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Title: Excitonic pathway to photoinduced magnetism in colloidal nanocrystals with nonmagnetic dopants

Abstract

Electronic doping of colloidal semiconductor nanostructures holds promise for future device concepts in optoelectronic and spin-based technologies. Ag + is an emerging electronic dopant in III–V and II–VI nanostructures, introducing intragap electronic states optically coupled to the host conduction band. With its full 4d shell Ag + is nonmagnetic, and the dopant-related luminescence is ascribed to decay of the conduction-band electron following transfer of the photoexcited hole to Ag +. This optical activation process and the associated modification of the electronic configuration of Ag + remain unclear. Here in this paper, we trace a comprehensive picture of the excitonic process in Ag-doped CdSe nanocrystals and demonstrate that, in contrast to expectations, capture of the photohole leads to conversion of Ag+ to paramagnetic Ag 2+. The process of exciton recombination is thus inextricably tied to photoinduced magnetism. Accordingly, we observe strong optically activated magnetism and diluted magnetic semiconductor behaviour, demonstrating that optically switchable magnetic nanomaterials can be obtained by exploiting excitonic processes involving nonmagnetic impurities.

Authors:
ORCiD logo [1];  [2];  [1];  [3];  [1];  [4];  [1];  [2]; ORCiD logo [5]; ORCiD logo [1]
  1. Univ. degli Studi di Milano-Bicocca, Milano (Italy). Dipartimento di Scienza dei Materiali
  2. Beijing Inst. of Technology, Beijing (China). Beijing Key Lab. of Construction Tailorable Advanced Functional Materials and Green Applications, School of Materials Science and Engineering
  3. Politecnico di Milano, Milano (Italy). Dipartimento di Fisica
  4. Politecnico and IFN-CNR, Milano (Italy). Dipartimento di Energia
  5. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
National Science Foundation (NSF); USDOE
OSTI Identifier:
1471349
Report Number(s):
LA-UR-17-25541
Journal ID: ISSN 1748-3387
Grant/Contract Number:  
AC52-06NA25396
Resource Type:
Accepted Manuscript
Journal Name:
Nature Nanotechnology
Additional Journal Information:
Journal Volume: 13; Journal Issue: 2; Journal ID: ISSN 1748-3387
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
High Magnetic Field Science

Citation Formats

Pinchetti, Valerio, Di, Qiumei, Lorenzon, Monica, Camellini, Andrea, Fasoli, Mauro, Zavelani-Rossi, Margherita, Meinardi, Francesco, Zhang, Jiatao, Crooker, Scott A., and Brovelli, Sergio. Excitonic pathway to photoinduced magnetism in colloidal nanocrystals with nonmagnetic dopants. United States: N. p., 2017. Web. doi:10.1038/s41565-017-0024-8.
Pinchetti, Valerio, Di, Qiumei, Lorenzon, Monica, Camellini, Andrea, Fasoli, Mauro, Zavelani-Rossi, Margherita, Meinardi, Francesco, Zhang, Jiatao, Crooker, Scott A., & Brovelli, Sergio. Excitonic pathway to photoinduced magnetism in colloidal nanocrystals with nonmagnetic dopants. United States. doi:10.1038/s41565-017-0024-8.
Pinchetti, Valerio, Di, Qiumei, Lorenzon, Monica, Camellini, Andrea, Fasoli, Mauro, Zavelani-Rossi, Margherita, Meinardi, Francesco, Zhang, Jiatao, Crooker, Scott A., and Brovelli, Sergio. Mon . "Excitonic pathway to photoinduced magnetism in colloidal nanocrystals with nonmagnetic dopants". United States. doi:10.1038/s41565-017-0024-8. https://www.osti.gov/servlets/purl/1471349.
@article{osti_1471349,
title = {Excitonic pathway to photoinduced magnetism in colloidal nanocrystals with nonmagnetic dopants},
author = {Pinchetti, Valerio and Di, Qiumei and Lorenzon, Monica and Camellini, Andrea and Fasoli, Mauro and Zavelani-Rossi, Margherita and Meinardi, Francesco and Zhang, Jiatao and Crooker, Scott A. and Brovelli, Sergio},
abstractNote = {Electronic doping of colloidal semiconductor nanostructures holds promise for future device concepts in optoelectronic and spin-based technologies. Ag+ is an emerging electronic dopant in III–V and II–VI nanostructures, introducing intragap electronic states optically coupled to the host conduction band. With its full 4d shell Ag+ is nonmagnetic, and the dopant-related luminescence is ascribed to decay of the conduction-band electron following transfer of the photoexcited hole to Ag+. This optical activation process and the associated modification of the electronic configuration of Ag+ remain unclear. Here in this paper, we trace a comprehensive picture of the excitonic process in Ag-doped CdSe nanocrystals and demonstrate that, in contrast to expectations, capture of the photohole leads to conversion of Ag+ to paramagnetic Ag2+. The process of exciton recombination is thus inextricably tied to photoinduced magnetism. Accordingly, we observe strong optically activated magnetism and diluted magnetic semiconductor behaviour, demonstrating that optically switchable magnetic nanomaterials can be obtained by exploiting excitonic processes involving nonmagnetic impurities.},
doi = {10.1038/s41565-017-0024-8},
journal = {Nature Nanotechnology},
number = 2,
volume = 13,
place = {United States},
year = {2017},
month = {12}
}

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Works referenced in this record:

Quantum dot bioconjugates for imaging, labelling and sensing
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