- Email: [email protected]
Constructing carbon dots and CdTe quantum dots multi-functional composites for ultrasensitive sensing and rapid degrading ciprofloxacin
Sensors & Actuators: B. Chemical 289 (2019) 242–251
Contents lists available at ScienceDirect
Sensors and Actuators B: Chemical journal homepage: www.elsevier.com/locate/snb
Constructing carbon dots and CdTe quantum dots multi-functional composites for ultrasensitive sensing and rapid degrading ciprofloxacin ⁎
Xiqing Liua, Tao Wangb, Yang Luc, Wenjuan Wangb, Zhiping Zhoua, , Yongsheng Yanb,
T
⁎⁎
a
School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, China Institute of Green Chemistry and Chemical Technology, School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang, 212013, China c Yangzhong tiande electrical equipment co.LTD, Zhengjiang, 212013, China b
A R T I C LE I N FO
A B S T R A C T
Keywords: Carbon dots Fluorescent detection Molecular imprinting Ratiometric fluorescence sensor Photocatalytic degradation Ciprofloxacin
The sensitive monitoring and rapid removal antibiotics residues are great challenges and hugely significant for the environmental protection. In this work, a green and facile strategy was obtained for the fabrication of highly fluorescent carbon dots (CDs) through hydrothermal treatment of osmanthus fragrans leaves as carbon source and polyethyleneimine as nitrogen source. Then the prepared blue CDs were combined with red CdTe quantum dots (QDs) for constructing MIPs@CdTe/CDs@SiO2 was applied to selectively and sensitively assay ciprofloxacin (CIP) and TiO2/CDs/CdTe QDs as photocatalyst for the degradation of CIP. Under optimum conditions, MIPs@CdTe/CDs@SiO2 has exhibited lower detection limit of 0.0127 nM with the linear range of 0–60 nM, and successfully applied to monitor CIP in human urine samples. Moreover, the TiO2/CDs/CdTe QDs also displayed good photocatalytic degradation of activity to CIP under sunlight irradiation. This present work which was rational constructed materials based on CDs and CdTe QDs illustrates the great practicability and potential to rapid and efficient determination and removal environmental pollutants in the future.
1. Introduction Ciprofloxacin (CIP) as one of the most important second generation of fluoroquinolone antibiotics, was widely used for prevention or healing of commonly bacterial infections in humans and animals [1–4]. There are studies have indicated that about 70% of the dose CIP has been excreted to environment by urine and feces, which could easily generate resistance pathogens and arouse serious effects on the animal husbandry and ecological systems [5]. Moreover, the excessive usage of CIP has eventually caused the CIP concentrations at high content of μg/ L in surface water [6,7] and even mg/L in wastewater [5]. Therefore, the preparation of multi-functional materials for the quantification and removal of residue levels of CIP in wastewater sample is a particularly arduous task. In recent years, quantum dots (QDs), a kind of up-and-coming fluorescent nanomaterial has exhibited noteworthy superiorities in high luminescence efficiency, excellent photostability, tunable emission colors and ease of synthesis has received tremendous concerns due to their incomparable properties and promising applications in various fields, such as fluorescent probe, catalytic materials, lighting devices and bioimaging [8–14]. Especially carbon dots (CDs) and CdTe QDs,
⁎
they have been on the basis of their robust and multi-functional properties were effectively offered service for the detection or enhancing photocatalytic degradation of targets [15–17]. For example, Guo’s group has fabricated nitrogen and phosphor co-doped CDs (NP-CQDs) for assaying Fe3+ and boosting photocatalytic degradation of methylene blue (MB) [18]. The novel study has achieved a satisfactory result on degrading MB but not exactly quantify the contents of MB based on NP-CQDs simultaneously. Our group have once chosen red CdTe QDs with APBA modification as response signal and blue CDs as reference signal to construct the ratio fluorescence probe for the detection of dopamine, which have greatly eliminated the influence of environmental interfering factors. But they were lack of selectivity for specific recognition of dopamine and their analogues [19]. Therefore, the challenge of fabrication composite materials should be accelerated to work out for selective recognition of CIP. Molecular imprinting technology (MIT) provides a flexible and useful method to pre-design precise tailored binding sites and absolutely match with the template molecules in size, shape and functional groups in a 3D-polymeric network [20–23]. The molecularly imprinted polymers (MIPs) primarily show the affinity to toward target molecules in shape and functionality, thus they have been extensively applied in
Corresponding author at: School of Materials Science and Engineering, Jiangsu University, Zhenjiang, Jiangsu Province, 212013, China. Corresponding author. E-mail addresses: [email protected] (Z. Zhou), [email protected] (Y. Yan).
⁎⁎
https://doi.org/10.1016/j.snb.2019.03.094 Received 14 January 2019; Received in revised form 18 March 2019; Accepted 21 March 2019 Available online 23 March 2019 0925-4005/ © 2019 Elsevier B.V. All rights reserved.
Sensors & Actuators: B. Chemical 289 (2019) 242–251
X. Liu, et al.
sensors, bioassay, catalysis, separation and other fields [24–26]. As for sensing, the target analytes are precisely recognized by the fluorescence MIPs and resulted in quenching or enhancement of fluorescence intensity for quantification [27,28]. Therefore, the exploration of unique fluorescence MIPs sensors for assaying CIP residue and other analytes has never stopped which is not just for the detection of trace pollutant residues to protect environments but also striving for perfection of MIPs-based synthetic methodologies. In view of this, we have prepared a ratio fluorescent molecular imprinting sensor (MIPs@CdTe/CDs@SiO2) for quantifying the trace of CIP residue in waste water based on blue CDs and red CdTe QDs. Briefly, the CDs were performed by hydrothermal treatment of osmanthus fragrans leaves and polyethyleneimine. In the process of imprinting polymer, the CIP, APTEs, TEOS and ammonia were played the role of template molecular, functional monomers, cross-linker and initiator, respectively. The additions of CIP have induced a highly selective fluorescence enhance of CDs because of the fluorescence enhancement property of CIP, but caused the CdTe QDs fluorescence quenching which resulted from the non-covalent interactions between amino and carboxyl functional groups. It has found that the MIPs@CdTe/CDs@SiO2 can be employed to selectively and sensitively assay CIP in environmental water. Therefore, a unique fluorescence MIPs sensor for the detection of CIP has been created. Additionally, the catalytic applications of CDs and CdTe QDs were also explored. As expected, the construction of TiO2/CDs/CdTe QDs can considerably photocatalytic degrade CIP, which was far superior to the TiO2/CDs photocatalytic activity. Thus, the study has further demonstrated that the CDs and CdTe QDs have prospective applications in assaying and degradation of environmental pollutants.
CdTe QDs were synthesized according to the previous report with some modification [30]. Firstly, the precursor solution of fresh NaHTe was prepared by tellurium powder and NaBH4 under the ultrasonic condition. Then CdCl2 solution and the stabilizing agent of TGA were mixed together and adjusted the pH to 11.2 under N2 saturation. The obtained NaHTe solution was quickly added into the mixture solutions to a reflex with condenser attached at 120 ℃ for several days until the CdTe QDs with emission maximum at the range of 645–665 nm for further use. It should be noticed that the molar ratio of [Cd2+]: [TGA]: [HTe−] was set at 1: 2.2: 0.4.
2. Experimental section
2.5. Preparation of MIPs@CdTe/CDs@SiO2
2.1. Materials and instruments
For the preparation of MIPs@CdTe/CDs@SiO2, the sol-gel method was applied again. [29] In the synthesis of MIPs@CdTe/CDs@SiO2, 800 μL CdTe QDs was mixed with 40 mL ethanol under ultrasonic condition and 50 μL APTEs was added to for stirring 6.0 h. Then 50 mg CDs@SiO2, 10 mg CIP and 200 μL TEOs were dispersed into the above solutions with drastic agitation. After 30 min, 200 μL NH3·H2O were used to initiate the reaction and stirred for 24 h at room temperature. Finally, the product was collected by centrifuging and washing with ethanol several times and dried in vacuum at 50 ℃. The template CIP was extracted by Soxhlet extractor elution of acetic acid and methanol (1:9, v/v). As a contrast, the nonimprinted polymer (NIP@CdTe/CDs@ SiO2) were fabricated by the same procedure but without addition of CIP.
with dramatically stirring then transferred to 100 mL Teflon-lined auto clave and heated at 200 ℃ for 24 h. Afterward, the autoclave was cooling down to room temperature naturally and the leaf residues was removed by centrifuged at 10,000 rpm for 10 min. The obtained dark brown suspension was purified through a 0.22 μm micron filter and stored at 4 °C for further use. 2.3. Synthesis of CDs@SiO2 CDs@SiO2 was synthesized by sol-gel process according to the reported method with some modifications. [29] Normally, 3.0 mL CDs were dispersed into 40 mL ethanol and stirred for 15 min. Subsequently, 100 μL TEOs and 100 μL NH3·H2O were successively added the above solution at a 30-minute interval and kept striation for 12 h. Finally, the product was collected by centrifugation, washing with ethanol and DDW and dried in vacuum at 50 ℃. 2.4. Preparation of CdTe QDs
The osmanthus fragrans leaves were picked from Jiangsu university campus. All other chemical reagents were of analytical grade and received without further purification. CdCl2 ·2.5H2O (99.99%), polyethyleneimine (PEI) (MW:1500), tellurium powder (˜100 mesh, 99.99%), thioglycolic acid (TGA) (98%), NaBH4 (99%), tetraethoxysilane (TEOS), 3-aminopropyltriethoxysilane (APTEs) and ammonia solution (25–28%) were all purchased from Aladdin reagent Co., Ltd. (Shanghai, China).Ciprofloxacin (CIP), enrofloxacin (ENX), norfloxacin (NFX), gatifloxacin (GAT) and lomefloxacin (LFX) were obtained from the National Institute for the Control of Pharmaceutical and Biological Products (Beijing, China). Double distilled water (DDW) was supplied by the experimental procedures. The morphologies and sizes surveys of fabricated samples were taken on a transmission electron microscope (TEM, JEOL, JEM-2100). The X-ray photoelectron spectroscopy (XPS) was performed with American electronics physical HI5700ESCA system by Al Kα (1486.6 eV) monochromatic X-ray radiation. The Infrared spectra analyses (4000-400 cm−1) were conducted by a Nicolet NEXUS-470 FTIR apparatus (USA) using KBr disks. The phosphorescence measurements were performed on a Cary Eclipse spectrofluorometer (USA) equipped with a plotter unit and a quartz cell (1.0 cm × 1.0 cm). The UV–vis adsorption spectra of the samples were measured on a Cary 5000 (Agilent, USA) UV–vis spectrophotometer.
2.6. Detection of CIP with MIPs@CdTe/CDs@SiO2 To make sure the accuracy and reproducibility of the experiment, all fluorescence measurements were completed at the same conditions. Firstly, 50 mg L−1 MIPs@CdTe/CDs@SiO2 and NIP@CdTe/CDs@SiO2 were dispersed into DDW by ultrasonication to get a well-dispersed solution and stored at 4 ℃. For the detection of CIP in solution, 10 μL CIP stock solutions with different concentrations (3 μM, 6 μM, 9 μM, 12 μM, 15 μM, 18 μM, 21 μM, 24 μM, 27 μM and 30 μM) were added into above mentioned 5.0 mL MIPs@CdTe/CDs@SiO2 or NIP@CdTe/CDs@ SiO2 suspension, respectively. Moreover, the fluorescence detection experiments were conducted at the photo multiplier tube voltage was adjusted to 700 V, the excitation wavelength was set at 340 nm, and the slit widths of the excitation and emission were both 10 nm.
2.2. Synthesis of CDs Before preparing CDs, a certain amount of osmanthus fragrans leaves were washed by water several times and then placed to oven until fully dehydration, and the obtained drying leaves were smashed by disintegrator and sifted out the larger dregs. CDs were synthesized through simple and typical hydrothermal reaction. Briefly, 1.0 g above mentioned leaves powder and 1.0 mL PEI were dispersed to 60 mL DDW
2.7. Preparation of TiO2 and TiO2/CDs/CdTe QDs The photochemical catalyst of TiO2/CDs/CdTe QDs was prepared as following procedures. Primarily, 7.5 mL acetic acid was mixed with 55 mL ethanol and stirred for 10 min, then 0.6 mL titanium butoxide 243
Sensors & Actuators: B. Chemical 289 (2019) 242–251
X. Liu, et al.
as functional monomer and cross-linker of TEOS. Under the excitation at 340 nm, the constructed ratiometric fluorescent sensor MIPs@CdTe/ CDs@SiO2 exhibited dual fluorescence emission peaks at 465 nm and 657 nm, respectively. Moreover, the fluorescence of CdTe QDs at 657 nm were quenched on the basis of electron transfer between CdTe QDs and CIP, and the CDs have been enhanced the fluorescence intensity at 465 nm and gradually blue-shift due to CIP itself property of fluorescence enhancement. Herein, a conspicuous fluorescence color varied from red to blue could be employed for visual detection of CIP. The TEM of CDs, CdTe QDs, CDs@SiO2 and MIPs@CdTe/CDs@SiO2 were displayed in Fig. 1. From Fig. 1a, it could be seen that the uniform sizes of the well-dispersed CDs were spherical shape. The corresponding particle size distribution histogram (the inset of Fig. 1a) were also shown that the CDs were ranged from 3.6 to 3.9 nm. The CdTe QDs kept similar morphology of spherical but the average size was about 4.9 nm (Fig. 1b), which is consistent with that prepared from the previous reported works [19]. Fig. 1c has revealed the CDs@SiO2 were the uniform spherical and the diameter has about 50 nm, and CDs were successfully coated by silica layer. After surface imprinting polymerization, the obvious changes from Fig. 1d were found that MIPs@CdTe/CDs@SiO2 were constructed by the bCDs@SiO2 nanocore and silica nanoshell and the diameter has markedly enlarged to 170 ± 5.0 nm but the sizes of CDs and CdTe QDs were too small to evidently observe. These indicated that the MIPs@CdTe/CDs@SiO2 were prepared successfully via sol-gel polymerization. The functional groups and elemental composition of the MIPs@CdTe/CDs@SiO2 were further analyzed by Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The FTIR spectra displayed in Fig. 2a that the MIPs@CdTe/CDs@SiO2 and NIPs@CdTe/CDs@SiO2 were exhibited similar appearance and locations of the main absorption peaks which demonstrated the template of CIP were eluted completely. The broad bands at 2941 cm−1 and the small band at 1636 cm−1 represented the stretching vibrations of NeH and C–N which were contributed from APTEs [33]. The peaks of 801 cm−1 and 1159 cm−1 were identified to the stretching vibrations of Si-O and Si-O-Si [34]. As shown in Fig. 2b, the full range XPS spectra were not only confirmed the elemental component of MIPs@CdTe/ CDs@SiO2 but also further verified the results were in accordance with the FTIR measurements. The high-resolution spectrum of C 1 s in Fig. 2c presented three main peaks at 284.5 eV, 285.3 eV and 287.9 eV, which can be attribute to (C]C/CeC), (C–N/CeO) and (C]O) groups, respectively [35]. The high-resolution spectrum of O 1 s mainly shows
was added into the above mixed solution and kept stirring until the solution was transparent in a dark. Subsequently, the mixture was transferred into a Teflon-lined autoclave and heated at 160 ℃ for 16 h. After cooling to room temperature naturally, the result product was obtained by centrifugation, washed several times with DDW and ethanol alternately, and dried at 50 ℃ overnight. Finally, the TiO2 was further calcined at 550 ℃ in a tube furnace for 2 h with a heating rate of 2 ℃/min and collected for further use. The construction of TiO2/CDs/CdTe QDs CdTe was according to the previous reports with some modifications [31,32]. Briefly, 1 mL CdTe QDs, 200 μL CDs and 0.584 g TiO2 were added into 5 mL ethanol for sonication 1 h and stirring 6 h, then the sample was dried in oven at 50 ℃. 2.8. Photodegradation test of CIP using TiO2/CDs/CdTe QDs To evaluate photocatalytic activity of the as-prepared samples through degrading CIP under visible-light illumination (250 W Xe lamp and a cutoff filter > 420 nm). As the typical procedure: Firstly, photocatalyst of TiO2/CDs/CdTe QDs (50 mg) was added into 100 mL of CIP solution (10 mg/L). Before irradiation, the suspension was stirred for 30 min in the dark to achieve an adsorption-desorption equilibrium. After that, about 4 mL of suspension was taken out and filtered using filter in the 10-minute interval. Finally, the concentration was determined via a UV–vis spectrophotometer. 3. Results and discussion 3.1. Synthesis and characterization of ratiometric fluorescent sensor The construction process of the MIPs@CdTe/CDs@SiO2 ratiometric fluorescence sensor for visual detection of CIP was displayed in Scheme 1. Firstly, the stable and high fluorescence CDs was fabricated by typical hydrothermal treatment using the osmanthus fragrans leaves as carbon source and PEI as nitrogenous source, and the obtained CdTe QDs were synthesized via refluxing several days under N2 saturation with the modification of stabilizing agent TGA. To present a trustworthy detection result, the CDs were coated a silica layer to construct a core-shell composite which could be effectively apart from CdTe QDs. Subsequently, the imprinting molecular polymer of ratiometric fluorescent sensor (MIPs@CdTe/CDs@SiO2) was prepared by sol-gel procedure in the presence of CdTe QDs, CDs@SiO2, template of CIP, APTS
Scheme 1. Schematic illustration for preparation of the ratiometric fluorescence MIPs@rCDs/bCDs@SiO2 sensors for CIP monitoring. 244
Sensors & Actuators: B. Chemical 289 (2019) 242–251
X. Liu, et al.
Fig. 1. TEM image of (a) CDs (insert: size distribution histogram of CDs), (b) CdTe QDs (insert: size distribution histogram of CdTe QDs), (c) CDs@SiO2 and (d) MIPs@CdTe/CDs@SiO2.
3.2. Optical properties
two peaks at 530.8 eV (C]O) and 531.8 eV (Si-O) in the Fig. 2d [34]. The Fig. 2e revealed that the N 1 s spectrum was deconvoluted into typica peak with the binding energies of 399.6 eV originated from C–NC [36]. The existed silicon-involving bonds as shown in Fig. 2f were confirmed by the Si 2p signal which including Si-O/SiO2 (102.1 eV) and Si-C (102.8 eV) [37]. The Cd3d spectrum generally displayed two peaks at 404.5 and 411.3 eV, which were corresponded to the Cd in CdTe (Fig. 2g). [38] Meanwhile, the Fig. 2h presented the Te3d spectrum peaks at 571.9 and 582.4 eV, which were accorded with the Cd-Te bonding state [38]. All above the FTIR and XPS characterization results were demonstrated the MIPs@CdTe/CDs@SiO2 have been fabricated successfully. For investigation the CIP recognition property of MIPs@CdTe/ CDs@SiO2 ratio fluorescence sensors, the fluorescence emission spectra of MIPs@CdTe/CDs@SiO2 and NIPs@CdTe/CDs@SiO2 were subsequently examined and displayed in Fig. 3a. As can be seen a strong emission at 465 nm and a relatively weak emission at 647 nm with the maximum emission wavelength could be caught under the excitation at 340 nm when MIPs@CdTe/CDs@SiO2 was combined with target of CIP. After eluting CIP, the fluorescence of a strong emission at 465 nm has slightly weakened but emission wavelength at 647 nm was recovered swiftly from MIPs@CdTe/CDs@SiO2, which was close to NIPs@CdTe/ CDs@SiO2. Correspondingly, the notable fluorescent changes of MIPs@CdTe/CDs@SiO2 suspension have taken place from pale blue to magenta which was similar to NIPs@CdTe/CDs@SiO2 under UV lamp. The phenomena were revealed that MIPs@CdTe/CDs@SiO2 has an excellent recognition to CIP and could be applied to eye-naked detect CIP under UV lamp.
Of all the factors interfering the recognition performance of the MIPs@CdTe/CDs@SiO2 ratiometric fluorescence sensor, including stability, responding time and pH of MIPs@CdTe/CDs@SiO2. The stability of MIPs@CdTe/CDs@SiO2 was investigated by repeated measurement of fluorescence intensity for 130 min at room temperature. As displayed in Fig. 3b, the fluorescence intensity of MIPs@CdTe/CDs@SiO2 was significantly stable and this phenomenon was illustrated that the tailored polymer has well-protected CdTe QDs and CDs to resist the neutral external environments. In order to achieve the optimizing tested parameters, the response time and pH of the ratiometric fluorescence MIPs@CdTe/CDs@SiO2 sensors to CIP were investigated systematically. From Fig. 3c it can be found that the fluorescence intensity of MIPs@CdTe/CDs@SiO2 sensors was not changed by adding CIP 4.0 min. There have been more apparently fluorescence intensity distinctions of CdTe/CDs@SiO2 than MIPs@CdTe/CDs@SiO2 with the solutions pH changed from 3.0 to 12 (Fig. 3d). The fluorescence of CdTe/CDs@SiO2 have been dramatically quenched when pH was less 6.0 or over 8.0, but MIPs@CdTe/CDs@SiO2 could keep favorable fluorescent intensities in the range of 5.0 to 10 and the strongest fluorescence was at pH = 7.0. The phenomenon demonstrated that the presence of silica layers has well-protected CdTe QDs and CDs to adapt the pH value variations from weak acid to alkaline. Therefore, the optimal analytical reaction time of 4.0 min and pH of 7.0 were used for the following measurements.
245
Sensors & Actuators: B. Chemical 289 (2019) 242–251
X. Liu, et al.
Fig. 2. (a) The FT-IR spectra of MIPs@rCDs/bCDs@SiO2 and NIPs@rCDs/bCDs@SiO2, the XPS spectrum of MIPs@rCDs/bCDs@SiO2: (b) XPS survey spectrum, the high resolution XPS peaks of C1 s (c), O1 s (d), N1 s (e), Si2p (f), Cd3d (g) and Te3d (h).
246
Sensors & Actuators: B. Chemical 289 (2019) 242–251
X. Liu, et al.
Fig. 3. (a) The fluorescence spectra and corresponding photo under UV lamp of NIPs@CdTe/CDs@SiO2 (curve I, 1), MIPs@CdTe/CDs@SiO2 (curve II,2) and MIPs@CdTe/CDs@SiO2@CIP (curve III, 3); (b) The fluorescence stability of MIPs@CdTe/CDs@SiO2; (c) The fluorescence response time of MIPs@CdTe/CDs@SiO2; (d) The effects of different pH on the fluorescence intensity of MIPs@CdTe/CDs@SiO2 and CdTe/CDs@SiO2.
same conditions. As shown in Fig. 4d, the results demonstrated that the fluorescence of MIPs@CdTe at 647 nm was gradually quenched with the increasing concentrations of CIP and at 425 nm was slightly enhanced due to CIP itself fluorescent property. However, the fluorescent photo of MIPs@CdTe for the detection of CIP was difficult to discern the color changes for naked eye observation under a UV lamp. Thus, the results verified that the MIPs@CdTe has poor visual detection of CIP than the ratiometric fluorescence sensors MIPs@CdTe/CDs@SiO2.
3.3. Sensitivity of MIPs@CdTe/CDs@SiO2 The sensitivity of the ratiometric fluorescence sensor was assessed by adding different amount of CIP into the MIPs@CdTe/CDs@SiO2 and NIPs@CdTe/CDs@SiO2 solutions under the optimal conditions. As illustrated in Fig. 4a, the fluorescence intensity of MIPs@CdTe/CDs@ SiO2 at 657 nm was regularly quenched but at around 465 nm was gradually enhanced with the addition of CIP in the concentration range of 0–60 nM. With the increase same amount of CIP, the fluorescence intensity of the NIPs@CdTe/CDs@SiO2 at around 657 nm decreased slowly and at 465 nm were increased gradually (Fig. 4b). Correspondingly, the relative fluorescence photo of the MIPs@CdTe/CDs@SiO2 has more distinct changes from red to blue under a UV lamp than NIPs@CdTe/CDs@SiO2. This phenomenon was mainly caused by the MIPs@CdTe/CDs@SiO2 was existing lots of recognizing sites to selectively and rapidly match with CIP after imprinting process. As can be seen in Fig. 4c, the value of log((I465/I647)/(I465/I647)0) increased gradually with the additions of CIP and a fitting linear curve equation was obtained by the MIPs@CdTe/CDs@SiO2 that was log [(I465/I647)/(I465/I647)0] = 1.2516*10−7 + 0.02119*(CCIP/nM) (R2 = 0.9998). The limits of detection (LOD) for CIP were down to 0.0127 nM on the basis of three times the standard deviation rule (LOD = 3δ/s, where δ was defined as the standard deviation of the blank signals and s signified the slope of the calibration curve), which was far more sensitive than NIPs@CdTe/CDs@SiO2. Therefore, the fabricated MIPs@CdTe/CDs@SiO2 had the advantage of rapid and highly sensitive for the detection of CIP with broad linear range. To illustrate the superiority of MIPs@CdTe/CDs@SiO2 ratiometric fluorescence sensor for visual detection of CIP, MIPs@CdTe was also fabricated to evaluate the practical property for assaying CIP under the
3.4. Selectivity of MIPs@CdTe/CDs@SiO2 The selectivity was another pivotal factor that can determine a unique analyte target in a mixture without intervention from other components in complicated system. To evaluate the selectivity of MIPs@CdTe/CDs@SiO2 for detecting CIP, two series of controlled experiments were conducted under the optimized conditions. Firstly, there were 30 nM different kinds of metal cations (including K+, Na+, Ca2+, Zn2+, Mg2+, Al3+, Ag+, Cu2+, Hg2+ and Fe3+) mixed with MIPs@CdTe/CDs@SiO2 for the specific recognition CIP. From Fig. 5a it can be seen that the fluorescence of MIPs@CdTe/CDs@SiO2 have been slightly quenched by a few of metal ions such as Hg2+ and Ag+, but the result of MIPs@CdTe/CDs@SiO2 for assaying CIP have no distinct changes. Thus, the reference signal is significant for the elimination of the deviation from ambient interferences and amelioration of the detection accuracy. The impact of CIP and several CIP analogues (including ENX, NFX, GAT and LOM) on MIPs@CdTe/CDs@SiO2 and NIPs@CdTe/CDs@SiO2 were also investigated. Fig. 5b exhibited that the ENX, NFX, GAT and LOM have slightly influenced on the fluorescences of MIPs@CdTe/ CDs@SiO2 and NIPs@CdTe/CDs@SiO2, while CIP has an evident 247
Sensors & Actuators: B. Chemical 289 (2019) 242–251
X. Liu, et al.
Fig. 4. (a) The fluorescence spectra and corresponding photographs of MIPs@CdTe/CDs@SiO2; (b) the fluorescence spectra and corresponding photographs of NIPs@CdTe/CDs@SiO2; (c) the linear relationships between MIPs@CdTe/CDs@SiO2 and NIPs@CdTe/CDs@SiO2 and (d) fluorescence spectra and corresponding photographs of MIPs@CdTe.
fluorescence quenching to MIPs@CdTe/CDs@SiO2 but only a little quenching effect on NIPs@CdTe/CDs@SiO2. Moreover, the fluorescence quenching of the MIPs@CdTe/CDs@SiO2 solution caused by the mixture (CIP and ENX, CIP and NFX, CIP and LOM, CIP and GAT) was
approximately equal to CIP. The above experimental results fully illustrated the high selectivity of MIPs@CdTe/CDs@SiO2 for the detection of CIP.
Fig. 5. (a) The effects of 30 nM different metal ion on the MIPs@CdTe/CDs@SiO2 to recognize CIP (24 nM); (b) The effects of CIP and some analogues on MIPs@CdTe/CDs@SiO2 and NIPs@CdTe/CDs@SiO2. 248
Sensors & Actuators: B. Chemical 289 (2019) 242–251
X. Liu, et al.
urine were determined by this strategy which were collected from our group students who have taken in ciprofloxacin hydrochloride tablets after 12 h. Although to CIP was detected after sample extraction process, different concentrations of the CIP were also spiked in four human urine samples for the recovery experiment. From Table 1 it can be seen the recoveries of CIP were in the range of 98.78%–102.08% and the relative standard deviations (RSDs) were below 0.96% for urine samples, indicating the satisfied precision and accuracy for monitoring CIP in real samples. Compared with other reported different probes for CIP detection as displayed in Table 2, which indicated the sensitivity of our detecting system was superior to most previously reported ones. These may be caused by the changes in the fluorescence intensity ratio of the two emission wavelengths and a distinct color change from purplish red to blue in a range of 0–60 nM. Moreover, we proposed the ratiometric fluorescence MIPs@CdTe/CDs@SiO2 sensor was comparatively easy to operate which was favorable for visual detection of CIP by eye-naked.
Table 1 Quantitative determination of CIP in human urine samples. Found (nM)
Spiked concentration (nM)
Total found (nM)
Recovery (%)
RSD (%, n = 6)
9.164 8.548 9.213 8.622 9.463
0 10 15 20 25
9.248 18.934 23.918 28.787 34.843
100.86 102.08 98.78 100.58 101.10
0.42 0.96 0.87 0.94 0.58
Table 2 Comparison of this work with different methods for CIP assaying. Sensing Elements
Linear Range
LOD
References
carbon dot/silicon dot carbon dots carbon dots MIPs@SiO2-FITC MIPs@CdTe/CDs@SiO2
0.01−150 μM 10 nM–90 μM 0.02–1.0 μM 0−250 nM 0−60 nM
2.0 nM 5.88 nM 6.7 nM 4.04 nM 0.0127 nM
[39] [40] [41] [42] This work
3.6. Exploration of photocatalytic activity of TiO2/CDs/CdTe QDs The photocatalytic performance of TiO2/CDs/CdTe QDs and TiO2/ CDs for the degradation of CIP were also studied. Firstly, in order to investigate the morphology and structure of the TiO2/CDs/CdTe QDs, the SEM images were presented in Fig. 6. It could be seen from Fig. 6a that TiO2 prepared by the hydrothermal method were near-spherical
3.5. Practical applications and approach performance comparison After investigating the sensitivity and selectivity of MIPs@CdTe/ CDs@SiO2 sensors towards CIP, the practicality of the CIP in human
Fig. 6. SEM images of TiO2 (a) and TiO2/CDs/CdTe QDs (b) and elemental mapping images of TiO2/CDs/CdTe QDs (c). 249
Sensors & Actuators: B. Chemical 289 (2019) 242–251
X. Liu, et al.
Fig. 7. (a) The photocatalytic activities for TiO2/CDs and TiO2/CDs/CdTe QDs to CIP; (b) The corresponding kinetic fit of TiO2/CDs and TiO2/CDs/CdTe QDs for the degradation of CIP; (c) The absorption spectra variations of the TiO2/CDs/CdTe QDs to CIP solution.
and quantitative assay environmental pollutants.
with excellent dispersity and the diameters were ranged from 300 to 600 nm. After mixing with CDs and CdTe QDs, the TiO2/CDs/CdTe QDs SEM images revealed the CDs and CdTe QDs did not remarkably change the size and morphology of TiO2 nanoparticles, but the surface was rougher than TiO2 (as shown in Fig. 6b). Moreover, the elemental mapping analysis also displayed the related elements were homogeneously distributed on TiO2/CDs/CdTe QDs (Fig. 6c), which indicated the TiO2/CDs/CdTe QDs were successfully prepared. As the Fig. 7a shown, the TiO2/CDs/CdTe QDs exhibited higher photocatalytic activity than TiO2/CDs, which attributed to the effective electron-hole pair separation due to quantum effect of CdTe QDs. The kinetic curves of CIP degradation (Fig. 7b) were studied by fitting according to a pseudo-first-order, and the calculated removal rate constant over TiO2/CDs/CdTe QDs was 0.008 min−1, which was 1.3 times higher than TiO2/CDs (0.006 min−1). In addition, the corresponding of absorbance variation curves was presented in Fig. 7c, directly proving that the CIP molecules were photo-degraded into small molecules. The results vividly proved that the CdTe QDs could further enhance the photocatalytic performance of TiO2/CDs towards CIP.
Acknowledgments This work was financially supported by the National Natural Science Foundation of China (No. 21507045 and No. 21607013), Natural Science Foundation of Jiangsu Province (No. BK20160569), Postgraduate Research & Practice Innovation Program of Jiangsu Province (KYCX18_2232). References [1] S. Li, X. Zhang, Y. Huang, Zeolitic imidazolate framework-8 derived nanoporous carbon as an effective and recyclable adsorbent for removal of ciprofloxacin antibiotics from water, J. Hazard. Mater. 321 (2017) 711–719. [2] M.K. Pawar, K.C. Tayade, S.K. Sahoo, P.P. Mahulikar, A.S. Kuwar, B.L. Chaudhari, Selective ciprofloxacin antibiotic detection by fluorescent siderophore pyoverdin, Biosens. Bioelectron. 81 (2016) 274–279. [3] Y. Li, C. Zeng, C. Wang, L. Zhang, Preparation of C@silica core/shell nanoparticles from ZIF-8 for efficient ciprofloxacin adsorption, Chem. Eng. J. 343 (2018) 645–653. [4] A. Xie, J. Dai, X. Chen, P. Ma, J. He, C. Li, Z. Zhou, Y. Yan, Ultrahigh adsorption of typical antibiotics onto novel hierarchical porous carbons derived from renewable lignin via halloysite nanotubes-template and in-situ activation, Chem. Eng. J. 304 (2016) 609–620. [5] X. Van Doorslaer, J. Dewulf, H. Van Langenhove, K. Demeestere, Fluoroquinolone antibiotics: an emerging class of environmental micropollutants, Sci. Total Environ. 500-501 (2014) 250–269. [6] Q. Bu, B. Wang, J. Huang, S. Deng, G. Yu, Pharmaceuticals and personal care products in the aquatic environment in China: a review, J. Hazard. Mater. 262 (2013) 189–211. [7] Q.Q. Zhang, G.G. Ying, C.G. Pan, Y.S. Liu, J.L. Zhao, Comprehensive evaluation of antibiotics emission and fate in the river basins of China: source analysis, multimedia modeling, and linkage to bacterial resistance, Environ. Sci. Technol. 49 (2015) 6772–6782. [8] Z. Shen, C. Zhang, X. Yu, J. Li, Z. Wang, Z. Zhang, B. Liu, Microwave-assisted synthesis of cyclen functional carbon dots to construct a ratiometric fluorescent
4. Conclusions In summary, a ratiometric fluorescence sensor MIPs@CdTe/CDs@ SiO2 was constructed and applied in the sensitive and selective detection of CIP in human urine samples. This novel strategy was presented an excellent linear CIP assay range of 0–60 nM with a detection limit as low as 0.0127 nM. In addition, the photocatalytic degradation of CIP was also investigated by TiO2/CDs/CdTe QDs composite under visible light irradiation and achieved satisfied result. Therefore, the construction of CdTe QDs and CDs composites by different methods could efficiently detect and degrade CIP, which provide a novel thought to treat 250
Sensors & Actuators: B. Chemical 289 (2019) 242–251
X. Liu, et al.
[9]
[10]
[11]
[12]
[13] [14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23]
[24]
[25]
probe for tetracycline detection, J. Mater. Chem. C Mater. Opt. Electron. Devices 6 (2018) 9636–9641. V. Sharma, N. Kaur, P. Tiwari, A.K. Saini, S.M. Mobin, Multifunctional fluorescent “Off-On-Off” nanosensor for Au3+ and S2− employing N-S co-doped carbon-dots, Carbon 139 (2018) 393–403. W. Xu, J. Chen, S. Sun, Z. Tang, K. Jiang, L. Song, Y. Wang, C. Liu, H. Lin, Fluorescent and photoacoustic bifunctional probe for the detection of ascorbic acid in biological fluids, living cells and in vivo, Nanoscale 10 (2018) 17834–17841. M.K. Barman, A. Patra, Current status and prospects on chemical structure driven photoluminescence behaviour of carbon dots, J. Photochem. Photobiol. C Photochem. Rev. 37 (2018) 1–22. J. Jiang, G. Ye, Z. Wang, Y. Lu, J. Chen, K. Matyjaszewski, Heteroatom-doped carbon dots (CDs) as a class of metal-free photocatalysts for PET-RAFT polymerization under visible light and sunlight, Angew. Chem. Int. Ed. 57 (2018) 12037–12042. L. Xiao, H. Sun, Novel properties and applications of carbon nanodots, Nanoscale Horiz. 3 (2018) 565–597. K. Chullasat, P. Nurerk, P. Kanatharana, F. Davis, O. Bunkoed, A facile optosensing protocol based on molecularly imprinted polymer coated on CdTe quantum dots for highly sensitive and selective amoxicillin detection, Sens. Actuator B: Chem. 254 (2018) 255–263. Y. Zhan, T. Geng, Y. Liu, C. Hu, X. Zhang, B. Lei, J. Zhuang, X. Wu, D. Huang, G. Xiao, B. Zou, Near-ultraviolet to near-infrared fluorescent nitrogen-doped carbon dots with two-photon and piezochromic luminescence, ACS Appl. Mater. Inter. 10 (2018) 27920–27927. T. Wang, X. Liu, C. Ma, Z. Zhu, Y. Liu, Z. Liu, M. Wei, X. Zhao, H. Dong, P. Huo, C. Li, Y. Yan, Bamboo prepared carbon quantum dots (CQDs) for enhancing Bi3Ti4O12 nanosheets photocatalytic activity, J. Alloys. Compd. 752 (2018) 106–114. L. Weidong, L. Yuan, W. Min, F. Xiaolei, A.T.R. Simon, S. Yuan, Y. Xue, F. Tanglue, W. Kaifeng, L. Zhongyi, L. Baojun, C. Zhimin, S.T. John, L. Siyu, Y. Bai, Carbon‐quantum‐Dots‐Loaded ruthenium nanoparticles as an efficient electrocatalyst for hydrogen production in alkaline media, Adv. Mater. 30 (2018) 1800676. Y. Guo, F. Cao, Y. Li, Solid phase synthesis of nitrogen and phosphor co-doped carbon quantum dots for sensing Fe3+ and the enhanced photocatalytic degradation of dyes, Sens. Actuator B: Chem. 255 (2017) 1105–1111. Y. Xu, X. Wei, H. Li, X. Zheng, K. Lu, X. Liu, K. Wang, Y. Yan, Boric acid functionalized ratiometric fluorescence probe for sensitive and on-site naked eye determination of dopamine based on two different kinds of quantum dots, RSC Adv. 6 (2016) 72715–72721. Y. Yuan, Y. Yang, M. Faheem, X. Zou, X. Ma, Z. Wang, Q. Meng, L. Wang, S. Zhao, G. Zhu, Molecularly imprinted porous aromatic frameworks serving as porous artificial enzymes, Adv. Mater. 30 (2018) 1800069. T. Takeuchi, H. Sunayama, Beyond natural antibodies- a new generation of synthetic antibodies created by post-imprinting modification of molecularly imprinted polymers, Chem. Commun. 54 (2018) 6243–6251. Q. Li, T. Kamra, L. Ye, A modular approach for assembling turn-on fluorescence sensors using molecularly imprinted nanoparticles, Chem. Commun. 52 (2016) 12237–12240. Q. Li, T. Kamra, L. Ye, A modular approach for assembling turn-on fluorescence sensors using molecularly imprinted nanoparticles, Chem. Commun. 52 (2016) 12237–12240. J. Tan, M. Guo, L. Tan, Y. Geng, S. Huang, Y. Tang, C. Su, C.C. Lin, Y. Liang, Highly efficient fluorescent QDs sensor for specific detection of protein through double recognition of hybrid aptamer-molecular imprinted polymers, Sens. Actuator B: Chem. 274 (2018) 627–635. Z. Wanqing, D. Dawei, L. Shanqin, Z. Yongsheng, L. Leipeng, L. Xinli, C. Na,
[26]
[27]
[28]
[29] [30] [31]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
[39]
[40]
[41]
[42]
251
Z. Yuping, Metal-organic framework-based moleculary imprinted polymer as a high sensitive and selective hybrid for the determination of dopamine in injections and human serum samples, Biosens. Bioelectron. 118 (2018) 129–136. T. Kan, M. Qiang, L. Jing, X. Sheng, Z. Ye, W. Wei, L. Xiaoya, G. Yao, Water-dispersible molecularly imprinted nanohybrids via co-assembly of carbon nanotubes with amphiphilic copolymer and photocrosslinking for highly sensitive and selective paracetamol detection, Biosens. Bioelectron. 117 (2018) 713–719. W. Gui, H. Wang, Y. Liu, Q. Ma, Ratiometric fluorescent sensor with molecularly imprinted mesoporous microspheres for malachite green detection, Sens. Actuator B: Chem. 266 (2018) 685–691. H. Zhu, H. Yao, K. Xia, J. Liu, X. Yin, W. Zhang, J. Pan, Magnetic nanoparticles combining teamed boronate affinity and surface imprinting for efficient selective recognition of glycoproteins under physiological pH, Chem. Eng. J. 346 (2018) 317–328. W. Stöber, A. Fink, E. Bohn, Controlled growth of monodisperse silica spheres in the micron size range, J. Colloid Interface Sci. 26 (1968) 62–69. C. Wang, Q. Ma, X. Su, Synthesis of CdTe nanocrystals with mercaptosuccinic acid as stabilizer, J. Nanosci. Nanotechno. 8 (2008) 4408–4414. M. Ji, Y. Liu, J. Di, R. Chen, Z. Chen, J. Xia, H. Li, N-CQDs accelerating surface charge transfer of Bi4O5I2 hollow nanotubes with broad spectrum photocatalytic activity, Appl. Catal. B 237 (2018) 1033–1043. P. Wang, X. Li, J. Fang, D. Li, J. Chen, X. Zhang, Y. Shao, Y. He, A facile synthesis of CdSe quantum dots-decorated anatase TiO2 with exposed {001} facets and its superior photocatalytic activity, Appl. Catal. B 181 (2016) 838–847. X. Wei, M. Meng, Z. Song, L. Gao, H. Li, J. Dai, Z. Zhou, C. Li, J. Pan, P. Yu, Y. Yan, Synthesis of molecularly imprinted silica nanospheres embedded mercaptosuccinic acid-coated CdTe quantum dots for selective recognition of λ-cyhalothrin, J. Lumin. 153 (2014) 326–332. J. Wang, R. Cheng, Y. Wang, L. Sun, L. Chen, X. Dai, J. Pan, G. Pan, Y. Yan, Surfaceimprinted fluorescence microspheres as ultrasensitive sensor for rapid and effective detection of tetracycline in real biological samples, Sens. Actuator B: Chem. 263 (2018) 533–542. W. Song, W. Duan, Y. Liu, Z. Ye, Y. Chen, H. Chen, S. Qi, J. Wu, D. Liu, L. Xiao, C. Ren, X. Chen, Ratiometric detection of intracellular lysine and pH with one-pot synthesized dual emissive carbon dots, Anal. Chem. 89 (2017) 13626–13633. A. Kumar, M. Khan, X. Zeng, I.M.C. Lo, Development of g-C3N4/TiO2/Fe3O4@ SiO2heterojunction via sol-gel route: a magnetically recyclable direct contact Zscheme nanophotocatalyst for enhanced photocatalytic removal of ibuprofen from real sewage effluent under visible light, Chem. Eng. J. 353 (2018) 645–656. X. Li, W. Wang, Q. Li, H. Lin, Y. Xu, L. Zhuang, Design of Fe3O4@SiO2@mSiO2organosilane carbon dots nanoparticles: Synthesis and fluorescence red-shift properties with concentration dependence, Mater. Design 151 (2018) 89–101. W. Zhu, S. Pan, W. Wang, C. Zhao, L. Lu, X. Liu, Hydrothermal synthesis of raisinbun-like CdTe@C nanocomposites toward enhanced photoluminescence and low cytotoxicity, New J. Chem. 37 (2013) 2751–2757. R. Gui, X. Bu, W. He, H. Jin, Ratiometric fluorescence, solution-phase and filterpaper visualization detection of ciprofloxacin based on dual-emitting carbon dot/ silicon dot hybrids, New J. Chem. 42 (2018) 16217–16225. S. Wang, Y. Wang, K. Yang, Y. Zhong, X. Yang, Z. Chen, Synthesis of carbon dots originated from hydroxypropylmethyl cellulose for sensing ciprofloxacin, Anal. Sci. 33 (2017) 1129–1134. J. Hua, Y. Jiao, M. Wang, Y. Yang, Determination of norfloxacin or ciprofloxacin by carbon dots fluorescence enhancement using magnetic nanoparticles as adsorbent, Microchim. Acta 185 (2018) 137. C. Wu, R. Cheng, J. Wang, Y. Wang, X. Jing, R. Chen, L. Sun, Y. Yan, Fluorescent molecularly imprinted nanoparticles for selective and rapid detection of ciprofloxacin in aquaculture water, J. Sep. Sci. 41 (2018) 3782–3790.
Contents lists available at ScienceDirect
Sensors and Actuators B: Chemical journal homepage: www.elsevier.com/locate/snb
Constructing carbon dots and CdTe quantum dots multi-functional composites for ultrasensitive sensing and rapid degrading ciprofloxacin ⁎
Xiqing Liua, Tao Wangb, Yang Luc, Wenjuan Wangb, Zhiping Zhoua, , Yongsheng Yanb,
T
⁎⁎
a
School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, China Institute of Green Chemistry and Chemical Technology, School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang, 212013, China c Yangzhong tiande electrical equipment co.LTD, Zhengjiang, 212013, China b
A R T I C LE I N FO
A B S T R A C T
Keywords: Carbon dots Fluorescent detection Molecular imprinting Ratiometric fluorescence sensor Photocatalytic degradation Ciprofloxacin
The sensitive monitoring and rapid removal antibiotics residues are great challenges and hugely significant for the environmental protection. In this work, a green and facile strategy was obtained for the fabrication of highly fluorescent carbon dots (CDs) through hydrothermal treatment of osmanthus fragrans leaves as carbon source and polyethyleneimine as nitrogen source. Then the prepared blue CDs were combined with red CdTe quantum dots (QDs) for constructing MIPs@CdTe/CDs@SiO2 was applied to selectively and sensitively assay ciprofloxacin (CIP) and TiO2/CDs/CdTe QDs as photocatalyst for the degradation of CIP. Under optimum conditions, MIPs@CdTe/CDs@SiO2 has exhibited lower detection limit of 0.0127 nM with the linear range of 0–60 nM, and successfully applied to monitor CIP in human urine samples. Moreover, the TiO2/CDs/CdTe QDs also displayed good photocatalytic degradation of activity to CIP under sunlight irradiation. This present work which was rational constructed materials based on CDs and CdTe QDs illustrates the great practicability and potential to rapid and efficient determination and removal environmental pollutants in the future.
1. Introduction Ciprofloxacin (CIP) as one of the most important second generation of fluoroquinolone antibiotics, was widely used for prevention or healing of commonly bacterial infections in humans and animals [1–4]. There are studies have indicated that about 70% of the dose CIP has been excreted to environment by urine and feces, which could easily generate resistance pathogens and arouse serious effects on the animal husbandry and ecological systems [5]. Moreover, the excessive usage of CIP has eventually caused the CIP concentrations at high content of μg/ L in surface water [6,7] and even mg/L in wastewater [5]. Therefore, the preparation of multi-functional materials for the quantification and removal of residue levels of CIP in wastewater sample is a particularly arduous task. In recent years, quantum dots (QDs), a kind of up-and-coming fluorescent nanomaterial has exhibited noteworthy superiorities in high luminescence efficiency, excellent photostability, tunable emission colors and ease of synthesis has received tremendous concerns due to their incomparable properties and promising applications in various fields, such as fluorescent probe, catalytic materials, lighting devices and bioimaging [8–14]. Especially carbon dots (CDs) and CdTe QDs,
⁎
they have been on the basis of their robust and multi-functional properties were effectively offered service for the detection or enhancing photocatalytic degradation of targets [15–17]. For example, Guo’s group has fabricated nitrogen and phosphor co-doped CDs (NP-CQDs) for assaying Fe3+ and boosting photocatalytic degradation of methylene blue (MB) [18]. The novel study has achieved a satisfactory result on degrading MB but not exactly quantify the contents of MB based on NP-CQDs simultaneously. Our group have once chosen red CdTe QDs with APBA modification as response signal and blue CDs as reference signal to construct the ratio fluorescence probe for the detection of dopamine, which have greatly eliminated the influence of environmental interfering factors. But they were lack of selectivity for specific recognition of dopamine and their analogues [19]. Therefore, the challenge of fabrication composite materials should be accelerated to work out for selective recognition of CIP. Molecular imprinting technology (MIT) provides a flexible and useful method to pre-design precise tailored binding sites and absolutely match with the template molecules in size, shape and functional groups in a 3D-polymeric network [20–23]. The molecularly imprinted polymers (MIPs) primarily show the affinity to toward target molecules in shape and functionality, thus they have been extensively applied in
Corresponding author at: School of Materials Science and Engineering, Jiangsu University, Zhenjiang, Jiangsu Province, 212013, China. Corresponding author. E-mail addresses: [email protected] (Z. Zhou), [email protected] (Y. Yan).
⁎⁎
https://doi.org/10.1016/j.snb.2019.03.094 Received 14 January 2019; Received in revised form 18 March 2019; Accepted 21 March 2019 Available online 23 March 2019 0925-4005/ © 2019 Elsevier B.V. All rights reserved.
Sensors & Actuators: B. Chemical 289 (2019) 242–251
X. Liu, et al.
sensors, bioassay, catalysis, separation and other fields [24–26]. As for sensing, the target analytes are precisely recognized by the fluorescence MIPs and resulted in quenching or enhancement of fluorescence intensity for quantification [27,28]. Therefore, the exploration of unique fluorescence MIPs sensors for assaying CIP residue and other analytes has never stopped which is not just for the detection of trace pollutant residues to protect environments but also striving for perfection of MIPs-based synthetic methodologies. In view of this, we have prepared a ratio fluorescent molecular imprinting sensor (MIPs@CdTe/CDs@SiO2) for quantifying the trace of CIP residue in waste water based on blue CDs and red CdTe QDs. Briefly, the CDs were performed by hydrothermal treatment of osmanthus fragrans leaves and polyethyleneimine. In the process of imprinting polymer, the CIP, APTEs, TEOS and ammonia were played the role of template molecular, functional monomers, cross-linker and initiator, respectively. The additions of CIP have induced a highly selective fluorescence enhance of CDs because of the fluorescence enhancement property of CIP, but caused the CdTe QDs fluorescence quenching which resulted from the non-covalent interactions between amino and carboxyl functional groups. It has found that the MIPs@CdTe/CDs@SiO2 can be employed to selectively and sensitively assay CIP in environmental water. Therefore, a unique fluorescence MIPs sensor for the detection of CIP has been created. Additionally, the catalytic applications of CDs and CdTe QDs were also explored. As expected, the construction of TiO2/CDs/CdTe QDs can considerably photocatalytic degrade CIP, which was far superior to the TiO2/CDs photocatalytic activity. Thus, the study has further demonstrated that the CDs and CdTe QDs have prospective applications in assaying and degradation of environmental pollutants.
CdTe QDs were synthesized according to the previous report with some modification [30]. Firstly, the precursor solution of fresh NaHTe was prepared by tellurium powder and NaBH4 under the ultrasonic condition. Then CdCl2 solution and the stabilizing agent of TGA were mixed together and adjusted the pH to 11.2 under N2 saturation. The obtained NaHTe solution was quickly added into the mixture solutions to a reflex with condenser attached at 120 ℃ for several days until the CdTe QDs with emission maximum at the range of 645–665 nm for further use. It should be noticed that the molar ratio of [Cd2+]: [TGA]: [HTe−] was set at 1: 2.2: 0.4.
2. Experimental section
2.5. Preparation of MIPs@CdTe/CDs@SiO2
2.1. Materials and instruments
For the preparation of MIPs@CdTe/CDs@SiO2, the sol-gel method was applied again. [29] In the synthesis of MIPs@CdTe/CDs@SiO2, 800 μL CdTe QDs was mixed with 40 mL ethanol under ultrasonic condition and 50 μL APTEs was added to for stirring 6.0 h. Then 50 mg CDs@SiO2, 10 mg CIP and 200 μL TEOs were dispersed into the above solutions with drastic agitation. After 30 min, 200 μL NH3·H2O were used to initiate the reaction and stirred for 24 h at room temperature. Finally, the product was collected by centrifuging and washing with ethanol several times and dried in vacuum at 50 ℃. The template CIP was extracted by Soxhlet extractor elution of acetic acid and methanol (1:9, v/v). As a contrast, the nonimprinted polymer (NIP@CdTe/CDs@ SiO2) were fabricated by the same procedure but without addition of CIP.
with dramatically stirring then transferred to 100 mL Teflon-lined auto clave and heated at 200 ℃ for 24 h. Afterward, the autoclave was cooling down to room temperature naturally and the leaf residues was removed by centrifuged at 10,000 rpm for 10 min. The obtained dark brown suspension was purified through a 0.22 μm micron filter and stored at 4 °C for further use. 2.3. Synthesis of CDs@SiO2 CDs@SiO2 was synthesized by sol-gel process according to the reported method with some modifications. [29] Normally, 3.0 mL CDs were dispersed into 40 mL ethanol and stirred for 15 min. Subsequently, 100 μL TEOs and 100 μL NH3·H2O were successively added the above solution at a 30-minute interval and kept striation for 12 h. Finally, the product was collected by centrifugation, washing with ethanol and DDW and dried in vacuum at 50 ℃. 2.4. Preparation of CdTe QDs
The osmanthus fragrans leaves were picked from Jiangsu university campus. All other chemical reagents were of analytical grade and received without further purification. CdCl2 ·2.5H2O (99.99%), polyethyleneimine (PEI) (MW:1500), tellurium powder (˜100 mesh, 99.99%), thioglycolic acid (TGA) (98%), NaBH4 (99%), tetraethoxysilane (TEOS), 3-aminopropyltriethoxysilane (APTEs) and ammonia solution (25–28%) were all purchased from Aladdin reagent Co., Ltd. (Shanghai, China).Ciprofloxacin (CIP), enrofloxacin (ENX), norfloxacin (NFX), gatifloxacin (GAT) and lomefloxacin (LFX) were obtained from the National Institute for the Control of Pharmaceutical and Biological Products (Beijing, China). Double distilled water (DDW) was supplied by the experimental procedures. The morphologies and sizes surveys of fabricated samples were taken on a transmission electron microscope (TEM, JEOL, JEM-2100). The X-ray photoelectron spectroscopy (XPS) was performed with American electronics physical HI5700ESCA system by Al Kα (1486.6 eV) monochromatic X-ray radiation. The Infrared spectra analyses (4000-400 cm−1) were conducted by a Nicolet NEXUS-470 FTIR apparatus (USA) using KBr disks. The phosphorescence measurements were performed on a Cary Eclipse spectrofluorometer (USA) equipped with a plotter unit and a quartz cell (1.0 cm × 1.0 cm). The UV–vis adsorption spectra of the samples were measured on a Cary 5000 (Agilent, USA) UV–vis spectrophotometer.
2.6. Detection of CIP with MIPs@CdTe/CDs@SiO2 To make sure the accuracy and reproducibility of the experiment, all fluorescence measurements were completed at the same conditions. Firstly, 50 mg L−1 MIPs@CdTe/CDs@SiO2 and NIP@CdTe/CDs@SiO2 were dispersed into DDW by ultrasonication to get a well-dispersed solution and stored at 4 ℃. For the detection of CIP in solution, 10 μL CIP stock solutions with different concentrations (3 μM, 6 μM, 9 μM, 12 μM, 15 μM, 18 μM, 21 μM, 24 μM, 27 μM and 30 μM) were added into above mentioned 5.0 mL MIPs@CdTe/CDs@SiO2 or NIP@CdTe/CDs@ SiO2 suspension, respectively. Moreover, the fluorescence detection experiments were conducted at the photo multiplier tube voltage was adjusted to 700 V, the excitation wavelength was set at 340 nm, and the slit widths of the excitation and emission were both 10 nm.
2.2. Synthesis of CDs Before preparing CDs, a certain amount of osmanthus fragrans leaves were washed by water several times and then placed to oven until fully dehydration, and the obtained drying leaves were smashed by disintegrator and sifted out the larger dregs. CDs were synthesized through simple and typical hydrothermal reaction. Briefly, 1.0 g above mentioned leaves powder and 1.0 mL PEI were dispersed to 60 mL DDW
2.7. Preparation of TiO2 and TiO2/CDs/CdTe QDs The photochemical catalyst of TiO2/CDs/CdTe QDs was prepared as following procedures. Primarily, 7.5 mL acetic acid was mixed with 55 mL ethanol and stirred for 10 min, then 0.6 mL titanium butoxide 243
Sensors & Actuators: B. Chemical 289 (2019) 242–251
X. Liu, et al.
as functional monomer and cross-linker of TEOS. Under the excitation at 340 nm, the constructed ratiometric fluorescent sensor MIPs@CdTe/ CDs@SiO2 exhibited dual fluorescence emission peaks at 465 nm and 657 nm, respectively. Moreover, the fluorescence of CdTe QDs at 657 nm were quenched on the basis of electron transfer between CdTe QDs and CIP, and the CDs have been enhanced the fluorescence intensity at 465 nm and gradually blue-shift due to CIP itself property of fluorescence enhancement. Herein, a conspicuous fluorescence color varied from red to blue could be employed for visual detection of CIP. The TEM of CDs, CdTe QDs, CDs@SiO2 and MIPs@CdTe/CDs@SiO2 were displayed in Fig. 1. From Fig. 1a, it could be seen that the uniform sizes of the well-dispersed CDs were spherical shape. The corresponding particle size distribution histogram (the inset of Fig. 1a) were also shown that the CDs were ranged from 3.6 to 3.9 nm. The CdTe QDs kept similar morphology of spherical but the average size was about 4.9 nm (Fig. 1b), which is consistent with that prepared from the previous reported works [19]. Fig. 1c has revealed the CDs@SiO2 were the uniform spherical and the diameter has about 50 nm, and CDs were successfully coated by silica layer. After surface imprinting polymerization, the obvious changes from Fig. 1d were found that MIPs@CdTe/CDs@SiO2 were constructed by the bCDs@SiO2 nanocore and silica nanoshell and the diameter has markedly enlarged to 170 ± 5.0 nm but the sizes of CDs and CdTe QDs were too small to evidently observe. These indicated that the MIPs@CdTe/CDs@SiO2 were prepared successfully via sol-gel polymerization. The functional groups and elemental composition of the MIPs@CdTe/CDs@SiO2 were further analyzed by Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The FTIR spectra displayed in Fig. 2a that the MIPs@CdTe/CDs@SiO2 and NIPs@CdTe/CDs@SiO2 were exhibited similar appearance and locations of the main absorption peaks which demonstrated the template of CIP were eluted completely. The broad bands at 2941 cm−1 and the small band at 1636 cm−1 represented the stretching vibrations of NeH and C–N which were contributed from APTEs [33]. The peaks of 801 cm−1 and 1159 cm−1 were identified to the stretching vibrations of Si-O and Si-O-Si [34]. As shown in Fig. 2b, the full range XPS spectra were not only confirmed the elemental component of MIPs@CdTe/ CDs@SiO2 but also further verified the results were in accordance with the FTIR measurements. The high-resolution spectrum of C 1 s in Fig. 2c presented three main peaks at 284.5 eV, 285.3 eV and 287.9 eV, which can be attribute to (C]C/CeC), (C–N/CeO) and (C]O) groups, respectively [35]. The high-resolution spectrum of O 1 s mainly shows
was added into the above mixed solution and kept stirring until the solution was transparent in a dark. Subsequently, the mixture was transferred into a Teflon-lined autoclave and heated at 160 ℃ for 16 h. After cooling to room temperature naturally, the result product was obtained by centrifugation, washed several times with DDW and ethanol alternately, and dried at 50 ℃ overnight. Finally, the TiO2 was further calcined at 550 ℃ in a tube furnace for 2 h with a heating rate of 2 ℃/min and collected for further use. The construction of TiO2/CDs/CdTe QDs CdTe was according to the previous reports with some modifications [31,32]. Briefly, 1 mL CdTe QDs, 200 μL CDs and 0.584 g TiO2 were added into 5 mL ethanol for sonication 1 h and stirring 6 h, then the sample was dried in oven at 50 ℃. 2.8. Photodegradation test of CIP using TiO2/CDs/CdTe QDs To evaluate photocatalytic activity of the as-prepared samples through degrading CIP under visible-light illumination (250 W Xe lamp and a cutoff filter > 420 nm). As the typical procedure: Firstly, photocatalyst of TiO2/CDs/CdTe QDs (50 mg) was added into 100 mL of CIP solution (10 mg/L). Before irradiation, the suspension was stirred for 30 min in the dark to achieve an adsorption-desorption equilibrium. After that, about 4 mL of suspension was taken out and filtered using filter in the 10-minute interval. Finally, the concentration was determined via a UV–vis spectrophotometer. 3. Results and discussion 3.1. Synthesis and characterization of ratiometric fluorescent sensor The construction process of the MIPs@CdTe/CDs@SiO2 ratiometric fluorescence sensor for visual detection of CIP was displayed in Scheme 1. Firstly, the stable and high fluorescence CDs was fabricated by typical hydrothermal treatment using the osmanthus fragrans leaves as carbon source and PEI as nitrogenous source, and the obtained CdTe QDs were synthesized via refluxing several days under N2 saturation with the modification of stabilizing agent TGA. To present a trustworthy detection result, the CDs were coated a silica layer to construct a core-shell composite which could be effectively apart from CdTe QDs. Subsequently, the imprinting molecular polymer of ratiometric fluorescent sensor (MIPs@CdTe/CDs@SiO2) was prepared by sol-gel procedure in the presence of CdTe QDs, CDs@SiO2, template of CIP, APTS
Scheme 1. Schematic illustration for preparation of the ratiometric fluorescence MIPs@rCDs/bCDs@SiO2 sensors for CIP monitoring. 244
Sensors & Actuators: B. Chemical 289 (2019) 242–251
X. Liu, et al.
Fig. 1. TEM image of (a) CDs (insert: size distribution histogram of CDs), (b) CdTe QDs (insert: size distribution histogram of CdTe QDs), (c) CDs@SiO2 and (d) MIPs@CdTe/CDs@SiO2.
3.2. Optical properties
two peaks at 530.8 eV (C]O) and 531.8 eV (Si-O) in the Fig. 2d [34]. The Fig. 2e revealed that the N 1 s spectrum was deconvoluted into typica peak with the binding energies of 399.6 eV originated from C–NC [36]. The existed silicon-involving bonds as shown in Fig. 2f were confirmed by the Si 2p signal which including Si-O/SiO2 (102.1 eV) and Si-C (102.8 eV) [37]. The Cd3d spectrum generally displayed two peaks at 404.5 and 411.3 eV, which were corresponded to the Cd in CdTe (Fig. 2g). [38] Meanwhile, the Fig. 2h presented the Te3d spectrum peaks at 571.9 and 582.4 eV, which were accorded with the Cd-Te bonding state [38]. All above the FTIR and XPS characterization results were demonstrated the MIPs@CdTe/CDs@SiO2 have been fabricated successfully. For investigation the CIP recognition property of MIPs@CdTe/ CDs@SiO2 ratio fluorescence sensors, the fluorescence emission spectra of MIPs@CdTe/CDs@SiO2 and NIPs@CdTe/CDs@SiO2 were subsequently examined and displayed in Fig. 3a. As can be seen a strong emission at 465 nm and a relatively weak emission at 647 nm with the maximum emission wavelength could be caught under the excitation at 340 nm when MIPs@CdTe/CDs@SiO2 was combined with target of CIP. After eluting CIP, the fluorescence of a strong emission at 465 nm has slightly weakened but emission wavelength at 647 nm was recovered swiftly from MIPs@CdTe/CDs@SiO2, which was close to NIPs@CdTe/ CDs@SiO2. Correspondingly, the notable fluorescent changes of MIPs@CdTe/CDs@SiO2 suspension have taken place from pale blue to magenta which was similar to NIPs@CdTe/CDs@SiO2 under UV lamp. The phenomena were revealed that MIPs@CdTe/CDs@SiO2 has an excellent recognition to CIP and could be applied to eye-naked detect CIP under UV lamp.
Of all the factors interfering the recognition performance of the MIPs@CdTe/CDs@SiO2 ratiometric fluorescence sensor, including stability, responding time and pH of MIPs@CdTe/CDs@SiO2. The stability of MIPs@CdTe/CDs@SiO2 was investigated by repeated measurement of fluorescence intensity for 130 min at room temperature. As displayed in Fig. 3b, the fluorescence intensity of MIPs@CdTe/CDs@SiO2 was significantly stable and this phenomenon was illustrated that the tailored polymer has well-protected CdTe QDs and CDs to resist the neutral external environments. In order to achieve the optimizing tested parameters, the response time and pH of the ratiometric fluorescence MIPs@CdTe/CDs@SiO2 sensors to CIP were investigated systematically. From Fig. 3c it can be found that the fluorescence intensity of MIPs@CdTe/CDs@SiO2 sensors was not changed by adding CIP 4.0 min. There have been more apparently fluorescence intensity distinctions of CdTe/CDs@SiO2 than MIPs@CdTe/CDs@SiO2 with the solutions pH changed from 3.0 to 12 (Fig. 3d). The fluorescence of CdTe/CDs@SiO2 have been dramatically quenched when pH was less 6.0 or over 8.0, but MIPs@CdTe/CDs@SiO2 could keep favorable fluorescent intensities in the range of 5.0 to 10 and the strongest fluorescence was at pH = 7.0. The phenomenon demonstrated that the presence of silica layers has well-protected CdTe QDs and CDs to adapt the pH value variations from weak acid to alkaline. Therefore, the optimal analytical reaction time of 4.0 min and pH of 7.0 were used for the following measurements.
245
Sensors & Actuators: B. Chemical 289 (2019) 242–251
X. Liu, et al.
Fig. 2. (a) The FT-IR spectra of MIPs@rCDs/bCDs@SiO2 and NIPs@rCDs/bCDs@SiO2, the XPS spectrum of MIPs@rCDs/bCDs@SiO2: (b) XPS survey spectrum, the high resolution XPS peaks of C1 s (c), O1 s (d), N1 s (e), Si2p (f), Cd3d (g) and Te3d (h).
246
Sensors & Actuators: B. Chemical 289 (2019) 242–251
X. Liu, et al.
Fig. 3. (a) The fluorescence spectra and corresponding photo under UV lamp of NIPs@CdTe/CDs@SiO2 (curve I, 1), MIPs@CdTe/CDs@SiO2 (curve II,2) and MIPs@CdTe/CDs@SiO2@CIP (curve III, 3); (b) The fluorescence stability of MIPs@CdTe/CDs@SiO2; (c) The fluorescence response time of MIPs@CdTe/CDs@SiO2; (d) The effects of different pH on the fluorescence intensity of MIPs@CdTe/CDs@SiO2 and CdTe/CDs@SiO2.
same conditions. As shown in Fig. 4d, the results demonstrated that the fluorescence of MIPs@CdTe at 647 nm was gradually quenched with the increasing concentrations of CIP and at 425 nm was slightly enhanced due to CIP itself fluorescent property. However, the fluorescent photo of MIPs@CdTe for the detection of CIP was difficult to discern the color changes for naked eye observation under a UV lamp. Thus, the results verified that the MIPs@CdTe has poor visual detection of CIP than the ratiometric fluorescence sensors MIPs@CdTe/CDs@SiO2.
3.3. Sensitivity of MIPs@CdTe/CDs@SiO2 The sensitivity of the ratiometric fluorescence sensor was assessed by adding different amount of CIP into the MIPs@CdTe/CDs@SiO2 and NIPs@CdTe/CDs@SiO2 solutions under the optimal conditions. As illustrated in Fig. 4a, the fluorescence intensity of MIPs@CdTe/CDs@ SiO2 at 657 nm was regularly quenched but at around 465 nm was gradually enhanced with the addition of CIP in the concentration range of 0–60 nM. With the increase same amount of CIP, the fluorescence intensity of the NIPs@CdTe/CDs@SiO2 at around 657 nm decreased slowly and at 465 nm were increased gradually (Fig. 4b). Correspondingly, the relative fluorescence photo of the MIPs@CdTe/CDs@SiO2 has more distinct changes from red to blue under a UV lamp than NIPs@CdTe/CDs@SiO2. This phenomenon was mainly caused by the MIPs@CdTe/CDs@SiO2 was existing lots of recognizing sites to selectively and rapidly match with CIP after imprinting process. As can be seen in Fig. 4c, the value of log((I465/I647)/(I465/I647)0) increased gradually with the additions of CIP and a fitting linear curve equation was obtained by the MIPs@CdTe/CDs@SiO2 that was log [(I465/I647)/(I465/I647)0] = 1.2516*10−7 + 0.02119*(CCIP/nM) (R2 = 0.9998). The limits of detection (LOD) for CIP were down to 0.0127 nM on the basis of three times the standard deviation rule (LOD = 3δ/s, where δ was defined as the standard deviation of the blank signals and s signified the slope of the calibration curve), which was far more sensitive than NIPs@CdTe/CDs@SiO2. Therefore, the fabricated MIPs@CdTe/CDs@SiO2 had the advantage of rapid and highly sensitive for the detection of CIP with broad linear range. To illustrate the superiority of MIPs@CdTe/CDs@SiO2 ratiometric fluorescence sensor for visual detection of CIP, MIPs@CdTe was also fabricated to evaluate the practical property for assaying CIP under the
3.4. Selectivity of MIPs@CdTe/CDs@SiO2 The selectivity was another pivotal factor that can determine a unique analyte target in a mixture without intervention from other components in complicated system. To evaluate the selectivity of MIPs@CdTe/CDs@SiO2 for detecting CIP, two series of controlled experiments were conducted under the optimized conditions. Firstly, there were 30 nM different kinds of metal cations (including K+, Na+, Ca2+, Zn2+, Mg2+, Al3+, Ag+, Cu2+, Hg2+ and Fe3+) mixed with MIPs@CdTe/CDs@SiO2 for the specific recognition CIP. From Fig. 5a it can be seen that the fluorescence of MIPs@CdTe/CDs@SiO2 have been slightly quenched by a few of metal ions such as Hg2+ and Ag+, but the result of MIPs@CdTe/CDs@SiO2 for assaying CIP have no distinct changes. Thus, the reference signal is significant for the elimination of the deviation from ambient interferences and amelioration of the detection accuracy. The impact of CIP and several CIP analogues (including ENX, NFX, GAT and LOM) on MIPs@CdTe/CDs@SiO2 and NIPs@CdTe/CDs@SiO2 were also investigated. Fig. 5b exhibited that the ENX, NFX, GAT and LOM have slightly influenced on the fluorescences of MIPs@CdTe/ CDs@SiO2 and NIPs@CdTe/CDs@SiO2, while CIP has an evident 247
Sensors & Actuators: B. Chemical 289 (2019) 242–251
X. Liu, et al.
Fig. 4. (a) The fluorescence spectra and corresponding photographs of MIPs@CdTe/CDs@SiO2; (b) the fluorescence spectra and corresponding photographs of NIPs@CdTe/CDs@SiO2; (c) the linear relationships between MIPs@CdTe/CDs@SiO2 and NIPs@CdTe/CDs@SiO2 and (d) fluorescence spectra and corresponding photographs of MIPs@CdTe.
fluorescence quenching to MIPs@CdTe/CDs@SiO2 but only a little quenching effect on NIPs@CdTe/CDs@SiO2. Moreover, the fluorescence quenching of the MIPs@CdTe/CDs@SiO2 solution caused by the mixture (CIP and ENX, CIP and NFX, CIP and LOM, CIP and GAT) was
approximately equal to CIP. The above experimental results fully illustrated the high selectivity of MIPs@CdTe/CDs@SiO2 for the detection of CIP.
Fig. 5. (a) The effects of 30 nM different metal ion on the MIPs@CdTe/CDs@SiO2 to recognize CIP (24 nM); (b) The effects of CIP and some analogues on MIPs@CdTe/CDs@SiO2 and NIPs@CdTe/CDs@SiO2. 248
Sensors & Actuators: B. Chemical 289 (2019) 242–251
X. Liu, et al.
urine were determined by this strategy which were collected from our group students who have taken in ciprofloxacin hydrochloride tablets after 12 h. Although to CIP was detected after sample extraction process, different concentrations of the CIP were also spiked in four human urine samples for the recovery experiment. From Table 1 it can be seen the recoveries of CIP were in the range of 98.78%–102.08% and the relative standard deviations (RSDs) were below 0.96% for urine samples, indicating the satisfied precision and accuracy for monitoring CIP in real samples. Compared with other reported different probes for CIP detection as displayed in Table 2, which indicated the sensitivity of our detecting system was superior to most previously reported ones. These may be caused by the changes in the fluorescence intensity ratio of the two emission wavelengths and a distinct color change from purplish red to blue in a range of 0–60 nM. Moreover, we proposed the ratiometric fluorescence MIPs@CdTe/CDs@SiO2 sensor was comparatively easy to operate which was favorable for visual detection of CIP by eye-naked.
Table 1 Quantitative determination of CIP in human urine samples. Found (nM)
Spiked concentration (nM)
Total found (nM)
Recovery (%)
RSD (%, n = 6)
9.164 8.548 9.213 8.622 9.463
0 10 15 20 25
9.248 18.934 23.918 28.787 34.843
100.86 102.08 98.78 100.58 101.10
0.42 0.96 0.87 0.94 0.58
Table 2 Comparison of this work with different methods for CIP assaying. Sensing Elements
Linear Range
LOD
References
carbon dot/silicon dot carbon dots carbon dots MIPs@SiO2-FITC MIPs@CdTe/CDs@SiO2
0.01−150 μM 10 nM–90 μM 0.02–1.0 μM 0−250 nM 0−60 nM
2.0 nM 5.88 nM 6.7 nM 4.04 nM 0.0127 nM
[39] [40] [41] [42] This work
3.6. Exploration of photocatalytic activity of TiO2/CDs/CdTe QDs The photocatalytic performance of TiO2/CDs/CdTe QDs and TiO2/ CDs for the degradation of CIP were also studied. Firstly, in order to investigate the morphology and structure of the TiO2/CDs/CdTe QDs, the SEM images were presented in Fig. 6. It could be seen from Fig. 6a that TiO2 prepared by the hydrothermal method were near-spherical
3.5. Practical applications and approach performance comparison After investigating the sensitivity and selectivity of MIPs@CdTe/ CDs@SiO2 sensors towards CIP, the practicality of the CIP in human
Fig. 6. SEM images of TiO2 (a) and TiO2/CDs/CdTe QDs (b) and elemental mapping images of TiO2/CDs/CdTe QDs (c). 249
Sensors & Actuators: B. Chemical 289 (2019) 242–251
X. Liu, et al.
Fig. 7. (a) The photocatalytic activities for TiO2/CDs and TiO2/CDs/CdTe QDs to CIP; (b) The corresponding kinetic fit of TiO2/CDs and TiO2/CDs/CdTe QDs for the degradation of CIP; (c) The absorption spectra variations of the TiO2/CDs/CdTe QDs to CIP solution.
and quantitative assay environmental pollutants.
with excellent dispersity and the diameters were ranged from 300 to 600 nm. After mixing with CDs and CdTe QDs, the TiO2/CDs/CdTe QDs SEM images revealed the CDs and CdTe QDs did not remarkably change the size and morphology of TiO2 nanoparticles, but the surface was rougher than TiO2 (as shown in Fig. 6b). Moreover, the elemental mapping analysis also displayed the related elements were homogeneously distributed on TiO2/CDs/CdTe QDs (Fig. 6c), which indicated the TiO2/CDs/CdTe QDs were successfully prepared. As the Fig. 7a shown, the TiO2/CDs/CdTe QDs exhibited higher photocatalytic activity than TiO2/CDs, which attributed to the effective electron-hole pair separation due to quantum effect of CdTe QDs. The kinetic curves of CIP degradation (Fig. 7b) were studied by fitting according to a pseudo-first-order, and the calculated removal rate constant over TiO2/CDs/CdTe QDs was 0.008 min−1, which was 1.3 times higher than TiO2/CDs (0.006 min−1). In addition, the corresponding of absorbance variation curves was presented in Fig. 7c, directly proving that the CIP molecules were photo-degraded into small molecules. The results vividly proved that the CdTe QDs could further enhance the photocatalytic performance of TiO2/CDs towards CIP.
Acknowledgments This work was financially supported by the National Natural Science Foundation of China (No. 21507045 and No. 21607013), Natural Science Foundation of Jiangsu Province (No. BK20160569), Postgraduate Research & Practice Innovation Program of Jiangsu Province (KYCX18_2232). References [1] S. Li, X. Zhang, Y. Huang, Zeolitic imidazolate framework-8 derived nanoporous carbon as an effective and recyclable adsorbent for removal of ciprofloxacin antibiotics from water, J. Hazard. Mater. 321 (2017) 711–719. [2] M.K. Pawar, K.C. Tayade, S.K. Sahoo, P.P. Mahulikar, A.S. Kuwar, B.L. Chaudhari, Selective ciprofloxacin antibiotic detection by fluorescent siderophore pyoverdin, Biosens. Bioelectron. 81 (2016) 274–279. [3] Y. Li, C. Zeng, C. Wang, L. Zhang, Preparation of C@silica core/shell nanoparticles from ZIF-8 for efficient ciprofloxacin adsorption, Chem. Eng. J. 343 (2018) 645–653. [4] A. Xie, J. Dai, X. Chen, P. Ma, J. He, C. Li, Z. Zhou, Y. Yan, Ultrahigh adsorption of typical antibiotics onto novel hierarchical porous carbons derived from renewable lignin via halloysite nanotubes-template and in-situ activation, Chem. Eng. J. 304 (2016) 609–620. [5] X. Van Doorslaer, J. Dewulf, H. Van Langenhove, K. Demeestere, Fluoroquinolone antibiotics: an emerging class of environmental micropollutants, Sci. Total Environ. 500-501 (2014) 250–269. [6] Q. Bu, B. Wang, J. Huang, S. Deng, G. Yu, Pharmaceuticals and personal care products in the aquatic environment in China: a review, J. Hazard. Mater. 262 (2013) 189–211. [7] Q.Q. Zhang, G.G. Ying, C.G. Pan, Y.S. Liu, J.L. Zhao, Comprehensive evaluation of antibiotics emission and fate in the river basins of China: source analysis, multimedia modeling, and linkage to bacterial resistance, Environ. Sci. Technol. 49 (2015) 6772–6782. [8] Z. Shen, C. Zhang, X. Yu, J. Li, Z. Wang, Z. Zhang, B. Liu, Microwave-assisted synthesis of cyclen functional carbon dots to construct a ratiometric fluorescent
4. Conclusions In summary, a ratiometric fluorescence sensor MIPs@CdTe/CDs@ SiO2 was constructed and applied in the sensitive and selective detection of CIP in human urine samples. This novel strategy was presented an excellent linear CIP assay range of 0–60 nM with a detection limit as low as 0.0127 nM. In addition, the photocatalytic degradation of CIP was also investigated by TiO2/CDs/CdTe QDs composite under visible light irradiation and achieved satisfied result. Therefore, the construction of CdTe QDs and CDs composites by different methods could efficiently detect and degrade CIP, which provide a novel thought to treat 250
Sensors & Actuators: B. Chemical 289 (2019) 242–251
X. Liu, et al.
[9]
[10]
[11]
[12]
[13] [14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23]
[24]
[25]
probe for tetracycline detection, J. Mater. Chem. C Mater. Opt. Electron. Devices 6 (2018) 9636–9641. V. Sharma, N. Kaur, P. Tiwari, A.K. Saini, S.M. Mobin, Multifunctional fluorescent “Off-On-Off” nanosensor for Au3+ and S2− employing N-S co-doped carbon-dots, Carbon 139 (2018) 393–403. W. Xu, J. Chen, S. Sun, Z. Tang, K. Jiang, L. Song, Y. Wang, C. Liu, H. Lin, Fluorescent and photoacoustic bifunctional probe for the detection of ascorbic acid in biological fluids, living cells and in vivo, Nanoscale 10 (2018) 17834–17841. M.K. Barman, A. Patra, Current status and prospects on chemical structure driven photoluminescence behaviour of carbon dots, J. Photochem. Photobiol. C Photochem. Rev. 37 (2018) 1–22. J. Jiang, G. Ye, Z. Wang, Y. Lu, J. Chen, K. Matyjaszewski, Heteroatom-doped carbon dots (CDs) as a class of metal-free photocatalysts for PET-RAFT polymerization under visible light and sunlight, Angew. Chem. Int. Ed. 57 (2018) 12037–12042. L. Xiao, H. Sun, Novel properties and applications of carbon nanodots, Nanoscale Horiz. 3 (2018) 565–597. K. Chullasat, P. Nurerk, P. Kanatharana, F. Davis, O. Bunkoed, A facile optosensing protocol based on molecularly imprinted polymer coated on CdTe quantum dots for highly sensitive and selective amoxicillin detection, Sens. Actuator B: Chem. 254 (2018) 255–263. Y. Zhan, T. Geng, Y. Liu, C. Hu, X. Zhang, B. Lei, J. Zhuang, X. Wu, D. Huang, G. Xiao, B. Zou, Near-ultraviolet to near-infrared fluorescent nitrogen-doped carbon dots with two-photon and piezochromic luminescence, ACS Appl. Mater. Inter. 10 (2018) 27920–27927. T. Wang, X. Liu, C. Ma, Z. Zhu, Y. Liu, Z. Liu, M. Wei, X. Zhao, H. Dong, P. Huo, C. Li, Y. Yan, Bamboo prepared carbon quantum dots (CQDs) for enhancing Bi3Ti4O12 nanosheets photocatalytic activity, J. Alloys. Compd. 752 (2018) 106–114. L. Weidong, L. Yuan, W. Min, F. Xiaolei, A.T.R. Simon, S. Yuan, Y. Xue, F. Tanglue, W. Kaifeng, L. Zhongyi, L. Baojun, C. Zhimin, S.T. John, L. Siyu, Y. Bai, Carbon‐quantum‐Dots‐Loaded ruthenium nanoparticles as an efficient electrocatalyst for hydrogen production in alkaline media, Adv. Mater. 30 (2018) 1800676. Y. Guo, F. Cao, Y. Li, Solid phase synthesis of nitrogen and phosphor co-doped carbon quantum dots for sensing Fe3+ and the enhanced photocatalytic degradation of dyes, Sens. Actuator B: Chem. 255 (2017) 1105–1111. Y. Xu, X. Wei, H. Li, X. Zheng, K. Lu, X. Liu, K. Wang, Y. Yan, Boric acid functionalized ratiometric fluorescence probe for sensitive and on-site naked eye determination of dopamine based on two different kinds of quantum dots, RSC Adv. 6 (2016) 72715–72721. Y. Yuan, Y. Yang, M. Faheem, X. Zou, X. Ma, Z. Wang, Q. Meng, L. Wang, S. Zhao, G. Zhu, Molecularly imprinted porous aromatic frameworks serving as porous artificial enzymes, Adv. Mater. 30 (2018) 1800069. T. Takeuchi, H. Sunayama, Beyond natural antibodies- a new generation of synthetic antibodies created by post-imprinting modification of molecularly imprinted polymers, Chem. Commun. 54 (2018) 6243–6251. Q. Li, T. Kamra, L. Ye, A modular approach for assembling turn-on fluorescence sensors using molecularly imprinted nanoparticles, Chem. Commun. 52 (2016) 12237–12240. Q. Li, T. Kamra, L. Ye, A modular approach for assembling turn-on fluorescence sensors using molecularly imprinted nanoparticles, Chem. Commun. 52 (2016) 12237–12240. J. Tan, M. Guo, L. Tan, Y. Geng, S. Huang, Y. Tang, C. Su, C.C. Lin, Y. Liang, Highly efficient fluorescent QDs sensor for specific detection of protein through double recognition of hybrid aptamer-molecular imprinted polymers, Sens. Actuator B: Chem. 274 (2018) 627–635. Z. Wanqing, D. Dawei, L. Shanqin, Z. Yongsheng, L. Leipeng, L. Xinli, C. Na,
[26]
[27]
[28]
[29] [30] [31]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
[39]
[40]
[41]
[42]
251
Z. Yuping, Metal-organic framework-based moleculary imprinted polymer as a high sensitive and selective hybrid for the determination of dopamine in injections and human serum samples, Biosens. Bioelectron. 118 (2018) 129–136. T. Kan, M. Qiang, L. Jing, X. Sheng, Z. Ye, W. Wei, L. Xiaoya, G. Yao, Water-dispersible molecularly imprinted nanohybrids via co-assembly of carbon nanotubes with amphiphilic copolymer and photocrosslinking for highly sensitive and selective paracetamol detection, Biosens. Bioelectron. 117 (2018) 713–719. W. Gui, H. Wang, Y. Liu, Q. Ma, Ratiometric fluorescent sensor with molecularly imprinted mesoporous microspheres for malachite green detection, Sens. Actuator B: Chem. 266 (2018) 685–691. H. Zhu, H. Yao, K. Xia, J. Liu, X. Yin, W. Zhang, J. Pan, Magnetic nanoparticles combining teamed boronate affinity and surface imprinting for efficient selective recognition of glycoproteins under physiological pH, Chem. Eng. J. 346 (2018) 317–328. W. Stöber, A. Fink, E. Bohn, Controlled growth of monodisperse silica spheres in the micron size range, J. Colloid Interface Sci. 26 (1968) 62–69. C. Wang, Q. Ma, X. Su, Synthesis of CdTe nanocrystals with mercaptosuccinic acid as stabilizer, J. Nanosci. Nanotechno. 8 (2008) 4408–4414. M. Ji, Y. Liu, J. Di, R. Chen, Z. Chen, J. Xia, H. Li, N-CQDs accelerating surface charge transfer of Bi4O5I2 hollow nanotubes with broad spectrum photocatalytic activity, Appl. Catal. B 237 (2018) 1033–1043. P. Wang, X. Li, J. Fang, D. Li, J. Chen, X. Zhang, Y. Shao, Y. He, A facile synthesis of CdSe quantum dots-decorated anatase TiO2 with exposed {001} facets and its superior photocatalytic activity, Appl. Catal. B 181 (2016) 838–847. X. Wei, M. Meng, Z. Song, L. Gao, H. Li, J. Dai, Z. Zhou, C. Li, J. Pan, P. Yu, Y. Yan, Synthesis of molecularly imprinted silica nanospheres embedded mercaptosuccinic acid-coated CdTe quantum dots for selective recognition of λ-cyhalothrin, J. Lumin. 153 (2014) 326–332. J. Wang, R. Cheng, Y. Wang, L. Sun, L. Chen, X. Dai, J. Pan, G. Pan, Y. Yan, Surfaceimprinted fluorescence microspheres as ultrasensitive sensor for rapid and effective detection of tetracycline in real biological samples, Sens. Actuator B: Chem. 263 (2018) 533–542. W. Song, W. Duan, Y. Liu, Z. Ye, Y. Chen, H. Chen, S. Qi, J. Wu, D. Liu, L. Xiao, C. Ren, X. Chen, Ratiometric detection of intracellular lysine and pH with one-pot synthesized dual emissive carbon dots, Anal. Chem. 89 (2017) 13626–13633. A. Kumar, M. Khan, X. Zeng, I.M.C. Lo, Development of g-C3N4/TiO2/Fe3O4@ SiO2heterojunction via sol-gel route: a magnetically recyclable direct contact Zscheme nanophotocatalyst for enhanced photocatalytic removal of ibuprofen from real sewage effluent under visible light, Chem. Eng. J. 353 (2018) 645–656. X. Li, W. Wang, Q. Li, H. Lin, Y. Xu, L. Zhuang, Design of Fe3O4@SiO2@mSiO2organosilane carbon dots nanoparticles: Synthesis and fluorescence red-shift properties with concentration dependence, Mater. Design 151 (2018) 89–101. W. Zhu, S. Pan, W. Wang, C. Zhao, L. Lu, X. Liu, Hydrothermal synthesis of raisinbun-like CdTe@C nanocomposites toward enhanced photoluminescence and low cytotoxicity, New J. Chem. 37 (2013) 2751–2757. R. Gui, X. Bu, W. He, H. Jin, Ratiometric fluorescence, solution-phase and filterpaper visualization detection of ciprofloxacin based on dual-emitting carbon dot/ silicon dot hybrids, New J. Chem. 42 (2018) 16217–16225. S. Wang, Y. Wang, K. Yang, Y. Zhong, X. Yang, Z. Chen, Synthesis of carbon dots originated from hydroxypropylmethyl cellulose for sensing ciprofloxacin, Anal. Sci. 33 (2017) 1129–1134. J. Hua, Y. Jiao, M. Wang, Y. Yang, Determination of norfloxacin or ciprofloxacin by carbon dots fluorescence enhancement using magnetic nanoparticles as adsorbent, Microchim. Acta 185 (2018) 137. C. Wu, R. Cheng, J. Wang, Y. Wang, X. Jing, R. Chen, L. Sun, Y. Yan, Fluorescent molecularly imprinted nanoparticles for selective and rapid detection of ciprofloxacin in aquaculture water, J. Sep. Sci. 41 (2018) 3782–3790.