Reactivity of ZrO(MFP) and ZrO(RP) Nanoparticles with LnCl3 for Solvatochromic Luminescence Modification and pH‐Dependent Optical Sensing

• Published in: Chemistry : a European journal Vol. 25; no. 72; pp. 16630 - 16638
• Main Authors: Wehner, Tobias, Heck, Joachim, Feldmann, Claus, Müller‐Buschbaum, Klaus
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 20.12.2019; John Wiley and Sons Inc
• Subjects: Chemistry; Chromaticity; Chromophores; Composite materials; Dichloromethane; Fluorescence; Halides; lanthanides; Luminescence; Metal ions; Nanoparticles; organic–inorganic hybrid composites; Particulate composites; pH effects; pH sensors; Rare earth elements; Resorufin; sensors; Toluene
• ISSN: 0947-6539; 1521-3765; 1521-3765
• DOI: 10.1002/chem.201903744

The luminescence of the inorganic–organic hybrid nanoparticles ZrO(MFP) (MFP=methylfluorescein phosphate) and ZrO(RP) (RP=resorufin phosphate) was modified by addition of different rare earth halides LnCl3. The resulting composite materials form dispersible nanoparticles that exhibit modified nanoparticle fluorescence depending on the rare earth ion. The resulting chromaticity of the luminescence is further variable by the employment of different solvents for ZrO(MFP)‐based composite systems. The strong solvatochromic effect of the MFP chromophore leads to different luminescence chromaticities of the composite materials between green, yellow, and blue in THF, toluene, and dichloromethane, respectively. The luminescence of ZrO(RP)‐based composite particles can be modified between the red and blue spectral regions in dependence on the applied reaction temperature. Beside a luminescence shift that is derived from nanoparticle modification by LnCl3, a strong turn‐on effect of ZrO(RP) particles results after contact with different Brønsted acids and bases in combination with a respective chromaticity shift. Both effects enable the potential employment of such particles as highly sensitive optical pH sensors. Hybrid nanoparticles: The luminescence of inorganic–organic hybrid nanoparticles ZrO(MFP) (MFP = methylfluorescein phosphate) and ZrO(RP) (RP = resorufin phosphate) was modified by addition of different rare earth halides LnCl3. This resulted in Ln‐dependent solvatochromic luminescence and acid/base‐stimulated optical sensing (see figure).