BO4 Tetrahedra Research Articles

Effect of Bismuth on Physical and Spectroscopic Properties of ZnO-Li2B4O7-TbF3 Glasses

The effect of Bismuth on zinc-lithium tetra borate glasses were discussed based on structural, physical, and spectroscopic properties. Glass systems of Bi2O3-ZnO-Li2B4O7-TbF3 [BZLT] were cast by melt-quench process. Transparent glasses were analysed by diffracted Roentgen X-rays. Peak free and broad nature X-ray diffraction revealed the amorphous arrangement prevailing in these glasses. Density was estimated using the Archimedes principle. Bismuth grossly affected the density of BZLT glasses by increasing its value 2.722 gm/cc [BZLT-0] to 4.6739 gm/cc [BZLT-40]. Optical absorption provides valuable information about optical band gap energy and Urbach energy and some of its derived physical quantities. The effect of bismuth is felt in decreased Eopt values [3.312 eV in BZLT-0] [2.619 eV in BZLT-40] in BZLT glasses. Bismuth altered the structure of the borate network by forming non-bridging oxygens which in turn reduced the band gap energy by large margin (ΔEopt = 0.693 eV). Fourier transform infrared spectroscpy and Raman studies revealed the presence of several triangular BO3 and tetrahedral BO4 and BiO3 units and also the existence of metal cation vibrations and supported the large deviations in the optical bandgap energies. Election paramagnetic resonance studies support the presence of Tb3+ ions and absence of Tb4+ions in BZLT glasses.

Impact of SnO2 doping on spectroscopic characteristics of the SnO2-Na2O-CoO-B2O3 borate glass matrix

The role of tin oxide (SnO2) on the structure-optical features of borate glasses containing low cobalt oxide impurities was studied. The study was carried out on a glass system [x SnO2 – (80-x) B2O3 – 19.5 Na2O – 0.5 CoO]; x = 0.0, 0.5, 1.0, 2.0 and 3.0 mol%. Glass synthesis was carried out by the melt-quench technique. Structure and optical absorption spectroscopy were carried out to explore the optical transitions of Co cations inside the present glass matrix. The obtained results indicate that, with the further addition of SnO2 content, the molar volume decreased from 31.675 cm3/mol to 29.147 cm3/mol. FTIR studies indicated the basic structural units of trigonal BO3 units and BO4 tetrahedra. Herein also, additional contents of tin oxide increased the nonbridging oxygen contents. The reason behind such increment is attributed to the existence of Sn4+ ions in octahedral coordination acting as network modifiers. Optical absorption spectra indicated the existence of Co ions in both Co2+ and Co3+ oxidation states. Moreover, the existence of significant SnO2 concurred with the significant blue shift in the visible absorption bands and red shift in near infrared absorption bands. The positions absorption bands of Co ions were analyzed in the context of ligand field parameters determinations. The obtained data of the crystal field splitting parameter (10Dqt) showed decreased values from 3451 cm−1 to 3364 cm−1 with more SnO2 addition. While Racah parameter B values were also, attained showing increased values from 967 cm−1 to 985 cm−1 when additional SnO2 is added. Further, the impacted role of SnO2 addition on the structural and optical properties of the present glasses was finally estimated.

An investigation of the structural and optical properties of modified barium magnesium fluoroborate glasses with hafnium oxide (HfO2)

AbstractGlasses of nominal composition xHfO2–(35-x)B2O3–15MgF2–35BaO, where x ranged from 0 to 0.2 mol% were fabricated using a melt-quenching technique. Structural characterization techniques, including X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and Raman spectroscopy, were employed to elucidate the glass network structure. The XRD patterns confirmed the amorphous nature of the studied glasses, while the FTIR and Raman spectra revealed that the incorporation of HfO2 may led to a transformation of trigonal BO3 units to tetrahedral BO4 units in the borate glass network. Deconvolution analysis of the FTIR and Raman bands provided quantitative insights into the extent of this structural rearrangement as a function of HfO2 content. UV–Vis absorption studies demonstrated that the optical bandgap of the glasses was widened with increasing HfO2 additions. This blue shift in the absorption edge was attributed to the increased formation of bridging oxygen bonds and reduced non-bridging oxygen content in the glass network. The results indicate that the studied glasses exhibit excellent compositional tunability through the incorporation of HfO2. The structural modifications and concomitant optical property enhancements suggest the potential of this glass system for various integrated photonic applications where low phonon energy and tailored transparency are highly desirable. The present work introduces a comprehensive investigation of the structural and optical property modifications in barium magnesium fluoroborate glasses induced by the addition of hafnium oxide (HfO2).

New Er3+-doped gadolinium borogermanate glasses for optical telecommunication

New Er3+-doped gadolinium borogermanate glasses were synthesized to investigate their physical, structural, optical, and luminescence properties in this work. The influence of Er2O3 concentration on those properties were studied to determine the optimum glass composition for photonics material. Glass density, molar volume, refractive index, polarizability, and field strength increase, while Er3+ inter-ionic distance decreases via adding Er2O3 concentration. From XRD and FTIR results, the tetrahedral BO4 and trigonal BO3 borates are the main structural units those connect in amorphous nature to form as a glass network. Glasses absorb the photons in ultraviolet, visible light and near-infrared region under Er3+ transitions. Glasses generate the strong infrared emission around 1.5 μm under the 4I13/2 → 4I15/2 transition of Er3+ ion. The 3.0 mol%-Er2O3 doped glass performs the highest emission intensity due to the concentration quenching effect. The luminescence decay time is shortened from ∼0.8 to ∼0.4 ms by adding Er2O3 content. Judd-Ofelt and MacCumber analysis indicate high potential of glass for using as an optical amplifier in telecommunication applications, due to its large luminescence bandwidth.

Study of the Structure of Zn and Na Borophosphate Glasses Using X-ray and Neutron Scattering Techniques

The atomic structures of Zn and Na borophosphate glasses were studied using X-ray and neutron scattering techniques. Peaks assigned to the B−O, P−O, and O−O distances confirm that only BO4 units co-exist with the PO4 tetrahedra. The Zn−O and Na−O coordination numbers are found to be a little larger than four. The narrowest peaks of the Zn−O first-neighbor distances exist for the glasses along a line connecting the Zn(PO3)2 and BPO4 compositions (50 mol% P2O5), which is explained by networks of ZnO4, BO4, and PO4 tetrahedra with twofold coordinated oxygens. The calculated amounts of available oxygen support this interpretation. Broadened peaks occur for glasses with lower P2O5 contents, which is consistent with the presence of threefold coordinated oxygens. The two distinct P−O peak components of the Zn and Na borophosphate glasses differ in their relative abundances. This is interpreted as follows: Na+ cations coordinate oxygens in some P−O−B bridges, which is something not seen for the Zn2+ ions.

Development of Dy3+ doped lithium magnesium borate glass system for thermoluminescence based neutron dosimetry applications

Abstract The manuscript reports the synthesis of Dy3+ incorporated lithium magnesium borate glass by melt quenching technique. FTIR study revealed the presence of both BO3 as well as tetrahedral BO4 units through their characteristic frequencies. Photoluminescence (PL) study of unirradiated samples confirmed the presence of Dy dopant in the ‘+3’ oxidation states from the characteristic emissions at 482, 578, 666 and 716 nm corresponding to 4F9/2 → 6H15/2, 4F9/2 → 6H13/2 and 4F9/2 → 6H11/2, 4F9/2 → 6H9/2 transitions, respectively. Thermal neutron and gamma irradiated PL emission and lifetime characteristics were discussed in details based on the different defect centers. Thermal neutron irradiated TL study showed that the material has a broad and single dosimetry glow peak at about 450 K which showed high fading due to low temperature peak. TL based neutron sensitivity of LMB: Dy3+ was found to be about 37.4 times less than that of standard TLD-100 (LiF: Mg, Ti) powder. The net TL response from about 3 to 83 mSv of neutron dose was found to be linear (Adj. R2 = 0.9994) which is one of the most desirable properties for dosimetry applications. In addition, the TL trap parameters were evaluated using both deconvolution of TL glow curve and peak shape method as suggested by Chen which were found to be matching with each other.

Antibiofilm Efficiency of CaF<sub>2</sub>/TiO<sub>2</sub> Strontium Borate Bioactive Glass Composites against <i>Pseudomonas aeruginosa</i> and Gamma Radiation Effect

Microbial drug resistance has emerged as one of the most fundamental health threats. The current work aims to assess the antibacterial and antibiofilm potential of strontium borate bio-glasses (BBGs). Three CaF2/TiO2 strontium borate compositions have been prepared through melting annealing methods. The XRD pattern displays the amorphous nature of the glassy samples. The primary structural components of the borate, the trigonal BO3 and tetrahedral BO4 group, can be observed in FTIR spectra. Sharpness and shifting peaks to longer wavenumbers were evident after 40 kGy of gamma radiation. In contrast, density and molar volume (Vm) reveal an obvious change after irradiation. The agar diffusion technique was conducted as a preliminary screening of the antibacterial activity against Pseudomonas aeruginosa. The studied samples possessed no antimicrobial activity toward this strain; however, samples with 2% CaF2 strontium borate (T1) and 5% TiO2 strontium borate (T3) had higher biofilm inhibition potential (inhibition percentages of 75.17 and 65.77%, respectively). The gamma irradiation procedure had an unexpected detrimental effect on the bio-glass antibiofilm activity, making it unsuitable for use in sterilization procedures. Collectively, BBGs could be further investigated as possible antibacterial agents against biofilm-producing resistant strains.

Chemical durability and shielding study of borosilicate glass systems from solid municipal waste ash for radiation shielding applications

Based on municipal solid waste (MSW) ash as a main raw material, three novel borosilicate glasses with the composition of 70 waste + 20 borax + 10 Na2O + x ZrO2, where x = 0, 0.1 or 0.3 (wt. %),were prepared by the traditional melting-annealing technique. The prepared glasses were analyzed by EDX analysis, revealing the rich compositions of the prepared glasses correlated to the MSW ash used by 70 wt.% in preparing glasses. Some optical, chemical and radiation shielding properties of the prepared glasses were investigated. Either Zr addition or 80 kGy of gamma radiation revealed improvement of the glasses optical transmittance and chemical durability in neutral dis H2O, alkaline 0.1 N NaOH and acidic 0.1 N HCl leaching media for 70 days. Electron spin resonance (ESR) revealed the same spectra before and after irradiation, referring to the prevention of free radical formation by irradiation.The shielding parameters were measured by the experimental gamma spectroscopy (NaI detector) and the theoretical Phy-X/PSD software e.g., linear attenuation coefficients (LAC) and the findings revealed high unanimity among them at photon energies 0.662, 1.173 and 1.333 MeV. Another shielding parameters were also studied e.g., mass attenuation coefficients (MAC), effective atomic number (Zeff), effective electron density (Neff) and effective conductivity (Ceff). Presence of various metal oxides and the host trigonal BO3 and tetrahedral BO4 and SiO4 units, and ZrO2 provide the glasses compactness and effectual stability against ionizing irradiation. The prepared borosilicate glasses have highly strong and compacted structures that can inhibit the passage of radiation photons, because of the variety of many glass network formers, intermediates and modifiers present in the used waste ash. The results indicate the highly economic benefit of the prepared glasses, where the useless MSW ash are used mainly by 70 wt.% to produce effective borosilicate glass systems for promising radiation shielding purposes, especially 0.3 Zr borosilicate glass that has the best radiation shielding properties.

Chemical and radiation shielding effectiveness of some heavy metal oxide glasses for immobilizing radioactive wastes

Ce/Sb/Mn different borate glass systems based PbO in concentrations of 50, 35, and 15 mol%, respectively, were prepared by the melting–annealing method. Wide chemical, structural, and radiation shielding characterizations were studied before and after 120 kGy of gamma radiation to test the possible use of glasses for immobilizing radioactive wastes. The results showed suitable density values ranging from 3.34 to 5.30 g/cm3 increased by irradiation. FTIR spectra revealed high structural stability against irradiation correlated to the trigonal BO3, tetrahedral BO4 groups, high polarizable Pb2+ ions, and the doped metal ions. Unexpectedly, the chemical durability after in situ leaching process in H2O, 0.1 N HCl, and 0.1 N NaOH for ~ 3 months revealed clear improving after irradiation e.g., enhanced by ~ 25% for Ce-lead borate glass. Scanning electron microscope (SEM) images of the glass surfaces revealed more smooth and homogenous surfaces after irradiation. Shielding parameters by Monte Carlo code (MCNP5) and Phy-X/PSD software were studied, e.g., mass and linear attenuation coefficients (MAC and LAC), effective atomic number (Zeff), radiation protection efficiency (RPE%), half and tenth value layers (HVL and TVL), and heaviness%. Comparing the shielding behavior of the three glasses revealed that Ce-lead borate glass has the highest values of LAC, MAC, Zeff, heaviness%, and RPE% and the lowest values of HVL, TVL, and MFP, referring to the best shielding efficiency. The whole study indicates the desired properties of glasses as immobilizers or containers for radioactive wastes, e.g., nuclear medicine units in hospitals, especially lead borate glass doped Ce ions.Graphical

Structural and luminescence properties of transparent borate glass co-doped with Gd3+/Pr3+ for photonics application

A new glass system of lithium borate doped with Gd2O3 and Pr2O3 has been fabricated using a conventional melt quenching technique. The physical parameters, such as density, molar volume, and refractive index, were measured and found to increase as the concentrations of lanthanide oxide (Gd2O3 and Pr2O3) in the glass increased, revealing the underlying structural changes. According to the results of XRD and FTIR, the synthesized glasses exhibited an amorphous structure, and borate complexes served as the triangular BO3, tetrahedral BO4, and OH group amounts in oxide glass. The photoluminescence (PL) spectra show characteristic emission bands resulting from f-f transitions of Pr3+ ions. The strongest emission occurred at 603 nm, corresponding to the transition from the 1D2 state to the 3H4 state. The optimal concentration of Gd2O3 for maximizing emission intensity was found to be 5.0 mol%, and this concentration will be used in the next experiment with varying Pr2O3 concentrations. In the subsequent experiment, emission spectra were recorded by exciting the glass with light at wavelengths of 445 nm, 469 nm, and 483 nm. The resulting emission spectra displayed the characteristic pattern associated with the emission of Pr3+. This emission peak at 603 nm represented the strongest intensity in the spectra, which is a common characteristic of Pr3+ emission. The emission intensity of the glasses initially increases with increasing concentrations of Pr2O3 up to 0.3 mol%, but beyond this concentration, the emission intensity starts to decrease. This behavior indicates the occurrence of a quenching effect at the 0.3 mol% concentration of Pr2O3. X-ray absorption near-edge structure (XANES) analysis confirmed that praseodymium ions were predominantly in the 3 + oxidation state. The chemical composition of the created glass was confirmed to be suitable for photonics applications.

Fabrication of zirconium borosilicate glasses using municipal waste ash for radiation shielding applications; optical and structural investigations

In this study, three borosilicate glass systems were successfully prepared by using the melting–annealing technique from municipal waste ash and doped with ZrO2 at 0, 0.1, and 0.3 wt.%. The glasses were analyzed by electron dispersive X-ray spectroscopy (EDX), which indicated their rich compositions with various metal ions, and X-ray diffraction analysis (XRD) confirmed their amorphous glassy nature. The effects of gamma radiation at 80 kGy on the optical, physical, structural, and chemical properties of the glasses were evaluated. The optical spectra contained ultraviolet peaks at 260–340 nm and visible peaks at 440–470 nm due to the different valence states of transition metal ions, e.g., Ti4+/Ti3+, Cu2+/Cu+, Zn2+, Fe3+/Fe2+, and/or Zr4+. The optical band gap energy (Egap) decreased from 2.0 to 1.0 eV and from 2.8 to 1.90 eV for indirect and direct transitions after irradiation, respectively, whereas the linear refractive index (n) increased. Fourier transform-infrared spectroscopy (FTIR) indicated high structural stability against irradiation due to the connected borosilicate network comprising trigonal BO3 and tetrahedral BO4 and SiO4 units. The band at 960 cm−1 in the undoped and 0.1% Zr4+ glasses shifted to 980 cm−1 in 0.3% Zr4+ glass because of the different compositions and silica contents of the glasses. Analysis of the chemical durability of the glasses in H2O at 100 °C indicated their high chemical stability before and after irradiation with a weight loss not exceeding 0.05%. BO3, BO4, SiO4, transition metal ions, and ZrO2 all contributed to the compact structure of the glasses, and their high stability against irradiation indicates the potential applications of the glasses in radiation shielding.

The effect of cobalt/copper ions on the structural, thermal, optical, and emission properties of erbium zinc lead borate glasses

A host glass network of 70B2O3–10Pb3O4–18ZnO–2Er2O3 (ErCoCu1) was proposed and the impact of 1 mol% of Co or/and Cu ions on its structural, thermal, optical, and green emission properties was studied extensively. The X-ray diffraction spectra confirmed the amorphous structure of the produced glasses. Density and density-based parameters behavior showed that the Co or/and Cu ions fill the interstitial positions of the proposed ErCoCu1 network, causing its compactness. Both ATR-FTIR and Raman Spectra affirmed the formation of the fundamental structural units of the borate network, B–O–B linkage, BO3, and BO4. Additionally, the penetration of Co or/and Cu ions inside the ErCoCu1 converts the tetrahedral BO4 units to triangle BO3 causing its richness by non-bridging oxygens. The addition of Co or/and Cu reduces the glass transition temperature as a result of the conversion of the BO4 to BO3 units. Optical absorption spectra for the host glass ErCoCu1 showed many of the distinguished absorption bands of the Er3+ ion. Penetration of Co ion generates two broadbands referring to the presence of Co2+ ions in both tetrahedral and octahedral coordination and Co3+ ions in the tetrahedral coordination. In the Cu-doped glasses, the characteristic absorption bands of Cu2+ and Cu+ were observed. A green emission was generated from the ErCoCu1 glass under 380 nm excitation wavelength. Moreover, no significant effect of Co or/and Cu on the emission spectra was recorded. The considered glasses had appropriate properties qualifying them for optoelectronics and nonlinear optics applications.

Boron-Doping Induced Electron Delocalization in Fluorophosphate Cathode: Enhanced Na-Ion Diffusivity and Sodium-Ion Full Cell Performance.

Na3 V2 (PO4 )2 O2 F (NVPOF) is widely accepted as advanced cathode material for sodium-ion batteries with high application prospects ascribing to its considerable specific capacity and high working voltage. However, challenges in the full realization of its theoretical potential lie in the novel structural design to accelerate its Na+ diffusivity. Herein, considering the important role of polyanion groups in constituting Na+ diffusion tunnels, boron (B) is doped at the P-site to obtain Na3 V2 (P2- x Bx O8 )O2 F (NVP2- x Bx OF). As evidenced by density functional theory modeling, B-doping induces a dramatic decrease in the bandgap. Delocalization of electrons on the O anions in BO4 tetrahedra is observed in NVP2- x Bx OF, which dramatically lowers the electrostatic resistance experienced by Na+ . As a result, the Na+ diffusivity in the NVP2- x Bx OF cathode has accelerated up to 11 times higher, which secures a high rate property (67.2mAhg-1 at 60 C) and long cycle stability (95.9% capacity retention at 108.6mAhg-1 at 10C after 1000 cycles). The assembled NVP1.90 B0.10 OF//Se-C full cell demonstrates exceptional power/energy density (213.3Wkg-1 @ 426.4Whkg-1 and 17970W kg-1 @ 119.8Whkg-1 ) and outstanding capability to withstand long cycles (90.1% capacity retention after 1000 cycles at 105.3mAhg-1 at 10 C).

Mixed Rare-Earth Chalcogenide Borate Eu9–xRExMgS2B20O41 (RE = Sm, Gd) Featuring a 3D {[B20O41]22–}∞ Framework Connected by [B6O9(O0.5)6]6– and [B7O13(O0.5)3]8– Clusters

Rare-earth (RE) chalcogenide borates are very rarely discovered in view of the difficulties in synthesis though they have demonstrated attractive physical performances. Here, the first mixed RE chalcogenide borates Eu5.4Sm3.6MgS2B20O41 (1) and Eu3Gd6MgS2B20O41 (2) are synthesized by combining RE, sulfur, and borate ions into one structure. They crystallize in the centrosymmetric hexagonal space group P63/m, and their 3D honeycomb-like {[B20O41]22-}∞ open frameworks are built by [B6O9(O0.5)6]6- and [B7O13(O0.5)3]8- polyanionic clusters and consolidated by Mg2+ ions; both of which are formed by BO4 tetrahedra and BO3 planar triangles. The coordination modes of RE ions are rare REO6S2 bicapped trigonal prisms and REO8S irregular polyhedra, and their band gaps are determined to be 2.25 and 2.22 eV, respectively. They exhibit antiferromagnetic interactions and distinct photocurrent responses. The corresponding theoretical calculations are also performed. The study of 1 and 2 perhaps stimulates interest in exploring new functional RE chalcogenide borates.

Synthesis, optical, chemical and electrical characterizations of γ-irradiated transition metal ions reinforced borate glasses

Co2+/ Ni2+/ Fe3+ borate glasses were prepared by melting-annealing procedure and extensively characterized towards gamma irradiation (up to 8 kGy). UV–visible spectra revealed Co2+ (3d7) in octahedral and tetrahedral coordinations, while Ni2+ (3d8) and Fe2+ (3d6) favored the octahedral coordination. Optical energy gap (Eopt) appeared dependent on glass density in a direct relation. ESR spectra revealed values of g// ∼ 2.01 and g┴ ∼ 2.025 correlated to the transition metal (TM) ion valence state. Chemical durability in H2O, HCl, and NaOH revealed good behavior from 15 to 35 days. Trigonal BO3 units appeared more extensive than tetrahedral BO4 on FTIR spectra after irradiation. AC conductivity, dielectric constants and dielectric loss revealed rising with incorporating TM ions and irradiation. TM ions provide the glasses stable behavior to irradiation because of their flexible configuration to heal radiation defects affording the possible use of glasses as radiation shielding materials (up to 5 kGy).

Structural, optical and radiation shielding parameters of sodium aluminium borate glasses modified with chromium oxide

Samples of nominal composition xCr2O3. (60-x)B2O3.5Al2O3.35Na2O: x = 0 (Cr0), 0.1 (Cr0.1), 0.2 (Cr0.2), 0.4 (Cr0.4), 0.6 (Cr0.6), 0.8 (Cr0.8), and 1 (Cr1) mol% were prepared via the traditional melt quenching route. Structural FTIR absorption spectra of the prepared glasses reveal distinct absorption bands which are characteristic of both triangular BO3 and tetrahedral BO4 groups within their varying wavenumber vibrational sites. The dopant chromium ions are observed to have no distinct variations on the FTIR spectra because of low dopant percent. Optical absorption characterization indicates that the undoped glass shows only UV absorption which is related to originating from unavoidable trace ferric ions present as impurities in the used chemicals. The Cr2O3-doped glasses reveal additional UV absorption at about 370-385 nm correlated with the hexavalent state of chromium, producing this distinct charge transfer band. Additionally, two visible bands are identified at about 420-400 nm and 580-640 nm originating from trivalent chromium ions with distorted octahedral coordination. Optical parameters including band gap, refractive index, molar refraction, and reflection losses were calculated together with optical dielectric properties, electronic and molar polarizability. In terms of radiation shielding capacity, increasing Cr2O3 mol% of the sample encoded Cr1 that possessed the highest mass (μm) and linear (μ) attenuation coefficients, but the lowest half value layer (HVL) at low and high incident photon energy, results showed that Cr1 can be used in optical and radiation shielding safety.

Use of Eggshell Waste as a source of CaO in Sm3+-Doped Na2O-B2O3-CaO-SiO2 Glass Preparation

In this research, calcium carbonate from eggshell waste was used to prepare the soda-lime borosilicate glass samples (Na2O-B2O3-CaO-SiO2) doped with samarium ions (Sm3+) at different Sm2O3 concentrations (0, 0.1, 0.2, 0.3, 0.4 and 0.5 mol%). A conventional melt-quenching method at 1,100°C for 3 h was applied in this work to produce the glass samples. The samples were then characterized by XRD, DTA, FT-IR, UV-Vis spectrophotometer and PL techniques. The results showed that the obtained glasses had amorphous structure, and the glass density tended to increase with the addition of Sm2O3. The FTIR spectra of the main glass structure revealed that it was composed of trigonal BO3 and tetrahedral BO4 borate groups mixing with SiO4 tetrahedra and non-bridging oxygen. The addition of samarium ions to the glass resulted in a strong orange emission at 562 nm (4G5/2→6H5/2), 600 nm (4G5/2→6H7/2), 646 nm (4G5/2→6H9/2) and 708 nm (4G5/2→6H11/2) under excitation at 403 nm. The results confirmed that 0.3 mol% Sm2O3-doped glass exhibited the highest emission intensity, which suggested that eggshells have a high potential to be used as an alternative CaCO3-raw material in the production of an efficient luminescent and environmentally-friendly optical electronics material

Nanofibrous hybrid scaffolds based on PCL-borosilicate system by a green sol-gel process

Tissue regeneration is yet a critical issue, and to mimic the natural extracellular matrix (ECM) innovative scaffolds need to be developed to ensure the functional and safe repair of the damaged organs or tissues. Hybrid biomaterials based on the combination of a biodegradable polymer and bioactive glasses (BGs) are potential candidates for tissue engineering (TE), since they exhibit tailored physical, biological, and mechanical properties, as well as controlled degradation behavior. Thus, the main purpose of this research was to develop by electrospinning (ES) a hybrid nanofibrous membrane composed of a synthetic polymeric matrix (PCL) and a boron and calcium silicate glass, formed via in situ sol-gel, and based on a non-aqueous and green fabrication route. Formic acid (FA) and glacial acetic acid (AA) were used as green solvents to dissolve the PCL. Different compositions were prepared: neat PCL and PCL/SiO2–B2O3–CaO with different sol-gel aging times and green solvent systems. All prepared hybrid solutions, except the composition with only AA, were spinnable. Structural features of the hybrids were assessed by ATR-FTIR spectroscopy, which confirmed the presence of siloxane (Si–O–Si) bonds of silica and carbonyl (CO) bonds characteristic of PCL polymer as well as intermolecular hydrogen-bonding interactions between the carbonyls of PCL and the silanol hydroxyls (Si–OH) of silica networks. Boron (B–O–B) and borosiloxane (B–O–Si) bonds were not visible due to the overlapping of PCL bands in the spectra. Only the solid state 11B NMR technique allowed to find peaks assigned to trigonal BO3 and tetrahedral BO4 groups, which evidence the boron linkages to silica. Thermal analysis showed a change in the crystallinity of PCL with the incorporation of inorganic domains, confirming the formation of chemical interactions between the polymer and the inorganic part. Microstructure and chemical analysis, by SEM/EDS, showed a homogenous distribution of Ca and Si elements into the fibers, as well as an increase of the fiber diameter with the incorporation of boron and calcium silicate glass in the PCL. The developed compositions of PCL/boron and calcium-containing silicate were feasible to electrospin into fibrous meshes, proving its potential for further design of multicomponent nanofibrous microstructures closer to extra cellular matrix architectures.

Tetrahedrally coordinated rigid crystal structure enables partial self-reduction of mixed-valence europium for optical thermometric application.

Mixed-valence europium-activated phosphors are receiving attention in many fields, such as lighting, anti-counterfeiting, optical recording, encryption, and temperature sensing. However, it remains difficult to construct mixed-valence europium-activated compounds due to the reductive and oxidative synthesis conditions required to obtain Eu2+ and Eu3+ ions, respectively. Herein, mixed-valence Eu2+/Eu3+ was realized in the CaBPO5 built by rigidly connected BO4 and PO4 tetrahedrons by partial Eu3+ → Eu2+ self-reduction in the air atmosphere. Commendably, the CaBPO5:Eu2+/Eu3+ phosphor exhibits excellent ratiometric temperature sensing performance with the maximum absolute and relative sensitivity being as high as 0.184 K-1 and 3.444% K-1 with good signal discriminability, due to the high and low, respectively, temperature-dependence of Eu2+ and Eu3+ emissions. The rapid dropping intensity of Eu2+ in CaBPO5 with increasing temperature was due to the small energy gap (∼0.48 eV) between the Eu2+-5d state and the conduction band. Our work not only provides a novel thermometer candidate but also enlightens researchers to a method of effectively designing new mixed-valence metal-ion activated luminescent thermometers via selective tetrahedrally coordinated rigid crystal structure.

The crystal chemistry of plutonium(IV) borophosphate.

In this work, we report the synthesis and characterization of a plutonium(IV) borophosphate, Pu(H2O)3[B2(OH)(H2O)(PO4)3] (1). The basic building unit of 1 has a B : P ratio of 2 : 3 with an equal number of BO4 and PO4 groups that assemble into 12-membered rings and take on a sheet topology due to presence of hydroxyl groups or a water molecule on one vertex of each BO4 tetrahedron. This unique borophosphate anion topology is not observed in other members of the borophosphate family; it is the plutonium(IV) metal centers, rather than borate or phosphate groups, that link the sheets to form an extended framework. The presence of boron in 1 was confirmed using single crystal X-ray diffraction, electron microprobe analysis, and infrared spectroscopy. Peaks corresponding to the tetrahedral BO45- and tetrahedral PO43- anions were all identified in the fingerprint region (500-1500 cm-1) of the infrared spectrum. Additionally, peaks in the higher wavenumber region corresponded to crystalline water and B-OH vibrations, providing further evidence for the water molecules surrounding plutonium in the structure and the protonation of the BO4 tetrahedron, respectively. This compound represents the first Pu(IV) borophosphate structure and a novel borophosphate anion topology. Furthermore, the long time-frame required for crystallization of 1 and the suspected leaching of boron from the borosilicate vial used during synthesis indicate that 1 could serve as a model for the crystalline materials that are expected to form during the corrosion of vitrified nuclear waste.