ORIGINAL PAPER
Aqueous Synthesis of Nontoxic Ag
2
Se/ZnSe Quantum Dots
Designing as Fluorescence Sensors for Detection of Ag(I)
and Cu(II) Ions
Chunlei Wang & Shuhong Xu & Zengxia Zhao & Zhuyuan Wang &
Yiping Cui
Received: 25 July 2014 /Accepted: 23 October 2014 /Published online: 14 November 2014
#
Springer Science+Business Media New York 2014
Abstract We reported the synthesis of water-soluble and
nontoxic Ag
2
Se/ZnSe Quantum Dots (QDs) using for fluores-
cence sensors. The influences of various experimental condi-
tions including the synthesis pH, types of ligand, feed ratios,
and the refluxed time on the growth process and fluorescence
of QDs were investigated in detail. Under optimal conditions,
Ag
2
Se/ZnSe QDs show a single emission peak around 490 nm
with the maximal photoluminescence (PL) quantum yield
(QYs) of 13.7 %. As-prepared Ag
2
Se/ZnSe QDs can be used
for detection of Ag(II) and Cu(II). The detection limits are 1×
10
−6
mol/L to 5×10
−5
mol/L for Ag (I), and 2×10
−6
mol/L to
1.10×10
−4
mol/L for Cu(II).
Keywords Ag
2
Se/ZnSe
.
Quantum dots
.
Fluorescence
sensors
Introduction
Due to the high cytotoxicity of Cd-contained QDs, more
attention has been paid to nontoxic Zn-contained QDs [1–3].
Since the emission of pure ZnSe QDs is located in the ultra-
violet range, metal impurities are often added as dopant into
crystalline of the ZnSe QDs to modulate the emission of ZnSe
QDs into the visible range. Due to the lattice mismatch of the
dopant with QDs, metal impurities tend to present on the
surface of QDs. The PL of these surface doped QDs is easily
quenched when QDs surface conditions change in different
application surroundings [4]. To avoid the PL quenching, the
impurities are required to dope inside QDs. In 2009, Zhang’s
group reported the first case of internally doped Cu:ZnSe and
Mn:ZnSe QDs in aqueous solution [5]. They found that these
water-soluble internally doped Cu:ZnSe QDs had extremely
weak chemical stability in the open air due to the inevitable
oxidation of mercapto-ligands by Cu impurities. This huge
disadvantage makes these internally doped water-soluble
Cu:ZnSe QDs impossible to apply in biology. Then, we
reported the first example of water-soluble Cu:ZnSe/ZnS
QDs with excellent stability [6]. The key for the excellent
stability of as-prepared QDs is attributed to the simultaneous
preparation of core-shell QDs and internally doped impurities.
Although we improve the stability of water-soluble doped
Cu:ZnSe QDs using ZnS shell, the preparation of shell in this
paper is complex, and cost more materials. In addition, PL
intensity of water-soluble doped ZnSe is weak. This would
limit their development in application field. In this paper,
Ag
2
Se/ZnSe core-shell QDs have been synthesized. The pre-
pared Ag
2
Se/ZnSe QDs not only has good stability but also
has better PL. Moreover, our QDs are synthesized in aqueous
solution and do not contain toxic component. Thus, they can
be used in sensitive sensors field. As we have known, there is
no report on water-soluble Ag
2
Se/ZnSe QDs using to detect
Ag(I) and Cu(II) ions.
Experimental Section
Chemicals
All materials used in this work were analytical reag ents.
Zn(NO
3
)
2
and AgNO
3
were purchased from Beijing Chemical
Factory. NaBH
4
was purchased from Guangdong Chemical
Reagent Engineering Technological Research and Develop-
ment Center. NaOH was purchased from Shanghai Zhongshi
Chemical Company. 3-Mercaptopropionic acid (MPA), 1-
C. Wang
:
S. Xu
:
Z. Zhao
:
Z. Wang
:
Y. C u i ( *)
Advanced Photonics Center, School of Electronic Science and
Engineering, Southeast University, Nanjing 210096, People’s
Republic of China
e-mail: cyp@seu.edu.cn
J Fluoresc (2015) 25:41–48
DOI 10.1007/s10895-014-1476-y