arXiv subjects

Alex I. Smirnov

Publications and source records attributed to Alex I. Smirnov.

3 recordsLinked to original sources

arXiv2026

Quantitative Detection of Molecular Oxygen in the Gas Phase with Fluorescent Nanodiamonds

The quantitative detection of paramagnetic molecular oxygen (O2) in gas mixtures using optically detected magnetic resonance (ODMR) from negatively charged nitrogen-vacancy (NV-) centers in fluorescent nanodiamonds is described. Fluorescent nanodiamonds approximately 70 nm in diameter were deposited on the glass surface of a microfluidic channel, and the oxygen concentration varied from 0 to 100% (0 to 760 mmHg O2 partial pressure) by mixing O2 and N2 gases at ambient pressure. Continuous-wave (CW) ODMR contrast was measured using a double-modulation (lock-in) detection scheme applied to both optical excitation and microwave drives. The ODMR contrast decreases linearly with oxygen partial pressure, with a sensitivity coefficient k of (-10.1 +/- 0.3) x 10^-4 % mmHg^-1. The oxygen detection limit of the experimental setup was estimated to be approximately 8 mmHg O2 partial pressure (corresponding to about 1% O2 in the gas mixture). Cycling of the content of O2 in the gas mixture in the range of 0-5% revealed slight hysteresis and corresponding repeatability of 0.006 in percent ODMR contrast. The observed fluorescence quenching and relatively slow response (ranging from several to tens of minutes) upon changes in oxygen concentration suggest that physisorption of gas molecules on the nanodiamond surfaces contributes to equilibration dynamics. The applicability of the nanodiamond-based oxygen quantum sensor was further demonstrated by detecting transient bursts of molecular oxygen generated by enzyme-catalyzed decomposition of hydrogen peroxide.

cond-mat.mtrl-sci↗

arXiv2019

Tuning friction at material-nanoparticle-liquid interfaces with an external electric field

The use of electrophoretic forces to tune friction at material-nanoparticle-liquid interfaces with static or low frequency (0.6-50 mHz) electric fields is reported for the first time. External electric fields were employed to reposition negatively charged TiO2 or positively charged Al2O3 nanoparticles suspended in water in directions perpendicular to a planar platinum surface of a quartz crystal microbalance, which was then used to monitor frictional shear forces at the interface. Active electro-tunable control of friction has been demonstrated for both TiO2 and Al2O3 suspensions. For TiO2 suspensions, significant drops in frictional shear forces, not observed for Al2O3, were likely attributed to the presence of molecularly thin interstitial water layers remaining in regions between the TiO2 particles and the substrate. Timescales associated with motion of nanoparticles in directions perpendicular to the surface were also investigated by varying the frequency of the external electric field, and were determined to be similar to those of glass-like or polymeric materials. Overall, the studies reveal that nanoparticles actively driven by electric fields can act as "cantilever-free" atomic force probes capable of "tapping mode" exploration of interfacial properties and nanoscale interactions in geometries inaccessible to optical and micromechanical probes.

cond-mat.soft↗

arXiv2012

Quantum Phase Transition in a Resonant Level Coupled to Interacting Leads

An interacting one-dimensional electron system, the Luttinger liquid, is distinct from the "conventional" Fermi liquids formed by interacting electrons in two and three dimensions. Some of its most spectacular properties are revealed in the process of electron tunneling: as a function of the applied bias or temperature the tunneling current demonstrates a non-trivial power-law suppression. Here, we create a system which emulates tunneling in a Luttinger liquid, by controlling the interaction of the tunneling electron with its environment. We further replace a single tunneling barrier with a double-barrier resonant level structure and investigate resonant tunneling between Luttinger liquids. For the first time, we observe perfect transparency of the resonant level embedded in the interacting environment, while the width of the resonance tends to zero. We argue that this unique behavior results from many-body physics of interacting electrons and signals the presence of a quantum phase transition (QPT). In our samples many parameters, including the interaction strength, can be precisely controlled; thus, we have created an attractive model system for studying quantum critical phenomena in general. Our work therefore has broadly reaching implications for understanding QPTs in more complex systems, such as cold atoms and strongly correlated bulk materials.

cond-mat.mes-hall↗