Trimetallic PtPdRu Dendritic Nanocages with Three-Dimensional Electrocatalytic Surfaces

Control over composition and structure on the nanoscale level is critical for designing highly active and durable catalyst to implement in electrochemical energy conversion. Herein, we report a facile strategy for an efficient synthesis of trimetallic PtPdRu dendritic nanocages with hollow cavity and porous dendritic shell by eroding the interior of the starting PtPdRu nanodendrites in acidic solution. The newly discovered trimetallic dendritic nanocages with an open-framework surface afford 3D molecular accessibility and can be used as highly active and durable catalysts for oxygen reduction reaction due to the synergetic effect derived from their unique porous structure and multimetallic composition

Mesoporous Iron Phosphonate Electrodes with Crystalline Frameworks for Lithium-Ion Batteries

A new family of mesoporous iron phosphonate (FeP) materials has been prepared through cooperative assembly of cetyltrimethylammonium bromide (CTAB), iron nitrate, and nitrilotris­(methylene)­triphosphonic acid (NMPA). CTAB is used as a structure directing agent, while the other two chemicals are used as precursors for the formation of pore walls. An extraction procedure is employed to remove the template without damaging the as-prepared ordered mesostructure. The obtained mesoporous FeP materials are well characterized by low angle X-ray diffraction (XRD), N₂ adsorption isotherms, and transmission electron microscopy. The mesostructural ordering of the obtained materials strongly depends on the synthetic conditions. The morphology and the crystallinity of the pore walls are investigated by scanning electron microscopy and wide-angle XRD measurements, respectively. It is revealed that the FeP framework is crystallized in the tetragonal crystal phase (<i>I</i>4₁/<i>amd</i>), according to the Rietveld refinement of the XRD patterns through the MAUD program. The unit cell parameters of the obtained crystals are <i>a</i> = <i>b</i> = 5.1963 (3) Å, <i>c</i> = 12.9808 (1) Å (α = β = γ = 90°). Also, the homogeneous distribution of both Fe species and organo-phosphonic acid groups in the mesoporous architectures is confirmed by Fourier transform infrared spectroscopy and elemental mapping. Mesoporous FeP materials with high surface area have great applicability as high performance electrode materials for lithium-ion (Li-ion) batteries, due to several advantages including a large contact area with the electrolyte, high structural stability, and short transport paths for Li⁺ ions. Mesoporous FeP electrodes exhibit high reversible specific capacity with very good cycling stability and excellent retention of capacity

Observation of Quantum Confinement in Monodisperse Methylammonium Lead Halide Perovskite Nanocrystals Embedded in Mesoporous Silica

Hybrid organic–inorganic metal halide perovskites have fascinating electronic properties and have already been implemented in various devices. Although the behavior of bulk metal halide perovskites has been widely studied, the properties of perovskite nanocrystals are less well-understood because synthesizing them is still very challenging, in part because of stability. Here we demonstrate a simple and versatile method to grow monodisperse CH₃NH₃Pb­Br_<i>x</i>I_<i>x</i>‑3 perovskite nanocrystals inside mesoporous silica templates. The size of the nanocrystal is governed by the pore size of the templates (3.3, 3.7, 4.2, 6.2, and 7.1 nm). In-depth structural analysis shows that the nanocrystals maintain the perovskite crystal structure, but it is slightly distorted. Quantum confinement was observed by tuning the size of the particles via the template. This approach provides an additional route to tune the optical bandgap of the nanocrystal. The level of quantum confinement was modeled taking into account the dimensions of the rod-shaped nanocrystals and their close packing inside the channels of the template. Photoluminescence measurements on CH₃­NH₃PbBr clearly show a shift from green to blue as the pore size is decreased. Synthesizing perovskite nanostructures in templates improves their stability and enables tunable electronic properties via quantum confinement. These structures may be useful as reference materials for comparison with other perovskites, or as functional materials in all solid-state light-emitting diodes

Trap-Assisted Transport and Non-Uniform Charge Distribution in Sulfur-Rich PbS Colloidal Quantum Dot-based Solar Cells with Selective Contacts

This study reports evidence of dispersive transport in planar PbS colloidal quantum dot heterojunction-based devices as well as the effect of incorporating a MoO₃ hole selective layer on the charge extraction behavior. Steady state and transient characterization techniques are employed to determine the complex recombination processes involved in such devices. The addition of a selective contact drastically improves the device efficiency up to 3.15% (especially due to increased photocurrent and decreased series resistance) and extends the overall charge lifetime by suppressing the main first-order recombination pathway observed in device without MoO₃. The lifetime and mobility calculated for our sulfur-rich PbS-based devices are similar to previously reported values in lead-rich quantum dots-based solar cells. Nevertheless, strong Shockley–Read–Hall mechanisms appear to keep restricting charge transport, as the equilibrium voltage takes more than 1 ms to be established

Multimodal Superparamagnetic Nanoparticles with Unusually Enhanced Specific Absorption Rate for Synergetic Cancer Therapeutics and Magnetic Resonance Imaging

Superparamagnetic nanoparticles (SPMNPs) used for magnetic resonance imaging (MRI) and magnetic fluid hyperthermia (MFH) cancer therapy frequently face trade off between a high magnetization saturation and their good colloidal stability, high specific absorption rate (SAR), and most importantly biological compatibility. This necessitates the development of new nanomaterials, as MFH and MRI are considered to be one of the most promising combined noninvasive treatments. In the present study, we investigated polyethylene glycol (PEG) functionalized La_1–<i>x</i>Sr_<i>x</i>MnO₃ (LSMO) SPMNPs for efficient cancer hyperthermia therapy and MRI application. The superparamagnetic nanomaterial revealed excellent colloidal stability and biocompatibility. A high SAR of 390 W/g was observed due to higher colloidal stability leading to an increased Brownian and Neel’s spin relaxation. Cell viability of PEG capped nanoparticles is up to 80% on different cell lines tested rigorously using different methods. PEG coating provided excellent hemocompatibility to human red blood cells as PEG functionalized SPMNPs reduced hemolysis efficiently compared to its uncoated counterpart. Magnetic fluid hyperthermia of SPMNPs resulted in cancer cell death up to 80%. Additionally, improved MRI characteristics were also observed for the PEG capped La_1–<i>x</i>Sr_<i>x</i>MnO₃ formulation in aqueous medium compared to the bare LSMO. Taken together, PEG capped SPMNPs can be useful for diagnosis, efficient magnetic fluid hyperthermia, and multimodal cancer treatment as the amphiphilicity of PEG can easily be utilized to encapsulate hydrophobic drugs

Electrochemical Synthesis of Mesoporous Au–Cu Alloy Films with Vertically Oriented Mesochannels Using Block Copolymer Micelles

We synthesized Au–Cu bimetallic alloy films with a controlled mesoporous architecture through electrochemical deposition using an electrolyte solution containing spherical polymeric micelles. The composition of the alloy films can be easily controlled by tuning the ratio between the Au and Cu species present in the electrolyte solution. At low Cu content, cage-type mesopores are formed, reflecting the parent micellar template. Surprisingly, upon increasing the Cu content, the cage-type mesopores fuse to form vertically aligned one-dimensional mesochannels. The vertical alignment of these mesopores is favorable for enhanced mass and ion transfer within the channels due to low diffusion resistance. The atomic distribution of Au and Cu is uniform over the entire film and free of any phase segregation. The as-synthesized mesoporous Au–Cu films exhibit excellent performance as a nonenzymatic glucose sensor with high sensitivity and selectivity, and the current response is linear over a wide range of concentrations. This work identifies the properties responsible for the promising performance of such mesoporous alloy films for the clinical diagnosis of diabetes. This micelle-assisted electrodeposition approach has a high degree of flexibility and can be simply extended from monometallic compounds to a multimetallic system, enabling the fabrication of various mesoporous alloy films suitable for different applications