Shedding light on novel nanomaterials

27 December 2020

For Professor Andrey Rogach (Croucher Senior Research Fellowship 2019), a pioneering nanoscience researcher, it was a visionary supervisor in his home country of Belarus who set him on a research path that would lead to recognition as one of the world’s top materials scientists.

Rogach, named 51st worldwide among Thomson Reuters 100 Top Materials Scientists of the Past Decade in 2011, undertook his tertiary studies at the Belarusian State University in Minsk. There, he began work with metal nanoparticles, learning to synthesise these tiny materials during his PhD studies in physical chemistry.

“I joined because my PhD supervisor, an old academician from Minsk, had a kind of clear vision that this field would develop as well as it did. So, I followed his advice,” he recalled.

More than a quarter of a century later, Rogach, Chair Professor of Photonics Materials, at City University of Hong Kong’s Department of Materials Science and Engineering, is no longer the one in the lab coat doing chemical syntheses. He is office-based, supervising the work of his team, processing results, and compiling articles. But he retains his passion for his chosen field, the more so because of the enthusiasm of his students.

“We do it because we love science,” said Rogach, who is also Founding Director of the university’s Centre for Functional Photonics. “It’s very important to discover – it could be a big discovery, a small discovery. We do small discoveries every day in science so this is very rewarding.”

During his three-year, HK$2 million Croucher Senior Research Fellowship, Rogach and his team are working on perovskite nanocrystals. This is a semiconductor material developed in the past five years, described in a review that he and colleagues wrote for Materials Today early in 2020 as “a new class of light-harvesting and light-emitting materials”. These had, they wrote, attracted much attention for an impressive variety of optoelectronic applications.

In the review, they noted this attention is sometimes described as “perovskite fever” – not a term Rogach said he would use. The review explained that excitement is partly because these materials are low-cost to produce and have other advantages including their exceptionally strong photoluminescence.

Further down the track, there are practical applications to be developed – for example, the brightness and colour saturation of mobile phone displays and televisions – but those are not normally the team’s major role. “For example, we seldom make real devices. When we are satisfied, we pass it on to someone else for the applications and devices,” he said.

Their role is to design and make nanoparticles from a variety of chemical elements and then pick up those that make them most useful and stable. While they may not be ready for real- world applications, for example, in displays or in LCD televisions, many people are working hard to make that happen, he added.

“The perovskite materials are very easy to make. Their emitted light is very bright and high- quality light, especially for displays or mobile phones. Every colour which is offered by perovskites is high-quality colour,” Rogach said.

But there are obstacles to overcome. “There is an issue that they are often based on lead as one of the constituting elements, that can be toxic,” Rogach explained Research is underway to find alternatives to substitute for lead while not compromising the materials’ optical properties and stability.

Rogach and his team bring together interconnected arms of his field, each of which was part of his studies. “During my PhD in Minsk, I mostly worked as a chemist, with metal nanomaterials. Starting from my post-doc stay in Hamburg, Germany, I switched from metals to semiconductors and since then I’ve worked mostly with semiconductors,” he said.

“So, during my career I started as a chemist, my education and PhD were physical chemistry, and I’m now in materials. It’s a natural development because we always develop and explore new materials.”

Between his post-doctoral years at the University of Hamburg and present research work in Hong Kong, Rogach spent seven years as a tenured lead staff scientist with the University of Munich, where his focus was physics, not chemistry. Capitalising on that expertise, his team now includes students in both, working on the optical properties of nanomaterials, which he describes as “more physics”, and on the chemistry side, making those materials.

“We do both. This is a kind of uniqueness of approach that we pursue. There are not many people in the world who can do this at the same level of sophistication we do.”

It is a uniqueness that has led to worldwide recognition. Rogach is the author of more than 500 scientific publications cited more than 40,000 times and has won prestigious international accolades, including a Carl Friedrich von Siemens Research Award from the German-based Alexander von Humboldt Foundation in 2018.

Work in his field is moving quickly. In NPG Asia Materials in 2016, Rogach and colleagues wrote on the properties and applications of perovskite nanocrystals: “Despite all of the challenges remaining, perovskites have rapidly advanced as one of the premier materials for a plethora of applications. With the vast amount of research being conducted in this field, it is to be expected that many of these challenges can be overcome rapidly, enabling consumer-friendly device applications.”

For Rogach, the key to his work is “fundamental research”, pioneering efforts by inquiring minds. He was given great freedom during his PhD studies and he gives his students the same. “We always develop new materials and study their optical properties, and you need particular expertise to be able to do so as an expert. This is what we do in our lab most of the time.”

Rogach, who moved to Hong Kong with his family almost 12 years ago and loves the outdoor life and hiking in the New Territories, also enjoys the intensity of life there. “Hong Kong is very busy in a positive way. Europe feels a bit too slow for me now. Here people work hard and are rewarded for this,” he said.

He has no regrets about shifting both his family and research focus to Asia and is seeing the fruits of his effort as a new generation – his former postdoctoral students, many based in Mainland China – take his work to the next stage.

“Many of them became professors in engineering departments and schools. They follow my research, my publications. When they read about recently developed materials that are interesting for them and which could be applied in devices, they approach me. This is how many of our new collaborative publications and projects evolve.”

Professor Andrey Rogach is Chair Professor of Photonics Materials in the Department of Materials Science and Engineering, City University of Hong Kong (CityU), and Founding Director of CityU’s Centre for Functional Photonics. He was awarded his PhD in Physical Chemistry from Belarusian State University in Minsk in 1995, before working as a postdoc (with Horst Weller) and then as a staff scientist at the Institute of Physical Chemistry, University of Hamburg, Germany, until 2002. This was followed by a tenured position as a lead staff scientist in the Department of Physics and Centre for NanoScience, University of Munich, Germany. In 2009, he was appointed to the position of Professor at CityU, advancing to Chair Professor in 2012. He was awarded a Croucher Senior Research Fellowship in 2019.

To view Professor Rogach’s Croucher profile, please click here.