Role of protolytic interactions in photo-aging processes of carminic acid and carminic lake in solution and painted layers (Articolo in rivista)

Type

• Prodotto della ricerca (Classe)
• Articolo in rivista (Classe)

Label

• Role of protolytic interactions in photo-aging processes of carminic acid and carminic lake in solution and painted layers (Articolo in rivista) (literal)

Anno

• 2002-01-01T00:00:00+01:00 (literal)

Alternative label

• Favaro G. 2, Miliani C. 1, Romani A. 2, Vagnini M. 2 (2002)
  Role of protolytic interactions in photo-aging processes of carminic acid and carminic lake in solution and painted layers
  
  (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori

• Favaro G. 2, Miliani C. 1, Romani A. 2, Vagnini M. 2 (literal)

Pagina inizio

• 192 (literal)

Pagina fine

• 197 (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#altreInformazioni

• L`articolo e` pubblicato dalla Royal Society of Chemistry in rivista con I.P. = 1.911 (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#descrizioneSinteticaDelProdotto

• Lo studio della fotochimica e della fotofisica del acido carminico e dalla lacca carminio in funzione del pH ha permesso di stabilire il ruolo del processo di trasferimento di protone nell`interazione del colorante con il suo microambiente chimico (legante o vernice). Il lavoro fornisce quindi una valida comprensione dei processi che sono alla base del degrado dei coloranti antrachinonici nelle pellicole pittoriche esposte alla luce solare. (literal)

Note

• ISI Web of Science (WOS) (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni

• 1 CNR-ISTM sez. di Perugia 2 Università di Perugia (literal)

Titolo

• Role of protolytic interactions in photo-aging processes of carminic acid and carminic lake in solution and painted layers (literal)

Abstract

• In this paper absorption and fluorescence spectra and emission quantum yields and lifetimes of the red colorants, carminic acid and its metal complex, carminic lake, were studied in solution and on painted surfaces. Accelerated photo-aging of carminic acid and lake was investigated in solution, in the presence and absence of a binder (arabic gum) commonly used in water-colour painting, while natural ageing was followed for several months on water-colour painted paper. The study of carminic acid in water as a function of pH showed that the absorption spectrum changes with pH. Four acid–base dissociation steps were detected and the corresponding pKs were determined from spectrophotometric and fluorimetric titrations. The fluorescence quantum yields (in the 10-2–10-4 range) and the lifetimes (on the sub-nanosecond timescale, 90–1000 ps) were markedly dependent on the pH of the medium. Excited state pK*s were calculated by means of the Förster cycle. The acidity decreased upon excitation for the first deprotonation step involving the –COOH group (DpK* = -1.9), but increased slightly for the successive deprotonation steps involving three phenolic hydroxy groups (DpK* = 0.6, 2.0 and 0.2, respectively). The results obtained from the aging experiments indicate that both carminic acid and lake are bleached during irradiation. While the binder prevents lake from fading, it destabilises the carminic acid. These findings are discussed in the light of the interactions of the dye with the solvent and matrix. (literal)

Prodotto di

• Institute of molecular science and technologies (ISTM) (Istituto)

Autore CNR

• COSTANZA MILIANI (Unità di personale interno)

Insieme di parole chiave

• Keywords of "Role of protolytic interactions in photo-aging processes of carminic acid and carminic lake in solution and painted layers" (Insieme di parole chiave)

Incoming links:

Prodotto

• Institute of molecular science and technologies (ISTM) (Istituto)

Autore CNR di

• COSTANZA MILIANI (Unità di personale interno)

Insieme di parole chiave di

• Keywords of "Role of protolytic interactions in photo-aging processes of carminic acid and carminic lake in solution and painted layers" (Insieme di parole chiave)