Interplay of Stimulated Emission and Fluorescence Resonance Energy Transfer in Electrospun Light-Emitting Fibers

Concomitant amplified spontaneous emission (ASE) and F\"orster resonance energy transfer (FRET) are investigated in electrospun light-emitting fibers. Upon dye-doping with a proper FRET couple system, free-standing fibrous mats exhibit tunable FRET efficiency and, more importantly, tailorable threshold conditions for stimulated emission. In addition, effective scattering of light is found in the fibrous material by measuring the transport mean free path of photons by coherent backscattering experiments. The interplay of ASE and FRET leads to high control in designing optical properties from electrospun fibers, including the occurrence of simultaneous stimulated emission from both donor and acceptor components. All tunable-optical properties are highly interesting in view of applying electrospun light-emitting materials in lightening, display, and sensing technologies.Comment: 32 pages, 13 figure

"Siihen se tarina loppuu" Osallisuuden tukeminen saduttamalla

Opinnäytetyö oli toiminnallinen opinnäytetyö, jonka tavoitteena oli osallisuuden tukeminen sadutusmenetelmää hyödyntäen ja työn tarkoituksena oli myös tuottaa satukirja lasten kertomista saduista. Opinnäytetyö toteutettiin yhteistyössä päiväkoti Touhula Kangasalan kanssa kevään 2018 aikana. Työn tietoperusta koostui sadutuksesta, osallisuudesta, lasten kuulluksi tulemisesta, sekä varhaiskasvatuksesta. Opinnäytetyön toiminnallisessa osuudessa yksilösadutettiin lapsia ja näistä saduista koottiin työn liitteissä oleva satukirja. Lapset saivat kuvittaa omat satunsa ja kuvat liitettiin osaksi satukirjaa. Toiminnallinen osuus toteutettiin huhtikuussa 2018 ja sen aikana sadutettiin seitsemää 4-5-vuotiasta lasta. Työn tilaaja sai opinnäytetyön aikana syntyneen satukirjan jaettavaksi toiminnalliseen osuuteen osallistuneille lapsille. Lapset saivat antaa palautetta valmiista satukirjasta ja palaute heiltä oli positiivista. Lisäksi työ auttoi tukemaan lasten osallisuutta saduttamisen yhteydessä sekä opinnäytetyö toivottavasti innosti päiväkodin henkilökuntaa käyttämään sadutusmenetelmää myös tulevaisuudessa.This Bachelor’s thesis was practice-based and the aim was to support inclusion in the daycare centre Touhula in Kangasala by using the storycrafting method. Another goal was to make a storybook from the stories the children told. The thesis was implemented in spring 2018. The theoretical background consists of the storycrafting method, inclusion, what being heard is and early childhood education. In the practice part of the thesis, seven children aged four to five attended individual storycrafting sessiona. The children drew pictures to their stories and the stories were collected into a storybook. This practice part was carried out in April 2018. The Touhula Kangasala daycare centre received the finished storybook in May 2018. The children who took part into the storycrafting, also received copies of the storybook. The children also gave feedback about the book. The feedback was positive and the main aim of the thesis, to support the inclusion in the group, was achieved. The thesis also hopefully inspired the personnel to use the storycrafting method in the future

Tailoring the Random Lasing Properties by Controlled Phase Separation Process in PMMA:PVK Dye-Doped Polymeric Blends

This article describes the random lasing (RL) phenomenon obtained in a dye-doped, polymeric double-phase system composed of PMMA and PVK polymers. It shows how relative concentrations between mentioned macromolecules can influence lasing parameters of the resulting blends, including obtained emission spectra and threshold conditions. We describe the influence of lasers’ composition on their morphologies and link them with particular RL properties. Our studies reveal that the disorder caused by phase separation can support the RL phenomenon both in the waveguiding and quasi-waveguiding regimes. Changing the relative concentration of polymers enables one to switch between both regimes, which significantly influences threshold conditions, spectral shift, number of lasing modes, and ability to support extended and/or localized modes. Finally, we show that a simple phase separation technique can be used to fabricate efficient materials for RL. Moreover, it enables the tailoring of lasing properties of materials in a relatively wide range at the stage of the laser material fabrication process in a simple way. Therefore, this technique can be seen as a fast, cheap, and easy to perform way of random lasers fabrication

Air-Water Interface Assembly of Protein Nanofibrils Promoted by Hydrophobic Additives

Herein we demonstrate a novel way of modifying the colloidal stability of proteins by the presence of hydrophobic molecules. A protein capable of self-assembly into protein nanofibrils (PNFs) is milled with a hydrophobic molecular material. Upon dissolution in acidic water followed by heating, the proteins are converted into PNFs containing hydrophobic dyes. When aqueous dispersions of such PNFs are heated, films are formed at the air-water interface. The films contain ordered, optically anisotropic domains, and the shape of the reaction vessel can influence the PNF packing. We demonstrate the generality of the process by employing PNFs derived from the three proteins bovine insulin (INS), beta-lactoglobulin (BLG), and hen egg white lysozyme (HEWL) in combination with the dyes alpha-sexithiophene (6T) and 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM). As individual dye molecules are oriented along the long PNF axis, whole ensembles of dyes become aligned and, as a result, display emission of polarized light. Moreover, in the case of PNFs stained with DCM, stimulated emission is demonstrated.Funding Agencies|China Scholarship Council (CSC)China Scholarship Council; Carl Tryggers foundation; Polish National Agency for Academic Exchange Bekker programmePolish National Agency for Academic Exchange (NAWA); Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]</p

Legislative Documents

Also, variously referred to as: Senate bills; Senate documents; Senate legislative documents; legislative documents; and General Court documents

Distributed Feedback Lasing in Amorphous Polymers with Covalently Bonded Fluorescent Dyes: The Influence of Photoisomerization Process

International audienceWe present the synthesis and characterization of a new type of organic materials for light amplification purposes. These materials consist in branched polymers based on 9,10-bis(4-(diethylamino)phenylethynyl)anthracene or 2-(3-(4-(diethylamino)styryl)-5,5-dimethylcyclohex-2-enylidene)malononitrile chromophore cores with covalently attached poly(methyl methacrylate) chains, named Ant-PMMA and Lem-PMMA, respectively. In both cases, polymers with controlled molecular weight of about 30 kDa were synthesized by atom transfer radical polymerization (ATRP), using functionalized chromophores as initiators. Thin layers of the two polymers were fabricated by a simple drop-casting technique. We describe the spectroscopic properties of these materials and their ability for light amplification through the measurements of amplified spontaneous emission, random lasing process, and distributed feedback (DFB) lasing achieved via holographic-type excitation. Considering the different chemical structures of the chromophores, and related distinct interaction pathways with light, we postulate two slightly different DFB lasing mechanisms in investigated organic solid-state gain media. The Lem-PMMA ability to undergo photoisomerization, providing material refractive index modulation upon holographic-type pumping, is supposed to be responsible for superior DFB lasing performance as compared to Ant-PMMA, for which similar type of excitation results in lasing coupling solely dominated by gain modulation

Natural Born Laser Dyes: Excited-State Intramolecular Proton Transfer (ESIPT) Emitters and Their Use in Random Lasing Studies

A series of five excited-state intramolecular proton transfer (ESIPT) emitters based on a 2-(2&prime;-hydroxyphenyl) benzoxazole (HBO) scaffold, functionalized with a mono-or bis-(trialkylsilyl) acetylene extended spacer are presented. Investigation of their photophysical properties in solution and in the solid-state in different matrix, along with ab initio calculations gave useful insights into their optical behavior. Random lasing studies were conducted on a series of PMMA doped thin films, showing the presence of stimulated emission above the threshold of pumping energy density (&rho;th &asymp; 0.5&ndash;2.6 mJ cm&minus;2). In this work, the similarity of four level laser systems is discussed in light of the ESIPT photocycle

Physically Transient Photonics: Random versus Distributed Feedback Lasing Based on Nanoimprinted DNA

The authors report on a room-temperature nanoimprinted, DNA-based distributed feedback (DFB) laser operating at 605 nm. The laser is made of a pure DNA host matrix doped with gain dyes. At high excitation densities, the emission of the untextured dye-doped DNA films is characterized by a broad emission peak with an overall linewidth of 12 nm and superimposed narrow peaks, characteristic of random lasing. Moreover, direct patterning of the DNA films is demonstrated with a resolution down to 100 nm, enabling the realization of both surface-emitting and edge-emitting DFB lasers with a typical linewidth<0.3 nm. The resulting emission is polarized, with a ratio between the TE- and TM-polarized intensities exceeding 30. In addition, the nanopatterned devices dissolve in water within less than two minutes. These results demonstrate the possibility of realizing various physically transient nanophotonics and laser architectures, including random lasing and nanoimprinted devices, based on natural biopolymers.Comment: 20 pages, 5 figures, 31 reference