Dong-Lin Zhao

Enhanced mechanical properties of ammonia-modified graphene nanosheets/epoxy nanocomposites

Ammonia-modified graphene nanosheets (AMGNSs)/epoxy nanocomposites were prepared by using a facile blend method. Graphene nanosheets (GNSs) were modified with aqueous ammonia (NH3·H2O) and hydrogen peroxide (H2O2), to obtain amine (–NH2) functionalized GNSs and to enhance the bonding between the GNSs and epoxy resin matrix. The effects of the AMGNSs on the static and dynamic mechanical properties of the nanocomposites were investigated. The results indicated that the tensile and flexural strength and modulus of the AMGNS/epoxy nanocomposites first increased and then decreased with increasing addition of AMGNSs. The addition of 0.5 wt% AMGNSs improved the tensile strength and flexural modulus of the pristine epoxy by 27.84% and 7.75%, respectively. Meanwhile, the addition of 0.1 wt% AMGNSs improved the tensile modulus and flexural strength of the pristine epoxy by 14.16% and 94.38%, respectively. The reinforcing effect of the AMGNSs in enhancing the impact properties of the epoxy nanocomposites was also examined. It was demonstrated that the amine-functionalization of GNSs with ammonia had an obvious effect on the mechanical performances of epoxy matrix nanocomposites.

Bio-compatible poly(ester-urethane)s based on PEG-PCL-PLLA copolymer with tunable crystallization and bio-degradation properties

Multi-block copolymer poly(ester-urethane)s with ethoxy or polyhedral oligomeric silsesquioxane (POSS) terminal functional groups were designed and synthesized by using polyethylene glycol–poly(e-caprolactone)–poly(L-lactide) (PEG–PCL–PLLA) diols via urethane linkages. In addition, an efficient and green catalyst, bismuth ethylhexanoate, was used to prepare high molecular weight copolymers, and the influences of molecular compositions on the crystallinity, mechanical properties, biodegradability, cytocompatibility and blood-compatibility were systematically studied. By varying the terminal functional groups, as well as PEG, PCL and PLLA segment ratios, the materials exhibited highly tunable properties, especially including crystallinity, mechanical properties and degradation rate. Notably, these new functional materials may effectively be applied in the treatment of blood vessels because of the mentioned tunable properties.

Preparation and characterization of modified hydroxyapatite particles by heparin

Heparin-modified hydroxyapatite (HAP-HP) particles were prepared by an in situ coprecipitation method and were characterized by Fourier transform infrared spectrometry, x-ray diffraction and transmission electron microscopy. The heparin content in the particles was determined by a colorimetric assay and energy dispersive x-ray spectroscopy. Final results indicated that the crystallinity and crystal size decreased as both the Ca/P molar ratio and sulfur content increased by adding heparin. Blood compatibility of the HAP-HP particles was evaluated by activated partial thrombin time and prothrombin time. The clotting time of HAP-HP was prolonged remarkably compared with that of HAP. Above all, this novel HAP-HP material can be potentially applied as compatible blood materials for drug carriers of intravenous injection and artificial blood vessels.

Inductive heat property of Fe3O4 nanoparticles in AC magnetic field for local hyperthermia

Abstract Magnetite (Fe3O4) nanoparticles with different magnetic properties were prepared by coprecipita-tion of Fe3 + and Fe2 + with aqueous NaOH solution. The inductive heat properties of Fe3O4 nanoparticles in an alternating current (AC) magnetic field were investigated for local hyperthermia. The maximum saturation magnetization Ms of Fe3O4 nanoparticles is 65.53 emu·g−1 under the optimum conditions of Fe3+/Fe2+ molar ratio at 1.8: 1. The Ms of Fe3+/Fe2+ nanoparticles decreased as the Fe3+/Fe2+ molar ratio increased. But the coercivity Hc increases with the increasing of Fe3+/Fe2+ molar ratio. Exposed in the AC magnetic field for 29 min, the temperatures of physiological saline suspension containing Fe3O4 nanoparticles were 42 — 97.5 °C. The inductive heat property of Fe3O4 nanoparticles in AC magnetic field decreases as Hc increases, but increases with the increasing of Ms. The Fe3O4 nanoparticles would be useful as good thermoseeds for localized hyperthermia treatment of cancers.