High-quality and easy-to-regenerate personal filter.

Proper respiratory tract protection is the key factor to limiting the rate of COVID-19 spread and providing a safe environment for health care workers. Traditional N95 (FFP2) respirators are not easy to regenerate and thus create certain financial and ecological burdens; moreover, their quality may vary significantly. A solution that would overcome these disadvantages is desirable. In this study a commercially available knit polyester fleece fabric was selected as the filter material, and a total of 25 filters of different areas and thicknesses were prepared. Then, the size-resolved filtration efficiency (40-400 nm) and pressure drop were evaluated at a volumetric flow rate of 95 L/min. We showed the excellent synergistic effect of expanding the filtration area and increasing the number of filtering layers on the filtration efficiency; a filter cartridge with 8 layers of knit polyester fabric with a surface area of 900 cm2 and sized 25 × 14 × 8 cm achieved filtration efficiencies of 98% at 95 L/min and 99.5% at 30 L/min. The assembled filter kit consists of a filter cartridge (14 Pa) carried in a small backpack connected to a half mask with a total pressure drop of 84 Pa at 95 L/min. In addition, it is reusable, and the filter material can be regenerated at least ten times by simple methods, such as boiling. We have demonstrated a novel approach for creating high-quality and easy-to-breathe-through respiratory protective equipment that reduces operating costs and is a green solution because it is easy to regenerate.

Laser Desorption Ionization Time-of-Flight Mass Spectrometry of Silver-Doped (GeS2)50(Sb2S3)50 Chalcogenide Glasses.

Mass spectra of (GeS2)50(Sb2S3)50 glass and Ag-doped glasses [5% Ag (GeS2)50(Sb2S3)50 and 15% Ag (GeS2)50(Sb2S3)50] obtained using laser desorption ionization (LDI) time-of-flight coupled with quadrupole ion trap mass spectrometry were studied. The analysis of the mass spectra indicated the formation of Ag a Ge b Sb c S d clusters. In addition to the SbS d + (d = 1 and 2), Sb2S d + (d = 1-3), Sb3S d + (d = 1-5), Sb4S d + (d = 3 and 4), Sb5S2 +, and Sb c + (c = 3 and 5) clusters, various clusters containing Ag, such as Ag a + (a = 1 and 2), AgGeS+, AgSb c + (c = 1, 2, and 4), AgSbS+, AgSb2S d + (d = 1-5), AgSb3S3 +, AgSb4S4 +, Ag2Sb3S d + (d = 4 and 5), Ag4Sb2S3 +, and Ag5SbS3 +, were generated. Moreover, in spite of the five-ninth purity of all glass components, several hydrogenated clusters (SbS3H8 +, Sb4S2H+, Ag2H11 +, Ag2Sb3H4 +, Ag3Sb2H4 +, Ag4Sb2H2 +, and Ag4S3H8 +) and some low-intensity oxidized clusters, such as Sb3O+ and Sb3O5 +, were also detected. When applying LDI on (GeS2)50(Sb2S3)50 glass, no Ge-containing clusters were detected in the positive ion mode, and just one Ge-containing cluster was observed after doping the glass with Ag. Hydrogen plays an important role in the glasses studied. The knowledge gained concerning cluster stoichiometry contributes to the elucidation of the structure of Ag-doped Ge-Sb-S chalcogenide glasses. It should be noted that some of the clusters were considered to be structural fragments. Furthermore, mass spectrometry was complemented with Raman spectroscopy.

Structural elucidation of AgAsS2 glass by the analysis of clusters formed during laser desorption ionisation applying quadrupole ion trap time-of-flight mass spectrometry.

RATIONALE: The structure of AgA(s)S2 glass, which has a broad range of applications, is still not well understood and a systematic mass spectrometric analysis of AgA(s)S2 glass is currently not available. Elucidation of the structure should help in the development of this material. METHODS: The AgA(s)S2 glass was prepared by the melt-quenched technique. Laser desorption ionisation (LDI) using quadrupole ion trap time-of-flight mass spectrometry (QIT-TOFMS) was used to follow the generation of Ag(m)As(n)S(x) clusters. The stoichiometry of the clusters generated was determined via collision-induced dissociation (CID) and modelling of isotopic patterns. The AgA(s)S2 glass was characterised by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. RESULTS: The LDI of AgA(s)S2 glass leads to the formation of unary (Ag+/− and As(3+)) species, 38 binary (As(n)S(x), Ag(m)S(x)), and 98 ternary (Ag(m)As(n)S(x)) singly charged clusters. The formation of silver-rich nano-grains during AgA(s)S2 glass synthesis has been identified using TEM analysis and also verified by QIT-TOFMS. CONCLUSIONS: TOFMS was shown to be a useful technique to study the generation of Ag(m)As(n)S(x )clusters. SEM, TEM and EDX analysis proved that the structure of AgA(s)S2 glass is 'grain-like' where grains are either: (1) Silver-rich 'islands' (Ag(m,) m up to 39) connected by arsenic and/or sulfur or arsenic sulfide chains or (2) silver sulfide (Ag2S)m (m = 9-20) clusters also similarly inter-connected. This obtained structural information may be useful for the development of ultra-high-density phase-change storage and memory devices using this kind of glass as a base.