This lecture was delivered at Punjab University, Chandigarh during International Nano-Sci-Tech Conference in Feb. 2012.

1. Fabrication of Nanomaterials by
Chemical Route: An Overview
Hardev Singh Virk
Professor Emeritus, Eternal
University, Baru Sahib (HP), India

2. Changing Idea into Reality
Eric Drexler of MIT, the Chemist, established
the modern field of nanotechnology, with a
draft of his seminal Ph.D. thesis in the mid
1980s. His 1991 doctoral thesis at MIT was
revised and published as the book
"Nanosystems, Molecular Machinery
Manufacturing and Computation" (1992),
which received the Association of American
Publishers award for Best Computer Science
Book of 1992.

3. Routes to Nanotechnology
• Physical, chemical, biological and nature’s self
assembly.
• Top-down and bottom-up approaches.
• Chemical route to nanotechnology is simpler,
cheaper and allows fabrication at bench top
conditions.
• Reverse micelles (microemulsions route) is a
versatile method to produce a variety of
nanoparticles.

4. Bottom Up Techniques Used
• Reverse micelles, co-precipitation, solvo-
thermal, sol-gel and seed growth technique.
• Quantum dots, nanorods and nanoneedles of
Barium Carbonate, Barium Oxalate, Iron
Oxalate, Barium hexaferrite, Zinc Oxide,
Cadmium Sulphide, Cadmium Oxide and Silver
prepared for characterization using SEM, TEM,
UV-Vis, FTIR, XRD, TGA & VSM techniques.

5. Synthesis of Barium Carbonate
Nanorods using ME Technique
• Microemulsion A (25ml) prepared by adding 2.5ml of 0.1M
aqueous solution of barium nitrate,3.5ml of n-butanol as co-
surfactant, 15ml of iso-octane as the non-polar solvent and
4.20g of CTAB as surfactant.
• Microemulsion B (25ml) prepared by adding 2.5ml of 0.1M
aqueous solution of ammonium carbonate, 3.5ml of n-
butanol as co-surfactant, 15ml of iso-octane as the non-polar
solvent and 4.20g of CTAB as surfactant.
• A and B were stirred separately, mixed slowly and then kept
for stirring overnight. The final product was separated by
centrifugation and washed with 1:1 mixture of chloroform
and methanol and dried at room temperature.

6. SEM image of Barium Carbonate
Nanorods

7. TEM images of Barium Carbonate
Nanorods

8. TEM images of Iron Oxalate and
Barium Oxalate Nanocrystals

9. Synthesis of CdO Quantum dots
• Cadmium oxide is an n-type semiconductor
with applications in photodiodes, photo-
voltaics, liquid crystal displays, IR detectors,
storage batteries, phosphors and pigments.
• Synthesis of CdO quantum dots was achieved
by sintering 4 g of CdO powder at 900°C in a
muffle furnace for 5 h and then quenching
into 7 wt% aqueous ethyl alcohol kept at ice
cold temperature, followed by stirring.

10. TEM image of CdO Quantum Dots
(Mean Diameter 9.3nm)

11. Heavy Ion Irradiation Effects using
90 MeV carbon ion beam (dia.27nm)

12. Enhancement in the size of the
Quantum dots
• Enhancement in the size of the quantum dots
with ion beam irradiation has been reported
for Co, Au, Sn and Pt by some other groups.
• Several models have been developed to
explain the complex interaction between SHI
and matter. The thermal spike model, which
predicts the formation of a molten track
round the ion path, is one plausible
explanation for shape change of metallic
nanocrystals.

13. Conversion of Quantum Dots ofConversion of Quantum Dots of
CdO to Nanorods using EDACdO to Nanorods using EDA

14. Synthesis of CdS Nanoparticles
• The CdS nanoparticles were synthesized by
using the reverse micellar route.
• ME(A):15 ml cyclohexane, 4.20 gm surfactant
(CTAB), 2.5 ml of 0.1M aqueous Na2S.9H2O,
3.5ml n-butanol or n-hexanol as co-surfactants
• ME (B): The same solvents but by replacing
Na2S.9H2O with CdCl2.5H2O of equal molarity
(0.1M). A & B were mixed together by shaking
to obtain the yellow precipitates of CdS.

15. CdS Nanocrystals(CTAB+n-butanol)

16. CdS Nanoneedles(CTAB+n-
hexanol)

17. CdS Quantum Dots( molar ratio=5)

18. CdS Nanorods (molar ratio=15)

19. Synthesis of ZnO Nanocrystals
• Zinc oxide nanocrystals were prepared by
quenching sintered ZnO powder at 800C with
ice - cold ethanol and polyvinyl alcohol.
Addition of ethylenediamine (EDA) to reaction
mixture produced nanorods of ZnO and EDA
acts as a shape directing agent.
• XRD spectrum reveals hexagonal wurtzite
structure of ZnO nanocrystals.
• SEM micrographs show clustering phenomena

20. SEM image of ZnO Nanocrystals in
Ethanol and Nanorod(adding EDA)

21. Synthesis of Silver Nanoparticles by
Seed Growth Technique
• Seed solution was prepared by keeping silver
nitrate [AgNO3] = 0.5mM and sodium citrate
[Na3Cit] =0.5mM, followed by the addition of
0.6 ml of aqueous sodium borohydride
([NaBH4] = 0.1mol dm-3
) solution under
constant stirring. A growth solution consists of
[TritonX-100] = 1mM in 5ml water along with
[AgNO3] = 0.5mM, 0.2ml of ascorbic acid
aqueous solution (0.1M), and different
quantities of prepared seed solution.

22. TEM image of Ag quantum dots
and embedded nano particles

23. Electrochemical Synthesis
• Electrochemistry has been used to fabricate
nanowires and heterojunctions of Cu, Cu-Se
and Cd-S. The results of our investigations can
be exploited for fabrication of nanodevices for
application in opto-electronics and nano-
electronics. During failure of our Experiments,
exotic patterns (nanoflowers, nanocrystals,
nanobuds) were produced under nature’s self
assembly.

24. Electrolytic CellElectrolytic Cell

25. Electrodeposition of Nanowires
• The electrolyte used is CuSO4.5H2O acidic
solution. The rate of deposition depends
upon current density, inter-electrode
distance, cell voltage, electrolyte
concentration and temperature etc. The
technique has been tested for growth of
nanowires of Copper and heterojunctions of
Cu-Se and Cd-S electrochemically using anodic
alumina and polymer templates (Nuclepore
Filters).

26. Atomic Force Microscope(NT-MDT)

27. AFM image of hexagonal pores ofAFM image of hexagonal pores of
Anodic Alumina Membrane (AAM)Anodic Alumina Membrane (AAM)

28. SEM Images of Cu Nanowires usingSEM Images of Cu Nanowires using
Electrodeposition TechniqueElectrodeposition Technique

29. Capping Effect of Current VariationCapping Effect of Current Variation

30. Copper Lillies grown due to over-Copper Lillies grown due to over-
deposition of Copper in AAMdeposition of Copper in AAM

31. Copper Nanoflowers grown in
Polymer Template (100nm pores)

32. Copper Marigold (Gainda) Flower

33. A Garden of Copper NanoflowersA Garden of Copper NanoflowersA Garden of Copper NanoflowersA Garden of Copper Nanoflowers

34. SEM micrograph of Nanocrystals ofSEM micrograph of Nanocrystals of
Polycrystalline CopperPolycrystalline Copper

35. XRD Spectrum of polycrystallineXRD Spectrum of polycrystalline
Copper nanocrystalsCopper nanocrystals
Position [°2Theta] (Copper (Cu))
10 20 30 40 50 60 70
Counts
0
20000
40000
60000
36.637[°]
38.283[°]
43.461[°]
45.448[°]
48.920[°]
50.580[°]
54.304[°]
54.956[°]
64.809[°]
74.299[°]
KK1

36. XRD spectrum of Cu nanowiresXRD spectrum of Cu nanowires
Position [°2Theta] (Copper (Cu))
30 40 50 60 70 80 90
Counts
0
400
1600
Cu polycrystalline

37. SEM Image of CdS NanowiresSEM Image of CdS Nanowires

38. HRTEM image showing CdSHRTEM image showing CdS
Nanowire & HeterojunctionsNanowire & Heterojunctions

39. I-V plot of CdS Nanowire arraysI-V plot of CdS Nanowire arrays
showing RTD characteristicsshowing RTD characteristics

40. SEM image of Cu-Se NanowiresSEM image of Cu-Se Nanowires

41. Cu-Se nanowires exhibit p-nCu-Se nanowires exhibit p-n
junction diode characteristicsjunction diode characteristics

42. Role of Nanowires for Next-
Generation Electronics
• The chemical and physical characteristics of
nanowires, including composition, size,
electronic and optical properties, can be
rationally controlled during synthesis in a
predictable manner, thus making these
materials attractive building blocks for
assembling electronic and optoelectronics
nanosystems.

43. Some Observations & Remarks
• Nanotechnology will be the driving force for
next technology revolution.
• Nanowires open door to a wonderland where
the next generation electronics would emerge.
• Scope for innovating new synthesis method
and complex functional nanostructures.
• New device and interconnect concepts will
emerge from horizon, driven by materials
synthesis.

44. Our Publications
• My website: http:// drhsvirk.weebly.com
for list of our published research papers.
Go to www.docstoc.com for purchase of
reprints.
Free download of Review Paper on Nanowires:
visit: ttp://www.intechopen.com/articles/show
• Chapter 20 of Book “Nanowires - Implementations
and Applications”, InTech Open, Abbass Hashim
(Ed).

45. Thank
You !!!