Eden, Cigdem; Çırak, Çağrı

Herein, Ag@CuxO and Ag@CuxO:rGO core–shell nanocomposite architectures were synthesized in the wet chemical method which was further analyzed by UV–Vis, XRD, XPS, SEM and TEM study. The as-prepared colloidal nanostructures were drop-casted onto n-type Si substrates to obtain n-Si/Ag@CuxO and n-Si/Ag@CuxO:rGO heterojunction photodetector devices. Current–voltage (I–V) characteristics under different light intensity and 365, 395, 590 and 850 nm wavelengths of illumination were measured. Under 365 nm illumination at −2 V bias, the responsivities of the n-Si/Ag@CuxO and n-Si/Ag@CuxO:rGO devices were determined to be 1.53 A/W and 4.26 A/W, respectively, indicating external quantum efficiencies exceeding 100 %. The better UV photosensitivity of n-Si/Ag@CuxO:rGO heterojunction is probably due to the improved electron transport capacity by rGO. Our findings demonstrate homojunction structure-based nanocomposites with very good photodetection performance, thus opening the door for next-generation optoelectronic device application.

Huseyin, Ahmad; Salih, Ahmed Jalal Salih

Energy storage devices, especially batteries and supercapacitors, are essential components in portable electronics and electric vehicles, and their role in supporting renewable energy systems is becoming increasingly critical. This review investigates their principles, types, and performance challenges, with a particular focus on energy density, power density, charge/discharge rates, and cycle life. While lithium-ion batteries are widely used for their high energy density, they face significant challenges such as long charging times, high costs, and safety concerns. Consequently, alternative battery technologies, including lithium-sulfur, lithium-air, sodium-ion, and zinc-based systems, are under active investigation. Supercapacitors, known for their rapid charge/discharge cycles and high power density, are limited by their low energy density. A key area of ongoing research is the optimization of electrode materials, such as carbon-based compounds, metal oxides, and conductive polymers, to enhance the performance of both batteries and supercapacitors. This work discusses the mechanisms of energy storage, electrode degradation, and electrolyte stability, while offering insights into future developments. It underscores the importance of distinguishing between the performance characteristics of batteries and supercapacitors to avoid misconceptions, as each technology operates on distinct principles that affect their efficiency and applications.

Acar, M.T.; Çomaklı, O.; Arslan, M.E.

This study investigates the effects of graphene amount on TiO2 nanotubes (TNT) synthesized on Ti6Al4V alloy via selective laser melting (SLM) to optimize corrosion resistance and biocompatibility. XRD analysis indicated the presence of anatase and rutile phases in TNTs, and the peak shifts indicated that graphene was successfully incorporated into the TNT structure. SEM images revealed that increasing the amount of graphene resulted in smaller nanotube diameters, increased contact angles, and imparted hydrophobic properties. Corrosion tests including Tafel polarization and electrochemical impedance spectroscopy (EIS) showed that graphene, especially C4-TNTs, exhibited superior corrosion resistance with high Ecorr and Rt values. Biocompatibility tests with human dermal fibroblast cells (HDFa) demonstrated cell viability with the incorporation of graphene into TNTs. The findings suggest that the optimum amount of graphene can significantly improve the corrosion resistance and biocompatibility of TiO2 nanotubes on Ti6Al4V alloy, making them more suitable for biomedical implants.

Ismail, Ismayadi; Muhammad Zulkimi, Muhammad Misbah; Azis, Raba'ah Syahidah; Mustaffa, Muhammad Syazwan; Hamidon, Mohd Nizar; Ertugrul, Mehmet; Yesilbag, Yasar Ozkan; Tuzluca, Fatma Nur; Hasan, Intan helina; Ozturk, Gokhan

In the present work, substitution of strontium U-type hexaferrite with the composition of Sr4Mn2-xZnxFe36O60 (x = 0.5,0.6,0.8, and 1.0) was prepared via high energy ball milling (HEBM) and sintered at 1100 °C. The phase, microstructure, magnetic, dielectric and electromagnetic wave absorbing properties of U-type strontium hexaferrite composites were measured using XRD, FESEM, and Vector Network Analyzer in the frequency range of 8–18 GHz (X-band and Ku-band). MnZn doping was found to shift the natural resonance of the materials by affecting its magnetocrystalline anisotropy. The reflection loss (RL) indicated that the composite possessed good microwave-absorbing properties with U-type strontium hexaferrite ( Sr4Mn2-xZnxFe36O60) of x = 0.8 resulted in high minimum RL value for all thickness of 1 mm and two peaks at approximately − 32.50 and − 41.50 dB at 14.00 and 15.60 GHz, with bandwidth of 0.60 and 0.80 GHz for losses less than − 10 dB.

Yesilbag, Yasar Ozkan; Tuzluca Yesilbag, Fatma Nur; Huseyin, Ahmad; Salih, Ahmed Jalal Salih; Ertugrul, Mehmet

In the present study, nitrogen-doped vertically aligned carbon nanotubes (N-VACNTs) were synthesized on carbon cloth (CC) using the floating catalyst chemical vapor deposition (FCCVD) method, and MnO2 nanosheets were grown on them using the hydrothermal method to produce an N-VACNT@MnO2 nanocomposite structure. In this structure, a synergistic effect was obtained by combining N-VACNTs, which allow high electrical conductivity and fast ion transfer. In the galvanostatic charge-discharge (GCD) measurements performed separately in a three-electrode test cell using 1 M of Na2SO4 electrolyte, the specific capacitance of the N-VACNTs was found to be 53.7 F g−1 at a current density of 0.5 A g−1, and the specific capacitance of the N-VACNT@MnO2 electrode structure was found to be 497 F g−1. In addition, after 10,000 charge-discharge cycles at a current density of 10 A g−1, the N-VACNT electrode retained 99 % of its initial specific capacitance, while the N-VACNT@MnO2 electrode exhibited outstanding cyclic stability with 76 % of its initial specific capacitance. Moreover, in the as-fabricated asymmetric supercapacitor (ASC) using N-VACNTs and N-VACNTs@MnO2, the negative and positive electrodes achieved a stable voltage window of 0–1.7 V, with a specific capacitance of 59.4 F g−1 at a current density of 1 A g−1. Additionally, this ASC showed good cycling stability retaining 84 % of its specific capacitance at the end of 10,000 cycles. Therefore, this ASC structure with an energy density of 24.7 Wh kg−1 and a power density of 15.7 kW kg−1 are promising electrode materials for energy storage.

Caglar, Bulent; Guner, Eda Keles; Ersoy, Selin; Caglar, Sema; Özdemir, Agah Oktay; Özdokur, Kemal Volkan; Doğan, Bilge; İçer, Fatih; Çırak, Çağrı

In this study, we prepared bentonite-Bi2S3 nanocomposite via decoration of Bi2S3 nanorods on bentonite for the first time to enhance the photocatalytic performance of Bi2S3 nanorods under visible light irradiation. XRD, TEM, SEM-EDX, XPS, UV-DRS, PL, electrochemical impedance spectroscopy, chronoamperometry, zeta potential, and BET techniques were used to compare analysis of structural, morphological, optical, electrochemical and textural properties of raw bentonite, bare Bi2S3 nanorods and bentonite-Bi2S3 nanocomposite. The photocatalytic performances of bentonite-Bi2S3 nanocomposite and bare samples were also investigated and comparatively evaluated by photodegradations of crystal violet and rhodamine B dyes under visible light irradiation. The photocatalytic degradation efficiencies of fabricated bentonite-Bi2S3 nanocomposite for crystal violet and rhodamine B were determined as 100% and 85% after the periods of 30 min and 90 min, respectively, which were more superior compared with those of bare Bi2S3 nanorods. The enhanced photodegradation activity of bentonite-Bi2S3 nanocomposite was assigned to the good visible light absorption ability, enlarged surface area, increased adsorption capability and decreased aggregation of Bi2S3 nanorods with the inclusion of bentonite platform as well as suppressed hole-electron recombination process due to electrostatic interaction between negatively charged bentonite surface and positively charged holes. The reactive species trapping revealed that hydroxyl radicals played a major role on the photodegradation and a plausible mechanism for photodegradation of dye molecules on bentonite-Bi2S3 nanocomposite was suggested. The photodegradation of dyes was found to follow the pseudo-first-order kinetic model. The prepared photocatalyst exhibited good reusability and stability after 4 cycles.

Chachuli, Siti Amaniah Mohd; Hamidon, Mohd Nizar; Ertugrul, Mehmet; Mamat, Md Shuhazlly; Coban, Omer; Tuzluca, Fatma Nur; Yesilbag, Yasar Ozkan; Shamsudin, N.H.

Various doping materials, such as MWCNTs, graphene nanoflakes and MXene, have been doped into TiO2 and the hydrogen sensing properties investigated. Using a similar volume, MWCNTs (5 wt.%) and graphene nanoflakes (5 wt.%) and MXene (10 wt.%) were added to TiO2 and prepared in a paste form by mixing the sensing material with the organic binder. The sensing film was deposited on an alumina substrate using a screen-printing technique and annealed at 500 °C for 30 min in ambient air. The crystallinity of TiO2 and the doped material in the sensing film after the annealing treatment were verified using FESEM, EDX, XRD and Raman Spectroscopy. By depositing an interdigitated electrode at the bottom of the sensing film, the thick film gas sensors (TiO2/MWCNT, TiO2/Gr, TiO2/MXene) were exposed to 100–1000 ppm of hydrogen at an operating temperature of 100–250 °C. The responses showed that the addition of MWCNTs and MXene to TiO2 reduced the operating temperature of the TiO2 gas sensor from 150 °C to 100 °C, while the addition of graphene nanoflakes did not affect the operating temperature of the TiO2 gas sensor. The TiO2/MWCNT gas sensor showed linear sensitivity as hydrogen concentrations increased for operating temperatures of 100–250 °C. The optimal operating temperature for TiO2/MXene occurred at 100 °C, while the optimal operating temperature for the TiO2/Gr gas sensor occurred at 200 °C. The highest sensitivity for 100–500 ppm hydrogen was generated by the TiO2/MXene gas sensor, and for 600–1000 ppm hydrogen was generated by the TiO2/MWCNT gas sensor at an operating temperature of 250 °C. The TiO2/MWCNT gas sensor produced the highest sensitivity to hydrogen at the operating temperature of 250 °C with sensitivity values of approximately 6.36, 33.61, 67.64, 102.23 and 159.07 for 100, 300, 500, 700 ppm and 1000 ppm of hydrogen, respectively.

Gülnahar, Murat; Karacali, Tevhit; Efeoglu, Hasan

In this paper is discussed the current transport characteristics of an Al/PS/p-Si/Al heterojunction device with a porous silicon layer (PS) fabricated by the electrochemical anodization process and its current transport properties are investigated by the using temperature dependent current-voltage (I-V) measurements in a wide temperature range from 50 K to 300 K. The electrical parameters are characterized with the thermionic emission theory. It is observed that the main characteristics such as ideality factor and apparent barrier height demonstrate resolute temperature dependences and this situation is related to the structure of porous region. In addition, it is obtained the conductance curves for the forward and reverse bias values of Al/PS/p-Si/Al sample and as a result, the value of the relative dielectric constant er of porous layer is calculated as epsilon(r):3.72. From the reverse bias I-V curves, it is discussed the current conduction mechanism of porosity region by using Poole-Frenkel emission and Schottky emission. In result, it is commented that the charge transport in PS is through Poole-Frenkel conduction mechanism for Al/PS/p-Si/Al. (C) 2019 Published by Elsevier B.V.

Yıldırım, M. Ali; Yıldırım, Sümeyra Tuna; Ateş, Aytunç

The nanostructured CdxZn1-xO (x = 0, 0.25, 0.50, 0.75, 1) thin films were synthesized on glass substrates via Successive Ionic Layer Adsorption and Reaction (SILAR) method. To investigate the effect of cadmium (Cd) concentration (x) on the characteristics the films, the synthesized films were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible spectroscopy and dc-electrical measurements. The XRD results showed that all the films exhibited polycrystalline nature and that the crystal structure changed from hexagonal wurtzite (ZnO) to cubic (CdO) structure with increasing Cd concentration (x) in the films. The energy bandgap values decreased from 3.30 to 2.22 eV with Cd concentration (x). The refractive index (n) and dielectric constants (εo, ε∞) values were calculated using optical data. The nanostructured CdxZn1-xO thin films were found to be very sensitive to light.

Gülnahar, Murat; Efeoğlu, Hasan; Şahin, Mustafa

This paper deals with the capacitive properties of an unintentionally doped Au/p-GaTe/In Schottky junction. The capacitance-voltage (C-V) measurements are realized at 120–300 K temperature range and also, the deep level characteristics at bulk of p-GaTe are investigated by thermally stimulated capacitance measurement technique (TSC). The C-V measurements yield the C−2− Vrcurves with fairly high correlation at high temperatures. However, the anomaly decreasing of the capacitance values with the temperature is attributed to the ionization of the deep levels which are electrically active at closely 100–270 K temperature ranges. In addition, due to the effect on the measured capacitance curves of the series resistance, the true capacitance characteristics are obtained. The values of barrier height are calculated to be 0.639 eV at 300 K and 1.556 eV at 140 K and it does not follow to the variation of forbidden energy band gap of p-GaTe. In addition, it is seen that the barrier height values from true capacitance curves are the more resolute from the barrier heights of measured capacitance curves. Moreover, the rapid increasing of the barrier height values at low temperatures is only attributed to the effect of the deep levels.