Supporting Information

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1 Supporting Information Stimulated Emission Controlled Photonic Transistor on a Single Organic Triblock Nanowire Kang Wang, Wenqing Zhang, Zhenhua Gao, Yongli Yan,* Xianqing Lin, Haiyun Dong, Chunhuan Zhang, Wei Zhang, Jiannian Yao, Yong Sheng Zhao* Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing , China ylyan@iccas.ac.cn, yszhao@iccas.ac.cn S1

2 Contents 1. Experimental details 1). Synthesis of model compounds 2). Preparation of organic triblock nanowires (TNWs) 3). Characterizations 2. Figure S1. Synthetic route of compound OPV-D. 3. Figure S2. Synthetic route of compound OPV-A. 4. Figure S3. Normalized absorption and PL spectra of OPV-D and OPV-A in tetrahydrofuran. 5. Figure S4. PL images of OPV-D and OPV-A co-assembled binary nanostructures prepared at different conditions. 6. Figure S5. TEM images and corresponding SAED patterns of OPV-D and OPV-A nanowires. 7. Figure S6. Normalized PL spectra of OPV-D and OPV-A nanowires. 8. Figure S7. Fluorescence lifetime imaging microscopy image and corresponding PL decay curve of a single pure OPV-D nanowire. 9. Table S1. Fitted lifetime components and corresponding relative weights for the areas a and b in Figure 2D. 10. Figure S8. Time-resolved photoluminescence decay profiles of the donor and the acceptor. 11. Figure S9. Schematic illustration of the home-built far-field micro-pl system. S2

3 12. Figure S10. Power dependent profiles of the full-width at half-maximum at 465 nm and 540 nm of a TNW. 13. Figure S11. Light amplification in an individual pure OPV-D nanowire. 14. Figure S12. Group refractive index of OPV-D nanowires and TNWs. 15. Figure S13. Response times of different light signal amplification processes within the TNW. S3

4 Experimental details Synthesis of model compounds The model compounds of 1,4-bis(α-cyano-4-diphenyl)-2,5-diphenylbenzene (referred to as OPV-D) and 1,4-bis(α-cyano-4-diphenylaminostyryl)-2,5-diphenylbenzene (referred to as OPV-A) used in this work were synthesized with Knoevenagel condensation reactions (Figure S1 and Figure S2). Materials: 2,5-Dibromobenzene-1,4-dicarbaldehydewas purchased from Innochem Science & Technology (Beijing, China). 1,4-Dibromo-2,5-dimethylbenzene, 4-(diphenylamino)benzaldehyde, potassium tertobutoxide, and tetra-butyl ammonium hydroxide were purchased from Sigma-Aldrich. All compounds were used without further treatment. Synthesis of 1,4-bis(α-cyano-4-diphenyl)-2,5-diphenylbenzene (OPV-D) Step 1: Synthesis of [1,1';4',1'']terphenyl-2',5'-dicarbaldehyde 1 A mixture of 2,5-dibromobenzene-1,4-dicarbaldehyde (1.0 g), phenylboronic acid (1.1 g), Pd(PPh3)4 (0.2 g), toluene (12.5 ml) and 2 M Na2CO3 solution (2.5 ml) was refluxed at 85 C for 36 hours under nitrogen, then poured into water and extracted using dichloromethane. The organic layer was washed with brine and water and dried over MgSO4. The crude product was purified by flash column chromatography with dichloromethane as eluent. After recrystallized form chloroform, compound S4

5 [1,1';4',1'']terphenyl-2',5'-dicarbaldehyde was obtained in 81% yield. Step 2: Synthesis of OPV-D 2 Phenylacetonitrile (0.6 mmol) and [1,1';4',1''] terphenyl-2',5'-dicarbaldehyde (0.3 mmol) were dissolved in THF (1 ml) and tert-butanol (2 ml) at 40 C under a nitrogen atmosphere. Tetra-n-butylammonium hydroxide (0.05mmol, 1 M solution in methanol) and potassium tert-butoxide (0.05 mmol) were added quickly; then, the mixture was stirred vigorously at 50 C. 20 min later, the mixture was poured into acidified methanol. The precipitate was collected and dissolved in chloroform and then reprecipitated in methanol. The crude product was purified by column chromatography (dichloromethane as eluent) in darkness to give OPV-D (70% yield) as green solid. OHC CHO CN t-buok/tbah THF/t-BuOH CN CN OPV-D Figure S1. Synthetic route of compound OPV-D. Synthesis of 1,4-bis(α-cyano-4-diphenylaminostyryl)-2,5-diphenylbenzene (OPV-A) Step1: Synthesis of 2-(cyanomethyl)-4-(diphenylamino)benzene 3 2-(Cyanomethyl)-4-(diphenylamino)benzene was prepared from 4-(diphenylamino) benzaldehyde upon treatment with tosylmethylisocyanide (TosMIC) and t-buok in a single step. S5

6 Step 2: Synthesis of OPV-A 4 2-(Cyanomethyl)-4-(diphenylamino)benzene (0.21 mmol) and [1,1';4',1''] terphenyl-2',5'-dicarbaldehyde (0.1 mmol) were dissolved in tert-butanol (1.2 ml) and THF (0.8 ml) under a nitrogen atmosphere. Potassium tert-butoxide (0.02 mmol) and tetra-n-butylammonium hydroxide (0.02 mmol, 1 M solution in methanol) were added quickly; then, the mixture was stirred vigorously at 50 C. 20 min later, the mixture was poured into acidified methanol. The crude product was precipitated from methanol and further purified by column chromatography in darkness. OHC CHO N CN t-buok/tbah THF/t-BuOH CN CN N N Figure S2. Synthetic route of compound OPV-A. OPV-A Preparation of organic TNWs The nanowire heterostructures were prepared through a liquid-phase co-assembly method. In a typical preparation, 15 μl of 5 mm OPV-D in tetrahydrofuran (THF) was quickly injected into 1 ml non-solvent, n-hexane, under vigorous sonication at 35 o C. The rapid change of the surroundings induced the nucleation and self-assembly of OPV-D molecules. With the gradual evaporation of THF, the 1D OPV-D nuclei grew epitaxially in the two opposite directions, which provided matrices for the OPV-A S6

7 dopants. After sonicating for 2 min, OPV-D nanowire matrices were formed. Then, 15 μl of 2 mm OPV-A in THF was added into the above colloid solution and sonicated for another 2 min. OPV-A molecules started to assemble cooperatively with OPV-D molecules on both ends of the preformed nanowire matrices, which finally led to the termination of growth in these heterostructures. 1D TNWs would be precipitated from the solution after aging for several hours. By changing the preparation conditions (e.g. solution concentrations and aging times), we can tune the composition of the TNWs from uniform doping nanowires to triblock nanowires with controlled doping ratios. A drop of as-prepared solution was drop-casted onto glass slides and copper grids for further characterizations. Characterizations The morphologies and crystallinity of TNWs were characterized by transmission electron microscopy (TEM, JEOL JEM-1011). The absorption and PL spectra were measured with Shimidazu UV-2600 spectrophotometer and Hitachi F-7000, respectively. The confocal PL images and fluorescence lifetime imaging microscopy (FLIM) images were taken by a Nikon inverted microscope with PicoQuant GmbH time-correlated single-photon counting (TCSPC) mode using 405 nm picosecond pulsed diode laser. Light amplification was investigated with a home-built far-field micro-pl system. The single TNW was locally excited with a focused 400 nm femtosecond laser (fs-laser), which was generated from the second harmonic of the S7

8 fundamental output of a regenerative amplifier (Solstice, Spectra-Physics, 800 nm, 100 fs, 1 khz). For the two-beam excitation, laser beams delivered from a semiconductor laser (Spectra-Physics, 405 nm CW-laser) and fs-laser (400 nm) recombined onto a beam-splitter, and then focused on the samples. The TNWs on glass substrates (refractive index ~1.5) were excited with laser beams through an objective (Nikon CFLU Plan, 50, N.A. = 0.8), with input power altered by neutral density filters. The excitation laser was filtered with a 420 nm long-pass emission filter. The PL signal from the collection point were dispersed with a grating and recorded with a thermal-electrically cooled CCD (Princeton Instruments, ProEm: 1600B). The time-resolved photoluminescence (TRPL) decay profiles of the donor and the acceptor were measured with a streak camera (Hamamatsu photonics, C10910) upon the excitation of a femtosecond laser (100 fs, 1 khz). S8

9 Abs Intensity (a.u.) PL Intensity (a.u.) Wavelength (nm) Figure S3. Normalized absorption (dash) and PL (solid) spectra of OPV-D (blue) and OPV-A (green) in THF solutions. The PL spectrum of OPV-D shows a large overlap with the absorption spectrum of OPV-A in nm wavelength range, which ensures efficient energy transfer in the heterostructures. S9

10 A Triblock increasing OPV-A doping ratio OPV-D Matrices Uniform doping B C D Cyan-Blue-Cyan Green-Blue-Green Orange-Blue-Orange E F G Cyan Green Yellow Figure S4. (A) Schematic illustration for color evolution in binary nanostructures via variation of the preparation conditions. (B-D) PL microscopy images of TNWs prepared with varied OPV-A concentrations. 15 μl of (B) 1 mm, (C) 2 mm, (D) 5 mm OPV-A in THF was added into 1 ml n-hexane 2 min after the addition of OPV-D in THF (15 μl, 5 mm). (E-G) PL microscopy images of NWs prepared with varied OPV-A volumes. Firstly, a stock solution of OPV-D in THF (15 μl, 5 mm) was mixed together with (E) 2 μl, (F) 5 μl, (G) 20 μl of 1 mm OPV-A in THF. Subsequently, the mixed solutions were rapidly injected into 1 ml n-hexane. As illustrated in Figure S4A, several types of binary nanowire heterostructures with distinct color distributions along the axis could be synthesized through carefully S10

11 controlling the co-assembly process of OPV-A molecules in OPV-D matrices. When a small quantity (15 μl, 1 mm) of OPV-A was added into the OPV-D matrices solution, the cyan-blue-cyan triblocks were obtained by the selective doping at the ends of nanowire matrices (Figure S4B). The triblocks turned to be green-blue-green when the concentration of OPV-A was increased to 2 mm (Figure S4C). Orange-blue-orange triblocks were observed if the concentration of OPV-A reached 5 mm (Figure S4D). In addition, three kinds of uniformly doped nanowires (cyan, green, yellow) were prepared by adding different volume (2 μl for Figure S4E, 5 μl for Figure S4F, 20 μl for Figure S4G, respectively) of 1 mm OPV-A with OPV-D (15 μl, 5 mm) simultaneously. Different emission colors in these binary heterostructures were ascribed to the energy transfer from OPV-D to OPV-A as well as the aggregation-induced spectral shift of OPV-A. The morphology and composition of the heterostructures were tuned by varying the doping ratio and preparation conditions, further demonstrating the controllable synthesis of TNWs. S11

12 A (001) B (100) (110) (020) Figure S5. (A-B) TEM images of an OPV-D nanowire (A) and an OPV-A nanowire (B). Scale bars are 500 nm. Insets: SAED patterns of the corresponding wires collected from the microareas marked with the white squares. The SAED patterns of a single OPV-D nanowire (Figure S5A) and a single OPV-A nanowire (Figure S5B) clearly reveal that the wires have single crystal structures growing along the [100] and [010] crystal direction, respectively. In comparison with that of TNWs, we clearly identify that the entire TNWs are almost made up of OPV-D crystals, and only a small amount of guest OPV-A molecules were doped in OPV-D matrices at the ends of TNWs. Meanwhile, both pure and doped OPV-D nanowires exhibit identical SAED patterns, which can be indexed to a OPV-D monoclinic crystal structure (P21/n, a = 6.645(13), b = (6), c = (15), α = 90, β = (3), γ = 90. CCDC No.: ). This indicates that the OPV-D microcrystals retain their original crystal structure and relatively high crystallinity after being doped with OPV-A, which might be ascribed to simple replacement of OPV-D molecules by the acceptor in its crystal lattice because of the structural similarity of the two molecules. 5 On this basis, the S12

13 intermolecular distance can be roughly estimated to be no larger than the parameters of a unite cell, 2.8 nm (b = Å). Such a small intermolecular distance together with large spectroscopic overlap integral (Figure S3) are beneficial for efficient energy transfer via Förster resonance mechanism. S13

14 OPV-D nanowires Normalized Intensity (a.u.) OPV-A nanowires Wavelength (nm) Figure S6. Normalized PL spectra of OPV-D nanowires (blue line) and OPV-A nanowires (green line). The OPV-D and OPV-A nanowires exhibit maximum emission at ~465 and ~560 nm, respectively. The recorded PL spectrum from the central part of TNW is in good consistence with the emission of OPV-D nanowires, indicating that the central part of TNW is composed of OPV-D. The PL spectra from the ends of TNW are dominated by the green emission from OPV-A, which should be ascribed to the efficient energy transfer from OPV-D to the OPV-A dopant. S14

15 A B 4 ns 0 ns C Normalized Intensity (a.u.) IRF t D = 1.19 OPV-D Decay time (ns) Figure S7. (A) Confocal PL image and (B) FLIM image of an OPV-D nanowire in donor channel (450 ± 35 nm). Scale bar is 10 μm. (C) Instrumental response function (IRF, black line) and corresponding PL decay (blue dots) in selected area marked with white frame in (B). As shown in Figure S7A, the confocal PL image exhibits uniform emission in the wavelength range of 450 ± 35 nm, indicating the microwire is made up of pure OPV-D molecules. The fluorescence lifetime image is displayed in Figure S7B and the PL decay curve in the selected area marked with white frame is plotted in Figure S7C. The average lifetime of OPV-D is fitted to be td=1.19 ns, composed of t1=0.94 ns, w1=83% and t2=2.41 ns, w2=17% with χ 2 =0.99. This decay time is almost constant along the entire OPV-D microwire in the absence of energy acceptors. S15

16 Table S1. Fitted lifetime components and corresponding relative weights for the area a and b in Figure 2D. t1 (ns) w1 t2 (ns) w2 t3 (ns) w3 χ 2 td (ns) tda (ns) EFRET a b % The PL decay curves were fitted to multiple exponential function I = A (w1e t/t 1 + w2e t/t 2 + ) + B, where I is the fluorescence intensity of OPV-D, A is the intensity constant, and B is the instrumental background, respectively. The average lifetime was calculated according to the formula tav=w1t1 + w2t2+. The corresponding FRET efficiency were calculated according to EFRET=1-tDA/tD, 6 where tda is the lifetime of donor in presence of acceptor molecules (area a), and td is the lifetime of donor OPV-D in absence of acceptor OPV-A (area b), respectively. The FRET efficiency was determined to be 74.1%, which is pretty high compared with the ever reported heterostructures, 5,7 facilitating significant light amplification within the TNWs. S16

17 A Normalized Intensity (a.u.) OPV-A OPV-D B Normalized Intensity (a.u.) 110 ps OPV-A OPV-D Decay time (ns) Decay time (ns) Figure S8. (A) Intensity normalized time-resolved photoluminescence (TRPL) decay profiles of OPV-D (blue curve) and OPV-A (green curve). (B) Magnified PL decay curves around the peak intensities from (A). Figure S8A gives the PL decay profiles of the donor (~465 nm) and the acceptor (~540 nm) emissions with average decay lifetimes of 0.34 ns and 2.52 ns, respectively, which are in consistence with the FLIM data and the ever-reported results. 8 Furthermore, the PL decay of the acceptor shows a longer rise time than that of the donor, which was displayed in the magnified decay curves in Figure S8B, implying the occurrence of efficient energy transfer. 9 S17

18 405 nm CW Laser ND Filter BS1 800 nm fs-laser 720 SP BBO ND Filter DM Objective 50 LP Iris Lens BS2 CCD Substrate Sample Spectrometer Figure S9. Schematic illustration of the home-built far-field micro-pl system. Light amplification was investigated with a home-built far-field micro-pl system. The single TNW was locally excited with a focused 400 nm fs-laser, which was generated from the second harmonic of the fundamental output of a regenerative amplifier (Solstice, Spectra-Physics, 800 nm, 100 fs, 1 khz). For the two-beam excitation, 405 nm CW-laser and 400 nm fs-laser recombined onto a beam-splitter (BS), and then focused on the sample. The sample on glass substrate (refractive index ~1.5) was excited with laser beams through an objective (Nikon CFLU Plan, 50, N.A. = 0.8), with input power altered by neutral density filters. After passing through a 420 nm long-pass emission filter, the output signal was spatially selected by the iris and analyzed with a spectrometer. S18

19 FWHM (nm) nm 540 nm FWHM (nm) 15 P th = 11.5 μj/cm Pump fluence ( J/cm 2 ) Figure S10. Power dependent profiles of FWHM at 465 nm (blue) and 540 nm (green) of a TNW. The FWHM at 465 nm dramatically decreased from 31.8 nm down to 12.6 nm before and after the threshold (11.5 μj/cm 2, black dash line), exhibiting a typical behavior of lasing performance in OPV-D. In contrast, the FWHM at 540 nm remains unchanged (~140 nm) with pump power increasing, implying the nonlinear enhanced spontaneous emission in the acceptor. S19

20 A Intensity (a.u.) Pump fluence (μj/cm 2 ) B Intensity (a.u.) 15k 10k 5k Wavelength (nm) Pump fluence (μj/cm 2 ) Figure S11. (A) PL spectra taken from an individual pure OPV-D nanowire under varied pump fluences. (B) Power-dependent profiles of the PL intensities at 465 nm. Light amplification at 465 nm was investigated in an individual pure OPV-D nanowire with similar length to that of the triblock nanowire in Figure 3A in the main text. As displayed in Figure S11A, upon excitation of a fs-laser, the outcouplings from the OPV-D nanowire show broad PL emissions covering the wavelength range from 420 nm to 600 nm with the peak centered at 465 nm. The PL intensities at 465 nm display a remarkable growth with the increase of pump power (Figure S11A). The plot of PL intensity at 465 nm versus pump fluence exhibits a nonlinear behavior with a threshold of 3.05 μj/cm 2 (Figure S11B), which demonstrates the occurrence of stimulated emission. In the triblock nanowire, the plot of PL intensity at 465 nm versus pump fluence exhibits a nonlinear behavior with a threshold of 11.5 μj/cm 2 (Figure 3C), which is much larger than that in pure OPV-D nanowire (3.05 μj/cm 2 ). This can be ascribed to S20

21 the highly efficient energy transfer in the TNW. The nonlinear amplification of the acceptor emission in TNW should be ascribed to the cooperative effect of stimulated emission of the donor, and the energy transfer process between them. S21

22 A L = 31.9 μm B y = 2.42*x Intensity (a.u.) L = 28.1 μm L = 25.9 μm λ 2 /2 λ Wavelength (nm) L (μm) 35 Figure S12. (A) Modulated lasing spectra of TNWs with different lengths. (B) The plot and fitted curve of λ 2 /2Δλ (λ= 465 nm) versus the length of TNWs. The lasing spectra of TNWs with different lengths were measured to study the microcavity effects (Figure S12A). For Fabry-Pérot (FP)-type resonance, the mode spacing is given by the equation Δλ = λ 2 /2ngL, where L is the length of nanowire resonator, λ is the emission wavelength, and ng is the group refractive index, respectively. The relation of λ 2 /2Δλ of TNWs against the length (L) of nanowires was plotted (Figure S12B). The linear relationship indicates that the TNWs behave as axial FP optical resonators. Based on the linear fitting relationship, the group refractive index ng at 465 nm was calculated to be ~2.42 for TNWs, which is high enough to induce the tight confinement of the FP-type modes in nanowire structures and enhance the light-matter interactions. The FP-type TNW microcavity can support a standing-wave optical field between the two end facets 10 with the light traveling back and forth to enhanced modulation of S22

23 excitonic emission, which is beneficial for nonlinear signal amplification. (i) Excitation (~fs) (ii) Energy transfer (~ps) (iv) Waveguiding (~fs) (iii) Radiative decay (~ns) Organic Triblock Nanowire Figure S13. Response times of different light signal amplification processes within the organic TNW. (i) absorption induced optical transition of the donor; (ii) energy transfer from the donor to the acceptor; (iii) radiative decay of the acceptor; (iv) optical waveguiding of acceptor emission. In the nanowire-based photonic transistor, light signal amplification can be divided into four processes with different response times: (i) absorption induced optical transition of OPV-D, which takes place at femtosecond scale (~fs), 11 (ii) energy transfer from OPV-D to OPV-A caused by the dipole-dipole interaction (~ps, Figure S8), (iii) radiative decay of OPV-A (~ns, Figure S8), and (iv) the transport of OPV-A photons within tens of micrometers (~fs). Hence, the response time was determined by the slowest step, radiative decay of OPV-A with nanosecond lifetime. It means that the frequency of such organic active devices may reach as high as the order of GHz for the potential high-speed integrated photonics. S23

24 References (1) Xie, Z.; Yang, B.; Liu, L.; Li, M.; Lin, D.; Ma, Y.; Cheng, G.; Liu, S. J. Phys. Org. Chem. 2005, 18, (2) Li, Y.; Li, F.; Zhang, H.; Xie, Z.; Xie, W.; Xu, H.; Li, B.; Shen, F.; Ye, L.; Hanif, M.; Ma, D.; Ma, Y. Chem. Commun. 2007, 3, (3) He, F.; Tian, L. L.; Tian, X. Y.; Xu, H.; Wang, Y. H.; Xie, W. J.; Hanif, M.; Xia, J. L.; Shen, F. Z.; Yang, B.; Li, F.; Ma, Y. G.; Yang, Y. Q.; Shen, J. C. Adv. Funct. Mater. 2007, 17, (4) Li, Y.; Shen, F.; Wang, H.; He, F.; Xie, Z.; Zhang, H.; Wang, Z.; Liu, L.; Li, F.; Hanif, M.; Ye, L.; Ma, Y. Chem. Mater. 2008, 20, (5) Chen, P. Z.; Weng, Y. X.; Niu, L. Y.; Chen, Y. Z.; Wu, L. Z.; Tung, C. H.; Yang, Q. Z. Angew. Chem., Int. Ed. 2016, 55, (6) Biju, V.; Itoh, T.; Baba, Y.; Ishikawa, M. J. Phys. Chem. B 2006, 110, (7) Yang, D.; Duan, P.; Zhang, L.; Liu, M. Nat. Commun. 2017, 8, (8) Li, X.; Gao, N.; Xu, Y.; Li, F.; Ma, Y. Appl. Phys. Lett. 2012, 101, (9) Zhang, Q.; Liu, H.; Guo, P.; Li, D.; Fan, P.; Zheng, W.; Zhu, X.; Jiang, Y.; Zhou, H.; Hu, W.; Zhuang, X.; Liu, H.; Duan, X.; Pan, A. Nano Energy 2017, 32, (10) Zhang, W.; Yan, Y.; Gu, J.; Yao, J.; Zhao, Y. S. Angew. Chem., Int. Ed. 2015, 54, (11) McCusker, J. K. Acc. Chem. Res. 2003, 36, S24