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Shape and phase control of CdS nanocrystals using cationic surfactant in noninjection synthesis.

Zou Y, Li D, Yang D - Nanoscale Res Lett (2011)

Bottom Line: Monodispersed CdS nanocrystals with controllable shape and phase have been successfully synthesized in this study by adding cationic surfactant in noninjection synthesis system.With the increase of the amount of cetyltrimethylammonium chloride (CTAC) added, the shape of the CdS nanocrystals changed from spherical to multi-armed, and the phase changed from zinc-blende to wurtzite.In addition, it was found that the multi-armed CdS nanocrystals lost quantum confinement effect because of the increase of the size with the increase of the concentration of CTAC.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China. mselds@zju.edu.cn.

ABSTRACT
Monodispersed CdS nanocrystals with controllable shape and phase have been successfully synthesized in this study by adding cationic surfactant in noninjection synthesis system. With the increase of the amount of cetyltrimethylammonium chloride (CTAC) added, the shape of the CdS nanocrystals changed from spherical to multi-armed, and the phase changed from zinc-blende to wurtzite. It was found that halide ion Cl- plays a key role in the transformation, and other halide ions such as Br- can also induce similar transformation. We proposed that the strong binding between Cd2+ and halide ions reduced the reactivity of the precursors, decreased the nuclei formed in the nucleation stage, and led to the high concentration of precursor in the growth stage, resulting in the increase of size and phase transformation of CdS nanocrystals. In addition, it was found that the multi-armed CdS nanocrystals lost quantum confinement effect because of the increase of the size with the increase of the concentration of CTAC.

No MeSH data available.


Related in: MedlinePlus

UV-Vis absorption spectra of the CdS nanocrystals obtained with different amounts of CTAC added. The multi-armed nanocrystals lose quantum confinement effect.
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Figure 6: UV-Vis absorption spectra of the CdS nanocrystals obtained with different amounts of CTAC added. The multi-armed nanocrystals lose quantum confinement effect.

Mentions: Figure 6 depicts the UV-Vis absorption spectra of the CdS nanocrystals prepared with different amounts of CTAC added. For the spherical CdS nanocrystals synthesized without CTAC, a strong exciton peak at 425 nm appears because of quantum confinement effect. The narrow peak also reveals narrow size distribution. With the increase of the amount of CTAC added, the absorption peak red-shifts and gradually disappears due to the increase of the size of CdS nanocrystals. Since the size of the multi-armed CdS nanocrystals is far beyond the exciton Bohr radius of CdS (approx. 3 nm), they lose quantum confinement effect, confirmed by the absorption onset located at approx. 512 nm, matching well with the band gap energy of bulk CdS (2.42 eV).


Shape and phase control of CdS nanocrystals using cationic surfactant in noninjection synthesis.

Zou Y, Li D, Yang D - Nanoscale Res Lett (2011)

UV-Vis absorption spectra of the CdS nanocrystals obtained with different amounts of CTAC added. The multi-armed nanocrystals lose quantum confinement effect.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211467&req=5

Figure 6: UV-Vis absorption spectra of the CdS nanocrystals obtained with different amounts of CTAC added. The multi-armed nanocrystals lose quantum confinement effect.
Mentions: Figure 6 depicts the UV-Vis absorption spectra of the CdS nanocrystals prepared with different amounts of CTAC added. For the spherical CdS nanocrystals synthesized without CTAC, a strong exciton peak at 425 nm appears because of quantum confinement effect. The narrow peak also reveals narrow size distribution. With the increase of the amount of CTAC added, the absorption peak red-shifts and gradually disappears due to the increase of the size of CdS nanocrystals. Since the size of the multi-armed CdS nanocrystals is far beyond the exciton Bohr radius of CdS (approx. 3 nm), they lose quantum confinement effect, confirmed by the absorption onset located at approx. 512 nm, matching well with the band gap energy of bulk CdS (2.42 eV).

Bottom Line: Monodispersed CdS nanocrystals with controllable shape and phase have been successfully synthesized in this study by adding cationic surfactant in noninjection synthesis system.With the increase of the amount of cetyltrimethylammonium chloride (CTAC) added, the shape of the CdS nanocrystals changed from spherical to multi-armed, and the phase changed from zinc-blende to wurtzite.In addition, it was found that the multi-armed CdS nanocrystals lost quantum confinement effect because of the increase of the size with the increase of the concentration of CTAC.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China. mselds@zju.edu.cn.

ABSTRACT
Monodispersed CdS nanocrystals with controllable shape and phase have been successfully synthesized in this study by adding cationic surfactant in noninjection synthesis system. With the increase of the amount of cetyltrimethylammonium chloride (CTAC) added, the shape of the CdS nanocrystals changed from spherical to multi-armed, and the phase changed from zinc-blende to wurtzite. It was found that halide ion Cl- plays a key role in the transformation, and other halide ions such as Br- can also induce similar transformation. We proposed that the strong binding between Cd2+ and halide ions reduced the reactivity of the precursors, decreased the nuclei formed in the nucleation stage, and led to the high concentration of precursor in the growth stage, resulting in the increase of size and phase transformation of CdS nanocrystals. In addition, it was found that the multi-armed CdS nanocrystals lost quantum confinement effect because of the increase of the size with the increase of the concentration of CTAC.

No MeSH data available.


Related in: MedlinePlus