Interactive Relationship between Silver Ions and Silver Nanoparticles with PVA Prepared by the Submerged Arc Discharge Method

.is study uses the submerged arc discharge method (SADM) and the concentrated energy of arc to melt silver metal in deionized water (DW) so as to prepare metal fluid with nanoparticles and submicron particles..e process is free from any chemical agent; it is rapid and simple, and rapid and mass production is available (0.5 L/min). Aside from the silver nanoparticle (Ag), silver ions (Ag) exist in the colloidal Ag prepared by the system. In the preparation of colloidal Ag, polyvinyl alcohol (PVA) is used as an additive so that the Ag/Ag concentration, arcing rate, peak, and scanning electron microscopic (SEM) images in the cases with and without PVA can be analyzed. .e findings show that the Ag/Ag concentration increases with the addition level of PVA, while the nano-Ag and Ag electrode arcing rate rises. .e UV-Vis absorption peak increases Ag absorbance and shifts as the dispersity increases with PVA addition. Lastly, with PVA addition, the proposed method can prepare smaller and more amounts of Ag nanoparticles, distributed uniformly. PVA possesses many distinct features such as cladding, dispersion, and stability.


Introduction
e production of nanosized metallic silver particles with different morphologies and sizes using different methods has been reported in previous studies, such as the electric spark discharge system (ESDS) [1][2][3].PVA (Mw 89,000-98,000, 99+% hydrolyzed, 341584, 9002-89-5, MDL: MFCD00081922) was the eligible polymer since it stands out for its viscoelastic behavior, hydrophilicity, chemical stability [4] and biocompatibility [5].PVA contains a large amount of -OH functional groups, which can form chelate composed of metal ions [6].It is a white powdered resin polymer, with features of viscoelasticity, hydrophilicity, chemical stability, and biocompatibility [7][8][9].PVA is used in many medical devices approved by the FDA (Food and Drug Administration, USA) such as contact lenses, membranes, drug delivery systems, and orthopedic devices [10], It is extensively used in biomedical and pharmaceutical applications [11,12], waste water treatment, and artificial articular cartilages [13].Initially, we used a biocompatible polymer, PVA, as a reducing agent to convert silver salt (AgNO 3 ) to Ag-NP.en, we obtained PVA/Ag-NP composite nanofibers via electrospinning [14].A series of monodispersed Ag-NPs with 25, 35, 45, 60, and 70 nm sizes was reported by using PVP as the surfactant [15].Also, Ag-NPs can be incorporated within biodegradable poly(lactic acid) [16] or deposited onto modified titanium surfaces [17] as an antibacterial scaffold for tissue engineering and medical applications.Poly(vinyl alcohol) (PVA) is a biodegradable polyester that has been investigated extensively as a biomedical material.Many researchers have utilized electrospinning to fabricate nanofibrous PVA scaffolds for use in wound healing [18][19][20].PVA and its nanocomposites have found a wide range of industrial applications such as fiber and textile sizing, coating, adhesives, emulsifiers, and film packaging in food and optical holographic industries [21].Nevertheless, there were only two articles about PVA/TiO 2 nanocomposite prepared by the ultrasonic irradiation method.To the best of our knowledge [22,23], high molecular materials, such as PVA [24], by stabilizing with polymer matrix, the silver nanoparticles, are surface modi ed.Hence, they can also act as capping agents.e homogeneous distribution of silver nanoparticles into the polymer matrix will also increase the surface area and make them t for catalytic applications.ere are several methods to fabricate silver nanoparticle polymer composites [25][26][27].Due to PVA's special characteristics, the nano-Ag will distribute uniformly on antibacterial dressings such that the index of the antibacterial dressing becomes more smooth and consistent.e products can be made as a lm or gel, or weaved into a ber.
In recent researches of nanoparticles, it is shown that the color of the Ag nanoparticle, produced by di erent methods such as presented in literature [28], is getting darker with the increase in concentration, usually from light yellow (since the peak absorption of Ag nanoparticle is 395 nm) to dark brown.In this study, the color of the 10 ppm, 35 ppm, and 60 ppm nanoparticles is light yellow, yellow, and dark brown, respectively, as shown in Figure 1.

Research Method and Process
e microelectric discharge machine system comprises the overall mechanism, hardware circuit, power supply, chuck, and so on.e motion control adapter card of the computer is used as the global core.e process performance of parameter setting is observed by changing the arcing rate, thus obtaining the parameter setting for the optimum process e ciency and quality of the nano-Ag colloid.Figure 2 shows the micro-EDM system [29,30].

Preparation of Nanosilver by Electrical Spark.
is study used SADM to split silver material into nanosized particles by arc discharge.
e process was free from chemical agents.Pure solutions, such as pure water, were used as the medium [1].
e silver (99.99% pure) wires with a diameter of 1 mm are used as anode and cathode and are submerged in DW or ethanol.e 200 ml DW is loaded, the positive and negative electrodes are manually xed and aligned, and then the discharge parameters are set before discharge.e discharge is nished after a period of time, and the product is taken out.e system framework is shown in Figure 3 [3].is study uses DW as a liquid medium to prepare Ag particles.e prepared sample is analyzed by spectrophotometry for the spectral characteristic of the product.e absorbance of nano-Ag colloid is analyzed by spectrophotometry based on the concentration index of nanoparticles.e conductivity of dielectric fluid is measured by a conductivity meter, the purity of dielectric fluid is guaranteed, and the conductivity of general DW is lower than 5.00 μs/cm.
Nanosilver fluid is fabricated.For energy dispersive X-ray spectroscopy (EDX) analysis, a silicon wafer was used as a carrier.Carbon, oxygen, and sodium were typically accompanied with the PVA, and therefore, Ag, C, O, and Na were present.Table 1 and Figure 4 display the EDX analysis results, and SEM analysis is shown in Figures 5(a   Advances in Materials Science and Engineering

Experimental Results and Discussion
3.1.Experimental Procedure.e 2.3 μs/cm Ag + solution (without PVA) and 20 μs/cm Ag + solution (with 10 ml PVA) preparation processes are designed, and the nano-Ag is then prepared at intervals of 6 min.e correlation between Ag + and nano-Ag of the nano-Ag colloid and the concentration in the preparation process are de ned by electrical conductivity and spectrophotometry (UV-Vis).
3.1.1.Silver Ions.200 ml DW is mixed with 2 ml, 4 ml, 6 ml, 8 ml, and 10 ml of the PVA, respectively.Ag is driven in 5 min, and the electrical conductivity is measured after the PVA is added to DW.When the PVA addition is 8 ml and 10 ml, the electrical conductivity does not distinctly increase, approaching the saturation concentration, as shown in Table 2.

Silver Ion Solution (with/without PVA).
e 2.3 μs/cm Ag + solution (DW) and 20 μs/cm Ag + solution (with 10 ml PVA) preparation processes are designed.en, the nano-Ag is prepared at intervals of 6 min.e correlation between Ag + and nano-Ag of the nano-Ag colloid and the concentration in the preparation process are de ned by electrical conductivity and spectrophotometry (UV-Vis), as shown in Table 3.

Vissim and UV-Vis.
e laboratory report chart of PVA additive in Ag nanoparticle preparation (Vissim and UV-Vis) is shown in Figures 6-11.

Zeta Potential and Size Distribution.
e laboratory report chart of PVA additive in Ag nanoparticle preparation (zeta potential and size distribution) is shown in Figures 12-15.

Results and Discussion.
e experimental discussion about the interactive relationship between Ag + /nano-Ag and PVA is described below.
(1) With PVA, when 8 ml (52.7 μs/cm) or 10 ml (59.5 μs/cm) of DW (200 ml) is added, the electric conductivity has no signi cant change, meaning that it has reached saturation.Advances in Materials Science and Engineering (2) During the discharge process, since the PVA covers the Ag particle and increases the surface charge of the Ag particle, it is seen that, from Figures 6 and 7, the discharging e ciency rises with the increase in the PVA concentration.e diameter of the Ag particle is 30 nm, and it remains 30 nm after the PVA covers the Ag particle; the overall complex may be larger than 30 nm after cladding.is complex is relatively big, and the distance between particles is relatively long.e overall complex is connected after cladding, the complex distance increases, two complexes cannot be connected, the covered complex appearance is negatively charged, and each covered complex is negatively charged.e repulsive e ect is generated during mutual collision, whereby the negative electric eld on the covered complex appearance is higher than the original surface electric eld, from 30 mv to 40-45 mv; and the negative electric eld on the covered complex appearance is strong so that the covered nano-Ag particles are farther from each other in liquid or colloid.e following situation is tenable.In the same electric eld, the farther the Ag particle is, the more unlikely the Ag particle is to cause a short-circuit bridge.As long as the short-circuit bridge does not occur in the discharge process, the controller makes a continuous electrode discharge, and thus, a lot of nano-Ag 0 and Ag + are generated so that the electrode consumption per unit time increases.
(3) According to Figure 8, the UV-Vis absorbance peak of DW discharge is driven in Ag + < 190 nm and the peak of absorption is a waveform < 190 nm (near 190 nm).According to Figure 9, the UV-Vis absorption peak of DW + PVA discharge is driven in Ag + 194 nm.According to Figures 8 and 9, the UV absorbance peak of DW + PVA shifts right.Carefully inspecting Figures 8 and 9, it is obvious that Ag + may shift right under the addition of PVA introduced. is is the rst breakthrough of the current study.(4) According to Figure 10, in the case of DW-Ag 0 (6 min), Ag 0 surrounds the AgOH and Ag 2 O, and the corresponding wavelength of UV-Vis absorbance peak is 394 nm.As shown in Figure 11, when the Ag 0 surrounds the Ag + -PVA − compound, the corresponding wavelength of absorption peak in the UV-Vis (300-600) spectrum is 410 nm, and the UV-Vis Advances in Materials Science and Engineering (190-300) absorption peak increases to at least 1.2. is suggests that the Ag + concentration rises to 12 ppm, and 1 ppm in general approximates to 1 μm/cm.e total electrical conductivity is 24 μm/cm, meaning at least 12 μm/cm of the concentration results from Ag + and the rest of 12 μm/cm results from the PVA derivant.Figures 10 and 11 indicate that the DW-Ag 0 (6 min) wavelength is 76 nm at absorbance 70%, and the PVA (6 min) wavelength is 94 nm at absorbance 70%.Another new finding is that the particle size is measured by the Zetasizer.It is deduced that the Ag 0 complex is combined with PVA, which leads to increase in the equivalent diameter, thus causing the peak of Ag 0 shifting from 394 nm to 410 nm.Moreover, at the neck of the UV-Vis absorbance wavelength 70% in Figures 10 and 11, the wavelength of DW-Ag 0 (6 min) is 76 nm. e width of the neck of DW + 0.5%/w/w-Ag 0 (6 min) UV-Vis wavelength at 70% is 96 nm.
is is because the (Ag + -PVA − ) complex makes the overall Ag 0 UV-Vis spectrum neck width wavelength increase from 76 nm to 96 nm.
(5) According to Figures 14 and 15, the particle size and distribution are 50-100 nm in the DW solution without PVA.When (0.05%/w/w) PVA is added, the particle diameter is 25-75 nm.

Conclusion
e experimental results about the interactive relationship between Ag + /Nano-Ag and PVA are described below.
(1) According to the increment ratio of electrical conductivity and absorption peak in the experiment, the PVA is correlated to the Ag 0 /Ag + concentration.(2) As the electrode discharges continuously, a lot of Ag 0 and Ag + are generated, and the electrode consumption per unit time increases, so that the Ag 0 and Ag + arcing rate rises.(3) When Ag + is combined with PVA (0.05%/w/w), it forms a (Ag + • PVA − ) compound.e molecular weight of this compound is much heavier than (Ag + ) 2 O − and Ag + OH − , and the absorption peak of Ag + shifts right to 194 nm.(4) e PVA not only helps the formation of Ag + but also increases the formation of Ag 0 .After the PVA is added, the concentration of Ag + increases 5 times (1.2/0.227� 5.28) and Ag 0 increases 3 times (0.899/0.247 � 3.63).Here, Ag 0 is covered by PVA, increasing its dispersity and forming the Ag + -PVA − compound.e neck width of Ag 0 on the UV-Vis absorbance wavelength at the height of 70% shifts from 76 nm to 96 nm, with its Ag 0 peak shifting from 394 nm to 410 nm.(5) According to SEM image in Figures 5(a) and 5(b), the particle agglomeration is severe before the Ag 0 is mixed with PVA. e particles have irregular shape, and the particle size and distribution are nonuniform.
When 0.5% PVA is added in, the particle size becomes smaller and is distributed over the PVA surface uniformly.Meanwhile, the surface zeta potential of Ag 0 increases, and the catalytic activity rises, so that the Ag-PVA complex is easier to disperse.

Figure 1 :
Figure 1: e color of the nanosilver particle suspension changed from yellow to dark brown.

Figure 5 :
Figure 5: (a) SEM diagram of aggregated silver nanoparticles.(b) SEM diagram of silver + 0.5% PVA particles.(c) 3D structure of nanocolloid distribution.(d) Zoomed in picture of the 3D structure of the nanocolloid.

Table 1 :
EDX application for the analysis of the proportion of elements in silver.