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ARTICLES IN THE BOOK

  1. Atomic force microscope
  2. Atomic nanoscope
  3. Atom probe
  4. Ballistic conduction
  5. Bingel reaction
  6. Biomimetic
  7. Bio-nano generator
  8. Bionanotechnology
  9. Break junction
  10. Brownian motor
  11. Bulk micromachining
  12. Cantilever
  13. Carbon nanotube
  14. Carbyne
  15. CeNTech
  16. Chemical Compound Microarray
  17. Cluster
  18. Colloid
  19. Comb drive
  20. Computronium
  21. Coulomb blockade
  22. Diamondoids
  23. Dielectrophoresis
  24. Dip Pen Nanolithography
  25. DNA machine
  26. Ecophagy
  27. Electrochemical scanning tunneling microscope
  28. Electron beam lithography
  29. Electrospinning
  30. Engines of Creation
  31. Exponential assembly
  32. Femtotechnology
  33. Fermi point
  34. Fluctuation dissipation theorem
  35. Fluorescence interference contrast microscopy
  36. Fullerene
  37. Fungimol
  38. Gas cluster ion beam
  39. Grey goo
  40. Hacking Matter
  41. History of nanotechnology
  42. Hydrogen microsensor
  43. Inorganic nanotube
  44. Ion-beam sculpting
  45. Kelvin probe force microscope
  46. Lab-on-a-chip
  47. Langmuir-Blodgett film
  48. LifeChips
  49. List of nanoengineering topics
  50. List of nanotechnology applications
  51. List of nanotechnology topics
  52. Lotus effect
  53. Magnetic force microscope
  54. Magnetic resonance force microscopy
  55. Mechanochemistry
  56. Mechanosynthesis
  57. MEMS thermal actuator
  58. Mesotechnology
  59. Micro Contact Printing
  60. Microelectromechanical systems
  61. Microfluidics
  62. Micromachinery
  63. Molecular assembler
  64. Molecular engineering
  65. Molecular logic gate
  66. Molecular manufacturing
  67. Molecular motors
  68. Molecular recognition
  69. Molecule
  70. Nano-abacus
  71. Nanoart
  72. Nanobiotechnology
  73. Nanocar
  74. Nanochemistry
  75. Nanocomputer
  76. Nanocrystal
  77. Nanocrystalline silicon
  78. Nanocrystal solar cell
  79. Nanoelectrochemistry
  80. Nanoelectrode
  81. Nanoelectromechanical systems
  82. Nanoelectronics
  83. Nano-emissive display
  84. Nanoengineering
  85. Nanoethics
  86. Nanofactory
  87. Nanoimprint lithography
  88. Nanoionics
  89. Nanolithography
  90. Nanomanufacturing
  91. Nanomaterial based catalyst
  92. Nanomedicine
  93. Nanomorph
  94. Nanomotor
  95. Nano-optics
  96. Nanoparticle
  97. Nanoparticle tracking analysis
  98. Nanophotonics
  99. Nanopore
  100. Nanoprobe
  101. Nanoring
  102. Nanorobot
  103. Nanorod
  104. Nanoscale
  105. Nano-Science Center
  106. Nanosensor
  107. Nanoshell
  108. Nanosight
  109. Nanosocialism
  110. Nanostructure
  111. Nanotechnology
  112. Nanotechnology education
  113. Nanotechnology in fiction
  114. Nanotoxicity
  115. Nanotube
  116. Nanovid microscopy
  117. Nanowire
  118. National Nanotechnology Initiative
  119. Neowater
  120. Niemeyer-Dolan technique
  121. Ormosil
  122. Photolithography
  123. Picotechnology
  124. Programmable matter
  125. Quantum dot
  126. Quantum heterostructure
  127. Quantum point contact
  128. Quantum solvent
  129. Quantum well
  130. Quantum wire
  131. Richard Feynman
  132. Royal Society's nanotech report
  133. Scanning gate microscopy
  134. Scanning probe lithography
  135. Scanning probe microscopy
  136. Scanning tunneling microscope
  137. Scanning voltage microscopy
  138. Self-assembled monolayer
  139. Self-assembly
  140. Self reconfigurable
  141. Self-Reconfiguring Modular Robotics
  142. Self-replication
  143. Smart dust
  144. Smart material
  145. Soft lithography
  146. Spent nuclear fuel
  147. Spin polarized scanning tunneling microscopy
  148. Stone Wales defect
  149. Supramolecular assembly
  150. Supramolecular chemistry
  151. Supramolecular electronics
  152. Surface micromachining
  153. Surface plasmon resonance
  154. Synthetic molecular motors
  155. Synthetic setae
  156. Tapping AFM
  157. There's Plenty of Room at the Bottom
  158. Transfersome
  159. Utility fog

 



NANOTECHNOLOGY
This article is from:
http://en.wikipedia.org/wiki/Self-assembled_monolayer

All text is available under the terms of the GNU Free Documentation License: http://en.wikipedia.org/wiki/Wikipedia:Text_of_the_GNU_Free_Documentation_License 

Self-assembled monolayer

From Wikipedia, the free encyclopedia

 

Self assembled monolayers (SAMs) are surfaces consisting of a single layer of molecules on a substrate. Rather than having to use a technique such as chemical vapor deposition or molecular beam epitaxy to add molecules to a surface (often with poor control over the thickness of the molecular layer), self assembled monolayers can be prepared simply by adding a solution of the desired molecule onto the substrate surface and washing off the excess.

A common example is an alkane thiol on gold. Sulfur has particular affinity for gold, with a binding energy in the range of 2035 kcal/mol (85145 kJ/mol). An alkane with a thiol head group will stick to the gold surface and form an ordered assembly with the alkyl chains packing together due to van der Waals forces. For alkyl thiols on gold, the extended alkyl chains typically orient with an angle of ~30 degrees from the perpendicular of the substrate, and are assumed to be in a fully extended linear arrangement. There has been a great deal of work done determining the process by which alkyl thiol on gold assemblies are produced. It is generally thought that alkyl thiol molecules first bind to the gold surface in a 'lying down' position, where the alkyl chain tails of the molecules lie flat on the gold surface. The thiol interaction provides about 2030 kcal/mol (85130 kJ/mol) of driving force for the initial binding, which is modeled as a Langmuir binding isotherm. These binding events continue until the lying down molecules are dense enough on the surface to interact with each other. At some point the alkyl chains lift off the substrate and point outwards, tethered by the thiol anchor to the surface. There is a shift to a mixture of lying down molecules and island domains of upright alkyl chains, tilted at 30 degrees to the normal. At this stage binding kinetics become more complex and can no longer be modeled with a simple Langmuir binding isotherm. Over time the island domains merge and cover the bulk of the substrate, and the process can be compared to a 2-D crystallization process on a surface. Alkyl thiol SAMs exhibit grain boundaries and defects even after long periods of assembly. The initial stage of SAM formation usually takes minutes or less under the normal conditions of 0.1-10 mmol/L thiol concentration in a solvent. More ordering of the assembly can take place over days or months, depending on the molecules involved.

A variety of other self-assembled monolayers can be formed, although there is always debate about the degree to which systems self-assemble. Alkyl thiols are known to assemble on many metals, inluding silver, copper, palladium, and platinum. Alkyl silane molecules (e.g. octadecyltrichlorosilane) are another well-known example of self-assembly on silicon oxide surfaces and potentially be of greater technical relevance than alkyl thiol assembly on metals. Alkyl carboxylates are known to assemble on a variety of surfaces, such as aluminium and mica.

Retrieved from "http://en.wikipedia.org/wiki/Self-assembled_monolayer"