Photoinduced Acceleration of the Effluent Rate of Developing Solvents in Azobenzene-Tethered Silica Gel

Abstract

The switching of a molecular length of azobenzene between its trans and cis forms by photoirradiation originates various photoresponsive systems in the molecular level and/or nanolevel. Recently, we and another group separately reported that some azobenzene-modified mesoporous silicas remarkably promote the release of molecules from the inside of the mesopore to the outside, when the lights, both UV and visible lights, were irradiated simultaneously. In these cases, the release rates of molecules were enhanced by the impeller-like effect of molecular motion of azobenzene moiety attributed to the continuous photoisomerization between the trans and cis isomers. This paper presents that azobenzene-substituent-tethered amorphous silica gel could promote the development of solvents in chromatography systems by photoirradiation. In column chromatography system where azobenzene-tethered silica gel was packed, the irradiation of both UV and visible lights increased the effluent rate of the developing solvents. The single irradiation of UV light scarcely enhanced the rate, while the visible light irradiation longer than 400 nm in wavelength also accelerated the development of the solvent moderately. The same kinds of phenomena were observed when this photopromoted chromatography system was applied to thin layer chromatography (TLC). Hydrocarbon developing solvents in the regions, where UV and visible lights were irradiated, moved up the TLC plate higher than those without photoirradiation. When the pyrene solution in the developing solvent was utilized in the chromatography systems, the similar photoacceleration of pyrene development was observed at the same level as the developing solvents.

Direct Observation of a Dark State in the Photocycle of a Light-Driven Molecular Motor

“…12−27 Indeed, E – Z isomerization results in large amplitude changes in structure as well as chemical and physical properties. 28−32 …”

Photo Induced Membrane Separation for Water Purification and Desalination Using Azobenzene Modified Anodized Alumina Membranes

“…[9][10][11][12][13][14][15] On the other hand, we reported before that the structural changes of the organic substituents loaded into nanosized pore voids effectively control the movements of molecules inside the nanopores. [18][19][20][21][22] Especially, the simultaneous irradiation of UV and visible lights to grafted azobenzene substituents induces its consecutive motion between the trans and cis isomers to accelerate the release of molecules from mesoporous silica 20 and to increase the flow rate of the organic solvents in silica gel column. 21 These results suggest us to apply the azobenzene isomerization technique to membrane separation.…”

“…[18][19][20][21][22] Especially, the simultaneous irradiation of UV and visible lights to grafted azobenzene substituents induces its consecutive motion between the trans and cis isomers to accelerate the release of molecules from mesoporous silica 20 and to increase the flow rate of the organic solvents in silica gel column. 21 These results suggest us to apply the azobenzene isomerization technique to membrane separation. Anodized alumina membranes are thin porous alumina membranes with ordered nanopore arrays prepared electrochemically from aluminum metal, which are expected to contribute new technologies of 4 water treatment.…”

Photosensitizer anchored gold nanorods for targeted combinational photothermal and photodynamic therapy

“…18 ZnPc-Si in anhydrous dimethylformamide (DMF) solution was directly used to graft onto the silica coated AuNR (AuNR-Si) using a method similar to one that was previously reported. 25 Since hyaluronic acid (HA) could target over-expressed CD44 receptors of many cancer cell lines often involved in metastasis, 26 and also provide the hydrophilicity to improve the dispersity of the functionalized AuNR in water, it was integrated through electrostatic interaction as the last step to yield the final hybrid 711-AuNR-Si-ZnPc-HA (see Fig. 1a).…”