Scanning probe microscopy and spectroscopy: theory, techniques, and applications
This indicates that the complexity of intercalation mechanisms of alkali metal cations into the films might be oversimplified. Further, we demonstrate the influence of the electrolyte pH on the net charge of the pure Pt poly electrode surface. All the obtained data emphasize the role of the electrolyte composition for the kinetics and mechanisms of the interfacial processes.
Resume : Secondary ion mass spectroscopy SIMS is a characterization technique with ultra high chemical sensitivity and high depth resolution, widely established for materials analysis in the field of semiconductors. Recent advances, including the reduction of the lateral resolution to ca. We investigate the impact of different analysis conditions which unravel the impact of the analysis conditions Bi analysis beam, sputtering with large Oxygen clusters on various artifacts induced by the ion-beam such as sputtering process, topographic ion yield variations, charging effects and bias-induced electro-migration of mobile cations.
This allows us to establish the correlation between the electrical and the chemical inhomogeneities in the materials and identify the role of nanoscopic non uniformities. Resume : Interfaces between two immiscible electrolyte solutions ITIES are a promising model mimicking some functional biomembranes in nature charge carrier separation by two interacting photocenters-z-scheme and offer novel opportunities for catalyst regeneration or exchange at the interfaces of liquids . Polarizable interface represents molecularly sharp platform suitable for assembling of nanostructured semiconductor photocatalysts which have been proposed as a novel approach, generating charge careers electron-holes pair reactants in either side of interface, involving in photo-induced charge transfer reactions at liquid-solid-liquid boundaries .
We studied O2 evolution by hyperbranched nanocrystaline BiVO4 at chemically polarized ITIES by [Co bpy 3] PF6 3 as an electron-acceptor compound in organic phase , which dramatically inhibits fast unfavorable electron-hole recombination, similar to z-schemes in natural photosynthesis .
Then, it clearly influences the efficiency of the parallel reaction of photo-generated hole-driven water oxidation by increasing the O2 evolution rate. This systems also allows to interrogate the photoelectrochemical reaction by oxidation of [Co bpy 3]2 as a photo-induced electron transfer product in an organic phase of interface by utilizing detector microelectrode ME in the organic phase in a scanning electrochemical microscope SECM. Furthermore, interfacial polarization effects on the photogenerated charge transfer reactions were investigated by recording regeneration of the reduced form of [Co bpy 3] PF6 3 in organic side of the BiVO4 layer in SECM feedback approach curves and detection of O2 as main product of water photo-oxidation in aqueous side in the generation collection mode.
Firstly, the micropipette can be prepared with orifices much smaller than the Au ME so that very high collection efficiencies for [Co bpy 3]2 is attained. This mode allows quantitative assessment of adsorbed hydroxyl radicals OH? In the interrogation step, the ME-generated titrant Co2 reacts with adsorbed hydroxyl radicals.
Proximal Probes | Center for Functional Nanomaterials
Reference:  D. Weinberg, C. Gagliardi, J. Hull, C. Murphy, C. Kent, B. Westlake, A.
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Paul, D. Ess, D. McCafferty, T. Meyer, Chem. Smirnov, P.
Peljo, H. Girault, Chem. Rastgar, M. Pilarski, G. Wittstock, Chem. Dymond, C. Hague, A.
Postle, G. Attard, J.
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Zhu, S. Yan, S. Wang, Chem. Park, K. Leonard, A. Bard, J. C , , Resume : Charging and discharging of nanometer-sized and tunable-shaped objects are very important to fundamental research as well as to potential applications. For instance, isolated external charges can be used as an electrostatic gating for material transport in the nano-channels.
On the other hand charging and discharging of objects provide a powerful tool to studying the electrostatic properties on the nanometer scale. Here, we report on the charging of individual graphene oxide GO sheets with varied degrees of reduction by using electrically biased atomic force microscope AFM tips. AFM measurements indicate that the apparent height of reduced GO rGO sheets increases sharply after charging, while the charging ability is enhanced when the GO sheets are deeply reduced.
Charging on isolated areas with tunable shape and size on single-layered GO has been achieved. In addition, charge transfer between rGO sheets separated in hundreds of nanometers on insulating substrates was investigated. It was found that the rGO sheet collects charges from the adjacent charged rGO sheet through the dielectric surfaces. The efficiency of charge transfer between the separated rGO sheets is dependent on their separation distance, gap length, and the substrate type. The findings suggest that the charge interflow should not be neglected in a graphene circuit.
Resume : Local dielectric property detecting is of great importance in many scientific research and application. In the last two decades, many scanned probe microscopy SPM techniques have been developed to fast detection of surface dielectric properties of nanoscale materials.
Here, we report a novel method for characterization of local dielectric property based on surface adhesion mapping by atomic force microscopy AFM. We use two dimensional 2D materials—graphene oxide GO and partially reduced graphene oxide rGO sheets, which have similar height but large difference in dielectric property, as the model systems. By comparing with scanning polarization force microscopy SPFM , our approach is found to have higher sensitivity and lateral resolution.
It is expected to provide a better and faster characterizing of local dielectric property of nanoscale materials, and will further facilitate applications in future nanomaterial based device.
Scanning tunneling microscopy and spectroscopy: Theory, techniques and applications
Resume : Efficient charge extraction within solar cells explicitly depends on the optimization of the internal interfaces. Potential barriers, unbalanced charge extraction or interfacial trap states can prevent cells from reaching high power conversion efficiencies. In the case of perovskite solar cells, slow processes happening on timescales of seconds cause hysteresis in the current-voltage characteristics. Although hysteresis can nowadays be mostly avoided by selection of suitable selective electrode materials, its origin is not yet fully understood.
Here, we report on local and time-dependent potential measurements with Kelvin probe force microscopy KPFM on cross sections of planar methylammonium lead iodide MAPI perovskite solar cells. Our experiments revealed distinct differences in the charging dynamics at interfaces of the MAPI to adjacent layers. Measurements while switching on and off the illumination attest that more than one process is involved in hysteresis. Furthermore, we used KPFM to investigate perovskite solar cells with different electron transport materials ETM , which exhibited a different hysteretic behavior.
Depending on the ETM we observed oppositely oriented electric fields within the perovskite layer, which either aid or counteract the charge carrier extraction from the active layer. Our findings suggest that the introduction of electric fields in the perovskite layer and thus the occurrence of J-V hysteresis could be controlled by the choice of ETM. Hou, Y.