Investigating the effect of capping agent PVP on the synthesis of silver nanowires by polyol method and its application as flexible transparent conducting electrode

Thu Thi Hoang,Trung Quang Tran

doi:10.32508/stdj.v16i4.1596

Abstract

In this report, we present a rapid and efficient polyol method - the solution-phase approach for the large scale synthesis of silver nanowires with diameters in the range of 40 - 50 nm, and lengths up to 20 μm. Although the polyol process is a popular method of preparing metal nanostructures, so far most of the published works mainly focused on the synthesis process regardless of amount of surfactants. In this article, we successfully synthesized large-scale uniform silver nanowires with high aspect ratios by introducing the long-chain PVP (MW = 58 000) and investigated the effect of the amount of PVP on the synthesis of Ag nanowires by studying their morphologies, structures and optical properties. The dependency of nanowire morphology and aspect ratio on synthesis parameters was shown via SEM images. The diameter of nanowires decreased when the molar ratio of PVP to silver nitrate was increased. Further more, the molar ratios decided the morphology (particle, rod or wire) of the Silve solution. Synthesized silver nanowires were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). This aqueous dispersions of silver nanowires were used to prepare thin, flexible, transparent, conducting films on polyethylene terephthalate substrate (PET) by spraying method. The prepared silver nanowire films on PET substrate had a transparency of 82% and sheet resistance of 10 Ω/□.

Highlights

The demand for printed electronic devices on plastic substrates has generated a need for solution processable flexible electrodes with high transparency and low sheet resistance.Conducting polymers, metal inks, nanoparticulate metal oxides, carbon nanotubes, and graphene have been investigated as potential alternatives to brittle indium tin oxide (ITO), but none can yet TAÏP CHÍ PHAÙT TRIEÅN KH&CN, TAÄP 16, SOÁ T5 - 2013 compete in terms of transparency and sheet resistance.Thin meshes of silver nanowires (Ag-NWs) have recently emerged as promising electrodes due to their ability to provide transmittances greater than 85% at sheet resistances less than 20 Ω /sq [2].For the synthesis of silver nanowires, plenty of chemical routes have been developed during these years
In most of synthetic routes, AgNO3 was usually adopted as the precursor and polyol always acted as both solvent and reducing reagent, while the capping reagent varies in abundance of candidates
Our results showed that when a higher PVP:AgNO3 molar ratios was used the diameter of the nanowires decreased and amount of collected Ag-NWS increased gradually

Summary

Introduction

The demand for printed electronic devices on plastic substrates has generated a need for solution processable flexible electrodes with high transparency and low sheet resistance.Conducting polymers, metal inks, nanoparticulate metal oxides, carbon nanotubes, and graphene have been investigated as potential alternatives to brittle indium tin oxide (ITO), but none can yet TAÏP CHÍ PHAÙT TRIEÅN KH&CN, TAÄP 16, SOÁ T5 - 2013 compete in terms of transparency and sheet resistance.Thin meshes of silver nanowires (Ag-NWs) have recently emerged as promising electrodes due to their ability to provide transmittances greater than 85% at sheet resistances less than 20 Ω /sq [2].For the synthesis of silver nanowires, plenty of chemical routes have been developed during these years. The demand for printed electronic devices on plastic substrates has generated a need for solution processable flexible electrodes with high transparency and low sheet resistance. Soft solution method has been widely considered as the most feasible route to large-scale production of silver nanowires. For the polyol synthesis of silver nanowires (Fig.1), Xia et al [3] had contributed a lot to the basic research and proposed many reasonable and important view-points on the mechanism, which had been widely adopted and accepted by other peer-researchers [3]. In most of synthetic routes, AgNO3 was usually adopted as the precursor and polyol always acted as both solvent and reducing reagent, while the capping reagent varies in abundance of candidates. After Xia et al detected the presence of glycol aldehyde (GA) in the polyol reactive system the reaction formats were elucidated as follows: HOCH2OH CH3CHO + H2O (1) 2Ag+ + 2CH3COOH3 + 2Ag + 2H+ (2)

Methods

Results

Conclusion