Application Of Functional Organsilica Nanoparticles Modified Au Electrode For The High Sensitive Determination Of Heavy Metal

Heavy metals (lead, mercury and copper) are widely distributed in can, accumulate though food chian,enter the human body, and cause a variety of serious diseases when the content is excess. In recent years, the water pollution problems of heavy metal are concerned. It is of great practical significance to establish fast and sensitive trace analysis method. High sensitivity detection methods, such as inductively coupled plasma mass spectrometry (ICP-MS), atomic fluorescence spectrometry (AFS), are expensive, complicated to operate, and not suitable for on-site monitoring. On the contrary, electrochemical technology is increasing popular because of high sensitivity, simple equipment and low cost. Nanomaterials show a series of unique physical and chemical properties due to small scale (1-100nm). The sensitivety and selectivity of sensing can be improved when applying the nanoparticles-based material to modify electrode.In this thesis, functionalized organsilica nanoparticles with small size were synthesized. The organsilica nanoparticles modified Au electrode was obtained by self-assembling or drip coating was applied for the determination of trace heavy metal in aqueous solution. The major results and conclusions are as follows:1、By a facile one step synthesis route, the unifrom organosilica nanoparticles with small size were fabricated at room temperature using (3-mercaptopropyl)-trimethoxysilane (MPTS) as a single silica source and cetyltrimethylammonium bromide (CTAB) as an additive. The morphology of the organosilica nanoparticles was characterized by atomic force microscope (AFM). The average particle size was about2.5nm as measured by transmission electron microscope (TEM). By simple self-assembling, the uniform and stable organosilica nanoparticle modified Au electrode with high density of thiol group was obtained, and the modified electrode was applied to determine Pb(Ⅱ) and Hg(Ⅱ) by square wave stripping voltammetry (SWV). Several experimental parameters such as surfactant type, CTAB content, supporting electrolyte, pH values, accumulation potential and accumulation time were studied. The results showed that the organosilica nanoparticle modified electrode has sensitive electrochemical response to trace Pb(Ⅱ). Under the optimized experimental conditions, the stripping current has linear relationship with Pb(Ⅱ) concentration in three ranges between of4.8×10-12～4.8×10-9mol/L;2.4”10-9～2.4×10-7mol/L and2.4×10-7～1.2×10-6mol/L by10min preconcentration at-1.0V in the0.2mol/L acetic acid-sodium acetate buffer solution (pH=5). The lowest detectable concentration was as low as4.8×10-12mol/L (S/N=3). The MPTS modified electrode was also used for Hg(Ⅱ) detection. The linear relationship between peak current and mercury concentration was achieved in the range of1.5×10-12～7.5×10-11mol/L with10min preconcentration at-0.4V in0.1mol/L hydrochloric acid solution. The correlation coefficient was0.9980and the detection limit was5.0×10-13mol/L. The developed sensor was successfully applied for the detection of lead and mercury in actual water, and the results were consistant with that of the atomic fluorescence spectrometry (AFS).2、The unifrom amino-functionalized organosilica nanoparticles were fabricated at room temperature using3-Aminopropyltriethoxysilane (AMPTS) as a single silica source and cetyltrimethylammonium bromide (CTAB) as an additive. The organosilica nanoparticles were grafted onto the surface of Au electrode with the by self-assembling MPTS monolayer. The modified electrode has been used for the determation of Cu(Ⅱ) due to the coordination of Cu(Ⅱ) to amino group on the electrode. The major factors, such as supporting electrolyte, accumulation potential and accumulation time, on the electrochemical response for Cu(Ⅱ) determination were investigated by square stripping voltammetry (SWV). The results showed that the modified electrode had a sensitive response to trace Cu(Ⅱ). The three linear relationship ranges between peak current and Cu(Ⅱ) concentration were obtained with1.6×10-12-1.6×10-11mol/L;3.1×10-11～-3.1×10-10mol/L and3.1×10-8～3.1×10-6mol/L, respectively. And the determination limit was1.6×10-12mol/L (S/N=3).3, Gold/silica composite nanoparticles were synthesized. The morphology of the gold/silica nanoparticles ware characterized by UV-Vis spectrometer, AFM and TEM. Au electrode modified with composite nanoparticles by droping coating was used for detection of mercury in aqueous solution. The electrochemical properties of nanoparticles modified electrode were investigated by cyclic voltammetry (CV) and square wave stripping voltammetry (SWV). Under the optimal conditions, the stripping peak current and the concentration of Hg(Ⅱ) ions showed a good linearity in the range of9.6×10-10～9.6×10-9mol/L and4.8×10-8～4.8×10-7mol/L. The detection limit was1.4×10-10mol/L with single-to-noise ratio of3.