•Di-functional probe with luminescence and recognition was synthesized.•The turn-on sensor constructed can avoid interference of excess probes.•The method was sensitive, selective and simple without complex operation.•The sensor has potential for on-site visual assay of pesticide in complex system.In this paper, a novel turn-on sensor was constructed for quantification and imaging of acetamiprid. Acetamiprid aptamer-modified ZnS:Mn probe (ZnS:Mn-Aptamer) was obtained by conjugating ZnS:Mn QDs with acetamiprid binding aptamer. The fluorescence of the probe was turn off by multi-walled carbon nanotubes (MWCNTs) based on fluorescence resonance energy transfer (FRET) between ZnS:Mn-Aptamer and MWCNTs. After acetamiprid was introduced, the fluorescence was turn on because ZnS:Mn-Aptamer specifically binded with acetamiprid. Based on the above-mentioned principle, the quantitative detection and imaging of acetamiprid in real samples were achieved. The linear equation could be described as F/F0 = 1.101 + 0.0312CA (CA represented the concentration of acetamiprid, nM) in a linear range of 0–150 nM with a detection limit of 0.7 nM. The results suggested this method had remarkable sensitivity, selectivity, and was very simple without complex operation. Meanwhile, this novel turn-on sensor has the potential of in situ visual determination for pesticide residues in complex system.

Dual stabilizer (D-penicillamine and L-cysteine)-capped CdSe nanocrystals were prepared by direct aqueous synthesis method, and their fluorescence intensities were significantly quenched by the trace amounts of Hg(II). A new method to determine trace Hg(II) was established by using the as-prepared nanomaterials as sensing elements. When the molar ratio of Cd2+(HSe−(D-Pen(L-Cys is adjusted to 1(0.25(2(1.2 at pH 7.5, CdSe/D-Pen/L-Cys possesses a better luminescent strength and stability than CdSe/D-Pen and CdSe/L-Cys. TEM results show that CdSe nanocrystals are spherical particles, and their sizes are about 50 nm and 80 nm. In phosphate buffer solution of pH 7.38, the maximum peak of the fluorescence spectra of CdSe/D-Pen/L-Cys is at 516 nm; the fluorescence could be selectively quenched by Hg(II). The fluorescence quenching was found to be proportional to the concentration of Hg(II), with a remarkable detection limit of 40 pM. The method was applied to determine Hg(II) in different water samples, and the obtained results were in good agreement with those obtained by the standard method. The average recovery was 96.7%-102.5%.

An analytical method was developed for the identification of primary vitamin D3 metabolites in human urine using liquid chromatography tandem mass spectrometry in positive mode. Urine samples were purified using C18 solid-phase extraction cartridges and analytical separations were performed by reversed phase liquid chromatography in gradient mode using ammonium acetate (0.01 mol L−1) and acetonitrile as the mobile phases. Identification and structural elucidation of the metabolites were carried out by comparison with mass spectral fragmentation behavior of vitamin D3 and retention characteristics. Three primary urinary vitamin D3 metabolites were identified as 25-hydroxyvitamin D3, 1α,25-dihydroxyvitamin D3 and vitamin D3 sulphate, respectively.

Luminescent quantum dots (QDs)-semiconductor nanocrystals are a promising alternative to organic dyes for fluorescence-based applications. We have developed procedures to use CdS to encapsulate CdTe and synthesize a new kind of functionalized CdTe/CdS QDs for the quantitative and selective determination of bovine serum albumin (BSA). Maximum fluorescence intensity was produced at pH 6.83, with excitation and emission wavelengths at 336 and 524 nm, respectively. Under optimal conditions, the straight line equation: ΔF = 6.84 + 62.29 C (10−6 mol dm−3) was found between the relative fluorescence intensity and the concentration of BSA in the range of 0–1.2 × 10−6 mol dm−3, and the limit of detection was 5.4 × 10−8 mol dm−3. Based on this approach, a novel quantitative method for the determination of BSA is presented in this paper.

A new fluorescence probe, CdSe nanocrystal has been prepared and modified with 11-mercaptoundecanoic acid [HS-(CH2)10-COOH]. The functionalized nanoparticles were characterized using transmission electron microscopy (TEM), ultraviolet–visible (UV–vis) spectroscopy and photoluminescence (PL) spectroscopy. The results demonstrate that CdSe is dispersed homogeneously in aqueous solution and well protected from the environmental oxygen. They can be used as a new fluorescence probe for lysozyme, which was simple, rapid and specific. Under the optimum condition, the response is linearly proportional to the amount of lysozyme from 0.20 to 26.0 μg ml−1, and the limit of detection is 0.115 μg ml−1. The proposed method has been applied to the determination of lysozyme in egg white, with the recovery of 96–105%.