Hydrothermal synthesis of novel two-dimensional ?-quartz nanoplates and their applications in energy-saving, high-efficiency, microalgal biorefineries

A facile template-free hydrothermal method was successfully developed for the controlled synthesis of ultrathin ?-quartz nanoplates (NPLs) for the first time. Analyses of the ?-quartz NPLs revealed the characteristic anisotropic nanostructures of highly crystalline ?-quartz with an average lateral size and thickness of 1.14 ? 0.32 ?m and 7.7 ? 0.6 nm, respectively. Importantly, efficient extraction of highly valuable chemicals such as astaxanthin (ATX) from the microalgal cells of Haematococcus pluvialis (H. pluvialis) was accomplished by lacerating the cell walls using the ultrathin ?-quartz NPLs under mild ultrasonication. The incorporation of ?-quartz NPLs enhanced the ATX extraction efficiency significantly (99%, 18.0 ? 0.6 mg ATX/g cell) when coupled with 5 min of ultrasonication. The dosage of ?-quartz NPLs (800.0 mg/L) for maximum ATX extraction was reduced substantially to only 8% of the nanomaterial dose used in the extraction controls. The enhanced extraction efficiency and dosage were explained by the role of the structural anisotropy of ?-quartz NPLs in multiple phase separationextraction processes. This work provides a novel, facile, and economical route for the synthesis of uniform ultrathin nanoplates, offering a new material for the highly efficient harvesting of chemical products from various microalgal biorefinery processes.