Research Article pubs.acs.org/journal/ascecg
Water-Soluble Photoluminescence On−Of f−On Probe for Speedy and Selective Detection of Fluoride Ions Pooja Singh,† Asmita A. Prabhune,† Chandra Shekhar Pati Tripathi,*,‡ and Debanjan Guin*,§ †
Biochemical Sciences Division, Pashan Road, Pune 411008, India Department of Physics and §Department of Chemistry, University of Rajasthan, JLN Marg, Jaipur, Rajasthan 302004, India
‡
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S Supporting Information *
ABSTRACT: A CdTe QDs based new type of water-soluble switch on−off−on photoluminescence (PL) probe has been developed for specific detection of fluoride ions (F−). Europium ions (Eu3+) stabilized by the carboxylic groups of 3mercaptopropanoic acid (MPA) capped CdTe QDs result in quenching of PL (switch of f) of QDs. PL is regained (switch on) with the addition of F− due to the formation of EuF3 as Eu3+ has higher bonding affinity with F− compared to carboxylic acid groups. The quenching of the PL property of CdTe-MPA QDs toward Eu3+ and its regeneration in the presence of F− is highly selective, sensitive (detection limit 5 ppm to 75 ppm), and prompt (less than 10 s). The technique has been successfully applied for the detection of HF vapors, which is actually an important issue from the industrial perspective. To the best of our knowledge, this is the first report of the use of one step synthesized water-soluble 3-MPA capped CdTe QDs, as a rapid, efficient, and most importantly selective photoluminescence on−off−on probe for fluoride ion detection. KEYWORDS: Photoluminescence sensor, Quantum dots, Fluoride ions, Switch on−off−on, HF vapor
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INTRODUCTION Colloidal semiconductor quantum dots (QDs), with radii of around several nanometers, have unique photoluminescence (PL) properties due to the quantum confinement effect of the charge carriers aided by surface functionalization effects.1 QDs possess higher PL quantum efficiency, tunable luminescence depending on their size, wide band continuous absorption, narrow PL emission band, and higher photostability over conventional organic fluorescent dyes.2 Following the first use of hydrophilic QDs as fluorescence probes in cellular labeling in 1998,3,4 QDs have continued to attract extensive attention from the fields of biology and medicine and have made remarkable inroads in biomedical application domain.5−7 Additionally, sensing schemes based on fluorescence resonance energy transfer (FRET) or photoinduced electron transfer (PET) have also been developed for detecting small molecules and for tracing biorecognition events as well as biocatalytic transformations.8,9 Chen and Rosenzweig reported the first practical use of CdS QDs as chemical sensors to determine Zn(II) and Cu(II) ions in aqueous media.10 Recently, a great deal of attention has been © 2016 American Chemical Society
paid to the applications of QDs as metal ion probes because of the environmental and biological importance of such ions.11,12 Depending on the nature of QDs as well as surface coatings, a number of QDs-based probes were developed for transition metal ions, including Hg2+, Cu2+, Ag+, and Pb2+. Nevertheless, relatively very little attention has been paid to the fluorescence behavior of QDs in the presence of various chemical species, mainly anionic pollutants.13−16 Li et al. have reported that cyclodextrin modified CdSe/ZnS QDs allow a highly sensitive determination of environmental pollutant phenols.17 Recently, Johnson and co-workers have developed a single QD-based aptameric sensor that is capable of sensing the presence of cocaine.14 Owing to the sustained interests of a selective chemosensor in environmental monitoring, the design of sensing devices based on QDs is a topic of great interest.18,19 Among various ionic species, the fluoride anion (F−) has unique chemical and physiological properties. It is also Received: September 22, 2016 Revised: October 19, 2016 Published: November 7, 2016 982
DOI: 10.1021/acssuschemeng.6b02296 ACS Sustainable Chem. Eng. 2017, 5, 982−987
Research Article
ACS Sustainable Chemistry & Engineering Scheme 1
temperature and precipitated with acetone and washed with water to get rid of Na+ ions and unbound MPA. The solution was centifuged, and finally the pellet was collected, which comprised of CdTe QDs. The pellet was dried with a rotary evaporator. The resulting soild CdTe QDs were readily redispersed in water resulting in a clear solution. Instrumentation. Photoluminescence measurements were performed on a PerkinElmer LS 55 spectrophotometer. All the samples were prepared in distilled water. The initial concentration of CdTeMPA in all the experiments was kept constant, i.e., 2 mg/mL. Transmission electron microscopy (TEM) images were obtained on a model JEOL 1200 EX operating at 200 kV. The CdTe-MPA QDs colloid, CdTe-MPA-Eu3+ QD aggregates, and CdTe-MPA-Eu-F system were diluted 1000-fold with distilled H2O, deposited onto a 200 mesh copper grid coated with a Formvar film, and dried overnight. Field emission scanning electron microscope (FESEM) images were acquired on a model FEI QUANTA 200 microscope, equipped with a tungsten filament gun, operating at WD 10.6 mm and 20 kV. 10 μL aliquots of all three sample-CdTe-MPA QD colloids, CdTe-MPA-Eu3+ QD aggregates, and the CdTe-MPA-Eu-F system were placed on a silicon wafer and then dried overnight at room temperature. The silicon wafers were then fixed on copper stubs with the help of carbon tape, and images were recorded after that. Selectivity Study. The selectivity of the method was investigated by checking PL absorption maxima of CdTe-Eu3+ QDs on interaction with various other anions such as thiosulfate, chloride, peroxydisulfate−, phosphate, bromide, sulfate, nitrite, nitrate, iodide, and dichromate, cations such as nickel(II), iron(II), and iron(III), and amino acids such as proline (Pro), serine (Ser), alanine (Ala), and histidine (His). To confirm the precision and recovery of the probe, each set of experiments was carried out in triplicate. Similar results were obtained within the maximum error of 2−3%. Hydrogel Preparation. Immobilization of CdTe-MPA QDs into agarose 1 mL-CdTe-MPA QDs stock solution was mixed with 10 mg of agarose powder in 10 mL of Millipore water and heated to 45 °C to get a clear homogeneous solution. The solution was then cooled to room temperature to obtain the CdTe-MPA QD immobilized agarose hydrogel.
associated with systems such as nerve gases, drinking water, and the refinement of uranium.20−22 Therefore, it is important to develop an effective fluorescent sensor from the environmental and biological perspective that could selectively detect fluoride ions. Most studies on the optical or PL based detection of F− ions have been carried out with organic molecules16 and the synthesis of which generally involves more than one step that causes overall higher production cost. Importantly, many of these molecules are mostly water insoluble, and, hence, the detection of F− ion in water samples cannot be carried out directly by their use. Thus, although a variety of organic molecule based fluorescent sensors for fluoride detection have been presented in the literature,23−28 to the best of our knowledge, there is no report of one step synthesized watersoluble MPA capped CdTe QDs as a selective photoluminescence on−off−on probe for fluoride ion detection.
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EXPERIMENTAL SECTION
Chemicals and Materials. Cadmium chloride (CdCl2), tellurium powder (Te), nickel(II) chloride hexahydrate, iron(II) chloride hexahydrate, anhydrous iron(III) chloride (SD Fine Chemicals), 3mercaptopropanoic acid (MPA) (SRL Chemicals), ammonium hydroxide (NH4OH) (Merck Laboratories), sodium borohydride (NaBH4) (Merck Laboratories), and europium nitrate pentahydrate (Sigma-Aldrich, India) were used as obtained. Isopropyl alcohol and acetone (Merck Laboratories) were used as received. Deionized water was acquired from Millipore milli-Q system. Thio sulfate, sodium chloride, potassium persulfate, sodium sulfate, potassium bromide, sodium nitrite, ammonium dichromate, sodium triphosphate, and sodium nitrate (Merck laboratories) were used as obtained. All amino acids - proline, serine, alanine, histidine - were obtained at the highest purity from Sigma-Aldrich (India). Synthesis of CdTe QDs. 3-Mercaptopropanoic acid (MPA) capped water-soluble monodispersed CdTe QDs were synthesized using an organometallic route.29−31 In brief, NaHTe was prepared by reacting NaBH4 and Te powder in a molar ratio of 3:1 in nitrogen atmosphere. Te powder (3.0 mM) was mixed with NaBH4 in 1 mL of nitrogen purged distilled water under a nitrogen saturated condition. The reaction was carried out at room temperature under nitrogen flow with the magnetic stirring until the color of the solution turned to transparent pink. This freshly prepared NaHTe solution was then hot injected (100 °C) into the N2 saturated solution containing CdCl2 (15 mM) and MPA (36 mM) at pH 9. This solution was then refluxed for 2 h in inert atmosphere. The CdTe solution was cooled to room
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RESULTS AND DISCUSSION The principle of our F− sensing concept is shown in Scheme 1. Along with solution form, we have also immobilized the CdTe-MPA QDs into agarose to get a highly fluorescent hydrogel, which also acts as a PL based probe, i.e. PL- switch off with addition of Eu3+ in solution, followed by PL- switch on 983
DOI: 10.1021/acssuschemeng.6b02296 ACS Sustainable Chem. Eng. 2017, 5, 982−987
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Figure 1. Photoluminescence spectra of CdTe-MPA with an increasing concentration of Eu3+ ions carried out in water. The inset shows the respective graphical relationship of the PL intensity against an increasing concentration of Eu3+.
with addition of F−. We have extended the PL sensing mechanism further to detect HF vapors, which is important from the industrial point of view. MPA capped water-soluble CdTe QDs were synthesized as reported earlier.30 The quantum yield of the as-synthesized CdTe-MPA in water was 21% using Rhodamine B as a reference. The PL intensity of CdTe-MPA QDs (switch on) quenched instantly with the addition of Eu(NO3)3, as initially the Eu3+ ions coordinate to the free carboxylate groups of MPA on the surface of the CdTe QDs. These result in a network structure, which leads to aggregation as shown in Scheme 1. As a consequence, the PL of CdTe QDs is quenched (switch off) through electron-transfer processes. Then, such nonfluorescent CdTe-MPA-Eu3+ QD aggregates get dissociated on the introduction of F− because Eu3+ displays a higher affinity for a small fluoride anion than for the carboxylate groups existing on the CdTe-MPA QD surface. In this case, the subsequent redistribution of QDs results in the restoration of PL (switch on). The PL quenching of CdTe-MPA, upon continuous addition of Eu3+, is shown in Figure 1. It is observed that the PL quenching of CdTe-MPA increases with an increasing Eu3+ concentration in Millipore water. The corresponding calibration curve is shown in the inset of Figure 1. It is also observed that the PL intensity at 560 nm decreases as the concentration of Eu3+ ions increases. More than 90% of the PL of CdTe-MPA is quenched by the addition of 50 μM Eu3+ ions. Time-resolved PL spectra were recorded to evaluate the response time of PL quenching. The results revealed that the reaction time for PL quenching to be less than 45 s (Supporting Information SI Figure S3). A similar pattern of PL quenching of CdTe-MPA with Eu3+ addition was observed in other experiments, which were carried out in PBS buffer (pH-7.2) solution (Supporting Information SI Figure S1). With addition of F−, the small F− can easily penetrate into the CdTe-MPA-Eu3+ network. Also F− have stronger bonding affinity than the carboxylic acid group toward Eu3+, which results in the formation of EuF3 and releases bare CdTe-MPA QDs. Subsequently the recovery of PL emission takes place to the desorption of Eu3+ from the surface of the CdTe-MPAEu3+. Figure 2 shows the PL recovery with the addition of F−
Figure 2. Photoluminescence spectra of CdTe-MPA-Eu3+ with an increasing concentration of fluoride ions carried out in water. The inset shows the respective graphical relationship of the PL intensity against an increasing concentration of fluoride ion.
and corresponding calibration curve (Figure 2 inset). A linear relationship between the enhanced PL intensity of CdTe-MPAEu3+ and the concentration of added F− is observed in Figure 2 (inset). The response time to recover PL is less than 10 s (Supporting Information SI Figure S4). A similar result was also observed in a PBS buffer solution at pH-7.2 (Supporting Information SI Figure S2). The PL switch on−of f−on phenomenon was repeated three times. The detection limit of the developed probe was found to be 5 ppm to 75 ppm.32−34 To determine possible selective sensing of HF vapors, a PBS buffer solution and hydrogels of CdTe-MPA-Eu3+ (switch of f) were kept under vapors of different acids and bases (HCl, HF, NHO3, NH3, NH2NH2, H2S). The PL recovery was observed only in the case of HF vapors, whereas, in all other cases, no change was observed in PL. The PL recovery phenomena are shown in Figure 3. Transmission electron microscopy was used to study the change in the morphology of CdTe-MPA QDs, to identify the formation of aggregates on interaction with Eu3+ and their eventual disruption of aggregates when coming into contact with F−. TEM micrographs of CdTe QDs show nearly monodispersed spherical morphology with an average diameter 984
DOI: 10.1021/acssuschemeng.6b02296 ACS Sustainable Chem. Eng. 2017, 5, 982−987
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spacing of 0.37 nm, which correspond to the (111) plane of a face centered cubic phase of the CdTe QDs, are observed.35 Field emission scanning electron microscopy (FESEM) images were also recorded to further validate TEM image based analyses. These show particle features of 2 types: one, monodispersed and another in aggregated form. The formation of agglomerates of the CdTe-MPA-Eu3+ complex and their further disruption with the addition of F− is also verified by the FESEM analysis of the CdTe-MPA samples. Figure 5 (a) shows the presence of 5 nm monodispersed particles, which on addition of Eu3+ salt start forming clear 1−2 μm sized spherical Figure 3. Pictures of CdTe-MPA-Eu3+ in PBS buffer pH-7.2 and agarose gels before (left) and after (right) contact with HF fumes in UV light.
of 5 ± 1 nm (Figure 4 (a)), which gets changed, with the addition of Eu3+ due to the formation of agglomerates (Figure
Figure 4. TEM and HRTEM images of CdTe-MPA a) and b); CdTeMPA-Eu3+ c) and d); and CdTe-MPA with Eu-F e) and f).
4(c)). When F− ions are introduced, Eu3+ induced larger agglomerates get disrupted and redispersed back to the original QDs of size 5 ± 1 nm (Figure 4(e)). The corresponding HRTEM images of CdTe-MPA, CdTe-MPA-Eu3+, and CdTeMPA-Eu-F systems are shown in Figure 4 (b), (d) and (f), respectively. In all the cases the lattice fringes with a d-line
Figure 5. FESEM of A) CdTe-MPA, B) CdTe-MPA-Eu3+, and C) CdTe-MPA-Eu-F, respectively. 985
DOI: 10.1021/acssuschemeng.6b02296 ACS Sustainable Chem. Eng. 2017, 5, 982−987
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Figure 6. Visual and UV light pictures of a) CdTe-MPA, b) CdTe-MPA-Eu3+, c) CdTe-MPA-Eu-F, d) CdTe-MPA-Eu-thiosulfate, e) CdTe-MPAEu-NaCl, f) CdTe-MPA-Eu-potassium per sulfate, g) CdTe-MPA-Eu-sodium sulfate, h) CdTe-MPA-Eu-Kbr, (i) CdTe-MPA-Eu-sodium nitrite, j) CdTe-MPA-Eu-ammonium dichromate, k) CdTe-MPA-Eu-sodium triphosphate, and l) CdTe-MPA-Eu-sodium nitrate.
aggregates due to the formation of the CdTe-MPA-Eu3+ complex as shown in Scheme 1. With the introduction of F− into the solution of CdTe-MPA-Eu3+, Eu3+ forms EuF3 leaving the carboxylic group free of CdTe-MPA QDs. This leads to the disruption of the CdTe-MPA-Eu3+ aggregate and recovery of pristine CdTe-MPA QDs as shown in Figure 5 (c). The corresponding elemental mapping of CdTe-MPA, Eu3+, and EuF3 was also done which clearly shows the presence of all the expected elements, as shown in the Supporting Information SI Figure S6 (a), (b), and (c). To validate the application of the CdTe-MPA-Eu3+ nanocomposite as a PL probe system for application in biological and environmental detection in water, the selectivity of the developed probe for F− was tested. This was done by monitoring the PL responses of the CdTe-MPA-Eu3+ nanocomposite complex upon addition of F− and some coexisting substances, including anions such as thiosulfate, chloride, peroxydisulfate, phosphate, bromide, sulfate, nitrite, nitrate, iodide, and dichromate, cations such as nickel(II), iron(II), and iron(III), and amino acids such as proline (Pro), serine (Ser), alanine (Ala), and histidine (His). All of the ions were kept at a concentration 50 times higher than that of F−. As shown in Figure 6, the PL intensity of the CdTe-MPA-Eu3+ nanocomposite gets significantly restored upon the addition of F− in the presence of all possible potential challengers tested. In contrast, no clear enhancement was observed with any other ions or amino acids. Thus, it can be concluded that this on− off−on PL probe is highly specific for F− ions, as well as several times more sensitive for F−, as compared to all the other substances tested. This high specificity could be attributed to the specific and robust affinity between Eu3+ ions and F− and the of f−on nature of the assay presented. The bar diagram of PL quenching and recovery with all the tested samples are shown in Figure 7. We have also studied the effect of interfering radicals in the PL detection of the F− ions (SI Figure S7). It was observed that in the absence of F− ions, even when other ions are present, almost no PL recovery was observed. In the presence of F− ions, with other ions, the PL was significantly recovered. It clearly establishes that our PL based optical probe is highly selective for the detection of F− ions in water at neutral pH.
Figure 7. Bar diagram for the selectivity test results obtained with the addition of different anions, cations, and amino acids into the CdTeMPA-Eu system: a) CdTe-MPA, b) CdTe-MPA-Eu3+, c) CdTe-MPAEu-F, d) CdTe-MPA-Eu-thiosulfate, e) CdTe-MPA-Eu-Cl, f) CdTeMPA-Eu-potassium per sulfate, g) CdTe-MPA-Eu-SO42−, h) CdTeMPA-Eu-Br−, (i) CdTe-MPA-Eu-NO3−, j) CdTe-MPA-Eu-Cr2O72−, k) CdTe-MPA-Eu-sodium triphosphate, l) CdTe-MPA-Eu-NO2−, m) CdTe-MPA-Eu-Ni2+, n) CdTe-MPA-Eu-Fe2+, o) CdTe-MPA-Eu-Fe3+, p) CdTe-MPA-Eu-Proline, q) CdTe-MPA-Eu-cysteine, r) CdTeMPA-Eu-alanine, and s) CdTe-MPA-Eu-histidine.
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CONCLUSION In conclusion, we have demonstrated a new type of rapid, sensitive, and specific PL on−off−on assay for the detection of fluoride ions. Furthermore, the assay allows the selective detection of F− from vapors generated by hydrofluoric acid. To the best of our knowledge, this is the first report of the use of water-soluble CdTe-MPA QDs, as a PL probe for speedy and specific photochemical sensing of F−. The selectivity and sensitivity of PL quenching only for F− suggests the wide use of CdTe-MPA-Eu3+ as a versatile probe in the fields of analytical determination, water treatment, and biotechnology in the future.
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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/acssuschemeng.6b02296. Figures S1−S7 (PDF) 986
DOI: 10.1021/acssuschemeng.6b02296 ACS Sustainable Chem. Eng. 2017, 5, 982−987
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(17) Li, H.; Han, C. Sonochemical Synthesis of Cyclodextrin-Coated Quantum Dots for Optical Detection of Pollutant Phenols in Water. Chem. Mater. 2008, 20 (19), 6053−6059. (18) Basabe-Desmonts, L.; Reinhoudt, D. N.; Crego-Calama, M. Design of fluorescent materials for chemical sensing. Chem. Soc. Rev. 2007, 36 (6), 993−1017. (19) Li, H.; Li, Y.; Cheng, J. Molecularly Imprinted Silica Nanospheres Embedded CdSe Quantum Dots for Highly Selective and Sensitive Optosensing of Pyrethroids. Chem. Mater. 2010, 22 (8), 2451−2457. (20) Kimura, E.; Koike, T. Recent development of zinc-fluorophores. Chem. Soc. Rev. 1998, 27 (3), 179−184. (21) Yang, C.; Zheng, M.; Li, Y.; Zhang, B.; Li, J.; Bu, L.; Liu, W.; Sun, M.; Zhang, H.; Tao, Y.; Xue, S.; Yang, W. N-Monoalkylated 1,4diketo-3,6-diphenylpyrrolo[3,4-c]pyrroles as effective one- and twophoton fluorescence chemosensors for fluoride anions. J. Mater. Chem. A 2013, 1 (16), 5172−5178. (22) McDonagh, C.; Burke, C. S.; MacCraith, B. D. Optical Chemical Sensors. Chem. Rev. 2008, 108 (2), 400−422. (23) Sui, B.; Kim, B.; Zhang, Y.; Frazer, A.; Belfield, K. D. Highly Selective Fluorescence Turn-On Sensor for Fluoride Detection. ACS Appl. Mater. Interfaces 2013, 5 (8), 2920−2923. (24) Xu, G.; Tarr, M. A. A novel fluoride sensor based on fluorescence enhancement. Chem. Commun. 2004, 9, 1050−1051. (25) Melaimi, M.; Gabbaï, F. P. A heteronuclear bidentate Lewis acid as a phosphorescent fluoride sensor. J. Am. Chem. Soc. 2005, 127 (27), 9680−9681. (26) Hu, R.; Feng, J.; Hu, D.; Wang, S.; Li, S.; Li, Y.; Yang, G. A rapid aqueous fluoride ion sensor with dual output modes. Angew. Chem., Int. Ed. 2010, 49 (29), 4915−4918. (27) Jose, D. A.; Kumar, D. K.; Ganguly, B.; Das, A. Efficient and simple colorimetric fluoride ion sensor based on receptors having urea and thiourea binding sites. Org. Lett. 2004, 6 (20), 3445−3448. (28) Ke, I.-S.; Myahkostupov, M.; Castellano, F. N.; Gabbaï, F. P. Stibonium Ions for the Fluorescence Turn-On Sensing of F− in Drinking Water at Parts per Million Concentrations. J. Am. Chem. Soc. 2012, 134 (37), 15309−15311. (29) Rogach, A. L.; Franzl, T.; Klar, T. A.; Feldmann, J.; Gaponik, N.; Lesnyak, V.; Shavel, A.; Eychmüller, A.; Rakovich, Y. P.; Donegan, J. F. Aqueous synthesis of thiol-capped CdTe nanocrystals: state-of-the-art. J. Phys. Chem. C 2007, 111 (40), 14628−14637. (30) Singh, P.; Joshi, K.; Guin, D.; Prabhune, A. A. Chemically conjugated sophorolipids on CdTe QDs: a biocompatible photoluminescence nanocomposite for theranostic applications. RSC Adv. 2013, 3 (44), 22319−22325. (31) Singh, P.; Prabhune, A. A.; Ogale, S. B.; Guin, D. Glucose oxidase conjugated H 2 O 2 sensitive CdTe QDs: an effective fluorescence tool for glucose sensing. J. Mater. Chem. B 2013, 1 (47), 6538−6543. (32) Yang, C.; Xu, J.; Ma, J.; Zhu, D.; Zhang, Y.; Liang, L.; Lu, M. An efficient long fluorescence lifetime polymer-based sensor based on europium complex as chromophore for the specific detection of F−, CH 3 COO−, and H 2 PO 4−. Polym. Chem. 2012, 3 (9), 2640−2648. (33) Yang, C.; Xu, J.; Zhang, R.; Zhang, Y.; Li, Z.; Li, Y.; Liang, L.; Lu, M. An efficient Eu-based anion-selective chemosensor: Synthesis, sensing properties, and its use for the fabrication of fluorescent hydrogel probe. Sens. Actuators, B 2013, 177, 437−444. (34) Yang, C.; Xu, J.; Li, J.; Lu, M.; Li, Y.; Wang, X. An efficiently colorimetric and fluorescent probe of fluoride, acetate and phosphate ions based on a novel trinuclear Eu-complex. Sens. Actuators, B 2014, 196, 133−139. (35) Deng, D.; Qu, L.; Li, Y.; Gu, Y. Versatile self-assembly of watersoluble thiol-capped CdTe quantum dots: external destabilization and internal stability of colloidal QDs. Langmuir 2013, 29 (34), 10907− 10914.
AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected] (C.S.P.T.). *E-mail:
[email protected] (D.G.). Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS
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REFERENCES
P.S. was financially supported by the Council of Scientific and Industrial Research (CSIR-India), New Delhi, India. C.S.P.T and D.G. acknowledge UGC and DST-SERB for research funding. The authors would like to thank Satishchandra B. Ogale for fruitful discussions.
(1) Murray, C. B.; Kagan, C. R.; Bawendi, M. G. Synthesis and Characterization of Monodisperse Nanocrystals and Close-Packed Nanocrystal Assemblies. Annu. Rev. Mater. Sci. 2000, 30 (1), 545−610. (2) Qu, L.; Peng, X. Control of Photoluminescence Properties of CdSe Nanocrystals in Growth. J. Am. Chem. Soc. 2002, 124 (9), 2049− 2055. (3) Chan, W. C. W.; Nie, S. Quantum Dot Bioconjugates for Ultrasensitive Nonisotopic Detection. Science 1998, 281 (5385), 2016−2018. (4) Bruchez, M.; Moronne, M.; Gin, P.; Weiss, S.; Alivisatos, A. P. Semiconductor Nanocrystals as Fluorescent Biological Labels. Science 1998, 281 (5385), 2013−2016. (5) Ma, J.; Chen, J.-Y.; Zhang, Y.; Wang, P.-N.; Guo, J.; Yang, W.-L.; Wang, C.-C. Photochemical Instability of Thiol-Capped CdTe Quantum Dots in Aqueous Solution and Living Cells: Process and Mechanism. J. Phys. Chem. B 2007, 111 (41), 12012−12016. (6) Thanh, N. T.; Green, L. A. Functionalisation of nanoparticles for biomedical applications. Nano Today 2010, 5 (3), 213−230. (7) Selvan, S.; Patra, P. K.; Ang, C. Y.; Ying, J. Y. Synthesis of SilicaCoated Semiconductor and Magnetic Quantum Dots and Their Use in the Imaging of Live Cells. Angew. Chem. 2007, 119 (14), 2500−2504. (8) Yildiz, I.; Tomasulo, M.; Raymo, F. ß. M. A mechanism to signal ̀ receptor,Ä isubstrate interactions with luminescent quantum dots. Proc. Natl. Acad. Sci. U. S. A. 2006, 103 (31), 11457−11460. (9) Chan, Y.-H.; Ye, F.; Gallina, M. E.; Zhang, X.; Jin, Y.; Wu, I. C.; ̀ Chiu, D. T. Hybrid Semiconducting Polymer Dot,Ä iQuantum Dot with Narrow-Band Emission, Near-Infrared Fluorescence, and High Brightness. J. Am. Chem. Soc. 2012, 134 (17), 7309−7312. (10) Chen, Y.; Rosenzweig, Z. Luminescent CdS Quantum Dots as Selective Ion Probes. Anal. Chem. 2002, 74 (19), 5132−5138. (11) Chen, C.-Y.; Cheng, C.-T.; Lai, C.-W.; Wu, P.-W.; Wu, K.-C.; Chou, P.-T.; Chou, Y.-H.; Chiu, H.-T. Potassium ion recognition by 15-crown-5 functionalized CdSe/ZnS quantum dots in H2O. Chem. Commun. 2006, 3, 263−265. (12) Freeman, R.; Finder, T.; Bahshi, L.; Willner, I. Œ ≤ -Cyclodextrin-Modified CdSe/ZnS Quantum Dots for Sensing and Chiroselective Analysis. Nano Lett. 2009, 9 (5), 2073−2076. (13) Jin, W. J.; Costa-Fernández, J. M.; Pereiro, R.; Sanz-Medel, A. Surface-modified CdSe quantum dots as luminescent probes for cyanide determination. Anal. Chim. Acta 2004, 522 (1), 1−8. (14) Zhang, C.-y.; Johnson, L. W. Single Quantum-Dot-Based Aptameric Nanosensor for Cocaine. Anal. Chem. 2009, 81 (8), 3051− 3055. (15) Wu, P.; Zhang, J.; Wang, S.; Zhu, A.; Hou, X. Sensing during In Situ Growth of Mn-Doped ZnS QDs: A Phosphorescent Sensor for Detection of H2S in Biological Samples. Chem. - Eur. J. 2014, 20 (4), 952−956. (16) Zhou, Y.; Zhang, J. F.; Yoon, J. Fluorescence and Colorimetric Chemosensors for Fluoride-Ion Detection. Chem. Rev. 2014, 114 (10), 5511−5571. 987
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