Near-Infrared Luminescence from Small Gold Nanocrystals

Abstract

A novel photoluminescence is reported for small metal nanocrystals in the near-infrared region (1.1-1.6 µm). Near-infrared photoluminescence spectra were measured at room temperature for 1.1 and 1.7 nm Au nanocrystals using a 1.06 µm excitation source. This photoluminescence is attributed to sp to sp-like transitions, analogous to intraband transitions in bulk gold; however, the exact mechanism is unknown. A conservative estimate for the quantum yield for the 1.7 nm gold nanocrystals is (4.4 ( 1.5) × 10 -5 at room temperature, more than 5 orders of magnitude greater than that of bulk gold.

Functionalized Au22 Clusters: Synthesis, Characterization, and Patterning

“…The fast-moving fraction was collected and evaporated to dryness to yield the desired product (0.10 g, 85%). The product was characterized by 1 The synthesis of compound III was carried out using a variant of the reported method (59). To a stirred solution of compound II (0.065 g, 0.073 mmol), in freshly distilled THF (40 mL), was added hexamethyldisilathiane (0.04 mL, 0.2 mmol) under an inert atmosphere; tetrabutylammonium fluoride (0.05 g) was added subsequently, and the solution was stirred for a period of 3 h. To the reaction mixture was added distilled water (50 mL), and the resulting solution was stirred for a further period of 30 min.…”

UV–visible absorption of small gold clusters in neon: Aun (n = 1–5 and 7–9)

“…This is related to the finding that gold nanoparticles and in particular very small gold clusters containing as few as 7-8 atoms show pronounced catalytic activity [3][4][5][6] and remarkable luminescent properties. [7][8][9][10][11] A number of theoretical calculations [12][13][14][15][16] predict, contrary to alkali metal clusters, the persistence of planar structures as the energetically favorable conformation up to a large number of atoms, depending on the charge state of the Au n clusters. This behavior, which is not found in the case of the other noble metal clusters, 13,17 has been correlated with relativistically enhanced s-d hybridization and d-d interaction.…”

Microspectroscopic characterisation of gold nanorods for cancer detection

“…[179][180][181][182][183] The localized surface plasmons near rough metal nanostructures are presumed to perform a mediating role in the IR emission, 184,185 because these strongly confined fields possess resonances of electrons in the metal, and the associated field gradients give rise to higher-order multipolar transitions. 179 Independently, Varnavski et al also speculated upon a possible role of surface plasmons in intraband excitations.…”

“…Different names to apparently similar objects have also been used: nanospheres are sometimes referred to as nanodots 148 and nanoclusters are also called nanocrystals, 180,198 because of their atomic crystalline arrangements. For example, Lugunov et al refer to gold arrangements of roughly 200 gold atoms, which are approximately 1.9 nm in diameter, as gold nanocrystals, 198 and Schaaff et al use the term nanoclusters for structures with diameters up to 4 nm.…”

“…180,198 There is a general consensus on the fluorescence capabilities of gold nanoclusters resulting from the many studies that have been conducted (Table 5.1).…”