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Given the strong hydration propensity of fluoride ions, it is difficult to detect fluoride, especially inorganic fluoride, in aqueous samples. Resolving the issue of fluoride detection in aqueous samples is a scientific undertaking of great practical significance. Herein, we propose a new method for the sensitive and selective detection of fluoride in aqueous samples without the addition of organic solvents. The method involves surface-enhanced Raman spectroscopy using 1,4-diketo-3,6-diphenylpyrrolo[3,4- c ]pyrrole (DPP) compounds and Ag nanoparticles. The method is based on a diketopyrrolopyrrole compound linked to 1-butyl iodide (DPP1), which can sense fluoride sensitively and selectively. When DPP1 was combined with Ag NPs and reacted with tetrabutylammonium fluoride or inorganic fluoride in aqueous samples, an obvious Raman enhancement was obtained at the excitation wavelength of 633 nm. This response arises because the introduction of fluoride anions into the system changes the molecular orientation of DPP1 on the Ag NP substrate from horizontal to vertical, inducing a signal enhancement in the Raman spectrum. This system can detect inorganic fluoride at concentrations as low as 1.0 μmol L −1 (0.018 ppm), which is far below the public health service recommended levels for drinking water (0.7–1.2 ppm). Furthermore, using the proposed method, a linear response for fluoride in the concentration range of 1.0 × 10 −3 –1.0 × 10 −6 mol L −1 was obtained, which makes fluoride detection possible in practical samples, such as fluoride-containing toothpaste. [ABSTRACT FROM AUTHOR]

Potassium ions play pivotal roles in biological systems. A simple and effective Raman scattering-based protocol for the detection of physiological potassium ions level in human serum has been developed. We employed sodium cobaltinitrite, which can react with potassium to form potassium-sodium cobaltinitrite. Combining hydrophobic surface and the Raman scattering for potassium detection, highly reproducible Raman spectra of the potassium-sodium cobaltinitrite can be obtained with highly sensitivity. The characteristic Raman peak of potassium-sodium cobaltinitrite was used to distinguish it from other kinds of matter, and its intensity was used to monitor the amounts of potassium ions in human serum. Because of the contribution of the hydrophobic surface aggregation to the Raman, this protocol has great potential for practical detection of the potassium in human serum and has extended the measuring potential use in the detection of potassium in human serum by spectrum method. [ABSTRACT FROM AUTHOR]