Preparation of ZrO2/silicone hybrid materials for LED encapsulation via in situ sol‐gel reaction

Organic silicones have been used as encapsulant materials for light‐emitting diodes (LEDs) for many years, while their performances need to be improved in order to satisfy the requirements of high‐power LEDs. A ZrO₂/silicone hybrid resin (ZHR) was synthesized for LEDs encapsulation by in situ sol‐gel reactions. The oligosiloxane was synthesized as polymeric matrix by nonaqueous sol‐gel condensation using diphenylsilanediol (DPSD), vinyltrimethoxysilane (VTMS), and 3‐methacryloxy propyl trimethoxysilane (MPTMS) as monomers. Then zirconium propoxide was added into this polymeric matrix to be hydrolyzed to obtain the hybrid resin with a uniform dispersion of ZrO₂ nanoparticles. The Si–O–Zr covalent bond was detected and benefited for excellent dispersibility of the ZrO₂ nanoparticles and the well compatibility between organic and inorganic phases. The cured ZHR with 5 wt% ZrO₂ content showed high light transmittance (greater than 80% in visible light range), high refractive index (=1.56), and high thermal stability (no yellowing at 150°C for 240 hours). The luminous flux of the LED chip with ZHR encapsulant was 10% higher than that of the pure silicone resin, suggesting that ZHR has great application potential in the field of LED packaging.     

Cell-based assays in practice: cell markers from autofluorescent proteins of the GFP-family

The more recently discovered anthozoan fluorescent proteins (FPs) and the classic Aequorea victoria Green Fluorescent Protein (avGFP) as well as their derivatives have become versatile tools as live cell markers in fluorescence microscopy. In this review, we show the use of these FPs in drug discovery assays. Assay examples are given for the application of FPs in multiplexed imaging, as photosensitizers, as fluorescent timers, as pulse-chase labels and for robotically integrated compound testing. The development of fast microscopic imaging devices has enabled the application of automated fluorescence microscopy combined with image analysis to pharmaceutical high throughput drug discovery assays, generally referred to as High Content Screening (HCS).     

Multispectral optical imaging combined in situ with XPS or ToFSIMS and principal component analysis

All X‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) instruments have optical cameras to image the specimen under analysis, and often to image the sample holder as it enters the system too. These cameras help the user find the appropriate points for analysis of specimens. However they seldom give as good images as stand‐alone bench optical microscopes, because of the limited geometry, source/analyser solid angle and ultra‐high‐vacuum (UHV) design compromises. This often means that the images displayed to the user necessarily have low contrast, low resolution and poor depth‐of‐field. To help identify the different regions of the samples present we have found it useful to perform multispectral imaging by illuminating the sample with narrow‐wavelength‐range light emitting diodes (LEDs). By taking an image under the illumination of these LEDs in turn, each at a successively longer wavelength, one can build up a set of registered images that contain more information than a simple Red–Green–Blue image under white‐light illumination. We show that this type of multispectral imaging is easy and inexpensive to fit to common XPS and ToF‐SIMS instruments, using LEDs that are widely available. In our system we typically use 14 LEDs including one emitting in the ultraviolet (so as to allow fluorescent imaging) and three in the near infra‐red. The design considerations of this system are discussed in detail, including the design of the drive and control electronics, and three practical examples are presented where this multispectral imaging was extremely useful. Copyright © 2016 The Authors Surface and Interface Analysis Published by John Wiley & Sons Ltd.     

Bis‐substituted thiophene‐containing oxime sulfonates photoacid generators for cationic polymerization under UV–visible LED irradiation

Three novel types of thiophene‐containing oxime sulfonates with a big π‐conjugated system were reported as non‐ionic photoacid generators. The irradiation of the newly synthesized photoacid generators using near UV–visible light‐emitting diodes (LEDs) (365–475 nm) results in the cleavage of two weak N O bonds in single molecules, which lead to the generation of different sulfonic acids in good quantum and chemical yields. The mechanism for the N O bond cleavage for acid generation was supported by the UV–visible spectra and real‐time ¹H NMR spectra. They are developed as high‐performance photoinitiators without any additives for the cationic polymerization of epoxide and vinyl ether upon exposure to near‐UV and visible LEDs (365–475 nm) at low concentration. In the field of photopolymerization, especially visible light polymerization, it has great potential for application. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 776–782     

Synthesis and Applications of Red‐Emissive Carbon Dots

Carbon dots (CDs), a new class of fluorescent carbon nanoparticles (less than 10 nm in size), have been widely applied in various fields, including sensors, bioimaging, catalysis, light‐emitting devices (LEDs), and photoelectronic devices, owing to their unique properties such as low toxicity, bio‐compatibility, high photostability, easy surface modification, and up‐conversion fluorescence, over the past decades. Recently, multiple‐color‐emissive CDs, especially red‐emissive CDs (RCDs), have drawn much attention owing to their unique advantages, like the ability to penetrate the animal bodies without the disturbance of strong tissue autofluorescence, multiple‐color fluorescence displaying or sensing, and the capacity to be one essential component to obtain white LED (WLED). In this review, we focused on the progress of recently‐emerging RCDs in the past five years, including their synthetic methods (hydrothermal, solvothermal, reflux condensation and microwave techniques), influencing factors (precursors, solvents, elements doping, surface chemistry) and various applications (bioimaging, sensor, photocatalysis and WLEDs), with a perspective on the future advancements.     

Synthesis of an adhesion‐enhancing polysiloxane containing epoxy groups for addition‐cure silicone light emitting diodes encapsulant

Addition‐cure silicone resin is considered as a good choice for light emitting diodes (LEDs); however, it has very poor adhesion to the substrate, which limits its practical application. A novel polysiloxane with self‐adhesion ability and higher refractive index for the encapsulating of high‐power LEDs is prepared and characterized. This polysiloxane containing vinyl groups, phenyl groups, and epoxy groups was synthesized by a sol‐gel condensation process from methacryloxy propyl trimethoxyl silane, γ‐(2,3‐epoxypropoxy)propytrimethoxysilane, and diphenylsilanediol under the catalysis of an anion exchange resin. Then, the resin‐type encapsulation material was prepared by hydrosilylation of methylphenyl hydrogen‐containing silicone resin and the newly synthesized polysiloxane material. The novel polysiloxane was characterized by ¹H‐NMR and Fourier transform infrared spectroscopy. On the basis of higher refractive index, higher transparency, excellent thermal stability, and appropriate hardness, as well as good adhesive strength between the encapsulating material and the LED lead frame (polyphthalamide), the curable silicone resin‐type encapsulation material can be used as an encapsulant for LEDs. Copyright © 2014 John Wiley & Sons, Ltd.     

Electrically Conductive Porous Metal–Organic Frameworks

Owing to their outstanding structural, chemical, and functional diversity, metal–organic frameworks (MOFs) have attracted considerable attention over the last two decades in a variety of energy‐related applications. Notably missing among these, until recently, were applications that required good charge transport coexisting with porosity and high surface area. Although most MOFs are electrical insulators, several materials in this class have recently demonstrated excellent electrical conductivity and high charge mobility. Herein we review the synthetic and electronic design strategies that have been employed thus far for producing frameworks with permanent porosity and long‐range charge transport properties. In addition, key experiments that have been employed to demonstrate electrical transport, as well as selected applications for this subclass of MOFs, will be discussed.     

Feasibility of light-emitting diode uses for annular reactor inner-coated with TiO2 or nitrogen-doped TiO2 for control of dimethyl sulfide

Limited environmental pollutants have only been investigated for the feasibility of light‐emitting diodes (LED) uses in photocatalytic decomposition (PD). The present study investigated the applicability of LEDs for annular photocatalytic reactors by comparing PD efficiencies of dimethyl sulfide (DMS), which has not been investigated with any LED‐PD system, between photocatalytic systems utilizing conventional and various LED lamps with different wavelengths. A conventional 8 W UV/TiO₂ system exhibited a higher DMS PD efficiency as compared with UV‐LED/TiO₂ system. Similarly, a conventional 8 W visible‐lamp/N‐enhanced TiO₂ (NET) system exhibited a higher PD efficiency as compared with six visible‐LED/NET systems. However, the ratios of PD efficiency to the electric power consumption were rather high for the photocatalytic systems using UV‐ or visible‐LED lamps, except for two LED lamps (yellow‐ and red‐LED lamps), compared to the photocatalytic systems using conventional lamps. For the photocatalytic systems using LEDs, lower flow rates and input concentrations and shorter hydraulic diameters exhibited higher DMS PD efficiencies. An Fourier‐transformation infrared analysis suggested no significant absorption of byproducts on the catalyst surface. Consequently, it was suggested that LEDs can still be energy‐efficiently utilized as alternative light sources for the PD of DMS, under the operational conditions used in this study.     

One‐pot synthesis of carbon dots@ZrO2 nanoparticles with tunable solid‐state fluorescence

In recent years, fluorescent carbon dots (CDs) have been developed and showed potential applications in biomedical imaging and light‐emitting diodes (LEDs) for their excellent fluorescent properties. However, it still remains a challenge to incorporate fluorescent CDs into the host matrix in situ to overcome their serious self‐quenching. Herein, a one‐pot hydrothermal method is used to prepare nano‐zirconia with CDs (CDs@ZrO₂) nanoparticles. During the reaction, CDs and nano‐zirconia are generated simultaneously and connected with silane coupling agent. The CDs@ZrO₂ nanoparticles exhibit tunable emission wavelength from 450 to 535 nm emission by regulating the content of citric acid in the feed. The quantum yield of the CDs@ZrO₂ is up to 23.8%. Furthermore, the CDs@ZrO₂ nanoparticles with regulable fluorescence emission can be used for the fluorescent material to prepare white LEDs. The prepared LED has significant white light emission with color coordinates of (0.30, 0.37) and its color rendering index (CRI) is 67.1. In summary, we have developed the solid‐state CDs@ZrO₂ nanoparticles with tunable emission by a valuable strategy, that is, one‐pot method, for white LEDs.     

DNAzyme‐Mediated Genetically Encoded Sensors for Ratiometric Imaging of Metal Ions in Living Cells

Genetically encoded fluorescent proteins (FPs) have been used for metal ion detection. However, their applications are restricted to a limited number of metal ions owing to the lack of available metal‐binding proteins or peptides that can be fused to FPs and the difficulty in transforming the binding of metal ions into a change of fluorescent signal. We report herein the use of Mg²⁺‐specific 10–23 or Zn²⁺‐specific 8–17 RNA‐cleaving DNAzymes to regulate the expression of FPs as a new class of ratiometric fluorescent sensors for metal ions. Specifically, we demonstrate the use of DNAzymes to suppress the expression of Clover2, a variant of the green FP (GFP), by cleaving the mRNA of Clover2, while the expression of Ruby2, a mutant of the red FP (RFP), is not affected. The Mg²⁺ or Zn²⁺ in HeLa cells can be detected using both confocal imaging and flow cytometry. Since a wide variety of metal‐specific DNAzymes can be obtained, this method can likely be applied to imaging many other metal ions, expanding the range of the current genetically encoded fluorescent protein‐based sensors.     

Recent Advances in Rare Earth‐Doped Hydrides

The optical properties of rare earth ions in different inorganic host materials, for instance oxides, silicates, borates, or nitrides, have been used in applications for many years, from color TV to fluorescent tubes, lasers, or pc‐LEDs. However, rare earth metal ion‐doped hydrides have not really been considered as host lattices and up to now only been studied in a relatively small number of investigations. Yet, for certain metal hydrides these studies, e.g., allowed the determination of the crystal field strength and nephelauxetic effect of the hydride anion using the Eu²⁺ 5d excited state. In air‐sensitive hydrides, the use may be restricted to fundamental studies and local probes. But recently more and more air‐stable mixed anionic hydrides have been discovered, which may serve as hosts. This short review summarizes the synthesis and characterization of rare earth metal ion‐doped hydrides reported so far.     

蓝光钙钛矿发光二极管:机遇与挑战

金属卤化钙钛矿由于具有优异的光电性能(如:高电子/空穴迁移率,高荧光量子产率,高色纯度,以及光色可调性等),成为应用于发光二极管(LED)的理想材料。近年来,钙钛矿LED的发展十分迅速,红光和绿光钙钛矿LED的外量子效率(EQE)均已超过20%。然而,蓝光(尤其是深蓝光)钙钛矿LED的EQE以及稳定性依然相对落后,这严重制约了钙钛矿LED在高性能、广色域显示领域和高显色指数白光照明领域的应用。因此,总结现阶段蓝光钙钛矿LED的发展,并剖析其机遇与挑战,对未来蓝光甚至整个钙钛矿LED领域的发展至关重要。本文将蓝光钙钛矿LED根据光色细分为天蓝光、纯蓝光、深蓝光三大部分进行总结,回顾了三种LED器件的发展历程,并详细阐述了现阶段实现他们的主要手段以及相关的基础原理,最后分析了它们各自的问题并提出了相应的解决思路。     

Advances in Synchrotron Radiation‐based X‐ray Absorption Spectroscopy to Characterize the Fine Atomic Structure of Single‐atom Nanozymes

Single‐atom nanozymes (SAzymes) with high atomic utilization, excellent catalytic activities, and selectivity have recently attracted significant interest. Usually, they contain only isolated metal atoms embedded in host matrices. However, traditional measuring instruments are extremely difficult to obtain their useful structural information due to ultra‐low metal loading, amorphous structure, coordination with light‐weight surface atoms and/or co‐existing of other metal elements. Synchrotron radiation‐based X‐ray absorption fine structure spectroscopy (XAFS) has demonstrated its usefulness for this type of catalyst. In this mini‐review, we have summarized the recent progress using XAFS to characterize the fine atomic structure of these nanozymes. The synthetic strategies of SAzymes, the principle of XAFS, delicate structural information by XAFS, and the applications of SAzymes have been presented. Furthermore, the outlook and challenges in this active research field have also been discussed. We expect that the help of XAFS can offer a wealth of opportunities to design and develop more efficient SAzymes and apply them to various fields.     

Carbon Dots as a Promising Green Photocatalyst for Free Radical and ATRP‐Based Radical Photopolymerization with Blue LEDs

Carbon dots (CDs) have been used for the first time as a sensitizer to initiate and activate free radical and controlled radical polymerization, respectively, based on an ATRP protocol with blue LEDs. Consideration of diverse heteroatom‐doped CDs indicated that N‐doped CDs could serve as an effective photocatalyst and photosensitizer in combination with LEDs emitting either at 405 nm or 470 nm. Free radical polymerization was initiated by combining the CDs with an iodonium or sulfonium salt in tri(propylene glycol) diacrylate. Polymerization of methyl methacrylate (MMA) by photo‐induced ATRP was achieved with CDs and ethyl α‐bromophenylacetate using Cu^II as catalyst in the ppm range. The polymers obtained showed temporal control, narrower dispersity ?1.5, and chain‐end fidelity. The first‐order kinetics and ON/OFF experiments additionally gave evidence of the constant concentration of polymer radicals. No remarkable cytotoxic activity was observed for the CDs, underlining their biocompatibility.     

Prismarene: An Emerging Naphthol‐Based Macrocyclic Arene

Phenol‐based macrocyclic arenes have been widely used in supramolecular chemistry, significantly enriching the toolbox of the field. In contrast, naphthol‐based macrocyclic arenes are rather underdeveloped. Very recently, Gaeta and co‐workers successfully synthesized such macrocycles (referred to as prism[n]arenes) with good guest‐binding ability by reacting 2,6‐dimethoxynaphthalene with paraformaldehyde under optimized conditions. In view of the simple synthesis and good host–guest chemistry, we anticipate that this macrocycle will find similar success and wide applications as the phenol‐based macrocyclic arenes.     

Metal‐Free,Room‐Temperature,Radical Alkoxycarbonylation of Aryldiazonium Salts through Visible‐Light Photoredox Catalysis

The first radical alkoxycarboxylation of aryldiazonium salts using CO gas through visible‐light‐induced photoredox catalysis (16 W blue LEDs) has been developed. This reaction is entirely metal‐free, is carried out at room temperature with a low loading of an organic dye as a photocatalyst (0.5 mol %), and provides a wide range of arylcarboxylic acid esters in high yields. Importantly, this photocatalytic system can be successfully extended to other carboxylation reactions.     

Metal‐Free,Room‐Temperature,Radical Alkoxycarbonylation of Aryldiazonium Salts through Visible‐Light Photoredox Catalysis

The first radical alkoxycarboxylation of aryldiazonium salts using CO gas through visible‐light‐induced photoredox catalysis (16 W blue LEDs) has been developed. This reaction is entirely metal‐free, is carried out at room temperature with a low loading of an organic dye as a photocatalyst (0.5 mol %), and provides a wide range of arylcarboxylic acid esters in high yields. Importantly, this photocatalytic system can be successfully extended to other carboxylation reactions.     

Photochemical characterization of biomimetic molecular switches

The performance of fluorenylidene-pyrroline (FPs) and N-alkylated fluorenylidene-pyrroline (NAFPs) derivatives for their use as light-driven molecular switches has been studied. Both types of compounds share fast and controllable photoisomerization. Other competitive reaction pathways that could lead to low efficiency have been considered. Only weak fluorescence was measured and high photostability was found when irradiating these compounds for long times, together with high photoisomerization quantum yields. NAFPs are capable of using visible light, which could be useful for practical applications.