Synthesis of Silver Oxide Nanoparticles (Ag2O Nps) and Study Their Dispersion into New Polymer Matrix

INTRODUCTION
Polymers form a very important class of materials without which the life seems very difficult. They are all around us in everyday use; in rubber, in plastic, in resins, and in adhesives and adhesives tapes. The word polymer is derived from Greek words, poly is many and mer is parts or units of high molecular mass each molecule of which consists of a very large number of single structural units joined together in a regular manner [1]. Nanotechnology is a burning field for the researchers. Nanotechnology deals with the Nanoparticles having a size of 1-100 nm in one dimension used significantly concerning medical chemistry, atomic physics, and all other known fields. Nanoparticles are used immensely due to its small size, orientation, physical properties, which are reportedly shown to change the performance of any other material which is in contact with these tiny particles [2]. The silver oxide nanoparticles were synthesized due to their excellent physical and chemical properties [3]. The Ag2O NPs were aimed to prepare by green synthesis approach using Zephyranthes Rosea flower extract, which includes the low cost, non-toxic by utilizing the extract acts as an excellent reducing and capping agents. The prepared Ag2O NPs were investigated for structural, functional, morphological, and optical studies [4]. Further, the antibacterial, antioxidant, anti-inflammatory, anti-diabetic activities were tested to ensure the bioactivity of Ag2O-NPs [5]. Silver nanoparticles combined with polymers have attracted great consideration because of the widened application goal offered by these hybrid materials. Particularly, silver nanoparticles and polymer composites are promising functional materials in several field such as optical, electrical, and mechanical properties. Many reports in the literature show attempts to synthesize silver nanoparticles-based polymer nanocomposites, with their application in high performance capacitors, conductive inks, and other electronic components Silver nanoparticles have received considerable attention due to their attractive physical and chemical properties and it has been combined with polymers such as polyvinyl alcohol (PVA), poly vinyl pyrrolidone (PVP), poly methyl methacrylate (PMMA) [6,7]. Hence the present study was carried out to synthesize and characterize the silver nanoparticles and Ag-NPs/polymer composite using eco-friendly method [8].

MATERIALS AND METHODS
Materials
Silver nitrate (THOMAS BAKER, 99%), sodium hydroxide (NaOH) (THOMAS BAKER, 99%) , Ethanol (scharlau, 99%), acrylic acid (CDH, 98% ), benzene (CDH 99%), Nitrogen gas  (Iraq,  98%),  azo bis iso butyronitrile (AIBN) (Germany, 98%) methanol (scharlau, 99%), deoxygenated distilled water and orange leaves. 
Preparation of orange leaves extract
The orange leaves were collected from orange trees in Diyala government, then cleaned from suspended dirty by tap water then washed with distilled water dried in shade. They were grinded with electric grinder then sifting then stored away.  30 g of leaves powder was added to 400 mL of deionized water and boiled for 2 hours at 80°C until the solution color change, leaves extract was cool at room temperature and filtered it and stored in refrigerator at 4°C for further studies. 

Green synthesis of Ag2O-NPs using orange leaves extract
Silver nitrate solution was prepared by dissolving (0.5g AgNO3) in the deionized water (50 mL). Plant extract solution was added gradually on the precursor solution under stirring at (40 °C), raise temperature of solution to (90 °C), NaOH (1M) solution was added drop wise to the mixture (salt solution and orange leaves extract) to obtain pH 14 approximately under continuous stirring for (1hour), subsequently the the precipitate was collected and dried in an oven at 80 °C for 2 hours [9,10]. The detailed procedural steps for synthesis of Ag2O nanoparticles is described in Fig. 1.

Synthesis of polymers 
General procedure for the preparation of polymers (p1 and P2) are illustrated in Fig. 2. In a 50 mL two-necked round-bottomed flask equipped with a reflux condenser, a nitrogen gas inlet tube, and a magnetic stirrer bar, a mixture of solution of compound (B1, B2) (0.01 mole) and acrylic acid (0.01 mole ,0.72 g) dissolved in benzene (30mL ). AIBN (0.008 mole, 1.3g) was added to the mixture under refluxed for (10 hours), acid was refluxed under a stream of N2 at 130 °C for 12 h to produce P1 and P2, respectively. After cooling the flask to room temperature, the polymer solution was poured into a 25 mL methanol. The formed precipitate was collected by filtration and washed thoroughly with hot water. The polymer was formed and hardened with time [12].  

Preparation of Ag2O-NPs /polymer matrices
Matrices (Ag-NPs/ polymer) were synthesized by dissolving (0.5 g) polymer in THF (20 mL) in beaker (A) and suspended (0.5 g) Ag-NPs in the ethanol (20 mL) in beaker (B) at room temperature.  Beakers (A and B) were placed in ultrasonic bath about (30 min) at 50°C.  The beaker (A) content was added to beaker (B), the mixture were placed in ultrasonic bath at 70-80 C period (3 hours). The matrices (Ag-NPs/ polymer) as a binary composite [9] were formed after the solvent evaporated [12]. 

RESULT AND DISCUSSION
Synthesis and Characterization of Polymers     
FT-IR analysis 
The objective of this study was the preparation of novel polymers (P1 and P2) by solution polymerization method from the acrylic acid to using as matrices and stabilizer of silver nanoparticles. The FT-IR spectrum, and 1H and GPC polymers (P1 and P2) spectra of are shown in Figs. 3-8, respectively. FT-IR data as shown in Figs. 3, 4 and Table 1. 

1H-NMR analysis
1HNMR spectra of the polymers (P1 and P2) and their data were illustrated in Figs. 5, 6 and Table 2, where all the peaks could be readily assigned to the protons. The proton of C-H in the (CH-COOH) group was observed at (1.4 and 1.5) ppm as triplet peak, the proton of C-H attached (CH2-NH) group show an absorption at (3.27-3.4) ppm as doublet peak. The proton of amine and carboxylic groups were observed at (3.2 and 3.4) ppm and (7.2-7.8 and 7.2-7.8) ppm as singlet and multiple peak, respectively.
Gel permeation chromatography (GPC) analysis
GPC is a type of size exclusion chromatography (SEC), that separates analyses on the basis of size. Polymers can be chromatography by a variety of definitions for molecular weight including the number average molecular weight (Mn), the weight average molecular weight (Mw) and the size average molecular weight (Mz). Table (3) and Figs. 7 and 8 shown the factors calculate using GPC technique [13] and the GPC chromatogram for the polymers synthesized.

Characterization of synthesized silver oxide nanoparticles
FT-IR analysis
As shown in Fig. 9, FTIR spectrum (400 to 4000 cm-1) confirms the presence of synthesized silver nanoparticles (Ag2O- NPs). The broad peak at 3309 cm-1 was assigned to the presence of O-H group [14]. The band at 544 cm−1corresponding to Ag–O bond, thus confirming the presence of Ag–O [15]. The absorption at 1457 and 1354 cm−1 can be attributed to the symmetrical and asymmetrical bending vibrations of –CH3. The bands at 1623 to approximately 1650 cm−1 should belong to the stretching vibrations of C=C or the O–H bending mode.  From FTIR results, it can be concluded that some of the bioorganic compounds from orange leaves extract formed the strong coating or capping on the Ag2O-NPs.

XRD analysis 
Fig. 10 shows the XRD pattern of Ag2O- NPs synthesized by the green method. All the diffraction peaks of (111), (200), (220), and (311) can be well matched with the cubic phase structure with pattern peaks in T able 4. The structure of the resultant data is well matched with the JCPDS card number 03-0921[16]. The average crystallite size was calculated using the Debye–Scherrer equation and was found to be 38.69 nm. Expansive and sharp peaks were observed, which indicates the crystallite size and purity of Ag2O-NPs [17].
The microstrain (ε) and dislocation density (δ) of Ag2O- NPs was evaluated by using the respective formula [18]. The microstrain and dislocation density (lines/m2) values are reported in Table 4.
FE-SEM images of the silver oxide nanoparticles
The FE-SEM images of the silver oxide nanoparticles are shown in Fig. 11. The surface morphology of silver oxide nanoparticles showed a shape and spherical nature agglomerated with average size about 47.45 nm, this value was further supported from the calculations made on the XRD pattern [19].

Energy-dispersive X-ray (EDX) study
Fig. 12 shows the energy dispersive spectrum of the synthesized silver nanoparticles, which suggests the presence of silver as the ingredient element. Silver nanoparticles generally show a typically signal peak at 3 keV, due to surface plasmon resonance. Fig. 12 shows the quantitative information of biosynthesized Ag2O-NPs. The presence of elements such as Ag, O and C are shown in the inset of Fig. 12.

DLS analysis 
The dynamic light scattering (DLS) data for Ag2O-NPs displayed distribution in two peaks as a Fig. 13. It is observed that the size distribution of Ag2O-NPs ranges from 30 to 70 nm and 450 to 1200 nm.  The increase in the mean particle size can also be attributed to the agglomeration of smaller particles [20].

FE-SEM images of Ag2O-NPs / polymer matrices
The FE-SEM images of the Ag2O-NPs/ polymer matrices are shown in Figs. 14 and 15.  The FE-SEM images, shows that the average size  are 57.18 nm and 68.78 nm for  the Ag2O-NPs /P1 and Ag2O –NPs/P2 matrices, respectively with few increase in the size of nanoparticles compare with Ag2O-NPs image (Fig. 11) , and it shows  that the Ag2O- NPs are  in  spherical shape in the both cases.

CONCLUSION
In this study, novel copolymers were synthesized and Ag2O nanoparticles was successfully synthesized achieved using the aqueous extract of the orange leaves extract. The process is easy, fast, cheap, environmentally friendly, and does not require any organic solvent or surfactant. Therefore, this synthesis method is more advantageous than traditional methods for the synthesis of Ag2O nanoparticles.  Ag2O / polymer matrix were prepared from Ag2O nanoparticles and polymers (P1 and P2) by chemical solution method were successful. The Ag2O nanoparticles and their matrices Ag2O / P1 and Ag2O /P2 matrix were almost spherical, of cubic crystalline nature, and the average crystal sizes are 47.45nm, 57.18nm, and 68.78nm respectively. 

CONFLICT OF INTEREST
The authors declare that there is no conflict of interests regarding the publication of this manuscript.