Fano-type Effect in Hydrogen-Terminated Pure Nanodiamond.

Two novel properties, unique for semiconductors, a negative electron affinity and a high p-type surface electrical conductivity, were discovered in diamond at the end of the last century. Both properties appear when the diamond surface is hydrogenated. A natural question arises: is the influence of the surface hydrogen on diamond limited only to the electrical properties? Here, for the first time to our knowledge, we observe a transparency peak at 1328 cm-1 in the infrared absorption of hydrogen-terminated pure (undoped) nanodiamonds. This new optical property is ascribed to Fano-type destructive interference between zone-center optical phonons and free carriers (holes) appearing in the near-surface layer of hydrogenated nanodiamond. This work opens the way to explore the physics of electron-phonon coupling in undoped semiconductors and promises the application of H-terminated nanodiamonds as a new optical material with induced transparency in the infrared optical range.

Spontaneous Light Emission Assisted by Mie Resonances in Diamond Nanoparticles.

Spontaneous light emission is known to be affected by the local density of states and enhanced when coupled to a resonant cavity. Here, we report on an experimental study of silicon-vacancy (SiV) color center fluorescence and spontaneous Raman scattering from subwavelength diamond particles supporting low-order Mie resonances in the visible range. For the first time to our knowledge, we have measured the size dependences of the SiV fluorescence emission rate and the Raman scattering intensity from individual diamond particles in the range from 200 to 450 nm. The obtained dependences reveal a sequence of peaks, which we explicitly associate with specific multipole resonances. The results are in agreement with our theoretical analysis and highlight the potential of intrinsic optical resonances for developing nanodiamond-based lasers and single-photon sources.

A new approach to precise mapping of local temperature fields in submicrometer aqueous volumes.

Nanodiamonds hosting temperature-sensing centers constitute a closed thermodynamic system. Such a system prevents direct contact of the temperature sensors with the environment making it an ideal environmental insensitive nanosized thermometer. A new design of a nanodiamond thermometer, based on a 500-nm luminescent nanodiamond embedded into the inner channel of a glass submicron pipette is reported. All-optical detection of temperature, based on spectral changes of the emission of "silicon-vacancy" centers with temperature, is used. We demonstrate the applicability of the thermometric tool to the study of temperature distribution near a local heater, placed in an aqueous medium. The calculated and experimental values of temperatures are shown to coincide within measurement error at gradients up to 20 °C/µm. Until now, temperature measurements on the submicron scale at such high gradients have not been performed. The new thermometric tool opens up unique opportunities to answer the urgent paradigm-shifting questions of cell physiology thermodynamics.

Laser-Assisted Synthesis of Composite Nanoparticles of Perovskite BaTiO3 in Aqueous Solutions and Their Optical Properties.

Experimental results are presented on laser-assisted synthesis of composite nanoparticles of perovskite BaTiO3 with gold nanoparticles using the technique of laser ablation in water and aqueous solution of hydrogen peroxide. Nanoparticles of BaTiO3 are generated by near IR laser radiation with pulse durations of 170 fs, 1 ps, and 200 ns. Nanoparticles of barium titanate BaTiO3 (BTO) have tetragonal structure for all used pulse durations. Two ways of synthesis are tested. In the first one a gold target is ablated in the colloidal solution of BaTiO3 nanoparticles. The second way consists of laser exposure of the mixture of colloidal solutions of nanoparticles of BaTiO3 and Au. Synthesized composite nanoparticles are characterized by optical spectroscopy, Raman spectroscopy, X-Ray diffractometry, and Transmission Electron Microscopy. Composite BaTiO3­Au nanoparticles have the absorption band in the visible range of spectrum and demonstrate plasmonic luminescence.

Boron-Doped Nanodiamonds as Anticancer Agents: En Route to Hyperthermia/Thermoablation Therapy.

Local targeted "inside-out" hyperthermia of tumors via nanoparticles is able to sensitize tumor cells to chemotherapy, radiation therapy, gene therapy, immunotherapy, or other effects, significantly reducing the duration and intensity of treatment. In this article, new nanomaterials are proposed to be used as anticancer agents: boron-doped nanodiamonds with sizes of about 10 nm synthesized for the first time by the high-temperature high-pressure (HTHP) method. The heating ability of boron-doped nanodiamonds was investigated under different heating conditions in different environments: water, chicken egg white, and MCF-7 breast cancer cells. It was discovered that, with the same conversion of the absorbed energy into heat, the ability to heat the environment when excited at a wavelength of 808 nm of boron-doped nanodiamonds is much higher than that of detonation nanodiamonds. It was established that boron-doped nanodiamonds are extremely promising for carrying out hyperthermia and thermoablation of tumors.

High-Pressure Synthesis of Boron-Doped Ultrasmall Diamonds from an Organic Compound.

The first application of the high-pressure-high-temperature (HPHT) technique for direct production of doped ultrasmall diamonds starting from a one-component organic precursor is reported. Heavily boron-doped diamond nanoparticles with a size below 10 nm are produced by HPHT treatment of 9-borabicyclo [3,3,1]nonane dimer molecules.