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  1. Atomic force microscope
  2. Atomic nanoscope
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  5. Bingel reaction
  6. Biomimetic
  7. Bio-nano generator
  8. Bionanotechnology
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  15. CeNTech
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  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
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  63. Molecular assembler
  64. Molecular engineering
  65. Molecular logic gate
  66. Molecular manufacturing
  67. Molecular motors
  68. Molecular recognition
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  70. Nano-abacus
  71. Nanoart
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  131. Richard Feynman
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  133. Scanning gate microscopy
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  138. Self-assembled monolayer
  139. Self-assembly
  140. Self reconfigurable
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  142. Self-replication
  143. Smart dust
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  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/Molecular_logic_gate

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 

Molecular logic gate

From Wikipedia, the free encyclopedia

 

A molecular logic gate in nanotechnology is a logic gate on a molecular level. Much academic research is dedicated to the development of these systems and several prototypes now exist. Because of their potentional utility in simple arithmetic these systems are also called moleculators.


Molecular logic gates work with input signals based on chemical processes and with output signals based on spectroscopy. One of the earlier water solution-based systems exploit the chemical behavior of compounds A and B in scheme 1 [1].


 

Scheme 1. Molecular logic gates de Silva 2000


Compound A is a push-pull olefin with the top receptor containing four carboxylic acid anion groups (and non-disclosed counter cations) capable of binding to calcium. The bottom part is a quinoline molecule which is a receptor for hydrogen ions. The logic gate operates as follows.

Without any chemical input of Ca2+ or H+, the chromophore shows a maximum absorbance in UV/VIS spectroscopy at 390 nm. When calcium is introduced a blue shift takes place and the absorbance at 390 nm decreases. Likewise addition of protons causes a red shift and when both cations are in the water the net result is absorption at the original 390nm. This system represents a XNOR logic gate in absorption and a XOR logic gate in transmittance.

In compound B the bottom section now contains a tertiary amino group also capable of binding to protons. In this system fluorescence only takes place when both cations are present and therefore the system represents an AND logic gate.

With both systems run in parallel and with monitoring of transmittance for system A and fluorescence for system B the result is a half-adder capable of reproducing the equation 1+1=2.

In a modification of system B not two but three chemical inputs are simultaneously processed in an AND logic gate [2].An enhanced fluorescence signal from the compound depicted below is obtained only in the presence of hydrogen, zinc and sodium ions through interaction with respectively the amine, carboxyl and crown ether receptors and this system can be potentially applied in disease screening (lab-on-a-molecule) because these ions are all physiologically relevant.

Scheme 2. Lab On A Molecule

In another XOR logic gate system the chemistry is based on the pseudorotaxane [3] depicted in scheme 3. In organic solution the electron deficient diazapyrenium salt (rod) and the electron rich 2,3-dioxynaphthalene units of the crown ether (ring) self-assemble by formation of a charge transfer complex.

An added tertiary amine like tributylamine forms a 1:2 adduct with the diazapyrene and the complex gets dethreaded. This process is accompanied by an increase in emission intensity at 343 nm resulting from freed crown ether. Added trifluoromethanesulfonic acid reacts with the amine and the process is reverted. Excess acid locks the crown ether by protonation and again the complex is dethreaded.

Scheme 3. Pseudorotaxane logic gate

A full adder system based on fluorescein [4] is able to compute 1+1+1=3.

References

  1.   Proof-of-Principle of Molecular-Scale Arithmetic A. Prasanna de Silva and Nathan D. McClenaghan J. Am. Chem. Soc.; 2000; 122(16) pp 3965 - 3966; Abstract
  2.   Communicating Chemical Congregation: A Molecular AND Logic Gate with Three Chemical Inputs as a "Lab-on-a-Molecule" Prototype David C. Magri, Gareth J. Brown, Gareth D. McClean, and A. Prasanna de Silva J. Am. Chem. Soc.; 2006; 128(15) pp 4950 - 4951; (Communication) Abstract
  3.   Logic Operations at the Molecular Level. An XOR Gate Based on a Molecular Machine Alberto Credi, Vincenzo Balzani, Steven J. Langford, and J. Fraser Stoddart J. Am. Chem. Soc.; 1997; 119(11) pp 2679 - 2681; (Article) Abstract
  4.   A Molecular Full-Adder and Full-Subtractor, an Additional Step toward a Moleculator David Margulies, Galina Melman, and Abraham Shanzer J. Am. Chem. Soc.; 2006; 128(14) pp 4865 - 4871; (Article) DOI: 10.1021/ja058564w
Retrieved from "http://en.wikipedia.org/wiki/Molecular_logic_gate"