Optical Characteristics of ZnCuInS/ZnS (Core/Shell) Nanocrystal Flexible Films Under X-Ray Excitation

George Saatsakis,Konstantinos Ninos,Ioannis Valais,George E Karpetas,Ioannis Sianoudis,George Fountos,Christina Fountzoula,Athanasios Bakas,George Panayiotakis,Christos Michail,Nektarios Kalyvas,Ioannis Kandarakis

doi:10.3390/cryst9070343

George Saatsakis, Konstantinos Ninos + Show 10 more

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https://doi.org/10.3390/cryst9070343

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Abstract

The aim of this article is to evaluate optical characteristics, such as the intrinsic conversion efficiency and the inherent light propagation efficiency of three polymethyl methacrylate (PMMA)/methyl methacrylate (MMA) composite ZnCuInS/ZnS (core/shell) nanocrystal flexible films. The concentrations of these were 100 mg/mL, 150 mg/mL, and 250 mg/mL, respectively. Composite films were prepared by homogeneously diluting dry powder quantum dot (QD) samples in toluene and subsequently mixing these with a PMMA/MMA polymer solution. The absolute luminescence efficiency (AE) of the films was measured using X-ray excitation. A theoretical model describing the optical photon propagation in scintillator materials was used to calculate the fraction of the generated optical photons passed through the different material layers. Finally, the intrinsic conversion efficiency was calculated by considering the QD quantum yield and the optical photon emission spectrum.

Highlights

In recent years nanophosphors [1,2,3,4] and quantum dots (QDs) [5,6] have been investigated as possible sensors for many applications, including but not limited to, medicine, displays, and solar energy harvesting
1.5 mL of the polymethyl methacrylate (PMMA)/methyl methacrylate (MMA) solution was added to each sample, with samples stirred in a vortex to fabricate the final solution
The intrinsic conversion efficiency was found to be equal to 0.22. This value is higher than other values reported for non-QD scintillators [1,35,36]

Summary

Introduction

In recent years nanophosphors [1,2,3,4] and quantum dots (QDs) [5,6] have been investigated as possible sensors for many applications, including but not limited to, medicine, displays, and solar energy harvesting. QDs are semiconductor nanocrystals, in which optical properties are controlled by their particle size, which is in the nanoscale range, as well as shape and composition [7,8]. QDs have attracted attention since their emission spectra and electronic properties have found application as biological labels, light emitting devices, and optoelectronic sensors [9,10,11]. QDs and other scintillating materials have been proposed as candidates for ionizing radiation detectors [12,13,14,15].

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