Baoyang Lu

Thiadiazolo[3,4-c]pyridine as an Acceptor toward Fast-Switching Green Donor–Acceptor-Type Electrochromic Polymer with Low Bandgap

Thiadiazolo[3,4-c]pyridine (PT), an important analog of benzothiadiazole (BT), has most recently been explored as a novel electron acceptor. It exhibits more electron-accepting ability and other unique properties and potential advantages over BT, thus inspiring us to investigate PT-based donor-acceptor-type (D-A) conjugated polymer in electrochromics. Herein, PT was employed for the rational design of novel donor-acceptor-type systems to yield a neutral green electrochromic polymer poly(4,7-di(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-[1,2,5] thiadiazolo[3,4-c]pyridine) (PEPTE). PEPTE revealed a lower bandgap (Eg,ele=0.85 eV, Eg,opt=1.12 eV) than its BT analog and also favorable redox activity and stability. Furthermore, electrochromic kinetic studies demonstrated that PEPTE displayed higher coloration efficiency than BT analog, good optical memory, and very fast switching time (0.3 s at all three wavelengths), indicating that PT would probably be a promising choice for developing novel neutral green electrochromic polymers by matching with various donor units.

Facile Fabrication of PEDOT:PSS/Polythiophenes Bilayered Nanofilms on Pure Organic Electrodes and Their Thermoelectric Performance

A pure organic PEDOT:PSS nanofilm was used as a working electrode for the first time to electrodeposit polymer films of polythiophene (PTh) and its derivatives in a boron trifluoride diethyl ether (BFEE) solution, fabricating a novel generation of bilayered nanofilms. Cyclic voltammetry (CV) demonstrated good electrochemical stability of the as-formed films. Structures and surface morphologies were systematically investigated by the characterizations of cross-section SEM, FT-IR, UV-vis, SEM, and AFM. The resulting films revealed stable and enhanced thermoelectric (TE) performances. The electrical conductivity values of PEDOT:PSS/PTh, PEDOT:PSS/P3MeT, and PEDOT:PSS/P3HT nanofilms were determined to be 123.9, 136.5, and 200.5 S cm(-1), respectively. The power factor reached up to be a maximum value of 5.79 μW m(-1) k(-2). Thus, this technique offers a facile approach to a class of bilayered nanofilms, and it may provide a general strategy for fabricating a new generation of conducting polymers for more practical applications.

Poly(thieno[3,4- b ]-1,4-oxathiane): Medium Effect on Electropolymerization and Electrochromic Performance

The asymmetrical sulfur analog of 3,4-ethylenedioxythiophene (EDOT), thieno[3,4-b]-1,4-oxathiane (EOTT), was synthesized, and its electropolymerization was comparatively investigated by employing different solvent-electrolyte systems (room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6), CH2Cl2-Bu4NPF6, and CH2Cl2-BmimPF6). Further, the effect of solvents and supporting electrolytes on the structure, morphology, electrochemical, electronic, and optical properties and electrochromic performance of the obtained poly(thieno[3,4-b]-1,4-oxathiane) (PEOTT) films were minutely studied. PEOTT film with a band gap (Eg) of about 1.6 eV could be facilely electrodeposited in all the solvent-electrolytes and displayed excellent electroactivity, outstanding redox stability in a wide potential window, and improved thermal stability. Cyclic voltammetry showed that EOTT could be electropolymerized at a lower oxidation potential in BmimPF6 (∼1.0 V vs Ag/AgCl) due to several advantanges of RTIL BmimPF6 itself, such as high intrinsic conductivity and mild chemical conditions, etc., and the resulting PEOTT film exhibited compact morphology with better electroactivity and stability and higher electrical conductivity. On the other hand, PEOTT films from all the sovent-electrolytes also showed the electrochromic nature by color changing from gray blue to green, and further kinetic studies revealed that PEOTT had decent contrast ratios (36%), higher coloration efficiencies (212 cm(2)/C in BmimPF6), low switching voltages, moderate response time (1.2 s), excellent stability, and color persistence. From these results, PEOTT provides more plentiful electrochromic colors and holds promise for display applications.

Molecular design of DBT/DBF hybrid thiophenes π-conjugated systems and comparative study of their electropolymerization and optoelectronic properties: from comonomers to electrochromic polymers

A novel series of comonomers, which comprise dibenzothiophene (DBT) and dibenzofuran (DBF) cores symmetrically linked to thiophene and 3-alkylthiophenes at 2 and 8-positions, were designed and electropolymerized to yield the corresponding electrochromic polymers. The structure–property relationships of comonomers and polymers, including electrochemistry, thermal stability, fluorescence, and electrochromic properties, were systematically explored. In relation to the core group, the alkyl chain group of these polymers had a relatively significant influence on the redox behavior, band gap, neutral state colour, stability, and electrochromic performance (optical contrast, CE, and switching time) of the system. Furthermore, all the polymer films displayed unique electrochromic characteristics with switching the color from yellow to blue. Further kinetic results showed moderate to high optical contrast (20–70%), high colouration efficiency (typically 170–370 cm2 C−1), and favorable switching time (0.8–9.4 s). Among them, the electrochromic performances of 3-hexylthiophene-end-capped polymers were superior to those with thiophene/3-methylthiophene as terminal groups. These results demonstrated that DBT/DBF-based π-conjugated polymer materials hold promise for display applications and DBT/DBF could be further employed for the rational design of excellent electrochromic polymers by matching with other heterocycle units.

Electrosynthesis and characterization of poly(hydroxy-methylated-3,4-ethylenedioxythiophene) film in aqueous micellar solution and its biosensing application

A new and efficient synthetic route to hydroxymethylated-3,4-ethylenedioxylthiophene (EDOT-MeOH) was developed by a simple four-step sequence, and its global yield was approximately 41.06%. The poly(hydroxymethylated-3,4-ethylenedioxylthiophene) (PEDOT-MeOH) film was electrosynthesized in aqueous sodium dodecylsulfate micellar solutions and characterized by different methods. The EDOT-MeOH possessed better water solubility, and lower onset oxidation potential than EDOT. The as-obtained PEDOT-MeOH film displayed good reversible redox activity, stability and capacitance properties in a monomer-free electrolyte, especially the good solubility of PEDOT-MeOH film in strong polar organic solvents such as dimethyl sulfoxide and tetrahydrofuran created a potential application in many different fields. Fluorescent spectra indicated that PEDOT-MeOH was a yellow-green-light-emitter with maximum emission at 568 nm. The as-formed PEDOT-MeOH film had good biocompatibility and was used for fabricating the electrochemical vitamin C biosensor. The proposed biosensor showed a linear range of 3 × 10−6 mol/L to 1.2 × 10−2 mol/L with the detection limit of 1 μmol/L, a sensitivity of 95.6 μA (mmol/L)− cm−2, and a current response time less than 10 s and a fairly good stability (The relative standard deviation was 0.43% for 20 successive assays, the proposed biosensor still retained 93.5% of bioactivity after 15 days storage. This result indicated that the prepared PEDOT-MeOH film as immobilization matrix of biologically-active species could be a promising candidate for the design and application of biosensor.

Chalcogenodiazolo[3,4-c]pyridine based donor–acceptor–donor polymers for green and near-infrared electrochromics

A series of thiadiazolo[3,4-c]pyridine (PT)/selenadiazolo[3,4-c]pyridine (PSe) in alternation with a variety of thiophenes including thiophene (Th), 3-methylthiophene (MeTh), 3-hexylthiophene (HexTh) and 3,4-ethoxylenedioxythiophene (EDOT) based donor–acceptor–donor (D–A–D) monomers were designed and electropolymerized to yield their corresponding polymers. The structure–property relationships of these monomers/polymers, including band gap, electrochemical behavior, and optical properties, were comparatively investigated. The monomers exhibited orange, red, and purple emission characteristics with quantum yields ranging from 0.072 to 0.849 and could probably be used as building blocks for rational design of fluorescent materials. Also, it was noted that these donor and acceptor units played key roles in optical absorption, leading to neutral electrochromic polymers with different colors including green, purple, gray, sky blue and dark blue. In particular, the obtained EDOT based polymers revealed an obvious color change from green to blue with a faster response time (0.3–0.6 s) relative to their benzochalcogenodiazole analogues. Furthermore, the thiophene and alkyl thiophene-based polymers kept their color constant under different applied voltages and showed superior optical contrast (∼37%) in the near-infrared region compared with that in the visible region. These intriguing features of polymeric materials demonstrated that insertion of chalcogenodiazolo[3,4-c]pyridine into a D–A–D system allowed the formation of green and near-infrared electrochromes.

Synthesis of novel chiral L-leucine grafted PEDOT derivatives with excellent electrochromic performances

Two amino acid-functionalized poly(3,4-ethylenedioxythiophene) (PEDOT) derivatives, poly(N-(tert-butoxycarbonyl)-L-leucyl(3,4-ethylenedioxythiophene-2′-yl)methylamide) (PEDOT–Boc–Leu) and poly(L-leucyl(3,4-ethylenedioxythiophene-2′-yl)methylamide) (PEDOT–Leu) were synthesized electrochemically via potentiostatic polymerization of corresponding monomers N-(tert-butoxycarbonyl)L-leucyl(3,4-ethylenedioxythiophene-2′-yl)methylamide (EDOT–Boc–Leu) and L-leucyl(3,4-ethylenedioxythiophene-2′-yl)methylamide (EDOT–Leu), which were synthesized by grafting Boc-L-leucine and L-leucine into a 3,4-ethylenedioxythiophene (EDOT) side chain. The electrochemical behaviors, structural characterization, circular dichroism, spectroscopic properties, surface morphology, electrochromic properties and thermal stabilities of PEDOT–Boc–Leu and PEDOT–Leu films were systematically investigated. These L-leucine grafted PEDOT derivatives displayed excellent reversible redox activities, rough and compact surface, and good thermal stability. The circular dichroism spectra suggested the chirality of these polymers. Importantly, the introduction of the L-leucine group enhanced the electrochromic properties of PEDOT and resulted in high contrast ratios (ΔT% = 49% at 600 nm for PEDOT–Boc–Leu) and high coloration efficiencies (431 cm2 C−1 at 960 nm for PEDOT–Leu). Satisfactory results implied that the obtained polymer films can probably be further developed in various applications, such as electrochromic devices, optical displays and chiral recognition.

Synthesis and electro-optical properties of new conjugated hybrid polymers from EDOT end-capped dibenzothiophene and dibenzofuran

Two novel EDOT end-capped monomers, namely, 2,8-di-2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl-dibenzothiophene (DBT-EDOT), and 2,8-di-2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl-dibenzofuran (DBF-EDOT), were synthesised via Stille coupling and electropolymerised to form conjugated polymers P(DBT-EDOT) and P(DBF-EDOT). The monomers exhibited blue-light-emitting characteristics, and DFT calculations revealed band gap values of 4.20 eV for DBT-EDOT and 4.34 eV for DBF-EDOT, while those of the corresponding polymers were brought down to 2.46 eV for P(DBT-EDOT) and 2.58 eV for P(DBF-EDOT), respectively. Moreover, both of the polymers displayed good electrochromic properties with colour switching between yellow in the reduced state and purple in the oxidised state. Structure characterisation and properties of monomers and as-formed polymers using FTIR spectroscopy, UV-vis spectroscopy, surface morphology, fluorescence spectroscopy, electrochemistry, and spectroelectrochemistry, together with structure–property relationships, were systematically investigated and comprehensively discussed.

A cost-effective and practical polybenzanthrone-based fluorescent sensor for efficient determination of palladium (II) ion and its application in agricultural crops and environment.

A highly selective and sensitive fluorescent chemosensor suitable for practical measurement of palladium ion (Pd(2+)) in agricultural crops and environment samples has been successfully fabricated using polybenzanthrone (PBA). PBA was facilely electrosynthesized in the mixed electrolyte of acetonitrile and boron trifluoride diethyl etherate. The fluorescence intensity of PBA showed a linear response to Pd(2+) in the concentration range of 5 nM-0.12 mM with a detection limit of 0.277 nM and quantification limit of 0.925 nM. Different compounds existing in agricultural crops and environment such as common metal ions, anions, natural amino acids, carbohydrates, and organic acids were used to examine the selectivity of the as-fabricated sensor, and no obvious fluorescence change could be observed in these interferents and their mixtures. A possible mechanism was proposed that the coordination of PBA and Pd(2+) enhance the aggregation of polymer chains, which led to a significant quenching of PBA emission, and this was further confirmed by absorption spectra monitoring and transmission electron microscopy. The excellent performance of the proposed sensor and satisfactory results of the Pd(2+) determination in practical samples suggested that the PBA-based fluorescent sensor for the determination of Pd(2+) will be a good candidate for application in agriculture and environment.

Poly(mono-, bi- or trifuran): effect of oligomer chain length on the electropolymerization performances and polymer properties

Most recently, oligo-/polyfurans have regained widely attention due to their unique properties and promising applications in organic electronics. Herein, to acquire a thorough fundamental understanding of the electrosynthesis and properties of polyfuran (PFu) from different initial oligomers, the synthesis, fluorescence, and electropolymerization performances of α-oligofurans, namely furan (Fu), bifuran (2Fu), trifuran (3Fu), were comprehensively reported and the effect of oligomer chain length on the structure and properties of the resulting PFu films were evaluated. The oligofurans introduced here revealed higher fluorescence efficiency (0.05 for Fu, 0.19 for 2Fu and 0.27 for 3Fu) than the corresponding oligothiophenes and oligoselenophenes. The onset oxidation potential of oligofurans decreased obviously (1.25 V for Fu, 0.8 V for 2Fu, and 0.7 V for 3Fu) with the chain length of the starting monomers increasing, thus leading to the electrodeposition of high quality free-standing PFu films with improved optoelectronic properties. Structure characterization and properties of the as-formed PFu from different initial oligomers, including FT-IR, UV-vis, surface morphology, fluorescence, electroactivity and stability, electrochromic properties, etc., were systematically investigated and comprehensively discussed.