This dissertation describes the advantages and feasibility of newly synthesized near-infrared (NIR) bis-heptamethine cyanine (BHmC) dyes for non-covalent labeling schemes. The NIR BHmCs were synthesized for biomolecule assay. The advantages of NIR BHmCs for biomolecule labeling and the instrumental advantages of the near-infrared region are also demonstrated. Chapter 1 introduces the theory and applications of dye chemistry. For bioanalysis, this chapter presents covalent and non-covalent labeling. The covalent labeling depends on the functionality of amino acids and the non-covalent labeling relies on the binding site of a protein. Due to the complicated binding process in non-covalent labeling, this chapter also discusses the binding equilibria in spectroscopic and chromatographic analyses. Chapter 2 and 3 evaluate the novel BHmCs for non-covalent labeling with human serum albumin (HSA) and report the influence of micro-environment on BHmCs. The interesting character of BHmCs in aqueous solutions is that the dyes exhibit non- or low-fluorescence compared to their monomer counterpart, RK780. It is due to their H-type closed clam-shell form in the solutions. The addition of HSA or organic solvents opens up the clam-shell form and enhances fluorescence. The binding equilibria are also examed. Chapter 4 provides a brief introduction that summaries the use of capillary electrophoresis (CE), and offers a detailed instrumentation that discusses the importance and advantage of a detector in NIR region for CE separation. Chapter 5 focuses on the use of NIR cyanine dyes with capillary electrcophoresis with near-infrared laser induce fluorescence (CE-NIR-LIF) detection. The NIR dyes with different functional groups show that RK780 is a suitable NIR dye for HSA labeling. The use of BHmCs with CE-NIR-LIF reduces signal noises that are commonly caused by the interaction between NIR cyanine dyes and negatively charged capillary wall. In addition, bovine carbonic anhydrase II (BCA II) is applied to study the influence of hydrophobicity on non-covalent labeling. Finally, chapter 6 presents the conformational dependency of BHmCs on the mobility in capillary and evaluates the further possibility of BHmCs for small molecule detection. Acridine orange (AO) is used as a sample and it breaks up the aggregate and enhances fluorescence. The inserted AO into BHmC changes the mobility in capillary, owing to the conformational changes by AO.

The widespread pollution of mercury motivates research into its atmospheric chemistry and transport. Gaseous elemental mercury (Hg(0)) dominates mercury emission to the atmosphere, but the rate of its oxidation to mercury compound (Hg(II)) plays a significant role in controlling where and when mercury deposits to ecosystems. Atomic bromine is regarded as the main oxidant for Hg(0) oxidation, known to initiate the oxidation via a two-step process in the atmosphere – formation of BrHg (R1) and subsequent reactions of BrHg with abundant free radicals Y, i.e., NO2, HOO, etc. (R2), where the reaction of BrHg +Y could also lead to the reduction of Hg(I) to Hg(0) (R3). A different oxidation pathway of BrHg + O3 (R4) is currently regarded as the dominant Hg(II) oxidation pathway in the atmosphere. Hg + Br + M → BrHg + M (R1) BrHg + Y + M → BrHgY + M (R2) BrHg + Y → BrY +Hg (R3) BrHg + O3 → BrHgO + O2 (R4) While the rate constants of R1 have been experimentally measured a decade ago, this research focuses on the experimental kinetic studies on the reaction of R2-R4 to better assist the efforts to predict how emission reductions impact the spatial distribution of mercury entry into ecosystems. The kinetic studies of BrHg redox chemistry are conducted by utilizing laser photolysis-laser induced fluorescence-cavity ringdown spectroscopy (LP-LIF-CRDS) systems, where BrHg radicals are generated via laser photolysis and monitored in the reaction via LIF and CRDS measurements. We report mainly on our experimental kinetic studies of the redox reactions of BrHg with relatively abundant trace gases such as NO2, NO, O3, O2, and VOCs, especially on the temperature and pressure dependence of the reaction rate constants using our LP-LIF system. We present the development and the characterization of a novel LP-CRDS system, which is a powerful tool to study reactions during which fluorescence quenching interferes with LIF measurement, and to study the spectroscopy of Hg(I) and Hg(II) compounds.