Restriction Of Intramolecular Rotation Research Articles

Fluorescence Entrenched Probe for Onsite Detection of Amoxicillin Residue in Bovine Milk.

A novel fluorescent probe (E)-3-(4-hydroxyphenyl)-2-((pyrene-1-ylmethylene) amino)propanoic acid (PyT) was developed for the 'turn-on' detection of amoxicillin(AM), residues. The PyT molecule was developed by a simple condensation reaction between a biologically important tyrosine amino acid and pyrene carboxaldehyde. The small fluorophore molecule has spectacular photoluminescence properties such as large stock shift, high photostability, selectivity and sensitivity toward the analytes. The PyT upon dispersion in the liquid phase becomes highly luminescent possessing the restricted intramolecular rotation (RIR) and excited stated intramolecular proton transfer (ESIPT) properties which are the major criteria for aggregation induced emission enhancement (AIEE) mechanism prevailing the aggregation caused quenching (ACQ). PyT molecule shows a binding constant of 3.285 × 104 L mol-1for amoxicillin (AM). The limit of detection(LOD) values are found to be 1.67µM. Consuming bovine milk with antibiotic residues exceeding the maximum residue limit (MRL) can lead to food toxicity and life threatening diseases in humans. The milk sample with AM antibiotic residue in presence of PyT probe shows a distinct blue colour which infers the selectivity and sensitivity of the probe towards the analyte. The fluorescence probe adheres with merits like on site and visual examination by naked eye without aid of any instruments.

A combination of covalent and noncovalent restricted‐intramolecular‐rotation strategy for supramolecular AIE‐type photosensitizer toward photodynamic therapy

AbstractPhotodynamic therapy (PDT) is a promising noninvasive method for targeted cancer cell destruction. Still, its effectiveness is often hindered by the aggregation‐caused quenching effect of organic photosensitizer (PS) in aqueous environments. Here, we have employed a combination of covalent and noncovalent restricted‐intramolecular‐rotation strategies to develop supramolecular PSs with aggregation‐induced emission (AIE) characteristics. Firstly, a water‐soluble octacationic molecular cage (1) with a bilayer tetraphenylethene (TPE) structure has been designed and synthesized, which minimizes intramolecular rotation of TPE moieties and achieves the single‐molecule‐level aggregation by the covalent restriction of intramolecular rotation (RIR) via molecular engineering synthesis. Compared with its single‐layer TPE analog, 1 exhibits superior efficiency in generating reactive oxygen species (ROS) including superoxide radical (O2−•) and singlet oxygen (1O2) upon white‐light irradiation. Subsequently, by forming a 1:4 host–guest complex (1@CB[8]4) between 1 and cucurbit[8]uril (CB[8]), O2−• generation can be further enhanced by the noncovalent RIR via the host–guest assembly. Additionally, 1@CB[8]4 as a photocatalyst promotes rapid oxidation of nicotinamide adenine dinucleotide (NADH) in water. Given its Type‐I ROS generation and catalytic activity for NADH oxidation, 1@CB[8]4 acts as a supramolecular AIE‐type PS to exhibit strong photo‐induced cytotoxicity upon white‐light irradiation under hypoxic conditions, showcasing its potential for synergistic PDT.

Restricted Intramolecular Rotation: A Dual Fluorescence Response to Hg2+ Quenching and Ag+ Enhancement in Live Rhizoctonia Solani Cells.

A novel imidazo[1,2-a]pyridine derivative probe (R) was designed, synthesized, and characterized via various characterization techniques, such as ESI-MS, 1H NMR, 13C NMR, and Dept-135 NMR. The data obtained from single-crystal XRD reveal that probe R has a coplanar configuration and is part of the monoclinic crystal system, designated the P2(1)/n space group. The fluorescence of (R) is further enhanced by silver (I) ions. On the other hand, Hg2+ significantly quenches the fluorescence of probe R. The presence of other common metal ions does not influence the fluorescence of probe R in the CH3CN: H2O (1:1) mixture, as they neither increase nor quench it. From the fluorescence enhancement data, the low detection limit (LOD) for Ag + ions was determined to be 1.24 × 10- 8 M, whereas the quenching caused by Hg2+ resulted in an LOD of 5.69 × 10- 9 M. The complex of probe R with Ag+/Hg2+ exhibited a 1:1 stoichiometry, as confirmed by mass spectrometry and a Job plot. Single-crystal XRD analysis of R and its complex with Hg2+ revealed a loss of coplanarity, which confirmed their nonfluorescent behavior. We present a promising application of probe R in visualizing living Rhizoctonia oryzae cells exposed to silver (I) and mercury (II) ions.

A mitochondria-targeted dual-response fluorescent probe with large Stokes shift for visualizing viscosity and cysteine in cancer cells and zebrafish

Mitochondrial cysteine (Cys) and viscosity are closely associated with numerous cellular processes and diseases. Developing a method capable of real-time tracking of viscosity and Cys in mitochondria is crucial for understanding cell status and mitochondria-related diseases. In this study, we developed a mitochondria-targeted fluorescent probe (Mito-QP) with a large Stokes shift of 171 nm for detecting Cys and viscosity. The acryloyl group enabled Mito-QP specific response to Cys with high sensitivity. The probe exhibited significant red fluorescence enhancement with increasing viscosity due to restricted intramolecular rotation. Additionally, Mito-QP showed low cytotoxicity and excellent mitochondrial-targeting ability. The probe was successfully employed to monitor fluctuations in mitochondrial viscosity and Cys in cancer cells and zebrafish. This work provides a convenient and effective sensor for studying mitochondrial dysfunction.

Studies of Anticancer Activities In Vitro and In Vivo for Butyltin(IV)-Iridium(III) Imidazole-Phenanthroline Complexes with Aggregation-Induced Emission Properties.

Organotin(IV) and iridium(III) complexes have shown good application potential in the field of anticancer; however, the aggregation-caused quenching (ACQ) effect induced by high concentration or dose has limited the research on their targeting and anticancer mechanism. Then, a series of aggregation-induced emission (AIE)-activated butyltin(IV)-iridium(III) imidazole-phenanthroline complexes were prepared in this study. Complexes exhibited significant fluorescence improvement in the aggregated state because of the restricted intramolecular rotation (RIR), accompanied by an absolute fluorescence quantum yield of up to 29.2% (IrSn9). Complexes demonstrated potential in vitro antiproliferative and antimigration activity against A549 cells, following a lysosomal-mitochondrial apoptotic pathway. Nude mouse models further confirmed that complexes had favorable in vivo antitumor and antimigration activity in comparison to cisplatin. Therefore, butyltin(IV)-iridium(III) imidazole-phenanthroline complexes possess the potential as potential substitutes for platinum-based drugs.

AIE paper shred for the detection of evolved amine vapor from putrefaction processes of fish

Seafood plays a major role in the human diet. During transportation, without proper storage and supply chain, its quality deteriorates easily. The post-harvesting processes such as the storage of food play a crucial role in human health. So it is highly imperative to have a technique for identifying food spoilage earlier to ensure the food safety and security of the consumers. Herein we have developed a highly selective and sensitive fluorescent ‘Turn-on’ probe 2-amino-5-nitrobenzo [d] thiazol-2-yl) imino)methylphenol ANT based on aggregation induced emission (AIE). ANT molecule possesses both restricted intramolecular rotation (RIR) and excited state intramolecular proton transfer (ESIPT) properties leading to fluorescent enhancement rather than aggregation caused quenching (ACQ). The probe shows high selectivity and sensitivity towards the NH3 vapor. This probe with the AIE property is employed for the real-time detection of NH3 in both aqueous and gaseous phases. ANT molecule is deposited on the paper shred by a physical method is utilized to monitor NH3 vapor from red snapper fish as a real-time sample during its degradation processes. After two days there is a ratiometric color change in the paper shred from yellow to orange for the fish stored at room temperature indicating its rotten and unpalatability nature. Paper shred is reused by immersing it into the tetrahydrofuran (THF), in which it retains its initial color due to deprotonation of NH3, keto to enol tautomerism discloses the reusability of the fluorescent probe. Studies carried out using UV–visible and fluorescence spectroscopy infer that the ANT probe has high affinity towards NH3 vapor.

Ultrafast restricted intramolecular rotation in molecules with aggregation induced emission.

In this work, the ultrafast intramolecular rotation behavior of 1,1,2,3,4,5-hexaphenylsilole has been investigated in several solutions with different viscosities using femtosecond transient absorption spectroscopy combined with density functional theory and time-dependent density functional theory calculations. It is demonstrated that the nonradiative process, which competes with radiative decay, involves two main stages, namely the restricted intramolecular rotation and internal conversion processes. The intramolecular rotation depends on viscosity and presents a significant restriction. The restricted rotational rate is determined to be dozens of picoseconds. The following nonradiative process is strongly dominated by intramolecular rotation. The nonradiative decay rate will decrease with the increase in viscosity, leading to a rise in the radiative probability and photoluminous yield. These results have borne out the mechanism of ultrafast restricted intramolecular rotation of aggregation induced emission and provided a detailed photophysical picture of nonradiative processes.

Aggregation induced emission dynamic chiral europium(III) complexes with excellent circularly polarized luminescence and smart sensors

The synthesis of dynamic chiral lanthanide complex emitters has always been difficult. Herein, we report three pairs of dynamic chiral EuIII complex emitters (R/S-Eu-R-1, R = Et/Me; R/S-Eu-Et-2) with aggregation-induced emission. In the molecular state, these EuIII complexes have almost no obvious emission, while in the aggregate state, they greatly enhance the EuIII emission through restriction of intramolecular rotation and restriction of intramolecular vibration. The asymmetry factor and the circularly polarized luminescence brightness are as high as 0.64 (5D0 → 7F1) and 2429 M−1cm−1 of R-Eu-Et-1, achieving a rare double improvement. R-Eu-Et-1/2 exhibit excellent sensing properties for low concentrations of CuII ions, and their detection limits are as low as 2.55 and 4.44 nM, respectively. Dynamic EuIII complexes are constructed by using chiral ligands with rotor structures or vibration units, an approach that opens a door for the construction of dynamic chiral luminescent materials.

Cooperativity of ESPT and Aggregation-Induced Emission Effects-An Experimental and Theoretical Analysis of a 1,3,4-Thiadiazole Derivative.

4-[5-(Naphthalen-1-ylmethyl)-1,3,4-thiadiazol-2-yl]benzene-1,3-diol (NTBD) was extensively studied through stationary UV-vis absorption and fluorescence measurements in various solvents and solvent mixtures and by first-principles quantum chemical calculations. It was observed that while in polar solvents (e.g., methanol) only a single emission band emerged; the analyzed 1,3,4-thiadiazole derivative was capable of producing dual fluorescence signals in low polarity solvents (e.g., n-hexane) and certain solvent mixtures (e.g., methanol/water). As clearly follows from the experimental spectroscopic studies and theoretical modeling, the specific emission characteristic of NTBD is triggered by the effect of enol → keto excited-state intramolecular proton transfer (ESIPT) that in the case of solvent mixture is reinforced by aggregation of thiadiazole molecules. Specifically, the restriction of intramolecular rotation (RIR) due to environmental hindrance suppresses the formation of non-emissive twisted intramolecular charge transfer (TICT) excited keto* states. As a result, this particular thiadiazole derivative is capable of simultaneously producing both ESIPT and aggregation-induced emission (AIE).

AIE‐Active Ferrocene Appended Linear (D‐π‐A) Aromatic Ester Chromophores: Structural, Theoretical and Effect on Phenyl Ring on Luminescence and Nonlinear Optical Properties

AbstractIn the present research, a new ferrocene‐appended linear donor‐π‐acceptor (D‐π‐A) ester chromophore Fc‐(C6H4)2‐COOC2H5 (2) was synthesized and characterized using various spectroscopic techniques. The molecular structure of chromophore 2 was determined using single‐crystal X‐ray diffraction analysis, revealing its crystallization in the monoclinic crystal system with the P21/n space group. The chromophore Fc‐C6H4‐COOC2H4 (1) was utilized to compare its photophysical and nonlinear optical characteristics with those of 2. Cyclic voltammetry revealed a single‐electron transfer mechanism from Fe2+↔Fe3+. The emission solvatochromism studies show a polarized excited state in response to increasing solvent polarity, indicating charge transfer processes. Interestingly, in mixed aqueous media (THF/H2O), the chromophores exhibit intensified fluorescence due to restricted intra‐molecular rotation (RIR), despite weak emission in THF solvent. Chromophore 2 demonstrated 1.5 times higher second harmonic generation (SHG) efficiency than 1, attributed to its extended π‐conjugation from an additional phenyl ring and reduced antiparallel alignments. Despite its centrosymmetric crystal packing, chromophore 2 exhibited SHG efficiency due to non‐covalent interactions (C−H⋅⋅⋅π) in the crystal lattice. Density Functional Theory (DFT) calculations, employing various functionals, provided insights into dipole moment and first hyperpolarizability, with B3LYP‐hybrid functional underestimating hyperpolarizability values owing to long‐range charge transfer interactions within the D‐π‐A systems, aligning closely with experimental findings.

Organotin(IV)-tetraphenylethylene acylhydrazone compounds with aggregation-induced emission property and application in anticancer therapy

Organotin (IV)-tetraphenylethylene (TPE) acylhydrazone compounds with aggregation-induced emission (AIE) property were prepared and characterized. The organotin (IV) compounds showed a conspicuous fluorescence improvement with a high absolute fluorescence quantum yield of 25.2 % (ClSnTPE) in the aggregation state, and restriction of intramolecular rotation (RIR) contributed to this AIE property. Using suitable fluorescence, confocal tests verified that these compounds could accumulate in the mitochondria of A549 cancer cells and decrease the mitochondrial membrane potential. Meanwhile, compounds could improve the intracellular reactive oxygen species (ROS) levels and inhibit the cell cycle (G1/G0 phase), then contributing to apoptosis. In addition to favorable in-vitro anti-proliferative activity (the similar to cisplatin), these compounds could also suppress A549 cancer cell migration. Above all, organotin (IV)-TPE acylhydrazone compounds show the promise as the mitochondrial targeting anticancer drugs for further study.

1,4-Dihydropyridine-based FA1 site-specific fluorescent probes for the selective detection and quantification of HSA levels in biofluids.

Human serum albumin (HSA) is a multifunctional circulatory protein essential for many physiological processes including oncotic pressure maintenance, ligand/drug binding and transport, antioxidant activity, etc. Abnormal HSA levels in biological fluids have been reported in a variety of clinical disorders, making it a potential biomarker for early diagnosis. Low serum albumin levels have been linked to increased long- and short-term mortality rates in ICU patients. Therefore, quantifying HSA in biofluids such as serum and urine offers a convenient approach for the early identification of underlying clinical conditions and assessing the risk factors. Herein, we report a series of fluorescent 1,4-dihydropyridine (DHP) derivatives for the detection and quantification of HSA in biofluids. Their response towards HSA can be tuned by varying the substituents at the C-4 and the N-1 of the DHP ring. Depending on the nature of the substituents, they generated either a turn-on or ratiometric response with a LoD in low nanomolar or subnanomolar levels. A pair of enantiomers obtained by introducing a chiral center on the N-substituents highlighted the importance of stereochemistry in HSA-ligand interactions. Quantification of HSA in complex biofluids, such as blood serum and urine, was also accomplished using these probes. The high selectivity of some of the probes towards HSA over the homologous BSA allowed the discrimination of these two proteins. The preferred binding location of the probes was the hemin binding site and the detection mechanism was identified as the restriction of intramolecular rotation. Additionally, a prototype of a smartphone-integrated point-of-care device was also fabricated to demonstrate the feasibility of utilizing these probes in clinical settings.

Exploring the synergistic effect of aggregation and hydrogen bonding: a fluorescent probe for dual sensing of phytic acid and uric acid.

We synthesized an unoxidized bis-indolyl methane (BIM) derivative (probe 1) comprising of tetraphenylethylene (TPE) as the signalling moiety. The amphiphilic probe could form self-assembled nanoscopic aggregates in the aqueous medium. The emission of 1 in non-polar solvents originates from the LE state, while in polar solvents, it is dominated by TICT. Moreover, probe 1 exhibited a 'turn-on' fluorescence response for both uric acid (with a blue shift in emission maxima) and phytic acid (with a red shift in emission maxima). Therefore, the present system provides an exceptional opportunity to distinguish between phytic acid and uric acid by considering two different emission channels. Mechanistic investigations revealed that both H-bonding and electrostatic interactions between the probe and analytes could effectively cause restricted intramolecular rotations, leading to a turn-on response. Additionally, in the case of phytic acid, larger aggregates were observed with prominent CT characteristics. The change in the extent of charge transfer interaction in the formed adducts resulted in distinct fluorescence responses with phytic acid and uric acid. Furthermore, we explored the applicability of the present system in the screening of real-life samples, such as uric acid in urine samples and phytic acid in grains. The LOD for phytic acid and uric acid was found to be ∼5.48 nM and 10.4 nM, respectively. The quantitative nature of the system was confirmed, showing promising results in terms of recovery values (between 95.6% and 104.2%) and detection limits. Additionally, we also employed handy paper strips for the on-site monitoring of phytic acid and uric acid, thereby eliminating the need for complex instrumentation or trained technicians.

Unveiling the aggregation-induced chromic emission of triazine anchored BODIPYs

Triazine-based BODIPY dyes exhibiting restricted intramolecular rotation and J-aggregation, leading to aggregation-induced chromic emission (AICE) with green-to-red emission color switching and self-assembly behaviour in the aggregated state.

ESIPT‐AIE Active Schiff Base Fluorescent Organic Nanoparticles Based on 2‐(2‐(4‐(4‐bromo Phenyl) Thiazol‐2‐yl)Vinyl)Phenol (BTVP) Utilized as a Multi‐Functional Fluorescent Probe

AbstractThe present study reports the synthesis and characterization of Aggregation‐Induced Emission (AIE) – Excited‐state intramolecular proton transfer (ESIPT) active 2‐(2‐(4‐(4‐bromo phenyl) thiazol‐2‐yl)vinyl)phenol (BTVP). The AIE properties of BTVP in Acetone/Water solution are investigated, and fluorescent organic nanoparticles (FONs) (sizes ranging from 150–200 nm) are prepared in various water fractions (fH2O). The established visco‐chromic property suggests that the restriction of intramolecular rotation is responsible for the AIE‐ESIPT behavior of the molecule, providing a means to sense viscosity. The synthesized FONs act as fluorescence chemosensors to detect Al3+ ions via a photoinduced electron transfer (PET) mechanism. Job's, Benesi–Hildebrand method, and 1HNMR titration confirm the 1:1 binding of BTVP with the metal ion. Studies on the emission concerning pH reveal the high stability of FONs over a broad range of pH, and a gradual change in the emission wavelength for the BTVP‐Al3+ complex (BTVP‐Al) is observed, providing a means to sense pH ranging from 2–8. The solid‐state photoluminescence of BTVP is used for latent fingerprint detection, demonstrating its efficiency in detecting both primary and secondary information. Additionally, both BTVP FNOs and BTVP‐Al are used in cell imaging, where specific nuclear staining with BTVP‐Al and cytoplasm staining with BTVP are observed.

A photoluminescence strategy for detection nanoplastics in water and biological imaging in cells and plants

Nanoplastics exposure poses a significant threat to the environment and human health, and accurate measurement of nanoparticles in aqueous solutions remains challenging. In this work, we synthesized the cationic fluorescent probe 4-[1-Cyano- 2-[4-(Diethylamino)−2-hydroxyphenyl]ethenyl]−1-ethylpyridinium (PCP) through a straightforward procedure for the rapid and accurate detection and labeling of nanoplastics in aqueous solutions. PCP binds to nanoplastics through electrostatic and hydrophobic interactions with restricted intramolecular rotation and exhibits enhanced fluorescence emission. Using carboxylation-modified polystyrene nanoplastics as a model, PCP could accurately detect concentrations as low as 0.525 mg∙L−1 in aqueous solution and perform wash-free semi-quantitative direct observation. The method demonstrated good reproducibility and recovery in actual sample spiking experiments. In addition, PCP-labeled nanoplastics were successfully used to visualize the uptake and distribution of cells and Arabidopsis thaliana when exposed to different concentrations of nanoplastics. This work provides a simple and sensitive method for efficiently identify, track, and quantify nanoplastics without requiring additional pretreatment and complex instrumentation, making it an ideal tool for accurately quantifying nanoplastics in aqueous solutions and studying the biological interactions of nanoplastics.

Development of peptide-based ratiometric fluorescent probe for sensing heparan sulfate and heparin in aqueous solutions at physiological pH and quantitative detection of heparan sulfate in live cells

Heparan sulfate (HS) plays a critical role in various biological processes as a vital component of the extracellular matrix. In this study, we synthesized three fluorescent probes (1–3) comprising Arg-rich peptides as HS receptors and a fluorophore capable of exhibiting red-shifted emissions upon aggregation. All three probes demonstrated ratiometric responses to HS and heparin in aqueous solutions. Remarkably, probe 3 exhibited a unique ratiometric response to HS in both aqueous solutions at physiological pH and HS proteoglycans on live cells. Probe 3 displayed exceptional sensing properties, including high biocompatibility, water solubility, visible light excitation, a large Stokes shift for ratiometric detection and remarkable selectivity and sensitivity for HS (with a low limit of detection: 720 pM). Binding mode studies unveiled the crucial role of charge interactions between probe 3 and negatively charged HS sugar units. Upon binding, the fluorophore segments of the probes overlapped, inducing green and red emission changes through restricted intramolecular rotation of the fluorophore moiety. Importantly, probe 3 was effectively employed to quantify the reduction of HS proteoglycan levels in live cells by inhibiting HS sulfation using siRNA and an inhibitor. It successfully detected decreased HS levels in cells treated with doxorubicin and irradiation, consistent with results obtained from western blot and immunofluorescence assays. This study presents the first ratiometric fluorescent probe capable of quantitatively detecting HS levels in aqueous solutions and live cells. The unique properties of peptide-based probe 3 make it a valuable tool for studying HS biology and potentially for diagnostic applications in various biological systems.

Novel AIEE pillar[5]arene-fluorene fluorescent copolymer for selective recognition of paraquat by forming polypseudorotaxane

A novel conjugated polymer (Co-P[5]Flu) was synthesized by copolymerizing a difunctionalized pillar[5]arene and a fluorene derivative monomer. Co-P[5]Flu displayed an aggregation-induced emission enhancement (AIEE) effect because of the restricted intramolecular rotations of the pillar[5]arene unit. Co-P[5]Flu exhibited high selectivity and sensitivity towards the pesticide paraquat (PQ) with excellent anti-interference properties. It presented fluorescence quenching response (1–I/I0=96.6%) only towards paraquat and not towards other competitive guests. The fluorescence titration experiments revealed that the detection limit (LOD) for paraquat was as low as 1.69×10−8 M, and the Stern-Volmer constant (KSV) was determined to be 2.11×104 M−1. The recognition mechanism was studied using both 1H NMR titration and theoretical calculations. The Co-P[5]Flu showed fluorescence quenching for PQ due to the synergistic effect of polypseudorotaxane formation and photoinduced electron transfer (PET). Additionally, the polymer chemosensor demonstrated potential for the detection of paraquat in practical samples.

Regulating donor-acceptor system toward highly efficient dual-state emission for sensitive response of nitroaromatic explosives

Dual-state emission luminogens (DSEgens) as fluorophores emit efficiently in solution and solid forms have gained increasing concern in the field of chemical sensing. Recent efforts by our group led to the identification of DSEgens as an easy-to-visualize nitroaromatic explosives (NAEs) detection platform. However, none of the previously studied NAEs probes show effective improvement in sensitivity. Here, we designed a series of benzoxazole-based DSEgens through multiple strategies driven by theoretical calculations, revealing their improved detecting performance on NAEs. Compounds 4a-4e exhibit thermal- and photo-stability, large Stokes shift as well as sensitivity solvatochromism (except for 4a and 4b). A subtle balance between rigid conjugation and distorted conformation endows these D-A type fluorophores 4a-4e with DSE properties. Furthermore, 4d and 4e show aggregation-induced emission phenomenon caused by distorted molecular conformation and restricted intramolecular rotation. Interestingly, DSEgen 4e displays anti-interference and sensitivity towards NAEs with a detection limit of 10-8 M. It can be applied for expedient and distinct visual identification of NAEs not only in solution but also on filter paper and film, supporting this new DSEgen as reliable NAEs chemoprobe.

Discovery of aggregation-induced emission luminogens (AIEgens) from orange peel

In recent years, aggregation-induced emission luminogens (AIEgens) have been widely developed for bio-imaging, theranostics, organic photoelectronics, and chemo/biosensors. While, the existing AIEgens are almost all obtained by organic synthesis, experiencing complicated synthesis routes, high cost, environmentally unfriendly, and poor biocompatibility. Therefore, exploration of AIEgens from natural products is an attractive alternative approach. In this contribution, two natural AIE-active materials, Tangeretin and Nobiletin, were found, which can be extracted from orange peel. Single crystal structure, fluorescence spectra and viscosity analyses verified that restriction of intramolecular rotation was responsible for the AIE phenomenon of Tangeretin and Nobiletin. The theoretical calculation results indicated that the intermolecular charge transfer (ICT) was related with the bathochromic-shift in the solid-state. Moreover, Tangeretin and Nobiletin were biocompatible and could selectively target lysosomes. In short, these natural products provided a new approach for obtaining new kinds of AIEgens, and showing great potential in bioimaging.