Issue 1, 2010

Functionalized monolayers on mesoporous silica and on titaniananoparticles for mercuric sensing

Abstract

Heterogeneous “naked-eye” colorimetric and spectrophotometric cation sensors were prepared by immobilization of an azobenzene-coupled receptor onto mesoporous silica (AR-SiO2) or titania nanoparticles (AR-TiO2) via sol–gel or hydrolysis reactions. The optical sensing ability of AR-SiO2 was studied by addition of metal ions such as K+, Ca2+, Sr2+, Co2+, Cd2+, Pb2+, Zn2+, Fe3+, Cu2+ and Hg2+ ions (all as chlorides) in aqueous solution. Upon the addition of Hg2+ ion in suspension, the AR-SiO2 resulted in a color change from yellow to deep red. No significant color changes were observed in the parallel experiments with K+, Ca2+, Sr2+, Co2+, Cd2+, Pb2+, Zn2+, Fe3+ or Cu2+ ion. These findings confirm that the AR-SiO2 can be useful as chemosensors for selective detection of Hg2+ ion over a range of metal ions in aqueous solution. Also, the color change of AR-SiO2 was independent of the presence of anions NO3, ClO4, Br and I. We also prepared a portable chemosensor kit by coating a 4 μm thick film of AR-TiO2 onto a glass substrate. We found that this AR-TiO2 film detects Hg2+ ion at pH 7.4 with a sensitivity of 28 nM. Finally, we tested the effect of pH on AR-TiO2 with Hg2+ ion between pH 1.0 to 11.0. The absorbance and color changes of AR-TiO2 were almost constant between pH 4 and 11. The results imply that the AR-TiO2 film is applicable as a portable colorimetric sensor for the detection of Hg2+ ion in the environmental field.

Graphical abstract: Functionalized monolayers on mesoporous silica and on titania nanoparticles for mercuric sensing

Supplementary files

Article information

Article type
Paper
Submitted
04 Aug 2009
Accepted
04 Nov 2009
First published
13 Nov 2009

Analyst, 2010,135, 149-156

Functionalized monolayers on mesoporous silica and on titania nanoparticles for mercuric sensing

E. Kim, S. Seo, M. L. Seo and J. H. Jung, Analyst, 2010, 135, 149 DOI: 10.1039/B915975D

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