Synthesis Of Fluorescent Gold Nanoclusters Research Articles

Synthesis of fluorescent gold nanoclusters in the presence of adenosine monophosphate: effect of azide ions

It has been demonstrated that fluorescence of gold nanoclusters formed via HAuCl4 reduction with citrate buffered solution in the presence of adenosine monophosphate can be tuned via addition of NaN3. No fluorescent products have been detected at large excess of NaN3, whereas at intermediate concentrations of NaN3 blue–green fluorescence has been gradually changed to yellow and weakened.

DNA as a template for synthesis of fluorescent gold nanoclusters

Water-soluble blue-emitting gold nanoclusters have been synthesized using dsDNA as a template without any additional reducing agent. The features of the formed nanoclusters have been revealed by fluorescence and electronic absorption spectroscopy as well as transmission electron microscopy. The prepared gold nanoclusters have been highly stable at physiological pH without any further modification.

Telechemistry 2.0: Remote monitoring of fluorescent chemical reactions

Implementation of the Internet-of-Things in chemistry research has the potential to improve research methodologies. Here, we describe a cloud-integrated real-time laboratory monitoring system for: (i)monitoring reactions involving fluorescent chemical species, and (ii) monitoring laboratory environment for safety purpose. A probe-type fluorescence detection system has been constructed to monitor reactions that involve fluorescent molecules. This device incorporates an in-house-built 3D-printed probe, two optical fibers, a light-emitting diode, a photoresistor, and a microcontroller board (MCB). The MCB relays experimental data to a single-board computer (SBC), which then uploads the data to a cloud-based platform (ThingSpeak) for data storage and visualization. The SBC is also connected to auxiliary sensors to measure relative alcohol vapor concentration, temperature, and humidity at different locations in the laboratory. The device has been validated and tested for its performance by monitoring a fluorescent chemical reaction (synthesis of fluorescent gold nanoclusters) for a period of 12 h.

Diphenylalanin nanofibers-inspired synthesis of fluorescent gold nanoclusters for screening of anti-amyloid drugs

Protein misfolding and aggregation into amyloid structures is linked with a number of pathophysiological disorders. In the past decade, significant progresses have been made in the drug discovery strategies against toxic aggregates. Although lack of specificity and high sensitivity for in vitro screening system still seen. Here we demonstrate a new targeting probe based on FF diphenylalanine peptide -protected gold nanoclusters (FF AuNCs). Diphenylalanine peptide has previously been shown to self-assemble into well-ordered fiber like the fibers that are observed in amyloid aggregates. We used of the self-assembly properties along with the ability of FF dipeptide in reduction of gold ions for synthesis of novel Au nanoclusters. We used FF AuNCs for monitoring of effectiveness of anti-amyloid drugs. Fluorescence was considerably diminished when drugs at different concentrations added, due to destruction of the amyloid fibers. Furthermore, the analysis of several components demonstrates significant selectivity against the amyloid disrupting molecules. Prepared FF AuNCs will gain possible strategy for in vitro screening of amyloid disrupting molecules.

One pot synthesis of fluorescent gold nanoclusters from Curcuma longa extract for independent detection of Cd2+, Zn2+ and Cu2+ ions with high sensitivity

Abstract The current research describes that the development of a novel fluorescence strategy for the monitoring of metal ions (Cd2+, Zn2+ and Cu2+) from various environments. The fluorescence sensing platform was developed for parallel detection of three divalent ions i.e., Cd2+, Zn2+ and Cu2+ ions from aqueous solution by synthesizing highly orange red-emission gold nanoclusters derived from Curcuma longa root extract (CE) and 11- mercapto undecanoic acid (11-MUA) (CE/11-MUA-AuNCs) as reducing and capping ligands. In order to reduce the interference from co-existing metal ions, different masking agents were used to mask their interference during target metal ion analysis in the presence of other metal ions. Using CE/11-MUA-AuNCs, fluorescence enhancement mechanism was noticed for Cd2+ and Zn2+ ions, whereas fluorescence “turn-off” mechanism was observed for Cu2+ ion. The CE/11-MUA-AuNCs probe exhibited good quantitative response to Cd2+ and Zn2+ ions through fluorescence enhancement (0.01–2.5 and 0.025–5.0 μM for Cd2+ and Zn2+ ions) and to Cu2+ ion via turn-off (0.05–10 μM). Importantly, 0.012, 0.016 and 0.026 μM detection limits represent the better sensitivity among the reported analytical methods for the analysis of Cd2+, Zn2+ and Cu2+ ions. The practical application of the probe was applied to quantitative detection of Cd2+, Zn2+ and Cu2+ ions in real samples (urine, plasma, spinach, and wheat germ), which proves that the probe could be established as one of the routine and reliable analytical platform for parallel sensing of three metal ions (Cd2+, Zn2+ and Cu2+ ions).

Microwave-assisted in situ synthesis of fluorescent gold nanoclusters with BSA/montmorillonite and application on latent fingermark imaging

A method for in situ preparation of fluorescent gold nanoclusters (AuNCs) with bovine serum albumin/montmorillonite composite powder (AuNC-BSA/MMT) was developed, and the products were used to detect latent fingermarks. In this work, AuNCs were “grown” both inside and on the surface of BSA/MMT clay using one-step reduction of HAuCl4 by BSA. The as-prepared AuNC-BSA/MMT nanocomposites emit intensive red fluorescence under the excitation of UV-visible light and show stable chemical features and low toxicity. The obtained fluorescent powders were characterized by UV-visible absorption spectroscopy, fluorescence spectroscopy, infrared spectroscopy, transmission electron microscopy/high-resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction to depict their sizes, structural information and optical features. Given their environmentally friendly preparation, simple operation, low cost, efficient UVvisible radiation-dependent photoluminescence and good affinity with finger residues, the in situ synthesized AuNC-BSA/MMT nanocomposite powders were used as an alternative fluorescent developing reagent for developing latent fingermarks deposited on various object surfaces (such as glass, aluminum foil, painted metal, plastic products and weighing papers) for individual identification. As results, the developed fingermarks with clear patterns and satisfactory level-2 (minutiae points) and level-3 (sweat pores) ridge details were obtained. Notably, treated prints could be excited by red light and emitted near infrared fluorescence, which was beneficial to avoid background interference and reduce the damage caused by UV light. With the advantages of the simple preparation process and good enhancement performance for latent fingermarks, the proposed method might be used in the preparation of various fluorescent probes for detecting trace evidence in forensic sciences.

Inositol directed facile “green” synthesis of fluorescent gold nanoclusters as selective and sensitive detecting probes of ferric ions

In this paper, we developed one-pot facile synthetic approach for preparing fluorescent gold nanoclusters (AuNCs) by utilizing reducing-cum-stabilizing inositol (INOS). The as-prepared INOS protected gold nanoclusters (INOS@AuNCs) have excellent monodispersity with uniform size <2.0nm and exhibit strong inherent fluorescence at 470nm with a decay time of 12.01ns. Interestingly, ferric ions (Fe3+) can significantly quench the fluorescence of the synthesized INOS@AuNCs leading to the efficient Fe3+ sensing. On the basis of results obtained from high-resolution transmission electron microscopy (HRTEM), an aggregation-induced fluorescence quenching mechanism was proposed. Based on these fascinating findings, a facile, fast, “green” and highly sensitive AuNCs-dependant fluorescent sensor probe was developed to detect Fe3+ ions in water resources and Over-The-Counter (OTC) medicines. Stern-Volmer plot showed a good linear calibration curve for Fe3+ assay in the range of 1.0–1000μM (R2=0.996) and good precision response to 100.0μM Fe3+ with RSD of 2.94% (n=3) was also achieved. The obtained limit of detection of 0.54μM for the determination of Fe3+ ions is 10 times lower than the limit value (≈5.5μM) allowed by the U.S. Environmental Protection Agency in drinkable water, indicating the sensitivity of the fluorescent probe of Fe3+ sensing. The excellent selectivity obtained among 16 types of metal ions underpins INOS@AuNCs as a promising sensor for real time detection of Fe3+ in environmental water samples and pharmaceutical tablets.

Disulfide-functionalized hyperbranched poly(amidoamine) derivatives as both reductant and stabilizer for the synthesis of fluorescent gold nanoclusters

Hyperbranched polymers were successfully used as reductant and stabilizer for the synthesis of stable water-soluble fluorescent gold nanoclusters (AuNCs) through a one-step bottom-up strategy. The hyperbranched polymers having such performance were acetamide terminated hyperbranched poly(amidoamines) (HPA-Acs) with disulfide functional groups. Small sized (less than 2nm) AuNCs were formed under the optimal conditions of 80°C, weak acidic condition (around pH 4.3) for 15–20h. Through adjusting the feed ratio of HAuCl4 to HPA-Ac, the emitting light could be tuned from yellow to near-infrared. The measurements of UV–vis spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy further verified the formation of AuNCs. The quantum yields of the yellow and near-infrared fluorescent AuNCs were ca. 3.6% and 1.2%, respectively. The as-prepared AuNCs showed an excellent stability in a wide pH range (pH 2–12) and possessed low cytotoxicity for cancer HeLa cell, making it a suitable candidate for bioimaging.

Rapid one-pot synthesis of MMTA protected fluorescent gold nanoclusters for selective and sensitive detection of ferric ion

Herein, we demonstrate a straightforward synthesis of fluorescent gold nanoclusters (AuNCs), employing 2-Mercapto-4-methyl-5-thiazoleacetic acid (MMTA) as a reducing and protecting agent by a rapid one-pot synthesis method with a short time of 20min. The as-synthesized MMTA-AuNCs exhibited bright blue emission with a strong peak centered at 430nm and the quantum yield (QY) was evaluated to be 4.0%. Based on the fluorescence quenching mechanism of a surface chelating reaction between MMTA and ferric ion (Fe3+), the MMTA-AuNCs were exploited as a fluorescence sensor for sensitive and selective detection of Fe3+. Two linear ranges of 9.9–3000.0nM and 3.0–1100μM with a detection limit of 3.0nM were obtained. The detection limit was lower than the maximum level (0.3mgL−1, equivalent to 5.4μM) of Fe3+ permitted in drinking water by the U.S. Environmental Protection Agency. Furthermore, the proposed fluorescent sensing system was successfully applied to the analysis of Fe3+ in real samples such as water and human serum samples with satisfactory recoveries. These results indicated that the as-prepared MMTA-AuNCs could pave an avenue for the development of sensing probes for detection of Fe3+ in environmental and biomedical applications.

Facile preparation of fluorescent gold nanocluster via polysaccharide-templated approach and its application for Cu2+ sensing

In this report, we have constructed a simple, eco-friendly and one-pot synthetic strategy for the synthesis of fluorescent gold nanoclusters (GNCs) using a native polysaccharide (chondroitin sulfate) as the novel template. Moreover, we used some analytical instruments for characterizing the formation of Au clusters, containing ultraviolet-visible spectrometer, fluorescence spectrometer, high resolution transmission electron microscope (HRTEM) and X-ray photoelectron spectroscopy (XPS). The obtained data indicated that the Au nanoclusters were successfully formed. The chondroitin sulfate-capped gold nanoclusters (CS-GNCs) displayed excitation and emission bands at 450 and 520nm, respectively. The fluorescence quantum yield was 4.78%. We further used CS-stabilized gold nanoclusters selectively and sensitively for sensing Cu2+ in real samples via non-covalent d10-d10 metallophilic bond. The linear range of the method was 0.01–1.8μM with the limit of detection (LOD) was 8nM (signal/noise=3), and the recoveries of the spiked samples in lake water and tap water samples ranged from 90% to 108%, suggesting that the proposed method could be used in the practice detection of Cu2+.

Exploring the potential of linear polymer structures for the synthesis of fluorescent gold nanoclusters

In this study, fluorescent gold nanoclusters (AuNCs) were synthesized via the one-pot reduction of gold ions (Au3+) in the presence of thiolated copolymers.

In situ Synthesis of Fluorescent Gold Nanoclusters by Nontumorigenic Microglial Cells.

To date, the directed in situ synthesis of fluorescent gold nanoclusters (AuNCs) has only been demonstrated in cancerous cells, with the theorized synthesis mechanism prohibiting AuNC formation in nontumorigenic cell lines. This limitation hinders potential biostabilized AuNC-based technology in healthy cells involving both chemical and mechanical analysis, such as the direct sensing of protein function and the elucidation of local mechanical environments. Thus, new synthesis strategies are required to expand the application space of AuNCs beyond cancer-focused cellular studies. In this contribution, we have developed the methodology and demonstrated the direct in situ synthesis of AuNCs in the nontumorigenic neuronal microglial line, C8B4. The as-synthesized AuNCs form in situ and are stabilized by cellular proteins. The clusters exhibit bright green fluorescence and demonstrate low (<10%) toxicity. Interestingly, elevated ROS levels were not required for the in situ formation of AuNCs, although intracellular reductants such as glutamate were required for the synthesis of AuNCs in C8B4 cells. To our knowledge, this is the first-ever demonstration of AuNC synthesis in nontumorigenic cells and, as such, it considerably expands the application space of biostabilized fluorescent AuNCs.

Fabrication of peptide stabilized fluorescent gold nanocluster/graphene oxide nanocomplex and its application in turn-on detection of metalloproteinase-9

This study introduces the double-ligands stabilizing gold nanoclusters and the fabrication of gold nanocluster/graphene nanocomplex as a “turn-on” fluorescent probe for the detection of cancer-related enzyme matrix metalloproteinase-9. A facile, one-step approach was developed for the synthesis of fluorescent gold nanoclusters using peptides and mercaptoundecanoic acid as co-templating ligands. The peptide was designed to possess a metalloproteinase-9 cleavage site and to act not only as a stabilizer but also as a targeting ligand for the enzyme detection. The prepared gold nanoclusters show an intense red fluorescence with a broad adsorption spectrum. In the presence of the enzyme, due to the excellent quenching properties and the negligible background of graphene oxide, the developed peptide-gold nanocluster/graphene nanocomplex yielded an intense “turn-on” fluorescent response, which strongly correlated with the enzyme concentration. The limit of detection of the nanocomplex was 0.15nM. The sensor was successfully applied for “turn-on” detection of metalloproteinase-9 secreted from human breast adenocarcinoma MCF-7 cells with high sensitivity, selectivity, significant improvement in terms of detection time and simplicity.

A multi-responsive intrinsically disordered protein (IDP)-directed green synthesis of fluorescent gold nanoclusters.

Herein we demonstrate the green synthesis of fluorescent gold nanoclusters (AuNCs) using a multi-responsive intrinsically disordered protein (IDP) polymer, Rec1-resilin, as a multi-functional template. In a controlled environment, Rec1-resilin acts simultaneously as the directing agent and the reducer, and performs the role of a highly efficient stabilizer once AuNCs are formed. The evolution of the photophysical properties and the chemical states of AuNCs formed are measured using UV-Vis, fluorescence and X-ray photoelectron spectroscopy. Circular dichroism (CD) spectroscopy measures the intrinsically disordered nature of Rec1-resilin stabilizing AuNCs. High resolution transmission electron microscopy (HR-TEM) reveals the detailed structure and morphology of the generated AuNCs of <1.5 nm size. A local ordering resembling that of a face-centered cubic (FCC) structure with evidence of twinning was observed for the generated AuNCs. The AuNCs so formed exclude the use of toxic reducing agents and display excellent water dispersibility, photostability and environmental stability towards aggregation.

Synthesis of functionalized fluorescent gold nanoclusters for acid phosphatase sensing.

A novel and convenient one-pot but two-step synthesis of fluorescent gold nanoclusters, incorporating glutathione (GSH) and 11-mercaptoundecanoic acid (MUA) as the functionalized ligands (i.e. AuNCs@GSH/MUA), is demonstrated. Herein, the mixing of HAuCl4 and GSH in aqueous solution results in the immediate formation of non-fluorescent GSH-Au(+) complexes, and then a class of ∼2.6 nm GSH-coated AuNCs (AuNCs@GSH) with mild orange-yellow fluorescence after several days. Interestingly, the intense orange-red emitting ∼1.7 nm AuNCs@GSH/MUA can be synthesized within seconds by introducing an alkaline aqueous solution of MUA into the GSH-Au(+) complexes or AuNC@GSH solution. Subsequently, a reliable AuNC@GSH/MUA-based real-time assay of acid phosphatase (ACP) is established for the first time, inspired by the selective coordination of Fe(3+) with surface ligands of AuNCs, the higher binding affinity between the pyrophosphate ion (PPi) and Fe(3+), and the hydrolysis of PPi into orthophosphate by ACP. Our fluorescent chemosensor can also be applied to assay ACP in a real biological sample and, furthermore, to screen the inhibitor of ACP. This report paves a new avenue for synthesizing AuNCs based on either the bottom-up reduction or top-down etching method, establishing real-time fluorescence assays for ACP by means of PPi as the substrate, and further exploring the sensing applications of fluorescent AuNCs.

One-step facile synthesis of fluorescent gold nanoclusters for rapid bio-imaging of cancer cells and small animals

Fluorescent bio-imaging has become a major topic of the modern biomedical research field.

Dithiothreitol-capped fluorescent gold nanoclusters: An efficient probe for detection of copper(II) ions in aqueous solution

We report here a Green method for the synthesis of fluorescent gold nanoclusters using dithiothreitol (DTT) as both a capping agent and reducing agent at 22°C and pH 8. The physical and chemical properties of the synthesized AuNCs@DTT were studied by TEM and UV–vis absorption, fluorescence, and X-ray photoelectron spectroscopy. AuNCs@DTT recognizes cupric ions with high selectivity and sensitivity, which allows this material to act as a copper(II) sensor in aqueous solution. A linear relationship was observed between the fluorescence intensity of the DTT capped gold nanoclusters and the concentration of copper(II) ions, in the range of 0–60μM with a detection limit of 80nM. The copper content in serum was also analyzed by using this copper sensor. It was shown that data obtained using the proposed method was comparable to values obtained by the traditional colorimetric method. This technique represents an alternative method for the determination of serum copper in clinical diagnosis especially for those laboratories which lack expensive analytical facilities.

Synthesis of Fluorescent Gold Nanoclusters Directed by Bovine Serum Albumin and Application for Nitrite Detection

In the present work, gold nanocluster (GNC) induced by bovine serum albumin (BSA) was synthesized as a novel fluorescence probe to detect nitrite (NO2(-)) sensitively and selectively. The fluorescence of GNC was found to be quenched effectively by NO2(-). Under the optimum conditions, it was found that the change of fluorescence intensity was proportional with the concentration of NO2(-) in the linear range of 0.1-50 μM (R = 0.9990), with a detection limit (S/N = 3) of 30 nM. The absorption spectroscopy, circular dichroism (CD), and X-ray photoelectron spectroscopy (XPS) studies were employed to discuss the quenching mechanism. In addition, the present approach was successfully applied in real water samples.

Human insulin fibril-assisted synthesis of fluorescent gold nanoclusters in alkaline media under physiological temperature

Fluorescent insulin fibrils gold nanoclusters (Au NCs) have been synthesized through the reduction of gold by human insulin in fibrillated form. Likewise, nanocluster formation has been regulated by insulin, working as a protein-based template. Environment- and surface-controlled experiments have shown the optimized synthesis conditions is comprised of a pure aqueous alkaline solvent for insulin under constant heat at physiological temperature (37°C) prior to addition of the Au precursor (HAuCl4), followed by subsequent heating (37°C) and vigorous stirring after the addition of HAuCl4 until the completion of the synthetic approach. Microscopy experiments detected the presence of primordial fibril structures in samples of heated human insulin in the alkaline medium prior to addition of HAuCl4, while encountering more developed insulin fibrils in the terminal production of Au NCs. This investigation provides insight to the development of a novel synthesis of Au NCs in the alkaline medium, while providing a graphical description of the environmental and surface-dependent effects that were presented in the synthesis of human insulin nanoclusters. The study provides pertinent information for future synthetic procedures, as the protein state of several protein-nanoparticle systems may reflect on the results that were obtained herein.

In-situ synthesis of fluorescent gold nanoclusters with electrospun fibrous membrane and application on Hg (II) sensing

In the present study, a method for in-situ preparation of fluorescent gold nanoclusters with bovine serum albumin/poly(ethylene oxide) electrospun membrane (BSA/PEO-Au NCs) has been developed to detect Hg2+. In this work, Au NCs were immobilized both inside and on the surface of fibrous membrane using one-step reduction of HAuCl4 by BSA. The as-prepared BSA/PEO-Au NCs were able to emit intensive red fluorescence under the excitation of visible light, and the fluorescence could be quenched by Hg2+. The results indicate that the as-prepared BSA/PEO-Au NCs exhibit good sensitivity towards Hg2+, which might be benefit from the large specific surface area of BSA/PEO fibrous membrane. The biosensor exhibits a linear response to Hg2+ concentrations ranging from 0.5nM to 75nM with a limit of detection (LOD) of 57pM. Moreover, BSA/PEO-Au NCs shows good selectivity towards other common metal ions. With the advantages of the simple preparation process and good detection performance, the proposed method is anticipated to fabricate other sensitive fluorescence fiber-based sensors of metal nanoclusters.