ChemMat PhD Projects 2017-2nd

List of PhD research projects to be choosen by the candidates. Further details on the research projects can be requested by e-mail to the Programme Director or directly to the project supervisors.

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Study and Development of New Lanthanide Complexes  as Single Molecule Toroics (Ref. 02-2017)

Supervisor: Laura C.  J. Pereira  (C2TN/IST-UL), lpereira@ctn.tecnico.ulisboa.pt

Co-Supervisor: Abílio Sobral (FCTUC),  asobral@ci.uc.pt

Coordination compounds of f-elements, particularly those of lanthanides have accounted for some of the most eye-catching advances in molecular magnetics such as Single Molecule Magnets (SMM) [1]. In SMMs an anisotropy barrier obstructs the reversal of the molecular magnetic moment at very low temperatures [2].

More recently molecules with a toroidal magnetic state, (SMTs: single-molecule toroics) provided a new paradigm of SMMs, more promising for future applications such as quantum computing, high-density information storage and as multiferroics materials with magnetoelectric effect [3]. So far, SMTs have been made by assembly of wheel-shaped complexes in clusters of high symmetry with strong intra-molecular dipolar interactions between anisotropic metal ions. The advantage of lanthanides for obtaining SMTs is the strong uniaxial magnetic anisotropy of the ions in common low-symmetry ligand environments [4]. Large values of local magnetic moments afford strong intramolecular dipolar coupling, which was found to be responsible for the toroidal moment of the ground states of all investigated SMTs. While a wide range of synthetic chemistry has been used to create new SMMs, SMTs compounds are so far restricted to a small group of complexes with dysprosium [4]. The identification of relaxation processes is straightforward to obtain from AC susceptibility measurements but the precise description of the mechanism involved remains challenging, and a theoretical quantum mechanics modeling has just started to be pursued. By analogy with SMMs, lanthanide ions other than Dy are also good candidates to the assembling of SMTs. Our aim is therefore to extend these studies to a variety of new lanthanide compounds with different structural and electronic characteristics and fully characterize them establishing a correlation between their magnetic behaviour and the chemical structure and identifying the key features for the slow relaxation in magnetic toroidal systems. O-donor chelate ligands (based on O-donors, namely phenolate, carboxylate, acetylacetonate, alkoxides) and phosphine oxide derivatives or N-donor chelate ligands like poliazolates derivatives and Schiff base ligands will be used to prepare the SMT clusters.

The synthesis and structural characterization of these new materials will be done at the Physics and Chemistry Dept./FCTUC using different techniques such as X-ray Diffraction, Infrared spectroscopy, Differential Scanning Calorimetry, X-ray Fluorescence. Once the synthesized compounds are structurally characterized, magnetization measurements will be made. The facilities to perform the magnetic data are available in the C2TN/IST. Both static and dynamic magnetic properties of all the synthesized compounds will be characterized by magnetization and AC susceptibility measurements in extended temperature range down to 03K and under magnetic fields up to 12T. The effective magnetic moment, transition temperatures and paramagnetic Curie temperatures will be studied. These measurements will be done in the absence and in applied external magnetic fields, by varying temperature, frequency and time. When possible, Ab initio calculations in collaboration with international partners will be performed in order to elucidate the nature of the electronic states and calculate the toroidal moment.

  • [1]. Gatteschi, D.; Sessoli, R.; Villain, J. Molecular Nanomagnets; Oxford University Press: New York, 2006; Monteiro B. et al., J. Inorg. Chem. (2013) 5059.
  • [2]. Ishikawa N. et. al., J. Am. Chem. Soc. 2003, 125, 8694–8695; Martín-Ramos P. et al., J., Eur. J. Inorg. Chem, (2014) 511–517; Pineda E.M. et al., Nature Comm., 5, 5243.
  • [3]. Spaldin N.A. et al., J. Phys Cond. Matter, 2008, 20, 434203.
  • [4]. Ungur, L. et al.,Chem. Soc. Rev. (2014), 43, 6894-6905; Xue S. et al., Inorg Chem. (2012), 51, 13264-13270.

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Nanostructured Sol-Gel Coatings for Solar Energy Applications (Ref. 03-2017)

Supervisor: Rui M. Almeida (CQE / IST-UL), rui.almeida@ist.utl.pt

Co-supervisor: Carlos Baleizão (CQFM-IN/IST-UL), carlos.baleizao@tecnico.ulisboa.pt

Co-supervisor:  Alex Martucci (Univ. Padova, Italy), alex.martucci@unipd.it

 For many applications related to solar energy management (i.e. harvesting, absorption/reflection, conversion), it is necessary to develop coatings with tailored microstructure. Sol-gel (SG) processing is a low-cost liquid deposition process for optical films at room temperature, which can be subsequently densified through heat treatment at moderate temperatures. The SG technique is ideal for depositing films on a variety of substrates (glass, metal, plastic, etc.), including multilayer films with complex structures [1].

One application concerns frequency-converting phosphor coatings (up-converting, UC [1] and down-converting, DC) for the improvement of solar cell efficiency (Fig. 1). The aim is to increase the light harvesting efficiency of Si-based photovoltaic (PV) solar cells by means of glassy/ceramic UC and DC coatings deposited by SG, designed to increase the absorption of long-wavelength and short-wavelength solar light, respectively, by the cell material. The SG coatings will be prepared in Lisboa, where structural and functional characterization will be performed in collaboration with the other laboratories. The research activity can be divided in two main tasks. The first one is aimed at c-Si solar cells and deals with the sol-gel deposition of nanostructured oxide layers like Y2O3 or TiO2 for DC, doped with Yb and Tb. The second task is aimed at wider bandgap thin film cells and it deals with (Yb, Er, Tm)-doped nanostructured oxide layers for UC, also deposited by SG. Characterization will include XRD, SEM, vibrational and photoluminescence spectroscopies and lifetime measurements. These coatings will also include layers with tailored porosity for the encapsulation of organic chromophores, in order to further increase the light harvesting capacity of the materials, for which perylenediimides will be used. These are versatile molecules with excellent photophysical properties, such as near-unity fluorescence quantum yield, absorption in the visible or NIR regions and high photochemical stability [2]. These properties can be modulated by the introduction of substituents in the imide group (affecting the solubility or immobilization), or in the perylene core (affecting the electronic and optical properties).

The other application involves solar control coatings (SCCs). Transparent conductor materials, including transparent conducting oxides (TCOs), play a critical role in many current and emerging optoelectronic applications due to their unique combination of electronic conductivity and transparency in the visible region of the spectrum. TCOs can be used both as transparent electrodes in PV solar cells, enabling light transmission in and out of those devices and as solar control coatings. A particular type of SCCs are the low-emissivity (low-ε) coatings which control the heat and light flux passing through a window and offer a route for energy savings. For solar control applications, the TCO coatings, which consist of doped oxide films, are used mostly for their optical properties, in particular their high reflectivity in the infrared spectral range above a wavelength of about 1 μm. Today, typical low-ε coatings consist of a three-layer stack on a glass sheet, such as SnO2 (ZnO or Bi2O3), Ag, and SnO2 (ZnO or Bi2O3). Such a stack can achieve sheet resistances Rs = 2.5-3.5 Ω/□ for an Ag thickness of about 12 nm. TCO coatings based on ZnO doped with cations such as Ga3+ or Al3+ (GZO and AZO) will be prepared in Padova (mixed Ph.D. program Lisboa-Padova) and their structural and functional characterization will be performed in collaboration with the other laboratories. GZO and AZO nanocrystals (NCs) will be synthesized by colloidal chemistry [3] and, once dispersed in proper solvents (colloidal inks), they will be used for the deposition of TCO coatings by spinning or spraying. These NC inks would be of great advantage for many applications, since their deposition by spraying, inkjet/gravure printing and spinning allows coating of a broad choice of substrates at reasonable cost, including deposition at low temperature on plastic substrates, which are temperature sensitive.

Fi1_RA

Fig.1 – Up-converting solar cell (Shalav et al., 2003).

Fig 2 RA

Fig. 2 – Solar control (low-emissivity) coating for insulating glass window.

  • [1] L.M. Fortes, M.C. Gonçalves, R.M. Almeida, Y. Castroand A. Durán, “Nanostructured glass coatings for solar control with photocatalytic properties”, J.Non-Crystalline Solids, 377 (2013) 250 -253
  • [2] R. Pinto, E. Maçôas, A. Neves, S. Raja, C. Baleizão, I. Santos, H. Alves, “Effect of Molecular Stacking on Exciton Diffusion in Crystalline Organic Semiconductors”, J. Am. Chem. Soc., 137 (2015) 7104-7110.
  • [3] E. Della Gaspera, M. Bersani, M. Cittadini, M. Guglielmi, D. Pagani, R. Noriega, S. Mehra, A. Salleo, A. Martucci, “Low-temperature processed Ga-doped ZnO coatings from colloidal inks”, J. Am. Chem. Soc., 135 (2013) 3439-3448.

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G2D – Gold-Graphene Dots: Fabrication, Characterization and Application in Bioimaging and Sensing (Ref. 10-2017)

Supervisor:  José M. Gaspar Martinho (CQFM/IN/IST-UL); jgmartinho@tecnico.ulisboa.pt;

Co-supervisors: Eduardo Marques (CIQ-UP/Univ.Porto); efmarque@fc.up.pt

                            Ermelinda Maçôas(CQFM/IN/IST-UL); ermelinda.macoas@tecnico.ulisboa.pt

 GOALS  The GOAL of this project is to develop Au nanoclusters (AuNCs) supported by graphene quantum dots (GQDs), using surfactant nanoaggregates as soft templates for the assembly of the hybrid particles. These gold-graphene dots (G2D) will be a NOVEL active platform for the design of multifunctional materials suitably tailored for imaging and sensing applications. At the end of the project, the PhD student is expected to have a competitive background for the global job market, with skills in advanced synthetic methods for nanostructured hybrid materials, in their structural and photophysical characterization, and in the development of innovative applications in the area of materials properties.

 BACKGROUND AuNCs are built up from a small number of atoms, with sizes smaller than the electron’s Fermi wavelength (~0.5 nm for gold and silver) and possess completely different features from bulk gold and gold nanoparticles [1]. One of the most striking properties of AuNCs is their high emission yields and size-dependent luminescence spanning the UV-Vis and IR regions [2]. On the other hand, GQDs are crystalline graphene sheets arranged in a few layer structure with lateral dimensions below 20 nm, which have recently captured attention of the scientific community not only due to their emission properties but mainly due to their photostability, water solubility and ease of functionalization.[3] The major drawback of GQDs is that their emission is not easily tunable. We envisage that by (i) combining the ease of functionalization of GQDs with the tunable luminescent properties of AuNCs, (ii) using appropriate surfactant nanoreactors to build-up and precisely control the size of the hybrid particles and (iii) taking advantage of the photochemical stability, low toxicity and high two-photon absorption of both materials, we will be able to produce completely new hybrid materials that can be suitably explored for bioimaging and biomedical applications(e.g.cancer diagnostics and therapeutics, biolabeling and immunoassays).

 Strategy and WORKPLAN  One of the most efficient methods – if not the only – to control the size of the Au-clusters relies on the use of tailor-made self-assembled templates. Various types of surfactant aggregates have the advantage of being stable (chemically and thermodynamically), monodisperse and providing high surface-to-volume ratio. In the initial stage, micelles, nanoemulsions and nanovesicles will be used as templates: (i) to ab initio synthesize and control the size of the functionalized GQDs; (ii) for the controlled synthesis of AuNCs in the presence of GQDs decorated with suitable functional groups to capture the AuNCs. The most efficient and robust templating method will be selected and fine-tuned for the production of the hybrid particles. The key structural-optical properties relationship will be investigated by a variety of spectroscopic methods and optical and electronic microscopy techniques.

 

PLACE OF WORK AND FACILITIES

In line with its goal and scope, this proposal involves two research units (CQFM-IN, Univ. Lisbon and FCUP/CIQ, Univ. Porto) and supervisors with complementary expertise. The proponents are Prof. Eduardo Marques from FCUP, an expert in surfactant self-assembly, which lies on the basis of the soft templating design [4,5], Prof. Gaspar Martinho, who has expertise in the physical, chemical and photophysical characterization of nanoclusters [6,7] and Dr. Ermelinda Maçôas with expertise in the production and characterization of nonlinear absorption materials, including GQDs.[8] Complementary infrastructures and experimental methods are available in the two Universities, namely microscopy (SEM, TEM and AFM), XRD, ICP-MS, NMR, DSC/TGA, multiphoton and confocal microscopy facilities, conventional and home-built spectroscopic methods.

REFERENCES

  • [1] Lu, Y; Chen, W, Chem. Soc. Rev. 2012, 41, 3594-3623
  • [2] Zheng, J; Zhou, C; YU, M.; Liu, J. Nanoscale 2012, 4, 4073-4083.
  • [3]  Zheng, X. T.; Ananthanarayanan, A. , Luo, K. Q., and Chen P., Small 2015, 11, 1620-1636
  • [4]  Margulis-Goshen, K; Silva, B.F.B; Marques, E.F.; Magdassi, S., Soft Matter, 2011, 7, 9359–9365
  • [5] Marques, E.F.; Silva, B.F.B., Surfactant Self-Assembly, in Encyclopedia of Colloid and Interface Science, T. Tadros (ed.), Springer: Berlin, 2013, pp 1202-1241.
  • [6] Gonzalez, B. S. ; Rodriguez, M. J.; Blanco, C.; Rivas, J.; Lopez-Quintela, M. A.; Martinho, J. M. G. Nano Lett. 2010, 10, 4217–4221.
  • [7]  Santiago-González B.; Vázquez-Vázquez , C.; Blanco-Varela, M. C.; Martinho J. M. G.; Ramallo-López , J.M.; Requejo, F.G.; López-Quintela, M. A. J. Colloid Interf. Sci. 2015, 455, 154-162.
  • [8] Maçôas, E. M. S. ; Marcelo, G.; Pinto, S.; Cañeque, T.; Cuadro, A. M; Vaquero, J. J; Martinho, J. M. G.A Chem. Commun., 2011, 47, 7374-7376.

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Iron (III) polynuclear clusters as single-molecule magnets (Ref. 13-2017)

Supervisor: Manuela Ramos Silva (FCT/Univ. Coimbra), e-mail: manuela@pollux.fis.uc.pt

Co-supervisor: João Carlos Waerenborgh (C2TN/IST-UL), e-mail: jcarlos@ctn.ist.utl.pt

Single molecule magnets (SMM) consist of ion clusters with unpaired electrons, surrounded and bridged by organic ligands. The metal ions interact strongly intramolecularly and very weakly intermolecularly so that each molecule can be considered independent. The identical molecules are self-assembled in a periodic three-dimensional lattice. They possess a high spin ground state and strong Ising type magnetic anisotropy so that the magnetisation can be retained after the removal of the magnetic field. At very low temperatures the magnetization can be retained for several months [1,2].

SMMs can be applied in the storage of information with each molecule stocking one bit of information. In a suitable disk support, these molecules can be nanoscale magnetic particles of a sharply defined size and increase the current storage capacity by 10 000. SMMs are also strong candidates for the construction of quantum computers. They offer two main advantages when compared with other candidate systems for quantum computation: chemical synthesis provides a large number of identical nano-objects in a cheap straightforward way and molecules/clusters being larger than single ion impurities relax constraints for a local read out. Fe(III) polynuclear clusters [3] have recently attracted interest in this field due to their structural and redox stability in air [4].

The aim of this project is to obtain new Fe(III)SMMs with larger metal-metal interactions so that the critical temperature would be higher and the blocking temperatures, i.e., temperatures below which the magnetization remains for several months, would also be higher. Different ligands such assiliconcarboxylate or Schiff bases and synthesis strategies such as building clusters of higher dimensionality based on trimers of magnetic ions bridged by aminoacids will be used. All complexes will be characterized by single crystal X-ray diffraction. Magnetization studies will be done in a SQUID magnetometer in the 300 mK – 300 K temperature range. All materials will be studied by Mössbauer spectroscopy in the 2-300 K temperature range in order to obtain information on the Fe(III) spin states. A theoretical study will accompany the experimental work (synthesis, structuralcharacterization, magneticevaluation, etc.) so that magneto-structural correlations can be established.

The experimental work will take place at the Physics Department of FCT Univ. Coimbra and at C2TN, Instituto Superior Técnico, Loures.

The student should enrol in the University of Coimbra.

  • [1] R. Sessoli, D. Gatteschi, A. Caneschi, M. A. Novak, Nature 1993, 365, 141.
  • [2] M. Ramos Silva, P. Martín-Ramos, J. T. Coutinho, L. C. J. Pereira, J. Martín-Gil, Dalton Trans. 2014, 43, 6752-6761.
  • [3] M. Ramos Silva, J. N. J. Nogueira, P. A. O. C. Silva, C. Yuste-Vivas, L. C. J. Pereira, J. C. Waerenborgh, Solid State Phenomena 2013, 194 162-170.
  • [4] Y.-Y. Zhu, T.-T. Yin, S.-D. Jiang, A.-L. Barra, W. Wernsdorfer, P. Neugebauer, R. Marx, M. Dörfel, B.-W. Wang, Z.-Q. Wu, J. Slageren, S. Gao, Chem. Commun., 2014, 50, 15090-15093.

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Heterometallic Metal-Organic and Supramolecular Networks for Magnetically-Driven Applications (Ref. 16-2017)

Supervisor: Alexander Kirillov (CQE/IST-UL), kirillov@tecnico.ulisboa.pt

Co-supervisor: Laura Cristina Pereira (C2TN/IST-UL),   lpereira@ctn.tecnico.ulisboa.pt

 

This project proposes to design new heterometallic metal-organic frameworks (MOFs) and related supramolecular networks (SNs) for applications driven by their intrinsic magnetic properties.

The research on MOFs and SNs is an intensively growing area in crystal engineering, coordination, supramolecular, and materials chemistry. It attracts high attention due to the structural and practical characteristics of such materials, namely their high structural diversity, porosity, hydrogen bonding, interesting molecular sorption, ion exchange, host-guest, and magnetic properties, usually different from simple discrete metal-organic molecules [1-4].

Although great progress has been achieved in the synthesis and applications of homometallic MOFs, the metal-organic and supramolecular networks which bear two different metal ions are less common, while the heterotrimetallic compounds are limited to single cases. The presence of different types of metals within one molecule often leads to a remarkable synergic effect that may dramatically alter their magnetic and other properties. Hence, this feature of synergic effect is a key inspiring point in designing novel heterometallic materials. Another feature of such materials consists in the possibility of altering their properties by external stimuli (e.g., temperature, pH, magnetic field, light, exposure to solvents or gases) or modifying their structure and functionality during the self-assembly synthesis or crystallization steps.

The key objectives of the present project will be focused on:

(A) Synthesis of new hetero(di- and tri-)metallic coordination or related supramolecular networks bearing various combinations of transition metals (Cu, Fe, Co, Ni, Mn, etc.) by self-assembly and post-synthetic modification methods;

(B) Full structural and topological characterization of the obtained compounds and investigation of their specific properties (porosity, stability, host-guest interactions);

(C) In-depth investigation of magnetic properties of the obtained compounds by magnetic susceptibility techniques, followed by modelling and theoretical interpretation of magnetic behavior. Novel single molecule magnets (SMMs), single-chain magnets, or spin crossover compounds will also be explored and their magnetic properties will be studied and compared before and after their incorporation into MOFs and related host-guest systems [4];

(D) Optimization of selected systems, preparation of tuned compounds, and composite materials therefrom; search for advanced magnetically-driven applications of the most promising materials (molecular magnets, magnetically recoverable catalysts, or bioactive nanocomposites).

The principal synthetic advantages for the heterometallic MOFs and SNs will include the mild reaction conditions, the use of inexpensive metal sources (typically salts or oxides of transition metals) and commercially available and biorelevant chemicals as main building blocks (e.g., aminoalcohols, aminophosphines, N-heterocycles), and spacers/auxiliary ligands (aromatic carboxylates, simple metal-complex ions [M(CN)6]n-, or inorganic anions capable of transmitting magnetic interactions). Besides, a special attention will be paid to the implementation of principles of green chemistry, namely by using mild reaction conditions and water as a preferable reaction medium.

It is expected that the prospective student will get a good experience in the self-assembly synthesis, crystallization methods, and characterization of various heterometallic coordination compounds, as well as in the investigation of their magnetic properties and advanced applications.

This PhD work plan involves two research units, CQE and C2TN of IST-UL. The proponents are Alexander Kirillov (CQE) with expertise in Coordination Chemistry and Crystal Engineering and Laura Pereira (C2TN) with expertise in Solid State Chemistry and Physics and Magnetic Materials. The experimental work will take place mainly at CQE. The magnetic characterization of the materials will be performed at C2TN. The student will be enrolled in a PhD Program of IST.

References

  • [1] Metal-Organic Framework Materials (Eds.: L. R. MacGillivray, C. M. Lukehart), Wiley, 2014, 592 pp.
  • [2] S. R. Batten, D. R. Turner, S. M. Neville, Coordination Polymers: Design, Analysis and Application, RSC, 2009, 300 pp.
  • [3] Y. Cui, B. Li, H. He, W. Zhou, B. Chen, G. Qian,Acc. Chem. Res. 2016, 49, 483.
  • [4] D. Aulakh, J. B. Pyser, X. Zhang, A. A. Yakovenko, K. R. Dunbar, M. Wriedt, J. Am. Chem. Soc. 2015, 137, 9254.

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Development of new thermoelectric sulfides (Ref. 17-2017)

Supervisor: António Pereira Gonçalves (C2TN/IST), apg@ctn.tecnico.ulisboa.pt

Co-supervisor: Luis Santos (CQE/IST), luis.santos@tecnico.ulisboa.pt

The ever-increasing demand of energy all over the world, with the consequent increase of raw materials consumption and pollution, stresses the need for the replacement of old sources for green energies and a more efficient use of it. In fact, almost 2/3 of the energy produced by men is lost as waste heat [1], which is seen as a huge reservoir for a future use. Thermoelectric devices can directly convert heat into electricity (and vice versa) and produce heat or cool through the passage of an electrical current. Consequently, these devices have high potential to recover waste heat, optimizing the use of energy and leading to a more sustainable world. Albeit their potential, thermoelectric equipments are expensive, have low efficiencies and contain toxic elements, which are reflected, nowadays, in the low use of these systems. The efficiency of a thermoelectric device is directly related with the performance of the thermoelectric components. This performance can be evaluated through the so-called thermoelectric figure of merit, zT, which is a function of temperature and of the basic properties of the compounds and/or materials, being given by:

zT = sa2T/k

where a is the Seebeck coefficient, T is the absolute temperature and s and k are the electrical and thermal conductivities, respectively. The increase of zT is not easy to achieve, as the different properties are connected in an unfavorable way [2]. Nevertheless, a great effort has been made to use new thermoelectric compounds and build devices with better characteristics. Nowadays most commercial devices still require rare, expensive or toxic components, but new, sustainable systems have been identified as having good thermoelectric potential [3]. The family of sulfides is one of these systems, with tetrahedrites (Cu12Sb4S13-based) being reported as presenting good thermoelectric performance after doping [4]: their chemical and physical properties must be optimized through the adjustment of composition before being suitable to be used in applications. For their practical use, technological issues are of fundamental importance, namely: the compounds should be stable under the working atmospheres and temperatures; their thermal expansion must be similar to those of electrical contacts and other constituents; and they should be robust from the thermomechanical point of view. Moreover, apart from tetrahedrites, other sulfides are also expected to present good thermoelectric performance.

The main objective of this project is (i) to synthesize, study and optimize the properties of tetrahedrites and (ii) to prepare and explore new sulfides for thermoelectric applications.

The work will start with the synthesis and characterization of the co-doped Cu12-xNixSb4S13-ySey tetrahedrites, due to the good properties observed in those with  Cu12-xNixSb4S13 and Cu12Sb4S13-ySey compositions [5,6]. Other stoichiometry’s can after also be selected taking into account the reported data on the maximization of zT and the thermal, chemical and mechanical stability of the compounds.

Tetrahedrites will be synthesized by:

  • Solvothermal synthesis [7];
  • High temperature methods (fusion and annealing);
  • Glass crystallization (technique developed in our group [8]).

In order to relate the properties with the crystal structure, the characterization will be made through the study of the microstructure (opt. microscopy, SEM/EDS, TEM), crystal structure (XRD, Raman), decomposition and melting temperatures (DSC, TG, DTA), corrosion resistance, reactivity with gases (air, O2) and metals (Ni, Cr, Ta), stability under vacuum, thermoelectric properties (Seebeck coefficient, electrical and thermal conductivities) and thermal expansion;

In parallel, other sulfide systems, as the famatinites, will be synthesized and explored. The crystal structures and microstructures of the new samples will be characterized by XRD and SEM/EDS, respectively, and thermoelectric properties (Seebeck coefficient, electrical and thermal conductivities) will be determined. The systematization of the results in these sulfide systems is expected to allow the establishment of relations between the crystal structure and the properties.

  • [1]-  R. Saidur, M. Rezaei, W.K. Muzammil, M.H. Hassan, S. Paria, M. Hasanuzzaman, Renew. Sust. Energy Rev. 16, 5649 (2012).
  • [2]- A.P. Gonçalves, C. Godart in: “New Materials for Thermoelectric Applications: Theory and Experiment”, NATO ASI Series B – Physics and Biophysics, V. Zlatić, A. Hewson (Eds.), Springer, (2013), pp. 1-24.
  • [3]- A.P. Gonçalves, C. Godart, Eur. Phys. J. B, 87, 42 (2014).
  • [4]- X. Lu, D.T. Morelli, Y. Xia, F. Zhou, V. Ozolins, H. Chi, X. Zhou, C. Uher, Adv. Energy Mater. 3, 342 (2013).
  • [5]- K. Suekuni, K. Tsuruta, M. Kunii, H. Nishiate, E. Nishibori, S. Maki, M. Ohta, A. Yamamoto, M. Koyano, J. Appl. Phys 113, 043712 (2012).
  • [6]- X. Lu, D.T. Morelli, Y. Wang, W. Lai, Y. Xia, V. Ozolins, Chem Mater. 28, 1781 (2016).
  • [7]- D.J.  James, X. Lu, D.T.  Morelli, S.L.  Brock, ACS Appl. Mater. Interfaces 7, 23623 (2015).
  • [8]- A.P. Gonçalves, E.B. Lopes, J. Monnier, J. Bourgon, J.B. Vaney, A. Piarristeguy, A. Pradel, B. Lenoir, G. Delaizir, M.F.C. Pereira, E. Alleno, C. Godart, J. Alloys Compd. 664, 209 (2016).

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Tailoring of MOFs for Energy Storage Applications (Ref. 18-2016)

Supervisor: Maria Teresa Duarte (CQE – CTBM group / IST-UL) teresa.duarte@tecnico.ulisboa.pt

Co-supervisores: Cristina Freire (LAQV-Requimte, FC-U. Porto) acfreire@fc.up.pt

Fátima Montemor (CQE/IST-UL) mfmontemor@tecnico.ulisboa.pt

INTRODUCTION:

The tailored chemical composition and microporous structure of MOFs, combined with good stability, turn them into attractive materials for energy storage applications. The large surface areas, adjustable pore sizes and redox metal centres make MOFs promising electrode materials for redox-based supercapacitors [1]. Co-modified Zn MOFs have shown good electrochemical performance and charge retention performance in aqueous electrolytes [2]. The design and production of highly porous MOFs for enhanced ion transportation is crucial to develop an electroactive material for redox-based supercapacitors. Various steps and routes have been proposed to design and produce such structures as reviewed elsewhere [1]. However, a key feature for assembling electrodes for energy storage is good adhesion to the metallic substrates acting as current collector. An interesting route to achieve this objective proposes the electro synthesis of MOFs directly over metallic current collectors. Anodic deposition has been widely used to produce Cu-containing MOFs whose structure and properties can be controlled by varying the electrolyte composition, pH, pulse type and time [3]. Carbon nanomaterials (carbon nanotubes and graphene) are high surface materials that displaying important electrical properties making them important components in the design of electrodes for supercapacitors. [4] The combination of carbon nanomaterials with MOFs is still in its early stages, for many applications, including the fabrication of composites for energy storage. [5]

THE NOVEL APPROACH:

Recent work report the use of aqueous, neutral and environmental friendly electrolytes to electrodeposit, in the anodic regime, MOFs directly on current collectors. The deposition of MOFs in aqueous electrolytes is still in its infancy and significant work must be carried out to design tailored structures, to understand the nucleation and growth mechanisms on the electrode surface and to tune the electrochemical response. The potential of electrochemistry to shape and tailor the matter is largely unexplored in the MOFs synthetic routes. The possibility of doping the MOFs structures with redox metallic species, opens a wide array of possibilities to tailor materials for energy storage applications, particularly for redox responsive supercapacitors. This proposal aims at developing breakthrough knowledge on the tailoring, design and production of MOFs for energy storage applications using mechanochemistry and electrosynthesis route, environmentally friendly techniques, with high scale up potential.

WORK PLAN

1 – Production and tailoring of MOFs via electro synthesis

The possibility to deposit the material over the current collector will be explored by depositing MOFs onto metallic parts. MOFs will be synthesised recurring to mechanochemistry and microwave green techniques. Synergistic metal combinations are expected to widen the operating potential windows of the electrodes, thus increasing the energy and power densities.

2 – Preparation and functionalization of doped carbon nanomaterials and incorporation into MOFs

Carbon nanotubes (CNT) and graphene (G) doped with heteroatoms (N, B, S) will be prepared by standard methodologies involving ball-milling followed by adequate thermal treatments. The incorporation of CNT and G into MOFs will be performed in situ during MOFs preparation by mechanochemical methods, by microwave assisted reactions or during the electropolymerization.

3 – Understanding the nucleation and growth mechanisms

The potential of electrochemistry to shape the matter is practically unexplored in the design and production of MOFs. Nucleation and growth processes will be studied via electrochemical routes. In-situ AFM measurements will be performed to follow the first stages of nucleation and growth by using a potentiostat coupled to the AFM.

4 – Electrochemical performance of MOFs-based electrodes for energy storage

Cyclic voltammetry will be used to study: the redox reactions, the associated mechanisms and determine the specific capacitance of the electrode. Specific capacitance and rate capability will also be assessed (chronoamperometry). Electrochemical Impedance Spectroscopy will be performed to evaluate the ESR of the electrodeposited films and to obtain mechanistic information on the electrochemical behaviour of the materials.

5 – Advance physicochemical characterisation of fresh and aged electrodes

Scanning electron microscopy (FEG-SEM) and transmission electron microscopy (HR-TEM) will be used. Composition of the materials will be studied by Raman spectroscopy and X-ray diffraction (XRD). Chemical analysis will be done by energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) will giveinformation on the oxidation state of the metallic species.

RESULTS: tailored MOFs and their composites with carbon nanomaterials for high power electrodes for energy storage applications; comprehension of the mechanisms governing the electrochemical processes in electrosynthesis of MOFs containing redox responsive species; Evaluation of the electrochemical response of these new materials/composites and understanding the mechanisms governing them; advanced physicochemical characterisation of the new MOFs structures.

STRATEGIC INTEREST AND IMPACT

Energy storage is recognised as one of the XXI century challenges and is being included on Europe strategic agenda. High energy density and high power rate devices are crucial for implementing electrochemical energy storage solutions. To meet this objective is crucial to develop new materials tailored to maximise the electrochemical performance; therefore new fabrication routes and new classes of materials play a pivotal role in advancing new electrochemical energy storage solutions.

References:

  • [1] L. Wang, Y. Han, X. Feng, J. Zhou, P. Qi, Bo Wang,  Coordination Chemistry Reviews, 307 (2016) 361–381
  • [2] D.Y. Lee, S.J. Yoon, N.K. Shrestha, S.-H. Lee, H. Ahn, S.-H. Han,  Microporous Mesoporous Mater. 153 (2012) 163–165.
  • [3] H. Al-Kutubi, J. Gascon, E. J. R. Sudhçlter, L. Rassaei,  ChemElectroChem 2015, 2, 462 – 474
  • [4] T. Chen, L. Dai, Flexible, J. Mater. Chem. A, 2014, 2, 10756
  • [5] Q. Zhu, Q. Xu, Metal–organic framework composites, Chem. Soc. Rev., 2014, 3, 5468.

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New Biomaterials Based in Metal Organic Frameworks (BioMOFs) for Cancer Photodiagnostic and Cancer Magnetic Hyperthermia Therapy (Ref. 20-2017)

Supervisor: Abílio Sobral (FCTUC), asobral@ci.uc.pt

Co-supervisor: Laura C. J. Pereira (C2TN/IST-UL),  lpereira@ctn.ist.utl.pt

Summary: Advanced materials with optical and magnetic properties, adequate for use in medicine and medical sciences, constitute an area of great importance in modern materials chemistry research. This subject is of great social, ethical and scientific importance and presents great potential for innovation and patent applications. The student that choose this project will work in an interdisciplinary plan involving chemical organic and inorganic synthesis and the use of optical and magnetic physical techniques, that all together will be applied in a medicinal and biologic environment.

Objectives: The aim of this project is to perform the synthesis, characterization and evaluation of new biomimetic and biological oriented Metal Organic Frameworks (BioMOFs), designed as biomaterials for application in medicine, in the areas of cancer diagnostic and cancer therapy.

The new biomaterials will be designed to present a multiple mode of action. Their organic ligands will be strongly fluorescent molecules that allow for their application in cancer photodiagnostic and its inorganic components will present magnetic properties that, once under an external magnetic field, will perform a hyperthermia therapeutic effect, leading to local cancer tissue degradation and inactivation.

As a secondary objective, since MOFs present a large surface area and controllable porosity, they can also be used in the delivery of anti-cancer drugs, in a controlled and efficient way.

Background: MOFs are among the most interesting classes of compounds. They have structures that intercalate organic linkers with metal cation units, presenting well-defined porous and large surface areas, like IRMOF-3 presented in Figure 1. In the last years they were used in research applications were large surface areas were needed, like in catalysis and in gas sequestering [1] [2]. Nowadays, new areas of applicability for MOFs are emerging, extending its use to drug release and medicinal therapies [3].

Expected outputs: The final output would be the synthesis of several new BioMOF and a full characterization of theirs structures and total evaluation of the optical and magnetic properties, followed by some in vitro studies to evaluate its anticancer potential. The possibility of patent protection in some of those new biomaterials will be pursued.

The PhD student will acquire important expertise in materials science and biomaterials, both from the chemical point of view of small molecules and MOFs synthesis (thermal, microwave, surface assisted and photosynthesis), purification and characterization (HPLC-MS, GC-MS, ICP-MS and SEC), and characterization both by molecular spectroscopy (NMR, FTIR, VIS-UV, and Fluorescent techniques) and material analysis (X-ray, SEM, AFM, TEM and SQUID magnetometry).

BioMof Fig Fig 1.

Place of Work: This PhD work plan involves two research units (Chemistry Department of the UC and C2TN from the IST/UL). The proponents are Abílio Sobral (UC), who has expertise in Organic Synthesis and Medicinal Chemistry and Laura Pereira (UL) with expertise in Solid State Chemistry and Physics and Magnetic Materials. The experimental work will take place mainly at University of Coimbra, Chemistry and Physics Departments and, for periods of at least one week every 3 months, at C2TN Instituto Superior Técnico from University of Lisboa to perform the magnetic characterization of the new BioMOF samples. The student will be enrolled in the Chemistry Doctoral Program of the University of Coimbra. Is expected the candidates to have a good background in organic synthetic chemistry and materials characterization. For the final bio studies we have the support of the Life Sciences Department of the University of Coimbra and from the Faculty of Pharmacy of the University of Coimbra.

Timetable:

First Year: attending the classes of the Chemistry Doctoral Program of the University of Coimbra; planning the synthesis of the MOF’s ligands by using retrosynthetic analysis; synthesizing the first MOFs; learning some new characterization techniques, bot at the University of Coimbra and University of Lisbon.

Second year: synthetic work with production of several new structures of new BioMOFs; use of hydrothermal, high pressure and microwave assisted synthesis and also photosynthesis; presenting innovative work at international congresses and publishing one paper in peer review journals.

Third year: full characterization of the optical and magnetic properties of the new biomaterials; evaluation of the new MOFs in the drug delivery of some cancer drugs; presenting innovative work at international congresses and publishing one papers in peer review journals.

Fourth year: in vitro evaluation of the new BioMOFs; presenting innovative work at international congresses and publishing one paper in peer review journals; analysis of a provisional patent request; writing of the PhD thesis.

References:

  • [1] “Postsynthetic modification of metal–organic frameworks—a progress report”,Kristine K. Tanabe and Seth M. Cohen, Chem. Soc. Rev., (2011) 40, 498–519 (DOI: 10.1039/c0cs00031k).
  • [2] “Crystalline metal-organic frameworks (MOFs): synthesis, structure and function”, Chandan Dey, Tanay Kundu, Bishnu P. Biswal, Arijit Mallickand Rahul Banerjee, Acta Cryst. (2014) B70, 3–10 (DOI: 10.1107/S2052520613029557).
  • [3] “The preparation of metal–organic frameworks and their biomedical application”, Rong Liu, Tian Yu, Zheng Shi,Zhiyong Wang, International Journal of Nanomedicine (2016) 11, 1187–1200 (DOI: 10.2147/IJN.S100877).

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CoPoS: multifunctional Coordination Polymers for optical Sensing applications (Ref. 24-2017)

Supervisor: Carlos Baleizão (CQFM-IN/IST/ULisboa), carlos.baleizao@tecnico.ulisboa.pt

Co-supervisor: Alexander Kirillov (CQE/IST/ULisboa), kirillov@tecnico.ulisboa.pt

The main GOAL of the “CoPoS” proposal is to prepare new coordination polymers incorporating ruthenium phenanthroline complexes as active materials for temperature and oxygen optical sensing.

The INNOVATION of this project is combine the modular structural properties of coordination polymers with the sensing ability of ruthenium phenanthroline complexes in the same material.

Oxygen, being essential for life, is an immensely important chemical species. Determination of oxygen levels is required in numerous areas, including medicine, biotechnology, and aerospace. Temperature is a basic physical parameter, and its measurement is often required both in scientific research and in industrial applications. Real-time temperature monitoring is of paramount importance in industrial testing and manufacturing and also in many biomedical diagnostic and treatment processes. Among the many optical methods employed for sensing, luminescence has attracted special attention because it is sensitive and versatile. In comparison with contact sensors, luminescence-based sensors have advantages in applications where electromagnetic noise is strong or it is physically difficult to connect a wire as there is no contact with the medium in the sensing process. Additional advantages of a luminescence-based thermometer are the usually fast response and the spatial resolution that can extend from the macroscale (in the case of luminescent paints) down to the nanoscale (such as in fluorescence microscopy).[1]

The luminescences of ruthenium(II) phenanthroline and related polypyridyl complexes exhibit a strong temperature dependence and are very sensitive toward the presence of oxygen. The luminescence of such Ru(II) complexes is quenched by oxygen, and ruthenium(II) tris(4,7-diphenyl-1,10-phenanthroline) (Ru(dpp)3) is one of the most sensitive luminescence oxygen sensors due to the long luminescence lifetime. However, if the Ru complex (e.g., ruthenium(II) tris(1,10-phenanthroline); Ru(phen)3) is incorporated in an oxygen impermeable matrix, the Ru complex luminescence exhibits a strong temperature dependence. The photostability of such complexes is high and they can be excited in the visible region. These complexes exhibit luminescence lifetimes in the micro second range, allowing the use of simple measurements set-up.[2]

Coordination polymers (CPs) are typically compounds composed of metal cations and organic ligands that extend “infinitely” into one, two, or three dimensions. The design of new CPs is an intensively growing interdisciplinary research field, which attracts special attention due to unique structural and functional characteristics of such metal-organic materials, as well as many potential applications that also include molecular recognition and sensing.[3] The presence of multiple ligands and/or multinuclear metal centers in the same moiety, and the possibility to adjust the porosity and the particle size, motivate us to propose CPs as key material in the development of new temperature and O2 sensing materials. The objective is to use the versatility of CPs and ruthenium(II) polypyridyl complexes to obtain new sensing materials with improved characteristics and applicability.

As a STRATEGY, the “CoPoS” project comprises the following tasks:

  1. Synthesis and characterization of a series of multifunctional organic building blocks comprising 1,10-phenanthroline, 2,2’- and 4,4’-bipyridine and related cores with carboxylic acid groups.
  2. Application of these organic N,O-blocks for the self-assembly or solvothermal generation of ruthenium-based coordination polymers or discrete complexes. Use of the obtained compounds as secondary building units or precursors for the generation of more complex coordination polymers by introducing additional metal nodes selected from Ru or other metals (e.g., Cu, Fe, Co, Zn).
  3. Full structural and topological characterization of the obtained CPs, as well as the investigation of their thermal, host-guest, and luminescence properties. Selection of the most promising structures for sensing applications.
  4. The materials with higher porosities, and consequently high oxygen permeability, will be tested in the sensing of oxygen (trace analysis / partial pressure, 0-21% O2). The parameters to follow are the relative sensitivity, response time, and long term stability. This data will be compared against reference sensors.
  5. The temperature sensing evaluation will use the materials with higher degree of network condensation and reduced porosity, to decrease (or even avoid) the oxygen penetration. Due to the high thermal stability of CPs, we expect to cover a high range of temperatures (-100ºC up to 100ºC).
  6. The final task of the project will test the best materials in real applications, such as mapping the oxygen concentration in cells (cancer cells exhibit lower oxygen concentration) or measuring the temperature in fuel tanks for security reasons.

The ORIGINALITY and NOVEL concepts in this proposal are demanding and require high commitment from the team. This way, the supervisors combine expertise covering all areas of the project from organic synthesis, to CPs preparation and characterization, and sensing performance evaluation. Carlos Baleizão, is Principal Researcher at IST with expertise and a strong background in the development of new optical sensing systems and synthesis of new photoactive molecules.[4] Alexander Kirillov, Assistant Professor at IST, brings to the proposal a large experience in the design and assembly of functional multinuclear complexes and coordination polymers, and topological analysis of such materials.[5]

  • [1] R. Narayanaswamy, O. S. Wolfbeis, Optical Sensors for Industrial, Environmental and Clinical Applications, Springer, Berlin, 2004.
  • [2] J. N. Demas, B. A. DeGraff, Coord. Chem. Rev., 2001, 211, 317-351; X.-D. Wang, O. S. Wolfbeis, Chem. Soc. Rev., 2014, 43, 3666-3761
  • [3]  A. Morsali, L. Hashemi, Main Group Metal Coordination Polymers: Structures and Nanostructures, Wiley, 2017.
  • [4] C. Baleizão et al., Anal. Chem., 2008, 80, 6449-6457; C. Baleizão et al., RSC Advances, 2017, 7, 4627-4634.
  • [5] A. M. Kirillov et al., Inorg. Chem., 2016, 55, 125-135;   A. M. Kirillov, Coord. Chem. Rev., 2011, 255, 1603-1622.

 

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New Iron, Cobalt and Nickel Organotransition-Metal Molecular Magnets (Ref. 25-2017)

Supervisor: Pedro T. Gomes (CQE/IST-ULisboa), pedro.t.gomes@tecnico.ulisboa.pt

Co-Supervisor: Manuel Almeida (C2TN/IST-ULisboa), malmeida@ctn.tecnico.ulisboa.pt

A rapid progress has been observed in the field of single molecular magnets (SMMs), owing to their potential use to encode information, and fulfil applications in areas such as data storage, quantum computing or magnetic refrigeration. A SMM is a molecule that shows slow relaxation of the magnetization of purely molecular origin. It is a molecule that can be magnetized in a magnetic field, and that will remain magnetized even after switching off the magnetic field. This is a property of the molecule itself. No interaction between the molecules is necessary for this phenomenon to occur, which makes SMMs fundamentally different from traditional bulk magnets, and ultimate miniature elements, at molecular scale, for data storage and processing. The slow relaxation of molecular magnetisation was first observed in metal clusters, but a recent approach to obtain SMMs is based on molecules with a single metal ion, the so called single ion magnets (SIMs). Although f-elements were initially regarded as choice candidates for SIMs, more recently d-elements were found also to be suitable for providing such behaviour. In fact, such magnetic properties can arise from a single first-row transition metal ion provided it has a suitable ligand field environment that creates magnetic anisotropy.1

This project aims at exploring new organotransition-metal complexes based on Iron, Cobalt and Nickel as SIMs, and to enlighten the key factors correlating the magnetic behaviour and slow relaxation of the magnetisation with chemical and structural features.

One type of compounds to be explored is based on derivatives of cobalt(II) complexes bearing mononegative N,N-bidentate 2-iminopyrrolyl and 5-aryl-2-iminopirrolyl ligands (see scheme), which can be prepared from the neutral 2-iminopyrrole (HL1) and 5-aryl-2-iminopirrole (HL2) ligand precursors. It was recently found that homoleptic complexes of the type [Co(L1)2] (a and b),2 do not behave as SMMs, while the increase in the steric bulk and variation of electronic properties of these ligands, through the substitution of position 5 of the pyrrolyl ring with a phenyl group, lead to complexes of the type [M(L2)2] (M= Fe, Co) displaying SMM behaviour.3 Part of this PhD project aims at designing and modifying 5-aryl-2-iminopyrrole ligand precursors, by the employment of appropriate substituents that may alter their electronic (R1=R3=H, R2=CF3, CH3 or R1=R2=H, R3=F, CF3, CH3, OMe, CN) or stereochemical (R2=H, R1=R3=CH3, OMe, iPr) properties. These ligand precursors will be subsequently coordinated to iron (A) and cobalt (B) atoms to obtain homoleptic complexes of the type [M(L)2] (see scheme), which will be molecularly characterised, and their magnetic behaviour thoroughly assessed.

Another family of compounds to be explored in this project is that of [Cp*Ni(NHC)X] complexes (Cp*=pentamethylcyclopentadienyl (C5Me5); NHC= N-heterocyclic carbene; X= Cl, Br, I) (C) (see scheme). Previously, we have studied an analogous family of compounds with normal cyclopentadienyl ligands (C5H5) and NHCs donors with varying R substituents (typically R= Me, tBu) and found that, depending on the substituents R and X, these molecules exhibited singlet (S=0) ‒ triplet (S=1) spin-equilibria, producing interesting gradual spin transitions in a range of temperatures close to room temperature.4 In the present PhD project, we intend to vary the stereochemical and electronic nature of the Cp and NHC ligands in such a way that they can evolve to molecules showing either gradual or abrupt spin transitions with temperature. These properties are relevant in possible applications such as magnetic thermometers or molecular switches.

The newly synthesised materials will be extensively characterised, namely:

1) The molecular structure will be studied by X-ray diffraction, NMR spectroscopy (when possible), UV/Vis, EPR and Mössbauer spectroscopies (the latter one in the case of Fe complexes);

2) The magnetic properties will be studied using different techniques. A first measurement of the magnetic susceptibilities in solution will be performed by NMR (Evans method). Solid state studies will include the measurement of the magnetic susceptibilities using SQUID and AC magnetometers. In both cases the dependence of magnetisation with temperature and magnetic field will be studied, as well as the frequency dependence to characterise the SMM behaviour and the mechanism of slow relaxation.

The experimental work will take place at the Centro de Química Estrutural-IST (synthesis and molecular characterisation), at the Lisboa IST campus, and at C2TN-IST (magnetism and Mössbauer measurements), at the Loures IST campus.

The work will be developed in collaboration with Dr. Laura Pereira (C2TN/IST) (Magnetism Measurements), Dr. João Carlos Waerenborgh (Mössbauer Spectroscopy), Prof. Luís Veiros (CQE/IST) (DFT calculations) and Prof. M. Teresa Duarte (CQE/IST) (X-ray crystallography).

  • [1] Craig, G. A.; Murrie, M. Chem. Soc. Rev.2015, 44, 2135-2147.
  • [2] Carabineiro, S. A.; Silva, L. A., Gomes, P. T.; Pereira, L. C. J.; Veiros, L. F.; Pascu, S. I.; Duarte, M. T.; Namorado, S.; Henriques, R. T. Inorg. Chem. 2007, 46, 6880-6890.
  • [3] Cruz, T. F. C., PhD Thesis, IST, Univ. Lisboa, ongoing work (2014- present).
  • [4]  (a) Silva, L. C. PhD Thesis, IST, Univ. Técnica Lisboa, 2007; (b) Silva, L. C. Silva; Gomes, P. T.; Veiros, L. F., Pascu, S. I.; Duarte, M. T.; Namorado, S.; Ascenso, J. R.; Dias, A. R., Organometallics2006, 25, 4291-4403.

 

Institutions
ChemMat is a partnership between different research units in three different Universities: Instituto Superior Técnico (proponent institution). Faculdade de Ciências da Universidade de Coimbra. Faculdade de Ciências da Universidade do Porto. Centro de Ciências e Tecnologias Nucleares (C2TN). Centro de Química Física Molecular (CQFM). Centro de Química Estrutural (CQE). Instituto de Telecomunicações-Lisboa (IT Lisboa).
Scope
ChemMat is a PhD programme in Materials Chemistry with emphasis on optic electric and magnetic functionalities. It aims at providing advanced education and training in Chemistry including on advanced preparative tools, with a deep knowledge of electrical optical and magnetic properties of materials in order to address the most recent challenges in the development of advanced materials with emphasis on nanostructured and multifunctional materials.