X
Clickhere
to START
X
*What Are Nanocrystals???
*How Are Nanocrystals Prepared???
*How To obtain Silicon
Nanocrystals???
1-Electrochemical Etc...
X
*A nanocrystal is a crystalline nanoparticle.
*Some sources define it as any single crystalline
nanomaterial with at lea...
X
*Silicon nanocrystals can provide efficient light
emission even while bulk Silicon can't!
*Nanocrystals embedded in soli...
*The traditional way :
Prepare nanocrystals of a new material involved
choosing molecular precursors, surfactants, and
sol...
X
*Silicon nanocrystals are prepared using
electrochemical etching of silicon wafers.
X
*The procedure takes place under normal
atmosphere, in Teflon chambers with electrical
current flowing through the elect...
X
*Disadvantage of this method: The natural
tendency of oxide-covered silicon nanocrystals
to form strongly bound large ag...
X
1: Electrochemical etching
*The electrochemical etching, is based on the use of
hydrofluoric acid.
*Fluorine ions attack...
*This dissolution forms voids in the silicon wafers,
resulting in a porous structure with small chunks of
silicon consisti...
X
2: Pulverization
*Obtaining the sample in the powder-like form,
consisting of larger agglomerates of small silicon
nanoc...
X
*Synthesis of Water-Soluble Blue Photoluminescent Silico
http://research.ncku.edu.tw/re../articles/e/20091113/2.html
*Na...
X
of 13

Nanocrystal synthesis

*What Are Nanocrystals??? *How Are Nanocrystals Prepared??? *How To obtain Silicon Nanocrystals??? 1-Electrochemical Etching 2-Pulverization
Published on: Mar 3, 2016
Published in: Science      
Source: www.slideshare.net


Transcripts - Nanocrystal synthesis

  • 1. X Clickhere to START
  • 2. X *What Are Nanocrystals??? *How Are Nanocrystals Prepared??? *How To obtain Silicon Nanocrystals??? 1-Electrochemical Etching 2-Pulverization *References
  • 3. X *A nanocrystal is a crystalline nanoparticle. *Some sources define it as any single crystalline nanomaterial with at least one dimension ≤ 100 nm. *others define it as a nanoparticle with any kind of crystalline structure. e.g., multiply twinned configurations.
  • 4. X *Silicon nanocrystals can provide efficient light emission even while bulk Silicon can't! *Nanocrystals embedded in solids can exhibit much more complex melting behavior than conventional solids!
  • 5. *The traditional way : Prepare nanocrystals of a new material involved choosing molecular precursors, surfactants, and solvents using optimized reaction conditions causing the atoms to self-assemble into monodisperse nanocrystals. X *The newer and simpler strategy: Use of preformed nanocrystals as templates and chemical transformation to change the composition.
  • 6. X *Silicon nanocrystals are prepared using electrochemical etching of silicon wafers.
  • 7. X *The procedure takes place under normal atmosphere, in Teflon chambers with electrical current flowing through the electrolyte. *The final product are oxide-covered silicon nanocrystals.
  • 8. X *Disadvantage of this method: The natural tendency of oxide-covered silicon nanocrystals to form strongly bound large agglomerates of tiny nanocrystals!
  • 9. X 1: Electrochemical etching *The electrochemical etching, is based on the use of hydrofluoric acid. *Fluorine ions attack silicon surface, causing its dissolution into hexafluorosilicate ions.
  • 10. *This dissolution forms voids in the silicon wafers, resulting in a porous structure with small chunks of silicon consisting of nanocrystals between the pores. *Ethanol, which is added in order to increase wettability and facilitate the penetration of the etching solution into the tiny pores. *The etching procedure yields a layer of interconnected silicon nanocrystals. X
  • 11. X 2: Pulverization *Obtaining the sample in the powder-like form, consisting of larger agglomerates of small silicon nanocrystals. The powder can be stored for a long time in air without any detrimental effect on its properties.
  • 12. X *Synthesis of Water-Soluble Blue Photoluminescent Silico http://research.ncku.edu.tw/re../articles/e/20091113/2.html *Nanocrystal http://en.wikipedia.org/wiki/Nanocrystal *Nanocrystalline Silicon for Nanophotonics http://nanotech.fzu.cz/26/index.php?file=1 *Journal of the Korean Physical Society, Vol. 42, February 2003 Synthesis of Silicon Nanocrystals By: Cho Joon Wo & Lee So Jin *Nanocrystal Synthesis By: Nathanael Smith
  • 13. X

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