Graphene Oxide as a Template for Nb₂O₅ Nanosheets: Linking Advanced Morphology to Biocompatibility

The development of synthesis strategies capable of controlling the morphology and surface properties of metal oxide nanostructures remains essential for expanding their technological and biomedical applications. Two-dimensional carbon-based materials, such as graphene oxide (GO), have been explored as structural templates due to their oxygenated functional groups and ability to direct heterogeneous nucleation. However, the cytotoxicity and biocompatibility of nanomaterials are governed by multiple interconnected factors, including specific surface area, nanosheet thickness, morphology, surface chemistry, aggregation state, synthesis route, and residual species. In this work, GO synthesized by a modified Hummers’ method was used as a template for the preparation of Nb₂O₅ nanosheets and compared with Nb₂O₅ obtained by a microwave-assisted solvothermal route without a template. The samples were evaluated using XRD, SEM, TEM, EDS, XPS, UV-Vis spectroscopy, BET analysis, and MTT cytotoxicity assays. The GO-templated route promoted the formation of more homogeneous, ultrathin, and structurally organized Nb₂O₅ nanosheets, with a higher specific surface area of 115.7 m²/g compared with 55.8 m²/g for the non-templated sample. XPS confirmed the predominance of Nb⁵⁺ in both materials, while slight differences in the Nb 3d region suggest changes in the surface chemical environment induced by the GO template. Despite the higher surface area, both Nb₂O₅ samples maintained cell viability above 70% under the tested concentrations and exposure times. This behavior suggests that the biological response was not governed by surface area alone, but by the combined influence of nanosheet thickness, morphology, aggregation state, crystallinity, and surface chemistry. These results indicate that GO-assisted synthesis improves the morphological and textural properties of Nb₂O₅ nanosheets while maintaining an acceptable in vitro cytocompatibility profile.