Surface-Enhanced Raman Scattering of MEH-PPV on Gold and Silver Nanoparticles

Abstract

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.

MEH‐PPV/SBS composite films: Localization and luminescence properties of conductive polymers with microphase separation

“…The Raman spectra of the MEH‐PPV film and MEH‐PPV/SBS composite film ( ε = 1/30) are shown in Figure 1B, while those of the SBS, MEH‐PPV/PS, and MEH‐PPV/PB films are shown in Figure S1 in the Supporting Information. The characteristic peaks of MEH‐PPV at 1578 cm −1 (attributed to ring ν (CC)), 1302 cm −1 (attributed to vinyl ν (CC) and δ (CC–H)), 1274 cm −1 (attributed to the ring ν (CC) and δ (CCH)), 1104 cm −1 , and 954 cm −1 (attributed to β (CCH)) were observed in the spectra of the MEH‐PPV film 21 and MEH‐PPV/SBS composite. However, the peaks due to SBS (992 cm −1 , attributed to the ν (CC) of the PB unit) 22 were observed only in the spectrum of the MEH‐PPV/SBS composite film, confirming that MEH‐PPV was composited in the SBS film without any chemical modification.…”

In Situ Surface-Enhanced Raman Spectroscopy on Organic Mixed Ionic-Electronic Conductors: Tracking Dynamic Doping in Light-Emitting Electrochemical Cells

“…This similarity indicates our ability to track the doping profile of MEH-PPV within the LEC device. The strong band at 1580 cm –1 corresponds to the symmetric CC stretching vibration of the phenyl ring, − while two adjacent weaker bands at 1621 and 1554 cm –1 are attributed to the asymmetric CC stretching of vinylene and the CC stretching on the phenyl, respectively. ,, The two bands observed at 1307 and 1283 cm –1 are associated with the asymmetric CC stretching and CC interring stretching coupled with CC–H bending of the phenyl ring, respectively. ,,, It is worth noting that a weaker peak linked to vinylene CC–H bending might be expected around 1330 cm –1 , but it could be overshadowed by a neighboring strong band. , The results also reveal a weak peak around 1180 cm –1 , attributed to CC–H ring bending, and a band at 1108 cm –1 , which emerges from the mixing of C–C stretching and C–H in-plane-bending vibrations within the phenyl group. − The band at 963 cm –1 is attributed to the out-of-plane CH bending of the vinylene group. This particular vibration arises from the dihedral angle between two monomer units, which is forbidden in the Raman spectrum of planar polymer configuration. , …”

“…The strong band at 1580 cm –1 corresponds to the symmetric CC stretching vibration of the phenyl ring, 54 − 57 while two adjacent weaker bands at 1621 and 1554 cm –1 are attributed to the asymmetric CC stretching of vinylene and the CC stretching on the phenyl, respectively. 54 , 58 , 59 The two bands observed at 1307 and 1283 cm –1 are associated with the asymmetric CC stretching and CC interring stretching coupled with CC–H bending of the phenyl ring, respectively. 54 , 56 , 57 , 60 It is worth noting that a weaker peak linked to vinylene CC–H bending might be expected around 1330 cm –1 , but it could be overshadowed by a neighboring strong band.…”

“… 61 , 62 The results also reveal a weak peak around 1180 cm –1 , attributed to CC–H ring bending, and a band at 1108 cm –1 , which emerges from the mixing of C–C stretching and C–H in-plane-bending vibrations within the phenyl group. 55 − 58 The band at 963 cm –1 is attributed to the out-of-plane CH bending of the vinylene group. This particular vibration arises from the dihedral angle between two monomer units, which is forbidden in the Raman spectrum of planar polymer configuration.…”