Open AccessEPR and Structural Characterization of Water-Soluble Mn2+-Doped Si Nanoparticles
Author(s) -
Tonya M. Atkins,
Jeffrey H. Walton,
Mukesh Kumar Singh,
Shreyashi Ganguly,
Oliver Janka,
Angelique Y. Louie,
Susan M. Kauzlarich
Publication year - 2017
Publication title -
journal of physical chemistry. c./journal of physical chemistry. c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.401
H-Index - 289
eISSN - 1932-7455
pISSN - 1932-7447
DOI - 10.1021/acs.jpcc.6b11000
Subject(s) - photoluminescence , high resolution transmission electron microscopy , electron paramagnetic resonance , transmission electron microscopy , materials science , nanoparticle , analytical chemistry (journal) , doping , crystallography , nuclear magnetic resonance , chemistry , nanotechnology , physics , organic chemistry , optoelectronics
Water-soluble poly(allylamine) Mn 2+ -doped Si (Si Mn ) nanoparticles (NPs) were prepared and show promise for biologically related applications. The nanoparticles show both strong photoluminescence and good magnetic resonance contrast imaging. The morphology and average diameter were obtained through transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM); spherical crystalline Si NPs with an average diameter of 4.2 ± 0.7 nm were observed. The doping maximum obtained through this process was an average concentration of 0.4 ± 0.3% Mn per mole of Si. The water-soluble Si Mn NPs showed a strong photoluminescence with a quantum yield up to 13%. The Si Mn NPs had significant T 1 contrast with an r 1 relaxivity of 11.1 ± 1.5 mM -1 s -1 and r 2 relaxivity of 32.7 ± 4.7 mM -1 s -1 where the concentration is in mM of Mn 2+ . Dextran-coated poly(allylamine) Si Mn NPs produced NPs with T 1 and T 2 contrast with a r 1 relaxivity of 27.1 ± 2.8 mM -1 s -1 and r 2 relaxivity of 1078.5 ± 1.9 mM -1 s -1 . X-band electron paramagnetic resonance spectra are fit with a two-site model demonstrating that there are two types of Mn 2+ in these NP's. The fits yield hyperfine splittings ( A ) of 265 and 238 MHz with significant zero field splitting ( D and E terms). This is consistent with Mn in sites of symmetry lower than tetrahedral due to the small size of the NP's.