Application of gold nanoparticles produced by laser ablation for immunochromatographic assay labeling.

Nanodispersed gold is widely used as a marker in different analytical systems. For such purposes, it is usually obtained by the reduction of salts. This work studied the potential analytical applications of nanodispersed gold obtained by laser ablation because gold produced with this method has no chemical coating. The nanoparticles produced were characterized by transmission electron microscopy and spectrophotometry. The average size of the particles was 24.5 nm. Concentration dependences of antibody immobilization on ablative gold were obtained. With the use of antibody-conjugated nanoparticles, an immunochromatographic system was constructed for the detection of zearalenone mycotoxin. This immunoassay was characterized by a detection limit of 0.1 ng/ml antigen with an assay duration of only 15 min, which is on par with current test systems comprising nanodispersed gold obtained by chemical reduction. The simplicity of ablative dispersing makes this a prospective method for the labeling of various antibodies for analytical use.

Self-organization of ascending-bubble ensembles.

Self-organization of hydrogen bubbles generated by laser-treated areas of an aluminum plate etched in a basic aqueous solution of ammonia is studied experimentally and theoretically. The dynamics of the establishment of a stationary pattern of gas bubbles is experimentally is shown. In the theoretical model, the velocity field of liquid flows around an ensemble of several bubbles is obtained. Modeling of the process of self-organization of gas bubbles is performed on the basis of a continuum model of a bubble jet. Under certain assumptions, the pressure of a diluted system of bubbles is described by an equation similar to that for nonideal gas, which follows the van der Waals equation of state. The model predicts an alignment of gas bubbles along bisectors of the laser-treated area limited by a square, which is in good agreement with experimental observations. Further development of the model leads to an equation with a negative diffusion coefficient that may be responsible for symmetry breakdown and pattern formation.

Self-organization of hydrogen gas bubbles rising above laser-etched metallic aluminum in a weakly basic aqueous solution.

Self-organization of hydrogen bubbles is reported under etching of metallic Aluminum in a weakly basic solution. The ascending gas bubbles drift to the areas with higher density of bubbles. As a result, ascending bubbles form various stationary structures whose symmetry is determined by the symmetry of the etched area. Bubbles are aligned along the bisectors of the contour of the etched area. The special laser-assisted profiling of the etched area in shape of a vortex induces a torque in the fluid above the etched area. The process is interpreted on the basis of Bernoulli equation.