Transcript How Do We Control Material Processes at the Level of Electrons? (J

How Do We Control Material Processes at the Level of Electrons?
Progress on Grand Challenge
What parts of the Grand Challenge have been solved?
Computational techniques have improved and now can model larger
molecules more quickly. Molecular dynamics has allowed the quantum
mechanical calculation of reaction landscapes much more quickly and
accurately to discover accessible transition state pathways depending on the
reaction conditions and excited states of the reactants and intermediates.
On an experimental and computational level, the study of plasmonics has
contributed to understanding light induced excited states (featured as a
focus area in Nature Photonics focus in Nov 2012). Quantum coherence and
dynamics with respect to superconducting qubits, quantum transport in
quantum dots, and in light harvesting is much better understood (DOI:
10.1038/srep00885 and references therein.)
Remaining Challenge
• Does enough remain to be grand?
Yes; further questions based on the fundamental issues still remain, but
with different directions and applications than previously existed or
explored. Significant progress has been made to several of the questions on
a fundamental level, contributing to the expansion applications.
• Is it tractable on the decadal scale or longer?
Yes; addition of new questions based on the quantum control of electrons
in atoms, molecules, and materials would be increase the scope of the
challenge and would add to the comprehensive understanding and level of
control for more applications.
New Horizons for Grand Challenge
Has the focus/scope of the Grand Challenge evolved?
Challenges remain in using computation to quantitate properties for larger
length scales in materials and predict/explain their reactivity. Also,
developments are necessary to move beyond Newtonian based molecular
dynamics to accelerated dynamics that can more quickly map potential
energy landscapes for more complicated reactions (also useful for
Challenge #5). This can assist the accurate representation of reaction
pathways that occur at varying temperatures or with reactants in higher
energy excited states. The experimental measurement of thermodynamic
parameters in different solvents has assisted improved solvation models in
quantum mechanical models, but still needs to be refined further.
Refreshed Grand Challenge?
• Is a new statement of the Grand Challenge needed?
Yes; the questions answered by the past decade of research has
spawned new directions in areas that are still not well understood. A
new statement could encompass these new challenges and directions.
For example, understanding the electron dynamics in light harvesting
and photosynthesis has made significant progress, but this is less well
understood in electrode materials and heterogeneous catalysis, as well
as other materials in the nanoscale.
• Should the Grand Challenge be retired?
No, it should be restated/expanded, as described above.
Submitted by: Jenny Yang
Affiliation: University of California, Irvine
How do we design and perfect atom- and energy-efficient synthesis of
revolutionary new forms of matter with tailored properties?
Progress on Grand Challenge
What parts of the Grand Challenge have been solved?
Soft materials: Progress has been made towards catalytic design via first principles,
especially combining experiment with theory and correlating reactivity and thermodynamic
properties with function; however, only the most basic reactions (i.e. hydrogen evolution
reaction) have been described thoroughly at this point. Catalyst considerations have been
described for cascade reactivity (i.e. CO2 to CH3OH, relevant to artificial fuel production,
DOI: 10.1021/ja208760j). Elegant solutions for self repair in polymers have been
demonstrated (DOI: 10.1021/ja5097094), but primarily for soft materials using weak
interactions. OLED have now achieved commercialization for a variety of applications .
Hard materials: The use of quantum mechanical methods and experiment to understand
heterogeneous catalysis has assisted in the identification of catalytic active sites, whether
they are edges, specific faces, or defects. This has contributed to the development of new
synthetic methods to target materials with a greater density of catalytic active sites.
Remaining Challenge
• Does enough remain to be grand?
Yes; although significant progress has been made, directed level of control for complex
atom and energy efficient synthesis has yet to be achieved. The use of tailored micro-scale
environments to promote selectivity and influence reaction pathways under mild conditions
is just beginning to be explored. Much of these advances will require improved techniques
to examine reactions in situ, especially on surfaces. Additionally, the use of non-thermal
methods such as light or electrochemical potential to drive “uphill catalysis” or form metastable forms of matter has expanded but not reached its full capabilities. More complicated
problems such as reducing biomass to liquids or stimulus control of materials has presented
more challenges.
• Is it tractable on the decadal scale or longer?
Given the progress that has been made since the original report, great strides can be made
on the decadal scale for atomic level control of new materials and catalysts.
New Horizons for Grand Challenge
Has the focus/scope of the Grand Challenge evolved?
Soft materials: Many small molecule transformation with homogeneous,
heterogeneous, and enzymatic catalysts follow similar modes of activation, and
selectivity often emerges through common intermediates. These shared
themes are just beginning to emerge, and the use of computational and
experimental tools has greatly improved the understanding of critical
intermediates and how they can be stabilized by the catalyst. An example of
this is the use of activity descriptors, initially used for heterogeneous catalysts,
being applied for homogeneous catalysts and enzymatic active sties. Some of
the initial studies on cascade catalysis has described the problem of designing
catalysts that are tolerant to the same conditions to allow one-pot catalysis.
Hard materials: New methods of non-thermal synthesis will promote formation
of meta-stable phases that are predicted to have unique properties.
Refreshed Grand Challenge?
• Is a new statement of the Grand Challenge needed?
A new statement would unite common themes in the reactivity and
intermediates discovered in catalysis by heterogeneous, homogeneous, and
enzymatic active sites. This could lead to the development of hybrid catalysts
that incorporate micro-environment or bi-functional capabilities necessary to
control and direct electron, proton, and atom transfer events. Additionally, as
some of the materials challenges have made great advances (such as OLEDs),
new desirable properties in soft and hard materials could be proposed.
• Should the Grand Challenge be retired?
No, the current state of the research presents new opportunities for fruitful
cross disciplinary advances to achieve the primary goals.
How do remarkable properties of matter emerge from complex correlations of
the atomic or electronic constituents and how can we control these properties?
Progress on Grand Challenge
What parts of the Grand Challenge have been solved?
The understanding of high temperature superconductors
appears to have made steady progress, although I am not
very familiar with the field. Work on correlated properties in
heterostructures, particular for quantum dots has been
exciting in the context of quantum dot photovoltaics. I am not
familiar enough with correlation in soft matter or biological
systems to comment.
Remaining Challenge
• Does enough remain to be grand?
Yes, but the challenges with electron correlation in materials seem like they
may fit more appropriately into other grand challenges (#1, 2, & 5), especially
given the need for improved methods of material synthesis, experimental
methods, and theoretical models. Some issues with bio-complexity and
evolution far from equilibrium may also fit into grand challenge #5.
• Is it tractable on the decadal scale or longer?
Yes; any of the fundamental properties may be tractable. Greater
computational modeling /instruments for biological correlation behavior
would be beneficial to many other areas of biophysical research.
New Horizons for Grand Challenge
Has the focus/scope of the Grand Challenge evolved?
Many of the challenges associated with electron correlation in
materials would work synergistically with the research
working towards grand challenge #1. However, the focus on
collective phenomenon in super-fluids and Bose-Einstein
condensates, and biology remain relevant.
Refreshed Grand Challenge?
• Is a new statement of the Grand Challenge needed?
Yes; the current challenge represents diverse fields of
research, some of which may benefit more from interdisciplinary work encompassed within other challenges
• Should the Grand Challenge be retired?
Possibly; emergent phenomenon in condensed matter
physics and biology should will answer many
fundamental questions important to other fields, but not
sure if this should be a grand challenge itself.
How can we master energy and information on the nanoscale to create new
technologies with capabilities rivaling those of living things?
Progress on Grand Challenge
What parts of the Grand Challenge have been solved?
The first part of the grand challenge described the need for advances in
microscopy and other experimental or analytical tools to examine cells and other
biological material at the nanoscale in situ. There has been significant progress in
both optical microscopy and scanning probe techniques (DOI:
10.1016/j.biocel.2013.05.010, DOI: 10.1038/nnano.2011.186). The development
of wave guiding materials will also add to the toolbox of studying cells at greater
resolution. Additionally, the challenge of synthetic immunology, or
communicating to cells directly via chemical signals to tailor and direct immune
responses, has begun to be addressed in earnest (DOI: 10.1038/nchembio.477,
DOI: 10.1016/j.tibtech.2014.10.006). Advances have been made in
understanding photon-chemical coupling, but the interface and charge transport
from photo-absorbers and delivery to catalysts or architectures that can utilize
the energy is still poorly understood.
Remaining Challenge
• Does enough remain to be grand?
Yes, the original challenge was very ambitious, and the tools
necessary to advance the research have now been developed. The
growth of the field is rapid, and the fundamental science involved has
the potential to span many different scientific areas and used for
many different applications
• Is it tractable on the decadal scale or longer?
Yes, many of the fundamental questions will progress quickly with
the development of new analytical tools.
New Horizons for Grand Challenge
Has the focus/scope of the Grand Challenge evolved?
Synthetic immunology has described new methods to replicate the chemical signals
that are used in natural cell communication. Expanding these discoveries to other cell
responses would be an entry into biological communication for a variety of
applications. Additionally, although microbial fuel cells or hybrid energy conversion
devices is an old idea, recent studies (DOI: 10.1016/j.rser.2010.10.005, DOI:
10.1039/c1ee02531g) have reinvigorated the field and modern tools can be used to
provide more detailed information about interfacial electron transfer. Additionally,
new directed evolution techniques can be used to optimize microbial response and
function. Coupling microbes to electrodes provides an opportunity to interchange
chemical and electrical energy efficiently, and even coupling wastewater
oxidation/cleanup with fuel generation (DOI: 10.1007/s00253-012-4456-7). These
types of electricity-chemical interchanges are also necessary to obtain a better
understanding of natural photosynthetic pathways.
Refreshed Grand Challenge?
• Is a new statement of the Grand Challenge needed?
Yes, the specific challenges (relating to synthetic cell communication
and hybrid bio-electrode materials) could be expanded, and new
experimental or computational tools that would advance the research
could be described.
• Should the Grand Challenge be retired?
No, although the ultimate goals are ambitious in scope, these are
important areas of research and the potential for game-changing
advances is high.
How do we characterize and control matter away
- especially very far away - from equilibrium?
Progress on Grand Challenge
What parts of the Grand Challenge have been solved?
Many advances have been made in modeling atmospheric chemistry, a classic
example of a non-equilibrium system, although the complexity of the system has
contributed to an incomplete picture. Heat transfer, particularly to oceans, is still
a problem. New tools have been developed to measure molecular dynamics for
single molecules (DOI: 10.1038/nphoton.2014.143), and single molecule catalysis
by enzymes (DOI: 10.1126/science.1248859) and will contribute to
understanding their activity to ensembles in statistical mechanics. The
application of the concept of jamming has been applied to protein folding in
biological systems (DOI: 10.1038/ncomms2177). New catalytic activity by metastable natural minerals (in this case, formed under hydrothermal conditions)
have been explored recently (DOI: 10.1073/pnas.1324222111). Some methods
for increasing minority carrier diffusion lengths in photovoltaic materials have
been answered. (DOI: 10.1063/1.3247969)
New Horizons for Grand Challenge
Has the focus/scope of the Grand Challenge evolved?
New methods of synthesis (primarily non-thermal) are required to generate meta-stable
phases of matter. For example, targeted synthesis can be coupled using experiment and
theory to maximize the concentration of site most likely to display catalytic activity. An
example of this is the edge sites of MoS2 display the highest activity for electrocatalytic
hydrogen evolution, but is a higher energy configuration. New synthetic methods that
utilize electrochemical or photochemical methods would avoid thermal equilibrium in the
synthesis of meta-stable materials (i.e. Cu for CO2 reduction electrocatalysis, DOI:
10.1038/nature13249). Biological mechanisms often utilize very small amounts of energy
to achieve transformations under ambient conditions that can currently only be replicated
using high heat and pressure (i.e. N2 reduction to ammonia). This is another area where
non-equilibrium effects can be utilized to improve catalysis. The development of improved
accelerated dynamics computational methods (also suggested in Challenge #1) will
improve descriptions of energetic landscapes and facilitate identification of local minima.
Remaining Challenge
• Does enough remain to be grand?
Yes; although this problem has been studied for a long time, the
complexity of the problems and potential importance in many
different fields should maintain it’s status as a grand challenge.
• Is it tractable on the decadal scale or longer?
Many of the tools (particularly more advanced computational power
for modeling systems, and single molecule spectroscopic tools) are
just being developed; the use of these will contribute to tangible
advancements on the decadal scale or longer.
Refreshed Grand Challenge?
• Is a new statement of the Grand Challenge needed?
Possibly, to incorporate more applications and utilization of some
of the new experimental and computational tools. Some of the
challenges related to synthesis of meta-stable materials is also
covered in Challenge #2.
• Should the Grand Challenge be retired?
No, the discovery of fundamental rules to non-equilibrium systems
are too important and ubiquitous to nearly all scientific fields.