Gold nanoclusters with enhanced tunable fluorescence as bioimaging probes

Abstract

Development of unique bioimaging probes offering essential information's about bio environments are an important step forward in biomedical science. Nanotechnology offers variety of novel imaging nanoprobes having high-photo stability as compared to conventional molecular probes which often experience rapid photo bleaching problem. Although great advances have been made on the development of semiconductor nanocrystals-based fluorescent imaging probes, potential toxicity issue by heavy metal component limits their in vivo therapeutic and clinical application. Recent works show that fluorescent gold clusters (FGCs) can be a promising nontoxic alternative of semiconductor nanocrystals. FGCs derived imaging nanoprobes offer stable and tunable visible emission, small hydrodynamic size, high biocompatibility and have been exploited in variety in vitro and in vivo imaging applications. In this review, we will focus on the synthetic advances and bioimaging application potentials of FGCs. In particular, we will emphasize on functional FGCs that are bright and stable enough to be useful as bioimaging probes.

Reversible Size Control of Silver Nanoclusters via Ligand-Exchange

“…Thus obtained clusters show a spectacular absorption band at 490 nm. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Ligand-exchange reaction of Ag 35 (SG) 18 with different organic-soluble thiols To start, approximately 12.5 mM DCM solutions of all thiol ligands were prepared separately.…”

“…Here, we present a process for the ligand-exchange-induced growth of atomically precise silver NCs, in a biphasic liquid-liquid system, which is particularly of interest because of its complete reversibility and ability to occur at room temperature. We explore this phenomenon in-depth using Ag 35 (SG) 18 …”

“…[11][12][13] The emerging opportunities in catalysis, 14 energy, 15,16 environment, 17 and biology 18 enabled by the small size and often precise nature of these materials has spurred researchers to explore a multitude of synthetic routes to attain them including borohydride and gaseous reduction; 19,20 26 ; and templated growth in proteins, 27 polymers, 24 and gel cavities. 26 Each of these methods produces size-specific NCs.…”

“…The process occurs at room temperature in an immiscible liquid-liquid biphasic system that is remarkable for its complete reversibility. The method was studied in-depth for the interconvertibility of Ag 35 (SG) 18 [SG= glutathionate] into Ag 44 30 . The reaction, depending on its direction, can be rapid and direct or may occur slowly through several transition states of intermediate NC sizes.…”

“…35 The model fits well with the experimental observations and highlights, among other parameters, the critical role played by small changes in the ligand-metal binding energy in determining the final size of the NC. Based on the insight provided by the model, we demonstrate experimentally that by varying the chemical structure of the incoming thiol ligands, one can tune the size of Ag 35 (SG) 18 to obtain a substantial set of NC sizes beyond Ag 44 30 . Our findings showcase ligand-exchange as a versatile tool to explore the landscape of NC sizes, akin to size focusing in gold NCs, 22 and provides a straightforward lever for controlling the final NC size by varying the incoming ligand.…”