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Photo-controllable and aggregation-induced emission based on photochromic bithienylethene
Dyes and Pigments 123 (2015) 112e115
Contents lists available at ScienceDirect
Dyes and Pigments journal homepage: www.elsevier.com/locate/dyepig
Short communication
Photo-controllable and aggregation-induced emission based on photochromic bithienylethene Lele Chen 1, Jiaqi Zhang 1, Qiaochun Wang, Lei Zou* Key Laboratory for Advanced Materials, Institute of Fine Chemicals, East China University of Science & Technology, Shanghai 200237, PR China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 29 June 2015 Received in revised form 21 July 2015 Accepted 24 July 2015 Available online 1 August 2015
In this article a series of photochromic bithienylethenes containing coumarin fluorescent unit were synthesized and their properties including photochromic behavior and fluorescent properties were also investigated. One compound not only exhibited photochromic behaviors but also had aggregationinduced emission characteristics. The fluorescence could also be enhanced continuously by the photoisomerization reaction. As ring-closed isomer formed, the rigid structure of compound enhanced the aggregation so that the nanoparticle in the solution increased constantly. Thus, this may provide a novel approach for preparing a new family with AIE characteristics and photochromic properties which may have the potential application in the optical memory and nonlinear optics. © 2015 Published by Elsevier Ltd.
Keywords: Photochromic Bithienylethene Coumarin AIE Aggregation Fluorescence
Photochromic compounds as photo-responsive functional materials have been widely investigated due to their potential applications in many fields such as optical memory [1] and optical switches [2]. During the reversible photoisomerization, their photochemical and photophysical properties such as absorption spectra [3], photo luminescence [4] and geometrical structure [5] maybe changed upon photo excitation. In particular, bithienylethene derivatives are the most promising compounds because of their excellent fatigue resistant and thermal irreversible properties [6]. Recently, the design and synthesis of novel complex systems based on bithienylethenes that integrate several switchable functional units into a single molecule is a main aspect in the progress of molecular switches [7]. Coumarin derivatives, another kind of optical active material, are widely used in the fields of biology, medicine and polymer science [8]. The combination of coumarin with dithienylethene should not only involve a multi-addressed memory system, but also entail the possibilities drug release mechanism [9]. In the present study, we designed and prepared a complex multi-addressable compound containing both coumarin and diarylethene. Moreover,
* Corresponding author. Tel./fax: þ86 21 64252758. E-mail address: [email protected] (L. Zou). 1 These authors contributed equally to the work. http://dx.doi.org/10.1016/j.dyepig.2015.07.031 0143-7208/© 2015 Published by Elsevier Ltd.
this novel structure represents a unique example of aggregationinduced emission (AIE) [10]. To the best of our knowledge, the phenomenons of dithienylethene derivatives linked to coumarin fluorescent unit based on AIE characteristics have been rarely reported. In this letter, we have prepared a series of photochromic bithienylethenes named as B2C and B1C to investigate their AIE behavior (Scheme 1). Although with the fluorescent group coumarin linked, compound B2C could emit very weak fluorescence in any organic solvent. After water was added into the THF solution of B2C, the fluorescence began to appear. With the increasing of the water content in the solution, the fluorescence increased strongly. After irradiated by the UV light, the color of this solution changed from colorless to purple due to the formation of closed ring isomer. Also the fluorescence would be enhanced continuously because of the photo-isomerization reaction. The possible mechanism was proposed. Due to the hydrophobic interactions, the photochromic molecules aggregated to nanoparticles when water added, which led to the fluorescence emission. After UV irradiation, the ring closed isomer formed, and the rigid structure enhanced the aggregation so that the nanoparticle in the solution increased constantly. The compound B2C was prepared by simple esterification reaction of carboxyl bithienylethene and 7-Hydroxycoumarin, and the synthetic route is shown in Scheme S1 (ESI). The absorption
L. Chen et al. / Dyes and Pigments 123 (2015) 112e115
113
Scheme 1. Schematic representation of the morphology and fluorescence transition by water addition and UV light irradiation.
500000
THF THF:H2O=1:99
400000
Fluorescence Intensity
spectrum of B2C is illustrated in Fig. 1. The maximum absorption of compound o-B2C is observed at 315 nm. Upon irradiation with 254 nm UV light, the colorless solution of B2C gradually turns purple due to the appearance of a new visible absorption band centered at 562 nm, which is attributed to the formation of the closed-ring form c-B2C. The photo-stationary state is attained after about 4 min UV light irradiation. Alternatively, the purple solution could be bleached to colorlessness upon irradiation with visible light (l > 550 nm), indicating that c-B2C returned to the initial state o-B2C. Next, the fluorescent property of compound B2C was also investigated by fluorescence spectrophotometer (Fig. 2). The fluorescent emission behaviors of compound B2C were measured in different solvents. In the THF aqueous solution the strong fluorescence was found. Since THF is a good solvent and water is poor solvent of B2C, the molecules must aggregate in the aqueous mixtures with high water fractions. The phenomenon shows this compound may be with AIE behaviors. For further study the fluorescent emission behavior of B2C in aqueous solutions, the fluorescence of B2C with different water content was investigated (Fig. 3). With the increasing of the water
CH3OH CH3CN C6H12
300000
DMF DCM C6H5CH3
200000
100000
0
400
500
Wavelength
600
nm
Fig. 2. Fluorescence spectral changes of the compound B2C in different solvents.
0.6
0.5
UV
VIS 400000
Fluorescence Intensity
Absorption
0.4
0.3
0.2
UV
VIS
H2O 0-99%
200000
0.1
0.0 300
400
500
Wavelength
600
700
nm
Fig. 1. UVevis spectral changes of the compound B2C upon 254 nm light irradiation in THF (1.0 105 M) at 25 C.
0
400
500
Wavelength
600
nm
Fig. 3. Fluorescence spectral changes of the compound B2C with different water content.
114
L. Chen et al. / Dyes and Pigments 123 (2015) 112e115
Fig. 4. Fluorescence changes of the compound B2C with water content from 0 to 99%.
ratio in THF solution, the week fluorescent emission at 350 nm decreased, and the emission at 455 nm increased heavily when excited at 315 nm. Compared to the value in the THF solution, the emission maximum is red-shift of 100 nm occurs in the THFewater mixtures, suggesting that the B2C molecules aggregate in such aqueous media. When the H2O/THF ratio reached to 99:1, the fluorescence reached up to the maximum value, which is 1000 times than the initial value. This indicates that the compound B2C has AIE properties. The corresponding changes are shown in Fig. 4. With the increasing of the water ratio in the solution of B2C, the molecules began to aggregate due to the intermolecular hydrophobic interaction. The fluorescent characters of compound B2C conformed to the aggregation-induced emission well, such as the red-shift wavelength, broad and strong emission peak. Further, the photochromic properties of B2C in aqueous solution were also investigated, and the corresponding spectra changes are shown in Fig. 5. Compared to the photochromism in THF, the absorption wavelengths of the open-ring and closed-ring isomers show little changes. But the reaction time to PSS increased to 10 min from 4 min, which indicated the ring-closed quantum efficiency decreased in the aqueous solution. We supposed that the aggregation of the molecules reduced the photo reaction efficiency. Then, the fluorescent changes of B2C in aqueous solution were measured (Fig. 6). Upon the irradiation of 254 nm UV light, the fluorescence spectra continue to increase with the formation of the ring-closed isomers. After 10 min irradiated, the fluorescent intensity increased by 10%. We assumed when the photochromic unit was converted from the open-ring to the closed-ring form upon irradiation with 254 nm, the structure of the compound became rigid due to bisthienylethene units being restricted and may not freely rotating around the ethene bridge. With the structure rigidity of the compound increased as the freedom of two coumarin arms was restricted, the AIE phenomenon was promoted.
As shown in Fig. S8 the morphology change of B2C before and after UV irradiation was demonstrated by transmission electron microscopy (TEM). After the THF solution of B2C was added into the water, the nanoparticles with 100 nm diameter began to form due to the aggregation of small molecules, which triggered the fluorescent emission. After the THF/H2O solution of B2C was irradiated with 254 nm UV light, there are much more nanoparticles formed in the cross-linked form, which were consistent to the higher fluorescent quantum efficiency. Dynamic light scattering (DLS) studies also imply that the morphology transition is due to the aggregation process of the nanoparticles in solution (Fig. 7). The initial DLS signal corresponds to species of 80 nm approximately. However, upon the introduction of water, aggregates with bigger size were observed, and the amount of aggregates with a size of about 600 nm was increased with increasing of the H2O/THF ratio to 99:1. After irradiation at 254 nm UV light, accompanied by the structure rigidity of the compound increased, the nanoparticle aggregations were tightened and the particle sizes were reduced to about 180 nm. To further investigate the fluorescent emission mechanism of compound B2C, B1C was prepared as the reference. The synthesis method was similar with the preparation of compound B2C, and its photochromism is shown in Fig. S9. The fluorescence behavior of compound B1C was also studied and it doesn't display any special luminescent property. The fluorescence emission of B1C was so weak that could be hardly found neither in the organic solvent nor in THF/H2O solution (Fig. S10). These results further demonstrated that the bi-coumarins structure of B2C molecule is helpful to the aggregation into the nanoparticles and promotion the fluorescence emission. In conclusion, a novel photochromic compound B2C was prepared and well characterized, and it has hardly fluorescent in any organic solvent. However, their aggregates could be formed in the THF aqueous solution. Also its fluorescence could be increased
0.5 500000
UV
VIS Fluorescence Intensity
Absorbance
0.4
0.3
0.2
0.1
UV
VIS
400
500
Wavelength
600
300000
200000
100000
0.0 300
UV
400000
700
nm
Fig. 5. UVevis spectral changes of the compound B2C upon 254 nm light irradiation in solution (THF:H2O ¼ 1:99, 1.0 105 M) at 25 C.
0
400
500
Wavelength
600
nm
Fig. 6. Fluorescence spectral changes of the compound (THF:H2O ¼ 1:99, 1.0 105 M) with 254 nm UV irradiation.
B2C
in
solution
L. Chen et al. / Dyes and Pigments 123 (2015) 112e115
[2]
[3]
[4]
Fig. 7. DLS profiles of B2C with different water content before and after UV irradiation.
strongly in this process because of the formation of the nanoparticles, exhibiting typical AIE behaviors. Moreover, upon UV light irradiation, the amount of nanoparticles increased continuously owing to the rigid structure of ring closed isomers, and the fluorescent was also enhanced. This work provides a new family with AIE characteristics and photochromic properties. It indicated which may have the potential application in the optical memory, nonlinear optics and LangmuireBlodgett films.
[5]
[6] [7]
Acknowledgment [8]
This work was financially supported by National Basic Research 973 Program (2013CB733700), National Natural Science Foundation of China (Nos. 21190033, 21302056, 21372076) and the Open Foundation of State Key Laboratory of Electronic Thin Films and Integrated Devices (KFJJ201311). Professor He Tian is also acknowledged for helpful discussion. Appendix A. Supplementary material Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.dyepig.2015.07.031. References [1] (a) Irie M. Diarylethenes for memories and switches. Chem Rev 2000;100: 1685e716. (b) Tian H, Yang S. Recent progresses on diarylethene based photochromic
[9]
[10]
115
switches. Chem Soc Rev 2004;33:85e97. (c) Li H, Pu S, Liu G, Chen B. Photochromism of new diarylethene derivatives based on the hybrid photochromic skeleton of benzofuran and benzene moieties. Dyes Pigm 2014;101:15e24. (a) Raymo F, Tomasulo M. Optical processing with photochromic switches. Chem Eur J 2006;12:3186e93. (b) Carling C, Boyer J, Branda N. Remote-control photoswitching using NIR light. J Am Chem Soc 2009;131:10838e9. (c) Zhang J, Jin J, Zou L, Tian H. Reversible photo-controllable gels based on bisthienylethene-doped lecithin micelles. Chem Commun 2013;49:9926e8. (d) Ding H, Liu G, Pu S, Zheng C. Multi-addressable fluorescent switch based on a photochromic diarylethene with triazole-bridged methylquinoline group. Dyes Pigm 2014;103:82e8. (a) Jin J, Zhang J, Zou L, Tian H. Near-infrared photochromic behavior in a donor-acceptor type diarylethene modulated by the cyanide anion. Analyst 2013;138:1641e4. (b) Zhang J, Jin J, Zhang J, Zou L. An optic/proton dual-controlled fluorescence switch based on novel photochromic bithienylethene derivatives. Chin J Chem 2012;30:1741e7. (a) Pu S, Tong Z, Liu G, Wang R. Multi-addressable molecular switches based on a new diarylethene salicylal Schiff base derivative. J Mater Chem C 2013;1: 4726e39. (b) Zhang J, Wang Q, Zou L, Jia C. Synthesis and properties of novel photochromic bisthienylethenes containing imidazole and imidazolium derivatives. Chin Chem Lett 2014;25:762e6. (c) Al-Atar U, Fernandes R, Johnsen B, Baillie D, Branda N. A photocontrolled molecular switch regulates paralysis in a living organism. J Am Chem Soc 2009;131:15966e7. tivier R, Zhang Q, Guillot R, Xie Y, et al. Unprecedented (a) Zhu W, Yang Y, Me stability of a photochromic bisthienylethene based on benzobisthiadiazole as six-membered ethene bridge. Angew Chem Int Ed 2011;50:10986e90. (b) Florea L, Scarmagnani S, Benito-Lopez F, Diamond D. Self-assembled solvato-morphologically controlled photochromic crystals. Chem Commun 2014;50:924e6. Zhang J, Zou Q, Tian H. Photochromic materials: more than meets the eyes. Adv Mater 2013;25:378e99. Yang T, Liu Q, Pu S, Dong Z, Huang C, Li F. Fluorophore-photochrome coembedded polymer nanoparticles for photoswitchable fluorescence bioimaging. Nano Res 2012;5:494e503. it D, Udum Y, Güllü M, Toppare L. Electrochemical and optical prop(a) Yig erties of novel terthienyl based azobenzene, coumarine and fluorescent containing polymers: multicolored electrochromic polymers. J Electroanal Chem 2014;712:215e22. (b) Zhang Q, Qu D, Wu J, Ma X, Wang Q, Tian H. A dual-modality photoswitchable supramolecular polymer. Langmuir 2013;29:5345e50. (c) Zhang Q, Yao X, Qu D, Ma X. Multistate self-assembled micro-morphology transitions controlled by hosteguest interactions. Chem Commun 2014;50: 1567e9. (d) Karthik S, Puvvada N, Prashanth Kumar B, Rajput S, Pathak A, Mandal M, et al. Photoresponsive coumarin-tethered multifunctional magnetic nanoparticles for release of anticancer drug. ACS Appl Mater Interf 2013;5:5232e8. (a) Li H, Wang J, Lin H, Xu L, Xu W, Wang R, et al. Amplification of fluorescent contrast by photonic crystals in optical storage. Adv Mater 2010;22:1237e41. (b) Xiao S, Yi T, Li F, Huang C. A multi-photo responsive photochromic dithienylethene containing coumarin derivative. Tetrahedron Lett 2005;46: 9009e12. (a) Hong Y, Lam J, Tang B. Aggregation-induced emission: phenomenon, mechanism and applications. Chem Commun 2009;10:4332e53. (b) Yao X, Ma X, Tian H. Aggregation-induced emission encoding supramolecular polymers based on controllable sulfonatocalixarene recognition in aqueous solution. J Mater Chem C 2014;2:5155e60.
Contents lists available at ScienceDirect
Dyes and Pigments journal homepage: www.elsevier.com/locate/dyepig
Short communication
Photo-controllable and aggregation-induced emission based on photochromic bithienylethene Lele Chen 1, Jiaqi Zhang 1, Qiaochun Wang, Lei Zou* Key Laboratory for Advanced Materials, Institute of Fine Chemicals, East China University of Science & Technology, Shanghai 200237, PR China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 29 June 2015 Received in revised form 21 July 2015 Accepted 24 July 2015 Available online 1 August 2015
In this article a series of photochromic bithienylethenes containing coumarin fluorescent unit were synthesized and their properties including photochromic behavior and fluorescent properties were also investigated. One compound not only exhibited photochromic behaviors but also had aggregationinduced emission characteristics. The fluorescence could also be enhanced continuously by the photoisomerization reaction. As ring-closed isomer formed, the rigid structure of compound enhanced the aggregation so that the nanoparticle in the solution increased constantly. Thus, this may provide a novel approach for preparing a new family with AIE characteristics and photochromic properties which may have the potential application in the optical memory and nonlinear optics. © 2015 Published by Elsevier Ltd.
Keywords: Photochromic Bithienylethene Coumarin AIE Aggregation Fluorescence
Photochromic compounds as photo-responsive functional materials have been widely investigated due to their potential applications in many fields such as optical memory [1] and optical switches [2]. During the reversible photoisomerization, their photochemical and photophysical properties such as absorption spectra [3], photo luminescence [4] and geometrical structure [5] maybe changed upon photo excitation. In particular, bithienylethene derivatives are the most promising compounds because of their excellent fatigue resistant and thermal irreversible properties [6]. Recently, the design and synthesis of novel complex systems based on bithienylethenes that integrate several switchable functional units into a single molecule is a main aspect in the progress of molecular switches [7]. Coumarin derivatives, another kind of optical active material, are widely used in the fields of biology, medicine and polymer science [8]. The combination of coumarin with dithienylethene should not only involve a multi-addressed memory system, but also entail the possibilities drug release mechanism [9]. In the present study, we designed and prepared a complex multi-addressable compound containing both coumarin and diarylethene. Moreover,
* Corresponding author. Tel./fax: þ86 21 64252758. E-mail address: [email protected] (L. Zou). 1 These authors contributed equally to the work. http://dx.doi.org/10.1016/j.dyepig.2015.07.031 0143-7208/© 2015 Published by Elsevier Ltd.
this novel structure represents a unique example of aggregationinduced emission (AIE) [10]. To the best of our knowledge, the phenomenons of dithienylethene derivatives linked to coumarin fluorescent unit based on AIE characteristics have been rarely reported. In this letter, we have prepared a series of photochromic bithienylethenes named as B2C and B1C to investigate their AIE behavior (Scheme 1). Although with the fluorescent group coumarin linked, compound B2C could emit very weak fluorescence in any organic solvent. After water was added into the THF solution of B2C, the fluorescence began to appear. With the increasing of the water content in the solution, the fluorescence increased strongly. After irradiated by the UV light, the color of this solution changed from colorless to purple due to the formation of closed ring isomer. Also the fluorescence would be enhanced continuously because of the photo-isomerization reaction. The possible mechanism was proposed. Due to the hydrophobic interactions, the photochromic molecules aggregated to nanoparticles when water added, which led to the fluorescence emission. After UV irradiation, the ring closed isomer formed, and the rigid structure enhanced the aggregation so that the nanoparticle in the solution increased constantly. The compound B2C was prepared by simple esterification reaction of carboxyl bithienylethene and 7-Hydroxycoumarin, and the synthetic route is shown in Scheme S1 (ESI). The absorption
L. Chen et al. / Dyes and Pigments 123 (2015) 112e115
113
Scheme 1. Schematic representation of the morphology and fluorescence transition by water addition and UV light irradiation.
500000
THF THF:H2O=1:99
400000
Fluorescence Intensity
spectrum of B2C is illustrated in Fig. 1. The maximum absorption of compound o-B2C is observed at 315 nm. Upon irradiation with 254 nm UV light, the colorless solution of B2C gradually turns purple due to the appearance of a new visible absorption band centered at 562 nm, which is attributed to the formation of the closed-ring form c-B2C. The photo-stationary state is attained after about 4 min UV light irradiation. Alternatively, the purple solution could be bleached to colorlessness upon irradiation with visible light (l > 550 nm), indicating that c-B2C returned to the initial state o-B2C. Next, the fluorescent property of compound B2C was also investigated by fluorescence spectrophotometer (Fig. 2). The fluorescent emission behaviors of compound B2C were measured in different solvents. In the THF aqueous solution the strong fluorescence was found. Since THF is a good solvent and water is poor solvent of B2C, the molecules must aggregate in the aqueous mixtures with high water fractions. The phenomenon shows this compound may be with AIE behaviors. For further study the fluorescent emission behavior of B2C in aqueous solutions, the fluorescence of B2C with different water content was investigated (Fig. 3). With the increasing of the water
CH3OH CH3CN C6H12
300000
DMF DCM C6H5CH3
200000
100000
0
400
500
Wavelength
600
nm
Fig. 2. Fluorescence spectral changes of the compound B2C in different solvents.
0.6
0.5
UV
VIS 400000
Fluorescence Intensity
Absorption
0.4
0.3
0.2
UV
VIS
H2O 0-99%
200000
0.1
0.0 300
400
500
Wavelength
600
700
nm
Fig. 1. UVevis spectral changes of the compound B2C upon 254 nm light irradiation in THF (1.0 105 M) at 25 C.
0
400
500
Wavelength
600
nm
Fig. 3. Fluorescence spectral changes of the compound B2C with different water content.
114
L. Chen et al. / Dyes and Pigments 123 (2015) 112e115
Fig. 4. Fluorescence changes of the compound B2C with water content from 0 to 99%.
ratio in THF solution, the week fluorescent emission at 350 nm decreased, and the emission at 455 nm increased heavily when excited at 315 nm. Compared to the value in the THF solution, the emission maximum is red-shift of 100 nm occurs in the THFewater mixtures, suggesting that the B2C molecules aggregate in such aqueous media. When the H2O/THF ratio reached to 99:1, the fluorescence reached up to the maximum value, which is 1000 times than the initial value. This indicates that the compound B2C has AIE properties. The corresponding changes are shown in Fig. 4. With the increasing of the water ratio in the solution of B2C, the molecules began to aggregate due to the intermolecular hydrophobic interaction. The fluorescent characters of compound B2C conformed to the aggregation-induced emission well, such as the red-shift wavelength, broad and strong emission peak. Further, the photochromic properties of B2C in aqueous solution were also investigated, and the corresponding spectra changes are shown in Fig. 5. Compared to the photochromism in THF, the absorption wavelengths of the open-ring and closed-ring isomers show little changes. But the reaction time to PSS increased to 10 min from 4 min, which indicated the ring-closed quantum efficiency decreased in the aqueous solution. We supposed that the aggregation of the molecules reduced the photo reaction efficiency. Then, the fluorescent changes of B2C in aqueous solution were measured (Fig. 6). Upon the irradiation of 254 nm UV light, the fluorescence spectra continue to increase with the formation of the ring-closed isomers. After 10 min irradiated, the fluorescent intensity increased by 10%. We assumed when the photochromic unit was converted from the open-ring to the closed-ring form upon irradiation with 254 nm, the structure of the compound became rigid due to bisthienylethene units being restricted and may not freely rotating around the ethene bridge. With the structure rigidity of the compound increased as the freedom of two coumarin arms was restricted, the AIE phenomenon was promoted.
As shown in Fig. S8 the morphology change of B2C before and after UV irradiation was demonstrated by transmission electron microscopy (TEM). After the THF solution of B2C was added into the water, the nanoparticles with 100 nm diameter began to form due to the aggregation of small molecules, which triggered the fluorescent emission. After the THF/H2O solution of B2C was irradiated with 254 nm UV light, there are much more nanoparticles formed in the cross-linked form, which were consistent to the higher fluorescent quantum efficiency. Dynamic light scattering (DLS) studies also imply that the morphology transition is due to the aggregation process of the nanoparticles in solution (Fig. 7). The initial DLS signal corresponds to species of 80 nm approximately. However, upon the introduction of water, aggregates with bigger size were observed, and the amount of aggregates with a size of about 600 nm was increased with increasing of the H2O/THF ratio to 99:1. After irradiation at 254 nm UV light, accompanied by the structure rigidity of the compound increased, the nanoparticle aggregations were tightened and the particle sizes were reduced to about 180 nm. To further investigate the fluorescent emission mechanism of compound B2C, B1C was prepared as the reference. The synthesis method was similar with the preparation of compound B2C, and its photochromism is shown in Fig. S9. The fluorescence behavior of compound B1C was also studied and it doesn't display any special luminescent property. The fluorescence emission of B1C was so weak that could be hardly found neither in the organic solvent nor in THF/H2O solution (Fig. S10). These results further demonstrated that the bi-coumarins structure of B2C molecule is helpful to the aggregation into the nanoparticles and promotion the fluorescence emission. In conclusion, a novel photochromic compound B2C was prepared and well characterized, and it has hardly fluorescent in any organic solvent. However, their aggregates could be formed in the THF aqueous solution. Also its fluorescence could be increased
0.5 500000
UV
VIS Fluorescence Intensity
Absorbance
0.4
0.3
0.2
0.1
UV
VIS
400
500
Wavelength
600
300000
200000
100000
0.0 300
UV
400000
700
nm
Fig. 5. UVevis spectral changes of the compound B2C upon 254 nm light irradiation in solution (THF:H2O ¼ 1:99, 1.0 105 M) at 25 C.
0
400
500
Wavelength
600
nm
Fig. 6. Fluorescence spectral changes of the compound (THF:H2O ¼ 1:99, 1.0 105 M) with 254 nm UV irradiation.
B2C
in
solution
L. Chen et al. / Dyes and Pigments 123 (2015) 112e115
[2]
[3]
[4]
Fig. 7. DLS profiles of B2C with different water content before and after UV irradiation.
strongly in this process because of the formation of the nanoparticles, exhibiting typical AIE behaviors. Moreover, upon UV light irradiation, the amount of nanoparticles increased continuously owing to the rigid structure of ring closed isomers, and the fluorescent was also enhanced. This work provides a new family with AIE characteristics and photochromic properties. It indicated which may have the potential application in the optical memory, nonlinear optics and LangmuireBlodgett films.
[5]
[6] [7]
Acknowledgment [8]
This work was financially supported by National Basic Research 973 Program (2013CB733700), National Natural Science Foundation of China (Nos. 21190033, 21302056, 21372076) and the Open Foundation of State Key Laboratory of Electronic Thin Films and Integrated Devices (KFJJ201311). Professor He Tian is also acknowledged for helpful discussion. Appendix A. Supplementary material Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.dyepig.2015.07.031. References [1] (a) Irie M. Diarylethenes for memories and switches. Chem Rev 2000;100: 1685e716. (b) Tian H, Yang S. Recent progresses on diarylethene based photochromic
[9]
[10]
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