Probing the Interaction of Poly(vinylpyrrolidone) with Platinum Nanocrystals by UV−Raman and FTIR

Abstract

The vibrational spectra of platinum nanoparticles (2.4-9 nm) capped with poly(N-vinylpyrrolidone) (PVP) were investigated by deep UV-Raman and FTIR spectroscopy and compared with those of pure PVP. Raman spectra of PVP/Pt show selective enhancement of C=O, C-N, and CH2 vibrational modes attributed to the pyrrolidone ring. Selective enhancement of ring vibrations is attributed both to the resonance Raman effect and SERS chemical enhancement. A red shift of the PVP carbonyl frequency on the order of 60 cm-1 indicates the formation of strong >C=O-Pt bonds. It is concluded that PVP adheres to the nanoparticles through a charge-transfer interaction between the pyrrolidone rings and surface Pt atoms. Heating the Pt nanoparticles under reducing conditions initiates the decomposition of the capping agent, PVP, at a temperature 100 degrees C below that of pure PVP. Under oxidizing conditions, both PVP/Pt and PVP degrade to form amorphous carbon.

Total oxidation of naphthalene using palladium nanoparticles supported on BETA, ZSM-5, SAPO-5 and alumina powders

“…The XPS binding energies revealed the presence of two peaks corresponding to the 3d 3/2 and 3d 5/2 transitions. In the case of prepared samples, the presence of Pd (II) on the surface of the Pd nanoparticles is attributed to the carbonyl function of the protecting polymer interacting with the metallic palladium, removing electron density from the surface, as has been established in our previous work [24] and by Somorjaiet al for Pt nanoparticles capped with this kind of agent [31][32][33]. In short, what appears in this case as Pd(II) in the XPS spectra, is attributed to the palladium atoms on the surface of the nanoparticle, which are electron deficient due to their interaction with the protecting polymer.…”

Inquiring the mechanism of formation, encapsulation, and stabilization of gold nanoparticles by poly(vinyl pyrrolidone) molecules in 1-butanol

“…2. As noticed from the spectrum (b), a visible amplification in band intensity in C-H (2,961, 2,936, 2,872 cm -1 ) stretching in the pyrrolidone ring of PVP molecules was observed and occurs only when PVP molecules get adsorbed on the surface of NP via nonbonding electron of O-atom of lactam unit (Borodko et al 2006). Our earlier reports on gold and fullerene (C 60 ) nanofluids showed similarly enhanced intensities in those vibrational bands of PVP owing to chemisorption via O-atom of pyrrolidone ring onto the gold and C 60 nanosurfaces, respectively (Behera and Ram 2012a, b, c).…”

“…It was reported that PVP reduce gold ions to Au atom and subsequently encapsulate those metal NPs via O-atom of pyrrolidone ring (Hoppe et al 2006;Xian et al 2012;Zhou et al 2009). PVP forms a charge transfer (CT) complex with Pt NPs via nonbonding electron transfer from the O-atom to the electron-deficient NP (Borodko et al 2006). As reported by Xian et al, PVP ligand interacts with Pd NPs through O-atom of pyrrolidone ring.…”

“…Raman spectrum exhibits selective enhancement of C=O (1,656 cm -1 ), CH 2 bending (1,453, 1,442, 1,421, 1,371, 1,307 cm -1 ), and C-N (1,490 cm -1 ) vibrational modes of PVP in the presence of GNPs attributed to the surfaceenhanced Raman scattering (SERS) chemical enhancement. SERS effect results in when PVP molecules get adsorbed via O-atom (C=O group) of pyrrolidone ring on the surface of GNP through a donor-acceptor type interaction between two interacting moieties (Borodko et al 2006). Zeta potential and XPS spectra…”

Effect of organic capping layers over monodisperse platinum nanoparticles upon activity for ethylene hydrogenation and carbon monoxide oxidation

“…PVP, the most studied of these capping agents, decomposed to form carbonaceous materials, which covered a portion of the Pt surface. 5,11,12 Consequently, the effective particle size calculated from the metal dispersion will not reflect the true particle size. These factors are demonstrated when comparing the dispersions obtained after treatments at different temperatures.…”