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   Budker, Dmitry; Graham, Peter W.; Ramani, Harikrishnan; Schmidt-Kaler, Ferdinand; Smorra, Christian; Ulmer, Stefan (August 2021, ArXivorg)

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2. Ion detection in a DNA nanopore FET device

   https://doi.org/10.1088/1361-6528/ad460b  

   Livernois, William; Cao, Purunc Simon; Saha, Soumyadeep; Ding, Quanchen; Gopinath, Ashwin; Anantram, M P (May 2024, Nanotechnology)

   Abstract An ion detection device that combines a DNA-origami nanopore and a field-effect transistor (FET) was designed and modeled to determine sensitivity of the nanodevice to the local cellular environment. Such devices could be integrated into a live cell, creating an abiotic-biotic interface integrated with semiconductor electronics. A continuum model is used to describe the behavior of ions in an electrolyte solution. The drift-diffusion equations are employed to model the ion distribution, taking into account the electric fields and concentration gradients. This was matched to the results from electric double layer theory to verify applicability of the model to a bio-sensing environment. The FET device combined with the nanopore is shown to have high sensitivity to ion concentration and nanopore geometry, with the electrical double layer behavior governing the device characteristics. A logarithmic relationship was found between ion concentration and a single FET current, generating up to 200 nA of current difference with a small applied bias. 

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3. Ultra-sensitive nitrate-ion detection via transconductance-enhanced graphene ion-sensitive field-effect transistors

   https://doi.org/10.1038/s41378-024-00768-4  

   Xu, Yingming; Zhou, Peng; Simon, Terrence; Cui, Tianhong (September 2024, Microsystems & Nanoengineering)

   Abstract Current potentiometric sensing methods are limited to detecting nitrate at parts-per-billion (sub-micromolar) concentrations, and there are no existing potentiometric chemical sensors with ultralow detection limits below the parts-per-trillion (picomolar) level. To address these challenges, we integrate interdigital graphene ion-sensitive field-effect transistors (ISFETs) with a nitrate ion-sensitive membrane (ISM). The work aims to maximize nitrate ion transport through the nitrate ISM, while achieving high device transconductance by evaluating graphene layer thickness, optimizing channel width-to-length ratio (R_WL), and enlarging total sensing area. The captured nitrate ions by the nitrate ISM induce surface potential changes that are transduced into electrical signals by graphene, manifested as the Dirac point shifts. The device exhibits Nernst response behavior under ultralow concentrations, achieving a sensitivity of 28 mV/decade and establishing a record low limit of detection of 0.041 ppt (4.8 × 10⁻¹³M). Additionally, the sensor showed a wide linear detection range from 0.1 ppt (1.2 × 10⁻¹²M) to 100 ppm (1.2 × 10⁻³M). Furthermore, successful detection of nitrate in tap and snow water was demonstrated with high accuracy, indicating promising applications to drinking water safety and environmental water quality control. 

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4. Photonic microresonator based sensor for selective nitrate ion detection

   https://doi.org/10.1016/j.snb.2020.129027  

   Zhang, Zhongbo; Zhang, Xufeng; Rajh, Tijana; Guha, Supratik (February 2021, Sensors and Actuators B: Chemical)

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5. High-fidelity simultaneous detection of a trapped-ion qubit register

   https://doi.org/10.1103/PhysRevA.103.062614  

   Zhukas, Liudmila A.; Svihra, Peter; Nomerotski, Andrei; Blinov, Boris B. (June 2021, Physical Review A)

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