Cu(II) can be reduced to Cu(I) by sodium ascorbate (SA) in situ, which in turn induces CuAAC reaction between the weak fluorescent compound (3-azido-7-hydroxycoumarin) and propargyl alcohol to form a strong fluorescent compound. Based on such principle, a simple and sensitive fluorescence sensor for Cu(II) can be developed, which combines the character of high selectivity of click chemistry and high sensitivity of fluorescence detection. The value of fluorescence increase factor shows a good linear relationship with the concentration of Cu(II) in the range of 0.25 μM–2.5 μM with a detection limit of 0.08 μM. In addition, the developed sensor shows high selectivity towards Cu(II) assay even in the presence of other common metal ions and it has been successfully applied to detect Cu(II) in human serum with satisfactory results.

•A electrochemiluminescence sensor for folate receptor was proposed.•The sensor combines the advantages of ECL and terminal protection.•The detection limit is 0.1204 nmol/L and the linear range is between 0.66 nmol/L and 26.31 nmol/L.•The sensor has been successfully applied to detect HeLa cells concentration.Owning to the characteristics such as high sensitivity and simplicity of apparatus, electrochemiluminescence (ECL) has become a powerful analytical technique and has been widely used. Ru(phen)32+ can be intercalated into the grooves of dsDNA and act as an ECL probe efficiently, which has been applied to develop a sensitive ECL biosensor for folate receptor in this study. One ssDNA with a thiol group at its 3′ termini had been modified on the Au electrode first, and the other ssDNA with folic acid at its 3′ termini hybridized with the former one being modified on the electrode surface to form a dsDNA. In the absence of folate receptor, the 3′-terminus in the dsDNA region can be specificity hydrolyzed into mononucleotides by ExoIII and on dsDNA presents on the electrode surface, leading to the lower of ECL intensity detected. However, in the presence of the target (folate receptor), ExoIII failed to hydrolyze the dsDNA since the one 3′-terminus had been protected by the target and the other protected by the Au electrode, resulting in the enhancement of ECL intensity. The enhanced ECL intensity has a linear relationship with the logarithm of folate receptor concentration in the range of 0.66 nmol/L and 26.31 nmol/L with a detection limit of 0.1204 nmol/L. The proposed biosensor had been applied to detect HeLa cells concentration with satisfied results.

The interaction of Gemini surfactant C12-s-C122Br with aqueous suspension of fumed silica have been investigated by DLS, Zeta potential, conductivity, pH value and fluorescence. With the increase of surfactant concentration, four regions exist during the adsorption and aggregation process, which can be recognized as ion exchange adsorption, electrostatic repulsion, adsorption layer formation by hydrophobic interactions and free micelle formation. The Gemini surfactant C12-s-C122Br shows strong adsorption ability on the fumed silica. Zeta potential was turned from negative to positive by the addition of small quantitates of C12-s-C122Br. The “dispersion-flocculation-dispersion” phenomena was observed for the addition of s=2 during 0.1 to 4 mmol L-1. 5% fumed silica dispersion system can be gelled by s=2 of 1mmol L-1. These phenomena have never been observed for the systems containing s=4 and s=6.