X射线衍射里特沃尔德全谱图拟合法测定粉尘中游离的SiO2

应用X射线衍射技术与Rietveld全谱图拟合法测定了粉尘中游离SiO2的含量,并同时得到粉尘样品中其它晶相和非晶相物质的含量。实验采用日本理学D/MAX 2500V型X射线衍射仪,CuKα辐射带石墨单色器,管电压44 kV,管电流150 mA,步进扫描收集衍射数据,经Jade 5.0软件定性分析,DBWS9807a软件定量分析,结果为:Rp平均等于11.29%,Rwp平均等于13.74%,Rexpected平均等于4.04%。SiO2在各样品中的含量为15.61%~37.83%;加标回收率为102.6%~119.9%;重现性测定相对标准偏差(RSD)为1.14%。结果表明:用Rietveld全谱图拟合法测定粉尘中游离SiO2的含量是一种快速、准确、方便的方法。     

固相微萃取-电化学发光法检测玉米中的氯氟吡氧乙酸

以Hummers法为基础,合成了磁性氨基化石墨烯(NH2-G/Fe3O4),用NH2-G/Fe3O4-Nafion修饰了玻碳电极,用于氯氟吡氧乙酸的固相微萃取处理,结合电化学发光技术(ECL),建立了高灵敏度检测环境中氯氟吡氧乙酸残留的分析方法。考察了吸附时间、溶液p H等相关参数对电化学发光强度的影响。在最优实验的条件下,体系的ECL猝灭值ΔI与氯氟吡氧乙酸的浓度的对数值在0.01~25μg/m L的范围内呈良好的线性关系(相关系数R2=0.9989),检出限(LOD)为3 ng/m L(S/N=3)。方法对玉米和河水样品的加标回收率分别为94.8%~104.3%和93.4%~103.2%,相对标准偏差分别为2.5%~4.5%和1.5%~5.7%。     

磁固相萃取-气相色谱/质谱联用法测定环境水中的邻苯二甲酸二丁酯和邻苯二甲酸二(2-乙基己基)酯

建立了磁固相萃取结合气相色谱/质谱联用测定环境水中邻苯二甲酸二丁酯(DBP)和邻苯二甲酸二(2-乙基己基)酯(DEHP)的方法。萃取的最佳条件为:在100 mL水样中加入20 mg磁性Fe3O4@SiO2-C18微球,振摇萃取10 min后,用2.0 mL二氯甲烷解析5 min。在优化条件下,DBP和DEHP的检出限分别为0.1μg/L和0.3μg/L(S/N=3),线性范围为1.0~100μg/L,线性相关系数分别为0.9992和0.9990。方法应用于河水、湖水和井水样的分析,DBP的加标回收率为83.2%~103%,相对标准偏差小于6.8%,DEHP的加标回收率为82.2%~107%,相对标准偏差小于7.9%。     

聚乙烯亚胺修饰磁性纳米材料固相萃取-火焰原子吸收光谱法测定水样中痕量Mo(Ⅵ)

以聚乙烯亚胺(PEI)和二氧化硅包覆四氧化三铁(SiO2-Fe3O4)为原料,通过加热搅拌,制备了聚乙烯亚胺修饰磁性纳米材料(PEI-SiO2-Fe3O4)。利用红外光谱、扫描电镜和振动样品磁强计对PEI-SiO2-Fe3O4进行了表征。将PEI-SiO2-Fe3O4作为吸附剂应用于Mo(Ⅵ)的磁固相萃取,结合火焰原子吸收光谱,建立了一种检测水样中痕量Mo(Ⅵ)的新方法。该方法对Mo(Ⅵ)的线性范围为10~200 μg/L,检出限(LOD,S/N=3)为1.3 μg·L-1,定量下限(LOD,S/N=10)为4.3 μg/L,富集因子达172。应用建立的方法分析了环境水样、饮用水和工业废水中的Mo(Ⅵ),加标回收率为91.0%~110%,相对标准偏差(RSD)为0.90%~6.1%。该方法具有前处理速度快、灵敏、准确等特点,适用于各种水样中痕量Mo(Ⅵ)的检测。     

MSPD-RRLC-UV/MS法同时检测果蔬中9种三嗪类除草剂残留量

基于基质固相分散萃取(MSPD)-快速高分离液相色谱紫外和质谱检测法, 测定了果蔬中9种三嗪类除草剂的残留量. 以浓度与色谱峰面积之间的线性关系定量, 保留时间结合质谱信息进行定性. 9种待测物在0.02～4.0 mg/kg范围内峰面积与浓度具有良好的线性关系, 相关系数(r2)在0.9996～0.9998之间; 方法的最低检出限(LOD)为0.002 mg/kg; 低、中和高3个浓度点的加标回收率介于75.2%～95.6%之间, 相对标准偏差(RSD)小于11%.     

新型Fe3O4纳米颗粒修饰玻碳电极对头孢噻肟钠的电催化还原及其测定

采用滴涂法将Fe3O4磁性纳米颗粒修饰在玻碳电极上,制得新型纳米Fe3O4修饰电极(Fe3O4-np/GC 电极).X射线衍射光谱表明,纳米Fe3O4为面心立方尖晶石结构,透射电子显微镜表明,纳米Fe3O4粒径15～20 nm的微球结构.采用扫描电子显微镜和交流阻抗法(EIS)对修饰电极表面进行了表征,发现纳米Fe3O4在电极表面形成了均匀的修饰膜.采用循环伏安法(CV)、微分脉冲伏安法(DPV)研究了头孢噻肟钠(CS)在修饰电极上的电化学行为及动力学性质,结果表明,CS在Fe3O4-np/GC电极上有敏锐的催化还原峰,且CS的还原峰电流与其浓度在7.0×10-8～1 ×10-6和1 ×10-6～4.5×10-5 mol/L范围内呈线性关系;检出限达到5.0×10-8 mol/L.该方法可用于市售头孢噻肟钠针剂中CS含量的测定,加标回收率达到96.6％～102.7％.     

电感耦合等离子体发射光谱(ICP-OES)法测定电气石中的B2O3

建立了氢氟酸-硝酸-磷酸-高氯酸体系密闭溶矿,电感耦合等离子体发射光谱(ICP-OES)法测定电气石中B_2O_3的方法。实验表明,方法的检出限为0.096mg/L,相对标准偏差(RSD)为0.38%,加标回收率为97.2%~102%。方法流程简单,精密度高,准确度好,可进行批量样品的分析测定,具有实际应用意义。     

磁固相萃取与高效液相色谱-等离子体质谱联用检测癌症病人尿样中的卡铂药物

制备了甲基丙烯酸(MAA)改性Fe3O4纳米颗粒(Fe3O4@SiO2@MAA),建立了磁固相萃取(MSPE)-高效液相色谱(HPLC)-等离子体质谱(ICP-MS)检测癌症病人尿样中药物卡铂(CBP)的新方法。在最优条件下,该方法对CBP的检出限为29.9ng/L,相对标准偏差(RSD,cCBP=0.2μg/L)为9.5%,富集倍数为27.7,线性范围为0.1~100μg/L。不同批次合成的Fe3O4@SiO2@MAA萃取CBP的RSD为11.5%(n=5)。将该方法用于同一癌症病人在化疗过程中和化疗结束后两个尿样中CBP的分析,尿样中完整CBP的浓度分别为51.15μg/L和24.65μg/L,加标回收率为93.2%~103.7%。     

ICP-MS测定电子级丙二醇甲醚中的钠、镁、钙、铁和铅含量EI北大核心CSCD

本方法结合冷等离子体技术和碰撞反应池技术,消除质谱干扰。采用标准加入法定量检测电子级丙二醇甲醚中5种金属元素。优化实验条件为射频功率冷等离子体750 W,热等离子体1550 W;钠、镁、钙、铁、铅载气流速分别为0.6, 0.6, 0.65, 0.7, 0.42 L/min;积分时间0.3 s;H2和He流速分别为2和3 mL/min。结果表明,钠、镁、钙、铁、铅在1~5μg/L范围内线性相关系数(R2)均不小于0.9996,检出限(LOD)为6~87 ng/L,加标回收率分别为95.4%~103.2%, 98.1%~101.6%, 88.3%~117.2%, 94.0%~99.7%和86.0%~91.4%,相对标准偏差(RSD)≤9.2%。     

分散固相萃取净化气相色谱-质谱联用法快速检测纸质包装材料中18种光引发剂

建立了一种分散固相萃取(d-SPE)净化、气相色谱-质谱联用法(GC-MS)检测纸质包装材料中18种光引发剂(PIs)的分析方法。样品经水浸润后,用乙腈对样品进行超声提取,提取液经正己烷-乙酸乙酯溶液(3∶7,V/V)液液萃取后,用无水MgSO4、N-丙基乙二胺(PSA)和C18粉末分散固相萃取净化,以GC-MS法测定,内标法定量。18种PIs在0.01～0.2 mg/L内线性关系良好(R2>0.997),3个加标水平(0.1,0.4和2 mg/m2)的回收率在81.6%～123.8%之间,相对标准偏差(RSD)为0.2%～9.6%,检出限(LOD)为0.007～0.023 mg/m2。结果表明:本方法简便、测定结果准确,可用于纸质包装材料中18种光引发剂残留的高通量检测。     

Synthesis of Fe3O4, Fe2O3, Ag/Fe3O4 and Ag/Fe2O3 nanoparticles and their electrocatalytic properties

Two important iron oxides:Fe3O4 and Fe2O3,as well as Fe3O4 and Fe2O3 nanoparticles mingling with Ag were successfully synthesized via a hydrothermal procedure.The samples were confirmed and characterized by X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS).The morphology of the samples was observed by transmission electron microscopy(TEM).The results indicated Fe3O4,Fe2O3,Ag/Fe3O4 and Ag/Fe2O3 samples all were nanoparticles with smaller sizes.The samples were modified on a glassy carbon electrode and their elctrocatalytic properties for p-nitrophenol in a basic solution were investigated.The results revealed all the samples showed enhanced catalytic performances by comparison with a bare glassy carbon electrode.Furthermore,p-nitrophenol could be reduced at a lower peak potential or a higher peak current on a glassy carbon electrode modified with Ag/Fe3O4 or Ag/Fe2O3 composite nanoparticles.     

Ein neuer Bautyp der Oxohalogenoferrate: Ba3 Fe2 O5 Cl2 und Ba3 Fe2 O5 Br2

New Structure Type of the Two Oxohalogenoferrites: Ba₃Fe₂O₅Cl₂ and Ba₃Fe₂O₅Br₂ The hitherto unknown compounds Ba₃Fe₂O₅Cl₂ (A) and Ba₃Fe₂O₅Br₂ (B) are pre-pared and examined by single crystal techniques. (A) and (B) crystallizes in the cubic space group I2₁ 3-T⁵; (A) a = 9.9705(3) and (B) a = 10.0039(8) Å, Z = 4. The new structure consists of 10 corner-shared tetrahedra which are connected to a two-dimensional ring system. The differences to the previously investigated compound Sr₃Fe₂O₅Cl₂ are discussed.     

Fe2O3/Al2O3氧载体制备方法的研究

采用溶胶-凝胶法、共沉淀法、水热合成法、低热固相合成法、机械混合法、燃烧合成法和冷冻成粒法制备铁基氧载体Fe₂O₃/Al₂O₃,并通过物理和化学表征手段来筛选和优化制备方法和制备工艺。对煅烧后的氧载体进行硬度测试,结果表明,溶胶-凝胶法、共沉淀法、机械混合法、燃烧合成法和冷冻成粒法制备的氧载体硬度较高;载体的X射线衍射(XRD)谱图表明,各种制备方法均能制得物相组成为Fe₂O₃/Al₂O₃的氧载体,且随着煅烧温度的提高、煅烧时间的延长,氧载体的结晶度、晶体粒径逐渐增大,煅烧温度1 200℃的氧载体的机械性能、晶体结构、晶相组成更稳定。借助化学吸附仪的程序升温还原(TPR)实验表征氧载体的反应活性,并计算氧载体活性度。综合物理和化学表征实验结果表明,最优制备方法为溶胶-凝胶法和冷冻成粒法。     

Thermal Characterization and Physico-Chemical Properties of Fe2O3−Mn2O3/Al2O3 Systems

The effect of ferric and manganese oxides dopants on thermal and physicochemical properties of Mn-oxide/Al₂O₃ and Fe₂O₃/Al₂O₃ systems has been studied separately. The pure and doped mixed solids were thermally treated at 400–1000°C. Pyrolysis of pure and doped mixed solids was investigated via thermal analysis (TG-DTG) techniques. The thermal products were characterized using XRD-analysis. The results revealed that pure ferric nitrate decomposes into Fe₂O₃ at 350°C and shows thermal stability up to1000°C. Crystalline Fe₃O₄ and Mn₃O₄phases were detected for some doped solids precalcined at 1000°C. Crystalline γ-Al₂O₃ phase was detected for all solids preheated up to 800°C. Ferric and manganese oxides enhanced the formation of α-Al₂O₃ phase at1000°C. Crystalline MnAl₂O₄ and MnFe₂O₄ phases were formed at 1000°C as a result of solid–solid interaction processes. The catalytic behavior of the thermal products was tested using the decomposition of H₂O₂ reaction. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thick Fe2O3, Fe3O4 films prepared by the chemical solution deposition method

Fe₂O₃, Fe₃O₄ films have been prepared from Fe(OCH₂CH(CH₃)₂)₃–(CH₃)₂CHCH₂OH–2.2′-diethanola- mine (DEA)–poly(vinylpyrrolidone) (PVP) solutions by the spin-(SC) and dip-coating (DC) technique on SiO₂ and Si substrates. The maximum film thickness achieved without crack formation has been increased by incorporation of PVP (relative molecular weights 40000 and 360000) into the precursor solution. The stability of the precursor solutions was remarkably increased by addition of DEA. Compact, dense, and crack-free Fe₂O₃ films with thicknesses 900 nm (DC), 450 nm (SC), have been obtained via single-step deposition cycle. Higher-molecular-weight PVP has been more effective in increasing the thickness. The minimum concentration of DEA, which results in pronounced increase of solutions stability, is about R _P (n(DEA)/n(Fe) = 0.1). The high content of carboneous residue in the pyrolysed Fe₂O₃ films promotes the formation of Fe₃O₄ films via reduction in a gas flow of H₂/N₂ gas mixture. Microstructure, surface morphology, and magnetic properties of the films have been also investigated using SEM, AFM, and SQUID, respectively.     

具有良好热稳定性的Al2O3改性Fe2O3基金催化剂

通过共沉淀法和沉积-沉淀法制备出了具有良好热稳定性的Al2O3改性Fe2O3基金催化剂, 并通过透射电镜(TEM)、X射线衍射(XRD)、N2吸附-脱附及热重和差示扫描量热(TG-DSC)分析等表征手段对催化剂的结构与表面形貌进行了研究分析. TEM测试结果表明: 500 ℃焙烧后, 未掺杂Al2O3的催化剂中金颗粒粒径分布较宽, 平均粒径约为7.0 nm, 载体颗粒尺寸在50-100 nm范围内; 而掺杂Al2O3的催化剂中金颗粒粒径分布变窄, 平均粒径约为5.0 nm, 且载体颗粒大小也明显小于未掺杂Al2O3的催化剂, 保持在30-50 nm的范围内. N2吸附-脱附测试结果表明, Al2O3的掺杂有利于保持催化剂的介孔结构和比表面积, 从而提高了载体的热稳定性. XRD和TG-DSC测试结果表明, Al2O3的掺杂可以有效地抑制Fe2O3的结晶, 进而抑制了高温焙烧过程中金颗粒的长大. 选用CO低温氧化反应对催化剂的活性进行了评价, 即使在500 ℃高温下焙烧12 h, 掺杂了Al2O3的催化剂仍然可在26.7 ℃将CO完全转化, 而未掺杂Al2O3的催化剂CO最低完全转化温度(T100)高达61.6 ℃. Al2O3的掺杂显著提高了催化剂的热稳定性能.     

Influence of mechanical activation time,annealing, and Fe/O ratio on Fe3O4/Fe composites formation from Fe2O3 and Fe powders mixture

Commercially, iron (α-Fe) and hematite (α-Fe₂O₃) powders were used for the synthesis of composite powders of Fe₂O₃/Fe type by mechanical milling. Several ratios of Fe₂O₃/Fe were chosen for the composite synthesis; the atomic percent of oxygen in the starting mixtures ranged from 21 to 46 %. The Fe₂O₃/Fe composite samples with various Fe/O ratios were milled for different milling times. The milled composite samples were subjected to the heat treatments in argon up to 900 °C. During the heat treatment at temperatures that do not exceed 550 °C, Fe₃O₄/Fe composite particles are formed by the reaction between the Fe₂O₃ and Fe. Further increase of the heat treatment up to 700 °C leads to the reaction of the Fe₃O₄/Fe composite component phases, resulting thus in the formation of FeO/Fe composite. The heat treatment up to 900 °C of the Fe₂O₃/Fe leads to the formation of a composite of FeO/Fe₃O₄/Fe independent of the milling time and Fe₂O₃/Fe ratios. The onset temperatures of the Fe₃O₄ and FeO formations decrease upon increasing the milling time. Another important aspect is that, in the case of the same milling time but with a large amount of iron into the composite powder the formations temperatures of Fe₃O₄ and FeO are also decreasing. The influence of the mechanical activation time, heat treatment temperature, and Fe/O ratio on the formation of the (Fe₃O₄, FeO)/Fe composite from Fe₂O₃+Fe precursor mixtures was studied by differential scanning calorimetry and X-ray diffraction techniques.     

多功能Fe3O4@SiO2 Janus颗粒

采用溶剂热法和溶胶-凝胶法制备了顺磁性Fe₃O₄@SiO₂颗粒,以Pickering乳液界面保护法实现颗粒表面分区获得Fe₃O₄@SiO₂ Janus颗粒,进一步选区复合生长Pt或Ag纳米颗粒制备Fe₃O₄@SiO₂-Pt和Fe₃O₄@SiO₂-Ag Janus颗粒.Fe₃O₄@SiO₂-Pt Janus颗粒的Pt一侧进行催化过氧化氢的反应,具有自驱动功能.因其顺磁性和两亲性,Fe₃O₄@SiO₂-Ag Janus颗粒能够作为磁响应颗粒乳化剂稳定油水乳液,并将Ag的催化功能引入界面.     

Catalytic Properties of the System Fe2O3-Ga2O3 in Ammonia Oxidation

The catalytic properties of the system Fe₂O₃-Ga₂O₃ in high-temperature oxidation of ammoniaand the influence exerted by the phase composition of the system on the physicochemical, catalytic properties of the catalysts were studied.     

ZrO2、Y2O3对CH4燃烧催化剂Fe2O3/γ-Al2O3的改性作用

γ-Ａｌ2Ｏ3作为催化剂载体具有较大的比表面积,机械强度高,孔结构适宜,但不耐高温。近年来,氧化锆载体以其耐高温等[1]独特性质引起多方面的关注[2-4],它能与所负载的金属产生强烈的电子相互作用,影响催化剂的吸附、氧化和还原性能。但是ＺｒＯ2比表面积较小,且随焙烧温度的升高急剧下降,如单独作为催化剂载体,其应用受到很大限制。若将ＺｒＯ2分散到γ-Ａｌ2Ｏ3表面上,可制得兼备两者优点的复合载体。当ＺｒＯ2中加入Ｙ2Ｏ3,能产生特殊的氧空穴[5],具有氧离子传导功能和导电性;与活性组分相结合能在很大程度上提高反应速度。我们用Ｙ…