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In this work, we have linked the dihydroazulene (DHA)/vinylheptafulvene (VHF) photo-/thermoswitch and the boron subphthalocyanine (BsubPc) fluorophore via an axial oligo(phenyleneethynylene) bridging unit into new DHA-BsubPc conjugates. The objectives were to elucidate the influence of BsubPc on the DHA/VHF switching reactions and the influence of DHA/VHF on the BsubPc fluorescence in these conjugates for which the entire axial substituent connected to boron comprises one large, conjugated scaffold. We present the synthesis and properties of DHA-BsubPc conjugates with varying peripheral substituents on the BsubPc core, being either unsubstituted (H12BsubPc) or partially fluorinated (F6BsubPc). Fluorination of the BsubPc core provided a remarkable increase in the reversibility of the DHA-VHF interconversions promoted by light and heat, respectively, and accompanied by on/off switching of the BsubPc fluorescence. Synthetically, the units were connected using Sonogashira coupling reactions of suitable acetylenic building blocks.

This paper describes tunneling junctions comprising self-assembled monolayers that can be converted between resistor and diode functionality in-place. The rectification ratio is affected by the hydration of densely packed carboxylic acid groups at the interface between the top-contact and the monolayer. We studied this process by treatment with water and a water scavenger using three different top-contacts, eutectic Ga-In (EGaIn), conducting-probe atomic force microscopy (CP-AFM), and reduced graphene oxide (rGO), demonstrating that the phenomena is molecular in nature and is not platform-speciffc. We propose a mechanism in which the tunneling junctions convert to diode behavior through the lowering of the LUMO, which is suffcient to bring it close to resonance at positive bias, potentially assisted by a Stark shift. This shift in energy is supported by calculations and a change in polarization observed by X-ray photoelectron spectroscopy and Kelvin probe measurements. We demonstrate light-driven modulation using spiropyran as a photoacid, suggesting that any chemical process that is coupled to the release of small molecules that can tightly bind carboxylic acid groups can be used as an external stimulus to modulate rectification. The ability to convert a tunneling junction reversibly between a diode and a resistor via an effect that is intrinsic to the molecules in the junction extends the possible applications of Molecular Electronics to reconfigurable circuits and other new functionalities that do not have direct analogs in conventional semiconductor devices.

Theworkpresentedinthisthesisisfocussingontheutilizationofgraphenederivativesas electrodematerialindifferentapplications.Itcanbedividedintotwomainapplications.The firstisregardingprintingoflarge-areathinfilmsofreduced grapheneoxide,andtheelectron conductanceofthese.Thesecondisfocussingonmolecularelectronicdevices,andhowgraphene derivativescanbeimplementedasantopelectrode. Large-areathinfilmsofreducedgrapheneoxidewereinvestigated,asapotentialmaterial forfabricationoftransparentandflexibleelectrodesatan industrialscale.Differentvariations oftheHummers’oxidationreactionwasutilizedtoproducegrapheneoxidefromgraphite.A grapheneoxidesuspensionwasup-concentratedintoahighly viscousaqueousgrapheneoxide ink.Theinkwasscreenprintedintomacroscopicelectrodestructures.Theinsulatinggraphene oxideelectrodeswerereducedwithhydroiodicacidvapourintosemi-transparent,flexibleand conductivereducedgrapheneoxideelectrodes. Itwasshownthatmicroscopicstructuresinthethinfilms,introducedbytheprintingpro- cess,influencedtheoptoelectronicpropertiesofthereducedgrapheneoxideelectrodes.The- refore,wesetouttoinvestigatethechargetransportinreducedgrapheneoxidethinfilms, inordertoimprovethenext-generationgrapheneoxideinks forscreenprintingmacroscopic electrodes.Itwasfound,thatbettercontroloverthephysicalpropertiesofthegrapheneoxide inkwasofdemandforprintingofhighlytransparentandconductiveelectrodes. Anotherfindingfromthechargetransportstudies,wasthatan improvedqualityofredu- cedgrapheneoxideshowednearlytemperatureindependentchargetransport.Thisfinding openedupforlowtemperatureconductancemeasurementsand InelasticElectronTunnelling spectroscopyoflargeareamolecularmonolayers. Theusabilityofgrapheneoxideinmolecularsolidstatedeviceswasfurtherinvestigated.It wasshownthatasinglesheetofgrapheneoxidecouldfunction asamonoatomicprotectionlayer inmolecularjunctions,preservingtheintegrityofthemolecularmonolayer.TheLangmuir