Reversible Photobleaching of Gold Nanoclusters: A Mechanistic Investigation

Hemmateenejad, Bahram; Shahrivarkevishahi, Arezoo; Shakerizadeh-Shirazi, Fatemeh

doi:10.1021/acs.jpcc.6b07999

Cited by 15 publications

(11 citation statements)

References 47 publications

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“…When the UV light was turned off, reversible photobleaching leads to a complete recovery of luminescence after 30 min for the cluster, which was not observed in the case of the dye (Figure S19). Similar reversible photobleaching for clusters was observed by Hemmateenejad et al 74 Hence, these clusters can be used effectively for diagnosis and imaging purposes. The tumor-specific targeting of gold clusters was achieved in earlier studies by targeting specific molecules on cancer cells such as integrins and folate receptors using RGD peptides and folate-conjugated gold clusters, respectively.…”

Section: Origin Of Luminescence and Enhancedsupporting

confidence: 81%

Molecular Materials through Microdroplets: Synthesis of Protein-Protected Luminescent Clusters of Noble Metals

Bose

Amit

Jenifer

et al. 2021

ACS Sustainable Chem. Eng.

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Atomically precise noble metal nanoclusters protected with proteins have emerged as a new research frontier in nanoscience due to their unique optical and chemical properties as well as promising applications. In the present work, we have employed an ambient electrospray technique to synthesize proteinprotected luminescent clusters of gold and silver within the time scale of a few microseconds, which typically takes hours. In the absence of an electric field, the spray results in nanoparticles and no cluster formation was noticed. Synthesis of these clusters in microdroplets leads to severalfold enhancement in the rate of cluster formation. Spectroscopic investigations such as optical absorption, transmission electron microscopy, and matrix-assisted laser desorption ionization mass spectrometry confirm the molecular nature of the particles formed. Luminescence of electrospray-synthesized clusters shows multifold enhancement as compared to the clusters synthesized in the solution phase. Luminescence of the clusters synthesized in microdroplets increases with the distance traveled by the spray. The formation of clusters via electrospray affects the secondary structure of the protein, and its conformation is different from that of the parent protein. The Au@BSA cluster is utilized for in vitro imaging of retinoblastoma NCC-RbC-51 cells demonstrating a biological application of the resultant material. The absence of solvents and additional reagents enhances the sustainability of the method.

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Section: Origin Of Luminescence and Enhancedsupporting

confidence: 81%

Molecular Materials through Microdroplets: Synthesis of Protein-Protected Luminescent Clusters of Noble Metals

Bose

Amit

Jenifer

et al. 2021

ACS Sustainable Chem. Eng.

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“…The 4f 5/2 peak is deconvoluted into two distinctive peaks 87.39 and 87.88 eV (wine and orange curve). The higher binding energies (84.20 and 87.88 eV) are assigned for Au + and the lower energies (83.68 and 87.39 eV) are due to presence of Au 0 . Therefore, the coexistence of both Au + and Au 0 is a special characteristic of Au NCs.…”

Section: Resultsmentioning

confidence: 97%

Core-Size Dependent Fluorescent Gold Nanoclusters and Ultrasensitive Detection of Pb²⁺ Ion

Bain

Maity

Paramanik

et al. 2018

ACS Sustainable Chem. Eng.

100

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Gold nanoclusters (Au NCs) are new class of fluorescent nanomaterials with widespread applications in energy, water and healthcare. Here, we report a green synthesis of Au NCs with tunable emission wavelength from 590 to 510 nm in aqueous medium by core etching and ligand exchange method. Investigation reveals that the number of Au atoms present in the core of nanoclusters controls the emission wavelength. The quantum yield (QY) of nanoclusters increases from 0.57 to 3.15% with changing core from Au 12 to Au 6 . Time resolved spectroscopic study reveals that the emission with higher lifetime (>100 ns) originates from ligand to metal charge transfer (LMCT; S to gold core of NCs). It is demonstrated that the highly green emitting NCs (Au-510) are more sensitive than orange emitting NCs (Au-590) toward Pb 2+ . The detection limit of Pb 2+ is found to be 10 nM which is much lower than allowed concentration of Pb 2+ in drinking water. Thus, Au NCs based optical sensor is promising for the selective detection of Pb 2+ in drinking water.

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“…34 On the other hand, EGCG introduction leads to maximum wavelength back-shifting by terminating this radical induced oxidation process. 49 It should be noted that dispersed AuNCs with the identical lattice distance are observed in the presence of O 2 • ̅ (SI Figure S4A), which suggests no particle aggregation during the Fenton reaction process. Besides, no significant AuNC morphology change is found after the EGCG treatment (SI Figure S4B), indicating a nonaggregation induced fluorescence alteration in the whole system.…”

Section: ■ Results and Discussionmentioning

confidence: 85%

Fluorescence Turn-On Antioxidant Recognition by Interface-Mediated Radical Termination ofl-Cysteine-Capped Gold Nanoclusters

Kar

Chang

Chen

et al. 2021

ACS Appl. Nano Mater.

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Selective antioxidant recognition plays a critical role in various scientific and clinical fields, however, development of straightforward detection mechanisms and reduction of technique operation are still barriers nowadays. For example, convenient detection of epigallocatechin gallate (EGCG), the most effective antioxidant among all tea catechins, is highly sought but is severely limited due to the lack of appropriate indicators. To overcome the aforementioned obstacles and to provide more adequate processes that can be employed in antioxidant detection, specific analyte targeting and efficient signal reporting are necessary for the platform design. In this work, a fluorescence "turn on" strategy based on gold nanocluster (AuNC) interface-mediated radical scavenging for selective antioxidant detection is reported. This approach utilizes Lcysteine capped AuNCs with great fluorescence stability as the reporter, where the presence of reactive oxygen species (ROS) generated from the Fenton reaction results in obvious fluorescence quenching. The introduction of antioxidants, that is, EGCG molecules, interestingly, neutralizes the ROS by initiating direct electron and hydrogen atom transfer to eliminate the unpaired free radicals. Besides, the phenolic OH groups and the gallate ring of EGCG also provide a selective and efficient complexation orientation toward Fenton reaction metal ions, where ROS generation is consequently prohibited. This dual-effect phenomenon recovers the originally ROS quenched AuNC fluorescence, which is dependent upon the introduced EGCG quantity. Relying on this fluorescence turn on strategy, the current platform delivers a low detection limit of 1.20 μM with excellent selectivity toward EGCG under the presence of other interfering species. Meanwhile, this approach also provides great accuracy on detecting total antioxidant capacity in commercial green tea samples. This antioxidant fluorometric turn on design therefore gives a more straightforward route on EGCG detection, and its specific recognition capability is very suitable for practical real sample analysis.

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Reversible Photobleaching of Gold Nanoclusters: A Mechanistic Investigation

Cited by 15 publications

References 47 publications

Molecular Materials through Microdroplets: Synthesis of Protein-Protected Luminescent Clusters of Noble Metals

Molecular Materials through Microdroplets: Synthesis of Protein-Protected Luminescent Clusters of Noble Metals

Core-Size Dependent Fluorescent Gold Nanoclusters and Ultrasensitive Detection of Pb²⁺ Ion

Fluorescence Turn-On Antioxidant Recognition by Interface-Mediated Radical Termination ofl-Cysteine-Capped Gold Nanoclusters

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Reversible Photobleaching of Gold Nanoclusters: A Mechanistic Investigation

Cited by 15 publications

References 47 publications

Molecular Materials through Microdroplets: Synthesis of Protein-Protected Luminescent Clusters of Noble Metals

Molecular Materials through Microdroplets: Synthesis of Protein-Protected Luminescent Clusters of Noble Metals

Core-Size Dependent Fluorescent Gold Nanoclusters and Ultrasensitive Detection of Pb2+ Ion

Fluorescence Turn-On Antioxidant Recognition by Interface-Mediated Radical Termination ofl-Cysteine-Capped Gold Nanoclusters

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Core-Size Dependent Fluorescent Gold Nanoclusters and Ultrasensitive Detection of Pb²⁺ Ion