Electrochemiluminescence System Of Acridine Compounds And Investigation Of Ionic Liquid Functionalized Nanomaterials

In this dissertation, the state of arts in the field of electrochemiluminescence (ECL), ionic liquid (IL). metal nano-materials/nano-hybrids and nano-based ECL biosensor were reviewed.For ECL-based biassays, new electrochemiluminescent system is an important subject. Besides, metal nanoparticles play an important role in the nano-based biosensor, which can affect the stability, repeatability, and sensitivity of the sensor. Therefore, in the present dissertation, acridine compounds were utilized to design new ECL systems. The ECL behaviors, rules, and mechanisms of these novel ECL systems were investigated. Moreover, based on the new ECL system, a biosensor was developed to determine DNA. On the other hand, IL stabilized metal nanoparticles/nanohybrids were synthesized. The interactions among metal nanoparticles, IL and carbon nanotubes were also explored.The main results are as follows:1. Compared with the ECL of lucigenin in aqueous solution, three new anodic ECL peaks (ECL-2 at-0.53 V, ECL-3 at 0.20 V, and ECL-4 at 0.51 V) were observed. Depending on the semi-derivative voltammogram curves and different electrochemical techniques such as pre-electrolyzing and linear sweep voltammetry, the ECL peaks were characterized and the mechanisms were proposed. ECL-2 was likely due to the luminescent reactions between lucigenin and the radicals O2 generated during the electro-reduction of hydrogen peroxide. ECL-3 was possibly due to the luminescent reactions between Luc*+generated by the electro-oxidation of N,N'-dimethyl-9,9'-biacrylidene (DBA) and dissolved oxygen. ECL-4 was possibly due to the reaction between the DBA isomer and lucigenin in the presence of dissolved oxygen. The novel ECL peaks were related to radicals. The radicals can exist longer in non-aqueous solution than aqueous solution. And the reduction products of lucigenin have preferred dissolution ability in ethanol than H2O. Therefore, these differences might induce the novel ECL peaks in ethanol solution.2. The ECL behavior between lucigenin and tributylamine (TBA) was firstly studied. A novel anodic ECL peaks with two shoulders was observed. The effects of various factors such as media, material of electrode, concentration of lucigenin and TBA, atmosphere, and electrolytes on ECL peaks were examined and the mechanisms were proposed. ECL-1 (0.91 V vs. SCE) and S1 (0.52 V vs. SCE) were possibly due to the luminescent reactions between lucigenin and the electro-oxidized products of TBA. And the intermediate species could also react with lucigenin and generate S2 (1.19 V vs. SCE). ECL-2 (0.66 V vs. SCE), S3 (0.33 V vs. SCE), and S4 (1.07 V vs. SCE) were the counter-peaks of ECL-1, S1, and S2, respectively. Therefore, those peaks had the same luminescent processes with the counter-peaks. Moreover, the ECL behavior between several amines (such as tripropylamine and triethylamine, etc.) and lucigenin was examined. It was found that the ECL intensity decreased either as the length of aliphatic substituents decreased, or as the number of aliphatic chains decreased. The present work provides a way to design the ECL system of acridine compounds.3. It was found that tripropylamine (TPA) could induce the ECL behavior of acridinium ester (AE) labels. The radicals generated in the electro-oxidation process of TPA attacked 9 position of acridine, which would induce the multiple bond cleavage of acridine and generate excited.N-methylacridone. The excited N-methylacridone returned to ground state and released photons. The AE/TPA ECL system was used as the detection system for developing a sandwich-type ECL-based DNA sensor. The experimental conditions were optimized when a model DNA was chosen as a target analyte. Under the optimized conditions, the linear range of the DNA sensor was from 5.0×10-15 mol·L-1 to 5.0×10-12 mol·L-1. The detection limit (S/N= 3) was 3.0×10-15 mol·L-1. Moreover, the ECL-DNA sensor could selectively detect the model DNA among the one-base mismatched DNA, two-based mismatched DNA, and non-complementary DNA. It is of great application potential in clinic analysis.4. Carboxylic acid-and amino-functionalized ionic liquids were used as the stabilizer for the systhesis of metal nanoparticles in aqueous solution. Smaller gold nanoparticles (3.5 nm) and platinum nanoparticles (2.5 nm) were prepared with NaBH4 as the reductant. Larger gold nanospheres (23,42, and 98 nm) were synthesized using different quantities of trisodiumcitrate reductant. The morphology and the surface state of the metal nanoparticles were characterized by high-resolution transmission electron microscropy, UV-visible spectroscopy, and X-ray photoelectron spectroscopy. It was found that the electron clouds inclined to transfer from the metal surface to imidazolium ring, which induced the negative shifts in C 1s and N 1s binding energies. It was deduced that the nanoparticles were stabilized via three possible modes:(1) The electrostatic interaction between the imidazolium cation in ILs and the negatively charged metal atom. (2) The coordination between the functional group in ILs and metal atoms. (3) The simultaneous coordination mode involved in both (1) and (2). All the IL-stabilized metal nanoparticles were found to easily decorate on untreated multiwalled carbon nanotubes. In the microstructure of the nanohybrids, the imidazolium ring moiety of ILs might interact with theπ-electronic nanotube surface by virtue of cation-πand/orπ-πinteractions, and the functionalized group moiety might interact with the metal nanoparticles surface. The ILs acted as a linker. During all the decoration procedures, no additional reagents were needed, and the carbon nanotubes were used without any treatment. Moreover, the obtained nanohybrids had a remarkable hydrophilic ability, which might find future applications in fields such as catalysis, nanoscale electronics, as well as sensors. Additionally, amino-functionalized IL stabilized gold nanoparticles showed lower resonance Rayleigh scattering intensity than trisodiumcitrate stabilized gold nanoparticles, which may have potential application in DNA, amino acid, and dye analysis based on resonance Rayleigh scattering technique.5. Ionic liquid stabilized anisotropic gold nanoparitcles were synthesized by one-step chemical reduction method in aqueous solutions at room temperature. In the presence of amino-functionalized ILs, gold nanoparitcles with long-wavelength surface plasmon resonance (SPR) absorption (> 600 nm) could be obtained by using of tannic acid as a reductant. The specific SPR absorption was related to the non-spherical gold nanoparticles including gold triangle, decahedra, and icosahedra nanocrystals, which could be observed by transmission electron microscropy. The component and the size of the anisotropic gold nanoparitcles could be adjusted by the amount of reducing agent. It was deduced that the formation of non-spherical gold nanoparticles was related the hydroxyls in tannic acid, and ILs acted as the synthesis template because of the specific interactions between IL and gold surface.