Silicon photomultipliers applications to biosensors

A novel Si-based detector, having a low noise and a high sensitivity, up to a single photon detection, was used for a biosensor application. It is a Silicon photomultiplier (SiPM), a device formed by avalanche diodes operating in Geiger mode, in parallel connections. Arrays with different dimensions were electro-optically characterized (5×5; 10×10 and 20×20 pixels) in order to identify the best geometry to be used in terms of signal-to-noise ratio, for our purposes. The SiPM array was used to study both traditional and innovative fluorophores. CY5 was chosen as “reference” marker. It has an absorption peak at 649 nm and an emission peak at 670 nm. Ru(bpy)3[Cl]2 was identified as innovative fluorophore, since it has absorption and emission peaks at 455 and 630 nm, respectively. Measurements were carried out in both functional regimes: continuous and pulsed. Emission spectra in the range 550–750 nm were measured with both traditional photomultipliers tubes (PMT) and SiPM operating at room temperature in continuous mode. More interestingly, fluorophore lifetimes were monitored showing that SiPM can measure lifetimes as short at 1 ns (CY5 lifetime), well below the lowest PMT limit (23 ns). Ru(bpy)3[Cl]2 lifetime characterization was performed with both PMT and SiPM (being in the hundreds of ns range), as a function of the solvent and after deposition and drying on glass substrates.