DonorâAcceptor Conjugated Polymer Dots for Tunable

Letter pubs.acs.org/JPCL

Cite This: J. Phys. Chem. Lett. 2018, 9, 5296−5302

Donor−Acceptor Conjugated Polymer Dots for Tunable Electrochemiluminescence Activated by Aggregation-Induced Emission-Active Moieties Ziyu Wang,†,§ Yaqiang Feng,‡,§ Ningning Wang,‡ Yixiang Cheng,*,† Yiwu Quan,*,† and Huangxian Ju*,‡

Downloaded via KAOHSIUNG MEDICAL UNIV on November 24, 2018 at 09:39:50 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

†

MOE Key Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, PR China ‡ State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, PR China S Supporting Information *

ABSTRACT: Low-potential electrochemiluminescence (ECL) luminophores with excellent ECL behavior have attracted considerable interest in biological analysis. Herein, we describe the synthesis of two aggregation-induced emission (AIE)-active conjugated polymers with a donor−acceptor (D−A) system via a Suzuki coupling polymerization reaction. The intramolecular D− A pairs enhanced their luminescence intensity in aggregate states, which was beneficial for preparation of conjugated polymer dots (Pdots) as ECL materials. The ECL emission of the P-2 Pdots showed obvious red shift from 578 to 598 nm after the fluorene moiety (P-1) was replaced with a stronger electron-donating carbazole moiety. The ECL property could be regulated with intramolecular charge transfer of the D−A moieties, which led to a sharp decline (553 mV) of ECL anodic potential. Furthermore, the ECL intensity significantly increased about 6 times because of the low lowest unoccupied molecular orbital level, which facilitated the electron injection into the conjugated polymer backbone. This work provides an effective strategy for developing AIE-active ECL materials with low potential and high ECL emission intensity via adjusting the D−A electronic structure.

A

devices,14 memory devices,15 and OLEDs.16 The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of D−A type conjugated polymers can be easily tuned from the donor− acceptor electron ability.17,18 Owing to the strong electron accepting ability, boron-dipyrromethene (BODIPY) derivatives have become one of the most excellent acceptors for design of D−A type organic materials.19,20 Furthermore, the excellent electrochemical properties have also led to their ECL application.21 The ECL process involves the electron transfer of luminophores at electrode surface to form excited states and emit photons.22−25 Thus, adjusting the D−A electronic structure of the conjugated Pdots can efficiently tune the ECL behaviors of the D−A type luminophores.17,26 To achieve small band gap and low ECL potential, which benefit high selectivity and sensitivity of ECL biosensing and avoid some backgrounds,27,28 this work designed and synthesized two kinds of three-component AIE-active conjugated polymers, P-1

ggregation-induced emission (AIE) effects can cause fluorescent emission enhancement of chromophores in the aggregate state1 and have been successfully applied in various fields, such as organic light-emitting diodes (OLEDs),2 bioprobes,3 enantioselective recognition,4 photodynamic cancer therapy,5 and circularly polarized luminescence.6 Among the known AIE-active luminogens, tetraphenylethene (TPE)based luminophores have been regarded as one of the most important families because of their excellent properties, including simple synthesis procedure and high photoquantum yields.7,8 Recently, two AIE-active TPE-bridged tetraimidazolium salts have been reported to display “turn-on” fluorescence signal after complexing with AgI and AuI because of the inhibition to the intramolecular rotation of phenyl rings in the chelate complex,9 and AIE-active Pt(II) complexes have been designed to produce the enhanced electrochemiluminescence (ECL) signals.10 The donor−acceptor (D−A) type conjugated polymers generally undergo the intramolecular charge transfer (ICT) from electron donor to acceptor,11 which forms an inner complex donor−acceptor pair because the band gap depends on the overlap of D/A wave functions.12 These polymers have been used as organic photovoltaic materials,13 electrochromic © 2018 American Chemical Society

Received: July 4, 2018 Accepted: August 29, 2018 Published: August 29, 2018 5296

DOI: 10.1021/acs.jpclett.8b02087 J. Phys. Chem. Lett. 2018, 9, 5296−5302

Letter

The Journal of Physical Chemistry Letters Scheme 1. Synthetic Routes of P-1 and P-2

Figure 1. AFM images of P-1 Pdots (A) and P-2 Pdots (D) and corresponding height profiles along the lines for P-1 Pdots (B) and P-2 Pdots (E). DLS of P-1 Pdots (C) and P-2 Pdots (F). Vertical color bar: 20 nm.

intramolecular FRET pair, fluorene or carbazole unit as the FRET donor, and TPE component as the FRET acceptor. (iii) The TPE-BODIPY components acted as the second intramolecular FRET pair, TPE component as the FRET donor, and BODIPY component as the FRET acceptor. Both P-1 and P-2 contained one electron D−A pair and two intramolecular FRET pairs. The P-1 and P-2 Pdots could be prepared by a nanoprecipitation method utilizing P-1 and P-2 as luminescent precursor and poly(styrene-co-maleic anhydride) (PSMA) as functional reagent (Supporting Information). The latter could produce the carboxyl groups on the Pdots surface by hydrolysis of the maleic anhydride.29 The AFM images of the P-1 and P-2 Pdots demonstrated an essential spherical morphology and monodisperse feature (Figure 1A,D), and their corresponding height profiles indicated the average particle size of 8.9 nm for P-1 Pdots (Figure 1B) and 13.4 nm for P-2 Pdots (Figure 1E). DLS data gave an average hydration diameter of 10.4 nm for P1 Pdots (Figure 1C) and 15.1 nm for P-2 Pdots (Figure 1F), which were consistent with the AFM analysis. P-1 and P-2 in THF showed strong ultraviolet−visible (UVvis) absorption at 346 and 300 nm with a shoulder peak (343

and P-2, with D−A type structure (Scheme 1). When the fluorene linker of P-1 was replaced by the strong electrondonating carbazole moiety (P-2), the ECL anodic potential sharply decreased by 553 mV and the ECL emission intensity increased obviously by about 6 times. Two intramolecular Förster resonance energy transfer (FRET) pairs in the D−A type Pdots went from fluorene or carbazole linker to AIEactive TPE moiety and then from TPE moiety to BODIPY chromophore, which greatly enhanced the luminescence emission intensity and activated ECL behavior in aggregate states. This work provides a new strategy for developing excellent ECL materials with low ECL potential and high ECL signal promoted from the D−A electronic structure and intramolecular FRET mechanism. The detailed synthesis procedures and characterization data of P-1 and P-2 and model polymers 1−4 are outlined in Scheme S1 and Table S1 (Supporting Information). Here, the groups in P-1 and P-2 acted with different functions: (i) The fluorene/carbazole-BODIPY components acted as the D−A electronic system, fluorene or carbazole unit as the electron donor, and the BODIPY component as the electron acceptor. (ii) The fluorene/carbazole-TPE components acted as the first 5297


Letter

The Journal of Physical Chemistry Letters

increasing from 0% to 40%, the emission peak at 411 nm did not obviously change (Figure S1), but it decreased and completely disappeared at f w > 60%. In addition, the emission peak at 575 nm appeared to gradual increase at f w > 40% and reached the maximum intenisty at f w = 80% with a 5 nm red shift (photoquantum yield: 16% using 3.33 μg mL−1 quinine sulfate in 0.1 M H2SO4 solution as a standard), which could be attributed to the intramolecular FRET from the TPE moiety to BODIPY chromophore.35,36 Because of the nonemission character of the TPE moiety, the intramolecular FRET process could not occur in solvent THF. Therefore, P-1 exhibited an obvious fluorene emission signal at f w < 40%. With the increase of f w, the polymer gradually formed the aggregate, which restricted molecular vibration of phenyl rings in the TPE moiety and led to aggregation-induced fluorescence enhancement. At f w > 50%, AIE-active P-1 emitted strong orangecolored fluorescence from the BODIPY chromophore that enhanced gradually via intramolecular FRET mechanism. P-2 exhibited similar AIE behavior (photoquantum yield: 10%) but much weaker emission intensity than P-1 (Figure 3B). Two emission peaks situated at 426 and 595 nm could be assigned to carbazole moiety and BODIPY moiety, respectively. The emission peak at 426 nm disappeared at f w > 10%, while the emission of BODIPY chromophore gradually enhanced at f w > 40% and reached the maximum intensity at f w = 80% with a 5 nm red shift (Figure S2). Compared with the weaker electrondonating fluorene group in P-1, P-2 showed a 20 nm red shift due to the stronger intramolecular donor−acceptor interaction between carbazole and BODIPY moieties.37 To explain the mechanism of two intramolecular FRET pairs in P-1 and P-2, we synthesized four model polymers, 1−4. The fluorescence emission peak of model polymer 1 with only a fluorene moiety centered at 416 nm (Figure 3C, curve b), which overlapped with the UV-vis absorption of P-1 (Figure 3C, curve a) in the region from 380 to 430 nm, demonstrating the first FRET pair from fluorene moiety to TPE moiety.38 As evidence for the second intramolecular FRET process, the fluorescence spectrum of model polymer 2 in aggregate state (Figure 3C, curve c) overlapped with the UV-vis absorption of P-1 (Figure 3C, curve a) in the region of 490−580 nm, indicating the effective energy transfer from TPE moiety to BODIPY moiety. Similarly, the mechanism of two intramolecular FRET pairs in P-2 could be confirmed in Figure 3D. To further explore the second intramolecular FRET of these two polymers, we recorded the fluorescence emission spectra at excitation wavelength (λex) of 520 nm (Figure 3E,F). Only the emission of BODIPY could be observed at 578 nm (P-1) and 597 nm (P-2), which indicated that no FRET process from TPE to BODIPY occurred because of the nonemission transition of fluorene and TPE moieties. Interestingly, both P1 and P-2 in the aggregate state showed obvious aggregationcaused quenching (ACQ) behavior, which could further demonstrate the second intramolecular FRET pair from TPE to BODIPY chromophore. Meanwhile, the weighted average lifetimes of P-1 (2.17 ns) and P-2 (1.59 ns) were much longer than those of model polymer 2 (1.10 ns) and model polymer 4 (0.88 ns), respectively (Figure S3), which confirmed the second FRET process. The electrochemical studies of P-1 and P-2 were carried out in CH2Cl2 solution containing 0.1 M Bu4NBF4 as the supporting electrolyte. The energy levels were evaluated from the cyclic voltammograms (CVs) and are summarized in Table 1. The CVs of P-1 showed two quasi-reversible oxidation peaks

nm), respectively (Figure 2), which could be assigned to the extended π-conjugation polymer backbone. Compared with P-

Figure 2. UV-vis absorbance of P-1 and P-2 in THF at 1.0 × 10−5 M corresponding to fluorene or carbazole moiety.

1, P-2 showed a ∼46 nm blue shift and another shoulder peak owing to the difference of electron-donating ability between fluorene and carbazole moieties30,31 and the cross-shaped conjugation structure of P-2.32−34 Both P-1 and P-2 showed weak absorbance peaks at around 538 nm, which could be attributed to the ICT between electron-rich donor and electron-deficient acceptor along the conjugated polymer chain backbone.30 The fluorescence spectrum of P-1 in THF-H2O mixture with the excitation wavelength of 370 nm gave two main emission peaks at 411 and 575 nm (Figure 3A). The weaker emission at 411 nm was from the fluorene moiety, while the strong peak at 575 nm could be regarded as the emission of the BODIPY chromophore. With the water fraction ( f w )

Figure 3. (A) P-1 and (B) P-2 in THF-H2O mixtures; λex = 370 nm. (C) UV-vis absorbance of P-1 in THF (a) and PL spectra of model polymer 1 in THF (b) and model polymer 2 in THF-H2O mixture (f w = 99%) (c); λex = 370 nm. (D) UV-vis absorbance of P-2 in THF (a) and PL spectra of model polymer 3 in THF (b) and model polymer 4 in THF-H2O mixture (f w = 99%) (c); λex = 370 nm. (E) P1 and (F) P-2 in THF-H2O mixtures; λex = 520 nm. Polymer concentration: 1 × 10−5 M corresponding to fluorene or carbazole moiety. 5298


Letter


Figure 3A) and 2.084 eV for P-2 (emission wavelength: 595 nm, Figure 3B) through the formula Eg = 1239.8/λ (eV). The electrochemical gaps were very close to their optical energy gaps, indicating that the electrochemical measurement of the LUMO and HOMO energy levels were reliable. Moreover, the band gap of P-2 showed an obvious decline compared with P1, which could be mainly assigned to its stronger ICT interaction. In nitrogen-saturated 0.1 M pH 7.4 PBS, the P-1 Pdotsmodified electrode showed an oxidation peak at +0.984 V (Figure 5, curve a), which was lower than the +1.422 V of P-2

Table 1. Electrochemical data and calculated energy levels of P-1 and P-2 polymer

EOx onset (Va)

ERed onset (Va)

HOMO (eVb)

LUMO (eVb)

Eg (eVb)

P-1 P-2

+0.788 +0.778

−1.396 −1.123

−5.468 −5.458

−3.284 −3.557

2.184 1.901

a Potential was versus Ag/Ag+. bFerrocene couple (Fc/Fc+) was used as the internal reference. The energy levels were calculated using the following equations: EHOMO = −(EOx onset − EFc/Fc+ + 4.8) eV, ELUMO = + −(ERed onset − EFc/Fc+ + 4.8) eV, EFc+/Fc = 0.12 V vs Ag/Ag , Eg = ELUMO − EHOMO.

at +0.982 and +1.385 V with an onset oxidation potential of +0.788 V, while the oxidation peak potentials of P-2 appeared at +0.911 and +1.257 V, respectively, with an onset oxidation potential of +0.778 V (Figure 4A,B). These oxidation peaks

Figure 5. CVs (a and b) and ECL (a′ and b′) of P-1 Pdots (a and a’) and P-2 Pdots (b and b’) modified GCE in 0.1 M pH 7.4 nitrogensaturated PBS. Scan rate: 100 mV s−1 for CV and 500 mV s−1 for ECL. PMT: 850 V.

Pdots (Figure 5, curve b), indicating that both Pdots could be electrochemically oxidized to radical cation and that the oxidization of P-2 Pdots was more difficult in the aqueous medium. Both P-1 and P-2 Pdots exhibited ECL emission in the anodic potential window (Figure 5, curves a′ and b′), indicating that the radical anions of Pdots were more stable than their radical cations. The P-1 Pdots-modified electrode showed an anodic ECL emission peak at +1.476 V with an onset potential of +1.174 V, while the P-2 Pdots-modified electrode showed an anodic ECL emission peak at +0.923 V with an onset potential of +0.722 V. Interestingly, compared with P-1 Pdots, P-2 Pdots-modified electrode not only gave an obvious decline of ECL peak potential by 553 mV but also exhibited a significantly enhanced ECL emission. This phenomenon could be attributed to the stronger D−A electronic structure in P-2 than P-1, which led to a lower LUMO energy level and facilitated the electron injection into the polymer. The mechanism for this annihilation ECL could be proposed as in eqs 1−4:

Figure 4. CVs of P-1 and P-2 (A), TPE (C), and BODIPY (D) in 0.1 M Bu4NBF4 CH2Cl2 solution. (B) Magnified CVs from black rectangle in panel A. Concentration: 1.0 mM. Scan rate: 100 mV s−1.

were mainly contributed by the oxidation of TPE, which gave two consecutive one-electron oxidation peaks at +1.246 V and +1.549 V (Figure 4C).39 The D−A electronic structure could be extended to the whole conjugated system, which led to it being more prone to oxidation in the polymer than that in the TPE monomer. Moreover, the acceptor BODIPY monomer showed a Nernstian one-electron oxidation and reduction at half-wave potential of +1.009 and −1.434 V, respectively (Figure 4D).40 More carefully, P-2 could be oxidized more easily than P-1 (Figure 4B), which could be attributed to the stronger electron-donating ability of the carbazole moiety in P2.41 Moreover, P-2 showed better reversibility than P-1, indicating the radical cations of P-2 were more stable than P-1, which was helpful for improving the efficiency in the annihilation routes or coreactant routes. Both P-1 and P-2 did not show the reduction wave until −1.396 and −1.123 V, respectively (Figure 4A), where electrons began to inject into the polymer to produce corresponding radical anions. The band gaps of P-1 and P-2 could be calculated by the separation between the onset oxidation potential and onset reduction potential (Table 1) and gave the values of 2.184 and 1.901 eV for P-1 and P-2, respectively. Their optical band gaps in THF could also be calculated as 2.156 eV for P-1 (emission wavelength: 575 nm,

Pdots + e− → Pdots•−

(1)

Pdots − e− → Pdots•+

(2)

Pdots•+ + Pdots•− → Pdots*

(3)

Pdots* → Pdots + hv

(4)

To explore the most suitable coreactant, four kinds of coreactants were examined, and only TPrA could obviously enhance the ECL emission of these Pdots (Figures 6, S4, and S5). After coreactant TPrA was added into the PBS, the Pdotsmodified electrodes displayed a strong ECL emission at +1.515 V for P-1 Pdots (Figure 6A, curve a) and +1.028 V for P-2 Pdots (Figure 6A, curve b). The obviously enhanced ECL emission of P-2 Pdots could also be observed, which gave about 6 times enhancement compared with P-1 Pdots. Meanwhile, the oxidation of TPrA appeared between +0.588 and +1.305 V (Figure 6B, curve c), which was between the 5299


Letter


the excited state decayed back to the ground state (eq 9). The ECL efficiencies of P-1 and P-2 Pdots relative to the Ru(bpy)32+/TPrA system were calculated to be 5.8% and 11.8%, respectively (see Experimental Section and Table S2 in the Supporting Information). It should be noted that the ECL signals of both P-1 and P-2 Pdots-modified GCEs in 0.1 M PBS (pH 7.4) containing 0.1 M KNO3 and 0.1 M TPrA constantly decreased with the continuous cyclic voltammetric scanning. This was ascribed to the consumption of the immobilized Pdots (Figures S6). In summary, two AIE-active D−A type conjugated polymers P-1 and P-2 containing fluorene, carbazole, TPE, and BODIPY moieties were synthesized via Suzuki reaction. Two intramolecular FRET pairs were introduced in the polymers with TPE moiety as a linker, which was beneficial to the enhancement of luminescence intensity in the aggregate state. After the fluorene moiety in P-1 was replaced with the stronger electron-donating carbazole moiety, the AIE emission of the P-2 displayed an obvious red shift of 25 nm and relatively weaker AIE intensity than P-1 due to the stronger ICT mechanism. The strong electron-donating carbazole moiety made the electrochemical oxidation of the polymer easier and the ECL emission from corresponding Pdotsmodified electrode significantly stronger, in both annihilation and coreactant ECL emission. In the annihilation route, the presence of carbazole moiety decreased the anodic ECL peak potential by 553 mV. In the coreactant route, the ECL emission originated from the band gap emission of corresponding Pdots. This work provides a novel strategy for developing AIE-active ECL luminphor with low potential and high ECL intensity via adjusting the D−A electronic structure.

Figure 6. (A) Coreactant ECL and (B) corresponding CVs of P-1 Pdots (a), P-2 Pdots (b) modified GCE, and bare GCE (c) in 0.1 M pH 7.4 PBS in the presence of 0.1 M TPrA as anodic coreactant. Scan rate: 100 mV s−1. PMT: 700 V.

oxidation peaks of P-1 Pdots- and P-2 Pdots-modified electrodes (Figure 6B, curves a and b), indicating that the direct charge transfer for oxidizing TPrA was apparently blocked.42 The large potential window up to +1.8 V of PBS solutions provided a suitable medium for ECL study. In the presence of TPrA in PBS, the ECL spectrum of P-1 Pdots-modified carbon electrode showed an ECL emission peak at 578 nm with a full width at half-maximum (fwhm) of 123.2 nm (Figure 7A), which was consistent with the

■ S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jpclett.8b02087. Experimental section; synthesis of P-1 and P-2 and model polymers 1−4; AFM and DLS of P-1 and P-2 Pdots; UV-vis absorbance and fluorescence of P-1 and P-2; CVs and ECL of P-1 and P-2 Pdots; fluorescence lifetime and 1H NMR spectra of P-1 and P-2 and model polymers 1−4 (PDF)

fluorescence emission peak of P-1 in 80% H2O/THF mixtures (580 nm), indicating the same excited species. Similarly, the ECL spectrum of P-2 Pdots-modified electrode displayed a more symmetric and sharp ECL emission peak at 598 nm with a fwhm of 58.6 nm (Figure 7B), which was consistent with the fluorescence emission peak of P-2 in 80% H2O/THF mixtures (600 nm). Thus, both ECL emissions originated from the band gap emission of corresponding Pdots.29 The detailed ECL mechanism of the Pdots/TPrA system is described as follows: TPrA − e− → TPrAH•+

(5)

TPrAH•+ − H+ → TPrA•

(6)

Pdots − e− → Pdots•+ Pdots

•+

Pdots* → Pdots + hv

■

+

AUTHOR INFORMATION

Corresponding Authors

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

(7)

+ TPrA → Pdots* + Pr2N HCCH 2CH3 •

ASSOCIATED CONTENT

* Supporting Information

Figure 7. ECL spectra of P-1 Pdots (A) and P-2 Pdots (B) in 0.1 M pH 7.4 PBS containing 30 mM TPrA as coreactant.

ORCID (8)

Yixiang Cheng: 0000-0001-6992-4437 Yiwu Quan: 0000-0001-6017-1029 Huangxian Ju: 0000-0002-6741-5302

(9)

During the anodic scanning, the coreactant TPrA first became TPrAH+• between +0.60 and +1.20 V (eq 5) and then underwent deprotonation to produce TPrA• as a strong reducing agent (eq 6). At higher potentials (>1.20 V), the Pdots were oxidized to form Pdots radical cation (eq 7). Then the TPrA• injected electrons into the LUMO energy level of the Pdots radical cation to produce an excited state (eq 8). Finally, the intense ECL was obtained to give P-1 Pdots centered at 578 nm and P-2 Pdots centered at 598 nm, while

Author Contributions §

Z.W. and Y.F. contributed equally to this work.

Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was supported by National Natural Science Foundation of China (21674046, 51673093, 21635005, and 5300


Letter


(17) Omer, K. M.; Ku, S.-Y.; Cheng, J.-Z.; Chou, S.-H.; Wong, K.-T.; Bard, A. J. Electrochemistry and Electrogenerated Chemiluminescence of a Spirobifluorene-Based Donor (Triphenylamine)− Acceptor (2, 1, 3-Benzothiadiazole) Molecule and Its Organic Nanoparticles. J. Am. Chem. Soc. 2011, 133, 5492−5499. (18) Lai, R. Y.; Fabrizio, E. F.; Lu, L.; Jenekhe, S. A.; Bard, A. J. Synthesis, Cyclic Voltammetric Studies, and Electrogenerated Chemiluminescence of A New Donor Acceptor Molecule: 3, 7-[Bis [4-Phenyl-2-Quinolyl]]-10-Methylphenothiazine. J. Am. Chem. Soc. 2001, 123, 9112−9118. (19) Loudet, A.; Burgess, K. BODIPY Dyes and Their Derivatives: Syntheses and Spectroscopic Properties. Chem. Rev. 2007, 107, 4891− 4932. (20) Usta, H.; Yilmaz, M. D.; Avestro, A. J.; Boudinet, D.; Denti, M.; Zhao, W.; Stoddart, J. F.; Facchetti, A. BODIPY-Thiophene Copolymers as p-Channel Semiconductors for Organic Thin-Film Transistors. Adv. Mater. 2013, 25, 4327−4334. (21) Hesari, M.; Swanick, K. N.; Lu, J. S.; Whyte, R.; Wang, S.; Ding, Z. Highly Efficient Dual-Color Electrochemiluminescence from BODIPY-Capped PbS Nanocrystals. J. Am. Chem. Soc. 2015, 137, 11266−11269. (22) Miao, W. J. Electrogenerated Chemiluminescence and Its Biorelated Applications. Chem. Rev. 2008, 108, 2506−2553. (23) Liu, Z. F.; Qi, W. J.; Xu, G. B. Recent Advances in Electrochemiluminescence. Chem. Soc. Rev. 2015, 44, 3117−3142. (24) Hesari, M.; Ding, Z. A Grand Avenue to Au Nanocluster Electrochemiluminescence. Acc. Chem. Res. 2017, 50, 218−230. (25) Swanick, K. N.; Sandroni, M.; Ding, Z.; Zysman-Colman, E. Enhanced Electrochemiluminescence from a Stoichiometric Ruthenium(II)-Iridium(III) Complex Soft Salt. Chem. - Eur. J. 2015, 21, 7435−7440. (26) Ishimatsu, R.; Matsunami, S.; Kasahara, T.; Mizuno, J.; Edura, T.; Adachi, C.; Nakano, K.; Imato, T. Electrogenerated Chemiluminescence of Donor-Acceptor Molecules with Thermally Activated Delayed Fluorescence. Angew. Chem., Int. Ed. 2014, 53, 6993−6996. (27) Dong, Y.; Wu, H.; Shang, P.; Zeng, X.; Chi, Y. Immobilizing Water-Soluble Graphene Quantum Dots with Gold Nanoparticles for A Low Potential Electrochemiluminescence Immunosensor. Nanoscale 2015, 7, 16366−16371. (28) Xu, S.; Liu, Y.; Wang, T.; Li, J. Positive Potential Operation of A Cathodic Electrogenerated Chemiluminescence Immunosensor Based on Luminol and Graphene for Cancer Biomarker Detection. Anal. Chem. 2011, 83, 3817−3823. (29) Ye, M.; Wu, C.; Jin, W.; Wang, M.; Chan, Y. H.; Yu, J.; Sun, W.; Hayden, S.; Chiu, D. T. A Compact and Highly Fluorescent OrangeEmitting Polymer Dot for Specific Subcellular Imaging. Chem. Commun. 2012, 48, 1778−1780. (30) Ma, X.; Azeem, E. A.; Liu, X. H.; Cheng, Y. X.; Zhu, C. J. Synthesis and Tunable Chiroptical Properties of Chiral BODIPYBased D-π-A Conjugated Polymers. J. Mater. Chem. C 2014, 2, 1076− 1084. (31) Zhang, L.; Zeng, S. H.; Yin, L. X.; Ji, C. Y.; Li, K. C.; Li, Y. Q.; Wang, Y. The Synthesis and Photovoltaic Properties of A-D-A-Type Small Molecules Containing Diketopyrrolopyrrole Terminal Units. New J. Chem. 2013, 37, 632−639. (32) Wang, H.; Wan, J. H.; Jiang, H. J.; Wen, G. A.; Feng, J. C.; Zhang, Z. J.; Peng, B.; Huang, W.; Wei, W. Synthesis and Characterization of Cross-Shaped p−n Diblock Oligomers. J. Polym. Sci., Part A: Polym. Chem. 2007, 45, 1066−1073. (33) Sung, H. H.; Lin, H. C. Novel Alternating Fluorene-Based Conjugated Polymers Containing Oxadiazole Pendants with Various Terminal Groups. Macromolecules 2004, 37, 7945−7954. (34) Ahrens, M. J.; Sinks, L. E.; Rybtchinski, B.; Liu, W.; Jones, B. A.; Giaimo, J. M.; Gusev, A. V.; Goshe, A. J.; Tiede, D. M.; Wasielewski, M. R. Self-Assembly of Supramolecular Light-Harvesting Arrays from Covalent Multi-Chromophore Perylene-3,4:9,10-bis(dicarboximide) Building Blocks. J. Am. Chem. Soc. 2004, 126, 8284−8294.

21361162002) and State Key Laboratory of Analytical Chemistry for Life Science (SKLACLS1807).

■

REFERENCES

(1) Mei, J.; Leung, N. L. C.; Kwok, R. T. K.; Lam, J. W. Y.; Tang, B. Z. Aggregation-Induced Emission: Together We Shine, United We Soar! Chem. Rev. 2015, 115, 11718−11940. (2) Huang, J.; Nie, H.; Zeng, J.; Zhuang, Z.; Gan, S.; Cai, Y.; Guo, J.; Su, S. J.; Zhao, Z.; Tang, B. Z. Highly Efficient Nondoped OLEDs with Negligible Efficiency Roll-Off Fabricated from AggregationInduced Delayed Fluorescence Luminogens. Angew. Chem., Int. Ed. 2017, 56, 12971−12976. (3) Shi, H. B.; Liu, J. Z.; Geng, J. L.; Tang, B. Z.; Liu, B. Specific Detection of Integrin αvβ3 by Light-Up Bioprobe with AggregationInduced Emission Characteristics. J. Am. Chem. Soc. 2012, 134, 9569− 9572. (4) Xiong, J. B.; Feng, H. T.; Sun, J. P.; Xie, W. Z.; Yang, D.; Liu, M.; Zheng, Y. S. The Fixed Propeller-Like Conformation of Tetraphenylethylene That Reveals Aggregation-Induced Emission Effect, Chiral Recognition, and Enhanced Chiroptical Property. J. Am. Chem. Soc. 2016, 138, 11469−11472. (5) Wu, W. B.; Feng, G. X.; Xu, S. D.; Liu, B. A Photostable FarRed/Near-Infrared Conjugated Polymer Photosensitizer with Aggregation-Induced Emission for Image-Guided Cancer Cell Ablation. Macromolecules 2016, 49, 5017−5025. (6) Liu, J. Z.; Su, H. M.; Meng, L. M.; Zhao, Y. H.; Deng, C. M.; Ng, J. C. Y.; Lu, P.; Faisal, M.; Lam, J. W. Y.; Huang, X. H.; Wu, H. K.; Wong, K. S.; Tang, B. Z. What Makes Efficient Circularly Polarised Luminescence in The Condensed Phase: Aggregation-Induced Circular Dichroism and Light Emission. Chem. Sci. 2012, 3, 2737− 2747. (7) He, B. Z.; Su, H. F.; Bai, T. W.; Wu, Y. W.; Li, S. W.; Gao, M.; Hu, R. R.; Zhao, Z. J.; Qin, A. J.; Ling, J.; Tang, B. Z. Spontaneous Amino-Yne Click Polymerization: A Powerful Tool Toward Regioand Stereospecific Poly(Β-Aminoacrylate)s. J. Am. Chem. Soc. 2017, 139, 5437−5443. (8) Han, J. L.; You, J.; Li, X. G.; Duan, P. F.; Liu, M. H. Full-Color Tunable Circularly Polarized Luminescent Nanoassemblies of Achiral AIEgens in Confined Chiral Nanotubes. Adv. Mater. 2017, 29, 1606503. (9) Sinha, N.; Stegemann, L.; Tan, T. T.; Doltsinis, N. L.; Strassert, C. A.; Hahn, F. E. Turn-On Fluorescence in Tetra-NHC Ligands by Rigidification through Metal Complexation: An Alternative to Aggregation-Induced Emission. Angew. Chem., Int. Ed. 2017, 56, 2785−2789. (10) Carrara, S.; Aliprandi, A.; Hogan, C. F.; De Cola, L. Aggregation-Induced Electrochemiluminescence of Platinum (II) Complexes. J. Am. Chem. Soc. 2017, 139, 14605−14610. (11) Lv, X. J.; Li, W. J.; Ouyang, M.; Zhang, Y. J.; Wright, D. S.; Zhang, C. Polymeric Electrochromic Materials with Donor-Acceptor Structures. J. Mater. Chem. C 2017, 5, 12−28. (12) Mulliken, R. S. The Interaction of Electron Donors and Acceptors. J. Phys. Chem. 1952, 56, 801−822. (13) Wu, J. S.; Cheng, S. W.; Cheng, Y. J.; Hsu, C. S. DonorAcceptor Conjugated Polymers Based on Multifused Ladder-Type Arenes for Organic Solar Cells. Chem. Soc. Rev. 2015, 44, 1113−1154. (14) Steckler, T. T.; Henriksson, P.; Mollinger, S.; Lundin, A.; Salleo, A.; Andersson, M. R. Very Low Band Gap Thiadiazoloquinoxaline Donor-Acceptor Polymers as Multi-Tool Conjugated Polymers. J. Am. Chem. Soc. 2014, 136, 1190−1193. (15) Lee, W. Y.; Wu, H. C.; Lu, C.; Naab, B. D.; Chen, W. C.; Bao, Z. n-Type Doped Conjugated Polymer for Nonvolatile Memory. Adv. Mater. 2017, 29, 1605166. (16) Furue, R.; Nishimoto, T.; Park, I. S.; Lee, J.; Yasuda, T. Aggregation-Induced Delayed Fluorescence Based on Donor/Acceptor-Tethered Janus Carborane Triads: Unique Photophysical Properties of Nondoped OLEDs. Angew. Chem., Int. Ed. 2016, 55, 7171− 7175. 5301


Letter

The Journal of Physical Chemistry Letters (35) Fö rster, T. Zwischenmolekulare Energiewanderung Und Fluoreszenz. Ann. Phys. 1948, 437, 55−75. (36) Prevo, B.; Peterman, E. J. G. Förster Resonance Energy Transfer and Kinesin Motor Proteins. Chem. Soc. Rev. 2014, 43, 1144−1155. (37) Pannipara, M.; Asiri, A. M.; Alamry, K. A.; Arshad, M. N.; ElDaly, S. A. Synthesis, Spectral Behaviour and Photophysics of DonorAcceptor Kind of Chalcones: Excited State Intramolecular Charge Transfer and Fluorescence Quenching Studies. Spectrochim. Acta, Part A 2015, 136, 1893−1902. (38) Wang, Z. Y.; Liu, S.; Wang, Y. X.; Quan, Y. W.; Cheng, Y. X. Tunable AICPL of (S)-Binaphthyl-Based Three-Component Polymers via FRET Mechanism. Macromol. Rapid Commun. 2017, 38, 1700150. (39) Schreivogel, A.; Maurer, J.; Winter, R.; Baro, A.; Laschat, S. Synthesis and Electrochemical Properties of Tetrasubstituted Tetraphenylethenes. Eur. J. Org. Chem. 2006, 2006, 3395−3404. (40) Nepomnyashchii, A. B.; Bard, A. J. Electrochemistry and Electrogenerated Chemiluminescence of BODIPY Dyes. Acc. Chem. Res. 2012, 45, 1844−1853. (41) Booker, C.; Wang, X.; Haroun, S.; Zhou, J.; Jennings, M.; Pagenkopf, B. L.; Ding, Z. Tuning of Electrogenerated Silole Chemiluminescence. Angew. Chem., Int. Ed. 2008, 47, 7731−7735. (42) Tan, X.; Zhang, B.; Zou, G. Electrochemistry and Electrochemiluminescence of Organometal Halide Perovskite Nanocrystals in Aqueous Medium. J. Am. Chem. Soc. 2017, 139, 8772−8776.

5302


DonorâAcceptor Conjugated Polymer Dots for Tunable

Recommend Documents

DonorâAcceptor Conjugated Polymer Dots for Tunable