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Metal Element-containing Micro-nano Materials: Rapid Preparation And Their Photo-/electrochemical Properties

Posted on:2017-02-11Degree:DoctorType:Dissertation
Country:ChinaCandidate:M M GuoFull Text:PDF
GTID:1221330482488110Subject:Analytical Chemistry
Abstract/Summary:PDF Full Text Request
Compared with non-nano materials, nanomaterials with unique structure have a series of special effects, such as quantum size effect, surface and boundary effect, macro quantum tunnel effect, small size effect, and dielectric confinement effect, which give specific properties and have been widely used in many fields such as energy, chemical industry, electronics, communications, metallurgy, biology and medicine. Therefore, to explore novel simple, mild, cheap, green and controllable preparation methods of nanostructure functional materials with very important application value have received extensive attention of the researchers. This doctoral dissertation developed several electrochemical methods and gas-liquid interface assembly methods for rapid preparation of micro/nanostructure functional materials, which involved in nonenzymatic glucose sensors based on Ni(OH)2-coated nanoporous gold film(Ni(OH)2/NPGF), Cu/NPGF, stalactite-like copper micropillar arrays and Cu nanodendrites decorated reduced graphene oxide, SERS substrate and superhydrophobic surface with different micro/nano-structure Cu films, anode material Ni Fe(OH)x QDs/Cu Ox microarrays for electrocatalytic oxygen evolution reaction, semiconductor nanofilms with photoelectrochemical characteristics. The main contents are as follows:1. Literatures about the preparation of metal element-containing micro/nano materials and their applications in nonenzymatic glucose sensors, electrocatalytic water splitting, superhydrophobic surface, SERS substrate, and photoelectrochemical solar cells have been systematically reviewed.2. Fabrication of new advanced nonenzymatic electrochemical nano-sensors of glucose has recently attracted intensive attention. In this work, we designed a novel ultrasensitive nonenzymatic amperometric sensor for detection of glucose by incorporating two pairs of effective electron mediators, Ni(II)/Ni(III) and Au/Au(I), into a nanoporous structure, namely a nanoporous gold film(NPGF) coated with a thin layer of nickel hydroxide about 4 nm in thickness. The NPGF with high roughness was quickly prepared by anodic potential step, and the thin surface coating of Ni(OH)2 was easily obtained by electrooxidizing the electrodeposited Ni coverlayer. The incorporation of thin Ni(OH)2 coating into/on the NPGF led to mutual stabilization without changing the nanoporous structure. The Ni(OH)2/NPGF electrode fabricated totally by facile electrochemical methods at room temperature showed high electrocatalytic activity for the oxidation of glucose within a wide potential range(-0.5~0.2 V) due to co-mediating of the two pairs of electron mediators including their coupling Ni(III) + Au = Ni(II) + Au(I). The electrode also demonstrated excellent performance in sensing glucose concentration with a wide linear range(2 μM~7 m M), ultrasensitivity(3529 μA m M-1 cm-2), low detection limit(0.73 μM), good repeatability, and long-term stability(3 weeks), which was successfully applied to detect glucose in a human blood serum sample by standard addition method with satisfactory recovery. This work is expected to open a new avenue to fabricate nonenzymatic electrochemical sensors of glucose involving co-mediating.3. We constructed an ultrasensitive non-enzymatic amperometric glucose sensor based on a Cu-coated nanoporous gold film(Cu/NPGF) for the first time, which comprised two pairs of electron mediators, Cu(II)/Cu(III) and Au/Au(I). The nanoporous gold film with high roughness was prepared by anodic potential step and the very thin Cu coating into/on the nanoporous Au was electrodeposited at constant current. In comparison with electrodeposited Cu on a smooth gold surface and with the nanoporous Au, the prepared Cu/NPGF showed significantly enhanced electrocatalytic activity for the oxidation of glucose around 0.1 V due to its nanoporous structure and the pronounced co-mediating of Cu(II)/Cu(III) and Au/Au(I), as well as their coupling Cu(III) + Au = Cu(II) + Au(I). The Cu functionalized NPGF electrode also exhibited an extraordinary performance in sensing glucose with a wide linear range(2 μM-8.11 m M), short response time(3 s), ultrasensitivity(3643 μA m M-1 cm-2), low detection limit(0.59 μM), good anti-interference and anti-toxicity, long-term stability(over 3 weeks), and satisfactory quantification of glucose concentration in human serum. We expect that functionalization of nanoporous gold films will provide a new platform for electrochemical sensors.4. An ultrasensitive nonenzymatic amperometric glucose sensor was facilely constructed based on a novel stalactite-like copper micropillar array, which was fabricated by surface rebuilding of a smooth Cu electrode in a blank H2SO4 electrolyte without using templates and precursor solutions. During repeated square wave potential pulse perturbation, the smooth surface of Cu electrode was reshaped into a thin film of aggregated nanoparticles, assembled microspheres and then stalactite-like Cu micropillar arrays consisting of layered irregular Cu nanoflakes through repeated electrodissolution/electrodeposition of Cu. This is similar to the natural formation processes of stalactites that involve repeated dissolution/precipitation of Ca CO3. Moreover, the accompanying evolution of hydrogen bubbles led to the pillar arrays porous. Such micro/nanostructured Cu pillar arrays are beneficial both for surface reactions and for mass transport. The influence of pulse potential, pulse frequency, perturbation time, and electrolyte concentration on the electrocatalytic activity of the treated Cu electrode was investigated in detail. The Cu pillar arrays not only had better electrocatalytic activity for oxidation of glucose than the aggregated Cu nanoparticles and assembled Cu microspheres, but also showed excellent electrochemical performance in sensing glucose with a wide linear range(500 n M~4.711 m M), short response time(5 s), ultrasensitivity(2432 μA m M-1 cm-2), low detection limit(190 n M), good anti-interference and anti-toxicity, long-term stability(over 4 weeks), and satisfactory quantification of glucose concentration in human serum.5. The copper nanodendrites coated by reduced graphene oxide nano-membrane(Cu-r GO) were obtained by a single-step electrochemical synthesis on a smooth glassy carbon(Gc) electrode. Without a large amount of reagent including Cu precursor, this method is simple, fast, cheap and easy to control. Due well composite structure and uniform surface, the electrocatalysis of glucose on Cu-r GO/Gc electrode was controlled by the diffusion process, which showed excellent electrochemical performance in sensing glucose with good anti-interference and anti-toxicity, wide linear range(500 n M~8 m M), small errors of small signal noise, low detection limit(226 n M), long-term stability(3 weeks), and favorable quantification of glucose concentration in human serum.6. Direct electrochemical shaping of metal surfaces into micro/nano-structures with desired functions isinteresting and attractive. In this work, we employed square wave potential pulses(SWPP) to shapea smooth Cu surface into micro/nano-structures efficiently in a blank H2SO4 solution. Delightedly, we obtained Cu sub-micrometric islands on the surface with very strong surface enhanced Raman scattering(SERS) effect in 5 s, and fabricated a coral-like micro/nano-structured copper film with superhydrophobicity in 40 s. This method is green, facile, fast, and easy to control.7. Fe Ni hydroxyl nanoparticles(NPs) were modified via successive ionic layer adsorption and reaction(SILAR) method on coral-like micro/nano-structured Cu Ox film from a rapid electrochemical processing. The whole preparation process is simple, green, low-cost, easy to control and suitable for mass production and promotion without special and expensive apparatuses. By altering the ratio between Fe and Ni precursors, electrocatalytic oxygen evolution reaction(OER) performances of the anode material were optimized. Eventually, a high-performance anode catalyst with consumption of little non-noble metal was obtained for electrocatalytic OER with low onset potential, small Tafel slope, low interface reaction impedance, excellent mass transfer and conduction properties, and favorable stability.8. Thin films of Cd Se nanoparticles(NPs) with good photoelectrochemical performances were rapidly fabricated by gas/liquid interface reactions and self-assembly. While dropping Na HSe ethanol solution onto the surface of Cd Cl2 solution, Cd Se NPs(~5-7 nm) formed, rapidly spread over the solution’s surface, and then assembled into a dense film with the help of a surfactant(dodecyl sulfate). After annealing, the film loaded on conducting glass of fluorine-doped tin oxide(FTO) became flat, uniform and dense, with improved light absorption, reduced electrical resistance and stable well crystalline transformation. Photoelectrochemical tests show that the prepared thin film of Cd Se NPs(as photoanode) could generate a saturated photocurrent density as high as 4.4 m A cm-2 at 0.69 V(versus RHE) and a solar-to-electricity conversion efficiency up to 2.85 % under visible light illumination of 100 m W cm-2 in a Na2SO3 solution for photoelectrochemical hydrogen production.9. We proposed a template-free method for preparation of micro-nanoporous Ti O2 thin films via gas/liquid interface assembly of Ti O2 nanoparticles and layer-by-layer transfer for thirteen times, which possessed good adhesion onto the fluorine-doped tin oxide(FTO) conductive glass after being dried. Cd S nanocrystals were filled into the micropores and adsorbed on the surface of micro-nanoporous Ti O2 film by successive ionic layer adsorption and reactions(SILAR) for six times. This unique composite structure made the optimized photoanode of FTO/Ti O2(assembled)/Cd S exhibit enhanced photoelectrochemical performances, which had a saturated photocurrent density as high as 6.28 m A cm-2 at about-0.9 V under visible light illumination of 100 m W cm-2 in a mixed solution of 1 M Na2SO3 + 0.2 M Na2 S, with a solar-to-electricity conversion(for H2 evolution) efficiency up to 5.09 %. We expect that this facile and low-cost method has potential applications in preparation of high-performance photoanodes.
Keywords/Search Tags:micro/nano functional materials, nonenzymatic glucose sensor, electrocatalysis, surface enhanced Raman scattering, photoelectrochemistry
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