Unusual emission from norbornene derived phosphonate molecule--a sensor for Fe(III) in aqueous environment

Nonconventional luminophores: characteristics, advancements and perspectives

Nonconventional luminophores devoid of remarkable conjugates have attracted considerable attention due to their unique luminescence behaviors, updated luminescence mechanism of organics and promising applications in optoelectronic, biological and medical fields. Unlike classic luminogens consisting of molecular segments with greatly extended electron delocalization, these unorthodox luminophores generally possess nonconjugated structures based on subgroups such as ether (-O-), hydroxyl (-OH), halogens, carbonyl (CO), carboxyl (-COOH), cyano (CN), thioether (-S-), sulfoxide (SO), sulfone (OSO), phosphate, and aliphatic amine, as well as their grouped functionalities like amide, imide, anhydride and ureido. They can exhibit intriguing intrinsic luminescence, generally featuring concentration-enhanced emission, aggregation-induced emission, excitation-dependent luminescence and prevailing phosphorescence. Herein, we review the recent progress in exploring these nonconventional luminophores and discuss the current challenges and future perspectives. Notably, different mechanisms are reviewed and the clustering-triggered emission (CTE) mechanism is highlighted, which emphasizes the clustering of the above mentioned electron rich moieties and consequent electron delocalization along with conformation rigidification. The CTE mechanism seems widely applicable for diversified natural, synthetic and supramolecular systems.

Metal Cation-Responsive and Excitation-Dependent Nontraditional Multicolor Fluorescent Hydrogels for Multidimensional Information Encryption

Fluorescent polymeric hydrogels especially multicolor fluorescent polymeric hydrogels (MFPHs) have important applications in information storage, encryption, and encoding. MFPHs are generally prepared by incorporating multiple traditional fluorescent materials into hydrogels. In recent years, nontraditional luminescent polymers without any traditional π-conjugated chromophores have received increasing attention. Here, we report a novel type of nontraditional MFPHs prepared by in situ polymerization of acrylamide (AAm) in the presence of poly(itaconic acid) (PITAc). The hydrogen-bonded mechanically strong PAAm/PITAc hydrogels show strong intrinsic fluorescence, and the fluorescence emission is excitation-dependent and metal cation-responsive. More impressively, the hydrogels treated with metal cations also possess excitation-dependent fluorescence. We developed a multi-ion inkjet printing (MIIP) technique to print texts or designed patterns onto the hydrogel surface using different metal cation solutions as inks, and then variable texts or patterns appear under the irradiation of UV, violet, and blue lights. Patterns can be further changed by selective printing, erasing, or reprinting on some regions. Therefore, multidimensional information encryption is achieved. This work provides a new strategy for preparing MFPHs for wide applications.

Dramatically Enhanced and Red-shifted Photoluminescence Achieved by Introducing an Electron-withdrawing Group into a Non-traditional Luminescent Small Organic Compound

Small organic compounds without any traditional fluorescent chromophores are generally non-emissive, and only very few are reported to emit weak blue fluorescence. Here we synthesized a non-traditional luminescent small organic compound N-(2,2,2-trifluoroethyl)acrylamide (TFAM) with dramatically enhanced and red-shifted photoluminescence by introducing a strong electron-withdrawing group into acrylamide (AM). Very impressively, TFAM emits cyan (472 nm) and yellow-green (560 nm) fluorescence in solutions and solid state, respectively. TFAM also shows aggregation-induced emission enhancement (AIEE) and excitation-dependent fluorescence (EDF) characteristics, as well as temperature and metal cations-responsive fluorescence. Theoretical calculations show that the introduction of electron-withdrawing group leads to a lower energy gap between the HOMO-LUMO energy levels in TFAM than in AM. And strong cooperative hydrogen bonds are formed in TFAM molecules, resulting in rigidification of molecular conformations. The study provides a strategy for preparing non-traditional luminescent compounds with enhanced and red-shifted photoluminescence.

The fluorescence turn-off mechanism of a norbornene-derived homopolymer – an Al3+ colorimetric and fluorescent chemosensor

A norbornene-derived hydrazone polymer was developed for high selectivity, and to be used as an effective colorimetric and fluorescent chemosensor of Al³⁺ in aqueous solutions.

Hyperbranching-Enhanced-Emission Effect Discovered in Hyperbranched Poly(4-(cyanomethyl)phenyl methacrylate)

To disclose the effect of architecture over fluorescence behaviors of polymers, linear and hyperbranched poly(4-(cyanomethyl)phenyl methacrylate)s (PCPMAs) were synthesized by using atom transfer radical polymerization (ATRP). Compared to linear PCPMAs with weakly AIE (AIE: aggregation-induced-emission) characteristics and small-molecule analogues of 4-(cyanomethyl)phenyl isobutyrate (CPB) with ACQ (ACQ: aggregation-caused-quenching) behaviors, hyperbranched PCPMA showed dramatically stronger fluorescence at both solution and solid states and more significant AIE characteristics, which were further enhanced by increasing the branching degree, indicating a significant hyperbranching-enhanced-emission effect (HEE). The HEE effect was attributed to the strong promotion of hyperbranched architecture over the formation of a nitrile group cluster with through-space conjugation (TSC). The HEE effect provided a promising methodology to construct efficient nontraditional fluorescent polymers without large-conjugated, rigid, and planar emitter groups.

A non-conjugated polyethylenimine copolymer-based unorthodox nanoprobe for bioimaging and related mechanism exploration

A non-conjugated polyethylenimine copolymer-based nanoprobe for lysosome-specific staining and tumor-targeted bioimaging and related mechanism exploration.

A small molecular boron-phenylpyrrin sensor for H+/Fe3+ and its application as a digital demultiplexer

A julolidine-based boron-phenylpyrrin small molecule has been designed and synthesized through a one-pot condensation-complexation procedure. Systematic optical studies show that this compound displays two distinct optical responses to the addition of HCl and Fe[Formula: see text] in succession: the addition of HCl induces an obvious red shift in its maximum absorption and fluorescence emission bands accompanied with the fluorescence quenching, whereas after synchronously adding H[Formula: see text] and Fe[Formula: see text], the maximum absorption and fluorescence emission wavelength were found to shift little but with an obvious decrease in the absorbance and fluorescence intensity, suggesting the dual-detecting nature of this compound to H[Formula: see text] and Fe[Formula: see text] under acid conditions. More interestingly, based on the HCl/Fe[Formula: see text]-mediated absorption and fluorescence signal features, JBPP can function as AND, NAND, INH and IMP logic gates which can be further developed into a 2:4 digital demultiplexer These will endow this small molecule compound with great potential for applications in molecular logic material, chemosensors and biological fields.

Thiolactone-maleimide: a functional monomer to synthesize fluorescent aliphatic poly(amide-imide) with excellent solubility via in situ PEGylation

Combining aminolysis of thiolactones and amine-maleimide Michael addition contributed to the synthesis of fluorescent aliphatic poly(amide-imide)s, accomplishing excellent solubility via in situ PEGylation.

Unexpected fluorescence from polymers containing dithio/amino-succinimides

Nonfluorescent succinimides become fluorescent only by thiol and amine group substitutions, without employing any fluorescent units.

Unique norbornene based triazole molecule for selective Fe(ii) sensing

A triazole functionalized norbornene monomer (NFTZ) and its corresponding homopolymer (NFTZH) are synthesized for selective Fe(ii) sensing.

Rhodamine B derivative-functionalized upconversion nanoparticles for FRET-based Fe(3+)-sensing

A novel fluorescence resonance energy transfer (FRET)-based probe, γ-cyclodextrin modified oleic acid-NaYF4:Yb, Ho upconversion nanoparticles functionalized with a rhodamine B derivative (RBD), has been achieved for Fe(3+)-sensing in aqueous solution with high sensitivity and selectivity.

Polynorbornene derived 8-hydroxyquinoline paper strips for ultrasensitive chemical nerve agent surrogate sensing

The detection of nerve agent simulants is achieved by the photoinduced electron transfer (PET) mechanism.