ORIENTAL JOURNAL OF CHEMISTRY
www.orientjchem.org
An International Open Access, Peer Reviewed Research Journal
ISSN: 0970-020 X
CODEN: OJCHEG
2019, Vol. 35, No.(3):
Pg. 1054-1061
This is an Open Access article licensed under a Creative Commons license: Attribution 4.0 International (CC- BY).
Published by Oriental Scientific Publishing Company © 2018
Rhodamine-triazole Functionalized Fe
3
O
4
@SiO
2
Nanoparticles
as Fluorescent Sensors for Heavy Metal Ions
KANOKORN WECHAKORN
1
*, PAIRSUNAN CHANPANICH
2
, PIMFA KAMKALONG
2
and SURANAN ANANTACHISILP
2
1
Department of Chemistry, Faculty of Science and Technology, Rajamangala University of Technology
Thanyaburi, Pathum Thani 12110, Thailand.
2
Kamnoetvidya Science Academy, Rayong 21210, Thailand.
*Corresponding author E-mail: kanokorn_w@rmutt.ac.th
http://dx.doi.org/10.13005/ojc/350318
(Received: May 30, 2019; Accepted: June 06, 2019)
ABSTRACT
Rhodamine-triazole sensor functionalized Fe
3
O
4
@SiO
2
nanoparticles were developed for the
detection of heavy metal ions, namely Cu
2+
, Ni
2+
, Hg
2+
, Co
2+
, Fe
3+
, and Pb
2+
. Rhodamine conjugated
with a triazole moiety (RBT) was utilized as the metal ion binding site. The RBT-Fe
3
O
4
@SiO
2
nanoparticles were fully characterized by XRD, FTIR, TGA, SEM and TEM techniques. Additionally,
RBT-functionalized Fe
3
O
4
@SiO
2
nanoparticles can be separated from aqueous phase by application
of an external magnet, leading to clear naked-eye observation of the color changes and fluorescence
enhancement. From UV-Vis absorption spectra, aqueous solutions of RBT-Fe
3
O
4
@SiO
2
in the
presence of heavy metal ions show an absorption peak at 554 nm. Fluorescence titration experiments
reveal that the intensity of the fluorescence emission band at 574 nm is linearly dependent on Cu
2+
concentration over a 100-800 μM range. Furthermore, complexation of Cu
2+
by RBT-Fe
3
O
4
@SiO
2
nanoparticles can induce ring-opening of the rhodamine spirolactam ring followed by hydrolysis,
confirmed by mass spectrometry.
Keywords: Fluorescent sensor, Magnetic nanoparticles, Heavy metal ions, Triazole, Rhodamine.
INTRODUCTION
Contamination of water sources by heavy
metal ions (e.g. Co
2+
, Cu
2+
, Fe
3+
, Hg
2+
, Ni
2+
and Pb
2+
)
is a major environmental concern. In addition, their
toxicity and accumulation in living organisms can
have profound impacts on the overall ecology of
environmental systems. Accordingly, great effort is
being extended into devising ways of removing such
pollutants and the development of new analytical
tools for their detection. Although conventional
analytical techniques such as atomic absorption
spectrometry (AAS)
1
, flame atomic absorption
spectroscopy (FAAS)
2
, inductively coupled plasma
mass spectrometry (ICP-MS)
3
and voltammetry
4
are typically used in metal ion detection, they have
drawbacks in requiring expensive and sophisticated
hardware, long analysis time, and a high level of
technical expertise. Fluorescence spectroscopy, on
the other hand, is an emerging technique for metal