Introduction

Selectivity and activity are two features that organo-inorganic hybrid compounds can have [1,2]. They promote CO₂ adsorption and conductivity, among other physicochemical features. They also have more active site types, more active site exposure, and altered reaction pathways [3,4]. Because of their many phases, lead oxides are intriguing substances. PbO (α, β and amorphous), Pb₂O₃, Pb₃O₄, and PbO₂ (α, β and amorphous) are the four basic kinds [3,4]. PbO is polymorphic and has a large band gap. The yellow -PbO is one of these two forms and it is stable at temperatures over 425 °C. The red α-PbO, which is stable at low temperatures, is the second form. At around 490 °C, the α-PbO phase transforms to β-PbO [5,6]. The high-temperature yellow form, on the other hand, may persist at normal temperature. PbO is a high-dielectric-constant transparent conducting oxide (TCO) [7]. Furthermore, it is a substance with a high refractive index.

Hematite (Fe₂O₃) has a 2.1 eV of band gap and it is a semiconductor compound of n-type. As an inexpensive semiconductor material, iron oxide is extensively used in gas sensing applications, catalyzed reactions, conversion methods of solar energy, batteries of lithium ion, purification processes, splitting of water, and bio-medicine claims among further applications [8,9]. Due to their unique properties and potential applications, conductive polymers have attracted a lot of attention in the last three decades [10,11]. Nanocomposites made of conductive polymers and metal oxides are becoming increasingly popular in a number of applications. Previous research has shown that metal oxides can raise the dielectric, electrical, mechanical, and optical characteristics of conductive polymers [12].

Conductive polymers having conjugated double bonds have recently attracted a lot of interest for application in conductive thin films. Polypyrrole (PPy) has sparked particular attention because to its excellent environmental stability, ease of synthesis, and high electrical conductivity [13]. Chemical oxidation of pyrrole (Py) or electrochemical polymerization techniques can be used to synthesize PPy. Many parameters can influence PPy characteristics, including synthesis technique, polymerization rate, solvent nature, and reaction medium pH [14]. The chemical polymerization of pyrrole is particularly essential, since it allows for the manufacture of PPy on a larger scale [15]. The aim of the study is to synthesize novel nanocomposites to improve the physical features of lead oxide, as well as to investigate the structures of nanocomposites created using a new microemulsion process.

Experimental

First step: synthesis of lead oxide (PbO)

10 molars of sodium hydroxide were prepared by dissolving 40 gm of it in 100 mL of deionized water. Then, lead nitrate [Pb (NO₃)₂] solution was prepared by dissolving 11.871 g of lead nitrate in 100 mL of deionized water through 30 minutes. The above solution of sodium hydroxide was added from the burette dropwise to the nitrate solution at a pH = 8 and a temperature of 60 °C. The appearance of a white foggy solution indicates the formation of lead hydroxide and the stirring was continued for 4 hours. The precipitate was dried for 12 hours at a temperature of 110 °C, and then was burned at a temperature of 600 °C and ground in a ceramic mortar to obtain a very fine powder.

Second step: synthesis of lead iron oxide (PbFe₈O₁₈)

By dissolving 40 gm of sodium hydroxide in 100 mL of deionized water 10 molars of sodium hydroxide were yielded. Then, 5.9355 gm of lead nitrate [Pb (NO₃)₂] and 10.1197 gm of iron nitrate [Fe (NO₃)₃.9H₂O] were dissolved in 100 mL of deionized water to prepare a lead iron nitrate solution. At pH=8and 60 °C, the sodium hydroxide solution was dropped into the nitrate solution from the burette. The formation of a dark brown solution indicated the production of lead iron hydroxide and stirring was continued for another four hours. The precipitate was dried for 12 hours at 110 °C, then calcined at 600 °C and was grounded into a fine powder in a ceramic mortar.

Third step: synthesis of lead iron oxide polypyrrole (PbFe₂O₇:PYY)

0.2884 gm of Sodium dodecyl sulfate (SDS) was dissolved in 100 mL of deionized water at 60 °C until a clear and homogeneous solution was reached. 0.81102 gm of ferric chloride (FeCl₃) was dissolved in the above solution and the mixture was placed at a temperature of (0-4) °C. Newly distilled pyrrole was added to the mixture drop by drop and at the same time, 3 gm of lead iron oxide was added and stirring was continued for 4 hours. Then, the precipitate was washed with ethanol and with deionized water many times.

Results and discussion

FESEM analysis

Field-emission scanning electron microscopy was utilized to investigate the surface morphology of the produced nanomaterials as in Figure 1. The shape of PbOmassicot with the stacked folded sheet’s structure created by the co-precipitation approach and PbFe₈O₁₈ take the large lumps of small granules. The scanning pictures designate a relative uniformity distribution of particle size and the particles seem to be sphere-shaped and agglomerative due to a variety of attractive interactions such as coulomb and Vander Waal attractions, hydrogen bonding as well as physical contact between the nanoparticles. Pb₃Fe₂O₇: PYY is a folded paper-like material with very minute grains.

XRD analysis

Figure 2 shows the XRD patterns of the synthesized lead oxide and its nanocomposites. PbO has thirty diffractions at maxima of 2θ (28.5592) and d-spacing 3.12558, PbFe₈O₁₈ has twenty diffractions at maxima 2θ (29.0561), and d-spacing 3.07326, whereas Pb₃Fe₂O₇: PYY has twenty-three diffractions at maxima of 2θ (29.8132) and d-spacing 2.99691.

To identify the lead oxide XRD peaks, (Crystallographic Database Code Amcsd 0010011) was employed [16-21]. Peaks at 2θ (29.1, 30.38, and 53.14) had been discovered to be appropriately cataloged to β-PbO (massicot kind) which had a crystal form of orthorhombic system. Miller indices were estimated via utilizing phase identification programs of XRD and specified at the XRD peaks. In XRD diffractograms of PbFe₈O₁₈ nanoparticles, 2θ at (29.1, 30.3, and 38) refers to lead oxide (PbO) of massicot type and peaks at (2θ 27.5, 32.01, and 49.11) belonged to iron oxide (Fe₈O₁₇) of schwertmannite type according to Database numbered 0017807 of acta crystallographic.

From the XRD phase identification for the Pb₃Fe₂O₇:PYY nanocomposite at 2θ (26.85, 30.85, and 33.6), lead oxide possessed minium kind (Pb₃O₄)whereas iron oxide was hematite type (Fe₂O₃) by indexing at 2θ (26.85, 28.4, and 29.9). It has already been noted that a broader peak at 2θ between 20–28° corresponds to the distinctive peak of PYY [22].

Table 1 indicates the decrease in the density of unit cell due to the increase in the number and size of unit cells. The contact between the segments was discovered to be the cause of the association between crystal deformations and dislocation density [23]. PbO possessed greater crystallinity, while Pb₃Fe₂O₇:PYY had lower crystallinity, due to the increased amorphousness for amorphous Fe₂O₃ and amorphous polypyrrole [24-26].

Raman identification

Raman spectra collected over a wide spectral range (60 to 3500) cm^-1 indicated distinct massicot peaks at (87.1764, 142.4454, 290.0771, and 383.8443) cm^-1, as displayed in Figure 3. The Raman bands are consistent with previous references [27]. Changes in the methodology and the location of holes in the unit cell might cause the relative positions of the peaks to shift [28]. Figure 4 depicts the loss of massicot peaks (87.1764, 142.4454, and 290.0771) cm^-1 and the creation of additional peak at 131.0657 cm^-1, as well as weak schwertmannite peaks at (219.9227, 319.3932, and 545.9959) cm^-1, demonstrating the formation of the PbFe₈O₁₈.

According to the IRUG Filename: RMP00042 database, the peak at 89.7375, 138.424, and 262.6492 cm^-1 belongs to lead oxide of the minium kind. The peak at 407.9952 and 498.9260 cm^-1 represents hematite, whereas the peaks at 1060 and 1368cm^-1 indicate polypyrrole [29]. Findings which were acquired by using the Raman analysis are comparable to those obtained using the XRD technique.

Conductivity tests 

The dielectric and electrical conductivity behavior of the prepared nanomaterials were depicted in Figure 4. A frequency range of 50 Hz to 1 MHz was employed in the experiment. In the low-frequency domain, β- PbO nanoparticles exhibit minimal conductivity, which lasts up to 40 kHz, although PbFe₈O₁₈ and Pb₃Fe₂O₇:PYY nanoparticles have conductivity up to 3.5 kHz and 2.5 kHz, respectively. Pb₃Fe₂O₇:PYY exhibited a greater conductivity of 17.4564 x 10^-4 Sm^-1 than β-PbO, which was 18.281 x 10^-7 Sm^-1., as observed in Table 2.

Because enormous charge carriers of Fe₂O₃, Fe₈O₁₈, and polypyrrole are produced as a result of their own adequate energy, the conductivity of synthesized nanocomposites rises with frequency, especially at high frequencies. A non-continuous leap transition charge carrier or its reorientation between local levels of crystal boundaries increases the frequency of the electric field applied to the samples [30].

Thermogravimetric studies

With a temperature range of (30-800) °C and a flow rate of 40 mL/min, the thermodynamic features and thermal stability of produced nanocomposites were examined using thermogravimetric analysis. The TGA graph between temperature and weight loss, as displayed in Figure 5, demonstrated the thermal behavior of the nanocomposites. β-PbO and PbFe₈O₁₈ nanocomposites were demonstrated to be exceptionally stable and did not break down appreciably across a wide temperature range, whereas Pb₃Fe₂O₇:PYY showed only the moderate thermal stability.

The thermal behavior of nanocomposites includes two main stages: the initial stage is connected with a relatively tiny percentage of humidity loss, with PbFe₈O₁₈ losing more than others due to its wide pore diameter, whereas β-PbO had tiny porosity because of its small diameter. The adsorbed oxygen molecules are released in the second stage, and PbFe₈O₁₈ frees much more humidity in both temperature series than other nanoparticles. The beginning, final temperature, weight loss, and onset temperature were illustrated in Table 3. Tables 4, 5, and 6 provide the thermogravimetric functions of β-PbO, PbFe₈O₁₈, and Pb₃Fe₂O₇:PYY for the various temperature ranges. Pb₃Fe₂O₇:PYY had the lowest activation energy (Ea), whereas β-PbO had the highest. The change in entropy (S) was increased by adding other components to β-PbO as composites due to the rise in amorphous nature and porosity (polypyrrole and iron oxide). Likewise, the thermal processes occurred spontaneously due to the minus sign of the Gibbs free energy.

VSM measurements

The VSM approach was used to test the magnetic performance of nanocomposites at moderate temperatures using hysteresis graphs of the samples at a set of fields from -10000 to 10000. It was found that massicot is paramagnetic and the magnetic material (schwertmannite) in PbFe₈O₁₈ produces more magnetism than massicot as noticed from the rising in the magnetization with the applied magnetic field, the data were illustrated in Figure 6.

Sublattices in magnetic materials contain two magnetic moments, one per each. Consequently, even if the moments have a similar sign, they do not eliminate completely, leading to a nonzero net moment. Between the ferro and antiferromagnetic states, the ferrimagnetic state occurs. As a result, a ferrimagnet’s magnetic properties are identical to those of a ferromagnet at any temperature. The magnetic characteristics of Pb₃Fe₂O₇: PYY core shells are due to the Fe₂O₃ core. A little amount in the Ms value for Pb₃Fe₂O₇:PYY core shells further indicates the existence of the polypyrrole shell on the Fe₂O₃ core surface [31,32]. Table 7 illustrates that the saturation magnetization (Ms) of β-PbO is 0.01277 emu/g, whereas the Ms of PbFe₈O₁₈ core-shell is 1.42604 emu/g.

Conclusion

A co-precipitation approach was used to synthesize lead oxide and its new nanocomposites. According to the XRD analysis, the lead oxide was massicot type in PbO and in PbFe₈O₁₈, whereas the iron oxide was schwertmannite type. In Pb₃Fe₂O₇:PYY, lead oxide had minium type phase, while iron oxide had a hematite type.It is worth to note that nanocomposites’ surface shape altered considerably which revealed that synthesis was successful. According to Raman spectra, nanocomposites display a wavelength shift, and the results were comparable to XRD investigations. As frequency increased, conductivity increased, and the Pb₃Fe₂O₇:PYY had a higher conductivity. Due to the presence of more magnetic hematite, VSM analysis revealed that PbFe₈O₁₈ has a strong magnetism, and TGA study revealed that nanocomposites are stable.

Acknowledgments

The authors are grateful to Al-Qadisiyah University’s Chemistry Department for finishing the laboratory synthesis of nanomaterials, Baghdad University’s Chemistry Department, and Tehran University for different characterizations.

Orcid:

Ahmed K. Abass: https://orcid.org/0000-0002-4243-4793

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How to cite this article: Ahmed K. Abass*‎, Wadhah Naji Jassim Al Sieadi, Abdul Karim M.A. Al-Sammarraie. ‎Investigation of the electrical, compositional, and ‎magnetic features of hybrid lead oxide ‎nanocomposites. Eurasian Chemical Communications, 2022, 4(11), 1044-1053. Link: http://www.echemcom.com/article_151319.html

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Copyright © 2022 by SPC (Sami Publishing Company) + is an open access article distributed under the Creative Commons Attribution License(CC BY)  license  (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.