Scientific American ：化学十大难题 博主按：这是 Scientific American 科普杂志为国际化学年推出的专题。化学一直声称自己是中心学科，是因为化学其实也就是分子科学，而无论物理还是生命科学，研究到最后，还是要在分子机制这个层面才能解决问题。下面列出的化学十大难题，其实值得所有科学家关注，大家都能在这个舞台里一显身手，但是，化学家或许能在里面找到最好的切入点，从而找到解决问题的关键！ 1. How Did Life Begin? 生命从何而来 ? 2. How Do Molecules Form? 分子如何形成 ? 3. How Does the Environment Influence Our Genes? 环境如何影响人类基因 ? 4. How Does the Brain Think and Form Memories? 大脑如何思考 , 并形成记忆 ? 5. How Many Elements Exist? 到底存在多少种元素 ? 6. Can Computers Be Made Out of Carbon? 我们能用碳元素制造出电脑吗 ? 7. How Do We Tap More Solar Energy? 如何捕获更多太阳能 ? 8 What Is the Best Way to Make Biofuels? 制造生物燃料的最佳途径是什么 ? 9. Can We Devise New Ways to Create Drugs? 我们能研制出全新类型的药物吗 ? 10. Can We Continuously Monitor Our Own Chemistry? 我们能实时监测自身的化学变化吗 ? CHEMISTRY ： The 10 Unsolved Mysteries Many of the most profound scientific questions—and some of humanity’s most urgent problems—pertain to the science of atoms and molecules By Philip Ball Philip Ball has a Ph.D. in physics from the University of Bristol in England and was an editor at Nature for more than 20 years. He is the award-winning author of 15 books, including The Music Instinct: How Music Works, and Why We Can’t Do without It. 1 How Did Life Begin? the moment when the first living beings arose from inanimate matter almost four billion years ago is still shrouded in mystery. How did relatively simple molecules in the primordial broth give rise to more and more complex compounds? And how did some of those compounds begin to process energy and replicate(two of the defining characteristics of life)? At the molecular level, all of those steps are, of course, chemical reactions, which makes the question of how life beganone of chemistry.The challenge for chemists is no longer to come up with vaguely plausible scenarios,of which there are plenty. For example, researchers have speculated about minerals such as clay acting as catalysts for the formation of the first self-replicating polymers(molecules that, like DNA or proteins, are long chains of smaller units); about chemical complexity fueled by the energy of deep-sea hydrothermal vents; and about an "RNA world," in which DNA’s cousin RNA—which can act as an enzyme and catalyze reactions the way proteins do—would have been a universal molecule, before DNA and proteins appeared. No, the game is to figure out how to test these ideas in reactions coddled in the test tube. Researchers have shown, for example, that certain relatively simple chemicals can spontaneously react to form the more complex building blocks of living systems, such as amino acids and nucleotides, the basic units of DNA and RNA. In 2009 a team led by John Sutherland, now at the MRC Laboratory of Molecular Biology in Cambridge, England, was able to demonstrate the formation of nucleotides from molecules likely to have existed in the primordial broth.Other researchers have focused on the ability of some RNA strands to act as enzymes,providing evidence in support of the RNA world hypothesis. Through such steps, scientists may progressively bridge the gap from inanimate matter to selfreplicating, self-sustaining systems. Now that scientists have a better view of strange and potentially fertile environments in our solar system—the occasional flows of water on Mars, the petrochemical seas of Saturn’s moon Titan, and the cold, salty oceans that seem to lurk under the ice of Jupiter’s moons Europa and Ganymede—the origin of terrestrial life seems only a part of grander questions: Under what circumstances can life arise? And how widely can its chemical basis vary? That issue is made richer still by the discovery, over the past 16 years, of more than 500 extrasolar planets orbiting other stars—worlds of bewildering variety. These discoveries have pushed chemists to broaden their imagination about the possible chemistries of life. For instance, NASA has long pursued the view that liquid water is a prerequisite, but now scientists are not so sure. How about liquid ammonia, formamide, an oily solvent like liquid methane or supercritical hydrogen on Jupiter? And why should life restrict itself to DNA, RNA and proteins? After all, several artificial chemical systems have now been made that exhibit a kind of replication from the component parts without relying on nucleic acids. All you need, it seems, is a molecular system that can serve as a template for making a copy and then detach itself. Looking at life on Earth, says chemist Steven Benner of the Foundation for Applied Molecular Evolution in Gainesville,Fla.,“we have no way to decide whether the similarities reflect common ancestry or the needs of life universally.”But if we retreat into saying that we have to stick with what we know, he says,“we have no fun.” 2 How Do Molecules Form? molecular structures may be a mainstay of high school science classes,but the familiar picture of balls and sticks representing atoms and the bonds among them is largely a conventional fiction. The trouble is that scientists disagree on what a more accurate representation of molecules should look like. In the 1920s physicists Walter Heitler and Fritz London showed how to describe a chemical bond using the equations of then nascent quantum theory, and the great American chemist Linus Pauling proposed that bonds form when the electron orbitals of different atoms overlap in space.A competing theory by Robert Mulliken and Friedrich Hund suggested that bonds are the result of atomic orbitals merging into“molecular orbitals”that extend over more than one atom. Theoretical chemistry seemed about to become a branch of physics. Nearly 100 years later the molecularorbital picture has become the most common one, but there is still no consensus among chemists that it is always the best way to look at molecules. The reason is that this model of molecules and all others are based on simplifying assumptions and are thus approximate, partial descriptions. In reality, a molecule is a bunch of atomic nuclei in a cloud of electrons, with opposing electrostatic forces fighting a constant tug-of-war with one another, and all components constantly moving and reshuffling. Existing models of the molecule usually try to crystallize such a dynamic entity into a static one and may capture some of its salient properties but neglect others. Quantum theory is unable to supply a unique definition of chemical bonds that accords with the intuition of chemists whose daily business is to make and break them. There are now many ways of describing molecules as atoms joined by bonds. According to quantum chemist Dominik Marx of Ruhr University Bochum in Germany, pretty much all such descriptions“are useful in some cases but fail in others.” Computer simulations can now calculate the structures and properties of molecules from quantum first principles with great accuracy—as long as the number of electrons is relatively small. “Computational chemistry can be pushed to the level of utmost realism and complexity,”Marx says. As a result, computer calculations can increasingly be regarded as a kind of virtual experiment that predicts the course of a reaction. Once the reaction to be simulated involves more than a few dozen electrons, however, the calculations quickly begin to overwhelm even the most powerful supercomputer, so the challenge will be to see whether the simulations can scale up—whether, for example, complicated biomolecular processes in the cell or sophisticated materials can be modeled this way. 3 How Does the Environment Influence Our Genes? the old idea of biology was that who you are is a matter of which genes you have. It is now clear that an equally important issue is which genes you use. Like all of biology, this issue has chemistry at its core. The cells of the early embryo can develop into any tissue type. But as the embryo grows, these so-called pluripotent stem cells differentiate, acquiring specific roles (such as blood, muscle or nerve cells) that remain fixed in their progeny. The formation of the human body is a matter of chemically modifying the stem cells’ chromosomes in ways that alter the arrays of genes that are turned on and off. One of the revolutionary discoveries in research on cloning and stem cells, however, is that this modification is reversible and can be influenced by the body’s experiences. Cells do not permanently disable genes during differentiation, retaining only those they need in a “ready to work” state. Rather the genes that get switched off retain a latent ability to work—to give rise to the proteins they encode—and can be reactivated, for instance, by exposure to certain chemicals taken in from the environment. What is particularly exciting and challenging for chemists is that the control of gene activity seems to involve chemical events happening at size scales greater than those of atoms and molecules—at the so-called mesoscale—with large molecular groups and assemblies interacting. Chromatin, the mixture of DNA and proteins that makes up chromosomes, has a hierarchical structure. The double helix is wound around cylindrical particles made from proteins called histones, and this string of beads is then bundled up into higher-order structures that are poorly understood . Cells exercise great control over this packing—how and where a gene is packed into chromatin may determine whether it is active or not. Cells have specialized enzymes for reshaping chromatin structure, and these enzymes have a central role in cell differentiation. Chromatin in embryonic stem cells seems to have a much looser, open structure: as some genes fall inactive, the chromatin becomes increasingly lumpy and organized. “The chromatin seems to fix and maintain or stabilize the cells’ state,” says pathologist Bradley Bernstein of Massachusetts General Hospital. What is more, such chromatin sculpting is accompanied by chemical modification of both DNA and histones. Small molecules attached to them act as labels that tell the cellular machinery to silence genes or, conversely, free them for action. This labeling is called “epigenetic” because it does not alter the information carried by the genes themselves. The question of the extent to which mature cells can be returned to pluripotency—whether they are as good as true stem cells, which is a vital issue for their use in regenerative medicine—seems to hinge largely on how far the epigenetic marking can be reset. It is now clear that beyond the genetic code that spells out many of the cells’ key instructions, cells speak in an entirely separate chemical language of genetics—that of epigenetics. “People can have a genetic predisposition to many diseases, including cancer, but whether or not the disease manifests itself will often depend on environmental factors operating through these epigenetic pathways,” says geneticist Bryan Turner of the University of Birmingham in England. 4 How Does the Brain Think and Form Memories? the brain is a chemical computer. Interactions between the neurons that form its circuitry are mediated by molecules: specifically, neurotransmitters that pass across the synapses, the contact points where one neural cell wires up to another. This chemistry of the mind is perhaps at its most impressive in the operation of memory, in which abstract principles and concepts—a telephone number, say, or an emotional association—are imprinted in states of the neural network by sustained chemical signals. How does chemistry create a memory that is both persistent and dynamic, as well as able to recall, revise and forget? We now know parts of the answer. A cascade of biochemical processes, leading to a change in the amounts of neurotransmitter molecules in the synapse, triggers learning for habitual reflexes. But even this simple aspect of learning has short and long-term stages. Meanwhile more complex so-called declarative memory (of people, places, and so on) has a different mechanism and location in the brain, involving the activation of a protein called the NMDA receptor on certain neurons. Blocking this receptor with drugs prevents the retention of many types of declarative memory. Our everyday declarative memories are often encoded through a process called long-term potentiation, which involves NMDA receptors and is accompanied by an enlargement of the neuronal region that forms a synapse. As the synapse grows, so does the “strength” of its connection with neighbors—the voltage induced at the synaptic junction by arriving nerve impulses. The biochemistry of this process has been clarified in the past several years. It involves the formation of filaments within the neuron made from the protein actin—part of the basic scaffolding of the cell and the material that determines its size and shape. But that process can be undone during a short period before the change is consolidated if biochemical agents prevent the newly formed filaments from stabilizing. Once encoded, long-term memory for both simple and complex learning is actively maintained by switching on genes that give rise to particular proteins. It now appears that this process can involve a type of molecule called a prion. Prions are proteins that can switch between two different conformations. One of the conformations is soluble, whereas the other is insoluble and acts as a catalyst to switch other molecules like it to the insoluble state, leading these molecules to aggregate. Prions were first discovered for their role in neurodegenerative conditions such as mad cow disease, but prion mechanisms have now been found to have beneficial functions, too: the formation of a prion aggregate marks a particular synapse to retain a memory. There are still big gaps in the story of how memory works, many of which await filling with the chemical details. How, for example, is memory recalled once it has been stored? “This is a deep problem whose analysis is just beginning,” says neuroscientist and Nobel laureate Eric Kandel of Columbia University. Coming to grips with the chemistry of memory offers the enticing and controversial prospect of pharmacological enhancement. Some memory-boosting substances are already known, including sex hormones and synthetic chemicals that act on receptors for nicotine, glutamate, serotonin and other neurotransmitters. In fact, according to neurobiologist Gary Lynch of the University of California, Irvine, the complex sequence of steps leading to long-term learning and memory means that there are many potential targets for such memory drugs. 5 How Many Elements Exist? the periodic tables that adorn the walls of classrooms have to be constantly revised, because the number of elements keeps growing. Using particle accelerators to crash atomic nuclei together, scientists can create new “superheavy” elements, which have more protons and neutrons in their nuclei than do the 92 or so elements found in nature. These engorged nuclei are not very stable—they decay radioactively, often within a tiny fraction of a second. But while they exist, the new synthetic elements such as seaborgium (element 106) and hassium (element 108) are like any other insofar as they have well-defined chemical properties. In dazzling experiments, researchers have investigated some of those properties in a handful of elusive seaborgium and hassium atoms during the brief instants before they fell apart. Such studies probe not just the physical but also the conceptual limits of the periodic table: Do superheavy elements continue to display the trends and regularities in chemical behavior that make the table periodic in the first place? The answer is that some do, and some do not. In particular, such massive nuclei hold on to the atoms’ innermost electrons so tightly that the electrons move at close to the speed of light. Then the effects of special relativity increase the electrons’ mass and may play havoc with the quantum energy states on which their chemistry—and thus the table’s periodicity—depends. Because nuclei are thought to be stabilized by particular “magic numbers” of protons and neutrons, some researchers hope to find what they call the island of stability, a region a little beyond the current capabilities of element synthesis in which superheavies live longer. Yet is there any fundamental limit to their size? A simple calculation suggests that relativity prohibits electrons from being bound to nuclei of more than 137 protons. More sophisticated calculations defy that limit. “The periodic system will not end at 137; in fact, it will never end,” insists nuclear physicist Walter Greiner of the Johann Wolfgang Goethe University Frankfurt in Germany. The experimental test of that claim remains a long way off. 6 Can Computers Be Made Out of Carbon? computer chips made out of graphene—a web of carbon atoms—could potentially be faster and more powerful than silicon-based ones. The discovery of graphene garnered the 2010 Nobel Prize in Physics, but the success of this and other forms of carbon nanotechnology might ultimately depend on chemists’ ability to create structures with atomic precision. The discovery of buckyballs—hollow, cagelike molecules made entirely of carbon atoms—in 1985 was the start of something literally much bigger. Six years later tubes of carbon atoms arranged in a chicken wire–shaped, hexagonal pattern like that in the carbon sheets of graphite made their debut. Being hollow, extremely strong and stiff, and electrically conducting, these carbon nanotubes promised applications ranging from high-strength carbon composites to tiny wires and electronic devices, miniature molecular capsules, and water-filtration membranes. For all their promise, carbon nanotubes have not resulted in a lot of commercial applications. For instance, researchers have not been able to solve the problem of how to connect tubes into complicated electronic circuits. More recently, graphite has moved to center stage because of the discovery that it can be separated into individual chicken wire–like sheets, called graphene, that could supply the fabric for ultraminiaturized, cheap and robust electronic circuitry. The hope is that the computer industry can use narrow ribbons and networks of graphene, made to measure with atomic precision, to build chips with better performance than silicon-based ones. “ Graphene can be patterned so that the interconnect and placement problems of carbon nanotubes are overcome,” says carbon specialist Walt de Heer of the Georgia Institute of Technology. Methods such as etching, however, are too crude for patterning graphene circuits down to the single atom, de Heer points out, and as a result, he fears that graphene technology currently owes more to hype than hard science. Using the techniques of organic chemistry to build up graphene circuits from the bottom up—linking together “ polyaromatic” molecules containing several hexagonal carbon rings, like little fragments of a graphene sheet—might be the key to such precise atomicscale engineering and thus to unlocking the future of graphene electronics. 7 How Do We Tap More Solar Energy? with every sunrise comes a reminder that we currently tap only a pitiful fraction of the vast clean-energy resource that is the sun. The main problem is cost: the expense of conventional photovoltaic panels made of silicon still restricts their use. Yet life on Earth, almost all of which is ultimately solar-powered by photosynthesis, shows that solar cells do not have to be terribly efficient if, like leaves, they can be made abundantly and cheaply enough. “ One of the holy grails of solar-energy research is using sunlight to produce fuels,” says Devens Gust of Arizona State University. The easiest way to make fuel from solar energy is to split water to produce hydrogen and oxygen gas. Nathan S. Lewis and his collaborators at Caltech are developing an artificial leaf that would do just that using silicon nanowires. Earlier this year Daniel Nocera of the Massachusetts Institute of Technology and his co-workers unveiled a silicon-based membrane in which a cobalt-based photocatalyst does the water splitting. Nocera estimates that a gallon of water would provide enough fuel to power a home in developing countries for a day. “Our goal is to make each home its own power station,” he says. Splitting water with catalysts is still tough. “Cobalt catalysts such as the one that Nocera uses and newly discovered catalysts based on other common metals are promising,” Gust says, but no one has yet found an ideal inexpensive catalyst. “ We don’t know how the natural photosynthetic catalyst, which is based on four manganese atoms and a calcium atom, works,” Gust adds. Gust and his colleagues have been looking into making molecular assemblies for artificial photosynthesis that more closely mimic their biological inspiration, and his team has managed to synthesize some of the elements that could go into such an assembly. Still, a lot more work is needed on this front. Organic molecules such as the ones nature uses tend to break down quickly. Whereas plants continually produce new proteins to replace broken ones, artificial leaves do not (yet) have the full chemical synthesis machinery of a living cell at their disposal. 8 What Is the Best Way to Make Biofuels? instead of making fuels by capturing the rays of the sun, how about we let plants store the sun’s energy for us and then turn plant matter into fuels? Biofuels such as ethanol made from corn and biodiesel made from seeds have already found a place in the energy markets, but they threaten to displace food crops, particularly in developing countries where selling biofuels abroad can be more lucrative than feeding people at home. The numbers are daunting: meeting current oil demand would mean requisitioning huge areas of arable land. Turning food into energy, then, may not be the best approach. One answer could be to exploit other, less vital forms of biomass. The U.S. produces enough agricultural and forest residue to supply nearly a third of the annual consumption of gasoline and diesel for transportation. Converting this low-grade biomass into fuel requires breaking down hardy molecules such as lignin and cellulose, the main building blocks of plants. Chemists already know how to do that, but the existing methods tend to be too expensive, inefficient or difficult to scale up for the enormous quantities of fuel that the economy needs. One of the challenges of breaking down lignin—cracking open the carbon-oxygen bonds that link “aromatic,” or benzenetype, rings of carbon atoms—was recently met by John Hartwig and Alexey Sergeev, both at the University of Illinois. They found a nickel-based catalyst able to do it. Hartwig points out that if biomass is to supply nonfossil-fuel chemical feedstocks as well as fuels, chemists will also need to extract aromatic compounds (those having a backbone of aromatic rings) from it. Lignin is the only major potential source of such aromatics in biomass. To be practical, such conversion of biomass will, moreover, need to work with mostly solid biomass and convert it into liquid fuels for easy transportation along pipelines. Liquefaction would need to happen on-site, where the plant is harvested. One of the difficulties for catalytic conversion is the extreme impurity of the raw material—classical chemical synthesis does not usually deal with messy materials such as wood. “There’s no consensus on how all this will be done in the end,” Hartwig says. What is certain is that an awful lot of any solution lies with the chemistry, especially with finding the right catalysts. “Almost every industrial reaction on a large scale has a catalyst associated” with it, Hartwig points out. 9 Can We Devise New Ways to Create Drugs? the core business of chemistry is a practical, creative one: making molecules, a key to creating everything from new materials to new antibiotics that can outstrip the rise of resistant bacteria. In the 1990s one big hope was combinatorial chemistry, in which thousands of new molecules are made by a random assembly of building blocks and then screened to identify those that do a job well. Once hailed as the future of medicinal chemistry, “combi-chem” fell from favor because it produced little of any use. But combinatorial chemistry could enjoy a brighter second phase. It seems likely to work only if you can make a wide enough range of molecules and find good ways of picking out the minuscule amounts of successful ones. Biotechnology might help here—for example, each molecule could be linked to a DNA-based “ bar code” that both identifies it and aids its extraction. Or researchers can progressively refine the library of candidate molecules by using a kind of Darwinian evolution in the test tube. They can encode potential protein-based drug molecules in DNA and then use error-prone replication to generate new variants of the successful ones, thereby finding improvements with each round of replication and selection. Other new techniques draw on nature’s mastery at uniting molecular fragments in prescribed arrangements. Proteins, for example, have a precise sequence of amino acids because that sequence is spelled out by the genes that encode the proteins. Using this model, future chemists might program molecules to assemble autonomously. The approach has the advantage of being “green” in that it reduces the unwanted by-products typical of traditional chemical manufacturing and the associated waste of energy and materials. David Liu of Harvard University and his co-workers are pursuing this approach. They tagged the building blocks with short DNA strands that program the linker’s structure. They also created a molecule that walks along that DNA, reading its codes and sequentially attaching small molecules to the building block to make the linker—a process analogous to protein synthesis in cells. Liu’s method could be a handy way to tailor new drugs. “ Many molecular life scientists believe that macromolecules will play an increasingly central, if not dominant, role in the future of therapeutics,” Liu says. 10 Can We Continuously Monitor Our Own Chemistry? increasingly, chemists do not want to just make molecules but also to communicate with them: to make chemistry an information technology that will interface with anything from living cells to conventional computers and fiber-optic telecommunications. In part, it is an old idea: biosensors in which chemical reactions are used to report on concentrations of glucose in the blood date back to the 1960s, although only recently has their use for monitoring diabetes been cheap, portable and widespread. Chemical sensing could have countless applications—to detect contaminants in food and water at very low concentrations, for instance, or to monitor pollutants and trace gases present in the atmosphere. Faster, cheaper, more sensitive and more ubiquitous chemical sensing would yield progress in all of those areas. It is in biomedicine, though, that new kinds of chemical sensors would have the most dramatic potential. For instance, some of the products of cancer genes circulate in the bloodstream long before the condition becomes apparent to regular clinical tests. Detecting these chemicals early might make prognoses more timely and accurate. Rapid genomic profiling would enable drug regimens to be tailored to individual patients, thereby reducing risks of side effects and allowing some medicines to be used that today are hampered by their dangers to a genetic minority. Some chemists foresee continuous, unobtrusive monitoring of all manner of biochemical markers of health and disease, perhaps providing real-time information to surgeons during operations or to automated systems for delivering remedial drug treatments. This futuristic vision depends on developing chemical methods for selectively sensing particular substances and signaling about them even when the targets occur in only very low concentrations. MORE TO EXPLORE Beyond the Molecular Frontier: Challenges for Chemistry and Chemical Engineering. National Research Council. National Academies Press, 2003. Beyond the Bond. Philip Ball in Nature, Vol. 469, pages 26–28; January 6, 2011. Let’s Get Practical. George M. Whitesides and John Deutch in Nature, Vol. 469, pages 21–22; January 6, 2011.
化学形象代言人（1）： George C. Pimentel 博主按：据说化学已经臭大街了，化学品在大众尤其是所谓营养学家眼里直接就等同于毒品（chemical=drug?）。或许化学这门曾经的“中心的、创造的、实用的”学科（ ACS前会长Ronald Breslow语 ）现在到需要拯救的时候了，于是“国际化学年”恰逢其时的出现了。或许媒体的宣传能改观大众对化学恶劣的负面印象？ 但是现在公关宣传时兴搞“形象代言人”，而我们化学界又有谁能有资格充当“化学形象代言人”的角色呢？我的“化学形象代言人”的系列博文试着提出我心目中的候选人。 化学激光的发现者、伯克利教授、ACS的前会长George.Pimentel是我读硕士时老板杨学锋的博士后老板。杨是他狂热的崇拜者，我现在还清晰记得在组会上杨向我们介绍老P时的激动和激情。 老p同学虽然在基质隔离技术、自由基（HCO/KrF2)、化学激光、氢键、选键化学、火星生命等领域有突出贡献。但是其实他一直在搞的莫过就是 红外/振动光谱 而已。 Biography of George C. Pimentel (The Journal of Physical Chemistry, Vol. 95, No. 7, 1991, 2607) George Pimentel devoted his unbounded energy and passion to science, to his students and colleagues, to his family, and to an occasional ball game. George was born 2 May 1922 in California’s Central Valley. He grew up in a poor section of Los Angeles, attended public schools, and earned a bachelor’s degree in chemistry from the University of California, Los Angeles, in 1943. Following a short stint at Berkeley working on the Manhattan Project, George trained for submarine duty in the Navy. At the close of the war he participated in the formation of the Office of Naval Research and in early consideration of nuclear-powered ships. In 1946 George returned to Berkeley to do graduate work with Kenneth Pitzer on infrared spectroscopy. Three years later he had earned his Ph.D. in chemistry and joined the faculty. During his career George developed methods of vibrational spectroscopy to study molecular bonding and chemical reactivity, to produce the first chemical lasers, and to explore the planet Mars. George attacked the important problems. During the 1950s he developed the matrix-isolation technique to trap free radicals and other reactive species that play a central role in chemical reactions. A solid matrix of inert gas molecules, cooled to the temperature of liquid hydrogen, prevented a free radical embedded inside it from reacting, thus allowing leisurely spectroscopic study of the radical. This method was used first to record spectra of molecular species involving the hydrogen-bonding interaction, which is central to molecular biology. With Aubrey McClellan, George wrote The Hydrogen Bond (1960), the classic book on hydrogen bonding that guided the field for many years. The matrix technique was employed to investigate the HCO free radical, an important intermediate in combustion processes, and later to study rare gas compounds like KrF2, which was discovered in George’s laboratory. Many other interesting new chemical species were produced for infrared spectroscopic characterization using photochemical, metal reaction, and microwave discharge techniques. Matrix-isolation spectroscopy is now employed routinely in chemical laboratories around the world for a wide range of analytical, synthetic, and physical chemical studies. George opened the field of infrared photochemistry in 1960 by showing that cis - trans isomerization could be caused by excitation of specific vibrational transitions of cis-HONO in a matrix. This was the first chemical transformation induced by infrared photons. Later, a similar study was conducted on the light-induced matrix isomerization of unstable forms of N2O3. The much-sought mode-selective excitation of bimolecular chemical reactions has proven to be elusive under normal reaction conditions. George recognized the possibility that cryogenic matrix conditions might provide an environment in which this exciting goal could be demonstrated. A number of bimolecular reactions have now been studied in solid inert gas matrices with tuned-laser, hence vibrationally selective, excitation of one of the reactants. Distinct evidence for mode-specific influence on the quantum yield has been found for reactions such as F2 + C2H4. In the mid- 1960s George’s studies of fast reactions unlocked the secret to converting chemical energy directly into laser light. While searching for the CF3 spectrum he and Jerry Kasper first discovered the iodine-atom photodissociation laser, CF3I + hn → CF3 + I(2P1/2), which lased on the 2P1/2 → 2P3/2 transition. Atomic iodine became a spectacular laser system that was developed into a candidate laser fusion source in its pulsed mode. Atomic iodine has also been scaled into a high-energy laser, with powers in excess of 100 kW, in its continuous wave (CW) mode in which atomic iodine is pumped into its upper spin-orbit fine structure level by energy transfer from singlet oxygen. During the period 1964-1970, many other types of chemical lasers were discovered in George Pimentel’s laboratory: the hydrogen/chlorine (H2/Cl2) chain-reaction chemical laser: C12 + hv → 2C1 C1+ H2→ HCI + H H + C12 → HCl*(n≤6) + C1 the atomic fluorine/molecular hydrogen (F/H,) bimolecular reaction chemical laser: UF6 + hn →F + UFS F + H2 → HF* (n≤3) + H H + F2 → HF* (n≤6)+ F the l,l,1-trifluoroethane (CF3CH3) unimolecular reaction chemical laser: CF3I + hn → CF3 + I CH3I + hn → CH3 + I CF3 + CH3 → CF3CH3* + HF*(n≤3) + CF2CH2 the 1,l-difluoroethylene (CF2=CH2) photochemical laser: CF2=CH2 + hv → HF*(n≤4) + FC≡CH All of these molecular chemical lasers operate in the infrared spectral region on vibration-rotation transitions of vibrationally excited (t) hydrogen halides (and corresponding deuterium halides) “born” in excited states by the process of breaking and making chemical bonds. The diversity of reaction types used to produce chemical laser action was due to George’s creativity and to his ability to stimulate creative efforts by his students and postdoctoral fellows. George and his students also greatly enjoyed developing techniques to measure the energy contents of chemical laser species quantitatively and to understand the intimate details of chemical reaction dynamics that generate characteristic energy distributions in chemical reaction products. During the period 1970-1990, George Pimentel and his group extended chemical laser studies to include operation on overtone (n= 2) vibrational transitions, on pure rotational transitions, and on many other products of chemical reactions. Nearly a hundred elementary chemical reactions that yielded chemical lasers were studied in George’s laboratory. In addition to the impact of the fundamental work on chemical reaction (and relaxation) dynamics that chemical lasers provided, chemical lasers have proven to be useful sources for applications in defense and medicine. The HF and DF chemical lasers have been engineered into the world‘s most powerful high-energy lasers, with megawatt class CW powers. Pulsed HF chemical lasers have also proven to be highly useful for controlled microsurgical removal of tissue. George wanted to know whether there was life on Mars, and so with Ken Herr he persuaded NASA to put one of his rapid-scan infrared spectrometers on a Mariner spacecraft to determine the Chemical constituents of the Martian surface. His instrument was novel and clever, built from scratch on the Berkeley campus to NASA space-flight standard. No evidence for biological material was observed, but much was learned about the planet’s surface and atmosphere. George was chosen as a member of the first group of scientist-astronauts, but he withdrew when he learned that he would probably never get into space. In addition to his legacy of research articles and textbooks, George Pimentel bequeathed his style of doing and enjoying chemistry to thousands of students and colleagues. He was a perfect friend, mentor, and role model. He excelled at selecting and achieving important goals and at motivating his coworkers to do significant work. George Pimentel was strongly intuitive in his research approach and was a great believer in the ability of the individual marcher to devise and perform key experiments needed to advance knowledge markedly. George was fond of pointing out that chemistry is an experimental science and he directed his talents toward conceiving and executing superb experiments that were often the first of their kind. Discoveries and first-generation work were George’s natural domain. George was a national leader in science and science policy. He served as deputy director of the National Science Foundation from 1977 to 1980 and as president of the American Chemical Society in 1986. He organized and edited the National Academy of Sciences report Opportunities in Chemistry, often called the “Pimentel Report”, which was published in 1985 and later revised and released for use in high schools under the title Opportunities in Chemistry: Today and Tomorrow. In George’s final lecture, his Priestley Medal Address, he urged members of the scientific community to mount a massive and ongoing campaign of public education”, so that our society can sensibly weigh the risks and benefits of science and technology. George loved to teach. He brought the significance of chemistry and the excitement of research to Berkeley freshmen, to his research students and collaborators, to national leaders, and, through the CHEM study program, to secondary school teachers and students. He helped each of his research students attain a level of achievement well beyond reasonable expectations. Whether he was in the halls of Congress, in the classroom, or eating a peanut butter sandwich, George’s clear logic, his openness and candor, and his concern for others always won his audience. George Pimentel did everything with tremendous vigor, intensity, commitment, and, above all, desire to succeed. Squash partners and opposing softball teams quickly found this out. George’s idea of relaxation was winning a ball game, mixing concrete, or having a hundred friends over for a party. George Pimentel chose his own epitaph, which is more than an epitaph; it is a description of the man. He went to the ballpark every day And he let them know he came to play W. Lester S. Andrews Bruce S. Ault Michael J. Berry C. Bradley Moore 以Pimentel大师为榜样,做一名合格的博士生导师 杨学锋(大连理工大学教授) Pimentel教授是我一生中近距离接触过的国内外人群中，唯一一位可以用“伟大”来形容的人。 自上世纪六十年代中读研究生以来，我有幸先后在国内外与四位后来成为中科院学部委员及院士的中国学者、两位英国皇家学会院士（FRS）及两位美国科学院院士（其中一位是诺贝尔奖获得者）在一个小组较长期工作过，他们每人都有自己的治学特点，但在全面教书育人方面给我留下最深印象的是Pimentel大师。 George Pimentel（1922-1989）是加州大学伯克利化学系（该系近几十年来化学博士教育一直排名全美第一）教授，化学激光技术和基质隔离光谱技术的发明人，一生中获得过除诺贝尔奖以外的各种最重要的化学大奖。在教学方面他晚年在伯克利主讲最有声望教授方可 担纲的大一新生化学，并曾亲自为全美高中化学实验录制教学演示片。在社会服务方面，他在五十几岁时曾任一届美国家科学基金会（NSF）兼职副主席并荣膺金质服务奖章；六十几岁时曾任一届美国 最大的专业学会—美国化学会（ACS）的会长；八十年代初，他曾领导四百余位美国化学家编写了数百页的“Opportunity in Chemistry（化学中的机遇）”化学学科发展展望报告, 以后美化学史上称此书 为“Pimentel Report ”。他67岁去世时，被誉为“当代最伟大的化学家之一和美国最伟大的化学教育家”，美化学会并以他的名字命名新设立的“化学教育奖”。1982年初至1985年底,我曾两次以访问学者身份在他的实验室工作，依据我与他长达近三年的的亲身接触，我将Pimentel大师在培养博士生方面的经验归纳为五个方面。 一、坚持正面教育，最大限度调动研究生的主观能动性 我当时所在的Pimentel小组中，近十位美国研究生的能力、努力程度等都有相当大差别，我知道Pimentel教授对个别学生也感到相当头痛，但他总是对每一个学生和颜悦色、一视同仁，耐心启发后进者的积极性。我那时算是非常努力的一个，每做出一点成绩，他总 是多次给予最大限度的称赞，如：“Marvelous! (真是神奇)”，“We are proud of you! (我们为你而骄傲)”，“You are a hero of our work! (你是我们工作的英雄)”等。这些话虽已过去二十多年，但仍经常在我耳边响起，成为激励我不断向上的一种动力。 二、开展Pimentel式的研讨型小组学术活动 那三年中开学期间,只要Pimentel教授不出差，每周四晚上全组都会举行小组学术活动，大家轮流主讲，气氛极其随便，通常是边讲、边吃、边喝、边讨论，还夹杂了不少玩笑，而且往往是不等主讲人讲几句，就会被打断进行长时间你一言我一语的讨论。我大约每5个月 讲一次，每次只准备讲40分钟，但边讲边讨论总会延续大约两个小时。Pimentel教授总是问题问得最多也回答得最多，同时他也不断启发在场每一个人最大限度地参加到讨论中来。讨论既涉及有专业深度的问题，也包括非常基础的理化知识。应当说，那三年中从小组学术活动所得到的知识是令人终生难忘的。 三、精益求精撰写每一篇自己以通信作者署名的研究论文 Pimentel教授一生发表了一百余篇研究论文，极其难能可贵的是，每一篇他作为通信作者的论文中的每一句话都是由他反复推敲写成。1983年底，在我日以继夜地工作了近两年之后，他告诉我可以着手写一篇论文了，他先让我写一份非常详细的论文大纲，然后他与我认真讨论并亲笔进行仔细修改（他修改的这份大纲我一直保存了十余年不舍得丢掉）。当我把写了一个月的初稿交给他后，他又用了两个月时间反复加工，这期间又不断就一些实验结果与我反复讨论以提升认识，当他把他写完的秘书打印稿(当时美国的计算机打印也刚刚出现)返给我时，我发现，正像周围研究生事先告诉我的，我写的话他一句也未用，除了实验数据外完全是他另起炉灶，而这是Pimentel教授的一贯写作传统。对他的第一稿，我一口气从科学观点到英文修辞又写了二十多条书面意见，他不但不生气，反倒十分高兴，甚至一再表示感谢。后来我们又不知讨论了多少次才将这篇论文投出，这也是我与Pimentel教授合作发表的唯一一篇论文。这时候的Pimentel教授有多忙？他刚从美国家科学基金会任副主席回到伯克利并仍身兼数职，有三位秘书为其服务。他此时每年平均出国五、六次，每月经常还要去华盛顿和国内他处开会数次，在如此繁重的工作压力下，Pimentel教授仍如此亲自动手撰写每一篇学术论文，他无疑是我一生中见到的对研究论文最为严肃认真的科学家。 四、严把博士生出口质量关 伯克利化学系的每位教师从助教授（即讲师）到副教授都经过严格的选拔和淘汰(淘汰率超过50%)，因此几乎每位教授在四十岁左右都会成为自己所在领域国际上的佼佼者。伯克利化学系的博士生毕业既无发表论文要求，也没有任何答辩手续，一般是学位论文经导师修改打印后，导师一签名另两位系内教授看也不看跟着签名就算获得学位。因此，伯克利化学系实行的是最彻底的博士生培养质量导师完全负责制。就在这种导师对学生毕业与否持有绝对权利的情况下，我在伯克利的那几年中，Pimentel的学生（全部是硕博连读）平均是5-6年毕业，最快的一个三年就毕业了, 但有两位我很熟悉的学生都呆到了第八年才毕业，而且到毕业时一篇论文也未能发表。Pimentel教授依据每人不同情况严把博士生出口质量关的认真程度可见一斑。 五、用自己的高尚人格对学生言传身教 Pimentel教授身上有诸多优秀品格, 最突出之一是他的平等待人。在全系举行学术活动时，他不象大多数教授那样坐在第一排，而是永远坐在学生中间，但同时他又是会场上提问最多的教授之一。他把自己的小组当成一个临时大家庭，大约每四个月邀请大家到他家里举行一次“Party”, 这时候他会和年轻人一起唱歌、跳舞、游泳等，并非常周到地与每位与会者个别交谈。对我这个来自发展中国家、但勤奋工作并有独立见解的人，他不但没有丝毫歧视，反倒因为我的努力往往给予特别的礼遇。记得在我离开伯克利时，他不仅在家里举行了有几人共享的迎送“Party”, 而且还破例在小组学术活动时，亲自购买了葡萄酒，专门为我致欢送词并要我发表即席告别演说。他主张东西方文化的融合，在他的办公室里，他的座位左边插着一幅巨大的美国国旗，座位顶上竟是一幅硕大的列宁像，表明了他不简单地拘泥于东西方意识形态冲突的一种政治态度。总之，Pimentel教授是我一生中近距离接触过的国内外人群中，唯一一位可以用“伟大”来形容的人。 在我1995年成为博士生导师后，我也时时注意效仿Pimentel教授，做好研究生培养工作。如，多年来我们坚持每周举行一次 “Pimentel式”的小组学术活动，每次有两名学生主讲（每人准备约半小时讲稿），但每次边讲边讨论总会持续约三个小时。在自己动手撰写论文方面，我每年集中精力写好2-3篇自己作为通信作者的英文论文，认真琢磨每一个实验素材和每一句话，并与学生反复讨论修改数月后尽可能投给国外本学科较高SCI影响因子的杂志。在为人师表方面，考虑到我从学校得到的待遇相对高一点，自1994年到大工以来，我一直把带研究生酬金、研究基金提成的个人份额、市优秀专家及校论文奖励、出国期间的国内工资、津贴全部提供实验室公用。诚然，无论在学识、学术成就和做人等方面要达到Pimentel大师那样的高度对我而言是完全不可能的，但我仍然决心以他为榜样，在十分有限的为学校和学生服务的年限内，努力做一名合格的博士生导师。 此文发表于《大连理工大学学报》
早晨打开邮箱，收到一封来自Taylor Francis的邮件。Taylor Francis 是国际知名的学术出版商，每年出版期刊近1000种，图书近1800册。今年是国际化学年，Taylor Francis 积极参与2011国际化学年活动，这封信就是他们向化学工作者投放的宣传材料吧。感兴趣的朋友可以登录他们的网站，查阅他们出版的期刊文献。 Dear Mr. ZHENG 2011 is an exciting year at Taylor Francis, not only are we launching our New Chemistry Arena but we also have monthly and weekly promotions planned in celebration of the International Year of Chemistry! To start the special year off in style is Chemistry Craziness…We’re giving you free access to all current and back content of our Chemistry Journals until 31st January! All the journals in the promotion are listed below, click on the links to take you to the Journal's online contents. Analytical Letters Applied Spectroscopy Reviews Catalysis Reviews Chemical Engineering Communications Chemistry and Ecology Combustion Science and Technology Comments on Inorganic Chemistry Critical Reviews in Analytical Chemistry Crystallography Reviews Drying Technology Environmental Forensics Fullerenes, Nanotubes and Carbon Structures Green Chemistry letters and Reviews High Pressure Research Instrumentation Science and Technology International Journal of Environmental Analytical Chemistry International Journal of Green Nanotechnology International Journal of Green Nanotechnology: Biomedicine International Journal of Green Nanotechnology: Physics Chemistry International Journal of Polymer Analysis and Characterization International Journal of Polymeric Materials International Journal of Smart and Nano Materials International Reviews in Physical Chemistry Isotopes in Environmental and Health Studies Journal of Adhesion Journal of Asian Natural Product Research Journal of Carbohydrate Chemistry Journal of Coordination Chemistry Journal of Dispersion Science and Technology Journal of Energetic Materials Journal of Experimental Nanoscience Journal of Immunoassay and Immunochemistry Journal of Liquid Chromatography and Related Techniques Journal of Macromolecular Science, Part A: Pure and Applied Chemistry Journal of Plant Interactions Journal of Sulfur Chemistry Journal of Wood Chemistry and Technology Liquid Crystals Liquid Crystals Today Molecular Crystals and Liquid Crystals Molecular Physics Molecular Simulation Natural Products Research Nucleosides, Nucleotides and Nucleic Acids Organic Preparations and Procedures International Ozone: Science Engineering Phase Transitions Phosphorus, Sulfur, and Silicon and the Related Elements Physics and Chemistry of Liquids Polycyclic Aromatic Compounds Polymer Reviews Polymer-Plastics Technology and Engineering Preparative Biochemistry and Biotechnology SAR QSAR in Environmental Research Separation and Purification Reviews Separation Science and Technology Soft Materials Solvent Extraction and Ion Exchange Spectroscopy Letters Supramolecular Chemistry Synthesis and Reactivity in Inorganic Metal-Organic, and Nano-Metal Chemistry Synthetic Communications Toxicological and Environmental Chemistry Transaction of the Royal Society of South Africa From the individual journal homepages you will also be able to subscribe to the journal or download a library recommendation form . Taylor Francis Launches New Chemistry Arena! Visit our NEW Chemistry Arena and access all things Chemistry in one place – from high-quality journal reviews and cutting-edge articles to the latest news, conference listings, and interviews with journal editors and experts. WWW.CHEMISTRYARENA.COM Happy New Year! Angela Dickinson Senior Marketing Executive angela.dickinson@tandf.co.uk
标签: 国际化学年
