Low dimensional metallic nanostructures have seen a lot of recent attention, due to their potential across printed electronics, wearable electronics, catalysis and sensor applications. However, most synthetic development processes rely on inorganic/organic or polymeric additive materials to direct and define the shape and dimension of the structure through templating-mediated synthesis.
This in turn has created a problem, in that, for metal nanostructure products to be used, the templating materials must be removed through complex procedures post-synthesis.
A team of Researchers from South Korea have now produced a method for the low-temperature and additive-free synthesis of nanobelt-like silver-nanocarbon hybrid nanostructures.
Low dimensional metallic nanostructures have the potential to be used across a myriad of applications. Through the hybridization of metal substrates, by either spin coating or fiber spinning approaches, various forms of carbon nanostructures can be produced as flexible and stretchable electrodes.
However, in the real-world and the commercial sector, these materials have yet to reach their potential as they have been limited by the low electrical conductivity of nanocarbon materials after solution processing. It has been possible to overcome this using metal additives, but to date have required a complex process for their removal post-synthesis.
The Researchers from South Korea have looked towards nature and employed a biologically inspired approach. Commonly referred to as biomineralization-inspired approach, the Researchers established a shape control process, facilitated by introduction of supramolecular 2-ureido-4[1H]pyrimidinone (UPy) groups onto the nanocarbon surface via a nanocarbon-mediated nucleation reaction.
The resulting product was multi-walled carbon nanotubes (MWCNT), or graphene, fictionalized with carboxylic acid groups, whereupon UPy and silver were added in to form a 1D metal-nanocarbon hybrid nanobelt material.
To characterize the nanostructures, the Researchers used a combination of field-emission scanning electron microscopy (FE-SEM, HITACHI S4800), transmission electron microscopy (TEM) and selected-area electron diffraction (SAED) (Titan G2 60–300, FEI), X-ray diffraction (XRD, Philips PW 3830), confocal Raman spectrometry (NTEGRA SPECTRA, NT-MDT), X-ray photoelectron spectroscopy (XPS, Multilab2000, Thermo VG Scientific Inc), thermogravimetric analysis (TGA, TGA Q500, TA Instruments) and a four-point probe electrical conductivity method (MCP-T610, Loresta).
The reaction was performed at room temperature, and was due to UPy groups possessing the ability to control the kinetics of the reaction by providing multiple interaction points with the silver ions using a slow hydrazine reduction method. Evidence of formation was provided through the detachment of UPy groups from the nanocarbon surface.
Many advantages have been found with this strategy, but the most prominent and useful advantage is the ability to easily control the silver structure, without the need for extra templating agents that would require removal of post-synthesis.
Upon realizing that the structure had formed correctly, the Researchers set to work applying it to different flexible electronic devices. The Researchers took the silver nanobelt/CNT hybrid material and used it to create a highly conductive and stretchable fiber, with a conductivity greater than 1000 S/cm (S=Siemens, which is colloquial with Amplitude/Voltage, or Ω-1), in order to produce a material that could be used as both a conformable electrode or a highly tolerant strain sensor.
As a second application, the Researchers fabricated highly conductive and robust paper-like sheets, which possessed a conductivity of 10000 S/cm after thermal treatment. These were achieved using a silver nanobelt/graphene hybrid and displayed a high stability when it was folded or crumpled.
It is thought that the production of template-free 1D hybrid nanostructures will set a precedence for future work in this area and will open-up new opportunities towards the development of novel nanocarbon/nanometal hybrid materials, with use as conformable electrodes and sensors in wearable/flexible electronic devices.
“Synthesis of nanobelt-like 1-dimensional silver/nanocarbon hybrid materials for flexible and wearable electronics”- Han J. T., Scientific Report, 2017, DOI:10.1038/s41598-017-05347-4