Optimization of quantum yield of highly luminescent graphene oxide quantum dots and their application in resistive memory devices

Abstract

A facile chemical method of acid treatment has been followed for the cutting of graphene oxides sheet to extract graphene oxide quantum dots (GOQDs) in aqueous medium at different pH. Strong blue emission and excitation dependent photoluminescence (PL) spectrum are observed in GOQDs. Relative PL quantum yield is measured as high as ∼30% for the GOQDs synthesized at pH11. Presence of defect related states and oxygen containing functional groups in GOQDs are confirmed through Raman and Fourier transform infrared analysis, respectively. High resolution transmission electron microscopy analysis suggests that the sizes of GOQDs are distributed in the range ∼2.0–8.0 nm with d-spacing of 0.245 nm. AFM measurement confirms the topography height of GOQDs in the range ∼6.0–9.0 nm. Synthesized GOQDs at different pH are dispersed in poly (vinyl alcohol) (PVA) matrix and spin coated to fabricate polymer nanocomposites (PNCs) devices. Electrical studies have been performed which display write-once-read-many characteristics and the set voltage () increases with the increase in pH of the GOQDs. Very low ∼−0.9 V and ∼104 have been obtained for the device containing GOQDs synthesized at pH1. Retention tests up to 104 s are performed for the PNCs devices in order to confirm the stability. A suitable energy band diagram is proposed to discuss the carrier transport through the composites devices.