A highly selective Ag⁺ sensor based on 8-hydroxyquinoline functionalized graphene oxide -silica nanosheet and its logic gate behaviour

An 8-hydroxyquinoline functionalized graphene oxide-mesoporous silica nanocomposite (GS-Q) was synthesized and its fluorescence properties were studied to evaluate the sensing capability of GS-Q toward metal cations. By selection of the appropriate excitation wavelength as 360 nm, the aqueous suspension of GS-Q showed a broad emission peak around 480 nm that was influenced by some cations such as alkaline earth and transition metal ions. Besides, a second-order scattering (SOS) signal, amounting to twice the excitation wavelength 720 nm, was observed in the emission spectra that selectively responded to Ag⁺ ions in the presence of other metal ions. The linear response of the SOS signal to the concentration of Ag⁺ makes for a versatile and selective probe for the detection of silver ions based on the enhancement of the SOS signal. Furthermore, the remarkable dual-output signal effect of GS-Q was exploited to study the logic behavior of GS-Q in the aqueous media and consequently a solid support logic circuit was constructed by producing two optical outputs under the stimulation of Al³⁺, Fe³⁺ and Ag⁺ ions, as inputs.