Spectroscopic study of maghemite nanoparticles surface-grafted with DMSA.
Nanosized maghemite (below 10 nm average diameter), surface-functionalized with meso-2,3-dimercaptosuccinic acid (DMSA), was investigated with respect to the content of DMSA molecules attached onto its surface and the onset of S-S bridges due to oxidation of neighboring S-H groups. To support our investigation, we introduced the use of photoacoustic spectroscopy to monitor thiol groups (S-H) conjugated with Raman spectroscopy to monitor the disulfide bridges (S-S). The normalized intensity (N(R)) of the Raman feature peaking at 500 cm(-1) was used to probe the S-S bridge whereas the normalized intensity (N(P)) of the photoacoustic band-S (0.42-0.65 μm) was used to probe the S-H moiety. The perfect linearity observed in the N(R) versus (1 - N(P)) plot strongly supports the oxidation process involving neighboring S-H groups as the DMSA surface grafting coefficient increases whereas the approach used in this report allows the evaluation of the [S-H]/[S-S] ratio. The observation of the reduction of the hydrodynamic diameter as the nominal DMSA-grafting increases supports the proposed model picture, in which the intraparticle (interparticle) S-S bridging takes place at higher (lower) DMSA-grafting values.
Instituto de Física, Universidade de Brasília, Brasília DF, Brazil.
Maria A G
MA
Soler
Emilia C D
EC
Lima
Eloiza S
ES
Nunes
Fabio L R
FL
Silva
Aderbal C
AC
Oliveira
Ricardo B
RB
Azevedo
Paulo C
PC
Morais
D005290:Ferric Compounds / Q000737:chemistry*; D057446:Hydrodynamics; D046529:Microscopy, Electron, Transmission / Q000379:methods; D008956:Models, Chemical; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D010084:Oxidation-Reduction; D013057:Spectrum Analysis / Q000379:methods; D013059:Spectrum Analysis, Raman; D004113:Succimer / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013499:Surface Properties; D014961:X-Ray Diffraction / Q000379:methods
D005290:Ferric Compounds; D013438:Sulfhydryl Compounds; C000499:ferric oxide; D004113:Succimer