### Abstract

Displacement of cadmium oleate (Cd-(oleate)2) ligands for the exciton-delocalizing ligand 4-hexylphenyldithiocarbamate (C6-PTC) on the surfaces of CdS quantum dots (QDs) causes a decrease in the band gap (Eg) of the QD of ∼100 meV for QDs with a radius of 1.9 nm and ∼50 meV for QDs with a radius of 2.5 nm. The primary mechanism of this decrease in band gap, deduced in previous work, is a decrease in the confinement barrier for the excitonic hole. The increase in apparent excitonic radius of the QD that corresponds to this decrease in Eg is denoted ΔR. The dependence of ΔR on the surface coverage of C6-PTC, measured by 1H NMR spectroscopy, appears to be nonlinear. Calculations of the excitonic energy of a CdS QD upon displacement of native insulating ligands with exciton-delocalizing ligands using a 3D spherical potential well model show that this response includes the contributions to ΔR from both isolated, bound C6-PTC ligands and groups of adjacent C6-PTC ligands. Fits to the experimental plots of ΔR vs surface coverage of C6-PTC with a statistical model that includes the probability of formation of clusters of bound C6-PTC on the QD surface allow for the extraction of the height of the confinement barrier presented by a single, isolated C6-PTC molecule to the excitonic hole. This barrier height is less than 0.6 eV for QDs with a radius of 1.9 nm and between 0.6 and 1.2 eV for QDs with a radius of 2.5 nm.

Original language | English |
---|---|

Pages (from-to) | 1395-1403 |

Number of pages | 9 |

Journal | ACS Nano |

Volume | 10 |

Issue number | 1 |

DOIs | |

Publication status | Published - Jan 26 2016 |

### Fingerprint

### Keywords

- Dithiocarbamate
- Exciton delocalization
- Ligand-ligand coupling
- Quantum dot

### ASJC Scopus subject areas

- Materials Science(all)
- Engineering(all)
- Physics and Astronomy(all)

### Cite this

*ACS Nano*,

*10*(1), 1395-1403. https://doi.org/10.1021/acsnano.5b06837

**Role of interligand coupling in determining the interfacial electronic structure of colloidal CDS quantum dots.** / Harris, Rachel D.; Amin, Victor A.; Lau, Bryan; Weiss, Emily A.

Research output: Contribution to journal › Article

*ACS Nano*, vol. 10, no. 1, pp. 1395-1403. https://doi.org/10.1021/acsnano.5b06837

}

TY - JOUR

T1 - Role of interligand coupling in determining the interfacial electronic structure of colloidal CDS quantum dots

AU - Harris, Rachel D.

AU - Amin, Victor A.

AU - Lau, Bryan

AU - Weiss, Emily A

PY - 2016/1/26

Y1 - 2016/1/26

N2 - Displacement of cadmium oleate (Cd-(oleate)2) ligands for the exciton-delocalizing ligand 4-hexylphenyldithiocarbamate (C6-PTC) on the surfaces of CdS quantum dots (QDs) causes a decrease in the band gap (Eg) of the QD of ∼100 meV for QDs with a radius of 1.9 nm and ∼50 meV for QDs with a radius of 2.5 nm. The primary mechanism of this decrease in band gap, deduced in previous work, is a decrease in the confinement barrier for the excitonic hole. The increase in apparent excitonic radius of the QD that corresponds to this decrease in Eg is denoted ΔR. The dependence of ΔR on the surface coverage of C6-PTC, measured by 1H NMR spectroscopy, appears to be nonlinear. Calculations of the excitonic energy of a CdS QD upon displacement of native insulating ligands with exciton-delocalizing ligands using a 3D spherical potential well model show that this response includes the contributions to ΔR from both isolated, bound C6-PTC ligands and groups of adjacent C6-PTC ligands. Fits to the experimental plots of ΔR vs surface coverage of C6-PTC with a statistical model that includes the probability of formation of clusters of bound C6-PTC on the QD surface allow for the extraction of the height of the confinement barrier presented by a single, isolated C6-PTC molecule to the excitonic hole. This barrier height is less than 0.6 eV for QDs with a radius of 1.9 nm and between 0.6 and 1.2 eV for QDs with a radius of 2.5 nm.

AB - Displacement of cadmium oleate (Cd-(oleate)2) ligands for the exciton-delocalizing ligand 4-hexylphenyldithiocarbamate (C6-PTC) on the surfaces of CdS quantum dots (QDs) causes a decrease in the band gap (Eg) of the QD of ∼100 meV for QDs with a radius of 1.9 nm and ∼50 meV for QDs with a radius of 2.5 nm. The primary mechanism of this decrease in band gap, deduced in previous work, is a decrease in the confinement barrier for the excitonic hole. The increase in apparent excitonic radius of the QD that corresponds to this decrease in Eg is denoted ΔR. The dependence of ΔR on the surface coverage of C6-PTC, measured by 1H NMR spectroscopy, appears to be nonlinear. Calculations of the excitonic energy of a CdS QD upon displacement of native insulating ligands with exciton-delocalizing ligands using a 3D spherical potential well model show that this response includes the contributions to ΔR from both isolated, bound C6-PTC ligands and groups of adjacent C6-PTC ligands. Fits to the experimental plots of ΔR vs surface coverage of C6-PTC with a statistical model that includes the probability of formation of clusters of bound C6-PTC on the QD surface allow for the extraction of the height of the confinement barrier presented by a single, isolated C6-PTC molecule to the excitonic hole. This barrier height is less than 0.6 eV for QDs with a radius of 1.9 nm and between 0.6 and 1.2 eV for QDs with a radius of 2.5 nm.

KW - Dithiocarbamate

KW - Exciton delocalization

KW - Ligand-ligand coupling

KW - Quantum dot

UR - http://www.scopus.com/inward/record.url?scp=84989926896&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84989926896&partnerID=8YFLogxK

U2 - 10.1021/acsnano.5b06837

DO - 10.1021/acsnano.5b06837

M3 - Article

VL - 10

SP - 1395

EP - 1403

JO - ACS Nano

JF - ACS Nano

SN - 1936-0851

IS - 1

ER -