The optical properties of five different nanocrystalline samples are presented and discussed. Green and red emission was observed following excitation with 488 nm and attributed to 2 4 and 4 transitions, respectively. Striking red enhancement was observed in the upconversion spectra when exciting the samples with 978 nm, and it became more pronounced with an increase in concentration. A cross relaxation mechanism and 4 was responsible for directly populating the 4 state but did not explain the difference in the magnitude of red enhancement between identically doped bulk and nanocrystalline samples. The 4 level was populated via a nonresonant mechanism that involved the 4 transition that is more prevalent in the nanocrystals, which is due to the high energy phonons inherent in this type of material. In nanocrystalline we observe a change in the upconversion mechanism responsible for populating the 4 state, from a two-photon to a three-photon process with an increase in concentration. An explanation to account for this behavior is presented.
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1 July 2004
Research Article|
July 01 2004
Significance of concentration on the upconversion mechanisms in codoped nanocrystals
Fiorenzo Vetrone;
Fiorenzo Vetrone
Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke Street West, Montreal, QC H4B 1R6, Canada
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John-Christopher Boyer;
John-Christopher Boyer
Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke Street West, Montreal, QC H4B 1R6, Canada
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John A. Capobianco;
John A. Capobianco
Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke Street West, Montreal, QC H4B 1R6, Canada
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Adolfo Speghini;
Adolfo Speghini
Dipartimento Scientifico e Tecnologico, Università di Verona and INSTM, UdR Verona, Ca’ Vignal, Strada Le Grazie 15, I-37134 Verona, Italy
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Marco Bettinelli
Marco Bettinelli
Dipartimento Scientifico e Tecnologico, Università di Verona and INSTM, UdR Verona, Ca’ Vignal, Strada Le Grazie 15, I-37134 Verona, Italy
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J. Appl. Phys. 96, 661–667 (2004)
Article history
Received:
February 26 2004
Accepted:
March 24 2004
Citation
Fiorenzo Vetrone, John-Christopher Boyer, John A. Capobianco, Adolfo Speghini, Marco Bettinelli; Significance of concentration on the upconversion mechanisms in codoped nanocrystals. J. Appl. Phys. 1 July 2004; 96 (1): 661–667. https://doi.org/10.1063/1.1739523
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