Abstract
Reddish Au condensates, predominant atom clusters and minor amount of multiply twinned particles and fcc nanoparticles with internal compressive stress, were produced by pulsed laser ablation on gold target in de-ionized water under a very high power density. Such condensates were self-assembled as lamellae and then nano- to micro-diameter tubes with multiple walls when aged at room temperature in water for up to 40 days. The nano- and micro-tubes have a lamellar- and relaxed fcc-type wall, respectively, both following partial epitaxial relationship with the co-existing multiply twinned nanoparticles. The entangled tubes, being mesomorphic with a large extent of bifurcation, flexibility, opaqueness, and surface-enhanced Raman scattering, may have potential encapsulated and catalytic/label applications in biomedical systems.
Highlights
Under ambient pressure condition, Au atoms condense in the order of increasing particle size, as structural motifs of atom clusters with planar, cage or pyramid structures [1,2,3], an anomalous multiply twinned particle (MTP) of decahedral (Dh) and icosahedron (Ih) types [4, 5] and a facecentered cubic structure
We used an alternative route of pulsed laser ablation in liquid (PLAL) to form more Au atom clusters for further formation of lamellae and multiple-walled tubes (MWT) in a subsequent water-driven assembly process
The optical absorbance of the as-deposited nanocondensates and further developed MWTs in solution with specified dwelling times was acquired by a UV–vis spectrophotometer (U-3900H, Hitachi) operating at an instrumental resolution of 0.1 nm in the range of 300–800 nm
Summary
Au atoms condense in the order of increasing particle size, as structural motifs of atom clusters with planar, cage or pyramid structures [1,2,3], an anomalous multiply twinned particle (MTP) of decahedral (Dh) and icosahedron (Ih) types [4, 5] and a facecentered cubic (fcc) structure. We used an alternative route of pulsed laser ablation in liquid (PLAL) to form more Au atom clusters for further formation of lamellae and multiple-walled tubes (MWT) in a subsequent water-driven assembly process. This stabilizer-free approach is analogous to the fabrication of carbon onions via arc discharge in water [10], but different from surfactant/copolymers or other template-assisted assembly of Au nanoparticles in a desired manner and quantum-size-related properties for applications toward biology, catalysis, and nanotechnology [11, 12]. The self-assembled Au tube has potential biomedical applications in view of its good bending flexibility, partial epitaxial filling of MTP/fcc particles, and surfaceenhanced Raman scattering (SERS) effect useful for the detection of molecules or nanoparticles adsorbed on rough metal surfaces [13, 14]
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