Brief interviews with scientists: Junbai Li (Chinese Academy of Sciences).


Prof. Junbai Li
Prof. Junbai Li

With molecules similar to those that nature uses to make up proteins, Professor Junbai Li produces nanomaterials for biomedical applications. More precisely, the Chinese scientist uses an amino acid known as diphenylalanine as the basic unit to form structures based on peptides (amino acid chains) by means of self-assembling processes. Although these processes occur spontaneously, Prof. Li has his own recipes in order to control the format of the resulting structures.

The fabrication and applications of these self-assembled nanomaterials will be the subject of Professor Li’s plenary lecture at the XVII B-MRS Meeting, entitled “Molecular Assembly of Peptide Based Materials towards Biomedical Application”.

Junbai Li is a professor at the Institute of Chemistry at the Chinese Academy of Sciences. He is the author of over 280 articles published in international journals and 8 book chapters, and owner of 20 authorized patents. He is also the editor of 5 books. His scientific production has 10.100 citations and his index h is 55. Li serves as editor-in-chief of the journal Colloids & Surfaces A (Elsevier) and editor of the self-assembling section in Current Opinion in Colloid & Interface Science (Elsevier). Junbai Li received his Ph.D. in Chemistry from the University of Jilin (China) in 1992 and held postdoctoral studies at the Max Planck Institute for Colloids and Interfaces (Germany) from 1994 to 1996.

See our mini interview with Professor Li.

B-MRS Newsletter: – What do you think are the most promising applications of peptide-based self-assembled materials and why?

Junbai Li: – Peptide-based nanostructures have attracted considerable attention owing to their biocompatibility, capability of molecular recognition, and well-defined structures. Firstly, the cationic dipeptides self-assemble into nanotubes at physiological pH values, and these cationic dipeptide nanotubes can also rearrange to form vesicles upon dilution. Furthermore, they can traverse cell membranes and be absorbed by the cells upon spontaneous conversion into vesicles. With such a surface highly positive charged property, peptide-based self-assembled materials can effectively be used for the genic transfer and delivery. Secondly, the traced quantum dots (QDs) can be well distributed in a peptide-based gel against QDs aggregation and oxidation to improve the stability for bioimaging and biosensor.

B-MRS Newsletter: – We want to know more about your work. Please choose two papers/ patents of your own (your favorites) and briefly describe them, as well as share the references.

Junbai Li: – Our group have worked on the self-assembly of aromatic dipeptides for a long time. We find that cryogenic treatment at 77 K enabled the tunable transition of a self-assembled diphenylalanine organogel into a hexagonal crystal and form a well-defined chiral crystal structure. These assemblies exhibit enhanced emission. (X.C. Liu, et al. Angew. Chem. Int. Ed. 2017, 56, 2660-2663).https://onlinelibrary.wiley.com/doi/pdf/10.1002/anie.201612024

Another work is under light illumination, a long-lived photoacid generator releases a proton and mediates the dissociation of dipeptide-based organogel, resulting in sol formation. Under darkness, the photoswitchable moiety entraps a proton to lead to the gel regeneration. It opens a new possibility for the light-controlled phase transition of peptide-based biomaterials. (X. B. Li, et. al. Angew. Chem. Int. Ed. 2018, 57, 1903 -1907). https://onlinelibrary.wiley.com/doi/pdf/10.1002/anie.201711547

a) Encapsulation of the CdSeS nanocrystals in dipeptide gel. PL photograph of four different encapulated QDs gels, TEM image of the encapsulated QD523 nanocrystals in the fibril network and magnified TEM image of the QD523 nanocrystals immobilized to the fibril. (X. H. Yan, et. al, Chem. Mater. 2008, 20, 1522-1526). b) TEM images of FF-based nanocontainer after incubation at pH 5.0, 7.2, and optical image of the in vivo clotting measurement. (J. B. Fei, et. al, Adv. Healthcare Mater. 2017, 6, 1601198). c) Optical waveguiding of dipeptide single crystals. Photoluminescence image of platelets excited at 330–380 nm. The red circle marks the excitation area, and the green arrow denotes the out-coupling of PL emission at the other end. (X. H. Yan, et. al, Angew. Chem. Int. Ed. 2011, 50, 11186-11191). d) Characterization of ultralong FF single crystals. Image, 3D-AFM image and SAED pattern of FF single crystals deposited on a silica surface. (B. B. Sun, et. al, ACS Nano 2017, 11, 10489-10494)
a) Encapsulation of the CdSeS nanocrystals in dipeptide gel. PL photograph of four different encapulated QDs gels, TEM image of the encapsulated QD523 nanocrystals in the fibril network and magnified TEM image of the QD523 nanocrystals immobilized to the fibril. (X. H. Yan, et. al, Chem. Mater. 2008, 20, 1522-1526). b) TEM images of FF-based nanocontainer after incubation at pH 5.0, 7.2, and optical image of the in vivo clotting measurement. (J. B. Fei, et. al, Adv. Healthcare Mater. 2017, 6, 1601198). c) Optical waveguiding of dipeptide single crystals. Photoluminescence image of platelets excited at 330–380 nm. The red circle marks the excitation area, and the green arrow denotes the out-coupling of PL emission at the other end. (X. H. Yan, et. al, Angew. Chem. Int. Ed. 2011, 50, 11186-11191). d) Characterization of ultralong FF single crystals. Image, 3D-AFM image and SAED pattern of FF single crystals deposited on a silica surface. (B. B. Sun, et. al, ACS Nano 2017, 11, 10489-10494)

For more information on this speaker and the plenary talk he will deliver at the XVII B-MRS Meeting, click on the speaker’s photo and the title of the speech here https://www.sbpmat.org.br/17encontro/home/

Interviews with plenary lecturers of the XIII SBPMat Meeting: Jean-Marie Dubois (Institut Jean-Lamour, França).


The author, Jean-Marie Dubois (left) and Nobel Prize winner Dan Shechtman (right) celebrating Shechtman’s 70th birthday two years before he was awarded his Nobel Prize. Observe that both carry the same tie, which is decorated by a Penrose tiling, a prototypical example of aperiodicity in the art of drawing and painting.

The French scientist Jean-Marie Dubois, PhD in Physics from National Polytechnic Institute of Lorraine (France) is a Distinguished Director of Research at the French National Center for Scientific Research, CNRS (France), where he chairs a committee dedicated to materials chemistry, nanomaterials and processing.  He is the former director of Institut Jean Lamour in Nancy (France), a major research institute in field of materials.

His curriculum shows an international scientific trajectory. Dubois holds Honorary Doctorates (Dr Hon. Causa) from Iowa State University (USA) and Federal University of Paraïba (Brazil), is a former “overseas fellow” of Churchill College at University of Cambridge (U.K.) and a permanent visiting professor at Dalian University of Technology (China). He was recently elected as Honorary Member of Jožef Stefan Institute in Ljubljana (Slovenia). He is a member of Lorraine Academy of Sciences (France).

He is the author of more than 250 scientific articles in refereed journals, 14 international patents, and 7 books. His papers were cited more than 5400 times (H index = 39).

Read our interview with the lecturer.

SBPMat newsletter: – Under your viewpoint, which are your main contributions to the field of Materials Science and Engineering? And your scientific/technological contributions with more social impact (patents, products)?

A part of 20x20x30 cm, used by a French car producer, made of a polymer reinforced by a quasicrystalline powder. It that can be produced by additive machining with no restriction regarding complexity of its shape.

Jean-Marie Dubois: – My first contribution that was aimed at a social impact was the discovery of Al-based metallic glasses, which could be good candidates for light-weight alloys useful for the aeronautic industry. I patented them in 1982, listing a number of favorable examples, and as is the rule for a patent, also counter examples. One such composition was in fact a stable quasicrystal, which was unraveled in Japan few years later. Based on this discovery, I was the first to patent few application niches of quasicrystals that are Al-based intermetallics showing no periodic order as do conventional crystals. The discovery of quasicrystals dates back to 1982, but was published in literature only in 1984, whereas my first patent on these materials was filed in 1988. From that on, I dedicated quite some efforts to discover, patent, and produce new research, about different areas of the physics of quasicrystals including thermal conductivity, adhesion and friction, corrosion resistance, etc. My leadership in this area of materials science is recognized by the international community through the “International Jean-Marie Dubois Award” that is offered every three year “to recognize important, sustained research on any aspect of quasicrystals within the 10-year period preceding the award”. Altogether, I own 14 international patents, with more than 35 extensions. I was responsaible for few tens of collaboration contracts with the industry, including a good dozen of contracts financed by the European Commissions with on average half a dozen of industrial partners and the same number of academic partners. The last one was a so-called Network of Excellence that started the field of Complex Metallic Alloys in Europe, with 20 partner institutions from 12 European countries and some 400 scientists on board.

SBPMat newsletter: –  Please choose some of your main publications (about 3 or 4) to share them with our public.

Jean-Marie Dubois:

1) Useful Quasicrystals; J.M. DUBOIS, World Scientific, Singapour (2005), 470 pages.

2) Complex Metallic Alloys, Fundamentals and Applications; Eds. J.M. DUBOIS and E. BELIN-FERRÉ, Wiley (Weinheim, 2010), 409 p.

3) Topological instabilities in metallic lattices and glass formation; J.M. DUBOIS, J. Less Common Metals 145 (1988), 309-326.

4) The applied physics of quasicrystals; J.M. DUBOIS, Scripta Physica, T49 (1993) 17-23.

5) Properties- and applications of complex metallic alloys, J.M. DUBOIS, Chem. Soc. Rev., 41 (2012) 6760-6777.

SBPMat newsletter: – Please give us a short teaser about your plenary talk at SBPMat meeting. What do you intend to broach?

Jean-Marie Dubois: – My talk will be a laudation to the discoverer of quasicrystals who was awarded a Nobel Prize in Chemistry in 2011 for his discovery that forced the scientific community to revise its understanding of ordered condensed matter. Members of the MRS Brazil are used to know what is a crystal, a periodically ordered solid. I wish to introduce them to another type of order in solid, that is not periodic, and leads to unprecedented properties. Alloys that exhibit such a type of order are specific and I call them push-pull alloys. Then, I wish to show that this type of order is not restricted to metallic alloys, but may also be encountered in soft matter like polymers, oxides, artificial nanostructures, and even artistic drawings from ancient Islamic tilings. The talk will therefore be a review for the non-expert in quasicrystals and complex intermetallics

Interviews with plenary lecturers of the XII SBPMat Meeting: Mercouri G. Kanatzidis (Northwestern University – USA).


About two-thirds of all used energy is lost as waste heat. Bulk thermoelectrics (materials that can directly convert temperature differences to electric voltage and vice-versa) can improve this current situation by transforming some of the waste heat into useful electricity, but, in most cases their conversion efficiency is not sufficient to allow for commercial use. This efficiency is related to the ability of electrons to traverse the materials as they are excited by heat and to phonon scattering, and it is measured by the so-called ZT values (the higher a material’s ZT, the higher its conversion efficiency).

Efforts have been made to enhance the efficiency of thermoelectric materials, mainly by nanostructuring them. In his plenary talk at the XII SBPMat Meeting, professor Mercouri Kanatzidis (Northwestern University, USA) will present his panoscopic approach to highly efficient thermoelectrics. This approach considers not only the nanostructure of the material but also its mesoscale architecture. Using this strategy, professor Kanatzidis and his collaborators developed the top-performing thermoelectric system at any temperature, a lead telluride (PbTe) – based material. The achievement was published in the journal Nature in September 2012 (doi:10.1038/nature11439). The speaker will also address in his talk the substitution of tellurium by sulfur or selenium in thermoelectric materials for cost reduction.

Professor Kanatzidis obtained his BSc from Aristotle University (Greece) and his PhD in chemistry from the University of Iowa. He was a University Distinguished Professor of Chemistry at the Michigan State University before moving to the Northwestern University, where he heads a research group focused in solid-state inorganic chemistry. Mercouri is also the editor-in-chief of the Journal of Solid State Chemistry and Senior Scientist at the Materials Science Division of the Argonne National Laboratory.

See below our interview with the lecturer.

SBPMat: – Could you exemplify some possible concrete applications of high-performance thermoelectric materials in daily life? In your opinion, how far is the real use of thermoelectric materials from the state-of-the-art?

Mercouri Kanatzidis (M.K.):  – Thermoelectric materials can be applied to internal combustion engines to help harvest exhaust heat and generate electricity that can be applied to the vehicle’s electrically driven devices. This will raise the overall efficiency of the vehicle. There is a staggering amount of energy in exhaust heat of a fossil fuel powered engine. Major auto companies in the US, Germany and Japan are actively developing this technology. Depending on the price of oil, government regulations and cost of the technology the implementation of thermoelectric materials in autos, trucks, etc may take anywhere from a couple of years to decades.

SBPMat: – Which are the thermoelectrics´ next challenges for materials science and engineering?

M.K.: – The current state of performance of thermoelectric materials is adequate for commercial applications. The next challenges lie in the fabrication of actually thermoelectric modules and devices that will pass the necessary testing before final application. Challenges such as long term stability, low cost assembly and fatigue testing need to be addressed.

SBPMat: – Can you share with us, very briefly, the story of the genesis of your panoscopic approach to highly efficient thermoelectric materials?

M.K.:  – About ten years ago we had a novel material composition which had two unlikely characteristics. It had a very high electrical conductivity and thermoelectric power combined with surprisingly low thermal conductivity. The thermal conductivity was lower than theory could explain. This material was first of its kind (referred to as LAST for lead, antimony, silver, tellurium) at that time to display a breakthrough ZT of 1.6, nearly double of the then state of the art. Because of this we delved deeply onto its “guts” using transmission electron microscopy in collaboration with Professors Polychroniadis and Frangis of the University of Thessaloniki in Greece. A few months after they received the samples they reported to us on their findings with a somewhat disappointing note saying that the materials were very complex and inhomogeneous on the nanoscale, therefore impure. In discussions I detected reluctance to deal with the material again. They did. In my lab however we immediately recognized that this very inhomogeneity and the nanoscale precipitates it contained was the root cause of the surprisingly very low thermal conductivity and the very high ZT. This was consistent with theoretical predictions emerging at the time that nanoscale precipitation in a matrix can result in great reduction in thermal conductivity. So we got very excited. We had discovered nanostructuring in thermoelectrics. After our paper appeared in Science in 2004, the thinking of the thermoelectrics community quickly shifted from pursuing single phase materials to focusing on more complex two-phase nanostructured materials. Now the great majority of activity in the community is in nanostructured materials.

The new paradigm led to additional breakthroughs such as how to design and synthesize nanostructured materials, and to higher ZT as well. The panoscopic approach was realized when we were challenged to create two-phase materials that did not degrade electronic transport through them. While matrix of a thermoelectric material with a small amount of a second phase in it can achieve unprecedented levels of low thermal conductivity, it nevertheless is an “impure system” and electrons transported through such a medium know this. Thus, in most cases the second phase degrades the electrical properties and higher ZTs are not realized.

State of the art thermoelectric: (a) A mesoscaled granular composite of broad range of grain sizes to scatter long mean free path phonons. (b) Wwithin a single grain a ubiquitous nanostructuring is in place of a second phase that scatters short and intermediate mean free path phonons. The (a)/(b) combination results in a very low levels of thermal conductivity.

My group members Kanishka Biswas and Lidong Zhao and our collaborators Ctirad Uher and Vinayak Dravid noticed that when SrTe was added to p-type PbTe in as much as 2-4% concentration the hole carriers were behaving as if no SrTe was there. The explanation to this puzzle came from the recognition which was backed by theoretical calculations that the conduction bands in PbTe and SrTe were similar in energy and the holes as a result could traverse the SrTe nanoparticles with no scattering. This led to the concept to band alignment between matrix and second phase. The PbTe-SrTe material with its nanostructuring and band alignment was another material with ZT~1.7. As we realized that different ZT improving mechanisms could be integrated in a single system without the effect of one interfering with those of the other, we extended our approach to trying to integrate all possible mechanisms. We managed to properly introduce electronic band engineering for thermoelectric power enhancement and mesoscale engineering for further reduction on the thermal conductivity to reach the point we now are a record breaking ZT of 2.2. This is very exciting and bodes well for further breakthroughs in the near future.

SBPMat: – Feel free to leave any other comments about your plenary lecture for our readers.

M.K.: – My lecture will be aimed at reaching the broad but scientifically informed audience at the meeting to outline the current state and thinking in the field of thermoelectrics.

See the abstract of Mercouri Kanatzidis plenary lecture “Electrical power from heat: All-scale hierarchical thermoelectrics with and without earth-abundant materials”.

See Professor Kanatzidis biographical sketch.