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The strongly enhanced electromagnetic “hotspots” from the edges and tips of nanoplates are highly preferred to significantly promote the surface enhanced Raman scattering (SERS) activity. Here, Ag nanotriangles with a sharp edge of 20 nm were prepared by the reduction of AgNO 3 using N,N-Dimethylformamide (DMF) with the assistance of Polyvinyl pyrrolidone (PVP). By loading of Ag nanotriangles onto the filter paper, a flexible SERS substrate with good activity and reproducibility was obtained and the ultratrace detection of p -aminothiophenol (pATP) with a concentration as low as 10 −8 M was achieved. The sharp edges and tips boosted SERS activity was proved by the finite element method modeling of the plasmonic properties of Ag nanotriangles with different edge thicknesses (10 − 80 nm), Ag nanosheets with different tip acutances (squares and hexagons) together with Ag nanorods, nanocubes and nanospheres. The experimental and theoretical results confirmed that the interspacing created by filter paper plays an important role in enhancing the overall SERS activity. Furthermore, it is shown that the present silver nanotriangles-loaded filter paper SERS substrate can be employed to sensitive and selective detecting ultratrace military explosives picric acid (PA) of 10 −6 M. [ABSTRACT FROM AUTHOR]

In solid targets analyzing, independent sampling pretreatment steps are usually necessary to ensure the sensitivity and robustness. Although integrated devices provide one-step sampling-analysis strategy, the enhancement of the promotion of the safe sampling and ultrasensitive sensing still needs deep-going investigation. Here, a bilayer hydrogel device was designed to realize on-site sampling and reaction with the restriction of the colorimetric signal dispersion by constructing asymmetrical diffusion. The restricted diffusion tendency of the reaction product in the bilayer hydrogel system was verified by mapping the reaction distribution. The detection of nitrite was realized through the bilayer hydrogel device with a good linear relationship towards solid nitrite residues in a range of 0–20 nmol and a naked-eye detection limit of 2.898 ng (0.042 nmol). The applicability in the analysis of practical scenarios was demonstrated by the well-sampling of the nitrite residues on different surfaces and the retention of the pattern shapes. A portable colorimetric detector incorporated with this hydrogel device was explored and showed a promising utilization for the on-site detection of nitrite residues on trolley case, bag and pickles. We expect that this bilayer hydrogel signal enhancing strategy will be favorable for the ultrasensitive probe-based analyses and integrated sensing device investigations. [Display omitted] • An ultrasensitive bilayer hydrogel sensor for solid nitrite residue analysis. • Two-step detection with safe sampling and stable chromogenic reaction. • Construction of asymmetry diffusion to enhance the colorimetric sensing signal. • High-performance portable detector for practical scenarios toward ng-level nitrite. [ABSTRACT FROM AUTHOR]

Single-crystalline (Mn,Ni)-co-doped ZnO nanosheets were in situ synthesized by a pulsed electrodeposition-assisted chemical bath deposition technique. In addition to structure and composition characterizations, detailed X-ray photoelectron spectroscopic analysis revealed that the magnetic dopants had been doped into the ZnO matrix. The nanosheets exhibited tunable room-temperature ferromagnetism. As well as spintronics, this kind of co-doped ZnO nanosheet could find interesting applications due to their large specific surface area and high population of polar faces. [Copyright &y& Elsevier]