Wenming Yang

Selective Adsorption of Dibenzothiophene using Magnetic Molecularly Imprinted Polymers

In this study, a novel and quick method for selective adsorption of dibenzothiophene (DBT) from gasoline using magnetic molecularly imprinted polymers (MMIPs) as the adsorbent has been employed. The MMIPs were prepared by a surface molecular imprinting technique, using Fe3O4 magnetite nanoparticles as a magnetically susceptible component, DBT as template molecule, 4-vinylpyridine (4-VP) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker. The synthetic MMIPs were characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). The adsorption performances of MMIPs were investigated by batch adsorption experiments in terms of adsorption kinetics, isotherms and selective recognition. The results of the study indicated that MMIPs were able to adsorb DBT well, the adsorption equilibrium time was about 5 h and the equilibrium adsorption amount was 22.23 mg/g at 318 K. In the corresponding selectivity test, MMIPs exhibited a greater adsorption capacity towards DBT than the other three analogues.

Computer-aided design and synthesis of magnetic molecularly imprinted polymers with high selectivity for the removal of phenol from water.

A molecular simulation method was introduced to compute the phenol-monomer pre-assembled system of a molecularly imprinted polymer. The interaction type and intensity between phenol and monomer were evaluated by combining binding energy and charge transfer with complex conformation. The simulation results indicate that interaction energies are simultaneously affected by the type of monomer and the ratio between phenol and monomers. At the same time, we considered that by increasing the amount of functional monomer is not always better for preparing molecularly imprinter polymers. In this study, three kinds of novel magnetic phenol-imprinted polymers with favorable specific adsorption effects were prepared by the surface imprinting technique combined with atom transfer radical polymerization. Various measures were selected to characterize the structure and morphology to obtain the optimal polymer. The characterization results show that the optimal polymer has suitable features for further adsorption process. A series of static adsorption experiments were conducted to analyze its adsorption performance, which follows the Elovich model from the kinetic analysis and the Sips equation from the isothermal analysis. To further verify the reliability and accuracy of the simulation results, the effects of different monomers on the adsorption selectivity were also determined. They display higher selectivity towards phenol than 4-nitrophenol.The results from the simulation of the pre-assembled complexes are in reasonable agreement with those from the experiment.

Preparation and characterization of self-assembly organic multilayer films on silica surface

Abstract The preparation and characterization of self-assembly organic multilayer films on hydroxylated silica (SiO 2 ) surface are reported. The multilayer films, constructed via SiO cross-links and Schiff base reactions alternately, are characterized by advancing-contact-angle measurement, grazing-incidence IR spectroscopy and X-ray photoelectron spectroscopy. The results indicate that both SiO bonding and Schiff base reactions at the solid/liquid interface, on the employed strict experiment condition, are successful. The superlattice multilayer films have an ABAB…stacking sequence and good structural regularity. The aromatic moiety is interlocked between two short alkyl chains and perpendicular to the surface.

Thermosensitive molecularly imprinted polymers based on magnetic nanoparticles for the recognition of sulfamethazine

In this study, a thermosensitive molecularly imprinted polymer (TMIP) was successfully synthesized for the selective recognition of sulfamethazine (SMZ) on the surface of magnetic nanoparticles. N-Isopropylacrylamide (NIPAM) as the thermosensitive monomer, methacrylic acid (MAA) as the functional monomer, ethyleneglycol dimethacrylate (EGDMA) as the cross-linking agent and azodiisobutyronitrile (AIBN) as the initiator were selected to prepare the TMIPs. The thermosensitive magnetic molecularly imprinted polymers were sensitive to the temperature and the adsorption/desorption process could be controlled by changing the temperature because the thermoresponsive monomer NIPAM can undergo a reversible volume transition between the swollen and collapsed phases. Moreover, the resultant TMIPs showed high adsorption capacity and specific affinity towards SMZ. The adsorption capacity of TMIPs reached the maximum when the adsorption temperature was around the LCST of NIPAM. The magnetic property of TMIPs provided fast separation while the thermoresponsive property offered simple elution for templates. Finally, the imprinted polymers were used for the enrichment of SMZ from real water with recoveries ranging from 83.2% to 96.8% determined by high performance liquid chromatography. The results indicated that the TMIPs were efficient for thermally modulated capture and release of the template, which enable its application for trace sulfamethazine in complicated samples.

Rational design and preparation for novel denitrogenation adsorbents by computational simulation and improved atom transfer radical polymerization

Novel denitrogenation adsorbents with favourable specific adsorption effect were designed by computational simulation and prepared rationally by combining the modified surface imprinting technique with improved atom transfer radical polymerization. The simulated results show that interaction energies are simultaneously affected by both the type of monomer and the ratio between indole and monomers. Adding more monomers wrongly will affect the interaction energy between template and monomer. The structural properties of the adsorbents are discussed by using various characterization measures such as nitrogen sorption measurements, infrared spectrophotometry, scanning electron microscopy and thermogravimetric analysis. A series of static adsorption tests such as kinetic, isotherm, thermodynamic and selectivity were used to analyse the adsorption performance. The test results show that the novel adsorbents conformed to the Elovich kinetic equation and followed the Langmuir isothermal model. Meanwhile, they display higher selectivity towards indole than towards other analogues. The novel adsorbents have a potential application value in the denitrogenation field.

Electrochemical sensor based on lead ion-imprinted polymer particles for ultra-trace determination of lead ions in different real samples

In this paper, a self-manufactured lead(II)-selective electrode, which was based on the use of lead(II) ion imprinted polymer particles (IIPs) to detect lead ions, was studied using differential pulse voltammetry. The synthesis and preparation of the IIPs was by precipitation polymerization with methacrylic acid (function monomer and lead-binding ligand), ethylene glycol dimethacrylate (the cross-linker) 2,2-azobisisobutyronitrile (the initiator) and lead ions (the template ion) in an acetonitrile solution. The IIPs were prepared to establish the electrochemical sensor by leaching out the lead(II) from the imprinted polymer particles, and a carbon paste electrode was modified with lead(II) IIPs. There is a distinct difference in the response between the electrodes modified with IIPs and the electrodes modified with NIPs, which included the open circuit sorption of Pb2+ on the electrode and its reduction to its metallic form. The influence factors on the response behavior of the electrodes were investigated and optimized. The results show the introduced sensor was linear from 1.0 × 10−9 to 7.5 × 10−7 mol L−1, and the limit of detection (LOD) was 1.3 × 10−11 mol L−1 (S/N = 3). Finally, the sensor was successfully applied to the trace determination of lead ions in various real samples.

Development of surface imprinting polymer as a selective adsorbent for adsorbing and separating dibenzothiophene from fuel oil

A novel surface molecular imprinting approach was used to synthesize a desulfurization imprinting polymer (MIP–SiO2/TiO2). Its structure and characters were investigated by using infrared spectrophotometry, X-ray diffraction, field emission scanning electron microscopy, and nitrogen sorption measurements. The structural superiority of MIP–SiO2/TiO2 was reflected by the above measurements. The adsorption behavior of MIP–SiO2/TiO2 was evaluated by using batch static adsorption experiments by the kinetic, isotherm, and thermodynamic analyses. The experimental results show that the adsorption process follows a pseudo-second-order kinetic model and that the experimental data are well fitted with the Freundlich isothermal equation. The thermodynamic analysis indicate that the adsorption process is endothermic in nature. Meanwhile, it was further demonstrated that the prepared adsorbent has high specificity for dibenzothiophene. The approach we described would provide a new opportunity in the deep desulfurization field.

A core–shell CdTe quantum dots molecularly imprinted polymer for recognizing and detecting p-nitrophenol based on computer simulation

In this study, molecularly imprinted technology, combined with fluorescence measurement and computer simulation, was used to detect contaminant p-nitrophenol. Seven molecular dynamics simulations of molecular imprinting prepolymerization systems were performed to optimize the imprinting shell. Results indicated that the system with a p-nitrophenol (4-NP): 3-aminopropyltriethoxysilane (APTES): tetraethylorthosilicate (TEOS) mole ratio of 8 : 8 : 12 led to the best stable template–functional monomer clusters and the hybrid SiO2 layer with CdS-like clusters on the surface of CdTe was synthesized by a simple reflux procedure. The prepared imprinted materials (CdTe@SiO2-MIPs) on the surface of silica contained CdTe nanoparticles (CdTe@SiO2) by surface imprinting and Stober method polymerization were characterized by transmission electron microscopy, fluorescence spectroscopy, Fourier-transform infrared spectroscopy, ultraviolet–visible analysis and X-ray diffraction. A linear relationship between relative fluorescence intensity and the concentration of 4-NP was obtained with a limit of detection of 0.08 μmol L−1 and the imprinting factor (IF) was 2.23 which indicated that special binding sites with binding property to p-nitrophenol were created on the surface of the CdTe@SiO2-MIPs materials. Ultimately, the feasibility of the fluorescent materials was successfully evaluated through the analysis of 4-NP in tap water and lake water. The recoveries were above 97.3%.

Selective Solid-phase Extraction of Pb(II) Ions Using an Ion-imprinted Functionalized Sodium Trititanate Whisker Adsorbent Prepared by a Surface-imprinting Technique

Lead(II) ion-imprinted functionalized sodium trititanate whisker polymers [Pb(II)-IIPs/Na2Ti3O7] for solid-phase extraction (SPE) were prepared by the copolymerization of Pb(II) as the template ion, chitosan (CTS) as the functional monomer and γ-glycidoxypropyl trimethoxysilane (KH-560) as the linking agent in the presence of sodium trititanate whiskers (Na2Ti3O7) as the carrier. The Pb(II)-IIPs/Na2Ti3O7 materials capable of selectively adsorbing Pb(II) ions thus obtained were used for the pre-concentration and determination of the Pb(II) ion concentration in Chinese traditional medicine samples. The prepared sorbent was characterized by Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). A series of batch adsorption experiments was performed to evaluate the adsorption behaviour of the Pb(II)-IIPs/Na2Ti3O7 materials towards Pb(II) ions, as assessed by inductively coupled plasma–atomic emission spectrometry (ICP–AES). The maximum adsorption capacity, the distribution coefficient (Kd) and the relative selectivity coefficients (k′) of Pb(II)-IIPs for Pb(II)/Co(II), Pb(II)/Cd(II), Pb(II)/Cu(II), Pb(II)/Hg(II), Pb(II)/Mg(II), Pb(II)/Mn(II), Pb(II)/Zn(II) and Pb(II)/Ni(II) were calculated. Compared with non-ionimprinted polymers functionalized sodium trititanate whisker polymers (non-IIPs/Na2Ti3O7), the Pb(II)-IIPs/Na2Ti3O7 material had a higher selectivity towards Pb(II) ions. The relative selectivity factor (k′) values were all greater than 2.5. The developed method was successfully applied to the determination of the amounts of trace Pb(II) ions in traditional Chinese medicine samples with satisfactory results.

Synthesis and evaluation of a molecularly imprinted polymer with high-efficiency recognition for dibutyl phthalate based on Mn-doped ZnS quantum dots

In this study, molecularly imprinted polymers with Mn-doped ZnS quantum dots (ZnS:Mn QDs) were prepared using dibutyl phthalate (DBP) as the template molecule, 3-aminopropyltriethoxysilane (APTES) as the functional monomer and the tetraethoxysilane (TEOS) as the cross-linker. ZnS:Mn QDs offer a readout signal to monitor the amount of DBP bound to the imprinted matrix and to evaluate the efficiency of imprinting. The products MIPs-ZnS:Mn QDs were characterized by transmission electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction and fluorescence spectroscopy. In addition, optical stability and the effect of pH on fluorescence intensity were evaluated. The obtained polymers can sensitively and selectively recognize template molecules in real samples via fluorescence intensity. The fluorescence intensity decreases linearly with increasing concentration in the range of 5.0–50 μmol L−1. It reaches a detection limit of 0.27 μmol L−1. The average recovery rate of DBP at three spiking levels is more than 98.1%.