Ion conducting and paramagnetic d-PCL(530)/siloxane-based biohybrids doped with Mn 2+ ions

Amorphous α,ω-hidroxylpoly(ε-caprolactone) (PCL(530))/siloxane ormolytes doped with manganese perchlorate (Mn(ClO4)2) (d-PCL(530)/siloxanenMn(ClO4)2) with n = 20, 50, and 100), thermally stable up to at least 200 ºC, were synthesized by the sol-gel method. Ionic conductivity values up to 4.8×10−8 and 2.0×10−6 S cm−1 at about 25 and 100 ºC, respectively, where obtained for n = 20. FT-IR data demonstrated that the hydrogen bonding interactions present in the non-doped d-PCL(530)/siloxane host hybrid matrix were significantly influenced by the inclusion of Mn(ClO4)2 which promoted the formation of more oxyethylene/urethane and urethane/urethane aggregates. In addition, the Mn2+ ions bonded to all the “free” C=O groups of the urethane cross-links and to some of the “free” ester groups of the amorphous PCL(530) chains. In the electrolytes, the ClO4 − ions were found “free” and bonded to the Mn2+ ions along a bidentate configuration. The magnitude of the electron paramagnetic resonance (EPR) hyperfine constant of the analyzed samples (A ≈ 90×10-4 cm−1 ) suggested that the bonding between Mn2+ ions and the surrounding ligands is moderately ionic. The synthetized d-PCL(530)/siloxanenMn(ClO4)2 biohybrids have potential application in paramagnetic, photoelectrochemical and electrochromic devices.This work was supported by Fundacao para a Ciencia e a Tecnologia (FCT) and Feder (contracts PTDC/CTM-BPC/112774/2009, PEst-OE/QUI/UI0616/2014 and PEst-C/QUI/UI0686/2013) and COST Action MP1202 "Rational design of hybrid organic-inorganic interfaces". R.F.P.P. acknowledges FCT for a grant (SFRH/BPD/87759/2012). M.M.S. acknowledges CNPq (PVE grant 406617/2013-9), for a mobility grant. The financial support of the Brazilian agencies Capes and CNPq are gratefully acknowledged. Research was partially financed by the CeRTEV, Center for Research, Technology and Education in Vitreous Materials, FAPESP 2013/07793-6.info:eu-repo/semantics/publishedVersio

Gallium incorporation into phosphate based glasses: bulk and thin film properties

The osteogenic ions Ca2+, P5+, Mg2+, and antimicrobial ion Ga3+ were homogenously dispersed into a 1.45 mum thick phosphate glass coating by plasma assisted sputtering onto CP grade titanium. The objective was to deliver therapeutic ions in orthopedic/dental implants such as hip prosthesis or dental screws. The hardness 4.7 GPa and elastic modulus 69.7 GPa, of the coating were comparable to plasma sprayed hydroxyapatite/dental enamel, whilst superseding femoral cortical bone. To investigate the manufacturing challenge of translation from a target to vapour condensed coating, structural/compositional properties of the target (P51MQ) were compared to the coating (P40PVD) and a melt-quenched equivalent (P40MQ). Following condensation from P51MQ to P40PVD, P2O5 content reduced from 48.9 to 40.5 mol%. This depolymerisation and reduction in the P-O-P bridging oxygen content as determined by 31P-NMR, FTIR and Raman spectroscopy techniques was attributed to a decrease in the P2O5 network former and increases in alkali/alkali-earth cations. P40PVD appeared denser (3.47 vs. 2.70 g cm-3) and more polymerised than it’s compositionally equivalent P40MQ, showing that structure/ mechanical properties were affected by manufacturing route

Effect of controlled crystallization on polaronic transport in phosphate‐based glass‐ceramics

The effect of induced crystallization on changes in electrical transport of two types of glass‐ceramics, pure polaron conductive 40Fe2O3‐60P2O5 (F40) (mol%) and predominantly polaronic 5Li2O‐5ZnO‐40P2O5‐50WO3 (Li‐50W) (mol%) was investigated. F40 glass‐ceramics produced at low heat‐treatment temperatures contain single‐phase Fe3(P2O7)2 whereas at higher temperatures two more phases Fe4(P2O7)3 and Fe(PO3)3 are formed. Structural modifications strongly depend on the crystallization temperature and time. The appearance of crystalline phases studied by Mössbauer spectroscopy exhibits changes in Fe2+/Fetot ratio in crystalline/glassy phases. The detailed analysis of different iron sites allows their correlation with changes in electrical conductivity as crystallization progresses. Depending on the course of crystallization, the contribution of each phase to the overall conductivity is determined by the frequency dependence of Zʺ(ω) and Mʺ(ω). DC conductivity shows a sharp decrease as Fe3(P2O7)2 phase appears and consequently glass matrix remains impoverished in Fe2+‐Fe3+ pairs. In the multiphase systems prepared at higher crystallization temperatures, the overall electrical conductivity increases although the continuous grain boundaries along different crystalline grains play a limiting factor. In contrast, the slight conductivity change in Li‐ 50W glass‐ceramics upon crystallization is a result of remaining W5+‐W6+ pairs in the residual glassy phase. Independence of electrical transport on Li+ ions confirms predominantly polaronic transport in Li‐50W glass‐ceramics

Electrical Properties of Sodium Phosphate Glasses Containing Al₂O₃ And/Or Fe₂O₃. Part II

The electrical properties for three series of glasses: xNa2O-(40−x)Al2O3-60P2O5, (20less-than-or-equals, slantxless-than-or-equals, slant35), (NAP); 20Na2O-xAl2O3-(20−x)Fe2O3-60P2O5, (5less-than-or-equals, slantxless-than-or-equals, slant15), (NAFP), and xNa2O-(40−x)Fe2O3-60P2O5, (20less-than-or-equals, slantxless-than-or-equals, slant35), (NFP) glasses were measured by impedance spectroscopy in the frequency range from 1 Hz to 1 MHz and over the temperature range from 303 to 473 K. It was shown (in Part I) that the addition of Fe2O3 has significant effects on the structure of these glasses and Fe ions play a different structural role in phosphate network than that of Al ions. Such effects reflect changes in the origin of electrical conduction. with increasing Fe2O3 content in NAFP and NFP glasses the dc conductivity depends upon distance between iron ions and the activation energy of 53.1 kJmol−1 indicates electronic conduction. On the other hand, the decrease in dc conductivity and activation energy for glasses in NAP series is attributed to the decrease in Na2O content from 35 to 20 mol%. The activation energy varies from 80.1 to 72.4 kJmol−1 for NAP glasses suggesting ionic conduction. The impedance analysis for these glasses shows that the changes in the electrical conduction mechanisms coincide with the changes in the structure

Study of Electrical Properties of MoO₃-Fe₂O₃-P₂O₅ and SrO-Fe₂O₃-P₂O₅ Glasses by Impedance Spectroscopy. II

The electrical and dielectric properties for three series of MoO3-Fe2O3-P2O5 and one series of SrO- Fe2O3-P2O5 glasses were measured by impedance spectroscopy in the frequency range from 0.01 Hz to 3 MHz and over the temperature range from 303 to 473 K. It was shown in Part I that the MoO3 is incorporated into phosphate network and the structure/properties are strongly influenced by the overall O/P ratio. The Fe2O3 content and Fe(II)/Fetot ratio in these glasses have significant effects on the electrical conductivity and dielectric permittivity. with decreasing Fe2O3 content in MoO3-Fe2O3-P2O5 glasses with O/P at 3.5 the dc conductivity, σdc(ω) decreases for two orders of magnitude, which indicates that the conductivity for these glasses depends on Fe2O3 and is independent of the MoO3 content. Also, the dielectric properties such as ε′(ω), ε″(ω) and σac(ω) and their variation with frequency and temperature indicates a decrease in relaxation intensity with increase in the concentration of MoO3. On the other hand, the dc conductivity for MoO3-Fe2O3-P2O5 glasses with O/P \u3e 3.5 increases with the substitution of MoO3 which has been explained by an increase in the number of non-bridging oxygens and formation of Fe-O-P bonds that are responsible for formation of small polarons. The increase in the dielectric permittivity, ε′(ω) with increasing MoO3 content is attributed to the increase in the deformation of glass network with increasing bonding defects. For SrO- Fe2O3-P2O5 glasses the conductivity and dielectric permittivity remained constant with increasing SrO

Spectroscopic Investigation of MoO₃-Fe₂O₃-P₂O₅ and SrO-Fe₂O₃-P₂O₅ Glasses I

The relationship between the composition, structure and selected properties for four series of iron phosphate glasses containing MoO3 and SrO has been investigated. The three series of MoO3-Fe2O3-P2O5 glasses were prepared with increasing MoO3 content. In series A the molar Fe/P ratio was constant at 0.67, in series B the O/P ratio was 3.5, whereas, in series C the molar percentages of Fe2O3 was fixed at 40 mol%. In the fourth series, M, SrO was added to maintain the Fe/P ratio constant at 0.67. The structural changes in these glasses have been studied by Raman spectroscopy. The Raman spectra show that MoO3 is incorporated into the phosphate network. However, the structure/properties are strongly influenced by the overall O/P ratio. In glasses with O/P \u3e 3.5 the addition of MoO3 depolymerized some of the bridging oxygens in pyrophosphate units to form isolated (PO4)3− orthophosphate groups. The decrease in glass temperature, Tg, and glass density, D, increase in thermal expansion coefficient, α, and glass density, D, for these glasses are attributed to an increase in the number of weaker P-O-Mo bonds connected to both orthophosphate and pyrophosphate units. The replacement of the stronger P-O-P bonds for the weaker Mo-O-P bonds imparts greater covalency to the network and contributes to the lower bond strength as the bond covalence decreases from P-O to Mo-O. The addition of up to 20 mol% SrO does not produce any changes in the Raman spectra and any further disruption of pyrophosphate chains

Dielectric Behavior and Impedance Spectroscopy of Bismuth Iron Phosphate Glasses

The electrical and dielectrical properties of Bi2O3-Fe2O3-P2O5 glasses were measured by impedance spectroscopy in the frequency range from 0.01 Hz to 4 MHz and over the temperature range from 303 to 473 K. It was shown that the dc conductivity strongly depends on the Fe2O3 content and Fe(II)/Fetot ratio. With increasing Fe(II) ion content from 17% to 34% in the bismuth-free 39.4Fe2O3-59.6P2O5 and 9.8Bi2O3-31.7Fe2O3-58.5P2O5 glasses, the dc conductivity increases. On the other hand, the decrease in dc conductivity for the glasses with 18.9 mol% Bi2O3 is attributed to the decrease in Fe2O3 content from 31.7 to 23.5 mol%, which indicates that the conductivity for these glasses depends on Fe2O3 content. The conductivity for these glasses is independent of the Bi2O3 content and arises mainly from polaron hopping between Fe(II) and Fe(III) ions suggesting an electronic conduction. The evolution of the complex permittivity as a function of frequency and temperature was investigated. At low frequency the dispersion was investigated in terms of dielectric loss. The thermal activated relaxation mechanism dominates the observed relaxation behavior. The relationship between relaxation parameters and electrical conductivity indicates the electronic conductivity controlled by polaron hopping between iron ions. The Raman spectra show that the addition of up to 18.9 mol% of Bi2O3 does not produce any changes in the glass structure which consists predominantly of pyrophosphate units

Structure of Sodium Phosphate Glasses Containing Al₂O₃ And/Or Fe₂O₃. Part I

The relationship between the composition and structure for three series of glasses: Na2O-Al2O3-P2O5 (NAP); Na2O-Al2O3-Fe2O3-P2O5 (NAFP), and Na2O-Fe2O3-P2O5 (NFP) has been studied. The structural changes in the NAP, NAFP and NFP glasses have been investigated by Raman and by Raman difference spectroscopy (RDS). The Raman spectra show that the addition of Al2O3 content to sodium phosphate glasses has a different effect on the phosphate network than the addition of Fe2O3. with increasing Fe2O3 content up to 20 mol% the structure changes from the chain-like metaphosphate to the pyrophosphate structure. The iron ions play an important role in forming P-O-Fe bonds that strengthen the cross-bonding of shorter pyrophosphate chains. On the other hand, with increasing Al2O3 content up to 20 mol%, the sodium metaphosphate is replaced by aluminium metaphosphate where Al(OP)6 units cross-link phosphate chains. The addition of Fe2O3 to Al2O3 in phosphate glasses containing both Al2O3 and Fe2O3 (NAFP series), enhances the formation of pyrophosphate units because iron ions have stronger effect on the depolymerization of metaphosphate chains if compared to the aluminium ions

Electrical Conductivity and Relaxation in MoO₃-Fe₂O₃-P₂O₅ Glasses

The electrical conductivity and dielectric properties of MoO3-Fe2O3-P2O5 glasses have been investigated by impedance spectroscopy in the frequency range from 0.01 Hz to 3 MHz and over the temperature range from 303 to 473 K. with decreasing Fe2O3 content in MoO3-Fe2O3-P2O5 glasses with O/P at 3.5 the dc conductivity, σdc(ω) decreases by two orders of magnitude, which indicates that the conductivity for these glasses depends on Fe2O3 and is independent of the MoO3 content. Also, the dielectric properties such as ε′(ω), ε″(ω) and σac(ω) and their variation with frequency and temperature indicates a decrease in relaxation intensity with increase in the concentration of MoO3. on the other hand, the dc conductivity for MoO3-Fe2O3-P2O5 glasses with O/P \u3e 3.5 increases with the substitution of MoO3 which has been explained by an increase in the number of non-bridging oxygens and formation of Fe-O-P bonds that are responsible for the formation of small polarons. the increase in the dielectric permittivity, ε(ω) with increasing MoO3 content is attributed to the increase in the deformation of the glass network with increasing bonding defects

Electrical Properties of Cr₂O₃-Fe₂O₃-P₂O₅ Glasses II

The electrical properties of xCr2O3-(40-x)Fe2O3-60P2O5, 0 ≤ x ≤ 10, (mol%) glasses have been investigated by impedance spectroscopy. In the glasses containing up to ~ 5 mol% Cr2O3, electrical conductivity increases due to the increase in the Fe2+/Fetot ratio. The conduction in these glasses is independent on Cr2O3 and it is controlled by the polaron hopping between iron ions. The electrical conductivity of the partially crystallized sample with 10 mol% Cr2O3 slightly increases although the Fe2O3 content and the fraction of Fe2+ ions are smaller. This effect is related to the formation of highly disruptive regions around the β-CrPO4 and Fe3(P2O7)2 crystallites in the glass matrix of this sample. These interconnected disruptive regions form the easy conductive pathways leading to a higher conductivity. Changes in the dielectric permittivity in chromium iron phosphate glasses are dependent on the Fe2+/Fetot ratio and, therefore, associated with the concentration of polarons related to Fe2+ and Fe3+ sites