Prof. Nieves Casañ-Pastor
1.- Intercalation processes that lead to notable changes in physical properties in bulk and thin layer forms lead to electrodes of various configurations that can be applied in tuning of materials properties, structure, energy storage, transport or in biological applications.
Electrochemical Oxygen intercalation at room temperature
La2-xSrxCuO4 structure in which oxygen intercalation is possible by electrochemical oxidation resulting in induction of superconducting properties with higher Tc values. The Mn equivalent behaves equally, resulting in dramatic changes in its magnetic properties
Electrochemical solid state transformations at room temperature
The same electrochemical treatment induces structure transformations in solid state at room temperature. Ej. Ag2Cu2O3 to Ag2Cu2O4 as shown below 1 O atom “intercalated” per unit formula. Pass from a 3D structure to a 2D one at r.t. !!!!; The final phase is a peculiar case where all elements are shown to be in mixed valence states.
Other soft chemistry methods : Low T Hydrothermal inducing oxidation state effects in nanostructure
Ag2Cu3Cr2O8(OH)4:A new bidimensional silver-copper mixed -oxyhydroxide with in-plane ferromagnetic coupling
Dalton Transactions, 2016, DOI: 10.1039/C6DT03986C
Oxidazing conditions render layered Silver-Copper oxides . In some cases are metallic, Ag2Cu2O4, in some others , ferromagnetic, Ag2CuMnO4 or Ag2Cu3Cr2O8(OH)4. In the last two cases, a significant difference lies on the connection among Cu-O layers. In one case direct bonding through Ag orbitals allows further antiferromagnetic coupling at lower temperatires, rendering a ferro-antiferrotransition. In the other Cu-O layers behave as completely isolated from each other.
Electrochemical exfoliation of Graphite to yield Pristine Graphene
Anodic exfoliation in presence of surfactants or without them , has been possible from Carbon in the form of graphite. The pristine graphene obtained shows no defects as compared with the reduced graphene oxide, and has yielded a series of hybrid materials with a superior charge capacity useful in supercapacitors and electrostimulation electrodes
3.- Electrodeposition methods
Reduction of metal precursors in presence of complexing agents, and further annealing has allowed the synthesis of YBa2Cu3O7 on Ag wires. As an alternative electrophoresis of suspensions of the preformed oxide also yields coatings of the oxide as shown in the figure. The opposite electrodeposition, Ag on the oxide , difficult for the rich redox chemistry of the oxide , is also possible in certain conditions
4. Electroactive materials for biological applications.
Interfase studies with neural systems and Electrostimulation
IrOx electrodeposited transparent coatings as the best substrates for neural growth in absence of electric fields and in presence of them when amorphous. Thermal evolution results in rutile structures. A channel spongy- like original oxohydroxide results: IrOx(OH)y.nH2O with a local rutile-like structure. Dynamic deposition has allowed a fourfould increase in charge capacity for this iridium oxide, and fully improved adhesion to the substrate
Cell culture studies on neural cortex cells from rat embryo , show survival above controls
(collaboration with HNP Toledo and IIBB-CSIC)
Conducting polymers based on polypyrrole or PEDOT with various counterions. Best cell growth when counterion is an aminoacid.
Thin coatings and interdigitated patterns as substrates for cell growth in absence and presence of electric fields
Cells survive significantly better in aminoacid containing polymers (collaboration with IIBB-CSIC)
IrOx-nanocarbon Hybrids
IrOx-Pristine Graphene Hybrids as Electrostimulation Electrodes: Enhancement of neural repair under short term DC electric field. The electrode material changes the magnitude of the effect
Neuronal scratch response to ELECTRIC FIELD DC applications. And neurotransmitters release under field effects using IrOx-Graphene nanostructured electrodes
Large charge capacity electrodes such as IrOx-graphene allow DC electrostimulation without secondary effects due to radical formation. In that case, neurite extension is greatly enhanced above the effects of standard electrodes. Neurotransmitter release shows an enhancement in neural function under the electric field. http://dx.doi.org/10.1016/j.apmt.2016.12.002
5.- Bipolar electrochemistry effects in biosystems and electrochemical energy storage devices: Electrostimulation may be induced indirectly with a conducting un-connected substrate , an observation that opens up a new way of thinking on implants in biological systems
6. Redox Gradient Materials and Bipolar Electrochemistry
Iridium oxide redox gradient material: Operando X Ray absorption of Ir gradient oxidation states during IrOx bipolar electrochemistry. Laura Fuentes-Rodriguez, Llibertat Abad, Laura Simonelli, Dino Tonti, N. Casañ-Pastor* J. Phys. Chem. C, in press , july 2021