Spectroscopic properties of Er3+ doped germanate glasses before and after a heat treatment process

In this paper structural, thermal and optical properties of Er3+ doped germanate glasses with the composition of 63.0GeO2-9.8Ga2O3-11.1BaO-4.9X-8.8Na2O-2.5Er2O3 (in mol%), where X = ZnO, TiO2, Al2O3 and Y2O3 are reported. The investigated glasses exhibit low phonon energies (<1000 cm−1) and high glass transition temperature varying between 588 and 642 °C. The Raman spectra evidence about different polymerization degree of the glasses. The thermal treatment leads to the precipitation of various crystals, the composition of which depends on the glass composition. According to the spectroscopic properties Er3+ ions are suspected to have similar local environment in the as-prepared glasses. However, Er-doped crystals are expected to precipitate upon devitrification, which leads to significant change of the spectroscopic properties, in particular increase in the intensity of upconversion and MIR emissions is observed. It is demonstrated that the glasses with Y2O3, ZnO and TiO2 are promising glasses especially for MIR applications.publishedVersionPeer reviewe

Occurrence of persistent organic pollutants at Alqueva's surface water at touristic spots

Freshwater pollution is a huge concern. A study aiming to evaluate water quality and occurence of two groups of persistent environmental pollutants with similar chemical properties (polycyclic aromatic hydrocarbons-PAHs and microplastics -MPs) in Alqueva’s surface water was performed during 2021. Samples were collected at three spots related to touristic activities (two beaches and one marina) once by season. In addition, we assessed and compared the presence of biofilms on plastic and natural materials. Water quality was acceptable with a low eutrophication level. PAHs concentration levels were lower than the standard limits established for surface waters. PAHs profiles showed significant differences when comparing the dry and rainy seasons, with a higher number of different compounds detected in Spring. Low molecular weight compounds, usually associated with the atmospheric deposition and petroleum contamination, were more prevalent. MPs were detected in all samples except one during Winter. Eight polymers were detected being polyethylene the most frequent. Plastics were more prone to biofilm colonization than natural materials. In addition, biofilms detected on plastics were more complex with higher microbial diversity and richer in EPS. Among microbiota were identified microorganisms previously linked to plastic and PAHs detoxification suggesting the need for further studies to evaluate the viability of using biofilms as part of a green bioremediation strategy to mitigate water pollution.This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreementNo 730872. INSA [2020DSA1756, 2020], Helmholtz- Zentrum Berlin für Materialien und Energie (Proposals No 202-10133-ST/ UR, 2020 and 212-10726-ST/UR, 2021).N/

Easy-plane to easy-axis anisotropy switching in a Co(ii) single-ion magnet triggered by the diamagnetic lattice

Single ion magnets SIMs with large magnetic anisotropy are promising candidates for realization of single molecule based magnetic memory and qubits. Creation of materials with magnetically uncoupled spatially separated SIMs requires dilution in a diamagnetic matrix. Herein, we report that progressive dilution of paramagnetic Co II by diamagnetic Zn II in the SIM [CoxZn 1 amp; 8722;x piv 2 2 NH2 Py 2], x 1 0 beyond a threshold of 50 reveals an abrupt structural change, where the distorted tetrahedral Zn coordination structure is superimposed on the remaining Co ions, which were initially in a distorted octahedral environment. Dilution induced structure modification switches the magnetic anisotropy from easy plane D 36.7 cm amp; 8722;1 to easy axis type D amp; 8722;23.9 cm amp; 8722;1 , accompanied by a fivefold increase of the magnetic relaxation time at 2 K. Changes of the static and dynamic magnetic properties are monitored by electron paramagnetic resonance spectroscopy and AC susceptibility measurements. Complementary quantum chemical ab initio calculations quantify the influence of structural changes on the electronic structure and the magnetic anisotropy. Thus, magnetic dilution hits two goals at once, the creation of isolated magnetic centres and an improvement of their SIM propertie

Revisiting the Incorporation of Ti(IV) in UiO-type Metal–Organic Frameworks: Metal Exchange versus Grafting and Their Implications on Photocatalysis

Revisiting the Incorporation of Ti(IV) in UiO-type Metal–Organic Frameworks: Metal Exchange versus Grafting and Their Implications on Photocatalysi

The criteria for evaluation of efficiency of heat technical installations considering general energy costs with the aim of increasing their environmental friendliness and reducing negative effect on the environment

The features of the physical meaning of the thermal coefficient useful action (CUA) ηt as a criterion for the efficiency of reversible direct circular processes are considered. In particular, we demonstrate that accounting for all energy costs when applying ηt is made by adopting a number of assumptions by default. In order to expand the possibilities for conducting thermodynamic assessments of the efficiency of various thermal power plants, a new criterion of efficiency Ku is proposed as a coefficient that takes into account in a comparable form all types of energy spent on the implementation of the cycle. In determining the criterion Ku, useful effect obtained from the implementation of a direct circular process is considered to be the specific work of the expansion of the working fluid in the cycle. Such work, in particular, can be the work of steam expansion in the turbine. The total energy cost is the sum of the specific heat supplied to the working body in a circular process and the specific mechanical work spent in the cycle on compression and pressure increase of the working body. In particular, the work is taken into account in a comparable form-taking into account the heat that was spent on its production. The analysis of the Ku criterion is carried out. As a result of the analysis we have established that at transition from the general physical model of reception of specific work of expansion in direct circular process for which Ku criterion can be applied, to the special case assuming a number of assumptions, Ku criterion can become equal to thermal coefficient useful action of a cycle. Using the Ku criterion, the efficiency of Carnot and Rankine cycles on a saturated pair is compared. The Ku score showed that the Rankine cycle was more efficient

Impact of ZnO addition on Er3+ near-infrared emission, the formation of ag nanoparticles, and the crystallization of sodium fluorophosphate glass

The impact of the progressive addition of ZnO up to 5 mol% on the thermal, structural, and optical properties of Er3+-doped phosphate glasses within the system NaPO3-NaF-ZnO-Ag2O is discussed. The glass network was found to depolymerize upon the addition of ZnO. This promotes a slight increase in the intensity of the emission at 1.5 μm as well as enhances the silver ions clustering ability under the heat treating. The Ag-nanoparticles formed after moderate heat-treatment can further enhance the emission at 1.5 μm, whereas an excessive amount of the clusters leads to the opposite effect. The addition of ZnO helps to slightly increase the glass ability of the system. The crystallization behavior study revealed that surface crystallization is observed for all the glasses. It is found that even a small ZnO addition changes the crystalline phases formed after devitrification. Moreover, the addition of ZnO decreases the crystallization tendency of the glass.publishedVersionPeer reviewe

Exploring the interplay between microplastics and biofilms in freshwater

Plastic inevitably accumulates in the environment becoming a persistent. In the present work, we aim at documenting MPs occurrence in three collection spots of the biggest European artificial lake over one year period using infrared microscopy. Scanning electron microscopy was used to evaluate MPs colonization by biofilms. PE was the most abundant polymer and biofilms were identified in all plastics.CALIPSOplus: 1004; 202-10133 ST/UR; 212-10726 ST/URN/

Exploring the Potential of Microscopy Techniques to Study Microplastics and Biofilms in Environmental Samples

Micro and nanoplastic are found worldwide in aquatic ecosystems ranging from highly populated industrialized areas to the most remote regions of the planet being a hot research topic and a concern. Marine waters have been the major research focus. Despite less studied, freshwaters are of crucial importance since life in general and human beings in particular are highly dependent of freshwater for drinking and food production. This fact shows that freshwater could function as a vehicle for MPs toxicity through all levels of the ecosystem. Although it has been suggested that toxicity is driven not only by the plastic forming units (monomers) but also by adsorbed pollutants (such as PAH, pesticides, PCBs) and associated microorganisms little is known about the underlying mechanisms. The lack of validated protocols for isolation and a gold standard technique to identify micro/nanoplastics are important issues. Infrared microscopy (IRM) with diffraction-limited infrared synchrotron radiation sources adds resolution to the traditional fingerprint IR spectra being a potential candidate to a gold standard technique not only for micro/nanoplastic identification but also for adsorbed pollutants. In the present work, IRM allowed us to identify MPs isolated from freshwater samples. Polyethylene (PE) and polystyrene (PS) were among the most common plastic polymers identified. The colonization of environmental samples of MPs by biofilms was monitored by scanning electron microscopy (SEM). Our data suggests that the presence of biofilms on MPs does not interfere with polymer identification by IRM. Biofilm assembly on MPs by microorganisms isolated from water samples in conditions mimic those found in their natural’s habitats was followed over 3 months. Biofilm biomass was accessed by spectrophotometric methods whereas SEM was used to evaluate biofilm distribution on the MPs particles. The results obtained in vitro correlate with those observed in “real samples”. Biofilms assembled by the microbial consortium used were more abundant on the most common plastics detected in the environmental samples (PE and PS).Financial Support: INSA (2018DSA1555) and HZB (202-10133-ST/UR-1,1-P)N/

Coupling Raman, Brillouin and Nd3+ Photo Luminescence Spectroscopy to Distinguish the Effect of Uniaxial Stress from Cooling Rate on Soda−Lime Silicate Glass

Evolution of spectroscopic properties of a soda–lime silicate glass with different thermal history and under applied uniaxial stress was investigated using Raman and Brillouin spectroscopies as well as Nd3+ photoluminescence techniques. Samples of soda–lime silicate with a cooling rate from 6 × 10−4 to 650 K/min were prepared either by controlled cooling from the melt using a differential scanning calorimeter or by a conventional annealing procedure. Uniaxial stress effects in a range from 0 to −1.3 GPa were investigated in situ by compression of the glass cylinders. The spectroscopic observations of rearrangements in the network structure were related to the set cooling rates or the applied uniaxial stress to calculate an interrelated set of calibrations. Comparing the results from Raman and Brillouin spectroscopy with Nd3+ photoluminescence analysis, we find a linear dependence that can be used to identify uniaxial stress and cooling rate in any given combination concurrently. The interrelated calibrations and linear dependence models are established and evaluated, and equations relating the change of glass network due to effects of cooling rate or uniaxial stress are given.Deutsche ForschungsgemeinschaftPeer Reviewe