Oriented aggregation of lepidocrocite and impact on surface charge development

Philipp A. Kozin, German Salazar-Alvarez, and Jean-François Boily

Langmuir 30 (2014) 9017–9021

DOI: 10.1021/la500507e

Abstract

The impact of lepidocrocite (γ-FeOOH) nanoparticle aggregation on mineral surface charge development was resolved in aqueous solutions of NaCl and NaClO4. Synthetic rod-like particles exhibiting charged edge (100) and neutrally/low-charged (010) faces self-aggregated in salt-free solutions. Aggregation was notably imaged by high-resolution transmission electron microscopy, and inferred by decreases in N2(g)-B.E.T. specific surface area from 94 m2/g to 77 m2/g after 12 months, and to 66 m2/g after 33 months storage. Potential determining (H+, OH–) ions loadings in the 4–11 pH range were unchanged only if the particles remained aggregated in NaCl but only if they were disaggregated in NaClO4. These differences, alongside molecular simulations and experimental ion loadings resolved in other studies from our group, point to important controls on background electrolyte ion identity on the aggregation and charge development in lepidocrocite. These results may apply further to other mineral surfaces of comparable surface (hydr)oxo populations.

[Summer school] Organic–inorganic hybrids and composites: from basic understanding to functional materials

The Chalmers Soft Matter Graduate School is organizing a summer school on “Organic–inorganic hybrids and composites: from basic understanding to functional materials”.  Please find attached the announcement. The summer school will take place between 2-5 of september lunch to lunch and it will be held in Djurönäset in the Stockholm archipelago (www.djuronaset.com).

Scope:
Organic–inorganic hybrids and composites have been playing a major role in research and society in recent years. Traditionally, organic–inorganic hybrids have had a focus on the polymeric matrix filled with relatively passive inorganic components. In parallel, with increased interest in alternatives to fossil fuels, there has been a strong move towards the fabrication of functional materials based on biopolymers that can be extracted from renewable sources. Hybrids and composites based on biopolymers are an ideal component for the fabrication of multifunctional materials in combination with various useful inorganic nanomaterials as they can combine impressive properties with environmentally benign and energy efficient production routes.
This course aims to give the participants an understanding of the properties of the organic and inorganic components, preparation methods, characterisation techniques and also examples of functional hybrid materials.

Topics that will be covered:
• Biopolymers: Properties of biopolymers (cellulose, chitin, DNA, proteins) in solutions and dispersions, JL.
• Bionanomaterials: Types of bionanomaterials, sources and isolation methods, GSA
• Nucleation and assembly: i) Nucleation and growth of inorganic materials, ii)Colloidal processing and assembly of hybrids, LB
• Optical characterisation: Polarised light microscopy, JL
• Morphological characterisation: Electron microscopy and X-ray scattering, GSA
• Surface characterisation: Catechols as model systems, DRM
• Interfacial characterisation: Solid state NMR, DL
• Mechanical characterisation: Tensile, flexural, compression testing and fracture toughness measurements, RL
• Bioinspired composites: High performance composites, RL

Lecturers:

Lennart Bergström (Stockholm University)
Jan Lagerwall (University of Luxembourg)
Danielle Laurencin (Institute Charles Gerhardt of Montpellier, France)
Rafael Libanori (ETH, Zurich, Switzerland)
Daniel Ruiz-Molina (Institut Català de Nanociència i Nanotecnologia, Spain)

German Salazar-Alvarez (Stockholm University)

Registration: 
To apply to the summer school send an email to Christina Schütz (christina.schuetz@mmk.su.se) not later than July 28, 2014. The number of participants is limited to 30 and there is a priority to those students enrolled in the “Soft Matter Graduate School”at Chalmers University (www.chalmers.se/soft/); other students and participants are accepted on a first come, first serve basis. The summer school is free of charge for all students doing their PhD at a Swedish university. For students abroad and other participants, the fee is 6000 SEK (incl. accommodation and all meals; excl. VAT).

Schedule and examination:

time\date	Tuesday 2nd	Wednesday 3rd	Thursday 4th	Friday 5th
9-11.30		Nucleation and assembly	Surface characterisation	Project presentations
11.30-13.00	Arrival and lunch	Lunch	Lunch	Lunch and departure
13.00-15	Biopolymer dispersions and solutions	Optical characterisation	Interfacial characterisation
15-17	Bionanomaterials	Morphological characterisation	Mechanical characterisation
17-18	Free time
18-20	Dinner	School dinner	Dinner
20-21	Project assignments		Bioinspired composites

The students are expected to work actively during the course and the participants will receive material to study in advance. During the course there will be individual assignments and individual presentations. We recommend that students after completing the course will be given 3 ECTS.


Contact:
• German Salazar-Alvarez (course leader) (german@mmk.su.se)
• Christina Schütz (registration and practical issues) (christina.schuetz@mmk.su.se) 

Postdoctoral fellowship in 3D electron microscopy studies of nanoparticles and nanoparticle arrays

Re. SU FV-1248-14. Last application date: 2014-05-09.

Stockholm University, a modern university with a multicultural environment, is one of the world’s top 100 higher education institutes. Here more than 60,000 students and 5,000 staff are active within science, the humanities and the social sciences. Stockholm is a cultural hub and economic centre, with many green areas and surrounded by water, making it an ideal place in which to enjoy a relaxed and exciting student life.

         MMK is a leading institution in materials synthesis and structure characterization. We have recently obtained a large grant for the project “3D Electron Microscopy for Nanostructure Research (3DEM- NATUR)” from the Knut and Alice Wallenberg Foundation. The 3DEM-NATUR project aims at developing new transmission electron microscopy methods to obtain 3D structural information for studying atomic and mesoscopic arrangements in solids, on surfaces and at interfaces. More information about the 3DEM-NATUR project can be found at http://www.mmk.su.se/page.php?pid=945.

         We are interested in studying nanoparticles and self-assembled nanoparticle arrays using various 3-dimensional transmission electron microscopy (TEM) techniques. Techniques involve the recently developed Rotation Electron Diffraction (RED) method and other EM techniques such as electron tomography, and STEM‐HAADF, STEM‐EELS and electron holography may also be applied.

Assessment criteria

The candidate must have obtained a PhD degree in chemistry, physics, materials science or other relevant field no more than three years prior the application deadline, unless there are special circumstances that should be taken into account. These might be illness, parental leave, union duties or similar. The applicant should have excellent English language skills, both oral and written communication.

         Proven experience in TEM and nanoparticle synthesis is essential. Experience in nanoparticle assembly and crystallography is desirable.

Terms of employment

The scholarship is for one year with the possibility of one-year extension. The preferred starting date is 4th of August 2014.

Stockholm University strives to be a workplace free from discrimination and offers equal opportunities to everyone.

More information
For further information about the position, please contact German Salazar-Alvarez, telephone +46-(0)8-163942 or german@mmk.su.se

Application

The application should be written in Swedish or English and contain:

    – Cover letter describing the interest and skills of the applicant

    – CV with publication list (including DOI),

    – Copy of PhD degree certificate,

    – Contact information for 2 reference persons

Welcome with your application, marked with the reference number SU FV-1248-14, no later than 9 May, 2014 by e-mail to: registrator@su.se.

Applications that are submitted electronically should be in Word (.doc/.docx) or PDF format. Please include the reference number SU FV-1248-14 also in the message line.

[OPEN ACCESS] Carbon aerogels from bacterial nanocellulose as anodes for lithium ion batteries - RSC Advances

Liping Wang, Christina Schütz, German Salazar-Alvarez, and M. Magdalena Titirici
RSC Advances, 2014
DOI: 10.1039/C3RA47853J


Abstract:
Carbon aerogels with large open pores and high surface area are fabricated via pyrolysis of a readily available natural resource, e.g., bacterial nanocellulose (BNC) aerogels. Freeze-drying of the BNC hydrogels is used to preserve the 3D open network structure upon calcination whereas using Fe(III) improves the yield and H/C ratio. These carbon aerogels are explored as anodes in lithium ion batteries where it is shown that they deliver superior capacity retention and rate performance compared to other carbon-based materials.

Macroscopic Control of Helix Orientation in Films Dried from Cholesteric Liquid-Crystalline Cellulose Nanocrystal Suspensions

ChemPhysChem, 2014

DOI: 10.1002/cphc.201400062

Ji Hyun Park; JungHyun Noh; Christina Schütz; German Salazar-Alvarez; Giusy Scalia; Lennart Bergström; Jan P. F. Lagerwall

Abstract:

The intrinsic ability of cellulose nanocrystals (CNCs) to self-organize into films and bulk materials with helical order in a cholesteric liquid crystal is scientifically intriguing and potentially important for the production of renewable multifunctional materials with attractive optical properties. A major obstacle, however, has been the lack of control of helix direction, which results in a defect-rich, mosaic-like domain structure. Herein, a method for guiding the helix during film formation is introduced, which yields dramatically improved uniformity, as confirmed by using polarizing optical and scanning electron microscopy. By raising the CNC concentration in the initial suspension to the fully liquid crystalline range, a vertical helix orientation is promoted, as directed by the macroscopic phase boundaries. Further control of the helix orientation is achieved by subjecting the suspension to a circular shear flow during drying.

Spin excitations in cubic maghemite nanoparticles studied by time-of-flight neutron spectroscopy

Phys. Rev. B 89, 064402 (2014)
DOI: 10.1103/PhysRevB.89.064402

S. Disch, R. P. Hermann, E. Wetterskog, A. A. Podlesnyak, K. An, T. Hyeon, G. Salazar-Alvarez, L. Bergström, and Th. Brückel

Abstract:

We have determined the field dependence of collective magnetic excitations in iron oxide nanoparticles of cubic shape with 8.42(2) nm edge length and a narrow log normal size distribution of 8.2(2)% using time-of-flight neutron spectroscopy. The energy dependence of the uniform precession modes was investigated up to 5 T applied field and yields a Landé factor g=2.05(2) as expected for maghemite (γ-Fe2O3) nanoparticles. A large effective anisotropy field of BA,eff=0.45(16) T was determined, in excellent agreement with macroscopic measurements. This anisotropy is attributed to enhanced shape anisotropy in these monodisperse cubic nanoparticles. The combination of our results with macroscopic magnetization information provides a consistent view of the energy scales of superparamagnetic relaxation and collective magnetic excitations in magnetic nanoparticles.

Robust antiferromagnetic coupling in hard-soft bi-magnetic core/shell nanoparticles

Nature Communications 4 (2013) 2960.

doi:10.1038/ncomms3960

M. Estrader, A. López-Ortega, S. Estradé, I. V. Golosovsky, G. Salazar-Alvarez, M. Vasilakaki, K. N. Trohidou, M. Varela, D. C. Stanley, M. Sinko, M. J. Pechan, D. J. Keavney, F. Peiró, S. Suriñach, M. D. Baró & J. Nogués

Abstract:

The growing miniaturization demand of magnetic devices is fuelling the recent interest in bi-magnetic nanoparticles as ultimate small components. One of the main goals has been to reproduce practical magnetic properties observed so far in layered systems. In this context, although useful effects such as exchange bias or spring magnets have been demonstrated in core/shell nanoparticles, other interesting key properties for devices remain elusive. Here we show a robust antiferromagnetic (AFM) coupling in core/shell nanoparticles which, in turn, leads to the foremost elucidation of positive exchange bias in bi-magnetic hard-soft systems and the remarkable regulation of the resonance field and amplitude. The AFM coupling in iron oxide—manganese oxide based, soft/hard and hard/soft, core/shell nanoparticles is demonstrated by magnetometry, ferromagnetic resonance and X-ray magnetic circular dichroism. Monte Carlo simulations prove the consistency of the AFM coupling. This unique coupling could give rise to more advanced applications of bi-magnetic core/shell nanoparticles.

PhD Position in Analytical Transmission Electron Microscopy::Stockholm University, Sweden

Project title: Studies and characterization of interfaces in nanoscale materials using novel 3DEM techniques. 

Reference number: SU FV-3142-13 (project HT13-1).

Deadline: November 20, 2013

General information.

Stockholm University (http://www.su.se) is a modern university with a multicultural environment and is one of the world’s top 100 higher education institutes. Here more than 60,000 students and 5,000 staff are active within science, humanities and social sciences. The Department of Materials and Environmental Chemistry (MMK, http://www.mmk.su.se) is a leading institution with research spanning over Materials and Solid State Chemistry focusing on different classes of materials, from ceramics and glasses to self-assembled and porous materials. The work often encompasses synthesis, characterisation by X-ray diffraction and electron microscopy, NMR studies, and modelling with computer simulations. Environmental aspects are also an important part of the research activities, where refined natural or anthropogenic chemicals and materials are studied in relation to their impact in our global environment.

Project description.

Synthetic and naturally occurring nanostructured materials are the building blocks of nanoscience and nanotechnology. These nanostructures often exhibit novel properties as their physical dimensions become comparable to certain characteristic length scales, which situate them at the border between quantum effects and bulk properties.

Nanomaterials composed of two phases often shown interesting interfacial phenomena. This project focuses on developing element specific three-dimensional electron microscopy (3DEM) to obtain compositional and crystallographic information at the interface of such nanoscale materials and correlate it with optical and magnetic properties. The project will be carried out in close collaboration with other groups at Stockholm University and international partners in Spain, Denmark and USA.

Relevant publications:

1.   E. Wetterskog, C.W. Tai, J. Grins, L. Bergström and G. Salazar-Alvarez, ACS Nano 2013 7, 7132.

2.   G. Salazar-Alvarez, H. Lidbaum, A. López-Ortega, M. Estrader, K. Leifer, J. Sort, S. Suriñach, M. D. Baró, and J. Nogués, Journal of the American Chemical Society 2011 133, 16738.

3.   K.L. Krycka, J. A. Borchers, G. Salazar-Alvarez, A. López-Ortega, M. Estrader, S. Estradé, E. Winkler, R.D. Zysler, J. Sort, F. Peiró, Maria Dolors Baró, C.C. Kao, and J. Nogués, ACS Nano 2013 7, 921.

4.   S. Disch, E. Wetterskog, R. P. Hermann, G. Salazar-Alvarez, P. Busch, T. Brueckel, L. Bergström, S. Kamali, Nano Letters 2011, 11, 1651.

Funding: The project will be funded by the recently approved KAW project “3DEM-
NATUR” (http://www.mmk.su.se/page.php?pid=945).

More information.

About the project: Doc. Germán Salazar-Alvarez, Group leader, german@mmk.su.se (http://www.mmk.su.se/page.php?pid=155&id=1303)

About MMK: Prof. Gunnar Svensson, Head of Department, gunnar.svensson@mmk.su.se.

Starting date: the anticipated starting date is February 1, 2014, or later.

How to apply.

Interested candidates should send their application and supporting material to: registrator@su.se with reference number SU FV-3142-13 in the subject field.

Your application should contain:

• An application on the form (can be found at www.mmk.su.se/page.php?pid=413) together with CV and documentation of study merits, where your eligibility is clearly documented (see below).
• A "Letter of intent", describing your expectations of the PhD studies connected to the project.
• IMPORTANT: Please combine all your documents into a single, self-contained pfd-file, including the cover letter.

Eligibility.

To be eligible for PhD studies in chemistry, an education at the undergraduate level of at least 240 credits is required (corresponding to three years of full-time studies on undergraduate level and one year on advanced level) with at least 60 credits in chemistry or physics. Those studies should include at least one specialized course or a thesis in the research subject. In order to facilitate the evaluation of merits and suitability for the PhD studies your curriculum vitae (CV) should contain information about the extent and focus of the academic studies. The quantity (as part of an academic year) and the quality mark of courses in chemistry and physics are of particular interest. Please, state titles of undergraduate theses and project works. Further information is found in the home page, www.mmk.su.se/page.php?pid=413.

A selection committee will assess the candidate´s ability to successfully complete the PhD program and invite short-listed candidates to an interview in person or via internet. The study merits are an important selection criterion. Economic support for the graduate studies is guaranteed for full time studies during the time agreed in the individual study syllabus (study plan), normally for four years of full time studies, see  www.mmk.su.se/page.php?pid=413.

See link at http://www.nature.com/naturejobs/science/jobs/351442-phd-position-in-analytical-transmission-electron-microscopy

[OPEN ACCESS] Dynamic growth modes of ordered arrays and mesocrystals during drop-casting of iron oxide nanocubes

Cryst. Eng. Comm. 2013
DOI: 10.1039/C3CE41871E
Michael Agthe, Erik Wetterskog, Johanne Mouzon, German Salazar-Alvarez and Lennart Bergström

Abstract:
The growth modes of self-assembled mesocrystals and ordered arrays from dispersions of iron oxide nanocubes with a mean edge length of 9.6 nm during controlled solvent removal have been investigated with a combination of visible light video microscopy, atomic force microscopy and scanning electron microscopy. Mesocrystals with translational and orientational order of sizes up to 10 μm are formed spontaneously during the final, diffusion-controlled, drop-casting stage when the liquid film is very thin and the particle concentration is high. Convection-driven deposition of ordered nanocube arrays at the edge of the drying droplet is a manifestation of the so called coffee-ring effect. Dendritic growth or fingering of rapidly growing arrays of ordered nanocubes could also be observed in a transition regime as the growth front moves from the initial three-phase contact line towards the centre of the original droplet.

Video abstract:


Cover page:
http://pubs.rsc.org.ezp.sub.su.se/en/content/articlepdf/2014/ce/c4ce90010c?page=search

Application to the PhD programme at the Department of Materials and Environmental Chemistry, Stockholm University, November 2013

Original text at http://www.mmk.su.se/page.php?pid=983

Application to the graduate research program (PhD studies) at MMK, November 2013

Ref number SU FV-3142-13

The Department of Materials and Environmental Chemistry (MMK), offers 6 new places for graduate students after an application procedure as described below.

General information:

The extensive research activities of MMK, hosting the Berzelii Center EXSELENT for development of nanoporous materials for catalysis, span over Materials and Solid State Chemistry focusing on different classes of materials; e.g. ceramics and glasses, self-assembled and porous materials, and soft matter. The work often encompasses synthesis, characterisation by x-ray diffraction and electron microscopy, NMR studies, modelling with computer simulations of materials with a potential for various applications. Environmental aspects are an important part of the research activities, where refined natural or anthropogenic inorganic and organic chemicals and materials are studied in relation to their sole or combined impact on, and interaction with biological and non-biological systems in our global environment.

For project and application information please read the PhD advert