Xuebing Ma

Ultrasensitive detection of bisphenol A in aqueous media using photoresponsive surface molecular imprinting polymer microspheres

Photoresponsive surface molecular imprinting polymer (SMIP) microspheres were synthesized on silica microspheres by surface polymerization using a water-soluble azobenzene-containing 4-[(4-methacryloyloxy)phenylazo]benzenesulfonic acid as the functional monomer. The SMIP microspheres displayed good photoresponsive properties and specific affinity towards bisphenol A (BPA) with high recognition ability (maximal adsorption capacity: 6.96 μmol g−1) and fast binding kinetics (binding constant: 2.47 × 104 M−1) in aqueous media. Upon alternate irradiation at 365 and 440 nm, the SMIP microspheres could quantitatively bind and release BPA. Analytical application of the SMIP microspheres for the detection of trace BPA concentration in mineral water and tap water has been carried out successfully, and therefore a simple and quick detection method for trace BPA in the environment was established.

Photocontrolled solid-phase extraction of guanine from complex samples using a novel photoresponsive molecularly imprinted polymer

A novel photoresponsive molecularly imprinted polymer (MIP) was developed for the selective extraction of guanine from complex samples. The photoresponsive MIP was fabricated using guanine as the template, water-soluble 5-[(4-(methacryloyloxy)phenyl)diazenyl]isophthalic acid as the functional monomer, and water-soluble triethanolamine trimethacrylate as the cross-linker. The MIP displayed good selectivity toward guanine with a dissociation constant of (2.70 ± 0.16) × 10(-5) mol L(-1) in aqueous media. The density of the guanine-specific receptor sites in the MIP material was (4.49 ± 0.22)μmol g(-1). Quantitatively release and uptake of guanine by the MIP occurred with irradiation at 365 and 440 nm, respectively. The MIP could efficiently extract guanine from beer and then release it into aqueous media under photocontrol. This method could be used for selective separation and subsequent determination of a specific analytes from complex samples.

Homogenization of inorganic material-supported palladium catalysts in Suzuki coupling reaction at room temperature

Novel and homogeneous zirconium phosphonate-supported Pd catalysts with modest BET surface areas (25.6 and 24.7 m2 g−1), high pore volumes (0.39 and 0.73 cc g−1) and nano-sized pores (1–10 nm) were prepared by embedding Na2PdCl4 particles in an organosoluble, porous and layered zirconium phosphonate with a filiform architecture structure for the first time. In the homogeneous palladium-catalyzed Suzuki coupling reaction at room temperature, various substituted benzene bromides with phenylboronic acids were smoothly converted into corresponding biphenyl compounds (82–97% yields), even in cases of electron–rich derivatives. These supported homogeneous Pd catalysts could be quantitatively recovered by using a solid/liquid separation technique and be highly active without loss of catalytic activity in three consecutive runs.

Photoresponsive surface molecularly imprinted polymer on ZnO nanorods for uric acid detection in physiological fluids

A photoresponsive surface molecularly imprinted polymer for uric acid in physiological fluids was fabricated through a facile and effective method using bio-safe and biocompatible ZnO nanorods as a support. The strategy was carried out by introducing double bonds on the surface of the ZnO nanorods with 3-methacryloxypropyltrimethoxysilane. The surface molecularly imprinted polymer on ZnO nanorods was then prepared by surface polymerization using uric acid as template, water-soluble 5-[(4-(methacryloyloxy)phenyl)diazenyl]isophthalic acid as functional monomer, and triethanolamine trimethacryl ester as cross-linker. The surface molecularly imprinted polymer on ZnO nanorods showed good photoresponsive properties, high recognition ability, and fast binding kinetics toward uric acid, with a dissociation constant of 3.22×10(-5)M in aqueous NaH2PO4 buffer at pH=7.0 and a maximal adsorption capacity of 1.45μmolg(-1). Upon alternate irradiation at 365 and 440nm, the surface molecularly imprinted polymer on ZnO nanorods can quantitatively uptake and release uric acid.

Facile one-pot fabrication of magnetic nanoparticles (MNPs)-supported organocatalysts using phosphonate as an anchor point through direct co-precipitation method

In this paper, a novel type of efficient, magnetically recoverable magnetic nanoparticles (MNPs)-supported 9-amino-9-deoxy-epicinchonidine organocatalysts were prepared through a facile co-precipitation method using phosphonic acid (–PO3H2) as an anchor point. These MNPs-supported organocatalysts possessed the high and tunable loading capacities of an organocatalyst (0.18–0.52 mmol g−1), 2–25 nm regular mesopores and 10.6–44.06 emu g−1 saturated magnetization. In the catalytic asymmetric aldol reactions of cyclohexanone with various o, m and p-substituted benzaldehydes in water, the aromatic aldehydes with electron-withdrawing substituents including-NO2, X and –CN afforded the relevant aldol adducts in excellent yields (86–100%) and steroselectivities (anti/syn = 82–98/18–2 and 93–98%ee anti). Moderate to good yields (36–97%) and steroselectivities (anti/syn = 82–96/18–4 and 75–97%ee anti) for the aromatic aldehydes with strong electron-donating substituents (–CH3 and –OCH3) were also satisfactorily achieved. Futhermore, these MNPs-supported organocatalysts could be quantitatively recovered from the reaction mixture using an external magnet, and reused six times with excellent catalytic performance (93%, anti/syn = 89/11 and 96%ee anti). Meanwhile, MNPs-supported organocatalysts, prepared by the surface-modification method, were investigated in detail as comparative samples.

Colorimetric test paper for cyanide ion determination in real-time

A colorimetric cyanide ion (CN−) sensor 4-[(1E)-2-(2-hydroxyphenyl)ethenyl]-1-allylpyridinium bromide (2-HPEAPB) was synthesized via condensation and N-alkylation reactions using 4-methylpyridine and salicylaldehyde as the starting materials. 2-HPEAPB displayed good selectivity, fast response, and high sensitivity toward CN− over other competing anions in acetonitrile–water (95:5, v/v) with a limit of detection of 8.0 × 10−6 mol L−1 by the naked eye. The sensing mechanism and the influence of pH and temperature on sensing properties were investigated. Colorimetric test paper for CN− was prepared by absorption of 2-HPEAPB to a chromatography paper, which could be used to detect CN− directly and quickly. Analytical application of measuring CN− concentration in an electroplating wastewater in real-time was conducted successfully.

Organosoluble zirconium phosphonate nanocomposites and their supported chiral ruthenium catalysts: The first example of homogenization of inorganic-supported catalyst in asymmetric hydrogenation

In this article, we report the synthesis, structure, morphologies, and asymmetric catalytic properties of a series of novel organosoluble zirconium phosphonate nanocomposites and their supported chiral ruthenium catalysts, which have a good organosolubility (0.1-0.5 g mL(-1)) in various solvents and mesoporous, filiform, and layered structures. Due to the organosoluble properties in various organic solvents, the first homogenization of zirconium phosphonate-supported catalyst was realized in the field of catalysis. In the asymmetric hydrogenation of substituted α-ketoesters, enantioselectivities (74.3-84.7% ee) and isolated yields (86.7-93.6%) were higher than the corresponding homogeneous Ru(p-cymene)(S-BINAP)Cl(2) due to the confinement effect caused by the remaining mesopores in the backbone of the zirconium phosphonate. After completing the reaction, the supported catalyst can be readily recovered in quantitative yield by adding cyclohexane and centrifugation, and reused for five consecutive runs without significant loss in catalytic activity.

Photoresponsive molecularly imprinted hydrogel casting membrane for the determination of trace tetracycline in milk

This study aimed to develop a photoresponsive molecularly imprinted hydrogel (MIH) casting membrane for the determination of trace tetracycline (TC) in milk. This MIH casting membrane combined the specificity of MIHs, the photoresponsive properties of azobenzene, and the portable properties of a membrane. Photoresponsive TC‐imprinted MIHs were initially fabricated and then cast on sodium dodecyl sulfonate polyacrylamide gel. After TC removal, a photoresponsive MIH casting membrane was obtained. The photoresponsive properties of the MIH casting membrane were robust, and no obvious photodegradation was observed after 20 cycles. The MIH casting membrane displayed specific affinity to TC upon alternate irradiation at 365 and 440 nm; it could quantitatively uptake and release TC. The TC concentration (0.0–2.0 × 10−4 mol l−1) in aqueous solution displayed a linear relationship with the photoisomerization rate constant of azobenzene within the MIH casting membrane. As such, a quick detection method for trace TC in aqueous foodstuff samples was established. The recovery of this method for TC in milk was investigated with a simple pretreatment of milk, and a high recovery of 100.54–106.35% was obtained. Therefore, the fabricated membrane can be used as a portable molecular sensor that can be easily recycled. Copyright

Phosphonate-containing polystyrene copolymer-supported Ru catalyst for asymmetric transfer hydrogenation in water

A series of phosphonate-containing copolystyrenes with chiral ligand (1R,2R)-(+)-N1-toluenesulfonyl-1,2-diphenylethylene-1,2-diamine were prepared by radical copolymerization. The supported Ru catalysts with excellent catalytic performances (94–98% yields, 93.9–97.8% ee and 100% chemoselectivity) in aqueous asymmetric transfer hydrogenation could be easily recycled by centrifugal separation.

A photoswitchable organocatalyst based on a catalyst-imprinted polymer containing azobenzene

An L-proline-catalyzed aldol reaction was photo-controlled using an L-proline-imprinted polymer containing azobenzene. Upon UV irradiation, azobenzene chromophores underwent trans → cis isomerization, thereby releasing L-proline to catalyze the aldol reaction.