[en] Square plate shaped magnetite nanocrystals have been synthesized by chemical precipitation from solution using arabinogalactan. A high crystal quality was observed in the plate plane while, across the plate, there is some stratification. The magnetic hysteresis in such particles is determined by the bulk magnetocrystalline anisotropy, plate shape anisotropy, and surface magnetic anisotropy. It is shown using the micromagnetic simulation that the ferromagnetic square nanoplates exhibit the extraordinary magnetization switching anisotropy, which should be taken into account for understanding the hysteretic properties of the particles.

[en] To utilise the full potential of CsPbBr₃ perovskite nanocrystals as optoelctronic material, we have studied the dynamics of recombination of photo-generated charge carriers by probing the photoluminescence blinking of single NCs. Our study reveals that three kinds of recombination processes contribute to the blinking behavior of the NC. Tetrafluoroborate salt treatment leads to suppression of blinking by elimination of undesired recombination processes. (author)

[en] Samba is a Xenopus hnRNP that was recently identified and has been shown to inhibit animal cap spreading and affect neural crest migration. It is expressed in all developmental stages and the expression appears elevated during neurula stages. At early neurula stages Samba is concentrated at the neural plate and later in the neural and neural crest tissues. At tail bud stages it is restricted in neural and neural crest derivatives including the brain, the spinal cord, the eyes and the brachial arches. Here we examined the protein localization at the cellular and embryonic level and also explored the role of the protein during development. We show that the protein is localized in the nucleus, the cytoplasm and the plasma membrane. It becomes associated with microtubules during mitosis and it is transported in axons. We also show using FRAP and FLIP that Samba shuttles between the cytosol and the nucleus consistent with a role as an hnRNP. Loss of function experiments using antisense Morpholinos leads to defective neural development in agreement with the elevated expression of Samba in neural tissues. However, we also show that the Morpholino down regulates the splice variant 40LoVe and a paralog, hnRNP AB, which shares 93% identity with 40Love. Despite the high homology between 40LoVe/Samba and hnRNP AB, the proteins localize in distinct manners suggesting distinct functions in the embryo. We map the differences between the two proteins to the c-terminus and show that the neural phenotype is a consequence of 40LoVe/Samba downregulation arriving at the surprising conclusion that 40LoVe/Samba and hnRNP AB despite their extremely high homology are in fact functionally distinct. The aforementioned project required the application of advanced imaging modalities including the use of fluorescent protein fusions for live imaging, FRAP and FLIP and highlighted the limitations of protein fluorophores with respect to photostability and brightness. Quantum Dots (QDs) are nanometer semiconductor nanocrystals with ideal optical properties for use in biological imaging. However no methodologies exist that will allow the covalent and site specific conjugation of QDs to target proteins in vivo. The second part of this thesis focused on developing a methodology that would resolve these issues. We describe an intein based method to site-specifically conjugate QDs to target proteins in vivo. This approach allows the covalent conjugation of any nanostructure and/or nanodevice to any protein and thus the targeting of such material to any intracellular compartment or signaling complex within the cells of the developing embryo. The C-terminus half (IC) of the intein was conjugated to QDs in vitro. IC-QD's and RNA encoding PH-IN were microinjected into Xenopus embryos. In vivo intein-splicing resulted in fully functional QD-PH conjugates that could be monitored in real time within live embryos. Use of Near Infra Red (NIR)-emitting QDs allowed monitoring of QD-conjugates within the embryo at depths where EGFP is undetectable demonstrating the advantages of QD's for this type of experiment. (author)

[en] Pb(Zr_0.52Ti_0.48)O₃ nanocrystals were synthesized by a hydrothermal method. The poly(vinyl pyrrolidone) (PVP) was used as the surfactant to control growth of the Pb(Zr_0.52Ti_0.48)O₃ nanocrystals. The effect of PVP concentration, reaction temperature and time on morphologies and crystallinity of Pb(Zr_0.52Ti_0.48)O₃ nanocrystals were investigated. The tetragonal PbZr_0.52Ti_0.48O₃ grains were obtained, as they were prepared at 200 °C for 4 h with PVP concentration from 0.1 to 10.0 g/L. With increasing the PVP concentration from 0.1 to 10.0 g/L, the size of PbZr_0.52Ti_0.48O₃ grains decreased. When the PbZr_0.52Ti_0.48O₃ grains were prepared at 200 °C for 12 h with PVP concentration of 6.0 g/L, the PbZr_0.52Ti_0.48O₃ nanocrystals with average diameter of 30 nm were formed.

[en] Highlights: • Creation of a 3D exact copy of a nanostructure. • No connection between crystal type with the morphology of nanostructure. • Used to prepare single crystal silver nanorods for visible plasmonics. In most template directed preparative methods, while the template decides the nanostructure morphology, the structure of the template itself is a non-general outcome of its peculiar chemistry. Here we demonstrate a template mediated synthesis that overcomes this deficiency. This synthesis involves overgrowth of silica template onto a sacrificial nanocrystal. Such templates are used to copy the morphologies of gold nanorods. After template overgrowth, gold is removed and silver is regrown in the template cavity to produce a single crystal silver nanorod. This technique allows for duplicating existing nanocrystals, while also providing a quantifiable breakdown of the structure – shape interdependence.

[en] In the present paper, we have investigated the effects of reaction temperature and duration of reaction on the properties of hydrothermally derived nano-crystalline Cu₂SnSe₃ (CTSe) powder. We report here for the first time, the morphology dependent photocatalytic performance of CTSe nanocrystals, which was analyzed by monitoring the photo-degradation of methylene blue (MB) dye under visible light irradiation. The reaction temperature and time was found to greatly influence the morphology of the nano-crystals, which consisted of flakes, discs or sheets in the nanometer range, depending upon the experimental conditions. Nanoflakes with rough surfaces degrade 73% of the dye in 3 h of light irradiation thus showing that highly crystalline CTSe nanocrystals having rough surfaces have the highest photocatalytic activity. (paper)

[en] Highlights: • The nanocrystals were synthesized by direct injection of precursors into toluene. • The oleylamine to perovskite ratio (OPR) controls morphology and optical properties. • The size of unit cells of CH₃NH₃PbBr₃ nanocrystals can be varied by increasing OPR. • Possible formation mechanism for nanocrystals by different OPR values was suggested. Methylammonium lead bromide (CH₃NH₃PbBr₃) nanocrystals have great potentials for lighting and display applications. Previously we synthesized CH₃NH₃PbBr₃ nanocrystals using oleylamine as capping molecule and found that by increasing the oleylamine to CH₃NH₃PbBr₃ perovskite ratio (OPR), the photoluminescence wavelengths and morphology of CH₃NH₃PbBr₃ nanocrystals could be varied from 530 nm (green) platelets to 460 nm (blue) particles. Here we modified the synthesis to direct injection of precursors into toluene and found that increasing OPR not only changes the wavelength and morphology of nanocrystals but also the size of the unit cells.

[en] Light is one of the endemic forms of energy which decides the advancement of the human civilization. More than 20% of the electrical energy output of the world is invested for light harvesting. Phosphor based light emitting diodes (LEDs) are one of the key participants to play the pronounced role in this regard. Performance of an LED is principally dictated by the luminescence efficiency of its emissive layer. Considerable attention has been paid to increase its luminescence efficiency in recent decades by fabricating the emissive layer with several semiconductor materials and quantum dots. Regarding this aspect, small molecular ligand protected luminescent copper nanoclusters (SLCuNC) have emerged as one of the prospective candidates owing to its potential applicability over the field of optoelectronics and photosensitization

[en] Highlights: • We firstly obtained CsPbCl₃ NCs at room temperature. • The spectral bandgap of as-prepared blue CsPbCl_3−xBr_x (x = 0.0–2.5) NCs can be precisely regulated from 2.54 to 3.06 eV. • The NCs showed high PLQY and exhibited excellent stability. -- Abstract: With the development of blue-emitting all-inorganic Pb-based perovskite nanocrystals (NCs), the perovskite family (e.g., CsPbCl_3−xBr_x NCs) has drawn researchers’ attention. Although the hot injection method has been widely used to fabricate blue-emitting perovskite NCs, this synthesis method generally needs an inert gas atmosphere, high temperature, and localized injection operation, leading to high cost and limiting the applications of perovskite NCs. Herein, we synthesized mixed-halide blue-emitting CsPbCl_3−xBr_x (x = 0.0–2.5) perovskite NCs rapidly at room temperature. The as-prepared perovskite NCs exhibited excellent stability and high photoluminescence quantum yields up to 89% because of their low non-radiative recombination rate. The photoluminescence wavelength of the NCs was precisely regulated across the whole visible region (406–488 nm). Importantly, this facile method to synthesize perovskite NCs not only requires mild experimental conditions, dramatically lowering the cost of synthesis, but also provides a feasible route for the industrial production of efficient blue-emitting devices.

[en] Polyethylene (PE) telechelics with carboxylate functional groups at both ends have been shown to assemble into hexagonal nanocrystal platelets with a height defined by their chain length in basic CsOH-solution. In this coarse grained (CG) simulation study we show how properties of the functional groups alter the aggregation and crystallization behavior of those telechelics. Systematic variation of the parameters of the CG model showed that important factors which control nanoparticle stability and structure are the PE chain length and the hydrophilicity and the steric demand of the head groups. To characterize the aggregation process we analyzed the number and size of the obtained aggregates as well as intramolecular order and intermolecular alignment of the polymer chains. By comparison of CG and atomistic simulation data, it could be shown that atomistic simulations representing different chemical systems can be emulated with specific, different CG parameter sets. Thus, the results from the (generic) CG simulation models can be used to explain the effect of different head groups and different counterions on the aggregation of PE telechelics and the order of the obtained nanocrystals. (paper)