Development of n-type silver-nanoparticles-modified carbon materials doped by triphenylphosphine
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Research Letter
Development of n-type silver-nanoparticles-modified carbon materials doped by triphenylphosphine Akira Ohnuma and Kouta Iwasaki, Research Laboratories, Toyota Boshoku Corporation, Kariya, Aichi 448-8651, Japan Address all correspondence to Akira Ohnuma at [email protected] (Received 22 March 2017; accepted 20 June 2017)
Abstract Here we report a doping method based on charge transfer interaction for an easily obtainable carbon material, carbon black (acetylene carbon black and Ketjenblack), as a main raw material. The n-type doping of those carbon blacks, generally p-type material, was conducted with a molecular dopant, triphenylphosphine (tpp). The key was to modify the surface of carbon blacks with silver (Ag) nanoparticles to attach tpp molecules on the surface of Ag. Our method is expected to be used for the fabrication of functional devices (such as thermoelectric devices) from p- and n-type materials.
Introduction Increasing attention has been paid to nanometer-sized carbon materials, including carbon black, carbon nanotubes, and graphene because of their unique mechanical, thermal, and electrical properties.[1–3] The p- and n-type doping of carbon materials through charge–transfer interaction has been investigated as an important technique of the functionalization, such as for thermoelectric power generation with π-shaped modules.[4–6] Since carbon materials are generally p-type and there are essentially only a few reports on n-type doping of carbon materials, the development of n-type doping method is still desirable. Nonoguchi et al.[4] reported that absorption of molecular dopants altered the type of majority carriers of pristine single-walled carbon nanotubes (SWNTs) from positive to negative, and they displayed a relatively large Seebeck coefficient (S = −72 µV/K at 310 K) of the flexible film fabricated from phosphine-doped SWNTs (i.e., the electrons from phosphine molecules compensated the holes in p-type SWNTs and further electron transfer induced n-type charge carriers and increased the n-type thermoelectric power).[4] Matsumoto et al.[5] reported that thermoelectric properties of commercially available graphite sheets could be manipulated by intercalating chemical species into the graphite interlayers, and they showed a Seebeck coefficient (S = −58 µV/Κ at room temperature) and a large power factor (σS2 > 10−2 W/m/K2 at room temperature, σ stands for the electrical conductivity) of the sheet with potassium–graphite intercalation compounds.[5] In spite of their successes, there has been essentially no report about the functionalization of carbon blacks with such doping method even though it should be easy to use them for large-scale production because of the lower price compared with other carbon materials.[7]
In the present study, therefore, we tried to fabricate an n-type material using an easily obtainable carbon material, carbon black [acetylene carbon black (AB) and Ketjenblack (KB)], as a main raw material. The n-type doping of those carbon blacks, generally p-type m
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