Electrodeposition Of Metal Nanoparticles On Ionic Liquid Composite Film And Their Application In Fabricating Nonenzymatic Electrochemical Sensors

Metal nanoparticles generally show unique optical, electrical, magnetic characteristics and high chemical stability, high catalysis activity, make them very useful in sensor and catalyst area. Since the morphology and surface composition greatly affect the characteristics of metal nanoparticles. The development of effective methods for the preparation of nanoparticles with well-controlled surface composition and morphology has attracted much attention of researchers. Electrodeposition has some advantages over the conventional approaches employed. Some modified electrochemical approach such as pulsed electrodeposition and ultrasonic electrodeposition, combining the features of pulse, ultrasonication and electrodeposition, can promote the electrodeposition efficiency markedly.Ionic liquids (ILs) possess many unique properties and have great application potential in electrochemistry fields. Most recently, the advantages of ILs in synthetic metal nanoparticles processes have been gradually realized. To the best of our knowledge, the use of ILs substrate for the electrodeposition of metals is seldom reported.In this dissertation, three types of ILs (i.e., 1-octyl-3-methylimidazolium hexafluorophosphate, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide, 1-methyl-3(2-mercaptoacetoxyethyl) imidazolium hexafluophosphate) were mixed with carbon nanotube, chitosan and graphite to form ILs composition. Several metal nanoparticles were deposited on this composition support film by cyclic voltammetric deposited, plused deposited and ultrasonic electrodeposition. Seven types of modified electrode were fabricated and applied as nonenzymatic sensor for the determination of purine, alcohol, nitrite, glucose, hydrogen peroxide, formaldehyde and hydroquinone. The thread of research and the method for the fabrication of the nonenzymatic sensor are novel.The main points are summarized as follows: Section one:Cyclic voltammetric electrodeposition of Au nanoparticles on [OMIM][PF6]-MWNT composition film and their application in fabricating nonenzymatic purine sensors.IL1-octyl-3-methylimidazolium hexafluorophosphate ([OMIM][PF6])-multi-wall carbon nanotube (MWNT) gel was fabricated by grinding, then Au nanoparticles were deposited on the [OMIM][PF6]-MWNT composition film through cyclic voltammetric electrodeposition. [OMIM][PF6]-MWNT gel film was a benign support for the deposition of metal nanoparticles owing to theπ-πor cation-πinteraction between [OMIM][PF6] and MWNT. Well dispersed Au nanoparticles could be electrodeposited on [OMIM][PF6]-MWNT gel film. The quantity of Au nanoparticles could be controlled by changing the cycle number of the cyclic voltammetric electrodeposition. The resulting Au-[OMIM][PF6]-MWNT composition modifide electrode was used to construct a nonenzymatic purine sensors for the sensitive determination of guanine and adenine. At the interface the components of the composite could not only efficiently promote the electron transfer between the analytes and electrode surface but also enhance the accumulation efficiency. After optimizing physicochemical parameters, guanine and adenine exhibited well separated and well-defined oxidation peaks on the modified electrode. In addition, the composite film coated electrode exhibited good reproducibility, long-term stability and simplicity to construct and operate. This proposed procedure was successfully applied to the simultaneous detection of guanine and adenine in milk, plasma and urine samples.Section two:Pulsed electrodeposition of PtRuNi ternary alloy nanopaticles on [OMIM][PF6]-MWNT gel composition film and their application in fabricating nonenzymatic alcohol sensor.PtRuNi, PtRuCo ternary alloy and PtRu bimetal nanoparticles were firstly electrodeposited on [OMIM][PF6]-MWNT gel film by pulsed electrodeposition. The composition, morphology and catalytic activity of the obtained nanoparticles were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and voltammetry, respectively. The result showed that the obtained PtRuNi nanoparticles exhibited alloy properties both in composition and structure. Amoug these three types of alloy nanopartices, PtRuNi ternary alloy showed excellence electrocatalysis and poison tolerance toward the oxidation of alcohol. The analytical characteristics of the resulting nonenzymatic alcohol sensor, in terms of response time, linear range, detection limit, sensitivity, reproducibility, anti-interfere and long-term stability were satisfying.Section three:Ultrasonic potentiostatic electrodeposition of PtAu alloy nanopaticles on [P6,6,6, 14][NTf2]-MWNT composition film and their application in fabricating nonenzymatic nitrite sensor.A novel IL (i.e., trihexyltetradecylphosphonium bis (trifluoromethylsulfonyl) imide, [P6,6,6, 14][NTf2])-MWNTs composition was fabricated. PtAu nanoparticles could be fabricated on the [P6,6,6, 14][NTf2]-MWNT composite substrate through ultrasonic potentiostatic electrodeposition. The obtained PtAu nanoparticles were characterized by SEM, XRD and X-ray photoelectron spectrum (XPS). It was found that the support material and the application of ultrasonic electrodeposition technology had the great effect on the morphology of metal nanoparticls. PtAu nanoparticles were well-dispersed on the [P6,6,6, 14][NTf2]-MWNT composite substrate, with particle size about 10 nm. The atomic ratio of PtAu was roughly consistent with the concentration ratio in the electrodeposition solution. Furthermore, the electrochemical impedance spectroscopy (EIS) and voltammetric experiments showed that the resulted PtAu-[P6,6,6, 14][NTf2]-MWNT modified electrode possessed rather small electron transfer resistance and good catalytic activity towards nitrite oxidation, and hence could be used as a nonenzymatic nitrite sensor. The analytical applicability of the approach was examined by measuring the nitrite content in soil, sewage and sausage real samples and the results showed that this approach was promising.Section four:Ultrasonic potentiostatic electrodeposition of PtRu, PtPd and PtAu alloy nanopaticles on [P6,6,6, 14][NTf2]-MWNT composition film and their application in fabricating nonenzymatic glucose sensor.Bimetallic PtRu, PtPd and PtAu alloy nanoparticles were prepared on [P6,6,6, 14] [NTf2]-MWNTs composition film by using ultrasonic-electrodeposition. The obtained alloy nanoparticles were characterized by SEM, XPS, XRD, and CV, which showed that the size, composition and the active surface coverage of these three alloy nanoparticles were distinguishing. Electrochemical observation showed that comparing with PtAu and PtPd alloy, the PtRu-MWNT-IL modified electrode had high electrocatalytic activity for glucose oxidation in neutral solutions, not only provided a remarkable synergistic augmentation of the response current toward glucose, but also lowerd the overpotential effectly. When used as a glucose sensor, it exhibited high sensitivity, good stability and reproducibility. Meanwhile, the interference of ascorbic acid, uric acid, acetamidophenol and fructose which commonly present in physiological samples were effectively avoided. The good selectivity of this sensor was mainly due to the appropriate working potential (-0.1 V). The as-made sensor was applied to the determination of glucose in serum and urine samples. The results agreed closely with the results obtained by a hospital. The good recoveries indicated that the novel sensor has potential application in glucose detection.Section five:Ultrasonic potentiostatic electrodeposition of PtAu alloy nanopaticles on [P6,6,6, 14][NTf2]-chitosan composition film and their application in fabricating nonenzymatic hydrogen peroxide sensor.PtmAun alloy nanoparticles (where m and n represent the relative ratio of PtCl62-/AuCl4- in the solution) were fabricated on [P6,6,6, 14][NTf2]-chitosan(Ch) film by using an ultrasonic electrodeposition method. As a support, the [P6,6,6, 14][NTf2]-Ch composition film exhibited unique microcosmic morphology. The obtained AuPt nanoparticles deposited on it with tuneable lattice structure, the atomic ratio of Pt/Au in the alloy nanoparticles and size was accomplished by controlling the ratio of PtCl62- and AuCl4- in solution and the condition of electrodeposition. When the ratio of PtCl62-/AuCl4- was 1:3, the resulting electrode (i.e.,Pt1Au3-[P6,6,6,14][NTf2]-Ch modified electrode) displayed high catalytic activity to the reduction of hydrogen peroxide, it could effectively decrease the overpotential of hydrogen peroxide and make detection at low concentration levels possible. The electrode also had advantages in terms of rapid response, simplicity, low cost, excellent stability, reproducibility and high selectivity. Various biological molecules, metallic cations and inorganic anion could not interfere in the determination of hydrogen peroxide. The hydrogen peroxide contents in four real samples (i.e., honey, milk, urine, and plasma) were determined with this sensor, and the measurement results were acceptable.Section six:Ultrasonic potentiostatic electrodeposition of PtAuPd ternary alloy nanopaticles on mercapto IL film and their application in fabricating nonenzymatic formaldehyde sensor.A newly mercapto IL (i.e., 1-methyl-3(2-mercaptoacetoxyethyl) imidazolium hexafluophosphate) was prepared synthesized and fistly used as a support. A PtAuPd ternary alloy nanoparticle film with high particle density, small particle size and narrow size distribution were fabricated on a novel mercapto IL film via ultrasonic-electrodeposition. The obtained alloy nanoparticles were compared with PtAu and PtPd deposited on IL film, and the PtAuPd alloy nanoparticles deposited on bare electrode by SEM, EDX, XRD, XPS and CV. The result showed that mercapto imidazolium IL was an effective support and could interacted with noble metal nanoparticles such as Pt, Au and Pd in the electrodeposition. Owing to the excellent poison-tolerance and the large active surface coverage of the PtAuPd ternary alloy nanoparticles, the resulting modified electrode presented high electrocatalytic activity and stability toward formaldehyde electro-oxidation, hence could be used as a novel nonenzymatic formaldehyde sensor.Section seven:Ultrasonic potentiostatic electrodeposition of AuNi and AuCo alloy nanopaticles on mercapto IL-graphite gel film and their application in fabricating nonenzymatic hydroquinone sensor.A novel mercapto imidazolium IL (1-methyl-3(2-mercaptoacetoxyethyl) imidazolium hexafluophosphate))-graphite gel was fabricated by grinding. Bimetallic AuNi and AuCo nanoparticles were electrodeposited on it by using an ultrasonic electrodeposition method. During the electrodeposition, the imidazolium ring moiety of IL might interact with theπ-electronic nanotube surface by virtue of cation-πand/orπ-πinteractions, and the functionalized group-SH of IL might interact with the novel metal nanoparticles, therefore the function of mercapto IL had acted as a "bridge". The resulting catalysts were characterized by SEM, EDX, XPS and EIS, respectively. It was found that the mercapto IL-graphite was an ideal catalyst support for the electrodeposition of metal nanoparticles. The nanoparticles were well-dispersed on its surface and exhibited many unique features. The alloy formation with tunable composition, size and SEAS electrocatalytic active had been accomplished by controlling the composition of the support material and the electrodepositon potential. The electrocatalytic results showed that the resulting electrocatalyst had excellent catalytic activity as well as high reproducibility and stability for hydroquinone redox. The proposed procedure was successfully applied to the detection of hydroquinone in environmental samples.