| ABSTRACT: Optically and electrically active materials, including organic dyes, fluorescent molecules, metal complexes, quantum dots (QDs) and etc., due to their excellent chemical and physical properties, have wide applications in photoelectric conversion, photocatalysis, and analytical chemistry. Dye-sensitized solar cells (DSSCs), as a type of alternative, renewable energy source, have attracted a great deal of attention because of their low production cost, environmentally friendly fabrication processes. So far, the highest achieved efficiency for DSSCs is13%which is much less that for silicon based solar cell (e. g.30%). The mismatch in the energy between the redox potential and the HOMO level of the sensitizers lowers the open-circuit voltage and consequently the conversion efficiency of the DSSC. And the recombination between electrons injected by excited dyes at the anode with the oxidized redox species prevent using electrolyte with higher energy level, compared with the normally used triiodide/iodide redox shuttle. To surmount this problem, silane-treated (coated) one-dimensional TiO2nanowire arrays as the photoanode of DSSC was proposed. The open and spatially accessible structure of the TiO2nanowire arrays would be favorable for the coating with uniform polysiloxane which could act as effective insulating layers for blocking the recombination reaction while using high-potential redox couple. Owing to their unique electrical and optical properties, QDs have been widely used to construct various sensors for inorganic ions and biomolecules. But most of those QDs-based sensors require sophisticated procedures for surface decoration, so the development of facile sensors using QDs in combination with chemical reactions is noteworthy. Colorimetric method is extremely attractive because of the convenient and direct readout for detection result. The design of novel dyes as effective colorimetric probes for various analytes has attracted enormous attentions.In this thesis, several kinds of optically, electrically active materials were designed. And their applications in DSSCs and analytical chemistry were also explored. The main contents are as follows:(1) Effective blockage of recombination electron transfer of a high reactive redox couple (Fc+/Fc) at TiO2nanowire array electrodes was achieved by silanization of the dye loaded TiO2nanowire array. FT-IR clearly showed the formation of polysiloxane network at fluorine doped tin electrodes covered with TiO2nanowire arrays and the dye molecules. Energy-dispersive X-ray spectroscopy (EDS) also reveals the presence of Si over multiple spots at the cross sections of the silanized TiO2nanowire array electrodes. As a result, a rather high open-cell voltage Voc (0.69V) and an enhanced efficiency (0.749%) for DSSC with the Fc+/Fc couple were obtained. Contrary to the passivated TiO2nanoparticle film electrodes at which a complex, biphasic dependence of electron lifetime on Voc was observed, we recorded a logarithm linear dependence of the lifetime on Voc after the silanization treatment.(2) By reducing free and/or weakly coordinated Cu2+with a Cu2+-reducing agent (ascorbic acid for example) and detecting the photoluminescence peak of Cu2S-covered CdS QDs at650nm, Cu2+concentrations ranging from1nM to1?M can be readily determined. The detection limit of0.5nM was achieved, which is at least2-3orders of magnitude lower than QD-based detection methods. Among a number of metal ions interferences, only Cu2+causes the red shift of the CdS photoluminescence. Analyses of Cu2+in a river water sample and Cu2+coordinated by amino acids and proteins in cerebrospinal fluids were performed.(3) The photoelectrochemical response at electrodes immobilized with CdS quantum dots whose surface were enriched with sulfide ions was found to change when sulfide ions are replaced by thiol-containing compounds. A sensitive photoelectrochemical method was therefore developed for selective detection of Cys. Immersion of the resultant electrode in sample solution containing a sulfhydryl compound allows the sulfide anions to be gradually replaced by the Cys. The adsorption, hence the decrease in photoelectrochemical response (photocurrent) correlates with the concentration of the Cys in solution. The dynamic range is 1-100nM and the detection limit is0.4nM.(4) A novel reversible colorimetric sensor, which based on a competitive ligation of Hg2+by thiols and thiocyanate (SCN) on the N3dye (bis(4,4'-dicarboxy-2,2'-bipyridine) dithiocyanato ruthenium (II)), was developed for the detection of Cys. First, Hg2+ions coordinated to the sulfur atom of the dyes' SCN groups, and this interaction induces a change in color from red to yellow, owing to the formation of a complex of Hg2+-N3. Then, in the presence of Cys, the red color of N3is recovered concomitantly with the dissociation of the Hg2+-N3complex, due to the extraction of Hg2+by biothiols. The dynamic range of this method is0.5-25?M and the detection limits is57nM. Furthermore, by using phosphate group-incorporated bipyridine liagand, we synthesized a water soluble ruthenium-contaning dye which was successfully used for the colorimetric detection of Hg2+in aqueous solution.(5) A naphthalimide-based azo dye (1) used as a colorimetric and ratiometric probe for the detection of CN-was synthesized by incorporating a salicylaldehyde moiety, which acts as a recognition unit, to the naphthalimido diazonium salt. Upon reacting with CN-, probe1display dramatic color changes rapidly from yellowish to red, corresponding to the absorption bands shift from408nm to497nm. The colorimetric probe allows ratiometric detection of CN-with a linear range of2-45?M and a LOD (limit of detection) of0.4?M. In the optimized H2O/DMSO (7/3, v/v) mixed solvent, probe1displays excellent selectivity for CN-over other anions. In addition,1was successfully employed to prepare the filter paper-based test strips which can be used to monitor CN-conveniently, and the discernible concentration of CN-can be as low as20?M. |
PDF Full Text Request