10 Questions with Fang Lu
Interview with a CFN Scientist
May 13, 2015
Scientists at the Center for Functional Nanomaterials specialize in exploiting phenomena that only emerge on the billionths-of-a-meter scale. Fang Lu, a member of CFN’s Soft and Bio Nanomaterials Group, explores novel methods of synthesizing materials to enhance their electronic, photonic, and magnetic properties for a wide range of applications.
In particular, Lu meticulously controls the size, shape, composition, and assembly of nanostructures to manipulate their physical and chemical properties and tackles fundamental physics puzzles, including the metal-insulator transition and superparamagnetism.
What technology—current or future—will be advanced by these finely controlled nanoparticles?
I mainly work on metallic materials, which represent more than two thirds of the elements in the periodic table. Since the size and shape of nanocrystals provide the most powerful means to manipulate their properties, we can explore applications in catalysis, electronics, photography, and information storage. Technologies in other areas, such as detectors, medicine, imaging, and photonics, also benefit from the nanocrystal control.
What tools and techniques allow you to manipulate nanoparticle size and shape?
Our synthesis techniques are based mainly on a solution-phase, seed-mediated strategy in which the nucleation step—the initial clustering of crystals—and growth step can be disentangled. We control the growth kinetics and use capping agents to create specific designs as the nanocrystals take shape. For example, capping agents like polyvinylpyrrolidone and bromide ions have a “magic” ability to bind selectively to the planes of metals such as gold, silver, and palladium. We introduce these during nanoparticle synthesis to create cube-shaped products with specific planes exposed. Nanoparticle size can even be tuned by precisely controlling the amount of raw materials and growth time.
What role does DNA play in assembling these nanostructures?
Scanning electron image (SEM) of binary superlattices formed by nanoscale spheres and cubes with DNA recognition interaction. The inset is a scattering image taken by synchrotron-based small angle x-ray scattering (SAXS, NSLS beamline X9) for probing the in situ structure of particle assemblies. These results indicate that the nano-sized building blocks decorated with DNA tethers can coordinate the assembly of spherical nanoparticles coated with complementary DNA strands.
DNA-driven nanoparticle assembly provides a powerful tool for the fabrication of superlattices with tunable composition, structure, and inter-particle distance. DNA is chemically stable and can be conveniently applied to functionalize nano-objects and provide a high degree of encoding in the assembly process. The high specificity of DNA—its unique ability to recognize and bond with complementary sequences—permits the programming of nanoparticle interconnections and allows us to create multi-functional materials. We can then leverage that synthesis knowledge to investigate any emergent and collective phenomena.
What tools and techniques do you use to characterize these custom-made materials?
We usually use small-angle x-ray scattering (SAXS) and electron microscopy (EM) techniques to perform structural characterizations. SAXS is a powerful in situ, or real-time, characterization tool for nanoparticles in solutions, while EM provides more visual breakdowns of these materials. We conducted the synchrotron-based SAXS at beamline X9 of the National Synchrotron Light Source and EM studies with CFN’s in-house instruments.
Why do this work at Brookhaven’s Center for Functional Nanomaterials?
There is a long-term demand for novel materials with extraordinary optical, mechanical, and energy storage/conversion properties. Beyond the tools mentioned before, our facilities allow for precise material fabrications across different size scales, from atomic arrangements to DNA-driven micrometer-scale assemblies.
As an open facility for the nanoscience research community, CFN provides a passionate environment for us to share our expertise with users from both academia and industry. In the Soft and Bio Nanomaterials group, Oleg Gang leads a diverse set of technical expertise and scientific interests, enabling research at stages from nanoparticle synthesis to hierarchical assembly to structural and functional characterization. We also lead the way in utilizing soft materials, polymers, and biomolecules to control self-assembly. People and science benefit from friendly collaborations with others from different research fields. Challenging topics and precious chances to broaden my knowledge keep inspiring new collaborations and experiments.
What’s one recent example of your work synthesizing and characterizing nanoparticles?
As I mentioned above, the shape of nanoparticle defines the surface and thus the arrangement of atoms on the faces—traditional cutting and polishing techniques often result in small but important structural defects. Shape-controllable synthesis of nanoparticles provides an alternative strategy to atomically tailor the surface via chemical methods. Recently, we collaborated with the electrochemistry group in Brookhaven’s Chemistry Department and CFN’s Theory and Computation Group to explore model catalytic systems. We successfully synthesized a series of gold nanoparticles with specified crystalline planes exposed in the shapes of octahedrons, cubes, and truncated ditetragonal prims. The highly pure and clean surfaces of these nanoparticles allowed us to conduct an in-depth understanding of catalytic reaction mechanisms.
What excites you about the future of your research at CFN?
I am looking forward to investigating dynamics related to nanoparticles and how their assemblies may reveal aspects of cosmic movements. My research will also be pushed into new frontiers by the National Synchrotron Light Source II. The world-leading x-ray coherence will capture fast dynamics at the sub-millisecond time regime. The more focused beam and higher x-ray flux will also allow us to probe a local zone of a sample more precisely. As just one example, NSLS-II will facilitate the detection of catalytic processes on specific parts of sample, like a tiny facet of a nanoparticle with well-defined atomic arrangement—this then helps enhance catalyst design.
What do you find personally rewarding about your research?
I handle the precise organization of building blocks in a microcosm—a small, proof-of-principle scale that can be applied to larger materials. Our nanoscale architectural arts can actually inspire exciting and unexpected applications. It is a great thrill for a science-lover like me to use cutting-edge nanotechnology and advanced facilities to explore the beauty of science.
Nanoscience and nanotechnology provide a thrilling platform to attract a confluence of brilliant inter-disciplinary researchers. I personally enjoy a purposeful process—including design, fabrication, and study—where fundamental physics sets a goal and materials science provides the tools to investigate.
Why did you become a scientist?
I have been passionate about the unknown world and science since my childhood. At that time, I liked the plant sciences and wrote a paper about nepenthes mirabilis, a variety of pitcher plant. But when I was in high school, I fell in love with physics, math, and chemistry due to the enlightening guidance of excellent teachers. Physics became my major in college, which my teacher called the “truth of the universe,” and it gave me a power to solve interesting problems. Being a scientist, I have more chances to collaborate with different experts to explore new things and face new challenges. The beauty of science that I find in my research gives me the same happiness I earn when I digest every fragment of a work of art in the Metropolitan Museum of Art.
Why should other scientists come to CFN to conduct research?
CFN acts as a perfect platform for users and staff scientist to collaborate and interact across disciplines. Such an open and free environment is what CFN, as a user-oriented facility, aims to create. We have many cutting-edge instruments as well as a great group of scientist and professional experts who are ready to discuss new experiments with users and provide advice.
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