Effect of Fullerene on Photocurrent Performance of 6‐O‐Porphyrin‐2,3‐di‐O‐stearoylcellulose Langmuir‐Blodgett Films

Abstract

Thin films consisting of 6‐O‐porphyrin‐2,3‐di‐O‐stearoylcellulose (H2PCS) and fullerene (C60) were fabricated for anodic photocurrent generation systems by the Langmuir‐Blodgett (LB) technique. The π‐complexation between the porphyrin moiety and C60 in the LB films was investigated by means of the surface pressure (π)‐area (A) isotherms, UV‐vis, and fluorescence spectroscopy. The photocurrent density generated from the H2PCS–C60 LB monolayer films exhibited an increase with increasing the C60 proportion and reached a maximum at a mixing ratio of 1:2, yielding a quantum yield of 12.5% and an IPCE (incident photon‐to‐current efficiency) of 0.50% at a bias potential of +100 mV vs. SCE. Furthermore, the LB five‐layer films could give rise to the IPCE value of 1.5% at +100 mV without significant decline of the quantum yields, which was due to the function of C60 as an electron carrier to improve the interlayer electron transfer through each layer. These results have demonstrated a promising method for preparing the donor–acceptor systems using cellulose as a scaffold in the LB films.magnified image

Self-Organized Porphyrinic Materials

“…This assembly is interesting because the scaffold can be immobilized onto gold surface through a thio-terminated linker to create a functionalized electrode for photoelectrochemical applications. In another report, porphyrins have been attached to a cellulose motif designed to encapsulate C 60 , and the films of this material fabricated by a LB technique exhibited photo-currents 289. Mixtures of C 60 with simple tetraphenylporphyrins, and those appended with long alkyl chains, cast on ITO surfaces do not form films and often separate into the two components because the π-π interactions are insufficient to maintain an organized structure.…”

Photoactive polysaccharides

“…The chromophores are spaced at a fixed distance using cellulose with its rigid structure and thus the photocurrent quantum yields for the LB films are increased (Sakakibara & Nakatsubo, 2008b). A further improvement of photocurrent performance was obtained by the incorporation of fullerene (C60) in porphyrin-cellulose films (Sakakibara & Nakatsubo, 2008a).…”

Effect of Central Metals in the Porphyrin Ring on Photocurrent Performance of Cellulose Langmuir‐Blodgett Films

“…ZnPCS [7] : To a solution of H 2 PCS (9.0 mg, 5.9 mmol based on porphyrin moiety) in CH 2 Cl 2 (2 mL), zinc(II) acetate (20 mg, excess) in MeOH (1 mL) was added. The reaction mixture was stirred under light shielding overnight and then treated with the same work-up procedure as MgPCS to give ZnPCS (6.0 mg, 64%).…”

“…The uniform and well‐defined structure affords precise control of the positioning of porphyrins attached to cellulose scaffold, mimicking the array of natural photosynthetic light‐harvesting systems. In addition, we have recently reported the fabrication of mixed LB films of H 2 PCS and fullerene C 60 and found that the photocurrent quantum yield was rather improved because of the complexation of C 60 with the porphyrin moieties attached to rigid cellulose scaffold 7…”

“…In addition, we have recently reported the fabrication of mixed LB films of H 2 PCS and fullerene C 60 and found that the photocurrent quantum yield was rather improved because of the complexation of C 60 with the porphyrin moieties attached to rigid cellulose scaffold. [7] Several factors are known to affect photocurrent performance in porphyrin LB films: side chain structure [8] and length of peripheral alkyl chain. [9] Additionally, another factor is central metal ion in porphyrin ring.…”