Capillary electrophoretic study of thiolated alpha-cyclodextrin-capped gold nanoparticles with tetraalkylammonium ions.
Capillary zone electrophoresis (CZE) has been employed to characterize nanometer-sized thiolated alpha-cyclodextrin-capped gold nanoparticles (alpha-CD-S-AuNPs). The addition of tetrabutylammonium (Bu(4)N(+)) ions to the run buffer greatly narrows the migration peak of alpha-CD-S-AuNP. The optimal run buffer was determined to be 10mM Bu(4)N(+) in 30 mM phosphate buffer at pH 12 and an applied voltage of 15 kV. The effect of various tetraalkylammonium ions on the peak width and electrophoretic mobility (mu(e)) of alpha-CD-S-AuNP was studied in detail. Bu(4)N(+) ions assist in inter-linking the alpha-CD-S-AuNPs and narrowing the migration peak in CZE. This observation can be explained by the fact that each Bu(4)N(+) ion can simultaneously interact with several hydrophobic cavities of the surface-attached alpha-CDs on AuNPs. The TEM images show that alpha-CD-S-AuNPs with Bu(4)N(+) are linked together but in the absence of Bu(4)N(+), they are more dispersed. The migration mechanism in CZE is based on the formation of inclusion complexes between Bu(4)N(+) and alpha-CD-S-AuNPs which induces changes in the charge-to-size ratio of alpha-CD-S-AuNPs and mu(e). An inverse linear relationship (r(2)>0.998) exists between the mu(e) and size of alpha-CD-S-AuNPs in the core range 1.4-4.1 nm. The CZE analyses are rapid with migration time less than 4 min. A few nanoliters of each of the alpha-CD-S-AuNP samples were injected hydrodynamically at 0.5 psi for 5s. Our work confirms that CZE is an efficient tool for characterizing the sizes of alpha-CD-S-AuNPs using Bu(4)N(+) ions.
Paau
Man Chin
MC
Department of Chemistry, Hong Kong Baptist University, 224 Waterloo Road, Kowloon Tong, Hong Kong SAR, China.
Lo
Chung Keung
CK
Yang
Xiupei
X
Choi
Martin M F
MM
D002021:Buffers; D019075:Electrophoresis, Capillary / Q000379:methods*; D006046:Gold / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007477:Ions; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D047391:alpha-Cyclodextrins / Q000737:chemistry*
D002021:Buffers; D007477:Ions; D000644:Quaternary Ammonium Compounds; D013438:Sulfhydryl Compounds; D047391:alpha-Cyclodextrins; D006046:Gold; C009405:tetrabutylammonium; C032613:alpha-cyclodextrin