Adsorption and gas sensing properties of CuFe2O4 nanoparticles

Spinel ferrite nanoparticles in the form CuFe2O4 were tested for gas sensing applications. Nanoparticles pressed in a disk form were used to construct conductometric gas sensors. The disk was placed between two electrical electrodes wherein the top electrode had a grid structure. The produced sensors were tested against H2S and H2 gases and they were found to be selective and sensitive to H2S concentration as low as 25 ppm. The composition of the nanoparticles was confirmed by X-ray diffraction and energy dispersive X-ray spectroscopy measurements. The crystal structure was verified by both X-ray diffraction and transmission electron microscope. The observations obtained from the experiments demonstrated the high potential of using CuFe2O4 nanoparticles for H2S sensing applications.This work was supported by the Khalifa University under the Grant Number RIFP-14312 and the Qatar University under the Grant Number QUCG-CAS-2018\2019-1.Scopu

H₂S removal by copper enriched porous carbon cuboids

Hydrogen sulfide (H2S) removal by adsorption from gas streams is crucial to prevent the environmental and industrial damage it causes. Amongst the nanostructures considered excellent candidates as sorbents, porous carbon has been studied extensively over the last years. In the present work we present a synthetic procedure for three high potential sorbents based on carbon cuboids, namely a low-surface-area copper-rich structure, a highly porous aggregate without metal addition, and lastly the same porous carbon decorated with copper. The properties and performance as catalysts of these three sorbents were evaluated by powder X-ray diffraction, X-ray photoelectron spectroscopy, thermal analysis, scanning electron microscopy with energy dispersive X-ray analysis, surface area determination through N2 adsorption and desorption, as well as by H2S adsorption measurements

Facile Organometallic Synthesis of Fe-Based Nanomaterials by Hot Injection Reaction

Fe-based colloids with a core/shell structure consisting of metallic iron and iron oxide were synthesized by a facile hot injection reaction of iron pentacarbonyl in a multi-surfactant mixture. The size of the colloidal particles was affected by the reaction temperature and the results demonstrated that their stability against complete oxidation related to their size. The crystal structure and the morphology were identified by powder X-ray diffraction and transmission electron microscopy, while the magnetic properties were studied at room temperature with a vibrating sample magnetometer. The injection temperature plays a very crucial role and higher temperatures enhance the stability and the resistance against oxidation. For the case of injection at 315 °C, the nanoparticles had around a 10 nm mean diameter and revealed 132 emu/g. Remarkably, a stable dispersion was created due to the colloids’ surface functionalization in a nonpolar solvent

Study of synthesis and surface modification of magnetic nanoparticles for biomedical applications

The purpose of this thesis was the synthesis, surface modification and characterization of magnetic nanoparticles (γ-Fe2O3, Fe3O4, MnFe2O4, Fe, FeCo, FePt) which are suitable for biomedical applications. The nanoparticles were prepared by wet chemical routes such as thermolysis, coprecipitation and modified polyol process and their characterization was processed with a plethora of techniques such as XRD, TEM, SEM, Μössbauer spectroscopy, FT-IR, TGA, VSM and SQUID. Specifically, organophilic γ-Fe2O3 and Fe3O4 nanopartcicles with controllable size (2-20 nm) and narrow size distribution, were initially prepared by thermolysis and then transformed into hydrophilic particles, through simple processes in emulsions, in the presence of cationic or anionic surfactant molecules. Such nanoparticles consist of an organophilic and hydrophilic shell and are suitable for the encapsulation of non-water soluble drugs. Second, hydrophilic Fe3O4 nanoparticles were successfully prepared through a one step precipitation method, which they brought on their surface a doubly hydrophilic copolymer which was responsible for their ferrofluid behaviour. However, replacing the copolymer with a biocompatible, synthetic silicate material (Laponite), a composite material was produced (γ-Fe2O3@ laponite) which was suitable for biomedical applications due to its high rate increasement of temperature (SAR = 131 W/g) in magnetic hyperthermia and high relaxation coefficient (r2=64 mM-1s1) in magnetic resonance imaging (MRI). Moreover, amphiphilic γ-Fe2O3, Fe3O4 and MnFe2O4 nanoparticles were also prepared by modified polyol process. Especially in the case of MnFe2O4 nanoparticles, found that exhibit excellent contrast in MRI technique as they reveal a very high coefficient relaxation, r2 reached up to 453 mM-1s1. The synthesis of metallic Fe nanoparticles was also studied by the modified polyol process. The reaction leads to Fe nanoparticles with mean diameter 20 nm, which display a very high value of saturation magnetisation (168 emu/g) that approximates the value of the magnetization for the bulk material by 80%. Finally FeCo and FePt nanoparticles were also synthesized. The FeCo nanoparticles exhibit the highest saturation magnetization, which is 145 emu/g when the size of the particles is about 8 nm and FePt nanoparticles show very high coercivity values (up to 2.8 kOe) due to their large magnetocrystalline anisotropy which are appropriate as T1 contrast agents in MRI.Ο σκοπός της διατριβής, ήταν η σύνθεση, επιφανειακή τροποποίηση και ο χαρακτηρισμός μαγνητικών νανοσωματιδίων (γ-Fe2O3, Fe3O4, MnFe2O4, Fe, FeCo, FePt) που είναι κατάλληλα για βιοϊατρικές εφαρμογές. Τα νανοσωματίδια παρασκευάστηκαν με μεθόδους υγρής χημείας όπως η θερμόλυση, η συγκαταβύθιση και η μέθοδος της τροποποιημένης πολυόλης ενώ ο χαρακτηρισμός τους έγινα με πληθώρα τεχνικών όπως XRD, TEM, SEM, φασματοσκοπία Μössbauer, FT-IR, TGA, VSM και SQUID. Συγκεκριμένα με τη μέθοδο της θερμόλυσης παρασκευάστηκαν οργανόφιλα νανοσωματίδια γ-Fe2O3 και Fe3O4, με ελεγχόμενο μέγεθος (2-20 nm) και στενή κατανομή μεγέθους και στην συνέχεια μετατράπηκαν σε υδρόφιλα, μέσω απλών διεργασιών σε γαλακτώματα, παρουσία κατιονικών ή ανιονικών επιφανειοδραστικών μορίων. Τέτοια νανοσωματίδια αποτελούνται από ένα οργανόφιλο και ένα υδρόφιλο φλοιό και θεωρούνται κατάλληλα για τον εγκλωβισμό μη-διαλυτών στο νερό φαρμακευτικών ουσιών. Αφετέρου, με την μέθοδο της καταβύθισης παρασκευάστηκαν, σε ένα στάδιο, υδρόφιλα νανοσωματίδια Fe3O4 που φέραν στην επιφάνειά τους ένα διπλά υδρόφιλο συμπολυμερές, λόγω του οποίου εμφανίζουν συμπεριφορά σιδηρορευστού. Αντικαθιστώντας, ωστόσο, το συμπολυμερές με ένα βιοσυμβατό, συνθετικό διαστρωματωμένο πυριτικό υλικό (νανοδισκία λαπονίτη), παρασκευάστηκαν με την ίδια μέθοδο, σύνθετα μαγνητικά υλικά γ-Fe2O3@λαπονίτης, που παρουσιάζουν υψηλό ρυθμό αύξησης της θερμοκρασίας με τιμή SAR=131 W/g και ισχυρό σήμα φωτοαντίθεσης (r2=64 mM-1s1) κάνοντάς τα κατάλληλα για την εφαρμογή τους στην μαγνητική υπερθερμία και στην τομογραφία (MRI). Με τη μέθοδο της τροποποιημένης πολυόλης παρασκευάστηκαν αμφίφιλα νανοσωματίδια γ-Fe2O3, Fe3O4 και MnFe2O4. Ιδιαίτερα στην περίπτωση νανοσωματιδίων MnFe2O4, διαπιστώθηκε ότι αυτά παρουσιάζουν εξαιρετική φωτοαντίθεση στην τεχνική MRI με πολύ υψηλό ρυθμό εφυσηχασμού, r2 που φθάνει τα 453 mM-1s1. Με την ίδια μέθοδο παρασκευάστηκαν και νανοσωματίδια μεταλλικού Fe με μέσο μέγεθος 20 nm, τα οποία εμφανίζουν πολύ υψηλή τιμή μαγνήτισης κορεσμού (168 emu/g) που προσεγγίζει την τιμή της μαγνήτισης για το bulk υλικό κατά 80%. Τέλος, παρασκευάστηκαν και διμεταλλικά κράματα FeCo και FePt. Τα νανοσωματίδια FeCο εμφανίζουν την υψηλότερη τιμή μαγνήτισης κορεσμού, που για μέση διάμετρο σωματιδίων μόλις 8 nm, φτάνει στα 145 emu/g. Αφετέρου, τα νανοσωματίδια FePt εμφανίζουν πολύ υψηλό συνεκτικό πεδίο (2.8 kOe) που οφείλεται στην μεγάλη μαγνητοκρυσταλλική τους ανισοτροπία και αυτά τα σωματίδια μπορούν να χρησιμοποιηθούν Τ1 παράγοντες αντίθεσης

Ni2P Nanoparticles Embedded in Mesoporous SiO2 for Catalytic Hydrogenation of SO2 to Elemental S

Highly active nickel phosphide nano clusters (Ni2P) confined in mesoporous SiO2 catalyst were synthesized by a two-step process targeting tight control over the Ni2P size and phase. The Ni precursor was incorporated into the MCM-41 matrix by one-pot synthesis, followed by the phosphorization step which was accomplished in oleylamine with trioctylphosphine at 300 oC so to achieve the phase transformation from Ni to Ni2P. For benchmarking, Ni confined by the mesoporous SiO2 (absence of phosphorization) and 11 nm Ni2P nanoparticles (absence of SiO2), were also prepared. From the microstructural analysis, it was found that the growth of Ni2P nano clusters was restricted by the mesoporous channels, thus forming ultrafine and highly dispersed Ni2P nano clusters ( n-Ni2P > u-Ni@m-SiO2 > c-Ni2P in the selective hydrogenation of SO2 to S. In particular, u-Ni2P@m-SiO2 exhibited an SO2 conversion of 94 % at 220 oC and ~99 % at 240 oC, which is higher than the 11 nm stand-alone Ni2P particles (43 % at 220 oC and 94 % at 320 oC), highlighting the importance of the role played by SiO2 in stabilizing ultrafine nanoparticles of Ni2P. The reaction activation energy Ea over u-Ni2P@m-SiO2 is ~33 kJ/mol, which is lower than over n-Ni2P (~36 kJ/mol) and c-Ni2P (~66 kJ/mol), suggesting that the reaction becomes energetically favored over the ultrafine Ni2P nano clusters

Ni2P Nanoparticles Embedded in Mesoporous SiO2 for Catalytic Hydrogenation of SO2 to Elemental S

Highly active nickel phosphide nano clusters (Ni2P) confined in mesoporous SiO2 catalyst were synthesized by a two-step process targeting tight control over the Ni2P size and phase. The Ni precursor was incorporated into the MCM-41 matrix by one-pot synthesis, followed by the phosphorization step which was accomplished in oleylamine with trioctylphosphine at 300 oC so to achieve the phase transformation from Ni to Ni2P. For benchmarking, Ni confined by the mesoporous SiO2 (absence of phosphorization) and 11 nm Ni2P nanoparticles (absence of SiO2), were also prepared. From the microstructural analysis, it was found that the growth of Ni2P nano clusters was restricted by the mesoporous channels, thus forming ultrafine and highly dispersed Ni2P nano clusters ( n-Ni2P > u-Ni@m-SiO2 > c-Ni2P in the selective hydrogenation of SO2 to S. In particular, u-Ni2P@m-SiO2 exhibited an SO2 conversion of 94 % at 220 oC and ~99 % at 240 oC, which is higher than the 11 nm stand-alone Ni2P particles (43 % at 220 oC and 94 % at 320 oC), highlighting the importance of the role played by SiO2 in stabilizing ultrafine nanoparticles of Ni2P. The reaction activation energy Ea over u-Ni2P@m-SiO2 is ~33 kJ/mol, which is lower than over n-Ni2P (~36 kJ/mol) and c-Ni2P (~66 kJ/mol), suggesting that the reaction becomes energetically favored over the ultrafine Ni2P nano clusters

Different modulated structures of topological defects stabilized by adaptive targeting nanoparticles

It is demonstrated that interactions between nanoparticles and topological defects induce a twist-grain boundary phase in a chiral liquid crystal. The occurrence of this phase, the analogue of the Shubnikov phase in type-II superconductors, is driven by direct interactions between surface-functionalized CdSe quantum dots and screw dislocations. It is shown that, within an adaptive-defect-core-targeting mechanism, nanoparticles of appropriate size and functionalization adapt to qualitatively different cores of topological defects such as disclination lines and screw dislocations. This mechanism enables the effective reduction of the energetically costly, singular defect core volume, while the surrounding phase ordering remains relatively weakly affected. The findings suggest new pathways towards the controlled assembly of superstructures in diverse, symmetry-broken, condensed-matter systems, ranging from nanoparticle-decorated liquid crystals to superconductors.status: publishe

Different modulated structures of topological defects stabilized by adaptive targeting nanoparticles

It is demonstrated that interactions between nanoparticles and topological defects induce a twist-grain boundary phase in a chiral liquid crystal. The occurrence of this phase, the analogue of the Shubnikov phase in type-II superconductors, is driven by direct interactions between surface-functionalized CdSe quantum dots and screw dislocations. It is shown that, within an adaptive-defect-core-targeting mechanism, nanoparticles of appropriate size and functionalization adapt to qualitatively different cores of topological defects such as disclination lines and screw dislocations. This mechanism enables the effective reduction of the energetically costly, singular defect core volume, while the surrounding phase ordering remains relatively weakly affected. The findings suggest new pathways towards the controlled assembly of superstructures in diverse, symmetry-broken, condensed-matter systems, ranging from nanoparticle-decorated liquid crystals to superconductors.info:eu-repo/semantics/publishe

Facile MoS2 Growth on Reduced Graphene-Oxide via Liquid Phase Method

10.3389/fmats.2018.00029Frontiers in Materials52