BIOGENIC SYNTHESIS AND APPLICATIONS OF METAL NANOPARTICLES

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BIOGENIC SYNTHESIS AND APPLICATIONS OF METAL
NANOPARTICLES
By Dr. M.G. Sethuraman Professor and
Head Department of Chemistry Gandhigram Rural
Institute DU Gandhigram 624
302 mgsethu_at_rediffmail.com
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Why Nano Particles ?

• Nanoparticles are of interest because of the new
  properties (such as chemical reactivity and
  optical behaviour) that they exhibit compared
  with larger particles of the same materials.
• For example, titanium dioxide and zinc oxide
  become transparent at the nanoscale and have
  found application in sunscreens.
• Nanoparticles have a range of potential
  applications
• in cosmetics, textiles and paints.
• in drug delivery.
• as catalysts.

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Nanoparticles and Bulk Materials

• Metallic nanoparticles have different physical
  and chemical properties from bulk metals
• Nanoparticles have unique optical, electronic
  and chemical properties.
• As the dimensions of the material is reduced the
  electronic properties change drastically.
• Magnetic properties are also different between
  bulk and nanomaterials

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Nano-scale effects on properties
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Synthesis- Bottom Up - Liquid Phase Methods

• The chemical reduction (liquid/liquid) method
  carried out by the reduction of metal ions to
  their zero oxidation states (i.e., Mn ? M0)
• Principal advantage of this method is the facile
  fabrication of particles of various shapes viz.,
  nanorods, nanowires, nanoprisms, nanoplates, and
  hollow nanoparticles
• It is possible to fine-tune the shape and size of
  the nanoparticles by changing the reducing agent,
  dispersing agent, reaction time and the
  temperature

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Plant Extracts as Reducing Agents

• Plant sources containing the phyto constituents
  viz., Tannins, Alkaloids, Polyphenols,
  Flavonoids, Citric acid are
• Good reducing agents
• Easily available
• Cost effective
• Eco-friendly
• Different size and shapes of nanoparticles are
  also prepared using plant extracts

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Silver Nanoparticles

• Among various noble metal nanoparticles, silver
  nanoparticles (AgNPs) are of great interest to
  the researchers because of easy availability,
  very low cost and emerging applications in the
  areas viz., catalysis, medicine, energy, sensors
  and optics.

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Factors affecting the formation of AgNps

• Concentration of AgNO3
• pH of the reaction
• Concentration of the Extract
• Temperature and Environment
• Reaction time and Light

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Characterization of Nanoparticles

• Visual observation and UV-Vis spectroscopy
• FT-IR Spectroscopy (To analyze capping mechanism)
• X-Ray Diffraction (To analyze geometry)
• DLS (To analyze size distribution)with Zeta
  potential (To analyze the stability)
• HR-TEM (To investigate the size and distribution)
• EDS (To analyze elements presents in colloidal
  nano)

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Shape dependent SPR of AgNPs
Various colors of AgNPs with different shapes
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Size dependent SPR of AgNPs
Blue Shift Decrease in particle size Red Shift
Increase in particle size
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High Resolution Transmission Electron Microscopy
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TEM images of Different size of AgNPs

• TEM images of silver nanoparticles with
  diameters of 20 nm, 60 nm and 100 nm.
• Scale bars are 50 nm.

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Triangular gold nanoparticles using Lemongrass
extract
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Dynamic Light Scattering

• Dynamic Light Scattering (DLS) is an important
  tool for characterizing the size of nanoparticles
  in solution.
• DLS measures the light scattered from a laser
  that passes through a colloidal solution and by
  analyzing the modulation of the scattered light
  intensity as a function of time, the hydrodynamic
  size of particles and particle agglomerates can
  be determined.
• Larger particles will diffuse slower than smaller
  particles.

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Zeta potential

• Zeta Potential analysis is a technique for
  determining the surface charge of nanoparticles
  which attracts a thin layer of ions of opposite
  charge to the nanoparticle surface from solution
  (colloids).
• The magnitude of the zeta potential is predictive
  of the colloidal stability.
• Nanoparticles with Zeta
• Potential values greater
• than 25 mV or less than -25 mV typically
  have high degrees of stability. Dispersions with
  a low zeta potential value will eventually
  aggregate due to van der Waal inter-particle
  attractions.

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Works done in our lab
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Synthesis of AgNPs by T. chebula
Visual observation and UV-Vis spectrum of AgNPs
synthesized using T. chebula
Effect of pH on formation of AgNPs synthesized
using T. chebula
Blue shift was observed (acidic to basic pH)
Particle size decreases
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Characterization of AgNPs synthesized using T.
chebula
FT-IR spectra of aq. Extract of T. chebula (A)
and synthesized AgNPs (B)
XRD pattern of synthesized AgNPs using T. chebula
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Characterization of AgNPs synthesized using T.
chebula
DLS (30 nm) and Zetapotential (-30.2 mV)
HR-TEM and SAED images of AgNPs (25 nm)
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Reduction of methylene blue using biogenic AgNPs
synthesized
UVVis spectra of methylene blue reduction by
Terminalia chebula capped AgNPs
Catalytic action of AgNPs in the presence of
Terminalia chebula on the degradation of
methylene blue (electron relay effect)
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Characterization of AgNPs synthesized using P.
granatum
UV-Vis spectra of Aq. Extract of P. granatum (A)
synthesized AgNPs (initial) (B) After 10 min (C)
FT-IR spectra of Aq. Peel extract of P. granatum
(A) synthesized AgNPs (B)
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Characterization of AgNPs synthesized using P.
granatum
HR-TEM and DLS images of AgNPs synthesized using
P. granatum (40 nm distorted spherical)
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Reduction of 4-NP by NaBH4 in the presence of
AgNPs synthesized using P. granatum
A- 4-nitrophenol B- 4-nitrophenolate C-
4-aminophenol
UV-Vis spectra of 4-nitrophenol reduction by
NaBH4 using AgNPs as catalyst
Catalytic action of AgNPs on the reduction of
4-NP (Langmuir-Hinshelwood model)
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Capping Mechanism
Stabilized through electrostatically
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Characterization of AgNPs synthesized using A.
nilotica
Phytoconstituents of Acacia nilotica
Effect of concentration of Acacia nilotica extract
Visual observation at various pH
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Characterization of AgNPs synthesized using A.
nilotica
FT-IR spectra of Acacia nilotica and synthesized
AgNPs
HR-TEM images of AgNPs synthesized using A.
nilotica
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Role of AgNPs synthesized using A. nilotica on
reduction of benzyl chloride
Negative shift of reduction potential of
GC/AgNPs Indicates the catalytic activity of
biogenic AgNPs
Electrode Potential (V) Current density 10-5 (A)
GC -0.81 -6.14
Bulk silver -0.78 -7.19
GC/AgNPs -0.74 -8.22
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Synthesis of AgNPs using Terminalia cuneata
(Revision submitted to Colloids and Surfaces B)
Major Phytoconstituents -Terminalia cuneata
Terminalia cuneata
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Characterization of AgNPs synthesized using
Terminalia cuneata
Red shift Size increases
Absorbance increases
Red shift Size increases
?max- 413 Mostly spherical
Synthesis of AgNPs at 10 min usingTerminalia
cuneata
Synthesis of AgNPs at 24 h usingTerminalia cuneata
Efeect of pH on AgNPs synthesis at 10 min
Efeect of pH on AgNPs synthesis at 24 h
Blue shift Size decreases anisotropic
Blue shift Size decreases
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Characterization of AgNPs synthesized using
Terminalia cuneata
XRD pattern of AgNPs synthesized by T. cuneata
extract
FT-IR spectra of AgNPs synthesized by T. cuneata
extract
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Characterization of AgNPs synthesized using
Terminalia cuneata
HR-TEM images of synthesized AgNPS using T.
cuneata (Average size 40 nm)
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Catalytic action of AgNPs synthesized using
Terminalia cuneata on the reduction of Direct
Yellow 12
Degradation of Dirct Yellow-12 by AgNPS
synthesized by T. cuneata follow
Langmuir-Hinshelwood model
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Synthesis of AgNPs using Tamarindus indica
(Submitted to Spectroscopy Letters)
Phytoconstituents of T. indica seed coat
Tamarindus indica
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Characterization of AgNPs synthesized using
Tamarindus indica
Red shift Size increases
Red shift Size increases
Synthesis of AgNPs at 10 min using T. indica
Synthesis of AgNPs at 24 h using T. indica
Effect of pH on AgNPs synthesis at 10 min
Effect of pH on AgNPs synthesis at 24 h
Blue shift Size decreases
Blue shift Size decreases
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Characterization of AgNPs synthesized using
Tamarindus indica
FT-IR spectra of AgNPs synthesized by T. indica
extract
HR-TEM images of synthesized AgNPS using T.
indica (30 nm) Spherical
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Characterization of AgNPs synthesized using
Tamarindus indica
DLS (30 nm) Zeta potential (-35 mV) of AgNPs
synthesized by T. indica
XRD patterns of AgNPs synthesized by T. indica
extract
UV-Vis spectra of 2nitro aniline
Reduction of 2nitro aniline by AgNPs synthesized
by T. indica
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Synthesis of AgNPs using Anacardium occidentale
(Revision submitted to Process Biochemistry)
Anacardium occidentale seed coat
Anacardium occidentale
Phytoconstituents of Anacardium occidentale
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Characterization of AgNPs synthesized using
Anacardium occidentale
UV-Vis spectroscopy
Effect of Concentration of Extract

• Red shift was observed at different times
• Particle size increased with increase of
  concentration of extract

Blue shift Size decreases
Effect of pH

• Blue shift was observed at different times
• Particle size decreased with change of pH from
  acidic to basic

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Characterization of AgNPs synthesized using
Anacardium occidentale
HR-TEM images of synthesized AgNPS using A.
occidentale (40 nm)
FT-IR spectra of AgNPs synthesized by A.
occidentale extract
XRD pattern of AgNPs synthesized by A.
occidentale extract
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Electrocatalytic oxidation of hydrazine hydrate
by AgNPs
Negative shift of oxidation potential indicates
the catalytic activity of biogenic AgNPs
Cyclic voltammogram of electrocatalytic oxidation
of hydrazine hydrate in K2SO4 at GC, bulk silver
and GC modified AgNPs
Voltammeteric data for the oxidation of hydrazine
at GC, bulk silver and GC/AgNPs in K2SO4
Electrode Potential (V) Current density 10-5 (A)
GC 0.73 2.12
Bulk silver 0.69 2.98
GC/AgNPs 0.60 5.03
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Synthesis of AgNPs using Areca catechu nut
(Submitted to Spectrochimica Acta A)
Chemical constituents present in the Areca
catechu nut
Areca catecheu
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Characterization of AgNPs synthesized using Areca
catechu nut
Average particle size 40 nm
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Electrocatalytic oxidation of glucose in NaOH
Negative shift of oxidation potential indicates
the catalytic activity of biogenic AgNPs
CV of electrocatalytic oxidation of glucose in
NaOH at GC, bulk silver and GC modified AgNPs
CV data of oxidation of glucose at GC, bulk
silver and GC/AgNPs in NaOH
Electrode Potential (V) Current density 10-4 (A)
GC 1.29 1.77
Bulk silver 0.71 2.39
GC/AgNPs 0.52 4.14
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Synthesis of silver nanoparticles using
microorganisms

• Synthesis of silver nanoparticles using
  Penicillium fungi, Bacillus strain, marine
  bacterium (Idiomarina sp. PR58-8) Pseudomonas
  fluorescens has also been reported.
• The extracellular mechanism of silver
  nanoparticle creation was investigated by regular
  methods viz., UV-Vis spectroscopy, FT-IR, TEM,
  DLS, zeta potential and XRD

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Irradiation methods

• Laser ablation method
• Microwave irradiation
• Sun light exposure
• Highly stable nanoparticles
• High purity

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Other Applications of biogenic nanoparticles

• Antibacterial agents
• Antiviral agents
• Anti-oxidants
• Anti biofilm
• Larvicidal agents
• Disinfection of water
• Decrease of biofouling
• Wettability of hair

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Conclusions

• All the plant extracts chosen for the present
  study act as good reducing agents and protecting
  agents for the formation and stabilization of
  AgNPs.
• Upon increasing the concentration of the chosen
  plant extracts, the size of AgNps increased, as
  evident from the results of UV-Vis spectroscopic
  studies.
• In the AgNPs synthesis, pH played a crucial role
  to control the size and shape of AgNPs.
• In neutral pH, the synthesized AgNPs are highly
  stable when compared with other pH ranges.
  Moreover, the sizes of the AgNPs were decreased
  on changing the pH from acidic to basic in the
  case of studied extracts.
• The synthesized AgNPs using all the chosen plant
  extracts were found to have the absorbance in the
  wavelength of 400-450 nm which suggested the
  spherical shape of biogenic AgNPs.

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Conclusions

• The phytoconstituents (mainly tannins and
  polyphenols) present in all the studied plant
  extracts were responsible
• for reduction of Ag and protection of AgNPs
  which was analyzed by FT-IR studies.
• The average size distribution of AgNPs
  (synthesized using all the extracts) was found to
  be 20-50 nm in size as studied using DLS
  measurement.
• The high negative zeta potential (30-40 mV) of
  synthesized AgNPs suggested the high stability.
• HR-TEM and EDS profile corroborated the results
  of DLS studies

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To Conclude

• It is true that there is plenty of room at the
  bottom
• Future will see Biogenic nanotechnology in
  Medicine, Environment and other domains

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Thank U
Olny post by Maruthupandi
M Indian-TN-MDU