No abstract

Polyamidoamine (PAMAM) dendrimers have an amine surface and an ethylenediamine core and are of great interest in various applications such as in drug delivery. Physiochemical properties of PAMAM dendrimers vary with pH. At neutral to basic pH, PAMAM dendrimers are either weakly charged or uncharged and tend to adsorb on to the neutral packing material, making chromatographic separation of the dendrimers difficult. Asymmetrical flow field-flow fractionation (AsFlFFF) was tested as an alternative to the chromatographic techniques for separation of the PAMAM dendrimers. AsFlFFF provided generation-based separation of the dendrimers even at neutral and basic pH. The elution time increased gradually as the generation number (and thus the size) increased. Separation of impurities such as generational or missing-arm impurities and aggregates from the main population was also achieved. Electrostatic and hydrophobic interactions (e.g., repulsive elecrostatic interaction among the dendrimer molecules or attractive hydrophobic interaction between the dendrimer molecules and the membrane) may result in an inaccurate size measurement. Careful optimization of experimental conditions such as the flow rate, pH, and the salt concentration may be required to minimize the interactions with the membrane. AsFlFFF was also tested for a study on the interaction between the PAMAM dendrimers and proteins. AsFlFFF was able to show the growth in the size of bovine serum albumin (BSA) when BSA is mixed with increasing amounts of PAMAM dendrimers. Results suggest that, with proper optimization, AsFlFFF could become a useful tool for separation and characterization of large charged molecules such as PAMAM dendrimers.

초록: 메탄올 용매에서 고분자 촉진 단량체와 소디윰 스티렌 슐포네이트를 방사선 그래프트 방법으로 양이온 교 환 PVdF 맴브레인을 제조하였다. 고분자 촉진 단량체로서 스티렌, 아크릴산, 비닐 피롤리돈을 사용하였다. 또한, 음이온 교환 PVdF 맴브레인도 방사선 그래프트 중합법에 의해 제조하였다. 양이온 및 음이온 교환 PVdF 맴브레인은 SEM, XPS 그리고 열분석기기를 통해 특성평가를 하였고 성공적으로 합성됨을 확인할 수 있었다. 그래프트 수율, 이온교환기 의 양 및 침투율은 각각 30.0∼32.3%, 2.81∼3.01 mmol/g 그리고 66.6∼147%로 평가되었으며, 20 ℃에서 이온 전 도도를 측정한 결과 0.020∼0.053 S/cm 이었다. 최종적으로, 제조된 양이온 및 음이온교환 PVdF 맴브레인은 전지 격막으로서 충분히 사용될 수 있음을 확인할 수 있었다.Abstract: A cation-exchange nanofiber poly(vinylidene fluoride) (PVdF) membrane was prepared by a radiation-induced graft polymerization (RIGP) of sodium styrene sulfonate (NaSS) in the presence of the polymerizable access agents in methanol solution. The used polymerizable access agents include styrene, acrylic acid, and vinyl pyrrolidone. The anion-exchange nanofiber PVdF membrane was also prepared by RIGP of glycidyl methacrylate (GMA) and its subsequent chemical modification. The successful preparations of cation-and anion-exchange PVdF membranes were confirmed via SEM,XPS and thermal analysis. The content of the grafting yield, ion-exchange group, and water uptake was in the range of 30.0∼32.3%, 2.81∼3.01 mmol/g and 66.6∼147%, respectively. The proton conductivity at 20 ℃ was in the range of 0.020∼0.053 S/cm. From the result, the prepared ionexchange PVdF membrane can be used as a separator in battery cells.

No abstract

Non-enzymatic biosensors employing multi-walled carbon nanotube (MWNT) with highly dispersed Pt-M (M = Ru, Sn, and Au) nanoparticles (Pt-M@MWNT catalysts) were fabricated by radiolytic deposition. The Pt-M nanoparticles on the MWNTs were characterized by transmittance electron microscopy, elemental analysis, and X-ray diffraction. They were found to be well-dispersed and to exhibit alloy properties on the MWNT support. Electrochemical testing showed that these non-enzymatic biosensors had larger currents (mA) than that of a bare glassy carbon (GC) electrode and one modified with MWNTs. The sensitivity (μA mM-1), linear range (mM), and detection limit (mM) (S/N = 3) of the glucose biosensor with the Pt-Ru, Pt-Sn and Pt-Au catalysts in PBS electrolyte were determined, respectively. The experimental results show that such biosensors can be applied to glucose detection in food chemistry field.