Mario Kotlar

Morphological and Electrical Properties of Stretched Nanoparticle Layers

To examine perspectives of nanoparticle films in the role of active elements in strain sensors, morphological and electrical properties of self-assembled Au nanoparticle monolayer prepared by modified Langmuir-Schaefer technique onto supporting Mylar foil were studied under elongation. Along the probing of electrical response (characterized by the gauge factor of about 60), the small-angle x-ray scattering (SAXS) characterization assessed an average interparticle distance change, which was shown to vary proportionally to the substrate elongation. The approach allowed to unambiguously address the mechanism of the deformation-resistivity transduction.

P3HT:PCBM Based Organic Solar Cells: Structure Optimization and Improving External Quantum Efficiency by Plasmonic Nanoparticles Incorporation

We optimized morphology of the active layer of organic solar cells based on poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction. The optimization process includes a 20 min solvent annealing followed by a 5 min thermal annealing at 110 ∘C. After such a procedure a ∼ 3 % power conversion efficiency (PCE) was achieved. Adding of gold plasmonic nanoparticles (0.1 wt %) resulted in external quantum efficiency improvement.

Silicon substrates for nanoparticle gas sensors with embedded electrodes and planar surface

Standard ceramic substrates with patterned surface electrodes few hundred nm thick are not appropriate for advanced nanoparticle gas sensors. Smooth silicon planar substrates with embedded metallic electrodes are introduced in our work. They give the chance to cover the small substrate surface irregularities by fragile nanoparticle arrays and provide an opportunity to integrate sensors into electronic circuits. The suppression of high power consumption of integrated sensor heater due to the high thermal conductivity of Si is resolved using substrates hanging on thin contacting wires without getting in touch with the socket. Embedded Au electrodes were created in sputtered amorphous silicon layer by lift-off technique. The ridges at Au – a:Si interface were reduced due to improved Au wettability of a:Si vertical walls. γ-Fe2O3 nanoparticle deposits on the Si patterned substrates were studied.Standard ceramic substrates with patterned surface electrodes few hundred nm thick are not appropriate for advanced nanoparticle gas sensors. Smooth silicon planar substrates with embedded metallic electrodes are introduced in our work. They give the chance to cover the small substrate surface irregularities by fragile nanoparticle arrays and provide an opportunity to integrate sensors into electronic circuits. The suppression of high power consumption of integrated sensor heater due to the high thermal conductivity of Si is resolved using substrates hanging on thin contacting wires without getting in touch with the socket. Embedded Au electrodes were created in sputtered amorphous silicon layer by lift-off technique. The ridges at Au – a:Si interface were reduced due to improved Au wettability of a:Si vertical walls. γ-Fe2O3 nanoparticle deposits on the Si patterned substrates were studied.

Control of interparticle distance of ordered iron-oxide nanoparticle assemblies by means of surfactant design

Effect of the nanoparticle effective size on interparticle distance in ordered nanoparticle films was investigated. To obtain different interparticle distance, the iron oxide nanoparticles (IONPs) with the size of 6.5u2005nm were functionalized by three kinds of surfactants: mixture of oleic acid/oleylamine, polybutylacrylate and polystyrene. Both hydrodynamic diameter and size distribution of nanoparticles in colloidal solution were measured by dynamic light scattering (DLS) in range from 8 to 17u2005nm. The ordering and homogeneity of the prepared Langmuir monolayers on solid surface was studied by scanning electron microscope (SEM) and atomic force microscopy (AFM). Method of pair correlation function was used for calculation of interparticle distance ensuing from SEM images. The distances from center to center of particles varied in the range from 6.75 to 11.75u2005nm. From the results it follows that we are able to change of interparticle distance on a solid substrate using of nanoparticles with different surfactant size.Effect of the nanoparticle effective size on interparticle distance in ordered nanoparticle films was investigated. To obtain different interparticle distance, the iron oxide nanoparticles (IONPs) with the size of 6.5u2005nm were functionalized by three kinds of surfactants: mixture of oleic acid/oleylamine, polybutylacrylate and polystyrene. Both hydrodynamic diameter and size distribution of nanoparticles in colloidal solution were measured by dynamic light scattering (DLS) in range from 8 to 17u2005nm. The ordering and homogeneity of the prepared Langmuir monolayers on solid surface was studied by scanning electron microscope (SEM) and atomic force microscopy (AFM). Method of pair correlation function was used for calculation of interparticle distance ensuing from SEM images. The distances from center to center of particles varied in the range from 6.75 to 11.75u2005nm. From the results it follows that we are able to change of interparticle distance on a solid substrate using of nanoparticles with different surfac...

Thermal stability of γ-Fe2O3 nanoparticles and their employment for sensing of acetone vapours

Stability of γ-Fe2O3 nanoparticles-based films upon an isochronal annealing in air was investigated by x-ray diffraction, differential scanning calorimetry, and thermogravimetry. The γ-α transformation temperature increased owing to the nanoscaling of Fe2O3; the higher stability of the γ phase was explained on the ground of the surface free energy of nanoparticles (with the size of about 6.4 nm). Further, chemiresistors based on the Fe2O3 nanoparticle bilayer prepared by the Langmuir-Schaefer method were fabricated and examined in terms of their sensitivity to acetone vapours down to 500 ppb concentration in air.

Cyclopean gauge factor of the strain-resistance transduction of indium oxide films

The resistance of indium-oxide covered polyethylene terephthalate foils (IO-PET) shows an extreme sensitivity to tensile strain. In terms of the deformation-resistance transduction, the gauge factor as high as about 60 000 was recorded upon the relative elongation up to 1%. Except the onset of deformation, the nearly exponential dependence of the resistance on strain suggests that the conductivity of the strained films is governed by tunnelling mechanism; this notion is supported by the formation of scattered cracks in the IO- PET film. The cracks are oriented perpendicularly to the strain vector and are characterized by a rather similar and uniform width. Appropriateness of the standard definition of the gauge factor for strain sensors, which are governed by tunnelling conductance, is critically discussed.