Focus-Induced Photoresponse: a novel way to measure distances with photodetectors.

We present the Focus-Induced Photoresponse (FIP) technique, a novel approach to optical distance measurement. It takes advantage of a universally-observed phenomenon in photodetector devices, an irradiance-dependent responsivity. This means that the output from a sensor is not only dependent on the total flux of incident photons, but also on the size of the area in which they fall. If probe light from an object is cast on the detector through a lens, the sensor response depends on how far in or out of focus the object is. We call this the FIP effect. Here we demonstrate how to use the FIP effect to measure the distance to that object. We show that the FIP technique works with different sensor types and materials, as well as visible and near infrared light. The FIP technique operates on a working principle, which is fundamentally different from all established distance measurement methods and hence offers a way to overcome some of their limitations. FIP enables fast optical distance measurements with a simple single-pixel detector layout and minimal computational power. It allows for measurements that are robust to ambient light even outside the wavelength range accessible with silicon.

Effects of multiple ion loading on redox and luminescence properties of ruthenium trisphenanthroline crown ether hybrids.

Homoleptic and heteroleptic ruthenium trisphenanthrolines were prepared with azacrown ethers attached to the 4,7-positions of the phenanthrolines to maximise the electronic communication between the ruthenium and the crown ethers as complexation sites. Redox and spectral data were processed to explain the non-steady trends in the absorption and emission spectra in the series. Addition of Ba2+ entailed large shifts in the redox potential (up to 370 mV) and in the emission spectra (up to 87 nm). Due to the crowded situation of the azacrown ether units in, this complex showed a non-linear behaviour both in the redox and emission properties upon loading with Ba2+ that is postulated to originate from the intermediate formation of sandwich type complexes.

Toward understanding the mechanism of chromophore-assisted laser inactivation--evidence for the primary photochemical steps.

Chromophore-assisted laser inactivation (CALI) is a light-mediated technique used to selectively inactivate proteins of interest to elucidate their biological function. CALI has potential applications to a wide array of biological questions, and its efficiency allows for high-throughput application. A solid understanding of its underlying photochemical mechanism is still missing. In this study, we address the CALI mechanism using a simplified model system consisting of the enzyme beta-galactosidase as target protein and the common dye fluorescein. We demonstrate that protein photoinactivation is independent from dye photobleaching and provide evidence that the first singlet state of the chromophore is the relevant transient state for the initiation of CALI. Furthermore, the inactivation process was shown to be dependent on oxygen and likely to be based on photooxidation of the target protein via singlet oxygen. The simple model system used in this study may be further applied to identify and optimize other CALI chromophores.