Abstract
Nanoscale phosphorene quantum dots (PQDs) with few-layer structures were fabricated by pulsed laser ablation of a bulk black phosphorus target in diethyl ether. An intense and stable photoluminescence (PL) emission of the PQDs in the blue-violet wavelength region is clearly observed for the first time, which is attributed to electronic transitions from the lowest unoccupied molecular orbital (LUMO) to the highest occupied molecular orbital (HOMO) and occupied molecular orbitals below the HOMO (H-1, H-2), respectively. Surprisingly, the PL emission peak positions of the PQDs are not red-shifted with progressively longer excitation wavelengths, which is in contrast to the cases of graphene and molybdenum disulphide quantum dots. This excitation wavelength-independence is derived from the saturated passivation on the periphery and surfaces of the PQDs by large numbers of electron-donating functional groups which cause the electron density on the PQDs to be dramatically increased and the band gap to be insensitive to the quantum size effect in the PQDs. This work suggests that PQDs with intense, stable and excitation wavelength-independent PL emission in the blue-violet region have a potential application as semiconductor-based blue-violet light irradiation sources.
Highlights
In this work, the phosphorene quantum dots (PQDs) samples were synthesized by pulsed laser ablation of a bulk black phosphorus target in diethyl ether
It is noted that the PL emission peak positions of the PQDs are not red-shifted with the increase of excitation wavelengths, which is in contrast to the cases of graphene and molybdenum disulphide quantum dots
Nanoscale PQDs with few-layer structure were fabricated by pulsed laser ablation of a bulk black phosphorus crystal
Summary
The PQD samples were synthesized by pulsed laser ablation of a bulk black phosphorus target in diethyl ether. Because of the activity of black phosphorus, the periphery and surfaces of the PQDs are saturatedly passivated by substituents from cracked diethyl ether by laser ablation. This leads to the dramatic increase of the electron density on the periphery and surfaces of the PQDs. This leads to the dramatic increase of the electron density on the periphery and surfaces of the PQDs This causes the band gap of the PQDs to be relatively insensitive to the quantum size effect[12,25]. PQDs with intense, stable and excitation wavelength-independent PL emission in blue-violet region have a potential application as semiconductor-based blue-violet light irradiation sources
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