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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.


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TEM images of the CdS nanocrystals synthesized with the addition of different cationic surfactants: (a) 0.5 mmol CTAOH and (b) 0.5 mmol CTAB.
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Figure 4: TEM images of the CdS nanocrystals synthesized with the addition of different cationic surfactants: (a) 0.5 mmol CTAOH and (b) 0.5 mmol CTAB.

Mentions: Compared to our previous study [19], the only difference in this study is the addition of CTAC into the reaction mixture, and so CTAC must be the key to control the shape and phase of the CdS nanocrystals. Although it has been found that cationic surfactant can induce the formation of CdSe tetrapods, the exact role that cationic surfactant played in the reaction is still not clear. Wong and colleagues [24] suggested the degradation product of cationic surfactant at high temperature might be responsible for the phase transformation. To gain insight into the role of cationic surfactant, we replaced CTAC with other cationic surfactants. When CTAOH was used, amines should be the degradation products which are well known as activation agents for nanocrystal growth and which can induce the formation of wurtzite structure [27]. However, from the TEM image of the CdS nanocrystals synthesized with 0.5 mmol CTAOH shown in Figure 4a, we found that the size and shape changed little although the mean diameter of the CdS nanocrystals increased to 4 nm because of the existence of amines. While CTAB was used, remarkable morphology transformation was observed again. XRD analysis (Figure 5) further confirms the phase transformation that occurred when CTAB was used, while the nanocrystals still had zinc-blende structure when CTAOH was used. Therefore, we believe that halide ions play a key role in the shape and phase control of CdS nanocrystals.


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

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

TEM images of the CdS nanocrystals synthesized with the addition of different cationic surfactants: (a) 0.5 mmol CTAOH and (b) 0.5 mmol CTAB.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: TEM images of the CdS nanocrystals synthesized with the addition of different cationic surfactants: (a) 0.5 mmol CTAOH and (b) 0.5 mmol CTAB.
Mentions: Compared to our previous study [19], the only difference in this study is the addition of CTAC into the reaction mixture, and so CTAC must be the key to control the shape and phase of the CdS nanocrystals. Although it has been found that cationic surfactant can induce the formation of CdSe tetrapods, the exact role that cationic surfactant played in the reaction is still not clear. Wong and colleagues [24] suggested the degradation product of cationic surfactant at high temperature might be responsible for the phase transformation. To gain insight into the role of cationic surfactant, we replaced CTAC with other cationic surfactants. When CTAOH was used, amines should be the degradation products which are well known as activation agents for nanocrystal growth and which can induce the formation of wurtzite structure [27]. However, from the TEM image of the CdS nanocrystals synthesized with 0.5 mmol CTAOH shown in Figure 4a, we found that the size and shape changed little although the mean diameter of the CdS nanocrystals increased to 4 nm because of the existence of amines. While CTAB was used, remarkable morphology transformation was observed again. XRD analysis (Figure 5) further confirms the phase transformation that occurred when CTAB was used, while the nanocrystals still had zinc-blende structure when CTAOH was used. Therefore, we believe that halide ions play a key role in the shape and phase control of CdS nanocrystals.

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