Dip DLS Technology, ?=658 nm). 1 ml of liquid

Dip and
Electrochemical Coating of Bio-Synthetic Metallic Nanoparticles for
Electrocatalytic Water Splitting

                             
              

 

Session: 2016-2018

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Supervised By:

 Dr. Syeda Rubina Gilani

Submitted By:

 Zeshan Ahmad

Registration No:
2016-MPHIL-APP-CHEM-34

DEPARTMENT
OF CHEMISTRY

UNIVERSITY
OF ENGINEERING AND TECHNOLOGY

LAHORE-PAKISTAN

Results and Discussion:

                                                                       Nanoparticles of five different metals
(W, Ag, Cu, Co and Ni) were prepared with different plant leaves extracts.
Different Tests and characterizations of these fabricated FTOs were performed.
The results and data of all metal-extract NPs combinations, acquired from the
investigations are discussed one by one in detail. But before this, here is the
brief discussion of the techniques used and also the operation which is common
in the characterization of NPs prepared samples.

Particle size Analyzer:

                                                      The particle size of NPs present in liquid
solution was identified by using Particle size analyzer (Anton Paar Litesizer
500, using DLS Technology, ?=658 nm). 1 ml of liquid NPs samples of NP solution
were placed one by one into disposable sample cells at 30oC. These
samples were run under standard parameters and results acquired from each run
are discussed under their respective heads.

UV-Visible Spectrophotometer:

                                                                               Optical
absorbance spectra of NPs were measured by using Agilent UV-Visible
Spectrophotometer (Carry 60 UV-Vis). About 2 ml of liquid NPs solution was
placed in sterilized and dry quartz sample cells, sample was run and absorbance
was measured between 200nm to 800nm. This procedure was repeated for all
prepared NPs solutions. The optical absorbance results of all NPs are discussed
in respective sections. 

Fourier Transform Infrared Spectrometer:

                                                                                                              Functional
group studies were carried out by using Agilent Carry 630 FTIR equipped with
DTGS detector.  The NPs samples were
dried at 200oC in infrared oven (Memmert UN 110 Plus). The dried
samples were run from 650cm-1 to 4000cm-1 and their
transmittance data was measured. The same procedure was repeated for all
synthesized NPs samples.

Potentiostatic Measurements:

                                                                               Electrochemical
and cyclic voltametric measurements were determined by using Potentiostat
(PGSTAT-30, Metrohm AutoLab), having a three-electrode configuration cell.
Fabricated FTOs; on which Ag NPs, W NPs, Cu NPs, Co NPs and Ni NPs thin films
were deposited, were used as working electrodes. An Ag/AgCl (3M KCl) electrode
was used as reference electrode. Platinum plate having 1 cm2 area
was used as counter electrode. Cyclic voltametric measurements were done and
current density changes were measured between 1.0V to -0.8V at scan rate 0.2.
Above procedure was repeated with all fabricated FTO plates.  During cyclic voltametric analysis onset
potential and also water splitting was observed. The measured data and
graphical representation of the acquired results is discussed in detail.

Antimicrobial Tests:

                Antibacterial
Tests were done by following Disk Diffusion Method. There were basically three
steps involved in this test which are as followed.

1.      Preparation
of solid culture media

2.      Inoculation
of sample and Bacterial colony onto the medium & their growth

3.      Observation
of results and data collection

In
the first step, 4g of nutrient broth and 7.5g of gum agar (purchased from Sigma
Aldrich) was weighed and added into 200ml of double distilled water. Stirring
was done for 5 minutes at 50oC until all clumps of agar becomes
invisible. When the agar was completely dissolved then 300ml of distilled water
was added to stirring solution. This solution is stirred for two minutes more,
at this time the solution was opaque. Then flask was covered with aluminum foil
and tightened with paper tape. This flask was placed into the autoclave and
sterilization was carried out at 121OC for 15 minutes. After that flask
was removed from autoclave and clear solution was stirred at room temperature
until the temperature of the solution drops to 50OC. Next procedure
was performed into the laminar flow cabinet in which a Dettol solution was
sprayed to ensure the sterile environment and prevention from any bacterial
contamination due to any already present bacteria in LFC. Sterilized petri
dishes were taken and about 20 ml the prepared agar media solution was poured
in 25 petri dishes. These plates were remained inside for 30 minutes until the
liquid media turned into solid gel. These plates were arranged by placing their
upside down to prevent from moisture and then these media plates were incubated
at 37OC for 24 hours.

In
second step the bacterial culture and sample inoculation on to the prepared
agar media was done. Bacillus subtilis
and Pseudomonas aeruginosa were taken
as gram positive and gram negative bacteria respectively. Wire loop was taken
and it was sterilized by dipping it in 70% ethanol and then placed on burner
flame till red hot. Wire loop was cooled down and dipped into bacterial broth
culture without touching the wire loop to the walls of broth culture tube. The
streaks of bacterial culture were applied on all over the agar plates.

NPs
original solution without being diluted was used as sample solution.  Paper disks of 6mm diameter was dipped into
the sample solutions and placed over agar plates and pressed little gently with
tweezes tip. Then these petri dishes was again covered with lid, labeled and
placed in incubator at 37OC for 24 hrs. After that bacterial growth
was observed and data regarding susceptible or resistive behavior of bacteria
to NPs and plant leaves extract without metal was collected. On the basis of
it, zone of inhibition was calculated with the help of scale and antibacterial
behaviors of all NPs are discussed along with snapshots.   

Silver Nanoparticles:

                                Silver
nanoparticles were prepared by adding metal 1mM solution of AgNO3 to
different plant leaves extracts resulting in deep brown color NPs
solution.  After characterization, the
results of all NPs are discussed below.

Particle Size Analyzer Results:

                                                The
particle size of all plant extracts was above 100nm as shown in graph but after
mixing with metal solution, different size and shaped particles were formed.
Banyan, Sapodilla, Jujube, Lemon and P. Lime gave NPs with size 1.4nm, 10nm, 11nm,
22nm and 47nm respectively. Ag NPs with Banyan, Sapodilla and Jujube provided
very small sized NPs as compared to others. These are average sizes but still
satisfactory for the confirmation

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