We synthesize colloidal nanocrystals (NCs) of Rb 3 InCl 6 , composed of isolated metal halide octahedra (“0D”), and of Cs 2 NaInCl 6 and Cs 2 KInCl 6 double perovskites, where all octahedra share corners and are interconnected (“3D”), with the aim to elucidate and compare their optical features once doped with Sb 3+ ions. Our optical and computational analyses evidence that the photoluminescence quantum yield (PLQY) of all these systems is consistently lower than that of the corresponding bulk materials due to the presence of deep surface traps from under-coordinated halide ions. Also, Sb-doped “0D” Rb 3 InCl 6 NCs exhibit a higher PLQY than Sb-doped “3D” Cs 2 NaInCl 6 and Cs 2 KInCl 6 NCs, most likely because excitons responsible for the PL emission migrate to the surface faster in 3D NCs than in 0D NCs. We also observe that all these systems feature a large Stokes shift (varying from system to system), a feature that should be of interest for applications in photon management and scintillation technologies. Scintillation properties are evaluated via radioluminescence experiments, and re-absorption-free waveguiding performance in large-area plastic scintillators is assessed using Monte Carlo ray-tracing simulations.

We devised a hot-injection synthesis to prepare colloidal double-perovskite Cs 2 NaBiCl 6 nanocrystals (NCs). We also examined the effects of replacing Na + with Ag + cations by preparing and characterizing Cs 2 Na 1– x Ag x BiCl 6 alloy NCs with x ranging from 0 to 1. Whereas Cs 2 NaBiCl 6 NCs were not emissive, Cs 2 Na 1– x Ag x BiCl 6 NCs featured a broad photoluminescence band at ∼690 nm, Stokes-shifted from the respective absorption by ≥1.5 eV. The emission efficiency was maximized for low Ag + amounts, reaching ∼3% for the Cs 2 Na 0.95 Ag 0.05 BiCl 6 composition. Density functional theory calculations coupled with spectroscopic investigations revealed that Cs 2 Na 1– x Ag x BiCl 6 NCs are characterized by a complex photophysics stemming from the interplay of (i) radiative recombination via trapped excitons localized in spatially connected AgCl 6 –BiCl 6 octahedra; (ii) surface traps, located on undercoordinated surface Bi centers, behaving as phonon-assisted nonradiative decay channels; and (iii) a thermal equilibrium between trapping and detrapping processes. These results offer insights into developing double-perovskite NCs with enhanced optoelectronic efficiency.

We report here the synthesis of undoped and Cu-doped Cs2ZnCl4 nanocrystals (NCs), in which we could tune the concentration of Cu from 0.7% to 7.5%. According to electron paramagnetic resonance analysis, in 0.7% and 2.1% Cu-doped NCs the Cu ions were present in the +1 oxidation state only, while in NCs at higher Cu concentrations we could detect Cu(II) ions. The undoped Cs2ZnCl4 NCs were non emissive, while the Cu-doped samples had a bright intra-gap photoluminescence (PL) at 2.6eV mediated by band-edge absorption. The PL quantum yield was maximum (~55%) for the samples with low Cu concentration (≤ 2.1%) and it systematically decreased when further increasing the concentration of Cu, reaching 15% for the NCs with the highest doping level (7.5%). Density functional theory calculations indicated that the PL emission could be ascribed only to Cu(I) ions: these ions introduce intra-gap states that promote the formation of selftrapped excitons, through which an efficient emission takes place.

The most developed approaches for the synthesis of InAs nanocrystals (NCs) rely on pyrophoric, toxic, and not readily available tris-trimethylsilyl (or tris-trimethylgermil) arsine precursors. Less toxic and commercially available chemicals, such as tris(dimethylamino)arsine, have recently emerged as alternative As precursors. Nevertheless, InAs NCs made with such compounds need to be further optimized in terms of size distribution and optical properties in order to meet the standard reached with tristrimethylsilyl arsine. To this aim, in this work we investigated the role of ZnCl 2 used as an additive in the synthesis of InAs NCs with tris(dimethylamino)arsine and alane N,N-dimethylethylamine as the reducing agent. We discovered that ZnCl 2 helps not only to improve the size distribution of InAs NCs but also to passivate their surface acting as a Z-type ligand. The presence of ZnCl 2 on the surface of the NCs and the excess of Zn precursor used in the synthesis enable the subsequent in situ growth of a ZnSe shell, which is realized by simply adding the Se precursor to the crude reaction mixture. The resulting InAs@ZnSe core@shell NCs exhibit photoluminescence emission at ∼860 nm with a quantum yield as high as 42±4%, which is a record for such heterostructures, given the relatively high mismatch (6%) between InAs and ZnSe. Such bright emission was ascribed to the formation, under our peculiar reaction conditions, of an In−Zn−Se intermediate layer between the core and the shell, as indicated by X-ray photoelectron spectroscopy and elemental analyses, which helps to release the strain between the two materials.

The localized surface plasmonic resonance absorption wavelength can be tuned effectively by varying the crystal structure, morphology and surface ligands, which can be manipulated by varying the Cu : S precursor ratios and the post-treatment temperature by dodecanethiol.

2D CuGaS2 nanoplates exhibit an improved photocatalytic hydrogen activity as compared to 1D nanorods and quasi-2D nanodisks.

Ternary alloyed Cu2–x S y Se1–y nanocrystals (NCs) were synthesized by using a simple and phosphine-free colloidal approach, in which sulfur powder and 1-dodecanethiol (DDT) were used as sulfur sources. In both cases, the crystal phase transformed from cubic berzelianite to monoclinic djurleite structure together with the morphology evolution from quasi-triangular to spherical or discal with an increase of sulfur content. Accordingly, the near-infrared (NIR) localized surface plasmon resonance (LSPR) absorption of the as-obtained sulfur-rich NCs exhibited obvious red-shift of wavelength and widening of absorption width. When the sulfur powder was chosen as sulfur sources, the LSPR wavelength of the as-obtained alloyed Cu2–x S y Se1–y NCs could be tuned from 975 to 1230 nm with a decrease of selenium content in the NCs. In contrast, the region of the red-shift could be up to 1250 nm for the alloyed NCs synthesized by incorporation of different DDT dosage into the reaction system. The different sulfur sources and the electron donating effects of the DDT as a ligand played an important role in the LSPR absorption tuning. This deduction could be testified by the post-treating the quasi-triangular Cu2–x Se NCs with DDT under different temperatures and over different reaction time, which exhibited a red-shift of LSPR wavelength up to 450 nm due to coordination of DDT to Cu atoms on the NC surface while incorporating some sulfur anions into the lattice. This study offers a convenient tool for tuning the LSPR absorption of copper chalcogenide NCs and makes them for application in biological and optoelectronic fields.

We demonstrate efficient, stable, and fully RoHS-compliant nearinfrared (NIR) light-emitting diodes (LEDs) based on InAs/ZnSe quantum dots (QDs) synthesized by employing a commercially available amino-As precursor. They have a record external quantum efficiency of 5.5% at 947 nm and an operational lifetime of ∼32 h before reaching 50% of their initial luminance. Our findings offer a new solution for developing RoHS-compliant light-emitting technologies based on Pb-free colloidal QDs.