As a child, “Medicine doctor” was Marie-Paule’s immediate answer to whoever asked her about what she wanted to be when she grew up. Life is full of surprises, and eventually, Marie-Paule took a different path. Although she did not have the faintest idea about her professional future, she decided to study physical chemistry. And how glad we are Marie-Paule has decided so. Today, she is a renowned scientist, internationally recognized, with outstanding achievements in colloid science and nanoscience, namely discoveries of self-assembly of inorganic nanocrystals into 3D crystalline structures. Also, Marie-Paule is part of the UT Austin Portugal’s Program External Review Committee. However, her collaboration with the Program goes back a few years, as Marie-Paule evaluated several exploratory research project proposals assigned to the Nanotechnologies area. Are you ready for an inspirational story?
When you are a child if someone asked you what you wanted to be when you grew up, did you use to say you wanted to become a scientist? Was that something reachable to a little girl born in Madagascar?
I had a happy childhood. My godfather was a medicine professor. I was impressed by this man who was very attentive to all of us. When someone asked me what I wanted to do, I answered: medicine doctor. When I had to go in this direction, I was afraid of killing people! Then I knew what I didn’t want to do but I didn’t know what I could do. I decided to start my studies in physical chemistry without any idea of my professional future.
Your research has been at the frontiers of physics, chemistry, biophysics, and biomedicine. What exactly do you do and how does your work intersect with Nanotechnologies? You have been working for a long time in colloid science and nanoscience and are acknowledged on many occasions for your outstanding achievements.
That’s a long story. I will try to make this story short. I decided to study physical chemistry. I had a photophysics and photochemistry professor whose courses were animated by scientific narratives. He was describing the latest discoveries in this research area. I decided to join his laboratory to learn more and more. I did my master’s degree in his lab on photoisomerisation of pyrazine to pyrimidine in gas phase. This topic was adequate for Woodward and Hoffmann rules but poorly adapted for biological processes. So, I started my PhD thesis on studying the photophysical and photochemical properties of tyrosine and tryptophan in aqueous solutions. This was extended to oxidation products of tryptophane which are strong photosensitizers and highly present in dermatology photosensitizer diseases. All these processes were studied in aqueous phase. Again, I thought that biological models were needed. I did my post-doctorate in a molecular biophysical and biochemical center (CBM, Orléans-France). I study the photophysical properties of tryptophan associated with biological vesicles. With Prof. C. Helene, we demonstrated that biological impurities markedly perturb these amino-acid photoemission properties. I decided to orientate my research to colloidal systems with highly purified surfactants. I got a position as visiting scientist at Ecole Polytechnique Fédérale de Lausanne (EPFL) to work with Pr. M. Graetzel. That gave me the opportunity to use colloidal assemblies to control charge separation induced by photoelectron transfer process. In Lausanne, I met and worked with a very large number of top scientists. Prof J. Fendler, invited Professor in Lausanne, was chairing a Gordon Conference and he invited me to be part of the meeting. There, I met Prof. P.L. Luisi from ETH (Zurich). Pier was solubilizing proteins in reverse micelles. I asked him to spend some time in his lab. His answer was strength forward: “Send me a nice project, you will be welcome in my department”. He appreciated the project and I spent some months in Zurich. Later on, when I came back to Paris, I used cytochrome c as a photosystem model for energy conversion. Simultaneous with Profs P. Stenius, K.Thomas, J. Fendler, I used reverse micelles to produce nanoparticles. The major difference between the syntheses described by others and those developed in our group was to use functionalized surfactants i.e the counter ions of the surfactants are one of the reactors. This permits: (i) producing nanocrystals instead of amorphous nanomaterials, (ii) preventing the oxidation of metallic nanomaterials and (iii) manufacturing a solid solution of binary nanocrystals.
We needed to decrease the size distribution of the nanocrystals to identify specific nanocrystal size properties and remove impurities (see below). This is a key factor to produce 2D and 3D superlattices nanocrystals. We discovered unexpected intrinsic and collective properties bearing the imprint of the building blocks.
This discovery was a great opportunity for me. It’s opened up a new research field. All hypotheses were allowed. That has been the most fantastic part of my career. Over these past 25 years, we have discovered collective and intrinsic properties due to the order of nanocrystals. These findings are just the tip of the iceberg. A large number of other properties could be discovered over the next few years. I dream of helping young researchers to go further in this direction.
What does it take to succeed in this world? Is it all about passion, self-discipline, natural curiosity…? Is it right to assume that you need to prove yourself two, three times more because you are a woman?
If you dream of success, you are wasting your time. None of us can schedule returns from your searches. These successes are ephemeral and one discovery chases the other. So you have to be constantly creative without ever being sure that it will succeed. You cannot control success. As in life, you have to be brave and not be afraid to make mistakes. We are all free to make seemingly impossible assumptions. In this case, there is no fear of being wrong. One can be a very good researcher without taking great risks, He/she will do a nice job but he/she will not discover new concepts. It’s a real joy to imagine a seemingly impossible phenomenon and to be able to prove that it was not a far-fetched hypothesis. When this happens, you cannot imagine the deep joy that overwhelms you. My lab has been constantly composed of more or less 50% men and 50% women. Of course, the woman must prove more and more that she can be on the same level as the men. I have a funny story: I was a young researcher and I had a hard time holding the attention of famous colleagues. I wondered why this was happening. I had this weird idea that maybe it was because I was a woman. Why does this young woman spend her time going to meetings? Is she a real scientist? So I decided to take my daughter there. From then on, my colleagues were much more attentive to my work! Then, I received many invitations as a speaker in meetings. The same people were proud to promote a young female scientist! I like to say that my daughter helped me promote my research.
From 2005 to 2007, you were the Vice-President of the Women in Science Committee reporting to the French Minister of Research. Can you tell us more about this experience? What were the most important discoveries and lessons you would tell to girls and women in science?
It was a very enriching experience. I was for equality between men and women. So, I was very happy to be vice-chair of this committee. The minister remained chair. It has been created by President Chirac because a group of militant women had complained that no women were appointed to the director board of our research centre. These women were asking for specific benefits for women. For me, it was the worst proposal for gender equality. Women must be recognized with equal competence. If women benefit from special conditions, they will never be equal. We have had difficult but also positive discussions. In the end, we found nice compromises and we have been able to make great proposals that resulted in real changes.
How do your discoveries of self-assembly of inorganic nanocrystals into 3D crystalline structures known as colloidal crystals impact society and science development, especially in areas such as cancer?
In the middle of the 90s, a few years after making nanomaterials, we were producing Ag2S nanocrystals and studying their primary photophysical properties with Prof. F. Willig from the Fritz Haber Institute (Berlin). Frank was a top physicist but his consideration for chemists was very poor. He attributed our unexpected photophysical transients to impurities. To get rid of such criticisms, L. Motte decided to extract the nanocrystals from reverse micelles. By using such a procedure, she reduced the nanocrystal size distribution and consequently produced 2D and 3D superlattices of Ag2S nanocrystals. In parallel, Prof. M. Bawendi group produced 3D superlattices of CdSe nanocrystals. This discovery was the best gift of my career.
In these recent years, energy release start to be a major problem for our society. All the 3D superlattices studied were hydrophobic and dried. However, water is a major element in the problems associated with energy conversion. In order to overcome the difficulties of obtaining assemblies in water and not to lose the skills acquired, we have tried to manipulate our assemblies and make them hydrophilic. This again was a challenge. How to transform hydrophobic assemblies into hydrophilic ones? Another challenge was to produce stable assemblies over time. We used, in this new project, the concepts developed several years ago for the manufacture of nanocrystals. We were able to show that we were producing a “nanoheater”. One possible application is in biomedicine. Again these systems are potentially so rich that they should open the way to a large number of applications. Yes 3D superlattices are magic systems.
Recently, you have been invited to serve on the UT Austin Portugal’s Program External Review Committee. However, your collaboration with the Program goes back a few years – you evaluated several exploratory research project proposals assigned to the Nano area in Phase 2 and also in Phase 3. What is your perception about the Program and the research it has been supporting?
I really like this collaboration. I am very often invited for such evaluations all over the world. The UT Austin program is the one I like the most for the following reasons: The staff of this program is very efficient and very open. They are always ready to facilitate the assessment. Applications are, on average, at a very high level. I’m happy not to be alone for the final decision. Each time, I am sad not to have more possibilities to name more groups. Most of the time, the discussions are very friendly. We are all ready to select the best program. There are no attempts by the decision-makers to change the rankings and that’s rare. We’re having a good time.
You are a scientist with an unquestionable international profile – you have collaborated with several institutions from many countries. What is the best thing you get from collaborating across borders when researching?
We discovered collective optical properties of metallic nanocrystals self-assembled into 2D superlattices. The signature of such collective property was the appearance of a new high-energy peak revealing the electric field distribution of different coupled plasmon modes between the nanocrystals. Many physicists disagreed with my explanations. It was difficult to deal with so many sceptical people. Faced with such scepticism, I had two options: i) Continue my explanation at the risk of losing all credit, (remember, I am a chemical physicist and all sceptical scientists were physicists). ii) Provide the samples and try to convince these sceptical scientists. So, I proposed to these scientists to use our samples and to do the experiments together in their laboratory using the technique they would choose. Two of them accepted the challenge. Thus, to convince Prof. H. Freund of the Fritz Haber Institute (Berlin) we measured the photon emission process induced by STM from our samples. As obtained by reflectivity, two emission spectra were observed and attributed to plasmon modes oscillating parallel and perpendicular to the substrate. Similarly, to dispel the scepticism of Pr. S. Kooij from the University of Twente (Netherlands), we have developed spectroscopic ellipsometry experiments. As with the Berlin group, we confirmed these collective properties. It was very stimulating and fruitful. We all wanted to know the truth. The atmosphere was fantastic: friendly and focused. I had the opportunity to work with top scientists and use new techniques. I was afraid that I had made a mistake and was ready to publish my potential error but we all concluded: I was right! These two adventures were real happiness.