Ultrasensitive Mercury Ion Detection Using DNA-Functionalized Molybdenum Disulfide Nanosheet/Gold Nanoparticle Hybrid Field-Effect Transistor Device

Mercury, one of the most harmful pollutants in water, has a significant negative impact on human health. The molybdenum disulfide (MoS₂) nanosheet, due to its unique electronic properties, is a promising candidate for high-performance sensing materials. Here, we report a DNA-functionalized MoS₂ nanosheet/gold nanoparticle hybrid field-effect transistor (FET) sensor for the ultrasensitive detection of Hg²⁺ in an aqueous environment. Specific DNA was used in the hybrid structure as the capture probe for the label-free detection. By monitoring the electrical characteristics of the FET device, the performance of the sensor was investigated. Our sensor shows a rapid response (1–2 s) to Hg²⁺ and an ultralow detection limit of 0.1 nM, which is much lower than the maximum contaminant level (MCL) for Hg²⁺ in drinking water (9.9 nM) recommended by the U.S. Environmental Protection Agency (EPA). In addition, the sensor shows a high selectivity to Hg²⁺ compared with other interfering metal ions, e.g., As⁵⁺, Cd²⁺, Pb²⁺, and so forth. This rapid and ultrasensitive method for Hg²⁺ detection can either be potentially developed into stand-alone hand-held sensors or be integrated into existing water equipment for continuously monitoring the water quality

Pulse-Driven Capacitive Lead Ion Detection with Reduced Graphene Oxide Field-Effect Transistor Integrated with an Analyzing Device for Rapid Water Quality Monitoring

Rapid and real-time detection of heavy metals in water with a portable microsystem is a growing demand in the field of environmental monitoring, food safety, and future cyber-physical infrastructure. Here, we report a novel ultrasensitive pulse-driven capacitance-based lead ion sensor using self-assembled graphene oxide (GO) monolayer deposition strategy to recognize the heavy metal ions in water. The overall field-effect transistor (FET) structure consists of a thermally reduced graphene oxide (rGO) channel with a thin layer of Al₂O₃ passivation as a top gate combined with sputtered gold nanoparticles that link with the glutathione (GSH) probe to attract Pb²⁺ ions in water. Using a preprogrammed microcontroller, chemo-capacitance based detection of lead ions has been demonstrated with this FET sensor. With a rapid response (∼1–2 s) and negligible signal drift, a limit of detection (LOD) < 1 ppb and excellent selectivity (with a sensitivity to lead ions 1 order of magnitude higher than that of interfering ions) can be achieved for Pb²⁺ measurements. The overall assay time (∼10 s) for background water stabilization followed by lead ion testing and calculation is much shorter than common FET resistance/current measurements (∼minutes) and other conventional methods, such as optical and inductively coupled plasma methods (∼hours). An approximate linear operational range (5–20 ppb) around 15 ppb (the maximum contaminant limit by US Environmental Protection Agency (EPA) for lead in drinking water) makes it especially suitable for drinking water quality monitoring. The validity of the pulse method is confirmed by quantifying Pb²⁺ in various real water samples such as tap, lake, and river water with an accuracy ∼75%. This capacitance measurement strategy is promising and can be readily extended to various FET-based sensor devices for other targets

Rapid, Sensitive, Label-Free Electrical Detection of SARS-CoV‑2 in Nasal Swab Samples

Rapid diagnosis of coronavirus disease 2019 (COVID-19) is key for the long-term control of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) amid renewed threats of mutated SARS-CoV-2 around the world. Here, we report on an electrical label-free detection of SARS-CoV-2 in nasopharyngeal swab samples directly collected from outpatients or in saliva-relevant conditions by using a remote floating-gate field-effect transistor (RFGFET) with a 2-dimensional reduced graphene oxide (rGO) sensing membrane. RFGFET sensors demonstrate rapid detection (<5 min), a 90.6% accuracy from 8 nasal swab samples measured by 4 different devices for each sample, and a coefficient of variation (CV) < 6%. Also, RFGFET sensors display a limit of detection (LOD) of pseudo-SARS-CoV-2 that is 10 000-fold lower than enzyme-linked immunosorbent assays, with a comparable LOD to that of reverse transcription-polymerase chain reaction (RT-PCR) for patient samples. To achieve this, comprehensive systematic studies were performed regarding interactions between SARS-CoV-2 and spike proteins, neutralizing antibodies, and angiotensin-converting enzyme 2, as either a biomarker (detection target) or a sensing probe (receptor) functionalized on the rGO sensing membrane. Taken together, this work may have an immense effect on positioning FET bioelectronics for rapid SARS-CoV-2 diagnostics