[en] Highlights: • CsPbBr_3 perovskite nanocrystals have been synthesized in the presence of organic amines with different hydrocarbon length. • The photoluminescence of the CsPbBr_3 nanocrystals is affected by the varying the carbon length of the organic amines. • The lower reaction temperature and hydrocarbon chain length of the organic ligands play a significant role in the self-assembly of CsPbBr_3 nanocrystals. - Abstract: All-inorganic halide perovskites have become one of the most prospective materials for lightening and display technology due to their color-tunable and narrow-band emission. Herein, we have systematically studied the effects of organic amines with different hydrocarbon chain length on the optical properties and morphology as well as the crystal structure of colloidal CsPbBr_3 nanocrystals (NCs), which were synthesized in the presence of oleic acid (OA) and organic amines by using a simple hot-injection approach. The hydrocarbon chain length has shown an independent correlation to the morphology and crystal structure of the as-obtained CsPbBr_3 NCs at 160 °C, but their optical properties can be affected to some extent. The photoluminescence quantum yields (PLQYs) of the CsPbBr_3 NCs synthesized in the presence of organic amines with long carbon chain length are generally in the range of 55–80% for different reaction time, but the PLQYs of less than 20% are obtained for the products synthesized in the presence of octylamine (OTAm) with short carbon chain length. The effects of the reaction temperature on the optical properties, size and crystal structure of the CsPbBr_3 NCs synthesized in the presence of cetylamine (CTAm) are studied. Interestingly, some nanoplates also appear in these CsPbBr_3 NCs obtained at relatively low temperatures (120 and 140 °C), which have a strong tendency to self-assemble into face-to-face nanostructures. Such a similar self-assembly behavior is also observed in the product synthesized in the presence of oleylamine (OLAm), but only flat nanoplates are observed in the products in the presence of OTAm at 120 °C. The results indicate that the lower reaction temperature and hydrocarbon chain length of the organic ligands play a significant role in the self-assembly of CsPbBr_3 NCs. This work opens up an alternative approach to controllable-synthesis of perovskite NCs through varying the carbon chain length of organic surfactants, and enlightens the fabrication of different nanostructures via self-assembly methods for further optoelectronic applications.

[en] Colloidal semiconductor nanocrystals have been extensively used for illumination, displays, bioimaging, and other fields. However, the most extensively used Cd-based nanocrystals are toxic. Recently, non-toxic multinary copper-based chalcogenide semiconductor nanocrystals have been studied intensively. The mostly studied in these materials are ternary Cu–In–S nanocrystals which have large adjustable luminescence range, good luminescence efficiency, and excellent device applications. Therefore, this material has been the most potential candidates to replace Cd-based materials. To date, different synthetic methods have been developed to prepare ternary Cu–In–S nanocrystals, which include hot-injection, non-injection, thermal decomposition, and solvothermal route. In order to enhance the luminescence property, incorporating of Zn²⁺ or overgrowth of a ZnS shell is the comment ways that researchers often use. This review will introduce the synthesis methods of multinary copper-based chalcogenide semiconductor nanocrystals and their potential applications in quantum-dot light-emitting diodes and bioimaging fields. Finally, the conclusion and prospect are provided.

[en] In the past five years, all-inorganic metal halide perovskite (CsPbX₃, X = Cl, Br, I) nanocrystals have been intensely studied due to their outstanding optical properties and facile synthesis, which endow them with potential optoelectronic applications. In order to optimize their physical and chemical properties, different strategies have been developed to realize the controllable synthesis of CsPbX₃ nanocrystals. In this short review, we firstly present a comprehensive and detailed summary of existed synthesis strategies of CsPbX₃ nanocrystals and their analogues. Then, we introduce the regulations of several reaction parameters and their effects on the morphologies of CsPbX₃ nanocrystals. At the same time, we provide stability improvement methods and representative applications. Finally, we propose the current challenges and future perspectives of the promising materials. (paper)

[en] Photocatalytic hydrogen evolution is one of the most promising ways to solve environmental problems and produce a sustainable energy source. To date, different types of photocatalysts have been developed and widely used in photocatalytic hydrogen evolution. Recently, multinary copper chalcogenides have attracted much attention and exhibited potential applications in photocatalytic hydrogen evolution due to their composition-tunable band gaps, diverse structures and environmental-benign characteristics. In this review, some progress on the synthesis and photocatalytic hydrogen evolution of multinary copper chalcogenide nanocrystals (NCs) was summarized. In particular, considerable attention was paid to the rational design and dimensional or structural regulation of multinary copper chalcogenide NCs. Importantly, the photocatalytic hydrogen evolution of multinary copper chalcogenide NCs were reviewed from the aspects of energy level structures, crystal facets, morphology as well as composition. Finally, the current challenges and future perspectives of copper chalcogenide were proposed. (paper)

[en] In this study, electrically bistable devices were fabricated by incorporating cuprous sulfide (Cu₂S) nanospheres with mean size less than 10 nm into a poly(N-vinylcarbazole) (PVK) matrix. A remarkable electrical bistability was clearly observed in the current–voltage curves of the devices due to an electric-field-induced charge transfer between the dodecanethiol-capped Cu₂S nanospheres and PVK. The maximum ON/OFF current ratio reached up to value as large as 10⁴, which was dependent on the mass ratios of Cu₂S nanospheres to PVK, the amplitude of the scanning voltages, and the film thickness. The charge-transport mechanisms of the electrically bistable devices were described on the basis of the experimental results using different theoretical models of organic electronics.

[en] A one-step colloidal process has been adopted to prepare silver (Ag) and silver sulfide (Ag₂S) nanocrystals, thus avoiding presynthesis of an organometallic precursor and the injection of a toxic phosphine agent. During the reaction, a layered intermediate compound is first formed, which then acts as a precursor, decomposing into the nanocrystals. The composition of the as-obtained products can be controlled by selective cleavage of S–C bonds or Ag–S bonds. Pure Ag₂S nanocrystals can be obtained by directly heating silver acetate (Ag(OAc)) and n-dodecanethiol (DDT) at 200 ° C without any surfactant, and pure Ag nanocrystals can be synthesized successfully if the reaction temperature is reduced to 190 ° C and the amount of DDT is decreased to 1 ml in the presence of a non-coordinating organic solvent (1-octadecene, ODE). Otherwise, the mixture of Ag and Ag₂S is obtained by directly heating Ag(OAc) in DDT by increasing the reaction temperature or in a mixture of DDT and ODE at 200 ° C. The formation mechanism has been discussed in detail in terms of selective S–C and Ag–S bond dissociation due to the nucleophilic attack of DDT and the lower bonding energy of Ag–S. Interestingly, some products can easily self-assemble into two- or three-dimensional (2D or 3D) highly ordered superlattice structures on a copper grid without any additional steps. The excess DDT plays a key role in the superlattice structure due to the bundling and interdigitation of the thiolate molecules adsorbed on the as-obtained nanocrystals. (paper)

[en] A simple one-pot method is developed to prepare size- and shape-controlled copper(I) sulfide (Cu₂S) nanocrystals by thermolysis of a mixed solution of copper acetylacetonate, dodecanethiol and oleylamine at a relatively high temperature. The crystal structure, chemical composition and morphology of the as-obtained products are characterized by powder x-ray diffraction (PXRD), x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The morphology and size of the Cu₂S nanocrystals can be easily controlled by adjusting the reaction parameters. The Cu₂S nanocrystals evolve from spherical to disk-like with increasing reaction temperature. The spherical Cu₂S nanocrystals have a high tendency to self-assemble into close-packed superlattice structures. The shape of the Cu₂S nanodisks changes from cylinder to hexagonal prism with prolonged reaction time, accompanied by the diameter and thickness increasing. More interestingly, the nanodisks are inclined to self-assemble into face-to-face stacking chains with different lengths and orientations. This one-pot approach may extend to synthesis of other metal sulfide nanocrystals with different shapes and sizes.

[en] The characterization of Au nanoclusters (AuNCs) on indium-tin-oxide (ITO) substrates fabricated by nanosecond pulsed laser irradiations of thin Au films is reported. By several hundreds of pulsed laser irradiations of 2.5 × 10⁷ W cm⁻² and 5 × 10⁷ W cm⁻² intensity in 1 min, the nanoscale clusters are formed in an ultrafast melting, collecting, growing-up and solidification process of 5, 7.5 and 10 nm Au films. The mean diameter and size distribution of nanoclusters are quantified by the statistical analysis on scanning electron microscopy (SEM) images. The melt dynamics and temperature changes of Au film under pulsed laser irradiation are obtained by quantitative evaluation. The extinction spectra of the initial Au films and formed Au nanoclusters on the ITO surface have also been measured. It has been found that the mean diameter, the surface density and extinction spectra of the induced AuNCs are influenced by the thickness of Au films and the laser intensity. The evolutional mechanism of the nanoscale clusters formation is discussed by the comparison on the morphology of the Au films with and without laser irradiations.

[en] Wurtzite CuInS₂ nanoplates have been synthesized using a simple one-pot colloidal chemical method, which is a direct heating process without any injection and pre-synthesis of any metal precursors. The transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) have been employed to characterize their morphology, crystalline phase, and composition, respectively. By changing the reaction conditions, such as reaction time, reaction temperatures and the Cu:In precursors ratio, the nanoplate thickness and composition can be tailored effectively. By monitoring the growth process of the as-obtained CuInS₂ nanoplates, it found that the monoclinic Cu_1.94S nanocrystals were firstly formed and gradually transformed to CuInS₂ nanoplates with the increasing reaction time.

[en] Organic light-emitting diodes were fabricated with a structure of indium-tin-oxide (ITO)/poly(N-vinylcarzole)(PVK):4-(dicyanom-ethylene)-2-t-butyl-6-(1,1,7, 7-tet= ramethyljulolidyl-9-enyl)-4H-pyran (DCJTB)/8-tris-hydroxyquinoline aluminum (Alq₃)/lithium fluoride (LiF)/Al. The energy transfer from PVK to Alq₃ then to DCJTB and the charge trapping processes were investigated by employing the photoluminescence (PL) and electroluminescence (EL) spectra. With increasing thickness of the Alq₃ layer, the PL and EL emission from PVK were decreased gradually, which indicated that the effective energy transfer occurred from PVK to Alq₃ and then from Alq₃ to DCJTB. At the same time, we found that the exciton recombination zone could be adjusted by controlling the Alq₃ layer thickness and the applied voltages. The effects of different DCJTB concentrations on the optical and electrical characteristics of the devices were investigated, and an obvious red-shift was observed with the DCJTB dopant concentrations increasing in the PL and EL spectra