Highly sensitive modified glassy carbon sensor based on TDAN for nitrate detection in real water

Graphene Nanoparticle-Based, Nitrate Ion Sensor Characteristics

Gathering and sensing of nitrate ions in the environment due to the abundant use in industry and agriculture have become an important problem, which needs to be overcome. On the other hand, new materials such as carbon-based materials with unique properties have become an ideal choice in sensing technology. In this research, the high-density polyethylene (HDPE) polymer as a carbon source in the melted form was used and carbon nanoparticles in the form of a strand between two electrodes were analyzed. It was fabricated between copper electrodes by the pulsed arc discharge method. Subsequently, the constructed metal–nanoparticle–metal (MNM) contact was employed to recognize the nitrate ions. Therefore, NaNO₃, Pb(NO₃)₂, Zn(NO₃)₂, and NH₄NO₃ samples as a usual pollutant of industrial and agricultural wastewater were examined. All nitrate compounds in ten different densities were tested and sensor I-V characteristic was investigated, which showed that all the aforesaid compounds were recognizable by the graphene nano-strand. Additionally, the proposed structure in the presence of ions was simulated and acceptable agreement between them was reported. Additionally, the proposed structure analytically was investigated, and a comparison study between the proposed model and measured results was carried out and realistic agreement reported.

Development of a label-free electrochemical aptasensor based on diazonium electrodeposition: Application to cadmium detection in water

In this study we have developed a new aptasensor for cadmium (Cd²⁺) detection in water. Gold electrode surface has been chemically modified by electrochemical reduction of diazonium salt (CMA) with carboxylic acid outward from the surface. This was used for amino-modified cadmium aptamer immobilization through carbodiimide reaction. Chemical surface modification was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). This latter was also used for Cd²⁺ detection. The aptasensor has exhibited a good linear relationship between the logarithm of the Cd²⁺ concentration and the impedance changes in the range from 10^-3 to 10^-9 M with a correlation R² of 0.9954. A high sensitivity was obtained with a low limit of detection (LOD) of 2.75*10^-10 M. Moreover, the developed aptasensor showed a high selectivity towards Cd²⁺ when compared to other interferences such as Hg²⁺, Pb²⁺ and Zn²⁺. The developed aptasensor presents a simple and sensitive approach for Cd²⁺detection in aqueous solutions with application for trace Cd²⁺ detection in spring water samples.