scholarly journals Au/TiO2 catalysts prepared by borohydride reduction for preferential CO oxidation at near-ambient temperature

2019 ◽  
Vol 6 (1) ◽  
pp. 6-12 ◽  
Author(s):  
Georgia Barbalho Leal ◽  
Daniela C. Loureiro da Silva ◽  
Beatriz Naomy Watacabe ◽  
Ligia Ciotti ◽  
Rodolfo M. Antoniassi ◽  
...  
Keyword(s):  
Sodium Citrate ◽  
Au Nanoparticles ◽  
Borohydride Reduction ◽  
X Ray Diffraction ◽  
Excellent Performance ◽  
Preferential Co Oxidation ◽  
X Ray ◽  
Synthesis Parameters ◽  
Transmission Electron ◽  
Oxidation Of Carbon Monoxide

Abstract Au nanoparticles were prepared in solution using HAuCl4.3H2O as Au precursor, sodium citrate as stabilizing agent and sodium borohydride as reducing agent. The influence of synthesis parameters such as BH4:Au and Citrate:Au ratios were studied. In a further step, the stabilized Au nanoparticles were supported on TiO2 with different Au loadings (wt%). The resulting Au/TiO2 catalysts were characterized by Energy-dispersive X-ray spectroscopy, X-ray diffraction and Transmission Electron Microscopy and tested for the preferential oxidation of carbon monoxide in hydrogen-rich stream. Au nanoparticles stabilized in solution were obtained with sizes in the range of 3-4 nm. After supported on TiO2, the Au nanoparticles size did not change and the Au/TiO2 catalysts exhibited excellent performance and stability in the temperature range of 20 - 50°C.

Effect of Au on the Performance of Porous Silicon/V2O5 Nanorods Heterojunctions to NO2 Gas

NANO ◽  
2016 ◽  
Vol 11 (07) ◽  
pp. 1650079 ◽  
Author(s):  
Wenjun Yan ◽  
Ming Hu ◽  
Jiran Liang ◽  
Dengfeng Wang ◽  
Yulong Wei ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Porous Silicon ◽  
Room Temperature ◽  
Au Nanoparticles ◽  
Analytical Techniques ◽  
Heating Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Electron

A novel composite of Au-functionalized porous silicon (PS)/V2O5 nanorods (PS/V2O5:Au) was prepared to detect NO2 gas. PS/V2O5 nanorods were synthesized by a heating process of pure vanadium film on PS, and then the obtained PS/V2O5 nanorods were functionalized with dispersed Au nanoparticles. Various analytical techniques, such as field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), have been employed to investigate the properties of PS/V2O5:Au. Herein, the PS/V2O5:Au sample exhibited improved NO2-sensing performances in response, stability and selectivity at room temperature (25[Formula: see text]C), compared with the pure PS/V2O5 nanorods. These phenomena were closely related to not only the dispersed Au nanoparticles acting as a catalyst but also the p-n heterojunctions between PS and V2O5 nanorods. Whereas, more Au nanoparticles suppressed the improvement of response to NO2 gas.

scholarly journals Synthesis of Dandelion-like Porous Au Nanoparticles for Catalytic Reduction of Nitrophenol

2020 ◽  
Vol 01 ◽  
Author(s):  
Huiying Wu ◽  
Feng Liang
Keyword(s):  
Active Sites ◽  
Au Nanoparticles ◽  
Catalytic Reduction ◽  
Molar Ratio ◽  
Void Space ◽  
X Ray Diffraction ◽  
Uniform Size ◽  
Templating Method ◽  
X Ray ◽  
Transmission Electron

Background: Porous Au nanomaterials show great potential in the fields of biomedicine, drug delivery and catalysis for the merits of low density, large void space and large specific surface area. The preparation of porous Au nanomaterials is usually carried out by using a hard-templating method which is cumbersome. Methods: Dandelion-like porous Au nanoparticles were synthesized through a soft-templating method in our work. The synthesized porous Au nanoparticles were characterized via transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX) and cyclic voltammetry (CV). The reduction of nitrophenol was carried out to evaluate the catalytic behavior of porous Au nanoparticles. Results: Porous Au nanoparticles prepared were in uniform size (47.9±6.4 nm) and the morphology could be regulated by adjusting the molar ratio of reactants. The apparent rate constant (kapp) value of reducing nitrophenol catalyzed by porous Au nanoparticles was higher than Au nanospheres and nanobranches in similar size. It could be attributed to the large amount of active sites and high proportion of high-order crystal faces proved by CV and XRD. Conclusion: We developed a facile and reproducible method for synthesizing porous Au nanoparticles. The morphology of porous Au nanoparticles can be ajusted by changing the molar ratio of reactants. Porous Au nanoparticles we prepared behaved better in catalysis compared with Au nanospheres and Au nanobranches.

Plasmon Enhanced Emission of Perovskite Quantum Dot Films

MRS Advances ◽  
2018 ◽  
Vol 3 (14) ◽  
pp. 733-739 ◽  
Author(s):  
Seyma Dadı ◽  
Yemliha Altıntas ◽  
Emre Beskazak ◽  
Evren Mutlugun
Keyword(s):  
Quantum Dot ◽  
Au Nanoparticles ◽  
Au Nanoparticle ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Transmission Electron ◽  
Coating Method ◽  
Photoluminescence Enhancement ◽  
Time Resolved Photoluminescence

ABSTRACTWe propose and demonstrate the photoluminescence enhancement of CsPbBr3 perovskite quantum dot films in the presence of Au nanoparticles. Embedded into a polymer matrix, Au nanoparticle- quantum dot film assemble prepared by an easy spin coating method enabled the photoluminescence enhancement of perovskite quantum dot films up to 78%. The properties of the synthesized perovskite QDs and gold nanoparticles have been analysed using high resolution transmission electron microscopy, X-ray diffraction, energy dispersive X- ray spectroscopy, UV-Vis absorption spectrophotometer, steady state and time-resolved photoluminescence spectrometer.

Synthesis and Characterization of Nano Hydroxylapatite by Reaction Precipitation in Impinging Streams

2010 ◽  
Vol 160-162 ◽  
pp. 1301-1308 ◽  
Author(s):  
Jun Yuan ◽  
Yuan Wu ◽  
Qi Xin Zheng ◽  
Xiao Lin Xie
Keyword(s):  
Electron Microscopy ◽  
Xrd Analysis ◽  
Synthesis And Characterization ◽  
Preparation Process ◽  
X Ray Diffraction ◽  
Excellent Performance ◽  
X Ray ◽  
Operation Conditions ◽  
Transmission Electron

Hydroxylapatite(HAP) nano-whiskers are prepared by reaction-precipitation in the submerged circulative impinging stream reactor(SCISR), with (NH4)2HPO4 and Ca(NO3)2 as the reagents; and the products are characterized by X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). The results TEM measured indicate that the product prepared under typical operation conditions is average-sized 15nm and 50-70nm long. Multiply repeated experiments illustrates that, because of the excellent performance of the reactor, the preparation process can be easily controlled to yield nano rod/whisker hydroxylapatite with very narrow size distribution.

Photoinduced formation of colloidal Au by a near-infrared femtosecond laser

2003 ◽  
Vol 18 (7) ◽  
pp. 1710-1714 ◽  
Author(s):  
Chongjun Zhao ◽  
Shiliang Qu ◽  
Jianrong Qiu ◽  
Congshan Zhu
Keyword(s):  
Femtosecond Laser ◽  
Absorption Spectra ◽  
Near Infrared ◽  
Au Nanoparticles ◽  
X Ray Diffraction ◽  
Local Formation ◽  
X Ray ◽  
Transmission Electron ◽  
Red Color ◽  
Yellow Orange

A Au colloid was prepared in a 5 mM HAuCl4 solution through irradiation with a focused infrared femtosecond laser at 800 nm. The Au colloid was characterized by absorption spectra, transmission electron microscopy, and x-ray diffraction analysis. The appearance of absorption peak around 526 nm in the absorption spectra and the wine-red color of sample solution HAuCl4 under focused laser irradiation verified the formation of Au colloid. The solution color changed in the order of yellow → orange → wine-red due to the local formation of Au nanoparticles near the focus. The pulse energy, focus position of laser beam, and solvent composite play important roles in formation, grain size, and stability of the Au colloid. A mechanism for the precipitate of Au nanoparticles was proposed, and a multiphoton process of femtosecond laser was involved.

Physical Properties of the Amorphous Silica Encapsulated Fluorescence Dye

2013 ◽  
Vol 686 ◽  
pp. 285-289
Author(s):  
Zakaria Nor Dyana ◽  
Abdul Razak Khairunisak ◽  
Abdul Aziz Azlan
Keyword(s):  
Electron Microscope ◽  
Effect Of Temperature ◽  
Halogen Lamp ◽  
X Ray Diffraction ◽  
Dye Tracing ◽  
X Ray ◽  
Synthesis Parameters ◽  
Transmission Electron ◽  
Fluorescence Dye ◽  
Silica Precursor

Amorphous nanosilica entrapped fluorescence dye intended to be used as tracing agent for imaging of cell or tissue in human cell was prepared using micelle entrapment approach. Micelles were produced by mixing a surfactant in water with additives such as butanol and ammonia in a preheated bioreactor. Then, 1,1%-dioctadecyl-3,3,3%,3% tetramethylindocarbocyanine perchlorate (DiI) dye tracing agent was added into the mixture followed by the addition of silica precursor. The parameters studied including effect of surfactant amount, effect of temperature and amount of Si precursor. Silica encapsulated DiI produced were then characterized using Transmission Electron Microscope (TEM), X-ray diffraction (XRD) and UV-Vis NIR spectrophotometer. Dynamic light scattering (DLS) showed that tunable size of nanoparticles in the range of 30-150 nm can be produced by varying synthesis parameters. The results showed that the silica encapsulated DiI became bigger and uniform in size with the increase of temperature and amount of surfactant. The silica encapsulated with DiI is photostable which the intensity of fluorescence value is 279.12 after 90 minutes exposure to halogen lamp (200W) compared to bare DiI that degraded to 100.61.

scholarly journals Hydrothermal synthesis of monocopper sulfide for hydrogen peroxide-assisted photodegradation of paraquat

2020 ◽  
Vol 26 (1) ◽  
Author(s):  
Rattabal Khunphonoi ◽  
Kitirote Wantala ◽  
Nurak Grisdanurak
Keyword(s):  
Photoelectron Spectroscopy ◽  
Reaction Rate ◽  
Ageing Time ◽  
Reaction Rate Constant ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Energy Band Gap ◽  
X Ray ◽  
Synthesis Parameters ◽  
Transmission Electron

Copper sulfide was prepared by a hydrothermal method at 130°C. The copper to sulfur molar ratio (6-10) and ageing time (24-72 h) were their synthesis parameters. The obtained materials were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), transmission electron microscope (TEM), UV-DR spectroscopy and X-ray photoelectron spectroscopy (XPS). In order to obtain monocopper sulfide, CuS, named as covellite, the molar recipe ratio of sulfur to copper should be less than 8 in any hydrothermal ageing time. The morphology showed spherical-like structure with energy band gap of 1.88-2.04 eV. CuS was tested for its photocatalytic degradation of paraquat under visible light irradiation. It exhibited excellent activities in the presence of H<sub>2</sub>O<sub>2</sub>. The kinetic of paraquat degradation was also investigated using Langmuir-Hinshelwood-Hougen-Watson (LHHW) model. The reaction rate constant was three times higher than TiO<sub>2</sub> under the same studied conditions.

Synthesis of Highly Dispersed Carbon Supported Platinum Nanocatalyst for Fuel Cells

2011 ◽  
Author(s):  
Hanna S. Abbo ◽  
Ivan R. Green ◽  
Salam J. J. Titinchi
Keyword(s):  
Sodium Citrate ◽  
Particle Distribution ◽  
Size Range ◽  
X Ray Diffraction ◽  
Particle Size Range ◽  
X Ray ◽  
Supported Platinum ◽  
Transmission Electron ◽  
Highly Dispersed ◽  
Colloidal Method

Pt/C and Pt/CNT catalysts were prepared by colloidal method using sodium citrate as a stabilizer, and ethylene glycol as the reducing agent and solvent. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) results showed that the Pt particles were highly dispersed on the support and had a very narrow particle distribution with particle size range of 1.5–2.4 nm for both catalysts. Based on the electrochemical properties characterized by cyclic voltammetry, it was found that the as-synthesized electrocatalysts possessed a significantly higher catalytic activity than those of commercial Pt/C Johnson Matthey catalyst.

Sunlight-Driving Formation and Characterization of Size-Controlled Gold Nanoparticles

2007 ◽  
Vol 7 (2) ◽  
pp. 708-711 ◽  
Author(s):  
Yonglan Luo
Keyword(s):  
Gold Nanoparticles ◽  
Sodium Citrate ◽  
Noble Metal Nanoparticles ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Electron Microcopy ◽  
Uv Visible ◽  
Size Controlled

Exposing a sodium citrate-HAuCl4 aqueous solution to sunlight results in the formation of size-controlled, citrate-capped gold nanoparticles. The gold nanoparticles were characterized by UV-visible, transmission electron microscopy (TEM), scanning electron microcopy (SEM), and X-ray diffraction (XRD) spectroscopic methods. It provides a general methodologyfor the economic, convenient, mild preparation of citrate-capped noble metal nanoparticles.

scholarly journals Structure and Optical Property of Gold Nanoparticles Synthesized by Modified Polyol Method

2021 ◽  
Vol 31 (3) ◽  
Author(s):  
Long Nguyen Viet
Keyword(s):  
Gold Nanoparticles ◽  
Au Nanoparticles ◽  
Average Particle Size ◽  
Nir Spectroscopy ◽  
Polyol Method ◽  
Average Particle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Modified Polyol Method

In this research, Au nanoparticles were successfully synthesized by modified polyol method with commercial precursors to be gold (III) chloride trihydrate (HAuCl4·3H2O), ethylene glycol (EG), poly(vinylpyrrolidone) (PVP), sodium borohydride (NaBH4). The structure and properties of as-prepared Au nanoparticles have been investigated by X ray diffraction (XRD), transmission electron microscopy (TEM), and UV-vis-NIR spectroscopy. As a result, Au nanoparticles with the average particle size of 28.80 nm were successfully synthesized in the range of about 50 nm. It is evidenced that the assembly of gold nanoparticles was presented in their nucleation, growth, and formation. 

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