The document discusses the green synthesis and applications of silver nanoparticles. It begins by outlining the need for advanced disinfectant nanomaterials to prevent disease outbreaks caused by overpopulation and poor sanitation. It then describes how silver nanoparticles are a promising material for developing antimicrobial products due to their high antimicrobial activity. The document goes on to detail a green synthesis method for producing silver nanoparticles using the extract of Bougainvillea plant bracts, and characterizes the nanoparticles. It finds that the synthesized silver nanoparticles demonstrate effective antimicrobial properties against bacteria as well as antifouling effects.

1. GREEN SYNTHESIS AND
APPLICATIONS OF SILVER
NANOPARTICLES
Presented By
Manish Kumar Dash
MSc. Biotechnology
Regd. No: 1661701020

2.  The outbreak of different infectious diseases has been a significant burden on global
economies and public health.
 Reason- overpopulation, urbanization, poor supply of water and environmental hygiene.
 The comprehensive treatments of environments containing infectious pathogens using
advanced disinfectant nanomaterials have been proposed for prevention of the
outbreaks.
 Silver nanoparticles (Ag-NPs) with unique properties of high antimicrobial activity have
attracted much interest from scientists and technologists to develop nanosilver-based
disinfectant products.
Introduction

3.  Nanotechnology is the study of manipulating matter on an atomic and molecular basis.The term
‘nanotechnology’ was introduced by Professor NorioTaniguchi in 1974.
 Deals with synthesis and manipulation of particles structure ranging from approximately 1 to 100
nm in size.
• Good conductor of electricity and heat
• Chemically stable
• Efficient catalytic activity
• Strong inhibitory and bactericidal effects
• Anti-fungal properties
• Anti-inflammatory effect
• Anti- viral effect
• Anticancer effect
Important Properties of AgNPs

4. Nano-particles can be synthesised chemically, physically and biological.
Method Advantage
s
Limitations
Physical • Uniformly distributed
NPs
• Non-toxic
• Low yield
• Machinery occupies a large space
• Massive energy consumption
• Time-consuming
Chemical • High yield
• Rapid
• Hazardous
• Inflammable
• Toxic
• Non-eco-friendly
Biological • Eco-friendly
• Non-toxic
• Economical protocol
• Single step technique
• Time-consuming
Why Biogenic Approach?

5.  Synthesis of Silver nanoparticles by plant extract
 Characterization of the Silver nanoparticles by
spectrophotometer
 Study of antimicrobial effect of the Silver nanoparticles
Study of antifouling effect of silver nanoparticles
Objectives

6. Plant
Dried plant material
Powder
AgNO3
Solution
Aq. Plant
extract
Heating with
continuous stirring
Silver Nanoparticles
1. Collection of samples ( bract of Bougainvillea)
2. Preparation of bract extract.
3. Preparation of Silver nitrate solution (1mM)
4. Incubation of bract extract and silver nitrate
(1: 9)
5. Characterization through UV/Vis Spectroscopy
6. Antibacterial effect of silver nanoparticles
7. Antifouling effect of silver nanoparticles
Materials & Methods

7. Bougainvillea, a genus of flowering plants a tropical and sub-tropical
woody, evergreen clambering vine.
The bracts can be white, pink, orange, yellow, purple or burgundy in
colour.
The ease of availability of the bract and its properties encouraged to
use it’s aqueous extract for the reduction of silver nitrate to silver
nano-particles.
1.Collection of samples ( Bract of Bougainvillea)
a) Fresh bract b) Dried bract c) Bract Powder
a b cPresence of secondary metabolites like
phenolic compounds, betacyanins, alkaloids,
quinones, tannins, furanoids, flavanoids,
betalain, oxidase and pinitol are responsible
for the reducing properties of the plant
extracts.

8. 2. Preparation of bract extract
• 24 gm powder mixed with 500 ml ddH2O
• solution boiled for 20 minutes.
• Filtered using filter paper
• Filtrate was stored for further use.
This aqueous bract extract was treated as crude enzyme solution.

9. 1mM of AgNO3 solutionwas prepared by adding 5 ml of 0.1M AgNO3 to 495
ml of ddH2o and was stored in the bottle and kept in dark.
 The synthesis of silver nano-particles was carried out in a 1L conical
flask containing 450ml of 1mM AgNO3 and 50ml of bract extract (9:1).
 And then it was kept for 2 hr incubation in dark.
3. Preparation of Silver nitrate solution (1mM)
4. Incubation of bract extract and silver nitrate (1:
9)
The colour of the solution changed
from pink colour to brown
colour.
This colour change indicated the
probable formation of silver
nano-particles. Change in colour reaction mixture along with
time;
(a) time = 0, (b) time = 5hr
a b

10. 5. Spectro scanning at regular interval to check the
activity of reaction mixture
The absorption spectra of the solution was taken from 300 to 700 nm using a UV-vis
spectrophotometer (HITACHI, Model UH5300).
The absorption spectra was determined in regular intervals.
Smaller nanospheres primarily absorb light at
visible range and have peaks near 400 nm, while
larger spheres exhibit increased scattering and
have peaks that broaden and shift towards longer
wavelengths (known as red-shifting).
Source: https://nanocomposix.com/pages/silver-nanoparticles-optical-properties

11. 432 nm
528 nm 534 nm
468 nm
c
a b
d
a-5 hr, b-10 hr, c-15 hr, d-30 hr
UV/Vs Spectral analysis of silver nanoparticles
NB:The broadening of the peak indicates the particles are poly dispersed.

12. Probable mechanism
Silver nanoparticleSilver salt
Quinone
reduced
Quinone oxidised
Step-1
Ag+ reduced to Ag0 by gaining an e-
from ReducedQuinone
Step-3
NADP+ reduced to NADPH gaining e-
from NO2
-
Step-2
Oxidised Quinone is reduced back
gaining e- from NO3
-
.

13. The antibacterial experiment of silver nanoparticles (5mg/ml)
was tested against 4 different microorganisms:-
Antibacterial effect of silver nanoparticles
a b
dc
Antibacterial property of silver nanoparticles
by showing the zone of inhibition; a- S.
marcescens, b- K. Pneumonia, c- S. aureus, d-
Staphylococcus
Name of the
bacterial strains
Diameter of
Zone of inhibition
Serratia marcescens 1.7 cm
Klebsiella pneumoniae 1.5 cm
Staphylococcus aureus 1 cm
Staphylococcus 0.9 cm
From the diameter values, it is confirmed that
S. marcescens is most sensitive to the AgNPs
and Staphylococcus is least.

14. Antifouling effect
Secretion of exopolysaccharide plays important role for the formation of biofilm.
The effect of silver nanoparticle on exopolysaccharide production from E. coli were
confirmed by Congo red agar (CRA) plate assay.
Then silver nano particle solution was added in different concentration (4/25, 6/25
and 8/25 V/V) to these media.
Control 4 ml 6 ml 8 ml
Concentration of silver nanoparticles solution: 5 mg/ml

15. Synthesis method is economical, energy efficient, cost effective; provide healthier work place
and communities, protecting human health and environment leading to lesser waste and safer
products.
 Plants can be advantageous over other biological entities which can overcome the time
consuming process of employing microbes and maintaining their culture which can lose their
potential towards synthesis of nanoparticles.
The synthesised silver nanoparticles showed efficient antimicrobial activities against both
gram positive and gram negative bacteria at very low concentration (5mg/ml).
Silver nanoparticles solution also shows antifouling effect on E. coli.
This eco-friendly method could be a competitive alternative to the conventional physical and
chemical methods thus has a potential to use in biomedical applications in future.
Conclusions