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Abstract
Noncovalent modification plays a key role in surface modification of allotropes of nanocarbon family owing to its unique characteristic of non-disruption of materials' surface conjugate system. This thesis introduces noncovalent functionalization on the surface of highly oriented pyrolytic graphite (HOPG) and reduced graphene oxide (rGO) from pyrene derivatives. 1-bromomethylpyrene, 1-bromopyrene, 1-fluoropyrene, 1-pyrenebutyrate, 1-pyrene carboxylic acid and 1-aminopyrene were selected to modify HOPG due to the difference of the charge and polarity of the molecules. The surface functionalization of rGO in suspension was carried out by 1-pyrene carboxylic acid and polyaniline (PANI). Atomic-force microscopy and X-ray photoelectron spectroscopy were used to confirm the successful assembly (i.e. π-π stacking) of pyrene derivatives on HOPG. The affinity of pyrene derivatives to HOPG depends strongly on the functional groups of the pyrene molecules in the order of –NH2, –(CH2)3COOH, –COOH , –CH2–Br, –Br, and –F. the pyrene with amino groups revealed highest affinity. Most of pyrene derivative molecules were mono-dispersed on HOPG. However, the stacking of 1 to 2 layers was also observed. This stacking phenomenon is ascribed to the effect of HOPG due to the fact that the absorption spectra of the pyrene derivative solution indicated the molecules are better stabilized in polar solvent. The synergistic effects of mixed pyrene molecules (with two different pyrene derivative molecules) were also investigated. For 1-pyrene carboxylic acid and PANI modified rGO, electrochemical characterization successively proved the assembly of PANI layer on rGO. To further confirm the successful functionalization of rGO and to investigate its extending optical application, carbon nitride (C3N4) nanosheets and CdTe quantum dots (QDs) were used for the decoration of PANI and carboxyl group modified rGO. The heterostructures of rGO-based CdTe QDs composite material and C3N4 composites were fabricated through controlling cross linker molecules--1-pyrene carboxylic acid and PANI. Both quantum dots and carbon nitride were monodispersed on the modified rGO surface. The carbon nitride composite material revealed enhanced conductive property and photocatalytic property. Change in photoluminescence properties of the QDs was observed in the composite material as a result of charge separation and recombination control.