Inorganic nanocrystals: Synthesis and shape control

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Inorganic nanocrystals Synthesis and shape
control
Trina Mandal Whitmire research Group
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Inorganic nanocrystals of interest
Transition metal and heavy metal carbides,
nitrides, phosphides, arsenides,
oxides, sulfides, selenides and telurides
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Why Inorganic nanocrystals?

• Different property from bulk
• Change in property with size and shape
• High surface to volume ratio
• Building blocks for advanced nano-devices

Variation of color by varying sizes of
nanocrystals
www.chem.rochester.edu
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Applications and future prospects

• Biological labeling
• Photovoltaic device
• Light emitting diodes
• Single electron transistor

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Methods of synthesis
www.chem.umn.edu/netstep/2007/january/3stein.ht
ml
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Liquid phase bottom-up synthesis of nanoparticles
Surfactant molecule
Surfactant surrounded nanoparticles
Reaction setup
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Research at Whitmire group

• CdS, PbS, semiconductor nanocrystals ( biological
  diagnostics)
• FeOx, Fe3P, MnOx, In2O3 magnetic nanocrystals
  (photocatalysis)
• Hybrid nanostructures FeMnOx

200 nm
FeP
FeOx
FeMnOx
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single source molecular precursor technique

• More control over reaction conditions
• One step synthesis
• Unusual crystal growth selectivity

Single-source precursor for Fe3P Preformed Fe-P
bond, both Fe and P present in the same molecule
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Instrumental set-up

• Steps
• Precursor solution in 3-necked flask
• Argon flow-inert atmosphere
• Heating the solution
• Collecting and washing the precipitate

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Synthesis of precursors for PbS and CdS
A
Salicylic acid
Picolinic acid
Dipicolinic acid
Th
Thiourea
Thiosemicarbazide
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Single-source molecular precursor for PbS
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Single-source molecular precursor for CdS
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Method of synthesis of nanocrystals

• Suspension of precursor in surfactant solution
• Maintaining inert atmosphere
• Varying temperature, time, concentration,
  surfactants
• Isolation and washing

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Nanocrystal shape evolution with time of growth
2 hrs
Scale bar 1µm
6 hrs
Scale bar 5 µm
12 hrs
Scale bar 3 µm
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Variation of shape with surfactant
100 nm
50 nm
Precursor Pb(pic)2(ts)2
PrecursorPb(Hsal)2(tu)2
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CdS nanocrystals
20 nm
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Challenges and future work

• Complete control of reaction to produce
  nanocrystals of uniform shape and sizes
• Understand and control the crystal growth
• Make nanocrystals water soluble for application
  purpose
• Extend work towards other materials

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conclusions

• Inorganic nanocrystals show size and shape
  dependent property
• Liquid phase colloidal synthesis
• Single-source precursor-better control of
  reaction conditions
• Surfactant, temperature, concentration affect
  shape and size of nanoparticle