Flexible Ag NCs/CNFs film for colorimetric and SERS dual-mode ultrasensitive detection of mercury ions (II)

Flexible Ag NCs/CNFs films had been successfully synthesized and used as dual-mode colorimetric/SERS nanosensors for ultrasensitive detection of mercury ions. • Large area flexible Ag NCs/CNFs film has been successfully synthesized. • Ag NCs/CNFs films are used as dual-mode colorimetric/SERS nanosensors for ultrasensitive detection of mercury ions. • Ag NCs/CNF film can realize rapid and in situ detection of pollutant. As toxic heavy metal ions, mercury ions seriously affect environmental safety and human health. Therefore, prepare a rapid and sensitive sensor for mercury ions detection is of great significance. In this work, dual-mode colorimetric/SERS Ag nanocrystals (NCs)/cellulose nanofibers (CNFs) film nanosensor for ultrasensitive detection of mercury ions (II) was constructed by simple filtration method with Ag NCs and CNFs mixture. Ag NCs/CNFs film was immersed into mercury ions solutions and separated for the following experiments. Mercury ions react with Ag, reducing the content of Ag in the film, which would depress the peroxidase-like activity and SERS properties of Ag NCs/CNFs film, achieving the ultrasensitive detection of mercury ions. 3,3′,5,5′-tetramethylbenzidine (TMB) was used both as the chromogenic substrate and SERS probe. The linear detection range of the colorimetric method is 100 nM - 1 mM and the limit of detection (LOD) is 33 nM. The sensitivity of SERS method is 10 times higher than that of colorimetry. Moreover, Ag NCs/CNFs film is also proved to be an ultrasensitive SERS sensor for malachite green (MG) detection (LOD 1.1 nM). The results suggest that Ag NCs/CNF film can realize rapid and in-situ detection of pollutants, which should have a good application prospect in environmental monitoring.