A Little Nickel Goes a Long Way: Ni Incorporation into RhP for Stable Bifunctional Electrocatalytic Water Splitting in Acidic Media.

In acidic media, many transition-metal phosphides are reported to be stable catalysts for the hydrogen evolution reaction (HER) but typically exhibit poor stability toward the corresponding oxygen evolution reaction (OER). A notable exception appears to be RhP/C nanoparticles, reported to be active and stable toward both the HER and OER. Previously, we investigated base-metal-substituted RhP, specifically CoRhP and NiRhP, for HER and OER as a means to reduce the noble-metal content and tune the reactivity for these disparate reactions.

Electrochemical Gelation of Metal Chalcogenide Quantum Dots: Applications in Gas Sensing and Photocatalysis.

ConspectusMetal chalcogenide quantum dots (QDs) are prized for their unique and functional properties, associated with both intrinsic (quantum confinement) and extrinsic (high surface area) effects, as dictated by their size, shape, and surface characteristics. Thus, they have considerable promise for diverse applications, including energy conversion (thermoelectrics and photovoltaics), photocatalysis, and sensing. QD gels are macroscopic porous structures consisting of interconnected QDs and pore networks in which the pores may be filled with solvent (i.

Homogeneous Nanoparticles of Multimetallic Phosphides via Precursor Tuning: Ternary and Quaternary MP Phases (M = Fe, Co, Ni).

Transition metal phosphides (TMPs) are a highly investigated class of nanomaterials due to their unique magnetic and catalytic properties. Although robust and reproducible synthetic routes to narrow polydispersity monometallic phosphide nanoparticles (MP; M = Fe, Co, Ni) have been established, the preparation of multimetallic nanoparticle phases (M M' P; M, M' = Fe, Co, Ni) remains a significant challenge. Colloidal syntheses employ zero-valent metal carbonyl or multivalent acetylacetonate salt precursors in combination with trioctylphosphine as the source of phosphorus, oleylamine as the reducing agent, and additional solvents such as octadecene or octyl ether as "noncoordinating" cosolvents.

Electrochemical gelation of quantum dots using non-noble metal electrodes at high oxidation potentials.

Relative to conventional chemical approaches, electrochemical assembly of metal chalcogenide nanoparticles enables the use of two additional levers for tuning the assembly process: electrode material and potential. In our prior work, oxidative and metal-mediated pathways for electrochemical assembly of metal chalcogenide quantum dots (QDs) into three-dimensional gel architectures were investigated independently by employing a noble-metal (Pt) electrode at relatively high potentials and a non-noble metal electrode at relatively low potentials, respectively. In the present work, we reveal competition between the two electrogelation pathways under the condition of high oxidation potentials and non-noble metal electrodes (including Ni, Co, Zn, and Ag), where both pathways are active.

Correction to : Issue 2 Highlights and Call for 2022 Rising Stars.

[This corrects the article DOI: 10.1021/acsmaterialsau.1c00061.

Photoexcited NO Enables Accelerated Response and Recovery Kinetics in Light-Activated NO Gas Sensing.

Slow response and recovery kinetics is a major challenge for practical room-temperature NO gas sensing. Here, we report the use of visible light illumination to significantly shorten the response and recovery times of a PbSe quantum dot (QD) gel sensor by 21% (to 27 s) and 63% (to 102 s), respectively. When combined with its high response (0.

Atomically dispersed Pb ionic sites in PbCdSe quantum dot gels enhance room-temperature NO sensing.

Atmospheric NO is of great concern due to its adverse effects on human health and the environment, motivating research on NO detection and remediation. Existing low-cost room-temperature NO sensors often suffer from low sensitivity at the ppb level or long recovery times, reflecting the trade-off between sensor response and recovery time. Here, we report an atomically dispersed metal ion strategy to address it.

Reversible Electrochemical Gelation of Metal Chalcogenide Quantum Dots.

The ability to dictate the assembly of quantum dots (QDs) is critical for their integration into solid-state electronic and optoelectronic devices. However, assembly methods that enable efficient electronic communication between QDs, facilitate access to the reactive surface, and retain the native quantum confinement characteristics of the QD are lacking. Here we introduce a universal and facile electrochemical gelation method for assembling metal chalcogenide QDs (as demonstrated for CdS, ZnS, and CdSe) into macroscale 3-D connected pore-matter nanoarchitectures that remain quantum confined and in which each QD is accessible to the ambient.

Effect of metal ion solubility on the oxidative assembly of metal sulfide quantum dots.

The versatility of the oxidative assembly method for the creation of 2D and 3D quantum dot (QD) architectures represents both an opportunity and a challenge as a method enabling controlled placement of chemically distinct QDs in multicomponent systems. The opportunity lies in the ability to independently tune the kinetics of the different components so that they are similar (leading to well-mixed systems) or different (enabling gradient or phase-segregated composites) using a wide range of variables; the challenge lies in understanding those variables and how their interplay affects the overall kinetics. Here, we show that the identity of the cation in the sulfide matrix (M = Cd vs Zn) plays a large role in the kinetics of assembly of mass spectrometry QDs, attributed to differences in solubility.

Exploiting kinetics for assembly of multicomponent nanoparticle networks with programmable control of heterogeneity.

Kinetic control of metal chalcogenide nanoparticle oxidative assembly is realized by varying the redox potential of the chalcogenide, structure (wurtzite vs. zinc blende), and ligand chain length. This knowledge is exploited to form two-component (ZnS + CdSe) hybrid aerogels with minimal heterobonding (phase-segregated) or maximal heterobonding (intimately mixed).

Anisotropic manganese antimonide nanoparticle formation by solution-solid-solid growth mechanism: consequence of sodium borohydride addition towards reduced surface oxidation and enhanced magnetic moment.

A new approach to the solution-phase synthesis of manganese antimonide nanoparticles was developed to reduce competitive oxide formation by exploitation of sodium borohydride (NaBH4) (0.53-2.64 mmol) as a sacrificial reductant.

Surface Chemistry and Nano-/Microstructure Engineering on Photocatalytic InS Nanocrystals.

Colloidal nanocrystals (NCs) compete with molecular catalysts in the field of homogenous catalysis, offering easier recyclability and a number of potentially advantageous functionalities, such as tunable band gaps, plasmonic properties, or a magnetic moment. Using high-throughput printing technologies, colloidal NCs can also be supported onto substrates to produce cost-effective electronic, optoelectronic, electrocatalytic, and sensing devices. For both catalytic and technological application, NC surface chemistry and supracrystal organization are key parameters determining final performance.

Metal Oxide Aerogels with Controlled Crystallinity and Faceting from the Epoxide-Driven Cross-Linking of Colloidal Nanocrystals.

We present a novel method to produce crystalline oxide aerogels which is based on the cross-linking of preformed colloidal nanocrystals (NCs) triggered by propylene oxide (PO). Ceria and titania were used to illustrate this new approach. Ceria and titania colloidal NCs with tuned geometry and crystal facets were produced in solution from the decomposition of a suitable salt in the presence of oleylamine (OAm).

CuGaS₂ and CuGaS₂-ZnS Porous Layers from Solution-Processed Nanocrystals.

The manufacturing of semiconducting films using solution-based approaches is considered a low cost alternative to vacuum-based thin film deposition strategies. An additional advantage of solution processing methods is the possibility to control the layer nano/microstructure. Here, we detail the production of mesoporous CuGaS₂ (CGS) and ZnS layers from spin-coating and subsequent cross-linking through chalcogen-chalcogen bonds of properly functionalized nanocrystals (NCs).

CdS Aerogels as Efficient Photocatalysts for Degradation of Organic Dyes under Visible Light Irradiation.

Synthesis of efficient photocatalysts based on CdS nanomaterials for oxidative decomposition of organic effluents typically focuses on (a) enhancement of surface area of the catalysts and (b) promotion of the separation of photogenerated electron-hole pairs. CdS aerogel, which are synthesized by simple sol-gel assembly of discrete nanocrystals (NCs) into a porous network followed by supercritical drying, could provide higher surface area for photocatalytic reactions along with facile charge separation due to direct contact between NCs via covalent bonding. We evaluated the efficiency of CdS aerogel materials for degradation of organic dyes using methylene blue (MB) and methyl orange (MO) as test cases.

When Ligand Exchange Leads to Ion Exchange: Nanocrystal Facets Dictate the Outcome.

This study demonstrates that ligand exchange of nanocrystals (NCs) is not always an innocuous process, but can lead to facile (room temperature) ion exchange, depending on the surface crystal faceting. Rock salt PbTe NCs prepared as cubes with neutral facets undergo room-temperature ligand exchange with sulfide ions, whereas cuboctahedron-shaped particles with neutral {100} and polar {111} facets are transformed to PbS, driven by ion exchange along the ⟨111⟩ direction. Likewise, cation exchange (with Ag) occurs rapidly for cuboctahedra, whereas cubes remain inert.

Role of Crystal Structure and Chalcogenide Redox Properties on the Oxidative Assembly of Cadmium Chalcogenide Nanocrystals.

Oxidative assembly of metal chalcogenide nanocrystals (NCs) enables the formation of 2-D (dense) and 3-D porous structures without the presence of intervening ligands between particles that can moderate transport properties. This route has been demonstrated to be successful for a range of single-component structures including CdQ, PbQ, and ZnQ (Q = S, Se, Te). En route to the controllable assembly of multicomponent nanostructures, the roles of Q redox properties (2Q → Q + 2e) responsible for particle cross-linking and the native structure (cubic zinc blende vs hexagonal wurtzite) in the kinetics of assembly in single-component CdQ NCs are evaluated using time-resolved dynamic light scattering (TR-DLS).

Efficient Water Oxidation Using CoMnP Nanoparticles.

The development of efficient water oxidation catalysts based on inexpensive and Earth-abundant materials is a prerequisite to enabling water splitting as a feasible source of alternative energy. In this work, we report the synthesis of ternary cobalt manganese phosphide nanoparticles from the solution-phase reaction of manganese and cobalt carbonyl complexes with trioctylphosphine. The CoMnP nanoparticles (ca.

Solvothermal Synthesis of Tetrahedrite: Speeding Up the Process of Thermoelectric Material Generation.

Derivatives of synthetic tetrahedrite, Cu12Sb4S13, are receiving increasing attention in the thermoelectric community due to their exploitation of plentiful, relatively nontoxic elements, combined with a thermoelectric performance that rivals that of PbTe-based compounds. However, traditional synthetic methods require weeks of annealing at high temperatures (450-600 °C) and periodic regrinding of the samples. Here we report a solvothermal method to produce tetrahedrite that requires only 1 day of heating at a relatively low temperature (155 °C).

Effect of Synthetic Levers on Nickel Phosphide Nanoparticle Formation: Ni5P4 and NiP2.

Due to their unique catalytic, electronic, and redox processes, Ni5P4 and NiP2 nanoparticles are of interest for a wide-range of applications from the hydrogen evolution reaction to energy storage (batteries); yet synthetic approaches to these materials are limited. In the present work, a phase-control strategy enabling the arrested-precipitation synthesis of nanoparticles of Ni5P4 and NiP2 as phase-pure samples using different Ni organometallic precursors and trioctylphosphine (TOP) is described. The composition and purity of the product can be tuned by changing key synthetic levers, including the Ni precursor, the oleylamine (OAm) coordinating solvent and TOP concentrations, temperature, time, and the presence or absence of a moderate temperature soak step to facilitate formation of Ni and/or Ni-P amorphous nanoparticle intermediates.