A structure found in nature but previously unattainable artificially in metals has been realized, earning a Nature cover and advancing next-generation optical materials and catalysts.
A joint team comprising Professor Junsuk Rho's mechanical/chemical engineering group, EE Professor Wook-Sung Kim, Seoul National University Professor Ki-Tae Nam's group and Dr. Ki-Seok Jang of LG Display Research synthesized the world's first gold nanoparticles with mirror-image structures previously regarded as unique to biomolecules, using peptides.
Based on interactions between peptides and specific gold surfaces, they synthesized uniform 100 nm particles twisted clockwise or counterclockwise and explained the underlying mechanism, presenting a new paradigm. The results appeared in Nature on April 19, 2018, were selected for its cover and were discussed in News & Views, where leading scientists explain important research.
Right and left hands look alike but a left-handed baseball glove cannot fit the right hand. Such non-superimposable mirror symmetry is chirality. Molecules involved in life, including amino acids that form proteins, have chiral structures. Their geometry produces structural selectivity and optical-control properties, attracting interest for catalysts, optical materials and sensing platforms. Creating and controlling chirality in inorganic materials has been difficult because of process complexity and stability issues.
The team used mirror-structured peptide biomolecules in inorganic crystal synthesis to create uniquely shaped gold nanoparticles: cubes about 100 nm per side with clockwise or counterclockwise twisted features on each face. Measurements of their response to rotating light showed giant chirality, about 100 times that of protein biomolecules. Because this response lies in the visible spectrum, polarization-control experiments also produced various colors.
The first demonstration that peptide sequences and corresponding structure and chirality can be directly reflected on inorganic surfaces opens a new paradigm in biomolecule-directed synthesis. The method is readily expandable and generalizable to other materials, providing foundational nanomaterial synthesis technology. Korean and overseas patent applications have been completed.
SNU Professor Ki-Tae Nam said this is the first biomimetic synthesis of chiral inorganic nanocrystals with structures found in nature but previously impossible to realize artificially. He said the particles can immediately serve as a new visible-light polarization material for displays, while the deeper understanding of interactions between inorganic materials and chiral biomolecules could underpin enantioselective catalysts. LG Display Principal Researcher Dr. Ki-Seok Jang expects applications in flexible ultrathin next-generation displays.
Co-corresponding author Junsuk Rho analyzed the optical properties and said their optical-rotation selectivity could become central to polarization-control devices, structural color, negative-index materials, invisibility cloaks and biosensing.
Chemical engineering's Jung-Ho Moon, mechanical engineering's Min-Kyung Kim, co-first author Dr. Hye-Eun Lee of SNU and coauthors Hyo-Yong Ahn, Yoon-Young Lee and Nam-Heon Cho all performed this work during doctoral studies in Korea, demonstrating the excellence of Korean science and engineering students.
Support came from the Ministry of Science and ICT's Future Materials Discovery “d-Orbital Control Materials” group (director Ki-Tae Nam), Global Frontier Multiscale Energy Systems group (director Man-Soo Choi), Center for Advanced Meta-Materials (director Hak-Joo Lee), and the leading-research Center for Optomechatronics (director Shin-Il Kang).
This is also an important industry–university outcome. Supporting company LG Display has operated the LG Display–SNU Incubation Program, directed by Jong-Rae Park, since 2015 to discover future technologies. LG Display CTO and Executive Vice President In-Byung Kang called it a successful collaboration securing creative fundamental research and foundational technology, and pledged joint efforts to make it a basis for next-generation display research.
The first mirror-symmetric gold nanoparticles synthesized by mimicking biomolecular geometry could affect industries through energy/environmental catalysts, optical communications and holograms. Better understanding peptide–inorganic-surface interactions deepens chemistry, materials and nanoscience and may help explain enantioselectivity in life.
