RESUMO
Bi2Se3 attracts intensive attention as a typical thermoelectric material and a promising topological insulator material. However, previously reported Bi2Se3 nanostructures are limited to nanoribbons and smooth nanoplates. Herein, we report the synthesis of spiral Bi2Se3 nanoplates and their screw-dislocation-driven (SDD) bidirectional growth process. Typical products showed a bipyramid-like shape with two sets of centrosymmetric helical fringes on the top and bottom faces. Other evidence for the unique structure and growth mode include herringbone contours, spiral arms, and hollow cores. Through the manipulation of kinetic factors, including the precursor concentration, the pHâ value, and the amount of reductant, we were able to tune the supersaturation in the regime of SDD to layer-by-layer growth. Nanoplates with preliminary dislocations were discovered in samples with an appropriate supersaturation value and employed for investigation of the SDD growth process.
RESUMO
We report a rational design of CaHPO(4)-α-amylase hybrid nanobiocatalytic system based on allosteric effect and an explanation of the increase in catalytic activity when certain enzymes are immobilized in specific nanomaterials. Employing a calcification approach in aqueous solutions, we acquired such new nanobiocatalytic systems with three different morphologies, i.e., nanoflowers, nanoplates, and parallel hexahedrons. Through studying enzymatic performance of these systems and free α-amylase with/without Ca(2+), we demonstrated how two factors, allosteric regulation and morphology of the as-synthesized nanostructures, predominantly influence enzymatic activity. Benefiting from both the allosteric modulation and its hierarchical structure, CaHPO(4)-α-amylase hybrid nanoflowers exhibited dramatically enhanced enzymatic activity. As a bonus, the new system we devised was found to enjoy higher stability and durability than free α-amylase plus Ca(2+).