Extraction of hydrophobic analytes from organic solution into a titanate 2D-nanosheet host: Electroanalytical perspectives

Abstract

a b s t r a c tTitanate nanosheets (single layer, typically 200 nm lateral size) deposited from aqueous colloidal solution onto electrode surfaces form lamellar hosts that bind redox active molecular redox probes. Here, hydrophobic redox systems such as anthraquinone, 1-amino-anthraquinone, deca-methylferrocene, 5,10,15,20-tetraphenyl-21H,23H-porphine manganese (III) chloride (TPPMnCl), and a-tocopherol are shown to bind directly from cyclopentanone solution (and from other types of organic solvents) into the titanate nanosheet film. For anthraquinone derivatives, stable voltammetric responses are observed in aqueous media consistent with 2-electron 2-proton reduction, however, independent of the pH of the outside solution phase environments. For decamethylferrocene a gradual decay of the voltammetric response is observed, but for TPPMnCl a more stable voltammetric signal is seen when immersed in chloride containing (NaCl) electrolyte. a-Tocopherol exhibits chemically irreversible oxidation and is detected with 1 mMe20 mM linear range and approximately 10 À3 M concentration limit of detection. All redox processes exhibit an increase in current with increasing titanate film thickness and with increasing external electrolyte concentration. This and other observations suggest that important factors are analyte concentration and mobility within the titanate host, as well as ion exchange between titanate nanosheets and the outside electrolyte phase to maintain electroneutrality during voltammetric experiments. The lamellar titanate (with embedded tetrabutyl-ammonium cations) behaves like a hydrophobic host (for hydrophobic redox systems) similar to hydrophobic organic microphase systems. Potential for analytical applications is discussed.

Polymer nanocomposites having a high filler content: synthesis, structures, properties, and applications

“…Some transition metal and its metal oxides, especially Cu-, Ni-, Co-based oxides, have attracted attention as glucose oxidation catalysts of high sensitivity 326 . Several materials such as TiO2 nanosheets 327,328 and conducting polymer (e.g., polyaniline) 329 can be used to bind the boronic acid moieties, which have a strong affinity towards polyols such as carbohydrates derivatives, making it a promising for saccharide and organic analysis. By combining metal oxide with conducting polymer and boronic acid, the charge carriers of the metal oxide will be improved and boronic acid functionalities may induce selective detection of saccharides.…”

Voltammetric characterisation of diferrocenylborinic acid in organic solution and in aqueous media when immobilised into a titanate nanosheet film

“…Titanate nanosheet material has been shown recently to provide a good host for ferroceneboronic acid 25 and for a range of other redox active and hydrophobic redox systems. 19 Therefore, the glassy carbon electrode is firstly covered with a thin (ca. 5 μm) layer of 2D titanate nanosheets according to the previously published procedure.…”

“…In this way, metal complexes such as diferrocenylborinic acid 1 can be investigated for potential applications in electroanalysis in aqueous electrolyte environments. A versatile way of immobilising hydrophobic metal complexes at the surface of glassy carbon electrodes can be based on a 2D titanate nanosheet host, 19 which is able to bind the redox active molecule from organic solvents. Nanomaterials such as titanate nanosheets have been widely investigated due to their catalytic, semiconducting, photo-and electrochemical properties and for their potential use in advanced, next-generation nanoelectronics.…”

Processes associated with ionic current rectification at a 2D-titanate nanosheet deposit on a microhole poly(ethylene terephthalate) substrate

“…The zeta potential for the colloidal titanate solution was measured on a Zetasizer Nano ZS (Malvern Instruments Ltd., Malvern, UK) confirmed an average of − 32.5 mV and an average size of 216 nm [26]. In order to form films of titanate nanosheets on PET substrates (20-μm diameter hole in 6-μmthick PET from Laser Micromaching Ltd., Birmingham, UK), 10 μL aqueous titanate nanosheet colloidal solution (2.56 g L −1 ) was applied to a PET film on a glass substrate (the glass was pre-coated with a thin layer of 1% agarose gel by solution casting to stop titanate nanosheet material penetrating through the PET microhole).…”