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Karst bauxites have recently received renewed attention for their potential as non-conventional REE sources. Karst bauxites from the Pedernales Peninsula in the Dominican Republic stand among the world’s richest in REE. Bauxite ore from two deposits from this bauxite district, Aceitillar and El Turco, have been selected for this study due to their outstanding REE contents and contrasting mineralogy. REE (La to Lu) contents in Aceitillar, range from 0.07 to 0.16 wt%, and Y from 0.01 to 0.13 wt%, whereas El Turco contains between 0.28 and 1.40 wt% REE, and 0.33 to 1.48 wt% Y. The characterisation of REE mineralisation was performed through powder and monocrystal XRD, SEM-EDS, and EMP analyses. REE phosphates and carbonates reveal textural features that suggest significant REE mobilisation and re-deposition within the bauxite profile. The identified REE minerals can be classified into: i) primary monazite(-Ce) and minor monazite(-La); ii) secondary Y- and Nd-dominant phosphates; and iii) secondary Gd- and Nd-carbonates of the (hydroxyl)bastnäsite group. While monazites are ubiquitous in the two studied deposits, secondary phosphates are predominant in El Turco while secondary carbonates are exclusive of Aceitillar. This contrasting mineralogy is explained by the total concentration of carbonate and/or phosphate in the karst bauxite groundwater solutions. REE phosphates are the most stable phases at [CO32−]total/[PO43-]total ≤ 2; whereas REE carbonates are stable at near neutral pH when the total aqueous carbonate concentration is two orders of magnitude higher than that of phosphate. Results of this investigation contribute to a better understanding of the formation REE minerals in the supergene environment and can be applied in REE separation methods. Validerad;2023;Nivå 2;2023-04-21 (sofila);Funder: MESCYT (Ministry of HigherEducation, Science and Technology of the Dominican Republic) (grant nos. 2014-1B4-133 & 2022-1A4-189) PID2019-105625RB-C21 (IP J.A. Pro-enza)

L’accés a una Font fiable de matèries primeres s’ha convertit en un repte per a la Unió Europea (UE). Actualment, la Comissió té com a objectiu implementar esquemes circulars i valoritzar els residus per garantir aquest accés. En aquest context, les aigües àcides de mina (AMW) es poden considerar com una alternativa per tenir accés a determinats metalls valuosos, com ara el Zn o el Cu, però també a les terres rares (REEs) o el Mg, tots dos catalogats com a matèries primeres crítiques per la UE. Tradicionalment, aquests corrents es tracten amb calç per neutralitzar l’acidesa i precipitar metalls, però la recuperació d’aquests elements es pot aconseguir integrant la precipitació selectiva i el procés d’intercanvi iònic. Aquest Treball de Final de Màster es va centrar en el tractament d’AMW per la conca d’Aznalcóllar (caracteritzada per 1,63 g/L de Mg, 547 mg/L de Zn y 18,56 mg/L de REEs) per a la recuperació de recursos mitjançant: i) eliminació de Fe i Al mitjançant una oxidació i precipitació selectiva, ii) recuperació de Zn com a sulfur, iii) tecnologia d’intercanvi iònic utilitzant dues resines en series (TP272 amb un grup àcid organofosfídic i S930 amb un grup iminiodiacètic) per fraccionar REEs en lleugers i pesats, iv) recuperació de REEs mitjançant precipitació selectiva amb àcid oxàlic de l’eluat de la resina, i v) recuperació de Mg mitjançant una precipitació selectiva. Aquest treball es centra principalment en la recuperació de REEs mitjançant la integració de la tecnologia d’intercanvi iònic i la precipitació selectiva d’oxalats de REEs, i es va realitzar una optimització de l’elució canviant la concentració del regenerant. Addicionalment, es va estudiar la recuperació de Mg utilitzant diferents productes químics i es van avaluar la puresa dels sòlids recollits. A més, es van utilitzar eines d’equilibri com PHREEQC per avaluar les capacitats de predicció al llarg del procés. El acceso a una fuente confiable de materias primas se ha convertido en un desafío para la Unión Europea (UE). Hoy en día, la Comisión tiene como objetivo implementar esquemas circulares y valorizar los residuos para garantizar dicho acceso. En este contexto, las aguas ácidas de mina (AMW) pueden considerarse como una alternativa para tener acceso a ciertos metales valiosos, como Zn o Cu, pero también a tierras raras (REEs) o Mg, ambos catalogados como materias primas críticas por la UE. Tradicionalmente, estas corrientes son tratadas con cal para neutralizar la acidez y precipitar los metales, pero con la recuperación de estos elementos se puede lograr integrando la precipitación selectiva y el proceso de intercambio iónico. Este Trabajo de Final de Máster se ha centrado en el tratamiento de AMW de la balsa de Aznacóllar (caracterizada por 1,63 g/L de Mg, 547 mg/L de Zn y 18,56 mg/L de REEs) para la recuperación de recursos mediante: i) eliminación de Fe y Al mediante una oxidación y precipitación selectiva, ii) recuperación de Zn como sulfuro, iii) tecnología de intercambio iónico usando dos resinas en serie (TP272 con un grup ácido organofosfídico y S930 con un grupo iminodiacético) para el fraccionamiento de REEs en ligeros y pesados, iv) recuperación de REEs usando precipitación selectiva con ácido oxálico del eluato de la resina, y v) recuperación de Mg por precipitación selectiva. Este trabajo se centra en la recuperación de REEs mediante la integración de la tecnología de intercambio iónico y precipitación selectiva como oxalatos de REEs, y se realizó una optimización de la elución cambiando la concentración del regenerante usado. Adicionalmente, se estudió la recuperación de Mg mediante el uso de diferentes químicos y se evaluó la pureza de los sólidos recolectados. Además, se utilizaron herramientas de equilibrio como PHREEQC para evaluar las capacidades de predicción a lo largo del proceso. The access to a reliable source of raw materials has become a challenge for the European Union (EU). Nowadays, the Commission is aiming to implement circular schemes and to valorise wastes to guarantee such access. Within this context, Acidic Mine Waters (AMWs) can be considered as an alternative to have access to certain valuable metals, such as Zn or Cu, but also to Rare Earth Elements (REEs) or magnesium, being both listed as critical raw materials by the EU. Traditionally, these streams are currently treated with lime to neutralize acidity and precipitate metals, but the recovery of these elements can be pursued by integrating selective precipitation and ion-exchange process. This Master Thesis focused on the treatment of AMW for the Aznalcóllar open-pit (characterized by 1.63 g/L Mg, 547 mg/L Zn and 18.56 mg/L REEs) for resource recovery by: i) removal of Fe and Al by an oxidation and selective precipitation, ii) recovery of Zn as sulfide, iii) ion exchange technology using two resins in series (TP272 with a organophosphidic acid group and S930 with an iminodiacetic group) for fractionating REEs into light and heavies, iv) recovery of REEs using selective precipitation with oxalic acid from the resin eluates, and v) recovery of Mg by a selective precipitation. This work is mainly focused on the recovery of REEs by integrating ion exchange technology and selective precipitation of REEs oxalates, and an optimization of the elution was performed by changing the concentration of regenerant. Additionally, the recovery of Mg was studied by using different chemicals and an assessment of the purity of solids collected was evaluated. Moreover, equilibrium tools such as PHREEQC were used to assess the prediction capabilities along the process.

Acidic mine Drainage (AMD) is still considered one of the greatest mining sustainability challenges due to the large volumes of wastes generated and the high associated treatment cost. New regulation initiatives on sustainable development, circular economy and the need for strategic elements as Rare Earth Elements (REE) may overcome the traditional research initiatives directed to developing low cost treatment options and to develop research initiatives to identify the potential benefit of considering such AMD as a potential secondary resource. As an example, this study develops the integration of a three-stage process where REE are selectively separated from base metals (e.g. Fe, Al, Mn, Ca, Mg, Cd, Pb) and then concentrate to produce a rich REE by-product recovered as REE-phosphates. Selective separation of Fe (>99%) was achieved by total oxidation to Fe(III) and subsequent precipitation as schwertmannite at pH 3,6 ± 0.2. REE were then extracted from AMD using a sulfonic ion-exchange resin to produce concentrated REE sulfuric solutions up to 0.25 gREE/L. In a final stage selective separation of REE from Al(III), Ca(II) and Mg(II) and transitions elements (Cu, Zn, Ni) was achieved by precipitation with phosphate solutions under optimized pH control and total phosphate concentration. XRD analysis identified low-crystalline minerals. By using a thermal treatment the presence of PrPO4(s) and Cheralite (CePO4(s)) where Ce is substituted by La and Ca and Xenotime (YPO4(s)) were found as main minerals AlPO4(s) Ca,MgYPO4(s) were also identified., This research was supported by the W4V project (ref. PID2020-114401RB-C21) and the R2MIT project (CTM2017-85346-R) financed by the Ministerio de Economía y Competitividad (MINECO), the Catalan Government (Project Ref. 2017SGR312), Spain. And the European Commission through the OpenInnotrain project MSCA-RISE-2018-823971. Additionally, the Kempe Foundation is thanked for their financial support to Dr. Mehrez Hermassi at Umeå University (projekt med referensnummer SMK-1856). We also want to thank the contribution of Purolite Spain (J. Barios / R. Salvatierra) for the supply of IX Resins, to G. Chavez for their help during the experimental work and to the Institut de Diagnosi Ambiental i Estudis de l'Aigüa -IDAEA, Consejo Superior de Investigaciones Científicas-CSIC for the ICP analysis.

Immunemetabolism; Metabolism; Nanoceria Inmunometabolismo; Metabolismo; Nanoceria Immunemetabolisme; Metabolisme; Nanocèria Dysregulation of the immune system is associated with an overproduction of metabolic reactive oxygen species (ROS) and consequent oxidative stress. By buffering excess ROS, cerium oxide (CeO2) nanoparticles (NPs) (nanoceria) not only protect from oxidative stress consequence of inflammation but also modulate the immune response towards inflammation resolution. Immunomodulation is the modulation (regulatory adjustment) of the immune system. It has natural and human-induced forms, and it is part of immunotherapy, in which immune responses are induced, amplified, attenuated, or prevented according to therapeutic goals. For decades, it has been observed that immune cells transform from relative metabolic quiescence to a highly active metabolic state during activation(1). These changes in metabolism affect fate and function over a broad range of timescales and cell types, always correlated to metabolic changes closely associated with mitochondria number and morphology. The question is how to control the immunochemical potential, thereby regulating the immune response, by administering cellular power supply. In this regard, immune cells show different general catabolic modes relative to their activation status, linked to their specific functions (maintenance, scavenging, defense, resolution, and repair) that can be correlated to different ROS requirements and production. Properly formulated, nanoceria is highly soluble, safe, and potentially biodegradable, and it may overcome current antioxidant substances limitations and thus open a new era for human health management.

Made available in DSpace on 2022-04-28T19:41:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-11-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Mg-based alloys are promising light materials for structural applications such as spare parts and assembles in aerospace manufacturing, but most of them are prone to corrode. In this work, the corrosion behavior of the WE43 Mg alloy in 0.6 M NaCl solution was appraised and compared to that of commercially pure Mg. Immersion tests allowed to assess the corrosion rate and the products formed on the exposed surfaces for up to 168 h. It was found that the corrosion rate of the WE43 was about 10- to 100-fold lower compared to commercially pure Mg. The onset of the corrosion resistance of the WE43 was ascribed to the nature of the corrosion product layer and its integrity on the surface, related to the low kinetics of the cathodic reaction of hydrogen gas evolution. The electrochemical impedance spectroscopy, potentiodynamic polarization, and kelvin probe force microscopy data reinforced the effect of the alloying elements on i) the formation of Y- and Nd-rich oxides, ii) the reduction of the intensity of the hydrogen gas evolution at the underneath surface, and iii) the formation of micro-anode second phases that did not compromise the corrosion resistance. Thus, this study contributes to the prospect of using alloys such as WE43 for applications where strong and light alloys with attractive corrosion resistance in a chloride-rich environment are requested. Engineering School of São Carlos University of São Paulo Department of Materials Engineering, Av. Joao Dagnone, 1100 Jd. Sta Angelina Federal University of São Carlos Department of Materials Science and Engineering, Rod. Washington Luis, CEP, SP São Paulo State University (UNESP) Campus of São João da Boa Vista, Av. Profa Isette Corrêa Fontão, 505, Jardim Das Flores, SP Embraer, SP São Paulo State University (UNESP) Campus of São João da Boa Vista, Av. Profa Isette Corrêa Fontão, 505, Jardim Das Flores, SP

Six homodinuclear lanthanide complexes with formula [Ln2(μ2-9-AC)4(9-AC)2(phen)2] (Ln(III) = Nd (1), Eu (2), Gd (3), Tb (4), Er (5) and Yb (6) are reported and complexes 1–3 and 6 are structurally characterized. 9-HAC = 9-anthracenecarboxylic acid, phen = 1,10-phenanthroline. The luminescence properties of compounds 1–6 have been studied at different temperatures in the solid state and show the sensitization of the 4f–4f emission bands in the NIR range for compounds 1, 5 and 6. The molar magnetic susceptibility measurements of 1–6 in the 2–300 K temperature range indicate weak antiferromagnetic exchange for the isotropic Gd(III) compound 3. Furthermore, slow relaxation of the magnetization is found in complexes 5 and 6 with effective energy barriers of 9.5 cm−1 (0.1 T) and 22.7 cm−1 (0.15 T), respectively.

International audience; The single-molecule magnet (SMM) properties of a series of ferrocenium complexes, [Fe(h5-C5R5)2]+ (R=Me, Bn), are reported. In the presence of an applied dc field, the slow dynamics of the magnetization in [Fe(h5-C5Me5)2]BArF are revealed. Multireference quantum mechanical calculationsshow a large energy difference between the ground and first excited states, excluding the commonly invoked, thermally activated (Orbach-like) mechanism of relaxation. In contrast, a detailed analysis of the relaxation time highlights that both direct and Raman processes are responsible forthe SMM properties. Similarly, the bulky ferrocenium complexes, [Fe(h5-C5Bn5)2]BF4 and [Fe(h5-C5Bn5)2]PF6, also exhibit magnetization slow dynamics, however an additional relaxation process is clearly detected for these analogous systems.

Treballs Finals de Grau de Química, Facultat de Química, Universitat de Barcelona, Any: 2021, Tutora: E. Carolina Sañudo Zotes, The increment of documents or currency counterfeiting is being a problem for society, making it necessary to find a solution. One possible method is the development of smart inks, which are luminescent under certain light wavelength. To do it, metal-organic frameworks (MOFs) with structure [Ln(CH3COO)(PhCOO)2] of Ln = Tb, Eu and Sm are used. Homometallic and heterometallic compounds are synthetized with Ln:Ln’ proportions of approximately 0,5:0,5, 0,25:0,75 and 0,75:0,25. All of them are luminescent under UV light: Tb is green, Eu red and Sm violet. Due to the great properties of 2D materials, such as graphene, exfoliations of homometallic MOFs are carried out to achieve single-layer compounds dispersed in i-propanol. Both for MOFs and for exfoliations, a luminescence study has been done to see where the electronic transitions responsible of their colour appear. Although f-f transitions are prohibited, due to the antenna effect of the ligand, the expected electronic transitions of Lanthanides can be observed in all compounds. Furthermore, Tb in heterometallic compounds acts as sensitizer, making the emission of the partner Ln’ more intense. After the confirmation of exfoliations luminescence, they are stamped. In a preliminary study, it is observed that through the fluorimeter the corresponding electronic transition appears, but it is not possible to see its luminescence at naked eye under UV light.

This article belongs to the Special Issue 2D Magnetic Molecular Materials., The synthesis of a terbium-based 2D metal–organic framework (MOF), of formula [Tb(MeCOO)(PhCOO)2] (1), a crystalline material formed by neutral nanosheets held together by Van der Waals interactions, is presented. The material can be easily exfoliated by sonication and deposited onto different substrates. Uniform distributions of Tb-2D MOF flakes onto silicon were obtained by spin-coating. We report the luminescent and magnetic properties of the deposited flakes compared with those of the bulk. Complex 1 is luminescent in the visible and has a sizeable quantum yield of QY = 61% upon excitation at 280 nm. Photoluminescence measurements performed using a micro-Raman set up allowed us to characterize the luminescent spectra of individual flakes on silicon. Magnetization measurements of flakes-on-silicon with the applied magnetic field in-plane and out-of-plane display anisotropy. Ac susceptibility measurements show that 1 in bulk exhibits field-induced slow relaxation of the magnetization through two relaxation paths and the slowest one, with a relaxation time of τlf ≈ 0.5 s, is assigned to a direct process mechanism. The reported exfoliation of lanthanide 2D-MOFs onto substrates is an attractive approach for the development of multifunctional materials and devices for different applications., This research was funded by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO, Grant Nos. MAT2017-83468-R; PGC2018-098630-B-I00 (ECS)) and from the regional Government of Aragon (E12-20R RASMIA project).

© 2020. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ Increasing population growth and rise global energy petition have made congregation the requests of energy generation and safety a major challenge global. In another hand nanogeoscience is commencing to develop a viable remediation approach of attention in coal mine drainage (CMD) around spontaneous coal combustion (SCC). On the ecological context, nanophases (minerals and/or amorphous phases) are more reactive than bulk compounds, a property that powerfully influences the fate of pollutants in topsoils and drainages. In this work petrographic and geochemical investigations of selected CMD sediments were conducted. The substitution of As, Cd, Hg, and Se in pyrite was most apparent in the CMD sediments. The sampled CMD contained carbon nanotube (CNTs) structures and many others C-nanophases. The CNTs contained several elements, including Hg, Pb, F, Cl, and halogens. While CNTs are known to be produced from coal fires of varying ranks, this seems to be the first report of naturally occurring CNTs. This work also denotes the occurrence of historical NPs-locations in near vicinity to all other, as for illustration deposits of C-NPs and non-crystalline compounds appear only nano-meters separately from each other on the contradictory sides of non-altered amorphous phases. In addition, non-conventional sources, including CMD hosting elevated concentrations of Rare Earth Elements and Yttrium (REY), have been explored as attractive secondary sources for elements recovery. Consequently, in this study we investigate CMD from abandoned coal mines in the South America as a potential REY resource. It is suggested that more work is required on CMD and a few research areas are proposed for future research.

This work demonstrates the effective use of automatic sensor-based sorting technology as a viable separation method for rare earth element (REE) rich ores composed primarily of xenotime minerals with gagarinite-(Y) and fluocerite-(Ce, La) inclusions. A dual energy X-ray transmission (DE-XRT) sensor affinity was used to evaluate forty-two heavy rare earth element (HREE) ore grab samples from the Madeira deposit. These samples and separated products were scanned by the sensor under many operating parameters. Subsequent analyses, including petrographic and multi-element chemical analyses were performed on the grab samples. Specific mass tests were also compared with energy attenuation curves from the sensor, which correlated strongly with every concentration stage – the highest achieved density being 3.01 g/cm3. The best estimated HREE recovery from laboratory-scale sorting of the samples identified by the sensor was effectively 100%, however this occurred in conjunction with a mass recovery equal to 97% of the feed. Such results are expected knowing that the sample method was not entirely representative. Ongoing research into automatic sorting technology for the upgrading of Brazilian ores is being performed by the Federal University of Rio Grande do Sul (UFRGS), Brazil.

The importance of rare earth elements in high-tech materials has promoted the necessity to develop new materials for sensing and separating them. Luminescent metal-organic frameworks (MOFs) due to their promising applications as functional materials for chemical sensing and separation, which upon introducing analytes create multi-responsive systems, have been receiving great attention by scientists. In this regard, we have designed and synthesized a novel three-dimensional copper framework, [Cu2(3,4-pydc)2(H2O)5]n.2nH2O (1; 3,4-H2pydc = 3,4-pyridine dicarboxylic acid), in ambient condition with an interesting topology and potential application as a cation exchange material. Upon Tb3+ ions uptake, compound 1 exhibited the antenna effect to sensitize Tb3+ ions and its fluorescent emission was enhanced. It also showed selective sensing ability based on turn-on fluorescence response towards Tb3+ ions, in a mixture of main and transition metal ions and Tb3+ ions. Furthermore, the results showed that the Tb3+ ion exchange process is reversible. Therefore, compound 1 is a promising multifunctional luminescent MOF for simultaneous sensing and chemical separation of Tb3+ ions which is an advantage over the previously used MOFs in this regard. Furthermore, the reusability experiment demonstrated that 1 can be utilized for long-term detection and separation of Tb3+ ions.

A new CoII2YIII2 complex with the formula [{Co(μ-L)Y(NO3)}2(μ-CO3)2]·2CH3OH·2H2O (where H2L = N,N′,N′′-trimethyl-N,N′′-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine) has been prepared and its structure solved by single-crystal X-ray diffraction. The tetranuclear structure is formed by the connection of two [Co(μ-L)Y(NO3)] dinuclear units through two carbonate bridging ligands, which exhibit a μ3-κ2-O,O′:κ-O:κ-O′′ tetradentate coordination mode. The CoII ion exhibits a slightly distorted octahedral CoN3O3 coordination environment. From direct-current magnetic data a large and positive axial anisotropy parameter was extracted (D = +80.6 cm−1) and its sign unambiguously confirmed by HFEPR spectra and ab initio calculations. The extracted D value is rather larger than those previously reported for the analogous CoIIYIII dinuclear complexes, which agrees with the fact that the CoII ion in the CoII2YIII2 complex exhibits a lower distortion from the octahedral geometry in this family of CoIInYIIIn complexes. Dynamic ac magnetic measurements show that the reported compound presents field-induced slow relaxation for magnetization reversal, through a combination of direct and Raman processes. Magnetic measurements on the diluted magnetic counterpart (Zn/Co = 10/1) show the persistence of these processes, pointing out their single-ion origin. The Raman relaxation process for the CoII2YIII2 complex is faster that those observed for its CoIIYIII dinuclear counterparts. This fact and the existence of the persistent direct process at low temperature could be attributed to the former molecule being larger and more flexible than the latter ones.

The synthesis, structural characterization and magnetic study of novel CoII/4f and CoII/YIII clusters are described. In particular, the initial employment of di-2-pyridyl ketone, (py)2CO, in mixed metal Co/4f chemistry, provided access to four triangular clusters, [CoII2MIII{(py)2C(OEt)(O)}4(NO3)(H2O)]2[M(NO3)5](ClO4)2 (M = Gd, 1, Dy, 2, Tb, 3, Y, 4), where (py)2C(OEt)(O)&minus, is the monoanion of the hemiketal form of (py)2CO. Clusters 1&ndash, 4 are the first reported Co/4f (1&ndash, 3) and Co/Y (4) species bearing (py)2CO or its derivatives, despite the fact that over 200 metal clusters bearing this ligand have been reported so far. Variable-temperature, solid-state dc and ac magnetic susceptibility studies were carried out on 1&ndash, 4 and revealed the presence of weak ferromagnetic exchange interactions between the metal ions (JCo-Co = +1.3 and +0.40 cm&minus, 1 in 1 and 4, respectively, JCo-Gd = +0.09 cm&minus, 1 in 1). The ac susceptibility studies on 2 revealed nonzero, weak out-of-phase (&chi, &rsquo, M) signals below ~5 K.

Since the molecular electronic spin emerged as one of the promising technologies to implement the quantum processing of information, coordination complexes of lanthanides and actinides have become protagonists as suitable molecular realizations of qubits and qugates. In this chapter, we revise the most recent developments on the production of rare earth (RE) based qubits, qugates and most recently qudits, which also make use of the nuclear spin degrees of freedom to encode and process quantum information. Essential concepts such as the spin relaxation and the phase memory times in these systems are described, as well as the development of multiqubit molecular systems for the realization of basic quantum gate operations. The most advanced achievements consisting on the realization of the Grover algorithm or the demonstration of a quantum error correction protocol constitute the culmination of this chapter, which concludes with the challenges yet lying ahead for implementing the molecular spin as an essential component of quantum computing

Treballs Finals de Grau de Química, Facultat de Química, Universitat de Barcelona, Any: 2019, Tutora: Saskia Speed Castro, Five compounds have been synthesized in this work: [Co4(μ3-py2C(OH)O)4(4-Br-3-CF3-PhNCN)2 (PhCOO)2] (1), [Co4(μ2-py2C(OH)O)2(μ3-py2C(OCH3)O)2(μ2-4-Cl-PhNCN)2(4-Cl-PhNCN)2] (2), [Co(py2C(OH)O)(py2C(OCH2CH3)O)][NO3]·3H2O (3), [Zn2Tb(μ2-py2C(OCH2CH3)O)3(μ3-py2C(OCH2CH3)O) (NO3) (H2O)][Tb(NO3)5] (4) and [Dy5Co4(py2C(OH)O)4(μ3-py2CO2)4(μ4-py2CO2)2(O)2(H2O)6(NO3)2][NO3]5 (5). The metal ions of the five compounds are connected through oxo-bridges from the Di(2-pyridil) ketone derivatives formed after solvolysis and a posterior deprotonation. In addition the Co(II) atoms of compound 2 are connected by two R-phenylcyanamides in the end-on coordination mode. The magnetic susceptibility measurements were performed for compounds 1, 2, 4 and 5. Compound 1 and 2 exhibit a ferromagnetic coupling between the Co(II) metal ions. Compound 4 shows paramagnetic behaviour and 5 exhibit weak antiferromagnetic coupling between the Dy(II) ions. Compounds 1, 2 and 5 show SMM (Single Molecular Magnet) behaviour. The relaxation time of magnetization hasn’t been calculated.

The first structurally characterized hexafluorido complex of a tetravalent actinide ion, the [UF6]2− anion, is reported in the (NEt4)2[UF6]⋅2 H2O salt (1). The weak magnetic response of 1 results from both UIV spin and orbital contributions, as established by combining X‐ray magnetic circular dichroism (XMCD) spectroscopy and bulk magnetization measurements. The spin and orbital moments are virtually identical in magnitude, but opposite in sign, resulting in an almost perfect cancellation, which is corroborated by ab initio calculations. This work constitutes the first experimental demonstration of a seemingly non‐magnetic molecular actinide complex carrying sizable spin and orbital magnetic moments.

Petrographic, geochemical, and electron microbeam investigations of selected anthracites and anthracite-rank coaly shales were conducted. The Pennsylvania, Rhode Island, and KwaZu-Natal anthracites show an enrichment in the middle to heavy rare earths (REE) while the Virginia semi-anthracite exhibited a decreasing trend through the light REE, a peak in Gd, and a depletion in the heavy REE. Substitution of As, Hg, and Se in pyrite was most apparent in the Virginia coal. The Pennsylvania, Rhode Island, and KwaZu-Natal anthracites contained spherical carbon nanotube (CNT) structures. The CNTs contained several elements, including Hg, Cd, F, Cl, and Br. While CNTs are known to be produced from coals of varying ranks, this seems to be the first report of naturallyoccurring CNTs.

A family of lanthanide metal complexes with the general formula [Ln(H2O)3(18-crown-6)](ClO4)3 (Ln = TbIII, DyIII, ErIII, and YbIII) has been synthesized. Their magnetic properties have been characterized by direct- and alternating-current SQUID measurements and analyzed with the help of CASSCF-type calculations. The DyIII and YbIII compounds show slow relaxation of magnetization under an external magnetic field. Analysis of the dependence of the relaxation time with the temperature and external magnetic field reveals that the main contributions are the quantum tunneling and Raman relaxation terms, respectively. Analysis of the β electron density and electrostatic potentials indicates that the axial ligands (three water molecules) generate a relatively small repulsion, with the lanthanide electron density being the reason for the moderate magnetic anisotropy found in these systems.

Karst bauxite deposits are currently investigated as a new resource for rare earth elements (REE) in order to avoid present and future supply shortfalls of these critical metals. The present work focuses on the geochemistry and mineralogy of the REE in karst bauxite deposits of the Catalan Coastal Range (CCR), NE-Spain. It is revealed that the studied bauxitic ores have a dominant breccia and local ooido-pisoidic and pelitomorphic texture. The bauxitic ores are mostly composed of kaolinite and hematite, as well as of lesser amounts of boehmite, diaspore, rutile and calcite. The mineralogy and major element composition indicate incomplete bauxitization of an argillaceous precursor material possibly derived from the erosion of the Mesozoic Ebro massif paleo-high. The studied bauxites are characterized by &sum, REE (including Sc, Y) between 286 and 820 ppm (av. 483 ppm) and light REE to heavy REE (LREE/HREE) ratios up to 10.6. REE are mainly concentrated in phosphate minerals, identified as monazite-(Ce) and xenotime-(Y) of detrital origin and unidentified REE-phosphates of a possible authigenic origin. REE remobilization presumably took place under acidic conditions, whereas REE entrapment in the form of precipitation of authigenic rare earth minerals from percolating solutions was related to neutral to slightly alkaline conditions. During the bauxitization process no significant REE fractionation took place and the REE distribution pattern of the bauxitic ores was governed by the REE budget of the precursor material. Finally, adsorption as a main REE scavenging mechanism in the studied CCR bauxite deposits should not be considered, since the presented data did not reveal significant REE contents in Fe-and Mn-oxyhydroxides and clay minerals.

The reactions of hydrated lanthanide(III) [Ln(III)] nitrates and salicylideneaniline (salanH) have provided access to two families of mononuclear complexes depending on the reaction solvent used. In MeCN, the products are [Ln(NO3)3(salanH)2(H2O)]&middot, MeCN, and, in MeOH, the products are [Ln(NO3)3(salanH)2(MeOH)]&middot, (salanH). The complexes within each family are proven to be isomorphous. The structures of complexes [Ln(NO3)3(salanH)2(H2O)]&middot, MeCN (Ln = Eu, 4&middot, MeCN_Eu, Ln = Dy, 7&middot, MeCN_Dy, Ln = Yb, 10&middot, MeCN_Yb) and [Ln(NO3)3(salanH)2(MeOH)]&middot, (salanH) (Ln = Tb, 17_Tb, Ln = Dy, 18_Dy) have been solved by single-crystal X-ray crystallography. In the five complexes, the LnIII center is bound to six oxygen atoms from the three bidentate chelating nitrato groups, two oxygen atoms from the two monodentate zwitterionic salanH ligands, and one oxygen atom from the coordinated H2O or MeOH group. The salanH ligands are mutually &ldquo, cis&rdquo, in 4&middot, MeCN_Eu, 7&middot, MeCN_Dy and 10&middot, MeCN_Yb while they are &ldquo, trans&rdquo, in 17_Tb and 18_Dy. The lattice salanH molecule in 17_Tb and 18_Dy is also in its zwitterionic form with the acidic H atom being clearly located on the imine nitrogen atom. The coordination polyhedra defined by the nine oxygen donor atoms can be described as spherical tricapped trigonal prisms in 4&middot, MeCN_Dy, and 10&middot, MeCN_Yb and as spherical capped square antiprisms in 17_Tb and 18_Dy. Various intermolecular interactions build the crystal structures, which are completely different in the members of the two families. Solid-state IR data of the complexes are discussed in terms of their structural features. 1H NMR data for the diamagnetic Y(III) complexes provide strong evidence that the compounds decompose in DMSO by releasing the coordinated salanH ligands. The solid complexes emit green light upon excitation at 360 nm (room temperature) or 405 nm (room temperature). The emission is ligand-based. The solid Pr(III), Nd(III), Sm(III), Er(III), and Yb(III) complexes of both families exhibit LnIII-centered emission in the near-IR region of the electromagnetic spectrum, but there is probably no efficient salanH&rarr, LnIII energy transfer responsible for this emission. Detailed magnetic studies reveal that complexes 7&middot, MeCN_Dy, 17_Tb and 18_Dy show field-induced slow magnetic relaxation while complex [Tb(NO3)3(salanH)2(H2O)]&middot, MeCN (6&middot, MeCN_Tb) does not display such properties. The values of the effective energy barrier for magnetization reversal are 13.1 cm&minus, 1 for 7&middot, MeCN_Dy, 14.8 cm&minus, 1 for 17_Tb, and 31.0 cm&minus, 1 for 18_Dy. The enhanced/improved properties of 17_Tb and 18_Dy, compared to those of 6_Tb and 7_Dy, have been correlated with the different supramolecular structural features of the two families. The molecules [Ln(NO3)3(salanH)2(MeOH)] of complexes 17_Tb and 18_Dy are by far better isolated (allowing for better slow magnetic relaxation properties) than the molecules [Ln(NO3)3(salanH)2(H2O)] in 6&middot, MeCN_Tb and 7&middot, MeCN_Dy. The perspectives of the present initial studies in the Ln(III)/salanH chemistry are discussed.

Single functional molecules are regarded as future components of nanoscale spintronic devices. Supramolecular coordination chemistry provides unlimited resources to implement multiple functions to individual molecules. A novel coordination [Fe2 ] helicate exhibiting spin-crossover is demonstrated to be ideally suited to encapsulate a [Cr(ox)3 ]3- complex anion (ox=oxalate), unveiling for the first-time single ion slow relaxation of the magnetization for this metal. A possibility of tuning the dynamics of this relaxation as well as the performance of the CrIII center as qubit arises from the observation that metastable high spin FeII centers from the host can be generated by irradiation with green light at low temperature., G.A. thanks the Generalitat de Catalunya for the prize ICREA Academia 2008 and 2013 and the ERC for a Starting Grant (258060 FuncMolQIP). The authors thank the Spanish MINECO for funding through MAT2014-53961-R, MAT2017-86826-R (O.R.) and CTQ2015-68370-P (G.A. and L.A.B.). M.D. thanks Avempace II Erasmus Mundus Action 2 program for a PhD scholarship. This research used resources of the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231.

[spa] En la primera parte de esta tesis, se basó en la síntesis de ligandos basados en la heptazina y los complejos formados con CuII. Utilizando 2-dipiridilamina para funcionalizar el núcleo de heptazina, (ligando que presenta propiedades fotoquímicas remarkables) se logró crear una caja molecular con tres CuII que se coordinaba a dos ligandos tris(2-dipirilamina)1,5,9-heptazina. Siguiendo en esta línea, se funcionalizó el núcleo de heptazina con piperidina-4-acido carboxílico para formar el ligando tris(piperidina-4-ácido carboxílico)-1,5,9-heptazina, que mediante la coordinación con átomos metálicos CuII se puedo generar un compuesto bastante grande, con un diámetro de 24 Å. Esta caja molecular, se encuentra formada por 8 ligandos y 12 átomos metálicos que forman el compuesto [Cu12(tpach)8(H2O)12]. En la segunda parte de este trabajo, se estudió compuestos magnéticos, que presentan propiedades de imán. Este tipo de moléculas se conocen como imanes unimoleculares, generalmente se denominan SMM por sus siglas en inglés Single Molecule Magnets. El segundo objetivo principal a raíz del descubrimiento realizado por los Profesores Dante Gatteschi y Roberta Sessoli en 1993 en qué una sola molécula presenta una lenta relajación de su magnetización por debajo de una temperatura conocida como temperatura de bloqueo (Tb). En un trabajo realizado por los profesores Jeffrey Long y Jeffrey Rinehard, se reportaron un método en el cual de manera sistemática y cualitativa, se pueden sintetizar imanes unimoleculares basados en lantánidos. Dependiendo de la densidad electrónica del ion lantánido la cual fue definida como forma de achatada (oblato) o alargada (prolato) la anisotropía magnética podría ser máxima, propiedad de la cual depende principalmente la relajación de la magnetización. Parte de esta tesis, se enfocó en esa propuesta publicada por Long y para eso se utilizó compuestos basados en éteres coronas (18-corona-6) y lantánidos (Nd, Tb, Dy, Er y Yb), con la idea de generar compuestos en el que la densidad electrónica del ion lantánido se acomode en el plano ecuatorial del éter corona y posicionar ligandos axiales cargados, para ejercer la mayor repulsión posible, con la idea de obtener una densidad electrónica tipo oblato y maximizar la anisotropía. Siguiendo con la línea de los imanes unimoleculares, se estudió los sistemas con espín ½ sistemas que presentan propiedades para ser usados en computación cuántica como qbits. Se estudió principalmente metalocenos basados en ferricinio y cobaltoceno. De entrada el cobaltoceno debería presentar una relajación lenta de la magnetización, ya que su electrón desapareado se encuentra en un orbital degenerado, que por distorsión de Jahn Teller esa degeneración se rompe obteniéndose un estado excitado de con una diferencia de energía baja, que en el caso de los metales de transición es la fuente de la anisotropía magnética. En el caso del ferricinio, esa energía de excitación era alta, por lo cual no presentaría anisotropía. Los resultados experimentales en solución congelada (separación de centros metálicos) mostraron que el ferricinio poseía relajación de la magnetización y el cobaltoceno no, esto debido a un cambio en la configuración de los orbitales, donde los dos compuestos poseían su electrón desapareado en orbitales degenerados, pero en el caso del cobaltoceno, la distorcion de Jahn Teller, se produce en orbitales antienlazantes (separación de energía mayor, menor anisotropía) en contraparte del ferricionio, en el cual su electron desapareado se encuentra en orbitales de no-enlace (menor distorsión) . Para mejorar las propiedades, se decidió encapsular esta molécula, con dos polisacáridos 𝛼 y 𝛽 ciclodextrina, con la misión de aislar la molécula aún más, para suprimir la interacción con moléculas vecinas, las cuales generan que la relajación lenta sea acelere. Los resultados obtenidos indicaron que las propiedades mejoraron sustancialmente, el mecanismo de relajación por efecto túnel, se suprimió en gran medida debido al aislamiento del ferricinio., [eng] The first part of this thesis focuses on the synthesis of heptazine-based ligands and the formation of its coordination compounds with CuII. The functionalization of this ligand with 2-dipiridilamine leads to the synthesis of a CuII trinuclear molecular cage. On the other hand, by using piperidin-4-carboxylic acid the supramolecular compound [Cu12(tpach)8(H2O)12] can be obtained, which possesses a cavity diameter of 24 Å. The second part of this thesis focuses on the synthesis, characterization and study of the single molecule magnet (SMMs) properties for different systems containing lanthanide ions. SMMs exhibit a slow relaxation of the magnetization below the blocking temperature (Tb). Using previously published work that describes systematic ways of synthetizing lanthanide-based SMMs based on the shape of the electron density (oblate or prolate), we used crown ethers (18-crown-6) and several lanthanides (Nd, Tb, Dy, Er and Yb) to build up molecules in which the electron density will be in the equatorial plane. By later addition of anionic axial ligands, it should be possible to generate molecules with an electronic density such as the anisotropy of the system maximizes, which will lead to SMMs behavior. Finally, for SMMs with total spin S=1/2 exists the possibility of using them as qbits for Quantum Computing. The last part of the thesis centered on the study of the cobaltocene and ferrocenium SMM behavior applied to Quantum Computing. One should expect, based on their electronic structure, that cobaltocene will be a much better candidate when it comes to SMM behavior, however, experimental data shows that it is the ferrocenium the one that displays better properties. This fact can be rationalized on basis of the Single-occupied Molecular Orbital (SOMO) for both complexes, and its antibonding or non-bonding character. To improve the properties of the ferrocenium, we encapsulated the molecule using polysaccharids (a and b cyclodextrin). This process does increase the SMM properties of ferrocenium, due to the isolation of the magnetic centers, which block the tunnel-effect relaxation mechanism.

The employment of three structurally related Schiff bases H(2)L1, H(2)L2, and H(3)L3 with zinc and lanthanide salts under various reaction conditions, gave four families of compounds formulated as [Zn(2)(II)Ln(2)(III)(L1)(4)(EtOH)(6)][ClO4](2) (1-3), [Zn(5)(II)Ln(OH)(L1)(6)(H2O)] (4-6), [Zn(4)(II)Ln(2)(III)(OH)(2)(L2)(4) (OAc)(2)(NO3)(2)(DMF)3]center dot DMF (7-9), and [Zn(2)(II)Ln(2)(III)(L3)(2)(NO3)(2) (CO3)(2)(CH3OH)(2)] (10-12) with robust and novel topologies. Synthetic aspects are discussed. A comprehensive topological analysis of all reported Zn-II/Ln(III) CCs with a core nuclearity of four and above is presented and identifies that families (4-6) and (7-9) are the first examples of the 2,3,4M6-1 motif in Zn-II/Ln(III) chemistry. Magnetic studies are presented for the Dy-II analogues (1, 7, and 10) are presented, 7 demonstrates field -induced slow relaxation of the magnetization. Fluorescence studies are also discussed.

Treballs Finals de Grau de Química, Facultat de Química, Universitat de Barcelona, Any: 2017, Tutors: Anna Rigol Parera, Oriol Ramírez Guinart, One of the techniques used for the remediation of contaminated water is the use of sorbents. In these techniques, the sorbents retain the contaminants from the water. One of the most common sorbents is the activated charcoal. It is an effective commercial sorbent. However, there are some greener, cheaper and equally effective alternatives that might be investigated. For this reason, this project evaluates the efficacy of some materials as sorbents for pollutants, concretely lanthanides . The materials studied include different biochars and a by-product that comes from the metallurgical industry. A previous study1 showed a high efficiency of the studied materials for the sorption of lanthanides (Sm, La, Lu) at a single concentration of 0.05 meq/L. The present study aims to keep going in that direction by doing more experiments to obtain additional information about these materials as sorbents. In this work, it has been evaluated the sorption capacity (sorption percentage and solid-liquid distribution coefficient) of the target materials and of a commercial activated charcoal, all tested at different samarium concentrations in water. This test allows us to see until which contaminant concentration is the material efficient as a sorbent. It has also been tested the desorption of Sm from these materials at the different Sm concentrations, since a good sorbent needs to have a low desorption as well as a good retention of the contaminant. Finally, some information about the existing mechanisms in the sorption process were derived form the sorption-desorption experiments. The obtained results show a very good efficacy of the materials for the sorption of Sm until arriving at high concentrations, and as well as, low desorption. Biochars are very good sorbents, as they only sature at very high concentrations that are not common in environmental situations. An exception was the biochar obtained from sugarcane bagasse, that showed worse results. The coal fines material, which is a by-product of the metallurgical industry, showed a similar behaviour to a studied commercial activated charcoal. It showed a 100% of sorption in the hole concentration range tested . This confirms that the materials studied can be an environmentally friendly, economical and equally effective alternative to the commercial activated charcoal. Keywords: Biochars

Treballs Finals de Grau de Química, Facultat de Química, Universitat de Barcelona, Any: 2017, Tutor: Albert Escuer Fite, Coordination compounds containing lanthanide ions can potentially present emission and magnetic properties; specifically single-molecule magnet (SMM) behaviour at low temperatures is being widely studied, since it is thought it can lead to applications in information storage. In this research project two series of dinuclear chiral coordination compounds have been synthesised, containing nickel(II) or zinc(II) ions and a lanthanide(III) ion, using a chiral Schiff base as ligand. Single crystals have been obtained and used to characterise the structure of the compounds with single-crystal X-Ray Diffraction. With the obtained powder samples the characterisation of the compounds have been made through UV-visible spectroscopy, UV and NIR emission spectroscopy, circular dichroism, powder X-Ray Diffraction and IR spectroscopy. The magnetic properties of the samples have been studied using DC and AC susceptibility measures.Obtained compounds have not presented emission properties deriving from the lanthanide ion, but presented single-molecule magnet (SMM) behaviour and the potential barrier values have been calculated

Màster en Nanociència i Nanotecnologia, Facultat de Física, Universitat de Barcelona, Curs: 2016-2017. Tutors: Oriol Blázquez, Sergi Hernández, In this Master Thesis, the fabrication and the structural, optical and electrical properties of Al/rare earth (RE)/Al/SiO2 and RE/SiO2 nanomultilayers have been studied. The nanomultilayers were deposited by means of e-beam evaporation on top of p-type Si substrates. Two different RE species were considered: Tb3+ and Eu3+ ions, as they exhibit a narrow and strong emission in the green and red spectral ranges, respectively. The main goal of the present work is achieving optical activation of those rare earth elements, and thus obtaining light emission from their intra-4f and 5d-to-4f shell transitions. Optical characterization indicates that optically active RE3+ ions had been successfully fabricated. The electrical and electroluminescence analysis yielded promising results to include this material in future applications of illumination and integrated emitting devices for optoelectronics.

Three new sets of mononuclear Ln(III) complexes of general formulas [LnL3 ]⋅CH3 OH [Ln(III) =Yb (1), Er (2), Dy (3), Gd (4), and Eu (5)], [LnL2 (tmh)(CH3 OH)]⋅n H2 O⋅m CH3 OH [Ln(III) =Yb (1 b), Er (2 b), Dy (3 b), Gd (4 b)], and [LnL2 (tta)(CH3 OH)]⋅CH3 OH [Ln(III) =Yb (1 c), Er (2 c), Dy (3 c), Gd (4 c)] were prepared by the reaction of Ln(CF3 SO3 )⋅n H2 O salts with the tridentate ligand 2-(tetrazol-5-yl)-1,10-phenanthroline (HL) and, for the last two sets, additionally with the β-diketonate ligands 2,2,6,6-tetramethylheptanoate (tmh) and 2-thenoyltrifluoroacetonate (tta), respectively. In the [LnL3 ]⋅CH3 OH complexes the Ln(III) ions are coordinated to three phenanthroline tetrazolate ligands with an LnN9 coordination sphere. Dynamic ac magnetic measurements on 1-3 reveal that these complexes only exhibit single-molecule magnet (SMM) behavior when an external dc magnetic field is applied, with Ueff values of 11.7 K (1), 16.0 K (2), and 20.2 K (3). When the tridentate phenanthroline tetrazolate ligand is replaced by one molecule of methanol and the β-diketonate ligand tmh (1 b-3 b) or tta (1 c-3 c), a significant increase in Ueff occurs and, in the case of the Dy(III) complexes 3 b and 3 c, out-of-phase χ'' signals below 15 and 10 K, respectively, are observed in zero dc magnetic field. CASSCF+RASSI ab initio calculations performed on the Dy(III) complexes support the experimental results. Thus, for 3 the ground Kramers' doublet is far from being axial and the first excited state is found to be very close in energy to the ground state, so the relaxation barrier in this case is almost negligible. Conversely, for 3 b and 3 c, the ground Kramers' doublet is axial with a small quantum tunneling of the magnetization, and the energy difference between the ground and first Kramers' doublets is much higher, which allows these compounds to behave as SMMs at zero field. Moreover, these calculations support the larger Ueff observed for 3 b compared to 3 c. Additionally, the solid-state photophysical properties of 1, 2, 4, and 5 show that the phenanthroline tetrazolate ligand can act as an effective antenna to sensitize the characteristic Yb(III) , Er(III) , and Eu(III) emissions through an energy-transfer process.

Treballs Finals de Grau de Química, Facultat de Química, Universitat de Barcelona, Any: 2016, Tutor: Laura Rodríguez Raurell, Supramolecular fluorescent chemosensors in water are very appealing because luminescence exhibits low detection limits and a high selectivity. Macrocyclic structures with polydentate nitrogen ligands represent a fundamental and extensive type of compounds in this group. The strategy employed in this work consists on the connection of the central amine to a naphtalene group (chromophore) and to two pyridine moieties at the end positions, to be involved in self-assembly processes giving rise to metallomacrocyclic structures. These systems can be used in molecular recognition processes. The encapsulation of the metallomacrocycles on hydrogels facilitates the use of the chemosensors in daily life applications. Furthermore, these type of compounds gives stability to the hydrogels and also photophysical acquired properties. In addition, the use of these polydentate nitrogen ligands in order to synthesize new silver and gold containing compounds, provide new tools for the recognition and/or encapsulation of molecules. Due to these properties, a synthetic way has been assayed, in order to obtain supramolecular cages with luminescent properties

Several factors including fossil fuels scarcity, prices volatility, greenhouse gas emissions or current pollution levels in metropolitan areas are forcing the development of greener transportation systems based on more efficient electric and hybrid vehicles. Most of the current hybrid electric vehicles use electric motors containing powerful rare-earth permanent magnets. However, both private companies and estates are aware of possible future shortages, price uncertainty and geographical concentration of some critical rare-earth elements needed to manufacture such magnets. Therefore, there is a growing interest in developing electric motors for vehicular propulsion systems without rare-earth permanent magnets. In this paper this problematic is addressed and the state-of-the-art of the electric motor technologies for vehicular propulsion systems is reviewed, where the features required, design considerations and restrictions are addressed.

Ni laterites are considered worthy targets for critical metals (CM) exploration as rare earth elements (REE), Sc and platinum group elements (PGE) can be concentrated during weathering as a result of residual and secondary enrichment. In this investigation geochemical and mineralogical data of CM from two different nickel laterite types (i) from the Moa Bay mining area in Cuba (oxide type) and (ii) from the Falcondo mining area in the Dominican Republic (hydrous Mg silicate type) are presented. Emphasis is given on examining their potential to accumulate CM and on processes involved. Results show that CM are concentrated towards the surface in specific zones: (i) REE in clay minerals rich horizons and within zones composed of secondary Mn oxide(s) (ii) Sc within zones rich in secondary Fe and Mn bearing oxide(s) and (iii) PGE in zones with high concentrations of residual chromian spinel and secondary Fe and Mn bearing oxide(s) at upper levels of the Ni laterite profiles. Concentration factors involve (i) residual enrichment by intense weathering (ii) mobilization of CM during changing Eh and pH conditions with subsequent reprecipitation at favourable geochemical barriers (iii) interactions between biosphere and limonitic soils at highest levels of the profile (critical zone) with involved neoformation processes. Total contents of CM in both Ni laterite types are low when compared with conventional CM ore deposits but are of economic significance as CM have to be seen as cost inexpensive by-products during the Ni (+Co) production. Innovative extraction methods currently under development are believed to boost the significance of Ni laterites as future unconventional CM ore deposits. Two Ni laterite profiles from the Falcondo mining area have been compared for their platinum group element (PGE) geochemistry and mineralogy. One profile (Loma Peguera) is characterized by PGE-enriched (up to 3.5 ppm total PGE) chromitite bodies incorporated within the saprolite, whereas the second profile is chromitite-free (Loma Caribe). Total PGE contents of both profiles slightly increase from parent rocks (36 and 30 ppb, respectively) to saprolite (-50 ppb) and reach highest levels within the limonite zone (640 and 264 ppb, respectively). Chondrite-normalized PGE patterns of saprolite and limonite reveal rather flat shapes with positive peaks of Ru and Pd. Three types of platinum group minerals (PGM) were found by using an innovative hydroseparation technique: (i) primary PGM inclusions in fresh Cr-spinel (laurite and bowieite), (ii) secondary PGM (e.g., Ru-Fe-Os-Ir compounds) from weathering of preexisting PGM (e.g., serpentinization and/or laterization), and (iii) PGM precipitated after PGE mobilization within the laterite (neoformation). Results provide evidence that (i) PGM occurrence and PGE enrichment in the laterite profiles is independent of chromitite incorporation; (ii) PGE enrichment is residual on the profile scale; and (iii) PGE are mobile on a local scale leading to in situ growth of PGM within limonite, probably by bioreduction and/or electrochemical metal accretion. Free grains of PGM with delicate morphologies were discovered in limonite hosted chromitite samples (“floating chromitites”) from highest levels in the Falcondo Ni laterite deposit (Dominican Republic). Textural and chemical evidence obtained via SEM and EMP analysis points to a multistage formation: (i) primary PGM formation at magmatic stage; (ii) transformation to highly porous secondary Os-Ru PGM during serpentinization; (iii) neoformation of Ir-Fe-Ni-(Pt) mineral phases during early stages of lateritization; (iv) neoformation of Pt-(Ir) mineral phases within the critical zone of the profile resulting in nugget shaped accumulation of rounded particulates during late stages of lateritization. The observation of accumulations of most likely biogenic mediated in situ growth of Pt rich nanoparticles in supergene environments could help to explain (i) why Pt bearing nuggets are the most abundant PGM found in surface environments, (ii) why Pt nuggets from placer deposits generally surpass the grain sizes of Pt grains found in parent rocks by several orders of magnitude (few micrometers vs. several millimeters) and (iii) how anthropogenic PGE contamination may affect our biosphere. Osmium chromitite, saprolite and limonite (Falcondo mining area), suggest that serpentinization of the Loma Caribe peridotite has not significantly affected the Re-Os system in Os-rich PGM. This is noted by the fact, that primary PGM formed at magmatic stage and secondary Ru-Os-Mg- isotope characteristics from primary and secondary PGM, separated from Si PGM formed due desulphurization of primary PGM with significant incorporation of Mg silicates, have almost identical Os isotope characteristics, typical of the mantle. However, the Re-Os system can be significantly disturbed during stages of lateritization when porous secondary PGM react with Fe-rich fluids, thus forming hexaferrum and magnetite in the 187 188 interstices of secondary PGM. Here presented data indicate that more radiogenic ratios in higher levels of the weathering profile are linked to steady mobilization of PGE within secondary PGM resulting in subsequent loss of Os counterbalanced by the incorporation of Fe. Os/ Os In this investigation presented data clearly states that PGE are neither noble nor inert in surface environments, at least in those related to tropical Ni laterites from the Northern Caribbean.

A new family of pentanuclear 3d-4f heterometal complexes of general composition [Ln(III)2(M(II)L)3(μ3-O)3H](ClO4)·xH2O (1-5) [Ln = Nd, M = Zn, 1; Nd, Ni, 2; Nd, Cu, 3; Gd, Cu, 4; Tb, Cu, 5] have been synthesized in moderate yields (50-60%) following a self-assembly reaction involving the hexadentate phenol-based ligand, viz., N,N-bis(2-hydroxy-3-methoxy-5-methylbenzyl)-N('),N(')-diethylethylenediamine (H2L). Single-crystal X-ray diffraction analyses have been used to characterize these complexes. The compounds are all isostructural, having a 3-fold axis of symmetry that passes through the 4f metal centers. The [M(II)L] units in these complexes are acting as bis-bidentate metalloligands and, together with μ3-oxido bridging ligands, complete the slightly distorted monocapped square antiprismatic nine-coordination environment around the 4f metal centers. The cationic complexes also contain a H(+) ion that occupies the central position at the 3-fold axis. Magnetic properties of the copper(II) complexes (3-5) show a changeover from antiferromagnetic in 3 to ferromagnetic 3d-4f interactions in 4 and 5. For the isotropic Cu(II)-Gd(III) compound 4, the simulation of magnetic data provides very weak Cu-Gd (J1 = 0.57 cm(-1)) and Gd-Gd exchange constants (J2 = 0.14 cm(-1)). Compound 4 is the only member of this triad, showing a tail of an out-of-phase signal in the ac susceptibility measurement. A large-spin ground state (S = 17/2) and a negative value of D (-0.12 cm(-1)) result in a very small barrier (8 cm(-1)) for this compound. Among the three Nd(III)2M(II)3 (M = Zn(II), Ni(II), and Cu(II)) complexes, only the Zn(II) analogue (1) displays an NIR luminescence due to the (4)F(3/2) → (4)I(11/2) transition in Nd(III) when excited at 290 nm. The rest of the compounds do not show such Nd(III)/Tb(III)-based emission. The paramagnetic Cu(II) and Ni(II) ions quench the fluorescence in 2-5 and thereby lower the population of the triplet state.

By exciting at 788 nm, we have characterized the near infrared emissions of trivalent thulium ions in monoclinic KGd(WO4)2 single crystals at 1.48 and 1.84 mm as a function of dopant concentration from 0.1% to 10% and temperature from 10 K to room temperature. We used the reciprocity method to calculate the maximum emission cross-section of 3.0310220 cm2 at 1.838 mm for the polarization parallel to the Nm principal optical direction. These results agrees well with the experimental data. Experimental decay times of the 3H4!3F4 and 3F4!3H6 transitions have been measured as a function of thulium concentration.

The present study discusses the magnetic dynamics of a previously reported cyanide bridged 3d-4f dinuclear DyIIICoIII complex. Following the axial anisotropy suggested by previous Electron Paramagnetic Resonance spectroscopy (EPR) analysis, the complex turned out to show slow relaxation of the magnetization at cryogenic temperature, and this was studied in different temperature and field regimes. The existence of multichannel relaxation pathways that reverse the magnetization was clearly disclosed: a tentative analysis suggested that these channels can be triggered and controlled as a function of applied static magnetic field and temperature. Persistent evidence of a temperature independent process even at higher fields, attributable to quantum tunneling, is discussed, while the temperature dependent dynamics is apparently governed by an Orbach process. The broad distribution of relaxation rates evidenced by the ac susceptibility measurements suggest a relevant role of the intermolecular interactions in this system.

We present an analysis of factors influencing carrier transport and electroluminescence (EL) at 1.5 µm from erbium-doped silicon-rich silica (SiOx) layers. The effects of both the active layer thickness and the Si-excess content on the electrical excitation of erbium are studied. We demonstrate that when the thickness is decreased from a few hundred to tens of nanometers the conductivity is greatly enhanced. Carrier transport is well described in all cases by a Poole-Frenkel mechanism, while the thickness-dependent current density suggests an evolution of both density and distribution of trapping states induced by Si nanoinclusions. We ascribe this observation to stress-induced effects prevailing in thin films, which inhibit the agglomeration of Si atoms, resulting in a high density of sub-nm Si inclusions that induce traps much shallower than those generated by Si nanoclusters (Si-ncs) formed in thicker films. There is no direct correlation between high conductivity and optimized EL intensity at 1.5 µm. Our results suggest that the main excitation mechanism governing the EL signal is impact excitation, which gradually becomes more efficient as film thickness increases, thanks to the increased segregation of Si-ncs, which in turn allows more efficient injection of hot electrons into the oxide matrix. Optimization of the EL signal is thus found to be a compromise between conductivity and both number and degree of segregation of Si-ncs, all of which are governed by a combination of excess Si content and sample thickness. This material study has strong implications for many electrically-driven devices using Si-ncs or Si-excess mediated EL.

We grew good-optical-quality KYb~WO4)2 single crystals doped with erbium ions by the top seeded solution growth slow cooling method. Optical absorption of erbium was performed at room temperature ~RT! and at 6 K. Green photoluminescence of erbium was achieved at RT and 6 K after selective excitation of ytterbium ions at 940 nm (10 638 cm21). The splitting of all found excited energy levels and the ground energy level of erbium in KYb~WO4)2 is presented derived from the accurate absorption and emission measurements, respectively. The lifetime of the Stokes and the anti-Stokes green emissions of erbium were measured after excitation at 488 nm (20 490 cm21) and 940 nm(10 638 cm21), respectively. We propose applying the up-conversion model to the observed green emission.

Aquesta memòria es centra en un gran tema de la química orgànica que és la catàlisi asimètrica de les addicions de Michael. Més concretament, en aquest treball s’estudia la enantioselectivitat que proporcionen dos lligand en qüestió, un d’ells basat en metalls i l’altre organocatalític, en unes reaccions de Michael. Així doncs, s’estudiaren dos tipus de sistemes. El primer cas és l’addició de Michael entre 2-tert-butoxicarbonil-1-indanona i tres acceptors de Michael diferents com són la metilvinilcetona, el Nacriloïloxazolidinona i l’azodicarboxilat de di-tert-butil, catalitzat per combinacions de metalls lantànids (majoritariament Yb) amb lligands quirals de tipus pybox. La segona part de la memòria es centra en l’estudi d’enantioinducció que proporciona un nou organocatalitzador en les addicions de Michael esmentades en l’apartat anterior. Aquest catalitzador està format pel derivat de la cincona 11-(9-mercaptononiltio)-10,11-dihidrocinconina suportat en nanopartícules d’or.

En la presente memoria se expone el trabajo realizado en el marco de partículas nanométricas de óxido de cerio (IV) dopado con gadolinio (Ce0,9Gd0,1O2‐y) crecidas por métodos químicos sobre sustratos de tipo perovskita previamente modificados por nanoindentación. El estudio de la influencia de las deformaciones mecánicas del sustrato en la ordenación espontánea de las nanoestructuras nos permitirá poder prever y diseñar sistemas de autoensamblaje asistido y asomarnos al ansiado control en la fabricación de sistemas en el rango nanométrico.

By exciting at 940nm, we have characterized the 1.84μm near infrared emission of trivalent thulium ions in Yb3+, Tm3+:KGd(WO4)2 single crystals as a function of the dopant concentration and temperature, from 10K to room temperature. An overall H63 Stark splitting of ∼470cm−1 for the Tm3+ ions in the Yb3+, Tm3+:KGd(WO4)2 was obtained. We also studied the blue emission at 476nm (Tm3+) and the near infrared emissions at 1.48μm (Tm3+) and 1μm (Yb3+) as a function of the dopant concentration. Experimental decay times of the G41, H43, and F43 (Tm3+) and F5∕22 (Yb3+) excited states have been measured as a function of Yb3+ and Tm3+ ion concentrations. For the F43→H63 transition of Tm3+ ions, we used the reciprocity method to calculate the maximum emission cross section of 3.07×10−20cm2 at 1.84μm for the polarization parallel to the Nm principal optical direction.