Observation of strong direct-like oscillator strength in the photoluminescence of Si nanoparticles

Smith, Audrey; Yamani, Zain H.; Roberts, Nick A.; Turner, Jeff; Habbal, Shadia Rifai; Granick, Steve; Nayfeh, Munir H.

doi:10.1103/physrevb.72.205307

Cited by 48 publications

(44 citation statements)

References 44 publications

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“…28 exhibit more intense PL than larger ones. 29 The latter result is further supported by calculated mean sizes from theoretical correlations. 28 The PL decay times, , of species a were obtained from tri-exponential decay fittings of the PL traces detected at 450 nm upon 388 nm excitation (see in Table 1 These observations agree satisfactorily with reported cytotoxicity studies of SiNPs with surface attached amino groups.…”

Section: Silicon Nanoaparticles Characterization: the Analysis Of Thesupporting

confidence: 69%

Impact of Iron Incorporation on 2–4 nm Size Silicon Nanoparticles Properties

et al. 2015

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Iron-containing silicon nanoparticles were synthesized in an attempt to understand the effect of iron on the silicon nanoparticle (SiNP) photoluminescence and singletoxygen generation capacity. A wet chemical oxidation procedure of the sodium silicide precursor, obtained from the thermal treatment in anaerobic conditions of a mixture of sodium, silicon, and an iron (III) organic salt under anaerobic conditions, was employed. Surface-oxidized and propylamine-terminated SiNPs were characterized using high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, time-resolved and steady-state photoluminescence, and time-correlated fluorescence anisotropy. Based on differences in the morphology, crystal structure, density, and photoluminescence spectrum, two distinct types of SiNPs were identified in a given synthesis batch: iron-free and iron-containing SiNPs. The results show that iron is inhomogeneously incorporated in the SiNPs leading to an efficient photoluminescence quenching. Emission arrives mainly from 2 nm size iron-free SiNPs.The nanoparticles were shown to generate singlet oxygen ( 1 O 2 ) upon 355 nm irradiation, though they were able to quench 1 O 2 . Analysis of cytotoxicity using MTT assay on rat glioma C6 cells showed a strong dependence on the nature of the surface groups, as 100 g/ml of propylamine-terminated iron-containing SiNPs leads to 85% decrease in cell viability while equal amounts of surface oxidized particles induced a 35% of cell death.

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Section: Silicon Nanoaparticles Characterization: the Analysis Of Thesupporting

confidence: 69%

Impact of Iron Incorporation on 2–4 nm Size Silicon Nanoparticles Properties

et al. 2015

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“…The high measured quantum yield of the blue luminescence (0.60, k ex = 300 nm) [42] is in accord with previously reported values for other silicon nanoparticles (0.05-0.82). [13,[43][44][45] Although the intense blue luminescence of nanoparticles has been recently ascribed to a dipole allowed "direct band" transition, particularly associated with the smaller (∼ 1-2 nm) nanoparticles [46,47] , further experiments, including lifetime measurements, are still needed to definitively determine the origin of the PL in our systems. Finally, the silicon nanoparticles have been shown to maintain their PL intensity for at least 6 months in air.…”

mentioning

confidence: 97%

Mechanochemical Synthesis of Blue Luminescent Alkyl/Alkenyl‐Passivated Silicon Nanoparticles

Heintz¹,

Fink²,

Mitchell³

2007

Advanced Materials

143

118

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Silicon is a key material in the microelectronics industry. Recently, there has been great interest in nanocrystalline phases of silicon due to their size dependent electronic and optical properties.[1] Nanoparticles with physical dimensions less than the bulk Bohr exciton radius of silicon (4 nm) typically display intense photoluminescence due to quantum size effects and have potential use both in optoelectronic devices [2][3][4] and as fluorescent biomarkers. [5,6] In the case of crystalline silicon nanoparticles, the photoluminescence (PL) will shift to higher energies as the average size of the nanoparticles is reduced. [7,8] Particle sizes of the order of ∼ 1 nm have been termed "ultrabright" and show an intense emission in the blue region of the visible spectrum. [9][10][11] In addition to a dependence on the particle size, the photoluminesence of silicon nanoparticles is also influenced by the nature of the passivating layer on the particle surface. [12][13][14][15] Passivation of the surface provides chemical stability to air-oxidation and Ostwald ripening and also ties down defect states at the surface caused by dangling bonds. Successful passiviation of the silicon surface has been recently achieved by chemically inert alkyl groups. A surface passivated with strong Si-C bonds is chemically stable and the effective band gap of the silicon nanoparticle is relatively unperturbed by the alkyl passivation.[16] Alkyl passivated nanoparticles have been previously produced by chemical and electrochemical etching of bulk silicon, [17][18][19][20] the reduction of halosilanes, [21,22] the oxidation of metal silicides, [23,24] and the thermal decomposition of silanes in the gas phase [25][26][27] and supercritical fluids.[28] Each of these approaches requires the use of highly reactive or corrosive chemicals and often requires the modification of unstable hydrogen or halogen terminated surfaces. [29,30] Direct approaches, commonly involving the mechanical scribing of silicon in the presence of reactive organic reagents, have found success in the patterning of silicon surfaces though reaction of a freshly exposed surface with the organic reagent. [31][32][33][34] However, these techniques are limited to large and regular surfaces, and are not practical for use with nanoparticles. Here we describe a novel top-down procedure for the synthesis of stable alkyl/alkenyl passivated silicon nanoparticles using high energy ball milling (HEBM). [35] The main advantage of this mechanochemical approach is the simultaneous production of silicon nanoparticles and the chemical passivation of the particle surface by alkyl/alkenyl groups covalently linked through strong Si-C bonds. The overall procedure for production of alkyl/alkenyl passivated silicon nanoparticles is illustrated in Figure 1. A milling vial is loaded under inert atmosphere with non-spherical millimeter-sized pieces of semiconductor-grade silicon and either an alkene or alkyne. Stainless steel milling balls are added to the vial, which is then sealed and placed in...

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“…The particles are produced by dispersion of (100) oriented, 1 -10 ohm-cm resistivity, ptype boron doped Si, by lateral anodization in hydrogen peroxide and HF acid [15][16][17][18][19][20][21][22]26 . Subsequent immersion in an ultra-sound acetone or water bath dislodges the ultrasmall particles.…”

Section: Methodsmentioning

confidence: 99%

“…The particles are nearly spherical with 1 nm diameter, with insignificant size or shape dispersion 23 . The particles exhibit several novel properties including strong direct-like optical activity 18,19 , which enables detection of single particles 15 , gain and stimulated emission 16,17 , and nonlinear optical behavior, such as harmonic generation 20 . Electronically, electron affinity values drop to those characteristic of atoms and molecules, and single electron charging exceeds the thermal energy 21 .…”

Section: Methodsmentioning

confidence: 99%

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Observation of linear solid-solid phase transformation in silicon nanoparticles

et al. 2012

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In bulk single crystal silicon, the semiconducting diamond to metallic ß-Sn phase transformation nucleates on defects, and is manifested by a sharp uptake in light absorption at a threshold of ~ 11 Gpa, accompanied with the creation of nanosized (20-50 nm) fragmentation domains. We report on the observation of linear uptakes in the absorption and in the luminescence, and with insignificant spectral change in ultrasmall 1 nm Si particles. We associate the gradual absorption uptake and luminescence yield with silicon-metal transformation on the surface. The insignificant change in the spectral content of the luminescence points to surface stability for particles, which are smaller than the bulk fragmentation domain. First-principle atomistic calculations yield absorption behavior that exhibits gradual uptake followed by sharp uptake at ~ 9-11 Gpa. The results point to the conclusion that two dimensional surface-like phase transformations are manifested by linear uptake in absorption and luminescence. a) m-nayfeh@illinois.edu 2

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Observation of strong direct-like oscillator strength in the photoluminescence of Si nanoparticles

Cited by 48 publications

References 44 publications

Impact of Iron Incorporation on 2–4 nm Size Silicon Nanoparticles Properties

Impact of Iron Incorporation on 2–4 nm Size Silicon Nanoparticles Properties

Mechanochemical Synthesis of Blue Luminescent Alkyl/Alkenyl‐Passivated Silicon Nanoparticles

Observation of linear solid-solid phase transformation in silicon nanoparticles

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