scholarly journals Study of Composite Structures Based on a Porous Silicon Matrix and Nanoparticles Ag/Zno Used as Non-Invasive Highly Sensitive Biosensor Devices

2021 ◽  
Author(s):  
Veniamin Koshevoi ◽  
Anton Belorus ◽  
Ilya Pleshanov ◽  
Anton Timchenko ◽  
Roman Denisenko ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Hydrofluoric Acid ◽  
Emission Spectroscopy ◽  
Composite Structures ◽  
Electrochemical Etching ◽  
Silicon Matrix ◽  
Non Invasive ◽  
Highly Sensitive ◽  
Porous Matrices ◽  
Scanning Electron

In this work composite structures based on a porous silicon were obtained and studied. Porous matrices were formed by electrochemical etching in aqueous solutions of hydrofluoric acid. Based on the obtained substrates, por-silicon (Si)/silver (Ag) and por-Si/zinc oxide (ZnO) composite structures were formed. These composites were functionalized by various methods (electro (E)-, thermo (T)-, electrothermal exposure) as a result of which the structures were modified. When studying the samples by scanning electron microscopy (SEM), it was concluded that silver nanoparticles actively diffused into the pores under these technological modes of functionalization. The por-Si/Ag and por-Si/ZnO composite structures were also studied using the following methods: infrared (IR) spectroscopy and Raman ultrasoft X-ray emission spectroscopy. Also, the photoluminescent characteristics of the samples were studied. Based on the obtained results, it was concluded that functionalization methods actively change the phase composition of structures and the optical properties of composites.

scholarly journals In Situ Growth of ZnO inside a Porous Silicon Matrix Obtained by Electrochemical Etching with a Hydrofluoric Acid-Formaldehyde Solution

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
R. Juárez-Nahuatlato ◽  
G. García ◽  
M. Pacio ◽  
Roberto Portillo ◽  
N. Perez-Amaro ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Hydrofluoric Acid ◽  
Electrochemical Etching ◽  
Nitrogen Adsorption ◽  
Ultraviolet Region ◽  
Ultraviolet Emission ◽  
Silicon Matrix ◽  
Electrolytic Process ◽  
Band Emission ◽  
Before And After

We present zinc oxide (ZnO) particles obtained inside a porous silicon matrix in the same electrolytic process using a p-type silicon wafer in a hydrofluoric acid (HF) solution containing formaldehyde (CH2O) and hydrated zinc sulfate as additives. The X-ray diffraction pattern of the sample confirmed the presence of ZnO with a hexagonal-type wurtzite structure. Photoluminescence (PL) spectra of the samples, before and after the functionalization process, were measured to observe the effect of ZnO inside the porous silicon. The PL measurements of porous silicon functionalized with ZnO (ZnO/PS) revealed infrared, red, blue, and ultraviolet emission bands. The ultraviolet region corresponds to the band-band emission of ZnO, and the visible emission is attributed to defects. The results of the nitrogen adsorption/desorption isotherms of the PS and ZnO/PS samples revealed larger BET surface areas and pore diameters for the ZnO/PS sample. We conclude that ZnO/PS can be obtained in a one-step electrolytic process. These types of samples can be used in gas sensors and photocatalysis.

Photoluminescence in Porous Silicon: Evidence for the Quantum Confinement Model

1991 ◽  
Vol 256 ◽  
Author(s):  
David L. Naylor ◽  
Sung B. Lee ◽  
John C. Pincenti ◽  
Brett E. Bouma
Keyword(s):  
Porous Silicon ◽  
Hydrofluoric Acid ◽  
Quantum Wire ◽  
Quantum Confinement ◽  
Electrochemical Etching ◽  
Photoluminescence Spectra ◽  
Peak Wavelength ◽  
Effects Of Temperature ◽  
Good Agreement ◽  
Confinement Model

ABSTRACTPhotoluminescence spectra have been measured in porous silicon following electrochemical etching in dilute hydrofluoric acid (HF). The effects of HF concentration during etching on the efficiency and peak wavelength of photoluminescence have been investigated. The effects of temperature between 25°C and 200°C on PL spectra have been recorded. Photoluminescence lifetimes as a function of wavelength have been studied following ultrashort UV photoexcitation. A number of lifetime components in the decay are observed the longest in good agreement over the wavelength range of 500 to 600 nm with a silicon quantum wire model. At longer wavelengths a departure from lifetimes of the wire model is observed and two hypotheses for the discrepancy are presented.

scholarly journals PHOTOSENSITIVE MATRIX BASED ON POROUS MICROCRYSTALLINE SILICON

2017 ◽  
Vol 17 (5) ◽  
pp. 115-121
Author(s):  
N.V. Latukhina ◽  
D.A. Pisarenko ◽  
A.V. Volkov ◽  
V.A. Kitaeva
Keyword(s):  
Porous Silicon ◽  
Hydrofluoric Acid ◽  
Electrochemical Etching ◽  
Etching Process ◽  
Microcrystalline Silicon ◽  
Artificial Retina ◽  
Experimental Researches ◽  
Water Alcohol Solutions ◽  
Water Alcohol

The article presents the results of experimental researches of optoelectric properties of porous silicon. Layers of porous silicon were formed using electrochemical etching process in water-alcohol solutions of hydrofluoric acid on plates with a pre-established microrelief surface. Evaluation of possibility of using of created structure as the artificial retina component was performed based on the results of the research.

POROUS SILICON: INFLUENCE OF ETCHING TEMPERATURE ON MICROSTRUCTURE AND LUMINESCENCE

2001 ◽  
Vol 08 (05) ◽  
pp. 429-433 ◽  
Author(s):  
D. J. BLACKWOOD ◽  
Y. ZHANG
Keyword(s):  
Porous Silicon ◽  
Light Source ◽  
Hydrofluoric Acid ◽  
Uv Light ◽  
Electrochemical Etching ◽  
Light Emitting ◽  
Influence Of Temperature ◽  
Etching Solution ◽  
Experimental Parameters

Electrochemical etching in solutions based on hydrofluoric acid has been widely used to form light-emitting porous silicon. However, the effects of a number of the experimental parameters on the quality of the porous silicon produced have yet to be fully investigated. In the present paper the influence of temperature and viscosity of the etching solution is evaluated in terms of the morphology and porosity of the porous silicon produced as well as the wavelength of the photoluminescence or electroluminescence subsequently emitted. It was found that under stimulation from a UV light source the wavelength of the photoluminescence emitted from the porous silicon films blueshifted with decreasing etching temperature. SEM and AFM investigations revealed that this blueshifting of the photoluminescence resulted from the production of smaller nanocrystals at the lower etching temperatures.

scholarly journals AGGREGATION OF MS-MONOPYRIDYL-Β-OCTAALKYLPORPHYRINS IN DICHLOROMETHANE IN PRESENCE OF Pd(II)

2020 ◽  
Vol 63 (11) ◽  
pp. 35-40
Author(s):  
Yulia B. Ivanova ◽  
Nugzar Zh. Mamardashvili ◽  
Natalya E. Kochkina
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Elemental Analysis ◽  
Scattered Light ◽  
Incident Light ◽  
Aggregate Size ◽  
Non Invasive ◽  
Highly Sensitive ◽  
Porphyrin Aggregation ◽  
Scanning Electron

Aggregation of 13,17-diethyl-2,3,7,8,12,18-hexamethyl-5-(pyridin-4-yl) porphyrin (I), 13,17-diethyl-2,3,7,8,12,18-hexamethyl-5-(pyridin-3-yl)porphyrin (II) and 13.17-diethyl-2,3,7,8,12,18-hexamethyl-5-(pyridin-2-yl)porphyrin (III) in the presence of trans-bis(benzonitrile)palladium(II) dichloride was studied by dynamic light scattering and electronic absorption spectroscopy in dichloromethane at 293 K. The average aggregate size and the nature of their distribution were determined. Using scanning electron microscopy, it was determined the size and composition of clusters formed by aggregates of complexes of the palladium(II) cation with the studied porphyrins. It was shown that minimal acetic acid additions lead to the destruction of the corresponding clusters. At the same time, complete destruction of the aggregates does not occur even with a 100-fold molar excess of acid.We used the Zetasizer Nano ZS (model ZEN3600, Malvern Instruments), equipped with a 633nm laser and non-invasive backscattering (NIBS) technology when the scattered light detector is positioned at an angle of 173° to the incident light. Confirmation of porphyrin aggregation was performed by additional study of the structure using a Hitachi TM4000Plus desktop electron microscope equipped with a 4-segment highly sensitive semiconductor detector and a secondary electron detector for low vacuum mode. Elemental analysis of the obtained aggregates in the cluster was performed using a silicon drift detector with a working area of 30 mm2, combined with a Hitachi TM4000Plus microscope. It was found that aggregates consisting of a para-pyridyl derivative of alkylporphyrin and trans-bis (benzonitrile) palladium (II) dichloride are formed in dichloromethane at 293 K. The best results of porphyrin structures were observed for mixtures of 13,17-diethyl-2,3,7,8,12,18-5-hexamethyl-5-(pyridine-4-yl)porphyrin with TRANS-bis(benzonitrile)- palladium (II) dichloride in a ratio of 1:3, which is probably due to less spatial shielding of the reaction center of the macrocycle and, as a result, better stabilization of the resulting particles. The size of a cluster consisting of individual aggregates was measured using scanning electron microscopy. An elemental analysis of a single aggregate was obtained.

Preparation of Porous Silicon and Effect of Gettering on the Resistivity

2012 ◽  
Vol 476-478 ◽  
pp. 1794-1797 ◽  
Author(s):  
Su Xia Guo ◽  
Yi Tan ◽  
Jia Yan Li ◽  
Ya Qiong Li ◽  
Chen Guang Liu
Keyword(s):  
Porous Silicon ◽  
Raman Spectra ◽  
Pore Diameter ◽  
Crystalline Silicon ◽  
Electrochemical Etching ◽  
Silicon Layer ◽  
Porous Silicon Layer ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron

The porous silicon layer was fabricated by electrochemical etching process using an aqueous HF-based electrolyte. The characterizations of porous silicon layer were investigated by Emission-type scanning electron microscope (SEM), Raman spectra and X-ray diffraction (XRD). With the current density increasing, the pore diameter and density become much bigger. This result also was confirmed by Raman spectra and XRD result of samples, which revealed the decreasing of grain size of silicon. The resistivity of crystalline silicon increased when the porous layer was removed after heat treatment at 850°C for 2.5h, which should be attributed to the gettering process of porous silicon.

Electrochemical Sensor for Detection of Para-Nitrophenol Based on Modified Porous Silicon

2014 ◽  
Vol 605 ◽  
pp. 115-118 ◽  
Author(s):  
S. Belhousse ◽  
K. Lasmi ◽  
I. Mezaache ◽  
T. Sedrati ◽  
N. Belhaneche ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cyclic Voltammetry ◽  
Porous Silicon ◽  
Silicon Surface ◽  
Electrochemical Etching ◽  
High Sensitivity ◽  
Hybrid Structures ◽  
Porous Silicon Surface ◽  
Very High ◽  
Scanning Electron

The behavior of a modified porous silicon surface (PSi) with polythiophene (PTh) for para-nitrophenol (p-NPh) detection by cyclic voltammetry was studied. Nitrophenols are organic compounds which are the most used in the production of pesticides but also in the dyes and pharmaceuticals. In particular, p-NPh is a toxic derivative of the parathion insecticide and is considered as major toxic polluant because it is soluble and stable in water so it can affect soil. Porous silicon was prepared by electrochemical etching and it was modified by an oxide layer. PTh films were grown on this surface using electropolymerization in acetonitrile in the presence of thiophene monomer.The morphology of the fabricated PSi/PTh hybrid structures were characterized by scanning electron microscopy (SEM). Cyclic voltammetry and amperometry were used to study the proposed electrochemical p-NPh sensor. The performance of the proposed sensor was tested under differents conditions and we note a very high sensitivity; in particular, the linearity of the sensor for the detection of para-nitrophenol was observed from 3×108to 1.5 ×104M with a detection limit of 6×109M.

scholarly journals Role of MRI evaluation in acute secondary inability to walk in children

2021 ◽  
Vol 52 (1) ◽  
Author(s):  
K. H. Sedeek ◽  
K. Aboualfotouh ◽  
S. M. Hassanein ◽  
N. M. Osman ◽  
M. H. Shalaby
Keyword(s):  
Transverse Myelitis ◽  
High Sensitivity ◽  
Acute Disseminated Encephalomyelitis ◽  
Limb Weakness ◽  
Non Invasive ◽  
Highly Sensitive ◽  
Common Causes ◽  
Bilateral Lower Limb ◽  
Severity Of The Disease

Abstract Background Acute bilateral lower limb weakness is a common problem in children which necessitates a rapid method for diagnosis. MRI is a non-invasive imaging technique that produces high-quality images of the internal structure of the brain and spinal cord. Results MRI was very helpful in reaching rapid and prompt diagnosis in children with acute inability to walk. Acute disseminated encephalomyelitis (ADEM), Guillain–Barré syndrome (GBS), and acute transverse myelitis (ATM) were the most common causes in our study. MRI proved to be of high sensitivity in detecting the lesions and reaching the diagnosis in ADEM and GBS; however, there was no significant relation between the lesions’ size, enhancement pattern, and severity of the disease or prognosis, yet in ATM the site of the lesion and number of cord segment affection were significantly related to the severity of the disease and prognosis. Conclusion MRI is a quick tool to reach the diagnosis of children with acute secondary inability to walk, and to eliminate other differential diagnosis which is essential for proper treatment and rapid full recovery. It is highly sensitive in detecting the lesions, their site and size.

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