One-step preparation and characterization of core-shell SiO2/Ag composite spheres by pulse plating

2017 ◽  
Vol 24 (3) ◽  
pp. 423-427 ◽  
Author(s):  
Li Xiong ◽  
Xiangping Huang ◽  
Ya Liu ◽  
Liqing Pan
Keyword(s):  
Structural Characteristics ◽  
Pulse Plating ◽  
Core Shell ◽  
X Ray Diffraction ◽  
Simple Method ◽  
Transmission Electron ◽  
Surface Enhanced Raman ◽  
One Step ◽  
Enhanced Raman Scattering ◽  
20 Nm

AbstractA simple method of one-step pulse plating was used in the fabrication of core-shell SiO2/Ag composite spheres. Structural characteristics and morphologies of the prepared SiO2/Ag composite spheres are characterized by means of X-ray diffraction, scanning electron microscope, and transmission electron microscopy. The Ag shell is uniformly coated on the surface of SiO2 spheres with the thickness of about 20 nm. Photoluminescence (PL) spectrum has revealed that PL of the core-shell samples is much stronger than that of bare SiO2 spheres. Raman spectrometer measurements show that the SiO2/Ag composite spheres have excellent surface-enhanced Raman scattering performance. In addition, the current-voltage characteristic of SiO2/Ag composite spheres has improved at the same time.

scholarly journals Performance Improving Method of Aligned Silver Nanorod by Grafting Au@Ag Core–Shell Nanoparticles for Surface-Enhanced Raman Scattering

NANO ◽  
2017 ◽  
Vol 12 (11) ◽  
pp. 1750131 ◽  
Author(s):  
Jian Chen ◽  
Peitao Dong ◽  
Chaoguang Wang ◽  
Chenyu Zhang ◽  
Junfeng Wang ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Surface Enhanced Raman Scattering ◽  
Core Shell ◽  
Sers Substrate ◽  
Shell Nanoparticles ◽  
Simple Method ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Enhanced Raman Scattering ◽  
Core Shell Nanoparticles

A simple method for improving surface-enhanced Raman scattering (SERS) performance of aligned silver nanorod (Ag NR) array was investigated. This method was to construct a kind of hybrid substrate by grafting Au@Ag core–shell nanoparticles (NPs) into Ag NR array using poly(2-vinylphridine) (P2VPy) as a bridging agent. The hybrid substrate yielded excellent SERS performance as its detection limit improved from 10[Formula: see text] M to 10[Formula: see text] M using trans-1,2-bis(4-pyridyl)ethylene (BPE) as probe molecule, which was increased by two orders of magnitude compared with Ag NR array substrate. The significant improvement of SERS performance of Ag NR arrays was attributed to the addition of Au@Ag core–shell NPs. As a result of surface plasmon resonance generated by the interaction of electromagnetic (EM) (IAEM) filed between NP and NR structures, increasing hotspots were found at the connections of NPs and NRs, the gaps of adjacent rods, and the gaps of two particles consequently. These results were validated by the finite difference time domain (FDTD) calculation. Besides, hybrid substrate shows good performance in stability and reproducibility. The proposed method was simple and robust, which promoted SERS performance of Ag NR array effectively, showing great potential in the application of SERS substrate fabrication and SERS-based bio-chemical sensing.

A Comparative Study on Ternary Low-Platinum Catalysts with Various Constructions for Oxygen Reduction and Methanol Oxidation Reactions

NANO ◽  
2016 ◽  
Vol 11 (07) ◽  
pp. 1650081 ◽  
Author(s):  
Yan Ni Wu ◽  
Hai Fu Guo ◽  
Peng Hu ◽  
Xiao Peng Xiao ◽  
Zhao Wang Xiao ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Methanol Oxidation ◽  
Reduction Reaction ◽  
Methanol Oxidation Reaction ◽  
Core Shell ◽  
Oxidation Reactions ◽  
X Ray Diffraction ◽  
Structured Catalyst ◽  
Transmission Electron ◽  
One Step

Three types of ternary low-platinum nanocatalysts, alloy PdPtIr/C, core–shell PdPt@PtIr/C and Pd@PtIr/C, have been prepared, and their catalytic behaviors toward methanol oxidation reaction (MOR)/oxygen reduction reaction (ORR) are comparatively investigated via cyclic voltammetry and chronoamperometry analysis in an acidic medium. Through a two-step colloidal technique, the synthesized core–shell structured catalyst PtPd@PtIr/C with alloy core and alloy shell show the best catalytic activity toward MOR and the best poisoning tolerance. The alloy PdPtIr/C catalyst prepared via a one-step colloidal technique exhibits the best performance toward ORR among the three catalysts. All the three catalysts are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and other characterization techniques.

Controlled Growth of ZnO Nanocrystals on the Surface of SiO2 Spheres

2009 ◽  
Vol 151 ◽  
pp. 264-268 ◽  
Author(s):  
Yuliya V. Yermolayeva ◽  
Yuriy N. Savin ◽  
Alexander V. Tolmachev
Keyword(s):  
Average Diameter ◽  
Core Shell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Zno Nanocrystals ◽  
Transmission Electron ◽  
Zno Particles ◽  
One Step ◽  
Shell Particles ◽  
Sio2 Spheres

The “islands” of ZnO nanocrystals on amorphous monodisperse 200 nm SiO2 spheres (core-shell particles) were obtained by simple one-step technique based on low-temperature crystallization from liquid phase. The influence of starting reagents types and concentration of zinc ions in the reaction mixture on the morphology of ZnO shells obtained was studied. Crystalline structure of ZnO nanocrystals obtained was proofed by the X-ray diffraction data. The average diameter of ZnO nanocrystals on SiO2 spheres is 10 nm according to X-ray diffraction (XRD) and transmission electron microscopy (TEM) data. It was shown that SiO2/ZnO particles obtained have high luminescence characteristics. Photoluminescence spectra of core-shell SiO2/ZnO particles show two emission peaks centred at 386 nm and 570 nm. Core-shell SiO2/ZnO particles obtained are perspective for active photonic crystals creation for UV-spectral region.

A NOVEL SYNTHESIS METHOD FOR SILVER NANOPARTICLES USING MOLTEN ε-CAPROLACTAM AS SOLVENT AND REDUCING AGENT

NANO ◽  
2014 ◽  
Vol 09 (08) ◽  
pp. 1450085
Author(s):  
PENG LI ◽  
HOUSHENG XIA ◽  
GUISHENG YANG
Keyword(s):  
Silver Nanoparticles ◽  
Synthesis Method ◽  
Reducing Agent ◽  
Synthesis Process ◽  
Precipitation Reaction ◽  
X Ray Diffraction ◽  
Ag Nps ◽  
Transmission Electron ◽  
Surface Enhanced Raman ◽  
Enhanced Raman Scattering

A precipitation–reduction synthesis method for silver nanoparticles ( Ag NPs) was developed. Molten ε-caprolactam (CL) was used not only as solvent but also as reducing agent and stabilizer. At first, Ag 2 O NPs was prepared by precipitation reaction of silver nitrate ( AgNO 3) and sodium hydroxide ( NaOH ) using molten CL as solvent at 100°C. Then, Ag 2 O NPs was in situ reduced into Ag NPs by molten CL at 120°C. Techniques of X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to monitor the synthesis process. With the increase of reduction time, monodispersed Ag 2 O NPs (ca. 3.7 nm) were integrated and larger Ag NPs (10–90 nm) were formed. Fourier transform infrared (FT-IR) results showed that the surface of Ag NPs was capped with about 0.9 wt.% of CL molecules. Surface enhanced Raman scattering (SERS) effect of Ag NPs was investigated using Rhodamine 6G as a probe molecule.

Surface Enhanced Raman Scattering (SERS) Effects of 4-Aminothiophenol on Au Nanoparticles with Different Shapes

2020 ◽  
Vol 20 (9) ◽  
pp. 5959-5963 ◽  
Author(s):  
Xiaochuan Xu ◽  
Xiaofang Liu ◽  
Min He ◽  
Bin Liu ◽  
Jianhui Yang
Keyword(s):  
Catalytic Activity ◽  
Raman Scattering ◽  
Au Nanoparticles ◽  
Surface Enhanced Raman Scattering ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Enhanced Raman Scattering ◽  
Different Shapes

Au nanoparticles with different shapes (nanosphere, nanoplate and nanorod) have been synthesized and were characterized by scanning electron microscope, transmission electron microscopy, X-ray diffraction and UV-vis absorption spectroscopy. We investigated the catalytic activity of Au nanoparticles with different morphologies as surface-enhanced Raman scattering substrates for the conversion of p-aminothiophenol to p,p′-dimercaptoazobenzene. The experimental results indicated that the order of catalytic activity is nanorod> nanoplate> nanosphere under 633 and 785 nm excitation. The current research provides some reliable insights and important references for exploration new catalysts and their catalytic activities from the perspectives of different sizes, morphology and crystal composition of nanomaterials.

scholarly journals Photosynthesis of Silver Nanoparticle – Carbon Quantum Dots Nanocomposites

2019 ◽  
Vol 16 (2) ◽  
pp. 118-124
Author(s):  
Xuan-Dung Mai ◽  
Quang-Trung Le ◽  
Lan-Anh Nguyen Thi ◽  
Phuong Nguyen Thi ◽  
Phuong Le Thi ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Silver Ions ◽  
Carbon Quantum Dots ◽  
X Ray Diffraction ◽  
Ag Nps ◽  
Transmission Electron ◽  
Ir And Raman Spectroscopies ◽  
Surface Enhanced Raman ◽  
Potential Applications ◽  
Enhanced Raman Scattering

Nanocomposites (NCs) of silver nanoparticles (Ag NPs) and carbon quantum dots (CQDs) have been received increasing attention for diverse applications including sensing, photocatalyst, surface enhanced Raman scattering detection and antibacterial. Herein, we report a unique photosynthesis of Ag NPs-CQD using CQDs as photo-reducing agent. Highly luminescent CQDs were prepared by a hydrothermal method using a mixture of citric acid (CA) and ethylenediamine (EDA) as starting precursors. X-ray diffraction pattern (XRD), transmission electron microscope (TEM), infrared (IR) and Raman spectroscopies confirmed the formation of NCs. We have demonstrated that the formation of Ag NPs accompanied with the degradation of surface fluorophores, which responded for the resolved absorption peak at ca. 346 nm and high luminescence of pristine CQDs. The NCs showed excellent antibacterial affinity to Escherichia coli. The results provide new understandings on the interactions between CQDs and silver ions as well as potential applications of Ag NP – CQD nanocomposites.

scholarly journals One-step approach for the synthesis of CoFe2O4@rGO core-shell nanocomposites as efficient adsorbent for removal of organic pollutants

2016 ◽  
Vol 75 (2) ◽  
pp. 397-405 ◽  
Author(s):  
Z. J. Song ◽  
W. Ran ◽  
F. Y. Wei
Keyword(s):  
Graphene Oxide ◽  
Adsorption Capacity ◽  
Average Diameter ◽  
Core Shell ◽  
X Ray Diffraction ◽  
Anionic Dyes ◽  
Reduced Graphene ◽  
Key Factor ◽  
One Step ◽  
20 Nm

CoFe2O4-reduced graphene oxide nanocomposites (CFG) have been successfully synthesized via one-step solvothermal method. The prepared CFG are characterized by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy (FESEM), vibrating sample magnetometer and so on. The FESEM results show that CFG have uniform core-shell structure with an average diameter of about 75 nm and the thickness of the outer graphene shell is about 15–20 nm. The mass ratio of CoFe2O4 to graphene oxide is a key factor affecting the formation of core-shell hybrids. CFG display much higher adsorption capacity for anionic dyes than cationic dyes owing to the favorable electrostatic interaction. The adsorption capacity for methyl orange is observed as high as 263 mg g–1 at 298 K, and the adsorption isotherms follow the Langmuir model. Furthermore, the specific saturation magnetization (Ms) of CFG is 32.8 emu g–1, and the as-synthesized nanocomposites can be easily separated by external magnetic field after adsorption. The results suggest that CFG have great potential for the practical industrial wastewater treatment.

A High Resolution Study of G.P. Zones in Aluminum - 4.2 at % Silver

1982 ◽  
Vol 40 ◽  
pp. 722-723 ◽  
Author(s):  
R. Gronsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Computer Simulations ◽  
Structural Characteristics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Resolution Study

The phenomenon of clustering in Al-Ag alloys has been extensively studied since the early work of Guinierl, wherein the pre-precipitation state was characterized as an assembly of spherical, ordered, silver-rich G.P. zones. Subsequent x-ray and TEM investigations yielded results in general agreement with this model. However, serious discrepancies were later revealed by the detailed x-ray diffraction - based computer simulations of Gragg and Cohen, i.e., the silver-rich clusters were instead octahedral in shape and fully disordered, atleast below 170°C. The object of the present investigation is to examine directly the structural characteristics of G.P. zones in Al-Ag by high resolution transmission electron microscopy.

scholarly journals Synthesis of Densely Immobilized Gold-Assembled Silica Nanostructures

2021 ◽  
Vol 22 (5) ◽  
pp. 2543
Author(s):  
Bomi Seong ◽  
Sungje Bock ◽  
Eunil Hahm ◽  
Kim-Hung Huynh ◽  
Jaehi Kim ◽  
...  
Keyword(s):  
Potential Method ◽  
Sers Substrate ◽  
Chloroauric Acid ◽  
Au Nps ◽  
Sio2 Surface ◽  
Color Changes ◽  
Surface Enhanced Raman ◽  
Nanoparticle Preparation ◽  
Enhanced Raman Scattering ◽  
20 Nm

In this study, dense gold-assembled SiO2 nanostructure (SiO2@Au) was successfully developed using the Au seed-mediated growth. First, SiO2 (150 nm) was prepared, modified by amino groups, and incubated by gold nanoparticles (ca. 3 nm Au metal nanoparticles (NPs)) to immobilize Au NPs to SiO2 surface. Then, Au NPs were grown on the prepared SiO2@Au seed by reducing chloroauric acid (HAuCl4) by ascorbic acid (AA) in the presence of polyvinylpyrrolidone (PVP). The presence of bigger (ca. 20 nm) Au NPs on the SiO2 surface was confirmed by transmittance electronic microscopy (TEM) images, color changes to dark blue, and UV-vis spectra broadening in the range of 450 to 750 nm. The SiO2@Au nanostructure showed several advantages compared to the hydrofluoric acid (HF)-treated SiO2@Au, such as easy separation, surface modification stability by 11-mercaptopundecanoic acid (R-COOH), 11-mercapto-1-undecanol (R-OH), and 1-undecanethiol (R-CH3), and a better peroxidase-like catalysis activity for 5,5′-Tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2) reaction. The catalytic activity of SiO2@Au was two times better than that of HF-treated SiO2@Au. When SiO2@Au nanostructure was used as a surface enhanced Raman scattering (SERS) substrate, the signal of 4-aminophenol (4-ATP) on the surface of SiO2@Au was also stronger than that of HF-treated SiO2@Au. This study provides a potential method for nanoparticle preparation which can be replaced for Au NPs in further research and development.

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