Ultrasensitive Molecular Sensors Based on Real‐Time Impedance Spectroscopy in Solution‐Processed 2D Materials

Abstract

Chemical sensors based on solution‐processed 2D nanomaterials represent an extremely attractive approach toward scalable and low‐cost devices. Through the implementation of real‐time impedance spectroscopy and development of a three‐element circuit model, redox exfoliated MoS2 nanoflakes demonstrate an ultrasensitive empirical detection limit of NO2 gas at 1 ppb, with an extrapolated ultimate detection limit approaching 63 ppt. This sensor construct reveals a more than three orders of magnitude improvement from conventional direct current sensing approaches as the traditionally dominant interflake interactions are bypassed in favor of selectively extracting intraflake doping effects. This same approach allows for an all solution‐processed, flexible 2D sensor to be fabricated on a polyimide substrate using a combination of graphene contacts and drop‐casted MoS2 nanoflakes, exhibiting similar sensitivity limits. Finally, a thermal annealing strategy is used to explore the tunability of the nanoflake interactions and subsequent circuit model fit, with a demonstrated sensitivity improvement of 2× with thermal annealing at 200 °C.

Immobilized Molecules’ Impact on the Efficacy of Nanocarbon Organic Sensors for Ultralow Dopamine Detection in Biofluids

“…Thus, a highly efficient new carbon-based organic sensor must be designed as a single component to suit the users' needs. [66] The one-step molecular engineering (ME) approach [67][68][69][70] is adopted in this work to tune both the physical and chemical characteristics of the desirable material. This technique has drawn much attention among experts after the award of the Nobel Prize in chemistry this year.…”

High Throughput Data-Driven Design of Laser-Crystallized 2D MoS2 Chemical Sensors: A Demonstration for NO2 Detection

“…Dependent on the chemical composition and phase configuration, TMDCs can present as semiconductors, semi-metals, and metals − and are comprised of covalently bonded layer sheets held together by weak van der Waals forces in the bulk form. The electrical and optical properties of TMDCs can be tuned by varying the number of layers, − applying strain, − and introducing dopants or defects. − Moreover, the high surface area-to-volume ratio, high electron mobility, and ease of functionalization make TMDC materials an ideal platform for the electronic detection of a multitude of liquid and vapor analytes . In particular, NO 2 vapor remains one of the gold standards for evaluating 2D TMDC sensor performance, as the strong electron-withdrawing characteristics have been known to significantly modify the electronic and optical properties of TMDCs even at extremely low concentrations below 1 ppb. − Despite this, the understanding of material parameters dictating sensor performance is lacking as the variable space including grain size, thickness, strain, and doping are all expected to be strong contributors.…”

“…Data-driven design of electronic sensors is an attractive approach to efficiently and rapidly correlate multibody intrinsic material properties relevant to sensor performance optimization . In the case of 2D MoS 2 chemical sensors, detection sensitivity is known to be non-monotonically responsive to the layer thickness, grain size, − and defect density. , Moreover, 2D sensor devices are often fabricated from a finite batch of samples grown by wafer-scale, relatively uniform techniques including thermal decomposition, metal–organic chemical vapor deposition, or magnetron sputtering. − Following the growth process, annealing strategies such as thermal or photonic annealing can tailor the crystallinity, induce defects, or even manipulate electronic properties. ,, For films produced by such wafer-scale techniques, the tuning of these material properties must be done on a per-sample basis or must rely on film variation intrinsically present . As a result, evaluating the relationships between the varying material properties is a time-consuming process.…”

“…27 Following the growth process, annealing strategies such as thermal or photonic annealing can tailor the crystallinity, induce defects, or even manipulate electronic properties. 17,30,31 For films produced by such wafer-scale techniques, the tuning of these material properties must be done on a per-sample basis or must rely on film variation intrinsically present. 32 As a result, evaluating the relationships between the varying material properties is a time-consuming process.…”

MoS2 Defect Healing for High-Performance Chemical Sensing of Polycyclic Aromatic Hydrocarbons

“…Low-dimensional materials are ideal scaffolds for the development of highly sensitive and selective sensors which are unexpensive and easy to fabricate, enabling fast and reliable detection of specific chemical species in liquid and gas media. , Due to their nanometric size and highest surface-to-volume ratio, they exhibit quantum confinement effects combined with other exclusive properties such as extraordinary thermal and electrical conductivity, markedly high catalytic activity, and unique optical properties making them extremely reactive and suitable candidates for environmental pollution sensing and remediation . In particular, 2D transition metal dichalcogenides (TMDCs) and graphene are considered ideal sensory materials, , since their unique physical and chemical properties are highly sensitive to environmental changes. Graphene oxide and reduced graphene oxide have been widely exploited for chemical sensing, − yet the presence of oxygen-containing functional groups on the material’s basal plane and edges brings into play background dipole–dipole interactions with multiple potential analytes, thus drastically limiting the selectivity in the sensing process. − …”