An electrochemical sensor for sodium dodecyl sulfate detection based on anion exchange using eosin Y/polyethyleneimine modified electrode

A simple and effective method for the detection of electrochemically inactive sodium dodecyl sulfate (SDS) has been designed, based on different binding affinity of polyethyleneimine (PEI) toward electrochemically active eosin Y and electrochemically inactive SDS. The stronger binding affinity of the PEI toward SDS than eosin Y results in the decrease of the redox peak current of surface confined eosin Y and provides a quantitative readout for the SDS. The difference in value of the cathodic peak current showed a linear relationship with SDS concentration in a concentration range from 1 to 40 μg mL⁻¹, and a detection limit of 0.9 μg mL⁻¹ for SDS was obtained. Furthermore, the method has been successfully applied to the detection of SDS in real samples. The developed approach provided a simple and reliable detection for SDS and might have potential applications in electrochemical methods for inactive molecules.     

阴离子硫氧化还原与Li1-xNiO2-ySy的结构稳定性:第一性原理研究

Ni-rich layered oxides are the preferred cathode materials for high-energy-density lithium-ion batteries currently used in electric vehicles. In this paper, we present a systematic first-principles evaluation of the deintercalation process in the Li_1-xNiO_2-yS_y. The partial density of states (PDOS) characters of the electrons near the Fermi level, redox behaviors, and thermal stability have been investigated within the GGA+U scheme. The results show that the introduction of sulfur alleviates the lattice distortion during charging, suppresses nickel migration, and enhances the stability of oxygen according to the contribution of sulfur anion redox to the charge compensation for the overcharged Li_1-xNiO_2-yS_y. This study provides a new insight on improving the stability of Ni-rich cathode materials by tuning of the electrochemical behaviors based on sulfur anion redox.     

Design of Advanced MnO/N‐Gr 3D Walls through Polymer Cross‐Linking for High‐Performance Supercapacitor

Three‐dimensional, vertically aligned MnO/nitrogen‐doped graphene (3D MnO/N‐Gr) walls were prepared through facile solution‐phase synthesis followed by thermal treatment. Polyvinylpyrrolidone (PVP) was strategically added to generate cross‐links to simultaneously form 3D wall structures and to incorporate nitrogen atoms into the graphene network. The unique wall features of the as‐prepared 3D MnO/N‐Gr hybirdes provide a large surface area (91.516 m² g^?1) and allow for rapid diffusion of the ion electrolyte, resulting in a high specific capacitance of 378 F g^?1 at 0.25 A g^?1 and an excellent charge/discharge stability (93.7 % capacity retention after 8000 cycles) in aqueous 1 m Na₂SO₄ solution as electrolyte. Moreover, the symmetric supercapacitors that were rationally designed by using 3D MnO/N‐Gr hybrids exhibit outstanding electrochemical performance in an organic electrolyte with an energy density of 90.6 Wh kg^?1 and a power density of 437.5 W kg^?1.     

There are infinitely many Perrin pseudoprimes

This paper proves the existence of infinitely many Perrin pseudoprimes, as conjectured by Adams and Shanks in 1982. The theorem proven covers a general class of pseudoprimes based on recurrence sequences. The result uses ingredients of the proof of the infinitude of Carmichael numbers, along with zero-density estimates for Hecke L-functions.     

n‐Dopants Based on Dimers of Benzimidazoline Radicals: Structures and Mechanism of Redox Reactions

Dimers of 2‐substituted N,N′‐dimethylbenzimidazoline radicals, (2‐Y‐DMBI)₂ (Y=cyclohexyl (Cyc), ferrocenyl (Fc), ruthenocenyl (Rc)), have recently been reported as n‐dopants for organic semiconductors. Here their structural and energetic characteristics are reported, along with the mechanisms by which they react with acceptors, A (PCBM, TIPS‐pentacene), in solution. X‐ray data and DFT calculations both indicate a longer C?C bond for (2‐Cyc‐DMBI)₂ than (2‐Fc‐DMBI)₂, yet DFT and ESR data show that the latter dissociates more readily due to stabilization of the radical by Fc. Depending on the energetics of dimer (D₂) dissociation and of D₂‐to‐A electron transfer, D₂ reacts with A to form D⁺ and A^? by either of two mechanisms, differing in whether the first step is endergonic dissociation or endergonic electron transfer. However, the D⁺/0.5 D₂ redox potentials—the effective reducing strengths of the dimers—vary little within the series (ca. ?1.9 V vs. FeCp₂^+/0) (Cp=cyclopentadienyl) due to cancelation of trends in the D^+/0 potential and D₂ dissociation energy. The implications of these findings for use of these dimers as n‐dopants, and for future dopant design, are discussed.     

高比容量锂离子电池正极材料LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)的制备及性能北大核心CSCD

以LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)为研究对象,通过共沉淀法制备了不同F物质的量分数(0%、1%、3%、5%)的LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)三元正极材料(NCM),通过对NCM材料的晶格结构、微观形貌、电化学性能进行分析,结果表明:F掺杂后提高了NCM材料的结晶度,降低了阳离子混乱程度,适量的F掺杂有助于减小NCM三元正极材料的尺寸和提高均匀性,F的掺杂还能够降低NCM三元正极材料的极化现象,初始放电比容量随着F的掺杂含量升高呈现出先升高后降低的趋势,循环性能随着F的掺杂得到了提高,F掺杂物质的量分数为3%的NCM三元正极材料初始放电比容量167.2 mA·h/g,容量保持率达到98.5%,阻抗较小,电化学性能最优。     

掺杂对钠离子电池正极材料性能影响机制的研究

钠元素在地壳中的丰度是锂元素的1000倍,资源丰富,价格低廉。同时,钠离子电池负极可采用廉价的铝箔替代铜箔,且低温特性更加优异,在能量型、备用型储能场景均具有较好应用前景,因而钠离子电池被认为是下一代大规模储能技术的理想选择之一。然而,相对锂离子而言,钠离子较大的离子半径和质量极大限制了其在电极材料中的可逆脱嵌,导致电池的工作电压和能量密度相对较低。在钠离子电池材料体系中,正极材料的研究尤为需要长足的进步。本文对现有的典型钠离子电池正极材料进行了综述,包括层状金属氧化物、聚阴离子化合物和普鲁士蓝类化合物,并重点分析了掺杂对钠离子电池正极材料性能的影响。通过元素掺杂可提高材料的循环可逆性、增加其可逆容量、提升钠离子扩散动力学性能,能够在一定程度上改变晶格的性质,增强晶格稳定性、电子导电性、钠离子嵌脱动力学性能等。本文总结了掺杂应用在现有材料中获得的成果,并对正极材料未来的研究方向以及发展前景提出了展望。     

铒铥共掺氧化锌薄膜近红外宽带发射及变温行为的研究

采用磁控共溅射技术制备了铒铥共掺杂氧化锌发光薄膜. 通过优化退火温度, 实现了薄膜的近红外 平坦宽带发射, 总带宽可达到~ 500 nm, 覆盖了光通信S+C+L+U 区波段. 此发射带由Er³⁺ 的1535 nm (⁴I_13/2 → ⁴I_15/2) 发射峰及Tm³⁺ 的1460 nm (³H₄ → ³F₄), 1640 nm (¹G₄ → ³F₂), 1740 nm (³F₄ → ³H₆) 发射峰组成. 研究表明: 退火温度低于800 ℃ 时, 没有观察到薄膜样品明显的光致发光现象; 随着退火温度 从800 ℃ 升高到1000 ℃, I₁₆₄₀/I₁₅₃₅ 发射峰强度比从0.2 升高到0.3, I₁₇₄₀/I₁₅₃₅ 发射峰强度比从0.5 降低 到0.4, 发射峰强度比均基本保持稳定; 当退火温度高于1000 ℃ 时, I₁₆₄₀/I₁₅₃₅ 发射峰强度比从0.3 升高到 0.6, I₁₇₄₀/I₁₅₃₅ 发射峰强度比从0.4 升高到0.8, 发射峰强度比均急剧增加. 变温行为表明: 随着温度从10 K 逐渐升高到300 K, 谱线的总带宽基本不变, 在340—360 nm 之间; Tm³⁺ 在1640 和1740 nm 处的发射峰强度 分别降低了2/3 和1/2, Er³⁺ 在1535 nm 的发射峰强度增大了1.2 倍. 这是因为随着温度的升高, 声子数目增 多, Er³⁺ 与Tm³⁺ 离子之间发生能量传递的概率不断变大, 并且在Tm³⁺ 离子之间没有发生交叉弛豫现象.