Devising a universal tailored monomer molecular strategy for SiO_x/carbon hollow spheres as a synergistic electrocatalyst in azathioprine sensing

Designing hollow spheres (HS) structures of polymer materials with uniformly dispersed SiO_x and surface attributes is currently attracting much attention due to their vital roles in catalysis and energy storage applications. Instances of their compilation exist, but such morphological scaffolds require easy yet versatile conceptual approaches. Despite the easy yet controllable assembly of uniformly adorned SiO_x and carbon HS (C-HS), producing copious voids simultaneously through a one-step reaction still remains a major challenge. In this study, an ultrafast additive and template-free molecular polymerization strategy were designed to fabricate uniformly dispersed SiO_x/C-HS for electrocatalysis. Dual-aldehydes and (3-aminopropyl)triethoxysilane (APTES) were judiciously designed as C and silicon precursors to yield the polymer HS (P-HS) via a simple one-step aldimine condensation. Two different P-HS morphologies were obtained utilizing glyoxal (GL) and glutaraldehyde (GA) as the cross-linkers, proving the great tunability of the methodology. Prominently, in situ carbonization of the P-HS guarantees the uniform integration of SiO_x in C-HS at a nanoscale range. As an example of the application of the synthesized P-HS and SiO_x/C-HS, the electrochemical performance for azathioprine (AZP) detection was tested. Benefiting from high conductivity, large surface area, and fast electron transfer due to the well-dispersed SiO_x in the C-HS substrate surface, the resultant SiO_x/C-GA modified electrode showed a low limit of detection (2.26 nM), high sensitivity (4.26 μA μM^-1cm^-2) and good repeatability and reproducibility for AZP detection. Detection was also validated in actual samples. The strategy adopted, not only implements Si-based C-HS composites as efficient and scalable electrode materials but also paves the way toward a new platform for the synthesis of additive and template-free HS.