Gradient refractive index structure of phosphor-in-glass coating for packaging of white LEDs

A gradient refractive index (GRIN) structure, with a gradual increase in the refractive index from the glass substrate, was successfully obtained by multilayer screen printing for white light-emitting diodes (w-LEDs) packaging. Each phosphor-in-glass (PiG) coating consisted of B₂O₃–SiO₂–ZnO glass matrix and yellow phosphor. The gradually increased refractive index (1.62, 1.72, and 1.82) of glass matrices were obtained from higher molecular weight of La₂O₃ and WO_3. After sintering at 600°C, no obvious interface was observed and the phosphor particles were mixed thoroughly in the glass matrix. When the phosphor content was 50 wt%, the white-light emission was obtained. Compared with those based on the nongradient and low-refractive PiG coating, the luminous efficacy of w-LEDs constructed by the PiG coating with GRIN was enhanced. It shows that the GRIN structure is beneficial to improve the luminous efficacy of w-LEDs.     

Preparation and performance of high refractive index silicone resin‐type materials for the packaging of light‐emitting diodes

A novel high refractive index and highly transparent silicone resin‐type material for the packaging of high‐power light‐emitting diodes (LEDs) is introduced, which was synthesized by hydrosilylation of vinyl end‐capped methylphenyl silicone resin and methylphenyl hydrosilicone oil catalyzed by Karstedt's catalyst. The vinyl end‐capped methylphenyl silicone resins were prepared by hydrolysis?polycondensation method from methylphenyl diethoxysilane (MePhSi(OEt)₂), phenyl triethoxysilane (PhSi(OEt)₃), and vinyl dimethylethoxy silane (Me₂ViSiOEt) in toluene/water mixture catalyzed by cation‐exchange resin. The vinyl end‐capped methylphenyl silicone resins were characterized by ¹H‐NMR and Fourier‐transform infrared. The performances of the cured silicone resin‐type materials for LED packaging have been examined in detail. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of alkali metal ion on imprinting GRIN microstructure in GeS2-Ga2S3-MCl (M=Na,K, Cs) glasses for visible to mid-infrared microgratings

Gradient refractive index (GRIN) micro-optics present unique opportunities for control of the chromatic properties, new degrees of freedom for optical design as well as the potential for use in new optical system applications. GRIN microgratings were imprinted in GeS₂-Ga₂S₃-MCl (M = Na, K, Cs) chalcohalide glasses by microthermal poling, and the effects of the type and concentration of alkali cations on their performance were investigated. Two effective imprinting formation regions of the GRIN microstructure based on the poling saturation voltage (U_s) and glass composition are observed at fixed poling time and temperature. The U_s increases from 140 to 750 and 2600 V in accordance with the activation energy (E_a) of alkali ions (Na⁺ to K⁺ and Cs⁺) increasing from 45.15 to 58.62 and 92.58 kJ/mol for studied samples. The saturated numbers of diffraction order (N_s) of the gratings in these samples are 7, 9 and 6, respectively, the highest number being provided by the K⁺-containing sample. This is in accordance with imprinting-induced phase differences (0.14λ, 0.19λ and 0.09λ) measured in the fabricated samples containing Na⁺, K⁺ and Cs⁺ ions. Furthermore, the U_s of samples decreases from 1500 to 300 V with four concentrations of K⁺ from 10 to 30%, associated with their E_a of K⁺ decreasing from 69.62 to 53.46 kJ/mol, while N_s increases from 8 to 14, which is attributed to the increase of the phase difference in the GRIN structures. The controllable GRIN microstructures are realized by adjusting the type and concentration of alkali cations in chalcohalide glasses, which is expected to drive the design of broadband GRIN microgratings.     

Stable and efficient all-inorganic color converter based on phosphor in tellurite glass for next-generation laser-excited white lighting

Laser lighting is considered as a next-generation high-power lighting due to its high-brightness, directional emission, and quasi-point source. However, thermally stable color converter is an essential requirement for white laser diodes (LDs). Herein, we proposed a stable and efficient phosphor-in-glass (PiG) in which YAG:Ce³⁺ and MFG:Mn⁴⁺ phosphors were embedded into tellurite glass matrixes. The glass matrixes with low-melting temperature and high refractive index were prepared by designing their composition. The luminescence of YAG:Ce³⁺ PiGs was adjusted by controlling phosphor thickness. Aiming to compensate for red emission, multi-color PiGs were realized by stacking MFG:Mn⁴⁺ layers on YAG:Ce³⁺ layer. The phosphor crystals are chemically stable and maintain intact in the glass matrix. Furthermore, white LDs were fabricated by combining the PiGs with blue LDs. As the phosphor thickness increases, the chromaticity of white LDs shifts from cool to warm white, and the white LDs exhibit excellent thermal stability under different excitation powers.     

Some properties of poly(carbonates) and poly(thiocarbonates) from diphenols with methyl groups in the 3-position in the phenyl rings

Glass transition temperatures and the corresponding activation energies of poly(carbonates) and poly(thiocarbonates) with different side-chain substituents obtained from diphenols with methyl groups in the 3-position in the phenyl rings have been determined by differential scanning calorimetry at several scanning speeds. Partial specific volume and specific refractive index increments have also been obtained by densimetry and refractometry measurements in benzene at 25°C. The effect of the different substituents on these properties has been analysed. © 1998 SCI.     

免疫磁性微球的制备及其应用于食品微生物检测的研究进展

由于一系列食品安全事件的发生,食品安全在我国进一步受到重视,应用免疫磁性微球检测食品中的致病微生物比常规检测方法更加方便、快捷。本文介绍了免疫磁性微球的应用原理和微球的制备方法,并进一步阐述了免疫磁性微球在食品微生物检测中的应用,以及食品致病菌的快速检测中免疫磁性微球与PCR、ELISA、FIA、ECL等检测手段的联用,表明该方法将成为食品微生物检测的一个发展趋势。     

Optical and electrochemical properties and sensing application for iron(II) and mercury(II) ions of polyfluorenes with imidazole in the main chain

Polyfluorenes bearing imidazole and triphenylamine moieties in the main chain were synthesized. The imidazole/triphenylamine molar ratios in the polymer backbone were 100/0 (PFIM100), 50/50 (PFIM50) and 25/75 (PFIM25). Cyclic voltammetry revealed reversible oxidation only for polymers containing triphenylamine moieties (PFIM50 and PFIM25) and irreversible reduction for all polymers. Optical properties of the polymers were investigated using UV‐visible and photoluminescence spectroscopies in solution. The sensing properties of PFIM100 were investigated. The polymer showed recognition towards two analytes, Fe²⁺ and Hg²⁺. PFIM100 exhibited selective fluorescence ‘turn‐off’ response to Fe²⁺ cations. Interaction of PFIM100 with I^? anions produced a non‐emissive complex. The PFIM100/I^? complex exhibited excellent ‘turn‐on’ sensing properties for detection of Hg²⁺. © 2019 Society of Chemical Industry     

SEC-MALS method for the determination of long-chain branching and long-chain branching distribution in polyethylene

This paper systematically describes a LCB determination method that can quantify both LCB content and LCB distribution across the molecular weight distribution in polyethylene homopolymers as well as copolymers. Coupling size-exclusion chromatography with multi-angle light scattering (SEC-MALS), this method quantifies molecular weights (MW) and radii of gyration (R_g) simultaneously. The number of LCB per molecule and LCB frequency as a function of MW can be calculated by comparing R_g of a branched polymer with that of a linear control at the same MW using the Zimm-Stockmayer approach. Because the presence of short-chain branching in copolymers results in changes in R_g of the copolymers, their LCB contents cannot be obtained before the short-chain branching (SCB) effect is corrected. Using well-characterized linear PE copolymers as standards, an empirical method is successfully established in this paper to correct the SCB effect. Consequently, this method can be applied to determine LCB in PE copolymers as well. Some practical aspects, such as the selection of formalism for data processing, the LCB detection sensitivity and precision, and long-term reproducibility of this method are also discussed. Finally, examples are given to demonstrate how this method is applied to determine LCB and LCB distribution in practical PE homopolymers and copolymers.     

Synthesis of graphene nanosheets modified with the Fe3O4@ phenol formaldehyde resin or PFR nanoparticles for their application in bio‐imagine and thermal treatment

Two different types of graphene‐based composites have been synthesized with simple assays. The multifunctional composites were obtained through loading Fe₃O₄@phenol formaldehyde resin (PFR) nanoparticles (NPs) synthesized with Fe₃O₄ NPs, hexamethylene‐tetramine, and phenol onto the surface of graphene oxide sheets in the presence of coupling agent. The Fe₃O₄@PFR loaded graphene oxide composites bring several merits. It prevents PFR NPs aggregation due to the existed graphene oxide but also endows the composites photothermal conversion property. Furthermore, the graphene‐wrapped PFR composites were prepared by mixing oxide graphene and PFR NPs at 110 °C by means of the good reduction of the hydroxyl group on the surface of PFR NPs to graphene. Under the assistance of chitosan, a building block consists of graphene‐wrapped PFR composites could be obtained. Thus, an ideal method may be developed to synthesize graphene‐wrapped PFR composites for constructing building blocks. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45007.     

Relation of glass transition temperature to the hydrogen bonding degree and energy in poly(N-vinyl pyrrolidone) blends with hydroxyl-containing plasticizers: 3. Analysis of two glass transition temperatures featured for PVP solutions in liquid poly(ethylene glycol)

The phase behaviour of poly(N-vinyl pyrrolidone)-poly(ethylene glycol) (PVP-PEG) blends has been examined in the entire composition range using Temperature Modulated Differential Scanning Calorimetry (TM-DSC) and conventional DSC techniques. Despite the unlimited solubility of PVP in oligomers of ethylene glycol, the PVP-PEG system under consideration demonstrates two distinct and mutually consistent glass transition temperatures (T_g) within a certain concentration region. The dissolution of PVP in oligomeric PEG has been shown earlier (by FTIR spectroscopy) to be due to hydrogen bonding between carbonyl groups in PVP repeat units and complementary hydroxyl end-groups of PEG chains. Forming two H-bonds through both terminal OH-groups, PEG acts as a reversible crosslinker of PVP macromolecules. To characterise the hydrogen bonded complex formation between PVP (M_w=10⁶) and PEG (M_w=400) we employed an approach described in the first two papers of this series that is based on the modified Fox equation. We evaluated the fraction of crosslinked PVP units and PEG chains participating to the complex formation, the H-bonded network density, the equilibrium constant of complex formation, etc. Based on the established molecular details of self-organisation in PVP-PEG solutions, we propose a three-stage mechanism of PVP-PEG H-bonded complex formation/breakdown with increase of PEG content. The two observed T_gs are assigned to a coexisting PVP-PEG network (formed via multiple hydrogen bonding between a PEG and PVP) and a homogeneous PVP-PEG blend (involving a single hydrogen bond formation only). Based on the strong influence of coexisting regions on each other and the absence of signs of phase separation (evidenced by Optical Wedge Microinterferometry) we conclude that the PVP-PEG blend is fully miscible on a molecular scale.     

A correlation for the estimation of critical micellization concentrations and temperatures of polyols in aqueous solutions

An empirical correlation is presented for the estimation of critical micellization concentrations (CMC) and critical micellization temperatures (CMT) for poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) copolymers in aqueous solutions. The CMC and CMT are expressed as a function of the polyol molecular weight, composition, and temperature (for CMC determination) or concentration (in the case of CMT). The correlation was developed from experimental CMT data for a set of 12 polyols that covered a wide range of molecular weights (2900–14600) and poly(ethylene oxide) contents (30–80 wt%) and is based on a simple expression for the standard free energy of micellization. Such a correlation should be useful to practitioners of the field as it allows easy prediction of CMC and CMT for a wide range of polyols with a minimal number of input parameters.