The unique features of high porosity, shape selectivity, and multiple active sites make metal–organic frameworks (MOFs) promising as novel stationary phases for high-performance liquid chromatography (HPLC). However, the wide particle size distribution and irregular shape of conventional MOFs lead to lower column efficiency of such MOF-packed columns. Herein, the fabrication of monodisperse MOF@SiO₂ core–shell microspheres as the stationary phase for HPLC to overcome the above-mentioned problems is reported. Zeolitic imidazolate framework 8 (ZIF-8) was used as an example of MOFs due to its permanent porosity, uniform pore size, and exceptional chemical stability. Unique carboxyl-modified silica spheres were used as the support to grow the ZIF-8 shell. The fabricated monodisperse ZIF-8@SiO₂ packed columns (5 cm long × 4.6 mm i.d.) show high column efficiency (23 000 plates m⁻¹ for bisphenol A) for the HPLC separation of endocrine-disrupting chemicals (bisphenol A, β-estradiol, and p-(tert-octyl)phenol) and pesticides (thiamethoxam, hexaflumuron, chlorantraniliprole, and pymetrozine) within 7 min with good relative standard deviations for 11 replicate separations of the analytes (0.01–0.39, 0.65–1.7, 0.70–1.3, and 0.17–0.91 % for retention time, peak area, peak height, and half peak width, respectively). The ZIF-8@SiO₂ microspheres combine the advantages of the good column packing properties of the uniform monodisperse silica microspheres and the separation ability of the ZIF-8 crystals.

Strategies for exploring anionic templates to direct sophisticated supramolecular assembly have attracted attention. Herein, a series of new anion receptors 1–3 containing two indole-based binding sites bridged by linking spacer pyrazino[2.3-g]quinoxaline (PQ) have been rationally designed and prepared from the precursors 2,3-diindol-3′-yl quinoxaline (DIQ) and 5,6-dihydrodiindolo[3,2-a:2′,3′-c]phenazine (DIPZ). X-ray analyses showed a self-connected network and dimeric packing through hydrogen bonding and π–π stacking interaction in the solid state in the structures of 1 and 2, respectively. All three receptors exhibited a series of prominent absorption bands from the expanded π system. The indole-based expanded receptors were found to strongly and selectively bind F⁻, AcO⁻, and H₂PO₄⁻ among the tested anions (F⁻, Cl⁻, Br⁻, AcO⁻, H₂PO₄⁻, HSO₄⁻, NO₃⁻, and ClO₄⁻), and operated as efficient colorimetric sensors for naked-eye detection of fluoride anions in DMSO. These tailored building blocks captured two anions located at far-spaced binding sites, and adopted noninterfering anion-binding processes to guarantee the anion-binding affinity, topology, and dimensionality. Solid-state studies elucidated that the neutral 1–3 interacted with the tetrahedral dihydrogen phosphate anion in proper proportions and designed topologies, thus leading to the formation of a series of multidimensional networks by self-assembly in the solid state. The observations showed a well-characterized phosphate-directed assembly of multidimensional metal-free coordination polymers in the solid state, in which the formed phosphate aggregates, including dimer encapsulated in an indole-mediated hydrogen-bonded pocket and an infinite chain, behaved as anionic templates to direct the self-assembly. However, no evidence proved the presence of such phosphate-directed infinite coordination polymers in solution.

Although quantum dot (QD)-based room temperature phosphorescence (RTP) probes are promising for practical applications in complex matrixes such as environmental, food and biological samples, current QD-based-RTP probes are not only quite limited but also exclusively based on the RTP quenching mechanism. Here we report an ascorbic acid (AA) induced phosphorescence enhancement of sodium tripolyphosphate-capped Mn-doped ZnS QDs, and its application for turn-on RTP detection. The chelating ability allows AA to extract the Mn and Zn from the surface of the QDs and to generate more holes which are subsequently trapped by Mn²⁺, while the reducing property permits AA to reduce Mn³⁺ to Mn²⁺ in the excited state, thereby enhancing the excitation and orange emission of the QDs. The enhanced RTP intensity of the QDs increases linearly with the concentration of AA in the range of 0.05–0.8 μM. Thus, a QD-based RTP probe for AA is developed. The proposed QD-based turn-on RTP probe avoids tedious sample pretreatment, and offers good sensitivity and selectivity for AA in the presence of the main relevant metal ions and other molecules in biological fluids. The limit of detection (3s) of the developed method is 9 nM AA, and the relative standard deviation is 4.8 % for 11 replicate detections of 0.1 μM AA. The developed method is successfully applied to the analysis of real samples of human urine and plasma for AA with quantitative recoveries from 96 to 105 %.

L-cysteine functionalized multi-walled carbon nanotubes (MWCNTs-cysteine) are synthesized and characterized by XPS, FT-IR, XRD, and TEM. The capability of MWCNTs-cysteine for selective separation and preconcentration of heavy metal ions are statically and dynamically evaluated with Cd²⁺ as a model heavy metal ion. Unlike MWCNTs, the sorption of Cd²⁺ onto MWCNTs-cysteine is not influenced by ionic strength in a wide range. The MWCNTs-cysteine is demonstrated to be good column packings for on-line microcolumn separation and preconcentration of Cd²⁺. Effective preconcentration of Cd²⁺ on the MWCNTs-cysteine packed microcolumn is achieved in a pH range of 5.5 to 8.0. The retained Cd²⁺ is efficiently eluted with 0.5 mol L⁻¹ HCl for on-line flame atomic absorption spectrometric determination. The MWCNTs-cysteine exhibit fairly fast kinetics for the adsorption of Cd²⁺, and offer up to 1600-fold improvement of the tolerable concentrations of co-existing metal ions over the MWCNTs for on-line solid-phase extraction of Cd²⁺. With a preconcentration time of 60 s at a sample loading flow rate of 5.0 mL min⁻¹, an enhancement factor of 33 and a sample throughput of 36 h⁻¹ along with a detection limit (3s) of 0.28 µg L⁻¹ are obtained. The precision (RSD) for 11 replicate measurements is 1.6% at the 10 µg L⁻¹ level. The developed method using the MWCNTs-cysteine as sorbent is successfully applied to determination of trace cadmium in a variety of biological and environmental materials.

A facile procedure was developed to prepare size-tunable and water soluble CdTe/Cd(OH)₂ core/shell nanoparticles with high quantum yields and good stability using inexpensive inorganic precursors (CdCl₂ and elemental Te). The emission colors of the prepared CdTe/Cd(OH)₂ core/shell nanoparticles can be readily tuned from cyan to salmon pink by varying incubation time to control the growth of the Cd(OH)₂ shell onto the CdTe nanoparticles. The CdTe/Cd(OH)₂ core/shell nanoparticles were characterized by transmission electron microscopy, high-resolution transmission electron microscopy, X-ray powder diffraction spectrometry, photoluminescence and UV-Vis spectrometry. The good water-soluble nature of the CdTe/Cd(OH)₂ core/shell nanoparticles offers great potentiality for their bio-labeling application. This approach is simple, mild and readily scaled up, affording a simple way for synthesis of size-tunable inorganic metal hydroxide capped core/shell nanoparticles.