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Failure of Debye-H??ckel Screening in Low-Charge Colloidal Suspensions

机译：低电荷胶体悬浮液中Debye-H ?? ckel筛选的失败

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Derjaguin–Landau–Verwey–Overbeek (DLVO) theory remains the cornerstone of colloid stability. Electrostatic interactions dominate van der Waals attractions at large colloid-colloid separations h, unless strongly screened. Under these conditions, the potential U ( h ) between charged colloids is expected to be exponentially screened, U ( h ) ∼ exp ( − κ h ) / h , with κ − 1 = λ D where λ D is the classical Debye-Hückel screening length. By measuring the force between individual charged particles at dilute electrolyte concentrations (&mM) using optical tweezers, we tested experimentally the prediction κ − 1 = λ D in a nonpolar solvent. At low salt concentrations, we found close agreement between the directly-measured decay length κ − 1 and Debye-Hückel predictions. However, above a critical electrolyte concentration (≈450 μ M), we obtained significant discrepancies between measured and predicted screening lengths, with κ − 1 a?? λ D . In marked contrast to expectations, we found that the measured screening length κ − 1 appears to grow as the ionic strength of the solution is increased. The origin of this discrepancy is discussed and the importance of considering the surface is highlighted.
机译：Derjaguin＆ Landau＆ Verwey＆ndash; Overbeek（DLVO）理论仍然是胶体稳定性的基础。除非经过严格筛选，否则静电相互作用在较大的胶体-胶体间距h处占范德华吸引力的主要部分。在这些条件下，带电胶体之间的电势U（h）有望被指数筛选。 exp（＆minus;＆kappa; h）/ h与＆kappa; ＆减去; 1 =＆lambda; D其中＆lambda; D是经典的Debye-Hückel筛选长度。通过使用光学镊子在稀电解质浓度（＜mM）下测量单个带电粒子之间的力，我们通过实验测试了预测值。 ＆减去; 1 =＆lambda; D在非极性溶剂中。在低盐浓度下，我们发现直接测量的衰变长度κ紧密相关。 ＆减去; 1和Debye-Hückel预测。然而，在临界电解质浓度以上（＆asymp; 450μM），我们获得了实测和预测的筛查长度之间的显着差异，k为κ。 ＆减去; 1个？ ＆lambda; D．与预期形成鲜明对比的是，我们发现测得的筛查长度kappa; ＆减去;随着溶液离子强度的增加，图1中的分子似乎增长。讨论了这种差异的根源，并强调了考虑表面的重要性。

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