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The aim of this Note is to give a generalisation of the following theorem of Henkin and Passare: let Y be an analytic subvariety of pure codimension p in a linearly p-concave domain U, and ω a meromorphic q-form (q>0) on it; if the Abel–Radon transform A(ω∧[Y]), which is meromorphic on U*, has a meromorphic prolongation to U*, then Y extends to an analytic subvariety of U, and ω to a meromorphic form on it. The problem is to show the analogous statement when we replace ω∧[Y] by a current α of a more general type, called locally residual. We give the proof if α is of bidegree (N,1), or (q+1,1), 0 in the particular case where A(α)=0. We conclude with some applications of the theorem. To cite this article: B. Fabre, C. R. Acad. Sci. Paris, Ser. I 338 (2004). [Copyright &y& Elsevier]

The copper-based catalyst is considered to be the only catalyst for electrochemical carbon dioxide reduction to produce a variety of hydrocarbons, but its low selectivity and low current density to C2 products restrict its development. Herein, a core-shell xZnO@yCu2O catalysts for electrochemical CO2 reduction was fabricated via a two-step route. The high selectivity of C2 products of 49.8% on ZnO@4Cu2O (ethylene 33.5%, ethanol 16.3%) with an excellent total current density of 140.1 mA cm−2 was achieved over this core-shell structure catalyst in a flow cell, in which the C2 selectivity was twice that of Cu2O. The high electrochemical activity for ECR to C2 products was attributed to the synergetic effects of the ZnO core and Cu2O shell, which not only enhanced the selectivity of the coordinating electron, improved the HER overpotential, and fastened the electron transfer, but also promoted the multielectron involved kinetics for ethylene and ethanol production. This work provides some new insights into the design of highly efficient Cu-based electrocatalysts for enhancing the selectivity of electrochemical CO2 reduction to produce high-value C2 products. [ABSTRACT FROM AUTHOR]

One of the major aspects and advantages of solar energy conversion is the photocatalytic hydrogen generation using semiconductor materials for an eco-friendly technology. Designing a low-cost efficient material to overcome limited light absorption as well as rapid recombination of photogenerated charge carriers is essential to achieve considerable hydrogen generation. In recent years, sulfide based semiconductors have attracted scientific research interest due to their excellent solar response and narrow band gap. The present review focuses on the recent approaches in the development of hierarchical ternary sulfide based photocatalysts with a special focus on ZnIn2S4. We also observe how the electronic structure of ZnIn2S4 is beneficial for water splitting and the various strategies involved for improving the material efficiency for photocatalytic hydrogen generation. The review places emphasis on the latest advancement/new insights on ZnIn2S4 being used as an efficient material for hydrogen generation through photocatalytic water splitting. Recent progress on essential aspects which govern light absorption, charge separation and transport are also discussed in detail. [ABSTRACT FROM AUTHOR]

The reaction of [Re6Qi 8(OH)a 6]4- (Q = S, Se) with p-tert-butylpyridine (TBP) in water leads to neutral trans- [Re6Q8(TBP)4(OH)2] whose hydroxyl reactivity with carboxylic acid and TBP exchange reaction with functional pyridine have been investigated. [ABSTRACT FROM AUTHOR]

Stable, efficient, and low‐cost photoanodes are urgently required for manufacturing water‐splitting photoelectrochemical cells. Although silicon is a promising photoelectrode substrate, photocorrosion prevents its use in such devices, especially when employed as photoanodes for the oxygen evolution reaction (OER). Here, it is shown that Fe nanoparticles (NPs), deposited by cathodic electrodeposition onto n‐Si, can promote hole transfer for the OER. The influence of the surface coverage, the Si structure, as well as the electrolyte are studied here in detail. It is reported that the NP density and the Si structuration drastically affect the photoelectrochemical performance and that the electrolyte influences the stability, allowing operation times as long as 130 h for these inhomogeneously coated photoelectrodes. [ABSTRACT FROM AUTHOR]

A new approach for the design of logic gates that do not involve chemical inputs is presented here. This concept is based on the polarization of a light-sensitive interface. AND and OR logic gates, working with cheap reactants, which locally triggered water splitting half reactions, were designed and operated. [ABSTRACT FROM AUTHOR]

p-Si type electrodes modified with different organic monolayers were investigated by reaction with radical anion and cation electrogenerated at a microelectrode operating in the configuration of a scanning electrochemical microscope. The method proves to be a convenient tool for investigating both the quality and the redox properties of the layer as previously demonstrated on metallic electrodes especially when the sample cannot be electrically connected. Approach curves recorded with the different mediators were used to investigate the electron-transfer rates across alkyl monolayers bound to p-type silicon substrates. Preliminary results indicate that the interracial electron transfer occurs via electron tunneling through the organic layer as generally described for SAMs grafted on gold electrodes. [ABSTRACT FROM AUTHOR]

Hybrid materials taking advantage of the different physical properties of materials are highly attractive for numerous applications in today's science and technology. Here, it is demonstrated that epitaxial bi‐domain III–V/Si are hybrid structures, composed of bulk photo‐active semiconductors with 2D topological semi‐metallic vertical inclusions, endowed with ambipolar properties. By combining structural, transport, and photoelectrochemical characterizations with first‐principle calculations, it is shown that the bi‐domain III–V/Si materials are able within the same layer to absorb light efficiently, separate laterally the photo‐generated carriers, transfer them to semimetal singularities, and ease extraction of both electrons and holes vertically, leading to efficient carrier collection. Besides, the original topological properties of the 2D semi‐metallic inclusions are also discussed. This comb‐like heterostructure not only merges the superior optical properties of semiconductors with good transport properties of metallic materials, but also combines the high efficiency and tunability afforded by III–V inorganic bulk materials with the flexible management of nano‐scale charge carriers usually offered by blends of organic materials. Physical properties of these novel hybrid heterostructures can be of great interest for energy harvesting, photonic, electronic or computing devices. [ABSTRACT FROM AUTHOR]

• A new Bi-coated graphite felt decorated with silver particles was prepared. • The parameters of the spontaneous deposition were optimized to achieve a homogenous material. • The bimetallic electrode exhibited high selectivity of 88% for formate production. • Ag and Bi played a complementary role instead to perform competitive reactions. • The high performance of the electrode evidenced its potential for CO 2 reduction. A 3D porous Ag-Bi electrode was developed to achieve the highly selective reduction of CO 2 into formate. Ag particles were deposited on Bi coated graphite felt by galvanic displacement reaction. The selectivity of the reduction was enhanced with the Ag-Bi electrode compared with Bi coated graphite felt. The bimetallic catalytic system converted CO 2 into formate with a high selectivity of 88% at -1.6 V SCE. The highly porous structure and large surface area of the electrode facilitated the mass transport, leading to a high surface current density of 76 mA cm−2 and a production rate of 8.1 ± 0.4 mmol cm−3 h−1 (62 ± 3 mg cm−2 h−1). These results are very promising in the context of the electrochemical conversion of CO 2. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The development of high-efficiency photoelectrodes at low manufacturing cost is of great interest for the production of renewable and green hydrogen through solar-driven water splitting. In this work, we use structural, optical, and photoelectrochemical characterizations to study the performance of unprotected epitaxial GaAs/Si photoelectrodes during photocorrosion. More specifically, we demonstrate that photoanodes including 1-μm thick GaAs epitaxially grown thin film on a low-cost Si substrate can produce a higher photocurrent than those measured for expensive commercial GaAs wafers. Based on photoelectrochemical experiments under monochromatic excitation, we show that the improved photocurrent has to be related to the dual-bandgap operation of the GaAs/Si photoelectrode, benefiting from both GaAs and Si photo-generated carriers. This result opens new possibilities to further design efficient and low-cost dual-bandgap photoelectrodes. A dual bandgap photoelectrode operation is demonstrated with GaAs thin films grown on Si. The III-V/Si photoelectrode is able to generate a larger photocurrent than a conventional photoelectrode made of a commercial GaAs substrate, due to the fact that de Si is photoactive. [Display omitted] • High photocurrents can be generated within cost-efficient GaAs/Si photoelectrodes. • Improved photocurrent performances are related to the Si substrate which is found to be photoactive and contributes to the photo-response of the GaAs/Si photoelectrode. • The concept of dual-bandgap III-V/Si single photoelectrode enables high efficiency and cost efficient photoelectrodes. [ABSTRACT FROM AUTHOR]

The article describes the covalent modification of n-type Si(III) substrates with an oxidizable ferrocene center-terminated alkyl monolayer. According to the authors, n-type silicon behaves as an insulator in dark and as a quasi-conductor upon illumination, providing a way to switch the contribution of the surface in the electron transfer. They add that the procedure yields a densely packed monolayer with a surface coverage of ca. 3.5 x 10-10 mol of ferrocene cm-2.

At the occasion of the fiftieth birthday of the introduction of the term 'metal atom cluster' by F. A. Cotton in inorganic chemistry, it is the good time to make a review on the advances in the engineering of molecular assemblies and nanomaterials based on octahedral Re metal atom clusters. The latter exhibit unique intrinsic structural and physicochemical properties (orthogonal disposition of metallic sites that can be selectively functionalized, photoluminescence, redox, generation of singlet oxygen) that make them relevant building blocks for the structuration at the nanometric scale and functionalization of hybrid organic-inorganic materials and supramolecular frameworks. After synthesis by solid state chemistry techniques at high temperature, inorganic precursors built up on face-capped $$\left[ {\left( {{\text{Re}}_{ 6} {\text{Y}}_{ 8}^{\text{i}} } \right){\text{Y}}_{ 6}^{\text{a}} } \right]$$ cluster units (Y = chalcogen and/or halogen) can be functionalized via solution chemistry techniques or organic melts to form $$\left[ {\left( {{\text{Re}}_{ 6} {\text{Y}}_{ 8}^{\text{i}} } \right){\text{L}}_{ 6}^{\text{a}} } \right]$$ (L = CN, OH, various organic ligands...). This work reports advances in the synthesis of $$\left[ {\left( {{\text{Re}}_{ 6} {\text{Y}}_{ 8}^{\text{i}} } \right){\text{Y}}_{ 6}^{\text{a}} } \right]$$ and $$\left[ {\left( {{\text{Re}}_{ 6} {\text{Y}}_{ 8}^{\text{i}} } \right){\text{L}}_{ 6}^{\text{a}} } \right]$$ cluster units as well as on their use in the elaboration of supramolecular frameworks, nanoparticles, hybrid nanomaterials (co-polymers and liquid crystals) and active molecular junctions. [ABSTRACT FROM AUTHOR]

Abstract: Shortened and oxidized multi-walled carbon nanotubes (MWCNTs) were functionalized with adenine using the amidation strategy. The adenine functionalized MWCNTs (Ad-MWCNTs) were complexed with a uracil substituted ferrocene and characterized by transmission electron microscopy (TEM), high resolution TEM (HRTEM), electron diffraction X-ray spectroscopy (EDX), and atomic force microscopy (AFM). The electrochemical properties of these novel nanohybrids were studied by cyclic voltammetry. The favorable supramolecular interaction of the electroactive species with the functionalized nanotubes through the efficient adenine–uracil base-pairing can be exploited for the design of new electronic devices. [Copyright &y& Elsevier]

We report the synthesis and characterization of adenine-single-walled carbon nanotube (SWCNT) hybrid materials, where for the first time nucleobases are covalently attached to the exosurface of SWCNTs. The structural properties of all hybrids have been characterized using usual spectroscopic and microscopic techniques. The degree of functional groups for functionalized SWCNTs (f-SWCNT5) 2a and 2b is one adenine group for each 26 and 37 carbon atoms, respectively. Solid-state magic angle spinning 13C NMR spectroscopy (MAS NMR) and electrochemistry have been also applied for the characterization of these f-SWCNTs. AFM images of f-SWCNT 2b showed an interesting feature of horizontally aligned nanotubes along the surface when deposited on highly oriented pyrolytic graphite surface. Furthermore, we evaluated the coordinating ability of these hybrid materials toward silver ions, and interestingly, we found a pattern of silver nanoparticles localized over the surface of the carbon nanotube network. The presence of aligned and randomly oriented CNTs and their abilityto coordinate with metal ions make this class of materials very interesting for applications in the development of novel electronic devices and as new supports for different catalytic transformations. [ABSTRACT FROM AUTHOR]

The preparation of monolayers based on an organic radical and its diamagnetic counterpart has been pursued on hydrogen-terminated silicon surfaces. The functional monolayers have been investigated as solid-state metal/monolayer/semiconductor (MmS) junctions showing a characteristic diode behavior which is tuned by the electronic characteristics of the organic molecule. The eutectic gallium-indium liquid metal is used as a top electrode to perform the transport measurements and the results clearly indicate that the SOMO-SUMO molecular orbitals impact the device performance. The junction incorporating the radical shows an almost two orders of magnitude higher rectification ratio ( R (| J 1V / J -1V |) = 10 4.04 ) in comparison with the nonradical one ( R (| J 1V / J -1V |) = 10 2.30 ). The high stability of the fabricated MmS allows the system to be interrogated under irradiation, evidencing that at the wavelength where the photon energy is close to the band gap of the radical there is a clear enhancement of the photoresponse. This is translated into an increase of the photosensitivity ( S ph ) value from 68.7 to 269.0 mA/W for the nonradical and radical based systems, respectively.

Introduction: Sustainable growth and environmental issues are currently a topic for all human activities, and dialysis represents a real challenge in this field because of high water and power consumption and the production of large amounts of care-related waste. In this article we describe data collection implemented in the NephroCare centres in France and the changes observed during a 13-year period regarding environmental parameters., Methods: Monthly data collection (eco-reporting) was implemented in NephroCare centres in France in 2005. It covers three topics designed as key performance indicators (KPIs): electricity and water consumption and care-related waste production expressed, respectively, as kilowatt-hour (kWh), litres (L) and kilograms per session. We report on the three action plans (2005-10, 2011-14 and 2015-18) and changes observed during this 13-year period., Results: During the period, power and water consumption declined by 29.6% (from 23.1 to 16.26 kWh/session) and 52% (from 801 to 382 L/session), respectively. At the same time, the yearly number of dialysis sessions has increased from 169 335 to 399 336. The sources of savings came both from improvements in the dialysis technology (dialysis machines and water treatment systems) and from updating and remodelling of the dialysis unit equipment and buildings. The care-related waste decreased from 1.8 to 1.1 kg because of regular staff training and the retrofiltration system, allowing the voiding of the remaining saline solution after dialysis. These savings have been estimated as equivalent to 102 440 tons of carbon dioxide., Discussion: Implementation of KPIs and their regular monitoring by trained staff to evaluate water and power consumption and the reduction of care-related water production are essential to implement actions to reduce the impact of dialysis on the environment. These data show the importance of water treatment and dialysis technology to decrease water and power consumption and the production of care-related waste as well as upgrading or remodelling of buildings housing dialysis units. Other measures are discussed, including the reuse of rejected water by reverse osmosis, as well as behavioural changes that are needed to reach sustainable development of dialysis., Conclusion: The first step to reach 'green' dialysis is to collect precise information from defined KPIs. This is the only way to design action plans to reduce the impact of dialysis therapy on the environment. Beyond this, the nephrology community must be sensitized to this challenge to be proactive and to anticipate future regulations., (© The Author(s) 2020. Published by Oxford University Press on behalf of ERA-EDTA.)

The incorporation of terminal alkynes into the chemical structure of persistent organic perchlorotriphenylmethyl (PTM) radicals provides new chemical tools to expand their potential applications. In this work, this is demonstrated by the chemical functionalization of two types of substrates, hydrogenated SiO 2 -free silicon (Si-H) and gold, and, by exploiting the click chemistry, scarcely used with organic radicals, to synthesise multifunctional systems. On one hand, the one-step functionalization of Si-H allows a light-triggered capacitance switch to be successfully achieved under electrochemical conditions. On the other hand, the click reaction between the alkyne-terminated PTM radical and a ferrocene azide derivative, used here as a model azide system, leads to a multistate electrochemical switch. The successful post-surface modification makes the self-assembled monolayers reported here an appealing platform to synthesise multifunctional systems grafted on surfaces., (This journal is © The Royal Society of Chemistry 2020.)

Molecular engineering of efficient HER catalysts is an attractive approach for controlling the spatial environment of specific building units selected for their intrinsic functionality required within the multistep HER process. As the {Mo 3 S 4 } core derived as various coordination complexes has been identified as one as the most promising MoS x -based HER electrocatalysts, we demonstrate that the covalent association between the {Mo 3 S 4 } core and the redox-active macrocyclic {P 8 W 48 } polyoxometalate (POM) produces a striking synergistic effect featured by high HER performance. Various experiments carried out in homogeneous conditions showed that this synergistic effect arises from the direct connection between the {Mo 3 S 4 } cluster and the toroidal {P 8 W 48 } units featured by a stoichiometry that can be tuned from two to four {Mo 3 S 4 } cores per {P 8 W 48 } unit. In addition, we report that this effect is preserved within heterogeneous photoelectrochemical devices where the {Mo 3 S 4 }-{P 8 W 48 } (thio-POM) assembly was used as cocatalyst ( cocat ) onto a microstructured p-type silicon. Using a drop-casting procedure to immobilize cocat onto the silicon interface led to high initial HER performance under simulated sunlight, achieving a photocurrent density of 10 mA cm -2 at +0.13 V vs RHE. Furthermore, electrostatic incorporation of the thio-POM anion cocat into a poly(3,4-ethylenedioxythiophene) (PEDOT) film is demonstrated to be efficient and straightforward to durably retain the cocat at the interface of a micropyramidal silicon ( SimPy ) photocathode. The thio-POM/PEDOT-modified photocathode is able to produce H 2 under 1 Sun illumination at a rate of ca. 100 μmol cm -2 h -1 at 0 V vs RHE, highlighting the excellent performance of this photoelectrochemical system.

Silicon photocathodes coated with drop-casted {Mo 3 S 4 }-based polyoxothiometalate assemblies are demonstrated to be effective for sunlight-driven hydrogen evolution reaction (HER) in acid conditions. These photocathodes are catalytically more efficient than that coated with the parent thiomolybdate incorporating an organic ligand, as supported by a higher onset potential and a lower overvoltage at 10 mA cm -2 . At pH 7.3, the trend is inversed and the beneficial effect of the polyoxometalate for the HER is not observed. Moreover, the polyoxothiometalate-modified photocathode is found to be also more stable under acid conditions and can be operated at the light-limited catalytic current for more than 40 h. Furthermore, X-ray photoelectron spectroscopy and atomic force microscopy measurements indicate that the cathodic polarization of both photocathodes leads to the release of a large amount of the deposited material into the electrolyte solution concomitantly with the formation of mixed valence species {Mo(IV) 3- x Mo(III) x O 4- n S n } (4- x )+ resulting from the replacement of S 2- sulfido ligands in the cluster by oxo O 2- groups; these combined effects are shown to be beneficial for the photoelectrocatalysis., Competing Interests: The authors declare no competing financial interest.

Boronic acid monolayers covalently bound to hydrogen-terminated Si(111) surfaces have been prepared from the UV-directed hydrosilylation reaction of 4-vinylbenzeneboronic acid. X-ray photoelectron spectroscopy (XPS) analysis of the modified surface revealed characteristic peaks from the attached organic molecule with the expected molecular composition and without the oxidation of underlying silicon. From XPS data, the surface coverage was estimated to be ca. 0.34 ± 0.04 ethylbenzene boronic acid chain per surface silicon atom (i.e., (4.4 ± 0.5) × 10 -10 mol cm -2 ), which is consistent with a densely packed monolayer. The electrochemical impedance spectroscopy measurements performed at pH 7.4 in the presence of the Fe(CN) 6 3- /Fe(CN) 6 4- reporter couple showed specific dopamine-induced changes as a result of the binding of the guest molecule to the immobilized boronate species. The charge-transfer resistance (R ct ) was found to decrease from 4.9 MΩ to 14 kΩ upon increasing the dopamine concentration in the range of 10 μM-1 mM. Furthermore, the presence of the interfering ascorbic acid until a concentration of 10 mM did not significantly change the electrochemical response of the functionalized surface. Comparative electrochemical data obtained at the reference ethylbenzene monolayer provided clear evidence that the immobilized boronic acid units were responsible for the observed changes.

The electroless deposition of Pt nanoparticles (NPs) on hydrogen-terminated silicon (H-Si) surfaces is studied as a function of the temperature and the immersion time. It is demonstrated that isolated Pt structures can be produced at all investigated temperatures (between 22 and 75 °C) for short deposition times, typically within 1-10 min if the temperature is 45 °C or less than 5 min at 75 °C. For longer times, dendritic metal structures start to grow, ultimately leading to highly rough interconnected Pt networks. Upon increasing the temperature from 22 to 75 °C and for an immersion time of 5 min, the average size of the observed Pt NPs monotonously increases from 120 to 250 nm, and their number density calculated using scanning electron microscopy decreases from (4.5 ± 1.0) × 10 8 to (2.0 ± 0.5) × 10 8 Pt NPs cm -2 . The impact of both the morphology and the distribution of the Pt NPs on the photoelectrocatalytic activity of the resulting metallized photocathodes is then analyzed. Pt deposited at 45 °C for 5 min yields photocathodes with the best electrocatalytic activity for the hydrogen evolution reaction. Under illumination at 33 mW cm -2 , this optimized photoelectrode shows a fill factor of 45%, an efficiency (η) of 9.7%, and a short-circuit current density (|J sc |) at 0 V versus a reversible hydrogen electrode of 15.5 mA cm -2 .

Macroporous layers are grown onto n-type silicon by successive photoelectrochemical etching in HF-containing solution and chemical etching in KOH. This specific latter treatment gives highly antireflective properties of the Si surface. The duration of the chemical etching is optimized to render the surface as absorbent as possible, and the morphology of the as-grown layer is characterized by scanning electron microscopy. Further functionalization of such structured Si surface is carried out by atomic layer deposition of a thin conformal and homogeneous TiO2 layer that is crystallized by an annealing at 450 °C. This process allows using such surfaces as photoanodes for water oxidation. The 40 nm thick TiO2 film acts indeed as an efficient protective layer against the photocorrosion of the porous Si in KOH, enhances its wettability, and improves the light absorption of the photoelectrode. The macroporous dual-absorber TiO2/Si has a beneficial effect on water oxidation in 1 M KOH and leads to a considerable negative shift of the onset potential of ∼400 mV as well as a 50% increase in photocurrent at 1 V vs SCE.

This review provides a comprehensive survey of the derivatization of hydrogen-terminated, oxide-free silicon surfaces with electroactive assemblies (from molecules to polymers) attached through strong interactions (covalent, electrostatic, and chimisorption). Provided that surface modification procedures are thoroughly optimized, such an approach has appeared as a promising strategy toward high-quality functional interfaces exhibiting excellent chemical and electrochemical stabilities. The attachment of electroactive molecules exhibiting either two stable redox states (e.g., ferrocene and quinones) or more than two stable redox states (e.g., metalloporphyrins, polyoxometalates, and C60) is more particularly discussed. Attention is also paid to the immobilization of electrochemically polymerizable centers. Globally, these functional interfaces have been demonstrated to show great promise for the molecular charge storage and information processing or the elaboration of the electrochemically switchable devices. Besides, there are also some relevant examples dealing with their activity for other fields of interest, such as sensing and electrochemical catalysis.

We report the formation of covalently bound alkyl layers onto oxidized Pt (PtOx) substrates by reaction with 1-alkenes as a novel way to bind organic molecules to metal surfaces. The organic layers were characterized by static contact angle, infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The grafted alkyl layers display a hydrolytic stability that is comparable to that of alkyl thiols on Au. PtOx-alkene attachment is compatible with terminal ester moieties enabling further anchoring of functional groups, such as redox-active ferrocene, and thus has great potential to extend monolayer chemistry on noble metals.

The combination of monocrystalline silicon's well-defined structure and the ability to prepare hydrogen-terminated surfaces (Si-H) easily and reproducibly has made this material a very attractive substrate for immobilizing functional molecules. The functionalization of Si-H using the covalent attachment of organic monolayers has received intense attention due to the numerous potential applications of controlled and robust organic/Si interfaces. Researchers have investigated these materials in diverse fields such as molecular electronics, chemistry, and bioanalytical chemistry. Applications include the preparation of surface insulators, the incorporation of chemical or biochemical functionality at interfaces for use in photovoltaic conversion, and the development of new chemical and biological sensing devices. Unlike those of gold, silicon's electronic properties are tunable, and researchers can directly integrate silicon-based devices within electronic circuitry. Moreover, the technological processes used for the micro- and nanopatterning of silicon are numerous and mature enough for producing highly miniaturized functional electronic components. In this Account, we describe a powerful approach that integrates redox-active molecules, such as ferrocene, onto silicon toward electrically addressable systems devoted to information storage or transfer. Ferrocene exhibits attractive electrochemical characteristics: fast electron-transfer rate, low oxidation potential, and two stable redox states (neutral ferrocene and oxidized ferrocenium). Accordingly, ferrocene-modified silicon surfaces could be used as charge storage components with the bound ferrocene center as the memory element. Upon application of a positive potential to silicon, ferrocene is oxidized to its corresponding ferrocenium form. This redox change is equivalent to the change of a bit of information from the "0" to "1" state. To erase the stored charge and return the device to its initial state, a low potential must be applied to reduce the whole generated ferrocenium. In this type of application, the electron is transferred from the ferrocene headgroups to the underlying conducting silicon surface by a tunneling process across the monolayer. To produce a stable and reproducible electrical response, this process must be efficient, fast, and reversible. The stability, charge density, and capacitance performances of high-quality ferrocene-terminated monolayers could compete with those of the existing semiconductor-based memory devices, such as dynamic random access memories, DRAMs. Moreover, we provide experimental evidence that a series of immobilized ferrocene centers can efficiently communicate via a lateral electron hopping process. Using these modified interfaces, we demonstrate that the thin redox-active monolayer can behave as a purely conducting material, highlighting an unprecedented very fast electron communication between immobilized redox groups. Perhaps more importantly, the surface coverage of ferrocene allows us to precisely control the rate of this process. Such characteristics are relevant not only for electrocatalytic reactions but also for widening the potential applications of these assemblies to novel molecular electronic devices (e.g. chemiresistors, chemically sensitive field-effect transistors (CHEMFETs)) and redox chemistry on insulating surfaces.

Carborane-functionalized conducting polymer films have been electrogenerated in dichloromethane from the anodic oxidation of ortho- (1), meta- (3) and para-carborane (4) isomers linked to two 2-thienyl units. The corresponding electrochemical response was characterized by a broad reversible redox system corresponding to the p-doping/undoping of the polythiophene backbone, the formal potential of which increased in the order poly(1) < poly(3) < poly(4), from ca. 0.50 to 1.15 V vs Ag/Ag(+) 10(-2) M. From further UV-visible spectroscopy analysis, the optical band gap was estimated at 1.8, 2.0 and 2.2 eV for poly(1), poly(3) and poly(4), respectively. The more conjugated and electroconductive character of poly(1) is ascribed to a more planar conformation of the conjugated backbone resulting from an intramolecular β-β' cyclization reaction in the monomer, consequently yielding a fused conjugated polymer. Molecular modeling calculations using the DFT method support this hypothesis. The surface topography and maps of the conductive domains of the electropolymerized films were evaluated by conducting probe AFM. The three polymers exhibit fairly similar morphological characteristics and a surface roughness of ~2 nm. Current-voltage (I-V) characteristics of conducting AFM tip-carborane polymer-ITO junctions showed that poly(1) had the highest conductivity.

Vinyl-terminated heptapodyl beta-cyclodextrins react with hydrogenated silicon surfaces to generate covalently-bound molecular recognition devices.