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GCCES2016 Plenary Lectures

 

The Role of Particle Technology in Thermal Energy Storage
Professor Yulong Ding, University of Birmingham 
Thermal energy is at the heart of the whole energy chain providing a main linkage between the primary and secondary energy sources. Thermal energy storage (TES) has a pivotal role to play in the energy chain and hence in future clean energy systems. However, a competitive TES technology requires a number of scientific and technological challenges to be addressed including materials, components and devices, and system integration within energy networks and associated dynamic optimization. This requires fundamental understanding of the underlying physics across a very large temporal and spatial length scale ranging from atomic/molecular scale (~10-10m) to system scale (~10+3m).
This presentation will first briefly outline the background and challenges of energy storage and review the use of particle technology in different energy storage technologies. Discussion will then be focused on thermal energy storage (TES) particularly the role of particle technology in TES materials formulation and processing, and associated advanced manufacture technologies. TES can be sensible heat, latent heat or thermochemical based. Latent heat storage materials, which are often called phase change materials (PCMs), will be used as an example in the presentation particularly inorganic salts based PCMs. Two key challenges for such materials are chemical incompatibility and low thermal conductivity. The use of composite materials provides an avenue to meeting the challenges. Such composite materials use a structural supporting material and a thermal conductivity enhancement material. A right combination of the salt, the structural supporting material and the thermal conductivity enhancement material could give a hierarchical structure that is able to encapsulate the molten salt and give a substantial enhancement in the thermal conductivity. This example will be also used to illustrate recent progress in fundamental research in linking the materials properties to the TES system level performance.

 

 

 

Thermodynamic parameters for adsorption equilibrium from aqueous solutions
Professor Duu-Jong Lee, National Taiwan University  
With adsorption isotherms, the changes in Gibbs free energy, the isosteric heat of adsorption, and the changes in entropy could be assessed. However, an unlikely "enthalpy-entropy compensation" noted normally for transfer of hydrophobic substances between water and oil phases was observed when data from different sources were presented. Apparently such an occurrence is an artifact, indicating that the thermodynamic parameters reported in open literature may not be properly assessed. Caution should be paid to any conclusions thus drawn since the enthalpy and the entropy were not evaluated independently.

 

 

 

AIE Probes for Biomedical Applications
Professor Bin Liu, National University of Singapore 
Fluorogens with aggregation induced emission (AIE) characteristics have recently aroused significant research interest. The unique AIE process offers a straightforward solution to the aggregation caused quenching problem faced by traditional fluorophores. In this talk, we summarize our recent AIE work to highlight the utility of AIE effect in the development of new fluorescent bioprobes, which allows the use of highly concentrated fluorogens for biosensing and imaging.[1] The simple design and fluorescence turn-on feature of the molecular AIE bioprobes offer direct visualization of specific analytes and biological processes in aqueous media with higher sensitivity and better accuracy than traditional fluorescence turn-off probes. The AIE dot-based bioprobes with different formulations and surface functionalities show advanced features over quantum dots and small molecule dyes, such as large absorptivity, high luminosity, excellent biocompatibility, free of random blinking, and strong photobleaching resistance. In addition, our recent discovery that AIE fluorogens with enhanced reactive oxygen species generation in solid state further expanded their applications to cancer therapy.[2] These features enable cancer cell detection, long term cell tracing, and tumor imaging in a noninvasive and high contrast manner.

References
[1] D. Ding, K. Li, B. Liu, and B. Z. Tang. Acc. Chem. Res. 2013, 2441-2453.
[2] J. Liang, B. Z. Tang, and B. Liu. Chem. Soc. Rev. 2015, 44, 2798-2811.

 

 

Nanostructured enzyme catalysts for industrial biocatalysis
Professor Zheng Liu, Tsinghua University
This presentation will summarize our recent progress in developing nanostructured enzyme catalysts for chemical synthesis particularly those carried out in organic solvents at elevated temperatures. We will show that, by suitable integration with tailor-made nanostructures such as polymers, inorganic nanocrystals, metal organic framework, and etc, nanostructured enzyme catalysts appear enhanced stability at no compromise of their activity, as compared to their native counterpart in free form. For those multi-enzyme catalysts, enhanced catalysis can be obtained via substrate channeling. The affinity of the supporting matrix towards substrates may also be applied to enhance the enzymatic catalysis.  The recycle and operation of nanostructured enzyme catalysts is facilitated by incorporating magnetic- and or temperature- responsiveness into those nanostructures. The availability of nanostructures essentially enables unprecedented applications of enzymatic catalysis.

 

 

 

Membrane Technology & Water in Singapore – Achievements & Challenges
Mr Harry Seah, Singapore Public Utilities Board (PUB)
Over the last five decades, Singapore has overcome its lack of natural water resources through integrated water resource management as well as commitment to research and development. Today, the nation has built a robust, diversified and sustainable water supply with four different sources, termed locally as the Four National Taps. The Four National Taps are namely water from local catchments, imported water, high-grade reclaimed water called NEWater and desalinated water.
Membrane technology has played a critical role in the augmentation of Singapore’s water resources as it is the key enabler for the production of NEWater and desalinated water. While membrane technology has served Singapore well in enhancing its resilience in its water resources, it is more energy-intensive than conventional water treatment processes, thus there is a significant energy impact as current membrane-based treatment processes are widely adopted to meet growing water demand. Projecting into 2060, water demand is projected to double, and NEWater and desalinated water are expected to meet 80% of the nation’s water demand as compared to the current 40%. The energy requirement based on today’s technologies would triple.  Therefore, there is a long term need to reduce this energy requirement in future NEWater and desalination processes. Through 15 years’ experience of R&D, Singapore has demonstrated that the energy requirements for seawater desalination could be halved through the implementation of technologies and innovative processes such as the variable salinity process, electrochemical desalination and exploiting technologies at the system level. Research work on leading-edge membrane materials is ongoing to further drive down this energy consumption. In this paper, the author will introduce PUB’s R&D efforts on the development of membrane technologies in Singapore.

 

 

 

Multiscale molecular simulations of polymer-matrix nanocomposites
Professor Doros N. Theodorou, National Technical University of Athens
In polymer-matrix nanocomposites the quantitative relationships between composition and size of polymer chains and nanoparticles, processing conditions, degree of dispersion of the nanoparticles, dynamics of the matrix chains, and macroscopic properties are still elusive. Molecular simulation holds great promise as a means for understanding and predicting these relationships, but faces serious challenges associated with the broad spectra of length and time scales governing nanocomposite properties. We are developing a multiscale simulation strategy for materials consisting of nanoparticles of roughly spherical shape within amorphous polymer matrices. This strategy encompasses atomistic molecular dynamics (MD), coarse-grained connectivity-altering Monte Carlo (MC), Field Theory-inspired Monte Carlo (FTiMC), and Brownian Dynamics/Transition State theory (BD/TST) calculations. Each level of representation invokes parameters that can be extracted from the previous (more detailed) levels, such that all predictions are ultimately based on an atomistic force field. 

Atomistic MD is useful for elucidating the details of molecular packing and in quantifying how segmental dynamics is affected by the presence of nanoparticles.  Coarse-grained MC is of strategic importance in achieving equilibration at all length scales.  By developing coarse-grained effective potentials from detailed atomistic ones via the Iterative Boltzmann Inversion method, vigorous MC sampling of the coarse-grained models with connectivity-altering algorithms, and reverse-mapping back to the atomistic level, one can generate well-equilibrated atomistic configurations to study structure and dynamics. We have applied this strategy to quantify the effects of incorporating fullerenes on the segmental motion and the glass transition of long-chain atactic polystyrene (PS) [1].

In the FTiMC approach polymer chains are represented as freely jointed sequences of statistical segments, and nanoparticles as single spherical entities. Polymer non-bonded interactions are taken into account via a functional of local density, while nanoparticle-polymer and nanoparticle-nanoparticle interactions are represented via integrated atomistic potentials. This approach can elucidate changes in the conformation and spatial extent of polymer chains resulting from the presence of the nanoparticles. We have applied FTiMC to systems consisting of silica nanoparticles dispersed in monodisperse atactic PS. The nanoparticles carry monodisperse surface-grafted PS chains of prescribed molar mass and grafting density.  Predicted scattering curves from the grafted polymer corona are validated against Small Angle Neutron Scattering measurements [2].

BD/TST calculations are targeted at tracking the temporal evolution of the nanocomposite over time scales in excess of milliseconds and predicting its stress relaxation modulus. The polymer is modeled as a set of coarse-grained beads connected along the chain contours by “entropy springs”, with “slip springs” representing entanglements between different chains.  A coarse-grained free energy function incorporating spring and nonbonded contributions is used as a starting point for deriving the dynamics. Adsorption/desorption of beads on the nanoparticle surfaces is also included.  To extract rate constants for the latter from molecular-level information, a new approach combining self-consistent field theory and Kramers theory has been developed and validated [3].

[1] Vogiatzis, G.G.; Theodorou, D.N. Macromolecules 2014, 47, 387-404.
[2] Vogiatzis, G.G.; Theodorou, D.N. Macromolecules 2013, 46, 4670-4683.
[3] Theodorou, D.N.; Vogiatzis, G.G.; Kritikos, G. Macromolecules 2014, 47, 6964-6981.

 

 

 

Interplay of mass transfer and phase separation and their roles in controlling membrane morphology
Professor Da-Ming Wang, National Taiwan University
Nonsolvent-induced phase separation (NIPS) has been used for decades to prepare polymeric membranes for different membrane separation processes. But, a clear insight into how membrane forms still remains a challenge. For NIPS, homogeneous polymer solution is cast on a substrate and then immersed in a coagulant (polymer nonsolvent) bath, where phase separation of the polymer solution occurs because of the exchange of solvent and nonsolvent, and the resulting polymer-poor phase becomes the membrane pores and the polymer-rich phase forms the membrane matrix. It has been noticed by many that the morphology of the polymer membranes prepared by NIPS is strongly influenced by the mass transport of solvent and nonsolvent during membrane formation and its interplay with phase separation. The presentation is focused on a point being overlooked in the literature: that phase separation may need time to occur. For example, phase separation via the mechanism of nucleation and growth may not occur if there is not enough time for the nuclei to form; a polymer solution with a composition in the crystallization region may not crystallize if not enough time is given for the crystalline nuclei to occur. Therefore, the times given and needed for the nuclei to occur play important roles in the formation of membrane pores. The time given for the nuclei to occur is the time that the casting solution stays in the meta-stable region, strongly related to the exchange rate of solvent and nonsolvent. And the time needed for the nuclei to form is strongly related to the degree of polymer chain entanglement in the casting solution, which can be characterized by using the solution viscoelasticity. We will give examples showing that by varying solvent quality, polymer concentration, polymer molecular weight, we can change the degree of polymer chain entanglement and thus change the phase separation mechanism and the resulting membrane morphology. Also, examples will be given to show how the knowledge about the interplay of mass transfer and phase separation can lead to the preparation of highly porous membranes with inter-connected pores and polymer membranes with superhydrophobic properties.

 

 

Toward a distributed renewable electrochemical energy and mobility system (DREEMS): Polymer electrolytes and electrocatalysis
Professor Yushan Yan, University of Delaware
One of the grand challenges facing humanity today is the development of an alternative energy system that is safe, clean, and sustainable and where combustion of fossil fuels no longer dominates. A distributed renewable electrochemical energy and mobility system (DREEMS) could meet that challenge. At the foundation of this new energy system are a number of electrochemical devices including fuel cells, electrolyzers, and flow batteries that we have chosen to study. For all these devices polymer electrolytes and electrocatalysis play a critical role in controlling their performance and cost, and thus their commercial viability. In this presentation, I will focus on our recent work on hydroxide exchange membrane fuel cells which can work with non-precious metal catalysts and inexpensive polymer electrolytes, and thus can be economically viable. More specifically I will show how we have discovered a super-stable organic cation, why hydrogen oxidation reactions are slower in base than in acid, and what we have developed as the most active non-precious metal hydrogen oxidation reaction catalysts.

 

 

Understanding the Design of Nanostructured Catalysts through In Situ Techniques
Professor Hong Yang, University of Illinois at Urbana-Champaign
The requirement for high activity, selectivity and stability post a challenge for the design of advanced catalysts.  The conventional impregnation method does not have the fine control to meet various structural requirements, such as catalytic surface with controlled single atom position or sub-monolayer atoms. New approaches are developed in the preparation of nanocrystal size, facet, composition and various fine structures (e.g., site specific bimetallic).  In this presentation, I will discuss principles of solution phase design and post-synthesis treatment of metal nanoparticles, especially uniform, facet-defined catalysts, with several focuses on a) theoretical and experimental understanding of ligand chemistry in the design and controlled synthesis of metal catalysts; b) in situ liquid transmission electron microscopy (LTEM) in the understanding of nucleation and growth of heterogeneous nanoparticle catalysts; c) in-situ variable temperature environmental TEM (ETEM) study of structural behaviors of catalysts under reactive conditions; and d) structure-property relationship.

 

 

 

 

Designing novel enzymes, pathways and cells towards engineering of biology
Professor An-Ping Zeng, Hamburg University of Technology
Microbial processes for the production of biofuels, chemicals and other materials play more and more important roles in the future development of chemical industry. To this end, it is necessary to create novel enzymes, pathways and microbes for economically competitive bioproduction processes. Previous efforts in the engineering of biology have been put mainly on issues related to genes (genome), their gene expression and regulation in the waves of genomic research, systems and synthetic biology. For the purpose of developing more efficient production strains and bioprocesses it is important to precisely engineer enzymes and metabolic pathways that are directly responsible for the biosynthesis and for the cell physiology. In this talk, I will give an overview of the major approaches and strategies for designing novel enzymes, metabolic pathways and microbes in the context of metabolic engineering and synthetic biology for chemical biotechnology. Several concrete examples will be illustrated and future development for next-generation of bioproduction systems will be discussed.

 

 

 

Preparation of Stable Metal-Organic Frameworks for Practical Applications
Professor Hong-Cai Zhou, Texas A&M University
As an emerging class of porous crystalline solids, metal-organic frameworks (MOFs) have enjoyed an almost unparalleled rapid growth in the last two decades owing to their intriguing properties and vast application potential. This remarkable success was built upon the establishment of cluster science, organic chemistry, and X-ray crystallography. Initially topological analysis and symmetry guided rational design of MOFs have propelled the development of the MOF field. The participation of synthetic chemists with advanced organic preparation skills has played an important role in ligand design and synthesis as well as post-synthetic modification.
Although most of the MOF chemists are engaged in teaching inorganic chemistry, the cluster science aspect of MOF research has remained mostly dormant. MOF synthetic work has relied almost exclusively on the “one-pot” approach. In the last few years, attentions have been refocused on coordination chemistry, especially the labile nature of the metal-carboxylate bonds. Using existing coordination assemblies, including metal-organic polyhedron (MOPs) and MOFs, as templates, through bridging ligand substitution, new MOPs and MOFs that are otherwise difficult or impossible to obtain are now readily accessible. The key is to systematically analyze the kinetics of ligand substitution reactions and apply kinetic control in the preparation of MOFs.

111For high-valent MOFs, the kinetic inertness of the metal-carboxylate bonds is a double-edged sword: The MOFs are difficult to make but they are generally exceptionally stable. This has posed a synthetic challenge for the preparation of high-valent MOFs. Through judicious kinetic control, we have developed the following synthetic methods: (1) Kinetically tuned dimensional augmentation (KTDA), in which a robust cluster with terminal carboxylate groups has been extended to 3D frameworks by systematically tuning the kinetics of the synthetic procedure;1 (2) Post-synthetic metathesis and oxidation (PSMO) and post-synthetic reduction, metathesis and oxidation (PSRMO), where redox chemistry has been applied to tune the kinetics of bridging ligand substitution;2 and (3) Sequential linker installation (SLI), through which up to three different linkers can be installed sequentially to obtained mixed linker MOFs with ordered structure by applying kinetic adjustments.3

  1. (a) Feng, D.; Wang, K.; Wei, Z.; Chen, Y.-P.; Simon, C. M.; Arvapally, R. K.; Martin, R. L.; Bosch, M.; Liu, T.-F.; Fordham, S.; Yuan, D.; Omary, M. A.; Haranczyk, M.; Smit, B.; Zhou, H.-C., “Kinetically Tuned Dimensional Augmentation as A Versatile Synthetic Route Towards Robust Metal–Organic Frameworks”,Nature Comm.2014, DOI: 10.1038/ncomms6723. (b) Park, J.; Feng, D.; Zhou, H.-C., "Structure-Assisted Functional Anchor Implantation in Robust Metal‒Organic Frameworks with Ultralarge Pores", J. Am. Chem. Soc., 2015137, 1663-1672. (c) Feng, D.; Liu, T.-F.; Su, J.; Bosch, M.; Wei, Z.; Wan, W.; Chen, Y.-P.; Wang, X.; Wang, K.; Lian, X.; Gu, Z.-Y.; Park, J.; Yuan, D.; Zou, X.; Zhou, H.-C., “Stable Metal-Organic Frameworks Containing Single-Molecule Traps for Enzyme Encapsulation”, Nature Comm., 2015, DOI: 10.1038/ncomms6979. (d) Wang, K.; Feng, D; Liu, T –F.; Su,J.; Yuan, S.; Ying-Pin Chen, Y. –P.; Bosch, M; Zou. X.; Zhou. H. –C., “A Series of Highly Stable Mesoporous Metalloporphyrin Fe-MOFs”, J. Am. Chem. Soc.2014136 (40), 13983–13986.
  2. Liu, T.-F.; Zou, L.; Feng, D.; Chen, Y.-P.; Fordham, S.; Wang, X.; Liu, Y.; Zhou, H.-C., “Stepwise Synthesis of Robust Metal-Organic Frameworks via Post-Synthetic Metathesis and Oxidation of Metal Nodes in a Single-Crystal to Single-Crystal Transformation”, J. Am. Chem. Soc.2014136, 7813–7816.
  3. Yuan, S.; Lu, W.; Chen, Y.-P.; Zhang, Q.; Liu, T.-F.; Feng, D.; Wang, X.; Qin, J.; Zhou. H.-C., “Sequential Linker Installation: Precise Placement of Functional Groups in Multivariate Metal–Organic Frameworks”, J. Am. Chem. Soc.2015, 137, 3177–3180.

 



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