Evaluation of Polymeric Nanocomposites for the Detection of Toxic Gas Analytes Kate Stewart and Alex Penlidis Department of Chemical Engineering University of Waterloo

Toxic Gas Analytes There are numerous applications in which sensing gas analytes is important Ethanol detection to reduce drinking and driving Acetone detection as a disease indicator Benzene and formaldehyde detection in air In any application, target gases are present with other interferent gases

Sensing Characteristics Sensitivity Related to the detection limit of a sensor; the lower the detection limit, the more sensitive the sensor. Selectivity Ratio between the responses of target analyte to interferent analyte. Operational Temperature Temperature at which the sensor operates. Response/Recovery Times Time it takes to reach 90% of full signal/time it takes to return to 10% of the baseline.

Selecting Sensing Materials Target Analyte Functional Groups Molecule Size Application Constraints Operational Temperature Environmental Stability Sensor Constraints Type of Sensor Potential Polymeric Sensing Materials Resistive? Conductive Capacitive? Dielectric Mass-based? Light weight Add group(s)? Dopants? Metal or Metal oxide Acids Tg Chemically Stable? Interferents? Dominant Mechanisms Polar? H-bond? Lewis acid/base? Aromatic? Bulky? Polymer Modification Dopants

Poly (2,5-dimethyl aniline) P25DMA Amine group attracts polar molecules, especially molecules able to hydrogen bond Two methyl side groups reduce the ability of P25DMA to pack closely Doped with 5 metal oxide nanoparticles CuO, Al2O3, ZnO, NiO, TiO2 N H CH3

Characterization X-ray Diffraction (XRD) to determine crystallinity of the polymer composites Energy Dispersive X-ray (EDX) to determine composition of samples Scanning Electron Microscopy (SEM) to look at the morphology of the polymer composites

Experimental Test System Very Sensitive Gas Chromatograph with PDHID MFC: Mass Flow Controller; PC: Pressure Controller; FM: Flow Meter

Polymeric Nanocomposite P25DMA Doped with CuO (c) 5 μm (b) 1 μm (d) (a) 200 nm Polymeric Nanocomposite Weight Percent P25DMA 5% CuO 0.16 P25DMA 10% CuO 0.07 P25DMA 20% CuO 0.11

P25DMA Doped with CuO

Polymeric Nanocomposite P25DMA Doped with Al2O3 (a) 200 nm 1 μm (c) 5 μm (b) (d) Polymeric Nanocomposite Weight Percent P25DMA 5% Al2O3 0.61 P25DMA 10% Al2O3 0.57 P25DMA 20% Al2O3 0.49

P25DMA Doped with Al2O3 P25DMA P25DMA 5% Al2O3 P25DMA 10% Al2O3

Polymeric Nanocomposite P25DMA Doped with ZnO (a) 200 nm 1 μm (c) 5 μm (b) (d) 100 nm Polymeric Nanocomposite Weight Percent P25DMA 5% ZnO 0.34 P25DMA 10% ZnO 0.86 P25DMA 20% ZnO 46.89 1 μm

P25DMA Doped with ZnO

Polymeric Nanocomposite P25DMA Doped with NiO (b) 5 μm (c) 1 μm 100 nm (d) (a) Polymeric Nanocomposite Weight Percent P25DMA 5% NiO 5.58 P25DMA 10% NiO 8.11 P25DMA 20% NiO 19.14

P25DMA Doped with NiO

Polymeric Nanocomposite P25DMA Doped with TiO2 (b) 5 μm (c) (d) (a) 1 μm Polymeric Nanocomposite Weight Percent P25DMA 5% TiO2 3.68 P25DMA 10% TiO2 12.37 P25DMA 20% TiO2 17.09

P25DMA Doped with TiO2

Summary of P25DMA Doped with 5% Metal Oxides

Sensor Array Unknown

Gas Mixtures Gas Mixture

Concluding Remarks Sensing mechanisms to choose sensing materials Not all metal oxide nanoparticles can be fully incorporated into a polymer matrix Metal oxide nanoparticles affect the morphology and sensing properties of a polymer composite Selectivity can be improved by combining different partially selective sensing materials into an array Able to separate 6 different gas analytes using 5 different sensing materials Able to identify unknown gases

Thank you

References Stewart, K. M E. and A. Penlidis. “Designing Polymeric Sensing Materials for the Detection of Ethanol” Macromolecular Symposia 360 (2016) 123-132. Stewart, K. M. E., W. T. Chen, R. R. Mansour, and A. Penlidis. “Doped Poly (2,5- dimethyl aniline) for the Detection of Ethanol” Journal of Applied Polymer Science 132 (2015) 42259-42264. Stewart, K. M. E., N. T. McManus, E. Abdel-Rahman, and A. Penlidis. “Doped Polyaniline for the Detection of Formaldehyde” Journal of Macromolecular Science, Part A 49, 1 (2012) 1-6. Chen, W. T., K. M. E. Stewart, R. R. Mansour, and A. Penlidis. “Novel Undercoupled Radio-frequency (RF) Resonant Sensor for Gaseous Ethanol and Interferents Detection” Sensors and Actuators A 230 (2015) 63-73.

Sensing Mechanisms Primary Mechanisms Secondary Mechanisms Polarity and Hydrogen Bonding Lewis Acid-Base p-orbitals and π-stacking Metal Coordination van der Waals Forces Steric Hindrance Secondary Mechanisms Swelling Solvent Effects

Weight Percent of Metal Oxide Incorporated Polymeric Nanocomposite CuO Al2O3 ZnO NiO TiO2 P25DMA 5% MOx 0.16 0.61 0.34 5.58 3.68 P25DMA 10% MOx 0.07 0.57 0.86 8.11 12.37 P25DMA 20% MOx 0.11 0.49 46.89 19.14 17.09

EDX and SEM Reproducibility P25DMA 20% TiO2 Polymeric Nanocomposite P25DMA 5% Al2O3 5% ZnO 5% TiO2 Replicate 1 0.61 0.34 3.68 Replicate 2 0.57 0.33 3.79 Replicate 3 0.72