Two dimensional nano-dot array engineering of block copolymer surface micelles on water surface

When an amphiphilic block copolymer is directly spread from an organic solution, the morphology of the surface micelles is not in general controlled because the structure is rapidly frozen after the solvent evaporation. In contrast, we have developed a new versatile method to generate highly regular ordered nanopatterns of the surface micelles on water, which involves the process of two dimensional (2D) hybridization with a polar liquid crystal molecule, 4′-pentyl-4-cyanobiphenyl (5CB) [Langmuir 22 (2006) 5233]. The present work extends this approach using a family of diblock copolymers of polystyrene-block-poly(4-vinylpyridine) changing the chain length of the two polymer blocks. It is found here that the dot-to-dot distance and the dot size can be precisely controlled on-demand by the length of the polymer blocks. Such structural regulations cannot be attained without the 5CB hybridization. Due to the high reproducibility of the morphology formation, this process should be of practical significance to ‘engineer’ the 2D patterns in the range of some tens of nanometers.     

Surface characterization of aspirin crystal planes by dynamic chemical force microscopy

Tapping mode (TM) atomic force microscopy (AFM) has been applied in a novel fashion to characterize and distinguish the (001) and (100) surfaces of individual aspirin crystals. The surface characterization was achieved by amplitude-phase, distance (a-p,d) measurements employing gold-coated AFM probes functionalized with self-assembled monolayers (SAM). Experiments using model probes coated with -CH3 and -COOH terminated SAMs have been performed on the two aspirin crystal planes (001) and (100). Results indicate that the hydrophobic -CH3 terminated AFM probes had a greater degree of interaction with the crystal plane (001), whereas the -COOH terminated AFM probes had a larger interaction with the crystal plane (100). Interpretation of these data, based upon the chemistries of the probes, correlates with current understanding of the crystal surface chemistry derived from X-ray diffraction data and dissolution rate studies.     

Electrostatic Properties of Ideal and Non‐ideal Polar Organic Monolayers: Implications for Electronic Devices

Molecules in (or as) electronic devices are attractive because the variety and flexibility inherent in organic chemistry can be harnessed towards a systematic design of electrical properties. Specifically, monolayers of polar molecules introduce a net dipole, which controls surface and interface barriers and enables chemical sensing via dipole modification. Due to the long range of electrostatic phenomena, polar monolayer properties are determined not only by the type of molecules and/or bonding configuration to the substrate, but also by size, (dis‐)order, and adsorption patterns within the monolayer. Thus, a comprehensive understanding of polar monolayer characteristics and their influence on electronic devices requires an approach that transcends typical chemical designs, i.e., one that incorporates long‐range effects, in addition to short‐range effects due to local chemistry. We review and explain the main uses of polar organic monolayers in shaping electronic device properties, with an emphasis on long‐range cooperative effects and on the differences between electrical properties of uniform and non‐uniform monolayers.     

Self-assembled monolayer of 3-aminopropyltrimethoxysilane for improved adhesion between aluminum alloy substrate and polyurethane coating

A good adhesion between a polymer coating and a metal or metal alloy substrate such as Al 2024-T3 plays a critical role in corrosion protection of metal substrates. In our study, a self-assembled monolayer film of 3-aminopropyltrimethoxysilane was formed on Al 2024-T3 substrate by covalent bonding. The adhesion property of a self-priming polyurethane coating was evaluated by pull-off adhesion test, wet tape test and thermal cycling test. All the testing results indicate that both dry and wet adhesion properties of the polyurethane coating were improved significantly after APS treatment of Al 2024-T3 in polar solvents such as methanol and acetone. In nonpolar solvents such as hexane, the APS treatment led to inconsistent improvement or sometime decreased adhesion of polyurethane coating. X-ray photoelectron spectroscopic study revealed that while a monolayer film was formed on the aluminum alloy surface after treating the substrate with APS in methanol and acetone, a multilayer film was formed on the substrate surface when the treatment was conducted in hexane. The APS monolayer film served as a covalent bond linkage between polymer coating and aluminum alloy substrates, which led to the increased adhesion property of polymer coating and corrosion resistance of the metal alloy substrate.     

不同化学官能团对无机相碳酸钙晶体的调控

选择了具有代表性的化学官能团, 羟基(—OH)、 氨基(—NH₂)、 羧基(—COOH)和甲基(—CH₃), 通过在单晶硅片上进行接枝改性, 并在改性后的硅基底上进行碳酸钙体外矿化模拟实验, 以研究这些官能团对碳酸钙矿化的影响。利用接触角实验对接枝效果进行了分析, 结果显示接枝成功。根据拉曼光谱(Raman)确定了碳酸钙的晶型; 采用扫描电子显微镜(SEM)获得了碳酸钙的形貌、 尺寸、 数量和取向信息。结果显示羟基化硅基底上出现了方解石的聚集; 氨基化硅基底和羧基化硅基底上均出现一定量的球文石, 但形貌各异; 甲基化硅基底上晶体数目较少。通过对结果的对比分析, 认为羟基和甲基对碳酸钙的晶型选择无明显影响, 氨基和羧基能通过对碳酸根离子或钙离子的吸附而诱导球文石结晶。      

Formation of lambda-DNA's in parallel- and crossed-line arrays by molecular combing and scanning-probe lithography

With the combination of a molecular combing technique and scanning-probe lithographic patterning, lambda-DNA's were stretched and aligned to form line array structures on patterned organic monolayer surfaces. The pattern was generated by anodizing a silicon surface using scanning-probe lithography to implant a polar organic layer in the middle of a nonpolar layer. The molecule in the polar layer, (aminopropyl)triethoxysilane (APS), has a -NH(3)(+) terminal group, which interacts strongly with phosphate backbone of DNA and provides a site for selective attachment of DNA. When parallel lines of APS were patterned, followed by combing along the lines, a single DNA was attached from the very top of each line and stretched along the line all the way to the bottom. The DNA-APS interaction was strong enough to withstand the second combing applied perpendicular to the first one. Thereby, the crossed-line array of DNA's was formed on the crossed-line array pattern of APS on a silicon substrate.     

Investigation of adsorption behavior of bisphenol A on well fabricated organic surfaces using surface plasmon resonance spectroscopy

Molecular adsorption of bisphenol A (BPA) on three types of self-assembled monolayers with different functionalities, such as -CH3, -SH, and -COOH, was examined using surface plasmon resonance (SPR) spectroscopy. BPA molecules in an aqueous solution were easily adsorbed onto a hydrophobic surface compared to a hydrophilic surface. Sorption behavior of BPA into poly(2-methoxyethyl acrylate) (PMEA) layer, which is known as a biocompatible polymer, was also investigated. Sorption and desorption dynamics of BPA into PMEA were found to be very rapid and quite reversible. The swelling of PMEA by sorption of BPA results in the change in SPR angle and allows one to quantify the BPA concentration below 100 ppm. In addition, the transport mechanism of BPA within the membrane of organ can be inferred by the experimental results.     

Probing molecular junctions using surface plasmon resonance spectroscopy

The optical absorption spectra of nanometer-thick organic films and molecular monolayers sandwiched between two metal contacts have been measured successfully using surface plasmon resonance spectroscopy (SPRS). The electric field within metal-insulator (organic)-metal (MIM) cross-bar junctions created by surface plasmon-polaritons excited on the metal surface allows sensitive measurement of molecular optical properties. Specifically, this spectroscopic technique extracts the real and imaginary indices of the organic layer for each wavelength of interest. The SPRS sensitivity was calculated for several device architectures, metals, and layer thicknesses to optimize the organic film absorptivity measurements. Distinct optical absorption features were clearly observed for R6G layers as thin as a single molecular monolayer between two metal electrodes. This method also enables dynamic measurement of molecular conformation inside metallic junctions, as shown by following the optical switching of a thin spiropyran/polymer film upon exposure to UV light. Finally, optical and electrical measurements can be made simultaneously to study the effect of electrical bias and current on molecular conformation, which may have significant impact in areas such as molecular and organic electronics.     

Recent Progress in Metal‐Free Covalent Organic Frameworks as Heterogeneous Catalysts

Covalent organic frameworks (COFs), connecting different organic units into one system through covalent bonds, are crystalline organic porous materials with 2D or 3D networks. Compared with conventional porous materials such as inorganic zeolite, active carbon, and metal‐organic frameworks, COFs are a new type of porous materials with well‐designed pore structure, high surface area, outstanding stability, and easy functionalization at the molecular level, which have attracted extensive attention in various fields, such as energy storage, gas separation, sensing, photoluminescence, proton conduction, magnetic properties, drug delivery, and heterogeneous catalysis. Herein, the recent advances in metal‐free COFs as a versatile platform for heterogeneous catalysis in a wide range of chemical reactions are presented and the synthetic strategy and promising catalytic applications of COF‐based catalysts (including photocatalysis) are summarized. According to the types of catalytic reactions, this review is divided into the following five parts for discussion: achiral organic catalysis, chiral organic conversion, photocatalytic organic reactions, photocatalytic energy conversion (including water splitting and the reduction of carbon dioxide), and photocatalytic pollutant degradation. Furthermore, the remaining challenges and prospects of COFs as heterogeneous catalysts are also presented.     

微波等离子体在不锈钢上制备抵抗蛋白质吸附表面

本文利用微波低温等离子体表面改性技术,对医用316L型不锈钢进行改性以增强其表面抵抗蛋白质粘附的能力,提高生物相容性。经过X射线光电子能谱和衰减全反射傅立叶变换红外光谱的分析和表征,发现沉积的涂层为类PEG结构,表面主要聚集大量—CH2—CH2—O键,并且氧原子和碳原子在金属和有机物界面层之间形成共价键结合。血浆蛋白吸附试验显示,与改性前相比,等离子体沉积在不锈钢表面的类PEG涂层可以有效抵抗蛋白质粘附。     

液相电沉积类金刚石薄膜的相关物理化学问题

利用液相电沉积技术制备了含氢类金刚石薄膜(ＤＬＣ);讨论了应用电位和沉积碳源对沉积过程和薄膜结构的影响;结果表明有高介电常数、低粘度、分子中甲基基团直接与极性基团键合的有机液体是合适的沉积碳源;通过增加沉积电位将有利于薄膜中ｓｐ^３碳的生长;最后,作者提出了液相沉积类金刚石薄膜的反应机理－极化－反应机制,在电场的作用下,有机分子被极化并在电极表面反应生成ＤＬＣ薄膜和其他产物．     

Steering molecular organization and host-guest interactions using two-dimensional nanoporous coordination systems

Metal-organic coordination networks (MOCNs) have attracted wide interest because they provide a novel route towards porous materials that may find applications in molecular recognition, catalysis, gas storage and separation. The so-called rational design principle-synthesis of materials with predictable structures and properties-has been explored using appropriate organic molecular linkers connecting to metal nodes to control pore size and functionality of open coordination networks. Here we demonstrate the fabrication of surface-supported MOCNs comprising tailored pore sizes and chemical functionality by the modular assembly of polytopic organic carboxylate linker molecules and iron atoms on a Cu(100) surface under ultra-high-vacuum conditions. These arrays provide versatile templates for the handling and organization of functional species at the nanoscale, as is demonstrated by their use to accommodate C(60) guest molecules. Temperature-controlled studies reveal, at the single-molecule level, how pore size and chemical functionality determine the host-guest interactions.     

From an Organometallic Monolayer to an Organic Monolayer Covered by Metal Nanoislands: A Simple Thermal Protocol for the Fabrication of the Top Contact Electrode in Molecular Electronic Devices

In this contribution, a novel method for practical uses in the fabrication of the top contact electrode in a metal/organic monolayer/metal device is presented. The procedure involves the thermally induced decomposition of an organometallic compound, abbreviated as the TIDOC method. Monolayers incorporating the metal organic compounds (MOCs) [[4‐{(4‐carboxy)ethynyl}phenyl]ethynyl]‐(triphenylphosphine)‐gold, 1, or [1‐isocyano‐4‐methoxybenzene]‐[4‐amino‐phenylethynyl]‐gold, 2, were annealed at moderate temperatures (1: 150 °C for 2h and 2: 100 °C for 2 h), resulting in cleavage of the Au‐P or Au‐C bond and reduction of Au(I) to Au(0) as metallic gold nanoparticles (GNPs). These particles are distributed on the surface of the film resulting in formation of metal/molecule/GNP sandwich structures. Electrical properties of these nascent devices were determined by recording I–V curves with a conductive‐AFM. The I–V curves collected from these metal/organic monolayer/GNPs sandwich structures are typical of metal‐molecule‐metal junctions, with no low resistance traces characteristic of metallic short circuits observed over a wide range of set‐point forces. The TIDOC method is therefore an effective procedure for the fabrication of molecular junctions for the emerging area of molecular electronics.     

Aroused problems in the deposition of diamond-like carbon films by using the liquid phase electrodeposition technique

Hydrogenated diamond-like carbon (DLC) films were prepared by using liquid phase electrodeposition technique. The effects of the applied potential and the carbon sources on the deposition process and film structures were studied. It has been found that the organic liquids with high dielectric constants, small viscosities and the methyl group bonding to the polar group are appropriate carbon sources. The increasing of potential improves the formation of sp³ carbon during the deposition process. In a high electric field, organic molecules are polarized and reacted on the surface of the electrode, turning out DLC and other products. It is believed that the reaction follows a polarization-reaction mechanism.     

Nanodomain Swelling Block Copolymer Lithography for Morphology Tunable Metal Nanopatterning

Ordered metal nanopatterns are crucial requirements for electronics, magnetics, catalysts, photonics, and so on. Despite considerable progress in the synthetic route to metal nanostructures, highly ordered metal nanopatterning over a large‐area is still challenging. Nanodomain swelling block copolymer lithography is presented as a general route to the systematic morphology tuning of metal nanopatterns from amphiphilic diblock copolymer self‐assembly. Selective swelling of hydrophilic nanocylinder domains in amphiphilic block copolymer films during metal precursor loading and subsequent oxygen based etching generates diverse shapes of metal nanopatterns, including hexagonal nanoring array and hexagonal nanomesh and double line array in addition to common nanodot and nanowire arrays. Solvent annealing condition of block copolymer templates, selective swelling of hydrophilic cylinder nanodomains, block copolymer template thickness, and oxygen based etching methods are the decisive parameters for systematic morphology evolution. The plasmonic properties of ordered Au nanopatterns are characterized and analyzed with finite differential time domain calculation. This approach offers unprecedented opportunity for diverse metal nanopatterns from commonly used diblock copolymer self‐assembly.     

Effect of chemical termination of self-assembled organic monolayers on the tip induced local anodic oxidation of silicon(100)

We evaluated the scanning probe microscope based anodization process of silicon(100) terminated by organic monolayers of the same thickness but with different surface properties. The surface energy of these monolayers with its dispersive and polar component was determined by contact angle measurements. We discovered that the anodization oxide characteristics depend ceteris paribus clearly on the surface properties of the sample. With an increased polar component, and therefore hydrophilic character of the surface, the formed oxide structures became broader and thinner. On the other hand a hydrophilic surface allowed the generation of oxide structures at higher tip velocities and lower applied voltages. The absolute amount of formed oxide is independent of the monolayer indicating a dominating influence of initially formed oxide on the following oxidation process.     

Simple colloidal lithography approach to generate inexpensive stamps for polymer nano-patterning

In this work we propose a simple method, based on colloidal crystal monolayer templating, to obtain good quality stamps for polymer patterning. By metal evaporation over colloidal monolayers we fabricate (i) metal-coated colloidal crystals, and (ii) arrays of triangular nanoparticles on glass substrate, obtained by subsequently removing the colloids. The applicability of these two types of nanostructured surfaces as lithographic stamps is demonstrated by transferring their patterns onto polyvinyl alcohol polymer surfaces. The morphology of the resulting polymer nanostructures is analyzed by atomic force microscopy. The proposed nanolithographic technique is remarkable for its simplicity, decreased cost of stamp fabrication, and high resolution of achievable nanopatterns.     

High-resolution electron-beam patternable nanocomposite containing metal nanoparticles for plasmonics

Polymer nanocomposites containing noble metal nanoparticles are promising materials for plasmonic applications. In this paper, we report on a high-resolution negative-tone nanocomposite resist based on poly(vinyl alcohol) where silver nanoparticles and nanopatterns are simultaneously generated by electron-beam lithography. Our results indicate nanostructures with a relatively high concentration of nanoparticles and, consequently, an electromagnetic coupling among the nanoparticles. Therefore, the patternable nanocomposite described in this work may be a suitable material for future plasmonic circuitry.     

Metal–Organic Framework (MOF)‐Based Drug/Cargo Delivery and Cancer Therapy

Metal–organic frameworks (MOFs)—an emerging class of hybrid porous materials built from metal ions or clusters bridged by organic linkers—have attracted increasing attention in recent years. The superior properties of MOFs, such as well‐defined pore aperture, tailorable composition and structure, tunable size, versatile functionality, high agent loading, and improved biocompatibility, make them promising candidates as drug delivery hosts. Furthermore, scientists have made remarkable achievements in the field of nanomedical applications of MOFs, owing to their facile synthesis on the nanoscale and alternative functionalization via inclusion and surface chemistry. A brief introduction to the applications of MOFs in controlled drug/cargo delivery and cancer therapy that have been reported in recent years is provided here.     

Reduction of 3T3 Fibroblast Adhesion on SS316L by Methyl-Terminated SAMs

Inhibiting the non-specific adhesion of cells and proteins to biomaterials such as stents, catheters and guide wires is an important interfacial issue that needs to be addressed in order to reduce surface-related implant complications. Medical grade stainless steel 316L was used as a model system to address this issue. To alter the interfacial property of the implant, self assembled monolayers of long chain phosphonic acids with -CH(3), -COOH, -OH tail groups were formed on the native oxide surface of medical grade stainless steel 316L. The effect of varying the tail groups on 3T3 fibroblast adhesion was investigated. The methyl terminated phosphonic acid significantly prevented cell adhesion however presentation of hydrophilic tail groups at the interface did not significantly reduce cell adhesion when compared to the control stainless steel 316L.