Raman and FTIR spectra of iron phosphate glasses containing cerium

Potential Use of Nucleic Acids as a Preceramic Polymer to Synthesize Nanodiamond-Embedded Phosphate Glass for Hard Tissue Engineering

In recent years, nucleic acid has emerged as a versatile molecule that has been strategically used in material synthesis and biomedical applications. Keeping in mind the presence of the phosphate group, a glass former in the nucleic acids, we synthesized a transparent glass-like material by the thermal treatment of nucleic acids (DNA and RNA) at 900 °C at atmospheric pressure. Characterization of this material by transmission electron microscopy, X-ray photoelectron spectroscopy, and confocal fluorescence microscopy suggested the presence of in situ-formed nanodiamonds within the phosphate glass matrix. The molecular structure of glass investigated by X-ray photoelectron and infrared spectroscopy indicated a nearly equal proportion of metaphosphates and smaller phosphate units (pyro- and ortho-phosphate) that form the phosphate glass matrix. Thereafter, in vitro biological experiments showed that the nucleic acid-derived glass was non-toxic and cytocompatible, enhanced extracellular matrix secretion, and increased intracellular alkaline phosphatase activity, with potential application in hard tissue engineering. Our work offers insights into nanodiamond synthesis at atmospheric pressure and proves that nucleic acids could be used as a precursor to making an innovative glass-ceramic biomaterial.

Raman and Infrared Spectroscopy of Barium-Gallo Germanate Glasses Containing B2O3/TiO2

Modified barium gallo-germanate glass hosts are still worthy of attention in studying structure-property relationships. In this work, two different series of glass systems based on (60-x)GeO₂-xTiO₂-30BaO-10Ga₂O₃ and (60-x)GeO₂-xB₂O₃-30BaO-10Ga₂O₃ (x = 10, 30, 50 mol%) were synthesized, and their properties were studied using spectroscopic techniques. X-ray diffraction (XRD) patterns revealed that all fabricated glasses were fully amorphous material. The absorption edge shifted toward the longer wavelengths with a gradual substitution of GeO₂. The spectroscopic assignments of titanium ions were performed with excitation and emission spectra compared to the additional sample containing an extremely low content of TiO₂ (0.005 mol%). On the basis of Raman and FT-IR investigations, it was found that increasing the TiO₂ content caused a destructive effect on the GeO₄ and GeO₆ structural units. The Raman spectra of a sample containing a predominantly TiO₂ (50 mol%) proved that the band was located near 650 cm^-1, which corresponded to the stretching vibration of Ti-O in TiO₆ unit. The deconvoluted IR results showed that the germanate glass network consisted of the coexistence of two BO₃ and BO₄ structural groups. Based on the experimental investigations, we concluded that the developed materials are a promising candidate for use as novel glass host matrices for doping rare-earth and/or transition metal ions.

Thermally stable red luminescence from Eu3+ -activated telluro zinc phosphate glass under near-ultraviolet light excitation for photonic applications

Telluro zinc phosphate (TZP) glasses doped with different concentrations of Eu³⁺ ions were prepared and their physical, structural, and luminescence properties were studied in detail to reveal the utility of the as-prepared glass for white light-emitting diode (w-LED) applications. The broad hump in the diffraction pattern specified the amorphous behaviour of the TZP glass. The various vibrational shoulder linkages were characterized using the Fourier transform infrared (FT-IR) spectroscopy. The optical absorption spectrum was measured in the ultraviolet (UV)-visible (Vis) light region for the Eu³⁺ -doped TZP (TZPE) glass and the optical band gap was found to be 3.12 eV. Eu³⁺ -doped TZP glasses showed several emission peaks in the visible region including an intense red emission peak due to the ⁵ D₀ →⁷ F₂ transition under an excitation wavelength of λ_ex  = 393 nm, which was matched with the emitting wavelength of the near-UV LED chip. Commission Internationale de I'Eclairage (CIE) chromaticity coordinates were situated in the red region and nearly matched with the coordinates of the commercial red phosphor (Y₂ O₃ S:Eu³⁺ ). The decay profile of the TZPE50 glass exhibited a single exponential fit with a decay time ( τ ) of 1.76 ms. Temperature-dependent photoluminescence (TDPL) studies demonstrate that the as-prepared glass consist of excellent thermal stability. The detailed analysis and results confirmed that the red-emitting TZPE glasses were potential candidates for white-LED and other photonic applications.

Nanocrystalline Iron Pyrophosphate-Regulated Amorphous Phosphate Overlayer for Enhancing Solar Water Oxidation

A rational regulation of the solar water splitting reaction pathway by adjusting the surface composition and phase structure of catalysts is a substantial approach to ameliorate the sluggish reaction kinetics and improve the energy conversion efficiency. In this study, we demonstrate a nanocrystalline iron pyrophosphate (Fe₄(P₂O₇)₃, FePy)-regulated hybrid overlayer with amorphous iron phosphate (FePO₄, FePi) on the surface of metal oxide nanostructure with boosted photoelectrochemical (PEC) water oxidation. By manipulating the facile electrochemical surface treatment followed by the phosphating process, nanocrystalline FePy is localized in the FePi amorphous overlayer to form a heterogeneous hybrid structure. The FePy-regulated hybrid overlayer (FePy@FePi) results in significantly enhanced PEC performance with long-term durability. Compared with the homogeneous FePi amorphous overlayer, FePy@FePi can improve the charge transfer efficiency more significantly, from 60% of FePi to 79% of FePy@FePi. Our density-functional theory calculations reveal that the coexistence of FePi and FePy phases on the surface of metal oxide results in much better oxygen evolution reaction kinetics, where the FePi was found to have a typical down-hill reaction for the conversion from OH* to O₂, while FePy has a low free energy for the formation of OH*.

Influence of multi valent states of vanadium ions in ZnO doped novel calcium fluoro phosphate bio glasses

ZnO-CaF₂-P₂O₅ glasses doped with different concentrations of V₂O₅ (ranging from 0 to 1.0 mol %) were prepared. The prepared bio glasses are soaked in SBF for duration of 2, 3, 7 and 10 days in separate plastic containers and then kept in incubator maintained at body temperature 36.5 °C. The influence of valence states of vanadium ions (V⁴⁺/V⁵⁺) with respect to the structural aspects by means of FTIR and Raman Spectra, elastic properties by means of relevant parameters, the thermal stability by means of DTA studies and other spectroscopic properties by using OA and ESR studies are studied. The raise in wavenumber and comparative areas of the two absorption bands corresponding to electronic transitions 2B_2g → E_2g, 2B_2g → 2B_1g respectively in optical absorption spectra of these CZPV glasses clearly indicate that vanadium ions have octahedral co-ordination with tetragonal compression due to modifier action of V₂O₅in the glass network. The optical absorption and ESR studies have revealed that vanadium ions exist in V⁴⁺ states. The characteristic temperatures of these prepared glasses obtained from DTA curves explain modifications taking place in the structure of glass network. The structural changes are explained with the aid of FTIR and Raman studies. The bio active nature of the titled glasses is evident from dissociation and pH studies by SEM &EDS of these glasses before and after immersion into SBF.

Degradable Tumor-Responsive Iron-Doped Phosphate-Based Glass Nanozyme for H2O2 Self-Supplying Cancer Therapy

Tumor microenvironment (TME)-responsive chemodynamic therapy (CDT) mediated by nanozymes has been extensively studied both experimentally and theoretically, but the low catalytic efficiency due to insufficient H₂O₂ in the TME and the poor biodegradability of the nanozymes are still main challenges for clinical translation of nanozymes. Herein, we designed a H₂O₂ self-supplying nanozyme bearing glucose oxidase (GOX) and polyethyleneimine based on a degradable iron-doped phosphate-based glass (FePBG) nanomimic (FePBG@GOX), which can convert endogenous glucose into toxic hydroxyl radicals. The GOX loaded on the nanozyme can effectively consume glucose in tumor cells to produce a large amount of H₂O₂ to make up for the lack of H₂O₂ in the TME. Thereafter, enormous hydroxyl radicals, based on a Fenton reaction of FePBG without any exogenous H₂O₂, are generated to induce severe apoptosis of tumor cells. The nanozyme exhibits enhanced in vitro cytotoxicity in a high-glucose medium than in a low-glucose medium, illustrating sufficient generation of H₂O₂ by GOX. The excellent in vivo antitumor efficacy is manifested by a high tumor growth inhibition ratio of 94.65% in model mice. Excellent intrinsic biodegradability owing to its phosphate-based glass nature is a remarkable advantage of the prepared FePBG nanozyme over most other reported nanozymes. Big concerns about side effects caused by long-time residence in living organisms are eliminated since it degrades not only in an acid medium but also in a neutral physiological environment. Therefore, this novel strategy of the TME-responsive H₂O₂ self-supplying nanozyme based on an endogenous cascade catalytic reaction opens up an avenue for designing degradable nanozymes in CDT.

A Comparative Study on the Anti-Corrosive Performance of Zinc Phosphate in Powder Coatings

Powder coatings are gaining popularity for their economic and environmental benefits. Additives (pigments) such as zinc phosphate enhance the anti-corrosive properties of coatings, but their behavior in powder coatings has not been extensively studied. In this study, zinc phosphate was incorporated into three powder coating systems: polyester clearcoat, polyester and epoxy coatings with filler BaSO4. Neutral salt spray and electrochemical tests (OCP, LPR, and EIS) confirmed that the anti-corrosive performance improved with the addition of zinc phosphate. The optimal additive dosage was determined to be 2% for all of the coating systems studied here, based on salt spray tests. Here, the time until failure increased by 1.5 to 2 times. Using electrochemical tests, an optimal additive dosage of 8% was found for the polyester clearcoat, while the other coating systems maintained an optimal additive dosage of 2%. Performance increased by as much as one order of magnitude based on resistance/impedance measurements. This suggested a synergistic effect between the additive and the filler. The passivation layer was confirmed by both X-ray diffraction and Raman spectroscopy. Based on the results and discussion presented in this article, the discrepancy was caused by different features of the two tests, such that the electrochemical tests probe the function of intact coatings, whereas salt spray measures only the corrosion spreading from the scribe. It is proposed that the two test methods characterize different aspects of the coatings, corresponding to their service conditions. This has theoretical and practical significance in the evaluation of anti-corrosive coatings. Other properties of the coatings, including adhesion, gloss, distinctness-of-image, and pencil hardness, were measured as per applicable standards and the conformance was verified.

Structural and optical absorption studies on Cr2O3 doped SrO-P2O5 glasses

Cr₂O₃ doped glasses in the system xCr₂O₃-(60-x) P₂O₅-40SrO, where x = 0.0, 0.025, 0.05, 0.1, 0.2, 0.4 & 0.6 mol% were prepared and investigated by X-ray, UV-Vis, and FT infrared spectroscopy. According to the X-ray data, no sharp peaks can be observed, but only abroad halo which points the amorphous nature of the glass samples. Optical absorptions have shown that Cr ions are present in two possible oxidation states (trivalent & hexavalent). Increasing Cr₂O₃ concentrations in the glass network cause a reduction in the indirect and direct optical energy gap of prepared samples from 3.94-3.5 eV and 4.92-4.4 eV, respectively. This behavior is related to the network forming ability of Cr₂O₃. FTIR spectra of Cr₂O₃ containing glass showed some differences compared to base glass samples. In addition, calculated physical and optical parameters reveals a close similarity to base glass that can be correlated to the minor addition of Cr₂O₃.

Ga and Ce ion-doped phosphate glass fibres with antibacterial properties and their composite for wound healing applications

Novel gallium/cerium-doped phosphate glass fibres (PGF) were successfully manufactured by the melt-quenching and melt-spinning process. The amorphous character of the materials produced was confirmed using X-ray powder diffraction (XRD), and the elemental composition was investigated with X-ray fluorescence confirming the presence of 2 mol% of Ga₂O₃ or CeO₂. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the presence of Q¹ and Q² structural phosphate species. Mechanical properties of the PGFs revealed tensile strength values of 428 ± 94 MPa and 379 ± 80 MPa, with elastic modulus values of 45 ± 4 GPa and 54 ± 9 GPa for Ce-PGF (diameter 25 μm) and Ga-PGF (diameter 18 μm), respectively. The influence of both dopants on the glass degradation properties was evaluated by tests in deionised water, which revealed a decreased dissolution rate for gallium-doped PGF in comparison to cerium-doped PGF. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) measurements were used to explore ion release in cell culture medium, while ICP-mass spectrometry (ICP-MS) was used to measure ion release in deionised water. These techniques showed controlled release of therapeutic and antibacterial ions from the PGF. Antibacterial properties of Ce-PGF and Ga-PGF, based on turbidity measurements, were confirmed against Gram-positive bacteria. Moreover, Ce-doped phosphate glass fibres did not disturb the proliferation of human epidermal keratinocyte (HaCaT) cells or the mobility of mice embryonic fibroblasts (MEF). Applying an in vitro scratch assay showed full wound closure after 24 h of indirect incubation with Ga-PGF. Due to their superior processability as compared with Ga-PGFs, a fully degradable mesh based on Ce-PGF was designed and found to achieve high water uptake (up to 800%), suggesting its suitability for wound healing applications.

Oxygen-Vacancy-Dominated Cocatalyst/Hematite Interface for Boosting Solar Water Splitting

Surface suppression is one of critical issues for semiconductors in photoelectrochemical (PEC) water splitting. Deposition of oxygen evolution cocatalysts on photoanodes can improve the oxygen evolution rate, but still it has some limits in some cases. In this work, we propose a new and simple precipitation approach to transform the surface of hematite into iron phosphate (Fe-Pi). Further, Ar-plasma treatment on Fe-Pi/Fe₂O₃ introduces oxygen vacancies on the phosphorous and photoanode. A surface phosphate treatment accelerates the transfer of holes from the bulk to the surface. Besides, creating oxygen vacancy defects on Fe-Pi/Fe₂O₃ can significantly increase the reactivity of active sites, leading to the remarkable enhancement in oxygen evolution reaction activity and PEC performance. The resulting photoanode has a current density of 2.71 mA cm^-2 at 1.23 V_RHE and 3.5 mA cm^-2 at 1.50 V_RHE under simulated solar light condition. The reduced surface recombination by Fe-Pi layer and Ar-plasma treatment is confirmed by electrochemical analysis. These findings give a great potential of the use of a combination strategy for cocatalyst deposition and optimizing the performance of hematite.

Chitosan as a Coupling Agent for Phosphate Glass Fibre/Polycaprolactone Composites

This study shows that chitosan (CS) could be highly useful as a coupling agent in phosphate glass fibre/polycaprolactone (PGF/PCL) composites, as it improved the interfacial shear strength by up to 78%. PGFs of the composition 45P2O5–5B2O3–5Na2O–24CaO–10MgO–11Fe2O3 were dip-coated with CS (with a degree of deacetylation >80%) dissolved in acetic acid solution (2% v/v). Different CS concentrations (3–9 g L−1) and coating processes were investigated. Tensile and fragmentation tests were conducted to obtain the mechanical properties of the single fibres and interfacial properties of the PGF/PCL composites, respectively. It was observed that post-cleaning, the treated fibres had their tensile strength reduced by around 20%; however, the CS-coated fibres experienced strength increases of up to 1.1–11.5%. TGA and SEM analyses were used to confirm the presence of CS on the fibre surface. FTIR, Raman, and X-ray photoelectron spectroscopy (XPS) analyses further confirmed the presence of CS and indicated the protonation of CS amine groups. Moreover, the nitrogen spectrum of XPS demonstrated a minimum threshold of CS coating required to provide an improved interface.

Ce@STANPs/ZrO2 as Nanocatalyst for Multicomponent Synthesis of Isatin-Derived Imidazoles under Green Reaction Conditions

A highly efficient and recyclable catalyst, cerium-immobilized silicotungstic acid nanoparticle-impregnated zirconia (Ce@STANPs/ZrO₂), has been synthesized. The catalytic activity of Ce@STANPs/ZrO₂ was investigated for the first time in multicomponent synthesis of isatin-based imidazoles under microwave irradiation in water. Ce@STANPs/ZrO₂ was used for C=O bond activation in overall reaction to synthesize isatin-based imidazoles. The structure of catalyst was confirmed by characterization techniques, such as Fourier transform infrared (FTIR), scanning electron microscopy (SEM)/energy dispersive X-ray, elemental mapping, transmission electron microscopy, ζ-potential and diffraction light scattering, X-ray diffraction (XRD), thermogravimetric analysis, temperature-programmed desorption-NH₃, electron paramagnetic resonance (EPR), and inductively coupled plasma atomic emission spectroscopy (ICP-AES) analyses. The recovered catalyst was found to be efficient up to seventh cycle and was confirmed by FTIR, SEM, XRD, EPR, and ICP-AES analyses. The advantages of the present protocol are recyclability of catalyst, green reaction conditions, excellent yield (94%) of the products, shorter reaction time period (5-7 min), and clean reaction profile.

Optical spectroscopy, 1.06μm emission properties of Nd3+-doped phosphate based glasses

Neodymium doped phosphate based glasses with composition of (P₂O₅+K₂O+Al₂O₃+CaF₂) were prepared. The samples were analysed through differential thermal analysis (DTA), Fourier transform infrared (FTIR), absorption, emission and decay measurements. Judd-Ofelt parameters (Ω_λ) have been determined from the spectral intensities of absorption bands in order to calculate the radiative parameters like radiative transition probabilities (A_R), radiative lifetime (τ_R) and branching ratios (β_R) for the ⁴F_3/2→⁴I_11/2 laser transition of Nd³⁺ ion. The effective emission bandwidths (Δλ_eff), experimental branching ratios (β_exp) and stimulated emission cross-sections (σ_e) have been determined from the emission spectrum. The decay curves of the ⁴F_3/2 level exhibited almost single exponential nature for all the Nd³⁺ ion concentrations.

Effect of boron oxide addition on the viscosity-temperature behaviour and structure of phosphate-based glasses

In this study, nine phosphate-based glass formulations from the system P₂ O₅ -CaO-Na₂ O-MgO-B₂ O₃ were prepared with P₂ O₅ content fixed as 40, 45 and 50 mol%, where Na₂ O was replaced by 5 and 10 mol% B₂ O₃ and MgO and CaO were fixed to 24 and 16 mol%, respectively. The effect of B₂ O₃ addition on the viscosity-temperature behaviour, fragility index and structure of the glasses was investigated. The composition of the glasses was confirmed by ICP-AES. The viscosity-temperature behaviour of the glasses were measured using beam-bending and parallel -plate viscometers. The viscosity of the glasses investigated was found to shift to higher temperature with increasing B₂ O₃ content. The kinetic fragility parameter, m and F_1/2 , estimated from the viscosity curve were found to decease with increasing B₂ O₃ content. The structural analysis was achieved by a combination of Fourier transform infrared spectroscopy and solid state nuclear magnetic resonance. ³¹ P solid-state magic-angle-spinning nuclear magnetic resonance (MAS-NMR) showed that the local structure of the glasses changes with increasing B₂ O₃ content. As B₂ O₃ was added to the glass systems, the phosphate connectivity increases as the as the Q¹ units transforms into Q² units. The ¹¹ B NMR results confirmed the presence of tetrahedral boron (BO₄ ) units for all the compositions investigated. Structural analysis indicates an increasing level of cross-linking with increasing B₂ O₃ content. Evidence of the presence of P-O-B bonds was also observed from the FTIR and ³¹ P NMR analysis. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 764-777, 2017.

Structural evolution of CeO2-doped alkali boroaluminosilicate glass and the correlation with physical properties based on a revised structural parameter analysis

CeO₂ ruptures Si(B)–O bonds in reedmergnerite- and danburite-like groups with cerium ion balance charged units enhancing network interconnectivity.

The crystallization and structure features of barium-iron phosphate glasses

The crystallization and structure features of xBaO·(90-x)(60P2O5-40Fe2O3)·10CaF2 glasses, where x=0, 5, 10, 15 and 20 mol%, are investigated in details by using X-ray diffraction analysis, Fourier transform infrared spectroscopy, Raman spectroscopy and differential thermal analysis. It is found that the major crystalline phase of barium iron phosphate glasses annealed between 650 °C and 850 °C is FePO4, and the crystallization is restrained by barium. The predominant infrared absorption band is attributed to the antisymmetric stretching vibrations of (PO3)(2-) in Q(1) units. Raman and Fourier transform infrared spectra reveal that the glasses' main structural networks are Q(1) and Q(0) tetrahedrons connected by P-O-P linkages. Moreover, the glass transition temperature increases with BaO content, which suggests that barium can strengthen the thermal stability of the iron phosphate glass.

Structural properties of iron-phosphate glasses: spectroscopic studies and ab initio simulations

Vitrification is the most effective method for the immobilization of hazardous waste by incorporating toxic elements into a glass structure. Iron phosphate glasses are presently being considered as matrices for the storage of radioactive waste, even of those which cannot be vitrified using conventional borosilicate waste glass. In this study, a structural model of 60P2O5-40Fe2O3 glass is proposed. The model is based on the crystal structure of FePO4 which is composed of [FeO4][PO4] tetrahedral rings. The rings are optimized using the DFT method and the obtained theoretical FTIR and Raman spectra are being compared with their experimental counterparts. Moreover, the proposed model is in very good agreement with X-ray absorption fine structure spectroscopy (XANES/EXAFS) and Mössbauer spectroscopy measurements. According to the calculations the Fe(3+) is in tetrahedral and five-fold coordination. The maximal predicted load of waste constituents into the glass without rebuilding of the structure is 30 mol%. Below this content, waste constituents balance the charge of [FeO4](-) tetrahedra which leads to their strong bonding to the glass resulting in an increase of the chemical durability, transformation and melting temperatures and density.

A review of the structures of oxide glasses by Raman spectroscopy

The family of oxide glasses is very wide and it is continuously developing.