Jordi Martínez-Esaín, Jordi Faraudo*, Teresa Puig, Xavier Obradors, Josep Ros, Susagna Ricart, and Ramón Yáñez*. J. Am. Chem. Soc., Article ASAP. DOI: 10.1021/jacs.7b09821
Ligand-to-surface interactions are critical factors in surface and interface chemistry to control the mechanisms governing nanostructured colloidal suspensions. In particular, molecules containing carboxylate moieties (such as citrate anions) have been extensively investigated to stabilize metal, metal oxide, and metal fluoride nanoparticles. Using YF3 nanoparticles as a model system, we show here the self-assembly of citrate-stabilized nanostructures (supraparticles) with a size tunable by temperature. Results from several experimental techniques and molecular dynamics simulations show that the self-assembly of nanoparticles into supraparticles is due to ionic bridges between different nanoparticles. These interactions were caused by cations (e.g., ammonium) strongly adsorbed onto the nanoparticle surface that also interact strongly with nonbonded citrate anions, creating ionic bridges in solution between nanoparticles. Experimentally, we observe self-assembly of nanoparticles into supraparticles at 25 and 100 °C. Interestingly, at high temperatures (100 °C), this citrate-bridge self-assembly mechanism is more efficient, giving rise to larger supraparticles. At low temperatures (5 °C), this mechanism is not observed, and nanoparticles remain stable. Molecular dynamics simulations show that the free energy of a single citrate bridge between nanoparticles in solution is much larger than the thermal energy and in fact is much larger than typical adsorption free energies of ions on colloids. Summarizing our experiments and simulations, we identify as key aspects of the self-assembly mechanism the requirement of NPs with a surface able to adsorb anions and cations and the presence of multidentate ions in solution. This indicates that this new ion-mediated self-assembly mechanism is not specific of YF3 and citrate anions, as supported by preliminary experimental results in other systems.
Prof. Teresa Puig was invited to give a talk on superconducting materials at “Dissabtes de la Física” at Universitat Autònoma de Barcelona. More than 100 secondary school students listened to her talk, and then experienced the levitating phenomena with some members of her team
X. Obradors, T. Puig, Z. Li, C. Pop, B. Mundet, N. Chamorro, F. Vallés, M. Coll, S. Ricart, B. Vallejo, F. Pino, A. Palau, J. Gázquez, J. Ros and A. Usoskin, Supercond. Sci. Technol. 2018 044001
Susagna va fer una excel·lent exposició de les possibilitats i oportunitats que representa la tecnologia, fonamentalment, a partir de l’impuls de la nanotecnologia: “A partir d’àtoms i molècules, bàsicament, les agrupem per obtenir materials, dispositius i, fins i tot, màquines que tenen noves aplicacions i propietats”.
També va explicar que treballen en dimensions inferiors als virus o els anticossos, un segment que ha permès impulsar, per exemple, la denominada superconducció: “Fa 100 anys, Heike Kamerlingh Onnes va descobrir que a temperatures molt baixes s’aconsegueix una superconducció perquè els àtoms, no se sap per què, s’agrupen en parells i no xoquen, el que fa que no es desprengui energia i, per tant, la conducció és més efectiva”.
Ja a finals del segle XX, aquest camp va millorar a partir d’aconseguir aquesta conducció a partir de temperatures molt més altes, el que permet refredar el material només amb nitrogen, molt abundant a l’atmosfera. Aquest fenomen ha impulsat, per exemple, aplicacions com ‘efecte meissner’ –atracció magnètica molt potent- o la ressonància magnètica, considerada la segona gran revolució després dels Raigs ‘X’.
Segons Ricart, doncs, aquest camp té molta projecció i usos tant en el camp de la medicina, l’energia i la tecnologia. I, en el fons, té molt a veure amb els processos naturals, perquè, tal i com ha explicat, la natura està plena de processos nanotecnològics tant a les espècies animals com vegetals. Identificar-los pot derivar en grans oportunitats per l’ésser humà.
MÉS INFORMACIÓ
Starting on 3 February, 2018, and during 5 consecutive Saturdays, the Faculty of Sciences of the UAB will host the XVIII Edition of the “Dissabtes de la Física” (Saturdays of Physics). An initiative of the Department of Physics, whose main objective is to bring physics and science to pre-university young students, and motivate them to know the world that surrounds us in a rigorous and, at the same time, comprehensible way.
¡Hola!
My name is Max and I am a material scientist from Dresden, Germany. I will continue my work on superconducting tapes as PostDoc in the ULTRASUPERTAPE project under the supervision of Prof. Teresa Puig and I look forward to learn from and collaborate with you!
Also I like sports (running, riding bike and Judo) and travelling sunny countries ;)
You can find him at 1.32 office, next to Mariona Coll!
The COST TO-BE Spring Meeting 2018 will be co-organized by our researcher Mariona Coll (ICMAB) and will be held in Hotel Eden Roc, Sant Feliu, Spain 12-14th March 2018. The meeting, which will be the last one of the series organised by the TO-BE consortium, will be the stage for the presentation of the contents of the Roadmap “Towards oxide electronics” prepared within the context of TO-BE Cost Action.
The different contributions to the Roadmap will be presented by the corresponding authors. The meeting will also offer the opportunity to present latest results by attendants on the general topics of “Fundamental Understanding: Theory and Experiments”, “Oxides Growth and Fabrication Methods”, “Oxides Applications”.
Participation at the meeting is free of charge and is open to scientists, both from the public research sector and from the private sector. Support for travel and subsistence will be offered to a limited numbers of participants. Requests for support should be made before the deadline, together with the abstract submission.
Register here and submit your abstract before January 1, 2018!
Right after this TO-BE Spring Meeting, Mariona Coll (ICMAB) co-organizes at the same venue the “Technologies for Oxide Electronics School 2018”, on 15-17th March 2018, to discuss about potentialities, needs and bottlenecks of oxide electronics and the new opportunities that they offer in many emergent fields.
More information in the COST TO-BE website: https://congresses.icmab.es/tobe2018/
HERLALD (Hooking together European Research in Atomic Layer Deposition), a COST Action that aims to structure and integrate European research activity in ALD (Atomic Layer Deposition), organizes the 2nd HERALD.ECI Workshop with hands-on training for “bonding HERALD.ECIs from ideas to proposals”, which will be held at ICMAB on 1-2 March 2018.
Deadline for registration: 15 February 2018
So far, over a 150 researchers from academia and industry are taking part in HERALD and we welcome new members. If you would like to take part, please sign up here.
Within HERALD, the ECI (Early Career Investigator) network aims to promote the next generation of young ALD scientists and help to establish themselves as research leaders in the ALD community. If you want to become a member of the HERALD.ECI network, please contact the ECI committee at heraldeci@gmail.com and join our HERALD.ECI group on LinkedIn. Broadening out the COST definition of ECI, we welcome investigators from within a year of submitting their PhD dissertation to PhD +10 years.
The main objective of this 2nd HERALD.ECI Workshop with hands-on training is to create an ignition point for competitive proposals resulting in joint, EU-funded research projects under ECI (early career investigator) participation or leadership.
We want the trainees to:
The 2nd HERALD.ECI Workshop is organized by researchers from ICMAB, Ruhr-University Bochum and Technische Universität Dresden:
The online registration is now open until February 15, 2018. Click here for more information.
