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1.
Xiaojing Yan Pengcheng Zhu Zhiguo Zhou Hong Yang Haichuang Lan Shuzhang Xiao 《RSC advances》2019,9(61):35872
A novel class of solid-emissive boron-difluoride derivatives, using phenanthrenequinone hydrazone as ligands, were designed and efficiently synthesized. These dyes exhibit weak fluorescence in dilute solutions, but much higher fluorescence efficiency in aggregate states with a large stokes shift (over 70 nm) due to the their aggregation-induced emission enhancement (AIEE) characteristics. According to their photophysical properties and X-ray single crystal structure analysis, the AIEE was ascribed to the H(J)-aggregate formation aided by multiple intermolecular interactions to restrict intramolecular motion in the solid state. Moreover, their solid emissions could be reversibly tuned between “on” and “off” by mechanical grinding and recrystallization, due to the stacking model transition between H(J)-aggregation with loose molecular packing and J-aggregation with intense intermolecular interactions.A class of AIEE-active mechanochromic boron-difluorides were reported, and the mechanochromism was ascribed to the transition between H(J)-aggregation with loose molecular packing and J-aggregation with intense intermolecular interactions. 相似文献
2.
Four thiophene-containing tetraphenylethene derivatives were successfully synthesized and characterized. All these highly fluorescent compounds showed typical aggregation-induced emission (AIE) characteristics and emitted different fluorescence colors including blue-green, green, yellow and orange in the aggregation state. In addition, these luminogens also exhibited various mechanofluorochromic phenomena.Four thiophene-containing AIE-active TPE derivatives were synthesized. Furthermore, these luminogens exhibited various mechanofluorochromic phenomena.High-efficiency organic fluorescent materials have attracted widespread attention due to their potential applications in organic light-emitting devices and fluorescent switches.1–8 Meanwhile, smart materials sensitive to environmental stimuli have also aroused substantial interest. Mechanochromic luminescent materials exhibiting color changes under the action of mechanical force (such as rubbing or grinding) are one important type of stimuli-responsive smart materials, which can be used as pressure sensors and rewritable media.9–18 Bright solid-state emission and high contrast before and after grinding are very significant for the high efficient application of mechanochromic fluorescence materials.19–28 However, a majority of traditional emissive materials usually exhibit poor emission efficiency in the solid state due to the notorious phenomenon of aggregation caused quenching (ACQ), and the best way to solve the problem is to develop a class of novel luminescent materials oppositing to the luminophoric materials with ACQ effect. Fortunately, an unusual aggregation-induced emission (AIE) phenomenon was discovered by Tang et al. in 2001.29 Indeed, the light emission of an AIE-active compound can be enhanced by aggregate formation.30–32 Obviously, it is possible that AIE-active mechanochromic fluorescent compounds can be applied to the preparation of high-efficiency mechanofluorochromic materials. Numerous luminescent materials exhibiting mechanochromic fluorescent behavior have been discovered up to now.33 Whereas, examples of fluorescent molecules simultaneously possessing AIE and mechanofluorochromic behaviors are still limited, and the exploitation of more AIE-active mechanofluorochromic luminogens is necessary. Organic solid emitters with twisted molecular conformation can effectively prevent the formation of ACQ effect, thus exhibiting strong solid-state luminescence. Tetraphenylethene is a highly twisted fluorophore. Meanwhile, it is also a typical AIE unit, which can be used to construct high emissive stimuli-responsive functional materials.34–37The design and synthesis of novel organic emitters with tunable emission color has become a promising research topic at present. Only a limited number of organic fluorescent materials with full-color emission have been reported to date.38,39 For example, in 2018, Tang et al. reported six tetraphenylpyrazine-based compounds. Interestingly, in film states, these luminogens exhibited different fluorescence colors covering the entire visible range, and this is the first example of realizing full-color emission based on the tetraphenylpyrazine unit.40 It is still an urgent challenge to develop novel organic luminophors with tunable emission color basing on the same core structure.In this study, four organic fluorophores containing tetraphenylethene unit were successfully synthesized (Scheme 1). Introducing the thiophene and carbonyl units into the molecules possibly promoted the formation of weak intermolecular interactions such as C–H⋯S or C–H⋯O interaction, which was advantageous to the exploitation of interesting stimuli-responsive fluorescent materials. Indeed, all these compounds showed obvious AIE characteristics. Furthermore, these luminogens emitted a series of different fluorescent colors involving blue-green, green, yellow and orange in the aggregation state. In addition, these luminogens also exhibited reversible mechanofluorochromic phenomena involving different fluorescent color changes.Open in a separate windowScheme 1The molecular structures of compounds 1–4.To investigate the aggregation-induced properties of compounds 1–4, the UV-vis absorption spectra of 1, 2, 3 and 4 (20 μM) in DMF–H2O mixtures of varying proportions were studied initially (Fig. S1†). Obviously, level-off tails were obviously observed in the long-wavelength region as the water content increased. This interesting phenomenon is generally associated with the formation of nano-aggregates.41 Next, the photoluminescence (PL) spectra of 1–4 in DMF–H2O mixtures with various water fraction (fw) values were explored. As shown in Fig. 1, almost no PL signals were noticed when a diluted DMF solution of luminogen 1 was excited at 365 nm, and thus almost no fluorescence could be observed upon UV illumination at 365 nm, and the corresponding absolute fluorescence quantum yield (Φ) was as low as 0.04%. However, when the water content was increased to 50%, a new blue-green emission band with a λmax at 501 nm was observed, and a faint blue-green fluorescence was noticed under 365 nm UV light. As the water content was further increased to 90%, a strong blue-green emission (Φ = 30.81%) could be observed. Furthermore, as shown in Fig. S2,† the nano-aggregates (fw = 90%) obtained were confirmed by dynamic light scattering (DLS). Therefore, the compound 1 with bright blue-green emission caused by aggregate formation showed typical AIE feature.Open in a separate windowFig. 1(a) Fluorescence spectra of the dilute solutions of compound 1 (2.0 × 10−5 mol L−1) in DMF–water mixtures with different water contents (0–90%). Excitation wavelength = 365 nm. (b) Fluorescence images of 1 (2.0 × 10−5 mol L−1) in DMF–water mixtures with different fw values under 365 nm UV light.Similarly, as can be seen in Fig. 2–4, compounds 2–4 also showed obvious aggregation-induced green emission, aggregation-induced yellow emission, and aggregation-induced orange emission, respectively. When the water content was zero, the quantum yields of compounds 2–4 were 0.04%, 0.05% and 0.46%, respectively, while as the water content increased to 90%, the corresponding quantum yields of compounds 2–4 also increased to 30.67%, 45.57% and 26.53%, respectively. Hence, luminogens 2–4 were also AIE-active species. In addition, as shown in Fig. 5, the DFT calculations for the compounds 1–4 were performed. The calculated energy gaps (ΔE) of four compounds were 3.6178416 eV (compound 1), 3.276084 eV (compound 2), 3.3073755 eV (compound 3) and 3.0766347 eV (compound 4) respectively. Therefore, the various numbers and the various kinds of the substituents had slight effects on their molecular orbital energy levels of 1–4.Open in a separate windowFig. 2(a) Fluorescence spectra of the dilute solutions of compound 2 (2.0 × 10−5 mol L−1) in DMF–water mixtures with different water contents (0–90%). Excitation wavelength = 365 nm. (b) Fluorescence images of 2 (2.0 × 10−5 mol L−1) in DMF–water mixtures with different fw values under 365 nm UV light.Open in a separate windowFig. 3(a) Fluorescence spectra of the dilute solutions of compound 3 (2.0 × 10−5 mol L−1) in DMF–water mixtures with different water contents (0–90%). Excitation wavelength = 365 nm. (b) Fluorescence images of 3 (2.0 × 10−5 mol L−1) in DMF–water mixtures with different fw values under 365 nm UV light.Open in a separate windowFig. 4(a) Fluorescence spectra of the dilute solutions of compound 4 (2.0 × 10−5 mol L−1) in DMF–water mixtures with different water contents (0–90%). Excitation wavelength = 365 nm. (b) Fluorescence images of 4 (2.0 × 10−5 mol L−1) in DMF–water mixtures with different fw values under 365 nm UV light.Open in a separate windowFig. 5(a) HOMO and LUMO frontier molecular orbitals of molecule 1 based on DFT (B3LYP/6-31G*) calculation. (b) HOMO and LUMO frontier molecular orbitals of molecule 2 based on DFT (B3LYP/6-31G*) calculation. (c) HOMO and LUMO frontier molecular orbitals of molecule 3 based on DFT (B3LYP/6-31G*) calculation. (d) HOMO and LUMO frontier molecular orbitals of molecule 4 based on DFT (B3LYP/6-31G*) calculation.Subsequently, the mechanochromic fluorescent behaviors of compounds 1–4 were surveyed by solid-state PL spectroscopy. As shown in Fig. 6, the as-synthesized powder sample 1 exhibited an emission band with a λmax at 444 nm, corresponding to a blue fluorescence under 365 nm UV light. Intriguingly, a new blue-green light-emitting band with a λmax at 507 nm was observed after the pristine solid sample was ground. After fuming with dichloromethane solvent vapor for 1 min, the blue-green fluorescence was converted back to the original blue fluorescence. Therefore, luminogen 1 exhibited reversible mechanochromic fluorescence feature. Furthermore, this reversible mechanofluorochromic conversion was repeated many times by grinding-exposure without showing signs of fatigue (Fig. 10).Open in a separate windowFig. 6(a) Solid-state PL spectra of compound 1 before grinding, after grinding, and after treatment with dichloromethane solvent vapor. Excitation wavelength: 365 nm. Photographic images of compound 1 under 365 nm UV light: (b) the as-synthesized powder sample. (c) The ground sample. (d) The sample after treatment with dichloromethane solvent vapor.Open in a separate windowFig. 10Repetitive experiment of mechanochromic behavior for compound 1.Similarly, as evident from Fig. 7–9, luminogens 2–4 also exhibited obvious mechanofluorochromic characteristics. Moreover, the repeatabilities of their mechanochromic behaviors were also satisfactory (Fig. S3†). Hence, all the compounds 1–4 showed reversible mechanofluorochromic phenomena involving different fluorescent color changes, and the various numbers of the substituents could effectively influence the mechanofluorochromic behaviors of 1–4. Obviously, luminogen 3 or 4 after grinding exhibited more red-shifted fluorescence in comparison with that of the corresponding luminogen 1 or 2 after grinding.Open in a separate windowFig. 7(a) Solid-state PL spectra of compound 2 before grinding, after grinding, and after treatment with dichloromethane solvent vapor. Excitation wavelength: 365 nm. Photographic images of compound 2 under 365 nm UV light: (b) the as-synthesized powder sample. (c) The ground sample. (d) The sample after treatment with dichloromethane solvent vapor.Open in a separate windowFig. 8(a) Solid-state PL spectra of compound 3 before grinding, after grinding, and after treatment with dichloromethane solvent vapor. Excitation wavelength: 365 nm. Photographic images of compound 3 under 365 nm UV light: (b) the as-synthesized powder sample. (c) The ground sample. (d) The sample after treatment with dichloromethane solvent vapor.Open in a separate windowFig. 9(a) Solid-state PL spectra of compound 4 before grinding, after grinding, and after treatment with dichloromethane solvent vapor. Excitation wavelength: 365 nm. Photographic images of compound 4 under 365 nm UV light: (b) the as-synthesized powder sample. (c) The ground sample. (d) The sample after treatment with dichloromethane solvent vapor.In order to further explore the possible mechanism of mechanofluorochromism of 1–4, the powder X-ray diffraction (PXRD) measurements of various solid states of 1–4 were carried out. As depicted in Fig. 11, the pristine solid powder 1 showed many clear and intense reflection peaks, suggesting its crystalline phase. However, after the pristine powder sample was ground, the sharp and intense diffraction peaks vanished, which indicated the crystalline form was converted to the amorphous form. Interestingly, when the ground solid sample was fumigated with dichloromethane solvent vapor for 1 min, the corresponding sample powder exhibited the PXRD pattern of the initial crystalline form. Meanwhile, the structural transformations of the solid samples of 2–4 were similar to that of 1 (Fig. S4–S6†). Obviously, the morphological changes of solid samples of 1–4 from crystalline state to amorphous state and vice versa could be attributed to the reversible mechanical switching in compounds 1–4, and the mechanofluorochromic phenomena observed in 1–4 were related to the morphological transition involving the ordered crystalline phase and the disordered amorphous phase.Open in a separate windowFig. 11XRD patterns of compound 1: unground, ground and after treatment with dichloromethane solvent vapor.Fortunately, single crystals of compounds 1 and 2 were obtained by slow diffusion of n-hexane into a trichloromethane solution containing small amounts of 1 or 2. As shown in Fig. 12 and and13,13, the molecular structures of 1 and 2 exhibited a twisted conformation due to the existence of tetraphenylethene unit. Meanwhile, some weak intermolecular interactions, such as C–H⋯π interaction (d = 2.866 Å) for 1, π⋯π interaction (d = 3.371 Å) for 1, C–H⋯S interaction (d = 2.977 Å) for 2, and π⋯π interaction (d = 3.189 Å) for 2, were observed. These weak intermolecular interactions gave rise to a loose packing motif of 1 or 2, which indicated their ordered crystal packings might readily collapse upon exposure to external mechanical stimulus. Therefore, their solid-state fluorescence could be adjusted by mechanical force.Open in a separate windowFig. 12The structural organization of compound 1.Open in a separate windowFig. 13The structural organization of compound 2.In summary, four fluorescent molecules containing thiophene and tetraphenylethene units were successfully designed and synthesized in this study. All these compounds showed obvious AIE characteristics. Furthermore, these luminogens emitted various fluorescence colors involving blue-green, green, yellow and orange in the aggregation state. Meanwhile, these luminogens basing on the same core structure also exhibited reversible mechanofluorochromic phenomena involving different fluorescent color changes. The results of this study will be beneficial for the exploitation of novel luminophors with full-color emission. 相似文献
3.
A new colorimetric and fluorescent ‘on–off’ chemosensor, 1O, based on a photochromic diarylethene with a quinoline unit was designed and synthesized. The chemosensor 1O demonstrated selective and sensitive detection of Hg2+ ions in the presence of other competitive metal ions in acetonitrile. The stoichiometric ratio of the sensor 1O for Hg2+ was determined to be 1 : 1, and the limit of detection of the probe 1O was calculated to be 56.3 nM for Hg2+. In addition, a molecular logic circuit with four inputs and one output was successfully constructed with UV/vis light and metal-responsive behavior. ESI-MS spectroscopy, Job''s plot analysis, and 1H NMR titration experiments confirm the binding behavior between 1O and Hg2+.A new colorimetric and fluorescent ‘on–off’ chemosensor, 1O, based on a photochromic diarylethene with a quinoline unit was designed and synthesized. 相似文献
4.
To fabricate a novel biomimetic fluorescent chemosensor, PSaAEMA-co-PMPC was synthesized via atom transfer radical polymerization, and this copolymer could be used for the detection of zinc(ii) and cell imaging. A series tests with various metal ions verified the specific fluorescence response behavior. This novel biomimetic fluorescent chemosensor exhibits excellent selectivity for Zn2+ ions over a wide range of tested metal ions in an aqueous solution. Moreover, cytotoxicity and bio-imaging tests were conducted to study the potential bio-application of the chemosensor. Owing to the biomimetic portion (phosphorylcholine), this copolymer possesses outstanding biocompatibility and could clearly image cells. The results indicated that PSaAEMA-co-PMPC has great potential for application in zinc(ii) detection and cell imaging.To fabricate a novel biomimetic fluorescent chemosensor, PSaAEMA-co-PMPC was synthesized via atom transfer radical polymerization, and this copolymer could be used for the detection of zinc(ii) and cell imaging. 相似文献
5.
A novel solvent-dependent chemosensor 1o based on a diarylethene containing a rhodamine B unit has been designed. It could be used as a dual-functional chemosensor for selective detection of Hg2+ and Cu2+ by monitoring the changes in the fluorescence and UV-vis spectral in different solvents. A striking fluorescence enhancement at 617 nm was observed in DMSO upon the addition of Hg2+. However, 1o showed a remarkable absorption band appeared with maximum absorption at 555 nm after the addition of Cu2+ in THF. The results of ESI-MS spectra and Job''s plot confirmed a 1 : 1 binding stoichiometry between 1o and the two ions. The limits of detection of Hg2+ and Cu2+ were determined to be 0.14 μM and 0.51 μM, respectively. A 1 : 2 demultiplexer circuit was constructed by using UV light as data input, Cu2+ as the address input, and the absorbance at 555 nm and the absorbance ratio of (A603/A274) as the dual data outputs.A novel solvent-dependent chemosensor based on a diarylethene derivative for fluorescent “turn-on” recognition of Hg2+ and colorimetric detection of Cu2+ was synthesized, its multi-controllable photoswitchable behaviors with light and chemical stimuli were investigated. 相似文献
6.
In this study, a new fluorescent sensor dicyanoisophorone Rhodanine-3-acetic acid (DCI-RDA) (DCI-RDA) has been developed by employing a DCI-based push–pull dye as the fluorophore and RDA as the recognition moiety for the simultaneous sensing of Fe3+ and Hg2+ with a large Stokes Shift (162 nm), high selectivity and sensitivity, and low LOD (1.468 μM for Fe3+ and 0.305 μM for Hg2+). In particular, DCI-RDA has a short response time (30 s). The Job''s plot method in combination with 1H NMR titration and theoretical calculations was used to determine the stoichiometry of both DCI-RDA-Fe3+/Hg2+ complexes to be 1 : 1. Moreover, DCI-RDA is applied as a fluorescent probe for imaging in HeLa cells and zebrafish, indicating that it can be potentially applied for Fe3+/Hg2+ sensing in the field of biology.A new fluorescent sensor dicyanoisophorone rhodanine-3-acetic acid has been developed by employing a DCI-based push–pull dye as the fluorophore and RDA as the recognition moiety for the simultaneous sensing of Fe3+ and Hg2+. 相似文献
7.
Kalyani Rout Amit Kumar Manna Meman Sahu Jahangir Mondal Sunil K. Singh Goutam K. Patra 《RSC advances》2019,9(44):25919
A triazole-based novel bis Schiff base colorimetric and fluorescent chemosensor (L) has been designed, synthesized and characterized by elemental analysis, 1H-NMR, ESI-MS, FTIR spectra and DFT studies. The receptor L showed selective and sensitive colorimetric sensing ability for Cu2+ and Pb2+ ions by changing color from colorless to yellow and light yellow respectively in CH3OH–tris-buffer (1 : 1, v/v). However, it displayed strong fluorescence enhancement upon the addition of both Cu2+ and Pb2+ ions, attributed to the blocking of PET. The fluorometric detection limits for Cu2+ and Pb2+ were found to be 12 × 10−7 M and 9 × 10−7 M and the colorimetric detection limits were 3.7 × 10−6 M and 1.2 × 10−6 M respectively; which are far below the permissible concentration in drinking water determined by WHO. Moreover, it was found that chemosensor L worked as a reversible fluorescence probe towards Cu2+ and Pb2+ ions by the accumulation of S2− and EDTA respectively. Based on the physicochemical and analytical methods like ESI-mass spectrometry, Job plot, FT-IR, 1H-NMR spectra and DFT studies the detection mechanism may be explained as metal coordination, photoinduced electron transfer (PET) as well as an internal charge transfer (ICT) process. The sensor could work in a pH span of 4.0–12.0. The chemosensor L shows its application potential in the detection of Cu2+ and Pb2+ in real samples, living cells and building of molecular logic gate.A novel triazole-based bis Schiff base colorimetric and fluorescent chemosensor (L) has been designed, synthesized and characterized. The chemo-sensor L shows its application potential in the detection of Cu2+ and Pb2+ in living cells and building molecular logic gate. 相似文献
8.
9.
Qian Jiang Mingguang Zhang Zhonglong Wang Jie Song Yiqin Yang Wenchao Li Wen Gu Xu Xu Haijun Xu Shifa Wang 《RSC advances》2018,8(52):30055
Four difluoroboron (BF2) β-diketonate nopinone complexes 3a–3d that exhibited typical aggregation-induced emission (AIE) properties were synthesized using the natural renewable β-pinene derivative nopinone as the starting material. The thermal, photophysical, electrochemical and electroluminescent properties as well as the AIE properties of complexes 3a–3d were analyzed systematically. The data of photophysical and electrochemical demonstrated that compound 3b with a methoxy group exhibited the largest bathochromic shift, the highest absolute photoluminescence quantum yields and narrowest optical bandgap among 3a–3d. Using 3b as the emitter, electroluminescent (EL) device I exhibits blue-green light with CIE coordinates of (0.2774, 0.4531) and showed a better performance with a luminous efficacy (ηp) of 7.09 lm W−1 and correlated color temperature (TC) of 7028 K. The results demonstrate that new AIE compounds are promising solid-state luminescent materials with practical utility in electroluminescent materials.Four difluoroboron (BF2) β-diketonate nopinone complexes 3a–3d which exhibited typical AIE property were synthesized. Owing to high absolute fluorescence quantum yields of 3b, EL device based on 3b was fabricated, which exhibits a blue-green light. 相似文献
10.
Yuesong Wang Haichang Ding Shuai Wang Congbin Fan Yayi Tu Gang Liu Shouzhi Pu 《RSC advances》2019,9(21):11664
In this work, a rhodamine derivative was developed as a colorimetric and ratiometric fluorescent probe for Hg2+. It exhibited a highly sensitive fluorescence response toward Hg2+. Importantly, studies revealed that the probe could be used for ratiometric detection of Hg2+, with a low detection limit of 0.679 μM. The mechanism of Hg2+ detection using compound 1 was confirmed by ESI-MS, 1H NMR, and HPLC. Upon the addition of Hg2+, the rhodamine receptor was induced to be in the ring-opening form via an Hg2+-promoted hydrolysis of rhodamine hydrazide to rhodamine acid. In addition to Hg2+ detection, the naphthalimide–rhodamine compound was proven to be effective in cell imaging.A new probe based on naphthalimide–rhodamine was applied in recognition of Hg2+ by a FRET mechanism. 相似文献
11.
Conjugate polymer nanoparticles (CPNs) were constructed based on poly(fluorenone-co-thiophenes) (PFOTs) synthesized through a direct arylation polymerization (DArP) approach. Results demonstrate that the developed novel CPNs have potential applications in two-photon fluorescence imaging of both cells and tissues.Novel conjugate polymer nanoparticles (CPNs) based on poly(fluorenone-co-thiophenes) (PFOTs) were constructed for two-photon cell and tissue fluorescence imaging.Fluorescence imaging has been widely applied in biological studies on subcellular microenvironments and tissues to develop disease diagnostic methods and clinical treatment.1–3 The emerging two-photon fluorescence imaging approach has demonstrated some advantages over traditional single-photon fluorescence imaging, including deeper penetration depth, less photo-damage, reduced self-absorption and background signal due to autofluorescence, etc.4–6 Several two-photon absorption (TPA) materials have been reported thus far, such as organic molecules, quantum dots, metal complexes, carbon quantum dots, graphene quantum dots, et al.,7–11 both small-molecule fluorescent probes and nano-sized imaging agents fabricated by CPs are attractive and versatile materials for studying biological systems, and their size, composition, surface ligands, optical properties are important for their application.12–14 So, developing new TPA materials remains challenging but is needed to improve fluorescence quantum yield, biocompatibility, photostability, and ease of preparation compared to existing TPA probes.Conjugated polymers (CPs) with extended π-conjugation structure have been studied as promising fluorescent probes over the past two decades. Due to their effective absorption and fluorescence, high photostability, signal amplification effect, and excellent biocompatibility, they have been widely implemented in biosensing, drug delivery, and imaging.15–19 For instance, CPs-based nanoparticles with two-photon excitation character were applied as high contrast cell imaging probes by Xu et al.20,21 It was reported that synthesized chromophores with donor–acceptor (D–A) structures, which tend to exhibit relatively large two-photon absorption cross-section, and thus, enhanced TPA properties by the charge transfer effect.22,23 Wu et al. fabricated CPNs with polyfluorene derivative that were characterized by cross sections values up to 2.0 × 105 GM.24 Recently, Schanze et al. reported anionic conjugated polyelectrolytes (CPEs), such as PPE-SO3−, with moderate two-photon absorption cross-sections in the near-infrared (NIR) region for two-photon fluorescence cell imaging.25 Their work disclosed the potentials of CPEs and CPNs as TPA fluorescent materials in tissue imaging.Herein, we developed novel PFOT-based nanoparticles to exploit their single- and two-photon fluorescence properties for imaging applications in living cells and tissues (Scheme 1).Open in a separate windowScheme 1Illustration of PFOT nanoparticles as two-photon imaging probes.Direct arylation polymerization (DArP) has emerged as a simple and atom-economic method for polymer synthesis compared to traditional metal-catalyzed coupling polymerization, as shown in Fig. 1a.26 In this work, 4 novel D–A type CPs composed of fluorenone and thiophene moieties were synthesized via the DArP method, as displayed in Fig. 1b and c. All polymers are soluble in typical organic solvents, such as chloroform, THF, methanol, acetone, and DMF. PFOT-2 and PFOT-3 are slightly soluble in water due to the increased length of their hydrophilic side chains. Under optimized experimental conditions, we acquired PFOT-1, PFOT-2, PFOT-3, and PFOBT with reasonable Mn of 1.99, 2.57, 5.14, and 4.76 kg mol−1 respectively.Open in a separate windowFig. 1(a) Comparison of traditional coupling reactions and direct arylation polymerization, X is halogen. (b) Designed synthetic route of novel poly(fluorenone-co-thiophene) conjugated polymer. (c) Acquired novel poly(fluorenone-co-thiophene) (PFOT) conjugated polymers.Photophysical properties of CPs are affected by their main chain conjugated structure, molecular weight, side chain structure, solvent, and etc. For the fluorenone-based copolymers, it has been reported that the intermolecular CO⋯HC (aromatic) hydrogen bonds (H-bonds) would exert influence on absorption maximum position.27,28 In addition, side chains of the CPs could also have impact on the conformation of the backbone and the aggregation state of the polymers. Photophysical properties of the obtained four CPs (PFOT-1, PFOT-2, PFOT-3, and PFOBT) were studied. UV-visible absorption and fluorescence emission spectra of the four CPs in chloroform are shown in Fig. 2a. The absorption of all the four polymers in chloroform features a strong band in the UV range and a broader and weaker band in the visible range. PFOT-1 and PFOBT show UV absorption with two maxima at 287 and 265 nm, that are assigned, respectively, to cisoid and transoid conformations of the conjugated backbone, while PFOT-2 and PFOT-3 only demonstrate one peak at about 305 nm, suggesting that the cisoid conformation dominates which enhance the polymer aggregation. Strong and wide fluorescence emission bands of the 4 polymers can be observed with the full width at half maxima (FWHM) at about 200 nm (Fig. 2b). Polymers with single thiophene in their repeat units, such as PFOT-1, PFOT-2, and PFOT-3, demonstrated red-shifted emission maximum wavelengths (595 to 630 nm) compared to that of the polymer PFOBT (555 nm), which contains bithiophene in its repeat units. We believe that PFOBT is in a less aggregated state than all other three PFOT polymers, leading to a blue-shifted absorption and emission band. It has been reported that D–A type CPs usually demonstrate lower bandgaps and large Stokes shifts due to the intramolecular charge transfer (ICT).29 As the spectra shown, PFOT-1, PFOT-2, PFOT-3, and PFOBT CPs exhibit large Stokes shifts of 220, 260, 250, and 170 nm respectively, which is in favour of diminishing the reabsorption effect. Quantum yields (QYs) of PFOT-1, PFOT-2, PFOT-3, and PFOBT CPs in CHCl3 were determined to be 0.081, 0.193, 0.376, and 0.432, respectively, via the reference method with coumarin 6 in ethanol as a reference. Then, PFOT-2, PFOT-3, and PFOBT were selected for further imaging studies.Open in a separate windowFig. 2Absorption (a) and fluorescence emission spectra (b) of PFOT-1 (red), PFOT-2 (yellow), PFOT-3 (blue), and PFOBT (green) polymers in CHCl3, λex = 380 nm. The concentration of all polymers is 10 μM in chloroform.For bio-imaging, efficient internalization of probes by cells is an essential step. In order to improve the biocompatibility of the CPs, CPNs were fabricated via the nanoprecipitation method using polymers and Pluronic-F127 as a surfactant and encapsulation matrix, as shown in Fig. 3a. The diameters of CPNs were characterized by dynamic light scattering (DLS) for three times with the average diameters range from 45.1 to 142.3 nm († revealed the core–shell morphology of the CPNs, probably formed by the hydrophobic inner cores and hydrophilic outer shells. This core–shell morphology of the CPNs helps with improving their stability in aqueous environment, and demonstrates their potential application as fluorescent probes and drug nano-vehicles. In Fig. 3b, compared to the corresponding CPs in solutions, fluorescence emission spectra of the four CPNs revealed red-shifts. This may be ascribed to the internal stress of the particles that increases with the formation of CPNs, which leads to variation in the energy band structures, incremental overlap of the electron wave function, narrowing of energy band-gap, and red-shift of the emission peak length.30 Also, it has been reported that aggregated particles fabricated via nanoprecipitation method usually exhibit red-shifted emission compared to their non-aggregated forms, which can be ascribed to the bending, kinking, and interchain interactions of polymer backbones in the aggregation.31,32 Cellular cytotoxicity assay of the PFOT CPNs towards HeLa cells displayed no apparent cytotoxicity with a concentration up to 200 μg mL−1 as shown in Fig. 4a. The low cytotoxicity and efficient endocytosis (Fig. S4†) demonstrated a good biocompatibility of the synthesized CPNs. Also, the photostability assay of PFOT-2 NPs, PFOT-3 NPs, and PFOBT NPs was carried out via a photobleaching experiment. As shown in Fig. 4b and c, fluorescence of PFOT-2 NPs, PFOT-3 NPs, PFOBT NPs, and LysoTracker Green remained at 55%, 54%, 54%, and 8% respectively, after 20 times scans, suggesting that the CPNs exhibited stronger photostability than the small molecular probe LysoTracker Green. Our results also show that the CPs and CPNs are stable at pH ranging from 5.0–7.4, which cover the biological pH ranges of tumor tissues, late endosomes and lysosomes, normal tissues and blood (Fig. S6†).Open in a separate windowFig. 3(a) Fabrication of CPNs via nanoprecipitation method. Absorption (b) and fluorescence emission (c) spectra of PFOT-1 (red), PFOT-2 (yellow), PFOT-3 (blue), and PFOBT (green) NPs in water, λex = 480 nm (b).Characterization of PFOT series CPNs
Open in a separate windowaThe hydrodynamic diameter (Dh) and polydispersity index (PDI) of PFOT nanoparticles.bQuantum yields (QYs) were measured via the reference method with coumarin 6 in ethanol as a reference.cStokes shift of PFOT series CPNs.Open in a separate windowFig. 4(a) Cell viability of HeLa cells after treatment with PFOT-2 (black), PFOT-3 (red), and PFOBT (blue) NPs at the concentration range from 0 to 200 μg mL−1. Cells without treatment of NPs were used as control. (b) Photobleaching measurements: fluorescent images of HeLa cells cultured with the CPNs and LysoTracker Green respectively at 1 scan and 20th scan. (c) The cellular fluorescence intensity of PFOT-2 (red), PFOT-3 (green), PFOBT (blue) NPs, and LysoTracker Green (yellow) respectively vs. the number of scans.Then, HeLa cells were incubated with PFOT-2, PFOT-3, and PFOBT NPs (concentration of 5 μM each) for 4 h and observed with a one-photon confocal fluorescence microscope. As shown in Fig. S4,† almost all cells demonstrated CPNs internalization signals of red fluorescence. Furthermore, to explore the endocytosis process of these CPNs, organelle location was investigated via a lysosome co-localization probe, LysoTracker green. Fig. 5 displays the fluorescence imaging of HeLa cells co-stained with CPNs (red) and the LysoTracker probe (green). As shown in Fig. 5, red signal of PFOT-2, PFOT-3, and PFOBT NPs and green signal well overlapped with Pearson correlation coefficients (PCCs) of 0.94 (±0.03), 0.94 (±0.02), and 0.97 (±0.02), respectively. This means that most NPs localized in lysosomes, while others appear in early or late endosomes, suggesting that lysosomes are the primary organelle participating in the endocytosis process of these CPNs.33Open in a separate windowFig. 5Fluorescence imaging of intracellular distribution of PFOT-2 NPs (b), PFOT-3 NPs (c) and PFOBT NPs (d), respectively, co-stained with LysoTracker Green (66.7 nM) and DAPI (blue channel) in HeLa cells. Polymer concentration is 5 μM. For control group (a), cells were washed before imaging.Many researchers have high interest in investigating D–A type CPs with TPA property for use in photoelectric devices and bio-probes.34,35 It has been acknowledged that molecules constructed by electron donating and accepting functional groups with extended π-conjugated systems are capable of displaying two-photon absorption cross-sections.36,37 In this work, the application of PFOT CPNs as two-photon imaging probes were explored by an Olympus FVMPE RS two-photon microscope with femtosecond laser excitation at 720 and 960 nm. The pictures taken by the two-photon microscope in Fig. 6 show that 5 μM of CPNs is sufficient to give clear cells fluorescent images of high quality with an emission wavelength range of 575–645 nm. It should also be noted that both excitation and emission wavelengths of CPNs are located in the 575–960 nm range, encompassing the deep red and near-infrared areas. Combining these properties, PFOT CPNs as NIR probes could provide both deep tissue penetration and low autofluorescence, which has great potential in medical fluorescent imaging applications. To further verify the advantages of deep-red emission and two-photon absorption of PFOT CPNs, fluorescence images of mice liver tissue slices were studied. The tissue slices were pre-treated with PFOT-2, PFOT- 3, and PFOBT NPs for 1 h, then one-photon and two-photon confocal imaging in Z-scan mode were performed to obtain fluorescence images as shown in Fig. 7. All the PFOT CPNs were effectively applied as tissue imaging probes with penetration depths of 120–240 μm. Compared with one-photon confocal Z-scan imaging, two-photon Z-scan imaging showed a deeper penetration depth up to 240 μm due to the longer absorption and emission wavelength in deep red and NIR areas. All results suggest that the CPNs based on PFOT polymers possess excellent tissue-penetrating, staining, and imaging capabilities. Also, to investigated the in vivo NIR fluorescence imaging ability of PFOBT NPs, we established the common BALB/c murine breast cancer (4T1) model. As shown in Fig. 8, the PFOBT CPNs were able to accumulate in tumor tissue efficiently after 48 h tail vein injection, due to the enhanced permeability and retention (EPR) effect.Open in a separate windowFig. 6Two-photon imaging of HeLa cells incubated with PFOT-2 NPs (b), PFOT-3 NPs (c), and PFOBT NPs (d), respectively (NPs at 5 μM, λex = 720 nm, emission wavelength ranged from 575 to 645 nm). The 3rd and 4th columns are magnification of the corresponding groups. For control experiment (a), cells were washed before imaging (λex = 960 nm).Open in a separate windowFig. 7Fluorescence imaging of fresh mice liver tissue slices incubated with NPs (10 μM) for 1 h in PBS buffer at different penetration depths. PFOT-2 NPs (a and b), PFOT-3 NPs (c and d), and PFOBT (e and f) NPs tissue imaging of one-photon (left) (λex = 559 nm, λem = 575–675 nm) and two-photon condition (right) (λex = 960 nm for PFOT-2 NPs, PFOT-3 NPs, λex = 720 nm for PFOBT NPs, λem = 575–645 nm). The step size is 20 μm.Open in a separate windowFig. 8 In vivo fluorescence images of 4T1 tumor (on the lower left side of the mouse''s back) bearing BALB/c mouse injected with PFOBT NPs at 24 h and 48 h post-injection. (λex = 470 nm, λem = 600 nm). 相似文献
Sample name | D a (nm) | PDIa | QYsb | Stokes shiftc |
---|---|---|---|---|
PFOT-1 | 91.7 ± 1.5 | 0.12 | 0.012 | 120 |
PFOT-2 | 82.6 ± 0.5 | 0.17 | 0.021 | 200 |
PFOT-3 | 142.3 ± 1.9 | 0.44 | 0.029 | 150 |
PFOBT | 45.1 ± 0.5 | 0.32 | 0.027 | 145 |
12.
Zengchen Liu Shujing Li Genwu Ge Yanxia Li Chunxiang Zhao Hui Zhang Zhiguang Yang 《RSC advances》2019,9(10):5377
In the study, a highly selective and sensitive fluorescence sensor derived from nitrogen heterocycle was synthesized and characterized. By the fluorescence experiments, it was found to show a higher response toward Al3+ than other commonly coexistent metal ions in C2H5OH/H2O media (pH = 7.2). Moreover, the large binding constant (3.44 × 1014 M−1) between Al3+ and the sensor was calculated by fluorescence titration experiment. In addition, the synergistic effect mechanism due to photoinduced electron transfer (PET) and C N isomerization was deduced according to the fluorescence behavior. In addition, the fluorescence imaging in living cells was studied systemically, which exhibited high fluorescence sensing activity toward Al3+.In the study, a highly selective and sensitive fluorescence sensor derived from nitrogen heterocycle was synthesized and characterized. 相似文献
13.
Xuejing Liu Yuangong Zhang Haijing Hao Wanju Zhang Libin Bai Yonggang Wu Hongchi Zhao Hailei Zhang Xinwu Ba 《RSC advances》2018,8(11):5776
Thermo-responsive hyperbranched copoly(bis(N,N-ethyl acrylamide)/(N,N-methylene bisacrylamide)) (HPEAM-MBA) was synthesized by using reversible addition–fragmentation chain-transfer polymerization (RAFT). Interestingly, the zinc ion (Zn2+) was found to have a crucial influence on the lowest critical solution temperature (LCST) of the thermo-responsive polymer. The tetraphenylethylene (TPE) unit was then introduced onto the backbone of the as-prepared thermo-responsive polymer, which endows a Zn2+-responsive “turn-off” effect on the fluorescence properties. The TPE-bearing polymer shows a highly specific response over other metal ions and the “turn-off” response can even be tracked as the concentration of Zn2+ reduces to 2 × 10−5 M. The decrement of fluorescence intensity was linearly dependent on the concentration of Zn2+ in the range of 4–18 μmol L−1. The flexible, versatile and feasible approach, as well as the excellent detection performance, may generate a new type of Zn2+ probe without the tedious synthesis of the moiety bearing Zn2+ recognition units.A novel fluorescent HPEAM-TPEAH, possessing a highly selective and sensitive response to Zn2+, was synthesized using RAFT. 相似文献
14.
Vaupel DB Tella SR Huso DL Wagner VO Mukhin AG Chefer SI Horti AG London ED Koren AO Kimes AS 《The Journal of pharmacology and experimental therapeutics》2005,312(1):355-365
2-[(18)F]fluoro-3-(2(S)-azetidinylmethoxy)pyridine (2-[(18)F]F-A-85380), a positron emission tomography (PET) radioligand for neuronal alpha4beta2(*) nicotinic acetylcholine receptors, was evaluated for its pharmacology and safety. In the Ames test for mutagenicity, 2-F-A-85380 was without effect in five bacterial strains. No evidence of gross pathology or histopathological changes occurred in either 2-day acute (0.4-4000 nmol/kg i.v.) or 14-day expanded acute (40-4000 nmol/kg i.v.) toxicity studies in mice. Similarly, hematology and serum chemistry values in rhesus monkeys administered 60 nmol/kg i.v. were not affected over 14 days. Like nicotine, 2-F-A-85380 produced convulsions in mice at very high doses. The ED(50) value of 2-F-A-85380 for eliciting tonic-clonic convulsions (5.0 micromol/kg i.v.) was nearly 4 times greater than that of nicotine (ED(50) = 1.4 micromol/kg i.v.). Lower doses of 2-F-A-85380 (30-300 nmol/kg i.v.) and nicotine (20-400 nmol/kg i.v.) increased systolic and diastolic blood pressure, heart rate, and cardiac contractility in rats. Notably, the PR, QRS, or QTc intervals of the rat electrocardiogram were unaffected by either drug. Dosimetry studies indicated that the urinary bladder wall was the critical organ and total radiation exposure was within acceptable limits. Estimated doses of 2-F-A-85380 required to elevate blood pressure and heart rate by 10% ranged from 40 to 58 nmol/kg i.v. Nevertheless, the estimated radiopharmaceutically relevant dose of [(18)F]2-F-A-8380 required for initial PET imaging studies, 10 pmol/kg, is less than 1/4000th of the doses calculated (40-58 nmol/kg i.v.) to elevate blood pressure and heart rate by 10% in humans and should elicit no clinically significant effects and have acceptable dosimetry. 相似文献
15.
Ruth A. Odhiambo Austin O. Aluoch Lydia W. Njenga Stanley M. Kagwanja Shem O. Wandiga Ola F. Wendt 《RSC advances》2018,8(7):3663
A series of complexes with oxathiacrown ethers appended to a [Ru(bpy)2]2+ moiety have been synthesized and characterised using 1H NMR, 13C NMR, IR, electronic absorption and emission spectroscopies, mass spectrometry and elemental analyses. The complexes exhibit strong MLCT luminescence bands in the range 608–611 nm and one reversible metal centred oxidation potential in the range 1.00–1.02 V. Their selectivity and sensitivity towards Hg2+, Cd2+ and Pb2+ metal ions have been investigated using electronic absorption, luminescence, cyclic and differential pulse voltammetry titrations. Their responses towards selected cations and anions have also been investigated using electronic absorption and luminescence. While the complexes are selective towards Hg2+ and Cd2+ ions, none of them is selective towards Pb2+ ions. In particular, complex 2 gives a selective change in the UV/Vis absorbance with Hg2+ making it possible to detect mercury down to a detection limit of 68 ppm. The binding constants and limits of detection of the complexes have been calculated, with values ranging from 4.37 to 5.38 and 1.4 × 10−3 to 6.8 × 10−5 for log Ks and LOD respectively.Oxathiacrown ether modified ruthenium complex 2 facilitates a selective naked-eye detection of Hg2+ with an instrumental detection limit of 68 ppm. 相似文献
16.
Hui Zhang Baoling Wang Xiaoyi Liu Hongxu Zhang Jiangyu Yao Xingchu Gong Jizhong Yan 《RSC advances》2022,12(15):9121
The current study highlights the advantages of using the quality by design (QbD) approach to synthesise and optimize SERS substrates for the detection of Hg2+. Considering that the performance of Au@AgNPs is affected by many factors, Plackett–Burman (PB) experimental design was used to determine the critical process parameters (CPPs) for evaluating the performance of Au@AgNPs. The quantitative relationships between the CPPs and the critical quality attributes (CQAs) were assessed by Box-Behnken Design (BBD). The optimal design space for Au@AgNPs was calculated via a Monte Carlo algorithm. Finally, detection of Hg2+ in the range of 1 ∼ 100 ng mL−1 (R2 = 0.9891) was achieved by SERS in combination with 4,4-bipyridine (Dpy) as signal molecules. The recoveries for licorice ranged from 83.53% to 92.96%. Specificity and practicality studies indicated that the method based on the QbD concept and design space not only met the optimal performance of Au@AgNPs but also improved the rapid detection of Hg2+ in Chinese medicine samples.The current study highlights the advantages of using the quality by design (QbD) approach to synthesise and optimize SERS substrates for the detection of Hg2+. 相似文献
17.
A highly sensitive and selective colorimetric assay for the dual detection of Hg2+ and As3+ using gold nanoparticles (AuNPs) conjugated with d-penicillamine (DPL) was developed. When Hg2+ and As3+ ions coordinate with AuNP-bound DPLs, the interparticle distance decreases, inducing aggregation; this results in a significant color change from wine red to dark midnight blue. The Hg4f and As3d signals in the X-ray photoelectron spectra of Hg2+ (As3+)-DPL-AuNPs presented binding energies indicative of Hg2+–N(O) and As3+–N(O) bonds, and the molecular fragment observed in time-of-flight secondary ion mass spectra confirmed that Hg2+ and As3+ coordinated with two oxygen and two nitrogen atoms in DPL. The detection of Hg2+ and As3+ can be accomplished by observing the color change with the naked eye or by photometric methods, and this was optimized to provide optimal probe sensitivity. The assay method can be applied for environmental monitoring by first selectively quantifying Hg2+ in water samples at pH 6, then estimating the As3+ concentration at pH 4.5. The efficiency of the DPL-AuNP probe was evaluated for the sequential quantification of Hg2+ and As3+ in tap, pond, waste, and river water samples, and absorbance ratios (A730/A525) were correlated with Hg2+ and As3+ concentrations in the linear range of 0–1.4 μM. The limits of detection in water samples were found to be 0.5 and 0.7 nM for Hg2+ and As3+, respectively. This novel probe can be utilized for the dual determination of Hg2+ and As3+, even in the presence of interfering substances in environmental samples.A highly sensitive and selective colorimetric assay for the dual detection of Hg2+ and As3+ using gold nanoparticles (AuNPs) conjugated with d-penicillamine (DPL) was developed. 相似文献
18.
Julio Rodríguez-Lavado Alejandro Lorente Erick Flores Andrs Ochoa Fernando Godoy Pablo Jaque Claudio Saitz 《RSC advances》2020,10(37):21963
This article reports the synthesis and characterisation of two lower rim calix[4]arene derivatives with thiourea as spacer and pyrene or methylene–pyrene as fluorophore. Both derivatives exhibit a fluorimetric response towards Hg2+, Ag+ and Cu2+. Only methylene–pyrenyl derivative 2 allows for selective detection of Hg2+ and Ag+ by enhancement or decrease of excimer emission, respectively. The limits of detection of 2 are 8.11 nM (Hg2+) and 2.09 nM (Ag+). DFT and TD-DFT computational studies were carried out and used to identify possible binding modes that explain the observed response during fluorescence titrations. Calculations revealed the presence of different binding sites depending on the conformation of 2, which suggest a reasonable explanation for non-linear changes in fluorescence depending on the physical nature of the interaction between metal centre and conformer. INHIBITION and IMPLICATION logic gates have also been generated monitoring signal outputs at pyrene monomer (395 nm) and excimer (472 nm) emission, respectively. Thus 2 is a potential primary sensor towards Ag+ and Hg2+ able to configure two different logic gate operations.This article reports the synthesis and characterisation of two lower rim calix[4]arene derivatives with thiourea as spacer and pyrene or methylene-pyrene as fluorophore. 相似文献
19.
In this work, a new rhodamine chemosensor (P) with excellent photochromic properties upon vis irradiation was designed and synthesized. The fabricated chemosensor P could detect Al3+via the opening of the spirolactam ring of the rhodamine unit with high selectivity and sensitivity. The spirolactam ring opening was confirmed by NMR and infrared spectroscopy. Upon binding with Al3+, the generated 1 : 1 P-Al3+ complex, confirmed by Job''s plot titrations and mass spectrometry analysis, could exhibit a remarkable fluorescence enhancement with a limit of detection (LOD) of 0.16 μM. Furthermore, the sensing of P to Al3+in vivo was also studied quantitatively and qualitatively in detail, and the results showed that the coordination between P with Al3+ was reversible in living cells.In this work, a new rhodamine chemosensor (P) with excellent photochromic properties upon vis irradiation was designed and synthesized. 相似文献
20.
The glass–ceramic form of phosphor materials can overcome the many serious issues of phosphor/silicone composite in commercial phosphor-converted LEDs and are considered as new-generation color converters. In this report, we have shown a novel approach of developing inorganic red phosphor [Eu3+:La2(MoO4)3] in the glass–ceramic form based on lanthanum molybdate system. The ceramic form of the compound was found to have a glass transition temperature of 1002 °C, as confirmed by TGA and DSC studies. Further, XRD, FTIR and Raman studies also confirmed that the compounds prepared at 1050 °C are in glass–ceramic form, while those prepared at 750 °C are in ceramic form. Photoluminescence studies showed that both the ceramic and glass–ceramic forms of the phosphor are red color-emitting materials. However, the glass–ceramic forms have better color purity and more radiation transition probabilities. Further, the decay kinetics of both ceramic and glass–ceramic forms confirmed that only those Eu3+ ions which exist in the grain boundaries of the ceramics go inside the glass network structure upon heating the compound at or above the glass transition temperature. On the other hand, Eu3+ ions which exist at the La-site in the bulk of the particles are retained in the ceramic form in the glass–ceramic mixture.The glass–ceramic Eu-LMO-1050 is more suitable as a red-color-emitting phosphor material than the ceramic Eu-LMO-750. Further, Eu-LMO-1050 can overcome the problems related to the phosphor/silicone composite in commercial LEDs. 相似文献