Heat-Up Colloidal Synthesis of Shape-Controlled Cu-Se-S Nanostructures-Role of Precursor and Surfactant Reactivity and Performance in N Electroreduction

Copper selenide-sulfide nanostructures were synthesized using metal-organic chemical routes in the presence of Cu- and Se-precursors as well as S-containing compounds. Our goal was first to examine if the initial Cu/Se 1:1 molar proportion in the starting reagents would always lead to equiatomic composition in the final product, depending on other synthesis parameters which affect the reagents reactivity. Such reaction conditions were the types of precursors, surfactants and other reagents, as well as the synthesis temperature. The use of 'hot-injection' processes was avoided, focusing on 'non-injection' ones; that is, only heat-up protocols were employed, which have the advantage of simple operation and scalability. All reagents were mixed at room temperature followed by further heating to a selected high temperature. It was found that for samples with particles of bigger size and anisotropic shape the CuSe composition was favored, whereas particles with smaller size and spherical shape possessed a CuSe phase, especially when no sulfur was present. Apart from elemental Se, AlSe was used as an efficient selenium source for the first time for the acquisition of copper selenide nanostructures. The use of dodecanethiol in the presence of trioctylphosphine and elemental Se promoted the incorporation of sulfur in the materials crystal lattice, leading to Cu-Se-S compositions. A variety of techniques were used to characterize the formed nanomaterials such as XRD, TEM, HRTEM, STEM-EDX, AFM and UV-Vis-NIR. Promising results, especially for thin anisotropic nanoplates for use as electrocatalysts in nitrogen reduction reaction (NRR), were obtained

Ultrafast exciton dynamics in CdxHg(1-x)Te alloy quantum dots

Ultrafast transient absorption spectroscopy is used to investigate sub-nanosecond exciton dynamics in CdxHg(1−x)Te alloy colloidal quantum dots. A bleach was observed at the band gap due to state-filling, the mono-exponential decay of which had a characteristic lifetime of 91 ± 1 ps and was attributed to biexciton recombination; no evidence of surface-related trapping was observed. The rise time of the bleach, which is determined by the rate at which hot electrons cool to the band-edge, ranged between 1 and 5 ps depending on the pump photon energy. Measuring the magnitude of the bleach decay for different pump fluences and wavelengths allowed the quantum yield of multiple exciton generation to be determined, and was 115 ± 1% for pump photons with energy equivalent to 2.6 times the band gap

Amine-Terminated Water-Dispersible FePt Nanoparticles

Chemically disordered face-centered cubic FePt nanoparticles (NPs) were synthesized via pyrolysis of iron(III)ethoxide and platinum(II)acetylacetonate. The surface ligands of these NPs were then exchanged from oleic acid to 2-aminoethanethiol (AET). The AET-capped FePt NPs were found to be well dispersed in water when pH<8, and the zeta potential was more than +30 mV when pH≤7

Theoretical Assessment of FePt Nanoparticles as Heating Elements for Magnetic Hyperthermia

FePt magnetic nanoparticles (MNPs) are expected to be a high-performance nanoheater for magnetic hyperthermia because of their high Curie temperature, high saturation magnetization, and high chemical stability. Here, we present a theoretical performance assessment of chemically disordered fcc-phase FePt MNPs. We calculate heat generation and heat transfer in the tissue when an MNP-loaded tumor is placed on an external alternating magnetic field. For comparison, we estimate the performances of magnetite, maghemite, FeCo, and L1_0-phase FePt MNPs. We find that an fcc FePt MNP has a superior ability in magnetic hyperthermia

Photoinduced fluorescence intensity oscillation in a reaction-diffusion cell containing a colloidal quantum dot dispersion

The nonlinear spontaneous oscillation of photoluminescence (PL) intensity in an ensemble of semiconductor quantum dots (QDs), which differs from the fluorescence intermittency of a single QD, is investigated. The PL intensity in a QD dispersion slowly oscillates with time under continuous illumination. The oscillatory behavior is found to vary with changing QD concentration, solvent viscosity, volume fraction of irradiated region, and irradiation intensity. On the basis of the Gray-Scott model [Chemical Oscillation and Instabilities: Non-linear Chemical Kinetics (Clarendon, Oxford, 1994); J. Phys. Chem. 89, 22 (1985); Chem. Eng. Sci. 42, 307 (1987)], and its comparison with the experimental results, it is revealed that the following processes are important for PL oscillation: (1) mass transfer of QDs between the illuminated and dark regions, (2) autocatalytic formation of vacant sites on QD surfaces via photodesorption of ligand molecules, and (3) passivation of vacant sites via photoadsorption of water molecules

Intensified Blinking, Continuous Memory Loss, and Fluorescence Enhancement of Interacting Light-Emission Quantum Dots

We propose a microscopic quantum-mechanical model for describing the nonstochastic dynamics of the nanoscopic light-emissive quantum dot. The model is extended beyond a single quantum dot to consider the Coulomb repulsion between neighboring quantum dots in the ionic states caused by the random fluctuations of charge carriers. We find that the interaction gives rise to intensified blinking intermittency, continuous memory loss of the dynamics, and fluorescence enhancement in an ensemble of light-emissive quantum dots, which explains the recent experimental results. Our findings clarify the nature of the interaction underlying in the ensemble

Synthesis of High-Quality Al-Doped ZnO Nanoink

Al-doped ZnO (AZO) nanoparticles (NPs) have been synthesized via the thermal decomposition of metal acetylacetonate precursors in a nonoxygen and nonpolar solvent. Long-chain alkyl amines have been utilized to terminate the growth of AZO NPs and to stabilize them. The NPs have been characterized by a number of techniques as monocrystalline, exhibiting a hexagonal (wurtzite) structure with sizes from 8 to 13 nm. The composition of Al in the resulting NP is related solely to the composition of the reaction mixture and the size is controllable with the temperature of the reaction. The AZO NP dispersion has been proven to be stable over a 24 h period by dynamic light scattering measurements. The influence of the synthetic conditions, such as temperature, reaction time and the Al doping content, on the properties of NPs have also been investigated. An optically transparent AZO thin film was fabricated using the AZO nanoink by spin casting followed by annealing. The resulting film resistivity was measured to be 5.0×10^ Ω cm

MUTAGENICITY OF WATER-SOLUBLE FePt NANOPARTICLES IN AMES TEST

A mutagenicity test was conducted on water-soluble FePt nanoparticles capped with tetramethylammonium hydroxide in a bacterial reverse mutation assay using Salmonella typhimurium strains TA98, TA100, TA1535 and TA1537, and Escherichia coli strain WP2uvrA/pKM101, with and without metabolic activation by S9 mix in the preincubation method. Mutagenicity was weakly positive in the TA100 strain without S9 mix (maximum specific activity was 61.6 revertants/mg), but negative in other cases

Evaluation of genotoxicity of amine-terminated water-dispersible FePt nanoparticles in the Ames test and in vitro chromosomal aberration test

Genotoxicity of superparamagnetic iron-platinum (FePt) nanoparticles (NPs) capped with 2-aminoethanethiol (AET) was evaluated using the bacterial reverse mutation assay (Ames test) and in vitro chromosomal aberration test. Mutagenicity of AET-capped FePt NPs was found to be negative in the Ames test, while clastogenicity of FePt NPs seemed to be false-positive in the in vitro chromosomal aberration test using Chinese hamster lung fibroblast cells. However, further detailed in vitro genotoxicity tests, such as DNA adduct studies, are necessary to conclude that a positive aberration result is irrelevant