In a condensed matter system, phonons and plasmons are well-known quasiparticles that represent unusual dispersion behavior of energy and momentum at nanoscales. In a nanoscale Mo/Si multilayer structure, phonon modes in Raman scattering indicated the coexistence of crystalline Si (c-Si) nanoclusters within an amorphous silicon (a-Si) matrix. The TO mode was red-shifted with a decrease in the nanocluster size of Si in nanolayer films. This was associated with the momentum of phonons and it is fundamentally correlated to phonon confinement. The correlation length of the Si network was significantly smaller in a-Si and the TO mode broadened asymmetrically and redshifted due to localized phonon density of state. Consequently, with a decrease in the thickness of the Si layer, blue shifts of plasmon energy for Mo 3d, Mo 4p, and Si 2p spectra were observed in X-ray photoelectron spectroscopy. Plasmon energy of the c-Si nanocluster was related to the forbidden gap, which increased with a decrease in cluster size. The concept of quantum confinement of phonon and electron states was used to determine the size of the c-Si nanoclusters in the a-Si matrix.

The search for efficient technologies empowering the selective capture of environmentally harmful heavy metals from wastewater treatment plants, at affordable prices, attracts wide interest but constitutes an important technological challenge. We report here an eco-friendly single-walled carbon nanotube buckypaper (SWCNT-BP) enriched with a multivariate amino acid-based metal–organic framework (MTV-MOF) for the efficient and selective removal of Pb 2+ in multicomponent water systems. Pristine MTV-MOF was easily immobilized within the porous network of entangled SWCNTs, thus obtaining a stable self-standing adsorbing membrane filter ( MTV-MOF/SWCNT-BP ). SWCNT-BP alone shows a moderately good removal performance with a maximum adsorption capacity of 180 mg·g –1 and a considerable selectivity for Pb(II) ions in highly concentrated multi-ion solutions over a wide range of lead concentration (from 200 to 10000 ppb). Remarkably, these features were outperformed with the hybrid membrane filter MTV-MOF/SWCNT-BP , exhibiting enhanced selectivity and adsorption capacity (310 mg·g –1 , which is up to 42% higher than that of the neat SWCNT-BP) and consequently enabling a more efficient and selective removal of Pb 2+ from aqueous media. MTV-MOF/SWCNT-BP was able to reduce [Pb 2+ ] from the dangerous 1000 ppb level to acceptable limits for drinking water, below 10 ppb, as established by the current EPA and WHO limits. Thus, the eco-friendly composite MTV-MOF/SWCNT-BP shows the potential to be effectively used several times as a reliable adsorbent for Pb 2+ removal for household drinking water or in industrial treatment plants for water and wastewater lead decontamination.

No abstract

No abstract

No abstract