Fabrication of chromium oxide nanoparticles by laser-induced deposition from solution

Abstract

Metallic wires and dots can be obtained by reducing a metallic salt in the pores of a membrane. Electrodeposition processes in nanometer-sized pores of aluminum oxide membranes was reported more than 30 years ago [1]. Ultra-dense arrays (reaching 10 11 cm −2 ) of nanometer-size electrodeposited columns have been successfully produced on substrates made by electron lithography [2]. The use of plastic porous membranes has been extensively investigated and a variety of nano-materials have been successfully made by this method [3 and 4]. The reduction of metal ions in the membrane creates an assembly of wires, several micrometers in length, with a diameter chosen in the range 30 nm to a few micrometers [5, 6 and 7]. This is of great interest because magnetic systems of very small dimensions can reveal mesoscopic and quantum effects. Single electron blocking effects have been evidenced in oxidized STM tips or substrates [8], and similar effects were reported in nanowires smaller than 0.01 μm 2 [5]. Initial results on magnetoresistance measurements on nanometer diameter Ni/NiO/Co wires [6] provide evidence of an impurity in the tunnel barrier playing a role in Coulomb blockade [6 and 9], and indeed negative tunnel magnetoresistance might be observed when impurities are present in the barrier [6]. The extension of the Coulomb blockade effect to the ferromagnetic case is at its infancy, but initial measurements [10, 11 and 12] and theories [13 and 14] indicate that such systems can show enhanced magnetoresistive properties. An estimate for the spin-fl ip time τ SF , deduced from diffusive transport bulk values is of the order of 10 −12 s. A more relevant time scale for very small metallic particles can be found in the results of Ralph et al. [15 and 16] nanoparticles. They gave an estimate of 10 −8 -10 −9 s for the relaxation rate of excited states. Making nanoscale particle of ferromagnetic and antiferromagnetic particles is the key to future research in this area. Chromium oxides have attracted much attention recently because of their importance both in science and technology. Band-structure calculations [17] predict that CrO 2 is a half-metallic ferromagnet -a system which is metallic for one spin direction and insulating for the opposite spin direction. This contention is supported by refl ectivity measurements [18] and Andreev scattering [19 and 20]. Unfortunately, it is very diffi cult to fabricate CrO 2 nanoparticles by using conventional methods due to the high temperatures required and the metastablity of CrO 2 phase, nor there has been much success with the fabrication of nanoparticles in the antiferromagnetic insulating Cr 2 O 3 phase.Laser-assisted deposition from solution is clearly compatible with electrochemical deposition. The laser-assisted deposition from solution (LISD) techniques has been successfully used to deposit ReB 6 (Re=rareearthmetal) [21,22,23 [29]. Laser assisted deposition from a solution of silver nitrate was also used to deposit silver clusters [30]. In both the deposition of coppe...

Preparation of Cr2O3 nanoparticles via C2H5OH hydrothermal reduction

“…In fact, there have been already a lot of ways to prepare Cr 2 O 3 nanoparticles, including precipitation-gelation process [5], gas condensation [6], sonochemical reaction [7], microwave plasma [8], decomposition of chromium nitrate solution [9], laser-induced deposition [10], but most of them have difficulties in being scaled up due to the more complex processes or more expensive reaction apparatus. A better process should be implored to meet the demands of industrialization.…”

Structure and Magnetic Properties of Cr2O3/CrO2Nanoparticles Prepared by Reactive Laser Ablation and Oxidation under High Pressure of Oxygen

“…These methods usually involve the use of wet chemicals or several steps that can be somewhat timeconsuming. Recently, laser beams have been employed to synthesize Cr 2 O 3 nanostructures, and well-dispersed nanoscale chromium oxide particles have been prepared via laser-induced solution deposition from solution with CrCl 2 and organic solvents [6]. α-Cr 2 O 3 nanocondensates were fabricated using pulsed laser ablation in air [7], and Cr 2 O 3 thin films were prepared on Cr thin film surfaces via laser photothermal oxidation and laser deposition using a Cr 2 O 3 target [8,9].…”

Synthesis and structure screening of nanostructured chromium oxide powders

“…A wide variety of applications such as hydrogen storage [1][2][3], catalysts [4][5][6], coating materials and wear resistance [7,8], dye and pigment [9,10], advanced colorants [11], digital recording system [12], solar energy application [13], wear resistance materials [12], photonic and electronic devices and drug delivery [14,15]. Various techniques have been developed to synthesize Cr 2 O 3 nanoparticles such as hydrothermal [16], solid thermal decomposition [17], bio-method [18], combustion [19], nanocasting method [20], sol-gel [21], precipitation-gelation [22], oxidation of chromium in oxygen [23], laser induced deposition [24], mechanochemical reaction and subsequent heat treatment [25] and sonochemical methods [26].…”