Quantum dots are a part of very important our technological future because of their intriguing and useful properties. These properties are different in character from those of the corresponding bulk material. Quantum dots are inorganic artificial semiconductor nanocrystal whose electrons influence their physical and chemical properties. Zinc oxide quantum dots were synthesized through an ethanol based precipitation via colloidal synthesis method at various pH values. Various emission colors were obtained because the excited quantum dots of various sizes emitted specific wavelengths of light. The emission spectra indicated that the pH dependent quantum dots were successfully synthesized. Zinc oxide quantum dots were also encapsulated and the luminescence properties examined. The quantum dots that were immobilized in polyisoprene (PI) through chemiluminescence (CL) analyses were found to be stable and were capable of continuing their luminescence properties with extended uses and long- term storage. Linear calibration curves were acquired for concentration of 8.75 x 10-5 M H2O2 in TCPO-CL.

Quantum dots are semiconductive particles whose properties are highly influenced by the presence of at least one electron. Cadmium selenide quantum dots were synthesized via colloidal synthesis. Contrary to previous preparations, more focus was placed on the temperature rather than the duration of time at which they form. A series of colored solutions were obtained because the excited quantum dots of various sizes emitted specific wavelengths of light. The emission spectra showed that the temperature-dependent quantum dots were successfully synthesized. The quantum dots were also immobilized on various surfaces, and the luminescence properties were examined. The quantum dots that were immobilized in sol-gels through chemiluminescence (CL) analyses were found to be stable and were able to maintain their luminescence properties with extensive uses and long-term storage. Linear calibration curves were obtained for concentrations of hydrogen peroxide from 1.75 x 10-4 M to 1.75 x 10-2 M in TCPO-CL.

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Biogenic monoamines such as dopamine play an important role as major neurotransmitters. Simultaneous determination of the concentration changes is thus crucial to understand brain function. Additionally, quantification of pharmaceutically active compounds (PhACs) and their metabolites in biological fluids is an important issue for forensic tests, clinical toxicology and pharmaceutical analysis. We have developed two postcolumn luminescence detection methods coupled to a 2-dimensional-solid phase extraction (2D-SPE) system. The postcolumn reaction methods used in this study are the redox-dependent photoluminescence-following electron-transfer (PFET) and Fenton-based chemiluminescence techniques, for the determination of certain neurotransmitter and nonsteroidal anti-inflammatory drugs (NSAIDs). A stable [Os(tmphen)3]3+ (tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline) reagent was prepared in neutral aqueous solution by oxidation of [Os(tmphen)3]2+ with lead(IV) oxide. [Os(tmphen)3]2+ and [Os(tmphen)3]3+ are characterized by absorption spectroscopy. [Os(tmphen)3]3+ stability is compared with [Ru(tmphen)3]3+ in the same pH 7 environment. The properties of Os(III) and Ru(III) complexes were investigated for use as the oxidant in a PFET system. Studies of photophysical and electrochemical properties, the stability of the Os(III) and Ru(III) complexes, and analytical application in PFET detection of oxidizable analytes are presented. The spectroscopic properties of the complexes were not very advantageous, but careful control of the detection system and reaction conditions enabled sensitive detection of the analytes. The method was fully validated and the optimized system was capable of detecting dopamine and acetaminophen at about 30.2 µg L-1 and 33.5 µg L-1, respectively. The limit of detection (LOD) was 1.5 µg L-1 for acetaminophen and 4.3 µg L-1 for dopamine. The accuracy and precision were within bioanalytical method validation limits (90.9 to 101.5 % and RSD < 12.0 %, respectively). Typical analysis time was less than 15 minutes. Two Fenton-based flow-injection chemiluminescence (CL) methods were developed and validated for the determination of naproxen. Under the optimal experimental conditions the proposed methods exhibited advantages in a larger linear range from 2,760 ng mL-1 to 207,000 ng mL-1 for the first CL method and 41.4 ng mL-1 to 700.0 ng mL-1 for the second CL method. The LOD was 13.8 ng mL-1 for naproxen. The CL mechanisms for the system, H2O2-FeIIEDTA-naproxen was further studied by batch experiments, chemiluminescence spectroscopy, fluorometry, high pressure liquid chromatography (HPLC) and Fourier transform infrared spectroscopy (FTIR). The effects of various interferences commonly found in biological and wastewater systems on the chemiluminescence intensity were also investigated. We used these methods to determine NSAIDs in commercial pharmaceutical formulations. Another application of these method was for detecting NSAIDs in biological samples. A 2x-1-Dimensional Solid Phase Extraction (2x-1D SPE) method was developed for determination of acetaminophen and naproxen in urine. This method uses both the methanol concentration and the pH advantageously to preferentially isolate analytes of interest from complex sample matrix. These methods were fully validated and had sufficient sensitivity (limit of quantification: acetaminophen; 40.41 mg L-1 - 360.0 mg L-1 and naproxen; 23.03 mg L-1 - 214.8 mg L-1) for biological matrices and applications. / Chemistry

The need for sensitive and selective detectors in supercritical fluid chromatography (SFC) is particularly evident since SFC can be used to analyze classes of compounds that are not readily amenable to either gas chromatography (GC) or liquid chromatography (LC). These compounds include species that are nonvolatile or thermally labile and , in addition, contain no chromophore that can be used for spectrophoto detection. The objective of this research is therefore to interface selective chemilumninescent detectors with SFC in the sensitive detection of nitrogen- and/or sulfur containing compounds. The chemiluminecent nitrogen detector (CLND), a gas-phase detector which is specific for nitrogen-containing compounds, was first evaluated as a detector for use with capillary SFC. The potential use of the CLND for food flavor and petroleum samples was demonstrated. In addition to equimolar nitrogen response, the CLND showed good sensitivity and large linear dynamic range. Minimum detectable quantity (MDQ) was 60 pg of nitrogen with a linear range of over 3 orders of magnitude. Nitrogen to carbon selectivity of 105 was obtained. Capillary SFC with simultaneous flame ionization and chemiluminescent detection was also demonstrated. The second portion of the research investigated the CLND for packed column SFC with methanol modified CO2. The only modification made in the CLND for packed column SFC is the pyrolysis furnace. The CLND and UV were used to interface with SFC via a post-column split. Methanol-modified CO2 was also demonstrated to be compatible with the CLND even with a high mobile phase flow rate. The use of pressure and modifier programs appears to be feasible as is evidenced by the baseline studies which have been performed, as well as by the applications demonstrated. The last portion of the research focused on the evaluation of a new generation sulfur chemiluminescent detector (SCLD), which is also a gas-phase detector, with packed column SFC using both pure and methanol modified CO2. The minimum detectable quantities were determined to be 2.6 pg or 14 pg sulfur for mobile phase employing pure CO2 or 8% methanol modified CO2 respectively. The evaluation study also showed excellent selectivity and linearity, as well as day-to-day repeatability. The capabilities of the SFC-SCLD system for sulfur speciation and detection of thermally labile pesticides and polar sulfonamides, as well as petrochemical samples were presented. / Ph. D.

Foram sintetizados, purificados e caracterizados os peróxidos cíclicos: peróxido de difenoíla (1), dimetil-1,2-dioxetanona (2), e spiro-adamantil α-peróxi lactona (3), e determinados seus parâmetros de quimiluminescência. Foram redeterminados os rendimentos quânticos singlete na decomposição catalisada de 1 e 2 em condições análogas as utilizadas anteriormente na literatura, obtendo-se valores várias ordens de grandeza menores que os inicialmente relatados para estes sistemas padrão para a formulação do mecanismo Luminescência Iniciada Quimicamente por Troca de Elétron (Chemically Initiated Electron Exchange Luminescence - CIEEL). O efeito de gaiola de solvente, utilizando-se o sistema binário tolueno/difenilmetano, sobre o rendimento quântico na decomposição de 1 catalisada por rubreno, mostrou-se consideravelmente menor para este sistema intermolecular do que o observado no sistema intramolecular da decomposição induzida de 1,2-dioxetanos fenóxi-substituidos. Foram determinados pela primeira vez os parâmetros de quimiluminescência na decomposição unimolecular e catalisada da spiro-adamantil α-peróxi lactona (3), mostrando que esta é a α-peróxi lactona mais estável sintetizada e estudada até o momento. Este peróxido é sujeito à decomposição catalisada por ativadores adequados, envolvendo transferência de elétron, porém, com eficiência baixa devido a um impedimento estérico exercido pelo substituinte spiro-adamantila sobre a interação do peróxido com o ativador. O rendimento quântico singlete máximo obtido na decomposição catalisada de 3 é de 1%, valor consideravelmente menor que os determinados para sistemas intramoleculares. A decomposição dos peróxidos cíclicos 1 a 3 é catalisada por fenolatos como ativadores, porém, os rendimentos singlete obtidos nesta reação são baixos, entre 10-3 e 10-7 E mol-1. Os resultados obtidos com este sistema modelo intermolecular para a decomposição induzida por transferência intramolecular de elétron de 1,2-dioxetanos fenóxi-substituidos, demonstram claramente que esta última transformação quimiluminescente de alta eficiência deve ocorrer por uma retro-transferência de elétron intramolecular e não intermolecular como proposto na literatura, e como é necessariamente o caso no sistema modelo estudado no presente trabalho. / The cyclic peroxides diphenoyl peroxide (1), dimethyl-1,2-dioxetanone (2) and spiro-adamantyl α-peroxy lactone (3) were synthesized, purified and characterized, as well as its chemiluminescence parameters determined. The singlet quantum yields in the catalyzed decomposition of 1 and 2 were re-determined in experimental conditions equivalent to those formerly utilized in the literature, obtaining values various orders of magnitude lower than the ones initially reported for these model systems for the formulation of the Chemically Initiated Electron Exchange Luminescence\" (CIEEL) mechanism. The solvent-cage effect on the singlet quantum yields in the rubrene catalyzed decomposition of 1, using the binary system toluene / diphenylmethane, showed to be considerably lower for this intermolecular system than the one observed in the intramolecular system of the induced phenoxy-substituted 1,2-dioxetane decomposition. The chemiluminescence parameters in the unimolecular and catalyzed spiro-adamantyl α-peroxylactone (3) decomposition were determined for the first time, showing that 3 is the most stable α-peroxylactone synthesized and studied up to now. This peroxide is subject to catalyzed decomposition by appropriate activators involving electron transfer, however, with low efficiency due to the steric effect of the spiro-adamantyl substituents on the interaction of the peroxide with the activator. The maximum singlet quantum yield obtained in the catalyzed decomposition of 3 is 1 %, a value considerably lower than those determined for intramolecular systems. The decomposition of the cyclic peroxides 1 to 3 is catalyzed by fenolato ions as activators, thus the singlet quantum yields measured for this reaction are low, between 10-3 e 10-7 E mol-1. The results obtained for this intermolecular model system for the induced phenoxy-substituted 1,2-dioxetane decomposition demonstrate clearly that the latter highly efficient chemiluminescent transformation should occur by an intramolecular back-electron transfer and not by an intermolecular one as proposed in the literature, and as is necessarily the case in the model system studied in this work.