Clay minerals, like beidellite or nontronite, spontaneously exfoliate in water and form colloidal suspensions of nanosheets. In a given range of concentration, these suspensions display a nematic liquid–crystalline phase whose structure and properties can be conveniently studied in detail by polarized-light microscopy and small-angle X-ray scattering (SAXS). Moreover, in situ SAXS investigations of sheared clay suspensions provide information about their flow properties, both in the isotropic and nematic phases. The colloidal nematic phase shows the classical properties of usual nematics, such as surface anchoring and electric-field and magnetic-field alignment. Thus, nematic single domains can be produced. The isotropic phase also displays strong electro-optic effects in moderate electric fields. Finally, we describe a few examples of applications of such systems and we show how these studies could be extended to suspensions of other types of nanosheets.

粘土矿物（如贝得石或绿脱石）在水中自发脱落并形成纳米片的胶体悬浮液。在给定的浓度范围内，这些悬浮液显示出向列型液晶相，可以通过偏振光显微镜和小角X射线散射（SAXS）方便地详细研究其结构和性质。而且，就地SAXS对剪切黏土悬浮液的研究提供了有关各向同性和向列相流动特性的信息。胶体向列相显示了常规向列相的经典性质，例如表面锚定以及电场和磁场对准。因此，可以产生向列单域。在各向同性的电场中，各向同性相也显示出强大的电光效应。最后，我们描述了此类系统的一些应用示例，并展示了如何将这些研究扩展到其他类型的纳米片的悬浮液中。