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Understanding light-matter interactions in nanomaterials is crucial for optoelectronic, photonic, and plasmonic applications. Specifically, metal nanoparticles (NPs) strongly interact with light and can undergo shape transformations, fragmentation and ablation upon (pulsed) laser excitation. Despite being vital for technological applications, experimental insight into the underlying atomistic processes is still lacking due to the complexity of such measurements. Herein, atomic resolution electron tomography is performed on the same mesoporous-silica-coated gold nanorod, before and after femtosecond laser irradiation, to assess the missing information. Combined with molecular dynamics (MD) simulations based on the experimentally determined 3D atomic-scale morphology, the complex atomistic rearrangements, causing shape deformations and defect generation, are unraveled. These rearrangements are simultaneously driven by surface diffusion, facet restructuring, and strain formation, and are influenced by subtleties in the atomic distribution at the surface.

Alloyed metal nanorods offer a unique combination of enhanced plasmonic and photothermal properties with a wide variety in optical and catalytic properties as a function of the alloy composition. Here, we show that fully alloyed anisotropic nanoparticles can be obtained with complete retention of the particle shape via thermal treatment at surprisingly low temperatures. By coating Au-Ag, Au-Pd and Au-Pt core-shell nanorods with a protective mesoporous silica shell the transformation of the rods to a more stable spherical shape was successfully prevented during alloying. For the Au-Ag core-shell NRs the chemical stability was drastically increased after alloying, and from Mie-Gans and finite-difference time-domain (FDTD) calculations it followed that alloyed AuAg rods also exhibit much better plasmonic properties than their spherical counterparts. Finally, the generality of our method is demonstrated by alloying Au-Pd and Au-Pt core-shell NRs, whereby the AuPd and AuPt alloyed NRs showed a surprisingly high increase in thermal stability of several hundred degrees compared with monometallic silica coated Au NRs.

Composite noble metal-based nanorods for which the surface plasmon resonances can be tuned by composition and geometry are highly interesting for applications in biotechnology, imaging, sensing, optoelectronics, photovoltaics, and catalysis. Here, we present an approach for the oxidative etching and subsequent metal overgrowth of gold nanorods, all taking place while the nanorods are embedded in mesoporous SiO2 shells (AuNRs@meso-SiO2). Heating of the AuNRs@meso-SiO2 in methanol with HCl resulted in reproducible oxidation of the AuNRs by dissolved O2, specifically at the rod ends, enabling precise control over the aspect ratio of the rods. The etched-AuNRs@meso-SiO2 were used as a template for the overgrowth of a second metal (Ag, Pd, and Pt), yielding bimetallic, core-shell structured nanorods. By varying the reaction rates of the metal deposition both smooth core-shell structures or gold nanorods covered with a dendritic overlayer could be made. This control over the morphology, including metal composition, and thus the plasmonic properties of the composite rods were measured experimentally and also confirmed by Finite-Difference Time-Domain (FDTD) calculations. The presented synthesis method gives great control over tuning over both plasmonic properties and the particle stability/affinity for specific applications.

ZnO nanowires with the average diameter of 20 nm and the length of longer than 10 μm were synthesized on GaAs substrate by chemical vapor deposition（CVD）. As-doped ZnO nanowires were obtained by annealing the samples at 600 ℃ for 30 min in oxygen. Single ZnO nanowire field effect transistors（FET） were fabricated by electron beam exposure and magnetron sputtering deposition and Ti/Au deposited as ohmic-contact electrodes. Based on the electrical properties of the single ZnO nanowire FET before and after annealing, we verified that p-type ZnO nanowire can be obtained by As doping effectively. The parameters of the single As doped ZnO nanowire FET were as follows: the transconductance was 35 nA/V, the hole density was 1.4×1018 cm-3, and the mobility was 6.0 cm2/V·s. We also obtained the photoluminescence spectrum of single As-doped ZnO nanowire: strong ultraviolet light at 383 nm, weaker yellow-green light, and red light due to the existence of AsZn-2VZn shallow acceptors.