An ensuing repercussion of solvent alteration on biological and photocatalytic efficacy of Emilia sonchifolia (L.) phytochemicals capped zinc oxide nanoparticles

Article abstract of DOI:10.1016/j.colsurfa.2021.127162

In the framework of the present study, a triumphant attempt was made to obtain biocompatible ZnOES NPs using E. sonchifolia (L.) plant extracts. A repercussion of solvent alteration on the biological and photocatalytic properties of ZnOES NPs has also been delineated employing two solvents viz. water and ethanol during the extraction of plant material. The formation of ZnOES NPs was confirmed through FTIR, PXRD, and UV–visible spectroscopy, which was further upheld by the elemental mapping study. Additionally, the NPs were examined through Rietveld refinement of P-XRD data obtained, FE-SEM, and BET analyses. The results of these analyses have substantiated the formation of mesoporous ZnOES NPs with divergent shapes and sizes ranging between 18.12 and 25.70 nm. The in-vitro antidiabetic activity of ZnOES NPs carried out revealed their excellent α-amylase inhibition activity (85.53 ± 0.002%). Furthermore, the in-vitro anti-inflammatory activity unfolded their biocompatibility by exhibiting a % HRBCMS up to 89.31 ± 0.002%. The NPs also displayed anti-microbial activities against Staphylococcus aureus, Bacillus subtulis, Pseudomonas aeroginosa, Pseudomonas syringae, and Escherichia coli. Therewithal the photo-degradation experiments of ZnOES nanocatalysts manifested superlative dye degradation efficacies exhibiting a % degradation of 92.01 and 79.36 for Methylene Blue and Methyl orange dyes respectively. Thus the studies have evinced the antidiabetic, antimicrobial, and dye degradation potentialities of biocompatible ZnOES NPs with excellent stability and reusability.

Full text of DOI:10.1016/j.colsurfa.2021.127162

Colloids and Surfaces A: Physicochemical and Engineering Aspects 627 (2021) 127162
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Colloids and Surfaces A: Physicochemical and
Engineering Aspects
journal homepage: www.elsevier.com/locate/colsurfa
An ensuing repercussion of solvent alteration on biological and
photocatalytic efficacy of Emilia sonchifolia (L.) phytochemicals capped zinc
oxide nanoparticles
,
Josline Neetha D’Souzaa, G.K. Nagarajaa *, K. Meghana Navadaa, Sabia Kousera, B.
R. Nityasreeb, D.J. Manasac
a Department of Chemistry, Mangalore University, Mangalagangothri, 574199 Karnataka, India
b Department of Applied Botany, Mangalore University, Mangalagangothri, 574199 Karnataka, India
c Department of Botany, Davanagere University, Davanagere 577007, Karnataka, India
H I G H L I G H T S
G R A P H I C A L A B S T R A C T
• Bio-compatible ZnOES nanoparticles
were biosynthesized via Emilia sonchifo-
lia plant extract.
• The structural and morphological char-
acterizations have revealed the forma-
tion of ZnOES nanoparticles with
distinct morphologies and size not more
than 26 nm.
• ZnOES nanoparticles exhibited up to
85.53 ± 0.002 of % α-amylase inhibition
and excellent antimicrobial activity
against four tested bacteria.
• ZnOES nanoparticles used as nano-
catalyst showed impressive MB and MO
dye degradation property with an
excellent stability and reusability.
A R T I C L E I N F O
A B S T R A C T
Keywords:
In the framework of the present study, a triumphant attempt was made to obtain biocompatible ZnOES NPs using
E. sonchifolia (L.) plant extracts. A repercussion of solvent alteration on the biological and photocatalytic
properties of ZnOES NPs has also been delineated employing two solvents viz. water and ethanol during the
extraction of plant material. The formation of ZnOES NPs was confirmed through FTIR, PXRD, and UV–visible
spectroscopy, which was further upheld by the elemental mapping study. Additionally, the NPs were examined
through Rietveld refinement of P-XRD data obtained, FE-SEM, and BET analyses. The results of these analyses
have substantiated the formation of mesoporous ZnOES NPs with divergent shapes and sizes ranging between
18.12 and 25.70 nm. The in-vitro antidiabetic activity of ZnOES NPs carried out revealed their excellent
ZnOES nanoparticles
E. sonchifolia
α
-amylase inhibitor
Antibacterial
Photocatalyst
Reusability
α
-amylase inhibition activity (85.53 ± 0.002%). Furthermore, the in-vitro anti-inflammatory activity unfolded
their biocompatibility by exhibiting a % HRBCMS up to 89.31 ± 0.002%. The NPs also displayed anti-microbial
activities against Staphylococcus aureus, Bacillus subtulis, Pseudomonas aeroginosa, Pseudomonas syringae, and
Escherichia coli. Therewithal the photo-degradation experiments of ZnOES nanocatalysts manifested superlative
dye degradation efficacies exhibiting a % degradation of 92.01 and 79.36 for Methylene Blue and Methyl orange
* Corresponding author.
E-mail address: nagarajagk@gmail.com (G.K. Nagaraja).
https://doi.org/10.1016/j.colsurfa.2021.127162
Received 20 May 2021; Received in revised form 6 July 2021; Accepted 7 July 2021
Available online 9 July 2021
0927-7757/© 2021 Elsevier B.V. All rights reserved.

J.N. D’Souza et al.
Colloids and Surfaces A: Physicochemical and Engineering Aspects 627 (2021) 127162
dyes respectively. Thus the studies have evinced the antidiabetic, antimicrobial, and dye degradation potenti-
alities of biocompatible ZnOES NPs with excellent stability and reusability.
1. Introduction
Therefore on account of the far-flung uses of ZnO NPs, an attempt
was made to synthesize zinc oxide nanoparticles (ZnOES NPs) through a
The demand for both natural and synthetic dyes manufactured from
organic molecules has been increasing worldwide owing to their wide
range of applications from redox reactions in analytic laboratories to
large-scale industries like textile, paper, furniture, and food industries
[1,2]. These industries are one of the major causes of water contami-
nation as they release the untreated or insufficiently removed dye ef-
fluents directly into the water resources along with other polluting
substances. Once these dyes reach the water bodies, they can make a
harmful impact on aquatic flora and fauna even at their lower concen-
tration [3]. Therefore in the perspective of environmental safety and
water purification, removal of these dye materials from water is of
tremendous importance. In this way, researchers have developed many
methods like adsorption [4], biodegradation [5], bio-coagulation [6],
membrane process [7], Advanced Oxidation Processes (AOP’s) [8], and
catalytic degradations such as photocatalysis [9]. Among the various
techniques developed catalytic degradation using nanoparticles (NPs) in
the presence of UV or visible light is the most efficient method as it
degrades the poisonous synthetic organic dyes into non-poisonous car-
bon dioxide (CO2) and water (H2O) in an aqueous medium [10]. The
substantial advantage of the photocatalytic process is that it does not
involve mass transfer and could be carried out at ambient conditions
with atmospheric oxygen without any additional oxidants [11]. The
principal requirement for the photo-degradation of organic dye is the
selection of suitable and potent catalysts, which can promise the effi-
cient breakdown of dye molecules into harmless byproducts. Many NPs
both in a pure and doped form such as CuO [12,13], TiO2 [14], CeO2
[15], etc. have been reported as good catalyst candidates for the pho-
tocatalytic degradation of various organic dyes. But these nanoparticles
have some disadvantages as they need either additional oxidizing agents
or the UV light irradiated during the process poses some practical
problems in them [16].
combustion synthesis method. The present study employed two different
extracts of E. sonchifolia plant viz. ethanolic and aqueous as both
reducing and stabilizing agents. The study illustrates the role of
E. sonchifolia plant extracts in ushering the formation of ZnOES NPs
influencing the structural, surface, morphological, and hence their bio-
logical and catalytic properties. The synthesized NPs were scrutinized
for their anti-inflammatory, antidiabetic, and antimicrobial activities.
Also, the photocatalytic degradation efficacies of these NPs against
Methylene Blue (MB) and Methyl Orange (MO) dyes under the influence
of UV light were evaluated. The studies have evidenced superlative anti-
inflammatory, antidiabetic, and antimicrobial potentialities with
excellent performance, reusability, and stability of ZnOES NPs during
the dye degradation process.
2. Experimental
2.1. Materials
The analytical grade Zinc nitrate hexahydrate (Zn(NO3)2⋅6H2O,
98%), methylene blue (MB, 98%), and methyl orange (MO, 98%) dyes,
ascorbic acid (98%), 2,2-Diphenyl-1- picrylhydrazyl (DPPH, 99%), and
all the reagents used for the phytochemical quantification were pro-
cured from MERK, India. Mueller Hinton Agar (MHA, pH: 7.3 ± 0.1 at
25 ◦C) and nutrient agar media (pH: 7.4 ± 0.2 at 25 ◦C) were acquired
from HiMedia Laboratory Ltd., India. Starch (soluble),
α-amylase
(porcine pancreas), and 3, 5-dinitrosalicylic acid (DNSA, 98%) were
procured from Sigma Aldrich.
2.2. Collection of E. sonchifolia (L.) plant
The fresh, whole plants of E. sonchifolia were collected at the flow-
ering stage from Shirva village at Udupi. The herb was identified by Dr.
Shenoy, a taxonomist at Pilikula Nisarga Dhama Herbarium, and
matched with voucher specimen no. 591. The collected plants were
cleaned by washing with double-distilled water and shade dried for 2
weeks. The dry plant material was then powdered and stockpiled at RT
(room temperature) for future use.
Zinc Oxide nanoparticles (ZnO NP’s) could be the substituent
nanocatalysts for the photocatalysis process with interesting efficacy in
dye degradation [17–27]. The synthesis of ZnO NPs can be performed by
various physical and chemical methods [28–30]. But those synthesized
using the principles of green chemistry are eco-friendly and less toxic.
The green synthesis of ZnO NPs could be achieved from various mi-
croorganisms like bacteria, fungi, and algae [31]. In addition to this, the
synthesis of NPs by employing the phytochemicals present in the ex-
tracts of various plant parts is trending which is in fact more advanta-
geous than the biological systems as the plant materials could be easily
handled and maintained [32,33]. The additional benefit of the green
synthesized NPs is that they could also be used in biomedical and bio-
logical applications such as anticancer, antidiabetic, anti-inflammatory,
and antimicrobial agents [34–37]. Though there are several studies on
the green synthesis of ZnO NPs using plant materials; to the best of our
knowledge E. sonchifolia plant has never been used for the synthesis of
ZnO NPs.
2.3. Preparation of ethanolic and aqueous plant extracts
To prepare the ethanolic extract of E. sonchifolia, about 20 g of the
dry plant powder was extracted with 300 mL of ethanol in a Soxhlet
extraction apparatus for 4 hrs. And the aqueous extract was prepared by
refluxing about 20 g of plant material in 150 mL double-distilled water
for 5 hrs. Both the extracts were filtered using Whatman no. 41 filter
paper and dried on a hot plate until free from extra solvent. The extracts
were employed as reducing and capping agents in the synthesis of
ZnOES NPs.
E. sonchifolia is a plant from a composite family. It is widespread
around the tropical regions and commonly known by the names “lilac
tassel flower” or “cupid’s shaving brush”. The plant E. sonchifolia is
known by the name “Sasaruti” in traditional medicine. And it is one
among the ‘ten sacred flowers’ in the state of Kerala in India, collectively
known as ‘Dhashapushpam’(Dhasha: ten, pushpam: flower), used in the
treatment of cancer by traditional healers. Besides this, the plant has
also been proven to possess medicinal benefits in treating sore throat,
asthma, night blindness, diarrhea, rashes, inflammatory diseases, fever,
chest pain, burns, snakebite, dysentery, and roundworm infections
[38–41].
2.4. Phytochemical quantification of E. sonchifolia (L.) plant extracts
The total content of phenols (TPC), flavonoids (TFC), ascorbic acid
(TAC), tannins (TTC), and the ferric ion reducing antioxidant power
(FRAP) of the ethanolic and aqueous extracts of E. sonchifolia were
quantified spectrophotometrically following our previously reported
method [42].
The assays were conducted in triplicates and the means were
enumerated along with the standard deviation. The amount of TPC, TFC,
TAC, and TTC are expressed in milligrams of gallic acid, quercetin,
2

J.N. D’Souza et al.
Colloids and Surfaces A: Physicochemical and Engineering Aspects 627 (2021) 127162
Scheme 1. Bio-fabrication of ZnOES NPs.
Fig. 1. Concentration vs. absorbance graph of FRAP assay of aqueous (A) and ethanolic (B) extracts, inset: change in color intensity of solution with increased
E. sonchifolia plant extract concentration.
ascorbic acid, and tannin acid equivalents (GAE, QE, AAE, and TAE) per
ascertained by matching their mass spectra with the National Institute of
Standards and Technology (NIST) mass spectra library.
gram dry weight of E. sonchifolia plant extract respectively.
2.5. Gas chromatography-mass spectroscopy (GC-MS) analysis
2.6. Bio-fabrication of ZnOES NPs
The GC-MS chemical profiles of ethanolic and aqueous extracts of
E. sonchifolia plant were obtained from TSQ 8000 Thermo Scientific GC-
Mass spectrometer. The initial oven temperature was 40 ◦C and it was
edged up to 290 ◦C at a rate of 5 ◦C/min for 50.09 min 1 µL of extract
sample was injected for the analysis and the mass spectra were recorded
across a range of 30–350 m/z. The eluted phytochemicals were
The ZnOES NPs were synthesized by dissolving 2.97 g of Zn
(NO3)2⋅6H2O in 10 mL of aqueous and ethanolic extracts of E. sonchifolia
and the reaction mixture was magnetically agitated for 10 min at
75–80 ◦C. The mixture was then kept in a muffle furnace which was pre-
heated and maintained at a temperature of 410 ± 10 ◦C. The obtained
NPs were calcined at 600 ◦C for 2 h and have been named ZnOESA
3

J.N. D’Souza et al.
Colloids and Surfaces A: Physicochemical and Engineering Aspects 627 (2021) 127162
Fig. 2. GC chromatogram of aqueous (A) and ethanolic (B) extracts of E. sonchifolia plant.
(aqueous) and ZnOESE (ethanolic) NPs. Scheme 1 illustrates the steps
involved in the bio-fabrication of ZnOES NPs.
Abcontrol ꢀ Absample
%
membrane stabilization =
× 100… … ..
(1)
Abcontrol
2.7. In-vitro anti-inflammatory activity of ZnOES NPs
Where, Absample and Abcontrol are the absorbance of ZnOES NPs/ Diclo-
fenac sodium and control respectively.
The anti-inflammatory activity of ZnOES NPs was assessed through
the membrane stabilization method using human RBC (HRBC’s),
following an earlier reported procedure [43]. About 3 mL of the
non-steroidal anti-inflammatory drug (NSAID) free blood sample was
obtained from a healthy volunteer. The blood sample was mixed with an
equal volume of Alsever’s solution (a solution of 0.8%, 0.42%, 0.5%, and
2% wt/vol of sodium citrate, sodium chloride citric acid, and dextrose
respectively) and centrifuged for 05 min at 3000 rpm. The segregated
HRBCs were washed twice with isosaline (0.8% wt/vol) and further
diluted (10% vol/vol) before use. 0.5 mL of different concentrations
(6.25, 12.5, 25, 50, and 100 µg/mL) of ZnOESA and ZnOESE NPs were
prepared and mingled with 0.5 mL of phosphate buffer (pH 7.4 ± 0.1;
0.15 M) and 1 mL of hyposaline (0.36% wt/vol) respectively. In the end,
0.25 mL of HRBC suspension was introduced. The reaction system was
incubated for 30 min at 37 ◦C, centrifuged at 3000 rpm for 5 min, and
the absorbance of the supernatant was recorded at 560 nm in a spec-
trophotometer. Isosaline (0.8% wt/vol) and diclofenac sodium (com-
mercial grade) were taken as control and standard respectively. From
the absorbance, the percentage membrane stabilization was calculated
using Eq. (1).
2.8. In-vitro antidiabetic activity of ZnOES NPs
The in-vitro antidiabetic activity of ZnOES NPs was evaluated by
α
-amylase inhibition assay following a previously reported protocol
[44]. Briefly, 0.5 mL of NPs solution with different concentrations
(100–500 µg/mL) was mixed with 1 mL of phosphate buffer (0.15 M; pH
6.9 ± 0.1). The solution was well sonicated at RT for 15 min. Then
200 µL of α-amylase solution (0.5 mg/mL) was added, followed by the
addition of 200 µL of starch solution (1%). The solution was then kept at
RT for 15 min. Finally, the reaction was terminated by the addition of
400 µL of DNSA reagent (mixture of 1 g of DNSA, 30 g Potassium So-
dium (+) tartrate, 20 mL, 2 M NaOH). Then the reaction contents were
heated in a boiling water bath for 10 min. The % α-amylase inhibition
activity was determined using Eq. (2) from the absorbance of the solu-
tions noted at 540 nm. Metformin was used as a standard.
Abcontrol ꢀ Ab
%
α
ꢀ amylase inhibition =
sample × 100… … .
(2)
Abcontrol
4

J.N. D’Souza et al.
Colloids and Surfaces A: Physicochemical and Engineering Aspects 627 (2021) 127162
Table 1
List of identified phytochemicals of ethanolic extract of E. sonchifolia plant from GC-MS analysis.
Peak no.
r.t (min)
Name of compound
Molecular formula
Structure
Molecular weight
98.14
Area%
0.60
1
5.81
3-Penten-2-one,4-methyl-
C6H10
O
2
3
9.65
1,3-Dioxolane-4-methanol,2,2-dimethyl-
C6H12O3
132.16
0.19
10.46
15.57
1,4-Cyclohexadiene,1-methyl-
Glycerin
C7H10
94.15
92.09
0.35
0.61
C3H8O3
5
20.19
Phenol,2-methyl-5-(1-methyl ethyl)-
C10H14
O
150.22
1.25
6
7
25.53
27.84
Erythritol
C4H10O4
122.12
150.22
1.93
2.84
Phenol,2-(1-methylpropyl)-
C10H14O
8
9
30.28
34.48
2-Decenoic acid
C10H18O2
170.25
256.42
0.45
4.09
n-Hexadecanoic acid
C16H32O2
solution) of ZnOESA and ZnOESE NPs solution and later the biosystems
were incubated at 37 ◦C for 24 h. The bacterial growth inhibition po-
tentiality of NPs was evaluated by measuring the zone of inhibition
around the well and comparing them with the standard Ciprofloxacin
and the plant extracts in the same concentration as the NPs. The ex-
periments were carried out in triplicates and the zones of inhibition have
been expressed as mean values ± standard deviation.
Where, Absample and Abcontrol are the absorbance of ZnOES NPs/ Met-
formin and control respectively.
2.9. Antimicrobial activity of ZnOES NPs
The ZnOES NPs were perused for their antimicrobial property
through the agar-well diffusion method against two gram-positive and
three gram-negative bacterial strains viz. Bacillus subtulis (American
Type Culture Collection [ATCC-6633]), Staphylococcus aureus (National
Collection of Industrial Microorganisms [NCIM-2079]), Pseudomonas
aeroginosa (NCIM-2200), Pseudomonas syringae (NCIM-5102), and
Escherichia coli (NCIM-2931) acquired from National Chemical Labora-
tory, Pune in India. The nutrient agar plates (NAP) were prepared by
pouring about 20 mL of autoclaved Mueller Hinton Agar (MHA) into
sterilized Petri plates. The NAPs were allowed to stand and upon so-
lidification of MHA, the microbial subcultures were introduced using
cotton-tipped sticks (100 µL; 24 h mature). The required numbers of
wells were made with a sterile cork borer (6 mm) on the swabbed MHA
surface. The wells were then loaded with 20 µL (from 10 mg/mL stock
2.10. Photocatalytic performance of ZnOES NPs
The photocatalytic performance of ZnOES NPs as nanocatalysts was
evaluated by taking an aqueous solution of MB and MO dye and illu-
minating it with UV light from Osram 125 W HQL mercury vapor lamp
source. In a typical experiment, 10 mg of ZnOESA and ZnOESE nano-
catalysts was dispersed in 50 mL of 5 ppm MB and MO dye solutions by
stirring magnetically for 30 min in dark. Then the photocatalytic solu-
tion was exposed to UV light placed at a distance of 15 cm up to
180 min. The dye solution was observed for its degradation by removing
3 mL of photocatalytic solution for an interval of 30 min, centrifuging it
5

J.N. D’Souza et al.
Colloids and Surfaces A: Physicochemical and Engineering Aspects 627 (2021) 127162
Table 2
List of identified phytochemicals of aqueous extract of E. sonchifolia plant from GC-MS analysis.
Peak no.
r.t (min)
Name of compound
Molecular formula
Structure
Molecular weight
203.19
Area%
8.15
1
15.93
N-Acetylaspartic acid,dimethyl ester
C8H13NO5
2
3
17.27
20.20
2-Hydroxyiscocaproic acid,methyl esther, methyl ester
Phenol,2-methyl-5-(1-methylethyl)-
C8H16O3
160.21
150.22
0.79
2.58
C
C
10H14O
4
38.44
9-Octadecenoic acid(Z),-methyl ester
19H36O2
296.49
1.09
5
6
39.03
39.16
1,E-11,Z-13-Octadecatriene
C
C
18H32
248.45
210.35
5.69
7.52
9-Tetradecenal,(Z)-
14H26O
7
49.55
9,12-Octadecadienoic acid (Z,Z)-
C
18H32O2
280.44
0.82
at 10,000 rpm for 2 min to remove the solid nanocatalyst, and
measuring the absorbance at 663 nm for MB and 466 nm for MO using a
spectrophotometer. The effect of nanocatalyst dose and dye concentra-
tions on the photocatalytic degradation process was examined by
varying the catalyst dosage from 10 to 50 mg and 5–15 ppm of dye so-
lution. The effect of the presence of only nanocatalyst and UV-light was
investigated by carrying out blank experiments with the most potent
nanocatalyst viz. ZnOESA in 50 mL of 5 ppm dye solution. The photo-
catalytic degradation efficiency was measured using Eq. (3).
Surface morphology and elemental composition were analyzed using a
Sigma series Field-Emission Scanning Electron Microscope (FE-SEM)
and Energy Dispersive Microscopy (EDS) respectively. Brunauer-
Emmett-Teller (BET) method at liquid nitrogen temperature was used
to determine the surface area and pore size distribution using BELSORP-
minill BET surface area and pore volume analyzer.
3. Results and discussion
3.1. Quantification of E. sonchifolia plant phytochemicals
Ai ꢀ Af
PDeff(%) =
× 100… … .
(3)
Ai
The phytochemical quantification studies performed to scrutinize
the presence of different phytochemicals in ethanolic and aqueous plant
extracts of E. sonchifolia unfolded the presence of 73.86 ± 0.45 mg/g
and 252.12 ± 0.35 mg/g TPC in GAE, 225.33 ± 1.67 mg/g, and
Where, Ai and Af are the initial and final absorbance respectively.
2.11. Characterization of ZnOES NPs
192.55 ± 1.92 mg/g
TFC
in
QE,
33.48 ± 0.28 mg/g,
and
42.32 ± 2.36 mg/g, TTC in TAE, and 16.06 ± 0.28 mg/g and
39.33 ± 0.07 mg/g of ascorbic acid in AAE per gram dry weight of
E. sonchifolia ethanolic and aqueous plant extracts respectively. The
FRAP assay performed has revealed the reducing power of E. sonchifolia
plant extracts which was found to be concentration-dependent. The re-
sults of the FRAP assay have been illustrated in Fig. 1. The reducing
power assay method is based on the principle that substances, which
Fourier-transform infrared (FTIR) spectra of ZnOES NPs and the
E. sonchifolia fruit extract were captured in Perkin Elmer spectrometer in
transmittance mode from 450 to 4000 cmꢀ 1 using KBr pellets. The phase
and crystalline structures were studied by Rigaku Miniflex 600 (5th gen)
powder X-ray Diffractometer (PXRD)[Cu-K
α radiation, 40 kV and
15 mA]. UV–visible spectra of well sonicated ZnOES NPs were recorded
in Shimadzu UV-1800 spectrophotometer from 200 to 800 nm at RT.
6

J.N. D’Souza et al.
Colloids and Surfaces A: Physicochemical and Engineering Aspects 627 (2021) 127162
Fig. 3. FTIR spectra of E. sonchifolia plant extract ethanolic (a), aqueous (b), ZnOESA (c), and ZnOESE (d) NPs (A), P-XRD diffraction patterns of ZnOESA (a) and
ZnOESE (b) NPs (B), and narrowing of peaks and shift in 2θ positions observed for aqueous (a) and ethanolic (b) E. sonchifolia plant extract (C).
Table 3
Rietveld residuals and cell parameters of ZnOESA and ZnOESE NPs.
Crystal structure: Hexagonal
Space group: P 63m c
Hall symbol: P 6-2c
Parameters
a=b (Å)
c (Å)
R
bragg (%)
RF (%)
Rwp (%)
Rp (%)
Rexp (%)
χ2
GoF
Unit cell volume (cm3)
ZnOESA
ZnOESE
3.2522
3.2520
5.2079
5.2030
2.60
1.47
1.41
1.25
9.14
19.3
7.27
15.6
5.59
9.01
2.67
4.57
1.63
2.14
47.7
47.6
substantiated the presence of copious polyphenols, flavonoids, tannins,
and ascorbic acid in the E. sonchifolia ethanolic and aqueous plant ex-
tracts with significant reducing power, which plays the foremost role
during the formation of ZnOES NPs.
Table 4
Appraised strains and crystallite size of ZnOESA and ZnOESE NPs.
NPs
Crystallite size (nm)
Strain ϵ x 10ꢀ 3
Debye-Scherrer
W-H plot
ZnOESA
ZnOESE
18.12
25.70
28.12
49.94
1.58
1.51
3.2. GC-MS analysis of E. sonchifolia plant extracts
To identify the phytochemical components of the ethanolic and
aqueous plant extracts of E. sonchifolia and ergo to know their role
during the formation and capping of ZnOES NPs GC-MS study was
conducted. The obtained GC-MS profiles are shown in Fig. 2. From the
GC-MS chromatograms and the mass spectra, nine and seven major
phytochemicals were ascertained in the ethanolic and aqueous plant
extracts of E. sonchifolia. The retention time (R.T), molecular formula,
compound name, and the structures along with the area % are marked
down in Tables 1 and 2. The components identified were categorized as
alcohols, esters, aldehydes, and carboxylic acids, the presence of which
was also substantiated by the FTIR analysis.
have reduction potential, react with potassium ferricyanide (Fe3+) to
form potassium ferrocyanide (Fe2+), which then reacts with ferric
chloride to form a ferric–ferrous complex that has an absorption
maximum at 700 nm. Ferrous to ferric reducing power was found to
escalate from 0.01 to 0.05 mg/mL of E. sonchifolia plant extracts with an
absorbance rise from 0.0587 ± 0.0015–0.1667 ± 0.0015 and
0.2333 ± 0.0006–0.6190 ± 0.0015. This increased reducing power in-
dicates that as the concentration of extract in the reacting mixture in-
crease, more and more Fe3+ ions get reduced to Fe2+ thus causing a rise
in the absorbance of solution [45]. Thus the performed assays
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J.N. D’Souza et al.
Colloids and Surfaces A: Physicochemical and Engineering Aspects 627 (2021) 127162
Fig. 4. Refinement (Rietveld) profiles of ZnOESA (A), ZnOESE (B) NPs (inset: corresponding crystal structure) and W-H (Williamson-Hall) plots of ZnOESA (C) and
ZnOESE (D) NPs.
3.3. Stability of ZnOES NPs by FTIR analysis
62.8(103), 66.2(200), 67.7(112), 69.0(201), 72.6(004), and 76.9◦ (202)
2 theta values, in the diffraction patterns depicted in Fig. 3(B) sub-
stantiate the formation of crystalline, hexagonal ZnO NPs (JCPDS card
No: 89-1397). Additionally, the narrowing and shift of peaks in ZnOESE
NPs compared to ZnOESA illustrated in Fig. 3(C) indicates the formation
of large crystallite-sized NPs with altered cell parameters in the etha-
nolic extract [49,50]. This observation was further corroborated by the
results estimated from W-H (Williamson-Hall) plots and the
Debye-Scherrer equation as listed in Table 4. Forbye, the PXRD dif-
fractograms were refined using the FullProf-Suit program. Pseudo-Voigt
peak function was employed in the refinement of the cell parameters and
as depicted in Fig. 4(A&B) the match between calculated and the
observed data was found to be on fleek (Table 3).
The phytochemicals of plant extracts induce a significant effect on
the formation and stability of NPs in a green synthesis pathway.
Therefore, to ascertain the group of phytochemicals present and to
bespeak the formation of stable ZnOES NPs, FTIR spectra of E. sonchifolia
plant extracts and ZnOES NPs were captured in transmittance mode
between the 400–4500 cmꢀ 1. Fig. 3(A) depicts the FTIR spectra of
ethanolic and aqueous extracts of E. sonchifolia and ZnOESA and ZnO-
ESE NPs. The peaks positioned at 3241, 3431, 3427, and 3417 cmꢀ 1
could be due to the phenolic O-H stretching vibrations. Whereas the
peaks at 2097, 2076, 1664, 1643, 1407, and 1386 cmꢀ 1 could be
accredited to the asymmetric stretching frequency of -CH2 bonds,
–
stretching frequency of free –C O group, -C-O stretching frequency of
The PXRD data of ZnOES NPs was also used for the estimation of
crystallite size from Debye-Scherrer Eq. (4).
–
amino acids, and -C-N stretching vibrations respectively. The bands at
1107, 1056, and 643 cmꢀ 1 could be assigned to the –C-H bonds and
halogen compounds [36,46,47]. Additionally, the FTIR spectra of
0.94 × λ
dp =
… … .
(4)
β
Cosθ
ZnOES
NPs
manifest
conspicuous
peaks
at
488
and
478 cmꢀ 1corresponding to Zn-O stretching evincing the formation of
stable ZnOES NPs [48].
Where dp is the crystallite size, λ is the X-Ray wavelength, β is the full
width at half max. (FWHM), and θ is the diffraction angle. Moreover, the
grain size and the strain were determined from W-H plots (Fig. 4).
Employing Eq. (5), the intercept and slope were obtained from the
straight line between βCosθ (y-axis) and 4sinθ (x-axis). From the inter-
cept and slope, the crystallite size and the strain were determined. The
particle sizes obtained for ZnOES NPs from the W-H plots were proxi-
mate to those obtained from the Debye-Scherrer equation. The strain
3.4. Phase and structural analysis of ZnOES NPs by PXRD
The crystalline phase and structure of ZnOES NPs were studied by
recording the PXRD spectrum. The diffraction peaks (crystal planes)
observed at 31.6(100), 34.2(002), 36.0(101), 47.5(102), 56.3(110),
8

J.N. D’Souza et al.
Colloids and Surfaces A: Physicochemical and Engineering Aspects 627 (2021) 127162
Fig. 5. (A) UV–visible spectra, (B) energy band gap, and (C) energy band positions of ZnOESA (a) and ZnOESE (b) NPs, ethanolic (c), and aqueous (d) extracts.
Fig. 6. FE-SEM (false colored) micrographs of ZnOESA (a) and ZnOESE (b) in low (200 nm) and high (100 nm) magnification.
values were found to be in accordance with their crystallite size (strain
Kλ
dp
∝1/dp). The strain and the crystallite size obtained for ZnOES NPs are
βcosθ =
+ 4ϵ sinθ… … ..
(5)
enumerated in Table 4.
Where ϵ is the microstrain and Kλ/dp is the intercept.
9

J.N. D’Souza et al.
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Fig. 7. Elemental mapping and Energy Dispersive X-ray spectra of ZnOESA (a) and ZnOESE (b) NPs.
Fig. 8. Multi-point BET plots of ZnOESA (A) and ZnOESE (B) and N2 isotherms of ZnOESA (C) and ZnOESE (D) NPs, inset: corresponding BJH plots (pore size
distribution).
10

J.N. D’Souza et al.
Colloids and Surfaces A: Physicochemical and Engineering Aspects 627 (2021) 127162
absorption maxima at 370 nm This is a characteristic peak of ZnOES NPs
arising due to the excitation of electrons from the valence band (VB) to
the conduction band (CB) (2pO-3dZn), which is absent in E. sonchifolia
extracts [22,51]. The optical band gap energies of ZnOES NPs were
Table 5
BJH and BET parameters of ZnOESA and ZnOESE NPs.
NPs
BJH
Pore
size
BET
Pore
size
Surface
area
Total pore
volume
Surface
area
Total pore
volume
estimated from the plots of
Eq. (6).
αh
ν
2 vs. energy (Eg), using Tauc and Wood
(m2gꢀ 1
)
(nm)
(cm3gꢀ 1
)
(m2gꢀ 1
)
(nm)
(cm3gꢀ 1
)
ZnOESA
ZnOESE
5.3464
2.2806
24.43
2.43
0.0454
0.0059
6.6293
2.0242
28.08
11.33
0.0465
0.0057
(
αh
ν
) = K(h
ν
-Eg)n… … .
(6)
Where , h, ν, and Eg are the absorption coefficient, Planck’s constant,
α
frequency, and the bandgap energy, and n = 1/2 for the direct allowed
electronic transition [52]. The direct bandgap energies estimated from
Tauc plots were 3.75 and 3.31 eV for ZnOESA and ZnOESE NPs
respectively (Fig. 5(C)).
3.5. Absorption properties of ZnOES NPs by UV–visible spectroscopy
To evaluate the absorption properties of plant extracts and the
ZnOES NPs, UV–visible spectra were recorded between 200 and 800 nm
at RT. Fig. 5(A) delineates the absorption spectra of ZnOES NPs with
The energies of the valence band (VBE) and the conduction band
Fig. 9. In-vitro anti-inflammatory activity of ZnOESA and ZnOESE NPs (n = 3, p < 0.05).
Fig. 10. In-vitro antidiabetic activity of ESA and ESE NPs: (A) %
α-amylase inhibition, (B) Sample images with DNS reagent (n = 3, p < 0.05).
11

J.N. D’Souza et al.
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Fig. 11. Antimicrobial activity of ZnOES NPs against Staphylococcus aureus, Bacillus subtulis, Pseudomonas aeroginosa, Pseudomonas syringae, and Escherichia coli (ESE:
ethanolic extract, ESA: aqueous extract).
Table 6
Antibacterial activity of ZnOES NPs: Zone of inhibition observed for different bacterial strains.
S. No.
Microorganisms
Gram reaction
Zone of inhibition ± SD (mm)
Ciprofloxacin
ESE
ESA
ZnOESE
ZnOESA
1
2
3
4
5
S. aureus
B. subtulis
P. aeroginosa
P. syringae
E. coli
G +ve
G +ve
G -ve
G -ve
G -ve
26.0 ± 0.0
20.5 ± 0.71
29.5 ± 0.71
24.0 ± 5.66
27.0 ± 1.41
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
12.5 ± 2.12
15.5 ± 0.71
12.5 ± 0.71
14.5 ± 2.12
NA
13.0 ± 0.0
16.5 ± 4.95
13.0 ± 1.41
15.5 ± 0.71
0.95 ± 0.07
(CBE) in ZnOES NPs were calculated using Eqs. (7) and (8) and are
represented in Fig. 5(C). The VBE and the CBE values of ZnOESA and
ZnOESE were determined to be + 3.12, + 2.90 eV, and ꢀ 0.62,
ꢀ 0.40 eV respectively.
with hexagon textures Fig. 6(b). Further, the elemental mapping profiles
and the EDS spectra displayed in Fig. 7 corroborate the formation of
ZnOES NPs with an elemental composition of zinc (Zn) and oxygen (O).
The element carbon (C) should be ascribed to the carbon tape employed
as the substrate.
CBE = Z- eE- 0.5Eg… .
VBE = CBE + Eg … … …
(7)
(8)
3.7. Surface properties of ZnOES NPs through BET analysis
Where, Z = 5.75 eV i.e., electronegativity of ZnO, Eg = bandgap en-
ergy, eE = 4.5 eV i.e. energy of free electron on hydrogen scale [53].
Appraising the pore size and the surface area are the means to un-
derstand the performance of NPs in catalytic and biological applications.
Ergo to evaluate the pore size, surface area, and pore volume BET
(Brunauer-Emmett-Teller) study was carried out at liquid N2 tempera-
ture (77 K). Fig. 8(A & B) depicts the BET curves of ZnOES NPs. The BET
curves unveil that the ZnOESA and ZnOESE NPs possess a surface area of
6.6293 and 2.0242 m2gꢀ 1 respectively which is inversely proportional
to the crystallite size. Moreover, the morphologies of the NPs also un-
derpin this observation. Between ZnOES NPs, a high surface area
recorded for ZnOESA NPs indicate the accessibility of a large number of
active sites on the NPs surface for the adsorption of dye molecules hence
supporting its superlative catalytic performance recorded during the
course of photocatalytic degradation of MB and MO dye. Fig. 8(C & D)
3.6. Morphology of ZnOES NPs by FE-SEM analysis
To contemplate the surface morphology and to look over the
elemental composition together with the elemental mapping of ZnOES
NPs, FE-SEM images were captured. Fig. 6 displays the FE-SEM micro-
graphs of ZnOES NPs in low (200 nm) and high (100 nm) magnifica-
tions. The micrographs manifest the formation of NPs in heterogeneous
agglomerations. As evidenced by Fig. 6(a), ZnOESA NPs were found in
small, roughly rectangular to spherical aggregations of particles,
whereas the ZnOESE NPs were discerned in agglomerations of spheres
12

J.N. D’Souza et al.
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Fig. 12. Percentage degradation of MB (A,B) and MO (C,D) for different catalytic loads of ZnOESA (A&C) and ZnOESE (B&D) NPs.
illustrates the nitrogen adsorption-desorption isotherms of ZnOES NPs
with the BJH (Barret-Joyner-Halenda) pore size distribution recorded at
liquid N2 temperature (77 K). According to the IUPAC classification, the
observed isotherms were found to resemble type IV isotherm accom-
panied by a hysteresis loop of H3 type evidencing the mesoporous nature
of ZnOES NPs [50]. The multi-modal BJH curves unfold the distribution
of pores in a non-uniform manner. The parameters determined from the
BET study are provided in Table 5.
the superlative membrane stabilization ability and hence the haemo-
compatibility and the anti-inflammatory activity of ZnOES NPs close to
the standard drug.
3.9. In-vitro antidiabetic activity
The pancreatic enzyme
lysis of starch into glucose. Therefore the postprandial glucose level
could be reduced by controlling the catalytic activity of -amylase which
could therapeutically benefit diabetic patients [44]. Ergo, to evaluate
the -amylase inhibition potentiality and thus the antidiabetic activity of
ZnOES NPs,
α-amylase brings about the catalytic hydro-
α
3.8. In-vitro anti-inflammatory activity
α
The entry of harmful invaders or stimuli like pathogens, irritants, and
the damaged cells expedite the generic response of the tissues causing
inflammation in the body. To isolate these intruders the damaged cells
release certain chemical substances like prostaglandins, histamine, and
bradykinin. These chemicals make the blood vessels leak some fluids
into the tissues causing swelling. On the attack of intruders, even the
RBCs (red blood cells) show a similar mechanism of defense. Thus, the
membrane stabilization assay using human RBCs was performed to
know the haemocompatibility and hence the in-vitro anti-inflammatory
potentiality of green synthesized ZnOES NPs. Fig. 9 delineates the results
of the assay. The study has unfolded the dose-dependent membrane
stabilization activity of synthesized NPs. % membrane stabilization up
to 89.31 ± 0.002, 87.89 ± 0.001, and 93.24 ± 0.001 were recorded for
ZnOESA, ZnOESE, and diclofenac sodium. Thus, the study has divulged
α-amylase inhibition assay was performed using the DNSA
method. The reagent DNSA (yellow colored) on reacting with glucose
gets reduced to 3-amino-5-nitrosalicylic acid (an orange-colored com-
pound). But the presence of NPs annihilates the hydrolyzing ability of
α
-amylase, precluding the conversion of starch into the reducing sugar
glucose. This reflects in the retention of the yellow color of DNSA in the
test samples treated with NPs.
Fig. 10 illustrates the % α-amylase inhibition of ZnOES NPs and the
standard metformin. Inhibition percentages of 85.53 ± 0.002,
66.24 ± 0.003, and 86.89 ± 0.001 were obtained for ZnOESA, ZnOESE,
and metformin respectively at the concentration of 500 µg/mL. Addi-
tionally, the α-amylase inhibition activity was evaluated by IC50 values,
where the concentration of NPs required for the 50% inhibition was
determined and was found to be 162.88, 186.97, and 68.12 µg/mL
13

J.N. D’Souza et al.
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Fig. 13. UV–visible spectra of 50 mg/50 mL photocatalytic solution of MB (A,B) and MO (C,D) with ZnOESA (A&C) and ZnOESE nanocatalyst (B&D).
ZnOESA, ZnOESE, and metformin respectively. Thus, the acquired re-
sults substantiate a superlative potential of bio- synthesized ZnOES NPs
synthesized from the ethanolic plant extract (ZnOESE) in inhibiting the
bacterial growth.
in the inhibition of α-amylase enzyme proximate to standard metformin.
3.11. Photocatalytic activity
3.10. In-vitro antimicrobial activity
The ZnOESA and ZnOESE NPs were used as nanocatalysts in the
degradation study experiments of MB and MO dye under the influence of
UV light. The study was carried out to analyze the effects of nanocatalyst
dosage, initial dye concentration, and to investigate the stability and
reusability of ZnOESA and ZnOESE nanocatalysts as explained below.
To scrutinize the biological applicability of green synthesized ZnOES
NPs as an antimicrobial agent, the agar-well diffusion method was
performed against two gram-positive viz. Staphylococcus aureus and
Bacillus subtulis and three gram-negative bacterial strains viz. Pseudo-
monas aeroginosa, Pseudomonas syringae, and Escherichia coli. As evi-
denced from Fig. 11, ZnOES NPs exhibited appreciable antibacterial
activity at a concentration of 10 mg/mL against all the tested bacteria.
However, the study has manifested that the ZnOES NPs are more potent
against Bacillus subtulis with a zone of inhibition 15.5 ± 0.71 and
16.5 ± 4.95 mm for ZnOESE and ZnOESA NPs respectively compared to
other strains. In line with the literature, the ZnOES NPs might have
damaged the bacterial cell membrane by penetrating into the bacterial
cytoplasm and producing the reactive oxygen species (ROS) causing the
damage of DNA and other cellular components [54]. The zones of in-
hibition measured for ethanolic (ESE), aqueous (ESA) plant extracts,
ZnOESE, and ZnOESA NPs are given in Table 6. The study has revealed
that the synthesized NPs are better antimicrobial agents than the plant
extracts and additionally the study has also substantiated the superiority
of ZnOESA NPs obtained from aqueous plant extract than the one
3.11.1. Effect of nanocatalyst dosage
To study the effect of nanocatalyst dosage on the dye degradation
process, the catalytic amount of each nanocatalyst was varied from 10 to
50 mg in 50 mL of 5 ppm dye solution. The results of the experiments
are illustrated in Fig. 12, Fig. 13, and Fig. S1 of Supporting Data. As the
curves depict, the degradation percentage was found to be directly
proportional to the nanocatalyst dosage. This could be due to the
availability of more active sites at the high catalytic dose that supports
the harvesting of light in an effective way thus enhancing the production
of electrons and hydroxyl radicals [55]. The decreased percentage
degradation observed in ZnOESE compared to ZnOESA NPs could be the
result of the large size of ZnOESE nanocatalyst, which lessens the
available catalytic area needed for dye molecule adsorption [56].
The rate constants (pseudo-first-order) of photocatalytic degradation
14

J.N. D’Souza et al.
Colloids and Surfaces A: Physicochemical and Engineering Aspects 627 (2021) 127162
Fig. 14. Curves of lnCt/C0 vs. time for MB (A,B) and MO (C,D) of ZnOESA (A&C) and ZnOESE (B&D) nanocatalyst.
increasing the dye solution concentration from 5 to 15 ppm. This could
be due to the reduction of active sites on the catalytic surfaces as the dye
molecules tend to cover them at their high concentration. Another
possible reason could be the absorption of light by dye molecules instead
of photocatalyst causing reduced photocatalytic reaction [57].
Table 7
Rate constants of ZnOESA and ZnOESE NPs at different doses of catalyst.
Dye
NPs
Rate constant (minꢀ 1
)
Catalytic dosage (mg)
10
20
30
40
50
MB
MO
ZnOESA
ZnOESE
ZnOESA
ZnOESE
0.0101
0.0049
0.0028
0.0014
0.0115
0.0054
0.0038
0.0016
0.0113
0.0066
0.0043
0.0016
0.0123
0.0072
0.0069
0.0016
0.0136
0.0097
0.0077
0.0022
3.11.3. Blank photocatalytic experiments
The independent effects of UV light and the nanocatalyst on MB and
MO dye degradation were evaluated by carrying out blank experiments.
As illustrated in Figs. S3 and S4 of Supporting Data, only 10.56, 12.63%
and 15.62, 11.68% of degradation were observed with nanocatalyst and
UV-light respectively. These values suggest that the presence of the only
nanocatalyst becomes insignificant without UV-light, as it cut-offs the
generation of a sufficient number of electron-hole pairs required for the
degradation. Therefore, the effective dosage of nanocatalyst and the
presence of UV light are the essential conditions for the effective
degradation of dye.
reactions determined from the slopes of ln Ct/C0 vs. time plots (Fig. 14)
demonstrated high degradation rates for high catalytic dosage of the NPs
as detailed in Table 7.
3.11.2. Effect of dye concentration
The effect of MB and MO dye concentration on photocatalytic
degradation capability of ZnOESA and ZnOESE nanocatalysts was
analyzed by taking 50 mg of ZnOESA and ZnOESE nanocatalysts for
various dye concentrations (5, 10, and 15 ppm). The outcomes of the
study are shown in Fig. S2 of Supporting Data. The figures clearly
demonstrate the decrease in the dye degradation percentage on
3.11.4. Reusability and stability of ZnOVI nanocatalysts
The practical applicability of a nanocatalyst used in the degradation
process lies in its stability and reusability. Therefore, in order to evaluate
the stability of ZnOES nanocatalysts, repeated degradation experiments
15

J.N. D’Souza et al.
Colloids and Surfaces A: Physicochemical and Engineering Aspects 627 (2021) 127162
Fig. 15. Reusability and stability and tests: (A) Percentage degradation vs. number of cycles, (B) Ct/C0 vs. time, and (C) PXRD patterns after 1st and 4th cycle (MB
dye, 50 mg/50 mL ZnOESA NPs).
were carried out using the most efficient ZnOESA nanocatalyst with its
optimal amount (50 mg) and suitable dye concentration (5 ppm/
50 mL). The nanocatalyst after every use was washed with double
distilled water, dried at 60 ◦C in a hot air oven, and used for the next
cycle. The nanocatalyst was tested for its degradation efficiencies up to
four catalytic cycles and the degradation percentage along with the Ct/
C0 vs. time graphs are shown in Figs. 15(A) and (B) & 16(A) and (B). The
results reveal excellent and almost similar photocatalytic degradation
efficiencies of the nanocatalyst even after the fourth cycle. The nano-
catalyst maintained constant degradation efficiency even after its
repeated use indicating its good cycle stability. In line with this, the
PXRD graphs of ZnOESA nanocatalyst obtained after the fourth cycle
support this factor (Figs. 15 & 16(C)). The slight differences observed in
the degradation percentages could be due to the blockage of active sites
on the catalytic surface by the dye molecules [58]. Moreover the
consistent dye degradation rate recorded during the recycling test cor-
roborates their photo-corrosion stability and this stability could be
attributed to the capping of ZnOES NPs by E. sonchifolia phytochemicals
[59,60].
3.11.5. Mechanism of photocatalytic activity
The mechanism of photocatalytic degradation of MB and MO dye by
the ZnOES NPs under the illumination of UV-light is represented in
Mechanism 1. The UV light has enough energy to excite the electrons
from the valence band (VB) to the conduction band (CB), thus creating
the holes (h+) and the photo-excited electrons (e-). These electrons later
combine with the dissolved oxygen and produce the superoxide ions (O2-
•), whereas the holes oxidize the water molecules to hydroxyl ions
(•OH). Both these ions are being good oxidizers, leads the oxidation and
subsequent degradation of MB dye into less toxic products such as CO2
and H2O [61].
4. Conclusions
The present work delineates the biosynthesis of ZnOES NPs by using
ethanolic and aqueous plant extracts of E. sonchifolia. The method used
in the study is an economical and expeditious pathway for the green
synthesis of ZnOES NPs with potential antidiabetic, antibacterial, and
photocatalytic properties. The study has manifested the impact of the
E. sonchifolia phytochemicals extracted in the ethanolic and aqueous
16

J.N. D’Souza et al.
Colloids and Surfaces A: Physicochemical and Engineering Aspects 627 (2021) 127162
Fig. 16. Reusability and stability and tests: (A) Percentage degradation vs. number of cycles, (B) Ct/C0 vs. time, and (C) PXRD patterns after 1st and 4th cycle (MO
dye, 50 mg/50 mL ZnOESA NPs).
extracts in the initiation, stabilization, and hence on the structural,
surface, and morphological properties of ZnOES NPs. The Rietveld
refined cell parameters of ZnOES NPs have exhibited a good match with
the standards with crystallite sizes ranging between 18.12 and
25.70 nm. The morphological study of obtained NPs has revealed the
formation of ZnOES NPs in heterogeneous agglomerations having
roughly rectangular to spherical aggregations with hexagon textures.
nanocatalyst for the degradation of organic pollutants during the puri-
fication of water in near future.
CRediT authorship contribution statement
Josline Neetha D’Souza: Methodology, Investigation, Data cura-
tion, Writing – original draft. G.K. Nagaraja: Resources, Conceptuali-
zation, Validation, Review, Supervision of overall research work. K.
Meghana Navada: Software, Formal analysis. Sabia Kouser: Data
curation, Visualization, and Review. B.R. Nityasree: Data curation and
Visualization of antimicrobial study. D.J. Manasa: Visualization of the
data.
The
α-amylase assay of ZnOES NPs performed has illustrated appre-
ciable antidiabetic property with an inhibitory percentage of
85.53 ± 0.002. Wherein the agar well diffusion method carried out has
affirmed the antibacterial property of ZnOES NPs with the appreciable
zone of inhibition upto16.5 ± 4.95. The biocompatibility and non-
toxicity of ZnOES NPs were confirmed by membrane stabilization
studies using human erythrocytes. The surface and optical properties of
ZnOES NPs have supported the superlative photocatalytic dye degra-
dation property (92.01%) of NPs with excellent stability and reusability
up to four catalytic cycles. In terms of solvents, the NPs obtained from
aqueous extract were found to be superior in quality and properties than
to ones synthesized using ethanolic extract. Nevertheless, the overall
outcome of the present study shows that the ZnOES NPs could be used as
alternatives for antidiabetic, antibacterial agents and as a potent
Declaration of Competing Interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
17

J.N. D’Souza et al.
Colloids and Surfaces A: Physicochemical and Engineering Aspects 627 (2021) 127162
Mechanism 1. Possible mechanism of photocatalytic degradation of MB/MO dyes by ZnOES nanocatalyst in the influence of UV-light.
by cation transfer membranes, Langmuir 15 (1999) 185–192, https://doi.org/
Acknowledgement
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The coordinator of DST-PURSE, Mangalore University, and the vision
group of science and technology (VGST- Karnataka government) are
acknowledged for the instrumentation facility. JND is thankful to the
Directorate of Minorities, Karnataka government for fellowship. The
authors are grateful to Prof. Raju Krishna chalannavar, Department of
Applied Botany, Mangalore University.
[9] M.R. Abhilash, G. Akshatha, S. Srikantaswamy, Photocatalytic dye degradation and
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Appendix A. Supporting information
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presence of nanostructured titanium dioxide: influence of the chemical structure of
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molcata.2010.05.023.
Supplementary data associated with this article can be found in the
online version at doi:10.1016/j.colsurfa.2021.127162.
[12] J. Singh, V. Kumar, K.H. Kim, M. Rawat, Biogenic synthesis of copper oxide
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