Study of Graphene Oxide and Silver Nanowires Interactions and Its Association with Electromagnetic Shielding Effectiveness

9.04.9 Study of Graphene Oxide and Silver Nanowires Interactions and Its Association with Electromagnetic Shielding Effectiveness Mila Milenković, Warda Saeed, Muhammad Yasir, Dusan Sredojević, Milica Budimir, Andjela Stefanović, Danica Bajuk-Bogdanović and Svetlana Jovanović Article https://doi.org/10.3390/ijms252413401 Citation: Milenkovi´c, M.; Saeed, W.; Yasir, M.; Sredojevi´c, D.; Budimir, M.; Stefanovi´c, A.; Bajuk-Bogdanovi´c, D.; Jovanovi´c, S. Study of Graphene Oxide and Silver Nanowires Interactions and Its Association with Electromagnetic Shielding Effectiveness. Int. J. Mol. Sci. 2024,25, 13401. https://doi.org/10.3390/ ijms252413401 Academic Editor: Christian Julien Received: 16 November 2024 Revised: 8 December 2024 Accepted: 9 December 2024 Published: 13 December 2024 Copyright: © 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Article Study of Graphene Oxide and Silver Nanowires Interactions and Its Association with Electromagnetic Shielding Effectiveness Mila Milenkovi´c 1, Warda Saeed 2, Muhammad Yasir 2,* , Dusan Sredojevi´c 1, Milica Budimir 1, Andjela Stefanovi´c 1, Danica Bajuk-Bogdanovi´c 3and Svetlana Jovanovi´c 1,* 1Vinˇca Institute of Nuclear Sciences-National Institute of the Republic of Serbia, University of Belgrade, Mike Petrovi´ca Alasa 12-14, Vinˇca, 11351 Belgrade, Serbia; [email protected] (M.M.); [email protected] (D.S.); [email protected] (M.B.) 2Division of Microrobotics and Control Engineering, Department of Computing Science, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany; [email protected] 3Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16, 11158 Belgrade, Serbia; [email protected] *Correspondence: [email protected] (M.Y.); [email protected] (S.J.) Abstract: Technological development has led to the need for materials able to block electromagnetic waves (EMWs) emitted from various devices. EMWs could negatively affect the working performance and lifetime of multiple instruments and measuring devices. New EMW shielding materials are being developed, while among nanomaterials, graphene-based composites have shown promising features. Herein, we have produced graphene oxide (GO), silver nanowires (AgNWs) composites, by varying the mass ratios of each component. UV-Vis, infrared, Raman spectroscopies, and thermogravimetric analysis proved the establishment of the interactions between them. For the first time, the strength and the nature of the interaction between GO sheets with various levels of oxidation and AgNWs were investigated using density function theory (DFT). The interaction energy between ideal graphene and AgNWs was calculated to be − 48.9 kcal/mol, while for AgNWs and GO, this energy is almost doubled at − 81.9 kcal/mol. The DFT results confirmed the interfacial polarization at the heterointerface via charge transfer and accumulation at the interface, improving the efficacy of EMW shielding. Our results indicated that AgNWs create a compact complex with GO due to charge transfer between them. Charge redistributions in GO-AgNWs composites resulted in an improved ability of the composite to block EMWs compared to GO alone. Keywords: graphene; silver nanowires; density functional theory; electromagnetic shielding 1. Introduction Electronic devices emit electromagnetic waves (EMWs), which interfere with electronics due to the interactions of electrons in metal conductors with the electric field of radiation. Electromagnetic interferences (EMIs) can cause electronic devices to malfunction and leak information [ 1 ]. Thus, shielding materials are required for both electronics and radiation sources. The shielding effectiveness (SE) of material is expressed as the loss of power due to the interaction of the incident wave with the material. Power loss is measured in decibels (dB) and is referred to as total shielding effectiveness. The loss can be due to the absorption and is referred to as a dissipation loss (SEA) or due to the reflection, known as a reflection loss (SE R ) [ 1 ]. A total shielding effectiveness of 20 dB is equivalent to blocking 99% of incident EMWs, and it is the minimum needed for commercial applications [2]. Nowadays, the most commonly used materials for EMI shielding can be divided into three groups: metals [ 3 ], polymers [ 4 ], and inorganic non-metallic materials [ 5 ]. Metals are conductive but have a heavy weight, low flexibility, high cost, and are corrosive. A possible solution is making metal in the form of films, or metallic wires [ 6 , 7 ], or applying them as a Int. J. Mol. Sci. 2024,25, 13401. https://doi.org/10.3390/ijms252413401 https://www.mdpi.com/journal/ijms Int. J. Mol. Sci. 2024,25, 13401 2 of 18 conductive filler in composites. The advantages of polymers are their non-corrosive nature and adjustable density. Both conductive polymers and non-conductive polymers with conductive fillers are being developed. As a filer, conductive polymers, metal nanoparticles, carbon nanostructures [ 5 , 8 , 9 ], carbon aerogel [ 10 , 11 ], and carbon fiber [ 12 ] are studied. However, polymers face several difficulties, including precise control over the shape and characteristics, good filler dispersion, and polymer–polymer interaction. Therefore, inorganic non-metallic materials with the aforementioned benefits and no clear drawbacks have been extensively researched. Carbon-based and ceramic materials make up the majority of it. Carbon-based materials include carbon fiber [ 13 ], carbon nanotubes [ 13 , 14 ], graphene [2,15,16], MXene [17], and others. Demand for thinner, lighter, and more flexible EMI shielding materials is increasing, favoring carbon nanomaterials [ 18 ]. Graphene possesses remarkable properties such as high electrical conductivity (10 4 –10 5 S m −1 ), good flexibility, chemical inertness, mechanical strength, excellent electron mobility (~15,000 cm 2 V −1 s −1 ), tunable electrical property [19–21] , and great heat conductivity (~5000 Wm −1 K −1 ) [ 22 – 24 ]. These extraordinary properties make graphene a good candidate for EMI shielding in various electronics [5,25–27]. Single-layer graphene produced using chemical vapor deposition showed an EMI SETof 2.27 dB, where the main shielding mechanism was absorption [4]. The preparation of graphene oxide (GO), using a modified Hummer’s method followed by the reduction (rGO), is one of the most common preparation methods of graphene. Wen et al. reported the shielding effectiveness of graphene/paraffin wax composites to be higher than 20 dB, with 20 wt.% of graphene [ 28 ]. In another study, Chen et al. prepared graphene/epoxy composites and obtained a shielding effectiveness of 21 dB for the 15 wt.% loading of graphene [ 29 ]. Combining graphene with metal nanostructures, such as silver nanowires (AgNWs), is one approach to increase electrical conductivity and EMI SE. AgNWs create highly conducting composites, such as thin films, sandwich structures, foams, and fibers [30–33]. However, with their high reactivity and surface area, they oxidize and react with atmospheric S oxides, making them unstable in the air. AgNWs must therefore be isolated from contact with air or water [34]. In this study, we prepared GO and AgNWs composites by changing the mass ratios between the two nanomaterials. We investigated the interaction between these nanomaterials using UV-Vis, Raman, and infrared spectroscopic techniques. The thermal stability of composites was studied as well. Considering that the GO and rGO are non-uniformly coated with hydroxyl and epoxy groups at the surface, including the regions with no basal groups (ideal-like graphene), we constructed several GO clusters to model the interactions with AgNWs. For the first time, theoretical modeling of interactions between the surfaces of AgNWs and GO at different levels of oxidation was employed and connected to the ability of composites to block the propagation of electromagnetic waves at frequencies in the range of 8–12 GHz. Namely, the effects of the content of GO and AgNWs in composite on the shielding effectiveness and mechanism were investigated using a vector network analyzer. We observed that the increased mass content of AgNWs improves EMI SE. Previous studies were focused on AgNW’s improvement of electrical conductivity of GO-AgNWs composites, which consequently amplifies the shielding efficiency of composites [ 35 – 37 ]. Therefore, we have examined and observed two different nanomaterials, their interactions, and the effects of these interactions on incident EMWs. Considering the results of experimental and theoretical studies, we observed the charge transfer from the graphene core to the AgNWs, leading to the enhancement of EMI SE at heterointerfaces. 2. Results and Discussion 2.1. Investigation of GO-AgNWs Interactions UV-Vis spectra of GO, AgNWs, and composites are shown in Figure 1a,b, and in Figure S1 (Supporting Information). The main absorption band in the GO spectrum (Figure 1a) is centered at 234 nm while the shoulder band with a lower intensity is around Int. J. Mol. Sci. 2024,25, 13401 3 of 18 310 nm. The first one is associated with the π→π * electronic transition of aromatic Csp 2 - Csp 2 while the shoulder band is a result of electronic transition n →π transitions of C=O bonds. In the UV-Vis spectrum of AgNWs (Figure 1a), bands at 355 nm and 420 nm are observed. The peak at 355 nm stems from longitudinal plasmon resonance absorption while the second one stems from transversal plasmon resonance absorption [ 38 , 39 ]. In the case of GO–AgNWs 5:5 (Figure 1b), bands at 213, 234, 355, and 410 nm are observed. While the main band assigned to sp 2 domains in the graphene structure is not shifted, the shoulder band is shifted to 300 nm. In the same spectrum, the band assigned to transversal plasmon resonance is also shifted to 430 nm. Furthermore, a new band at 213 nm is detected. The same band is even more pronounced in the UV-Vis spectrum of GO-AgNWs 4:6 composite (Figure S1, Supporting Information), while the largest changes in spectra of GO-AgNWs 3:7 (Figure 1b) and GO-AgNWs 2:8 (Figure S1, Supporting Information) composites showing shift to 415 and 420 nm, respectively, or 430 nm in the case of GOAgNWs 1:9 (Figure 1b). The appearance of a new band and the shifts in the existing ones indicate the establishment of interactions between the sp 2 region and functional groups of GO with the AgNW surfaces. π→π →π ffi tt Figure 1. UV-Vis spectra of GO and AgNWs (a), GO-AgNWs 5:5, GO-AgNWs 3:7, and GO-AgNWs 1:9 (b). Thermal stability and the efficiency of the reduction reaction are investigated using TGA. These results are presented in Figure 2for GO-AgNWs 5:5, GO-AgNWs 3:7, and GOAgNWs 1:9 composites, as well as for reduced forms. In Figure S2 (Supporting Information), thermograms for GO-AgNWs 4:6 and GO-AgNWs 2:8 are displayed. All oxidized forms of GO-AgNWs show similar trends, with two degradation steps, first in the range up to 130 ◦ C and second between 130 ◦ C and 250 ◦ C (black curves in Figures 2and S2, Supporting Information). At temperatures above 250 ◦ C, the weight loss is gradual. The first step is assigned to the evaporation of physically adsorbed water [ 40 ], while the second weight loss is attributed to the pyrolysis of oxygen-containing functional groups and the formation of CO2and H2O as main decomposition products [41]. Reduced composites (rGO-AgNWs) show improved thermal stability with the reduced total weight loss from 4.37 wt% as measured for GO-AgNWs 1:9 and rGO-AgNWs 1:9 up to 18.64 wt% which is calculated for GO-AgNWs 5:5 and rGO-AgNWs 5:5. Presented TGA results indicate that the selected reduction procedure removes partially oxygen-containing functional groups from GO in composites and improves the thermal stability of materials. Int. J. Mol. Sci. 2024,25, 13401 4 of 18 − − − tt − − − Figure 2. Thermograms of GO-AgNWs 5:5 and rGO-AgNWs 5:5 (a), GO-AgNWs 3:7 and rGOAgNWs 3:7 (b), and GO-AgNWs 1:9 and rGO-AgNWs 1:9 (c). FTIR spectroscopy was used to identify the functional groups of GO, rGO, and the GOAgNWs composites. The results are presented in Figures 3and S3, Supporting Information. − − − tt − − − Figure 3. FTIR spectra of GO, rGO, GO-AgNWs 5:5, rGO-AgNWs 5:5, GO-AgNWs 3:7, rGO-AgNWs 3:7, GO-AgNWs 1:9, and rGO-AgNWs 1:9. All non-reduced samples exhibit peaks around 3270 cm −1 and 3705 cm −1 , corresponding to the O-H stretching vibration [ 42 , 43 ]. These peaks are most prominent and clearly defined in the GO sample. The peak at 1713 cm −1 is attributed to C=O stretching vibrations, while the peaks at 1580 cm −1 , 1220 cm −1 , and 1040 cm −1 correspond to C=C and C-O-C bonds, respectively [ 44 , 45 ]. After the reduction in GO to rGO, the O-H and C=O peaks become almost unnoticeable, indicating the removal of oxygen-containing functional groups. In addition, all corresponding peaks in rGO exhibit significantly lower intensities than GO, confirming successful reduction. For GO-AgNWs composites (Figure 3), slight peak shifts and reduced intensities are noticed, suggesting the establishment of the interactions between GO and AgNWs. In the composites with higher AgNW content (Figure 3, GOAgNWs 3:7, rGO-AgNWs 3:7, GO-AgNWs 1:9, and rGO-AgNWs 1:9), the band assigned to Int. J. Mol. Sci. 2024,25, 13401 5 of 18 O-H (around 3705 cm −1 ) is still visible but with lowered intensity. In contrast, the bands assigned to C=O and C-O bonds are diminished, suggesting both the reduction in the sample and the successful establishment of interactions between GO and AgNW. Raman spectra of all composites are presented in Figures 4and S4, Supporting Information. All spectra show bands around 1350 cm −1 which is assigned to inherent defect or disorder in sp 2 domains of graphene sheets and at 1596 cm −1 which is a so-called G or graphitic band associated with the phonon vibration of sp 2 region with E 2g symmetry [ 46 , 47 ]. Both D and G bands of composites are redshifted compared to GO and rGO (Table S1, Supporting Information), which was previously assigned to AgNWs adhesion to graphene flakes [ 48 ]. The lowering I D /I G ratio is proportional to AgNWs content, and these results could be explained as the correction or “healing” of inherent defects [48,49]. − − − − − − Figure 4. Raman spectra of GO, GO-AgNWs 5:5, GO-AgNWs 3:7, GO-AgNWs 1:9, (a) rGO, rGOAgNWs 5:5, rGO-AgNWs 3:7, and rGO-AgNWs 1:9 (b). Bands between 2700 and 3200 cm −1 are also related to graphene-like structures (2D and D + G bands). Additional bands were observed at 235, 663, and 1769 cm −1 in spectra of GO-AgNWs 3:7, GO-AgNWs 2:8, and GO-AgNWs 1:9 composites (Figures 4a and S4, Supporting Information), as well as in the Raman spectra of the same composite after reduction (Figure 4b). The band at 235 cm −1 stems from Ag–O stretching vibration [ 50 ]. It indicates that the PVP molecule is coordinately bonded to the atom of Ag at the nanowire’s surface, and the nonbonding electrons of the O atom in carbonyl functional groups are donating the electron pair [51]. In the spectra of composites GO-AgNWs 5:5, GO-AgNWs 4:6, and GO-AgNWs 3:7, bands characteristic for AgNWs are not observed; it can be concluded that their surface is tightly covered with GO sheets. Experimental studies (UV-Vis, FTIR, and Raman spectra, Figures 1,3and 4) proved that GO and AgNWs create surface interactions. We used DFT to closely understand the nature of the interaction between GO sheets, both sp 2 region and functional groups with AgNWs, and areas of GO surface that are engaged in the interaction with edges and tips of AgNWs. 2.2. Theoretical Investigation of GO-AgNWs Interactions First, the optimized structure of the Ag 30 cluster is presented in Figure 5a (side and top views). The Ag 30 cluster consists of five consecutive pentagonal rings with five silver atoms placed between these rings along the central C 5 -axis of symmetry. This implies that one silver atom is pressed into the cluster, and the other stays out (Figure 5). Interatomic distances between silver atoms vary from 2.78 to 3.00 Å depending on the position in the Int. J. Mol. Sci. 2024,25, 13401 6 of 18 cluster. The distance between successive pentagons is about 3 Å, while their thickness is 4.4 Å (0.44 nm) as indicate with a red arrow (Figure 5c). It has been shown that {100} ends of silver nanowires are more reactive than their {111} facets [52]. ⁻ − − ⁻ ff Figure 5. The optimized structure (a), natural bond orbital (NBO) charges (b), the molecular electrostatic potentials (MEP) (c), and the total density of states of the Ag30 cluster (d). Green and maroon denote positive and negative regions of the wavefunction. According to the NBO charge analysis, the silver atoms in the cluster’s interior are negatively charged, whereas those on the cluster’s exterior are positively charged (Figure 5b). The exception is the silver atom that sticks out and is almost neutral. While the positive charges of silver atoms at the surface vary from +0.22 to +0.30 e − , those buried inside the cluster are much more negative, spanning from − 1.40 to − 1.72 e − . On the other hand, Figure 5c combines various colors to represent different MEP values. Red and blue represent the electron-rich (negative) and electron-deficient (positive) parts of the Int. J. Mol. Sci. 2024,25, 13401 7 of 18 molecules, respectively, while green denotes areas with zero potential. The MEP shows that the electropositive regions are at the edges of the cluster (blue), while the negative parts are within the cluster (red), which is consistent with the NBO values. In addition, the MEP reveals electro-negative regions that surround the {100} surfaces. The computed electronic structure of the Ag 30 cluster illustrated through the density of state diagram indicates the metallic property of AgNW (Figure 5d). The electronic states near the Fermi level depicted via FMO’s wave-functions may suggest a smooth conductivity of AgNW. To model an ideal graphene surface, the C 40 H 16 cluster was constructed. To mimic the surface of graphene-oxide or reduced graphene-oxide, covered with epoxy and hydroxy groups, different molecular systems were employed, such as C 40 H 16 O n and C 40 H 16 (OH) n (n = 1–4), respectively. In addition, the C 40 H 16 O 2 (OH) 2 cluster was utilized to describe the GO surface filled with both epoxy and hydroxyl groups. To estimate the binding strength between AgNW, modeled using the Ag 30 cluster, and pristine graphene, as well as GO/rGO, we generated various Ag 30 @C 40 H 16 (O) n (OH) n adducts and reoptimized them by preserving the Ag 30 structure. The optimized structures of these adducts are presented in Figure 6. The short distances between oxygen atoms from epoxy and hydroxyl groups and Ag atoms (<2.5 Å) indicate strong interactions, according to Dannenberg et al. [ 53 ]. The interplane distance of 3.2 Å within the Ag 30 @C 40 H 16 adduct is typical for stacking interactions, suggesting the dispersion nature of the interactions (Figure 6a). On the other side, geometrical parameters in Ag 30 @C 40 H 16 (O) n (OH) n structures, with short O ··· Ag distances, point to the electrostatic and dispersion nature of bonding (Figure 6b–d). Figure 6. The optimized structures of Ag 30 @C 40 H 16 (a), Ag 30 @C 40 H 16 O 4 (b), Ag 30 @C 40 H 16 (OH) 4 (c), and Ag 30 @C 40 H 16 O 2 (OH) 2 (d) adducts as calculated at the B3LYP-D3/6-31G(d,p)/LANL2DZ level. The interaction energies, which represent interfacial bonding between the Ag 30 cluster and various Gand rGO/GO-based systems, are calculated with the inclusion of Grimme’s dispersion correction (GD3). The counterpoise correction is used to remove the BSSE. All these energy values are listed in Table 1. The computed interaction value of − 48.9 kcal/mol in the Ag 30 @C 40 H 16 adduct suggests that there would be significant noncovalent binding between pristine graphene and AgNW. Since the C 40 H 16 cluster has five condensed C 6 -rings along the C 2 -axis of symmetry, overlapping with four Ag 4 fused rings of the Ag 30 cluster, it could be roughly estimated that the interaction per C 6 -ring is − 9.78 kcal/mol. For comparison, the energy of stacking interaction between two benzene rings is − 2.78 kcal/mol [ 54 ]. On the other hand, including epoxy groups in graphene leads to a significant rise in interaction (binding) energy in Ag 30 @C 40 H 16 O n adducts, reaching − 92.9 kcal/mol for Ag 30 @C 40 H 16 O 4 . The dispersion energy loss caused by an interplane digression from 3.20 to 3.80 Å is compensated by strong (Ag ··· O) electrostatic interactions Int. J. Mol. Sci. 2024,25, 13401 8 of 18 (Figure 6b). Considering the Ag 30 @C 40 H 16 (OH) n adducts, it can be seen that the dangling OH groups interact with Ag atoms less strongly, which is reflected through longer Ag ··· O distances (Figure 6c). Including three OH groups into the graphene core overcomes the energy loss, impacted by larger interplane distance (~4.0 Å). The Ag 30 @C 40 H 16 (OH) 4 adduct has the strongest binding energy between fragments, which is determined to be − 75.1 kcal/mol (Table 1). The C 40 H 16 O 2 (OH) 2 cluster is created to more closely resemble the GO surface coated with epoxy and hydroxyl groups. The interaction energy between Ag 30 and C 40 H 16 O 2 (OH) 2 fragments is calculated to be − 81.9 kcal/mol, which is the value in between those calculated for the Ag 30 @C 40 H 16 O 4 and Ag 30 @C 40 H 16 (OH) 4 adducts. All these findings indicate that AgNW binds to the GO/rGO surface more firmly than it does to the ideal graphene surface. Table 1. The interaction energies (kcal/mol) in various AgNW/G/GO/rGO adducts, all calculated at the B3LYP-D3//HF/6-31G(d,p)/LANL2DZ level. Energy values are corrected for BSSE. Species Interaction Energy (kcal/mol) B3LYP-D3 HF Ideal graphene Ag30@C40H16 −48.9 31.8 GO with epoxy groups Ag30@C40H16O−49.4 −6.6 Ag30@C40H16O2−60.6 −35.9 Ag30@C40H16O3−77.7 −71.3 Ag30@C40H16O4−92.9 −101.9 GO with hydroxy groups Ag30@C40H16(OH) −42.5 - Ag30@C40H16(OH)2−46.6 −14.3 Ag30@C40H16(OH)3−58.1 −39.4 Ag30@C40H16(OH)4−75.1 −68.6 GO with epoxy and hydroxyl groups Ag30@C40H16O2(OH)2−81.9 −80.0 The interaction energies were also calculated at the Hartree–Fock (HF) level, which does not account for the electron correlations. The contribution of the dispersion interaction based on the difference between the B3LYP-D3 and HF energies was estimated (Table 1). It can be observed that in the Ag 30 @C 40 H 16 system, the dispersion interactions are the dominant binding forces. On the other hand, in both systems containing oxygen species, the electrostatic interactions prevail by increasing the number of epoxy/hydroxy groups. For the Ag 30 @C 40 H 16 O 2 (OH) 2 complex, a slightly stronger interaction energy using the B3LYP-D3 method was obtained as compared to the pure HF which indicates a dominant electrostatic contribution to the overall binding. According to zeta potential analysis, graphene oxide materials are negatively charged through a wide pH range [ 55 ]. The edge phenolic hydroxyl and carboxyl groups contribute more to the negative charge than the basal-plane hydroxyl and epoxy groups, according to FT-IR and UV-VIS spectroscopic investigations [ 55 ]. Thus, we introduced one or two negative charges into the graphene core via carboxyl and edge phenolic hydroxyl groups to estimate charge transfer behavior within Ag 30 /GO/rGO composites. Mulliken (Q Mulliken ) and natural bond orbital (Q NBO ) analyses are performed, and the results are listed in Table 2. The data indicate charge transfers from the graphene core to the Ag 30 cluster considering monoand di-anionic pristine graphene. According to the Q NBO analysis on [Ag 30 @C 40 H 15 -COO] − and [Ag 30 @C 40 H 15 -COO-O] 2− adducts, the Ag 30 accepts electron densities of − 0.59 and − 0.67 e − , respectively. For rGO/GO filled with epoxy groups, the successive introduction of each epoxy group causes a reduction in electron transfer to the Ag30 cluster, making it even more positively charged in [Ag30@C40H15O3(O4)-COO]− systems (Table 2). Such a trend is less pronounced in rGO/GO with hydroxyl groups. On the other hand, the Ag 30 accepts electron densities from rGO/GO, ranging from − 0.07 to Int. J. Mol. Sci. 2024,25, 13401 15 of 18 microwave reflections occur at the MUT interface. Measurement configurations include thru (empty structure), reference (aluminum), and GO-based samples. Samples are inserted between two cellulose sheets with 90 µ m thickness. A conventional short-open-load-thru (SOLT) coaxial calibration is applied at the outputs of the coaxial cables using an Anritsu ® TOSLKFOA-43.5 reference K-coaxial calibration kit (Anritsu, Kanagawa Prefecture, Japan). An amplitude normalization to the thru connection (direct connection of the coaxial apertures) is considered to remove residual systematic errors. To estimate the shielding effectiveness of GO and GO-AgNWs composites, Equations (3)–(5) were used [77]: SET=−S21 dB (3) SER=−10log(1 −|S11|2) (4) SEA=−10log(|S21|2/(1 −|S11|2)) (5) where SE T is the shielding effectiveness due to transmission; SE A is the result of EMW dissipation; SE R is due to the wave reflection (SE R ); S 11 is the reflection coefficient, and S 21 is the transmission coefficient. A vector network analyzer was used to measure S 11 and S21 coefficients. Electrical resistivity was measured using a 4-point probe Jandel RM3000+ (Leighton Buzzard, UK) test unit. The distance between probes is 1 mm. The samples of GO-AgNWs composites were analyzed at 3 different locations, and the average values were calculated. 4. Conclusions Composites based on GO and AgNWs are produced in different mass ratios of each component. The interaction between the two different nanomaterials is studied using experimental (Raman, UV-Vis, FTIR, and TGA) and theoretical approaches (DFT). By analyzing the Mulliken and NBO atomic charges, as well as MEPs, it is revealed that charge transfer occurs from GO to AgNWs, resulting in the redistribution of charges across the interface. As a result, a conductive network is created, improving the EMI shielding properties. Our results confirm the establishment of electron transfer between GO and AgNWs, leading to an improvement of the shielding effectiveness of the composites. Supplementary Materials: The supporting information can be downloaded at: https://www.mdpi. com/article/10.3390/ijms252413401/s1. Author Contributions: Conceptualization, S.J. and M.Y.; validation, W.S., M.M., D.S., D.B.-B., M.B., and A.S.; investigation, W.S., M.M., D.B.-B., D.S., and A.S.; resources, S.J. and M.Y.; writing—original draft preparation, M.M., M.B., D.S., and S.J.; writing—review and editing, S.J. and M.Y.; supervision, S.J. and M.Y.; project administration, S.J.; funding acquisition, S.J. All authors have read and agreed to the published version of the manuscript. Funding: This research was supported by the European Union’s Horizon Europe Coordination and Support Actions program under grant agreement No 101079151—GrInShield. M.M., M.B., D.S., S.J., and D.B.-B. thank the Ministry of Education, Science, and Technological Development of the Republic of Serbia (grant number 451–03–66/2024–03/200017, 451–03–66/2024–03/200146). Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. 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