Derivatives of dipicolinic acid with a polyoxyethylene pendant arm at the pyridine 4-position have been functionalized for potential grafting with biological material. Four ligands with different terminal functions (alcohol, methoxy, phtalimide and amine) have been synthesized, which react with trivalent lanthanide ions Ln (III) to yield triple helical [Ln(L) 3] (3-) complexes, as shown by NMR and UV-vis titrations. The tris chelates display large thermodynamic stability with log beta 13 approximately 19-20 for all Eu (III) complexes for instance. Photophysical measurements reveal adequate sensitization of the metal-centered luminescence in the europium (eta sens = 33-72%) and terbium complexes, which is modulated by the nature of the terminal function. The lifetimes of the metal-centered excited states are long, up to 1.4 ms for [Eu(L) 3] (3-) and 1.6 ms for [Tb(L) 3] (3-) at room temperature, in line with hydration numbers essentially equal to zero. Quantum yields are as high as 29% for the [Eu( L ( NH2 )) 3] (3-) and 18% for the [Tb( L ( OH )) 3] (3-) tris chelates in water at physiological pH. These series of complexes demonstrate the extent of fine-tuning achievable for lanthanide luminescent probes and are simple models for investigating the effect of binding to biological molecules on the metal-centered luminescent properties.

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A soft stylus microelectrode probe has been developed to carry out scanning electrochemical microscopy (SECM) of rough, tilted, and large substrates in contact mode. It is fabricated by first ablating a microchannel in a polyethylene terephthalate thin film and filling it with a conductive carbon ink. After curing the carbon track and lamination with a polymer film, the V-shaped stylus was cut thereby forming a probe, with the cross section of the carbon track at the tip being exposed either by UVphotoablation machining or by blade cutting followed by polishing to produce a crescent moon-shaped carbon microelectrode. The probe properties have been assessed by cyclic voltammetry, approach curves, and line scans over electrochemically active and inactive substrates of different roughness. The influence of probe bending on contact mode imaging was then characterized using simple patterns. Boundary element method simulations were employed to rationalize the distance-dependent electrochemical response of the soft stylus probes.Scanning electrochemical microscopy (SECM) is a scanning probe technique that provides spatially resolved detection of electrochemical and chemical surface reactivity.1,2 Typically, the probe is an amperometric disk-shaped ultramicroelectrode (UME) enclosed in an insulating sheath, e.g. glass. Due to the hemispherical diffusion occurring at the microdisc electrode, a steadystate current can be monitored as a function of the horizontal (x, y) and vertical (z) probe positions. SECM has found many applications ranging from surface reactivity imaging 3-13 to the study of the kinetics of homogeneous and heterogeneous reactions at solid/liquid, gas/liquid, and liquid/liquid interfaces. 14-20 Because the response of a SECM probe can be described by continuum models of mass transport coupled to electrochemical kinetics, quantitative kinetic information can be extracted by comparing experimental and simulated curves in many practically relevant situations. 21-25The response of a SECM probe depends on the surface reactivity of the sample and the distance d between the surface and the active area of the probe electrode. In order to obtain a reactivity image that is not influenced by topography, d must be kept constant. In conventional SECM operations, this is achieved by working on samples with a roughness that is considerably smaller than the radius r T of the UME and by leveling the plane of the sample surface with respect to the x,y-scanning plane of the positioning system. However, this approach becomes inappropriate on rough surfaces of large aspect ratios or when large scan areas (in the mm 2 range) have to be investigated so that leveling becomes a major obstacle. Similar limitations apply when imaging curved samples. This drawback has been recognized for a long time. In the case of a small r T , a constant d can be maintained by combining