- Spin-dependent phenomena in semiconductors are analyzed starting from a theory of the dynamic nuclear polarization via numerous insightful findings in the realm of characterization and control through the nuclear spin polarization in nanoparticles and their aggregates into microparticles as potential contrast agents for magnetic resonance imaging (MRI) applications.
- Electron spin-dependent process of the photosensitized generation of singlet oxygen in porous silicon (Si) for photodynamic therapy application and design of Si-based nanoparticles with electron spin centers for MRI contrasting for cancer theranostics are discussed.
The present overview of spin-dependent phenomena in nonmagnetic semiconductor microparticles (MPs) and nanoparticles (NPs) with interacting nuclear and electron spins is aimed at covering a gap between the basic properties of spin behavior in solid-state systems and a tremendous growth of the experimental results on biomedical applications of those particles. We represent modern achievements of spin-dependent phenomena in the bulk semiconductors from the theory of optical spin orientation under indirect optical injection of carriers and spins in the bulk crystalline silicon (c-Si)—via numerous insightful findings in the realm of characterization and control through the spin polarization—to the design and verification of nuclear spin hyperpolarization in semiconductor MPs and NPs for magnetic resonance imaging (MRI) diagnostics. The electron spin-dependent phenomena in Si-based nanostructures include the photosensitized generation of singlet oxygen in porous Si and design of Si NPs with unpaired electron spins as prospective contrast agents in MRI. The experimental results are analyzed by considering both the quantum mechanical approach and several phenomenological models for the spin behavior in semiconductor/molecular systems. Advancements and perspectives of the biomedical applications of spin-dependent properties of Si NPs for diagnostics and therapy of cancer are discussed.