Electrosynthesis and comparative studies on carboxyl-functionalized polythiophene derivatives

Electrochemical synthesis of a novel carboxylic acid functionalized polythiophene – poly(3-thiophene-butyric-acid), PTBA – has been realized. Its morphology, electrochemical, spectral and conducting properties have been compared to those of poly(3-thiophene-acetic-acid), PTAA, which is widely used to immobilise both bioactive molecules and inorganic nanoparticles. According to scanning electron microscopic (SEM) images, the difference in the real and geometric surface area of the modified electrodes is much more expressed in the case of PTBA. Both the symmetry of the cyclic voltammograms and the concurrent, sustained optical changes proved that this polymer possesses an improved and more stable redox activity. According to simultaneously performed in situ ac. impedance and UV–Vis measurements, both films could be uniformly transformed between the insulating and conducting forms, but PTAA exhibited some degradation. The development of the conducting state during the redox switching of both thiophene derivative polymers proved to be primarily connected to the formation of di-cationic species. The electrochemical quartz crystal microbalance (EQCM) results evidenced also differences between the two polymers, which difference can be interpreted by assuming the more expressed effect of the deprotonation-connected (self-) doping process in PTAA. The results confirm that the new conducting polymer, PTBA is much more convenient for being considered as the polymer matrix of practically applicable composites.     

Detailed XPS analysis and anomalous variation of chemical state for Mn- and V-doped TiO2 coated on magnetic particles

Manganese (Mn)- and vanadium (V)-doped titania (TiO₂) coated on iron oxide (γ-Fe₂O₃) nanoparticles (TM and TV) were reduced in H₂/N₂ mixture atmospheres at different reducing temperatures T_R. Furthermore, TM and TV reduced at T_R = 800 °C (TM8 and TV8) were subsequently nitrided in the ammonia (NH₃) atmosphere at different temperatures T_N in order to change the chemical state (CS) of the Mn, V, Fe, Ti, O, and N elements. Samples were characterized by X-ray diffraction and X-ray photoelectron spectroscopy. For reduced samples, with increasing T_R, anomalous variation of CS is as follows: Ratios of V⁴⁺ and V⁵⁺ increased, while the ratio of V³⁺ decreased, and the ratio of oxygen vacancy O_v decreased. Data conflict with the effect of reduction reaction could be understood as follows: O_v was occupied by O from H₂O (product of the reduction reaction), according to previous theoretical result. For nitrided samples, compared to TM8 and TV8 samples, as T_N increased, ratios of Mn⁴⁺ and V⁵⁺ with the highest valence state exhibited an increase at T_N = 400 °C. Moreover, the ratio of TiO_x decreased and the ratio of TiO₂ increased, even though NH₃ exhibited good reducibility. Data could be well interpreted as follows: O_v was occupied by N along with adsorbed O, possibly in the form of neutral NO radical and NO₂²⁻ radical ion. Till date, these phenomena have not been reported experimentally, which are important to understand the mechanism for photocatalytic performance of Mn-, V-, N-, and self-doped TiO₂.     

聚合物PPV,PDMPV自掺杂导电性研究

报道用带有晶体轨道的ＥＨＭＯ量子化学计算程序对ＰＰＶ及其取代物ＰＤＭＰＶ本征态、双极化子进行了理论计算，合理地解释了由于ＣＨ３Ｏ－自掺杂导致ＰＤＭＰＶ特殊电性能这一实验事实。同时利用电离势、分子电荷图对两种聚合物导电性能的差异性作了讨论。     

Influence of oxygen content on the magnetic properties of B-site deficient lanthanum manganites

The results of X-ray diffraction and magnetization measurements performed for LaMn_0.94O_x (2.91 ≤ x ≤ 3.00) manganites have been presented. The solid solutions have been found to possess three different structural forms (orbitally ordered orthorhombic, orbitally disordered orthorhombic, and monoclinic ones), depending on the oxygen concentration. The transitions from an antiferromagnetic to an inhomogeneous ferromagnetic, and then to a spin-glass phase have been observed with increasing oxygen content. The experimental results have been discussed in the framework of the ionic distribution model adapted to the case of B-site deficient manganites.     

外延淀积过程中的自掺杂抑制

外延层杂质浓度是影响器件电学性能的重要参数。文章对外延淀积过程中自掺杂的产生过程进行了分析，提出了在外延淀积过程中可以通过改变气流、温度及采用背封技术、二步外延等方法来解决外延自掺杂，从而改善器件的特性参数。     

Self-doped 2D-V2O5 nanoflakes – A high electrochemical performance cathode in rechargeable zinc ion batteries

Aqueous zinc-ion batteries (AZIBs) are highly promising energy storage systems owing to their high energy and power density, along with their inherent safety in large-scale energy storage. The well-known low-cost potential cathode materials, such as vanadium oxides (e.g., V₂O₅), exhibit lower cycling performance, particularly at higher current densities because of dissolution in the electrolyte and lower electrical conductivity. We synthesized two-dimensional (2D) V₂O₅ nanoflakes, self-doped with V⁴⁺ ions from ammonium vanadates, using an annealing process. These porous V₂O₅ nanoflakes formed by the relatively larger agglomerated V₂O₅ nanoparticles consisting of a significant amount of V⁴⁺ ions, which possess higher electrical conductivity than commercial V₂O₅. V⁴⁺-doped V₂O₅ (d-V₂O₅) were used as the cathode material in AZIBs and delivered a stable specific capacity of 430 mAh g⁻¹ (@ 0.5 A g⁻¹). Furthermore, their electrochemical performance was better than that of the undoped commercial V₂O₅ samples. At a higher current density (10 A g⁻¹), d-V₂O₅ exhibited an excellent highly reversible specific capacity of 190 mAh g⁻¹ and retained 86% of its initial capacity after 1000 cycles. This stable electrochemical performance is attributed to the enhanced electrical conductivity, higher diffusion coefficient of Zn ions, and delayed electrode solubility in the electrolyte owing to the presence of self-doped V⁴⁺ ions in V₂O₅.     

Pd nanoparticles on self-doping-defects mesoporous carbon supports for highly active ethanol oxidation and ethylene glycol oxidation

The high activity electrocatalysts with low cost are crucial for large-scale direct alcohol fuel cells (DAFCs) applications. In this study, the “self-doping-defects” mesoporous carbon (SDMC) as support of uniformly-dispersed Pd nanoparticles (Pd/SDMC) was prepared for high active electrooxidation by a simple route without additional surfactant and acid treatment. According to the mutually corroborated experimental and theoretical calculation results, our route can significantly increase the carbon defect, which is conducive to the anchoring and uniform distribution of Pd nanoparticles. Meanwhile, the uniquely and hierarchically mesoporous nanostructure of SDMC provides abundant pathways for mass transport in the electrooxidation reaction. Benefitting from the above advantages, Pd/SDMC exhibits superior activity than commercial Pd/C and previously reported carbon-based electrocatalysts. The mass activities and specific activities of Pd/SDMC toward ethanol oxidation reaction (EOR) are 3404.3 mA mg⁻¹, 4.48 mA cm⁻², respectively. The mass activities and specific activities of Pd/SDMC for ethylene glycol oxidation reaction (EGOR) are 4002 mA mg⁻¹, 5.26 mA cm⁻², respectively. We believe that the facile strategy to synthesis mesoporous carbon with “self-doping” defects would promote large-scale DAFCs applications in the future.     

Electrochemical copolymerisation of luminol with aniline: A new route for the preparation of self-doped polyanilines

Electrochemical copolymerisation of luminol and aniline from acidic aqueous medium onto gold electrodes has been investigated. Cyclic voltammetry in combination with electrochemical quartz crystal microbalance (EQCM) have been used to study both the in situ growth and redox switching process. In monomer free solution, the deposited polymers are stable and electrochemically active but distinct behaviour is shown by poly(luminol-aniline) films obtained from solutions with different monomers concentration ratio. In acidic medium, the current-voltage profiles range from a polyluminol (one pair of redox couple) to a polyaniline like redox conversion (three redox couples) as the aniline concentration increases. Unlike polyaniline, all prepared copolymers display well expressed electroactivity in sodium carbonate medium (pH 8), which also extends with the aniline content. The self-doping role assured by luminol moiety in the copolymer is also retrieved from the simultaneously recorded EQCM data.     

硅CVD外延自掺杂效应的分析研究

本文首先对自掺杂机理进行了分析。并采用反向补偿原理,吸附-解吸、滞流层静态-动态转换等,对工艺进行优化,在通常条件下有效地控制了自掺杂。     

A simple Bi3+ self-doping strategy constructing pseudo-tetragonal phase boundary to enhance electrical properties in CaBi2Nb2O9 high-temperature piezoceramics

Calcium bismuth niobate (CaBi₂Nb₂O₉, CBN)-based ceramics are promising candidates for high temperature application, the electrical properties of which are commonly enhanced by complex ion substitution or texture processes. Here, we report that high piezoelectricity and high resistivity were achieved in Ca_1-xBi_2+xNb₂O₉ by constructing pseudo-tetragonal boundary through a simple strategy of Bi³⁺ self-doping. At the pseudo-tetragonal boundary, Ca_0.96Bi_2.04Nb₂O₉ ceramics maintain high Curie temperature T_c = 942 °C, and show high piezoelectric coefficient d₃₃ = 15.1 pC/N and high resistivity ρ_dc = 2 × 10⁶ Ω cm (@600 °C). It is proved that the good piezoelectric property mainly originates from the increase of domain density. In addition, Ca_0.96Bi_2.04Nb₂O₉ ceramics reveal good thermal depoling performance, remaining 90% of piezoelectricity after thermal depoling at 900 ℃, which is due to small thermal expansion and structural distortion. Our work provides a promising candidate for high temperature applications and an easy way to improve the performance of Aurivillius-type piezoelectric ceramics.