Tongfan Hao

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.

Molecularly imprinted polymer nanospheres based on Mn-doped ZnS QDs via precipitation polymerization for room-temperature phosphorescence probing of 2,6-dichlorophenol

In this paper, novel molecularly imprinted polymers (MIPs) based on Mn doped ZnS quantum dots (QDs) with molecular recognition ability were successfully synthesized by precipitation polymerization using 2,6-dichlorophenol (2,6-DCP) as template, methacrylic acid (MAA) as the functional monomer and ethylene glycol dimethacrylate (EGDMA) as the cross-linker. The obtained materials (MIPs-ZnS:Mn QDs), which were composed of Mn doped ZnS QDs as phosphorescence signal and MIPs as molecular selective recognition sites, could sensitively and selectively recognize the template molecules by using the spectrofluorometer. After the experimental conditions were optimized, a linear relationship was obtained covering the range of 1.0–56 μmol L−1 with a correlation coefficient of 0.9994. The developed method was applicable to routine trace determination of 2,6-DCP in real examples. This study also provides a general strategy to fabricate MIPs-coated QDs with excellent performance and is desirable for chemical sensor application.

A novel molecularly imprinted polymer thin film at surface of ZnO nanorods for selective fluorescence detection of para-nitrophenol

Inspired by a surface imprinting-directing polymerization system, an effective and simple synthesis method was first developed to prepare an imprinted polymer thin film at the surface of ZnO nanorods (ZnO NRs), and the composites were used as fluorescence sensors for sensitively and selectively recognizing the target para-nitrophenol (4-NP). The vinyl-modified ZnO NRs were used as the solid supports and optical materials. The obtained materials (MIPs-ZnO NRs), which were composed of ZnO NRs as fluorescence signal and MIPs as molecular selective recognition sites, could sensitively and selectively recognize the template molecules by using the spectrofluorometer. After the experimental conditions were optimized, a linear relationship was obtained covering the linear range of 0.5–14 μmol L−1 with a correlation coefficient of 0.9981. The developed method was applicable to routine trace determination of 4-NP in the spiked river water samples. This study provides a general strategy to fabricate imprinted polymer thin films-coated ZnO NRs with excellent performance for sensor application.

Determination of Aspirin Using Functionalized Cadmium-Tellurium Quantum Dots as a Fluorescence Probe

A simple and sensitive method is reported for the synthesis of photoluminescent semiconductor CdTe quantum dots. The CdTe quantum dots were synthesized by using mercaptosuccinic acid for protection in the aqueous phase and used for the determination of aspirin by a quenching reaction. By comparison with thioglycolic acid stabilized CdTe quantum dots, the mercaptosuccinic acid shortened the reaction time. Transmission electron microscopy was used to characterize the CdTe quantum dots; their size was approximately 5.0 nm. The interaction between the CdTe quantum dots and aspirin was characterized by fluorescence and absorption spectroscopy. The optimum pH for measurements was 8.0. Under the optimized conditions, the fluorescence intensity of the CdTe quantum dots had a linear relationship with the concentration of aspirin between 1.7 and 56 µmol/L and the quenching reaction was shown to have a static mechanism. As the concentration of aspirin increased, the fluorescence quenching of mercaptosuccinic acid stabilized CdTe quantum dots increased. This method was successfully used for the determination of aspirin in tablets.

Relaxation and Crystallization of Oriented Polymer Melts with Anisotropic Filler Networks

The coexistence of nanofillers and shear flow can influence crystallization of polymer melts. However, the microscopic mechanism of the effect is not completely revealed yet. Thus, dynamic Monte Carlo simulations were used to study the effect of the filler networks formed by one-dimensional nanofillers on relaxation and crystallization of oriented polymer melts. The filler networks restrict the relaxation of oriented polymers and impose confinement effect on the chains inside the filler networks, resulting in higher orientation and lower conformational entropy of the inside chains compared to those of the outside chains. Thus, the confined inside chains have stronger crystallizability. During crystallization, the confined chains are nucleated on the filler surface and then form nanohybrid shish-kebab structures. Furthermore, the effect of fillers and chain orientation closely depends on some factors, such as polymer-filler interaction, filler content, and filler spacing. Our simulation results are consistent with some experimental findings. Thus, these results can provide new insights into the mechanism of crystallization of filled polymers and also guide researchers to develop new polymer nanocomposites with high performance.

Segmental dynamics in interfacial region of composite materials

In this work, we preformed dynamic Monte Carlo simulations to investigate the interfacial behaviors of polymers with two-dimensional filler. It was found that both the distributions of local segmental mobility and local glass transition temperatures in interfacial regions are controlled by interfacial interaction. For the system without interfacial interaction, the segments near interface have stronger mobility than those in bulk, due to the lower segment density. If the interfacial interaction is weakly attractive, there is no obvious difference of mobility between the interfacial and internal segments and no bound polymer exists near the interface. If the attractive interfacial interaction is strong, a gradient of local glass transition temperatures was observed, which demonstrates the presence of bound polymers in many layers with different segmental mobility. These findings could be used to explain the various experimental results about the segmental dynamics in the interfacial regions of polymer nanocomposites.Graphical abstract

A mesoporous fluorescent sensor based on ZnO nanorods for the fluorescent detection and selective recognition of tetracycline

Due to tetracycline (TC) being harmful to the environment and animals, versatile fluorescent sensors have been developed and applied for the specific recognition and determination of TC. In the present paper, a mesoporous fluorescent sensor was successfully prepared by using TC as the template, cetyl trimethyl ammonium bromide (CTAB) as the porogen, and ZnO nanorods (NRs) as the core substrate material and optical material. The synthesized composite materials were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Fluorescent measurements of the target TC were then measured by a spectrofluorometer. Under optimal conditions, the linear range and correlation coefficient of the mesoporous MIPs-ZnO NRs were 2.0–120 μmol L−1 and 0.9993, respectively, and the imprinting factor (IF) was up to 3.50. Moreover, in order to further investigate the effect of the mesoporous structure, a fluorescent sensor without a mesoporous structure was synthesized as a comparison and measured by the same processes. Through analysis of the data, it was found that the mesoporous fluorescent sensor showed a lower response time, higher utilization, and higher selective recognition and sensitive determination than the non-mesoporous fluorescent sensor. This study provides a novel strategy to fabricate mesoporous-imprinted polymer layer-coated ZnO NRs with excellent fluorescent performance for TC.

Preparation of a novel magnetic and thermo-responsive composite and its application in drug release

A novel hyperbranched multi-arms star block copolymer with magnetic oriented target and thermo-responsive characters was synthesized. The atom transfer radical polymerization initiators were anchored on the surfaces of magnetic mesoporous silica by the chemical reaction of surface-modified amides with α-bromoisobutyryl bromide. The composites (FexOy@SBA-15@HPCMS-g-PNIPAAm) with magnetic mesoporous silica nanoparticles as core and hyperbranched star block copolymers as arms were prepared by iron(III)-mediated surface-initiated polymerization with FeCl3·6H2O as catalyst, PPh3 as ligand, ascorbic acid as reducing agent, N,N-dimethylformamide as solvent, and 4-chloromethylstyrene (CMS) and N-isopropylacrylaminde (NIPAAm) as monomer, respectively. The resultant materials were characterized by Fourier transform infrared, thermogravimetric analysis, N2 adsorption/desorption measurements, scanning electron microscopy, transmission electron micrographs, differential scanning calorimeter, and vibrating sample magnetometer. With aspirin as model drug, the drug release behavior of the hybrid materials was investigated in detail. Due to both the thermo-responsive and the magnetic property, the product may be used as a drug delivery system aiming at a cancer treatment.Graphical abstract

Swelling technique inspired synthesis of a fluorescent composite sensor for highly selective detection of bifenthrin

Pesticide pollution has become a serious problem that threatens public health, so it is necessary to develop a method that can detect pesticides rapidly and sensitively. In this study, we report a novel fluorescent imprinted sensor based on quantum dots (QDs) synthesized via a facile and versatile swelling technique for highly selective detection of bifenthrin (BI). Compared with other fluorescent molecularly imprinted polymers (MIPs), it has three significant differences: firstly, polystyrene (PS) microspheres make up the polymer matrix and were prepared in advance; secondly, the interactions are not hydrogen bonding and covalent interactions, but van der Waals and hydrophobic forces; thirdly, aqueous QDs were successful applied to the swelling process using a polymerizable surfactant. The unique fluorescent sensor (MIPs (PS)-OVDAC/CdTe QDs) possesses the strong fluorescence and sensitivity of QDs and the high selectivity of molecularly imprinted polymers as well as a uniform morphology via this novel swelling strategy. As a result, the fluorescence intensity of the MIPs (PS)-OVDAC/CdTe QDs was strongly decreased within less than 25 min upon binding BI, and the quenching fractions of the MIPs (PS)-OVDAC/CdTe QDs presented a good linearity with BI concentrations in the range of 0.5–40 μM with a correlation coefficient of 0.9918. In addition, the limit of detection (LOD) was as low as 0.08 μmol L−1 and a high imprinting factor of 4.11 was obtained. The developed method was successfully applied to the determination of BI in honey samples. The present study provides a facile and efficient strategy to develop fluorescent sensors for rapid recognition and selective detection of organic pollutants from complex matrices.

One-dimensional nanofiller induced crystallization in random copolymers studied by dynamic Monte Carlo simulations

ABSTRACT Understanding crystallization mechanism of random copolymers is beneficial for the design and development of new polymeric materials. We performed dynamic Monte Carlo simulations to investigate the crystallization behaviours of random copolymers in polymer solutions induced by one-dimensional nanofiller. The effects of comonomer content on crystallinity and crystalline morphology were studied in detail. In the copolymers with relatively low comonomer contents, the final absolute crystallinity is independent of comonomer contents, while in the copolymers with relatively high comonomer contents the final absolute crystallinity decreases with increasing comonomer contents. In addition, the one-dimensional nanofiller can induce the formation of nanohybrid shish-kebab structures in the copolymers with low comonomer contents. However, in the copolymer with very high comonomer content, the presence of a large number of comonomers with no ability of parallel arrangements hinders the formation of nanohybrid shish-kebab structures.