Effect of Fe3O4 on the Electro-Optic and Magneto-Electric Characteristics of (PANI/Fe3O4)-Ag Film

(PANI/Fe3O4)-Ag films have been successfully synthesized on a glass substrate. In this study, PANI functioned as a matrix, Ag as a catalyst enhancing the conductivity of PANI, and Fe3O4 as the influence of magnetic properties. (PANI/Fe3O4)-Ag was synthesized by a combination of chemical polymerization method to introduce Ag doping into PANI, and coprecipitation method of Fe3O4. The samples were characterized by using FTIR, X-RD, SEM, EDAX, 4-probe electrical conductivity under the employing of magnetic fields, and under the influence of light intensity. It was shown that there was a Fe2O3 phase as the consequence of Fe3O4 oxidized as AgNO3 protonation on the ultrasonication treatment. introducing Fe3O4 into (PANI/Fe3O4)-Ag film, increase the surface density, but reduce the electrical conductivity. The increasing of magnetic field might also reduce the conductivity of (PANI/Fe3O4)-Ag. Further, We also obtained that the increasing of light intensity employed to the samples enhances the electrical conductivity. The electrical conductivity of (PANI/Fe3O4)-Ag can be tuned by controlling the Fe3O4, magnetic field, as well as the light intensity


Introduction
A research of Polyaniline (PANI) conductive polymer has become a fascinating topic recently due to its promising application potential along with a search of another natural polymer for electronics [1][2]. Many PANI related research have been focused on the application such as for gas sensor [1], the raw matrix material composition of lithium battery [2], and super-capacitor [3]. The polymer is basically as an insulator. The polymer can be modified until raising conductive characteristic through synthesis development. The synthesis method of PANI with polymerization of a chemical reaction is because it is mostly used since the synthesis is relatively simple, easy, inexpensive and efficient [4].
The effort to increase the magneto-electric on PANI composite by using PMME has been reported resulting in the highest conductivity which was 73 Scm -1 [5]. PANI/Fe 3 O 4 produced conductivity of 2

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The 4th International Conference on Advanced Materials Science and Technology IOP Publishing IOP Conf. Series: Materials Science and Engineering 202 (2017) 012062 doi: 10.1088/1757-899X/202/1/012062 10 -9 Scm -1 [6], while the study on an electro-optical characteristic of PANI/chlorophyll could enhance the conductivity from 1 S/cm-8 S/cm [7]. Magneto-electric is an interesting study because of the application potential on the electronic and sensor [8,9], but in the synthesis conducted, it is still challenging to get a significant and excellent material for optimizing the magneto-electric characteristic to [10]. Besides the idea of magneto-electric characteristic, the electro-optical characteristic was considered as well [11].
So far, it is rare to find the study of Ag, and Fe 3 O 4 doped PANI films. It is also hard to find the reports of the films primarily effect of magnetic fields and light intensity on the electrical conductivity of the films. In this work, we report on the fabrication of PANI/Fe3O4/Ag films and its microstructure, electrical conductivity as a function of magnetic fields, and light exposures for various Fe 3 O 4 dopant. It is necessary to know the correlation of electrical and magnetic characteristic of PANI. The electrical characteristic of PANI/Ag is a function of the magnetic characteristic of Fe 3 O 4 . Those parameters are presumably interrelated. This works also would like to infer fundamental knowledge of how to tune the electrical properties of PANI/Fe3O4/Ag by controlling dopant, magnetic fields, and light intensity.

Fe 3 O 4 Coprecipitation.
Firstly, the iron sand was extracted and purified by using permanent magnetic tube to get iron sand powder. The sand powder was reacted with HCl by using magnetic stirrer at a temperature of 140 o C for 30 minutes. After that, the solution was filtered by using filter paper. The solution penetrating the filter paper was taken since Fe 3 O 4 dissolved in HCl. The solution then was dropped with NH 4 OH gradually while being stirred for around 30 minutes until formed a black precipitate. The formed precipitated was then washed using distilled water up to pH 7 (normal pH) to get the real sample which was free from impurity. The obtained precipitate was dried on a hotplate at a temperature of 70 o C. 3 O 4 Polymerization. PANI polymerization was conducted through chemical reaction method following the method in the literature [1]. The first solution was made from aniline monomer (1.82 mL) reacted with HCl (50 mL; 0.2 M). Another solution was prepared by mixing (NH 4 ) 2 S 2 O 8 (5.71 g) with 50 mL distilled water. Both solutions were mixed and then stirred mechanically by using magnetic stirrer for 30 minutes. After stirring, the mixed solution was let precipitating for 24 hours until a green deposit was obtained. The precipitated materials were then washed with deionized water (DI water) many times until it looked like a crystal. PANI obtained from the first polymerization was PANI-ES 1 and it was then added in dropwise with NH 4 OH (0.

PANI/Ag/Fe 3 O4 Protonation.
The fabrication of PANI/Ag/Fe 3 O4 was basically followed the previous work [3] with several modifications. Firstly, introducing Ag doping was done by grinding 0.5 g of ready PANI/Fe 3 O 4 mixed with 0.5 g CSA. The mixture was ground for 15 minutes. Along with this, an AgNO 3 was dissolved in acetone (5 mL; 0.5 M). All prepared materials were mixed and dissolved in 10 mL chloroform for chemical reaction breaking of the atoms bonds. The sonification process was done for 45 minutes for one hour. The last step was precipitating the solution for 24 hours for protonation process. The precipitated was then filtered to obtained PANI/Ag/Fe 3 O 4 paste which will be used for XRD and FTIR characterization. The PANI/Fe 3 O 4 were similarly treated and designated as PAF1M, PAF2M, PAF3M, PAF4M, and PAF5M.

Functional Groups of (PANI/Fe 3 O 4 )-Ag
Spectrum of FTIR for PANI, PANI/Fe 3 O 4 , and PANI/Ag/Fe 3 O 4 is shown in Figure 1. This result is closely similar to our previous work [1]. The peak at 1591,27cm -1 occurred due to the stretch vibration of C-N bond on quinoid ring; the peak at 1504,48 cm -1 occurred due to benzoid C-N bond; the peak at 1307,74 cm -1 was a stretch vibration of bipolar structure of C-N bond, the wavenumber of 1147,65 cm -1 was a bending section result of aromatic C-H bond, and the wavenumber at the range of 831,32 cm -1 was the consequence of aromatic C-H bond. The absorption difference of IR Fe 3 O 4 infused when PANI-ES polymerization occurred toward PANI-EB peak is shown in Figure 1 (b). From the figure, we can see that the transmittance plain was at the wave number of 3176,76 cm -1 , 1631,77 cm -1 , 565,14 cm -1 , and 420,28 cm -1 . The absorption of IR Fe 3 O 4 at 3176,76 cm -1 identified the function cluster of -OH-occurring in the range of 3000-4000 cm -1 , the wavenumber of 1631,77 cm -1 identified function cluster of H 2 O, the wavenumber of 565.14 cm -1 happened as a consequence of the presence of (Fe 3+ -O 2+ ) and for the wavenumber of 420.28 cm -1 , it was a functional group of (Fe-O). From Figure 1 (b), it was identified that Fe 3 O 4 was bound with PANI matrix during the polymerization process. When Ag added to PANI/Fe 3 O 4 it might change the origin bonds of PANI and were replaced by Ag + ion from AgNO 3 of which bond was broken. The identification of FTIR for Ag ion at the spectrum of 2965.15 cm -1 occurred due to the presence of C-Ag bond; the wavenumber at 1693, 5  showed a functional group of -N-H-enabling -H-atom attached with-N-was replaced by Ag into -N-Ag-. While the wave number of 1026,13 cm -1 represent a function of -OH-.

Crystal Structure of (PANI/Fe 3 O 4 )-Ag
The XRD diffraction patterns is provided to study the crystallinity and phase formed from PANI/Ag/Fe 3 O 4 film. The un-doped and Fe 3 O 4 doped (PANI/Fe 3 O 4 )-Ag is displayed in Figure 2. it is oxidized becomes Fe 2 O 3 . The third factor is Fe 3 O 4 particle becomes reactive in nano-size, enabling such condition may happen in the process of giving Ag doping by some of Fe 3 O 4 oxidized becomes Fe 2 O 3 phase.

Microstructure of (PANI/Fe 3 O 4 )-Ag
The effect of Fe 3 O 4 to the (PANI/Fe 3 O 4 )-Ag film on its microstructure could be seen based on the topography surface by SEM characterization as depicted in Figure 3. These SEM images do not contain the same features with the metallic doped of PANI [1]. It is seen that the morphology of (PANI/Fe 3 O 4 )-Ag samples are plate-like. It might be due to the synthesis of PANI was by using chemical reaction polymerization. In Figure 3 (A1), the elemental content of Fe 3 O 4 was fewer than the other samples, so the granular microstructure of (PANI/Fe 3 O 4 )-Ag surface remained plate-like and smooth. The size of PANI formed was around 0.3-0.5 μm. In

Magneto-Electric of (PANI/Fe 3 O 4 )-Ag by Using 4 Probes
The magneto-electric characteristic of (PANI/Fe 3 O 4 )-Ag film is an interesting complement study in which the Fe 3 O 4 has a magnetic characteristic as the PANI of which conductivity is increased by giving Ag doping. It is observed in Figure 4, that employing magnetic field resulting to reduce electrical conductivity for all ranges of Fe 3 O 4 doping. This feature is similar to the pure extracted PANI as reported by other work [8]. Another group, reported that at low magnetic field, electrical conductivity is obviously increased by increase of magnetic field. [16]. When the more Fe 3 O 4 compound was added to PANI/Ag/Fe 3 O 4 , the conductivity is getting reduced. In general also observed that the magnetic field affected to decrease the electrical conductivity. Interesting phenomena achieved in this figure, both increased of Fe 3 O 4 dopant as well as increase of magnetic intensity give rise to reduced the electrical conductivity. It means that, we can control electrical conductivity of PANI/Ag/Fe 3 O 4 films by controling Fe 3 O 4 dopant and or employed external magnetic field. The magnetic field applied to the (PANI/Fe 3 O 4 )-Ag material made the magnetic dipoles of inactive Fe 3 O 4 became magnetized by external magnetic field (H) applied. The magnetic dipole influenced by magnetic field made the electron dissipation brought the charge on the PANI bond chain or from ferrites compounds. The dissipation disturbed the electron path in the PANI bond chain, so the electron became harder to move to deliver the electric charge since it was quantized by the magnet dipole of Fe 3 O 4 .

Electro-Optic Characteristics of (PANI/Fe 3 O 4 )-Ag Film by Using 4 Probes
The electric-optic characteristic of (PANI/Fe 3 O 4 )-Ag sample is an influence of light intensity on the conductivity. Inducing doping of Fe 3 O 4 as well as the light intensity significantly change the electrical conductivity of (PANI/Fe 3 O 4 )-Ag. The light intensity applied on (PANI/Fe 3 O 4 )-Ag made the electrical conductivity of material increased. It is presumably that the intensity caused thermal energy causing electron energy increased in the PANI bond chain within the valence band. Such condition made the electron easily moved to the conduction band. The band energy from the sample could be derived by giving light intensity in the range in which quantum energy hv should exceed the band energy. The light intensity applied on (PANI/Fe 3 O 4 )-Ag sample was about 550 to 2770 Lux. This feature may be similar to the thermal applied to PANI which also increase as the temperature increase [16]. It is revealed that the effect of light intensity below 550 Lux did not affected to the (PANI/Fe 3 O 4 )-Ag conductivity. There is no step-like patterns of intensity induced of electrical conductivity as in borosilicate glass [17].

Conclusion
Based on the characterization of microstructure by using SEM, the bigger the addition of Fe 3 O 4 , the density of (PANI/Fe 3 O 4 )-Ag film increases as well. The increase of surface density also induces to the reduce of electrical conductivity. This implies that introducing Fe 3 O 4 into (PANI/Fe 3 O 4 )-Ag film, is not in line with the increase in surface density. The response of increasing of magnetic field might also reduce the conductivity of (PANI/Fe 3 O 4 )-Ag . film. Further, we also obtained that the increasing of light intensity employed to the samples enhances the electrical conductivity. The electrical conductivity of (PANI/Fe 3 O 4 )-Ag can be tuned by controlling the Fe 3 O 4 , magnetic field, as well as the light intensity.