Selective Packaging of Ferricyanide within Thermoresponsive Microgels
Selective Packaging of Ferricyanide within Thermoresponsive Microgels
复制标题
DOI：
10.1021/jp508711k
复制
发表时间：
2014-11-13
影响因子：
3.7
通讯作者：
Plamper, Felix A.
中科院分区：
文献类型：
--
作者：
Mergel, Olga;Gelissen, Arjan P. H.;Plamper, Felix A.
这项研究有效地证明了温度响应性的阳离子poly(N-isopropylacrylamide-co-methacrylamidopropyltrimethylammonium)P(NIPAM-co-MAPTAC)微凝胶是三价六氰亚铁(III)(铁氰化物)的选择性闭合载体。同时，微凝胶忽略了更高电荷的铁氰酸盐(II)(亚铁氰化物)。通过循环伏安法(CV)、流体动力学伏安法(旋转圆盘电极，RDE)和电化学阻抗谱(EIS)研究了六氰基铁酸盐在多孔微凝胶颗粒存在下的电化学行为。为了进行分析，介绍了每种技术的温度校正参数。假设六氰基铁酸盐与微凝胶之间的掺入/络合作用，通过讨论微凝胶内六氰基铁酸盐的不同寿命，提出了电子途径的不同限制方案：快速交换(方案1：所有反离子的完全电化学可寻址)、永久捕获(方案2：通过将电子注入微凝胶对所有反离子仍然完全可寻址)和完全捕获(方案3：仅剩余的自由反离子可寻址)。此外，可以假设六氰基高铁酸盐和微凝胶之间的相互作用可以忽略不计，就像亚铁氰化物[Fe(CN)(6)](4-)的实验发现的那样。相反，对于铁氰化物[Fe(CN)(6)](2-)，温度甚至允许在冷中的主要情景1(快速交换)和热中的情景3(完全捕获)之间进行切换。更详细地说，由于热响应性聚(N-异丙基丙烯酰胺)(PNIPAM)组分的崩塌和电荷密度的增加，铁氰化物和微凝胶之间的吸引力在高温下会增强，而PNIPAM在高温下又更像是一种绝缘体。因此，只有游离的六氰高铁酸盐在高温下是电化学可及的。此外，EIS和CV表明，在电荷传输过程中，永久捕获(情景2)的贡献很小。
This study effectively demonstrates that thermoresponsive, cationic poly(N-isopropylacrylamide-co-methacrylamidopropyltrimethylammonium chloride) P(NIPAM-co-MAPTAC) microgels act as selective, closable carriers for trivalent hexacyanoferrate(III) (ferricyanide). At the same time, the microgel disregards even higher charged hexacyanoferrate(II) (ferrocyanide). This is seen by investigating the electrochemistry of hexacyanoferrates in the presence of porous microgel particles with help of cyclic voltammetry (CV), hydrodynamic voltammetry (rotating disk electrode, RDE), and electrochemical impedance spectroscopy (EIS). For analysis, temperature-corrected parameters for each technique are introduced. Assuming incorporation/complexation between hexacyanoferrates and microgels, different limiting scenarios for the electron pathway are proposed by discussing different life times of the hexacyanoferrates within the microgel: fast exchange (scenario 1: full electrochemical addressability of all counterions), permanent entrapment (scenario 2: still full addressability of all counterions by injection of electrons into the microgels), and full entrapment (scenario 3: only remaining free counterions are addressable). Also, negligible interaction between hexacyanoferrates and microgels can be postulated, as found experimentally for ferrocyanide [Fe(CN)(6)](4-). In contrast for ferricyanide [Fe(CN)(6)](2-), temperature even allows a switching between a dominant scenario 1 (fast exchange) in the cold and the scenario 3 (full entrapment) in the heat. In more detail, the attraction between ferricyanide and microgel is enhanced at elevated temperatures due to the collapse and increasing charge density induced by the thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) component, which in turn acts more as an insulator in the heat. Hence, only the free hexacyanoferrates are electrochemically accessible in the heat. In addition, EIS and CV indicate only a minor contribution of permanent entrapment (scenario 2) during charge transport.