Search results for "Colloid"
showing 10 items of 1288 documents
Light-Emitting Electrochemical Cells Using Cyanine Dyes as the Active Components
2013
Light-emitting electrochemical cells (LECs) based on cyanine molecules were prepared. High photoluminescence quantum yields were obtained for host-guest films using two cyanine dyes, reaching 27%. Sandwiching these films in between two electrodes allows for very stable near-infrared emission with a maximum radiant flux of 1.7 W m(-2) at an external quantum efficiency of 0.44%.
Cd12Ag32(SePh)36: Non-Noble Metal Doped Silver Nanoclusters
2019
While there are numerous recent reports on doping of a ligand-protected noble metal nanocluster (e.g., Au and Ag) with another noble metal, non-noble metal (e.g., Cd) doping remains challenging. Here, we design a phosphine-assisted synthetic strategy and synthesize a Cd doped Ag nanocluster, Cd12Ag32(SePh)36 (SePh: selenophenolate), which exhibits characteristic UV–vis absorption features and rare near-infrared (NIR) photoluminescence at ∼1020 nm. The X-ray single crystal structure reveals an asymmetric two-shell Ag4@Ag24 metal kernel protected by four nonplanar Cd3Ag(SePh)9 metal–ligand frameworks. Furthermore, the electronic structure analysis shows that the cluster is a 20-electron “supe…
Active photonic devices based on colloidal semiconductor nanocrystals and organometallic halide perovskites
2016
Semiconductor nanocrystals have arisen as outstanding materials to develop a new generation of optoelectronic devices. Their fabrication under simple and low cost colloidal chemistry methods results in cheap nanostructures able to provide a wide range of optical functionalities. Their attractive optical properties include a high absorption cross section below the band gap, a high quantum yield emission at room temperature, or the capability of tuning the band-gap with the size or the base material. In addition, their solution process nature enables an easy integration on several substrates and photonic structures. As a consequence, these nanoparticles have been extensively proposed to devel…
Oxygen-defective ZnO films with various nanostructures prepared via a rapid one-step process and corresponding photocatalytic degradation application…
2018
Abstract The deposition of oxygen-defective ZnO films exhibiting varied nanostructures via Solution Precursor Plasma Spray (SPPS) route, a one-step, minute-scaled duration and large scale method, is reported. The in situ formation of oxygen vacancies in ZnO films was confirmed by UV–Visible, Raman and photoluminescence (PL) spectroscopy and the as-prepared samples exhibit a bandgap as low as 3.02 eV. Density functional theory (DFT) simulation demonstrates that the polarization of ZnO is enhanced by the created oxygen vacancies, leading to substantially improved photocatalytic activity. The comparative experiments also revealed that forming and preserving appropriate ZnO precursor clusters i…
Efficient Cementing of CH3NH3PbBr3Nanoparticles to Upconversion Nanoparticles Visualized by Confocal Microscopy
2016
Upconversion-perovskite nanohybrids are prepared by assembling CH3NH3PbBr3 perovskite nanoparticles (PK) with naked NaYF4:Yb3+,Tm3+ nanoparticles (UCn) via an innovative strategy consisting of using cucurbit[7]uril (CB[7]) to anchor the perovskite nanoparticles firmly and closely to the upconversion nanoparticles, thus leading to UCn@PKCB nanohybrids. A commercial multiphoton laser scanning confocal microscope is used to demonstrate the successful assembly. This technique proves to be useful to evaluate luminescence lifetime in the range of several tens of μs and allows visualization of the extraordinarily efficient nontrivial resonance energy transfer from the upconversion nanoparticle to …
Photoluminescence Enhancement of CdSe Quantum Dots: A Case of Organogel–Nanoparticle Symbiosis
2012
Highly fluorescent organogels (QD-organogel), prepared by combining a pseudopeptidic macrocycle and different types of CdSe quantum dots (QDs), have been characterized using a battery of optical and microscopic techniques. The results indicate that the presence of the QDs not only does not disrupt the supramolecular organization of the internal fibrillar network of the organogel to a significant extent, but it also decreases the critical concentration of gelator needed to form stable and thermoreversible organogels. Regarding the photophysical properties of the QDs, different trends were observed depending on the presence of a ZnS inorganic shell around the CdSe core. Thus, while the core-s…
Synthesis and Characterization of Highly Luminescent CdSe—Core CdS/Zn0.5Cd0.5S/ZnS Multishell Nanocrystals.
2005
We report on the preparation and structural characterization of CdSe nanocrystals, which are covered by a multishell structure from CdS and ZnS. By using the newly developed successive ion layer adhesion and reaction (SILAR) technique, we could gradually change the shell composition from CdS to ZnS in the radial direction. Because of the stepwise adjustment of the lattice parameters in the radial direction, the resulting nanocrystals show a high crystallinity and are almost perfectly spherical, as was investigated by X-ray diffraction and electron microscopy. Also, due to the radial increase of the respective valence- and conduction-band offsets, the nanocrystals are well electronically pas…
Dibenzo[hi,st]ovalene as Highly Luminescent Nanographene: Efficient Synthesis via Photochemical Cyclodehydroiodination, Optoelectronic Properties, an…
2019
Dibenzo[hi,st]ovalene (DBOV), as a new nanographene, has demonstrated promising optical properties, such as red emission with a high fluorescence quantum yield of 79% and stimulated emission, as well as high thermal stability and photostability, which indicated its promise as a light-emitting and optical gain material. However, the previous synthetic routes required at least 12 steps. This obstructed access to different derivatives, e.g., to obtain crystals suitable for X-ray diffraction analysis and to tune the optoelectronic properties. Here, we report an efficient synthetic pathway to DBOV based on a sequential iodination-benzannulation of bi(naphthylphenyl)diyne, followed by photochemic…
Nanoparticle One-Dimensional Photonic-Crystal Dye Laser
2009
The stimulated emission from an organic dye adsorbed within the void network of a NP 1D (photonic crystals) PC, was studied. The nanoparticle one-dimensional photonic crystals (NP 1DPCs) were assembled by polyelectrolyte-assisted layer-by-layer deposition with subsequent calcination of the films to remove the polymer components. Each layer was prepared by spin-coating a block-copolymer-templated titania- or silica-based sol solution followed by a calcination step. To maximize the photonic-crystal effect, PCs consisting of eleven bilayers, compared to the four-bilayer NP 1D PCs, were fabricated with good structural and optical quality over 2 cm ×2 cm areas. The effective refractive index of …
Color Tuning and White Light by Dispersing CdSe, CdTe, and CdS in PMMA Nanocomposite Waveguides
2013
In this paper, active nanocomposite waveguides based on the dispersion of CdS, CdTe, and CdSe colloidal quantum dots (QDs) in PMMA are proposed. Their propagation properties are studied as a function of the concentration of nanoparticles in the polymer using the variable length stripe method. When the three nanostructures are dispersed in the same film, the structure is able to waveguide the three basic colors: red (CdSe), green (CdTe), and blue (CdS), it being possible to engineer any waveguided color by an appropriate choice of the filling factor of each QD in the PMMA matrix. For this purpose, it is important to take into account reabsorption effects and the Förster energy transfe…