Identification of Luminescence Centers in Molecular-Sized Silicon Carbide Nanocrystals

Abstract

Understanding the fluorescence of complex systems such as small nanocrystals with various surface terminations in solution is still a scientific challenge. Here we show that the combination of advanced time-resolved spectroscopy and ab initio simulations, aided by surface engineering, is able to 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 2 identify the luminescence centers of such complex systems. Fluorescent water soluble silicon carbide (SiC) nanocrystals have been previously identified as complex molecular systems of silicon, carbon, oxygen and hydrogen held together by covalent bonds that made the identification of their luminescence centers unambiguous. The aqueous solutions of molecular-sized SiC nanocrystals are exceedingly promising candidates to realize bioinert non-perturbative fluorescent nanoparticles for in vivo bioimaging, thus the identification of their luminescent centers is of immediate interest. Here we present identification of two emission centers of this complex system: surface groups involving carbon -oxygen bonds and a defect consisting of silicon -oxygen bonds which becomes the dominant pathway for radiative decay after total reduction of the surface. The identification of these luminescent centers reconciles previous experimental results on the surface and pH dependent emission of SiC nanocrystals and helps design optimized fluorophores and nanosensors for in vivo bioimaging.

Immunomodulatory Potential of Differently-Terminated Ultra-Small Silicon Carbide Nanoparticles

“…The particles were then terminated with a variety of oxygen-containing species with a high concentration of carboxyl groups [33]. The preparation of the OH-terminated nanoparticles (SiC-OH) involved the reduction of SiC-x NPs via NaBH 4 in an aqueous solution [34]. The SiC-OH were then silanized for the preparation of the SiC-NH 2 particles.…”

Reversible/Irreversible Photobleaching of Fluorescent Surface Defects of SiC Quantum Dots: Mechanism and Sensing of Solar UV Irradiation

“…Therefore, the SiC QDs can be used as stable light sources for sensors, cell imaging, and light‐emitting diodes . On the other hand, the surface of the SiC QD offers fruitful emission colors owing to existence of various surface defect‐related luminescence centers . For the SiC QDs with very small sizes, their surface defects play important roles in luminescence .…”

“…On the other hand, the surface of the SiC QD offers fruitful emission colors owing to existence of various surface defect‐related luminescence centers . For the SiC QDs with very small sizes, their surface defects play important roles in luminescence . The study had indicated that for the SiC QDs smaller than 1 nm, the surface defect‐related luminescence dominates .…”

“…For the SiC QDs with very small sizes, their surface defects play important roles in luminescence . The study had indicated that for the SiC QDs smaller than 1 nm, the surface defect‐related luminescence dominates . There have been heated investigations on the luminescent defects in SiC.…”

“…There have been heated investigations on the luminescent defects in SiC. It was reported that elimination of both carboxy and hydroxyl groups causes dramatic blue shift of photoluminescence (PL) of the SiC QDs . The calculation suggests that the H‐terminated 4H‐SiC QD has pronounced interband light absorption, whereas the OH‐ or F‐terminations result in surface defects‐related light absorption .…”