scholarly journals Optical Properties of Silicon Nanoparticles Prepared by Laser Ablation Method in Various Media

2014 ◽  
Vol 24 (3S1) ◽  
pp. 143-148
Author(s):  
Chu Anh Tuan ◽  
Nguyen Thi Thu Trang ◽  
Le Anh Tu ◽  
Duong Thi Giang ◽  
Pham Hong Duong ◽  
...  
Keyword(s):  
Optical Properties ◽  
Silicon Nanoparticles ◽  
Peak Position ◽  
Quenching Effect ◽  
Laser Ablation Method ◽  
Silicon Target ◽  
Si Nanoparticle ◽  
Si Nanoparticles ◽  
532 Nm ◽  
Si Wafer

Bright photoluminescent silicon nanoparticles were successfully fabricated from porous silicon target in air and n-hexane using 532 nm line of YAG:Nd pulsed laser. The whole procedure was carried out at room temperature, in atmosphere. The morphology and composition of as-synthesized nanoparticles were characterized by SEM and EDS measurements. Their optical properties were investigated. The PL peak position of the as-synthesized Si nanoparticle ablated in air is slightly blue-shifted in comparison with those ablated in n-hexane, while it was almost no change of peak position of Si nanoparticles fabricated from p-Si in hexane and original p-Si wafer target. In contrast to PL intensity quenching of original p-Si sample and particles produced in air, those produced in n-hexane solvent exhibited an enhancement. The presence of dangling bonds or energy transfer from excited Si particles to oxygen molecules on the surface can be the cause of the quenching effect.

Size and Surface Control of Optical Properties in Silicon Nanoparticles

2006 ◽  
Vol 45 ◽  
pp. 2620-2626 ◽  
Author(s):  
F. Fabbri ◽  
Elisabetta Borsella ◽  
M. Carpanese ◽  
Roberta Fantoni ◽  
R. Caterino ◽  
...  
Keyword(s):  
Optical Properties ◽  
Gas Phase ◽  
Silicon Nanoparticles ◽  
Surface Passivation ◽  
Synthesis Process ◽  
Surface Control ◽  
Si Nanoparticles ◽  
Ideal Tool ◽  
Process Dispersion ◽  
And Control

Si-nanoparticles (NP) are attracting steadily growing interest due to their intriguing sizedependent optical properties. The most challenging task in preparing Si-NP is to succeed in controlling the particle size and size distribution and the surface properties. To this respect, the method of laser synthesis of Si-NP from gas phase reactants appears as an ideal tool, being a very versatile and controllable synthesis technique, but the collected Si-NP are strongly agglomerated. Here we report on attempts to decrease the agglomeration of the Si NP by following two complementary strategies: - investigation and control of nanoparticle formation and growth during the synthesis process; - dispersion of the agglomerates and termination of the particle surfaces by controlled chemical etching followed by surface passivation and stabilization treatments. The properties of as-prepared and processed Si NP will be presented and discussed.

scholarly journals Study of Filtration in Polyethylene Fibers used in Masks for Protection Against SARS-CoV-2 via Luminescent Aerosolized Silicon Nanoparticles

2021 ◽  
Author(s):  
Ayman Rezk ◽  
Juveiriah Ashraf ◽  
Wafa Alnaqbi ◽  
Sabina Abdul Hadi ◽  
Ghada Dushaq ◽  
...  
Keyword(s):  
Silicon Nanoparticles ◽  
Optical Microscope ◽  
The Novel ◽  
Filtration Process ◽  
Fiber Network ◽  
Spider Web ◽  
Si Nanoparticle ◽  
Si Nanoparticles ◽  
Novel Coronavirus ◽  
Polyethylene Fibers

Abstract Commercial polyethylene (PE) fiber-based masks are currently used as personal filters for protection against various microorganisms. Due to the coronavirus (SARS-CoV-2) pandemic of 2020, the use of masks has become the critical mechanism in reducing the spread. The PE mask filter uses a sieve (geometry) in a spider web fashion to filter out microorganisms using Van der Waals atomic forces. However, the non-geometrical part of the filtration process is not fully understood. In this work, we utilized luminescent ultra-small silicon nanoparticles, which are Si-H or/and Si-OH terminated to examine how the filter operates at a chemical level. The particles were sprayed onto the fiber network by an atomizer and we used scanning electron microscopy (SEM), optical microscope and fluorescence spectroscopy under UV radiation. The images and measurements clearly showed that the Si nanoparticles bonded to the PE fiber network. The results were analyzed in terms of chemical bonding between Si nanoparticle and fiber. Our findings suggest that the PE fibers could act as a chemical filter via hydrogen or hydrolysis–based bonding or via Si-C bonding, which is complementary to their physical filtration ability via the geometric sieve process. Moreover, the results indicate that the filter would be effective against the novel coronavirus, not only by the geometrical sieve but can be additionally enhanced as a chemical filter by allowing the amine, carboxyl and hydroxyl function groups of the virus to attach to fibers via C-N and C-O bonds.

Tomographic Study of Silicon Nanoparticles in Nanocrystalline Non-Volatile Flash Memory Devices by EFTEM

2012 ◽  
Author(s):  
YongKai Zhou ◽  
Jie Zhu ◽  
AnYan Du ◽  
YouNan Hua ◽  
ZhiQiang Mo ◽  
...  
Keyword(s):  
Flash Memory ◽  
Silicon Nanoparticles ◽  
Tomographic Reconstruction ◽  
Memory Devices ◽  
Plan View ◽  
Si Nanoparticle ◽  
Thin Film Layer ◽  
Si Nanoparticles ◽  
Key Factor ◽  
Film Layer

Abstract The distribution of Si nanoparticles, both dimensional and spatial, is a key factor affecting the performance of non-volatile flash memory devices. A new FIB method has been developed to prepare ultra-thin plan view specimens, containing only the Si nanoparticle matrix thin film layer, from fully processed nanocrystalline flash memory devices. The morphology and distribution of Si nanoparticles were then studied by EFTEM 3D tomographic reconstruction.

Formation Process of Si Nanoparticles Formed by Laser Ablation Method

1998 ◽  
Vol 536 ◽  
Author(s):  
T. Makimura ◽  
T. Mizuta ◽  
T. Ueda ◽  
K. Murakami
Keyword(s):  
Laser Ablation ◽  
Formation Process ◽  
Silicon Nanoparticles ◽  
Rare Gas ◽  
Formation Processes ◽  
Measuring Time ◽  
Time Resolved ◽  
Chemically Modified ◽  
Laser Ablation Method ◽  
Si Nanoparticles

AbstractUtilizing laser ablation of Si targets, nanoparticles can be cleanly formed in rare gas. In order to fabricate nanoparticles with well-defined structures such as those whose surfaces are chemically modified, it is important to investigate the formation process of the nanoparticles. We have developed a decomposition method for measuring time-resolved spatial distributions of nanoparticles in rare gas. Applying this method, we have investigated formation processes of silicon nanoparticles in 2-Torr argon gas. The nanoparticles are found to grow from 300 Ais to 1 ms after the ablation.

Nonlinear optical properties of colloidal carbon nanoparticles: nanodiamonds and carbon dots

RSC Advances ◽  
2014 ◽  
Vol 4 (76) ◽  
pp. 40152-40160 ◽  
Author(s):  
Irene Papagiannouli ◽  
Athanasios B. Bourlinos ◽  
Aristides Bakandritsos ◽  
Stelios Couris
Keyword(s):  
Optical Properties ◽  
Carbon Dots ◽  
Carbon Nanoparticles ◽  
Nonlinear Optical ◽  
Laser Excitation ◽  
Optical Limiting ◽  
Nonlinear Optical Properties ◽  
Nlo Response ◽  
Colloidal Carbon ◽  
532 Nm

Nanodiamonds (NDs) and carbon-dots (CDs) suspensions exhibit significant NLO response under both ps and ns laser excitation. NDs exhibit important optical limiting action under nanosecond visible (532 nm) and infrared (1064 nm) laser excitation.

scholarly journals One year of Raman lidar observations of free-tropospheric aerosol layers over South Africa

2015 ◽  
Vol 15 (10) ◽  
pp. 5429-5442 ◽  
Author(s):  
E. Giannakaki ◽  
A. Pfüller ◽  
K. Korhonen ◽  
T. Mielonen ◽  
L. Laakso ◽  
...  
Keyword(s):  
South Africa ◽  
Optical Properties ◽  
Biomass Burning ◽  
Mean Value ◽  
Aerosol Layer ◽  
Raman Lidar ◽  
Tropospheric Aerosol ◽  
Wide Range ◽  
Significant Difference ◽  
532 Nm

Abstract. Raman lidar data obtained over a 1 year period has been analysed in relation to aerosol layers in the free troposphere over the Highveld in South Africa. In total, 375 layers were observed above the boundary layer during the period 30 January 2010 to 31 January 2011. The seasonal behaviour of aerosol layer geometrical characteristics, as well as intensive and extensive optical properties were studied. The highest centre heights of free-tropospheric layers were observed during the South African spring (2520 ± 970 m a.g.l., also elsewhere). The geometrical layer depth was found to be maximum during spring, while it did not show any significant difference for the rest of the seasons. The variability of the analysed intensive and extensive optical properties was high during all seasons. Layers were observed at a mean centre height of 2100 ± 1000 m with an average lidar ratio of 67 ± 25 sr (mean value with 1 standard deviation) at 355 nm and a mean extinction-related Ångström exponent of 1.9 ± 0.8 between 355 and 532 nm during the period under study. Except for the intensive biomass burning period from August to October, the lidar ratios and Ångström exponents are within the range of previous observations for urban/industrial aerosols. During Southern Hemispheric spring, the biomass burning activity is clearly reflected in the optical properties of the observed free-tropospheric layers. Specifically, lidar ratios at 355 nm were 89 ± 21, 57 ± 20, 59 ± 22 and 65 ± 23 sr during spring (September–November), summer (December–February), autumn (March–May) and winter (June–August), respectively. The extinction-related Ångström exponents between 355 and 532 nm measured during spring, summer, autumn and winter were 1.8 ± 0.6, 2.4 ± 0.9, 1.8 ± 0.9 and 1.8 ± 0.6, respectively. The mean columnar aerosol optical depth (AOD) obtained from lidar measurements was found to be 0.46 ± 0.35 at 355 nm and 0.25 ± 0.2 at 532 nm. The contribution of free-tropospheric aerosols on the AOD had a wide range of values with a mean contribution of 46%.

The Preparation and Characterization of Novel Nonlinear Optical Active Dye

2013 ◽  
Vol 750-752 ◽  
pp. 899-902
Author(s):  
Lin Feng Li ◽  
Hong Yao Xu
Keyword(s):  
Optical Properties ◽  
Optical Property ◽  
Nonlinear Optical ◽  
Nonlinear Optical Property ◽  
Condensation Reaction ◽  
Nonlinear Optical Properties ◽  
532 Nm ◽  
Triazine Dye

A novel nonlinear optical active triazine dye 2-(4-methyl-4-amino-azobenzene )-4-sodium sulfanilate-6-chloro-1,3,5-triazine was synthesized by condensation reaction and characterized by FTIR, 1HNMR, respectively. Their nonlinear optical properties were investigated using 5 ns pulse at 532 nm, which showed excellent nonlinear optical property.

Investigation of the third-order nonlinear optical properties in porphyrin solutions in the picosecond regime

2015 ◽  
Vol 24 (03) ◽  
pp. 1550030 ◽  
Author(s):  
M. Chniti ◽  
C. Cassagne ◽  
J. L. Godet ◽  
G. Boudebs
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Time Dependence ◽  
Nonlinear Optical ◽  
Optical Response ◽  
Spectral Width ◽  
Incident Laser ◽  
Third Order ◽  
The Third ◽  
532 Nm

The D4σ-Z-scan technique is used to evaluate the sign and the magnitude of the nonlinear (NL) refractive index and the NL absorption (NLA) coefficient with a laser delivering single pulses in the picosecond regime at 355 nm, 532 nm and 1064 nm. The NL optical response of the zinc porphyrins (Pph) has been found to be significantly enhanced. The study of the NLA and refraction is performed, taking into account the time dependence and the spectral width of the incident laser. The variations of the NL coefficients as a function of the intensity and the concentration are provided and are found to be linear.

scholarly journals Airborne pollen observations using a multi-wavelength Raman polarization lidar in Finland: characterization of pure pollen types

2020 ◽  
Author(s):  
Xiaoxia Shang ◽  
Elina Giannakaki ◽  
Stephanie Bohlmann ◽  
Maria Filioglou ◽  
Annika Saarto ◽  
...  
Keyword(s):  
Optical Properties ◽  
Airborne Pollen ◽  
Pollen Grains ◽  
Wavelength Dependence ◽  
Depolarization Ratio ◽  
Mean Values ◽  
Pollen Types ◽  
Pine Pollen ◽  
Significant Wavelength ◽  
532 Nm

Abstract. We present a novel algorithm for characterizing the optical properties of pure pollen particles, based on the depolarization values obtained in lidar measurements. The algorithm was first tested and validated through a simulator, and then applied to the lidar observations during a four-month pollen campaign from May to August 2016 at the European Aerosol Research Lidar Network (EARLINET) station in Kuopio (62°44′ N, 27°33′ E), in Eastern Finland. Twenty types of pollen were observed and identified from concurrent measurements with Burkard sampler; Birch (Betula), pine (Pinus), spruce (Picea) and nettle (Urtica) pollen were most abundant, contributing more than 90 % of total pollen load, regarding number concentrations. Mean values of lidar-derived optical properties in the pollen layer were retrieved for four intense pollination periods (IPPs). Lidar ratios at both 355 and 532 nm ranged from 55 to 70 sr for all pollen types, without significant wavelength-dependence. Enhanced depolarization ratio was found when there were pollen grains in the atmosphere, and even higher depolarization ratio (with mean values of 25 % or 14 %) was observed with presence of the more non-spherical spruce or pine pollen. The depolarization ratio at 532 nm of pure pollen particles was assessed, resulting to 24 ± 3 % and 36 ± 5 % for birch and pine pollen, respectively. Pollen optical properties at 1064 nm and 355 nm were also estimated. The backscatter-related Ångström exponent between 532 and 1064 nm was assessed as ~ 0.8 (~ 0.5) for pure birch (pine) pollen, thus the longer wavelength would be better choice to trace pollen in the air. The pollen depolarization ratio at 355 nm of 17 % and 30 % were found for birch and pine pollen, respectively. The depolarization values show a wavelength dependence for pollen. This can be the key parameter for pollen detection and characterization.

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