Wavelength-Selective Nonlinear Imaging and Photo-Induced Cell Damage by Dielectric Harmonic Nanoparticles

We introduce a nonlinear all-optical theranostics protocol based on the excitation wavelength decoupling between imaging and photoinduced damage of human cancer cells labeled by bismuth ferrite (BFO) harmonic nanoparticles (HNPs). To characterize the damage process, we rely on a scheme for in situ temperature monitoring based on upconversion nanoparticles: by spectrally resolving the emission of silica coated NaGdF4:Yb³⁺/Er³⁺ nanoparticles in close vicinity of a BFO HNP, we show that the photointeraction upon NIR-I excitation at high irradiance is associated with a temperature increase >100 °C. The observed laser-cell interaction implies a permanent change of the BFO nonlinear optical properties, which can be used as a proxy to read out the outcome of a theranostics procedure combining imaging at 980 nm and selective cell damage at 830 nm. The approach has potential applications to monitor and treat lesions within NIR light penetration depth in tissues.

Energetics driving the short-range order in CuxPd1-x/Ru(0001) monolayer surface alloys

The energetics determining the distinct short-range order in two-dimensional (2D) monolayer Cu(x)Pd(1-x) surface alloys on a Ru(0001) substrate were investigated by Monte Carlo simulations and density functional theory calculations. Using a 2D lattice gas Hamiltonian based on effective pair interaction (EPI) parameters, the EPIs were derived for different Cu concentrations with Monte Carlo (MC) simulations by comparing with the atomic distributions obtained from atomic resolution STM images and the related Warren-Cowley short-range order parameters (Hoster et al., Phys. Rev. B, 2006, 73 165413). The ground state structures and mixing energies at 0 K derived from these EPIs agree well with mixing energies determined from DFT calculations of different ordered surface alloys. Additional MC simulations yield rather low transition temperatures which explain the absence of ordered 2D phases in the experiments. The consequences of our findings for the use of alloy surfaces and surface alloys as model systems for adsorption and catalytic reaction studies are discussed.