One of the challenges in the development of molecular scale devices is the integration of nano-objects or molecules onto desired locations on a surface. This integration comprises their accurate positioning, their alignment, and the preservation of their functionality. Here, we proved how capillary assembly in combination with soft lithography can be used to perform DNA molecular combing to generate chips of isolated DNA strands for genetic analysis and diagnosis. The assembly of DNA molecules is achieved on a topologically micropatterned polydimethylsiloxane stamp inducing almost simultaneously the trapping and stretching of single molecules. The DNA molecules are then transferred onto aminopropyltriethoxysilane-coated surfaces. In fact, this technique offers the possibility to tightly control the experimental parameters to direct the assembly process. This technique does not induce a selection in size of the objects, therefore it can handle complex solutions of long (tens of kbp) but also shorter (a few thousands of bp) molecules directly in solution to allow the construction of future one-dimensional nanoscale building templates.

We investigated a simple and low-cost route for the formation of metallic nanodots on Si substrates ordered in size and position and laterally isolated by SiO2. The method was based on a two-step process: (i) the formation of a nanopattern of ordered cylindrical pores on oxidized Si substrates through self-assembly of diblock copolymers, and successive oxide dry etching down to the Si; (ii) the deposition of gold nanodots and thermal diffusion over the nanopatterned oxide substrates. After diffusion, the nanodot density outside the nanopores was found to decrease, and most of the nanodots were found to saturate the nanopores. The process was followed in situ by transmission electron microscopy (TEM) and ex situ by scanning electron microscopy (SEM) analysis for different thermal budgets. This patterned substrate can be used for catalyst mediated growth, for example, through vapor-liquid-solid (VLS), of nanowires for the formation of absorber materials in novel photovoltaic architectures.

Highly aligned microstrip patterns consisting of biaxial CaF2 nanorods have been successfully self-assembled by simply using capillary pressure. The alignment direction of the microstrips is perpendicular to the flux direction during nanorod growth. Aligning behavior and pattern width can be controlled by changing wetting time and surface tension of the liquid. Higher surface tension and longer wetting time result in wider pattern width and better alignment. Taller nanorod height also results in better pattern alignment. Simple and cost-effective self-aligned microstrip patterns can be potentially used as a template for various applications, such as superhydrophobic surfaces, tissue scaffolds, microchannels, and optical polarizers.

The heterocomponent films of polypyridine ruthenium(II) complexes and methyl viologen derivatives, and polypyridine ruthenium(II) complexes and alkyl chain derivatives have been successfully obtained using a layer-by-layer fabrication method. We determined their photocurrent generation properties and noted that the photocurrent generation strongly depended on the inner layer. A higher photocurrent generation in the donor–acceptor film was obtained than in a single-component film of the chromophore.

Thin-film aggregation characteristics of a series of oligothiophenes with a central thieno[3,4-b]thiophene ester unit and 4 (M5), 8 (M9), and 16 (M17) regioregular hexylthiophene units were investigated. These oligomers exhibited length-dependent self-assembly characteristics upon spin coating. M9 formed long fibers, while M5 and M17 formed random domains. Grazing incidence x-ray diffraction was performed to understand the reason for this length dependence. The M5 had a dominant ester–ester interaction that disrupted long-range order. The M9 morphology was due to a balance of orthogonal backbone and ester effects, which imposed long-range order on the M9 aggregates. Meanwhile, the M17 ester chain had a smaller relative contribution to packing and functioned as a molecular defect, disrupting long-range order. As a result, though the local self-assembly between monomers was very similar for the molecules, backbone length dependent changes in intermolecular forces dominated long-range structure. The analysis of self-assembly characteristics in these materials provides guidance in the design of organic conjugated materials for use in semiconductor devices.

An increasing number of technologies benefit from or require patterned surfaces on a micro- and nanoscale. Methods developed to structure polymer films can be adapted to fabricate low-cost patterned ceramics using nonlithographic techniques, for example, dewetting and phase separation in thin films. In this paper we describe a simple patterning process that does not require a template and is able to produce Fe2O3 microdots with a spatial periodicity. Our method involves the dewetting of a silicon substrate by a thin metal oxide precursor film, in which the liquid film breaks up because of fluctuations in the film thickness induced by solvent evaporation or an external applied electric field. The patterning is followed by a thermal treatment at 550 °C to produce crystalline Fe2O3 microdots with a diameter range of 200 nm to 3 μm.

The current study revealed the effects of reflow temperature and the reflow time on the interfacial embrittlement of SnBi/Cu joints. When the reflow temperature is below 220 °C, the joints reflowed for 150 min often fail in brittle mode because the Bi atoms from the SnBi solder easily segregated at the Cu3Sn/Cu interface. In contrast, Bi embrittlement did not occur for joints reflowed at above 260 °C for 150 min because the Bi particles were frozen in the Cu3Sn layer during the formation of intermetallic compounds (IMC) at the initial reflow stage, mainly located at the Cu3Sn grain boundary. It is interesting to note that the Bi embrittlement did occur when the joints were reflowed at above 260 °C for 250 min, which should be attributed to Bi diffusion. It is concluded that the Bi particles are frozen in the Cu3Sn layer with increasing reflow temperature, that cannot eliminate Bi embrittlement, and can only delay the occurrence of Bi embrittlement.

We have developed novel photovoltaic systems composed of the fullerene derivative (6,6)-phenyl C61 butyric acid methyl ester as electron acceptor with a second functional organic molecule, in this case bacteriochlorophyll c, as the light-harvesting and photosensitizing part. It was found that heat treatment of a thin film of bacteriochlorophyll c altered the morphological states of the aggregates and conductivity of the thin film could be regulated through the annealing process. Blended fullerene derivative and bacteriochlorophyll c thin films were fabricated on the surface of an indium-tin oxide/poly(ethylene dioxythiophene) doped with polystyrene sulfonic acid substrate layer and their photovoltaic properties were characterized and evaluated. Formation of fullerene-coordinated bacteriochlorophyll c complex was confirmed by changes in the visible absorption spectra and by FTIR. Such complexation promoted generation of photocurrent in the region of the Qy band and the current density of the thin film increased. A maximum incident photon-to-current conversion efficiency of 5.1% was attained at 745 nm.

Surface-enhanced Raman scattering (SERS) coupled with micro- or nanofluidics integrated into optofluidic devices offer many advantages over conventional SERS conducted under static conditions. Higher reproducibility, larger intensity, as well as greater enhancement can be achieved by efficient mixing of analytes and SERS enhancers under a continuous flow. Progress and advances in the past 10 years, including the design of channels and efficient mixing conditions, assemblies of SERS substrates for optimal enhancement, and advantages of optofluidic-SERS analysis, are reviewed. Recent results show that optofluidic-SERS effectively overcomes many of the difficulties and limitations plaguing conventional SERS and the novel technique has enormous application potential.

TiO2 nanotube arrays were synthesized by anodic oxidation on a pure titanium substrate in solutions containing 0.175 M NH4F composed of mixtures with different volumetric ratios of DI water and glycerol. According to the results of the current curve recorded during anodization, the time of the first sharp current slope (corresponding to the initial oxide layer formation time) was found to vary from 8 to 171 s depending not only upon the water content in the electrolytes but also upon the voltage. The current curves exhibit oscillation with different amplitudes and periods. In combination with the scanning electron microscope (SEM) images, a growth mechanism, layer-by-layer model, of TiO2 nanotube arrays was presented. Based on this mechanism, many phenomena that appeared during anodization can be reasonably explained. Our results would be helpful for the design of nanoarchitectures in related material systems.

We present a versatile and flexible method to sequentially self-assemble micron-scale components at specific locations onto unconventional substrates, such as glass and plastic. In this method, components are independently batch fabricated and assembled onto a series of receptor sites incorporated onto a substrate in a fluid medium. Initially, all self-assembly sites are blocked with a photoresist polymer. Controlled light exposure can be used to remove the polymer and make a site available for receiving a microcomponent. By repeating this procedure, various microcomponents may be integrated onto specific locations on the substrate. To demonstrate the process, we prepared four types of 20 μm thick, 320 μm diameter circular silicon components and showed their optically controllable self-assembly in arrays of 640 receptor sites on glass and plastic with yields reaching 85%. The integration and operation of two types of functional components, red light-emitting diodes and silicon resistors, on plastic substrates was also demonstrated.

We report the processing and immobilization of enzyme Ribonuclease A (RNase A) onto SiO2 glass collectors using the matrix assisted pulsed laser evaporation (MAPLE) technique. The experiments were performed inside a stainless steel irradiation chamber. A pulsed UV KrF* (λ = 248 nm, τFWHM ≈ 25 ns, ν = 10 Hz) excimer laser source was used for the irradiations. The laser fluence was varied in the range 0.4–0.7 J/cm2. The morphology of the obtained films was investigated by atomic force microscopy (AFM) and their structure and composition by Fourier transform infrared spectroscopy (FTIR). The FTIR spectra of the films obtained from composite MAPLE targets consisting of 1% (w/v) RNase A in Hepes-KOH 10 mM pH 7.5 buffer exhibit the same bands as the spectrum of the initial, nonirradiated material. The enzymatic activity of the obtained structures was analyzed using synthetic substrate polycytidylic acid (poly(C)). The poly (C) cleavage by the immobilized enzyme and the products of formation were analyzed by means of reverse phase high performance liquid chromatography (HPLC).

Technological progress in the synthesis and characterization of nanometer-scale structures has improved understanding of molecular and colloidal aggregation, self-assembly, and crystal growth. While substrates are commonly used to control nucleation and growth in metal and semiconductor crystals, their use in protein epitaxy has been limited by the lack of substrate structures commensurate with protein sizes. In this paper we describe the use of polished cross sections of amorphous alumina–silica nanolaminates whose periods varied from 8 to 200 nm in the formation of self-assembled monolayers of the protein macromolecule aspartate transcarbamoylase (ATCase). Scanning force microscopy images of rapidly deposited ATCase demonstrates one-dimensional protein ordering along 13.5 nm wide silica nanolaminate. Numerical studies of irreversible adhesion indicate that patterning can induce a higher degree of ordering by varying the substrate periodicity. We expect this to have implications for nucleation and growth of both two-dimensional crystalline layers and bulk protein crystals.

This work investigated the cell labeling of 12-nm meso-2,-3-dimercaptosuccinic acid (DMSA)-coated Fe3O4 magnetic nanoparticles with multiple mammalian cells. Six different cells, including RAW264.7, Hepa1-6, THP-1, HepG2, HeLa, and HL-7702, were treated with the nanoparticles at various concentrations (20~100 μg/mL) for different times (2~72 h), and the labeling effect was evaluated by observing the intracellular internalization of the nanoparticles with Prussian blue staining and measuring the corresponding cellular iron loading with colorimetric assay. The results demonstrated that the nanoparticles could label all cells studied. However, the labeling efficiency was not the same between different cells, which depended on the cell types, the nanoparticles’ concentration, and the time of treating cells with the nanoparticles. In comparison, RAW264.7 was labeled more effectively than other cells at any concentration of the nanoparticles. The iron loading of RAW264.7 significantly increased with the concentration of the nanoparticles and the treatment time. However, both human liver cells (HepG2 and HL-7720) were labeled with the lowest iron loading. The measurement of cell viability revealed that the growth of all cells was not affected by the nanoparticles at a common in vivo application dose of iron nanoparticles (30 μg/mL), demonstrating that the nanoparticles have better biocompatability.

Ordered nanoparticle assemblies can exhibit collective properties that are quite different from those displayed by the individual nanoparticles or their bulk counterpart. This paper reviews recent progress on the assembly of superparamagnetic nanoparticles, with emphasis on different strategies for their chemical fabrication with highly ordered nanostructures as well as their novel properties. Prospective applications of superparamagnetic nanoparticles in the fields of photonic crystals, biomedicine, and biology are also discussed.

A 〈110〉 oriented Tb0.3Dy0.7Fe1.95 alloy rod was annealed at 500 °C under a magnetic field of 0.3 T, which was applied 35° away from the rod axis. X-ray diffraction characterization and optical microscopy observation showed that both the crystal orientation and morphologies were retained after magnetic annealing. Magnetic force microscopy images exhibited obvious change of the magnetic domain configurations. The magnetostrictive performance was changed drastically. Saturation axial magnetostriction λ‖s increased from 1023 to 1650 ppm by the ratio of 61.3%, but saturation perpendicular magnetostriction λ⊥s decreased from −802 to −624 ppm. Maximum magnetostrictive strain coefficients d33 and d31 were found to be enhanced by 29.3% and 32.6%, respectively. In addition, the fields for obtaining both optimum d33 and d31 decreased, which indicates that better magnetostrictive performance can be achieved at lower external fields after magnetic annealing.

Both low and high resistance states (which were written by voltage application in a local region of NiO/Pt films using conducting atomic force microscopy [C-AFM]) were observed with scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The writing regions are distinguishable as dark areas in a secondary electron image and thus can be specified without using a complicated sample fabrication process to narrow down the writing regions such as the photolithography technique. In addition, the writing regions were analyzed using energy-dispersive x-ray spectroscopy (EDS) mapping. No difference between the inside and outside of the writing regions is observed for all the mapped elements including C and Rh. Here, C and Rh are the most probable candidates for contamination that affect the secondary electron image. Therefore, our results suggested that the observed change in the contrast of the secondary electron image is related to the intrinsic change in the electronic state of the NiO film and a secondary electron yield is correlated to the physical properties of the film.

The temperature dependence of the various electric relaxation times in the perovskite oxide CaCu3Ti4O12 (CCTO) is determined (i) by trap state spectroscopy and (ii) by the dielectric loss function. A similarity in both number and properties of the (i) and (ii) relaxation times was found, suggesting that the dielectric response is strongly correlated with the trap state relaxation, although some differences remain. One or more dipoles developing charged trap states are considered responsible, and the experimental dielectric response of CCTO and Mn substituted CCTO are explored.

As deposited amorphous and crystallized thin films of Ti 37.5% Si alloy deposited by pulsed laser ablation technique were irradiated with 100 keV Xe+ ion beam to an ion fluence of about 1016 ions-cm−2. Transmission electron microscopy revealed that the implanted Xe formed amorphous nanosized clusters in both cases. The Xe ion-irradiation favors nucleation of a fcc-Ti(Si) phase in amorphous films. However, in crystalline films, irradiation leads to dissolution of the Ti5Si3 intermetallic phase. In both cases, Xe irradiation leads to the evolution of similar microstructures. Our results point to the pivotal role of nucleation in the evolution of the microstructure under the condition of ion implantation.