MILLER INSTITUTE NEWSLETTER Miller Fellow Focus: Prashant Jain
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Miller institute newsletter Spring 2010 Miller Fellow Focus: Prashant Jain Lighting Up the Nanoscale World method of taking snapshots of our re- action flask, such as the color of the ‘Chemistry’! The word typically reacting solution, results in a statis- conjures up an image of a bespecta- tically averaged picture of the ~1023 cled lab-coat wearing scientist mix- molecules at any given time. The re- ing up colorful reagents in a test tube active molecules are not all in phase, in anticipation of a new molecule’s so the snapshots do not give us a birth – a molecule that may serve as real-time trajectory of the molecule the next drug for cancer, or a won- in the course of its transformation der-material for the next-generation (dynamics); all we can know is the of solar cells. Chemistry, however, proportion of molecules in the flask has long moved past this lay percep- that have transformed into the prod- tion. Chemists have developed not uct. Furthermore, we cannot estimate only a comprehensive understanding how different one molecule’s activity of the structural makeup and proper- is from every other one (heterogene- ties of molecules, but also the ability ity); we can only measure the aver- to rationally control the synthesis of age reactivity of the molecules in our known molecules and their transfor- flask. Thus, our reaction flask (Fig. mation into newer ones. But a long- 1) gives us no information about standing dream that has remained the dynamics and heterogeneity of elusive until recently is that of being molecular reactivity – two aspects Being trained as a laser spectrosco- able to watch molecules in “live ac- that make chemistry rich and inter- pist by the best in the field (former tion” as they form or transform. esting. This is especially true in the Visiting Miller Professor M. A. El- case of complex chemical systems Sayed at Georgia Tech and later Traditionally, we perform and study like the ones we encounter in the real Adam Cohen at Harvard) is an as- chemical transformations in the reac- world, covering the gamut from the set for Prashant. Spectroscopists tion flask, where an Avogadro’s num- biochemistry of life to the catalytic have been skilled at interrogating ber (~1023) of molecules is allowed converter in our car. Prashant, a sec- molecules using laser light since the to react. Individual molecules in this ond-year Miller Fellow, believes that 1960s. However, around 1990, the flask stochastically switch, gener- watching the transformation of one community led by W. E. Moerner at ally after being activated, from the single reactant molecule can reveal Stanford and Michel Oritt learned reactant to product state, and some- hidden secrets about the complexity how to image a single molecule by times even backwards, if it’s a revers- and stochasticity of the underlying illuminating it with a laser beam and ible transformation! But our current chemistry. then using clever optics to detect the continued on page 2 Call for Nominations NEW ONLINE SYSTEM COMING SOON INSIDE THIS EDITION Miller Fellow nominations are due on Miller Fellow Focus 1 Thursday, September 9, 2010 Call for Nominations 3 Miller Professor applications are due on 2010-13 Miller Fellows 4-5 Thursday, September 16, 2010 Chancellor’s Outstanding 6 Staff Award Visiting Miller Professor Departmental nominations are due on Awards & Honors 7 Monday, September 20, 2010 Publications 7 Please see the enclosed insert for details on making nominations for Birth Announcements 7 the Miller Fellowship program. For complete information on all our programs, visit: http://millerinstitute.berkeley.edu Spring Dinner Photos 8 The Adolph C. and Mary Sprague Miller Institute for Basic Research in Science University of California, Berkeley continued from page 1 Figure 1: (left) Traditional “flask approach” for studying a chemical transformation (A → B) where we can only estimate the propor- tion of species A converted to species B at any given time. (right) We can measure an average rate of transformation for the entire flask of molecules; however, individual molecules can have significantly different rates from one another. tiny amount of light emitted by the highly size-dependent. In addition, dividual nanocrystals in his optical molecule. Inspired by the develop- a significant part of the nanocrystal microscope by tracking the cadmium ment of single-molecule spectrosco- constitutes a surface or interface to released from the nanocrystal (Fig. py, Prashant is carrying out chemical the external environment. This large 2). He used an indicator dye which reactions inside a microfluidic “reac- surface/volume ratio makes nano- emits light when it “sees” the released tion flask” mounted inside an optical crystals remarkably more reactive cadmium ions. To his amazement, he microscope, designed to sensitively and responsive to the outside world, was able to actually see a plume of and selectively light up the reacting compared to their macroscopic coun- cadmium ions being released from molecules anchored to the base of the terparts. It’s no wonder that catalytic individual nanocrystals. He found reaction chamber. Prashant selects converters nowadays use nanopar- that nanocrystals seem to “wait”, pre- chemical reactions where the trans- ticles of platinum for enhanced ca- sumably for a nucleation or activation formation from reactant to product talysis of carbon monoxide detoxi- event, for a random amount of time, results in a dramatic change in the fication. Furthermore, the nature of before they start exchanging. Once light emission, either its intensity or the nanocrystal surface (its geometry, nucleated, the nanocrystal seems to spectrum. By following changes in crystalline arrangement, and labile rapidly exchange in a single shot. A the emission, he is able to observe nature) strongly influences its chem- nucleation process prior to an actual the transformation of individual mol- istry. Each nanocrystal is unique transformation, one of the hallmarks ecules. Currently, his experiment from every other one of its seemingly of nanoscale chemistry, may have relies on light emission, but in the identical counterparts making hetero- been directly imaged for the first time. future, he hopes to generalize his ap- geneity one of the salient features of The “waiting time” before nucleation proach by using a spectral signature nanoscale chemistry. seems to be uniquely defined for each that is a finger-print of the structure nanocrystal – they don’t all start ex- of the molecule. Prashant’s interest in nanoscale changing at the same time, a classic chemistry directly results from being example of nanoscale heterogeneity. The kind of ‘molecules’ that fasci- in the midst of one of the pioneering nate Prashant are quite unique: tiny groups in nanoscience, led by LBNL Prashant hopes to extend his ap- crystals of metals and semiconduc- Director and former Miller Professor proach to learn more about semicon- tors with sizes of a few nanometers A. Paul Alivisatos. One particular ductor nanocrystals that mimic pho- (a nanometer = 10-9 m). ‘Nanocrys- phenomenon discovered in this lab tosynthetic systems. Lilac Amirav in tals’ represent the missing size-scale caught Prashant’s attention – when the Alivisatos lab has been designing between small molecules and mac- a nanocrystal of cadmium sulfide is a multi-component nanocrystal that is roscopic materials, made accessible exposed to silver ions, the silver re- able to absorb sunlight and produce by the relatively newfound ability places the cadmium in the nanocrys- energetic charge carriers that can of chemists and physicists to engi- tal almost instantaneously, orders of be used to split water into hydrogen neer such tiny structures. At this in- magnitude faster than a macroscopic and possibly oxygen – fuel that can termediate size-scale, the behavior crystal. The nanocrystal transforms be used as a “green” energy source. of electrons in the crystal is highly into silver sulfide and cadmium ions Prashant aims to measure the rate dependent on the size and geometry are released into solution. A flask full at which useful charge carriers are of the boundaries within which they of these transforming nanocrystals produced by a single nanocrystal in are confined. As a result, nanocrys- exhibits a fast color change, which is response to the light. This rate is an tals manifest attributes (e.g. color, mostly uninformative. So, Prashant important determinant of the intrinsic conductivity, or reactivity) that are watched the transformation of in- continued on page 6 The Adolph C. and Mary Sprague Miller Institute for Basic Research in Science University of California, Berkeley Page 2 The Adolph C. and Mary Sprague Miller Institute for Basic Research in Science University of California, Berkeley MILLER RESEARCH FELLOWSHIPS FOR 2011-2014 TERM Please watch for the Miller Institute’s new online nomination system at http://millerinstitute.berkeley.edu Nomination Deadline: 9 September 2010 The Miller Institute for Basic Research in Science invites department chairs, faculty advisors, professors and research scientists at institutions around the world to submit nominations for Miller Research Fellowships in the basic sciences. The Miller Institute seeks to discover and encourage individuals of outstanding talent, and to provide them with the opportunity to pursue their research on the Berkeley campus. Fellows are selected on the basis of their academic achievement and the promise of their scientific research. The Miller Institute is the administrative home department for each Miller Fellow who is hosted by an academic department on the Berkeley campus. All research is performed in the facilities provided by the UC Berkeley academic department. A list of current and former Miller Research Fellows can be found at: http://millerinstitute.berkeley.edu/all.php?nav=46 Miller Research Fellowships are intended for brilliant young women and men of great promise who have recently been awarded, or who are about to be awarded, the doctoral degree. The Fellowship term must commence between July 1 and October 1, 2011.