Figure 5: Selective Hg²⁺ sensing with AuNP functionalized OFETs.

(a) Time-resolved measurement of I_sd at constant V_sd and V_bg at constant pump speed of 1 ml min⁻¹. Solutions of seawater and 1 mM Hg²⁺ dissolved in seawater are alternately exposed to OFET, resulting in reproducible plateaus in I_sd. (b) Selective response of the OFET sensor to Hg²⁺ (black line) dissolved in seawater (1 mM), as opposed to its response to Zn²⁺ (red-dotted line) or Pb²⁺ (blue-dashed line) dissolved in seawater (both at 1 mM). For AuNPs that were not functionalized with DNA, there was no response of the OFET to dissolved Hg²⁺ ions (green line). Data collected from three different samples. The small sharp change in I_sd immediately following injection of a new solution is a coupling response to switching the automatic valve (inset) that occurs in samples of high ion concentrations. The following V_sd and V_bg values were used: Zn²⁺, −0.8/−3 V; Pb²⁺, −0.8/−2.75 V; Hg²⁺, −0.8/−3 V; no DNA, −0.8/−4 V.