Çayir Taşdemi̇rci̇, Tuba

This study explores the effects of copper (Cu) doping on the structural and optical properties of cadmium oxide (CdO) thin films, which are widely employed in optoelectronic applications. CdO thin films were synthesized using the Successive Ionic Layer Adsorption and Reaction (SILAR) method on glass substrates, followed by doping with CuO at varying concentrations. The resulting films were characterized using X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDAX), and UV–Vis spectroscopy. XRD results revealed a cubic polycrystalline structure for both undoped and Cu-doped films. SEM analysis indicated a morphological shift from spherical to flower-like structures with increased Cu content, supported by elemental analysis via EDAX. Particle size distribution was calculated using SEM images. Optical studies showed a progressive decrease in the energy band gap from 2.48 eV (undoped CdO) to 1.99 eV (highest Cu doping level), highlighting the potential for tuning the electronic properties of CdO films through Cu doping. When the electrical properties of CdO and Cu-doped CdO thin films were examined, it was found that Cu doping decreased the resistivity. These findings demonstrate the effectiveness of Cu doping in enhancing the optoelectronic characteristics of CdO thin films for advanced device applications.

Özdemir, Agah Oktay; Caglar, Bulent; Çubuk, Osman; Coldur, Fatih; Kuzucu, Mehmet; Guner, Eda Keles; Doğan, Bilge; Caglar, Sema; Özdokur, Kemal Volkan

TiO2 nanoparticles-coated cotton fabric was readily prepared by the hydrolysis of TiCl4 solution over cotton fabric and characterized various techniques in comparison with pristine cotton fabric. Initially, the photocatalytic application of the obtained fabric was carried out by using it as a catalyst for the photodegradation of rhodamine B. A higher degradation ratio for rhodamine B in the presence of TiO2-coated cotton fabric as photocatalyst was observed under visible light compared to the one performed under UVA. The reactive species trapping experiments revealed that the superoxide radicals played a major role than other radical species and two different degradation mechanisms were proposed according the trapping results. Subsequently, considering that the fabricated TiO2-coated cotton fabric is a very suitable sensor material for the development of a wearable flexible pH sensor, a potentiometric solid state pH sensor prototype was constructed and tested for pH measurements. The proposed prototype exhibited a linear potentiometric response in the pH range from 2.0 to 9.0 with a slope of −23.9 mV/decade. The pH accuracies (as relative error %) calculated for the current electrode with respect to the commercial electrode in the studied buffer solutions were ranged between −1.8% and 1.9%. The presently proposed pH electrode allowed pH measurements highly coherent with commercially available pH electrode. Finally, the antibacterial activity of the TiO2 nanoparticles was evaluated by minimum bactericidal concentration (MBC), minimum inhibitory concentration (MIC) testing and also antibacterial property of the TiO2 nanoparticles-coated cotton fabric was demonstrated by GB/T 20944.3–2008 method using Staphylococcus aureus (ATCC 6538) and Escherichia coli (ATCC 25922) as representative strains of Gram-positive and Gram-negative bacteria, respectively. This study would be indicative to design of nano metal oxide-coated cotton fabrics in the application of photocatalyst, pH sensor and antibacterial agent against bacteria.

Caglar, Bulent; İçer, Fatih; Özdokur, Kemal Volkan; Caglar, Sema; Özdemir, Agah Oktay; Guner, Eda Keles; Beşer, Burcu Meryem; Altay, Ahmet; Çırak, Çağrı; Doğan, Bilge

Herein, we synthesized ferromagnetic BiFeO3 nanoparticles with sizes of 20–60 nm and rhombohedral distorted perovskite structure without any co-formed impurity phases by sol-gel method. Structural, morphological, magnetic, electronic and textural properties of BiFeO3 nanoparticles were characterized by using XRD, SEM-EDX, TEM, FTIR, XPS, VSM, UV-DRS, PL and BET techniques. The peroxidase was isolated from the Cress (Lepidium sativum) and purified by using precipitation of ammonium sulfate and chromatographic techniques; gel filtration and ion exchange chromatography which is showed wide range of thermal stability, maximum activity in the acidic environment and close to the body temperature. Afterwards, a novel amperometric biosensor based on Cress peroxidase entrapped on BiFeO3 nanoparticles modified carbon paste electrode was prepared for the first time to sensitive detection of H2O2. The prepared H2O2 biosensor was operated with the aid of choro-amperometry technique by applying −0.8 V vs Ag/AgCl electrode. The developed biosensor exhibited a linear response towards to H2O2 in the concentration range of 2.0 10−7 to 1.0 10−5 M under the optimal conditions and limit of detection and quantification were estimated as 7.0 10−8 M (2.7 μg L−1) and 2.0 10−7 M (8.7 μg L−1), respectively. The repeatability of the electrode was calculated as 19.2 for 2.0 10−7 M (N = 7) and the accuracy was 81.2% for this concentration. In addition, the H2O2 biosensor exhibited excellent stability up to ten days. Finally, the sensor developed was used for the analysis of H2O2 in milk samples and satisfactory recoveries were obtained under the operating conditions.