Facile fabrication of two-dimensional inorganic nanostructures and their conjugation to nanocrystals

Nanocomposites of two-dimensional (2D) inorganic nanosheets and inorganic nanocrystals are fabricated. Freestanding atomically flat gamma-AlOOH nanosheets (thickness <1 nm) are synthesized from a one-pot hydrothermal reaction. The freestanding and binder-free film composed of the gamma-AlOOH nanosheets is fabricated by sedimentation. Because they have positive zeta potentials in the pH range below ca. 9.3, the gamma-AlOOH nanosheets can function as positively charged 2D inorganic matrices in a broad pH range. By solution phase (pH 7.0) mixing of the gamma-AlOOH nanosheets (zeta potential: 30.7 +/- 0.8 mV) and inorganic nanocrystals with negative surface charge, including Au nanoparticles, Au nanorods, CdSe quantum dots, CdSe/CdS/ZnS quantum dots and CdSe nanorods, the nanocomposites are self-assembled via electrostatic interactions. Negatively charged inorganic nanostructures with a wide range of chemical compositions, shapes, sizes, surface ligands and adsorbates can be used as building blocks for gamma-AlOOH nanocomposites. Adsorption densities of inorganic nanocrystals on the nanocomposites can be controlled by varying concentrations of nanocrystal solutions. Nanocomposite films containing alternating layers of gamma-AlOOH and nanocrystals are obtained by a simple drop casting method.