Nanotechnology involves designing, synthesizing, and manipulating structures between 1-100 nanometers in size. One synthesis method is flame spray pyrolysis, where a metal salt solution is sprayed into a flame and pyrolyzed to form metal oxide nanoparticles. This technique allows for homogeneous mixing on an atomic level and formation of crystallized nanoparticles with sizes typically between 5-500 nm through controlled precursor concentration, residence time, and temperature near the flame. The synthesized nanoparticles have applications in areas like sensors, catalysts, and solar cells due to their tunable properties and low production costs.

2.  Nanotechnology is a discrete field which has emerged as a
dynamically developing area of scientific interest in the world.
This modern research dealing with design, synthesis and manipulation
of particle structures ranging from approximately
1-100nm.
 Nanoparticles are defined as a Nano scale particle of size ranging
form 1 to 100 nm
Application of metal nanoparticles is the versatile fields like, catalyst,
electronic, magnetic, mechanic, optical optoelectronic, materials for
solar cell and fuel cell, medical, bio imaging, cosmetic, ultrafast data
communication and optical data storage, etc, is increasing their value.

5. PHYSICAL
METHOD
CHEMICAL
METHOD
BIOLOGICAL
METHOD
ELECTROCHEMICAL,
ULTRA SONICATION,
LASER ABLATION,
IRRADIATION,
EVAPORATION,
CONDENSATION
CHEMICAL
REDUCTION,
SOL-GEL
BACTERIA,
FUNGI,
YEAST,
PLANT EXTRACTS

7. Figure: Schematic of flame spray pyrolysis synthesis

8.  The synthesis of nanoparticles by flame spray pyrolysis (FSP) is a newer
but already well-developed process in terms of product diversity.
In flame spray pyrolysis an aqueous metal salt solution is sprayed as a
fine mist, through a capillary and into a flame.
Then, small droplets are formed while the solvent burns inside the flame.
 The conversion of the salt into the metal oxide occurs upon the pyrolysis
reaction and the metal oxide atoms aggregate into nanoparticles which are
then collected on a substrate.
In figure it is possible to observe a schematic of flame spray pyrolysis
synthesis that can be used to produce metal oxide nanoparticles.

9. PROCESS
•Many elements of the periodic table can be turned into oxides, salts, or
even metal nanoparticles in laboratory-scale reactors with production rates of a
few grams per hour.
• Pure oxygen is utilized as the dispersion gas and atomizes the liquid
precursor in fine droplets with a mass median diameter of ~ 10 μm.
•Flamelets feed by a mixture of methane and oxygen allows a permanent ignition
of the spray.
•Droplet evaporation, nucleation, cluster formation, coalescence, and finally
agglomeration of product nanoparticles are determined as respective process
steps in FSP.
• The combustion of organic solvents and precursors causes a huge release of
thermal energy with temperature > 2300 K within the flame.
• In these reactors, low-cost metallic precursors (e.g., hexamethyldisiloxane)
dissolved in a liquid fuel(e.g., xylene) are supplied into a two-substance nozzle.

10. ADVANTAGES AND APPLICATIONS
This technique has two main advantages for the synthesis of fine particles.
 First, materials are mixed in solution hence they are homogeneously
mixed on the atomic level at the start.
 Second, only subsintering temperatures are necessary to form crystallized
particles.
It allows the creation of particle sizes typically in the range of5to500 nm.
 It also allows the production of nanoparticles with a high specific surface
area with low production costs, but with a major limitation—the poor
mechanical stability of nano structured films.
 To control the morphology, the precursor concentration, the residence
time, and the temperature next to the flame must also be controlled.

11. Flame spray pyrolysis synthesis allows the investigation of a wide variety of
nano structured metal oxides.
Eg: ZnO, Nb-doped TiO2 nanoparticles that were used in ethanol sensors.
Many other authors have reported the production of other metal oxide nano
structures such as Al2O3, Fe2O3, V2O5, SnO2, ZrO2, Mn2O3, or WO3
Another big advantage in using this synthesis method is the possibility of
using low-cost metal precursors that can be combined during synthesis,
resulting in unlimited combinations of metal ions and stoichiometric ratios,
enabling the production of complex and mixed oxides.
Eg: synthesis of composites of WO3/TiO2 and WO3/ZnO.

12. REFERENCES
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