Spontaneous Shape Alteration and Size Separation of Surfactant-Free Silver Particles Synthesized by Laser Ablation in Acetone during Long-Period Storage

Abstract

The technique of laser ablation in liquids (LAL) has already demonstrated its flexibility and capability for the synthesis of a large variety of surfactant-free nanomaterials with a high purity. However, high purity can cause trouble for nanomaterial synthesis, because active high-purity particles can spontaneously grow into different nanocrystals, which makes it difficult to accurately tailor the size and shape of the synthesized nanomaterials. Therefore, a series of questions arise with regards to whether particle growth occurs during colloid storage, how large the particle size increases to, and into which shape the particles evolve. To obtain answers to these questions, here, Ag particles that are synthesized by femtosecond (fs) laser ablation of Ag in acetone are used as precursors to witness the spontaneous growth behavior of the LAL-generated surfactant-free Ag dots (2–10 nm) into different polygonal particles (5–50 nm), and the spontaneous size separation phenomenon by the carbon-encapsulation induced precipitation of large particles, after six months of colloid storage. The colloids obtained by LAL at a higher power (600 mW) possess a greater ability and higher efficiency to yield colloids with sizes of <40 nm than the colloids obtained at lower power (300 mW), because of the generation of a larger amount of carbon ‘captors’ by the decomposition of acetone and the stronger particle fragmentation. Both the size increase and the shape alteration lead to a redshift of the surface plasmon resonance (SPR) band of the Ag colloid from 404 nm to 414 nm, after storage. The Fourier transform infrared spectroscopy (FTIR) analysis shows that the Ag particles are conjugated with COO– and OH– groups, both of which may lead to the growth of polygonal particles. The CO and CO2 molecules are adsorbed on the particle surfaces to form Ag(CO)x and Ag(CO2)x complexes. Complementary nanosecond LAL experiments confirmed that the particle growth was inherent to LAL in acetone, and independent of pulse duration, although some differences in the final particle sizes were observed. The nanosecond-LAL yields monomodal colloids, whereas the size-separated, initially bimodal colloids from the fs-LAL provide a higher fraction of very small particles that are <5 nm. The spontaneous growth of the LAL-generated metallic particles presented in this work should arouse the special attention of academia, especially regarding the detailed discussion on how long the colloids can be preserved for particle characterization and applications, without causing a mismatch between the colloid properties and their performance. The spontaneous size separation phenomenon may help researchers to realize a more reproducible synthesis for small metallic colloids, without concern for the generation of large particles.

Hierarchical microstructures with high spatial frequency laser induced periodic surface structures possessing different orientations created by femtosecond laser ablation of silicon in liquids

“…Close observation of particle morphologies also indicated that small particles were also captured by the networks (Fig. 8(c)), similarly to the cases of LAL of Ag 13 and Fe 61 in acetone. The LAL findings lead to the following insights: 1) in presence of liquids, melting during fs laser ablation is significantly inhibited (Fig.…”

“…Laser ablation offers a versatile platform that can simultaneously induce surface structures [1][2][3] and synthesize nanomaterials [4][5][6][7][8][9][10][11][12][13] for diverse applications, such as wettability control [14][15][16][17] , bioimaging 6,18 , cellular growth manipulation [19][20][21] , lithium-ion batteries 22 , surface enhanced Ra-man scattering (SERS) detection 23,24 , catalysis/ photocatalysis/electrochemical-catalysis 6,7,25 and antifriction [26][27][28][29] . Laser processing also enables the microfabrication of three-dimensional structures and devices 30,31 .…”

“…In the case of LAL in acetone ( Fig. 5(c)), since acetone decomposition 10,11,13,61 consumes more laser energy, the effective laser energy for ablation is reduced. As a result, the poly-crystallization rate is further reduced (see Fig.…”

Facile Formation of Stable Water‐Dispersed Luminescent Silicon Nanocrystals by Laser Processing in Liquid: Toward Fluorescent Labeling for Bio‐Imaging

“…It should be noted that the Si−CH 2 signal indicates the decomposition of the 10‐undecenoic acid by pulsed laser irradiation. In fact, several literatures report such an effect by the intense laser irradiation, e. g., the decomposition of water and acetone at the plasma plume and liquid interface . In addition, new peaks appear at ∼1650 cm −1 , and 3400 cm −1 .…”

“…In fact, several literatures report such an effect by the intense laser irradiation, e. g., the decomposition of water and acetone at the plasma plume and liquid interface. [34,54,55] In addition, new peaks appear at~1650 cm À 1 , and 3400 cm À 1 . These peaks are corresponding to the stretching vibration modes of C=O and OÀ H. [52,53,56] We can thus conclude that hydrophilic Si-nc is functionalized with carboxylic acid groups originating from 10-undecenoic acid (UA-F: Si-nc).…”