Search results for "Silver nanoparticle"

Bipyridine based metallogels: an unprecedented difference in photochemical and chemical reduction in the in situ nanoparticle formation

2017

Metal co-ordination induced supramolecular gelation of low molecular weight organic ligands is a rapidly expanding area of research due to the potential in creating hierarchically self-assembled multi-stimuli responsive materials. In this context, structurally simple O-methylpyridine derivatives of 4,4′-dihydroxy-2,2′-bipyridine ligands are reported. Upon complexation with Ag(I) ions in aqueous dimethyl sulfoxide (DMSO) solutions the ligands spontaneously form metallosupramolecular gels at concentrations as low as 0.6 w/v%. The metal ions induce the self-assembly of three dimensional (3D) fibrillar networks followed by the spontaneous in situ reduction of the Ag-centers to silver nanopartic…

An Intermetallic Au24Ag20 Superatom Nanocluster Stabilized by Labile Ligands

2015

An intermetallic nanocluster containing 44 metal atoms, Au24Ag20(2-SPy)4(PhC≡C)20Cl2, was successfully synthesized and structurally characterized by single-crystal analysis and density funtional theory computations. The 44 metal atoms in the cluster are arranged as a concentric three-shell Au12@Ag20@Au12 Keplerate structure having a high symmetry. For the first time, the co-presence of three different types of anionic ligands (i.e., phenylalkynyl, 2-pyridylthiolate, and chloride) was revealed on the surface of metal nanoclusters. Similar to thiolates, alkynyls bind linearly to surface Au atoms using their σ-bonds, leading to the formation of two types of surface staple units (PhC≡C-Au-L, L …

All-thiol-stabilized Ag44 and Au12Ag32 nanoparticles with single-crystal structures

2013

Noble metal nanoparticles stabilized by organic ligands are important for applications in assembly, site-specific bioconjugate labelling and sensing, drug delivery and medical therapy, molecular recognition and molecular electronics, and catalysis. Here we report crystal structures and theoretical analysis of three Ag44(SR)30 and three Au12Ag32(SR)30 intermetallic nanoclusters stabilized with fluorinated arylthiols (SR=SPhF, SPhF2 or SPhCF3). The nanocluster forms a Keplerate solid of concentric icosahedral and dodecahedral atom shells, protected by six Ag2(SR)5 units. Positive counterions in the crystal indicate a high negative charge of 4(-) per nanoparticle, and density functional theory…

Photosynthesized silver-polyaminocyclodextrin nanocomposites as promising antibacterial agents with improved activity

2016

Ag nanocomposites were prepared by photoreduction of ammoniacal silver acetate in the presence of poly-{6-[3-(2-(3-aminopropylamino)ethylamino)propylamino]}-(6-deoxy)-β-CD (amCD). The obtained systems were characterized by means of various complementary techniques (UV-vis, FT-IR, TEM, SAED). In particular, FT-IR spectroscopy evidenced a partial oxidative degradation of the polyamine branches of the capping auxiliary, due to the fact that these groups function as a sacrificial reducing agent in the photoinduced formation of the Ag metal core. TEM and SAED micrographs showed that the Ag cores possess a relatively low polydispersity and a significantly crystalline character. The Ag–amCD system…

Noble metal nanoparticles in organic matrix

2020

Abstract The purpose of this work is the synthesis and study of the properties of nanocomposite structures created by noble metal (silver) nanoparticles (NP's), an exciting class of materials with unique properties differ from both bulk and atomic behavior, which are self-organize in a thin organic film of copper phthalocyanine (CuPc). The structure and morphology of this material, depending on the amount of deposited silver, was studied in ultrahigh vacuum using transmission electron microscopy (TEM) and photoelectron spectroscopy (PES). Metallic atoms deposited on the surface of an organic substrate diffuse into the substrate, forming NPs with a narrow size distribution, which correlates …

Biogenic iron-silver nanoparticles inhibit bacterial biofilm formation due to Ag+ release as determined by a novel phycoerythrin-based assay

2020

Silver nanoparticles (Ag-NPs) can be considered as a cost-effective alternative to antibiotics. In the presence of Fe(III)-citrate and Ag+, Klebsiella oxytoca DSM 29614 produces biogenic Ag-NPs embedded in its peculiar exopolysaccharide (EPS). K. oxytoca DSM 29614 was cultivated in a defined growth medium–containing citrate (as sole carbon source) and supplemented with Ag+ and either low or high Fe(III) concentration. As inferred from elemental analysis, transmission and scanning electron microscopy, Fourier transform infrared spectrometry and dynamic light scattering, Ag-EPS NPs were produced in both conditions and contained also Fe. The production yield of high-Fe/Ag-EPS NPs was 12 times …

Synergistic Activity of Silver Nanoparticles and Polyaminocyclodextrins in Nanosponge Architectures

2019

Four new composite materials, formed by silver nanoparticles embedded in polyamino-cyclodextrin nanosponge architectures, were designed exploiting the affinity of polyamino-cyclodextrins towards Ag+ ions. These materials were characterized by means of different techniques (thermogravimetry, FT-IR, solid state NMR, SEM, HR-TEM), and tested as catalysts for the reduction of nitroarenes and the oxidative coupling of anilines. The results obtained showed synergistic activity between the supramolecular binding abilities of the nanosponge matrix and the catalytic properties of the metal nanoparticle, and open the way towards the design of new composite smart nanomaterials with improved catalytic …

Reduced graphene oxide/silver nanoparticles/β-cyclodextrin nanosponges composites with improved photocatalytic activity

2023

Significant activity improvement was achieved by associating graphene oxide-silver composite photocatalysts with cyclodextrin-based nanosponge materials, due to the synergistic effect provided by the supramolecular host abilities of the nanosponge. Three photocatalysts were prepared, fully characterized (FT-IR, ss-NMR, Raman, XRD, SEM, EDX, AFM, ICP, TGA, potentiometric titration), and tested for the oxidative photodegradation of some dyes and phenols, chosen as model organic pollutants. Compared to the unsupported photocatalyst, the nanosponge-based materials showed enhanced performances (being able to carry out the degradation even of dyes which do not react in the presence of the unsuppo…

PROPERTIES AND APPLICATIONS OF POLYAMINOCYCLODEXTRIN DERIVATIVES

Nel presente lavoro sono state prese in esame le potenziali applicazioni delle poliamminociclodestrine. In particolare, diversi derivati poliamminociclodestrinici (amCD) sono stati ottenuti utilizzando un approccio sintetico diretto, tramite reazione di sostituzione nucleofila tra la heptakis-(6-deossi)-(6-bromo)-βCD (BrβCD) e poliammine lineari. Una volta effettuata l’opportuna caratterizzazione NMR, ESI-MS e potenziometrica, sono state investigate diverse possibili utilizzazioni di tali materiali. Anzitutto, sono state valutate le capacità di dare complessi di inclusione host-guest con diversi derivati organici sia delle amCD libere che di materiali costituiti da nanospugne a base di amCD…

Plasmonic twinned silver nanoparticles with molecular precision

2016

Determining the structures of nanoparticles at atomic resolution is vital to understand their structure–property correlations. Large metal nanoparticles with core diameter beyond 2 nm have, to date, eluded characterization by single-crystal X-ray analysis. Here we report the chemical syntheses and structures of two giant thiolated Ag nanoparticles containing 136 and 374 Ag atoms (that is, up to 3 nm core diameter). As the largest thiolated metal nanoparticles crystallographically determined so far, these Ag nanoparticles enter the truly metallic regime with the emergence of surface plasmon resonance. As miniatures of fivefold twinned nanostructures, these structures demonstrate a subtle dis…