The missing link: Ferrocene and porphyrin monolayers are tethered on silicon surfaces with short (see picture, left) or long (right) linkers. Electron transfer to the silicon substrate is faster for monolayers with a short linker.Ferrocene and porphyrin derivatives are anchored on Si(100) surfaces through either a short two-carbon or a long 11-carbon linker. The two tether lengths are obtained by using two different grafting procedures: a single-step hydrosilylation is used for the short linker, whereas for the long linker a multistep process involving a 1,3-dipolar cycloaddition is conducted, which affords ferrocene-triazole-(CH(2))(11)-Si or Zn(porphyrin)-triazole-(CH(2))(11)-Si links to the surface. The modified surfaces are characterized by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Cyclic voltammetry experiments show that the redox activity of the tethered ferrocene or porphyrin is maintained for both linker types. Microelectrode capacitor devices incorporating these modified Si(100) surfaces are designed, and their capacitance-voltage (C-V) and conductance-voltage (G-V) profiles are investigated. Capacitance and conductance peaks are observed, which indicates efficient charge transfer between the redox-active monolayers and the electrode surface. Slower electron transfer between the ferrocene or porphyrin monolayer and the electrode surface is observed for the longer linker, which suggests that by adjusting the linker length, the electrical properties of the device, such as charging and discharging kinetics and retention time, could be tuned.

In this paper, we show the analysis software we created for a fast and reliable automatic characterization of a silicon photomultiplier. The program can be used both in dark and under continuous low-level light illumination. It grabs Ims long waveforms, each containing many single cell pulses, from an oscilloscope connected to the PC via Ethernet. On-line data analysis is done both on the raw waveform as well as on a filtered (with DLED technique) version in order to facilitate the pulse identification and the extraction of some parameters also in cases of high count rates or cross-talk. The main outcomes of the program are: single-cell signal shape, gain, primary dark count rate, after-pulse probability, direct and delayed cross-talk probability and excess charge factor. It can be used also to determine the actual photo-detection efficiency with the proper hardware set-up.

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