Lithium-ion batteries powering electric vehicles can contain up to ∼100 liters of electrolyte solution. This solution typically consists of LiPF6 salt dissolved in a mixture of organic carbonates such as ethylene carbonate and diethyl carbonate. LiPF6 decomposes upon exposure to water vapor or other protic impurities, leading to the formation of up to 3 equivalents of hydrofluoric acid (HF) per molecule of decomposed salt. HF is a deadly and volatile substance that is corrosive to cell and battery components. Here, we describe an all-optical method that can report on the concentration of HF in LiPF6-based electrolytes. The method is based on a specially designed fluorescent dye incorporated in the working electrolyte. The dye response to HF is quantified so that photographic imaging or even visual inspection can be used to indicate the HF concentration in the electrolyte. The method is, moreover, compatible, in principle, with in situ reporting of HF levels during cell assembly and operation.

Solid additives have garnered significant attention due to their numerous advantages over liquid additives. This study explores the potential of the green-fluorescent conjugated polymer denoted Atums Green as a solid additive in green-solvent-based PBDB-TF-T1:BTP-4F-12 solar cells. Even tiny amounts of Atums Green doping significantly improve the device performance. For the reference solar cell without any additive, we find that device degradation is not caused by chemical redox reactions but by changes in crystallinity and microstructure evolution during aging in air under illumination. Operando GIWAXS and GISAXS are used to investigate the structure evolution. We discover a four-stage degradation process for the reference cell. In general, the lattice spacing and crystallite coherence length decrease, while the domain sizes increase, which causes the loss of shirt-circuit current J SC and fill factor FF. Furthermore, a decomposition component is detected in GIWAXS and GISAXS, corresponding to the loss of the open-circuit voltage V OC. Atums Green doping effectively suppresses the evolution of crystallinity and domain sizes as well as the continuous decomposition, thereby enhancing the device stability under illumination in air. This finding reveals the kinetic degradation process of organic solar cells, establishes a correlation between the morphological properties and device performance, and further demonstrates the promising potential of Atums Green doping in organic solar cells.

Commonly employed pH-sensing dyes include coumarins, rhodamines, fluoresceins, and cyanines, each offering distinct spectral properties and tunability. The design of fluorescent acid-base sensors typically involves organic dye molecules with functional groups that can interact with OH- ions. Here, we demonstrate a distyrylbenzenebased fluorescent base-sensing dye (double-protonated carboxy-functionalized 1,4-bis(4-pyridyl-2-vinyl)benzene; c-P4VB & sdot;2HX, where X = Cl but can also be other anions) that provides a larger color change and a wider range of base concentrations due to the two-step deprotonation, compared to any previously-reported fluorescent base sensors. The c-P4VB & sdot;2HCl is orange luminescent in its doubly protonated state, which evolves through yellow, greenish, and finally electric blue in its unprotonated state, with fluorescence quantum efficiencies typically higher than 50 %. The c-P4VB & sdot;2HCl and its unprotonated form (c-P4VB) are highly soluble in moderately polar solvents like (short-chained) alcohols, dimethyl sulfoxide, and dimethyl formamide, and modestly soluble in water, due to the combination of pyridine groups and the caproic acid functional group. The reaction equilibria for the two deprotonation stages were investigated, the effect of the added OH- concentration and ambient temperature on the emission color and spectra were quantified, and biological imaging was finally demonstrated.

This work proposes a new electrochemical impedance model for the redox mechanism of polyimide anodes in aqueous Na-ion batteries. It provides key insights into the discrepancy between experimental and theoretical specific capacities.

A poly(para)phenylene conjugated polymer is developed to store information via a quick and facile optical writing method. After exposure to UV light, co-fluorescence (films with two or more written emission colors -, i.e., "double-on") and "on-off" states are written into the flexible polymer films. The hidden information is invisible under ambient lighting and can only be read with an appropriate light source, optical filter, and/or magnifier, thus providing a level of security for information encoded into the films. The physical and chemical mechanisms are discussed responsible for the rapid fluorescence changes that occur under UV exposure and demonstrate microscale multi-colored artwork and hidden QR codes written into pliable and freestanding films. Depending on the preparation, the written patterns remained easily visible and stable after exposure to water and to ambient levels of UV background radiation. Information can be encoded onto a fluorescent polymer via facile ultraviolet light exposure. The inscriptions can be written as a single color or in a polychromic format. The polymer can then be removed from the substrate as a freestanding, flexible, transparent film. When exposed to certain wavelengths, the written information becomes visible, especially if aided by the appropriate filter. image

Crescent-shaped hydrogel microparticles have been shown to template uniform volume aqueous droplets upon simple mixing with aqueous and oil media for various bioassays. This emerging “lab on a particle” technique requires hydrogel particles with tunable material properties and dimensions. The crescent shape of the particles is attained by aqueous two-phase separation of polymers inside a spherical droplet followed by photopolymerization of the curable precursor. In this work, we have investigated the phase separation of photo-curable poly(ethylene glycol) diacrylate (PEGDA, M w 700) and dextran ( M w 40,000) for tunable manufacturing of crescent-shaped particles. The particles’ morphology was precisely tuned by following a phase diagram, varying the UV intensity, and adjusting the flow rate ratio between the three streams, containing PEGDA, dextran, and oil, within a microfluidic droplet generation device. The fabricated particles with variable cavity sizes and outer diameters encapsulated uniform aqueous droplets upon mixing with a continuous oil phase. The particles were fluorescently labeled with red and blue emitting dyes at variable concentrations to produce six color-coded particles. The blue fluorescent dye showed a moderate response to the pH change from 1 to 7 in terms of an increase in emitted intensity. The fluorescently labeled particles were able to tolerate an extremely acidic solution (pH 1) but disintegrated within an extremely basic solution (pH 14). The particle-templated droplets were able to effectively retain the disintegrating particle and the fluorescent signal at pH 14, indicating completely segregated compartments.

This work synthesizes a green-fluorescent conjugated polymer and performs basic photophysical characterization of this new material. Atums Green is synthesized by a Suzuki cross-coupling polymerization reaction between isostructural dibromo and diboronic acid monomers and is structurally characterized by nuclear magnetic resonance and gel permeation chromatography. The polymer consists of an alkoxy-substituted 1,4-bis((E)-styryl)benzene repeating unit with molecular weight up to M-n = 50 kDa relative to polystyrene. Atums Green shows a strong green fluorescence maximized at approximate to 500 nm in chloroform and tetrahydrofuran solutions, with an absolute quantum efficiency as high as 98%. The photobleaching dynamics and time-resolved photoluminescence (TRPL) are measured both in solutions and in solid films. Finally, solution-based lasing is demonstrated in a bulk lasing cavity and in a cylindrical microcavity. Lasing emission is readily achieved in both formats, indicating that Atums Green has excellent emission characteristics, and further suggesting that it may present a viable green-emitting conjugated polymer materials system for light emission applications.

During 1990s, poly(para)phenylenes (PPPs) are one of the most prominent and hyped classes of conjugated polymers. Even though they have been heavily investigated for different applications, they are now eking out a rather niche existence. It is believed that this decline of interest partly has come from the early obstacle of synthesizing high-molecular weight, processable, and defect-free PPPs. Early examples of PPPs are not only rather oligomers than polymers but also contain many regiochemical and structural defects. Furthermore, early unsubstituted materials are infusible and insoluble, which have made their practical application almost impossible. Another reason for the decline of research interest in PPPs may be their underperformance in early applications, particularly in organic light-emitting diodes (OLEDs), which ultimately lead to a lack of follow-up publications. However, over the last two decades not only more precise and advanced synthesis methods have arisen but also a more profound understanding of those applications has been achieved within which new technological approaches have emerged. It is believed that PPPs would benefit from this development. Accordingly, in this perspective, the synthesis, structures, properties, and applications of PPPs reported so far as well as their potential in future technologies are discussed.

A paper-based microfluidic detection device for the detection of ethanol is demonstrated in this work. The method is based on a fluorophore consisting of short-chain conjugated molecular unit susceptible to the protonation of its terminal pyridine groups, along with a carboxyl-functionalized sidechain that acts as a binder and renders it water-soluble. The resulting fluorescent paper device yields large fluorescence changes when exposed to reactions that yield H2O2 in aqueous solutions. Using an enzyme-catalyzed rection that produces H2O2 from ethanol, we developed a two-zone, cut-out paper device containing a reaction zone in which the ethanol-containing analyte is placed, and an adjacent sensor zone where we observe a fluorescence color shift proportional to the ethanol concentration. The limit of detection of the fluidic ethanol biosensor was 0.05 v/v% and the dynamic range was 0.05–2 v/v%. This method was employed to detect the alcohol concentration of consumer vodkas using only a paper sensor and a smartphone camera.

Substituted poly(para)phenylenes (PPPs) are conjugated polymers with an attractive application potential in various fields of materials science. They are synthesized nearly exclusively using catalytic cross-coupling polymerization reactions based on Pd- or Ni-catalysts. Among these synthetic approaches to access alkoxy-substituted PPPs, Kumada catalyst transfer polymerization (KCTP or GRIM polymerization) would offer certain economic advantages over Suzuki-type polymerization as it relies on the utilization of a non-precious metal for catalysis. It also results in less total costs of the utilized reagents, avoiding additional preparative steps such as synthesis, isolation, and purification of boronic acid derivatives necessary for the Suzuki reaction. In fact, KCTP is nowadays the state-of-the-art method for the synthesis of polythiophenes. However, the application of KCTP for the synthesis of alkoxy-substituted PPPs leads to polymers with low molecular weights, limiting their practical applicability. Here, we developed a synthesis protocol that resulted in MEH-PPP with a molecular weight of Mn = 133 kg/mol and BHex-PPP with Mn = 153 kg/mol relative to polystyrene, outperforming the previous state of the art by a factor more than 5. Also, a tetra(ethylene glycol)-substituted PPP has been prepared by this procedure, with a molecular weight exceeding the previously reported results for analogous structures. Such molecular weights can be obtained in a reasonable reaction time (5 days) using low concentrations of an N-heterocyclic carbene-coordinated Ni complex. The polymerization kinetics suggested a chain-growth mechanism with a chain transfer step. The latter is caused most likely by a bimolecular interaction of the Ni-species at the polymer chain ends.

An indium salan-type catalyst shows very high activities in the ring-opening polymerization of various cyclic esters, including β-butyrolactone, γ-butyrolactone, lactide, ε-caprolactone and ε-decalactone.

We investigate the two-photon fluorescence (TPF) of conjugated polymer (CP) microspheres with diameters up to tens of micrometers. Two polymers, emitting in either the violet or red, were first synthesized and characterized in terms of their one-photon fluorescence and three-dimensional internal microstructure. Under femtosecond infrared excitation, both types of microspheres showed a strong TPF, which was investigated by the excitation intensity dependence, emission spectroscopy, time-resolved luminescence, and photobleaching dynamics. While the violet-fluorescent microspheres performed similarly compared to dye-doped polystyrene counterparts emitting at a similar wavelength, the red-fluorescent microspheres showed a two-orders-of-magnitude stronger TPF. This excellent performance is attributed to enhanced hyperpolarizability associated with intermolecular interactions in the polymer solid, indicating a route toward designed CP microspheres that could outperform currently-available microparticles for sensing or imaging applications involving two-photon fluorescence.

We show a double-functional fluorescence sensing paradigm that can retrieve nanometric pH information on biological structures. We use this method to measure the extent of protonic condensation around microtubules, which are protein polymers that play many roles crucial to cell function. While microtubules are believed to have a profound impact on the local cytoplasmic pH, this has been hard to show experimentally due to the limitations of conventional sensing techniques. We show that subtle changes in the local electrochemical surroundings cause a double-functional sensor to transform its spectrum, thus allowing a direct measurement of the protonic concentration at the microtubule surface. Microtubules concentrate protons by as much as one unit on the pH scale, indicating a charge storage role within the cell via the localized ionic condensation. These results confirm the bioelectrical significance of microtubules and reveal a sensing concept that can deliver localized biochemical information on intracellular structures.

We report on a fluorescent-droplet-based acid-sensing scheme that allows limits of detection below 100 pM for weak acids. The concept is based on a strong partitioning of acid from an aqueous phase into octanol droplets. Using salicylic acid as a demonstration, we show that at a high concentration, the acid partitions into the organic phase by a factor of 260, which is approximately consistent with literature values. However, at lower concentrations, we obtain a partition coefficient as high as 106, which is partly responsible for the excellent sensing performance. The enhanced equilibrium partitioning is likely due to the interaction of the dissociated acid phase with the sensor dye employed for this work. The effect of droplet size was determined, after which we derived a simple model to predict the time dependence of the color change as a function of droplet size. This work shows that color-change fluorescent-droplet-based detection is a promising avenue that can lead to exceptional sensing performance from an aqueous analyte.

Conjugated polymers (CPs) can potentially provide an alternative to conventional fluorescent microsphere technologies; however, examples of CP microspheres encompassing an extensive range of sizes are few, and wide‐ranging spectral control, as needed for many applications, has never been demonstrated. Blended CP microspheres consisting of individual polymers are synthesized here. They are blended to have widely separated Commission Internationale de l'Éclairage (CIE) color coordinates and a compatible synthesis while at the same time forming well‐defined domain structures. By developing appropriate mixtures of selected blue, green, and red fluorescent CPs, blended CP microspheres are demonstrated to cover an extensive range of color coordinates including white. It is shown that multi‐CP microspheres with core–shell or related structures can provide optimum characteristics, while energy and/or charge transfer in finer mixtures result in microspheres without the desired emission properties. Pre‐ or postprocessing further directs consistent changes in the CP microspheres that ultimately regulate the overall spectral response. This approach can lead to a new class of bright fluorescent microparticles with applications in a wide range of disciplines that demand maximum brightness and highly specific emission spectra.

We demonstrate a versatile and easily fabricated paper-based CO2 sensor. The sensor consists of a specially designed fluorescent color-shift chromophore infused into standard filter paper. The emission color of the resulting fluorescent paper changes upon exposure to CO2 due to the formation of carbonic acid, which underlies the sensing mechanism. By using a ratiometric method, the undesirable effects of photobleaching can be eliminated, leading to a stable and repeatable sensor performance. These multiuse sensors have a response time on the order of 1 min and feature low detection limits for a paper-based CO2 gas sensor, suggesting possible low-cost applications in smart buildings or other facilities in which CO2 levels are required to be continuously monitored.

Borata-alkenes can serve as anionic olefin equivalent ligands in transition metal chemistry. A chelate ligand of this type is described and used for metal coordination.

Hybrid fluorescent metal-organic frameworks (MOFs) use long-range intermolecular structural motifs in which the properties of the scaffold molecular system can be designed for specific applications. In this work, we constructed a MOF-chromophore system with a strongly polarized fluorescence and a large emission wavelength shift. To achieve this, we first devised a fluorophore with a linear conjugated backbone, bulky and noninteracting side chains, and easily accessible nitrogen atoms on its pyridine end groups. The linear nature of the conjugated backbone can lead to a strongly polarized luminescence, the side groups assist structural stability and minimize intermolecular interactions, and the sterically accessible pyridines provide a large fluorescence color-changing ability. These features were demonstrated by synthesizing a planar Zn-based MOF in which the linear backbone of the chromophore molecules was highly aligned. The MOFs demonstrated a strong polarization effect and a color-shifting ability from green-yellow to orange. The results show that hybrid metal-organic materials can be designed to generate a strong command of the material luminescence, in terms of both emission color and polarization.

Fluorescent microspheres are used for biomarkers, assay substrates, chemical diagnostics, flow cytometry, and biological imaging. These applications demand the highest fluorescence intensity achievable; however, concentration quenching limits the amount of dye that can be practically incorporated in conventional fluorescent microspheres. Conjugated polymers (CPs) can be less susceptible to concentration quenching, suggesting that they can be excellent candidates for a new class of light-emitting microspheres. Due to their long-chain-conjugated backbone, however, CPs can be resistant to forming smoothly curved or spherical structures. Here, strongly fluorescent CP microspheres as large as 100 mu m in diameter are synthesized. Whispering gallery modes (WGMs) appear in the fluorescence spectra, and the microspheres show clear evidence of lasing above a threshold pump intensity. These conjugated polymer beads are up to 50 times larger than CP microspheres obtained by other methods, and they exceed the emission intensity of conventional fluorescent microspheres by more than an order of magnitude.

Utilization of group transfer polymerization for the synthesis of poly(diethyl vinylphosphonate) (PDEVP) allows its controlled end-group functionalization. Thus, a new fluorescent chromophore/PDEVP conjugate is prepared and subjected to biocompatibility tests on two different human cell lines. In contrast to the previous studies, the tagged polymer is not absorbed by cells from the solution and has nearly no impact on cell mortality rate.