Nucleation Of Silver Nanoparticles Research Articles

Direct Nucleation of Silver Nanoparticles on Graphene Sheet

Silver (Ag) nanoparticles were synthesized on the surface of graphene sheet by the simultaneous reduction of Ag+ and graphene oxide (GO) in the presence of simple reducing agent, hydrazine hydrate (N2H4 x H2O). Both the Ag+ and GO were reduced and Ag+ was nucleated onto graphene. GO flakes were prepared by conventional chemical exfoliation method and in the presence of strong acidic medium of potassium chlorate. Silver nanoparticles were prepared using 0.01 M AgNO3 solution. The reduced GO sheet decorated with Ag is referred as G-Ag sample. G-Ag was characterized by FTIR (Fourier transform infrared) spectroscopy using GO as standard. An explicit alkene peak appeared around 1625 cm(-1) was observed in G-Ag sample. Besides, the characteristic carbonyl and hydroxyl peaks shows well reduction of GO. The FTIR therefore confirms the direct interaction of Ag into Graphene. SEM (scanning electron microscopy) and TEM (transmission electron microscopy) analysis were performed for morphological probing. The average size of Ag nanoparticles was confirmed by around 5-10 nm by the high-resolution TEM (HRTEM). The Ag quantum dots incorporated nanocomposite material could become prominent candidate for diverse applications including photovoltaic, catalysis, and biosensors etc.

Cover Picture: Topographically controlled growth of silver nanoparticle clusters (Phys. Status Solidi RRL 5/2012)

It has been well known that a nanometer- or micrometer-scale surface roughness affects the heterogeneous nucleation and controls the growth kinetics of nanocrystals. In their Letter on pp. 202–204, Wi, Shrestha and Nagao demonstrate that the preferred nucleation of silver nanoparticles inside lithographically defined silicon nanowells allows to locate the silver nanoclusters in predetermined positions, and thus to form ordered arrays of surface enhanced Raman scattering (SERS)-active sensors. Highly enhanced surface plasmon fields from the Ag nanoparticle clusters were successfully confirmed by three-dimensional electromagnetic simulation and by confocal measurements of increased Raman signals. The proposed approach, which enables to combine a top–down nanoscale templating and a bottom–up nanoparticles synthesis, can be utilized for the growth and assembly of functional nanomaterials in a broad range of materials, array designs, and applications.

Origin of room temperature broadband light emission and carrier dynamics in Ag ion-implanted Silicon nanocrystals

We studied the origin of broad band light emission in the Ultraviolet (UV) to the red from silicon nanoparticles fabricated using a single low energy (32 keV) silver ion implantation with a fluence of 5*1015 ions/cm2 in crystalline Si. It is found from a systematic study of the annealing carried out at certain temperatures that the spectral characteristics in the UV and blue region remains unchanged except for the enhancement of light emission intensity due to annealing. The annealing results in nucleation of Ag nanoclusters in the vicinity of Si nanoparticles which enhances the emission intensity. Time-resolved photoluminescence (TRPL) measurement demonstrates that the emission originates from both highly localized defect bound excitons at the nanoscale Si interface, as well as surface and interface traps associated with the increased surface area of the Si nanocrystals. The emission in the UV is due to interband transitions from localized excitonic states at the interface of Si/SiO2 or from the surface of Si nanocrystals. The radiative efficiency of the UV and the green emission from the Si nanoparticles can be modified by the localized plasmons interaction induced by the nucleation of Silver nanoparticles on controlled annealing of the samples. Broadband emission ranging from the UV to the red wavelength range can be obtained on Ag implanted onto a single silicon substrate.

Silver–clay nanohybrid structure for effective and diffusion-controlled antimicrobial activity

We describe here the synthesis and antimicrobial activity of silver–clay nanohybrid structure that was processed to exhibit a combination of accelerated and diffusion-controlled antimicrobial activity, with long term impact. The antimicrobial activity is assessed in terms of interaction with Escherichia coli, where the constituents of the nanohybrid structure play a synergistic role. Clay provides a physically stable surface for nucleation of silver nanoparticles. Additionally, the parallel- stacked layered structure of clay facilitates diffusion-controlled antimicrobial activity of in-situ precipitated silver. The antimicrobial activity is about four orders of magnitude greater than ex-situ precipitated bare silver particles. The study emphasizes the significance of controlling antimicrobial activity in nanostructured systems, which in the present case is enhanced and controlled antimicrobial activity with long term implication.

Influence of the heat treatment on the nucleation of silver nanoparticles in Tm3+ doped PbO-GeO2 glasses

Nucleation of silver nanoparticles (NPs) in Tm3+ doped PbO-GeO2 (PGO) glass is reported. The influence of the heat treatment on the nucleation of silver NPs is studied by means of transmission electron microscopy and optical spectroscopy. Two heat treatment procedures were applied in order to compare their performance. Observation of infrared-to-visible frequency upconversion (UC) luminescence of Tm3+ ions is reported and correlated with the heat-treatment procedure. Enhancement of the UC emission for samples heat treated during various time intervals is attributed to the increased local field in the vicinity of the NPs. Quenching of the UC signal was also observed and correlated with the growth of NPs amount and size.

Synthesis and Photoluminescence Properties of Porous Silicon Nanowire Arrays

Herein, we prepare vertical and single crystalline porous silicon nanowires (SiNWs) via a two-step metal-assisted electroless etching method. The porosity of the nanowires is restricted by etchant concentration, etching time and doping lever of the silicon wafer. The diffusion of silver ions could lead to the nucleation of silver nanoparticles on the nanowires and open new etching ways. Like porous silicon (PS), these porous nanowires also show excellent photoluminescence (PL) properties. The PL intensity increases with porosity, with an enhancement of about 100 times observed in our condition experiments. A “red-shift” of the PL peak is also found. Further studies prove that the PL spectrum should be decomposed into two elementary PL bands. The peak at 850 nm is the emission of the localized excitation in the nanoporous structure, while the 750-nm peak should be attributed to the surface-oxidized nanostructure. It could be confirmed from the Fourier transform infrared spectroscopy analyses. These porous SiNW arrays may be useful as the nanoscale optoelectronic devices.

Influence of the temperature on the nucleation of silver nanoparticles in Tm 3+/Yb 3+ codoped PbO–GeO 2 glasses

The influence of the temperature on the nucleation of silver nanoparticles (NPs) in Tm 3+/Yb 3+ codoped PbO–GeO 2 glasses was studied in this work. The infrared-to-visible frequency upconversion (UC) luminescence of Tm 3+ ions was used to probe the NPs nucleation and the results were correlated with the increase of the heat-treatment temperature. Emission spectra in the blue–red region were measured by exciting the samples with a cw 980 nm diode laser in resonance with the Yb 3+ transition ( 2F 7/2 → 2F 5/2). The results were correlated with transmission electron microscopy measurements and revealed the different behavior of the nucleation process as a function of temperature. The enhanced UC emission in the visible region is attributed to the increased local field in the proximity of the silver NPs combined with the Yb 3+ → Tm 3+ energy transfer.

Study of Tb-doped Li2O-LaF3-Al2O3-SiO2 Glasses Containing Silver Nanoparticles

AbstractTb-doped Li2O-LaF3-Al2O3-SiO2 (LLAS) glasses containing silver were fabricated using melt-quenching technique. Silver nanoparticles (NPs) in glass matrix were confirmed by optical absorption and X-ray diffraction (XRD). The nucleation of silver NPs was controlled by heat-treatment. A broad absorption band peaked at about 420 nm was observed due to surface plasmon resonance (SPR) of the silver NPs. This SPR absorption of silver NPs increases with the time of heat-treatment. Photoluminescence (PL) emission and excitation spectra were measured on Tb-doped LLAS glasses with and without silver NPs. Strong Tb3+ luminescence was observed. For excitation at 325 nm, luminescence of Tb3+ ions increases for the glass containing silver NPs compared to that in the glass without silver NPs. After further heat-treatment at 520 °C for 5 hours, Tb3+ luminescence decreased. Our luminescence results suggest that there are two competitive effects, enhancement and quenching effects, acting on Tb3+ luminescence in the glass containing silver NPs. The enhancement of Tb3+ luminescence is attributed to local field effects due to the excitation of SPR of silver NPs. The quenching effect in the presence of Ag NPs suggests an energy transfer from Tb3+ ions to silver NPs exists, which may provide an additional non-radiative relaxation pathway for the excited Tb3+ ions.

Float glass colouring by ion exchange

Abstract Back in the Middle Ages, glass artists used to produce yellowish colorations in soda-lime glasses using mixtures that contained silver salts, clay composites and natural oils. The resulting colour was a characteristic pale yellow known as silver-stain. This coloration is mainly caused by the extinction – absorption and, to a lesser extent, scattering – of light occasioned by silver nanoparticles formed inside the glass. This colouring technique comprises a heat treatment divided in two stages: in the first one, an ion exchange between the silver ions in the mixture and the alkali ions in the glass takes place. This process is called nucleation of silver nanoparticles. The second stage consists of a reduction process that causes the growth of these nanoparticles and the development of colour. This is known as growth and aggregation of nanoparticles. In our work, systematic working procedures have been developed with the aim of reproducing silver-stain in modern soda-lime glasses formed by flotation.

Highly Efficient Silver Nanoparticle Formation on Dialdehyde-Modified DNA

ABSTRACTWe investigated the efficient nucleation of silver nanoparticles on aldehyde-modified DNA strands. The aldehyde-bearing DNA was prepared by PCR incorporation of diol-modified synthetic deoxyuridine derivatives and subsequent cleavage of the diol groups to aldehyde functions using sodium periodate. Formerly unavailable dialdehyde-bearing DNA could be prepared by this mild and selective method. Both dialdehyde-DNA and monoaldehyde-DNA are capable of inducing silver nanoparticle formation without the addition of any external reductant. Interestingly, dialdehyde-DNA shows a different kinetic behavior and is about four times as efficient in silver nanoparticle formation as monoaldehyde-DNA. These data suggest a potentially unique mechanism of silver nanocluster formation induced by the dialdehyde groups. SEM measurements of fully metallized DNA strands show homogeneous metal coverage and selective metal deposition exclusively on the DNA template.

The kinetics of homogeneous nucleation of silver nanoparticles stabilized by polymers

The formation of Ag nanoparticles synthesized by homogeneous nucleation, stabilized by polymers (PVA and PVP) was monitored by UV–Vis spectrophotometry and transmission electron microscopy. Our aim was to differentiate between the two main phases of particle formation, i.e. nucleation and growth and to characterize their rates with the help of appropriate kinetic equations. Time resolved spectrophotometric measurements revealed that particle formation is an autocatalytic process: a slow, continuous nucleation phase (3–5 min) is followed by a rapid, autocatalytic growth phase where the maximal particle size is 5–7 nm. By freezing the reaction mixture, the process of particle growth can be followed from 5 to 40 min on TEM pictures. The first order rate constants were calculated and they are strongly depend on the polymer concentration. If the growing particles are attached by PEI to the surface of a solid support, the formation of silver nanoparticles can also be followed by atomic force microscopy (AFM) and we can control the particle growth on mica surface. The cross section analysis of the pictures show, that the particle growing process can be also monitored at solid–liquid interface.

Enhancement of Pr3+ luminescence in PbO–GeO2 glasses containing silver nanoparticles

Pr 3 + -doped PbO–GeO2 (PGO) glasses containing silver nanoparticles (NPs) were prepared and their spectroscopic characteristics were studied. The PGO samples and the nucleation of silver NP were obtained melting the starting oxide powders, quenching and annealing. Transmission electron microscopy was used to characterize the NP size distribution. Isolated silver particles with average diameter of 2 nm and aggregates with dimensions smaller than 100 nm were observed. Optical absorption and luminescence experiments were performed to investigate the properties of the composite system. Enhancement of the Pr3+ ions’ luminescence was observed due to the presence of the silver NP.