Author’s Accepted Manuscript
Sulfur and nitrogen binary doped carbon dots
derived from ammonium thiocyanate for selective
probing doxycycline in living cells and multicolor
Mingyue Xue, Liangliang Zhang, Zhihua Zhan,
Mengbing Zou, Yong Huang, Shulin Zhao
To appear in:
Received date: 28 October 2015
9 December 2015
Accepted date: 10 December 2015
Cite this article as: Mingyue Xue, Liangliang Zhang, Zhihua Zhan, Mengbing
Zou, Yong Huang and Shulin Zhao, Sulfur and nitrogen binary doped carbon
dots derived from ammonium thiocyanate for selective probing doxycycline in
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Title: Sulfur and nitrogen binary doped carbon dots derived from
ammonium thiocyanate for selective probing doxycycline in
living cells and multicolor cell imaging
Key Laboratory for the Chemistry and Molecular Engineering of
Medicinal Resources (Ministry of Education), College of Chemistry
and Pharmacy, Guangxi Normal University, Guilin, 541004, China
Guilin Normal College, Guilin, 541001, China.
Professor Shulin Zhao, Liangliang Zhang
College of Chemistry and Pharmacy
Guangxi Normal University
Guilin, 541004, China
Tel: +86 773 5845973
Fax: +86 773 5832294
A novel sulfur and nitrogen binary doped carbon dots (S,N-CDs) was synthetized by
one-step manner through the hydrothermal treatment of citric acid (CA) and
ammonium thiocyanate, and the procedures for biomedical applications, including
probing doxycycline in living cells and multicolor cell imaging were developed. The
obtained S,N-CDs are stable in aqueous solution, possess a very high quantum yield
(QY, 74.15%) and good photostability. The fluorescence of S,N-CDs can be
specifically quenched by doxycycline, providing a convenient turn-off assay of
doxycycline. This assay shows a wide linear detection range from 0.08 to 60 μM with
a low detection limit of 20 nM. The present method also displays a good selectivity.
More importantly, the S,N-CDs have an excellent biocompatibility and low
cytotoxicity, allowing the multicolor cell imaging and doxycycline detection in living
cells. Consequently, the developed doxycycline methods is facile, low-cost,
biocompatible, sensitive and selective, which may hold the potential applications in
the fields of food safety and environmental monitoring, as well as cancer therapy and
related mechanism research.
Keywords: Sulfur; Nitrogen; Doped carbon dots; Multicolor cell imaging;
Doxycycline, a tetracycline derivative with a wide range of antibacterial activities,
is frequently used to treat many infections such as chronic prostatitis, respiratory tract
infections, sinusitis  and sexually transmitted diseases . Additionally, it also
applied in the fields of veterinary medicine and animal nutrition. But the abuse of
doxycycline may lead to an unsafe residue level in the environment or food samples.
To protect the safety of consumers, the European Union, America, Canada and China
have legally set the maximum residue level for various antibiotics. Consequently,
developing efficiently methods for the detection of doxycycline concentration is of
great importance in pharmaceutical preparations, food safety and environmental
monitoring. In the past 20 years, numerous analytical techniques including
chromatography [3-5], capillary electrophoresis , spectrophotometry [7, 8],
fluorescence , electrochemistry [10, 11], coupled technique [12-16] were used for
doxycycline monitoring. However, these methods commonly suffered from low
sensitivity and/or complicated preparation. In addition to the anti-microbial activity,
doxycycline also shows an anti-tumour property in the treatment of prostate,
pancreatic and colon cancer [17-19]. Thus, detecting doxycycline in cancer cells may
provide more useful and direct information for cancer therapy and related mechanism
research. But the reports about doxycycline monitoring in living cells are still rare at
As fascinating carbon nanomaterials, fluorescent carbon dots (CDs) have attracted
lots of research interests due to their excellent photostability, favorable
biocompatibility, low toxicity without heavy metal ions and toxic elements, tunable
fluorescence emission and excitation, and large Stokes shifts . Based on these
outstanding properties, CDs have been widely applied in the fields of bioimaging,
biosensor and drug delivery [20-28]. Additionally, at present, great efforts were made
to develop heteroatom-doped CDs for improving the optical and electrical properties
of CDs. Boron, nitrogen, fluorine and sulfur were the commonly introduced doping
chemical elements [29, 30]. Among these heteroatom-doped CDs, sulfur and nitrogen
co-doped CDs were extremely attractive, which exhibited a high QY [31-33].
In this work, a novel low-cost strategy is developed for the synthesis of S,N-CDs
by using CA and ammonium thiocyanate as precursors. The CA serves as the carbon
source, while the ammonium thiocyanate provides sulfur and nitrogen. The
as-obtained S,N-CDs are stable in aqueous solution and exhibit a very high QY
(74.15%). The fluorescence can be specifically quenched by doxycycline. Thus, using
S,N-CDs as fluorescent probes, a simple doxycycline detection was achieved (Scheme
1). The high QY of obtained S,N-CDs offers a high sensitive for doxycycline assay.
There are few works about the CDs-based detection of tetracyclines [34,35], but each
tetracycline derivative could induce a similar response signal in these works. The
proposed S,N-CDs probe here exhibits an approving selectivity and can distinguish
between doxycycline and tetracycline. The high sensitivity and selectivity may ensure
a more accurate analysis of doxycycline in complex samples. Remarkably, the
synthesized S,N-CDs possess high photostability and excellent biocompatibility, good
stability under the entire physiological pH range and high ionic strength. Coupled
with these outstanding features
, S,N-CDs are promising in the cell imaging and
doxycycline monitoring in living cells.
2.1. Reagents and materials
3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) were purchased
from Sigma-Aldrich Chemical Co. (St. Louis, MO, USA). Other chemical materials
were purchased from Aladdin Chemistry Co., Ltd. (Shanghai, China). All reagents
were of analytical grade and were used without further purification. Water was
puriﬁed with a Milli-Q plus 185 equip from Millipore (Bedford, MA, USA) and used
throughout the work.
2.2. Synthesis of S,N-CDs
The S,N-CDs were prepared by thermal treatment of molecular organic salts with
the mixed carbon source and the surface modifier in the single precursor. Briefly,
2.1080 g CA and 1.5439 g of ammonium thiocyanate were dissolved into 5 mL water.
The solutions were heated hydrothermally in a Teflon-equipped stainless-steel
autoclave at 200 °C for 3 h with a heating rate of 10 °C min
. The obtained S, N-CDs
solution was adjusted to pH 7 with 1 M NaOH solution and centrifuged at 10000 rpm
for 20 min. A dialysis membrane (MWCO: 1 kDa; pore size: ca. 1.0 nm) was then
used to separate the S,N-CDs from any residual unreacted species and obtained a
brown solution. The solvent was removed with the aid of a rotary evaporator. Then
the obtained S,N-CDs was dispersed into deionized (DI) water and preserved at a 4 °C
for further characterization and use.
2.3. Instruments and characterizations
The morphology and microstructure of S,N-CDs were examined by high-resolution
transmission electron microscopy (HRTEM) on a Tecnai G2 F20 microscope (FEI,
Philips, Netherlands) with an accelerating voltage of 200 kV. The sample for HRTEM
was made by dropping an aqueous solution onto a 300-mesh copper grid coated with a
lacy carbon film. The X-ray diffraction (XRD) measurement was performed with a
D/max-2500V/PC powder X-ray diffractometer (Rigaku,
Tokyo, Japan). The X-ray
photoelectron spectroscopy (XPS) spectra of the sample were measured on a
ESCALAB 250Xi X-ray Photoelectron Spectroscopy (Thermo Scientific, Waltham,
MA, USA). Fourier transform infrared spectroscopy (FT-IR) study was conducted
from KBr pellets on a PerkinElmer FT-IR spectrophotometer (Perkin-Elmer, Norwalk,
Connecticut, USA). Elemental analyses (C, H, N, S) were carried out on a Perkin
Elmer Series II CHNS/O 2400 elemental analyzer (Perkin-Elmer, Norwalk,
Connecticut, USA). Fluorescence lifetime experiments were performed by a
FL3-P-TCSPC time-resolved fluorescence spectrometer (Horiba Jobin Yvon,
Longjumeau, France). Raman spectra were obtained on a Raman Microscope
(Renishaw, Gloucestershire, UK). All fluorescence spectra were obtained on a LS-55
fluorescence spectrometer (Perkin-Elmer, Norwalk, Connecticut, USA). The emission
spectra were recorded in the wavelength range of 400-600 nm. Ultraviolet–visible
(UV-Vis) absorption spectra were characterized by a Cary 60 UV-Vis
spectrophotometer (Agilent Technologies, Santa Clara, CA, USA). Cell imaging was
examined by Zeiss LSM 710 confocal microscopy (Carl Zeiss, Oberkochen,
2.4. Measurement of fluorescence QY
Quinine sulfate (0.1 M H
as solvent; QY=0.54) was chosen as a standard. The
QY of S,N-CDs (in water) were calculated according to the following equation:
Where φ is the QY, Ι is the measured integrated emission intensity, η is the refractive
index of the solvent, and A is the optical density. The subscript "st" refers to standard
with known QY and "x" refers to the unknown samples. For these aqueous solutions,
2.5. Detection of doxycycline
Doxycycline samples with various concentration was incubated with 1 μg mL
S,N-CDs in 120 μL phosphate buffer (PB, 0.1 M, pH 6.0) at room temperature for 10
min. The fluorescence measurements were then carried out.
2.6. Cell imaging
Hepatocellular carcinoma cell (HepG2) were grown in a humidified atmosphere
containing 5% CO
at 37 °C in Roswell Park Memorial Institute (RPMI) 1640
medium supplemented with 10% fetal bovine serum (FBS, Invitrogen), 100 μg mL
streptomycin and 100 units mL
penicillin. Cells were seeded on 35 mm glass bottom
culture dishes for 24 h before confocal imaging. Then, the culture medium was
replaced by 2.5 mL fresh medium containing 100 μg mL
S,N-CDs, and the cells
were incubated for another 12 h at 37 °C under 5% CO
. The S,N-CDs labeled cells
were then imaged by confocal microscopy.
2.7. Cytotoxicity evaluation
Cytotoxicity of S,N-CDs on cells was evaluated through MTT assay. HepG2 cells
were seeded and incubated in a 96-well plate at a density of 1×10
cells per well for
24 h. Then, the culture medium was removed, and the S,N-CDs were added into each
well with the increasing concentrations from 100 to 500 μg mL
. The mixture was
incubated for 24 h before replacing the medium with 200 μL fresh complete medium
containing 20 μL MTT (5 mg mL
in PBS). After 4 h incubation, all medium was
removed and 150 μL well
DMSO was added followed by shaking for 15 min. The
absorbance of each well was measured at 570 nm using a using an Enzyme Linked
Immunosorbent Assay reader with pure DMSO as a. blank. Non-treated cell was used
as a control and the relative cell viability (mean% ± SD, n=3) was expressed as
3. Results and discussion
3.1. Synthesis and characterization of S,N-CDs
The S,N-CDs were prepared by the hydrothermal treatment of CA and ammonium
thiocyanate. Some synthetic conditions including the masses of CA and thiocyanate,
the reaction time, and the reaction temperature were explored to obtain a higher QY.
As shown in Table S1, the optimal conditions for S,N-CDs synthesis were set to be
2.1080 g CA, 1.5439 g ammonium thiocyanate, and hydrothermal treatment at 200 °C
for 3 h. The obtained S,N-CDs (QY 74.15%) under these conditions are used for the
further characterization and application.
The transmission electron microscopy (TEM) image (Fig. 1a) clearly indicates that
the obtained S,N-CDs have a well dispersion and a diameter distribution between 4-9
nm with an average size of ~7 nm. The high resolution TEM images display two
lattice spacing of 0.23 and 0.32 nm, which may correspond to the (100) and (002)
facet of graphite, respectively [31,36]. The disordered D band and crystalline G band
are observed in the Raman spectra at 1348 cm
and 1573 cm
respectively (Fig. 1b).
The intensity ratio between D band and G band is estimated to be 0.833,
demonstrating that the S,N-CDs are highly crystalline and graphitic . The X-Ray
powder diffraction (XRD) pattern (Fig. 1C) shows a broader peak of (002) facet
centered at about 25.5
, which is resulted from highly disordered carbon atoms and
confirms the graphene structure of the obtained S,N-CDs .
The Fourier transform infrared (FTIR) spectra (Fig. S1) indicate the presence of
N-H, S-H, oxygen-containing groups (O-H, -COO-, C=O, C-O), C-N and C-S in
S,N-CDs. The doping of N and S atoms in the prepared S,N-CDs was also confirmed
by XPS. The data in Fig. 2a clearly reveal the presence of C, O, N and S elements in
the used CDs. The high resolution spectrum of C1s exhibits three main peaks (Fig.
2b). The binding energy peak at 284.6 eV confirms the graphitic structure (sp2 C-C)
of the S,N-CDs. The peak at about 285.4 eV suggests the presence of C-O, C-S, and
C-N, and the peak around 288.4 eV could be assigned to C=O. The high resolution of
the S2P XPS spectrum of S,N-CDs shows two peaks at 163.1, 164.3 (Fig. 2c), which
are similar to the reported 2P
positions of the–C–S– covalent bond of the
thiophene-S. The high resolution N1s spectra (Fig. 2d) indicates the presence of both
pyrrolic (400.1 eV) and graphitic (401.5 eV) N atoms . Elemental analysis results
further verify that the S,N-CDs are mainly composed of C (50.34%), O (35.27%,
calculated), N (4.73%), S (6.68%), and H (2.98%). All of these demonstrate the
successfully doping of N and S atoms into the framework of carbon dots.
The UV-Vis spectrum shows two typical peaks centered at 232 and 335 nm, which
are assigned to π→π* transition of C=C and n→π* transition of C=O, respectively.
While the absorption of CA and ammonium thiocyanate is very weak at 232 or 335
nm (Fig. 3, curves a and b). It is reported that the adsorption at 232 nm leads to nearly
no observed fluorescence signal, and the adsorption at 335 nm due to the trapping of
excited-state energy by the surface states results in strong emission .
Consequently, the light yellow S
,N-CDs aqueous solution emitted a strong blue
fluorescence under the irradiation at 365 nm (Fig. 3, inset). An excitation dependent
emission wavelength and intensity was observed (Fig. S2). Furthermore, the
fluorescence intensity was not significantly affected even after continuous irradiation
at 365 nm UV light for 2 h or stored for 3 months (Fig. S3), while other conditions
were kept unchanged. At the same time, the S,N-CDs solution exhibits a long-term
homogeneous phase without any noticeable precipitation at room temperature. The
fluorescence test of the S,N-CDs under different pH solutions indicates that the
S,N-CDs are stable in the pH range from 3 to 11, and no obvious fluorescence change
is observed (Fig. S4). The effect of ionic strength on the stability of S,N-CDs was also
investigated by recording the fluorescence upon the addition of NaCl or KCl with
different concentrations (from 0.25 M to 2.5 M) into the PB solution (pH 7.4). As
shown in Fig. S5, the fluorescence intensities remained constant with the increase of
ionic strength. As a result, according to the above discussion, the synthetized
S,N-CDs have high QY, excellent photostability, good stability under the entire
physiological pH range and high ionic strength, facilitating wider applications in
sensing, labeling and imaging.
3.2. Doxycycline detection
The outstanding properties of S,N-CDs motivate us to explore their potential
applications. A fluorescence quenching effect of doxycycline on S,N-CDs was
observed. As shown in Fig. 4 (inset), the bright blue fluorescence of S,N-CDs is
significantly quenched after the addition of doxycycline. Corresponding emission
spectra also show that 80% of fluorescence intensity at 450 nm was lost in the
presence of 60 μM doxycycline. In order to further understand the quenching
mechanism, fluorescence lifetime and fluorescence intensity-based Stern-Volmer plot
of S,N-CDs in the presence of doxycycline were investigated. As shown in Fig. S6,
the plots of the F
/F versus doxycycline concentration is nearly fitted to the
Stern-Volmer equation (F
[Q]+1), where F
and F are the fluorescence
intensity of S,N-CDs in the absence and presence of doxycycline respectively, [Q] is
the doxycycline concentration and K
is the Stern-Volmer constant. The average
fluorescence lifetime for S,N-CDs is 2.89 ns, and it was about 2.86 ns in the presence
of doxycycline. The addition of doxycycline did not significantly change the
fluorescence lifetime (Fig. S7), indicating a static quenching process .
Before the doxycycline detection, several experiments were carried out to achieve
the best assay performance. The effect of pH on the doxycycline assay was
investigated by recording the fluorescence intensity under different pH values with
and without doxycycline. A maximum fluorescence quenching was obtained when the
pH value was adjusted to 6.0 (Fig. S8). Thus, a 0.1 M PB buffer with a pH value of
6.0 was applied for this sensing system. The quenching time was also optimized. As
shown in Fig.S9, about 80% fluorescence quenched was achieved when the
doxycycline was added into the solution at 1 min, and the fluorescence kept stable
during the following 10 min. Thus, to obtain effective quenching, 5 min was used as
the optimal quenching time. This also indicated that the detection method is fast and
easy by simply mixing the target and S,N-CDs.
The sensitivity of the fabricated S,N-CDs fluorescent probe for doxycycline assay
was then investigated by analyzing doxycycline with different concentrations under
the optimal conditions. Fig. 5 shows the relationship between fluorescence quenching
and doxycycline concentrations. It can be found that the
fluorescence quenching efficiency increased with the increase of doxycycline
concentration. And in the doxycycline concentration range from 0.08 to 60 μM (0.037
-28 μg mL
), the value of (F
was linear to the concentration of doxycycline
(Fig. 5, inset). The linear regression was represented by the following equation:
= 0.01312 C+0.00657 (R
=0.9985, C is the concentration of doxycycline).
The detection limit (deﬁned as 3σ, where σ is the standard deviation of the blank) was
20 nM (~0.009 μg/mL). Compared to the most previous methods (Table S2), the
proposed probes have wider linear detection range, and the detection limit is much
The selectivity of the prepared S,N-CDs for doxycycline detection was investigated
by testing the fluorescence response to some other antibiotics or biomolecules. Some
antibiotics which were commonly found in food or environmental samples, including
ampicillin, penicillin, streptomycin, tetracycline, were added in S,N-CDs-contained
solutions. As shown in Fig. 6, under a large concentration (60 μM), only doxycycline
rather than other antibiotics could induce a remarkable fluorescence quenching.
Additionally, some other usually co-existed foreign biomolecules in biological or
pharmaceutical samples, such as such as glucose, ascorbic acid, albumin human
serum, glutathione and amino acids, were also tested. As show in Fig. S10, these
foreign species have negligible effects on the fluorescence of S,N-CDs. The above
results demonstrated an excellent selectivity for doxycycline detection. It should note
that tetracycline, a common interference in fluorescence-quenching-based
doxycycline detection methods [34,35], did not cause a distinct fluorescence
quenching. This implies that the present S,N-CDs probes can distinguish between
doxycycline and tetracycline, may offering a more accurate analysis of doxycycline in
food or environmental samples.
3.3. Cytotoxicity and Cell imaging
To explore the possible application of the C-dots in bioimaging, the cytotoxicity of
the as-prepared S,N-CDs was evaluated by MTT assay using HepG2 cells. As shown
in Fig. S11, after the incubation with S,N-CDs for 24 h, the cell viability was still
larger than 90% even the concentration of S,N-CDs up to 500 μg mL
. It is worthy to
note that this concentration of S,N-CDs is much higher and the incubation time is
much longer than those required for the potential bioimaging application. These
results confirmed the low toxic and excellent biocompatibility of the prepared
Because of it’s small size, good photostability and excellent biocompatibility, the
prepared S,N-CD holds great potential for bioimaging application. We then used
S,N-CDs for cell imaging and intracellular doxycycline monitoring. Fig. 7 shows
confocal microscopy images of HepG2 cells incubated with S,N-CDs for 12 h at
37 ℃. The S,N-CDs-stained cells exhibited blue
, green and red colors upon the
respective excitation at 405 nm, 488 nm and 514 nm. This result also indicates that
the fluorescence can be collected with a broad range of excitation wavelength, and the
prepared S,N-CDs can be used as excellent optical imaging probes for the further
The S,N-CDs were then applied for detecting doxycycline in living cells based on
the doxycycline-induced fluorescence quenching. Exogenous doxycycline was
introduced into the S,N-CDs-pretreated HepG2 cells. One can find in Fig. 8 that upon
supplementing cells with 100 μM of doxycycline in the growth medium for 20 min at
37 ℃, microscope images showed no intracellular fluorescence. This result indicates
that the proposed S,N-CDs could serve as an fluorescent probes for the detection of
doxycycline in living cells.
In summary, we introduced a one-step synthesis of S,N-CDs by the hydrothermal
treatment of CA and ammonium thiocyanate, and applied the S,N-CDs for
doxycycline detection in living cells and multicolor cell imaging. The fluorescence of
S,N-CDs can be specifically quenched by doxycycline. The present fluorescent
doxycycline assay has several important features. First, the prepared S,N-CDs exhibit
a very high QY (74.15%), ensures a high sensitivity for quenching-based doxycycline
assay. The detection limit in this work is much lower than that of most previous
methods. Second, this method displays a satisfying selectivity and it can be used to
distinguish between doxycycline and different antibiotics or biomolecules, which may
provide a more accurate analysis of doxycycline in complex samples. Third, the
proposed detection method is fast, low-cost and facile. Fourth, the S,N-CDs possess a
good biocompatibility and low cytotoxicity, facilitating doxycycline detection in
living cells. These advantages implied that the present S,N-CD-based doxycycline
detection method have a wonderful prospect in the fields of food safety and
environmental monitoring, as well as cancer therapy and related mechanism research.
Furthermore, the outstanding properties of as-prepared S,N-CDs in preparation,
stability, photostability and biocompatibility also make the S,N-CDs to be a
promising material for the other wider applications.
Financial support from the Natural Science Foundation of China (21405025,
(2014GXNSFBA118047), Key Laboratory for the Chemistry and Molecular
Engineering of Medicinal Resources of Education Ministry (CMEMR2013-A12), The
Scientific Research Project of Guangxi Higher Learning (KY2015YB368) and
Guangxi Normal University (2013ZD002) is gratefully acknowledged.
 P. J. Ramesh, K. Basavaiah, N. Rajendraprasad, Acta Pharm. 60 (2010) 445-454.
 M. Augenbraun, L. Bachmann, T. Wallace, L. Dubouchet, W. Mccormack, E. W.
Hook III, Sex. Transm. Dis. 25 (1998), 1-4.
 W. Naidong, S. Geelen, E. Roets, J. Hoogmartens,
J. Pharm. Biomed. Anal. 8
 X. Hu, X.; Pan, J.; Hu, Y.; Huo, G. Li, J. Chromatogr. A 1188 (2008) 97-107.
 E. Angelakis, N. Armstrong, C. Nappez, M. Richez, E. Chabriere, D. Raoult,
Journal of Infection 71 (2015) 511-517.
 R. Injac, N. Kocevar, S. Kreft, Anal. Chim. Acta 594 (2007) 119-127.
 A. Espinosa-Mansilla, F. Salinas, I. De Orbe Paya, Anal. Chim. Acta 313 (1995)
 P. J. Ramesh, K. Basavaiah and N. Rajendraprasad, Acta, Pharm, 60 (2010)
 W. H. Liu, Y. Wang, J. H. Tang, G. L. Shen, R. Q. Yu, Analyst 123 (1998) 365-369.
 D. Vega, L. Agüí, A. González-Cortés, P.Yáñez-Sedeño, J. M. Pingarrón, Anal.
Bioanal. Chem. 389 (2007) 951-958.
 B. Gürler, S. F. Özkorucuklu, E. Kır,
J. Pharm. Biomed. Anal. 84 (2013) 263-268.
 J. L. Lopez Paz, J. M. Calatayud, J. Pharm. Biomed. Anal. 1993 1093-1098.
 G. M. Hadad, A. El-Gindy, W. M. M. Mahmoud, Spectrochim. Acta A 70 (2008)
 S. S. Mittić, G. Ž. Miletić, D. A. Kostić, D. Č. Nasković-Đokić, B. B. Arsić and I.
D. Rašić, J. Serb. Chem. Soc. 73 (2008) 665-671.
 S. M. Sunaric, S. S. Mitic, G. Z. Miletic, A. N. Pavlovic, D. Naskovic-Djokic, J.
Anal Chem. 64 (2009) 231-237.
 A. Gajda1, A. Posyniak1, G. Tomczyk, Bull Vet Inst Pulawy 58 (2014) 573-579.
 R. S. Fife, G. W. Sledge Jr, B. J. Roth, C. Proctor, Cancer Lett. 127 (1998) 37-41.
 T. Onoda, T. Ono, D. K. Dhar, A. Yamanoi, N. Nagasue, Int. J. Cancer 118 (2006)
 P. X. E. Mouratidis, K. W. Colston, A. G. Dalgleish, Int. J. Cancer 120 (2006)
 S. N. Baker, G. A. Baker, Angew. Chem. Int. Ed. 49 (2010) 6726-6744.
 S. Zhu, G. Meng, L. Wang, J. Zhang, Y. Song, H. Jin, K. Zhang, H. Sun, H. Wang,
B. Yang, Angew. Chem, 125 (2013) 4045-4049.
 A. D. Zhao, Z. W. Chen, C. Q. Zhao, N. Gao, J. S. Ren, X. G. Qu, Carbon 85
Y. B. Song, S. J. Zhu, B. Yang, RSC Adv. 4 (2014) 27184–27200.
 C. Q. Ding, A. W. Zhu, Y. Tian, Accounts of chemical research 47 (2014) 20-30.
 S. K. Bhunia, N. Pradhan, N. R. Jana, ACS Appl. Mater. Interfaces 6 (2014)
 R. Sun, Y. Wang, Y. Ni, S. Kokot, Talanta 125 (2014) 341–346.
 L. Fan, Y. Hua, X. Wang, L. Zhang, F. Li, D. Han, Z. Li, Q. Zhang, Z. Wang, L.
Niu, Talanta 117 (2013) 152–157.
 B. Shi, L. Zhang, C. Lan, J. Zhao, Y. Su, S. Zhao, Talanta 142 (2015) 131-139.
 L. Zhang, Z. Zhang, R. Liang, Y. Li, J. Qiu, Anal. Chem.86 (2014) 4423-4430.
 S. Kundu, R. M. Yadav, T. N. Narayanan, M. V. Shelke, R. Vajtai, P. M. Ajayan,
V. K. Pillai, Nanoscale 7( 2015) 11515–11519.
 Y. Dong, H. Pang, H. Yang, C. Guo, J. Shao, Y. Chi, C. Li, T. Yu, Angew. Chem.
Int. Ed. 52 (2013) 7800-7804.
 D. Qu, M. Zheng, P. Du, Y. Zhou, L. G. Zhang, D. Li, H. Q. Tan, Z. Zhao, Z. G.
Xie, Z. C. Sun, Nanoscale 5 (2013) 12272–12277.
 D. Sun, R. Ban, P.-H. Zhang, G.-H. Wu, J.-R. Zhang, J.-J. Zhu, Carbon 64 (2013)
 X. Yang, Y. Luo, S. Zhu, Y. Feng, Y. Zhuo, Y. Dou, Biosens. Bioelectron. 56
 Y. Feng, D. Zhong, H. Miao, X. Yang, Talanta 140 (2015) 128-133.
 X. Qin, W. Lu, A. M. Asiri, A. Q. Al-Youbi, X. Sun, Sensor. Actuat. B 184 (2013)
 H. Tetsuka, R. Asahi, A. Nagoya, K. Okamoto, I. Tajima, R. Ohta, A. Okamoto,
Adv. Mater. 24 (2012) 5333-5338.
 Z. Yang, M. Xu, Y. Liu, F. He, F. Gao, Y. Su, H. Wei, Y. Zhang, Nanoscale 6
 D. Xu, M. Zheng, L. Zhang, H. Zhao, Z. Xie, X. Jing, R. E. Haddad, H. Fan, Z.
Sun, Sci. Rep. 4 (2014) 5294.
 J. Hou, J. Yan, Q. Zhao, Y. Li, D. Ding, L. Ding, Nanoscale 5 (2013) 9558-9561.
Scheme 1. Scheme 1 Schematic illustration of S,N-CDs preparation and doxycycline
Fig. 1. (a) TEM images and size distribution of S,N-CDs. (b) Raman spectroscopy of
the N,S-CDs. (c) XRD pattern of the N
Fig. 2. (a) XPS spectra of the S,N-CDs. (b) High resolution C1S peak of the S,N-CDs.
(c) High resolution S2p peak of the S,N-CDs. (d) High resolution N1s peak of the
Fig. 3. Fluorescence spectra of the S,N-CDs and UV-Vis absorption spectra of the CA
(a), ammonium thiocyanate (b) and S,N-CDs (c). Inset: Photograph of the S,N-CDs
solution under irradiation of natural light (left) and UV light (right).
Fig. 4. The fluorescence spectra of the S,N-CDs in the absence (a) or presence (b) of
doxycycline. Inset: photographs of the S,N-CDs solution in the absence (right) and
presence (left) of 60 μM doxycycline under irradiation of UV light.
Fig. 5. The relationship between quenching efficiency and the concentration of
doxycycline. Inset shows the linear response range.
Fig. 6. Comparison of fluorescence intensities of S,N-CDs in the presence of 60 μM
doxycycline, 60 μM ampicillin, 60 μM penicillin, 60 μM streptomycin, and 60 μM
Fig. 7. Confocal microscopy images of HepG2 cells incubated with 100 μg mL
S,N-CDs for 12 h. (a) fluorescent image excited with a 405 nm laser, (b) fluorescent
image excited with a 488 nm laser, (b) fluorescent image excited with a 514 nm laser,
and (d) merged image of a, b and c.
Fig. 8. Confocal microscopy images of HepG2 cells incubated with 100 μg mL
S,N-CDs (a) and after addition of 100 μM of doxycycline (b).
sulfur and nitrogen binary doped carbon dots derived from ammonium
thiocyanate was synthesized.
► The sulfur and nitrogen binary doped carbon dots can be used for multicolor cell
► High selective and sensitive method for doxycycline detection in living cells was
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