Carboxyl functionalization of ultrasmall luminescent silicon nanoparticles through thermal hydrosilylation

Rogozhina, Elena V.; Eckhoff, Dean A.; Gratton, Enrico; Braun, Paul V.

doi:10.1039/b509868h

Cited by 89 publications

(91 citation statements)

References 66 publications

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“…This modification preserves the strong PL of the Si core, adds a hydrophilic interface for stability in aqueous media, and is easily reacted with primary amines to label biomolecules, all while adding only a small amount to the overall size. 7 Work with the Si and Ge systems has also shown that surface chemistry can play a more direct role in their photophysical behavior. The analysis has generally focused on the source of PL and the debate between the quantum confinement (delocalized) and surface state (localized) mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Optical Characterization of Ultrasmall Si Nanoparticles Prepared through Electrochemical Dispersion of Bulk Si

Eckhoff¹,

Sutin²,

Clegg³

et al. 2005

J. Phys. Chem. B

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Studying the properties and stability of silicon nanoparticles (Si-np) in aqueous environments may lead to novel applications in biological systems. In this work, we use absorption and photoluminescence (PL) spectroscopy to characterize ultrasmall Si-np prepared through anodic etching and ultrasonic fractionation of a crystalline Si wafer. Their behavior is studied over time in 2-propanol and during treatments with water, NaOH, HCl, and H 2 O 2 . The observed population is divided into two types of material: bright species consisting of well-etched Si-np, ∼1 nm in diameter, and dark species derived from partially etched or aggregated Si structures. The dark material is seen by its scattering in the 2-propanol and water solutions and is largely removed via precipitation with the NaOH or HCl treatment. The bright material includes three distinct species with their respective emissions in the UV-B, UV-A, and hard-blue regions of the spectrum. The hard-blue PL is shown to have a simple pH dependence with a pK a ∼3, providing an important insight into its chemical origin and signaling for possible application of Si-np as environmental probes. Our results offer some potential for tailoring the PL properties of ultrasmall Si-np through control of their surface chemistry.

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Section: Introductionmentioning

confidence: 99%

Optical Characterization of Ultrasmall Si Nanoparticles Prepared through Electrochemical Dispersion of Bulk Si

Eckhoff¹,

Sutin²,

Clegg³

et al. 2005

J. Phys. Chem. B

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“…10 The Si-np-COOH were shown to preserve the strong fluorescence of the Si core, have sizes comparable to small organic fluorophores ͑ϳ1 nm͒, and to be stable in polar solutions. The carboxyl functionality can also be reacted with primary amines to attach them to various biomolecules.…”

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confidence: 99%

Capillary electrophoresis of ultrasmall carboxylate functionalized silicon nanoparticles

Eckhoff

Stuart

Sutin

et al. 2006

The Journal of Chemical Physics

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Capillary electrophoresis is used to separate ultrasmall (∼1nm) carboxylate functionalized Si nanoparticles (Si-np-COO−) prepared via hydrosilylation with an ω-ester 1-alkene. The electropherograms show a monodisperse Si core size with one or two carboxylate groups added to the surface. On-column detection of their laser-induced fluorescence demonstrates that the individual Si-np-COO− have narrow emissions (full width at half maximum =30–40nm) with a nearly symmetric lineshape. Preparative scale electrophoresis should be a viable route for purification of the Si-np-COO− for further study and future applications.

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“…As can be seen in Figure 2.1, the IR spectrum of the dried polymer contains overlapping peaks at 1050 cm -1 and 1090 cm -1 , both of which are in the region that has been attributed to Si-O bonding. 9,34,40,47,58,63,69,72,[75][76][77][78][79][80][81][82][83] Evidence for the preservation of Si-H bonding is also shown by the peak at 2240 cm -1 in the IR spectrum.…”

Section: Synthesis Of Polymeric Hsio 15 From Hsiclmentioning

confidence: 91%

“…[36][37][38][39] In addition, Si NPs have been envisioned as replacements for traditional organic dyes in a variety of sensing and tracking applications owing to their strong visible PL and superior resistance to photobleaching and photodegredation. 22,23,[40][41][42] For biomedical imaging and sensing applications, red-to-NIR-fluorescence is desired, since these wavelengths penetrate tissue, and do not damage cells. While the number of red-to-NIR-emitting molecular organic dyes is limited (e.g., to…”

Section: Technological Developments Leading To Photoluminescent Siliconmentioning

confidence: 99%

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Investigation into Effects of Instability and Reactivity of Hydride-Passivated Silicon Nanoparticles on Interband Photoluminescence

Radlinger¹

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While silicon has long been utilized for its electronic properties, its use as an optical material has largely been limited due to the poor efficiency of interband transitions. However, discovery of visible photoluminescence (PL) from nanocrystalline silicon in 1990 triggered many ensuing research efforts to optimize PL from nanocrystalline silicon for optical applications. Currently, use of photoluminescent silicon nanoparticles (Si NPs) is commercially limited by: 1) the instability of the energy and intensity of the PL, and 2) the low quantum yield of interband PL from Si NPs.Herein, red-emitting, hydrogen-passivated silicon nanoparticles (H-Si NPs) were synthesized by thermally-induced disproportionation of a HSiCl 3 -derived (HSiO 1.5 )n polymer. The H-Si NPs produced by this method were then subjected to various chemical and physical environments to assess the long-term stability of the optical properties as a function of changing surface composition. This dissertation is intended to elucidate correlations between the reported PL instability and the observed changes in the Si NP surface chemistry over time and as a function of environment.First, the stability of the H-Si NP surface at slightly elevated temperatures towards reactivity with a simple alkane was probed. The H-Si NPs were observed by FT-IR spectroscopy to undergo partial hydrosilylation upon heating in refluxing hexane, in addition to varying degrees of surface oxidation. The unexpected reactivity of the Si surface in n-hexane supports the unstable nature of the H-Si NP surface, and furthermore implicates the presence of highly-reactive Si radicals on the surfaces of the Si NPs. We propose that reaction of alkene impurities with the Si surface radicals is largely responsible for the observed surface alkylation. However, we also present an alternate ii mechanism by which Si surface radicals could react with alkanes to result in alkylation of the surface.Next, the energy and intensity stability of the interband PL from H-Si NPs in the presence of a radical trap was probed. Upon addition of (2,2,6,6,-tetramethyl-piperidin-1-yl)oxyl (TEMPO), the energy and intensity of the interband transition was observed to change over time, dependent on the reaction conditions. First, when the reaction occurred at 4ºC with minimal light exposure, the interband transition exhibited a gradual hypsochromic shift to between 595 nm and 655 nm, versus the λ max of the original low energy emission peak at 700 nm, depending on the amount of TEMPO in the sample.Second, when the reaction proceeded at room temperature with frequent exposure to 360 nm irradiation, the original interband transition at 660 nm was quenched while a new peak at 575 nm developed. Based on all the data collected and analyzed, we assign the 595 -655 nm transition as due to interband exciton recombination from Si NPs with reduced diameters relative to the original Si NPs. We furthermore assign the 575 nm transition as due to an oxide-related defect state resulting from rapid oxidation of pho...

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Carboxyl functionalization of ultrasmall luminescent silicon nanoparticles through thermal hydrosilylation

Cited by 89 publications

References 66 publications

Optical Characterization of Ultrasmall Si Nanoparticles Prepared through Electrochemical Dispersion of Bulk Si

Optical Characterization of Ultrasmall Si Nanoparticles Prepared through Electrochemical Dispersion of Bulk Si

Capillary electrophoresis of ultrasmall carboxylate functionalized silicon nanoparticles

Investigation into Effects of Instability and Reactivity of Hydride-Passivated Silicon Nanoparticles on Interband Photoluminescence

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