Novel gomutra cow urine mediated synthesis of silver oxide nanoparticles and their enhanced photocatalytic photoluminescence and antibacterial studies

Original ArticleNovel Gomutra cow urine mediated synthesis of silver oxide nanoparticles and their enhanced photocatalytic, photoluminescence and antibacterial studies S.P.. combus-tion

Original Article

Novel Gomutra (cow urine) mediated synthesis of silver oxide

nanoparticles and their enhanced photocatalytic, photoluminescence

and antibacterial studies

S.P Vinaya, Udayabhanub, G Nagarajub, C.P Chandrappac, N Chandrasekhara,*

a Research and Development Center, Department of Chemistry, Shridevi Institute of Engineering and Technology, Tumakuru, 572106, India

b Energy Materials Research Laboratory, Department of Chemistry, Siddaganga Institute of Technology, Tumakuru, 572103, India

c Department of Biotechnology, Shridevi Institute of Engineering and Technology, Tumakuru, 572106, India

a r t i c l e i n f o

Article history:

Received 7 April 2019

Received in revised form

18 July 2019

Accepted 10 August 2019

Available online xxx

Keywords:

Silver oxide nanoparticles

Gomutra

Combustion method

Photocatalytic

Photoluminescence

Antibacterial

a b s t r a c t

This work successfully synthesizes silver oxide (Ag2O) nanoparticles (Nps) using cow urine The presence

of different biological components in cow's urine may acts as fuel for the synthesis of Ag2O Nps by a combustion method at 500
C This is a rapid and environmentally benign procedure, which has the added advantage of shorter response times and better control over size and shape The synthesized nanoparticles were characterized by XRD, FTIR, UV-vis, SEM, EDAX and TEM studies and have been tested for photoluminescence and for photocatalytic and biological activities They show good photocatalytic degradation of methylene blue, due to their sensitivity to absorb light with a wide band gap energy Furthermore, we have examined the photoluminescence properties of the synthesized material and found that it has a yellow emission for excitation at 436 nm In addition, the synthesized material ex-hibits good antibacterial activity for both gram-positive and gram-negative bacterial strains by the disc diffusion method In this study it is shown that these combustion methods produce nano sized Ag2O within less time suited for large scale synthesis in an economic way

© 2019 Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an

open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

1 Introduction

Cow urine has significant medicinal drink used for therapeutic

purposes in Ayurveda Nowadays cows are rare to see; in older days

in everybody's house we could able to see the cows irrespective of

the religion in India Cows were adopted because of the multiple

health benefits, starting with urine, dung, manure, milk, yogurt and

ghee products Human urine received its own medical benefits but

was not as popular as cow urine; therefore, cow urine has always

been superior and divine[1]

In Hinduism, cows are thought to be sacred and called

“KAMADHENU” means the mother of all entities since thousands of

years In India, we use panchagavya (The urine, milk, ghee, curd and

dung), obtained from cows are beneficial in different ways as a food

supplement, medicine, etc which holds its own importance in

mythological and medicinal aspects Cow's urine has promoted as

single or in combination with other drugs for medicine and spiri-tual uses traditionally

The cow is considered as a dwelling place for all God and Goddess In concern with Gomutra, the spiritual, medicinal and traditional values are higher Traditionally, Gomutra is being sprinkled in courtyards and home for its holy purposes; it confers the happiness, purity, prosperity, positive health, wealth, etc.[2] The laboratory analysis of cow's urine shows that it contains iron, copper, nitrogen, sulphur, manganese, carbolic acid, silicon, chlorine, magnesium, citric, calcium salts, enzymes, mineral salts, vitamins like A, B, C, D, E, creatinine, uric acid, hormones, gold acids, etc and most interestinglye hip uric acid, which removes toxins through urine, aureum hydroxide, which acts as a germicide and thereby acts as immune-modulatory in increasing immunity if body and build resistance against all minor to major infectious agents

The above-mentioned contents of Gomutra are found to be very useful in balancing our body constitutes Thus, whenever we uri-nate there is a loss of such micro e nutrients, which are well compensated by the daily intake of Gomutra

* Corresponding author.

E-mail address: chandruharshu@gmail.com (N Chandrasekhar).

Peer review under responsibility of Vietnam National University, Hanoi.

Contents lists available atScienceDirect Journal of Science: Advanced Materials and Devices

j o u r n a l h o m e p a g e : w w w e l s e v i e r c o m / l o c a t e / j s a m d

https://doi.org/10.1016/j.jsamd.2019.08.004

Paper, dyeing, plastic, and textile industries use different colours

for staining their products and hence consume a large amount of

water for cleaning It leads to wastewater with dye contaminant

and which can be harmful to human and nature[3e6] Currently,

hundred thousand various types of dyes are produced with an

annual production rate of 7 105per year Among them, textile

which is released as dye content waste-water into the environment

which can lead to a pollution of marine life Hence, it is a very

important task to reduce the release of dye and other organic

pollutants into the aquatic life

Presently, photocatalytic degradation is an alarming technique

for making wastewater free from organic and inorganic toxic

pollutants [7] Semiconductor photo-catalysis is a favourable

technique with various advantages such as air and water puri

fi-cation, water disinfection and the remediation of hazardous waste

in the environment Silver oxide assisted photocatalytic

degra-dation is an ideal and excellent technique for degradegra-dation of

organic pollutants and dye in wastewater [8] The organic

pol-lutants are entirely mineralized into the water, into CO2and into

corresponding mineral acids without creating any hazardous

by-products This technique has been used for the

photo-mineralization of carcinogenic dyes such as methylene blue,

direct acid dyes, azo dyes and reactive black[9]

Silver is an important and distinctive inorganic substance,

because of its distinctive characteristics and novel applications in

variousfields of science and technology[10] Silver oxide has the

capacity to exhibit piezoelectric, pyroelectric, optoelectronic,

catalysis and semiconducting properties [11] Due to these

ca-pacities, silver oxide is a multifunctional compound which is used

in thefield of light emitting diodes, biosensors, spintronic solar

cells and transistors and which also acts as antioxidant and

antibacterial agent[12e14] Various methods were discovered for

synthesizing the Ag2O Nps viz hydrothermal, direct precipitation,

solegel and solvothermal methods[15e19] These methods need

costliest starting materials, sophisticated laboratories and these

require lengthy procedures [20e25] In contrast, the Gomutra

assisted combustion method is favourable as it is an easier, less

energy- and time-consuming method among all the other

methods This technique will reduce the pollution or is even a

pollution free method Useful materials can be synthesized easily,

eco-friendly and in reasonable quantities[26e30]

Gomutra as a reducing agent The prepared Nps were characterized

using powder X-ray diffraction (PXRD), Fourier transform infrared

analysis (FTIR), UV-visible spectrum (UV-vis), scanning electron

microscopy (SEM) and transmission electron microscopy (TEM) of

the Ag2O Nps

2 Experimental

Silver nitrate was procured from Merck and used as precursor

(without further purification) Gomutra is collected from cows of

the Tumkur city

combus-tion method using Gomutra as a fuel and silver nitrate as

Gomutra solution The solution mixture is stirred to obtain a

homogeneous solution This mixture is transferred to a preheated

muffle furnace maintained at 500
C and subjected for

combus-tion resulting in a smouldering type of the combuscombus-tion reaccombus-tion

in which nano-crystalline Ag2O was formed within 5 min Afine

material was stored in an airtight container until supplementary use

Phase and purity of the sample was measured by X-ray diffraction (XRD) recorded by Rigaku Smart Lab XRD Stretching frequencies of the functional groups in the sample were measured

by a FTIR analysis using a Bruker Alpha-p spectrometer The morphology of the synthesized nanoparticles was observed using Scanning Electron Microscope (JEOL Model JSM-6390LV) EDAX (OXFORD XMX N) determines the elemental analysis Shape and size of the Nanoparticles were determined by Transmission Elec-tron Microscopy (TEM) (JEOL/JEM 2100) Photoluminescence

(Agilent technology Cary Eclipse)

The Photo-catalytic activity of the synthesized Ag2O Nps was assessed by considering the dye degradation of Methylene blue (MB) in an aqueous solution at ambient temperature utilizing a

300 W visible light as radiance source Twenty mg of catalyst (Ag2O Nps) was mixed with 100 mL of 5 ppm Methylene blue and the solution was unceasingly stimulated in the dark chamber for about

30 min to attain the adsorptionedesorption equilibrium Further, the visible light was switched on Two mL of aliquot were with-drawn for every 1 h interval The samples were centrifuged using a micro-centrifuge for 10 min in order to segregate the Ag2O Nps Spectrophotometric evaluations were carried out by utilizing a quartz cell having a path length of 0.3 cm The absorbance was

spectrophotom-eter[31] Degradation mechanism of the dye solution was stated in the following equations

Ag2Oþ hv/Ag2O hvbþþ ecb

Ag2Oðecb Þ þ O2/Ag2Oþ O$2

H2O/ Hþþ OH$

O$2þ H/HO2

Ag2Oðecb Þ þ HO2þ Hþ/H2O2

Ag2O hvbþ

þ Dye/Degradation products

HO2/ Hþþ H2O2

HO$2/ eþ HO2 

From the reaction, the hydroxyl radical (OH) and the

photo-degradation performance of the MB dye molecules

The degradation percentage of the dye has been determined by the following equation

where Ciand Cfare the initial andfinal concentration of the dye

3 Results and discussion 3.1 XRD study

The XRD pattern of Ag2O Nps is shown inFig 1 The diffraction peaks at 2q¼ 38
, 44
, 64
, and 77
were indexed with the planes

(111), (200), (220) and (311) for the resultant particles with cubic

phase The structure of the resultant data is according to the JCPDS

calculated using the DebyeeScherrer equation and was found to be

11 nm

where K value 0.94, lis wavelength, b is the full width at half maxima and D is the crystallite size

3.2 FTIR study The FTIR spectrum of the prepared Ag2O nanoparticles, recorded between 350 and 4000 cm1, is represented inFig 2 The strong peaked that appeared at 3396 cm1is due to the stretching vi-bration ofeOH, the strong absorption peak at 2916 cm1could be assigned toeCH stretching vibrations of eCH3andeCH2functional groups, the peak at 1638 cm1is associated with a NeH bond and is assigned to the amide-I bond of the proteins present in the fuel (reducing agent) The peak at 1376 cm1is possibly due to the NeO symmetry stretching that is typical for the nitro compound The band at 1033 cm1corresponds to the CeF alkyl halide stretch vi-bration of proteins The band at 520 cm1 clearly confirms the formation of silver oxide (AgeO)[33]

3.3 UV-visible study The UVevis spectrum of the synthesized materials is displayed

in Fig 3a The spectrum shows a strong absorption peak at the wavelength region of 430 nm (confirming the formation of Ag2O nanoparticles) due to electronic transitions from the valence band

to the conduction band The energy gap (Eg) was found to be around ~2.74 eV, which is in good agreement with the earlier re-ported values (Fig 3b)[34]

3.4 Scanning electron microscopy (SEM) and energy-dispersive X-ray (EDAX) studies

SEM images of Ag2O nanomaterials are shown inFig 4a and b From the SEM images, it is clearly confirmed that the synthesized material contains small grain-like particles Those particles are agglomerated to form spherical-shaped Motichoorboondi-like structures [35].Fig 4c shows the EDAX spectrum of Ag2O Nps, which describes the elemental analysis of the material Theob-tained spectrum exhibits strong silver and oxygen peaks

3.5 Transmission electron microscopy (TEM) studies

Fig 5 shows TEM image, HR-TEM image, SAED pattern, and Histogram of synthesized Ag2O nanomaterials These particles are

Fig 1 PXRD pattern of the Ag 2 O Nps.

Fig 2 FTIR spectrum of Ag 2 O Nps.

well dispersed, with an acquired size around 20 nm diameter, and

are looking like the spherical shape in nature HR-TEM images give

clear information about the d-spacing value of the AgeO material

which is found to be 0.21 nm, and belong to the (111) plane The

(111), (200), (220) and (311) planes have the highest intensity in

XRD and are matched with the bright circular fringes in the SAED

pattern and the HR-TEM images[36]

4 Photocatalytic degradation

Mechanism: Degradation mechanism of dye solution was stated

in the following equations

Ag2Oþ hv/Ag2O hvbþþ ecb 

OHadsþ hvb þ/OHads $ðin basic mediumÞ

Under visible light irradiation, a semiconductor absorbs

photon energy with equal to or higher than the bandgap of the

semiconductors and generates electrons and holes on the surface

of the photocatalyst If the charge carriers do not recombine,

they can migrate on the surface where free electrons from a

reduction of oxygen and form peroxide and superoxide radicals,

and the generated holes oxidize water and form OH This species

is highly reactive and unstable It ultimately acts on organic

inorganic acids, which is shown inScheme 1 The photocatalytic

action of the dye is enhanced by various factors of the photo-catalyst, viz particle size, phase composition, shape, crystallinity, size distribution, surface area, surface hydroxyl group density and band gap[37] Synthesized Ag2O Nps were used as photo-catalysts to investigate the degradation of methylene blue in UV sources[38]

The absorbance of the MB dye solution decreases with increase

in time of the irradiation in the presence of the Ag2O photo-catalyst The absorbance of MB is decreased to 83.63% of degrada-tion in 4 h (Fig 6)[39]

5 Photoluminescence (PL) study The PL study is a useful method for determining the efficiency

of charge carrier separation in semiconductors [40] Fig 7a

nanoparticles recorded at room temperature The emission spectrum of Ag2O Nps with the excitation wavelength of 436 nm reveals emission peaks at 566 and 596 nm

The corresponding CIE (Commission International De I'Eclair-age) colour coordinates (x and y) are given in the inset ofFig 7b It

is clear from the CIE diagram that pure Ag2O Nps emits yellow light

6 Antibacterial activity Synthesized Ag2O nanoparticles show significant antibacterial activities against pathogenic bacterial strains (Staphylococcus aureus, Escherichia coli, Pseudomonas desmolyticum, and Klebsiella aerogenes) by the disc diffusion process[41] The zone of inhibition

Fig 4 (a), (b) SEM images (c) EDAX spectrum of synthesized Ag 2 O Nps.

of Ag2O nanoparticles (500mg/mL and 1000mg/mL) with respect to

the positive control (Ciprofloxacin) is showing higher significant

antibacterial activity on all the 4 bacterial strains and are depicted

inTable 1

FromTables 2 and 3clearly shows that, the combustion method has more advantages such as (shorter reaction time and enhanced reaction rate, improve the yields and high energy of efficiency) compared with some other preparation methods

Fig 5 (a) TEM image (b) HR-TEM images (c) SAED pattern and (d) Histogram of Ag 2 O Nps.

Scheme 1 Schematic mechanism for the dye degradation.

Fig 6 (a) Degradation of Methylene blue (b) Percentage degradation.

Fig 7 (a) Photoluminescence Emission spectrum of Ag 2 O Nps: excited at 436 nm (b) CIE diagram.

Table 1

Antibacterial activity of Ag 2 O Nps on pathogenic bacterial strains.

S No Treatment Escherichia

coli (mean ± SE)

Pseudomonas desmolyticum (mean ± SE)

Klebsiella aerogenes (mean ± SE)

Staphylococcus aureus (mean ± SE)

2 Ag 2 O Nps (500mg/mL) 8.10 ± 0.21 8.47 ± 0.30 6.50 ± 0.29 5.50 ± 0.29

3 Ag 2 O Nps (1000mg/mL) 9.73 ± 0.33 10.50 ± 0.30 7.33 ± 0.17 8.50 ± 0.29

4 Ciprofloxacin (5mg/mL) 18.36 ± 0.32 19.63 ± 0.17 18.33 ± 0.44 18.17 ± 0.44 Values are the mean ± SE of inhibition zone in mm NA Symbols represent no antibacterial activity was found in this work.

Table 2

Comparison of antimicrobial activity with some other synthesized silver and silver oxide nanoparticles.

Sl No Bacterial culture Samples Zone of Inhibition (mm) Ref.

Staphylococcus aureus Ag 2 O Nps 4 Pseudomonas aeruginosa Ag 2 O Nps 5

Pseudomonas aeruginosa Ag Nps 4.8

Staphylococcus aureus Ag 2 O Nps 8.5 Klebsiella aerogenes Ag 2 O Nps 7.3 Pseudomonas aeruginosa Ag 2 O Nps 10.5

7 Conclusion

In the present research, we have, for thefirst time, successfully

accomplished the one-pot rapid synthesis of spherical shaped Ag2O

Nps using Gomutra (cow urine) The Ag2O Nps were confirmed by a

XRD study The TEM analysis showed spherical shaped particles

with 20 nm particle size They show a good photocatalytic

degra-dation of methylene blue, due to their sensitivity to absorb light

with a wide band gap energy Hence, the synthesized material is

measured as a potent aspirant for the degradation of dye MB In

addition, they can be used for the yellow emitting LED applications

as shown by the PL spectrum The obtained results confirm that the

produced Ag2O Nps show effective antibacterial activity against

foodborne pathogens This is a rapid and environmentally benign

method which has the added advantage of reduced reaction time

and better control over size and shape

Conflict of interest

The authors declare that they have no conflict of interest

Acknowledgement

Udayabhanu thanks to CSIR, New Delhi, for Senior Research

Fellowship {09/1204(0001)/2018-EMR-1} Dr Chandrasekhar and

Vinay thank Dr M R Hulinaykar, Managing Trustee, Sri Shridevi

Charitable Trust, and Shridevi Institute of Engineering and

Tech-nology for encouragement and support for research work Dr GN

support The authors also thank Siddaganga Institute of Technology

for providing the lab facilities

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