Purification and characterization of solvent‐tolerant,thermostable, alkaline metalloprotease from alkalophilic Pseudomonas aeruginosa MTCC 7926

BACKGROUND: Microbial proteases are becoming imperative for commercial applications. The protease secreted by Pseudomonas aeruginosa MTCC 7926, isolated from solvent‐contaminated habitat was purified and characterized for activity at various edaphic conditions. The purified alkaline protease was investigated for dehairing of animal skin, anti‐staphylococcal activity and processing of X‐ray film. RESULTS: The protease was 24‐fold purified by ammonium sulfate fractionation, sephadex G‐100 gel filtration and DEAE‐cellulose, with 36% recovery. K_M and V_max, using casein were 2.94 mg mL^?1 and 1.27 µmole min^?1, respectively. The apparent molecular mass by SDS‐PAGE was 35 kDa. Alkaline protease was active at pH 6–11 and temperature 25–65 °C. Its activity was (a) 86.8% in 100 mmol L^?1 NaCl, (b) >95% in metal ions (Mn²⁺, Ca²⁺, Mg²⁺, Fe²⁺) for 1 h, (c) >90% in bleaching agents and chemical surfactants, (d) 135.4 ± 2.0% and 119.9 ± 6.2% with rhamnolipid and cyclodextrin, respectively, (e) stable in solvents for 5–30 days at 27 °C, and (f) inhibited by EDTA, indicating metalloprotein. CONCLUSION: This work showed that purified protease retained its activity in surfactants, solvents, metals, and bleaching agents. The enzyme is an alternative for detergent formulations, dehairing of animal skin, X‐ray film processing, treatment of staphylococcal infections and possibly non‐aqueous enzymatic peptide synthesis. Copyright © 2009 Society of Chemical Industry     

Kinetic data and substrate specificity of a keratinase from Chryseobacterium sp. strain kr6

BACKGROUND: Keratinases are important enzymes for biotechnological processes involving keratin hydrolysis. In this work substrate specificity and kinetic properties of a keratinase from Chryseobaterium sp. were investigated. RESULTS: The optimal conditions for activity of purified keratinase with respect to pH, temperature and sodium chloride concentration were established using factorial design and surface response techniques. The optimum conditions for keratinase activity were pH from 7.4 to 9.2, temperature from 35 °C to 50 °C and NaCl concentration from 50 to 340 mmol L^?1, having azocasein as substrate. Subsequently, the kinetic parameters for this substrate were determined to be K_m = 0.75 mg mL^?1 and V_max = 59.5 U min^?1. The K_i value for 1,10‐phenanthroline was estimated at 0.78 mmol L^?1. The enzyme specificity was evaluated over different synthetic and insoluble substrates. The protease exhibited specificity with selectivity for hydrophobic and positively charged residues. In relation to the insoluble substrates, the enzyme hydrolyzed preferably chicken nails. CONCLUSIONS: This enzyme effectively hydrolyzes insoluble keratin substrates. The knowledge of keratinase properties is an essential step in the development of biotechnological processes involving keratin hydrolysis. Copyright © 2008 Society of Chemical Industry     

Detergent‐Compatible Robust Alkaline Protease from Newly Isolated Halotolerant Salinicoccus sp. UN‐12

Currently, enzyme‐containing blended detergent preparations are favored in the detergent industry. The detergent compatibility of an enzyme depends on its robustness to withstand harsh operating conditions and maintain efficient functioning in the presence of various surfactants and detergents. Alkaline proteases from halotolerant microbes having the capability to work in demanding environments are desirable for their application in the detergent industry. The protease secreted by a halotolerant soil isolate Salinicoccus sp. UN‐12 was evaluated for its suitability in detergent formulations. The studied enzyme is an alkaline serine protease (63 kDa) with an optimum temperature of 55 °C and optimum pH of 8.5. The protease was purified 17‐fold with a 4% yield. The protease was active in NaCl (up to 4 mol) and showed enhanced activity in the presence of CaCl₂, KCl, and MnCl₂. In addition, the proteolytic activity was sustained in the presence of various organic solvents, cyclodextrin, disodium cocoamphodiacetate, ionic liquids, hydrotropes, and ultrasound. This report is the first to document the multifarious robustness and novel attributes of a protease secreted by the newly isolated Salinicoccus sp. UN‐12. The protease‐detergent formulation efficiently removes blood, egg, grass, and tomato sauce stains. This protease is now available for efficient and eco‐friendly applications in the detergent industry.     

Detergent Compatible Extracellular Lipase from Streptomyces cellulosae AU‐10: A Green Alternative for the Detergent Industry

Enzymes can decrease the environmental and economic load of detergent products by reducing the amount of chemicals used in detergents and by allowing washing at ambient temperatures. In this study, Streptomyces cellulosae AU‐10 (GenBank accession number: MG780240) lipase was purified 7.08‐fold with 68% yield using an aqueous 2‐phase system. The Streptomyces sp. AU‐10 lipase showed maximal activity at pH 9.0 and 40 °C. Hundred percent activities were measured in the pH range from 9.0 to 11.0 for 1 h. The enzyme was also highly stable at 30–50 °C. The values of K_m and V_max were calculated as 0.34 mM and 0.83 mM min^?1, respectively. The lipase has high hydrolytic activity for olive oil and sunflower oil. The effect of ethylenediamine tetraacetic acid on the enzyme has shown that the lipase is a metalloenzyme. The activity increased in the presence of Fe²⁺, Cu²⁺, and various boron compounds. The enzyme has shown a good stability not only with surfactants but also with oxidizing agents. In addition, activities in the presence of Omo, Ariel, Tursil, Pril, and Fairy were measured as 108.8%, 115.6%, 98.35%, 140.4%, and 107.6%, respectively. Considering its remarkable ability, the S. cellulosae AU‐10 lipase can be considered as a potential additive in the detergent industry.     

Correlation Between Enzyme Activity and Stability of a Protease, an Alpha-Amylase and a Lipase in a Simplified Liquid Laundry Detergent System, Determined by Differential Scanning Calorimetry

Enzymes used during washing in laundry detergents have become a universal tool to lower energy consumption and to generate a broad, consumer-relevant, cleaning effect. However, the stability of these enzymes remains a major obstacle, particularly in liquid products, due to increased interaction between the enzymes and the other components of the detergent. The process of formulation involves extensive shelf-life stability studies where residual enzyme activities are correlated with formulation variations. As a way to improve the formulation process, we evaluated the possible use of differential scanning calorimetry (DSC) as a tool to predict enzyme stability in liquid detergents. Thus, residual enzyme activity after incubation in a multitude of formulations was determined and compared to thermodynamic data obtained by DSC. The enzymes tested were a protease, an alpha-amylase and a lipase. We found a strong linear correlation between DSC-derived data, in particular T _max (temperature at peak maximum of the transition from the folded to unfolded state) and enzyme activity studies with R ²-values: 0.98 (protease), 0.99 (amylase) and 0.98 (lipase), respectively. Thus, a higher T _max for the same enzyme in a particular formulation is directly proportional to longer storage stability. These results suggest a new way of greatly accelerating this type of formulation study, allowing estimation of enzyme compatibility with a specific formulation on a daily, rather than the weekly or monthly basis used at present.     

Protease and Amylase Stability in the Presence of Chelators Used in Laundry Detergent Applications: Correlation Between Chelator Properties and Enzyme Stability in Liquid Detergents

Chelators are a common ingredient in most laundry detergents. They have a number of different functions such as reducing water hardness, assisting in keeping particulate soil in suspension and the removal of certain stains, thus complementing the action of the anionic surfactants. Another important group of components in a modern liquid detergent is enzymes, mainly proteases and amylases. As the most commonly used enzymes within the detergent industry are dependent on bound calcium ions to maintain conformational stability and function, the presence of both chelators and enzymes in a liquid detergent presents a challenge. The three commonly used Ca²⁺ chelators: citrate, DTPA (diethylene triamine pentaacetic acid) and HEDP (1-hydroxyethane-1,1-diyl)bis(phosphonic acid), were studied with regard to their impact on protease and amylase stability in buffer and in a model liquid detergent. Enzyme stability was characterized by differential scanning calorimetry (DSC) and activity studies, and correlated to the chelator-Ca²⁺ interaction properties. The results show that a chelator’s ability to reduce water hardness and its Ca²⁺ affinity are in reality two separate aspects in the context of their use in liquid detergents. In the presence of DTPA, stoichiometric surplus of free Ca²⁺ is required to maintain sufficient amylase and protease stability. In the presence of the weaker chelators, HEDP and citrate, the total Ca²⁺ concentration is more important to protein stability than stoichiometric balancing between chelator and Ca²⁺. Thus, for these chelators their total concentration only has a minor impact on the Ca²⁺ concentration required to maintain or improve enzyme storage stability. The results underline the importance of Ca²⁺ in liquid detergent formulations, and suggest how proper balancing of chelators and Ca²⁺ can be used to improve overall enzyme stability.     

Removal of heavy‐metal ions by magnetic beads containing triazole chelating groups

The aim of this study was to prepare magnetic beads that could be used for the removal of heavy‐metal ions from synthetic solutions. Magnetic poly(ethylene glycol dimethacrylate–1‐vinyl‐1,2,4‐triazole) [m‐poly(EGDMA–VTAZ)] beads were produced by suspension polymerization in the presence of a magnetite Fe₃O₄ nanopowder. The specific surface area of the m‐poly(EGDMA–VTAZ) beads was 74.8 m²/g with a diameter range of 150–200 μm, and the swelling ratio was 84%. The average Fe₃O₄ content of the resulting m‐poly(EGDMA–VTAZ) beads was 14.8%. The maximum binding capacities of the m‐poly(EGDMA–VTAZ) beads from aquous solution were 284.3 mg/g for Hg²⁺, 193.8 mg/g for Pb²⁺, 151.5 mg/g for Cu²⁺, 128.1 mg/g for Cd²⁺, and 99.4 mg/g for Zn²⁺. The affinity order on a mass basis was Hg²⁺ > Pb²⁺ > Cu²⁺ > Cd²⁺> Zn²⁺. The binding capacities from synthetic waste water were 178.1 mg/g for Hg²⁺, 132.4 mg/g for Pb²⁺, 83.5 mg/g for Cu²⁺, 54.1 mg/g for Cd²⁺, and 32.4 mg/g for Zn²⁺. The magnetic beads could be regenerated (up to ca. 97%) by a treatment with 0.1M HNO₃. These features make m‐poly(EGDMA–VTAZ) beads potential supports for heavy‐metal removal under a magnetic field. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Cu2+ sensing via noncovalent complexes of fluorescent whitening agents and imidazole-based polymeric dye transfer inhibitors

Fluorescent whitening agents (FWAs) and polymeric dye transfer inhibitors (DTIs) are widely used in detergent formulations to combat garment yellowing, fading, and discoloration. We report a new application for these inexpensive, mass-produced, laundry additives as sensitive fluorescence “turn-off” sensors for Cu²⁺. We show that Cu²⁺-sensitive FWA–DTI complexes form spontaneously when aqueous solutions of FWA and imidazole-based DTI are mixed. We also show that the imidazole groups present in the resulting fluorescent FWA–DTI complex selectively bind Cu²⁺, a potent fluorescence quencher, to form nonfluorescent FWA–DTI-Cu²⁺ complexes. Our Cu²⁺-sensing FWA–DTI complexes are completely water-soluble and have a Cu²⁺ detection limit of ~ 0.14 μM in water. Our simple approach not only converts the Cu²⁺-insensitive FWAs into sensitive fluorescent probes for the metal ion but also significantly enhances the brightness of triazinylaminostilbene FWAs. The present study provides a facile, synthesis-free strategy for producing inexpensive fluorescent sensors for Cu²⁺. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48915.     

Production and Characteristics of an Enantioselective Lipase from Burkholderia sp. GXU56

The lipase production of Burkholderia sp. GXU56 was influenced by carbon and nitrogen sources, inorganic salts, initial pH of the medium and cultivation temperature. The maximum lipase production was 580.52 U/mL and reached 5 times the level of the basic medium in the optimum medium at pH 8.0, 32 °C, 200 rpm and 40–48 h. The lipase was purified 53.6 fold to homogeneity and the molecular weight was 35 KDa on SDS‐PAGE. The optimum pH and temperature of the lipase were 8.0 and 40 °C, respectively, and it was stable in the range of pH 7–8.5 and at temperatures below 45 °C. The lipase activity was strongly inhibited by Zn²⁺, Cu²⁺, Co²⁺, Fe²⁺, Fe³⁺ ions and SDS, while it was stimulated by Li⁺ and Ca²⁺ ions and in presence of 0.1 % CTAB, 0.1 % Triton X‐100 and 10 % DMSO. K_m and V_max of the lipase were calculated to be 0.038 mmol/L, and 0.029 mmol/L min^–1, respectively, with PNPB as the substrate. The GXU56 lipase showed enantioselective hydrolysis of (R,S)‐methyl mandelate to (R)‐mandelic acid, which is an important intermediate in the pharmaceutical industry.     

Synthesis,characterization, and metal ions adsorption properties of chitosan–calixarenes (I)

Calixarene‐modified chitosans (CTS–CA‐I and CTS–CA‐II) were first synthesized by the reaction of chitosan (CTS‐NH₂) with 1,3‐bis‐chloroethoxyethoxy‐2,4‐dihydroxy‐p‐tert‐butylcalix[4]arene (CA‐I) or its benzoyl derivative (CA‐II). Their structures were characterized by infrared and X‐ray diffraction spectroscopy and scanning electron microscopy (SEM). The adsorption of Ni²⁺, Cd²⁺, Cu²⁺, Pd²⁺, Ag⁺, and Hg²⁺ by CTS–CA‐I and CTS–CA‐II was studied and the thermodynamic parameter of two calixarene‐modified chitosans toward Hg²⁺ was deduced. The adsorption properties of CTS–CA‐I and CTS–CA‐II were greatly varied compared with that CTS‐NH₂, especially with the adsorption capacity toward Ag⁺ and Hg²⁺, because of the presence of the calixarene moiety. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1139–1144, 2003     

Catalytic potential of a poly(AAc‐co‐HPMA‐cl MBAm)‐matrix‐immobilized lipase from a thermotolerant Pseudomonas aeruginosa MTCC‐4713

A purified alkaline thermo‐tolerant lipase from Pseudomonas aeruginosa MTCC‐4713 was immobilized on a series of five noble weakly hydrophilic poly(AAc‐co‐HPMA‐cl MBAm) hydrogels. The hydrogel synthesized by copolymerizing acrylic acid and 2‐hydroxy propyl methacrylate in a ratio of 5 : 1 (HG_5:1 matrix) showed maximum binding efficiency for lipase (95.3%, specific activity 1.96 IU mg^?1 of protein). The HG_5:1 immobilized lipase was evaluated for its hydrolytic potential towards p‐NPP by studying the effect of various physical parameters and salt‐ions. The immobilized lipase was highly stable and retained ～92% of its original hydrolytic activity after fifth cycle of reuse for hydrolysis of p‐nitrophenyl palmitate at pH 7.5 and temperature 55°C. However, when the effect of pH and temperature was studied on free and bound lipase, the HG_5:1 immobilized lipase exhibited a shift in optima for pH and temperature from pH 7.5 and 55°C to 8.5 and 65°C in free and immobilized lipase, respectively. At 1 mM concentration, Fe³⁺, Hg²⁺, NH₄⁺, and Al³⁺ ions promoted and Co²⁺ ions inhibited the hydrolytic activities of free as well as immobilized lipase. However, exposure of either free or immobilized lipase to any of these ions at 5 mM concentration strongly increased the hydrolysis of p‐NPP (by ～3–4 times) in comparison to the biocatalysts not exposed to any of the salt ions. The study concluded that HG_5:1 matrix efficiently immobilized lipase of P. aeruginosa MTCC‐4713, improved the stability of the immobilized biocatalyst towards a higher pH and temperature than the free enzyme and interacted with Fe³⁺, Hg²⁺, NH₄⁺, and Al³⁺ ions to promote rapid hydrolysis of the substrate (p‐NPP). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4252–4259, 2006     

Nickel(II)‐imprinted monolithic columns for selective nickel recognition

Ni²⁺‐imprinted monolithic column was prepared for the removal of nickel ions from aqueous solutions. N‐Methacryloyl‐L ‐histidine was used as a complexing monomer for Ni²⁺ ions in the preparation of the Ni²⁺‐imprinted monolithic column. The Ni²⁺‐imprinted poly(hydroxyethyl methacrylate‐N‐methacryloyl‐L ‐histidine) (PHEMAH) monolithic column was synthesized by bulk polymerization. The template ion (Ni²⁺) was removed with a 4‐(2‐pyridylazo) resorcinol (PAR):NH₃? NH₄Cl solution. The water‐uptake ratio of the PHEMAH–Ni²⁺ monolith increased compared with PHEMAH because of the formation of nickel‐ion cavities in the polymer structure. The adsorption of Ni²⁺ ions on both the PHEMAH–Ni²⁺ and PHEMAH monoliths were studied. The maximum adsorption capacity was 0.211 mg/g for the PHEMAH–Ni²⁺ monolith. Fe³⁺, Cu²⁺, and Zn²⁺ ions were used as competitive species in the selectivity experiments. The PHEMAH–Ni²⁺ monolithic column was 268.8, 25.5, and 10.4 times more selective than the PHEMAH monolithic column for the Zn²⁺, Cu²⁺, and Fe³⁺ ions, respectively. The PHEMAH–Ni²⁺ monolithic column could be used repeatedly without a decrease in the Ni²⁺ adsorption capacity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

How the Influence of Different Salts on Interfacial Properties of Surfactant–Oil–Water Systems at Optimum Formulation Matches the Hofmeister Series Ranking

In this work, we present the effects of salts on sodium dodecyl benzene sulfonate micellization and on the interfacial performance of a sodium dodecyl benzene sulfonate–heptane–brine system at optimum formulation, i.e., hydrophilic–lipophilic deviation (HLD) = 0. In order to do that, interfacial tension and dilational interfacial rheology properties of surfactant–heptane–water systems at optimum formulation are measured using an interfacial spinning drop tensiometer with an oscillating velocity, which can accurately measure interfacial rheology properties at both low and ultralow interfacial tensions. The brines used contain one of the following salts: MgCl₂, CaCl₂, NaCl, NH₄Cl, NaNO₃, CH₃COONa, or Na₂SO₄. We performed a one-dimensional salinity scan with each of these salts to achieve an optimum formulation. In relation to the Hofmeister series, we found that, at optimum formulation, systems with chaotropic ions (NH₄⁺, NO₃⁻) present interfaces with ultralow interfacial tensions, very low dilational modulus, and a low phase angle, whereas kosmotropic ions (Mg²⁺, Ca²⁺, SO₄⁻²) generate high interfacial tension and high rigidity monolayers. Intermediate ions in the Hofmeister series (Na⁺, CH₃COO⁻, Cl⁻) present interfaces with intermediate properties. Furthermore, according to the Hofmeister series, interfaces can be respectively ordered from higher to lower rigidity for surfactant counterions Mg²⁺ > Ca²⁺ > Na⁺ > NH₄⁺ and coions SO₄²⁻ > CH₃COO^– > Cl⁻ > NO₃⁻, which correspond to a salting-out (highest rigidity) and salting-in (lowest rigidity) effect. We observed that counterions have a more significant effect on surfactant–oil–water system properties than those that act as coions.     

Potentiometric,kinetic, and thermodynamic investigations into Cu2+ ion binding properties of vinyl imidazole containing IMAC adsorbent

In this study, the use of the potentiometric method for the determination of the protonation constant of vinyl imidazole (VIM) and the stability constant of the Cu²⁺ ion complex of VIM used in the immobilized metal ion affinity chromatography (IMAC) was investigated. For this purpose, poly(ethylene glycol dimethacrylate‐n‐vinyl imidazole) [poly(EGDMA–VIM)] microspheres (average diameter 150–200 μm) were prepared. The microspheres were characterized by elemental analysis, N₂ adsorption/desorption isotherms, elemental analysis, energy dispersive spectroscopy (EDS). Protonation constants of vinyl imidazole and the metal‐ligand stability constant of vinyl imidazole with Cu²⁺ ions have been determined potentiometrically in 0.1M NaCl aqueous solution at 298, 318, and 338 K, respectively. The corresponding thermodynamic parameters of protonation and complexation processes (ΔG, ΔH, and ΔS) were derived and discussed. The formation kinetics of Cu²⁺‐vinyl imidazole complex were also investigated, and the process obeyed the pseudo‐second‐order kinetic model. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39751.     

Characteristics of poly(AAc5‐co‐HPMA3‐cl‐EGDMA15) hydrogel‐immobilized lipase of Pseudomonas aeruginosa MTCC‐4713

Four series of noble networks were synthesized with acrylic acid (AAc) copolymerized with varying amount of 2‐hydroxy propyl methacrylate or dodecyl methacrylate (AAc/HPMA or AAc/DMA; 5:1 to 5:5, w/w) in the presence of ethylene glycol dimethacrylate (EGDMA; 1, 5, 10, 15, and 20%, w/w) as a crosslinker and ammonium per sulfate (APS) as an initiator. Each of the networks was used to immobilize a purified lipase from Pseudomonas aeruginosa MTCC‐4713. The lipase was purified by successive salting out with (NH₄)₂SO₄, dialysis, and DEAE anion exchange chromatography. Two of the matrices, E_15a, i.e. [poly (AAc₅‐co‐DMA₁‐cl‐EGDMA₁₅)] and I_15c, i.e. [poly (AAc₅‐co‐HPMA₃‐cl‐EGDMA₁₅)], that showed relatively higher binding efficiency for lipase were selected for further studies. I_15c‐hydrogel retained 58.3% of its initial activity after 10th cycle of repetitive hydrolysis of p‐NPP, and I_15c was thus catalytically more stable and efficient than the other matrix. The I_15c‐hydrogel‐immobilized enzyme showed maximum activity at 65°C and pH 9.5. The hydrolytic activity of free and I_15c‐hydrogel‐immobilized enzyme increased profoundly in the presence of 5 mM chloride salts of Hg²⁺, NH₄⁺, Al³⁺, K⁺, and Fe³⁺. The immobilized lipase was preferentially active on medium chain length p‐nitrophenyl acyl ester (C:8, p‐nitrophenyl caprylate). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4636–4644, 2006     

Removal of concentrated heavy metal ions from aqueous solutions using polymers with enriched amidoxime groups

Particulate and fibrous adsorbents with enriched amidoxime groups were synthesized by using a novel monomer N,N′‐dipropionitrile acrylamide. The adsorption properties of amidoximated poly(N,N′‐dipropionitrile acrylamide) [poly(DPAAm)] particles and a nonwoven fabric grafted with the same for UO₂²⁺, Pb²⁺, Cu²⁺, and Co²⁺ at high concentrations were investigated by batch process. Metal ion adsorption studies were conducted from metal ion solutions with different initial concentrations (100–1500 ppm). It was shown that particulated amidoximated poly(DPAAm) has higher adsorption capacity than amidoximated nonwoven fabrics for all metal ions, especially for uranyl ions. The results of the adsorption studies showed that the interaction between UO₂²⁺ and amidoximated groups agree with the Langmuir‐type isotherm. From the Langmuir equation, the adsorption capacities were found as 400 mg UO₂²⁺/g dry amidoximated poly(DPAAm) and 250 mg UO₂²⁺/g dry amidoximated graft polymer. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1705–1710, 2004     

Quadri‐Synergetic Effect for Highly Effective Carbon Dioxide Fixation and Its Application to Indoloquinolinone

The first copper‐catalyzed cyclic anti‐nucleometallation–carboxylation of 2‐alkynylanilines with carbon dioxide in the presence of dimethylzinc (ZnMe₂) and cesium fluoride (CsF) for the effective synthesis of indolyl‐3‐carboxylic acids and indolodihydropyran‐2‐one is described. Through a mechanistic study, it is unveiled that the metal ions Cu²⁺, Zn²⁺, Cs⁺ and F⁻ are working together for this CO₂‐based highly efficient carboxylation.     

A Single‐Phase Phosphor NaLa9 (GeO4)6O2: Tm3+, Dy3+ for Near Ultraviolet‐White LED and Field‐Emission Display

Single‐phase white‐light‐emitting phosphors NaLa_9(1?x?y) (GeO₄)₆O₂: xTm³⁺, yDy³⁺ (NLGO: xTm³⁺, yDy³⁺) have been synthesized by a traditional solid‐state reaction method. The powder X‐ray diffraction (XRD), photoluminescence (PL), PL excitation (PLE) spectra, fluorescence decay curves, chromaticity coordinates, correlated color temperature (CCT), and the cathodoluminescence (CL) properties of the obtained phosphors are measured and discussed in detail. It is discovered that the series samples could be color‐tunable (from blue to yellow) by tuning the doping content of Dy³⁺ with a fixed Tm³⁺ content excited at 357 nm and white light (0.341, 0.324) could be obtained with the CCT of 5079 K. A NLGO: 0.01Tm³⁺, 0.02Dy³⁺ is studied carefully as representative. The main emissions of Tm³⁺ (453 nm, ¹D₂–³F₄) and Dy³⁺ (478 nm, ⁴F_9/2–⁶H_15/2; 572 nm, ⁴F_9/2–⁶H_13/2) make it emit white light with good thermal stability (67% of the initial till 523 K). The energy transfer from Tm³⁺ to Dy³⁺ is noticed and further research has been done to explain the enhancement of Dy³⁺ emission and the excellent thermal stability. It also keeps stable under continuous electron bombardment with high intensity. All of these indicate that it could be a suitable candidate for white‐emitting phosphor applied for near ultraviolet‐white light‐emitting diode (NUV‐WLED) and field‐emission display (FED).     

Synthesis,Characterization, and swelling behaviors of acrylic acid/carboxymethyl cellulose superabsorbent hydrogel by glow‐discharge electrolysis plasma

This article exploits a new approach for synthesis of acrylic acid/carboxymethyl cellulose (AA/CMC) superabsorbent hydrogel in aqueous solution by a simple one‐step using glow‐discharge electrolysis plasma, in which N,N′‐methylenebisacrylamide (MBA) was used as a crosslinking agent. The reaction parameters affecting the equilibrium swelling, that is, discharge voltage, discharge time, mass ratio of AA to CMC, content of crosslinker, and degree of neutralization, were systematically optimized to achieve a superabsorbent hydrogel with a maximum equilibrium swelling. The structure, thermal stability, and morphology of AA/CMC superabsorbent hydrogel were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction analysis, thermogravimetric analysis, and scanning electron microscopy. The swelling kinetics in distilled water and swelling behaviors in various pH solutions and salts solutions (NaCl, KCl, MgCl₂, CaCl₂, AlCl₃, and FeCl₃) were investigated in detail. The effect of six cationic salt solutions on the equilibrium swelling had the following order K⁺ > Na⁺ > Mg²⁺ > Ca²⁺ > Al³⁺ > Fe³⁺. In addition, the pH‐reversibility was preliminarily investigated with alternating pH between 6.5 and 2.0. The results showed that the equilibrium swelling of AA/CMC was achieved in 90 min. The hydrogel was responsive to the pH and salts, and was reversible swelling and deswelling behavior. POLYM. ENG. SCI., 54:2310–2320, 2014. © 2013 Society of Plastics Engineers     

Significantly Enhanced Infrared Emissivity of LaAlO3 by Co‐Doping with Ca2+ and Cr3+ for Energy‐Saving Applications

In this study, Ca²⁺–Cr³⁺ co‐doped LaAlO₃, a novel energy‐saving material with significantly enhanced infrared emissivity, was synthesized by solid‐state reaction. The experimental results demonstrated that 20 mol% Ca²⁺ and 10 mol% Cr³⁺‐doped LaAlO₃, namely La_0.8Ca_0.2Al_0.9Cr_0.1O₃, had an infrared emissivity as high as 0.92 in the spectral region of 1–5 μm, which was 12 times higher than that of pure LaAlO₃. The first‐principles electronic structure calculations revealed that the Ca²⁺–Cr³⁺ co‐doping results in the occurrence of impurity energy levels in the forbidden band of LaAlO₃, which were mainly composed of the Cr 3d orbitals. Electrons partly occupied these impurity donor states and significantly reduced the energy bandgap, thus the infrared radiation property of LaAlO₃ was enhanced. This novel material with high infrared emissivity shows promising applications for energy‐saving in the field of thermal process equipment.