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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.


Papers
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Journal ArticleDOI
TL;DR: Self-assembled monolayers (SAMs) have been formed on disordered, polymeric substrates, such as polyethylene (PE) and polydimethylsiloxane (PDMS) as discussed by the authors.
Abstract: Self-assembled monolayers (SAMs) have been formed on disordered, polymeric substrates. On polyethylene (PE), preparation of the SAM entailed three steps: oxidation of the surface of the PE with an oxygen plasma; formation of a silicate layer anchored to the oxidized surface by reaction with SiCL; formation of an aikylsiloxane surface layer by adsorption of alkyltrichlorosilanes from the vapor phase, and reaction with SiOH groups (and adsorbed water) on the surface of the silicate layer. On poly(dimethylsiloxane) (PDMS), plasma oxidation produced a surface silicate layer that could be used for subsequent adsorption of an alkylsiloxane layer without additional steps. The wettability of these SAMs is similar to that of comparable SAMs formed by adsorption onto better defined substrates (silicon wafers and gold). Reaction of SAMs on PE or PDMS bearing terminal vinyl groups with an aqueous permanganate/periodate solution produced surfaces bearing carboxylic acid moieties.

164 citations

Journal ArticleDOI
01 Jul 1993-Langmuir
TL;DR: In this paper, the authors compare the reactivity of the surface organosulfur species generated from alkanethiols and dialkyl disulfides on gold surfaces.
Abstract: Chemisorption of alkanethiols, RSH, or dialkyl disulfides, RSSR, on gold gives ordered monolayers-l-S SAMs (self-assembled monolayers) formed from either precursor are believed to comprise the sattte species on the gold surface-gold(I) alkyl thiolate (RS-Aus+ on these predominately Au(111) surfaces) adsorbed epitaxially on the gold(0) substrate-but the only direct experimental eviderrce supporting this belief is the observation of indistinguishable S(2p) binding energies for both systems measured by X-ray photoelectron spectroscopy (XPS).0'z The objective of the work described in this paper was to compare the reactivity of the surface organosuHur species generated from alkanethiols and dialkyl disulfides in a iype of reaction we expected to be senstive to details of bonding to the surface-interchange of these surface organosulfur species with thiols or disulfides in solution. This study examined the reactivity of species formed on gold from an unsymmetrical disulfide LgSSMd (HO(CH21tr55(CHtsCFs; LB = long chain; Md = medium chain). We wanted to address two questions (Scheme I): (1) Are both halves of LgSSMd incorporated in the SAM to the same extent when a solution of this disufide is allowed to react with a bare gold surface? Is the snr\"e result observed on a surface already covered with an alkyl thiolate? (2) Do the hypothesized surface species, LgS-AuI and MdS-AuI, behave as independent entities in their reactions with species in solution, or are their reactivities

163 citations

Journal ArticleDOI
TL;DR: This paper describes a microfluidic immunoassay that is applicable to the parallel determination of multiple analytes and that requires only a few microliters of sample and relies on a microchannel network that achieves serial dilution of analytes.
Abstract: This paper describes a microfluidic immunoassay that is applicable to the parallel determination of multiple analytes and that requires only a few microliters of sample. This assay relies on a microchannel network that achieves serial dilution of analytes; this network replaces manual dilutions employed in traditional immunoassays and enables the analysis of multiple analytes simultaneously. The immunoassay was demonstrated by an analysis of concentrations of antibodies against the HIV viral proteins gp120 and gp41 in human serum.

163 citations

Journal ArticleDOI
19 Mar 1999-Langmuir
TL;DR: Elastomeric membranes that contained regular arrays of well-defined holes were formed by spin-coating a prepolymer onto a photolithographically defined master to produce structures with greater complexity than those generated with a single membrane.
Abstract: Elastomeric membranes that contained regular arrays of well-defined holes were formed by spin-coating a prepolymer onto a photolithographically defined master. These membranes were used as dry resists or as masks in dry lift-off to produce simple features as small as 5 μm on both planar and nonplanar surfaces. These procedures were “dry” because the membranes conformed and sealed reversibly to surfaces: no solvent was required either to deposit the membrane or to remove it from the substrate. A variety of materials, some of which would be difficult to pattern using conventional methods, were patterned using this technique. These materials included metals, sol−gels, hydrogels, biological macromolecules, and organometallic molecules. The membranes were used in sequential, dry-lift off steps to produce structures with greater complexity than those generated with a single membrane.

162 citations


Cited by
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[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
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 …

33,785 citations

28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组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�ly.
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。

18,940 citations

Journal ArticleDOI
TL;DR: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols used xiii 1.
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

14,171 citations

Journal ArticleDOI
05 Feb 2009-Nature
TL;DR: The direct synthesis of large-scale graphene films using chemical vapour deposition on thin nickel layers is reported, and two different methods of patterning the films and transferring them to arbitrary substrates are presented, implying that the quality of graphene grown by chemical vapours is as high as mechanically cleaved graphene.
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.

10,033 citations

Journal ArticleDOI
29 Aug 1997-Science
TL;DR: In this article, a general approach for multilayers by consecutive adsorption of polyanions and polycations has been proposed and has been extended to other materials such as proteins or colloids.
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.

9,593 citations