Stability of colloidal solutions containing various surface-modified cadmium sulfide particles under stationary illumination

Influences of proton-dissociation equilibrium of capping agents on the photo-chemical events of the colloidal solutions containing the thiol-capped cadmium sulfide particles

“…The transient absorption spectrum of MA-CdS colloidal solution grew within the duration of a pump pulse (ca. <1 ps) over whole monitoring wavelength region as shown in the inset as an example and showed a very broad spectral shape with its absorption maximum around 700 nm, as well as that of TG-CdS colloidal solution already reported [26,27]. And further its spectral shape hardly changed, even if pH of the colloidal solution was changed.…”

“…The colloidal solutions were usually circulated between a non-fluorescent quartz cell (2 mm in pass length) and a sample reservoir by a roller pump during the measurements to avoid the damage from the pump pulse though ordinary quartz cells (2 mm in pass length) were also used for some of the measurements. Other details for the measurements of the transient absorption and data processing were described elsewhere [25][26][27].…”

“…The relative change of absorbance that reflects the dissociation and the aggregation of CdS particles was used for the discussion of the photo-stability of the CdS colloidal solutions. Other experimental details were described elsewhere [30].…”

“…On the other hand, for aqueous colloidal solutions containing the surface-modified CdS particles such as MA-CdS and TG-CdS, we have already reported their photo-stability as follows [30]. The capping agent that covers the surface of CdS particles can sufficiently compete with CdS itself (Eq.…”

“…As there is possibility that the capping agents on the surface of the particles act as a relay for the transfer of the photo-generated electrons and holes to reactants locating nearby, it may be meaningful to investigate the role of the capping agent on the primary photo-chemical events of the particles in order to design effective photo-catalysts. For this reason, we have studied the behavior of electrons and holes photo-generated on CdS nanoparticles with the surface modified by capping agents such as thiols, which governs the efficiency of photo-catalytic reactions, from the analysis of their time-resolved transient absorption spectra measured by pump-probe techniques [23][24][25][26][27].…”