Sensitive Molybdenum Disulfide Based Field Effect Transistor Sensor for Real-time Monitoring of Hydrogen Peroxide.
ABSTRACT: A reliable and highly sensitive hydrogen peroxide (H2O2) field effect transistor (FET) sensor is reported, which was constructed by using molybdenum disulfide (MoS2)/reduced graphene oxide (RGO). In this work, we prepared MoS2 nanosheets by a simple liquid ultrasonication exfoliation method. After the RGO-based FET device was fabricated, MoS2 was assembled onto the RGO surface for constructing MoS2/RGO FET sensor. The as-prepared FET sensor showed an ultrahigh sensitivity and fast response toward H2O2 in a real-time monitoring manner with a limit of detection down to 1 pM. In addition, the constructed sensor also exhibited a high specificity toward H2O2 in complex biological matrix. More importantly, this novel biosensor was capable of monitoring of H2O2 released from HeLa cells in real-time. So far, this is the first report of MoS2/RGO based FET sensor for electrical detection of signal molecules directly from cancer cells. Hence it is promising as a new platform for the clinical diagnosis of H2O2-related diseases.
Project description:We report a precise measurement of the sensor behavior of the field effect transistor (FET) formed with the MoS2 channel when the channel part is exposed to Cl2 gas. The gas exposure and the electrical measurement of the MoS2 FET were executed with in situ ultrahigh-vacuum (UHV) conditions in which the surface analysis techniques were equipped. This makes it possible to detect how much sensitivity the MoS2 FET can provide and understand the surface properties. With the Cl2 gas exposure to the channel, the plot of the drain current versus the gate voltage (I d-V g curve) shifts monotonically toward the positive direction of V g, suggesting that the adsorbate acts as an electron acceptor. The I d-V g shifts are numerically estimated by measuring the onset of I d (threshold voltage, V th) and the mobility as a function of the dosing amounts of the Cl2 gas. The behaviors of both the V th shift and the mobility with the Cl2 dosing amount can be fitted with the Langmuir adsorption kinetics, which is typically seen in the uptake curve of molecule adsorption onto well-defined surfaces. This can be accounted for by a model where an impinging molecule occupies an empty site with a certain probability, and each adsorbate receives a certain amount of negative charge from the MoS2 surface up to the monolayer coverage. The charge transfer makes the V th shifts. In addition, the mobility is reduced by the enhancement of the Coulomb scattering for the electron flow in the MoS2 channel by the accumulated charge. From the thermal desorption spectroscopy (TDS) measurement and density functional theory (DFT) calculations, we concluded that the adsorbate that is responsible for the change of the FET property is the Cl atom that is dissociated from the Cl2 molecule. The monotonic shift of V th with the coverage suggests that the MoS2 device sensor has a good sensitivity to detect 10-3 monolayers (ML) of adsorption corresponding to the ppb level sensor with an activation time of 1 s.
Project description:A facile one-step solution reaction route for growth of novel MoS2 nanorose cross-linked by 3D rGO network, in which the MoS2 nanorose is constructed by single-layered or few-layered MoS2 nanosheets, is presented. Due to the 3D assembled hierarchical architecture of the ultrathin MoS2 nanosheets and the interconnection of 3D rGO network, as well as the synergetic effects of MoS2 and rGO, the as-prepared MoS2-NR/rGO nanohybrids delivered high specific capacity, excellent cycling and good rate performance when evaluated as an anode material for lithium-ion batteries. Moreover, the nanohybrids also show excellent hydrogen-evolution catalytic activity and durability in an acidic medium, which is superior to MoS2 nanorose and their nanoparticles counterparts.
Project description:Three dimensional (3D) MoS2 nanoflowers are successfully synthesized by hydrothermal method. Further, a composite of as prepared MoS2 nanoflowers and rGO is constructed by simple ultrasonic exfoliation technique. The crystallography and morphological studies have been carried out by XRD, FE-SEM, TEM, HR-TEM and EDS etc. Here, XRD study revealed, a composite of exfoliated MoS2 with expanded spacing of (002) crystal plane and rGO can be prepared by simple 40 minute of ultrasonic treatment. While, FE-SEM and TEM studies depict, individual MoS2 nanoflowers with an average diameter of 200 nm are uniformly distributed throughout the rGO surface. When tested as sodium-ion batteries anode material by applying two different potential windows, the composite demonstrates a high reversible specific capacity of 575 mAhg(-1) at 100 mAg(-1) in between 0.01 V-2.6 V and 218 mAhg(-1) at 50 mAg(-1) when discharged in a potential range of 0.4 V-2.6 V. As per our concern, the results are one of the best obtained as compared to the earlier published one on MoS2 based SIB anode material and more importantly this material shows such an excellent reversible Na-storage capacity and good cycling stability without addition of any expensive additive stabilizer, like fluoroethylene carbonate (FEC), in comparison to those in current literature.
Project description:Porphyrin functionalized reduced graphene oxide (rGO) is attractive for multi-disciplinary research studies, and its improvements for an rGO-based field effect transistor (rGO-FET) were exploited to realize ultrasensitive biochemical and clinical assay. Although it was believed that the hybrids of porphyrin and rGO can make positive impacts on the rGO-FET's electronic performances, the understandings of its functions are still piecemeal. Herein, the reduced mixtures of tetra (4-aminophenyl) porphyrin (TAP), GO (TAP-rGO), and the FET channeled by them are examined to throw a light on the possible approaches through which TAP affects rGO's quality and its carrier mobilities. A TAP-caused game relationship is established by deliberating about the results of the intentionally altered experimental conditions, including TAP contents and the overmixing pretreatment. The p-type doping deduction for the right-shifted ambipolar transfer characteristic curves is evidenced by X-ray photoelectron spectroscopy (XPS). The problems posed by the TAP-induced FET features' improvement, regression, and deterioration are clarified by the integrated proofs from Raman fingerprints, the amide and carboxyl groups' changing trajectory found by C1s XPS core spectra, and the enlarged few-layer graphene morphology from atomic force microscope and transmission electron microscope. We hope that this effort will provide some constructive recommendations for producing low-cost graphene derivatives and promoting their applications in FET-like electronic components.
Project description:Zirconia and 10%, 20%, and 30% cerium-doped zirconia nanoparticles (ZCO), ZCO-1, ZCO-2, and ZCO-3, respectively, were prepared using auto-combustion method. Binary nanohybrids, ZrO2@rGO and ZCO-2@rGO (rGO = reduced graphene oxide), and ternary nanohybrids, ZrO2@rGO@MoS2 and ZCO-2@rGO@MoS2, have been prepared with an anticipation of a fruitful synergic effect of rGO, MoS2, and cerium-doped zirconia on the tribo-activity. Tribo-activity of these additives in paraffin oil (PO) has been assessed by a four-ball lubricant tester at the optimized concentration, 0.125% w/v. The tribo-performance follows the order: ZCO-2@rGO@MoS2 > ZrO2@rGO@MoS2 > ZCO-2@rGO > ZrO2@rGO > MoS2 > ZrO2 > rGO > PO. The nanoparticles acting as spacers control restacking of the nanosheets provided structural augmentation while nanosheets, in turn, prevent agglomeration of the nanoparticles. Doped nanoparticles upgraded the activity by forming defects. Thus, the results acknowledge the synergic effect of cerium-doped zirconia and lamellar nanosheets of rGO and MoS2. There is noncovalent interaction among all the individuals. Analysis of the morphological features of wear-track carried out by scanning electron microscopy (SEM) and atomic force microscopy (AFM) in PO and its formulations with various additives is consistent with the above sequence. The energy dispersive X-ray (EDX) spectrum of ZCO-2@rGO@MoS2 indicates the existence of zirconium, cerium, molybdenum, and sulfur on the wear-track, confirming, thereby, the active role played by these elements during tribofilm formation. The X-ray photoelectron spectroscopy (XPS) studies of worn surface reveal that the tribofilm is made up of rGO, zirconia, ceria, and MoS2 along with Fe2O3, MoO3, and SO42- as the outcome of the tribo-chemical reaction.
Project description:MoS2 has attracted attention as a promising hydrogen evolution reaction (HER) catalyst and a supercapacitor electrode material. However, its catalytic activity and capacitive performance are still hindered by its aggregation and poor intrinsic conductivity. Here, hollow rGO sphere-supported ultrathin MoS2 nanosheet arrays (h-rGO@MoS2) are constructed via a dual-template approach and employed as bifunctional HER catalyst and supercapacitor electrode material. Because of the expanded interlayer spacing in MoS2 nanosheets and more exposed electroactive S-Mo-S edges, the constructed h-rGO@MoS2 architectures exhibit enhanced HER performance. Furthermore, benefiting from the synergistic effect of the improved conductivity and boosted specific surface areas (144.9 m2 g-1, ca. 4.6-times that of pristine MoS2), the h-rGO@MoS2 architecture shows a high specific capacitance (238 F g-1 at a current density of 0.5 A g-1), excellent rate capacitance, and remarkable cycle stability. Our synthesis method may be extended to construct other vertically aligned hollow architectures, which may serve both as efficient HER catalysts and supercapacitor electrodes.
Project description:An olfactory biosensor based on a reduced graphene oxide (rGO) field-effect transistor (FET), functionalized by the odorant-binding protein?14 (OBP14) from the honey bee (Apis mellifera) has been designed for the in?situ and real-time monitoring of a broad spectrum of odorants in aqueous solutions known to be attractants for bees. The electrical measurements of the binding of all tested odorants are shown to follow the Langmuir model for ligand-receptor interactions. The results demonstrate that OBP14 is able to bind odorants even after immobilization on rGO and can discriminate between ligands binding within a range of dissociation constants from K(d)=4??M to K(d)=3.3?mM. The strongest ligands, such as homovanillic acid, eugenol, and methyl vanillate all contain a hydroxy group which is apparently important for the strong interaction with the protein.
Project description:The transition metal dichagenides and their metallic 1T structure are attracting contemporary attentions for applications in high-performance devices because their peculiar optical and electrical properties. The single and few layers 1T structure is generally obtained by mechanical or chemical exfoliation. This work presents facile one-step synthesis of 2H-1T MoS2:Cu/reduced graphene oxide nanosheets. The experiment results indicated that the MoS2 and MoS2:Cu prepared by simple chemical solution reaction possessed 2H-1T structures. The reduced graphene oxide (rGO) incorporation further induced the phase transition from 2H-MoS2 to 1T-MoS2 and morphology transition from granular/nanosheet to more nanosheet. The 2H-1T structure and 2H???1T phase transition, together with the Cu doping and interface effect between the MoS2 and rGO, remarkably enhanced the conduction and photoconduction of the nanostructures. Thus, Cu doping and rGO incorporation obviously enhanced the catalytic activity and its stability, making the MoS2:Cu/rGO nanosheet a most active and stable catalyst for hydrogen evolution. This work clearly indicates that the 1T-MoS2 nanosheets with high catalytic activity for hydrogen evolution can be easily obtained by the facile low temperature chemical method and induction of rGO.
Project description:This work describes the construction of a sensitive, stable, and label-free sensor based on a dual-gate field-effect transistor (DG FET), in which uniformly distributed and size-controlled silicon nanowire (SiNW) arrays by nanoimprint lithography act as conductor channels. Compared to previous DG FETs with a planar-type silicon channel layer, the constructed SiNW DG FETs exhibited superior electrical properties including a higher capacitive-coupling ratio of 18.0 and a lower off-state leakage current under high-temperature stress. In addition, while the conventional planar single-gate (SG) FET- and planar DG FET-based pH sensors showed the sensitivities of 56.7 mV/pH and 439.3 mV/pH, respectively, the SiNW DG FET-based pH sensors showed not only a higher sensitivity of 984.1 mV/pH, but also a lower drift rate of 0.8% for pH-sensitivity. This demonstrates that the SiNW DG FETs simultaneously achieve high sensitivity and stability, with significant potential for future biosensing applications.
Project description:Two-dimensional MoS2 has emerged as promising material for nanoelectronics and spintronics due to its exotic properties. However, high contact resistance at metal semiconductor MoS2 interface still remains an open issue. Here, we report electronic properties of field effect transistor devices using monolayer MoS2 channels and permalloy (Py) as ferromagnetic (FM) metal contacts. Monolayer MoS2 channels were directly grown on SiO2/Si substrate via chemical vapor deposition technique. The increase in current with back gate voltage (Vg) shows the tunability of FET characteristics. The Schottky barrier height (SBH) estimated for Py/MoS2 contacts is found to be +28.8?meV (at Vg = 0V), which is the smallest value reported so-far for any direct metal (magnetic or non-magnetic)/monolayer MoS2 contact. With the application of positive gate voltage, SBH shows a reduction, which reveals ohmic behavior of Py/MoS2 contacts. Low SBH with controlled ohmic nature of FM contacts is a primary requirement for MoS2 based spintronics and therefore using directly grown MoS2 channels in the present study can pave a path towards high performance devices for large scale applications.