Effect of laser energy and pulses on size and concentration of gold nanoparticles in DDDW by LALP method

The size and the concentration of the gold nanoparticles (GNPs)synthesized in double distilled deionized water (DDDW) have beenfound to be affected by the laser energy and the number of pulses.The absorption spectra of the nanoparticles DDDW, and thesurface plasmon resonance (SPR) peaks were measured, and found tobe located between (509 and 524)nm using the UV- Visspectrophotometer. SPR calculations, images of transmissionelectron microscope, and dynamic light scattering (DLS) methodwere used to determine the size of GNPs, which found to be rangedbetween (3.5 and 27) nm. The concentrations of GNPs in colloidalsolutions found to be ranged between (37 and 142) ppm, andmeasured by atomic absorption spectroscopy (AAS).

Because of the NPs unique properties of small size, large surface area to volume ratio [4], they have optical, electrical, magnetic, chemical, and mechanical properties which are completely different from bulk materials [5]. There is a growing interest in the fabrication of nanomaterials and their applications in various fields of life and technology such as electronics, health care, energy generation, and storage [6].
The GNPs have a long storied history in the usage, alike , in art or medicine from B.C years to present days [7]. The use of gold particles of extremely small size was only first published in 1971 [8].

General properties of gold
Gold belongs to Group II (IB) of the periodic table of the elements and often being referred to as the "coinage metals. The physical appearance of gold is yellow. Gold isn't soluble in mineral acids, but it is soluble in aqua regia (Con. HCl and Con. HNO 3 in 3:1 ratios). Au 3+ is hard acids. Gold is unique in a number of respects. It is the most electronegative metal, comparable to selenium, and only slightly more electropositive than sulfur and iodine. Its electron affinity is greater than that of oxygen. The Au + /Au° has a reduction potential value of +1.62 V. Gold is one of the few metallic elements that can be used in nanoscale devices and systems due to its resistance to oxidation [9]. Although gold is a noble metal and a commonly used material because of its resistance to oxidation and interesting electrical, magnetic, optical, and physical properties, it forms many and diverse compounds. The oxidation state of gold in its compound ranges from -1 to +5, but Au(I) and Au(III) dominate. Only salts and radioisotopes of gold are of pharmacological value, as elemental (metallic) gold is inert to all chemicals it encounters inside the body. Pure gold is non-toxic and nonirritating when ingested and is sometimes used as a food decoration in the form of gold leaf [10].
There are many of methodologies for classification of the techniques and methods of nanomateriales' synthesis credential on, assembly and dismemberment, matter phase, nature of phase (physical, chemical, and biological), consorting with the environment or not, or on the dimensions or shapes of the result materials Among the physical methods, pulsed laser ablation has been demonstrated to be a powerful and versatile technique for preparing highpurity nanoparticles or nanofilms. In general, the targets used for the preparation of nanoparticles or films by laser ablation are bulk sizes, and the lasers are either excimer, pulsed yttrium aluminum garnet (YAG), or femtosecond lasers [11]. Laser ablation/irradiation in liquid (LAL) [12], so-called pulsed laser ablation (PLA) is a simple and "green" technique that normally operates in water or organic liquids under ambient conditions [13]. The introduction in laser fragmentation in liquid has become a well-established technique to produce nanoparticles in 1987 [12].
Laser ablation of solids in liquids is an efficient way for the generation of a large variety of metallic nanospheres (NSs) and nanoparticles (NPs). Under sufficiently high laser fluence the surface of the target melts, and the melt is subsequently dispersed into the surrounding liquid under the recoil pressure of its vapor [14]. The synthesis procedure of the metal nanoparticles affects the final colloidal state and its evolution in terms of aggregation, reaction and The SPR spectra of the prepared GNPs in DDDW were measured at room temperature and found to be located at (509-524) nm as shown in Fig. 2.   Fig. 2: SPE spectra of GNPs in DDDW for various energies, (a) 100 pulses, (b) 150 pulses,  (c) 250 pulses, and (d) 300 pulses. (b) (c) (d) Fig. 3 shows, the TEM images, and the size distribution size of the prepared GNPs with (300, 400, 500 and 600) mJ, and 300 pulses of laser. The comparative measurements between the sizes of the three ways listed above were shown in Fig. 4, the size measurements have been shown that the values of size were measured by transmission electron microscope images with SPR calculations even closer than those measured in way that DLS. 300 pulses at (300, 400, 500and 600) [19,20]. This work coincides with the second interpretation with prepared GNPs by 600mJ with 500 pulses were shot by 600 mJ with 100 pulses laser for four times, and the SPR peak has been measured in each time sequence. The SPR peak shifted to blue region by (0.15, 0.17, 0.2 and 0.23) % as shown in Fig. 6.