Session: 02-03-01: Session #1: Nanomanufacturing: Novel Processes, Applications, and Process-Property Relationships

Paper Number: 99238

99238 - Laser Photothermal Generation of 3d Graphene With Multifunctionality 

Nanomaterials have shown potential for high-performance functional materials especially in sensing and energy applications. Structuring of nanomaterials, including atomically-thin two-dimensional (2D) materials (e.g. graphene) and combining 2D materials with conventional materials such as metals and polymers can enable new functionalities and high performance by engineering exceptional and outstanding mechanical, electrical, and optical properties. The existing methods for synthesizing hybrid materials comprising graphene and metal NPs involve complicated processes. Graphene-based nanomaterials are fabricated using chemical vapor deposition or methods involving the reduction of graphene oxides and subsequent integration of metal NPs with carbon nanomaterials via thermal annealing or chemical and electrochemical processes. Recently, a scalable and fast laser photothermal method to generate laser-induced graphene (LIG) with high electrical conductivity and large specific surface area from commercial polyimide films has been developed, which has triggered significant development in research for various applications including energy storage, energy harvesting, and detection. Furthermore, this method has been utilized to fabricate LIG-based hybrids including heteroatom-doped LIG, LIG-metal-sulfide nanocomposite materials, as well as LIG-metal-oxide nanocomposite materials for high-performance energy storage, sensing, and detection. However, the application of the laser photothermal method to the fabrication of porous graphene-metal NP nanocomposite material for flexible electrochemical sensing systems has not been explored till date.

We present a facile and rapid laser photothermochemical processing method to produce 3D porous graphene as well as a nanoassembly of 3D porous graphene and PdNPs from polymer films. Multi-dimensional hybrid nanomaterials combining 3D graphene and 1D metallic nanoparticles are produced in large scale with low production cost by transient laser photothermal processing. The films are photothermally processed using a laser to generate a nanohybrid via photo-induced thermal and chemical processes. A CO₂ laser was irradiated on the polymer films to create a hybrid nanoassembly of 3D porous graphene and PdNPs via photothermal and photochemical processes. A laser induced photothermal excitation within the irradiated area, releasing volatile by-products. Thus, photothermal processes generated vapor bubbles while inducing structural rearrangement of the carbon atoms (sp²-hybridized) in the polymer chains in aromatic polymer precursors, affording nano- to microscopic 3D porous graphene. Simultaneously, the organic functional groups of Pd-ligands were decomposed via the photophysical mechanism of photon-induced thermal and non-thermal chemical reactions involving the bond breakage of the ligand molecules, thereby allowing the nucleation and crystallization of Pd atoms into the nanoparticles. The resultant metal NP-graphene nanohybrid material showed outstanding crystallinity, structural homogeneity with uniform NP sizes and distribution, and large surface area resulting from the hierarchical (micro/meso/macro) pore structure. Moreover, the nanohybrid exhibited excellent mechanical robustness attributed to strong covalent and metallic carbon-Pd bonds in the hybrid nanostructures. The nanohybrid exhibits four-times-enhanced electrical conductivity compared to plain porous graphene, high crystallinity, and coherent covalent metal bonds with a homogeneous size and distribution of PdNPs in the hierarchical micro/meso/macro porous graphene structures, allowing high-performance hydrogen sensing (1 ppm) with outstanding mechanical reliability, flexibility, and durability upon bending and twisting. The nanoassembly is integrated with a wireless sensing platform and hydrogen leakage (1 ppm) is detected by a smartphone. This laser-based nanomanufacturing of the nanoassembly can potentially be applied to wearable detector production platforms in the military and industry. A facile, fast, and scalable laser-induced photothermal method was also used to achieve flexible monolithic bilayer sheets (MBS) of hierarchically porous graphitic carbon (HPGC) and polymeric foam for use in salt-resistant and flexible solar steam generators.^[2] The MBS-based self-floating solar steam generator shows outstanding solar desalination performance with a solar thermal efficiency of 83.2% under 1-sun illumination and a high salt-rejection ratio (99.9%). The all-in-one multi-functionalities of the MBS, including broad-spectrum solar light absorption, heat localization, and capillary action enabled efficient solar thermal energy transformation. Our laser-based photothermal method holds promise to achieve high-performance solar thermal systems with substantial cost reduction by scalable production of multiscale hierarchically structured materials from micro-structured polymers.

Presenting Author: Pilgyu Kang George Mason Unviersity

Presenting Author Biography: Pilgyu Kang is an Assistant Professor in the Department of Mechanical Engineering and Affiliate Faculty in Department of Bioengineering and Department of Electrical and Computer Engineering at George Mason University. Prior to joining GMU, he conducted postdoctoral research at University of Illinois at Urbana-Champaign. He obtained his Ph.D. in Mechanical Engineering in 2014 at Cornell University and earned a M.S. degree in Mechanical Engineering in 2009 from Carnegie Mellon University. He earned a B.S. degree in Mechanical Engineering with a minor in Electrical Engineering in 2007 at Seoul National University. His research at the GMU focuses on Micro/Nano Scale Mechanics and Photonics with Atomically-Thin 2D Materials. His research aims to create high performance materials with new functionalities in mechanical, optical, electronic properties by using a main approach of nanostructuring 2D materials into 3D structures. He explores various fields including Nanophotonics, Optofluidic, Optoelectronics, and Plasmonics for broad applications of Nano Bio Sensors. Dr. Kang has published many papers in high impact journals including Nature Electronics and Advanced Materials, and his work has been recognized through a number of journal covers and reception of awards.

Authors:

Pilgyu Kang George Mason Unviersity
Byoung Gak Kim Korea Research Institute of Chemical Technology
Minsu Kim Korea Research Institute of Chemical Technology
Seung Min Lee George Mason University
Shirin Movaghgharnezhad George Mason University