Photoassisted synthesis of CdSe and core-shell CdSe/CdS quantum dots

Yang-Wei Lin, Ming Mu Hsieh, Ching Piao Liu, Huan Tsung Chang

Research output: Contribution to journalArticle

82 Citations (Scopus)

Abstract

This paper describes the synthesis of core-shell CdSe/CdS quantum dots (QDs) in aqueous solution by a simple photoassisted method. CdSe was prepared from cadmium nitrate and 1,1-dimethylselenourea precursors under illumination for up to 3 h using a pulsed Nd:YAG laser at 532 nm. The effects that the temperature and the laser irradiation process have on the synthesis of CdSe were monitored by a series of experiments using the precursors at a Cd:Se concentration ratio of 4. Upon increasing the temperature (80-140 °C), the size of the CdSe QDs increases and the time required for reaching a maximum photoluminescence (PL) is shortened. Although the as-prepared CdSe QDs possess greater quantum yields (up to 0.072%) compared to those obtained by microwave heating (0.016%), they still fluoresce only weakly. After passivation of CdSe (prepared at 80 °C) by CdS using thioacetamide as the S source (Se:S concentration ratio of 1) at 80 °C for 24 h, the quantum yield of the core-shell CdSe/CdS QDs at 603 nm is 2.4%. Under UV irradiation of CdSe/CdS for 24 h using a 100-W Hg-Xe lamp, the maximum quantum yield of the stable QDs is 60% at 589 nm. A small bandwidth (W1/2 < 35 nm) indicates the narrow size distribution of the as-prepared core-shell CdSe/CdS QDs. This simple photoassisted method also allows the preparation of differently sized (3.7-6.3-nm diameters) core-shell CdSe/CdS QDs that emit in a wide range (from green to red) when excited at 480 nm.

Original languageEnglish
Pages (from-to)728-734
Number of pages7
JournalLangmuir
Volume21
Issue number2
DOIs
Publication statusPublished - 2005 Jan 18

Fingerprint

Semiconductor quantum dots
quantum dots
synthesis
Quantum yield
Thioacetamide
irradiation
Microwave heating
Laser beam effects
Electric lamps
Passivation
Cadmium
cadmium
passivity
luminaires
nitrates
YAG lasers
Nitrates
pulsed lasers
Photoluminescence
Lighting

All Science Journal Classification (ASJC) codes

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

Cite this

Lin, Yang-Wei ; Hsieh, Ming Mu ; Liu, Ching Piao ; Chang, Huan Tsung. / Photoassisted synthesis of CdSe and core-shell CdSe/CdS quantum dots. In: Langmuir. 2005 ; Vol. 21, No. 2. pp. 728-734.
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title = "Photoassisted synthesis of CdSe and core-shell CdSe/CdS quantum dots",
abstract = "This paper describes the synthesis of core-shell CdSe/CdS quantum dots (QDs) in aqueous solution by a simple photoassisted method. CdSe was prepared from cadmium nitrate and 1,1-dimethylselenourea precursors under illumination for up to 3 h using a pulsed Nd:YAG laser at 532 nm. The effects that the temperature and the laser irradiation process have on the synthesis of CdSe were monitored by a series of experiments using the precursors at a Cd:Se concentration ratio of 4. Upon increasing the temperature (80-140 °C), the size of the CdSe QDs increases and the time required for reaching a maximum photoluminescence (PL) is shortened. Although the as-prepared CdSe QDs possess greater quantum yields (up to 0.072{\%}) compared to those obtained by microwave heating (0.016{\%}), they still fluoresce only weakly. After passivation of CdSe (prepared at 80 °C) by CdS using thioacetamide as the S source (Se:S concentration ratio of 1) at 80 °C for 24 h, the quantum yield of the core-shell CdSe/CdS QDs at 603 nm is 2.4{\%}. Under UV irradiation of CdSe/CdS for 24 h using a 100-W Hg-Xe lamp, the maximum quantum yield of the stable QDs is 60{\%} at 589 nm. A small bandwidth (W1/2 < 35 nm) indicates the narrow size distribution of the as-prepared core-shell CdSe/CdS QDs. This simple photoassisted method also allows the preparation of differently sized (3.7-6.3-nm diameters) core-shell CdSe/CdS QDs that emit in a wide range (from green to red) when excited at 480 nm.",
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Photoassisted synthesis of CdSe and core-shell CdSe/CdS quantum dots. / Lin, Yang-Wei; Hsieh, Ming Mu; Liu, Ching Piao; Chang, Huan Tsung.

In: Langmuir, Vol. 21, No. 2, 18.01.2005, p. 728-734.

Research output: Contribution to journalArticle

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N2 - This paper describes the synthesis of core-shell CdSe/CdS quantum dots (QDs) in aqueous solution by a simple photoassisted method. CdSe was prepared from cadmium nitrate and 1,1-dimethylselenourea precursors under illumination for up to 3 h using a pulsed Nd:YAG laser at 532 nm. The effects that the temperature and the laser irradiation process have on the synthesis of CdSe were monitored by a series of experiments using the precursors at a Cd:Se concentration ratio of 4. Upon increasing the temperature (80-140 °C), the size of the CdSe QDs increases and the time required for reaching a maximum photoluminescence (PL) is shortened. Although the as-prepared CdSe QDs possess greater quantum yields (up to 0.072%) compared to those obtained by microwave heating (0.016%), they still fluoresce only weakly. After passivation of CdSe (prepared at 80 °C) by CdS using thioacetamide as the S source (Se:S concentration ratio of 1) at 80 °C for 24 h, the quantum yield of the core-shell CdSe/CdS QDs at 603 nm is 2.4%. Under UV irradiation of CdSe/CdS for 24 h using a 100-W Hg-Xe lamp, the maximum quantum yield of the stable QDs is 60% at 589 nm. A small bandwidth (W1/2 < 35 nm) indicates the narrow size distribution of the as-prepared core-shell CdSe/CdS QDs. This simple photoassisted method also allows the preparation of differently sized (3.7-6.3-nm diameters) core-shell CdSe/CdS QDs that emit in a wide range (from green to red) when excited at 480 nm.

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