Pressure tuned photoluminescence and band gap in two-dimensional layered g-C3N4: the effect of interlayer interactions.

We show that the photoluminescence (PL) emission color of few layered g-C3N4 (FL-CN) can be tuned from blue to yellow by applying pressure. FL-CN also exhibits an anomalous PL enhancement and obvious change in the light absorption at very low pressure. Further studies reveal that the increase of pressure-induced interlayer interactions affects the charge separation of photo-induced electrons and holes and thus leads to PL enhancement. An obvious decrease in interlayer compressibility probably due to interlayer stacking transition in FL-CN has been observed at above 3 GPa, which becomes less compressible than that of graphite, accompanied by obvious PL intensity weakening and emission band broadening. The results suggest that interlayer interactions may play dominant roles in the optical properties of FL-CN, shedding new insights into our understanding on PL engineering in g-C3N4.