Polymer–Metal Organic Framework Composite Films as Affinity Layer for Capacitive Sensor Devices

Abstract

We report a simple method for sensor development using polymer-MOF composite films. Nanoparticles of NH 2 -MIL-53(Al) dispersed in a Matrimid polyimide were applied as a thin film on top of capacitive sensor devices with planar electrodes. These drop-cast films act as an affinity layer. Sensing studies carried out with methanol vapor using impedance spectroscopy demonstrate that the presence of MOF enhances the overall response and lowers the detection limit compared to MOF-free polymer films and bare devices. This can be understood by additional changes of the local polarity of the composite films due to higher adsorption of methanol by the porous MOF particles. We expect that this work will stimulate the design of composite polymeric affinity layers for a range of analytes by a proper choice of dispersed MOF particles.

Gas Phase Sensing of Alcohols by Metal Organic Framework–Polymer Composite Materials

“…The fabrication of the devices was performed as described previously. 29 Briefly, the active electrode area consisted of aluminum metal stacked between TiN layers over underlying dielectric layer of SiO 2 to mimic the final layer of a typical 140 nm CMOS platform. Devices were processed to obtain meander-patterned planar aluminum electrodes by photolithography.…”

“… 31 The presence of these MOF particles inside the polymeric matrix alter their physical and chemical properties. 29 , 31 For example, it has been observed from membrane studies that variations of the concentration of MOF particles can lead to alterations in the gas transport and adsorption properties. 31 , 33 Furthermore, upon blending the overall dielectric constant—and hence the electrical polarizability—changes.…”

“…After deposition of polymer-MOF affinity layers of 10 μm in thickness onto our electrode, the capacitance increases to 28–36 pF as a result of the higher dielectric constant of the deposited layer (ε r = ∼3.5–4.5) as compared to air (ε r = 1), as previously discussed. 29 If analyte molecules are adsorbed in the polymer-MOF matrix, then the overall dielectric constant will also change, resulting in a capacitance change. 29 We have performed such sensing experiments using methanol and water as the analyte, varying the polymer-MOF composition ratio.…”

“… 29 If analyte molecules are adsorbed in the polymer-MOF matrix, then the overall dielectric constant will also change, resulting in a capacitance change. 29 We have performed such sensing experiments using methanol and water as the analyte, varying the polymer-MOF composition ratio. In addition, cross-sensitivity studies with ethanol and 2-propanol and temperature-dependent response studies were performed.…”

Metal–Organic Frameworks as Active Materials in Electronic Sensor Devices

“…In 2016, Sachdeva et al reported the use of a NH 2 -MIL-53(Al)/polyimide composite to fabricate a capacitive sensor for methanol vapor [23]. Devices fabricated with the composite material displayed a lower detection limit as compared to the polymer alone or bare electrodes.…”