Guiying Liao

Immobilization of horseradish peroxidase enzymes on hydrous-titanium and application for phenol removal

In this work, hydrous titanium was utilized to immobilize horseradish peroxidase (HRP) in order to improve its stability and adaptability under different water qualities using a biomimetic titanification process. The catalytic performance of immobilized HRP for phenol removal from aqueous solution was evaluated. The physicochemical properties of immobilized HRP (IM-HRP) were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR). The effects of the reaction conditions (H2O2 and IM-HRP dosages and initial phenol concentration) on phenol removal were investigated. Enzymatic activity analysis indicated that the immobilization process has no adverse effects on the catalytic performance of HRP, and a slight increase in the enzymatic catalytic kinetic constant (km) of IM-HRP was observed compared to its free enzymes. It was found that at a synthetic temperature of 37 °C ± 3 °C, IM-HRP exhibited excellent phenol removal of over 90% after reaction for 15 min. In addition, the enzyme activity of IM-HRP was very stable over a wide range of reaction conditions (e.g., temperatures from 20 °C to 90 °C and pH from 3.0 to 11.0). Therefore, HRP enzymes loaded on hydrous titanium are very effective at improving the stability of enzymes and can alleviate the adverse effects of various environmental and water conditions on contaminant removal.

DNA cleavage activities of two dinuclear copper coordination polymers

The DNA cleavage activities of two coordination polymers of Robson-type macrocycles, {[Cu4L1(4,4′-bipy)2](ClO4)4·H2O}∞ (1) and {[Cu4L2(4,4′-bipy)4](ClO4)4·2CH3CN·2H2O}∞ (2) (where H2L1 and H2L2 are the [2 + 2] condensation products of 1,3-diaminopropane with 2,6-diformyl-4-methylphenol and 2,6-diformyl-4-fluorophenol, respectively), have been studied. The interactions of the complexes with calf thymus-DNA were investigated by UV–vis spectroscopy, CD spectroscopy, and gel electrophoresis. The binding constants of 1 and 2 are 7.2 × 104 and 2.1 × 105 M−1, respectively. The complexes exhibit DNA cleavage activity, with the cleavage process involving oxidative cleavage of DNA. The DNA cleavage activities of two new coordination polymers of Robson-type macrocycles, {[Cu2L1(bipy)]·(ClO4)2·CH3CN}∞ (1) and {[Cu2L2(bipy)]·(ClO4)2·H2O}∞ (2), have been studied. The interactions of the complexes with calf thymus-DNA were studied by UV–vis and CD spectroscopic techniques. The complexes exhibit good DNA cleavage activity. The results show that the substituent on the benzene ring plays an important role in DNA cleavage and the cleavage process occurs via oxidative cleavage.

Supramolecular architectures based on various macrocyclic metallic tectons with 1,3,5-triazine-2,4,6-triamine hexaacetic acid ligand

Reactions of series of macrocycle derivatives [Ni(hto)]Cl2·2H2O (1) (hto = 1,3,6,9,11,14-hexaazatri-cyclo[12.2.1.16,9]octadecane), [Ni(CHA)](ClO4)2 (2) (CHA = 1,3,6,8,11,14-hexaazatri-cyclo[12.2.1.18,11]octadecane), [Ni(PCHA)](ClO4)2 (3) and [Cu(PCHA)](ClO4)2 (4) (PCHA = 4-methyl-1,3,6,8,11,14-hexaazatri-cyclo[12.2.1.18,11]octadecane), with a flexible hexapodal ligand H6TTHA (H6TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid) resulted in eight supramolecular coordination polymers (SCPs), formulated as α-[Ni(hto)][H4TTHA]·5H2O (5), β-[Ni(hto)][H4TTHA]·4H2O (6), [Ni(CHA)][H4TTHA]·2H2O (7), [Ni(PCHA)][H4TTHA]·3H2O (8), [Cu(PCHA)][H4TTHA]·1.5H2O (9), [Ni(PCHA)][H5TTHA](ClO4)·4H2O (10), [Ni(PCHA)][H4TTHA]·DMSO·H2O (11) and [Ni(PCHA)][H4TTHA]·DMF (12). These compounds are structurally characterized by X-ray diffraction analyses. The predominant driving forces that connect macrocyclic metallic tectons with hexaacetic acid ligand in compounds 5–12 are hydrogen bonds, by which the compounds assemble into SCPs with versatile structures. The single-crystal X-ray diffraction analysis reveals that compounds 5 and 6 contain a rhombic 2-D layer network structure constructed of hydrogen bonds. Compound 7 exhibits a 3-D supramolecular network with 12 × 10.4 A2 1-D brick wall net structure along the c-axis, and all the water molecular guests adorned the brick wall net. Compounds 8 and 9 show a nonporous 3-D framework also stabilized by the hydrogen bonds. Tuning by solvents, in compound 10, an elliptical 2-D network was found to accommodate water molecules and perchlorate in the channels, with grid dimensions of 11 × 10 A2; compounds 11 and 12 show 2-D honeycomb-like networks with diameter 12 A. In conclusion, the crystal structures and regulatory effect of thev N-donor on the macrocyclic ligands in these compounds are discussed.

Preparation and Characterization of Aligned PLLA/PCL/HA Composite Fibrous Membranes

Aligned poly(L-lactide) (PLLA)/poly(ϵ-caprolactone) (PCL)/hydroxyapaite (HA) composite fibrous membranes were fabricated by electrospinning. Their morphology, thermal stability, mechanical properties, hydrophilic properties and biocompatibility were investigated. The electrospun fibers are highly aligned and the HA are oriented along the fiber axis. When HA are incorporated, the PLLA/PCL/HA composite fibers become thinner due to the increased conductivity. In addition, the aligned HA reinforce the electrospun fibrous membranes. The larger porosity and higher hydrophilic properties induced by HA in the electrospun fibers have improved the degradation of the PLLA/PCL/HA fibrous membranes which have no toxic effect on proliferation of adipose-derived stem cells.

Synthesis and Characterization of Biodegradable Poly(ϵ-caprolactone)-b-Poly(L-lactide) and Study on Their Electrospun Scaffolds

A series of multi-block copolymers, poly(L-lactide)-b-poly (ϵ-caprolactone) (PLLA-b-PCL) were synthesized. The first step of the synthesis consisted of the transesterification between the PLLA and 1,4-Butanediol, followed by the copolymerization of PLLA-diols and PCL, using isophorone diisocyanate (IPDI) as a coupling agent. The synthesized polymers were characterized by Fourier transform infrared (FTIR) spectra, differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). PLLA/PCL block copolymers were electrospun into ultrafine fibers. The morphology of the electrospun fibrous scaffolds were investigated by Scanning Electron Microscopy (SEM). Results showed that the morphology and diameter of the fibers were affected by the electrospinning solution concentrationan and different weight ratio of PLLA/PCL. These electrospun PLLA-b-PCL fibrous membranes exhibited good flexibility and deformability. In comparison with the electrospun PLLA membrane, the electrospun fibrous membranes of PLLA-b-PCL demonstrated an enhanced elongation with still high tensile strength and Youngs modulus to be beneficial for tissue engineering scaffolds.

Syntheses, crystal structures, and magnetic properties of 1-D coordination polymers

Three coordination polymers of Robson-type macrocycles, {[Cu4L1(4,4′-bipy)2]·4ClO4·H2O}∞ (1), {[Cu4L2(4,4′-bipy)4]·2CH3CN·4ClO4·2H2O}∞ (2), and {[Zn2L2(4,4′-bipy)2]·(ClO4)2}∞ (3) (where H2L1 and H2L2 are the [2 + 2] condensation products of 1,3-diaminopropane with 2,6-diformyl-4-methylphenol and 2,6-diformyl-4-fluorophenol, respectively), have been synthesized and characterized. Magnetic susceptibility was measured for 1 and 2 from 2 to 300 K. The optimized magnetic data were J = –368.5 cm−1, J′ = 40.5 cm−1 with R = 1.69 × 10−6 for 1 and J = –291.22 cm−1, J′ = 83.74 cm−1, ρ = 0.00168 with R = 1.8 × 10−11 for 2, respectively. The data reveal strong antiferromagnetic interactions between two Cu(II) ions in the macrocyclic unit and ferromagnetic interaction between the Cu(II) ions in two adjacent macrocyclic units for 1 and 2. Graphical Abstract Three novel coordination polymers of Robson-type dinuclear macrocyclic complexes, bridged by 4,4′-bipyridine, were synthesized and fully characterized, Magnetic data reveal that there are strong antiferromagnetic between two Cu(II) ions in the macrocyclic unit and ferromagnetic interaction between the Cu(II) ions in two adjacent macrocyclic units for complexes 1 and 2.

Electrospun Aligned Poly(L-lactide)/Poly(ϵ-caprolactone) /Poly(ethylene glycol) Blend Fibrous Membranes

Aligned poly(L-lactide) (PLLA)/poly(ϵ-caprolactone) (PCL)/poly(ethylene glycol)(PEG) fibrous membranes were fabricated by electrospinning. Their morphology, thermal stability, mechanical properties, hydrophilic properties and in vitro degradation behaviors were investigated. With increasing the content of PEG, the PLLA/PCL/PEG blend fibers become thinner due to the increment in solution conductivity and decrease in solution viscosity. The thermal stability, hydrophilic properties, the tensile strength and elongation-at-break of PLLA/PCL/PEG blend fibrous membranes were improved, but porosity were decreased with the content of PEG changing from 10 wt% to 30 wt%. Furthermore, the incorporation of PEG enhanced the degradation of the PLLA/PCL/PEG fibrous membranes due to the better hydrophilic properties. In addition, the PLLA/PCL/PEG fibrous membranes have no toxic effect on proliferation of adipose-derived stem cells.

One-pot synthesis of g-C3N4-doped amine-rich porous organic polymer for chlorophenol removal

A novel graphitic carbon nitride (g-C3N4)/amine-rich porous organic polymer (RAPOP) was synthesized via one-pot polymerization using various molar ratios of melamine (MA)/terephthalaldehyde (TA)/g-C3N4 of 4/4/1, 4/4/2 and 4/4/4. The g-C3N4 was used as a supporting scaffold, and its stratified structure provided a skeleton. Polymerization between MA and TA mostly occurred on the surface of g-C3N4, which formed porous spatial structures, in particular, that of MA/TA/g-C3N4 (4/4/2), of which the surface area and pore volume reached 540.36 m2 g−1 and 1.502 cm3 g−1, respectively. Their excellent adsorption performance towards 2,4-dichlorophenol was investigated under different conditions. A solution pH of 7 was favorable for adsorption. The presence of Na+ and Cl− ions had no adverse effects on the adsorption process, whereas humic acid (HA) led to a slight decrease in performance. Adsorption equilibrium was reached within 40 seconds, and the maximum adsorbed amounts were 188.70 mg g−1, 217.39 mg g−1, 238.10 mg g−1 and 270.27 mg g−1 for MA/TA (4/4), MA/TA/g-C3N4 (4/4/4), MA/TA/g-C3N4 (4/4/1) and MA/TA/g-C3N4 (4/4/2), respectively, at 298 K. Thermodynamic tests indicated that the adsorption proceeded spontaneously and endothermically. Moreover, the adsorbents maintained their high performance and stability after regeneration via treatment with alkali. This work demonstrates that g-C3N4/RAPOP can be practically employed to remove chlorophenols from aqueous solutions.

Two new carboxylate-bridged one-dimensional coordination polymers based on macrocyclic metallic tectons

Two new one-dimensional coordination polymers: {[Cu(L1)(H4TTHA)] · H2O}n (I), {[Cu2(L2)2(H4TTHA)2] · 10H2O}n (II) (L1 = 1,3,10,12,15,18-hexaazatetracyclodocosane; L2 = 3,10-bis(2-hydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetradecane), based on a flexible hexapodal ligand H6TTHA (1,3,5-triazine-2,4,6-triamine hexaacetic acid), have been synthesized and structure characterized. Single-crystal X-ray diffraction analyses indicated that the central metal atom displays distorted six-coordinate octahedral coordination geometry by coordination with four nitrogen atoms of L1 or L2, and two oxygen atoms of H6TTHA liagand. Both of the compounds show one-dimensional chain structures, which are constructed of [Cu(L)]2+ and [H4TTHA]2− anion with 1 : 1 ratio. Interestingly, the nature of the macrocycle influences the structure of the coordination polymer produced with H6TTHA for each of the two compounds. TG, IR, PXRD, and photoluminescent of the compounds are investigated.

One-step preparation of polyimide-inlaid amine-rich porous organic block copolymer for efficient removal of chlorophenols from aqueous solution

A novel polyimide-inlaid amine-rich porous organic block copolymer (PI-b-ARPOP) was prepared via one-step polymerization by using different molar ratios of melamine (MA)/terephthalaldehyde (TA)/pyromellitic dianhydride (PMDA), at molar ratios of 4/3/1, 4/2/2 and 4/1/3. The copolymer contained both aminal groups belonging to ARPOP and imide groups belonging to PI, and the bonding styles of the monomers and growth orientations of the polymeric chains were diversiform, forming an excellent porous structure. Notably, MA/TA/PMDA (4/2/2) had a surface area and pore volume of 487.27 m2/g and 1.169 cm3/g, respectively. The adsorption performance of the materials towards 2,4-dichlorophenol (2,4-DCP) in ultra-pure water was systematically studied. The pH value of 7 was optimal in aqueous solution. Na+ and Cl- ions did not negatively affect the adsorption process, while humic acid (HA) slightly decreased the capacity. The equilibrium time was 40 sec, and the maximum adsorption capacity reached 282.49 mg/g at 298 K. The removal process was endothermic and spontaneous, and the copolymer could maintain its porous structure and consistent performance after regeneration by treatment with alkali. Moreover, to further assess the practical applicability of the material, the adsorption performance towards 2,4-DCP in river water was also investigated. This paper demonstrated that the PI-b-ARPOP can be an efficient and practical adsorbent to remove chlorophenols from aqueous solution.