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Synthesis and bio-imaging application of highly luminescent mercaptosuccinic acid-coated CdTe nanocrystals.

Ying E, Li D, Guo S, Dong S, Wang J - PLoS ONE (2008)

Bottom Line: In contrast to the use of oxygen-sensitive NaHTe or H(2)Te as Te source in the current synthetic methods, we employ more stable sodium tellurite as the Te source for preparing highly luminescent CdTe nanocrystals in aqueous solution.The influence of parameters such as the pH value of the precursor solution and the molar ratio of Cd(2+) to Na(2)TeO(3) on the QY of CdTe nanocrystals was systematically investigated in our experiments.The biological application of luminescent MSA-CdTe to HEK 293 cell imaging was also illustrated.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Electroanalytical Chemistry Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, China.

ABSTRACT
Here we present a facile one-pot method to prepare high-quality CdTe nanocrystals in aqueous phase. In contrast to the use of oxygen-sensitive NaHTe or H(2)Te as Te source in the current synthetic methods, we employ more stable sodium tellurite as the Te source for preparing highly luminescent CdTe nanocrystals in aqueous solution. By selecting mercaptosuccinic acid (MSA) as capping agent and providing the borate-citrate acid buffering solution, CdTe nanocrystals with high quantum yield (QY >70% at pH range 5.0-8.0) can be conveniently prepared by this method. The influence of parameters such as the pH value of the precursor solution and the molar ratio of Cd(2+) to Na(2)TeO(3) on the QY of CdTe nanocrystals was systematically investigated in our experiments. Under optimal conditions, the QY of CdTe nanocrystals is even high up to 83%. The biological application of luminescent MSA-CdTe to HEK 293 cell imaging was also illustrated.

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QYs of CdTe NCs prepared at different molar ratio (Cd2+/TeO32−): 2.0, 3.0, 4.0, 5.0, 8.0, 16.0 and 20.0 (pH = 5.0, [Cd2+] = 1 mM).
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pone-0002222-g003: QYs of CdTe NCs prepared at different molar ratio (Cd2+/TeO32−): 2.0, 3.0, 4.0, 5.0, 8.0, 16.0 and 20.0 (pH = 5.0, [Cd2+] = 1 mM).

Mentions: The influence of the molar ratio (Cd2+/TeO32−) on the QYs of CdTe NCs is shown in Figure 3. When the molar ratio of Cd2+/TeO32− is equal to 4.0, the maximal QYs of CdTe NCs is up to 83% under the condition of optimal pH value. With the increasing or decreasing in the molar ratio of Cd2+/TeO32−, the maximal QYs of CdTe NCs markedly decreased. Such a trend for this influence may be related with the number of CdTe nuclei and the amount of sulfur ions doped in CdTe NCs. Once the formation of CdTe NCs was completed, the growth of the CdTe NCs during the refluxing was controlled by the Ostwald ripening process, in which smaller particles dissolve and the monomers released are consumed by the larger ones. The number of CdTe nuclei produced in the precursor solution may have an impact on the growth process of CdTe NCs. Moreover, as showed by our X-ray photoelectron spectroscopy (XPS) spectra (see Text S1, Figure S1), some sulfur ions sourced from the decomposition of Cd2+-thiol complex are incorporated into the CdTe NCs, which may also have an effect on the PL of CdTe NCs. A CdS shell on the surface of the CdTe NCs was known to effectively passivate the surface trap states, thus enhancing the QYs of thiol coated CdTe NCs [30], [35]. It could be reasoned that with the molar ratio of Cd2+/TeO32− = 4.0, CdTe NCs with less surface defects and proper doped amount of sulfur ions were produced, and thus the QY of them was higher than that of other samples. Other studies also emphasized the importance of the molar ratio of Cd/Te in the synthesis of high-quality CdTe QDs [34], [36].


Synthesis and bio-imaging application of highly luminescent mercaptosuccinic acid-coated CdTe nanocrystals.

Ying E, Li D, Guo S, Dong S, Wang J - PLoS ONE (2008)

QYs of CdTe NCs prepared at different molar ratio (Cd2+/TeO32−): 2.0, 3.0, 4.0, 5.0, 8.0, 16.0 and 20.0 (pH = 5.0, [Cd2+] = 1 mM).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2377334&req=5

pone-0002222-g003: QYs of CdTe NCs prepared at different molar ratio (Cd2+/TeO32−): 2.0, 3.0, 4.0, 5.0, 8.0, 16.0 and 20.0 (pH = 5.0, [Cd2+] = 1 mM).
Mentions: The influence of the molar ratio (Cd2+/TeO32−) on the QYs of CdTe NCs is shown in Figure 3. When the molar ratio of Cd2+/TeO32− is equal to 4.0, the maximal QYs of CdTe NCs is up to 83% under the condition of optimal pH value. With the increasing or decreasing in the molar ratio of Cd2+/TeO32−, the maximal QYs of CdTe NCs markedly decreased. Such a trend for this influence may be related with the number of CdTe nuclei and the amount of sulfur ions doped in CdTe NCs. Once the formation of CdTe NCs was completed, the growth of the CdTe NCs during the refluxing was controlled by the Ostwald ripening process, in which smaller particles dissolve and the monomers released are consumed by the larger ones. The number of CdTe nuclei produced in the precursor solution may have an impact on the growth process of CdTe NCs. Moreover, as showed by our X-ray photoelectron spectroscopy (XPS) spectra (see Text S1, Figure S1), some sulfur ions sourced from the decomposition of Cd2+-thiol complex are incorporated into the CdTe NCs, which may also have an effect on the PL of CdTe NCs. A CdS shell on the surface of the CdTe NCs was known to effectively passivate the surface trap states, thus enhancing the QYs of thiol coated CdTe NCs [30], [35]. It could be reasoned that with the molar ratio of Cd2+/TeO32− = 4.0, CdTe NCs with less surface defects and proper doped amount of sulfur ions were produced, and thus the QY of them was higher than that of other samples. Other studies also emphasized the importance of the molar ratio of Cd/Te in the synthesis of high-quality CdTe QDs [34], [36].

Bottom Line: In contrast to the use of oxygen-sensitive NaHTe or H(2)Te as Te source in the current synthetic methods, we employ more stable sodium tellurite as the Te source for preparing highly luminescent CdTe nanocrystals in aqueous solution.The influence of parameters such as the pH value of the precursor solution and the molar ratio of Cd(2+) to Na(2)TeO(3) on the QY of CdTe nanocrystals was systematically investigated in our experiments.The biological application of luminescent MSA-CdTe to HEK 293 cell imaging was also illustrated.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Electroanalytical Chemistry Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, China.

ABSTRACT
Here we present a facile one-pot method to prepare high-quality CdTe nanocrystals in aqueous phase. In contrast to the use of oxygen-sensitive NaHTe or H(2)Te as Te source in the current synthetic methods, we employ more stable sodium tellurite as the Te source for preparing highly luminescent CdTe nanocrystals in aqueous solution. By selecting mercaptosuccinic acid (MSA) as capping agent and providing the borate-citrate acid buffering solution, CdTe nanocrystals with high quantum yield (QY >70% at pH range 5.0-8.0) can be conveniently prepared by this method. The influence of parameters such as the pH value of the precursor solution and the molar ratio of Cd(2+) to Na(2)TeO(3) on the QY of CdTe nanocrystals was systematically investigated in our experiments. Under optimal conditions, the QY of CdTe nanocrystals is even high up to 83%. The biological application of luminescent MSA-CdTe to HEK 293 cell imaging was also illustrated.

Show MeSH
Related in: MedlinePlus