High-Quality Conjugated Polymers Achieving Ultra-Trace Detection of Cr2O72− in Agricultural Products

Abstract

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.

3D-Printed Fluorescent Hydrogel Consisting of Conjugated Polymer and Biomacromolecule for Fast and Sensitive Detection of Cr(VI) in Vegetables

“…Unlike other organic solvents, the polymerization of conjugated polymers in BFEE not only eliminates the need for supporting electrolytes, but also takes advantage of the Lewis acidic nature of BFEE. This property facilitates the formation of π-complexes with aromatic monomers, reducing the aromaticity of monomers and lowering their oxidation potential. , Our previous works have demonstrated the feasibility of producing high-quality polymer films of fluorene and its derivatives through electrochemical methods in BFEE. − Fmoc-Osu has good solubility in BFEE, and its polymer P(Fmoc-Osu) was synthesized in this system. As shown in Figure a, the first cycle of cyclic voltammograms (CVs) showed an oxidation potential of Fmoc-Osu at 1.30 V. Subsequently, with an increasing number of cycles, a pair of reversible redox peaks appeared, accompanied by a rise in current density.…”

Amino Acid-Functionalized Polyfluorenes: A Class of Ultra-Sensitive Fluorescent Sensors Favoring Cr2O72−

“…Considering that six monomers cannot be electrochemically polymerized in common organic solvents such as tetrahydrofuran (THF), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) containing supporting electrolytes, an attempt was made to add trifluoroacetic acid (TFA) into BFEE as the electrolyte solution. On one hand, BFEE, as a Lewis acid, has a catalytic effect on the electropolymerization of aromatic compounds [2,3,6,11]. On the other hand, the addition of TFA to BFEE leads to the formation of complexes between the monomer and TFA, which reduces the resonance of the aromatic ring and improves the stability of the radical ion while increasing the electrical conductivity [2,3,10,11].…”

“…On one hand, BFEE, as a Lewis acid, has a catalytic effect on the electropolymerization of aromatic compounds [2,3,6,11]. On the other hand, the addition of TFA to BFEE leads to the formation of complexes between the monomer and TFA, which reduces the resonance of the aromatic ring and improves the stability of the radical ion while increasing the electrical conductivity [2,3,10,11].…”

“…2023, 48, 52 2 of 5 our group proposed a design strategy, selecting fluorene as the fluorescence group and introducing amino acid moieties at the C9 position as recognition groups. Then, six polyfluorene fluorescent derivatives were successfully fabricated via electrochemical polymerization to construct fluorescence sensors for Cr2O7 2− detection [2,3,10,11].…”

“…Fluorene is a classical blue luminescent polymer material that not only has a high fluorescence quantum yield and good optical stability, but can also further improve its photoelectric performance by introducing amino acid groups containing N and O atoms in the side chain [8,9]. Amino acids containing N and O atoms are characterized by high ion-binding ability, good selectivity, and a strong pH response, which give them certain advantages in the development of efficient and sensitive ion sensors [10,11]. Therefore, our group proposed a design strategy, selecting fluorene as the fluorescence group and introducing amino acid moieties at the C9 position as recognition groups.…”