Beijing National Laboratory of Molecular Science, Joint Laboratory of Polymer Science and Materials, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
J Chem Phys. 2009 Dec 21;131(23):231103. doi: 10.1063/1.3276278.
Single chain conformation of a polyelectrolyte (polystyrene sulfonate, PSS(-)Na(+)) during its re-entrant condensation was studied by fluorescence correlation spectroscopy (FCS) with single molecule sensitivity. The contraction and re-expansion of PSS(-)Na(+) chain were observed with the addition of counterions of different valencies. The formation of aggregation and precipitation of PSS(-)Na(+) and its redissolution were observed in accordance with the chain contraction and re-expansion process for the PSS(-)Na(+) chain upon the addition of trivalent La(3+) ion. Chain contraction and re-expansion of the PSS(-)Na(+) chain were also observed with the addition of monovalent Cs(+) and divalent Ca(2+) ions, under which condition, the re-entrant condensation was not observed. The results demonstrate that the high sensitivity of FCS can really study single PSS(-)Na(+) chain under extremely dilute situation.
通过具有单分子灵敏度的荧光相关光谱（FCS）研究了聚电解质（聚苯乙烯磺酸钠，PSS（-）Na（+））在再进入凝聚过程中的单链构象。随着添加不同价态的抗衡离子，观察到 PSS（-）Na（+）链的收缩和再扩展。随着三价 La（3+）离子的加入，观察到 PSS（-）Na（+）的聚集和沉淀的形成以及其再溶解，这与 PSS（-）Na（+）链的链收缩和再扩展过程一致。在添加单价 Cs（+）和二价 Ca（2+）离子的情况下，也观察到 PSS（-）Na（+）链的收缩和再扩展，在这种情况下，未观察到再进入凝聚。结果表明，FCS 的高灵敏度确实可以在极其稀有的情况下研究单个 PSS（-）Na（+）链。
