Showing papers on "Nanoparticle published in 2015"
TL;DR: This review covered ZnO-NPs antibacterial activity including testing methods, impact of UV illumination,ZnO particle properties (size, concentration, morphology, and defects), particle surface modification, and minimum inhibitory concentration.
Abstract: Antibacterial activity of zinc oxide nanoparticles (ZnO-NPs) has received significant interest worldwide particularly by the implementation of nanotechnology to synthesize particles in the nanometer region. Many microorganisms exist in the range from hundreds of nanometers to tens of micrometers. ZnO-NPs exhibit attractive antibacterial properties due to increased specific surface area as the reduced particle size leading to enhanced particle surface reactivity. ZnO is a bio-safe material that possesses photo-oxidizing and photocatalysis impacts on chemical and biological species. This review covered ZnO-NPs antibacterial activity including testing methods, impact of UV illumination, ZnO particle properties (size, concentration, morphology, and defects), particle surface modification, and minimum inhibitory concentration. Particular emphasize was given to bactericidal and bacteriostatic mechanisms with focus on generation of reactive oxygen species (ROS) including hydrogen peroxide (H2O2), OH− (hydroxyl radicals), and O2 −2 (peroxide). ROS has been a major factor for several mechanisms including cell wall damage due to ZnO-localized interaction, enhanced membrane permeability, internalization of NPs due to loss of proton motive force and uptake of toxic dissolved zinc ions. These have led to mitochondria weakness, intracellular outflow, and release in gene expression of oxidative stress which caused eventual cell growth inhibition and cell death. In some cases, enhanced antibacterial activity can be attributed to surface defects on ZnO abrasive surface texture. One functional application of the ZnO antibacterial bioactivity was discussed in food packaging industry where ZnO-NPs are used as an antibacterial agent toward foodborne diseases. Proper incorporation of ZnO-NPs into packaging materials can cause interaction with foodborne pathogens, thereby releasing NPs onto food surface where they come in contact with bad bacteria and cause the bacterial death and/or inhibition.
2,627 citations
TL;DR: In this article, a facile hydrothermal method was used to produce luminous carbon dots (L-CDs) with high quantum yield value (44.7%) and controllable emission wavelengths.
Abstract: Luminescent carbon dots (L-CDs) with high quantum yield value (44.7%) and controllable emission wavelengths were prepared via a facile hydrothermal method. Importantly, the surface states of the materials could be engineered so that their photoluminescence was either excitation-dependent or distinctly independent. This was achieved by changing the density of amino-groups on the L-CD surface. The above materials were successfully used to prepare multicolor L-CDs/polymer composites, which exhibited blue, green, and even white luminescence. In addition, the excellent excitation-independent luminescence of L-CDs prepared at low temperature was tested for detecting various metal ions. As an example, the detection limit of toxic Be2+ ions, tested for the first time, was as low as μM.
587 citations
TL;DR: The objective of the present review is to show examples of polymer/metal composites designed to have antimicrobial activities, with a special focus on copper and silver metal nanoparticles and their mechanisms.
Abstract: Metals, such as copper and silver, can be extremely toxic to bacteria at exceptionally low concentrations. Because of this biocidal activity, metals have been widely used as antimicrobial agents in a multitude of applications related with agriculture, healthcare, and the industry in general. Unlike other antimicrobial agents, metals are stable under conditions currently found in the industry allowing their use as additives. Today these metal based additives are found as: particles, ions absorbed/exchanged in different carriers, salts, hybrid structures, etc. One recent route to further extend the antimicrobial applications of these metals is by their incorporation as nanoparticles into polymer matrices. These polymer/metal nanocomposites can be prepared by several routes such as in situ synthesis of the nanoparticle within a hydrogel or direct addition of the metal nanofiller into a thermoplastic matrix. The objective of the present review is to show examples of polymer/metal composites designed to have antimicrobial activities, with a special focus on copper and silver metal nanoparticles and their mechanisms.
556 citations
TL;DR: It is demonstrated that such novel Au NPs-N-GQDs nanocomposite is promising for fabrication of nonenzymatic H2O2 biosensors and has shown great potential applications for detection of H 2O2 levels in human serum samples and that released from human cervical cancer cells with satisfactory results.
Abstract: In this work, we report a green and simple strategy for the in situ growth of surfactant-free Au nanoparticles (Au NPs) on nitrogen-doped graphene quantum dots (Au NPs–N-GQDs). The formation of hybrid was achieved by just mixing the N-GQDs and HAuCl4·4H2O without addition of any other reductant and surfactant. High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) characterizations clearly showed the formation of Au nanoparticles with predominantly exposed (111) facets which can provide more adsorption sites. Such nonsurfactant-capped Au NPs can provide naked catalytic surface with highly electrocatalytic activity. The Au NPs–N-GQDs exhibit high sensitivity and selectivity for electrochemical detection of hydrogen peroxide (H2O2) with a low detection limit of 0.12 μM and sensitivity of 186.22 μA/mM cm2. Importantly, the Au NPs–N-GQDs-based electrochemical biosensor has shown great potential applications for detection of H2O2 levels in ...
498 citations
TL;DR: It is shown that lignin nanoparticles infused with silver ions and coated with a cationic polyelectrolyte layer form a biodegradable and green alternative to silver nanoparticles.
Abstract: Silver nanoparticles have antibacterial properties, but their use has been a cause for concern because they persist in the environment. Here, we show that lignin nanoparticles infused with silver ions and coated with a cationic polyelectrolyte layer form a biodegradable and green alternative to silver nanoparticles. The polyelectrolyte layer promotes the adhesion of the particles to bacterial cell membranes and, together with silver ions, can kill a broad spectrum of bacteria, including Escherichia coli, Pseudomonas aeruginosa and quaternary-amine-resistant Ralstonia sp. Ion depletion studies have shown that the bioactivity of these nanoparticles is time-limited because of the desorption of silver ions. High-throughput bioactivity screening did not reveal increased toxicity of the particles when compared to an equivalent mass of metallic silver nanoparticles or silver nitrate solution. Our results demonstrate that the application of green chemistry principles may allow the synthesis of nanoparticles with biodegradable cores that have higher antimicrobial activity and smaller environmental impact than metallic silver nanoparticles.
469 citations
TL;DR: A synthesis of highly durable and active intermetallic ordered face-centered tetragonal (fct)-PtFe nanoparticles (NPs) coated with a "dual purpose" N-doped carbon shell to open a new simple and effective route for the commercialization of fuel cells.
Abstract: Demand on the practical synthetic approach to the high performance electrocatalyst is rapidly increasing for fuel cell commercialization. Here we present a synthesis of highly durable and active intermetallic ordered face-centered tetragonal (fct)-PtFe nanoparticles (NPs) coated with a “dual purpose” N-doped carbon shell. Ordered fct-PtFe NPs with the size of only a few nanometers are obtained by thermal annealing of polydopamine-coated PtFe NPs, and the N-doped carbon shell that is in situ formed from dopamine coating could effectively prevent the coalescence of NPs. This carbon shell also protects the NPs from detachment and agglomeration as well as dissolution throughout the harsh fuel cell operating conditions. By controlling the thickness of the shell below 1 nm, we achieved excellent protection of the NPs as well as high catalytic activity, as the thin carbon shell is highly permeable for the reactant molecules. Our ordered fct-PtFe/C nanocatalyst coated with an N-doped carbon shell shows 11.4 times...
454 citations
TL;DR: This synthesized nanocluster is the only silver nanoparticle that has a virtually identical analogue in gold, i.e., [Au25(SR)18](-), in terms of number of metal atoms, ligand count, superatom electronic configuration, and atomic arrangement.
Abstract: Silver nanoparticles with an atomically precise molecular formula [Ag25(SR)18]− (−SR: thiolate) are synthesized, and their single-crystal structure is determined. This synthesized nanocluster is the only silver nanoparticle that has a virtually identical analogue in gold, i.e., [Au25(SR)18]−, in terms of number of metal atoms, ligand count, superatom electronic configuration, and atomic arrangement. Furthermore, both [Ag25(SR)18]− and its gold analogue share a number of features in their optical absorption spectra. This unprecedented molecular analogue in silver to mimic gold offers the first model nanoparticle platform to investigate the centuries-old problem of understanding the fundamental differences between silver and gold in terms of nobility, catalytic activity, and optical property.
431 citations
TL;DR: The extremely high catalytic activity, facile preparation, and low cost of the single crystalline FexNi1-xO nanoparticles make them very promising catalysts for the oxygen evolution reaction.
Abstract: Efficient electrochemical water splitting to hydrogen and oxygen is considered a promising technology to overcome our dependency on fossil fuels. Searching for novel catalytic materials for electrochemical oxygen generation is essential for improving the total efficiency of water splitting processes. We report the synthesis, structural characterization, and electrochemical performance in the oxygen evolution reaction of Fe-doped NiO nanocrystals. The facile solvothermal synthesis in tert-butanol leads to the formation of ultrasmall crystalline and highly dispersible FexNi1-xO nanoparticles with dopant concentrations of up to 20%. The increase in Fe content is accompanied by a decrease in particle size, resulting in nonagglomerated nanocrystals of 1.5-3.8 nm in size. The Fe content and composition of the nanoparticles are determined by X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy measurements, while Mossbauer and extended X-ray absorption fine structure analyses reveal a substitutional incorporation of Fe(III) into the NiO rock salt structure. The excellent dispersibility of the nanoparticles in ethanol allows for the preparation of homogeneous ca. 8 nm thin films with a smooth surface on various substrates. The turnover frequencies (TOF) of these films could be precisely calculated using a quartz crystal microbalance. Fe0.1Ni0.9O was found to have the highest electrocatalytic water oxidation activity in basic media with a TOF of 1.9 s(-1) at the overpotential of 300 mV. The current density of 10 mA cm(-2) is reached at an overpotential of 297 mV with a Tafel slope of 37 mV dec(-1). The extremely high catalytic activity, facile preparation, and low cost of the single crystalline FexNi1-xO nanoparticles make them very promising catalysts for the oxygen evolution reaction.
417 citations
TL;DR: This Account provides a review on the recent progresses in the controlled synthesis and assembly of uniformly sized iron oxide nanoparticles for medical applications, and focuses on stringent control of particle size during synthesis via the "heat-up" process, surface modification for the high stability and biocompatibility of the nanoparticle for diagnostic purposes, and assembly for theranostic applications.
Abstract: ConspectusMagnetic iron oxide nanoparticles have been extensively investigated for their various biomedical applications including diagnostic imaging, biological sensing, drug, cell, and gene delivery, and cell tracking. Recent advances in the designed synthesis and assembly of uniformly sized iron oxide nanoparticles have brought innovation in the field of nanomedicine. This Account provides a review on the recent progresses in the controlled synthesis and assembly of uniformly sized iron oxide nanoparticles for medical applications. In particular, it focuses on three topics: stringent control of particle size during synthesis via the “heat-up” process, surface modification for the high stability and biocompatibility of the nanoparticles for diagnostic purposes, and assembly of the nanoparticles within polymers or mesoporous silica matrices for theranostic applications.Using extremely small 3 nm sized iron oxide nanoparticles (ESION), a new nontoxic T1 MRI contrast agent was realized for high-resolution ...
398 citations
TL;DR: In this article, the synthesis of zinc oxide nanoparticles (ZnO NPs) using leaf aqueous extract of Azadirachta indica (L.) and its antimicrobial activities was described.
394 citations
TL;DR: The core-shell IrNiO(x)/Meso-ATO catalyst displayed high water-splitting activity and unprecedented stability in acidic electrolyte providing substantial progress in the development of PEM electrolyzer anode catalysts with drastically reduced Ir loading and significantly enhanced durability.
Abstract: Active and highly stable oxide-supported IrNiOx core-shell catalysts for electrochemical water splitting are presented. IrNix@IrOx nanoparticles supported on high-sur- face-area mesoporous antimony-doped tin oxide (IrNiOx / Meso-ATO) were synthesized from bimetallic IrNix precursor alloys (PA-IrNix /Meso-ATO) using electrochemical Ni leach- ing and concomitant Ir oxidation. Special emphasis was placed on Ni/NiO surface segregation under thermal treatment of the PA-IrNix /Meso-ATO as well as on the surface chemical state of the particle/oxide support interface. Combining a wide array of characterization methods, we uncovered the detrimental effect of segregated NiO phases on the water splitting activity of core- shell particles. The core-shell IrNiOx /Meso-ATO catalyst displayed high water-splitting activity and unprecedented stability in acidic electrolyte providing substantial progress in the development of PEM electrolyzer anode catalysts with drastically reduced Ir loading and significantly enhanced durability.
TL;DR: These core-shell biopolymer nanoparticles could be useful for incorporating curcumin into functional foods and beverages, as well as dietary supplements and pharmaceutical products.
TL;DR: An overview of shape-controlled synthesis of silver nanoparticles using various methods is given in this article, where the authors present an overview of the shape controlled synthesis of Silver nanoparticles.
TL;DR: This review provides an overview of different steady-state single particle spectroscopy techniques that provide detailed insight into the spectral characteristics of plasmonic nanoparticles.
Abstract: This tutorial review surveys the optical properties of plasmonic nanoparticles studied by various single particle spectroscopy techniques. The surface plasmon resonance of metallic nanoparticles depends sensitively on the nanoparticle geometry and its environment, with even relatively minor deviations causing significant changes in the optical spectrum. Because for chemically prepared nanoparticles a distribution of their size and shape is inherent, ensemble spectra of such samples are inhomogeneously broadened, hiding the properties of the individual nanoparticles. The ability to measure one nanoparticle at a time using single particle spectroscopy can overcome this limitation. This review provides an overview of different steady-state single particle spectroscopy techniques that provide detailed insight into the spectral characteristics of plasmonic nanoparticles.
TL;DR: Liquid metal nanoparticles that are mechanically sintered at and below room temperature are introduced and are compatible with inkjet printing, a process not applicable to the bulk liquid metal in air.
Abstract: Liquid metal nanoparticles that are mechanically sintered at and below room temperature are introduced. This material can be sintered globally on large areas of entire deposits or locally to create liquid traces within deposits. The metallic nanoparticles are fabricated by dispersing a liquid metal in a carrier solvent via sonication. The resulting dispersion is compatible with inkjet printing, a process not applicable to the bulk liquid metal in air.
TL;DR: In this paper, uniform NiO nanoparticles on different substrates were successfully synthesized by a simple and low-cost solvothermal method and achieved high capacitance (1386 F g−1 at 1 ǫg−1) and excellent rate capability.
TL;DR: In this paper, the molar ratio between CH3NH3Br, PbBr2, a medium-size alkyl-chain ammonium salt, and 1-octadecene was fine-tuned.
Abstract: Highly luminescent and photostable CH3NH3PbBr3 nanoparticles have been prepared by fine-tuning the molar ratio between CH3NH3Br, PbBr2, a medium-size alkyl-chain ammonium salt, and 1-octadecene. The nanoparticles exhibit an excellent photoluminescence quantum yield (ca. 83%) and average recombination lifetime (ca. 600 ns) in toluene dispersion.
TL;DR: It is shown that firmly grafted polymer shells around gold nanoparticles may degrade when injected into rats, and in vitro studies suggest that degradation of the polymer shell is caused by proteolytic enzymes in the liver.
Abstract: The polymeric shell surrounding gold nanoparticles may degrade when injected into rats, suggesting that even highly stable colloidal nanoparticles are susceptible to physicochemical changes in vivo
TL;DR: The results of this study confirm that the leaves extract of Ziziphora tenuior can synthesis silver nanoparticles, and the methods of making nanoparticles using plant extracts are view.
TL;DR: In this paper, the main physical properties of ZnO nanoparticles synthesized for the first time by a completely green process using Agathosma betulina plant extract as an effective chelating agent are reported.
TL;DR: Graphene acts not only as a structural support, but also as a space barrier to prevent the growth of MgH2 nanoparticles and as a thermally conductive pathway, leading to outstanding performance.
Abstract: Monodisperse MgH2 nanoparticles with homogeneous distribution and a high loading percent are developed through hydrogenation-induced self-assembly under the structure-directing role of graphene. Graphene acts not only as a structural support, but also as a space barrier to prevent the growth of MgH2 nanoparticles and as a thermally conductive pathway, leading to outstanding performance.
TL;DR: In SCEINs the single carbon layer does not prevent desired access of the reactants to the vicinity of the iron nanoparticles but protects the active metallic core from oxidation, which opens new avenues for utilizing active transition metals such as iron in a wide range of applications.
Abstract: Efficient hydrogen evolution reaction (HER) through effective and inexpensive electrocatalysts is a valuable approach for clean and renewable energy systems. Here, single-shell carbon-encapsulated iron nanoparticles (SCEINs) decorated on single-walled carbon nanotubes (SWNTs) are introduced as a novel highly active and durable non-noble-metal catalyst for the HER. This catalyst exhibits catalytic properties superior to previously studied nonprecious materials and comparable to those of platinum. The SCEIN/SWNT is synthesized by a novel fast and low-cost aerosol chemical vapor deposition method in a one-step synthesis. In SCEINs the single carbon layer does not prevent desired access of the reactants to the vicinity of the iron nanoparticles but protects the active metallic core from oxidation. This finding opens new avenues for utilizing active transition metals such as iron in a wide range of applications.
TL;DR: The aqueous beetroot extract was used as reducing agent for silver nanoparticles synthesis and revealed faster catalytic activity, offering a valuable contribution in the area of green synthesis and nanotechnology avoiding the presence of hazardous and toxic solvents and waste.
TL;DR: This review of the interactions within nanoparticle dispersions in ionic liquids and of the structure of nanoparticle and ionic liquid hybrids provides guidance on the rational design of novel ionic Liquid-based materials, enabling applications in broad areas.
Abstract: Ionic liquids (ILs), defined as low-melting organic salts, are a novel class of compounds with unique properties and a combinatorially great chemical diversity. Ionic liquids are utilized as synthesis and dispersion media for nanoparticles as well as for surface functionalization. Ionic liquid and nanoparticle hybrid systems are governed by a combined effect of several intermolecular interactions between their constituents. For each interaction, including van der Waals, electrostatic, structural, solvophobic, steric, and hydrogen bonding, the characterization and quantitative calculation methods together with factors affecting these interactions are reviewed here. Various self-organized structures based on nanoparticles in ionic liquids are generated as a result of a balance of these intermolecular interactions. These structures, including colloidal glasses and gels, lyotropic liquid crystals, nanoparticle-stabilized ionic liquid-containing emulsions, ionic liquid surface-functionalized nanoparticles, and nanoscale ionic materials, possess properties of both ionic liquids and nanoparticles, which render them useful as novel materials especially in electrochemical and catalysis applications. This review of the interactions within nanoparticle dispersions in ionic liquids and of the structure of nanoparticle and ionic liquid hybrids provides guidance on the rational design of novel ionic liquid-based materials, enabling applications in broad areas.
TL;DR: The results indicate that the sensor based on Pt activated SnO2 not only has ultrahigh sensitivity but also possesses good response-recovery properties, linear dependence, repeatability, selectivity and long-term stability, demonstrating the potential to use Pt activatedsnO2 nanoparticle clusters as ammonia gas sensors.
Abstract: Pt activated SnO2 nanoparticle clusters were synthesized by a simple solvothermal method. The structure, morphology, chemical state and specific surface area were analyzed by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and N2-sorption studies, respectively. The SnO2 nanoparticle cluster matrix consists of tens of thousands of SnO2 nanoparticles with an ultra-small grain size estimated to be 3.0 nm. And there are abundant random-packed wormhole-like pores, caused by the inter-connection of the SnO2 nanoparticles, throughout each cluster. The platinum element is present in two forms including metal (Pt) and tetravalent metal oxide (PtO2) in the Pt activated SnO2 nanoparticle clusters. The as-synthesized pure and Pt activated SnO2 nanoparticle clusters were used to fabricate gas sensor devices. It was found that the gas response toward 500 ppm of ammonia was improved from 6.48 to 203.44 through the activation by Pt. And the results indicate that the sensor based on Pt activated SnO2 not only has ultrahigh sensitivity but also possesses good response–recovery properties, linear dependence, repeatability, selectivity and long-term stability, demonstrating the potential to use Pt activated SnO2 nanoparticle clusters as ammonia gas sensors. At the same time, the formation mechanisms of the unique nanoparticle clusters and highly enhanced sensitivity are also discussed.
TL;DR: The present work demonstrates that the 3D mesoporous SnO2/rGO composites with extremely large surface area and stable nanostructure are excellent candidate materials for gas sensing.
Abstract: A facile and cost-efficient hydrothermal and lyophilization two-step strategy has been developed to prepare three-dimensional (3D) SnO2/rGO composites as NO2 gas sensor. In the present study, two different metal salt precursors (Sn2+ and Sn4+) were used to prepare the 3D porous composites. It was found that the products prepared from different tin salts exhibited different sensing performance for NO2 detection. The scanning electron microscopy and transmission electron microscopy characterizations clearly show the macroporous 3D hybrids, nanoporous structure of reduce graphene oxide (rGO), and the supported SnO2 nanocrystals with an average size of 2–7 nm. The specific surface area and porosity properties of the 3D mesoporous composites were analyzed by Braunauer–Emmett–Teller method. The results showed that the SnO2/rGO composite synthesized from Sn4+ precursor (SnO2/rGO-4) has large surface area (441.9 m2/g), which is beneficial for its application as a gas sensing material. The gas sensing platform fab...
TL;DR: A template-free procedure to synthesize Co3O4 hollow-structured nanoparticles on a Vulcan XC-72 carbon support exhibited excellent lithium storage capacity, rate capability, and cycling stability when used as the anode material in lithium-ion batteries.
Abstract: We have developed a template-free procedure to synthesize Co3O4 hollow-structured nanoparticles on a Vulcan XC-72 carbon support. The material was synthesized via an impregnation–reduction method followed by air oxidation. In contrast to spherical particles, the hollow-structured Co3O4 nanoparticles exhibited excellent lithium storage capacity, rate capability, and cycling stability when used as the anode material in lithium-ion batteries. Electrochemical testing showed that the hollow-structured Co3O4 particles delivered a stable reversible capacity of about 880 mAh/g (near the theoretical capacity of 890 mAh/g) at a current density of 50 mA/g after 50 cycles. The superior electrochemical performance is attributed to its unique hollow structure, which combines nano- and microscale properties that facilitate electron transfer and enhance structural robustness.
TL;DR: In this article, an indium (In)-doped titanium dioxide (TiO2) nanoparticles were synthesized using a controlled sol-gel method and the structures and properties of the catalysts were characterized by XRD, FE-SEM, TEM, XPS, BET, UV-vis and PL spectroscopy.
Abstract: Indium (In)-doped titanium dioxide (TiO2) nanoparticles were synthesized using a controlled sol–gel method. The structures and properties of the catalysts were characterized by XRD, FE-SEM, TEM, XPS, BET, UV–vis and PL spectroscopy. Indium, present over the TiO2 in metal state, inhibited crystal growth and produced anatase phase of mesoporous TiO2 nanoparticles. Doping In in TiO2 also increased the surface area and enlarged the band gap. The photocatalytic activities of In-doped TiO2 nanoparticles were considerably improved for CO2 reduction with H2O vapors in a cell type photoreactor. CO was observed as the main product over TiO2, but doping In in TiO2 remarkably increased the CH4 yield. CH4 production rate over 10 wt.% In-doped TiO 2 was 7.9-fold higher than the bare TiO2 at 100 °C and CO2/H2O ratio of 1.43. In addition, C1–3 higher hydrocarbons namely C2H4, C2H6, C3H6 and C3H8 were detected in the product mixture. The enhanced photoactivity in mesoporous In-doped TiO2 nanoparticles can be attributed to interfacial transfer of photogenerated charges, which led to effective charge separation and inhibited recombination of photogenerated electron–hole (e−/h+) pairs. Langmuir–Hinshelwood model, developed to investigate reaction rate parameters, fitted well with the experimental data.
TL;DR: This work highlights the benefit of quantum dot length-scale nanocrystal electrodes for nanoscale metal sulfide compounds that store energy through chemical conversion reactions, where alloying or intercalation processes limit the performance of ultrafine nanoparticles.
Abstract: Nanocrystals with quantum-confined length scales are often considered impractical for metal-ion battery electrodes due to the dominance of solid-electrolyte interphase (SEI) layer effects on the measured storage properties. Here we demonstrate that ultrafine sizes (∼4.5 nm, average) of iron pyrite, or FeS2, nanoparticles are advantageous to sustain reversible conversion reactions in sodium ion and lithium ion batteries. This is attributed to a nanoparticle size comparable to or smaller than the diffusion length of Fe during cation exchange, yielding thermodynamically reversible nanodomains of converted Fe metal and NaxS or LixS conversion products. This is compared to bulk-like electrode materials, where kinetic and thermodynamic limitations of surface-nucleated conversion products inhibit successive conversion cycles. Reversible capacities over 500 and 600 mAh/g for sodium and lithium storage are observed for ultrafine nanoparticles, with improved cycling and rate capability. Unlike alloying or intercala...
TL;DR: A method for determining three-dimensional (3D) structures of individual nanoparticles in solution is introduced that enables the analysis of heterogeneous populations of potentially unordered nanoparticles that are synthesized in solution, thereby providing a means to understand the structure and stability of defects at the nanoscale.
Abstract: Knowledge about the synthesis, growth mechanisms, and physical properties of colloidal nanoparticles has been limited by technical impediments. We introduce a method for determining three-dimensional (3D) structures of individual nanoparticles in solution. We combine a graphene liquid cell, high-resolution transmission electron microscopy, a direct electron detector, and an algorithm for single-particle 3D reconstruction originally developed for analysis of biological molecules. This method yielded two 3D structures of individual platinum nanocrystals at near-atomic resolution. Because our method derives the 3D structure from images of individual nanoparticles rotating freely in solution, it enables the analysis of heterogeneous populations of potentially unordered nanoparticles that are synthesized in solution, thereby providing a means to understand the structure and stability of defects at the nanoscale.