Formation and investigation of optical media containing gold nanoparticles

Abstract

Consideration has been given to certain aspects of condensation processes occurring in laser-induced erosion plumes of metals and giving rise to fluxes of metallic nanoparticles. Samples of colloidal solutions of gold and gold-containing polymer films have been produced as a result of precipitation of nanoobjects formed in laser erosion of gold into aqueous and polymer-containing media. The experimental samples formed have been comprehensively investigated using optical spectroscopy and transmission and scanning electron microscopy.Keywords: laser synthesis of metal nanoparticles, erosion laser plume, colloidal solution of gold, gold-containing polymer film, surface plasmon resonance.Introduction. The increasing practical interest currently expressed in methods of formation and investigation of isolated metal nanoparticles is due to the wide range of advantages which are offered by traditional media modified by metallic nanostructures. Ultradisperse metal-containing media may exhibit exotic electrical, magnetic, optical, thermophysical, chemical, biological, and other properties [1-3]. The mentioned features are determined by the presence of the so-called dimensional effects in isolated metal particles with a diameter less than 100 nm [2].Numerous methods of formation of ultradisperse metal-containing media have been developed to date. All these approaches can be subdivided into three conventional groups, as far as the principle of formation is concerned, i.e., physical (e.g., [4,5]), chemical [6,7], and combination (physicochemical) [8] ones. The enumerated methods offer their own advantages and drawbacks and can be applied to the solution of certain technological problems.However, properties characteristic of gold as a metal (chemical stability, inertia, relative infusibility, and high specific weight) make it impossible to use in full measure most of the existing methods of obtaining nanostructures. Chemical methods traditionally used for these purposes are rather labor-intensive and expensive [7]. We can consider the technique of laser synthesis of colloidal solutions of gold [9] as an alternative solution; this technique is based on the fact that the products of laser erosion from gold targets enter trapping media whose composition may vary. The use of today's frequency-modulated lasers for production of gold-containing colloids makes it possible to improve the competitiveness of the procedure of laser synthesis compared to other techniques of formation of ultradisperse metalcontaining media. Additional advantages of the indicated technique are the technological simplicity of the synthesis plant, the possibility of controlling the process of synthesis on line, and the high rates of formation of colloids. Character of Destruction of Metallic Targets by Submicrosecond Laser Pulses.In the process of exposure of metals to intense submicrosecond optical radiation pulses in a thin surface region of the target, part of the pulse is absorbed by conduction electrons [10]. It should be noted that the initially high co...

Physics of Laser-Induced Plasma Streams Under Irradiation of Metals with Nanosecond Laser Radiation Pulses at Atmospheric Pressure

“…On the other hand, recent works [19][20][21][22][23][24], because of their narrow practical purposefulness, are characterized by widely disconnected topics, and, therefore, it is very diffi cult to reconstruct on their basis the integral physical picture of the phenomenon under investigation. However, the results of a number of works [25][26][27][28] show that the processes of plasma initiation under the action of high-power nanosecond laser pulses on metals in air can serve as the basis for developing effective technologies of laser treatment, including those aimed at bulk [29][30][31] and surface [32] modifi cation of functional materials by metal nanostructures.…”

“…Nanosized particles formed in the erosion torch of metals can be precipitated into liquid media to form colloidal solutions of corresponding metals [29]. Figure 5 presents the data of investigations of particles precipitated from such colloidal solutions on substrates by the methods of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) [28,30]. It should be noted that proper treatment of such colloidal solutions permits obtaining metal-polymer composite fi lms (Fig.…”

“…It should be noted that proper treatment of such colloidal solutions permits obtaining metal-polymer composite fi lms (Fig. 5c) [30,31] exhibiting promising optical and magnetic properties.…”