Nanoleaf-derived carbon materials as a sensitivity coating for solid­phase microextraction of polycyclic aromatic hydrocarbons.

Metal-organic framework-derived carbon materials have shown extensive application in the sensitive extraction of polycyclic aromatic hydrocarbons (PAHs), but more active sites for its adsorption were still a tireless pursuit. In this study, ZIF-nanoleaf-derived carbon (NLCs) was synthesized and developed as a solid-phase microextraction (SPME) fiber (NLCs-F). The extraction performance was compared with ZIF-dodecahedron-derived carbon (DHCs) coated fiber (DHCs-F), which was prepared by only changing the ratio of the reactants. The unique morphology of NLCs provided abundant adsorption active sites for the selected PAHs, while the large average aperture facilitated selective extraction of high molecular weight analytes. Additionally, the high carbon content enhanced the strong enrichment capability for hydrophobic PAHs. Hence, the prepared NLCs-F coupled with GC-MS showed a good correlation coefficient (0.9975) in a wide linear range, low limits of detection (0.3-1.8 ng L-1), satisfactory repeatability, and reproducibility, which made it apply in the enrichment of PAHs in actual tea and coffee samples.

Efficient removal of tylosin by nitrogen-doped mesoporous carbon nanospheres with tunable pore sizes.

Efficient and selective removal of antibiotics from wastewater is quite important but challenging. In this work, the nitrogen-doped mesoporous carbon nanospheres (NMCN) with different pore size (from 2.67 to 4.62 nm) were successfully prepared by changing the hydrothermal condition, and their removal performance on tylosin was evaluated. The adsorption experimental data were fitted well with the pseudo-second-order kinetic model. Besides, Langmuir isotherm model could better describe the adsorption process. Notably, the NMCN with medium pore size (3.36 nm) exhibited the highest adsorption capacity (1333 mg g-1), which was 24% and 14% higher than that of NMCNs with smaller and larger pore size, respectively. In order to study the adsorption mechanism, the mesoporous carbon nanospheres without N-doped was prepared, and the comparison of nitrogen adsorption-desorption isotherms was conducted. The result proved that in addition to the modified surface property, large specific surface area, and high pore volume, the pore size could precisely influence the adsorption performance of the proposed adsorbent. Furthermore, the proposed NMCN material possessed a selective adsorbing ability toward tylosin in the presence of tetracycline. Clearly, the NMCN was a promising alternative to be used as high efficient and selective adsorbent in practical environment pollution treatment, especially in large-size molecule adsorption.

Double -shelled hollow ZnO/carbon nanocubes as an efficient solid-phase microextraction coating for the extraction of broad-spectrum pollutants.

Efficient extraction of pollutants with different chemical properties from environmental samples has attracted great attention in the development of analytical chemistry. However, it is still a challenge to develop an appropriate and sensitive adsorbent for determining broad-spectrum analytes. Herein, zeolitic imidazole framework-8 (ZIF-8)-derived double-shelled hollow zinc oxide/carbon (ZnO/C) nanocubes were reported as a novel coating for solid-phase microextraction (SPME). The nanocubes with a unique structure and composition were obtained by controlled etching of ZIF-8 with tannic acid (TA) followed by pyrolysis. When a ZnO/C nanocube-coated fiber (ZnO/C-F) was used to extract the complex environmental samples containing both nonpolar (benzene compounds (BTEX)) and polar (chlorophenols (CPs)) pollutants, excellent extraction performance was achieved; we obtained low detection limits (0.14-0.56 ng L-1 for BTEX and 1.10-2.84 ng L-1 for CPs), good repeatability (2.2-5.9% for six replicated extractions) and excellent reproducibility (0.61-7.8%, fiber to fiber). The broad-spectrum SPME performance was ascribed to the synergistic effect between the composition and structure of ZnO/C nanocubes. Compositionally, the uniform dispersion of ZnO and carbon framework could provide abundant adsorption active sites, where Zn-OHs bound CPs by hydrogen bonding and carbon absorbed BTEX through π-π stacking interaction and hydrophobic interaction. Structurally, the double-shelled hollow morphology of the nanocubes was favorable for the sensitive extraction. Finally, the established ZnO/C-F-based headspace-SPME method was used for the preconcentration and determination of abundant analytes from real water samples. These findings open the door for the practical use of double-shelled hollow multicompositional inorganic materials.

Large-pore ordered mesoporous carbon as solid-phase microextraction coating for analysis of polycyclic aromatic hydrocarbons from aqueous media.

In this study, large pore ordered mesoporous carbon (LP-OMC) material was first applied as solid-phase microextraction (SPME) coating for the extraction of polycyclic aromatic hydrocarbons (PAHs) from aqueous media. The LP-OMC SPME fiber was prepared via the dip-coating method in-combination with evaporation-induced self-assembly (EISA) approach. The LP-OMC coating material possessed large specific surface area with the BET surface area of 629 m2 g-1 and uniform large pore size at the mean value of 13.5 nm with a narrow pore-size distribution. The extraction performance of LP-OMC fiber for PAHs was compared with another kind of OMC fiber with pore diameter of 4.1 nm. The results implied that the LP-OMC fiber showed better extraction capability towards PAHs. The developed LP-OMC-SPME method for PAHs exhibited wide linear ranges (0.01-50 µg L-1), low detection limits (1.6-10.0 ng L-1) and good repeatabilities (3.9-7.4% for one fiber, 6.7-11.7% for fiber-to-fiber). The method was successfully applied for the analysis of PAHs in real environmental water samples with satisfactory recovery ranging from 82.6% to 112.1%.

Metal-Organic Framework-Derived Hollow Carbon Nanocubes for Fast Solid-Phase Microextraction of Polycyclic Aromatic Hydrocarbons.

Developing novel coating materials for fast and sensitive solid-phase microextraction (SPME) is highly desired but few are achieved. In this work, a new material of metal-organic framework (MOF)-derived hollow carbon nanocubes (HCNCs) was prepared as a fiber coating material for SPME. The HCNC-coated fiber (denoted as HCNCs-F) exhibited a better enrichment performance than solid carbon nanocube (SCNC)-coated fiber (denoted as SCNCs-F) and commercial fibers based on the abundant active sites of the hollow structure, hydrophobic interactions, and π-π interactions. Moreover, because of the reduced mass-transport lengths of the hollow mesoporous structure, the HCNCs-F demonstrated a faster mass transfer compared with the SCNCs-F. The HCNCs-F was used to determine the six hydrophobic polycyclic aromatic hydrocarbons (PAHs) with wide linear ranges (10-2000 ng L-1 for naphthalene and 5-2000 ng L-1 for the other five analytes), good reproducibility (relative standard deviation < 8.8%), and low detection limits (0.03-0.70 ng L-1). Finally, the HCNCs-F was successfully applied for the determination of PAHs from the real water samples. It can be concluded from the results that MOF-derived hollow carbon materials are promising candidates for the fast SPME and can be used for practical applications in analytical chemistry.

Hollow mesoporous carbon spheres-based fiber coating for solid-phase microextraction of polycyclic aromatic hydrocarbons.

In this study, a novel hollow mesoporous carbon spheres-based fiber (HMCSs-F) was fabricated to immobilize HMCSs onto a stainless steel wire for solid-phase microextraction (SPME). Characterization results showed that the HMCSs-F possessed a large specific surface area, high porosity and uniform pore size. To demonstrate the extraction performance, a series of polycyclic aromatic hydrocarbons (PAHs) was chosen as target analytes. The experimental parameters including extraction and desorption conditions were optimized. Compared to commercial fibers, the HMCSs-F exhibited better extraction efficiency for PAHs. More interestingly, a good extraction selectivity for PAHs from the complex matrix was observed in these HMCSs-F. The enhanced SPME performance was attributed to the unique pore structure and special surface properties of the HMCSs. Furthermore, under the optimum conditions, the limits of detection (LODs) for the HMCSs-F were in the range of 0.20-1.15ngL-1 with a corresponding relative standard deviation that was below 8.6%. The method was successfully applied for the analysis of PAHs in actual environmental water samples with recoveries ranging from 85.9% to 112.2%. These results imply that the novel HMCSs-F have potential application in environmental water analysis.

Ordered mesoporous silica film as a novel fiber coating for solid-phase microextraction.

Ordered mesoporous silica (OMS) film supported on anodized titanium wire was fabricated as a new solid phase microextraction (SPME) fiber for the extraction of chlorophenols (CPs) from aqueous media followed by the determination with gas chromatography flame ionization detection (GC-FID). The supported OMS film was prepared via a solvent evaporation-induced self-assembly approach (EISA) combined with dip-coating technology. Commonly used fragile fused silica fiber was replaced by anodized titanium wire. The coating materials were characterized by N2 adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetric (TG) analysis. The N2 adsorption-desorption results show the OMS material has well-ordered mesostructure with uniform pore diameter. The SEM images verify that the OMS film was successfully grafted onto the surface of anodized titanium wire. The resultant method based on the OMS fiber exhibited wide linear ranges (0.2-200µgL-1), low detection limits (0.03-0.12µgL-1) and good repeatabilities (6.2-9.8% for one fiber, 8.9-13.2% for fiber-to-fiber). No significant change was observed after being subjected into high temperature or immersed in organic solvents. The new fiber was successfully applied to the extraction and determination of three CPs compounds in the natural water samples. Thus, the OMS fiber is a promising alternative to the commercial fiber as it is easily and inexpensively prepared with high extraction capacity and good stability.

Nanostructured CoP: An efficient catalyst for degradation of organic pollutants by activating peroxymonosulfate.

A new catalyst system of CoP/peroxymonosulfate (PMS) is presented, which achieved significant improvement in catalytic activity. Nanostructured CoP, obtained by a simple solid-state reaction, exhibited dramatic catalytic activity with 97.2% degradation of orange II of 100ppm within 4min. Moreover, the high efficiency could be reached for other phenolic pollutants, i.e., phenol and 4-chlorophenol. The reaction rate is much higher than the most reported catalysts. Effect of parameters on catalytic activity of the catalyst was studied in detail. Notably, initial pH of the solution had a slight negative effect on the catalytic performance over the pH range 4.07-10.92, suggesting that CoP has the great adaptability of pH. CoP/PMS demonstrated excellent anti-interference performance toward anions (Cl-, NO3-, and HCO3-). In addition, the pathway of degradation of orange II is proposed by analyzing its intermediates. Based on the XPS spectra of CoP, the identification of the reactive species (OH and SO4-) by electron paramagnetic resonance (EPR) analysis and quenching tests, a possible mechanism for activation of PMS by CoP was proposed. Considering the dramatic catalytic activity, a wide range of pH catalyst suited, CoP is believed to provide robust support for the promising industrial application of AOPs.