Electrochemical Properties Research Articles

Laser cladded Co08–xTi3AlC2 coatings: Microstructure, corrosive–wear and electrochemical corrosion

MAX phase played the positive role during the corrosive–wear process of metal coatings, and Ti3AlC2 was added into Co08 coating by laser cladding to improve its corrosive–wear and electrochemical properties. The effects of Ti3AlC2 mass fraction on the corrosive–wear and electrochemical properties of obtained coatings in 3.5% NaCl solution were investigated using a reciprocating wear tester and electrochemical workstation, respectively. The results show that the Co08–xTi3AlC2 coatings are composed of Co (Ni, Cr, W, Mo), AlFe and Ti3AlC2 phases, and their hardness is increased with the Ti3AlC2 mass fraction. The average coefficients of friction of Co08–5%Ti3AlC2, –10%Ti3AlC2 and –15%Ti3AlC2 coatings are 0.56, 0.47, and 0.41, respectively, and the corresponding wear rates are 418.99, 389.67, and 339.33 μm3•N−1•s−1, respectively, showing that the Co08–15%Ti3AlC2 coating has the best friction reduction and wear resistance among the three kinds of coatings. The wear mechanism of Co08–5%Ti3AlC2, –10%Ti3AlC2 and –15%Ti3AlC2 coatings are abrasive wear, adhesive wear, and abrasive wear/adhesive wear, respectively. Moreover, the corrosion resistance of Co08–xTi3AlC2 coatings is increased by the Ti3AlC2 mass fraction, which is attributed to the protection role of corrosion products by the addition of Ti3AlC2.

The screening of reasonable copper and phosphorus content in weathering steel by a high-throughput experimental method

The effect of coupling of copper and phosphorus in steel on atmospheric corrosion behavior was investigated using high-throughput experimental methods. Wire beam electrodes and plates with discrete distribution of composition gradients were prepared through a selective laser melting method. By combining array electrode scanning tests and EPMA, the electrochemical properties and the relationship between different copper and phosphorus contents were rapidly determined. Plenty of data obtained were analyzed according to relevant standards and screened to identify compositional ranges corresponding with the relevant compositions of existing grades of steel. To further analyze the effect of copper and phosphorus on the corrosion behavior, dry/wet cyclic corrosion test were performed using plates. A combination of XRD, FTIR, SEM, EDS, and EPMA were used to analyze the corrosion behavior. It was observed that both copper and phosphorus promoted the formation of amorphous substances, supporting the proposed mechanism by previous researchers. Furthermore, in the absence of manganese interference, copper could accumulate at the metal/rust layer interface, rendering the rust layer cation-selective and effectively inhibiting the deep penetration of chloride ions. Moving forward, we expect to develop this high-throughput experiments to investigate the coupling effects of other elements on corrosion behavior.

Tube-Like Copper Cobalt Oxide Anchored with Multiwalled Carbon Nanotube Nanocomposite Modified Glassy Carbon Electrode for the Electrochemical Detection of Nilutamide

Developing a precise and effective method to detect Nilutamide (NIL) is essential due to its contamination of the environment, which poses significant risks to human health and the biosphere. In this study, we employed a simple hydrothermal technique to create a nanocomposite of CuCo2O4 (copper cobalt oxide) and multi-walled carbon nanotube (MWCNT), which was then anchored onto a glassy carbon electrode for NIL detection. Various spectroscopic techniques were employed to confirm the structure of the nanomaterial, and its electrochemical properties were examined using cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. The CuCo2O4/MWCNT nanocomposite-modified electrode exhibited a wide linear detection range from 0.01 to 170 μM, a high sensitivity of 1.50 μA μM−1 cm−2, a low detection limit of 0.01 μM, outstanding stability, repeatability, and practical applicability for NIL detection.

A novel anode with improved electrochemical performance based on cobalt squarate for lithium-ion batteries

Organics matter squaric acid with small molecules and multiple active sites are of great potential to obtain a high theoretical specific capacity. However, square acids are easily dissolved in the electrolyte, causing it to exhibit characteristics of low capacity and poor cycling performance. Metal ions are introduced to create metal–organic frameworks (MOFs), which is one of the efficient solutions for the aforementioned problems. MOFs based on π-d systems can improve stabilities and inhibit the dissolution of organic ligands. Meanwhile, different metal ions can modify its electrochemical properties, especially those with redox activity, which can significantly improve the capacity and stability of the MOFs. In this paper, the M−SQ (M = Co, Ni, Mn) based on square acid was synthesized, compare to Ni-SQ and Mn-SQ, Co-SQ with multiple redox-active centers shown greater reversible capacity and cycle stability, which has 1242.2 mA h g−1 at 0.1 A g−1, it is present an excellent capacity, and Co-SQ also has good rate capacity, when current density added to 2 A g−1, it has 807.9 mA h g−1. Meanwhile, Co-SQ showing an outstanding long cycle life with 481.8 mA h g−1 after 700 cycles at 1 A g−1. In addition, Co-SQ with a porous structure has a higher capacity than Co-SQ-NaOH with rod-like structure. Further, the Li+ storage advantage of the porous structure Co-SQ was revealed by kinetic studies. The strategy though tunable active sites of metals and carbonyl is great potential for obtaining high-performance energy storage materials.

A closer look at the magnetic, photo-electrochemical, and optical properties of rare earth (Sm, Dy, Ho, Er, and Yb)-doped manganese ferrite for potential use as a photocatalyst

For photocatalysis technology to be applied industrially, there has been a significant increase in the need for visible-light-driven photocatalysts that possess exceptional superparamagnetic characteristics to facilitate easy separation. Hence, in this study, rare earth elements (RE) (Sm, Yb, Dy, Er, and Ho) were systematically doped into manganese ferrite (MF) using the coprecipitation method to serve two purposes, namely, reducing the photogenerated electron-hole recombination during photocatalysis and modifying the magnetic properties of MF to become superparamagnetic. The synthesised Re-doped MF was found to be visible light active, as evidenced by the transient photocurrent response and the obtained band gaps, which were in the range of 1.84–1.93 eV. From the cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization plots, it was evident that different RE element dopants have different effects on improving the electrochemical properties of MF. Overall, fast electron transfer of the synthesised materials was found to decrease in the following order: Sm-MF > Dy-MF > Ho-MF > MF > Er-MF > Yb-MF. The g-factor and peak-to-peak line width were found to be in the range of (2.221–2.317) and (93.17–149.85 mT), respectively. The resonance field and hysteresis loop (Hc) were found to be in the range of (289.2–301.86 mT) and (8.24–32.61 mT), respectively. Overall, the synthesised RE-doped MF exhibits ferromagnetic properties, and the obtained small Hc values hint at these particles exhibiting superparamagnetic properties. In summary, doping MF with Sm, Dy, and Ho is more desirable as it alters the magnetic properties towards superparamagnetic and improves its electrochemical properties. Thus, this study is of importance in advancing the field of photocatalysis in water treatment and material science.

Facile design of structurally robust, highly conductive and well-flexible hybrid film based on MXene, cellulose nanofiber and poly (3,4-ethylenedioxythiphoenes):polystyrene sulfonate for supercapacitors

Robust, conductive and flexible electrode materials have been the focus of attention in portable, wearable electronics. However, it is still a significant challenge to achieve synergistic development of multiple properties simultaneously. Herein, we propose a combination of microscale design and nanostructures strategy to prepare MXene/cellulose nanofiber-poly (3,4-ethylenedioxythiphoenes):polystyrene sulfonate (Ti3C2Tx/CNF-PEDOT:PSS, TC-P) hybrid film by a simple in-situ polymerization and vacuum filtration process. CNF serves as the supporting skeleton of PEDOT:PSS, effectively mitigating its self-aggregation and structural deformation due to the expansion/contraction of the polymer network. And the CNF-PEDOT:PSS composite is capable to open up the interlayer space of Ti3C2Tx, which reduces the self-stacking of Ti3C2Tx nanosheets. The strong interactions among the three components enable the hybrid film electrode to possess both flexibility and high electrochemical properties. As a result, the film electrode exhibits a remarkable tensile strength of 77.4 MPa and an excellent conductivity of 162.5 S cm−1, as well as an outstanding areal specific capacitance of 896 mF cm−2 at 4 mA cm−2. Moreover, the assembled symmetric supercapacitor (SSC) device displays a large areal energy density of 62 µWh cm−2 at a power density of 800 µW cm−2 and demonstrates a long cycle life with 85.1 % capacitance retention after 10,000 GCD cycles. This study provides an effective strategy to balance mechanical flexibility and electrochemical properties, providing an inspiration to prepare flexible electrodes that are widely applied in a new generation of portable, wearable electronics.

The Superior Electrochemical Property of LiTFSI@(Ba+Nb)-co-doped Li7La2.75Ba0.25Zr1.75Nb0.25O12@PEO Composite Membrane in All-Solid-State Lithium Battery

It is popular to choose the cubic phase Li7La3Zr2O12(c-LLZO) to synthesize the PEO-based complex membrane in all-solid-state battery. In this work, Ba/Nb elements were selected to achieve Li6.75La3Zr1.75Nb0.25O12 (LLZNO) and Li7La2.75Ba0.25Zr1.75Nb0.25O12 (LLBZNO) with high ion conductivity, which effectively enhance the electrochemical properties of the complex solid membrane and the all-solid-state battery. The higher ion mobility of LLBZNO compared to that of LLZNO and LLZO is calculated by ab-initio molecular dynamics (AIMD) simulation and further confirmed by experiments. Results show that the cubic phase of LLBZNO is more stable than that of LLZNO. The complex membrane of LLBZNO@ polyethylene oxide (PEO) (CPE-2-x wt%) exhibits the better electrochemical properties than LLZNO@PEO (CPE-1-x wt%) complex membrane. In detail, the CPE-2–10 wt% has the outstanding lithium transfer number ( tLi+ ) of 0.63, as well as the excellent compatibility with lithium metal anode. In addition, at 0.1 mA∙cm−2, the lithium/CPE-2–10 wt%/lithium symmetric cell remains stable after 1000 h. It is LLBZNO that makes LLBZNO@PEO composite polymer electrolyte(CPE) the potential for the application in all-solid-state lithium battery.

Post-macrocyclization strategy to octaphenoxy-substituted zinc pyrazinoporphyrazine, its photochemical and electrochemical properties

An efficient post-macrocyclization strategy to new octaphenoxy-substituted zinc pyrazinoporphyrazine has been developed. This approach allows avoiding the template synthesis of the target compound from the phenoxy-substituted dinitrile, during which oligomerization and phenol release occur. The possibility of obtaining the initial octachloropyrazinoporphyrazine using template synthesis activated thermally and using microwave irradiation has been shown. Octaphenoxy-substituted zinc pyrazinoporphyrazine demonstrates short but intense triplet signals in triplet absorption spectrum and substantial singlet oxygen quantum yield (ΦΔ = 0.34). The fluorescent properties and fluorescence decay kinetics of target porphyrazines were studied. In contrast to the initial poorly soluble chlorinated complex, cyclic voltammetric measurements show both reduction and oxidation processes. Two waves of reduction and one wave of oxidation were observed. The electron-donating nature of phenoxy groups compared to chlorine groups is shown.

Fabrication of pyrolytic carbon interdigitated microelectrodes by maskless UV photolithography with epoxy-based photoresists SU-8 and mr-DWL

Maskless UV photolithography is increasingly used, especially in research environments where low turn-around time for new designs improves productivity. Here, we fabricate pyrolytic carbon interdigitated microelectrodes with small interelectrode gaps, good adhesion to the carrier substrate, high surface area and excellent electrochemical properties using maskless UV photolithography with two negative epoxy-based photoresists, namely the commonly used SU-8 and the recently developed mr-DWL. The minimum realizable trench width in 15 μm thick photoresist films is 2.4 ± 0.15 μm for mr-DWL 5 and 3.1 ± 0.10 μm for SU-82035. After pyrolysis, the two resulting pyrolytic carbon materials show similar electrochemical properties. However, shrinkage during pyrolysis is significantly lower for mr-DWL compared to SU-8, which is beneficial for the fabrication of interdigitated microelectrodes. Furthermore, delamination of the electrodes during processing and operation is prevented due to the introduction of poly silicon adhesion structures. This work provides valuable insights into maskless UV lithography as well as into the pyrolytic carbon process to increase the yield, performance and productivity for fabrication of microelectrodes.

Rational design of germanium–copper based nanocomposite anodes for high-performance lithium-ion storage

The rising energy demand in the 21st century has necessitated a shift from fossil fuels to irregular renewable sources for carbon neutrality. Therefore, energy-storage systems are crucial for storing intermittently produced energy. Electric vehicles (EVs), which are expected to replace internal combustion engines, are in high demand for achieving carbon neutrality. The development of efficient secondary batteries (such as lithium-ion batteries; LIBs) is vital for increasing the energy-storage capacity and driving range of EVs. Currently, the most commercialized carbon-based anode material has a capacity of 372 mAh g-1. However, this capacity is insufficient to produce the high-capacity batteries required in the current market. Therefore, in this study, GeO2, which can store 8.4 lithium atoms in one molecule, was selected as the target material. To enhance its electrochemical properties, conductive Cu and C were introduced into GeO2. The composites were synthesized via high-energy ball milling, a simple and easy method to scale up. Three types of GeO2/Cu@C composites, GeO2/Cu@C (10, 20, and 30wt%), were prepared by varying the carbon content. Among them, GeO2/Cu@C (20wt%) exhibited an average reversible capacity of 660.6 mAh g-1 after 200 cycles, with a capacity retention of 75.4% at a current density of 0.1Ag-1. Even at a high current density of 0.5Ag-1, its average capacity and capacity retention were 672.3 mAh g-1 and 99.5%, respectively, after 100 cycles. Moreover, galvanostatic intermittent titration technique analysis revealed that the Li+ diffusion coefficient of GeO2/Cu@C (20wt%) was higher than those of the other electrodes. The full-cell with the NCM622 cathode exhibited a high energy density of 284.9Whkg-1. Therefore, the GeO2/Cu@C (20wt%) electrode is anticipated to be a potential anode for long-term LIB cycling.

Additive manufacturing of AA5083/TiN-Diamond hybrid nanocomposite parts via additive friction stir deposition: Metallurgical structure, mechanical, tribological, and electrochemical properties

Nano-diamond (ND) is a special ultrafine reinforcement whose agglomeration properties and weak interfacial bonding limit its application in aluminum matrix composites. This study used the additive friction stir deposition (AFSD) technique to produce AA5083-H321/2.5 wt% nano TiN/ND additive manufacturing deposition hybrid composite parts (AMDCPs) and a non-composite part (AMDNCP) was also deposited for comparative analysis. The aim was to improve the microstructure and examine the effect of the deposition process parameters, which include 900, 1250, and 1600 rpm rod rotation speed and 5 and 12 mm/min feed rate. The AFSD process parameters were used to calculate the heat input. The consumable rod and AMD parts were evaluated for their macrostructure, microstructure, macro-hardness, tribological, and corrosion properties. The microstructural features were examined using an OM, XRD, and SEM equipped with an EDS. The worn and corrosion surface morphology was investigated using SEM, and hardness was also evaluated as contour maps. The results show that defect-free deposited multilayer AA5083-nano TiN/ND hybrid composite parts were successfully manufactured, and analysis revealed a lower D/H ratio, well-bonded layers, homogeneously distributed TiN/ND and fragmented IMC components, and equiaxed refined grain microstructures. The deposited composites via AFSD showed a lower corrosion rate, higher hardness, and wear resistance than the deposited AA5083 consumable rod and AMDNCP. The AMDP C900-12 demonstrates an optimized deposition process parameter (900 rpm, 12 mm/min) with superior properties, including an increase in hardness by 9.3%, a reduction in grain size by 54%, and a decrease in corrosion rate by 45.2% related to the AMDNC part.

Synthesis, characterization, and antimicrobial activity of novel ferrocene-containing 1-(thio)acetyl pyrazolines

The pyrazoline pharmacophore is the source of numerous biological activities. The synthesis and biological evaluation of new pyrazoline heterocycles is the first step in the development of new potential drugs. Therefore, ferrocene-containing 1-(thio)acetyl pyrazolines were synthesized to test their in vitro antimicrobial activity. All new heterocycles were characterized by standard spectroscopy methods due to confirmation of the structures. In addition, single-crystal X-ray analyses were performed for three representative pyrazole derivatives. Their electrochemical properties were investigated by cyclic voltammetry indicating a reversible one-electron redox couple originating from the ferrocene/ferrocenium pair. All obtained products were evaluated for their antibacterial and antifungal activity. It has been shown that pyrazolines have slightly better antifungal activity compared with their antibacterial activity.

Optimization of cobalt-based MOFs for super-capacitor electrode materials of new energy vehicle

Super-capacitors (SCs), as new energy conversion storage elements, have attracted much attention, but there is still a research gap in the design of electrode materials. In this study, the optimization scheme of Metal-Organic Frameworks (MOFs) and cobalt-based MOF composites as electrode materials for SCs in new energy vehicles is explored, and a series of experiments are conducted to evaluate their performance. Scanning Electron Microscope (SEM) images reveal that the cobalt-based MOF composites have a surface morphology of particles with uniform distribution. The electrochemical performance test results show that the specific capacitance of the cobalt-based MOF composites is much higher than the sum of the two individual electrode materials and presents a remarkable increase with the scanning rate. Additionally, in the constant current charge-discharge test, cobalt-based MOF composites exhibit the longest charge-discharge time and good symmetry. Electrolyte particle contact tests for samples at different preparation temperatures display that high-temperature samples have better structural stability and electrolyte ion contact. In Cyclic Voltammetry (CV) and Galvanostatic Charge Discharge (GCD) tests, the 250 °C sample demonstrates the best electrochemical properties and the highest specific capacitance (269 F/g). Moreover, as the current density increases, the specific capacitance of the 600 °C sample decreases at a lower rate, showing stronger stability. However, the use of cobalt-based MOF materials may pose environmental and safety risks, such as the environmental impact of cobalt resource mining, instability under high-temperature conditions, and the possible production of hazardous substances. Therefore, these factors need to be fully considered when designing and using SCs to ensure the environmental friendliness and safety of cobalt-based MOFs. These results provide an important reference for selecting and optimizing electrode materials for SCs in new energy vehicles. Furthermore, this study offers research suggestions for improving new energy materials, filling the research gaps in related fields, and supporting the further development of SC technology.

Characteristics of hydride electrodes using Mg-Ti-Ni-Co-Al-based alloys synthesized by mechanical milling

For Ni-MH batteries, crystalline Mg-based alloys such as MgNi, Mg2Ni, REMg12, and La2Mg17 are regarded as hopeful negative electrode materials. Even though these alloys are inexpensive and have promising discharge capacity, they hardly ever electrochemically absorb or desorb hydrogen at room temperature. In this paper, the MgNi-based Mg50-xTixNi45Al3Co2 (x = 0, 1, 2, 3, 4) alloy electrodes were fabricated. The surface of the as-cast alloys was modified by mechanical Ni coating. The nanocrystalline and amorphous Mg50-xTixNi45Al3Co2 (x = 0, 1, 2, 3, 4) + 50 wt.%Ni alloys for Ni-MH batteries were prepared using mechanical ball milling. The effects of Ti content and ball milling time on the structure and electrochemical hydrogen storage properties of the alloys were investigated. The electrochemical testing reveals that the as-milled alloys can electrochemically absorb and desorb hydrogen well at room temperature. Without any activation, the milled alloys can achieve maximum discharge capacity in the first cycle. With the extension of ball milling time and the increase of Ti content, the cycle stability and discharge capacity of the alloys are significantly enhanced. The electrochemical impedance spectrum, high rate discharge ability, potentiodynamic polarization curve, and potential-step measurement all indicate that the electrochemical kinetics of the prepared alloys initially increase and subsequently decrease with the increase of Ti content, while significantly improve with the prolongation of milling time.

Simple synthesis of CdO@CuO nanopetals for its electrical, electrochemical and catalytic properties: an investigation

Simple synthesis of CdO@CuO nanopetals for its electrical, electrochemical and catalytic properties: an investigation

Boosting electrochemical energy storage properties of SrGd2O4 through Yb3+ and Tm3+ rare earth ion doping

Electrochemical supercapacitors represent advanced energy storage devices that excel in the swift storage and delivery of electrical energy, effectively bridging the gap between conventional capacitors and batteries. The present work, aimed to investigate charge storage properties of SrGd2O4 and rare earth ions Yb3+ and Tm3+ doped in SrGd2O4. Both materials were prepared via simple sol-gel synthesis and characterized by XRD, XPS, and FE-SEM with EDS. Characterization confirmed the presence of Tm3+ and Yb3+ in the SrGd2O4 matrix with a uniform distribution of elements. The charge storage behavior of pure SrGd2O4 and SrGd2O4:Yb4Tm1 in various electrolytes was thoroughly explored. Large electrochemical potential windows were shown by both electrode materials in aqueous 6M KOH (1.7 V), which is essential for supercapacitors to achieve high specific energy. Furthermore, SrGd2O4:Yb4Tm1 demonstrated a substantially more pronounced charge storage effect in 6M KOH electrolyte, with almost double times higher specific capacitance values compared with an un-doped SrGd2O4 sample. The main impact on the electrochemical window had matrix SrGd2O4, while the main impact on specific capacitance had rear earth dopants (Yb3+ and Tm3+). Improved charge storage characteristics of SrGd2O4:Yb4Tm1 were also evident through a notable reduction in overall resistance observed in electrochemical impedance spectroscopy experiments. Concerning the two-electrode GCD measurements, the SrGd2O4:Yb4Tm1 electrode in 6M KOH showed a specific capacitance of 143 F g−1, with the specific energy of 12.5 Wh kg−1 at 0.6 A g−1. These findings demonstrate the potential of rare earth ion doping in enhancing the energy storage properties of SrGd2O4, offering promising avenues for the development of high-performance supercapacitors.

Synthesis and characterization of ZnCo2O4 nanocomposites with enhanced electrochemical features for supercapacitor applications

Supercapacitors have recently emerged as a promising alternative to conventional batteries due to their improved energy storage capabilities. The optical, electrochemical, and structural properties of ZnCo2O4 nanocomposites produced by hydrothermal synthesis are detailed in this study. In order to study the physicochemical properties of the synthesized goods, the created nanocomposite samples were analyzed using XRD, FT-IR, UV–Vis, SEM with EDAX, HR-TEM, BET, XPS, and charge storage potential. Crystallite size was found to be inversely proportional to increasing range of 5.01 nm to 10.62 nm in the XRD data, which compared the cubic structure. Electron microscopy and high-resolution transmission electron microscopy (HR-TEM) indicated a morphological shift indicative of improved electrochemical capabilities. The absorption research showed that different molar ratios were successful in increasing the optical bandgap from zero to 1.93 eV, whereas functional component adsorption lowered it from 2.35 eV. A maximum specific capacitance of 383.3 Fg−1 was determined by the electrochemical research, which indicated an inherent pseudo capacitance. Experimental results show that the ZnCo2O4 nanocomposite can effectively store charges, which is in line with expectations given its high capacitance and very inexpensive production.

Multiphase transformation and mechanical analysis of polycrystalline [formula omitted] nanoparticle during lithiation via phase diagram-guided phase-field approach

The fabrication of tin (Sn)-based materials with exceptional electrochemical and mechanical properties requires a thorough understanding of the multiphase evolution that occurs during lithiation. However, predicting the microstructural changes during this process using analytical models is challenging due to the intricate interactions among electrode materials, cell operating parameters, complex geometries, and polycrystalline structures. To tackle this challenge, we propose the application of the phase-field method in a grand-potential formulation, that is combined with the smooth boundary method to apply constant-current (de-)lithiation boundary conditions. This approach effectively describes the migration of lithium and the multiphase transitions in polycrystalline electrodes with arbitrary geometries. To investigate nanoparticles with hundreds of grains in two/three dimensions efficiently, we have incorporated this model into the self-developed open-source phase-field solver package MInDes in a highly optimized manner. Further, comparing the output voltage of the simulated lithiation process of LixSn nanoparticles in three dimensions demonstrates an excellent correlation with experimental results. Based on this, we analyze the mechanical performance of polycrystalline nanoparticles with varying amounts of copper doping and evaluate the maximal von Mises stress during lithiation to predict the onset of crack formation.

Tunable optoelectronic performances of fluorinated benzene-EDOT based hybrid electrochromic polymers

Due to its high electronegativity and small atomic radius without undesirable steric hindrance, the incorporation of fluorine atoms into the benzene unit which started from the commercially available compounds is a feasible way to tune the energy levels of polymers, and its electrochromic application is expected to achieve a new breakthrough. Herein, in this paper, benzene units with different fluorine atom numbers were selected as the core and 3,4-ethylenedioxythiophene (EDOT) as the terminal unit, three fluorinated electrochromic precursors (FPh-EDOT, 2FPh-EDOT, and 4FPh-EDOT) were designed and synthesized by Stille coupling reaction, and the corresponding fluorinated π-conjugated electrochromic polymers (P(FPh-EDOT), P(2Ph-EDOT), and P(4FPh-EDOT)) were prepared by electrochemical polymerization method. The effects of different fluorinated benzene units on the photophysics, electrochemistry, and electrochromic properties of precursors and polymers were systematically investigated, and the structure-property relationship was further revealed. All of them have low initial oxidation potentials {FPh-EDOT (0.65 V), 2FPh-EDOT (0.72 V), and 4FPh-EDOT (0.70 V)}, which makes it easy to obtain high-quality new fluorinated polymers at low polymerization potential. With the increase of the number of F atoms, the UV–vis absorption spectra and emission spectra of fluorinated monomer firstly red-shifted and then blue-shifted. The corresponding fluorinated polymers have good electrochemical activity and stability (the P(2Ph-EDOT) activity remained 82.7% after 500 cycles), making it possible to realize their electrochromic devices. All these three fluorinated polymers show obvious color change from the neutral state to the fully oxidized state (P(FPh-EDOT) changes from brown to grayish blue, P(2FPh-EDOT) changes from brown to gray, and P(4FPh-EDOT) changes from dark blue to light blue). The kinetic study further shows that all of them have distinguish electrochromic properties with good optical stability, very short response time (0.9 s for P(2FPh-EDOT) at 700 nm), and favorable coloration efficiency (130.7 cm2 C−1 for P(FPh-EDOT) at 503 nm). Overall, all these three fluorinated polymers have low optical band gap, good redox stability and electrochromic properties, are very promising electrochromic materials, which is worthy for the further research and development.

The layer-by-layer assembled ERGO+/ERGO− multilayer modified electrode for sensitive detection of dopamine

Graphene materials represented by graphene oxide (GO) have been widely regarded as functional coatings or films to modify surface of the electrode for detecting dopamine molecules. However, interfacial material properties for detection sensitivity, film stability, and applicability to electrodes are still highly desired. Herein, we first present a screen-printing carbon electrode (SPCE) coated with an electrochemically reduced layer-by-layer (LbL) assembled multilayer driven by an electrostatic interaction between positively charged polyethyleneimine-modified GO with amine groups (ERGO+) and negatively charged carboxyl-functionalized GO (ERGO−), which is briefly described as (ERGO+/ERGO−)n/SPCE. Firstly, without using conventional glassy carbon and gold electrodes, SPCE was tried to make coatings adapt to more flexible and unstable electrodes, simultaneously guaranteeing higher detection performance. Secondly, although a variety of electrochemical sensors such as GO−/SPCE and ERGO−/SPCE were obtained through the drop-casting technique, as-prepared (ERGO+/ERGO−)n/SPCE showed much higher electrocatalytic activities with enhanced peak current signals and reduced charge transfer resistance. Finally, excellent electrochemical properties and sensing performances of the (ERGO+/ERGO−)n/SPCE sensor for detection of dopamine were demonstrated, especially having a linear range of 1 μM to 1000 μM. Meanwhile, the detection limit is as low as 0.39 μM and S/N is equal to 3. The present work offers a potential direction to develop GO modified electrodes for sensitive biomolecular detection.