Riskin Michael, Katz Eugenii, Gutkin Vitaly, Willner Itamar
Institute of Chemistry and Center of Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Langmuir. 2006 Dec 5;22(25):10483-9. doi: 10.1021/la061101z.
A photoisomerizable thiolated nitrospiropyran SP, (1a), monolayer is assembled on a Au electrode by the primary deposition of thiolated nitromerocyanine isomer 1b as a monolayer on the electrode, followed by the irradiation of the surface with visible light, lambda > 475 nm. The surface coverage of nitrospiropyran units (1a) on the electrode is 2 x 10-10 mole cm-2. Irradiation of the electrode with UV light, 320 nm < lambda < 360 nm, results in the nitromerocyanine, MR, monolayer on the electrode that binds Ag+ ions to the phenolate units. The Ag+ ions associated with the MR monolayer undergo cyclic reduction to surface-confined Ag0 nanoclusters, and reoxidation and dissolution of the Ag0 nanoclusters to Ag+ ions associated with the monolayer are demonstrated. The electron-transfer rate constants for the reduction of Ag+ to Ag0 and for the dissolution of Ag0 were determined by chronoamperometry and correspond to ketred = 12.7 s-1 and ketox = 10.5 s-1, respectively. The nanoclustering rate was characterized by surface plasmon resonance measurements, and it proceeds on a time scale of 10 min. The size of the Ag0 nanoclusters is in the range of 2 to 20 nm. The electrochemically induced reduction of the MR-Ag+ monolayer to the MR-Ag0 surface and the reoxidation of the MR-Ag0 surface control the hydrophilic-hydrophobic properties of the surface. The advancing contact angle of the MR-Ag0-functionalized surface is 59 degrees , and the contact angle of the MR-Ag+-monolayer-functionalized surface is 74 degrees . Photoisomerization of the Ag0-MR surface to the Ag0-SP state, followed by the oxidation of the Ag0 nanoclusters, results in the dissolution of the Ag+ ions into the electrolyte solution.
一种可光异构化的硫醇化硝基螺吡喃SP（1a）单层通过以下方式组装在金电极上：首先将硫醇化硝基部花青异构体1b作为单层沉积在电极上，然后用波长大于475nm的可见光照射表面。电极上硝基螺吡喃单元（1a）的表面覆盖率为2×10⁻¹⁰摩尔/平方厘米。用波长在320nm至360nm之间的紫外光照射电极，会在电极上形成硝基部花青（MR）单层，该单层将Ag⁺离子结合到酚盐单元上。与MR单层相关的Ag⁺离子经历循环还原形成表面受限的Ag⁰纳米团簇，并且证明了Ag⁰纳米团簇再氧化并溶解为与单层相关的Ag⁺离子。通过计时电流法测定了Ag⁺还原为Ag⁰以及Ag⁰溶解的电子转移速率常数，分别对应于ketred = 12.7 s⁻¹和ketox = 10.5 s⁻¹。纳米团簇形成速率通过表面等离子体共振测量进行表征，其过程在10分钟的时间尺度上进行。Ag⁰纳米团簇的尺寸在2至20nm范围内。MR - Ag⁺单层的电化学诱导还原为MR - Ag⁰表面以及MR - Ag⁰表面的再氧化控制了表面的亲水 - 疏水性质。MR - Ag⁰功能化表面的前进接触角为59度，而MR - Ag⁺单层功能化表面的接触角为74度。Ag⁰ - MR表面光异构化为Ag⁰ - SP状态，随后Ag⁰纳米团簇氧化，导致Ag⁺离子溶解到电解质溶液中。
