A large variety ol optical sensors based on thin plasticized PVC membranes have been realized In the past. The organic membrane (bulk optode) contains the analyte recognition molecule such as a selective neutral lonophore, a H+-set active chromolonophore, and lipophilic anionic sites. In order to Improve the lifetime of analytically relevant sensing layers, their active components are covalently Immobilized to the polymeric matrix. Different Ca2+-selectlve bulk optodes with mobile or fixed chromolonophores and anionic sites are characterized and discussed with respect to sensor behavior such as dynamic range, repeatability, response time, selectivity, and lifetime. In general, the response time Increases upon Immobilization of components owing to limited diffusion within the membrane phase, whereas the lifetime Is enhanced drastically by a hindered loss of membrane components into the sample.

No abstract

No abstract

Intramolecular charge transfer processes play an important role in many biological, chemical and physical processes including photosynthesis, redox chemical reactions and electron transfer in molecular electronics. These charge transfer processes are frequently influenced by the dynamics of their molecular or atomic environments, and they are accompanied with energy dissipation into this environment. The detailed understanding of such processes is fundamental for their control and possible exploitation in future technological applications. Most of the experimental studies of the intramolecular charge transfer processes so far have been carried out using time-resolved optical spectroscopies on large molecular ensembles. This hampers detailed understanding of the charge transfer on the single molecular level. Here we build upon the recent progress in scanning probe microscopy, and demonstrate the control of mixed valence state. We report observation of single electron transfer between two ferrocene redox centers within a single molecule and the detection of energy dissipation associated with the single electron transfer.

Electrospray ionization mass spectrometry (ESI-MS) is used to probe the metal-binding selectivity of a macrocyclic thiacrown ether (C(44)H(32)S(20)) towards Co(II), Ni(II), Cu(II), and Zn(II). In homogeneous 1:1 v/v methanol/dichloromethane solutions, it is found that the thia ligand very selectively binds traces of copper even in the presence of an excess of the other metal ions. The large selectivity is ascribed to the redox-active nature of copper which enables a reduction from Cu(II) to Cu(I), occurring upon ESI-MS, whereas Co(II), Ni(II) and Zn(II) cannot undergo similar redox reactions.