Precursor-ligand induced steric control over morphology in anisotropically consistent (α-quartz) GeO₂ nanomaterials and its photocatalytic potential under direct sunlight

The notable correlation between morphology and physicochemical properties of nanomaterials has called for particular attention to the synthetic methods of fine control over it. Modern theories of nucleation and crystal growth have often presented an incomplete picture of its understanding and do not apply universally. Here, we investigated a case wherein oxime-modified ligands (L)-based Ge precursors [Ge {OPrⁱ}_4-n{L}_n] were synthesized from [Ge (OPrⁱ)₄] and subjected further to hydrolysis under a sol-gel scheme. The synthesis of precursors seems to have displayed a mechanistic and thermodynamic limitation over the extent of substitution due to the steric factor of the ligands. Whereas the hydrolysis of these precursors substituted with varying sizes (steric factor) of ligand yielded spherical (20 nm), sheet (16 nm) and rod-shaped (14 nm) nano α-quartz-like GeO₂. These morphological variations and reduction in the size of NPs, on account of precursors, are understood to have arisen due to the changes in nucleation and Ostwald ripening processes coupled with the hydrolytic behavior of the precursors. The nanosheet structures of α-quartz-like GeO₂ with a band gap of 5.47eV have shown different degradation efficiency, indicating altered surface-interface with two dyes, viz. methylene orange and rhodamine 6G. This work extends the understanding of “Ge” coordination chemistry and the role of precursor assemblies in nano synthesis and application.