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Interface Components: Nanoparticles, Colloids, Emulsions, Surfactants, Proteins, Polymers
Close-packed Langmuir Monolayers of SaccharideBased Carbon Dots at the Air-Subphase Interface Elif S. Seven, Shiv Kumar Sharma, Dihya Meziane, Yiqun Zhou, Keenan J. Mintz, Raja R. Pandey, Charles C Chusuei, and Roger M. Leblanc Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.9b00920 • Publication Date (Web): 30 Apr 2019 Downloaded from http://pubs.acs.org on May 3, 2019
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Langmuir
Close-packed Langmuir Monolayers of SaccharideBased Carbon Dots at the Air-Subphase Interface Elif S. Seven1, Shiv K. Sharma1, Dihya Meziane1, Yiqun Zhou1, Keenan J. Mintz1, Raja R. Pandey2, Charles C. Chusuei2 and Roger M. Leblanc1* 1Department
of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, Florida 33146, United States 2Department
of Chemistry, Middle Tennessee State University, 2672 Greenland Drive, Murfreesboro, TN 37132, United States
*Corresponding author E-mail:
[email protected] 1 ACS Paragon Plus Environment
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Abstract Carbon dots (CDs) are zero-dimensional carbon-based spherical nanoparticles with diameters less than 10 nm. Here we report for the first time CDs forming stable Langmuir monolayers at the airsubphase interface. Langmuir monolayers are of great interest both fundamentally to study the interactions at the interfaces and for many applications such as the development of sensors. However, CDs usually don’t form Langmuir monolayers because of their highly hydrophilic nature. In this study, amphiphilic CDs were prepared through hydrothermal carbonization using saccharides as the precursor. The surface chemistry behavior and optical properties of CDs at the air-subphase interface were studied. CDs derived from saccharides are consistently formed stable Langmuir monolayers which show all the essential phases, namely gas, liquid expanded, liquid condensed and solid phases. Compression-decompression cycle method showed minimum hysteresis (4.3%) confirming the retaining capacity of the CDs as a monolayer. Limiting CD areas from surface pressure-area isotherm at the air-subphase interface were used to calculate the average diameter of CDs at the air-subphase interface. UV/vis absorption spectra of CDs dispersed in water and in Langmuir monolayers had the same bands in UV region. The intensity of the UV/vis absorption increases with increasing surface pressure at the air-subphase interface. Interestingly, PL of the Langmuir monolayer of CDs was excitation independent while the same CDs had excitation dependent PL when dispersed in water.
Keywords: Carbon Dots, Langmuir monolayer, Photoluminescence, Self-assembly, saccharides
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Langmuir
Introduction Carbon dots (CDs) are a new type of zero-dimensional carbon-based nanomaterials discovered in 2004 during the synthesis of carbon nanotubes.1 Since their discovery, CDs have attracted tremendous attention because of their unique photoluminescence (PL) properties, small size (
