Synthesis of Water-Soluble Blue Photoluminescent Silicon Nanocrystals with Oxide Surface Passivation

Small ◽  
2009 ◽  
Vol 5 (1) ◽  
pp. 72-76 ◽  
Author(s):  
Sheng-Wei Lin ◽  
Dong-Hwang Chen
Keyword(s):  
Silicon Nanocrystals ◽  
Surface Passivation ◽  
Water Soluble ◽  
Oxide Surface

Comparative Optical Studies of Chemically Synthesized Silicon Nanocrystals

1996 ◽  
Vol 452 ◽  
Author(s):  
Gildardo R. Delgado ◽  
Howard W.H. Lee ◽  
Susan M. Kauzlarich ◽  
Richard A. Bley
Keyword(s):  
Porous Silicon ◽  
Silicon Nanocrystals ◽  
Surface Passivation ◽  
Theoretical Calculations ◽  
Dominant Role ◽  
Blue Emission ◽  
Surface States ◽  
Si Nanocrystals ◽  
Optical And Electronic Properties ◽  
Passivation Layers

AbstractWe studied the optical and electronic properties of silicon nanocrystals derived from two distinct fabrication procedures. One technique uses a controlled chemical reaction. In the other case, silicon nanocrystals are produced by ultrasonic fracturing of porous silicon layers. We report on the photoluminescence, photoluminescence excitation, and absorption spectroscopy of various size distributions derived from these techniques. We compare the different optical properties of silicon nanocrystals made this way and contrast them with that observed in porous silicon. Our results emphasize the dominant role of surface states in these systems as manifested by the different surface passivation layers present in these different fabrication techniques. Experimental absorption measurements are compared to theoretical calculations with good agreement. Our results provide compelling evidence for quantum confinement in both types of Si nanocrystals. Our results also indicate that the blue emission from very small Si nanocrystals corresponds to the bandedge emission, while the red emission arises from traps.

Influence of reaction parameters on the photoluminescence properties of free standing functionalized silicon nanocrystals

2010 ◽  
Vol 1260 ◽  
Author(s):  
Anoop Gupta ◽  
Hartmut Wiggers
Keyword(s):  
Optical Properties ◽  
Surface Functionalization ◽  
Silicon Nanocrystals ◽  
Organic Molecules ◽  
Surface Passivation ◽  
Light Emission ◽  
Emission Spectra ◽  
Surface Oxidation ◽  
Free Standing ◽  
The Stability

AbstractWhile silicon nanostructures acquire novel optical properties due to miniaturization, the stability of light emission is severely limited because of exciton trapping due to surface oxidation coming along with the formation of defects. Grafting of organic molecules on a hydrogen-terminated silicon surface via hydrosilylation provides a promising route to stabilize their surface against oxidation. In this communication, we report on the effect of surface passivation on the optical properties of freestanding silicon nanocrystals (Si-NCs). The surface functionalization of hydrogen-terminated Si-NCs with organic molecules was achieved via liquid phase hydrosilylation. We demonstrate that surface functionalization does not preserve the original emission of hydrogen-terminated Si-NCs. It is observed that the emission spectrum of green emitting hydrogen-terminated Si-NCs is red shifted after surface functionalization. We find that the direction of shift does not depend on the type of organic ligands and the reaction conditions, however, the amount of shift can be altered. The factors influencing the shift in the emission spectra of functionalized Si-NCs with respect to hydrogen-terminated samples are discussed.

Improved size dispersion of silicon nanocrystals grown in a batch LPCVD reactor

2004 ◽  
Vol 830 ◽  
Author(s):  
Y. M. Wan ◽  
K. van der Jeugd ◽  
T. Baron ◽  
B. De Salvo ◽  
P. Mur
Keyword(s):  
Silicon Nanocrystals ◽  
Batch Reactor ◽  
Chemical Vapor ◽  
Nucleation And Growth ◽  
Oxide Surface ◽  
Growth Step ◽  
Step Process ◽  
Pressure Chemical ◽  
Higher Temperature ◽  
Size Dispersion

ABSTRACTNanocrystal memories are widely invoked as potential solutions to overcome the scaling limitations of conventional FLASH memories beyond the 80nm technology node. In this study, the deposition of uniform silicon nanocrystals has been developed and optimized in a commercially available vertical furnace, an A400 from ASM.It has been shown that low pressure chemical vapor deposition (LPCVD) of nanocrystals is feasible in a batch reactor but with a bad size dispersion of the silicon nanocrystals. To improve the size dispersion of the nanocrystals, a novel 2-step process with silane was introduced. In the conventional 1-step process, the oxide surface is exposed to silane at the same partial pressure and temperature during both nucleation and growth of the silicon nanocrystals. In this novel 2-step process, the surface is first exposed briefly to silane at a higher temperature (580–600°C) and following that, the temperature is lowered to allow selective growth on the existing silicon nuclei over the oxide surface. With such an approach, the nucleation step can be separated from the growth step and consequently the size dispersion can be improved by 50%.

Water-soluble silicon nanocrystals as NIR luminescent probes for time-gated biomedical imaging

Nanoscale ◽  
2020 ◽  
Vol 12 (14) ◽  
pp. 7921-7926 ◽  
Author(s):  
Francesco Romano ◽  
Sara Angeloni ◽  
Giacomo Morselli ◽  
Raffaello Mazzaro ◽  
Vittorio Morandi ◽  
...  
Keyword(s):  
Silicon Nanocrystals ◽  
Signal To Noise Ratio ◽  
Water Soluble ◽  
Signal To Noise ◽  
Luminescent Probes ◽  
Guided Surgery ◽  
Tumor Accumulation ◽  
Gated Imaging ◽  
Soluble Silicon

In vivo studies demonstrated tumor accumulation of luminescent SiNCs, 48 hours clearance and a 3-fold improvement of signal-to-noise ratio in time-gated imaging compared to steady-state acquisition, demonstrating their potentiality for luminescence guided surgery.

scholarly journals Polyimide-Coated Glass Microfiber as Polysulfide Perm-Selective Separator for High-Performance Lithium-Sulphur Batteries

Nanomaterials ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1612 ◽  
Author(s):  
Mi-Jin Kim ◽  
Kwansoo Yang ◽  
Hui-Ju Kang ◽  
Hyun Jin Hwang ◽  
Jong Chan Won ◽  
...  
Keyword(s):  
High Performance ◽  
Surface Passivation ◽  
Specific Capacity ◽  
Composite Cathode ◽  
Amic Acid ◽  
Water Soluble ◽  
Carbon Cloth ◽  
Free Standing ◽  
Metal Anode ◽  
Capacity Loss

Although numerous research efforts have been made for the last two decades, the chronic problems of lithium-sulphur batteries (LSBs), i.e., polysulfide shuttling of active sulphur material and surface passivation of the lithium metal anode, still impede their practical application. In order to mitigate these issues, we utilized polyimide functionalized glass microfibers (PI-GF) as a functional separator. The water-soluble precursor enabled the formation of a homogenous thin coating on the surface of the glass microfiber (GF) membrane with the potential to scale and fine-tune: the PI-GF was prepared by simple dipping of commercial GF into an aqueous solution of poly(amic acid), (PAA), followed by thermal imidization. We found that a tiny amount of polyimide (PI) of 0.5 wt.% is more than enough to endow the GF separator with useful capabilities, both retarding polysulfide migration. Combined with a free-standing microporous carbon cloth-sulphur composite cathode, the PI-GF-based LSB cell exhibits a stable cycling over 120 cycles at a current density of 1 mA/cm2 and an areal sulphur loading of 2 mgS/cm2 with only a marginal capacity loss of 0.099%/cycle. This corresponds to an improvement in cycle stability by 200%, specific capacity by 16.4%, and capacity loss per cycle by 45% as compared to those of the cell without PI coating. Our study revealed that a simple but synergistic combination of porous carbon supporting material and functional separator enabled us to achieve high-performance LSBs, but could also pave the way for the development of practical LSBs using the commercially viable method without using complicated synthesis or harmful and expensive chemicals.

Inert Gas Condensation of Iron and Iron-Oxide Nanoparticles

2002 ◽  
Vol 746 ◽  
Author(s):  
C. Baker ◽  
S. Ismat Shah ◽  
S. K. Hasanain ◽  
B. Ali ◽  
L. Shah ◽  
...  
Keyword(s):  
Saturation Magnetization ◽  
Surface Passivation ◽  
Volume Fraction ◽  
Passivation Layer ◽  
Inert Gas ◽  
Oxide Surface ◽  
Fe Oxide ◽  
Gas Condensation ◽  
Inert Gas Condensation ◽  
20 Nm

ABSTRACTAn inert gas condensation technique has been used to prepare nanometer-sized particles of metallic iron by evaporation and agglomeration in a flowing inert gas stream. The resulting Fe nanoparticles were protected from complete oxidation either by the formation of a thin Fe-oxide surface passivation layer or by immersion in an oil bath. X-ray diffraction and transmission electron microscopy measurements indicated that the nanoparticles were typically between 10 and 20 nm in size, that the thickness of the Fe-oxide surface passivation layer was between 3 and 4 nm, and that the oil immersed samples exhibited a significant smaller volume fraction of Fe-oxides than did the surface passivated samples. Room temperature magnetization measurements were also carried out and the coercivity and saturation magnetization of the surface passivated and oil immersed samples determined. Although the coercivities and saturation magnetization values of both samples were very similar, the Fe/Fe-oxide samples exhibited a single component hysteresis loop while the Fe/oil samples exhibited a two component loop.

Demonstration of c-Si Solar Cells With Gallium Oxide Surface Passivation and Laser-Doped Gallium p+Regions

2015 ◽  
Vol 5 (6) ◽  
pp. 1586-1590 ◽  
Author(s):  
Thomas G. Allen ◽  
Marco Ernst ◽  
Christian Samundsett ◽  
Andres Cuevas
Keyword(s):  
Solar Cells ◽  
Gallium Oxide ◽  
Surface Passivation ◽  
Oxide Surface ◽  
Si Solar Cells

Plasma Synthesis and Surface Passivation of Silicon Quantum Dots with Photoluminescence Quantum Yields higher than 60%

2006 ◽  
Vol 934 ◽  
Author(s):  
Lorenzo Mangolini ◽  
David Jurbergs ◽  
Elena Rogojina ◽  
Uwe Kortshagen
Keyword(s):  
Quantum Dots ◽  
Silicon Nanocrystals ◽  
Room Temperature ◽  
Surface Passivation ◽  
Organic Ligands ◽  
Quantum Yields ◽  
Plasma Synthesis ◽  
Silicon Quantum Dots ◽  
Chemical Surface ◽  
Wet Chemical

ABSTRACTSilicon nanocrystals with diameters of less than 5 nm show efficient room temperature pho-toluminescence (PL). Previous reports of PL quantum yields for ensembles of silicon quantum dots have usually been in the few percent range, and generally less than 30%. Here we report the plasma synthesis of silicon quantum dots and their subsequent wet-chemical surface passivation with organic ligands while strictly excluding oxygen. Photoluminescence quantum yields as high as 62% have been achieved at peak wavelengths of about 789 nm.

Sign in / Sign up

Export Citation Format

Share Document