Daniel Mandler, Hebrew University of Jerusalem

Personal summary/biography

Daniel Mandler was born in Buenos Aires, Argentina on April 12, 1958. He immigrated to Israel when he was five years old. He studied at the Hebrew University in Jerusalem where he obtained his BSc degree (1983) and his PhD (1988) under the supervision of I. Willner. The thesis involved the development of artificial systems for photosynthesis. He spent two years as a post-doctoral fellow in the laboratory of A. J. Bard in Austin Texas where he dealt with the scanning electrochemical microscope and returned to the Hebrew University where he accepted a Lecturer position (1990) in the Department of Inorganic and Analytical Chemistry. In 1994 he became a senior lecturer and in 1998 an associate professor. In 2002–2003 he spent one sabbatical year at the University of Warwick together with P. R. Unwin. His main scientific interests are the scanning electrochemical microscope, application of self-assembly in electroanalytical chemistry, sol–gel technology, forensic chemistry and environmental chemistry. D. Mandler has published close to one hundred papers in peer-reviewed journals and has been awarded a number of prizes. His research group includes more than ten PhD and MSc students. He is currently the head of the chemistry studies at the Hebrew University of Jerusalem.

Interview questions

1. What early influences encouraged you to take up science?

I was attracted to science, in general, and in particular to chemistry, since I was a young child. My mother who was a chemistry teacher probably influenced me although I have a twin brother and he pursued his career in the high-tech industry and not in chemistry. My mother became later our (me and my brother studied in the same class) chemistry teacher in high school. My brother and I had a chemistry lab at home and carried out numerous experiments. This more or less ended when we had a small explosion while filling a balloon with hydrogen that we produced by adding zinc pieces into hydrochloric acid.

2. Do you remember your first experiment and what it involved?

Not quite. My first chemistry experiments were carried out before I was ten years old. These included building small rockets, producing hydrogen and other gases, cleaning old coins and so on. Maybe one of the first experiments was making colourful flames. I remember finding a procedure where I could get most of the materials from household shops. The more exotic compounds, such as a strontium salt I bought from a chemical supplier (where I went together with my mother) and I still remember the guy there staring at me and asking my mother if she knew what I was going to do, and finally telling me that if I had come alone he would have called the police.

3. When did you first become interested in electrochemistry and for what reason?

I first performed experiments in electrochemistry while doing my PhD and after taking a class given by the late Prof. Joseph Jordan in electrochemistry who visited the Hebrew University. The subject of my thesis was “Development of Artificial Models for Photosynthesis” and it was clear that instead of generating the active materials photochemically it was possible to do so electrochemically and study in a simpler way the mechanism of electron transfer. However, my romance with electrochemistry basically started during my post-doctoral studies which were carried out in Prof. Allen Bard's laboratory in Texas.

4. Tell us about some of your current research projects

My current research deals with at least five different topics:

(a) Studying and modifying surfaces with high resolution using the scanning electrochemical microscope (SECM)—during the last ten years we have been involved in the application of the SECM, in particular, for driving chemical and electrochemical reactions locally on surfaces. Among the different reactions and approaches that have been explored by us are metal etching and deposition, metal hydroxide deposition, electropolymerization and attachment of biological and organic materials. Recently, we have developed completely new approaches for metal deposition based on microelectrode dissolution and potential assisted ion transfer across a liquid–liquid interface. Moreover, we have used the SECM for studying charge transfer processes, such as lateral charge transfer in tungsten bronze and ion transfer across two immiscible liquids. Studying the interactions of metal ions and monolayers assembled at the liquid–air and solid–liquid interface is presently being conducted. Many of our approaches have been used by other laboratories and our work in this field is very well recognized in the SECM community.

(b) Development of highly selective and sensitive sensors for heavy metals based on self-assembled monolayers and thin polymeric films—we have designed and developed selective electrochemical probes for detecting very low levels of heavy metals, e.g., mercury and cadmium. The electrodes are based on structuring their solid–liquid interface by monolayers that selectively interact with the analyte. Our aim has been to understand the rules in such interfacial architecture on a molecular base. For example, a highly selective electrode for chromate was assembled in which the source of the selectivity originates from the interaction between a pyridinium moiety and Cr(VI) ions. The voltammetric electrodes can measure concentrations as low as 10⁻¹² M. Recently, we have focused on the formation of self-assembled monolayers on glassy carbon and silicon surfaces. Our laboratory is one of the first to apply self-assembled monolayers for electroanalytical applications.

(c) Electrochemical deposition of sol–gel film—the formation of controllable sol–gel films has been accomplished by electrochemical deposition. A new approach, in which the condensation of sol–gel films is accelerated upon changing the pH on the surface, has been developed by us. This is achieved by stepping the potential either to negative or positive potentials. Silane as well as zirconia and titania based layers have successfully been deposited. A wide range of different experiments enabled us to propose a detailed mechanism. Moreover, this technology has been applied for corrosion prevention, deposition of thin films onto complex geometries and the development of sensors based on molecular imprinting.

(d) Self-assembled monolayers—in addition to designing electrochemical sensors based on self-assembled monolayers, we have focused on developing new tools for studying their interaction with metal ions (determining heterogeneous complexation constants of monolayers), developing new approaches for attaching monolayers directly onto silicon wafers and studying the formation and properties of self-assembled monolayers on mercury. Furthermore, we have studied the effect of chiral monolayers on their organization on surfaces and rate of electron transfer. In this respect, we have made significant contributions in this field, such as the first example of creating a 2D conducting polymer on top of a self-assembled monolayer and the first study on the differences between enantiomeric monolayers on mercury.

(e) Forensic studies—our research and experience in electrochemistry and surface science has also been applied to address forensic issues. Two research projects have been conducted in collaboration with the department of forensic science of the Israeli Police. The first project aimed at understanding the fate of fingerprints printed on cartridge cases as a result of the firing event. Besides developing a new method for visualizing latent fingerprints on cartridges, we suggested an explanation for the effect of firing on the fingerprints based on a laboratory surface study. Recently, we have focused on understanding the mechanism of iron transfer from arms to a human hand. This issue is important in identifying an arm holder and optimizing the conditions for a colour test that is currently used for this purpose. Finally and as a result of a visit to the Forensic Science Service of the Scotland Yard, we have initiated a third project that addresses the issue of developing fingerprints on wet papers. The current method that is based on electroless deposition is not well understood and more importantly often fails. Our aim is to reveal the scientific basis of the method and to improve it.

5. What are your ultimate goals in research?

I am above all motivated by curiosity; however, what could be an ultimate goal is to combine physical and analytical chemistry. Namely, I believe that if on one hand we achieve a much better control in designing the interface on a molecular level and on the other hand, we reveal the rules that control molecular interaction and electron transfer at the solid–liquid interface, we will gain a better understanding on how to develop interfaces with superior electroanalytical characteristics. This might be the point where nanotechnology and electroanalytical chemistry will be combined into a powerful tool.

6. If you had to choose one of your papers as being one that gives you most pride, which would that be and why?

Difficult to choose but I would choose either a work I carried out myself while on Sabbatical in the UK,¹ or the work by one of my students.² The reason is similar, i.e., the ideas behind these papers were original and did not require any sophisticated tools. In general, I prefer that the ideas rather than the available tools will control our progress.

7. You have organised two workshops on SECM. In your opinion what are the most exciting developments in this field?

I strongly believe that the SECM has a few unique features, which makes it an ideal tool for studying and modifying interfaces. Clearly what we are going to see in this field is primarily the reduction of the size of the electrodes used. Nanoelectrodes will become the common probe in future SECM studies. The strength of the SECM is in its ability to study charge transfer processes at different interfaces, such as solid/liquid, liquid/liquid and liquid/air. Moreover, as compared with other scanning probe microscope techniques, e.g., STM and AFM, the SECM is superior for local modification of surfaces which could, in principle, make it the leading SPM technique for nanopatterning. Finally, I believe that we will witness more studies where the SECM is combined with other SPM techniques.

This is also a good opportunity to disclose that the next SECM meeting will take place in Italy in 2006 and is organized by D. Salvatore from Venice.

8. Please comment on the health and vibrancy of analytical chemistry in Israel

Analytical chemistry is probably the strongest chemistry discipline in Israel at least by the number of chemists. The annual meeting of the Israel Analytical Chemistry Society attracts several hundred chemists from industry, research institutes and academia. Nevertheless, the number of analytical chemists in academia in Israel is small. It is evident that we in the academy need to change and improve the attitude of the best students towards analytical chemistry.

9. What do you think will be the most profound challenges that analytical scientists face in the next few years?

The fast development of instrumentation poses challenges to the analytical community. Due to governmental regulations analytical scientists will have to provide more sensitive and selective tools. However, these tools will have to be also cheaper, more accurate and be applied under different conditions.

Electroanalytical chemistry has the potential to successfully confront this challenge. As mentioned above, we will have to apply physical chemistry approaches and techniques to better analyse and understand the intimate structure of the solid/electrolyte structure. For example, combinatorial and computational approaches for assembling sensors will have to be developed. The “trial and error” approach which used to be applied has to be replaced with systematic studies that will be based on the ability to architecture the electrode/electrolyte interface on a molecular level. This will allow, for example, designing of electroanalytical tools with speciation capabilities.

References

1. J. Zhang, A. L. Barker, D. Mandler and R. Unwin Patrick, Effect of Surface Pressure on the Insulator to Metal Transition of a Langmuir Polyaniline Monolayer, J. Am. Chem. Soc., 2003, 125, 9312–9313.
2. Y. Yatziv, I. Turyan and D. Mandler, A New Approach to Micropatterning: Application of Potential-Assisted Ion Transfer at the Liquid–Liquid Interface for the Local Metal Deposition, J. Am. Chem. Soc., 2002, 124, 5618–5619.

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