Highly Efficient Multiple-Anchored Fluorescent Probe for the Detection

3 May 2017 - Among gaseous analytes, detection of aniline vapor is extraordinarily important in the control of environmental issues and human diseases...
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Highly efficient Multiple-Anchored Fluorescent Probe for the detection of aniline vapor based on synergistic effect: chemical reaction and PET Zinuo Jiao, Yu Zhang, Wei Xu, Xiangtao Zhang, Haibo Jiang, pengcheng wu, Yanyan Fu, Qingguo He, Huimin Cao, and Jiangong Cheng ACS Sens., Just Accepted Manuscript • Publication Date (Web): 03 May 2017 Downloaded from http://pubs.acs.org on May 7, 2017

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Highly efficient Multiple-Anchored Fluorescent Probe for the detection of aniline vapor based on synergistic effect: chemical reaction and PET Zinuo Jiao a, b, Yu Zhang a, Wei Xu a, b, Xiangtao Zhang a, b, Haibo Jiang a, b, Pengcheng Wu a, b, Yanyan Fu a, Qingguo He a*, Huimin Cao a and Jiangong Cheng a* a

State Key Lab of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Changning Road 865, Shanghai 200050, China. E-mail: [email protected]; [email protected]. b University of the Chinese Academy of Sciences, Yuquan Road 19, Beijing,100039, China KEYWORDS: fluorescence probe, aniline vapor, low detection, synergistic effect, multiple active sites

ABSTRACT: A multiple-anchored fluorescent probe ((((Hexane-1,6-diylbis(2,7-bis(4-Formyl)-phenyl)-9H-fluorine-9,9-diyl)) bis(hexane-6,1-diyl)) bis-(9H-carbazole-9,3,6-triyl)) tetrakis(benzene-4,1-diyl)) tetra formyl-(8FP-2F) with eight aldehyde groups was designed and synthesized. The molecule has four branches and highly twisted structure. Furthermore, it tends to self-assemble into nano-spheres, which is beneficial for gaseous analytes penetration and high fluorescence quantum efficiency. Among gaseous analytes, detection of aniline vapor is extraordinarily important in the control of environmental issues and human diseases. Herein, 8FP-2F was introduced to detect aniline vapor with distinguished sensitivity and selectivity via simple Schiff base reaction at room temperature. After exposure to saturate aniline vapor, the 89% fluorescence of 8FP-2F was quenched in 50 s and the detection limit was as low as 3 ppb. Further study showed the suitable HOMO/LUMO energy levels and matched orbital symmetry between probe and aniline molecules ensured chemical reaction and PET process work together. The synergistic effect resulted in a significant sensing performance and fluorescence quenching towards aniline vapor. Moreover, the multiple active sites structure of 8FP-2F means it could be applied for constructing many interesting structures and highly efficient organic optoelectronic functional materials.

Over past decades, environmental issues are becoming more and more serious and have drawn a great attention. Among environmental pollutants, the detection of aniline has gained extra attention because aniline as an intermediate of many raw and fine chemicals is widely used in industrial process1, which not only leads to heavy water and air pollution2,3 but also induces severe human diseases4-6. Up to now, a series of analytical methods such as high performance liquid chromatography (HPLC)7,8, electrochemistry9,10, GC-MS11,12 and spectrofluorimetry13-15 have been developed to detect aniline in water. However, these methods cannot meet needs for the onsite and real time determination of aniline vapor in air with selectivity and sensitivity. Facile, fast and highly selective methods for the determination of aniline vapor are thus still in demand. Recently, more and more attention was focused on fluorescence sensory materials due to their apparent advantages including real-time response, high sensitivity and selectivity16-18. To date, several fluorescent probes for trace gaseous aniline were reported. Zhang and co-workers19 detected aniline vapor based on nanofibers which also showed high sensitivity towards other volatile organic amines and

pyridine. Liu20 reported an organ gel fibers for probing aniline vapor and the detection limit was 8.6 ppm. Wang21 developed a kind of film of ZnS/PTCDA to distinguish aniline vapor from other amines with a detection limit of 100 ppb. Jiang22 reported a reversible sensory material for selectively sensing aniline vapor based on the π-stacking aggregation and the detection limit was 80 ppb. Furthermore, towards aniline vapor detection, these probes depended on either photoinduced electron transfer (PET) or only weak reactions. So there is still a great space to develop new aniline vapor probes with high sensitivity and selectivity for its real time and on site detection based on highly efficient sensing mechanism. It is known that aldehyde groups can act as active sites to react with many substances by Wittig reaction, Knoevenagel reaction, Grignard reaction and Schiff base reaction et al. For example, some amines can react with aldehyde unit to form imines via Schiff base reaction. Recently, Fu23 introduced imine group into a molecule via Schiff base reaction to prominently improve the sensing efficiency to H2O2. Huang24 described a few aldehyde groups can be incorporated with various organic amino-groups. Pyles and co-workers25 synthesized 2D benzobisoxazole-linked covalent organic

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Scheme 1 synthetic procedure of probe 8FP-F and 2FP-F

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O Br Br

Br

N

Br

N Br

Br

Br

HO B HO

O

O

O

N

O HBr

Pd(PPh3)4/ K2CO 3 (aq) THF/reflux, 72 h

N

O

O O

Br

1

O

Br

Br

HO B HO

O

8FP-2F

O

O

Pd(PPh3)4/ K2CO3 (aq) THF/reflux, 36 h

2

2FP-F

frameworks by the reaction between multiple aldehyde and amino groups. As we know, conjugated fluorescent polymers generally exhibited more excellent sensitivity than small molecule materials due to molecular wire effect.16 However, some obvious advantages of small fluorescent molecule materials lie in such as easy purification, definite structure and versatile structure.26,27 Moreover, if small molecule has nice absorption and emission property, suitable and well-arranged sensing units, especially, if it could form Nano-structure film, the sensing performance could be greatly improved.28-30 Currently, our group reported several fluorescent dimers of fluorene bridged by a 1,6-hexanyl unit for highly efficient explosive or drug detection.31-33 These dimers have large molar extinction coefficient, high fluorescent quantum yield and tend to assemble into Nano-sized spheres, which will contribute to increase the sensing performance of the probes. Herein, eight benzaldehyde units were introduced to substitute eight bromines moieties as demonstrated in scheme 1. In this contribution, eight benzaldehyde-substituted fluorene dimer (8FP-2F) can directly sense aniline vapor at room temperature based on a highly efficient synergistic sensing mechanism of both chemical reaction and PET. The fluorescence quenching rate of 8FP-2F film could be ~90% within 50 s and the detection limit could be as low as ~3 ppb in the presence of aniline vapor. The whole process could be monitored by fluorescence spectroscopy. The changes of fluorescence color, CIE chromaticity diagram and spectroscopic experiments towards aniline vapor showed a prominent selectivity over other organic amines and common solvents. NMR and energy levels were used for clarifying the sensing mechanism. Firstly, the NMR experiments proved the detection was mainly based on Schiff base reaction. Secondly, the electron calculation of probe and aniline via DMOL3 of Materials Studio 8.0 showed suitable energy levels which can result in PET from aniline vapor to probe and reaction product. In a word, we have designed and synthesized an excellent fluorescent probe which showed high efficiency and distinguished selectivity towards aniline vapor based on the synergistic effect of Schiff base reaction and PET.

Experimental Section Materials and Measurements. Compound 1 was synthesized based on our previous work.31 compound 2 and

other chemicals used during synthesized process were purchased from commercial sources. Aniline and other organic amines used were analytical grade. The 1H-NMR and 13CHMR spectra were obtained on a Bruker DRX500 instrument with tetramethylsilane (TMS) used as an internal standard. Mass spectra were recorded on a BIFLEX III MALDI-TOF (Bruker Daltonics Inc.) mass spectrometer. UV–Vis absorption and fluorescence analysis were achieved on Jasco V-670 spectrophotometer and HORIBA Fluoro-Max-4 spectrometer. The optimized structure was carried on Materials Studio provided by Accelrys America. The calculations of energy levels were conducted by the module DMOL3 of Materials Studio 8.0 software. The detailed methodology and parameters were listed in Table S1 in supporting information. All the sensing films were prepared by spin coating their THF solutions onto quartz plate (10 mm × 20 mm) at constant rate of 2000 rpm by using KW-4 spin coater. The films were all placed under vacuum for half an hour before use. The reaction processes of films to different analytes were accomplished by inserting the films into a battery of sealed vials (3.8 mL) containing cottons and different amines some time at room temperature. The analytes will not contact with the sensory films directly and can maintain a constant vapor pressure by this method. The fluorescence responses were recorded after the films were exposed to the analytes vapor at an angle of 60° to incident light. Synthesis of ((((Hexane-1,6-diylbis(2,7-bis(4-Formyl)phenyl)-9H-fluorine-9,9-diyl)) bis(hexane-6,1-diyl)) bis-(9Hcarbazole-9,3,6-triyl)) tetrakis(benzene-4,1-diyl)) tetra formyl(8FP-2F): compound 1 31 (0.386 g, 0.25 mmol), 4Formylphenylboronic acid (0.480 g, 3 mmol), Pd(PPh3)4 (98 mg, 0.085 mmol) were added into a flask under N2 atmosphere. Subsequently, THF (20 mL) and K2CO3 (12 mL, 2 M) which had been degassed for 30 min were injected the reaction flask. The mixture was stirred 72 h under 85 °C. Then it was poured into 50 mL brine and extracted with dichloromethane. The organic layer was dried over anhydrous MgSO4. After filtration, rotary evaporation and purification by column chromatography, the product was recrystallized in dichloromethane/methanol. Ultimately, 0.175 g yellowish solid was collected with a yield of 41%. 1H-NMR (500 MHz, CDCl3, ppm) δ 10.06 (s, 4H), 10.03 (s, 4H), 8.36 (d, 4H, J =

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1.9 Hz), 7.96 (d, 8H, J = 8.1 Hz), 7.90 (d, 8H, J = 8.0 Hz), 7.82 (d, 8H, J = 7.9 Hz), 7.73 (m, 16H), 7.55 (dd, 4H, J = 7.8, 1.8 Hz), 7.45 (s, 4H), 7.33 (d, 4H, J = 8.6 Hz), 4.17 (t, 4H, J = 7.1 Hz), 1.95 (t, 4H, J = 8.1 Hz), 1.88 (m, 4H), 1.48 (t, 4H , J = 7.3 Hz), 1.11 (s, 8H), 0.79 (d, 4H, J = 20.6 Hz), 0.62 (s, 4H), 0.47 (s, 4H). 13C NMR (500 MHz, CD3SOCD3, ppm) δ191.91, 191.72, 181.33, 151.59, 147.79, 147.19, 140.95,140.80, 138.83, 135.14, 134.61, 130.99, 130.37, 130.24, 127.55, 126.57,125.56,123.47, 121.44, 120.51, 119.35, 109.38, 55.29, 53.01, 43.15,40.20,29.70, 29.41, 28.76, 26.75, 23.69,13.9; MALDI-TOF MS for C124H100N2O8: m/z 1744.7; Anal. Calcd. (1744.74). Synthesis of 2,7-bis((4-Formyl)-phenyl)-9,9-Dihexylfluorine-(2FP-F): 9,9-Dihexyl-2,7-dibromofluorene (0.492 g, 1 mmol), 4-formylphenylboronic acid (0.375 g, 2.5 mmol) Pd(PPh3)4 (92 mg, 0.08 mmol), K2CO3 (2.76 g, 20 mmol) were added into a flask under N2 atmosphere, then 25 mL of degassed THF/H2O (2:1) was injected. The solution was heated to reflux for 48 hrs. After extracted with CH2Cl2 (20 mL×3), the organic layer was washed with water, dried over anhydrous MgSO4. After filtration, rotary evaporation and purification by column chromatography, the product was recrystallized in dichloromethane / methanol to get yellow solid (0. 33 g, yield 60%). 1H NMR (500 MHz, CDCL3, ppm) δ 10.08 (s, 2H), 7.99 (d, 4H, J = 8.2 Hz), 7.84 (dd, 6H, J = 7.9, 3.4 Hz), 7.69 – 7.60 (m, 4H), 2.11 – 2.04 (m, 4H), 1.16 – 1.01 (m, 12H), 0.74 (q, 10H, J = 8.3, 7.5 Hz). 13CNMR (125MHz, Chloroform-d, ppm) δ 191.86, 152.09, 147.58, 140.96, 138.94,135.18, 130.33, 127.74, 126.57, 121.75, 120.53, 55.54, 40.37, 31.45, 29.65, 23.83, 22.54, 13.96; MALDI-TOF MS for C39H42O2: m/z 543.3; Anal. Calcd: 543.32.

Optical and Electrochemical Properties. The excitation and emission spectra of 8FP-2F and 2FP-F were shown in Fig.2. As exhibited in Fig.2a, in THF solution, the excitation and emission peaks of 8FP-2F are at 405 and 437 nm. While, in film state, the maximum excitation and emission peaks of 8FP-2F are located at 380 nm and 483 nm, respectively. From solution to film state, both the excitation and emission in film state of 8FP-2F are much broader than those in solution state. By contrast, the phenomenon of 2FP-F probe was unobvious. The results indicated 8FP-2F presented a more serious selfaggregation in solid state relative to solution than that of 2FPF.

Figure 2. The normalized excitation and fluorescence emission spectra of 8FP-2F(a) and 2FP-F (b) in solution and film. Figure 1. Geometric structure of 8FP-2F (top view (a) and side view (b))

For directly perceiving the structure of 8FP-2F, the calculation was performed by using COMPASS II of Materials Studio 8. Fig.1 showed the geometry optimization of 8FP-2F. As we can see, the four branches of 8FP-2F expanded to all directions and the molecule demonstrated a highly twisted structure, which could guarantee an easy capture of the analytes in all directions. Besides, the large and twisted structure is beneficial for gaseous analyte penetration and high fluorescence quantum efficiency. In other words, the prominent character may provide high sensing performance and fluorescent efficiency for the detection of analytes.

Results and Discussion

Fig.S9 showed the absorption spectra of 8FP-2F/2FP-F in film states and solution. Their peaks data were summarized in Table 1. As shown in Table 1, the molar extinction coefficient of 8FP-2F probe is 2.9 times as much as that of 2FP-F probe. As we know, molar extinction coefficient is a significant parameter, which reflected the absorption capacity of probes. Apparently, the higher molar extinction coefficient of 8FP-2F probe indicates it is more efficient and suitable for detection devices compared with 2FP-F probe. The scanning electron microscopy (SEM) was used to investigate the morphology of sensing films. According to our previous work28,32, sensing performance towards gaseous analytes will be increased by introduction of some nanostructures with a high area-to-volume ratio. As exhibited in Fig. 3, the morphology of 8FP-2F film was composed of self-assembled nanospheres with diameters of 100-200 nm fabricated from its THF solutions (1 mg/mL). As comparison,

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Table 1. Optical and Electrochemical Properties of 8FP-2F and 2FP-F

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the morphology of 2FP-F film was composed of much larger particles with a size ~1 µm. The surface to volume ratio of 8FP-2F was far larger than that of 2FP-F and the contact area of the probe molecules with the analytes will be much bigger for 8FP-2F, corresponding to a much higher sensitivity. To acquire the most appropriate concentration for the fabrication of 8FP-2F film, different concentrations were tested from 1 mg/mL to 4 mg/mL. It was found that the selfassembled spheres turned larger with the concentrations and the spheres were largest at 4 mg/mL with an average size of 370 nm as shown in Fig.S10. Fig.S11 exhibited stabilities and sensitivities of the films fabricated from different concentrations. From Fig.S11, the sensing performance was the most prominent at the concentration of 1 mg/mL. Therefore, in the following parts, the concentration of 1 mg/mL was adopted for the sensing films fabrication.

fluorescence responses of 8FP-2F/2FP-F films in air and saturate aniline vapor (860 ppm) were carried out, respectively. As illustrated in Fig.4, the 8FP-2F film presented good fluorescence stability in air judged from its much less photobleaching (~6%) than that of 2FP-F film (~20%) within 100 s. It indicated that 8FP-2F is more suitable for long time use for aniline vapor detection. In order to monitor the entire sensing process, the saturated aniline vapor was injected into 8FP-2F/2FP-F films a few seconds later as the test started. Then the 8FP-2F and 2FP-F films showed fast and significant fluorescence quenching in 25 s. The fluorescence quenching rates of 8FP-2F probe and 2FP-F were 89% and 92%, respectively. After that, the sensing curves kept stable, suggesting a complete reaction within 100 s. The fluorescence images before and after exposure of probes films to aniline vapor were presented in Fig.4 as inset photos.

Figure 4. Fluorescence stability and sensing properties of 8FP-2F and 2FP-F films after exposure to air and saturated aniline vapor (860 ppm) respectively within 100 s (8FP-2F films: λex = 383 nm, λem = 483 nm; 2FP-F films: λex = 363 nm λem = 434 nm). The inset picture was taken at the excitation of UV lamp before and after exposure of 8FP-2F films to aniline vapor within 300 s.

Figure 3. SEM image of 8FP-2F (a) and 2FP-F (b) films on a quartz substrate prepared with THF solvents (with a concentration of 1 mg/mL).

Sensory properties. To investigate the photostability in air and sensing performance in aniline vapor, the time-course

Beyond that, selectivity is another important aspect for a nice fluorescent probe. Fig.5 showed the fluorescence quenching rates of 8FP-2F films against common interfering saturated vapors such as air, benzylamine (saturated vapor pressure, 4.98×105 ppm), propylamine (3.25×105 ppm), dimethylamine (2.48×105 ppm), trimethylamine (3.95×107 ppm), H2O, toluene, CH2Cl2, THF and acetone. Compared with the rate of ~89% in aniline vapor, the responses rates of other volatile organic amines indicated they would not interfere with the detection dependent on the fluorescence quenching process. Meanwhile, in common solvents vapors, such as H2O, toluene, CH2Cl2, THF and acetone, the responses were so small that the interference can be ignored as shown in Fig.5.

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Figure 5. Fluorescence responses of 8FP-2F film in different saturated vapor compounds in 3 minutes

benzylamine, (0.15, 0.12) in propylamine, (0.16, 0.28) in dimethylamine, (0.16, 0.28) in trimethylamine, respectively, according to the fluorescent spectra. The value of 8FP-2F in aniline vapor could not be calculated because of its weak fluorescence in Fig.6b. Meanwhile, the result of 8FP-2F film in propylamine vapor was significantly different from other amines. Hence, there is no interference in the presence of propylamine vapor. Fig.S12 exhibited the emission maximum of 8FP-2F film blue-shifted 22 nm and 8 nm in saturated propylamine and benzylamine vapor, respectively. As comparison, there was almost no fluorescence in aniline vapor. Fig. S13 demonstrated the excitation peak of 8FP-2F film red shifted 25 nm upon exposure to saturated aniline vapor. However, there only witnessed breadth changes in other amines vapor. The result indicated there existed chemical reaction between 8FP-2F and aniline. Furthermore, the chemical reaction was not effective in benzylamine and propylamine. Therefore, all these results indicated propylamine and benzylamine vapor would not interfere with the detection of aniline vapor.

Figure 6. (a) 8FP-2F filters excited by UV lamp 365 nm after 3 minutes’ exposure in (1, air; 2, aniline; 3, benzylamine; 4, propylamine; 5, dimethylamine; 6, trimethylamine;). (b) CIE 1931 (x, y) chromaticity diagram of the 8FP-2F films in above saturated vapors.

In order to check if 8FP-2F probes could selectively detect aniline vapor over other amines, we tested fluorescence colors of 8FP-2F film after exposed a series of saturate organic amines within 180 s. As shown in Fig.6a, aniline, benzylamine, propylamine, dimethylamine and trimethylamine represented aromatic, primary, tertiary and secondary amines, respectively. The fluorescence of 8FP-2F was totally quenched in aniline vapor in 180 s while there were no obvious fluorescent color change in benzylamine, dimethylamine and trimethylamine vapor. Hence, they will not interfere the detection of aniline vapor by naked eyes. Fig.6b described the accurate fluorescence colors based on CIE 1931 system. The values of the color were (0.18, 0.33) in air, (0.16, 0.30) in

Figure 7. (a) Quenching efficiency of the 8FP-2F film towards different vapor pressures of aniline after an exposure of 100 s (λex= 383 nm, λem= 483 nm). (b) Fluorescence rates (1 − I/I0) of 8FP-2F films as a function of the vapor pressure of aniline, data (error 5%) fitted with the Langmuir equation.

To acquire the detection limit, the quenching extent of 8FP2F films in different vapor pressure of aniline were carried out. Starting from saturated vapor, the aniline vapor was diluted with fresh air by half after each test. Fig.S14 provided the emission spectra changes of 8FP-2F films against different aniline vapor concentration. Cleary, the emission intensity

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decreased with the increase of aniline vapor pressure at room temperature. Fig.7a showed the actual quenching rates of 8FP2F films against a series of aniline vapor pressure (860−0.21 ppm). The detectable aniline vapor pressure was as low as 0.21 ppm and the corresponding quenching rate was ~ 10%. Fig.7b showed the linear fitting of quenching efficiency versus the changes of aniline concentration by the Langmuir equation. If allowing for the Signal Noise Ratio (SNR) as 1%, the detection limit of aniline vapor is calculated to be ~ 3 ppb, which is far below the Immediately Dangerous to Life or Health concentration (IDLH) of 200 ppm. The result demonstrated that the 8FP-2F probe is highly sensitive to aniline vapor. Sensing Mechanism and the Expansion of Sensing Method. To determine detection mechanism, nuclear magnetic resonance (NMR) experiments were carried out. Considering the complicated molecular structure of 8FP-2F, the relatively simple and similar molecular 2FP-F was selected as the model probe for verifying the sensing mechanism. Protons signal of aldehyde groups of 2FP-F is at 10.08 ppm (Figure S3). After exposure to aniline, benzylamine and propylamine vapor, the proton signal at 10.08 ppm almost disappeared and new protons with single peak at 8.53, 8.462 and 8.33 ppm appeared for aniline, benzylamine and propylamine, respectively, corresponding to the formation of Schiff base (Figure S5−S8). Mass spectra also support the formation of the Schiff base (Figure S6). So the sensing of amines is related to a chemical reaction mechanism. 2AF-F, 2 PF-F and 2BF-F were generated after reaction in aniline, propylamine and benzylamine respectively (Figure S15). The final products with Schiff base structure are known to show poor fluorescence26, which resulted in fluorescence quenching.

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between the Schiff base reaction product and aniline, which triggered more efficient fluorescence quenching. As comparison, the HOMO energy levels of 8FP-2F/2FP-F are higher than that of benzylamine and propylamine, so the PET did not occur from them to 8FP-2F/2FP-F. Hence, the chemical reaction and PET worked together to greatly enhance the sensing performance and both contribute to the efficient fluorescence quenching for tracing aniline vapor in this manuscript.

Conclusions In summary, we designed and synthesized a multipleanchored fluorescent probe 8FP-2F. Compared with other fluorescent probes for aniline detection, 8FP-2F exhibited distinguish advantages such as: (a) low detection (~3 ppb), fast response, excellent selectivity (b) the suitable HOMO/LUMO energy levels of 8FP-2F probe ensured chemical reaction and PET process could work together to significantly enhance the sensing performance only towards aniline vapor. SEM images showed 8FP-2F tended to self-assemble into nanoparticles and the size of the nanospheres could be tuned by concentration to provide excellent contact area for analytes and hence high sensitivity. However, since the detection is related to a chemical reaction mechanism, the disadvantage of the probe is it could not be reused. But, considering the very cheap price to make the thin film device, it could be used as a throwaway device. More importantly, due to the multiple active sites structure of 8FP-2F, it could be applied for constructing many interesting structures such as conjugated organic frame and highly efficient organic optoelectronic functional materials. Hence, 8FP-2F may find its broad application in many fields. Further study is in progress in our lab.

ASSOCIATED CONTENT The Supporting Information includes NMR data, MS data, SEM, fluorescence excitation spectra, sensing performance data, and simulation Parameter settings is available free of charge on the ACS Publications website at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author Qingguo He* E-mail: [email protected]; Figure 8. Energy levels and electron distributions of 2FP-F and 2AF-F

Jiangong Cheng *Email:[email protected].

Combined with the result in Fig.4, if the sensing of amines is solely based on a Schiff base reaction mechanism, the reaction will proceed completely within 25 s. But generally such organic reaction could not happen so quickly. There may be other sensing mechanism to make the fluorescence quench so quickly. It is known PET between some fluorophores and receptors can also result in fluorescence quenching. In order to verify if PET mechanism also worked in the sensing process, the energy levels of 8FP-2F/2FP-F and different amines were calculated using DMOL3 of Materials Studio 8.0. The detailed parameters and specific methods were shown in supporting information Table S1. As shown in Fig.8 and Table S2, the HOMO levels of 2FP-F and the Schiff base (2AF-F) are both lower than that of aniline, which could guarantee PET from aniline to 2FP-F/2AF-F at their excited states, leading to fluorescence quenching. In other words, PET not only happened between the probe and aniline, but also occurred

All authors have given approval to the final version of the manuscript.

Author Contributions

ACKNOWLEDGMENT This work was supported by the research Programs from Ministry of Science and technology (Grant No.: 2016YFA0200800), the National Natural Science Foundation of China (Grant No. 61325001, 51473182, and 51641307), and a grant from the Youth Innovation Promotion Association CAS (2015190).

REFERENCES (1) Sangeetha, P. T.; Ramesh, M. N.Prapulla, S. G. Fructooligosaccharide production using fructosyl transferase obtained from recycling culture of Aspergillus oryzae CFR 202. Process Biochemistry 2005, 40 (3-4), 10851088. (2) Kataoka, H. Derivatization reactions for the determination of amines by gas chromatography and their applications in environmental analysis. J. Chromatogr. A 1996, 733, 19-34.

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Table of Contents/Abstract Graphics

A multiple-anchored fluorescence probe was designed and synthesized for detection of aniline vapor with distinguished sensitivity and selectivity based on synergistic effect of chemical reaction and PET.

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