Browsing by Author "Ozturk, O."

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Advanced NH3 Detection by 1D Nanostructured La:ZnO Sensors with Novel Intrinsic p-n Shifting and Ultrahigh Baseline Stability
(2024.01.01) Ajjaq, A.; Bulut, F.; Ozturk, O.; Acar, S.
Due to its stability, transportability, and ability to be produced using renewable energy sources, NH3 has become an attractive option for hydrogen production and storage. Detecting NH3 is then essential, being a toxic and flammable gas that can pose dangers if not properly monitored. ZnO chemiresistive sensors have shown great potential in real NH3 monitoring applications; yet, research and development in this area are ongoing due to reported limitations, like baseline instabilities and sensitivity to environmental factors, including temperature, humidity, and interferent gases. Herein, we suggest an approach to obtain sensors with competitive performance based on ZnO semiconducting metal oxides. For this purpose, one-dimensional nanostructured pure and La-doped ZnO films were synthesized hydrothermally. Incorporating large rare earth ions, like La, into the bulk lattice of ZnO is challenging and can lead to surface defects that are influential in gas-sensing reactions. The sensors experienced a temperature-induced p-n shifting at about 100 degrees C, verified by the Hall effect and AC impedance measurements. The doped sensor showed exceptional stepwise baseline stability and outstanding performance at a relatively low operating temperature (150 degrees C) with a sensing response of 91 at best (@ 50 ppm NH3) and recorded a tolerance to water vapor up to 70% RH. Alongside p-n shifting, the enhanced performance was discussed in correlation with La doping-triggered changes in the nanostructural and surfacial properties of the films. We validated the proposed technique by producing similar sensors and performing multiple replicates to ensure consistency and reproducibility. We also introduced the fill factor concept into the gas sensor field as a new trustworthy parameter that could improve sensor performance assessment and help rate sensors based on deviation from ideality.
Advanced NH3 Detection by 1D Nanostructured La:ZnO Sensors with Novel Intrinsic p-n Shifting and Ultrahigh Baseline Stability
(2024) Ajjaq, A.; Bulut, F.; Ozturk, O.; Acar, S.
Due to its stability, transportability, and ability to be produced using renewable energy sources, NH has become an attractive option for hydrogen production and storage. Detecting NH is then essential, being a toxic and flammable gas that can pose dangers if not properly monitored. ZnO chemiresistive sensors have shown great potential in real NH monitoring applications; yet, research and development in this area are ongoing due to reported limitations, like baseline instabilities and sensitivity to environmental factors, including temperature, humidity, and interferent gases. Herein, we suggest an approach to obtain sensors with competitive performance based on ZnO semiconducting metal oxides. For this purpose, one-dimensional nanostructured pure and La-doped ZnO films were synthesized hydrothermally. Incorporating large rare earth ions, like La, into the bulk lattice of ZnO is challenging and can lead to surface defects that are influential in gas-sensing reactions. The sensors experienced a temperature-induced p-n shifting at about 100 °C, verified by the Hall effect and AC impedance measurements. The doped sensor showed exceptional stepwise baseline stability and outstanding performance at a relatively low operating temperature (150 °C) with a sensing response of 91 at best (@ 50 ppm NH) and recorded a tolerance to water vapor up to 70% RH. Alongside p-n shifting, the enhanced performance was discussed in correlation with La doping-triggered changes in the nanostructural and surfacial properties of the films. We validated the proposed technique by producing similar sensors and performing multiple replicates to ensure consistency and reproducibility. We also introduced the fill factor concept into the gas sensor field as a new trustworthy parameter that could improve sensor performance assessment and help rate sensors based on deviation from ideality.
Advanced NH3 Detection by 1D Nanostructured La:ZnO Sensors with Novel Intrinsic p-n Shifting and Ultrahigh Baseline Stability
(American Chemical Society, 2024) Ajjaq, A.; Bulut, F.; Ozturk, O.; Acar, S.
Due to its stability, transportability, and ability to be produced using renewable energy sources, NH3 has become an attractive option for hydrogen production and storage. Detecting NH3 is then essential, being a toxic and flammable gas that can pose dangers if not properly monitored. ZnO chemiresistive sensors have shown great potential in real NH3 monitoring applications; yet, research and development in this area are ongoing due to reported limitations, like baseline instabilities and sensitivity to environmental factors, including temperature, humidity, and interferent gases. Herein, we suggest an approach to obtain sensors with competitive performance based on ZnO semiconducting metal oxides. For this purpose, one-dimensional nanostructured pure and La-doped ZnO films were synthesized hydrothermally. Incorporating large rare earth ions, like La, into the bulk lattice of ZnO is challenging and can lead to surface defects that are influential in gas-sensing reactions. The sensors experienced a temperature-induced p-n shifting at about 100 °C, verified by the Hall effect and AC impedance measurements. The doped sensor showed exceptional stepwise baseline stability and outstanding performance at a relatively low operating temperature (150 °C) with a sensing response of 91 at best (@ 50 ppm NH3) and recorded a tolerance to water vapor up to 70% RH. Alongside p-n shifting, the enhanced performance was discussed in correlation with La doping-triggered changes in the nanostructural and surfacial properties of the films. We validated the proposed technique by producing similar sensors and performing multiple replicates to ensure consistency and reproducibility. We also introduced the fill factor concept into the gas sensor field as a new trustworthy parameter that could improve sensor performance assessment and help rate sensors based on deviation from ideality.
Chemical precursor-dependent dual effect of doping on the gas-sensing performance of metal oxide semiconducting materials
(2024.01.01) Ajjaq, A.; Bulut, F.; Ozturk, O.; Acar, S.
In this study, we report a chemical precursor-dependent dual effect of doping on the gas-sensing performance of metal oxide semiconducting materials. Our findings challenge the conventional notion that optimal doping consistently enhances gas-sensing properties. Acetate and nitrate salts were used as chemical precursors, lanthanum (La) was used as a dopant, and ZnO was used as a semiconducting material. All materials were synthesized under identical conditions by a two-step process involving dip coating and hydrothermal methods. Gas-sensing results demonstrated an improvement in the performance of the acetate-based doped film and a decline in that of the nitrate-based doped film compared to their respective pure counterparts. Among the produced sensors, 1 wt% La-doped ZnO sensor produced by the acetate precursor proved to be convenient for usages in real markets. It showed superior performance with a high response (62) at a relatively low operating temperature (150degree celsius) towards 50 ppm of NH3 gas. The sensor also demonstrated exceptional baseline stability, high short-term and long-term consistency, good selectivity, and strong tolerance to humidity (up to 70 RH%) with slightly slow adsorption-desorption rates. The dual effect was discussed with respect to dopant- and precursor-induced variations in structural and surficial characteristics, revealed by XRD, Raman, FESEM, AFM, and XPS. The discussion delved deeper into the role of chemical precursors on nanostructure growth and, for the first time, illuminated a temperature-dependent complex gas-sensing principle governed by the detected p-n shift of the semiconductor type of the sensing elements, confirmed by Hall effect.
Chemical precursor-dependent dual effect of doping on the gas-sensing performance of metal oxide semiconducting materials
(Elsevier B.V., 2024) Ajjaq, A.; Bulut, F.; Ozturk, O.; Acar, S.
In this study, we report a chemical precursor-dependent dual effect of doping on the gas-sensing performance of metal oxide semiconducting materials. Our findings challenge the conventional notion that optimal doping consistently enhances gas-sensing properties. Acetate and nitrate salts were used as chemical precursors, lanthanum (La) was used as a dopant, and ZnO was used as a semiconducting material. All materials were synthesized under identical conditions by a two-step process involving dip coating and hydrothermal methods. Gas-sensing results demonstrated an improvement in the performance of the acetate-based doped film and a decline in that of the nitrate-based doped film compared to their respective pure counterparts. Among the produced sensors, 1 wt% La-doped ZnO sensor produced by the acetate precursor proved to be convenient for usages in real markets. It showed superior performance with a high response (62) at a relatively low operating temperature (150℃) towards 50 ppm of NH3 gas. The sensor also demonstrated exceptional baseline stability, high short-term and long-term consistency, good selectivity, and strong tolerance to humidity (up to 70 RH%) with slightly slow adsorption-desorption rates. The dual effect was discussed with respect to dopant- and precursor-induced variations in structural and surficial characteristics, revealed by XRD, Raman, FESEM, AFM, and XPS. The discussion delved deeper into the role of chemical precursors on nanostructure growth and, for the first time, illuminated a temperature-dependent complex gas-sensing principle governed by the detected p-n shift of the semiconductor type of the sensing elements, confirmed by Hall effect.
Effect of foreign impurity and growth temperatures on hexagonal structure and fundamental properties of ZnO nanorods
(John Wiley and Sons Inc, 2024) Seydioglu, T.; Kurnaz, S.; Tokeşer, E.A.; Yildirim, G.; Ozturk, O.
This study examined the influence of growth temperature and dopant concentration on the properties of Gd- and Ni-doped zinc oxide nanorods (ZnO NRs). ZnO seed layers were deposited on glass substrates using a sol–gel and dip-coating approach. Gd- and Ni-doped ZnO NRs were hydrothermally grown on the seed layers at different temperatures such as 75, 90, and 105°C for a constant growth time of 5 h. The crystal structure, optical, surface morphology views, and electrical properties of the NRs were extensively investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible spectroscopy, and four probe experimental methods. The XRD analysis confirmed the successful substitution of Zn2+ ions by Gd3+ and Ni2+ within the ZnO main matrices. The reordering of hexagonal structures with varied electronegativity, ionic radius dimensions, and valence electron states of Gd and Ni dopants affected seriously the fundamental characteristic features of NRs. The SEM images showed that the ZnO NRs grown at 90°C possessed a more favorable surface morphology and well-defined hexagonal shape compared with those grown at other growth temperatures. Higher dopant concentration led to an increase in NR diameter but a decrease in density depending on the increase in the space between the NRs. Additionally, the optical transmittance was found to generally enhance with increasing dopant concentration. The results obtained highlighted the interplay between growth temperature, dopant type and concentration in tailoring the structural, morphological, and optical properties of Gd- and Ni-doped ZnO NRs, paving the way for the development of optimized nanomaterials for various applications. Research Highlights: The XRD analysis confirmed the successful substitution of Zn2+ ions by Gd3+ and Ni2+ within the ZnO main matrices. The SEM images showed that the ZnO NRs grown at 90°C possessed a more favorable surface morphology and well-defined hexagonal shape compared with those grown at other growth temperatures. The optical transmittance was found to generally enhance with increasing dopant concentration. The results obtained highlighted the interplay between growth temperature, dopant type and concentration in tailoring the structural, morphological, and optical properties of Gd- and Ni-doped ZnO NRs, paving the way for the development of optimized nanomaterials for various applications.
Evolution of fundamental mechanical properties with aliovalent Co/Cu partial substitution and preparation method for Y-123 system
(2024.01.01) Ozturk, O.; Safran, S.; Ada, H.; Bulut, F.; Seydioglu, T.; Nefrow, A.R.A.; Akkurt, B.; Terzioglu, C.; Yildirim, G.
This study investigates the effect of aliovalent Co/Cu replacement and preparation method on fundamental mechanical performance features of YBa2Cu3-xCoxO7-delta (Y-123) ceramic system depending on the crack propagation mechanism by Vickers hardness measurements (H-v) and mechanical investigation models for the first time. All the findings are verified by the scanning electron microscopy (SEM) examinations. Besides, the electron-dispersive X-ray (EDX) technique verifies the successful substitution mechanism. Besides, the Vickers hardness parameters improve systematically with the increment in the Co/Cu partial substitution (serving as a barrier) level due to formation of operable slip systems, ionic bond formations, and decrement of stress-amplified strain fields. Moreover, the Y-123 ceramic produced by solid-state reaction method and molecular weight of 0.20% presents the densest and smoothest surface morphology with the largest particle distributions and well-linked cobblestone-like grains. On the other hand, the Y-123 ceramic compounds produced by the sol-gel method are more sensitive and responsive to the indentation test loads. All the findings are wholly supported by the mechanical performance properties, including the shear modulus, resilience, and degree of granularity. Furthermore, the mechanical models indicate that every compound prepared exhibits the untypical reverse indentation size effect (RISE). Additionally, the modeling studies display that the induced cracking (IIC) approach is found to be the most appropriate method to examine true Vickers hardness parameters in the plateau limit regions. All in all, this comprehensive study reports efficiently exploiting the process-structure-property relationships in Y-123 ceramic material design for physical science and mechanical application fields using the aliovalent partial substitution and preparation condition.
Evolution of fundamental mechanical properties with aliovalent Co/Cu partial substitution and preparation method for Y-123 system
(Springer, 2024) Ozturk, O.; Safran, S.; Ada, H.; Bulut, F.; Seydioglu, T.; Nefrow, A.R.A.; Akkurt, B.; Terzioglu, C.; Yildirim, G.
This study investigates the effect of aliovalent Co/Cu replacement and preparation method on fundamental mechanical performance features of YBa2Cu3−xCoxO7−δ (Y-123) ceramic system depending on the crack propagation mechanism by Vickers hardness measurements (Hv) and mechanical investigation models for the first time. All the findings are verified by the scanning electron microscopy (SEM) examinations. Besides, the electron-dispersive X-ray (EDX) technique verifies the successful substitution mechanism. Besides, the Vickers hardness parameters improve systematically with the increment in the Co/Cu partial substitution (serving as a barrier) level due to formation of operable slip systems, ionic bond formations, and decrement of stress-amplified strain fields. Moreover, the Y-123 ceramic produced by solid-state reaction method and molecular weight of 0.20% presents the densest and smoothest surface morphology with the largest particle distributions and well-linked cobblestone-like grains. On the other hand, the Y-123 ceramic compounds produced by the sol–gel method are more sensitive and responsive to the indentation test loads. All the findings are wholly supported by the mechanical performance properties, including the shear modulus, resilience, and degree of granularity. Furthermore, the mechanical models indicate that every compound prepared exhibits the untypical reverse indentation size effect (RISE). Additionally, the modeling studies display that the induced cracking (IIC) approach is found to be the most appropriate method to examine true Vickers hardness parameters in the plateau limit regions. All in all, this comprehensive study reports efficiently exploiting the process–structure–property relationships in Y-123 ceramic material design for physical science and mechanical application fields using the aliovalent partial substitution and preparation condition.