Quenching of the Photoluminescence of Gold Nanoclusters Synthesized by Pulsed Laser Ablation in Water upon Interaction with Toxic Metal Species in Aqueous Solution

Abstract

Sensors for the detection of heavy metal ions in water are in high demand due to the danger they pose to both the environment and human health. Among their possible detection approaches, modulation of the photoluminescence of gold nanoclusters (AuNCs) is gaining wide interest as an alternative to classical analytical methods based on complex and high-cost instrumentation. In the present work, luminescent oxidized AuNCs emitting in both ultraviolet (UV) and visible (blue) regions were synthesized by pulsed laser ablation of a gold target in NaOH aqueous solution, followed by different bleaching processes. High-resolution electron microscopy and energy-dispersive X-ray scattering confirmed the presence of oxygen and gold in the transparent photoluminescent clusters, with an average diameter of about 3 nm. The potentialities of the bleached AuNCs colloidal dispersions for the detection of heavy metal ions were studied by evaluating the variation in photoluminescence in the presence of Cd2+, Pb2+, Hg2+ and CH3Hg+ ions. Different responses were observed in the UV and visible (blue) spectral regions. The intensity of blue emission decreased (no more than 10%) and saturated at concentrations higher than 20 ppb for all the heavy metal ions tested. In contrast, the UV band emission was remarkably affected in the presence of Hg2+ ions, thus leading to signal variations for concentrations well beyond 20 ppb (the concentration at which saturation occurs for other ions). The limit of detection for Hg2+ is about 3 ppb (15 nmol/L), and the photoluminescence intensity diminishes linearly by about 75% up to 600 ppb. The results are interpreted based on the ligand-free interaction, i.e., the metallophilic bonding formation of Hg2+ and Au+ oxide present on the surface of the UV-emitting nanoclusters.

Pulsed‐Laser‐Driven CO2 Reduction Reaction for the Control of the Photoluminescence Quantum Yield of Organometallic Gold Nanocomposites

“…Two distinct emission bands, one in the ultraviolet (UV) and the other in the visible (blue) region, were detected. [ 36,57 ]…”

“…As reported previously, gold PLAL or LFL in water containing NaOH leads to the formation of transparent photoluminescent non-atomically precise AuNCs. [36,57] To characterize their optical emission, the pristine colloidal dispersion containing the nanomaterial was bleached by centrifugation, resulting in a clear dispersion with a gold concentration on the order of 25 ppb. Two distinct emission bands, one in the ultraviolet (UV) and the other in the visible (blue) region, were detected.…”

“…Two distinct emission bands, one in the ultraviolet (UV) and the other in the visible (blue) region, were detected. [36,57] To obtain deeper insights into the effect of the laser-driven CO 2 RR on morphological and optical AuNCs properties, a bleaching process was applied to the colloidal nanomaterial dispersions synthesized herein. Images of the bleached nanomaterial were obtained by HRTEM or high-resolution scanning TEM (HRSTEM) at low acceleration voltages, as depicted in Figure 5.…”

“…In fact, as reported in refs. [36,57], both fully inorganic AuNCs or AuNCs synthesized by PLAL in water containing low NaOH concentrations (c NaOH = 0.02 mmol L À1 ) are characterized by similar UV and visible emission bands, and AuNCs with average dimensions of 2.4 nm exhibit an emission centered around 415 nm. This observation suggests that OMNCs emission is still associated with the HOMO-LUMO transition of metallic cores.…”

NaBH4-Mediated Co-Reduction Synthesis of Glutathione Stabilized Gold/Silver Nanoclusters for Detection of Magnesium Ions

“…MNCs, including AuAg NCs, have been reported as showing fancy numerous responses to different metal ions [7,23,29]. To provide a new fluorescence probe for Mg 2+ , the recognition conditions of GSH@AuAg NCs to Mg 2+ were optimized.…”