Nanoparticle shape anisotropy and photoluminescence properties : Europium containing ZnO as a model case
Gerigk, Melanie (University of Konstanz)
Ehrenreich, Philipp (University of Konstanz)
Wagner, Markus R.. (Institut Català de Nanociència i Nanotecnologia)
Wimmer, Ilona (University of Konstanz)
Reparaz, Juan Sebastian (Institut Català de Nanociència i Nanotecnologia)
Sotomayor Torres, Clivia M. (Institut Català de Nanociència i Nanotecnologia)
Schmidt-Mende, Lukas (University of Konstanz)
Polarz, Sebastian (University of Konstanz)

Date:	2015
Abstract:	The precise control over electronic and optical properties of semiconductor (SC) materials is pivotal for a number of important applications like in optoelectronics, photocatalysis or in medicine. It is well known that the incorporation of heteroelements (doping as a classical case) is a powerful method for adjusting and enhancing the functionality of semiconductors. Independent from that, there already has been a tremendous progress regarding the synthesis of differently sized and shaped SC nanoparticles, and quantum-size effects are well documented experimentally and theoretically. Whereas size and shape control of nanoparticles work fairly well for the pure compounds, the presence of a heteroelement is problematic because the impurities interfere strongly with bottom up approaches applied for the synthesis of such particles, and effects are even stronger, when the heteroelement is aimed to be incorporated into the target lattice for chemical doping. Therefore, realizing coincident shape control of nanoparticle colloids and their doping still pose major difficulties. Due to a special mechanism of the emulsion based synthesis method presented here, involving a gelation of emulsion droplets prior to crystallization of shape-anisotropic ZnO nanoparticles, heteroelements can be effectively entrapped inside the lattice. Different nanocrystal shapes such as nanorods, -prisms, -plates, and -spheres can be obtained, determined by the use of certain emulsification agents. The degree of morphologic alterations depends on the type of incorporated heteroelement M, concentration, and it seems that some shapes are more tolerant against doping than others. Focus was then set on the incorporation of Eu³⁺ inside the ZnO particles, and it was shown that nanocrystal shape and aspect ratios could be adjusted while maintaining a fixed dopant level. Special PL properties could be observed implying energy transfer from ZnO excited near its band-gap (3. 3 eV) to the Eu³⁺ states mediated by defect luminescence of the nanoparticles. Indications for an influence of shape on photoluminescence (PL) properties were found. Finally, rod-like Eu@ZnO colloids were used as tracers to investigate their uptake into biological samples like HeLa cells. The PL was sufficient for identifying green and red emission under visible light excitation.
Grants:	European Commission 628197 Ministerio de Economía y Competitividad SEV-2013-0295 Ministerio de Ciencia e Innovación MAT2012-31392 Ministerio de Ciencia e Innovación CSD2010-0044
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Subject:	Bottom up approach ; Defect luminescence ; Electronic and optical properties ; Nanoparticle colloids ; Photoluminescence properties ; Quantum size effects ; Special mechanisms ; Visible light excitation
Published in:	Nanoscale, Vol. 7, issue 40 (2015) , p. 16969-16982, ISSN 2040-3372

DOI: 10.1039/c5nr02550h

14 p, 3.6 MB

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Research literature > UAB research groups literature > Research Centres and Groups (research output) > Experimental sciences > Catalan Institute of Nanoscience and Nanotechnology (ICN2)
Articles > Research articles
Articles > Published articles