2025 - Publications Repository - Gdańsk University of Technology

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Publications from the year 2025

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Investigation of structural, thermal, and electrical properties of sodium-doped oxynitride glass-ceramics
- Natalia Wójcik
- Abbas Saeed Hakeem
- Zuzanna Mielke
- Sharafat Ali
2025 MATERIALS CHEMISTRY AND PHYSICS
This study aimed to investigate the influence of Na2O addition on the structural, thermal, and electrical characteristics of oxynitride glass-ceramics within the Na–K–Mg–Ca–Al–Si–O–N system. Oxynitride glass-ceramic samples were prepared via spark plasma sintering (SPS) with sodium oxide doping levels ranging from 0 wt% to 12 wt%. FESEM analysis revealed changes in sample morphology with increasing sodium content, indicating the formation of granular structures and sodium-rich clusters in the glass matrix. XRD revealed the presence of nanocrystalline phases in doped samples, primarily (Na,Ca)(Si,Al)4O8. IR spectroscopy demonstrated changes in the glass network structure due to sodium, affecting both silicate and aluminum units. Increasing sodium content led to higher crystallinity and a corresponding decrease in sample density. The thermal expansion increased notably with sodium content, attributed to the disruptive effect of sodium ions on the glass-ceramics structure, while thermal conductivity decreased also attributed to this disruption. AC conductivity increased significantly with sodium, indicating enhanced ionic conductivity, while DC conductivity was observed in doped samples at higher temperatures, with activation energies consistent with ionic conduction mechanisms. The exponent-dependent (s) parameter decreased with higher sodium content, suggesting limited ion diffusion.
Investigation of the thrust generated by active isolated hydrofoils via wave-induced ship motion
- Mohammad Sadeghi
- Hamid Zeraatgar
- Mohammad Ghaemi
- Vernengo Giuliano
2025 OCEAN ENGINEERING
Wave Augmented Hydrofoil Technology (WAHT) aims to convert hydrofoil movement, induced by ship motion, into thrust force, and ship's resistance reduction in waves. Despite the growing interest in WAHT, a significant research gap remains in understanding the complex interactions between hydrofoil design parameters and wave-induced thrust generation. A hydrofoil attached to a ship serves dual roles; reducing the ship resistance in waves and generating thrust force. To distinguish the resistance reduction to the thrust generation, this study considers an isolated active hydrofoil without the ship's hull. This approach captures the critical interactions driven by ship motion, while allowing for a focused analysis on thrust generation. The active hydrofoil orientation is harmonically adjusted according to the flow vertical velocity that results in a suitable angle of attack. The generated thrust is studied by varying the hydrofoil rotation angle, aspect ratio, wavelength, and forward speed. The vertical velocity of KRISO Container Ship (KCS) in a range of regular waves is already available where KCS model alone (without WAHT) was simulated using Computational Fluid Dynamics (CFD). Simulation of isolated hydrofoil reveals increase of the vertical velocity, span-to-chord ratio, and forward speed of the hydrofoil enhances thrust force. For the studied cases, a 2.5% enhancement of mean generated power relative to required power in waves is concluded.
ISO test track influence on the EU tyre label noise value
- Truls Berge
- Piotr Mioduszewski
- Maciej Hałucha
- Janusz Bohatkiewicz
2025 APPLIED ACOUSTICS
In 2009, the European Union (EU) introduced a directive governing the labelling of tyres, which underwent revision in 2020. This labelling system encompasses three key parameters related to tyre performance: wet grip (safety), rolling resistance (energy consumption), and external rolling noise (environmental impact). These label values serve as crucial information for customers seeking to purchase replacement tyres for their vehicles. However, the accuracy and reliability of noise measurements have been a concern. Testing conducted across various ISO-standardized tracks has revealed significant inconsistencies in noise levels, with variations of 4–5 dB between tracks. Such discrepancies directly impact the labelling process, introducing uncertainty. This paper presents results of tyre noise measurements conducted on a limited number of ISO test tracks and proposes a methodology to mitigate track-to-track variability. The study exclusively focuses on passenger car tyres. By addressing these inconsistencies, this research aims to enhance the accuracy and reliability of tyre noise labelling, thereby facilitating informed consumer decision-making and promoting environmental sustainability.
Isolation Improvement in MIMO Antenna with a Simple Hybrid Technique of Orthogonal and Inverse Currents
- Manzoor Elahi
- Sławomir Kozieł
- Leifur Leifsson
2025 AEU-INTERNATIONAL JOURNAL OF ELECTRONICS AND COMMUNICATIONS
This paper presents a compact high-isolation multiple-input multiple-output (MIMO) antenna developed using a hybrid approach. The proposed technique combines induced orthogonal currents and self-inverse currents to enhance the antenna's performance. Orthogonal currents are generated by strategically etching open slots on the antenna patches, while self-inverse currents are introduced by integration of annular vias. By carefully adjusting the radius and position of the annular vias and optimizing the patch geometry, the design achieves optimal resonance frequency alignment and signicantly improved isolation. The fabricated prototype exhibits an exceptional isolation of 55 dB at 5.75 GHz, accompanied by a realized gain of 6.7 dB. Measured radiation patterns in the ϕ = 0◦ and ϕ = 90◦ planes show excellent agreement with simulated results. The proposed low-prole antenna design has a substantial potential for enhancing MIMO applications in contemporary wireless communication systems.
Magnetic deep eutectic solvents for vortex-assisted liquid phase microextraction method for selective and green extraction of patulin from fruits and fruit juices
- Hameed Ul Haq
- Grzegorz Boczkaj
- Nail Altunay
2025 MICROCHEMICAL JOURNAL
In this study, a vortex assisted magnetic deep eutectic solvent based liquid phase microextraction (VA-MDES-LPME) technique was developed for the extraction of patulin prior to its determination by ultraviolet–visible spectrophotometry (UV–Vis). For this purpose, the use of a magnetic deep eutectic solvent (MDES) consisting of trihexyltetradecylphosphonium chloride, MnCl2, and octanoic acid (molar ratio 1:2:2) was tested to perform an efficient extraction. Important experimental parameters (MDES-3 vol, pH, vortex time, and ethanol volume) were optimized using Box-Behnken Design. Under optimum conditions (MDES-3 vol 560 µL, pH 3.5, vortex time 300 s, and ethanol volume 300 µL), the limits of detection for the model solution and matrix-matched solution were 0.06 ng mL−1 and 0.37 ng mL−1, and the calibration ranges were 0.2–400 ng mL−1 and 1.2–300 ng mL−1, respectively. Furthermore, the extraction recovery was calculated to be 96.3–97.4 % with a low relative standard deviation (2.1–2.5 %). The VA-MDES-LPME technique was successfully applied for the determination of patulin from fruit and juice samples with an enrichment factor between169 and 185.
Metamodel-based optimization of a high-tension cable barrier in crash tests with a large SUV
- Dawid Bruski
- Hongbing Fang
2025 ENGINEERING STRUCTURES
Road safety barriers play an important role in improving road safety. Cable barriers are one of the types of road barriers. Cable barriers have favorable collision-related properties, especially in terms of the safety of the vehicle occupants. Despite the continuous development of road barrier systems, the current European standard EN1317, which is used to evaluate the performance of road barriers, does not take into account all possible crash scenarios and all possible types of impacting vehicles. Sport utility vehicles (SUVs) are one of the types of vehicles that the EN1317 standard does not consider. SUVs are widely used on European roads. The work aims to optimize a high-tension 3-cable barrier system in crash tests with a large SUV. The research utilized the methods related to the design of the experiment, numerical simulations of crash tests, metamodeling, and multi-objective optimization (MOO) algorithms – WSF and NSGA-II. In the optimization, two aspects of the barrier were considered, economical and structural. The primary result of the study was the determination of four optimized designs for the cable barrier. These designs represent different trade-offs between the objective functions, offering various solutions depending on the specific engineering needs. The proposed barrier designs are characterized, among others, by a reduction in barrier mass, a reduction in the lateral deflections of the barrier, and a reduction in the number of posts that would need to be replaced after an SUV collision. The methodology used and the results achieved may be useful in the process of designing, testing, and optimizing other road safety barriers.
Methods and Instruments | Scanning Electrochemical Microscopy
- Gunther Wittstock
- Marius Muhle
- Monika Wilamowska-Zawłocka
2025
Scanning electrochemical microscopy is based on the recording of electrolysis currents (Faradaic currents) at a microelectrode (ME) probe that is scanned over the sample. Different working modes are available to couple the electrolysis at the ME to reactions at the sample. The article explains their principles and provides examples of their application. The feedback mode, the sample-generation/tip collection mode, the redox-competition mode and the surface interrogation mode are most frequently applied to the characterization of interphases and interfaces occurring in electrochemical power sources.
MHD Casson flow across a stretched surface in a porous material: a numerical study
- Sadia Irshad
- Shah Jahan
- Jose Mendes Machado
- Paweł Śliwiński
- Krzysztof Kędzia
- Zubair Ahmed Jan
2025 Multiscale and Multidisciplinary Modeling, Experiments and Design
In this study, we examine the nature of magnetohydrodynamic (MHD) Casson flow of fluid across a stretched surface in a porous material. It studies how the behaviour of Casson fluids is affected by a number of variables, including thermal radiation, chemical processes, Joule heating, and viscosity dissipation. The Keller box strategy, based on the finite difference method (FDM), is used to tackle the complex numerical problem. Graphical representations are used to show the effects of different system parts. Comprehensive tables displaying surface transfer of mass, heat, and drag rates are given for your convenience. The study focuses on how particle motion transforms kinetic energy into heat. Increased Brownian motion leads to a higher temperature profile and a reduced concentration profile. Thicker concentration profiles are created by increased Lewis number ( ) values and rates of chemical reactions, resulting in changes in mass transfer across fluids. This in-depth investigation focuses on the complicated interactions between various variables and how they influence the Casson fluid's behaviour in the system under study.
Modeling the effect of external load variations on single, serie and parallel connected microbial fuel cells
- Szymon Potrykus
- Janusz Nieznański
- Filip Kutt
- Francisco-Jesus Fernandez-Morales
2025 BIORESOURCE TECHNOLOGY
This paper presents a microbial fuel cell (MFC) model designed to analyze the effect of the external load on MFC performance. The model takes into account the voltage and the chemical oxygen demand (COD) dependence on the external load. The value of the model parameters were calibrated by means of the voltage relaxation method tests using a controlled load current. Laboratory measurements and MATLAB Simulink model computations were used to validate the proposed model. The tests results demonstrated that the proposed model accurately predicts the voltage and COD evolution during the batch cycle of the MFC. The root mean square error (RMSE) was used to assess the fitting goodness of the model. The RMSE of COD and voltage generation was in all the cases lower than 4%, predicting accurately the behaviour of single MFC as well as MFC connected in series or parallel.
Monitoring of absorptive model biogas purification process using sensor matrices and gas chromatography
- Edyta Słupek
- Dominik Dobrzyniewski
- Patrycja Makoś-Chełstowska
- Bartosz Szulczyński
- Jacek Gębicki
2025 MEASUREMENT
This study examined the process of purifying model biogas using a new type of absorbent based on a Deep Eutectic Solvent (DES) and a commercially available absorbent (Genosorb) to remove acetone, toluene, and cyclohexane. The main aim of the research was to control the purification efficiency using gas chromatography (GC) and an alternative method based on sensor matrices (SM). As a result of comparing the multidimensional SM signals with the GC result, the lowest difference between SM and GC (3.69%) was achieved with the DES. When using Genosorb, the differences between the methods were slightly more pronounced, reaching 10.26%. The studies also confirmed that SM results showed significant agreement, accuracy, precision, and equivalence compared to GC results. Nowadays, the literature has not reported this issue. The presented research fills the current gap in the literature and contributes to the development of knowledge in the practical application of SM.
MXene-based materials as adsorbents, photocatalysts, membranes and sensors for detection and removal of emerging and gaseous pollutants: A comprehensive review
- Mohammad Hadi Dehghani
- Nadeem Hussain Solangi
- Nabisab Mujawar Mubarak
- Natarajan Rajamohan
- Subrajit Bosu
- Amina Othmani
- Md. Ahmaruzzaman
- Soumya Ranjan Mishra
- Baishali Bhattacharjee
- Vishal Gadore
- Talib Hussain Banglani
- Nawab Waris
- Ali Hyder
- Ayaz Ali Memon
- Khalid Hussain Thebo
- Payal Joshi
- Grzegorz Boczkaj
- Rama Rao Karri
2025 Full text Arabian Journal of Chemistry
2D materials have garnered significant attention as potential solutions to various environmental challenges. Graphene, molybdenum disulfide, MXenes, and boron nitride have emerged as the most popular candidates among these materials. This article presents a comprehensive review and discussion on the emerging applications of MXenes in environmental engineering. MXenes have demonstrated immense potential as future materials for adsorption purposes. They have proven to be highly effective in removing emerging pollutants (heavy metals and organic pollutants) through the adsorption phenomenon. The effectiveness of MXenes in removing lead (Pb2+), chromium (Cr6+), copper (Cu2+), uranium (U6+), and mercury (Hg2+) has been confirmed, with a sorption capacity ranging from 100 to 250 mg g−1. Furthermore, MXenes have effectively removed several radionuclides, including uranium, europium, strontium, barium, and thorium. MXenes have proven to be highly efficient in treating water through adsorption in emerging organic pollutants, even for various organic dyes such as methylene blue, acid blue, congo red, methyl orange, and rhodamine B (RhB). Additionally, MXenes exhibit high treatment performance in adsorbing several pharmaceuticals like cloxacillin (CLX), ampicillin (AMP), amoxicillin (AMX), ciprofloxacin (CPX), amitriptyline (AMT), verapamil (VRP), carbamazepine (CBM), 17 α-ethinyl estradiol, ibuprofen (IBP), and diclofenac (DCF). Overall, MXenes offer several advantages, such as good conductivity, thermal performance, high surface area, and selectivity of intermolecular interactions. However, their application requires thoroughly evaluating their environmental impact and life cycle assessment.
On a fully three-dimensional bending analysis of very thick smart composite cube-like bulk structures
- Mohammad Malikan
- Shahriar Dastjerdi
- Victor Eremeev
- Mehran Kadkhodayan
2025 Full text COMPOSITE STRUCTURES
Here we discuss the behaviour of very thick composite plates considering electro-magneto-elastic coupling of various types using fully three-dimensional (3D) kinematics. Published research highlights a lack of studies on the 3D mechanics of smart composite plates that integrate both higher-order (flexoelectric/flexomagnetic) and lower-order (piezoelectric/piezomagnetic) multiple physical fields (electro-magneto-elastic). The common approach to achieving the targeted and desired mechanical behavior within such composites could involve using structural elements. This gap can potentially be addressed by amalgamating the term ∂/∂z with the 2D governing equations of plates. This expression indicates alterations in thickness, in which z is the coordinate dedicated to the thickness. The governing equations can be created by operating on the variational method which enables us to establish and settle the 3D bending equations of the bulk structure. The pointed-out equations have been influenced by the implementation of additional hypotheses, such as von Kármán’s strain and complicated 3D tensor relations. Inserting the term ∂/∂z into the mathematical model renders that the analytical solution techniques are unable to assist us in obtaining numerical results. Consequently, a semi-analytical solving method grounded on the polynomial phrases facilitates the acquisition of the required solution. This fully 3D bending study of very thick piezocomposite cube-like bulk structures (CBS) can be an original reference in the field of mechanics of intelligent plate-like structures.
On nonlinear 3D electro-elastic numerical modeling of two-phase inhomogeneous FG piezocomposites reinforced with GNPs
- Mohammad Malikan
- Shahriar Dastjerdi
- Magdalena Rucka
- Mehran Kadkhodayan
2025 INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE
The novelty here comes from not only the perfect nonlinear three-dimensional (3D) electro-elasticity investigation but also the mixed material itself. The literature widely showed mechanical assessments on the piezoelectric structures; however, a lack of nonlinear three-dimensional elasticity studies has been witnessed on these kinds of smart materials. Therefore, a nonlinear 3D elasticity-piezoelectricity coupling is considered in this study. What is more, this research brings about an era in the field of sensing manufacturing such as sensors and actuators by proposing the construction of these devices in an advanced composite framework. The piezoelectric medium can be electro-mechanically improved with the aggregation of graphene platelets/nanoplatelets (GPLs/GNPs) based on the functionally graded (FG) composition. The assumption for such a smart composite has been made to provide higher flexibility smart tools while their elastic strength can also get further. To accomplish this, the derivation of a rigorous mathematical model has come out for a transversely isotropic inhomogeneous FG-piezoelectric beam-like sensor/actuator using 3D kinematic displacements, geometrically nonlinear strains, Lagrange technique, 3D stress-strains tensors, linear elastic material, and in particular Halpin-Tsai micro-mechanic model. Numerical modeling has been built by the generalized differential quadrature (GDQ) technique. A comprehensive parametric study has also been established for intelligent FG beams.
Spectrophotometric determination of chlorpyrifos in foodstuffs after vortex-assisted surfactant-enhanced emulsification microextraction using magnetic deep eutectic solvents: Analytical greenness profile
- Nail Altunay
- Adil Elik
- Hameed Haq
- Grzegorz Boczkaj
2025 JOURNAL OF FOOD COMPOSITION AND ANALYSIS
In this work a novel and green vortex-assisted surfactant-enhanced emulsification microextraction (VA-SEEME) based on magnetic deep eutectic solvents (MDESs) was developed for the determination of chlorpyrifos in foodstuffs by UV-Vis spectrophotometric analysis. MDES (trihexyltetradecylphosphonium chloride: MnCl2: octanoic acid) was used as the extractant, non-ionic surfactant Tween-80 was used as an extraction medium, and ethanol as the eluent solvent. In the VA-MDES-SEEME procedure, a vortex was applied for agitation, and a neodymium magnet was used to separate the MDES from the aqueous solution. Under optimized conditions, a linear dynamic range was obtained in the range of 0.3–260 µg L−1 with a detection limit of 0.09 µg L−1. The intraday and interday precisions of the method, defined as relative standard deviation, ranged from 1.3 % to 2.5 %. The recovery of the spiked sample after the VA-MDES-SEEME procedure ranged from 88±6 % to 98±1 %, and the enrichment factor was obtained as 91-fold. The VA-MDES-SEEME procedure was validated by analysis of the certified reference materials including 7507a-Green Onion and 7508a-Cabbage. The VA-MDES-SEEME procedure is based on inexpensive equipment and green chemicals and is compatible with UV-Vis spectrophotometer analysis. The green profile of the VA-MDES-SEEME procedure within the scope of the current study was calculated as 0.71 using AGREE.
Stabilization Method for Speed Observer of Induction Machine
- Marcin Morawiec
- Lelisa Wogi
- Piotr Kołodziejek
2025 IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS
This article proposes the speed estimation principles dedicated to the observer structures based on the machine mathematical model. The rotor speed is reconstructed based on the mathematical model of a machine by using both adaptive and nonadaptive schemes. The presented principle is generalized to the classical nonlinear system in the vector form and can be applied to induction machines. The proposed rotor speed reconstruction approach is based on an algebraic relationship, and the observer system mathematical model has the same rank as the induction machine. The speed observer structure can be unstable due to the challenge of stabilizing the sensorless control of the induction machine at low-speed, near zero speed, or in the low-speed regenerating mode of operation. As a result, the new stabilizing functions based on Lagrange identity are proposed in this work to improve the range of observer stability. The proposed approach includes newly developed stabilization mechanisms that ensure observer stability under both motoring and regenerating modes of operations at the low rotor speed and improve the observer range of stability. The Lyapunov theorem is used during the design procedure for stability purposes. The simulation and experimental studies are carried out for an induction machine adaptive and nonadaptive full-order observer. The experimental results show that stable operation of the system is obtained, and the range of observer stability is improved, especially at low-speeds and in a regenerating mode of operation, concluding that the proposed solution is suitable for use in industrial applications.
The influence of chitosan's molecular weight, concentration, and dissolution method on the properties of electrophoretically deposited coatings on the Ti13Nb13Zr alloy surface
- Łukasz Pawłowski
- Szymon Mania
- Adrianna Banach-Kopeć
- Karol Staszczyk
- Aleksandra Mirowska
- Aleksandra Mielewczyk-Gryń
- Robert Tylingo
2025 MATERIALS CHEMISTRY AND PHYSICS
In this study, the effects of molecular weight (high, medium, and low), concentration (0.1 and 0.5 %) and dissolution method (in a rarely used hydroxyacetic acid and utilizing a novel CO2 saturation) of chitosan on the microstructure, chemical composition, wettability, surface roughness, adhesion, corrosion resistance and antibacterial activity of chitosan coatings electrophoretically deposited (10 V, 1 min) on β titanium alloy Ti13Nb13Zr were investigated. Microstructural analysis showed that low molecular weight chitosan at low concentrations formed uniform coatings while increasing these parameters resulted in uneven coatings with agglomerates. Energy-dispersive X-ray and Fourier transform infrared spectroscopy analyses confirmed the presence of chitosan on all coated samples. Higher concentrations of chitosan yielded thicker coatings. Wettability tests confirmed hydrophilic properties for all samples, with contact angles around 70°. Surface roughness varied with chitosan concentration, showing increased roughness for higher concentrations. Adhesion tests showed the highest critical load for high molecular weight chitosan coatings with a concentration of 0.1 %. Corrosion tests revealed that low molecular weight chitosan coatings provided the best protection. Antimicrobial assays showed that chitosan coatings prepared using acid dissolution had strong bactericidal activity against both Gram-positive and Gram-negative bacteria, while those prepared using CO2 saturation showed limited bacteriostatic activity. These findings suggest that chitosan coatings, especially those prepared using acid dissolution, hold promise for biomedical applications requiring corrosion resistance and antibacterial properties.
Thermoelectric and electrical properties of triple-conducting multicomponent oxides based on substituted barium cerate-zirconate
- Martyna Czudec
- Daniel Jaworski
- Jagoda Budnik
- Aleksandra Mielewczyk-Gryń
- Tamilarasan Subramani
- Maria Gazda
- Alexandra Navrotsky
- Tadeusz Miruszewski
2025 Full text DALTON TRANSACTIONS
Multicomponent oxides often have exceptional thermal stability and interesting electronic properties. The present work presents the thermoelectric and electrical properties of the Ba(Zr0.2Hf0.2Sn0.2Ti0.2Fe0.2)O3−δ and Ba(Zr0.1Hf0.1Sn0.1Ti0.1Co0.1Ce0.1Bi0.1Fe0.1Y0.1Zn0.1)O3−δ multicomponent perovskites. Single-phase cubic perovskites were synthesized using the solid-state reaction method. They were characterized using X-ray diffraction, drop-solution calorimetry, and thermogravimetry methods. The total electrical conduc tivity and Seebeck coefficient measurements were performed in dry and wet air at temperatures between 600 and 1050 K. It was found that Ba(Zr0.1Hf0.1Sn0.1Ti0.1Co0.1Ce0.1Bi0.1Fe0.1Y0.1Zn0.1)O3−δ is thermo dynamically less stable than Ba(Zr0.2Hf0.2Sn0.2Ti0.2Fe0.2)O3−δ. Moreover, this oxide incorporates a higher amount of water and exhibits higher conductivity and lower Seebeck coefficient. Charge transport in both perovskites can be assigned to the small-polaron hopping process via electron holes. An interesting temperature dependence of the Seebeck coefficient was found and, at temperatures above 750 K, related to hopping between energetically inequivalent states
Thermoelectric and electrical transport properties of mixed-conducting multicomponent oxides based on Ba(Zr,Ce)O3-δ
- Konrad Kuc
- Martyna Czudec
- Daniel Jaworski
- Jagoda Budnik
- Aleksandra Mielewczyk-Gryń
- Maria Gazda
- Tadeusz Miruszewski
2025 JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS
In this work, the chosen physicochemical properties of single-phase multicomponent oxides BaTi1/8Fe1/8Co1/8Y1/8Zr1/8Sn1/8Ce1/8Hf1/8O3-δ and BaTi1/9Fe1/9Co1/9Y1/9Zr1/9Sn1/9Ce1/9 Hf1/9Bi1/9O3-δ were studied. The microstructure of the compounds strongly depended on the presence of bismuth in the structure. The electrical transport studies showed a level of electrical conductivity of ∼10−3 - 10−2 S/cm in the temperature range 673–1073 K. Electrical conductivity was thermally activated and the dominant conduction mechanism was the hopping of small polarons. Moreover, total electrical conductivity changes in the dry and humidified atmosphere at lower temperatures due to the presence of protonic defects in the structure. Thermoelectric measurements showed a relatively high value of the Seebeck coefficient for studied ceramics. Its values ranged between 50 and 250 μV/K depending on the sample and temperature. The Seebeck coefficient sign was positive, meaning that electron holes and/or oxygen vacancies were predominant charge carriers in oxidizing atmospheres. Additionally, the Seebeck coefficient was found to be different in the humidified atmosphere which indicates an influence of protonic defects on thermoelectric transport. The obtained power factor Pf turned out to be low and dependent on the presence of protonic defects in the structure. This indicates, that the efficiency of the MOs-based operating thermoelectric generators can be controlled by changing the partial pressure of water vapor
UV light-activated gas mixture sensing by ink-printed WS2 layer
- Katarzyna Drozdowska
- Janusz Smulko
- Artur Zieliński
- Andrzej Kwiatkowski
2025 Full text SENSORS AND ACTUATORS B-CHEMICAL
We fabricated a sensing layer from ink-printed WS2 flakes and utilized it for UV-activated gas sensing. The optical imaging of the structure made by repeated printing revealed the continuous layer comprising sub-µm flakes, confirmed independently by small-area AFM images (1×1 µm2). The activity of the sensing surface was investigated locally via AFM scanning of the surface with a polarized probing tip. The results indicated that the applied UV light amplifies the existing conducting paths in the dark. These hot spots are associated with the sensing activity of the WS2 surface (local adsorption-desorption centers). Gas sensing experiments revealed that the DC resistance of the WS2 sensor changes in the opposite direction for increasing concentrations of NO2 and NH3, which correlates with the electron-accepting and electron-donating properties of these species. On the contrary, low-frequency noise intensifies gradually in both gases, and relative changes in noise responses are higher than DC resistance responses for all investigated concentrations. The lowest detection limit obtained was 103 ppb from DC responses for NO2 and 168 ppb from noise responses for NH3. The studies of sensing responses for mixtures of the mentioned target gases revealed that the amplitude of resistance fluctuations is not a direct summation of spectra obtained for pure compounds. Such an effect observed for mixed gases indicates that the intermittent reactions between both species before adsorbing at the sensing surface or in the adsorption centers impact their detection.