Photostabilized Chlorophyll a in Mesoporous Silica:  Adsorption Properties and Photoreduction Activity of Chlorophyll a

• Published in: Journal of the American Chemical Society Vol. 124; no. 45; pp. 13437 - 13441
• Main Authors: Itoh, Tetsuji, Yano, Kazuhisa, Inada, Yuji, Fukushima, Yoshiaki
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 13.11.2002
• Subjects: Adsorption; Bacterial Proteins - chemistry; Biological and medical sciences; Chlorophyll - chemistry; Chlorophyll A; Drug Stability; Fundamental and applied biological sciences. Psychology; Hydrogen - chemistry; Molecular biophysics; Nitrogen - chemistry; Nuclear Magnetic Resonance, Biomolecular; Oxidation-Reduction; Paraquat - chemistry; Photochemistry - methods; Silicon Dioxide - chemistry; Spirulina; Surface properties. Adsorption; X-Ray Diffraction; Liquid solid interface; Liquid solid adsorption; Organic adsorbate; Adsorption isotherm; Cationic surfactant; Electron transfer; Inorganic adsorbent; Experimental study; Chlorophyll a; Quaternary ammonium compound; Photochemical stability; Adsorption structure; Silica gel; Aqueous solution; Ultraviolet visible spectrometry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja0203059

Chlorophyll a was adsorbed to mesoporous silica (FSM, folded-sheet mesoporous material) to form a chlorophyll−FSM conjugate, in which a nanometer-scale interaction between chlorophyll a molecules resembles a living plant leaf. The mesopores of FSM acted as nanoscale spaces not only for an interaction between chlorophyll molecules and the silica support but also for a nanoscale interaction between the absorbed chlorophyll molecules. These interactions contribute to photostability. An increase in the amount of chlorophyll adsorbed to the pores of FSM leads to an enhancement of the photostability accompanied by a shift in the absorbance maximum to a longer wavelength. The physiological function of the chlorophyll−FSM conjugate was explored as chlorophyll−FSM exhibited the photoinduced ability to catalyze the reduction of methyl viologen (an electron carrier). The evolution of hydrogen gas was observed for 14 h without deterioration when an aqueous suspension containing chlorophyll−FSM, methyl viologen, 2-mercaptoethanol (an electron donor), and platinum was illuminated with visible light.