TY - JOUR
T1 - Capillary electrophoretic study of amine/carboxylic acid-functionalized carbon nanodots
AU - Hu, Qin
AU - Paau, Man Chin
AU - Zhang, Yan
AU - Chan, Wan
AU - Gong, Xiaojuan
AU - Zhang, Lei
AU - Choi, Martin M.F.
N1 - Funding Information:
Financial supports from the HKBU Faculty Research Grant ( FRG2/10-11/112 ) and Hundred Talent Programme of Shanxi Province are gratefully acknowledged. Q. Hu acknowledges the receipt of a postgraduate studentship from the University Grants Committee of the Hong Kong Special Administrative Region. We would express our sincere thanks to Ms Winnie Y.K. Wu of the Institute of Advanced Materials for taking the TEM image and Ms Silva T. Mo of the Department of Chemistry, Hong Kong Baptist University for acquiring the MALDI-TOF MS. The TEM used in this work was supported by the Special Equipment Grant from the University Grants Committee of the Hong Kong Special Administrative Region, China (Grant SEG_HKBU06). This work was presented at the 20th Symposium on Chemistry Postgraduate Research in Hong Kong on 27 April 2013.
PY - 2013/8/23
Y1 - 2013/8/23
N2 - Capillary zone electrophoresis (CZE) coupled with UV absorption and laser-induced fluorescence detections has been applied to study the complexity of carbon nanodots (C-dots) products synthesized with microwave-assisted pyrolysis of citric acid (CA) and 1,2-ethylenediamine (EDA). The effects of pH and concentration of run buffer on the CZE separation of C-dots are studied in detail. The optimal acetate run buffer (30mM, pH 3.6) is subsequently employed to investigate the effect of reaction time and mole ratio of amine (NH2) to carboxylic acid (COOH) moieties of the precursors on the C-dots species present in C-dots products. Our results confirm that the synthesis of C-dots could be improved by lengthening the microwave irradiation time and optimizing the initial mole ratio of NH2/COOH in the precursors. Negatively charged C-dots are obtained only when the amount of CA exceeds that of EDA, i.e., the mole ratio of NH2/COOH is 0.25-0.80. By contrast, when the quantity (mole) of NH2 in EDA is equal to or larger than that of COOH in CA, only positively charged and neutral C-dots species are formed, inferring that the C-dots species are predominantly covered by the surface-attached ammonium and amido moieties. This work highlights the merit of CZE to identify the composition of an as-prepared C-dots product which is pretty much dependent on the mole ratio of NH2/COOH. It is anticipated that our CZE methodology will open a new avenue in optimizing the synthetic conditions for producing specific C-dots of desired composition.
AB - Capillary zone electrophoresis (CZE) coupled with UV absorption and laser-induced fluorescence detections has been applied to study the complexity of carbon nanodots (C-dots) products synthesized with microwave-assisted pyrolysis of citric acid (CA) and 1,2-ethylenediamine (EDA). The effects of pH and concentration of run buffer on the CZE separation of C-dots are studied in detail. The optimal acetate run buffer (30mM, pH 3.6) is subsequently employed to investigate the effect of reaction time and mole ratio of amine (NH2) to carboxylic acid (COOH) moieties of the precursors on the C-dots species present in C-dots products. Our results confirm that the synthesis of C-dots could be improved by lengthening the microwave irradiation time and optimizing the initial mole ratio of NH2/COOH in the precursors. Negatively charged C-dots are obtained only when the amount of CA exceeds that of EDA, i.e., the mole ratio of NH2/COOH is 0.25-0.80. By contrast, when the quantity (mole) of NH2 in EDA is equal to or larger than that of COOH in CA, only positively charged and neutral C-dots species are formed, inferring that the C-dots species are predominantly covered by the surface-attached ammonium and amido moieties. This work highlights the merit of CZE to identify the composition of an as-prepared C-dots product which is pretty much dependent on the mole ratio of NH2/COOH. It is anticipated that our CZE methodology will open a new avenue in optimizing the synthetic conditions for producing specific C-dots of desired composition.
KW - Amine and carboxylic acid functionality
KW - Carbon dots
KW - Synthesis
UR - http://www.scopus.com/inward/record.url?scp=84881030449&partnerID=8YFLogxK
U2 - 10.1016/j.chroma.2013.07.035
DO - 10.1016/j.chroma.2013.07.035
M3 - Journal article
C2 - 23885674
AN - SCOPUS:84881030449
SN - 0021-9673
VL - 1304
SP - 234
EP - 240
JO - Journal of Chromatography A
JF - Journal of Chromatography A
ER -