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This study reports the humidity sensing characteristics of aluminum (Al) and fluorine (F) co-doped zinc oxide (ZnO) nanostructured thin films with different Al concentrations. Sol–gel method was used in the synthesis of Al and F doped ZnO nanoparticles. The Al concentration was changed to 0.5 mol%, 1 mol% and 1.5 mol% while F concentration was kept constant at 2 mol%. Al and F co-doped ZnO (AFZO) nanostructured thin films for manufacturing relative humidity (RH) sensors were fabricated on glass substrates with a dip coating technique and then annealed at 500 °C for 1 h. The scanning electron microscopy (SEM) micrographs indicated that all AFZO films had uniform and homogeneous surfaces. The X-ray diffraction (XRD) patterns revealed that AFZO films were polycrystalline and have a hexagonal wurtzite structure with a preferential orientation along the (002) plane. The RH sensing characteristics of AFZO sensors was determined by electrical resistance measurements in the range of 40–90% RH at room temperature (RT). Both the electrical resistivity and RH sensing characteristics of AFZO sensors were found to be highly dependent on the Al concentration. All AFZO sensors exhibited high sensitivity, excellent stability, fast response and recovery times and a repeatable characteristic. The lowest electrical resistivity and best humidity sensor characteristics were obtained for AFZO sensor containing 1 mol% Al (AFZO–010). The sensitivity ratio between 40 and 90% RH is approximately 247 × for AFZO–010. This study showed that AFZO nanostructured thin films are promising for high performance humidity sensor applications.

In this study, the effect of fluorine (F) doping on the humidity sensing properties of F doped zinc oxide structures was investigated. Undoped zinc oxide (ZnO) and F doped zinc oxide (FZO) nanoparticles were synthesized by sol gel method. The synthesized nanoparticles were coated on glass substrates by dip coating method. In the coating process, the glass substrates were immersed in undoped ZnO and FZO solutions and withdrawn at a rate of 25 cm/s at room temperature. Then, the thin film coated glasses are annealed in a square furnace at 500 °C for 1 h. Structural analyzes of the produced thin films were performed using X-ray diffraction and scanning electron microscopy. The thin film nanostructures were placed in the homemade system in order to investigate the humidity sensing characteristics such as relative humidity dependent resistance change, sensitivity, hysteresis, stability, response and recovery times and reproducibility. As a result, it is predicted that the FZO structures can be used in the humidity sensing applications and it is determined that the optimal F additive amount for application is 2 mol%.

Undoped ZnO and Zn0.995−x Al0.005Y x O (x = 0.0 (AZO), 0.005, 0.01, and 0.02) solutions were prepared by sol–gel method and grown on soda–lime glass substrates by using dip coating method. In this study, the effects of dopant concentration on the morphology, crystal structure, electrical and optical properties of Al/Y co-doped ZnO (AZOY) thin films were investigated. Structural characterization of produced thin films were examined using Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and X-ray Diffractometer (XRD), respectively. SEM images indicated that the nanoparticles are formed on the thin films surface and the particle sizes of nanostructures decrease with increasing Yttrium (Y) doping concentration. XRD results revealed that undoped ZnO and Y/Al co-doped ZnO nanostructures have single phase hexagonal (wurtzite) structure with (002) orientation. Optical properties of thin films were investigated by Varian UV–Vis. Spectrophotometer in 350–800 nm range and the band gaps of nanoparticles were calculated from the transmission data using Tauc equation. We found that the optical transmittance of AZOY samples increases up to 95% and the band gaps (Eg) of samples decrease from 3.272 to 3.242 eV with increasing the Y doping concentration. The resistance measurements were employed to understand the DC electrical performance by Y amount of each Zn995−x Al0.005Y x O thin film in the 50–300 K temperature range in the voltage interval −10 to 10 V using four point method. This measurement showed the resistivity increases with increasing Y concentration and different types of conductivity mechanisms were observed for high and low temperature regions. Finally, humidity sensing properties of AZOY films were investigated at room temperature. It was observed that the humidity sensing properties increase with increasing Y doping ion in AZOY samples.

The paper reports the fabrication of zinc oxide/porous silicon (ZnO/PS) heterojunction solar cells based on porous material and the effects of etching current density and porous structure on the performance of these solar cells. PS samples were produced by electrochemical etching on a p-type crystalline-silicon (c-Si) wafer with boron (B) doped and (111) orientation. The etching process was carried out in a HF:C2H5OH (1:3) electrolyte solution at different etching current densities of 5, 10, 15, and 25 mA/cm2 for 15 min at room temperature (RT). ZnO nanoparticles synthesized by sol–gel method were coated on PS layers by the sol–gel spin coating technique at a speed of 300 rpm for 20 s at RT for fabrication of ZnO/PS heterojunction solar cells. The structural analyses were performed using a field emission scanning electron microscope. Depending on the increase of etching current density, the pore diameter and porosity in the etched structures increased approximately from 200 to 920 nm and from 19 to 62%, respectively. Reflection characteristics of ZnO/PS heterojunction solar cells were determined using reflection measurements. The lowest optical reflection was obtained in ZnO/PS heterojunction solar cell with PS layer formed at high etching current density. The dark I–V measurements indicated that all the solar cells exhibited a typical rectifying behavior, and the ideality factor increased with the increase of etching current density. Light I–V measurements were performed under AM1.5G conditions. The short circuit current, open circuit voltage, and energy conversion efficiency (η) increased with the increase of etching current density. The best photovoltaic performance was obtained in ZnO/PS heterojunction solar cell having the PS layer produced at high etching current density of 25 mA/cm2. The highest energy conversion efficiency of 6.05% was obtained in this solar cell. It was determined that the etching current density and porous structure are important parameters affecting the photovoltaic performance of ZnO/PS heterojunction solar cells.

We measured the absorption/transmission performance of ZnO thin films doped with europium (Eu) and aluminum (Al). ZnO and Zn1−(y+0.01)(Al0.01, Euy)O (y = 0.00, 0.01, 0.03 and 0.05) nano particles were synthesized using sol–gel method and covered on a soda-lime glass surface by spin coating. After annealing at 500 °C, UV–Vis. measurements were performed in wavelength range of 300 and 800 nm to calculate the band gap of nano particles from the absorption/transmission performances. The resistivity measurements were employed to understand the relationship between band gap and DC electrical performance by Eu amount of each Zn1−(y+0.01)(Al0.01, Eu y )O thin film. As a conclusion, after reaching a minimum value with 1 mol% Eu doping, a monotonic increase in band gap was observed by enhancing Eu amounts in Zn0.99Al0.01O lattice.

In this study, the effect of zinc oxide (ZnO) coating amount on the efficieny of n-type zincoxide/p-type silicon (n-ZnO/p-Si) heterojunction solar cell was investigated. ZnO nanoparticles weresynthesized by sol gel method. The synthesized nanoparticles were coated on glass substrates and p-Sisubstrates using spin coating method. The coating process was carried out in different amounts as 2, 4,5 and 15 times. After the coating process, the thin film coated substrates were placed in a squarefurnace and annealed at 500 oC for 30 min. Structure characterization and surface morphology wereanalyzed using X-ray diffraction (XRD) method and scanning electron microscopy (SEM). For each nZnO/p-Siheterojunction solar cell structure, short circuit current (Isc) and open circuit voltage (Voc)were determined by electrical measurements and efficiency (n) calculations were made. All processeswere performed at room temperature. According to this study, the efficiency of solar cells increaseswith increasing the amount of ZnO coating up to a critical thickness and decreases when the criticalthickness is exceeded (due to the more ZnO coating). From this it was concluded that the amount ofZnO coating (ZnO layer thickness) is an important parameter affecting the performance of solar cells., Bu çalışmada, n-tipi çinko oksit/p-tipi silisyum (n-ZnO/p-Si) heteroeklem güneşhücresinin verimliliği üzerinde çinko oksit (ZnO) kaplama miktarının etkisi incelendi. ZnOnanoparçacıklar sol-jel yöntemi ile sentezlendi. Sentezlenen nanoparçacıklar, döndürerekkaplama metodu kullanılarak cam alttaşlar ve p-Si alttaşlar üzerine kaplandı. Kaplama işlemi,2, 4, 5 ve 15 kat olarak farklı miktarlarda gerçekleştirildi. Kaplama işleminden sonra, incefilm kaplı alttaşlar, kare bir fırın içerisine konuldu ve 500 oC de 30 dk tavlandı. Yapıkarakterizasyonu ve yüzey morfolojisi, X-ışını kırınımı metodu (X-ray diffraction; XRD) vetaramalı elektron mikroskobu (scanning electron microscopy; SEM) kullanılarak analiz edildi.Her bir n-ZnO/p-Si heteroeklem güneş hücresi yapısı için, kısa devre akımı (Isc) ve açık devrevoltajı (Voc) elektriksel ölçümler ile tespit edildi ve verimlilik (n) hesapları yapıldı. Tümişlemler oda sıcaklığında gerçekleştirildi. Yapılan bu çalışmaya göre, güneş hücrelerininverimi, kritik bir kalınlığa kadar, ZnO kaplama miktarının artışı ile artmakta, kritik kalınlıkaşıldığında (daha fazla ZnO kaplama yapıldığında) da düşmektedir. Buradan, ZnO kaplamamiktarının (ZnO tabaka kalınlığının) güneş hücrelerinin performansını etkileyen önemli birparametre olduğu sonucuna varıldı.

The wide uses of zinc oxide nanoparticles (nano-ZnO) in industrial, cosmetics, medicine, food production and electronics associate with increase in occupational and public exposure. Although, toxicity of nano-ZnO has been extensively studied on many different cell types and animal systems, there is a significant lack of toxicological data focus on nephrotoxic potential of nano-ZnO. In this study, the cyto- and genotoxic effects of nano-ZnO on rat kidney epithelial cells (NRK-52E) were investigated by using different assays. Nano-ZnO (10-50 nm of sizes) were synthesized by sol-gel method. For the cytotoxic effect of nano-ZnO, mean of inhibition concentration (IC50) values in cell line was evaluated by MTT, Trypan Blue (TB) and Neutral Red Uptake (NRU) assays at 25.0-100.0 μg/mL exposure concentrations. Nano-ZnO showed cytotoxic activity by acting on different targets in renal cells, with IC50 ≥ 73.05 μg/mL. Comet assay was used to evaluate the genotoxicity of nano-ZnO (12.5-50.0 μg/mL). Nano-ZnO caused statistically significant DNA damage. Our results highlight the important risk of cyto- and genotoxic effects of nano-ZnO over the kidney.