Various researchers reported the interactions of leaf phytocompounds with metallic salts or ions during ZnO NPs green synthesis^25-28. During synthesis, plant antioxidants chelated the Zn ions which forms metal complex by thermoreduction process metal complex converted into ZnO NPs²⁹. Rafique et al.¹⁹ reported green synthesis of ZnO NPs by using Syzygium cumini extracts. During biosynthesis, plant extracts act as stabilizing and capping agent and finally zinc acetate reduced into ZnO NPs.

X-ray diffraction patterns
XRD patterns for green synthesized Ag and ZnO NPs were shown in Fig. 1. The standard diffraction peaks showed the center faced cubic phase of silver NPs (confirmed by JCPDS data card no: 89-3722) and hexagonal wurtzite structure for zinc NPs (JCPDS data card no. 36-1451). By using Scherer formula, the average Ag and ZnO NPs size were calculated as 35.36nm and 45nm respectively.

Vidya et al.³⁰ reported the leaf extracts of Calotropis gigantea used green synthesised ZnO NPs. XRD patterns showed spherical nano crystallites with average size as 30-35nm. Thema et al.³¹ reported the ZnO NPs green synthesis along with Agathosma betulina plant extracts XRD analysis showed quasi-spherical nanoparticles with average size 15.8nm. Selim et al.³² reported green synthesized ZnO NPs and confirmed the average size as 15.22nm by using TEM, FTIR, XRD and UV spectroscopy.

X ray photoelectron spectroscopy (XPS) analysis
The XPS wide spectrum of Phyllanthus niruri leaf extracts mediated Ag NPs showed oxidation state of C1s and Ag 3d state. In Ag NPs, traces of leaf extract responsible for the C (1s) signals. In Gaussian fitting, XPS spectra of ZnO showed asymmetric O (1s) signals contains three symmetrical signals namely O1s₁, O1s₂ and O1s₃. The Aristolochia indica leaf extracts synthesized ZnO NPs results showed three signals O1s₁ at 531.49eV, O1s₂ at 533.24eV and O1s₃ at 534.65eV due to the O2^– ion in Zn²⁺ ion (Fig. 2)

These results were evidenced by De la Rosa et al.³³, Remashan et al.³⁴ and Armelao et al. ³⁵ reported adsorbed H₂O and lattice oxygen on the ZnO surface, Zn-O-Zn surface and Zn-OH surface respectively.

FTIR spectroscopic studies
Functional groups in Ag and ZnO NPs were conferment by FTIR analysis¹⁵. FTIR spectra for Phyllanthus niruri leaf extracts synthesized Ag NPs (Fig. 3) showed the presence of phytochemical components like steroids phenols, glycosides, tannins, triterpenoids, flavonoids, saponines and glycerides. The Ag metal peak observed at 424cm^-1 for silver NPs by Phyllanthus niruri leaf extracts and the C-H bending vibration observed at 839cm^-1 for silver nanoparticles. FTIR spectra of green synthesized ZnO NPs by Aristolochia indica showed the O-H stretching band at 3428cm^-1, asymmetric C-H stretching at 2904cm^-1, C=O symmetric stretching at 1458cm^-1, O-H asymmetric stretching at 1022cm^-1, Zn-O stretching 440cm^-1 for ZnO NPs (Fig. 3).

The medicinal plant extract are act as dual role like reducing and capping agent³⁶. FTIR spectra of Anigozanthos manglesii green synthesized Ag NPs with broad absorption band at 3448cm^-1 and hydroxyl (-OH) group present in the bio-macromolecules on leaf extract³⁷. FTIR spectra of biosynthesis Ag NPs vibration frequency observed at 1381cm^-1 and corresponding to –NO₃ stretching whereas the peak at 692cm^-1responsible for the reduction and capping during the synthesis of Ag NPs^36,38. Zandi et al.³⁹, Munoz-Hernández et al.⁴⁰ and Xiong et al.⁴¹ reported results evidenced our ZnO NPs FTIR results.

Photoluminescence (PL) spectroscopic studies
By using photoluminescence spectroscopy, synthesized nanoparticles optical and photonic properties were studied. Ag NPs excitation wavelength observed at 42nm. Three peaks observed as blue, blue-green and green emission spectrum at 484, 486 and 529nm respectively. Luminescence emission peaks observed at 440 and 600nm due to presence of antioxidant compounds in Phyllanthus niruri leaf extracts while the green emission peak observed at 529 nm due to organic matrix bound to silver nanoparticles.

Whereas photoluminescence spectra of Aristolochia indica leaf extracts green synthesized ZnO NPs excitation wavelength observed at 350nm. The emission spectra showed four peaks at 398, 408, 419 and 434nm. A peak observed at 398nm due to the radiative recombination of collision process during ZnO NPs green synthesis (Fig. 4). Fan et al.⁴² reported two violet emission bands at 408 and 419nm due to the electron transition between the Zn at interstitial with the high incidence ones. Mishra Sheo et al.⁴³ also reported blue emissions peaks at 434nm, where strongly ascribed due to singly ionized Zn vacancies.

TEM analysis
TEM images showed morphology of green synthesized Ag NPs by Phyllanthus niruri extract as spherical shape and their average size was 30nm (Fig. 5). TEM images of green synthesized ZnO NPs by Aristolochia indica extract showed spherical shaped particles with average size of 30-60nm (Fig. 6). Suresh et al.⁴⁴ reported Phyllanthus niruri mediated AgNO2 NPs where the average particle size found as 30-60nm.

Antibacterial activities
Three different concentrations of green synthesized Ag and ZnO nanoparticles antibacterial activities were tested against three gram positive and five gram negative bacteria such as S. aureus, S. pneumoniae, B. subtilis and K. pneumoniae, E. coli, P. aeruginosa, P. vulgaris, S. dysenteriae respectively. Table 1 showed zone of inhibition results of green synthesized Ag and ZnO NPs with control amoxicillin in culture plates. Ag NPs showed high antibacterial activities to the all the bacterial types than compared to amoxicillin whereas increased concentrations of Ag NPs showed increased zone of inhibition. The inhibition of bacterial cells was due to the disruption of bacterial lipopolysaccharide layers with the green synthesized Ag and ZnO NPs. This interaction developed ROS in the bacterial cytoplasm leads to the disintegration of membrane potential and reduced cell growth. These results were evidenced by similar reports observed from Jung et al.⁴⁵, Santhoshkumar et al.⁴⁶ and Tong et al.⁴⁷ Albizia procera leaf extract mediated Ag NPs showed high antibacterial activities against gram positive and gram negative bacteria⁴⁸. Khalid et al.⁴⁹ reported the significant antibacterial activity of Cu NPs against gram positive and gram negative bacteria.

Table (1):
Zone of inhibition (in mm) observed in various bacteria treated with green synthesized Ag and ZnO NPs.

1-3: Gram positive bacteria; 4-8: Gram negative bacteria; *Positive control