Jianming Pan

Preparation of molecularly imprinted nanoparticles with superparamagnetic susceptibility through atom transfer radical emulsion polymerization for the selective recognition of tetracycline from aqueous medium.

In the work, we reported an effective method for the preparation of molecularly imprinted nanoparticles with superparamagnetic susceptibility through atom transfer radical emulsion polymerization (ATREP), and then as-prepared magnetic molecularly imprinted nanoparticles (MMINs) were evaluated as adsorbents for selective recognition of tetracycline (TC) molecules from aqueous medium. The resulting nanoparticles were characterized by FT-IR, TGA, VSM, SEM and TEM. The results demonstrated MMINs with a narrow diameter distribution were cross-linked with modified Fe3O4 particles, composed of imprinted layer and exhibited good magnetic sensitivity, magnetic and thermal stability. Batch rebinding studies were carried out to determine the specific adsorption equilibrium, kinetics, and selective recognition. The estimated adsorption capacity of MMINs towards TC by the Langmuir isotherm model was 12.10 mgg(-1) at 298 K, which was 6.33 times higher than that of magnetic non-molecularly imprinted nanoparticles (MNINs). The kinetic property of MMINs was well-described by the pseudo-second-order rate equation. The results of selective recognition experiments demonstrated outstanding affinity and selectivity towards TC over competitive antibiotics. The reusability of MMINs showed no obviously deterioration at least five repeated cycles in performance. In addition, the MMINs prepared were successfully applied to the extraction of TC from the spiked pork sample.

Extraction and mechanism investigation of trace roxithromycin in real water samples by use of ionic liquid-salt aqueous two-phase system.

The ionic liquid, as a green solvent, has several advantages over the organic solvents in traditional liquid-liquid extraction. Aqueous two-phase system (ATPS) consisting of a hydrophilic ionic liquid (1-butyl-3-methylimidazolium tetrafluoraborate, [Bmim]BF(4)) and Na(2)CO(3), which is a novel, simple, non-toxic and effective sample pretreatment technique coupled with molecular fluorescence spectrophotometry, was developed for the simultaneous separation, enrichment and rapid analysis of roxithromycin. The extraction yield of roxithromycin in [Bmim]BF(4)-Na(2)CO(3) aqueous two-phase system is influenced by the types of salts, concentrations of Na(2)CO(3) and [Bmim]BF(4), as well as the extracting temperature. Under the optimum conditions, the average extraction efficiency is up to 90.7%. The mechanism of ionic liquid-salt ATPS formation was discussed by hydration theory, and the extraction mechanism of the [Bmim]BF(4)-salt ATPS was investigated by FT-IR spectroscopy and UV-vis spectroscopy. The results demonstrate that no chemical (bonding) interactions are observed between ionic liquid and roxithromycin, while the nature properties of the roxithromycin are not altered. This method was practical when applied to the analysis of roxithromycin in real water samples with the detection limit of 0.03 microg mL(-1), relative standard deviation (RSD) of 1.9% (n=13), and linear ranges of 1.00-20.00 microg mL(-1). The proposed extraction technique will be promising in the separation of other small biomolecules.

Fabrication and Evaluation of Magnetic/Hollow Double-Shelled Imprinted Sorbents Formed by Pickering Emulsion Polymerization

Magnetic/hollow double-shelled imprinted polymers (MH-MIPs) were synthesized by Pickering emulsion polymerization. In this method, attapulgite (ATP) particles were used as stabilizers to establish a stable oil-in-water emulsion, and a few hydrophilic Fe3O4 nanoparticles were allowed to be magnetic separation carriers. The imprinting system was fabricated by radical polymerization in the presence of the functional and polymeric monomers in the oil phase. The results of characterization indicated that MH-MIPs exhibited magnetic sensitivity (Ms = 4.76 emu g(-1)), thermal stability (especially below 200 °C), and hollow structure and were composed of exterior ATP shells and interior imprinted polymers shells. Then MH-MIPs were evaluated as sorbents for the selective binding of λ-cyhalothrin as a result of their magnetism, enhanced mechanical strength, hydrophilic surface, and recognition ability. The kinetic properties of MH-MIPs were well described by the pseudo-second-order equation, indicating that the chemical process could be the rate-limiting step in the adsorption process for λ-cyhalothrin. The equilibrium adsorption capacity of MH-MIPs was 60.06 μmol g(-1) at 25 °C, and the Langmuir isotherm model gave a better fit to the experimental data, indicating the monolayer molecular adsorption for λ-cyhalothrin. The selective recognition experiments also demonstrated the high affinity and selectivity of MH-MIIPs toward λ-cyhalothrin over fenvalerate and diethyl phthalate.

Synthesis, characterization, and adsorption performance of Pb(II)-imprinted polymer in nano-TiO2 matrix.

Surface ion-imprinted in combination with sol-gel process was applied to synthesis a new Pb(II)-imprinted polymer for selective separation and enrichment of trace PbO(II) from aqueous solution. The prepared material was characterized by using the infrared spectra, X-ray diffractometer, and scanning electron microscopy. The batch experiments were conducted to study the optimal adsorption condition of adsorption trace Pb(II) from aqueous solutions on Pb(II)-imprinted polymer. The equilibrium was achieved in approximately 4.0 h, and the experimental kinetic data were fitted the pseudo second-order model better. The maximum adsorption capacity was 22.7 mg/g, and the Langmuir equation fitted the adsorption isotherm data. The results of selectivity experiment showed that selectively adsorbed rate of Pb(II) on Pb(II)-imprinted polymer was higher than all other studied ions. Desorption conditions of the adsorbed Pb(II) from the Pb(II)-imprinted polymer were also studied in batch experiments. The prepared Pb(II)-imprinted polymer was shown to be promising for the separation and enrichment of trace Pb(II) from water samples. The adsorption and desorption mechanisms were proposed.

Synthesis of chitosan/γ-Fe2O3/fly-ash-cenospheres composites for the fast removal of bisphenol A and 2,4,6-trichlorophenol from aqueous solutions.

The chitosan/fly-ash-cenospheres/γ-Fe(2)O(3) (CTS/γ-Fe(2)O(3)/FACs) magnetic composites were prepared by microemulsion process. The resulting composites were characterized by XRD, FT-IR, SEM, TGA, DTG and VSM, and the results indicated that CTS/γ-Fe(2)O(3)/FACs exhibited magnetic property (M(s)=6.553 emu g(-1)) and thermal stability, and composed of chitosan wrapping magnetic γ-Fe(2)O(3) and fly-ash-cenospheres (thickness of the cross-linked chitosan was about 5.2 μm). Then the CTS/γ-Fe(2)O(3)/FACs were employed as adsorbents for the fast removal of bisphenol A (BPA) and 2,4,6-trichlorophenol (TCP) from aqueous solutions. The adsorption performances of CTS/γ-Fe(2)O(3)/FACs were investigated by batch mode experiments with respect to pH, temperature, initial concentration, contact time and binary solution system. The Langmuir isotherm model was fitted to the equilibrium data better than the Freundlich model, and the kinetic properties were well described by the pseudo-second-order equation. The effects of binary solution systems also demonstrated that BPA adsorption onto CTS/γ-Fe(2)O(3)/FACs was more affected by the simultaneous presence of competitive phenolic compound than that of TCP. In addition, the resulting composite reusability without obviously deterioration in performance was demonstrated by at least three repeated cycles.

Selective recognition of 2,4,5-trichlorophenol by temperature responsive and magnetic molecularly imprinted polymers based on halloysite nanotubes

Fe3O4/Halloysite nanotube magnetic composites (MHNTs) were firstly prepared via an effective polyol-medium solvothermal method, and then the surface of the MHNTs was endowed with reactive vinyl groups through modification with 3-(methacryloyloxy)propyl trimethoxysilane (MPS). Based on the MHNTs-MPS, temperature responsive and magnetic molecularly imprinted polymers (t-MMIPs) were further synthesized by adopting methacrylic acid (MAA) and N-isopropylacrylamide (NIPAM) as the functional monomer and temperature responsive monomer, respectively. The as-prepared t-MMIPs were characterized by FT-IR, TEM, TGA and VSM, which indicated that the t-MMIPs exhibit magnetic sensitivity (Ms = 2.026 emu g−1), magnetic stability (especially in the pH range of 4.0–8.0) and thermal stability and are composed of an imprinted layer. The molecular interaction between 2,4,5-trichlorophenol (TCP) and MAA was investigated by 1H-NMR spectroscopy and ultraviolet absorption spectroscopy, which suggest that hydrogen bonding may be largely responsible for the recognition mechanism. The t-MMIPs were then applied to selectively recognise and release TCP molecules at 60 °C and 20 °C, respectively. The maximum amount of binding at 60 °C was 197.8 mg g−1 and 122.6 mg g−1 for t-MMIPs and temperature responsive and magnetic non-imprinted polymers (t-MNIPs), respectively. At 20 °C, about 32.3%–42.7% of TCP adsorbed by t-MMIPs was released, whereas 25.3%–39.9% of TCP was released by t-MNIPs. The selective recognition experiments demonstrated the high affinity and selectivity of t-MMIPs towards TCP over competitive phenolic compounds, and the specific recognition of binding sites may be based on the distinct size, structure and functional group to the template molecules.

Highly-controllable imprinted polymer nanoshell at the surface of magnetic halloysite nanotubes for selective recognition and rapid adsorption of tetracycline

Here, a general and effective method for preparing molecularly a imprinted polymer nanoshell on magnetic halloysite nanotubes (MHNTs) to make highly-controllable core–shell nanorods (MMINs) is described for the first time, and the as-obtained nanomaterials were then used for selective recognition and rapid adsorption of tetracycline (TC) from aqueous solution. Magnetic nanoparticles were uniformly loaded into the lumen of halloysite nanotubes (cheap, abundantly available and durable) using the impregnation and pyrolysis method. Vinyl groups were then anchored at the surface of MHNTs, subsequently directing the highly selective occurrence of imprinted polymerization at the surface, and the uniformly core–shell imprinted nanorods were easily produced via in situ precipitation polymerization, with tunable nanoshell thickness, by controlling the total amounts of monomers. The MMINs with a shell thickness of 35 nm exhibited the largest saturation adsorption capacity to TC, and the equilibrium data was well-described using the Langmuir isotherm model. The kinetic experiment showed the adsorption process reached equilibrium in about 10 min, and a pseudo-second-order kinetic model was used to fit the data well. The nanocomposites displayed selective recognition for TC and could be rapidly separated from solution by a magnet, with good stability and regeneration property, which provided practical applications for wastewater treatment, biological molecule purification and drug extraction.

Recent advances in non-enzymatic electrochemical glucose sensors based on non-precious transition metal materials: opportunities and challenges

With the booming requirements for diabetes management, food quality control, and bioprocess inspection, monitoring of glucose in various matrices has drawn unprecedented interest of both academic and industrial researchers recently. As a relatively new class of glucose sensors, enzyme-free detection of the target is capable of providing several fascinating characters such as ultra-high sensitivity, excellent stability, and simple fabrication. Considering the rapid expansion of the glucose determination field without using any biological enzymes, here we focus our attention on updating the latest advances in non-enzymatic electrochemical glucose sensors based on non-noble transition metal materials achieved in the past few years. In this minireview, both the superiorities and the intrinsic drawbacks of detecting glucose by employing non-precious materials including Ni, Cu, Co, Mn, and Fe are intensively highlighted, followed by a systematic discussion on the important progress harvested for enzymeless glucose sensing. Finally, the potential opportunities of non-noble transition metal materials in fabricating high-performance enzyme-free glucose sensors are given, and the current challenges for their practical applications are also summarized.

Acid–chromic chloride functionalized natural clay-particles for enhanced conversion of one-pot cellulose to 5-hydroxymethylfurfural in ionic liquids

By grafting –SO3H and Cr(III) onto the surface of treated attapulgite (ATP) and halloysite nanotubes (HNTs), two acid–chromic chloride bi-functionalized catalysts i.e. ATP–SO3H–Cr(III) and HNTs–SO3H–Cr(III) were successfully synthesized. Then the as-prepared catalysts were characterized by SEM, TEM, EDS, XPS, BET, NH3–TPD, nitrogen adsorption–desorption and TG analysis. The catalytic activities of the synthesized ATP–SO3H–Cr(III) and HNTs–SO3H–Cr(III) were evaluated for the conversion of one-pot cellulose to 5-hydroxymethylfurfural (HMF) in an ionic liquid ([EMIM]-Cl) system. The amount of catalyst, reaction time and reaction temperature were optimized for cellulosic conversion over the two catalysts, resulting in a maximum yield of 31.20% for ATP–SO3H–Cr(III) and 41.22% for HNTs–SO3H–Cr(III) under the optimized conditions. The clay supported catalysts developed in this work showed greatly improved performances in cellulose-to-HMF conversion over other solid catalysts. In addition, the prepared catalysts could be very easily recycled, at least three times for ATP–SO3H–Cr(III) and twice for HNTs–SO3H–Cr(III) without significant loss of activity.

Molecularly imprinted polymer surfaces as solid‐phase extraction sorbents for the extraction of 2‐nitrophenol and isomers from environmental water

The novel surface molecularly imprinted polymer (MIP) with 2-nitrophenol (2-NP) as the template has been prepared and used as the adsorbent for the solid-phase extraction (SPE). The selectivity of the polymer was checked toward several selected nitrophenols (NPs) such as 2-NP, 3-nitrophenol (3-NP), 4-nitrophenol (4-NP) and 2,4,6-trichlorophenol (2,4,6-TCP). Under the optimized conditions, high sensitivity (detection limits: 0.07-0.12 ng/mL) and good reproducibility of analytes (2.3-4.8% for four cycles) were achieved. Then, the method was applied for the analysis of selected phenols in spiked tap, lake and river water samples. High recoveries (>83.3%) for nitrophenols (NPs) were obtained, but lower recoveries (<63.4%) were achieved for 2,4,6-TCP. The method was found to be linear in the range of 1-300 ng/mL with correlation coefficients (R(2) ) greater than 0.99 and repeatability relative standard deviation (RSD) below 7.2% in all cases. For analysis of 120 mL water samples, the method detection limits (LODs) ranged from 0.10 to 0.22 ng/mL and the limit of quantification (LOQs) from 0.33 to 0.72 ng/mL. These results showed the suitability of the MIP-SPE method for the selective extraction of a group of structurally related isomeric compounds.