Metal-passivated PbS nanoparticles: fabrication and characterization

Abstract

Organic-shell-free PbS nanoparticles have been produced in the size range relevant for quantum-dot solar cells (QDSCs) by a vapor aggregation method involving magnetron reactive sputtering. This method creates a beam of free 5-10 nm particles in a vacuum. The dimensions of the particles were estimated after their deposition on a substrate by imaging them using ex situ SEM and HRTEM electron microscopy. The particle structure and chemical composition could be deduced "on the fly", prior to deposition, using X-ray photoelectron spectroscopy (XPS) with tunable synchrotron radiation. Our XPS results suggest that under certain conditions it is possible to fabricate particles with a semiconductor core and 1 to 2 monolayer shells of metallic lead. For this case the absolute energy of the highest occupied molecular orbital (HOMO) in PbS has been determined to be (5.0 ± 0.5) eV below the vacuum level. For such particles deposited on a substrate HRTEM has confirmed the XPS-based conclusions on the crystalline PbS structure of the semiconductor core. Absorption spectroscopy on the deposited film has given a value of ∼1 eV for the lowest exciton. Together with the valence XPS results this has allowed us to reconstruct the energy level scheme of the particles. The results obtained are discussed in the context of the properties of PbS QDSCs.

Tin Oxides: Insights into Chemical States from a Nanoparticle Study

“…32−35 For the semiconductor particles, their dimensions have been determined after their deposition and scanning electron microscopic (SEM) imaging, similarly to our previous works. 42,43 Figure 4 illustrates SEM results for two characteristic cases of the present work: when the particles deposited from the beam contain weakly oxidized tin (left image) and strongly oxidized tin (right image). The dominant size of the quasi-circular objects in the left image is around 10 nm.…”

Evaluation of protective effect of Thiocetam drug by morphological changes in the heart and vessels after administration of lead nanoparticles of various sizes (experimental study)

“…The introduction of nanotechnology into modern production has opened wide prospects for technological development and significantly improves the consumer properties of products. In particular, synthesized nanocrystals of lead compounds, the so-called "quantum dots" 4-10 nm in size, have been successfully used in the manufacturing of semiconductors, solar cells, biosensors, polymer composites, paints, electronic systems, including LEDs, and flat light emitting panels [8,12,19,23,29]. Today, the production and use of metal nanoparticles has become commercially available, which enables their penetration into the production areas and the environment and raises a number of questions about the potential risks of nanomaterials for human health [9,11,13,27].…”