石墨烯的表征方法

单层石墨烯的厚度为0.335nm,在垂直方向上有约1nm的起伏,且不同工艺制备的石墨烯层数和结构有所不同,如何有效地鉴定石墨烯的层数和结构是获得高质量石墨烯的关键步骤之一。介绍了光学显微镜、扫 描 电 子 显 微 镜(SEM)、透 射 电 子 显 微 镜(TEM)、原子力显微镜(AFM)、拉曼光谱(Raman)、红外光谱(IR)、X射线光电子能谱(XPS)和紫外可见光谱(UV-Vis)等几种用来表征石墨烯的主要方法。     

两步水热法制备枝干状ZnO纳米结构的研究

采用两步水热法,第1步利用Au作为催化剂生长ZnO纳米杆;第2步利用醋酸锌分解成ZnO纳米颗粒作籽晶层在ZnO纳米杆的侧壁生长ZnO纳米枝条,在Si片上成功制备了枝干状ZnO纳米结构。利用SEM、XRD分别表征枝干状ZnO纳米结构的形貌和晶体结构,研究籽晶层、反应液浓度、反应时间等参数对枝干状ZnO纳米结构形貌的影响。结果表明,Au作为催化剂生长的ZnO纳米杆具有沿(103)面择优取向生长的特性,而籽晶层对在侧壁生长ZnO纳米枝条至关重要。通过调节反应参数,可控制枝干状ZnO纳米结构的形貌,当反应液浓度越小,反应时间越长,纳米枝条越细、越长。所制备的枝干状ZnO纳米结构具有很好的生物兼容性,可作为细胞支架材料。     

低温非晶硅/金圆片键合技术(英文)

本文研究了低温非晶硅/金圆片键合技术.具有不同金硅比的键合片在400℃键合温度和1 MPa键合压力下维持30 min,其键合成功区域均高于94%,平均剪切强度均大于10.1 MPa.键合强度测试结果表明键合成品率与金硅比大小无关,平均剪切强度在10～20 MPa范围内.微观结构分析表明键合后单晶硅颗粒随机分布在键合层内,而金则充满其他区域,形成了一个无空洞的键合层.无空洞键合层确保不同金硅比非晶硅/金键合片均具有较高的键合强度,可实现非晶硅/金键合技术在圆片键合领域的应用.     

石墨烯的制备和应用

石墨烯因具有优良的电学、热学和机械性能,以及高透光率和超大比表面积等而备受人们关注。尤其是2004年稳定存在的石墨烯被成功的获得,更是掀起了石墨烯的研究高潮。获得低成本、大面积、高质量的石墨烯,并将其用于实际生产是研究人员奋斗的目标。主要对近几年一些改进的或新的石墨烯的制备方法以及其主要的潜在应用做了综述,从中可以看到石墨烯的巨大发展潜力。     

热障涂层隔热性能研究进展

热障涂层(TBCs)具有良好的隔热效果和抗高温氧化性能,是航空发动机和燃气轮机高温部件的关键材料。隔热性能是热障涂层研究的关键点,从热障涂层的材料、制备工艺、涂层组织结构方面综述了其隔热性能的研究现状和最新进展,展望了热障涂层的发展方向。     

碳纳米管工具电极的制备

纳米工具电极是进行纳米电解加工的必备条件,其特征尺寸直接影响纳米结构的最终尺寸.提出了利用电弧放电将碳纳米管束焊接在钨针尖上的纳米工具电极制备方法,并通过试验研究了钨针的针尖圆弧半径和放电电压对制备碳纳米管工具电极的影响.试验结果表明,不同尖端圆弧半径的钨针,所需有效放电电压不同,圆弧半径越小,有效放电电压越小,强电场分布越集中,越容易将碳纳米管束焊接在针尖的顶端;圆弧半径越大,强电场分布区域越大,越不容易控制碳纳米管束焊接的方向性.在针尖圆弧半径约为100 nm和300 nm的钨针上,放电电压分别为25 V和35 V时,成功制备出碳纳米管工具电极.     

基于空心钢管结构的声学超材料

提出了一 种基于空心 钢管(hollowsteeltube;HST)的“超原子”结构模型,声学透射实验和数值计算结果表明基于该模型的声学超材料可以实现负等效质量密度。为了说明空心钢管结构性质,研究了空心钢管微结构几何尺寸(例如空心钢管直径)变化时材料的透射性质,结果表明空心钢管几何尺寸的改变对声学超材料的透射禁带频率有影响。     

HA/PLA复合材料界面相互作用及其力学性能的MD模拟

基于HA/PLA复合材料可以在很大程度上实现HA与PLA两者的优势互补,有望成为一种理想的骨替换材料。运用分子动力学(MD)方法,从分子理论的角度研究了羟基磷灰石(HA)的3个晶面(001)、(100)、(110)分别与聚乳酸(PLA)相互作用后混合体系的结合能,并对(110)晶面径向分布函数和力学性能进行了计算分析。结果表明,3晶面所对应结合能大小为HA(110)>HA(100)>HA(001);其相互作用主要源自PLA中的O原子分别与HA中的H原子形成的氢键以及Oa1—Ca之间形成了离子键;PLA组分能够对HA的力学性能起到明显的加强作用,且HA/PLA混合体系在各个方向的力学性能较单组分HA更为接近,从而克服了因材料各向异性而导致的缺陷。     

基于中空钴微米颗粒的磁流变液性能研究

采用水热法制备钴微米颗粒,通过X射线衍射仪、扫描电镜和振动样品磁强计对颗粒的相结构、形貌及磁性能进行表征。结果表明,颗粒为密排六方结构的单质钴,粒径3~5μm,内部呈中空结构,饱和磁化强度为161A·m2/kg。以中空钴微米颗粒为悬浮相,以硅油为基液,制备颗粒体积分数为12%的磁流变液。测试结果表明,基于中空钴微米颗粒的磁流变液的磁 致 剪 切 屈 服 强 度 在250kA/m磁 场 下 达 到37kPa,剪切应力的时间稳定性、长期静置的沉降稳定性等均优于同体积浓度的羰基铁粉磁流变液。     

铋钼复合氧化物的研究进展

综述了多种铋钼复合氧化物的制备方法:固相反应法、沉淀法、溶胶-凝胶法、水热法以及喷雾干燥法等,分析了这些方法的优缺点。同时综述了铋钼复合氧化物在氧化反应催化、光催化、电解质材料等领域的应用以及材料的结构、形貌对于其性能的影响。针对铋钼复合氧化物不同的应用领域提出了制备技术、材料组分和结构与形貌的发展方向。     

Stability of DNA Origami Nanostructures in Physiological Media: The Role of Molecular Interactions

Programmable, custom-shaped, and nanometer-precise DNA origami nanostructures have rapidly emerged as prospective and versatile tools in bionanotechnology and biomedicine. Despite tremendous progress in their utilization in these fields, essential questions related to their structural stability under physiological conditions remain unanswered. Here, DNA origami stability is explored by strictly focusing on distinct molecular-level interactions. In this regard, the fundamental stabilizing and destabilizing ionic interactions as well as interactions involving various enzymes and other proteins are discussed, and their role in maintaining, modulating, or decreasing the structural integrity and colloidal stability of DNA origami nanostructures is summarized. Additionally, specific issues demanding further investigation are identified. This review – through its specific viewpoint – may serve as a primer for designing new, stable DNA objects and for adapting their use in applications dealing with physiological media.     

Progress toward Understanding the Interactions between DNA Nanostructures and the Cell

Advances in DNA nanotechnology empower the programmable assembly of DNA building blocks (oligonucleotides and plasmids) into DNA nanostructures with precise architectural control. As DNA nanostructures are biocompatible and can naturally enter mammalian cells without the aid of transfection agents, they have found numerous biological or biomedical applications as delivery carriers of therapeutic and imaging cargoes into mammalian cells for at least a decade. Nevertheless, mechanistic studies on how DNA nanostructures interact with cells have remained limited and incomprehensive until 2–3 years ago. This Review presents the recent progress in elucidating the “cell–nano” interactions of DNA nanostructures, with an emphasis on three key classes of structures commonly utilized in intracellular applications: tile‐based structures, origami‐based structures, and nanoparticle‐templated structures. Structural parameters of DNA nanostructures and strategies of biochemical modification for promoting intracellular delivery are discussed. Biological mechanisms for cellular uptake, including specific pathways and receptors involved, are outlined. Routes of intracellular trafficking and degradation, together with strategies for re‐directing their trafficking, are delineated. This Review concludes with several aspects of the “bio–nano” interactions of DNA nanostructures that warrant future investigations.     

Self-Assembly of DNA Nanostructures in Different Cations

The programmable nature of DNA allows the construction of custom-designed static and dynamic nanostructures, and assembly conditions typically require high concentrations of magnesium ions that restricts their applications. In other solution conditions tested for DNA nanostructure assembly, only a limited set of divalent and monovalent ions are used so far (typically Mg²⁺ and Na⁺). Here, we investigate the assembly of DNA nanostructures in a wide variety of ions using nanostructures of different sizes: a double-crossover motif (76 bp), a three-point-star motif (~134 bp), a DNA tetrahedron (534 bp) and a DNA origami triangle (7221 bp). We show successful assembly of a majority of these structures in Ca²⁺, Ba²⁺, Na⁺, K⁺ and Li⁺ and provide quantified assembly yields using gel electrophoresis and visual confirmation of a DNA origami triangle using atomic force microscopy. We further show that structures assembled in monovalent ions (Na⁺, K⁺ and Li⁺) exhibit up to a 10-fold higher nuclease resistance compared to those assembled in divalent ions (Mg²⁺, Ca²⁺ and Ba²⁺). Our work presents new assembly conditions for a wide range of DNA nanostructures with enhanced biostability.     

Combining Qdot Nanotechnology and DNA Nanotechnology for Sensitive Single-Cell Imaging

Immunohistochemistry (IHC) can provide detailed information about protein expression within the cell microenvironment and is one of the most common techniques in biology and medicine due to the broad availability of highly specific antibodies and well-established bioconjugation methods for modification of these antibodies with chromogens and fluorophores. Despite recent advances in this field, it remains challenging to simultaneously achieve high multiplexing, sensitivity, and throughput in single-cell profiling experiments. Here, the combination of two powerful technologies is reported, quantum dot and signal amplification by exchange reaction (QD-SABER), for sensitive and multiplexed imaging of endogenous proteins. Compared to the conventional IHC process using dye-labeled secondary antibodies (which already has a built-in signal amplification mechanism), QD-SABER provides an additional 7.6-fold signal amplification. In addition, the DNA hybridization-based IHC can be rapidly removed to regenerate the sample for subsequent cycles of immunostaining (>10 cycles), greatly expanding the multiplexing capability.     

Smart Drug Delivery Nanocarriers with Self‐Assembled DNA Nanostructures

Self‐assembled DNA nanostructures have emerged as a type of nano‐biomaterials with precise structures, versatile functions and numerous applications. One particularly promising application of these DNA nanostructures is to develop universal nanocarriers for smart and targeted drug delivery. DNA is the genetic material in nature, and inherently biocompatible. Nevertheless, cell membranes are barely permeable to naked DNA molecules, either single‐ or double‐ stranded; transport across the cell membrane is only possible with the assistance of transfection agents. Interestingly, recent studies revealed that many DNA nanostructures could readily go into cells with high cell uptake efficiency. In this Progress Report, we will review recent advances on using various DNA nanostructures, e.g., DNA nanotubes, DNA tetrahedra, and DNA origami nanorobot, as drug delivery nanocarriers, and demonstrate several examples aiming at therapeutic applications with CpG‐based immunostimulatory and siRNA‐based gene silencing oligonucleotides.     

DNA Nanotechnology as an Emerging Tool to Study Mechanotransduction in Living Systems

The ease of tailoring DNA nanostructures with sub‐nanometer precision has enabled new and exciting in vivo applications in the areas of chemical sensing, imaging, and gene regulation. A new emerging paradigm in the field is that DNA nanostructures can be engineered to study molecular mechanics. This new development has transformed the repertoire of capabilities enabled by DNA to include detection of molecular forces in living cells and elucidating the fundamental mechanisms of mechanotransduction. This Review first describes fundamental aspects of force‐induced melting of DNA hairpins and duplexes. This is then followed by a survey of the currently available force sensing DNA probes and different fluorescence‐based force readout modes. Throughout the Review, applications of these probes in studying immune receptor signaling, including the T cell receptor and B cell receptor, as well as Notch and integrin signaling, are discussed.     

Daunorubicin‐Loaded DNA Origami Nanostructures Circumvent Drug‐Resistance Mechanisms in a Leukemia Model

Many cancers show primary or acquired drug resistance due to the overexpression of efflux pumps. A novel mechanism to circumvent this is to integrate drugs, such as anthracycline antibiotics, with nanoparticle delivery vehicles that can bypass intrinsic tumor drug‐resistance mechanisms. DNA nanoparticles serve as an efficient binding platform for intercalating drugs (e.g., anthracyclines doxorubicin and daunorubicin, which are widely used to treat acute leukemias) and enable precise structure design and chemical modifications, for example, for incorporating targeting capabilities. Here, DNA nanostructures are utilized to circumvent daunorubicin drug resistance at clinically relevant doses in a leukemia cell line model. The fabrication of a rod‐like DNA origami drug carrier is reported that can be controllably loaded with daunorubicin. It is further directly verified that nanostructure‐mediated daunorubicin delivery leads to increased drug entry and retention in cells relative to free daunorubicin at equal concentrations, which yields significantly enhanced drug efficacy. Our results indicate that DNA origami nanostructures can circumvent efflux‐pump‐mediated drug resistance in leukemia cells at clinically relevant drug concentrations and provide a robust DNA nanostructure design that could be implemented in a wide range of cellular applications due to its remarkably fast self‐assembly (≈5 min) and excellent stability in cell culture conditions.