We present a simple and universal technique for assembling gold nanorods (NRs) using self-assembled stacks of lyotropic chromonic materials, without covalent bonding between NRs and the linking agent. The anisotropic electrostatic interaction between the chromonic stacks and NRs allows one to achieve either side-by-side or end-to-end assembly, depending on the surface charge of NRs. The assembled superstructures are stable within an extended temperature range; the degree of NR aggregation can be controlled by a number of factors influencing the self-assembly of chromonic materials, such as the concentration and pH of the solution.
A novel nanostructured composite film (see figure) that takes advantage of two different natural materials—layered nacre and the marine adhesive of mussels—is prepared. L-3,4-Dihydroxyphenylalanine (DOPA) molecules impart unusual adhesive strength to the clay composite and the hardening mechanism found in the natural "cement" plays an equally important role in the strengthening of the "nanostructured nacre".
The safety, function, and longevity of implantable neuroprosthetic and cardiostimulating electrodes depend heavily on the electrical properties of the electrode-tissue interface, which in many cases requires substantial improvement. While different variations of carbon nanotube materials have been shown to be suitable for neural excitation, it is critical to evaluate them versus other materials used for bioelectrical interfacing, which have not been done in any study performed so far despite strong interest to this area. In this study, we carried out this evaluation and found that composite multiwalled carbon nanotube-polyelectrolyte (MWNT-PE) multilayer electrodes substantially outperform in one way or the other state-of-the-art neural interface materials available today, namely activated electrochemically deposited iridium oxide (IrOx) and poly(3,4-ethylenedioxythiophene) (PEDOT). Our findings provide the concrete experimental proof to the much discussed possibility that carbon nanotube composites can serve as excellent new material for neural interfacing with a strong possibility to lead to a new generation of implantable electrodes.
The files go with the manuscript of Zhang et al.Achiral and chiral ligands synergistically harness the chiral self-assembly of inorganics. The files include the Raw data for Figs. 1-5 and Supplementary Information Figs. 2-12, 15, 18-19, 22, 24, 26-27, and 29-34.
Self-assembled complex nanoparticles are promising charge carriers for energy storage and conversion systems. High specific capacities have been realized in these materials, which has been attributed to various factors such as their high surface area with complex topology and quantum effects caused by nanoscale dimensions. They have nevertheless found limited use in applications beyond metal-ion batteries. We have investigated the deployment of micron-sized FeSe 2 particles with nanostructured spikes as charge carriers in redox flow batteries. These so-called “hedgehog” particles (HPs) were found to be dispersible in aqueous media, and displayed shear-thinning rheology in suspension, which facilitated operation in a flow cell. Suspensions of HPs exhibited redox activity around -0.88 V vs Ag/AgCl at pH 14, leading to a 1.0 V open circuit voltage when deployed as the negolyte with ferro/ferricyanide as the posolyte. High current efficiencies (> 97 %) during cycling, and a volumetric capacity of up to 1.4 mol e /L (~ 36.4 Ah/L) were attained. Mechanisms for capacity fade and potential strategies for its mitigation will be discussed.
CdS nanoparticles (NP), 22 Å, have been synthesized from cadmium 2-ethylhexanoate in DMSO as a uniformly sized dispersion. After ripening, CdS exhibits a sharp excitonic emission peak at 402 nm, while in freshly prepared dispersions a broad trapped emission at 510 nm dominates. By using one- and two-dimensional NMR spectroscopy, the conformation of the stabilizer adsorbed to the NP has been determined. The long hexyl chain of 2-ethylhexanoate ions spreads over the surface of NP, whereas the short ethyl end is primarily surrounded by DMSO. Surface modification of CdS with nucleophiles such as 4,4-bipyridine, thiophene, trimethylamine, and thiomolybdate anion results in a partial replacement of the stabilizer and reorientation of the hexyl chain away from the surface. The difference in the degree of replacement and/or conformational changes of 2-ethylhexanoate ion depends on the electron donor activity of the modifier.
Abstract We describe the peculiar conditions under which optically driven gold nanoparticles (NPs) can significantly increase temperature or even melt a surrounding matrix. The heating and melting processes occur under light illumination and involve the plasmon resonance. For the matrix, we consider water, ice, and polymer. Melting and heating the matrix becomes possible if a nanoparticle size is large enough. Significant enhancement of the heating effect can appear in ensembles of NPs due to an increase of a volume of metal and electric-field amplification.
Chiral inorganic nanostructures discovered over the last two decades include individual nanoparticles (NPs), their assemblies in dispersions and surfaces, as well as 2D/3D lithographic patterns. For many of them exceptionally strong polarization rotation was observed. In this talk, I will address, the (1) origin of enhanced polarization rotation; (2) methods of enantioselective assembly of nanostructures; and (3) their fundamental relevance to life homochirality on Earth, Special effort will be placed on the translation of enhanced chiroptical properties of plasmonic and excitonic NPs to applications. It will be exemplified by the bioanalytical applications for detection of DNA oligomers using CD spectroscopy that enables 1-3 order of magnitude improvement of detection of protein, DNA oligomers, and small chiral molecules. Other technological applications in chiral catalysis and polarization-based optical devices. Should time permit, recent data on the preparation and properties of chiral graphene quantum dots and chiral ceramic nanoparticles relevant to the chiroplasmonc and chiroexcitonic technologies will be presented. Figure 1
The ability of semiconductor nanoparticles (NPs) to self-assemble has been known for several decades. However, the limits of the geometrical and functional complexity for the self-assembled nanostructures made from simple often polydispersed NPs are still continuing to amaze researchers. We report here the self-assembly of primary ∼2-4 nm FeSe2 NPs with puck-like shapes into either (a) monocrystalline nanosheets ∼5.5 nm thick and ∼1000 nm in lateral dimensions or (b) mesoscale hedgehogs ∼550 nm in diameter with spikes of ∼250 nm in length, and ∼10-15 nm in diameter, the path of the assembly is determined by the concentration of dodecanethiol (DT) in the reaction media. The nanosheets represent the constitutive part of hedgehogs. They are rolled into scrolls and assembled around a single core with distinct radial orientation forming nanoscale "needles" approximately doubling its fractal dimension of these objects. The core is assembled from primary NPs and nanoribbons. The size distribution of the mesoscale hedgehogs can be as low as 3.8%, indicating a self-limited mechanism of the assembly. Molecular dynamics simulation indicates that the primary FeSe2 particles have mobile edge atoms and asymmetric basal surfaces. The top-bottom asymmetry of the puck-like NPs originates from the Fe-rich/Se-rich stripes on the (011) surface of the orthorhombic FeSe2 crystal lattice, displaying 2.7 nm periodicity that is comparable to the lateral size of the primary NPs. As the concentration of DT increases, the NPs bind to additional metal sites, which increases the chemical and topographic asymmetry and switches the assembly pathways from nanosheets to hedgehogs. These results demonstrate that the self-assembly of NPs with non-biological surface ligands and without any biological templates results in morphogenesis of inorganic superstructures with complexity comparable to that of biological assemblies, for instance mimivirus. The semiconductor nature of FeSe2 hedgehogs enables their utilizations in catalysis, drug delivery, optics, and energy storage.
A series of fulleropyrrolidine- and fulleropyrrolidinium-based donor−acceptor ensembles were tested in light of intrinsic reorganization energies for photoinduced electron transfer events. Among these complexes, the fulleropyrrolidinium ions are particularly well-suited for the role of an acceptor moiety. In fact, once reduced, fulleropyrrolidinium ions exhibit a zwitterionic character, due to the contemporary presence of a positive pyrrolidinium ion together with the fullerene radical ion. We demonstrate that this zwitterionic character of the acceptor plays a central role in improving acceleration of charge separation and deceleration of charge recombination. While the charge separation occurs with dynamics close to the top region of the Marcus parabola, the charge recombination rates are pushed deeply into the inverted region of the parabolic dependence. Overall, we determined reorganization energies (λ) for the fulleropyrrolidinium-based ensemble that are appreciably smaller than those seen for the fulleropyrrolidine-based analogue, while keeping the electronic coupling element constant (!). Remarkable is the oxygen effect on the zwitterionic fulleropyrrolidinium acceptornot seen on the fulleropyrrolidine acceptorin the charge-separated radical pair.
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