Sensing Molecules with Metal–Organic Framework Functionalized Graphene Transistors

Abstract

Graphene is inherently sensitive to vicinal dielectrics and local charge distributions, a property that can be probed by the position of the Dirac point in graphene field‐effect transistors. Exploiting this as a useful sensing principle requires selectivity; however, graphene itself exhibits no molecule‐specific interaction. Complementarily, metal–organic frameworks can be tailored to selective adsorption of specific molecular species. Here, a selective ethanol sensor is demonstrated by growing a surface‐mounted metal–organic framework (SURMOF) directly onto graphene field‐effect transistors (GFETs). Unprecedented shifts of the Dirac point, as large as 15 V, are observed when the SURMOF/GFET is exposed to ethanol, while a vanishingly small response is observed for isopropanol, methanol, and other constituents of the air, including water. The synthesis and conditioning of the hybrid materials sensor with its functional characteristics are described and a model is proposed to explain the origin, magnitude, and direction of the Dirac point voltage shift. Tailoring multiple SURMOFs to adsorb specific gases on an array of such devices thus generates a versatile, selective, and highly sensitive platform for sensing applications.

Chemically Integrating a 2D Metal–Organic Framework with 2D Functionalized Graphene

“…Recently, 2D metal–organic frameworks (MOFs) have emerged as a new class of 2D materials , even with the realization of the atomically precise single-crystal structure . MOFs are porous coordination polymers with a high degree of crystallinity, comprising organic linkers and metal nodes connected via coordination bonds, known for their long-range structural order and finely tunable properties. , The primary advantage of 2D MOFs over 3D MOFs is the superior electrical conductivity with porosity, making them promising material platforms for a variety of electronic and electrochemical applications like chemiresistive sensing, field-effect transistor, rechargeable batteries, supercapacitors, thermoelectrics, fuel cells, and superconductivity. − In view of further improvising the properties vis-à-vis device performance, there is an emergence of combining 2D MOFs with conventional 2D materials, specifically 2D functionalized graphene, here named as reduced graphene oxide (rGO). − Integrating graphene-based material with 2D MOFs is less explored than with 3D MOFs. − In this direction, a Cd-based 2D MOF was synthesized by taking nanosheets of graphene oxide (GO) and functionalized GO into the reaction mixture, and the isolated solid exhibited a modulation in the CO 2 uptake characteristics …”

Two‐Dimensional Metal‐Organic Frameworks and Covalent Organic Frameworks

“…Krupke et al . [ 144 ] directly grew surface‐mounted metal organic frameworks (SURMOFs) on graphene field effect transistors (GFETs) to design ethanol‐sensitivity sensors. When SURMOF/GFET was exposed to ethanol, an unprecedented shift of the Dirac point was observed, as high as 15 V, and the response to isopropanol, methanol, and other air components (including water) was very small.…”

The Adsorption of Small Molecules on the Copper Paddle-Wheel: Influence of the Multi-Reference Ground State

“…For example, we recently investigated CO oxidation taking place in HKUST-1, one of the most classical MOFs that has CUSs [ 45 ]. At the same time, adsorption of small molecules (i.e., alcohols) on the copper paddle-wheel of Cu 2 (BDC) 2 SURMOF is a promising technique in building sensors of new generation [ 46 ]. In general, dicopper tetracarboxylate paddle-wheel ( Figure 1 ) is a key structural motif of many MOFs: Cu 3 (BTC) 2 (more commonly known as HKUST-1 [ 47 ], also known as MOF-199 [ 48 ]), Cu-BDC [ 49 ], Cu 4 (TDHB) (BUT-155) [ 50 ], Cu 2 (EBTC) (MOF-505) [ 51 ], etc., as well as of some giant supramolecules (i.e., MOP-1 [ 52 ]).…”