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Straightforward fabrication of stable white LEDs by embedding of inorganic UV-LEDs into bulk polymerized polymethyl-methacrylate doped with organic dyes.

ABSTRACT: Stable white-emitting down-converted LEDs are straightforwardly prepared by bulk polymerization of an organic dye doped polymethyl-methacrylate (PMMA) shell directly on top of a highly efficient commercial blue-emitting InGaN LED. Our optimized polymerization procedure allows for extending the form factor of achievable luminescence converter (LUCO) material beyond the conventional thin film form and to directly produce devices with light bulb design. The selected organic dyes, the blue-emitting Coumarin 30 and a red-emitting diketopyrrolopyrrole derivative, exhibit high compatibility with the free radical polymerization reaction of the PMMA matrix and ensure high stability of the final hybrid device. The control of both the thickness of the PMMA shell and the concentration of the dopant dyes allow for fine tuning of the emission color of the LUCO LED and to obtain white light with CIE chromatic coordinates x = 0.32 and y = 0.33, with rendering index as high as 80. This simple and versatile procedure is not dye-exclusive and is therefore extendable to other molecular systems for color-tunable efficient solid-state lighting sources.

SUBMITTER: Di Martino D

PROVIDER: S-EPMC3957127 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Straightforward fabrication of stable white LEDs by embedding of inorganic UV-LEDs into bulk polymerized polymethyl-methacrylate doped with organic dyes.

Di Martino Daniela D Beverina Luca L Sassi Mauro M Brovelli Sergio S Tubino Riccardo R Meinardi Francesco F

Scientific reports 20140318

Stable white-emitting down-converted LEDs are straightforwardly prepared by bulk polymerization of an organic dye doped polymethyl-methacrylate (PMMA) shell directly on top of a highly efficient commercial blue-emitting InGaN LED. Our optimized polymerization procedure allows for extending the form factor of achievable luminescence converter (LUCO) material beyond the conventional thin film form and to directly produce devices with light bulb design. The selected organic dyes, the blue-emitting ...[more]

PMID: 24638041

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Project description:This study aimed to investigate the cleansing effects of grapefruit seed extract (GSE) on biofilms of Candida albicans (C. albicans) formed on denture-base resin and the influence of GSE on the mechanical and surface characteristics of the resin. GSE solution diluted with distilled water to 0.1% (0.1% GSE) and 1% (1% GSE) and solutions with Polident® denture cleansing tablet dissolved in distilled water (Polident) or in 0.1% GSE solution (0.1% G+P) were prepared as cleansing solutions. Discs of acrylic resin were prepared, and the biofilm of C. albicans was formed on the discs. The discs with the biofilm were treated with each solution for 5 min at 25°C. After the treatment, the biofilm on the discs was analyzed using a colony forming unit (CFU) assay, fluorescence microscopy, and scanning electron microscopy (SEM). In order to assess the persistent cleansing effect, the discs treated with each solution for 5 min were aerobically incubated in Yeast Nitrogen Base medium for another 24 h. After incubation, the persistent effect was assessed by CFU assay. Some specimens of acrylic resin were immersed in each solution for 7 days, and changes in surface roughness (Ra), Vickers hardness (VH), flexural strength (FS), and flexural modulus (FM) were evaluated. As a result, the treatment with 1% GSE for 5 min almost completely eliminated the biofilm formed on the resin; whereas, the treatment with 0.1% GSE, Polident, and 0.1% G+P for 5 min showed a statistically significant inhibitory effect on biofilms. In addition, 0.1% GSE and 0.1% G+P exerted a persistent inhibitory effect on biofilms. Fluorescence microscopy indicated that Polident mainly induced the death of yeast, while the cleansing solutions containing at least 0.1% GSE induced the death of hyphae as well as yeast. SEM also revealed that Polident caused wrinkles, shrinkage, and some deep craters predominantly on the cell surfaces of yeast, while the solutions containing at least 0.1% GSE induced wrinkles, shrinkage, and some damage on cell surfaces of not only yeasts but also hyphae. No significant changes in Ra, VH, FS, or FM were observed after immersion in any of the solutions. Taken together, GSE solution is capable of cleansing C. albicans biofilms on denture-base resin and has a persistent inhibitory effect on biofilm development, without any deteriorations of resin surface.

Dataset Information

Straightforward fabrication of stable white LEDs by embedding of inorganic UV-LEDs into bulk polymerized polymethyl-methacrylate doped with organic dyes.

Publications

Straightforward fabrication of stable white LEDs by embedding of inorganic UV-LEDs into bulk polymerized polymethyl-methacrylate doped with organic dyes.

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