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)