Materials Horizons Emerging Investigator Series: Jun Zhang, Qingdao University, China

Jun Zhang is an Associate Professor in the College of Physics at Qingdao University. He received his PhD in chemistry in 2011 from Nankai University. After graduation, he started his career at the University of Jinan, where he worked from 2011–2014. Prior to joining Qingdao University in 2016, he worked with Prof. Nicola Pinna at Humboldt University, Berlin, in 2014–2015. Current research in his group is focused on the elaboration of nanostructured materials for applications in gas sensors and energy devices. He is the author of over 70 papers in international peer reviewed journals. He looks forward to contributing to the sensor research community by sharing his enthusiasm for science with graduate and undergraduate students through his teaching and research.

Read Jun Zhang's Emerging Investigator Series article “Platinum single atoms on tin oxide ultrathin films for extremely sensitive gas detection” and read more about him in the interview below:

MH: Your recent Materials Horizons Communication focuses on the use of single atom ultrathin films as sensing layers for gas sensors. How has your research evolved from your first article to this most recent article and where do you see your research going in the future?

JZ: I started my research in chemical gas sensors when I was pursuing my PhD in inorganic chemistry from 2006–2011. The research focus was on the structure–property relations. To this end, various metal oxide semiconductor (MOS) nanostructures and their hybrid materials have been synthesized by mainly wet-chemical methods and applied as the sensing layers in resistive-type gas sensors. It is quite encouraging that sensor properties such as the sensitivity and selectivity to particular gas molecules could be optimized by engineering the structure and surface properties of MOS. General strategies for the functionalization of MOS with noble metal nanoparticle catalysts have also been developed to modify their surface properties.

The fabrication of sensor devices using these synthesized MOS is usually based on the drop- or dip-coating technique to fabricate a thick film. This method is quite simple and works well in the laboratory; unfortunately, it suffers from poor control of the consistency between manually fabricated devices and poor contact between the sensing layer and the electrodes. Currently the quickly developing Internet of Things (IoT) and sensor networks require the high-throughput and reliable production of sensors with miniaturised size and low power consumption. Our recent work in Materials Horizons, in collaboration with Prof. Nicola Pinna at Humboldt University, demonstrates the batch fabrication of microsensors on a wafer scale with ultrathin SnO₂ thin films as the sensing layers deposited by atomic layer deposition (ALD). The sensing results revealed that uniform thin films guarantee reliable sensor fabrication to achieve stable sensor responses. From a wider perspective, the thin film technology is perfectly compatible with the micro-fabrication process and is conducive to the production of microsensors with low power consumption. To further optimize the sensor performance, we functionalized the ultrathin SnO₂ films with single atom Pt via ALD. In contrast to the widely used Pt nanoparticles, single atom Pt has a high utilization efficiently and activity. This results in a decrease of the working temperature of the sensor, an ultrahigh sensitivity and a very low detection limit at the ppb level upon exposure to triethylamine.

Currently we are making progress in developing microsensors with multi-functions such as transparency and flexibility. Sensor arrays via thin film technology are under investigation to achieve better selectivity for molecules such as acetone, which can serve as a biomarker for the non-invasive diagnosis of diabetes.

MH: What aspect of your work are you most excited about at the moment?

JZ: By using thin film technology such as ALD we were able to deposit ultrathin MOS films, which are highly different to the thick films. The thin films with a thickness of several nm are a good platform to study the surface functionalization, i.e. the promotion effect of metal catalysts in sensing reactions. With regard to our recent work in Materials Horizons, we showed that the single atom Pt catalyst enhanced the oxygen activation via chemical sensitization, which led to high sensor performance. This fundamental mechanistic investigation reveals the great potential of single atom catalysts with very low loading and high utilization efficiency in developing emerging gas sensors.

MH: In your opinion, what are the most important questions to be asked/answered in this field of research?

JZ: Although there has been plenty of work related to noble metal-enhanced MOS sensors, the sensing mechanism is still not very clear. Undoubtedly, clear knowledge of the sensing mechanism is highly helpful and this will guide our research to develop efficient sensor materials in a more rational manner, rather than by trial and error.

Besides, I think it is also quite important to tackle the unsatisfactory selectivity of current MOS sensors towards particular molecules, which will eventually lead from fundamental steps to real applications.

MH: What do you find most challenging about your research?

JZ: I think the research into the sensing mechanism has been challenging. This requires a reliable instrument and characterization techniques. In situ and in operando tests have been proposed by researchers as powerful methods, as these kinds of tests can collect information from sensing reactions occurring in real working conditions.

MH: At which upcoming conferences or events may our readers meet you?

JZ: I will probably attend the 8th International Congress on Ceramics (ICC8) in Busan, Korea, which has been postponed to April 2021 due to COVID19. I look forward to meeting colleagues working on gas sensors.

MH: How do you spend your spare time?

JZ: In my spare time I enjoy spending time with my wife and our 3-year-old son, wandering at the seaside near home, or playing Lego with my energetic boy. I also like to go back to my village for a couple of days when I am on vacation. This refreshes me from the stress of work.

MH: Can you share one piece of career-related advice or wisdom with other early career scientists?

JZ: Personally I would like to advise early career scientists to attend meetings/conferences and to establish collaborations with scientists in the field.

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