A comparative study of the singlet oxygen generation capability of a zinc phthalocyanine linked to graphene quantum dots through π-π stacking and covalent conjugation when embedded in asymmetric polymer membranes

Following the establishment of graphene quantum dots as potential phthalocyanine supports in photoactive membrane preparation for phthalocyanines lacking linkage functional groups, the practical efficiency of p-p stacking versus covalent linkage was investigated. Synthesized materials were characterized using FT-IR, Raman, powder X-ray diffraction, and UVeVis spectroscopies and also by transmission electron and scanning electron microscopies. Phthalocyanine loadings onto graphene quantum dots of 0.40 mg/mg and 0.14 mg/mg (Pc mass/conjugate mass) for the p-p stacked and covalent linked conjugates respectively were observed. Covalent linkage to graphene quantum dots proved to be functionally superior to p-p linkage, where singlet oxygen quantum yield value of the phthalocyanine in the membrane for the covalent linked conjugate was approximately twice that of the p-p stacked membrane