Ratiometric Fluorescence Platform Based on Modified Silicon Quantum Dots and Its Logic Gate Performance

Article abstract of DOI:10.1021/acs.inorgchem.8b00788

A novel optical nanoprobe based on silicon quantum dots (SiQDs) has been assembled through a one-pot low-temperature (40 °C) treatment by using 3-(aminopropyl)trimethoxysilane (APTMS) and ascorbic acid (AA) as two precursors. The water-soluble SiQDs demonstrate intense green luminescence in aqueous environment and the excitation-dependent feature has been explored. Meanwhile, the incorporation of salicylaldehyde (SA) serves to suppress the emission of SiQDs effectively via nucleophilic reaction and an on-off change is observed. Furthermore, the addition of Zn²⁺ can lead to evolution of emission peaks, and the green band at 500 nm gradually shifts toward the blue side at 455 nm. The corresponding ratiometric signal changes (I₄₅₅/I₅₀₀) can accurately determine the Zn²⁺ concentration and the limit of detection is calculated to be 0.17 μM in the linear range between 1 and 100 μM. In this research, a molecular logic gate (AND) system has been well established by using SA and Zn²⁺ as two inputs. The fluorescence emission changes based on SiQDs will shed new light on the development of functional sensors at the nanoscale level.

Full text of DOI:10.1021/acs.inorgchem.8b00788

Article
pubs.acs.org/IC
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
Ratiometric Fluorescence Platform Based on Modified Silicon
Quantum Dots and Its Logic Gate Performance
Xiangqian Li,†,‡ Zhan Zhou,*,∥ Cheng Cheng Zhang,⊥ Yuhui Zheng,‡ Jinwei Gao,§
and Qianming Wang*,†,‡
†Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education, School of Chemistry & Environment, ‡School of
§
Chemistry & Environment, and Guangdong Provincial Engineering Technology Research Center For Transparent Conductive
Materials, South China Normal University, Guangzhou 510006, China
∥College of Chemistry and Chemical Engineering, Henan Key Laboratory of Function-Oriented Porous Materials, Luoyang Normal
University, Luoyang 471934, PR China
⊥Departments of Physiology and Developmental Biology, University of Texas, Southwestern Medical Center, Dallas, Texas
75390-9133, United States
S
* Supporting Information
ABSTRACT: A novel optical nanoprobe based on silicon
quantum dots (SiQDs) has been assembled through a one-pot
low-temperature (40 °C) treatment by using 3-(aminopropyl)-
trimethoxysilane (APTMS) and ascorbic acid (AA) as two
precursors. The water-soluble SiQDs demonstrate intense green
luminescence in aqueous environment and the excitation-
dependent feature has been explored. Meanwhile, the
incorporation of salicylaldehyde (SA) serves to suppress the
emission of SiQDs effectively via nucleophilic reaction and an
“on−off” change is observed. Furthermore, the addition of Zn2+
can lead to evolution of emission peaks, and the green band at
500 nm gradually shifts toward the blue side at 455 nm. The
corresponding ratiometric signal changes (I455/I500) can
accurately determine the Zn2+ concentration and the limit of
detection is calculated to be 0.17 μM in the linear range between 1 and 100 μM. In this research, a molecular logic gate (AND)
system has been well established by using SA and Zn2+ as two inputs. The fluorescence emission changes based on SiQDs will
shed new light on the development of functional sensors at the nanoscale level.
materials will provide a variety of opportunities for achieving
tailor-made devices due to chemical and physical properties.
During the incorporation process, immobilization of the
organic frameworks into the accommodating hosts could be
realized through different interactions or linkages (including
covalent bonds, hydrogen bonds, van derWaals forces, electro-
static interactions, etc.). Lately, the decoration of specific
building blocks onto metal−organic frameworks (MOFs) has
been reported.14,15
Divalent zinc ions, as the second most abundant metal ion,
are distributed in different human tissues, including the brain,
intestine, pancreas, and retina.16,17 In addition, zinc ions are
considered to play critical roles in various physiological and
biochemical processes such as apoptosis, gene expression,
immune response, and neurotransmission.18 More importantly,
the inconsistency of Zn2+ concentration with the normal levels
in the human body will cause diverse diseases, such as infantile
INTRODUCTION
■
As a newly emerged fluorescent probe, semiconductor
quantum dots (QDs) have been widely used in chemo/
biosensing field and offer significant advantages over conven-
tional organic molecules and polymeric materials,1−3 but the
leaching problems of the main elements (such as Pb and Cd)
in these nanomaterials will severely restrict their applications.
Very recently, fluorescent silicon quantum dots (SiQDs) which
are composed of crystalline silicon and oxides have been
developed and attracted growing interests owing to their
unique properties, such as aqueous solubility, low cost, low
cytotoxicity, excitation-dependent multicolor emission, high
quantum yield, and high stability against photobleaching.4−6
On the basis of these excellent properties, SiQDs have been
widely employed as fluorescent probes for detecting a wide
range of targets, such as small molecules, ions, and biological
macromolecule.7−13
In optical sensor area, functional probes are generally
hybrid-type nanomaterials that lie at the interface between the
organic chromophores and the hosts. The nanocomposite
Received: March 24, 2018
© XXXX American Chemical Society
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Scheme 1. Schematic Illustration of SiQDs Synthesis and Zn2+ Detection
diarrhea, ischemic stroke, epilepsy, and Alzheimer’s disease.19
The previous mentioned fluorescent chemosensors for Zn2+
detection were designed based on quinolone,20,21 pyrazoline,22
furan,23 coumarin,24 BODIPY,25 and other organic fluoro-
phores.26,27 However, the exploration of label-free SiQDs as a
novel optical analytical platform to monitor Zn2+ concentration
has never been reported.
purification. All the solutions were prepared with ultrapure water
(18.2 MΩ) from a Milli-Q system.
Apparatus. High-resolution transmission electron microscopy
(HR-TEM) images were obtained by using a JEOL JEM-2100HR
microscope (Japan). UV−vis spectra were recorded on TECHCOMP
spectrophotometer in the range of 230−500 nm with a slit of 2 nm.
Fluorescence and excitation spectra were measured using a Hitachi F-
7000 fluorescence spectrophotometer with a 450 W xenon lamp as a
light source. The measurement of decay curves was performed on a
FLS920 Edinburgh Instrument (U.K.). X-ray photoelectron spectros-
copy (XPS) measurements were performed on a VG ESCALAB 220i-
XL surface analysis system. All the experiments were performed at
ambient temperature. All error bars represent standard deviations
As far as the signal response modes are concerned,
ratiometric fluorescent chemosensors can exhibit the delicate
variation of emission bands upon binding with analytes.
Moreover, ratiometric sensing technique possesses several
advantages as compared to classical detection methods at a
single wavelength since the former is free from errors
associated with receptor concentration, photobleaching, and
environmental effects. Therefore, it is valuable to exploit
functional ratiometric probes with low cost, easy operation,
and high selectivity for Zn2+ detection. Here, we have
assembled a novel SiQDs-based ratiometric fluorescent probe
for Zn2+ recognition and a “AND” logic gate operation has
been provided by using SA and Zn2+ as two inputs. First, we
have synthesized water-soluble SiQDs by simply mixing and
stirring the precursors APTMS and AA. The obtained SiQDs
have plentiful amino groups on its surface and exhibit a bright
green color emission under UV irradiation. In the presence of
SA, the striking luminescence from SiQDs displayed a stepwise
decrease due to the electrostatic forces and nucleophilic
addition reaction. The aldehyde groups of SA can easily attach
to amino groups on SiQDs and finally form SiQDs-SA complex
with CN bonds as linkages. Subsequently, Zn2+ can
coordinate with SiQDs-SA via imine-N and aromatic−OH
1
from three repeated experiments. H NMR spectra were recorded on
a Bruker Avance 600 MHz NMR Spectrometer. X-ray diffraction
(XRD) measurements were performed via a Bruker D8 diffrac-
tometer.
Preparation of SiQDs. SiQDs were synthesized by a simple one-
step synthesis method from APTMS and AA. Briefly, 10 mL of
APTMS was added in 40 mL of ultrapure water within a 200 mL
beaker with constant stirring, and the temperature was maintained at
40 °C. Then, 12.5 mL of AA (0.1 M) was added to the above mixed
solution by stirring for 0.5, 1.0, 1.5, 2.0, 2.5, 3, or 3.5 h. The SiQDs
containing solution was centrifuged at 10 000 rpm for 10 min to
remove the large precipitates. For further purifying the SiQDs, the
resultant solution was dialyzed in a dialysis bag (molecular weight
cutoff = 1000) for 3 days. The resulting SiQDs solution exhibited a
bright green color emission under UV irradiation (λ = 365 nm). The
white SiQDs powder was obtained by lyophilization.28−30
Detection of Zn2+ in Aqueous Solutions. First, 1 mL of the 0.1
mg/mL as-synthesized SiQDs solution was injected to a spectropho-
tometer quartz cuvette. Then, 0.3 mM SA and a series of various
concentrations of Zn2+ were added. The fluorescence spectra were
collected after the addition of Zn2+ into the solution for 30 s. The
photoluminescence spectra were measured by a fluorescence
spectrophotometer excited at 367 nm.
from the SA. Consequently, the strong blue emission (λem
=
455 nm) from the system was observed (Scheme 1). In this
way, a facile, fast, and sensitive method for recognizing Zn2+ by
using silicon-based quantum dots has been well-established.
RESULTS AND DISCUSSION
■
Silicon quantum dots have been assembled by one-pot
synthesis by using 3-(aminopropyl)trimethoxysilane as a
precursor at low temperature. Its microstructure was
characterized by transmission electron microscopy (TEM)
(Figure 1a). TEM images showed that SiQDs had good
monodispersity and spherical shapes of achieved particles were
EXPERIMENTAL SECTION
■
Reagents and Materials. 3-(Aminopropyl)trimethoxysilane
(APTMS 97%) and ascorbic acid (AA, 99.7%) were purchased
from Aladdin Chemistry Co., Ltd. All metal salts used were purchased
from Guangzhou Chemical Reagent Factory and used without further
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Figure 1. TEM images of the SiQDs (a). HRTEM images of the
SiQDs (b). A single QD is enlarged in the inset with a spacing of
about 0.31 nm.
confirmed. The average diameter of SiQDs is 7.5 0.5 nm.
Additionally, the HR-TEM image of SiQDs demonstrated a
crystal lattice with an interplanar distance of around 0.32 nm,
which would be ascribed to the (111) lattice plane of
crystalline Si30 (Figure 1b). Elemental analysis of the sample
by using energy-dispersive X-ray spectroscopy (EDS) indicated
that SiQDs were composed of Si, C, O, and N elements
(Figure 2a). The additional copper signal was induced by
copper grid used in the measurement. Furthermore, the full-
scan X-ray photoelectron spectroscopy (XPS) plot of SiQDs
was determined to explore their composition and binding
energies (Figure 2b). Five peaks, at 103.1, 154.1, 285.1, 399.1,
and 530.1 eV, corresponded to Si 2p, Si 2s, C 1s, N 1s, and O
1s, respectively. Figure S1 provided the XRD pattern of SiQDs,
and the three signals at 28.4, 47.3, and 56.4° were assigned to
(111), (220), and (311) planes of crystalline silicon.
The study of main functional groups and chemical bond
structures was performed by analyzing FT-IR spectra. As
illustrated in Figure 3, strong absorption bands at 2930 and
2863 cm−1 were corresponding to the antisymmetric stretching
vibration of the C−H bond.31 Two typical bands at 1024 and
744 cm−1 were caused by asymmetric vibration and symmetric
vibration of Si−O−Si. The strong absorbance at 1665 and
1602 cm−1 were assigned to N−H bending vibration.32
Doublet bands located at 3358 and 3291 cm−1 were attributed
to stretching vibrations of −NH2 groups from APTMS units,
indicating that the coupling agent has been successfully
incorporated into the nanosystem.33 Moreover, the above
information demonstrated that quantities of amino groups
were covered on the surface of obtained SiQDs.
Figure 3. FT-IR spectra of SiQDs.
measured to be situated at 500 nm, and an intense green
luminescence was observed upon the excitation at 367 nm
(Figure S2). We also investigated the emission curves of the
SiQDs at different reaction time (0.5, 1.0, 1.5, 2.0, 2.5, 3.0, and
3.5 h). The collected results displayed that the peak intensity
of SiQDs was gradually increased as the reaction hours were
extended (Figure S3). Therefore, the experimental condition
was optimized at 3.5 h for the preparation of SiQDs in the
following studies. In addition, we focused on the effects of
different excitation wavelengths on the luminescence of silicon
quantum dots. As given in Figure 4, the as-obtained SiQDs
exhibited typical excitation-dependent fluorescence behavior.
When the excitation wavelength increased from 360 to 510
nm, the emission peak of SiQDs gave rise to red-shifts from
470 to 550 nm. This excitation-dependent fluorescence
behavior of SiQDs might be due to the influence of different
particle sizes and the wide distribution of various surface
trapping states.
It is well-documented that aldehyde groups can easily react
with amino groups via the CN binding Schiff base reaction.
The nucleophilic reaction involves the addition of amine to the
carbonyl moiety and the elimination of water molecule. After
adding SA into the SiQDs solution, its aldehyde groups can
accept the attack of the amino groups and imine formation
reaction has been carried out. Interestingly, the photo-
luminescence feature of SiQDs was also changed significantly
during this process. In this case, 414 nm was employed as the
A valuable property of quantum dots will be their
photophysical features and the unique luminescence signal
occurs by transitions from electronically excited states to the
ground states. In this work, the emission peak of SiQDs was
Figure 2. (a) EDS pattern of the SiQDs; (b) XPS spectrum of SiQDs.
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luminescence decay curves, the lifetime of SiQDs was 10.9 ns.
In the presence of SA, the lifetime was dramatically reduced to
1.8 ns (Figure S6). The results again supported that the
covalent attachment of salicylaldehyde would cause intra-
molecular quenching.
In order to develop a ratio fluorescent probe, we expect that
the probe will have detectable fluorescent signals used for
recognizing the guest species. In this work, the emission
intensity of SiQDs was able to maintain 50% upon adding 0.3
mM SA (Figure S4B). Therefore, 0.3 mM SA was selected for
the following detection of Zn2+. The sensing ability of Zn2+
based on SiQDs-SA (0.1 mg/mL SiQDs, 0.3 mM SA) has also
been studied by the fluorescence spectra. As provided in Figure
5a, in the presence of Zn2+, the green luminescence at 500 nm
of SiQDs-SA converted to bright blue color at 455 nm (λex =
367 nm). Distinguishable changes from green to bright blue
color could be observed with the naked eye under irradiation
by 365 nm UV light (inset of Figure 5a). As described in
Figure 5b, the correlation between the emission change and
the concentration of Zn2+ followed the excellent linear
equation I455/I500 = 0.035x + 0.771 (R2 = 0.999). The
detection of limit (DL) was calculated to be 0.17 μM through
the equation DL = 3 × SD/slope, where SD is the standard
deviation of the blank sample. Parallel experiments were
carried out for ten times and the relative standard deviation
was calculated to be 1.9%. The detection performance for Zn2+
based on a series of analogous materials was summarized in
Table S1. It was found that some studies were carried out in
organic solvent (DMSO) or organic mixed phases (EtOH/
H2O). Here the experiment in this research was investigated
within pure aqueous environment. Although the detection
limit in this study (0.17 μM) was not the lowest one, the
simultaneous collection of fluorescence signals at two well-
resolved wavelengths (ratiometric measurement) would
effectively circumvent the problems such as concentration
changes of sensors, environmental conditions, and instrument
errors. Therefore, the precise quantitative determination could
be realized.
Figure 4. Fluorescence spectra of SiQDs (0.1 mg/mL) at different
excitation wavelengths.
excitation wavelength. The visible light sensitization might
provide a new choice for blue LED source and direct
irradiation of common tissue or biomolecules by ultraviolet
lamp could be avoided. Its emission intensity was severely
suppressed by the increasing concentration of SA. Finally, the
green luminescence was almost quenched upon the addition of
3 mM SA (λex = 414 nm) (Figure S4A). With the aim of
1
verifying the proposed sensing mechanism, H NMR spec-
troscopy was applied to explore the nature of the interaction
between APTMS and SA. Figure S5 displayed NMR spectral
changes of SA in the absence of various equivalents of APTMS.
It can be observed that the typical aldehyde proton (−CH
O) was situated at 11.0. Aromatic−OH signal was located at
9.91 ppm. Protons in benzene ring were situated at 7.56 and
7.53 ppm. Upon the addition of 0−1 equiv of APTMS to SA,
the proton of the aldehyde group at 11.0 ppm disappeared.
The aromatic −OH signal remained almost unchanged.
Moreover, a new −CHN group was formed at 8.34 ppm.
These results implied that amino groups of APTMS would
occur reaction with the aldehyde group of SA via the CN
binding Schiff base linkage. The molecular rearrangement and
formation of new covalent bond will drastically change the
electron distribution. Intramolecular photoinduced electron
transfer from donor (amino group) to the aromatic aldehyde
unit might result in the emission quenching. On the basis of
Selectivity is another critical point to evaluate the perform-
ance of a fluorescent sensor. Hence, the interferences from
other ions (Ag+, Mg2+, Cd2+, Pb2+, Hg2+, Cu2+, Ca2+, Al3+, Fe3+,
PO43−, SO42−, SO32−, HSO3 , NO3 , NO2 , and Cl−) were
investigated under the analogous conditions. As shown in
Figure 6, it was observed that other interfering biological ions
−
−
−
Figure 5. (a) Fluorescence response of SiQDs (0.1 mg/mL) + SA (0.3 mM) in the presence of Zn2+ at different concentrations (0, 10, 20, 30, 40,
50, 60, 70, 80, 90, and 100 μM). (b) linear relationship between the ratio of fluorescence intensities (I455/I500) and Zn2+ concentration (λex = 367
nm).
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Figure 6. I455/I500 of SiQDs (0.1 mg/mL) + SA (0.3 mM) in absence
and presence of various substances (1 mM), in the presence (red) and
absence (black) of Zn2+ (100 μM), respectively.
Figure 7. UV−vis absorption spectra of SiQDs (0.1 mg/mL), SA (0.3
mM), SiQDs-SA (SiQDs 0.1 mg/mL; SA 0.3 mM), and SiQDs-SA +
Zn2+ (SiQDs 0.1 mg/mL; SA 0.3 mM; Zn2+; 100 μM). Inset: UV−vis
absorption spectra of SA (0.3 mM).
exhibited no extraordinary changes on the fluorescence
intensity ratio of I455/I500. We also explored the selectivity
behavior of the nanoprobe in the presence of a mixture of
interference ions (Figure S7). The emission curves showed
SiQDs-SA could effectively recognize Zn2+ in the mixture of
coexisting ions at high concentration (1 mM). These results
supported that the SiQD-based nanoprobe was selective for
efficient monitoring Zn2+ in aqueous solution. In this way, this
nanoprobe will be promising in the practical uses in the
recognition of metal ions.
Additionally, the feature of reusability of the nanoprobe for
the detection of Zn2+ ion was explored. Zn2+ is able to bind
with carboxyl groups of ethylenediaminetetraacetic acid
(EDTA) effectively. Accordingly, we studied the emission
responses of the nanoprobe to Zn2+ by using EDTA as a
powerful chelator for metal ions. In Figure S8, the fluorescence
intensity ratio was increased in the presence of Zn2+, and it was
decreased sharply upon the addition of EDTA. This off−on−
off change was observed during five times repeated experi-
ments. Thus, it was deduced that the nanoprobe gave rise to a
luminescence response to Zn2+ ions and this specific process
could be reversible.
In order to clarify the sensing process between the organic
building blocks and Zn2+, Job’s plot was performed, and their
binding stoichiometry toward the target could be determined.
In Figure S9, the maximum emission change (F − F0) was
found to be situated at 0.34 of molar fraction ratio ([Zn2+]/
[(SA + APTMS) + Zn2+)]), and the analysis result indicated a
sensing procedure with binding stoichiometry of 2:1.
The UV−vis spectra of SiQDs, SA, SiQDs-SA, and SiQDs-
SA+Zn2+ were recorded. As can be seen in Figure 7, we can
hardly observe absorption signals from SiQDs (0.1 mg/mL) in
the wavelength range between 230 and 500 nm. In the
absorption curve of SA (0.3 mM), two peaks at 245 and 320
nm were identified, which can be attributed to the π−π*
transition of the aromatic ring structure and n−π* transition of
CO. When SA was added into the SiQDs solution, the two
absorption peaks shifted to 260 and 387 nm, indicating the
amino groups on SiQDs can easily combine to aldehyde
groups of SA and SiQDs-SA nanostructure with the CN
Schiff base unit has been formed.34 Upon the addition of Zn2+
into the SiQDs-SA solution, the intensity of an absorption
band at 387 nm decreased and its peak wavelength red-shifted
to 395 nm. The intensity of absorption signal at short
wavelength (260 nm) slightly increased, which also indicated
the formation of complexed structure upon coordination of
Zn2+ with SiQDs-SA via imine-N, and aromatic-OH from the
SA moiety.35,36 For comparison purpose, Zn2+ was directly
added into the free SiQDs solution, and there was no any
noticeable change in the corresponding UV absorption (Figure
S10A). Likewise, Zn2+ was also incorporated into the
salicylaldehyde solution and the two absorption lines were
almost overlapped (Figure S10B). Therefore, this amino-
modified SiQDs could be able to develop a typical two-input
“AND” logic gate.
It has been reported that molecular logic gates have been
employed for mimicking the functions of chemical circuits.
Herein, a fluorescent “AND” logic gate could be established by
using 0.3 mM SA and 100 μM Zn2+ as the inputs, and the blue
signal enhancement (λem = 455 nm) as the output. The output
values less than a predefined threshold level (I/Imax = 0.5, I
corresponds to the measured emission intensity; Imax
corresponds to the maximum emission intensity at 455 nm)
were referred to binary “0”. The emission output values larger
than the threshold were defined as binary “1” (Figure 8a). For
inputs, the absence and presence of SA or Zn2+ was translated
into 0 and 1, respectively. For outputs, fluorescence intensity at
455 nm enhancements and none was defined as 1 and 0,
respectively. In the absence of either (1/0 and 0/1) or both
(0/0) input, no significant changes of blue emission were
observed. While in the presence of both (1/1) input, the blue
fluorescence was increased enormously. The column bars of
the normalized emission intensity and the truth table for the
developed “AND” logic gate were given in Figure 8b. Only the
system received two inputs together (1/1), the fluorescence
signal could be responsive, and the gate was activated and
exerted an output signal of “1”.
The exploration of these changes according to the logic
operation provides direct detection for Zn2+ levels. Here,
various concentrations of Zn2+ (0, 10, 20, 30, 40, and 50 μM)
were selected as the input signals, and the output intensity
fluorescent signals were normalized (Figure 9a). As shown in
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Figure 8. (a) Column diagram of the normalized emission intensity of SiQDs toward 0.3 mM SA and 100 μM Zn2+. (b) Truth table for the
developed “AND” logic gate with a two-input logic circuit.
Figure 9. (a) Column diagram of the normalized emission intensity of SiQDs toward 0.3 mM SA and various concentrations of Zn2+ (0, 10, 20, 30,
40, and 50 μM). (b) Truth table of the logic analytical device for Zn2+ monitoring. (c) CIE chromaticity coordinates of SiQDs at different
concentration of Zn2+ calculated from the emission spectra shown in Figure 5a.
Figure 9b, 0 gate was triggered by 10 μM Zn2+, and the 1 gate
was triggered by 20 μM Zn2+. When the concentration was
below 10 μM, the 0 gate emerged. Consequently, the simple
binary codes were analyzed for the detection of Zn2+ levels.
Output 0 represented low concentrations of Zn2+ or no Zn2+.
The outputs 1 supported the presence of middle or high
concentration of Zn2+. On the basis of the detailed
investigation, we separated the concentrations (0, 10, 20, 30,
40, and 50 μM) into two groups with their representative
colors: 0−10 (blue-green) and 20−50 (blue). In Figure 9c,
every concentration of Zn2+ has a standard color that can be
observed from the CIE calculations using the emission spectra
in Figure 5a. In this way, this molecular circuit exhibiting an
“AND” logic function will pave a new way for recognizing
metal ions based on quantum sized particles.
luminescence at 500 nm under UV excitation (λex = 367
nm). Upon exposure to Zn2+, the nanoprobe displayed a
remarkable luminescence color change from green to blue. The
intensity ratios (I455/I500) gave rise to a rapid, sensitive and
selective response to Zn2+. Moreover, a new “AND” logic gate
was designed based on the fluorescent SiQDs for the detection
of Zn2+. This work will enable the utilization of unique
luminescence properties of SA functionalized SiQDs in
medical diagnostics, bioimaging, and environmental monitor-
ing.
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.8b00788.
CONCLUSION
XRD pattern of SiQDs; emission spectra of SiQDs with
■
different reaction times; emission spectra of SiQDs in
In summary, a label-free fluorescent “AND” logic gate has been
developed based on SiQDs for detection of Zn2+. At first, we
have synthesized water-soluble SiQDs by mixing and stirring
the precursors APTMS and AA under 40 °C for 3.5 h. In the
presence of SA, the SiQD-based nanoprobe exhibited
1
the presence of various concentrations of SA; H NMR
spectra of salicylaldehyde (SA, bottom) in the presence
of various equivalents of 3-(aminopropyl)-
trimethoxysilane (APTMS); table of comparison be-
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tween the current study and the reported literatures;
Article
(10) Su, Y. Y.; Ji, X. Y.; He, Y. Water-dispersible fluorescent silicon
nanoparticles and their optical applications. Adv. Mater. 2016, 28,
10567−10574.
interference ions experiments of SiQDs-SA; recycling
experiments of SiQDs-SA upon the repeated addition of
Zn2+ and EDTA; Job’s plot for the binding event of L (L
refers to the product of salicylaldehyde reacting with 3-
(aminopropyl)trimethoxysilane) with Zn2+ ions; UV−vis
spectra of SiQDs, Zn2+, and SA (PDF)
(11) Zhang, S. J.; Liu, R. H.; Cui, Q. L.; Yang, Y.; Cao, Q.; Xu, W.
Q.; Li, L. D. Ultrabright fluorescent silica nanoparticles embedded
with conjugated oligomers and their application in latent fingerprint
detection. ACS Appl. Mater. Interfaces 2017, 9, 44134−44145.
(12) Luo, L.; Song, Y.; Zhu, C. Z.; Fu, S. F.; Shi, Q. R.; Sun, Y. M.;
Jia, B. Z.; Du, D.; Xu, Z. L.; Lin, Y. H. Fluorescent silicon
nanoparticles-based ratiometric fluorescence immunoassay for
sensitive detection of ethyl carbamate in red wine. Sens. Actuators, B
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AUTHOR INFORMATION
Corresponding Authors
*E-mail: zhouzhan@lynu.edu.cn.
*E-mail: qmwang@scnu.edu.cn. Tel.: 86-20-39310258. Fax:
86-20-39310187.
■
(13) Xu, N.; Yuan, Y. Q.; Yin, J. H.; Wang, X.; Meng, L. One-pot
hydrothermal synthesis of luminescent silicon-based nanoparticles for
highly specific detection of oxytetracycline via ratiometric fluorescent
strategy. RSC Adv. 2017, 7, 48429−48436.
ORCID
Jinwei Gao: 0000-0002-4545-1126
Qianming Wang: 0000-0003-2795-6056
Notes
(14) El-Sewify, I. M.; Shenashen, M. A.; Shahat, A.; Yamaguchi, H.;
Selim, M. M.; Khalil, M. M. H.; El-Safty, S. A. Dual colorimetric and
fluorometric monitoring of Bi3+ ions in water using supermicroporous
Zr-MOFs chemosensors. J. Lumin. 2018, 198, 438−448.
(15) El-Sewify, I. M.; Shenashen, M. A.; Shahat, A.; Selim, M. M.;
Khalil, M. M. H.; El-Safty, S. A. Sensitive and selective fluorometric
determination and monitoring of Zn2+ ions using supermicroporous
Zr-MOFs chemosensors. Microchem. J. 2018, 139, 24−33.
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The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Q.M. acknowledges the support from National Natural Science
Foundation of China (grant no. 21371063) and Guangdong
Science and Technology plan (2016A050502053). Z.Z.
acknowledges the Scientific Research Fund of Henan
Provincial Education Department (17A150016) and Natural
Science Foundation of Henan (162300410200) for financial
assistance. Y.H. thanks the Research Fund of Higher Education
Committee of Guangdong Province (GDJ2016003).
(17) Tomat, E.; Lippard, S. J. Imaging mobile zinc in biology. Curr.
Opin. Chem. Biol. 2010, 14, 225−230.
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zinc in health and disease,. Nat. Rev. Neurosci. 2005, 6, 449−462.
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I. Zinc-amyloid β interactions on a millisecond time-scale stabilize
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