Fluorogenic Zn(II) and chromogenic Fe(II) sensors based on terpyridine-substituted tetraphenylethenes with aggregation-induced emission characteristics

Dynamic metal-ligand coordination for multicolour and water-jet rewritable paper

Rewritable paper has recently become prevalent in both academic research and marketplace due to the potential environmental advantages, including forest conservation, pollution reduction, energy saving and resource sustainability. However, its real-life applications are limited by a lack of effective strategy to realize multicolour and water-jet printing on rewritable paper with long legible image-lasting times. Herein, we report an effective strategy to construct rewritable paper based on colour or luminescence switching induced by dynamic metal–ligand coordination. This type of rewritable paper can be conveniently utilized for multicolour water-jet printing by using aqueous solutions containing different metal salts as ink. In addition, the printed images on the water-jet rewritable paper can be retained for a long time (> 6 months), which shows great progress compared to previous work. We believe that this type of rewritable paper could be considered as a prototype for multicolour water-jet printing to meet the practical needs.

Rewritable paper is environmentally favourable, but its practical realization is stifled by limited ink colour versatility and poor image retention times. Here, the authors exploit the relatively stable but reversible nature of metal–organic coordination bonds to produce long-lasting and multicoloured inks for rewritable paper.

Real-time monitoring of the dissolution kinetics of silver nanoparticles and nanowires in aquatic environments using an aggregation-induced emission fluorogen

We employed a fluorogenic Ag+ sensor, tetrazole-functionalized tetraphenylethylene derivative 1 (TEZ-TPE-1), to investigate the dissolution kinetics of AgNPs and AgNWs in aquatic environments.

Fluorescent organic nanoparticles with enhanced fluorescence by self-aggregation and their application for detection of Fe3+ ions

The chemosensor L has a detection limit of 5.57 nM for Fe³⁺ in a DMF/H₂O (9 : 1, v/v) mixture.

Self-agglomerated crystalline needles harnessing ESIPT and AIEE features for the ‘turn-on’ fluorescence detection of Al3+ ions

We report the synthesis of probe 2 for the fluorescence “turn-on” detection of Al³⁺ ions in CH₃OH.

Design and application of a tripodal on–off type chemosensor for discriminative and selective detection of Fe2+ ions

A simple and cost effective tris 2(amino ethyl) amine based chemosensor is synthesized via a single-step procedure.

2,5-bis(4-alkoxycarbonylphenyl)-1,4-diaryl-1,4-dihydropyrrolo[3,2-b]pyrrole () AIEgens: tunable RIR and TICT characteristics and their multifunctional applications

Novel propeller-like AIEgens with tunable emission were readily prepared and used as a fluorescent thermometer and selective chemosensor for Cd(ii) detection.

Aggregation-induced emission luminogens (AIEgens) have attracted extensive interest for their outstanding luminescence properties in the aggregated state and even in the solid state. In this work, we developed a series of novel AIEgens based on 2,5-bis(4-alkoxycarbonylphenyl)-1,4-diaryl-1,4-dihydropyrrolo[3,2-b]pyrrole (AAPP). The AIEgens can be facilely synthesized through a single-step reaction under mild conditions with satisfactory yields. Interestingly, AAPP was found to have multiple luminous mechanisms that result in variable fluorescence properties. The propeller-like structure of AAPP enables a restricted intramolecular rotation (RIR) process which significantly enhances its fluorescence in the aggregated state (i.e. AIE fluorescence). In addition, there is a donor–acceptor interaction between the heterocycle center and the alkoxycarbonyl units in AAPP which allows a typical twisted intramolecular charge transfer (TICT) process in the dispersed state, resulting in strong fluorescence emissions in non-polar or low-polarity solvents but fluorescence quenching in high-polarity solvents. Due to the tunable RIR and TICT processes and the multiple fluorescence, AAPP compounds exhibit multifunctional applications: (1) as a reversible fluorescent thermometer, AAPP exhibited excellent fatigue resistance. There was a good linear relationship between its fluorescence intensity and temperature from 10 °C to 60 °C. (2) The desethyl AAPP derivative (CAPP) was successfully applied in the detection of Cd(ii) in aqueous solution at neutral pH, and showed a 500-fold fluorescence “turn-on” response to Cd(ii) with good selectivity.

Aggregation-Induced-Emission Materials with Different Electric Charges as an Artificial Tongue: Design, Construction, and Assembly with Various Pathogenic Bacteria for Effective Bacterial Imaging and Discrimination

Imaging-based total bacterial count and type identification of bacteria play crucial roles in clinical diagnostics, public health, biological and medical science, and environmental protection. Herein, we designed and synthesized a series of tetraphenylethenes (TPEs) functionalized with one or two aldehyde, carboxylic acid, and quaternary ammonium groups, which were successfully used as fluorescent materials for rapid and efficient staining of eight kinds of representative bacterial species, including pathogenic bacteria Vibrio cholera, Klebsiella pneumoniae, and Listeria monocytogenes and potential bioterrorism agent Yersinia pestis. By comparing the fluorescence intensity changes of the aggregation-induced-emission (AIE) materials before and after bacteria incubation, the sensing mechanisms (electrostatic versus hydrophobic interactions) were simply discussed. Moreover, the designed AIE materials were successfully used as an efficient artificial tongue for bacteria discrimination, and all of the bacteria tested were identified via linear discriminant analysis. Our current work provided a general method for simultaneous broad-spectrum bacterial imaging and species discrimination, which is helpful for bacteria surveillance in many fields.

Selective recognition of Cu (II) and Fe (III) using a pyrene based chemosensor

A pyrene-based colorimetric chemosensor 1-(pyren-1-yl)-N,N-bis-(pyridine-2-ylmethyl)methanamine (1) was synthesised for selective detection of Cu (II) and Fe (III) over the other metal cations Ni²⁺, Mg²⁺, Cd²⁺, Hg²⁺, Na⁺, K⁺, Ca²⁺, Co²⁺, Cr³⁺, Pb²⁺ and Zn²⁺. The significant changes in UV-vis absorption band of receptor 1 and the emergence of 660nm band in presence of Cu²⁺ ion indicates the selective binding of Cu²⁺ ion as compared to other metal cations which could easily be identified from the naked eye strong colour change. Job plots suggest a 1:1 and 2:1 stoichiometric binding of Cu²⁺ and Fe³⁺, respectively, which was evidenced by ESI-MS analysis. Chemosensor 1 explores a cost-effective and selective colorimetric sensor for naked eye detection of trace amount of Cu²⁺ and Fe³⁺ ions in presence of other metal cations.

Transition-Metal-Free Oxidative C(sp2 )-H Hydroxylation of Terpyridines: A HOMO-Raising Strategy for the Construction of a New Super-Stable Terpyridine Chromophores

Direct functionalization of terpyridines is an increasingly important topic in the field of dyes and catalysis as well as supramolecular chemistry, but its synthesis and transformation is usually challenging. Herein, a HOMO-raising strategy is reported for the construction of a super-stable novel terpyridine chromophores, in which the selective oxidation of terpyridines at its 3-position was determined successfully to the synthesis of phenol-functionalization of terpyridines (TPyOHs) bearing a hydrogen bonding group. The corresponding TPyOHs displayed strong aggregation-induced emission and exhibited highly selective and visual detection of Zn^II cation with a record green terpyridine-based luminophore with nanomolar sensitivity (125 nm).

Chiral Supramolecular Gels with Lanthanide Ions: Correlation between Luminescence and Helical Pitch

We report the correlation between the fluorescence intensity and the helical pitch of supramolecular hydrogels with Tb(III) and Eu(III) as well as their inkjet printing patterning as an application. The luminescent gels, which exhibited three different emissions of red, green, and blue, could be prepared without and with Eu(III) and Tb(III). The luminescence intensity of supramolecular gels (gel-Tb and gel-Eu) composed of Tb(III) and Eu(III) was ca. 3-fold larger than that of the sol (1+Tb(III) or 1+Eu(III)), which was attributed to large tilting angles between molecules. By AFM observations, these gels showed well-defined right-handed helical nanofibers formed by coordination bonds in which the helical pitch lengths were strongly dependent on the concentrations of lanthanide ions. In particular, the large luminescence intensity of gel-Tb exhibited a smaller helical pitch length than that of gel-1 due to relatively weak π-π stacking with large tilting angles between molecules. The luminescence intensities were enhanced linearly with increasing concentrations of lanthanide ions. This is the first example of the correlation between the helical pitch length and the luminescence intensity of supramolecular materials. The coordination bonding in supramolecular hydrogels had a strong influence on rheological properties. We also developed a water-compatible inkjet printing system to generate luminescent supramolecular gels on A4-sized paper. The images of a logo and the text were composed of three different emissions and were well-printed on A4 sized paper coated with gel-1.

A selective and light-up fluorescent probe for β-galactosidase activity detection and imaging in living cells based on an AIE tetraphenylethylene derivative

An AIE based tetraphenylethylene derivative (TPE-Gal) was designed for light-up fluorescence detection and imaging of β-galactosidase activity in living cells.

A highly sensitive SERS-based platform for Zn(ii) detection in cellular media

HBA SERS peak frequency shifts in response to coordination are used to analyze the concentration of Zn(ii) with ultra-high sensitivity.

Aggregation-induced emission active tetraphenylethene-based sensor for uranyl ion detection

A novel tetraphenylethene-based fluorescent sensor, TPE-T, was developed for the detection of uranyl ions. The selective binding of TPE-T to uranyl ions resulted in a detectable signal owing to the quenching of its aggregation-induced emission. The developed sensor could be used to visually distinguish UO2(2+) from lanthanides, transition metals, and alkali metals under UV light; the presence of other metal ions did not interfere with the detection of uranyl ions. In addition, TPE-T was successfully used for the detection of uranyl ions in river water, illustrating its potential applications in environmental systems.

A selective fluorescent sensor for Zn(2+) based on aggregation-induced emission (AIE) activity and metal chelating ability of bis(2-pyridyl)diphenylethylene

Polypyridyl ethylenes have been prepared as heterocyclic analogues of tetraphenylethylene. In addition to conventional AIE effects, a derivative possessing a 1,1-bis(2-pyridyl)ethylene fragment displays Zn(2+)-selective enhanced fluorescence in aqueous solution, in contrast to the behavior of isomeric bis(3- and 4-pyridyl)ethylenes. The Zn(2+)-sensing capability of this material is attributed to formation of chelated Zn(2+)-bis(pyridyl) complexes and is supported by the X-ray crystal structure of a bis(2-pyridyl)ethylene-Zn(OAc)2 complex.

Hydrogen bond-assisted aggregation-induced emission and application in the detection of the Zn(ii) ion

The compounds of 3-aminopyridine-2-carboxylic acid with K(+) (1) and Zn(2+) (2) were found to be AIE-active. The AIE behaviours could be attributed to the restriction of intramolecular rotation (RIR) and vibration (RIV) via hydrogen bonds, resulting in rigidity enhancement of the molecules. An AIE-based fluorescence turn on chemosensor for the Zn(ii) ion has been developed in aqueous media with high selectivity and sensitivity.

Self-Assembly of Fluorescent Organic Nanoparticles for Iron(III) Sensing and Cellular Imaging

Fluorescent organic nanoparticles have attracted increasing attentions for chemical or biological sensing and imaging due to their low-toxicity, facile fabrication and surface functionalization. In this work, we report novel fluorescent organic nanoparticles via facile self-assembly method in aqueous solution. First, the designed water-soluble fluorophore shows a weak and negligible intrinsic fluorescence in water. Upon binding with adenosine-5'-triphosphate (ATP), fluorescent nanoparticles were formed immediately with strongly enhanced fluorescence. These fluorescent nanoparticles exhibit high sensitivity and selectivity toward Fe(3+) sensing with detection limit of 0.1 nM. In addition, after incubation with HeLa cells, the fluorophore shows excellent imaging performance by interaction with entogenous ATP in cells. Finally, this fluorescent system is also demonstrated to be capable of Fe(3+) sensing via fluorescence quenching in cellular environment.

Emission-Tunable Multicolor Graphene Molecules with Controllable Synthesis, Excellent Optical Properties, and Specific Applications

Series of graphene molecules with varied emission colors have been prepared by oxidative cyclodehydrogenation using anhydrous ferric chloride (FeCl3) as the catalyst under mild conditions. By controlling the oxidation time in the initial step only, molecules with different fluorescence colors are conveniently obtained. New colors can be recorded evidently because of the stepwise and controllable process, which highly related to the conjugation length. Blue emissive starting compounds in the solid state can be transformed into orange upon brief oxidation, whereas green emissive oligomers are varied to red with an emission wavelength redshift about 123 nm. Cyclic voltammetry measurements performed can give the corresponding data, which verify the results drawn from the UV and PL spectroscope. The gradual change of conjugation length with tunable emission is confirmed in the MALDI-TOF study as well. Further characterizations indicate that the graphene molecules possess satisfactory optical properties, which are highly emissive both in solution and in the solid state because of the alkyl group. In addition, the good thermal stability and the self-assembly of graphene molecules suggest that they are promising candidates for high-tech applications. Furthermore, the fabricated field-effect transistors possess the nice performance, whose mobilities are about 0.57 cm(2) V(-1) s(-1) with an on-off ratio of 1 × 10(4) and 0.81 cm(2) V(-1) s(-1) with an on-off ratio of 1 × 10(3), respectively.

Highly selective ratiometric fluorescent recognition of histidine by tetraphenylethene–terpyridine–Zn(ii) complexes

Fluorescent detection of histidine is achieved with distinctive color change from yellow to blue by using the Zn(ii) complexes of the terpyridine–tetraphenylethene conjugates.

Structural, optical and photoconductivity characteristics of pristine FeO·Fe2O3 and NTPI–FeO·Fe2O3 nanocomposite: aggregation induced emission enhancement of fluorescent organic nanoprobe of thiophene appended phenanthrimidazole derivative

In this manuscript we report the successful synthesis of pristine FeO·Fe₂O₃, 1-(naphthalen-1-yl)-2-(thiophen-2-yl)-1H-phenanthro[9,10-d]imidazole (NTPI), fluorescent organic nanoparticles (FONs) of NTPI and NTPI–FeO·Fe₂O₃ nanocomposite.

An AIE based tetraphenylethylene derivative for highly selective and light-up sensing of fluoride ions in aqueous solution and in living cells

MOTIPS-TPE displayed highly selectivity for F⁻ in PBS and was employed as an AIE light-up probe for F⁻ in living HeLa cells.

Circularly polarized luminescence of AIE-active chiral O-BODIPYs induced via intramolecular energy transfer

Two AIE-active chiral BINOL-based O-BODIPY enantiomers (R/S-5) were synthesized and showed mirror-image red-color CPL induced via intramolecular energy transfer. The chiroptical properties of the molecules indicate that the chirality of electronic ground and excited states is stable and independent of aggregation.

Enhancing the output current of a CdTe solar cell via a CN-free hydrocarbon luminescent down-shifting fluorophore with intramolecular energy transfer and restricted internal rotation characteristics

A CN-free hydrocarbon fluorophore (Perylene-TPE) was synthesized as a new luminescent down-shifting (LDS) material. Its photophysical properties in both the solution state and the solid state were studied. The unity fluorescence quantum yield of Perylene-TPE observed in its solid state is considered to be from the characteristics of intramolecular energy transfer (IET) and restricted internal rotation (RIR). This is supported by the results from theoretical calculations and spectroscopic measurements. For the photovoltaic application of Perylene-TPE, a theoretical modeling study suggests that using the LDS film of Perylene-TPE may increase the output short circuit current density (Jsc) of a CdTe solar cell by 2.95%, enhance the spectral response of a CdTe solar cell at 400 nm by 41%, and shift the incident solar photon distribution from short-wavelength (<500 nm) to long-wavelength (>500 nm). Experimentally, placing a LDS film of Perylene-TPE on a CdTe solar cell can enhance its output Jsc by as high as 3.30 ± 0.31%, which is comparable to the current commercially available LDS material – Y083 (3.28% ± 0.37%).

A turn-on fluorogenic Zn(ii) chemoprobe based on a terpyridine derivative with aggregation-induced emission (AIE) effects through nanofiber aggregation into spherical aggregates

The self-assembly of the terpyridine-based ligand exhibited strong emission in the presence of Zn²⁺ due to the formation of coordination bonds between the terpyridine moieties and the Zn²⁺ by the aggregation-induced emission effect.

An imidazo-phenanthroline scaffold enables both chromogenic Fe(ii) and fluorogenic Zn(ii) detection

A promising dual channel responsive probe, which can simultaneously induce chromogenic and fluorogenic responses to Fe(ii) and Zn(ii) ions, respectively, is described.

Spectroscopic analysis and in vitro imaging applications of a pH responsive AIE sensor with a two-input inhibit function

A novel terpyridine derivative formed stable aggregates in aqueous media (DMSO/H₂O = 1/99) with dramatically enhanced fluorescence compared to its organic solution.

Click synthesis of a novel triazole bridged AIE active cyclodextrin probe for specific detection of Cd2+

A novel aggregation induced emission (AIE) active cyclodextrin (CD) was synthesized via click chemistry, which is the first reported clicked AIE probe for the specific detection of Cd²⁺.

Fluorescence responsive conjugated poly(tetraphenylethene) and its morphological transition from micelle to vesicle

A crown ether-functionalized poly(tetraphenylethene) (AP-TPE) is synthesized and the rotation of the TPE group is successfully restricted, leading to a stepwise enhanced fluorescence accompanied by a morphological transition from micellar to vesicular.

Luminescent cation sensors: from host–guest chemistry, supramolecular chemistry to reaction-based mechanisms

This highlight provides a brief overview on luminescent cation detection strategies derived from a wide variety of organic and organometallic architectures, including those based on the ion-receptor complementarity, integrated with the extension of the concept of supramolecular chemistry and those using the irreversible analyte-specific reactions.

Fluorometric sensing of Hg2+ ions in aqueous medium by nano-aggregates of a tripodal receptor

Two new tripodal receptors (1–2) have been synthesized and characterized by various spectroscopic techniques. The nano-aggregates of 1 and 2 (N1 and N2) have been prepared by a re-precipitation method in aqueous medium and have shown different photo-physical properties. Nano-aggregates of 1 (N1) can selectively recognize Hg(2+) in aqueous medium in the presence of other metal ions with enhancement in fluorescent intensity. The response was linearly proportional to the concentration of Hg(2+) in the range 0–10 μM with a detection limit of 2.4 nM. The mechanism of selective binding of Hg(2+) by N1 has also been supported by theoretical studies. To the best of our knowledge, this work represents the first report on substituted thiourea based nano-aggregates for nano-molar detection of mercury in aqueous medium.