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We present experimental results on the multicolor (blue and green) photoluminescence from glycine-coated silver nanoclusters and small nanoparticles which can be used as novel probes for bio-imaging. Glycine-coated silver nanoclusters and nanoparticles were synthesized using thermal reduction of silver nitrate in a glycine matrix, according to a modified procedure described in literature. The size characterization with mass spectrometry, scanning electron microscopy and dynamic light scattering showed that the diameters of luminescent silver nanoclusters and small nanoparticles vary from 0.5 nm to 17 nm. Extinction spectroscopy revealed that the absorption band of the luminescent nanoclusters and nanoparticles was blue-shifted as compared to the nonluminescent larger silver nanoparticles. This effect indicated the well-known size dependence of the surface plasmon resonance in silver. The most pronounced photoluminescence peak was observed around 410 nm (characteristic SPR wavelength for silver) which strongly suggests the enhancement of the photoluminescence from silver nanoparticles by the SPR. The relative quantum yield of the photoluminescence of silver nanoclusters and nanoparticles was evaluated to be 0.09. In terms of their small size, brightness and photostability, noble metal nanoclusters and nanoparticles hold the most promise as candidates for biological cell imaging, competing with commonly used semiconductor quantum dots, fluorescent proteins and organic dyes. When applied to the problem of intracellular imaging, metal nanoclusters and small nanoparticles offer advantages over their much larger sized semiconductor counterparts in terms of ease of biological delivery. In addition, noble metal nanoparticles and nanoclusters are photostable. The high quantum yield (QY) of the photoluminescence emission signal enables the isolation of their photoluminescence from the cellular autofluorescence in cell imaging, improving the image contrast.

It is well known that optical phenomena in metals at IR spectral region are connected with intraband optical transitions and they are analogues of direct electrical conductivity (resistance) at low frequencies. It can be suggested that in case of alternating current flux through an amorphous metallic ribbon in external magnetic field, correlation between optical and magneto-transport properties can be emerged. It must be important that the objects of the investigations are magneto-optical effects linked with diagonal components of the optical tensor unlike Kerr or Faraday effects. Experimental appearance of magneto-optical effects comprises significant changes of optical conductivity and real part of dielectric permeability via influence of external magnetic field. The magneto-transport properties depend on the effective differential permeability, on the type of domain structure and corresponding densities of electron states at the Fermi level. Optical functions of the amorphous metallic alloys ribbons of Co-Ni-B are obtained at spectral region of 1.0-5.0 eV. Changes of optical conductivity spectra of the ribbons' surface in the presence of applied external magnetic field are revealed. Variations of optical and magneto-transport properties caused by superseding of one 3d transition metal (Co) to another (Ni) are obtained. Parameters of electronic subsystem were calculated. Interconnection between electronic structure of the amorphous metallic ribbons' surface and its magneto-transport properties is established.

Modern accelerators and light sources subject bunches of charged particles to quasiperiodic motion in extremely high electric fields, under which they may emit a substantial fraction of their energy. To properly describe the motion of these particle bunches, we require a kinetic theory of radiation reaction. We develop such a theory based on the notorious Lorentz-Dirac equation, and explore how it reduces to the usual Vlasov theory in the appropriate limit. As a simple illustration of the theory, we explore the radiative damping of Langmuir waves.