Preparation And Photoelectric Properties Of Photosensitizers And Graphene Oxide Multilayer Films

Layer-by-layer (LBL) self-assembly technique has many advantages such as the experimental simplicity, versatility, as well as the possibility to control film thickness and architecture at molecular scale. Graphene oxide (GO) is an outstanding carbon m aterial possessing unique two dimensional (2D) structures and excellent optical, electr onic and magnetic properties. Organic cations can be absorbed on the surface of GO b ecause the surface of GO sheets is negatively charged its. In this work, multilayer fil ms were fabricated using graphene oxide and cationic photosensitizers through LBL t echnique and their photoelectric properties were investigated.Multilayer films (GO/RuL)n (n=1～8, RuL=[Ru(bpy)2L]Cl2, L=[(2,2’-bipyridyl)-4-diazo]-2-naphthanol) were prepared by LBL self-assembly technique using GO and complex [Ru(bpy)2L]Cl2 (RuL, L=[(2,2’-bipyridyl)-4-diazo]-2-naphthanol) on FTO and quartz glasses respectively. Their structures were characterized by X-ray photoelectron spectroscopy (XPS), UV-vis absorption spectroscopy, scanning electron microscopy(SEM) and Cyclic voltammetry(CV). The MLCT band of RuL in the multilayer film was found to be red shifted by 15 nm compared to that of the complex in water, indicating that not only electrostatic attraction but also strong π-π interaction existed between GO and RuL. The photocurrent respond measurement showed that the four-layer film (GO/RuL)4 exhibited a large photocurrent density of 2.2 μA/cm2, while the photocurrent gradually decreased with the raising of the layer number. The mechanism of generated photocurrents were determined by changing the bias voltage, adding the electron donor or acceptor.In order to realize full light absorption in visible range and reduce the cost of the films, two photosensitizers without noble metals and with different absorption ranges, cationic phthalocyanine ImZnPc and rhodamine B (RhB) were used to fabricated LBL films with GO and (GO/ImZnPc/G0/RhB)n film (n=1～6) were obtained on the FTO and quartz glasses respectively. Their structures were characterized by UV-vis and SEM. Two-layer film FTO/(GO/ImZnPc/GO/RhB)2 gave a large photocurrent density of 3.0 pA/cm2. The mechanism of the generated photocurrent were determined by changing the bias voltage, adding the electron donor or acceptor.