The biggest challenge in the field of low-dimensional nanomaterials towards practical applications is scalable production with structural uniformity. As the size of materials is getting smaller, their tendency of the structure-dependent properties which directly affects device reliability of largescale applications is getting stronger due to quantum confinement effects. For example, one-dimensional (1D) carbon nanotubes have various electrical/optical properties based on their structures (e.g., diameter, chirality, etc.). Likewise, two-dimensional (2D) layered materials also exhibit different properties based on their thickness. To overcome such structural heterogeneity, isopycnic density gradient ultracentrifugation (i-DGU) will be introduced to achieve monodispersity of nanomaterials in structure based on their buoyant density differentiations. The i-DGU approach enables to sort 1D carbon nanotubes and 2D layered materials such as graphene, transition metal dichalcogenides, hexagonal boron nitride with high structural purity based on their structure. Various largescale optoelectronic applications, electrically driven light emitters and photodetectors demonstrated based on the monodisperse nanomaterials will be discussed.