Supercritical Fluids Extraction of Valuable Compounds from Algae: Future Perspectives and Challenges

Algae (macro and micro) can be used to produce several high–value metabolites to supply industries as cosmetics, additives and pigments, among others. Those metabolites can have physiological and nutritional benefits for human and animal health. However, the availability of high–value metabolites from algae is still unaffordable due to traditional extraction techniques and their requirements of energy and use of pollutant solvents. Recently, green extraction technologies for the extraction of high–value metabolites have become more desirable due to their sustainability and environmental benefits. Supercritical fluids extraction, as green extraction techniques, has been widely applied for extraction of high–value metabolites from algae. Here, the highlight of supercritical CO2 and subcritical water on the extraction of bioactive compounds from macro– and microalgae was presented. The perspective and challenge for using supercritical CO2 and subcritical water on the algae extraction were also concluded

Comparison of Conventional and Ultrasound Assisted Supercritical Carbon Dioxide Extraction of Curcumin from Turmeric (Curcuma longa L.)

Recently, ultrasound assisted supercritical fluid is used for extraction the valuable compounds from a number of plant materials as an alternative to conventional method because it can enhance the extraction rate and yield. Curcumin is an important component of turmeric (Curcuma longa L.) with many useful functions to human health. The objective of this study is using ultrasonic assisted supercritical carbon dioxide (USC-CO2) to extract curcumin from turmeric and compared to conventional method. The effect of operating conditions on extraction, including temperature (40 - 60oC), pressure (15 - 25 MPa), extraction time (30 - 120 min), CO2 flow rate (2 - 4 mL/min) and percentage of cosolvent (10 - 20% v/v) were also studied. The result shows that the high extraction yield of 7.17% w/w and curcumin content of 1.69% w/w were achieved at temperature of 50oC, pressure of 25 MPa, extraction time of 90 min, CO2 flow rate of 3 mL/min with 10% cosolvent. Compared to conventional method, USC-CO2 could provide higher curcumin content in extraction yield in a shorter extraction time. Scanning electron microscopy (SEM), thermal gravity (TG), and fourier transform infrared spectroscopy (FTIR) was used to analyse turmeric undergoing USC-CO2 and conventional extraction and showed that ultrasound could break down the cell walls and remove some functional groups from plant materials, resulting an increase the selectivity of compounds in extraction yield

Pulsed Discharge Plasma in Slug-flow Reactor System for Water Pollutant Removal and Nanoparticle Synthesis

The water pollutants removal and the metal nanoparticles synthesis were demonstrated by the applying high voltage discharge plasma at room temperature. The experiments were performed in continuous system by the flowing liquid and gas phases simultaneously in a glass capillary tube, where various gas types were employed as a gas phase. The optical emission spectroscopy (OES) equipment identified that the reactive oxidation species were obviously observed at each gas type. The generation rate of them can be enhanced significantly by changing the reactor type from straight to helical form. The water pollutants removal rate has order from oxygen > air > nitrogen > argon > helium. Furthermore, the silver or gold nanoparticles can be synthesized by this plasma reactor system. The transmission electron microscopy (TEM) images indicated that the particle products had spherical morphology with a diameter size smaller than 10 nm. It was deduced that the process presented here is an innovative and applicable in practice, and it can lead to advanced organic compounds degradation and nanoparticles synthesis technology

Hot Compressed Water Extraction of Lignin by Using a Flow-Through Reactor

Japanese rice straw, an agricultural by-product, was utilized for the extraction of lignin by hot compressed water at temperatures of 443 - 503 K and a pressure of 4.0 MPa using a flow-through system, a simple and environmentally friendly extraction method requiring no chemicals other than water. Under these conditions, thermal softening of the Japanese rice straw occurred, allowing the removal of lignin via depolymerization reactions. Lignin as an extraction product was analyzed using utraviolet-visible (UV-vis) spectrophotometry. Lignin recovery approached 85% when the extraction was performed at 443 and 473 K with a flow rate of 4.67 ml min-1. At a constant residence time, recovery amounts increased with increasing flow rate at each temperature. The results suggested that this process may result in an advanced plant biomass components extraction technology

Synthesis of Polyhedral Magnetite Particles by Hydrothermal Process Under High Pressure Condition

Magnetite particles were successfully generated by hydrothermal synthesis using water at subcritical conditions. By changing the temperature and pressure at subcritical water conditions, the thermodynamics and transport properties of the water can be controlled, thus enabling to manage the way of crystal formation, morphology, and particle size. In this work, the experiments were carried out at temperatures of 250 °C and 290 °C and a pressure of 10 MPa with a reactor made of SUS 316 in a batch system. The synthesized particles were dried in vacuum condition and characterized by SEM and XRD. The XRD patterns showed that magnetite particles were dominantly formed in the particle products with a black color. The results showed that the magnetite particles formed had diameters of around 60 nm in all experiments with irregular polyhedral shaped morphologies

Evaluation of Effective Field-Effect Mobility in Thin-Film and Single-Crystal Transistors for Revisiting Various Phenacene-Type Molecules

The magnitude of the field-effect mobility mu of organic thin-film and single-crystal field-effect transistors (FETs) has been over-estimated in certain recent studies. These reports set alarm bells ringing in the research field of organic electronics. Herein, we report a precise evaluation of the mu values using the effective field-effect mobility, mu(eff), a new indicator that is recently designed to prevent the FET performance of thin-film and single-crystal FETs based on various phenacene molecules from being overestimated. The transfer curves of a range of FETs based on phenacene are carefully categorized on the basis of a previous report. The exact evaluation of the value of mu(eff) depends on the exact classification of each transfer curve. The transfer curves of all our phenacene FETs could be successfully classified based on the method indicated in the aforementioned report, which made it possible to evaluate the exact value of mu(eff) for each FET. The FET performance based on the values of mu(eff) obtained in this study is discussed in detail. In particular, the mu(eff) values of single-crystal FETs are almost consistent with the mu values that were reported previously, but the mu(eff) values of thin-film FETs were much lower than those previously reported for mu, owing to a high absolute threshold voltage, vertical bar V-th vertical bar. The increase in the field-effect mobility as a function of the number of benzene rings, which was previously demonstrated based on the mu values of single-crystal FETs with phenacene molecules, is well reproduced from the mu(eff) values. The FET performance is discussed based on the newly evaluated mu(eff) values, and the future prospects of using phenacene molecules in FET devices are demonstrated

Extraction of Phytochemicals from Grains of Paradise Using Supercritical Carbon Dioxide

Supercritical carbon dioxide (SCCO2) is one of the green methods to extract plant matters substances. In this study, SCCO2 has been applied as a media to extract the grains of paradise seeds substances at temperatures of 40 – 80 oC and pressures of 20 – 40 MPa using a semi–continuous flow–type system. Results of FT–IR spectra analysis showed that the grains of paradise seeds substances were extracted by SCCO2. The SEM images of the grains of paradise seeds residues also showed that the physical changes of the grains of paradise seeds surface occurred after SCCO2 extraction. The main compounds in extracts were gingerols, shogaols, and paradols. However, the GC–MS may only identify paradol compounds due to gingerols, shogaols, and paradols are homologous series of phenolic ketones and paradols was more stable than gingerols and shogaols. The yields of gingerols, shogaols, and paradols were 9.12, 3.90, and 4.42 mg/g sample, respectively and affected by extraction temperatures and/or extraction pressures

Crystallization of All Trans–b–carotene by Supercritical Carbon Dioxide Antisolvent via Co–axial Nozzle

The crystallization of b-carotene through supercritical antisolvent process with carbon dioxide (CO2) as an antisolvent has been demonstrated. The experiments were conducted at temperatures of 40 - 60oC and pressures of 10 - 14 MPa at a constant CO2 flow rate. As a starting material, b-carotene powder was dissolved in dichloromethane (DCM). Results of UV-vis spectrophotometry analysis showed that there was no remaining DCM solvent in the b-carotene particles products. It showed that CO2 has successfully removed DCM from b-carotene particles products. The product characterization by using fourier transform infrared spectroscopy (FT-IR) showed that the CO2 solvent did not impregnate to the b-carotene particles products. Results from scanning electron microscope (SEM) images showed that the b-carotene particles products were successfully prepared in plate-like shape morphologies with size around 1 mm

Electric spectroscopy of vortex states and dynamics in magnetic disks

Spin-polarized radio frequency (RF) currents and RF-Oersted fields resonantly excite a magnetic vortex core confined in a micron-scale soft magnetic disk. In this study, we measured the rectifying voltage spectra caused by the anisotropic magnetoresistance oscillation due to the gyration of the vortex with different polarity and chirality. The measured spectra are presented such that we can determine the vortex properties and strength of the spin torques and Oersted field accurately and directly through analytical calculation.Comment: 39 pages,1 table, 10 figure

Facile synthesis of picenes incorporating imide moieties at both edges of the molecule and their application to n-channel field-effect transistors

Picene derivatives incorporating imide moieties along the long-axis direction of the picene core (Cn-PicDIs) were conveniently synthesized through a four-step synthesis. Photochemical cyclization of dinaphthylethenes was used as the key step for constructing the picene skeleton. Field-effect transistor (FET) devices of Cn-PicDIs were fabricated by using ZrO2 as a gate substrate and their FET characteristics were investigated. The FET devices showed normally-off n-channel operation; the averaged electron mobility (μ) was evaluated to be 2(1) × 10−4, 1.0(6) × 10−1 and 1.4(3) × 10−2 cm2 V−1 s−1 for C4-PicDI, C8-PicDI and C12-PicDI, respectively. The maximum μ value as high as 2.0 × 10−1 cm2 V−1 s−1 was observed for C8-PicDI. The electronic spectra of Cn-PicDIs in solution showed the same profiles irrespective of the alkyl chain lengths. In contrast, in thin films, the UV absorption and photoelectron yield spectroscopy (PYS) indicated that the lowest unoccupied molecular orbital (LUMO) level of Cn-PicDIs gradually lowered upon the elongation of the alkyl chains, suggesting that the alkyl chains modify intermolecular interactions between the Cn-PicDI molecules in thin films. The present results provide a new strategy for constructing a high performance n-channel organic semiconductor material by utilizing the electronic features of phenacenes