Nanoparticles as multimodal photon transducers of ionizing radiation

In biomedical imaging, nanoparticles combined with radionuclides that generate Cerenkov luminescence are used in diagnostic imaging, photon-induced therapies, and as activatable probes. In these applications, the nanoparticle is often viewed as a carrier inert to ionizing radiation from the radionuclide. However, certain phenomena such as enhanced nanoparticle luminescence and generation of reactive oxygen species cannot be explained by only Cerenkov luminescence interactions with nanoparticles. Herein, we report methods to examine the mechanisms of nanoparticle excitation by radionuclides, including interactions with Cerenkov luminescence, β particles, and γ radiation. We demonstrate that β scintillation contributes appreciably to excitation and reactivity in certain nanoparticle systems and that excitation of nanoparticles composed of large atomic number atoms by radionuclides generates X-rays, enabling multiplexed imaging through single photon emission computed tomography. These findings demonstrate practical optical imaging and therapy using radionuclides with emission energies below the Cerenkov threshold, thereby expanding the list of applicable radionuclides

Porous silicon gas sensing

In this chapter, the state of the art on porous silicon gas sensors, both electrical and optical, is reviewed by paying special emphasis on the advancement of gas sensor architectures that has occurred over the two last decades, as well as on the different functionalization approaches implemented in and chemical species sensed with such architectures. Ten main architectures, five for the electrical domain (capacitor, Schottky-like diode, resistor, FET-like transistor, and junction-like diode) and five for the optical domain (single layer, waveguide, Bragg mirror, resonant cavity, and rugate filter), have been proposed so far for improving gas sensor features. Several functionalization schemes have been integrated in such architectures to improve sensor performance, and more than 50 different chemical species have been sensed using porous silicon gas sensors. The latest trends on multiparametric sensing on single devices as well as on multisensor integration in a single chip, for both optical and electrical domains, are also discussed

Porous Silicon Micromachining Technology

In this chapter, silicon electrochemical micromachining (ECM) technology is reviewed with particular emphasis to the fabrication of complex microstructures and microsystems, as well as to their applications in optofluidics, biosensing, photonics, and medical fields. ECM, which is based on the controlled electrochemical dissolution of n-type silicon under backside illumination in acidic (HF-based) electrolytes, enables microstructuring of silicon wafers to be controlled up to the higher aspect ratios (over 100) with sub-micrometer accuracy, thus pushing silicon micromachining well beyond up-to-date both wet and dry microstructuring technologies. Both basic and advanced features of ECM technology are described and discussed by taking the fabrication of a silicon microgripper as case study