Diamond-like-carbon nanoparticle production and agglomeration following UV multi-photon excitation of static naphthalene/helium gas mixtures

Abstract

We report the formation of nanoparticles with significant diamond character after UV multi-photon laser excitation of gaseous naphthalene, buffered in static helium gas, at room temperature. The nanoparticles are identified in situ by their absorption and scattering spectra between 400 and 850 nm, which are modeled using Mie theory. Comparisons of the particles’ spectroscopic and optical properties with those of carbonaceous materials indicate a sp3/sp2 hybridization ratio of 8:1 of the particles formed. The particle extinction in the closed static (unstirred) gas-phase system exhibits a complex and quasi-oscillatory time dependence for the duration of up to several hours with periods ranging from seconds to many minutes. The extinction dynamics of the system is based on a combination of transport features and particle interaction, predominantly agglomeration. The relatively long period of agglomeration allows for a unique analysis of the agglomeration process of diamond-like carbon nanoparticles in situ.

Hydrogenated Silicon Nanoclusters with a Permanent Electric Dipole Moment for the Controlled Assembly of Silicon-Based Nanostructures

“…Incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) has been previously applied successfully in similar experiments to investigate the time-dependent extinction of naphthalene gas mixtures after multiphoton UV excitation. − In IBBCEAS, the extinction coefficient of a sample, ε­(λ), is determined by measuring the transmission of light through an optically stable high-finesse cavity containing the sample species. The cavity is formed by two highly reflective mirrors of reflectivity R (λ).…”