Jiangdong Dai

Selective adsorption behavior of Pb(II) by mesoporous silica SBA-15-supported Pb(II)-imprinted polymer based on surface molecularly imprinting technique.

In this study, a new Pb(II) ion-imprinted polymer (Pb(II)-IIP), which can be used for selective adsorption of Pb(II) from aqueous solutions, was successfully prepared based on the supported material of ordered mesoporous silica SBA-15 with the help of surface molecular imprinting technology. The prepared polymer was characterized by Fourier transmission infrared spectrometry, X-ray diffraction, transmission electron microscope and nitrogen adsorption-desorption isotherm. The results showed that the synthesized polymer possessed high ordered mesoporous structure. The adsorption behavior of the adsorbents for Pb(II) was investigated using batch experiments. The Pb(II)-IIP showed fast kinetics, high selectivity and satisfied adsorption capacity for adsorption of Pb(II). Under the optimum experimental condition, Pb(II) adsorption process over Pb(II)-IIP follows pseudo-second-order reaction kinetics and follows the Langmuir adsorption isotherm. In addition, the thermodynamic parameters calculated from the adsorption data suggested that the adsorption of Pb(II) onto Pb(II)-IIP was a spontaneous and exothermic nature of the process.

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.

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.

Accelerating the design of multi-component nanocomposite imprinted membranes by integrating a versatile metal–organic methodology with a mussel-inspired secondary reaction platform

Efforts to engineer novel membrane materials with enhanced anti-fouling and comprehensive properties as well as highly selective separation abilities are hampered by the lack of effective imprinted cavities and structure stability. In this work, a novel multi-component metal–organic nanocomposite imprinted membrane (MMO-MIM) has been prepared by integrating a bioinspired metal–organic methodology with the secondary surface sol–gel imprinting technique. The synthesis pathway of MMO-MIM involves two steps: initially, a self-polymerized polydopamine process followed by hydrolysis with ammonium fluotitanate on the surface of the PVDF membrane, a surface-initiated sol–gel imprinted procedure is then conducted on the obtained bio-adhesive nano-sized TiO2 surface system for the fabrication of MMO-MIM. Attributed to the formation of the multilayered membrane structure, stronger fouling resistance and largely enhanced adsorption capacities have been obtained in this case. Meanwhile, the as-prepared MMO-MIM not only exhibits rapid adsorption dynamics, but also possesses excellent separation performance (βMMO-MIM/MMO-NIM and βm-cresol/2,4-DP are higher than 2.6 and 4.0, respectively) of templates. In addition, all synthesis procedures were conducted in aqueous or ethanol solution at ambient temperature, which was environmental friendly for scaling up without causing pollution.

Molecularly imprinted polymer microspheres for optical measurement of ultra trace nonfluorescent cyhalothrin in honey.

In this study, we first present a general protocol for making fluorescent molecularly imprinted polymer microspheres via precipitation polymerisation. We first prepared the fluorescent molecularly imprinted polymer microspheres upon copolymerisation of acrylamide with a small quantity of allyl fluorescein in the presence of cyhalothrin to form recognition sites without doping. The as-synthesised microspheres exhibited spherical shape, high fluorescence intensity and highly selective recognition. Under optical conditions, polymer microspheres were successfully applied to selectively and sensitively detect cyhalothrin, and a linear relationship could be obtained covering the lower concentration range of 0-1.0nM with a correlation coefficient of 0.9936 described by the Stern-Volmer equation. A lower limit of detection was found to be 0.004nM. The results of practical detection suggested that the developed method was satisfactory for determination of cyhalothrin in honey samples. This study therefore demonstrated the potential of molecularly imprinted polymers for detection of cyhalothrin in food.

Design of mesoporous silica hybrid materials as sorbents for the selective recovery of rare earth metals

The importance of rare earth metals in the global economy has increased significantly in recent years due to their essential role in advanced technologies in the electronics and biomedical industries. The recovery and purification of rare earth metals from waste products is therefore appealing, both in terms of the sustainability of rare earth resources and ecological environmental protection. We herein present the preparation of novel mesoporous silica materials modified by maleic anhydride, which can be used in the recovery of rare earth metals through extraction of their ions from an aqueous solution. Our novel maleic anhydride functional hybrid materials demonstrate enhanced selectivity for heavy rare earth metals, which vastly improves the separation process and reduces recovery costs. In addition, the directly modified hybrid materials have been found to exhibit higher distribution coefficients for rare earth elements compared to other materials. Adsorption kinetics studies were also carried out, and the adsorption followed a pseudo-second order model, with particularly rapid adsorption observed in the case of Gd3+. The resulting adsorption isotherms of the materials were better represented by the Langmuir model than the Freundlich model. The singly modified material exhibited a Gd3+ capture capacity of 76.89 mg g−1. In addition, the proposed materials demonstrate a high degree of reusability over a number of cycles, thus enhancing their potential for application in rare earth metal recycling.

Highly-controllable imprinted polymer nanoshell at the surface of silica nanoparticles based room-temperature phosphorescence probe for detection of 2,4-dichlorophenol

This paper reports a facile and general method for preparing an imprinted polymer thin shell with Mn-doped ZnS quantum dots (QDs) at the surface of silica nanoparticles by stepwise precipitation polymerization to form the highly-controllable core-shell nanoparticles (MIPs@SiO2-ZnS:Mn QDs) and sensitively recognize the target 2,4-dichlorophenol (2,4-DCP). Acrylamide (AM) and ethyl glycol dimethacrylate (EGDMA) were used as the functional monomer and the cross-linker, respectively. The MIPs@SiO2-ZnS:Mn QDs had a controllable shell thickness and a high density of effective recognition sites, and the thickness of uniform core-shell 2,4-DCP-imprinted nanoparticles was controlled by the total amounts of monomers. The MIPs@SiO2-ZnS:Mn QDs with a shell thickness of 45 nm exhibited the largest quenching efficiency to 2,4-DCP by using the spectrofluorometer. After the experimental conditions were optimized, a linear relationship was obtained covering the linear range of 1.0-84 μmol L(-1) with a correlation coefficient of 0.9981 and the detection limit (3σ/k) was 0.15 μmol L(-1). The feasibility of the developed method was successfully evaluated through the determination of 2,4-DCP in real samples. This study provides a general strategy to fabricate highly-controllable core-shell imprinted polymer-contained QDs with highly selective recognition ability.

Bioinspired synthesis of high-performance nanocomposite imprinted membrane by a polydopamine-assisted metal-organic method

Significant efforts have been focused on the functionalization and simplification of membrane-associated molecularly imprinted materials, which can rapidly recognize and separate specific compound. However, issues such as low permselectivity and unstable composite structures are restricting it from developing stage to a higher level. In this work, with the bioinspired design of polydopamine (pDA)-assisted inorganic film, we present a novel molecular imprinting strategy to integrate multilevel nanocomposites (Ag/pDA) into the porous membrane structure. The molecularly imprinted nanocomposite membranes were then obtained through an in situ photoinitiated ATRP method by using tetracycline (TC) as the template molecule. Importantly, attributing to the formation of the Ag/pDA-based TC-imprinted layers, largely enhance TC-rebinding capacity (35.41mg/g), adsorption selectivity and structural stability (still maintained 92.1% of the maximum adsorption capacity after 10 cycling operations) could been easily achieved. Moreover, largely enhanced permselectivity performance toward template molecule (the permeability factor β values were also more than 5.95) was also obtained. Finally, all synthesis methods were conducted in aqueous solution at ambient temperature, which was environmental friendly for scaling up without causing pollution.

Selective separation of lambdacyhalothrin by porous/magnetic molecularly imprinted polymers prepared by Pickering emulsion polymerization

Porous/magnetic molecularly imprinted polymers (PM-MIPs) were prepared by Pickering emulsion polymerization. The reaction was carried out in an oil/water emulsion using magnetic halloysite nanotubes as the stabilizer instead of a toxic surfactant. In the oil phase, the imprinting process was conducted by radical polymerization of functional and cross-linked monomers, and porogen chloroform generated steam under the high reaction temperature, which resulted in some pores decorated with easily accessible molecular binding sites within the as-made PM-MIPs. The characterization demonstrated that the PM-MIPs were porous and magnetic inorganic-polymer composite microparticles with magnetic sensitivity (M(s) = 0.7448 emu/g), thermal stability (below 473 K) and magnetic stability (over the pH range of 2.0-8.0). The PM-MIPs were used as a sorbent for the selective binding of lambdacyhalothrin (LC) and rapidly separated under an external magnetic field. The Freundlich isotherm model gave a good fit to the experimental data. The adsorption kinetics of the PM-MIPs was well described by pseudo-second-order kinetics, indicating that the chemical process could be the rate-limiting step in the adsorption of LC. The selective recognition experiments exhibited the outstanding selective adsorption effect of the PM-MIPs for target LC. Moreover, the PM-MIPs regeneration without significant loss in adsorption capacity was demonstrated by at least four repeated cycles.

Optical detection of λ-cyhalothrin by core-shell fluorescent molecularly imprinted polymers in Chinese spirits.

In this study, fluorescent molecularly imprinted polymers (FMIPs), which were for the selective recognition and fluorescence detection of λ-cyhalothrin (LC), were synthesized via fluorescein 5(6)-isothiocyanate (FITC) and 3-aminopropyltriethoxysilane (APTS)/SiO2 particles. The SiO2@FITC-APTS@MIPs were characterized by Fourier transform infrared (FT-IR), UV-vis spectrophotometer (UV-vis), fluorescence spectrophotometer, thermogravimetric analysis (TGA), confocal laser scanning microscope (CLSM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The as-synthesized SiO2@FITC-APTS@MIPs with an imprinted polymer film (thickness was about 100 nm) was demonstrated to be spherically shaped and had good monodispersity, high fluorescence intensity, and good selective recognition. Using fluorescence quenching as the detection tool, the largest fluorescence quenching efficiency (F0/F - 1) of SiO2@FITC-APTS@MIPs is close to 2.5 when the concentration of the LC is 1.0 μM L(-1). In addition, a linear relationship (F0/F - 1= 0.0162C + 0.0272) could be obtained covering a wide concentration range of 0-60 nM L(-1) with a correlation coefficient of 0.9968 described by the Stern-Volmer equation. Moreover, the limit of detection (LOD) of the SiO2@FITC-APTS@MIPs was 9.17 nM L(-1). The experiment results of practical detection revealed that the SiO2@FITC-APTS@MIPs as an attractive recognition element was satisfactory for the determination of LC in Chinese spirits. Therefore, this study demonstrated the potential of SiO2@FITC-APTS@MIPs for the recognition and detection of LC in food.