Rhenium-Based Molecular Trap as an Evanescent Wave Infrared

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Rhenium-based Molecular Trap as an Evanescent Wave Infrared Chemical Sensing Medium for the Selective Determination of Amines in Air Genin Gary Huang, Chung-Jay Lee, Jyisy Yang, Che-Hao Chang, Malaichamy Sathiyendiran, Zong-Zhan Lu, and Kuang-Lieh Lu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b11767 • Publication Date (Web): 02 Dec 2016 Downloaded from http://pubs.acs.org on December 4, 2016

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ACS Applied Materials & Interfaces

Rhenium-based Molecular Trap as an Evanescent Wave Infrared Chemical Sensing Medium for the Selective Determination of Amines in Air Genin Gary Huang,1Chung-Jay Lee,2 Jyisy Yang2,*, Che-Hao Chang,3 Malaichamy Sathiyendiran,3 Zong-Zhan Lu,3 and Kuang-Lieh Lu3

1

Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung, 807, Taiwan

2

Department of Chemistry, National Chung Hsing University, Taichung 402, Taiwan, Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan

3

*Author to whom correspondence should be addressed. Phone: +886-422840411 ext. 514 Fax: +886-422862547 e-mail: [email protected]

ACS Paragon Plus Environment


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ABSTRACT An evanescent wave infrared chemical sensor was developed to selectively detect volatile amines with heterocyclic or phenyl ring. To achieve this goal, a rhenium-based metallacycle with a “molecular-trap” structure was designed and synthesized as host molecules to selectively trapping amines with heterocyclic or phenyl ring through Re···amine and π-π interactions. To explore the trapping properties of the material, a synthesized Re-based molecular trap was treated with an IR sensing element and wide varieties of volatile organic compounds (VOCs) were examined to establish the selectivity for detection of amines. Based on the observed IR intensities, the Re-based molecular trap favors to interact with amines as evidenced by the variation of absorption bands of the Re molecular trap. With extra π-π interaction force, molecules, such as pyridine and benzylamine, could be detected. After optimization of the parameters for IR sensing, a rapid response in the detection of pyridine was observed and the linear ranges were generally up to 10 mg/L with a detection limit around 5.7 µg/L. In the presence of other VOCs, the recoveries in detection of pyridine were all close to 100%.

KEYWORDS: Evanescent wave; Infrared; Chemical sensor; Rhenium; Supramolecule.

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1. INTRODUCTION The assembly and self-assembly of transition-metal-based supramolecules,1-5 such as porphyrins,6,7 calyx[n]arenes,8 and crown ethers,9,10 has attracted consideration attention in the past few decades. The host-guest behavior of these types of supramolecules provides a means to selectively interact with targeted analytes. Due to the custom design properties of the molecular trap, supramolecules have been widely utilized in the fabrication of sensors,11-13 probes,14 photonic devices,15 catalysts16-18 and in studies of basic host-guest chemistry.19-21 In this work, we report on the synthesis of a supramolecule that is specifically designed to interact with amines containing heterocyclic or phenyl rings, which is an important class of volatile organic compounds (VOCs) that are found in our environment.22,23 Although a number of analytical methods have been developed to determine the concentration of amines in different media,24-30 weaknesses are usually associated. For instance, chromatographic methods offer the ability to simultaneously analyze interested amines but the sample treatment, and separation are tedious and time consuming.28,29 Optical24,25 and mass-sensitive sensors26,27 have also been proposed for analysis of amines. The response time is short and could be within few mins.24-27 However, background fluctuation or system drifting can cause serious degradation of the analytical accuracy as this type of sensors lacks a second mechanism to identify the target compound out of interference. On the other hand, sensors based on infrared (IR) spectroscopy are highly demanded as the absorption features of amines can be used to further identify the targeted compound. Therefore, chemical sensor based on IR spectroscopy is developed in this work to overcome the weaknesses mentioned above. To improve the selectivity in detection of amines, a cavity-containing Re-complex was designed, synthesized, and was used as a host molecule to modify the surface of IR sensing 3



elements for selectively trapping targeted amines. The unique cavity and specific interactions of the modifying molecule can improve the selectivity of the material in attracting target molecules. The designed Re molecular trap for heterocyclic amine is schematically shown in Fig. 1A. In this structure, a flexible phenyl ring was designed on the molecular trap as a molecular cap to allow easy access to the cavity in the molecular trap and also to stabilize the trapped amines by π-π interactions. An extra chemical force between the Re and amine group was also designed to selectively attract and stabilize the trapped amines. By depositing the synthesized Re molecular trap on an evanescent wave infrared sensing element,31,32 it was possible to construct a highly sensitive and selective chemical sensor for the detection of amines with heterocyclic or phenyl ring, as shown in Fig. 1B. a

N

N

N N

N N

N

N

N

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N

Re

S Re

Re

S

S

Re

S

Molecular Clasp of Re-Complex

b N

IRE (ZnSe)

N

N

N

IR in

To IR Detector

Figure 1: (a) Schematic drawing of the concept in designing selective molecular trap and the designed and synthesized Re molecular trap for selective attraction heterocyclic amine. (b) Schematic diagram of the Re molecular trap on infrared internal reflection element (IRE) for detection of heterocyclic amines.

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2. EXERIMENTAL SECTION Chemicals

Dirhenium decacarbonyl Re2(CO)10, α,α’-dibromo-ο-xylene, benzimidazole

and 1-butanethiol were purchased from Acros Organics (Phillipsburg, NJ) and were used in the synthesis of the Re molecular trap. Nineteen volatile organic compounds with different characteristics were examined to explore the recognition ability of the synthesized rhenium-based molecular traps, where ethylamine, butylamine, di-ethylmethylamine, piperidine, pyridine, 2-methyl pyridine, benzylamine, and methylbenzylamine, were purchased from Acros Organics (Geel, Belgium); chloroform, chlorobenzene, ethanol, acetone, methanol, toluene, ammonia, carbon tetrachloride, trichloro ethylene, benzene, trichlorobenzene, nitrobenzene, and benzaldehyde, were obtained from TEDIA (Fairfield, OH). All chemicals are reagent grade and were used as received without further purification. A 45° trapezoidal (55 × 5 × 2 mm3) zinc selenide internal reflection element (IRE) procured from international crystal laboratory (Garfield, NJ) was used for modifying the prepared rhenium-based molecular traps. Apparatus

The sample cell of stainless steel was prepared with 30 mm × 30 mm × 100

mm, resulting in a volume of 90 cm3. This setup was used in our previous study.33 The surface of IRE was first modified with rhenium-based molecular traps. After placed across the stainless steel sample cell, IRE was carefully sealed with polytetrafluoroethene (PTFE) tape. To prevent leakage and the adsorption of the gas molecules, the cap of this cell was insulated with a thick PTFE film, with a rubber pad and a stainless steel plate, which was secured to the cell body with four screws. This cell was placed into the sample compartment of a Bruker Vector 22 Fourier Transform Infrared (FT-IR) spectrometer equipped with a medium-range mercury-cadmium-telluride (MCT) detector. All spectra were collected by co-adding 64 scans with 4 cm−1 resolution. 5



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Preparation of the Re-based molecular trap [Re2(CO)6(µ µ-XyBim)(µ µ-BuS)2] Re molecular trap was prepared with similar procedures in our previous work.34-36 In general, this molecule was obtained from the reaction of a mixture of Re2(CO)10 (130.4 mg, 0.199 mmol), and one equivalent of α,α'-di(N-benzimidazolyl)-o-xylene (XyBim, 70.0 mg, 0.207 mmol) in 1-butanethiol (BuSH)/toluene (2:16 mL) in a Teflon flask that was placed in a steel bomb. The bomb was placed in an oven maintained at 140oC for 72 h and then cooled to 30oC. The white-colored crystals were collected by filtration, washed with n-hexane and air-dried. The overall yield was 154.0 mg (73%). The structures of the molecular trap were characterized by spectroscopic methods (refer to supplemental data, S1). The FAB mass spectrum of molecular trap showed a molecular ion peak at m/z 1057, with an experimental isotope pattern that matches very closely with that calculated. Anal. Calcd for C36H36N4O6Re2S2 : C, 40.90; H, 3.43; N, 5.30. Found: C, 40.99; H, 3.09; N, 5.14. The purified rhenium-based molecular traps were dissolved in N,N-dimethylformamide to different concentrations of coating solutions. Fig. 2A shows the scheme for the self-assembly of the Re molecular trap. To prepare the Re molecular trap modified sensing element, a certain volume of this molecular trap solution was coated on the ZnSe sensing element by a micro pipet to produce the desired surface coverage and then dried in a fume hood to remove the solvent. Fig. 2B shows the infrared spectra of the Re molecular trap and the compounds used in the synthesis. The CO stretching vibrations around 2000 cm-1 were shifted to 1999 cm-1 (doublet) and 1888 cm-1 (triplet) compared to Re2(CO)10. The peak shifts of structure-sensitive CO stretching modes are simply caused by increased π-back-bonding from the Re to CO molecule.

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a

α,α'-Di(N-benzimidazoly1)-o-xyle

N N N N

CO

OC Re

CO Re

S

CO

S

Re

Re

S

OC OC

Di-Rhenium deca-carbonyl

b

1000 mAU Re-based molecular clasp

×10 Di-Rhenium deca-carbonyl

×5 α,α'-Di(N-benzimidazoly1)-o-xyle 4000

3000

2000

1000

Wavenumber (cm-1)

Figure 2: (A) Scheme for the self-assembly of the Re molecular trap. (B) IR spectra of the synthesized Re-based molecular trap, di-rhenium deca-carbonyl, and α,α'-di(N-benzimidazoly1)-o-xylene.

Regeneration of the Sensor In this study, the Re molecular trap coated sensing elements were regenerated after every single detection. The regeneration of the sensor can be accomplished easily by leaving the sample cell uncapped for a period of time. The IR signals of the residual adsorbed molecules show that the sensor can be regenerated completely at room temperature within a regeneration time of 10 min.

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3. RESULTS AND DISCUSSION Basic sensing property of the Re molecular trap in the Detection of VOCs

To

investigate the capability of the Re molecular trap for the detection of VOCs, four compounds, ethanol (high polarity), chloroform (low polarity), chlorobenzene (aromatic) and pyridine (heterocyclic amine), with different characteristics were examined individually. The sensing element with a surface coverage of the Re molecular trap of 100 µg/cm2 was used in this study. The IR spectra were acquired immediately after injecting VOCs at a concentration of 50 mg/L into the sample cell. Fig. 3 showed typical spectra detected by the Re molecular traps modified sensing element for the examined VOCs along with their neat spectra detected by the bare IREs. As can be observed from Fig. 3, the detected spectra by the Re molecular trap show similar spectral features compared to their own neat spectra. Also, with the Re molecular trap, the peak intensity of pyridine is much stronger than the other three VOCs. This result verifies that our designed molecular trap works for selective detection of amines with heterocyclic ring. On the other hand, two chemical forces need to co-exist and to be enough strong to permit an aromatic amine structural analog to be trapped efficiently. These two forces involve the π-π interaction and Re-amine interaction. To amplify these two forces, the size and the functional group of the VOCs need to match the molecular trap. In comparison to pyridine, the peak intensities of ethanol, chloroform and chlorobenzene detected by Re molecular traps were all much weaker than that of pyridine regardless the characteristics of the examined molecules. The detected time profiles of these VOCs are plotted in Fig. 4. It can be observed that the adsorption rates of the four examined molecules are all quite fast and maximal signals can be reached within 10 mins.

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300 mAU

×50

Chloroform - detected

Neat Chloroform ×50

Ethanol - detected

Neat Ethanol Chlorobenzene - detected

×30

Neat Chlorobenzene Pyridine - detected

Neat Pyridine

1800

1500

900

1200

Wavenumber (cm-1)

Figure 3: Spectra of chlorobenzene, chloroform, ethanol, and pyridine detected by Re molecular trap at a detection time of 10 min. The concentration of the injected VOCs was 50 mg/L; the coverage of the Re molecular trap on the surface of the sensing element was kept 100 µg/cm2. Neat spectra detected by the bare ZnSe are also plotted. Peak indicated by a star was used for quantitative analysis. 400 350 Peak Intensity (mAU)

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300 250 200 150 100 ×5

50 0 0

10

20

30

Detection time (min)

Figure 4: Typical detection time profiles of chlorobenzene (■), chloroform (●), ethanol (▼), and pyridine (▲). Peak intensities were enlarged 50 times for chlorobenzene, chloroform, and ethanol. The injected concentration of VOCs was 50 mg/L; the surface coverage of Re molecular trap was kept 100 µg/cm2. 9



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Selective trapping ability of the Re molecular trap Based on the results obtained in the previous section, an intense peak was observed in the detection of pyridine by the Re molecular trap. To understand the contribution from the formation of a cavity in trapping pyridine, two compounds, which were used to form the Re molecular trap, were examined for their adsorption abilities toward pyridine and also to understand the contributions from the chemicals and the trap structure. Dirhenium decacarbonyl and α,α'-di(N-benz-imidazoly1)-o-xylene were first coated on the surface of the sensing element with a surface coverage identical to that for the Re molecular trap (100 µg/cm2). The detection time profiles of pyridine are plotted in Fig. 5. As can be seen in this figure, the detected peak intensity of pyridine was much weaker for dirhenium decacarbonyl compared to that of Re molecular trap. This result indicates that only the chemical force between Re in dirhenium decacarbonyl and the amine is not sufficient enough to effectively attract pyridine. The detected peak intensity of pyridine by α,α'-di(N-benz-imidazoly1)-o-xylene was about 64 % compared to that observed by Re molecular trap. Also, by the coating layer of α,α'-Di(N-benz-imidazoly1)-o-xylene, the detection time to reach maximal peak intensity was extended to 20 min. The shorter time to reach maximal peak intensity for the Re molecular trap reveals that the cavity structure of the Re molecular trap allows for pyridine to reach the stable sites faster. On the other hand, the Re molecular trap includes two chemical forces, i.e., Re···amine interactions and π-π interactions. Also, the cavity structure of the Re molecular trap can effectively trap pyridine molecules.

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400

Peak Intensity (740 cm-1, mAU)

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350 300 250 200 150 100 50 0 0

5

10

15

20

25

30

35


Figure 5: Detection time profiles of pyridine detected by assembled Re molecular trap (▲), dirhenium decacarbonyl (●), and α,α'-Di(N-benz-imidazoly1)-o-xylene (◆). The injected concentration of VOCs was 50 mg/L; the surface coverage of Re molecular trap was kept 100 µg/cm2. Selectivity of the Re molecular trap in detection of VOCs To further examine the selectivity of the Re molecular trap in the detection aromatic amines, two classes of VOCs, aliphatic and aromatic VOCs, were examined. Several amine compounds were also added to these two classes of VOCs to examine the efficiency in attracting amine-containing VOCs. The detected spectra for the examined aliphatic VOCs are plotted in Fig. 6. Aromatic VOCs were also examined and the detected spectra are plotted in Fig. 7. To quantitatively examine the potential interferences from the VOCs, the peaks indicated by a star are used to calculate the peak heights and the obtained peak intensities at a detection time of 10 min are tabulated in Table I. As can be seen in Fig. 6 along with the intensities tabulated in Table I, the detected peak intensities are weak for aliphatic VOCs, indicating that the Re molecular trap does not attract aliphatic VOCs very efficiently. For VOCs of

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amines with heterocyclic or phenyl rings, the detected spectra in Fig. 7 and the tabulated peak intensities in Table I indicate that aromatic compounds without an amine group are not attracted effectively by the Re molecular trap. With an addition of an amine group to the aromatic VOCs, such as benzylamine or methylbenzylamine, the observed peak intensities were similar to pyridine. This reveals that the trapping cavity also is able to stabilize the amines with phenyl ring. However, the molecules should remain a certain flexibility to adjust the trapped position to maximize the chemical force of π-π interaction. For instance, the obtained IR intensity of 2-methyl pyridine was weaker than that of pyridine, which is highly possible caused by the hindering effect from methyl group in the heterocyclic ring. On the other hand, amino compounds with heterocyclic or aromatic ring can be attracted through π-π interaction but with different degrees only. Therefore, the Re molecular trap is not specific but selective for amines with heterocyclic or phenyl rings.

Figure 6: Detected spectra of carbon tetrachloride, trichloroethylene, methanol, acetone, ammonia, ethylamine, butylamine, diethylamine, and piperidine. The injected concentration of VOCs was 50 mg/L; the coverage of Re molecular trap on the surface of sensing element was kept 100 µg/cm2. 12


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Figure 7: Typical IR spectra detected for benzene, toluene, trichlorobenzene, nitrobenzene, benzaldehyde, aniline, benzylamine, methylbenzylamine, and 2-methyl pyridine. The injected concentration of VOCs was 50 mg/L; the coverage of Re molecular trap on the surface of sensing element was kept 100 µg/cm2. Effect of the thickness of the Re molecular trap on the sensing element To optimize the thickness of the Re molecular trap for IR sensing, different amounts of Re molecular trap were examined in which the surface coverage varied from 4 mg/cm2 to 24 mg/cm2. The observed detection time profiles for detecting 10 mg/L pyridine are plotted in Fig. 8. As can be observed in Fig. 8, the observed peak intensities are increased with the thickness of the covering Re molecular trap. However, the time required to achieve the detection equilibrium is increased when surface coverage of Re molecular trap is increased. For instance, more than 15 min was need to reach the maximal peak intensity for a coverage of 24 mg/cm2, while for a surface coverage of 12 mg/cm2, the time required to reach the maximal peak intensity was shortened to 7 min. By plotting the surface coverage of the Re molecular trap against the peak intensities at 10 min and 20 min, a linear relationship was 13



observed as shown in Fig. 9. This linear relationship reveals that the thickness of Re molecular trap is still within the depth of penetration of IR radiation. Peak Intensity (740 cm-1, mAU)

600 550 500 450 400 350 300 250 200 150 100 50 0 0

5

10

15

20

25

30

35


Figure 8: Detection time profiles of 10-mg/L pyridine with different amounts of Re molecular trap. The examined surface coverage was varied as 4 (■), 8 (●), 12 (▲), 16 (▼), and 24 mg/cm2 (◆).

600


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500 400 300 200 100 0 0

50

100

150

200

250

300

350

Surface coverage of Re molecular trap (µg/cm2)

Figure 9: Surface coverage of Re molecular trap against the detected pyridine peak intensity at a detection time of 10 (■) and 20 min (●). 14


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Quantitative Aspects To investigate the detection limits and the linear range for the Re molecular trap, a surface coverage of 100 µg/cm2 was used to detect pyridine. The observed detection time profiles for different concentrations of pyridine are plotted in Fig. 10. As can be seen in this plot, the maximal intensities can be achieved within a detection time of 10 min for any of the examined concentrations. To examine the linearity of the Re molecular trap in the detection of pyridine, the detected intensities at 10 min of detection time were plotted against the concentration of pyridine as shown in Fig. 11. As can be seen in this figure, the linear regression coefficient (R2) was 0.999 in the concentration region between 125 µg/L and 10 mg/L. Deviation from linear relationship in Fig. 11 indicates that under an adsorption time of 10 mins, the active sites of Re molecular trap was almost occupied by the pyridine with a concentration higher than 10 mg/L. Based on three blank signal runs, the estimated detection limit was ca. 5.7 µg/L.

350


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


300 250 200 150 100 50 0 0

10

20

30


Figure 10: Time profiles for detection by the Re molecular trap. The Re molecular trap was given a surface coverage of 80 mg/cm2 and the concentrations 2.5 (■), 5 (●), 10 (▲), 20 (▼), 30 (◆), and 50 mg/L (★), respectively.

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350


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300 250 200 150 100 50 0 0

10

20

30

40

50

Concentration of pyridine (mg/L)

Figure 11: Detected peak intensity of pyridine by Re molecular trap. The detection time was maintained at 10 mins. Selectivity study in the detection of pyridine in the presence of a second VOC The determination of pyridine in practical use is achievable, since the Re molecular trap is capable of selectively interacting with aromatic amines. To examine the effect of interferences by other VOCs, pyridine was mixed with a second VOC to examine the recovery which is defined as the peak intensity of pyridine with interference divided by the peak intensity of pyridine alone. Six VOCs, namely, acetone, chloroform, methanol, toluene, and butylamine were added to pyridine samples individually. The concentration of pyridine was kept at 10 mg/L and the concentration of the added interfering compound was also kept at 10 mg/L. The observed recoveries were 99.8 (±6.0), 98.7 (±4.5), 97.3 (±4.3), 100.4 (±3.7), and 98.7 (±3.5)% in the case of acetone, chloroform, methanol, toluene, and butylamine, respectively. The recoveries of pyridine were also measured under competition effect by addition of benzylamine and methylbenzylamine to pyridine samples individually. The estimated recoveries were 100.7 (±5.0) and 85.6 (±5.0)%, respectively. These values verify that the selective detection of amines with heterocyclic or phenyl rings by Re-based 16


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molecular traps modified infrared chemical sensor can be used successfully as an analytical tool. 4. CONCLUSION In this study, a Re molecular trap modified IR sensor was successfully prepared. By providing two chemical forces in Re molecular trap, the synthesized Re molecular trap selectively interacts with amines with heterocyclic or phenyl ring. To optimize the proposed sensing method, the effect of the surface coverage of the Re molecular trap was also examined. The results indicated that the obtained peak intensity of pyridine was linearly proportional with the surface coverage of Re molecular traps. Based on the detection time profiles collected under optimal conditions, the detection time is generally shorter than 10 mins for the detection of pyridine. In terms of quantitative analyses, the results indicated that this sensing phase is highly sensitive to amines with heterocyclic or phenyl ring and the linear range in detection of pyridine is generally up to 10 mg/L with a detection limit around 5.7 µg/L. In the presence of a second VOC, the recoveries of peak intensity of pyridine were all close to 100%. These results prove that a sensitive and selective chemical sensor for the determination of with targeted amine is feasible. SUPPORTING INFORMATION Detailed experimental procedures, 1H NMR spectrum of α,α'-di(N-benzimidazolyl)-o-xylene, IR spectrum of the Re molecular trap, 1H NMR spectrum of the Re molecular trap, reference for synthesis. ACKNOWLEDGEMENT All authors are grateful to the Ministry of Science and Technology of Republic of China (No. MOST 103-2113-M-005-003) and Executive Yuan of Environmental Protection Administration of Republic of China (No. NSC 95-EPA-Z-001-001). 17



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Table I: The IR signals of various VOCs detected by Re-based molecular traps. The sensing element was prepared by coating Re molecular trap with a surface coverage of 100 µg/cm2 on the IREs. The concentration of the VOC was 50 mg/L and the detection time was kept 10 min. Peak Intensity Peak Intensity Aliphatic VOC Aromatic VOC (mAU) (mAU) Chloroform

10.9 (±0.9)

Benzene

10.3 (±0.5)

Carbon Tetrachloride

17.9 (±1.1)

Toluene

10.9 (±0.1)

Chlorobenzene

15.9 (±0.6)

Trichloro Ethylene

6.3 (±0.1)

Methanol

15.7 (±0.1)

Trichloro Benzene

18.0 (±0.3)

Ethanol

11.4 (±0.6)

Benzaldehyde

18.2 (±0.2)

Acetone

6.0 (±0.1)

Nitrobenzene

47.0 (±0.1)

Ammonia

68.9 (±0.5)

Pyridine

299.0 (±14.3)

Ethylamine

58.5(±2.8)

2-methyl pyridine

57.7 (±1.4)

Butylamine

35.6 (±0.9)

Benzylamine

160.7 (±1.1)

Diethylmethylamine

37.1 (±1.1)

Methylbenzylamine

185.9 (±3.0)

Piperidine

170.6 (±9.6)

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(13) Chen, L.; Tian, L.; Liu, L.; Tian, X.; Song, W.; Xu, H.; Wang, X. Preparation and Assay Performance of Supramolecule of Cyclophane-complexed Polyoxometalates Supported on the Gold Surface. Sens. Actuators, B 2005, 110, 271-278. (14) Sacksteder, L.; Lee, M.; Demas, J. N.; DeGraff, B. A. Long-lived, Highly Luminescent Rhenium(I) Complexes as Molecular Probes: Intra- and Intermolecular Excited-state Interactions. J. Am. Chem. Soc. 1993, 115, 8230-8238. (15) Yang, S. I.; Seth, J.; Balasubramanian, T.; Kim, D.; Lindsey, J. S.; Holten, D.; Bocian, D. F. Interplay of Orbital Tuning and Linker Location in Controlling Electronic Communication in Porphyrin Arrays. J. Am. Chem. Soc. 1999, 121, 4008-4018. (16) Kang, J.; Hilmersson, G.; Santamaria, J.; Rebek, J. Jr. Molecules within Molecules: Recognition Through Self-assembly. J. Am. Chem. Soc. 1998, 120, 3650-3656. (17) Shafer, L. L.; Tilley, T. D. Efficient Diastereoselective Syntheses of Chiral Macrocycles via Zirconocene Coupling. Synthetic Control of Size and Geometry. J. Am. Chem. Soc. 2001, 123, 2683-2684. (18) Sanders, J. Supramolecular Catalysis in Transition. Chem. Eur. J. 1998, 4, 1378-1383. (19) Slone, R. V.; Yoon, D. I.; Calhoum, R. M.; Hupp, J. T. Luminescent Rhenium/Palladium Square Complex Exhibiting Excited State Intramolecular Electron Transfer Reactivity and Molecular Anion Sensing Characteristics. J. Am. Chem. Soc. 1995, 117, 11813-11814. (20) Sun, S.; Lees, A. J. Self-Assembly Triangular and Square Rhenium(I) Tricarbonyl Complexes: A Comprehensive Study of Their Preparation, Electrochemistry, Photophysics, Photochemistry, and Host−Guest Properties. J. Am. Chem. Soc. 2000, 122, 8956-8967. (21) Amabilino, D. B.; Stoddart, J. F. Interlocked and Intertwined Structures and Superstructures. Chem. Rev. 1995, 95, 2725-2828. (22) Golka, K.; Prior, V.; Blaszkewicz, M.; Bolt, H. M. The Enhanced Bladder Cancer Susceptibility of NAT2 Slow Acetylators Towards Aromatic Amines: a Review Considering Ethnic Differences. Toxicol. Lett., 2002, 128, 229-241. (23) Vineis, P.; Pirastus, R. Aromatic Amines and Cancer. Cancer Causes Control, 1997, 8, 346-355. (24) Zhou, X. C.; Ng, S. C.; Chan, H. S. O.; Li, S. F. Y. Detection of Organic Amines in Liquid with Chemically Coated Quartz Crystal Microbalance Devices. Sens. Actuators B, 1997, 42, 137-144. (25) Ma, G.; Cheng, Q. A Nanoscale Vesicular Polydiacetylene Sensor for Organic Amines by Fluorescence Recovery. Talanta, 2005, 67, 514-519. (26) Mohr, G. J. New Chromoreactands for the Detection of Aldehydes, Amines and 20


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Alcohols. Sens. Actuators B, 2003, 90, 31-36. (27) Oberg, K. I.; Hodyss, R.; Beauchamp, J. L. Simple Optical Sensor for Amine Vapors Based on Dyed Silica Microspheres. Sens. Actuators B, 2006, 115, 79-85. (28) Mishra, S.; Singh, V.; Jain, A.; Verma, K. Simultaneous Determination of Ammonia, Aliphatic amines, Aromatic amines and Phenols at µg L-1 Levels in Environmental Waters by Solid-phase Extraction of Their Benzoyl Derivatives and Gas Chromatography-mass spectrometry. Analyst, 2001, 126, 1663-1668. (29) Wu, Y.-C.; Huang, S.-D. Solid Phase Microextraction Coupled with High Performance Liquid Chromatography for the Determination of Aromatic Amines. Anal. Chem. 1999, 71, 310-318. (30) English, J. T.; Deore, B. A.; Freund, M. S. Biogenic Amine Vapour Detection Using Poly(anilineboronic acid) Films. Sen. Actuators B, 2006, 115, 666-671. (31) Griffiths, P. R.; de Haseth, J. A. In Fourier Transform Infrared Spectrometry, 2nd ed.; John Wiley & Sons Ltd: Hoboken, NJ, 2007; Chapter 15, pp 321-347. (32) Mirabella, F. M. In Handbook of Vibrational Spectroscopy; Chalmers, J. M., Griffiths, P. R., Eds.; John Wiley & Sons Ltd: Hoboken, NJ, 2002; Volume 2, pp 1091-1103. (33) Huang, G. G.; Wang, C.-T.; Tang, H.-T.; Huang, Y.-S.; Yang, J. Infrared Chemical Sensor for Selectively Detection of Volatile Organic Compounds. Anal. Chem. 2006, 78, 2397-2404. (34) Sathiyendiran, M; Liao, R. T.; Thanasekaran, P.; Luo, T. T.; Venkataramanan, N. S.; Lee, G. S.; Peng, S. M.; Lu, K. L. Gondola-Shaped Luminescent Tetrarhenium Metallacycles with Crown-Ether-like Multiple Recognition Sites. Inorg. Chem. 2006, 45, 10052-10054. (35) Thanasekaran, P.; Lee, C. H.; Lu, K. L. Neutral Discrete Metal–Organic Cyclic Architectures: Opportunities for Structural Features and Properties in Confined Spaces. Coord. Chem. Rev. 2014, 280, 96−175. (36) Thanasekaran, P.; Lee, C. C.; Lu, K. L. One-Step Orthogonal-Bonding Approach to the Self-Assembly of Neutral Rhenium-Based Metallacycles: Synthesis, Structures, Photophysics, and Sensing Applications. Acc. Chem. Res. 2012, 45, 1403–1418.

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Figure Captions: Figure 1: (a) Schematic drawing of the concept in designing selective molecular trap and the designed and synthesized Re molecular trap for selective attraction heterocyclic amine. (b) Schematic diagram of the Re molecular trap on infrared internal reflection element (IRE) for detection of heterocyclic amines. Figure 2: (A) Scheme for the self-assembly of the Re molecular trap. (B) IR spectra of the synthesized Re-based molecular trap, di-rhenium deca-carbonyl, and α,α'-di(N-benzimidazoly1)-o-xylene. Figure 3: Spectra of chlorobenzene, chloroform, ethanol, and pyridine detected by Re molecular trap at a detection time of 10 min. The concentration of the injected VOCs was 50 mg/L; the coverage of the Re molecular trap on the surface of the sensing element was kept 100 µg/cm2. Neat spectra detected by the bare ZnSe are also plotted. Peak indicated by a star was used for quantitative analysis. Figure 4: Typical detection time profiles of chlorobenzene (■), chloroform (●), ethanol (▼), and pyridine (▲). Peak intensities were enlarged 50 times for chlorobenzene, chloroform, and ethanol. The injected concentration of VOCs was 50 mg/L; the surface coverage of Re molecular trap was kept 100 µg/cm2. Figure 5: Detection time profiles of pyridine detected by assembled Re molecular trap (▲), dirhenium decacarbonyl (●), and α,α'-Di(N-benz-imidazoly1)-o-xylene (◆). The injected concentration of VOCs was 50 mg/L; the surface coverage of Re molecular trap was kept 100 µg/cm2. Figure 6: Detected spectra of carbon tetrachloride, trichloroethylene, methanol, acetone, ammonia, ethylamine, butylamine, diethylamine, and piperidine. The injected concentration of VOCs was 50 mg/L; the coverage of Re molecular trap on the surface of sensing element was kept 100 µg/cm2. Figure 7: Typical IR spectra detected for benzene, toluene, trichlorobenzene, nitrobenzene, benzaldehyde, aniline, benzylamine, methylbenzylamine, and 2-methyl pyridine. The injected concentration of VOCs was 50 mg/L; the coverage of Re molecular trap on the surface of sensing element was kept 100 µg/cm2. Figure 8: Detection time profiles of 10-mg/L pyridine with different amounts of Re molecular trap. The examined surface coverage was varied as 4 (■), 8 (●), 12 (▲), 16 (▼), and 24 mg/cm2 (◆). Figure 9: Surface coverage of Re molecular trap against the detected pyridine peak intensity at a detection time of 10 (■) and 20 min (●). Figure 10: Time profiles for detection by the Re molecular trap. The Re molecular trap was given a surface coverage of 80 mg/cm2 and the concentrations 2.5 (■), 5 (●), 10 (▲), 20 (▼), 30 (◆), and 50 mg/L (★), respectively. 22


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Figure 11: Detected peak intensity of pyridine by Re molecular trap. The detection time was maintained at 10 mins.

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TOC

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Figure 1: (a) Schematic drawing of the concept in designing selective molecular trap and the designed and synthesized Re molecular trap for selective attraction heterocyclic amine. (b) Schematic diagram of the Re molecular trap on infrared internal reflection element (IRE) for detection of heterocyclic amines. 508x381mm (300 x 300 DPI)



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Figure 2: (A) Scheme for the self-assembly of the Re molecular trap. (B) IR spectra of the synthesized Rebased molecular trap, di-rhenium deca-carbonyl, and α,α'-di(N-benz- imidazoly1)-o-xylene. 508x381mm (300 x 300 DPI)


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Figure 3: Spectra of chlorobenzene, chloroform, ethanol, and pyridine detected by Re molecular trap at a detection time of 10 min. The concentration of the injected VOCs was 50 mg/L; the coverage of the Re molecular trap on the surface of the sensing element was kept 100 µg/cm2. Neat spectra detected by the bare ZnSe are also plotted. Peak indicated by a star was used for quantitative analysis. 508x381mm (300 x 300 DPI)



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Figure 4: Typical detection time profiles of chlorobenzene (■), chloroform (●), ethanol (▼), and pyridine (▲). Peak intensities were enlarged 50 times for chlorobenzene, chloroform, and ethanol. The injected concentration of VOCs was 50 mg/L; the surface coverage of Re molecular trap was kept 100 µg/cm2. 508x381mm (300 x 300 DPI)


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Figure 5: Detection time profiles of pyridine detected by assembled Re molecular trap (▲), dirhenium decacarbonyl (●), and α,α'-Di(N-benz-imidazoly1)-o-xylene (◆). The injected concentration of VOCs was 50 mg/L; the surface coverage of Re molecular trap was kept 100 µg/cm2. 508x381mm (300 x 300 DPI)



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Figure 6: Detected spectra of carbon tetrachloride, trichloroethylene, methanol, acetone, ammonia, ethylamine, butylamine, diethylamine, and piperidine. The injected concentration of VOCs was 50 mg/L; the coverage of Re molecular trap on the surface of sensing element was kept 100 µg/cm2. 1016x762mm (120 x 120 DPI)


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Figure 7: Typical IR spectra detected for benzene, toluene, trichlorobenzene, nitrobenzene, benzaldehyde, aniline, benzylamine, methylbenzylamine, and 2-methyl pyridine. The injected concentration of VOCs was 50 mg/L; the coverage of Re molecular trap on the surface of sensing element was kept 100 µg/cm2. 1016x762mm (120 x 120 DPI)



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Figure 8: Detection time profiles of 10-mg/L pyridine with different amounts of Re molecular trap. The examined surface coverage was varied as 4 (■), 8 (●), 12 (▲), 16 (▼), and 24 mg/cm2 (◆). 508x381mm (300 x 300 DPI)


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Figure 9: Surface coverage of Re molecular trap against the detected pyridine peak intensity at a detection time of 10 (■) and 20 min (●). 508x381mm (300 x 300 DPI)



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Figure 10: Time profiles for detection by the Re molecular trap. The Re molecular trap was given a surface coverage of 80 mg/cm2 and the concentrations 2.5 (■), 5 (●), 10 (▲), 20 (▼), 30 (◆), and 50 mg/L (★), respectively. 508x381mm (300 x 300 DPI)


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Figure 11: Detected peak intensity of pyridine by Re molecular trap. The detection time was maintained at 10 mins. 508x381mm (300 x 300 DPI)


Rhenium-Based Molecular Trap as an Evanescent Wave Infrared

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