Double-pulse femtosecond laser ablation for synthesis of ultrasmall carbon nanodots

Abstract

Carbon nanodots (C-dots) with ultrasmall size possessing large surface-to-volume ratio are expected to improve their performance in sensing and catalytic applications. Here, we present a simple strategy to synthesis ultrasmall C-dots using double-pulse femtosecond laser ablation in solution. The size of C-dots reaches minimum value of ∼1 nm when the delay between the pulses was approaching the electron-ion relaxation time. In this case, the mean sizes of C-dots in double-pulse ablation are even smaller than that obtained in single-pulse ablation with the same laser fluence due to the suppression of rarefaction wave by the shock wave created by the second pulse. Furthermore, abundant functional groups are created on the surface of C-dots in double-pulse ablation because of reheating the nascent ablated materials by the second pulse. These results demonstrate that the double-pulse technique is therefore an effective strategy beyond single-pulse ablation to synthesis ultrasmall C-dots with abundant surface functional groups as well as other nanoparticle for catalytic and sensing applications.

A Review of Carbon Dots Produced from Biomass Wastes

“…The synthesis methods can be divided into two main categories, top-down and bottom-up approaches ( Figure 1 ). The top-down approaches include electrochemical oxidation [ 22 , 23 , 24 ], arc discharge [ 25 ] and laser ablation [ 26 , 27 , 28 ], which involve the exfoliation process of larger carbonaceous materials (e.g., large-size graphene, carbon nanotube, graphite, commercial activated carbon) into nanoscale C-dots. During the synthesis of C-dots using top-down approaches, harsh experimental conditions (e.g., strong acid and arc discharge), tedious operation steps and expensive equipment are usually employed, which greatly limit their practical application.…”

You Don’t Learn That in School: An Updated Practical Guide to Carbon Quantum Dots

“…The electron decay time in the CQDs surface state was found to be very brief. Nguyen et al [ 28 ] synthesized ultrasmall CQDs via double-pulse femtosecond laser ablation in solution, using graphite powders dispersed into ethanol. The minimum size of CQDs was ∼1 nm when the laser pulses approached electron-ion relaxation time, obtaining smaller CQDs than those produced via single-pulse ablation with the same laser fluence.…”

New trends in nonconventional carbon dot synthesis

“…Similarly, CDs were synthesized starting from graphite dispersed in ethanol by using two fs pulses on the material, with the size of the resulting materials depending on the delay between consecutive pulses. Interestingly, by using a time delay of 2 ps, ultrasmall CDs were formed (1.5 nm) with very narrow size distribution (0.5-2.0 nm), indicating an efficient control on the material size [67]. This effect was attributed to reduced ablation volumes caused by the shockwave of the second pulse.…”

“…Despite this, a great number of nanomaterials have been synthesized using lasers, including metal and semiconductor nanoparticles, along with CDs [26,65]. In particular, the latter have been obtained in both top-down and bottom-up approaches using various carbon sources (Table 3) [66][67][68][69][70]. The effect of laser fluence, wavelength, spot size, and irradiation time proved important in controlling the material properties (Figure 2).…”