For the first time, a versatile electrolyte bath is described that can be used to electrodeposit a wide range of p-block elements from supercritical difluoromethane (scCH₂F₂). The bath comprises the tetrabutylammonium chlorometallate complex of the element in an electrolyte of 50×10⁻³ mol dm⁻³ tetrabutylammonium chloride at 17.2 MPa and 358 K. Through the use of anionic ([GaCl₄]⁻, [InCl₄]⁻, [GeCl₃]⁻, [SnCl₃]⁻, [SbCl₄]⁻, and [BiCl₄]⁻) and dianionic ([SeCl₆]²⁻ and [TeCl₆]²⁻) chlorometallate salts, the deposition of elemental Ga, In, Ge, Sn, Sb, Bi, Se, and Te is demonstrated. In all cases, with the exception of gallium, which is a liquid under the deposition conditions, the resulting deposits are characterised by SEM, energy-dispersive X-ray analysis, XRD and Raman spectroscopy. An advantage of this electrolyte system is that the reagents are all crystalline solids, reasonably easy to handle and not highly water or oxygen sensitive. The results presented herein significantly broaden the range of materials accessible by electrodeposition from supercritical fluid and open up the future possibility of utilising the full scope of these unique fluids to electrodeposit functional binary or ternary alloys and compounds of these elements.

A versatile and simple methodology for the creation of mixed monolayers on glassy carbon (GC) surfaces was developed, using an osmium–bipyridyl complex and anthraquinone as model redox probes. The work consisted in the electrochemical grafting on GC of a mixture of mono-protected diamine linkers in varying ratios which, after attachment to the surface, allowed orthogonal deprotection. After optimisation of the deprotection conditions, it was possible to remove one of the protecting groups selectively, couple a suitable osmium complex and cap the residual free amines. The removal of the second protecting group allowed the coupling of anthraquinone. The characterisation of the resulting surfaces by cyclic voltammetry showed the variation of the surface coverage of the two redox centres in relation to the initial ratio of the linking amine in solution.

We report results for the electrochemistry of the germanium(II) tri-halide anions, [GeCl₃]⁻, [GeBr₃]⁻ and [GeI₃]⁻, in supercritical difluoromethane containing 60 mm [NⁿBu₄][BF₄] at 19.1 MPa and 358 K. The voltammetry shows mass-transport-limited currents for reduction to germanium at gold on the first scan. There is no evidence of a germanium stripping peak and, on subsequent scans, the electrode slowly passivates with the deposition of approximately 0.4 μm of material. The redox potentials for the reduction of the three tri-halides are in the order [GeCl₃]⁻ <[GeBr₃]⁻ <[GeI₃]⁻, with the iodide being the most easily reduced complex. Electrodeposition of germanium onto TiN electrodes from supercritical difluoromethane at 19.1 MPa and 358 K, using either 16 mm [EMIM][GeI₃] with 60 mm [EMIM][BF₄] or 16 mm [NⁿBu₄][GeI₃] with 60 mm [NⁿBu₄][BF₄], gave deposition rates of 2–3 μm h⁻¹. Raman spectroscopy and transmission electron microscopy showed that the resulting germanium films were protocrystalline, containing nanocrystals of germanium embedded in an amorphous germanium matrix.

Mixed two-component monolayers on glassy carbon are prepared by electrochemical oxidation of N-(2-aminoethyl)acetamide and mono-N-Boc-hexamethylenediamine in mixed solution. Subsequent N-deprotection, amide coupling and solid-phase synthetic steps lead to electrode-surface functionalisation with maleimide, with controlled partial coverage of this cysteine-binding group at appropriate dilution for covalent immobilisation of a model redox-active protein, cytochrome c, with high coverage (≈7.5 pmol cm⁻²).

The article describes the construction, immobilisation and electrochemistry of histidine tagged laccase from Melanocarpus albomyces. A facile method of functionalisation of glassy carbon electrodes with nitrilotriacetic acid (NTA) using diazonium grafting and solid state chemistry is described. NTA-modified electrodes are shown to bind laccase which reduces oxygen at neutral pH in the presence of soluble redox mediator. Laccase-modified electrodes are also prepared by enzyme immobilisation within poly(aniline)/poly(vinylsulfonate) films. The polymer is found to efficiently retain the enzyme as well as provide direct electrical contact between the electrode and the enzyme active centre. Cyclic voltammetry reveals the direct electron transfer to the enzyme is dependent on the redox state of the polymer film.

Glassy carbon electrodes functionalised with two redox centres have been prepared by using electrochemical and solid-phase synthetic methodologies. Initially the individual coupling of anthraquinone, nitrobenzene and dihydroxybenzene to a glassy carbon electrode bearing an ethylenediamine linker was optimised by using different coupling agents and conditions. Bifunctionalisation was then carried out, either simultaneously, with a mixture of nitrobenzene and dihydroxybenzene, or sequentially, with anthraquinone then nitrobenzene and with anthraquinone then dihydroxybenzene. Characterisation of these electrodes by cyclic voltammetry and differential pulse voltammetry clearly proved the attachment of the pairs of redox centres to the glassy carbon electrode. Their partial surface coverages can be controlled by varying the coupling agent or by controlling the substrate concentration during the solid-phase coupling process. Trifunctionalisation was also realised according to this methodology.

Organic linkers such as (N-Boc-aminomethyl)phenyl (BocNHCH₂C₆H₄) and N-Boc-ethylenediamine (Boc-EDA) have been covalently tethered onto a glassy carbon surface by employing electrochemical reduction of BocNHCH₂C₆H₄ diazonium salt or oxidation of Boc-EDA. After removal of the Boc group, anthraquinone as a redox model was attached to the linker by a solid-phase coupling reaction. Grafting of anthraquinone to electrodes bearing a second spacer such as 4-(N-Boc-aminomethyl)benzoic acid or N-Boc-β-alanine was also performed by following this methodology. The surface coverage, stability and electron transfer to/from the tethered anthraquinone redox group through the linkers were investigated by cyclic voltammetry. The effects of pH and scan rate were studied, and the electron-transfer coefficient and rate constant were determined by using Laviron's equation for the different types of linker. The combination of electrochemical attachment of protected linkers and subsequent modifications under the conditions of solid-phase synthesis provides a very versatile methodology for tailoring a wide range of organic functional arrangements on a glassy carbon surface.