Search

Thiolate‐stabilized gold nanoclusters (Au NCs) are widely used in bioimaging, chemical sensing, and emitting devices because of their good solubility, great stability and versatile optical/chemical properties. However, most conventional synthetic strategies reported so far suffer long reaction time, which limits the rapid and large‐scale synthesis of Au NCs. In this study, a simple electrostatic attraction‐assisted core approaching strategy was developed, which accelerates the synthesis of Au NCs by introducing polyamine (hyperbranched polyetheneimine, hPEI). As a case study, the tactic was demonstrated for the rapid preparation of Au NCs based on glutathione (GSH)‐HAuCl4 system within 1.5 h. The synthesis includes two steps: first, negatively charged Au(I)‐GSH complex under basic condition (pH 9) was adsorbed onto hPEI surface via electrostatic attraction; second, aurophilic attraction of Au(I) centers benefited the formation of Au NCs. With such a strategy, copper nanoclusters (Cu NCs) can also be quickly prepared within 30 min. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (Au NPs) have become one of the most popular materials for sensing of analytes of interest in the last decade, mainly because of their ease in preparation and conjugation, stability, biocompatibility, and size-dependent optical properties. We have witnessed many sensitive and selective Au NP based optical systems for the quantitation of metal ions, anions, proteins, and DNA, based on analyte induced changes in their absorption, fluorescence, and scattering. In this tutorial review, we briefly discuss wet chemical approaches for the preparation of Au NPs. Sensing mechanisms and strategies of Au NP based optical systems are provided to show basic concepts in designing sensitive and selective sensing systems. Strategies for signal amplification applied in Au NP based systems are emphasized for the analysis of trace amounts of analytes in real samples. Many excellent Au NP based optical sensing systems are discussed to highlight their practicality for the analysis of complicated biological and environmental samples. The tutorial review ends with the discussion of the challenges and future trends of Au NP based optical sensing systems. [ABSTRACT FROM AUTHOR]

As a well-known environmental pollutant but also an important gaseous transmitter, the specific detection of hydrogen sulfide (H2S) is significant in biological systems. In this study, fluorosurfactant functionalized gold nanorods (FSN-AuNRs) have been proposed to act as selective colorimetric nanoprobes for H2S. With the combination of strong gold–S interactions and small FSN bilayer interstices, FSN-AuNRs demonstrate favorable selectivity and sensitivity toward H2S over other anions and small biological molecules. The practical application of the present method in biological H2S detection was validated with human and mouse serum samples. Moreover, the proposed nanoprobe can also be used for evaluating the activity of H2S synthetase. [ABSTRACT FROM AUTHOR]

We report a novel approach for preparation of networked gold nanoparticles (AuNPs) using reactive oxygen species (i.e., peroxymonocarbonate, HCO4−) as a novel reducing agent, along with nonionic fluorosurfactant (FSN) assistance. The formation mechanism of the networked AuNPs is demonstrated by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), UV-visible spectroscopy, powder X-ray diffraction (XRD) measurement and energy dispersive X-ray spectroscopy (EDS). In this case, HCO4− serves as a reducing agent for the preparation of the networked AuNPs, and further as a strong oxidizing agent attached to the surface of networked AuNPs, which can trigger the strong CL emission from luminol without the addition of H2O2. In addition, FSN can control and stabilize the crystal morphology of the networked AuNPs, and improve the selectivity of the CL detection system for aminothiols. Finally, the networked AuNPs have been applied for ultrasensitive detection of aminothiols in human urine and plasma samples. [ABSTRACT FROM AUTHOR]

Abstract: The aggregation of gold nanoparticles (GNPs) capped with nonionic fluorosurfactant (FSN) could be induced rapidly and selectively by cephradine degradation products, but not by cephradine and other excipients in pharmaceutical formulations. A new detection method for cephradine has been developed based on the cephradine degradation products-induced aggregation of the GNPs. The present approach offers various advantages, such as simplicity and high selectivity. Under optimum conditions, the lowest detectable concentration of cephradine through this approach (S/N=3) is 0.8μgmL−1. The calibration curve was linear over the range of 2.0–10.0μgmL−1 for the detection of cephradine. The recoveries of cephradine were found to fall in the range between 97% and 105%. We have validated the applicability of our method through the analyses of cephradine in pharmaceutical formulations. Good agreements were obtained for the determination of cephradine between the present approach and official method. [Copyright &y& Elsevier]

Abstract: Gold nanoparticles (GNPs) have been stabilized with nonionic surfactant ligands, i.e., Brij@ 35, and their aggregation could be induced rapidly and selectively by biologically active low-molecular-mass thiols including sulphydryl-containing amino acids (cysteine and homocysteine) and small peptides (glutathione, cysteinylglycine, and glutamylcysteine). A new postcolumn detection method has been developed for high-performance liquid chromatography (HPLC) assay of these small biothiols based on the analyte-induced aggregation of the GNPs. Compared with conventional thiol-reactive probes, the GNP colloids are easier to prepare, much more stable in aqueous solution over a wide pH range and at ambient temperature, and exhibit relatively high selectivity toward small biothiols. The analysis of human urine samples demonstrated that the proposed method is promising in HPLC assay of the small thiol molecules in biological fluids. [Copyright &y& Elsevier]

Development of methods allowing cataluminescence at low temperatures is a particular scientific challenge. Low temperature-induced cataluminescence is usually performed by plasma-assisted catalytic oxidation on nanomaterials. High dispersed gold nanoparticles deposited on certain support could exhibit superior catalytic activities toward a series of reactions at low temperatures. There is apparently no good reason to disregard low temperature-induced cataluminescence on the surface of gold nanoparticle-support nanocomposites. Herein, layered double hydroxides (LDH)-supported gold nanoparticles were prepared using a colloid deposition method. Such the LDH-supported gold nanoparticle composite exhibits a remarkable cataluminescence response toward a series of organic compounds at high temperature (210 °C). Only acetaldehyde among the all tested organic compounds emerge an obvious cataluminescence signal on the surface of the LDH-supported gold nanoparticles at low temperature (105 °C). The synergy effects between gold nanoparticles and LDHs seem to play an important role in the acceleration of the rate-determining step at low temperatures. Therefore, the fabricated low-temperature cataluminescence sensor is validated for the analysis of acetaldehyde in fruit beverages with the minimized interferences. In principle, this work could be extended to other analytes by fabricating different nanoparticle-support nanocomposites. [ABSTRACT FROM AUTHOR]

Highlights: [•] Properties of non-ionic fluorosurfactant-modified electrodes and gold nanoparticles. [•] Analytical applications of non-ionic fluorosurfactant-modified electrodes. [•] Developments in sensing using non-ionic fluorosurfactant-modified gold nanoparticles. [ABSTRACT FROM AUTHOR]

Highlights: [•] The complete ligand transformation of CdTe QDs from thiolglycolic acid to citrate. [•] Negligible differences are observed between original QDs and new-born QDs. [•] The new-born CdTe QDs can induce minimal cytotoxicity against HepG2 cells. [Copyright &y& Elsevier]

Abstract: In this work, with the assistance of the additivity of surface plasmon resonance band of nonionic fluorosurfactant-stabilized gold nanoparticles, we developed a new colorimetric assay approach of cysteine (Cys) and homocysteine (Hcy) in biological fluids, requiring no use of separation techniques. The detection limits of Cys and Hcy can be as low as 0.4μM. The applicability of the method was validated by spiking known amount of Cys and Hcy in human urine and plasma samples. Recoveries were in the range of 97.2–106.7%. The present approach is simple, high selective and reproducible. In addition, the universality of the additivity of surface plasmon resonance band was demonstrated by virtue of silver nanoparticles. Therefore, the proposed method has a great potentiality in disease diagnosis associated with Cys and Hcy. [Copyright &y& Elsevier]

Abstract: Measurement of biological aminothiols (e.g., cysteine, homocysteine and glutathione) is important for clinical diagnosis. There is growing interest in the fabrication of optical nanoprobes due to their high sensitivity, low cost, low-power requirements and high biocompatibility. We give a general overview of the different strategies for gold nanoparticle (AuNP)-based optical probes for sensing aminothiols, including colorimetric, fluorescent, resonance-light scattering, chemiluminescent and surface-enhanced Raman scattering techniques. This review also summarizes these optical probes in terms of analytical performance, and discusses possible solutions to overcome some critical challenges facing these methods. [Copyright &y& Elsevier]

Abstract: In this paper, based on the enhancement effect on resonance light scattering (RLS) intensity of fluorosurfactant-capped gold nanoparticles (FSN-capped AuNPs), homocysteine can be discriminated from cysteine by tuning the pH values of the 14nm FSN-capped AuNP solutions. In contrast to the reported enhanced RLS of AuNPs for cysteine and homocysteine assays, the present method was improved by the following aspects: (1) cysteine and homocysteine could be determined simultaneously without separation techniques; (2) the incubation time of less than 2.0min for FSN-capped AuNP aggregation was employed in the proposed approach, which is much shorter than those reported by RLS probes (e.g., 25min and 60min). Under optimum experimental conditions, the calibration curve was found to be linear over the range of 0.08–6.0μM for cysteine and homocysteine with a detection limit of 0.04μM. The applicability of the proposed method has been validated by determining cysteine and homocysteine in human urine samples with satisfactory results. Recoveries from spiked urine samples were in the range of 96.0–113.0%. [Copyright &y& Elsevier]

Abstract: In this work, we utilize the triangular gold nanoparticles (AuNPs) prepared by trisodium citrate reduction of HAuCl4 in presence of nonionic fluorosurfactant (FSN) as a novel chemiluminescence (CL) probe for the determination of captopril. Captopril can induce a sharp decrease in CL intensity from the triangular AuNPs-catalyzed luminol system. Under the selected experimental conditions, a linear relationship was obtained between the logarithm of CL intensity and the logarithm of concentration of captopril in the range of 23.0–920nM, and the detection limit at a signal-to-noise ratio of 3 for captopril was 4.6nM. The as-prepared triangular AuNPs were easier to synthesize, stable at a wider pH range and high ionic strength, and exhibited a high selectivity and an excellent sensitivity toward captopril. The applicability of the proposed method has been validated by determining captopril in commercial pharmaceutical formulations and human urine samples with satisfactory results. The recoveries for captopril in spiked samples were found to be between 95.0% and 103.5%. The method shows promise for routine control analysis of pharmaceutical preparations and human urine samples. Moreover, based on the CL spectra, UV–vis spectra and transmission electron microscope (TEM) measurements, a possible CL mechanism was proposed. The mechanism of high selectivity toward captopril is supposed to originate from the tight binding of the sulphydryl groups of captopril to the active site of the as-prepared triangular AuNPs, leading to oxygen-related radicals cannot easily be generated from H2O2 on the surface of triangular AuNPs. [Copyright &y& Elsevier]

Abstract: Nonionic fluorosurfactant (FSN)-capped gold nanoparticles (GNPs) remain excellently stable at a wider pH range and high ionic strength, which is useful to investigate some CL systems involved in high salt and a strict pH range. In this study, we utilized FSN-capped GNPs of different sizes to distinguish the emitting species from H2O2-Co2+-NaOH and H2O2-Co2+-NaHCO3 systems. When the pH of FSN-capped gold colloidal solution was adjusted to 10.2 by dropwise addition of 0.05M NaOH, the CL intensity of H2O2-Co2+-NaHCO3 system was enhanced 6-fold or 60-fold respectively in the presence of FSN-capped 14nm or 69nm GNPs with comparison to H2O2-Co2+-NaOH. The variation of CL spectra and UV–vis spectra, as well as the quenching effect of reactive oxygen species scavengers were studied in detail to understand the CL enhancement mechanisms of FSN-capped GNPs on the two systems. For H2O2-Co2+-NaOH system, the gold(I) complexes intermediate and singlet oxygen dimol species were proposed as the emitting species. The excited states of the carbon dioxide dimers and singlet oxygen dimol species were considered responsible for the light emission of H2O2-Co2+-NaHCO3 system. To our knowledge, this work is the first time to study the two CL systems simultaneously using nanoparticles. [ABSTRACT FROM AUTHOR]

• One-pot and top-down synthesis of Au 8 NCs was represented. • Characterizations of the prepared Au 8 NCs and formation mechanism were discussed. • A sensitive and selective fluorescence probe for hemoglobin was proposed. • The capability of the present probe was validated by analyzing hemoglobin in blood samples. Gold nanoclusters (Au NCs) with atomic precision have huge application potentials in chemo/bio sensing, catalysis, and energy conversion. However, a precise atomic control of Au NCs still remains a great challenge. Herein, we developed a facile one-pot and top-down strategy to synthesize eight-atom numbered Au NCs (Au 8 NCs), aiming to understand their fundamental physicochemical properties and explore their potential applications. The etching of gold nanoparticles by their encapsulated hyperbranched polyethyleneimine was significantly promoted by a newly proposed catalyst, hydrogen peroxide, which gave rise to brightly blue-emitting Au 8 NCs (quantum yield = 28.8%). The as-prepared Au 8 NCs could sense hemoglobin with a detection limit of 5.0 nM through the combination of Fenton reaction and fluorescence resonance energy transfer. And the sensing behaviour is unaffected by the presence of various interferents such as proteins, small molecules, anions, and metal ions. In addition, a hemoglobin evaluation in blood samples with small relative standard deviations and satisfied recoveries was achieved using the proposed Au 8 NC nanoprobes. [ABSTRACT FROM AUTHOR]

Developing probes for sensitive H 2 O 2 detection is critical for understanding its related physiological and pathological processes. In this study, novel carbon quantum dot-gold nanocluster (CQD-AuNC) nanosatellite with high fluorescence energy transfer efficiency (∼40%) and dual-emission fluorescent properties have been exploited for fluorescence ratiometric sensing of H 2 O 2 . The sensing mechanism was based on the fact that H 2 O 2 can quench the red emission of AuNCs. Under the optimal conditions, the CQD-AuNC nanosatellite probe was sensitive to H 2 O 2 in the range from 5.0 nM to 80 nM with a limit of detection of 2.9 nM. The practicality of the proposed CQD-AuNC nanosatellite probe was validated by imaging H 2 O 2 in living cells. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel CL method for bisphenol A using gold nanoparticle–Co2+–HCO4 − is developed. [•] The present CL system exhibited high selectivity and sensitivity toward bisphenol A. [•] The proposed method has been validated by determining bisphenol A in real samples. [Copyright &y& Elsevier]

Abstract: Herein, a new postcolumn resonance light scattering (RLS) detection approach coupled with high-performance liquid chromatography (HPLC) was developed to detect cysteine and homocysteine. In the established system, the fluorosurfactant-capped gold nanoparticles (AuNPs) were first employed as postcolumn RLS reagents. The detection principle was based on the enhancement of RLS intensity of AuNPs upon the addition of cysteine/homocysteine. The RLS signals were detected by a common fluorescence detector at λ EX = λ EM =560nm. The linear ranges for both cysteine and homocysteine were in the range of 5.0–50μM. The detection limits were 5.9pmol for cysteine and 12pmol for homocysteine at a signal-to-noise ratio of 3. HPLC separation and RLS detection conditions were optimized in detail. The applicability of the proposed method has been validated by detecting cysteine and homocysteine in human urine samples. Recoveries from spiked urine samples were 95.0–103.0%. [Copyright &y& Elsevier]

Abstract: This study describes the use of 14nm nonionic fluorosurfactant-capped gold nanoparticles (FSN-capped AuNPs) for the simultaneous detection of cysteine (Cys) and homocysteine (Hcy) using colorimetric method, requiring no use of separation techniques. It was found that the kinetics of Cys/Hcy-induced aggregation of the 14nm FSN-capped AuNPs strongly depends on the pH value of gold colloidal solution. At a pH of 6.5, the Cys-induced aggregation kinetics of the FSN-capped AuNPs was almost identical to that induced by Hcy, facilitating simultaneous detection of total Cys and Hcy up to a concentration as low as 0.15μM; while at pH 12.0, the kinetics of Cys-induced aggregation was much faster than that inducted by Hcy, leading to selective detection of Cys at concentration as low as 1.0μM in the presence of Hcy. The applicability of the method was validated by spiking known amount of Cys and Hcy in human urine and plasma samples, obtaining a recovery of 95.4–105.5%. The present approach is simple, high selective and provides high reproducibility, and has a great potentiality in disease diagnosis. [Copyright &y& Elsevier]