Herein, we describe simple, fast and reproducible halide ion exchange reactions in CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) at room temperature. Through the simple adjustment of the halide ion concentration, the photoluminescence of these NCs can be tuned over the entire visible region (425-655 nm). Photodetector devices based on entirely inorganic CsPbI3 NCs are demonstrated for the first time. The photodetectors exhibited a good on/off photocurrent ratio of 10(5).

Synthesis of cadmium (Cd)-free quantum dots (QDs) with tunable emission and high color purity has been a big challenge for the academic and industrial research community. Among various Cd-free QDs, indium phosphide (InP) QDs exhibit reasonably good color purity with emission full width at half-maximum (fwhm) values between 45 and 50 nm for green and over 50 nm for red emission, which is not good enough, as values less than 35 nm are favorable in commercial display products. In this work, we present the synthesis of highly luminescent In­(Zn)­P/ZnSe/ZnS QDs with tunable emission from 488 to 641 nm and high color purity. We found that the addition of zinc during the conventional SILAR growth of shell (ZnSe or ZnS) deteriorated the absorption features of core InP QDs and resulted in broader emission line widths. We solved this issue by synthesizing Zn carboxylate covered In­(Zn)P QDs in a single step and dramatically decreased the emission fwhm to as low as 36 nm with quantum yields (QYs) up to 67% for the green emitting QDs. We also demonstrate an effective successive ion layer adsorption and reaction method to continuously tune the InP QDs size from 1.6 to 3.6 nm with narrow size distribution. This enables us to tune the emission up to 641 nm with fwhm values less than 45 nm and QY up to 56% for red emission. This is the first report on the synthesis of InP QDs with such high color purity. In addition, the obtained QDs show exceptional stability under air (>15 days) and heat treatment (150 °C in air for 24 h). Given the difficulty in synthesizing size tunable InP QDs with narrow emission fwhm and high quantum yield, the results presented here are an important step toward the realization of Cd-free QDs as a feasible alternative in commercial display technologies.

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We demonstrate a highly sensitive hybrid photodetector based on graphene–CsPbBr3−xIx perovskite nanocrystals.

High-sensitivity photodetectors are reported using solution synthesized GeS and GeSe nanosheets.

The visible green and red upconversion emissions in Er(3+)/Yb(3+) doped β-NaGdF4 nanoparticles were enhanced by tridoping with Fe(3+) ions (0-40 mol%). XRD, XPS, ICP-AES and EDS data demonstrated successful incorporation of Fe(3+) ions in NaGdF4:Yb(3+)/Er(3+) nanoparticles. The effect of Fe(3+) tridoping on the upconversion luminescence in NaGdF4:Yb(3+)/Er(3+) NPs was investigated in detail. The green and red emission intensities were enhanced by 34 and 30 times, respectively. The maximum emission was observed in a sample containing 30 mol% Fe(3+) ions. A possible mechanism for the enhanced upconversion emission is proposed. In addition, a layer of silica was coated onto the surface of UCNPs to improve the biocompatibility. Folic acid was covalently linked to the silica coated UCNPs to form UCNP@SiO2-FA nanoprobes, which have been successfully applied to the fluorescent imaging HeLa cells.

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We demonstrate that the presence of a small amount of water as an impurity during the hot-injection synthesis can significantly decrease the emission lines full width at half-maximum (FWHM) and improve the quantum yield (QY) of InP/ZnS quantum dots (QDs). By utilizing the water present in the indium precursor and solvent, we obtained InP/ZnS QDs emitting around 530 nm with a FWHM as narrow as 46 nm and a QY up to 45%. Without water, the synthesized QDs have emission around 625 nm with a FWHM of 66 nm and a QY of about 33%. Absorption spectra, XRD and XPS analyses revealed that when water is present, an amorphous phosphate layer is formed over the InP QDs and inhibits the QD growth. This amorphous layer favors the formation of a very thick ZnS shell by decreasing the lattice mismatch between the InP core and the ZnS shell. We further show the possibility to tune the emission wavelengths of InP/ZnS QDs by simply adjusting the amount of water present in the system while keeping all the other reaction parameters (i.e., precursor concentration, reaction temperature and time) constant. As an example of their application in light-emitting diodes (LEDs), the green and red InP/ZnS QDs are combined with a blue LED chip to produce white light.