A robust and reproducible methodology to prepare stable inorganic nanoparticles with chiral morphology may hold the key to the practical utilization of these materials. An optimized chiral growth method to prepare fourfold twisted gold nanorods is described herein, where the amino acid cysteine is used as a dissymmetry inducer. Four tilted ridges are found to develop on the surface of single‐crystal nanorods upon repeated reduction of HAuCl4, in the presence of cysteine as the chiral inducer and ascorbic acid as a reducing agent. From detailed electron microscopy analysis of the crystallographic structures, it is proposed that the dissymmetry results from the development of chiral facets in the form of protrusions (tilted ridges) on the initial nanorods, eventually leading to a twisted shape. The role of cysteine is attributed to assisting enantioselective facet evolution, which is supported by density functional theory simulations of the surface energies, modified upon adsorption of the chiral molecule. The development of R‐type and S‐type chiral structures (small facets, terraces, or kinks) would thus be non‐equal, removing the mirror symmetry of the Au NR and in turn resulting in a markedly chiral morphology with high plasmonic optical activity.

The natural chalcopyrite mineral CuFeS 2 is a semi-conductor material with potential for thermoelectric applications. This study presents the thermoelectric properties -electrical resistivity ρ, Seebeck coefficient S and thermal conductivity κ -of the substituted on the Cu site and/or sulfur deficiency CuFeS 2 chalcopyrite based series Cu 1-x M x FeS 2-y (M = Mn, Co,Ni, x ≤ 0.05 and y ≤ 0.02). All samples have been densified by Spark Plasma Sintering, allowing proper measurements of S, ρ and κ at high temperature. All compounds show n-type semi-conducting properties with large absolute values of S, from -220 to -340 µV.K -1 . Maximum ZT values up to 0.20 at 623 K were obtained for Cu 0.97 Mn 0.03 FeS 2 and Cu 0.98 Co 0.02 FeS 1.98 . The veracity of Mn for Cu substitution into the structure has been confirmed by EDS analyzes, coupled to electron diffraction within a transmission electron microscope. The latter study demonstrates the existence of twinned domains. The thermal conductivity reaches values as low as κ~1.2 W.m -1 .K -1 at 623 K. Magnetic properties of a Mn substituted sample did not show any significant modification in the magnetic behavior compared to the pristine CuFeS 2 compound. The small negative magnetoresistance observed in CuFeS 2 of about -2% at 5 K in 9 T is degraded in the Mn substituted sample. Cu 0.94 Mn 0.06 FeS 2 in terms of charge, Mn would be then 4+ charged. ZT are given in Fig. 8d, the highest ZT is found for Cu 0.98 Co 0.02 FeS 1.98 with ZT = 0.20 at 623 K. This value is similar with the previously reported Cu 0.94 Co 0.06 FeS 2 . It is found at 623 K that the resistivity and the Seebeck coefficient of Cu 0.98 Co 0.02 FeS 1.98 and Cu 0.94 Co 0.06 FeS 2 were comparable, with │S│= 247 and 240 µV.K -1 and ρ = 0.95 and 1.05 mΩ.cm, respectively.Conclusion SPS process optimization and substitution/deficiency study on the Cu 1-x M x FeS 2-y series with M = Mn, Co, Ni; x ≤ 0.05 and y ≤ 0.02 have been successfully carried out. In these substitutions ranges, the chalcopyrite is formed without significant amount of impurities.Among the three transition metals: Co, Ni and Mn, the solid solution with Mn has been more

Chiral plasmonics is a rapidly developing field where breakthroughs and unsolved problems coexist. We have recently reported binary surfactant-assisted seeded growth of chiral gold nanorods (Au NRs) with high chiroptical activity. Such a seeded-growth process involves the use of a chiral cosurfactant that induces micellar helicity, in turn driving the transition from achiral to chiral Au NRs, from both the morphological and the optical points of view. We report herein a detailed study on both transitions, which reveals intermediate states that were hidden so far. The correlation between structure and optical response is carefully analyzed, including the (linear and CD) spectral evolution over time, electron tomography, the impact of NR dimensions on their optical response, the variation of the absorption-to-scattering ratio during the evolution from achiral to chiral Au NRs, and the near-field enhancement related to chiral plasmon modes. Our findings provide further understanding of the growth process of chiral Au NRs and the associated optical changes, which will facilitate further study and applications of chiral nanomaterials.

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The development of optical nanothermometers operating in the near-infrared (NIR) is of high relevance toward temperature measurements in biological systems. We propose herein the use of Nd 3+ -doped lanthanum oxychloride nanocrystals as an efficient system with intense photoluminescence under NIR irradiation in the first biological transparency window and emission in the second biological window with excellent emission stability over time under 808 nm excitation, regardless of Nd 3+ concentration, which can be considered as a particular strength of our system. Additionally, surface passivation through overgrowth of an inert LaOCl shell around optically active LaOCl/Nd 3+ cores was found to further enhance the photoluminescence intensity and also the lifetime of the 1066 nm, 4 F 3/2 to 4 I 11/2 transition, without affecting its (ratiometric) sensitivity toward temperature changes. As required for biological applications, we show that the obtained (initially hydrophobic) nanocrystals can be readily transferred into aqueous solvents with high, long-term stability, through either ligand exchange or encapsulation with an amphiphilic polymer.

Environmental conditions during real‐world application of bimetallic core–shell nanoparticles (NPs) often include the use of elevated temperatures, which are known to cause elemental redistribution, in turn significantly altering the properties of these nanomaterials. Therefore, a thorough understanding of such processes is of great importance. The recently developed combination of fast electron tomography with in situ heating holders is a powerful approach to investigate heat‐induced processes at the single NP level, with high spatial resolution in 3D. In combination with 3D finite‐difference diffusion simulations, this method can be used to disclose the influence of various NP parameters on the diffusion dynamics in Au@Ag core–shell systems. A detailed study of the influence of heating on atomic diffusion and alloying for Au@Ag NPs with varying core morphology and crystallographic details is carried out. Whereas the core shape and aspect ratio of the NPs play a minor role, twin boundaries are found to have a strong influence on the elemental diffusion.