Laser Irradiation Of Solution Research Articles

Novel metal-organic super-hydrophobic surface fabricated by nanosecond laser irradiation in solution

This work aims to propose a newly-emerged method using laser irradiation in liquid for the fabrication of metal-organic highly hydrophobic aluminum surface with excellent corrosion resistant performance. The corrosion results revealed that the laser-induced porous structure with ovoid-like particles, and simultaneously integration of low-free-energy functional groups (-CH2, -CF2 and -CF3) contributed to the super-hydrophobicity, enhancing corrosion resistance due to the effect of Laplace pressure and air-cushion formation within the porous structures. The possible chemical reactions during laser irradiation process in liquid were proposed. The explosive ejection mechanism was proposed to explain the generation of micro/nano particles with inherent pores. This facile approach offers a new route to fabricate super-hydrophobic surface with excellent mitigation of metallic corrosion.

The Surprising in Vivo Instability of Near-IR-Absorbing Hollow Au–Ag Nanoshells

Photothermal ablation based on resonant illumination of near-infrared-absorbing noble metal nanoparticles that have accumulated in tumors is a highly promising cancer therapy, currently in multiple clinical trials. A crucial aspect of this therapy is the nanoparticle size for optimal tumor uptake. A class of nanoparticles known as hollow Au (or Au–Ag) nanoshells (HGNS) is appealing because near-IR resonances are achievable in this system with diameters less than 100 nm. However, in this study, we report a surprising finding that in vivo HGNS are unstable, fragmenting with the Au and the remnants of the sacrificial Ag core accumulating differently in various organs. We synthesized 43, 62, and 82 nm diameter HGNS through a galvanic replacement reaction, with nanoparticles of all sizes showing virtually identical NIR resonances at ∼800 nm. A theoretical model indicated that alloying, residual Ag in the nanoparticle core, nanoparticle porosity, and surface defects all contribute to the presence of the plasmon resonance at the observed wavelength, with the major contributing factor being the residual Ag. While PEG functionalization resulted in stable nanoparticles under laser irradiation in solution, an anomalous, strongly element-specific biodistribution observed in tumor-bearing mice suggests that an avid fragmentation of all three sizes of nanoparticles occurred in vivo. Stability studies across a wide range of pH environments and in serum confirmed HGNS fragmentation. These results show that NIR resonant HGNS contain residual Ag, which does not stay contained within the HGNS in vivo. This demonstrates the importance of tracking both materials of a galvanic replacement nanoparticle in biodistribution studies and of performing thorough nanoparticle stability studies prior to any intended in vivo trial application.

Facile synthesis of bimetallic nanoparticles by femtosecond laser irradiation method

Bimetallic Pt–Au and Fe–Pt nanoparticles are successfully fabricated by high-intensity laser irradiation of aqueous solution without any chemical reducing agent. The mechanism of the formation of bimetallic nanoalloys by laser irradiation of the solution without using any reducing agent was mainly attributed to the optically induced decomposition of water molecule. When an intense femtosecond laser field is focused in an aqueous solution containing metal ions, the free electrons will be produced by the dissociation of water molecules, these free electrons and hydrogen radicals contained in the plasma might be caught by H+ or OH− ions to form the bubbles of H2 and O2 gases or they can be trapped by metal ions, resulting in the formation of metal atoms during the femtosecond laser irradiation process. The average size of the bimetallic nanoparticles increases with irradiation time. This technique is simple and ‘green’ process without using any chemicals except for metal salt and dispersing agent.

Fabrication of Rh based solid-solution bimetallic alloy nanoparticles with fully-tunable composition through femtosecond laser irradiation in aqueous solution

Many late transition binary alloy nanoparticles (NPs) have been fabricated through a wide variety of techniques. Various steps are involved in the fabrication of such NPs. Here, we used a simple and green route to fabricate solid-solution Rh–Pd and Rh–Pt bimetallic alloy NPs through femtosecond laser irradiation in a solution without any chemicals like reducing agents. X-ray diffraction (XRD) peaks of NPs obtained in the solutions with different ratios of Rh–Pd and Rh–Pt ions monotonically varied from the position of pure Rh to those of Pd and to Pt which respectively indicated that these NPs were alloy. Composition of fabricated NPs was fully tuned over the entire range of Rh1−x –Pd x , and Rh1−x –Pt x with varying the mixing ratio of metal ions in the solution. Studies of Rh–Pd and Rh–Pt solid-solution system suggest that the alloy formation occurs through the nucleation of Rh and then followed by the diffusion of Rh, Pd and Rh, Pt to form a homogeneous alloy. The variety of average size of the alloy NPs for different compositions could be attributed to different reduction rate and surface energies of metal ions. Our result implies that femtosecond laser irradiation in aqueous solution is one of the potential methodologies to form multimetallic solid-solution alloy NPs with fully tunable composition.

Local surface modification of aluminum by laser irradiation

A novel method involving a combination of pulsed YAG laser irradiation and electrochemistry for chemical and physical modification of aluminum surface at a selected area is reviewed. Local metal deposition is carried out by successive steps of anodizing, laser irradiation, and electroplating (or electroless plating), and the fabrication of a prototype for printed circuit boards is attempted. Local organic film deposition with anodizing, laser irradiation, and electrophoretic deposition is introduced, and the formation of microtrenches and pores on aluminum surfaces with anodizing, laser irradiation, and electrochemical etching (or chemical etching) is also described. It is emphasized that the key technology in these procedures is to use aluminum as a target for the laser irradiation in solution, and that anodic oxide films on aluminum play an important role in the processes.

Nucleation of Metals on Aluminum by Laser Irradiation and the Effect on Ni‐P Electroless Deposition

The mechanism of direct Ni‐P electroless deposition on aluminum by pulsed yttrium aluminum garnet (YAG) laser irradiation in solution was investigated by X‐ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) with energy‐dispersive X‐ray (EDX) analysis. Aluminum specimens covered with porous anodic oxide films were irradiated with a pulsed YAG laser in solutions containing , , , or ions, and then localized Ni‐P electroless plating was attempted at the laser irradiated area in solution. It was found that laser irradiation in solutions containing , , or ions causes the deposition of small metallic particles of Pd, Cu, or Ni at the laser‐irradiated area on the aluminum surface which was exposed to the solution after removal of anodic oxide film. The deposition of the metals is due to a redox reaction between the aluminum substrate and the , , or ions. During laser irradiation in solution, Ni‐P and Ni were deposited by redox reactions between and as well as between and Al. Palladium and nickel (Ni‐P) particles deposited during the laser irradiation acted as catalytic centers for the subsequent Ni‐P electroless plating, while Cu particles did not promote the electroless plating. © 1999 The Electrochemical Society. All rights reserved.