Er3+单掺、Er3+/Yb3+共掺杂Ca12Al14O32F2的 制备及上转换发光性质

利用高温固相法成功制备了Er~(3+)单掺、Er~(3+)/Yb~(3+)共掺杂Ca_(12)Al_(14)O_(32)F_2上转换发光样品。在980 nm激光激发下,Er~(3+)单掺和Er~(3+)/Yb~(3+)共掺杂样品均呈现出较强的绿光(528,549 nm)和较弱的红光(655 nm)发射,分别归因于Er~(3+)离子的~2H_(11/2),~4S_(3/2)→~4I_(15/2)和~4F_(9/2)→~4I_(15/2)能级跃迁。随着Er离子浓度的增加,单掺杂样品上转换发光强度先增大后减小,最佳掺杂浓度为0.8%。共掺杂Yb~(3+)后,Er~(3+)的发光强度明显增大。还原气氛下合成的样品上转换发光强度增大约两倍,可能和笼中阴离子基团变化有关。发光强度和激发光功率的关系表明所得上转换发射为双光子吸收过程,借助Er~(3+)-Yb~(3+)体系能级结构详细讨论了上转换发射的跃迁机制。     

基于XPS对硫铁矿去除SeO2-3的机理研究

硒是动植物及人体生长必需的十五种微量元素之一，具有清除体内自由基、抗氧化、增强免疫力等功能，但其安全剂量的范围却很窄。利用扫描电子显微镜（SEM）和X射线衍射仪（XRD）对湿法球磨制备的硫铁矿形貌进行了表征。SEM观测发现加乙醇助磨后的硫铁矿为粒径大小较均匀的球形颗粒团聚体，粒径范围在17～200 nm之间，平均粒径138 nm。XRD衍射图谱中的特征峰与FeS₂衍射图谱中各峰位置基本一致，因此判定硫铁矿中主要化学组分为FeS₂，且图谱中基本没有杂峰，表明制备过程中并未混入杂质，样品纯度较高。实验结果表明，该法制备的硫铁矿具有颗粒粒径小、比表面积大、反应活性高等优点。研究中利用X射线光电子能谱仪（XPS）对硫铁矿去除水体中SeO2-₃的机理进行了研究。研究结果表明, （1）在较为广泛的实验pH范围（pH 2.2～11.5），硫铁矿均能有效去除水体中SeO2-₃，去除效率（除pH值7.8以外）均达到90%以上；（2）硫铁矿与SeO2-₃发生反应后，其主要组成元素的XPS特征峰结合能有所减小，表明硫铁矿表面发生了一定化学变化；（3）酸碱环境下硫铁矿去除SeO2-₃的机理不完全相同，酸性环境下，硫铁矿对SeO2-₃的去除是单纯的氧化还原过程，即硫铁矿中被酸活化的S2-₂将SeO2-₃还原为单质Se(0)，并且酸性越强，SeO2-₃去除效果越好；碱性环境下，SeO2-₃的去除过程中氧化还原与络合反应并存，硫铁矿表面有络合态Fe(OH)SeO₃和单质Se(0)两种存在形态，且碱性越强，络合态Fe(OH)SeO₃含量越高。以上研究结果为硫铁矿去除固定水体和土壤中以SeO2-₃为代表的可变价金属阴离子提供重要理论依据和应用基础。     

The self-assemblies of a newly designed star-shaped molecule end-capped with bromine atoms studied by scanning tunneling microscopy

A new star-shaped molecule StOF-Br_3 containing oligofluorenes and halogen atoms(Bromine) has been synthesized and studied by Scanning Tunneling Microscopy(STM) at the highly oriented pyrolytic graphite(HOPG) surface.We have obtained the high-resolution self-assembled STM images,from which the highly ordered and closely packed non-porous arrangements of the StOF-Br_3 molecular selfassemblies at the heptanoic acid/HOPG surface could be observed.The molecular models and selfassembled StOF-Br_3 architectures have been given in the following text.Besides,we have also figured out the surface free energy by the density functional theory(DFT) calculation,which proved that the halogen...halogen interaction was strong enough to stabilize the ordered molecular self-assemblies.This work verifies the existence of bromine...bromine interactions,and meanwhile provides a kind of effective approach for quickly building ordered molecular nanoarchitectures with large areas and different geometries.     

相位可控的核四极矩共振激励脉冲发生器设计

在核四极矩共振（NQR）领域，射频激励脉冲信号的优劣对NQR响应信号有重要影响.针对常规方法中射频激励脉冲参数不可控的问题，本文基于32位闪存微型控制器STM32和直接数字频率合成（DDS）芯片AD9910设计了一种相位可控激励脉冲发生器.采用STM32控制AD9910产生波形参数（脉冲宽度、脉冲间隔、脉冲个数和共振频率等）可控的射频激励脉冲，利用LabVIEW软件平台设计脉冲参数设置界面，并建立计算机与微控制器通信，实现波形参数的精确优化控制.实验结果表明，该方法实现了相位可控的NQR激励脉冲序列，可为后续NQR信号检测提供有效激励源.     

Low-temperature formation and characterization of Cu2O nanoparticles in the binary gold alloys

Thermal analyses, using differential scanning calorimetry (DSC) and dilatometry, reveal an important anomaly at low temperature for Au-25 wt.% Cu composition after homogenization at 700°C during 2 hours under vacuum followed by heating up to 160°C before water quenching. This anomaly has been already observed and not explained. Surface characterization, using scanning electron microscopy (SEM), atomic force microscopy (AFM), and scanning tunneling microscopy (STM), exhibits a specific topography, consisting of a nanostructured surface. The precipitates of nanostructured particles are homogeneously scattered all over the surface for this 18-carat gold alloy. Moreover, X-ray photoelectron spectroscopy (XPS) shows that the composition of the observed particles corresponds to cuprous oxide phase (Cu₂O). The formation of such material can be explained by the diffusion of copper atoms from the lattice to the surface at 160°C. Pulsed radio-frequency glow discharge optical emission spectroscopy (RF GD-OES) further proves the proposed Cu₂O formation through a diffusion process. The appearance of such cuprous oxide nanoparticles on the Au-Cu alloy surface explains the low-temperature DSC and dilatometry anomaly and affects directly the surface electrical resistance at low temperature. These results might open a large gate for new ideas to investigate in catalytic, electronic, and antimicrobial activities.     

Aryl Triflates in On-Surface Chemistry

The reactivity of aryl triflates in on-surface C−C coupling is reported. It is shown that the triflate group in aryl triflates enables regioselective homo coupling with preceding or concomitant hydrodetriflation on Cu(111). Three different symmetrical π-systems with two and three triflate functionalities were used as monomers leading to oligomeric conjugated π-systems. The cascade, comprising different intermediates at different reaction temperatures as observed for one of the molecules, proceeds via initial removal of the trifluoromethyl sulfonyl group to give an aryloxy radical which in turn is deoxygenated to the corresponding aryl radical. Thermodynamically driven regioselective 1,2-hydrogen atom transfer leads to a translocated aryl radical which in turn undergoes coupling. For a sterically more hindered bistriflate, where one ortho position was blocked, dehydrogenative coupling occurred at remote position with good regioselectivity. Starting materials, intermediates as well as products were analyzed by scanning tunneling microscopy. Structures and suggested mechanism were further supported by DFT calculations.     

A sensitive DNA biosensor based on the distance dependent quenching of Silica@Ru(bpy)32+-chitosan-GO electrochemiluminescence by Ferrocene@Gold nanoparticles

A sensitive electrochemiluminescence (ECL) biosensor for the specific DNA sequence of hepatitis C virus (HCV) was developed based on the efficient quenching effect of the ferrocene cluster functionalized gold nanoparticles (Fc@AuNPs) on the ECL of electrodeposited silica@Ru(bpy)₃²⁺-chitosan-graphene oxide nanocomposite (SiO₂@Ru−CS−GO). Graphene oxide (GO) can accelerate electron transfer rate, thus improving the ECL of Ru(bpy)₃²⁺ on electrode surface. The molecular beacons (MB) was fixed to SiO₂@Ru−CS−GO by glutaraldehyde (GA) using the Schiff reaction between amino groups of chitosan (CS) and MB. The ECL of SiO₂@Ru−CS−GO was depressed greatly by the Fc@AuNPs labelled at the end of MB, then, a stronger ECL was observed when the distance between Fc@AuNPs and SiO₂@Ru−CS−GO increased after the hybridization of target DNA with MB. Under optimum conditions, the restored ECL intensity increased linearly with the target DNA concentration in the range of 1.0×10⁻¹⁶∼1.0×10⁻¹⁰ mol ⋅ L⁻¹, and the limit of detection (LOD) is 1.4×10⁻¹⁷ mol ⋅ L⁻¹. The proposed method exhibits acceptable stability and reproducibility. In general, the constructed HCV biosensor can be used for the sensitive detection of HCV in human serum, suggesting potential application prospects in bioanalysis.     

电致化学发光法高灵敏度测定血清中的辛可宁

利用金电极为工作电极,研究了辛可宁-Ru(bpy)2+3体系的电致化学发光行为。研究表明,辛可宁对Ru(bpy)2+3在电极表面的电致化学发光具有显著的增强作用,据此建立了一种高灵敏度测定辛可宁的电致化学发光分析方法。考察了硼酸-硼砂缓冲溶液的浓度、p H值、联吡啶钌浓度、光电倍增管电压等参数对实验的影响。在12 mmol/L硼酸-硼砂缓冲溶液(p H 9.0)中,辛可宁浓度的对数lgc在3.0×10-9~6.0×10-6mol/L范围内与Ru(bpy)2+3的电致化学发光强度变化值(ΔI)呈线性关系,检出限(S/N=3)为1.76×10-10mol/L。应用此法对血清中辛可宁的浓度进行测试,加标回收率为102.1%~109.5%。