Excitonic optical transitions characterized by Raman excitation profiles in single-walled carbon nanotubes

We examine the excitonic nature of the E33 optical transition of the individual free-standing index-identified (23, 7) single-walled carbon nanotube by means of the measurements of its radial-breathing-mode and G-mode Raman excitation profiles. We confirm that it is impossible to determine unambiguously the nature of its E33 optical transition (excitonic vs band to band) based only on the excitation profiles. Nevertheless, by combining Raman scattering, Rayleigh scattering, and optical absorption measurements on strictly the same individual (23, 7) single-walled carbon nanotube, we show that the absorption, Rayleigh spectra, and Raman excitation profiles of the longitudinal and transverse G modes are best fitted by considering the nature of the E33 transition as excitonic. The fit of the three sets of data gives close values of the transition energy E33 and damping parameter G33. This comparison shows that the fit of the Raman excitation profiles provides with good accuracy the energy and damping parameter of the excitonic optical transitions in single-walled carbon nanotubes

Optically active cross-band transition in double-walled carbon nanotube and its impact on Raman resonances

International audienceDouble-walled carbon nanotubes (DWNTs), often regarded as the simplest one-dimensional (1D) van der Waals moiré superlattices, are the ideal structures to explore the interlayer coupling, including mechanical and electronical coupling, at the nanoscale in 1D systems. By combining spatial modulation spectroscopy (SMS) and resonant Raman scattering (RRS) experiments on well-identified individual free-standing DWNTs with the calculations of their optical absorption by using the recursion method with non-orthogonal tight-binding (NTB) basis functions, we are able to unambiguously assign the nature, namely mirror transition or cross transition, of each optical transitions in DWNTs. Our study identifies and allows to determine the conditions of the mixing of the electronic states leading to the appearance of cross transitions in the optical absorption of DWNTs, beyond of the so-called Koshino’s criteria previously derived. On the other hand, the striking behavior of the resonant excitation profile (REP) of the Raman active modes around the cross transition reveals the strong sensitivity of the modes intensity on the electronic interlayer coupling in DWNTs, emphasizing the relevance of Raman spectroscopy for studying the electronic and mechanical coupling at the nanoscale

Determinants, predictors and negative impacts of burnout among health care workers during COVID-19 pandemic

The first defense line of the battle, healthcare workers (HCWs), faces a significant challenge in managing the current COVID-19 pandemic. An online electronic survey was sent to HCWs via email and social media networks. Socio-demographic data and work environment-related variables were assessed. Consequences of burnout (BO) were reported, e.g., elicited medical errors. Maslach burnout inventory was used to diagnose BO. Two hundred and eighty-four participants were included with a mean age of 39.83 ± 7.34 years, 70.8% worked in the COVID-19 frontline, 91.9% were followed daily updates about COVID-19, 63.7% were not satisfied with the coordination between triage and isolation, 64.4% got COVID-19 infection, 91.9% had a colleague or family member developed COVID-19 infection, and 21.5% experienced a colleague /a family member died due to COVID-19. Multivariate analysis by linear regression revealed that; working as a frontline HCW (OR 1.28, CI = 0.14–2.55) and sleep deprivation (OR 3.93, CI = 1.88–8.22) were the predictors of burnout