Water-based route to ligand-selective synthesis of ZnSe and Cd-doped ZnSe quantum dots with tunable ultraviolet A to blue photoluminescence

Zhengtao Deng, Fee Li Lie, Shengyi Shen, Indraneel Ghosh, Masud Mansuripur, Anthony J Muscat

Research output: Contribution to journalArticle

113 Citations (Scopus)

Abstract

A water-based route has been demonstrated for synthesizing ZnSe and Cd-doped ZnSe (Zn xCd 1-xSe, 0 < x < 1) quantum dots (QDs) that have tunable and narrow photoluminescence (PL) peaks from the ultraviolet A (UVA) to the blue range (350-490 nm) with full-width at half-maximum (fwhm) values of 24-36 nm. Hydrazine (N 2H 4) was used to maintain oxygen-free conditions, allowing the reaction vessel to be open to air. The properties of the QDs were controlled using the thiol ligands, 3-mercaptopropionic acid (MPA), thiolglycolic acid (TGA), and L-glutathione (GSH). On the basis of optical spectra, linear three-carbon MPA attenuated nucleation and growth, yielding small ZnSe QDs with a high density of surface defects. In contrast, TGA and GSH produced larger ZnSe QDs with lower surface defect densities. The absorption spectra show that growth was more uniform and better controlled with linear two-carbon TGA than branched bifunctional GSH. After 20 min of growth TGA-capped ZnSe had an average diameter of 2.5 nm based on high-resolution transmission electron microscopy images; these nanocrystals had an absorbance peak maximum of approximately 340 nm (3.65 eV) and a band gap PL emission peak at 372 nm (3.34 eV). Highly fluorescent Zn xCd 1-x QDs were fabricated by adding a Cd-thiol complex directly to ZnSe QD solutions; PL peaks were tuned in the blue range (400-490 nm) by changing the Zn to Cd ratio. The Cd-bearing nanocrystals contained proportionally more Se based on X-ray photoelectron spectroscopy, and Cd-Se bonds had ionic character, in contrast to primarily covalent Zn-Se bonds.

Original languageEnglish (US)
Pages (from-to)434-442
Number of pages9
JournalLangmuir
Volume25
Issue number1
DOIs
StatePublished - Jan 6 2009

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Semiconductor quantum dots
Photoluminescence
Ligands
quantum dots
routes
photoluminescence
ligands
acids
Acids
Water
synthesis
water
hydrazine
Surface defects
surface defects
Sulfhydryl Compounds
thiols
Nanocrystals
nanocrystals
Bearings (structural)

ASJC Scopus subject areas

  • Electrochemistry
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Materials Science(all)
  • Spectroscopy

Cite this

Water-based route to ligand-selective synthesis of ZnSe and Cd-doped ZnSe quantum dots with tunable ultraviolet A to blue photoluminescence. / Deng, Zhengtao; Lie, Fee Li; Shen, Shengyi; Ghosh, Indraneel; Mansuripur, Masud; Muscat, Anthony J.

In: Langmuir, Vol. 25, No. 1, 06.01.2009, p. 434-442.

Research output: Contribution to journalArticle

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abstract = "A water-based route has been demonstrated for synthesizing ZnSe and Cd-doped ZnSe (Zn xCd 1-xSe, 0 < x < 1) quantum dots (QDs) that have tunable and narrow photoluminescence (PL) peaks from the ultraviolet A (UVA) to the blue range (350-490 nm) with full-width at half-maximum (fwhm) values of 24-36 nm. Hydrazine (N 2H 4) was used to maintain oxygen-free conditions, allowing the reaction vessel to be open to air. The properties of the QDs were controlled using the thiol ligands, 3-mercaptopropionic acid (MPA), thiolglycolic acid (TGA), and L-glutathione (GSH). On the basis of optical spectra, linear three-carbon MPA attenuated nucleation and growth, yielding small ZnSe QDs with a high density of surface defects. In contrast, TGA and GSH produced larger ZnSe QDs with lower surface defect densities. The absorption spectra show that growth was more uniform and better controlled with linear two-carbon TGA than branched bifunctional GSH. After 20 min of growth TGA-capped ZnSe had an average diameter of 2.5 nm based on high-resolution transmission electron microscopy images; these nanocrystals had an absorbance peak maximum of approximately 340 nm (3.65 eV) and a band gap PL emission peak at 372 nm (3.34 eV). Highly fluorescent Zn xCd 1-x QDs were fabricated by adding a Cd-thiol complex directly to ZnSe QD solutions; PL peaks were tuned in the blue range (400-490 nm) by changing the Zn to Cd ratio. The Cd-bearing nanocrystals contained proportionally more Se based on X-ray photoelectron spectroscopy, and Cd-Se bonds had ionic character, in contrast to primarily covalent Zn-Se bonds.",
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