1,721,103 research outputs found
Laser ablation synthesis in solution and size manipulation offunctional nanoparticles
No full textNanoparticles represent important tools in modern nanotechnology thanks to their properties, as intense surface plasmon absorption, chemical stability and easy surface chemistry in case of noble metal nanoparticles, or superparamagnetism in case of iron oxide nanoparticles. Laser Ablation Synthesis in Solution (LASiS) technique revealed as easy, versatile and rapid for obtaining nanoparticles in water or organic solvents, without the need for chemicals or stabilizers.[1] Size and structure of nanoparticles obtained by LASiS can be further manipulated by a chemical free laser processing, both with a top down or a bottom up approach.[1] In most cases, the one step functionalization of particles is possible simply by adding the ligands to particles solution. UV – visible spectroscopy allows the monitoring of functionalization process and the estimation of particles size and aggregation.
So obtained nanoparticles were studied for multiphoton absorption applications, for surface enhanced Raman labelling, for photothermal therapy in cancer cells and for linear and nonlinear modulation of photonic crystal pseudogap
Laser ablation synthesis in solution (LASiS) of functional nanoparticles
No full textFunctional nanoparticles are powerful tools in applied nanotechnology. In particular, noble metal nanoparticles and iron oxide nanoparticles attracted a great interest for their properties related, respectively, to surface plasmon resonance and to magnetism. Moreover, the control of surface chemistry and functionalization/bioconjugation are indispensable steps for real applications. Laser ablation synthesis in solution (LASiS) is an easy, versatile and rapid technique for obtaining nanoparticles in water or organic solvents, without the need for chemicals or stabilizers. The size and the structure of nanoparticles obtained by LASiS can be further manipulated by a chemical free laser processing, both with a top down or a bottom up approach. In some cases, the one step functionalization of nanoparticles is possible simply by adding the ligands to particles solution. UV – visible spectroscopy allows the monitoring of functionalization process and the estimation of particles size and aggregation. So obtained nanoparticles were studied for multiphoton absorptions, for linear and nonlinear modulation of photonic crystal pseudogaps, for surface enhanced Raman scattering labelling and for hyperthermal therapy in cancer cells
Surface plasmon resonance of silver and gold nanoparticles in the proximity of graphene studied using the discrete dipole approximation method
No full textThe integration of silver and gold nanoparticles with graphene is frequently sought for the realization of
hybrid materials with superior optical, photoelectric and photocatalytic performances. A crucial aspect
for these applications is how the surface plasmon resonance of metal nanoparticles is modified after
assembly with graphene. Here, we used the discrete dipole approximation method to study the surface
plasmon resonance of silver and gold nanoparticles in the proximity of a graphene flake or embedded in
graphene structures. Surface plasmon resonance modifications were investigated for various shapes of
metal nanoparticles and for different morphologies of the nanoparticle–graphene nanohybrids, in a
step-by-step approach. Calculations show that the surface plasmon resonance of Ag nanoparticles is
quenched in nanohybrids, whereas either surface plasmon quenching or enhancement can be obtained
with Au nanoparticles, depending on the configuration adopted. However, graphene effects on the
surface plasmon resonance are rapidly lost already at a distance of the order of 5 nm. These results
provide useful indications for characterization and monitoring the synthesis of hybrid nanostructures, as
well as for the development of hybrid metal nanoparticle/graphene nanomaterials with desired optical
properties
Bioconjugation of gold nanoparticles obtained by laser ablation in liquid solution for temperature controlled cell uptake and photothermal therapy
No full textGold nanoparticles (AuNP) obtained by laser ablation synthesis in liquid solution (LASiS) can be easily functionalized and bioconjugated. Stable AuNP solutions can be obtained by LASiS in water or in organic solvents, without any ligands or chemicals. Hence, nanoparticles surface is usually free and functionalization with a wide range of organic- and bio-molecules occurs in one step. Moreover AuNP multi-bio-conjugation can easily be obtained without place exchange reactions and real time monitoring of the surface coverage is possible by UV-Vis spectroscopy.[1-3]
The size of AuNP obtained by LASiS can be further manipulated by chemical free laser techniques inspired by top down and bottom up approaches. Gold nanoparticles with average radii of 4.5 nm were obtained in this way, which allowed the sensing of AuNP bioconjugation with bovine serum albumin (BSA) down to 10:1 AuNP:BSA.[4]
Thermosensitive gold nanoparticles have been obtained by surface conjugation of thiolated thermo-responsive poly-N-isopropylacrylamide. The polymer coated AuNP showed temperature controlled cell uptake. In human breast adenocarcinoma MCF7 cells, an 86 fold increase in the AuNP cell uptake was found by switching the temperature from 34°C to 40°C.[5]
Irradiation experiments with 532 nm (9 ns) laser pulses fostered the death of cells preliminarily incubated with polymer coated AuNP at 40°C. These results provide new perspectives for the photothermal therapy of cancerous tissues by using cancer selective plasmonic nanostructures.[5
Enhanced absorption or transparency in hybrids of nanoparticles and graphene
No full textThe appealing side of nanotechnology lies in the fact that ordinary materials show surprising
properties when their size is reduced to billionths of meters (nanometers). For example, we all
know that silver is gray and gold is yellow, but when they are turned into nanoparticles these colors
change, and the whole rainbow can be reproduced by controlling the geometrical shape and the
assembly of the metals. Another famous nanotechnology example is graphene, namely what you
would get if the graphite of your pencil can be spread on a sheet up to produce a layer with the
thickness of one atomic layer. Scientists investigated the physical properties of these
nanomaterials for several years, and many things are now well known about the optical, electronic
and mechanical behaviour. However, what happens when Ag or Au nanoparticles are combined
with graphene is still not well understood
A General Technique to Investigate the Aggregation of Nanoparticles by Transmission Electron Microscopy
No full textThe aggregation state of nanoparticles (NPs) must be precisely known in order to study the structure-property relationship and to evaluate the exploitability of NPs dispersion for a given application. Here we report a general technique for sample preparation to investigate with transmission electron microscopy (TEM) the state of aggregation of NPs dispersed in liquid solution. Following a simple procedure which requires few minutes, the aggregates of NPs are “frozen” in a polymeric matrix simultaneously to their deposition on a TEM grid. Our technique is of general applicability and it avoids the use of cryo-TEM, which is more expensive, more time consuming and less
common than ordinary TEM. Compared to the investigation of NPs aggregation in the liquid phase with dynamic light scattering, our approach avoids the problem of shielding by large aggregates
and it allows the full exploitation of TEM advantages, primarily the reliable determination of shape and size of each aggregate and the precise evaluation of the number of single NPs forming each cluster. As an example, we demonstrate the use of our technique to study two frequent topics related to aggregation: the plasmon properties of gold NPs aggregates and the stability of iron oxide NPs in physiological environment. The methodology described here will be useful to advance the knowledge about how aggregation influences the physical-chemical properties of NPs
SINTESI MEDIANTE ABLAZIONE LASER IN SOLUZIONE E MANIPOLAZIONE DI NANOPARTICELLE METALLICHE PER APPLICAZIONI IN FOTONICA
No full textLe nanoparticelle (Np) di oro e argento hanno un ruolo importante nelle nanotecnologie, per via delle loro proprieta’ plasmoniche, della loro stabilita’ chimica e della facilita’ con cui si funzionalizza la loro superficie. La sintesi per ablazione laser in soluzione (LASiS – Laser Ablation Synthesis in Solution) rappresenta una tecnica semplice, versatile e rapida per ottenere Np di metalli nobili in acqua o in solventi organici, senza la necessita’ di inserire stabilizzanti o altri reagenti chimici.1 La dimensione delle Np ottenute mediante LASiS puo’ essere ulteriormente modificata attraverso tecniche laser “chemical free” ispirate ad approcci “top down” e “bottom up”.2 Questo consente la funzionalizzazione in “one step” delle particelle per semplice aggiunta dei leganti di interesse, con risparmio di reagenti chimici e l’assenza di rifiuti rispetto alle tradizionali sintesi per riduzione chimica. Inoltre la spettroscopia UV – visibile consente di ricavare informazioni sul ricoprimento con leganti e di stimare le dimensioni medie, la concentrazione e l’aggregazione delle particelle. Le Np di oro ottenute mediante LASiS sono state utilizzate per studi di assorbimento ottico non lineare, di terapia fototermica in cellule tumorali e di modulazione delle proprieta’ di cristalli fotonici.3
1 V. Amendola, S. Polizzi, M. Meneghetti; J. Phys. Chem. B 2006, 110, 7232 – 7237; V. Amendola, S. Polizzi, M. Meneghetti; Langmuir 2007, 23, 6766 – 6770; V. Amendola, G. A. Rizzi, S. Polizzi, M. Meneghetti; J. Phys. Chem. B 2005, 109, 23125 – 23128.
2 V. Amendola, M. Meneghetti; J. Mater. Chem. 2007, 17, 4705-4710.
3 V. Amendola, S. Polizzi, K. Kadish, D. Dini, M. Hanack, M. Meneghetti; Submitted; S. Salmaso, P. Caliceti, V. Amendola, M. Meneghetti, G. Pasparakis, A. Cameron; Submitted; V. Morandi, F. Marabelli, V. Amendola, M. Meneghetti, D. Comoretto; Adv. Func. Mater. 2007, 17, 2779–2786
Synthesis of gold and silver nanoparticles for photonic applications
Full text linkSynthesis of gold and silver nanoparticles for photonic application
Laser-generated nanoalloys as theranostic and biodegradable platforms for cancer nanomedicine
No full textThe field of cancer nanomedicine is moving towards maturity thanks to innovative technologies and original nanomaterials. This is required to surpass the limitations of the previous generations of nanomedicines, such as biopersistence, experimental therapeutic approaches far from the clinic, long-term toxicity of heavy metals and other compounds used in nanoparticles. Here we show how laser processing is playing a crucial role for the realization of an emerging class of advanced inorganic nanomedicines based on nanoscale alloys. Nanoparticles of Au-Fe, Au-B, Fe-B and Fe-Ag alloys have been obtained by laser-assisted synthesis, even if most of them are thermodynamically unstable. These nanoalloys exhibited multiple appealing properties for imaging and therapy of cancer and have been designed to address the issues of previous nanostructured compounds for the treatment of cancer, by endowing mid-term biodegradability, complementarity and synergy of the theranostic functions. Therefore, laser technologies are contributing to the addition of new nano-tools for addressing the treatment of cancer with higher efficacy, feasibility and tolerability
Correlation of surface-enhanced Raman scattering (SERS) with the surface density of gold nanoparticles: evaluation of the critical number of SERS tags for a detectable signal
Full text linkThe use of plasmonic nanotags based on the surface-enhanced Raman scattering (SERS) effect is highly promising for several applications in analytical chemistry, biotechnological assays and nanomedicine. To this end, a crucial parameter is the minimum number of SERS tags that allows for the collection of intense Raman signals under real operating conditions. Here, SERS Au nanotags (AuNTs) based on clustered gold nanoparticles are deposited on a substrate and analyzed in the same region using Raman spectroscopy and transmission electron microscopy. In this way, the Raman spectra and the surface density of the SERS tags are correlated directly, showing that 1 tag/µm2 is enough to generate an intense signal above the noise level at 633 nm with an excitation power of only 0.65 mW and an acquisition time of just 1 s with a 50× objective. The AuNT density can be even lower than 1 tag/µm2 when the acquisition time is extended to 10 s, but must be increased to 3 tags/µm2 when a 20× objective is employed under the same excitation conditions. In addition, in order to observe a linear response, it was found that 10 SERS AuNTs inside the probed area are required. These findings indicate that a better signal-to-noise ratio requires high-magnification optics, while linearity versus tag number can be improved by using low-magnification optics or a high tag density. In general the suitability of plasmonic SERS labels for ultrasensitive analytical and biomedical applications is evident
- …
