The interaction of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) with Au or Ag nanospheres, Au nanostars, and Ag nanoprisms was investigated using surface-enhanced Raman scattering (SERS). The SERS investigation showed that adsorption of MEH-PPV strongly depends on the nature of the nanoparticle surface. On gold nanostars that present a thick layer of capping polymer, SERS spectrum is only observed in relatively concentrated MEH-PPV solution (1 mmol L −1 ). On the other hand, Au and Ag nanospheres present SERS spectra down to 10 −6 mol L −1 and no chemical interaction of MEH-PPV and metal surface is observed. The spectra of MEH-PPV on Ag nanoprisms with PVP as stabilizing agent suggest that the capping polymer induces a planar conformation of MEH-PPV and consequently an increase of conjugation length. These results give support for the application of MEH-PPV on optoelectronics in which interfacial effects are critical in the device efficiency and stability.
Recebido em 29/05/2019; aceito em 30/07/2019; publicado na web em 21/10/2019 TEMPERATURE EFFECTS ON RAMAN SPECTRA OF PEDOT AND MEH-PPV CONDUCTING POLYMERS. The present work shows the temperature dependence of the Raman spectra of two conjugated polymers: poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). In situ resonance Raman spectra of PEDOT from 77 to 423 K at 633 nm and of MEH-PPV from 77 to 473 K at 785 nm suggest that, for both polymers, as the temperature increases there is a decrease in the chain conjugation length. Raman bands of PEDOT assigned to the ν sim C α-C β are the most sensitive to temperature while bands due to oxyethylene rings do not show significant shifts in this temperature range. Raman and FT-IR spectra of MEH-PPV recorded above the thermal decomposition temperature provide some insights about the thermal degradation.
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