Ionic Liquids Smart Solvents for the Synthesis of Nano- and Open-Framework Materials

Background and Motivation

Manufacturing materials on the nanoscale has moved into the focus of chemists, materials scientists and engineers in the last decades. When a material is brought to the nanoscale, its chemical and physical properties can change significantly. These size dependent properties make nanostructured materials extraordinarily valuable functional materials in many applications ranging from sunscreen, cosmetics, food products and packaging, over clothing, disinfectants and household appliances to energy conversion and storage as well as construction materials. With growing societal demand for a high standard of living, products and devices that rely on nanomaterials are becoming increasingly important. In consequence, the development of more sustainable and environmentally less demanding (but also less energy consuming), value-adding and economically viable processes for manufacturing nanomaterials is becoming a particularly important task. In this context, ILs come into focus as a transformative tool because of their unique properties and property combinations. Taking advantage of the structuring in ionic liquids, they can be used as “nanoreactors”. In addition, ionic liquids feature a wide range of interactions with nanomaterials forming in the reaction medium such as cation-p-bonding, p-p-bonding, hydrogen bonding, van-der-Waals and dipole-dipole interactions, that can be deliberately used in steering and controlling nanomaterial formation. In addition, the electrosteric stabilization provided through the ionic liquids prevents particle coalescence and growth. Thus, the ionic liquid can act as the synthesis medium and NP stabilizer. In contrast to classical surfactants and NP stabilizers which are used to preserve the material at the nanoscale, the nanomaterials obtained from ionic liquids can be cleaned easily (a requirement for many applications). All of this makes ionic liquids particularly interesting for applications in nanosynthesis.

Similar to nanomaterials, open-framework materials spanning from conventional zeolites, alumosilicates, and related porous materials such as MOFs have attracted widespread attention. These materials are of scientific and technological interest in applications from microelectronics to medical diagnosis as the framework structures similarly are capable of interacting with atoms, ions and molecules not only at their surfaces, but also throughout the bulk of the material. The worldwide consumption of natural and synthetic open-framework materials for application in catalysis, adsorption and separation is about 5 million metric tons per year. This market share can be expanded by adding new framework architectures. The range of application of these materials could be substantially broadened if materials with new network architectures and larger pore sizes would become available. In this context, ionic liquids become interesting as they can be used as both solvents and templates, which removes the competition between template–framework and solvent–framework interactions that occur in conventional hydrothermal and solvothermal preparations. Multiple framework structures can be synthesized through variation of the other reaction parameters (such as precursor identity, concentration, heating etc.) even from the same IL and ionothermal synthesis, leading to some stunning results.

 

Research Questions

Important questions that guide our research activities are:

What are the dominating ionic liquid-solute/nucleus/particle interactions and how can they be used to control the morphology, size and crystalline phase of a desired open-framework or nanomaterial?

How can the pore size, surface, nanostructure and nanoassembly be controlled? Is it possible to obtain hybrid and composite materials with enhanced properties? Are there conversion methods that enhance the potency of ionic liquids in the manufacturing of nano- and open-framework materials? How can they be improved and advantageously used?

 

Research at the Mudring laboratory

In the Mudring laboratory, ionic liquids (ILs) are used as a transformational manufacturing platform for nanomaterials and open-framework materials. When used as the synthesis medium, ILs permit a more efficient, safer and environmentally benign production of high quality nanomaterials. A smart combination of ILs with (unconventional) production methods that draw added value from the exceptional properties and property combinations that ILs offer allows for new universal manufacturing techniques that provide solutions to the existing problems of nano-manufacturing. Examples that illustrate the power of ionic liquids in the improved manufacturing of nanomaterials are: the synthesis of light phosphors with exceptional quantum yields, efficient photocatalysts, record figure-of-merit thermoelectrics and unusual open-framework materials.

 

1: Development of unconventional synthesis techniques that take advantage of the special properties that ionic liquids offer

Ionic liquids have many properties, such as high ionic conductivity and extremely low vapour pressure, which make the use of synthetic techniques possible that are different from those for classical solvents.

 

Bottom-up

Microwave Synthesis. Ionic liquids are excellent media for absorbing microwaves as they are composed of large ions with high polarizability and conductivity, leading to high heating rates and, therefore, result in a high formation rates of nuclei which favor nanoparticle formation. Due to the short heating times, particle growth is not supported as with conventional heating which requires much longer heat treatment to achieve conversion. In addition, the ionic liquid can act as an NP-stabilizer, thus, no stabilizing agents are required. Yet the ionic liquid can easily be removed from the particle surface, which finally declares the obvious advantage of ionic liquids.

Ultrasound Assisted Synthesis. The chemical effects of ultrasound originate from acoustic cavitation, which occurs in several stages involving the steps of nucleation, growth and collapse of bubbles in the liquid. The collapse of the bubbles provokes extreme conditions locally: high temperatures of 5,000 K and high pressures of about 500 atm can be reached. Yet sonochemical synthesis is considered as a mild method as the overall temperature and pressure barely change. As many ionic liquids have an extremely low (in fact negligible) vapor pressure, they are uniquely suited for sonochemistry. This is because they do not interfere with the chemistry inside the bubble, unlike traditional volatile solvents. As most ionic liquids have a low heat capacity, they heat faster under ultrasound irradiation compared to aqueous solutions. Thus, in the synthesis of nanomaterials, a reduction of reaction time occurs – and, again, faster heating in small volumes, reduced mass transport (often supported by the relatively high viscosity of ionic liquids) favor the formation of nanomaterials. In addition, ultrasonic cavitation generates high shear that helps to break particle agglomerates into singly dispersed particles, supporting the materials’ dispersion.

 

Top-down, physical routes to nanomaterials in ionic liquids

Physical Vapor Deposition. As most ionic liquids have a negligible vapor pressure and an extremely low flammability, they can be handled under high vacuum conditions, even at elevated temperatures. The unique approach to obtain nanomaterials is to evaporate metals, pre-prepared intermetallic compounds and alloys, as well as ceramic materials and metal salts onto ionic liquids by employing physical vapor deposition (PVD) methods. Our group has pioneered the high temperature evaporation for the fabrication of nanoparticles in ionic liquids by modifying the SMAD (solvated metal atom dispersion) technique. The SMAD technique was originally developed by Klabunde for conventional VOCs, where substrate vapors and a solvent or stabilizing agent are co-condensed in high vacuum onto a target that is maintained at liquid nitrogen temperature. Instead of using conventional volatile organic solvents and stabilizing agents with significant vapor pressures (requiring cooling of the substrate to maintain the vacuum during evaporation), ionic liquids with negligible vapor pressure offer the possibility to work at ambient temperature with a liquid substrate. With this technique, we managed to develop universal synthetic procedures for long-term stable metal and metal-metal oxide colloids, as well as fluoride nanophosphors by thermal evaporation and e-gun evaporation.

Sputtering. The thermal evaporation rates for each source material are different due to thermodynamic restrictions. This limitation can be circumvented by sputtering. The method is also a fast method to establish libraries of materials with variable composition. By combinatorial sputtering, a large number of NPs with different composition can be manufactured (and tested for a given application). Two and more targets can be used or, alternatively, one target, containing a pre-prepared compound. In addition, the sputter power (discharge current) and sputter rate can be tuned, as well as the argon partial pressure and sputter time. The sputtering process does not rely on the different reactivity of starting materials and bears, in this case, a clear advantage if alloy particles are desired over core-shell particles. This method offers an approach to synthesize NPs with a high potential, and with an exact composition by just varying the sputter rate.

2: Nanophosphors

CFLs (compact fluorescent lamps) and LEDs (light emitting diodes) are widely used as energy-efficient light sources. One of the drawbacks of CFLs is that they contain small amounts of mercury. To replace it by environmentally benign materials, special nanophosphors with a quantum efficiency of higher than 100% (so-called quantum-cutters) are required. Eu3+ doped GdF3 is a material that is able to convert one high energy photon into two red ones. It has a theoretical quantum efficiency of 200%. However, it is a polymorphic material and only one polymorph (the thermodynamically unstable form) shows the desired photophysical effect. In addition, the material has to be of high purity, especially oxygen-free, as this would enable radiation-less decay. Thus, a polymorph-specific synthesis has to be achieved. By heating Gd- and Eu-acetate in the ionic liquid choline tetrafluoroborate for 10 min at 80°C in a microwave, the desired material (as small and uniform particles that are absolutely oxygen-free) is formed, containing 100% of the desired phase. It is the ionic liquid that controls which polymorph is formed. In addition to being a fast and energy-efficient low temperature process, the use of hazardous HF is totally omitted. This synthetic concept can be easily transferred to green quantum cutting materials and (white light) emitting phosphors for light emitting diodes (LEDs).

3: (Photo-)Catalysts

With an increasing energy and related fuel consumption in the world, developing tools for clean energy becomes an indispensable necessity to satisfy demands in a sustainable way. Hydrogen fuel, produced through water-splitting using sunlight as the energy source, can be regarded as an ultimately green technology. Of similar importance to the environment and to our welfare, is cleaning air and water of organic pollutants, for which sunlight may also be used. For both, potent nanostructured photocatalysts are needed. The requirements for a suitable photocatalyst are that it has a sufficiently large band gap (for water splitting it has to be larger than 1.23 eV) and that the valence and conduction band have the right position. The band gap should also make efficient use of the solar spectrum. For these purposes, semiconducting materials with a suitably wide band-gap that can absorb light in the near UV and in the visible region, such as cubic perovskites like MTiO3 (M = Ca, Sr, Ba) are turned to. However, only for SrTiO3 is the useful cubic aristotype the thermodynamically stable form at room temperature. Quite remarkably, employing sonochemistry in ILs produced the cubic polymorph of SrTiO3 as expected, but also for CaTiO3 and BaTiO3, seemingly at room temperature. However, under ultrasound irradiation (for a short time) locally high temperatures and high pressures are present, which clearly favor the formation of the high temperature phase; as pressure and temperature drop quite fast, no phase transformation to the thermodynamically stable polymorph occurs. The prepared materials not only show excellent performance for hydrogen evolution, but also in the degradation of methylene blue, which was investigated as a test substance for the decomposition of organics in solution. The different photocatalytic activities of the varied materials can be correlated with the different dominating  surface facets that are expressed. These materials show distinct differences for H2 production and photocatalytic decomposition of organic material. Which facet is expressed preferentially in the nanomaterial can be controlled by the IL used for the synthesis. This is an instructive example of how the expression of crystal facets can be tuned by ionic liquids.

 

4: Thermoelectrics

Solid state energy conversion is discussed as a main player for waste heat harvesting, e.g. in the cooling system of combustion engines. For this purpose, thermoelectric materials are of particular interest. Good thermoelectric converter materials have to have a high Seebeck coefficient a, ex-pressing the generated thermovoltage per temperature difference. Moreover, a high electrical conductivity s is needed in order to reduce the Joule energy dissipation within the thermoelectric generator. A low thermal conductivity k, with contribution from the electronic and phononic system, is further required so that the thermal shortcut due to Fourier’s heat conduction is small. This combination of properties is rather rare, and nanostructuring has been put forward as a solution to decouple the electronic from the phononic transport properties. By decomposing a single source precursor through microwave irradiation in an ionic liquid, we managed to obtain record figure-of-merit thermoelectrics. The single source precursors allow control of the product composition, and hence, the charge carrier concentration, leading to a high Seebeck coefficient; the use of a task-specific IL combined with microwave heating gives access to clean, impurity free, small particles resulting in a high carrier mobility and optimized for electrical and thermal conductivity.

 

5: Open-framework structures

The central point of porous solids for any application is the large pore volume and the accessibility of the pore network. Templates act as structure directing agents for framework precursors to condensate around them and, thus, achieving control of the pore size and connectivity. Ionic amphiphiles are already used in traditional syntheses. They find utility either in solutions of low concentration where they act as isolated ionic entities or at higher concentrations where they assemble into lyotropic liquid crystalline structures. This allows for spatially controlling the mineralization process along various scales, ranging from Ångstroms to micrometers. ILs bear the same key structural features as many ionic liquid amphiphiles. They are highly structured solvents and can be regarded as supramolecular reaction media. For many ILs, the formation of lyotropic liquid crystal (LC) phases has been proven; others form thermotropic LC phases. ILs provide the unique opportunity of having a highly ionic reaction medium where the competition between the solvent and the template can be excluded. Attempts to synthesize materials with large pores in conventional media also ends often in materials of low crystallinity. Potentially, this comes from the high concentration of water compared to the template which results in high reaction rates and low crystallinity. Application of ILs as the solvent allows for excellent control of water concentration and, thus, the hydrolysis rate, which should result in an improved crystallinity of the products. Through the increasing interest in IL chemistry, a plethora of new ions have become available, most of which have never been tested as templating agents in the synthesis of inorganic framework structures.

Newest synthetic efforts have yielded an isotopic open-framework phosphate which features large sized, inorganic bucky balls that are decorated with magnetic Ni2+ and Co2+ ions. We are currently in the state of fully characterizing these astonishing materials. Particularly, the magnetic properties of these materials are interesting, since the transition metal cations feature exchange interactions on the surface of a ball-like structure.

Funding

Current:

 

”Smart Materials from Ionic Liquids for Energy Applications”,

Kungl. Vetenskapsadademien, Göran Gustaffson Prize in Chemistry,

PI, 2018-2020

 

“Self-sterilizing surfaces through upconverting nanoparticles”,

Carl-Tryggers Stiftelse för Vetenskaplig Forskning, CTS 16/17:321, PI, 2016-2019

 

“Improved thermoelectric materials for a sustainable society”

Energimyndigheten, PI, 2019-2023

 

“Nya oorganiska öppna nätverksstrukturer möjliggjorda genom syntes i jonvätskor”,

Vetenskapsrådet (VR), PI, 2017-2020

 

“Unravelling complex magnetic structures of framework materials by Neutron Scattering”, Swedish Foundation for Strategic Research, SSF (Sweden), project lead within “SwedNESS – the Swedish research school on neutrons”,

2017-2021

 

 

Past:

“Energy Efficient Lighting”, Critical Materials Institute #2.2.6,

U.S. Department of Energy, 2015-2017

 

 

“Nanopartikel zur Katalyse aus Ionischen Flüssigkeiten (B11)”, #5484300,

DFG, PI, 2007-2012

 

 

“EXC R1069:  RESOLV (Ruhr Explores Solvation) – Verständnis und Design lösungsmittelabhängiger Prozesse“, DFG, co-PI, 2012-2018

 

“LUMINET (European Network on Luminescent Materials)”,

European Commission, Project ID: 316906, coordinator,

2013-2017

 

 

“BrightEMIL: EMIL goes green – Exceptional Materials

from Ionic Liquids for Energy Saving Applications in Photonics”,

ERC-PoC GA 297424, PI, European Research Council, ERC, 2013

 

 

“EMIL – Exceptional Materials via Ionic Liquids”,

European Research Council, ERC-StG GA 200475,

PI, 2008-2013

 

 

 

Publications

1: Nanosynthesis in ionic liquids: Physical vapor deposition, microwave synthesis and sonochemistry

Reviews and Book Chapters:

R3. K. Richter, P. S. Campbell, T. Bäcker, A. Schimitzek, D. Yaprak, A.-V. Mudring, Ionic Liquids for the Synthesis of Nanoparticles, physica status solidi b, 2013, 250, 1152-1164.

B9. A.-V. Mudring, T. Alammar, T. Bäcker, K. Richter, Nanoparticle Synthesis in ionic Liquids, in Ionic Liquids: From Knowledge to Application, Eds. N.V. Pechkova, R.D. Rogers, K.R. Seddon, ACS Symposium Series 2009, 1030, 177-188.

Original, peer-reviewed research publications:

  1. D. König, K. Richter, A. Siegel, A.-V. Mudring, A. Ludwig, High-throughput fabrication of binary alloy nanoparticle libraries by combinatorial sputtering in ionic liquids, Adv. Funct. Mat., 2014, 24, 2049-2056. DOI:10.1002/adfm.201303140.
  2. K. Richter, C. Lorbeer, A.-V. Mudring, A novel approach to optically active ion doped luminescent materials via electron beam evaporation into ionic liquids, Chem. Commun. 2015, 51, 114-117. DOI: 10.1039/C4CC05817H.
  3. M. Yang, P. Campbell, C. Santini, A.-V. Mudring, Small nickel nanoparticle arrays from long chain imidazolium liquids, Nanoscale, 2014, 6, 3367-3375. DOI:10.1039/c3nr05048c.
  4. S. Helgadottir, P.P. Arquillière, P. Bréa, C.C. Santini, P.-H. Haumesser, K. Richter, A.-V. Mudring, M. Aouine: Synthesis of bimetallic nanoparticles in ionic liquids: Chemical routes vs physical vapor deposition, Microelectronic Engineering, 2013, 107, 229-232. DOI: 10.1016/ j.mee.2012.09.015.
  5. T. Alammar, O. Shekhah, J. Wohlgemuth, A.-V. Mudring: Ultrasound-assisted synthesis of mesoporous β-Ni(OH)2 and NiO-nano-sheets using ionic liquids, J. Mater. Chem., 2012, 22, 18252-18260. DOI: 10.1039/C2JM32849F.
  6. K. Richter, A. Birkner, A.-V. Mudring: Stability and growth behavior of transition metal nanoparticles in ionic liquids prepared by thermal evaporation: how stable are they really?, Phys. Chem. Chem. Phys., 2011, 13, 7136–7141. DOI: 10.1039/C0CP02623A.
  7. K. Richter, A. Birkner, A.-V. Mudring: Stabilizer-Free Metal Nanoparticles and Metal–Metal Oxide Nanocomposites with Long-Term Stability Prepared by Physical Vapor Deposition into Ionic Liquids, Angew. Chem. Int. Ed., 2010, 49, 2431–2435. DOI: 10.1002/anie.200901562.
  8. T. Alammar, A.-V. Mudring: Ultrasound-Assisted Synthesis of CuO Nanorods in a Neat Room-Temperature Ionic Liquid, Eur. J. Inorg. Chem., 2009, 2765-2768. DOI:10.1002/ ejic.200900093.

2: Nanophosphors

Reviews and Book Chapters

R5. R.K. Sharma, A.-V. Mudring, P. Ghosh: Recent trends in binary and ternary rare-earth fluoride nanophosphors: How structural and physical properties influence optical behaviour, J. Lumin. 2017, 189, 44-63. http://doi.org/10.1016/j.jlumin.2017.03.062.

B10. P. Ghosh, C. Lorbeer, A.-V. Mudring, Nanofluorides for environmentally benign lighting and energy conversion in solar cells, in Florine-Related nanoscience with Energy Applications, ACS Symposium Series, 2011, 1064, 87-99.

Original, peer-reviewed research publications:

  1. G. Tessitore, A.-V. Mudring, K. W. Krämer, Luminescence and energy transfer in b-NaGdF4:Eu3+,Er3+ nanocrystalline samples from a room temperature synthesis, New J. Chem. 2018, 42, 237-245. DOI: 10.1039/C7NJ03242K.
  2. P. Ghosh, R.K. Sharma, Y.N. Chouryal, A.-V. Mudring: Size of the rare-earth ions: a key factor in phase tuning and morphology control of binary and ternary rare-earth fluoride materials, RSC Advances 2017, 7, 33467-33476. DOI: 10.1039/c7ra06741k.
  3. G. Tessitore, A.-V. Mudring, K. W. Krämer, Room temperature synthesis of β-NaGdF4:RE3+ (RE = Eu, Er) nanocrystallites and their luminescence, J. Lumin. 2017, 189, 91-98. http://doi.org/ 10.1016/j.jlumin.2017.03.021.
  4. J. Cybinska, M. Guzik, C. Lorbeer, E. Zych, Y. Guyot, G. Boulon, A.-V. Mudring, Design of LaPO4: Nd3+ materials by using ionic liquids, Opt. Mat. 2017, 63, 76-87. DOI: http://dx.doi.org/ 10.1016/j.optmat.2016.09.025
  5. J. Cybinska, C. Lorbeer, E. Zych, A.-V. Mudring, Ionic liquid supported synthesis of nano-sized rare earth doped phosphates, J. Lumin. 2017, 63, 76-87. DOI: http://doi.org/10.1016/ j.jlumin.2017.02.033
  6. S. Anghel, S. Golbert, A. Meijerink, A.-V. Mudring, Divalent Europium doped CaF2 and BaF2 nanocrystals from ionic liquids, J. Lumin. 2017, 189, 2-8. DOI: 10.1016/j.jlumin.2016.10.007
  7. P. Ghosh, A.-V. Mudring, Phase selective synthesis of quantum cutting nanophosphors and the observation of a spontaneous room temperature phase transition Nanoscale, 2016, 8, 8160-8169. DOI: 10.1039/c6nr00172f.
  8. J. Cybińska, C. Lorbeer, A.-V. Mudring, Ionic liquid assisted microwave synthesis route towards color-tunable luminescence of lanthanide- doped BiPO4, J. Lumin. 2016, 169, 541-647. DOI:10.1016/j.jlumin.2015.06.051.
  9. T. Alammar, J. Cybinska, P.S. Campbell, A.-V. Mudring, Sonochemical Synthesis of Highly Luminescent Ln2O3:Eu3+ (Gd, Y, La) Nanocrystals, J. Lumin. 2016, 169, 587-593. DOI:10.1016/ j.jlumin.2015.05.004.
  10. J. Cybińska, M. Wozniak, A.-V. Mudring, E. Zych, Controllable synthesis of nanoscale YPO4:Eu in an ionic liquid, J. Lumin. 2016, 169, 868-873. DOI:10.1016/j.jlumin.2015.07.008.
  11. K. Richter, C. Lorbeer, A.-V. Mudring, A novel approach to optically active ion doped luminescent materials via electron beam evaporation into ionic liquids, Chem. Commun. 2015, 51, 114-117. DOI: 10.1039/C4CC05817H.
  12. C. Lorbeer, F. Behrends, J. Cybinska, H. Eckert, A.-V. Mudring, Charge compensation in RE3+ (RE=Eu, Gd) and M+ (M=Li, Na, K) co-doped alkaline earth nanofluorides obtained by microwave reaction with reactive ionic liquids leading to improved optical properties, J. Mat. Chem. C 2014, 2, 9439-9450. DOI: 10.1039/C4TC01214C.
  13. C. Lorbeer, A.-V. Mudring, Quantum cutting in nanoparticles producing two green photons, Chem. Commun. 2014, 50, 13282-13284. DOI: 10.1039/C4CC04400B.
  14. C. Lorbeer, J. Cybinska, A.-V. Mudring, Reaching Quantum Yields >> 100% in nanomaterials, J. Mat. Chem. C, 2014, 2, 1862-1868. DOI: 10.1039/C3TC31662A.
  15. C. Lorbeer, A.-V. Mudring, Ionic Liquid-Assisted Route to Nanocrystalline Single-Phase Phosphors for White Light Emitting Diodes, ChemSusChem, 2013, 6, 2382-2387. DOI: 10.1002/cssc.201200915.
  16. P. S. Campbell, C. Lorbeer, J. Cybinska, A.-V. Mudring, One-Pot Synthesis of Luminescent Polymer-Nanoparticle Composites from Task-Specific Ionic Liquids, Adv. Funct. Mater., 2013, 23, 2924-2931. DOI: 10.1002/adfm.201202472.
  17. C. Lorbeer, A.-V. Mudring, White Light Emitting Single Phosphors via Triply Doped LaF3 Nanoparticles, J. Phys. Chem. C, 2013, 12229-12238. DOI: 10.1021/jp312411f.
  18. Q. Ju, A.-V. Mudring, Phase and Morphology Selective Interface-Assisted Synthesis of Highly Luminescent Ln3+-doped NaGdF4 Nanorods, RSC Advances, 2013, 3, 8172-8175. DOI: 10.1039/C3RA40755A.
  19. Ju, P.S. Campbell, A.-V. Mudring: Interface-assisted ionothermal synthesis, phase tuning, surface modification and bioapplication of Ln3+-doped NaGdF4 nanocrystals, J. Mater. Chem. B, 2013, 1,179-185. DOI: 10.1039/C2TB00052K.
  20. C. Lorbeer, J. Cybinska, E. Zych, A.-V. Mudring: Highly doped alkaline earth nanofluorides synthesized from ionic liquids,Opt. Mat.2011, 21, 3207. DOI: 10.1016/j.optmat.2011.04.019.
  21. P. Ghosh, S.-F. Tang, A.-V. Mudring: Efficient quantum cutting in hexagonal
    NaGdF4:Eu3+ nanorods, J. Mater. Chem. 2011, 21, 8640 (HOT Article). DOI: 10.1039/ C1JM10728C.
  22. N.-V. Prondzinski, J. Cybinska, -V. Mudring: Easy access to ultra long-time stable, luminescent europium(II) fluoride nanoparticles in ionic liquids, Chem. Commun., 2010, 46, 4393– 4395. DOI: 10.1039/c000817f.
  23. C. Lorbeer, J. Cybinska, A.-V. Mudring: Facile preparation of quantum cutting GdF3:Eu3+ nanoparticles from ionic liquids, Chem. Commun., 2010, 46, 571-573 (HOT Article). DOI: 10.1039/B919732J
  24.  K. Richter, T. Bäcker, -V. Mudring: Facile, environmentally friendly fabrication of porous silver monoliths using the ionic liquid N-(2-hydroxyethyl)ammonium formate, Chem.Commun., 2009, 301-303. DOI: 10.1039/B815498H.

2: (Photo-)Catalysis

Original, peer-reviewed research publications:

  1. T. Alammar, I. Hamm, M. Wark, A.-V. Mudring, Ionic Liquid Enabled Near-Room Temperature Synthesis of SrTiO3 Perovskite Nanoparticles for Photocatalytic Applications, ChemSusChem, 2018, submitted.
  2. T. Alammar, I. Slowing, J. Anderegg, A.-V. Mudring, Ionic Liquid-Assisted Microwave Synthesis of Solid Solutions of Perovskite Sr1-xBaxSnO3 Nanocrystals for Photocatalytic Applications, ChemSusChem 2017, 10, 3387-3401. DOI: 10.1002/cssc.201700615. Back cover.
  3. T. Alammar, I. Hamm, V. Grasmik, M. Wark, A.-V. Mudring, Microwave-Assisted Synthesis of Perovskite SrSnO3 Nanocrystals in Ionic Liquids for Photocatalytic Applications, Inorganic Chemistry, 2017, 56, 6920-6932. DOI: 10.1021/acs.inorgchem.7b00279
  4. .T. Alammar, Kit Chow, A.-V. Mudring, Energy efficient of microwave synthesis of mesoporous Ce0.5M0.5O2 (Ti, Zr, Hf) nanoparticles for low temperature CO Oxidation in an ionic liquid – a comparative study, New J. Chem., 2015, 39, 1339 – 1347. DOI: 10.1039/C4NJ00951G.
  1. T. Alammar, H. Noei, Y. Wang, W. Grünert, A.-V. Mudring, Ionic Liquid-Assisted Sonochemical Preparation of CeO2 Nanoparticles for CO Oxidation, ACS Sustainable Chemistry and Engineering 2015, 3, 42-54. DOI:10.1021/sc500387k.
  2. T. Alammar, I. Hamm, M. Wark, A.-V. Mudring, Low Temperature Route to Metal Titanate Perovskite Nanoparticles for Photocatalytic Hydrogen Formation, Appl. Catalysis B 2015, 178, 20-28. DOI:10.1016/j.apcatb.2014.11.010.
  3. T. Alammar, H. Noei, Y. Wang, A.-V. Mudring, Mild yet phase-selective preparation of TiO2 nanoparticles from ionic liquids – a critical study, Nanoscale, 2013, 5, 8045-8055. DOI: 10.1039/C3NR00824J.
  4. T. Alammar, A.-V. Mudring: Sonochemical Synthesis of 0D, 1D, and 2D Zinc Oxide Nanostructures in Ionic Liquids and Their Photocatalytic Activity, ChemSusChem, 2011, 12, 1796-1804. DOI:10.1002/cssc.201100263.
  5. C. Lorbeer, J. Cybinska, E. Zych, A.-V. Mudring: Ionic Liquid based Synthesis – A Low Temperature Route to Nanophosphates, ChemSusChem, 2011, 4, 595-598. DOI: 10.1002/ cssc.201100095.
  6. T. Alammar, A. Birkner, O. Shekhah, A.-V. Mudring: Sonochemical preparation of TiO2 nanoparticles in the ionic liquid 1-(3-Hydroxypropyl)-3-methylimdazoliumbis(trifluoromethyl-sulfonyl)imide, Mat. Chem. Phys., 2010, 120, 109-113. DOI:10.1016/j.matchemphys.2009.10.029.
  7. 73. T. Alammar, -V. Mudring: Facile preparation of Ag/ZnO nanoparticles via photoreduction, J. Mat. Sci. 2009, 44, 3218-3222. DOI:10.1007/s10853-009-3429-4.
  8. T. Alammar, A.-V. Mudring: Facile ultrasound-assisted synthesis of ZnO nanorods in an ionic liquid, Mat. Lett. 2009, 63, 732-735. DOI: 10.1016/j.matlet.2008.12.035.

 

4: Thermoelectrics

Reviews:

SR1. C. Celania, A.-V. Mudring, Structures, Properties, and Potential Applications of Rare Earth-Noble Metal Tellurides, J. Solid State Chem., 2018, submitted.

SR2. V. Smetana, M. Wilk-Kozubek, A.-V. Mudring, Active-transition-metal tellurides: through crystal structures to physical properties, Cryst. Growth Des., 2018, submitted.

Original, peer-reviewed research publications:

  1. J. Schaumann, M. Loor, D. Ünal, A.-V. Mudring, S. Heimann, U. Hagemann, S. Schulz, F. Maculewicz, G. Schierning, Improving the zT value of thermoelectrics by nanostructuring: Tuning the nanoparticle morphology of Sb2Te3 by ionic liquids, Dalton Trans. 2017, 46, 656-668. DOI: 10.1039/c6dt04323b. Inside Front Cover.
  2. S. Heimann, S. Schulz, J. Schaumann, A.-V. Mudring, J. Stoetzel, F. Maculewicz, G. Schierning, Record figure of merit values of highly stoichiometric Sb2Te3 porous bulk synthesized from tailor-made molecular precursors in ionic liquids, J. Mat. Chem. C 2015, 3, 10375-10380. DOI:10.1039/c5tc01248a.
  3. S. Schulz, S. Heimann, K. Kaiser, W. Assenmacher, T. Brüggemann, B. Mallick, A.-V. Mudring, Solution based synthesis of GeTe octahedra at low temperatures, Inorg. Chem. 2013, 52, 14326-14333. DOI: 10.1021/ic402266j.

 

4: Inorganic Open-Framework Structures

Review:

R4. M. Li, A.-V. Mudring, New developments in the synthesis, structure and applications of borophosphates and metalloborophosphates, Crystal Growth Des. 2016, 16, 2441-2458. DOI: 10.1021/acs.cgd.5b01035.

Original, peer-reviewed research publications:

  1. Alammar, I.Z. Hlova, S. Gupta, V.K. Pecharsky, A.-V. Mudring, Mechanochemical Synthesis, Characterization and Luminescent Properties of Lanthanide Benzene-1,4-Dicarboxylate Coordination Polymers (LnGd)(1,4-BDC)3(H2O)4; Ln = Sm, Eu, Tb, Dalton Trans., 2018, submitted. DOI: xxx.
  2. T. Alammar, I.Z. Hlova, S. Gupta, V.K. Pecharsky, A.-V. Mudring, Luminescent Properties of Mechanochemically Synthesized Rare-Earth Containing MIL-78 MOF, Dalton Trans. 2018, 47, 7594-7601. DOI: 10.1039/C7DT04771A.
  3. M. Li, V. Smetana, T. Alammar, Y. Mudryk, V. Pecharsky, A.-V. Mudring, Borophosphates with Helical Chains, Inorg. Chem. 2017, 56, 11104-11112. DOI: 10.1021/acs.inorgchem.7b01423.
  4. G. Wang, M. Valldor, B. Mallick, A.-V. Mudring, Ionothermal Synthesis of The First Open-Framework Metal Fluoro-phosphates with a Kagomé Lattice Network exhibiting Canted Anti-Ferromagnetism, J. Mat. Chem. C 2014, 2, 7417-7427. DOI: 10.1039/C4TC00290C.
  5. G. Wang, M. Valldor, E. Spielberg, A.-V. Mudring, Ionothermal Synthesis, Crystal Structure, and Magnetic Study of Co2PO4OH Isostructural with Caminite, Inorg. Chem. 2014, 53, 3072-3077. DOI:10.1021/ic4029904.
  6. G. Wang, M. Valldor, C. Lorbeer, A.-V. Mudring: Ionothermal Synthesis of the First Luminescent Open-Framework Manganese Borophosphate with Switchable Magnetic Properties, Eur. J. Inorg. Chem., 2012, 3032-3038. DOI: 10.1002/ejic.201200110.
  7. G.Wang, A.-V. Mudring: A New Open-Framework Iron Borophosphate from Ionic Liquids: KFe[BP2O8(OH)], Crystals, 2011, 1, 22-27. DOI: 10.3390/cryst1020022.