Fig. 4: “Chemical transistor” effect in anion transport under Cl⁻ gating.

a Experimental permeability of anions mixtures with Cl⁻: Cl⁻ and NO₃⁻, Cl⁻ and SO₄²⁻, Cl⁻ and PO₄³⁻, and quaternary anion mixtures (Cl⁻, NO₃⁻, SO₄²⁻, and PO₄³⁻). b Cooperative transport of Cl⁻ with NO₃⁻, SO₄²⁻, and PO₄³⁻ over time. Permeability of NO₃⁻, SO₄²⁻, and PO₄³⁻ was monitored for the first 12 h, after which NaCl was added, triggering a change in ion transport behavior. c Cl⁻ sorption capacity of am-GO membranes after saturation with NO₃⁻, SO₄²⁻, or PO₄³⁻, plotted against membrane thickness, revealing anion-dependent adsorption dynamics. d Reaction pathway for anion interactions with am-GO membranes. (i) Empty membrane nanochannel, (ii) nanochannel with a single trapped anion, (iii) membrane nanochannel of (ii) transition state upon Cl⁻ addition, and, and (iv) Cl⁻-trapped nanochannel with the release of another anion, illustrating Cl⁻-mediated anion exchange.