We report the dynamics of photoinduced carriers in a free-standing MoS2 laminate consisting of a few layers (1-6 layers) using time-resolved optical pump-terahertz probe spectroscopy. Upon photoexcitation with the 800 nm pump pulse, the terahertz conductivity increases due to absorption by the photoinduced charge carriers. The relaxation of the non-equilibrium carriers shows fast as well as slow decay channels, analyzed using a rate equation model incorporating defect-assisted Auger scattering of photoexcited electrons, holes, and excitons. The fast relaxation time occurs due to the capture of electrons and holes by defects via Auger processes, resulting in nonradiative recombination. The slower relaxation arises since the excitons are bound to the defects, preventing the defect-assisted Auger recombination of the electrons and the holes. Our results provide a comprehensive understanding of the non-equilibrium carrier kinetics in a system of unscreened Coulomb interactions, where defect-assisted Auger processes dominate and should be applicable to other 2D systems.

Optical pump-terahertz probe differential transmission measurements of as-prepared single layer graphene (AG) (unintentionally hole doped with Fermi energy E F at ∼180 meV), nitrogen doping compensated graphene (NDG) with E F ∼10 meV and thermally annealed doped graphene (TAG) are examined quantitatively to understand the opposite signs of photo-induced dynamic terahertz conductivity ∆σ. It is negative for AG and TAG but positive for NDG. We show that the recently proposed mechanism of multiple generations of secondary hot carriers due to Coulomb interaction of photoexcited carriers with the existing carriers together with the intraband scattering can explain the change of photoinduced conductivity sign and its magnitude. We give a quantitative estimate of ∆σ in terms of controlling parameters -the Fermi energy E F and momentum relaxation time τ .Further, the cooling of photoexcited carriers is analyzed using supercollision model which involves defect mediated collision of the hot carriers with the acoustic phonons, thus giving an estimate of the deformation potential.

Here, an efficient intracellular delivery of molecules with high cell viability is reported using plasmonic photoporation mediated by nano-corrugated mushroom-shaped gold-coated polystyrene nanoparticles at near-infrared wavelength.

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Targeted intracellular delivery of biomolecules and therapeutic cargo enables controlled manipulation of cellular processes. Laser-based optoporation has emerged as a versatile, non-invasive technique that employs light-based transient physical disruption of...