T. Pustelny

Studies of Reduced Graphene Oxide and Graphite Oxide in the Aspect of Their Possible Application in Gas Sensors

The paper presents the results of investigations on resistance structures based on graphite oxide (GRO) and graphene oxide (rGO). The subject matter of the investigations was thaw the sensitivity of the tested structures was affected by hydrogen, nitrogen dioxide and carbon dioxide. The experiments were performed at a temperature range from 30 °C to 150 °C in two carrier gases: nitrogen and synthetic air. The measurements were also aimed at characterization of the graphite oxide and graphene oxide. In our measurements we used (among others) techniques such as: Atomic Force Microscopy (AFM); Scanning Electron Microscopy (SEM); Raman Spectroscopy (RS); Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Microscopy (XPS). The data resulting from the characterizations of graphite oxide and graphene oxide have made it possible to interpret the obtained results from the point of view of physicochemical changes occurring in these structures.

A Study of a QCM Sensor Based on TiO2 Nanostructures for the Detection of NO2 and Explosives Vapours in Air

The paper deals with investigations concerning the construction of sensors based on a quartz crystal microbalance (QCM) containing a TiO2 nanostructures sensor layer. A chemical method of synthesizing these nanostructures is presented. The prepared prototype of the QCM sensing system, as well as the results of tests for detecting low NO2 concentrations in an atmosphere of synthetic air have been described. The constructed NO2 sensors operate at room temperature, which is a great advantage, because resistance sensors based on wide gap semiconductors often require much higher operation temperatures, sometimes as high as 500 °C. The sensors constructed by the authors can be used, among other applications, in medical and chemical diagnostics, and also for the purpose of detecting explosive vapours. Reactions of the sensor to nitroglycerine vapours are presented as an example of its application. The influence of humidity on the operation of the sensor was studied.

Impressing technology of optical Bragg's gratings on planar optical sol-gel waveguides

The aim of the presented investigations was to develop a technique of producing Bragg’s grating couplers on planar waveguides. Waveguides are obtained by means of the sol-gel technology. The introduction of a light beam into the structure of the waveguide is in the case of planar or strip optical systems always an essential technical problem, requiring simple and reproducible solutions without extending excessively the waveguide structure. The paper presents a technology of producing grating couplers by impressing the pattern of the network while forming the planar waveguide structure applying the sol-gel method. Some remarks concerning the sol-gel technology are also presented. The results of investigations on grating couplers obtained in such a way have been discussed, too.Attention has been drawn to the possibility of using such structures in optoelectronic sensors, particularly gas sensors, including sensors of water vapour as well as toxic gases.

Examination of thin films of phthalocyanines in plasmon system for application in NO2 sensors

Surface plasmon resonance spectroscopy is an optical technique that is capable of monitoring chemical and physical processes. It is sensitive to small changes of dielectric properties near a metal surface, and has been used to characterize a number of different types of films. This work analyzes the possibility of using the surface plasmon resonance phenomena for gas detection. We present examinations of thin films of phthalocyanines in plasmon systems from the point of view of their application in NO 2 sensors.

Photonic structures with grating couplers based on ZnO

The paper presents investigations concerning the design and realization of photonic structures with grating couplers. The first part of the paper deals with basic theoretical information on photonic structures with grating couplers and their application in optoelectronics. The further part presents the results of numerical investigations on photonic structures with grating couplers and shows the influence of geometrical parameters on the effectiveness of the input and output of optic power into and out of this photonic structure. The paper also provides the results of experimental investigations on a wideband gap semiconductor, viz. zinc oxide ZnO, as well as its application in planar waveguide structures and photonic structures with grating couplers.

Influence of External Gaseous Environments on the Electrical Properties of ZnO Nanostructures Obtained by a Hydrothermal Method

This paper deals with experimental investigations of ZnO nanostructures, consisting of a mixture of nanoparticles and nanowires, obtained by the chemical (hydrothermal) method. The influences of both oxidizing (NO2) and reducing gases (H2, NH3), as well as relative humidity (RH) on the physical and chemical properties of ZnO nanostructures were tested. Carrier gas effect on the structure interaction with gases was also tested; experiments were conducted in air and nitrogen (N2) atmospheres. The effect of investigated gases on the resistance of the ZnO nanostructures was tested over a wide range of concentrations at room temperature (RT) and at 200 °C. The impact of near- ultraviolet (UV) excitation (λ = 390 nm) at RT was also studied. These investigations indicated a high response of ZnO nanostructures to small concentrations of NO2. The structure responses to 1 ppm of NO2 amounted to about: 600% in N2/230% in air at 200 °C (in dark conditions) and 430% in N2/340% in air at RT (with UV excitation). The response of the structure to the effect of NO2 at 200 °C is more than 105 times greater than the response to NH3, and more than 106 times greater than that to H2 in the relation of 1 ppm. Thus the selectivity of the structure for NO2 is very good. What is more, the selectivity to NO2 at RT with UV excitation increases in comparison at elevated temperature. This paper presents a great potential for practical applications of ZnO nanostructures (including nanoparticles) in resistive NO2 sensors.

Evaluation of physicochemical properties of SiO2-coated stainless steel after sterilization.

The study of most of the literature devoted to the use of coronary stents indicates that their efficiency is determined by the physicochemical properties of the implant surface. Therefore, the authors of this study suggested conditions for the formation of SiO2 layers obtained with the use of sol-gel methodology showing physicochemical properties adequate to the specific conditions of the cardio-vascular system. Previous experience of authors helped them much to optimize the coating of 316LVM steel surface with SiO2. The values of parameters that determine the usefulness of the coating in medical applications have been determined. In order to identify the phenomena taking place at the boundary of phases and to evaluate the usefulness of the proposed surface modification, taking into consideration the medical sterilization (steam or ethylene oxide (EO)), the potentiodynamic, impedance, adhesion, surface morphology and biological assessment characterizations were performed. Regardless of the usage of the sterilizing agent (steam, EO) the study showed the reduction of critical force causing layers delamination. The research results of corrosion resistance study also confirmed a slight decrease of SiO2 barrier properties of the samples after sterilization in contact with the artificial plasma. SiO2 layers after the sterilization process did not show significant features of cytotoxicity and had no negative influence on blood cell counts, which confirmed the results of quantitative and qualitative studies.

Improvement of accuracy of the membrane shape mapping of the artificial ventricle by eliminating optical distortion

The paper presents new technique for correcting the desired shape of the flaccid membrane used in the artificial heart chamber. The original shape of membrane was obtained using specially developed type of method — Depth from Defocus. Accurately determining the shape of the diaphragm is very important. The shape of the membrane affects the final accuracy of determining the stroke volume of extracorporeal pneumatic heart assist pump. Three rigid membranes were used in the study. Each of them was developed on the basis of the original shape of the flaccid membrane and was examined.

Numerical analyses of optical couplers for planar waveguides

The paper presents the results of numerical analyses of optical structures realized in the form of planar waveguides made of materials with high values of the refractive index n ≈1.85. The analysed structures consist of a waveguide and input-output systems. Input-output couplers are realized in the form of prisms as well as Bragg’s grating couplers. Numerical investigations were carried out by applying the finite difference time domain (FDTD) method.

Acoustic system for the estimation of the temporary blood chamber volume of the POLVAD heart supporting prosthesis.

BackgroundThe paper presents a newly researched acoustic system for blood volume measurements for the developed family of Polish ventricular assist devices. The pneumatic heart-supporting devices are still the preferred solution in some cases, and monitoring of their operation, especially the temporary blood volume, is yet to be solved.MethodsThe prototype of the POLVAD-EXT prosthesis developed by the Foundation of Cardiac Surgery Development, Zabrze, Poland, is equipped with the newly researched acoustic blood volume measurement system based on the principle of Helmholtz’s acoustic resonance. The results of static volume measurements acquired using the acoustic sensor were verified by measuring the volume of the liquid filling the prosthesis. Dynamic measurements were conducted on the hybrid model of the human cardiovascular system at the Foundation, with the Transonic T410 (11PLX transducer - 5% uncertainty) ultrasound flow rate sensor, used as the reference.ResultsThe statistical analysis of a series of static tests have proved that the sensor solution provides blood volume measurement results with uncertainties (understood as a standard mean deviation) of less than 10%. Dynamic tests show a high correlation between the results of the acoustic system and those obtained by flow rate measurements using an ultrasound transit time type sensor.ConclusionsThe results show that noninvasive, online temporary blood volume measurements in the POLVAD-EXT prosthesis, making use of the newly developed acoustic system, provides accurate static and dynamic measurements results. Conducted research provides the preliminary view on the possibility of reducing the additional sensor chamber volume in future.