The excited state dynamics of protein-encapsulated Au nanoclusters

Abstract

a b s t r a c tA combination of static and time-resolved spectroscopic techniques has been applied to study the lowlying excited electronic states of protein-encapsulated Au nanoclusters in terms of their energy levels and relaxation mechanisms. The energy levels were determined using photoluminescence (PL) spectroscopy. The excited state dynamics were probed using time-resolved PL techniques as well as femtosecond transient absorption (TA) spectroscopy. A simple model was proposed to account for the key spectral and dynamic features observed. This study has added new insight to the optical and dynamic properties of metal nanoclusters of interest in many applications including solar energy conversion and biomedical imaging.

Dependence of ultrafast dynamics in gold–silver alloy nanoclusters on the proportion of the metal content

“…Characteristic featureless absorption spectra (Fig. 4a) suggest formation of stable Au and Au-Ag NCs [56]. In conventional noble metal nanoparticles, surface plasmon resonance dominates the optical response and shows strong quantum confinement effect with manifestations in the discrete UV-vis absorption spectrum [13].…”

“…Sfeir et al attributed the faster decaying component to rapid IC [67]. The slower component in Table 2 was assigned to the fraction of the NCs that lives longer with delayed non-radiative processes, such as, IC or intersystem crossing (ISC) [56]. In the present case, on irradiation at 365 nm the electron may directly get transited to the higher excited singlet states (S n ) followed by faster decay in ~ 1-2 and 100 ps ( Table 3).…”

Spiropyran-Functionalized Gold Nanoclusters with Photochromic Ability for Light-Controlled Fluorescence Bioimaging

“…With an appropriate fluorescent probe, fluorescence imaging allows noninvasive and real-time imaging of intracellular structures. − Thus, many fluorescent molecules and nanoscopic structures are designed as fluorescent probes because of their small size and easy entrance into cells. − Recently, gold nanoclusters (AuNCs) with a subnanometer scale and minimal toxicity have attracted much attention in biological applications. − More importantly, the ultrasmall size of AuNCs meets the de Broglie wavelength of the conduction electrons, thus evolving discrete energy levels . Electronic transitions among these energy levels could give the AuNCs a unique fluorescent property, which makes them as promising candidates for fluorescent probes. − …”

Charge State of Au25(SG)18 Nanoclusters Induced by Interaction with a Metal Organic Framework Support and Its Effect on Catalytic Performance

“…UV–visible absorption spectra (Figure S3) are carried out to identify the fingerprints absorption peaks of Au 25 (SG) 18 arose from molecular-like electron transition. , Unfortunately, these feature absorption bands cannot be discerned in Mil-101-Cr, because of strong substrates absorption in visible region. In contrast, the absorption peaks of Au 25 (SG) 18 at about 400, 450, and 670 nm can be discerned on Mil-125-Ti support.…”