Font Size: a A A

Studies On Graphene Oxide-based Materials: Liquid Crystals, Photonic Crystals And Cross-linked Enzyme Aggregates

Posted on:2015-12-11Degree:DoctorType:Dissertation
Country:ChinaCandidate:L P TongFull Text:PDF
GTID:1221330452470648Subject:Chemical Engineering
Abstract/Summary:PDF Full Text Request
Graphene oxide (GO) exhibits a range of unique properties, viz., remarkableoptoelectronic properties, extraordinary electrochemical properties and excellentbiocompatibilities, as well as many other supreme properties, all of which make ithighly attractive for optoelectronic and biological applications. In this thesis, in orderto explore the potentials of GO in various applications, including advancedoptoelectronic devices, chemical and biological sensors, our studies focued on theoptoelectronic properties and biocompatibilities of GO. The main conclusions wereshown as follow:(1) Graphite oxide liquid crystals: We firstly observed that stablely lyotropicnematic graphite oxide (GtO) liquid crystals could be quickly prepared by simple lychemical oxidation of graphite and subsequent concentration without sonication. Onthe basis of the statistical data of thickness and lateral width of GtO flakes, weestablished a phase diagram of GtO liquid crystals. A combination of polarized opticalmicroscope, scanning electron microscope, transmission electron microscope andsmall angle X-ray diffraction was used to examine structural details of GtO liquidcrystalline orientation and the results showed that GtO liquid crystals exhibitedlong-range ordered alignment. In order to explore the potential applications of GtOliquid crystals in the LCD field, an applied electric field was used. Results showedthat the Freedericksz transition was obvious and the macroscopic alignment of GtOliquid crystals could be readily controlled by the applied electric field.(2) Graphene oxide photonic crystals: For the first time, we described a simplemethod i.e. solvent evaproation for fabricating large-area1D GO photonic crystals(PhCs) exhibiting structural colors in the visible light region derived from GOaqueous suspensions. In the processing, we revealed the quantitative relationshipbetween the film thickness and reflection wavelength, and demonstrated how tosuppress the coffee ring effect to obtain the uniform photonic crystals. Based onexperimental analysis and characterization results, a1D model was proposed tosimulate the reflection and transmission spectra from certain angles of incident lightvia transverse-electric (TE) and transverse-magnetic (TM) Modes. For furtherapplications of GO PhCs, we investigated effects of different solvents on the GO PhCs, which exhibited quite sensitive to water.(3) Preparation of graphene oxide photonic crystals via electrophoreticdeposition: We firstly described the method to fabricate GO PhCs from GO aqueoussuspensions using electrophoretic deposition. Through the investigation of thesuspension pH, Zeta potential, conductivity and average particle size of GO, wesuccessfully fabricated GO PhCs deposited on Cu electrodes of different structuralcolors with different reflection wavelengths by controlling the deposition time.(4) Graphene oxide@lysozyme composite photonic crystals: On the basis ofinteraction analysis between GO and lysozyme (Lys), we proposed a strategy tofabricate the GO@Lys composite PhCs via evaporation self-assembly. SEM imagesand reflection spectra showed that GO@Lys PhCs possessed a uniformly periodiclayer structure and displayed different structural colors.Graphene oxide assisted cross-linked enzyme aggregates: In order to overcome thedisadvantage of low catalytic efficiency of conventional cross-linked enzymeaggregates (CLEAs), a new strategy to prepare GO-assisted CLEAs was proposed toimprove enzyme activity. Firstly, interaction analyses between GO, CRGO-0.5h,CRGO-2h and lysozyme were characterized by the combination of UV-Visspectroscopy, fluorescence spectroscopy and adsorption models, respectively. Theresults indicated that GO was found to strongly interact with lysozyme and inhibit theactivity of lysozyme through electrostactic interaction. The preparation ofGO-assisted CLEAs contained three steps i.e. the adsorption of lysozyme on GO,cross-linking and desorption of CLEAs from GO. GO was used to protect the activesites of lysozyme through electrostatic adsorption. Finally, GO-assisted CLEAs weresuccessful fabricated and exhibited the highest activity compared with conventionalCLEAs and free lysozyme.
Keywords/Search Tags:graphite oxide liquid crystals, graphene oxide photonic crystals, electrophoretic deposition, lysozyme, cross-linked enzyme aggregates
PDF Full Text Request
Related items