Search results for "Supercritical"

Dispersion polymerization of vinyl monomers in supercritical carbon dioxide in the presence of drug molecules: A one-pot route for the preparation of…

2008

Eumelanin Coating of Silica Aerogel by Supercritical Carbon Dioxide Deposition of a 5,6-Dihydroxyindole Thin Film

2018

Eumelanin integration in silica aerogel (SA) was achieved via supercritical adsorption of 5,6-dyhydroxyindole (DHI) from CO2. Notably, after the supercritical treatment, DHI evolved towards spontaneous polymerization, which resulted in uniform pigment development over the SA. The new material was characterized for its morphological and physicochemical properties, disclosing the formation of a eumelanin-like coating, as confirmed by UV&ndash

Optimisation of Conditions for Extraction of Biologically Active Compounds from Common Bryophytes in Latvia / Latvijâ Augoðu Briofîtu Ekstrakcijas Ap…

2015

Abstract Bryophytes are the second largest taxonomic group in the plant kingdom. They contain a high number of biologically active compounds. Studies of their composition are important for understanding evolutionary processes in the plant kingdom. The aim of this study was to assess bryophyte secondary metabolite extraction options and to increase the yields of polyphenols and substances determining the free radical scavenging activity of bryophyte extracts. Similar studies have been conducted using higher plants as model organisms, but not using bryophytes. Comparison of five extraction methods (conventional, Soxhlet extraction, treatment with microwaves, ultrasound, and supercritical CO2 …

Modification of Poly(vinilydenefluoride) Porous Membranes by Grafting of Acrylic Acid Assisted by Supercritical Carbon Dioxide

2010

Aim of this work is to study the preparation of pH sensitive membranes for biomedical applications via thermally induced graft polymerization of acrylic acid (AA) on poly(vinilydenefluoride) (PVDF) assisted by supercritical carbon dioxide (scCO2). Using scCO2 as a solvent and swelling agent, the monomer and the initiator (benzoyl peroxide) could diffuse faster into the polymer matrix, distribute more uniformly and allows a better control of the final molecular architecture promoting grafting reactions rather than chain degradation processes. As polymer matrixes we are using commercial hydrophobic porous PVDF membranes. Grafted polymers are characterized by Fourier transform infrared spectro…

Mechanics of invagination and folding: Hybridized instabilities when one soft tissue grows on another

2015

We address the folding induced by differential growth in soft layered solids via an elementary model that consists of a soft growing neo-Hookean elastic layer adhered to a deep elastic substrate. As the layer/substrate modulus ratio is varied from above unity towards zero we find a first transition from supercritical smooth folding followed by cusping of the valleys to direct subcritical cusped folding, then another to supercritical cusped folding. Beyond threshold the high amplitude fold spacing converges to about four layer thicknesses for many modulus ratios. In three dimensions the instability gives rise to a wide variety of morphologies, including almost degenerate zigzag and triple-ju…

The Application of Supercritical Fluids Technology to Recover Healthy Valuable Compounds from Marine and Agricultural Food Processing By-Products: A …

2021

Food by-products contain a remarkable source of bioactive molecules with many benefits for humans; therefore, their exploitation can be an excellent opportunity for the food sector. Moreover, the revalorization of these by-products to produce value-added compounds is considered pivotal for sustainable growth based on a circular economy. Traditional extraction technologies have several drawbacks mainly related to the consumption of hazardous organic solvents, and the high temperatures maintained for long extraction periods which cause the degradation of thermolabile compounds as well as a low extraction efficiency of desired compounds. In this context, supercritical fluid extraction (SFE) ha…

Pigments and their solubility in and extractability by supercritical CO2 - I: the case of curcumin

2000

A specially designed high-pressure cell was used simultaneously as extractor/autoclave and photometric cell in a Perkin Elmer Lambda 5 spectrophotometer. Based on this cell, a simple method was developed to determine the extractability of pigments by pure and by modified supercritical (sc) CO2. The method is demonstrated with curcumin from turmeric. With sc CO2 modified by 10% ethanol, the extraction yield for curcumin from two commercial finely ground dry turmeric samples was about 100%, measured by reference to the (complete) extraction of samples of the same charge with pure ethanol under standard conditions. Extractable curcumin content was from 1.8 to 2.5%, with three samples of turmer…

The formation, properties and impact of secondary organic aerosol: Current and emerging issues

2009

Hallquist, M. Wenger, J. C. Baltensperger, U. Rudich, Y. Simpson, D. Claeys, M. Dommen, J. Donahue, N. M. George, C. Goldstein, A. H. Hamilton, J. F. Herrmann, H. Hoffmann, T. Iinuma, Y. Jang, M. Jenkin, M. E. Jimenez, J. L. Kiendler-Scharr, A. Maenhaut, W. McFiggans, G. Mentel, Th. F. Monod, A. Prevot, A. S. H. Seinfeld, J. H. Surratt, J. D. Szmigielski, R. Wildt, J.; Secondary organic aerosol (SOA) accounts for a significant fraction of ambient tropospheric aerosol and a detailed knowledge of the formation, properties and transformation of SOA is therefore required to evaluate its impact on atmospheric processes, climate and human health. The chemical and physical processes associated wit…

In Vitro and In Vivo Regulation of SRD5A mRNA Expression of Supercritical Carbon Dioxide Extract from Asparagus racemosus Willd. Root as Anti-Sebum a…

2022

Oily skin from overactive sebaceous glands affects self-confidence and personality. There is report of an association between steroid 5-alpha reductase gene (SRD5A) expression and facial sebum production. There is no study of the effect of Asparagus racemosus Willd. root extract on the regulation of SRD5A mRNA expression and anti-sebum efficacy. This study extracted A. racemosus using the supercritical carbon dioxide fluid technique with ethanol and investigated its biological compounds and activities. The A. racemosus root extract had a high content of polyphenolic compounds, including quercetin, naringenin, and p-coumaric acid, and DPPH scavenging activity comparable to that of the standa…

Eco-friendly cavity-containing iron oxides prepared by mild routes as very efficient catalysts for the total oxidation of VOCs

2018

Iron oxides (FeOx) are non-toxic, non-expensive and environmentally friendly compounds, which makes them good candidates for many industrial applications, among them catalysis. In the present article five catalysts based on FeOx were synthesized by mild routes: hydrothermal in subcritical and supercritical conditions (Fe-HT, Few200, Few450) and solvothermal (Fe-ST1 and Fe-ST2). The catalytic activity of these catalysts was studied for the total oxidation of toluene using very demanding conditions with high space velocities and including water and CO2 in the feed. The samples were characterized by X-ray diffraction (XRD), scanning and high-resolution transmission electron microscopy (SEM and…