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1.
Small ; 16(11): e1904960, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32077633

RESUMO

Progress of thermal tumor therapies and their translation into clinical practice are limited by insufficient nanoparticle concentration to release therapeutic heating at the tumor site after systemic administration. Herein, the use of Janus magneto-plasmonic nanoparticles, made of gold nanostars and iron oxide nanospheres, as efficient therapeutic nanoheaters whose on-site delivery can be improved by magnetic targeting, is proposed. Single and combined magneto- and photo-thermal heating properties of Janus nanoparticles render them as compelling heating elements, depending on the nanoparticle dose, magnetic lobe size, and milieu conditions. In cancer cells, a much more effective effect is observed for photothermia compared to magnetic hyperthermia, while combination of the two modalities into a magneto-photothermal treatment results in a synergistic cytotoxic effect in vitro. The high potential of the Janus nanoparticles for magnetic guiding confirms them to be excellent nanostructures for in vivo magnetically enhanced photothermal therapy, leading to efficient tumor growth inhibition.

2.
Struct Dyn ; 6(2): 024304, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31041361

RESUMO

We demonstrate that highly ordered two-dimensional crystals of ligand-capped gold nanoparticles display a local photo-mechanical stiffness as high as that of solids such as graphite. In out-of-equilibrium electron diffraction experiments, a strong temperature jump is induced in a thin film with a femtosecond laser pulse. The initial electronic excitation transfers energy to the underlying structural degrees of freedom, with a rate generally proportional to the stiffness of the material. Using femtosecond small-angle electron diffraction, we observe the temporal evolution of the diffraction feature associated with the nearest-neighbor nanoparticle distance. The Debye-Waller decay for the octanethiol-capped nanoparticle supracrystal, in particular, is found to be unexpectedly fast, almost as fast as the stiffest solid known and observed by the same technique, i.e., graphite. Our observations unravel that local stiffness in a dense supramolecular assembly can be created by van der Waals interactions up to a level comparable to crystalline systems characterized by covalent bonding.

3.
Nanoscale ; 9(27): 9467-9480, 2017 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-28660946

RESUMO

The design of compact nanoprobes for multimodal bioimaging is a current challenge and may have a major impact on diagnostics and therapeutics. Multicomponent gold-iron oxide nanoparticles have shown high potential as contrast agents in numerous imaging techniques due to the complementary features of iron oxide and gold nanomaterials. In this paper we describe novel gold-iron oxide Janus magnetic-plasmonic nanoparticles as versatile nanoprobes for multimodal imaging. The nanoparticles are characterized as contrast agents for different imaging techniques, including X-ray computed tomography (CT), T2-weighted nuclear magnetic resonance imaging (MRI), photoacoustic imaging (PA), dark-field and bright-field optical microscopy, transmission electron microscopy (TEM), and surface enhanced Raman spectroscopy (SERS). We discuss the effect of particle size and morphology on their performance as contrast agents and show the advantage of a Janus configuration. Additionally, the uptake of nanoparticles by cells can be simultaneously visualized in dark- and bright-field optical microscopy, SERS mapping, and electron microscopy. These complementary techniques allow a complete view of cell uptake in an artifact-free manner, with multiplexing capabilities, and with extra information regarding the nanoparticles' fate inside the cells. Altogether, the results obtained with these non-invasive techniques show the high versatility of these nanoparticles, the advantages of a Janus configuration, and their high potential in multipurpose biomedical applications.


Assuntos
Meios de Contraste/química , Compostos Férricos/química , Ouro/química , Imagem Multimodal , Nanopartículas/química , Imagem por Ressonância Magnética , Microscopia Eletrônica de Transmissão , Técnicas Fotoacústicas , Análise Espectral Raman , Tomografia Computadorizada por Raios X
4.
Chem Soc Rev ; 46(13): 3866-3885, 2017 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-28447698

RESUMO

The optimization of the enhancement of Raman scattering by plasmonic effects is largely determined by the properties of the enhancing substrates. The main parameters behind this effect are related to the morphology of plasmonic nanoparticles and their relative distribution within the substrate. We focus this tutorial review on the effects of nanoparticle morphology, for the particular case of anisotropic metal nanoparticles. Anisotropy in silver and gold nanoparticles offers the possibility to tailor their plasmonic properties and intrinsic electromagnetic "hotspots". We describe the effect of varying particle size and shape on the SERS signal, focusing on the most common anisotropic morphologies used for SERS. Especial emphasis is made on existing comparative studies that shed light on the effect of nanoparticle anisotropy on their enhancement capabilities. We aim at providing a general perspective toward understanding the general key factors and highlighting the difficulty in quantitatively determining SERS performance.

5.
Nanoscale ; 8(37): 16589-16595, 2016 Sep 22.
Artigo em Inglês | MEDLINE | ID: mdl-27722594

RESUMO

Inorganic nanoparticles (NPs) appear as the forefront functional structure in nanotechnology. The preparation of functional materials based on inorganic NPs requires their assembly onto well-defined structures. Within this context, self-assembly at air-liquid interfaces is probably the best candidate for a universal procedure for active materials composed of assembled NPs. The detailed in situ mechanism of the lateral self-assembly and vertical organization of NPs at air-liquid interfaces is still unknown despite its extended use. The most common and promising methods for addressing this open issue are reviewed herein. The self-assembled films can be used in situ or further be transferred to solid substrates as the main constituents of novel functional materials. Plasmonic NPs at interfaces are highly interesting, given the broad range of applications of the plasmonic field, and will be discussed more in detail.

10.
Faraday Discuss ; 191: 47-59, 2016 10 06.
Artigo em Inglês | MEDLINE | ID: mdl-27419362

RESUMO

Multicomponent nanoparticles are of particular interest due to a unique combination of properties at the nanoscale, which make them suitable for a wide variety of applications. Among them, Janus nanoparticles, presenting two distinct surface regions, can lead to specific interactions with interfaces, biomolecules, membranes etc. We report the synthesis of Janus nanoparticles comprising iron oxide nanospheres and gold nanostars, through two consecutive seed-mediated-growth steps. Electron tomography combining HAADF-STEM and EDX mapping has been performed to evaluate the spatial distribution of the two components of the nanoparticle, showing their clear separation in a Janus morphology. Additionally, SERS measurements assisted by magnetic separation were carried out to assess the application of combined plasmonic and magnetic properties for sensing.

11.
Nano Lett ; 16(4): 2705-13, 2016 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-26918756

RESUMO

The design and the characterization of functionalized gold nanoparticles supracrystals require atomically resolved information on both the metallic core and the external organic ligand shell. At present, there is no known approach to characterize simultaneously the static local order of the ligands and of the nanoparticles, nor their dynamical evolution. In this work, we apply femtosecond small-angle electron diffraction combined with angular cross-correlation analysis, to retrieve the local arrangement from nanometer to interatomic scales in glassy aggregates. With this technique we study a two-dimensional distribution of functionalized gold nanoparticles deposited on amorphous carbon. We show that the dodecanethiol ligand chains, coating the gold cores, order in a preferential orientation on the nanoparticle surface and throughout the supracrystal. Furthermore, we retrieve the dynamics of the supracrystal upon excitation with light and show that the positional disorder is induced by light pulses, while its overall homogeneity is surprisingly found to transiently increase. This new technique will enable the systematic investigation of the static and dynamical structural properties of nanoassembled materials containing light elements, relevant for several applications including signal processing and biology.

15.
Nanoscale ; 7(13): 5665-73, 2015 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-25744221

RESUMO

Understanding how nanomaterials interact with interfaces is essential to control their self-assembly as well as their optical, electronic, and catalytic properties. We present here an experimental approach based on neutron reflectivity (NR) that allows the in situ measurement of the contact angles of nanoparticles adsorbed at fluid interfaces. Because our method provides a route to quantify the adsorption and interfacial energies of the nanoparticles in situ, it circumvents problems associated with existing indirect methods, which rely on the transport of the monolayers to substrates for further analysis. We illustrate the method by measuring the contact angle of hydrophilic and hydrophobic gold nanoparticles, coated with perdeuterated octanethiol (d-OT) and with a mixture of d-OT and mercaptohexanol (MHol), respectively. The contact angles were also calculated via atomistic molecular dynamics (MD) computations, showing excellent agreement with the experimental data. Our method opens the route to quantify the adsorption of complex nanoparticle structures adsorbed at fluid interfaces featuring different chemical compositions.

16.
Nat Commun ; 5: 4482, 2014 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-25042518

RESUMO

Recent work has demonstrated that charged gold nanoparticles (AuNPs) protected by an amphiphilic organic monolayer can spontaneously insert into the core of lipid bilayers to minimize the exposure of hydrophobic surface area to water. However, the kinetic pathway to reach the thermodynamically stable transmembrane configuration is unknown. Here, we use unbiased atomistic simulations to show the pathway by which AuNPs spontaneously insert into bilayers and confirm the results experimentally on supported lipid bilayers. The critical step during this process is hydrophobic-hydrophobic contact between the core of the bilayer and the monolayer of the AuNP that requires the stochastic protrusion of an aliphatic lipid tail into solution. This last phenomenon is enhanced in the presence of high bilayer curvature and closely resembles the putative pre-stalk transition state for vesicle fusion. To the best of our knowledge, this work provides the first demonstration of vesicle fusion-like behaviour in an amphiphilic nanoparticle system.


Assuntos
Membrana Celular/química , Lipídeos/química , Nanopartículas/química , Ouro , Interações Hidrofóbicas e Hidrofílicas , Cinética , Bicamadas Lipídicas/química , Microscopia de Força Atômica , Simulação de Dinâmica Molecular , Fosfatidilcolinas/química , Termodinâmica
17.
Chem Commun (Camb) ; 50(72): 10456-9, 2014 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-25068154

RESUMO

Scanning tunnelling microscopy (STM) studies have found stripe-like domains on gold nanoparticles (NPs) coated with certain binary mixtures of ligand molecules. The majority of these NPs' properties have been investigated for particles in solvents. Yet, most STM studies are for NPs in a dry state. Images of the same particles in air and liquid have not been obtained yet. In this work, a judicious choice of ligand molecules led to NPs with close-to-ideal STM imaging conditions in air and in 1-phenyloctane (PO). Large datasets under both conditions were acquired and rapidly evaluated through power spectral density (PSD) analysis. The result is a quantitative comparison of stripe-like domains in air and PO on the same NPs. PSD analysis determines a characteristic length-scale for these domains of ~1.0 nm in air and in PO showing persistence of striped domains in these two media. A length scale of ~0.7 nm for homoligand NPs was found.

18.
Nat Chem ; 6(6): 468-76, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24848231

RESUMO

Carbon nanostructures that feature two-dimensional extended nanosheets are important components for technological applications such as high-performance composites, lithium-ion storage, photovoltaics and nanoelectronics. Chemical functionalization would render such structures better processable and more suited for tailored applications, but typically this is precluded by the high temperatures needed to prepare the nanosheets. Here, we report direct access to functional carbon nanosheets of uniform thickness at room temperature. We used amphiphiles that contain hexayne segments as metastable carbon precursors and self-assembled these into ordered monolayers at the air/water interface. Subsequent carbonization by ultraviolet irradiation in ambient conditions resulted in the quantitative carbonization of the hexayne sublayer. Carbon nanosheets prepared in this way retained their surface functionalization and featured an sp(2)-rich amorphous carbon structure comparable to that usually obtained on annealing above 800 °C. Moreover, they exhibited a molecularly defined thickness of 1.9 nm, were mechanically self-supporting over several micrometres and had macroscopic lateral dimensions on the order of centimetres.


Assuntos
Carbono/química , Nanoestruturas/química , Nanotecnologia , Temperatura Ambiente , Água/química , Ar , Simulação por Computador , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Nanoestruturas/ultraestrutura , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície
19.
Langmuir ; 29(45): 13723-34, 2013 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-24083627

RESUMO

Ligand-protected gold nanoparticles exhibit large local curvatures, features rapidly varying over small scales, and chemical heterogeneity. Their imaging by scanning tunneling microscopy (STM) can, in principle, provide direct information on the architecture of their ligand shell, yet STM images require laborious analysis and are challenging to interpret. Here, we report a straightforward, robust, and rigorous method for the quantitative analysis of the multiscale features contained in STM images of samples consisting of functionalized Au nanoparticles deposited onto Au/mica. The method relies on the analysis of the topographical power spectral density (PSD) and allows us to extract the characteristic length scales of the features exhibited by nanoparticles in STM images. For the mixed-ligand-protected Au nanoparticles analyzed here, the characteristic length scale is 1.2 ± 0.1 nm, whereas for the homoligand Au NPs this scale is 0.75 ± 0.05 nm. These length scales represent spatial correlations independent of scanning parameters, and hence the features in the PSD can be ascribed to a fingerprint of the STM contrast of ligand-protected nanoparticles. PSD spectra from images recorded at different laboratories using different microscopes and operators can be overlapped across most of the frequency range, proving that the features in the STM images of nanoparticles can be compared and reproduced.


Assuntos
Ouro/química , Nanopartículas Metálicas/química , Microscopia de Tunelamento , Ligantes , Tamanho da Partícula
20.
ACS Nano ; 7(10): 8529-39, 2013 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-24024977

RESUMO

Gold nanoparticles protected by a binary mixture of thiolate molecules have a ligand shell that can spontaneously separate into nanoscale domains. Complex morphologies arise in such ligand shells, including striped, patchy, and Janus domains. Characterization of these morphologies remains a challenge. Scanning tunneling microscopy (STM) imaging has been one of the key approaches to determine these structures, yet the imaging of nanoparticles' surfaces faces difficulty stemming from steep surface curvature, complex molecular structures, and the possibility of imaging artifacts in the same size range. Images obtained to date have lacked molecular resolution, and only domains have been resolved. There is a clear need for images that resolve the molecular arrangement that leads to domain formation on the ligand shell of these particles. Herein we report an advance in the STM imaging of gold nanoparticles, revealing some of the molecules that constitute the domains in striped and Janus gold nanoparticles. We analyze the images to determine molecular arrangements on parts of the particles, highlight molecular "defects" present in the ligand shell, show persistence of the features across subsequent images, and observe the transition from quasi-molecular to domain resolution. The ability to resolve single molecules in the ligand shell of nanoparticles could lead to a more comprehensive understanding of the role of the ligand structure in determining the properties of mixed-monolayer-protected gold nanoparticles.

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