Electrogenerated Chemiluminescence Of Semiconductor Nanoparticles And Luminescence Analytical Methods For Pharmaceutical Analysis

Nanoparticles(NPs) have good applicational prospects in lumine-scence materials and optical sensors due to their unique size-dependent electronic, magnetic, optical, and electrochemical properties. Highly luminescent semiconductor NPs have gained increasing attention for use in light-emitting devices and tagging applications.Electrogenerated chemiluminescence (ECL) is a radioactive charge recombination originating from emitting excited states of electrogenerated species and has been used to investigate the nature of an emitting state, the mechanism by which it is produced, and electron transfer theory. It has also widely been used in pharmaceutical analysis, bioanalysis, enviormental analysis and clinical analysis. The development of a simple, rapid, sensitive and selective method and the fabrication of a simple, cheap and stable analytical detector in ECL analysis have been a long-term goal. Moreover, investigation of ECL of NPs has attracted increasing attentions because NPs have a great potential for developing novel ECL sensors and biological labels for ECL detection.The aim of the present work is to study the ECL behaviors of the semiconductor nanoparticles in aqueous medium and to explore the optical and electrochemical properties of the semiconductor NPs in order to better understand photons, charge-carrier transport, and electron injection phenomena of the semiconductor nanoparticle. Another work in the present thesis aims to develop and investigate a new immobilization approach for fabricating ECL-based detector with long-term stability. A novel ECL detector based on Ru(bpy)2(dcbpy)2+entrapped in a highly cross-linked polymer and mixed with carbon paste was fabricated. A novel ECL analytical method for the determination of raceanisodamine was developed. The ECL phenomena of a system of amoxicillin-surfactant-H2O2was first observed and investigated at graphite electrode at-0.7V during potential scan from+1.5V to-1.0V. The ECL mechanism of the system was discussed and a new ECL method for the determination of amoxicillin was developed. Chemiluminescence analysis is becoming increasing important in various fields owing to its simple instrumentation used, high sensitivity, wide dynamic range, reproducibility, simplicity and rapidity. To explore new CL reaction systems and to develop new chemiluminescence analytical methods is important. In this thesis, the chemiluminescence emission phenomena of the vitamin B4, rifampicin and amoxicillin was investigated respectively, and a new flow injection chemiluminescence analytical method for the determination of the VB4, rifampicin and amoxicillin was developed respectively.The major contents in this thesis are described as follows:In Chapter1, the principle of the ECL and the main ECL systems were introduced. The immobilization methods for Ru(by)32+were summarized and the research progress of the ECL analytical methods was reviewed. Moreover, the definition, classification, properties and synthesis methods of the nanomaterials were briefly introduced and the optical and electrochemistry properties of the semiconductor nanoparticles were mainly described.In Chapter2, the ECL behaviors of semiconductor nanoparticles (NPs) including ZnS, ZnO and TiO2NPs in alkaline solution were investigated.Electrogenerated Chemiluminescence of ZnS Nanoparticles in Alkaline Aqueous Solution A band gap ECL of ZnS NPs in alkaline aqueous solution was first observed at a platinum electrode during the potential applied between-2.0V (vs. Ag/AgCl, Sat. KCl) and+0.86V. The ECL peak of ZnS NPs in0.10M sodium hydroxide solution appeared at+0.86V and the ECL peak wavelength of the ZnS NPs was-460nm. A core/shell of ZnS/Zn(OH)2was demonstrated by a UV-visible absorption(UV absorption) and photoluminescence spectroscopy(PL) spectra, high resolution transmission electron microscopy(HRTEM), and energy dispersive X-ray spectroscopy. The ECL scheme of the ZnS NPs in alkaline aqueous solution was proposed, indicating that the surface passivation effect and the core/shell structure of ZnS/Zn(OH)2played a significant role in the ECL process and that the similarity of the ECL and PL spectra of semiconductor NPs was related with the extent of the surface passivation. The ECL intensity of ZnS NPs in alkaline aqueous solution was greatly enhanced by an addition of K2S2O8. Electrogenerated Chemiluminescence of ZnO Nanoparticles in Alkaline Aqueous Solution with Peroxydisulfate ZnO nanoparticles were prepared by the method of homogeneous precipitation with urea and zinc nitrate. ZnO NPs were characterized by TEM, UV-Vis, PL and X-ray diffraction. A strong ECL emission of ZnO NPs suspended in aqueous solution at a Pt electrode or in nanoparticulate layers modified electrodes including Pt, carbon past and graphite electrode was observed when a potential was applied between0V(vs. Ag/AgCl, Sat. KCl) and-2.0V in0.25M NaOH containing peroxydisulfate. A lineal range between the ECL intensity and the concentration of suspended ZnO NPs in the range from1.0×10-5to1.0×10-3g/mL was obtained. The electrochemical behavior of ZnO NPs was also studied at a ZnO NPs modified carbon paste electrode by entrapping ZnO NPs in carbon paste, which revealed that the electrochemical behavior of ZnO NPs was depended upon the surface passivation effect in a strong alkaline medium.Electrogenerated Chemiluminescence of TiO2Nanoparticles in Alkaline Aqueous Solution TiO2NPs were prepared by the sol-gel method and were characterized by TEM, UV-Vis and XRD. The ECL behavior of TiO2NPs in the alkaline aqueous solution containing K2S2O8was studied. An ECL emission was observed during cyclic potential scan between0V and-2.0V. The ECL intensity had good linear relationship with the concentration of TiO2in the range from2.0×10-5g/mL to4.0×10-4g/mL. Moreover the modified electrode by TiO2NPs was also investigated.In Chapter3, two ECL analytical methods for the determination of pharmaceuticals were developed.Electrogenerated Chemiluminescence of Ruthenium Complex Immobilized in a Highly Cross-linked Polymer and Its Analytical Applications ECL of a ruthenium complex polymer modified carbon paste electrode and its analytical applications were investigated. A ruthenium complex polymer was designed by a highly cross-linked polymer of ruthenium (Ⅱ) bis (2,2’-bipyridine)(2,2’-bipyridyl-4,4’-dicarboxylic acid). The ECL behaviors of ruthenium complex polymer modified carbon paste electrode were investigated in the absence and presence of tripropylamine (TPA). The modified carbon paste electrode exhibited a long-term stability and fine reproducibility. The ECL intensity of the modified electrode was linear with the concentration of TPA in the range from2.0×10-6to3.8×10-3M with a detection limit (S/N=3) of6×10-7M. It was also found that raceanisodamine can enhance the ECL intensity of the modified electrode. The ECL intensity of the modified carbon paste electrode was linear with the concentration of raceanisodamine in the range from3.3×10-6g/mL to1.8×10-4g/mL with a detection limit (S/N=3) of2×10-6M, and the standard deviation for1.0×10-4g/mL in repeated35times measurements is3.8%. This work demonstrates that the entrapment of ruthenium complex in a highly cross-linked polymer is a promising approach to construct an ECL modified electrode which has a long-term stability and fine reproducibility. This work demonstrates that the entrapment of ruthenium complex in a highly cross-linked polymer is a promising approach to construct an ECL modified electrode which has a long-term stability and fine reproducibility and that the ECL modified electrode has a potential application in the ECL detector.Electrogenerated Chemiluminescence Analysis for Amoxicillin It was founded that the amoxicillin produced a weak ECL emission at graphite electrode at-0.7V during potential scan from+1.5V to-1.0V. This weak ECL emission was enhanced greatly by H2O2and CTAB. Based on this finding, a novel sensitive ECL method for the determination of amoxicillin in pharmaceutical preparation was developed. Moreover, the mechanism of the ECL of amoxicillin-CTAB-H2O2was also discussed.In Chapter4. Three flow injection chemiluminescence analytical methods for the determination of vitamin B4, rifampicin and amoxicillin were developed respectively.Determination of VB4with Luminol-H2O2Chemiluminescence System A novel sensitive flow injection chemiluminescence(FI-CL) method for the determination of vitamin B4in pharmaceutical preparation is presented. It is based on the strong enhancement of VB4on the CL between luminol and H2O2in alkaline condition. Various factors affecting the CL emission intensity of the system have been investigated carefully. The enhancement of CL emission intensity is linear with the concentration of vitamin B4in the range from1.0×10-8to1.0×10-5g/mL. The limit of detection is3×10-9g/mL(3a). The relative standard deviation is1.4%for2.0×10-6g/mL vitamin B4in eleven replicate measurements. The proposed method has been successfully applied for the determination of vitamin B4in pharmaceutical preparation of tablets.Flow Injection Chemiluminescence Determination of Rifampicin It was founded that the rifampicin was oxidized by acidic potassium hypermanganate potassium, resulting in generating a weak chemiluminescence emission. Moreover, this weak chemiluminescence emission was greatly enhanced by sodium sulfite. Based on this finding, a novel sensitive FI-CL method for the determination of rifampicin in pharmaceutical preparation is developed. Various factors affecting the CL emission intensity of the system have been investigated. The enhancement of CL emission intensity is linear with the concentration of rifampicin in the range from5×10-8g/mL to1.0×10-5g/mL. The limit of detection is3×10-8g/mL (3σ). The relative standard deviation is2.6%for2.0×10-6g/mL rifampicin in eleven replicate measurements. The proposed method has been successfully applied for the determination of rifampicin in pharmaceutical preparation. Moreover the CL mechanism was also discussed.Flow Injection Chemiluminescence Determination of Amoxicillin It was founded that the amoxicillin was oxidized by potassium ferricyanide in alkaline medium, resulting in generating a weak chemiluminescence emission. The chemiluminescence intensity can be enhanced greatly by sodium sulfite. Based on these findings, a novel sensitive FI-CL method for the determination of amoxicillin in pharmaceutical preparation is developed. Various factors affecting the CL emission intensity of the system have been investigated. The enhancement of CL emission intensity is linear with the concentration of amoxicillin in the range from5.0×10-8to2.0×10-5g/mL. The limit of detection is3×10-8g/mL (3σ). The relative standard deviation is1.5%for2.0×10-6g/mL amoxicillin solution in eleven replicate measurements. The proposed method has been successfully applied for the determination of amoxicillin in pharmaceutical preparation of tablets.