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In view of that conjugated polymers (CPs) are an attractive option for constructing high-sensitive Cr2O72− sensors but suffer from lacking a general design strategy, we first proposed a rational structure design of CPs to tailor their sensing properties while validating the structure-to-performance correlation. Short side chains decorated with N and O atoms as recognition groups were instructed into fluorene to obtain monomers Fmoc-Ala-OH and Fmoc-Thr-OH. Additionally, their polymers P(Fmoc-Ala-OH) and P(Fmoc-Thr-OH) were obtained through electrochemical polymerization. P(Fmoc-Ala-OH) and P(Fmoc-Thr-OH) with high polymerization degrees have an excellent selectivity towards Cr2O72− in comparison to other cations and anions. Additionally, their limit of detection could achieve 1.98 fM and 3.72 fM, respectively. Especially, they could realize the trace detection of Cr2O72− in agricultural products (red bean, black bean, and millet). All these results indicate that short side chains decorated with N and O atoms functionalizing polyfluorene enables the ultra-trace detection of Cr2O72−. Additionally, the design strategy will spark new ideas for the construction of highly selective and sensitive Cr2O72− sensors. [ABSTRACT FROM AUTHOR]

Summary: Poly(2,7‐bis(carbazol‐9‐yl)‐9,9‐dimethylfluorene) (PBCMF) polymer with porous structure was fabricated, and its electropolymerization was studied comparatively in dichloromethane (CH2Cl2) systems in the presence of different contents of boron trifluoride diethyl etherate (BFEE). When adding BFEE in CH2Cl2 solution, the oxidation potential of BCMF could be decreased obviously. When the content of BFEE increased to 40%, BCMF was oxidized at 0.47 V, while it was oxidized at 1.07 V in pure CH2Cl2 solution. A series of experiments showed that the polymer PBCMF films could be easily obtained in CH2Cl2‐BFEE systems, and films obtained from the 40 vol% BFEE system showed best electrochemical behavior and best fluorescence property. Fourier transform infrared spectra and UV‐Vis proved the longer conjugated chains of polymers. And scanning electron microscopy images of polymer films showed that all these polymer films made from BFEE systems had a good porous structure. [ABSTRACT FROM AUTHOR]

By employing planar thieno[3,2‐b]thiophene (TT) as end‐capped units and famous 3,4‐ethylenedioxythiophene (EDOT) or its all‐sulfur analog 3,4‐ethylenedithiathiophene (EDTT) as cores, two conjugated oligomer, TT‐EDOT‐TT and TT‐EDTT‐TT, have been synthesized and electropolymerized into electrochromic polymer films, P(TT‐EDOT‐TT) and P(TT‐EDTT‐TT), respectively. Due to strongly noncovalent inter/intramolecular interactions from SS attraction of TT‐EDTT‐TT, it has twisted molecular configuration in contrast to planar TT‐EDOT‐TT. Spectroscopic, electrochemical, morphological as well as theoretical calculation studies of these oligomers or polymers were carried out to reveal the significant influence of such molecular geometry on their physicochemical and optoelectronic properties. According to electrochromic kinetics, P(TT‐EDTT‐TT) presented preferable electrochromic behavior such as the higher optical contrast (70.8%), favorable coloration efficiency (331.3 cm2 C−1) and fast response time (0.72 s). This research will help us deeply understand the effect of spatial organization of precursor molecules on the properties of electrochromic polymers and provides a promising strategy to develop high‐performance electrochromic materials. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1041–1048 [ABSTRACT FROM AUTHOR]

A fluorescent conjugated polymer thin film sensor via the electropolymerization for fluorescent detection of Fe 3+ in aqueous solution was successfully fabricated using a poly(5-cyanoindole) (P5CI), which was electrochemically prepared in the mixed electrolyte of boron trifluoride diethyl etherate, diethyl ether and tetrabutylammonium tetrafluoroborate on ITO electrodes by successive cyclic voltammetry. The thickness of the electropolymerized P5CI thin film could be precisely controlled by optimizing scan cycles and scan rates. The as-obtained fluorescent P5CI thin film sensor could effectively recognize Fe 3+ with outstanding sensitivity, selectivity, reversibility and reproducibility over other commonly coexistent metal ions and anions, and realize the quantitative determination of Fe 3+ in a linear range of 0.2 μM–0.5 mM with a detection limit of 0.897 ppb. The reversibility and reproducibility of P5CI thin film sensor were assessed. Satisfactory results indicated that fluorescent conjugated polymers via the electropolymerization provided a promising candidate for fluorescent thin film sensor. [ABSTRACT FROM AUTHOR]

Trivalent chromium (Cr 3 + ) can cause severely environment pollution, declining quality of edible agro-products in plants and animals, and human diseases. Poly( N -(9-fluorenylmethoxycarbonyl)- l -histidine) (PFLH) synthesized by the direct electro-polymerization of its corresponding commercially available monomer in both boron trifluoride diethyl etherate and dichloromethane mixed system. The “turn-on” type fluorescent sensor based on PFLH displayed high sensitivity and selectivity for Cr 3 + detecting. The structure of PFLH was rationally proved by 1 H NMR spectra, FT-IR spectra, quantum chemical calculations, and its optical properties were characterized. The electro-synthesized PFLH exhibited a “turn-on” fluorescent response towards Cr 3 + , which was employed as a sensing platform for the “turn-on” fluorescent analysis of Cr 3 + in a wide linear range from 5.1 nM to 25 μM with a low limit of detection as low as 1.7 nM. The possible mechanism of fluorescent “turn-on” sensor based on PFLH for Cr 3 + was proposed. The sensor displayed high sensitivity, good selectivity, satisfactory practicability, suggesting that PFLH has potential fluorescent application for “turn-on” sensing Cr 3 + in agricultural environments and edible agro-products of plants and animals. [ABSTRACT FROM AUTHOR]

An efficient and practical conjugated polymer-based fluorescent sensor for the nanomolar detection of iron(III) in color rice samples has been successfully fabricated using an alcohol-soluble poly(9-fluorenecarboxylic acid) (PFCA), which was facilely electrosynthesized in boron trifluoride diethyl etherate. PFCA displayed high selectivity toward Fe 3+ over different substances existing in agricultural crops and their products, such as common metal ions, anions, natural amino acids, carbohydrates, and organic acids, even organs of crops. Fluorescent intensities of PFCA showed a linear response to Fe 3+ in the concentration range of 1 nM–0.782 mM with a detection limit of 0.611 nM. Fe 3+ was tested by PFCA in real samples with satisfactory results, suggesting that the PFCA-based fluorescent sensor will provide a good model for constructing an advanced and promising fluorescent sensing platform for the determination of Fe 3+ in agricultural samples. The sensing mechanism that Fe 3+ induced the significant aggregation of PFCA chains and led to a significant fluorescent quenching of PFCA was proposed. [ABSTRACT FROM AUTHOR]

Graphical abstract A high-sensitive fluorescent sensor based on electrosynthesized poly(Fmoc- l -serine) enables ultra-trace analysis of Cr 2 O 7 2− in agro-product samples. Highlights • An electrosynthesized conjugated polymer PFOLS was first provided. • PFOLS has been used as a fluorescent probe for Cr 2 O 7 2− at ultra-trace levels. • Employing fluorescent conjugated polymer is a strategy designing high-sensitive sensors. Abstract A fluorescent sensor based on the electrosynthesized conjugated polymer poly(Fmoc- l -serine) (PFOLS) for highly sensitive analysis of Cr 2 O 7 2− at ultra-trace levels in water and agro-product samples was reported. PFOLS was obtained by potentiostatical electropolymerization of corresponding monomer Fmoc- l -serine in CH 2 Cl 2 -boron trifluoride diethyl etherate system. The introduction of serine group in PFOLS efficiently avoided the interference of anions and other acid substances in agro-products. Although metal ion Fe3+ could also quench the fluorescence of PFOLS , EDTA could recover the fluorescence of PFOLS -Fe3+ system. So in the presence of EDTA, PFOLS had a high-selectivity to Cr 2 O 7 2− and it could detect Cr 2 O 7 2− in linear ranges of 80 pM to 1.95 mM with a low detection limit of 72 pM. Then PFOLS was used to detect Cr 2 O 7 2− in water samples (tap water, lake water, and wastewater) and agro-product samples (white rice, red rice, and black rice) with satisfactory results, revealing that PFOLS could be as a practical sensing platform for ultra-trace analysis of Cr 2 O 7 2− in environment and agro-product samples. [ABSTRACT FROM AUTHOR]

A dissolvable conjugated polymer oligo(1-pyreneboronic acid) (OPYBA) as the fluorescent sensor was facilely electrosynthesized for highly selective analysis of Cu 2+ at ultra-trace levels in real samples. OPYBA was obtained by potentiostatical electropolymerization of corresponding monomer at 1.0 V vs. Ag/AgCl in acetonitrile containing tetrabutylammonium tetrafluoroborate and dedoped with dilute HCl. The tetrahydrofuran-solvable OPYBA showed good fluorescent properties and could specifically recognize Cu 2+ , and then it was employed for the quantification of Cu 2+ in linear ranges of 25 pM–88.2 μM and 188 μM–750 μM with a low detection limit of 23 pM. As the fluorescent sensor, OPYBA displayed a high sensitivity and selectivity for Cu 2+ over other substances existing in environment and agro-products such as metal ions, anions, organic acids, amino acids, and carbohydrates. Also, it was used to detect Cu 2+ in tap water, lake water, white rice, Chinese cabbage, and cropland soil samples with satisfactory results, revealing that OPYBA could be as a practical sensing platform for ultra-trace analysis of Cu 2+ in environment and agro-product samples. [ABSTRACT FROM AUTHOR]

The bis(alkoxy) group para -substituted para -phenylene (p -phenylene) based conjugated polymers exhibit good electronic property due to the existence of intra-molecular non-covalent interaction between oxygen and heteroatom. However, the strong inter-molecular aggregation inhibits the ionic transport of polymer. Here, the strategy of changing side chain substitution position is employed to improve the properties of conjugated polymer. Three organic solvent-soluble conjugated polymers based on the bis(hexyloxy) group ortho -substituted p -phenylene were synthesized. The three polymers display small dihedral angles between thiophene and benzene. As the conjugated chain length of repeat units increasing, the redox potentials of polymers decrease gradually. From P1 to P2 to P3, their optical absorption regions red shift gradually, leading to neutral polymers display yellow for P1, orange for P2, magenta for P3, respectively. And the three polymers display good electrochromic properties (coloration efficiency: 641 cm2 C−1; response time: 0.2 s; optical contrast: 54%). Also, P2 possess the specific capacitance value of 170 F g−1, which is higher than that of most reported soluble conjugated polymers. Combining energy storage and electrochromic performance of the three polymers, their visualization monitor of energy storage were investigated. [Display omitted] • Three p -phenylene based conjugated polymers were synthesized. • Specific capacitance of 170 F g−1 is higher than that of most soluble conjugated polymers. • Energy storage states of the three conjugated polymers could be monitored by color variation. [ABSTRACT FROM AUTHOR]

Fluorine atom as side chain substituted conjugated polymer exhibits enhanced photoelectric performance due to the intra- and inter-molecular interaction. However, the strong molecular aggregation due to the existence of fluorine atom inhibits the doping ion transport in conjugated polymer. Here, two fluorine substituted hybrid conjugated polymers, poly(BisTh- o -2F) and poly(BisTh- p -2F), based on para -phenylene and thiophene were prepared by electrochemical method. The molecular structure difference of the two hybrid conjugated polymers is the substitution position of fluorine atom. The two hybrid conjugated polymers exhibit similar redox property and optical absorption region. During oxidation process, the colors of the two hybrid conjugated polymers turn from dark red to blue. Kinetic studies demonstrate that fluorine atom ortho -substituted poly(BisTh- o -2F) possesses faster response time than that para -substituted poly(BisTh- p -2F) due to the decreased molecular aggregation. However, poly(BisTh- p -2F) exhibits higher optical contrast than poly(BisTh- o -2F) under different wavelengths. The charge-discharge experiments demonstrate that poly(BisTh- o -2F) possesses much higher specific capacitance than poly(BisTh- p -2F). And, the energy storage states of the two conjugated polymers could be monitored by the color variation, demonstrating they possess great application potential in electrochromic supercapacitor. [Display omitted] • Two fluorine substituted conjugated polymers were investigated comparatively. • Poly(BisTh- o -2F) possesses much higher capacitance than para-substituted poly(BisTh- p -2F). • Energy storage states of the two conjugated polymers could be monitored by color variation. [ABSTRACT FROM AUTHOR]

Amino acid group enables electrosynthesized polyfluorene to specifically recognize Cr 2 O 7 2−. [Display omitted] • Polyfluorene-based fluorescent sensor was prepared by electropolymerization. • The aminobutyric acid effectively enabled this sensor to have high selectivity. • The LOD of sensor was as low as 16.6 fM due to the signal amplification effect. • P(Fmoc-GABA-OH) was used to detect Cr 2 O 7 2− in fruits for the first time. Food health and safety has always been the top priority of the people's concern. Accurate and convenient methods for rapid detection of Cr(VI), an internationally recognized carcinogenic heavy metal ion, are becoming more and more important and meaningful in crops. In this work, we proposed a molecular design strategy to explore highly selective and sensitive Cr 2 O 7 2− fluorescent sensors. Fluorescent conjugated polymer (P(Fmoc-GABA-OH)) had been prepared via electrochemical polymerization. Dual effect of aminobutyric acid group and "molecular wire effect" of conjugated polymer enables ultra-trace detection of Cr 2 O 7 2− and the limit of detection was 16.6 fM. This approach could be applied for monitoring the Cr 2 O 7 2− concentrations in farmland water, soil, tangerine, orange, and grapefruit samples. The present finding will not only extend the scope of conjugated polymers-based sensors but also provide a new strategy for the ultra-trace detection of Cr 2 O 7 2−. [ABSTRACT FROM AUTHOR]

A hybrid thienylene-phenylene conjugated molecule with pendent double bond unit on side chain, 5,5'-(2,5-bis(hex-5-en-1-yloxy)-1,4-phenylene)bis (2,3-dihydrothieno[3,4- b ] [1,4] dioxine) (EDOT- ene -BE), was designed, and its corresponding polymer poly(EDOT- ene -BE) with similar-network structure was prepared by electrochemical method. The introduction of pendent double bond unit has little influence on the optical absorption and oxidation potential of EDOT- ene -BE. The pendent double bond unit could be attached on polymeric chain of poly(EDOT- ene -BE), leading to linear polymeric chain turning into similar-network structure. The microstructure makes poly(EDOT- ene -BE) film exhibit faster respond speed and higher coloration efficiency than poly(EDOT-BE) without pendent double bond unit. The kinetics indicate that poly(EDOT- ene -BE) could switch between oxidation and reduction states in 0.4 s, which is among one of the fastest respond times. After annealing, the polymerization between pendent double bond units leads to the formation of poly(EDOT-BE- net) with network molecular structure. As poly(EDOT- ene -BE), poly(EDOT-BE- net) possesses faster respond speed relative to poly(EDOT-BE), however, the respond speed is slower than that of poly(EDOT- ene -BE). These results demonstrate that the introduction of pendent double bond unit in side chain results into the formation of similar-network molecular structure, which is proved to be an effective strategy to improve the properties of polymer electrochromic materials. [Display omitted] • An electrochromic polymer with pendent double bond units on side chains was prepared. • The pendent double bonds make polymer possess similar-network structure. • The polymer exhibits faster respond speed and higher coloration efficiency than the control. [ABSTRACT FROM AUTHOR]

[Display omitted] • An electrochromic polymer with asymmetric substituents was prepared. • Asymmetric polymer exhibits different film morphology structure from symmetric polymers. • The relationship between molecular aggregation and electrochromic properties is discussed. The asymmetric structure could improve the electronic properties of molecules through changing the molecular packing style. In this paper, a conjugated molecule EDOT-BE-1 F (5,5′-(2-fluoro-5-(hexyloxy)-1,4-phenylene)bis(2,3-dihydrothieno[3,4–b] [1,4]dioxine)) was constructed based on the asymmetric chains (hexoxyl group and fluorine atom) para -substituted para -phenylene, and polymerized to poly(EDOT-BE-1 F) by electrochemical method. The asymmetric chains endow molecule possess compromised configuration, making poly(EDOT-BE-1 F) display different film morphology, hydrophobic property and molecular aggregation from symmetric polymers. The electrochromic result demonstrate that the asymmetric poly(EDOT-BE-1 F) could achieve color change between red and blue with the fast respond time (0.9 s) and high coloration efficiency (305C−1 cm2). Through the comparison of asymmetric poly(EDOT-BE-1 F) and symmetric poly(EDOT-BE- O), we found the decreased molecular aggregation has positive influence on respond speed and coloration efficiency of polymer during reduction process, however, displays no obvious help on that of polymer during oxidation process. The relationship between molecular aggregation and electrochromic properties of conjugated polymer is discussed in detail. The result prove that the asymmetric chains could effectively modify the molecular aggregation and balance the charge transport and ion migration, which provide a simple method to modify the performance of polymer. [ABSTRACT FROM AUTHOR]

Hexavalent chromium (Cr(VI)) pollution is related to human health, and the detection of its concentration has a decisive effect on pollution treatment. In this work, we designed a Cr 2 O 7 2− sensor P(Fmoc-Osu) and applied it in farmland. In the boron trifluoride diethyl etherate solution, the monomer Fmoc-Osu was electropolymerized and obtained its conjugated polymer P(Fmoc-Osu). The introduction of succinimide and carbonic ester group in side chain enabled it to show high selectivity to Cr 2 O 7 2− in comparison to anions and twenty amino acids. Furthermore, by taking advantage of the signal amplification effect of a conjugated polymer, P(Fmoc-Osu) could analyze Cr 2 O 7 2− in trace amounts and the limit of detection was 8.3 fM. For agricultural application, we employed it in farmland water, soil, Chinese cabbage, carrot and the results showed a satisfactory result. All these results showed that P(Fmoc-Osu) is an efficient tool to detect Cr 2 O 7 2− in practical application. An ultra-sensitive fluorescent sensor P(Fmoc-Osu) could directly detect Cr 2 O 7 2− in farmland. [Display omitted] • Conjugated polymer P(Fmoc-Osu) with blue fluorescence was easily obtained through electropolymerization. • P(Fmoc-Osu) had a high anti-interference ability when sensing Cr 2 O 7 2−, avoiding the interference of common anions and amino acids. • P(Fmoc-Osu) was highly sensitive to Cr 2 O 7 2−, and the limit of detection was 8 fM. • P(Fmoc-Osu) had a high anti-interference ability to Cr 2 O 7 2−, avoiding the interference of common anions and amino acids. [ABSTRACT FROM AUTHOR]