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.

Affinity layers play a crucial role in chemical sensors for the selective and sensitive detection of analytes. Here, we report the use of composite affinity layers containing Metal Organic Frameworks (MOFs) in a polymeric matrix for sensing purposes. Nanoparticles of NH2-MIL-53(Al) were dispersed in a Matrimid polymer matrix with different weight ratios (0–100 wt %) and drop-casted on planar capacitive transducer devices. These coated devices were electrically analyzed using impedance spectroscopy and investigated for their sensing properties toward the detection of a series of alcohols and water in the gas phase. The measurements indicated a reversible and reproducible response in all devices. Sensor devices containing 40 wt % NH2-MIL-53(Al) in Matrimid showed a maximum response for methanol and water. The sensor response time slowed down with increasing MOF concentration until 40 wt %. The half time of saturation response (τ0.5) increased by ∼1.75 times for the 40 wt % composition compared to devices coated with Matrimid only. This is attributed to polymer rigidification near the MOF/polymer interface. Higher MOF loadings (≥50 wt %) resulted in brittle coatings with a response similar to the 100 wt % MOF coating. Cross-sensitivity studies showed the ability to kinetically distinguish between the different alcohols with a faster response for methanol and water compared to ethanol and 2-propanol. The observed higher affinity of the pure Matrimid polymer toward methanol compared to water allows also for a higher uptake of methanol in the composite matrices. Also, as indicated by the sensing studies with a mixture of water and methanol, the methanol uptake is independent of the presence of water up to 6000 ppm of water. The NH2-MIL-53(Al) MOFs dispersed in the Matrimid matrix show a sensitive and reversible capacitive response, even in the presence of water. By tuning the precise compositions, the affinity kinetics and overall affinity can be tuned, showing the promise of this type of chemical sensors.

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In this work, the influence of surface modification of titania and alumina particles with carbon on their codeposition behavior with nickel during electroplating is studied. The surface modification was done using a two step procedure where a carbon rich precursor was first deposited on the particle surface by hydrolysis which was subsequently pyrolyzed in an inert atmosphere. The effect of synthesis conditions and the properties of the carbon coating were studied using XPS and Raman spectroscopy and were linked to the contact angle measurements and electrical conductivity of the carbon coating. Modified and unmodified particles were codeposited with nickel from a sulphamate base electrolyte at several current densities. It was found that large contact angles between particles and electrolyte and high electrical conductivity of the carbon coating, led to the highest incorporation rates, as long as particle agglomeration was limited. Optimized carbon synthesis conditions doubled the Al 2 O 3 and tripled the TiO 2 content in the nickel coating compared to the unmodified particles.

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