Search results for "PMMA"

Ce:YAG-PMMA nanocomposite for white LED

2012

Ce:YAG-PMMA composite was prepared by a melt compounding method. The characterization was performed using transmission electron microscopy, X-ray diffractometry, and photoluminescence spectroscopy. Results showed that Ce:YAG particles are well dispersed in the polymeric matrix. The luminescence properties of the nanocomposite do not show quenching or significant spectral shift indicating that the nanocomposite can be useful for advanced applications such as white LED construction.

Effect of methaacrylic acid on the structure of Eu:YAG-PMMA composites

2014

Polymeric composites of lanthanide-doped materials were recently considered as potential candidates for the development of light emitting diodes, lasers and luminescent concentrators for solar cells. In particular, nanoparticles of yttrium aluminum garnet (YAG) doped with cerium ions embedded in polymetylmetacrylate (PMMA) have been valuable for white LED devices [1,2]. Different structures and micromechanical properties have been observed when the methacrylic acid (MAA) is present in the composite. With the aim to understand the effect of MAA on the composite structure, a series of Eu:YAG composites prepared by in situ polymerization starting from mixtures of MAA and methylmetacrylate (MMA…

HYBRID WHITE LIGHT-EMITTING DIODES: STUDY AND FABRICATION OF THIN-FILM AND NANOWIRE-BASED DEVICES

I diodi ad emissione luminosa sono dei dispositivi a semiconduttore che posseggono straordinarie proprietà fisiche di generazione della luce. Il primo LED bianco si è mosso silenziosamente dalla metà degli anni 90 fino a un punto in cui, oggi, il mercato dell’illuminazione è stato totalmente rivoluzionato. A fronte dell’industria dell’illuminazione a stato solido che richiede LED sempre più luminosi ed economici, la ricerca scientifica risponde con strutture innovative, nuovi materiali più efficienti, anche combinati con l’uso delle nanotecnologie applicate. I diodi bianchi ibridi ad emissione luminosa, ad esempio, fanno anch’essi uso di un LED blu, come in un tradizionale diodo bianco, ma …

Frequency-Downconversion Stability of PMMA Coatings in Hybrid White Light-Emitting Diodes

2015

We report on the properties of a poly(methyl methacrylate)-based coating used as a host for an organic dye in hybrid white light-emitting diodes. The device is composed by a pump source, which is a standard inorganic GaN/InGaN blue light-emitting diode (LED) emitting at around 450 nm, and a spin-coated conversion layer making use of Lumogen® F Yellow 083. Under prolonged irradiation, the coating exhibits significant bleaching, thus degrading the color rendering performance of the LED. We present experimental results that confirm that the local temperature rise of the operating diode does not affect the conversion layer. It is also proven that, during the test, the photostability of the orga…

Optical Properties of Composite Films Based on Copper Chloride in PMMA Matrix

2014

The composite lms based on PMMA, CuCl2 and photoinitiator were prepared.Transmission spectra of the lms with and without photoinitiator were measured. The holo-graphic gratings were recorded, the sensitivity of the lms and surface structure of gratingswere studied. Microanalysis of the lms was performed in di erent part of structure elementsof grating.

Temperature Sensor Based on Colloidal Quantum Dots PMMA Nanocomposite Waveguides

2012

In this paper, integrated temperature sensors based on active nanocomposite planar waveguides are presented. The nanocomposites consist of cadmium selenide (CdSe) and cadmium telluride (CdTe) quantum dots (QDs) embedded in a polymethylmethacrylate (PMMA) matrix. When the samples are heated in a temperature range from 25$^{circ}{rm C}$ to 50 $^{circ}{rm C}$, the waveguided photoluminescence of QDs suffers from a strong intensity decrease, which is approximately quadratic dependent on temperature. Moreover, the wavelength peak of the waveguided emission spectrum of CdTe-PMMA shows a blue shift of 0.25 ${rm nm}/^{circ}{rm C}$, whereas it remains constant in the case of CdSe-PMMA. A temperature…

Photochemical synthesis of pyrene perfluoroalkyl derivatives and their embedding in a polymethylmethacrylate matrix: a spectroscopic and structural s…

2014

A photochemical, alternative and eco-compatible approach to perfluoroalkyl derivatives of pyrene is presented. The perfluoroalkyl chain is regiospecifically introduced at the 1 position of pyrene. The synthesized products have been embedded in a polymethylmethacrylate matrix by photocuring at 365 nm. Both the photochemical reactions can be considered a “green tool” for the synthetic chemist in order to obtain materials with prospective optoelectronic applications. The so-obtained composites have been the object of a study by UV and fluorescence spectroscopy in order to explore their luminescence properties. The small angle X-ray scattering and the transmission electron microscopy techniques…

Cobalt hexacyanoferrate–poly(methyl methacrylate) composite: Synthesis and characterization

2010

Abstract The preparation of cobalt hexacyanoferrate nanoparticles–poly(methyl methacrylate) (CoHCF–PMMA) composites are described together with their characterization and thermochromic properties. CoHCF nanoparticles – investigated by dynamic light scattering – were prepared by optimizing solvent composition and temperature to obtain nanoparticles with a reduced degree of aggregation. The nanoparticles were embedded in a PMMA matrix to obtain a transparent coloured composite which was studied by transmission electron microscopy. The nanoparticle chromic features, enhanced by their reduced sizes, were investigated by UV–vis and FT-IR spectroscopy.

Influence of the Ce: YAG amount on structure and optical properties of Ce:YAG-PMMA composites for white LED

2016

Ce:YAG-poly(methyl methacrylate) (PMMA) composites were prepared by using a melt compounding method, adding several amounts of Ce:YAG in the range 0.1–5wt.%. The optical properties of the obtained composites and of the composites combined with a blue LED were measured to investigate the effect of the amount of Ce:YAG on the resulting emitted light in view of possible application in white LED manufacture. An increase in Ce:YAG amount caused an increase in the emission and a shift of 15 nm, influencing the white LED performance. The structure and morphology of the composites were studied. The results show that the interaction between the two components, observed by using solid state NMR exper…

Effect of preparation method on the properties of poly(methyl methacrylate)/mesoporous silica composites

2019

The preparation method of a polymer composite and the filler loading are amongst the factors that influence the properties of the final composites. This article studies the effect of these factors on the thermal stability and thermal degradation kinetics of poly(methyl methacrylate) (PMMA)/mesoporous silica (MCM-41) composites filled with small amounts of MCM-41. The PMMA/MCM-41 composites were prepared through in situ polymerisation and melt mixing methods, with MCM-41 loadings of 0.1, 0.3, and 0.5 wt.%. The presence of MCM-41 increased the thermal stability of PMMA/MCM-41 composites prepared by melt mixing, but in the case of the in situ polymerised samples, the MCM-41 accelerated the deg…