Synthesis of nanomaterials

Synthesis of nanomaterials Top down Approach

1. Synthesis of Nanomaterials
Top-down Bottom-up
R.Gandhimathi

2. ▪Nanomaterial-Asingleunit,sizedbetween1-100nm
▪E.g.,metalnanoparticles,quantumdots(QDs),carbon
nanotubes(CNTs),graphene,andtheircomposites
▪Itpossessuniquephysiochemicalpropertieslike
ultrasmallsize,largesurfacearea,andtheabilityto
targetspecificactionswhicharisefromtheirnanoscale
dimensions
▪Nanomaterialscanoccurnaturally,becreatedasthe
by-productsofcombustionreactions,orbeproduced
purposefullythroughengineeringtoperforma
specializedfunction
https://www.nature.com/ar
ticles/s41392-019-0068-3
Nano materials

3. ▪Nanomaterials/nanoparticlesarepreparedthroughdiverserangeofsynthesis
approacheslikelithographictechniques,ballmilling,etching,andsputtering
▪Synthesis/Fabricationofnanomaterialswithtailoredpropertiesinvolvethecontrolof
size,shape,structure,compositionandpurityoftheirconstituents
▪Hencethenanomaterialpropertiescanbetunedasdesiredviapreciselycontrollingthe
size,shape,synthesisconditions,andappropriatefunctionalization.
Synthesis of Nanomaterials

4. Top-down approaches
Slicing of a bulk material to get nano sized particles
Bottom-up approaches
Build up materials atom by atom
(in which nanoparticles are grown from simpler molecules)
Fabrication of nanomaterials include nanostructured surface, nanoparticles
and nanoporous materials
Nanoparticles are typically synthesized from
a top-down or bottom-up approach
Approaches for the synthesis of nanomaterials

6. TOP-DOWNAPPROACH

7. Mechanical milling
▪Agrindingmethodthatgrindsnanotubesinto
extremelyfinepowders
▪Duringtheballmillingprocess,thecollision
betweenthetinyrigidballsinaconcealed
containerwillgeneratelocalizedhighpressure.
▪Usually,ceramic,flintpebblesandstainlesssteel
areused
▪Producesuniformfinepowderof2-20nminsize
▪Sizedependsuponthespeedoftherotationofthe
balls
▪Possibilityofcombiningitwithchemical
treatments,allowsobtainingthedesiredproducts
withminimaleffort.
▪Ball-milledcarbonnanomaterialsareconsidereda
novelclassofnanomaterial,providingthe
opportunitytosatisfyenvironmentalremediation,
energystorage,andenergyconversiondemands
https://pubs.rsc.org/en/content/articlehtml/2019/na/c8na00238j
•Cost-effectivemethod
•Idealmethodforproducingblendsof
differentphases
•Helpfulintheproductionof
nanocomposites
•Usedtoproduceoxide-andcarbide-
strengthenedaluminumalloys,wear-
resistant spray coatings,
aluminum/nickel/magnesium/copper-
basednanoalloys,andmanyother
nanocompositematerials.

8. Electrospinning
▪simplesttop-downmethod
▪usedtoproducenanofibersfromawidevarietyofmaterials,typicallypolymers.
▪Lengthsoftheseultrathinnanomaterialscanbeextendedtoseveralcentimeters.
▪Core–shellandhollowpolymer,inorganic,organic,andhybridmaterials
An electrostatic potential is
applied between a
spinneret and a collector
https://www.sciencedirect.com/scie
nce/article/pii/S136970210671389X

9. Lithography
Auseful tool for developing nanoarchitectures using a
focused beam of light or electrons
Mask less lithography
▪Inmasklesslithography,
arbitrarynanopatternwritingis
carriedoutwithoutthe
involvementofamask
▪3Dfreeformmicro-nano-
fabricationcan be
achievedviaionimplantation
withafocusedionbeamin
combinationwithwetchemical
etching
▪Includesscanningprobe
lithography,focusedionbeam
lithography,andelectronbeam
lithography
https://link.springer.com/referenceworkentry/10.1007%2F978-0-387-92897-5_1051
Masked lithography
In masked
nanolithography,nano-
patternsaretransferred
overalargesurfacearea
usingaspecificmaskor
template.
Includesphotolithography,
nano-imprintlithography&
softlithography

10. Sputtering
▪Aneffectivemethodforproducingthinfilmsofnanomaterials
▪Bombardingsolidsurfaceswithhigh-energyparticlessuchasplasmaorgas,it
producesnanomaterials
Steps involved
▪Ionsaregeneratedviaplasmaanddirectedtowardstargetwhichsputtertargetatoms
▪Ejectedatomsaretransportedtothesubstrate,thereitcondensesandformathinfilm
▪Performedinanevacuatedchamber
Different sputtering methods
•Magnetron
•Radio-frequencydiode
•DCdiodesputtering
Advantages
▪Sputterednanomaterialcomposition
remainsthesameasthetarget
materialwithfewerimpurities
▪Cost-effectivecomparedwith
electron-beamlithography

11. Laser ablation
▪Involvesnanoparticlegenerationusinga
powerfullaserbeamthathitsthetarget
material
▪Sourcematerialorprecursorvaporizes
duetothehighenergyofthelaser
irradiation,resultinginnanoparticle
formation
▪E.g.,metalnanoparticles,carbon
nanomaterials,oxidecomposites,and
ceramics
▪Utilizinglaserablationforthe
generationofnoblemetalnanoparticles
canbeconsideredasagreentechnique,
asthereisnoneedforstabilizingagents
orotherchemicals
https://www.researchgate.net/figure/Schematic-of-
experiment-setup-for-silver-nanoparticle-production-
with-laser-ablation_fig1_293637284

12. Bottom-up approaches
To be continued………

13. Thank you
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