Morphology Control and Structural Characterization of Au Crystals: From Twinned Tabular Crystals and Single-Crystalline Nanoplates to Multitwinned Decahedra

In this contribution, a general one-step route to synthesize ALL crystals with the shape of twinned tabular crystals, single-crystalline nanoplates. and multitwinned decahedra is proposed. By employing HAuCl4 in an aqueous medium as the oxidizing reagent, tetracycline hydrochloride as the reducing agent, and cetyltrimethylammonium bromide (CTAB) as the capping agent, we found it is very easy to get the three types of Au crystals by modulating the molar ratio of CTAB with HAuCl4. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution TEM (HRTEM) have been employed to characterize the three types of symmetric morphologies. Further investigations involve side-face analysis and growth mechanism of Au twinned tabular crystals, and the optical properties of the obtained crystals, Absorption and dark field light scattering images demonstrate their potential applications in cancer cell diagnostics and photothermal therapy. Moreover, a tentative explanation for the growth mechanism of ALL crystals with different morphologies has been made.