Characterization of Colloidal Platinum Nanoparticles by MALDI-TOF Mass Spectrometry

Abstract

In this work, matrix assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry has been applied to characterize colloidal platinum nanoparticles synthesized in the 1 to 4 nm size range. These nanoparticles were prepared via a solution-based method in which the size could be tuned by varying reaction conditions, such as the alcohol used as a reductant. Poly(vinylpyrrolidone), or PVP, (MW = 29,000) was utilized as a capping agent to stabilize the synthesized particles in solution. A model for determining the size of the metallic nanoparticle core has been developed and verified through correlation with results from transmission electron microscopy (TEM) and x-ray diffraction (XRD) measurements. In addition, experiments performed with capped and uncapped nanoparticles indicate that one nanoparticle is capped by one PVP chain. These findings clearly indicate the usefulness of MALDI-TOF mass spectrometry as a technique for fully characterizing nanoscale materials, as well as to provide further insight into the role of the PVP capping agent during catalytic reactions in solution.

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.…”

“…In the case of metal oxide catalysts [7] such as CeO 2 or mixed oxides (CuZnO) full conversion is reached at temperatures between 250ºC and 270ºC, respectively. Whilst for the case of metals supported on different oxides such as Pt/SiO 2 [33] the optimum temperature for naphthalene oxidation was 250ºC. Shie et al [34] indicated that Pt/γ-alumina decreased the reaction temperature for 95% naphthalene total oxidation to 207ºC.…”

Mass spectrometry for the characterization and quantification of engineered inorganic nanoparticles

“…A model for determining the size of the metallic nanoparticle core from MALDI-TOF mass spectra is proposed here and results were successfully verified by the correlation with particle sizes figures obtained by transmission electron microscopy and X-ray diffraction [65].…”

“…In one of the first reports on NPs analysis by MALDI-MS, the technique was utilized to characterize platinum NPs, synthesized in the 1-4 nm size range, and capped with Poly(vinylpyrrolidone), PVP, in order to stabilize the PtNPs in solution [65]. A model for determining the size of the metallic nanoparticle core from MALDI-TOF mass spectra is proposed here and results were successfully verified by the correlation with particle sizes figures obtained by transmission electron microscopy and X-ray diffraction [65].…”

A General Perspective of the Characterization and Quantification of Nanoparticles: Imaging, Spectroscopic, and Separation Techniques

“…LDI can be applied to aerosol characterization by aerosol time-of-flight mass spectrometer (ATOF-MS), 13 providing valuable insights for functionalized NPs also by using time of flight (TOF) as detection system. 260,261 The LOD of element gold can be as low as 1 part per trillion (pg·mL -1 ).…”