Metal–Organic Framework as a Chemosensor Based on

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Article Cite This: Inorg. Chem. 2019, 58, 8388−8395

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Metal−Organic Framework as a Chemosensor Based on Luminescence Properties for Monitoring Cetyltrimethylammonium Bromide and Its Application in Smartphones Zhe Sun, Yu Ling, Shi Gang Liu, Yu Zhu Yang, Xiao Hu Wang, Yu Zhu Fan, Nian Bing Li,* and Hong Qun Luo*

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Key Laboratory of Eco-Environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China S Supporting Information *

ABSTRACT: Rapid and sensitive detection of surfactants has attracted more and more attention since surfactants not only cause water pollution but also affect the health of human beings. Luminescent metal−organic frameworks combining unique optical property and inherent permanent porosity for guest−host encapsulation are widely used in fluorescence detection. Here we report a ratiometric fluorescent probe (denoted as UiO-66-NH2@PB) based on a Zr-based metal−organic framework (UiO-66-NH2) and a fluorescent dye, phloxine B (PB), for visual and fluorescent determination of cationic surfactants (cetyltrimethylammonium bromide; CTAB). The intensity ratio of dual-emission sensor exhibits a linear response to the CTAB concentrations of 0.1−17 μM and obtains a low detection limit (0.074 μM). Moreover, this method has been successfully utilized to monitor CTAB in the environmental water samples with satisfied recoveries. Importantly, this work provides a new insight into developing smartphone-based sensor to realize a rapid, on-site visual and quantification-based detection of CTAB.

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sensitivity. However, the fluorescent probes used to measure CTAB only have a sole responsive signal (turn-off or -on fluorescence intensity), which were easily interfered by environmental effects, concentration of probes, or similar interferences in complex samples, resulting in “false positive” or “negative errors”.22 Fortunately, ratiometric methods have the advantages to conquer these interferences and make the results more accurate, since two or more emission peaks provide built-in self-calibration to get rid of various analyteindependent factors and increase signal-to-noise ratio.23−25 For instance, Zhang et al. developed dual-emission CdTe quantum dots to detect trace trinitrotoluene explosives;26 cadmium(II) ions and L-ascorbic acid were monitored through a ratiometric fluorescent nanohybrid, which combined carbon quantum dots and gold nanoclusters.27 In Wang’s group, they designed a dual lanthanide-doped ratiometric fluorescent sensor to determine anthrax biomarker.28 As two or more emissions have significant differences in responding to analytes, the emission colors of probes obviously alter, which can be seen by the naked eyes during sensing (under UV lamp).29,30 Metal−organic frameworks (MOFs), comprising metal ions or clusters and organic ligands, are a class of crystalline porous materials, receiving considerable attention due to their high

INTRODUCTION Surfactants are a class of organics with distinct structural feature consisting of a hydrophilic region of the molecule, or the polar head group, and a hydrophobic tail (hydrocarbon chain).1 On the basis of the ionic charge of the hydrophilic portion, the surfactants can be classified as anionic, cationic, zwitterionic, and nonionic.2 All of these surfactants, in general, are widely employed as emulsifiers and dispersants in textile industry, leather technology, and in the preparation of general cleaning agents and paints.1 Since a high level of surfactants are diffusely used in various industries and daily life, a great deal of environmental problems have been aroused.3,4 When exposed, surfactants may deteriorate the water quality,5,6 endanger the biota in natural system,7 and irritate the skin and eyes of human beings.8,9 Thus, building active methods for monitoring the content of surfactants in environmental water samples is one of the main objectives especially at low concentrations. In all surfactants, cetyltrimethylammonium bromide (CTAB) is an important representative of quaternary ammonium salt cationic surfactants.10 Up to now, several approaches, such as mass spectrometry,11 capillary electrophoresis,12 colorimetry,13,14 electrochemistry,15 liquid chromatography−mass spectrometry,16 and fluorimetry,17−21 have been established to detect CTAB. Among them, fluorescent sensors have attracted a large number of interests for the simple operation, low cost, requisite selectivity, and high © 2019 American Chemical Society

Received: February 17, 2019 Published: June 18, 2019 8388

DOI: 10.1021/acs.inorgchem.9b00470 Inorg. Chem. 2019, 58, 8388−8395

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Inorganic Chemistry Scheme 1. Synthetic Process of UiO-66-NH2@PB and Ratiometric Detection Principle for CTAB

surface areas, intriguing topological structures, exposed active sites, and potential applications as functional materials across a broad range of fields.31−33 Particularly, luminescent metal− organic frameworks (LMOFs) have been successfully exploited as unique chemical sensors based on their nature of the pore surfaces, controllable structures, coordinated environment of metal ions, and their interactions with guest substances through rich π-conjugated structures, hydrogen bonding, coordination bonds, and so on.34,35 A LMOFs-based dualemitting probe for ratiometric sensing system with fluorescent dyes, nanomaterials, or earth metals via impregnation procedure, situ encapsulation, and postsynthetic methods (postsynthetic modification, postsynthetic exchange, and postsynthetic deprotection) is one of the most attractive aspects. For examples, Wu and co-workers reported a MOFsbased ratiometric nanocomposite by incorporating rhodamine B into a Zr-MOF for phosphate detection;36 Dong et al. encapsulated blue-emission carbon nanodots into red-emitting europium-MOFs, used as a dual-emitting nanohybrid sensor for the detection of water content in organic solvents;37 a twoemission Ln@UiO-66-hybrid film integrated lanthanide metals and luminescent ligand through the combination of postsynthetic modification and postsynthetic exchange, were applied to monitor the temperature changes.38 Tb-MOFs and Eu-MOFs were designed as zeolite-like MOFs via selfassembly to selectively detect lysophosphatidic acid in blood plasma.39 Additionally, two-emission LMOFs played an important role in fluorescent indication: 1,4-Dioxane can be prepared by the condensation reaction of glycol, so Cheng and co-workers employed bimetallic Eu/Tb-MOFs as a fluorescent indicator to monitor the ratio of 1,4-dioxane in glycol by fluorescence spectral measurements and the naked eye.40 Enlightened by the above studies, herein, a rapid, low-cost, and sensitive ratiometric method for visual and fluorescent detection of CTAB is constructed. We combine a blueemission Zr-MOF (UiO-66-NH2) and a yellow-emitting fluorescent dye, phloxine B (PB), to fabricate a ratiometric fluorescent nanocomposite (denoted as UiO-66-NH2@PB) because PB is directly adsorbed on the architecture of UiO-66NH2. This nanocomposite is utilized to efficiently capture and quantitatively detect CTAB for the first time (Scheme 1). Upon addition of different amounts of CTAB, the fluorescence intensity of PB is quenched for the electrostatic interaction between CTAB and PB, while the emission of UiO-66-NH2 unchanged. Hence, PB is employed as a sensitive response signal, and UiO-66-NH2 serves as a stable reference signal for self-calibration to alleviate environmental effects. Moreover, the visual detection of CTAB by the naked eye is achievable: In the presence of CTAB, the fluorescence color gradually varied from yellow to blue, resulting from the changes of emission peaks. Meanwhile, a smartphone is exploited as an analyzer for convenient, real-time, and quantification of CTAB except for

spectrometry, so the signal readout from the smartphone camera images is a feasible means of quantitative analyses.

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EXPERIMENTAL SECTION

Materials. 2-Aminoterephthalic acid (BDC-NH2), Tween 80, zirconium chloride (ZrCl4, ≥ 98%), and Triton X-100 were bought from Adamas Reagent, Ltd. (Shanghai, China). Trimethylstearylammonium bromide (TSAB), dodecyltrimethylammonium bromide (DTAB), decyltrimethylammonium bromide (DeTAB), myristyltrimethylammonium bromide (MTAB), melamine, and CTAB were obtained from Aladdin Reagent Co., Ltd. (Shanghai, China). PB (dye content ≥ 97%), sodium dodecyl sulfate (SDS), N,N-dimethylformamide (DMF), urea, ethylenediaminetetra-acetic acid disodium salt (EDTA), acetic acid (HAc), sodium acetate (NaAc), and various ions (Mg(NO3)2, HgCl2, Cu(NO3)2, KBr, Zn(NO3)2, MnCl2, Ca(NO3)2, Na2CO3, Fe(NO3)2, Pb(NO3)2, KI, and Al(NO3)3) were purchased from Chengdu Kelong Chemical Reagent Plant (Sichuan, China). All chemicals were utilized without further purification, and ultrapure water (18.2 MΩ cm) was used throughout the experiment. Instruments. Fluorescence spectra were collected with a Hitachi F-4500 spectrophotometer (Tokyo, Japan). Fourier transform infrared (FT-IR) spectra of the samples were performed by a Bruker IFS 113v spectrometer (Bruker, Germany) after pelleting the fine powder with KBr. Powder X-ray diffraction (PXRD) patterns were recorded with D8 Advance X-ray diffractometer (Bruker, Germany). X-ray photoelectron spectroscopy (XPS) analysis was performed by utilizing an Escalab 250Xi X-ray photoelectron spectrometer (Thermo Fisher Scientific, USA). The scanning electron microscopy (SEM) images of materials were taken on a Hitachi-4800 (Hitachi Co., Ltd., Japan). The Brunauer−Emmett−Teller (BET) surface areas of samples were measured on a nitrogen adsorption−desorption (Micromeritics ASAP 2460, USA). Zeta potentials were carried out on a NanoBrook Omni (Brookhaven Instrument Co., Ltd., USA). Preparation of UiO-66-NH2 Metal−Organic Framework. UiO-66-NH2 was prepared according to a previous report with slight modification.41 In a typical procedure, 0.1332 g of ZrCl4 was dissolved in 40 mL of DMF by stirring for about 5 min, and then 0.1451 g of BDC-NH2 was added. After being sonicated for 10 min, the asprepared solution was transferred into a 100 mL Teflon-lined autoclave in an oven and heated at 120 °C for 24 h. The yellow precipitation was collected by centrifugation, washed with fresh DMF and absolute ethanol, and dried at 60 °C under vacuum overnight. Fabrication of Ratiometric Fluorescent Probe (UiO-66NH2@PB). In a dark environment, UiO-66-NH2 powder (2 mg) was dispersed in a PB solution (8 mL), and the mixture was stirred for 2 h at room temperature, which resulted in a reddish-pink dispersion. Then, the dispersion was centrifuged and the supernatant was separated to remove undispersed UiO-66-NH2 powder. Eventually, a reddish-pink dispersion containing dual-emission UiO-66-NH2@PB was obtained, and the ratiometric fluorescent probe was stored at 4 °C for further use. General Procedure for Monitoring CTAB. For a typical CTAB detection procedure, 100 μL of UiO-66-NH2@PB, 500 μL of HAcNaAc buffer (pH 4.5), and a series of freshly prepared CTAB solutions were added to polypropylene microcentrifuge tubes. Subsequently, the mixtures were diluted to 1 mL with ultrapure water under shaking, followed by incubation for 5 min. All measurements were carried out at room temperature. Finally, the 8389

DOI: 10.1021/acs.inorgchem.9b00470 Inorg. Chem. 2019, 58, 8388−8395

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Inorganic Chemistry

Figure 1. (A) PXRD patterns of simulated UiO-66, UiO-66-NH2, UiO-66-NH2@PB nanocomposite, and UiO-66-NH2@PB upon addition of CTAB. (B) FT-IR spectra of UiO-66-NH2 (1), UiO-66-NH2@PB (2), and PB (3).

Figure 2. (A) Fluorescence spectra of UiO-66-NH2 (1), PB (2), and UiO-66-NH2@PB before (3) and after (4) addition of CTAB. Both excitations are 330 nm. Insets are photographs of synthesized UiO-66-NH2 (1), PB (2), and UiO-66-NH2@PB without (3) and with (4) CTAB under UV lamp (365 nm). (B) Zeta potential histogram of free UiO-66-NH2, UiO-66-NH2@PB, and UiO-66-NH2@PB upon addition of CTAB. (C) UV−vis absorption spectra of free UiO-66-NH2, pure PB, CTAB, UiO-66-NH2@PB nanocomposite, and UiO-66-NH2@PB with CTAB. (D) Fluorescence decay curves of UiO-66-NH2@PB before and after mixed with CTAB. fluorescence intensities were recorded on a fluorescence spectrophotometer with an excitation of 330 nm; the color changes were observed under a UV light (365 nm). For real sample analysis, Jialing River water (Chongqing, China) and tap water samples from Southwest University were employed. All raw water samples were centrifuged at 10 000 rpm for 20 min to remove particles, and the supernatant solutions were heated to boiling. In order to remove the suspended impurities, the as-prepared water samples were filtered through a 0.22 μm membrane after cooling to room temperature. The pretreatment water samples were spiked with ultrapure water or different concentrations of standard CTAB solutions, and following experiments were performed as that described above.

PB scarcely affected the lattice of UiO-66-NH2. The results of FT-IR spectra about UiO-66-NH2, PB, and UiO-66-NH2@PB are illustrated in Figure 1B. The peak appearing at 489 cm−1 was the stretching vibration of Zr−O bond, which indicated the coordination of −COOH to Zr4+ (curves 1 and 2);36 the absorption at 1413 and 1392 cm−1 (labeled with dashed circles in curves 1 and 2) can be attributed to the stretching modes of the carboxylic groups in the BDC-NH2 linkers,35 displaying no clear shift in the absence and presence of PB adsorption for UiO-66-NH2 (curves 1 and 2). In addition, the peaks identified at 984 and 1037 cm−1 (labeled with dashed circles in curve 3) from the out-of-plane bending vibration of C−H bond of aromatic hydrocarbon and the stretching vibration C−O−C were observed in PB (curve 3) but disappeared in UiO-66NH2@PB (curve 2), probably because they were hindered in the structure of UiO-66-NH2. The N2-sorption isotherms experiments further confirmed that PB was strongly adsorbed on the structure of UiO-66-NH2 (Figure S1). The Brunauer− Emmett−Teller (BET) surface area of UiO-66-NH2@PB was 610.5 m2 g−1 , which illustrated apparent decrease in comparison with the reported value of UiO-66-NH2 (732.2 m2 g−1).42 In addition, the XPS (Figure S2) and the SEM

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RESULTS AND DISCUSSION Characterization of Prepared UiO-66-NH2@PB. According to Bradshaw’s report,41 UiO-66-NH2 was solvothermally synthesized from ZrCl4 and BDC-NH2, and the UiO-66NH2@PB was obtained by mixing of UiO-66-NH2 and PB. Figure 1A exhibits that the PXRD pattern of UiO-66-NH2 is similar to that of the simulated one, demonstrating the successful synthesis of UiO-66-NH2; after adsorbing PB, the PXRD pattern did not change, revealing that the adsorption of 8390

DOI: 10.1021/acs.inorgchem.9b00470 Inorg. Chem. 2019, 58, 8388−8395

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Figure 3. Fluorescence spectra of (A) UiO-66-NH2@PB and (C) pure PB with different concentrations of CTAB. Linear relationship between fluorescence intensity and CTAB concentration: (B) UiO-66-NH2@PB with ratiometric intensities and (D) pure PB at a single peak at 560 nm (λex = 330 nm). Correspondingly, the inset images show the emission colors of the sensing systems under a UV light (365 nm).

aqueous solutions, the absorption peak at around 300−350 nm hardly changed (Figure 2C). Therefore, it is considered that PB did not leach from the architecture of UiO-66-NH2@PB during monitoring process. To further explore the nature of the fluorescence quenching of UiO-66-NH2@PB by CTAB, the PXRD experiments were first carried out. The patterns in Figure 1A confirmed that the sample of UiO-66-NH2@PB maintained the crystallinity after mixing with CTAB, illustrating that CTAB did not destroy the structure of UiO-66-NH2@PB. Zeta potential analysis was then introduced to discuss the mechanism. As shown in Figure 2B, UiO-66-NH2@PB had a distinct negative zeta potential at about −10.85 mV in 20 mM HAc-NaAc buffer (pH 4.5), which was much lower than that of UiO-66-NH2 (2.11 mV). After adding CTAB, the zeta potential of the solution shifted from −10.85 to −2.78 mV (pH 4.5), so the electrostatic interaction between the UiO-66-NH2@PB and CTAB might drive the fluorescence quenching. Notably, as displayed in Figure 2C, it is observed that when CTAB was added to the probe solution a new absorption peak appeared at around 575 nm indicating that the UiO-66-NH2@PB and CTAB formed a ground state complex resulting in static quenching. Also, the results of the fluorescence lifetime measurement further provided the evidence of the quenching mechanism. In static quenching, the fluorescence lifetime of the molecules did not change (τ0/τ = 1, where τ0 and τ are the fluorescence lifetimes before and after quenching, respectively). In dynamic quenching, τ0/τ = F0/F, the fluorescence lifetime will decrease with the addition of the quencher. The fluorescence decay curves of UiO-66-NH2@PB in the absence and presence of CTAB are shown in Figure 2D. The change in fluorescence lifetimes of UiO-66-NH2@PB was not obvious (τ0 = 1.91 ns, τ = 2.35 ns; τ0/τ is about 1), demonstrating that quenching behavior was a static quenching process.43,44 Hence, static quenching is considered to be the quenching mechanism of probe. Optimization of Experimental Parameters for CTAB. For providing optimal conditions and enhancing the perform-

images (Figure S3) also exhibit that the chemical constitution, morphology, and size of UiO-66-NH2 scarcely had a change with and without PB. Therefore, the UiO-66-NH2@PB retained the structure and composition of the constituent UiO-66-NH2 and PB, which confirmed successful synthesis of the dual-emission probe. The optical properties of UiO-66-NH2@PB were subsequently studied. Under excitation at 330 nm, blue fluorescence peak for UiO-66-NH2 was obtained at 430 nm (Figure 2A, curve 1), while PB displayed bright yellow emission at 560 nm (Figure 2A, curve 2). After incorporating two different colors of fluorescence materials together, the ratiometric fluorescent probe possessed dual emission at 430 and 560 nm when excited at a single wavelength of 330 nm (Figure 2A, curve 3). The interference of emissions between UiO-66-NH2 and PB was powerfully prohibited because the emission distance in the strong peak was as large as 130 nm. Moreover, the corresponding photographs, under UV lamp, are exhibited in the inset of Figure 2A. Taken together, these consequences remarkably recommended that the ratiometric fluorescence probe was successfully synthesized. Ratiometric Detection of CTAB. Such a ratiometric fluorescent probe UiO-66-NH2@PB inspired us to explore its promising utilization in fluorescent sensing. Dramatically, CTAB suppressed the fluorescence of PB; in contrast, it is distinct that the fluorescence spectrum of UiO-66-NH2 remained almost unchanged when CTAB was added (Figure 2A, curve 4). Accordingly, PB was selected as the response signal, and UiO-66-NH2 served as the reference signal for selfcalibration because of its chemical inertness upon addition of CTAB. At the same time, the fluorescence color of the sensing platform varied from yellow to blue, which can be observed under UV light without any complicated instrumentation on account of the changes of the dual emission ratios (Figure 2A, inset 4). In addition, it can be seen that the characteristic peak of PB in the absorption band of UiO-66-NH2@PB appeared at about 300−350 nm, which further demonstrated that PB was adsorbed on the UiO-66-NH2; after mixing with CTAB 8391

DOI: 10.1021/acs.inorgchem.9b00470 Inorg. Chem. 2019, 58, 8388−8395

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Inorganic Chemistry

hard to precisely quantify the concentrations of CTAB in each solution. Instead of transferring the samples into a cuvette and measuring the absorbance on the spectrophotometer, in this paper, a smartphone was utilized as an analyzer to read out the digital information on the samples in photograph to make our visual sensing system more accessible. After taking a photograph with the smartphone, the screen captures of CTAB analysis process (Figure S7) and the final results in RGB mode after image processing by the smartphone (Figure 4C) were

ance of the developed probe in the discrimination of CTAB, a series of experiments, including the mixing time between UiO66-NH2 and PB, the ratio of UiO-66-NH2 to PB, pH value, response time, and reaction temperature, were performed. First, the mixing time between UiO-66-NH2 and PB was optimized. The experimental results showed that the fluorescence intensity ratio (I430/I560, where I430 and I560 represent the fluorescence intensities at 430 and 560 nm, respectively) was not stable until 2 h (Figure S4). Therefore, the mixing time of 2 h was used for the ratiometric sensor to detect CTAB. Second, in order to obtain a dual-emission probe with a conspicuous color variation during sensing, we chose an appropriate ratio of UiO-66-NH2/PB based on the principle of designing a visual sensing platform. In Figure S5, when the ratio of UiO-66-NH2 to PB was 4:1, continuous color changes from yellow to blue with increasing CTAB concentrations were distinguishable by the naked eye. Therefore, the ratio of 4:1 was selected as the optimal ratio of UiO-66-NH2 to PB for preparing UiO-66-NH2@PB. Third, pH 4.5 was selected as the optimal pH during experiments (Figure S6A). Reaction time was another key element throughout investigation, so the response time between UiO-66-NH2@PB and CTAB was monitored subsequently. When CTAB was added, I430/I560 quickly increased and reached equilibrium 5 min later (Figure S6B), showing a rapid and convenient sensing of CTAB. Finally, the fluorescence intensity ratio (I430/I560) was almost the same at different temperatures (from 15 to 55 °C), demonstrating that temperature hardly influenced this system (Figure S6C), so the reaction of the sensing platform did not require fine control of temperature. Ratiometric Fluorescent Nanoprobe for Visual Determination of CTAB. The ability of the UiO-66-NH2@PB ratiometric probe for quantitative analysis of CTAB was estimated. The emission spectra of UiO-66-NH2@PB to various CTAB concentrations were collected for sensitive investigation under the optimized conditions. Figure 3A exhibited that the intensities at 560 nm gradually decreased with increasing CTAB concentration, whereas the reference peak at 430 nm barely changed. The emission intensity ratio, I430/I560, linearly varied as CTAB increased with two satisfying linear relationships versus CTAB concentrations in the range of 0.1−9 μM (R2 = 0.994) and 9−17 μΜ (R2 = 0.996) (Figure 3B), and the limit of detection (LOD) for CTAB based on 3σ/ s is 0.074 μM (σ: the standard deviation of blank signals of UiO-66-NH2@PB solutions, s: linear correlation slope of intensity ratio vs the concentration of CTAB). Dramatically, the changes of the two emission ratios, resulting in distinguishable emission color change from yellow to blue, can be obtained by UV lamp (inset in Figure 3B). As a comparison, a single-emission quenching experiment (Figure 3C), in which free PB was applied for monitoring CTAB to highlight the advantages of the ratiometric sensing in visual determination; it was difficult to discriminate the fluorescence color evolution of PB alone when adding different concentrations of CTAB (inset in Figure 3D). Moreover, as displayed in Figure 3D, the fluorescence quenching efficiency (I/I0, where I and I0 represent the emission intensity of PB with and without CTAB, respectively) showed a linear relationship against the CTAB concentration. Furthermore, it would be found that our ratiometric sensing platform is not inferior to those methods previously reported for CTAB detection (Table S1). Quantitation of CTAB by a Smartphone. Although the obvious color change can be visualized by the naked eye, it was

Figure 4. Ratiometric detection of CTAB using the smartphone as an analyzer: (A) different colors of solutions with addition of 0−30 μM CTAB; (B) fitting curve between color parameters and the CTAB concentrations in RGB mode obtained by the smartphone; (C) screen capture during the CTAB determination using Live Color application loaded in the smartphone.

recorded via an easy-to-access Live Color application. Considering that the color of solutions after reaction changed from yellow to blue, the B/(R + G) ratio was employed to evaluate the color difference of ratiometric probe upon addition of varied CTAB concentrations. According to the B/(R + G) ratio, in Figure 4, a calibration curve can be expressed by the linear equation: y = 0.047x + 0.514 (R2 = 0.990), in which y is the B/(R + G) and x is the CTAB concentration (ranging from 0.5 to 13 μM), and the lowest detectable concentration is 0.36 μM. Remarkably, coupling with the smartphone, a rapid, on-site visual and quantificationbased determination strategy for CTAB was actively built based on the ratiometric sensing platform. Detection for Different Alkyl Chain Lengths of Cationic Surfactants. Cationic surfactants have numerous homologues with different lengths of the alkyl chain. Accordingly, the response of the ratiometric fluorescence probe to several cationic surfactants including TSAB, CTAB, MTAB, DTAB, and DeTAB was investigated. As shown in Figure 5, accompanied by the increasing length of the alkyl chains in surfactant molecules, the relative emission intensity (I430/I560) of the ratiometric fluorescence probe increased, which might result from the change of their hydrophobicity. 8392

DOI: 10.1021/acs.inorgchem.9b00470 Inorg. Chem. 2019, 58, 8388−8395

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carried out with three concentrations (0.5, 5, and 10 μM) spiked in each sample. It can be found that there was no CTAB in either Jialing River water or tap water (Table S2). The satisfactory recoveries of CTAB are from 94 to 114%, and the relative standard deviations (RSD) were below 4.3% from three repetitive assays, which demonstrated that the ratiometric method for detecting CTAB in environmental water samples was trustworthy and practicable.

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CONCLUSIONS In summary, a rapid, visual, and sensitive method for ratiometric fluorescent detection of CTAB via fabricating a dual-emission probe (UiO-66-NH2@PB) was proposed. This sensing system was formed by combining PB and UiO-66NH2, as PB is directly adsorbed on the structure of UiO-66NH2. Since CTAB quenched emission of ratiometric probe via electrostatic interactions between PB and CTAB, a low detection limit and excellent selectivity toward CTAB was achieved. By comparison with a single-response fluorescencesensing system, UiO-66-NH2@PB displayed distinct color change to different concentrations of CTAB and eliminated the interferences from the environment and fluctuation of instrument. In addition, the probe had been successfully utilized to monitor CTAB in environmental water samples with satisfactory recoveries. Furthermore, the smartphonebased sensing platform supplied a convenient and user-friendly method for CTAB detection, which realized rapid quantification and on-site visual strategy without any spectrophotometer.

Figure 5. Plots of relative emission intensity (I430/I560) of the UiO-66NH2@PB in the presence of various cationic surfactants in pH 4.5 buffer.

With increasing length of the carbon chains, the hydrophobicity of surfactants was improved; upon addition to the UiO-66-NH2@PB solution, it was easier to induce surfactants being adsorbed onto the UiO-66-NH2 and react with PB. Hence, this strategy can be utilized to evaluate the molecular mass of cationic surfactants with similar structure. Effect of Interferential Molecules on UiO-66-NH2@PB. Minimal or no interference from other components is necessary for an assay strategy, so the selectivity of the established method was assessed for CTAB detection by recording the intensity ratios (I430/I560) of the sensing system. As illustrated in Figure 6, the metal ions, such as Na+, K+, Cu2+,

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.9b00470. N2 adsorption and desorption isotherms for UiO-66NH2@PB and UiO-66-NH2. XPS full scan spectra and the magnified C 1s, O 1s, and Zr 3d XPS spectra of the UiO-66-NH2 and UiO-66-NH2@PB; SEM images of prepared UiO-66-NH2 and UiO-66-NH2@PB; optimization of the mixing time between UiO-66-NH2 and PB. Different mixture ratios of UiO-66-NH2 to PB; optimization of reaction conditions for detecting CTAB based on UiO-66-NH2@PB; screen captures during the CTAB determination by the smartphone: mobile phone menu loaded application, main menu of Live Color, typical sample analysis process and final results in RGB mode obtained after image processing; analytical performance of various methods for CTAB detecting; analytical consequences of CTAB in tap water and Jialing River water (PDF)

Figure 6. Selectivity of UiO-66-NH2@PB for CTAB monitoring over other substances in 20 mM HAc-NaAc buffer (pH 4.5). Concentration: CTAB is 9 μM. The others are 50 μM, while Tween 80 and CPB are 20 μM.

Zn2+, Mg2+, Mn2+, Ca2+, Fe3+, Pb2+, Hg2+, and Al3+, and the common anions, including NO3−, Cl−, CO32−, Br−, I,− and SO42−, hardly interfered the sensing system even at a high concentration (metal ions and common anions were 50 μM); meanwhile, there was no obvious change in the ratio of I430/ I560 upon addition of other chemicals such as melamine, CPB, urea, Tween 80, EDTA, SDS, and Triton X-100. The results confirmed that the developed sensing system had a highly selective response to CTAB over other surfactants. Practical Application. The fast response combined with superior specificity and high sensitivity of the proposed method for CTAB detection recommended that the ratiometric sensing system might be directly utilized to monitor CTAB in real samples. To further investigate the applicability of the probe, a standard addition method was employed to detect CTAB in Jialing River water and tap water. Studies were

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (N.B.L.). *E-mail: [email protected] (H.Q.L.). ORCID

Nian Bing Li: 0000-0001-6395-2074 Hong Qun Luo: 0000-0002-2254-6034 Notes

The authors declare no competing financial interest. 8393

DOI: 10.1021/acs.inorgchem.9b00470 Inorg. Chem. 2019, 58, 8388−8395

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Inorganic Chemistry

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(19) Chen, X. Q.; Lee, J.; Jou, M. J.; Kim, J.-M.; Yoon, J. Colorimetric and fluorometric detection of cationic surfactants based on conjugated polydiacetylene supramolecules. Chem. Commun. 2009, 23, 3434−3436. (20) Dwivedi, A. K.; Pandeeswar, M.; Govindaraju, T. Assembly modulation of PDI derivative as a supramolecular fluorescence switching probe for detection of cationic surfactant and metal ions in aqueous media. ACS Appl. Mater. Interfaces 2014, 6, 21369−21379. (21) Li, N.; Hao, X.; Kang, B. H.; Li, N. B.; Luo, H. Q. Sensitive and selective turn-on fluorescence method for cetyltrimethylammonium bromide determination based on acridine orange-polystyrene sulfonate complex. Luminescence 2016, 31, 1025−1030. (22) Liu, D. Y.; Qu, F.; Zhao, X. E.; You, J. M. Generalized one-pot strategy enabling different surface functionalizations of carbon nanodots to produce dual emissions in alcohol-water binary systems. J. Phys. Chem. C 2015, 119, 17979−17987. (23) Wu, L.; Wu, I. C.; DuFort, C. C.; Carlson, M. A.; Wu, X.; Chen, L.; Kuo, C. T.; Qin, Y. L.; Yu, J. B.; Hingorani, S. R.; Chiu, D. T. Photostable ratiometric pdot probe for in vitro and in vivo imaging of hypochlorous acid. J. Am. Chem. Soc. 2017, 139, 6911−6918. (24) Liu, S. G.; Li, N.; Han, L.; Li, L. J.; Li, N. B.; Luo, H. Q. Sizedependent modulation of fluorescence and light scattering: a new strategy for development of ratiometric sensing. Mater. Horiz. 2018, 5, 454−460. (25) Wu, S. Y.; Min, H.; Shi, W.; Cheng, P. Multicenter metalorganic framework-based ratiometric fluorescent sensors. Adv. Mater. 2019, 1805871. (26) Zhang, K.; Zhou, H. B.; Mei, Q. S.; Wang, S. H.; Guan, G. J.; Liu, R. Y.; Zhang, J.; Zhang, Z. P. Instant visual detection of trinitrotoluene particulates on various surfaces by ratiometric fluorescence of dual-emission quantum dots hybrid. J. Am. Chem. Soc. 2011, 133, 8424−8427. (27) Niu, W. J.; Shan, D.; Zhu, R. H.; Deng, S. Y.; Cosnier, S.; Zhang, X. J. Dumbbell-shaped carbon quantum dots/AuNCs nanohybrid as an efficient ratiometric fluorescent probe for sensing cadmium (II) ions and L-ascorbic acid. Carbon 2016, 96, 1034−1042. (28) Wang, Q. X.; Xue, S. F.; Chen, Z. H.; Ma, S. H.; Zhang, S. Q.; Shi, G. Y.; Zhang, M. Dual lanthanide-doped complexes: the development of a time-resolved ratiometric fluorescent probe for anthrax biomarker and a paper-based visual sensor. Biosens. Bioelectron. 2017, 94, 388−393. (29) Lan, M. H.; Zhang, J. F.; Chui, Y. S.; Wang, P. F.; Chen, X. F.; Lee, C. S.; Kwong, H. L.; Zhang, W. J. Carbon nanoparticle-based ratiometric fluorescent sensor for detecting mercury ions in aqueous media and living cells. ACS Appl. Mater. Interfaces 2014, 6, 21270− 21278. (30) Wang, X. Y.; Yu, J. L.; Wu, X. Q.; Fu, J. Q.; Kang, Q.; Shen, D. Z.; Li, J. H.; Chen, L. X. A molecular imprinting-based turn-on ratiometric fluorescence sensor for highly selective and sensitive detection of 2,4-dichlorophenoxyaceticacid (2,4-D). Biosens. Bioelectron. 2016, 81, 438−444. (31) Zhou, H. C.; Long, J. R.; Yaghi, O. M. Introduction to metalorganic frameworks. Chem. Rev. 2012, 112, 673−674. (32) Hu, Z. C.; Deibert, B. J.; Li, J. Luminescent metal-organic frameworks for chemical sensing and explosive detection. Chem. Soc. Rev. 2014, 43, 5815−5840. (33) Zhang, H. T.; Zhang, J. W.; Huang, G.; Du, Z. Y.; Jiang, H. L. An amine-functionalized metal-organic framework as a sensing platform for DNA detection. Chem. Commun. 2014, 50, 12069− 12072. (34) Cui, Y. J.; Yue, Y. F.; Qian, G. D.; Chen, B. L. Luminescent Functional Metal-Organic Frameworks. Chem. Rev. 2012, 112, 1126− 1162. (35) Yang, J.; Dai, Y.; Zhu, X. Y.; Wang, Z.; Li, Y. S.; Zhuang, Q. X.; Shi, J. L.; Gu, J. L. Metal-organic frameworks with inherent recognition sites for selective phosphate sensing through their coordination-induced fluorescence enhancement effect. J. Mater. Chem. A 2015, 3, 7445−7452.

ACKNOWLEDGMENTS This work was financially supported by the National Natural Science Foundation of China (Nos. 21675131 and 21273174) and the Natural Science Foundation of Chongqing (No. CSTC-2015jcyjB50001).

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REFERENCES

(1) Vittal, R.; Gomathi, H.; Kim, K. J. Beneficial role of surfactants in electrochemistry and in the modification of electrodes. Adv. Colloid Interface Sci. 2006, 119, 55−68. (2) Levine, L. H.; Garland, J. L.; Johnson, J. V. Simultaneous quantification of poly-dispersed anionic, amphoteric and nonionic surfactants in simulated wastewater samples using C18 highperformance liquid chromatography-quadrupole ion-trap mass spectrometry. J. Chromatogr. A 2005, 1062, 217−225. (3) Ying, G. G. Fate, behavior and effects of surfactants and their degradation products in the environment. Environ. Int. 2006, 32, 417−431. (4) Purakayastha, P. D.; Pal, A.; Bandyopadhyay, M. Sorption kinetics of anionic surfactant on to waste tire rubber granules. Sep. Purif. Technol. 2005, 46, 129−135. (5) Yüksel, E.; Sengil, I. A.; Ö zacar, M. The removal of sodium dodecyl sulfate in synthetic wastewater by peroxi-electrocoagulation method. Chem. Eng. J. 2009, 152, 347−353. (6) Rosen, M.; Li, F.; Morrall, S.; Versteeg, D. The relationship between the interfacial properties of surfactants and their toxicity to aquatic organisms. Environ. Sci. Technol. 2001, 35, 954−959. (7) Chaturvedi, V.; Kumar, A. Diversity of culturable sodium dodecyl sulfate (SDS) degrading bacteria isolated from detergent contaminated ponds situated in Varanasi city, India. Int. Biodeterior. Biodegrad. 2011, 65, 961−971. (8) Lee, J. K.; Kim, D. B.; Kim, J. L.; Kim, P. Y. In vitro cytotoxicity tests on cultured human skin broblasts to predict skin irritation potential of Surfactants. Toxicol. In Vitro 2000, 14, 345−349. (9) North-Root, H.; Yackovich, F.; Demetrulias, J.; Gacula, M.; Heinze, v Evaluation of an in vitro cell toxicity test using rabbit corneal cells to predict the eye irritation potential of surfactants. Toxicol. Lett. 1982, 14, 207−212. (10) Szymczyk, K.; Zdziennicka, A.; Jánczuk, B.; Wójcik, W. The properties of mixtures of two cationic surfactants in water at water/air interface. Colloids Surf., A 2005, 264, 147−156. (11) Morrow, A. P.; Kassim, O. O.; Ayorinde, F. O. Evaluation of an in vitro cell toxicity test using rabbit corneal cells to predict the eye irritation potential of surfactants. Rapid Commun. Mass Spectrom. 2001, 15, 767−770. (12) Heinig, K.; Vogt, C.; Werner, G. Determination of cationic surfactants by capillary electrophoresis with indirect photometric detection. J. Chromatogr. A 1997, 781, 17−22. (13) Zheng, L. Q.; Yu, X. D.; Xu, J. J.; Chen, H. Y. Colorimetric detection of quaternary ammonium surfactants using citrate-stabilized gold nanoparticles (Au NPs). Anal. Methods 2014, 6, 2031−2033. (14) Zheng, L. Q.; Yu, X. D.; Xu, J. J.; Chen, H. Y. Rapid visual detection of quaternary ammonium surfactants using citrate-capped silver nanoparticles (Ag NPs) based on hydrophobic effect. Talanta 2014, 118, 90−95. (15) Hao, X.; Xu, Z.; Li, N.; Li, N. B.; Luo, H. Q. A cation exchange based electrochemical sensor for cetyltrimethylammonium bromide detection using an acridine orange/polystyrene sulfonate system. Anal. Methods 2015, 7, 3849−3854. (16) Merino, F.; Rubio, S.; Pérez-Bendito, D. P. Mixed aggregatebased acid-induced cloud-point extraction and ion-trap liquid chromatography-mass spectrometry for the determination of cationic surfactants in sewage sludge. J. Chromatogr. A 2003, 998, 143−154. (17) Lundgren, J. S.; Bright, F. V. Biosensor for the nonspecific determination of ionic surfactants. Anal. Chem. 1996, 68, 3377−3381. (18) Diao, X. L.; Xia, Y. S.; Zhang, T. L.; Li, Y.; Zhu, C. Q. Fluorescence-detecting cationic surfactants using luminescent CdTe quantum dots as probes. Anal. Bioanal. Chem. 2007, 388, 1191−1197. 8394

DOI: 10.1021/acs.inorgchem.9b00470 Inorg. Chem. 2019, 58, 8388−8395

Article

Inorganic Chemistry (36) Gao, N.; Huang, J.; Wang, L. Y.; Feng, J. Y.; Huang, P. C.; Wu, F. Y. Ratiometric fluorescence detection of phosphate in human serum with a metal-organic frameworks-based nanocomposite and its immobilized agarose hydrogels. Appl. Surf. Sci. 2018, 459, 686−692. (37) Dong, Y. Q.; Cai, J. H.; Fang, Q. Q.; You, X.; Chi, Y. W. Dualemission of lanthanide metal-organic frameworks encapsulating carbon-based dots for ratiometric detection of water in organic solvents. Anal. Chem. 2016, 88, 1748−1752. (38) Feng, J. F.; Gao, S. Y.; Liu, T. F.; Shi, J. L.; Cao, R. Preparation of dual-emitting Ln@UiO-66-hybrid films via electrophoretic deposition for ratiometric temperature sensing. ACS Appl. Mater. Interfaces 2018, 10, 6014−6023. (39) Zhang, S. Y.; Shi, W.; Cheng, P.; Zaworotko, M. J. A mixedcrystal lanthanide zeolite-like metal-organic framework as a fluorescent indicator for lysophosphatidic acid, a cancer biomarker. J. Am. Chem. Soc. 2015, 137, 12203−12206. (40) Zhou, J. M.; Li, H. H.; Zhang, H.; Li, H. M.; Shi, W.; Cheng, P. A bimetallic lanthanide metal-organic material as a self-calibrating color-gradient luminescent sensor. Adv. Mater. 2015, 27, 7072−7077. (41) Aguilera-Sigalat, J.; Bradshaw, D. A colloidal water-stable MOF as a broad-range fluorescent pH sensor via post-synthetic modification. Chem. Commun. 2014, 50, 4711−4713. (42) Shen, L. J.; Liang, R. W.; Luo, M. B.; Jing, F. F.; Wu, L. Electronic effects of ligand substitution on metal organic frameworks photocatalysts: The case study of UiO-66. Phys. Chem. Chem. Phys. 2015, 17, 117−121. (43) Yang, S. W.; Sun, J.; Li, X. B.; Zhou, W.; Wang, Z. Y.; He, P.; Ding, G. Q.; Xie, X. M.; Kang, Z. H.; Jiang, M. H. Large-scale fabrication of heavy doped carbon quantum dots with tunablephotoluminescence and sensitive fluorescence detection. J. Mater. Chem. A 2014, 2, 8660−8667. (44) Liu, Y.; Liu, Y. N.; Park, S. J.; Zhang, Y. F.; Kim, T. W.; Chae, S.; Park, M.; Kim, H. Y. One-step synthesis of robust nitrogen-doped carbon dots: acid-evoked fluorescence enhancement and their application in Fe3+ detection. J. Mater. Chem. A 2015, 3, 17747− 17754.

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DOI: 10.1021/acs.inorgchem.9b00470 Inorg. Chem. 2019, 58, 8388−8395