Oligo(phenyleneethynylene)s: Shape-Tunable Building Blocks for Supramolecular Self-Assembly

Oligo(phenyleneethynylene)s (OPEs) have attracted widespread attention due to their remarkable (opto)electronic and photophysical properties, which have enabled numerous applications. The versatile functionalization possibilities of OPEs make them unique candidates to form various shape-persistent geometries, including linear, triangular, rectangular, hexagonal and macrocyclic. However, as a result of this structural variety, it is oftentimes challenging to correlate molecular design with self-assembly properties. In this minireview, we have classified OPEs based on their molecular shapes and correlated them with their self-assembly behavior in solution. Particularly, we provide important insights into the aggregation propensity of the different molecular shapes and how to tune the association strength using various non-covalent interactions. Our classification will enable a better understanding of the structure-property correlation in OPEs, which is key to develop supramolecular functional materials.

A water-soluble conjugated polyelectrolyte for selective and sensitive detection of carcinogenic chromium(VI)

Environmental water pollution caused by hexavalent chromium (Cr(VI)) is a threat to living beings due to its carcinogenic nature. Herein, we report the synthesis of a highly fluorescent water-soluble conjugated polyelectrolyte PPMI and its application as a fluorescence sensor to monitor traces of carcinogenic Cr(VI) ions in water. PPMI was synthesized via the oxidative polymerization method followed by post-polymer functionalization. Fluorescent PPMI exhibited a photoluminescence quantum yield of 23.87 and displayed a rapid, very selective, and sensitive turn-off fluorescence signal in response to Cr(VI), with a significantly high quenching constant of 1.32 × 106 M-1. The mechanism of sensing was found to be static quenching. The limit of detection of this highly accessible analytical method was found to be in nanomolar ranges, i.e. 0.85 nM. Additionally, sensing on solid platforms such as economical paper strips was successfully achieved, which is very challenging and highly recommended for any reliable, portable, and economical analytical method.

Martini 3 coarse-grained force field for poly(para-phenylene ethynylene)s

Poly(para-phenylene ethynylene)s, or short PPEs, are a class of conjugated and semi-flexible polymers with a strongly delocalized π electron system and increased chain stiffness. Due to this, PPEs have a wide range of technological applications. Although the material properties of single-chains or mixtures of few PPE chains have been studied in detail, the properties of large assemblies remain to be fully explored. Here, we developed a coarse-grained model for PPEs with the Martini 3 force field to enable computational studies of PPEs in large-scale assembly. We used an optimization geometrical approach to take the shape of the π conjugated backbone into account and also applied an additional angular potential to tune the mechanical bending stiffness of the polymer. Our Martini 3 model reproduces key structural and thermodynamic observables of single PPE chains and mixtures, such as persistence length, density, packing and stacking. We show that chain entanglement increases with the expense of nematic ordering with growing PPE chain length. With the Martini 3 PPE model at hand, we are now able to cover large spatio-temporal scales and thereby to uncover key aspects for the structural organization of PPE bulk systems. The model is also predicted to be of high applicability to investigate out-of-equilibrium behavior of PPEs under mechanical force.

One- and Two-Photon Activated Release of Oxaliplatin from a Pt(IV)-Functionalized Poly(phenylene ethynylene)

We report a water-soluble poly(phenylene ethynylene) (PPE-Pt(IV)) that is functionalized with oxidized oxaliplatin Pt(IV) units and its use for photoactivated chemotherapy. The photoactivation strategy is based on photoinduced electron transfer from the PPE backbone to oxaliplatin Pt(IV) as an electron acceptor; this process triggers the release of oxaliplatin, which is a clinically used anticancer drug. Mechanistic studies carried out using steady-state and time-resolved fluorescence spectroscopy coupled with picosecond-nanosecond transient absorption support the hypothesis that electron transfer triggers the drug release. Photoactivation is effective, producing oxaliplatin with a good chemical yield in less than 1 h of photolysis (400 nm, 5 mW cm^-2). Photorelease of oxaliplatin from PPE-Pt(IV) can also be effected with two-photon excitation by using 100 fs pulsed light at 725 nm. Cytotoxicity studies using SK-OV-3 human ovarian cancer cells demonstrate that without photoactivation PPE-Pt(IV) is not cytotoxic at concentrations up to 10 μM in polymer repeating unit (PRU) concentration. However, following a short period of 460 nm irradiation, oxaliplatin is released from PPE-Pt(IV), resulting in cytotoxicity at concentrations as low as 2.5 μM PRU.

Optical Sensor Array for the Early Diagnosis of Alzheimer’s Disease

Alzheimer’s disease (AD) is the most common neurodegenerative disorder and has complicated pathobiology, leading to irreversible memory loss and severe cognitive dysfunction. For patients with AD, the advent of the disease usually occurs after years of pathological changes. The early diagnosis and monitoring of AD are of great significance as the early-stage intervention and treatment may be the most effective. Biomarkers, such as beta-amyloid and tau levels in cerebrospinal fluid (CSF) and brain, offer one of the most promising paths and are combined with neuroimaging and immunological detection for AD diagnosis. However, high expense and radiation of neuroimaging and low sensitivity of immunosorbent assay limited their applications. Meanwhile, the relevance of Aβ peptides and tau proteins to the development of AD remains highly debatable, meaning that detecting one specific biomarker holds limited prospects in achieving early and accurate detection of AD. Optical sensor arrays based on pattern recognition enable the discrimination of multiple analytes in complicated environments and are thus highly advantageous for the detection of AD with multi-biomarkers. In this review, we survey the recent advances of optical sensor arrays for the diagnosis of AD, as well as the remaining challenges.

Self-assembled organic and hybrid materials derived from oligo-(p-phenyleneethynylenes)

Oligo-(p-Phenyleneethynylenes) (OPEs) have garnered widespread interest over the past three decades due to their excellent opto-electronic properties. However, the chief focus has been on the use of mainly small molecules or polymeric systems for the study of their structural diversity in opto-electronic applications. Recently, researchers have started delving deeper into their utility in material applications. Purely organic materials such as supramolecular polymers, self-assembled nanostructures, nanostructured organogels and single-crystalline materials derived from OPEs have already been developed and researched. Chirality has also been introduced into these systems. Additionally, these have shown physical properties such as polymorphism, liquid crystallinity, melt formation, mechanochromism, etc. All these materials have also shown excellent luminescence properties with high quantum yield and some have even shown energy harvesting properties. There have also been sporadic reports on OPE linker based hybrid systems such as metallogels and metal-organic framework (MOF) structures where structural analysis reveals the origin of tunable emission in these materials. Furthermore, by innovative structural design, unexplored properties of OPEs such as water repellency, bioimaging, drug delivery, photocatalysis, energy transfer, nanomorphology control, photoconductivity, and colour tunability could be achieved. This feature article will, therefore, encompass a detailed discussion on the development of this field as well as the analysis of the properties realized in OPE derived self-assembled supramolecular materials. The main focus will be on the following classes of materials: soft supramolecular materials, crystalline supramolecular π-systems, nanoscale metal-organic frameworks (NMOFs) and bulk metal-organic frameworks (MOFs) and how their application horizon has been expanded by integrating OPEs into their structures.

Machine Learning-Assisted Pattern Recognition of Amyloid Beta Aggregates with Fluorescent Conjugated Polymers and Graphite Oxide Electrostatic Complexes

Five fluorescent positively charged poly(para-aryleneethynylene) (P1-P5) were designed to construct electrostatic complexes C1-C5 with negatively charged graphene oxide (GO). The fluorescence of conjugated polymers was quenched by the quencher GO. Three electrostatic complexes were enough to distinguish between 12 proteins with 100% accuracy. Furthermore, using these sensor arrays, we could identify the levels of Aβ40 and Aβ42 aggregates (monomers, oligomers, and fibrils) via employing machine learning algorithms, making it an attractive strategy for early diagnosis of Alzheimer's disease.

Leveraging the 1,3-azadiene-anhydride reaction for the synthesis of functionalized piperidines bearing up to five contiguous stereocenters

A modular and scalable strategy, which remodels 3-methylglutaric anhydride to 2-oxopiperidines bearing at least three contiguous stereocenters is described. The approach relies on the chemoselective and stereocontrolled annulation of 1,3-azadienes with the anhydride component. The resulting acid-tethered allylic 2-oxopiperidines are then engaged in several selective fragment growth processes, including catalytic denitrative alkenylation, halolactonization, and Vilsmeier–Haack functionalization.

A modular and scalable strategy, which converts 3-methylglutaric anhydride to 2-oxopiperidines bearing at least three contiguous stereocenters is described.

Chromatic Conductive Polymer Nanocomposites of Poly (p-Phenylene Ethynylene)s and Single-Walled Carbon Nanotubes

We report on dispersions and thin films of chromatic conductive nanocomposites of poly(p-phenylene ethynylene)s (PPEs) and single-walled carbon nanotubes (SWNTs) generated via solution mixing. The linear, conjugated PPEs with dialkyl- and dialkyloxy-side chain groups are shown to debundle and disperse high concentration (up to 2.5 mg/mL) SWNTs in various organic solvents. The solubilization of SWNTs and PPE wrapping is accompanied with the change in the solution color. Ultraviolet visible absorption spectra of nanocomposite solutions demonstrate a new absorption peak at a higher wavelength, supporting the observed chromatism. Fluorescence spectra of nanocomposite solutions display significant quenching of the fluorescence intensity and the Stern–Volmer model is used to analyze fluorescence quenching. Electron microscopy of the chromatic solid films of high mass fraction PPE/SWNT nanocomposites obtained by vacuum filtration reveals the debundled SWNTs in the PPE matrix. The tensile strength and Young’s modulus of these PPE/SWNT nanocomposite films are as high as 150 MPa and 15 GPa, respectively. The composite films exhibit remarkably high conductivities, ranging from ~1000 S/m to ~10,000 S/m for 10 wt% and 60 wt% SWNT nanocomposites, respectively.

Understanding the role of conjugation length on the self-assembly behaviour of oligophenyleneethynylenes

Oligophenyleneethynylenes (OPEs) are prominent building blocks with exciting optical and supramolecular properties. However, their generally small spectroscopic changes upon aggregation make the analysis of their self-assembly challenging, especially in the absence of additional hydrogen bonds. Herein, by investigating a series of OPEs of increasing size, we have unravelled the role of the conjugation length on the self-assembly properties of OPEs.

Highly Stable, Nondestructive, and Simple Visualization of Latent Blood Fingerprints Based on Covalent Bonding Between the Fluorescent Conjugated Polymer and Proteins in Blood

Latent blood fingerprints (LBFPs) can provide critical information of foul play and help identify the suspects at violent crime scenes. The current methods for LBFP visualization are still not satisfactory because of the low sensitivity or complicated protocol. This study demonstrates a simple and effective LBFP visualization strategy by integrating a new amphiphilic fluorescent amino-functionalized conjugated polymer with the cotton-pad developing protocol. LBFPs on various substrates are visualized by simply covering them with the polymer solution-soaked cotton pads. The images display clear fingerprint patterns, ridge details, and sweat pores, even on very challenging substrates such as painted wood and multicolored can. The gray value analysis confirms semiquantitatively the enhancement of the contrast between ridges and furrows. Even LBFPs with various contaminations or aged for more than 600 days are effectively developed and visualized. The developed fingerprint images show superior stability over long storage time and against solvent washing. Moreover, the polymer causes no degradation of DNAs in the blood, suggesting the possibility of further DNA profiling and identification after development. The mechanistic investigation suggests that the formation of positive or inverted images can be attributed to the synergistic effects from the affinity between polymer and blood, and the affinity betwen polymer and substrate, as well as the slight quenching of polymer fluorescence by blood. Furthermore, the covalent bonding between the protonated primary amino group and proteins in blood endows the stability of the developed fingerprints. The result rationalizes the molecular design of the fluorescent polymer and sheds new light on the future strategies to effective LBFP visualization in practical applications.

Well-Defined Conjugated Macromolecules Based on Oligo(Arylene Ethynylene)s in Sensing

Macromolecules with well-defined structures in terms of molar mass and monomer sequence became interesting building blocks for modern materials. The precision of the macromolecular structure makes fine-tuning of the properties of resulting materials possible. Conjugated macromolecules exhibit excellent optoelectronic properties that make them exceptional candidates for sensor construction. The importance of chain length and monomer sequence is particularly important in conjugated systems. The oligomer length, monomer sequence, and structural modification often influence the energy bang gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the molecules that reflect in their properties. Moreover, the supramolecular aggregation that is often observed in oligo-conjugated systems is usually strongly affected by even minor structural changes that are used for sensor designs. This review discusses the examples of well-defined conjugated macromolecules based on oligo(arylene ethynylene) skeleton used for sensor applications. Here, exclusively examples of uniform macromolecules are summarized. The sensing mechanisms and importance of uniformity of structure are deliberated.

Modular synthesis and transition metal-free alkynylation/alkenylation of Castagnoli–Cushman-derived N,O- and N,S-heterocyclic vinyl chlorides

A modular and functional group-tolerant protocol for the transition metal-free coupling of novel N,O- and N,S-heterocyclic vinyl chlorides with terminal acetylenes and styrenes has been developed, leading to the epimerization-free synthesis of fully carbofunctionalized dihydro-1,4-oxazines/thiazines. Bicyclic morpholines have also been prepared through the interrogation of newly synthesized cross-conjugated dienes in Diels–Alder reactions. The use of environmentally benign reaction media endows the current strategy with a practical advantage.

A functional group-tolerant and transition metal-free coupling of novel N,O- and N,S-heterocyclic vinyl chlorides, which affords fully carbosubstituted dihydro-1,4-oxazines/thiazines as well as bicyclic morpholines, is described.

Interplay between H-Bonding and Preorganization in the Evolution of Self-Assembled Systems

Cooperative π-π interactions and H-bonding are frequently exploited in supramolecular polymerization; however, close scrutiny of their mutual interplay has been largely unexplored. Herein, we compare the self-assembly behavior of a series of C2 - and C3 -symmetrical oligophenyleneethynylenes differing in their amide topology (N- or C-centered). This subtle structural modification brings about drastic changes in their photophysical and supramolecular properties, highlighting the reciprocal impact of H-bonding vs. preorganization on the evolution and final outcome of supramolecular systems.

Defining side chain successions in anthracene-based poly(arylene ethynylene)-alt-poly(phenylene vinylene)s: probing structure–property relationships

A detailed spectroscopic study of nine conjugated polymers with various octyloxy/2-ethylhexyloxy side chain sequences prepared using optimized regio-selective synthetic pathways.

Synthesis and photophysical properties of water-soluble fluorinated poly(aryleneethynylene)s

Reported are the synthesis of water-soluble fluorinated conjugated polymers, and photophysical properties, and fluorescence quenching response to arylamines.

Well-Defined Alkyne Metathesis Catalysts: Developments and Recent Applications

Although alkyne metathesis has been known for 50 years, rapid progress in this field has mostly occurred during the last two decades. In this article, the development of several highly efficient and thoroughly studied alkyne metathesis catalysts is reviewed, which includes novel well-defined, in situ formed and heterogeneous systems. Various alkyne metathesis methodologies, including alkyne cross-metathesis (ACM), ring-closing alkyne metathesis (RCAM), cyclooligomerization, acyclic diyne metathesis polymerization (ADIMET), and ring-opening alkyne metathesis polymerization (ROAMP), are presented, and their application in natural product synthesis, materials science as well as supramolecular and polymer chemistry is discussed. Recent progress in the metathesis of diynes is also summarized, which gave rise to new methods such as ring-closing diyne metathesis (RCDM) and diyne cross-metathesis (DYCM).

Sequence-definition in stiff conjugated oligomers

The concept of sequence-definition in the sense of polymer chemistry is introduced to conjugated, rod-like oligo(phenylene ethynylene)s via an iterative synthesis procedure. Specifically, monodisperse sequence-defined trimers and pentamers were prepared via iterative Sonogashira cross-coupling and deprotection. The reaction procedure was extended to tetra- and pentamers for the first time yielding a monodisperse pentamer with 18% and a sequence-defined pentamer with 3.2% overall yield. Furthermore, three novel trimers with a 9H-fluorene building block at predefined positions within the phenylene ethynylene chain were synthesised in 23–52% overall yields. Hence, it was confirmed that a functionality of interest can be incorporated selectively at a pre-defined position of these monodisperse oligomers. All respective intermediate structures were fully characterised by proton and carbon NMR, mass spectrometry, size-exclusion chromatography, and IR spectroscopy. Additionally, thermal and optical transitions are reported for the different oligomers.

A Tethered Tolane: Twisting the Excited State

The synthesis of a doubly bridged tolane is reported. The target is obtained in a five-step synthesis, starting from commercially available 2-amino-meta-xylene by a combination of a Sandmeyer reaction, radical bromination, and Stille-type coupling, followed by double ring closing. The doubly tethered tolane is crystalline; the two phenyl rings are highly twisted with respect to each other both in solution and in the solid state. Optical spectroscopy and quantum chemical calculations show that the doubly bridged tolane is twisted not only in the ground state, but also in the excited state, leading to emission from the twisted state in solution and in the solid state. Strong phosphorescence is observed at cryogenic temperatures.

Immobilized Poly(aryleneethynylene) pH Strips Discriminate Different Brands of Cola

Fluorescent, water-soluble poly(p-aryleneethynylene)s (PAE) were immobilized on commercially available nylon membranes by using a slot plotter, creating fluorescent, barcode-like sensor strips. Digital imaging by using a standard digital camera, before and after immersion of the strips in buffers of different pH, displays a unique color for each pH value. Statistical evaluation, multivariate analysis of variance (MANOVA) and principal component analysis (PCA), of the acquired data revealed that the immobilized PAEs are superior to the identical fluorophores when dissolved. The pH sensor array discriminates 20 different brands of commercial-cola soft drinks through differences in pH and colorant-PAE interactions.

Reversible mechanofluorochromism of aniline-terminated phenylene ethynylenes

Seven three-ring phenylene-ethynylene (PE) structural analogs, differing only in the lengths of alkyl chains on terminal aniline substituents, show 50-62 nm bathochromic shifts in emission maxima in response to mechanical force (mechanofluorochromism, MC). These shifts are fully reversible with heat or solvent fuming. Shearing of these solids yields a transition from green-emitting crystalline phases to orange-emitting amorphous phases as established by differential scanning calorimetry and X-ray diffraction. Molecules with shorter alkyl chain lengths required higher temperatures to recover the hypsochromically shifted crystalline phases after grinding, while the recovery with chain lengths longer than butyl occurred at room temperature. In addition to this structure-dependent thermochromism, these compounds retain their MC properties in polymer hosts to various extents. The crystalline phases of these materials have PE chromophores that are twisted due to non-covalent perfluoroarene-arene (ArF-ArH) interactions involving perfluorophenyl pendants and the terminal rings of the PE chromophore, resulting in interrupted conjugation and an absence of chromophore aggregation. The MC behavior of an analog without the perfluoroarene rings is severely attenuated. This work demonstrates the general utility of twisted PEs as stimuli-responsive moieties and reveals clear structure-property relationships regarding the effects of alkyl chain length on these materials.

Topology Effect of AIEgen-Appended Poly(acrylic acid) with Biocompatible Segments on Ca2+-Sensing and Protein-Adsorption-Resistance Properties

We recently reported that tetraphenylethene-appended poly(acrylic acid) derivatives (e.g., PAA-TPE_0.02) can serve as fluorescent Ca²⁺ sensors in the presence of physiological concentrations of biologically relevant ions, amino acids, and sugars. However, in the presence of basic proteins such as albumins, the Ca²⁺-sensing property of the polymer is significantly impaired due to the nonspecific adsorption of protein molecules, which competes with binding to Ca²⁺. To solve this problem, we explored new designs by focusing on the polymer-chain topology of PAA-TPE_0.02 with biocompatible segments. Here, we report the Ca²⁺-sensing and protein-adsorption-resistance properties of various types of PAA-TPE_0.02 copolymers with a poly(oligoethylene glycol acrylate) (polyOEGA) segment, featuring a random, diblock, triblock, or 4-armed-star-block structure. Through this study, we show an interesting topology effect; i.e., a branch-shaped PAA-TPE_0.02-co-polyOEGA with biocompatible segments at every terminal (i.e., 4-armed-star-block copolymer) exhibits both good Ca²⁺-sensing and protein-adsorption-resistance properties.

Poly(para-phenyleneethynylene)-Sensor Arrays Discriminate 22 Different Teas

Two nine-element sensor arrays, consisting of either three cationic poly(para-phenyleneethynylene)s (PPE) or the same PPEs complexed by cucurbituril[8] (CB[8]) at pH 3, 7, and 13 in water, discriminate 22 different teas and some of their small molecule components, including caffeine, theobromine and theophylline. Both arrays distinguish all of the black, green and oolong teas. The discrimination occurs by differential fluorescence modulation of the components of the sensor array and the treatment of the collected data by linear discriminant analysis. The signal is generated by either simple quenching (PPE only array) or the disruption of the PPE/CB[8] complex and quenching of the complex's or the PPEs' fluorescence through the polyphenolic colorants of the teas. Added amino acids, theobromine, theophylline, and caffeine give a fluorescence turn on of the PPE-CB[8] array, due to the disruption of the self-assembled complex, while for the PPE-alone tongue only caffeine, theobromine, and theophylline elicited useful fluorescence response. Both tongues discriminate different teas without any problem.

Molecular Wire Effects in Phenyleneethynylene Oligomers: Surprising Insights

The synthesis and quenching behavior of a series of water-soluble, carboxylate-carrying phenyleneethynylene oligomers-monomer to tetramer-and their polymers are reported; their quenching behavior with different test analytes (paraquat, lead salts, mercury salts, picric acid, methylpyridinium iodide) in water were investigated, and the results were compared to that of the conjugated polymer. Significant but analyte-dependent enhancement effects were found. For monovalent quenchers, only the molecular wire effect applies, but for divalent quenchers multivalency effects are also important.

A Hand-Held Optoelectronic Nose for the Identification of Liquors

Successful discrimination of 14 representative liquors (including scotch, bourbon and rye whiskies, brandy, and vodka) was achieved using a 36-element colorimetric sensor array comprising multiple classes of cross-reactive, chemically responsive inks. In combination with a palm-sized image analyzer, the sensor array permits real-time identification of liquor products based on vapor analysis within 2 min. Changes in sensor spot colors before and after exposure to the vapors of the liquors that are partially oxidized as they are pumped over the sensor array provides a unique color difference pattern for each analyte. Facile identification of each liquor was demonstrated using several different multivariate analyses of the digital data library, including principal component, hierarchical cluster, and support vector machine analysis. The sensor array is also able to detect dilution (i.e., "watering") of liquors even down to 1% addition of water. This colorimetric sensor array is a promising portable adjunct to other available techniques for quality assurance of liquors and other alcoholic beverages.

X-ray Generated Recombination Exciplexes of Substituted Diphenylacetylenes with Tertiary Amines: A Versatile Experimental Vehicle for Targeted Creation of Deep-Blue Electroluminescent Systems

Customizable and technology-friendly functional materials are one of the mainstays of emerging organic electronics and optoelectronics. We show that recombination exciplexes of simple substituted diphenylacetylenes with tertiary amines can be a convenient source of tunable deep-blue emission with possible applications in organic electroluminescent systems. The optically inaccessible exciplexes were produced via recombination of radiation-generated radical ion pairs in alkane solution, which mimics charge transport and recombination in the active layer of practical organic light-emitting diodes in a simple solution-based experiment. Despite varying and rather poor intrinsic emission properties, diphenylacetylene and its prototypical methoxy (donor) or trifluoromethyl (acceptor) monosubstituted derivatives readily form recombination exciplexes with N,N-dimethylaniline and other tertiary amines that produce emission with maxima ranging from 385 to 435 nm. The position of emission band maximum linearly correlates with readily calculated gas-phase electron affinity of the corresponding diphenylacetylene, which can be used for fast computational prescreening of the candidate molecules, and various substituted diphenylacetylenes can be synthesized via relatively simple and universal cross-coupling reactions of Sonogashira and Castro. Together, the simple solution-based experiment, computationally cheap prescreening method, and universal synthetic strategy may open a very broad and chemically convenient class of compounds to obtain OLEDs and OLED-based multifunctional devices with tunable emission spectrum and high conversion efficiency that has yet not been seriously considered for these purposes.

Pure white light emission and charge transfer in organogels of symmetrical and unsymmetrical π-chromophoric oligo-p-(phenyleneethynylene) bola-amphiphiles

The gelation behavior of two novel π-chromophoric bola-amphiphiles has been studied and solution processable pure white light emitting and CT gels have been realized.

Fluorescent Binary Ensemble Based on Pyrene Derivative and Sodium Dodecyl Sulfate Assemblies as a Chemical Tongue for Discriminating Metal Ions and Brand Water

Enormous effort has been put to the detection and recognition of various heavy metal ions due to their involvement in serious environmental pollution and many major diseases. The present work has developed a single fluorescent sensor ensemble that can distinguish and identify a variety of heavy metal ions. A pyrene-based fluorophore (PB) containing a metal ion receptor group was specially designed and synthesized. Anionic surfactant sodium dodecyl sulfate (SDS) assemblies can effectively adjust its fluorescence behavior. The selected binary ensemble based on PB/SDS assemblies can exhibit multiple emission bands and provide wavelength-based cross-reactive responses to a series of metal ions to realize pattern recognition ability. The combination of surfactant assembly modulation and the receptor for metal ions empowers the present sensor ensemble with strong discrimination power, which could well differentiate 13 metal ions, including Cu²⁺, Co²⁺, Ni²⁺, Cr³⁺, Hg²⁺, Fe³⁺, Zn²⁺, Cd²⁺, Al³⁺, Pb²⁺, Ca²⁺, Mg²⁺, and Ba²⁺. Moreover, this single sensing ensemble could be further applied for identifying different brands of drinking water.

Ultrabright Fluorescent Silica Nanoparticles Embedded with Conjugated Oligomers and Their Application in Latent Fingerprint Detection

Fluorescent micro- and nanosized particles have a broad range of applications in biology, medicine, and engineering. For these uses, the materials should have high emission efficiency and good photostability. However, many organic fluorophores suffer from aggregation-induced quenching effects and photobleaching. Here, we used a simple method based on covalently blending a fluorescent conjugated oligomer with silica nanoparticles to achieve emission quantum yields as high as 97%. The resulting system also showed excellent stability under continuous light illumination, in a range of pH values and temperatures, and in common solvents. This fluorescent material showed outstanding properties, including highly efficient blue emission, low cost, low toxicity, and easy synthesis. Furthermore, its effectiveness for latent fingerprint detection was demonstrated as a proof of concept on various substrates. The obtained emissive fingerprint powder gave good optical/fluorescent images with high contrast and resolution between the ridges and spaces.

Triazoliptycenes: A Twist on Iptycene Chemistry for Regioselective Cross-Coupling To Build Nonstacking Fluorophores

Triazoliptycene fluorophores have been designed and synthesized, in which a three-dimensional propeller-like iptycene motif is employed to suppress intermolecular π-π stacking in the solid state. Key to the success of this modular synthesis is a stereoelectronic bias imposed by the iptycene scaffold, which assists the desired regioselectivity in the C-N cross-coupling step as the last-stage structure diversification from a common precursor.

Distinct Interfacial Fluorescence in Oil-in-Water Emulsions via Exciton Migration of Conjugated Polymers

Commercial dyes are extensively utilized to stain specific phases for the visualization applications in emulsions and bioimaging. In general, dyes emit only one specific fluorescence signal and thus, in order to stain various phases and/or interfaces, one needs to incorporate multiple dyes and carefully consider their compatibility to avoid undesirable interactions with each other and with the components in the system. Herein, surfactant-type, perylene-endcapped fluorescent conjugated polymers that exhibit two different emissions are reported, which are cyan in water and red at oil-water interfaces. The interfacially distinct red emission results from enhanced exciton migration from the higher-bandgap polymer backbone to the lower-bandgap perylene endgroup. The confocal microscopy images exhibit the localized red emission exclusively from the circumference of oil droplets. This exciton migration and dual fluorescence of the polymers in different physical environments can provide a new concept of visualization methods in many amphiphilic colloidal systems and bioimaging.