2025, Vol. 36 
b College of Forestry, Shandong Agricultural University, Tai'an 271018, China;
c School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, China;
d Shandong Provincial Key Laboratory of Chemical Energy Storage and Novel Cell Technology, School of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng 252000, China;
e College of Chemistry, State Key Laboratory of Elemento–Organic Chemistry, Nankai University, Tianjin 300071, China
We are in an era of information explosion, all walks of life are emphasizing the importance of data, but to truly realize the value of data, we must first solve the problem of information security [1]. Up to now, a variety of advanced anti-counterfeiting and encryption strategies [2–5], including the use of luminescence [6], holograms [7], quick response codes [8], barcodes [9], and watermarks [10], have been developed. During which, stimuli- responsive organic luminescent materials [11], whose fluorescence behaviors could be dynamically modulated, upon exposure to external stimuli such as mechanical force [12], light [13], heat [14], solvents [15], acids/bases [16], electric field [17], and chemicals [18], have attracted wide attention because of their unprecedented potential application in smart coatings [19], drug carriers [20], soft robotics [21]. Furthermore, compared to single-stimulus responsive systems, multi-stimuli responsive luminescent systems have attracted more interest, since they demonstrate great potential application in high-level encryption and complex environments [22]. For example, Hu et al. [23] have designed and synthesized three new organic smart security ink materials with solvatochromic, trifluoroacetic acid response, aggregation-induced emission enhancement properties. Zhao et al. [24] demonstrated the first example of luminescent material showing smart responses to both electrical and light stimuli, through outer sphere electron transfer in ion pairs. Liu et al. [25] formed a [2] pseudorotaxane from a Eu3+ complex of terpyridinyldibenzo-24-crown-8 and an unsymmetrical diarylperfluorocyclopentene which revealed excellent dual-modulated luminescence switching behavior by host-guest and optical stimuli. Light, as a non-invasive stimuli, posesses the advantages of environmental friendliness, fast responsiveness, and convenient, has been regarded to be the most potentially candidate, compared to other stimuli [26]. Besides, different photoresponsive molecules can be selectively triggered with precise control through the change of exposed wavelengths. Photoisomerizable molecules, such as diarylethenes (DAEs) [27], azobenzenes [28], spiropyran [29], and fulgide [30], which constitute the core of light-controlled stimuli-responsive systems, can usually undergo photochemical reactions or configuration changes under the irradiation of light of a certain wavelength and intensity, have been well developed.
As one of P-type photochromic molecules, DAEs can undergo a reversible, photochemical 6π-electrocyclizaton between a ring-opened and a ring-closed isomer when irradiated with proper lights, were first reported by Irie and co-workers in 1988 [31]. Since then, their excellent thermal properties in colorless ring-opened and colored ring-closed isomers, exceptional photochromic efficiency, fatigue resistance, as well as the high sensitivity, have facilitated their extensive utilization in memory media, logic circuits, optical switches, magnetic materials, and liquid crystal displays, particularly for anti-counterfeiting systems [32–34]. Despite many elegant multi-stimuli responsive luminescent materials have been proposed, organic smart systems with photochromic, acidochromic, and solventchromic luminescent properties are rarely reported, to the best of our knowledge, as acid and solvent are also important regulatory factors utilized in sensors and security inks. Herein, we developed an intelligent multi-stimuli responsive luminescent system for multiple logical gates and multicolor luminescence information storage, in which photoacid sulfonato-merocyanine (MEH-D) acted as H+ donor [35,36], and diarylethene derivative DAE-A1 as H+ acceptor, by mixing them together in dichloromethane (Scheme 1). Compared to another similar work reported by Yokoyama [37], which exhibited no photochromism and fluorescence in acetonitrile before the capture of H+, our system presented excellent light-stimulus-responsiveness with bright fluorescence emission. Turn on luminescent effect of open formed DAE-A1 (OF-DAE-A1) was realized by the irradition of 440 nm visible light, in which OF-DAE-A1 captured MEH-D released protons and became protonated isomer OF-DAE-A1-H. Benefiting from the intramolecular charge transfer, OF-DAE-A1-H exhibited a bright blue fluorescence. When exposed to dark environment, the system showed fluorescence quenching, as ring-closed isomer spiropyran (SP-D) transferred to MEH-D. Furthermore, the fluorescence emission wavelength of OF-DAE-A1-H could be successfully controlled from 450 nm to 510 nm, through different solvents stimulation. Significantly, the fluorescence spectrum and the luminescent color of OF-DAE-A1-H could be reversibly switched between blue and colorless by altering the wavelength of 254 nm or >600 nm.
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| Scheme 1. Chemical structures and schematic illustration of constructing multi-stimuli-responsive luminescent system. | |
Firstly, OF-DAE-A1 was synthesized according to our previous work with slight modification [38]. As depicted in Fig. 1a, a solution of the open form of DAE-A1 (OF-DAE-A1) exhibited a maximum absorption peak at 325 nm and negligible absorbance in the range of 400–750 nm in the UV–vis spectrum. However, when the solution of OF-DAE-A1 was irradiated by 254 nm ultraviolet light, the peak at 325 nm gradually declined and redshifted to 335 nm, accompanied by the appearance of two isosbestic points at 341 and 430 nm during the transformation process. In addition, a new absorption band at 610 nm appeared and reached stable state after 6.5 min, leading to an remarkable color change from colorless to blue in day light, which could be assigned to close formed DAE-A1 (CF-DAE-A1). When the obtained CF-DAE-A1 was irradiated by >600 nm visible light for 20 s, the original UV–vis spectrum of OF-DAE-A1 recovered to its original sharp and intensity, and the interconversion could be repeated at least six times without any appreciable deterioration (Fig. 1b). Calculated from the 1H NMR spectral changes of DAE-A1, OF-DAE-A1 could quantitatively convert to CF-DAE-A1 on the 254 nm irradiated sample, and the CF-DAE-A1 could also quantitatively afford the OF-DAE-A1 upon irradiation with visible light (Fig. 1c). In comparison, the reference compound, perhydrocyclopentene bridged DAE derivative DAE-A2 gave lower ring-closing conversion yield to 48.6% upon irradiation with 254 nm light, while the CF-DAE-A2 quantitatively afforded the OF-DAE-A2 upon irradiation with >600 nm light (Fig. S1 in Supporting information). Different from DAE-A1, DAE-A2 suffered obvious bathochromic shift with the increase of the number of light experiments, indicating a lower stability (Figs. S2 and S3 in Supporting information). Subsequently, the luminous property of OF-DAE-A1 was investigated by fluorescence emission spectrum. As shown in Fig. S4 (Supporting information), OF-DAE-A1 did not show any obvious signals when excited by 350 nm ultraviolet light. Surprisingly, after 2 equiv. HCl were added, a strong peak around 450 nm appeared in fluorescence emission spectrum, and the 1H NMR spectrum suffered obvious downfield shifts (Fig. S22 in Supporting information), which could be ascribed to the formation of OF-DAE-A1-H with intramolecular charge transfer properties.
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| Fig. 1. (a) UV–vis absorption spectra changes of OF-DAE-A1 upon continuous irradiation with 254 nm light for up to 6.5 min in the solution of CH2Cl2 ([OF-DAE-A1] = 1.0 × 10–5 mol/L). Inset: changes of the chemical structure and images under daylight of DAE-A1 upon alternating 254 nm and >600 nm light irradiation. (b) UV–vis absorption spectra and intensity changes (inset) at 610 nm for DAE-A1 upon alternating ultraviolet and visible light irradiation. (c) 1H NMR spectral changes observed for OF-DAE-A1 (Ⅰ, 1.0 mmol/L) upon irradiation with 254 nm (Ⅱ) and subsequent irradiation with >600 nm (Ⅲ) in DMSO-d6 at 298 K. | |
It is well documented that the intramolecular charge transfer process is closely related to solvent. So, UV–vis absorption and fluorescence emission spectra of OF-DAE-A1-H were investigated in different solvents. As shown in Fig. 2a, the maximum absorption peaks of DAE-A1-H ranged from 330 nm to 365 nm among all the examined solvent, displayed 35 nm obvious bathochromic shift in dichloromethane (DCM) compared to that in toluene. However, DAE-A1-H showed the second-strongest fluorescent emission intensity in toluene, accompanied by the obvious bathochromic shift of 60 nm to 510 nm, compared to that (450 nm) in DCM (Fig. 2b). Intuitively, the luminous color of DAE-A1-H under 365 nm handhold ultraviolet lamp could be obviously observed by naked eyes, to be specific, blue fluorescence was shown in DCM, and the color in toluene was green (Fig. 2b inset). Since DAE-A1 has good photo-responsiveness, we wonder whether DAE-A1-H also retains advantages of DAE-A1. To our delight, upon irradiation of OF-DAE-A1-H with 254 nm light for 2 min, a new absorption band centered on 620 nm gradually appeared and increased in intensity, accompanied by an obvious color change from colorless to blue in DCM (Fig. S5 in Supporting information). When irradiated at wavelengths greater than 600 nm, CF-DAE-A1-H could be completely converted back to OF-DAE-A1-H and this process could be repeated at least six times (Fig. S6 in Supporting information). Of course, the luminescent feature of OF-DAE-A1-H was also investigated. As shown in Fig. S7 (Supporting information), with the increase of 254 nm illumination time, the fluorescence emission intensity of OF-DAE-A1 gradually decreased until completely quenched. When exposed to visible for 20 s, the fluorescence of OF-DAE-A1-H recovered to the original level. Importantly, the luminescence properties of DAE-A1-H did not exhibit apparent light fatigue over five cycles (Fig. S8 in Supporting information). As comparison, the reference compound OF-DAE-A2-H gave a maximum emission peak at 505 nm, but the intensity was much lower than that of OF-DAE-A1-H (Fig. S9 in Supporting information). To our surprise, the photoresponsiveness of DAE-A1-H in toluene was completely different from that in DCM. When we employed 254 nm ultraviolet light to stimulate OF-DAE-A1-H in toluene, the absorption maximum at 324 nm of OF-DAE-A1-H did suffered a slight gradual decrease, but new absorption around 620 nm corresponding to CF-DAE-A1-H state did not emerge (Fig. S10 in Supporting information). The slightly altered UV–vis spectra of OF-DAE-A1-H upon continuous ultraviolet irradiation, indicated its good stability in toluene. Accordingly, the fluorescence intensity of the solution reduced to 87% of the original, with no obviously change in color (Fig. S11 in Supporting information).
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| Fig. 2. (a) UV–vis absorption spectra. (b) Fluorescence emission spectra, and inset: photographs under 365 nm, of OF-DAE-A1-H in different solvents ([OF-DAE-A1-H] = 1.0 × 10–5 mol/L, λex = 350 nm). | |
As described above, the luminescent features of DAE-A1 could be effectively controlled through the acceptance and the loss of protons, we wondered weather the fluorescence could be adjusted by light, through the introduction of another photoresponsive molecule that could release protons under light irradition. MEH-D, as a photoisomer, which could release H+ under 440 nm irradiation became a ring-closed isomer SP-D, was added in the DCM solution of DAE-A1 to form a new system DAE-A1/MEH-D. More importantly, SP-D could effectively change to MEH-D in dark. As shown in Fig. 3a, after 440 nm light irradiation for 10 s, the maximum absorption peak of MEH-D at 450 nm decreased, accompanied by the appearance of a isosbestic point at 319 nm during the transformation process. Simultaneously, the solution color changed from yellow to colorless, suggesting a transformation from ring-opened isomer MEH-D to the ring-closed isomer SP-D. After the solution of SP-D obtained above was placed in the dark environment for 160 min, the characteristic absorption peak at 450 nm suffered a gradual recovery (Fig. 3b), indicating a reversed convert from SP-D to MEH-D. With the operation of 440 nm light irradiation and placed in dark, the change of pH (Fig. S21 in Supporting information), UV–vis absorption spectra, and solution color could be cycled more than 6 times without any appreciable deterioration (Fig. 3c). Besides, the MEH-D exhibited a low fluorescence at 565 nm when compared with OF-DAE-A1-H (Fig. S12 in Supporting information). Corresponded to UV–vis absorption, upon irradiation with the 440 nm light for 10 s, the fluorescence intensity of MEH-D quenched by 90.7%. Then, the luminescent behavior of DAE-A1/MEH-D was studied. As shown in Fig. 3d, the fluorescence intensity of DAE-A1 presented a gradual increase with the gradual addition of MEH-D, and finally enhanced 186 times after the addition of 5 equiv. MEH-D. More MEH-D than 5 equiv. did not result in further fluorescence increase, so the best ratio between DAE-A1 and MEH-D was 1:5. In contrast, DAE-A1/MEH-D only showed a slight fluorescence emission peak at 400 nm in toluene, which could be ascribed to the lower solubility of MEH-D in toluene (Figs. S13 and S14 in Supporting information). It should be emphasized that the DAE-A1/MEH-D system needed to be illuminated at 440 nm for 10 s before the luminescence spectrum test.
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| Fig. 3. (a) UV–vis absorption spectra changes of MEH-D upon continuous irradiation with 440 nm light for up to 30 s in the solution of CH2Cl2 ([MEH-D] = 1.0 × 10–5 mol/L), inset: changes of the photographic images upon 440 nm light irradiation. (b) UV–vis absorption spectra changes of SP-D in dark for up to 160 min in the solution of CH2Cl2 ([SP-D] = 1.0 × 10–5 mol/L). (c) UV–vis absorption spectra and intensity changes (inset) at 450 nm for MEH-D upon alternating light irradiation and dark environment. (d) Fluorescence spectra of OF-DAE-A1 with different equivalents MEH-D after 10 s 440 nm light irradition ([OF-DAE-A1] = 1.0 × 10–5 mol/L, λex = 350 nm). | |
Next, we further investigated the photo-responsive properties of DAE-A1/MEH-D by fluorescence spectroscopy. Initially, DAE-A1/MEH-D exhibited a weak fluorescence emission peak at 510 nm. A significant increase was observed with a 50 nm hypochromatic shift to 460 nm upon 10 s irradition at 440 nm, which was derived from the generation of OF-DAE-A1-H and the system changed to OF-DAE-A1-H/SP-D in DCM (Fig. 4a). After the irradiation, fluorescence color changed from yellow-green to blue. After that, the reversed luminescence transformation experiment was also carried out. After removing the external 440 nm light for 100 min, the emission peak at 510 nm not only returned to the initial state but also had a slight blue shift to 470 nm. Interestingly, the luminescent properties of OF-DAE-A1-H/SP-D that obtained from OF-DAE-A1/MEH-D, could be controlled by 254 nm ultraviolet light and >600 nm visible light. As shown in Fig. 4b, when OF-DAE-A1-H/SP-D (Fig. 4b, curve B) was irradiated at 254 nm for 30 s, the intensity of the fluorescence emission at 460 nm decreased and the fluorescence quenching efficiency was calculated to be 87% on the basis of this experiment, with the system changed to CF-DAE-A1-H/SP-D (Fig. 4b, curve C). When CF-DAE-A1-H/SP-D was subsequently irradiated with visible light, the fluorescence of the solution returned to its original level and the system converted to OF-DAE-A1-H/SP-D (Fig. 4b, curve D). After putting OF-DAE-A1-H/SP-D in the dark environment for 100 min, it switched to OF-DAE-A1/MEH-D with the decrease of fluorescence (Fig. 4b, curve E).
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| Fig. 4. (a) Fluorescence emission spectra of DAE-A1/MEH-D system after exposing and removing the light source (5[DAE-A1] = [MEH-D] = 5.0 × 10–5 mol/L, λex = 350 nm). (b) Fluorescence emission spectra of DAE-A1/MEH-D system that responsed to different wavelengths of light (5[DAE-A1] = [MEH-D] = 5.0 × 10–5 mol/L, λex = 350 nm). | |
In view of the multi-stimuli-controlled multicolor luminescence properties of the system, we applied it to logic gate systems. The logic device defined different components of the system and different stimulus-response elements as input, and blue light emission at 460 nm more than 40 k was defined as output. The input “1” and “0” states represented the application or non-application of the corresponding stimulus, respectively. For emission intensity more than 40 k output could be recorded as “1”, cannot output was recorded as “0” and the signal was in a “silent” manner by using dark and 254 nm irradition as a NOT gate, respectively, which displayed clearly in the truth table. Therefore, two kinds of fundamental logic gates were designed and constructed (Fig. 5a). In addition, the system was also suitable for information encryption as photocontrolled fluorescent ink. As shown in Fig. 5b, the digit of “5” was drawn in a 96-well plate with OF-DAE-A1, which was hidden both in daylight and 365 nm ultraviolet light. After introducing 2 equiv. HCl to it, the hidden information could be seen by naked eyes under 365 nm. When exposed to 254 nm ultraviolet light, the displayed information missed again under 365 nm, but could be readed out in daylight (Fig. 5b). Another digit “8” fabricated from OF-DAE-A1/MEH-D was also concealed under 365 nm ultraviolet lamp. After 440 nm irradition, the digit “8” was observed. When irradiated with the 254 nm light, the digit disappeared again. To our delight, the erased digit could completely recover, upon irradiation with >600 nm visible light, and the manifestation/concealment process could also be controlled by posing/removing 440 nm light (Fig. 5c).
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| Fig. 5. (a) Scheme representation for the two INHIBIT logic gates and the corresponding truth tables. (b, c) Encryption information constructed by OF-DAE-A1 and OF-DAE-A1/MEH-D under daylight or 365 nm ultraviolet lamp. | |
In conclusion, we successfully constructed an efficient multi-stimuli responsive luminescent system based on DAE-A1 and MEH-D. In this system, MEH-D acted as protons donor when exposed to 440 nm light and DAE-A1 acted as protons acceptor to form intramolecular charge transfer product DAE-A1-H. The formed DAE-A1-H could emit bright blue light under 365 nm ultraviolet lamp. On account of the reversible photoisomerization property of the MEH-D unit, the luminescence of DAE-A1 could be reversibly switched on/off under the stimulation of 440 nm/dark. In addition, the DAE-A1/MEH-D could also switch on/off the luminescence by alternating ultraviolet and visible light irradiation. Finally, the system was successfully utilized in logic gates and information encryption.
Declaration of competing interestThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
CRediT authorship contribution statementHong-Guang Fu: Writing – original draft, Supervision, Funding acquisition, Conceptualization. Xuan Wu: Data curation. Hui-Juan Wang: Formal analysis. Fanjun Zhang: Formal analysis, Data curation. Yong Chen: Validation, Supervision, Investigation. Jing Xu: Validation, Supervision.
AcknowledgmentsThis work was financially supported by Natural Science Foundation of Shandong Province (Nos. ZR2022QB061, 2022KJ181), National Key R&D Program of China (No. 2023YFD1700903).
Supplementary materialsSupplementary material associated with this article can be found, in the online version, at doi:10.1016/j.cclet.2024.110741.
| [1] |
R.F. Ali, P.D.D. Dominic, S.E.A. Ali, M. Rehman, A. Sohail, Appl. Sci. 11 (2021) 3383. DOI:10.3390/app11083383 |
| [2] |
D. Feng, Q. Guo, Z. Huang, et al., Adv. Mater. 36 (2024) 2314201. |
| [3] |
Y.X. Hu, X. Hao, D. Wang, et al., Angew. Chem. Int. Ed. 63 (2024) e202315061. |
| [4] |
X. Li, H. Wang, J. Chen, et al., Adv. Funct. Mater. 33 (2023) 2303765. |
| [5] |
Y. Xie, X. Zhao, H. Wang, et al., Angew. Chem. Int. Ed. 64 (2025) e202414846. DOI:10.1002/anie.202414846 |
| [6] |
J. Li, D. Xia, M. Gao, et al., Inorg. Chim. Acta 526 (2021) 120541. |
| [7] |
T. Li, L. Li, L. Jiang, et al., Adv. Opt. Mater. 12 (2024) 2400612. |
| [8] |
X. Xu, S. Liu, Y. Kuai, et al., Adv. Sci. 11 (2024) 2309862. |
| [9] |
Y. Zhou, G. Zhao, J. Bian, et al., ACS Appl. Mater. Interfaces 12 (2020) 28532-28538. DOI:10.1021/acsami.0c06272 |
| [10] |
A. Speidel, I. Bisterov, A.T. Clare, Adv. Funct. Mater. 32 (2022) 2208116. |
| [11] |
L. Shi, L. Ding, Y. Zhang, S. Lu, Nano Today 55 (2024) 102200. |
| [12] |
Y. Zhang, Y. Chen, J.Q. Li, S.E. Liu, Y. Liu, Adv. Sci. 11 (2024) 2307777. |
| [13] |
M. Zuo, W. Qian, T. Li, et al., ACS Appl. Mater. Interfaces 10 (2018) 39214-39221. DOI:10.1021/acsami.8b14110 |
| [14] |
D. Ren, L. Tang, Z. Wu, et al., Chin. Chem. Lett. 34 (2023) 108617. |
| [15] |
D. Chen, C. Bao, L. Zhang, et al., Adv. Funct. Mater. 34 (2024) 2314093. |
| [16] |
Z.M. Png, C.G. Wang, J.C.C. Yeo, et al., Mol. Syst. Des. Eng. 8 (2023) 1097-1129. DOI:10.1039/d3me00002h |
| [17] |
Y. Yang, P. Su, Y. Tang, ChemNanoMat 4 (2018) 1097-1120. DOI:10.1002/cnma.201800212 |
| [18] |
S. Ito, M. Gon, K. Tanaka, Y. Chujo, Polym. Chem. 12 (2021) 6372-6380. DOI:10.1039/d1py01170g |
| [19] |
W. Yao, M. Tebyetekerwa, X. Bian, et al., J. Mater. Chem. C 6 (2018) 12849-12857. DOI:10.1039/c8tc04175j |
| [20] |
Z. Wang, C. Sun, K. Yang, X. Chen, R. Wang, Angew. Chem. Int. Ed. 61 (2022) e202206763. |
| [21] |
W. Zhang, H. Liang, X. Qin, et al., ACS Appl. Mater. Interfaces 14 (2022) 40136-40144. DOI:10.1021/acsami.2c12490 |
| [22] |
L. Duan, Q. Zheng, Y. Liang, T. Tu, Adv. Mater. 36 (2024) 2409620. |
| [23] |
S. Chen, W. Zhang, Q. Jia, et al., Dyes Pigments 171 (2019) 107700. |
| [24] |
Y. Ma, L. Shen, P. She, et al., Adv. Opt. Mater. 7 (2019) 1801657. |
| [25] |
H.B. Cheng, H.Y. Zhang, Y. Liu, J. Am. Chem. Soc. 135 (2013) 10190-10193. DOI:10.1021/ja4018804 |
| [26] |
L. Dong, X. Shi, H. Li, et al., ACS Mater. Lett. 6 (2024) 3523-3532. DOI:10.1021/acsmaterialslett.4c00870 |
| [27] |
G. Liu, C. Tian, G. Li, et al., ACS Mater. Lett. 5 (2023) 2299-2307. DOI:10.1021/acsmaterialslett.3c00613 |
| [28] |
Y. Yu, X. Qu, J. Li, F. Huang, J. Yang, Chem. Commun. 59 (2023) 14265-14268. DOI:10.1039/d3cc05018a |
| [29] |
R. Zhang, Y. Chen, Y. Liu, Angew. Chem. Int. Ed. 62 (2023) e202315749. |
| [30] |
J. Zhang, H. Tian, Adv. Opt. Mater. 6 (2018) 1701278. |
| [31] |
M. Irie, M. Mohri, J. Org. Chem. 53 (1988) 803-808. DOI:10.1021/jo00239a022 |
| [32] |
Q. Luo, Y. Liu, H. Tian, Photochromic dithienylethene–phthalocyanines and their analogs, in: J. Jiang (Ed.), Functional Phthalocyanine Molecular Materials, Springer Berlin Heidelberg, Berlin, Heidelberg, 2010, pp. 89–103.
|
| [33] |
S. Zhu, W. Li, W. Zhu, Prog. Chem. 28 (2016) 975-992. |
| [34] |
J. Wang, X. Liu, J. Wang, et al., Luminescence 39 (2024) e4546. |
| [35] |
R. Zhang, Y. Chen, L. Chen, Y. Zhang, Y. Liu, Adv. Opt. Mater. 11 (2023) 2300101. |
| [36] |
J. Guo, H.Y. Zhang, Y. Zhou, Y. Liu, Chem. Commun. 53 (2017) 6089-6092. |
| [37] |
S. Mahvidi, S. Takeuchi, S. Kusumoto, et al., Org. Lett. 18 (2016) 5042-5045. DOI:10.1021/acs.orglett.6b02494 |
| [38] |
H.-G. Fu, J. You, Dyes Pigments 207 (2022) 110744. |