Preparation and Application of Nanomaterials

Preparation and Application of Nano clobbers2 -1IntroductionDuring the last ten years, nanoscience and nanotechnology have advanced rapidly in many aspects such as preparation and application of nanomaterials. A broad pad of nanomaterials has been developed for varieties of applications ranging from microelectronics circuits, food science, medicines to aerospace exploration.Laser excision in liquidnessNanostructures such as particles, wires, and tubes have become the focus of intensive research owing to their unique applications in microscopic physics and chemistry and fabrication of nanoscaled devices. Therefore, to obtain versatile nanometer size of itd building blocks, a lot of selfassembly and synthesis processes have emerged in new-made years. Similarly, optical maser cut of solids in liquids assailable a unique route to synthesize nanostructures. As a result, there has been rapid growth of studies on the formation of nanostructures by this technique in recent years.Las er ablation has been known since the invention of optical maser in 1960 as materials-processing technique. It was firstly developed after the invitation of ruby optical maser26. The last decade showed many data-based and theoretical investigations of optical maser ablation technique27. Laser ablation in liquid of solid targets conceders as new method that firstly presented in 199328. Laser ablation in liquid top-down method described as the manufacturing of nanostructures with various sizes, compositions, and morphologies. Many types of targets such as (metals, alloys, oxides, carbides, hydroxides, etc.) and several surface structures (nanoparticles, nanotubes, nanorods, nanocomposites, etc.) can be use as a precursor. 29The ablation of the target material by laser irradiation considered as a complex process. The ejected species of materials from the target surface pay backd by the interaction of short ( nanoseconds picoseconds), intense (106 to 1014 W/cm2) laser pulses at the surface. This probably useful in vacuum, gas, and liquid, providing that the gas or liquid does not strongly sublimate laser free pushing and the light fanaticism on the solid surface.30Laser ablation in liquid accomplished as a high function laser focused at the surface of the target material, which is immersed under laying a chosen liquid. The laser target interaction vaporized the surface and creates an ablation plume 31. Atoms, ions, and clusters comes in the producing plume have the ability to travel in a high speed with high kinetic energy. The species that ejected from the solid target containing in the plume can react with molecules of the certain ambient liquid, making new structural material involves atoms from the original target and the liquid.32 The combination effect of high intensity laser ranging in nanosecond, instant elevated temperatures and pressures within the reaction volume could thousands of K at tens of GPa 33. This special condion of pressure, tempera ture, and laser parameters have the ability to produce a brute force. This force define as a method of building new material that was incredible so far using techniques much moderate, and more traditional32. Figure(2-1) show a simple schematic of laser ablation in liquid.Fig.(2-1) illustrated laser ablation in liquid. 26Laser ablation MechanismThe initial step of laser ablation in liquid (LAL) process is the reaction of the laser light with the surface of the target material. The chemical reactions take place surrounded by the species in the plume and with Liquid environment molecules cause to collide, producing new compounds 1. The results argon naturally nanoparticles consist of atoms from the target and the liquid that suspended in the liquid. The aggregation accrues to the nanoparticles in the solution manufacturing a colloidal solution. Series reactions may occur with the laser radiation due to the colloidal solution, leading to further changes in the result structure, size and to the surface structure 34.The plasma creates and restricted in the liquid, it expand adiabatically at supersonic velocity producing a shock-wave in front of it. This in turns will induce an additional, immediate pressure when it passes through the liquid. The temperature increasing in the plasma is the result of laser- bring forth pressure. According to local high temperature a small quantity of the bordering liquid is vaporized creating bubbles inside the liquid. As evaporation of the material increased, and a bubble tends to expand, until the combination reaches certain critical temperature and pressure, the bubbles collapse 31 27.At the room temperature, when the kettle of fish pressure in the ambient liquid could not reach the vaporization pressure, the cavitation formed. It could be represented as a dynamic phenomenon which has an important role in producing nanoparticle. The cavitation caused by the elevated plasma pressure and directed towards balance pressure betwee n in and outside the bubble. Figure (2-2) illustrated the generation of shock wave, cavitation bubble, and high-pressure plasma plume. 35Fig. (2-2) Sketch of the laser plasma plume formation induced by LAL at different stages (1) initial, (2) expansion, and (3) saturation.35The laser ablation process was discussed in details in figure (2-3). The creation of the spherical shock wave noticed in 0.7s after irradiating with NdYAG laser pulse. The shock wave propagate in the sound speed and the initial cavitation bubble creation noticed in figure (2-3 a). Temperature and pressure begun to increased, and cavitation bubble expanded with time. A significant phenomenon can be detected in Fig. 2-3b after 26 s. It was the exception of tiny bubbles from the main bubble. In figure (2-3 c) the bubble size reach to its maximum size after 90 s, then cavitation bubble begun to collapse with time. The creation of a second shockwave was observed at around 186 s as shown in figure (2-3 d), which was i nduced by the shrunk of the first bubble. The production of the second shockwave submits the raised up in temperature and pressure at the breakdown of the cavitation bubble. Then, the generation of another cavitation bubble as illustrated in figure (2-3 e) follows the production of the second shock wave. The expansion and contraction of the bubble is not standardized after a long period (250 s), and was not a hemispherical shape. The final form of the bubble is spherical completely as seen in figure (2-3 f), which was perceived at 2.4 ms.36Fig.(2-3) Time-resolved shadowgraphs at different delays after the laser pulse superimposed with images of laser light scattering36.2-4.1 The advantage of Liquid phase laser ablationBy comparison with traditional physical methods such as chemical vapor deposition and pulse laser deposition, etc. with laser ablation in liquid technique take high attention harmonise the following characteristicsAny target material could be applied in LAL.29The inte nse laser pulse has the ability to reach the target material as the liquid is transpired to the laser.37Good crystalline nanoparticles presented in onestep process without graduated heattreatments.38The ablated materiel can be atoms and ions in extremely excited states being able to emit light. 29The presence of liquid generated high pressure which produced high confinement to the particles in small sizes and high density are probable in the initial of the ablation.39The low cost and simple because of the absence of any vacuum equipment.4041Simplicity gathering nanoparticles after the synthesis according to nanoparticles are kept as a colloidal result in liquid-phase laser ablation.42Using the colloidal production as a precursor for another chemical reaction, especially in the formation of the nano-particles.43Structure, size and form, and design of the manufactured nanostructures can easily control by changing laser parameters and practical supports.44The nanoparticles production relevant to use in optoelectronics, and medical application 452-4.2 Limitations of liquid-phase laser ablationDespite of the unique features of laser ablation in liquid there are limitations. A problem of liquid-phase laser ablation is the difficulty method for controlling plasma properties 36. The size distribution of the NPs prepared by this technique tends to be broadened due to agglomeration of nanoclusters and to the practical ejection of the relatively large target fragments during the laser ablation process 43. Relatively low product yield is one of the main disadvantages associated with LAL. 26parameters affected on laser ablationMany parameters can effect on laser ablation technique, some of them related to the solution such as transparency and liquid depth. Other parameters related to laser energy, time, and wavelength.2-5.1 laser parameterIt is found that for a certain laser energy applied and the ablation time increased the ejection particles decreases. For enlarging the ablation time, the growth of submergence intensity is observed. This behavior is related to the existence of scattering phenomena that reduce the essential absorption according to the increased concentration of nanoparticles per whole volume. Fig.(2-4) show the absorption peaks of indium oxide prepared by laser ablation in liquid at fixed laser flounce 3J/cm2 and different laser ablation (10, 30, 60, 120) min.46Fig.(2-4) UVvis absorption spectra of the indium oxide at the fixed laser fluence of 3 J.cm2 in 10, 30, 60 and 120 min. 46This is occur due to the decrease the transparency of the solution and the particles absorb the laser energy. Another factor affected on the laser ablation method at high laser fluence in LAL must be the absorption of the laser light through NPs suspension produced by LAL 37. Figure (2-5) explain a simple schematic of colloidal absorption in the LAL process causing reduction in the size and formation efficiency.Fig.(2-5) Schematic illustration of coll oidal absorption in the LAL process.37Another important laser parameter is the laser wavelength. It seems that the shorter wavelength laser such as UV-laser it gives lower ablation threshold of the flounce due to high absorbance. The long wavelength laser such as IR-lasers efficiently excites more free electrons in the plasma plume, so improve the ablation process 47.The ablation process can be affected by the laser energy. Increasing the laser energy leads to a broader range of particle size can be obtained. This broad range because of increasing laser energy supplied more energy to the target that drives the material removal by process satisfied by melting. The interaction between laser beam and the melting material makes the droplets to fragment and quenching rapidly produced large nanoparticle 48.To obtain accurate information about the size distribution of nanoparticles, fig.(2-6) show TEM images of InN-NCs obtained with a laser pulse energy of 8 mJ range from 5.9 to 25.3 nm (i nset, Fig. 2-6a), the sizes of InN-NCs obtained with a laser pulse energy of 12 mJ range from 5.4 to 34.8 nm (inset, Fig. 2-6b), and the sizes of InN-NCs obtained with a pulse energy of 16 mJ range from 3.24 to 36 nm (inset, Fig. 2-6c). It should be noted that increasing laser energy leads to obtain more smaller particles.20Fig. 2-6 TEM images of the laser-generated InN-NCs under laser pulse energy determine of 8 mJ (a), 12 mJ (b), and 16 mJ (c) with corresponding particle size distributions (insets). 202-5.2 liquid parameterThis parameter can effect on liquid phase laser ablation technique and its efficiency. The solution must be transparent to the laser wavelength in the case of vertical side irradiation. Even high purity body of water can absorb 20% of the overall laser energy at 1 cm depth. That means if the target placed very deep in the solution, the laser energy reaching the target could be very low 37.