Soranyel Gonzalez-Carrero

Nontemplate Synthesis of CH3NH3PbBr3 Perovskite Nanoparticles

To date, there is no example in the literature of free, nanometer-sized, organolead halide CH3NH3PbBr3 perovskites. We report here the preparation of 6 nm-sized nanoparticles of this type by a simple and fast method based on the use of an ammonium bromide with a medium-sized chain that keeps the nanoparticles dispersed in a wide range of organic solvents. These nanoparticles can be maintained stable in the solid state as well as in concentrated solutions for more than three months, without requiring a mesoporous material. This makes it possible to prepare homogeneous thin films of these nanoparticles by spin-coating on a quartz substrate. Both the colloidal solution and the thin film emit light within a narrow bandwidth of the visible spectrum and with a high quantum yield (ca. 20%); this could be advantageous in the design of optoelectronic devices.

Maximizing the emissive properties of CH3NH3PbBr3 perovskite nanoparticles

Highly luminescent and photostable CH3NH3PbBr3 nanoparticles have been prepared by fine-tuning the molar ratio between CH3NH3Br, PbBr2, a medium-size alkyl-chain ammonium salt, and 1-octadecene. The nanoparticles exhibit an excellent photoluminescence quantum yield (ca. 83%) and average recombination lifetime (ca. 600 ns) in toluene dispersion.

Blue-luminescent organic lead bromide perovskites: highly dispersible and photostable materials

The preparation of a blue-luminescent and photostable organic–inorganic hybrid perovskite with an X-ray powder diffraction spectrum consistent with a two-dimensional inorganic framework is reported. This perovskite can be produced with a high reaction yield and valuable optical properties, such as luminescence quantum yield over 20%, radiative rate constant of up to 80 × 106 s−1, and high photostability under UV light. This material remains stable as a solid, is toluene-dispersible, and can be reverted reversibly into its precursors by using dimethylformamide (DMF). Moreover, the DMF dispersion can be injected into toluene to produce a nanomaterial or be used to prepare films by spin-coating on a substrate; both, the nanomaterial and the film exhibit practically the same optical features as the initial perovskite.

The Luminescence of CH3NH3PbBr3 Perovskite Nanoparticles Crests the Summit and Their Photostability under Wet Conditions is Enhanced

CH3 NH3 PbBr3 perovskite nanoparticles (PAD ) are prepared with a photoluminescence quantum yield of ≈100% in air atmosphere by using the quasi-spherical shaped 2-adamantylammonium bromide (ADBr) as the only capping ligand. The photostability under wet conditions of this kind of nanoparticles is enhanced by using cucurbit[7]uril-adamantylammonium (AD@CB) host-guest complexes as the capping ligand.

Organic-inorganic and all-inorganic lead halide nanoparticles [Invited].

Organic-inorganic (hybrid) and all-inorganic lead halide perovskites, in particular APbX(3) where A is an organic cation (methylammonium or formamidinium) or cesium cation and X = Cl, Br, I, respectively, are of great interest in photovoltaic devices and as luminescent materials for light-emitting devices. It has recently been demonstrated that they can be prepared not only as nanoparticulate material by using the pores of mesoporous films, but also as colloidal nanoparticles, which exhibit enhanced optical properties with respect to the bulk material. We summarize here the methods reported for their preparation as well as their optical features. Experimental and theoretical studies on this class of materials are ongoing and there is still a demand for enhancing their emissive properties, stability in polar solvents, dispersibility in different media and/or photostability.

Pyrene-Capped CdSe@ZnS Nanoparticles as Sensitive Flexible Oxygen Sensors in Non-Aqueous Media.

A flexible, highly sensitive sensor of oxygen in non-aqueous solvents is described. It consists of CdSe/ZnS nanoparticles decorated with a considerable number of pyrene units, thus making the formation of the pyrene excimer possible. The emission of the pyrene excimer and that of the nanoparticle are suitably separated from each other and also from the excitation wavelength. This sensor can be applied as a ratiometric oxygen sensor by using the linear response of the pyrene excimer lifetime combined with the linear response of the nanoparticle excited state lifetime. This nanohybrid has been assayed in seven media with different dielectric constants and viscosities over the whole oxygen concentration range. In addition, the sensor versatility provides an easy way for monitoring oxygen diffusion through systems.

Highly photoluminescent, dense solid films from organic-capped CH3NH3PbBr3 perovskite colloids

The preparation of densely-packed films from hybrid lead halide perovskite nanocrystals is not trivial, as during assembly into the solid state both the charge transport and photoluminescence can be substantially altered. The objective of the present study was to retain the pre-engineered confined morphologies of hybrid lead halide perovskite nanocrystals in densely-packed solid films by using short organic ligands. Therefore, the roles of the organic ligands would be to provide stable colloids and a good passivation of the nanoparticle surface, as well as to enable the efficient assembly of the nanoparticles in the solid state. We report here an effective and reproducible process to deposit lead halide perovskite nanoparticle films from colloidal CH3NH3PbBr3 nanoparticles short organic ligands. Remarkably, we demonstrate that nanoparticle solid films with thicknesses of hundreds of nanometres can retain high photoluminescence, with a quantum yield of 80%, and still sustain charge transport.

Three independent channel nanohybrids as fluorescent probes

A properly designed pyrene-capped CdSe/ZnS nanohybrid can act as a three-channel fluorescent sensor due to the independent emission of the pyrene monomer and excimer as well as that of the nanoparticle. As proof of principle, it was tested for a simple and rapid quantification of TNT in the presence of interferents of the same chemical family.

Colloidal photoemissive nanoparticles

Nanoparticles possess distinctive properties compared to those of their bulk counterparts. They can be prepared as colloids using molecules which play a key role in their preparation, colloidal stability, functionality, and/or optical features. These molecules can act as solvents, surfactants, reactants and ligands. Photoactive nanoparticles exhibit unique optical features due to the combined effect of their nanometric scale and the derived quantum confinement effect. The degree and type of response to size is related to their composition. They can form either colourless or colourful colloids, emit light either at longer wavelengths than those of the absorbed light (down-conversion luminescence) or at shorter wavelengths (up-conversion luminescence). In addition, the nanostructures can exhibit enhanced properties compared with their bulk counterparts, (for example, superior chemical sensing) due to their intrinsic large surface/volume ratio and their functionality can be further enhanced by ligand exchange or modification. Moreover, the processability of colloidal nanoparticles is crucial to many of their applications, such as for light-emitting devices and in optoelectronics, among other applications.