Walled Carbon Nano-tubes a fabrication and application of a novel sensor of carbon paste electrode modified by silica gel/MWCNTs for the determination of salicylic acid (SA) by different voltammetric techniques such as Linear Sweep, Cyclic and Square Wave Voltammetry. The electrochemical behavior of SA has been investigated and the optimum experimental conditions such as the effect of supporting electrolyte, pH and scan rate on the anodic peak of SA was determined. Square Wave Voltammetry (SWV) was employed to determine SA, where the important parameters such as frequency were achieved. Moreover, the results showed that modified electrode exhibited excellent electrocatalytic activity towards the oxidation of SA. The results showed irreversible process with one oxidation peak of SA at the surface of modified electrode and the overpotential of SA decreased significantly compared with that at the bare carbon paste electrode (CPE). This electrochemical sensor shows an excellent performance for detecting SA with a detection limit and limit of quantification were 0.9 × 10 -9 M and 2.99 × 10 -9 M respectively. In addition, the peak currents increased linearly in the concentration range of 3.0-70 nM. The results showed also, the fabricated sensor was successfully applied to the detection of SA in tomato with good recovery ranging from 96.60 to 103%, Moreover, the proposed electrode revealed good reproducibility and stability, with standard deviation (S.D.) 2.3% for eight successive measurements of SA.

Detection of indole-3-acetic acid (IAA), as a phytohormone, is important for precision farming, plant phenotyping, and crop management. Herein, IAA was detected in bean and wheat plant seeds extractions using zinc oxide nanorods/carbon paste electrode (ZnO NRs/ CPE). ZnO NRs/CPE showed excellent electrocatalytic activity, high sensitivity, and selectivity toward the oxidation of IAA. The linearity range was from 30. × 10 À 8 to 5.0 × 10 À 6 M (r 2 = 0.996, n = 10), with a detection limit of 1.7 × 10 À 8 M. Moreover, ZnO NRs/CPE exhibited high reproducibility, with a standard deviation of 1.0 % for six successive measurements of IAA.

This investigation was conducted during the two successive seasons i.e. 2019 and 2020 on Zaghloul date palm grown at the experimental orchard, Faculty of Agriculture, South Valley University, Qena, Egypt. This work conducted to study the effect of different sources of potassium fertilizers on fruiting of Zaghloul date palm under Qena condition. Potassium fertilization via nano-technology, vinasse and potassin were used. The experiment was arranged in a complete randomized design with three replications. It is evident from the obtained results that using nano-potassium, either soil dressing or foliar spray, as well as foliar spray of vinasse or potassin significantly increased the fruit retention, bunch weight and yield/palm compared to fertilize by potassium sulphate (check treatment). Also, these treatments significantly improved dates quality in terms of increasing fruit weight, flesh percentage, TSS, sugar percentages and anthocyanin contents moreover, decreasing total acidity and total tannins compared to fertilize with the recommended potassium doses via potassium sulphate. From the results, it could be concluded that fertilized Zaghloul date palm with potassium fertilization via foliar spray of either nano-potassium, vinasse or potassium to improve the fertilization efficiency and get high yield with best dates quality. In addition, hasten advance the fruit ripening and overcome potassium fertilization problems.

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Carbon Paste Electrode Modified by silica gel /MWCNTs was manufactured and used for the electrochemical determination of Ascorbic acid (AA) in acetate buffer (pH=5.0) using cyclic, linear sweep voltammetry and square wave voltammetry(CV, LSV, and SWV). The results illustrated that the carbon paste modified electrode give a good response for an electrocatalytic activity toward the oxidation of AA. The electrochemical oxidation of AA at modified carbon paste electrode was diffusion-controlled and irreversible, using the optimum conditions to achieve the lower detection limit 1.07 × 10-8 M, good reproducibility, and high stability. This method has been applied to the determination of AA in orange and lemon fruits, and the recoveries were from 96% to 102%.