Featured Research Highlights
“Channeling” Electrons to a Topological State for Ultrahigh Mobility of Spin Current
Scientific Achievement A schematic of spin-polarized four-probe scanning tunneling microscopy to measure spin-dependent electrical conductance on the topological insulator Bi2Te2Se. By reducing the probe spacing at low temperature, most...
Unlocking Secrets of Controlled Assembly of Bimetallic Nanoparticles on Silica
Scientific Achievement Graphic depiction of multistep synthesis of bimetallic nanoparticles including PdPt, PtAu, RuIr, FeIr, NiIr, PdIr, PtIr, CoIr, RuPt. Lower part of image background shows a TEM image of synthesized nanoparticles on a...
This work successfully demonstrated size and geometry customizable carbon microelectrode sensors using templates produced with the CNMS Nanoscribe. These novel carbon electrodes were then implanted into a rat brain to detect dopamine release in vivo. The work exhibits great promise to mass-fabricate customizable sensors with high reproducibility and could open a platform for the development of novel implantable devices for neurotransmitter detection and neurostimulation in the brain.
C. Yang, Q. Cao, P. Puthongkham, S. T. Lee, M. Ganesana, N. V. Lavrik, and B. J. Venton, "3D-printed carbon electrodes for neurotransmitter detection," Angew.Chem. Int. Ed. 57, 14255–14259 (2018). DOI: 10.1002/anie.201809992
This work directly measured the intrinsic surface conductance of topological insulators by using a four-probe scanning tunneling microscope (4-Probe STM) to tune the crossover of bulk-to-surface conductance. A scattering-free spin transport was revealed at micrometer scale through topological surface states. This required using unique CNMS developments for spin-polarized 4-probe STM to achieve the spin-sensitive multi-probe transport measurements. In this manner, a direct and quantitative measurement of the intrinsic spin-polarized transport associated with topological surface states is possible.
W. Ko, G. D. Nguyen, H. Kim, J. S. Kim, X. G. Zhang, and A.-P. Li, "Accessing the intrinsic spin transport in a topological insulator by controlling the crossover of bulk-to-surface conductance," Phys. Rev. Lett. 121, 176801 (2018). DOI: 10.1103/PhysRevLett.121.176801
This research overcomes limitations in poor solubility of heterometallic double complex salt (DCS) precursors by using a clever sequential adsorption of metal cations and anions onto a silica support followed by an efficient reduction step which converts the electrostatically bound pairs into well-defined bimetallic nanoparticles. The synthesis breakthrough enables creation of many previously inaccessible bimetallic systems for a range of catalytic processes. Successful acetylene hydrogenation under both competitive and noncompetitive conditions demonstrated their unique performance.
K. Ding, D. A. Cullen, L. Zhang, Z. Cao, A. Roy, I. N. Ivanov, and D. Cao, "A general synthesis approach for supported bimetallic nanoparticles via surface inorganometallic chemistry," Science 362, 560-564 (2018). DOI: 10.1126/science.aau4414
This work shows that nonclassical multiphoton interferences can be achieved at the subwavelength scale in all-dielectric metasurfaces. Simultaneous imaging of multiple projections of quantum states with a single metasurface enables a robust reconstruction of amplitude, phase, coherence, and entanglement of multiphoton polarization-encoded states.
K. Wang, J. G. Titchener, S. S. Kruk, L. Xu, H.-P. Chung, M. Parry, I. I. Kravchenko, Y.-H. Chen, A. S. Solntsev, Y. S. Kivshar, D. N. Neshev, and A. A. Sukhorukov, "Quantum metasurface for multiphoton interference and state reconstruction," Science 361 (6407), 1104-1108 (2018). DOI: 10.1126/science.aat8196
This joint CNMS-CFN research effort built on unique capabilities of two NSRCs and resulted in a new hybrid nanocomposite sensor material with ~20 times higher gravimetric response than pure polymer thin films, and that could be further enhanced by additional 500% under ultraviolet (UV) activation.
E. S. Muckley, L. Collins, A. V. Ievlev, X. Ye, K. Kisslinger, B. G. Sumpter, N. V. Lavrik, C.-Y. Nam, and I. N. Ivanov, "Light-activated hybrid nanocomposite film for water and oxygen sensing," ACS Appl. Mater. Interfaces 10 (37), 31745-31754 (2018). DOI: 10.1021/acsami.8b08072
This work presents a direct observation of electric field induced motion/response of ionic diblockcopolymer thin films with nanoscale resolution using In situ neutron reflectometry measurements and molecular dynamics simulations.
J. W. Dugger, W. Li, M. Chen, T. E. Long, R. J. L. Welbourn, M. W. A. Skoda, J. F. Browning, R. Kumar, and B. S. Lokitz, "Nanoscale resolution of electric-field induced motion in ionic diblock copolymer thin films," ACS Appl. Matter. Interfaces 10 (38), 32678-32687 (2018). DOI: 10.1021/acsami.8b11220
Understanding the 3-D distribution and nature of active sites in heterogeneous catalysts is critical to developing useful structure−function relationships but it is very difficult to achieve such 3-D information. By using the CNMS Atom Probe Tomography (APT) the team was able to reveal the 3-D distribution of elements within a zeolite catalysis, SAPO-34, at different processing stages, including template containing, calcined, and methanol-to-hydrocarbons reacted SAPO-34 with Si as the active site.
J. E. Schmidt, L. Peng, A. L. Paioni, H. L. Ehren, W. Guo, B. Mazumder, D. A. Matthijs de Winter, O. Attila, D. Fu, A. D. Chowdhury, K. Houben, M. Baldus, J. D. Poplawsky, and B. M. Weckhuysen, "Isolating clusters of light elements in molecular sieves with atom probe tomography," J. Am. Chem. Soc. 140, 9154 (2018). DOI: 10.1021/jacs.8b04494
A general approach for quantitatively investigating the spatiotemporal dependence of structural relaxation in deformed polymers based on using small-angle neutron scattering alongside HPC-enabled nonequilibrium molecular dynamics simulations was developed and successfully applied to polymer melts over a wide range of precisely synthesized molecular weights. This work revealed that polymer relaxation at relatively high momentum transfer, Q, and short time can be described by a simple scaling law, with the relaxation rate simply proportional to Q. This is a novel and previously not resolved nor understood behavior and further exemplifies the need to reconsider the theory of polymer flow.
C. N. Lam, W.-S. Xu, W.-R. Chen, Z. Wang, C. B. Stanley, J.-M. Carrillo, D. Uhrig, W. Wang, K. Hong, Y. Liu, L. Porcar, C. Do, G. S. Smith, B. G. Sumpter, and Y. Wang, "Scaling behavior of anisotropy relaxation in deformed polymer," Phys. Rev. Lett. 121, 117801 (2018). DOI: 10.1103/PhysRevLett.121.117801
A unique combination of imaging tools and atomic-level simulations allowed the team to solve a longstanding debate about the properties of a promising material that can harvest energy from light. By using multimodal imaging to “see” nanoscale interactions within a thin film of hybrid organic–inorganic perovskite, CH3NH3PbI3, it was determined that the material is ferroelastic, meaning it can form domains of polarized strain to minimize elastic energy. The work was possible because of the unique environment at CNMS where characterization, theory and synthesis can be integrated to efficiently solve complex nanoscience problems. This alongside strong collaborations with industry allowed CNMS to develop/apply unique tools; in this case an instrument that uses helium ion microscopy (HIM) to remove and ionize molecules was coupled with a secondary ion mass spectroscopy (SIMS) to identify molecules based on their weights and an Interferometric Displacement Sensor (IDS) option for the Cypher AFM (Oxford Instruments Asylum Research) was used for measurements capable of separating cantilever dynamics from displacement of the material due to piezoresponse. Overall, the work demonstrated the ferroic property of twin domains, chemical segregation, and their interplay in CH3NH3PbI3, offering a new exploratory path to improving functional devices.
Y. Liu, L. Collins, R. Proksch, S. Kim, B. R. Watson, B. Doughty, T. R. Calhoun, M. Ahmadi, A. V. Ievlev, S. Jesse, S. T. Retterer, A. Belianinov, K. Xiao, J. Huang, B. G. Sumpter, S. V. Kalinin, B. Hu, and O. S. Ovchinnikova, "Chemical nature of ferroelastic twin domains in CH3NH3PbI3 perovskite," Nature Mater. (2018). DOI: 10.1038/s41563-018-0152-z