A lot of interesting and sophisticated examples of nanoparticle (NP) self-assembly (SA) are known. From both fundamental and technological standpoints, this field requires advancements in three ...principle directions: (a) understanding the mechanism and driving forces of three-dimensional (3D) SA with both nano- and microlevels of organization; (b) understanding disassembly/deconstruction processes; and (c) finding synthetic methods of assembly into continuous superstructures without insulating barriers. From this perspective, we investigated the formation of well-known star-like PbS superstructures and found a number of previously unknown or overlooked aspects that can advance the knowledge of NP self-assembly in these three directions. The primary one is that the formation of large seemingly monocrystalline PbS superstructures with multiple levels of octahedral symmetry can be explained only by SA of small octahedral NPs. We found five distinct periods in the formation PbS hyperbranched stars: (1) nucleation of early PbS NPs with an average diameter of 31 nm; (2) assembly into 100–500 nm octahedral mesocrystals; (3) assembly into 1000–2500 nm hyperbranched stars; (4) assembly and ionic recrystallization into six-arm rods accompanied by disappearance of fine nanoscale structure; (5) deconstruction into rods and cuboctahedral NPs. The switches in assembly patterns between the periods occur due to variable dominance of pattern-determining forces that include van der Waals and electrostatic (charge–charge, dipole–dipole, and polarization) interactions. The superstructure deconstruction is triggered by chemical changes in the deep eutectic solvent (DES) used as the media. PbS superstructures can be excellent models for fundamental studies of nanoscale organization and SA manufacturing of (opto)electronics and energy-harvesting devices which require organization of PbS components at multiple scales.
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The application of mesoporous bioactive glasses (MBGs) containing controllable amount of different ions, with the aim to impart antibacterial activity, as well as stimulation of ...osteogenesis and angiogenesis, is attracting an increasing interest.
In this contribution, in order to endow nano-sized MBG with additional biological functions, the framework of a binary SiO2-CaO mesoporous glass was modified with different concentrations of copper ions (2 and 5%mol.), through a one-pot ultrasound-assisted sol-gel procedure. The Cu-containing MBG (2%mol.) showed high exposed surface area (550m2g−1), uniform mesoporous channels (2.6nm), remarkable in vitro bioactive behaviour and sustained release of Cu2+ ions.
Cu-MBG nanoparticles and their ionic dissolution extracts exhibited antibacterial effect against three different bacteria strains, E. coli, S. aureus, S. epidermidis, and the ability to inhibit and disperse the biofilm produced by S. epidermidis.
The obtained results suggest that the developed material, which combines in single multifunctional agent excellent bioactivity and antimicrobial ability, offers promising opportunities for the prevention of infectious diseases and the effective treatment of bone defects.
In order to endow mesoporous bioactive glass, characterized by excellent bioactive properties, with additional biological functions, Cu-doped mesoporous SiO2-CaO glass (Cu-MBG) in the form of nanoparticles was prepared by an ultra-sound assisted one pot synthesis.
The analysis of the bacterial viability, using different bacterial strains, and the morphological observation of the biofilm produced by the Staphylococcus epidermidis, revealed the antimicrobial effectiveness of the Cu-MBG and the relative ionic extracts against both the bacterial growth and the biofilm formation/dispersion, providing a true alternative to traditional antibiotic systemic therapies.
The proposed multifunctional agent represents a promising and versatile platform for bone and soft tissues regeneration.
Spurred by the decreased availability of fossil fuels and global warming, the idea of converting solar energy into clean fuels has been widely recognized. Hydrogen produced by photoelectrochemical ...water splitting using sunlight could provide a carbon dioxide lean fuel as an alternative to fossil fuels. A major challenge in photoelectrochemical water splitting is to develop an efficient photoanode that can stably oxidize water into oxygen. Here we report an efficient and stable photoanode that couples an active barium-doped tantalum nitride nanostructure with a stable cobalt phosphate co-catalyst. The effect of barium doping on the photoelectrochemical activity of the photoanode is investigated. The photoanode yields a maximum solar energy conversion efficiency of 1.5%, which is more than three times higher than that of state-of-the-art single-photon photoanodes. Further, stoichiometric oxygen and hydrogen are stably produced on the photoanode and the counter electrode with Faraday efficiency of almost unity for 100 min.
Covalent organic frameworks (COFs) are commonly synthesized under harsh conditions yielding unprocessable powders. Control in their crystallization process and growth has been limited to studies ...conducted in hazardous organic solvents. Herein, we report a one-pot synthetic method that yields stable aqueous colloidal solutions of sub-20 nm crystalline imine-based COF particles at room temperature and ambient pressure. Additionally, through the combination of experimental and computational studies, we investigated the mechanisms and forces underlying the formation of such imine-based COF colloids in water. Further, we show that our method can be used to process the colloidal solution into 2D and 3D COF shapes as well as to generate a COF ink that can be directly printed onto surfaces. These findings should open new vistas in COF chemistry, enabling new application areas.
Elongated micro- and nanostructures of Sn doped or Sn and Cr codoped monoclinic gallium oxide have been grown by a thermal method. The presence of Sn during growth has been shown to strongly ...influence the morphology of the resulting structures, including Sn doped branched wires, whips, and needles. Subsequent codoping with Cr is achieved through thermal diffusion for photonic purposes. The formation mechanism of the branched structures has been studied by transmission electron microscopy (TEM). Epitaxial growth has been demonstrated in some cases, revealed by a very high quality interface between the central rod and the branches of the structures, while in other cases, formation of extended defects such as twins has been observed in the interface region. The influence of dopants on the energy levels of Ga and O within the structures has been studied by XPS. Micro-Raman spectroscopy was used to assess the influence of Sn doping, and Sn–Cr codoping, on the vibrational properties of single nanowires. Cathodoluminescence (CL) measurements show a Sn-related complex band in the Sn-doped structures. Temperature-dependent and excitation-density-dependent CL indicates that this is a thermally activated emission. In the Sn–Cr codoped samples, the characteristic, very intense Cr3+ red luminescence emission quenches the bands observed in the Sn-doped samples. Branched, Sn–Cr codoped structures were studied with microphotoluminescence imaging and spectroscopy, and waveguiding behavior was observed along the trunks and branches of these structures.
Nanoscale heterostructures of covalent intermetallics should give birth to a wide range of interface-driven physical and chemical properties. Such a level of design however remains unattainable for ...most of these compounds, due to the difficulty to reach a crystalline order of covalent bonds at the moderate temperatures required for colloidal chemistry. Herein, we design heterostructured cobalt silicide nanoparticles to trigger magnetic and catalytic properties in silicon-based materials. Our strategy consists in controlling the diffusion of cobalt atoms into silicon nanoparticles, by reacting these particles in molten salts. By adjusting the temperature, we tune the conversion of the initial silicon particles toward homogeneous CoSi nanoparticles and core–shell nanoparticles made of a CoSi shell and a silicon-rich core. The increased interface-to-volume ratio of the CoSi component in the core–shell particles yields distinct properties compared to the bulk and homogeneous nanoparticles. First, the core–shell particles exhibit increased ferromagnetism, despite the bulk diamagnetic properties of cobalt monosilicide. Second, the core–shell nanoparticles act as efficient precatalysts for alkaline water oxidation, where the nanostructure is converted in situ into a layered cobalt silicon oxide/(oxy)hydroxide with high and stable oxygen evolution reaction (OER) electrocatalytic activity. This work demonstrates a route to design heterostructured nanocrystals of covalent intermetallic compounds and shows that these new structures exhibit very rich, yet poorly explored, interface-based physical properties and reactivity.
Abstract
Octahedral molecular sieves (OMS) are built of transition metal-oxygen octahedra that delimit sub-nanoscale cavities. Compared to other microporous solids, OMS exhibit larger versatility in ...properties, provided by various redox states and magnetic behaviors of transition metals. Hence, OMS offer opportunities in electrochemical energy harnessing devices, including batteries, electrochemical capacitors and electrochromic systems, provided two conditions are met: fast exchange of ions in the micropores and stability upon exchange. Here we unveil a novel OMS hexagonal polymorph of tungsten oxide called
h’-WO
3
, built of (WO
6
)
6
tunnel cavities.
h’-WO
3
is prepared by a one-step soft chemistry aqueous route leading to the hydrogen bronze
h’-H
0.07
WO
3
. Gentle heating results in
h’-WO
3
with framework retention. The material exhibits an unusual combination of 1-dimensional crystal structure and 2-dimensional nanostructure that enhances and fastens proton (de)insertion for stable electrochromic devices. This discovery paves the way to a new family of mixed valence functional materials with tunable behaviors.
The influence of indium doping on morphology, structural, and luminescence properties of gallium oxide micro- and nanostructures is reported. Indium-doped gallium oxide micro- and nanostructures have ...been grown by thermal oxidation of metallic gallium in the presence of indium oxide. The dominant morphologies are beltlike structures, which in many cases are twisted leading to springlike structures, showing that In diffusion in Ga2O3 influences the microstructure shapes. High-resolution transmission electron microscopy has revealed the presence of twins in the belts, and energy-dispersive X-ray spectroscopy in the scanning electron microscopy (SEM) has detected a segregation of indium impurities at the edges of planar structures. These results suggest that indium plays a major role in the observed morphologies and support the assumption of a layer by layer model as growth mechanism. An additional assessment of indium influence on the defect structure has been performed by cathodoluminescence in the SEM, X-ray photoelectron microscopy, and spatially resolved Raman spectroscopy.
A novel nanocarrier based on functionalized mesoporous silica nanoparticles able to transport a non‐toxic pro‐drug and the enzyme responsible for its activation is presented. This nanodevice is able ...to generate in situ cytotoxic species once accumulated in the tumoral cell. Enzymes are sensitive macromolecules which can suffer denaturalization in biological media due to the presence of proteases or other aggressive agents. Moreover, the direct attachment of enzymes to the silica surface can reduce their activity by conformational changes or active site blockage. For these reasons, in order to create a robust system able to work in living organisms, the enzymes are previously coated with a protective polymeric shell which allows the attachment on the silica surface preserving their activity. The efficacy of this hybrid nanodevice for antitumoral purposes is tested against several human tumoral cells as neuroblastoma and leukemia showing significant efficacy. It converts this device in a promising candidate for further in vivo studies for oncology therapy.
Hybrid enzyme capsule‐silica nanoparticles: A novel nanocarrier based on mesoporous silica nanoparticles loaded with a non‐toxic pro‐drug within the silica matrix and the enzyme responsible for its activation grafted on surface. This device is able to generate cytotoxic species once accumulated in the target place. The efficacy of this hybrid nanodevice for antitumoral purposes is tested against human tumoral cells showing significant efficacy.
One of the most attractive applications of carbon nanomaterials is as catalysts, due to their extreme surface-to-volume ratio. The substitution of C with heteroatoms (typically B and N as p- and ...n-dopants) has been explored to enhance their catalytic activity. Here we show that encapsulation within weakly doping macrocycles can be used to modify the catalytic properties of the nanotubes towards the reduction of nitroarenes, either enhancing it (n-doping) or slowing it down (p-doping). This artificial regulation strategy presents a unique combination of features found in the natural regulation of enzymes: binding of the effectors (the macrocycles) is noncovalent, yet stable thanks to the mechanical link, and their effect is remote, but not allosteric, since it does not affect the structure of the active site. By careful design of the macrocycles' structure, we expect that this strategy will contribute to overcome the major hurdles in SWNT-based catalysts: activity, aggregation, and specificity.
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