Rapid simultaneous adsorption and SERS detection of acid orange II using versatile gold nanoparticles decorated NH2-MIL-101(Cr).

Acid orange II (AO II), a typical azo pigment, is strictly controlled by legislation and prohibited in foodstuffs. Herein, we prepared gold nanoparticles decorated amino-functionalized Cr-based metal-organic frameworks [NH2-MIL-101(Cr)@Au] via an in-situ reduction method as a surface-enhanced Raman scattering (SERS) substrate for simultaneous adsorption and detection of AO II. Gold nanoparticles are uniformly dispersed on the surface of NH2-MIL-101(Cr) owing to its three-dimensional (3D) structure and the interaction between -NH2 and Au ions, providing more SERS-active "hot spots". These NH2-MIL-101(Cr)@Au nanocomposites exhibited selective and high adsorption performance (419.85 mg g-1) for AO II, and could be used as superior SERS substrates for the detection of AO II with a low limit of detection (LOD) of 0.05 mg L-1 and wide detection range of 0.05-50 mg L-1 using portable Raman spectrometer. Furthermore, this SERS assay has been successfully used to determine AO II in orange juice and chili powder with good sensitivities.