sp 2/sp 3 bonding ratio dependence of the band-gap in graphene oxide

Although the band-gap in pure graphene is zero, the oxygenated graphene could have a considerable band-gap. The D/G peak intensity ratio is known as a measure of the size of sp3∕sp2 domains in graphene oxide (GO) sheets and determines the band-gap in GO sheets. Characterization results showed that the photoluminescence (PL) spectra of GO suspensions has a peak at ~604 nm and also the I(D)/I(G) intensity ratio of GO suspensions is 1.73. After reduction, a redshift appeared at PL spectrum (at 650 nm) and the I(D)/I(G) intensity ratio decrease to 1.26. Our results showed that the band-gap in GO is related to the I(D)/I(G) intensity ratio of GO suspensions and offers a mechanism for measuring the band gap according to Raman spectra. Moreover, GO is fluorescent over a broad range of wavelengths and can be used in the biological application.Graphical abstract