Combined Experimental and Computational Investigation of the Fluorescence Quenching of Riboflavin by Cinnamic Alcohol Chemisorbed on Silica Nanoparticles

VALERIA B. ARCE; JULIANA SCOTTO; PATRICIA E. ALLEGRETTI; MAURICIO A. MELO; CLAUDIO AIROLDI; MARÍA LAURA SALUM; ROSA ERRA-BALSELLS; REINALDO PIS DIEZ; DANIEL O. MÁRTIRE

JOURNAL OF PHYSICAL CHEMISTRY C

AMER CHEMICAL SOC

Lugar: Washington; Año: 2014 vol. 118 p. 15348 - 15355

1932-7447

Abstract Riboflavin (vitamin B2) is usually present in water courses, lakes and seas, and acts as a photosensitizer in the photoxidation of a range of contaminants. However, little is known about the interaction of this compound with aromatics sorbed on silica sediments or on suspended silica particles. This article describes the modification and characterization of silica nanoparticles by condensation of the silanol groups of the particles with E-cinnamic alcohol. The reaction was confirmed by FTIR, solid-state 13C and 29Si Cross-Polarization MAS (CPMAS) NMR, reduction of the specific surface area measured by BET, thermal analysis, and fluorescence spectroscopy. Toxicity to the marine bacteria Vibrio fischeri of the modified particles was also measured. Riboflavin fluorescence was quenched in aqueous medium in the presence of dissolved E-cinnamic alcohol or in suspensions of the modified particles. The results are interpreted in terms of formation of 1:1 complexes between the ground-states of riboflavin and the free or adsorbed cinnamic alcohol. DFT calculations in aqueous medium support the existence of the complex and explain the observed quenching of riboflavin fluorescence upon addition of cinnamic alcohol without affecting the emission maximum of riboflavin.