3 research outputs found
Doped Halide Perovskite Nanocrystals for Reabsorption-Free Luminescent Solar Concentrators
Halide perovskite
nanocrystals (NCs) are promising solution-processed
emitters for low-cost optoelectronics and photonics. Doping adds a
degree of freedom for their design and enables us to fully decouple
their absorption and emission functions. This is paramount for luminescent
solar concentrators (LSCs) that enable fabrication of electrode-less
solar windows for building-integrated photovoltaic applications. Here,
we demonstrate the suitability of manganese-doped CsPbCl<sub>3</sub> NCs as reabsorption-free emitters for large-area LSCs. Light propagation
measurements and Monte Carlo simulations indicate that the dopant
emission is unaffected by reabsorption. Nanocomposite LSCs were fabricated
via mass copolymerization of acrylate monomers, ensuring thermal and
mechanical stability and optimal compatibility of the NCs, with fully
preserved emission efficiency. As a result, perovskite LSCs behave
closely to ideal devices, in which all portions of the illuminated
area contribute equally to the total optical power. These results
demonstrate the potential of doped perovskite NCs for LSCs, as well
as for other photonic technologies relying on low-attenuation long-range
optical wave guiding
Facile Solvothermal Preparation of Monodisperse Gold Nanoparticles and Their Engineered Assembly of FerritināGold Nanoclusters
Herein,
we report a quick and simple synthesis of water-soluble gold nanoparticles
using a HAuCl<sub>4</sub> and oleylamine mixture. Oleylamine serves
as a reduction agent as well as a stabilizer for nanoparticle surfaces.
The particle sizes can be adjusted by modulating reaction temperature
and time. Solvothermal reduction of HAuCl<sub>4</sub> with oleylamine
can be confirmed by measuring the product in Fourier transform infrared
(FTIR) spectroscopy. The plasmon band shifting from yellow to red
confirms a nanosized particle formation. Amide bonds on the surface
of the nanoparticles formed hydrogen bonds with one another, resulting
in a hydrophobic monolayer. Particles dispersed well in nonpolar organic
solvents, such as in hexane or toluene, by brief sonication. Next,
we demonstrated the transfer of gold nanoparticles into water by lipid
capsulation using 1-myristoyl-2-hydroxy-<i>sn</i>-glycero-3-phosphocholine
(MHPC), 1,2-distearoyl-<i>sn</i>-glycero-3-phosphoethanolamine-<i>N</i>-(methoxy polyethylene glycol)-2000 (DPPE-PEG2k), and 1,2-dioleoyl-<i>sn</i>-glycero-3-<i>N</i>-{5-amino-1-carboxypentyl}Āiminodiacetic
acid succinyl nickel salt [DGS-NTAĀ(Ni)]. The particle concentration
can be obtained using an absorbance in ultravioletāvisible
(UVāvis) spectra (at 420 nm). Instrumental analyses using transmission
electron microscopy (TEM), energy-dispersive X-ray (EDX) analysis,
dynamic light scattering (DLS), and FTIR confirmed successful production
of gold nanoparticles and fair solubility in water. Prepared gold
particles were selectively clustered via engineered ferritin nanocages
that provide multiple conjugation moieties. A total of 5ā6
gold nanoparticles were clustered on a single ferritin nanocage confirmed
in TEM. Reported solvothermal synthesis and preparation of gold nanoclusters
may serve as an efficient, alternate way of preparing water-soluble
gold nanoparticles, which can be used in a wide variety of biomedical
applications
Nearly Monodisperse Insulator Cs<sub>4</sub>PbX<sub>6</sub> (X = Cl, Br, I) Nanocrystals, Their Mixed Halide Compositions, and Their Transformation into CsPbX<sub>3</sub> Nanocrystals
We
have developed
a colloidal synthesis of nearly monodisperse nanocrystals of pure
Cs<sub>4</sub>PbX<sub>6</sub> (X = Cl, Br, I) and their mixed halide
compositions with sizes ranging from 9 to 37 nm. The optical absorption
spectra of these nanocrystals display a sharp, high energy peak due
to transitions between states localized in individual PbX<sub>6</sub><sup>4ā</sup> octahedra. These spectral features are insensitive
to the size of the particles and in agreement with the features of
the corresponding bulk materials. Samples with mixed halide composition
exhibit absorption bands that are intermediate in spectral position
between those of the pure halide compounds. Furthermore, the absorption
bands of intermediate compositions broaden due to the different possible
combinations of halide coordination around the Pb<sup>2+</sup> ions.
Both observations are supportive of the fact that the [PbX<sub>6</sub>]<sup>4ā</sup> octahedra are electronically decoupled in these
systems. Because of the large band gap of Cs<sub>4</sub>PbX<sub>6</sub> (>3.2 eV), no excitonic emission in the visible range was observed.
The Cs<sub>4</sub>PbBr<sub>6</sub> nanocrystals can be converted into
green fluorescent CsPbBr<sub>3</sub> nanocrystals by their reaction
with an excess of PbBr<sub>2</sub> with preservation of size and size
distributions. The insertion of PbX<sub>2</sub> into Cs<sub>4</sub>PbX<sub>6</sub> provides a means of accessing CsPbX<sub>3</sub> nanocrystals
in a wide variety of sizes, shapes, and compositions, an important
aspect for the development of precisely tuned perovskite nanocrystal
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