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Surface charges and optical characteristic of colloidal cubic SiC nanocrystals.

Li Y, Chen C, Li JT, Yang Y, Lin ZM - Nanoscale Res Lett (2011)

Bottom Line: Fourier transform infrared spectra show that these cubic SiC nanocrystals contain carboxylic acid, SiH, CH, and CHx groups.The cubic SiC nanocrystals show different surface charges in water and ethanol solutions due to the interaction of water molecules with polar Si-terminated surfaces of cubic SiC nanocrystals.The results explain the distinctive optical characteristics of colloidal cubic SiC nanocrystals in water and ethanol, and reveal that quantum confinement and surface charges play a great role in determining the optical characteristics of colloidal cubic SiC nanocrystals.

View Article: PubMed Central - HTML - PubMed

Affiliation: Technical Institute of Physics and Chemistry, Chinese Academy of Science, Beijing 100190, PR China. chen.c.x@sjtu.edu.cn.

ABSTRACT
Colloidal cubic silicon carbide (SiC) nanocrystals with an average diameter of 4.4 nm have been fabricated by anisotropic wet chemical etching of microsized cubic SiC powder. Fourier transform infrared spectra show that these cubic SiC nanocrystals contain carboxylic acid, SiH, CH, and CHx groups. UV/Vis absorption and photoluminescence (PL) spectroscopy clearly indicate that water and ethanol colloidal suspensions of the as-fabricated colloidal samples exhibit strong and above band gap blue and blue-green emissions. The cubic SiC nanocrystals show different surface charges in water and ethanol solutions due to the interaction of water molecules with polar Si-terminated surfaces of cubic SiC nanocrystals. The results explain the distinctive optical characteristics of colloidal cubic SiC nanocrystals in water and ethanol, and reveal that quantum confinement and surface charges play a great role in determining the optical characteristics of colloidal cubic SiC nanocrystals.

No MeSH data available.


FTIR spectra of cubic SiC powder. (a) As-prepared and (b) etched 3C-SiC powder.
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Figure 2: FTIR spectra of cubic SiC powder. (a) As-prepared and (b) etched 3C-SiC powder.

Mentions: The surface features on etched SiC can influence the solubility, electronic structure, and optical characteristic of SiC nanocrystals [24]. The FTIR spectra of the as-prepared and etched cubic SiC powder are shown in Figure 2. The intense absorption band in 700 to approximately 1,000 cm-1 can be indexed as Si-C characteristic stretching mode of SiC (972 cm-1) [25]. The peak position of the etched sample (944 cm-1) shows a downshift with respect to that of the as-prepared sample (923 cm-1). The downshift may be ascribed to the phonon confinement induced by embedded SiC nanocrystals in the etched sample [26]. The peak at 478 cm-1 is assigned to Si-(OH)n vibrations [24]. After chemical etching, this peak disappears. There is a weak peaks v(C = O) band at 1,638 cm-1 in the spectrum of etched sample, and this indicates the oxidization and anisotropic chemical etching process on the surface of cubic SiC powders. The bands at 2,989 and 2,943 cm-1 reveal the presence of different aliphatic CHx groups in the etched sample. The v(OH) band centered at about 3,500 cm-1 corresponds to the absorbed water molecules. Our FTIR results are in agreement with former reports for electrochemical etching cubic SiC [27].


Surface charges and optical characteristic of colloidal cubic SiC nanocrystals.

Li Y, Chen C, Li JT, Yang Y, Lin ZM - Nanoscale Res Lett (2011)

FTIR spectra of cubic SiC powder. (a) As-prepared and (b) etched 3C-SiC powder.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211874&req=5

Figure 2: FTIR spectra of cubic SiC powder. (a) As-prepared and (b) etched 3C-SiC powder.
Mentions: The surface features on etched SiC can influence the solubility, electronic structure, and optical characteristic of SiC nanocrystals [24]. The FTIR spectra of the as-prepared and etched cubic SiC powder are shown in Figure 2. The intense absorption band in 700 to approximately 1,000 cm-1 can be indexed as Si-C characteristic stretching mode of SiC (972 cm-1) [25]. The peak position of the etched sample (944 cm-1) shows a downshift with respect to that of the as-prepared sample (923 cm-1). The downshift may be ascribed to the phonon confinement induced by embedded SiC nanocrystals in the etched sample [26]. The peak at 478 cm-1 is assigned to Si-(OH)n vibrations [24]. After chemical etching, this peak disappears. There is a weak peaks v(C = O) band at 1,638 cm-1 in the spectrum of etched sample, and this indicates the oxidization and anisotropic chemical etching process on the surface of cubic SiC powders. The bands at 2,989 and 2,943 cm-1 reveal the presence of different aliphatic CHx groups in the etched sample. The v(OH) band centered at about 3,500 cm-1 corresponds to the absorbed water molecules. Our FTIR results are in agreement with former reports for electrochemical etching cubic SiC [27].

Bottom Line: Fourier transform infrared spectra show that these cubic SiC nanocrystals contain carboxylic acid, SiH, CH, and CHx groups.The cubic SiC nanocrystals show different surface charges in water and ethanol solutions due to the interaction of water molecules with polar Si-terminated surfaces of cubic SiC nanocrystals.The results explain the distinctive optical characteristics of colloidal cubic SiC nanocrystals in water and ethanol, and reveal that quantum confinement and surface charges play a great role in determining the optical characteristics of colloidal cubic SiC nanocrystals.

View Article: PubMed Central - HTML - PubMed

Affiliation: Technical Institute of Physics and Chemistry, Chinese Academy of Science, Beijing 100190, PR China. chen.c.x@sjtu.edu.cn.

ABSTRACT
Colloidal cubic silicon carbide (SiC) nanocrystals with an average diameter of 4.4 nm have been fabricated by anisotropic wet chemical etching of microsized cubic SiC powder. Fourier transform infrared spectra show that these cubic SiC nanocrystals contain carboxylic acid, SiH, CH, and CHx groups. UV/Vis absorption and photoluminescence (PL) spectroscopy clearly indicate that water and ethanol colloidal suspensions of the as-fabricated colloidal samples exhibit strong and above band gap blue and blue-green emissions. The cubic SiC nanocrystals show different surface charges in water and ethanol solutions due to the interaction of water molecules with polar Si-terminated surfaces of cubic SiC nanocrystals. The results explain the distinctive optical characteristics of colloidal cubic SiC nanocrystals in water and ethanol, and reveal that quantum confinement and surface charges play a great role in determining the optical characteristics of colloidal cubic SiC nanocrystals.

No MeSH data available.