The main goal of this program is to prove the feasibility of photo-activating currents and photo-inducing magnetization in noble metal-nanorings using polarization controlled laser radiation.
The specific objectives of this investigation are: i) To couple the laser system with a microscale Hall-effect magnetometer, ii) To find, theoretically, optimum experimental configurations of two-dimensional Au-nanorings arrays to be tested, iii) To fabricate the first series of samples on quartz and GaAs wafers based on the theoretical predictions, iv) To demonstrate the generation of rotating polaritons in Au-Nanorings through the optical characterization of samples supported on quartz, v) To measure photo-induced magnetization in Au-nanorings supported on GaAs-wafers with the integrated microscale Hall-Effect magnetometer under perpendicular radiation geometry, using left and right circularly polarized light.
Intellectual Merit: This EAGER is a fundamental, high-risk, high-reward transformative research project that crosses traditional boundaries between chemistry, physics, optics, material sciences, engineering and nanotechnology.
? This project is transformative in that the current understanding of polariton propagation in conductive nanostructures will be enriched by a valuable fundamental study of the generation of controlled photo-induced transient rotating polaritons in closed metal nanorings using circularly polarized radiation with specific handedness. This exceptionally innovative research project offers the potential to pave the road of a new generation of nanodevices that could be used as photo-activated binary switchable nanomagnets, photo-activated nano-accelerators, photo-activated magnetic nano-transmitters, and meta-materials for negative refractive index, among others. ? The high-reward aspect of this EAGER resides in the deep understanding of an intriguing but fascinating effect that could revolutionize the field of nanotechnology through the development and design of novel nanodevices for computing and communication, nanoantennas and sensors. ? The high-risk facet of this study resides mainly on the intrinsic uncertainty involved in a high-impact, cutting edge research on an untested idea and, on the multidisciplinary experimental technical challenges that it will present. The latter include to couple a laser system with a microscale Hall-Effect magnetometer, to fabricate nanostructures with reduced defects and increase the density of Au-nanorings on the substrates avoiding surface Plasmon resonance coupling between neighbor nanorings, to detect the anticipated small photo-induced currents and magnetization in Au-nanorings and, to gain control on the sign of the magnetization using different handedness of circularly polarized radiation.
Broader Impact: This project includes the interdisciplinary training of two graduate students of two different disciplines (chemistry and physics) in a field that combines chemistry, physics, optics, material sciences, engineering and nanotechnology. The strong collaboration between USA and Taiwan, an Asian developing nation, will contribute to the preparation of the new generation of PhDs by providing them with global awareness. Results will be diseminated through publications in peer-reviewed journals and conference presentations.
PI: Florencio E. Hernandez, Chemistry Co-PIs: Enrique Del Barco, Physics and Sengli Zou, Chemistry University of Central Florida, Orlando, Florida 32816 During the last two years PIs Hernandez, Del Barco and Zou, and international collaborator Cheng worked on the design, fabrication, characterization, modeling, optimization and testing of metal nanostructures on different substrates to prove the feasibility of photo-activating currents and photo-induced magnetization in noble metal-nanorings using polarization controlled laser radiation. Year #1: The PIs performed the theoretical study of the optical response of 2D-patterns Au-Nanoring on quartz with different dimensions, built a portable µ-HEM with an optical window, prepared the first trial GaAs substrate for writing Au-Nanoring pattern on the sensor surface, performed the optical characterization of Au-Nanorings deposited on quartz with different 2D-patterns, and coordinated efforts for designing new strategies. Year #2: The PIs initiated studies of circular nanocurrents in solid metallic spherical nanostructures using light with different polarization, carried out experiments with the µ-HEM sensors on GaAs, modeled and predicted the optical properties of new nanostructures using numerical tools, and designed a novel experimental setup to measure the induced magnetic field in the rings by means of magnetic force microscopy using circularly polarized radiation of both handedness. Crossing traditional boundaries between chemistry, physics, optics, material sciences, engineering and nanotechnology, EAGER-PACMAN has helped expanding the understanding of an intriguing but fascinating effect that could revolutionize the field of nanotechnology through the development and design of novel nanodevices for computing and communication, nanoantennas and sensors. This project has established the foundations of a strong international collaboration between USA and Taiwan. We have trained a total of six graduate and two undergraduate students (50% from underrepresented groups in STEM careers), and have produced two publications in peer-reviewed journals. Outcomes: Based on initial calculations we were able to establish the best experimental conditions for the proposed research, and fabricated 2D arrays of Au-NRs of different dimensions and separation (Fig.1). Through the theoretical-experimental optical characterization of the 2D arrays of Au-NRs on quartz, using a setup designed for light scattering measurements, we validated the effect of polarization on the scattering spectra of these metal nanostructures and, correlated it with the existence of circular propagating polaritons (Fig.2). In coordination with Dr. Cheng’s group in Taiwan, we designed and fabricated Au-NRs patterns on GaAs wafer with the µ-HEM sensor (Fig.3). This effort demonstrated the feasibility of these nanostrures on the sensor surface through this coordinated effort. Trying to expand the scope of the proposed research we modeled new nanostructures and geometries (Fig.4). At present we are trying to overcome the obstacle imposed by the yet low sensitivity of our µ-HEM sensor. Future Plan: Henceforth, most of our effort will be focused on: i) the measurement of photo-activated currents and magnetization in Au-Nanorings using the AFM-MFM and SQUID magnetometry (Fig.5), ii) insist on our initial attempts to induce magnetization in 2D arrays of Au-Nanorings on quartz with an external magnet and detect the generated circular polariton by means of a CW laser with different polarization, and iii) continue modeling alternative 2D arrays of metal nanostructures on GaAs to broaden the spectrum of possibilities to demonstrate PACMAN.
