Changing the Blood Test: Accurate Determination of Mercury(II) in One Microliter of Blood Using Oriented ZnO Nanobelt Array Film Solution‐Gated Transistor Chips

Abstract The measurement of ultralow concentrations of heavy metal ions (HMIs) in blood is challenging. A new strategy for the determination of mercury ions (Hg²⁺) based on an oriented ZnO nanobelt (ZnO‐NB) film solution‐gated field‐effect transistor (FET) chip is adopted. The FET chips are fabricated with ZnO‐NB film channels with different orientations utilizing the Langmuir–Blodgett (L–B) assembly technique. The combined simulation and I–V behavior results show that the nanodevice with ZnO‐NBs parallel to the channel has exceptional performance. The sensing capability of the oriented ZnO‐NB film FET chips corresponds to an ultralow minimum detectable level (MDL) of 100 × 10⁻¹² m in deionized water due to the change in the electrical double layer (EDL) arising from the synergism of the field‐induced effect and the specific binding of Hg²⁺ to the thiol groups (‐SH) on the film surface. Moreover, the prepared FET chips present excellent selectivity toward Hg²⁺, excellent repeatability, and a rapid response time (less than 1 s) for various Hg²⁺ concentrations. The sensing performance corresponds to a low MDL of 10 × 10⁻⁹ m in real samples of a drop of blood.