Nanocrystallinity Engineering: Tailoring Properties and Functionalities of Metal Nanoparticles

1. Nanocrystallinity Engineering: Tailoring Properties and Functionalities of Metal Nanoparticles Min Ouyang, University of Maryland, DMR 0547194 SC- Ag 1.0 0.8 0.6 MT- Ag Normalized T/T (a.u.) 0.4 0.2 0.0 0.0 5.0 10.0 15.0 20.0 Time Delay (ps) SC- NPs 0.01 0.00 -0.01 MT- NPs Oscillation Amplitude (a.u.) 0.01 0.00 -0.01 8.0 11.0 14.0 17.0 20.0 5.0 Time Delay (ps) Metal nanoparticles (NPs) with size comparable to their electron mean free path possess unusual properties and functionalities, serving as model systems to explore quantum and classical coupling interactions as well as building blocks of practical applications. We have developed a facile synthetic route for controlling crystallinity of metal NPs, which enabled either 100% perfect single crystalline (SC-) or 100% disordered multiply twinning (MT-) NPs (inset of top right figure). This nanocrystallinity engineering facilitates investigation of their scope for fundamental physics and chemistry as well as practical device applications. We showed that fundamental electron- phonon interactions as well as nanomechanical properties are substantially modified by nanocrystallinity, in which the electron-phonon constant is reduced about four times and elastic modulus is increased ~37% in 10nm perfect SC- silver NPs as compared with the results from MT- system (top and bottom right figures). Furthermore, our nanocrystallinity engineering can optimize performance of NPs based molecular sensing devices with about three times improvement of figure-of-merit if SC- NPs are applied. Our effort marks an unprecedent control of metal NPs, then creating a rational pathway for understanding and manipulating fundamental chemical and physical processes at the nanoscale as well as technological applications of metal NPs. (Tang & Ouyang, Nature Materials, 2007)

2. Nanocrystallinity Engineering: Tailoring Properties and Functionalities of Metal Nanoparticles Min Ouyang, University of Maryland, DMR 0547194 Educational Outreach: As an important component of this NSF CAREER award we are actively involved in various educational outreach programs (connected with university of Maryland NSF MRSEC program) as well as undergraduate course development. Several activities over last one year were highlighted as follows:  I have supervised four REU students. One of our REU students, Ms. Paris Alexander, recently won the first place for Best Poster in the 30th Annual National Society of Black Physicists Conference in Boston. Right figure shows my REU student, Ms. Izath Agular, in her poster presentation.  We have dedicated to help improve middle/high school students’ abilities in and perceptions of science as well as research presentation skills. We have worked with two middle school students to help transform their science fair projects into scientific presentation in the annual Student Science Conference, which has gained wide recognition and more interest from the community.  I are currently developing an undergraduate courses entitled “Physics, Materials Chemistry and Device Applications at the Nanoscale”, which will be the first course in the university of Maryland integrating lecture and bench-top nanoscale experiments. This course is designed for advanced undergraduate in physics, chemistry and engineering with interest in the evolving interdisciplinary field of nanoscience and nanotechnology.