The requirement of a wire to each electrode is central to the design of any electronic device but can also be a major restriction. Herein it is shown how electrodes can be connected using light such that a multielectrode device requires only a single physical wire.

We seek to understand how the thermodynamics and kinetics of anthraquinone-containing self-assembled monolayer on silicon electrodes are affected by two key experimental variables: the intensity of the light assisting the anthraquinone/anthrahydroquinone redox process and the local solution environment. The substrates are chemically passivated poorly doped p-type silicon electrodes. The study presents a strategy for the selective modulation of either the anodic or the cathodic process occurring at the interface. Cyclic voltammetry studies showed that unlike for a proton-coupled electron transfer process performed at metallic electrodes, for the redox reaction of the anthraquinone unit on a silicon electrode it becomes possible to (i) selectively facilitate only the oxidation process by increasing the electrolyte pH or (ii) at a given pH value to increase the illumination intensity to anodically shift the onset of the reduction step only but leave the oxidation process thermodynamic unchanged. A model concerning the proton coupled electron transfer mechanism was proposed, where the electron transfer is the rate-determining step for the anthraquinone reduction while a deprotonation step is the rate-determining event for the anthrahydroquinone oxidation on poorly doped illuminated p-type silicon.

The impact of the coverage of ferrocene moieties, attached to a silicon electrode modified via hydrosilylation of a dialkyne, on the kinetics of electron transfer between the redox species and the electrode is explored. The coverage of ferrocene is controlled by varying the coupling time between azidomethyl ferrocene and the distal alkyne of the monolayer via the copper assisted azide-alkyne cyclo addition reaction. All other variables in the surface preparation are maintained identical. What is observed is that the higher the surface coverage of the ferrocene moieties the faster the apparent rates of electron transfer. This surface coveragedependent kinetic effect is attributed to electrons hopping between ferrocene moieties across the redox film toward hotspots for the electron transfer event. The origin of these hotspots is tentatively suggested to result from minor amounts of oxide on the underlying silicon surface that reduce the barrier for the electron transfer.

We demonstrate quantification of porosity, nanopore tortuosity, and electrical connectivity at the singlenanoparticle (NP) level for NPs synthesized by nanodropletmediated electrodeposition. Focused ion beam nanoslice tomography was used to slice NPs with ca. 10 nm slice resolution followed by imaging using scanning electron microscopy (SEM), allowing measurement of these parameters on NPs not amenable to transmission electron microscopy. Slices were reconstructed in three dimensions and revealed pores with an average size of 3 ± 2 nm and relative nanopore tortuosity of 46.8 ± 24.5. We also demonstrate a new technique to evaluate electrical connectivity at the single-NP level by taking advantage of material-selective electrodeposition. The rate of Cu electrodeposition differs significantly on Pt compared to carbon, implying Cu can be selectively electrodeposited onto Pt NPs adsorbed onto a carbon support. Following the Cu electrodeposition step, NP connectivity was determined by the presence of Cu on Pt, as studied by energy-dispersive X-ray spectroscopy and SEM. We demonstrate that NPs synthesized by electrodeposition have >97% connectivity with underlying highly oriented pyrolytic graphite (HOPG) or amorphous carbon electrodes. The same method was employed to study connectivity of citrate-capped Pt NPs (diameter of 70 nm) on HOPG and amorphous graphite adsorbed by drop-casting. Surprisingly, <80% of these NPs had connectivity on HOPG and <40% had connectivity on amorphous carbon. These techniques will find applications in nanomaterials characterization, particularly in the fields of electrocatalysis and energy storage and conversion.

. (2013). The detailed characterization of electrochemically switchable molecular assemblies on silicon electrodes. Physical Chemistry Chemical Physics, 15 (24), 9879-9890.The detailed characterization of electrochemically switchable molecular assemblies on silicon electrodes AbstractIn this paper we explore a multi-step synthetic strategy toward fabrication of monolayer-modified Si(100) electrodes that can be electrochemically switched. The synthetic scheme is modular and benefits from an established intramolecular lactonization scheme of benzoquinone analogs. A redox-tagged pendant group can be released from the surface such as to allow for in situ monitoring of the switch process. We show that this model system can be used to elucidate chemical and structural events for a surface dynamic system that is rapidly gaining popularity. The influence of polarization times, overpotentials and semiconductor doping type on the kinetic of the switch event is also investigated. In both basic and acidic aqueous electrolytes the release of suitable redox-active markers is found to require unexpectedly large cathodic overpotentials. The release event is accompanied by minor oxidation of the electrode surface and the switched constructs can be regenerated by chemical means with no appreciable deterioration of surface quality. 2013 the Owner Societies. The detailed characterization of electrochemically switchable molecular assemblies on silicon electrodes † Simone Ciampi, a Michael James,z b Moinul H. Choudhury, a Nadim A. Darwish a and J. Justin Gooding* aIn this paper we explore a multi-step synthetic strategy toward fabrication of monolayer-modified Si(100) electrodes that can be electrochemically switched. The synthetic scheme is modular and benefits from an established intramolecular lactonization scheme of benzoquinone analogs. A redox-tagged pendant group can be released from the surface such as to allow for in situ monitoring of the switch process. We show that this model system can be used to elucidate chemical and structural events for a surface dynamic system that is rapidly gaining popularity. The influence of polarization times, overpotentials and semiconductor doping type on the kinetic of the switch event is also investigated.In both basic and acidic aqueous electrolytes the release of suitable redox-active markers is found to require unexpectedly large cathodic overpotentials. The release event is accompanied by minor oxidation of the electrode surface and the switched constructs can be regenerated by chemical means with no appreciable deterioration of surface quality.