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Ales Hamacek

Bio: Ales Hamacek is an academic researcher from University of West Bohemia. The author has contributed to research in topics: Substrate (printing) & PEDOT:PSS. The author has an hindex of 12, co-authored 117 publications receiving 542 citations.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate the synergism of a high surface area heterojunction between TiO2 in the form of ordered 1D anodic nanotube layers of high aspect ratio and ZnO coatings of different thicknesses.
Abstract: The authors demonstrate, in this work, a fascinating synergism of a high surface area heterojunction between TiO2 in the form of ordered 1D anodic nanotube layers of a high aspect ratio and ZnO coatings of different thicknesses, produced by atomic layer deposition. The ZnO coatings effectively passivate the defects within the TiO2 nanotube walls and significantly improve their charge carrier separation. Upon the ultraviolet and visible light irradiation, with an increase of the ZnO coating thickness from 0.19 to 19 nm and an increase of the external potential from 0.4–2 V, yields up to 8-fold enhancement of the photocurrent density. This enhancement translates into extremely high incident photon to current conversion efficiency of ≈95%, which is among the highest values reported in the literature for TiO2 based nanostructures. In addition, the photoactive region is expanded to a broader range close to the visible spectral region, compared to the uncoated nanotube layers. Synergistic effect arising from ZnO coated TiO2 nanotube layers also yields an improved ethanol sensing response, almost 11-fold compared to the uncoated nanotube layers. The design of the high-area 1D heterojunction, presented here, opens pathways for the light- and gas-assisted applications in photocatalysis, water splitting, sensors, and so on.

47 citations

Journal ArticleDOI
TL;DR: In this paper, an electrochemical amperometric nitrogen dioxide sensor with solid polymer electrolyte was fabricated by means of screen printing technology on both rigid and flexible substrates, and the sensor concept is based on a semi-planar, three-electrode topology that enables low power, high performance, thin, and selective gas sensors to be produced on poly(ethylene terephthalate) (PET) and/or Kapton foil.
Abstract: An electrochemical amperometric nitrogen dioxide sensor with solid polymer electrolyte was fabricated by means of screen printing technology on both rigid and flexible substrates. The sensor concept is based on a semi-planar, three-electrode topology that enables low power, high performance, thin, and selective gas sensors to be produced on poly(ethylene terephthalate) (PET) and/or Kapton foil. The sensor response mechanism, i.e. the reduction of nitrogen dioxide at the boundary of a solid polymer electrolyte/working electrode/gas analyte, was predicted by using a Langmuir adsorption isotherm. It was demonstrated that a new platform for the electrochemical NO2 sensor can be completely manufactured by screen printing, which allows the fabrication of a flexible and low cost device suitable for mass production. Further, it was demonstrated that the fully printed sensor can be fabricated without using metal-based printing pastes, which is important from the point of view of the environment. The fully-printed, metal-free electrochemical sensor exhibited a linear response in the range of 0–10 ppm, fast response/recovery times (70/60 s, respectively), a resolution of 0.2 ppm, and a sensitivity of 590 nA/ppm, which enables the sensor to be used for both the monitoring of NO2 exposure in the workplace as well as environmental air pollution.

46 citations

Journal ArticleDOI
11 Nov 2015-Sensors
TL;DR: The study revealed that the sensor based on 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][N(Tf)2]) showed the best sensitivity, fast response/recovery times, and low sensor response hysteresis.
Abstract: A systematic study was carried out to investigate the effect of ionic liquid in solid polymer electrolyte (SPE) and its layer morphology on the characteristics of an electrochemical amperometric nitrogen dioxide sensor Five different ionic liquids were immobilized into a solid polymer electrolyte and key sensor parameters (sensitivity, response/recovery times, hysteresis and limit of detection) were characterized The study revealed that the sensor based on 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][N(Tf)2]) showed the best sensitivity, fast response/recovery times, and low sensor response hysteresis The working electrode, deposited from water-based carbon nanotube ink, was prepared by aerosol-jet printing technology It was observed that the thermal treatment and crystallinity of poly(vinylidene fluoride) (PVDF) in the solid polymer electrolyte influenced the sensitivity Picture analysis of the morphology of the SPE layer based on [EMIM][N(Tf)2] ionic liquid treated under different conditions suggests that the sensor sensitivity strongly depends on the fractal dimension of PVDF spherical objects in SPE Their deformation, eg, due to crowding, leads to a decrease in sensor sensitivity

43 citations

Journal ArticleDOI
TL;DR: In this paper, a chemoresistive ammonia sensor with sensitive polyaniline layer has been fabricated by gravure printing on flexible poly(ethylene terephthalate) substrate.
Abstract: A chemoresistive ammonia sensor with sensitive polyaniline layer has been fabricated by gravure printing on flexible poly(ethylene terephthalate) substrate. Novel colloids of polyaniline hydrochloride, which were synthetized in xylene or chloroform in the presence of surfactant, were used as a printing formulation. The sensor characteristics of the colloid-based sensitive layers were compared with in-situ polymerized layers of polyaniline. The colloid-based sensors showed a good response to ammonia concentrations in the range from hundreds of ppb to tens of ppm. This provides an opportunity to use these sensors for both monitoring of maximum exposure limits for humans in workplaces as well as environmental air-pollution. Therefore, these fully printed, metal-free, low cost and flexible ammonia sensors based on organic materials can be used in detection systems for monitoring of hazardous gases.

42 citations

Journal ArticleDOI
TL;DR: An amperometric NO 2 sensor with a new type of solid polymer electrolyte (SPE) and a glassy carbon working electrode is presented in this article, where the analyte, gaseous nitrogen dioxide, was detected by reduction at −500mV vs a platinum pseudoreference electrode.
Abstract: An amperometric NO 2 sensor with a new type of solid polymer electrolyte (SPE) and a glassy carbon working electrode is presented. The electrolyte is based on 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C 2 mim][NTf 2 ] ionic liquid immobilized in poly(vinylidene fluoride) matrix [PVDF]. The analyte, gaseous nitrogen dioxide, was detected by reduction at −500 mV vs. a platinum pseudoreference electrode. The sensor exhibited a linear behavior in the whole tested range, i.e., 0–10 ppm, and its sensitivity was 0.66 × 10 −6 A/ppm. The rise/recovery times were of the order of tens of seconds. In addition, the influence of the geometry (area and thickness) of the carbon working electrode on sensor response during short-term and long-term exposure to nitrogen dioxide was investigated. The area of the working electrode strongly influenced the stability and noise of the sensor: the smaller the electrode area, the better the stability of the sensor and the lower the noise level. The response times were influenced by the thickness of the carbon working electrode: the thicker the electrode, the longer the response time. It was also demonstrated that glassy carbon is a good candidate for the preparation of the working electrode. The use of a platinum pseudoreference electrode simplifies sensor fabrication and does not have any negative effect on sensor stability.

34 citations


Cited by
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Journal ArticleDOI
01 Jan 1977-Nature
TL;DR: Bergh and P.J.Dean as discussed by the authors proposed a light-emitting diode (LEDD) for light-aware Diodes, which was shown to have promising performance.
Abstract: Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

1,560 citations

Journal ArticleDOI
TL;DR: In this article, a comprehensive review of various printing technologies, commonly used substrates and electronic materials is presented, including solution/dry printing and contact/noncontact printing technologies on the basis of technological, materials, and process-related developments in the field.
Abstract: Printing sensors and electronics over flexible substrates are an area of significant interest due to low-cost fabrication and possibility of obtaining multifunctional electronics over large areas. Over the years, a number of printing technologies have been developed to pattern a wide range of electronic materials on diverse substrates. As further expansion of printed technologies is expected in future for sensors and electronics, it is opportune to review the common features, the complementarities, and the challenges associated with various printing technologies. This paper presents a comprehensive review of various printing technologies, commonly used substrates and electronic materials. Various solution/dry printing and contact/noncontact printing technologies have been assessed on the basis of technological, materials, and process-related developments in the field. Critical challenges in various printing techniques and potential research directions have been highlighted. Possibilities of merging various printing methodologies have been explored to extend the lab developed standalone systems to high-speed roll-to-roll production lines for system level integration.

951 citations

Journal ArticleDOI
12 Jan 2017-Sensors
TL;DR: This paper has presented and compared several low-cost and non-invasive health and activity monitoring systems that were reported in recent years and compatibility of several communication technologies as well as future perspectives and research challenges in remote monitoring systems will be discussed.
Abstract: Life expectancy in most countries has been increasing continually over the several few decades thanks to significant improvements in medicine, public health, as well as personal and environmental hygiene. However, increased life expectancy combined with falling birth rates are expected to engender a large aging demographic in the near future that would impose significant burdens on the socio-economic structure of these countries. Therefore, it is essential to develop cost-effective, easy-to-use systems for the sake of elderly healthcare and well-being. Remote health monitoring, based on non-invasive and wearable sensors, actuators and modern communication and information technologies offers an efficient and cost-effective solution that allows the elderly to continue to live in their comfortable home environment instead of expensive healthcare facilities. These systems will also allow healthcare personnel to monitor important physiological signs of their patients in real time, assess health conditions and provide feedback from distant facilities. In this paper, we have presented and compared several low-cost and non-invasive health and activity monitoring systems that were reported in recent years. A survey on textile-based sensors that can potentially be used in wearable systems is also presented. Finally, compatibility of several communication technologies as well as future perspectives and research challenges in remote monitoring systems will be discussed.

795 citations

Journal ArticleDOI
TL;DR: Ionic liquids have emerged as an environmentally friendly alternative to the volatile organic solvents and have been used in many applications in various fields like catalysis, electrochemistry, spectroscopy, and material science as discussed by the authors.

706 citations

Journal ArticleDOI
TL;DR: This work stresses the importance of developing CP films and reveals their critical role in the evolution of these next‐generation devices featuring wearable, deformable, printable, ultrathin, and see‐through characteristics.
Abstract: Substantial effort has been devoted to both scientific and technological developments of wearable, flexible, semitransparent, and sensing electronics (e.g., organic/perovskite photovoltaics, organic thin-film transistors, and medical sensors) in the past decade. The key to realizing those functionalities is essentially the fabrication of conductive electrodes with desirable mechanical properties. Conductive polymers (CPs) of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) have emerged to be the most promising flexible electrode materials over rigid metallic oxides and play a critical role in these unprecedented devices as transparent electrodes, hole transport layers, interconnectors, electroactive layers, or motion-sensing conductors. Here, the current status of research on PEDOT:PSS is summarized including various approaches to boosting the electrical conductivity and mechanical compliance and stability, directly linked to the underlying mechanism of the performance enhancements. Along with the basic principles, the most cutting edge-progresses in devices with PEDOT:PSS are highlighted. Meanwhile, the advantages and plausible problems of the CPs and as-fabricated devices are pointed out. Finally, new perspectives are given for CP modifications and device fabrications. This work stresses the importance of developing CP films and reveals their critical role in the evolution of these next-generation devices featuring wearable, deformable, printable, ultrathin, and see-through characteristics.

478 citations