Carbon dots (C-dots) is a type of fluorescent nanomaterials with excellent properties, which in combination with gold nanoparticles (AuNPs) generate structures that can be applied in various fields of science. This research developed a hybrid nanostructure between C-dots and AuNPs using a layer-by-layer (LbL) assembly to increase the surface-enhanced Raman scattering signals (SERS) for the detection of Escherichia coli. The created nanostructure was denoted as B@C-dots@AuNPs and proved by zeta potential, scanning electron microscopy, and fluorescence assays. The results showed that the introduction of AuNPs greatly enhanced the SERS signals of C-dots. The relative intensities of peaks at 2873 and 3082 cm–1 could be used for the detection of bacterium concentration with a detection limit of ca. 102 cfu/mL. In conclusion, an easy, quick, low-cost, and nontoxic technique for the detection of bacteria was developed through the coencapsulation of C-dots and AuNPs over bacteria. The findings are envisaged to facilitate the application of SERS in microbiology and related fields.

No abstract

No abstract

The X-ray fluorescence spectroscopy (XRF) has been widely applied on the analysis of elements. The traditional sample preparation needs a large sample weight and high temperature/pressure. To overcome these drawbacks, we used graphene oxide (GO) as a matrix for the carry of trace metal (copper was used as a model) and constructed a sandwich-layered GO which carried trace copper nanomembrane (SL-GO-Cu). After the optimization of filter membranes, nanomembrane composition and GO content in the bottom layer of SL-GO-Cu, the limit of detection (LOD) of SL-GO-Cu achieves 2.99 [Formula: see text]g/g. The LOD is ca. 1/3 or 1/1923 of the traditional melt pellets of trace CuO (MPT-Cu) and tabletting pellets of trace CuO (TPT-Cu) methods, respectively. The SL-GO-Cu is independent of CuO size, but varies with different Cu compounds. Recoveries of all the SL-GO-Cu samples prepared above are higher than 94% and do not show significant difference. In summary, the SL-GO-Cu is a promising method for the efficient and economical determination of trace elements.