催化碘酸钾氧化异硫氰酸荧光素荧光猝灭法测定痕量硒

基于异硫氰酸荧光素(FITC)可发射强而稳定的荧光信号,KIO3能氧化FITC而发生荧光猝灭,Se(Ⅳ)使FITC的荧光强烈猝灭,Se(Ⅳ)的含量与ΔF值呈线性关系,建立催化KIO3氧化FITC荧光猝灭法测定痕量硒的新方法.方法的线性范围为0.012～2.000×10-15g Se(Ⅳ)/mL,工作曲线回归方程ΔF=1.18+72.74CSe(Ⅳ)(×10-15g/mL)(n=6,r=0.9997),检出限为2.1×10-18g/mL(n=11).分别对Se(Ⅳ)浓度0.012和2.000×10-15g/mL进行7次测定,RSD依次为2.8%和3.5%.用于实际样品中痕量硒的测定和人体疾病的诊断与预报,结果满意.同时探讨了催化荧光猝灭法测定痕量硒的反应机理.     

荧光猝灭法测定中草药中痕量钴

在pH 7.4的磷酸盐缓冲溶液和十六烷基三甲基溴化铵(CTMAB)介质中,钙黄绿素与罗丹明B之间发生能量转移而导致后者的荧光增强(λem581nm)。当在此体系中加入痕量Co2+后,于发射波长581nm处产生荧光猝灭现象。据此提出了荧光猝灭法测定中草药中痕量钴含量。Co2+的质量浓度在4.0×10-4～1.35×10-2g.L-1范围内与反应液荧光强度的降低程度呈线性关系,方法的检出限(3S/N)为1.8×10-7g.L-1。方法用于中草药样品分析,回收率在97.6%～102%之间,测定值的相对标准偏差(n=6)在0.98%～1.5%之间。     

吖啶红高灵敏催化荧光光度法测定痕量钴(Ⅱ)

在H2SO4介质中,KIO3可氧化吖啶红使之褪色并伴随着吖啶红荧光强度的减弱,但其反应速率较慢。当加入痕量钴(Ⅱ)时,氧化反应明显加快,体系荧光猝灭程度加强,钴(Ⅱ)对该氧化反应具有显著的催化作用。据此建立了一种灵敏度高、选择性好的测定痕量钴(Ⅱ)的催化荧光分析新方法,并研究了该方法的动力学条件。反应体系的激发波长和发射波长分别为530和550nm,催化体系可允许较大量的多种常见离子同时存在。测定钴(Ⅱ)的线性范围为0.3～4.8μg/L,检出限为2.5×10-11g/mL。方法可用于茶叶、人发和面粉等实际样品中痕量钴(Ⅱ)的测定。     

CdTe量子点荧光猝灭法测定培氟沙星

在水相中合成了巯基乙酸包被的CdTe量子点(CdTe ODs),培氟沙星(PEF)对该量子点的荧光具有显著的猝灭,基于该猝灭作用,实现了用CdTe ODs作为荧光探针对痕量PEF的定量检测.实验发现,在pH为9.5的B-R缓冲溶液中,当CdTeODs的浓度为2.0×10-4 mol/L时,PEF的浓度在6.40×10-5～1.28×10-3mg/mL范围与CdTe ODs的荧光猝灭强度呈良好的线性关系,相关系数r为0.9917,检出限(S/N=3)为1.30×10-5 mg/mL.用该方法对犬猫倍福康和注射用PEF的含量进行了测定,回收率为94.6％～106％.     

固体基质室温燐光猝灭法测定人发和水中痕量汞

基于水杨基荧光酮羧甲基纤维素铅发光分子微球(Pb(CMC)2-THBF)在滤纸基质上可发射强而稳定的室温燐光,由此建立了Pb(CMC)2-THBF固体基质室温燐猝灭测定痕量汞的新方法.Hg2 的含量在2.5~100.0(pg/mL)内与ΔIp值成线性关系,其线性回归方程为ΔIp=12.73 0.4699CHg2 (pg/mL),r=0.9991,检出限为3.2×10-13g/mL.该方法用于人发和水样中痕量汞的测定,结果满意.同时探讨了固体基质室温燐光猝灭测定痕量汞的机理.     

巯基葡聚糖分离富集催化动力学荧光猝灭法测定痕量镉

痕量组分镉的测定对于工业、环境、健康有着重要的意义。研究了在pH=5.2邻苯二甲酸氢钾-NaOH介质中,痕量镉催化H2O2氧化3-(4′-氟苯基)-5-(2′-羧基苯偶氮)若丹宁,而荧光猝灭存在明显的催化作用,由此建立了动力学荧光法测定痕量镉的新方法。该体系的激发和发射波长分别为λex/λem=307nm/408nm,通过实验测定反应表观活化能为59.06kJ/mol;反应速率常数为0.101s-1;线性范围为0~10.0μg/L;检出限为3.9×10-7g/L。采用巯基葡聚糖凝胶分离富集,消除了共存离子的干扰,显著提高了方法的选择性和灵敏度。本方法应用于食品和人发中镉的测定获得满意的结果。     

联噻唑衍生物荧光猝灭汞离子传感器的研究

合成了一种新的荧光体4,4'-叔丁基-2,2'-联噻唑(DtBBT),并将其PVC敏感膜用于Hg(Ⅱ)的检测.实验表明,Hg(Ⅱ)对DtBBT的荧光具有猝灭作用,当HS(Ⅱ)浓度为1.0×10-9～1.0×10-5mol/L时,体系荧光猝灭度与Hg(Ⅱ)的浓度呈线性关系,据此建立了测定痕量Hg(Ⅱ)的高灵敏、高选择性方法,并用于河水中Hg(Ⅱ)的测定,获得了满意的结果.     

甲基绿-高碘酸钾系统催化动力学光度法测定痕量铱(Ⅳ)

基于以H3PO4为反应介质,用HAc-NaAc(1+8)(pH5.7)作缓冲溶液,在沸水浴中加热条件下,痕量铱(Ⅳ)能灵敏地催化高碘酸钾氧化甲基绿的褪色反应,建立了一种测定痕量铱(Ⅳ)的新催化光度法。研究了反应的最佳条件。催化反应吸光度A与非催化反应吸光度A0的差值ΔA与铱(Ⅳ)的质量浓度ρ在0～2.0μg/25mL范围内呈良好的线性关系。检出限为2.97×10-10g/mL。对1μg/25mL铱(Ⅳ)测定的相对标准偏差为1.7%(n=11)。测定了动力学参数。该催化反应对铱(Ⅳ)为一级反应,总反应为准一级反应。反应的表观速率常数为4.613×10-4/s,表观活化能为40.56kJ/mol。该方法用于分子筛样品和活性炭中痕量铱(Ⅳ)的测定,回收率97.9%～104.4%。     

2,3,7-三羟基-9-(2,4-二羟基)苯基荧光酮荧光猝灭法测定锰(Ⅱ)

在pH=9.33的NH3.H2O-NH4Cl缓冲介质中,于表面活性剂溴化十六烷基三甲铵(CTMAB)存在下,利用Mn(Ⅱ)与2,3,7-三羟基-9-(2,4-二羟基)苯基荧光酮(DHPF)形成Mn(Ⅱ)-DHPF-CTMAB三元配合物可产生荧光猝灭,建立了荧光猝灭法测定痕量Mn(Ⅱ)的新方法。该体系激发波长λex=520nm,发射波长λem=540nm,荧光猝灭值与Mn(Ⅱ)的含量在0～0.36μg/25mL范围内呈线性关系,检出限为0.02μg/25mL,在CTMAB存在下,配合物摩尔比Mn(Ⅱ)∶DHPF=1∶2。拟定方法用于测定尿样中微量锰的含量,结果满意。     

催化K2S2O8氧化亚甲基蓝固体基质室温磷光法测定痕量Bi(Ⅲ)

基于Bi(Ⅲ)能催化K₂S₂O₈氧化亚甲基蓝(MB)的反应,使MB的室温磷光（RTP）强度剧烈猝灭,且Bi(Ⅲ)的含量与体系的?IP成线性关系,据此可建立Bi(Ⅲ)催化K₂S₂O₈氧化R固体基质室温磷光法(SS RTP)测定痕量Bi(Ⅲ)的新方法。方法的线性范围为0.040~1.0 ×10-15 g/mL,工作曲线的回归方程?I_P=2.336+27.26×10–15C_Bi3+(g/mL),n=6,相关系数r=0.9980,检出限（LD）为1.9 ×10–15 g/mL,RSD为2.1%。方法灵敏、简便、快速、选择性与重现性好,用于水样品中痕量Bi(Ⅲ)的测定,结果满意。同时,讨论了催化K₂S₂O₈氧化MB SSRTP测定痕量Bi(Ⅲ)的反应机理。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.