Efficient selective 4-aminophenol sensing and antibacterial activity of ternary Ag2O3·SnO2·Cr2O3 nanoparticles

Article abstract of DOI:10.1039/c9nj01760g

In this study, Ag₂O₃·SnO₂·Cr₂O₃ nanoparticles (NPs) were synthesized via a simple and quick co-precipitation method. The produced materials were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), and photoluminescence (PL) spectroscopy. The hydrodynamic size and zeta potential were measured under acidic and basic pH conditions. The photocatalytic activities of the newly synthesized composite were studied considering various parameters. Antibacterial activity tests showed that Ag₂O₃·SnO₂·Cr₂O₃ is an excellent anti-bacterial agent. A reliable electrochemical sensor probe was designed by depositing the synthesized Ag₂O₃·SnO₂·Cr₂O₃ NPs onto the flat part of GCE, which showed excellent oxidation activity and selectivity towards 4-aminophenol (4-AP) in a phosphate buffer medium. During electrochemical analysis, the desired 4-AP sensor responded linearly over a large concentration range (0.1 nM-0.01 mM), which is known as the linear dynamic range (LDR), and exhibited appreciable sensitivity (25.1962 μA μM^-1 cm^-2). Furthermore, it showed a considerably low limit of detection (98.41 ± 4.92 pM), good reproducibility, fast response (20.0 s), and long-term stability in the phosphate buffer medium. This is an efficient method for the fabrication of a selective electrochemical sensor using the electrochemical approach for safety in environmental and healthcare fields.

Full text of DOI:10.1039/c9nj01760g

View Article Online
View Journal
NJC
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: M. A. A. Subhan, S.
S. Jhuma, P. Chandra Saha, M. M. Alam, A. M. Asiri, M. Al-Mamun, S. A. Attia, T. H. Emon, A. K. Azad and M.
M. Rahman, New J. Chem., 2019, DOI: 10.1039/C9NJ01760G.
Volume 40 Number
1
January 2016 Pages 1–846
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
NJC
New Journal of Chemistry
www.rsc.org/njc
A journal for new directions in chemistry
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1144-0546
PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
rsc.li/njc

Page 1 of 40
New Journal of Chemistry
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
Efficient selective 4-aminophenol sensing and antibacterial activity of ternary
Ag O ·SnO ·Cr O nanoparticles
2
3
2
2
3
Md Abdus Subhana, e*, Sanjida Sultana Jhuma , Pallab Chandra Saha , M. M. Alam
a
a
b
,
c
d
e
f
Abdullah M. Asiri , Mohammad Al-Mamun , Sara Aly Attia , Tanvir Hossain Emon , Abul
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
f
c,
Kalam Azad , and Mohammed M. Rahman *
aDepartment of Chemistry, School of Physical Sciences, Shah Jalal University of Science and
Technology, Sylhet-3114, Bangladesh
bDepartment of Chemical Engineering and Polymer Science, Shah Jalal University of Science
and Technology, Sylhet 3100, Bangladesh
cCenter of Excellence for Advanced Materials Research & Department of Chemistry, Faculty of
Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia,
dCenter for Clean Environment and Energy, Griffith School of Environment, Gold Coast
Campus, Griffith University, QLD 4222, Australia
eCenter for Pharmaceutical Biotechnology and Nanomedicine (CPBN), Department of
Pharmaceutical Sciences, Northeastern University, Boston, MA, USA.
fDepartment of Genetic Engineering & Biotechnology, Shah Jalal University of Science and
Technology, Sylhet-3114, Bangladesh
(
Corresponding author’s e-mail: subhan-che@sust.edu; mmrahman@kau.edu.sa)
Dr. Md Abdus Subhan
Professor of the Department of Chemistry
Shahjalal University of Science and Technology, Sylhet, Bangladesh
E-mail:subhan-che@sust.edu, md.subhan@northeastern.edu
Phone: +8801716073270
&
Dr. Mohammed M. Rahman,
Center of Excellence for Advanced Materials Research (CEAMR) &
Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589,
P.O. Box 80203, Saudi Arabia
Email: mmrahman@kau.edu.sa
Phone: +966-59-642-1830; Fax: +966-12-695-2292

New Journal of Chemistry
Page 2 of 40
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Abstract
In this approach, Ag O ·SnO ·Cr O nanoparticles (NPs) were synthesized by a simple
2
3
2
2
3
and quick co-precipitation method. The produced materials were characterized by X-ray powder
diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(
EDS), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy
FTIR), and Photoluminescence (PL). Hydrodynamic size and zeta potential were observed in
(
acidic and basic pH. Photocatalytic activities of the newly synthesized composite were studied
considering various parameters. Antibacterial activity tests showed Ag O ·SnO ·Cr O is an
2
3
2
2
3
excellent anti-bacterial agent. A consistent electrochemical sensor probe was designed by the
synthesized Ag O ·SnO ·Cr O NPs onto the flat part of GCE, which showed an excellent
2
3
2
2
3
oxidation activity towards the selective 4-aminophenol (4-AP) in phosphate buffer medium.
During the electrochemical analysis, the desired 4-AP sensor was found to response linearly over
the large concentration range (0.1 nM0.01 mM) known as linear dynamic range (LDR) and
-1
-2
exhibited appreciable sensitivity (25.1962 µAµM cm ). Furthermore, it was showed that the
considerably lower limit of detection (98.41±4.92 pM), good reproducibility, fast response (20.0
sec.), and long-term stability in phosphate buffer medium. This is an efficient method for the
fabrication of selective electrochemical sensor by the electrochemical approach for the safety of
environmental and healthcare fields.
Keywords: Ag O ·SnO ·Cr O
nanoparticles; Photo-catalysis; Antibacterial activity;
Electrochemical sensor development; 4-aminophenol; Environmental safety.
2
3
2
2
3

Page 3 of 40
New Journal of Chemistry
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
. Introduction
Nanostructured mixed metal oxides play a very important role due to their versatile
technological applications and outstanding properties.1-5 Depending on the size, structure and
morphology of the nanoparticles, their magnetic, optical, catalytic and electronic properties vary.
Thus, the nanosized particles exhibit a relatively higher performance compared to the bulk
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
6
materials due to the changes of semiconductor band structure. The multiphase nanocomposite
based on two or more different metal oxides coexisting in the same matrix could pose the
7
modified properties due to the metal-metal and metal-oxygen interactions. By the development
of new composite material could open up a new dimension for research and applications. The
numerous methods are involved for the preparation of the mixed metal oxides including sol-
gel,8,9 wet impregnation,10 mechanochemical synthesis,11 hydrothermal method,12,13
sonochemical, co-precipitation,14,15 electrochemical,16 and pyrolysis17,18.
The tin oxide (SnO ) is a semiconductor material with the band gap energy of 3.6 eV and
2
has the wider technological applications including transistors, electrodes, liquid crystal displays,
catalysts, photovoltaic devices, electrochemical sensors, and antistatic coating.19-23As the
electrochemical sensor in I-V approach, SnO is extensively applied to detect the environmental
2
toxic chemicals such as acetone,24,25 and Benzaldehyde . The silver (Ag) is a noble metal and
26
prominent in the field of the nanomaterial research, due to its unique properties such as sensing,
27
optoelectronic and catalytic, feasible to apply in the various technological fields including high
2
8
29
30,31
temperature resistant materials, corrosive resistant materials, liquid crystal display,
green
3
2
33,34
pigment, catalyst
and so on. Specifically, the silver oxide has been reported as a sensor to
detect various environmental toxic chemicals in electrochemical (I-V) approach.35-37 In this
study, the special attention has been focused on the formation and the properties of chromium
(III) oxide (Cr O ) among the different stable oxidation states of its. Due to its high stability and
2 3

New Journal of Chemistry
Page 4 of 40
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
electrochemical activity, it has been applied as a sensing material for the fabrication of
electrochemical sensor to detect various chemicals and biochemical.38,39 By the mixing of three
different oxides in the matrix, a new nanocomposite of Ag O ·SnO ·Cr O is formed, which
2
3
2
2
3
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
shows the deferent physical and electrochemical properties rather than the individual ones and
the co-precipitation method has been applied to prepare this ternary metal oxide. This method for
the preparation of the nanocomposite metal oxides is famous, due to easy operation, economical,
4
0
versatile, promising scale-up synthesis and effective for large scale production. This composite
has been characterized and the various applications have been studied. The most fascinating
applications of this nanocomposite as a photocatalyst to degrade the organic dye released by
textile and dyeing industries, which is burning issue nowadays due to the cause of pernicious
41
effect both human life and environment. Optical properties and antibacterial activities of the
synthesized nanocomposite also have been studied.
As the major ingredient for the formulation of paracetamol, the 4-aminophenol (4-AP) is
used as a drug to the relief of the fever and the pain associated with arthritis, backache, headache,
and postoperative pains. The 4-AP in the paracetamol is available in the form of syrups,
suspension, tablets and injections in the drug market depending on the patient’s requirement such
as pregnant women, children, and elderly people. Due to the accumulation of 4-AP in human
through the intake of paracetamol may cause numerous pathological syndromes such as
hepatotoxicity and nephrotoxicity.42-45 Therefore, considering the toxicity of 4-AP, it has been
restricted to 50 ppm as the maximum concentration in the formulation of paracetamol by
European Union and USA.46,47 Besides this, as a base industrial raw material, 4-AP is used
extensively to produce various chemicals such as inhibitor, dyestuff, petroleum additives and
developer.48 As it is stated that 4-AP has a hazardous effect on both human and environment.

Page 5 of 40
New Journal of Chemistry
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
Therefore, it is a necessity to the development of sensitive and reliable methods for the detection
of 4-AP. Up to date, the numerous conventional analytical methods are applying to detect 4-AP
such as capillary electrophoresis,49,50 electrochemical detection,51 high-performance liquid
chromatography (HPLC) coupled with UV-visible,52,53 fluorescence and flow-based analytical
techniques55,56. But these methods are limited due to various drawbacks such heavy and costly
instruments, expensive analyzing reagents, time-consuming and non-portable. On the other hand,
the electrochemical methods are sensitive, quick detection time, inexpensive with in-situ
detection facilities, simple and easy detection methods. A number of researches based on various
metal oxides or nanocomposites by electrochemical approach have been reported to detect the
various environmental toxicants, chemicals and biochemical and reported elsewhere.57-61
Furthermore, the electrochemical method particularly I-V approach becoming popular and the
regarding this, a number of researches based on the various oxides of transition metals as sensing
mediators have reported recently to detect numerous toxic chemicals and biochemicals62-71. This
study will be performed to develop an electrochemical sensor in electrochemical approach using
Ag O ·SnO ·Cr O NPs onto GCE.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
54
2
3
2
2
3
As an essential part of this study, the synthesized Ag O ·SnO ·Cr O NPs was deposited
2
3
2
2
3
onto the GCE as the thin uniform layer with conductive nafion (5% suspension in ethanol) to
develop the desire working electrode for the chemical sensor selective to 4-AP. A calibration
curve was plotted using current vs. concentration of 4-AP relation and identifying the linear
region in the calibration curve, where the linear dynamic range (LDR) was labeled. The
sensitivity of the proposed 4-AP chemical sensor was calculated from the slope of the calibration
2
curve by considering the active surface area of GCE (0.0316 cm ). The detection limit was also
computed from the slope of the calibration curve by considering the signal to noise ratio of 3.

New Journal of Chemistry
Page 6 of 40
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
2
. Experimental
.1 Materials and methods
All the chemicals used for this research purpose including silver nitrate (Sigma Aldrich,
Germany), tin chloride hydrate (Merck, Germany), chromium chloride hexahydrate (Sigma
Aldrich), acetone (Merck, Germany), sodium carbonate (AR, BDH) were purchased. As the
requirement of this study, the toxic chemicals in the form of analytical grade such as 2-
aminophenol (2-AP), 3-methoxyphenol (3-MP), 4-aminophenol (4-AP), 4-hexylresorcinol,
melamine, m-tolyl hydrazine hydrochloride (M-THydHCl), phenylhydrazine (PHyd),
zimtaldehyd were obtained from a local supplier of Sigma-Andrich. The auxiliary regents
including monosodium, disodium phosphate buffer, concentrated liquid ammonia and a
conductive binding agent (5% nafion suspension in ethanol) were used. Double beam UV-
Visible spectrophotometer (UV-1800 series, UV-Vis Spectrophotometer, Shimadzu Corporation,
Kyoto, Japan) was used for the measurement of absorbance. Quartz cells of 1 cm path were used
as a sample holder. For PL study Spectrofluorometer (Shimadzu Corporation, Kyoto, Japan) was
used. For calcination, electric muffle furnace was used. FTIR spectrophotometer (Shimadzu,
IRPrestige-21) was used in this work. Bulk crystal phase identification and other structural
information of the materials studied in this work were characterized by X-ray diffraction (XRD,
Bruker D8 Advance diffractometer, equipped with a graphite monochromator). The diffraction
patterns were recorded in the step scan mode at 0.05 steps and the measurement rate of 10 s/step.
The diffraction patterns were registered within the 2θ angle range from 10° to 80°. The surface
morphology and nanostructure characterizations were performed by using a Scanning Electron
Microscope (SEM) equipped with an Energy-Dispersive X-ray Spectrometer (EDS) (JSM-
7100F) linked with an EDS (Oxford) mapping device. XPS investigation was performed for
nanomaterials using a K-α1 spectrometer (Thermo scientific, K-α1 1066) with an excitation
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0

Page 7 of 40
New Journal of Chemistry
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
radiation source (A1 Kα1, Beam spot size = 300.0 μm, pass energy = 200.0 eV, pressure 10-8
torr). Hydrodynamic size and zeta potential were measured by Zetasizer Nanoseries (Nano-
ZS90). The Ag O ·SnO ·Cr O nanoparticle modified GCE electrode served as a working
2
3
2
2
3
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
electrode, whereas an Ag/AgCl (sat. KCl) and a Pt wire acted as a reference and counter
electrodes, respectively. All the electrochemical experiments were conducted in 0.1 M phosphate
buffer solution (PBS) under N atmosphere condition, where the volume of solution was 10 ml.
2
The Ag O ·SnO ·Cr O nanoparticle was characterized by means of electrochemical impedance
2
3
2
2
3
spectroscopy (EIS). The Keithly electrometer was used to the assembled the desire
electrochemical (sensor) cell.
2
.2 Synthesized of Ag O ·SnO ·Cr O NPs
2 3 2 2 3
The composite Ag O ·SnO ·Cr O was prepared by co-precipitation method from their
2
3
2
2
3
salts as precursors. At first solutions of 0.25 M, 20 mL of AgNO (0.849 gm), SnCl ·2H O
3
2
2
(
1.128 gm), CrCl ·6H O (1.332 gm) respectively and solution of 1.0 M Na CO were prepared
3 2 2 3
by using distilled water. Then the solutions were mixed together in a beaker in 1:1:1 ratio and
stirred vigorously at room temperature for 5 minutes. Then the solution of 1.0 M Na CO was
2
3
added slowly with agitation until precipitation was complete. The resultant mixture was stirred
for a further 4 hours at 45 ºC with constant stirring. Then white metal carbonate precipitates were
separated from the solution by centrifugation, washed several times with deionized water and
finally dried at 150 ºC for two hours in an oven. The obtained white precipitate was calcined in a
muffle furnace at 600 °C and 850 ºC for five hours respectively. Oxides are formed from their
carbonates by calcination.
2
.3 The fabrication of GCE working electrode using Ag O ·SnO ·Cr O NPs
2 3 2 2 3

New Journal of Chemistry
Page 8 of 40
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
The fabrication of a working electrode of the proposed electrochemical sensor by using
Ag O ·SnO ·Cr O NPs onto flat GCE is an essential part of this study. For this reason, the
2
3
2
2
3
thinner film with active Ag O ·SnO ·Cr O NPs in ethanol was prepared to make the thin
2
3
2
2
3
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
uniform-layer onto GCE. Then, the modified GCE with Ag O ·SnO ·Cr O NPs was kept at
2
3
2
2
3
ambient conditions to completely dry. After that, a drop of nafion (the nafion commercially
available as 5% suspension in ethanol and known as a conductive binding agent) was added on
the modified GCE to enhance the stability of the NPs on GCE during the electrochemical
analysis in phosphate buffer medium. When the Nafion is dropped onto
the Ag O ·SnO ·Cr O NPs coated GCE, it is soaked the coated nanomaterials homogeneously
2
3
2
2
3
and distributed throughout coated-film. When it is dried at 35 °C inside an oven for an hour, a
homogeneous thin-film is resulted to form onto the GCE by Ag O ·SnO ·Cr O NPs. To
2
3
2
2
3
assemble the electrochemical (sensor) cell, the modified GCE and a simple Pt-wire were
connected in a series with the Keithly electrometer. The resulted electrochemical sensor is based
on two electrodes system, where the connected modified GCE is functioned as working and the
Pt-wire as counter electrode respectively. The 4-AP was diluted in the deionized water to form
several solutions based on concentration ranging in the sequence from 0.1 mM to 0.1 nM. During
the electrochemical investigation, the sensor analytical performances such as sensitivity, linear
dynamic range, detection limit, reproducibility, stability and response time were measured at
ambient conditions. The phosphate buffer solution was taken in the investigating beaker as 10.0
mL as constant through the electrochemical analysis.
3
3
. Results and discussion
.1 Structural Analysis of Ag O ·SnO ·Cr O nanoparticles
2
3
2
2
3

Page 9 of 40
New Journal of Chemistry
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
As shown in Fig. 1, 2θ peaks observed at 26.579 °, 33.864 °, 37.941 °, 38.965 °, 42.625 °, 51.756
, 57.804 °, 61.861 °, 64.714 °, 65.943 °, 71.754 °, and 78.68 ° are due to tetragonal SnO2
°
(Cassiterite). The diffraction peaks of SnO was detected in the sample, can be indexed to (hkl)
2
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
values of (110), (101), (200), (111), (210), (211), (002), (310), (112), (301), (911), and (321)
diffraction planes. Peaks are confirmed by matching with PDF file number 99-0024 (Intensity
matching 91%). Similarly, the presence of orthorhombic silver oxide (Ag O ) in this nanoparticle
2
3
can be identified by the 2θ peaks at 26.665 °, 27.705 °, 33.246 °, 36.16 °, 41.405 °, 43.807 °,
5.508°, 51.849 °, 52.897 °, 54.724 °, 57.22 °, 60.19 °, 62.428 °, 69.278 °, 71.312 ° and 76.458 °
PDF file number 77-1829, Intensity matching 52%). Diffraction peaks of Ag O was detected in
4
(
2
3
(110), (400), (101), (131), (331), (511), (620), (211), (022), (351), (800), (622), (911), (280), and
(321) diffraction planes. Finally, rhombohedral chromium oxide (Cr O ) can be detected in
2 3
(101), (131), (222), (020), (220), (351), (130), (230), (342), (241), and (330) diffraction planes
by 2θ values at 33.606 °, 36.192 °, 39.765 °, 44.191 °, 50.215 °, 54.85 °, 63.451 °, 65.094 °,
3.348 °, 76.81 °, and 79.059 ° (PDF file number 85-0730, intensity matching 34%). The
7
deviation (observed by Intensity Matching) from the XRD patterns of individual oxides were
calculated using Jade MDI software and could be due to the synergic effect involved in mixing
three different metal oxides to form tri-metallic oxide. Hence, the nanocomposite might possess
different characteristics than its corresponding individual oxides. The particle size of the
nanocomposite was estimated from XRD data to be 34.6 nm using Scherrer’s formula τ =
Kλ/(βcosθ). Where τ is the mean size, K is a dimensionless shape factor with a value 0.94, λ is
the x-ray wavelength (0.1506 nm), β is the line broadening at half the maximum intensity
(FWHM) and θ is the Bragg angle.

New Journal of Chemistry
Page 10 of 40
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Fig. 1 X-Ray powder diffraction pattern of Ag O ·SnO ·Cr O nanoparticles
2
3
2
2
3
3
.2 Surface analysis of Ag O ·SnO ·Cr O nanoparticle
2 3 2 2 3
The SEM images in Fig. 2 revealed the morphology of Ag O ·SnO ·Cr O nanoparticles.
2
3
2
2
3
The nanoparticles formed irregular morphology with combination of three different oxides in the
matrix, which might have high surface activity, resulting in perhaps higher catalytic and sensor
activity. Fig 2 shows different morphologies of the particles on the surface.

Page 11 of 40
New Journal of Chemistry
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Fig. 2 SEM image of Ag O ·SnO ·Cr O nanoparticle
2
3
2
2
3
3
.3 Qualitative Analysis of Ag O ·SnO ·Cr O nanoparticle
2 3 2 2 3
The EDS study was carried out to map the elemental composition as well as the
distribution of the elements in the nanoparticle matrix (Figure 3). As is evident from Table 1, the
NPs are composed of Sn, Ag, Cr, and O with an atomic percentage of 13.98%, 18.21%, 15.28%,
and 52.54%.

New Journal of Chemistry
Page 12 of 40
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Fig. 3 EDS spectrum of Ag O ·SnO ·Cr O nanoparticle
2
3
2
2
3
Table 1. Elemental Analysis of Ag O ·SnO ·Cr O nanoparticle
2
3
2
2
3
Element
O K
(keV)
0.525
5.411
2.983
3.442
Mass%
15.99
15.1
Atom%
52.54
15.28
18.21
13.98
100
Cr K
Ag L
Sn L
37.36
31.55
100
Total
3
.4 XPS analysis of Ag O ·SnO ·Cr O nanoparticle
2 3 2 2 3
Fig. 4 shows the XPS spectrum of Ag O ·SnO ·Cr O NPs. XPS peaks are observed
2
3
2
2
3
corresponding to nano Ag O , Cr O , SnO in mixed metal nanoparticle oxide in
2
3
2
3
2
Ag O ·Cr O ·SnO . Peaks are assigned at different binding energies (eV) for each metal in metal
2
3
2
3
2
oxides from lower energy to higher energy, Sn(3d ), Sn(3d ), Sn(3p3), Cr(3p ), Sn(3p1),
5
/2
3/2
3/2
Sn(3s), Ag(3d ), Ag(3p ), Cr(2p ), and Sn(4d). The XPS results clearly indicated the
3
/2
5/2
1/2
formation of mixed metal nanoparticle oxide in Ag O ·SnO ·Cr O .
2
3
2
2
3

Page 13 of 40
New Journal of Chemistry
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Fig. 4 XPS spectrum of Ag O ·SnO ·Cr O nanoparticle
2
3
2
2
3
3
.5 FTIR analysis of Ag O ·SnO ·Cr O nanoparticle
2 3 2 2 3
In the FTIR spectrum (Fig. S1) of Ag O ·SnO ·Cr O nanoparticle, peaks are observed in
2
3
2
2
3
-1
the region of 400-1000 cm correspond to the vibration modes of M-O and M-O-M (M = Ag,
-1
Cr, Sn). IR band at 3358.07 cm due to the stretching mode of O-H group indicates the presence
-1
-
of absorbed water. IR peak observed at 943.19 cm may be assigned to Sn-O, peak at 855.33 cm
1
-1
is due to Cr-O low frequency vibration. Peaks observed at 690.5 and 503.42 cm are assigned
to Ag-O vibrations.
.6 Zeta potential and hydrodynamic size of Ag O ·SnO ·Cr O nanocomposite
3
2
3
2
2
3
Zeta potential and hydrodynamic size of Ag O ·SnO ·Cr O nanocomposite were studied
2
3
2
2
3
both in acidic (Na-citrate buffer) and basic (PBS buffer) pH at 25 °C to know the size and charge
in dispersed media. Hydrodynamic size, zeta potential and poly dispersive index (PDI) have been
listed in Table 2. The hydrodynamic size of Ag O ·SnO ·Cr O in acidic pH and basic pH was
2
3
2
2
3
found to be 1113.5 and 1174 nm respectively. Zeta potential in acidic and basic pH has been

New Journal of Chemistry
Page 14 of 40
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
observed to be -27.05 and -26.2 mV respectively. The results indicated that Ag O ·SnO ·Cr O
3
2
3
2
2
particles are negatively charged and can easily adsorb organic compounds, dyes and organic
chemical toxins on the particle surface either in acidic or basic media and perform catalytic
functions. Observation of single peak with 100% intensity during the measurement of the
hydrodynamic size designated the formation of a single particle by the mixing of individual
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
oxides Ag O , SnO and Cr O . Detailed structural investigations will provide further insight into
2
3
2
2
3
it.
Table 2. Hydrodynamic size and zeta potential of Ag O ·SnO ·Cr O
3
2
3
2
2
Nanocomposite
Na-citrate buffer
PBS buffer
(pH 7.4)
(pH 4.95)
Ag O ·SnO ·Cr O Size (nm) Zeta
PDI
Size (nm) Zeta
potential
PDI
2
3
2
2
3
potential
mV)
-27.05
(
(mV)
1
113.5
0.190
1174.0
-26.20
0.191
3.7 UV-Visible spectrum and band gap determination of Ag O ·SnO ·Cr O nanocomposite
2
3
2
2
3
The absorption spectrum of Ag O ·SnO ·Cr O nanocomposite dispersed in acetone
2
3
2
2
3
solution and band-gap determined from the UV-Visible spectra are shown in Fig. 5. It was found
that a broad diffusion peak is observed in the UV region at 349 nm. The UV-Visible spectral
study may be assisted in understanding the electronic structure of the optical band gap of the
material. Absorption in the near ultraviolet region arises from electronic transitions associated
within the sample.

Page 15 of 40
New Journal of Chemistry
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Fig.
Figure 5. (a) UV – Visible spectrum and (b) band gap of Ag O ·Cr O ·SnO nanocomposite
5
2
3
2
3
2
The optical band gap of the produced nanocomposite is calculated using the Tauc’s
equation
2
(h) = A(h-E )
g
where  is an absorption coefficient, h is the photon energy (h is the Planck’s constant and  is
the photon frequency), E is the optical band gap and A is a constant usually taken as unity. The
g
2
band gap is found by plotting (αhν) against h푣. The value of the band gap is determined by the
intercept of the straight line at α = 0. Since the band gap of Ag O ·Cr O ·SnO is 3.06 eV. The
2
3
2
3
2
nanocomposite is able to absorb UV and visible light and may show good photocatalytic activity.
.8 Study of PL property Ag O ·SnO ·Cr O nanoparticle
3
2
3
2
2
3
PL spectra of Ag O ·SnO ·Cr O nanoparticle annealed at 600 °C (as shown in Fig. 6(a))
2
3
2
2
3
and 850 °C (Fig. 6(b)) were measured at room temperature in acetone at different excitation
wavelengths. Two emission peaks at 436 nm and 467 nm were observed when it was excited at
320 nm in case of composite annealed at 600 °C. When the sample was excited at 350 nm
emission peaks were observed at 431 nm and 466 nm. Emission peaks at 426 nm and 464 nm
were observed at excitation wavelength 370 nm. Excitation at 380 nm provided emissions at 427
nm and 462 nm. Emissions in the visible region ranging from 420-470 nm indicate blue band.72
The broad blue emission band might arise from the ionized oxygen vacancies to the valence

New Journal of Chemistry
Page 16 of 40
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
band. Due to the radiative recombination of a photogenerated hole with an electron occupying
7
3
the oxygen vacancies the blue emission is observed. The structured emission peaks from 420-
470 nm resembles emission from d-d states of chromium ions in octahedral molecular
complexes. The chromium ions in Cr O are also in octahedral coordination sites and the
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
3
structured emission may be originated from the Cr d-d states. The emission data is compiled in
Table S1.
Fig. 6 PL spectra of Ag O ·SnO ·Cr O nanoparticles annealed (a) at 600 °C and (b) at 800 °C.
2
3
2
2
3
Similarly, three emission peaks at 403, 426 and 454 nm can be found when excited the
800 °C annealed composite with 330 nm energy. In the same way, peaks with three maxima and
different intensity were found when the nanoparticle was excited with 340 nm (404, 427 and 453
nm emissions), 350 nm (405, 426 and 452 nm emissions) and 370 nm (405, 428 and 454 nm
emissions). The emission energy is listed in Table S2.
3
.9 Study of Photocatalytic activity of Ag O ·SnO ·Cr O nanoparticle
2 3 2 2 3
To examine the photocatalytic activity of Ag O ·SnO ·Cr O nanoparticles an aqueous
2
3
2
2
3
solution of methyl violet 6b (MV) dye was irradiated with 200 W tungsten lamp. A certain
amount of photocatalyst was added to the methyl violet (6b) dye solution in a beaker which was

Page 17 of 40
New Journal of Chemistry
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
stirred for 1.0 h prior to irradiation to ensure adsorption-desorption equilibrium. 4.0 ml of dye
solutions were separated from the photocatalyst to record the changes of dye concentration at
regular gaps which were observed spectrophotometrically. The degradation was performed at pH
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
9
and pH 7 in the presence of photocatalyst under different conditions. Spectrophotometric
measurement evaluates degradation of MV dye as a function of time and it was observed that the
absorption intensity of MV dye decreases with increasing time in the presence of photocatalyst.
The following equation was used to calculate the photocatalytic efficiency η.
Photocatalytic efficiency η = (1-C/C ) ×100 = (1-A/A ) ×100
0
0
Where C denotes the concentration of MV before irradiation and C is the concentration
0
of irradiation time, A and A are the corresponding absorbances.
0
3
.10 Effect of photocatalytic amount of Ag O ·SnO ·Cr O nanoparticle on photo-
2 3 2 2 3
degradation
At first, to determine the effective dose for studying the photocatalytic activity of
Ag O ·SnO ·Cr O various amounts of photocatalyst were taken to examine the effect of
2
3
2
2
3
photocatalyst dose on dye degradation under visible light irradiation as shown in Fig. 7. Several
-1
-1
amounts of photocatalyst ranging from 0.03 gL to 0.06 gL MV solutions were taken in this
study. With increasing photocatalyst amount degradation percentages of MV were gradually
-1
increased and the highest degradation was observed in case of 0.05 gL (77.88%, 95.89%, 99%
-1
-1
-1
-1
and 87% for 0.03 gL , 0.04 gL , 0.05 gL and 0.06 gL , respectively). After reaching the
-1
highest peak for optimum dosage 0.05 gL the efficiency began to fall.

New Journal of Chemistry
Page 18 of 40
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Fig. 7 Effect of catalyst amount on degradation rate constants of MV under visible light, (a) 0.03
-1
-1
-1
-1
gL ; (b) 0.04 gL ; (c) 0.05 gL ; (d) 0.06 gL dosage; degradation of MV (MV concentration:

Page 19 of 40
New Journal of Chemistry
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
5
0 ppm; pH 9; irradiation time: 150 min) and (e) represents compiled percent of degradation
efficiency at different dose(a-d) of nanocomposite.
A 5.0 mg of photo-catalyst was added to the methyl violet (6b) dye solution in a beaker
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(100 ml solution) which was stirred for 1 h prior to irradiation for studying the photocatalytic
activity of Ag O ·SnO ·Cr O . As shown in Fig. 8(a) and 8(b) the absorbance of dye solutions
2
3
2
2
3
decreases as a function of time at pH 9 and pH 7 respectively. Fig. 8(c) for the blank solution,
photocatalyst was not present in it and Fig. 8(d) and 8(e) indicates dye degradation with time and
percent efficiency under different conditions, respectively. With 150 min visible light irradiation,
the degradation efficiency was found 99% and 41% at pH 9 and pH 7 respectively while for the
blank solution efficiency was only 6%. It was observed that the efficiency was much higher in
alkaline solution (at pH 9) than neutral medium (pH 7) because of the formation of hydroxyl
radicals at pH 9. In alkaline solution hydroxide ions are easily oxidized to form hydroxyl radicals
74
which are the key fact to degrade the organic bonds of cationic dye methyl violet 6b (MV). The
inclusion of one oxide to other oxides creates defect within the crystal that lead to the formation
of Schottky barrier at the interface between metal and semiconductor. As a result, hydroxyl
radicals are formed that enhance the catalytic activity of mixed metal oxide nanoparticle than
single metal oxide.75,76

New Journal of Chemistry
Page 20 of 40
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Fig. 8 Variation of the absorption spectra of Methyl Violet 6b solution (100 ml, 50 ppm dye,
-1
0
.05 gL dosage) under visible light irradiation at 30 min time intervals (a) catalyst at pH 9 (b)
catalyst at pH 7.0; (c) blank solution (d) degradation with time and (e) indicate the percent of
efficiency at pH 9, pH 7 and blank solution respectively.

Page 21 of 40
New Journal of Chemistry
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
3
.11 Evaluation of catalytic stability of Ag O ·SnO ·Cr O nanoparticle
2
3
2
2
3
The recycles and reuse of photocatalytic processes has become very exciting due to the
significant contribution to lowering the operational cost of the process for waste water
purification. The catalyst can be regenerated in a very simple way. The solution was kept
standing for 24 h after finishing the reaction and then decanted the supernatant. By thoroughly
washing the catalyst with water, it was dried at 70 °C for 2 h. Then it was reused for four times
to assess the stability of photocatalyst. For each new cycle, the solution was filtered, dried and
reused for the degradation of fresh MV solution under similar conditions. The results are
presented in Fig. 9. The percentage of efficiency at pH 9 was 99, 90.5, 79, 74.6 and 67%. The
result showed that the catalytic activity decreased consecutively as they were used for several
times. This decrease in photocatalytic activity may be attributed to the structural changes of
nanocomposite after several use. Furthermore, during filtration some quantity of catalyst may be
lost which is another reason to decrease the photocatalytic efficiency.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0

New Journal of Chemistry
Page 22 of 40
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Fig. 9 Recycle and reuse of photocatalyst for MV degradation (MV concentration: 50 ppm;
-1
photocatalyst dosage: 0.05 g L ; irradiation time: 120 min) in the presence of the catalyst at pH 9
(a-e) decrease in absorption for 1st to 5th use and (f) % of efficiency.

Page 23 of 40
New Journal of Chemistry
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
3
.12 Antibacterial test of Ag O ·SnO ·Cr O nanoparticles
2
3
2
2
3
Nanotechnology, especially pharmaceuticals nanotechnology has attracted the attention
7
7
of many researchers due to numerous advantages on the health issue. Nowadays development
of new antimicrobial therapies has become an important research topic. Nanocomposites of
metal oxide and metal sulfide exhibit excellent antimicrobial property.78 Having various
properties, potencies, and spectra of activity some metals such as silver, copper, gold, titanium,
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
7
9
and zinc have been used as antibacterial agent. Antibacterial agents are also very important in
the textile industry, water disinfection, medicine, and food packaging. Usually, organic
compounds used for disinfection have some disadvantages, including toxicity to the human body.
For this reason, the interest in inorganic disinfectants such as metal oxide nanoparticles is
increasing rapidly. Inorganic nanostructured materials and their surface modifications execute
good antimicrobial functions. These improved antibacterial agents in low concentrations locally
destroy bacteria, without being toxic to the surrounding healthy tissues.80,81 Here, the
antibacterial activity of Ag O ·SnO ·Cr O nanoparticle was investigated using well diffusion
2
3
2
2
3
method against gram-positive bacteria (Staphylococcus aureus) and gram-negative bacteria
Escherichia coli). Agar nutrients were used for the bacterial culture where the sample was
introduced creating 6 mm well and Gentamicin 10 (GEN 10) was used as a reference. The
(
8
2
different inhibition zone was measured after overnight incubation at 37 °C. Zone of inhibition
confirmed the antibacterial effect of Ag O ·SnO ·Cr O nanoparticle that killed both gram-
2
3
2
2
3
positive and gram-negative bacteria also indicates the more effectiveness against-gram negative
bacteria than gram-positive bacteria as summarized in Table 3 and Fig. 10.
Table 3 Antibacterial study of Ag O ·SnO ·Cr O nanoparticles
2
3
2
2
3

New Journal of Chemistry
Page 24 of 40
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Diameter of inhibition Diameter of well
Bacterial culture
Ratio R = Diz/Dw
zone Diz (mm)
Dw (mm)
Staphylococcus aureus
Escherichia coli
23
8
2.87
5.83
35
8
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Fig 10 Antibacterial activity of Ag O ·SnO ·Cr O nanoparticle with (a) Staphylococcus aureus
2
3
2
2
3
and (b) Escherichia coli
3
.13 Detection of 4-AP by Ag O ·SnO ·Cr O NPs
2 3 2 2 3
The possible application of Ag O ·SnO ·Cr O NPs on GCE to the fabrication of an
2
3
2
2
3
electrochemical sensor for the detection of 4-AP in phosphate buffer medium of pH 7.0 was
assessed. During the fabrication process of this desire electrochemical sensor, a drop of nafion
(
5% nafion suspension in ethanol) was applied on modified GCE coated Ag O ·SnO ·Cr O NPs
2 3 2 2 3
to bring the long-time stability in phosphate buffer medium. Since the nafion is a conductive
copolymer, it enhanced the stability of the sensor as well as the conductance and electron transfer
rate as described by the previous authors.83-88 The electrochemical properties with coated and
uncoated GCE electrode in 5.0 mM [Fe(CN)6]3-/4- containing 0.1 M KCl have been studied by
cyclic voltammogram (CV) and EIS and included in the supporting information section (Fig.
S2). The bare GC electrode gives well-defined redox peaks while NPs/GCE provides low-
currents response due to the slightly blocking the electrode surface. The NPs/GCE exhibited

Page 25 of 40
New Journal of Chemistry
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
substantial redox currents in comparison with those exhibited by the GCE electrode, which
demonstrated the most auspicious catalytic performance in presence of 4-AP. The EIS spectra
(5.0 mM [Fe(CN)6]3-/4- containing 0.1 M KCl) were recorded to explore the relative charge
transfer of the modified electrodes with NPs coated and uncoated GCE as shown in Fig. S2b.
Control experiment of 4-AP response with the fabrication of various mono and binary metal
oxides onto GCE were performed and presented in Fig. S3. In Fig. S3a, the sensor performance
of three Ag O /GCE, SnO /GCE Cr O /GCE electrodes for the detection of 4-AP was compared
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
3
2
,
2
3
with ternary Ag O ·SnO ·Cr O NPs/GCE electrode. Here, the highest response was observed
2
3
2
2
3
for the detection of 4-AP with the ternary Ag O ·SnO ·Cr O NPs/GCE electrode compared with
2
3
2
2
3
single metal oxides. Binary metal oxide performances were also analyzed and compared with
Ag O ·SnO ·Cr O NPs/GCE fabricated electrode in identical conditions and presented in Fig.
2
3
2
2
3
S3b. In this case too, the highest response was observed for the detection of 4-AP with the
ternary Ag O ·SnO ·Cr O NPs/GCE electrode compared with binary metal oxide. These control
2
3
2
2
3
experiments clearly indicated the enhanced 4-AP sensor performance of the trimetallic
Ag O ·SnO ·Cr O nanocomposite.
2
3
2
2
3
The electrochemical response is measured on the surface of the thin film of
Ag O ·SnO ·Cr O NPs/binder/GCE. The holding period in the electrometer is set as 1.0 sec. At
2
3
2
2
3
the very beginning of this study, the numerous environmental toxins were analyzed using the
recently assembled electrochemical sensor based on Ag O ·SnO ·Cr O NPs/binder/GCE sensor
2
3
2
2
3
and this performance was executed at potential 0+1.5V and 0.1µM of each toxin in phosphate
buffer medium of pH 7.0. The Fig. 11(a) represents the electrochemical responses of 2-AP, 3-
MP, 4-AP, 4-hexylresorcinol, melamine, M-THydHCl, PHyd, zimtaldehyd and obviously, 4-AP
shows the highest current response comparing to other toxins. Therefore, on the basis of the

New Journal of Chemistry
Page 26 of 40
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
supreme I-V response, 4-AP is identified as a selective toxin to the sensor assembly. To examine
the I-V responses of 4-AP in the various buffer medium with distinguished pH value, a test was
performed as illustrated in Fig. 11(b). From the observation in Fig. 11(b), 4-AP is found to show
the maximum electrochemical activity in the phosphate buffer medium of pH 7.0. After that, 4-
AP was subjected to analyze with distinct concentration ranging in a sequence from
0.1mM0.1nM and the resulted I-V responses are explored in Fig. 11(c). As it is demonstrated in
Fig. 11(c), the electrochemical responses can be distinguished from lower to a higher
concentration of 4-AP. This similar characteristic of the electrochemical sensor has reported to
the detection of the various toxins in our previous articles89-92 and it provides evidence that the I-
V responses are varied directly with the corresponding concentration of 4-AP. To establish the
calibration of the proposed 4-AP chemical sensor, the current data are separated from Fig. 11(c)
at potential +1.5V and plotted as current vs. concentration as illustrated in Fig. 11(d), which is
defined as a calibration curve. As it is seeming from Fig. 11(d), the current data are linearly
distributed with corresponding concentration from 0.1nM to 0.01mM known as linear dynamic
range (LDR). Perceptibly, the resultant LRD is very a wider range of concentration. The
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
-1
-2
sensitivity of the proposed 4-AP chemical sensor is equal to 25.1962 µAµM cm and it is
-1
calculated from the slope of the calibration curve (0.7962 µAµM ) and cross-sectional area of
2
GCE (0.0316 cm ). Perceivably, the obtained sensitivity is appreciable. Applying the signal to
noise ratio of 3, the detection limit (DL) is estimated and an appreciable result around
9
8.41±4.92 pM is experimented. To determine the linearity of LDR, log (conc.) vs current is
plotted as in Fig. 11(d) inset and as it is illustrated, the current data are fitted with the regression
2
co-efficient R =0.9986, provides the evidence of linearity of LDR.

Page 27 of 40
New Journal of Chemistry
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Fig. 11 Optimization of sensor analytical performances of Ag O ·SnO ·Cr O NPs/binder/GCE
2
3
2
2
3
electrode, (a) selectivity assessment with analytes concentration 0.1 µM, (b) pH optimization at
.1µM 4-AP, (c) electrochemical (I-V) responses to 4-AP concentration, and (d) exploration of
0
calibration curve [inset: log(4-AP-conc.) vs current].
The ability to perform similar electrochemical response in identical conditions is very
important measurable analytical performance of an electrochemical sensor. Thus, this test was
executed using 0.1µM concentration of 4-AP and potential 0 to +1.5V as illustrated in Fig. 12(a).

New Journal of Chemistry
Page 28 of 40
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Fig. 12 Evaluation of reliability performance of 4-AP sensor with Ag O ·SnO ·Cr O
3
2
3
2
2
NPs/binder/GCE. (a) Response time for 4-AP with concentration 0.1 µM, (b) the interference
test of 4-AP sensor with analytes concentration of 0.1µM at pH 7.0, (c) the reproducibility test
with 4-AP concentration of 0.1µM and (d) the longtime performance test of 4-AP sensor.
The response is defined as the time required to complete an electrochemical analysis and
it is an efficiency measurement criterion. Therefore, the 4-AP sensor based on
Ag O ·SnO ·Cr O NPs/binder/GCE was subjected to measure the response time and it was
2
3
2
2
3
experimented with 0.1µM of 4-AP in phosphate buffer medium with pH 7.0 as illustrated in Fig.
2(a). From Fig. 12(a), it is shown that 4-AP sensor is able to produce a steady state I-V
1
response within 20.0 sec and the obtained result is highly appreciable. As it is demonstrated in
Fig. 12(b), the I-V responses of 4-AP do not deviate from its original value in the presence of

Page 29 of 40
New Journal of Chemistry
View Article Online
DOI: 10.1039/C9NJ01760G
1
2
3
4
5
6
7
8
9
other analytes such as 2-AP, 3-MP, and Phyd with 0.1µM concentration at potential ranging as
+1.5V in phosphate buffer medium. Therefore, it provides evidence that the 4-AP sensor is
0
highly selective toward the 4-AP analyte only. The reproducibility of an electrochemical sensor
is the most important analytical performance and it is the symbol of the reliability of the sensor.
As it is perceived from Fig. 12(c), the electrochemical responses are replicated and completely
impossible to distingue and it is not changed even washing of electrode after each run. Thus, it
provides information about the reliability of this method and it is able to analyze the real
samples. This test was experimented using 0.1µM 4-AP at applied potential 0+1.5V in buffer
medium with pH 7.0. The precision of I-V response for reproducibility performance at potential
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
+
1.5 was calculated and it is found to be 1.22% in-term of relative standard deviation (RSD).
Thus, it confirmed the high precision of the reproducibility test. This similar test was executed at
similar identical conditions to evaluate the information about the stability of 4-AP chemical
sensor based on Ag O ·SnO ·Cr O NPs/binder/GCE in phosphate buffer medium as presented
2
3
2
2
3
in Fig. 12(d). From Fig. 12(d), the analogous observation like reproducibility in Fig. 12(c) is
observed during a long duration of around seven days. Therefore, the proposed 4-AP chemical
sensor has the stability to perform in an elongated period, in a phosphate buffer medium. To find
out the validity of this study, a comparison between the similar research works is presented in
Table 4 as following in term of sensitivity, LDR and DL.93-95
Table 4. Comparison of analytical performances with Ag O ·SnO ·Cr O NPs/binder/GCE for 4-
2
3
2
2
3
AP sensors.
Modified GCE
DL
LDR
Sensitivity
Ref.
[93]
[94]
−
1
−2
−2
Ag
ZnO/Yb
PANI/G/CNTs NCs/GCE
Ag ·SnO ·Cr
NPs/GCE
DL (detection limit), LDR (linear dynamic range), pM(picomole), mM(millimole).
2
O/CuO NSs/GCE
3.31 pM
19.0 pM
63.4 pM
98.41 pM
0.1 nM∼ 0.1mM
0.1 nM0.1 mM
0.1 nM 0.01 M
0.1 nM0.01mM
0.028 mAµM cm
−
1
2
O
3
NSs/GCE
5.063 μA μM cm
−
1
−2
2.187μA μM cm
[95]
This study
−
1
−2
2
O
3
2
2
O
3
25.19 μAμM cm
*