Structure modulated charge transfer in carbon atomic wires

Abstract

sp-Hybridized carbon atomic wires are appealing systems with large property tunability. In particular, their electronic properties are intimately related to length, structure, and type of functional end-groups as well as to other effects such as the intermolecular charge transfer with metal nanoparticles. Here, by a combined Raman, Surface Enhanced Raman Scattering (SERS) investigation and first principles calculations of different N,N-dimethylanilino-terminated polyynes, we suggest that, upon charge transfer interaction with silver nanoparticles, the function of sp-carbon atomic wire can change from electron donor to electron acceptor by increasing the wire length. In addition, the insertion into the wire of a strong electrophilic group (1,1,4,4-tetracyanobuta-1,3-diene-2,3-diyl) changes the electron-accepting molecular regions involved in this intermolecular charge transfer. Our results indicate that carbon atomic wires could display a tunable charge transfer between the sp-wire and the metal, and hold promise as active materials in organic optoelectronics and photovoltaics.

Size-selected polyynes synthesised by submerged arc discharge in water

“…In fact, after mixing Ag colloids with the filtered aqueous solution of polyynes after the synthesis, a shoulder at high wavelengths of the plasmonic band appears, as depicted in Figure 3. This allows to have SERS enhancement at 514.5 nm, in agreement with previous results [29,33,41,43].…”

“…Silver colloids (10 -3 M) made by Lee-Meisel method [32], with a size of 60-80 nm of diameter (from SEM image) and showing a plasmonic peak at about 413 nm, were added to the polyynes solution in water 50/50 v/v in order to perform SERS analysis in solution. SERS active substrates made of Ag nanoparticles on silicon were evaporated by Edwards E306A evaporation system, following the procedure reported elsewhere [33]. Solid-state SERS is performed by drop casting the solution of polyynes on the SERS active substrate and SERS spectra were acquired using a Renishaw InVia micro Raman spectrometer (spectral resolution of about 3 cm −1 ) with a laser power of 1 mW at the sample from an argon ion laser (λ=514.5 nm).…”

In situ synthesis of polyynes in a polymer matrix via pulsed laser ablation in a liquid

“…All the differences between the two samples can be caused by the different SERS effects in liquids and solids. 23,37,57 In liquids, polyynes can diffuse and be adsorbed more easily on Ag nanoparticles leading to creation of hot spots which can be very sensitive to the specific polyyne lengths. Conversely, in a solid phase, polyynes and Ag colloids are immobilized in the PVA matrix, and the different chemical environments of polyynes in proximity to metal nanoparticles may lead to a broad band, as observed in a previous work.…”

Hole Transfer in Open Carbynes

“…We discriminate between the terms transport and transfer: transport implies application of electric voltage between electrodes connected at the ends of the system; transfer implies that an extra electron or hole, created, e.g., by reduction or oxidation at a certain site, moves to more favorable sites, without application of external voltage. Experimental [ 1 , 2 , 3 , 4 ] as well as theoretical work [ 5 , 6 , 7 , 8 , 9 ] on charge transport in carbynes has been accomplished. However, it seems that there is no experiment of charge transfer along these molecules, apart from a very recent work [ 9 ].…”

“…Experimental [ 1 , 2 , 3 , 4 ] as well as theoretical work [ 5 , 6 , 7 , 8 , 9 ] on charge transport in carbynes has been accomplished. However, it seems that there is no experiment of charge transfer along these molecules, apart from a very recent work [ 9 ]. In this work, the authors study terminated carbon chains of two to eight carbon atoms, and report that the increase of the wire length alters its function from an electron donor to an electron acceptor, but no transfer rate was reported.…”