Electrochemical sensors based on gold nanoparticles modified with rhodamine B hydrazide to sensitively detect Cu(II)

Highlights: • An electrochemical sensor based on gold nanoparticles modified with rhodamine B hydrazide (AuNPs-RBH) was developed. • The sensor was applied in the highly sensitive and selective detection of Cu²⁺ in water. • The electrochemical sensor displays excellent regeneration, stability, and practicability for Cu²⁺ detection. • EIS was used to determine Cu²⁺ ions in an aqueous solution with the developed AuNPs-RBH-based electrochemical sensor. - Abstract: An electrochemical sensor based on gold nanoparticles (Au NPs) modified with rhodamine B hydrazide (RBH) (AuNPs-RBH) was developed and applied in the highly sensitive and selective detection of Cu²⁺ in water. RBH molecules were bounded onto the surface of AuNPs via the strong interaction between the amino groups and Au NPs. The chemical structure variations were characterized by X-ray photoelectron spectroscopy and fluoresence spectroscopy. Additionally, electrochemical impedance spectroscopy was used to determine Cu²⁺ ions in an aqueous solution with the developed AuNPs-RBH-based electrochemical sensor. Results show that the fabricated sensor exhibits good electrochemical performance because of the presence of Au NPs and high affinity with the Cu²⁺ resulting from the strong coordination chemistry between Cu²⁺ and RBH. The as-developed sensor towards detecting Cu²⁺ has a detection limitation of 12.5 fM within the concentration range of 0.1 pM–1 nM by using the electrochemical impedance technique. It also displays excellent selectivity, regeneration, stability, and practicability for Cu²⁺ detection. Therefore, the new strategy of the RBH-based electrochemical sensor exhibits great potential application in environment treatment and protection.