Probing the origin of fluorescence quenching of a graphene-porphyrin hybrid material Divya Sharma, Xiaoyan Zhang, Ben L. Feringa, Wesley R. Browne, Jennifer L. Herek and Annemarie Huijser EPJ Web of Conferences, 41 (2013) 04027 Published online: 13 March 2013 DOI: 10.1051/epjconf/20134104027