Chromatic detection of Cs ions using polydiacetylene-based vesicles containing crown-ether-like ethylene glycol units

Accepted Manuscript Title: Chromatic detection of Cs ions using polydiacetylene-based vesicles containing crown-ether-like ethylene glycol units Authors: Young Jin Gwon, Choongho Kim, Taek Seung Lee PII: DOI: Reference:

S0925-4005(18)31902-6 https://doi.org/10.1016/j.snb.2018.10.125 SNB 25559

To appear in:

Sensors and Actuators B

Received date: Revised date: Accepted date:

9-7-2018 21-10-2018 25-10-2018

Please cite this article as: Gwon YJ, Kim C, Lee TS, Chromatic detection of Cs ions using polydiacetylene-based vesicles containing crown-ether-like ethylene glycol units, Sensors and amp; Actuators: B. Chemical (2018), https://doi.org/10.1016/j.snb.2018.10.125 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Chromatic detection of Cs ions using polydiacetylene-based vesicles

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containing crown-ether-like ethylene glycol units

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Young Jin Gwon, Choongho Kim, Taek Seung Lee*

Organic and Optoelectronic Materials Laboratory, Department of Organic Materials

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Engineering, Chungnam National University, Daejeon 34134, Korea

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* Corresponding author: TSL ([email protected])

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Highlights

Colorimetric detection of Cs ions using polydiacetylene-based vesicles is

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proposed.

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Various lengths of EG groups were synthesized at the end of PDA to provide selective Cs ion responsivity. The colorimetric response value was used to quantify the degree of color change of PCDA upon exposure to Cs ions. 1

Abstract Radioactive

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Cs, which have a half-life of about 30.17 years, are a major source of

nuclear pollution and should be detected and removed. For this purpose, a

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colorimetric, polydiacetylene (PDA) vesicle-based sensor was synthesized to detect

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Cs ions. The polymer vesicles consisted of commonly used 10,12-pentacosadiynoic

acid (PCDA) and its derivatives. One of the derivatives that contained tetraethylene glycol (TEG) units at the end of the PCDA side chain, and thus it acted as a chelating

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agent that surrounded the Cs ion like a crown ether. As a result, the main chain of

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the PDA was distorted by the chelation of TEG and Cs ions, resulting in a blue-red

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color change. To provide selectivity to the PDA vesicles, another derivative was

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incorporated to the PDA vesicles with controlled amount, which was not responsive to alkali metal ions. The changes in the colorimetric response of the vesicles were not

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observed in the presence of other alkali metal ions such as Na, K, and Rb ions,

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indicating that the TEG units fitted well in size with the ionic radius of the Cs ion, resulting in high selectivity. Solid-state PDA film was also fabricated to provide

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selective detection of Cs ions.

Keywords: Cs ions; polydiacetylene vesicles; tetraethylene glycol; sensors; color change 2

1. Introduction A large amount of radioactive isotopes was released into the environment when the

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Fukushima nuclear power plant exploded in 2011, which contains a huge amount of radioactive Cs [1,2]. Exposure to radioactive materials can damage the body as it can

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ionize the water and organic species that form the body tissue [3]. Because

radioactive Cs have a long half-life of 30.17 years, it has a detrimental effect on crops

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and human health for a long time. In addition, because of the high solubility in water,

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the contamination by radioactive Cs ions is still continuing near the collapsed reactor.

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Thus, there is a strong demand for finding simple and facile techniques for detecting

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and removing Cs ions from water and soil and preventing further radiation damage.

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Although many investigations have been conducted to remove radioactive Cs ions by adsorption [4,5], most of the studies on Cs ion removal were related to limited

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adsorbent materials such as ferrocyanide-based Prussian blue [6-10] and crown

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ethers [11-14]. The crown ethers are well known for their strong binding ability to Cs ions, as their inner cavity matches well with the ionic radius of Cs ions [15].

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Current methods for detecting and quantifying Cs ions are based on the use of

radiation detectors and flash detectors. However, these techniques do not have spatial resolution, and thus have difficulty in identifying the radionuclides. Therefore, it is necessary to develop new techniques that can easily detect Cs ions, 3

but such development is not easy. Achieving a color change is effective for use in sensory materials because of easily recognizable signals by the naked eye. Visual detection methods for Cs ions have been rarely reported because it is difficult to develop an interacting ligand with Cs ions [16]. Polydiacetylenes (PDAs) can easily

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meet the color change requirement. The diacetylene (DA) monomers readily self-

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assemble in an aqueous solution and polymerize into PDA-based vesicles, which are often used as smart sensing materials because of their unique color change from blue

to red and the formation of red fluorescence upon exposure to various external

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stimuli such as temperature, pH, mechanical stress, and environmental changes [17-

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19].

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In this work, crown-ether-like ethylene glycol (EG) units of various lengths

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were introduced into a DA monomer to synthesize PDA vesicles as an interacting ligand to Cs ions. We expected that the EG units would bind to Cs ions to distort the

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main chain of PDA in the self-assembled, ordered vesicles, that alter their color from

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blue to red. The lengths of the EG units were adjusted to obtain a suitable cavity for the crown-ether-like EG units for Cs ions by investigation of the adsorption of other

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competing ions, including Na, K, and Rb ions [20].

2. Experimental section 4

2.1. Materials. PCDA was purchased from Alfa Aesar. 1-Fluoro-4-nitrobenzene, diethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, hexaethylene glycol

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monomethyl ether, benzyltriethylammonium chloride, toluene, NaOH, sodium sulfate, tetrahydrofuran (THF), ammonium chloride, Zn powder, oxalyl chloride, (DMF)

and

N-(3-dimethylaminopropyl)-N’-

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N,N-dimethylformamide

ethylcarbodiimide hydrochloride (EDC) were purchased from Sigma-Aldrich

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Chemicals. Methanol, ethyl acetate, and n-hexane were purchased from Samchun

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Pure Chemical. 4-(Dimethylamino)pyridine (DMP) was purchased from Acros

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Organics. All reagents and solvents were used as received without further

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2.2. Characterization

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purification.

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Nuclear magnetic resonance (NMR) spectra were recorded on a Bruker Fourier-300 spectrometer (Korea Basic Science Institute). Fourier transform infrared (FT-IR) spectra were recorded on a Varian Cary Eclipse spectrometer. Ultra-violet (UV-vis)

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absorption spectra were recorded on a PerkinElmer Lambda 35 spectrometer.

2.3.

Synthesis

of

N-(4-(2-(2-methoxyethoxy)ethoxy)phenyl)pentacosa-10,125

diynamide (PCDA-EG2) 1-(2-Methoxyethoxy)-4-nitrobenzene (1) was synthesized according to a previously reported method with a slight modification [21,22]. 1-Fluoro-4-nitrobenzene (2.0 g,

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14.2 mmol), diethylene glycol monomethyl ether (2.55 g, 21.3 mmol) and benzyltriethylammonium chloride (0.16 g, 0.71 mmol) were dissolved in toluene (20

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mL) under an Ar atmosphere and 5 M aqueous NaOH solution (10 mL) was added

to the mixture. The reaction mixture was stirred at 110 oC for 20 h. After cooling to

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room temperature, the mixture was diluted with water and extracted with ethyl

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acetate. The combined organic phases were washed with brine, dried over sodium

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sulfate, and evaporated. The concentrated mixture was purified by column

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chromatography (eluent: n-hexane/ethyl acetate = 4:1) to obtain a yellow powder

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(yield 1.83 g, 54 %). 1H NMR (300 MHz, CDCl3):  = 8.22 (d, 2H), 7.01 (d, 2H), 4.25 (t, 2H), 3.92 (t, 2H), 3.74 (t, 2H), 3.71 (t, 2H), 3.40 (s, 3H) ppm. FT-IR (KBr pellet, cm-1):

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3472 (N-O), 2883 (C-H), 1512 (C=C), 1261 (aromatic C-H), 1113 (C-O).

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4-(2-Methoxyethoxy)benzenamine (2) was synthesized by a modified literature method [23]. 1 (1.00 g, 4.1 mmol) and ammonium chloride (0.44 g, 8.3 mmol) were

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dissolved in a mixture of methanol (16 mL) and water (3 mL) under an Ar atmosphere. Zn powder was added to the solution and the reaction mixture was stirred at 65 oC for 1 h. After cooling to room temperature, precipitates were isolated by filtration and extracted with ethyl acetate. The combined organic phases were 6

washed with brine, dried over sodium sulfate, and evaporated. The concentrated mixture was purified by column chromatography (eluent: n-hexane/ethyl acetate = 1:4) to obtain a red oily compound (yield 0.72 g, 84%). 1H NMR (300 MHz, CDCl3):  = 6.87 (d, 2H), 6.64 (d, 2H), 4.05 (s, 2H), 3.81 (t, 2H), 3.73-3.68 (m, 4H), 3.55 (t, 2H),

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3.27 (s, 3H) ppm. FT-IR (KBr pellet, cm-1): 3362 (N-H), 2871 (C-H), 1510 (C=C), 1241

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(aromatic C-H), 1110 (C-O).

PCDA-EG2 was synthesized by a modified literature method [24,25]. PCDA (1

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g, 2.67 mmol) was dissolved in THF (20 mL) and the solution was added dropwise to

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oxalyl chloride (0.60 mL, 6.89 mmol). After stirring the mixture at room temperature

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for 30 min, a few drops of DMF were added to the mixture and stirred for 2 h. The

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mixture was dried under vacuum and dissolved in THF (10 mL). The solution was

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added dropwise to pyridine (20 mL) containing 2 (0.87 g, 4.14 mmol). The reaction mixture was stirred for 12 h, precipitated in ice water, and then isolated by filtration.

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The precipitate was purified by column chromatography (eluent: n-hexane/ethyl

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acetate = 4:1) to obtain PCDA-EG2 (yield 0.70 g, 28%). 1H NMR (300 MHz, CDCl3):  = 7.41 (d, 2H), 7.06 (s, 1H), 6.89 (d, 2H), 4.13 (t, 2H), 3.83 (t, 2H), 3.73 (t, 2H), 3.57 (t,

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2H), 3.39 (s, 3H), 2.34 (t, 2H), 2.27-2.25 (m, 4H), 1.74 (t, 2H), 1.67-1.62 (m, 4H), 1.561.52 (m, 6H), 1.49-1.26 (m, 20H), 0.93 (t, 3H) ppm. FT-IR (KBr pellet, cm-1): 3280 (N-H), 2844 (C-H), 2135 (C≡C), 1697(C=O), 1512 (C=C), 1241 (aromatic C-H), 1105 (C-O).

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The

synthetic

procedures

for

N-(4-(2-(2-(2-(2-

methoxyethoxy)ethoxy)ethoxy)ethoxy)phenyl)pentacosa-10,12-diynamide EG4)

and

(PCDA-

N-(4-(2-(2-(2-(2-(2-(2-

methoxyethoxy)ethoxy)ethoxy)ethoxy)ethoxy)ethoxy)phenyl)pentacosa-10,12-

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diynamide (PCDA-EG6) were depicted in the Supporting Information.

2.4 Synthesis of methyl pentacosa-10,12-diynoate (PCDA-Me) [26]

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PCDA (500 mg, 1.33 mmol), EDC (510 mg, 2.67 mmol), and DMP (20 mg, 0.16 mmol)

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were dissolved in THF (20 mL). Methanol (5.40 mL) was added to the solution and

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the reaction mixture was stirred at room temperature for 18 h. The mixture was dried under vacuum and dissolved in n-hexane (20 mL) then extracted with brine.

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The combined organic phase was dried over sodium sulfate and evaporated. The

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concentrated mixture was purified by column chromatography (eluent: nhexane/ethyl acetate = 4:1) to obtain PCDA-Me (yield 510 mg, 96%). 1H NMR (300

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MHz, CDCl3):  = 3.66 (s, 3H), 2.32-2.23 (m, 6H), 1.73 (t, 2H), 1.66-1.62 (m, 4H), 1.531.46 (m, 6H), 1.32-1.25 (m, 20H), 0.92 (t, 3H) ppm. FT-IR (KBr pellet): 2848 (C-H),

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2139 (C≡C), 1728(C=O) cm-1.

2.5 Synthesis of PDA-based vesicles 8

PDA vesicles were prepared by mixing PCDA, PCDA-Me, and PCDA-EG4. Three PCDA-based lipid monomer mixtures (PCDA: 5.2 mg (1.4 x 10-5 mol); PCDA-Me: 2.4 mg (0.6 x 10-5 mol); PCDA-EG4: 1.3 mg (0.2 x 10-5 mol)) were dissolved in chloroform in a vial. After evaporation of the chloroform by flowing N2 gas, distilled water (10

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mL) was added to the glass vial to obtain a final lipid concentration of 2.2 mM. The

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lipid suspension was sonicated at 70 oC for 25 min. To remove large lipid aggregates, the vesicle solution was filtered using a 0.8 μm syringe filter and the filtered solution was stabilized overnight at 4 oC. The resulting PDA vesicle solution was irradiated

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with 254 nm UV light for a few minutes and the colorless vesicles turned blue [27].

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Other PDA vesicles containing PCDA-EG2 and PCDA-EG6 were prepared according

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to the same procedure as described for the vesicles containing PCDA-EG4.

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2.6 Colorimetric detection of Cs ions To evaluate the color change of the vesicles in the presence of Cs ions, UV-vis

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spectroscopy was used with exposure times of 1 min and 3 h at various Cs ion concentrations. The colorimetric response value, CR(%), was used to quantify the

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degree of color saturation as follows:

𝐶𝑅(%) =

𝑃𝐵𝑜 − 𝑃𝐵1 × 100 𝑃𝐵𝑜

where PB0 and PB1 correspond to the absorbance ratio in the absence and presence of 9

the Cs ion, respectively.

𝑃𝐵 =

𝐴𝑏𝑙𝑢𝑒 𝐴𝑏𝑙𝑢𝑒 + 𝐴𝑟𝑒𝑑

where Ablue and Ared represent the absorbance values at 630 and at 540 nm,

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respectively [28].

2.7 PCDA-based solid sensor

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Three PCDA-based lipid monomer mixtures (PCDA: 41.6 mg (11.2 x 10-5 mol);

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PCDA-Me: 19.2 mg (4.8 x 10-5 mol); PCDA-EG4: 10.4 mg (1.6 x 10-5 mol)) were

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dissolved in chloroform in a vial. After evaporation of the chloroform by flowing N2

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gas, poly(methyl methacrylate) (PMMA) solution (2 mL) was added to the glass vial.

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The PMMA solution was prepared with chloroform at a concentration of 45 mg/mL.

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The spin-coated films was obtained using the PMMA solution (400 μL) on a glass slide. The resulting PDA film was irradiated with 254 nm UV light for a few minutes,

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observing the color change from colorless to blue. For comparison, a PMMA film

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containing PDA vesicles made from only PCDA was also fabricated.

3. Results and discussion In this study, PDA vesicles were modified with PCDA-based monomers to have a 10

color change upon exposure to Cs ions. To achieve such a Cs ion-responsiveness, PCDA-based monomers having various lengths of EG groups at the PCDA end were synthesized to obtain PCDA-EGn (n = 2, 4, and 6) (Scheme 1). The methyl group at the carboxylic acid end-group in PCDA was also synthesized and denoted as PCDA-

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C NMR (Fig. S1-S10). The

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spectroscopic methods, including FT-IR and 1H and

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Me. The chemical structures of the PCDA-EGn and PCDA-Me were confirmed by

PCDA-EGn series showed H-bonded amide and carbonyl stretching bands at 3284 and 1693 cm-1, respectively [29]. For use as a Cs ion sensor, the stabilized vesicles

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were irradiated with UV light (254 nm) to induce polymerization; under these

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conditions the color change to blue occurred, indicative of polymerization of DA to

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PDA. The PDA vesicles were prepared by the conventional method, mixing PCDA,

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PCDA-EGn, and PCDA-Me at a molar ratio of 7:3:1 (Scheme 2). The PCDA was used as a stimuli-responsive monomer. The PCDA-EGn were expected to act as captors

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for the Cs ions, in which the Cs ion was surrounded by the EG unit in the PCDA-

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EGn, resulting in the distortion of the conjugated main chain of PCDA [30]. When the vesicle was synthesized with PCDA and PCDA-EGn without the use of PCDAMe, the resulting PDA vesicle was prone to induce color change even upon exposure

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to competing alkali metal ions such as K and Na ions. The vesicles from PCDA-Me did not show any color change upon exposure to alkali metal ions, indicating that PCDA-Me-based PDA vesicles were not responsive to alkali metal ions (Fig. S11). 11

The use of small amount of PCDA-Me during PDA vesicle formation provided sensitivity toward Cs ions, because PCDA-Me was located among the positions of PCDA-EG4 and PCDA whose structure were easily perturbed upon exposure to all

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alkali metal ions. When Cs ions were exposed to PDA vesicles composed of PCDA-EG4, their

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color changed from blue to red (Fig. 1a). The color change of the PCDA-based

vesicles could be recognized by the naked eye and quantified using UV-vis spectra.

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As the exposure time to Cs ions increased, the absorption at 630 nm gradually

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decreased and, at the same time, the absorption at 500 nm increased. As a result, the

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color of the PDA vesicles changed from blue to red because of the distorted main

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chain that, subsequently, induced perturbation of the electronic structure of PDA.

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The conjugated structure of the copolymer of PCDA, PCDA-EG4, and PCDA-Me was distorted because of the interaction of the tetraethylene glycol (TEG) chain and

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the Cs ions (Scheme 3). In contrast, when K ions were exposed to the vesicles, the

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absorption at 630 nm decreased slightly and the absorption at 500 nm was almost unchanged (Fig. 1b). Thus, the TEG chain in the PDA vesicles did not interact with K

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ions, showing a negligible color change (CR values less than 5%) of the PDA vesicles even after a long exposure time of 24 h. The chelation ability of the TEG-based PDA vesicles for alkaline metal ions was affected by their radii as hydrated ions. This is similar to the mechanism of earlier studies that selectively captured metal ions along 12

the length of ethylene glycol [31]. The radius of the Cs ion is 1.19 Å, that of the K ion is 1.25 Å, and that of Na ion is 1.84 Å, in which the smaller radius of the Cs ion fitted in the crown-ether-like TEG. It is well known that K ions can compete with Cs ions because of a very similar hydration radius, but, in this case, TEG could selectively

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bind to Cs ions [8].

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To elucidate the relationship between the color change of the PDA vesicles and

Cs ion concentration, various CR(%) values of the PDA vesicles were investigated

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upon exposure to Cs and K ions (Fig. 2). The concentration of Cs and K ions was

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increased from 0 to 60 μM and maintained for 1 min or 3 h. The CR(%) values of the

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vesicles increased with increasing Cs ion concentration, indicating that the color

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change was highly dependent on Cs ions but not on K ions. A more apparent color

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change was observed after 3 h exposure to Cs ions. The limit of detection was calculated to be 8.34 M and 4.68 M for 1 min and 3 h exposure time, respectively,

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based on the 3σ/slope, where σ is the standard deviation of four independent

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measurements.

The selectivity of the PDA vesicles toward competing metal ions was

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investigated using CR (%) values. Among the series of monovalent cations investigated, including K, Na, and Rb, only Cs ions rendered spectroscopic changes of the vesicles (Fig. 3a, b). Upon exposure of the PDA vesicles to Cs ions, a decreases in absorption was observed at 630 nm and an increase at 540 nm; negligible 13

spectroscopic changes (CR value less than 5 %) were found for the other metal ions, mainly because of the selective crown-ether-like ring surrounding through the chelation of Cs ion with the four oxygen atoms in TEG. Comparison of the CR(%) values showed that only Cs ions were selectively bound to the PDA vesicle to induce

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distortion of the conjugated backbone of the PDA. The same sensing investigations

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were performed using PDA vesicles synthesized with PCDA-EG2 and PCDA-EG6, which had diethylene glycol (DEG) and hexaethylene glycol (HEG) units,

respectively (Fig. 4). The changes in the CR(%) values upon exposure to Cs, K, Na,

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and Rb ions were negligible (CR value less than 5 %) with no selectivity, indicating

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that effectively they could not surround the Cs ions as well as the PDA vesicles

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based on PCDA-EG4. Thus, it can be concluded that the chain length of TEG was

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suitable for the chelation of Cs ions.

To elucidate the practical use of the Cs ion-responsive PDA vesicles, solid-state

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sensor films containing PDA vesicles was fabricated. A PMMA film containing the

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PDA vesicles was prepared, and various metal ions were dropped on the surface of the film to investigate the color change (Fig. 5a). The PMMA film containing vesicle

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mixtures of PCDA, PCDA-EG4, and PCDA-Me was responsive to Cs ion with color change to red, whereas the PMMA film composed of only PCDA showed no color change upon exposure to alkali metal ions investigated. This suggests that the presence of PCDA-EG4 is essential to observe color-changeable responsivity toward 14

Cs ions, similar to the case in the solution. When the PMMA film containing vesicle mixtures was immersed in the alkali metal ions, the remarkable color change of the film was observed in Cs ion solution (Fig. 5b). The color change of the PDA film was observed at limited regions by K and Rb ions, which was due to the mechanical

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rupture of the film during the immersion in aqueous solution. UV-vis spectra of the

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film containing the vesicle mixture were investigated after immersion in the solutions of alkali metal ions, in which the significant color change was observed in

the Cs ions (Fig. 6a). The CR (%) values calculated from the measured UV-vis spectra

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also indicated that the film composed of the vesicle mixture selective to Cs ions (Fig.

4. Conclusions

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6b).

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PDA vesicles with EGs of various lengths were synthesized to detect Cs ions with a

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blue-to-red color change. The PDA vesicles were prepared by mixing PCDA-EGn, PCDA-Me, and PCDA, in which the TEG group in PCDA-EG4 played an important role as captor for Cs ions. Colorimetric Cs ion detection was achieved by the naked

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eye and was quantified by calculating the CR(%) values using the color change of the PDA vesicles. The Cs ions were selectively recognized, compared with other alkali metal ions (K, Na, and Rb ions), as the color change of PDA vesicles was more 15

pronounced upon exposure to Cs ions. The crown-ether-like TEG could accommodate the radius of the Cs ion, whereas DEG or HEG could not.

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Acknowledgment Financial support from the National Research Foundation (NRF) of Korean

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government through Basic Science Research Program (2018R1A2A2A14022019) and

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Nuclear R&D Project (2016M2B2B1945085) is gratefully acknowledged.

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Chem. Res. 41 (2008) 805-816. [20] T. Mori, M. Akamatsu, K. Okamoto, M. Sumita, Y. Tateyama, H. Sakai, J. P. Hill, M. Abe, K. Ariga, Micrometer-level naked-eye detection of caesium particulates in

[21]

G. C. Eastmond, J. Paprotny, Polyimides with main-chain ethylene oxide

SC R

units: synthesis and properties, Polymer. 43 (2002) 3455-3468. [22]

IP T

the solid state, Science and technology of advanced materials 14.1 (2013) 015002.

H. H. Dam, K. Sun, E. Hanssen, J. M. White, T. Marszalek, W. Pisula, J. Czolk,

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J. Ludwig, A. Colsmann, M. Pfaff, D. Gerthsen, W. W. H. Wong, D. J. Jones,

N

Morphology change and improved efficiency in organic photovoltaics via hexa-peri-

M. Lv, G. Lu, C. Cai, Catalyst-Free chemoselective reduction of nitroarenes

ED

[23]

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A

hexabenzocoronene templates, ACS Appl. Mater. Interfaces. 6 (2014) 8824-8835.

using thiourea as a hydrogen source, Asian J. Org. Chem. 4 (2015) 141-144. Y. K. Jung, H. G. Park, J. M. Kim, Polydiacetylene (PDA)-based colorimetric

PT

[24]

CC E

detection of biotin-streptavidin interactions, Biosens. Bioelectron. 21 (2006) 1536-1544. [25]

C. H. Lee, J. S. Kim, S. Y. Park, D. J. Ahn, J. M. Kim, A polydiacetylene

A

supramolecular system that displays reversible thermochromism, Chem. Lett. 36 (2007) 682-683. [26]

I. S. Park, H. J. Park, W. Jeong, J. Nam, Y. Kang, K. Shin, H. Chung, J. M. Kim,

20

Low temperature thermochromic polydiacetylenes: design, colorimetric properties, and nanofiber formation, Macromolecules. 49 (2016) 1270-1278. [27]

M. J. Shin J. D. Kim, Reversible chromatic response of polydiacetylene

[28]

IP T

derivative vesicles in D2O solvent, Langmuir. 32 (2016) 882-888. D. E. Wang, L. Zhao, M. S. Yuan, S. W. Chen, T. Li, J. Wang, Fabrication of

SC R

polydiacetylene liposome chemosensor with enhanced fluorescent self-amplification and its application for selective detection of cationic surfactants, ACS Appl. Mater.

D. J. Ahn, E. H. Chae, G. S. Lee, H. Y. Shim, T. E. Chang, K. D. Ahn, J. M. Kim,

N

[29]

U

Interfaces. 8 (2016) 28231-28240.

M

A

Colorimetric reversibility of polydiacetylene supramolecules having enhanced hydrogen-bonding under thermal and pH Stimuli, J. Am. Chem. Soc. 125 (2003)

T. Mori, M. Akamatsu, K. Okamoto, M. Sumita, Y. Tateyama, H. Sakai, J. P.

PT

[30]

ED

8976-8977.

CC E

Hill, M. Abe, K. Ariga, Micrometer-level naked-eye detection of caesium particulates in the solid state, Sci. Technol. Adv. Mater. 14 (2013) 015002.

A

[31] P. Narkwiboonwong, G. Tumcharern, A. Potisatityuenyong, S. Wacharasindhu, M. Sukwattanasinitt, Aqueous sols of oligo(ethylene glycol) surface decorated polydiacetylene vesicles for colorimetric detection of Pb2+, Talanta 83 (2011) 872-878.

21

Figure Captions and Table Legends Scheme 1. Synthesis of PCDA-EGn and PCDA-Me. Scheme 2. Formation of PCDA-based vesicles.

IP T

Scheme 3. Mechanism of blue-to-red color change of PCDA-based vesicles when

SC R

exposed to Cs ions.

Fig 1. Changes in UV-vis spectra of PCDA-EG4-based PDA vesicles upon exposure to (a) CsCl and (b) KCl (60μM). Arrow direction: Exposure time in 1 min; 3 h; 15 h;

N

U

24 h. Inset photographs indicate the color change from blue to red upon exposure to

A

Cs ions.

M

Fig. 2. Changes in CR (%) of PDA vesicles upon exposure to Cs and K ions with

ED

various concentrations. Exposure time: 1 min (a); 3 h (b). Fig. 3. Changes in CR (%) values of PDA vesicles composed of PCDA-EG4 upon

PT

exposure to various metal ions at the concentrations of (a) 12 μM and (b) 60 μM.

CC E

Exposure time: 3 h.

Fig. 4. Changes in CR (%) values of PDA vesicles composed of (a) PCDA-EG2 and (b)

A

PCDA-EG6 upon exposure to various metal ions. [metal ions] = 60 μM. Exposure time: 3 h. Fig. 5. (a) Color change of PMMA films of PDA vesicles composed of PCDA, PCDA22

EG4, and PCDA-Me (left) and of PCDA (right) by dropping of metal ion solutions. The white circles represent the dropping area of the solution. (b) Color change of PMMA films of PDA vesicles composed of PCDA, PCDA-EG4, and PCDA-Me by

IP T

immersing in metal ion solutions for 24 h. [metal ions] = 100 μM. Fig. 6. Changes in (a) UV-vis spectra and (b) CR (%) values of PMMA films of PDA

SC R

vesicles composed of PCDA, PCDA-EG4, and PCDA-Me upon immersion in various

A

CC E

PT

ED

M

A

N

U

metal ions for 24 h. [metal ions] = 100 μM.

23

O2N

F

+

HO

Toluene

O

O2N

O

O

n

110 oC

4

1 (n = 2), 3 (n = 4), 5 (n = 6)

Zn, MeOH

H2N

O

O

n

IP T

2 (n = 2), 4 (n = 4), 6 (n = 6)

O

2 or 4 or 6

SC R

OH

+

M

A

N

U

PCDA

+

CH3OH

O CH3(CH2)11C C C C(CH2)8COCH3 PCDA-Me

A

CC E

PCDA

PT

ED

PCDA-EGn (n = 2, 4, 6)

Scheme 1. Synthesis of PCDA-EGn and PCDA-Me.

24

O n O

O N H

SC R

IP T A

CC E

PT

ED

M

A

N

U

Scheme 2. Formation of PCDA-based vesicles.

25

IP T SC R

N

U

Scheme 3. Mechanism of blue-to-red color change of PCDA-based vesicles when

A

CC E

PT

ED

M

A

exposed to Cs ions.

26

0.05

400

450

500

550

600

650

SC R

Wavelength (nm)

U

(a)

A

N

0.15

M

0.10

ED

Absorbance

700

IP T

Absorbance

0.10

PT

0.05

CC E

400

450

500

550

600

650

700

Wavelength (nm)

(b)

A

Fig. 1. Changes in UV-vis spectra of PCDA-EG4-based PDA vesicles upon exposure to (a) CsCl and (b) KCl (60μM). Arrow direction: Exposure time in 1 min; 3 h; 15 h; 24 h. Inset photographs indicate the color change from blue to red upon exposure to Cs ions. 27

16 Equation

y = a + b*x

Weight

No Weighting 1.03693

Residual Sum of Squares

0.99036

Adj. R-Square

Value ?$OP:A=1

Intercept

?$OP:A=1

Slope

Standard Error

-0.40768

0.36849

0.23012

0.01014

8

IP T

CR (%)

12

0

0

12

24

36

48

Concentration (M)

60

Equation

y = a + b*x

Weight

No Weighting

30

Adj. R-Square

2.33402

M

Residual Sum of Squares

A

N

U

(a)

SC R

4

0.99349

20

0.89065

0.55285

?$OP:A=1

Slope

0.42059

0.01522

0

0

12

24

36

48

60

Concentration (M)

(b)

A

CC E

PT

10

Standard Error

Intercept

ED

CR (%)

Value

?$OP:A=1

Fig. 2. Changes in CR (%) of PDA vesicles upon exposure to Cs and K ions with various concentrations. Exposure time: 1 min (a); 3 h (b). 28

4

2

0

K

Na

Rb

SC R

Cs

IP T

CR (%)

6

A

N

U

(a)

M

PT

10

ED

CR (%)

20

Cs

K

Na

Rb

(b)

A

CC E

0

Fig. 3. Changes in CR (%) values of PDA vesicles composed of PCDA-EG4 upon exposure to various metal ions at the concentrations of (a) 12 μM and (b) 60 μM. Exposure time: 3 h. 29

CR (%)

20

Cs

K

Na

Rb

SC R

0

IP T

10

A

N

U

(a)

PT

10

ED

CR (%)

M

20

CC E

0

Cs

K

Na

Rb

(b)

A

Fig. 4. Changes in CR (%) values of PDA vesicles composed of (a) PCDA-EG2 and (b) PCDA-EG6 upon exposure to various metal ions. [metal ions] = 60 μM. Exposure time: 3 h. 30

SC R

IP T

(a)

U

(b)

N

Fig. 5. (a) Color change of PMMA films of PDA vesicles composed of PCDA, PCDA-

M

A

EG4, and PCDA-Me (left) and of PCDA (right) by dropping of metal ion solutions. The white circles represent the dropping area of the solution. (b) Color change of

ED

PMMA films of PDA vesicles composed of PCDA, PCDA-EG4, and PCDA-Me by

PT

immersing in metal ion solutions for 24 h. [metal ions] = 100 μM. Partial color changes in the cases of K and Rb ions were attributed to the mechanical rupture of

A

CC E

the films.

31

1.2 Control Cs+

0.4

0.0 300

400

500

600

700

Wavelength (nm)

N

U

(a)

800

IP T

Na+ Rb+

SC R

Absorbance

K+

0.8

A

100

M

60 40

PT

20

ED

CR (%)

80

Cs

Na

K

Rb

(b)

A

CC E

0

Fig. 6. Changes in (a) UV-vis spectra and (b) CR (%) values of PMMA films of PDA vesicles composed of PCDA, PCDA-EG4, and PCDA-Me upon immersion in various metal ions for 24 h. [metal ions] = 100 μM. 32