Exact synchronization and asymptotic synchronization for linear ODEs

Science China Mathematics - This paper studies exact synchronization and asymptotic synchronization problems for a controlled linear system of ordinary differential equations. In this paper, we...     

近紫外LED激发荧光粉Ba0.11Sr2.89-2xCexNaxAlO4F发光特性

采用高温固相法反应制备Ba0.11Sr2.89-2x Ce x Na x AlO4F(x=0.01,0.02,0.05,0.07,0.10,0.15)荧光粉。Ba0.11Sr2.89AlO4F体系中存在Sr(1)2+和Sr2+(2)两个格位。Sr2+(1)离子位于Wyck.4a格位,为十配位多面体构型。Sr2+(2)离子位于Wyck.8h格位,为八配位的多面体构型。研究了Ba0.11Sr2.89-2x Ce x Na x AlO4F荧光粉的紫外-可见激发、发射光谱、荧光寿命及能量传递过程,讨论并指认了Ce3+在上述两个格位中的激发带位置及能级重心,发射光谱曲线分别由两个~463,~505和~550 nm宽带发射构成。随着Ce3+浓度增加,长波发射~550 nm逐渐增强,而色品坐标(x=0.199,y=0.351)蓝绿区逐渐变化到黄绿区域(x=0.389,y=0.489)。     

近紫外LED用绿色荧光粉Ba0.11Sr2.89-2x-2yCexTbyNax+yAlO4F发光特性及Ce3+→Tb3+之间能量传递

高温固相法合成Ba0.11Sr2.89-2x-2yCexTbyNax+yAlO4F荧光粉,并用X射线衍射(XRD)、荧光光谱(PL)测定分析了其晶体结构及光谱性质。结果表明:当Tb3+掺杂量x=0.07时,发光强度最高,发射主峰位于545 nm,并进一步研究了Ce3+,Tb3+共掺的样品中Ce3+→Tb3+能量传递过程。其次,测试由近紫外LED(~380 nm)和三基色荧光粉(Ba0.11Sr2.89Ce0.01Tb0.07Na0.08AlO4F,BAM and Sr2Si5N8:Eu2+)封装的白光LED光电性能,其色品坐标(x=0.3223,y=0.3408),色温5500 K,显色指数为86.26。因此,Ba0.11Sr2.89-2x-2yCexTbyNax+yAlO4F可作为一种潜在的适用于近紫外LED激发的荧光材料。     

一种新型核壳型色谱固定相在高效液相色谱中的评价及应用

采用扫描电镜、透射电镜和氮气吸附法对制备的新型核壳型色谱固定相进行了表征,结果表明该固定相单分散性好、表面放射状孔道壳层结构均一、孔径分布窄。对该核壳材料的表面进行C18键合修饰,考察其基本色谱性能,色谱柱的理论塔板数超过150000块/m,色谱峰峰形对称,甲苯与乙苯的保留因子之比为1.45,亚甲基选择性优异。将该核壳材料应用于汽车尾气中醛酮类化合物的检测,在优化的色谱条件下,2,4-二硝基苯肼（DNPH）衍生的醛酮类化合物在15 min内获得了较好的分离效果。该核壳型C18色谱固定相具有分离速度快、选择性好、柱效高等特点,适于复杂样品的高效、快速分离分析。     

Graphene oxide‐SiO2 hybrid nanostructure as coating material for capillary electrochromatography

Graphene oxide (GO) has been considered as a promising stationary phase for chromatographic separation. However, the very strong adsorption of the analytes on the GO surface lead to the severe peak tailing, which in turn resulting in decreased separation performance. In this work, GO and silica nanoparticles hybrid nanostructures (GO/SiO₂ NPs@column) were coated onto the capillary inner wall by passing the mixture of GO and silica sol through the capillary column. The successful of coating of GO/SiO₂ NPs onto the capillary wall was confirmed by SEM and electroosmotic flow mobilities test. By partially covering the GO surface with silica nanoparticles, the peak tailing was decreased greatly while the unique high shape selectivity arises from the surface of remained GO was kept. Consequently, compared with the column modified with GO (GO@column), the column modified with GO and silica nanoparticles through layer‐by‐layer method (GO‐SiO₂ NPs@column), or the column modified with silica nanoparticles (SiO₂ NPs@column), GO/SiO₂ NPs@column possessed highest resolutions. The GO/SiO₂ NPs@column was applied to separate egg white and both acidic and basic proteins as well as three glycoisoforms of ovalbumin were separated in a single run within 36 min. The intra‐day, inter‐day, and column‐to‐column reproducibilities were evaluated by calculating the RSDs of the retention of naphthalene and biphenyl in open‐tubular capillary electrochromatography. The RSD values were found to be less than 7.1%.     

Packing capilllary electrochromatography columns using vacuum--a preliminary study

This paper introducesa novel method for packing Capillary Electrochromatography Columns (CEC). Using vacuum packing methodology, silica particles as small as 1 microm were successfully packed into the capillary columns with 75 microm inner diameter. The columns are verystable and show no noticeable loss in efficiency after 200 sample injections. The performance of these vacuum packed capillary columns was evaluated with a mixture of aromatic and non-aromatic compounds. A 24 cm long capillary column can produce peak efficiencies of around 45,000 plates for benzene.     

Poly(amidosulfonic acid) modified glassy carbon electrode for determination of isoniazid in pharmaceuticals

Amidosulfonic acid was electropolymerized by cyclic voltammetry onto the surface of glassy carbon electrode (GCE) to fabricate the chemically modified electrode, which showed high stability, good selectivity and reproducibility for determination of isoniazid. The modified electrode showed an excellent electrocatalytical effect on the oxidation of isoniazid. Under the optimum conditions, there was a good linear relationship between anodic peak current and isoniazid concentration in the range of 5.0 x 10(-8)- 1.0 x 10(-5) M, and a detection limit of 1.0 x 10(-8) M (S/N = 3) was obtained after 120 s at the accumulation potential of - 0.2 V (vs. SCE). This developed method had been applied to the direct determination of isoniazid in injection and tablet samples with satisfactory results.     

Voltammetric determination of sinomenine in biological fluid using a glassy carbon electrode modified by a composite film of polycysteic acid and carbon nanotubes

Polycysteic acid based electrochemical oxidation of L-cysteine (CySH) and carbon nanotubes (CNTs) formed a composite thin film material at a glassy carbon electrode (GCE) that was used a novel modifier for electroanalytical determination of sinomenine which is used for rheumatoid arthritis treatment. The determination of sinomenine at the composite modified electrode was studied by differential pulse voltammetry (DPV). The peak current obtained at + 0.632 V (vs SCE) from DPV was linearly dependent on the sinomenine concentration in the range of 1.0 x 10(-7) to 6.0 x 10(-5) M in a B-R buffer solution (0.04 M, pH 1.81) with a correlation coefficient of 0.998. The detection limit (S/N = 3) was 5.0 x 10(-8) M. The electrochemical reaction mechanism of sinomenine was also discussed. This new method was then applied to the high-throughput determination of sinomenine in human serum samples with satisfactory results. This polycysteic acid/CNTs composite film may be considered to be a promising, low-cost, durable, and biocompatible material for the modification of sensors in applications to pharmaceutical and biomedical analysis.     

Voltammetric determination of terbinafine in biological fluid at glassy carbon electrode modified by cysteic acid/carbon nanotubes composite film

The electrochemical oxidation of L-cysteine (CySH) in presence of carbon nanotubes (CNTs) formed a composite film at a glassy carbon electrode (GCE) as a novel modifier for directly electroanalytical determination of terbinafine without sample pretreatment in biological fluid. The determination of terbinafine at the modified electrode with strongly accumulation was studied by differential pulse voltammetry (DPV). The peak current obtained at +1.156 V (vs. SCE) from DPV was linearly dependent on the terbinafine concentration in the range of 8.0 x 10(-8)-5.0 x 10(-5 )M in a B-R buffer solution (0.04 M, pH 1.81) with a correlation coefficient of 0.998. The detection limit (S/N=3) was 2.5 x 10(-8 )M. The low-cost modified electrode showed good sensitivity, selectivity, and stability. This developed method had been applied to the direct determination of terbinafine in human serum samples with satisfactory results. It is hopeful that the modified electrode will be applied for the medically clinical test and the pharmacokinetics in future.