Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
Langmuir. 2010 May 18;26(10):7482-8. doi: 10.1021/la904161q.
Small angle neutron scattering (SANS) has been used to study the conformations, and response to added salt, of a polyelectrolyte layer grafted to the interfaces of well-defined gold nanoparticles. The polyelectrolyte layer is prepared at a constant coverage by grafting thiol-functionalized polystyrene (M(w) = 53k) to gold nanoparticles of well-defined interfacial curvature (R(c) = 26.5 nm) followed by a soft-sulfonation of 38% of the segments to sodium polystyrene sulfonate (NaPSS). The SANS profiles can be fit by Fermi-Dirac distributions that are consistent with a Gaussian distribution but are better described by a parabolic distribution plus an exponential tail, particularly in the high salt regime. These distributions are consistent with the predictions and measurements for osmotic and salted brushes at interfaces of low curvature. When the concentration of added salt exceeds the concentration of counterions inside the brush, there is a salt-induced deswelling, but even at the highest salt concentration the brush remains significantly swollen due to a short-ranged excluded volume interaction. This is responsible for the observed resistance to aggregation of these comparatively high concentration polyelectrolyte stabilized gold nanoparticle dispersions even in the presence of a high concentration of added salt.
小角中子散射（SANS）已被用于研究接枝在具有明确曲率的金纳米粒子界面上的聚电解质层的构象及其对添加盐的响应。通过将巯基功能化的聚苯乙烯（M（w）= 53k）接枝到具有明确界面曲率（R（c）= 26.5nm）的金纳米粒子上来制备聚电解质层，其覆盖率保持恒定，然后将 38%的片段软磺化得到聚苯乙烯磺酸钠（NaPSS）。SANS 图谱可以通过费米-狄拉克分布进行拟合，该分布与高斯分布一致，但通过抛物线分布加指数尾巴更好地描述，尤其是在高盐区。这些分布与低曲率界面处渗透压和盐化刷的预测和测量结果一致。当添加盐的浓度超过刷内抗衡离子的浓度时，会发生盐诱导的去溶胀，但即使在最高盐浓度下，由于短程排斥体积相互作用，刷仍然明显肿胀。这就是即使在添加盐的浓度很高的情况下，这些相对高浓度的聚电解质稳定的金纳米粒子分散体也表现出抗聚集性的原因。
