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The stability of metal halide perovskite (CsPbX3, X = Cl, Br, and I) nanocrystals (NCs) is crucial for their practical applications. In this paper, perovskite NCs were synthesized in situ in lead-based metal–organic frameworks (Pb-MOFs: [Pb2(1,3,5-HBTC)2(H2O)4]·H2O), and we obtained stable and bright luminescence composites with different colors. Namely, CsPbBr3@Pb-MOF composites were created by the in situ growth of CsPbBr3crystals (NCs) on Pb-MOF, which had high ion resistance, bright photoluminescence (PL), and excellent stability. The composites still had bright luminescence after 11 months of storage. The PL intensity of green-emitting CsPbBr3@Pb-MOF composites was increased compared with as-prepared CsPbBr3NCs. Bright and stable blue- and red-emitting CsPbX3@Pb-MOF composites were obtained by adjusting the amount of PbX2(X = Cl, Br, and I) in the synthesis process. These CsPbX3NCs were homogeneously distributed in Pb-MOF substrates. The growth of CsPbX3NCs in Pb-MOFs prevented NC aggregation and decreased surface defects against nonradiative recombination during emitting. Thus, the PL lifetime and stability were improved. Furthermore, white light-emission diodes were prepared using three color CsPbX3@Pb-MOF composites with Commission Internationale de I’Eclairage color coordinates of (0.296, 0.316). This result provided an efficient way to overcome the limitation of chemical solution synthesis and improve the stability of CsPbX3NCs.

Nanocrystalline metal chalcogenide (selenide/sulfide/telluride) semiconductors make great sense in the photoelectric applications. Since the size and shape of the nanomaterials have a strong influence on their properties, new methods with high feasibility are always expected for the synthesis of chalcogenides with different dimension and morphology. In the present work, a green acetate−paraffin route was introduced that is suitable for the preparation of different chalcogenides, such as PbSe, Cu2Se, ZnSe, CdSe, NiSe2, CoSe, ZnS, Cu7.2S4, and PbTe. All the experiment processes were conducted open to air. These chalcogenides show various morphologies like grains, nanospheres, nanoplates, and so on. A mechanism was proposed to explain the formation of the different chalcogenide nanostructures. The dimension and shape of the nanostructures are dependent both on the crystal structure and the action of oleic acid on the growth rate of crystal faces. The optical properties of the prepared chalcogenides were characterized by the UV−visible diffuse reflectance spectroscopy (UV-DRS) and photoluminescence (PL) spectroscopy.

Pure and Dy-doped ZnNb2O6nanoparticles have been prepared by a sol−gel combustion method using citric acid as a fuel and complexing agent and nitrates as oxidants at a relatively low temperature as compared to solid-state reaction methods. X-ray diffraction patterns of the pure ZnNb2O6samples show that the ZnNb2O6nanoparticles exhibit an orthorhombic phase. Photoluminescence (PL) properties of all the undoped and Dy-doped samples are studied in detail. For the pure ZnNb2O6samples, a strong blue emission band centered at 445 nm and two weak emission bands centered at 525 and 625 nm, respectively, can be observed. For Dy-doped ZnNb2O6samples, the luminescence of Dy3is observed with the host blue emission remaining and the host emission intensity varying with the Dy-doping concentrations. This novel PL characteristic of the doped samples may be attributed to the energy transfer between Dy3and niobate groups (NbO6).

We describe the measurement of low differential group delay and fiber birefringence using a commercial polarization analyzer based on a free-space rotating quarter waveplate polarimeter. Stress-induced birefringence is isolated from the 60-cm fiber under test by placing it in a suitably designed fiber chuck. A referencing scheme is used to eliminate system birefringence. The suitability of this setup for the measurement of low polarization mode dispersion (PMD) is demonstrated. We also report results that demonstrate limitations of the recently proposed Jones matrix exponential expansion for first-order PMD measurement in devices with high second-order PMD. © 2003 Society of Photo-Optical Instrumentation Engineers.

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 ±0.6° or 0.4% in ±0.3°. 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.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.