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Electroactive polymers such as polypyrrole (PPy) are receiving particular interest because they can combine inherent biological properties that can specifically trigger desired cellular responses for many biological applications. The aim of the present work was to evaluate more efficient solutions, achieved by different oxidisations of tosylate-doped PPy films in different chemico-physical conditions, in view of their long-term biomedical applications. The conductivity and the release of the tosylate ion were assessed. Morpho-functional studies were also performed. A gradual increase in impedance of the oxidised tosylate-doped PPy films soaked in MEM and a reduced conductivity after over-oxidation was found. Scanning electron microscopy (SEM) analysis showed the presence of a hierarchical organisation of the PPy films and a partially different morphology between oxidised and over-oxidised films. Cell behaviour was also randomly affected in relation to the oxidative state of the studied Ppy films. On the basis of the results, growth of these tosylate-doped Ppy films directly in the sol–gel matrix or on the surface of metal alloys could be hypothesised in order to improve bioactive materials of potential use in modern regenerative medicine. However, in view of their in vivo application, over-oxidation must be considered as it may represent the degraded material that is likely to form under a biological oxidising environment.

Dispersible single-walled carbon nanotubes grafted with poly(4-vinylpyr- idine), SWNT-PVP, were tested in coordination assays with zinc tetraphenylpor- phyrin (ZnP). Kinetic and spectroscopic evidence corroborates the successful for- mation of a SWNT-PVP·ZnP nanohybrid. Within this SWNT-PVP·ZnP nanohy- brid, static electron-transfer quenching (2.0 � 0.1) = 10 9 s � 1 converts the photoexcit- ed-ZnP chromophore into a radical-ion-pair state with a microsecond lifetime, namely one-electron oxidized-ZnP and reduced-SWNT.

Four Cu(I) complexes with general formulas [Cu((NN)-N-boolean AND)(2)][BF4] and [((PP)-P-boolean AND) Cu((NN)-N-boolean AND)][BF4] were prepared, where (NN)-N-boolean AND stands for 2-(2-tert-butyl-2H-tetrazol-5-yl)pyridine and (PP)-P-boolean AND is a chelating diphosphine, namely bis-(diphenylphosphino) methane (dppm), bis-(diphenylphosphino) ethane (dppe) or bis[2-(diphenylphosphino) phenyl] ether (POP). In an acetonitrile medium, the Electro-Spray Ionization Mass Spectrometry (ESI-MS) determination provided the preliminary evidence for the occurrence of the dppm-containing complex as a mixture of a cationic mononuclear [Cu((NN)-N-boolean AND)(dppm)](+) species and a bis-cationic dinuclear [Cu-2((NN)-N-boolean AND)(2)(dppm)(2)](2+)-type compound. Definitive evidence of peculiar structural features came from X-ray crystallography, which showed both the dppm-and, unexpectedly, the dppe-based heteroleptic compounds to crystallize as diphosphine-bridged Cu(I) dimers, unlike [Cu((NN)-N-boolean AND) 2](+) and [(POP) Cu( (NN)-N-boolean AND)]+ which are mononuclear species. In solutions of non-coordinating solvents, P-31 NMR studies at variable temperatures and dilution titrations confirmed that the dppm-based complex undergoes a monomer-dimer dynamic equilibrium, while the dppe-containing complex occurs as the bis-cationic dinuclear species, [Cu-2((NN)-N-boolean AND)(2)(dppe)(2)](2+), within a concentration range comprised between 10(-2) and 10(-4) M. Differences among heteroleptic complexes might be related to the smaller natural bite angle displayed by dppm and dppe phosphine ligands (72 and 85, respectively), with respect to that reported for POP (102). The electrochemical features of the new species have been investigated by cyclic voltammetry. Despite the irreversible and complicated redox behaviour, which is typical for copper complexes, the reductions have been attributed to the tetrazole ligand whereas the oxidations are characterized as Cu(I/II) processes with a substantial contribution from the (PP)-P-boolean AND-based ligands in the case of the heteroleptic species. All the four complexes are weakly or not luminescent in CH2Cl2 solution, but heteroleptic complexes are bright green luminophores in a solid matrix, with quantum yields as high as 45% (dppm complex) even at room temperature. This makes them potential candidates as cheap emitting materials for electroluminescent devices.

The photophysical and electrochemical properties of a novel metallopolymer containing [Re(bpy)(CO)3]+ moieties coordinated to a poly(4-vinylpyridine) polymer chain are reported. Significantly, the release of the metal complexes can be triggered by oxidation or reduction of the rhenium complex. Solvent rapidly binds to the vacant coordination site to give a luminescent product. The redox and photophysical properties of the parent metallopolymer and the released solvated complex are compared. Along with photoemission, the metallopolymer generates significant electrogenerated chemiluminescence upon reduction in the presence of benzoyl peroxide as coreactant.

A biomimetic bone-like composite, made of self-assembled collagen fibrils and carbonate hydroxyapatite nanocrystals, has been performed by an electrochemically-assisted deposition on titanium plate. The electrolytic processes have been carried out using a single type I collagen molecules suspension in a diluted Ca(NO3)2 and NH4H2PO4 solution at room temperature and applying a constant current for different periods of time. Using the same electrochemical conditions, carbonate hydroxyapatite nanocrystals or reconstituted collagen fibrils coatings were obtained. The reconstituted collagen fibrils, hydroxyapatite nanocrystals and collagen fibrils/apatite nanocrystals coatings have been characterized chemically, structurally and morphologically, as well as for their ability to bind fibronectin (FN). Fourier Transform Infrared microscopy has been used to map the topographic distribution of the coating components at different times of electrochemical deposition, allowing to single out the individual deposition steps. Moreover, roughness of Ti plate has been found to affect appreciably the nucleation region of the inorganic nanocrystals. Laser scanning confocal microscopy has been used to characterize the FN adsorption pattern on a synthetic biomimetic apatitic phase, which exhibits a higher affinity when it is inter-grown with the collagen fibrils. The results offer auspicious applications in the preparation of medical devices such as biomimetic bone-like compositecoated metallic implants. _ 2007 Elsevier B.V. All rights reserved. Keywords: Hydroxyapatite–collagen coating; Electrochemically-assisted deposition; Micro-imaging FTIR spectroscopy; Laser scanning confocal microscopy; Biomimetic crystal growth; Fibronectin binding

In this work, we report the results about the solution and solid-state phosphorescence emission properties of six Ru(II) complexes containing various 5-substituted tetrazolate ligands. The photo- and electrochemiluminescence spectra of all compounds revealed a red shifted emission with respect to the Ru(bpy)(3)(2+). Significant changes to the light emission energy and to the efficiency and sensitivity to oxygen were also determined by varying the nature of the substituent ring of the tetrazolate ligand. Light-emitting solid devices with active layers containing solid films of the same complexes were prepared, and preliminary studies of their electroinduced emission properties were performed. The electrochemiluminescence (ECL) emission intensity of two of the six complexes was of the same order of magnitude as the reference Ru(bpy)(3)(2+).

The electrochemical properties of a fullerene–ferrocene liquid crystal are reported. The electrochemical study was carried out under strictly aprotic conditions: a total of seven reduction peaks were detected in the negative potential region, and two oxidation peaks in the positive potential one. Comparison of the data with those obtained from suitable model compounds (i.e., analogous fullerene- or ferrocene-free materials ) has allowed the assignment of all reduction and oxidation steps. The CV study evidenced the occurrence of a fast follow-up chemical reaction coupled to the third (at 25 °C) or fourth (at –60 °C) reduction of either 1 or 3. Such a reaction, presumably related to the cleavage of one of the cyclopropane bonds, is quantitatively reversed upon re-oxidation. Conversely, under bulk electrolysis conditions (second reduction), the species undergo the retro-Bingel reaction, i.e. the irreversible removal of the bis(alkoxycarbonyl)methano adducts to give the parent C60.

Electrochemical, quantum chemical, and spectroscopic techniques are used to study the dynamics of the reduction of bpy-C{sub 61}. A thorough investigation of the temperature and scan rate dependence of the cyclic voltammetry peaks coupled with numerical simulations clearly reveals that the trianion and the tetraanion undergo two chemical reactions according to the same parallel ECE mechanism. Quantum chemical calculations show that three isomers are quasi equienergetic in the charged states and support the hypothesis that triply and quadruply reduced bpy-C{sub 61} undergoes facile conversion among three of its structural isomers, i.e., [5,6]-closed bpy-C{sub 61}, [5,6]-open bpy-C{sub 61}, and [6,6] closed bpy-C{sub 61}. Substituent and/or solvent effects may effectively reverse the roles of [5,6]-closed bpy-C{sub 61}, and [6,6]-closed bpy-C{sub 61}. As for [5,6]-closed isomer, it is the first time that its existence is proposed on the basis of the observation of a redox process. The six reduction peaks of C{sub 60} have been observed for the first time in a pure solvent (THF, - 60{degree}C), and the cyclic voltammetry peaks of the fullerene moiety and the bpy fragment have been assigned. 17 refs., 7 figs., 1 tab.

Marine toxins appear to be increasing in many areas of the world. An emerging problem in the Mediterranean Sea is represented by palytoxin (PlTX), one of the most potent marine toxins, frequently detected in seafood. Due to the high potential for human toxicity of PlTX, there is a strong and urgent need for sensitive methods toward its detection and quantification. We have developed an ultrasensitive electrochemiluminescence-based sensor for the detection of PlTX, taking advantage of the specificity provided by anti-PlTX antibodies, the good conductive properties of carbon nanotubes, and the excellent sensitivity achieved by a luminescence-based transducer. The sensor was able to produce a concentration-dependent light signal, allowing PlTX quantification in mussels, with a limit of quantification (LOQ = 2.2 μg/kg of mussel meat) more than 2 orders of magnitude more sensitive than that of the commonly used detection techniques, such as LC-MS/MS. journal article research support, non-u.s. gov't 2012 Sep 25 2012 08 30 imported

Covalent and non-covalent strategies are utilized for the functionalization of carbon nanotubes with positively charged groups and subsequently negatively charged, inorganic catalysts, leading nanomaterials for electrocatalytic water splitting. Both multi- and single-walled carbon nanotubes react with under microwave irradiation and solvent-free conditions, whereas the formation of non-covalent nanoconjugates is accomplished by reaction of carbon nanotubes with trimethylammonium acetyl pyrene.

Water is the renewable, bulk chemical that nature uses to enable carbohydrate production from carbon dioxide. The dream goal of energy research is to transpose this incredibly efficient process and make an artificial device whereby the catalytic splitting of water is finalized to give a continuous production of oxygen and hydrogen. Success in this task would guarantee the generation of hydrogen as a carbon-free fuel to satisfy our energy demands at no environmental cost. Here we show that very efficient and stable nanostructured, oxygen-evolving anodes are obtained by the assembly of an oxygen-evolving polyoxometalate cluster (a totally inorganic ruthenium catalyst) with a conducting bed of multiwalled carbon nanotubes. Our bioinspired electrode addresses the one major challenge of artificial photosynthesis, namely efficient water oxidation, which brings us closer to being able to power the planet with carbon-free fuels.

Two fullerene-peralkylated ferrocene derivatives were synthesized: (1) a liquid-crystalline dyad (compound 1) was obtained by introduction of nonamethyl ferrocene into a liquid-crystalline fullerene derivative and (2) a reference compound (compound 2) was synthesized by attachment of nonamethyl ferrocene to a fulleropyrrolidine. The liquid-crystalline dyad displayed an enantiotropic smectic A phase from 57 to 155 degrees C. Oxidation and reduction processes were investigated by cyclic voltammetry, and were in agreement with the electrochemical characteristics of the redox-active units (peralkylated ferrocene, fullerene, dendrimer). Photoinduced electron transfer from ferrocene derivative to fullerene was identified.

The electronic properties of functionalised single and multi wall carbon nanotubes (SWNTs and MWNTs, respectively) were investigated in depth by conventional electrochemical techniques in solution. Significant differences were observed between these two classes of carbon nanotubes. In fact, despite functionalisation strongly modified the electronic properties of carbon nanotubes, the enrichment of the density of states of MWNTs with respect to SWNTs, due to larger tube diameters, is still appreciated. In addition, the redox behaviour of the MWNTs shows a series of discrete single electron-transfer events (a coulomb staircase), which are undetected in the case of SWNTs. This quantised capacitance charging phenomena is analogous to that observed for other nanosystems which is attributed to the discrete charging of conducting core, coated with a dielectric film in an electrolyte solution.

Herein we describe a fullerene rotaxane, in which shuttling between two well-defined and distant co-conformations is both induced and monitored by the C60 stopper.

In this contribution, we report the synthesis, the chemical and photophysical characterization, and the study of the reactivity toward electrophiles of two mononuclear complexes of the type [Ru(bpy)2L]+ (bpy is 2,2'-bipyridyl), in which L is represented by the deprotonated form of 2-(1,H-tetrazol-5-yl)pyridine (L1) or 2-(1,H-tetrazol-5-yl)pyrazine (L2). The 1H and 13C NMR experiments that were performed on complexes RuL1 and RuL2 allowed us to establish that the tetrazolate moiety is bonded to the metal center via the N-1 nitrogen, while the coplanar arrangement adopted by the coordinated ligand upon coordination and the consequent interannular conjugation effect accounts for the unexpectedly low field resonance of the tetrazole carbon. The 13C NMR spectroscopy is also of fundamental importance to determine the chemo- and regioselectivity of the addition of a methyl group to RuL1 and RuL2, which takes place at the N-3 nitrogen of the five-membered ring. All these features were confirmed by the X-ray diffraction structures of RuL1 and of the methylated compounds RuL1Me and RuL2Me. Relative to these latter complexes, the presence of a methyl moiety does not cause any distortion from coplanarity of the coordinated tetrazolates. The redox properties of the complexes were investigated by cyclic voltammetry and indicated a quite different behavior between the pyrazinyl-tetrazolate and the pyridyl-tetrazolate complexes as the consequence of the higher electron-withdrawing character of the pyrazine ring. The study of the photophysical properties of the complexes also shows a significant diversity between the luminescent RuL1 and the rather poorly emissive RuL2. Interestingly, the methylated compounds RuL1Me and RuL2Me display radiative excited-state decays with longer lifetimes than their precursors; this feature indicates that methylation is a useful reaction for the tuning of the light emission performances of similar tetrazolate complexes. The synthesis and the characterization of a novel dinuclear complex of type [(bpy)2Ru-L3-Ru(bpy)2]2+, Ru(L3)Ru, where L3 is the bis-anion derived from bis-2,3-(1,H-tetrazol-5-yl)pyrazine, is also reported.

Single-wall carbon nanohorns (SWNHs) are a new class of material that is closely related to single-wall carbon nanotubes. Here, we describe the synthesis and characterization of a series of SWNHs functionalized with ethylene glycol chains and porphyrins. Functionalization of carbon nanohorns has been achieved using two different synthetic protocols: (1) direct attack of a free amino group on the nanohorn sidewalls (nucleophilic addition) and (2) amidation reaction of the carboxylic functions in oxidized nanohorns. The nanohorn derivatives have been characterized by a combination of several techniques, and the electronic properties of the porphyrin/nanohorn assemblies (SWNH/H2P) have been investigated by electrochemistry, spectroelectrochemistry, and a series of steady-state and time-resolved spectroscopy. The cyclic voltammetry curve of nanohorn/porphyrin conjugate 6 showed a continuum of faradic and pseudocapacitive behavior, which is associated with multiple-electron transfers to and from the SWNHs. Superimposed on such a pseudocapacitive current, the curve also displays three discrete reduction peaks at -2.26, -2.57, and -2.84 V and an oxidation peak at 1.12 V (all attributed to the porphyrin moiety). Steady-state and time-resolved fluorescence demonstrated a quenching of the fluorescence of the porphyrin in SWNH/H2P conjugates 5 and 6 compared to the reference free base porphyrin. Transient absorption spectra permitted the electron-transfer process between the porphyrins and the carbon nanostructures to be highlighted.

The photophysical and electrochemical properties of a fumaramide rotaxane stoppered with C(60) are reported. The results evidenced the strong binding interactions between the template and the macrocycle, which are also supported by molecular modelling.

This work provides an in-depth look at a range of physicochemical aspects of (i) single wall carbon nanotubes (SWNT), (ii) pyrene derivatives (pyrene(+)), (iii) porphyrin derivatives (ZnP(8)()(-)() and H(2)()P(8)()(-)()), (iv) poly(sodium 4-styrenesulfonate), and (v) their combinations. Implicit in their supramolecular combinations is the hierarchical integration of SWNT (as electron acceptors), together with ZnP(8)()(-)() or H(2)()P(8)()(-)() (as electron donors), in an aqueous environment mediated through pyrene(+). This supramolecular approach yields novel electron donor-acceptor nanohybrids (SWNT/pyrene(+)/ZnP(8)()(-)() or SWNT/pyrene(+)/H(2)()P(8)()(-)()). In particular, we report on electrochemical and photophysical investigations that as a whole suggest sizeable and appreciable interactions between the individual components. The key step to form SWNT/pyrene(+)()/ZnP(8)()(-)() or SWNT/pyrene(+)()/H(2)()P(8)()(-)() hybrids is pi-pi interactions between SWNT and pyrene(+), for which we have developed for the first time a sensitive marker. The marker is the monomeric pyrene fluorescence, which although quenched is (i) only present in SWNT/pyrene(+) and (ii) completely lacking in just pyrene(+). Electrostatic interactions help to immobilize ZnP(8)()(-)() or H(2)()P(8)()(-)() onto SWNT/pyrene(+) to yield the final electron donor-acceptor nanohybrids. A series of photochemical experiments confirm that long-lived radical ion pairs are formed as a product of a rapid excited-state deactivation of ZnP(8)()(-)() or H(2)()P(8)()(-)(). This formation is fully rationalized on the basis of the properties of the individual moieties. Additional modeling shows that the data are likely to be relevant to the SWNTs present in the sample, which possess wider diameters.

The electronic properties of the family of pyridyl− and pyrimidyl− ferrocenyl complexes [Fe(η5-C5H4-4-C5H4N)(η5-C5H5)] (1), [Fe(η5-C5H4-4-C5H4N)2] (2), [Fe(η5-C5H4-4-C5H4N)(η5-C5H4-5-C4H3N2)] (3), [Fe(η5-C5H4-5-C4H3N2)2] (4), [Fe(η5-C5H4−C6H4-4-C5H4N)(η5-C5H4-5-C5H4N)] (5), and [Fe(η5-C5H4−C6H4-4-C5H4N)2] (6), prepared by Suzuki coupling starting from ferrocenyl diboronic acid, have been investigated by electrochemical, spectroscopic, and quantum-chemical methods. All complexes display photo- and electrochemical stability and strong electronic interactions in the ground state between the ferrocenyl moiety and pyridine/pyrimidine rings. The efficient modulation of the potentials of ferrocenyl-based oxidation is shown to be strongly dependent on the nature of the hetero ring. These features, together with their high chelating ability, are potentially useful in the preparation of redox-active complexes of complexes such as mixed-metal metallamacrocycles.

The 1,3-dipolar cycloaddition reaction was used to assemble fullerene, ferrocene and a second-generation liquid-crystalline cyanobiphenyl-based dendrimer. The targeted compound displayed an enantiotropic smectic A phase from 40 to 135degreesC. The d-layer spacing was determined by X-ray diffraction, and was found to be independent of temperature with a value of 95 Angstrom. Molecular modeling and structural considerations suggested partial bilayer organization of the mesogenic molecular units within the smectic layers. Oxidation or reduction processes of the basic components (ferrocene, fullerene, dendrimer) were investigated by electrochemical techniques, and were in agreement with the structure. Photoinduced electron transfer from ferrocene to fullerene was identified, most likely with a "through space" mechanism.

Ferrocenyl-functionalised SWNTs are coupled to glucose oxidase within an amphiphilic polypyrrole matrix for the amperometric catalytic detection of glucose.

The cyclic voltammetric (CV) study of a series of novel bisfulleropyrrolidines (3) and bisfulleropyrrolidinium ions (4) is reported. The eight possible stereoisomers of each series were systematically investigated under strictly aprotic conditions that allowed the observation of up to four and five subsequent reversible reductions in 3 and 4, respectively. Because of the stabilizing effect of positive charges, a significant enhancement of the electronegative properties was observed in 4. In fact, 4-trans-2 and 4-trans-1 result among the strongest reversible electron-accepting C(60) oligoadducts. Furthermore, the study evidenced that, in both 3 and 4, the CV pattern, and in particular the potential separation between the second and third reductions, changes significantly with the addition pattern. A sequential pi-electron model that simulates the effect of subsequent reductions of C(60) bis-adducts gives a good correlation (r > 0.96) with the cyclic voltammetry data when the molecules are divided in two sets dependent on the location of the addends in the same or in opposite hemispheres.

Amidoferrocenyl-functionalised single wall carbon nanotubes (Fc-SWNT) are efficient exoreceptors for the redox recognition of H2PO4-.

A novel biosensor for the amperometric detection of glutathione is proposed in which glutathione reductase is coupled to a pyrrolofullerene bis-adduct playing the role of redox mediator between electrode and enzyme. The adoption of a simple procedure for realizing the immobilization of the redox mediator, together with the enzyme, within a polypyrrole film cast onto a glassy carbon electrode, was made possible by the amphiphilic properties of the fullerene derivative. The biosensor showed a fast and reproducible response to glutathione and, because of its lower sensitivity, a wider linear range with respect to a similar device based on a diffusional redox mediator.