ABSTRACT
Imidacloprid (IMI) is a systemic insecticide, which is widely used for seed treatment and pest control in vegetables. The unwarranted presence of traces of IMI in vegetables and groundwater is a matter of grave concern which needs to be detected and quantified in order to effect remedial measures for the sake of food safety. In this work, we communicate the fabrication of tungsten sulfide (WS2) nanosheets and the construction of an amperometric sensor for the precise determination of IMI. The sensor performances were evaluated by using cyclic voltammetry (CV). The presence of surface-active sites and the fast electron transfer on WS2/GCE favored the electrochemical reduction of the aromatic nitro group in IMI. The developed IMI sensor displayed a linear range of IMI detection from 10 to 90 µM with a detection limit of 0.28 µM. The developed WS2/GCE sensor also displayed good sensitivity, with a value of 3.98 µA µM-1 cm-2. The electrochemical measurements demonstrated the superior selectivity of the constructed WS2/GCE sensor for IMI detection, which makes it suitable for practical applications.
ABSTRACT
In this article we report the reversible redox switching of first hyperpolarizability of bimetallic ruthenium complexes bridged by bipyridyl tetrazine (bptz) ligands by second harmonic light scattering experiments (SHLS). We have synthesised [RuII(acac)2(CH3CN)2] and [(acac)2Ru-bptz-Ru(acac)2] complexes and measured their first hyperpolarizabilities as a function of in situ electrochemical oxidation/reduction of the metal centres. As a result of the oxidation of ruthenium centre from Ru(ii) to Ru(iii), the molecular hyperpolarizability of the complexes went up. The mixed-valence intermediate bimetallic complex and not the fully oxidized complex exhibit the highest ß value of 780 × 10-30 esu. We also demonstrated that the hyperpolarizability is reversible with the change of the oxidation state of the metal and both the complexes are stable for several cycles of redox switching. The experimental results are also supported by calculations.
