Simultaneous determination of fluorine and iodine in urine by ion chromatography with electrochemical pretreatment

A new method for the simultaneous determination of fluorine and iodine in urine by ion chromatography （IC） with electrochemical pretreatment has been developed. The pretreatment was performed in a novel electrochemical oxidationneutralization device （EOND）, in which iodide of the sample was oxidized to iodate and the alkaline digestion sample solution was neutralized. Under the optimized conditions, the limits of detection （LOD, S/N = 3） were 2.5 μg/L for fluoride and 20 μg/L for iodate, respectively. The recoveries were in the range of 93-102% for fluoride and 86-98% for iodate.

Constructing Bidirectional Fluorine-Rich Electrode/Electrolyte Interphase Via Solvent Redistribution toward Long-Term Sodium Battery

The high concentration electrolytes with specific solvation structure could passivate the electrodes to prolong battery cycle life but at the expense of increased cost,which limits the wide application in commercialization.The regular concentration(1_(M))electrolytes with suitable properties(viscosity,ionic conductivity,etc.)are cost-guaranteed,but undesired reactions would always occur and lead to battery degradation during long cycles.To promote the long-term cycle stability in a cost-effective way,this work constructs bidirectional fluorine-rich electrode/electrolyte interphase(EEI)by redistribution of solvents and electrochemical induction.The fluorinated effect with reasonable zoning planning restricts morphological disintegration,meanwhile,forms spatial confinement on cathode.In particular,the obtained cathode electrolyte interphase(CEI)gets the ample ability of Na^(+)transport,which benefits from the fluorinated organics arranged in the epitaxy and the hemi-carbonate content acting on the thickness.Thus,the electrochemical long cycling performance of F-NVPOFⅡF-CC full cells is significantly enhanced(the decay rate at 1 C per cycle is as low as 0.01%).Such a fluorine-rich EEI engineering is expected to take transitional layers against the degradation of cells and make ultra-long cycle batteries possible.

Effects of Fluorine and Silicon Incorporation on Tribological Performance of Diamond-Like Carbon Films

Diamond-like carbon (DLC) is a metastable amorphous film that exhibits unique properties. However, a number of limitations exist regarding the use of DLC, for instance, its tribological characteristics. In this article, the fluorine and silicon incorporated diamond-like carbon (F-DLC and Si-DLC) films are studied, taking into account the tribological properties of these films compared with pure DLC. The structures of the films were characterized using Auger electron spectroscopy and Raman spectroscopy. The hardness and elastic modulus were evaluated by nanoindentation hardness testing. The friction behavior was assessed using ball-on-disk friction testing and optical microscopy. The results indicated that the deposited DLC films contained 0.6 - 2.1 at.% F and 26.7 - 38.4 at.% Si. A decrease in the hardness and elastic modulus was obtained as F increased in content, which was the opposite of the behavior observed in the Si-DLC films. This was due to the shifting in the G-peak position, which is related to the sp3 bonding fraction in the film. When measured in ambient air, the addition of Si into the DLC film strongly influenced the friction coefficient, whereas doping with F only slightly influenced the films, as evidenced by their wear scars. In addition, only a 26.7 at.% Si-DLC film showed a very low friction coefficient when measured in dry air. This was attributed to the formation of silicon-rich transfer layer on the ball surfaces. Therefore, the addition of Si with 26.7 at.% content to a DLC film can be considered beneficial for improving tribological performance.

High Density Fluorine Negative-Ion Source Generated by Utilizing Magnetized SF₆

In a magnetized plasma column generated from an electronegative gas, negative-ions accumulate around the plasma column via radial diffusion. In this study, a dc discharge is applied in SF6 gas to produce a plasma column, and the radial density profile of negative-ions is measured by Langmuir probes using the modified Bohm criterion. The gas pressure and discharge current dependences of negative-ion density are also measured. It is found that the negative-ion density of 8.0 × 1017 m-3 is obtained around the plasma column at r = 1.0 cm when SF6 pressure is 0.13 Pa and discharge current is 0.50 A. The negative-ion density has radial gradient, and the electron density is much lower in this region.

Determination of fluorinated quinolone antibacterials by ion chromatography with fluorescence detection

For preparing fluorinated quinolone antibiotic medicine locally used in stomatology, simultaneous determination of norfloxacin, ciprofloxacin, and enoxacin was carried out by multiphase ion chromatography with fluorescence detection. Quinolone antibiotics were separated by Dionex OmniPac PAX-500 column with an eluent of 15 mmol/L H2SO4 and 35% methanol （v/v） at a flow-rate of 1.0 ml/min and detected with fluorescence with excitation and emission wave lengths of 347 ran and 420 ran respectively. The detection limits （S/N=3） of norfloxacin, ciprofloxacin and enoxacin were 50, 105 and 80 ng/ml respectively. The relative standard deviations of retention time, peak area and peak height were less than 1.1% and good linear relationship resulted. The developed method was applied to pharmaceutical formulations and biological fluids.

Exploring high-voltage fluorinated carbonate electrolytes for LiNi0.5Mn1.5O4 cathode in Li-ion batteries

Ethyl-(2,2,2-trifluoroethyl)carbonate(ETFEC)is investigated as a solvent component in high-voltage electrolytes for LiNi0.5Mn1.5O4(LNMO).Our results show that the self-discharge behavior and the high temperature cycle performance can be significantly improved by the addition of 10%ETFEC into the normal carbonate electrolytes,e.g.,the capacity retention improved from 65.3%to 77.1%after 200 cycles at 60℃.The main reason can be ascribed to the high stability of ETFEC which prevents large oxidation of the electrolyte on the cathode surface.In addition,we also explore the feasibility of electrolytes using single fluoriated-solvents with and without additives.Our results show that the cycle performance of LNMO material can be greatly improved in 1 MLiPF6+pure ETFEC-solvent system with 2 wt%ethylene carbonate(EC)or ethylene sulfate(DTD).The capacity retention of the LNMO materials is 93%after 300 cycles,even better than that of carbonate-based electrolytes.It is shown that the additives are oxidized on the surface of LNMO particles and contribute to the formation of cathode/electrolyte interphase(CEI)films.This composite CEI film plays a crucial role in suppressing the serious decomposition of the electrolyte at high voltage.

Diffusion Kinetics of Carbonate Hydroxyapatite (CHAP) for Adsorbing F^- Dissolved in Water

A systematic research was performed about diffusion kinetics of adsorbing F^- dissolved in water for carbonate hydroxyapatite （CHAP） from the natural hydroxyapatite which was modified by adulterating with CO3^2-. The result shows that the speed of F^- adsorption is controlled by membrane diffusion when F^- concentration is relatively low, which is expressed by the kinetic equation of diffusion Q=0.0005（Ci-C）（t-ti）＋0.3967, or by vacancy diffusion when F^- concentration is relatively high, which is expressed by the kinetic equation of diffusion In[C（o, t）]=8.4718-0.5048Int. Based on the feature of CHAP for adsorbing F^- dissolved in water and its special channel of the structure of CO3^3- modified hydroxyapatite, models of vacancy diffusion and membrane diffusion were established.

FLUORINE BEHAVIOR IN BF_2^+ IMPLANTED POLYSILICON FILMS SUBJECTED TO RAPID THERMAL ANNEALING

The physical and electrical properties of BF2+ implanted polysilicon films subjectedto rapid thermal annealing（RTA）are presented.It is found that the out diffusion of F and itssegregation at polysilicon/silicon oxide interface during RTA are the major causes of F anomalousmigration.Fluorine bubbles were observed in BF2+ implanted samples at doses of 1×1015 and5×1015cm-2 after RTA.

Low power fluorine plasma effects on electrical reliability of AlGaN/GaN high electron mobility transistor

The new electrical degradation phenomenon of the AlGaN/GaN high electron mobility transistor（HEMT） treated by low power fluorine plasma is discovered. The saturated current, on-resistance, threshold voltage, gate leakage and breakdown voltage show that each experiences a significant change in a short time stress, and then keeps unchangeable. The migration phenomenon of fluorine ions is further validated by the electron redistribution and breakdown voltage enhancement after off-state stress. These results suggest that the low power fluorine implant ion stays in an unstable state. It causes the electrical properties of AlGaN/GaN HEMT to present early degradation. A new migration and degradation mechanism of the low power fluorine implant ion under the off-stress electrical stress is proposed. The low power fluorine ions would drift at the beginning of the off-state stress, and then accumulate between gate and drain nearby the gate side. Due to the strong electronegativity of fluorine, the accumulation of the front fluorine ions would prevent the subsequent fluorine ions from drifting, thereby alleviating further the degradation of AlGaN/GaN HEMT electrical properties.

Addition of Pyridine to Dye-Sensitized Solar Cell Including Fluorinated Oligomer Gel Electrolyte

Fluorinated oligomer gel is suitable to the electrolyte of dye-sensitized solar cell for low cost production. In this article, addition of pyridine was investigated for the purpose of enhancing the short current density. Two kinds of ionic liquids were tested: imidazolium and pyrazolium systems. The two different stages of adding pyridine to the electrolyte were considered and the amount of pyridine was studied. It was found that the electrolyte including pyrazolium ionic liquids to which pyridine was added before the mixing with fluorinated oligomer showed the highest electric conductivity, short current density and open voltage. This resulted in the highest conversion efficiency of 4%. As the amount of pyridine increased, the fill factor and the open voltage were improved at first, and then the short current density increased. If the pyridine was added more, the short current density conversely decreased.

Electric Conductivity of Fluorinated Oligomer Gel Electrolyte Including Ionic Liquid and Performance of Dye Sensitized Solar Cell

Fluorinated oligomer gel is suitable to the electrolyte of dye sensitized solar cell. This article studied mainly in the scope of electric conductivity, including ionic liquid in the electrolyte. It was found that the ratio of mixing with dimetyl sulfoxide and the concentration of LiI affect the conductivity. The behavior is different depending on the type of ionic liquid. Although the mixing ionic liquid enhances the conductivity, the short circuit current density of assembled solar cell with it was suppressed so much.

F^-和Cl^-浓度对电沉积锌电化学过程的影响

目前,对电积锌过程中F^-、Cl^-的电化学过程研究较少。基于电化学原理,对含F^-、Cl^-的锌电解液体系电积锌时的极化曲线、循环伏安曲线、交流阻抗谱进行了测定。结果表明:电解液中存在F^-、Cl^-时,表现出去极化作用,Cl^-会使还原电位和氧化电位升高,F^-会抑制还原产物的析出,沉积过程中不伴随气体析出现象,且随着F^-、Cl^-浓度的增大,锌沉积越来越困难。

恩施市居民饮用水中F^-含量的测定

以恩施市居民饮用水为研究对象,通过氟离子选择电极法对恩施市自来水、恩施市纯净水、沸腾的自来水及购买的康师傅矿物质水中的氟离子含量进行测定,结果表明,恩施城区居民主要饮用水的氟离子含量符合国家水质质量标准.该方法简单快速、结果准确,可用于饮用水及其他水质中氟含量的测定.

新疆平原区饮用地下水中F^-含量的调查与评价

利用1997—1999年2058个饮用地下水中F-含量的测试成果,评价了新疆平原区饮用地下水中F-含量的状况,其结果为:F-含量变化范围为0 05～7 00mg/L,面积加权平均值为0 68mg/L,超标率18 9%。

测定牙菌斑氟浓度的超微型F^--ISFET电极的研制

目的 :了解局部牙菌斑氟的摄取与代谢情况。方法 :在氢离子敏场效应管 (H+ ISFET)的基础上研制出的一种新型的氟离子敏场效应管传感器 (F- ISFET) ,与毛细管盐桥的Ag/AgCl参比电极复合在一起 ,测定唾液和微量 (微升级 )牙菌斑液中的游离氟浓度 ,进行了性能测试和初步的定量检测。结果 :浓度检测范围 :10 -6～ 10 -1mol/L ,线性检测范围 :10 -6～ 10 -4mol/L ,灵敏度 :3 0～ 5 5mV/pF ,响应时间小于 3 0s ,线性相关系数r2 为 0 .97,回收率为 :94%～ 10 4%。测定唾液样本和菌斑液样本中氟离子浓度分别为 2 .3× 10 -6mol/L和3 .0 6× 10 -5mol/L。结论 :F- ISFET在低浓度测定牙菌斑的氟灵敏度较传统电极高 ,证实了这种F-小电极在口腔医学领域内的可用性。

Mg-Al改性膨润土对废水中F^-的吸附性研究

研究了改性前后膨润土对含氟废水的处理能力,以及F-浓度、时间、膨润土用量及温度对吸附的影响。结果表明:用10 g/LMg-Al溶液改性后的膨润土的吸附能力明显增强,对F-浓度为20 mg/L的低氟废水的去除率由改性前的12.7%提高到74.72%,且随膨润土用量的增加,去除率明显提高。

改性膨润土脱除废水中F^-的研究

研究了改性前后膨润土对含氟废水的处理能力,结果表明:用10 g/LMg-Al溶液改性后的膨润土的吸附能力明显增强,对F-浓度为20 mg/L的低氟废水的去除率由改性前的21.3%提高到78.8%,去除率明显提高。

离子色谱法测定氢氧化锂中F^-、Cl^-、SO_4^(2-)

研究氢氧化锂中F^-、Cl^-、SO_4^(2-)的测定方法。样品采用强酸性阳离子交换树脂进行样品溶液预处理以除去基体离子的干扰。采用离子色谱仪进行测定,分离柱为IonPac AS11-HC,3×10^(-3)mol/L NaOH溶液为流动相,流速为1 mL/min,测定了氢氧化锂中F^-、Cl^-、SO_4^(2-)的含量,线性相关系数分别为0.999 6,0.999 5,0.999 8,相对标准偏差≤2.1%,回收率均在85%以上。

活性MgO、La(OH)_3的表征及去除水中F^-的吸附性能研究

实验采用活性MgO和La(OH)3为吸附剂,对其去除水中氟离子的性能进行了研究.采用BET、XRD、TEM、SEM、FTIR等现代化手段对活性MgO和La(OH)3进行表征.探讨了pH、吸附时间、初始浓度、吸附剂投加量以及共存离子等因素对这两种吸附剂吸附性能的影响.影响因素的研究表明,活性MgO吸附剂最适宜的吸附条件为pH=6~7,温度20~25℃,吸附剂投加量约为1g/L;La(OH)3的最适宜条件为pH=4,温度20~25℃,吸附剂投加量约为1g/L.活性MgO的吸附容量约为55mg/g,La(OH)3的吸附容量约为7.2mg/g.

Pt Deposition on Anode Enhances the Performance of Dye-Sensitized Solar Cell with Non-Cross-Linked Gel Electrolyte

We fabricated dye-sensitized solar cells with non-cross-linked fluorinated gel electrolyte. The application of fluorinated gel to electrolyte is a challenging issue at present. The gelation of the electrolyte is of importance in order to solve the problem in the durability of the cell. We investigated, in this article, the effect of Pt deposition on the anode of the cell. The Pt was deposited by means of a DC sputtering technique. The studies showed that the deposition time strongly affected both open voltage and short-circuit current of the cell. The adaptive thickness of the Pt layer was determined to be 10 nm for the non-cross-linked fluorinated gel electrolyte cells.