in an Ar background gas. The synthesized ZnO nano-wires were characterized with a scanning electron microscopy and the photoluminescent characteristics were examined under an excitation with the third harmonics of a Nd:YAG laser. The nano-wires with a diameter in the range from 50 to 150 nm and a length of up to 5 μm were taken out of the substrate by laser blow-off technique and/or sonication. It was confirmed that the nano-wires showed the stimulated emission under optical pumping, indicating a high quality of the crystalinity. Pd nano-particles were generated by laser-ablating a Pd plate in pure water. The transmission electron microscope observation revealed that Pd nano-particles with a diameter in the range from 3 nm to several tens of nanometers were produced. Using these nano-structured materials, we successfully fabricated sensors by the dielectrophoresis techniques. In the case of the ultraviolet photosensor, a detection sensitivity of 10 nW/cm2 was achieved and in the case of hydrogen sensing, the response time of less than 10 s has been demonstrated with Pd nano-particles. 相似文献
8.
Effects of β, X and VUV irradiation on the optical properties have been studied in various simple and complex fluoride crystals by using optical absorption, X- and UV-excited luminescence (XL and PL), thermoluminescence (TL) and photo-transferred TL (PTTL) techniques. In most tested crystals, the main TL peaks with the same thermal activation energies appear after VUV as well as after X or β irradiation, thus indicating that the same traps are induced by the different types of radiation. The TL excitation spectra generally show absorption maxima on the long wavelengths tail of the fundamental absorption. Within this study, various dosimetric properties, as well as the possible application of the crystals as sensitive radiation detectors and dosimeters for the VUV have also been investigated. The TL sensitivities of the various studied materials have been compared to that of the classic dosimeter TLD-100 (LiF:Mg,Ti). For example, the sensitivity of SrF2:Pr3+ has been found to be the highest among the examined crystals and at a dose of 90 Gy its response is higher by a factor of ~3 than that of TLD-100. The sensitivity of CsGd2F7:Pr3+ and KYF4:Pr3+ are slightly higher than that of TLD-100, whereas that of nanostructured CaF2:ZnO crystals is about twice that of TLD-100, but the sensitivity of LiF:Eu is much lower. The SrF2:Pr3+ crystals also showed some important dosimetric properties. 相似文献
9.
K. Prassides 《Hyperfine Interactions》1997,106(1-4):125-135
The dynamic properties of pristine C60 and C70 are reviewed, emphasizing the results of the ZF‐ and ALC‐μ+SR techniques. In C60, the \mboxfcc\rightarrow\mboxsc transition is accompanied by a change in the dynamics from isotropic reorientational to quasi‐random
jump motion between nearly‐degenerate orientations. C70 is frozen on a timescale of 30 ns up to 170 K. At higher temperatures, the motion is found to be complex, consisting of a
uniaxial rotation part together with a nutational or jumping motion of the unique axis. Anisotropy on the 30 ns timescale
persists to 370 K, well into the fcc phase. The ZF‐μ+SR technique has been also employed to study the magnetic properties of fullerides. In the organic salt (TDAE)C60, spontaneous magnetic order is directly observed below a Curie temperature of 16.1 K, higher than any other organic material.
In the quasi‐one‐dimensional conductor CsC60, static magnetic order of a random nature is observed to develop in the vicinity of the metal–insulator transition at 30
K with no direct evidence of long range order present.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
10.
11.
12.
Linear canonical transform (LCT) form a three-parameter family of intergral transforms with wide application in optics. In this paper, we investigate the linear canonical Wigner distribution (LCWD) which is based on the LCT and the classical Wigner distribution (WD). Firstly, the definition of LCWD is discussed. Moreover, the transformation law for the LCWD through a first-order optical system is derived. This new phase-space distribution provides analysis of signals in both space and LCT domains simultaneously. Then, the main properties of LCWD are investigated in detail. Finally, the application of the LCWD is presented. The LCWD is found to be the appropriate phase-space distribution function for light-beam characterization in first-order optical system. Moreover, the moment matrix formalism for beam characterization is studied. 相似文献
13.
《Current Applied Physics》2002,2(3):241-244
We have synthesized PPV derivative containing an adamantane side group, poly(1-(2-ethylhexyloxy)-4-(1-adamantaneethyloxy)-2,5-phenylenevinylene, EHAE-PPV) and fabricated the segment device using this polymeric electroluminescent material. EHAE-PPV is solution processable and shows high photoluminescence intensity, probably due to the steric effect of the adamantyl group. This polymer also has exhibited good electroluminescent properties. 相似文献
14.
15.
Soon Hyung Kang Wonjoo Lee Yoon-Chae Nah Kug-Seung Lee Hyun Sik Kim 《Current Applied Physics》2013,13(1):252-255
Nanobranched TiO2 nanotubes (TONTs) were synthesized by a sol–gel dipping method for the formation of seed layer, followed by a solution-phase deposition process. The different concentrations of seed solution influence the density of nanobranches on the top surface of TONT, achieving complete surface coverage of nanobranches in 10 mM TiCl4 seed solution relative to 5 mM TiCl4 seed solution. With a control sample of bare TONT, the nanobranched TONTs were explored as a photoanode for dye-sensitized solar cells (DSSCs). In the 5 mM TiCl4 seed solution, the nanotree-shaped branches were sporadically formed on the top surface of TONT, with little effect on the photocurrent-voltage (J–V) properties, while in the 10 mM TiCl4 seed solution, Jsc and fill factor increased, which may have been on account of the increased surface area and light scattering effect from rutile nanobranches, whereas the fill factor may be also increased by the electron transport property, leading to the degraded charge recombination. Accordingly, the nanobranched TONT showed 33% improved efficiency compared to bare TONT. 相似文献
16.
In order to perform correlative light and electron microscopy (CLEM) more precisely, we have modified existing specimen preparation protocols allowing fluorescence retention within embedded and sectioned tissue, facilitating direct observation across length scales. We detail a protocol which provides a precise correlation accuracy using accessible techniques in biological specimen preparation. By combining a pre-embedding uranyl acetate staining step with the progressive lowering of temperature (PLT) technique, a methacrylate embedded tissue specimen is ultrathin sectioned and mounted onto a TEM finder grid for immediate viewing in the confocal and electron microscope. In this study, the protocol is applied to rat uterine epithelial cells in vivo during early pregnancy. Correlative overlay data was used to track changes in filamentous actin that occurs in these cells from fertilization (Day 1) to implantation on Day 6 as part of the plasma membrane transformation, a process essential in the development of uterine receptivity in the rat. CLEM confirmed that the actin cytoskeleton is disrupted as apical microvilli are progressively lost toward implantation, and revealed the thick and continuous terminal web is replaced by a thinner and irregular actin band, with individually distinguishable filaments connecting actin meshworks which correspond with remaining plasma membrane protrusions. 相似文献
17.
Synthesis, characterization and photophysical properties of the poly{[(2,2′-bis-(4-phenylquinoline)-1,4-phenylene]-alt-phenoxy}n, a novel quinoline derived copolymer with ether linkages, are described. Polymerization reaction occurred through nucleophilic aromatic substitution between an aromatic halogen and a phenol. Structural characterization was made by FTIR, NMR, DSC, TGA and GPC. Ultraviolet, fluorescence and excitation spectroscopy were used for analysis of photophysical properties. The ether linkages, apart from providing better solubility compared to full conjugated quinoline copolymers, made it possible to access the photophysical properties of the quinoline moiety as a constituent of a polymer backbone, since these linkages are responsible for the confinement of the chromophoric unit. The role played by protonation in photophysical behavior was also considered, since this class of polymers is only soluble in strong acid media. This work comprised the study of the photophysical properties of nitrogen containing polymers with confined conjugation and the role of this element in some interesting properties. 相似文献
18.
Based on a coupled nonlinear dynamic filter (NDF), a novel
chaotic stream cipher is presented in this paper and employed to
protect palmprint templates. The chaotic pseudorandom bit generator
(PRBG) based on a coupled NDF, which is constructed in an inverse
flow, can generate multiple bits at one iteration and satisfy the
security requirement of cipher design. Then, the stream cipher is
employed to generate cancelable competitive code palmprint
biometrics for template protection. The proposed cancelable
palmprint authentication system depends on two factors: the
palmprint biometric and the password/token. Therefore, the system
provides high-confidence and also protects the user's privacy. The
experimental results of verification on the Hong Kong PolyU Palmprint
Database show that the proposed approach has a large template
re-issuance ability and the equal error rate can achieve 0.02%.
The performance of the palmprint template protection scheme proves the
good practicability and security of the proposed stream cipher. 相似文献
19.
《Journal of Physics and Chemistry of Solids》2007,68(5-6):734-737
LiFePO4 nanoparticles were synthesized via polyol process. The temperature of the solution was rapidly increased up to 320 °C to obtain larger particles and the temperature was maintained for 16 h in a round-bottomed flask attached to a refluxing condenser. The X-ray diffractrion (XRD), pattern was indexed on the basis of orthorhombic olivine structure. The LiFePO4 compound prepared through polyol process exhibited a high crystallinity. The particles show the various shapes with size ranging from 100 to 300 nm. The initial discharge curve of LiFePO4 capacity shows 168 mA h/g at the 0.1C rate in the voltage range of 2.5–4 V with well-formed plateau. 相似文献
20.
Na-doped ZnO nanowires with an average diameter of ∼40 nm have been fabricated by a thermal decomposition route at temperature around 400 °C. Their properties have been investigated using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), UV-visible spectroscopy, Raman spectra, and photoluminescence (PL) spectroscopy. Room temperature photoluminescence (RT-PL) showed that the as-synthesized ZnO samples exhibited strong visible emission with a major peak at 420 nm. Furthermore, intensity of the visible emission increased and then decreased with increase in Na concentration. The improvement of visible emission at 420 nm in the Na-doped ZnO samples should be a result of the surface defects increased by doping of Na in zinc oxide. In addition, photocatalytic studies indicated that these nanomaterials showed good photocatalytic performance for organic pollutants in water. 相似文献