In this research, Pt1-xNix thin alloy films various counter electrode with different value of x (0, 0.5, 0.71, 0.79, 0.83, 0.91, 0.95, 0.96, 0.97, 0.98 and 1) were fabricated using electrodeposition method on FTO substrate form FTO/Pt-Ni anf too various CEs with thin layer of reduced Graphene Oxide (rGO) on FTO/Pt-Ni to FTO/Pt-Ni/rGO prepard and the effect of Ni content in the alloy layer on electocatalytic activity was investigated. Then the CEs for were used in dey-sensitized solar cells. Structural and morphology properties and electocatalytic activity properties of the various CEs, by using XRD, FESEM, CV and EIS digrams and optical properties of GO layer and rGO layer using UV-visible examined and evaluated respectively. The solar parameters were measured and studied. The results images of FESEM demonstrate yhat morphologies of Pt-Ni layer counter electrode are dependent on the stoichiometry of Pt and Ni. As results EDXA shown that by increasing the amount of Ni concentration in solution, atomic percentage of Ni atoms in the layer rises as we expected. The results of the XRD pattern CEs with a thickness of 400 nm, an amorphous structure. But by increasing the thickness of the alloy layer twice (800 nm) Pt-Ni alloy layer tetragonal structure can be seen. The XRD pattern photoelectrode, anatase phase’s tetragonal crystal displays. The results of CV measurement CEs show that all the curves are almost identical except that the peak of oxidation and reduction reaction for electrode with different Ni concentrations occurring at different voltages. The CEs without rGO layer, with Ni more in the alloy layer JRed1 is relatively less and the ERed1 more positive than and the Epp it is also larger. While foe CEs with rGO layer the highest peak JRed1 obtained JRed1 it is also more positive. The results of EIS measurement CEs show that Nyquist plot for CEs without rGO layer including a semicircle in the region of high-frequency and for CEs with rGO layer including two semicircles at the high-frequency and low-frequency regoins, respectively. By fitting the EIS experiment data with the Zview software was found that Rs for boyh types of CEs with and without rGO layer, with low level of Ni content in the alloy layers are smaller compared with that of other CEs. Rs values of the alloy CEs without rGO layer, compared with FTO/Pt, FTO/Ni Ces is less. The Rct1 and Rct2 valaues for CEs with rGO layer and low level of Ni content in the alloy layers are smaller compared with that of the other CEs. Bod-phase EIS plots for the CEs without rGO layer including one peak and for the CEs with rGO layer including CEs are two peaks. The results of photovoltaic parameters mesurment show that the solar cell with pure Pt layer as counter electrode has the highest energy conversion efficiency and fill factor compared to the other electrode. With the arrival of the Ni to alloy layer, the electrocatalytic activity in some solar cells without rGO layer in Ces decreases. The solar cells prepared with 2Pt-Ni5 and 2Pt-Ni7 counter electrode show better fill factor and energy conversion efficiency compared to other solar cells. The solar cells made with various CEs with rGO layer compared to solar celld with CEs without rGO layer, an open circuit voltage, energy conversion efficiency and fill factor less.

In this research, polymer-ZnO varistors were synthesized and their electrical nonlinear behavior investigated. Production of low voltage ceramic varistors is associated with some difficulties due to their low thickness and friability. Adding some flexible polymers to the initial compounds may be a way to solve this problem. Therefore here, several polymers such as polyethylene, polythiophene, polyprophylene and polystyrene were added to the ZnO nanopowder and as-prepared composits were formed as disk at various tempratures using hot press. Electrical bihavior of the disks was then studied by applying a DC voltage on two ends of each sample with measuring the current flowing through it. At first, polyethylene as a flexible polymer was added to zinc oxide nanopowder. Electrical behavior of this sample did not show any nonlinear effect. By adding a bit of conductive polymer such as polythiophene to the mixture of zinc oxide nanoparticles and polyethylene, nonlinear behavior was gradually appeared. In the optimized condition, breakdown voltage and nonlinear coeficient of this sample were determined to be 280V and 3.75, respectively. With replacing polyethylene by polyprophylene in this sample nonlinear coeficient and breakdown voltage increased to 4.22 and 285V, respectively. When polystyrene was utilized instead of polyethylene, the nonlinear coeficient increased to 3.83 and the breakdown voltage were decresed to 275V. In the next part of this work, ZnO nanopowder was produced from potato extract. FESEM images of the prepaerd powders show that the size of prepared ZnO nanoparticles are less than 50nm. The effect of reaction medium pH on particles size of the powder was studied and the results show that raising solvent pH causes an increase in ZnO nanoparticles size. Electrical behavior investigation of ZnO-polyethylene-polythiophene composite prepared with the latter ZnO nanoparticles shows the breakdown voltage and nonlinear coefficient are 160V and 2.95, respectively.
 

 Abstract: In this study, ZnO nanoparticles were prepared with an efficient co-precipitation method without any Surfactant. The particles were covered by ZnS and Ag2S in two steps using a chemical method at low temperature to form ZnO@ZnS and ZnO@Ag2S core-shell nanoparticles (CSNPs). In order to to produce ZnO@ZnS CSNPs, a solution of Na2S was used as a source of S2- ions. The samples were synthesized with three concentrations of the Na2S solution (0.025 M, 0.05 M, and 0.1 M).
In order to prepare a shell of Ag2S over the ZnO NPs, a specific amount of the as-grown ZnO@ZnS CSNPs was dispersed in isopropanol and a solution of AgNO3 was used as a source of Ag+ ions. The samples were synthesized with three concentrations of the later solution (0.005 M, 0.01 M, and 0.02 M).
The structural properties of core-shell nanoparticles were investigated using XRD, FTIR, and XPS. The results comfirm the presence of the shell on the surface of the core. The results of SEM and HRTEM demonstrate a full coverage of ZnO@ZnS and ZnO@Ag2S core-shell nanoparticles. The optical properties of the core-shell nanoparticles were investigated using UV-visible and PL spectroscopies. The results show that covering ZnO with ZnS and also Ag2S causes a reduction in band gap and leads to type II band alignment.
Photocatalytic degradation of Congo red dye via ZnO@ZnS CSNPs shows that, after 2h irradiation time, ZnO@ZnS CSNPs are preferable photocatalyst at pH=4 and 7 with 71% and 89% photocatalytic efficiency, respectively. While ZnO nanoparticles performe as a more active photocatalyst at pH=10. The photocatalytic activity of ZnO@ZnS CSNPs was also examined to degrade Rose Bengal dye at different pH values and compared to that of ZnO NPs. Although ZnO NPs perform as a more active photocatalyst at pH=7, the ZnO@ZnS CSNPs are preferable for degradation at a pH of 4.
Also highly sensitive and selective and easy-to-use paper sensor for detecting Cu2+ ions in aqueous solution was prepared using ZnO@ZnS core-shell nanoparticles. The reaction time were measured about 20 min and the optimum pH and buffer concentration of the Cu2+ solution presented here were obtained as 4 and 10 mM, respectively. In order to investigate the sensing activity, the paper sensor was tested in presence of different concentration of the Cu2+. The paper sensor was photographed and the results were analysed using ImageJ software. The results show that increasing the Cu2+ concentration leads to linear increase of the colour intensity of the paper sensor. Testing the paper sensor in a complex turbulent solution confirmed the practical applicability of the presented disposable paper sensor.
Also the photocatalytic activity of ZnO@Ag2S core-shell nanoparticles was investigated to degrade Eriochorom black T and Rose bangal dyes. The photocatalytic degradation of Eriochorom black T at three different pH values shows that, this dye can not be degraded at pH=7. Also photocatalytic activity of ZnO@Ag2S CSNPs is better than ZnO NPs at both acidic and basic mediums with the photocatalytic efficiency around 44% and 69%; respectively. The photocatalytic activity of ZnO@Ag2S CSNPs was also examined to degrade Rose Bengal dye at three pH values. The results demonstarate that ZnO@Ag2S CSNPs are preferable photocatalyst for degradation Rose Bengal dye at pH=4 while ZnO NPs perform as a more active photocatalyst at pH=7.