This dissertation focuses on fine tuning of the sensing properties of fluorescent conjugated polyelectrolytes via multidentate design. The molecular assembly approach of integrating the conjugated backbones and receptor units has been applied to create sensitive and selective polymeric sensory systems. The synthesis and sensing performance of the polyelectrolytes are presented to illustrate the structure-function relationship of the newly generated sensor probes.

The conjugated polyelectrolyte ttp-PPESO3 was designed by rationally assembling the terpyridine receptor and sulfonate ionic group onto the PPETE backbone. The polyelectrolyte exhibited high selectivity to copper(II) cations as demonstrated by the significant fluorescence quenching. The detection limit for Cu2+ was determined to be 0.93 ppb. This sensing behavior resulted from the non-radiative decay upon binding to copper. Computational studies suggested that the ttp-PPESO3/Cu binding event occurred through a coordination between the terpyridine receptor and the sulfonate group. The additional dentate from the sulfonate significantly enhanced the chelating ability of the sensor toward copper cations.

The copper screening experiments were performed in vitro biological systems using the ttp-PPESO3 sensor probe. At physiological conditions, the polyelectrolyte was able to detect free Cu ions from the source of CuCl 2 as evidenced by the progressive fluorescence quenching. Once copper was bound to high molecular weight ligands, such as albumin, or low molecular weight ligand like histidine, it appeared to cause a delayed response in fluorescence quenching. The difference in copper binding affinity might result from the environmental changes of the terpyridine receptor in the sensor.

Incorporation of versatile urea receptor moieties to polymer molecular-wire systems has been achieved for simultaneous determination of multiple analytes. The urea-PPESO3 polyelectrolyte revealed selective detection of Hg2+, Cu2+ and Pb2+ ions among the 15 cations. The detection limits for mercury, copper, and lead cations were 0.33 ppb, 0.31 ppb, and 1.42 ppb, respectively. Computational simulations suggested that the binding occurred through the two amino groups on the urea receptor. The urea moiety bound to the metal analyte and resulted in fluorescence quenching via photoinduced electron transfer. Lastly, recovery studies showed that the urea-PPESO3 sensory material could be potentially utilized to detect the metals in aqueous environment.

Effective approaches for processing cyanine and rhodamine dyes were developed to tune their photophysical behaviors. Three methods were discovered that would quench the fluorescence of cyanine dyes. First, incorporation of heavy groups like iodine atoms into the cyanine structure. Second, interaction with gold nanoparticles leads to the formation of gold-dye J-aggregates. Third, addition of graphene nanomaterials will also quench cyanine dyes. In addition, the rhodamine dye 575 has been confirmed to exist in two isomer states: the zwitterion and the lactone. Efficient pathways for converting the zwitterion isomer to the lactone have been identified to improve lasing capacity of the rhodamine materials.