Chinese researchers recently developed a novel strategy to high sensitivity and stability detect Hg²⁺ in the blood that is very hard to sense accurately in real samples of a drop of blood.

This work reported by a study team led by Prof. HUANG Xingjiu at Institute of Intelligent Machines (IIM), Hefei Institutes of Physical Science. It was published in journal of Small.

The measurement of ultralow concentrations of heavy metal ions (HMIs) in blood is challenging. Blood testing methods have been continuously improving, but large sample volumes are still needed, which is not desirable for patients.

Therefore, the development of ultrasensitive chips with an ultralow minimum detectable level (MDL) for Hg²⁺, a low cost, portability, and easy operation is a powerful trend in environmental and medical analysis.

Herein, based on a typical two-dimensional (2D) semiconductor materials of ZnO nanobelts (Zn-NBs), the team combined Langmuir-Blodgett (L-B) technology and method of thiol-functionalized molecular probe to design a solution-gated FET chip with oriented Zn-NBs array film.

The as-prepared FET chips presented ultrasensitive performance when applied in sensing analytes due to the synergism of the field-induced effect and thiol group (-SH) specific binding of Hg²⁺ causing the electrical double layer (EDL) to change.

Through further test, the present FET chip exhibited excellent response and selectivity toward Hg²⁺ as well as excellent repeatability and sensing capability was shown in the determination of Hg²⁺ in a drop of blood.

Moreover, this work accurately analyzed the influence of the resistance of different assembly directions of ZnO-NB films on the current density by simulation.

The results indicated that the nanodevices with the ZnO-NBs parallel to the channel (PTC) showed better responses than those with the ZnO-NBs disordered relative to the channel (DTC) or vertical to the channel (VTC).

This work was supported by the National Natural Science Foundation of China, the postdoctoral innovation talents supporting project, the China Postdoctoral Science Foundation, the Science and Technology Major Project of Anhui Province, the CASHIPS Key Program of 13th five-year plan, the Science and Technology Research Project of Anhui Province.

Figure 1. (a) The detection sketch map of the solution-gated FET device; (b) Real-time detection of Hg²⁺ at various concentrations in deionized water, the inset is a magnification of the low dropped concentration region (100 pM ~ 40 nM); (c) Selective responses of the FET chip to Hg2+ in the presence of other metal ions; (d) Optical photo of the oriented ZnO-NB array film FET chip and its SEM image of the sensitive area nanostructure. (Image by LI Yixiang) 

Figure 2. Two-dimensional simulation graph of the normalized current density, and comparison of the electric performances under the three assembly conditions. a) Simulation graph and b) I-V plots of the VTC nanobelt film. c) Simulation graph and d) I-V plots of the DTC nanobelt film. e) Simulation graph and f) I-V plots of the PTC nanobelt film. All insets in the I-V plots correspond to SEM images of the three assembly conditions. The length of the device channel is 2.5 μm. The drain voltage is 0.5 V for all simulations. (Image by LI Yixiang)