Functionalized Au₂₂ Clusters: Synthesis, Characterization, and Patterning

Abstract

We synthesized fluorescent, porphyrin-anchored, Au 22 clusters in a single step, starting from well-characterized Au 25 clusters protected with glutathione (-SG) by a combined core reduction/ligand exchange protocol, at a liquid-liquid interface. The prepared cluster was characterized by UV/vis, photoluminescence, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, elemental analysis, and matrix-assisted laser desorption ionization mass spectrometry. The absence of a 672 nm intraband transition of Au 25 and the simultaneous emergence of new characteristic peaks at 520 and 635 nm indicate the formation of the Au 22 core. An increase in the binding energy of 0.4 eV in Au 4f core-level peaks confirmed the presence of a reduced core size. Quantitative XPS confirmed the Au/S ratio. The presence of a free base, tetraphenylporphyrin (H 2 TPPOAS-), on the Au 22 core was confirmed by fluorimetric titrations with Cu 2+ and Zn 2+ ions. From all of these, the composition of the cluster was determined to be Au 22 [(-SG) 15 (-SAOPPTH 2 ) 2 ], which was supported by mass spectrometry and elemental analysis. We utilized the fluorescence nature of these water-soluble clusters for the fabrication of fluorescent patterns by soft lithography. The patterns were studied using tappingmode atomic force microscopy and confocal fluorescence imaging.

Protein stabilized Au nanoclusters: spectral properties and photostability

“…Currently, considerable research efforts are directed towards investigation of Au NCs synthesis [4][5][6][7][8][9][10], structure [7,11,12], optical properties [4,[13][14][15][16], photostability [17][18][19][20][21] and possible applications for material sensing [5,[22][23][24] as fluorescence [25,26] and dual-modality imaging contrast agents [27,28]. However, colloidal stability, photostability, dependence of optical properties on temperature, interaction of BSA-Au NCs with biomolecules are still poorly investigated.…”

Synthesis of DNA-templated fluorescent gold nanoclusters

“…Fluorescent Au NCs have been prepared mainly in a bottom-up manner by the reduction of gold precursors in the presence of various templates such as macromolecules (dendrimers [5][6][7][8][9], proteins [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24], poly-butadiene [25]), small molecules (histidine [26], carbohydrate [27], thiols [28][29][30][31][32][33], N, N-dimethylformamide [34,35], penicillamine [36]), and even solid functional organisms (eggshell membrane [37]). Alternatively, top-down etching of preformed large nanoparticles down to desired NC sizes has received much attention due to many available synthetic strategies for the large nanoparticles.…”

Luminescent Quantum Clusters of Gold in Bulk by Albumin‐Induced Core Etching of Nanoparticles: Metal Ion Sensing, Metal‐Enhanced Luminescence, and Biolabeling

“…[7] Two-photon emission, a process in which transition between energy levels occurs through the simultaneous emission of two photons, is observed in Au 25 QCs and hence they can be made useful for two-photon imaging with IR excitation. [9] Fçrster resonance energy transfer (FRET) between the metal core and the ligand in Au 25 SG 18 (SG: glutathione thiolate) has been demonstrated by using dansyl chromophores attached to the QC core through glutathione linkers. [10] Photon antibunching, a quantum phenomenon that occurs during luminescence, in which the emission of one photon reduces the probability that another photon will be emitted immediately afterwards, was observed in Au 23 QCs synthesized inside the dendrimer cavities.…”