Electrochemical control of two-color emission from colloidal dot-in-bulk nanocrystals

Sergio Brovelli, Wan Ki Bae, Francesco Meinardi, Beatriz Santiago González, Monica Lorenzon, Christophe Galland, Victor I Klimov

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Colloidal "dot-in-bulk" nanocrystals (DiB NCs) consist of a quantum confined core embedded into a bulklike shell of a larger energy gap. The first reported example of this class of nanostructures are CdSe/CdS DiB NCs that are capable of producing tunable two-color emission under both weak continuous-wave optical excitation and electrical charge injection. This property is a consequence of a Coulomb blockade mechanism, which slows down dramatically intraband relaxation of shell-localized holes when the core is already occupied by a hole. Here, we demonstrate electrochemical control of dual emission from DiB NCs. Spectro-electrochemical (SEC) experiments are used to tune and probe the photoluminescence (PL) intensity and branching between the core and the shell emission channels as a function of applied electrochemical potential (VEC). To interpret the SEC data we develop a model that describes the changes in the intensities of the shell and core PL bands by relating them to the occupancies of electron and hole traps. Specifically, application of negative electrochemical potentials under which the Fermi level is shifted upward in energy leads to passivation of electron traps at the surface of the CdS shell thereby increasing the total PL quantum yield by favoring the shell emission. Simultaneously, the emission color changes from red (VEC = 0) through yellow to green (VEC = -1). Time-resolved PL measurements indicate that as the Fermi level approaches the NC conduction band-edge electrons are injected into the NC quantized states, which leads to typical signatures of negative trions observed under optical excitation. Application of positive potentials leads to activation of electron traps, which quenches both core and shell PL and leads to the reduction of the overall PL quantum efficiency. A high sensitivity of emission intensity (especially pronounced for the shell band) and the apparent emission color of DiB NCs to local electrochemical environment can enable interesting applications of these novel nanostructures in areas of imaging and sensing including, for example, ratiometric probing of intracellular pH.

Original languageEnglish
Pages (from-to)3855-3863
Number of pages9
JournalNano Letters
Volume14
Issue number7
DOIs
Publication statusPublished - Jul 9 2014

Fingerprint

Nanocrystals
Photoluminescence
nanocrystals
Color
color
Electron traps
photoluminescence
Photoexcitation
Fermi level
traps
Nanostructures
electrons
Coulomb blockade
Hole traps
Charge injection
Quantum yield
Conduction bands
Quantum efficiency
Passivation
Energy gap

Keywords

  • core/shell heterostructure
  • dual emission
  • Nanocrystal quantum dot
  • ratiometric sensing
  • spectro-electrochemistry
  • trapping

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Mechanical Engineering

Cite this

Brovelli, S., Bae, W. K., Meinardi, F., Santiago González, B., Lorenzon, M., Galland, C., & Klimov, V. I. (2014). Electrochemical control of two-color emission from colloidal dot-in-bulk nanocrystals. Nano Letters, 14(7), 3855-3863. https://doi.org/10.1021/nl501026r

Electrochemical control of two-color emission from colloidal dot-in-bulk nanocrystals. / Brovelli, Sergio; Bae, Wan Ki; Meinardi, Francesco; Santiago González, Beatriz; Lorenzon, Monica; Galland, Christophe; Klimov, Victor I.

In: Nano Letters, Vol. 14, No. 7, 09.07.2014, p. 3855-3863.

Research output: Contribution to journalArticle

Brovelli, S, Bae, WK, Meinardi, F, Santiago González, B, Lorenzon, M, Galland, C & Klimov, VI 2014, 'Electrochemical control of two-color emission from colloidal dot-in-bulk nanocrystals', Nano Letters, vol. 14, no. 7, pp. 3855-3863. https://doi.org/10.1021/nl501026r
Brovelli S, Bae WK, Meinardi F, Santiago González B, Lorenzon M, Galland C et al. Electrochemical control of two-color emission from colloidal dot-in-bulk nanocrystals. Nano Letters. 2014 Jul 9;14(7):3855-3863. https://doi.org/10.1021/nl501026r
Brovelli, Sergio ; Bae, Wan Ki ; Meinardi, Francesco ; Santiago González, Beatriz ; Lorenzon, Monica ; Galland, Christophe ; Klimov, Victor I. / Electrochemical control of two-color emission from colloidal dot-in-bulk nanocrystals. In: Nano Letters. 2014 ; Vol. 14, No. 7. pp. 3855-3863.
@article{a88b04f0bfa54033a907f944fed89e20,
title = "Electrochemical control of two-color emission from colloidal dot-in-bulk nanocrystals",
abstract = "Colloidal {"}dot-in-bulk{"} nanocrystals (DiB NCs) consist of a quantum confined core embedded into a bulklike shell of a larger energy gap. The first reported example of this class of nanostructures are CdSe/CdS DiB NCs that are capable of producing tunable two-color emission under both weak continuous-wave optical excitation and electrical charge injection. This property is a consequence of a Coulomb blockade mechanism, which slows down dramatically intraband relaxation of shell-localized holes when the core is already occupied by a hole. Here, we demonstrate electrochemical control of dual emission from DiB NCs. Spectro-electrochemical (SEC) experiments are used to tune and probe the photoluminescence (PL) intensity and branching between the core and the shell emission channels as a function of applied electrochemical potential (VEC). To interpret the SEC data we develop a model that describes the changes in the intensities of the shell and core PL bands by relating them to the occupancies of electron and hole traps. Specifically, application of negative electrochemical potentials under which the Fermi level is shifted upward in energy leads to passivation of electron traps at the surface of the CdS shell thereby increasing the total PL quantum yield by favoring the shell emission. Simultaneously, the emission color changes from red (VEC = 0) through yellow to green (VEC = -1). Time-resolved PL measurements indicate that as the Fermi level approaches the NC conduction band-edge electrons are injected into the NC quantized states, which leads to typical signatures of negative trions observed under optical excitation. Application of positive potentials leads to activation of electron traps, which quenches both core and shell PL and leads to the reduction of the overall PL quantum efficiency. A high sensitivity of emission intensity (especially pronounced for the shell band) and the apparent emission color of DiB NCs to local electrochemical environment can enable interesting applications of these novel nanostructures in areas of imaging and sensing including, for example, ratiometric probing of intracellular pH.",
keywords = "core/shell heterostructure, dual emission, Nanocrystal quantum dot, ratiometric sensing, spectro-electrochemistry, trapping",
author = "Sergio Brovelli and Bae, {Wan Ki} and Francesco Meinardi and {Santiago Gonz{\'a}lez}, Beatriz and Monica Lorenzon and Christophe Galland and Klimov, {Victor I}",
year = "2014",
month = "7",
day = "9",
doi = "10.1021/nl501026r",
language = "English",
volume = "14",
pages = "3855--3863",
journal = "Nano Letters",
issn = "1530-6984",
publisher = "American Chemical Society",
number = "7",

}

TY - JOUR

T1 - Electrochemical control of two-color emission from colloidal dot-in-bulk nanocrystals

AU - Brovelli, Sergio

AU - Bae, Wan Ki

AU - Meinardi, Francesco

AU - Santiago González, Beatriz

AU - Lorenzon, Monica

AU - Galland, Christophe

AU - Klimov, Victor I

PY - 2014/7/9

Y1 - 2014/7/9

N2 - Colloidal "dot-in-bulk" nanocrystals (DiB NCs) consist of a quantum confined core embedded into a bulklike shell of a larger energy gap. The first reported example of this class of nanostructures are CdSe/CdS DiB NCs that are capable of producing tunable two-color emission under both weak continuous-wave optical excitation and electrical charge injection. This property is a consequence of a Coulomb blockade mechanism, which slows down dramatically intraband relaxation of shell-localized holes when the core is already occupied by a hole. Here, we demonstrate electrochemical control of dual emission from DiB NCs. Spectro-electrochemical (SEC) experiments are used to tune and probe the photoluminescence (PL) intensity and branching between the core and the shell emission channels as a function of applied electrochemical potential (VEC). To interpret the SEC data we develop a model that describes the changes in the intensities of the shell and core PL bands by relating them to the occupancies of electron and hole traps. Specifically, application of negative electrochemical potentials under which the Fermi level is shifted upward in energy leads to passivation of electron traps at the surface of the CdS shell thereby increasing the total PL quantum yield by favoring the shell emission. Simultaneously, the emission color changes from red (VEC = 0) through yellow to green (VEC = -1). Time-resolved PL measurements indicate that as the Fermi level approaches the NC conduction band-edge electrons are injected into the NC quantized states, which leads to typical signatures of negative trions observed under optical excitation. Application of positive potentials leads to activation of electron traps, which quenches both core and shell PL and leads to the reduction of the overall PL quantum efficiency. A high sensitivity of emission intensity (especially pronounced for the shell band) and the apparent emission color of DiB NCs to local electrochemical environment can enable interesting applications of these novel nanostructures in areas of imaging and sensing including, for example, ratiometric probing of intracellular pH.

AB - Colloidal "dot-in-bulk" nanocrystals (DiB NCs) consist of a quantum confined core embedded into a bulklike shell of a larger energy gap. The first reported example of this class of nanostructures are CdSe/CdS DiB NCs that are capable of producing tunable two-color emission under both weak continuous-wave optical excitation and electrical charge injection. This property is a consequence of a Coulomb blockade mechanism, which slows down dramatically intraband relaxation of shell-localized holes when the core is already occupied by a hole. Here, we demonstrate electrochemical control of dual emission from DiB NCs. Spectro-electrochemical (SEC) experiments are used to tune and probe the photoluminescence (PL) intensity and branching between the core and the shell emission channels as a function of applied electrochemical potential (VEC). To interpret the SEC data we develop a model that describes the changes in the intensities of the shell and core PL bands by relating them to the occupancies of electron and hole traps. Specifically, application of negative electrochemical potentials under which the Fermi level is shifted upward in energy leads to passivation of electron traps at the surface of the CdS shell thereby increasing the total PL quantum yield by favoring the shell emission. Simultaneously, the emission color changes from red (VEC = 0) through yellow to green (VEC = -1). Time-resolved PL measurements indicate that as the Fermi level approaches the NC conduction band-edge electrons are injected into the NC quantized states, which leads to typical signatures of negative trions observed under optical excitation. Application of positive potentials leads to activation of electron traps, which quenches both core and shell PL and leads to the reduction of the overall PL quantum efficiency. A high sensitivity of emission intensity (especially pronounced for the shell band) and the apparent emission color of DiB NCs to local electrochemical environment can enable interesting applications of these novel nanostructures in areas of imaging and sensing including, for example, ratiometric probing of intracellular pH.

KW - core/shell heterostructure

KW - dual emission

KW - Nanocrystal quantum dot

KW - ratiometric sensing

KW - spectro-electrochemistry

KW - trapping

UR - http://www.scopus.com/inward/record.url?scp=84904007401&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84904007401&partnerID=8YFLogxK

U2 - 10.1021/nl501026r

DO - 10.1021/nl501026r

M3 - Article

VL - 14

SP - 3855

EP - 3863

JO - Nano Letters

JF - Nano Letters

SN - 1530-6984

IS - 7

ER -