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Aggregation and Photophysics of Rose Bengal in Alumina‐Coated Colloidal Suspensions
Author(s) -
Daraio Marta E.,
San Román Enrique
Publication year - 2001
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20010919)84:9<2601::aid-hlca2601>3.0.co;2-x
Subject(s) - chemistry , rose bengal , adsorption , dimer , monomer , photochemistry , fluorescence , colloid , aqueous solution , absorption (acoustics) , nanoparticle , chemical engineering , organic chemistry , polymer , physics , quantum mechanics , engineering , acoustics
The absorption and emission properties of Rose Bengal (RB) have been studied in colloidal suspensions of positively charged alumina‐coated silica nanoparticles (Sil). Experimental spectra can be rationalized by the existence of an equilibrium between aqueous monomers and only one adsorbed species. However, a simple partition or a Langmuir ‐type adsorption‐aggregation equilibrium do not explain the observed results. No evidence regarding the existence of adsorbed monomers is found even at low surface coverage. Aggregation stops at the dimer level, though, at high enough dye concentrations, the surface coverage is almost complete. Comparative experiments performed on negatively charged silica nanoparticles show that monomers are the only species present in this case. Fluorescence experiments on Sil indicate that dimers are fluorescent. Laser excitation of adsorbed dye leads to the formation of RB radical cations, while the dye triplet state is not observed.