T60u spectrometer

Electrochemical measurements were performed using a portable PalmSens potentiostat (PalmSens, Houten, The Netherlands) controlled by means of the PSTrace 4 program (Vers. 4.4 PalmSens BV). All the experiments were conducted using a three screen-printed electrodes system from Orion High Technologies S.L. (Parla, Madrid, Spain). In particular: Nanostructured carbon (OHT-000), carboxylic acid functionalized multi-walled carbon nanotubes (OHT-069) and Carboxylic acid functionalized multi-walled carbon nanotubes-Fe₃O₄ superparamagnetic nanoparticles (OHT-102) screen printed electrodes, respectively. The working electrodes were different for each sensor (with a surface diameter of 4 mm) but the counter electrode (graphite) and the reference one (Ag/AgCl) were the same for all the SPEs.
All absorbance measurements were made at the specified wavelength (731 nm) of the selected spectrophotometric method (ABTS-based method) using a T60U Spectrometer PG Instruments Ltd. (Wibtoft Leicestershire, Lutterworth, UK).

All solvents and reagents were purchased from commercial suppliers and used as received, unless otherwise stated. Dry solvents were obtained by purging with N₂ and then passing through an MBraun MPSP-800 column. H₂O was deionised and microfiltered by using a Milli-Q Millipore machine. Et₃N was distilled and stored over KOH. TBA salts were stored in a vacuum desiccator containing P₂O₅ prior to use. ¹H, ¹³C, ¹⁹F and ³¹P NMR spectra were recorded on a Varian Mercury-VX 300, a Varian Unity Plus 500, a Bruker AVD500 or a Bruker AVII500 with cryoprobe at 293 K. Chemical shifts are quoted in parts per million relative to the residual solvent peak. Mass spectra were obtained by using a Micromass LCT (ESMS) instrument or a MALDI Micro MX instrument. Electronic absorption spectra were recorded on a PG instruments T60U spectrometer.