Wyznaczanie grubości warstw BN na podłożu Al2O3 za pomocą spektroskopii FT-IR

Hexagonal boron nitride (h-BN) is an attractive material for applications in electronics. The technology of devices based on BN requires non-destructive and fast methods of controlling the parameters of the produced layers. Boron nitride layers of different thickness were grown on sapphire substrates (Al2O3) using the MOCVD method. The obtained films were characterized by FT-IR spectroscopy using IRR and ATR techniques and by the XRR and SEM methods. We showed that by analyzing the ATR or reflectance spectrum in the range of 600-2500 cm-1 we can measure the thickness of a BN layer on the Al2O3 substrate. Our measuring method allows measuring the layers with a thickness from ~2 nm to approx. 20 nm.Heksagonalny azotek boru (h-BN) jest atrakcyjnym materiałem do zastosowań w elektronice. Technologia wytwarzania urządzeń z zastosowaniem warstw h-BN wymaga nieniszczących i szybkich metod kontroli parametrów produkowanych warstw. Warstwy azotku boru o różnej grubości wyhodowano na podłożach szafirowych metodą MOCVD. Otrzymane warstwy scharakteryzowano za pomocą spektroskopii FT-IR z użyciem technik IRR i ATR oraz metodami XRR i SEM. Pokazaliśmy, że analizując widmo ATR lub odbicia w zakresie 600-2500 cm-1 można zmierzyć grubość warstwy BN na podłożu Al2O3. Nasza metoda pomiarowa pozwala na pomiar warstw o grubości od ~2 nm do ok. 20 nm

Formation of GeO2 under Graphene on Ge(001)/Si(001) Substrates Using Water Vapor

The problem of graphene protection of Ge surfaces against oxidation is investigated. Raman, X-Ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) measurements of graphene epitaxially grown on Ge(001)/Si(001) substrates are presented. It is shown that the penetration of water vapor through graphene defects on Gr/Ge(001)/Si(001) samples leads to the oxidation of germanium, forming GeO2. The presence of trigonal GeO2 under graphene was identified by Raman and XRD measurements. The oxidation of Ge leads to the formation of blisters under the graphene layer. It is suggested that oxidation of Ge is connected with the dissociation of water molecules and penetration of OH molecules or O to the Ge surface. It has also been found that the formation of blisters of GeO2 leads to a dramatic increase in the intensity of the graphene Raman spectrum. The increase in the Raman signal intensity is most likely due to the screening of graphene by GeO2 from the Ge(001) surface

Recovery of ibuprofen from pharmaceutical wastes using ionic liquids

This work aims at developing a process to valorise pharmaceutical wastes through the recovery of pharmaceutically active compounds. The ibuprofen extraction and isolation from solid pharmaceutical wastes is used here as a case study and an integrated approach comprising the ibuprofen solid-liquid extraction, the removal of the insoluble excipients present in the pills, the target drug recovery and the recycling of the aqueous solutions is proposed. The present work is centred on the optimization of the first (solid-liquid extraction) and third (drug recovery) steps mentioned above. For the solid-liquid extraction step, various ionic liquid aqueous solutions were tested, tetrabutylammonium chloride ([N-4444]Cl) being adopted to further optimize the process. A solution composed of 45 wt% of [N-4444]Cl + 5 wt% of citrate buffer + 50 wt% of H2O led to the highest ibuprofen extraction efficiency (EEIBU = 97.92 +/- 2.65%) while in the absence of citrate the extraction efficiency was somewhat lower (EEIBU = 93.53 +/- 0.62%). The polishing task was affected by the type of aqueous solution utilized during the solid-liquid extraction step: in the presence of citrate buffer water was not prone to induce significant ibuprofen precipitation (maximum REIBU of 34.71 +/- 4.00%) the aqueous KCl solution being the best option (maximum REIBU of 87.97 +/- 1.00%); when no citrate buffer is used water can be used as an anti-solvent with a maximum REIBU of 91.60 +/- 0.19% while aqueous KCl solutions lead to an REIBU up to 97.07 +/- 0.14%. Based on these results an integrated process is proposed for the ibuprofen recovery and isolation aimed at adding value to pharmaceutical wastes

Aqueous biphasic systems using chiral ionic liquids for the enantioseparation of mandelic acid enantiomers

This work aims at extending the applicability of chiral aqueous biphasic systems (ABS) to enantioseparations by using chiral ionic liquids (CILs) simultaneously as phase forming agents and chiral selectors. After determining the ternary phase diagrams of ABS composed of CILs and salts, these were used to ascertain the CIL structure and salt role on the ABS aptitude to separate mandelic acid enantiomers. Representative CIL-based ABS were further employed in optimization studies, where the mandelic acid content, temperature, tie-line length, salt and phases weight ratio were studied. The influence of these parameters is shown to be highly dependent on the CIL-based ABS, nevertheless the results here reported suggest that the key driving the enantioseparation in these ABS is a combination of the enantiorecognition ability of a given CIL with the solubility of mandelic acid in the corresponding CIL-rich phase.publishe

Recovery of Nonsteroidal Anti-Inflammatory Drugs from Wastes Using Ionic-Liquid-Based Three-Phase Partitioning Systems

Aiming at outlining new strategies for the valorization of solid pharmaceutical wastes as viable alternatives to incineration, this work proposes the use of ionic liquids-based three phase partitioning (IL-based TPP) systems. Ibuprofen, naproxen, and ketoprofen, all belonging to the class of nonsteroidal anti-inflammatory drugs (NSAIDs), were adopted as model compounds. An integrated process has been conceptualized based on three steps: (1) extraction and purification of NSAIDs using the IL-based TPP systems, (2) drug isolation by precipitation with antisolvents, and (3) recycling and reusing the solvents. With the optimization of steps 1 and 2 as objects of this investigation, aqueous biphasic systems (ABS) composed of three distinct ILs (tetrabutylammonium chloride, 1-butyl-3-methylimidazolium chloride, and benzyldimethyl­(2-hydroxyethyl)­ammonium chloride) and potassium citrate buffer were studied. The corresponding IL-based TPP systems were further applied in the purification of each NSAID, and different antisolvents (citric acid aqueous solutions for ibuprofen and naproxen and aluminum sulfate aqueous solutions for ketoprofen) were evaluated as precipitating agents to isolate each drug. The success of the process developed is demonstrated by extraction efficiencies higher than 83.8 ± 7.7% attained in step 1 and isolation efficiencies higher than 76.2 ± 1.8% in step 2. The stability of the three NSAIDs in IL-based aqueous matrices was additionally checked by using a protocol adapted from the OECD guidelines. The economic efficiency and environmental benignity of the process herein developed is underlined, based on not only the low cost of the solvents chosen but also the possibility of recycling and reusing the phase-forming components and antisolvents employed