This is all about on the topic of synthesis of nanomaterials and the file gives information about the materails scienve

1. Synthesis Of Nano Materials
Subject: Methods and Techniques of Experimental Physics
By
Dr. Hafiz Naeem-ur-Rahman

2. Introduction
 Nanomaterials describe, in principle, materials of which a
single unit is sized (in at least one dimension) between 1
and 1000 nanometres.
 Biological systems often feature natural, functional
nanomaterials. The structure of foraminifera and viruses
(capsid), the wax crystals covering a lotus or nasturtium
leaf, spider and spider-mite silk are few examples of natural
nanomaterials.

3.  Natural inorganic nanomaterials occur through crystal
growth in the diverse chemical conditions of the earth's
crust. For example clays display complex nanostructures
due to anisotropy of their underlying crystal structure, and
volcanic activity can give rise to opals, which are an
instance of a naturally occurring photonic crystals due to
their nanoscale structure.
Introduction

5. Photonic Crystals
 A photonic crystal is a periodic optical nanostructure that
affects the motion of photons. They are used to
manipulate light flow. Used to form colour changing
paints and inks.

6. Synthesis
 Includes two methods
 Bottom Up Approach
 Top Down Approach

7. Top Down
 Start with bulk material and “cut away material “ to
make what you want.
 Examples:
 ATTRITION: In attrition, macro- or micro-scale
particles are ground in a ball mill, a planetary ball mill,
or other size-reducing mechanism. The resulting
particles are air classified to recover nanoparticles.

8. Top Down
 Lithography : It is a wafer scale process to prepare
homogenous 1D,2D or 3D nanomaterials.
 The method combines the advantages of both top down
and bottom up approaches and is a two step process :
 The preparation of colloidal crystal mask (CCM) made of nano
spheres.
 The decomposition of desired material through the mask.
 The mask is then removed and the layer keeps the ordered pattern
of the mask interstices.

9. Bottom Up
 Building what you want by assembling it from building
blocks (Such as atoms and molecules).
 Controlled
 Controlled Processes involve the controlled delivery of
the constituent atoms or molecules to the site(s) of
nanoparticle formation such that the nanoparticle can
grow to a prescribed sizes in a controlled manner.

10. Bottom Up
 Bottom up approach are further classified into 1.)
Gas (Vapor) Phase Fabrication: Pyrolysis
2.) Liquid Phase Fabrication: Solvothermal Reaction, Sol-
gel.

11. Bottom Up Approach Types

12. Simplest method of making nanoparticle in the form
of powder
Various types of mills
• Planetary
• Vibratory
• Rod
• Tumbler
HIGH ENERGY BALL
MILLING

14. Consists of a container filled with hardened steel or
tungsten carbide balls
Material of interest is fed as flakes
2:1 mass ratio of balls to materials
Container may be filled with air or inert gas
Containers are rotated at high speed around a central
axis
Material is forced to the walls and pressed against the
walls

15. Control the speed of rotation and duration of milling-
grind material to fine powder( few nm to few tens of
nm)
Some materials like Co, Cr, W, Al-Fe, Ag-Fe etc are
made nanocrystalline using ball mill.

17. To form or arrest nanoparticles in glass
Glass – amorphous solid, lacking symmetric
arrangement of atoms/molecules
Metals , when cooled at very high cooling rates (10⁵-
10⁶ K/s) can form amorphous solids- metallic glasses
Mixing molten streams of metals at high velocity with
turbulence- form nanoparticles
Ex: a molten stream of Cu-B and molten stream of Ti
form nanoparticles of TiB₂
MELT MIXING

18. Pyrolysis
 In pyrolysis, is a process in which a thin film is deposited by spraying a
solution on a heated surface, where the constituents react to form a
chemical compound. The chemical reactants are selected such that the
products other than the desired compound are volatile at the
temperature of deposition
 The advantages of vapor phase pyrolysis include it being a simple
process, cost effective, a continuous operation with high yield.

19. Solvothermal Process
 Precursors are dissolved in hot solvents (e.g., n-butyl
alcohol) and solvent other than water can provide milder
and friendlier reaction conditions. If the solvent is water
then the process is referred to as hydrothermal
method.
 It is synthesis method for growing for crystals from a non
aqueous solution in a autoenclave (a thick walled steel
vessel) at high temperature ( 400 deg.C) and pressure.

20. Sol-Gel
 The sol-gel process is a wet-chemical technique (also
known as chemical solution deposition) widely used
recently in the fields of materials science and ceramic
engineering.

21. Steps Include
 Formation of stable sol.
 Gelation
 Gel aging into a solid mass. This causes contraction of the
gel network, also phase transformations and Ostwald
ripening.
 Drying of the gel to remove liquid phases. This can lead
to fundamental changes in the structure of the gel.

22.  Nanoparticles synthesized by chemical methods form “colloids”
 Two or more phases (solid, liquid or gas) of same or different materials co-exist
with the dimensions of at least one of the phases less than a micrometre
 May be particles, plates or fibres
 Nanomaterials are a subclass of colloids, in which the dimensions of colloids is in
the nanometre range
COLLOIDS AND COLLOIDS IN
SOLUTION

24. Reduction of some metal salt or acid
Highly stable gold particles can be obtained by
reducing chloroauric acid (HAuCl₄)with tri sodium
citrate(Na₃C₆H₅O₇)
HAuCl₄+ Na₃C₆H₅O₇ Au ⁺+ C₆H₅O₇⁻+ HCl+3 NaCl
Metal gold nanoparticles exhibit intense
red, magenta etc., colours depending upon the
particle size
SYNTHESIS OF METAL NANOPARTICLES BY
COLLOIDAL ROUTE

26. Gold nanoparticles can be stabilised by repulsive
Coloumbic interactions
Also stabilised by thiol or some other capping
molecules
In a similar manner, silver, palladium, copper and few
other metal nanoparticles can be synthesized.

27. Wet chemical route using appropriate salts
Sulphide semiconductors like CdS and ZnS can be
synthesized by coprecipitation
To obtain Zns nanoparticles, any Zn salt is dissolved in
aqueous( or non aqueous) medium and H₂S is added
ZnCl₂+ H₂S ZnS + 2 HCl
SYNTHESIS OF SEMI-CONDUCTOR
NANOPARTICLES BY COLLOIDAL ROUTE

28. Steric hindrance created by “chemical capping”
Chemical capping- high or low temperature
depending on the reactants
High temp reactions- cold organometallic reactants
are injected in solvent like
trioctylphosphineoxide(TOPO) held at > 300ºC
Although it Is a very good method of synthesis, most
organometallic compounds are expensive.

29. 2types of materials or components- “sol” and “gel”
M. Ebelman synthesized them in 1845
Low temperature process- less energy consumption
and less pollution
Generates highly pure, well controlled ceramics
Economical route, provided precursors are not
expensive
Possible to synthesize
nanoparticles, nanorods, nanotubes etc.,
SOL GEL METHOD

30. Sols are solid particles in a liquid- subclass of colloids
Gels – polymers containing liquid
The process involves formation of ‘sols’ in a liquid and
then connecting the sol particles to form a network
Liquid is dried- powders, thin films or even monolithic
solid
Particularly useful to synthesize ceramics or metal
oxides

32. Hydrolysis of
precursors
condensation
polycondensation
Precursors-tendency to form gels
Alkoxides or metal salts
Oxide ceramics are best synthesized by sol gel route

33. For ex: in SiO₄, Si is at the centre
and 4 oxygen atoms at the apexes
of tetrahedron
Very ideal for forming sols
By polycondensation process
sols are nucleated and sol-gel is formed

35. Simple techniques
Inexpensive instrumentation
Low temperature (<350ºC) synthesis
Doping of foreign atoms (ions) is possible during
synthesis
Large quantities of material can be obtained
Variety of sizes and shapes are possible
Self assembly or patterning is possible
ADVANTAGES

36. BIOLOGICAL
METHODS

37. Green synthesis
3 types:
1.Use of microorganisms like fungi, yeats(eukaryotes)
or bacteria, actinomycetes(prokaryotes)
2. Use of plant extracts or enzymes
3.Use of templates like DNA, membranes, virusesand
diatoms

38. Microorganisms are capable of interacting with
metals coming in contact with hem through their cells
and form nanoparticles.
The cell- metal interactions are quite complex
Certain microorganisms are capable of separating
metal ions.
SYNTHESIS USING MICROORGANISMS

39. Pseudomonas stuzeri Ag259 bacteria are commonly found
in silver mines.
Capable of accumulating silver inside or outside their cell
walls
Numerous types of silver nanoparticles of different shapes
can be produced having size <200nm intracellularly
Low concentrations of metal ions (Au⁺,Ag⁺ etc) can be
converted to metal nanoparticles by Lactobacillus strain
present in butter milk.

40. Fungi – Fusarium oxysporum challenged with gold or
silver salt for app. 3 days produces gold or silver
nanoparticles extracellularly.
Extremophilic actinomycete Thermomonospora sp.
Produces gold nanoparticles extracellularly.
Semiconductor nanoparticles like CdS, ZnS, PbS
etc., can be produced using different microbial
routes.

41. Sulphate reducing bateria of the family
Desulfobacteriaceae can form 2-5nm ZnS nanoparticle.
Klebsiella pneumoniae can be used to synthesize CdS
nanoparticles.
when [Cd(NO₃)₂] salt is mixed in a solution containing
bacteria and solution is shaken for about1 day at
~38ºC ,CdS nanoparticle in the size range ~5 to 200 nm
can be formed.

42. Leaves of geranium plant ( Pelargonium graveolens)
have been used to synthesize gold nanoparticles
Plant associated fungus- produce compounds such as
taxol and gibberellins
Exchange of intergenic genetics between
fungus and plant.
Nanoparticles produced by fungus and
leaves have different shapes and sizes.
SYNTHESIS USING PLANT EXTRACTS

43. Nanoparticles obtained using Colletotrichum sp.,
fungus is mostly spherical while thoe obtained
from geranium leaves are rod and disk shaped.

44. finely crushed leaves
(Erlenmeyer flask)
boiled in water ( 1min)
cooled and decanted
added to HAuCl₄ aq. Solution
gold nanoparticles within a minute

45. CdS or other sulfide nanoparticles can be synthesized
using DNA.
DNA can bind to the surface of growing
nanoparticles.
ds Salmon sperm DNA can be sheared to an average
size of 500bp.
Cadmium acetate is added to a
desired medium like water, ethanol,
propanol etc.
SYNTHESIS USING DNA

46. Reaction is carried out in a glass flask- facility to purge
the solution and flow with an inert gas like N₂.
Addition of DNA should be made and then Na₂S can
be added dropwise.
Depending on the concentrations of cadmium
acetate, sodium chloride and DNA ,nanoparticles of
CdS with sizes less than ~10 nm can be obtained.
DNA bonds through its negatively charged PO₄ group
to positively charged (Cd⁺) nanoparticle surface.

47. Various inorganic materials such as carbonates,
phosphates, silicates etc are found in parts of bones,
teeth, shells etc.
Biological systems are capable of integrating with
inorganic materials
Widely used to synthesize nanoparticles
USE OF PROTEINS, TEMPLATES LIKE
DNA , S- LAYERS ETC

48. Ferritin is a colloidal protein of nanosize.
Stored iron in metabolic process and is abundant in
animals.
Capable of forming 3 dimensional hierarchical
structure.
24 peptide subunits – arranged in such a way that
they create a central cavity of ~6 nm.
Diameter of polypeptide shell is 12 nm.
Ferritin can accommodate 4500 Fe atoms.
FERRITI
N

50. Ferritin without inorganic matter in its cavity is called
apoferritin and can be used to entrap desired
nanomaterial inside the protein cage.
Remove iron from ferritin to form apoferritin
Introduce metal ions to form metal nanoparticles
inside the cavity

52. Horse spleen ferritin
diluted with sodium
acetate buffer (placedin
dialysis bag)
sodium+ thioglycolic
acetate acid
dialysis bag kept under
N₂ gas flow for 2-3 hrs
PROCEDURE TO CONVERT FERRITIN TO
APOFERRITIN

53. solution needs to be
replaced from time to time
for 4-5 hrs.
saline for 1 hr
refreshed saline
for 15-20 hrs
APOFERRITIN

54. APOFERRITIN
mixed with NaCl and N-tris
methyl-2-aminoethanosulphonic
acid (TES)
aq. Cadmium acetate added and
stirred with constant N₂ spurging
aq. Solution of Na₂S is added twice
with 1 hr interval.

55. Applications
 Drug delivery systems
 Anti-corrosion barrier coatings
 UV protection gels
 Lubricants and scratch free paints
 New fire retardant materials
 New scratch/abrasion resistant materials
 Superior strength fibres and films