scholarly journals Silicone Nanofilament Support Layers in an Open-Channel System for the Fast Reduction of Para-Nitrophenol

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1663
Author(s):  
Noah U. Naef ◽  
Stefan Seeger
Keyword(s):  
Electron Microscopy ◽  
Open Channel ◽  
Chemical Vapor ◽  
Catalytic Efficiency ◽  
Catalytic Performance ◽  
Metal Catalyst ◽  
Surface Tension Gradient ◽  
Channel System ◽  
Transition Electron Microscopy ◽  
Nitrophenol Reduction

Chemical vapor phase deposition was used to create hydrophobic nanostructured surfaces on glass slides. Subsequently, hydrophilic channels were created by sputtering a metal catalyst on the channels while masking the outside. The surface tension gradient between the hydrophilic surface in the channels and the outside hydrophobicity formed the open-channel system. The reduction of para-nitrophenol (PNP) was studied on these devices. When compared to nanostructure-free reference systems, the created nanostructures, namely, silicone nanofilaments (SNFs) and nano-bagels, had superior catalytic performance (73% and 66% conversion to 55% at 0.5 µL/s flow rate using 20 nm platinum) and wall integrity; therefore, they could be readily used multiple times. The created nanostructures were stable under the reaction conditions, as observed with scanning electron microscopy. Transition electron microscopy studies of platinum-modified SNFs revealed that the catalyst is present as nanoparticles ranging up to 13 nm in size. By changing the target in the sputter coating unit, molybdenum, gold, nickel and copper were evaluated for their catalytic efficiency. The relative order was platinum < gold = molybdenum < nickel < copper. The decomposition of sodium borohydride (NaBH4) by platinum as a concurrent reaction to the para-nitrophenol reduction terminates the reaction before completion, despite a large excess of reducing agent. Gold had the same catalytic rate as molybdenum, while nickel was two times and copper about four times faster than gold. In all cases, there was a clear improvement in catalysis of silicone nanofilaments compared to a flat reference system.

Synthesis of Ni@MWCNTs Magnetic Nanocatalysts and their Catalytic Activity towards 4-Nitrophenol Reduction

2012 ◽  
Vol 531 ◽  
pp. 358-361 ◽  
Author(s):  
Ming Mei Zhang ◽  
Qian Sun ◽  
Ji Min Xie
Keyword(s):  
Electron Microscopy ◽  
Catalytic Activity ◽  
Average Particle Size ◽  
Chemical Vapor ◽  
High Catalytic Activity ◽  
Average Particle ◽  
Ni Nanoparticles ◽  
Nitrophenol Reduction ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

A well-dispersed Ni nanoparticles on multi-walled carbon nanotubes (Ni@MWCNTs) was prepared by chemical vapor deposition (CVD) method using a vacuum quartz tube furnace at the temperature of 600°C. The scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) were performed to characterize the synthesized catalyst. It shows an unfirom dispersion of Ni nanoparticles on MWCNTs with the average particle size of 8.6 nm. The as synthesized catalyst was applied in a redox reaction of 4-nitrophenol, which showed very high catalytic activity, stability and well conversion. The catalyst can be easily separated due to the magnetical performance

scholarly journals Design and Characterization of Ag@Cu2O-rGO Nanocomposite for the p-Nitrophenol Reduction

Catalysts ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 43
Author(s):  
Chao Song ◽  
Shuang Guo ◽  
Lei Chen
Keyword(s):  
Electron Microscopy ◽  
Catalytic Activity ◽  
Catalytic Reduction ◽  
Catalytic Efficiency ◽  
Transmission Electron ◽  
Nitrophenol Reduction ◽  
Reduced Graphene ◽  
High Degree ◽  
Scanning Electron

In this paper, we designed Ag nanoparticles coated with a Cu2O shell, which was successfully decorated on reduced graphene oxide (rGO) via a solid-state self-reduction. The Cu2O, Ag@Cu2O, and Ag@Cu2O-rGO nanocomposites were synthesized and characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis, and XPS to evaluate the properties of the composites. In order to compare the chemical catalytic activity, the Cu2O, Ag@Cu2O, and Ag@Cu2O-rGO nanocomposites were employed for the catalytic reduction of p-nitrophenol (4-NP) into p-aminophenol (4-AP) in aqueous solution. The Ag@Cu2O-rGO nanocomposite exhibited excellent catalytic activity due to the intense interaction and high degree of electron transfer among Ag, Cu2O, and rGO. The rGO acted as the platform to bridge the isolated nanoparticles; furthermore, the electrons could quickly transfer from the Ag core to the Cu2O shell, which improved the chemical catalytic efficiency.

scholarly journals Direct Growth of AlGaN Nanorod LEDs on Graphene-Covered Si

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2372 ◽  
Author(s):  
Fang Ren ◽  
Yue Yin ◽  
Yunyu Wang ◽  
Zhiqiang Liu ◽  
Meng Liang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Quantum Wells ◽  
Electron Backscatter Diffraction ◽  
Single Layer ◽  
Chemical Vapor ◽  
Single Layer Graphene ◽  
Metal Catalyst ◽  
Organic Chemical ◽  
Multiple Quantum ◽  
Mocvd Growth

High density of defects and stress owing to the lattice and thermal mismatch between nitride materials and heterogeneous substrates have always been important problems and limit the development of nitride materials. In this paper, AlGaN light-emitting diodes (LEDs) were grown directly on a single-layer graphene-covered Si (111) substrate by metal organic chemical vapor deposition (MOCVD) without a metal catalyst. The nanorods was nucleated by AlGaN nucleation islands with a 35% Al composition, and included n-AlGaN, 6 period of AlGaN multiple quantum wells (MQWs), and p-AlGaN. Scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) showed that the nanorods were vertically aligned and had an accordant orientation along the [0001] direction. The structure of AlGaN nanorod LEDs was investigated by scanning transmission electron microscopy (STEM). Raman measurements of graphene before and after MOCVD growth revealed the graphene could withstand the high temperature and ammonia atmosphere in MOCVD. Photoluminescence (PL) and cathodoluminescence (CL) characterized an emission at ~325 nm and demonstrated the low defects density in AlGaN nanorod LEDs.

Optimized Preparation of Gold Nanoparticles-loaded Carbon Nanotubes (Au-CNTs) as an Efficient Catalyst for p-Nitrophenol Reduction

2021 ◽  
Vol 10 ◽  
Author(s):  
Farah Wahida Ahmad Zulkifli ◽  
Abdul Mutalib Md Jani ◽  
Hanani Yazid
Keyword(s):  
Electron Microscopy ◽  
Catalytic Activity ◽  
Aging Time ◽  
High Stability ◽  
Catalytic Efficiency ◽  
Precipitation Method ◽  
Synthesis Process ◽  
Order Kinetic ◽  
Nitrophenol Reduction ◽  
Nanocomposite Catalysts

Aim: The current work aims to enhance the catalytic performance of gold nanopar-ticle–carbon nanotube (Au-CNT) composites towards the reduction of p-nitrophenol. Background: The synthesis of Au-CNT has received extensive attention because of their high stability and catalytic efficiency, particularly as a heterogeneous catalyst in the reduction of p-nitrophenol (p-NP) to p-aminophenol (p-AP) However, most of the Au-CNT preparation processes reported in the literature are time-consuming or require expensive instrumentation. In the present work, Au-CNT catalysts were synthesized via a straightforward, low-cost deposition–precipitation (DP) method. Objective: The aim of the study was to evaluate the effect of pH and aging time on catalytic activity of Au-CNTs catalyst. Method: The Au-CNT nanocomposite catalysts were synthesized using a simple deposition–precipitation method and characterized by Brunauer–Emmett–Teller analysis, fourier transform infrared spectroscopy, atomic absorption spectroscopy, thermogravimetric analysis, field emission scanning electron microscopy, and trans-mission electron microscopy. Results: The particle size and the loading of Au nanoparticles on the CNTs can be easily controlled by varying the pH and aging time during the synthesis process. The nanocomposite catalysts exhibited excellent catalytic activity for the reduction of p-nitrophenol to p-aminophenol in the presence of excess sodium borohydride (NaBH4). The highest rate constant (k) achieved based on the pseudo-first-order kinetic model was 1.2 × 10-3 s-1. Conclusion: This study offers a simple and cost-effective route to synthesize Au-CNT catalysts with high stability and catalytic efficiency for large-scale applica-tions.

scholarly journals Design of Silica Nanoparticles-Supported Metal Catalyst by Wet Impregnation with Catalytic Performance for Tuning Carbon Nanotubes Growth

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 986
Author(s):  
Tairan da Cunha ◽  
Alberto Maulu ◽  
Jérôme Guillot ◽  
Yves Fleming ◽  
Benoit Duez ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Catalytic Efficiency ◽  
Sio2 Nanoparticles ◽  
Catalytic Performance ◽  
Metal Catalyst ◽  
Impregnation Method ◽  
Wet Impregnation ◽  
Supported Metal Nanoparticles ◽  
Size Dispersion ◽  
Supported Metal

The catalytic activity of cobalt and iron nanoparticles for the growth of carbon nanotubes (CNTs) was studied by a specific reproducible and up-scalable fabrication method. Co and Fe catalysts were deposited over SiO2 nanoparticles by a wet-impregnation method and two different annealing steps were applied for the catalyst formation/activation. The samples were calcined at an optimal temperature of 450 °C resulting in the formation of metal oxide nano-islands without the detection of silicates. Further reduction treatment (700 °C) under H2 successfully converted oxide nanoparticles to Co and Fe metallic species. Furthermore, the catalytic efficiency of both supported-metal nanoparticles at 2 and 5% in weight of silica was evaluated through the growth of CNTs. The CNT structure, morphology and size dispersion were tailored according to the metal catalyst concentration.

scholarly journals Facile Use of Silver Nanoparticles-Loaded Alumina/Silica in Nanofluid Formulations for Enhanced Catalytic Performance toward 4-Nitrophenol Reduction

2021 ◽  
Vol 18 (6) ◽  
pp. 2994
Author(s):  
Rashmi Mannu ◽  
Vaithinathan Karthikeyan ◽  
Murugendrappa Malalkere Veerappa ◽  
Vellaisamy A. L. Roy ◽  
Anantha-Iyengar Gopalan ◽  
...  
Keyword(s):  
Environmental Remediation ◽  
Catalytic Reduction ◽  
Catalytic Efficiency ◽  
Catalytic Performance ◽  
New Approach ◽  
Catalytic Rate Constant ◽  
Nitrophenol Reduction ◽  
Reduction Efficiency ◽  
Silver Nps ◽  
Ultrasonic Assisted

The introduction of toxic chemicals into the environment can result in water pollution leading to the degradation of biodiversity as well as human health. This study presents a new approach of using metal oxides (Al2O3 and SiO2) modified with a plasmonic metal (silver, Ag) nanoparticles (NPs)-based nanofluid (NF) formulation for environmental remediation purposes. Firstly, we prepared the Al2O3 and SiO2 NFs of different concentrations (0.2 to 2.0 weight %) by ultrasonic-assisted dispersion of Al2O3 and SiO2 NPs with water as the base fluid. The thermo-physical (viscosity, activation energy, and thermal conductivity), electrical (AC conductivity and dielectric constant) and physical (ultrasonic velocity, density, refractive index) and stability characteristics were comparatively evaluated. The Al2O3 and SiO2 NPs were then catalytically activated by loading silver NPs to obtain Al2O3/SiO2@Ag composite NPs. The catalytic reduction of 4-nitrophenol (4-NP) with Al2O3/SiO2@Ag based NFs was followed. The catalytic efficiency of Al2O3@Ag NF and SiO2@Ag NF, for the 4-NP catalysis, is compared. Based on the catalytic rate constant evaluation, the catalytic reduction efficiency for 4-NP is found to be superior for 2% weight Al2O3@Ag NF (92.9 × 10−3 s−1) as compared to the SiO2@Ag NF (29.3 × 10−3 s−1). Importantly, the enhanced catalytic efficiency of 2% weight Al2O3@Ag NF for 4-NP removal is much higher than other metal NPs based catalysts reported in the literature, signifying the importance of NF formulation-based catalysis.

Characterization of homoepitaxial diamond films by Electron microscopy

1991 ◽  
Vol 49 ◽  
pp. 880-881
Author(s):  
D.P. Malta ◽  
S.A. Willard ◽  
R.A. Rudder ◽  
G.C. Hudson ◽  
J.B. Posthill ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Surface Defects ◽  
Substrate Surface ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Polycrystalline Diamond ◽  
Large Degree ◽  
Rf Plasma ◽  
Semiconducting Diamond

Semiconducting diamond films have the potential for use as a material in which to build active electronic devices capable of operating at high temperatures or in high radiation environments. A major goal of current device-related diamond research is to achieve a high quality epitaxial film on an inexpensive, readily available, non-native substrate. One step in the process of achieving this goal is understanding the nucleation and growth processes of diamond films on diamond substrates. Electron microscopy has already proven invaluable for assessing polycrystalline diamond films grown on nonnative surfaces.The quality of the grown diamond film depends on several factors, one of which is the quality of the diamond substrate. Substrates commercially available today have often been found to have scratched surfaces resulting from the polishing process (Fig. 1a). Electron beam-induced current (EBIC) imaging shows that electrically active sub-surface defects can be present to a large degree (Fig. 1c). Growth of homoepitaxial diamond films by rf plasma-enhanced chemical vapor deposition (PECVD) has been found to planarize the scratched substrate surface (Fig. 1b).

The Influence of Ascorbic Acid on Platelet Structure and Function

1975 ◽  
Vol 34 (01) ◽  
pp. 050-062
Author(s):  
Dale H Cowan ◽  
Richard C Graham ◽  
Patricia Shook ◽  
Ronda Griffin
Keyword(s):  
Ascorbic Acid ◽  
Open Channel ◽  
Channel System ◽  
Short Intervals ◽  
Platelet Survival ◽  
Artifactual Changes ◽  
Survival Studies ◽  
And Function ◽  
Induced Aggregation ◽  
Platelet Structure

SummaryTo determine the effect on platelet behavior of transient exposure of platelets to ascorbic acid, studies of platelet function and ultrastructure were done before exposure to ascorbic acid at pH 6.5, during exposure to pH 6.5, and after restoration of pH to pre-acidifìcation levels. The effect of ascorbic acid (A. A.) was compared to that of HCl and citric acid (C. A.). ADP- and collagen-induced aggregation of normal platelets were significantly impaired by both A. A. and C. A. but were less affected by HCl. The release of 14C-serotonin was significantly reduced by each agent. The ultra-structure of normal platelets brought to pH 6.5 by A.A. was normal. After neutralization, there was marked dilatation of the open channel system and loss of the disc shape. When platelets were brought to pH 6.5 by A. A., then neutralized, the aggregates which formed after stimulation by ADP or collagen were smaller than normal, the platelets were less closely approximated, and degranulation was less complete. The data show that exposure of platelets to ascorbic acid for short intervals impairs their function when measured after restoration of pH to levels compatible with maximal responses. Platelet survival studies using autologous platelets labelled with 51Cr in the presence or absence of ascorbic acid showed that the recovery of normal platelets was unaffected by ascorbic acid, whereas recovery of platelets from patients with idiopathic thrombocytopenic purpura, idiopathic thrombocythemia, and alcohol-related thrombocytopenia was markedly reduced. The injury resulting from the use of ascorbic acid in preparing platelets for studies of platelet survival in patients with disorders affecting platelets may impair the recovery of the cells, resulting in artifactual changes in the survival studies.

Transmission Electron Microscopy (TEM) Specimen Preparation Technique using Focused Ion Beam (FIB): Application to Material Characterization of Chemical Vapor Deposition of Tungsten (W) and Tungsten Silicides (WSix)

1997 ◽  
Author(s):  
K. Doong ◽  
J.-M. Fu ◽  
Y.-C. Huang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Chemical Vapor ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Transmission Electron

Abstract The specimen preparation technique using focused ion beam (FIB) to generate cross-sectional transmission electron microscopy (XTEM) samples of chemical vapor deposition (CVD) of Tungsten-plug (W-plug) and Tungsten Silicides (WSix) was studied. Using the combination method including two axes tilting[l], gas enhanced focused ion beam milling[2] and sacrificial metal coating on both sides of electron transmission membrane[3], it was possible to prepare a sample with minimal thickness (less than 1000 A) to get high spatial resolution in TEM observation. Based on this novel thinning technique, some applications such as XTEM observation of W-plug with different aspect ratio (I - 6), and the grain structure of CVD W-plug and CVD WSix were done. Also the problems and artifacts of XTEM sample preparation of high Z-factor material such as CVD W-plug and CVD WSix were given and the ways to avoid or minimize them were suggested.

scholarly journals Microscopic evidence of strong interactions between chemical vapor deposited 2D MoS2 film and SiO2 growth template

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Woonbae Sohn ◽  
Ki Chang Kwon ◽  
Jun Min Suh ◽  
Tae Hyung Lee ◽  
Kwang Chul Roh ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Spherical Aberration ◽  
Van Der Waals ◽  
Chemical Vapor ◽  
Interface Layer ◽  
Van Der Waals Interactions ◽  
Strong Interactions ◽  
Transition Electron Microscopy ◽  
Oxide Substrates

AbstractTwo-dimensional MoS2 film can grow on oxide substrates including Al2O3 and SiO2. However, it cannot grow usually on non-oxide substrates such as a bare Si wafer using chemical vapor deposition. To address this issue, we prepared as-synthesized and transferred MoS2 (AS-MoS2 and TR-MoS2) films on SiO2/Si substrates and studied the effect of the SiO2 layer on the atomic and electronic structure of the MoS2 films using spherical aberration-corrected scanning transition electron microscopy (STEM) and electron energy loss spectroscopy (EELS). The interlayer distance between MoS2 layers film showed a change at the AS-MoS2/SiO2 interface, which is attributed to the formation of S–O chemical bonding at the interface, whereas the TR-MoS2/SiO2 interface showed only van der Waals interactions. Through STEM and EELS studies, we confirmed that there exists a bonding state in addition to the van der Waals force, which is the dominant interaction between MoS2 and SiO2. The formation of S–O bonding at the AS-MoS2/SiO2 interface layer suggests that the sulfur atoms at the termination layer in the MoS2 films are bonded to the oxygen atoms of the SiO2 layer during chemical vapor deposition. Our results indicate that the S–O bonding feature promotes the growth of MoS2 thin films on oxide growth templates.

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