Determination of complex dielectric function of CH3NH3PbBr3 perovskite cubic colloidal quantum dots by modified iterative matrix inversion method.

Recent advances in lead halide perovskite quantum dots appeal with their potential in various optoelectronic devices such as photovoltaics, photodetectors, light-emitting diodes (LEDs) and lasers. However, lack of information on the intrinsic optical properties of lead halide perovskite quantum dots (QDs) lags the progress in device performances and further development in various applications. In this letter, the complex dielectric function of CH3NH3PbBr3 perovskite cubic colloidal QDs was determined from the UV-Vis absorption by using a modified iterative matrix inversion (IMI) method. The modified IMI method takes into account the dilute solution with cubic inclusions, while the conventional method only considers spherical or elliptical inclusions by Maxwell-Garnett (MG) effective medium theory. In addition, singly subtractive Kramer Kronig (SSKK) relations have also been considered to compensate for possible errors arising from the finite wavelength range of the experimental absorption data.

Room-Temperature Synthesis of Hollow Polymer Microparticles with an Open Hole on the Surface and Their Application.

Compared with hollow microparticles with a completely closed shell structure, hollow polymer microparticles with an open hole on their surface have attracted considerable attention because of the obvious importance of the open hole on their surface; however, the development of a facile method to synthesize such unique open-ended hollow particles has remained a great challenge. In this study, an easy-to-use method was developed to rapidly produce monodispersed hollow and pored microparticles in high reaction yield at room temperature. The key to achieving the unusually shaped polystyrene (PS) microparticles was the use of anisotropic PS seeds. When hollow and dimpled PS seeds prepared using a modified dispersion polymerization method were dispersed in a water-toluene mixture followed by solvent evaporation under ambient conditions, they transformed into hollow PS microparticles with an open hole on their surface. A plausible mechanism for the transformation of the PS microparticles during the swelling and drying processes was proposed on the basis of our results and observations. The structural features of the hollow and pored PS microparticles motivated us to use the particles as a catalyst support. By using modified heterophase polymer dispersion processing involving the addition of a Ag precursor, hollow and pored PS microparticles covered with Ag nanocrystals were obtained on the basis of the in situ reduction of metal precursor on the surface of polymer particles. The resulting Ag nanocrystals/PS hybrid microparticles exhibited enhanced catalytic activity at low concentrations of nanocrystals and could be reused several times without loss of activity when used as catalysts for the reduction of 4-nitrophenol to 4-aminophenol with sodium borohydride.

Fluorescent Molecular Rotors for Viscosity Sensors.

Fluorescent molecular rotors (FMRs) can act as viscosity sensors in various media including subcellular organelles and microfluidic channels. In FMRs, the rotation of rotators connected to a fluorescent π-conjugated bridge is suppressed by increasing environmental viscosity, resulting in increasing fluorescence (FL) intensity. In this minireview, we describe recently developed FMRs including push-pull type π-conjugated chromophores, meso-phenyl (borondipyrromethene) (BODIPY) derivatives, dioxaborine derivatives, cyanine derivatives, and porphyrin derivatives whose FL mechanism is viscosity-responsive. In addition, FMR design strategies for addressing various issues (e.g., obtaining high FL contrast, internal FL references, and FL intensity-contrast trade-off) and their biological and microfluidic applications are also discussed.

Biological Properties of Fucoxanthin in Oil Recovered from Two Brown Seaweeds Using Supercritical CO2 Extraction.

The bioactive materials in brown seaweeds hold great interest for developing new drugs and healthy foods. The oil content in brown seaweeds (Saccharina japonica and Sargassum horneri) was extracted by using environmentally friendly supercritical CO2 (SC-CO2) with ethanol as a co-solvent in a semi-batch flow extraction process and compared the results with a conventional extraction process using hexane, ethanol, and acetone mixed with methanol (1:1, v/v). The SC-CO2 method was used at a temperature of 45 °C and pressure of 250 bar. The flow rate of CO2 (27 g/min) was constant for the entire extraction period of 2 h. The obtained oil from the brown seaweeds was analyzed to determine their valuable compounds such as fatty acids, phenolic compounds, fucoxanthin and biological properties including antioxidant, antimicrobial, and antihypertension effects. The amounts of fucoxanthin extracted from the SC-CO2 oils of S. japonica and S. horneri were 0.41 ± 0.05 and 0.77 ± 0.07 mg/g, respectively. High antihypertensive activity was detected when using mixed acetone and methanol, whereas the phenolic content and antioxidant property were higher in the oil extracted by SC-CO2. The acetone-methanol mix extracts exhibited better antimicrobial activities than those obtained by other means. Thus, the SC-CO2 extraction process appears to be a good method for obtaining valuable compounds from both brown seaweeds, and showed stronger biological activity than that obtained by the conventional extraction process.

The inhibitory activities of the edible green alga Capsosiphon fulvescens on rat lens aldose reductase and advanced glycation end products formation.

PURPOSE: Accumulating evidence suggests that inhibitors of aldose reductase (AR) may prevent hyperglycemia-induced long-term complications in diabetes mellitus. In the present study, we evaluated the AR inhibitory potential of ethanolic (EtOH) extracts from 22 seaweed species. METHODS: AR inhibitory activities of the selected seaweed species were evaluated using the rat lens aldose reductase (RLAR) inhibitory assay. RESULTS: All extracts exhibited RLAR inhibitory activity, which ranged from 5.87 to 92.71 % at a concentration of 50 µg/mL. Since Capsosiphon fulvescens exhibited significant inhibitory potential and is a frequently used foodstuff, it was selected for a detailed investigation using RLAR and advanced glycation end products (AGE) formation inhibitory assays. Among the different solvent-soluble fractions, the CH2Cl2, EtOAc, and n-BuOH fractions showed promising RLAR and AGE formation inhibitory activities. Considering the AR inhibitory potential, CH2Cl2 and EtOAc fractions were selected for chromatographic separation and yielded 11 compounds in which capsofulvesin A, capsofulvesin B, and chalinasterol showed potential RLAR inhibitory activity with the respective IC50 values of 52.53, 101.92, and 345.27 µM. Kinetic studies revealed that capsofulvesin A and chalinasterol exhibited mixed type inhibition, while capsofulvesin B exhibited noncompetitive inhibition. To our knowledge, this is the first report of AR inhibitory activity of the glycolipids capsofulvesin A and capsofulvesin B. CONCLUSIONS: Our results clearly indicate the potential RLAR and AGE formation inhibitory activities of C. fulvescens as well as its isolated constituents, which could be further explored to develop therapeutic modalities for the treatment of diabetes and related complications.

Optimal production of 4-deoxy-L-erythro-5-hexoseulose uronic acid from alginate for brown macro algae saccharification by combining endo- and exo-type alginate lyases.

Algae are considered as third-generation biomass, and alginate is the main component of brown macroalgae. Alginate can be enzymatically depolymerized by alginate lyases into uronate monomers, such as mannuronic acid and guluronic acid, which are further nonenzymatically converted to 4-deoxy-L-erythro-5-hexoseulose uronic acid (DEH). We have optimized an enzymatic saccharification process using two recombinant alginate lyases, endo-type Alg7D and exo-type Alg17C, for the efficient production of DEH from alginate. When comparing the sequential and simultaneous additions of Alg7D and Alg17C, it was found that the final yield of DEH was significantly higher when the enzymes were added sequentially. The progress of saccharification reactions and production of DEH were verified by thin layer chromatography and gas chromatography-mass spectrometry, respectively. Our results showed that the two recombinant enzymes could be exploited for the efficient production of DEH that is the key substrate for producing biofuels from brown macro algal biomass.

Hexane fraction from Laminaria japonica exerts anti-inflammatory effects on lipopolysaccharide-stimulated RAW 264.7 macrophages via inhibiting NF-kappaB pathway.

PURPOSE: Laminaria japonica is a representative marine brown alga used as a culinary item in East Asia. L. japonica extract was shown to exert various biological activities; however, its anti-inflammatory activity has not been reported. The aim of this study is to investigate the molecular mechanisms underlying its anti-inflammatory action. METHODS: Anti-inflammatory mechanisms of L. japonica n-hexane fraction (LHF) were assessed using lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. An anti-inflammatory compound isolated from LHF by reverse-phase chromatography was identified using nuclear magnetic resonance (NMR) spectroscopy. RESULTS: Our results indicate that LHF significantly inhibited LPS-stimulated nitric oxide (NO) and prostaglandin E(2) (PGE(2)) secretion in a dose-dependent manner and suppressed the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) with no cytotoxicity. As results, levels of pro-inflammatory cytokines were significantly reduced by pretreatment of LHF in LPS-stimulated RAW 264.7 cells. Treatment of LHF strongly suppressed nuclear factor-κB (NF-κB) promoter-driven expression and nuclear translocation of NF-κB by preventing proteolytic degradation of inhibitor of κB (IκB)-α in LPS-stimulated RAW 264.7 cells. Moreover, LHF inhibited the phosphorylation of Akt and mitogen-activated protein kinase (MAPK) in LPS-stimulated RAW 264.7 cells. One of the anti-inflammatory compounds was isolated from LHF and identified as fucoxanthin. CONCLUSIONS: These results indicate that the LHF-mediated inhibition of NO and PGE(2) secretion in LPS-stimulated macrophages is regulated by NF-κB inactivation through inhibition of IκB-α, MAPKs, and Akt phosphorylation. LHF may be considered as a functional food candidate for the prevention or treatment of inflammatory diseases.

Depolymerization of alginate into a monomeric sugar acid using Alg17C, an exo-oligoalginate lyase cloned from Saccharophagus degradans 2-40.

Macroalgae are considered to be promising biomass for fuels and chemicals production. To utilize brown macroalgae as biomass, the degradation of alginate, which is the main carbohydrate of brown macroalgae, into monomeric units is a critical prerequisite step. Saccharophagus degradans 2-40 is capable of degrading more than ten different polysaccharides including alginate, and its genome sequence demonstrated that this bacterium contains several putative alginate lyase genes including alg17C. The gene for Alg17C, which is classified into the PL-17 family, was cloned and overexpressed in Escherichia coli. The recombinant Alg17C was found to preferentially act on oligoalginates with degrees of polymerization higher than 2 to produce the alginate monomer, 4-deoxy-L: -erythro-5-hexoseulose uronic acid. The optimal pH and temperature for Alg17C were found to be 6 and 40 °C, respectively. The K (M) and V (max) of Alg17C were 35.2 mg/ml and 41.7 U/mg, respectively. Based on the results of this study, Alg17C could be used as the key enzyme to produce alginate monomers in the process of utilizing alginate for biofuels and chemicals production.

Characterization of a recombinant endo-type alginate lyase (Alg7D) from Saccharophagus degradans.

A gene, alg7D, from Saccharophagus degradans, coding for a putative alginate lyase belonging to the family of polysaccharide lyase-7, was overexpressed in Escherichia coli. The properties of the recombinant Alg7D were characterized. The enzyme endolytically depolymerized alginate by ß-elimination into oligo-alginates with degrees of polymerization of 2-5. Its activity was maximal at 50°C and pH 7 and was slightly increased in the presence of Na(+). The K(M), V(max), k(cat), and k(cat)/K(M) values were: 3 mg ml(-1), 6.2 U mg(-1), 1.9 × 10(-2) s(-1), and 6.3 × 10(-3) mg(-1 )ml s(-1), respectively.

Characterization of alginate lyase gene using a metagenomic library constructed from the gut microflora of abalone.

A metagenomic fosmid library was constructed using a genomic DNA mixture extracted from the gut microflora of abalone. The library gave an alginate lyase positive clone (AlyDW) harboring a 31.7-kbp insert. The AlyDW insert consisted of 22 open reading frames (ORFs). The deduced amino acid sequences of ORFs 11-13 were similar to those of known alginate lyase genes, which are found adjacent in the genome of Klebsiella pneumoniae subsp. aerogenes, Vibrio splendidus, and Vibrio sp. belonging to the phylum Gammaproteobacteria. Among the three recombinant proteins expressed from the three ORFs, alginate lyase activity was only observed in the recombinant protein (AlyDW11) coded by ORF 11. The expressed protein (AlyDW11) had the highest alginate lyase activity at pH 7.0 and 45°C in the presence of 1 mM AgNO(3). The alginate lyase activity of ORF 11 was confirmed to be endolytic by thin-layer chromatography. AlyDW11 preferred poly(ß-D: -mannuronate) as a substrate over poly(α-L: -guluronate). AlyDW11 contained three highly conserved regions, RSEL, QIH, and YFKAGVYNQ, which may act to stabilize the three-dimensional conformation and function of the alginate lyase.

Energy-efficient recovery of fermented butyric acid using octyl acetate extraction.

BACKGROUND: A butyric acid recovery process using octyl acetate is proposed, and the design details of the extraction and subsequent distillation processes were investigated. Ternary equilibrium data for the extractor design were derived from molecular simulations and experimental measurements. RESULTS: A new procedure for estimating the thermodynamic parameters was introduced to determine the effect of the parameters on extractor design by comparison with previously reported parameters. Using the proposed recovery process with the newly estimated thermodynamic model, 99.8% butyric acid was recovered from the fermentation broth at a recovery rate of 99%. The energy demand for the proposed process was found to be lower than the average demand for several reported butyric acid recovery processes. CONCLUSIONS: The investment cost is projected to be lower than that of other butyric acid processes due to the high efficiency of extraction solvent. The recovery cost of butyric acid was comparable to its selling price.

One-step green synthesis of 2D Ag-dendrite-embedded biopolymer hydrogel beads as a catalytic reactor.

Silver (Ag) nanocrystals with a dendritic structure have attracted intensive attention because of their unique structural properties, which include abundant sharp corners and edges that provide a large number of active atoms. However, the synthesis of Ag dendrites via a simple and environmentally friendly method under ambient conditions remains a challenge. In this paper, we report a simple water-based green method for the production of biopolymer hydrogel beads embedded with Ag dendrites without using an additional reducing agent, stabilizer, or crosslinking agent. The obtained Ag dendrites exhibit a unique two-dimensional (2D) structure rather than a conventional three-dimensional structure because Ag+ ions are reduced on the surface of the solid-phase hydrogel beads and grow into crystals. Reasonable mechanisms explaining the formation of the nanocomposite hydrogel beads and the formation of 2D Ag dendrites in the hydrogel are proposed on the basis of our observations and results. The hydrogel beads embedded the 2D Ag dendrites were used as an environmentally friendly catalytic reactor, and their catalytic performance was evaluated by adopting the reduction of 4-nitrophenol to 4-aminophenol with NaBH4 as a model reaction.

Completely green synthesis of rose-shaped Au nanostructures and their catalytic applications.

The importance of and demand for eco-friendly syntheses of metal nanocrystals are increasing. In this study, a novel protocol for the one-pot, template/seed-free, and completely green synthesis of rose-shaped Au nanostructures with unique three-dimensional hierarchical structures was developed. The synthesis of the nanostructures was carried out at room temperature using water as a reaction medium and an eco-friendly biopolymer (sodium salt of alginic acid (Na-alginate)) as a reducing agent. The morphologies of the Au nanostructures were controlled by adjusting the amount of capping ligand (polyvinylpyrrolidone (PVP)) in the reaction mixture, and a limited ligand protection (LLP) strategy was used to induce the formation of rose-shaped Au nanostructures. A formation mechanism for the rose-shaped Au nanostructures was proposed on the basis of structural characterizations and the shape evolution of the nanostructures. The unique structural features of the rose-shaped nanostructures, which include a high surface roughness, a large surface area-to-volume ratio, and abundant edges and sharp tips, motivated us to use them as a high-performance catalyst. They were used as an environmentally benign catalyst in an organic reaction to remove a hazardous chemical from an aqueous medium: specifically, the hydrogenation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by sodium borohydride. Without an additional supporting material, the rose-shaped Au nanostructures showed outstanding catalytic activity that was maintained when the catalyst was recycled and used a total of five times.

Solid-phase colorimetric sensing probe for bromide based on a tough hydrogel embedded with silver nanoprisms.

Sharp-tipped anisotropic silver (Ag) nanostructures are attracting increasing attention because of their unusual optical properties. However, the sharp tips make such nanostructures thermodynamically unstable; thus, they have been considered unsuitable for use in colorimetric sensing because of their tendency to aggregate or transform in a solution state. In the present study, a colorimetric sensing platform for detecting bromide (Br-) in an aqueous medium was developed. The platform is based on the localized surface plasmon resonance (LSPR) properties of Ag nanoprisms with sharp tips. The key to using such Ag nanocrystals with extreme anisotropic structures is to adopt a solid-phase sensing platform. A Ag-nanoprism-embedded tough hydrogel with interpenetrating polymer networks was synthesized via aqueous-phase polymerization and crosslinking processes. The Ag nanoprisms immobilized inside the hydrogel were stable and did not exhibit aggregation or degradation over time; specifically, when the hydrogel was dried, the nanoprisms retained their inherent LSPR properties for an extended period. By taking advantage of the rapid and spontaneous morphological transformation of Ag nanoprisms inside the hybrid hydrogel exposed to Br- and the corresponding changes in their LSPR properties, we designed a plasmonic sensing platform for the sensitive and selective detection of Br- in an aqueous medium. The proposed colorimetric sensing platform was found to exhibit a wide sensing range and high selectivity, with a low limit of detection (LOD) of 10 µM, and offers substantial advantages over previously developed systems; specifically, it is portable, eco-friendly, safe to use and handle, stable for extended periods, and enables naked-eye detection. We believe that the as-proposed sensing platform can be used as a point-of-care analytical tool for detecting Br- in a broad range of samples.

Eco-efficient recovery of bio-based volatile C2-6 fatty acids.

BACKGROUND: Volatile fatty acids (VFAs) are produced by fermentation of various bio-sources and human wastes at minimal cost; sometimes, even sources having a prepaid processing fee were used. However, low concentrations of VFAs in water have prevented their commercial production, even with modern separation technologies, due to the high operating costs. We have applied newly developed solvents, selected by chemical structure similarity, to the separation of five different VFAs. RESULTS: Since most of the water was separated by extraction using hexyl acetate and nonyl acetate, the utilities necessary for solvent recovery and product purification were a fraction of those required by the existing VFAs' separation processes. The solvents separated almost all the water in the feed at the extraction stage, consuming no energy. The energy use in this study is only 34% of the lowest case use among various processes of either distillation-only or combined extraction-distillation. CONCLUSIONS: The performance evaluation of the proposed VFAs separation process showed that product recovery was 99% and acid purity was 99.5% with eco-scores of 70% lower than those of the current processes.

Realizing a highly luminescent perovskite thin film by controlling the grain size and crystallinity through solvent vapour annealing.

Organometallic halide perovskite films were treated with novel facile solvent vapour annealing to control crystal grain size as well as the crystallinity of perovskite. As both polarity and vapour pressure of the treatment solvent for perovskite increase, luminance increases and the wavelength of the photoluminescence emission peak decreases due to enhanced crystallinity and reduced grain size.

Reshaping of triangular silver nanoplates by a non-halide etchant and its application in melamine sensing.

Although triangular silver (Ag) nanoplates are intrinsically unstable, this characteristic has been taken advantage of in the development of a novel sensing platform. However, most of these applications have relied on halide ions as etchants. In the current work, we used sodium 4-vinylbenzenesulfonate (Na-VBS) as a new powerful etchant of triangular silver (Ag) nanoplates. When aged with Na-VBS at room temperature, Na-VBS etched Ag nanoplates nearly as powerfully as halides did, and these nanoplates rapidly transformed into oblate nanospheroids. This shape evolution permitted tuning of the corresponding localized surface plasmon resonance (LSPR) features of the Ag nanostructures. Interestingly, passivation of the Ag nanoplate surface with melamine was shown to protect the nanoplates from Na-VBS-induced etching. The rate of change of the color and spectral features of the Ag nanoplate solution exposed to Na-VBS was found to be strongly correlated with the concentration of melamine in the solution. This association allowed us to apply this system to the development of a novel platform for sensing melamine.

Correction: Investigation of high contrast and reversible luminescence thermochromism of the quantum confined Cs4PbBr6 perovskite solid.

Correction for 'Investigation of high contrast and reversible luminescence thermochromism of the quantum confined Cs4PbBr6 perovskite solid' by Jong H. Kim et al., Nanoscale, 2019, DOI: 10.1039/c8nr10223f.

Investigation of high contrast and reversible luminescence thermochromism of the quantum confined Cs4PbBr6 perovskite solid.

Thermochromism of organic/inorganic halide perovskites has attracted particular interest due to their potential applications as photoluminescence (PL)-based temperature sensors. However, despite the outstanding PL characteristics, their use as a thermochromic material in practical temperature ranges has been limited because of their poor thermal stability. In this study, we used the quantum confinement effect and exceptional PL quantum efficiency of the Cs4PbBr6 perovskite to demonstrate their high on/off ratio (20) and reversible PL thermochromism in the solid state in practical temperature ranges including room temperature (RT). Systematic photophysical and optical characterization studies, including exciton-phonon scattering, exciton binding energy, exciton decay dynamics, and crystal structure change, were performed to investigate the origin of this unique thermochromic PL property. The results showed that the efficient and highly reversible thermochromic PL emission of the Cs4PbBr6 perovskite is due to its desirable optical properties such as highly luminescent emission, efficient PL quenching at high temperatures, and thermally reversible structural changes.

Ultrasound-mediated fucoxanthin rich oil nanoemulsions stabilized by κ-carrageenan: Process optimization, bio-accessibility and cytotoxicity.

This work aims to produce and optimize a κ-carrageenan-based nanoemulsion (NE) to encapsulate seaweed oil, which is rich in fucoxanthin (FX), using ultrasound-assisted emulsification. κ-Carrageenan was produced using subcritical water, and seaweed oil was extracted using supercritical carbon dioxide with sunflower oil as the co-solvent. Response surface methodology (RSM) was used to understand the influence of several process parameters such as ultrasound amplitude, time, temperature, and duty cycle to produce an NE. The RSM factor was used to focus on droplet size, polydispersity index, zeta potential, viscosity, antioxidant, FX, encapsulation efficiency, and emulsion stability. Our outcomes suggested that the ultrasound process had a noteworthy influence on the NE. The best conditions to obtain an NE were an ultrasound amplitude of 87 µm, a sonication time of 394 s, a temperature of 60 °C, and a duty cycle of 50%. The resulting NE was studied by UV-Vis, Fourier-transform infrared spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, scanning electron microscopy, atomic force microscopy, and X-ray diffraction. Moreover, the NE obtained from optimized conditions was checked for fatty acid content, color, oxidative stability, in vitro digestion, bioaccessibility of FX, and cytotoxicity. The results obtained suggest that lower droplet size of the emulsion can improve oxidative stability, in vitro digestion, bioaccessibility of FX, and good cell inhibition against a few cell lines. Therefore, a κ-carrageenan-stabilized NE can be used as a potential delivery system to endorse applications of seaweed oil, which is rich in FX, in functional foods, beverage systems, and pharmaceuticals.