Fabrication and chemical modification of carbon nanodots/monolayer hexagonal boron nitride/substrate heterostructures and their terahertz optoelectronic properties

•Carbon nanodots (CNDs)/monolayer (ML) hBN/substrate based van der Waals heterostructures are fabricated for the first time.•The problem of agglomeration of dried CNDs on a dielectric substrate can be solved by placing ML-hBN in the heterostructure.•Chemical modification, such as the formation of O- and N-based bonds and functional groups on CNDs, can affect and modify strongly the electronic and optoelectronic properties of CNDs.•Terahertz time-domain spectroscopy is applied for the first time to study the optoelectronic properties of CNDs/ML-hBN/sapphire based heterostructures.