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A method for precision small-angle measurement is proposed. This method is based on the total-internal-reflection effect of a light beam at a pair of glass prisms. Angular displacement of the light beam is measured when the intensity change of the reflected beam is detected as a result of the relative phase shift between the s- and the p-polarized beams. An initial phase shift between the s- and the p-polarized components is introduced to increase measurement sensitivity. For increased measurement linearity and reduced effect of laser power fluctuation on the output, a differential method is used in which the light beam is split equally into two beams, each reflected at a prism and detected by a photodiode. The output is obtained as the difference of the two detected intensities divided by their sum. A prototype device was built, which demonstrated a nonlinearity error of 1.3% in a measurement range of [+ or -] 0.6 [degrees] or 0.4% in [+ or -] 0.3 [degrees]. The peak-to-peak noise level was found to be at approximately 0.5 arc sec. This noise level can be reduced further and resolution increased by a reduction of the measurement range. [C] 2001 Optical Society of America OCIS codes: 120.0120, 120.3930, 120.3940, 120.5700, 260.3160, 260.5430, 260.6970.

Abstract: Hydrophobic oleic acid-capped CdSe/Cd x Zn1−x S core/shell quantum dots (QDs) with high photoluminescence (PL) efficiency of 62% and a PL peak wavelength of 602nm were assembled in SiO2 particles through a novel silanization technique. Ligand exchange (3-mercaptopropyltrimethoxysilane (MPS) instead of oleic acid) occurred via the connection of mercapto groups and QDs when MPS was added in the toluene solution of the QDs. After being silanized using MPS, partially hydrolyzed tetraethyl orthosilicate (TEOS) was attached to the surface of the silanized QDs. The hydrophobic CdSe/Cd x Zn1−x S QDs were then transferred from toluene phase to water phase by the hydrolysis of TEOS through the addition of ethanol, ammonia, and water. Further hydrolysis and condensation of the TEOS and MPS causes them to form assemblies in the water phase. MPS is crucial for proper assembly of the QDs in SiO2 particles and for controlling the size of resulting SiO2 particles. The resulting SiO2 particles exhibited tunable diameters from several tens to 100nm. After being encapsulated in SiO2 particles, the QDs revealed a PL efficiency of 25%. Because of the resulting SiO2 particles encapsulating multiple hydrophobic CdSe/Cd x Zn1−x S QDs and having a functional surface (mercapto group), they are applicable to bio-probes. [Copyright &y& Elsevier]

Abstract: A facile method has been developed to encapsulate Fe3O4 nanocrystals (NCs) in morphology-tunable fibers (belt-like, solid, and tubal) by using a sonochemistry driven synthesis and a subsequent reflux procedure. By adapting the use of tetraethyl orthosilicate, ammonia, Cd2+, and thiolglycolic acid (TGA) to an ultrasound-driven synthesis, the Fe3O4 NCs were coated with a thin composite shell. Supersonic treatment plays an important role to prevent the agglomeration of the Fe3O4 NCs in an alkaline condition. The composite shell became thicker due to the deposition of SiO2 monomers, Cd–TGA clusters, Cd2+, and free TGA molecules during reflux. In addition, these composite shell-coated Fe3O4 NCs were assembled in composite fibers which were created by the growth of Cd–TGA clusters and the deposition of SiO2 monomers. The Fe3O4 NCs mono-dispersed in fibers revealed superparamagnetic behavior. The magnetic saturation value of tubal fibers is lower than those of belt-like and solid fibers. These fibers with Fe3O4 NCs would be utilizable for further application. The strategy described here should give a useful enlightenment for the design and fabrication of morphology-tunable fibers with functional NCs. [ABSTRACT FROM AUTHOR]

Abstract: Eu3+-doped SrZrO3 nanocrystals with a size of about 10nm were synthesized by a simple sol–gel combustion method, and characterized by X-ray diffraction, transmission electron microscopy and photoluminescence spectroscopy. The nanocrystalline intend to assemble to a porous morphology. Both intrinsic defects related and activator luminescence were observed. The red emission of Eu3+ is intense and the spectra show a minor difference with different excitation wavelengths. [Copyright &y& Elsevier]

Abstract: The oxidation behaviour of nanometre and micrometre sized Al2O3–TiC–Co composites is investigated at 800–1000°C in air for 25h. The oxidation resistance of nanometre sized samples is better than of micrometre sized. Phase compositions and microstructures were studied by XRD and SEM. The values of general rate constant k and oxidation exponent n are dependent on oxidation temperature and composites. The oxidation kinetics followed a rate that is slightly faster than the parabolic-rate law at 800–1000°C. The activation energy of the nanometre sized is higher than of micrometre sized in the range of 800–1000°C. [Copyright &y& Elsevier]

Abstract: CdTe nanocrystals (NCs) were coated with a hybrid SiO2 shell containing CdS-like clusters by a facile reflux. These hybrid SiO2-coated CdTe NCs exhibited tunable photoluminescence (PL) and high fluorescence quantum yields (QYs) up to 70% (the QY of initial CdTe NCs is 24%) due to the CdS-like cluster in the SiO2 shell nearby the CdTe core. The average fluorescence lifetime of the hybrid SiO2-coated NCs and the CdTe NCs are 36 and 25ns, respectively. Because increased fluorescence QYs and slightly blue-shifted PL peak wavelength for these hybrid NCs were observed after the removing of TGA and Cd2+, the hybrid SiO2 shell can sufficiently passivate PL, improve chemical stability, and prevent the surface deterioration of the CdTe NCs. This is crucial for applications in biolabeling and optoelectronic devices. [Copyright &y& Elsevier]

Abstract: The oxidation behavior of nano-sized Al2O3–TiC–Co composite sintered at different temperature was investigated at 200–1000°C in air for 25h. Microstructures and phase compositions of oxidation surfaces were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results indicated that the oxidation reaction would take place when oxidation temperatures are 800°C and 1000°C. The oxidation resistance of Al2O3–TiC–Co composite increased with the sintering temperature rising when the sample was oxidized at 800°C and 1000°C. The mechanism of oxidation has been analyzed using thermodynamic and kinetics considerations. The oxidation kinetics follows a rate that is faster than the parabolic rate law at 800°C and 1000°C. The activation energy of the composite for oxidation in the range of 800°C to 1000°C was found to be 142.21kJ/mol. [Copyright &y& Elsevier]

Abstract: Eu2+, R3+ co-doped alkaline earth aluminates MAl2O4: Eu2+, R3+ (M=Sr, Ba and Ca; R=Dy, Nd and La) nanoparticles with high brightness and long afterglow have been prepared by solution-combustion synthesis at 600°C without a post-annealing process for the first time. The morphologies and the phase structures of the products have been characterized by transmission electron microscopy and X-ray diffraction. The excitation and emission spectra of the products have been measured by an Edinburgh FLS920 spectrometer at room temperature. The characteristic luminescence of the as-prepared sample has been evaluated, and the reason why the wavelength changed from yellow-green to blue-green and then to blue-purple in visible range when the composition changed from SrAl2O4: Eu2+, Dy3+ to BaAl2O4: Eu2+, Nd3+ and then to CaAl2O4: Eu2+, La3+ has been explained. Furthermore, a new persistent luminescence mechanism was proposed in this article. [Copyright &y& Elsevier]

Abstract: Strontium stannate (SrSnO3) nanocrystals have been synthesized by using an efficient combustion method for the first time. The corresponding nanorods integrated with nanoparticles are also obtained with the coprecipitation method. X-ray diffraction, transmission electron micrograph and scanning transmission electron micrograph are used to illustrate the crystal structure, phase purity and morphology of the synthesized nanocrystals. The growth mechanisms are investigated in detail. [Copyright &y& Elsevier]

Some of the metal vanadates have special self-activated luminescence. In order to further enrich its luminous color, luminescent impurity ions can be introduced into its lattice. The interaction between the self-activated emission and the impurity-related emission remains to be studied. In this work, the synergism between the two kinds of emission in LiCa 3 ZnV 3 O 12 was explored from these three aspects: lattice distortion, energy transfer and temperature effect. Eu 3+ ions replace Ca 2+ ions in the lattice of LiCa 3 ZnV 3 O 12 , leading to a lattice contraction of the LCZV host, which depresses the self-activating emission around 500 nm. The characteristic linear emissions of Eu 3+ ions are also observed benefiting from the energy transfer from [VO 4 ] 3- to Eu 3+ . Since the temperature quenching effect is more sensitive for the self-activated emission than that for the Eu 3+ -related ones, the phosphor can be applied as a luminescent temperature sensor, with the absolute and relative temperature sensitivities of 0.012 K -1 and 1.56% K -1 , respectively., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)