Multiscale and multicomponent layer by layer assembly of optical thin films triggered by electrochemical coupling reactions of N-alkylcarbazoles

The integration of multiscale and multicomponent of molecules and nanoparticles into thin films for applications requires the abilities of controlled their processing and assembly,which has been an great challenge because of the difficulty in manipulating the various materials such as small molecules,complexes,polymers,and inorganic nanomaterials through synergetic combinations of chemical or physical fabrications.Eletropolymerization is of great significance to fabricate polymeric film materials straight on the conductive substrates with tunable morphologies and thicknesses.However,unlimited electrochemical reactions(polymerization)have been usually leading to disadvantageous in ill-defined structure and highly doped state.Thanks to finding of exceptional electrochemical reaction(oligomerization)of N-alkylcarbazole,electrochemical layer by layer assembly has emerged as a promising strategy for a wide library of applications.The capability of this strategy can manipulate various molecules and nanoparticles into the scale and component controllable thin films.Unlike other electropolymerizable precursors such as aniline and thiophene,the resulting di-N-alkylcarbazole is transparent in the visible light region and thus does not impair the intrinsic properties of the components in the film.This account highlights of the typical findings in investigating both single-and multi-components thin films as a forum for discussing new opportunities in exploiting novel designs and applications of optical thin films.     

Mechanical unfolding of ensemble biomolecular structures by shear force

Mechanical unfolding of biomolecular structures has been exclusively performed at the single-molecule level by single-molecule force spectroscopy (SMFS) techniques. Here we transformed sophisticated mechanical investigations on individual molecules into a simple platform suitable for molecular ensembles. By using shear flow inside a homogenizer tip, DNA secondary structures such as i-motifs are unfolded by shear force up to 50 pN at a 77 796 s⁻¹ shear rate. We found that the larger the molecules, the higher the exerted shear forces. This shear force approach revealed affinity between ligands and i-motif structures. It also demonstrated a mechano-click reaction in which a Cu(i) catalyzed azide–alkyne cycloaddition was modulated by shear force. We anticipate that this ensemble force spectroscopy method can investigate intra- and inter-molecular interactions with the throughput, accuracy, and robustness unparalleled to those of SMFS methods.

Shear force in a homogenizer mechanically unfolds an ensemble set of biomolecular structures.     

Modelling the spindle–holder taper joint in machine tools: A tapered zero-thickness finite element method

This study presents a tapered zero-thickness finite element model together with its parameter identification method for modelling the spindle–holder taper joint in machine tools. In the presented model, the spindle and the holder are modelled as solid elements and the taper joint is modelled as a tapered zero-thickness finite element with stiffness and damping but without mass or thickness. The proposed model considers not only the coupling of adjacent degrees of freedom but also the radial, tangential and axial effects of the spindle–holder taper joint. Based on the inverse relationship between the dynamic matrix and frequency response function matrix of a multi-degree-of-freedom system, this study proposes a combined analytical–experimental method to identify the stiffness matrix and damping coefficient of the proposed tapered zero-thickness finite element. The method extracts those parameters from FRFs of an entire specimen that contains only the spindle–holder taper joint. The simulated FRF obtained from the proposed model matches the experimental FRF quite well, which indicates that the presented method provides high accuracy and is easy to implement in modelling the spindle–holder taper joint.     

Optimization of ZnSe film growth conditions for p-type doping

Wide bandgap semiconductors such as ZnSe and ZnO have attracted great interest due to their applications in solar cells, light emitting diodes, and lasers. However, these wide bandgap semiconductors are frequently difficult to be doped to heavy concentrations, greatly limiting their application. A substrate holder with a natural temperature gradient was developed for batch growth of films at different deposition temperatures, in order to investigate ZnSe film growth and doping challenges. Thin ZnSe films were grown by pulsed laser deposition and characterized using X-ray diffraction, optical transmission and reflection, Raman spectroscopy, and Energy Dispersive X-ray analysis. Deposition temperature and film stoichiometry (Zn:Se) are shown to be significant factors affecting ZnSe growth and doping. ZnSe films with improved crystallinity have been obtained by enriching with selenium and depositing at an optimized temperature. Heavily p-type ZnSe films with hole concentrations of ~2.7 × 10¹⁹ cm^?3 and resistivities of ~0.099 Ohm cm have been obtained (compared with previous reports of ~1 × 10¹⁸ cm^?3 and ~0.75 Ohm cm). The results, which are consistent with previous theoretical prediction of compensating defects in ZnSe films, can help to optimize ZnSe growth conditions and understand doping challenges in wide bandgap semiconductors.     

探空湿度测量太阳辐射误差修正流体动力学研究

针对太阳辐射加热导致的误差显著限制了相对湿度测量的准确度,提出一种新颖的相对湿度误差修正方法—–基于流体动力学的数值分析法.在流体-固体耦合传热数值模拟分析中考虑探空湿度传感器的外部热环境情况,施加对流-太阳辐射耦合热边界条件,建立了地面到32 km高空不同气压和温度条件下探空湿度传感器的温度误差分析模型.结合Goff-Gratch饱和水汽压逼近公式,进而提出了相应的相对湿度误差流体动力学数值分析模型,并且着重研究了太阳辐射方向、传感器尺寸、反射率和衬底材料热导率等物理参数对相对湿度误差的影响.分析数值仿真结果表明:随着海拨的升高,其与太阳辐射加热引起的相对湿度误差之间存在非线性的单调递增关系;太阳辐射方向对于湿度测量精度的影响显著,当太阳辐射方向垂直于传感器正面时误差最大、传感器顶部时次之、侧面时误差最小;虽然通过减小探空湿度传感器的尺寸、降低衬底材料的热导率以及提高反射率均可以一定程度地降低太阳辐射加热引起的相对湿度误差,但是在低气压高空条件下,太阳辐射加热误差对于湿度准确性的影响仍然十分明显,需加以修正.与实验结果对比表明,基于流体动力学模拟仿真的相对湿度误差数值分析法为辐射误差修正提供了一种新的途径.     

Ti/TiO_2包覆ZnO:Tb纳米纤维的光学性质

用电纺丝方法制备了ZnO:Tb纳米纤维.用X-射线衍射、Raman光谱对其形貌做了表征.结果显示,ZnO:Tb纳米纤维为六方纤锌矿结构,Tb掺杂对ZnO的结晶性有影响.利用表面等离激元,通过对纳米纤维表面包覆金属Ti和TiO_2,比较了其光致发光谱,得到在325 nm激发下ZnO:Tb纳米纤维中稀土发光效率低的原因是ZnO和Tb之间不能进行有效的能量传递;包覆TiO_2后能提高稀土发光效率.     

V高掺杂ZnO最小光学带隙和吸收光谱的第一性原理研究

对于V高掺杂ZnO,当摩尔分数为0.0417—0.0625时,随着掺杂量的增加,吸收光谱出现蓝移减弱和蓝移增强两种不同实验结果均有文献报道.采用密度泛函理论的第一性原理平面波超软赝势方法,构建未掺杂ZnO单胞模型、V高掺杂Zn1-xVxO(x=0.0417,0.0625)两种超胞模型,采用GGA+U方法计算掺杂前后体系的形成能、态密度、分波态密度、磁性和吸收光谱.结果表明,当V的掺杂量(原子含量)为2.083%—3.125%时,随着V掺杂量增加,掺杂体系磁矩增大,磁性增强,并且掺杂体系体积增加,总能量下降,形成能减小,掺杂体系更稳定,同时,掺杂ZnO体系的最小光学带隙增宽,吸收带边向低能级方向移动.上述计算结果与实验结果一致.     

3d过渡金属Co掺杂核壳结构硅纳米线的第一性原理研究

基于密度泛函理论的第一性原理计算,研究了横截面为五边形和六边形的核壳结构硅纳米线的过渡金属Co原子替代掺杂.通过比较形成能发现,核心位置掺杂、壳层单链掺杂以及外壳层全替代掺杂的硅纳米线都具有稳定性,其中核心位置掺杂结构的稳定性最高.掺杂体系均呈现金属性,随着掺杂浓度的增加,电导通道数增加.Co原子掺杂的硅纳米线呈现铁磁性,具有磁矩.Bader电荷分析表明,电荷从Si原子转移至过渡金属Co原子.与自由态时过渡金属Co原子的磁矩相比,体系中Co原子的磁矩有所降低,这主要是由Co原子4s轨道向3d/4p轨道的电荷转移以及4s,3d,4p的上自旋电子转移至下自旋导致的.