George M. Whitesides

Bio: George M. Whitesides is an academic researcher from Harvard University. The author has contributed to research in topics: Microcontact printing & Self-assembled monolayer. The author has an hindex of 240, co-authored 1739 publications receiving 269833 citations. Previous affiliations of George M. Whitesides include University of California, Davis & University of Texas at Austin.

Oxidative addition and reductive elimination reactions involving platinum metallacycles

Abstract: Thcrmal dccornposition of a series of platinacycloalklncs t-,pttC tt.)"CttR tL = n-ButP, Et3Pl L2 = Me2PCH2CH2PMe2.2 ,2'-bipyridyl; R=H,n=3,4: R=Mc,n=3lindichl oronrcthancanddi bromomcthancsolu tionsgcn- cratcd both cycloalkanes and alkenes derived from thc mctallacyclic nroictv and hornologous cl,cloalkanes and alkencs formed by incorporation of a solvent-derived mcthylcnc group. Thcrmal decornpositions of platinacycloalka nes in hydrocarbon or ethereal solutions yieldcd only alkcncs having the same carbon nuntber as the nrctallacyclic group. Thcsc products reflect two compcting rcaction paths. Olcfins arc formed by /3-hydride elinrination. C1'cloalkanes and homologatcd products arc gencrated by decomposition of platinum(lV) intermediates, produced by oxidativc addition of dihalomcthanc to platinum(ll) metalla- cycles. The thcrmolytic bchavior of two modcl systcms (ci.r-(BurP)2Pt( CIl2)1(CF.r)l and (bipy)Pt(CH:)+(C H2Cl)Cl)support these contentions.

New Strategy for Controlling the Size and Shape of Metallic Features Formed by Electroless Deposition of Copper: Microcontact Printing of Catalysts on Oriented Polymers, Followed by Thermal Shrinkage

Abstract: This paper describes a new method of reducing the size of the metal features made by electroless deposition and fabricating complex-shaped, patterned surfaces. Microcontact printing (μCP) was used to pattern oriented glassy polymers with palladium colloids, stabilized with tetraoctadecylammonium bromide. These colloids are catalysts for the selective electroless deposition of copper. Annealing of the activated polymer at a temperature slightly above its glass transition temperature led to a shrinkage of the substrate. Immersion of the shrunken substrate in the plating bath yielded the metal features. The maximum shrinkage of the feature size achieved was on the order of a factor of ∼4 in one direction of the oriented polymer and of ∼7 in the perpendicular direction. Control of the extent and direction of shrinkage allowed the fabrication of metal features with sizes and shapes different from those on the polydimethylsiloxane stamp used for the patterning of the substrate and from the draw ratios. Free-sta...

Chemical and enzymatic syntheses of 6-deoxyhexoses. Conversion to 2,5-dimethyl-4-hydroxy-2,3-dihydrofuran-3-one (Furaneol) and analogs

Abstract: 6-Deoxy-D-fructose 1-phosphate (6-deoxyF-1-P) forms when a solution containing D-fructose 1,6-diphosphate (FDP) and D-lactaldehyde is treated with the enzymes aldolase and triosephosphate isomerase. This transformation involves three reactions: aldolase-catalyzed cleavage of FDP to a mixture of dihydroxyacetone phosphate and D-glyceraldehyde phosphate, triosephosphate isomerase catalyzed equilibration of dihydroxyacetone phosphate and D-glyceraldehyde phosphate, and aldolase-catalyzed condensation of dihydroxyacetone phosphate and D-lactaldehyde to 6-deoxyF-1-P. An analogous process converts a mixture of FDP and L-lactaldehyde to 6-deoxysorbose 1-phosphate (6-deoxyS-1-P). Aldolase-catalyzed reaction of dihydroxyacetone phosphate, prepared separately, with D-lactaldehyde yields 6-deoxyF-1-P directly; similar reaction of dihydroxyacetone phosphate with α-hydroxybutyraldehyde yields a mixture of 6-methyl-6-deoxyhexose 1-phosphates. Acid-catalyzed hydrolysis of the sugar phosphates releases the corresponding free sugars. A mixture containing 6-deoxyhexoses is formed directly by base-catalyzed aldol condensation of dihydroxyacetone and D,L-lactaldehyde. Treatment of any of the 6-deoxyhexoses with acids generates 2,5-dimethyl-4-hydroxy-2,3-dihydrofuran-3-one (Furaneol, a flavor principle). Furaneol can also be prepared in moderate yields by hydrogenolysis of FDP and other hexose phosphates in alkaline media

Using Micromachining, Molecular Self-Assembly, and Wet Etching to Fabricate 0.1-1-.mu.m-scale structures of Gold and Silicon

Abstract: In this paper, we report a procedure that combines micromachining,l molecular self-assembly, and wet etching and provides the basis for a method to fabricate 0.1-1pm-scale structures of gold supported on glass or silicon. This procedure has four steps: (i) formation of a monolayer of the thiolate2 IHO(CHilzS] from B-mercaptoethanol IHO(CH2)2SH] on the surface of a film of gold; (ii) generation, by micromachining, of 0. l-l-pm-scale regions of bare gold in the monolayer of HO(CHdzS; (iii) selfassembly of a monolayer of CHa(CHdrsS on micromachined regions of bare gold;3 (iv) selective etching of gold film underlying HO(CH2)zS by using an aqueous solution of cyanide ions (CN-) saturated with Oz. Areas of gold film supporting self-assembled monolayers (SAMs) of CHs(CHz)rsS are protected from etchinga and form microstructures of gold with lateral dimensions as small as 0.1 pm and vertical dimensions as small as 25 nm.5 Because gold is a good electrical conductor and does not oxidize in air, it is frequently used in the fabrication of small structures. Microstructures of gold are used as microelectrodes,o small conductors for dense microelectronic devices,T scatterers and absorbers for ion projection lithography and etching,T'8 and masks for X-ray lithography.T'e Here we report a simple, wet chemical procedure for fabricating 0.1-1-pm-scale structures of gold. In

Self-Assembly of Hydrogen-Bonded Polymeric Rods Based on the Cyanuric Acid·Melamine Lattice

Abstract: This paper describes the self-assembly of hydrogen-bonded polymeric rods based on the lattice of cyanuric acid and melamine (CA·M). Data from 1H NMR spectroscopy, IR spectroscopy, gel permeation chromatography (GPC), and transmission electron microscopy (TEM) are interpreted as indicating that the self-assembly of a bisisocyanuric acid (bisCA) and a bismelamine (bisM) formed polymeric nanorods [(bisCA)n(bisM)n] composed of parallel CA·M rosettes. The TEM results suggest that these rods aggregate as bundles. The length of the bundles ranged from 100 to 1500 nm, and their diameter was in the range from 15 to 500 nm.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

The Theory of Island Biogeography

Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

Large-scale pattern growth of graphene films for stretchable transparent electrodes

Abstract: Problems associated with large-scale pattern growth of graphene constitute one of the main obstacles to using this material in device applications. Recently, macroscopic-scale graphene films were prepared by two-dimensional assembly of graphene sheets chemically derived from graphite crystals and graphene oxides. However, the sheet resistance of these films was found to be much larger than theoretically expected values. Here we report the direct synthesis of large-scale graphene films using chemical vapour deposition on thin nickel layers, and present two different methods of patterning the films and transferring them to arbitrary substrates. The transferred graphene films show very low sheet resistance of approximately 280 Omega per square, with approximately 80 per cent optical transparency. At low temperatures, the monolayers transferred to silicon dioxide substrates show electron mobility greater than 3,700 cm(2) V(-1) s(-1) and exhibit the half-integer quantum Hall effect, implying that the quality of graphene grown by chemical vapour deposition is as high as mechanically cleaved graphene. Employing the outstanding mechanical properties of graphene, we also demonstrate the macroscopic use of these highly conducting and transparent electrodes in flexible, stretchable, foldable electronics.

Fuzzy Nanoassemblies: Toward Layered Polymeric Multicomposites

Abstract: Multilayer films of organic compounds on solid surfaces have been studied for more than 60 years because they allow fabrication of multicomposite molecular assemblies of tailored architecture. However, both the Langmuir-Blodgett technique and chemisorption from solution can be used only with certain classes of molecules. An alternative approach—fabrication of multilayers by consecutive adsorption of polyanions and polycations—is far more general and has been extended to other materials such as proteins or colloids. Because polymers are typically flexible molecules, the resulting superlattice architectures are somewhat fuzzy structures, but the absence of crystallinity in these films is expected to be beneficial for many potential applications.