Supercritical fluid extracts with antioxidant and antimicrobial activities from myrtle (Myrtus communis L.) leaves. Response surface optimization

Supercritical Fluid Extraction (SFE) was used to obtain myrtle leaf extracts, and to study the antioxidant capacity (AOC) and in vitro antimicrobial activity of those extracts. To optimize the SFE operational conditions, the response surface methodology (RSM) was adopted. The parameters studied were: pressure (P), within the range 10 to 30 MPa; temperature (T), between 35 °C and 60 °C and supercritical carbon dioxide (SCCO₂) flow rate (Q) within the range 0.15 to 0.45 kg h⁻¹. The results show a good fit to the proposed model and the optimal conditions obtained (23 MPa, 45 °C, and SCCO₂ flow rate of 0.3 kg h⁻¹) were within the experimental range. The predicted values agreed with experimental ones, thus indicating the suitability of the RSM model for the optimization of the extraction conditions being investigated. With those values remaining constant, ethanol as a co-solvent was then studied. There was an observed rise in AOC as the amount of ethanol increased, within the range studied (0–30 wt% ethanol). The extract with the highest AOC was tested for its antimicrobial activity against gram-positive and gram-negative bacteria. The minimum inhibitory concentration (MIC) values obtained showed significant inhibitory effect against gram-positive bacteria.     

Synthesis and investigation of TiO2 nanotube arrays prepared by anodization and their photocatalytic activity

TiO₂ nanotube arrays were successfully prepared by anodic oxidation method in the electrolyte of ethylene glycol and deionized water mixed in 9:1 volumetric ration including 0.5 wt.% NH₄F. The microstructure and phase compositions of samples annealing from 0 °C to 800 °C were characterized by field-emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). FESEM showed that the obtained nanotubes with diameter 80–100 nm and length 4.89 μm were highly ordered and perpendicular to Ti substrate. The tubular structure collapsed at 680 °C. The photocatalytic activity of samples annealing at different temperature were calculated by the degradation of a model dye, methyl orange (MO), under UV light illumination. The results indicated the phase composition and the morphology of TiO₂ nanotubes both played an important role in the degradation of MO. In addition, the effects of initial solution pH and dye concentration on degradation of MO had also been investigated. As a result, the optimum values of calcination temperature, initial solution pH and dye concentration were found to be 550 °C, 3, 10 mg/l, respectively. The best photodegradation of MO was 76% under illumination for 3 h.     

Use of bulk liquid membrane for the removal of Cibacron Red FN-R from aqueous solution using TBAB as a carrier

The transport of Cibacron Red FN-R anionic dye through a methylene chloride bulk liquid membrane (BLM) containing a tetra butyl ammonium bromide (TBAB) as an excellent carrier was studied. The extracted dye simultaneously stripped into aqueous stripping solution. The basic fundamental parameters were determined. These include pH of the feed, nitric acid concentration in the strip solution, TBAB concentration in the membrane phase, initial dye concentration in the feed phase and rate of stirring. The transport efficiency of dye increased with increasing carrier concentration from 6.06 ± 0.1 × 10^?6 to 3.85 ± 0.1 × 10^?4 M. The transport study was highly selective for anionic dye and efficiency of transport was not affected by the presence of electrolytes such as sodium chloride and sodium sulphates in feed solution. The percentage of dye transported across the liquid membrane after 70 min, was 95 ± 0.1%. When the optimum parameters were used for real textile dyeing effluent for recovery of dyes, the results were found to be satisfactory.     

Control of refractive index by annealing to achieve high figure of merit for TiO2/Ag/TiO2 multilayer films

We modified the refractive index (n) of TiO₂ by annealing at various temperatures to obtain a high figure of merit (FOM) for TiO₂/Ag/TiO₂ (45 nm/17 nm/45 nm) multilayer films deposited on glass substrates. Unlike the as-deposited and 300 °C-annealed TiO₂ films, the 600 °C-annealed sample was crystallized in the anatase phase. The as-deposited TiO₂/Ag/as-deposited TiO₂ multilayer film exhibited a transmittance of 94.6% at 550 nm, whereas that of the as-deposited TiO₂/Ag/600 °C-annealed TiO₂ (lower) multilayer film was 96.6%. At 550 nm, n increased from 2.293 to 2.336 with increasing temperature. The carrier concentration, mobility, and sheet resistance varied with increasing annealing temperature. The samples exhibited smooth surfaces with a root-mean-square roughness of 0.37–1.09 nm. The 600 °C-annealed multilayer yielded the highest Haacke's FOM of 193.9×10⁻³ Ω⁻¹.     

Facile corrosion synthesis and sintering of disperse pure tetragonal zirconia nanoparticles

Disperse pure tetragonal zirconia (t-ZrO₂) nanoparticles smaller than 10 nm are essential for preparation of structural and functional zirconia materials, but syntheses of t-ZrO₂ nanoparticles using inorganic zirconium salts usually result in severe agglomeration. In this paper, we report a hydrothermal corrosion approach for improving the dispersity of t-ZrO₂ nanoparticles synthesized by precipitation using zirconium oxychloride without any surfactants. Disperse pure t-ZrO₂ nanoparticles with average sizes of 4.5 and 6 nm and size distributions of 2–11 and 3–12 nm were obtained by calcining precipitates at 400 °C for 2 h and 500 °C for 0.5 h followed by HCl corrosion at 120 °C for 75 h, respectively. Disperse t-ZrO₂ nanoparticles with an average size of 6 nm and a size distribution of 3–12 nm were pressed into green compacts at 500 MPa and sintered by two-step sintering (heating to 1150 °C without hold and decreasing to 1000 °C with a 10 h hold). The sintered bodies are dense pure monoclinic ZrO₂ nanocrystalline ceramic with a relative density of 99.9% and an average grain size of 110 nm.     

Formulation optimization of dihydroartemisinin nanostructured lipid carrier using response surface methodology

Response surface methodology (RSM) using the central composite rotatable design (CCRD) model was used to optimize formulations of dihydroartemisinin nanostructured lipid carrier (DHA–NLC). The CCRD consisting of three-factored factorial design with three levels was used in this study. The drug encapsulation efficiency (EE), drug loading (DL) percentage and particle size of DHA–NLC were investigated with respect to three independent variables including DHA concentration (X₁), lipid concentration (X₂) and ratio of liquid lipid to total lipid (X₃). The result showed that the optimal formulation could be obtained from this response surface methodology. The optimal formulation for DHA–NLC was composed of DHA concentration (X₁) of 1 g/l, lipid concentration (X₂) of 1% and ratio of liquid lipid to total lipid (X₃) of 0.1:1. DHA–NLC under the optimized conditions gave rise to the EE of (98.97 ± 2.3) %, DL of (15.61 ± 1.9) %, mean diameter of (198 ± 4.7) nm, polydispersity index (PI) of 0.146 and zeta potential value of (? 21.6 ± 1.3) mV. TEM of the optimized NLC showed spherical particles. The in vitro experiments proved that DHA in the NLC released gradually over the period of 48 h. This study showed that the RSM–CCRD could efficiently be applied for the modeling of DHA–NLC.     

Copper(I) oxide and metallic copper particles formed in 1,2-propane diol

Chemical composition, particle size, and structure formation of colloidal Cu₂O and metallic Cu synthesized from Cu(II) acetate in an environmentally friendly 1,2-propane diol were studied dependent on the temperature and concentration of the precursor. Cu₂O as a reaction intermediate is formed between 150 and 170 °C, while its reduction to metallic Cu occurs between 170 and 180 °C. Average particle sizes of non-agglomerated Cu powders varied from 100 nm to 1 μm.     

Statistical evaluation of a liquid desiccant dehumidification system using RSM and theoretical study based on the effectiveness NTU model

In the present study the performance of an air dehumidifier using lithium bromide (LiBr) as a desiccant was investigated. Response surface methodology (RSM) was used to assess individual and interactive effects of the six main factors (velocity, temperature and humidity of air, flow rate, temperature and concentration of desiccant) on dehumidification mass rate. A reduced quadratic statistical model was derived to predict dehumidification mass rate. The maximum dehumidification mass rate was obtained 0.154 g/s under the optimal conditions of an air velocity of 4.1 m/s, desiccant flow rate of 0.035 kg/s, air humidity ratio of 0.0185 kg/kg, desiccant concentration of 0.48 kg/kg, air temperature of 29.5 °C, and desiccant temperature of 21.8 °C. The effectiveness number of transfer unit (NTU) model was employed to describe the coupled heat and mass transfer. The results of the model and the experimental data show good agreement. Dimensionless mass and heat transfer coefficients correlations are proposed; the average absolute differences between the predicted values and the experimental findings for Sh and Nu numbers were calculated as 2.14% and 5.27%, with the discrepancies mainly within ±9% and ±13%, respectively.     

Ball milling assisted hydrothermal synthesis of ZrO2 nanopowders

The formation of ZrO₂ nanopowders under various hydrothermal conditions such as temperature, time, autoclave rotation speed, heating rate and particularly assistance of ball milling during reaction was investigated. Full ZrO₂ formation (with monoclinic phase) from zirconium solution was completed at shorter times with increasing temperature such as after 4 h at 150 °C, 2 h at 175 °C and less than 2 h at 200 °C. Crystallite size increased from 2.9 to 4 nm with increasing reaction temperature from 125 °C to 200 °C, respectively. Ball milling assisted hydrothermal runs were performed to understand the effect of mechanical force on phase formation, crystallinity and particle size distribution. Monoclinic ZrO₂ was formed in both milled and non-milled runs when zirconium solution was used. Mean particle size for the 2 M solution was measured to be 94 nm for the milled and 117 nm for the non-milled powders. However, when amorphous aqueous zirconia gels (precipitated at pH 5.8) were used, tetragonal phase was also formed in addition to monoclinic phase. Mean particle size was measured to be 0.7 μm (d₉₀≅1.3 μm) for the milled and 7.9 μm (d₉₀≅13 μm) for the non-milled powders. Ball milling during hydrothermal reactions of both zirconium solution and aqueous zirconium gel resulted in smaller crystallite size and mean particle size and, at the same time, effectively controlled particle size distribution (or agglomeration) of nanopowders.     

Colour removal of three reactive dyes by UV light exposure after electrochemical treatment

This study applies UV light irradiation after a low current density electrochemical treatment to degrade reactive dyes to remove wastewater colour. The combination of these two techniques improves the quality of the treated effluent with respect to only an electrochemical treatment. Synthetic dyeing effluents containing a reactive dye (C.I. Reactive Orange 4, C.I. Reactive Black 5 or Procion Navy H-EXL) and Na₂SO₄ were studied. Ti/Pt oxides electrodes and UV irradiation lamp (6 W, 254 nm maximum emission) were used. Kinetic constants of the UV irradiation step were calculated. The influence of chloride ion at 3 and 6 mA/cm² was evaluated. Results showed that, with a very small Cl^? concentration (in the order of the net water content) the combined techniques provided full decolourization. The possible presence of 25 organic halogenated compounds was studied by gas chromatography–mass spectrophotometry (GCMS). Only four of them were detected after the electrochemical treatment at low intensity, mainly chloroform. Its concentration was found to be highly dependent of the Cl^? concentration, being much lower when reducing the amount of chloride ion. In all cases, the chloroform concentration was dramatically reduced by further UV irradiation which destroyed it up to a 75%.     

Incorporation of dye into conducting polyaniline nanoparticles

Synthesis of polyaniline (PANi) nanodispersions with and without the presence of a reactive dye has been performed via micellar chemical oxidative polymerisation using dodecylbenzene sulfonic acid (DBSA) as the dispersant. The dye used was a textile reactive dye (Carbolan Blue – CB) which was chosen due to it’s structural similarity to DBSA. The polymers formed were PANi · DBSA and PANi · DBSA · CB. The inclusion of the CB dye appeared to facilitate the polymerisation process as observed from open circuit potential measurements during polymerisation. Using transmission electron microscopy, PANi · DBSA · CB was shown to have an average particle size larger than that observed for PANi · DBSA. The CB dye was shown to be incorporated into the polymer by Raman spectroscopy. The CB containing polymer was amenable to protonation/deprotonation as well as redox switching.     

Catalytic potential of cauliflower (Brassica oleracea) bud peroxidase in decolorization of synthetic recalcitrant dyes using redox mediator

We investigated the effect of cauliflower (Brassica oleracea) bud peroxidase along with redox mediators on decolorization of dyes (Reactive Red 2, Reactive Black 5, Reactive Blue 4, Disperse Orange 25 and Disperse Black 9). Results indicated that among the chosen mediators, 1-hydroxybenzotriazole (HOBT) followed by riboflavin were most effective for dye decolorization. At 0.36 EU/ml and with 0.8 mM HOBT in conjunction with 0.75 mM H₂O₂ the soluble cauliflower bud peroxidase proteins could decolorize the dyes. The enzyme worked in a broader range of pH and temperature and was adequately effective in batch processes when used with organic contaminants (dioxane and dimethylformide), detergents (Triton X-100 and sodium dodecyl sulfate), sodium chloride and heavy metals including zinc and cadmium chloride. Thus peroxidase from cauliflower bud is a better choice than other vegetable peroxidases as it is sufficiently thermostable, operates in a wide range of pH, economic and effective with low concentration of redox mediators in decolorizing recalcitrant synthetic dyes. Such peroxidases with better catalytic activity have potential of being used on a large scale.     

Fine grained Nd3+:Lu2O3 transparent ceramic with enhanced photoluminescence

Fine-grained Nd³⁺:Lu₂O₃ transparent ceramic was developed by a two-step sintering method in flowing H₂ atmosphere at T₁ = 1720 °C for 15 min and T₂ = 1620 °C for 10 h. The initial nanopowders were synthesized by a wet chemical processing with a uniform particle size of about 40 nm. The average grain size of the obtained 3 at.% Nd³⁺:Lu₂O₃ ceramic was 406 nm, which is ∼150 times smaller than the coarse-grained ceramic by normal H₂ sintering. The emission intensity of the fine-grained transparent ceramic is 3 times of its coarse-grained counterpart, indicating higher Nd concentration without serious quenching in fine-grained transparent ceramic is possible, which agreed well with the prediction of an atomistic modeling work with YAG. EXAFS research demonstrated that with decreasing grain size, higher degree of disorder factor of the local environment of doped Nd atoms was discovered.     

CFD simulations of enhanced condensational growth (ECG) applied to respiratory drug delivery with comparisons to in vitro data

Enhanced condensational growth (ECG) is a newly proposed concept for respiratory drug delivery in which a submicrometer aerosol is inhaled in combination with saturated or supersaturated water vapor. The initially small aerosol size provides for very low extrathoracic deposition, whereas condensation onto droplets in vivo results in size increase and improved lung retention. The objective of this study was to develop and evaluate a CFD model of ECG in a simple tubular geometry with direct comparisons to in vitro results. The length (29 cm) and diameter (2 cm) of the tubular geometry were representative of respiratory airways of an adult from the mouth to the first tracheobronchial bifurcation. At the model inlet, separate streams of humidified air (25, 30, and 39 °C) and submicrometer aerosol droplets with mass median aerodynamic diameters (MMADs) of 150, 560, and 900 nm were combined. The effects of condensation and droplet growth on water vapor concentrations and temperatures in the continuous phase (i.e., two-way coupling) were also considered. For an inlet saturated air temperature of 39 °C, the two-way coupled numerical (and in vitro) final aerosol MMADs for initial sizes of 150, 560, and 900 nm were 1.75 μm (vs. 1.23 μm), 2.58 μm (vs. 2.66 μm), and 2.65 μm (vs. 2.63 μm), respectively. By including the effects of two-way coupling in the model, agreements with the in vitro results were significantly improved compared with a one-way coupled assumption. Results indicated that both mass and thermal two-way coupling effects were important in the ECG process. Considering the initial aerosol sizes of 560 and 900 nm, the final sizes were most influenced by inlet saturated air temperature and aerosol number concentration and were not largely influenced by initial size. Considering the growth of submicrometer aerosols to above 2 μm at realistic number concentrations, ECG may be an effective respiratory drug delivery approach for minimizing mouth–throat deposition and maximizing aerosol retention in a safe and simple manner. However, future studies are needed to explore effects of in vivo boundary conditions, more realistic respiratory geometries, and transient breathing.     

Investigation on La2Zr2O7 multilayers by chemical solution deposition

The preparation of 80 nm, 140 nm, and 200 nm La₂Zr₂O₇ (LZO) multilayers on biaxially textured Ni-5 at% W (Ni5W) substrates using chemical solution deposition (CSD) was studied. The performance of multilayers was studied by means of X-Ray Diffraction (XRD), Electron Back Scattering Diffraction (EBSD), and Auger Electron Spectrometry (AES). The as-grown buffer layers exhibit sharp texture with texture components (0°−10°) about 96.7%, 98.9%, and 98.8%, respectively. The full-width at half maximum (FWHM) values of the ω-scans decreases with the number of layers, close to that of Ni5W substrates. The films exhibit dense, smooth, crack-free surface with a roughness Ra 3–5 nm, and sufficient barrier function against metal ionic diffusion from Ni5W substrates into buffer layers. The performance of LZO multilayers was confirmed by YBa₂Cu₃O_7−x (YBCO) films deposited by CSD technology.     

Modeling and optimizing of electrochemical oxidation of C.I. Reactive Orange 7 on the Ti/Sb–SnO2 as anode via response surface methodology

The decolorization and degradation of an organic dye, Reactive Orange 7 (RO7) in aqueous media by electrochemical oxidation process using Ti/Sb–SnO₂ electrode as anode was modeled and optimized using response surface methodology (RSM) based on central composite design (CCD). The anode electrode was prepared using dip-coating and thermal decomposition method. Accordingly reduced quadratic model was developed to give the substrate color removal efficiency percentage as function of effective parameters such as: initial dye concentration, pH of the solution, electrolyte concentration and current density. The fit of the model is checked by the determination coefficient (R²). In this case, the value of the determination coefficient (R² = 0.9949) is indicated. Maximum color removal efficiency was achieved at the obtained conditions of: pH = 4, concentration of electrolyte = 3.5 g/L and current density = 19 mA/cm². Dye removal rate increased by increasing the concentration of electrolyte, lowering pH and increasing the current density. In optimum conditions, decolorization was obtained completely after 5 min; and the removal of chemical oxygen demand (COD) was reduced to 70.3% after 90 min.     

Adsorption of Reactive Blue 114 dye by using a new adsorbent: Pomelo peel

This paper describes the removal of Reactive Blue 114 dye from aqueous solutions by using pomelo (Citrus grandis) peel. Pomelo peel can be described as a new, low cost, abundantly available adsorbent. The optimum adsorbent mass, dye concentration, contact time and pH were determined in this study. The parameters of Langmuir, Freundlich and Temkin adsorption isotherms were also obtained using concentrations of the dyes ranging from 1.0 to 200 mg/L. Maximum adsorption capacity was obtained as 16 mg/g at pH 2 and 303 K solution temperature. The adsorption process was observed to be reaching equilibrium after about 90 min.     

Spectrophotometric studies of photo-induced degradation of Tertrodirect Light Blue (TLB) using a nanostructure zinc zirconate composite

Zinc zirconate nanopowder (ZZN) photocatalyst was prepared by sol–gel method using zinc acetate and zirconium acetylacetonate as precursors. The optimal calcination temperature was 800 °C and ZnZrO₃ phase was formed. The structural and morphology properties of the nanocomposite were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDAX) and ultraviolet visible diffuse reflectance (UV-DRS). The SEM observation for ZZN showed the average grain size of 26 nm. UV–vis diffuse reflectance spectra (DRS) of the nanocomposite showed an absorption edge at 355 nm. The catalytic activity of ZZN was investigated by degradation of Tertrodirect Light Blue (TLB) dye in water using UV–vis spectroscopy (UV–vis) with an initial concentration of 20 mg/L dye. The influence of the catalyst concentration, time of irradiation and pH on photodegradation of dye was investigated. The results showed that degradation of TLB dye can be conducted in the photocatalytic process. Accordingly, a degradation of more than 97% of dye was achieved by applying the optimal operational parameters with 30 mg/L of catalyst, pH 9 at 1 h irradiation.     

Dense bulk silicon oxycarbide glasses obtained by spark plasma sintering

Dense silicon oxycarbide glasses (SiOC) have been produced by spark plasma sintering (SPS) of SiOC powders. Raw powders were obtained by pyrolysis under nitrogen at 1100 °C of tetraethylorthosilcate/polydimethylsiloxane (TEOS/PDMS) hybrids. SPS experiments were carried out at 1300 and 1500 °C at 10 and 80 MPa and then were studied by chemical analysis, ²⁹Si and ¹³C MAS NMR, ATR, Raman, XRD, FE-SEM, density, porosity, microhardness (H_v) and thermal conductivity (K). The SiOC materials are formed by Si_xOC_4?x units within a silica matrix where silicon carbide and graphite nanodomains are also present. After the SPS treatment the silicon carbide crystallite size is close to 2.5 nm. At 1300 °C and 1500 °C the carbon nanodomain size is close to 3 nm and 2 nm, respectively. H_v values vary from 3.4 to 9.15 GPa, for 30% and 1% of porosity, respectively. Finally, K is always close to 1.38 W m^?1 K^?1.     

Response surface optimization of supercritical CO2 extraction of α-tocopherol from gel and skin of Aloe vera and almond leaves

Supercritical fluid extraction (SFE) was studied as an alternative technology in the pharmaceutical industry for the separation of α-tocopherol from gel and skin of Aloe vera and almond leaves. The influence of operating conditions was investigated on the recovery of supercritical carbon dioxide (SC-CO₂) extraction of α-tocopherol from three-year old Aloe vera (Aloe barbadensis Miller) leaf gel. The obtained results were compared with the conventional Soxhlet extraction. Response surface methodology (RSM) was applied to optimize effective variables on the extracted recovery of α-tocopherol. The maximum α-tocopherol recovery of 53.41% from Aloe vera gel was obtained with employing RSM predicted optimal operating conditions of 32 MPa, 45.91 °C, 0.84 ml SC-CO₂/min and 140 min for extraction. The α-tocopherol extraction yield for gel and skin of Aloe vera and almond leaves at these optimal operating conditions were obtained 1.53, 16.29 and 2.61 mg/100 g dry sample, respectively.