REPORT ON

GREEN SYNTHESIS OF SILVER NANOPARTICLES USING

Bryophyllum pinnatum AQUEOUS LEAF EXTRACT.

INTERNSHIP/TRAINING

(DECEMBER 26-31, 2016)

SUBMITTED TO: SUBMITTED BY:

DR. RENU DESWAL PRIYANKA SIHAG

SUPERVISOR AAYUSHI TYAGI

MOLECULAR PLANT PHYSIOLOGY BOTANY HONORS

AND PROTEOMICS LABORATORY DYAL SINGH COLLEGE

DEPARTMENT OF BOTANY UNIVERSITY OF DELHI

UNIVERSITY OF DELHI REPORT (DEC, 2016)

DECLARATION

We, AayushiTyagi and PriyankaSihag, students of B.Sc Botany Honors, Dyal Singh College,

University of Delhi hereby declare that the research report entitled “GREEN SYNTHESIS OF

SILVER NANOPARTICLES USING Bryophyllum pinnatum AQUEOUS LEAF

EXTRACT”is successfully submitted to Dr.RenuDeswal, Supervisor, Molecular Plant

Physiology and Proteomics, Department of Botany, University of Delhi.

We further declare that the work reported in this project has not been submitted and will not be

submitted, either in part or in full, for any other purpose.

SIGNATURE OF CANDIDATES

AAYUSHI TYAGI

___________________________

PRIYANKA SIHAG

___________________________

DURATION: December 26-31, 2016 DATE: January 03, 2017

ACKNOWLEDGEMENT

This report is culmination of hard work and contribution from a number of people in all sort of

ways possible. It is a pleasure to convey our gratitude to each one of them in our humble

acknowledgement.

Foremost, we would like to thank our supervisor Dr. RenuDeswal for her constant support and

guidance and for allowing us to work in her laboratory and giving such a phenomenal experience

here. We are surely motivated to further continue our carriers in research field.

We would also like to convey our gratitude to Ms. Bhavana Sharma and whole heartedly thank

her for her instructions, guidance, suggestions and supports throughout this valuable experience.

Thank you so much ma’am for your help and easing out everything for us. You truly inspired

and motivated us.We would also like to thank all other colleagues and seniors who guided and

helped us throughout.

We thank you all for your cooperation and guidance in creating this a wonderful and remarkable

experience.

ABSTRACT

Nanotechnology is now becoming an allied science, commonly used in other

fields of science like electronic,Physics and engineering since decades. It has

created potential impact in various fields likeMedicine including immunology,

cardiology, endocrinology, ophthalmology, oncology, pulmunology etc.

Here we tried green chemistry approach to synthesize a cost effect and

simplemethod for synthesis of brown colored silver nanoparticles using

Bryophyllum pinnatumextract.UV-Vis spectroscopy analysis gave a

characteristic peak at 420 nm confirming synthesis of silver

nanoparticles.These silver nanoparticles are well known for their anti-bacterial

properties and other medical applications which would be explored further.

INTRODUCTION

The term “Nanoparticle” came into existence in 1990s during the launching of “National

Nanotechnology Initiative” in USA.“Nanotechnology” is an important field of modern research,

dealing with design, synthesis, and manipulation of particle structures. These are defined as the

inorganic particles with the size range of 1-100 nm.(Kiss et al. 1999)However, nanoparticles

used in the field of biotechnology ranges between 10 to 500 nm,in some cases exceeding 700

nm.Nanobiotechnology is referred as the intersection of the two branches Nanotechnology and

Biology and it serves as a blanket term for all the topics within. Nanobiotechnology covers the

use of nanoparticles, as they can be synthesized by both chemical method and green synthesis.

They can be easily modified using chemical processes which allow them to be attached or

collaborated with antibodies, drugs of interest and thus it opens a wide range of applications in

medicine and treatment, biotechnology, target analysis, targeted drug delivery and much more.

NANOMETALS (also called as Metal Nanoparticles) like silver, cobalt, gold, platinum, copper,

nickel and iron are now-a-daysattracting a lot of attention of researchers world-

wide.Characterization of these nanoparticles is based on the size, morphology and surfacecharge,

using advanced microscopic techniques likeatomic force microscopy(AFM), scanning electron

microscopy (SEM) and transmission electron

microscopy(TEM).(coloides.webs.uvigo.es/nano/main.html).

Most current nanomaterials could be organized into four types:

Carbon Based: These nanomaterials are commonly made of carbon, generally occurring in the

form of hollow spheres, ellipsoids, or tubes. Spherical and ellipsoidal carbon nanomaterials are

referred to as fullerenes and the cylindrical carbon-based nanoparticles are called as nanotubes.

Metal Based: These include metal oxides, nanogold and nanosilver.

Dendrimers: These are branched nanomaterials.

Composites: these are combination of nanoparticles with other nanoparticles or with larger,

bulk-type materials. (U.S. Environmental Protection Agency, 2007, www.epa.gov)

METAL NANOPARTICLES

IRON OXIDE NANOPARTICLES

Iron oxide nanoparticles possess many useful characteristics such as ultrafine size, magnetic

properties, and biocompatibility, super paramagnetic iron oxide nanoparticles (SPION) and they

have been used in biomedical applications, such as enhanced resolution contrast agents for MRI,

targeted drug delivery and imaging, hyperthermia, gene therapy, stem cell tracking, magnetic

separation technologies (e.g., rapid DNA sequencing) early detection of inflammatory, cancer,

diabetes, and atherosclerosis.(Kooi et al.2003)

GOLD NANOPARTICLES

The colloid/suspension of nanosized gold particles is known as colloidal gold. This suspension is

commonly of red (for particles less than 100 nm) or dirty yellowish color (for larger particles).

These particles have a strong absorption maximum around 520 nm.

SILVER NANOPARTICLES

Silver nanoparticles (AgNPs)(1-100 nm)are the particles composed of silver and large

percentage of silver oxide due to their large surface to bulk silver atoms ratio.Recently, there is

an effort to incorporate AgNPs into a wide range of medical devices including bone cement,

surgical instruments, surgical masks, etc. Moreover, it has also been shown that ionic silver, in

the right quantities is suitable in treating wounds. In fact, AgNPs are now replacing silver

sulfadiazine as an effective agent in the treatment of wounds (Qin et al., 2005).Chemically it

exists in four different oxidation states i.e. Ag0 , Ag1+ , Ag2+ and Ag3+ . (Riedel and Kaupp 2009)

AgNPs arebest known for its anti-bacterial properties. Li and coworkers have proposed three

possible antibacterial mechanisms of AgNPsin evaluating the antimicrobial activity (a) Bacterial

growth and proliferation are adversely inhibited by the adhesion of ultra-small sized AgNPs onto

the cell wall of bacteria, resulting in changes in the cell wall which in turn is unable to protect the

interior of the cell (b) Through the penetration of AgNPs into the bacterial cell, it leads to DNA

damage, or even cell death, by altering its normal functioning of bacterial DNA and (c) The

interaction of Ag+ ions with the proteins containing sulfur present in the bacterial cell wall

irreversibly caused the disruption of the bacterial cell wall(Li et al.2008).

Pictorial representation of various shapes of Nanoparticles

Fig1. 1-Nanosphere 2-hollow nanosphere 3-nanaobar 4-nanorod 5-nanobone 6-nanobeam 7-

nanobelt 8-nanowires 9-hollow nanorod 10-triangle 11-square 12-pentagon 13-hexagon 14-

truncated triangle 15-disc 16-nanoring 17-tetrahedron 18-cube 19-decahedron 20-octahedron 21-

icosahedron 22-rhombicuboctahedron 23-hollow nanocage 24-monopod 25-bipod 26-tripod 27-

tetrapod 28-star shaped 29-octapod 30-nanopyrimid 31-nanoclover 32-nanosnowflake 33-

nanaothorn 34-nanotree 35-dendrite 36-nanocrescent 37-hollow nanoshell(ring) 38-porous

triangles 39-hollow nanoshell(cubic) 40-truncated octahedron 41-hollow nanocage 42-

nanoskeleton 43-hollow nanobox(Tan et al., 2011).

Table 1.Classification of nanoparticles and their applications

Nanosystems Size (nm) Characteristics Applications

Carbon

Nanotubes

0.5–3

diameter

and

20–1000

Length

Third allotropic crystalline

form of carbon sheets either

single layer (single walled

nanotube, SWNT) or

multiplelayer (multi-walled

nanotube,MWNT). These crystals

haveremarkable strength

andunique electrical properties

(conducting, semi conducting,or

insulating)

Functionalization

enhancedsolubility,

penetration to cell

cytoplasm and to

nucleus, ascarrier for

gene delivery,peptide

delivery

Metallic

Nanoparticles

<100 Gold and silver colloids, very

small size resulting in high

surface area available for

functionalization, stable

Drug and gene delivery,

highly sensitive

diagnosticassays,

thermal ablation and

radiotherapy

enhancement

Polymeric

Nanoparticles

10–1000 Biodegradable, biocompatible,

Offer complete drug protection

Excellent carrier for

controlled and sustained

delivery of drugs.

Surface

modifiednanoparticles

can be used foractive

and passive delivery

of bioactives

DIFFERENT APROACHES FOR SYNTHESIS OF NANOPARTICLES:

It generally includes two main methods: “TOP DOWN” and “BOTTOM UP” approaches.

1. TOP DOWN:It is actually a synonym for the decomposition or step wise design. The bulk

material is reduced to its nanoscale form. This means that the inorganic substance will

decompose in smaller unit until obtains desirable shape and size. This approach includes

normal microfabrication, lithography, thermal decomposition, laser ablation, mechanical

milling, etching, and sputtering (Abou El-Nour et al., 2010) where under extremely

controlled condition the particles are cut, milled and shaped accordingly.

2. BOTTOM UP:It is more preferable approach during the synthesis of nanoparticles. In this

approach the smaller particles make up and form a more complex configuration. It involves

a homogenous system wherein catalysts (reducing and capping/stabilizing agents)

synthesize nanoparticles. This approach uses chemical properties of single molecule, which

self-assembles to a useful complex. This approach includes molecular self-assembly and

molecular recognition as tools.And the form particles can be controlled by catalytic

properties, reaction media and temperature conditions.

CHEMICAL SYNTHESIS OF NANOPARTICLES:

Chemical reduction is the most common way to synthesize Ag nanoparticles.In this process

reduction of aqueous silver nitrate in a controlled operating medium is carried out, using both

organic and inorganic reducing agentsand chemical reductants such as sodium citrate

(Na3C6H5O7) or branched polyethylenimine which produces different types of particles in the

solution, the former producing negatively charged Ag nanoparticles while the later forms

positively charged particles. However, the chemical process is less eco-friendly, often expensive,

uses lethal chemicals and is complex. These reducing agents reduce Ag+ to its neutral Ag0 form

which leads to the formation of a colloidal solution of silver metallic particles. It is important to

add a capping/stabilizing agent to prevent their aggregation. Polymeric compounds such as poly

(vinyl alcohol), poly (vinyl pyrrolidone), poly (ethylene glycol), poly (methacrylic acid), and

polymethylmethacrylate are examples of stabilizing agents used in the synthesis of

AgNPs.(Iravani et al. 2014)

GREEN SYNTHESIS OF NANOPARTICLES:

Chemical methods are extremely expensive and are a potential threat to environment due to the

use of lethal chemicals. Therefore, green and sustainable processesare utilized for synthesis of

nanoparticles using following methods:(Keat et al. 2015)

1. POLYSACCARIDE METHOD: This method administers the formation of nanoparticles

by using polysaccharides. Polysaccharides serve the purpose of reductants or capping

agents or sometimes both. For example, β-d-glucose is used as a reducing sugar and a

starch as the stabilizer to create AgNPs. (Mochochoko et al. 2013)

2. TOLLENS METHOD: It is a single-step process. Here, Ag+ ions are reduced by various

saccharides in the presence of Ammonia. The reaction yields different shapes and sizes of

AgNPs. (Dondi et al. 2012)

3. IRRADIATION METHOD: In this method reducing agents are not used. Nanoparticles

are synthesized by using temperature-dependent capping agents. For example, distinct

AgNPs can be synthesized by using aqueous solution of silver salt and surfactant in laser

irradiation. This method is manipulative as the morphology of synthesized particles can

be modified using different doses of radiation. (Abedini et al. 2013)

4. BIOLOGICAL METHOD: This approach simply uses extract from biological sources as

reducing or stabilizing agents or both. There are various resources for green synthesis of

NPs, such as bacteria, fungi, enzyme and plant extracts. The biosynthesis of NPs using

plant extracts is more favorable than other biological methods because of removing the

elaborate process of maintaining cell cultures. It is the most suitable method for large

scale production of NPs. In these extracts, secondary metabolites and biomolecules can

be found which have reduction potential and are environmentally benign. (Annamalai

and Nallamuthu 2015) (Moghaddam 2010).

5. POLYOXOMETALATES METHOD: These are known to be a wide family of

molecular metal oxide clusters. And in soluble forms these are capable of synthesizing

noble nanoparticles through multi-electron redox reactions. (Sharma et al. 2009)

PLANT MEDIATED SYNTHESIS OF SILVER NANOPARTICLES:

The process of formation of nanoparticles using plant extract is extremely cost effective and is

widely preferred for rapid production as well as it reduces the employment of hazardous

chemicals. Plants are found to have a property to tolerate harmful concentration of toxic

metals, essentials metals and non-essential metals such as copper, iron, zinc, and cadmium,

mercury, lead and arsenic. Plant extract contains a wide and vast range of metabolites with

redox potential which play an important role in AgNPs synthesis.Generally, the synthesis

includes three main steps: A) the activation phase in which reduction takes place and

nucleation of reduced metal takes place afterwards.B) The growth phase where the

spontaneous growth into nanoparticles in slightly bigger particles. This increase the stability of

AgNPs in terms of thermodynamics.C) The termination phase where the final shape and size of

nanoparticles is formed and further reaction is terminated to prevent aggregation of

nanoparticles.

THE PRINCIPLE OF PLANT MEDIATED SYNTHESIS OF AgNPs

The biogenic synthesis mainly employs plant extract in aqueous form and Ag salt solution.In

metal salt solution, metal is present in the form of ions Ag+, the plant extract acts as reducing

agent and donates electron in the solution changing Ag+ ions to its neutral form Ag0. The

reduced metal ions are acted upon by the stabilizing/capping agents and nucleation or

stabilization takes place thereby, resulting in the formation of Ag nanoparticles.

Fig2. Representative mechanism of plant-mediated synthesis of metal nanoparticles.

• Metal ions (M+)

• +

• Plant reducing agent (OH)

REDUCTION

• Reduced metal atoms(represented as)

• O=M0

NUCLEATION AND STABILIZATION • METAL

NANOPARTICLES FORMED

TERMINATION

APPLICATIONS OF AgNPs

AgNPs are of most importance because of its anti-microbial properties. The anti-microbial

and anti-bacterialproperties of AgNPs employ these in water purification process, air

disinfection, surface disinfection(through paints and polishes) and also in disinfecting medical

and household appliances. They can also be incorporated in food industry for food packaging.

It is also used in textile industries for mixing with cotton fibers to increase their antibiotic

property while preparing clothing.Furthermore, AgNPs are used as Nano-crystalline dressings

for wound healing, even for hospital-acquired infections. AgNPs along with polymethyl

methacrylate are used as bone cement for synthetic joint replacement.

In 2010, Xing et al., deduced that Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) PHBV

nanofiber scaffolds containing AgNPs have the tendency of aiding in bone and skin tissue

regeneration from their extensive study on both osteoblast (bone cells) and fibroblast (skin cells)

cultured on such scaffolds. Hence, the risk associated with implantation surgery can be overcome

by fabricating the surface of structure of the bone implants devices and scaffolds with AgNPs

(Xing et al. 2010).

AgNPs are widely applied in cosmetics and in skin treatment. The electrochemical property of

AgNPs is used as an advantage while making nanosensors, which have a huge application in

bioengineering.The catalytic propertyof AgNPs is different from that of the bulk material. The

catalytic potential of AgNPs was found to be better than that of gold and platinum

nanoparticles. The reduction of dyes by sodium borohydride can be enhanced by using AgNPs

on silica spheres.

TOXICITY OF SILVER NANOPARTICLES

AgNPs are observed to have toxic effects on humans as well as environment. According to

some researchers in vitro toxicity is caused by AgNPs as it causes oxidative stress in and cease

mitochondrial function in cells. Observations also showed that inhalation of certain amount of

AgNPs can cause neurotoxicity, pulmonary toxicity, inflammation and immunotoxicity in

humans.However, the in-vivo toxicology and in-vitro toxicology results varied drastically,

suggesting more evaluation and research in this field.

Table 2 :Different plant mediated synthesis of Silver nanoparticles

Sr No. Reducing agents Nanoparticles References

1 Pomegranate (peel) 5-50 nm Shanmugavadivu et al.(2014)

2 Aloe vera 500 nm Sarahlbrahim et al.(2014)

3 Aegle marmelos (fruit) 34.7 nm Krupa N.D and Raghavan(2014)

4 Bacillus

stearothermophilus

14±4 nm El Batal et al.(2013)

5 Sargassum muticum 5-15 nm Azizi et al.(2013)

6 Streptomyces sp. 35 nm Karthik et al.(2014)

7 Glycine max 7-29 nm Sasikala et al.(2102)

8 Lactobacillus Nanospheres f

6-15.7 nm

Sintubin et al., 2009 Appl.

Microbiol. Biotechnol. 84 741

9 Shewanella oneidensis Nanospheres

2-11 nm

Suresh A K et al., 2010 Environ.

Sci. Technol. 44 5210

10 Fungus T. viride Nanospheres and

nanorods

5-40 nm

Fayaz A M et al.,

2010 Nanomed.

Nanotechnol. 6 103

11 Cassia angustifolia Nanospheres and

nanorods

9-31 nm

Amaladhaset al., 2012 Adv. Nat.

Sci.: Nanosci.

Nanotechnol. 3 045006

12 Daucus carota Nanospheres

20 nm

Umadevi M, et al., 2012 Adv.

Nat.

Sci.Nanosci.Nanotechnol. 3 025

008

RELEVANCE OF Bryophyllum pinnatum

Bryophyllum is a succulent perennial herb found in tropical and sub-tropical areas of Asia,

Australia, Hawaii etc.(USDA GRIN 2007).Vernacular names for Bryophyllum pinnatum include

Cathedral Bells, Air Plant, Life Plant, Miracle Leaf, Goethe Plant and the Katakataka.

Bryophyllum pinnatum is well known for its medicinal uses and is used for the treatment of cold,

cough, fever, Dysentery, kidney stone, high blood pressure, cardiac problem, fever, constipation,

wound, soar or cuts, roundworms (clotrimazol),teething troubles, diabetes, hepatitis, difficult

urination, piles, stomach ache, gray hair, intestinal disorders, reduces inflammation,

Leucorrhea,cancer and weight management, kidney and gallbladder stones

.{www.homeremediess.com, Bryophyllum pinnatum (ayurvedic plant) uses and pics, 2016}

Various phytochemicals are known to be present in the plant including alkaloids, phenols,

flavanoids, tannins, phenolic compounds,anthocyanins, glycosides, bufadienolides, saponins,

coumarins, quinines, carotenoids, tocopherol and lectins. These secondary metabolites displays

anti-microbial activities, wound healing capacity, as astringent and analgesic potencies

respectively. Terpenoids are known for their major role in transformation of silver ions to

AgNPs. (Shankar 2003).Moreover, various classes of Flavonoids such as flavonols,

isoflavanoids, flavanones are known to actively chelate and reduce metal ions to metal ions. It is

considered that these flavonoids release a reactive hydrogen atom on tautomeric transformations

resulting in AgNPs production. Similiarly, monosaccharides and some disaccharides also act as

reducing agents and aminoacids attaches to the metal ion via amino and carboxyl groups of main

or side chain thereby helping in AgNPs formation (Makarov et al. 2014).

AgNPs of average size 18 nm have been already synthesized using Bryophyllumleaf extract as a

capping and reducing agent. Sakia et. al.in 2014 synthesized AgNPsshowingcharacterstic surface

Plasmon band at 405nm. Anti-microbial properties of AgNP’s were also determined against

gram positive Staphylococcus epidermidis and negative Pseudomonas fluorescensebacteria.

Therefore,an effort was made to synthesize AgNPs using aqueous Bryophyllum extract with

some minor modifications and then characterize theseusing UV-Visual spectroscopy.

Table 3 : Different secondary metabolites present in Bryophyllum pinnatum

PHYTOCHEMICALS PLANT

PART

USES REFRENCES

Phenolic glycosides

i)syringicacidβ-D-

glycopyranosyl ester

ii)4’-O-β-D-glucopyranosyl-cis-

p-coumaric acid

LEAF Anti-bacterial

properties

(Furek 2013)

Flavanoids

i)5-Methyl-4,5,7-trihydroxyl

flavones

ii)4,3,5,7-tetrahydroxyl-5-

methyl-5-

propenamineanthocyanidines

iii) Kaempferol, quecetin,

myricetin, acacetin, diosmetin

LEAF Anti-bacterial , Anti-

fungicide properties

against

Aspergillusniger,

Candida albicana,

Pseudomonas

aeruginosa, E. coli,

Staphylococcus aureus

(Furerk 2013)

(Donatus 2011)

Caffic Acid ROOTS Anti-oxidant,

Anti-carcinogenic,

Anti-oxidant

Activities

(Abhisek

Sharma 2016)

Bryophyllin-A, Bersaldegenin-

3-acetate

LEAF Anti-allergic,

Anti-viral, Anti-cancer,

treatment of psychiatric,

preterm labor,

insecticidal

(wachter R

2011)

Hexane, ethyl acetate, methanol WOOD,

STEM

Anti-microbial against

Microsporum sp. ,

Shigelladysentrial

, E. coli , Trichophyton

rubrum

(Linus U 2016)

Bufedienolide

FLOWERS Toxic to grazing

animals and anti-

carcinogenic

(Supratman U

2000)

OBJECTIVE: GREEN SYNTHESIS OF SILVER NANOPARTICLES USING

Bryophyllum pinnatum AQUEOUS LEAF EXTRACT.

MATERIALS AND METHODS

MATERIALS REQUIRED:

Bryophyllum leaves (young) collected from Department of botany, University of Delhi. Silver

nitrate was purchased from MP Biomedicals. Deionized water and analytical grade reagents were

used throughout the experiments. All the glass wares and other utilities were surface sterilized

prior to use.

PREPARATION OF AQUEOUS EXTRACT:

Collected tissue (Leaf) wasfirst washed with tap water followed by double distilled water and air

dried. The leaves were grounded into a homogenous paste and aqueous extract was prepared in

1:2ratio. The supernatant was collected by centrifugation at 10,000 rpm, 15 mins, 4 C.

SYNTHESIS OF SILVER NANOPARTICLES:

For the synthesis of AgNPs, Different volumes of extract (100 and 200µl) were mixed with

(3ml) 1mM of silver nitrate solution for synthesis of AgNPs at neutral and original pH at room

temperature. All the experiments were carried out in triplicates.

UV- VIS SPECTROSCOPY

Optical absorption spectra were scanned from 200-1100 nm with a data interval of 1nm to obtain

characteristic surface plasmon resonance of the synthesized AgNPs using UV-Visible

spectrophotometer (DU 800, Beckman coulter).

Fig3.Diagramatic representation of methodology of synthesis of AgNPs.

RESULT AND DISCUSSION

SYNTHESIS OF SILVER NANOPARTICLES:

Green synthesis of AgNPs using extract of Bryophyllum leaves was performed. Addition of

different volumes of extract (50, 100 and 200µl) to(3ml) 1mM of silver nitrate solutiondoes not

allow synthesis of AgNPs at original pH.However,after neutralizing thepH to 7.0 (using 1mM,

10 µl NaOH), the color of the solution changed to reddish brown in all the cases, thereby

confirming the formation of AgNPs.The intensity of AgNPs increased with the corresponding

volumes of extract, highestin 200 µl followed by 100 µl and lowest when 50 µl extract was used.

Complete bioreduction was observed when 100 µl extract was used as indicated by a clear peak

with high intensity. The characteristic flavonoids, tannins and acids was considered as the main

components involved in the reduction of metal ions Ag+ to Ag0 leading to synthesis of AgNPs.

UV- VIS SPECTROSCOPY

Plasmon resonance i.e. described as a collective oscillation of the conduction electrons is a

sensitive mechanism that may be used to exploit the optical properties of metal nanoparticles.

The surfaces of metals have free electrons (π/non-bonding electrons) in the conduction band and

positively charged nucleus. Collective excitation of the electrons in the conduction band near the

surface of the nanoparticles is performed by using UV-Visual region.

A strong broad absorption band was observed at in the range of 431-439 nm using different

volumes of extracts (50-200 µl) at neutral pH whereas no such peak was observed when extract

with unadjusted pH of 5.5 was used. However, in case of complete bioreduction a broad LSPR

peak at 436 nmconfirmed the synthesis of polydisperseAgNPs. In neutral and alkaline pH

number of hydroxyl ions increases whichleads to faster reduction of silver ions.Similiar results

were obtained for AgNPs(18nm) synthesized by Saikiaet al.,where brown colored AgNPs were

obtained showing characteristicLSPR band at 405nm. This minor difference maybe due to the

different approaches for obtaining the extract (boiling the material at 80˚C for about 30 minutes)

along with addition of higher ratio of extract:silver salt (9:1) used for synthesis (Saika D. 2014).

Fig4. µUV-Visible absorption spectra of silver nanoparticles after bioreduction of 1 mM

AgNO3 with Bryophyllum aqueous leaf extract (200, 100 and 50 µl) showing characteristic

SPR at 439, 436 and 431 nm.

REFERENCES

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UNIVERSITY OF DELHI

DEPARTMENT OF BOTANY

This certificate is presented to

PRIYANKA SIHAG

Dyal Singh College, Bsc. Botany(H); for her accomplishment as a research intern at the Molecular Physiology and Proteomics Laboratory, Department

of Botany, University of Delhi.

From 26 December 2016 to 31 December 2016

Dr. Renu Deswal

(Supervisor)

UNIVERSITY OF DELHI DEPARTMENT OF BOTANY

This certificate is presented to

AAYUSHI TYAGI

Dyal Singh College, Bsc. Botany(H); for her accomplishment as a research intern at the Molecular Physiology and Proteomics Laboratory, Department

of Botany, University of Delhi.

From 26 December 2016 to 31 December 2016

Dr. Renu Deswal

(supervisor)