The tendency to the miniaturization of devices and the peculiar properties of the nanoparticles have raised the interest of the scientific community in nanoscience. In particular, those systems consisting of nanoparticles dispersed in fluids, known as nanofluids, have made it possible to overcome many technological and scientific challenges, as they show extraordinary properties. In this work, the loss of the spectral stability in heterogeneous luminescent nanofluids is studied revealing the critical role played by the exchange of ions between different nanoparticles. Such ion exchange is favored by changes in the molecular properties of the solvent, making heterogeneous luminescent nanofluids highly unstable against temperature changes. This work demonstrates how both temporal and thermal stabilities of heterogeneous luminescent nanofluids can be substantially improved by core–shell engineering. This simultaneously avoids the leakage of luminescent ions and the effects of the solvent molecular changes. 相似文献
The scattering of nanoparticles plays a profound role in the recently flourishing fields of plasmonics and metamaterials. However, current investigations into nanoparticle scattering are based on the electric and magnetic resonances only, where their toroidal counterparts are usually not considered. The inclusion of toroidal terms can render new explanations for some fundamental scattering properties and thus may stimulate further breakthroughs in both scattering‐related basic researches and applications. Here we revisit the most fundamental problem of Mie scattering by individual spherical nanoparticles and show that compared to conventional interpretations in terms of electric and magnetic responses, the roles played by their toroidal counterparts are indispensable. Based on the demonstration of efficient toroidal dipole excitation in homogeneous dielectric particles, we reveal that the extensively studied scattering transparencies of core–shell nanoparticles can actually be classified into two categories: (i) the trivial transparency with no effective multipole excitations and (ii) the non‐trivial transparency induced by the destructive interferences of excited electric and toroidal multipoles. The incorporation of toroidal multipoles offers new insights into the study of nanoparticle scattering in both near and far fields, which may shed new light on many applications, such as biosensing, imaging, nanoantennas, photovoltaic devices, and so on.
Simultaneously acquired microanalytical X‐ray and electron energy loss signals are obtained from a bimetallic core–shell nanoparticle system (FePt@Fe3O4). The signals are decomposed using independent component analysis and the extracted components are used to separately quantify the composition of the spatially overlapping core and shell phases in the nanoheterostructure. The utilization of the complementary strengths of energy dispersive X‐ray and electron energy‐loss spectroscopy microanalysis has enabled the quantification of both light and heavy elements in a single spectrum image acquisition. 相似文献
Gold nanoshells with tunable surface plasmon resonances are a promising material for optical and biomedical applications. They are produced through seed‐mediated growth, in which gold nanoparticles (AuNPs) are seeded on the core particle surface followed by growth of the gold seeds into a shell. However, synthetic gold nanoshell production is typically a multistep, time‐consuming batch‐type process, and a simple and scalable process remains a challenge. In the present study, a continuous flow process for the seed‐mediated growth of silica–gold nanoshells is established by exploiting the excellent mixing performance of a microreactor. In the AuNP‐seeding step, the reduction of gold ions in the presence of core particles in the microreactor enables the one‐step flow synthesis of gold‐decorated silica particles through heterogeneous nucleation. Flow shell growth is also realized using the microreactor by selecting an appropriate reducing agent. Because self‐nucleation in the bulk solution phase is suppressed in the microreactor system, no washing is needed after each step, thus enabling the connection of the microreactors for the seeding and shell growth steps into a sequential flow process to synthesize gold nanoshells. The established system is simple and robust, thus making it a promising technology for producing gold nanoshells in an industrial setting. 相似文献
Core–shell bimetallic Au@Ni nanoparticles, with gold cores and thin nickel shells with overall size less than 10 nm, are synthesized and stabilized in pure cubic (fcc) and hexagonal (hcp) phase. Due to their unique crystal, electronic, and geometric structure, they show interesting magnetic and chemical properties. The Au@Nifcc is magnetic, whereas Au@Nihcp is non‐magnetic. Both the bimetallic nanostructures are stable to surface oxidation until 150 °C and show excellent catalytic activity for p‐nitrophenol reduction reaction. 相似文献
Gold nanoparticles (AuNPs) are functionalized with a thermoresponsive polymer shell of a cross‐linked poly(2‐(2‐methoxyethoxy)ethyl methacrylate) (P(MEO2MA)). To provide a covalent attachment of the polymer to the NP surface, AuNPs are first modified using butanoic acid to develop the encapsulation with the biocompatible thermoresponsive polymer formed by free‐radical precipitation polymerization. Both the MEO2MA concentration and the shell cross‐linking density can be varied and, in turn, the thickness and the shells' free volume can be fine‐tuned. By downscaling the size of the polymeric shell, the lower critical solution temperature (LCST) is decreased. The LCST in the nanohybrids changes from 19.1 to 25.6 °C when increasing the MEO2MA content; it reaches almost 26 °C for P(MEO2MA) (bulk). The maximum decrease in the volume of the nanohybrids is around 40%, resulting in a modification of the light scattering properties of the system and causing a change in the turbidity of the gel network. The sizes of the nanohybrids are characterized using both transmission electron microscopy and dynamic light scattering measurements. Optical properties of the colloidal systems are determined using the derived count rate measurements as an alternative to absorbance or transmittance measurements, confirming the colloidal stability of the nanohybrid systems. 相似文献
Due to their high spatial resolution and precise application of force, optical traps are widely used to study the mechanics of biomolecules and biopolymers at the single‐molecule level. Recently, core–shell particles with optical properties that enhance their trapping ability represent promising candidates for high‐force experiments. To fully harness their properties, methods for functionalizing these particles with biocompatible handles are required. Here, a straightforward synthesis is provided for producing functional titania core–shell microparticles with proteins and nucleic acids by adding a silane–thiol chemical group to the shell surface. These particles display higher trap stiffness compared to conventional plastic beads featured in optical tweezers experiments. These core–shell microparticles are also utilized in biophysical assays such as amyloid fiber pulling and actin rupturing to demonstrate their high‐force applications. It is anticipated that the functionalized core–shells can be used to probe the mechanics of stable proteins structures that are inaccessible using current trapping techniques. 相似文献
Spinel ferrites hold great promise as attractive electrode materials for high‐performance supercapacitors owing to their multiple valence states and abundant choice of metal cation. However, the main bottleneck for most of the currently reported spinel ferrite‐based electrodes is relatively low specific capacitance. Herein, a new kind of lithium ferrites (Li0.5Fe2.5O4, LFO)@polydopamine (PDA) (denoted as LFO@PDA) core–shell nanoparticles with extraordinary capacitive performance as negative electrodes for aqueous asymmetric supercapacitors (ASCs) are reported first. Taking advantage of increased active sites, improved conductivity, enhanced hydrophilicity, and good strain accommodation in terms of the interesting core–shell architecture and PDA shell, the as‐obtained LFO@PDA electrode reaches a remarkable capacitance of 276.4 F g−1 and prominent durability (no any capacitance loss after 15 000 cycles). Moreover, a robust aqueous 1.8 V‐ASC device with a preferable energy density of 33.9 Wh kg−1 is also achieved based on the LFO@PDA electrode as negative electrode. 相似文献
A scalable synthesis of magnetic core–shell nanocomposite particles, acting as a novel class of magnetic resonance (MR) contrast agents, has been developed. Each nanocomposite particle consists of a biocompatible chitosan shell and a poly(methyl methacrylate) (PMMA) core where multiple aggregated γ‐Fe2O3 nanoparticles are confined within the hydrophobic core. Properties of the nanocomposite particles including their chemical structure, particle size, size distribution, and morphology, as well as crystallinity of the magnetic nanoparticles and magnetic properties were systematically characterized. Their potential application as an MR contrast agent has been evaluated. Results show that the nanocomposite particles have good stability in biological media and very low cytotoxicity in both L929 mouse fibroblasts (normal cells) and HeLa cells (cervical cancer cells). They also exhibited excellent MR imaging performance with a T2 relaxivity of up to 364 mMFe?1 s?1. An in vivo MR test performed on a naked mouse bearing breast tumor indicates that the nanocomposite particles can localize in both normal liver and tumor tissues. These results suggest that the magnetic core–shell nanocomposite particles are an efficient, inexpensive and safe T2‐weighted MR contrast agent for both liver and tumor MR imaging in cancer therapy. 相似文献
The use of high‐shear microfluidization as a rapid, reproducible, and high‐yield method to prepare nanoparticles of porous silicon (pSi) with a narrow size distribution is described. Porous films prepared by electrochemical etch of a single‐crystal silicon wafer are removed from the substrate, fragmented, dispersed in an aqueous solution, and then processed with a microfluidizer, which generates high yields (57%) of pSi nanoparticles of narrow size distribution (PDI = 0.263) without a filtration step. Preparation of pSi nanoparticles via microfluidization improves yields (by 2.4‐fold) and particle size uniformity (by 1.8‐fold), and it lowers the total processing time (by 36‐fold) over standard ultrasonication or ball milling methods. The average diameter of the nanoparticles can be adjusted over the range 150–350 nm by appropriate adjustment of processing steps. If the fluid carrier in the microfluidizer contains an oxidant for Si, the resulting pSi particles are prepared with a core–shell structure, in which an elemental Si core is encased in a silicon oxide shell. When an aqueous sodium tetraborate processing solution is used, microfluidization generates photoluminescent core–shell pSi particles with a quantum yield of 19% in a single step in less than 20 min. 相似文献
Nanoparticle‐based electrodes often suffer from poor electrical properties due to high interparticle resistance, as well as low Coulombic efficiency attributed to large surface area induced parasitic reactions. In order to address this issue, a strategy of encapsulating two kinds of nanoparticles of both metal oxide and metallic nanoparticles is attempted, simultaneously, in microscale carbon cubic shells for highly reversible lithium storage. The unique structure is synthesized by simultaneous reactions of (1) decomposition of crystalline Co2(OH)3Cl microparticle precursor, synthesized in unique eggshell reactor systems, into nanoparticles, (2) partial reduction of CoO into metallic Co by eggshell membrane, (3) carbon coating by chemical vapor deposition facilitated by presence of catalytic Co with carbon released from the eggshell membrane, and (4) microscale carbon shell formed using the Co2(OH)3Cl particles as microtemplates. The carbon shells can prevent the encapsulated mixed nanoparticles from direct contact with electrolyte and reduce undesirable parasitic reactions, and accommodate volumetric variation during cycling. The introduction of metallic Co nanoparticles can reduce interparticle resistance. When evaluated for lithium storage, the unique structures of CoO–Co@C demonstrate superior electrochemical performances in terms of electrode stability and rate performance, as compared to that of pure CoO. 相似文献
