Chemical Transformation of Carboxyl Groups on the Surface of Silicon Carbide Quantum Dots

Abstract

Silicon carbide quantum dots in the size range of 1-10 nm are in the center of interest with unique properties that makes them very promising biomarkers. A central requirement for this application is the control over the complex structure of the surface to enable further surface functionalization processes, which are crucial for drug delivery.In this paper a temperature dependent infrared and photoluminescence spectroscopy study, combined with ab initio modeling, is presented in order to reveal the chemical transformations of the surface termination groups. We found that at temperatures above 370 K acid anhydride groups form by condensation of water between neighboring * To whom correspondence should be addressed 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 carboxyl groups. The presence of the anhydride groups reveals the proximity of the carboxyl groups, and represents a new possibility of selective engineering of new hybrid materials involving silicon carbide quantum dots.

Electrochemical Synthesis of Carbon Fluorooxide Nanoparticles from 3C-SiC Substrates

“…is practically explored in our work for the first time. Indeed, formation of "carbon-enriched layers" on the HF-etched SiC surface was observed before 11,35 and closely studied recently 36,37 , however, exact composition of a colored soluble etching products was, on our knowledge, not characterized up to now.…”

Identification of Luminescence Centers in Molecular-Sized Silicon Carbide Nanocrystals

“…NCs of diameter between 1-4 nm were terminated with a variety of oxygen-containing species with high concentration of carboxyl groups 15 that we label by 'as-prepared'. We prepared -OH, -H and -SiO x ter- prepared sample shows a strong and broad peak at around 3300 cm -1 because of the strongly hydrogenbonded OH groups on the surface and hydrogen-bonded water molecules 15 .…”

“…15,17,21 The details about the methodology are given in the SI. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 the nanocrystals, respectively) iv) majority of the hydrogen atoms substituted with -OH groups on both the silicon-and carbon-terminated faces of the nanocrystal, the remaining hydrogen atoms substituted with -COO -Na + moieties; v) hydrogen atoms substituted with -OH groups on the silicon terminated surface while the carbon atoms on the originally carbon terminated surface were substituted with oxygen atoms to form a thin SiO 2 layer.…”

“…While small SiC nanocrystals are often interpreted as a piece of bulk semiconductor 18 , recent studies 15,16 imply that SiC NCs in aqueous environment may be described as complex macromolecules with formula Si x C y O z (H). The surface modification of this complex system with a core of crystalline SiC can drastically affect its optical properties, as shown by previous theoretical calculations 15 . Ex-perimental results established that the optical properties of SiC NCs are also influenced by the environment and by intramolecular interactions 12,15,16,19,20 .…”

Dominant luminescence is not due to quantum confinement in molecular-sized silicon carbide nanocrystals

“…It also exhibits great application potential in ultraviolet (UV) photodiodes 4 , spintronics 5, 6 and quantum information processing 7,8,9 . Experimental results 24,25 and theoretical calculations showed that the luminescence of SiC NCs is strongly influenced by the surface groups 26 . These polytypes are identical in two dimensions (hexagonal basal plane) and differ in the Si-C bilayer sequences in the third dimension (c-axis perpendicular to the basal plane) 10 .…”