Zhang, Minwei

Grafen, en todimensional (2-D) sp2-hybridiseret type af kulstof, er blevet et af de mest interessante materialer, siden det blev opdaget i 2004. Denne enkelt-atom-tykke plade af kulstofatomer arrangeret i et bikubemønster udviser fremragende fysisk-kemiske egenskaber, nemlig fremragende ledningsevne for både varme og elektricitet og høj mekanisk styrke. Grafen udviser derfor stort potentiale til brug i sensorer, katalysatorer, elektroder, og i biologiske systemer m.v., og med videreudvikling af den teoretiske forståelse og praktiske anvendelse af grafen, vil dette materiale spille en væsentlig rolle for samfundet i moderne teknologi. Grafene-baserede materialer bør samles til makroskopiske arkitekturer med specifikke strukturelle og funktionelle egenskaber. En oxideret form af grafen, grafenoxid (GO), har en masse iltholdige funktionelle grupper, som giver mulighedfor funktionalisering og konstruering af 2-D grafenfilm/papir/membraner med forskelligemakroskala former gennem forskellige fabrikeringsteknikker. Disse 2-D materialer kan anvendes som ideelle stilladser til indarbejdelse af andre funktionelle materialer for at opnå specifikke funktionaliteter. Fordelene ved lette, supra-fleksibilitet, stort overfladeareal, stor mekanisk styrke,og høj elektrisk ledningsevne sikrer grafene-baserede arkitekturer bred anvendelse. I denne afhandling gives først et overblik over funktionelle makroskopiske grafene materialer ud fra tre synspunkter; 1) hvordan man forbereder 2-D grafenefilm/papir, 2) hvordan materialet kan funktionaliseres ved hjælp af enten polymerer eller nano-objekter, og 3) lovende mulige anvendelser af 2-D grafenfilm/papir som molekylær si til oprensning, biomimisk, fleksibelt substrat, sensorer og elektrokemiske energikomponenter. Derefter præsenteres arbejdet med grafeneoxideller grafenepapir modificeret med preussisk blå nanopartikler og -kuber. Flere avancerede teknikker (XRD, XPS, TEM, SEM m.m.) blev anvendt til karakteriseringen af de fremstillede nanokompositter. Baseret på disse materialer blev nye, højtydende, ultrafølsomme og billigeelektroder fremstillet og anvendt som elektrokemiske sensorer til detektering af hydrogenperoxid. Endelig blev grafenepapir designet som nedbrydelig skabelon for 2-D nanoporøse metaloxider (MO) via direkte dekomponering af GO-papir ved tilstedeværelse af metalioner. I kapitel 6 demonstreres, hvordan en række forskellige krystallinske MO kan fremstilles ved denne metode. Desuden blev lag-på-lag, nanoporøse og ultratynde 2-D CuO nanolag blev anvendt som i en fotocanode til energikonvertering. I kapitel 7 og 8 blev CuO/ZnO hybrid-nanolag og NiO nanolag designet som en ikke-enzymatisk sensor til højfølsom analytisk detektering af glukose og urea.Graphene has emerged as a highly interesting material since it was experimentally isolated for the first timein 2004. This single-atom-thick nanosheet consisting of carbon atoms arrayed in a honeycomb pattern,displays outstanding physicochemical properties, including as an excellent conductor of heat and electricity,large specific surface area, and high mechanical strength. Therefore, graphene based materials are expected to have great potential for use in the fields of sensors, catalysis, and as electrode materials for energy storage and conversion. In order to link practical applications of graphene-based materials to real world, graphene nanosheets must be assembled into macroscopic architecture with desired structures and functionality. To this end, graphene oxide (GO) is a very useful building block because it contains a significant number of oxygen-containing groups on the planar surface and at the edges. These functional groups offer various possibilities for functionalization and assembly of GO nanosheets into 2D graphene films, papers or membranes with controlled macroscopic shapes. Resulting 2D graphene films/papers/membranes can be used as ideal scaffolds for the further incorporation of functional materials with specific desired functionality. The advantages of light-weight, high flexibility, large specific surface area, tough mechanical strength, and high electrical conductivity ensure graphene-based architectures holding a wide range of applications particularly associated with sensor and energy technologies. This PhD project is devoted to the synthesis, characterization and applications of graphene paper based nanomaterials for electrochemical sensors and energy conversion. The thesis is divided into three parts with 8 chapters in total. In Chapter 1, we provide an overview of the functional macroscopic graphene materialscovering three key aspects: a) how to prepare 2D graphene films/papers, b) how to functionalize them with either polymers or other nanoscale objects, and c) what are their promising applications in the fields of molecular sieving purification, biomimetics, as flexible substrates, sensors and electrochemical energy devices. This is followed by an outline of the main experimental techniques and means used in the project (Chapter 2). In Chapters 3-5, the focus is on graphene-Prussian Blue (PB) composite materials. GO or graphene paper was functionalized by PB nanostructures including nanoparticles and interlocked PB cubes. A wide range of advanced techniques such as XRD, XPS, TEM, and SEM were employed to characterize the nanocomposites. The nanocomposites were tested for the construction of high-performance, ultrasensitive and low-cost electrochemical sensors for detection of hydrogen peroxide (H2O2). Graphene paper was finally explored as a sacrificial template for the synthesis of 2D ultra-fined nanostructured porous metal oxide (MO), as described in Chapters 6-8. In Chapter 6, we demonstrated that crystalline MO can be prepared by using GO papers as sacrificial templates, and furthermore layer-by-layer, nonporous and ultrathin 2D CuO nanosheets were assembled into flexible and ultralight papers as a photocathode used for photoelectrochemical catalysis of hydrogen evolution reaction. In Chapters 7 and 8, CuO-ZnO hybrid nanosheets and NiO nanosheets were synthesized, characterized and used in the fabrication of non-enzymatic electrochemical sensors for high-performance detection of glucose and urea, respectively

Online Research Database In Technology

Graphene Paper Based Nanomaterials for Electrochemical Sensing and Energy Conversion

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Graphene Paper Based Nanomaterials for Electrochemical Sensing and Energy Conversion

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