The influence of nanoparticles on the domain orientation in a particle co-operated self-assembly process in thin diblock copolymer films is investigated toward the preparation of ordered magnetic nanoparticle arrays. Thin films are prepared from a mixture of chemically masked iron oxide nanoparticles and a polystyrene-block-poly (methyl methacrylate) diblock copolymer. The resulting nanostructures are investigated with grazing incidence small-angle X-ray scattering, atomic force microscopy and scanning electron microscopy. Nanoparticles arrange themselves spontaneously inside the upright cylindrical domains due to the selective affinity to the poly (methyl methacrylate) minority phase during the microphase separation process and due to the balance of the surface free energies between the polymers and the nanoparticle coating after annealing. The incorporation of the nanoparticles inside the cylindrical domains increases the diameter of the cylindrical domains and the distance between two neighboring domains. A spatially ordered arrangement of magnetic nanoparticles is observed below a critical concentration of 0.2 vol % for the investigated molecular weight of 77 kg/mol.

Evaporation of colloidal nanoparticle solutions is known to produce ordered monolayers of nanoparticles, self-assembled arrays of magnetic nanoparticles being of special importance for applications. The in situ time-resolved grazing-incidence small-angle x-ray scattering with the temporal resolution down to 100 ms was employed to study the self-assembling process of iron oxide nanoparticles after a colloidal drop was applied on a silicon substrate. The x-ray scattering contributions from the evaporating drop volume, drop surface, and substrate surface were monitored and separated. The x-ray scattering from the drop for the distances from the substrate surface larger than Ϸ80 m shows the absence of self-assembled clusters in the drop volume or self-assembled domains on the drop surface. These results indicate that the nanoparticle self-assembling occurs in the vicinity of the three-phase drop contact line. The ordered nanoparticle monolayer exhibits hexagonal close-packed arrangement.

Fe3O4/γ-Fe2O3 nanoparticles (NPs) based thin films were used as active layers in solid state resistive chemical sensors. NPs were synthesized by high temperature solution phase reaction. Sensing NP monolayers (ML) were deposited by Langmuir-Blodgett (LB) techniques onto chemoresistive transduction platforms. The sensing ML were UV treated to remove NP insulating capping. Sensors surface was characterized by scanning electron microscopy (SEM). Systematic gas sensing tests in controlled atmosphere were carried out toward NO2, CO, and acetone at different concentrations and working temperatures of the sensing layers. The best sensing performance results were obtained for sensors with higher NPs coverage (10 ML), mainly for NO2 gas showing interesting selectivity toward nitrogen oxides. Electrical properties and conduction mechanisms are discussed.

We report on a reference-free Raman spectroscopy method for a precise thickness determination of the multilayered graphene oxide flakes. The method is based on the normalization of the total integral intensity of D and G Raman bands to the integral intensity of the second-order optical phonon peak of the silicon substrate in the Raman spectrum. The normalization provides discrete ratio values corresponding to the number of graphene oxide layers in the respective flakes with the intensity linearly increasing with the number of layers. This provides a fast and robust determination of the thickness of graphene oxide flakes in terms of the layer number up to high values. A comparison with conventional spectrally resolved reflectivity mapping shows similar sensitivity, while selectivity to particular functional chemical groups is a bonus of the Raman-based method. Copyright

An in situ small-angle x-ray scattering study of the nanoparticle displacement in a self-assembled monolayer as a function of a supporting membrane strain is presented. The average nanoparticle spacing is 6.7 nm in the unstrained state and increases in the applied force direction, following linearly the membrane strain which reaches the maximum value of 11%. The experimental results suggest a continuous mutual shift of the nanoparticles and their gradual separation with the growing stress rather than nanoparticle islands formation. No measurable shift of the nanoparticles was observed in the direction perpendicular to the applied stress.

We report on an in-situ observation of the colloidal silver nanoparticle self-assembly into a close-packed monolayer at the air/water interface followed by a 2D to 3D transition. Using the fast tracking GISAXS technique, we were able to observe the immediate response to the compression of the self-assembled nanoparticle layer at the air/water interface and to identify all relevant intermediate stages including those far from the equilibrium. In particular, a new nonequilibrium phase before the monolayer collapse via the 2D to 3D transition was found that is inaccessible by the competing direct space imaging techniques such as the scanning and transmission electron microscopies due to the high water vapor pressure and surface tension.

Functionality of organic photonic devices is markedly influenced by the electronic band structure of the used materials. An easy and quick determination of the density of states function (DOS) in the whole energy range from HOMO to LUMO, including the presence of defect states in the band gap, is a prerequisite to a successful design of photonic devices. In this study we present the fine band gap electronic structure mapping in P3HT with two electrochemical spectroscopic methods: the energy-resolved electrochemical impedance spectroscopy (ER-EIS) and the kinetic sensitive voltcoulometry (VCM). We showed that the P3HT exposition to air results in the change of light-induced polaron states in the band gap. The electrochemically measured data are compared with those from the literature, obtained with combined optical spectroscopic methods, electrical methods, or first-principles calculations. The ER-EIS method has been shown as capable of providing valuable information on the DOS in the whole energy range from HOMO to LUMO, the VCM method opens the possibility to study separately the charge transfer (redox) processes with different kinetics.

Schematic representation of the GIWAXS measurements on HA and VA MoS2 layers.