Structural studies of bio-mediated NiO nanoparticles for photocatalytic and antibacterial activities

Journal Pre-proofs Structural Studies of Bio-Mediated NiO Nanoparticles for Photocatalytic and Antibacterial Activities Karthik Kannan, D Radhika, Maria P. Nikolova, Kishor Kumar Sadasivuni, Hakimeh Mahdizadeh, Urvashi Verma PII: DOI: Reference:

S1387-7003(19)31134-7 https://doi.org/10.1016/j.inoche.2019.107755 INOCHE 107755

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Inorganic Chemistry Communications

Received Date: Revised Date: Accepted Date:

4 November 2019 13 December 2019 25 December 2019

Please cite this article as: K. Kannan, D. Radhika, M.P. Nikolova, K. Kumar Sadasivuni, H. Mahdizadeh, U. Verma, Structural Studies of Bio-Mediated NiO Nanoparticles for Photocatalytic and Antibacterial Activities, Inorganic Chemistry Communications (2019), doi: https://doi.org/10.1016/j.inoche.2019.107755

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Structural Studies of Bio-Mediated NiO Nanoparticles for Photocatalytic and Antibacterial Activities Karthik Kannana, D Radhikab*, Maria P. Nikolovac, Kishor Kumar Sadasivunia, Hakimeh Mahdizadehd, Urvashi Vermae a b

Centre for Advancced Materials, Qatar University, Doha, Qatar.

Department of Chemistry, School of Engineering and Technology, Jain-Deemed to be University, Jakkasandra, Ramnagara-562112, Karnataka, India.

c

d

Department of Material Science and Technology, University of Ruse Angel Kanchev, Ruse, Bulgaria

Department of Environmental Health, School of Public Health, Kerman University of Medical Sciences, Kerman, Iran.

e

Department of Botany, D. S. B. Campus, Kumaun University, Nainital (Uttarakhand) -26300 India *E-mail:

[email protected]

Abstract: Nickel Oxide (NiO) nano-sized sample was bio-synthesized by a microwave-assisted route consuming citrus variety fruit juice. The prepared NiO sample was investigated by various spectroscopy techniques. The X-ray diffractogram revealed the formation of a cubic spinel with a well crystalline nature of NiO nanoparticles with a very fine crystallite size of 20 nm. FTIR revealed Ni-O and smaller C-H and H-O-H characteristic functional groups, whereas the morphological characteristics determined by SEM and TEM disclosed a spherical shape of prepared nanoparticles. Elemental compositions present in NiO nanoparticles were found by EDAX as per the requirement. Emission peaks of luminescence were noticed at 350, 441, 485, and 531 nm. The spherical NiO nanoparticles showed 91% photodegradation efficiency for Evans blue under sunlight. Furthermore, the antibacterial performance of NiO sample was determined by agar well diffusion technique, which demonstrated significant cell inhibition in contradiction of both bacterial strains of gram-positive and gram-negative. Keywords: NiO, Citrus fruit, XRD, TEM, Evans blue and antibacterial activity.

1. Introduction Due to the rapid industrialization, population growth and climate change environmental pollution also increases rapidly because of the emission of toxic materials and is frightening the human society for sustainable growth. Various manufacturing industry units like printing, textile, fabric, and leather related etc. the release of micro-pollutants and contaminants as the synthetic dyes that are a major alarming issue to the environment because of their toxic and carcinogenic effects [1,2]. For the past few decades, water treatment was done by examining the exclusion of hazardous organic dye molecules, so many techniques like reverse osmosis, ozonolysis, ultrafiltration, adsorption of activated charcoal, biodegradation, chlorination, and photocatalytic degradation have been commenced. Among these studies, semiconductor photocatalysis has become more attractive as a green route synthesis amongst different described methods in gathering solar energy and aimed to combat the detrimental effects of the industrial dye effluents for the benefit of the people and environment since it involves environmentally friendly approach [3,4]. Currently, bacterial related diseases are common reasons and leading to death status. The antibiotics controlled the death related problems caused by infections due to bacteria. Frequently consuming usual medicines prevent the influence on the growth of bacteria [5]. Metal oxide nanoparticles have been enticed the scientific society, due to promising applications in the biomedical field such as targeted drug delivery, genetic screening, magnetic hyperthermia, magnetic resonance imaging, ferrofluids and medical diagnostics and radiation cancer therapy [6]. These nanoparticles can be effortlessly targeted or functioned by using an external magnetic field. Usually, the applications and properties are based on the shape, size, dopants, composition, preparation methods, and microstructure of nanoparticles. The colloidal stability and aiming of the nanostructure can be enhanced with the understanding of the nanoparticles which hinge on the surface area to volume ratio. In the medical field, the iron oxide nanoparticles have been synthesized and used for numerous applications such as bactericides, magnetic hyperthermia and targeted drug delivery [6-8]. Amongst all metal oxides, nickel oxide has attained ample attention due to rare magnetic and physical properties which direct to its extensive applications in the biomedical field. In the literature, biomedical and clinical uses of cobalt-nickel oxide nanoparticles are well established and have a broad array of antimicrobial activity contrary to

several pathogens. However, exposure to nickel oxides could cause skin irritations and carcinogenesis by inhalation. The skin irritation by nickel oxide is solely related to soluble nickel species or so-called bio-accessible fraction [9]. Surface oxide characteristics affect the reactivity and toxicity of NiO nanoparticles. It was found that Ni(III) encompassing oxides such as Ni2O3 were potentially more toxic than Ni(II) oxides (like NiO) because the former are more soluble [10]. Moreover, green NiO had weak solubility and to some extent minor respiratory toxicity than other nickel related compounds [9]. For carcinogenicity, not only Ni ion release but also particle solubility, size, intercellular dissolution, and in vivo clearance time have a determinative effect [9]. More recent studies discovered that at short doses (1 or 0.1 μg cm2 of total Ni), NiO nanoparticles enhanced the proliferation of A549 cells while at higher concentrations they induced significant cytotoxicity [11]. Nonetheless, NiO nanoparticles have also gained much attraction as potential candidates that can be used in the medical field like other nanomaterials [12]. Among metal oxide nanoparticles, nickel oxide (NiO) nanoparticles are characterized by outstanding high magnetic permeability, phase stability, low eddy current loss, high electronic conductivity, and bandgap of 3.6 eV [13] that made them suitable for sensing applications, and photocatalysis [14] at a low cost of production. Currently, synthesis of metal oxide nanoparticles using fruits, microorganisms, plant parts, marine algae, such as seed, roots, leaf, latex, and stem as chelating/reducing agents is highly preferred [15]. Table 1 gives a detailed comparison of NiO nanoparticles produced by green synthesis using different plant extracts. Table 1. Reports on various plant extracts to prepare NiO nanoparticles S.

Plant extract

No 1

2

3

Synthesis

Morphology

Size,

Characterization

nm

method

Nanoparticles

8-10

HR-TEM, XRD

[16]

Nanoparticles

15-55

HR-TEM,

[17]

15.23–23.15

XRD

Nanoparticles

10-12

HR-TEM

[18]

Nanoparticles

18

HR-TEM,

[19]

method Moringa Oleifera

Hot plate

Aegle marmelos

combustion

Agathosma

Green

betulina

synthesis

Neem leaf

Green

Ref.

synthesis 4

Sageretia thea

Green

(Osbeck)

synthesis

XRD

Callistemon

Green

viminalis

synthesis

Tamarix serotine

Green

5

6

Nanoparticles

Nanoparticles

20-40

SEM

21

XRD

10-14

TEM

5.29-8.31

XRD

Length:

HR-TEM

[20]

[21]

synthesis

7

Graviola (leaf

Green-

extract)

mediated

Nano-sticks

[22]

0.2µm, Diameter:200 nm

The present work assigns the synthesis of nickel oxide nanoparticles employing Limonia acidissima Christm (citrus fruit juice) as a unique fuel via a microwave-assisted method. This juice encompasses carbohydrates and lactic acids which plays as a strong reducing agent and accomplished hunting reactive oxygen species (ROS), which is accountable for the combustion method. Later, the morphological, structural, and optical properties of nanoparticles were examined.

Subsequently,

photocatalytic

bahaviour

and

antibacterial

properties

have

experimented. 2. Experimental procedure 2.1 Materials Here, the below mentioned materials used were of analytical grade and employed without further purification. Nickel acetate [Ni(CH3COO)2•4H2O] was supplied by HIMEDIA-India, while Limonia acidissima Christm was got from the market located at Bangalore, India. The dye named Evans blue (EB) was supplied from SD fine chemicals limited. Preparation of NiO nanoparticles The NiO nanoparticles were prepared by taking 0.5 M Ni (CH3COO)2. 4H2O, 10 mL of citrus fruit juice and 40 mL distilled water. This mixture was applied for stirring for about 1 h to get a uniform solution. This solution was irradiated by using a domestic microwave oven (2.45 GHz at 850 W) for 15 min. The resultant product was annealed at 600 °C for 4 h in a muffle furnace.

2.2 Characterization of NiO The phase of sample, size and crystal structure of the NiO nanoparticles were examined using Riakgu Mini Flexell Desktop Diffractometer. The functional groups of the sample analyzed using FTIR (JASCO 460 Plus) spectrophotometer in the range 4000-400 cm-1. The surface morphology of the sample was done by using a Zeiss electron microscope and Field Emission Gun-Transmission Electron Microscope. UV-Visible spectra were recorded by using a Perkin Elmer Lambda 25 spectrophotometer. Fluoromax 4 spectrophotometer was used. Perkin Elmer Lambda 25 spectrophotometer was employed during degradation to record the absorbance of the organic dye. 2.3 Photocatalytic activity Photodegradation investigations did underneath sunlight irradiation for Evans blue (EB) dye for NiO nanoparticles. NiO photocatalyst (50 mg) was supplied to a quartz tube comprising dye in a 100 mL solution. The reaction mixture was irradiated in sunlight with the intensity fluctuation of 950 ± 25 W m−2. Also, aliquots were gathered at intervals of 30 min to get the percentage of degradation for dye solution. The dye superannuate liquid was verified by recording the absorbance at 605 nm of EB (UV-Vis absorption spectra). The photodegradation of the dye was measured by equation 1: (1) where Co and Ct represent the initial and dye solution after time t in min absorbance, correspondingly. 2.4 Antibacterial activity It was screened by agar well diffusion process against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumonia bacterial strains. 100 ml of sterilized agar medium was spread in a 250 ml conical flask at room temperature. The nutrient broth was sub-cultured with bacterial strains for 24 h at 37℃ and the media was mixed systematically. Then petri dish was permitted for solidification and sonicated about 15 mins to make sure to get the uniform distribution of nanoparticles. These were filled onto the well at the concentration of 50, 75 and 100 μg/mL. NiO nanoparticles were exposed for about 30 min to natural light illumination to determine their antibacterial potential. Chloramphenicol (5 μg/mL)

has been consumed as an antibiotic for positive control. Zone of inhibition (ZOI) was observed after 24 h of incubation at 37℃ the values were taken. 3. Results and Discussion 3.1 Structural analysis

Fig. 1 XRD pattern of bio-mediated NiO nanoparticles The XRD pattern of NiO sample heat-treated at 600 °C is shown in Fig. 1. The Bragg diffraction peaks related to (1 1 1), (2 0 0), (2 2 0), (3 1 1), and (2 2 2) crystallographic reflections are in agreement with the characteristic nickel oxide crystallite reflections. The information regarding peaks revealed that the formation of sharp peaks and planes with cubic structure (lattice constant (a): 4.172 Å). There is only a single cubic NiO phase (JCPDS Card No. 89-7130) and no other secondary phase related extra compound detected indicating the higher degree of chemical purity. The average crystallite size of NiO nanoparticles was achieved to be 20 nm, was determined by the Debye-Scherrer equation. The dislocation density (δ) is attained to be 2.5×1015 lines/m2 computed by using equation 2 [23]: (2)

3.2 FTIR analysis From the spectrum, the main absorption peak is observed at 428 cm-1 and ascribed to the characteristic stretching mode of Ni-O vibration. The weak band at 2358 cm-1 is ascribed to the stretching mode of the C-H bond. The band at 3450 cm-1 characterize the vibration (stretching mode of H-O-H) of absorbed water molecules. The band near 1640 cm−1 can be assigned to the bending mode of water molecules vibrations, whereas the band at 1382 cm−1 is ascribed to the presence of C–O bonds [24-25].

Fig. 2 FTIR spectrum obtained on bio-mediated NiO nanoparticles 3.3 Morphological studies

Fig. 3 (a) SEM, (b) TEM and (c) EDAX images of bio-mediated NiO nanoparticles

The SEM micrograph (Fig. 3 a) shows agglomerated and uniformly distributed spherical in shape nanoparticles with narrow size distribution. The agglomeration of particles occurred due to the interfacial surface friction, during combustion. The images reveal the uniform distribution of particles and it clearly shows the spherical shape of nanoparticles (Fig. 3b). The elemental composition of synthesized nanoparticles determined by EDX inveterate the presence of both Ni and O. There are no extra peaks present in the spectra, which shows clearly the purity of the sample. 3.4 Optical studies

Fig. 4 (a) UV-Visible absorption spectrum (b) optical bandgap of bio-mediated NiO nanoparticles The optical absorption at 322 nm corresponding to NiO sample is indicated in Fig. 4a. The optical bandgap is calculated by using below equation: αhʋ = A (hʋ-Eg)n

(4)

The plot is shown in Fig. 4b from extrapolation was giving the optical bandgap (3.41 eV) [26]. The modified bandgap value may be attributed to the particle shape, size, and structural defect in the lattice. This data of NiO suggests that these nanoparticles can be employed in the photocatalysis and optoelectronics field.

3.5 Luminescence study From Fig. 5, NiO nanoparticles excited at 310 nm of wavelength and recorded at room temperature. The peaks of emission observed at 350, 441, 485, and 531 nm and 350 nm corresponds to NBE of NiO, whereas 441 and 485 nm (blue emissions) are attributed to surface oxygen vacancies of NiO. The peak at 531 nm (green emission) is ascribed to the defects in NiO lattice caused by charge transfer between Ni2+ and Ni3+ ions [27-29].

Fig. 5 Luminescence spectrum of bio-mediated NiO nanoparticles 3.6 Photodegradation studies Photocatalytic behaviour of bio-mediated NiO nanoparticles has been assessed by the degradation of EB (λ = 605 nm) dye under sunlight (Fig. 6). In the presence of NiO sample as the photocatalyst, with the increase of time of irradiation leads to the decrement of EB dye absorption. It has been intensely decreased and reaches 91% degradation in 150 mins. The degradation efficiency of microwave-synthesized NiO nanoparticles depends mainly on the surface morphology, unique charge separation, and nature of crystallite. According to the kinetic studies, degradation results pseudo-first-order kinetics, it is given as follows: (4) Alternatively,

(5) where C0 and Ct represented in section 2.3, K is the rate constant (min-1). The kinetics study for photocatalysis of EB dye by NiO sample is presented in Fig. 7. The pseudo-first-order degradation rate constant of NiO photocatalyst is 6.87×10-2 min-1 for EB dye.

Fig. 6 Photocatalytic absorbance spectrum of bio-mediated NiO nanoparticles of EB dye

Fig. 7 A plot of ln(C0/C) as a function of irradiation time for EB dye

3.7 Mechanism of photodegradation The photocatalytic behaviour of NiO nanoparticles is mostly associated with its various preparation circumstances, size of crystallite and morphological property. In this process, the concentration of surface defects also create a variance and also catch the electron to detain the recombination rate of photogenerated e-/h+ pairs. The reduction and oxidation of organic micro contaminants or pollutants enhanced by the superoxide and hydroxyl radicals formed when the light reaches [30-32]. Therefore, oxygen vacancies also favour the photocatalytic property and it has shown in following a general mechanism NiO + hυ (Vis) → NiO (eˉCB + h+VB)

(6)

NiO (eˉCB) + O2 → •O2ˉ

(7)

H2O → H+ + HOˉ

(8)

HOˉ + h+ → HO•

(9)

O2ˉ + H+ ↔ HOO•

(10)

HOO• + eˉ → HOOˉ

(11)

HOOˉ + H+ → H2O2

(12)

•

H2O2 + eˉ

→ HO• + HOˉ

(13)

NiO (h+VB) + H2O → HO• + H+

(14)

Dye + HO• → CO2 + H2O (Byproduct)

(15)

Dye + NiO (h+VB) → Oxidation product

(16)

Dye + NiO (eˉCB) → Reduction product

(17)

A comparison of the photocatalytic degradation efficiency of different nanomaterials produced by various synthesis process is given in Table 2.

Table 2 Comparison of EB dye and few more metal oxide nanoparticles with percentage of Photocatalytic degradation efficiency Photocatalyst

Method involved

Percentage of

Ref.

Degradation efficiency

NiO

Green synthesis

88.13

[33]

(A. Paniculata)

Undoped BiFeO3

Hydrothermal

34.71

[34]

Co doped

Hydrothermal

39.23

[34]

Cu2V2O7

Wet chemical

77.78

[35]

Cr2V4O13

Wet chemical

79.0

[35]

Green synthesis

91

Present work

BiFeO3

NiO

(citrus fruit juice)

3.8 Antibacterial activity The concentration of nanoparticles is varied between 50-100 μg/mL. The prepared NiO nanoparticles showed substantial antibacterial activity against the preferred pathogens likened with the standard antibiotic (chloramphenicol). The ZOI is measured by the interference of the strain in diameter and was depicted in Table 3. NiO nanoparticles show significantly higher antibacterial activity against E. coli and moderate activity against S. aureus. Less bactericidal activity is recorded against P. aeruginosa and K. pneumonia as compared to E. coli and S. aureus.

Table 3 Antibacterial performance of NiO nanoparticles Sample

Concentration

S. aureus

E. coli

P. aeruginosa

K. pnuemonia

(Mean±SE)#

(Mean±SE)

(Mean±SE)

(Mean±SE)

Chloramphenicol

(5 µg/mL)

20.00±0.29

21.17±0.17

20.50±0.29

20.85±0.17

NiO

(a = 50 µg/mL)

11.33±0.17

11.27±0.17

11.27±0.15

10.63±0.17

(b = 75 µg/mL)

13.17±0.17

13.50±0.29

12.17±0.17

11.83±0.33

(c = 100 µg/mL)

14.67±0.17

15.37±0.17

13.67±0.29

13.80±0.29

#The mean ± SE values of inhibition zone are indicated in mm.

Usually, the antibacterial property depends on the lesser crystallite size with a higher surface area of NPs. The hydrogen peroxide and superoxide radicals react to the ROS, harms the cellular proteins and deoxyribonucleic acid which ends with cell death. For antibacterial activity, the necessary mechanism is the light catalysis process [36-37]. Especially, the strain produced on the surface of the microorganism cells by the produced ROS in the presence of light leads to the death of the microorganisms. ROS comprises reactive hydroxyl radical (•OH), less toxic superoxide radical (•O2ˉ) and hydrogen peroxide (H2O2) as a poor oxidizer. The general reaction is given below Bacteria + •OH → Bacterial inactivation

(19)

NiO nanoparticles make interaction with the bacterial cell membrane and bind with the mesosome. This mesosome functions of DNA replication, cell division, cellular respiration were distracted and thus the cell membrane of bacteria surface area is enlarged. The generated ROS induces oxidative stress and causes changes in the function of the intracellular region of bacteria.

The prepared NiO nanoparticles release the heavy metal ions (Ni2+) on the surface and interact with the microbial cell membranes. The metal ions with a negative charge and positively charged cell membrane enticed reciprocally and the metal ions diffuse into it. The occurrence of metal ions on the bacteria surface shown by the thiol groups (-SH), which turns with proteins. Death of the bacteria causes due to the nutrients transmitted by the formed proteins diffuse via the bacterial cell membrane, and the inactivation of proteins triggered by the nanoparticles and decreases the cell permeability. From this, the nanoparticles immediately react on the pathogenic bacteria to destruct the membrane integrity and cells which finish up in the fatal of bacterial pathogens [38-48]. 4. Conclusion Bio-mediated NiO nanoparticles were productively prepared by employing citrus fruit as fuel via microwave-assisted route. The typical reflections having a most intense (2 0 0) peak in the XRD pattern revealed the formation of a cubic structure. TEM images confirmed the spherical shape of the nanoparticles. FTIR pointed out the stretching vibration modes of Ni-O in the NiO nanoparticles. The optical bandgap of bio-mediated NiO nanoparticles was equal to 3.41 eV. The degradation efficiency of photocatalytic activity against EB dye was found to be 91%. NiO nanoparticles demonstrated effective antibacterial performance against the tested pathogens. It follows that the prepared NiO nanoparticles were appropriate for photocatalytic, optoelectronic and pharmaceutical applications.

Funding: There is no funding for this study.

Compliance with ethical standards

Conflict of interest The authors declare that they have no conflict of interest.

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Graphical abstract

A plot of ln(C0/C) as a function of irradiation time for EB dye

Highlights: 

NiO nanoparticles were prepared by microwave-assisted green method using Limonia acidissima Christm (citrus fruit juice).



NiO nanoparticles were characterized through structural (XRD, FTIR), morphological (SEM with EDS, TEM) and optical (UV-Vis and luminescence) studies.



NiO nanoparticles were studied against organic pollutant (Evans blue) dye by photocatalytic activity.



It exhibits good antibacterial activity (foodborne pathogens).

Conflict of interest The authors declare that they have no conflict of interest.

Author statement: On behalf of all authors, the corresponding author states that there is no funding for this study.