FTIR Study of CO₂ and H₂O/CO₂ Nanoparticles and Their Temporal Evolution at 80 K

Abstract

Fourier transform infrared (FTIR) spectroscopy combined with a long-path collisional cooling cell was used to investigate the temporal evolution of CO2 nanoparticles and binary H2O/CO2 nanocomposites in the aerosol phase at 80 K. The experimental conditions for the formation of different CO2 particle shapes as slab, shell, sphere, cube, and needle have been studied by comparison with calculated data from the literature. The H2O/CO2 nanoparticles were generated with a newly developed multiple-pulse injection technique and with the simpler flow-in technique. The carbon dioxide nu3-vibration band at 2360 cm(-1) and the water ice OH-dangling band at 3700 cm(-1) were used to study the evolution of structure, shape, and contact area of the nanocomposites over 150 s. Different stages of binary nanocomposites with primary water ice cores were identified dependent on the injected CO2 portion: (a) disordered (amorphous) CO2 slabs on water particle surfaces, (b) globular crystalline CO2 humps sticking on the water cores, and (c) water cores being completely enclosed in bigger predominantly crystalline CO2 nanoparticles. However, regular CO2 shell structures on primary water particles showing both longitudinal (LO) and transverse (TO) optical mode features of the nu3-vibration band could not be observed. Experiments with reversed nucleation order indicate that H2O/CO2 composite particles with different initial structures evolve toward similar molecular nanocomposites with separated CO2 and H2O regions.

Infrared analysis of CO ice particles in the aerosol phase

“…The band intensity is predominantly distributed within the optical TO and LO modes as is common for the crystalline state 33 and it does not show a band shape projecting over the TO mode into the lower-frequency region as observed for fully amorphous films and particles of CO 2 and N 2 O. 33,30,34,26 Furthermore, it has to be mentioned that carbon monoxide has two low-temperature solid phases with the transition at 61.55 K. 35,36 The infrared spectral band shape of the higher-temperature phase is very similar to that of the liquid CO phase with band widths being about three times bigger compared to the lower-temperature phase. 35 In our experiments, performed at temperatures below 36 K, we did not detect such broader spectral structures and therefore we assume to observe the solid lower-temperature phase only.…”

“…19, 23, and 24͒. The cooling system includes a multiple-pulse sample-gas injection device for the generation of molecular nanocomposites, 19,23,25,26 which is used in this work for single pulse or repetitive pulse injection of the CO / He probe gas mixtures. The experimental setup is schematically shown in Fig.…”

CO2 INFRARED PHONON MODES IN INTERSTELLAR ICE MIXTURES

“…The CO 2 ν 3 LO phonon mode has also been observed in ASW films exposed to CO 2 at 90 K (Kumi et al 2006) and for H 2 O/CO 2 nanoparticles at 80 K (Taraschewski et al 2005). CO 2 deposited on amorphous solid water (ASW) ice at 90 K exhibits an LO mode at 2379 cm −1 , close to that of pure CO 2 ice.…”

Adsorption studies of hazardous malachite green onto treated ginger waste

“…The peak present at 806 cm À1 indicates the presence of aromatic heterocyclic molecules, but this peak is absent in TGW. This indicates that there is a possibility of ring cleavage after the acid treatment (Taraschewski et al, 2005;Ajuong and Breese, 1998). Fig.…”