A synthetic protocol developed to produce phase-pure, nearly monodisperse Ni 2-x Co x P nanoparticles (x≤1.7) is described. The Ni 2-x Co x P particles vary in size, ranging from 9-14 nm with standard deviations of <20% (based on TEM analysis) and the actual metal ratios obtained from EDS closely follow the targeted ratios. With increasing Co, samples with larger size distributions are obtained and include particles with voids, attributed to the Kirkendall effect. In order to probe the mechanism of ternary phosphide particle formation, detailed studies were conducted for Ni:Co = 1:1 as a representative composition. It was revealed that the P:M ratio, heating temperature and heating time have a large impact on the nature of both intermediate and final crystalline particles formed. By tuning these conditions, nanoparticles can be produced with different sizes (from ca 7-25 nm) and morphol0gy (hollow vs. dense).
Nickel
phosphide nanoparticles encapsulated in mesoporous silica
(Ni2P@mSiO2) were used to probe particle size
effects in the deep hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene
(4,6-DMDBT). The HDS properties of the well-defined nanoparticle catalysts
were compared to those of Ni2P/SiO2 catalysts
prepared by different methods and having different particle sizes.
The Ni2P@mSiO2 nanocatalysts had Ni2P particle sizes of 6.3, 11.4, and 16.0 nm, while the Ni2P/SiO2 catalysts had particle sizes of 3.2 and 5.7 nm.
Linear correlations of CO chemisorption capacity and 4,6-DMDBT HDS
activity with calculated Ni2P surface area were observed
for the Ni2P@mSiO2 nanocatalysts. The CO chemisorption
measurements yield a value of 0.28 CO molecules per surface Ni atom,
with some Ni sites likely blocked by the mesoporous silica shell that
encapsulates Ni2P nanoparticles, as well as possibly by
excess P at the particle surfaces. HDS turnover frequencies (TOFs),
normalized on the basis of surface Ni sites and CO chemisorption,
yield values of (1.1–2.1) × 10–5 s–1 (TOFNi) and (4.7–8.4) × 10–5 s–1 (TOFCO) for the
Ni2P@mSiO2 nanocatalysts at a reaction temperature
of 553 K. The TOFNi values are similar to or higher than
those measured for the Ni2P/SiO2 catalysts.
With respect to sites titrated by CO (TOFCO), the Ni2P/SiO2 catalyst prepared from a hypophosphite-based
precursor was over two times more active than the Ni2P@mSiO2 nanocatalysts and the Ni2P/SiO2 catalyst
prepared from a phosphate-based precursor. The Ni2P@mSiO2 nanocatalyst having 6.3 nm Ni2P nanoparticles
and the Ni2P/SiO2-hypo catalyst had higher HDS
activities than a commercial sulfided Ni–Mo/Al2O3 catalyst; the results indicate that a catalyst composed of
3–5 nm Ni2P particles would have a 4,6-DMDBT HDS
activity competitive with commercial Co–Mo/Al2O3 and Ni–Mo/Al2O3 catalysts. The
Ni2P@mSiO2 and Ni2P/SiO2 catalysts strongly favored products of the hydrogenation pathway
for sulfur removal as did the sulfided Ni–Mo/Al2O3 catalyst.
Metal–semiconductor hybrid nanomaterials (HNMs) exhibit unique properties that are distinct from individual nanostructures, leading to promising applications in optical technologies. The interfacial linkage of semiconductor and metal nanoparticles (NPs) via cogelation is an effective strategy to produce HNMs that show strong plasmon‐exciton coupling and improved physical properties. However, optical properties of these hybrids show little to no tunability. Herein, CdSe/Ag hybrid aerogels that show tunable absorption and photoluminescence (PL) are produced by cogelation of CdSe nanorods (NRs) or NPs with Ag hollow NPs. Hybrid electronic states are created by overlapping the excitonic absorption of CdSe NRs or NPs with the plasmonic absorption of Ag NPs. Physical characterization of the hybrids reveals an interconnected network of hexagonal CdSe and cubic Ag NPs, linked by Ag+ and Se2− surface species, without intervening ligands. PL spectra exhibit maxima at 640 and 720 nm for the CdSe NPs/Ag and CdSe NRs/Ag hybrids, respectively, corresponding to new radiative decay mechanisms. Time‐resolved PL data support the emergence of new radiative pathways, kinetically and energetically distinct from the excitonic and plasmonic properties of primary NPs. This new approach of metal–semiconductor hybrid formation through cogelation is intriguing for the design of high‐efficiency HNMs without detrimental PL quenching.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.