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Newsletter September 2017
EditorialLuís AmaralJoão Figueirinhas
The CeFEMA newsletter intents to disseminate the research activities in materials scienceand condensed matter physics developed in the Center to a wide scientific and non-scientificcommunity. In this third number, some of the most recent achievements or ongoing projectsare highlighted. Nanocomposite and nanostructured membranes for applications from watertreatment to medical devices and artificial organs are focused in two contributions. Functionalmono- and few-atomic layer materials for nanoelectronics are also featured. Finally, anothercontribution reports on a work on NMR of liquid crystal dendrimers, which was reviewed in arecently published book by the authors. The featured works are good examples of the excellenceand impact of the science developed in CeFEMA.
Tailoring struc-tures and perme-ation propertiesof asymmetricnanocompositecellulose acetate/silver membraneswith bactericideactivityM. Norberta [email protected]
In the 60s the synthesis by Loeb and Sourira-jan [1] of integrally skinned cellulose acetate(CA) membranes for reverse osmosis (RO) ledto the development at large scale not only ofRO but also of the other pressure-driven mem-brane processes, nanofiltration (NF), ultrafiltra-tion (UF) and microfiltration (MF). Moreoverthe versatility on these membranes synthesis,by the wet phase inversion method, namely theformulation of the casting solution compositionof different polymers and solvents and the set-up of different casting conditions is a strongasset on the tailoring of a multiplicity of asym-metric structures with the creation of intrinsi-cally different surfaces or different active layers[2-4]. Nanotechnology is currently used to en-hance the performance of ceramic and polymericconventional membranes and several conceptshave been proposed, such as zeolitic and cat-alytic nanoparticle coated ceramic membranes,hybrid inorganic-organic nanocomposite mem-branes and aligned nanotube membranes. In avery thorough review Pendergast and Hoek [5]proposed a semi-quantitative ranking based notonly on the performance enhancement but alsoon the commercial readiness, namely prediction
and knowledge of costs, use of technology atlarge scale and existence of manufacturing in-frastructures. Pressure-driven membrane pro-cesses are often associated to biofouling. Bycomplying with the requisite of large scalemanufacturing, our CA membranes preparedby the phase inversion technique offer multi-ple possibilities of developing novel materialsas membrane/Ag nanoparticles composites [6]with bactericide activity and biofouling control.In CeFEMA/MemChem group nanocompositemembranes, CA/Ag nanoparticles, CA/silica,CA/fluorite, are investigated for application rang-ing from water treatments to medical devices.[1] S. Loeb, S. Sourirajan, Adv. Chem. Ser. 38(1963) 117. [2] T. Matsuura and S. Sourirajan, Fun-damentals of Reverse Osmosis, National ResearchCouncil Canada, Ottawa, (1985), Chap. 3, p.165.[3] D. Murphy and M. N. de Pinho, J. MembraneSci., 106 (1995) 245-257. [4] D. F. Stamatialis, C. R.Dias, M. N. de Pinho, Biomacromolecules, 1 (2000)564-570. [5] M. T. M. Pendergast, E. M. V. Hoek,Energy Environ. Sci., 4 (2011) 1946-1971. [6] A.S. Figueiredo, M. G. Sanchez-Loredo, A. Mauricio,M. F. C. Pereira, M. Minhalma, M. N. de Pinho, J.Appl. Polym. Sci., 132 (2015), 41796.
Figure:Dense and porous layers of the UF CA400-22Ag0.1, CA400-30Ag0.1, CA400-34Ag0.1 mem-branes with Ag nanoparticles (0.1 wt%) withhydraulic permeabilities of 13.6; 52.5 and 58.2kgm−2h−1bar−1
CeFEMA Newsletter Number 3, 2017 1
Development ofmono- to few-layer TMDs fornanoelectronicsOlinda [email protected]
Transition metal dichalcogenides (TMD) are aclass of layered materials with chemical formulaMX2, where M is a transition metal and X achalcogen. Just like graphite, they can be exfoli-ated down to a monolayer (2D), exhibiting newproperties that are absent in bulk crystals. Someof the TMDs are semiconductors (e.g. M=Mo,X=S,Se) and this is one of the most excitingproperties of these 2D materials in contrast tothe zero bandgap of graphene. Furthermore,their band structure changes with the numberof layers in a way that the indirect band gap inbulk and few-layer TMD crystals transforms intoa direct band gap in the monolayer. Actually,semiconductor 2D TMDs have open the door fornew studies in fundamental science and applica-tions in nano-scale electronics and optoelectron-ics. Although exfoliation methods enable theproduction of nanolayers with a high degree ofcrystallinity, ideal for the characterization in thelaboratory, they present limitations on the con-trol of the number of layers and lateral sizes, notsuited for technological applications. Currently,Chemical Vapor Deposition (CVD) is the mostpromising fabrication technique for achieving areliable and scalable approach to the productionof large-scale 2D materials. It was almost threedecades ago when researchers from the LASYPGroup started a lab at the FCUL focused on thegrowth and characterization of functional thin
films (nitrides, carbides, complex oxides) by us-ing CVD-based methods. With the launch ofCeFEMA in 2015 and its structuring projectGOLDmater, taking profit of the know-how ongrowth techniques and on 2D materials proper-ties of several of its members, MoSe2 was addedaiming at exploring new physical properties withinterest for devices technology.Why MoSe2? The CVD synthesis of large-scalemonolayer MoSe2 is more challenging than thatof MoS2 due to the lower chemical reactivityof Se as compared to sulphur; however, MoSe2shows a stronger light absorption in the solarspectrum range and the band gap of 1.5 eV formonolayer MoSe2 is close to the optimal valuerequired for solar spectrum related applications,e.g. single-junction solar cells and photoelec-trochemical cells. Also, few-layer MoSe2 hasnearly degenerate indirect and direct band gaps,and an increase in temperature can effectivelydrive the system towards the 2D limit. Cur-rently, we are optimizing the optical and electri-cal properties of CVD-grown mono- to few-layerMoSe2 [1]. In parallel, we have been studyingMoSe2/ferroelectric hybrid structures where aswitchable diode effect was found suggestingthat these structures are promising candidatesfor non-volatile ferroelectric resistive memories[2]. This work is carried out in collaborationwith researchers from Minho University.
[1] C. Almeida Marques, MSc in Physics, Ciências,ULisboa, November 2016 [2] J.P.B. Silva, C.Almeida Marques, J. Agostinho Moreira, O. Conde,arXiv:1705.04475
Figure:FE-SEM micrograph of MoSe2 trian-gle flakes grown by CVD onto oxidized Si. Inset:AFM image.
Nanostructuredmembranes forartificial organsMónica [email protected]
Artificial organs are associated to membranebased treatments clinically well established.They assure in extracorporeal circulation themetabolic functions of a failing organ like thehemodialyzer (HD) in the case of the kidney andthe membrane blood oxygenator (MBO) in thecase of the lung. In order to have technical andmedical progress of HDs and MBOs two majorfactors need to be considered: 1) blood com-patibility of the membrane/blood interfaces and2) enhancement of the flow management/masstransfer associated to the metabolic functions ofthe artificial kidney and lung. The first factor isachieved through the tailoring of novel polymermembranes with specific chemical composition,morphology and topography for enhanced hemo-compatibility [14]. In the case of the artificiallung this can be achieved through the synthesis
of integrally skinned polyurethane urea (PUU)membranes with tailored surface topographies.The figure shows a direct correlation betweenthe submicron roughness of the blood contactingsurface and the degree of platelet adhesion forthe PUU membranes where the smoothest mem-branes exhibited very low platelet adhesion andinhibition of extreme states of platelet activation[5]. In the case of the artificial kidney, blood com-patibility can be achieved by the development ofasymmetric cellulose acetate-silica (CA-Si) mem-branes by a modified version of the phase inver-sion method coupled to the sol-gel technique.The introduction of silica into the polymer matrixof cellulose acetate membranes provides func-tionalization anchor points for molecules knownfor their enhanced hemocompatibility properties,such as heparin, polyethylene glycol, etc.
2 Center of Physics and Engineering of Advanced Materials · Newsletter Number 3, 2017
The second factor is achieved through the syn-thesis of PUU and CA-Si membrane-fiber com-posites to assure flow conditions that minimizethe boundary layer mass transfer resistance. Incontrast with the state of the art, where bound-ary layers disruption is achieved by introductionof spacers over the flat sheet membranes, inour research group, the creation of secondaryflows promoting mixing is achieved through thedeposition of PUU and CA-Si microfibers atthe blood contacting surface of the PUU andCA-Si membranes, respectively. In the case ofthe artificial lung, the efficiency of the PUUmembrane-fiber composites is evaluated by oxy-gen and carbon dioxide permeation studies ina custom-built benchmark device under variousflow and pressure conditions. With regard to themass transfer studies associated to the metabolic
functions of the kidney, also conducted incustom-built benckmark devices, particular em-phasis is given to model solutions of moleculesthat are very difficult to remove by standardhemodialysis, namely the middle-sized moleculesand the protein binding molecules such as β2macroglobulin and p-cresyl sulfate, respectively.[1] Besteiro, M. C. et al. J. Biomed. Mater. Res.A 93, 954-964 (2010). [2] Faria, M., Geraldes, V.and de Pinho, M. N. International Journal of Bio-materials (2012). [3] Faria, M. and Pinho, M. N. D.Extracorporeal Blood Oxygenation Devices, Mem-branes for. in Encyclopedia of Membranes (eds.Drioli, E. and Giorno, L.) 737-755 (Springer BerlinHeidelberg, 2016). [4] Faria, M. and de Pinho, M.N. Eur. Polym. J. 82, 260-276 (2016). [5] Faria,M., Brogueira, P. and de Pinho, M. N. Colloids Surf.B Biointerfaces 86, 21-27 (2011).
NMR of liq-uid crystal den-drimersCarlos [email protected]
The study of new materials with potential andactual technological impact is one of the centralpurposes of CeFEMA. Dendrimers are amongthe most interesting materials with applicationsboth in material science and biomedicine. Re-cently, as a result of more than one decade ofinvestigations, three members of the ComplexFluids NMR and Surfaces (CFNMRS) group ofthe Centre published a book on Nuclear Mag-netic Resonance of Liquid Crystal Dendrimers[1]. Dendrimers are hyperbranched moleculesresulting from sequential iterative synthetic pro-cedures. Unlike usual polymers, which moleculesare composed by similar segments, linearly con-nected forming very long chains of repetitivechemical units, in the dendritic molecules eachsegment branches up into a certain number ofsimilar units, forming a complex structure sim-ilar to a tree crown. The properties of a den-drimer are defined by the chemical nature of itssegments, the multiplicity of the core (numberof branches in the central unit),the degree ofbranching (number of branches starting at theend of each branch), and the generation
(number of levels of branching, correspondingto the number of inner branching layers of thedendrimer). Contrary to conventional polymers,the dendrimer molecules are typically monodis-persed, which means that, in a dendrimer sam-ple, practically all the molecules have the samesize, defined by the dendrimer generation. Thisway, the dimensions of a dendrimer (typicallyof the order of the nanometers) may be tunedby controlling the generation through the syn-thetic procedure. The outer shell of a dendrimermolecule corresponds to the peripheral branchesassociated to the external layer. In most appli-cations, the outward branches of the dendrimermay be appropriately functionalized, using chem-ical units suitable for the desired purpose. Mostof the interesting practical uses of dendrimersare based on this approach. If the dendrimersare functionalized with terminal units bearingliquid crystalline properties, peculiar materialsknown as liquid crystal dendrimers, can be ob-tained. Liquid crystal dendrimers combine theinteresting properties of dendrimers with thoseof liquid crystals (anisotropic molecular
Center of Physics and Engineering of Advanced Materials · Newsletter Number 3, 2017 3
organization, fluidity, anisotropic response toelectric and magnetic fields, and anisotropicphysical properties in general). The CFNMRSgroup of CeFEMA has a very long experience onthe study of liquid crystals by means of NMRspectroscopy and relaxometry, characterizing
NMR of Liquid Crystal Dendrimers
both the molecular order and dynamics of thosematerials. In more recent years this expertisehas been applied to study of other systems in-cluding liquid crystal dendrimers. The bookrecently published includes a general introduc-tion to dendrimers, liquid crystal dendrimers andNMR, both in theoretical and experimental as-pects applied to liquid crystalline materials, andan comprehensive review on the research workof the authors on this subject and a compara-tive study where the physical properties of manydifferent liquid crystal dendrimers accessible thor-ough NMR are compared and analyzed.[1] NMR of Liquid Crystal Dendrimers, Carlos R.Cruz, João L. Figueirinhas, Pedro J. Sebastião, PanStanford Publishing, 2016, ISBN 978-981-4745-72-7(Hardcover), 978-981-4745-73-4 (eBook)
News andEvents
2016
NewsCeFEMA at Industrial Technologies 2016Creating a Smart Europe, Amsterdam, TheNetherlands, June, 22, 2016CeFEMA at infoday: Nanotechnologies, Ad-vanced Materials and Advanced Mnufactoringand Processing, Biotechnology, Lisbon, July 7,2016
WorkshopsWorkshop on graphene and other 2D materialsIST, December 5, 2016CeFEMA WorkshopIST, December 12, 2016SeminarsCicle of CeFEMA Seminars, 7 heldCeFEMA Theory Group Seminars, 4 heldOther CeFEMA Seminars, 3 held
2017
Special EventsEmílio Ribeiro Conference on Quantum Chro-modynamics and other mattersSeptember 6, 2017
NewsCeFEMA at EuroNanoForum 2017, Mediter-ranean Conference Centre, Valletta, Malta, June21-23, 2017WorkshopsMini-Workshop on Theoretical Condensed Mat-ter PhysicsFebruary 21, 2017
SeminarsCicle of CeFEMA Seminars, 4 heldCeFEMA Theory Group Seminars, 6 held
Contacts
EditorsLuís [email protected]
João [email protected] EditorsNorberta de PinhoOlinda CondeMónica FariaCarlos Cruz
Instituto Superior Técnico,Universidade de LisboaAv. Rovisco Pais, 11049-001 Lisboa
OfficePhysics Building, 3rd floorTelephone number: +351 218 419 [email protected]://cefema.tecnico.ulisboa.pt
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