Polyamine Based Ratiometric Fluorescent Chemosensor for Strontium

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Polyamine based ratiometric fluorescent chemosensor for strontium metal ion in aqueous medium: Application in tap water, river water and in oral care Amanpreet Kaur, Gaganpreet Kaur, Amanpreet Singh, Narinder Singh, and Navneet Kaur ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.5b00772 • Publication Date (Web): 04 Dec 2015 Downloaded from http://pubs.acs.org on December 10, 2015

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ACS Sustainable Chemistry & Engineering

Polyamine based ratiometric fluorescent chemosensor for strontium metal ion in aqueous medium: Application in tap water, river water and in oral care Amanpreet Kaura, Gaganpreet Kaura, Amanpreet Singhb, Narinder Singhb,* Navneet Kaura,* *a Centre for Nanoscience and Nanotechnology (UIEAST), Panjab University, Sector -25, Chandigarh, India, 160014. Tel: 911722534464 E-mail (corresponding author): [email protected] *b Department of Chemistry, Indian Institute of Technology Ropar (IIT Ropar), Rupnagar, Panjab, India, 140001. E-mail: [email protected] Abstract: A pyrene-based polymer, 2 was synthesized via one step condensation reaction between pyrene-1-carboxaldehyde and polyamine in methanol. Organic nanoparticles (ONPs) of polymeric compound 2 were developed using reprecipitation method and investigated for their chemosensor application using fluorescence spectroscopy. Nano-aggregates of polymer compound 2 exhibit efficient and selective chemosensor properties for detection of strontium ions in aqueous medium, with a detection limit of 9 nM. To analyze the practical utility of the sensor, it was successfully employed to detect the amount of Sr2+ in tap water, river water and strontium based toothpastes. Keywords: Pyrene, Fluorescence sensor, Strontium detection, Aqueous, Organic nanoparticles

ACS Paragon Plus Environment


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INTRODUCTION Strontium is a soft alkaline earth metal frequently used in fireworks and signal flares for its brilliant red color, on tracer bullets, in alloys of tin and lead for enhanced resilience, as a deoxidizer of copper and bronze, igneous coloring agent, glass manufacture, condenser material, in toothpaste for sensitive teeth, lead removal, table faceplates, pyrotechnics and ferrite ceramic magnets [1-3]. In contrast to its innumerable applications, most strontium compounds like strontium nitrate, owing to their high water solubility, have been acknowledged as drinking water pollutants and cause detrimental effects on aquatic environment. Further, high uptake of strontium disrupts the bone development in children and its chromate salt is a renowned causative agent of lung cancer [4]. Oxide, hydroxide and carbonate salts of strontium are strong skin and eye irritants [5]. The anomalous effects of strontium in biological systems may be attributed to its chemical resemblance with calcium. Consequently, some living systems are incapable of differentiating between the two, which leads to its excessive uptake, absorption and storage in bones and teeth. The radioactive 90Sr (half life of 29 years) produced from nuclear fallout has been regrettably widely spread in the environment and causes many health problems [6]. Henceforth, the detection of strontium in water bodies seems pragmatic to check and regulate its environmental presence and prevent any public health hazard. A number of techniques such as ICP-AES, AAS, emission photometry and potentiometry are available for strontium determination [7-12]. However, their inability for instant and onsite detection, sample pretreatment and requirement of bulky infrastructure, renders them ineffective for comprehensive monitoring. Thus, a facile, economical and convenient scheme with prompt response is essential for analysis of environmental and industrial samples. Recently, fluorescent chemosensors have emerged as excellent probes for detection of metal ions in water [13]. Although, fluorescent inorganic nanoparticles are also available, their non-degradability and toxicity, renders them unfit for biomedical applications [14-19]. Fluorescent organic nanoparticles are particles derived from organic compounds with sizes varying from 10 nm to 1000 nm [20]. They are preferred over their inorganic counterparts owing to their superior water solubility, optical properties, structural variability, lower toxicity and biodegradable potential [21-22]. The substantial interest of researchers in ONPs may be attributed to their effortless synthesis, the accessibility of a vast library of tunable molecular scaffolds and their employment in water based environmental and biological samples [23]. Reprecipitation is often used for the preparation of ONPs as it offers high reproducibility and is costeffective. In this technique, desired amount of organic compound is dissolved in a minimum amount of organic solvent. From the above solution, small volume is taken in a syringe and injected slowly with continuous sonication into distilled water. After the injection, sonication is further continued for 15-30 minutes to stabilize organic nanoparticles. The large variation in the solubility of organic structures among the two solvents is the compelling force behind the formation of organic nanoparticles. In comparison to small organic sensors, polymer-based optical sensors are more lucrative as a consequence of its signal ampliﬁcation ability [24-25]. Furthermore, the pyrene moiety is widely used in fluorescence probes for selective recognition of


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chemical species owing to its long singlet lifetime [26-29]. The monomer emission for pyrene is observed between 370-430 nm, while the excimer formation is exhibited at around 480 nm. Taking the cognizance, of the reported water soluble optical sensors and their application in the field of metal recognition in aqueous media; fluorescent organic nanoparticles of the polymer were developed and utilized for the detection of strontium in water. To the best of our knowledge, rarely any reports in literature are available that describes the employment of fluorescent chemosensors for Sr2+ ion detection in water [30]. Furthermore, detection limit of the present sensor is lowest among all the previously reported sensors for Sr2+ ion [31-40]. In present work, our goal is to develop a fluorescent probe which detects Sr2+ ions in water and further investigate the practical utility of this sensor towards the detection of Sr2+ in tap water, river water and in toothpastes used in oral care. EXPERIMENTAL General Information Polyethylenimine and 1-pyrenecarboxyaldehyde were procured from Aldrich Co. and used without further purification. 1H and 13C- NMR spectra have been recorded on a Jeol instrument, which operates at 400 MHz for 1H NMR and at 100 MHz for 13C NMR. The photoluminescence experiments were performed on a Shimadzu Spectrofluorometer (RF-5301 PC) with fixed scanning speed. Excitation and emission slit width was 10 nm. ME/962P instrument was used for pH measurements. Particles size was analyzed using a Metrohm Microtrac Ultra Nanotrac Particle Size Analyser (Dynamic Light Scattering). The shape of nanoparticles was recorded using Transmission Electron Microscope (TEM), Hitachi (H-7500). The GPC analysis was carried out on a GPC instrument from Agilent Technologies, using DMF as the eluent and two PolarGel-M columns (7.5 × 300 mm). Atomic absorption spectroscopy experiment was performed on Perkin Elmer AAS. Synthesis of polymeric compound 2

Figure 1. Synthesis scheme of polymeric unit 2.


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Compound 2 has been synthesized by dissolving polyethylenimine 1 (460 mg) and pyrene-1-carboxaldehyde (930 mg) in dry methanol separately (Figure 1). The two solutions were mixed and the resulting mixture was refluxed with stirring for 6h. After 6h of refluxing semi solid material was separated out. The crude product was washed with CH3OH (50 mL) and dried under vacuum. Yield = 77%; 1H NMR (400 MHz, CDCl3) δ 8.89 (s, 1H) , 8.52 (d, 1H, J=9 Hz), 8.29 (d, 2H, J=9 Hz), 8.19 (d, 2H, J=9 Hz), 8.04 (d, 1H, J=9 Hz), 7.85 (d, 1H, J=9Hz), 7.68 (d, 2H, J=9Hz), 7.54-7.61 (d, 1H, J=9Hz), 7.49 (t, 1H, J=9 Hz), 4.00 (t, 2H, J=8Hz), 2.87 (t, 5H, J=8 Hz), 2.78 (t, 2H, J=8Hz). (Figure S1);

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C NMR (100 MHz, CDCl3) δ: 161.23, 131.55, 130.97,

130.84, 129.11, 128.16, 127.58, 127.31, 127.17, 126.95, 126.68, 126.38, 126.27, 126.07, 125.21, 124.67, 123.14, 122.91, 53.07, 51.42, and 50.90 (Figure S2). From gel permeation chromatography (GPC), number average molecular weight (Mn) and the weight average molecular weight (Mw) were determined by using DMF as eluent that found to be 27986 and 37895 (Table S1), respectively with a polydisperity index of 1.35 (Figure S4 & S5). For GPC experiment, 5mg of sample was dissolved in 1ml of DMF and filtered through neutral alumina, and then filtered again through a micropore filter. GPC completed analysis after 20 minutes. Calculation of limit of detection: To calculate the detection limit, a graph was plotted between concentration and fluorescence intensity. The slope and standard deviation was determined from linear regression graph. The detection limit was calculated by using formula

Here, m is slope of linear regression plot and S.D. is standard deviation. Development of organic nanoparticles (ONPs) of compound 2 The method used for fabrication of ONPs is generally governed by the field of application. The influencing factors being the the difference in solubility of the compound in aqueous and organic solvent, pattern of binding sites, pH and temperature etc. [41]. In the present study organic nanoparticles were constructed by using reprecipitation method. The compound, from which the ONPs were to be developed, was dissolved in DMF. This solution was slowly injected into water with sonication. After the injection, sonication was continued for another 30 minutes to ascertain the preparation of stable organic nanoparticles. Nanoparticle formation was scrutinized by the external probe of a particle size analyzer. Ultimately, synthesis of ONPs was optimized by trying different solvents and concentrations of organic compound. Size distribution of the ONPs was continuously analyzed using DLS. The size and shape of ONPs was further studied through TEM analysis. Recognition studies


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All solutions were shaken for a sufficient time and then kept aside for 15 minutes to ascertain the homogeneity of solutions, before recording the emission profile. The spectroscopic measurements were executed at 298 K. For the cation binding experiment, solutions of different metal nitrate salts of 5 mM concentration were made in distilled water. Titrations of strontium with the ONPs were done by addition of small amounts of strontium nitrate solution to the host solution in a 10 ml flask and recording of emission spectra after each increment. For evaluating the anion binding capability of the sensor, tetrabutyl ammonium salt solutions of various anions (5eq.) were added to the sensor. Real Sample Analysis For this study, a range of strontium containing samples was taken. S1, S2 and S3 were commercially accessible toothpastes often used for sensitive teeth. This experiment was based on evaluating the functioning of sensor in industrial samples. Further, the sensing properties of ONPs of compound 2 for Sr2+ in tap water and river water was also checked, for application of the proposed sensor in environmental samples. RESULT AND DISCUSSION Synthesis The one step condensation reaction between 1-pyrenecarboxaldehyde and polyethylenimine has been performed in methanol. A semi solid material was separated, which was further washed with methanol to obtain pure product. Formation of compound 2 was confirmed by 1H and 13C NMR as well as gel permission chromatography. Effect of concentration of compound 2 on the aggregation Nano-aggregates of 2 with four different concentrations were prepared in order to study the effect of concentration of compound 2 on emission spectra. As shown in the Figure 2A; as the concentration of compound 2 increase there was enhancement in the fluorescence intensity, without any red or blue shift which illustrates the formation of larger particles but with similar aggregate arrangements. DLS studies further demonstrated the increase in size of nanoparticles with increment in concentration of nano-aggregates of compound 2 (Figure 2B & 2C). It may be credited to the fact that non-polar interactions with restricted precipitation of compound results in generation of larger sized particles. Further, TEM image recorded for the nanoaggregates of 2 demonstrated that organic nanoparticles were identical in shape and un-agglomerated. The dimension of particles lied in nanoscale range (Figure 2D). Effect of water content on fluorescence spectra of compound 2 Effect of water content on the photophysical properties for nano-aggregates of 2 were explored by recording fluorescence spectra of compound 2 in both DMF as well as in aqueous system (by synthesizing nano-aggregates). The fluorescence spectra of


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compound 2 in organic solvent system depicted a prominent variation in the emission profile in comparison to the nanoaggregates of the compound in aqueous system (Figure 3A). The fluorescence spectra of compound 2, taken in an organic solvent, showed monomer peaks ranging from 407 to 424 nm. Whereas the nano-aggregates of 2 showed broad, featureless emission centered at 444-511 nm. The formation of a broad band between 444 to 511 nm is due to the ground state excimer emission of pyrene in 2 after the formation of nano-aggregates in water.

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50 40 30 20 10 0 0.39

0.49

0.59

0.69

Conentration (in µM) Figure 2. (A) Changes in the emission profile of nano-aggregates of 2 at different concentrations (0.4 to 0.7 µM); (B) DLS histogram of nano-aggregates of 2 (0.5 µM); (C) Plot showing the variation in the size of the nanoparticles with concentration of compound in aqueous medium; (D) TEM images of nano-aggregates of 2. Metal binding studies of nano-aggregates of 2 For assessing the metal binding aptitude of nano-aggregates of 2, preliminary screening was performed with a library of 19 different metal salts. Small aliquots of metal nitrate salt solutions were added to solutions of nano-aggregates of 2 (0.5 µM) taken in different vials and the respective emission spectra were recorded (λex=345 nm). For eliminating the influence of kinetic effects, in the fluorescence spectra, the solutions were kept aside for 15 minutes before recording the fluorescence spectra. The influence


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of the addition of various metal nitrate salts on the fluorescence signature of nano-aggregates of 2 in aqueous system is visible (Figure 3B). Upon addition of an excess of 5 equivalents of various metal ions like Li+, Na+, K+, Cs+, Mg2+, Ca2+, Sr2+, Ba2+, Al3+, Cr3+, Mn2+, Fe3+, Co3+, Cu2+, Zn2+, Ag+, Cd2+, Hg2+ and Pb2+ (as their nitrate salts); a fluorescence quenching was observed in the case of Sr2+ at 471 nm. No such significant change in the fluorescence intensity of nano-aggregates of 2 was observed with the addition of any other tested metal ions under the same conditions. The structure of the compound consists of pyrene moieties. These moieties exhibit π- π stacking between the pyrene groups of a molecule in aqueous medium which may be attributed to the hydrophobic nature of pyrene groups. This stacked structure subsequently results in excimer emission. But when strontium ion binds to host, some conformational changes in the structure of host may have led to formation of a cavity which was fit for strontium ion. These changes resulted in increasing the distance between two pyrene groups and as a consequence, the fluorescence intensity was quenched [42-44].

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Figure 3. (A) Fluorescence emission spectra of compound 2 in DMF and 2 in aqueous medium (0.5 µM) (λex = 345 nm); (B) Changes in fluorescence intensity of nano-aggregates of 2 (0.5 µM) upon addition of a particular metal nitrates (5eq.) in aqueous medium (λex = 345 nm); (C) Changes in emission profile of nano-aggregates of 2 (0.5 µM) in aqueous medium upon addition of a particular tetrabutyl ammonium anion salt (5 eq.) in aqueous media (λex = 345 nm). Anion binding studies of nano-aggregates of 2


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The anion binding studies were carried out to check if the present sensor may bind to some anions as well. This was done to explore the binding scope of the sensor for more number of analytes. The absence of any fluorescence change in this study further implied the high selectivity of the sensor for a particular analyte (strontium). The anion binding ability of nano-aggregates of 2 was checked by addition of 5 eq. of tetrabutyl ammonium anion salts (F-, Cl-, Br-, I-, CN-, CH3COO-, HSO4-, PO43-, NO3- and ClO4-) to a fixed concentration (0.5 µM) of nano-aggregates of 2 at excitation wavelength of 345 nm. Fluorescence spectra were recorded for each solution after appropriate mixing and waiting for adequate time to let the analytes bind with the sensor. No relevant changes were observed in the emission profile of nano-aggregates of 2 when investigated in the presence of the tested anions (Figure 3C). 560

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M e tal ions

Figure 4. (A) Changes in emission profile of nano-aggregates of 2 (0.5 µM) upon successive addition of Sr2+ (0-1.5 µM) (λex = 345 nm); (B) Linear regression graph between concentration of Sr2+ added and fluorescence intensity of nano-aggregates of 2 (λex = 345 nm); (C) Competitive binding studies of nano-aggregates of 2 containing Sr2+ over other selected metal ions at λex = 345 nm. 1) Host only 2) 2.Sr2+ only; 3) 2.Sr2+ + Li+; 4) 2.Sr2+ + Na+; 5) 2.Sr2+ + K+ ; 6) 2.Sr2+ + Cs+ ; 7) 2.Sr2+ + Mg2+ ; 8) 2.Sr2+ + Ca2+; 9) 2.Sr2+ + Ba2+; 10) 2.Sr2+ + Al3+; 11) 2.Sr2+ + Cr3+; 12) 2.Sr2+ + Mn2+; 13) 2.Sr2+ + Fe3+ ; 14) 2.Sr2+ + Co3+; 15) 2.Sr2+ + Cu2+ ; 16) 2.r2+ + Zn2+ ; 17) 2.Sr2+ + Ag+; 18) 2.Sr2+ + Cd2+; 19) 2.Sr2+ + Hg2+; 20) 2.Sr2+ + Pb2+. Titrations of nano-aggregates of 2 with Sr2+ ion


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The binding ability of nano-aggregates of 2 towards Sr2+ ions was further assessed by performing a titration of nanoaggregates of 2 (0.5 µM) with addition of successive amounts of Sr2+, starting from 0 µM to 1.5 µM (Figure 4A). With the increase in the concentration of Sr2+ ions there was a continuous decrease in the fluorescence intensity at 471 nm and slight increase in the fluorescence intensity of monomer peaks ranging from 407-424 nm. An isosbestic point was observed at 421 nm. Titrations showed a good linearity between the concentration range of 0 µM to 1.5 µM (Figure 4B). Using this titration data, nano-aggregates of 2 can detect Sr2+ ion in the solution up to 9 nM (3σ method). The limit of detection of present sensor was very low as compared to other reports in the literature (Table S2). Selectivity The selective nature of nano-aggregates of 2 (0.5 µM) for Sr2+ was investigated from the competitive experiment. In this study, the Sr2+ binding ability of the sensor was verified in the presence of Li+, Na+, K+, Cs+, Mg2+, Ca2+, Ba2+, Al3+, Cr3+, Mn2+, Fe3+, Co3+, Cu2+, Zn2+, Ag+, Cd2+, Hg2+ and Pb2+ (2 eq.). Lack of any noticeable change in the fluorescence spectrum on comparison with or without the other metal ions established the selective nature of the sensor (Figure 4C). pH Studies To analyze a suitable pH range in which nano-aggregates of 2 can selectively detect Sr2+, acid/basic titrations were performed. The fluorescence intensity nano-aggregates of 2 (0.5 µM) was found to remain invariable in a pH range from 2.7 to 11.2 (Figure 5A). Apparently, the nano-aggregates of 2 were found to be insusceptible to any change in pH. Response time In order to study the response time of nano-aggregates of 2 for Sr2+ ion, the fluorescence spectra were recorded upon addition of different concentrations of Sr2+ ion (0.1, 0.6, 1.4 µM) to the solutions of nano-aggregates of 2 (0.5 µM) and each solution was analyzed as a function of time. The interpretation of results revealed that after 100 seconds, the fluorescence intensity of all three solutions is independent of time; in other words, the response time of nano-aggregates of 2 for Sr2+ ion is less than 100 seconds (Figure 5B). Salt Effect The effect of ionic strength on the nano-aggregates of 2 was evaluated from the excitation spectrum of the nano-aggregates of 2 (0.5 µM) its comparison with the excitation spectrum of the same material recorded upon addition of 100 equiv. of the TBA salt of perchlorate (Figure 5C). There was no significant change in fluorescence spectra, which indicated that even excessive concentration of salts has no effect on nano-aggregates of 2 (0.5 µM).


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Figure 5. (A)Effect of pH on nano-aggregates of 2 (0.5 µM) in aqueous system (λex = 345 nm); (B) Response time of nanoaggregates of 2 for Sr2+ at λex = 345 nm; (C) Salt perturbation studies of nano-aggregates of 2 recorded with 0.5 µM concentration of sensor in aqueous system with the respective fluorescence spectrum recorded upon addition of 100 equiv. of tetrabutyl ammonium perchlorate under the same concentration of sensor and solvent system at λex = 345 nm. Real sample analysis Strontium acts as a desensitizing agent and is frequently used as a pain reliever in various medicated toothpastes. Samples containing strontium were procured and tested against the developed sensor. Strontium present in the samples showed loss in the emission intensity after interaction with the nano-aggregates of 2 (Figure 6). Hence, the results from real samples are in well agreement with the experiments performed with solutions of strontium prepared in the lab. The calibration curve was used to estimate the concentration of Sr2+ in the real samples. The fluorescence intensity of unknown sample was compared with corresponding concentration on calibration plot, which will gave estimated concentration of Sr2+ in sample. Hence, the proposed sensor is highly useful for the selective detection and estimation of strontium ions in water and exhibits superior practical utility. Table 1: Estimation of concentration of Sr2+ in commercially available samples using nano-aggregates

S. No.

Sample Name

Emission Intensity

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S1

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Figure 6. Real sample analysis of various commercially available toothpastes and their interaction with sensor Subsequently, To establish the practical application, water samples were collected from tap and river and filtered through syringe filter to eliminate any biological impurity. Now the known concentration of Sr2+ has been spiked into the samples and the fluorescence spectra were recorded. The results in Table 2 show an average recovery of 99.1% (as shown in Table 2). The above results conclude that the compound 2 has good practical applicability for environmental applications and has no effect on the other environmental analytes present in water. Further, to validate the experimental results we have performed AAS studies for these samples. The comparison between results obtained from AAS technique and our method confirms the reliability of the proposed sensor Hence, in conclusion a polymer-based sensor was synthesized using condensation reaction of polyamine and pyrene-1carboxaldehyde. Fluorescent organic nanoparticles were developed from this polymer using reprecipitation technique. TEM and DLS techniques were used to characterize the fluorescent organic nanoparticles of the polymer. The sensor properties of nanoaggregates of synthesized polymer are checked in aqueous medium. Nanoaggregates of polymer resulted in a sensor for Sr2+ by quenching the fluorescence intensity in 100 % aqueous system with a low LOD of 9 nM. Response time studies exhibited quick binding of the proposed sensor with strontium ions. Real sample analysis confirmed the practical applicability of the probe for environmental and medical applications


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Table 2: Results of Sr2+ Sensing in tap water and river water.

Sr2+ found(nM)

Sample

Present method 2+

AAS (nM)

Recovery, %

Sr added(nM)

(nM)

1

0

-

2

500

498

502

99.6

3

100

99.0

-

99.0

1

0

-

2

500

494

490

98.8

3

300

297

308

99.0

Tap Water -

River water -

Supporting information

NMR spectra, GPC results and LOD table. This material is available free of charge via the Internet at http://pubs.acs.org.

Notes

The authors declare no competing financial interest.

Corresponding author

*E-mail: [email protected], [email protected]

Acknowledgement

This work was supported with research grant (SR/FT/CS-97/2010(G) from Department of Science and Technology (DST), Government of India. A.K. acknowledges DST for fellowship. G.K. and A.S. is grateful to CSIR, New Delhi, India for their JRF fellowship.

REFERENCES

1.

Jain, A. K.; Gupta V. K.; Raisoni, J. R. Strontium (II)-selective potentiometric sensor based on ester derivative of 4tert-butylcalix(8)arene in PVC matrix, Sensors 2004, 4, 115-124.


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Page 13 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2.

MacMillan, J. P.; Park, J. W.; Gerstenberg, R.; Wagner, H.; Kohler, K.; Wallbrecht, P. Strontium and Strontium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim.

3.

Mear, F.; Yot, P.; Cambon, M.; Ribes, M. The characterization of waste cathode-ray tube glass, Waste management, 2006, 26, 1468–76.

4.

Sabovljevi, M.; Vukojevi, V.; Sabovljevi A.; Vujii, M. Deposition of heavy metals (Pb, Sr and Zn) in the county of Obrenovac (Serbia) using mosses as bioindicators, J. Ecol. Nat. Environ. 2009, 1, 147-155.

5.

Shamsipur, M.; Kazemi S. Y.; Sharghi, H. Design of a selective and sensitive PVC-membrane potentiometric sensor for strontium ion based on 1,10-diaza-5,6-benzo-4,7-dioxacyclohexadecane-2,9-dioneas a neutral ionophore, Sensors 2007, 7, 438-447.

6.

F. Patty, (ed.). Industrial Hygiene and Toxicology: Volume II: Toxicology. 2nd ed.New York: Interscience Publishers, 1963. 1132.

7.

Shamsipur, M.; Raoufi, F. Preconcentration and separation of trace amounts of strontium ions from alkali and alkaline earth metal ions using octadecyl silica membrane disks modified with decyl-18-crown-6 and its determination by flame atomic absorption spectrometry, Microchim. Acta. 2001 137, 163-167.

8.

Tautkus, S.; Uzdaviniene1, D.; Pakutinskiene1, I.; Kazlauskas1, R.; Zalieckiene, E. Determination of Strontium in Milk by Flame Atomic Absorption Spectrometry, Polish J. of Environ. Stud. 2007, 16, 771-775.

9.

Bondareva, N. V.; Zolotoritskaya, E. S. Flame-emission-photometric determination of rare alkali and alkaline earth metals in drinking water and waste waters, Zavod. Lab. 1991, 57, 36-41.

10. Salido, A. L.; Jones, B. T. Determination of Sr in soil by tungsten coil atomic emission spectrometry, Microchem. J. 2012, 101, 1-4. 11. Dalai T. K.; Sarin, M. Trace determination of strontium and barium in river waters by inductively coupled plasmaatomic emission spectrometry using an ultrasonic nebulizer, Geostd Newslett. 2002, 26, 301-306. 12. Khun, K.; Ibupoto, Z. H.; Chey, C.O.; Lub, Jun.; Nur O.; Willander, M. Comparative study of ZnO nanorods and thin films for chemical and biosensing applications and the development of ZnO nanorods based potentiometric strontium ion sensor, App. Surface Sci. 2013, 268, 37-43. 13. Kim, H. N.; Guo, Z.; Zhu, W.; Yoon J.; Tian, H. Recent progress on polymer-based fluorescent and colorimetric chemosensors, Chem. Soc. Rev. 2011, 40, 79-93. 14. Diez, I.; Ras, R. H. A. Fluorescent silver nanoclusters, Nanoscale 2011, 3 1963-1970. 15. Jin, R. Quantum sized, thiolate-protected gold nanoclusters, Nanoscale 2010, 2, 343-362. 16. Zhang, X.; Wang, S.; Xu, L.; Ji, Y.; Feng, L.; Tao, L.; Li S.; Wei, Y. Biocompatible polydopamine fluorescent organic nanoparticles: facile preparation and cell imaging, Nanoscale 2012, 4, 5581-5584.


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 17

17. Wang, X.; Xu, S.; Xu, W. Synthesis of highly stable fluorescent Ag nanocluster @ polymer nanoparticles in aqueous solution, Nanoscale 2011, 3, 4670-4675. 18. Wu, X.; He, X.; Wang, K.; Xie, C.;

Zhou B.; Qing, Z. Ultrasmall near-infrared gold nanoclusters for tumor

fluorescence imaging in vivo, Nanoscale 2010, 2, 2244-2249. 19. Hui, J.; Zhang, X.; Zhang, Z.; Wang, S.; Tao, L.; Wei Y.; Wang, X. Fluoridated HAp:Ln3+ (Ln = Eu or Tb) nanoparticles for cell-imaging, Nanoscale 2012, 4, 6967-6970. 20. Allouche, J. Synthesis of organic and bioorganic nanoparticles: An overview of the preparation methods, ch. 2, ISBN: 978-1-4471-4212-6. 21. Hardman, R. A toxicologic review of quantum dots: toxicity depends on physicochemical and environmental factors, Environ. Health Perspect. 2006, 114, 165-172. 22. Choi, H. S.; Liu, W.; Misra, P.; Tanaka, E.; Zimmer, J. P.; Ipe, B. I.; Bawendi M. G.; Frangioni, J. V. Renal clearance of quantum dots, Nat. Biotechnol. 2007, 25, 1165-1170. 23. Allouche, J. Synthesis of organic and bioorganic nanoparticles: An overview of the preparation methods, 2013, ISBN: 978-1-4471-4212-4216. 24. Brunsveld, L.; Folmer, B. J. B.; Meijer E. W.; Sijbesma, R. P. Supramolecular polymers, Chem. Rev. 2001, 101, 40714098. 25. Kim, H. N.; Guo, Z.; Zhu, W.; Yoon J.; Tian, H. Recent progress on polymer-based fluorescent and colorimetric chemosensors, Chem. Soc. Rev. 2011, 40, 79-93. 26. Agudelo-Morales, C. E.; Galian, R. E.; Perez-Prieto J. Pyrene-Functionalized Nanoparticles: Two Independent Sensors, the Excimer and the Monomer, Anal. Chem. 2012, 84, 8083−8087. 27. Zhou, Y.; Zhu, C. Y.; Gao, X. S.; You, X. Y., Yao, C. Hg2+-Selective Ratiometric and “Off-On” Chemosensor Based on the Azadiene-Pyrene Derivative, Org. Lett. 2010, 12, 2566-2569. 28. Guliyev, R.; Coskun, A.; Akkaya. E. U. Design Strategies for Ratiometric Chemosensors: Modulation of Excitation Energy Transfer at the Energy Donor Site, J. Am. Chem. Soc. 2009, 131, 9007–9013. 29. Dai, Q.; Liu, W.; Zhuang, X.; Wu, J.; Zhang, H.; Wang, P. Ratiometric Fluorescence Sensor Based on a Pyrene Derivative and Quantification Detection of Heparin in Aqueous Solution and Serum, Anal. Chem. 2011, 83, 6559– 6564. 30. Kaur, S.; Kaur, A.; Kaur N.; Singh, N. Development of chemosensor for Sr2+ using organic nanoparticles: application of sensor in product analysis for oral care, Org. Biomol. Chem. 2014, 12, 8230-8238. 31. Zanjanchi, M. A.; Arvand, M.; Mahmoodi N. O.; Islamnezhad, A. A fast response strontium ion-selective electrode prepared by sol-gel membrane technique, Electroanalysis 2009, 16, 1816-1821.


14

Page 15 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


32. Zavar, M. H. A.; Rounaghi G. H., Rad, E. F. Strontium ion-selective electrode based on 18-crown-6 in PVC matrix, Asian J. Chem. 2009, 21, 2224-2232. 33. Shamsipur, M.; Kazemi S. Y.; Sharghi, H. Design of a selective and sensitive PVC-membrane potentiometric sensor for strontium ion based on 1,10-diaza-5,6-benzo-4,7-dioxacyclohexadecane-2,9-dioneas a neutral ionophore, Sensors 2007, 7, 438-447. 34. Jain, A. K.; Gupta V. K.; Raisoni, J. R. Strontium (II)-selective potentiometric sensor based on ester derivative of 4tert-butylcalix(8)arene in PVC matrix, Sensors 2004, 4, 115-124. 35. Chandra, S.; Sharma K.; Kumar, A. Strontium(II) selective PVC membrane electrode based acetophenone semicarbazone (ACS) as an ionophore, J. Saudi Chem. Soc. 2014, 18, 555-560. 36. Singh, A. K.; Saxena, P.; Mehtab, S.; Gupta, B. Strontium(II)-selective electrode based on a macrocyclic tetraamide, Talanta 2006, 69,521-526. 37. Zanjanchi, M. A.; Arvand, M.; Islamnezhad A.; Mahmoodi, N.O. Novel potentiometric membrane sensor based on 6(4-nitrophenyl)-2-phenyl-4,4-dipropyl-3,5-diaza-bicyclo[3,1,0] hex-2-ene for detection of strontium (II) ions at trace levels, Talanta 2007, 74, 125-131. 38. Burgueraa, M.; Burgueraa, J. L.; Rond´ona, C.; Luisa di Bernardoa, M.; Gallignania, M.; Nietob E.; Salinasb, J. Appraisal of different electrothermal atomic absorption spectrometric methods for the determination of strontium in biological samples, Spectrochim. Acta Part B 1999, 54, 805-828. 39. Arslan, Z.; Tyson, J. F. Determination of calcium, magnesium and strontium in soils by flow injection flame atomic absorption spectrometry, Talanta 1999, 50, 929-937. 40. Vandecasteeleh, C.; Dams, V. R. Determination of strontium in human serum by inductively coupled plasma mass spectrometry and neutron activation analysis: A comparison, Talanta 1990, 37, 819-823 41. Yao H.; Funada, T. Mechanically inducible fluorescence colour switching in the formation of organic nanoparticles of an ESIPT molecule, Chem. Commun. 2014, 50, 2748-2750. 42. Ingale, S. A.; Seela, F. A ratiometric fluorescent On−Off Zn2+ chemosensor based on a tripropargylamine pyrene azide click adduct, J. Org. Chem. 2012, 77, 9352-9356. 43. Thirupathi, P.; Park, J.; Neupane, L. N.; Kishore, M. Y. L. N.; Lee, K. Pyrene excimer-based peptidyl chemosensors for the sensitive detection of low levels of heparin in 100% aqueous solutions and serum samples, ACS Appl. Mater. Interfaces, 2015, 7, 14243-14253. 44. Lopez, F.; Cuomo, F.; Ceglie, A.; Ambrosone, L.; Palazzo, G. Quenching and dequenching of pyrene fluorescence by nucleotide monophosphates in cationic micelles, J. Phys. Chem. B, 2008, 112, 7338-7344).


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For Table of Contents Use Only Polyamine based ratiometric fluorescent chemosensor for strontium metal ion in aqueous medium: Application in tap water, river water and in oral care Amanpreet Kaura, Gaganpreet Kaura, Amanpreet Singhb, Narinder Singhb,* Navneet Kaura*

Organic nanoparticles of polymer-based chemosensor 2 exhibit fluorescence emission. On binding with strontium ions, the fluorescence intensity of nanoparticles is quenched. 560 480


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A

Addition of Sr(II) from 0 µM to 1.5 µM

400 320 240 160 80 0 360

400

440

480

520

560

Wavelength (nm)


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Graphical Abstract

Polyamine based ratiometric fluorescent chemosensor for strontium metal ion in aqueous medium: Application in tap water, river water and in oral care Amanpreet Kaura, Gaganpreet Kaura, Amanpreet Singhb, Narinder Singhb,* Navneet Kaura*

Addition of Sr2+

Highly emissive nanoparticles of 2

less emissive nanoparticles of 2 after interaction with Sr2+

Organic nanoparticles of Polymer-based chemosensor 2 exhibit fluorescence emission. On binding with strontium ions, the fluorescence intensity of nanoparticles is quenched.


Polyamine Based Ratiometric Fluorescent Chemosensor for Strontium

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