Defect-Based Modulation of Optoelectronic Properties for Biofunctionalized Hexagonal Boron Nitride Nanosheets.

Defect engineering potentially allows for dramatic tuning of the optoelectronic properties of two-dimensional materials. With the help of DFT calculations, a systematic study of DNA nucleobases adsorbed on hexagonal boron-nitride nanoflakes (h-BNNFs) with boron (V ) and nitrogen (V ) monovacancies is presented. The presence of V and V defects increases the binding strength of nucleobases by 9 and 34 kcal mol , respectively (h-BNNF-V >h-BNNF-V >h-BNNF). A more negative electrostatic potential at the V site makes the h-BNNF-V surface more reactive than that of h-BNNF-V , enabling H-bonding interactions with nucleobases. This binding energy difference affects the recovery time-a significant factor for developing DNA biosensors-of the surfaces in the order h-BNNF-V >h-BNNF-V >h-BNNF. The presence of V and V defect sites increases the electrical conductivity of the h-BNNF surface, V defects being more favorable than V sites. The blueshift of absorption peaks of the h-BNNF-V -nucleobase complexes, in contrast to the redshift observed for h-BNNF-V -nucleobase complexes, is attributed to their observed differences in binding energies, the HOMO-LUMO energy gap and other optoelectronic properties. Time-dependent DFT calculations reveal that the monovacant boron-nitride-sheet-nucleobase composites absorb visible light in the range 300-800 nm, thus making them suitable for light-emitting devices and sensing nucleobases in the visible region.