Chemo/Biosensing For Small Molecules Based On Newly Synthesized Oligo-(Phenylene-ethynylene)s Derivatives

Quantitative and qualitative determination of physiologically-related species in complex food, medicine, biological matrixes, and environmental sample is the core issue of food safety, disease screening and diagnosis and sanitation, environmental monitoring and pollution. It is very important to develope fast, simple, sensitive methods for detection of individual and multiple components in the complex samples. Chemo/biosensing is a new detection technique, and has widely applied in food, medicine, biological matrixes and environmental samples. And innovativing sensing methods, developing effective and amflification material is the key to constructing biosensors for small molecules with higher sensitivity and selectivity.In this dissertation, we briefly reviewed the chemo/biosensors, and especially stated how to design and construct new chemical sensors. The recent applications of nanomaterials, electron mediators and molecular wires in the area of chemo/biosensing were reviewed in detail. As one of important molecular wires, oligo-(phenylene-ethynylene)s (OPEs) derivatives have excellent properities such as rectifier, storage and switch, and have widely employed in molecular electronics area. Take advantage of the good optical and electrotronic properties, it is expected to build some sensitive detection methods for small molecules. Based on this, serials of new OPEs were synthesized and characterized. Combined with nanomaterials and β-cyclodextrin, several biosensors for life-related biomolecules were constructed. The main contents are as follows:1. Four new conjugated oligo-phenylene-ethynylenes derivatives, N-methyl-4-(4-acetylthiophenylethynyl)-1,8-naphthalimide (1), thioacetic acid S-[4-(4-aminophenyl-ethynyl) phenyl]ester (2),4-methylthiophenylethynyl-benzenamine (3), and N-methyl-4-(4-methyl-thiophenyl-ethynyl)-1,8-naphthalimide (4), were synthesized by nucleophilic substitution, electrophilies addition and Sonogashira reactions. The structures of the four compounds were confirmed by1H NMR,13C NMR, MS and IR and their spectral characteristics were studied by ultraviolet and visible (UV-vis) spectroscopy as well as fluorescence spectroscopy in different mediums. It was found that the fluorescence properties of compounds2and3were notably improved in the aqueous solutions in the presence of β-cyclodextrin (β-CD). Spectral analysis supported the supposition that the fluorescence intensity enhancement was due to the formation of inclusion complex with β-CD. The supramolecular interaction was investigated in detail and the reaction mechanism was provided. A salicylaldehyde determination method in aqueous medium was established based on the supramolecular complex of compound3. Under the optimum conditions, the supramolecular complex exhibited a dynamic fluorescence response range for salicylaldehyde from0.6to240μM, with a detection limit of1×10-8M.2. Two new conjugated oligo-phenylene-ethynylenes derivatives,4-((4-(methylthio) phenyl)ethynyl)benzaldehyde (5),4-((4-(methylthio) phenyl) ethynyl) benzoic acid)(6) were designed and synthesized for the first time. Their structures of the two compounds were thoroughly confirmed by1H NMR,13C NMR, MS and IR. The spectral characteristics were studied by UV-vis spectroscopy as well as fluorescence spectroscopy in different solvents. The inclusion processes with β-CD were investigated in detail and the possible inclusion mechanism was induced. It was found that the fluorescence intensity of the two compounds was enhanced after the complex was formed. In the presence of melamine, the fluorescence intensity of the supramolecular complex was quickly quenched. A simple melamine determination method in aqueous medium was established based on the supramolecular complex of β-CD with compound5and6. Under the optimum conditions, the supramolecular complex exhibited dynamic fluorescence response ranges for melamine from0.15-10μM and0.15-25μM, respectively.3. A new ferrocene derivative (1-[(4-amino) phenyl ethynyl] ferrocene,(compound7, Fc-NH2) was synthesized for the first time. The ferrocene derivative molecule contained phenylethynyl skeleton, ferrocene and amino groups with excellent electrochemical property. Graphene/Fc-NH2nanocomposite was prepared by mixing graphene solution and Fc-NH2solution in one pot and the nanocomposite was utilized to construct Nafion/graphene/Fc-NH2modified glass carbon electrode (GCE). The ferrocene derivative immobilized on the graphene can enhance the charge-transport ability of the nanocomposite, stabilize the graphene and prevent the leakage of ferrocene. The detection signal of dopamine (DA) was significantly amplified on the Nafion/graphene/Fc-NH2/GCE. It was experimentally demonstrated that the signal enhancement is resulted from the synergy amplification effect of graphene and the Fc-NH2. The oxidation peak currents of DA were linearly related to the concentrations in the range of5×10-2×10-4M with the detection limit of20nM in the absence of urine acid (UA) and ascorbic acid (AA). In the presence of10-3M AA and10-4M UA, the linear response range was1×10-7-4×10-4M, and the detection limit was50nM at S/N=3. Using the proposed Nafion/Fc-NH2/graphene/GCE, DA was successfully determined in real samples with the standard addition method.4. A new ferrocene-terminated phenylethynyaniline (Fc-NH2, compound7) was synthesized by Sonogashira reaction. The structures of the new intermediate and target compound were identified by IR,1H NMR,13C NMR, MS. Stable GS/chi/Fc-NH2complex was prepared combined with graphene, and the GS/chi/Fc-NH2/Cytc modified electrode was fabricated. It was found that Cytc can immobilize on GS/chi/Fc-NH2and the fast electron transfer can be realized between the electrode and Cytc molecules. There is a pair of peaks near-0.2V, which can be attributed to Cytc. The GS/chi/Fc-NH2/Cytc modified GCE shows good catalysis towards NaNO2, and it shows good linearity in the range of1×10-7-1.5×10-4M,0.1-150μM, and the determination limit is bellow at4×10-8M.5. A new ferrocene benzyne derivative (Fc-SAc, compound9) that contained oligo-(phenylene-ethynylene) skeleton, ferrocene and thiolate terminal groups was firstly synthesized. The hydrolysis product of Fc-SAc (Fc-SH) was immobilized onto gold nanoparticles (AuNPs) modified glass carbon electrode (GCE) as sensing element for rutin detection with high sensitivity. The new sensing strategy was proposed by using two Fc-SH modified electrodes:Fc-S/AuNPs/GCE (Electrodel) and Fc-S/AuNPs/graphene-chitosan/GCE (Electrode2). The electrochemical oxidation of rutin on Electrode2was a diffusion-controlled process, which was different from a mass-controlled process on Electrode1. Under the optimal conditions, the peak currents of the sensors were linearly related to the concentrations of rutin. The linear response ranges were0.05-30μM and0.04-100μM with the regression coefficients of0.998and0.997on Electrodel and Electrode2, respectively. Electrode2presented wider linear range, superior sensitivity, lower detection limit and better stability on determination of rutin.6. A double signal amplification platform for ultrasensitive simultaneous detection of a quaternary mixture of ascorbic acid (AA), dopamine (DA), uric acid (UA) and acetaminophen (AC) is fabricated by assembling newly synthesized ferrocene thiolate (phenylethynyl ferrocene thiolate, Fc-SAc, compound9) on core/shell structured Fe3O4@Au and coupling with graphene sheet/chitosan (GS/chitosan). By immobilization of the electron mediator on Fe3O4@Au nanoparticles (NPs), a Fe3O4@Au-S-Fc nanocomposite possessing excellent electric-catalytic and signal amplification behavior was obtained. Mixing the Fe3O4@Au-S-Fc with GS/chitosan, the Fe3O4@Au-S-Fc/GS/chitosan nanocomposites were obtained and utilized to construct a multicomponent sensor. Using the Fe3O4@Au-S-Fc/GS/chitosan modified glass carbon electrode (GCE), the double signal amplification strategy was realized by the synergistic catalytic effect of Fe3O4@Au NPs and GS, and the amplification effect of the ferrocene electron mediator. The individual and simultaneous determinations of AA, DA, UA and AC were performed using differential pulse voltammetry (DPV) with the modified electrode. This modified electrode exhibits potent and persistent electro-oxidation behavior followed by well-separated oxidation peaks towards AA, DA, UA and AC. For the quaternary mixture, the four compounds can be well separated from each other at a scan rate of50mVs-1with the peak potentials at-0.03,0.15,0.24and0.35V, respectively. The peak-to-peak potential separations of AA-DA, DA-UA and UA-AC were0.18,0.09and0.11V, respectively, which were large enough to determine AA, DA, UA and AC simultaneously. The catalytic peak currents were linearly dependent on the concentrations of AA, DA, UA and AC in the range of5-100,0.5-80,2-120and0.5-35μM, respectively, in the individual detection of each component under the condition of keeping the concentrations of the other3compounds constant. By simultaneously changing the concentrations of the4constituents, good linear current responses were obtained in the range of6-350,0.5-50,1-90and0.4-32μM for AA, DA, UA and AC, respectively. And the determination limits for AA, DA, UA and AC were1,0.2,0.3and0.05μM, respectively. The analytical performance of this sensor has been evaluated for simultaneous detection of AA, DA, UA and AC in serum and urine samples.