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Scientific Reports Volume 5, Article Number: 14177 (2015) Cite this article
The emergence of stretchable devices that combine conductive properties provides exciting new opportunities for wearable applications. Here, a novel, convenient and inexpensive solution process is demonstrated, which can prepare in-situ silver (Ag) or platinum (Pt) nanoparticles (NPs) embedded in AgNO3 or H2PtCl6 at low temperature using formic acid duality rGO hybrid material. The reduction duality of formic acid can convert graphene oxide (GO) into rGO, and at the same time deposit positively charged metal ions on the metal NP on rGO, while formic acid itself is converted into environmentally friendly CO2 release gas. The rGO hybrid electrode embedded with AgNP on the elastomer substrate exhibits excellent stretchability, including maximum conductivity of 3012 S cm-1 (0% strain) and 322.8 S cm-1 (35% strain). Its manufacturing process using printing method is extensible. Surprisingly, the electrode can survive even in continuous stretching cycles.
Stretchable electronic devices have been regarded as an alternative technology to realize the next generation of wearable electronic devices. Stretchable electronic circuits and electrodes will make expandable, foldable and sticky electronic devices into wearable or epidermal electronic devices. For the manufacture of stretchable electrodes, carbon-based materials have been used so far, especially the integration of one-dimensional carbon nanotubes (CNT) and rigid inorganic conductive materials. Rigid and brittle inorganic conductive materials are chemically and/or physically embedded on the surface of carbon nanotubes. The resulting inorganic material embedded in the carbon nanotube electrode exhibits high conductivity and stretchability. Although carbon nanotubes embedded in inorganic materials, which are one of various carbon allotropes, show the possibility of being a stretchable electrode with high conductivity, there are still unresolved problems in the realization of stretchable electrodes. Obstacles, especially for poor device manufacturing processes, such as poor use of expensive raw materials, high solubility in common solvents and high manufacturing costs. Due to the poor solubility of inorganic materials and carbon nanotubes in water and other organic solvents, it is difficult to prepare homogeneous inorganic materials/carbon nanotube composite materials through simple reactions in the solution process.
On the contrary, graphene oxide (GO) is obtained from graphite after acid treatment. A single layer of sp2 and sp3 bonded carbon atoms are arranged into a typical two-dimensional carbonaceous nanomaterial, which is caused by its extraordinary solubility and easy-to-achieve chemical functions. Has a wide range of interests. Other inorganic materials under various solution treatments. In addition to GO, reduced GO (rGO) is used in sensing 2, 3, 4, 5, 6, 7, 8, nanoelectronics 9, 10, 11, 12, energy storage 13, 14, 15, catalysis 16 and nanobiotechnology 17 , 18. Recently, rGO/hybrid materials or nanocomposites made of metals have aroused strong research interest due to their optical, electronic, thermal, mechanical and catalytic properties19,20,21,22,23. The overall goal is to make composites or hybrid materials that integrate GO or rGO with polymers, metal nanoparticles (NP), and even nanotubes and fullerenes. Due to the large surface area and the above characteristics, GO or rGO as a matrix of nanocomposites has become an attractive alternative.
However, so far, few works have reported using GO or rGO as templates to directly synthesize metal NPs and fabricate metal NP-GO composites directly on the substrate. Metal nanoparticles are very important due to their optical, catalytic, electrical and antibacterial properties24. Manufacturing metal nanoparticles into composite materials is also conducive to exploring their properties and applications. Therefore, the integration of metal nanoparticles with GO or rGO and the synthesis of metal nanoparticles with GO or rGO as templates are key research interests. Mushinsky et al. Au NP has been synthesized by chemical reduction of HAuCl4 and NaBH425. In this method, they used a suspension of graphene-octadecylamine in THF and metal borohydride as the reducing agent. However, this process is not environmentally friendly. In addition, the gold particles are fixed on the octadecylamine-functionalized graphene instead of directly on the surface of the graphene. Recently, Nanda et al. Use zinc and H2SO426 to synthesize M@rGO. They use zinc acid as a medium to produce another metal nanoparticle, such as gold, platinum, palladium, and silver. The production of small metal nanoparticles requires a high concentration of H2SO4 (10 M), and a lower concentration will result in large nanoparticles (50 nm). However, these methods produce materials that are not suitable for use as conductive materials in stretchable conductive electrodes. Therefore, although there are many publications on the use of AgNWs27, fibers 28 and carbon nanotubes 1 to prepare stretchable conductive electrodes, there are no reports on the use of rGO-metal NPs hybrid composite materials. It is strongly recommended that if we carefully prepare a uniform AgNP embedded rGO film on an elastic polymer, the rGO-AgNP film through a printing process compatible with any substrate is expected to become an electrode with high conductivity and high stretchability, which can be used for Printable electronic equipment.
Here, we report a new method for preparing novel hybrid rGO-AgNP conductive materials by carefully designed reduction duality of formic acid at low temperature (Figure 1a). In order to obtain a homogeneous rGO-metal NP film without any aggregation, the issue of dispersion in any solvent system is very important. Since conductive rGO and silver NP are not dispersed in water at all, it is a key issue to find dispersible GO in situ and directly reduce it to rGO and at the same time to directly reduce the dispersible Ag ion to Ag metal NP in the water phase. Fortunately, we found that formic acid can reduce silver positive ions to silver metal NPs and at the same time reduce GO in the water phase to rGO. As expected, these composite materials can be applied to highly stretchable conductive electrodes using simple printing techniques. We also want to report how the hybrid rGO-AgNP conductive electrode prepared on the polymer matrix is stretched compared to the commercially available silver paste electrode on the same polymer matrix.
Schematic diagram of the in-situ synthesis of metal nanoparticles embedded in reduced graphene oxide (rGO-AgNP) and the stretchable mechanism of the rGO-AgNP hybrid film in a polymer matrix.
(a), Synthesis of metal-embedded rGO from GO through the reduction duality of formic acid. (B), a schematic diagram of a stretchable and conductive rGO-AgNP hybrid film.
We carefully designed the in-situ synthesis of rGO-metal NPs by using the reduction duality of formic acid in the presence of AgNO3 or other metal salts. Here, AgNO3 serves as the initiator of the reduction process and the source of AgNPs. Once the reduction process starts, the new positively charged metals (Ag and Pt) can convert formic acid into carbon dioxide, the two protons and electrons produced in the reaction solution. This step is very critical for determining the reaction rate of the entire reduction process. Although protons can diffuse into the solution, the generated electrons are transferred to the new positively charged metal, reducing them to metal nanoparticles. Then the excess electrons will accumulate on the surface of the metal nanoparticles. When metal nanoparticles are attached to the GO sheet, electrons will flow to the GO sheet, and with the help of protons, the oxygen functional groups from the GO sheet in the aqueous medium will be reduced. In the presence of formic acid, high concentrations of protons inhibit the reaction rate. Therefore, the reduction duality of formic acid can convert graphene oxide (GO) into rGO, and at the same time, it can also deposit positively charged metal ions on the metal NPs on the rGO nanosheets. We have hypothesized the mechanism of formic acid reduction duality, indicating that metal ions are converted into metal nanoparticles and at the same time GO is reduced to rGO.
In a typical reaction, 40 mg GO was dispersed in deionized water, and then 1-2 mL of formic acid and a catalytic amount (5 mg) of AgNO3 were added. The minimum amount of AgNO3 is 3 mg, which can reduce GO and metal precursors to rGO-metal nanoparticles). The reaction mixture was then heated to 80°C to produce the rGO-AgNP hybrid material (Figure 1a). We also performed these reactions using formic acid and AgNO3 under similar conditions for control experiments. In either case, GO did not decrease and AgNP was not produced. When a catalytic amount of AgNO3 is added to formic acid, the reaction proceeds well. As we mentioned before, AgNO3 initiates the reduction of GO by formic acid. Once the reduction process starts, formic acid simultaneously reduces GO and AgNO3 to produce AgNP-embedded rGO hybrid materials in situ. Formic acid has a dual role, it can reduce GO to rGO and at the same time convert Ag ions into AgNP through the reduction process.
During the reaction, the gas was observed to slowly escape and form bubbles, which is very consistent with the mechanism we proposed to generate CO2 gas during the reduction of formic acid. In this regard, by changing the AgNO3 concentration, different amounts of AgNP made rGO were prepared from 0.6 wt% to 20.01 wt% AgNP. This method has also been successfully extended to prepare PtNP-embedded rGO (rGO-PtNP) in a similar manner.
The Ag and Pt on rGO were characterized by X-ray diffraction (XRD). Figure 2(ac) shows the amount of rGO-AgNP and rGO-PtNP dependent on AgNP (Figure 2a, c) and the XRD patterns of GO and graphite, respectively. The 2θ peak of graphite powder is located at 26.71°, indicating that the interlayer distance is 3.34 Å (Figure 2c). The 2θ peak of GO appears at 10.27°, and the corresponding interlayer spacing is 8.60 Å (Figure 2c). The peaks at 38.1°, 44.3°, 64.5° and 77.3° correspond to the strongest reflections of the (1 1 1), (2 0 0), (2 2 0) and (3 1 1) crystal planes of the Ag NP phase , Respectively (Figure 2a) 30. The peaks at 39.9°, 46.6°, 68.1° and 81.7° correspond to (1 1 1), (2 0 0), (2 2 0) and (3 1 1 ) The strongest reflection of the crystal plane, respectively (Figure 2c) 31. Surprisingly, Figure 2b is an enlarged result of the GO and rGO diffraction peaks in Figure 2a, indicating that as more AgNO3 GO is added, the diffraction peaks begin to decrease, and finally the ~10° diffraction peak shifts to ~24°. Due to the removal of oxygen groups, this phenomenon in XRD is called the reduction process in GO. In addition, as mentioned earlier, this means that AgNO3 can be used as an initiator for the reduction of GO. The peak at 24.1° belongs to the (002) reflection of rGO33. Raman spectroscopy is used to further examine the preparation of metal nanoparticles and the effect of simultaneous reduction of GO through this reaction. Figure 2d shows the Raman spectra of GO powder and the amount of rGO-AgNP hybrid material dependent on AgNP, and Figure S1a shows the Raman spectra of GO and rGO-PtNP. The Raman spectra of GO prepared by this method and rGO embedded with metal nanoparticles are similar. All spectra show D band (due to defects), G band (derived from in-plane optical vibration), 2D band (from two phonon scattering processes), and a peak near 2980 cm-1 (S3 band) 34. However, when When the amount of AgNP was increased by adding more AgNO3, the ID/IG ratio changed significantly from GO to 9.57 wt% AgNP. The ID/IG ratios of GO and AgNP on rGO were 1.33, 3.71, 4.98, and 9.57 wt%, which were 0.71, 0.98, 1.12, 1.18, and 1.21, respectively, which increased from 0.71 (GO) to 1.21 (9.57 wt%). This is because the functionalized sp3 hybrid CC bond in GO is transformed into the sp2 hybrid CC double bond in rGO, which increases the disorder of the rGO basal plane; the higher deoxygenation of GO means the high quality reduction of GO to rGO. In addition, the enhanced 2D and S3 peak intensities of rGO near 2690 cm-1 and 2950 cm-1 (Figure 2d) are attributed to the good reduction of GO. In addition, in order to determine the influence of AgNO3 as the initiator in the reduction reaction, we performed Raman measurements on GO using only formic acid. As we expected above, it did not decrease in the absence of AgNO3, which is very consistent with our hypothetical mechanism (Figure 2d). Fourier transform infrared spectroscopy (FT-IR) is further used to study the reduction process. Figure 2e shows the FT-IR spectra of AgNP of GO and different amounts of rGO-AgNP mixed materials. The characteristic peaks in the GO IR spectrum (Figure 2e) are ~3409 cm-1 (width, OH stretch), 2948 cm-1 (CH2 stretch), 1728 cm-1 (C = O stretch), 1632 cm- 1 (C = C stretching) and 1404 cm-1 (OH bending) 35,36. It can be seen from the IR spectrum that all rGO-AgNP hybrid materials show no peak at 1404 or 3409 cm-1, and the intensity at 1728 cm-1 is very low, indicating that the largest amount of oxygen contained in GO has been removed Group. The infrared spectrum of rGO-PtNP is shown in Figure S1b, which provides good evidence for the in-situ reduction in the GO metal manufacturing process. Thermogravimetric analysis (TGA) is used to further evaluate the reduction level of rGO-AgNP hybrid materials. Figure 2f shows the TGA thermal analysis graph, which shows the weight loss of GO and different amounts of rGO-AgNP mixed materials as a function of temperature under N2 atmosphere. GO showed a significant weight loss, with the initial temperature being slightly higher than 100°C, which was attributed to the elimination of interlayer water, followed by the oxygen loss of GO itself at slightly higher temperatures. Interestingly, the TGA stability of the rGO-AgNP hybrid material increases sharply with the increase in the amount of AgNO3 initiator, because the graphitization and deoxidation of the rGO-AgNP hybrid material is better, and the van der Waals force interaction between layers is enhanced33.
Composition analysis of the prepared hybrid material.
(a) XRD spectrum of the amount of rGO-AgNP material dependent on AgNP. (b) Partially amplified XRD spectra of rGO-AgNP hybrid materials (0.61, 1.33 and 3.71 wt%) show that AgNO3 acts as an initiator to reduce GO. (c) XRD spectrum of rGO-PtNP synthesized using formic acid and hexachloroplatinic acid (H2PtCl6). (D, e), Raman spectra and FT-IR spectra of GO and the amount of rGO-AgNP dependent on AgNP. (f) Thermogravimetric analysis of GO and rGO-AgNP hybrid materials (1.33, 3.71 and 4.98 wt%).
X-ray photoelectron spectroscopy (XPS) was also used to characterize the incorporation of metal nanoparticles in rGO. Figure 3a shows the comparison of the XPS spectrum of GO with the different atomic weight percentages (0.61, 1.33, 3.71, 4.98, 9.57, 12.05, 13.74, 17.18, 19.17 and 20.01 wt%) of AgNP AgNP and rGO in the hybrid material. Figure 3b shows The difference between GO and rGO-PtNP. Figure 3c shows the typical C1s spectra in XPS results of GO, rGO-AgNP (1.33 wt% of AgNP), and rGO-PtNP. Figures 3d and e show the Ag 3d XPS spectra of rGO-AgNP and Pt 4f of rGO-PtNP. XPS spectra. Figures S2a and S2b respectively show the high-resolution C1s XPS spectra and Ag 3d XPS spectra of various rGO-AgNPs with different amounts of AgNP. An obvious Ag 3d double peak appeared at 368.76 eV (Ag 3d5/2) and 374.79 eV (Ag 3d3/2), confirming the formation of AgNP in rGO (Figure 3d and S2b)37. The doublet of Ag 3d comes from spin-orbit coupling (3d5/2 and 3d3/2)37. With the increase in the number of AgNPs on the rGO-AgNP hybrid material, the oxygen functional group dropped sharply from 0.61 wt% of AgNPs, and gradually decreased as the number of AgNPs increased to 20.01 wt% (Figure 3c and S2), indicating a decrease. Interestingly, when we added a smaller amount of AgNO3 than 0.61 wt% to the reaction solution, rGO and AgNPs were not formed in our experimental system. Therefore, the generation of protons and electrons in the reaction solution is crucial for determining the reaction rate of the entire reduction process.
(A) The investigation results of XPS spectra of GO and rGO embedded with different Ag nanoparticles prepared using formic acid and AgNO3 from GO. (b), XPS spectroscopic investigation results of GO prepared using formic acid and H2PtCl6 from GO and rGO embedded with Pt nanoparticles. (c), C1s leads to XPS spectra of GO, rGO-AgNP and rGO-PtNP. (d,e), Ag 3d and Pt 4f lead to XPS spectra of rGO-Ag and PtNP.
Scanning electron microscope (SEM) and transmission electron microscope (TEM) were also used to prove the decoration of AgNPs on rGO and calculate the size of nanoparticles embedded on rGO. Figures 4a and b show the SEM images of rGO-AgNP and rGO-PtNP, and Figures 4c, d, and S3 show the TEM images of rGO-AgNP and rGO-PtNP. It can be clearly seen from the TEM image that the size of the particles is about 5-15 nm. The AFM image shown in Figure S4 also shows the uniform size distribution of the metal nanoparticles. The SEM morphology of the compound we prepared is shown in Figure 4a, b and S5, which clearly shows that metal nanoparticles are deposited and embedded on rGO under the reaction conditions. Figure S4 shows the SEM images of rGO-AgNP hybrid materials with different amounts of AgNPs, indicating that due to the absence of a surfactant reaction, as the amount of AgNP increases, the morphology of AgNP on rGO gradually aggregates. This is also a good evidence for the formation of a nanoparticle-rGO hybrid structure.
Scanning electron microscope (SEM) and transmission electron microscope (TEM) of the morphology and microstructure of rGO-AgNP and rGO-PtNP hybrid materials.
(A) and (b) are SEM images of rGO-AgNP and rGO-PtNP, respectively. (c,d) TEM images of rGO-AgNP and rGO-PtNP, respectively.
In order to prepare a stretchable and conductive rGO-AgNP hybrid film, the prepared rGO-AgNP powder was ground and ultrasonically processed in a polyvinylidene fluoride (PVDF) solution. PVDF copolymer was chosen as the matrix because of its good electrical and mechanical properties1,38. First, prepare an rGO-AgNP hybrid film with an average thickness of 30 μm on a PET or glass substrate using a doctor blade technique, and then pour an elastic polymer solution such as nitrile rubber (NBR) onto the rGO-AgNP to embed the film. Finally, the rGO-AgNP hybrid film was easily peeled from the substrate after drying and hot roll curing at 150°C (Figure S6). The relationship between the conductivity of the rGO-AgNP hybrid film and the curing temperature was studied (Figure S7). Due to the shrinkage of the polymer matrix, the conductivity increases as the curing temperature increases.
Figure 5a shows the conductivity of the rGO-AgNP mixed film at 0% strain as a function of the mass fraction of AgNPs. The mass of the other components (rGO 100 mg, 100 μl 10 wt% PVDF solution in NMP) is fixed. When the mass fraction of AgNPs reached 9.0 wt%, the conductivity of the rGO-AgNP hybrid film began to increase. The mass fraction of AgNP higher than 20.01 wt% will cause the fragile film to undergo phase separation. Surprisingly, the bare AgNP film is not stretchable at all and has relatively low conductivity. The theoretical prediction of the conductivity of the hybrid membrane is calculated using the power law relationship and 3D permeation theory (see supporting information). Simply put, the power-law relationship 39 is described as
Electrical properties of rGO-AgNP hybrid film.
(a), The electrical conductivity of the mixed rGO-AgNP thin film, composed of rGO decorated with different amounts of silver nanoparticles, was studied at 0% strain. The red line is the prediction based on the power law relationship and the three-dimensional penetration theory. (b), the conductivity of the mixed rGO-AgNP film to five different proportions of silver nanoparticles under tensile strain. (c), cyclic test of rGO-AgNP hybrid film (19.17 wt%) under 20% tensile strain. (d,e), the operation of the LED chip connected to the hybrid rGO-AgNP hybrid film (19.17 wt%) and the visual image of the LED after 180° bending and wrinkling under an applied voltage of 3.0 V. (f) Before stretching (0% strain) and after stretching (12%, 25% and 50% strain respectively).
Where σ is the conductivity of the composite material, σ0 is the conductivity of the conductive filler, Vf is the volume fraction of the filler, Vc is the volume fraction of the permeation threshold, and s is the fitting index. AgNPs are modeled as uniformly distributed nanoparticles with random orientation, and the average interparticle distance model28,39 is used to calculate the penetration threshold. The calculated permeability threshold (5.86 vol% after the drying process, equivalent to 9.57 wt% in the initial mixture) and the power law relationship show that it is in good agreement with our experimental results. Figure 5b shows the measurement of the conductivity of the rGO-AgNP hybrid film (40 × 5 × 0.03 mm) under different tensile strains using a four-point probe system. The prepared hybrid film embedded with elastic polymer shows a maximum conductivity of about 3012 S cm-1 at 0% strain, and the conductivity of the rGO-AgNP hybrid film decreases with the increase of strain. The measured conductivity The rate is 322.8 Scm-1 and the strain is 35%. The mass fraction of AgNPs rarely affects the stretchability, and all the mixed films rupture at 50% strain. The cycle test was performed up to 4,000 cycles, as shown in Figure 5c. The conductivity initially fluctuates and then stabilizes after 1,500 cycles. The electrical properties of the rGO-AgNP hybrid film under different strains were visually measured using a green LED chip. The visual images of the LED chip before stretching (0% strain) and after stretching (12%, 25% and 50% strain) are shown in Figure 5f. Due to the energy band gap of the LED, when the applied bias is about 3.0 V, the LED turns on. When the film is stretched, the brightness of the LED chip decreases with the increase of the tensile strain (up to 50%), indicating that the resistance increases with the increase of the tensile strain. These results match Figure 5b. In addition, the rGO-AgNP hybrid film still maintains its performance after 180º bending and wrinkling tests (Figure 5d-e and Figure S8).
In order to explain the possible mechanism of the stretchability of the rGO-AgNP hybrid film, we performed a scanning electron microscope (SEM) to image its morphology at 10% strain. From the SEM image, we can compare with the morphology of the silver paste electrode without rGO. Figure 6a and d respectively show the cross-sectional SEM images of silver paste electrode and AgNP embedded rGO on an elastic polymer substrate after 10% strain. Although the surface morphology of the rGO-AgNP hybrid film is rougher than that of the silver paste electrode without rGO, large cracks will appear when there is only the silver paste electrode in the enlarged image (Figure 6b). This phenomenon can be explained in Figure 6c and f. The silver paste without rGO shown in Figure 6c shows that the Ag particles are separated from the non-conductive matrix, elastic polymer, and NBR. On the contrary, the soft and flexible rGO sheet with high aspect ratio can construct an effective electrical network between AgNPs, and the AgNPs adsorbed on the surface of the rGO sheet can enhance the contact interface (Figure 1b and Figure 6f). The simplest explanation is that although the silver paste electrode and the polymer matrix show a dense morphology, they are still rigid and brittle under external strain. In contrast, the rGO-AgNP hybrid film clearly shows that an electrical contact network can be formed even under strain, thereby providing high stretchability.
SEM image of silver paste electrode and rGO-AgNP hybrid film on elastomer substrate under 10% strain.
(ac) SEM image of silver paste electrode on elastomer substrate at 10% strain. (Df) SEM image of rGO-AgNP hybrid film on the same elastic polymer under 10% strain. (A and d) cross-sectional images and (bc and ef) represent the top view images of the silver paste electrode and the rGO-AgNP hybrid film, respectively.
In summary, a novel, convenient and inexpensive solution process is demonstrated for the production of metal NP-embedded rGO hybrid materials using the reductive duality of formic acid. The use of printable metal embedded rGO ink successfully prepared a highly conductive and stretchable electrode with 0% high conductivity of 3012 S cm-1 and 35% strain at 322.8 S cm-1 on a substrate. The substrate was made of elastic polymer The embedding process provides a high degree of stretchability. According to the power law relationship of equation (1), this can be minimized or overcome by using a polymer matrix with Poisson's ratio, because in Vf or increase in total volume can be reduced. Composite materials containing excessive silver may exhibit long-term instability, because phase separation of AgNP is observed when the concentration is higher than 20.01%. These wet-processable and stable rGO-metal hybrid materials can be applied to graphene-based conductive inks for stretchable electrodes, including large-area electronic circuits, skin electronic devices, and wearable energy storage devices as charge collectors and others Modern nanoelectronic equipment.
Natural graphite (Bay Carbon, SP-1 graphite), sulfuric acid (95-97%), hydrogen peroxide (30 wt.%), potassium permanganate, sodium nitrate, silver nitrate and formic acid were obtained from commercial sources and used as is .
Graphene oxide (GO) is prepared from natural graphite powder by a modified Hummers and Offenman method using sulfuric acid, potassium permanganate and sodium nitrate.
Disperse GO in deionized water (40 mL, 2 mg mL-1), and then add 1 to 2 mL of formic acid and a catalytic amount (5 mg) of AgNO3 (to prepare 1.33 wt% AgNP-AgNP in rGO). Chemical materials). The reaction mixture was then heated to 80°C for 6 hours with stirring. Then it was filtered, washed with deionized water several times, then washed with saturated sodium bicarbonate solution to remove excess formic acid, and washed with deionized water several times. Then it was vacuum dried at 60°C for 24 hours to obtain the rGO-AgNP hybrid material. By changing the amount of AgNO3, different rGO-AgNPs with different amounts of AgNPs were synthesized. This protocol is also used to synthesize rGO-PtNP using chloroplatinic acid (H2PtCl6).
Use a mortar to grind the prepared rGO-AgNP hybrid material (100 mg) and polyvinylidene fluoride (100 μL 10 wt% PVDF in NMP) for 30 minutes, and then sonicate for 60 minutes to make it uniform. In the next step, the prepared rGO-AgNP ink is printed on a substrate, such as PET or glass, using doctor blade technology. Then, the coated rGO-AgNP film was dried on the substrate (12 hours under atmospheric conditions and 90 minutes at 100°C). In order to prepare a stretchable rGO-AgNP hybrid film, the elastic polymer solution was poured on the rGO-AgNP film prepared on the substrate, and then dried at room temperature for 24 hours and cured at 150°C for 90 minutes. After peeling from the substrate, the rGO-AgNP hybrid film is also pressed by hot rolling equipment at 150°C within a few seconds. The final size of the film is 40 × 5 × 0.03 mm.
The Raman spectroscopy measurement was performed using a micro-Raman system (Renishaw, RM1000-In Via), with an excitation energy of 2.41 eV (514 nm). All X-ray optical emission spectroscopy (XPS) measurements were performed using Sigma Probe (ThermoVG, UK) and a 100 W monochromatic Al-Kα X-ray source. Powder X-ray diffraction (XRD) research uses D8-Adcance instrument (Germany) and Cu-Ka radiation. The thermal properties of rGO-AgNP materials are characterized by TGA (Polymer Laboratory, TGA 1000 plus). Observe the microstructure by field emission scanning electron microscope (SEM, JSM-6701F/INCA Energy, JEOL) and transmission electron microscope (TEM, JEOL JEM 3010). AFM is performed at room temperature using SPA400 instrument with SPI-3800 controller (Seiko Instrument Industry Co.). A Thermo Nicolet AVATAR 320 instrument was used to collect FT-IR spectra. A Hall effect measurement system (HMS-3000, ECOPIA) was used to measure the electrical conductivity of these hybrid films at different tensile strains at room temperature. The stretchability of the rGO-AgNP hybrid film is performed using a customized tensile testing system.
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This work was supported by IBS-R011-D1.
Yoon Yeoheung and Samanta Khokan made the same contribution to this work.
Center for Integrated Nanostructure Physics, Institute of Basic Science (IBS), Sungkyunkwan University, South Korea, 440-746, Suwon, South Korea
Yeoheung Yoon & Lee Hyo Young
Department of Chemistry and Energy Science, SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, 440-746, Suwon, South Korea
Khokan Samanta, Hanleem Lee, Keunsik Lee, Anand P. Tiwari, JiHun Lee, Junghee Yang, and Hyoyoung Lee
Samsung-SKKU Graphene Center (SSGC), Sungkyunkwan University, 2066 Seoburo, Jangan-Gu, 440-746, Suwon, Gyeonggi-Do, Korea
Yeoheung Yoon & Lee Hyo Young
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YY, KS, and HL designed the research, YY and KS conducted experiments, YY, SK, HL, KL, AT, JL, and JY analyzed and interpreted the data, and YY, KS, and HL jointly wrote the manuscript and supporting information.
The author declares that there are no competing economic interests.
This work is licensed under the Creative Commons Attribution 4.0 International License Agreement. The images or other third-party materials in this article are included in the Creative Commons license of the article, unless otherwise stated in the credit line; if the material is not included under the Creative Commons license, the user will need to obtain permission from the license holder to copy The material. To view a copy of this license, please visit http://creativecommons.org/licenses/by/4.0/
Yoon, Y., Samanta, K., Lee, H. etc. Highly stretchable and conductive silver nanoparticles prepared by in-situ double reduction reactions are embedded in graphene sheet electrodes. Scientific Report 5, 14177 (2015). https://doi.org/10.1038/srep14177
DOI: https://doi.org/10.1038/srep14177
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