Silver Nanoparticles in the Cultural Heritage Conservation

Our cultural heritage is our invaluable social and environmental resource and concern. Moreover, it is a key global economic driver. However, they are subjected to deterioration process and aging. Particularly, microorganisms are nowadays considered harmful agents of biodeterioration of artistic materials due to the fact that their interactions with the material cause not only an esthetical damage due to their visible growth on the surface, but they may affect the interested materials in different ways and at different degrees via mechanical and biochemical processes leading to the formation of pitting, scaling and, in the worst scenario, to the loss of material by its detachment. To protect our shared tangible cultural heritage from biodeterioration and preserve it for future generations, several methods have been developed. Notably, using nanomaterials, with antimicrobial features, has been considered an interesting and economical method to preserve valuable heritage materials. In this chapter, we will present an overview of the decay mechanisms that participate in the deterioration of tangible artworks, in particular microorganisms’ colonization. Next, current works that have been developed to use silver nanoparticles to protect heritage items from microbial colonization and prevent their deterioration have been detailed

The Effect of Glass Structure on the Luminescence Spectra of Sm³⁺-Doped Aluminosilicate Glasses

Peralkaline Sm3+-doped aluminosilicate glasses with different network modifier ions (Mg2+, Ca2+, Sr2+, Ba2+, Zn2+) were investigated to clarify the effect of glass composition and glass structure on the optical properties of the doped Sm3+ ions. For this purpose, the Sm3+ luminescence emission spectra were correlated with the molecular structure of the glasses derived by molecular dynamics (MD) simulations. The different network modifier ions have a clear and systematic effect on the peak area ratio of the Sm3+ emission peaks which correlates with the average rare earth site symmetry in the glasses. The highest site symmetry is found for the calcium aluminosilicate glass. Glasses with network modifier ions of lower and higher ionic radii show a notably lower average site symmetry. The symmetry could be correlated to the rare earth coordination number with oxygen atoms derived by MD simulations. A coordination number of 6 seems to offer the highest average site symmetry. Higher rare earth coordination probabilities with non-bridging oxygen result in an increased splitting of the emission peaks and a notable broadening of the peaks. The zinc containing glass seems to play a special role. The Zn2+ ions notably modify the glass structure and especially the rare earth coordination in comparison to the other network modifier ions in the other investigated glasses. The knowledge on how glass structure affects the optical properties of doped rare earth ions can be used to tailor the rare earth absorption and emission spectra for specific applications

The effect of rare earth (Er, Yb) element doping on the crystallization of Y2Ti2O7 pyrochlore nanoparticles developed by hydrothermal-assisted-sol-gel method

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Luminescent Sm-doped aluminosilicate glass as a substrate for enhanced photoresponsivity of MoS2 based photodetector

© 2021 Elsevier B.V.The choice of substrate is crucial for device applications, in particular for atomically thin materials such as monolayer transition metal dichalcogenides. The interaction between the active material and the substrate could be exploited to improve the device performance. In this work, we used a Sm-doped aluminosilicate glass (Sm-ASG) as a substrate for monolayer MoS2 based photodetector. Due to the strong high-energy emission lines of Sm, Sm-ASG substrate absorbs the incident light and acts as second excitation source compensating the low absorption of the MoS2 monolayer. On Sm-ASG substrate, the MoS2 photoresponsivity was increased up to 13,157 AW−1 as compared to 5,740 AW−1 on undoped ASG substrate, under illumination of a monochromatic laser with 520 nm wavelength at a power of 0.2 µW. The significantly enhanced photoresponse, which is amongst the highest reported values for unbiased photoconductors, is attributed to the dual function of Sm-ASG substrate, consisting of a surface charge transfer and an enhanced photoexcitation via a photon recycling effect. Our new approach, based on the simple use of substrate, paves the way for achieving high performance optoelectronic devices.11Nsciescopu

Pr3+:BaY2F8 crystal nanoparticles (24 nm) produced by high-energy ball milling: Spectroscopic characterization and comparison with bulk properties

Nanocrystals (NC) of Pr3+:BaY2F8 with average diameter of 24 nm have been successfully prepared by highenergy ball milling. The method is versatile, easily scalable, and does not require the use of surfactants or catalysts. NC were prepared starting from high quality single crystal pieces, and their spectroscopic features are analyzed and compared with those of a single bulk crystal. Under 445 nm excitation, we recorded the 10 K and room temperature emission spectra of the two samples. The spectra show the same peak positions and width, and this means that the milling process does not introduce substantial modifications to the crystal structure. Besides, there are strong differences in the relative intensity of the lines emitted toward different lower lying levels in the two samples. In particular, the high-energy transitions seem to be hyper intense in the NC with respect to the bulk sample. On the contrary, the emission lines that end at excited levels are less intense in the NC. In addition, the time evolution of the 3P0 decay shows striking differences between the nanosized materials and the bulk sample. Despite the exponential decay of the latter luminescence (τ = 43 μs), NC possess a strong nonlinear component with a lifetime much shorter than in the bulk. Calculations show that nearly 89% of the excited ions contribute to the short-time decay, which is attributed to ions residing near the NC surface