In recent years, field-effect transistors (FETs) have been very promising for biosensor applications due to their high sensitivity, real-time applicability, scalability, and prospect of integrating measurement system on a chip. Non-carbon 2D materials, such as transition metal dichalcogenides (TMDCs), hexagonal boron nitride (h-BN), black phosphorus (BP), and metal oxides, are a group of new materials that have a huge potential in FET biosensor applications. In this work, we review the recent advances and remarkable studies of non-carbon 2D materials, in terms of their structures, preparations, properties and FET biosensor applications. We will also discuss the challenges facing non-carbon 2D materials-FET biosensors and their future perspectives.

Molybdenum disulfide (MoS₂) features a band gap of 1.3 eV (indirect) to 1.9 eV (direct). This tunable band gap renders MoS₂ a suitable conducting channel for field-effect transistors (FETs). In addition, the highly sensitive surface potential in MoS₂ layers allows the feasibility of FET applications in biosensors, where direct immobilization and detection of biological molecules are conducted in wet conditions. In this work, we report, for the first time, the degradation of chemical vapor deposition (CVD) grown MoS₂ FET-based sensors in the presence of phosphate buffer and water, which caused false positive response in detection. We conclude the degradation was originated by physical delamination of MoS₂ thin films from the SiO₂ substrate. The problem was alleviated by coating the sensors with a 30 nm thick aluminum oxide (Al₂O₃) layer using atomic layer deposition technique (ALD). This passive oxide thin film not only acted as a protecting layer against the device degradation but also induced a strong n-doping onto MoS₂, which permitted a facile method of detection in MoS₂ FET-based sensors using a low-power mode chemiresistive I-V measurement at zero gate voltage (V_gate = 0 V). Additionally, the oxide layer provided available sites for facile functionalization with bioreceptors. As immunoreaction plays a key role in clinical diagnosis and environmental analysis, our work presented a promising application using such enhanced Al₂O₃-coated MoS₂ chemiresistive biosensors for detection of HIgG with high sensitivity and selectivity. The biosensor was successfully applied to detect HIgG in artificial urine, a complex matrix containing organics and salts.

Our study develops two configurations of MoS₂ and graphene heterostructures—MoS₂ on graphene (MG) and graphene on MoS₂ (GM)—to investigate biomolecule sensing in field-effect transistor (FET) biosensors. Leveraging MoS₂ and graphene’s distinctive properties, we employ specialized functionalization techniques for each configuration: graphene with MoS₂ on top uses a silane-based method with triethoxysilylbutyraldehyde (TESBA), and MoS₂ with graphene on top utilizes 1-pyrenebutyric acid N-hydroxysuccinimide ester (PBASE). Our research explores the application of MoS₂–Graphene heterostructures in biosensors, emphasizing the roles of synthesis, fabrication, and material functionalization in optimizing sensor performance. Through our experimental investigations, we have observed that doping MoS₂ and graphene leads to noticeable changes in the Raman spectrum and shifts in transfer curves. Techniques such as XPS, Raman, and AFM have successfully confirmed the biofunctionalization. Transfer curves were instrumental in characterizing the biosensing performance, revealing that GM configurations exhibit higher sensitivity and a lower limit of detection (LOD) compared to MG configurations. We demonstrate that GM heterostructures offer superior sensitivity and specificity in biosensing, highlighting their significant potential to advance biosensor technologies. This research contributes to the field by detailing the creation process of vertical MoS₂–graphene heterostructures and evaluating their effectiveness in accurate biomolecule detection, advancing biosensing technology.