Graphene-based mass sensors: Chaotic dynamics analysis using the nonlocal strain gradient model

Nonlinear oscillations of graphene resonators are unavoidable due to enhancing the mass sensitivity of graphene-based mass sensors and the nonlinear behavior of the systems provides the route to chaos. In this paper, the nonlinear and chaotic behavior of the graphene-based mass sensor is investigated. The nano-mechanical sensor includes an electrostatically actuated fully clamped single-graphene sheet as a nano-resonator with an attached concentrated mass. By neglecting the rotary inertia, the equation of motion of the nano- resonator and the attached mass is derived using the nonlocal strain gradient theory of elasticity. The nano-resonator is modeled as a Kirchhoff nano-plate with the von Kármán-type geometric nonlinearity. Applying the Galerkin decomposition method to the partial differential equation of motion leads to the ordinary differential equation. Based on the Melnikov's integral method two analytical criteria are derived which provide necessary conditions that determine the chaotic region of the system. The chaotic dynamics of the system are also scrutinized and verified through plotting the Lyapunov exponent diagram, phase plane trajectories and Poincaré maps.     

Fe doping promoted electrocatalytic N2 reduction reaction of 2H MoS2

Electrocatalytic N₂ reduction to ammonia is a fascinating alternative to Haber-Bosch process and also considered as an energy storage method. This work, Fe doped MoS₂/carbon cloth (CC) has been studied on the electro-catalysis fix nitrogen indicating the doped Fe can indeed enhance the MoS₂ material ability. Compared with MoS₂/CC, Fe-Mo-S-3/CC not only increases 10 times in the rate of production ammonia, but also 5 times in Faraday efficiency.     

Revisiting radiative leptonic B decay

In this paper, we summarize the existing methods of solving the evolution equation of the leading-twist \begin{document}$B$\end{document}-meson LCDA. Then, in the Mellin space, we derive a factorization formula with next-to-leading-logarithmic (NLL) resummation for the form factors \begin{document}$F_{A,V}$\end{document} in the \begin{document}$B \to \gamma \ell\nu$\end{document} decay at leading power in \begin{document}$\Lambda/m_b$\end{document}. Furthermore, we investigate the power suppressed local contributions, factorizable non-local contributions (which are suppressed by \begin{document}$1/E_\gamma$\end{document} and \begin{document}$1/m_b$\end{document}), and soft contributions to the form factors. In the numerical analysis, which employs the two-loop-level hard function and the jet function, we find that both the resummation effect and the power corrections can sizably decrease the form factors. Finally, the integrated branching ratios are also calculated for comparison with future experimental data.     

含镨稀土抛光粉的制备及其抛光性能研究

通过采用碳酸镧(铈、镨)为前驱体,经氟化、高温焙烧、机械湿磨的方法得到稀土抛光粉,研究了不同掺镨量对稀土抛光粉的物相结构、表面形貌、粒度、密度、抛蚀量的影响。通过XRD分析得出结论:La2O3,Pr6O11固溶于CeO2的晶格结构中,并且出现了新的物相LaOF;随镨掺量的增大,LaOF的衍射峰强度不断增加,晶化程度不断增加;CeO2的XRD特征峰向左偏移,晶胞参数变大,晶面间距变大。通过粒度分析得出结论:随镨掺量的增加,抛光粉的中位粒径出现了先减小后增大的规律性变化。通过抛蚀量测试得出结论:随镨掺量的增加,抛光粉的抛蚀量出现了先增大后减小的变化。掺镨稀土抛光在镨含量为4.8%时,具有最小的中位粒径、较好的表面形貌和最大的抛蚀量。     

层状多硫代锑(Ⅲ)酸镉(Ⅱ)化合物(1,4-DABH2)Cd2Sb2S6的溶剂热合成与表征

利用溶剂热方法合成了层状多硫代锑髥酸镉髤化合物(1,4-DABH2)Cd2Sb2S6(1)(1,4-DAB=1,4-丁二胺),并通过红外光谱、热重分析对其进行了表征,用X-射线衍射测定了化合物的单晶结构。单晶解析表明,化合物属正交晶系,Cmca空间群,Mr=750.77,a=0.860 3(5)nm,b=0.898 7(6)nm,c=2.273(2)nm,V=1.758(2)nm3,Z=4,λ=0.071 073 nm,R=0.032,wR=0.106 7。晶体结构中含有六元环的Cd2SbS3和八元环的Cd2Sb2S4的阴离子网络层状[CdSbS3]nn-,双质子化的有机阳离子在阴离子层之间以氢键N-H…S形式连接。另外紫外-可见漫反射光谱研究表明,化合物为半导体。     

炔桥联不对称苯基取代双二茂铁衍生物的设计合成和电化学性质

以四苯基环戊二烯酮为起始原料,经过八步连续反应,成功地合成了3个炔桥联不对称五苯基取代双二茂铁衍生物Fc''-C≡C-Fc（1）、Fc''-C≡C-C≡C-Fc（2）和Fc''-C≡C-C≡C-Fc''（3）（Fc''=五苯基二茂铁基,Fc=二茂铁基）。在设计合成双二茂铁衍生物的过程中,首先经过4步反应,制备出已知化合物Fc''-H（4）,再连续进行3步反应,分别得到3个中间化合物Fc''-COCH₃（5）,Fc''-CCl=CHCHO（6）和Fc''-C≡CH（7）,最后利用偶联反应,得到目标化合物1~3。利用X射线单晶衍射和循环伏安法,测定了化合物1、2和5、7的晶体结构,研究了化合物1~7的电化学性质。研究结果表明,分子的C-H…π键相互作用和空间位阻是导致化合物1和2分子中Fc''和Fc基空间排布取向不同的主要原因。当二茂铁的一个环戊二烯环上引入5个苯取代基时,铁中心的氧化还原电位将升高（E_p^a（Fc''-H）=0.658 V,E_p^a（Fc-H）=0.511 V）。与已知化合物Fc-C≡C-Fc（ΔE=0.215 V）和Fc-C≡C-C≡C-Fc（ΔE=0.134 V）相比,化合物1~3的氧化电位差值（ΔE）均有不同程度地提高（ΔE₁=0.236 V;ΔE₂=0.170 V;ΔE₃=0.146 V）。将1与Fc-C≡C-Fc,2与Fc-C≡C-C≡C-Fc和3进行比较发现,当炔桥两端连接不同的基团Fc''和Fc时,其氧化电位差值（ΔE）将明显提高。     

壳聚糖的改性及其纳米粒子的制备

通过壳聚糖上的氨基与硬脂酸和硫辛酸的羧基脱水缩合反应,将硬脂酸和硫辛酸接枝在壳聚糖上,引入的疏水性基团使修饰的壳聚糖具有两亲性。对修饰壳聚糖残留的自由氨基进行甲基化,使氨基的pKa值由6.6增加到6.8~7.1。修饰的壳聚糖在水介质中经超声分散即可形成纳米粒子,纳米粒子的Zeta电位为正值,说明修饰壳聚糖中残留的氨基和甲基化的氨基处于纳米粒子的表面。纳米粒子经二硫苏糖醇还原,然后经空气中的氧气氧化,在纳米粒子中形成二硫键交联结构。     

扫帚状氧化铈制备及其对Pt基阳极催化剂催化性能的影响

采用水热合成法,合成了比表面积为175 m²·g^-1,孔径在2~4nm范围内的扫帚状CeO₂。通过微波辅助乙二醇还原氯铂酸法制备了Pt-CeO₂/RGO催化剂,探究扫帚状CeO₂的添加对Pt基催化剂电催化性能的影响。利用X射线衍射仪（XRD）、扫描电镜（SEM）、N₂吸附-脱附、X射线光电子能谱（XPS）对所制备的CeO₂及催化剂进行表征。利用电化学工作站对催化剂进行电化学性能测试。结果表明,催化剂中CeO₂保持原有扫帚状,Pt纳米粒子均匀分布于石墨烯载体表面;当m_RGO∶m_CeO2=1∶2时,添加了扫帚状CeO₂的Pt-CeO₂/RGO催化剂的电催化性能最优,电化学活性表面积为102.83 m²·g^-1,对乙醇氧化的峰值电流密度为757.17 A·g^-1,1 000 s的稳态电流密度为108.17 A·g^-1,对乙醇催化氧化反应的电荷转移电阻最小,活化能最低。     

双(8-乙氧羰甲氧基-2-亚甲喹啉基)缩连氮的合成及其选择传感性能

以水合肼和2-甲酰基-8-乙氧羰甲氧基喹啉为原料合成了希夫碱双(8-乙氧羰甲氧基-2-亚甲喹啉基)缩连氮(BEQA),经1HNMR、元素分析等进行了结构表征,在乙醇-水混合溶剂中采用UV-Vis光谱法研究了H+、Ca2+、Mg2+、Sr2+、Mn2+、Co2+、Ni2+、Cu2+、Zn2+、Cd2+及Hg2+对BEQA光谱的影响,结果表明,BEQA分子的UV-Vis光谱仅对体系中的H+、Cu2+和Cd2+有特殊的选择传感性,在体系中的pH值或Cu2+、Cd2+浓度增大时,BEQA在380 nm处的吸收峰强度会逐渐减小,并伴随有不同程度的蓝移;Job′s法测定Cu2+和Cd2+与BEQA形成配合物的化学计量比为1∶4。