In this study, pure and 1%, 3% and 5% doped graphene oxide (GO) reinforced zinc oxide (ZnO) nanoparticles were synthesized by sol-gel method. The aim was to improve the electrical and dielectric properties of ZnO semiconductor metal oxide used in many electronic, optoelectronic and electrochemical technologies. FE-SEM, X-ray diffraction (XRD), Raman spectroscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy (FT-IR), were used to show the structural and morphological properties of the synthesized ZnO and GO doped ZnO nanoparticles. Impedance analysis was used to study the dielectric properties of the produced nanoparticles. XRD analysis revealed typical peaks of nGO and ZnO nanoparticles. Through the FE-SEM and XRD analysis, it was shown that the ZnO and GO nanopowders were successfully synthesized. The results revealed that ZnO-GO nanoparticles, having good dielectric constant with loss and AC conductivity values, such materials can be a good candidate for solar cells and photovoltaic devices.
Graphical Abstract
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Hinweise
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1 Introduction
With the recent developments in nanotechnology and nanoscience, it is evident that the utilization areas of diverse nanostructured materials with applications in electronics, energy storage, pharmacy, and medical sciences are rising and the research continue to grow day by day [1]. Transition metals, silicon, carbon, and metal oxides are the most commonly employed nanoparticles (NPs) in application sectors. Metal oxide NPs are of particular interest among NPs due to their distinct physical and chemical characteristics [2‐4]. Metal oxide nanoparticles (NPs) are currently generating a lot of scientific buzz due to their many prospective uses in biological, optical, and electronic sectors. Zinc oxide (ZnO), titanium dioxide (TiO2), copper oxide (CuO), zirconium dioxide (ZrO2), aluminum oxide (Al2O)3, silicon dioxide (SiO2), iron oxide (Fe3O4), magnesium oxide (MgO), nickel oxide (NiO), manganese dioxide (MnO2), and other materials can be used to develop metal oxide nanoparticles [4, 5].
Semiconductor metal oxides, which are widely used in new electronic, magnetic, dielectric, and optical applications in metal oxide structures, are of great research interest [6]. Bonding multiple metal oxides has a profound effect on the electrical structure at the combined metal-oxide interfaces and is expected to improve other physical properties. Semiconductor metal oxides with low dielectric loss and high dielectric constants are useful in microelectronics, semiconductor devices, sensors, electrochemical devices, optoelectronic devices, nonvolatile memory storage devices, and fuel cells, among other applications [7‐11]. Dielectric and alternating current (AC) conductivity tests analyze the uniqueness of producing a semiconductor metal oxide device, and these measurements are required to identify the presence of structural-related flaws in the material and to analyze the conduction process [12].
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The n-type semiconductor used as the study’s matrix material, ZnO nanoparticles, is widely researched and manufactured for use in solar cells, gas sensors, transistors, chemical absorbers, electrical and optical devices, liquid phase hydrogenation catalysts, and photocatalytic degradation catalysts [13]. As a result, having many advantages, there exist a lot of interest in studying the fabrication and manipulation of nanoscale ZnO structures. It is a substantial semiconductor first and foremost, with a big band gap of 3.37 eV and a high binding energy of 60 meV. Second, it plays a significant role in the creation of piezoelectric sensors and transducers that are coupled with electromechanical systems. ZnO can be applied directly in biological applications and due to its distinctive features, ZnO structures have emerged as one of the most significant nanomaterials in research and application studies [14]. For foundational studies, many techniques have been employed to generate nanostructured ZnO powders with varied morphologies and ionic dopants [15‐23]. Graphene has been one of the most investigated materials over the last 30 years due to its remarkable properties, such as its high specific surface area, mechanical flexibility, thermal conductivity, distinctive optical features, strong electrical conductivity, and rapid charge carrier mobility [24‐27].
Because of their numerous promising performances in device applications, graphene, and graphene-based materials have attracted the scientific community’s curiosity, and this enthusiasm appears to be growing [28, 29]. Graphene oxide (GO), a form of graphene, is a highly specialized material primarily due to its distinctive structure and remarkable properties [28, 29]. The oxygen-containing group in GO gives it an important interaction with other materials. Hybridization structures of localized sp2 GO support carrier migration to some extent. GO exhibits excellent application areas for dielectric composites in areas in the insulated state. Due to dielectric composites’ polarization and loss mechanisms, GO has a wide range of applications in this context [30]. Nanoparticles of graphene-metal oxide nanocomposites have been studied to improve dielectric, optical, and electrical properties. Graphene oxide (GO), reduced graphene oxide (RGO), and functionalized graphene oxide (FGO) have been demonstrated to increase their electrical, optical, and electrical properties when mixed with other materials such as ceramics, metal oxide, and polymers [5, 6, 30]. Due to these properties, it has many potential applications as a material in multifunctional electronic and optoelectronic devices [3, 4, 24‐29].
A review of the literature on the fabrication of GO-doped ZnO nanoparticles shows that GO addition effectively prevents the aggregation of ZnO particles and provides strong stability in the medium. The large surface area of GO and the wide bandgap of ZnO particles significantly enhance the electrochemical properties of ZnO/GO composites compared to pure ZnO particles and graphene oxide alone, and may increase the application area of ZnO nanoparticles [31‐35].
It is commonly acknowledged that nanoparticles can be produced chemically or physically. Sol-gel processing, electrochemical procedures, hydrothermal techniques, and chemical vapor deposition are examples of these processes. Larger specific surface area, superior homogeneity and purity, better microstructure control for metallic particles, smaller pores and uniform particle distribution, ease of manufacture, low cost, reproducibility, and homogeneous nanoparticle production are the main benefits of sol-gel processing over conventional methods [36, 37].
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In this study, ZnO nanoparticles, whose dielectric properties have not been investigated, were produced using sol-gel method by reinforcing GO nanoparticles at 1 wt.%, 3 wt.% and 5 wt.%. The main objective of this study is to improve the electrical and dielectric properties of ZnO semiconductor metal oxide, which can effectively be used in many electronic, optoelectronic and electrochemical technologies. XRD, FT-IR, Raman, FE-SEM, and EDX analyses were used to describe the structural and morphological properties of the synthesized nanoparticles. The structural and morphological properties of newly fabricated nanoparticles, as well as their interaction with dielectric properties, were comprehensively examined and analyzed.
2 Materials and method
2.1 Nanoparticle synthesis
The production of pure ZnO and GO-doped ZnO nanoparticles used in the study by sol-gel synthesis method was started by adding 0.5 M (Zn(CH3COO)22H2O) into 25 ml methanol in a beaker and stirring. The mixture was stirred on a magnetic stirrer (Mix-1) until dissolved. In another beaker, 2.5 M NaOH was added to 25 ml of methanol and swirled until dissolved with a magnetic stirrer. (Mixture-2). These two solutions were mixed in a beaker and another 10 ml of methanol was added to the mixture (Mixture-3). The completed solution was agitated in a magnetic stirrer at 90 °C for four hours. After stirring, the solution was allowed to reach room temperature. The nanoparticles were then filtered with filter paper and washed with alcohol. After cleansing with alcohol, the solution was rinsed several times with distilled water before being annealed in an oven at 450 °C for an hour and crushed with a crusher and pestle. Thus, pure ZnO nanoparticles were produced as sample 1, and the same process steps were repeated to produce ZnO nanoparticles with GO addition. The only modification made was that the nano-GO particles were added to 20 ml of methanol in weight percentages (10, 20, 30%) and then blended in another beaker using an ultrasonic homogenizer (Mix-4) for 30 min. Mix-4 was then added to Mix-3 and all the procedures to obtain pure ZnO were repeated. The nanoparticle synthesis flow chart and sol-gel production scheme are shown in Fig. 1 and the nomenclature with additive amounts of the nanoparticles produced are given in Table 1.
Fig. 1
a Preparation of mixtures. b Preparation of nanoparticles
Table 1
Nomenclature and additive amounts of synthesized nanoparticles
The functional groups of pure and GO-doped ZnO nanoparticles synthesized by the sol-gel method were characterized using FT-IR measurements (Thermo Scientific Nicolet IS5). The analysis was performed using a FT-IR spectrometer with a scanning range of 4000–500 cm−1, and XRD (PANalytical Empyrean) of fabricated nanoparticles were obtained at CuKa (=1.5406 A) radiation at 40 kV/40 mA in the scanning range 2 = 10 to 80°. A Raman spectrometer system (WITech alpha 300 R) with excitation wavelengths of 532 and 325 nm, respectively, was used to produce nonresonant and RRS results. FE-SEM (Zeiss Sigma 300) and EDX analyses were used to analyze the form and chemical content of the nanoparticles, as well as particle sizes and degree of doping.
2.3 ZnO-GO nanoparticle dielectric measurements
Using an impedance analyzer (HIOKI, Japan) with a frequency range of 1000 Hz to 2000000 Hz, the dielectric properties of the produced ZnO-GO nanoparticles were examined. The disc thicknesses were precisely measured with a digital caliper after the powder samples were initially pelletized under a 10-ton pressure. At room temperature, measurements of conductivity (Gp), loss factor (DF), and capacitance (Cp) were made on discs of a 13 mm diameter. Between the two capacitors, samples were consecutively collected, and in the impedance analyzer’s electric field region, dielectric parameters were calculated.
3 Results and discussion
3.1 XRD of ZnO-GO nanoparticles
Figure 2 shows XRD diffraction patterns of pure and GO-doped ZnO nanoparticles manufactured in various ratios. Tables 2 and 3 provide the two values and estimated values of diffraction planes, respectively, providing the lattice sizes, unit cell volumes, crystal and average crystal sizes. The crystal sizes of the samples were determined using the high-density (101) peak, and the structural parameters were determined using Bragg’s formulae. The Debye-Scherrer equation is employed in Eq. (1) to calculate the average crystal size of the nanoparticles [38‐40].
$$D=\frac{0.9\lambda }{B\cos {\theta }_{B}}$$
(1)
where the full width at half maximum is measured in radians, the diffraction angle is measured in degrees, and the X-ray wavelength is computed in nanometers. The distance (d) between two adjacent planes can be determined using Eq. (2) [34].
where the Miller indices are h, k, and l and d stands for the distance between two nearby planes. Using Eq. (3), the volumes of the unit cells (V) were computed [37‐39].
$$V=\frac{\sqrt{3}}{2}{a}^{2}c=0.866\,{a}^{2}c$$
(3)
Fig. 2
XRD diffraction patterns of the synthesized nanoparticles
Table 2
Two diffraction plane values of the synthesized nanoparticles
Sample/Diffraction plane
GO
ZnO
ZnO-1GO
ZnO-3GO
ZnO-5GO
(002) GO
26.514
–
26.659
26.673
26.687
(100)
–
31.913
31.928
31.942
31.957
(002)
–
34.541
34.570
34.598
34.613
(101)
–
36.345
36.360
36.388
36.403
(102)
–
47.605
47.620
47.648
47.663
(110)
–
56.642
56.685
56.714
56.743
(103)
–
62.893
62.936
62.965
62.979
(200)
–
66.430
66.444
66.487
66.502
(112)
–
68.003
68.047
68.061
68.090
(201)
–
69.115
69.187
69.216
69.245
(004)
–
72.536
72.579
72.652
72.666
(202)
–
77.055
77.069
77.112
77.127
Table 3
The calculated a = b, c, V and crystalline size values of synthesized nanoparticles [71]
Sample
2 theta (101)
a (Å)
c (Å)
V (Å3)
Crystallite size (nm)
ZnO
36.345
3,228
5.271
47.575
18.953
ZnO-1GO
36.360
3.226
5.269
47.518
16.512
ZnO-3GO
36.388
3.224
5.265
47.412
16.477
ZnO-5GO
36.403
3.223
5.263
47.356
16.467
×
The intense peaks corresponding to 31.913°, 34.541°, 36.345°, 47.605°, 56.642°, 62.893°, 66.430°, 68.003°, 69.115°, 72.536°, 77.055° 2θ degrees in pure ZnO sample are consistent with JCPDS card 36-1451 and these peaks are characteristic peaks of ZnO [41, 42]. Planes (100), (002), (101), (102), (110), (103), (200), (112), (201), (004), and (202) correspond to these peaks [42, 43]. These characteristic peaks of ZnO are indexed to the hexagonal Wurtzite structure. In addition to the characteristic peaks of pure ZnO in the nanoparticles, the characteristic carbon peak of GO is observed at 26.514° 2θ and this peak corresponds to the (002) plane [44‐46]. It is observed that the peak intensities in the (002) plane increase as the GO doping ratio increases and the shifts occur when combined with ZnO.
The lattice dimensions with corresponding lattice parameters calculated using Eqs. (1)–(3) were found to be very close to the lattice dimensions of the pure ZnO given in Table 3). The size of the crystallites was observed that the lattice parameters and unit cell volume decreased when ZnO was combined with GO, and XRD peaks shifted to higher angles [47]. With the addition of graphene oxide nanosheets, this decreasing behavior in lattice constants is thought to have occurred due to local lattice disorder or strain generation, evidencing the presence of empty lattice sites and the decreasing nature of the average crystallite size. The decrease in lattice parameters of GO-doped ZnO nanoparticles indicates the further reduction that may result from the aggregation of GO nanorods by the ZnO matrix. Moreover, this decreasing behavior in the lattice constants may have occurred due to local lattice disorder or strain formation, which evidences the presence of empty lattice sites and the decreasing nature of the average crystallite size [43]. Compared to pure ZnO, GO/ZnO nanoparticles showed a decrease in crystallite size with increasing GO concentration, which is related to the inhibition of the growth of ZnO nanoparticles by the presence of GO. The average crystallite size of the GO reinforced ZnO nanocomposites is found to be larger than that of pure ZnO [32, 48].
From the literature studies, the lattice parameters were found to be decreased as a result of different doping of ZnO nanoparticles [49]. It has been found that as the amount of GO reinforcement in ZnO nanoparticles increases, the crystallite size decreases. In the syntheses made by adding different reinforcement amounts to ZnO nanoparticles, it was observed that decreases in the lattice parameters of ZnO occurred. The changes and the reinforcements used are shown in Table 4.
Table 4
Effect of doping different nanoparticles in ZnO nanoparticles
Content
Synthesizing Method
Conclusion
Reference
Ag-ZnO
Green combustion with natural fuels
The lattice parameters of ZnO nanoparticles increased with Ag doping.
The FT-IR spectra of ZnO particles with GO added are shown in Fig. 3. Peaks at 383 cm−1, 407 cm−1, 480 cm−1, 512 cm−1, and 582 cm−1 in the FT-IR study correlate to Zn-O bonding [50, 51]. The 886 cm−1 vibrational mode is associated to substituted hydrogen in the oxygen region (HO) bound to the lattice Zn region (i.e., Zn-HO). These peaks correspond to the polar stretch vibration modes A1 (TO), E1 (TO), A1 (LO), and E1 (LO), respectively, for ZnO nanoparticles [50, 51].
Fig. 3
FT-IR spectra of the nanoparticles
×
The peak at 1066 cm−1 in the GO spectra displayed in Fig. 4 is attributable to C-O stretching. C-O-C bending is confirmed at 1288 cm−1, while C-OH bending is seen at 1587 cm−1. Carbonyl groups are also shown at 1724 cm−1 as C=O stretching, and a large peak at 3448 cm−1 is attributable to the C-OH groups’ O-H stretching vibration and the material’s water content [52‐54]. In the FT-IR spectra, the O-H, C=O and C-O vibrational bands were found to be severely reduced, weakened and slightly shifted to a lower wave number due to deoxygenation in GO. The difference in morphology provides a chemical shift due to the arrangement of atoms in the structure, which produces a different response in the change of the dipole moment when the material interacts with infrared radiation [31‐35].
Fig. 4
Raman spectroscopy of the synthesized nanoparticles
×
3.3 Raman spectroscopy of ZnO-GO nanoparticles
Raman scattering is a sensitive and non-destructive characterization technique used to investigate the vibrational characteristics of materials with nanostructures, as well as to define the nature and structure of ZnO nanoparticles. Wurtzite-type ZnO is a member of the C46v (P63mc) space group and has two formula units in the primitive cell. At the Brillouin zone point, the zone-center optical phonons exhibit irreducible representation: Γ opt = 1A1 + 2B1 + 2E1 + 2E2 [55, 56]. A1 and E1 are long-range electrostatic force polar modes, while B1 modes are Raman quiet modes. A1 and E1 are long-range electrostatic force polar modes, while B1 modes are Raman quiet modes [57, 58]. They are categorized as either longitudinal optical (LO) or transverse optical (TO) phonons. There are two frequencies in a nonpolar phonon mode with symmetry E2. The values of E2H and E2L, which correspond to oxygen atoms and the Zn sublattice, and A1, E1, and E2 are the active Raman modes [59, 60]. The weak peaks observed at about 307 and 603 cm−1 are driven by the transverse optical (TO) phonon mode emerging from the silicon substrate [61]. The second-order Raman (E2H) mode, which is characteristic of hexagonal wurtzite ZnO, is attributed to the peak at 432 cm−1. Two novel modes at 494 and 707 cm−1 in the ZnO Raman spectra were found, and they were attributed to surface optical (SO) phonon modes [62].
Figure 4 shows the GO nanoparticles’ Raman spectrum. The D and G bands are represented by two separate peaks in the 1000–2000 cm−1 area in the Raman spectra of GO. Graphene oxide shows two strong syndromic peak-to-peak modes, the G band at 1800–1900 cm−1 and the D band at 1250–1300 cm−1. The G band indicates that there are all sp2 hybrids in a two-dimensional hexagonal junction. As a result, a flawless crystal should not exhibit the D band, and Bahrami et al. saw a similar reflection in their research [62].
3.4 FE-SEM and EDX analyses of ZnO-GO nanoparticles
SEM pictures of synthesized GO-doped ZnO nanoparticles in various sizes are shown in Fig. 5, Fig. 6 shows EDX analysis results, and Table 5 shows the weight contribution amounts of the elements in the EDX analysis results. According to SEM views, the particles are observed to be in nano-sized, and the GO nanoparticles are equally distributed on ZnO nanorods and plates. SEM images revealed that ZnO-GO particles were produced in nano size. Zn, O, and C elements were detected in the EDX spectra. Because GO has a higher molecular weight than the other materials used, an excess amount was formed in the EDX results, and an increase in the amount of C occurred as the amount of GO rose (Table 6).
Fig. 5
FE-SEM images of nanoparticles a GO, b ZnO, c ZnO-1GO, d ZnO-3GO, e ZnO-5GO
Fig. 6
EDX spectra of nano ZnO
Table 5
EDX analysis results of different sample groups
Sample
Content (Wt.%)
Zn
O
C
GO
–
2.90
97.10
ZnO
88.07
11.93
–
ZnO-1GO
79.26
11.46
9.28
ZnO -3GO
71.13
12.99
15.87
ZnO-5GO
64.70
14.89
20.41
Table 6
Dielectric parameters of ZnO-GO composites at 10 kHz at room temperature
Sample
Dielectric constant (ɛ‘)
Dielectric Loss (ɛ‘)
AC Conductivity
Log σac (S/cm)
GO
172.78
110340.023
9.81 × 10−4
−3.038
ZnO-5 GO
117.55
75727.291
1.12 × 10−4
−3.948
ZnO-3 GO
104.98
75443.791
6.75 × 10−5
−4.170
ZnO-1 GO
27.75
17.322
1.27 × 10−8
−7.895
ZnO
12.07
0.844
3.43 × 10−8
−7.464
×
×
The FE-SEM images show that the thickness of the hexagonal plates decreases, while the average thickness of the ZnO nanoparticles is slightly higher than that of the GO reinforced nanoparticles due to the strong agglomeration and clustering of pure ZnO nanoparticles. The nanoparticles were found to be in an agglomerated form, which could depend on the calcination temperature. There is less particle aggregation and agglomeration in the nanocomposite as the ZnO nanoparticles bind to GO by interacting with residual functional groups of GO basal planes. Increasing the amount of GO does not affect the morphology of pure ZnO but slightly reduces the average thickness of ZnO nanoparticles in GO/ZnO nanocomposites. From the micrograph of GO/ZnO nanocomposites, it is observed that ZnO nanoparticles are continuously dispersed on the GO sheets and accordingly the clarity of GO sheets in the nanoparticle decreases [63‐68].
GO nanoparticles retain the original graphite’s layered structure; however, they have a very heterogeneous size and shape distribution, with some particles much larger than others, as well as lamellae with defects caused by the oxidation process, as evidenced by the irregular ends of the sheets and lumps. GO exhibits greater delamination, as seen with thinner stacking of nanosheets. The ultrasonication technique at the margins has made the structures almost transparent to electron beams. FE-SEM pictures reveal that the nanoparticles transition from a regular, layered arrangement to an asymmetric structure of varying sizes with a rough and discontinuous morphology of the layers. This morphology is associated with the application of ultrasound. The migration of ultrasound waves through the dispersed material in liquid media is thought to lead to the formation of bubbles, which collapse when their volume increases, releasing a large amount of energy that can break down the material structure [31, 32].
3.5 Investigation of dielectric properties of ZnO-GO nanoparticles
To determine the dielectric properties of the ZnO-GO nanoparticles, the samples were first formed into discs with a diameter of 13 mm under 10 tons of pressure.. By using a digital caliper with an accuracy of 0.001 mm to measure the thickness of the pellets, the surface area was determined. Using a computer-controlled HIOKI brand IM3536 impedance analyzer, measurements for capacitance (Cp), loss factor (DF), and conductivity (Gp) were measured from 1 kHz to 200 kHz. The following equations were used to compute the conductivity (log ac), dielectric constant (ε‘), and dielectric loss (ε“) values based on the data attained. Figures 7–9 displays the nanoparticles’ dielectric characteristics.
Dependence of dielectric constant of ZnO/GO composites as a function of frequency
Fig. 8
Dependence of dielectric loss of ZnO/GO composites as a function of frequency
Fig. 9
Dependence of ac conductivity of ZnO/GO composites as a function of frequency
×
×
×
Three essential factors—ionic, electronic, and orientation—contribute to a given material’s dielectric constant. One of the aspects of contribution, the orientations, result from the orientation of the molecules under the applied field and are connected to the material’s structure [63].
Figures 7–9 show the frequency dependent variation curves of dielectric constant (ε‘), dielectric loss (ε“) and (c) ac conductivity of ZnO-GO composites. As seen in Figs. 8 and 9, the values of ɛ‘ and ɛ“‘ decrease with increasing frequency. This decrease in the dielectric constant with increasing frequency is a result of the decrease in polarization with increasing frequency. Because of the interfacial polarization, dielectric loss exhibits a tendency to vary at different frequencies [64, 65]. Due to the oxygen functional group present in the GO structure, the addition of different ratios of GO to pure ZnO increased the concentration of oxygen vacancies and charge carriers. This leads to an increase in the interactions between the effects producing dipole moments [66]. The electrical conductivity distribution (σac) is an important parameter that gives information about the material. As shown in Fig. 10, σac values increase with increasing frequency. The decrease in polarization with increasing frequency leads to an increase in conductivity with increasing frequency as seen in this graph. Since the number of carriers may increase as a result of the decrease in polarization, there may be an increase in ac conductivity.
Fig. 10
Temperature dependence of dc conductivity for the ZnO/3GO composite
×
Polarization occurs in low-frequency electric fields, with negligible losses. As the frequency rises, it becomes more difficult to match the electric field, and losses cannot be ignored. As the frequency increases, there is no more polarization, and so the dielectric constant rapidly drops [67]. As the frequency rises, the influence of the dipoles grows, polarization occurs, and the dielectric constant falls. This reduction in the dielectric constant suggests that there is surface polarization at that site. When an electric field is applied to a dielectric substance, charges move over its surface [68].
The concentration of filler graphene oxide affected the AC conductivity of ZnO-GO nanocomposites. The ac values of ZnO-GO nanocomposites with 1 wt.%, 3 wt.%, and 5 wt.% graphene oxide were1.27 × 10−8, 6.75 × 10−5, and 1.12 × 10−4, respectively,
As a result, at 3 wt.% graphene oxide, the ZnO-GO nanocomposites’ behavior changed from insulating to partly conducting due to the percolation-induced creation of a conductivity network.
The loose clustering of ZnO particles led to a decrease in conductivity. While pure ZnO has a conductivity comparable to or greater than that of a pure composite containing 5 wt. % GO. This may be because the ZnO and GO have a strong interfacial contact, which boosts electronic and dipole polarizations [69].
From ambient temperature to 365 K, the DC conductivities of composites were examined. ZnO-3GO and ZnO-5GO composites dc conductivities varied between 10−4 and 10−2 S/m, and it can be shown that adding 5 wt.% graphene oxide caused σdc to rise reasonably. The DC conductivity of composites consisting of ZnO-3GO and ZnO-5GO is shown in Figs. 10 and 11 as a function of temperature. The behavior of the lnσdc was illustrated in the figure as a function of temperature (1/T). There was a linear association between lns 1000/T and the composites. The Arrhenius formula shown below may be used to express this connection as [70]:
where T is the temperature, Ea is the activation energy, kB is the Boltzmann constant, and so is the preexponential factor.
Fig. 11
Temperature dependence of dc conductivity for the ZnO/5GO composites
×
The DC electrical conductivity values of ZnO-3GO and ZnO-5GO composites at room temperature were calculated as 5.27 × 10−04 S/cm and 3.65 × 10−02 S/cm, respectively. According to these values, ZnO-3GO and ZnO-5GO composites showed semiconductivity and ZnO/5GO composite has the highest DC electrical conductivity at room temperature. The activation energies of ZnO-3GO and ZnO-5GO were calculated as 0.078 and 0.205 eV, respectively.
4 Conclusions
In this study, the synthesis of 1 wt.%, 3 wt.%, and 5 wt.% GO doped ZnO and GO doped ZnO nanoparticles was studied. Sol-gel synthesis was used for successfully synthesizing GO in the nanoscale. The results obtained in the study are summarized below.
Nanoparticles with great purity and homogeneity were synthesized.
The XRD peak intensities and positions were found to preserve the distinctive peaks of ZnO and GO.
As the amount of GO doping in ZnO-GO nanoparticles increased, the diffraction plane shifts and peak intensities also increased.
According to FE-SEM images, ZnO nanoparticles and GO nanoparticles were homogeneously distributed on the surface of ZnO nanorods and plates. The crystal diameters, unit cell volume and lattice properties of the nanoparticles increased with increasing GO addition.
The shift in charge centers in nanoparticles is assumed to be the cause of the dielectric constant rising with the amount of GO reinforcement.
The addition of GO to ZnO nanoparticles improved their dielectric response, and the addition of GO to electrical conductivity had a favorable impact on the ZnO nanoparticles.
When literature studies were examined, superior findings were obtained based on the dielectric and electrical conductivity values of pure ZnO nanoparticles.
These findings suggest that the study might be broadened and applied to a number of scenarios. According to data analysis of dielectric constant, loss, and AC conductivity, ZnO-GO nanoparticles could be an important component in the development of solar cells, photovoltaic devices, and semiconductor electronic devices.
Author contributions
The study’s design was contributed to by all of the writers. CKM and MH were in charge of nanoparticle preparation and characterization. CKM, BT, BA and MH wrote the first draft and general comments on the document. FB contributed to the understanding and interpretation of nanoparticle dielectric characteristics. The submitted version of the article has been read and approved by all authors.
Compliance with ethical standards
Conflict of interest
The authors declare no competing interests.
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