Fig. 2: Ferrocene oxidation using in situ generated electricity.

a Real-time UV-Vis absorption spectra of a well-stirred ferrocene (0.6 mM, in CH₃CN) and tetrabutylammonium perchlorate (TABP, 50 mM, in CH₃CN) solution, upon insertion of one o-SWNT/polymer particle (1 mm × 2 mm × 2 mm, AR = 4, volume = 4 mm³). The reactant (ferrocene) peak centers around 430 nm, whereas the product (ferrocenium perchlorate) peak centers around 615 nm. The UV-vis cuvette was filled with nitrogen to avoid interference from oxygen. b Top-left: reaction scheme of ferrocene oxidation driven by o-SWNT/PTFE particle generators. Bottom-left: control studies of the ferrocene oxidation kinetics using various particle constructs. Blue: standard condition, Janus particle made with o-SWNT half-coated with polymer thin film (100 nm); orange: o-SWNT particle fully coated with polymer; black: bare o-SWNT particle with no coating; red: Janus particle made with pristine non-oxidized SWNTs (p-SWNT) half-coated with polymer. All reactions are performed at 0.6 mM ferrocene concentration with 50 mM TBAP as electrolyte, with particle dimensions 1 mm × 2 mm × 2 mm. Right: schematic illustration of the cross-section of the 100 nm polymer coating. It also allows restricted solvent (blue dot)/electrolyte (orange dot) diffusion, as characterized by the solvent permeability through the polymer membrane. c The three-step Janus particle “recharging” cycle, consist of (i) re-oxidizing (using 2:1 volumetric mixture of concentrated HNO₃/H₂SO₄) the reduced o-SWNT (during ferrocene electro-oxidation reaction at the exposed, anodic surface) on the cathodic (polymer protected) o-SWNT surface, (ii) rinsing off adsorbed chemicals on the particle and baking at 250 °C to get rid of rinsing solution and residual acids, and (iii) vacuuming away any residual liquid for the next reaction cycle. d Calibrated ferrocene yield with recycled Janus particles. Error bars represent 95% confidence intervals of oxidation yields using different particles (n = 3). e Calibrated ferrocene oxidation yield at 30 min of reaction time using o-SWNT Janus particles (1 mm × 2 mm × 2 mm) half-coated with different polymers (c.a. 100 nm). Device conductivities are measured between the two terminals of the Janus particles using infiltrated silver (Ag) nanoparticles (initially dissolved in CH₃CN) as electrode contacts (see Supporting Information 10), which is a proxy for polymer permeabilities to CH₃CN. Error bars represent the standard deviations of both reaction yield and conductivity measured within different samples (n = 3).