Self assembled nanoparticle aggregates from line focused femtosecond laser ablation

In this paper we present the use of a line focused femtosecond laser beam that is rastered across a 2024 T3 aluminum surface to produce nanoparticles that self assemble into 5-60 micron diameter domed and in some cases sphere-shaped aggregate structures. Each time the laser is rastered over initial aggregates their diameter increases as new layers of nanoparticles self assemble on the surface. The aggregates are thus composed of layers of particles forming discrete layered shells inside of them. When micron size aggregates are removed, using an ultrasonic bath, rings are revealed that have been permanently formed in the sample surface. These rings appear underneath, and extend beyond the physical boundary of the aggregates. The surface is blackened by the formation of these structures and exhibits high light absorption

A non-vacuum process for preparing nanocrystalline CuIn\u3csub\u3e1−x\u3c/sub\u3eGa\u3csub\u3ex\u3c/sub\u3eSe\u3csub\u3e2\u3c/sub\u3e materials involving an open-air solvothermal reaction

A non-vacuum, two-step process has been used to prepare a series of nanocrystalline CuIn1−xGaxSe2 (x = 0, 0.25, 0.5, 0.75, 1) materials. An open-air solvothermal preparation in triethylenetetramine solvent was followed by annealing at 500 °C in a nitrogen atmosphere for 20 min. All materials have mixed clustered plate, spherical particle, and nanorod morphologies with the smallest particle diameters ranging between 20 and 40 nm. Raman spectroscopy and X-ray diffraction (XRD) confirm that indium/gallium ratio control is possible over a wide range. The solvothermal reaction step yields a mixture of chalcopyrite and Cu2−xSe. This is converted to pure chalcopyrite product by annealing at 500 °C

REACTION PATHWAY INSIGHTS INTO THE SOLVOTHERMAL PREPARATION OF Culn\u3csub\u3e1- x\u3c/sub\u3eGa\u3csub\u3ex\u3c/sub\u3eSe\u3csub\u3e2\u3c/sub\u3e NANOCRYSTALLINE MATERIALS

Reaction pathway investigations of the solvothermal preparation of nanocrystalline Culn1- xGaxSe2 in triethylenetetramine reveal the early formation of a previously unreported Cu2-xSe(S) intermediate. Over 24 hours, this reacts with In and Se species to form CulnSe2(s). If Ga is present, the reaction proceeds over an additional 48 hours to form Culn1-xGaxSe2. Adding ammonium halide salts reduces the CulnSe2 formation time to as little as 30 minutes. It is proposed that in these cases, Cu2-xSe particle growth is limited via a competitive Cu-halide complex formation. The smaller Cu2-xSe particles may react and form CulnSe2 more rapidly. A reaction pathway scheme consistent with experimental results and previous literature reports is proposed