scholarly journals Methionine controlled impediment of secondary nucleation leading to nonclassical growth within self-assembled de novo gold nanoparticles

2021 ◽  
Author(s):  
Jitendra Sahu ◽  
Shahbaz Lone ◽  
Kalyan Sadhu
Keyword(s):  
Photoelectron Spectroscopy ◽  
Self Assembly ◽  
De Novo ◽  
Metal Nanostructures ◽  
Secondary Nucleation ◽  
Growth Reaction ◽  
Aurophilic Interaction ◽  
Seed Mediated ◽  
Dependent Growth ◽  
Key Steps

Abstract The conventional key steps for seed mediated growth of noble metal nanostructures involve classical and nonclassical nucleation. Furthermore, the surface of the seed catalytically enhances the secondary nucleation involving Au+ to Au0reduction, thus providing in-plane growth of seed. In contrast to this well-established growth mechanism, herein we report the unique case of methionine (Met) controlled seed mediated growth reaction, which rather proceeds via impeding secondary nucleation in presence of citrate stabilized gold nanoparticle (AuNP). The interaction between the freshly generated Au+ and thioether group of Met in the medium restricts the secondary nucleation process of further seed catalyzed Au+ reduction to Au0. This incomplete conversion of Au+, as confirmed by X-ray photoelectron spectroscopy (XPS), results in a significant enhancement of the zeta (z) potential even at low Met concentration. Nucleation of in situgenerated small-sized particles (nAuNPs) takes place on the parent seed surface followed by their segregation from the seed. Self-assembly process of these nAuNPs arises from the aurophilic interaction among the Au+. Furthermore, the time dependent growth of smaller particles to larger sized particles through assembly and merging within the same self-assembly validates the non-classical growth. This strategy has been successfully extended towards the seed mediated growth reaction of AuNP in presence of three bio-inspired decameric peptides having varying number of Met residues. The study confirms the nucleation strategy even in presence of single Met residue in the peptide and also the self-assembly of nucleated particles with increasing Met residues within the peptide.

scholarly journals Methionine-stabilized nonclassical growth within self-assembled de novo gold nanoparticles in conjunction with secondary nucleation inhibition

2021 ◽  
Author(s):  
Jitendra Sahu ◽  
Shahbaz Lone ◽  
Kalyan Sadhu
Keyword(s):  
Self Assembly ◽  
De Novo ◽  
Noble Metal Nanoparticles ◽  
Secondary Nucleation ◽  
Unique Case ◽  
Primary Particles ◽  
Growth Reaction ◽  
Aurophilic Interaction ◽  
Key Steps

Abstract The key steps for seed mediated growth of noble metal nanoparticles involve primary and secondary nucleation, which depends upon the energy barrier and ligand supersaturation standards of the medium. Herein we report the unique case of methionine (Met) controlled growth reaction, which rather proceeds via impeding secondary nucleation in presence of citrate stabilized gold nanoparticle (AuNP). The interaction between freshly generated Au+ and thioether group of Met in the medium restricts the secondary nucleation process involving further Au+ reduction. This incomplete conversion of Au+ results in a significant enhancement of the zeta (ζ) potential even at low concentration of Met. Furthermore, the aurophilic interaction of Au+ controls the self-assembly process of the in situ generated emissive nucleated particles. Nucleation of primary particles on seed surface, their segregation and time dependent conversion to larger particles within self-assembly confirm the nonclassical growth, which has further been explored with Met containing bio-inspired peptides.

scholarly journals Improvement of the thermal stability of dendritic silver-coated copper microparticles by surface modification based on molecular self-assembly

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Tae Hyeong Kim ◽  
Hyeji Kim ◽  
Hyo Jun Jang ◽  
Nara Lee ◽  
Kwang Hyun Nam ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Photoelectron Spectroscopy ◽  
Self Assembly ◽  
Electrically Conductive ◽  
X Ray ◽  
Alkyl Chains ◽  
Conductive Film ◽  
Initial Resistance ◽  
Thermal Stability Of ◽  
Scanning Electron

AbstractIn the study reported herein, silver-coated copper (Ag/Cu) powder was modified with alkanethiols featuring alkyl chains of different lengths, namely butyl, octyl, and dodecyl, to improve its thermal stability. The modification of the Ag/Cu powders with adsorbed alkanethiols was confirmed by scanning electron microscopy with energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Each powder was combined with an epoxy resin to prepare an electrically conductive film. The results confirmed that the thermal stability of the films containing alkanethiol-modified Ag/Cu powders is superior to that of the film containing untreated Ag/Cu powder. The longer the alkyl group in the alkanethiol-modified Ag/Cu powder, the higher the initial resistance of the corresponding electrically conductive film and the lower the increase in resistance induced by heat treatment.

scholarly journals Microstructure and Properties of Self-Assembly Graphene Microcapsules: Effect of the pH Value

Nanomaterials ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 587 ◽  
Author(s):  
Yan-Dong Guo ◽  
Jun-Feng Su ◽  
Ru Mu ◽  
Xin-Yu Wang ◽  
Xiao-Long Zhang ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Photoelectron Spectroscopy ◽  
Self Assembly ◽  
Chemical Engineering ◽  
Ph Value ◽  
Liquid Paraffin ◽  
Energy Dispersive Spectrometer ◽  
Core Material ◽  
Microstructure And Properties ◽  
Ph Values

Graphene has attracted attention in the material field of functional microcapsules because of its excellent characteristics. The content and state of graphene in shells are critical for the properties of microcapsules, which are greatly affected by the charge adsorption equilibrium. The aim of this work was to investigate the effect of pH value on the microstructure and properties of self-assembly graphene microcapsules in regard to chemical engineering. Microcapsule samples were prepared containing liquid paraffin by a self-assembly polymerization method with graphene/organic hybrid shells. The morphology, average size and shell thickness parameters were investigated for five microcapsule samples fabricated under pH values of 3, 4, 5, 6 and 7. The existence and state of graphene in dry microcapsule samples were analyzed by using methods of scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). Fourier Transform Infrared Spectoscopy (FT-IR) and Energy Dispersive Spectrometer (EDS) were applied to analyze the graphene content in shells. These results proved that graphene had existed in shells and the pH values greatly influenced the graphene deposition on shells. It was found that the microcapsule sample fabricated under pH = 5 experienced the largest graphene deposited on shells with the help of macromolecules entanglement and electrostatic adherence. This microcapsules sample had enhanced thermal stability and larger thermal conductivity because of additional graphene in shells. Nanoindentation tests showed this sample had the capability of deforming resistance under pressure coming from the composite structure of graphene/polymer structure. Moreover, more graphene decreased the penetrability of core material out of microcapsule shells.

scholarly journals Nano-PAA-CuCl2 Composite as Fenton-Like Reusable Catalyst to Enhanced Degrade Organic Pollutant MB/MO

Catalysts ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 10
Author(s):  
Yang Dang ◽  
Yu Cheng ◽  
Yukun Zhou ◽  
Yifei Huang ◽  
Kaige Wang
Keyword(s):  
Photoelectron Spectroscopy ◽  
Self Assembly ◽  
Organic Pollutant ◽  
Energy Dispersive Spectrometer ◽  
Chemical Properties ◽  
Anodic Alumina ◽  
Alumina Substrate ◽  
Reusable Catalyst ◽  
X Ray ◽  
Nanoporous Anodic Alumina

The treatment of organic dye contaminants in wastewaters has now becoming more imperative. Fenton-like degradation of methylene blue (MB) and methyl orange (MO) in aqueous solution was investigated by using a nanostructure that a layer of CuCl2 nanoflake film grown on the top surface of nanoporus anodic alumina substrate (nano-PAA-CuCl2) as catalyst. The new nano-PAA-CuCl2 composite was fabricated with self-assembly approach, that is, a network porous structure film composed of CuCl2 nanoflake grown on the upper surface of nanoporous anodic alumina substrate, and the physical and chemical properties are characterized systematically with the X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and high-resolution transmission electron microscopy (HRTEM), Energy Dispersive Spectrometer (EDS), X-ray photoelectron spectroscopy (XPS). The experimental results showed that the nano-PAA-CuCl2 catalyst presented excellent properties for the degradation of two typical organic pollutants such as MB and MO, which were almost completely degraded with 8 × 10−4mol/L nano-PAA-CuCl2 catalyst after 46 min and 60 min at reaction conditions of H2O2 18 mM and 23 mM, respectively. The effects of different reaction parameters such as initial pH, H2O2 concentration, catalyst morphology and temperature were attentively studied. And more, the stability and reusability of nano-PAA-CuCl2 were examined. Finally, the mechanism of MB and MO degradation by the nano-PAA-CuCl2/H2O2 system was proposed, based on the experimental data of the BCA and the temperature-programmed reduction (H2-TPR) and theoretical analysis, the reaction kinetics belonged to the pseudo-first-order equation. This new nanoporous composite material and preparation technology, as well as its application in Fenton-like reaction, provide an effective alternative method with practical application significance for wastewater treatment.

scholarly journals De novo centriole formation in human cells is error-prone and does not require SAS-6 self-assembly

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Won-Jing Wang ◽  
Devrim Acehan ◽  
Chien-Han Kao ◽  
Wann-Neng Jane ◽  
Kunihiro Uryu ◽  
...  
Keyword(s):  
Self Assembly ◽  
De Novo ◽  
Human Cells ◽  
De Novo Synthesis ◽  
Current Paradigm

Vertebrate centrioles normally propagate through duplication, but in the absence of preexisting centrioles, de novo synthesis can occur. Consistently, centriole formation is thought to strictly rely on self-assembly, involving self-oligomerization of the centriolar protein SAS-6. Here, through reconstitution of de novo synthesis in human cells, we surprisingly found that normal looking centrioles capable of duplication and ciliation can arise in the absence of SAS-6 self-oligomerization. Moreover, whereas canonically duplicated centrioles always form correctly, de novo centrioles are prone to structural errors, even in the presence of SAS-6 self-oligomerization. These results indicate that centriole biogenesis does not strictly depend on SAS-6 self-assembly, and may require preexisting centrioles to ensure structural accuracy, fundamentally deviating from the current paradigm.

X-ray Photoelectron Spectroscopy Study of the Deposition of TiO2 Thin Films on Self-assembly Monolayer

1998 ◽  
Vol 14 (01) ◽  
pp. 57-62
Author(s):  
Xiao Zhong-Dang ◽  
◽  
Huang Dan ◽  
Gu Jian-Hua ◽  
Lu Zu-Hong
Keyword(s):  
Thin Films ◽  
Photoelectron Spectroscopy ◽  
Self Assembly ◽  
Spectroscopy Study ◽  
X Ray

scholarly journals Synthesis of Non-Uniform Functionalized Amphiphilic Block Copolymers and Giant Vesicles in the Presence of the Belousov–Zhabotinsky Reaction

Biomolecules ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 352 ◽  
Author(s):  
Isadora Berlanga
Keyword(s):  
Photoelectron Spectroscopy ◽  
Self Assembly ◽  
Triblock Copolymer ◽  
Raft Polymerization ◽  
Catalyst Support ◽  
Giant Vesicles ◽  
Bz Reaction ◽  
Reversible Addition ◽  
Morphological Transitions ◽  
New Perspective

Giant vesicles with several-micrometer diameters were prepared by the self-assembly of an amphiphilic block copolymer in the presence of the Belousov–Zhabotinsky (BZ) reaction. The vesicle is composed of a non-uniform triblock copolymer synthesized by multi-step reactions in the presence of air at room temperature. The triblock copolymer contains poly(glycerol monomethacrylate) (PGMA) as the hydrophilic block copolymerized with tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)3), which catalyzes the BZ reaction, and 2-hydroxypropyl methacrylate (HPMA) as the hydrophobic block. In this new approach, the radicals generated in the BZ reaction can activate a reversible addition-fragmentation chain transfer (RAFT) polymerization to self-assemble the polymer into vesicles with diameters of approximately 3 µm. X-ray photoelectron spectroscopy (XPS) measurements demonstrated that the PGMA-b-Ru(bpy)3-b-PHPMA triblock copolymer is brominated and increases the osmotic pressure inside the vesicle, leading to micrometer-sized features. The effect of solvent on the morphological transitions are also discussed briefly. This BZ strategy, offers a new perspective to prepare giant vesicles as a platform for promising applications in the areas of microencapsulation and catalyst support, due to their significant sizes and large microcavities.

Influence of Thermal Treatments on the Chemistry and Self-Assembly of Ge Nanoparticles on SiO2 Surfaces

2004 ◽  
Vol 830 ◽  
Author(s):  
Scott K. Stanley ◽  
Shawn S. Coffee ◽  
John G. Ekerdt
Keyword(s):  
Photoelectron Spectroscopy ◽  
Self Assembly ◽  
Chemical Vapor ◽  
Thermal Treatments ◽  
X Ray ◽  
Agglomeration Process ◽  
Oxide Substrate ◽  
Temperature Programmed ◽  
Hot Filament ◽  
Substrate Temperatures

ABSTRACTGeH4 is thermally cracked over a hot filament depositing 0.7–15 ML Ge onto 2–7 nm SiO2/Si(100) at substrate temperatures of 300–970 K. Ge, GeHx, GeO, and GeO2 desorption is monitored through temperature programmed desorption in the temperature range 300–1000 K. Ge bonding changes are analyzed during annealing from 300–1000 K with X-ray photoelectron spectroscopy (XPS). Low temperature desorption features are attributed to GeO and GeH4. No GeO2 desorption is observed, but GeO2 decomposition to Ge through high temperature pathways is seen above 700 K. Germanium oxidization results from Ge etching of the oxide substrate, which is demonstrated through XPS. Ge nanoparticle formation on SiO2 is demonstrated using the agglomeration process. With these results, explanations for the difficulties of conventional chemical vapor deposition to produce Ge nanocrystals on SiO2 surfaces are proposed.

scholarly journals Fabrication and in vitro evaluation of stable collagen/hyaluronic acid biomimetic multilayer on titanium coatings

2013 ◽  
Vol 10 (84) ◽  
pp. 20130070 ◽  
Author(s):  
Haiyong Ao ◽  
Youtao Xie ◽  
Honglue Tan ◽  
Shengbing Yang ◽  
Kai Li ◽  
...  
Keyword(s):  
Hyaluronic Acid ◽  
Photoelectron Spectroscopy ◽  
Self Assembly ◽  
Human Mesenchymal Stem Cells ◽  
Biological Properties ◽  
Covalent Immobilization ◽  
Layer By Layer ◽  
Titanium Coating ◽  
Assembly Technique

Layer-by-layer (LBL) self-assembly technique has been proved to be a highly effective method to immobilize the main components of the extracellular matrix such as collagen and hyaluronic acid on titanium-based implants and form a polyelectrolyte multilayer (PEM) film by electrostatic interaction. However, the formed PEM film is unstable in the physiological environment and affects the long-time effectiveness of PEM film. In this study, a modified LBL technology has been developed to fabricate a stable collagen/hyaluronic acid (Col/HA) PEM film on titanium coating (TC) by introducing covalent immobilization. Scanning electron microscopy, diffuse reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize the PEM film. Results of Sirius red staining demonstrated that the chemical stability of PEM film was greatly improved by covalent cross-linking. Cell culture assays further illustrated that the functions of human mesenchymal stem cells, such as attachment, spreading, proliferation and differentiation, were obviously enhanced by the covalently immobilized Col/HA PEM on TCs compared with the absorbed Col/HA PEM. The improved stability and biological properties of the Col/HA PEM covalently immobilized TC may be beneficial to the early osseointegration of the implants.

Methanobactin-Mediated One-Step Synthesis of Palladium Nanoparticles

NANO ◽  
2016 ◽  
Vol 11 (06) ◽  
pp. 1650064 ◽  
Author(s):  
Jia-Ying Xin ◽  
Hong-Chen Fan ◽  
Sheng-Fu Ji ◽  
Yan Wang ◽  
Chun-Gu Xia
Keyword(s):  
Photoelectron Spectroscopy ◽  
Palladium Nanoparticles ◽  
Fluorescence Spectra ◽  
Copper Binding ◽  
Secondary Nucleation ◽  
Visible Spectra ◽  
One Step ◽  
Ft Ir ◽  
Uv Visible ◽  
The One

The development of palladium nanoparticles (PdNPs) with a narrow size distribution is an important aspect of nanotechnology. Methanobactin (Mb) is a copper-binding small peptide that appears to function as an agent for copper sequestration and uptake in methanotrophs. Here, Mb was shown to bind and catalytically reduce Pd (II) to Pd (0). The one-step synthesis of monodisperse PdNPs using Mb as both coordination agent and reduction agent is reported. Fluorescence spectra, UV-visible spectra, X-ray photoelectron spectroscopy (XPS) and Fourier transform-infrared spectroscopy (FT-IR) suggested that the Mb molecules catalytically reduce Pd (II) to Pd (0) with the concomitant production of PdNPs. The Mb is then adsorbed onto the surface of the PdNPs to form an Mb–PdNPs coordination compound. This avoids secondary nucleation. The PdNPs are small with high monodispersity and are easily synthesized in Mb solution. The PdNPs were extremely stable and resisted aggregation even after several months.

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