Direct Production of Graphene Nanosheets for Near Infrared Photoacoustic Imaging
| Autor: | Pui Lam Chiu, Huabei Jiang, Daniel Mastrogiovanni, Keerthi Savaram, Mehulkumar Patel, Eric Garfunkel, Ashley Hemnarine, Hao Yang, Carol R. Flach, Huixin He, Richard Mendelsohn, Lesly Gomez |
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| Jazyk: | angličtina |
| Rok vydání: | 2013 |
| Předmět: |
Materials science
Fabrication Infrared Rays Oxide General Physics and Astronomy Nanotechnology Sensitivity and Specificity law.invention Photoacoustic Techniques chemistry.chemical_compound Optoacoustic spectroscopy law Materials Testing Oxidation Nitronium ion General Materials Science Graphite Particle Size Graphene oxides (GO) Microwaves Graphene oxide paper Nanosheet Phantoms Imaging Graphene General Engineering Reproducibility of Results Membranes Artificial Nitronium ions Graphene nanosheets Image Enhancement Graphene--Oxidation chemistry Microwave chemistry Elasticity Imaging Techniques Nanoparticles Photoacoustic imaging Graphene nanoribbons |
| DOI: | 10.7282/t3r21398 |
| Popis: | Hummers method is commonly used for the fabrication of graphene oxide (GO) from graphite particles. The oxidation process also leads to the cutting of graphene sheets into small pieces. From a thermodynamic perspective, it seems improbable that the aggressive, somewhat random oxidative cutting process could directly result in graphene nanosheets without destroying the intrinsic π-conjugated structures and the associated exotic properties of graphene. In Hummers method, both KMnO4 and NO2(+) (nitronium ions) in concentrated H2SO4 solutions act as oxidants via different oxidation mechanisms. From both experimental observations and theoretical calculations, it appears that KMnO4 plays a major role in the observed oxidative cutting and unzipping processes. We find that KMnO4 also limits nitronium oxidative etching of graphene basal planes, therefore slowing down graphene fracturing processes for nanosheet fabrication. By intentionally excluding KMnO4 and exploiting pure nitronium ion oxidation, aided by the unique thermal and kinetic effects induced by microwave heating, we find that graphite particles can be converted into graphene nanosheets with their π-conjugated aromatic structures and properties largely retained. Without the need of any postreduction processes to remove the high concentration of oxygenated groups that results from Hummers GO formation, the graphene nanosheets as-fabricated exhibit strong absorption, which is nearly wavelength-independent in the visible and near-infrared (NIR) regions, an optical property typical for intrinsic graphene sheets. For the first time, we demonstrate that strong photoacoustic signals can be generated from these graphene nanosheets with NIR excitation. The photo-to-acoustic conversion is weakly dependent on the wavelength of the NIR excitation, which is different from all other NIR photoacoustic contrast agents previously reported. |
| Databáze: | OpenAIRE |
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