The sensitive and selective determination of fluoride ions is particularly significant in environmental protection, food safety, and health care products. In this work, a highly selective turn-on fluorescent probe for fluoride ions has been synthesized by simply functionalizing fluorescent isophthalaldehyde with silicone-oxygen bonding. The selectivity of the probe is based on the specific reactivity of the silyl group toward fluoride ions in aqueous solution. The nucleophilic substitution reaction of fluoride ions triggers the cleavage of the Si-O bond to release a strongly fluorescent product, which can be used for the determination of fluoride ions by fluorescence intensity enhancement. The probe molecules are specifically responsive and highly selective for the fluoride anion over other relevant anions and cations. This fluorescent probe also shows high photostability and exhibits good sensitivity for fluoride ions, and the limit of detection is as low as 67 ppb. We have demonstrated its application for on-site sensitive determination of fluoride ions for environmental monitoring and protection.

This work reports a novel dual-emissive fluorescent probe based on dye hybrid silica nanoparticles for ratiometric measurement of the hydroxyl radical (˙OH). In the probe sensing system, the blue emission of coumarin dye (coumarin-3-carboxylic acid, CCA) immobilized on the nanoparticle surface is selectively enhanced by ˙OH due to the formation of a coumarin hydroxylation product with strong fluorescence, whereas the emission of red fluorescent dye encapsulated in the silica nanoparticle is insensitive to ˙OH as a self-referencing signal, and so the probe provides a good quantitative analysis based on ratiometric fluorescence measurement with a detection limit of 1.65 μM. Moreover, the probe also shows high selectivity for ˙OH determination against metal ions, other reactive oxygen species and biological species. More importantly, it exhibits low cytotoxicity and high biocompatibility in living cells, and has been successfully used for cellular imaging of ˙OH, showing its promising application for monitoring of intracellular ˙OH signaling events.

Silicon nanowire arrays (SiNWAs) decorated with metallic nanoparticle heterostructures feature promising applications in surface-enhanced Raman scattering (SERS). However, the densely arranged SiNWAs are usually inconvenient for the following decoration of metallic nanoparticles, and only the top area of silicon nanowires (SiNWs) contributes to the SERS detection. To improve the utilization of the heterostructure, herein, oblique SiNWAs were grown separately, and Ag nanoparticles (AgNPs) were uniformly deposited by magnetron sputtering to get the three-dimensional (3D) SiNWAs decorated with AgNPs (AgNPs-SiNWAs) SERS substrate. The large open surfaces of oblique SiNWs would create more surface area available for the formation of hotspots and improve the adsorption and excitation of analyte molecules on the wire. The optimized AgNPs-SiNWAs substrate exhibits high sensitivity in detecting chemical molecule Rhodamine 6G, and the detection limit can reach 1 × 10−10 M. More importantly, the substrate also can be used as an effective DNA sensor for label-free DNA detection.

Well-organized hybrid nanocables consisting of carbon nanotube (CNT) core and mesoporous TiO2 sheath has been synthesized through a combined sol–gel and hydrothermal process. By using hexadecylamine as a structure directing agent, mesoporous TiO2 with thickness ranging from 40 to 70 nm was uniformly deposited on multi-walled CNTs. The resultant one dimensional CNT core/mesoporous TiO2 sheath (CNT@mesoporous TiO2) hybrid nanocables shows well-crystallized quality, porous feature and large surface area, favoring its electrochemical performance. Compared with reference TiO2 without CNTs, the CNT@mesoporous TiO2 hybrid nanocables shows largely enhanced rate performance, which could be attributed to its unique structure as well as the improvement of electronic conductivity by adding conductive CNTs.