Flame-formed carbon nanoparticles exhibit quantum dot behaviors.

We examine the quantum confinement in the photoemission ionization energy in air and optical band gap of carbon nanoparticles (CNPs). Premixed, stretched-stabilized ethylene flames are used to generate the CNPs reproducibly over the range of 4-23 nm in volume median diameter. The results reveal that flame-formed CNPs behave like an indirect band gap material, and that the existence of the optical band gap is attributed to the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap in the polycyclic aromatic hydrocarbons comprising the CNPs.

Nanoparticles in dilute gases: Fundamental equivalence between momentum accommodation and surface adsorption.

Momentum accommodation is a key factor governing the transport of particles in gases from electric mobility and Brownian diffusion to thermophoresis. This paper explores the relationship between momentum accommodation of nanoparticles in dilute gases and surface adsorption. We demonstrate that the momentum accommodation factor is fundamentally equal to the probability of surface adsorption.

Phase Equilibrium of TiO Nanocrystals in Flame-Assisted Chemical Vapor Deposition.

Nano-scale titanium oxide (TiO ) is a material useful for a wide range of applications. In a previous study, we showed that TiO nanoparticles of both rutile and anatase crystal phases could be synthesized over the size range of 5 to 20 nm in flame-assisted chemical vapor deposition. Rutile was unexpectedly dominant in oxygen-lean synthesis conditions, whereas anatase is the preferred phase in oxygen-rich gases.

Theory and Experiment of Binary Diffusion Coefficient of n-Alkanes in Dilute Gases.

Binary diffusion coefficients were measured for n-pentane, n-hexane, and n-octane in helium and of n-pentane in nitrogen over the temperature range of 300 to 600 K, using reversed-flow gas chromatography. A generalized, analytical theory is proposed for the binary diffusion coefficients of long-chain molecules in simple diluent gases, taking advantage of a recently developed gas-kinetic theory of the transport properties of nanoslender bodies in dilute free-molecular flows. The theory addresses the long-standing question about the applicability of the Chapman-Enskog theory in describing the transport properties of nonspherical molecular structures, or equivalently, the use of isotropic potentials of interaction for a roughly cylindrical molecular structure such as large normal alkanes.

Drag force and transport property of a small cylinder in free molecule flow: A gas-kinetic theory analysis.

Analytical expressions are derived for aerodynamic drag force on small cylinders in the free molecule flow using the gas-kinetic theory. The derivation considers the effect of intermolecular interactions between the cylinder and gas media. Two limiting collision models, specular and diffuse scattering, are investigated in two limiting cylinder orientations with respect to the drift velocity.