Behaviors photoresponsive

Within the potential range where Ru(bpy)3 remains in the aqueous phase, photocurrent responses are clearly observed with a slow rising time of the order of 10 s as shown in Fig. 14(a). According to the convention employed by these authors, positive currents correspond to the transfer of a negative charge from water to DCE. No photoresponses were observed in the absence of either the dye in the aqueous phase or TCNQ in DCE. Further analysis of the interfacial behavior of the product TCNQ revealed that the ion transfer occurred outside of the polarizable window [cf. Fig. 14(d)], confirming that these photoresponses are not affected by coupled ion-transfer processes. An earlier report also showed photoeffects for the photoreduction of the viologen under similar conditions [131]. 

Figure 11.17 Aggregation behavior and photoresponsive properties of an amphiphilic azobenzene dendrimer.

Figure 11.44 (Left) Structures of photoresponsive poly(propylene imine) dendrimers. (Right) The isomerization behavior of pahnitoyl-functionalized amphiphilic dendrimers at the water surface.

Zhang W, Xie J, Yang Z, Shi W. Aggregation behaviors and photoresponsive properties of azobenzene constructed phosphate dendrimers. Polymer 2007 48 4466-4481. 

Chirality of derivatized cyclodextrin was used for recognition of stereoisomers. Phenylazobenzoyl modified y-cyclodextrin was anchored onto silica gel used as stationary phase in HPLC and photoresponsive chromatographic behavior of dansyl amino acid enantiomers was studied [64],... 

The introduction of azobenzene units into the side chains of poly(L-lysine) has been achieved be means of various procedures and different azo reagents. The polymers described initially contained azobenzene units linked to the lysine side chains by means of an amide moiety 29-311 (Scheme 4, Structure V). More recently, Fissi et al. 321 have described azo-modified poly(L-lysine) in which the azobenzene units are linked to the Lys side chains by means of a sulfonamide function (Scheme 4, Structure VI). The two families of azo-modified poly(L-lysine) have been found to exhibit completely different conformational and photoresponsive behavior. 

Quite interesting photoresponsive behavior was observed when spiropyran-modified poly(L-glutamate) was dissolved in HFP and a small amount of trifluoroacetic acid... 

Fig. 18 Schematic illustration of the preparation and photoresponsive behavior of the polypeptide XXIII, consisting oftwo amphiphilic helical rods linked by an azobenzene unit, a) Selective saponification of COOCH3 side...

More recently, Sugiura et al.11 developed a fully functional microvalve based on this photoresponsive behavior, which was composed of poly(/V-isopropylacrylamide) functionalized with the chromophore spirobenzopyran (pSPNIPAAm). The microvalve was fabricated in a polydimethylsiloxane (PDMS) microchannel by in situ photopolymerization. Blue light irradiation (18 to 30 s) to the gel induced photoisomerization of the spirobenzopyran chromophore which resulted in shrinkage due to dehydration of the gel, thus causing the microvalves to open, as seen in Figure 23.7. In this example, localized irradiation enabled independent control of three photoresponsive polymer gel microvalves, which had been fabricated on a single microchip. 

However, most of these attempts were found unsuccessful. This is mainly due to the fact that the mechanisms and processes responsible for the low photoresponse of hematite are far from being clearly understood. A deeper understanding of the semiconducting properties of this material is needed, such as its surface structure and a better description of the hematite/electrolyte interface. Extensive knowledge is also required to understand the photoelectro- chemical behavior of hematite and the kinetics involved in the photo-oxidation of water. Finally, for effective oxidation of water an efficient catalyst must most probably be coated onto the surface of hematite. 

The photoinduced discharge (PID) will be discussed within the framework of evaluating the photoresponse of a-Si H photoreceptor. The results of the study for the fast PID behavior lead us to conclude that the surface of a-Si H has significant influence either on the photoresponse or on the image quality. A typical device structure will be proposed for practical use. 

Kikuchi, H., Kitano, M., Takeuchi, M., Matsuoka, M., Anpo, M. and Kamat, P. V. (2006). Extending the photoresponse of Ti02 to the visible light region Photoelectrochemical behavior of Ti02 thin films prepared by the radio frequency magnetron sputtering deposition method. J. Phys. Chem. B 110(11), 5537-5541. 

Two kinds of photoresponsive azobenzene polyurethane functionalized multiwalled carbon nanotube (AzoPU-MWNT) composites were synthesized by in-situ polycondensation (50). Core-shell structures with MWNTs as hard core and polymer layer as soft shell were formed and the average thickness of the grafted polymers was about 7-10 nm. The AzoPU-MWNT composites showed reversible photoisomerism behavior. 

Anomalous Photoresponse of n-Ti02 Electrode in a Photo-electrochemical Cell The behavior of surface states at the TiCh-electrolyte interface is focus of this study. 240... 

Two extremes of Eq. (11) are of interest in considering the behavior following the instantaneous response. If the hole density at the surface (poe ° or pje 1 in the two conditions) is very small compared to the bulk donor density, Njj, then Y0 is equal to Yj and Ac is close to zero, i. e., there is no instantaneous photoresponse. On the other hand, if the hole density at the surface is large compared to the bulk donor density (and Pj still small compared to Np), then the instantaneous photovoltage is given by... 

The kinetic analysis presented in Section 1.2.2.1 should result in a first order of the reaction when all photoresponsive units are equivalent (uniform reaction). This is generally the case in homogeneous solution, but it may be different in solid matrices, especially if these consist of different molecular components, and even more so if there is some kind of complexing of the photoresponsive and a matrix molecule. Then there may be nonequivalent sites that influence the absorption coefficient and/or the quantum yield of the photoresponsive unit. This leads to deviations from the first order behavior. 

This section dealt with the novel functionality of a photoresponsive monolayer to carry out the displacement of liquids simply by photoirradiation as a result of the photocontrol of surface energy. Self-assembled monolayers of CRA-CM are designed and fabricated to ensure sufficient /Z photoisomerizability even in densely packed monomolecular layers, which are quite stable toward solvent treatments. The following critical condition should be met in order to realize the surface-mediated photomanipulation of liquid motion 0 ec < adv In this context, contact-angle hysteresis plays an essential role in this kind of dynamic behavior of liquid displacement. 

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