Epitaxy and Molecular Organization on Solid Substrates

The recent emergence of molecular films as candidates for functional electronic materials has prompted numerous investigations of the underlying mechanisms responsible for their structure and formation. This review describes the role of epitaxy in molecular organization on crystalline substrates. A much‐needed grammar of epitaxy is presented that classifies the various modes of epitaxy according to transformation matrices that relate the overlayer lattice to the substrate lattice. The different modes of epitaxy can be organized hierarchically to reflect the balance of overlayer–substrate and molecule–molecule energies. In the case of molecular overlayers, the mismatch of overlayer and substrate symmetries commonly leads to coincident epitaxy in which some of the overlayer lattice points do not reside on substrate lattice points. Analyses of numerous reported epitaxial molecular films reveal that coincidence is quite common even though, based on overlayer–substrate interface energies alone, not as energetically favorable as commensurism. The prevalence of coincidence can be attributed to overlayer elastic constants, associated with molecule–molecule interactions within the overlayer, that are larger than the elastic constants of the overlayer–substrate interface. This condition facilitates prediction of the epitaxial configuration and overlayer structure through simple and comparatively efficient geometric modeling that does not require the input of potential energies, while revealing the role of phase coherence between the overlayer and substrate lattices.     

Orthogonal Transformations on Solid Substrates: Efficient Avenues to Surface Modification

The performance of solid substrates is not only governed by their molecular constitution, but is also critically influenced by their surface constitution at the solid/gas or solid/liquid interface. In here, we critically review the use of orthogonal chemical transformations (so‐called click chemistry) to achieve efficient surface modifications of materials ranging from gold and silica nanoparticles, polymeric films, and microspheres to fullerenes as well as carbon nanotubes. In addition, the functionalization of surfaces via click chemistry with biomolecules is explored. Although a large host of reactions fulfilling the click‐criteria exist, pericyclic reactions are most frequently employed for efficient surface modifications. The advent of the click chemistry concept has led—as evident from the current literature—to a paradigm shift in current approaches for materials modification: Away from unspecific and nonselective reactions to highly specific true surface engineering.     

In situ Surface Functionalization of Hydrophilic Silica Nanoparticles via Flame Spray Process

Hydrophobic silica nanoparticles grafted with a high amount of organic molecules were successfully prepared by an in situ functionalization method in flame spray pyrolysis(FSP) process. Hydrophilic Si O2 nanoparticles were converted into hydrophobic ones by silylation between 3-methacryloxypropyltrimethoxyl silane(MPS) and silica's surface hydroxyl groups. The freshly formed silica nanoparticles in flame were continuously functionalized by a fine spray of 3-methacryloxypropyltrimethoxyl silane(MPS) solution at a preferred temperature. The functionalization extent, morphology structure and size of silica nanoparticles were characterized by transmission electron microscopy(TEM), Brunauer–Emmett–Teller(BET), thermogravimetric analysis(TGA), Fourier transform infrared spectroscopy(FT-IR) and X-ray photoelectronic spectroscopy(XPS). The influence of concentration, pH value and pre-activation of organic silane solution on the surface grafting density was investigated in detail. The obtained silica nanoparticles had a higher MPS functional content of 15.0 wt%(an average density of 2.7 MPS molecule/nm2) than that of the silica modified by wet chemistry route, showing an excellent, stable hydrophobic property. The results have demonstrated that the in situ FSP functionalization process is a simple, effective and promising route for the scalable preparation of advanced, hydrophobic nanomaterials.     

Study of ZnO Nanoparticles Growth Through Successive Chemical Solution Deposition onto Solid Substrates Patterned with Metallic Nanoparticles

We investigate the ability of gold nanoparticles of different size, shape, and organization to control the growing process of ZnO semiconductor nanoparticles onto solid substrates through the successive chemical solution deposition (SCSD) method. Flower-like assemblies of ZnO nanostructures were grown successfully on periodic arrays of triangular gold nanoparticles fabricated by nanosphere lithography and randomly deposited colloidal gold nanospheres. Their morphology, crystallinity, phase purity, and vibrational properties were correlated with the metallic features of the substrates.     

Propagation of Surface Acoustic Pulses Generated by a Femtosecond Laser in Thin Films on Solid Substrates

The technique of phase velocity dispersion measurements of surface acoustic waves in a thin film-substrate system was demonstrated. The excitation of surface acoustic waves (SAWs) was quite efficient with femtosecond laser pulses, and the damage of the surface was minimized. The measurements were performed with films of Al deposited on silicon wafers. The errors in the determination of the phase velocity and absorption were analyzed. The temperature changes in the propagation velocity on bare Si wafers were also measured. The data obtained permitted estimation of the accuracy of the temperature determination from measurements with SAW pulses.     

Fabrication of Coated/Uncoated Magnetic Nanoparticles to Determine Their Surface Properties

Fabrication of coated and uncoated magnetic nanoparticles (MNPs) was achieved in the present study. The preparation and characterization of MNPs were confirmed by Fourier transform infrared spectroscopy (FTIR) spectroscopy, streaming potential (SP), and magnetic force microscopy (MFM) techniques. Coated and uncoated nanoparticles were analyzed by dynamic light scattering method to obtain the mean size of nanoparticles. The SP was used to record the electrical surface charge of nanoparticles. The results obtained revealed that the bare nanoparticles were negative charged at higher pH (pH > 6.0) while coated nanoparticles were positive charged at lower pH (pH < 6.0). The porosity of surface of bare and coated nanoparticles was shown by MFM.     

Autonomous Surface Reconciliation of a Liquid-Metal Conductor Micropatterned on a Deformable Hydrogel

Spreading liquid droplets on solid surfaces is a core topic in physical chemistry with significant technological implications. Liquid metals, which are eutectic alloys of constituent metal atoms with low melting temperatures, are practically useful, but difficult to spread on solid surfaces because of their high surface tension. This makes it difficult to use liquid metals as deformable on-board microcircuitry electrodes, despite their intrinsic deformability. In this study, it is discovered that eutectic gallium–indium (EGaIn) can be spread onto the surface of chemically cross-linked hydrogels consisting of aliphatic alkyl chains with numerous hydroxyl groups ( OH), thus facilitating the development of directly micropatterned EGaIn electrodes. More importantly, EGaIn patterned on a hydrogel autonomously reconciliates its surface to form a firm hydrogel interface upon mechanical deformation of the hydrogel. This autonomous surface reconciliation of EGaIn on hydrogels allows researchers to reap the benefits of chemically modified hydrogels, such as reversible stretching, self-healing, and water-swelling capability, thereby facilitating the fabrication of superstretchable, self-healable, and water-swellable liquid-metal electrodes with very high conductance tolerance upon deformation. Such electrodes are suitable for a variety of deformable microelectronic applications.     

Microgranules and Nanoparticles on Their Surfaces

This review considers advances in the fabrication of metallic, oxide, sulfide, carbon, BN, and other microgranules—the building blocks of porous materials for various applications. It is shown that attaching nanoparticles to the surface of microgranules alters some of the most important properties of the matrix and offers the possibility of creating composite materials with unique physical properties and reactivity.     

Radical-scavenging Ability of Hydrophilic Carbon Nanoparticles: From Fullerene to Its Soot

We have recently developed a facile synthetic method for highly water-soluble fullerene, so-called fullerenol, for the treatment of fullerene with hydrogen peroxide. This method was applied to fullerene soot to yield the corresponding new hydrophilic carbon materials, and the obtained products were subjected to infrared spectroscopy and elemental analysis. The DLS particle size analysis demonstrated the relatively high dispersion of hydrophilic fullerene soot with a diameter of ?70 nm in water, while the hydrophilic activated carbon obtained by the same treatment showed the larger aggregation with diameters of 200 and 970 nm. The surface analysis using FE-SEM showed the difference in morphology between fullerene soot and activated carbon as well as between before and after hydrophilic treatment of the soot with hydrogen peroxide. Moreover, this hydrophilic fullerene soot exhibited high antioxidant activity (%AOA) up to 87% compared with fullerenol C₆₀(OH)₃₆ (54%) and C₆₀ (50%) evaluated by β-carotene bleaching method.     

Unconventional Atomic Structure of Graphene Sheets on Solid Substrates

The atomic structure of free‐standing graphene comprises flat hexagonal rings with a 2.5 Å period, which is conventionally considered the only atomic period and determines the unique properties of graphene. Here, an unexpected highly ordered orthorhombic structure of graphene is directly observed with a lattice constant of ≈5 Å, spontaneously formed on various substrates. First‐principles computations show that this unconventional structure can be attributed to the dipole between the graphene surface and substrates, which produces an interfacial electric field and induces atomic rearrangement on the graphene surface. Further, the formation of the orthorhombic structure can be controlled by an artificially generated interfacial electric field. Importantly, the 5 Å crystal can be manipulated and transformed in a continuous and reversible manner. Notably, the orthorhombic lattice can control the epitaxial self‐assembly of amyloids. The findings reveal new insights about the atomic structure of graphene, and open up new avenues to manipulate graphene lattices.     

纳米粒子在固体基质表面的吸附

分析了与纳米粒子在固体基质表面的吸附机理相关的问题,综述了一些纳米粒子在固体基质表面上的吸附.通过控制纳米粒子和固体基质的组成,对纳米粒子和固体基质表面进行修饰等,可以使溶液中的纳米粒子靠静电作用、疏水作用、络合作用、氢键、磁性作用、粒子之间的毛细作用等在固体基质表面上吸附.在纳米粒子吸附的过程中,水力作用对吸附有重要影响.纳米粒子被固体基质表面吸附的可逆性一般较差.结合吸附机理分析了金纳米粒子在无机和有机固体基质表面上的吸附、铂纳米粒子在聚电解质表面上的吸附、带正电的发光纳米粒子在纤维上的吸附、磁性纳米粒子在磁性基质上的吸附以及量子点在藻细胞上的吸附等.在上述分析的基础上展望了纳米粒子在固体基质表面上吸附的研究方向.     

Surface Tailoring of Nanoparticles via Mixed‐Charge Monolayers and Their Biomedical Applications

The recent convergence of nanomaterials and medicine has provided an expanding horizon for people to achieve encouraging advances in many biomedical applications such as cancer diagnosis and therapy. However, to realize desirable functions in the rather complex biological systems, a suitable surface coating is greatly in need for nanoparticles (NPs), regardless of the species. In this review, a recently developed surface modification strategy is highlighted—mixed‐charge monolayers—with an emphasis on the nanointerfaces of inorganic NPs. Two typical mixed‐charge gold NPs (AuNPs) prepared from surface modifications with different combinations of oppositely charged alkanethiols are shown as detailed examples to discuss how the mixed‐charge monolayer can help NPs meet the criteria for in vitro and in vivo biomedical applications, including those critical issues like colloidal stability, nonfouling properties, and smart responses (pH‐sensitivity) for tumor targeting.     

固体脂质纳米粒的制备和研究进展

固体脂质纳米粒是近年来发展起来的一类新型载体给药系统，由于其长效、无毒、良好靶向性等优点，拥有广阔的发展前景。本文参考了国内外诸多有代表性的论文，就这类载体的制备、常用检测分析方法、剂型应用及其发展趋势等方面加以阐述。