Propriedades físico-químicas e mecânicas de membranas porosas de carboximetilquitosana e hidrogéis de quitosana para aplicação em engenharia de tecidos

Este trabalho teve como principal objetivo produzir membranas porosas de carboximetilquitosana e hidrogéis de quitosana com propriedades físico-químicas e mecânicas adequadas para aplicações em Engenharia de Tecidos. Para isso, quitosanas com diferentes graus de acetilação (4,0%<GA<40%) e de elevada massa molar média viscosimétrica (Mv>750.000 g.mol-1) foram produzidas através da aplicação de processos consecutivos de desacetilação assistida por irradiação de ultrassom de alta intensidade (DAIUS) à beta-quitina extraída de gládios de lulas Doryteuthis spp. A carboximetilação de quitosana extensivamente desacetilada (Qs-3; GA=4%) foi realizada pela reação com ácido monocloroacético em meio isopropanol/solução aquosa de NaOH, gerando a amostra CMQs-0 (GS≈0,98; Mv≈190.000 g.mol-1). A irradiação de ultrassom de alta intensidade foi empregada para tratar solução aquosa de CMQs-0 durante 1 h e 3 h, resultando nas amostras CMQs-1 (Mv≈94.000 g.mol-1) e CMQs-3 (Mv≈43.000 g.mol-1), respectivamente. Para a produção de membranas reticuladas, genipina foi adicionada em diferentes concentrações (1,0x10-4 mol.L-1, 3,0x10-4 mol.L-1 ou 5,0x10-4 mol.L-1) às soluções aquosas das CMQs, que foram vertidas em placas de Petri e a reação de reticulação procedeu por 24 h. Em seguida, as membranas reticuladas (M-CMQs) foram liofilizadas, neutralizadas, lavadas e liofilizadas novamente, resultando em nove amostras, que foram caracterizadas quanto ao grau médio de reticulação (GR), grau médio de hidratação (GH), morfologia, propriedades mecânicas e quanto à susceptibilidade à degradação por lisozima. O grau médio de reticulação (GR) foi tanto maior quanto maior a concentração de genipina empregada na reação, variando de GR≈3,3% (M-CMQs-01) a GR≈17,8% (M-CMQs-35). As análises de MEV revelaram que as membranas reticuladas M-CMQs são estruturas porosas que apresentam maior densidade de poros aparentes quanto maiores os valores de Mve GR. Entretanto, as membranas preparadas a partir de CMQs de elevada massa molar (Mv>94.000 g.mol-1) e pouco reticuladas (GR<10%), apresentaram propriedades mecânicas superiores em termos de resistência máxima à tração (>170 kPa) e elongação máxima à ruptura (>40%). Por outro lado, as membranas mais susceptíveis à degradação enzimática foram aquelas preparadas a partir de CMQs de baixa massa molar (Mv≈43.000 g.mol-1) e que exibiram baixos graus de reticulação (GR<11%). Hidrogéis estáveis de quitosana sem o uso de qualquer agente de reticulação externo foram produzidos a partir da gelificação de soluções aquosas de quitosana com solução de NaOH ou vapor de NH3. Os hidrogéis produzidos a partir de soluções de quitosana de elevada massa molar média ponderal (Mw≈640.000 g.mol-1) e extensivamente desacetilada (DA≈2,8%) em concentrações poliméricas acima 2,0%, exibiram melhores propriedades mecânicas com o aumento da concentração polimérica, devido à formação de numerosos emaranhamentos físicos das cadeias poliméricas em solução. Os resultados mostram que as propriedades físico-químicas e mecânicas dos hidrogéis de quitosana podem ser controladas variando a concentração do polímero e o processo de gelificação. A avaliação biológica de tais hidrogéis para a regeneração de miocárdio infartado de ratos revelou que os hidrogéis de quitosana preparados a partir de soluções de polímero a 1,5% foram perfeitamente incorporados sobre a superfície do epicárdio do coração e apresentaram degradação parcial acompanhada por infiltração de células mononucleares.

Evaluation of hectorites, synthesized in different conditions, as soot combustion catalysts after impregnation with copper

Two microporous hectorites were prepared by conventional and microwave heating, and a delaminated mesoporous hectorite by an ultrasound-assisted synthesis. These three hectorites were impregnated with copper. The characterization techniques used were XRD, N2 adsorption, TEM and H2 reduction after selective surface copper oxidation by N2O (to determine copper dispersion). The catalytic activity for soot combustion of the copper-free and the copper-containing hectorites was tested under a gas mixture of 500 ppm NOx/5% O2/N2 (and 5% O2/N2 in some cases), evaluating their stability through three consecutive soot combustion experiments. The delaminated hectorite showed the highest surface area (353 m2/g) allowing the highest dispersion of copper. This copper-containing catalyst was the most active for soot combustion among those prepared and tested in this study. We have also concluded that the Cu/hectorite-catalyzed soot combustion mechanism is based on the activation of the O2 molecule and not on the NO2-assisted soot combustion.

Screen-printed electrode based electrochemical detector coupled with ionic liquid dispersive liquid–liquid microextraction and microvolume back-extraction for determination of mercury in water samples

A novel approach is presented, whereby gold nanostructured screen-printed carbon electrodes (SPCnAuEs) are combined with in-situ ionic liquid formation dispersive liquid–liquid microextraction (in-situ IL-DLLME) and microvolume back-extraction for the determination of mercury in water samples. In-situ IL-DLLME is based on a simple metathesis reaction between a water-miscible IL and a salt to form a water-immiscible IL into sample solution. Mercury complex with ammonium pyrrolidinedithiocarbamate is extracted from sample solution into the water-immiscible IL formed in-situ. Then, an ultrasound-assisted procedure is employed to back-extract the mercury into 10 µL of a 4 M HCl aqueous solution, which is finally analyzed using SPCnAuEs. Sample preparation methodology was optimized using a multivariate optimization strategy. Under optimized conditions, a linear range between 0.5 and 10 µg L−1 was obtained with a correlation coefficient of 0.997 for six calibration points. The limit of detection obtained was 0.2 µg L−1, which is lower than the threshold value established by the Environmental Protection Agency and European Union (i.e., 2 µg L−1 and 1 µg L−1, respectively). The repeatability of the proposed method was evaluated at two different spiking levels (3 and 10 µg L−1) and a coefficient of variation of 13% was obtained in both cases. The performance of the proposed methodology was evaluated in real-world water samples including tap water, bottled water, river water and industrial wastewater. Relative recoveries between 95% and 108% were obtained.

Obtenção de extratos de agaricus bisporus com ergosterol para incorporação em iogurtes e procedimentos de microencapsulação

Além de ser o cogumelo mais consumido no mundo, Agaricus bisporus é um dos cogumelos mais ricos em ergosterol, representando esta molécula quase 90% da sua fração de esteróis. Vários estudos têm atribuído ao ergosterol diferentes bioatividades, incluindo efeitos hipocolesterolémicos semelhantes aos exibidos pelos fitoesteróis. Isto torna o ergosterol uma molécula interessante para ser estudada como composto nutracêutico. Assim, este trabalho teve como objetivo avaliar o potencial de utilização dos extratos de A. bisporus ricos em ergosterol na produção de bebidas lácteas funcionais. Para o efeito, foram realizados testes de incorporação do extrato e do ergosterol puro em iogurtes que se compararam com bebidas lácteas funcionais comerciais (aditivadas com fitoesteróis). As amostras de A. bisporus foram submetidas a uma extração assistida por ultrassons e os extratos obtidos (IEXT), bem como a molécula de ergosterol em diferentes concentrações (IERG1 e IERG2), foram incorporados em iogurtes, e comparadas com amostras controlo (amostras de iogurte sem aditivos) (ICN) e iogurtes comerciais contendo fitoesteróis (ICP). Todas as amostras foram analisadas imediatamente após a incorporação (T0), e após sete dias de armazenagem a 4°C (T1), em relação aos parâmetros nutricionais, atividade antioxidante e propriedades citotóxicas em linhas celulares tumorais humanas e numa cultura primária de células de fígado de porco (não tumoral) para avaliação da toxicidade. O teor de ergosterol incorporado na forma pura, ou presente nos extratos, foi monitorizado por HPLC-UV. Adicionalmente, foi realizado um estudo de microencapsulação utilizando a técnica de coacervação, tendo o quitosano e o isolado proteico de soro como materiais encapsulantes. Num ensaio preliminar determinou-se o pH conducente a um maior rendimento de encapsulação e, seguidamente, verificou-se a influência da razão proteína:quitosano (P/Q) e da temperatura utilizada, no rendimento de encapsulação (Y1), na eficiência de encapsulação (Y2) e na carga (teor de ergosterol nas microesferas) (Y3). Posteriormente, o estudo foi realizado baseando-se nas melhores condições para encapsular ergosterol, sendo também avaliadas as respostas Y1, Y2 e Y3. Além de ser o cogumelo mais consumido no mundo, Agaricus bisporus é um dos cogumelos mais ricos em ergosterol, representando esta molécula quase 90% da sua fração de esteróis. Vários estudos têm atribuído ao ergosterol diferentes bioatividades, incluindo efeitos hipocolesterolémicos semelhantes aos exibidos pelos fitoesteróis. Isto torna o ergosterol uma molécula interessante para ser estudada como composto nutracêutico. Assim, este trabalho teve como objetivo avaliar o potencial de utilização dos extratos de A. bisporus ricos em ergosterol na produção de bebidas lácteas funcionais. Para o efeito, foram realizados testes de incorporação do extrato e do ergosterol puro em iogurtes que se compararam com bebidas lácteas funcionais comerciais (aditivadas com fitoesteróis). As amostras de A. bisporus foram submetidas a uma extração assistida por ultrassons e os extratos obtidos (IEXT), bem como a molécula de ergosterol em diferentes concentrações (IERG1 e IERG2), foram incorporados em iogurtes, e comparadas com amostras controlo (amostras de iogurte sem aditivos) (ICN) e iogurtes comerciais contendo fitoesteróis (ICP). Todas as amostras foram analisadas imediatamente após a incorporação (T0), e após sete dias de armazenagem a 4°C (T1), em relação aos parâmetros nutricionais, atividade antioxidante e propriedades citotóxicas em linhas celulares tumorais humanas e numa cultura primária de células de fígado de porco (não tumoral) para avaliação da toxicidade. O teor de ergosterol incorporado na forma pura, ou presente nos extratos, foi monitorizado por HPLC-UV. Adicionalmente, foi realizado um estudo de microencapsulação utilizando a técnica de coacervação, tendo o quitosano e o isolado proteico de soro como materiais encapsulantes. Num ensaio preliminar determinou-se o pH conducente a um maior rendimento de encapsulação e, seguidamente, verificou-se a influência da razão proteína:quitosano (P/Q) e da temperatura utilizada, no rendimento de encapsulação (Y1), na eficiência de encapsulação (Y2) e na carga (teor de ergosterol nas microesferas) (Y3). Posteriormente, o estudo foi realizado baseando-se nas melhores condições para encapsular ergosterol, sendo também avaliadas as respostas Y1, Y2 e Y3. As bebidas funcionalizadas com o extrato (IEXT) e com ergosterol na mesma concentração existente no extrato (IERG1) revelaram uma atividade antioxidante similar às bebidas comerciais com fitoesteróis. No entanto, as bebidas com ergosterol na mesma concentração do extrato de A. bisporus e de fitoesteróis (IERG2) revelaram uma atividade antioxidante superior. Além disso, apenas IEXT, IERG1 e IERG2 apresentaram um aumento na atividade antioxidante de T0 para T1, com destaque para a atividade exibida por IERG2, significando que o ergosterol e os extratos foram capazes de proteger a bebida láctea da oxidação, aumentando a vida de prateleira do produto. IERG2 foi a amostra que revelou a maior citotoxicidade para as linhas celulares tumorais, enquanto as bebidas com fitoesteróis mostraram a menor atividade, sem diferenças significativas entre T0 e T1. Os estudos de microencapsulação revelaram ainda que a técnica de coacervação permite obter cápsulas de distintos tamanhos e que as condições ótimas do processo ocorrem a pH 5,5, com temperatura de 55ºC e razão P/Q de 0,5, com um menor rendimento de encapsulação, mas com uma maior carga em ergosterol. Este trabalho contribuiu para o estudo do potencial da utilização de extratos de A. bisporus com ergosterol no desenvolvimento de novas bebidas funcionais. Constituiu um primeiro passo que necessita de estudos subsequentes relacionados com a avaliação da viabilidade da sua utilização ao nível industrial e demonstração clara da sua bioatividade in vivo.

Extraction and detection of mycotoxins in medicinal and aromatic plants: a case study with Aloysia citrodora P.

Plants frequently suffer contaminations by toxigenic fungi, and their mycotoxins can be produced throughout growth, harvest, drying and storage periods. The objective of this work was to validate a method for detection of toxins in medicinal and aromatic plants, through a fast and highly sensitive method, optimizing the joint co-extraction of aflatoxins (AF: AFB1, AFB2, AFG1 and AFG2) and ochratoxin A (OTA) by using Aloysia citrodora P. (lemon verbena) as a case study. For optimization purposes, samples were spiked (n=3) with standard solutions of a mix of the four AFs and OTA at 10 ng/g for AFB1, AFG1 and OTA, and at 6 ng/g of AFB2 and AFG2. Several extraction procedures were tested: i) ultrasound-assisted extraction in sodium chloride and methanol/water (80:20, v/v) [(OTA+AFs)1]; ii) maceration in methanol/1% NaHCO3 (70:30, v/v) [(OTA+AFs)2]; iii) maceration in methanol/1% NaHCO3 (70:30, v/v) (OTA1); and iv) maceration in sodium chloride and methanol/water (80:20, v/v) (AF1). AF and OTA were purified using the mycotoxin-specific immunoaffinity columns AflaTest WB and OchraTest WB (VICAM), respectively. Separation was performed with a Merck Chromolith Performance C18 column (100 x 4.6 mm) by reverse-phase HPLC coupled to a fluorescence detector (FLD) and a photochemical derivatization system (for AF). The recoveries obtained from the spiked samples showed that the single-extraction methods (OTA1 and AF1) performed better than co-extraction methods. For in-house validation of the selected methods OTA1 and AF1, recovery and precision were determined (n=6). The recovery of OTA for method OTA1 was 81%, and intermediate precision (RSDint) was 1.1%. The recoveries of AFB1, AFB2, AFG1 and AFG2 ranged from 64% to 110% for method AF1, with RSDint lower than 5%. Methods OTA1 and AF1 showed precision and recoveries within the legislated values and were found to be suitable for the extraction of OTA and AF for the matrix under study.

Modular continuous crystallizer: operation, experimental arrangement and identification of process parameters

Crystallization is employed in different industrial processes. The method and operation can differ depending on the nature of the substances involved. The aim of this study is to examine the effect of various operating conditions on the crystal properties in a chemical engineering design window with a focus on ultrasound assisted cooling crystallization. Batch to batch variations, minimal manufacturing steps and faster production times are factors which continuous crystallization seeks to resolve. Continuous processes scale-up is considered straightforward compared to batch processes owing to increase of processing time in the specific reactor. In cooling crystallization process, ultrasound can be used to control the crystal properties. Different model compounds were used to define the suitable process parameters for the modular crystallizer using equal operating conditions in each module. A final temperature of 20oC was employed in all experiments while the operating conditions differed. The studied process parameters and configuration of the crystallizer were manipulated to achieve a continuous operation without crystal clogging along the crystallization path. The results from the continuous experiment were compared with the batch crystallization results and analysed using the Malvern Morphologi G3 instrument to determine the crystal morphology and CSD. The modular crystallizer was operated successfully with three different residence times. At optimal process conditions, a longer residence time gives smaller crystals and narrower CSD. Based on the findings, at a constant initial solution concentration, the residence time had clear influence on crystal properties. The equal supersaturation criterion in each module offered better results compared to other cooling profiles. The combination of continuous crystallization and ultrasound has large potential to overcome clogging, obtain reproducible and narrow CSD, specific crystal morphologies and uniform particle sizes, and exclusion of milling stages in comparison to batch processes.

Development of procedures for the triazole fungicides determination in fruits and liquid samples using microextraction techniques and chromatographic separation

Agricultural crops can be damaged by funguses, insects, worms and other organisms that cause diseases and decrease the yield of production. The effect of these damaging agents can be reduced using pesticides. Among them, triazole compounds are effective substances against fungus; for example, Oidium. Nevertheless, it has been detected that the residues of these fungicides in foods as well as in derivate products can affect the health of the consumers. Therefore, the European Union has established several regulations fixing the maximum residue of pesticide levels in a wide range of foods trying to assure the consumer safety. Hence, it is very important to develop adequate methods to determine these pesticide compounds. In most cases, gas or liquid chromatographic (GC, LC) separations are used in the analysis of the samples. But firstly, it is necessary to use proper sample treatments in order to preconcentrate and isolate the target analytes. To reach this aim, microextraction techniques are very effective tools; because allow to do both preconcentration and extraction of the analytes in one simple step that considerably reduces the source of errors. With these objectives, two remarkable techniques have been widely used during the last years: solid phase microextraction (SPME) and liquid phase microextraction (LPME) with its different options. Both techniques that avoid the use or reduce the amount of toxic solvents are convenient coupled to chromatographic equipments providing good quantitative results in a wide number of matrices and compounds. In this work simple and reliable methods have been developed using SPME and ultrasound assisted emulsification microextraction (USAEME) coupled to GC or LC for triazole fungicides determination. The proposed methods allow confidently determine triazole concentrations of μg L‐1 order in different fruit samples. Chemometric tools have been used to accomplish successful determinations. Firstly, in the selection and optimization of the variables involved in the microextraction processes; and secondly, to overcome the problems related to the overlapping peaks. Different fractional factorial designs have been used for the screening of the experimental variables; and central composite designs have been carried out to get the best experimental conditions. Trying to solve the overlapping peak problems multivariate calibration methods have been used. Parallel Factor Analysis 2 (PARAFAC2), Multivariate Curve Resolution (MCR) and Parallel Factor Analysis with Linear Dependencies (PARALIND) have been proposed, the adequate algorithms have been used according to data characteristics, and the results have been compared. Because its occurrence in Basque Country and its relevance in the production of cider and txakoli regional wines the grape and apple samples were selected. These crops are often treated with triazole compounds trying to solve the problems caused by the funguses. The peel and pulp from grape and apple, their juices and some commercial products such as musts, juice and cider have been analysed showing the adequacy of the developed methods for the triazole determination in this kind of fruit samples.

Structural and mechanical properties of La0.6Sr0.4M0.1Fe0.9O3-δ (M: Co, Ni and Cu) perovskites

La0.6Sr0.4M0.1Fe0.9O3-δ (M: Co, Ni and Cu) perovskite nanostructures were synthesized using low frequency ultrasound assisted synthesis technique and effect of substitution of Fe by Co, Ni and Cu on crystal structure and mechanical properties in La0.6Sr0.4FeO3-δ perovskite were studied. The HRTEM and Rietveld refinement analyses revealed the uniform equi-axial shape of the obtained nanostructures with the existence of La0.6Sr0.4M0.1Fe0.9O3−δ with mixed rhombohedral and orthorhombic structures. Substitution of Cu decreases the melting point of La0.6Sr0.4FeO3-δ. The results of mechanical characterizations show that La0.6Sr0.4Co0.1Fe0.9O3−δ and La0.6Sr0.4Ni0.1Fe0.9O3−δ have ferroelastic behavior and comparable elastic moduli, however, subtitution of Ni shows higher hardness and lower fracture toughness than Co in Bsite doping

Development of antibacterial ZnO-loaded cotton fabric based on in situ fabrication

A method provided for the deposition of nanostructured ZnO on cotton fabric to introduce antibacterial functionality was presented in this article. This strategy enabled fabric to be coated with inorganic-based functional materials through in situ synthesis of nanoparticles using ultrasonic irradiation. The amino-terminated silicon sol (AEAPTS) was employed to generate nanostructured ZnO, and the mechanism of the ultrasound-assisted coating was proposed. Antibacterial activities, UV protection and other properties of ZnO-loaded cotton characterized by SEM, FTIR, XRD and TGA were investigated. The results indicated that ZnO-loaded cotton exhibited excellent UV protective property, efficient antibacterial activities, well water-resistant effect, together with moderate cytotoxicity against L929 and lower tensile strength. The developed method provides not only a facile way for in situ synthesis of ZnO on textile but also the production of antibacterial materials for healthcare applications.

InOx thin films deposited by plasma assisted evaporation: application in light shutters

An integration of undoped InOx and commercial ITO thin films into laboratory assembled light shutter devices is made. Accordingly, undoped transparent conductive InOx thin films, about 100 nm thick, are deposited by radiofrequency plasma enhanced reactive thermal evaporation (rf-PERTE) of indium teardrops with no intentional heating of the glass substrates. The process of deposition occurs at very low deposition rates (0.1-0.3 nm/s) to establish an optimized reaction between the oxygen plasma and the metal vapor. These films show the following main characteristics: transparency of 87% (wavelength, lambda = 632.8 nm) and sheet resistance of 52 Omega/sq; while on commercial ITO films the transparency was of 92% and sheet resistance of 83 Omega/sq. The InOx thin film surface characterized by AFM shows a uniform grain texture with a root mean square surface roughness of Rq similar to 2.276 nm. In contrast, commercial ITO topography is characterized by two regions: one smoother with Rq similar to 0.973 nm and one with big grains (Rq similar to 3.617 nm). For the shutters assembled using commercial ITO, the light transmission coefficient (Tr) reaches the highest value (Tr-max) of 89% and the lowest (Tr-min) of 1.3% [13], while for the InOx shutters these values are 80.1% and 3.2%, respectively. Regarding the electric field required to achieve 90% of the maximum transmission in the ON state (E-on), the one presented by the devices assembled with commercial ITO coated glasses is 2.41 V/mu m while the one presented by the devices assembled with InOx coated glasses is smaller, 1.77 V/mu m. These results corroborate the device quality that depends on the base materials and fabrication process used. (C) 2014 Elsevier Ltd. All rights reserved.

Computer-assisted motion compensation and analysis of perfusion ultrasound data

Magdeburg, Univ., Fak. für Informatik, Diss., 2014

A dissolution and reaction modeling for hydrolysis of TEOS in heterogeneous TEOS-water-HCl mixtures under ultrasound stimulation

A simplified dissolution and reaction modeling was employed to study the hydrolysis of heterogeneous tetraethoxysilane (TEOS)-water-HCl mixtures under ultrasound stimulation. The nominal pH was changed from 0.8 to 2.0. The acid specific hydrolysis rate constant was determined as k = 6.1 mol(-1) 1 min(-1) [H+](-1) at 39 degreesC, in good agreement with the literature. Along the heterogeneous step of the reaction, the ultrasound maintains an additional quantity of water under a virtual state of dissolution besides the water dissolved due to the homogenizing effect of the alcohol produced in the reaction. The forced virtually dissolved water is probably represented by water at the TEOS-water interface during the heterogeneous step of the reaction. The mean radius of the heterogeneity represented by water dispersed in TEOS phase, while hydrolysis has not started yet, was evaluated as about 290 A. The HCl concentration accordingly increases the hydrolysis rate constant but its fundamental role on the immiscibility gap of the TEOS-water-ethanol system has not been unequivocally established. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Ultrasound and microwave assisted extraction of ergosterol from Agaricus bisporus L.: optimization through response surface methodology

There is scientific evidence demonstrating the benefits of mushrooms ingestion due to their richness in bioactive compounds such as mycosterols, in particular ergosterol [I]. Agaricus bisporus L. is the most consumed mushroom worldwide presenting 90% of ergosterol in its sterol fraction [2]. Thus, it is an interesting matrix to obtain ergosterol, a molecule with a high commercial value. According to literature, ergosterol concentration can vary between 3 to 9 mg per g of dried mushroom. Nowadays, traditional methods such as maceration and Soxhlet extraction are being replaced by emerging methodologies such as ultrasound (UAE) and microwave assisted extraction (MAE) in order to decrease the used solvent amount, extraction time and, of course, increasing the extraction yield [2]. In the present work, A. bisporus was extracted varying several parameters relevant to UAE and MAE: UAE: solvent type (hexane and ethanol), ultrasound amplitude (50 - 100 %) and sonication time (5 min-15 min); MAE: solvent was fixed as ethanol, time (0-20 min), temperature (60-210 •c) and solid-liquid ratio (1-20 g!L). Moreover, in order to decrease the process complexity, the pertinence to apply a saponification step was evaluated. Response surface methodology was applied to generate mathematical models which allow maximizing and optimizing the response variables that influence the extraction of ergosterol. Concerning the UAE, ethanol proved to be the best solvent to achieve higher levels of ergosterol (671.5 ± 0.5 mg/100 g dw, at 75% amplitude for 15 min), once hexane was only able to extract 152.2 ± 0.2 mg/100 g dw, in the same conditions. Nevertheless, the hexane extract showed higher purity (11%) when compared with the ethanol counterpart ( 4% ). Furthermore, in the case of the ethanolic extract, the saponification step increased its purity to 21%, while for the hexane extract the purity was similar; in fact, hexane presents higher selectivity for the lipophilic compounds comparatively with ethanol. Regarding the MAE technique, the results showed that the optimal conditions (19 ± 3 min, 133 ± 12 •c and 1.6 ± 0.5 g!L) allowed higher ergosterol extraction levels (556 ± 26 mg/100 g dw). The values obtained with MAE are close to the ones obtained with conventional Soxhlet extraction (676 ± 3 mg/100 g dw) and UAE. Overall, UAE and MAE proved to he efficient technologies to maximize ergosterol extraction yields.

Microstructure, vibrational and visible emission properties of low frequency ultrasound (42 kHz) assisted ZnO nanostructures

Size and shape tuneable ZnO nanostructures were prepared by a low frequency ultrasound (42 kHz) route using various organic solvents as the reaction media. The crystalline nature, lattice parameters and microstructural parameters such as microstrain, stress and energy density of the prepared ZnO nanostructures were revealed through X-ray diffraction (XRD) analysis. The organic solvents influenced the size and morphology of the ZnO nanostructures, and interesting morphological changes involving a spherical to triangular shaped transition were observed. The visible emission properties and lattice vibrational characteristics of the nanostructures were drastically modified by the changes in size and shape. Raman spectral measurements revealed the presence of multiphonon processes in the ZnO nanostructures. The intensity of the visible emission band was found to vary with the size and morphology of the structures. The strongest visible emission band corresponded to the structure with the largest surface/volume ratio and could be attributed to surface oxygen vacancies. The control over the size and morphology of ZnO nanostructures has been presented as a means of determining the intensity of the visible emission band