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1.
Reverse micelle chemistry-derived Cu-doped Zn1?xCdxS quantum dots (QDs) with the composition (x) of 0, 0.5, 1 are reported. The Cu emission was found to be dependent on the host composition of QDs. While a dim green/orange emission was observed from ZnS:Cu QDs, a relatively strong red emission could be obtained from CdS:Cu and Zn0.5Cd0.5S:Cu QDs. Luminescent properties of undoped QDs versus Cu-doped ones and quantum yields of alloyed ZnCdS versus CdS QDs are compared and discussed. To enhance Cu-related red emission of CdS:Cu and Zn0.5Cd0.5S:Cu core QDs, core/shell structured QDs with a wider band gap of ZnS shell are also demonstrated. 相似文献
2.
V. N. Krasil’nikov O. I. Gyrdasova I. V. Baklanova L. Yu. Buldakova M. Yu. Yanchenko R. F. Samigullina O. V. Koryakova 《Russian Journal of Inorganic Chemistry》2013,58(2):120-126
Quasi-one-dimensional (1D) solid solutions Ti1 ? x Fe x (OCH2CH2O)2 ? x/2 (0 < x ≤ 0.1) with the structure of anatase were prepared by heating the glycolate Ti1 ? x Fe x (OCH2CH2O)2 ? x/2 in an atmosphere of air at a temperature of >450°C. The conditions of formation and the properties of the new glycolate Ti3Fe2(OCH2CH2O)9 were described. It was found that the synthesized Ti1 ? x Fe x O2 ? 2x/2 solid solutions exhibit photocatalytic activity in the reaction of hydroquinone oxidation in an aqueous solution on irradiation with UV light. A correlation between the rate of oxidation of hydroquinone and the concentration of iron in the catalyst was established. A procedure for the preparation of titanium dioxide with the structure of anatase doped with iron and carbon (Ti1 ? x Fe x O(2 ? x/2) ? yCy) and also composites on its basis, which contain an excess amount of carbon, was proposed. 相似文献
3.
Qin LX Ma W Li DW Li Y Chen X Kraatz HB James TD Long YT 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(19):5262-5271
Quantum dots (QDs) have been widely used for fluorescent imaging in cells. In particular, surface functionalized QDs are of interest, since they possess the ability to recognize and detect the analytes in the surrounding nanoscale environment based on electron and hole transfer between the analytes and the QDs. Here we demonstrate that fluorescence enhancement/quenching in QDs can be switched by electrochemically modulating electron transfer between attached molecules and QDs. For this purpose, a number of redox-active coenzyme Q (CoQ) disulfide derivatives [CoQC(n)S](2) were synthesized with different alkyl chain lengths (n=1, 5, and 10). The system supremely sensitive to NADH (nicotinamide adenine dinucleotide) and superoxide radical (O(2)(.)(-)), and represents a biomimetic electron-transfer system, modeling part of the mitochondrial respiratory chain. The results of our in situ fluorescence spectroelectrochemical study demonstrate that the reduced state of [CoQC(n)S](2) significantly enhanced the fluorescence intensity of CdTe/ZnS QDs, while the oxidized state of the CoQ conjugates quench the fluorescence to varying degrees. Fluorescence imaging of cells loaded with the conjugate QD-[CoQC(n)S](2) displayed strikingly differences in the fluorescence depending on the redox state of the capping layer, thus introducing a handle for evaluating the status of the cellular redox potential status. Moreover, an MTT assay (MTT=3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) proved that the cytotoxicity of QDs was significantly reduced after immobilization by CoQ derivatives. Those unique features make CoQ derivatived QDs as a promising probe to image redox coenzyme function in vitro and in vivo. 相似文献
4.
Aneeta Kharkwal Kiran Jain S. B. Tyagi A. K. Singh Shailesh N. Sharma Mamta Kharkwal 《Colloid and polymer science》2014,292(11):2913-2926
The single-pot synthesis of highly crystalline and fluorescent chalcopyrite CuInS2 (CIS) colloidal nanoparticles has been reported by thermal decomposition of metal ethyl xanthate (at ~110 °C) for the first time. The fluorescence emission wavelength can also be readily tuned from the UV to the visible region by merely prolonging the reaction time, as the PL emission may be varied from 550 to 675 nm. The synthesized CIS is subjected to postdeposition treatment with CdS/ZnS in one pot route using cadmium/zinc xanthate at low temperature (~80 °C) to improve the quantum yield of core–shell (CIS/CdS or ZnS) nanocrystallites as compared to CIS core. The stability of core–shell particularly CIS/ZnS system upon continuous laser exposure suggests the formation of surface bonds with superior mechanical stability. This low-cost synthesis of such nontoxic QDs using green chemical routes is a promising approach for the fabrication of optoelectronic and biosensing devices. Graphical Abstract
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5.
V. P. Gorelov V. B. Vykhodets T. E. Kurennykh V. B. Balakireva A. V. Kuz’min M. V. Ananiev 《Russian Journal of Electrochemistry》2013,49(9):915-918
The hydrogen content in CaZr1 ? x Sc x O3 ? x/2 (x = 0.00–0.20) and BaZr0.9Y0.1O3-α (for comparison) was studied by powder nuclear microanalysis. The samples were saturated with heavy water (D2O) vapors at 350 and 400°C in air. The chemical expansion of the CaZr0.95Sc0.05O3-α and BaZr0.95Y0.05O3-α samples at 700°C was measured at different water vapor pressures. A model was suggested to explain the lowered hydrogen content in oxides based on CaZrO3. 相似文献
6.
Esra Öztürk Nilgun Kalaycioglu Ozpozan Serkan Dayan 《Journal of Thermal Analysis and Calorimetry》2014,117(2):573-578
Mn4+ doped and Dy3+, Tm3+ co-doped MgAl2Si2O8-based phosphors were prepared by conventional solid state reaction at 1,300 °C. They were characterized by thermogravimetry, differential thermal analysis, X-ray powder diffraction, photoluminescence, and scanning electron microscopy. The luminescence mechanism of the phosphors, which showed broad red emission bands in the range of 600–715 nm and had a different maximum intensity when activated by UV illumination, was discussed. Such a red emission can be attributed to the 2E → 4A2 transitions of Mn4+. 相似文献
7.
Zheng W Kumar P Washington A Wang Z Dalal NS Strouse GF Singh K 《Journal of the American Chemical Society》2012,134(4):2172-2179
Despite a long history of success in formation of transition-metal-doped quantum dots (QDs), the origin of magnetism in diluted magnetic semiconductors (DMSs) is yet a controversial issue. Cr(II)-doped II-VI DMSs are half-metallic, resulting in high-temperature ferromagnetism. The magnetic properties reflect a strong p-d exchange interaction between the spin-up Cr(II) t(2g) level and the Se 4p. In this study, ultrasmall (~3.1 nm) Cr(II)-doped CdSe DMSQDs are shown to exhibit room-temperature ferromagnetism, as expected from theoretical arguments. Surprisingly, a low-temperature phase transition is observed at 20 K that is believed to reflect the onset of long-range ordering of the single-domain DMSQD. 相似文献
8.
Susan Gruhl Carla Vogt Jürgen Vogt Urte Hotje Michael Binnewies 《Mikrochimica acta》2005,149(1-2):43-48
Luminous zinc sulphide selenide crystals (ZnS1–xSex) with an anion-gradient in the µm-range within the crystal were quantitatively investigated by LA-ICP-MS. Reference standard crystals were synthesized by chemical vapour transport reaction and characterized by µ-XRF, SEM, PIXE, RBS and solution ICP-MS. Values from several analytical methods were then combined to describe the concentration in the reference crystals. Using these crystals, calibration curves with high correlation coefficients could be obtained for laser ablation ICP-MS determination of elemental concentrations. The gradient determined afterwards in the zinc sulphide selenide sample crystals was in the order of 30wt% in Se-content within an 800µm distance. This shows the promising capabilities of LA-ICP-MS in the field of elemental quantification in the µm-range. 相似文献
9.
《Annales de Chimie Science des Materiaux》2001,26(3):67-77
Preparation and characterization of tantalum-substituted PHT ceramics Pb1−x/2□x/2(HfyTi1−y)1−xTaxO3 (PTHT). This paper deals with the preparation of five oxalic precursors containing lead, hafnium, titanium and tantalum with Pb1−x/2) [(NH4)2(1−x)(1−y)+3x H2y(1−x)](2x/(2+x)) [(HfyTi(1−y))1−xTaxO(C2O4)(x+2)], dH2O general formula [for each precursor y = 0.52 but x takes different values (0.01 ; 0.025 ; 0.05 ; 0.075 ; 0.1)]. The pyrolysis of the complex was performed with a slow heating rate. The thermolysis led to the oxides which were characterized from the microstructural point of view (XRD) and grain size distribution. After the sintering, the electrical properties of the ceramic were studied using Complex Impedance Spectroscopy. 相似文献
10.
Keunjoo Kim Hong Seub Kim Hwack Joo Lee 《Journal of Solid State Electrochemistry》1999,3(7-8):417-423
The thermionic hole emissions from a p-type Si0.67Ge0.33 quantum well with a width of 7 nm and a point defect were investigated using deep level transient spectroscopy. An activation
energy of 0.22 eV from the quantum well is consistent with the heavy hole level from the bottom of the well. The defect-related
band with an energy of 0.30 eV originated from the space charge related to the point defect in the vicinity of the quantum
well heterostructure. The origin of the point-defect-related band was confirmed by photoluminescence and the deep level was
further clarified by using capacitance-voltage measurements and simulation by introducing a simple model of an interfacial
hole trap center. The deep hole trap center apparently disappeared by an annealing effect, indicating that point defects are
subject to thermal annealing. The microscopic measurement provides evidence on point defects in the quantum well structure
and the thermal annealing also enhances the thermionic hole emission from the quantum well structure.
Received: 22 August 1998 /Accepted: 15 February 1999 相似文献
11.
R. A. Grigoryan L. A. Grigoryan 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2014,88(3):537-540
The electrophysical properties of the multicomponent Zn2ZrO4 ? Zn2SnO4 ? ZnFe2O4 system are studied. The electrophysical parameters of solid solutions of Zn2 ? x (Zr a Sn b )1 ? x Fe2x O4 (x = 0–1.0, Δx = 0.1, a + b = 1) are determined. It is found that the formed solid solutions are semiconductors with electrophysical properties that change in a regular fashion with composition and are distinguished by high values of resistivity (107–1012 Ω cm). 相似文献
12.
Galian RE de la Guardia M Pérez-Prieto J 《Langmuir : the ACS journal of surfaces and colloids》2011,27(5):1942-1945
The size of core-shell CdSe/ZnS quantum dots can be decreased by using the combined action of an n,π* aromatic ketone and UVA light. Energy-dispersive X-ray spectroscopy as well as X-ray photoelectron spectroscopy techniques gave information on the photosensitization mechanism and the eventual destiny of Cd(2+) and Se(2-) core ions. Our data support the electron transfer from the BP ketyl radical to Cd(2+), leading to Cd(0) and H(+), as well as to the recovery of benzophenone. Elemental Cd remains on the core and, eventually, can be oxidized to CdO. In addition, Se(2-) counterions disperse inside the solution mainly attached to protonated amine ligands. The Se(2-) combines with H(+), leading to SeH(2), which is finally oxidized to Se(0) by oxygen. Therefore, quantum dots illumination in the presence of benzophenones brings about a profound nanoparticle reconstruction which takes place after dark storage; this agrees with the drastic quenching of the quantum dot emission detected immediately after illumination as well as the slow recovery in the dark. 相似文献
13.
N. A. Kochetova I. V. Spesivtseva I. E. Animitsa 《Russian Journal of Electrochemistry》2013,49(2):176-180
The electric conductivity of perovskite-like Ba2(In1 ? x Al x )2O5 solid solutions (0 < x ≤ 0.20) characterized by structural disordering in the oxygen sublattice was studied as a function of temperature and partial pressure of oxygen in an atmosphere with a low content of water vapors ( $p_{H_2 O}$ = 3 × 10?5 atm). When In3+ was partially replaced by Al3+, the oxygen ion conductivity increased because of the disordering of oxygen structural vacancies, leading to a significant increase in the total electric conductivity of the samples. 相似文献
14.
A multivariate analysis of the empirical structure data for isomeric homologues using principal-component analysis has been carried out, and the correlation with experimental melting points has been shown. Based on the data on the CSD structure, we discuss the impact of molecular H-aggregation. 相似文献
15.
《Solid State Sciences》2005,7(1):33-36
Thermal properties of γ-Fe2O3/poly(methyl methacrylate) (PMMA) core/shell particles with an average core size of 4 nm were studied through measurements of thermogravimetry, powder X-ray diffraction and magnetization. The thermal degradation of the PMMA shell in the air was found to occur at temperatures lower by about 60 °C than that of free PMMA. Random scission of the PMMA chains seemed to be catalyzed by the core oxide. The γ-Fe2O3 to α-Fe2O3 structural transformation took place at different temperatures depending upon the shell material. Namely, α-Fe2O3 was the only product for the caprylate-capped γ-Fe2O3 nanoparticles treated at 400 °C, whereas γ-Fe2O3 still remained for the γ-Fe2O3/PMMA composite treated at 500 °C. It is possible that some species containing silicon of the polymerization initiator origin were formed on the surface and prevented interparticle atomic diffusions needed for the γ–α transformation. 相似文献
16.
W. Wolski E. Wolska J. Kaczmarek P. Piszora 《Journal of Thermal Analysis and Calorimetry》1997,48(2):247-258
Products of hydrothermal treatment of the initial amorphous system MnxFe2–2x(OH)6–4x for 0x1 in 0.1x intervals, and products of their further thermal treatment, were examined by chemical analysis, X-ray, IR, and DTA techniques supported by magnetic measurements. After hydrothermal growth for lowx, hematite and goethite phases occurred. Although the goethite phase was still identifiable atx=0.6, formation of a solid solution with the isostructural groutite was not found. The ferrimagnetic spinel phase, which resists heating up to 400C, was present at 0.5x0.9. At higher temperatures, it transformed into the rhombohedral hematite type phase or into the cubic bixbyite phase. AtT900C, a ferrimagnetic spinel structure reappeared up tox=0.8. For x=0.9, the low- and high-temperature forms of the hausmannite phase occurred, forx= 1 passing from one form into another through Mn5O8 and partritgeite.For a primary mixture Mn0.5Fe(OH)4, corresponding to the manganese ferrite structure, the lattice parameter of which passes from 8.43 å through 8.33 å to 8.50 å, the probable crystallochemical formula was suggested.We are grateful to KBN (The State Committee for Scientific Research, Poland) for grant No. 3 T09A 064 08, which contributed substantially to the materialization of this project. 相似文献
17.
N. I. Sorokin 《Russian Journal of Electrochemistry》2006,42(1):106-108
Electrophysical properties of single-crystal Li2 + x Fe 2 ? 2x 2+ Fe x 3+ (MoO4)3 (x = 0.22) are studied at 25–400°C. It is found that the conduction is of electronic nature and the conductivity equals 5 × 10-2 S/cm at 300°C. The activation energy for the electron transport is 0.23 eV. The conductance in molybdate Li2.22Fe 1.56 2+ Fe 0.22 3+ (MoO4)3 is markedly anisotropic. 相似文献
18.
N. M. Kozhevnikova 《Russian Journal of Inorganic Chemistry》2014,59(9):992-997
Subsolidus phase ratios in the Na2MoO4-NiMoO4-Sc2(MoO4)3 system have been studied using X-ray diffraction, differential thermal analysis, and vibrational spectroscopy. A phase of variable composition Na1 ? x Ni1 ? x Sc1 + x (MoO4)3 (0 ≤ x ≤ 0.5) having NASICON structure (space group \(R\bar 3c\) ) and a triple molybdate crystallizing in triclinic system (space group \(P\bar 1\) ) have been obtained. The high conductivity of Na1 ? x Ni1 ? x Sc1 + x (MoO4)3 allows the phase of variable composition to be regarded as a promising sodiumion-conductive solid electrolyte. 相似文献
19.
W. Kara Mohamed F. Mezrag M. Boucenna N. Bouarissa 《Journal of Structural Chemistry》2013,54(6):1004-1011
The results of pseudopotential calculations of the band structure and related electronic and optical properties of quasi-binary (GaP)1?x (ZnSe) x crystals in the zinc blende structure are presented. Trends in bonding and ionicity are discussed in terms of electronic charge densities. Moreover, the composition dependence of the refractive index and dielectric constants are reported. The computed values are in reasonable agreement with experimental data. The results suggest that for a proper choice of the composition x, (GaP)1?x (ZnSe) x could provide more diverse opportunities to achieve the desired electronic and optical properties of the crystals which would improve the performances of devices fabricated on them. 相似文献
20.
V. I. Pet’kov I. A. Shchelokov E. A. Asabina V. S. Kurazhkovskaya D. A. Rusakov K. V. Pokholok B. I. Lazoryak 《Russian Journal of Inorganic Chemistry》2006,51(12):1855-1863
New complex phosphates of titanium, iron, and alkaline-earth metals have been synthesized. X-ray powder diffraction, differential thermal analysis (DTA), and IR spectroscopy are used to study phase formation in the series of M0.5(1+x)FexTi2?x (PO4)3 (M = Mg, Ca, Sr, Ba) phosphates. Individual compounds and solid solutions are found to crystallize in the NaZr2(PO4)3 and K2Mg2(SO4)3 structure types. Their crystal parameters are calculated. CaFeTi(PO4)3 is studied using Mössbauer spectroscopy. Its structure is refined by the Rietveld method: space group $R\bar 3$ c, Z = 6, a = 8.5172(1), Å, c = 21.7739(4) Å, V = 1367.91(4) Å3. 相似文献