Tetrachloroperylene diimide functionalized reduced graphene oxide sheets and their I-V behavior by current sensing atomic force microscopy

Reduced graphene oxide (rGO) sheets covalently functionalized with n-type tetrachloroperylene diimide (PDI) and oligomeric PDI have been prepared by a two-step approach. Firstly, graphene oxide (GO) was modified by an amidation reaction with 3-aminopropyldimethylethoxylsilane or 3-aminopropyldiethoxylmethylsilane, during which GO was reduced thermally. They then react with the silanol modified PDI by dehydration condensation to obtain PDI and oligomeric PDI modified rGO (rGO-PDI and rGO-(PDI)(n)). The successful preparation of rGO-PDI and rGO-(PDI)(n) were confirmed by FTIR, Raman, X-ray photoelectron spectroscopy and XRD. The morphologies of rGO-PDI and rGO-(PDI)(n) sheets were studied using AFM. It was found that surface morphologies and height of rGO-PDI and rGO-(PDI)(n) sheets are dependent on the solvents used for casting due to differences in the solubility of PDI. Moreover, the fluorescence emission spectrum of rGO-PDI and rGO-(PDI)(n) shows strong fluorescence quenching and blue shift, especially in ethanol. Current sensing atomic force microscopy (CSAFM) indicated that the rGO-PDI composite shows quite different electric conductivity and optical properties with grafting efficiency and different solvents used for casting. Significantly, the electronic conductivity of rGO-(PDI)(n) increased by 2-3 orders of magnitude compared to rGO-PDI.