MaterialsViews Interviews Professor Limin Qi

Prof. Limin Qi received his Ph.D degree in Physical Chemistry from Peking University in 1998. He then went to the Max Planck Institute of Colloids and Interfaces, Germany to perform his postdoctoral work on biomimetic mineralization. In 2000, he joined the College of Chemistry at Peking University, where he is now a full professor. He is an editorial board member of the Chinese Journal of Chemistry and Chinese Science Bulletin, and an advisory board member of Advanced Functional Materials. His current research focuses on the controlled synthesis and hierarchical assembly of inorganic micro- and nanostructures by colloidal chemical methods as well as bio-inspired approaches.

When did you embark on your career in materials research?

I entered the field of materials research in 1990, when I started my graduate study. Up to now, it’s been almost 20 years.

What motivated you to pursue research in materials science?

Mainly my interest in the subject. When I started my graduate study leading to my master's degree, I began my research in this area, but at first I found it quite taxing. At that time I was involved in an 863 project, which set a lot of limits on the materials we studied. The research work was not easy; at times, it was painful!

Later, when I was a senior graduate, I found a very interesting direction, called biomimetic synthesis; a way of using biomineralization mechanisms. So I could use my knowledge of colloid chemistry to do something in material synthesis, which greatly stimulated my interest. I pursued this research during and after my PhD research work, and have continued it until today. Of course, during this period, I keep making new discoveries and getting interesting research results, which has created a virtuous circle.

What are your current interests?

To put it simply, it is the use of colloid chemical methods to perform material synthesis. You know that there are various methods in material synthesis based on the solid phase, the gas phase, and the liquid phase. Colloid chemical methods mainly involve solution-phase synthesis. The advantage of these method is that they are relatively simple and more convenient and efficient. We also frequently use a number of biomimetic synthetic strategies. Our research work is focused on the precise control of the size, morphology, and architecture of micro- and nanostructures by colloid chemical methods in combination with bioinspired routes, through which we hope to obtain some materials with special properties and desirable functions. The development of new, facile, general synthesis methods is the core of the work we are engaged in. Of course, we are also exploring applications of the synthetic materials we develop.

Any new outcomes to share with us?

One recent direction which particularly interests us is the use of colloidal crystals as templates for the controlled synthesis of nanostructured materials with ordered patterns, or complex materials with hierarchical architectures.

Last year we reported some interesting work on the bioinspired fabrication of three dimensionally ordered macroporous (3DOM) calcite single crystals by templating colloidal crystals in Angewandte Chemie. Although the chemical composition is just calcium carbonate, a simple inorganic mineral, the product is unique single crystals with highly ordered nanopatterns.

At the same time, we are also playing with two-dimensional (2D) colloidal crystal templates. We try to employ monolayer colloidal crystals floating on the solution surface as a 2D template to prepare large-area, freestanding, high-quality nanonets and two dimensionally ordered macroporous thin films through the interface reaction; that is, colloidal lithography at the solution surface. We are trying to demonstrate that this method represents a general method that can be extended to a variety of materials. Next, we are considering using the porous thin films as masks for the lithographic fabrication of novel patterned materials, or using their unique properties of photonic crystals for biosensing.

Moreover, we have made some significant progress in the preparation of hollow structures and one-dimensional (1D) nanostructures by using various reactive templates in recent years.

Could you predict the future applications of the materials synthesized using this method of colloidal synthesis?

I think if this synthetic method is more thoroughly studied to clearly elucidate the mechanisms, and if the properties of the products are more accurately controlled, its scope of application will be very wide. For example, colloidal quantum dots and metal nanoparticles can be used in biological detection and biomedical diagnosis. Moreover, those materials with special optical features, such as photonic crystals, can be used in biosensing, environmental detection, and optical devices.

We are also carrying out some research work on energy-related materials. For example, we investigated the synthesis of noble metal nanomaterials and their application in fuel cells, and we also explored the synthesis of tin oxide nanotubes and their application in lithium ion batteries. Recently, we have been trying to synthesize novel titanium oxide mesocrystals, which are expected to show excellent performance in solar cells. Nevertheless, their performance remains to be demonstrated by experimental results.

How many students are you currently supervising? Among them, how many master students and how many PhDs?

Currently, I have around 10 graduate students, and all of them are PhD candidates. It usually takes a student at Peking University five years to get a PhD degree. In accordance with the provisions of the College of Chemistry, a group leader or principal investigator can recruit at most two graduate students a year. Since last year, an associate professor who is qualified to supervise one graduate student per year entered my group, so we can have three new students in my group each year.

How do you assess your students? In terms of personality types and knowledge structure, what kind of students do you like?

First of all, I think having a keen interest the subject matter is the most important thing. He or she should be willing to do research.

Second, he or she must be honest. Honesty is the fundamental quality of human beings, and of course the basis of research activities.

Third, he or she should have the necessary knowledge of chemistry.

Fourth is team spirit. A person can’t be too selfish. He should be able to get along harmoniously with others.

Of course, other qualities such as a good work ethic are also very important. For example, some advisors will require students to work 12 hours a day. I have the minimum requirements of 8 hours of work for my students but many motivated students like to spend more time doing research work.

What are the requirements for PhDs to graduate from the college of chemistry? I know many school require their PhD students publish at least one article in SCI (or EI)-cited journals.

We now look at journal impact factor. The minimum requirement is the sum of the impact factors of all the papers published by the candidate as the first author should be at least 4.0. In fact, this is not considered very difficult, because most of the popular chemical journals have impact factors larger than 4.0. So, one publication in such a journal would enable the student to reach the minimum requirement. Some excellent students can and do publish more than four high-quality articles in five years.

Share with us your most important or most impressive story in the laboratory.

I can say that most exciting and memorable stories happen while performing electron microscopy observations or checking the electron microscopy photographs.
On one occasion, when I was working toward my PhD, I tried to synthesize barium carbonate by using the reverse micelle method, which was actually a relatively simple experiment. Based on past experience, particulate products would come out, and I did not expect to get any unusual results from that experiment. But when I observed the product by transmission electron microscopy, I found many long nanowires with very high aspect ratios. I was really surprised and so excited.

That experiment was later published in the Journal of Physical Chemistry in 1997. Looking back, we can say that journal is not the very top journal in chemistry, but it was not very easy for Chinese author to publish there at that time.

Thanks to this experiment, my doctoral dissertation was awarded the National Award for Outstanding Doctoral Dissertation, as the results related to this experiment were a major contribution. The article has so far been cited over 140 times.

Similar experiences have also occurred several times, but the first one is really unforgettable.

What are your thoughts on China’s pursuit of impact factor? You have also worked and studied in Germany. People in western countries do not seem very concerned about impact factors, but place more emphasis on peer recognition. What do you think of this?

My feeling is that in foreign countries, although people do not look at the specific impact factors figures, they do have their own criteria: which are high quality, which are average, and which are relatively poor. One thing is the same: people want their papers published in high-quality journals.

A foreign professor told me that he was not concerned about the impact factor at all, but he knows which journals are good in his research field. He once asked one of his students to verify the specific impact factors of several journals, and the result indeed coincided with his own judgments. Unlike China, people in western countries do not think that a journal with an IF of 5.3 will certainly be better than that with an IF of 5.2. Frankly speaking, it is journal editors who are more concerned about the impact factor. Every time they come to introduce their journals, they always emphasize how high their impact factors are.

In short, foreigners are not fully unconcerned, but Chinese authors go a bit overboard; that is, we pay too much attention to impact factors. This is not a good thing. Some papers in good journals are actually not particularly good, while some articles published in journals with lower IF values are really good. In addition, we should also pay attention to the follow-up assessment or response after an article is published, which is also a very important criterion of judging a paper. We should not just look at the journal impact factor.

How do you guide your students to submit articles to international journals?

I tell them that it depends on the quality of the work itself, including the significance, the originality, the completeness, etc. Then, I will discuss with them which types and levels of journals they should consider, and finally find a suitable journal for submission. I usually spend a lot of time revising the manuscript drafts of their first articles. We will discuss and re-revise the drafts many times before submission.

What is the major source of your research funding?

I would say the National Natural Science Foundation of China is the main source of my funding. You may also know that NSFC's reputation is pretty good. The evaluation is fair and processing is quite standardized in all aspects. I am lucky that I can continuously get support from NSFC programs. The Ministry of Education is also a channel; after I returned from Germany in 2000, funding from the Ministry of Education (MOE) was especially helpful. At that time the MOE awarded me 600,000 RMB for 5 years, which helped me commence my research work in China. Recently, I also participated in a project belonging to the major basic research program on nanotechnology funded by the Ministry of Science and Technology (MOST), which is gave me a valuable support.

Regarding materials science in China, what areas are relatively hot, which are relatively strong, which are relatively weak?

The hottest topic is definitely nanomaterials. But even though China has done a lot, the overall level in the area is not very high. We have done a lot in the field of preparation and synthesis, while high-quality work in the area of applications and performance characterization is still lacking; moreover, theoretical study is relatively weak. Low-level repetition is a relatively big problem.

Regarding overall research levels, what is the position of China in the world?

Purely in terms of the numbers of publications, China has been pretty good, probably second only to the United States. However, in terms of quality, we lag behind the U.S., Europe and Japan. Of course, as the country continues R & D investment and as a growing number of high-level scholars return from abroad, the gap will get smaller and smaller.

Do you have any major barriers to your research activity?

It is in fact hard to pick out one major barrier to my research activity. I would say that it may involve comprehensive factors, including funding, students, laboratory space, equipment, administrative chores, and so on.

What are your short-term and long-term plans?

In terms of short-term plans, I hope to develop some facile, efficient, inexpensive, and environmentally benign methods to synthesize a number of interesting or useful materials.

The long-term goal is to realize the controllable synthesis of materials with desirable functions and performances in accordance with the needs of people. For example, we want to accurately control the composition, crystallinity, size, shape, architecture, and surface properties of the materials so as to achieve specific functions and applications. Not just to produce individual particles, but also to assemble them together into complex functional systems with hierarchical structures and life-like characteristics such environmental responsiveness, self-replication, self-repair, etc. Of course, this is a dream—a really amazing dream.

Any international co-operation?

Actually, I have many communications and discussions with my colleagues abroad. However, there is no substantial collaboration yet. We are still trying to find suitable opportunities, and I hope to team with my colleagues to do some fruitful collaboration work in the near future.

Can you provide some of your thoughts on research trends in the field of materials sciences in the next 10 years?

I would forecast that first, in the area of synthesis and preparation, a variety of general, facile, and environmentally-friendly methods with clear mechanisms will be developed.
Second, application-oriented investigations will become more and more popular. People will pay more attention to the applications of various materials in biomedicine, energy, environment, aerospace technology, microelectronics, and other high-tech industries. Many intelligent, multi-functional, and integrated functional materials will be developed. /mxh

This article was originally published in chinese on materialsviewschina.com; click on the link below to go to the original article.