(4hq) Chemical Engineering of Nanostructures and Interfaces for Molecular Sensing

Modern electronic devices (e.g. smartphones) are indispensable tools for billions of people. They interact with us through voice recognition, activity tracking, give us orientation, record videos and connect us by communication to the world. These functionalities are enabled typically by more than a dozen extremely small, low-power but high performance physical sensors. Surprisingly, chemical recognition is missing, despite the fact that our world is made of molecules. Equipped with chemical sensing, exciting new functionalities become possible to tackle some of humankind’s most pressing issues. For instance, portable gas sensors can provide critical health data on demand through non-invasive breath analysis, diseases could be detected earlier and their therapies personalized to reduce mortality, improve patient’s recovery and impede skyrocketing healthcare costs. The availability of high-performance chemical sensors will be critical also to tackle some of our society’s most pressing challenges. For instance, inevitable for a success transition from fossil to CO₂-neutral energy carriers (e.g., hydrogen, methanol) will be their safe handling. Also, we require tools for the distributed and permanent monitoring of air pollution to identify emission hotspots and assist policymakers in their efforts to adhere to emission agreements. Despite their great potential with a clear societal need, suitable gas sensors are hardly available yet.

Research on molecular interactions with surfaces is at the core of chemical sensing. However, we lack (1) fundamental understanding on such molecular interactions and (2) chemical engineering processes to rigorously design and fabricate suitable surfaces. Our research aims at addressing these needs by capitalizing on our recent advances on the nanoscale design of porous sensing layers with controlled mass transfer (i.e., diffusion, adsorption and reaction) properties that govern sensing performance. More specifically, we leverage combustion-aerosol processing of inorganic solid-state nanoparticles (oxides, nitrides, sulfides, bromides, carbides) [Prog. Energy Combust. Sci. 2022, 90, 100992] decorated with clusters [Adv. Sci., 2024, 11, 2308224] and single-atom catalysts with high flexibility and close control over material composition, crystallinity and morphology. This enables a systematic tailoring of selective, rapid and reversible interactions between material surfaces and molecules, as demonstrated already with porous CuBr films that recognize ammonia selectively at room temperature [Adv. Sci. 2020, 7, 1903390]. New methodologies for in situ characterization advance our understanding on chemically reactive sites and the electronic interactions between molecules and surfaces to provide fundamental insights into sensing phenomena.

To demonstrate immediate societal impact, we explore the utilization of these sensors for energy, environmental, food, health and space applications. Therefore, prototype devices have been developed and evaluated under real conditions. For instance, we achieved that way compact devices that track benzene selectively (e.g. over chemically similar toluene and xylene) in room air even at lowest parts-per-billion concentrations [Adv. Sci. 2022, 9, 2103853] fulfilling most national exposure guidelines. Similarly, formaldehyde has been detected in room air when emitted from wooden products [J. Hazard. Mater. 2020, 123052], as validated by high resolution mass spectrometry representing a long-standing challenge in environmental sensing. At the same time, we developed also sensors for the monitoring of living organism. For instance, the breath and skin emissions of entrapped people where tracked with compact sensor arrays [Anal. Chem. 2018, 90, 4940] while we are currently testing such detectors also at the University Hospital in Zürich for their capacity to sense metabolites in exhaled breath for medical applications [Adv. Sci. 2020, 7, 2001503]. Even toxic compounds in liquids like methanol can be detected that way [Nature Commun. 2019, 10, 4220] with results being communicated wirelessly to smartphones [Nature Food 2020, 1, 351]. The latter innovation has been granted as patent and commercialized by a spin-off company with device sales to 26 countries on six continents [Nat. Rev. Bioeng. 2023 1, 385-387].

This research is interdisciplinary requiring extensive collaboration between material scientists, environmental engineers, and chemists (among others) to advance sensor research and apply them in the described applications. Finally, our research has been extensively covered (100+ news outlets sin 2017) by intl. media, including BBC, Swiss TV SRF, Nature Asia, ETH News, American Chemical Society, Yale Scientific Magazine, Tagesanzeiger, and 100+ other intl. news outlets since 2017.

Research Interests: Chemical Engineering, Nanotechnology, Material Science, Inorganic Chemistry, Sensing, Microelectronics, Semiconductors, Surface Science, Transport Phenomena, Analytical Chemistry, Device Engineering, Mobile Health Technology, Breath Analysis.

Teaching Interests: Mass Transfer, Molecular Sensing, Micro- and Nanoparticle Technology, Microfabrication, Microsystems and Devices