Researchers have obtained and characterized two-dimensional (2D) boron monosulfide (BS) nanosheets. The bandgap energy of a single BS nanosheet was greater than that of the bulk material from which it came. As additional 2D layers were stacked, the bandgap energy eventually decreased to that of the bulk material. This result reflected the tunable electronic properties of BS nanosheets, which are suitable for electronic devices and photocatalytic applications.