electrochemical sesors.ppt

Structure of the thesis
CONTENTS
Chapter-I: Introduction
Chapter-II: Experimental
Chapter-III: “Highly sensitive electrochemical sensor for anticancer drug by a
zirconia nanoparticle-decorated reduced graphene oxide nanocomposite ”
Chapter-IV: “Simultaneous determination of Dopamine, Uric acid and Folic
acid with electrochemical techniques on Co3O4/rGO/CTAB Modified Carbon
Paste Electrode”
Chapter-V: “Facile preparation of ionic liquid-coated copper nanowire-
modified carbon paste electrode for electrochemical detection of etilefrine
drug”
Chapter-VI: “ Bimettalic PtCu Nanocubes embedded graphene oxide
nanocomposite: Highly electrochemical sensing of Citrus Flavonoid”
Chapter-VII: Summary and Conclusions

Objective of present works
 Fabrication of Transition metal oxide nanocomposites based
sensors
 Characterize the as-synthesized materials to evaluate the
required morphology.
 Testing of fabricated sensors in real samples analysis for their
efficacy.
 Over dosage and misuse of prescribed drugs have been found
to be a major cause of lever failure and human death nowadays.
 Early screening could save human health

Nanotechnology:
 Technology that deals with materials/particles in nano size
 Nano = 10-9 m
DIFFERENT DEFINITIONS FOR ‘NANO’
NANOCLUSTER:
A collection of units ( atoms/reactive molecules) of up to about 50 units
NANOCOLLOIDS:
A stable liquid phase containing particles in the 1-1000 nm range
NANOPARTICLE:
A solid particle in the 1-100 nm range that could be nanocrystalline, an aggregate
of crystalline or single crystalline nature
NANOCRYSTAL:
A solid particle that is a single crystal in the nanometer range

Schematic presentation of methods used for the formation of graphene–NP hybrids and
different structures of (a) graphene-encapsulated NPs, (b) graphene-wrapped NPs, (c) NPs
anchored to GSs, (d) mixed graphene–NP structures, (e) graphene–NP sandwich structures,
and (f) graphene–NP layered hybrids.

NANOCOMPOSITES:
 Nanocomposites are broad range of materials consisting of two or more
components, with at least one component having dimension in the range is 1-100
nm
 Nanocomposites consisting of two phases:
Nanocrystalline phase + Matrix phase
Phase may be ( Inorganic-Inorganic, Inorganic-Organic, or Organic-Organic
 Nanocomposites means nanosized particles ( Metals, Semiconductors, dielectric
conductors, etc.) embedded in different matrix materials ( Ceramics, Glasses,
polymers, etc).

Spectrophotometric Techniques
Electrochemical Techniques
Chromatographic Techniques
Techniques for Analysis of Pharmaceuticals drugs and
neurotransmitters

Why we have Chosen Electrochemical Sensors
 Chromatographic Techniques
 Time consuming
 Expensive
 Use of Toxic Solvents
 Require a pre treatment
step it difficult perform
routine analysis
 Electrochemical Sensors
 Simple
 Small
 Selective
 Fast
 Flexibility
 User Friendly

In my current work, I have synthesized different transition metal oxide
nanocomposites for fabricated electrochemical sensors and studied their
potential applications, which include ,
NANOCOMPOSITES ACTIVITY
ZrO2/rGO/GCE : Regorafenib (Anti cancer drug)
CuNWs/poly(EMIMS)/CPE : Etlifrine (Anti hypotensive drug)
Co3O4/rGO/CTAB : Dopamine, Uric acid and Folic acid
(Biomolecules)
PtCu/RGO/GCE : Rutin (Citrus Flavanoid)

13
CHAPTER – II
EXPERIMENTAL

Analytical techniques used in this study are-
1. Cyclic voltammetry and 2. Differential pulse voltammetry
Instrumentation
1. Potentiostat
2. Recording device
3. Electro chemical cell
Fig. 2.1. Experimental set set-up used to
record all electrochemical measurement
The main parts of the instrument are-

The Electrochemical Cell Set-up
Fig.2.2 Schematic representation of an assembled electrochemical cell

Important Parameters of a Cyclic Voltammogram
A – Reduced form
B – Oxidation
C – Oxidized form
D – Reduction
Formal potential,
E0 = ( Epa + Epc ) / 2
A typical cyclic voltammogram of current versus potential
Peak current for Faradaic processes is given by Randles - Sevcik equation
ip = (2.69 x 105) n3/2 A D0
1/2 C0 u ½
Where
n - is the number of electrons involved in the electrode reaction.
A - is the area of electrode in cm2.
Do - is the diffusion coefficient of the species in cm2 s-1
Co - is the concentration of the species in mol /cm3
u - is the scan rate in Vs-1.

Differential pulse voltammetry (DPV):
In DPV fixed magnitude pulses super imposed on a linear potential ramp are
applied to the working electrode. The potential pulse applied is of 50 mS
duration. The time gap between any two consecutive potential pulses is 0.5 to 5
S. In this technique, the current is sampled twice just before the pulse
application and again late in the pulse life. The difference of these two currents
is plotted against the applied potential to get differential pulse voltammogram.
Pulse voltammetric techniques are aimed at lowering the detection limits of
voltammetric measurements. This is possible by substantially increasing the
ratio of faradaic currents to non-faradaic currents.

Preparation of the working electrodes
carbon paste electrode :
The bare carbon paste electrode
(BCPE) was prepared by homogenous
mixing of 70% graphite powder +
30% silicone oil
Glassy carbon electrode :
Glassy carbon is non-graphitized carbon that combines the properties of
glassy and ceramics with the properties of graphite. The most important
properties include high temperature resistance, hardness, low density, low
electrical resistance, low friction, low thermal resistance, extreme resistance to
chemical attack and impermeability to gases and liquids.
In this study, we used commercially available GCE, polished with alumina
powder (1 μm, 0.3 μm and 0.05 μm), washed with ethanol, nitric acid solution,
and then with Millipore water under ultrasonic treatment and dried.

Characterization techniques
 FT-IR spectroscopy:
 Perkin Elmer Spectrum TwoTM FT-IR spectrometer in the range 500 – 4000 cm−1
(Dr. KSV Lab, Dept. of Chemistry, YVU)
 Raman spectroscopy:
 Renishaw inVia microscope. A HeNe laser (633 nm) was used as the light source
for excitation, range 1000 – 3000 cm−1 (IIT Chennai)
 Atomic force microscopy:
 (Multimode scanning probe microscope AFM/STM NT-MDT, PSG Tech,
Coimbatore)
 X-ray diffraction:
 Rigaku Miniplus-600 X-ray diffractometer with Cu Kα radiation
(λ- 1.5406 Å), scan rate 5o/s, 2θ values 5o
– 90o
(DST-FIST facility, Univ. of
Kalyani)

Characterization techniques
 Transmission electron microscopy (TEM) including high-resolution TEM,
selected area electron diffraction (SAED), Energy dispersive X-ray
spectroscopy(EDX) :
 JEOL JEM-2100 electron microscope operated at 200 kV equipped with an
Oxford Instruments’ energy-dispersive X-ray detector (PSG Tech, Coimbatore)
 Electrochemical characterization (Cyclic voltammetry and
chronoamperometry investigations) :
 CHI potentiostat (Model CHI 6002 E, USA) (Dr. G. Madhavi lab, Dept of
Chemistry, SVU)

CHAPTER – III
Highly sensitive electrochemical sensor for
anticancer drug by a zirconia nanoparticle-
decorated reduced graphene oxide
nanocomposite

“Highly sensitive electrochemical sensor for anti-cancer
zirconia nanoparticle decorated reduced graphene oxide
nanocomposite ”
Schematic diagram:
CHAPTER-III

XRD ANALYSIS
Debye-Scherrer equation
(D = 0.89λ/βcosθ).
Where D, λ, β and θ are the
average particle size, wavelength,
intensity at the full width at half-
maximum of the diffraction peak,
and diffraction angle of the (111).
The particle size of ZrO2 is about
7 nm.
standard cards (JCPDS card No. 49-1642 and 37-1484)

FT-IR ANALYSIS
The ZrO2/rGO sample shown in
Fig. b , here the the hydroxyl,
carbonyl and epoxide functional
group peak intensities were
decreased significantly, which
confirm the reduction of pristine
GO to the formation of ZrO2/rGO
nanocomposite

3. FE-SEM
XPS ANALYSIS
The chemical composition was confirmed
by XPS. ZrO2-doped rGO nanocomposite
(ZrO2/rGO) is shown in Fig. The major
peaks at 182.5, 284.9, and 530.2 eV are
attributed to Zr 4d, C 1s, and O 1s,
respectively. In addition, the peaks at 27,
333 and 433 eV are attributed to Zr 4p,
Zr 3p, and Zr 3s, respectively. The
deconvolution spectrum of the Zr 3d
peak, Figure (inset), shows binding
energies at 182.4 and 184.9 eV attributed
to Zr 3d5/2 and 3d3/2, respectively, which
can be assigned to the Zr (IV) oxidation
state. Based on these results, we
confirmed that ZrO2 is well embedded
into the wrinkled rGO

4. EDX ANALYSIS
The presence of carbon, zirconium, and oxygen elements,
confirming the presence of ZrO2 on to the GO surface

5. TEM ANALYSIS
TEM, HRTEM, and SAED images of (a–c) pristine ZrO2 and (d–f) ZrO2/rGO nanocomposite

CVs recorded in PBS 0.1 M, pH 7.0, at the scan rate of 100 mVs−1 (a) blank and bare
GCE electrode without REG, (b) bare GCE in the presence of 0.1 mM of REG, (c) ZrO2
modified GC electrode in the presence of 0.1 mM of REG, and (d) ZrO2/rGO modified
GC electrode in the presence of 0.01 mM of REG.
ELECTROCATALYTIC
APPLICATION

DPV voltammograms obtained with the ZrO2/rGO/GCE electrode in an electrolyte
solution at different pH values, with 0.01 mM REG. (b) Calibration plot of the anodic
peak current (curve-I) and the anodic peak potential (curve-II) vs the pH of the 0.1 M
PBS solution, during the electro-oxidation of 0.01 mM REG, at a scan rate of 100
mVs−1.
Effect of pH

CVs recorded at the ZrO2/rGO/GCE electrode in the electrolyte solution at different scan
rates from 10–100 mVs−1. (b) Calibration plot of the anodic and cathode peak currents
versus the square root of the scan rate, during the electro-oxidation of 0.01 mM REG in the
presence of 0.1 M PBS, pH 7.0.
electron transfer
coefficient (0.76)
ks is the standard
heterogeneous rate
constant (1.18)
determining the slowest
step of the REG
electrochemical oxidation
Influence of the Scan rate

(a) DPVs recorded at the ZrO2/rGO/GCE over a REG concentration of 11–
343 nM in 0.1 M PBS at pH 7.0. (b) Linear calibration plot of the anodic
peak current versus REG concentration.
From the calibration plot, LOD of 11 nM and LOQ of 59 nM were calculated,
These results confirmed that the ZrO2/rGO/GCE is a promising platform for the
determination of REG concentration.
Detection of Regorafenib

DPVs recorded on the ZrO2/rGO/GCE during simultaneous determination of 0.32–
0.66 mM REG, 0.58–1.26 mM AA, and 0.08-0.52 mM UA in 0.1 M PBS, pH 7.0.
Insets: plots of the anodic peak currents against concentrations of REG, AA, and UA.
Simultaneous detection of REG , AA and UA

Samples Spiked sample
(mM)
Found (mM) Recovery (%) RSD (%)
Drug injection 0.010 0.0098 98.0 2.54
0.050 0.0509 101.8 1.98
0.100 0.0990 99.0 1.32
Blood serum 0.010 0.0098 98.0 2.42
0.050 0.0486 97.2 1.65
0.100 0.1026 102.6 1.09
Table. Real-sample analysis of REG using the developed method
The results are summarized in Table. The recovery rates for the different volumes
of the samples were ranged between 97.2% and 102.6%.
The relative standard deviations were in the range of 1.09%–2.54%, showing the
accuracy and efficiency of the constructed electrochemical sensor. Therefore, the
ZrO2/rGO/GCE can be applied to real bio-clinical samples.

1. ZrO2/rGO modified Glassy Carbon electrode was successfully
prepared by hydrothermal method.
2. First time detection of anti-cancer drug by a zirconia
nanoparticle decorated reduced graphene oxide nanocomposite.
3. Detection limit was found to be 11 nM.
4. Real sample analysis for REG in pharmaceuical formulation
and blood serum gave the recovery of 99.6% and 99.3%
respectively.
Conclusions

CHAPTER – IV
SIMULTANEOUS DETERMINATION OF DOPAMINE, URIC ACID AND
FOLIC ACID WITH ELECTROCHEMICAL TECHNIQUES BASED ON
Co3O4/RGO/CTAB MODIFIED CARBON PASTE ELECTRODE

Synthesis: The synthesis of nanocomposites (Co3O4/rGO/CTAB ) has been
carried out in two steps as discussed below, in detail.
(i) rGO prepared by modified hammer’s method
(ii) Co3O4/rGO/CTAB nanocomposites prepared by Hydrothermal method
“Simultaneous determination of Dopamine, Uric acid and Folic
acid with electrochemical techniques on Co3O4/rGO/CTAB
Modified Carbon Paste Electrode”
CHAPTER-IV

1. XRD ANALYSIS
particle size of the Co3O4 nanoparticles
was calculated using
Debye-Scherrer equation
(D = 0.89λ/βcosθ)
according to diffraction peak of the
(311) and the average particle size of
Co3O4 is about 10 nm, which is very
close to the TEM result. The above
result confirms the formation of the
Co3O4/rGO/CTAB composite.
(JCPDS card No. 49-1467)

3. SEM and EDX
ANALYSIS
the morphology and composition was confirmed by SEM, EDX analysis shown in Fig.
(a-d). The EDX analysis Fig. (b) illustrates the presence of confirming the formation of
Co3O4/rGO. Whereas, after addition of CTAB Fig.(d) shows, the presence of cobalt,
oxygen, carbon and nitrogen elements which confirms the final Co3O4/rGO/CTAB
composite.

5. TEM ANALYSIS
Fig. (a, b). The bare GO nanosheets are highly crumpled shown in Fig. (a). The
spherical Co3O4 nanoparticles size nearly 12 nm (red arrow) are well embedded on the
surface of the crumpled rGO (green arrow) and due to the presence of CTAB (yellow
arrow) the Co3O4/rGO composite are slightly agglomerated shown in Fig. (b).
TEM images of GO (a) and Co3O4/rGO/CTAB (b) composite.

ELECTROCATALYTIC
APPLICATION
CVs recorded in PBS 0.1 M, pH 7.0 at the scan rate of 50 mV.s-1.at (a) bare
CPE, (b) Co3O4/CPE, (c) Co3O4/rGO/CPE and (d) Co3O4/rGO/CTAB/CPE
modified electrode in the presence of 1 mM of DA.

Effect of pH
CVs obtained at the Co3O4/rGO/CTAB/CPE electrode in electrolyte solution at different
pH values with 1 mM DA. (b).Calibration plot of the anodic peak current (curve-I) and
the anodic peak potential (curve-II) vs. pH of the 0.1 M PBS, pH 7.0 during
electrooxidation of 1 mM DA at scan rate 50 mV.s-1.

(a) CVs recorded at the Co3O4/rGO/CTAB/CPE in presence of electrolyte solution at
different scan rate from 50-500 mV.s-1. (b). calibration plots of redox peak current vs.
different scan rates from 50-500 mV.s-1. (c). plot of variations in the redox peak potential
values vs. log ʋ, with the scan rates from 50-500 mV.s-1. (d). linear relationship between
redox peak potential values and log ʋ with scan rates from 250-500 mV.s-1.
the charge transfer coefficient ks value was
calculated by using the following Laviron’s
equation.
Where, scan rate (ʋ), electron transfer
coefficient (α), charge transfer rate constant
(ks), number of electron transferred (n),
Farady constant (F), universal gas constant
(R) and absolute temperature (T). the ks
value was calculated to be 3.39 s-1,
representing that the electron transfer
between the electrode and DA was
enhanced by the addition of the
Co3O4/rGO/CTAB MCPE.

CVs recorded on the Co3O4/rGO/CTAB/CPE modified electrode during simultaneous
determination of 0.07-0.14 mM of DA and 0.7-1.46 mM of UA and 0.7-1.46 mM FA were
prepared in 0.1 M PBS, pH 7.0. Fig. 9(b, c, d) The linear calibration plot anodic peak current
versus the DA, UA, and FA concentrations

DPV obtained for Co3O4/rGO/CTAB/CPE with
0.04-0.22 mM of DA in 0.1 MPBS (pH 7.0) in the
preseance of 0.2 mM of UA, and 0.3 mM of FA. (b).
The linear calibration plot anodic peak current
versus the DA concentrations
DPV obtained for Co3O4/rGO/CTAB/CPE with 0.5-
1.1 mM of UA in 0.1 MPBS (pH 7.0) in the
preseance of 0.05 mM of DA, and 0.3 mM of FA. (b).
the linear calibration plot anodic peak current versus
the UA concentrations
DPV obtained for Co3O4/rGO/CTAB/CPE with 0.3-3.2
mM of FA in 0.1 MPBS (pH 7.0) in the presence of
0.06 mM of DA, and 0.5 mM of UA. (b). the linear
calibration plot anodic peak current versus the FA
concentrations

Electrode Detection Limit (µM) Method Ref
Highly exposed (001) facets of titanium dioxide modified with
reduced graphene oxide
6.0 DPV 50
Au-CA SAMS 2.3 DPV 51
Hydrogenated cylindrical carbon electrodes 7.5 CV 52
Metallothionenins self-assembled gold electrode 6.0 CV 53
Pd-NC/rGO/GCE 7.0 Amperometry 54
RGO-PAMAM-MWCNT-AuNP/GCE 3.3 DPV 55
Carbon paste-Modified GCE 1.5 DPV 56
Co3O4/rGO/CTAB CPE 2.8 DPV This
work
Caparison of limit of detection of DA with Co3O4/rGO/CTAB and various modified electrode

Sample Spiked (mM) Found (mM) Recovery (%) RSD (%)
Drug injection 0.1 0.098 98.0 2.3
0.2 0.211 105.5 4.8
0.3 0.029 96.6 5.9
Human serum 0.1 0.109 109.0 6.5
0.2 0.198 99.0 3.4
0.3 0.311 103.6 5.8
Determination of DA levels in injection sample and human blood serum using the
Co3O4/rGO/CTAB MCPE.
Co3O4/rGO/CTAB MCPE was used for the electrocatalytic detection of a dopamine hydrochloride injection
and human serum (From Health Centre of Sri Venkateswara University, Sri Venkateswara University,
Tirupati, India.) were using the following method. 0.1 M of the human serum sample were diluted to 100 mL
with pH 7.0 (PBS, 0.1 M) without any pretreatment and were used for further analysis. Each time 24 mL of
this solution were added with various volumes of DA solutions of known concentrations to obtain various
concentrations of spiked DA were analyzed by DPV.
DA contained diluted injection samples (specified content of DA is 200 mg in 5 mL) was diluted to 25 mL
with water, obtained various concentration of spiked DA levels were examined using the Co3O4/rGO/CTAB
MCPE. The quantitative recovery of the obtained human serum and injection solution of DA were listed in
Table Moreover, the results shows the proposed method for the determination of DA in human serum and
injection samples were validated. Hence, the fabricated sensor was used for electro analytical applications in
pharmaceutical industry and in the field of medicine for the diagnosis of DA deficiency.

Conclusions
1. Co3O4/rGO/CTAB Modified Carbon Paste Electrode was
successfully prepared for Simultaneous determination of
Dopamine, Uric acid and Folic acid.
2. The detection limt of the electrode for DA was found to be
2.8×10-6 M
3. Real sample analysis for Dopamine in drug injection and
human serum gave the recovery of 100.03% and 103.8%,
respectively, for the modified electrode.

CHAPTER – V
FACILE PREPARATION OF IONIC LIQUID COATED COPPER
NANOWIRE MODIFIED CARBON PASTE ELECTRODE FOR
ELECTROCHEMICAL DETECTION OF ETILEFRINE DRUG

“Facile Preparation of Ionic Liquide-coated Copper
Nanowire-modified Carbon Paste Electrode for
Electrochemical Detection of Etilefrine Drug”
Schematic diagram:
CHAPTER-V

XRD ANALYSIS
XRD patterns of the Cu NWs
The angular position of
Bragg’s diffracted peaks
observed at 43.2º, 50.3º
and 74.2º corresponding to
the (111), (200) and (220)
facets of the Cu.
which is confirmed with
standard JCPDS 04-0836,

FT-IR ANALYSIS
FT-IR peaks are identified at
the prominent band at 3365
cm-1 is the N-H stretching,
which designates the binding
of amine groups on Cu NWs.
The peak at 2971 and 2887
cm−1 corresponds to -C-H
stretching of the terminal -CH3
and -CH2 groups of alkyl
chains. The peak at 1922 cm−1
is due to the C-N with the
surface of Cu NWS. The
vibration mode at 1647 cm-1 is
connected with NH2 scissoring
mode vibrations. The peaks
1000 – 1400 cm-1
corresponding to carboxylic
acids, hydroxyl groups.
FTIR spectra in the range 4000–500 cm-1
for CuNWs .

SEM and TEM ANALYSIS
Fig. FE-SEM images of Cu NWs (a) and (b) top view with different magnification,
(c) and (d) cross sectional view of TEM image of Cu NWs on flexible polyethylene
terephthalate (PET) substrate

Electropolymerization of CuNWs/poly(EMIMS)/CPE
Fig. Electrochemical polymerization of EMIMS (30 cycles) onto the surface of
CuNWs/CPE.
Inset fig. Electropolymerization cycles on the dependence of the oxidation peak
current (Ipa) of 0.01 M ET HCl.

Fig. Cyclic voltammetric behaviors of ET HCl (0.01 M) in 0.1 M PBS (pH
7.0) on the bare CPE (a), CPE/CuNWs, (b) and CPE/CuNWs/poly(EMIMS),
(c) at scan rate 50 mV s−1
ELECTROCATALYTIC APPLICATION

Influence of the Scan rate and pH
Fig. CVs of 0.01 M ET HCl in 0.1 M PBS
(pH 7.0) on the CPE/CuNWs/poly(EMIMS)
at various scan rates. 50, 100, 150, 200, 250,
and 300 mV s−1, respectively. Fig.7 (Inset)
the plot shows the linear relationship
between Ipa and square root of the scan rate.
Fig. A plot of ET HCl oxidation peak
current vs. PBS solution of pH (5.5–
8.0) and formal potential vs. PBS
solution pH (5.5–8.0) at scan rate 50
mV s-1

Detection of Etlifrine HCl
Fig. DPV obtained for CPE/CuNWs/poly(EMIMS) due to the addition of 0.16, 0.33, 0.49,
0.65, 0.81, 0.91 and 1.2 μM ET HCl into 0.1MPBS (pH=7.0). (b) Calibration plot of
oxidation peak current vs. concentration of ET HCl.
LOD = 3* SD/M
LOQ = 10* SD/M
ET HCl LOD is 2.31 µM
ET HCl LOQ is 7.72 µM
The regression equation
expressed as
Ipa (µA) = 85.134 C (µM)
+ 4.227 (R2 = 0.9867).

Real sample Spiked (mM) Found (mM) Recovery (%) RSD (%)
Blood Plasma
0.1 0.096 103 3.68
0.2 0.195 102 8.15
0.3 0.30 100 2.33
Table: Determination of ET HCl levels in blood plasma using the
CPE/CuNWs/poly(EMIMS).
The CPE/CuNWs/poly(EMIMS) was used for the sensing of ET HCl in human blood
serum ( Obtained from Health center Sri Venkateswara University Andhra Pradesh, India)
The determination procedure is as follows 2 mL human serum sample (centrifuge 3000
rpm) was taken and added 100 mL of 0.1 M PBS of pH 7.0 and is used for the analysis.
Each time 24 mL of this solution was added with different volume ratios of ET HCl
solutions of standard concentration to obtain different concentrations of spiked ET HCl.
These solutions were analyzed by the DPV using the CPE/CuNWs/poly(EMIMS). The
quantitative recovery of ET HCl from sample solutions in human plasma is listed in table .

Conclusions
1. CPE/CuNWs/poly(EMIMS) Modified sensor was
effectively applied for the detection of Etilefrine
hydrochloride
2. The CPE/CuNWs/poly (EMIMS) was found to have a
linear response range of 0.1 µM to 1.3 µM for ET-HCl
detection with low LOD of 2.3 µM.
3. The synthesized sensor was effectively applied for the
detection of Etilefrine hydrochloride in the blood plasma
samples, which worked well without further purification
(or treatment) of the blood plasma.

CHAPTER – VI
PtCu NANOCUBES DECORATED REDUCED
GRAPHENE OXIDE NANOCOMPOSITE FOR HIGHLY
ELECTROCHEMICAL SENSING OF CITRUS
FLAVONOID

“PtCu nanocubes decorated graphene oxide nanocomposite for
highly electrochemical sensing of citrus flavonoid”
SYNTHESIS: Synthesis of Pt-Cu/rGO has been carried out in two steps.
i) Reduced graphene oxide prepared by Hammer’s method:
(ii) PtCu/rGO nanocomposite prepared by Hydrothermal method
CHAPTER-VI

1. XRD ANALYSIS
XRD pattern of pure GO and PtCu/rGO
nanocomposite.
The peaks at 41.2o, 47.9o,
70.1o, and 84.9o for the
reflection planes of (111),
(200), (220) and (311)
respectively, consistent with
cubic phase of alloy PtCu
NCbs (JCPDS card no 48-
1549), which indicates pure
intermetallic PtCu phase
Fig.(ii), and a peak at θ=22.6o
(002) indicates the reduced
form of graphene oxide rather
than pure GO Fig.(i).

2. FT-IR
ANALYSIS
Fig. i, ii) FT-IR spectra of pure GO and PtCu/rGO nanocomposite

3. EDX ANALYSIS
Fig. a) SEM and b)EDX images of PtCu/rGO
nanocomposite

3. TEM
ANALYSIS
Fig. a-c) TEM image of pure GO and PtCu NCbs doped
rGO nanocomposite; (d, e) HRTEM images of
nanocomposite; f) SAED pattern of PtCu/rGO
nanocomposite.
(Fig.a,b,c) shows the GO, PtCu
NCbs doped rGO, morphology size
of nearly 50 nm.
Fig.d (white circles) shows the PtCu
NCbs is a mixture of tiny PtCu
nanocrystals with the size of 2-4 nm.
Fig.e.shows the well-defined lattice
fringes of PtCu NCbs with
interplanar distance of 0.219 nm and
0.19 nm, correspond to the (111) and
(200) crystal plans of PtCu alloy.
To further confirm the
crystallization, the selected area
electron diffraction (SAED) pattern
exhibits bright concentric rings
indicates the polycrystalline nature
of PtCu nanoparticles, and the
diffraction rings indexed to the
(111), (200) and (220) planes of
PtCu alloy phases, illustrating the
face centered cubic structure, which
is well coincides XRD pattern
(JCPDS card no 48-1549).

3. XPS ANALYSIS
Fig.a) survey scan XPS spectrum of PtCu/rGO
nanocomposite; b-d) high resolution XPS spectrum of
Pt4f, Cu2p and C1s of PtCu/rGO nanocomposite.
Fig b. shows Pt with the binding energies of
71.2 and 74.7 eV corresponding to the Pt
4f7/2 and Pt 4f5/2 of zero valent metallic of
Pt, respectively. In addition, a weak binding
energies peaks at 72.45 and 75.6 eV
represents Pt is in PtO state. Nevertheless,
based on the peak intensities, which would
confirm Pt(0) is the dominating species.
Fig.c. shows the binding energies at 931.21
eV and 957.68 eV assigned the Cu2P3/2 and
Cu2P1/2 indicates Cu is in the metallic Cu(0)
state. a minor peak at 933.7 eV and 954.37
eV represents Cu(II). The above results
clearly indicate the PtCu/rGO is mainly
having metallic zero valent states of Pt and
Cu.
Fig.d. shows various binding energies at
284.47, 285.21, 286.33 and 288.6 eV, which
depicts C-C, C-O, C=O, and O-C=O
functional groups respectively. Among
these, the peak at 284.47 is having high
intensity, while the other peaks intensities
are weak, which indicates conversion of
pure GO to reduced GO.

Fig. CVs of (a) Blank, (b) bare GCE, (c) rGO/GCE, (d) Cu/rGO/GCE, (e) Pt/rGO/GCE
and (f) Pt-Cu/rGO/GCE modified electrode recorded in PBS 0.1 M, pH 7.0 containing 0.1
mM Rutin at the scan rate of 50 mV.s-1.
ELECTROCATALYTIC
APPLICATION

Fig. a) CVs obtained at the Pt-Cu/rGO/GCE electrode in electrolyte solution at different pH
values with 0.1 mM rutin. (b).Calibration plot of the anodic peak current (curve-I) and the anodic
peak potential (curve-II) vs. pH of the 0.1 M PBS, pH 5.0 during electrooxidation of 0.1 mM
rutin at scan rate 50 mV.s-1.
Effect of pH

Fig. CVs recorded at the Pt-Cu/rGO/GCE electrode in electrolyte solution at different scan rate
from 50-500 mV.s-1. (b,c,d). Calibration plot of the anodic and cathode peak current vs. square
root of scan rate with the presence of 0.1 M PBS, pH 7.0 during electrooxidation of 0.1 mM
rutin.
(1)
(2)

Detection of Rutin
Fig. DPVs recorded at the Pt-Cu/rGO/GCE in the presence of rutin over a concentration
range 0.005-2.2 µM in 0.1 M PBS, pH 7.0. (b). the linear calibration plot anodic peak
current versus the rutin concentrations.
LOD = 3* SD/M
LOQ = 10* SD/M
Rutin detection
limit is 0.019 µM
Rutin
quantification limit is
0.063 µM
Where SD is the
standard deviation of
blank, M is the slope
obtained from the
calibration plots.

To evaluate the practicality and reliability of the proposed method, a medicinal
rutin tablet (label amount: 20 mg per tablet) was employed as standard sample
for determination of its rutin content. Three parallel determinations were
performed and the results are listed in Table. As expected, the standard addition
recoveries in rutin tablet solution are (99.70%, 100.65%, 99.2%), indicating that
the Au-Ag NTs/NG can be efficiently used for the determination of real sample.
Sample
No.
Declared
(mg per tablet)
Found
(mg per
tablet)
Recovery(%) RSD (%)
1 20.00 19.94 99.70 1.5
2 20.00 20.13 100.65 2.3
3 20.00 19.84 99.20 2.1
Determination of rutin in commercial tablets

Conclusions
1. PtCu nanocubes decorated graphene oxide nanocomposite
decorated glassy carbon electrode was successfully prepared for
the determination of Rutin.
2. The detection limt of the electrode for Rutin was found to be
0.019×10-6 M.
3. Real sample analysis for Rutin in commerial tablet samples
gave the recovery of 99.70%, 100.65% and 99.20%, respectively,
for the modified electrode.

CHAPTER – VII
Summary and conclusions

7.1. Summary
The main goal of this research was to construct transition metal / metal oxide nanocomposites
as an electrochemical sensor that would be able to detect pharmaceuticals, small
biomolecules, and flavonoids such as regorafenib, dopamine, uric acid, folic acid, ascorbic
acid, etilefrine and rutin. Several applications of these nanomaterials are discussed in detail in
this chapter. From these discussions, intensive research is still needed to further improve the
properties of various carbon materials, transition metal oxides and their nanocomposites to
meet the required property requirements. It highlights the electrochemical sensors used for the
investigation in the present study and the advantages of these sensors with respect to the
selectivity, sensitivity, detection and quantification limits, stability, reproducibility, ease of
fabrication and availability over the ones used earlier for the similar investigations, as quoted
in the literature. In addition, the detailed transition metal nanocomposites synthesis methods,
analytical techniques, materials and the structure-constitution-morphology-property
relationships have been studied and studied in more detail. Given these goals, a summary of
each individual chapter has been given to recap the main and important findings. The thesis
is divided into seven chapters.

 Simple inorganic and organic molecules/substances such as ZrO2, Co3O4, CuO,
PtCu, EMIMS, CTAB, graphene oxide were successfully used as electrochemical
sensor can be used for fast and selective determination pharmaceuticals, small
biomolecules and flavonoids such as regorafenib, dopamine, uric acid, folic acid,
ascorbic acid, etilefrine and rutin.
 The structural and chemical properties of the synthesized transition metal oxide
nanocomposite was established using FT-IR, XRD, SEM, TEM, EDX and XPS
techniques.
 Avoided the costly electrochemical sensors and cumbersome methods of sensors
preparation.
 For each of investigations optimum conditions of effect of pH, number of cycles of
polymerization and medium of the reaction were unambiguously established.
 Fabricated electrodes are tested for their efficacy by applying to the real-life
situations in medicines and biochemical analysis of Transition metal oxide
nanocomposites based electrochemical sensors was fabricated and characterized.
7.2. Conclusions

LIST OF PUBLICATIONS
1. Manthrapudi Venu, S. Venkateswarlu, Y. Veera Manohara Reddy, A. Seshadri Reddy, Vinod Kumar
Gupta, M.Y. Yoon, G. Madhavi, Highly sensitive electrochemical sensor for anticancer drug by a
zirconia nanoparticle-decorated reduced graphene oxide nanocomposite, ACS Omega, 3 (11), 14597-
14605.
2. Manthrapudi Venu, V.K Gupta, Shilpi Agarwal, Sada Venkateswarlu, G Madhavi “Simultaneous
determination of Dopamine, Uric acid and Folic acid with Electrochemical Techniques based on
Co3O4/rGO/CTAB Modified Carbon Paste Electrode” Int. J. Electrochem. Sci., 13 (2018) 11702 –
11719.
3. Manthrapudi Venu, S. Venkateswarlu, Y.Veera Manohara Reddy, B. Sravani, K Mallikarjuna,
M.young Yoon, G Madhavi “Facile Preparation of Ionic Liquid‐coated Copper Nanowire modified
Carbon Paste Electrode for Electrochemical Detection of Etilefrine Drug” Bull. Korean Chem. Soc.,
40(2019) 560-565.
4. Manthrapudi Venu, Y. Veera Manohara Reddy, Sada Venkateswarlu, B. Saravani, Minyoung Yoon,
G. Madhavi. PtCu nanocubes decorated graphene oxide nanocomposite for highly electrochemical
sensing of citrus flavonoid. (Under review)
5. Manthrapudi Venu, Y.Veera Manohara Reddy, A. Vijaya Bhaskar Reddy, M.Moniruzzaman, Heri
Septya Kusuma, G. Madhavi, Development Of a Method For Quantification Of Two genotoxic
impurities In Lurasidone Using LC-MS/MS” Journal of Chemical Technology and Metallurgy, 54,
4, (2019), 750-757.
6. Manthrapudi Venu, Y.Veera Manohara Reddy, G. Madhavi, Vinod Kumar Guptha, Synthesis and
structural studies of L-Cysteine/Fe3O4 magnetic nanoparticles: Application of the particles for
catalytic reduction of Congo red dye in anaqueous medium at room temperature. (Under review)
7. D. Saritha, A.R. Koirala, Manthrapudi Venu, G. Dinneswara Reddy, A. Vijaya Bhaskar Reddy, B.
Sitaram, G. Madhavi, K. Aruna, “A simple, highly sensitive and stable electrochemical sensor for the
detection of quercetin in solution, onion and honey buckwheat using zinc oxide supported on carbon
nanosheet (ZnO/CNS/MCPE) modified carbon paste electrode,” Electrochimica Acta, 313, (2019),

1. Presented Oral in A.P. SCIENCE CONGRESS – 2016 “ Science and Technology for Health”
Jointly organized with Dr. N.T.R Health University, Acharya Nagarjuna University & Krishna
University November 7-9, 2016
2. Presented poster at The Indian Science Congress Association (ISCA-107) organized by University of
Agriculture Sciences held on 3rd to 7th January-2020 at Bangalore.
3. Participated and presented a paper entitled “Synthesis and structural studies of L-cysteine/Fe3O4
magnetic nanoparticles: Application of the particles for catalytic reduction of congo red dye in
aqueous medium at room temperature” in Two-day National conference on (ETCS-2019) in Dravidian
university, Kuppam on 11-12 March 2019.
4. Presented a poster at The Indian Science Congress Association (ISCA-104) organized by S. V.
University held on 3rd to 7th January-2017 at Tirupati
5. Presented a poster on National conference on Modern trends in chemistry research (MTCR),
organized by Dept. Of Chemistry held on 27 th & 28th January-2017 at Govt. Degree College,
Kadapa.
6. Participated in the Participated in the Participated in the “National Seminar on Emerging Trends in
Pharmaceutical and Chemical Sciences” (ETPCS) held at Sri Venkateswara University, Tirupati during
28 and 29 th March 2016.
7. Presented a paper entitled “Simultaneous determination of Dopamine, Ascorbic acid and Uric acid
using Dipicolinic acid modified carbon paste electrode” (RCEE 2014) held on 3-4 March 2014,
Tirupati.
Details of presentations in the symposia/Seminars

Acknowledgements
Dr. G. Madhavi (Research Supervisor)
Prof. N.Venkata Subba Naidu ( HOD) Dept. of Chemistry
Prof. N.Y. Sreedhar (BOS) Dept. of chemistry
Prof. N.Savithramma, Principal
Prof. G. M. Sundaravalli, Rector
Prof.P. Sreedhara Reddy, Registrar
Other faculty members and Research Colleagues
and all B7 staff
Sincere Gratitude To

THANK YOU VERY MUCH
FOR
KIND ATTENTION
“ A legitimate conflict between Science and Religion cannot exist.
Science without Religion is lame, Religion without Science is Blind."
-Albert Einstein

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