No abstract

No abstract

No abstract

No abstract

No abstract

Efficient infrared-to-visible upconversion luminescence excited by multiphoton absorption was systematically studied in yttrium silicate (Y 2 SiO 5 ) powders doped with trivalent terbium ions (Tb 3+ ). The sample was excited by ultrashort pulses at 800, 1500, 1800, 2000, and 2340 nm. The anti-Stokes luminescence from 300 to 650 nm was due to the absorption of three, four, and five photons depending on the excitation wavelengths. The green emission centered at 545 nm was the most intense emission and its origin was identified as due to the Tb 3+ : 5 D 4 → 7 F 5 transition. The results reveal that powders of Y 2 SiO 5 :Tb 3+ , prepared by the combustion synthesis method, are promising as optical upconverters and may have significant technological uses due to the large efficiency observed.

The development of composites with antibacterial activity represents an important strategy to avoid side effects such as increasing bacterial resistance to antibiotics. In particular, the green synthesis of metal nanoparticles avoids the use of hazardous chemical compounds and introduces the intrinsic beneficial properties of plant-derived compounds. Herein, the reduction of gold salt into metal nanoparticles was provided by the action of a cationic polymer derived from tannin (Tanfloc®). Comparative activity of antibacterial agents (pure Tanfloc and Au NPs—Tanfloc) at different concentrations were evaluated in terms of the antibiofilm activity, kill-time assays and inhibition haloes confirming the antibacterial activity of the Tanfloc that is reinforced by the incorporation of reduced gold nanoparticles, resulting in the complete elimination of S. aureus from an initial concentration of 108 CFU/mL after 120 min of reaction of Au NPs + Tanfloc solution in association with strong inhibition of the biofilm formation attributed to the Tanfloc.

No abstract