Mesoporous multimetallic nanospheres with exposed highly entropic alloy sites.

Multimetallic alloys (MMAs) with various compositions enrich the materials library with increasing diversity and have received much attention in catalysis applications. However, precisely shaping MMAs in mesoporous nanostructures and mapping the distributions of multiple elements remain big challenge due to the different reduction kinetics of various metal precursors and the complexity of crystal growth. Here we design a one-pot wet-chemical reduction approach to synthesize core-shell motif PtPdRhRuCu mesoporous nanospheres (PtPdRhRuCu MMNs) using a diblock copolymer as the soft template. The PtPdRhRuCu MMNs feature adjustable compositions and exposed porous structures rich in highly entropic alloy sites. The formation processes of the mesoporous structures and the reduction and growth kinetics of different metal precursors of PtPdRhRuCu MMNs are revealed. The PtPdRhRuCu MMNs exhibit robust electrocatalytic hydrogen evolution reaction (HER) activities and low overpotentials of 10, 13, and 28 mV at a current density of 10 mA cm-2 in alkaline (1.0 M KOH), acidic (0.5 M H2SO4), and neutral (1.0 M phosphate buffer solution (PBS)) electrolytes, respectively. The accelerated kinetics of the HER in PtPdRhRuCu MMNs are derived from multiple compositions with synergistic interactions among various metal sites and mesoporous structures with excellent mass/electron transportation characteristics.

Surface Filtration in Mesoporous Au Films Decorated by Ag Nanoparticles for Solving SERS Sensing Small Molecules in Living Cells.

For surface-enhanced Raman spectroscopy (SERS) sensing of small molecules in the presence of living cells, biofouling and blocking of plasmonic centers are key challenges. Here, we have developed a mesoporous Au (AuM) film coated with a Ag nanoparticles (NPs) as a plasmonic sensor (AuM@Ag) to analyze aromatic thiols, which is an example of a small molecule, in the presence of a living cell strain (e.g., MDA-MB-231) as a model living system. The resulting AuM@Ag provides 0.1 nM sensitivity and high reproducibility for thiols sensing. Simultaneously, the AuM@Ag film filters large biomolecules, preventing Raman signals from overlapping produced by large biomolecules. After analysis, the AuM@Ag film undergoes recycling by the full dissolution of the Ag-thiol layer and removal of thiols from AuM. Furthermore, fresh AgNPs are formed for further SERS analysis, which circumvents the Ag oxidation issue. The ease of the AgNPs deposition allows up to 12 cycles of on-demand recycling and sensing even after utilization as a sensor in multicomponent media without enhancement and sensitivity loss. The reported mesoporous film with surface filtering ability and prominent recycling procedure promises to offer a new strategy for the detection of various small molecules in the presence of living cells.

Adsorchromism: Molecular Nanoarchitectonics at 2D Nanosheets-Old Chemistry for Advanced Chromism.

Chromism induced by changes in the electronic states of dye molecules due to surface adsorption is termed "adsorchromism" in this article. These changes of molecular electronic states are induced by protonation, aggregation, intramolecular structural changes, and other processes, depending on the surface environment. Intramolecular structural changes, such as co-planarization and decreased molecular motion are the most characteristic and interesting behavior of dye molecules at the surfaces, resulting in spectral shift and/or emission enhancement. In this review, adsorchromism at the surfaces of layered materials are summarized since their flexibility of interlayer distance, surface flatness, and transparency is suitable for a detailed observation. By understanding the relationship between adsorchromism and the electronic states of molecules on the surfaces, it will be possible to induce some desired functions which can be realized simply by adsorption, instead of complicated organic syntheses. Thus, adsorchromism has potential applications such as effective solar energy harvesting systems, or biological/chemical sensors to visualize environmental changes.

A universal approach for the synthesis of mesoporous gold, palladium and platinum films for applications in electrocatalysis.

High-surface-area mesoporous materials expose abundant functional sites for improved performance in applications such as gas storage/separation, catalysis, and sensing. Recently, soft templates composed of amphiphilic surfactants and block copolymers have been used to introduce mesoporosity in various materials, including metals, metal oxides and carbonaceous compounds. In particular, mesoporous metals are attractive in electrocatalysis because their porous networks expose numerous unsaturated atoms on high-index facets that are highly active in catalysis. In this protocol, we describe how to create mesoporous metal films composed of gold, palladium, or platinum using block copolymer micelle templates. The amphiphilic block copolymer micelles are the sacrificial templates and generate uniform structures with tunable pore sizes in electrodeposited metal films. The procedure describes the electrodeposition in detail, including parameters such as micelle diameters, deposition potentials, and deposition times to ensure reproducibility. The micelle diameters can be controlled by swelling the micelles with different solvent mixtures or by using block copolymer micelles with different molecular weights. The deposition potentials and deposition times allow further control of the mesoporous structure and its thickness, respectively. Procedures for example applications are included: glucose oxidation, ethanol oxidation and methanol oxidation reactions. The synthetic methods for preparation of mesoporous metal films will take ~4 h; the subsequent electrochemical tests will take ~5 h for glucose sensing and ~3 h for alcohol oxidation reaction.

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.

Nafion®-coated mesoporous Pd film toward remarkably enhanced detection of lactic acid.

Mesoporous metal films can detect biomarkers with high sensitivity. Further coating the mesoporous metal with polymers enhances sensing selectivity by favoring specific biomarkers against other interferents. In the present study, we report the fabrication of a Nafion®-coated mesoporous Pd film to filtrate interferents present in sweat during non-invasive biosensing. By using a Nafion®-coated mesoporous Pd film, lactic acid, a metabolite present in sweat, can be successfully detected with high sensitivity.