. | . |
Tiny glow sticks by Staff Writers Beijing (SPX) Jun 12, 2017
Optical data transmission allows information to be transmitted as light by way of optical waveguides in fiber optic networks. Chinese researchers have now developed microscale optical waveguides. As reported in the journal Angewandte Chemie, they have made microrods of lanthanide metal-organic frameworks. Their particular crystal structure ensures low-loss light conduction and the emission of polarized light. Lanthanides are a group of metals whose special electronic structure makes them attractive for use in optoelectronic applications. Metal-organic frameworks (MOFs) based on lanthanides (Ln-MOFs) offer a wide range of possibilities for targeted variations in structure. MOFs are lattice-like structures made of metallic "nodes" bridged by organic connectors. Well-defined, microscale Ln-MOFs have remained a rarity, however. Now, things have changed with the new micro-rod Ln-MOFs, which have potential as microscale waveguides. Led by Dongpeng Yan and Yong Shen Zhao at Beijing Normal University and the Chinese Academy of Sciences (Beijing, China), the researchers chose to use benzenetricarboxylic acid (BTC) as their organic building block. This compound strongly absorbs UV light and has electronic energy levels well matched with lanthanides. In a self-organization process under certain synthetic conditions, the BTC molecules and lanthanide ions assemble into crystalline microrods. Within the crystal, the BTC molecules function as tiny "light antennas": they capture light and very efficiently pass it on to the lanthanide ions in a radiationless energy-transfer process. The lanthanide ions then emit the energy as luminescence whose color varies depending on the lanthanide used. Terbium MOFs emit green light; europium MOFs glow red. Doping terbium MOFs with 5% europium results in orange luminescence. Viewed under a microscope, rods evenly irradiated with UV light have very bright points at both ends while only weakly glowing otherwise. The spectrum of the emitted light is constant along the length of the rods. The microrods are thus acting as low-loss optical waveguides. It is also interesting that the light emitted at the ends is circularly polarized and evenly distributed over the cross-section of the rods. This behavior results from the special crystal structure of the microrods, in which the lanthanide ions wind in a helical chain along an axis of the crystal. The chains are bound together by phenyl groups of the BTC, which form impenetrable walls for the light. The overall result is a three-dimensional lattice penetrated by square channels. With their low light loss and high photoluminescence quantum yield, these novel one-dimensional microstructures could serve as an effective platform for the development of new systems of color tunable optical waveguides with polarized emissions.
Washington (AFP) June 2, 2017 Google is working to block "annoying" ads in its Chrome browser, part of a broader effort by industry players to filter out certain types of marketing messages that draw complaints. "We believe online ads should be better. That's why we joined the Coalition for Better Ads, an industry group dedicated to improving online ads," said Sridhar Ramaswamy, Google's senior vice president for adverti ... read more Related Links Wiley Satellite-based Internet technologies
|
|
The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us. |