Functional double-shelled silicon nanocrystals for two-photon fluorescence cell imaging: spectral evolution and tuning

Abstract

Functional near-IR (NIR) emitting nanoparticles (NPs) adapted for two-photon excitation fluorescence cell imaging were obtained starting from octadecyl-terminated silicon nanocrystals (ncSi-OD) of narrow photoluminescence (PL) spectra having no long emission tails, continuously tunable over the 700-1000 nm window, PL quantum yields exceeding 30%, and PL lifetimes of 300 μs or longer. These NPs, consisting of a Pluronic F127 shell and a core made up of assembled ncSi-OD kept apart by an octadecyl (OD) layer, were readily internalized into the cytosol, but not the nucleus, of NIH3T3 cells and were non-toxic. Asymmetrical field-flow fractionation (AF4) analysis was carried out to determine the size of the NPs in water. HiLyte Fluor 750 amine was linked via an amide link to NPs prepared with Pluronic-F127-COOH, as a first demonstration of functional NIR-emitting water dispersible ncSi-based nanoparticles.

Origin of the Photoluminescence Quantum Yields Enhanced by Alkane-Termination of Freestanding Silicon Nanocrystals: Temperature-Dependence of Optical Properties

“…Intensive studies are ongoing into freestanding silicon nanocrystals (ncSi), which is a promising material for applications including light emitting diodes (LEDs)123, optically-pumped lasers4, optical switching devices5, sensors67, hydrogen storage8, field-effect transistors9, solar photovoltaics1011, medical and biological applications12131415, photodiodes16, and lithium-ion batteries17. The appeal of ncSi in these applications is largely a result of its exceptional properties of nontoxicity18, continuous tunability of photoluminescence (PL) over a broad spectral range from UV to near-IR19, third-order nonlinear optical behavior2021, robustness of the covalent Si-Si bond versus ionic bonds, high compatibility with microelectronics, and being an abundant element.…”

Interaction of polymer-coated silicon nanocrystals with lipid bilayers and surfactant interfaces

“…Silicon currently dominates the microelectronics industry but has achieved limited success in the realm of photonics, in part because of relatively poor bulk optical characteristics (e.g., weak photoluminescence, indirect bandgap). At the nanoscale, however, the emission characteristics of silicon are greatly enhanced by changes in band structure imposed by quantum confinement, and a variety of routes to hydrophilic colloidal silicon nanocrystals (SiNCs) have emerged in just the past few years [11][12][13][14][15][16][17][18][19][20][21]. Although many of these provide broad color access with bright emission and single-particle dispersion, polyethylene glycol (PEG) remains the coating of choice [22].…”

Transition‐Metal‐Doped NIR‐Emitting Silicon Nanocrystals

“…Ther esulting (HSiO 1.5 ) n gel [9] loaded with metal ions is subjected to thermal disproportionation, HF-etching and hydrosilylation with octadecene,yielding free-standing metal-doped SiNCs (Figure 1). A related approach was used previously to prepare from blue- [10] to red-to-NIR-emitting SiNCs of high PL QY and outstanding photostability.…”

“…Like SiNCs, [9] metaldoped SiNCs absorb light over the entire UV range,w ith aweak tail in the visible range (Figure 4a,left axis). Their PL spectra exhibit narrow emission bands,c entered at 985, 992, and 1000 nm for Mn, Ni, and Co,r espectively,w hich correspond to red-shifts of 67, 74, and 82 nm, compared to the emission of SiNC (918 nm) (Figure 4a,b).…”

“…[23] Undoped SiNCs grown at 900 8 8Cs how an exceptionally short PL lifetime,c ompared to all the other SiNCs described, which may be related to the poor crystal- linity of SiNCs grown at 900 8 8C, which facilitates nonradiative decay through defects and shortens the PL lifetime. [24] In summary,wehave described anew synthesis of metaldoped SiNCs that enabled us to prepare the first near-IRemitting metal-doped SiNCs.W emonitored the effects of the synthesis parameters and the dopant nature and composition on the structural and photophysical properties of dopedSiNCs.Because organophilic nanocrystals,such as the doped SiNCs prepared, can be converted into stable water-dispersible nanoparticles through known interfacial transfer processes, [9] this study leads the way towards bimodal medical imaging agents of low toxicity and strong emission in the biological window.…”