9 research outputs found
Aminophosphine Reduction Mechanisms and the Synthesis of Indium Phosphide Nanomaterials
Indium phosphide (InP) nanomaterials are attractive for countless technological applications due to their well-placed band gap energies. The quantum confinement of these semiconductors can give rise to size-dependent absorption and emission features throughout the entire visible spectrum. Therefore, InP materials can be employed as low-toxicity fluorophores that can be implemented in high value avenues such as biological probes, lighting applications, and lasing technologies. However, large scale development of these quantum dots (QDs) has been stymied by the lack of affordable and safe phosphorus precursors. Syntheses have largely been restricted to the use of dangerous chemicals such as tris(trimethylsilyl)phosphine ((TMS)₃P), which is costly and highly sensitive to oxygen and water. Recently, less-hazardous tris(dialkylamino)phosphines have been introduced to produce InP QDs on par with those utilizing (TMS)₃P. However, a poor understanding of the reaction mechanics has resulted in difficulties tuning and optimizing this method.
In this work, density functional theory (DFT) is used to identify the mechanism of this aminophosphine precursor conversion. This understanding is then implemented to design an improved InP QD synthesis, allowing for the production of high-quality materials outside of glovebox conditions. Time is spent understanding the impact of different precursor salts on the reaction mechanisms and discerning their subsequent effects on nanoparticle size and quality. The motivation of this work is to formulate safer and less technical indium phosphide quantum dot syntheses to foster non-specialist and industrial implementation of these materials
Aminophosphine Reduction Mechanisms and the Synthesis of Indium Phosphide Nanomaterials
Indium phosphide (InP) nanomaterials are attractive for countless technological applications due to their well-placed band gap energies. The quantum confinement of these semiconductors can give rise to size-dependent absorption and emission features throughout the entire visible spectrum. Therefore, InP materials can be employed as low-toxicity fluorophores that can be implemented in high value avenues such as biological probes, lighting applications, and lasing technologies. However, large scale development of these quantum dots (QDs) has been stymied by the lack of affordable and safe phosphorus precursors. Syntheses have largely been restricted to the use of dangerous chemicals such as tris(trimethylsilyl)phosphine ((TMS)₃P), which is costly and highly sensitive to oxygen and water. Recently, less-hazardous tris(dialkylamino)phosphines have been introduced to produce InP QDs on par with those utilizing (TMS)₃P. However, a poor understanding of the reaction mechanics has resulted in difficulties tuning and optimizing this method.
In this work, density functional theory (DFT) is used to identify the mechanism of this aminophosphine precursor conversion. This understanding is then implemented to design an improved InP QD synthesis, allowing for the production of high-quality materials outside of glovebox conditions. Time is spent understanding the impact of different precursor salts on the reaction mechanisms and discerning their subsequent effects on nanoparticle size and quality. The motivation of this work is to formulate safer and less technical indium phosphide quantum dot syntheses to foster non-specialist and industrial implementation of these materials
An In Vitro Investigation of Cytotoxic Effects of InP/Zns Quantum Dots with Different Surface Chemistries
Indium phosphide quantum dots (QDs) passivated with zinc sulphide in a core/shell architecture (InP/ZnS) with different surface chemistries were introduced to RAW 264.7 murine “macrophage-like„ cells to understand their potential toxicities. The InP/ZnS quantum dots were conjugated with an oligonucleotide, a carboxylic acid, or an amino-polyethylene glycol ligand, and cell viability and cell proliferation were investigated via a metabolic assay. Membrane integrity was measured through the production of lactate dehydrogenase. Fluorescence microscopy showed cellular uptake. All quantum dots exhibited cytotoxic behaviour less than that observed from cadmium- or lead-based quantum dots; however, this behaviour was sensitive to the ligands used. In particular, the amino-polyethylene glycol conjugated quantum dots proved to possess the highest cytotoxicity examined here. This provides quantitative evidence that aqueous InP/ZnS quantum dots can offer a safer alternative for bioimaging or in therapeutic applications
Platinum Terpyridine Metallopolymer Electrode as Cost-Effective Replacement for Bulk Platinum Catalysts in Oxygen Reduction Reaction and Hydrogen Evolution Reaction
Conducting
polymers consisting of metal-selective coordination
units and a highly conductive backbone, so-called metallopolymers,
are interesting materials exposing single atoms for photo/electrocatalysis
and thus represent a potential low-cost alternative for bulk or nanoparticulate
platinum group metals (PGMs). We synthesized and fully characterized
an electropolymerisable monomer bearing a pendant terpyridine unit
for the selective complexation of PGMs. Electrocatalytic tests of
the resulting metallopolymer, poly-[(tThTerpy)PtCl]Cl, revealed activity
both in the oxygen reduction reaction and hydrogen evolution reaction.
Rotating disk experiments showed the direct four-electron reduction
of molecular oxygen to water at low angular velocities of the rotating
electrode. Furthermore, the fabrication of Pt metallopolymers proved
to be simple, nonhazardous and versatile. This proof-of-concept opens
up the possibility for developing future low-cost electro- and photocatalysts
to replace current systems
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Inter-ligand energy transfer in dye chromophores attached to high bandgap SiO2 nanoparticles.
Artificial light harvesters require ordered arrangement of chromophores. We covalently attach three organic chromophore ligands to silicon dioxide nanoparticles. This allows us to study inter-ligand energy transfer when attached to SiO2 nanoparticles, creating a simple system with a large ratio of donors to acceptors. Using steady-state and transient spectroscopy measurements we quantify this energy transfer between ligands. We show a maximum transfer efficiency of 30% and measure the 2D diffusion length of anthracene carboxylic acid on SiO2 to be between 0.6 and 2.2 nm
Interface-Dependent Selectivity in Plasmon-Driven Chemical Reactions
Plasmonic nanoparticles can drive chemical reactions
powered by
sunlight. These processes involve the excitation of surface plasmon
resonances (SPR) and the subsequent charge transfer to adsorbed molecular
orbitals. Nonetheless, controlling the flow of energy and charge from
SPR to adsorbed molecules is still difficult to predict or tune. Here,
we show the crucial role of halide ions in modifying the energy landscape
of a plasmon-driven chemical reaction by carefully engineering the
nanoparticle–molecule interface. By doing so, the selectivity
of plasmon-driven chemical reactions can be controlled, either enhancing
or inhibiting the metal–molecule charge and energy transfer
or by regulating the vibrational pumping rate. These results provide
an elegant method for controlling the energy flow from plasmonic nanoparticles
to adsorbed molecules, in situ, and selectively targeting
chemical bonds by changing the chemical nature of the metal–molecule
interface
The Evolution of Quantum Confinement in CsPbBr<sub>3</sub> Perovskite Nanocrystals
Colloidal
nanocrystals (NCs) of lead halide perovskites are considered
highly promising materials that combine the exceptional optoelectronic
properties of lead halide perovskites with tunability from quantum
confinement. But can we assume that these materials are in the strong
confinement regime? Here, we report an ultrafast transient absorption
study of cubic CsPbBr<sub>3</sub> NCs as a function of size, compared
with the bulk material. For NCs above ∼7 nm edge length, spectral
signatures are similar to the bulk material–characterized by
state-filling with uncorrelated charges–but discrete new kinetic
components emerge at high fluence due to bimolecular recombination
occurring in a discrete volume. Only for the smallest NCs (∼4
nm edge length) are strong quantum confinement effects manifest in
TA spectral dynamics; focusing toward discrete energy states, enhanced
bandgap renormalization energy, and departure from a Boltzmann statistical
carrier cooling. At high fluence, we find that a hot-phonon bottleneck
effect slows carrier cooling, but this appears to be intrinsic to
the material, rather than size dependent. Overall, we find that the
smallest NCs are understood in the framework of quantum confinement,
however for the widely used NCs with edge lengths >7 nm the photophysics
of bulk lead halide perovskites are a better point of reference