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SACS Report Summary

Project ID: 310651
Funded under: FP7-NMP
Country: Belgium

Periodic Report Summary 3 - SACS (Self-Assembly in Confined Space)

Project Context and Objectives:
Supramolecular chemistry studies chemistry beyond individual molecules, where molecules or macromolecules form larger entities with interesting, novel properties and this by spontaneous selfassembly. This concept of self-organizing nanoscale building blocks (which can be organic, organometallic, metallic and oxidic) into (hybrid) materials results in hierarchical systems that spatially can extend from nano to micron-size and beyond and this in 1, 2 or 3 dimensions. Uniquely, this supramolecular chemistry enables control and guiding the chemical properties (adsorption affinity, reactivity or catalytic activity) as well as the physical properties (mechanical, electrical, optical etc.), at different length scales and in different directions. Therefore, supramolecular self-assembled systems have potential functionalities that tremendously surpass the scope of classical molecular systems in the liquid state, or of classical porous solids. This potential functionality encompasses the type and number of functions that can simultaneously be fulfilled, as well as the range of viable operating conditions. SACS focuses on the formation of functional structures with novel, unique properties through self-assembly inrestricted or controlled space and on formation of assemblies with strictly controlled geometries, size and shape and outstanding properties. The functionalities that are specifically aimed for are: improved electrical conductivity, exceptional optical properties and outstanding catalytic activity.
We will generate highly performing materials via self-assembly of nano-scale building blocks at industrially relevant scales that can be used in multiple applications towards nanotechnology based products:
1) The creation of small luminescent clusters consisting of silver or copper stabilized in nanoporous materials as a novel type of phosphors (WP1). Some of these clusters were recently proven to be highly efficient in UV-to-visible light conversion; however, they are known to aggregate easily into non-luminescent particles. By hosting them into nanostructured materials, certain cluster types are selectively formed and stabilized, preventing aggregation by the steric constraints imposed by the zeolite/mesoporous silica/MOF framework. These materials have also potential catalytic properties.
2) The creation of well-defined nanostructured assemblies of organic and organometallic molecules as well as nano-particles in porous materials (WP2). Organic dye molecules are generally believed to be insufficiently photostable for use in industrial applications. However, the protective role of the matrix can provide a solution here. In particular the photochromic and electrochromic systems will benefit from rigidification of the medium as well as from the well-controlled environment. The materials we envision have potentially interesting emissive, electochromic and/or catalytic properties.
3) The realization of active inner and outer containers such as carbon nanotubes (CNTs) decorated with nanoparticles or in which conductive or catalytically active structures can be implemented (WP3). The photo- and redox properties of the CNT will be then complemented with the guest systems and their use in energy related applications will be proven. For these materials we foresee applications in catalysis, lighting and in display technology.
The ultimate goal of this project will then be the scaling up and implementation of these newly developed assembled hybrid materials into real proof-of-concept applications such as lamps and LEDs for the new phosphors, electrochromic display for the confined electro-active molecules, and conducting materials/catalysts for the carbon nanotube based materials. In order to ensure the realization of the devices and products the consortium includes industrial partners (Philips Lighting Roosendaal for the lamps/LEDs, Ynvisible for the electrochromic materials).

Project Results:
In the third period of this SACS project was mainly devoted to validation of the basic research results as the SACS consortium moves towards prototype development and establishment of proof-of-concept for our products.
In the research towards novel phosphors for lighting applications, many samples with different characteristic luminescence colors spanning the whole visible range upon UV excitation were found. A full portfolio of phosphors is now available with quantum yields comparable or even surpassing commercial rare earth phosphors.
In collaboration with industrial partner Philips, SACS silver containing zeolites are being used is phosphors in lamp prototypes, a process which is currently under optimization. Furthermore, this has been extended to LED preparations.

As an alternative to such zeolites, promising results were obtained from luminescent MOF materials, in which blue emitters were found when excited at 350 nm. Enhancement of the quantum yield was observed when the MOF material was exchanged with silver ions. Additionally, to avoid the use of silver, other metals have been assessed towards their potential use. The formation of luminescent Manganese, Lead and Gold clusters in FAU and MER zeolites respectively has been successfully observed. With potential use in niche applications, further optimization focused on the activation procedure and host zeolite topology is ongoing, while we focus on cost, availability and reduced toxicity.
The first examples of copper exchanged zeolites have been prepared, and were shown to be emissive. Self assembled luminescent cupper complexes in a porous host have been prepared and were shown to have excellent spectroscopic properties, with quantum yields close to 70%. These materials have been forwarded to the development of prototypes.
An in depth characterization of the metal exchanged zeolites has been initiated between the partners. The theoretical and structural study were able to shed light on the internal structure of Ag-exchanged FAU zeolites and of Ag exchanged LTA zeolites. This work is resulting in providing TEM images of the zeolites of an unprecedented resolution.
In collaboration with the industrial partner Ynvisible, electrochromic materials were combined with a variety of porous systems and polymers. The SACS materials were shown to have a tremendous beneficial effect on the properties of the electrochomic devices, and are moving towards IP protection and use in commercial devices.
Fe@MWCNTs were produced with a higher iron content than before. The MWCNTs were covalently and non-covalently derivatized with the synthesis of a polymer capable to blend around the MWCNTs. MWCNTs were also functionalized with titanium oxide and cerium oxide. Studies on the catalytic performance of these materials highlight a potential to compete with and improve upon current commercial catalysts. This potential has attracted industrial attention, and the SACS catalytic materials will be validated in this setting. This all is joined by a strong research network within the consortium, exemplified by numerous exchanges of both material and personnel between partners.

Potential Impact:
The SACS project strongly aims at bottom-up assembly of nanoscale building blocks, rather than at the top-down lithographic approaches. The innovative strategies outlined in the project allow combining building blocks with a strong degree of chemical diversity, and of sharply controlled size and shape. This will translate into an easy and flexible optimization of their properties with regard to the aimed applications.
As an example of the proposed strategies, we can consider the zeolite crystals incorporating luminescent clusters: control over luminescence properties is achieved at the scale of one cage (i.e., 1 nm), while control over moisture or gases intruding in the material is achieved at the crystal level (several μm). Finally, a strategy is foreseen to incorporate the crystals in lamps produced by Philips Lighting.
Based on this research, the consortium will be able to define roadmaps for further development to industrial mass production. Note as well that the scale of several of the direct applications will rapidly lead to mass production.
We believe that the strong commitment of industrial players will carry the findings to device level. Philips Lighting’s expertise in integrating phosphor compounds in lamps is obvious; Ynvisible will integrate the self-assembled materials in its proprietary technology platform. Strong ties with industrial providers and users of carbon nanomaterials provide a strong input on the best method to choose to guarantee future large scale production of the CNT based devices.

The major socio-economic impact of this application-driven project is illustrated for three of the applications that are within realistic reach, with a short track to industrial implementation. New emissive materials: The phosphors resulting from this project will provide an answer to the need for artificial light sources that have a similar light appearance as natural light. In this regard the proposed phosphors have the potential to surpass the performance of the rare-earth-based phosphors, which are becoming less available because of geopolitical issues. As they are non-toxic, stable, solid, inorganic based materials, SACS phosphors can be easily recycled and reused. The new materials proposed in this project will lead to a more independent and secured phosphor supply throughout Europe.

Moreover, recent EU regulations force the phase-out of energy-inefficient traditional incandescent bulbs, which can lead to a reduction of up to 70% of lighting electricity. This implies that each year more than € 300 billion can be saved on the global energy bill which will also provide significant individual savings. The annual emission of 1.9 million tons of CO2 could easily be cut in half. New conductive materials: Indium-Tin oxide has been extensively used as a transparent electrical conductive material. ITO has been one of the bottlenecks to commercialization of many technologies due to its high cost. Moreover, a shortage of indium sources is predicted. ITO replacement materials are a current hot topic within the printed electronics community.
Ynvisible will assess the use of carbon nanotube selfstructured materials as an ITO alternative material. Coatings over flexible plastics will be created. The development of new electrochromic inks showing different colors than blue will increase the electrochromic color palette. New catalytic materials: Catalysis is a key technology for greening the chemical industry and for efficient energy conversion. Nano-catalysts have the potential to lead to exploitation of renewable, efficient, and inexpensive sources for alternative energy production. Furthermore, the nanostructured photoactive systems have a strong potential in pushing photocatalysis towards industrial relevance. A very direct application of the SACS catalysts is providing high purity hydrogen for fuel cells. Uniquely stable and efficient catalysts will become available through the SACS approach.
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