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1.
Artigo em Inglês | MEDLINE | ID: mdl-33350557

RESUMO

In a magnetic field, cubic Fe3 O4 nanoparticles exhibit assembly behavior that is a consequence of a competition between magnetic dipole-dipole and ligand interactions. In most cases, the interactions between short hydrophobic ligands dominate and dictate assembly outcome. To better tune the face-to-face interactions, cubic Fe3 O4 nanoparticles were functionalized with DNA. Their assembly behaviors were investigated both with and without an applied magnetic field. Upon application of a field, the tilted orientation of cubes, enabled by the flexible DNA ligand shell, led to an unexpected crystallographic alignment of the entire superlattice, as opposed to just the individual particles, along the field direction as revealed by small and wide-angle X-ray scattering. This observation is dependent upon DNA length and sequence and cube dimensions. Taken together, these studies show how combining physical and chemical control can expand the possibilities of crystal engineering with DNA.

2.
Adv Mater ; 32(47): e2005316, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33089533

RESUMO

Colloidal crystals have emerged as promising candidates for building optical microdevices. Techniques now exist for synthesizing them with control over their nanoscale features (e.g., particle compositions, sizes, shapes, and lattice parameters and symmetry); however, the ability to tune macroscale structural features, such as the relative positions of crystals to one another and lattice orientations, has yet to be realized. Here, inspiration is drawn from epitaxial growth strategies in atomic crystallization, and patterned substrates are prepared that, when used in conjunction with DNA-mediated nanoparticle crystallization, allow for control over individual Wulff-shaped crystal growth, location, and orientation. In addition, the approach allows exquisite control over the patterned substrate/crystal lattice mismatch, something not yet realized for any epitaxy process. This level of structural control is a significant step toward realizing complex, integrated devices with colloidal crystal components, and this approach provides a model system for further exploration in epitaxy systems.

3.
Nano Lett ; 20(11): 8096-8101, 2020 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-33054221

RESUMO

Optical metamaterials, engineered to exhibit electromagnetic properties not found in natural materials, may enable new light-based applications including cloaking and optical computing. While there have been significant advances in the fabrication of two-dimensional metasurfaces, planar structures create nontrivial angular and polarization sensitivities, making omnidirectional operation impossible. Although three-dimensional (3D) metamaterials have been proposed, their fabrication remains challenging. Here, we use colloidal crystal engineering with DNA to prepare isotropic 3D metacrystals from Au nanocubes. We show that such structures can exhibit refractive indices as large as ∼8 in the mid-infrared, far greater than that of common high-index dielectrics. Additionally, we report the first observation of multipolar Mie resonances in metacrystals with well-formed habits, occurring in the mid-infrared for submicrometer metacrystals, which we measured using synchrotron infrared microspectroscopy. Finally, we predict that arrays of metacrystals could exhibit negative refraction. The results present a promising platform for engineering devices with unnatural optical properties.

4.
J Am Chem Soc ; 142(43): 18324-18329, 2020 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-33078944

RESUMO

Semiconductor nanowires (NWs) capped with metal nanoparticles (NPs) show multifunctional and synergistic properties, which are important for applications in the fields of catalysis, photonics, and electronics. Conventional colloidal syntheses of this class of hybrid structures require complex sequential seeded growth, where each section requires its own set of growth conditions, and methods for preparing such wires are not universal. Here, we report a new and general method for synthesizing metal-semiconductor nanohybrids based on particle catalysts, prepared by scanning probe block copolymer lithography, and chemical vapor deposition. In this process, metallic heterodimer NPs were used as catalysts for NW growth to form semiconductor NWs capped with metallic particles (Au, Ag, Co, Ni). Interestingly, the growth processes for NWs on NPs are regioselective and controlled by the chemical composition of the metallic heterodimer used. Using a systematic experimental approach, paired with density functional theory calculations, we were able to postulate three different growth modes, one without precedent.

5.
Sci Adv ; 6(39)2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32967836

RESUMO

Halide perovskites have exceptional optoelectronic properties, but a poor understanding of the relationship between crystal dimensions, composition, and properties limits their use in integrated devices. We report a new multiplexed cantilever-free scanning probe method for synthesizing compositionally diverse and size-controlled halide perovskite nanocrystals spanning square centimeter areas. Single-particle photoluminescence studies reveal multiple independent emission modes due to defect-defined band edges with relative intensities that depend on crystal size at a fixed composition. Smaller particles, but ones with dimensions that exceed the quantum confinement regime, exhibit blue-shifted emission due to reabsorption of higher-energy modes. Six different halide perovskites have been synthesized, including a layered Ruddlesden-Popper phase, and the method has been used to prepare functional solar cells based on single nanocrystals. The ability to pattern arrays of multicolor light-emitting nanocrystals opens avenues toward the development of optoelectronic devices, including optical displays.

6.
Proc Natl Acad Sci U S A ; 117(35): 21052-21057, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32817562

RESUMO

Anchoring nanoscale building blocks, regardless of their shape, into specific arrangements on surfaces presents a significant challenge for the fabrication of next-generation chip-based nanophotonic devices. Current methods to prepare nanocrystal arrays lack the precision, generalizability, and postsynthetic robustness required for the fabrication of device-quality, nanocrystal-based metamaterials [Q. Y. Lin et al. Nano Lett. 15, 4699-4703 (2015); V. Flauraud et al., Nat. Nanotechnol. 12, 73-80 (2017)]. To address this challenge, we have developed a synthetic strategy to precisely arrange any anisotropic colloidal nanoparticle onto a substrate using a shallow-template-assisted, DNA-mediated assembly approach. We show that anisotropic nanoparticles of virtually any shape can be anchored onto surfaces in any desired arrangement, with precise positional and orientational control. Importantly, the technique allows nanoparticles to be patterned over a large surface area, with interparticle distances as small as 4 nm, providing the opportunity to exploit light-matter interactions in an unprecedented manner. As a proof-of-concept, we have synthesized a nanocrystal-based, dynamically tunable metasurface (an anomalous reflector), demonstrating the potential of this nanoparticle-based metamaterial synthesis platform.


Assuntos
Coloides/química , Cristalização/métodos , Nanopartículas Metálicas/química , Anisotropia , DNA/química , Ouro/química , Tamanho da Partícula , Propriedades de Superfície
7.
Nano Lett ; 20(8): 6170-6175, 2020 08 12.
Artigo em Inglês | MEDLINE | ID: mdl-32787186

RESUMO

This Letter describes how the endosomal organization of immunostimulatory nanoconstructs can tune the in vitro activation of macrophages. Nanoconstructs composed of gold nanoparticles conjugated with unmethylated cytosine-phosphate-guanine (CpG) oligonucleotides have distinct endosomal distributions depending on the surface curvature. Mixed-curvature constructs produce a relatively high percentage of hollow endosomes, where constructs accumulated primarily along the interior edges. These constructs achieved a higher level of toll-like receptor (TLR) 9 activation along with the enhanced secretion of proinflammatory cytokines and chemokines compared to constant-curvature constructs that aggregated mostly in the center of the endosomes. Our results underscore the importance of intraendosomal interactions in regulating immune responses and targeted delivery.

8.
J Am Chem Soc ; 142(31): 13350-13355, 2020 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-32706250

RESUMO

We report the development of a new strategy for the chemical analysis of live cells based on protein spherical nucleic acids (ProSNAs). The ProSNA architecture enables analyte detection via the highly programmable nucleic acid shell or a functional protein core. As a proof-of-concept, we use an i-motif as the nucleic acid recognition element to probe pH in living cells. By interfacing the i-motif with a forced-intercalation readout, we introduce a quencher-free approach that is resistant to false-positive signals, overcoming limitations associated with conventional fluorophore/quencher-based gold NanoFlares. Using glucose oxidase as a functional protein core, we show activity-based, amplified sensing of glucose. This enzymatic system affords greater than 100-fold fluorescence turn on in buffer, is selective for glucose in the presence of close analogs (i.e., glucose-6-phosphate), and can detect glucose above a threshold concentration of ∼5 µM, which enables the study of relative changes in intracellular glucose concentrations.

9.
Proc Natl Acad Sci U S A ; 117(30): 17543-17550, 2020 07 28.
Artigo em Inglês | MEDLINE | ID: mdl-32669433

RESUMO

Highly heterogenous cancers, such as triple-negative breast cancer (TNBC), remain challenging immunotherapeutic targets. Herein, we describe the synthesis and evaluation of immunotherapeutic liposomal spherical nucleic acids (SNAs) for TNBC therapy. The SNAs comprise immunostimulatory oligonucleotides (CpG-1826) as adjuvants and encapsulate lysates derived from TNBC cell lines as antigens. The resulting nanostructures (Lys-SNAs) enhance the codelivery of adjuvant and antigen to immune cells when compared to simple mixtures of lysates with linear oligonucleotides both in vitro and in vivo, and reduce tumor growth relative to simple mixtures of lysate and CpG-1826 (Lys-Mix) in both Py230 and Py8119 orthotopic syngeneic mouse models of TNBC. Furthermore, oxidizing TNBC cells prior to lysis and incorporation into SNAs (OxLys-SNAs) significantly increases the activation of dendritic cells relative to their nonoxidized counterparts. When administered peritumorally in vivo in the EMT6 mouse mammary carcinoma model, OxLys-SNAs significantly increase the population of cytotoxic CD8+ T cells and simultaneously decrease the population of myeloid derived suppressor cells (MDSCs) within the tumor microenvironment, when compared with Lys-SNAs and simple mixtures of oxidized lysates with CpG-1826. Importantly, animals administered OxLys-SNAs exhibit significant antitumor activity and prolonged survival relative to all other treatment groups, and resist tumor rechallenge. Together, these results show that the way lysates are processed and packaged has a profound impact on their immunogenicity and therapeutic efficacy. Moreover, this work points toward the potential of oxidized tumor cell lysate-loaded SNAs as a potent class of immunotherapeutics for cancers lacking common therapeutic targets.


Assuntos
Antígenos de Neoplasias/imunologia , Imunomodulação , Ácidos Nucleicos/imunologia , Neoplasias de Mama Triplo Negativas/imunologia , Adjuvantes Imunológicos , Animais , Vacinas Anticâncer/administração & dosagem , Vacinas Anticâncer/imunologia , Linhagem Celular Tumoral , Células Dendríticas/imunologia , Células Dendríticas/metabolismo , Feminino , Humanos , Imunoterapia , Camundongos , Oligodesoxirribonucleotídeos/imunologia , Oligonucleotídeos/imunologia , Oxirredução , Resultado do Tratamento , Neoplasias de Mama Triplo Negativas/tratamento farmacológico , Neoplasias de Mama Triplo Negativas/metabolismo , Neoplasias de Mama Triplo Negativas/patologia
10.
ACS Cent Sci ; 6(5): 815-822, 2020 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-32490197

RESUMO

The translation of proteins as effective intracellular drug candidates is limited by the challenge of cellular entry and their vulnerability to degradation. To advance their therapeutic potential, cell-impermeable proteins can be readily transformed into protein spherical nucleic acids (ProSNAs) by densely functionalizing their surfaces with DNA, yielding structures that are efficiently taken up by cells. Because small structural changes in the chemical makeup of a conjugated ligand can affect the bioactivity of the associated protein, structure-activity relationships of the linker bridging the DNA and the protein surface and the DNA sequence itself are investigated on the ProSNA system. In terms of attachment chemistry, DNA-based linkers promote a sevenfold increase in cellular uptake while maintaining enzymatic activity in vitro as opposed to hexaethylene glycol (HEG, Spacer18) linkers. Additionally, the employment of G-quadruplex-forming sequences increases cellular uptake in vitro up to fourfold. When translating to murine models, the ProSNA with a DNA-only shell exhibits increased blood circulation times and higher accumulation in major organs, including lung, kidney, and spleen, regardless of sequence. Importantly, ProSNAs with an all-oligonucleotide shell retain their enzymatic activity in tissue, whereas the native protein loses all function. Taken together, these results highlight the value of structural design in guiding ProSNA biological fate and activity and represent a significant step forward in the development of intracellular protein-based therapeutics.

11.
J Am Chem Soc ; 142(26): 11343-11356, 2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32573219

RESUMO

DNA-based probes constitute a versatile platform for making biological measurements due to their ability to recognize both nucleic acid and non-nucleic acid targets, ease of synthesis and chemical modification, amenability to be interfaced with signal amplification schemes, and inherent biocompatibility. Here, we provide a historical perspective of how a transition from linear DNA structures toward more structurally complex nanostructures has revolutionized live-cell analysis. Modulating the structure gives rise to probes that can enter cells without the aid of transfection reagents and can detect, track, and quantify analytes in live cells at the single-organelle, single-cell, tissue section, and whole organism levels. We delineate the advantages and disadvantages associated with different probe architectures and describe the advances enabled by these structures for elucidating fundamental biology as well as developing improved diagnostic and theranostic systems. We also discuss the outstanding challenges in the field and outline potential solutions.

12.
Curr Protoc Nucleic Acid Chem ; 81(1): e110, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32530578

RESUMO

This protocol describes a method based on iodine and a base as mild coupling reagents to synthetize deoxyribonucleic guanidines (DNGs)-oligodeoxynucleotide analogues with a guanidine backbone. DNGs display unique properties, such as high cellular uptake with low toxicity and increased stability against nuclease degradation, but have been impeded in their development by the requirement for toxic and iterative manual synthesis protocols. The novel synthesis method reported here eliminates the need for the toxic mercuric chloride and pungent thiophenol that were critical to previous DNG synthesis methods and translates their synthesis to a MerMadeTM 12 automated oligonucleotide synthesizer. This method can be used to synthesize DNG strands up to 20 bases in length, along with 5'-DNG-DNA-3' chimeras, at 1- to 5-µmol scales in a fully automated manner. We also present detailed and accessible instructions to adapt the MerMadeTM 12 oligonucleotide synthesizer to enable the parallel synthesis of DNG and DNA/RNA oligonucleotides. Because DNG linkages alter the overall charge of the oligonucleotides, we also describe purification strategies to generate oligonucleotides with varying lengths and numbers of DNGs, based on extraction or preparative-scale gel electrophoresis, along with methods to characterize the final products. Overall, this article provides an overview of the synthesis, purification, and handling of DNGs and mixed-charge DNG-DNA oligonucleotides. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Preparation of a MerMadeTM synthesizer for guanidine couplings Basic Protocol 2: Synthesis of DNG strands on a MerMadeTM synthesizer Basic Protocol 3: Purification of DNG strands using preparative acetic acid urea (AU) PAGE Basic Protocol 4: Characterization of DNG strands using MALDI-TOF MS Basic Protocol 5: Characterization of DNG strands using AU PAGE Support Protocol 1: Synthesis of initiator-functionalized CPG Support Protocol 2: Synthesis of thiourea monomer.

13.
Adv Mater ; 32(30): e2002849, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32567137

RESUMO

A method to introduce high-index facets into colloidally synthesized nanoparticles is used to produce compositionally uniform Pt-M (M = Ni, Co, and Cu) and Rh-M (M = Ni and Co) tetrahexahedral nanoparticles. The realization of this method allows for a systematic study of catalyst activity as a function of particle composition for various electrooxidation reactions of liquid fuels (formic acid, methanol, and ethanol). The individual contributions of their high-index facets, internal alloying of transition metals, and surface Bi modification to their electrocatalytic properties are experimentally explored, resulting in three key findings. First, the presence of high-index facets is favorable for improving the catalytic activity for all three classes of reactions studied. Second, the effect of transition metal alloying on catalytic activity differs from reaction to reaction. For methanol electrooxidation in an acid electrolyte, due to the contribution from surface Bi modification being negligible, transition metal alloying can significantly the improve overall catalytic efficiency. However, for the other studied reactions, where the surface Bi is highly favorable for improving catalytic activity, there is little influence from transition metal alloying. Finally, multimetallic tetrahexahedral particles have improved stabilities during prolonged operation compared to their monometallic counterparts due to the presence of the alloyed transition metal atoms.

14.
J Am Chem Soc ; 142(19): 8596-8601, 2020 05 13.
Artigo em Inglês | MEDLINE | ID: mdl-32356981

RESUMO

A novel method for controlling the oligomerization of metastable DNA hairpins using the hybridization chain reaction (HCR) is reported. Control was achieved through the introduction of a base-pair mismatch in the duplex of the hairpins. The mismatch modification allows one to kinetically differentiate initiation versus propagation events, leading to DNA oligomers up to 10 monomers long and improving dispersities from 2.5 to 1.3-1.6. Importantly, even after two consecutive chain extensions, dispersity remained unaffected, showing that well-defined block co-oligomers can be achieved. As a proof-of-concept, this technique was then applied to hairpin monomers functionalized with a mutant green fluorescent protein to prepare protein oligomers. Taken together, this work introduces an effective method for controlling living macromolecular HCR oligomerization in a manner analogous to the controlled polymerization of small molecules.

15.
Anal Chem ; 92(11): 7845-7851, 2020 06 02.
Artigo em Inglês | MEDLINE | ID: mdl-32437125

RESUMO

We report a dual-readout, AuNP-based sandwich immunoassay for the device-free colorimetric and sensitive scanometric detection of disease biomarkers. An AuNP-antibody conjugate serves as a signal transduction and amplification agent by promoting the reduction and deposition of either platinum or gold onto its surface, generating corresponding colorimetric or light scattering (scanometric) signals, respectively. We apply the Pt-based colorimetric readout of this assay to the discovery of a novel monoclonal antibody (mAb) sandwich pair for the detection of an anthrax protective antigen (PA83). The identified antibody pair detects PA83 down to 1 nM in phosphate-buffered saline and 5 nM in human serum, which are physiologically relevant concentrations. Reducing gold rather than platinum onto the mAb-AuNP sandwich enables scanometric detection of subpicomolar PA83 concentrations, over 3 orders of magnitude more sensitive than the colorimetric readout.

16.
Nat Commun ; 11(1): 2495, 2020 05 19.
Artigo em Inglês | MEDLINE | ID: mdl-32427872

RESUMO

Colloidal crystal engineering with nucleic acid-modified nanoparticles is a powerful way for preparing 3D superlattices, which may be useful in many areas, including catalysis, sensing, and photonics. To date, the building blocks studied have been primarily based upon metals, metal oxides, chalcogenide semiconductors, and proteins. Here, we show that metal-organic framework nanoparticles (MOF NPs) densely functionalized with oligonucleotides can be programmed to crystallize into a diverse set of superlattices with well-defined crystal symmetries and compositions. Electron microscopy and small-angle X-ray scattering characterization confirm the formation of single-component MOF superlattices, binary MOF-Au single crystals, and two-dimensional MOF nanorod assemblies. Importantly, DNA-modified porphyrinic MOF nanorods (PCN-222) were assembled into 2D superlattices and found to be catalytically active for the photooxidation of 2-chloroethyl ethyl sulfide (CEES, a chemical warfare simulant of mustard gas). Taken together, these new materials and methods provide access to colloidal crystals that incorporate particles with the well-established designer properties of MOFs and, therefore, increase the scope of possibilities for colloidal crystal engineering with DNA.


Assuntos
Coloides/química , DNA/química , Estruturas Metalorgânicas/química , Nanopartículas/química , Cristalização , DNA/genética , Engenharia/métodos , Microscopia Eletrônica de Transmissão e Varredura/métodos , Nanopartículas/ultraestrutura , Nanotubos/química , Nanotubos/ultraestrutura , Tamanho da Partícula , Espalhamento a Baixo Ângulo , Prata/química , Difração de Raios X
17.
J Am Chem Soc ; 142(16): 7350-7355, 2020 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-32281796

RESUMO

A novel method for synthesizing arrays of uniform sub-2 nm particles on substrates is described. Such particles are made by (i) using dip-pen nanolithography to prepare nanoreactors consisting of metal-coordinated polymers; (ii) designing polymers with only one metal atom attached to each polymer chain; (iii) systematically controlling nanoreactor volume down to the yoctoliter scale; and (iv) transforming each nanoreactor into a metal nanoparticle through thermal annealing. Polymer design in this study is crucial, since it allows one to tightly control nanoparticle size by tuning the volume of the polymer reactors, which correlates with the number of polymer chains and, therefore, metal atoms. Mixtures of different metal-functionalized polymers were used to synthesize ultrasmall alloy particles. The technique and results described herein point toward a way of using these novel polymers to systematically explore the properties and uses of this important class of nanomaterials in many fields.

18.
Chem Rev ; 120(13): 6009-6047, 2020 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-32319753

RESUMO

Dip-pen nanolithography (DPN) is a nanofabrication technique that can be used to directly write molecular patterns on substrates with high resolution and registration. Over the past two decades, DPN has evolved in its ability to transport molecular and material "inks" (e.g., alkanethiols, biological molecules like DNA, viruses, and proteins, polymers, and nanoparticles) to many surfaces in a high-throughput fashion, enabling the synthesis and study of complex chemical and biological structures. In addition, DPN has laid the foundation for a series of related scanning probe methodologies, for example, polymer pen lithography (PPL), scanning probe block copolymer lithography (SPBCL), and beam-pen lithography (BPL), which do not rely on cantilever tips. Structures prepared with these methodologies have been used to understand the consequences of miniaturization and open a door to new capabilities in catalysis, optics, biomedicine, and chemical synthesis, where, in sum, a process originally intended to compete with tools used by the semiconductor industry for rapid prototyping has transcended that application to advanced materials discovery. This review outlines the major DPN advances, the subsequent methods based on the technique, and the opportunities for future fundamental and technological exploration. Most importantly, it commemorates the 20th anniversary of the discovery of DPN.

19.
Analyst ; 145(11): 3899-3908, 2020 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-32297889

RESUMO

The enzyme isocitrate dehydrogenase 1 (IDH1) catalyzes the conversion of isocitrate to alpha-ketoglutarate (αKG) and has emerged as an important therapeutic target for glioblastoma multiforme (GBM). Current methods for assaying IDH1 remain poorly suited for high-throughput screening of IDH1 antagonists. This paper describes a high-throughput and quantitative assay for IDH1 that is based on the self-assembled monolayers for matrix-assisted laser desorption/ionization-mass spectrometry (SAMDI-MS) method. The assay uses a self-assembled monolayer presenting a hydrazide group that covalently captures the αKG product of IDH1, where it can then be detected by MALDI-TOF mass spectrometry. Co-capture of an isotopically-labeled αKG internal standard allows the αKG concentration to be quantitated. The assay was used to analyze a series of standard αKG solutions and produced minimal error in measured αKG concentration values. The suitability of the assay for high-throughput analysis was evaluated in a 384-sample biochemical IDH1 screen. Cells expressing IDH1 were lysed and the lysate was applied to the monolayer to capture αKG, which was then quantitated using the SAMDI-MS assay. Cells in which IDH1 expression was reduced by small-interfering RNA exhibited a corresponding decrease in αKG concentration as measured by the assay. Application of the assay toward the high-throughput screening of IDH1 inhibitors or knockdown agents may facilitate the discovery of treatments for GBM.

20.
J Am Chem Soc ; 142(10): 4570-4575, 2020 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-32096988

RESUMO

Multimetallic heterostructured nanoparticles with high-index facets potentially represent an important class of highly efficient catalysts. However, due to their complexity, they are often difficult to synthesize. Herein, a library of heterostructured, multimetallic (Pt, Pd, Rh, and Au) tetrahexahedral nanoparticles was synthesized through alloying/dealloying with Bi in a tube furnace at 900-1000 °C. Electron microscopy and selected area diffraction measurements show that the domains of the heterostructured nanoparticles are epitaxially aligned. Although nanoparticles formed from Au alone exhibit low-index facets, Pt and Au form PtAu heterostructured nanoparticles with high-index facets, including domains that are primarily made of Au. Furthermore, the alloying/dealloying of Bi occurs at different rates and under different conditions within the heterostructured nanoparticles. This influences the types of architectures observed en route to the final high-index state, a phenomenon clearly observable in the case of PdRhAu nanoparticles. Finally, scanning probe block copolymer lithography was used in combination with this synthetic strategy to control nanoparticle composition in the context of PtAu nanoparticles (1:4 to 4:1 ratio range) and size (15 to 45 nm range).

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