In Situ Synthesis of Luminescent CdSe Quantum Dots Embedded in Cd(II) Metallohydrogels: A Hybrid Material for Selective and Naked-Eye Sensing of Hg Ions.

In situ synthesis and stabilization of quantum dots (QDs) with unique features toward environmental remediation is an area of current interest. Our present study has addressed the spontaneous formation of a metallohydrogel of Cd(II) and a mixed ligand system (sodium azide and 4,5-dicyanoimidazole). The gelation was highly selective to all three components and was only achieved when the components were present together.

Synthesis and Prospects of Holey Two-dimensional Platinum-group Metals in Electrocatalysis.

Advanced electrocatalysts can enable the widespread implementation of clean energy technologies. This paper reviews an emerging class of electrocatalytic materials comprising holey two-dimensional free-standing Pt-group metal (h-2D-PGM) nanosheets, which are categorically challenging to synthesize but inherently rich in all the qualities necessary to counter the kinetic and thermodynamic challenges of an electrochemical conversion process with high catalytic efficiency and stability. Although the 2D anisotropic growth of typical nonlayered metal crystals has succeeded and partly improved their atom-utilization efficiency, regularly distributed in-planar porosity can further optimize three critical factors that govern efficient electrocatalysis process: mass diffusion, electron transfer, and surface reactivity.

Harmonious Heterointerfaces Formed on 2D-Pt Nanodendrites by Facet-Respective Stepwise Metal Deposition for Enhanced Hydrogen Evolution Reaction.

The performance of nanocrystal (NC) catalysts could be maximized by introducing rationally designed heterointerfaces formed by the facet- and spatio-specific modification with other materials of desired size and thickness. However, such heterointerfaces are limited in scope and synthetically challenging. Herein, we applied a wet chemistry method to tunably deposit Pd and Ni on the available surfaces of porous 2D-Pt nanodendrites (NDs).

Sculpting In-plane Fractal Porous Patterns in Two-Dimensional MOF Nanocrystals for Photoelectrocatalytic CO Reduction.

Herein, by choosing few-nm-thin two-dimensional (2D) nanocrystals of MOF-5 containing in-planner square lattices as a modular platform, a crystal lattice-guided wet-chemical etching has been rationally accomplished. As a result, two attractive pore patterns carrying Euclidean curvatures; precisely, plus(+)-shaped and fractal-patterned pores via ⟨100⟩ and ⟨110⟩ directional etching, respectively, are regulated in contrast to habitually formed spherical-shaped random etches on MOF surface. In agreement with the theoretical calculations, a diffusion-limited etching process has been optimized to devise high-yield of size-tunable fractal-pores on the MOF surface that tenders for a compatibly high payload of catalytic Re -complexes using the existing large edge area once modified into a free amine-group-exposed inner pore surface.

Nanocrystal Conversion Chemistry within Slit-like 2D Nanogap for High-Rate Cyclic Stability of Lithium-Ion Battery Anodes.

Nanoscale optimization of late transition-metal oxides for fixing the reversible lithiation/delithiation mechanism with an in-depth mechanistic understanding of nanocrystal (NC) conversion chemistry is important for furthering next-generation Li-ion battery (LIB) technologies. Herein, 1 nm-thin NiCoO (1 nm-NCO) nanosheets synthesized through isomorphic transformation of NiCo layered double hydroxides within a two-dimensional (2D)-SiO envelope are chosen. The interconversion of metal/metal-oxide NCs under redox-switching thermal treatment, while retaining reversibility, inspired the accomplishment of identical consequences under the harsh operational conditions of LIB redox cycles by application of the thin-NCO-defined 2D nanospace.

Solid-State Reaction Synthesis of Nanoscale Materials: Strategies and Applications.

Nanomaterials (NMs) with unique structures and compositions can give rise to exotic physicochemical properties and applications. Despite the advancement in solution-based methods, scalable access to a wide range of crystal phases and intricate compositions is still challenging. Solid-state reaction (SSR) syntheses have high potential owing to their flexibility toward multielemental phases under feasibly high temperatures and solvent-free conditions as well as their scalability and simplicity.

Silica-Enveloped 2D-Sheet-to-Nanocrystals Conversion for Resilient Catalytic Dry Reforming of Methane.

Here, lamellar confinement strategy is introduced for "sheet-to-nanocrystals (NCs)" conversion within a 2D-SiO envelope, which constructs a catalytic nanocartridge holding a platoon of isolated and in-plane-aligned ultrasmall Ni-NCs, performing as a robust and coking-resistant catalytic system for dry reforming of methane. Overcoming the problem of unavoidable bulk crystal growth from multiple sheets-stack or sheet-on-open-support, silica bilayer-encasing tightly clamps the atomic-thin Ni(OH) -nanosheet during thermal conversion and further hinders the migratory fusion of the resultant Ni-NCs. Upon heating-cooling cycle, the flapping silica envelope clutches the Ni-NCs like "eggs in a carton," subsequently, ensuring their thermal stability.

Holey Pt Nanosheets on NiFe-Hydroxide Laminates: Synergistically Enhanced Electrocatalytic 2D Interface toward Hydrogen Evolution Reaction.

Next-generation electrocatalysts with smart integrated designs, maximizing the chemical cascade synergy for sustainable hydrogen production, are needed to address the urgent environmental threats, but scalable synthesis of precisely architectured nanohybrids rendering a few-nanometer interfacial controllability to augment the catalytic reactivity and operational stability is a major bottleneck. Herein, by inventing a surface-confined lateral growth of nanometer-thin and nanoporous two-dimensional (2D)-Pt on NiFe-LDH nanosheets, a highly reactive 2D-2D interfacially integrated nanoplatform is synthesized for an alkaline hydrogen evolution reaction (HER) which not only extracts high Pt-atomic utilization efficiency but also synergistically accelerates the water dissociation and hydrogen generation cascade on the colocalized Pt/M(OH) active sites, endowing a 6.1-fold higher Pt mass activity than 20% Pt/C and also empowers a record-high HER operational stability for 50 h, due to the chemically enforced lamellar architecture.

Nanosilica-Confined Synthesis of Orthogonally Active Catalytic Metal Nanocrystals in the Compartmentalized Carbon Framework.

Multifunctionalized porous catalytic nanoarchitectures are highly desirable for a variety of chemical transformations; however, selective installation of different catalysts with spatial and functional precision working synergistically and predictably, is highly challenging. Here, a synthetic strategy is developed toward the customizable combination of orthogonally reactive metal nanocrystals within interconnected carbon-cavities as a compartmentalized framework by employing aminated-silica-directed thermal solid-state nanoconfined synthesis of metal nanocrystals and endotemplating concomitant carbonization-mediated interlocking, as key processes. The main advantage of the strategy is the facility to choose any combination of metals, which can be further employed according to the desired application.

An Intriguing Pea-Like Nanostructure of Cobalt Phosphide on Molybdenum Carbide Incorporated Nitrogen-Doped Carbon Nanosheets for Efficient Electrochemical Water Splitting.

The development of noble-metal-free, efficient, electrochemical, water-splitting catalyst systems has attracted considerable attention in recent times. In this study, a metal-organic framework based synthetic route to couple two non-noble-metal-based catalysts, CoP and Mo C, supported on nitrogen-doped carbon has been developed. The strategy enables the formation of a nanohybrid with an attractive pea-like morphology, in which spherical CoP particles (≈10 nm) are embedded on two-dimensional nitrogen-doped carbon enriched with ultrafine Mo C nanoparticles.

Self-Supported Nickel Iron Layered Double Hydroxide-Nickel Selenide Electrocatalyst for Superior Water Splitting Activity.

The design of efficient, low-cost, and stable electrocatalyst systems toward energy conversion is highly demanding for their practical use. Large scale electrolytic water splitting is considered as a promising strategy for clean and sustainable energy production. Herein, we report a self-supported NiFe layered double hydroxide (LDH)-NiSe electrocatalyst by stepwise surface-redox-etching of Ni foam (NF) through a hydrothermal process.

Facile Synthesis of Unique Hexagonal Nanoplates of Zn/Co Hydroxy Sulfate for Efficient Electrocatalytic Oxygen Evolution Reaction.

Cost-effective, highly active water oxidation catalysts are increasingly being demanded in the field of energy conversion and storage. Herein, a simple modified hydrothermally (MHT) synthesized zinc and cobalt based hydroxyl double salt, that is, ZnCoSO(OH)·0.5HO (ZCS), has been exfoliated for the first time as an efficient electrocatalyst for oxygen evolution reaction (OER) in alkaline medium.

Suitable Morphology Makes CoSn(OH)6 Nanostructure a Superior Electrochemical Pseudocapacitor.

Morphology of a material with different facet, edge, kink, etc., generally influences the rate of a catalytic reaction.1,2 Herein, we account for the importance of altered morphology of a nanomaterial for a supercapacitor device and employed CoSn(OH)6 as an electrode material.

A pH dependent Raman and surface enhanced Raman spectroscopic studies of citrazinic acid aided by theoretical calculations.

A pH dependent normal Raman scattering (NRS) and surface enhanced Raman scattering (SERS) spectral patterns of citrazinic acid (CZA), a biologically important molecule, have been investigated. The acid, with different pKa values (~4 and ~11) for the two different functional groups (-COOH and -OH groups), shows interesting range of color changes (yellow at pH~14 and brown at pH~2) with the variation in solution pH. Thus, depending upon the pH of the medium, CZA molecule can exist in various protonated and/or deprotonated forms.

Metal Bromide Controlled Interfacial Aromatization Reaction for Shape-Selective Synthesis of Palladium Nanostructures with Efficient Catalytic Performances.

Herein, the effect of diverse metal bromides for the shape evolution of palladium nanostructures (Pd NS) has been demonstrated. Aromaticity-driven reduction of bromopalladate(II) is optimized to reproducibly obtain different Pd NS at the water/organic layer interface. In this soft interfacial strategy, a redox potential driven reaction has been performed, forming the thermodynamically more stable (>10(4) -fold) PdBr4 (2-) precursor from PdCl4 (2-) by adding extra metal bromides.

A new stable Pd-Mn3O4 nanocomposite as an efficient electrocatalyst for the hydrogen evolution reaction.

Herein, a Mn3O4 nanooctahedron (NO) supported Pd nanocomposite has been fabricated from a chosen thermodynamically allowed redox transformation reaction. The synthesized Pd-Mn3O4 (PMO) nanocomposite exhibits outstanding electrocatalytic activity for the hydrogen evolution reaction (HER) in acidic medium with a low overpotential (14 mV), small Tafel slope (42 mV dec(-1)) and high exchange current density (7.74 mA cm(-2)).

Fabrication of Nitrogen-Doped Mesoporous-Carbon-Coated Palladium Nanoparticles: An Intriguing Electrocatalyst for Methanol and Formic Acid Oxidation.

Inspired by the attractive catalytic properties of palladium and the inert nature of carbon supports in catalysis, a concise and simple methodology for in situ nitrogen-doped mesoporous-carbon-supported palladium nanoparticles (Pd/N-C) has been developed by carbonizing a palladium dimethylglyoximate complex. The as-synthesized Pd/N-C has been exfoliated as a fuel cell catalyst by studying the electro-oxidation of methanol and formic acid. The material synthesized at 400 °C,namely, Pd/N-C-400,exhibitssuperior mass activity and stability among catalysts synthesized under different carbonization temperaturesbetween300 and 500 °C.

Redox mediated synthesis of hierarchical Bi2O3/MnO2 nanoflowers: a non-enzymatic hydrogen peroxide electrochemical sensor.

Uniform hierarchical Bi2O3/MnO2 nanoflowers (BM NFs) are fabricated via a reaction strategy by combining redox reaction and hydrothermal treatment. This wet chemical method reports for the first time a one pot synthesis of Bi2O3/MnO2 nanoflowers via a thermodynamically allowed galvanic reaction between Bi(0) and KMnO4 in aqueous solution under modified hydrothermal (MHT) conditions. The Bi2O3/MnO2 NF composites are then applied as a catalyst for electrochemical hydrogen peroxide detection.

A ternary Cu2O-Cu-CuO nanocomposite: a catalyst with intriguing activity.

In this work, the syntheses of Cu2O as well as Cu(0) nanoparticle catalysts are presented. Copper acetate monohydrate produced two distinctly different catalyst particles with varying concentrations of hydrazine hydrate at room temperature without using any surfactant or support. Then both of them were employed separately for 4-nitrophenol reduction in aqueous solution in the presence of sodium borohydride at room temperature.

Liquor ammonia mediated V(V) insertion in thin Co3O4 sheets for improved pseudocapacitors with high energy density and high specific capacitance value.

Ultrathin 2D Co3O4 and Co3V2O8 nanosheets have been produced from our modified hydrothermal technique (MHT). Both the materials have been proved to be extraordinary electrode materials for pseudocapacitors. The neat nanosheets of Co3O4 and Co3V2O8 exhibit a record specific capacitance value of 1256 F g(-1) and 4194 F g(-1) at 1 A g(-1) current density, respectively.

Redox-Mediated Synthesis of a Fe₃O₄-MnO₂ Nanocomposite for Dye Adsorption and Pseudocapacitance.

A logically chosen redox reaction of submerged Fe(0) in an aqueous KMnO4 solution has been reported. The template-free reaction conditions produced gram amounts of a hierarchical flowerlike Fe3O4-MnO2 nanocomposite. More precisely, freshly prepared Fe(0) nanoparticles were prepared from air-free hot water under submerged conditions using a door magnet.

Biomolecule-mediated CdS-TiO2-reduced graphene oxide ternary nanocomposites for efficient visible light-driven photocatalysis.

We report an environmentally friendly synthetic strategy to fabricate reduced graphene oxide (rGO)-based ternary nanocomposites, in which glutathione (GSH) acts both as a reducing agent for graphene oxide and sulfur donor for CdS synthesis under modified hydrothermal (MHT) conditions. The report becomes interesting as pH variation evolves two distinctly different semiconducting nanocrystals of anatase/rutile TiO2 and hexagonal yellow/cubic red CdS, and their packaging makes them suitable photocatalysts for dye degradation. Herein, a titanium peroxo compound, obtained from commercial TiO2, is hydrolyzed to TiO2 nanostructures without any additives.

Intrinsic peroxidase-like activity of mesoporous nickel oxide for selective cysteine sensing.

Mesoporous nickel oxide nanoflowers (NiO NFs) can be easily synthesized by a two-step synthetic procedure based on modified hydrothermal (MHT) treatment of nickel acetate and ethanol amine in water followed by thermal decomposition at 350 °C for 4 h. After thermal treatment, the porosity is increased by 18% with retention of parental nickel hydroxide size. In this study, for the first time, a new catalytic application of NiO NFs has been revealed in terms of peroxidase-like activity where colorless 3,3',5,5' tetramethylbenzidine (TMB) is oxidized to blue color product in the presence of HO at room temperature.