Electrogenerated chemiluminescence. 67. Dependence of light emission of the tris(2,2')bipyridylruthenium(II)/tripropylamine system on electrode surface hydrophobicity

We describe the effect of electrode surface hydrophobicity on the electrochemical behavior and electrogenerated chemiluminescence (ECL) of Ru(bpy)3(2+) (bpy = 2,2'-bipyridyl)/tripropylamine (TPrA) system. Gold and platinum electrodes were modified with different thiol monolayers. The hydrophobicity of the electrode surfaces changed with different terminal groups of the thiol molecules. The oxidation rate of TPrA was found to be much larger at the modified electrode with a more hydrophobic surface. The adsorption of neutral TPrA species on this kind of surface was assumed to contribute to the faster anodic kinetics. Due to the rapid generation of the highly reducing radical, TPrA., ECL intensity increased significantly at more hydrophobic electrodes. This electrode surface effect in the ECL analytical system allows one to improve the detection sensitivity at low concentrations of Ru(bpy)3(2+). The surfactant effect on the ECL process was also examined and discussed based on the change of electrode hydrophobicity by the adsorption of surfactant species.     

Surfactant chain length effects on the light emission of tris(2,2'-bipyridyl)ruthenium(II)/ tripropylamine electrogenerated chemiluminescence

The effects of nonionic surfactant chain length on the properties of tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)3(2+) where bpy = 2,2'-bipyridine) electrochemiluminescence (ECL) have been investigated. The electrochemistry, photophysics, and ECL of Ru(bpy)3(2+) in the presence of a series of nonionic surfactants are reported (Triton X-100, 114, 165, 405, 305, and 705-70). These surfactants differ in the number of poly(ethylene oxide) units incorporated into the surfactant molecule. The anodic oxidation of Ru(bpy)3(2+) produces ECL in the presence of tri-n-propylamine (TPrA) in aqueous surfactant solution. Increases in ECL efficiency (> or = 5-fold) and TPrA oxidation current (> or = 2-fold) have been observed in surfactant media. Slight decreases in ECL intensity are observed as the chain length of the nonionic surfactant increases. The data supports adsorption of surfactant on the electrode surface, thus facilitating TPrA and Ru(bpy)3(2+) oxidation and leading to higher ECL efficiencies.     

Electrogenerated chemiluminescence of tris (2,2'-bipyridyl)ruthenium(II) ion-exchanged in nafion-silica composite films

The voltammetry and electrogenerated chemiluminescence (ECL) of tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)3 2+) ion-exchanged in Nafion and Nafion-silica composite materials have been investigated. The major goal of this work was to investigate and develop new materials and immobilization approaches for the fabrication of ECL-based sensors with improved reactivity and long-term stability. Nation-silica composite materials with varying contents of Nation (53-100 wt% relative to silica) were prepared via the two-step acid/base hydrolysis and condensation of tetramethoxysilane. The Nafion doped sols were spin cast on glassy carbon electrodes, dried, and then ion-exchanged with Ru(bpy)3 2+. The shapes of the cyclic voltammetric curves and the amount of Ru(bpy)3 2+ exchanged into the films strongly depends on the amount of Nafion incorporated into the hybrid sol. Nafion-silica films with a low content of Nafion ion-exchanged less Ru(bpy)3 2+ and exhibited tail-shaped voltammetry at 100 mV/s. The ECL of immobilized Ru(bpy)3 2+ in the presence of either tripropylamine or sodium oxalate in pH 5 acetate buffer was also strongly dependent on the amount of Nafion introduced into the composite with greater ECL observed for the Nafion-silica films relative to pure Nafion.     

Electrogenerated chemiluminescence from tris(2,2'-bipyridyl)ruthenium(II) immobilized in titania-perfluorosulfonated ionomer composite films

Electrochemical behavior and electrogenerated chemiluminescence (ECL) of tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)3(2+)) immobilized in sol-gel-derived titania TiO2)-Nafion composite films coated on a glassy carbon electrode have been investigated. The electroactivity of Ru(bpy)3(2+) ion exchanged into the composite films and its ECL behavior were strongly dependent upon the amount of Nafion incorporated into the TiO2-Nafion composite films. The ECL sensor of Ru(bpy)32+ immobilized in a TiO2-Nafion composite with 50% Nafion content showed the maximum ECL intensities for both tripropylamine (TPA) and sodium oxalate in 0.05 M phosphate buffer solution at pH 7. Detection limits were 0.1 microM for TPA and 1.0 microM for oxalate (S/N = 3) with a linear range of 3 orders of magnitude in concentration. The present ECL sensor showed improved ECL sensitivity and long-term stability, as compared to the ECL sensors based on pure Nafion films. The present Ru(bpy)3(2+) ECL sensor based on TiO2-Nafion (50%) composite films was applied as an HPLC detector for the determination of erythromycin in human urine samples. The present Ru(bpy)3(2+) ECL sensor was stable in the mobile phase containing a high content of organic solvent (30%, v/v), in contrast to a pure Nafion-based Ru(bpy)3(2+) ECL sensor. The detection limit for erythromycin was 1.0 microM, with a linear range of 3 orders of magnitude in concentration.     

Effect of nonionic fluorosurfactant on the electrogenerated chemiluminescence of the tris(2,2'-bipyridine)ruthenium(II)/tri-n-propylamine system: lower oxidation potential and higher emission intensity

Fluorosurfactants are commercially available, and their applications in electrochemical systems have been the interest of many studies. Here, we describe a novel effect of a nonionic fluorosurfactant (Zonyl FSN) on the electrogenerated chemiluminescence (ECL) of the tris(2,2'-bipyridine)ruthenium(II)/tri-n-propylamine (TPrA) system at gold and platinum electrodes. Compared with its hydrocarbon analogue (Triton X-100), the adsorbed fluorosurfactant species not only rendered the electrode surfaces more hydrophobic but also significantly retarded the growth of the electrode oxide layers. As a result, more facile direct oxidation of TPrA was achieved, which led to the appearance of a low oxidation potential ECL signal (below 1.0 V vs SCE). At the gold electrode, the ECL peak appeared at 0.82 V, approximately 400 mV more negative than usual; while its intensity was approximately 50 times higher. The generation of the intense ECL signal at low oxidation potential may lead to the development of more efficient ECL analysis.     

Electrogenerated chemiluminescence derivatization reagents for carboxylic acids and amines in high-performance liquid chromatography using tris(2,2'-bipyridine)ruthenium(II)

2-(2-Aminoethyl)-1-methylpyrrolidine and N-(3-aminopropyl)pyrrolidine (NAPP) were found to be selective and sensitive derivatization reagents for carboxylic acid by high-performance liquid chromatography (HPLC) with electrogenerated chemiluminescence detection using tris(2,2'-bipyridine)ruthenium(II). Free fatty acids and ibuprofen were used as model compounds of carboxylic acids, and the derivatization conditions were optimized with myristic acid as a representative of free fatty acids. All the fatty acids tested were reacted with NAPP to produce highly sensitive derivatives under the mild reaction conditions of room temperature for 30 min in acetonitrile containing 2-bromo-1-ethylpyridinium tetrafluoroborate and 9-methyl-3,4-dihydro-2H-pyrido[1,2-a]pyrimidin-2-one. The chemiluminescence intensities were similar for all fatty acids. The derivatives obtained from 10 free fatty acids were completely separated by reversed-phase chromatography under isocratic elution conditions. The on-column detection limits (signal-to-noise ratio of 3) with proposed HPLC separation and chemiluminescence detection were 70 and 45 fmol for myristic acid and ibuprofen, respectively. The free fatty acids in human plasma were successfully determined using the present method. Histamine, a model compound of primary amines, was also determined after precolumn derivatization with 3-(diethylamino)propionic acid at room temperature for 60 min in acetonitrile containing N,N'-dicyclohexylcarbodiimide and 3,4-dihydro-3-hydroxy-4-oxo-1,2,3-benzotriazine with the detection limit of 70 fmol.     

Electrogenerated chemiluminescence. 72. Determination of immobilized DNA and C-reactive protein on Au(111) electrodes using tris(2,2'-bipyridyl)ruthenium(II) labels

Anodic electrogenerated chemiluminescence (ECL) with tri-n-propylamine (TPrA) as a coreactant was used to determine DNA and C-reactive protein (CRP) by immobilizations on Au(111) electrodes using tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)(3)(2+)) labels. A 23-mer synthetic single-stranded (ss) DNA derived from the Bacillus anthracis with an amino-modified group at the 5' end position was covalently attached to the Au(111) substrate precoated with a self-assembled thiol monolayer of 3-mercaptopropanoic acid (3-MPA) in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC) and then hybridized with a target ssDNA tagged with Ru(bpy)(3)(2+) ECL labels. Similarly, biotinylated anti-CRP species were immobilized effectively onto the Au(111) substrate precovered with a layer of avidin linked covalently via the reaction between avidin and a mixed thiol monolayer of 3-MPA and 16-mercaptohexadecanoic acid on Au(111) in the presence of EDAC and N-hydroxysuccinimide. CRP and anti-CRP tagged with Ru(bpy)(3)(2+) labels were then conjugated to the surface layer. ECL responses were generated from the modified electrodes described above by immersing them in a TPrA-containing electrolyte solution. A series of electrode treatments, including blocking free -COOH groups with ethanol amine, pinhole blocking with bovine serum albumin, washing with EDTA/NaCl/Tris buffer, and spraying with inert gases, were used to reduce the nonspecific adsorption of the labeled species. The ECL peak intensity was linearly proportional to the analyte CRP concentration over the range 1-24 microg/mL. CRP concentrations of two unknown human plasma/serum specimens were measured by the standard addition method based on this technique.     

The effects of nonionic surfactants on the tris(2,2'-bipyridyl)ruthenium(II)--tripropylamine electrochemiluminescence system

The electrochemistry and electrogenerated chemiluminescence (ECL) of Ru(bpy)3(2+) (bpy = 2,2'-bipyridyl) were studied in the presence of the nonionic surfactants Triton X-100, Thesit, and Nonidet P40. The anodic oxidation of Ru(bpy)3(2+) produces ECL in the presence of tri-n-propylamine in both aqueous and surfactant solutions. Increases in both ECL efficiency (> or =8-fold) and duration of the ECL signal were observed in surfactant media. A shift to lower energies of the Ru(bpy)3(2+) ECL emission by approximately 8 nm was also observed. The one-electron oxidation of Ru(bpy)3(2+) to Ru(bpy)3(3t) occurs at + 1.03 V vs Ag/AgCl in aqueous buffered (0.2 M potassium phosphate) solution as found by square wave voltammetry. This potential did not shift in surfactant systems, indicating that the redshifts in ECL emission are due to stabilization of ligand pi* orbitals in the metal-to-ligand charge-transfer excited state. These results are consistent with hydrophobic interactions between Ru(bpy)3(2+) and the nonionic surfactants.     

Electrogenerated chemiluminescence. 68. Detection of sodium ion with a ruthenium(II) complex with crown ether moiety at the 3,3'-positions on the 2,2'-bipyridine ligand

We show here how a Ru(bpy)2(CE-bpy) complex can be used for the ECL detection of sodium ion in both aqueous and nonaqueous media. Recognition of Na+ by the crown ether moiety in CE-bpy results in a significant increase in the ECL emission intensity of the complex.     

Electrogenerated chemiluminescence derivatization reagent, 3-isobutyl-9,10-dimethoxy-1,3,4,6,7,11b-hexahydro-2H-pyrido[2,1-a]isoquinolin-2-ylamine,for carboxylic acid in high-performance liquid chromatography using tris(2,2'-bipyridine)ruthenium(II)

3-Isobutyl-9,10-dimethoxy-1,3,4,6,7,11b-hexahydro-2H-pyrido[2,1-a]isoquinolin-2-ylamine (IDHPIA) was found to be a selective and highly sensitive derivatization reagent for carboxylic acid by high-performance liquid chromatography (HPLC) with electrogenerated chemiluminescence detection using tris(2,2'-bipyridine)ruthenium(II). Free fatty acids and phenylbutylic acid were used as model compounds of carboxylic acids, and the derivatization conditions were optimized with myristic acid. Under the mild reaction conditions of room temperature for 45 min in acetonitrile containing 2-bromo-1-ethylpyridinium tetrafluoroborate and 9-methyl-3,4-dihydro-2H-pyridol1,2-a]pyrimidin-2-one, all the fatty acids tested were reacted with IDHPIA to produce highly sensitive derivatives. The chemiluminescence intensity was essentially the same for all fatty acids. The derivatives obtained from 10 free fatty acids were completely separated by reversed-phase chromatography under isocratic elution conditions. The on-column detection limit (signal-to-noise ratio of 3) with proposed HPLC separation and chemiluminescence detection was 0.5 and 0.6 fmol for myristic acid and phenylbutylic acid, respectively. IDHPIA was 100-fold more sensitive than previously developed reagents (Morita, H.; Konishi, M. AnaL Chem. 2002, 74, 1584-1589). The free fatty acids in human serum were successfully determined using the present method.     

Facile nano‐free electrochemiluminescence biosensor for detection of sulphamethoxazole via tris(2,2′‐bipyridyl)ruthenium(II) and N ‐methyl pyrrolidone recognition

The electrochemiluminescence (ECL) system based on the ruthenium complex has become a powerful tool in the field of analytical chemistry. However, the non‐aqueous ECL luminescence system, which does not involve complex nano‐modification, has not been widely used for the determination of analytes. In this study, N ‐methyl pyrrolidone was selected as the solvent, and it could also act as a co‐reactant of Rubpy32+. Based on this, a simple ECL system without nanomaterials was established. Strong ECL was generated. Furthermore, a quenching effect between the excited state of Rubpy32+ and sulphamethoxazole (SMZ) was observed. Based on this, a sensitive ECL sensor for detecting SMZ is constructed. A linear relationship between ECL signal quenching intensity (ΔI) and the logarithm of SMZ concentration (log C) in the concentration range of 1 × 10⁻⁷ –1 × 10⁻⁵ mol/l is obtained. The limit of detection is as low as 3.33 × 10⁻⁹ mol/l. The method has been applied to the detection of SMZ in tap water samples with different concentration levels with satisfactory results, and the recovery was 95.3–102.6%.Inspec keywords: biosensors, electrochemical sensors, electroluminescence, chemiluminescence, organic compounds, electrochemistryOther keywords: ruthenium complex, analytical chemistry, nonaqueous ECL luminescence system, complex nanomodification, quenching effect, ECL signal quenching intensity, ECL sensor system, nanofree electrochemiluminescence biosensor system, sulphamethoxazole detection, tris(2,2′‐bipyridyl)ruthenium(II), N‐methyl pyrrolidone recognition, analyte determination, nanomaterials, SMZ concentration detection     

Determination of Dansyl Amino Acids and Oxalate by HPLC with Electrogenerated Chemiluminescence Detection Using Tris(2,2'-bipyridyl)ruthenium(II) in the Mobile Phase

A new electrogenerated chemiluminescence detection method is investigated for use in detection in reversed-phase and reversed-phase ion-pair HPLC with Ru(bpy)(3)(2+) in the mobile phase. In this method, different concentrations of Ru(bpy)(3)(2+) are dissolved in the mobile phase and the HPLC column flushed with the mobile phase for 1 h until the column is saturated with Ru(bpy)(3)(2+). The separated analytes along with Ru(bpy)(3)(2+) pass through an optical-electrochemical flow cell which has a dual platinum electrode held at a potential of 1250 mV vs a Ag/AgCl reference electrode. On the surface of the electrode, Ru(bpy)(3)(2+) is oxidized to Ru(bpy)(3)(3+) which reacts with the analytes to emit light. The retention times, retention orders, detection limits, and linearity in working curves are compared to those obtained with the conventional postcolumn Ru(bpy)(3)(2+) addition method. The retention times for dansyl amino acids with Ru(bpy)(3)(2+) in the mobile phase are longer than those obtained with the postcolumn addition approach. This may be caused by π-to-π interactions between the aromatic groups of the dansyl derivatives and the bipyridyl groups of Ru(bpy)(3)(2+) in the Ru(bpy)(3)(2+)-saturated reversed-phase column. Similarly, oxalate is separated from urine and blood plasma samples by reversed-phase ion-pair HPLC. Plasma samples are obtained using ultrafiltration to remove proteins from whole blood. Retention times for oxalate with the two detection techniques are identical, and detection limits for these techniques are compared.     

Effects of spacer-chain length on the photoelectrochemical responses of monolayer assemblies with ruthenium tris(2,2′-bipyridine) - viologen linked disulfides

Photochemical and photoelectrochemical properties of ruthenium tris(2,2′-bipyridine) (Ru²⁺)-viologen (V²⁺) linked disulfides [RuCnVC₆S]₂ (n (number of methylene groups)=3, 7) with different spacer-chain lengths and Ru²⁺ disulfides [RuC_mS]₂ (m=13, 17) were compared. The luminescence intensity in CH₃CN was in the order of [RuC₁₃S]₂≈[RuC₁₇S]₂>[RuC₇VC₆S]₂[RuC₃VC₆S]₂, implying efficient photoinduced electron-transfer between Ru²⁺ and V²⁺ moieties in the linked compounds. The monolayer assembly of the compound was fabricated on a gold surface. In the presence of triethanolamine, the anodic photocurrent was clearly observed from the RuC_nVC₆S/Au (n=3, 7) electrode (gold electrode modified with [RuCnVC₆S]₂), and its intensity was substantially larger for n=7 than for n=3. Photocurrent action spectra for the RuC_nVC₆S/Au (n=3, 7) electrodes were well correlated with the corresponding electronic absorption spectra in solution. The photocurrent from the RuC₇VC₆S/Au electrode was reduced more effectively by the coexistence of a water-soluble viologen as compared with the RuC₃VC₆S/Au electrode. The photocurrent from the RuC_mS/Au (m=13, 17) electrode was very small. The results suggest that the spacer-chain length between the Ru²⁺ and the V²⁺ moieties profoundly affects the Ru²⁺-sensitized photocurrent.     

Synthesis of polyimide from 5,5'-bis(bromomethyl)-2,2':6',2'-terpyridine and investigation of the polymer sorption behavior towards some metal ions

The synthesis of a terpyridine-based polyimide sorbent for solid-phase extraction (SPE) of some metal ions is described. For this purpose, 5,5'-bis(bromomethyl)-2,2':6',2'-terpyridine was polymerized with the corresponding diimide derivatives of dianhyrides to give polyimides utilizing terpyridine unit in the main chain. This polymer was used for its extraction capabilities for Pb(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II), at different pH. Under competitive conditions and at pH<0.6, the selectivity order was Pb approximately Cd approximately Zn. Enhanced selectivity was observed at pH 3.5, the order was Cu>Ni>Zn approximately Cd approximately Pb. Quantitative recoveries>97% were observed for all metals in case loading was stopped before reaching the point of breakthrough. As the synthesized polyimides are insoluble in water, solid-liquid extractions have been carried out and the resins sorption for mixture of basic and/or precious metals have been studied under various experimental conditions (reaction time and hydrochloric acid concentration).     

Electrochemical studies of the interaction of metal chelates with DNA. 4. Voltammetric and electrogenerated chemiluminescent studies of the interaction of tris(2,2'-bipyridine)osmium(II) with DNA

Cyclic voltammetric and electrogenerated chemiluminescent data were used to study the binding of tris(2,2'-bipyridine)-osmium(II), Os(bpy)3(2+), an electrostatic binder, to calf thymus DNA. The oxidized form of the osmium complex, Os(bpy)3(3+), has a stronger association to DNA than the reduced form, Os(bpy)3(2+), as indicated by the negative shift of E0' of the CV waves (K3+/K2+ = 3.35). The calculated binding constant, K2+, and binding site size, s, for the Os(byp)3(2+)-DNA system depended slightly on whether a mobile or a static equilibrium was assumed. In 10 mM NaCl, 10 mM Tris pH 7, K2+ = (7.3 +/- 0.4) x 10(3) M-1 and s = 3 base pairs (mobile) and K2+ = (5.0 +/- 0.2) x 10(3) M-1 and s = 3 base pairs (static). Electrogenerated chemiluminescence (ECL) was produced upon oxidation of Os(bpy)3(2+) at a Pt electrode in a solution containing 10 mM C2O4(2-) and 10 mM phosphate at pH 5. Addition of DNA caused a decrease in the emission intensity (I); a plot of I vs relative DNA concentration yielded K2+ = (6.5 +/- 0.5) x 10(3) M-1 and s = 3 base pairs. The osmium complex produced ECL when bound to the DNA molecule with an efficiency of 30% that of the unbound chelate.     

A structural property study on the role of Sm ions in nano-textured Zn(1−x)Sm x O thin films for green emission

Sm doped ZnO nanocrystalline textures were deposited through pyrolytic reactions on preheated glass substrates to tune the green emissions from the wurtzite matrix. The textures were found to be well-defined, possessing grain like morphology; with their dimensional parameters depending on the level of Sm substitution. The films were then characterized using several analytic techniques to establish the origin of their green emissions. The structural data obtained using the 2θ plots revealed the polycrystalline nature of the species and their preferred orientation along (002) plane. The morphology studies revealed a gradual decrease in grain size, while increasing the Sm composition. Their evolution has been correlated with the heterogeneous nucleation taking place on the surface of the substrate. The role of defects and crystallinity of the Zn_1?xSm_xO has been explained using Raman spectroscopy. Taucs plot revealed a red shift in the optical energy band gap of the species, while the luminescence spectra illustrated the enhancement of green emissions.     

The effect of nanotube surface oxidation on the electrical properties of multiwall carbon nanotube/poly(vinylidene fluoride) composites

Carbon nanotube/poly(vinylidene fluoride) (CNT/PVDF) composites were prepared using CNT with different oxidation and thermal treatments. The oxidation procedure leads to CNT with the most acidic characteristics that lower the degree of crystallinity of the polymer and contribute to a large increase of the dielectric constant. The surface treatments, in general, increase the percolation threshold and decrease conductivity. The surface treatments do not seem to affect CNT interactions and similar degrees of dispersion are achieved in all cases, as shown by the SEM results. The maximum value of the dielectric constant is ~630. It is demonstrated that the composite conductivity can be attributed to a hopping mechanism that is strongly affected by the surface treatment of the CNT.     

Enhancement of red emission intensity of Ca9Y(VO4)7:Eu phosphor via Bi co-doping for the application to white LEDs

The present investigation aims at the luminescence properties of Ca₉Y(VO₄)₇:Eu³⁺, Bi³⁺ red phosphor materials. The red emission at 613 nm originating from ⁵D₀–⁷F₂ transition of Eu³⁺ in Ca₉Y(VO₄)₇ is enhanced strongly with Bi³⁺–V⁵⁺ couple as the sensitizer, under excitation either into the ⁵L₆ state or the ⁵D₂ state. The energy transfer from Bi³⁺–V⁵⁺ to Eu³⁺ is discussed. For a fixed Eu³⁺ concentration, there is an optimal Bi³⁺ concentration with 15 mol%, at which the maximum luminescence intensity of Eu³⁺ is achieved. The red emission of Ca₉Y(VO₄)₇:0.8Eu³⁺, 0.15Bi³⁺ (under 395 nm and 465 nm excitations) is stronger than that of commercial Y₂O₃:Eu³⁺ phosphor (under 395 nm and 467 nm excitations). Based on the ratios of the red emission at 613 nm to orange one at 592 nm, it is considered that the symmetry of Eu³⁺ site decreases with doping of Bi³⁺, leading to more opposite parity components. Lifetime and diffuse reflection spectra measurements indicate that the red emission enhancement is due to the enhanced transition probabilities from the ground state to ⁵L₆ and ⁵D₂ states of Eu³⁺ in the distorted crystal field. Therefore the present material is a promising red-emitting phosphor for white-light diodes with near-ultraviolet/blue GaN-based chips.     

Oxygen stoichiometry in the system (CaxSr1−x)FeO3−y. Its effect on crystallographic and thermodynamic properties

Oxygen-deficient perovskites of the system (Ca_xSr_1?x)FeO_3?y were prepared at high oxygen pressures up to 1900 atm (196 MPa), and measurements were made of their crystallographic and thermodynamic behavior. The a-spacing of perovskites expanded linearly with increasing oxygen deficiency for x = 0–0.4 and y = 0.01–0.19, and an eventual tetragonal distortion took place at the composition AFeO_2.82 (64% Fe⁴⁺). Thermogravimetric analysis of SrFeO_2.81 in vacuo revealed that oxygen atoms began to release from the perovskite lattice at 350°C. Thermodynamic analysis showed that oxygen deficiency had a linear relationship with the square root of the fugacity of oxygen gas, and the slope was $\text{?1.96 × 10}{}^{\mathrm{?3}}\text{atm}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{mol}{}^{\mathrm{?1}}$.