Conductivity Enhancement of Graphene and Graphene Derivatives by Silver Nanoparticles

Abstract

In this article, a facile way for the doping of graphene and graphene derivatives with silver nanoparticles at different Ag ratios is described. Ag nanoparticles were formed directly on the surface of two different graphene substrates dispersed in dimethylformamide by the reduction of Ag cations with NaBH4. A few layered graphene nanosheets (FLG) produced from graphite and reduced graphene oxide functionalized with amino arylsulfonates (f-rGO) were used as substrates. The final graphene/Ag nanoparticle hybrid in the form of solid, dense spots showed enhanced electrical conductivity, which can be attributed to the formation of conductive interconnections between the 2D nanosheets. Importantly, electrical conductivities of 20 and 167 103 S m−1 were measured for the hybrids of f-rGO and FLG, respectively, with the higher Ag percentage without an annealing process. A representative hybrid f-rGO with Ag nanoparticles was used for the development of a highly conductive water-based gravure ink with excellent printing properties.

One-Pot Synthesis of Functionalised rGO/AgNPs Hybrids as Pigments for Highly Conductive Printing Inks

“…Table 2 summarizes the R s values in kΩ sq −1 for four zones of different thicknesses of the ink layer when the Gravure/Flexo Ink P55/R45 and a special gravure cylinder were used. In accordance with our previous studies [30,31,44] it was observed that the more the thickness of the printed zones the less the R s values (Figures 10 and 11, Table 2). Table 2 also includes the R s values of other similar conductive inks, for the same four zones, after printing under the same conditions including the same printing cylinder and the same equipment [30,31,44].…”

“…In accordance with our previous studies [30,31,44] it was observed that the more the thickness of the printed zones the less the R s values (Figures 10 and 11, Table 2). Table 2 also includes the R s values of other similar conductive inks, for the same four zones, after printing under the same conditions including the same printing cylinder and the same equipment [30,31,44]. This comparison shows that although the percentage of Ag is less compared to other f -rGO/AgNPs hybrids prepared using different synthesis methods, the current method leads to printed patterns where lower R s values (and thus enhanced conductivity) were achieved.…”

“…This comparison shows that although the percentage of Ag is less compared to other f -rGO/AgNPs hybrids prepared using different synthesis methods, the current method leads to printed patterns where lower R s values (and thus enhanced conductivity) were achieved. It is clear that the dispersion of AgNPs on the f -rGO creates conductive interconnections between the graphene nanosheets, improving the electrical conductivity of the final pigments [31]. Similar, to our previous study [31], it was found that the best interaction between the ink and the substrate, and thus the best printing quality, was obtained with a common high glossy photo paper (Figure 10b).…”

“…These systems frequently present silver inhomogeneity issues [20,27] since producing stable AgNPs in water-based inks is challenging or requires time-consuming and complex methods [20,28,29]. However, the f -rGO derivative [6] that has been successfully used before for the development of hydrophilic and highly conductive composites such as f -rGO/Ag nanowires [30] and f -rGO/Ag nanoparticles (f -rGO/AgNPs) [31], favors the preparation of stable graphene/Ag conductive inks. Specifically, it has been shown that such hybrid carbon-based materials remain water-dispersible without the need for any additive, and of low sheet resistance without the necessity of sintering or annealing.…”

“…Specifically, it has been shown that such hybrid carbon-based materials remain water-dispersible without the need for any additive, and of low sheet resistance without the necessity of sintering or annealing. Especially, in the case of f -rGO/AgNPs [31], it was found that the carbon substrate (e.g., f -rGO or few-layered graphene nanosheets) had a crucial role in determining the morphology and the properties of the final hybrid, while AgNPs are much better dispersed in f -rGO than in the few-layered graphene nanosheets. Also, it was found that the homogeneous dispersion of AgNPs on the f -rGO creates conductive interconnections between the graphene nanosheets, improving the electrical conductivity of the hybrid.…”