氧化石墨烯吸附水体中酚类有机污染物的分子动力学模拟

研究采用分子动力学模拟(Molecular dynamics simulation, MD)的方法, 以苯酚、α-萘酚和4-辛基酚为代表, 研究了酚类有机污染物(Phenolic Organic Pollutants, POPs)在氧化石墨烯(Graphene Oxide, GO)上单独和竞争吸附过程。通过自由能计算得到三种POPs在GO表面的吸附能分别为: 4-辛基酚(41.34 kJ/mol)>α-萘酚(33.23 kJ/mol)>苯酚(19.31 kJ/mol)。吸附过程中的主要作用力为POPs的疏水作用, 而分子团簇、范德华相互作用、静电相互作用以及氢键等在一定程度上增加了GO对POPs的吸附能力。在混合体系中, POPs之间存在明显的竞争吸附现象, 吸附过程包含了直接吸附和形成分子团簇的间接性吸附两个过程。本研究结果为含POPs水体的治理以及GO材料的设计和筛选提供了一定的理论依据。     

甲醛在TiO2表面吸附的第一性原理研究

利用密度泛函理论研究了HCHO分子在TiO2金红石(110)面和锐钛矿(101)面上的吸附,结果表明甲醛在这些面上均能形成稳定的化学吸附与物理吸附。在物理吸附中,分子构型受吸附的影响均十分微弱。而在化学吸附中,甲醛分子明显变形,甲醛分子与表面的2配位O原子(O2C)一起形成双氧甲基(CH2O2)物种。化学吸附导致HCHO分子中的羰基延长14%~17%,表明吸附削弱了分子内原子之间的作用,从而有利于分解。此外,在这两种表面中,金红石(110)面对HCHO较强的吸附显示了其活性比锐钛矿(101)面高。     

分子动力学模拟聚电解质在聚苯乙烯微球表面的吸附

使用Materials Studio软件分别模拟阳离子聚电解质PDADMAC在PS微球表面和磺化PS微球表面的吸附。比较两个体系吸附平衡后的构型,发现PDADMAC可以更加舒展、均匀地吸附在磺化PS微球表面。并分别计算了PS-PDADMAC、磺化PS-PDADMAC体系的相互作用能,EPS-PDADMAC和EPS-SO3-PDADMAC的值分别在160kJ/mol和-90kJ/mol左右波动。模拟结果表明,PDADMAC在磺化PS微球表面吸附是一个自发过程,并且二者可以形成稳定的体系。     

Transport Properties of Undercooled Liquid Copper: A Molecular Dynamics Study

By using the embedded-atom method (EAM), a series of molecular dynamics (MD) simulations are carried out to calculate the viscosity and self-diffusion coefficient of liquid copper from the normal to the undercooled states. The simulated results are in reasonable agreement with the experimental values available above the melting temperature that is also predicted from a solid–liquid–solid sandwich structure. The relationship between the viscosity and the self-diffusion coefficient is evaluated. It is found that the Stokes–Einstein and Sutherland–Einstein relations qualitatively describe this relationship within the simulation temperature range. However, the predicted constant from MD simulation is close to 1/(3π), which is larger than the constants of the Stokes–Einstein and Sutherland–Einstein relations.     

胶原与壳聚糖分子间的作用力

胶原与壳聚糖分子间的作用力使得其复合材料具有作为优良生物材料的潜力。文中通过稀溶液黏度法、红外和X射线衍射法对胶原与壳聚糖分子间作用力进行了表征。结果发现,任何比例的胶原与壳聚糖在分子级都是相容的,两者之间具有较强的相互作用。     

皮胶原纤维吸附水分动力学

研究了皮胶原纤维对水分的吸附行为。结果表明,皮胶原纤维吸附水分一般在9h后就基本达到平衡,环境湿度越大,达到吸附平衡所需的时间越长。采用Lagergren一级速率模型和二级速率模型分别拟合了皮胶原纤维吸附水分的实验数据,发现二级速率模型与实验数据比较吻合。颗粒内扩散模型的分析结果表明,皮胶原纤维吸附水分的过程包含三个相对独立的阶段,各阶段的吸附速率分别受不同因素的控制。     

Adsorption and photocatalytic decomposition of organic molecules on carbon-coated TiO2

Carbon-coated anatase TiO₂ samples were prepared from the mixture of poly vinyl alcohol (PVA) and commercial TiO₂ (P-25) with different mass ratios and heating temperatures. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy dispersive spectrometer (EDX), transmission electron microscope (TEM), and nitrogen adsorption analyses. The adsorption properties and photocatalytic activity of commercial and carbon-coated TiO₂ catalysts were compared for the oxidation of methylene blue (MB) and bisphenol-A (BPA). It was interesting to find that the transition from anatase to rutile was suppressed by carbon coating of TiO₂ at high temperature up to 800 °C. The carbon-coated TiO₂ samples have a higher surface area and a greater adsorption amount than commercial P-25 because of the thin layer of carbon that covered TiO₂. It was also observed that the photodecomposition efficiency was dependent on the crystallinity of the carbon-coated sample.     

球壳状纳米介孔腔内药物释放特性的分子动力学研究

有序纳米介孔材料的有序性、大的比表面积、孔道均匀等特性使其在药物装载、吸附、释放等方面得到广泛的应用。近年来研究者对介孔材料在药物控释方面的研究主要是通过材料制备、表征以及吸附药物后介孔材料的性能测试等几方面实现的。大多数报道都是采用实验的方法进行研究,关于模拟计算方面的研究很少,力场的选择更是模拟计算的一项挑战。依据介孔材料的独特结构构建了球壳状纳米介孔腔内药物分子释放模型,通过分子动力学的方法计算分析了药物分子的释放特性,重点考察了药物分子大小、溶液环境、介孔腔结构特征对其释放特性的影响。     

Dynamic Adsorption of Albumin on Nanostructured TiO(2)Thin Films

Spectroscopic ellipsometry was used to characterize the optical properties of thin (<5 nm) films of nanostructured titanium dioxide (TiO(2)). These films were then used to investigate the dynamic adsorption of bovine serum albumin (BSA, a model protein), as a function of protein concentration, pH, and ionic strength. Experimental results were analyzed by an optical model and revealed that hydrophobic interactions were the main driving force behind the adsorption process, resulting in up to 3.5 mg/m(2) of albumin adsorbed to nanostructured TiO(2). The measured thickness of the adsorbed BSA layer (less than 4 nm) supports the possibility that spreading of the protein molecules on the material surface occurred. Conformational changes of adsorbed proteins are important because they may subsequently lead to either accessibility or inaccessibility of bioactive sites which are ligands for cell interaction and function relevant to physiology and pathology.     

竹炭负载纳米TiO2吸附与降解甲苯的研究

以竹炭为载体,采用浸渍.焙烧法制备竹炭/纳米TiO2材料(竹炭-TiO2材料),利用SEM和EPR对竹炭及竹炭-TiO2材料进行表征,并分别在紫外灯、日光灯、白炽灯以及自然光照射条件下研究了竹炭-TiO2材料对甲苯的净化效果.结果表明:竹炭的孔隙主要以200nm左右的大孔为主,有利于TiO2在其表面和边沿的负载;竹炭-TiO2材料自旋数由8.7×1013(竹炭)增加到8.9×1017,氧化-还原能力显著提高;竹炭-TiO2材料对甲苯具有良好的净化能力,紫外光照射条件下,12 h净化率达94.50%,CO2增加量达122 mg/m3;在可见光条件下,12 h净化率为76.80%,CO2增加量为60mg/m3,CO2的增加可能是由于载体竹炭扩展了二氧化钛的光谱响应范围.     

Kinetics Investigation of Sintering of Nanometer Size Metal Clusters： A Molecular Dynamics Study

The sintering process of nanometer size gold clusters is investigated by using molecular dynamics simulation in the frame of embedded atomistic method. Several molecular dynamics simulation techniques are used to observe and describe the evolution of the sintering process. The energy distribution for single cluster is examined and the snapshots of sintering process of two clusters are recorded. The evolution of sintering is also described by plotting the mass center changes with time for each cluster. The variations of kinetic and potential energy during the process of sintering are monitored and measured to analyze the dominant mechanisms of sintering from the energy point of view.     

纳米TiO2光催化降解双酚A的研究

采用溶胶-凝胶法制备了纳米TiO2.以纳米TiO2为光催化剂,研究了在氧气存在条件下对典型内分泌干扰物质双酚A的光催化降解反应.分别讨论了分子氧、不同晶型、不同晶粒尺寸的纳米TiO2以及光照时间对双酚A降解反应的影响.结果表明,以0.2L/min的通氧速度进行光化学反应5h,锐钛矿型TiO2晶粒尺寸在10～20nm时对双酚A的光催化降解效率最好.     

CeO2掺杂TiO2光催化剂的性能研究

采用液相合成法制备CeO2掺杂TiO2光催化粉体,利用X射线衍射仪、紫外-可见分光光度计、FT-IR傅里叶变换红外光谱仪等对粉体的晶相组成、光谱吸收性能进行了表征,结果表明,掺杂后的TiO2经800℃热处理后仍呈锐钛矿型;CeO2/TiO2吸收光谱的阈值波长发生红移,但Ce掺杂浓度的增大对粉体的可见光吸收影响不大.光催化降解甲醛的结果表明,粉体在普通日光灯下对甲醛气体的降解率明显优于P25.     

Scalable Fabrication of Superhydrophobic Coating with Rough Coral Reef-Like Structures for Efficient Self-Cleaning and Oil-Water Separation: An Experimental and Molecular Dynamics Simulation Study

Superhydrophobic coating has a great application prospect in self-cleaning and oil-water separation but remains challenging for large-scale preparation of robust and weather-resistant superhydrophobic coatings via facile approaches. Herein, this work reports a scalable fabrication of weather-resistant superhydrophobic coating with multiscale rough coral reef-like structures by spraying the suspension containing superhydrophobic silica nanoparticles and industrial coating varnish on various substrates. The coral reef-like structures effectively improves the surface roughness and abrasion resistance. Rapid aging experiments (3000 h) and the outdoor building project application (3000 m²) show that the sprayed superhydrophobic coating exhibits excellent self-cleaning properties, weather resistance, and environmental adaptability. Moreover, the combined silica-coating varnish-polyurethane (CSCP) superhydrophobic sponge exhibits exceptional oil-water separation capabilities, selectively absorbing the oils from water up to 39 times of its own weight. Furthermore, the molecular dynamics (MD) simulation reveals that the combined effect of higher surface roughness, smaller diffusion coefficient of water molecules, and weaker electrostatic interactions between water and the surface jointly determines the superhydrophobicity of the prepared coating. This work deepens the understanding of the anti-wetting mechanism of superhydrophobic surfaces from the perspective of energetic and kinetic properties, thereby paving the way for the rational design of superhydrophobic materials and their large-scale applications.     

聚丁二酸丁二醇酯玻璃化转变行为的分子模拟

玻璃化转变是决定聚合物改性与加工等综合性能的重要环节.基于分子动力学方法,采用NPT(等温等压)正则系综,研究了聚丁二酸丁二醇酯(PBS)的玻璃化转变行为及主要影响因素.结果表明,PBS玻璃化转变温度为243.7K,与前人实验结果较为吻合;二面角扭转能、非键能及分子内氢键强度在243.7K附近发生突变,对PBS的玻璃化转变行为起到重要作用,是导致PBS出现玻璃化转变的根源之一.     

AlF3—CdF2—PbF2—LiF玻璃的X射线衍射和分子动力学研究

采用Ｘ射线衍射和分子动力学计算机结构模拟（ＭＤ）等手段，研究了ＡｌＦ３－ＣｄＦ２－ＰｂＦ２－ＬｉＦ玻璃的结构。研究表明Ａｌ原子为６配位，Ｃｄ原子取６，７和配位，ｉ原子为４，５或６配位，Ｃｄ－Ｆ的平均键长力１．１５Ａ。在ＡＤ计算的玻璃中存在着很少的桥Ｆ（Ｆｂ），大量的非桥Ｆ（Ｆｎｂ），并出现了较多的游离Ｆ，Ｆｆ和Ａｌ原子成键。玻璃结构可以看到是由Ｃｄ＾２＋连接的孤立的「Ａｌ２Ｆ１１」等形式的多面体堆     

Ion Beam Assisted Deposition: A Molecular Dynamics Simulation

Molecular dynamics simulation of C film growth by ion assisted deposition is reported. The developed kinetic model of ion assistance offers a possibility to consider relatively low energies of assisting ions (lower than 1 keV) compared to traditional models. C-C atomic interactions are calculated using the Tersoff potential (1). Effects of deposition and assistance modes on the film properties are discussed. A conclusion is made that the Tersoff potential cannot provide accurate simulation of the low-density C phase formation, because it does not describe explicitly the passage between sp₃-sp sp₃ hybridizations.     

掺P锐钛矿相TiO2第一性原理计算

采用广义梯度近似处理的全电势线性缀加平面波法计算了掺P锐钛矿相TiO2的电子密度、能带结构和态密度.计算结果表明,P掺杂使锐钛矿相TiO2在费米能级附近出现3条杂质能带,使能带宽度减小,从而有效地提高了TiO2的可见光响应.     

A Molecular Dynamics Study of Irradiation Induced Cascades in Iron Containing Hydrogen

Damage cascades representative of those that would be induced by neutron irradiation have been simulated in systems of pure iron and iron containing 0.01 at.% hydrogen. Results from molecular dynamics simulations using three different embedded-atom method (EAM) type potentials are compared for primary knock-on atom energies of 5, 10, and 20 keV to assess the effect of hydrogen on the primary damage state. We examine the influence of hydrogen on the primary damage state due to a single radiation cascade. These results can serve as an atomistic database for methods and simulations for long time scale evolution of radiation damage.