Synthetic Architecture of Multiple Core-Shell and Yolk-Shell Structures of (Cu2O@)nCu2O (n=1-4) with Centricity and Eccentricity

In this work, we describe a seed-mediated approach with successive Ostwald ripening to synthesize various multiple-shell core-shell and yolk-shell structures of (Cu2O@)(n)-Cu2O (n = 1-4). In particular, the structure formed in a previous step can serve as a newer-generation seed for a subsequent shell growth; a total of 20 representative structures have been thus synthesized in a step-by-step manner. With an increase in shell number n, in principle, 2(n) shelled products can be fabricated, taking into account the centricity and eccentricity in their geometric symmetry. Synthetic chemistry and functions of chemical additives have also been investigated to explain the formation mechanism and to ensure the uniformity of the product. It has been found that symmetric or asymmetric Ostwald ripening during the hollowing process can be manipulated by controlling stirring conditions. Furthermore, optical properties of the resultant samples can be closely related to structural aspects of the products, such as the overall size, the thickness of shells, the number of shells, and, importantly, the centricity and eccentricity in the final products. To test their applicability, we have also studied the electrocatalytic properties of these complex structures in nonenzymatic glucose sensing. Quite encouragingly, (Cu2O@)Cu2O samples have shown an improved sensitivity as the number of thin shells increased.