Defects in ZnO nanoparticles laser-ablated in water–ethanol mixtures at different pressures

Abstract

The effect of liquid medium and its pressure on the photoluminescence of ZnO nanoparticles prepared via laser ablation of Zn targets in various water-ethanol mixtures is studied. As the ethanol content increases, the photoluminescence of the product changes, while metallic zinc is observed to emerge in nanomaterials prepared in ethanol-rich environments. The applied pressure had a less profound effect, mainly affecting materials produced in water or water-ethanol, and much less those generated in pressurized ethanol. Tuning the reactivity of the liquid and pressurizing it during laser ablation is demonstrated to be promising for tailoring the emission properties of the product.

ZnO nanorods prepared via ablation of Zn with millisecond laser in liquid media

“…Upon centrifugation (16,500 rpm, 15 min), the prepared suspensions were cast on a Si substrate and then characterized by means of X-ray photoelectron spectroscopy (XPS, Quantum 2000, ULVAC-PHI), X-ray diffractometry (XRD, D8 Discover from Bruker) and photoluminescence (PL) spectroscopy. For PL measurements, a homemade system previously described elsewhere was used [17,18]. The PL measurements were conducted at room temperature with a He-Cd laser (325 nm) as excitation source and using dry ZnO NPs drop-cast on Si wafers.…”

“…In the last decade, laser ablation in liquid (LAL) has proven to be an attractive, simple, and efficient technique to generate a large variety of nanostructures of diverse materials [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In this approach, laser beam is typically focused on a solid (often metal) target immersed into a liquid and produces various nanostructures whose chemistry, morphology and size distribution are defined by both the laser pulse parameters and the liquid [1,2,17]. This technique is attractive as a green approach using minimum solvents, easy-to-use, and even sometimes capable of controlling the morphology of produced nanomaterials [1,2,6,8,14].…”

“…The recent use of high pressures, i.e. ablating in pressurized cells, permits to expand the technique and allows for more control over the product [17][18][19][20].…”

“…Amongst metal oxides, ZnO is probably one of the most investigated semiconductor materials and accordingly its nanostructures have been synthesized by various methods, such as (to name a few) solvothermal synthesis [22][23][24]27,[30][31][32], microwave irradiation [31,33], and CVD [26,27]. The LAL method was also applied, and both doped and non-doped, as well as surface-stabilized or non-stabilized, ZnO nanoparticles (NPs) with different morphologies and sizes were reported [4][5][6][7][8][9][10]12,[14][15][16][17][18][34][35][36].…”

“…The product was characterized by means of several microscopic and spectroscopic techniques. It is shown that ZnO nanorods or nanospheres can be prepared in one step when water or ethanol are used as media, which was not observed when laser beams with shorter pulses were applied [5,6,17,18,34].…”