In this work, a simple and rapid synthesis method was developed to prepare silver nanoplates (AgNPLs) with a high aspect ratio. A microwave heating process with a high heating rate and uniform heating was used to promote the silver reduction reaction. Silver nitrate (AgNO 3 ) was used as the precursor of AgNPLs, and N,N-dimethylformamide (DMF) played the role of a solvent and reducing agent. Poly(vinylpyrrolidone) (PVP) with a molecular weight of 29,000 and a PVP/AgNO 3 ratio of 10 were used to control the shape of synthesized AgNPLs. By adjusting the optimal microwave heating parameters, temperature ramping rate, reaction time, and reaction temperature, triangular AgNPLs with high aspect ratios could be produced. The synthesized AgNPLs had an edge length up to 700 nm and a thickness of 35 nm with aspect ratios up to 20. The AgNPLs were also used to produce conductive patterns via pen writing with a conductivity of 2 × 10 6 S/ m to demonstrate the feasibility of applying the synthesized nanomaterials for electronic applications.
In this study, an ink formulation was developed to prepare conductive copper thin films with compact structure by using intense pulsed light (IPL) sintering. To improve inter-particle connections in the sintering process, a cuprous oxide shell was synthesized over copper nanoparticles (CuNP). This cuprous oxide shell can be reduced by IPL with the presence of a reductant and fused to form connection between large copper particles. However, the thermal yield stress after strong IPL sintering resulted in cracks of conductive copper film. Thus, a multiple pulse sintering with an off time of 2 s was needed to reach a low resistivity of 10−5 Ω·cm. To increase the light absorption efficiency and to further decrease voids between CuNPs in the copper film, cupric oxide nanoparticles (CuONP) of 50 nm, were also added into ink. The results showed that these CuONPs can be reduced to copper with a single pulse IPL and fused with the surrounding CuNPs. With an optimal CuNP/CuONP weight ratio of 1/80, the copper film showed a lowest resistivity of 7 × 10−5 Ω·cm, ~25% conductivity of bulk copper, with a single sintering energy at 3.08 J/cm2. The ink can be printed on flexible substrates as conductive tracks and the resistance remained nearly the same after 10,000 bending cycles.
In this study, we report a facile and green process to synthesize high-quality and few-layer graphene (FLG) derived from graphite via a liquid exfoliation process. The corresponding characterizations of FLG, such as scanning electron microscopy (SEM), transmission electron microscope (TEM), atomic force microscopy (AFM) and Raman spectroscopy, were carried out. The results of SEM show that the lateral size of as-synthesized FLG is 1–5 μm. The results of TEM and AFM indicate more than 80% of graphene layers is <10 layers. The most surprising thing is that D/G ratio of graphite and FLG are 0.15 and 0.19, respectively. The result of the similar D/G ratio demonstrates that little structural defects were created via the liquid exfoliation process. Electronic conductivity tests and resistance of composite film, in terms of different contents of graphite/polyvinylidene difluoride (PVDF) and FLG/PVDF, were carried out. Dramatically, the FLG/PVDF composite demonstrates superior performance compared to the graphite/PVDF composite at the same ratio. In addition, the post-sintering process plays an important role in improving electronic conductivity by 85%. The composition-optimized FLG/PVDF thin film exhibits 81.9 S·cm−1. These results indicate that the developed FLG/PVDF composite adhesives could be a potential candidate for conductive adhesive applications.
A simple and facile method is developed to prepare photocurable conductive resin for stretchable conductors. To prevent substrate damages, intense pulsed light (IPL) technology was introduced to simultaneously cure photoresins and sinter the silver nanomaterials at room temperature. During the IPL illuminating, the intense pulsed light not only can heat the silver nanomaterials locally but also cure the polymeric resin at the same time. Compared to a regular curing−heating process, this process can form a more effective conductive pathway with a low percolation threshold. The high aspect ratio of AgNWs makes its own low percolation threshold of only 10 wt %. A lower percolation threshold can not only save the amount of expensive conductive materials but also retain the stretchability of elastomer. The combination (AgNWs/Ag flakes) as conductive fillers can maintain great electrical conductivity during the stretching process with only 25 wt % loading of silver. The resistance ratio became only 1.5 times the original under 60% strain. The fast curing and sintering process, low bulk resistivity, and good stretchability of the photocurable resins show great potential for wearable printed electronics.
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