APTES and CTAB Synergistic Induce a Heterozygous CsPbBr3/Cs4PbBr6 Perovskite Composite and its Application on the Sensitive Fluorescent Detection of Iodide ions.

Recently, all-inorganic halide perovskite quantum dots (IPQD) as a new fluorescent material with excellent fluorescence properties have attracted wide attention. However, their instability in polar solvents is the main factor hindering their application in analysis. Herein, a heterozygous perovskite (CsPbBr3/Cs4PbBr6) was simultaneously prepared and stabilized by a silylanization strategy using (3-aminopropyl)-triethoxysilane (APTES) and cetyltrimethyl ammonium bromide (CTAB) assisted precipitation encapsulation method. The synthesized CsPbBr3/Cs4PbBr6 emitted an independent fluorescence at 520 nm. The obtained CsPbBr3/Cs4PbBr6 exhibited good stability in ethanol/water mixtures. It was used as a fluorescent probe for sensitively detecting iodide ions (I-) by fluorescence quenching mechanism in the concentration range of 1 ~ 70.0 µM with the detection limit (LOD) of 0.83 µM (relative standard deviation (RSD) = 1.33%, n = 20). The simplicity and high selectivity of the proposed fluorescent analysis method were the prominent features. This work could be extended to the other target ion detection by a perovskite fluorescent quenching.

Turn-on fluorescence determination of sulfide based on site-occupying modulation of MOF-copper nanocluster interaction.

A tunable interaction between Fe-MOFs (MIL-53(Fe) and kojic acid (KA)-functional copper nanoclusters (Cu NCs) has been studied. When introducing MIL-53(Fe), the Fe-O bonds can be formed between the KA on the surface of Cu NCs and MIL-53(Fe), which will induce the electron transfer from Cu NCs to MIL-53(Fe) and fluorescence quenching of Cu NCs. By introducing S2- it occupies the Fe-site of MIL-53(Fe) and impede the interaction between Cu NCs and MIL-53(Fe), rendering a "turn-on" fluorescence signal. Thus, the KA-Cu NC/MIL-53(Fe) pair is designed as fluorescence sensing for S2-, which displays a low detection limit of 18.6 nM and a wide linear detection range from 0.05 to 5 µM by fitting the fluorescence intensity at maximum wavelength of 500 nm with excitation at 400 nm. It was also applied to monitor S2- in water samples and food additives with satisfactory results, demonstrating the practicability and reliability of the sensing strategy based on the tuable MOF-Cu NC interactions.

The evaluation of the association constant between R-SN and Hg(2+).

The effective determination of heavy metals from environmental media is among the most important issues for many industrialized countries. The interaction between RS-N, as novel heavy metal probe, and metal ions was studied. RS-N shows selective color change from colorless to pink in the presence of Hg(2+) in methanol/water solvent and the UV-Vis study shows peak at 560 nm. Fluorescence data revealed that the fluorescence enhance of RS-N by Hg(2+) dramatically was the result of the formation of [Hg(2+)]RS-N complex. The effective association constants (K a ) were 3.97 × 10(5) and 0.204 × 10(5) M(-1) for Hg(2+) and Cu(2+) to RS-N, respectively. The thermodynamic parameters, enthalpy change (ΔH (0)) and entropy change (ΔS (0)), were calculated to be -6.431 ± 0.226 kJ/mol and -0.129 ± 0.008 J/K/mol, respectively, according to van't Hoff equation on the basis of Gibbs free energy (ΔG (0)) ranged from -33.8326 to -28.5389 kJ/mol.

Ratiometric fluorescent sensing of ethanol based on copper nanoclusters with tunable dual emission.

Copper nanoclusters (Cu NCs) have attracted a surge of interest in fluorescent sensors as their outstanding physicochemical and optical properties. However, most of the reports have focused on single-signal fluorescent sensors, which are susceptible to background interferences and affect accuracy of the results. Herein, we constructed a facile ratiometric fluorescent sensor for monitoring ethanol based on Cu NCs with tunable dual emission. Polyvinylpyrrolidone (PVP)-modified Cu NCs were simply prepared in water, which exhibit ratiometric dual emission, including a strong green emission at 520 nm and a weak blue emission at 450 nm. The PVP-Cu NCs in water with strong green emission display monodisperse state due to the formation of hydration shell around Cu NCs. In ethanol where the hydration shell is destructed, Cu NCs tend to aggregate and show strong blue emission. This emission shift might attribute to the enhancement of Cu-Cu metallophilic interaction with the aggregation of Cu NCs, which induces the excited-state level increasing. Thus, a ratiometric fluorescent probe for ethanol based on the PVP-Cu NCs is fabricated, which possesses rapid response (<1 min), and realize full-range detection from 0 to 100%. In addition, this ratiometric probe is successfully applied to determine the alcohol strength of alcohol beverages, demonstrating the great potential in practical application.

Diazinon determination using high performance liquid chromatography: a comparison of the ENVI-Carb column with the immunoaffinity column for the pretreatment of water and soil samples.

An immunoaffinity chromatography column was developed to remove diazinon from water and soil samples. In this paper, two types of absorbent columns, the immunoaffinity chromatography column and the ENVI-Carb column, were compared. To accomplish this, each of these columns was used to treat water and soil samples that had been spiked with diazinon at concentrations of 2.5 or 5 ng/mL (or ng/g). High performance liquid chromatography was then used to analyze the treated samples. The ENVI-Carb column recovered 87.99%-95.95% of the diazinon from water and soil with CVs of 5.08%-8.06%. The recoveries observed when the immunoaffinity chromatography column was used were slightly lower (52.61%-81.58%); however, it effectively clean up the soil samples.

Sensitive surface-enhanced Raman scattering detection of atrazine based on aggregation of silver nanoparticles modified carbon dots.

The development of precise detection methods with simply operation for pesticides in various environmental samples is a particular challenge. Here a highly sensitive surface-enhanced Raman scattering (SERS) approach for the selective detection of trace atrazine was proposed with R6G as a Raman reporter, which was adsorbed on silver nanoparticles modified carbon dots. The latter were prepared by the reduction of Ag+ by carbon dots. In the presence of atrazine, the aggregation of the modified carbon dots due to the interaction between silver nanoparticles and atrazine led to great enhancement of the SERS signal of R6G. Under optimal assay conditions, the limit of quantification was estimated to be 10 nM, which matched with the standard for drinking water quality of China and WHO defined limit. A good linear response to atrazine was found in the concentration range of 10-1000 nM with the relative standard deviations between 1.8% and 5.6%. The determination of atrazine in real water samples was also carried out to confirm the practicability of the proposed method, which showed the recoveries from 95% to 117.5%. The target induced aggregation for enhancing the signal offered great potential for sensitive on-site detection of atrazine in environments.

Development of fluorescence polarization immunoassay for the detection of organophosphorus pesticides parathion and azinphos-methyl.

Organophosphorus Pesticides (OPPs) are a group of artificially synthesized substances used in farms to control pests and to enhance agricultural production. Although these compounds show preferential toxicity to insects, they are also toxic to humans and mammals by the same mode of action. ELISA now is an alternative method to detect OPPs. But, it must bear heterogenous properties, since several separation steps are needed during the ELISA method protocols. The FPIAs, which belong to homogenous assay, for determination of OPPs parathion and zainphos-methyl have been developed. The characteristics of Dep-EDF and PM-B-EDF tracers binding with antibodies A and D were investigated in the antibodies dilution experiments. The PM-B-EDF tracer combination with antibody D was selected to construct the standard curve for parathion detection. The IC50 value and the detection of limit were 1.96 mg/L and 0.179 mg/L, respectively, as shown in the standard curve. The tracers of PBM-EDF 2 and 3, which were chased from 4 PBM-EDF tracers, exhibited the good standard curves based on the MAb AZI-110. The FPIA constructed to analyze the azinphos-methyl showed the IC50 1.003 mg/L and detection limit 0.955 mg/L when PBM-EDF 2 was employed and the IC50 0.1487 mg/L and detection limit 0.150 mg/L were obtained when PBM-EDF 3 was used.

Development of IC-ELISA for detection of organophosphorus pesticides in water.

Diethyl (carboxymethyl) phosphonate (DECP) was used as the hapten to develop an indirect competitive enzyme-linked immunosorbent assay (IC-ELISA) for detecting organophosphorus pesticides (OPs). Conjugator of DECP with bovin serum albumin (BSA) was used as the immunogen for producing the polyclonal antibodies (PcAbs). Three antisera were obtained after the immune procedure. Characterization studies of the PcAbs indicated that the titer of antiserum-1 was highest in 3 antisera, and antiserum-1 had high affinity and specificity to the parathion, dichlorvos and pirimiphos. The IC-ELISA showed an IC50 of 0.428 micro g/mL with a detection limit of 0.0125 micro g/mL to parathion. The assay also indicated that the IC50 values of pirimiphos and dichlorvos were 0.331 micro g/mL and 1.25 micro g/mL respectively, and the detection limits of pirimiphos and dichlorvos were 0.0116 micro g/mL and 0.048 micro g/mL respectively. Recoveries of parathion, pirimiphos and dichlorvos spiked into water samples ranged from 90% to 160%. The results indicated that the ELISA could be a convenient and supplemental analytical tool for monitoring OPs residues in environmental water samples.