Tuning the luminescence properties of Mn4+-activated CaYAlO4 phosphor by co-doping cations for indoor plant cultivation

To fulfil the demands of high-power plant growth lamps, cation co-doping is an effective way to tune the photoluminescence properties of manganese (Ⅳ)-activated aluminate phosphors. Therefore, we managed to synthesize a series of cations co-doped CaYAlO₄:xMn⁴⁺, mSr²⁺, M⁺ (M⁺ = Li⁺, Na⁺, and K⁺) (CYAO:Mn, Sr, M) far-red-emitting phosphors. The excitation spectrum of these phosphors contained two excitation bands, and the opposite effects of these two bands on the luminescence intensity have been observed with the increase of Mn⁴⁺ concentration. By adding 0.1 mol Sr²⁺ ions to replace Ca²⁺ site, the emission intensity and thermal stability of CYAO:Mn phosphors can be enhanced. Furthermore, the luminescence properties of CSYAO:Mn can be further improved by co-doping monovalent alkali metal ions to serve as charge compensators, the increased number of Mn⁴⁺ luminescence centers. Moreover, 0.6 mol% Na⁺ can increase the initial emission intensity of the phosphors by 117% as the best ratio. The characteristic emission spectrum of the phosphors CYAO:Mn,Sr,M correspond to the phytochrome P_FR of plants. These experiments and characterization results have certified that these phosphors have a potential application in indoor plants cultivation.     

Influence of Substructures on the Spreading Ability and Hydrolysis Resistance of Double-Tail Trisiloxane Surfactants

Four types of novel double-tail trisiloxane surfactants of the general formula Me₃SiOSiMeR¹OSiMe₃ (R ¹ = –(CH₂)₃NR²CH₂CH(OH)CH₂(OCH₂CH₂)_xOCH₃; R ² = –CH₂CH(OH)CH₂OCH₂(CH₂)_yCH₃, –CH₂(CH₂)₃CH₃, –CH₂CH₂CH(CH₃)₂; x = 8.4, 12.9, 17.5, 22; y = 2, 6), have been synthesized. Their structures were characterized by proton and carbon nuclear magnetic resonance. Most of them are able to reduce the surface tension of water to less than 24 mN/m at concentration levels of 10⁻⁵ mol/L and 10⁻⁴ mol/L. The emphasis was on the influence of substructures on their spreading ability and hydrolysis resistance. The results showed that a weaker hydrophilicity of a surfactant molecule, a larger molar ratio of methyl to methylene in the whole hydrophobic groups, more flexible hydrophobic groups and introduction of a methyl group in the spacer can all improve the spreading ability of the double-tail trisiloxane surfactant solutions on low-energy solid surfaces. The double-tail trisiloxane surfactants 1F and 2F are stable for more than 270 days in a neutral environment (pH 7.0). The hydrolysis resistance of the double-tail trisiloxane surfactants can be improved by a weaker hydrophilicity of the surfactant molecule, and a larger volume of the hydrophobic groups.     

Effect of Coordination Modes of HL Ligand on the Molecular Architecture of Its Transition Metal Complexes (HL = 5-Methyl-2-Phenyl-4-[(2-<Emphasis Type="Italic">o</Emphasis>-Tolylamino)-Phenylmethylene]pyrazol-3(2H)-one)

Abstract  Two Ag⁺ complexes [Ag(HL)₂(PF₆)] (1) and [(AgL) _n  · n(CH₂Cl₂) · n(0.5H₂O)] (2) (HL = 5-methyl-2-phenyl-4-[(2-o-tolylamino)-phenylmethylene]pyrazol-3(2H)-one) were synthesized and structurally characterized by EA analysis, IR spectra and X-ray crystallography. The result shows that two expected coordination modes (Modes I and III in Scheme 1) of the HL ligand, can be observed in its Ag⁺ complexes, while not in other transition metal ions (Ni²⁺, Co²⁺ or Cu²⁺) complexes whether deprotonation or not for the HL ligand. Graphical Abstract  Three possible coordination modes (Modes I, II or III in Scheme 1) of the selected HL (HL = 5-methyl-2-phenyl-4-[(2-o-tolylamino)-phenylmethylene]pyrazol-3(2H)-one) ligand, can be adopted, in which Modes I and III can be observed in its two Ag⁺ complexes [Ag(HL)₂(PF₆)](1) and [(AgL) _n  · n(CH₂Cl₂) · n(0.5H₂O)] (2), while Mode II just observed in its transition metal ions (Cu²⁺, Ni²⁺, or Co²⁺) complexes, resulting from the deprotonatd form of the HL ligand and the coordination characters of transition metal ions.      

Synthesis and Properties of Novel Double-Tail Trisiloxane Surfactants with High Spreading Ability

A new type of double-tail trisiloxane surfactants of the general formula R¹NR²CH₂CH(OH)CH₂O(CH₂CH₂O)xCH₃ (x = 8.4, 12.9, 17.5, 22; R ¹ = Me₃SiOSiMe(CH₂)₃OSiMe₃, R ² = CH₂CH(OH)CH₂OR³, R ³ = CH₂CH(C₂H₅)CH₂(CH₂)₂CH₃) has been synthesized by reacting single-tail trisiloxane surfactants with 2-ethylhexyl glycidyl ether. Their structures were characterized with ¹H-NMR and ¹³C-NMR spectroscopy. These double-tail trisiloxane surfactants reduce the surface tension of water to less than 24 mN/m at a level of 10⁻⁵ mol/L. The spreading ability (SA) of the double-tail trisiloxane surfactant solution on Parafilm (or Ficus microcarpa leaf) surfaces is better than that on polyethylene terephthalate surface. The SA of the solution of the double-tail trisiloxane surfactants 1J with average ethoxy units of 8.4 is far better than the others, and its solution (5.0 × 10⁻³ mol/L) possesses an SA value of over 15 within 10 min on Parafilm and Ficus microcarpa leaf surfaces. The surface tension values of aqueous solutions (1.0 × 10⁻³ mol/L) of the double-tail trisiloxane surfactants 1J are still less than 25 mN/m over 21 days in an acidic environment (pH 4.0) and 139 days in an alkaline environment (pH 10.0), respectively. It is suggested that the SA and hydrolysis resistance of double-tail trisiloxane surfactants are able to be improved by changing the structure of the hydrophobic group, such as increasing the molar ratio of methyl to methylene.     

Synthesis and Properties of Novel Double-Tail Trisiloxane Surfactants

To improve the hydrolysis resistant ability of trisiloxane surfactants, ethoxylated single-tail and double-tail trisiloxane surfactants of the general formulas Me₃SiOSiMeR¹OSiMe₃ (R ¹ = (CH₂)₃NHCH₂CH(OH)CH₂(OCH₂CH₂) _x OCH₃; x = 8.4, 12.9, 17.5, 22) and Me₃SiOSiMeR²OSiMe₃ (R ² = (CH₂)₃NR³CH₂CH(OH)CH₂(OCH₂CH₂) _x OCH₃; R ³ = CH₂(CH₂) _y CH₃; x = 8.4, 12.9, 17.5, 22; y = 2, 6) were synthesized. Their structures were characterized by ¹H NMR and ¹³C NMR. The surface activity and hydrolysis resistant properties of the trisiloxane surfactants prepared were also studied. The values of the critical micelle concentration of all trisiloxane surfactants prepared were at levels of 10⁻⁵ and 10⁻⁴ mol/L. They can reduce the surface tension of water to less than 24 mN/m. The hydrolysis resistant properties of double-tail trisiloxane surfactants are superior to those of single-tail trisiloxane surfactants. The double-tail trisiloxane surfactants 1B (x = 8.4; y = 2) and 2C (x = 12.9; y = 6) can be stable for 8 days in an acidic solution (pH 4.0) and 11 days in an alkaline environment (pH 10.0).     

Electrochemical assembly of [Ru(bpy)<Subscript>2</Subscript>tatp]<Superscript>2+</Superscript> associated with surfactants on the MWNTs/GC electrode

The electrochemical assembly of [Ru(bpy)₂tatp]²⁺ (where bpy = 2,2′-bipyridine, tatp = 1,4,8,9-tetra-aza-triphenylene) on the multi-walled carbon nanotubes-modified glassy carbon electrode (MWNTs/GC) in the presence of anionic and cationic surfactants has been investigated. A diffusion-controlled wave and three prewaves are exhibited on the differential pulse voltammogram of [Ru(bpy)₂tatp]²⁺. The formal potential of the prewaves is found to be much negative than that of the diffusion-controlled wave. An appropriate amount of anionic surfactants including dihexadecyl phosphate (DHP) and deoxyribonucleic acid (DNA) can prompt the assembly of [Ru(bpy)₂tatp]²⁺ on the MWNTs/GC electrode by using the method of repetitive voltammetric sweeping. In contrast, cationic surfactant such as hexadecyl trismethyl ammonium chrolide (HTAC) dispersed on the MWNTs surface is found to inhibit the assembly of [Ru(bpy)₂tatp]²⁺. Meanwhile, the assembled principle of [Ru(bpy)₂tatp]²⁺ on the MWNTs/GC electrode with the participation of surfactants is discussed in detail.     

Ferrocene-Based Cationic Surfactants: Surface and Antimicrobial Properties

A novel series of ferrocenyl surfactants was synthesized by the reaction of ferrocene disulfonic acid with different primary and tertiary fatty amines to produce the corresponding ammonium salts Fc[SO₃ ^{− +}NH₃(CH₂) _n CH₃]₂, where n = 9, 11, or 15 and Fc[SO₃^{− +}NH(CH₃)₂(CH₂) _n CH₃]₂, where n = 7 or 11, respectively, and where Fc = ferrocene. Chemical structures were confirmed by microelemental analysis, FTIR, and ¹H NMR spectroscopy. The critical micelle concentration of each prepared surfactant was determined using equilibrium surface tension. Furthermore, air/water interface parameters including effectiveness (π _CMC), efficiency (Pc₂₀), maximum surface excess (Г_max), and minimum surface area (A _min) were determined at 30, 40, and 50 °C. Thermodynamic parameters (ΔG°, ΔS°, and ΔH°) for both micellization and adsorption processes were recorded. The new synthesized surfactants were screened as antimicrobial agents against different bacterial and fungal organisms.     

Cation Field Strength Effects on Boron Coordination in Binary Borate Glasses

The field strength of modifier cations in boron‐containing oxide glasses has important but complex effects on boron coordination, and has long been known to have major effects on glass and liquid properties. With well‐constrained compositional and fictive temperature information in three binary borate glass series, we report how different modifier cations (Na⁺, Ba²⁺, Ca²⁺) affect boron coordination (¹¹B MAS NMR), as well as glass transition temperatures and configurational heat capacities (DSC). Using estimated reaction enthalpies for converting a ^[4]B to a ^[3]B with an NBO from previous studies, we compare boron coordinations in glasses with different modifier cations on an isothermal basis. Temperature and modifier cation effects can thus be isolated. At low modifier contents [R = (Na₂,Ca,Ba)O/B₂O₃<0.45], N₄ is systematically higher in the order Na>Ba>Ca, suggesting the enhanced stabilization of NBO for the divalent cations, especially for the smaller Ca²⁺. At higher R values, N₄ for Na borates drops below values for Ca and Ba borates. The trend in N₄ with modifier field strength reverses at high R values (~ R > 0.7), with Ca > Ba > Na. The transition may be related to the enhanced stabilization of ^[4]B‐O‐^[4]B groups by higher field strength cations in NBO‐rich glasses in which boron is the primary network component.     

Gemini surfactant controlled preparation of well-ordered lamellar mesoporous molybdenum oxide

A series of well-ordered lamellar mesoporous molybdenum oxides were prepared using gemini surfactant [C _n H_2n+1N⁺(CH₃)₂–(CH₂)₂–N⁺(CH₃)₂C _n H_2n+1] · 2Br⁻(denoted as C _n-2-n , n = 12, 14 and 16) as the structure-directing agent and ammonium heptamolybdate tetrahydrate (NH₄)₆Mo₇O₂₄ · 4H₂O as the precursor. The obtained samples were characterized by X-ray powder diffraction, thermal analysis, transmission electron microscopy and nitrogen adsorption–desorption. Results showed that contrary to complete structure collapse after removing tetradecyltrimethylammonium bromide (TTAB) from molybdenum oxide/TTAB composite, the lamellar mesostructure was retained after removal of C _n-2-n from corresponding composite. The effects of alkyl chain length and concentration of gemini surfactants on the structure of the mesoporous molybdenum oxide were also investigated. The specific surface area of extracted sample was as high as 116 m² g⁻¹. The maintenance of the lamellar mesostruture was due to the strong self-assembly ability of gemini surfactants and the strong electrical interaction between gemini surfactants and molybdenum oxide.     

Cation field-strength effects on ion irradiation-induced mechanical property changes of borosilicate glass structures

We examine the impact of the glass network-modifier cation field strength (CFS) on ion irradiation-induced mechanical property changes in borosilicate (BS) glasses for the ternary M₂O–B₂O₃–SiO₂ systems with M = {Na, K, Rb} and the quaternary [0.5M₍₂₎O–0.5Na₂O]–B₂O₃–SiO₂ systems with M = {Li, Na, K, Rb Mg, Ca, Sr, Ba}. ¹¹B nuclear magnetic resonance (NMR) experiments on the as-prepared BS glasses yielded the fractional population of four-coordinated B species (B^[4]) out of all {B^[3], B^[4]} groups in the glass network, along with the fraction of B^[4]–O–Si linkages out of all B^[4]–O–Si/B bonds. Both parameters correlated linearly with the (average) CFS of the M⁺ and/or {M⁽²⁾⁺, Na⁺} cations. Both the nanoindentation-derived hardness and Young's modulus values of the glasses reduced upon their irradiation by Si²⁺ ions, with the property deterioration decreasing linearly with increasing M^z+ CFS, that is, for higher M^z+⋅⋅⋅O interaction strength. The irradiation damage of the glass network also increased linearly with the fraction of B^[4]–O–Si linkages, which are the second weakest in the structure after the M^z+⋅⋅⋅O bonds. Our results underscore the advantages of employing BS glasses with high-CFS cations for enhancing the radiation resistance for nuclear waste storage.     

Optical Energy Storage Properties of (Ca1−xSrx)2Si5N8: Eu2+, Tm3+ Solid Solutions

While the reddish‐orange emitting phosphors M₂Si₅N₈:Eu²⁺(M = Ca, Sr) have been intensively investigated as potential materials for white‐light‐emitting diodes, in this study, optical energy storage properties of (Ca_1?xSr_x)₂Si₅N₈: Eu²⁺, Tm³⁺ (x = 0–1) solid solutions were tuned by cation substitution, which was commonly used to tune color point for improving w‐LEDs. Partial substitution of either Ca by Sr or Sr by Ca resulted in a redshifted Eu²⁺ emission which had a demarcation point at x = 0.5. Furthermore, the (Ca_1?xSr_x)₂Si₅N₈: Eu²⁺, Tm³⁺ materials exhibited similar persistent‐ and photostimulated luminescence behaviors with a maximum intensity at about x = 0.2. Such optical energy storage characters of the samples were attributed to the more appropriate trap depths (322–333 K) and higher density of energy level traps indicated by the thermoluminescence analysis.     

Polymerization of ethylene using zirconocenes supported on swellable cation-exchanged fluorotetrasilicic mica

Supported catalysts consisting of Cp₂ZrCl₂ and cation-exchanged fluorotetrasilicic mica (Mⁿ⁺-mica, Mⁿ⁺ = Na⁺, Mg²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺) were prepared and employed in the ethylene polymerization or ethylene/1-hexene copolymerization in the presence of R₃Al. The catalysts consisting of swellable Mg²⁺-mica and Zn²⁺-mica (both calcined at 200 °C) and Cp₂ZrCl₂ displayed high activity for the polymerization reaction. By contrast, when Mg²⁺-mica and Zn²⁺-mica were calcined above 250 °C, the swellability was lost, and the activities of Cp₂ZrCl₂ supported on these non-swellable micas were significantly reduced. The relationship between the activity and swellability of mica was clearly observed both in ethylene polymerizations employing (n-BuCp)₂ZrCl₂ in place of Cp₂ZrCl₂ and in ethylene/1-hexene copolymerizations using Cp₂ZrCl₂. The role of Mⁿ⁺-mica for the activation of the metallocene complex was investigated by surface observation using a scanning electron microscope and by XRD measurements of the catalysts after polymerization of ethylene for a short time. The results of the surface observations indicated that polyethylene was produced on the edges of Mⁿ⁺-mica lamellas at the initial stage of the polymerization. The XRD measurements show that the regularity of the stacked lamellas was immediately lost at this stage. The catalyst prepared by removing free Cp₂ZrCl₂ (i.e., unsupported Cp₂ZrCl₂, Cp₂ZrCl₂ dissolved into the catalyst slurry) showed extremely low activity, suggesting that the most of the active sites were formed through the reactions of Mⁿ⁺-mica and free Cp₂ZrCl₂. These results indicate that the lamellas of Mⁿ⁺-mica are peeled off at the initial stage of the polymerization and that exposed metal cations react with free-Cp₂ZrCl₂ to form additional active species. The swellability of Mⁿ⁺-mica strongly affects the formation of additional active sites, and therefore the supported catalysts based on non-swellable Mⁿ⁺-mica displayed only low activities.     

Chemical stability of KNbO3, NaNbO3, and K0.5Na0.5NbO3 in aqueous medium

In recent years, potassium sodium niobate (K_0.5Na_0.5NbO₃, KNN) has become popular and promising among perovskite lead‐free piezoceramic systems. In this study, the chemical stability of KNN powders in aqueous medium was investigated as a function of pH, time, and powder surface area. To better understand the dissolution behavior of the complex KNN stoichiometry, subconstituents such as potassium niobate (KNbO₃, KN) and sodium niobate (NaNbO₃, NN) were investigated separately first. Results showed that all of the cations in the structure underwent dissolution in different values. Indicating that KNN undergoes incongruent dissolution in aqueous medium, the dissolution of A site cations was higher at lower pH while the dissolution of B site cations increased at higher initial pH. The order of released cation concentrations (C_A1 = K > C_{A2 = Na} > C_B = Nb) fits with inverse relationship of cation field strength (FS) order, B = Nb⁵⁺_FS > A₂ = Na⁺_FS>A₁ = K⁺_FS, at pH 4, 7 and 10 for NN, KN, and KNN. Calculated diffuse layer thickness from the ICP data confirmed to outer amorphous layer in TEM image. Also, the ratio of normalized cation concentration versus surface area of powders showed that incongruent dissolution kinetic was driven by the diffusion step.     

Rapid Separation of Tl+ and Pb2+ from Various Binary Cation Mixtures Using Dicyclohexano-18-crown-6 Incorporated into Emulsion Membranes

Abstract

Relative transport rates of metal cation nitrates (Na⁺, K⁺, Rb⁺, Cs⁺, Ag⁺, Tl⁺, Ca²⁺, Sr²⁺, Ba²⁺, and Pb²⁺) in a water-toluene-water emulsion membrane system were measured. The toluene component contained the surfactant Span 80 and the crown ether dicyclohexano-18-crown-6. The aqueous receiving phase contained Li₄P2O₇. When each metal cation was individually present in the aqueous source phase, metal extraction was complete within 10 min with the order of extraction being Tl⁺ > Cs⁺ > Ag⁺ > Rb⁺ > K⁺ ≥m Na⁺ and Pb⁺ > Ca²⁺ > Sr²⁺ > Ba²⁺ for uni-and bivalent cations, respectively. Significant extraction was found for all cations except Na⁺, K⁺, and Ba²⁺. Some metal ions were concentrated nearly 10-fold in a 10-min period. Relative transport rates were determined when binary cation mixtures of either Tl⁺ or Pb²⁺ were present at equal concentrations with each of the remaining metal ions in the source phase. Tl⁺, when present with either Na⁺, Cs⁺, or Rb⁺, was selectively extracted from the source phase. Complete and nearly exclusive extraction of Pb²⁺ was observed in the presence of all cations including Tl⁺. The enrichment ratios of Pb²⁺ in the binary mixtures were approximately 10 while those of the second cation were less than 0.5 except for Sr²⁺ which was 0.86. Corresponding separation factors for Pb²⁺ ranged from 1000 to > 6000.     

Thermal stability of anisotropic bonded magnets prepared by additive manufacturing

In this research, anisotropic NdFeB + SmFeN hybrid and NdFeB bonded magnets are additively printed in a polyphenylene sulfide (PPS) polymer binder. Printed NdFeB + SmFeN PPS bonded magnets displayed excellent magnetic properties (B_r [remanence] = 6.9 kG [0.69 T], H_cj [coercivity] = 8.3 kOe [660 kA/m], and BH_max [energy product] = 9.9 MGOe [79 kJ/m³]) with superior corrosion resistance and thermal stability. The anisotropic NdFeB bonded magnet shows a high coercivity of 14.6 kOe (1162 kA/m) with a BH_max of 8.7 MGOe (69 kJ/m³). The coercivity and remanence temperature coefficients for NdFeB + SmFeN hybrid bonded magnets are −0.10%/K and −0.46%/K, and for NdFeB bonded magnets are −0.14%/K and −0.53%/K in the range of 300–400 K, indicating that the hybrid bonded magnets are thermally stable. The average flux aging loss for hybrid magnets was also determined to be very stable over 2000 h at 448 K (175°C) in air with 2.04% compared to that of NdFeB magnets with 3.62%.     

Response of Two-Dimensional Polymeric Cadmium Ferrocenyl Disulfonates to Heavy Metal Ions

A sandwich-like 2D infinite framework of {[Cd(pbbm)₂(SO₃FcSO₃)]·(CH₃OH)₂·(H₂O)₆} _n (1) with nanosized porous structure [Fc(SO₃)₂Na₂ = ferrocene-1,1′-disulphonate, pbbm = 1,1′-(1,3-propylene)-bis-1H-benzimidazole] was prepared by combining d ¹⁰ Cd²⁺ ions with highly conjugated pbbm and disodium ferrocene-1,1′-disulfonate. Experimental results show that 1 could serve as a new fluorescent probe for the detection of many divalent metal ions in water, such as Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Ag⁺, Cd²⁺, Hg²⁺ and Pb²⁺, and trace organic solvents, including acetone, toluene, methylene chloride, ether, tetrahydrofuran, and methanol. The main product was very different from previous chemosensory materials that only identify one or two metal ions. The powdery multipurpose chemosensory materials proposed here could also sequester dangerous heavy metal ions, especially Pb²⁺. A computational study of ferrocene-1,1′-disulfonate and 1 gave insight into the process of ion exchange and sorption. This study introduces a promising new field of fluorescent chemosensors based on nanoporous coordination polymers with free functional groups.     

The effects of (di-,tri-valent)-cation partitioning and intercalant anion-type on the solubility of hydrotalcites

Synthetic hydrotalcites were produced by a co-precipitation method. The hydrotalcites are represented by the general formula [M^II_(1-x)M^III_(x)(OH)₂][Aⁿ⁻]_x/n·zH₂O, where M^II is a divalent cation (eg, Mg²⁺or Ca²⁺), M^III is a trivalent cation (eg, Al³⁺) and Aⁿ⁻ is the interlayer anion. Herein, M^II = Mg, and M^III = Al such that [Mg/Al] = [2, 3] (atomic units) and Aⁿ⁻, represents intercalant species including: OH⁻, SO₄²⁻ and CO₃²⁻ anions. The thermochemical data of each compound including their solubility constants (K_so), density and molar volume were quantified at T = 25 ± 0.5°C, and P = 1 bar. The solubilities of the synthetic hydrotalcites, irrespective of their divalent-trivalent cation partitioning ratio, scaled as CO₃²⁻ < SO₄²⁻ < OH⁻; in order of decreasing solubility. The type of anion, very slightly, affected the solubility with less than ±1 log unit of variation for [Mg/Al] = 2, and ±2 log units of variation for [Mg/Al] = 3. The solubilities of these phases were strongly correlated with that of gibbsite (Al(OH)₃); such that activity of the [AlO₂⁻] species was solubility determining with increasing pH. The tabulated thermodynamic data were used to construct solid-solution models for phases encompassing both cation distribution ratios and to calculate stable phase equilibria relevant to alkali-activated slag (AAS) systems for diverse activator compositions.     

Biosurfactant Production by Bacillus tequilensis ZSB10: Structural Characterization,Physicochemical, and Antifungal Properties

A new biosurfactant was obtained from a moderately halophilic bacterium identified as Bacillus tequilensis ZSB10 that was isolated from a saline water pond located in Tehuacan-Cuicatlan valley, Mexico. A kinetic analysis of the bacterial growth of the ZSB10 strain showed a maximum growth at 24 h regardless of the initial pH (5, 7.4, and 9). The best results were found at pH = 7.4 in terms of bacterial growth, besides which the produced biosurfactant showed emulsifying and surfactant properties with an emulsification index (E₂₄) and surface tension change (ΔST) of 54 ± 0% and 26 mN m⁻¹, respectively. Extracted ZSB10 crude biosurfactant had a yield of 106 ± 6 mg L⁻¹, an E₂₄ = 58.4 ± 0.2%, and a ΔST = 26 mN m⁻¹ with a critical micelle concentration (CMC) of 44.82 mg L⁻¹. Also, its structure was characterized by MALDI-TOF mass spectrometry as a surfactin, iturin A, and fengycin mixture whose main isoform was leu/ile-7 C₁₅ surfactin [M + Na]⁺. Finally, the ZSB10 crude biosurfactant showed antifungal activity against Helminthosporium sp., with a 79.3% growth inhibition and an IC₅₀ of 1.37 mg per disc. Therefore, this biosurfactant could be used as biopesticide.     

Chemical durability of borosilicate pharmaceutical glasses: Mixed alkaline earth effect with varying [MgO]/[CaO] ratio

Glass for pharmaceutical packaging requires high chemical durability for the safe storage and distribution of newly developed medicines. In borosilicate pharmaceutical glasses which typically contain a mixture of different modifier ions (alkali or alkaline earth), the dependence of the chemical durability on alkaline earth oxide concentrations is not well understood. Here, we have designed a series of borosilicate glasses with systematic substitutions of CaO with MgO while keeping their total concentrations at 13 mol% and a fixed Na₂O concentration of 12.7 mol%. We used these glasses to investigate the influence of R = [MgO]/([MgO] + [CaO]) on the resistance to aqueous corrosion at 80°C for 40 days. It was found that this type of borosilicate glass undergoes both leaching of modifier ions through an ion exchange process and etching of the glass network, leading to dissolution of the glass surface. Based on the concentration analysis of the Si and B species dissolved into the solution phase, the dissolved layer thickness was found to increase from ~100 to ~170 nm as R increases from 0 to 1. The depth profiling analysis of the glasses retrieved from the solution showed that the concentration of modifier ions (Na⁺, Ca²⁺, and Mg²⁺) at the interface between the solution and the corroded glass surface decreased to around 40%–60% of the corresponding bulk concentrations, regardless of R and the leaching of modifier cations resulted in a silica-rich layer in the surface. The leaching of Ca²⁺ and Mg²⁺ ions occurred within ~50 and <25 nm, respectively, from the glass surface and this thickness was not a strong function of R. The leaching of Na⁺ ions varied monotonically; the thickness of the Na⁺ depletion layer increased from ~100 nm at R = 0 to ~200 nm at R = 1. Vibrational spectroscopy analysis suggested that the partial depletion of the ions may have caused some degree of the network re-arrangement or re-polymerization in the corroded layer. Overall, these results suggested that for the borosilicate glass, replacing [CaO] with [MgO] deteriorates the chemical durability in aqueous solution.     

Hydrothermal synthesis of potassium–sodium niobate powders

Potassium–sodium niobates (K_xNa_1−xNbO₃, 0 < x < 1, KNN) were hydrothermally synthesized under varying alkaline ratios (K⁺/Na⁺), total hydroxide concentration, reaction temperature, and time. Compositional surveys were developed by using Rietveld analyses derived quantitative volume fractions. The data demonstrated that phase pure KNN synthesis can be achieved by reacting the niobium source with the hydroxide solution having 6 M total hydroxide concentration, cation ratio (K⁺/Na⁺) of above 6 at temperatures ≥200°C for 24 h. Dissolution–precipitation events through intermediate products including hexaniobates were postulated as a plausible formation mechanism. It was shown also that the single-phase KNN approaching the morphotropic phase boundary (MPB) could be obtained by further incorporation of sodium ions into the crystal via post-annealing at 800°C/2 h, following the hydrothermal synthesis.