Biomedical subjects

Andrei Kolmakov

Publications and source records attributed to Andrei Kolmakov.

5 recordsLinked to original sources

PubMed2006

Toward the nanoscopic "electronic nose": hydrogen vs carbon monoxide discrimination with an array of individual metal oxide nano- and mesowire sensors.

The array of chemiresistors made of individual pristine SnO2, surface doped (Ni)-SnO2 nanowires, and TiO2 and In2O3 mesoscopic whiskers was fabricated on a Si/SiO2 wafer. Their conductance was measured under pulses of H2 and CO reducing gases in oxygen as background gas. The nanostructures were shown to be n-type semiconductors possessing high sensitivity to the target gases. Following the "electronic nose" concept, correlation analysis of response of three-chemiresistor array is shown to be sufficient to discriminate between H2 and CO signals.

Biosensing Techniques↗

PubMed2005

Pinning mass-selected Agn clusters on the TiO2(110)-1x1 surface via deposition at high kinetic energy.

We present the first scanning tunneling microscopy (STM) study of the deposition of mass-selected silver clusters (Ag(n),n=1, 2, 3) on a rutile TiO(2)(110)-1x1 surface at room temperature under hard-landing conditions. Under hard-landing conditions, only small features are observed on the surface in all cases without sintering or surface damage. This suggests that the high impact energy of the clusters mainly dissipates as thermal energy in the substrate, resulting in the recovery of any initial impact-induced surface damage and the formation of bound clusters on the surface near the impact point. STM images indicate that Ag(1) binds on the bridging oxygen rows twice as often as on the Ti rows. Density-functional Theory (DFT) calculations are consistent with Ag(1) binding at either bridging oxygen vacancies or with two adjacent bridging oxygen atoms in the same bridging oxygen row. STM images of Ag(2) and Ag(3) depositions indicate almost exclusive binding centered on the Ti-atom rows. DFT calculations suggest that the Ag(2) and Ag(3) clusters are bound between two bridging oxygen rows, which is consistent with the STM observations.

Journal Article↗

PubMed2005

Landing of size-selected Agn+ clusters on single crystal TiO2 (110)-(1x1) surfaces at room temperature.

Mass-selected Ag(n) (+) (n=1,2,3) clusters with impact energy less than 2 eV per atom were deposited from the gas phase onto rutile titania (110)-(1x1) single crystal surfaces at room temperature and imaged using ultra-high vacuum scanning tunneling microscopy. Upon reaching the surface, Ag monomers sintered to form three-dimensional islands of approximately 50 atoms in size, with an average measured height of 7.5 A and diameter of 42 A. This suggests that the monomers are highly mobile on the titania surface at room temperature. Dimers also sintered to form large clusters upon deposition, approximately 30 atoms in size, with an average height of 6.2 A and diameter of 33 A. Clusters formed from monomer deposition appeared approximately three times more frequently at step edges than clusters formed from dimer deposition, indicating that the surface mobility of deposited monomers is higher than that of deposited dimers. In sharp contrast to the deposition of monomers and dimers, the deposition of trimers resulted in a high density of very small clusters on the order of a few atoms in size, indicative of intact trimers on the surface, implying that deposited trimers have very limited mobility on the surface at room temperature.

Journal Article↗

PubMed2005

Encoding morphology in oxide nanostructures during their growth.

Programmable control over the overall structure of SnO(2) nanowires grown by vapor-solid synthesis is shown to be possible by pulse modulating the flow rate of the carrier gas in which oxygen (one of the reactants) is entrained. The control is shown to depend on the local oscillation of the supersaturation condition for the SnO vapor (another reactant) in the vicinity of the growing nanostructure. The latter triggers dramatic, reproducible oscillations in the lateral dimensions of the nanostructure and in the direction of its growth. The method provides a means for producing predictable morphological and compositional variations in 1D nanostructures, thereby potentially resulting in a high yield of custom-designed nanostructures.

Journal Article↗

PubMed2002

In situ scanning tunneling microscopy of oxide-supported metal clusters: nucleation, growth, and thermal evolution of individual particles.

An experimental approach was developed for imaging the nucleation and growth of individual oxide-supported nanoparticles and their subsequent in situ chemical and thermal treatments by scanning tunneling microscopy (STM). The potential of the method is demonstrated for Au nanoparticles supported on a reduced TiO(2) substrate where a cluster-by-cluster comparison is made of the morphological evolution and stability of nanoparticles during their nucleation and thermal annealing. Using this methodology the details of the nucleation and growth kinetics can be directly observed.

Journal Article↗