Plasmon Absorption of Au-in-CoAl₂O₄ Linear Nanopeapod Chains

We investigated the plasmon absorption of Au-in-CoAl₂O₄ linear nanopeapod chains experimentally and theoretically. The Au-in-CoAl₂O₄ nanopeapods with uniform Au nanospheres (25–40 nm in radius) were synthesized by pulsed electrodeposition, followed by heat treatment, and the plasmon absorption peaks of the Au nanospheres (AuNS) embedded in CoAl₂O₄ red-shifted due to the size effect of the AuNS and the effect of the cladding dielectric medium. As a result of localized surface plasmon resonance, the plasmon absorption of the peapods can be modulated by tuning the size of the AuNS in CoAl₂O₄, and the experimental data are in good agreement with the calculated results based on Mie theory. In addition, we carried out the first-principles calculation based on the density functional theory with the LDA+<i>U</i> scheme to study the electronic structure and dielectric properties of CoAl₂O₄, and the theoretical results are consistent with the experimental data, which proves that LDA+<i>U</i> is a good approximation for CoAl₂O₄ or other spinels containing transition elements

Bulk Transport and Interfacial Transfer Dynamics of Photogenerated Carriers in CdSe Quantum Dot Solid Electrodes

Practical solar-to-fuel conversion applications of quantum-confined semiconductor crystals require their integration into electrodes. We show that photogenerated electrons in quantum dot solid electrodes can be transported to the aqueous interface to reduce methyl viologen with 100% quantum efficiency and an effective time constant of 12 ± 2 ps. The charge separated state had a half-life of 200 ± 10 ns, limited by hole transport within the solid

A Versatile AuNP Synthetic Platform for Decoupled Control of Size and Surface Composition

While a plethora of protocols exist for the synthesis of sub-10 nm gold nanoparticles (AuNPs), the independent control over size and surface composition remains restricted. This poses a particular challenge for systematic studies of AuNP structure-function relationships and optimization of crucial design parameters. To this end, we report on a modular 2-step approach based on the synthesis of AuNPs in oleylamine (OAm) followed by the subsequent functionalization with target thiol ligands. The synthesis of OAm-capped AuNPs enables fine tuning of the core size in the range of 2–7nm by varying the reaction temperature. The subsequent thiol-for-OAm ligand-exchange allows a reliable generation of thiol-capped AuNPs with target surface functionality. The compatibility of this approach with a vast library of thiol ligands provides detailed control of mixed ligand composition and solubility in a wide range of solvents ranging from water to hexane. This decoupled control over the AuNP core and ligand shell provides a powerful toolbox for the methodical screening of optimal design parameters and facile preparation of AuNPs with target properties

Tunable Assembly of Colloidal Crystal Alloys Using Magnetic Nanoparticle Fluids

We demonstrate a magnetic technique for assembling bidisperse and tridisperse colloidal particle fluids into a variety of complex structures with dimensionality ranging from 0-D (rings) to 1-D (chains) to 2-D (tiles). Compared with prior work on bidisperse particles that are commensurate in size, here we explore the assembly of different sized particles, and we show that due to packing constraints, new particle structures can be realized experimentally. Extending these experiments to a tridisperse system, we demonstrate that at low concentrations the smallest particle does not change the underlying crystal structures of the bidisperse system; however, it can assist in the formation of crystallite structures that were not stable in a bidisperse system. Additionally, we discovered that the smallest particle mimics the role of the ferrofluid, by shifting the locations in phase space where the bidisperse crystal structures can be experimentally obtained. Finally, we demonstrate that 3-particle crystal structures can be tuned by varying the strength of the external field, which is not possible in a 2-particle system

Co₃O₄/Reduced Graphene Oxide Nanocomposites as Effective Phosphotriesterase Mimetics for Degradation and Detection of Paraoxon

In this work, Co₃O₄ nanoparticles supported on reduced graphene oxide (Co₃O₄/rGO) were prepared through a simple hydrothermal method. The phosphotriesterase (PTE) mimetic activity of the Co₃O₄/rGO nanocomposites was investigated for the first time, and the catalytic performance was evaluated by hydrolyzing paraoxon. The synergic effects of Co₃O₄ and rGO greatly improved the binding capacity of the nanocomposites with paraoxon and water molecules, and facilitated electron transfer in the hydrolysis process, resulting in an ∼5-fold enhancement in the hydrolysis efficiency of Co₃O₄/rGO nanocomposites, compared with that of rGO. Co₃O₄/rGO nanocomposites also exhibited excellent reusability and stability than other PTE mimetics. Based on the PTE activity of Co₃O₄/rGO nanocomposites, a simple and sensitive colorimetric sensor of paraoxon was developed and successfully used to determine the paraoxon in cabbage and river water, demonstrating its potential applicability for food and environmental analyses

Shearing Janus Nanoparticles Confined in Two-Dimensional Space: Reshaped Cluster Configurations and Defined Assembling Kinetics

The self-assembly of anisotropic nanoparticles (ANPs) possesses a wide array of potential applications in various fields, ranging from nanotechnology to material science. Despite intense research of the thermodynamic self-assembly of ANPs, elucidating their nonequilibrium behaviors under confinement still remains an urgent issue. Here, by performing simulation and theoretical justification, we present for the first time a study of the shear-induced behaviors of Janus spheres (the most elementary ANPs) confined in two-dimensional space. Our results demonstrate that the collective effects of shear and bonding structures can give rise to reshaped cluster configurations, featured by the chiral transition of clusters. Scaling analysis and numerical modeling are performed to quantitatively capture the assembling kinetics of dispersed Janus spheres, thereby suggesting an exotic way to bridge the gap between anisotropic and isotropic particles. The findings highlight confinement and shearing engineering as a versatile strategy to tailor the superstructures formed by ANPs toward unique properties

Strong Electronic Coupling and Ultrafast Electron Transfer between PbS Quantum Dots and TiO₂ Nanocrystalline Films

Hot carrier and multiple exciton extractions from lead salt quantum dots (QDs) to TiO₂ single crystals have been reported. Implementing these ideas on practical solar cells likely requires the use of nanocrystalline TiO₂ thin films to enhance the light harvesting efficiency. Here, we report 6.4 ± 0.4 fs electron transfer time from PbS QDs to TiO₂ nanocrystalline thin films, suggesting the possibility of extracting hot carriers and multiple excitons in solar cells based on these materials

Plasmon-Induced Hot Electron Transfer from the Au Tip to CdS Rod in CdS-Au Nanoheterostructures

The plasmon-exciton interaction mechanisms in CdS–Au colloidal quantum-confined plexcitonic nanorod heterostructures have been studied by transient absorption spectroscopy. Optical excitation of plasmons in the Au tip leads to hot electron injection into the CdS rod with a quantum yield of ∼2.75%. This finding suggests the possibility of further optimization of plasmon-induced hot electron injection efficiency through controlling the size and shape of the plasmonic and excitonic domains for potential light harvesting applications

Impact of Rett Syndrome Mutations on MeCP2 MBD Stability

Rett syndrome causing missense mutations in the methyl-CpG-binding domain (MBD) of methyl CpG-binding protein 2 (MeCP2) were investigated both <i>in silico</i> and <i>in vitro</i> to reveal their effect on protein stability. It is demonstrated that the vast majority of frequently occurring mutations in the human population indeed alter the MBD folding free energy by a fraction of a kcal/mol up to more than 1 kcal/mol. While the absolute magnitude of the change of the free energy is small, the effect on the MBD functionality may be substantial since the folding free energy of MBD is about 2 kcal/mol only. Thus, it is emphasized that the effect of mutations on protein integrity should be evaluated with respect to the wild-type folding free energy but not with the absolute value of the folding free energy change. Furthermore, it was observed that the magnitude of the effect is correlated neither with the burial of the mutation sites nor with the basic amino acid physicochemical property change. Mutations that strongly perturb the immediate structural features were found to have little effect on folding free energy, while very conservative mutations resulted in large changes of the MBD stability. This observation was attributed to the protein’s ability to structurally relax and reorganize to reduce the effect of mutation. Comparison between <i>in silico</i> and <i>in vitro</i> results indicated that some Web servers perform relatively well, while the free energy perturbation approach frequently overpredicts the magnitude of the free energy change especially when a charged amino acid is involved