DNA‐based chemiluminescent nanoprobes for highly sensitive and selective detection of mercury(II) ion

A simple and sensitive DNA‐stablized gold nanoparticle (AuNP)‐based chemiluminescent (CL) probe for detecting mercury ion (Hg²⁺) in aqueous solution has been developed. The CL strategy relies upon the catalytic activity of unmodified AuNPs on the luminol–H₂O₂ CL reaction, and the interaction of unmodified AuNPs with DNA. The unmodified AuNPs can effectively differentiate unstructured and folded DNA. The DNA desorbs from AuNPs in the presence of Hg²⁺, leading to the increase in CL signal. By rationally varying the number of thymine in single‐strand oligonucleotides, the detection range could be tuned. Employing single‐strand oligonucleotides with 14 thymine in the detecting system, a sensitive linear range for Hg²⁺ ions from 5.0 × 10^–10 to 1.0 × 10^–7 mol/L and a detection limit of 2.1 × 10^–10 mol/L are obtained. Changing the number of thymine to 10 and 6, it leads to a narrow detection range but a high sensitivity. Besides, DNA‐based CL nanoprobes exhibit a remarkable selectivity for Hg²⁺ ions over a variety of competing metal ions. Copyright © 2012 John Wiley & Sons, Ltd.     

Glutathione‐stabilized Cu nanocluster‐based fluorescent probe for sensitive and selective detection of Hg2+ in water

In this paper, an innovative and facile one‐pot method for synthesizing water‐soluble and stable fluorescent Cu nanoclusters (CuNCs), in which glutathione (GSH) served as protecting ligand and ascorbic acid (AA) as reducing agent was reported. The resultant CuNCs emitted blue‐green fluorescence at 440 nm, with a quantum yield (QD) of about 3.08%. In addition, the prepared CuNCs exhibited excellent properties such as good water solubility, photostability and high stability toward high ionic strength. On the basis of the selective quenching of Hg²⁺ on CuNCs fluorescence, which may be the result of Hg²⁺ ion‐induced aggregation of the CuNCs, the CuNCs was used for the selective and sensitive determination of Hg²⁺ in aqueous solution. The proposed analytical strategy permitted detection of Hg²⁺ in a linear range of 4 × 10^?8 to 6 × 10^?5 M, with a detection limit of 2.2 × 10^?8 M. Eventually, the practicability of this sensing approach was confirmed by its successful application to assay Hg²⁺ in tap water, Lotus lake water and river water samples with the quantitative spike recoveries ranging from 96.9% to 105.4%.     

A highly selective fluorescent sensor for mercury ion (II) based on azathia-crown ether possessing a dansyl moiety

An intramolecular charge transfer (ICT) fluorescent sensor 1 using a dansyl moiety as the fluorophore and an azathia-crown ether as the receptor was designed, synthesized and characterized. The ions-selective signaling behaviors of the sensor 1 were investigated in CH(3) CN-H(2) O (1:1, v/v) by fluorescence spectroscopy. It exhibited remarkable fluorescence quenching upon addition of Hg(2+), which was attributed to the 1:1 complex formation between 1 and Hg(2+), while other selected metal ions induced basically no spectral changes. The sensor 1 showed a rapid and linear response towards Hg(2+) in the concentration range from 5.0 × 10(-7) to 1.0 × 10(-5) mol L(-1) with the detection limit of 1.0 × 10(-7) mol L(-1). Furthermore, the whole process could be carried out in a wide pH range of 2.0-8.0 and was not disturbed by other metal ions. Thus, the sensor 1 was used for practical determination of Hg(2+) in different water samples with satisfactory results.     

A selective phosphorescent chemodosimeter for mercury ion

The synthesis and crystal structure of an anionic phosphorescent iridium complex TBA[Ir(dfppy)₂(NCS)₂] (1) were reported. 1 can selectively detect Hg²⁺ with the help of UV-Vis absorption and emission spectra titration. In the presence of Hg²⁺, the obvious decrease of the luminescence intensity at 475 nm was investigated, which could be observed by the naked eyes. The phosphorescence quantum efficiency in CH₃CN solution changed from 0.07 to 0.00085. No obvious spectra changes were observed upon addition of a large excess of other transition metals. Due to its strong thiophilic affinity, the special chemical reaction induced by Hg²⁺ is responsible for the significant change of absorption and luminescence spectra, which is confirmed by ESI-MS.     

Highly luminescent and stable CsPbBr3 perovskite nanocrystals coated with polyethersulfone for white light-emitting diode applications

Simultaneously improving the stability and photoluminescence quantum yield (PLQY) of all inorganic perovskite nanocrystals (NCs) is crucial for their practical utilization in various optoelectronic devices. Here, CsPbBr₃ NCs coated with polyethersulfone (PES) were prepared via an in-situ co-precipitation method. The sulfone groups in PES bind to undercoordinated lead ion (Pb²⁺) on the CsPbBr₃ NCs, resulting in significant reduction of surface defects, thus enhancing the PLQY from 74.2% to 88.3%. Meanwhile, the PES-coated NCs exhibit high water resistance and excellent heat and light stability, maintaining over 85% of the initial PL intensity under thermal aging (70°C, 4 h) and continuous 365 nm ultraviolet (UV) light irradiation (24 W, 8 h) conditions. By contrast, the PL intensity of the control NCs dramatically dropped to less than 40%. Finally, a diode emitting bright white light was fabricated utilizing the PES-coated CsPbBr₃ NCs, which exhibits a color gamut of ~110% NTSC standard.     

A highly selective and simple fluorescent sensor for mercury (II) ion detection based on cysteamine‐capped CdTe quantum dots synthesized by the reflux method

Cysteamine (CA)‐capped CdTe quantum dots (QDs) (CA–CdTe QDs) were prepared by the reflux method and utilized as an efficient nano‐sized fluorescent sensor to detect mercury (II) ions (Hg²⁺). Under optimum conditions, the fluorescence quenching effect of CA–CdTe QDs was linear at Hg²⁺ concentrations in the range of 6.0–450 nmol/L. The detection limit was calculated to be 4.0 nmol/L according to the 3σ IUPAC criteria. The influence of 10‐fold Pb²⁺, Cu²⁺ and Ag⁺ on the determination of Hg²⁺ was < 7% (superior to other reports based on crude QDs). Furthermore, the detection sensitivity and selectivity were much improved relative to a sensor based on the CA–CdTe QDs probe, which was prepared using a one‐pot synthetic method. This CA–CdTe QDs sensor system represents a new feasibility to improve the detection performance of a QDs sensor by changing the synthesis method. Copyright © 2014 John Wiley & Sons, Ltd.     

SDS-capped 1-pyrenecarboxaldehyde nanoprobe for selective detection of Cu2+ ion from water samples: Spectroscopic approach

Sodium dodecyl sulfate (SDS)-capped 1-pyrenecarboxaldehyde nanoparticles (PyalNPs) were prepared using a reprecipitation method in an aqueous medium and exhibited red-shifted aggregation-induced enhanced emission (AIEE). The dynamic light scattering (DLS) examination showed narrower particle size distribution with an average particle size of 41 nm, whereas −34.5 mV zeta potential value indicate the negative surface charge and good stability of nanoparticles (NPs) in an aqueous medium. The AIEE was seen at λ_max = 473 nm in a fluorescence spectrum of a PyalNP suspension. In the presence of Cu²⁺ ions, the fluorescence of PyalNPs quenches very significantly, even in the presence of other metal ions like Ba²⁺, Ca²⁺, Cd²⁺, Co²⁺, Al³⁺, Fe²⁺, Hg²⁺, Ni²⁺ and Mg²⁺. The changes in the fluorescence lifetime of PyalNPs in the presence of Cu²⁺ ions suggested that the type of quenching was dynamic. The fluorescence quenching data for the NPs suspension fitted well into a typical Stern–Volmer relationship in the concentration range 1.0–25 μg/ml of Cu²⁺ ions. The estimated value of the correlation coefficient R² = 0.9877 was close to 1 and showed the linear relationship between quenching data and Cu²⁺ ion concentration. The limit of detection (LOD) was found to be 0.94 ng/ml and is far below the tolerable intake limit value of 1.3 μg/ml accepted by the World Health Organization for Cu²⁺ ions in drinking water. The fluorescence quenching approach for a SDS-capped Pyal nanosuspension for copper ion quantification is of high specificity and coexisting ions were found to interfere very negligibly. The developed method was successfully applied for the estimation of copper ions in river water samples.     

A water-soluble 1,8-naphthalimide-based 'turn on' fluorescent chemosensor for selective and sensitive recognition of mercury ion in water

A water-soluble 1,8-naphthalimide-based fluorescent chemosensor 1, bearing two acetic carboxylic moieties, exhibited high selectivity and sensitivity for recognition of Hg(2+) ion in water over other heavy and transition metal (HTM) ions with fluorescent enhancement. An increase in the fluorescent intensity at 562 nm was due to the formation of a 1:1 1-Hg(2+) inclusion complex.     

Multimode selective detection of mercury by chiroptical fluorescent sensors based on methionine/cysteine

Two multimode Hg(II) sensors, L‐MethBQA and L‐CysBQA, were obtained by fusing methionine or S‐methyl cysteine, into a bis‐quinolyl amine‐based chiral podand scaffold. Quinolyl groups serve as the fluorophore and possess nitrogen lone pairs capable of chelating metal ions. On exposure to Hg²⁺ or Zn²⁺, these sensors show signal enhancement in fluorescence. However, Cu²⁺ quenches their fluorescence in 30:70 acetontrile/water. L‐CysBQA complexes with Hg²⁺, producing an exciton‐coupled circular dichroism spectrum with the opposite sign to the one that is produced by Cu²⁺ or Zn²⁺ complexation. L‐CysBQA binds Hg²⁺ more strongly than Zn²⁺ and is shown to differentiate Hg²⁺ from other metal ions, such as Zn²⁺, Cu²⁺, Ni²⁺, and Pb²⁺, exceptionally well. The synergistic use of relatively soft sulfur, quinoline‐based chiral ligands and chiroptically enhanced fluorescence detection results in high sensitivity and selectivity for Hg²⁺. Chirality, 2011. © 2011 Wiley‐Liss, Inc.     

Synthesis and luminescence properties of CaSnO3:Bi3+ blue phosphor and the emission improvement by Li+ ion

CaSnO₃:Bi³⁺ blue‐emitting phosphor was synthesized using a high‐temperature solid‐state reaction method in air. The crystal structures and luminescence properties were investigated. A broad emission band peaking at ~448 nm upon excitation at 262 and 308 nm was observed in the range 330–680 nm at room temperature due to ³P₁ → ¹S₀ transition of the Bi³⁺ ion. The chromaticity coordinate was (0.1786, 0.1665). The optimal Bi³⁺ ion concentration was ~0.6 mol% in CaSnO₃:Bi³⁺ phosphor. The emission spectrum of CaSnO₃:Bi³⁺ phosphor showed a blue‐shift with increasing temperature from 50 to 300 K due to the influence of temperature on the electron transition of the Bi³⁺ ion. The emission intensity of CaSnO₃:Bi³⁺ phosphor may be increased ~1.45 times by co‐doping Li⁺ ions as a charge compensator and fluxing agent. The luminescence mechanism is explained by a configurational coordinate diagram of Bi³⁺ ion in CaSnO₃:Bi³⁺ phosphor.     

Design of a highly specific and noninvasive biosensor suitable for real-time in vivo imaging of mercury (II) uptake

Mercury is a ubiquitous pollutant that when absorbed is extremely toxic to a wide variety of biochemical processes. Mercury (II) is a strong, "invisible" poison that is rapidly absorbed by tissues of the intestinal tract, kidneys, and liver upon ingestion. In this study, a novel fluorescence-based biosensor is presented that allows for the direct monitoring of the uptake and distribution of the metal under noninvasive in vivo conditions. With the introduction of a cysteine residue at position 205, located in close proximity to the chromophore, the green fluorescent protein (GFP) from Aequorea victoria was converted into a highly specific biosensor for this metal ion. The mutant protein exhibits a dramatic absorbance and fluorescence change upon mercuration at neutral pH. Absorbance and fluorescence properties with respect to the metal concentration exhibit sigmoidal binding behavior with a detection limit in the low nanomolar range. Time-resolved binding studies indicate rapid subsecond binding of the metal to the protein. The crystal structures obtained of mutant eGFP205C indicate a possible access route of the metal into the core of the protein. To our knowledge, this engineered protein is a first example of a biosensor that allows for noninvasive and real-time imaging of mercury uptake in a living cell. A major advantage is that its expression can be genetically controlled in many organisms to enable unprecedented studies of tissue specific mercury uptake.     

Facile Synthesis of a 3D Nanoarchitectured Li4Ti5O12 Electrode for Ultrafast Energy Storage

Despite enormous efforts devoted to the development of high‐performance batteries, the obtainable energy and power density, durability, and affordability of the existing batteries are still inadequate for many applications. Here, a self‐standing nanostructured electrode with ultrafast cycling capability is reported by in situ tailoring Li₄Ti₅O₁₂ nanocrystals into a 3D carbon current collector (derived from filter paper) through a facile wet chemical process involving adsorption of titanium source, boiling treatment, and subsequent chemical lithiation. This 3D architectural electrode is charged/discharged to ≈60% of the theoretical capacity of Li₄Ti₅O₁₂ in ≈21 s at 100 C rate (17 500 mA g^?1 ), which also shows stable cycling performance for 1000 cycles at a cycling rate of 50 C. Additionally, modified 3D carbon current collector with much smaller pores and finer fiber diameters are further used, which significantly improve the specific capacity based on the weight of the entire electrode. These novel electrodes are promising for high‐power applications such as electric vehicles and smart grids. This unique electrode architecture also simplifies the electrode fabrication process and significantly enhances current collection efficiency (especially at high rate). Further, the conceptual electrode design is applicable to other oxide electrode materials for high‐performance batteries, fuel cells, and supercapacitors.     

A highly selective fluorescent probe for pyrophosphate detection in aqueous solutions

A novel and simple fluorescence enhancement method is introduced for selective pyrophosphate (PPi) sensing in an aqueous solution. The method is based on a 1:1 metal complex formation between tris(8‐hydroxyquinoline‐5‐sulphonate) thulium(III) [Tm(QS)₃] and PPi ion. The linear response covers a concentration range of 1.6 × 10^?7–1.0 × 10^?5 mol/L PPi and the detection limit is 2.3 × 10^?8 mol/L. The association constant of Tm(QS)₃–PPi complex was calculated as 2.6 × 10⁵ mol/L. Tm(QS)₃ shows a selective and sensitive fluorescence enhancement toward PPi ion in comparion with I₃^?, NO₃^?, CN^?, CO₃^2?, Br^?, Cl^?, F^?, H₂PO₄^? and SO₄^2?, which is attributed to higher stability of the inorganic complex between pyrophosphate ion and Tm(QS)₃. Copyright © 2011 John Wiley & Sons, Ltd.     

Luminescent and hydrophilic LaF3–polymer nanocomposite for DNA detection

Luminescent LaF₃–Ce³⁺/Tb³⁺ nanocrystals have been successfully prepared via a simple wet chemical technique. For the next bioapplication, these nanoparticles dispersed in cyclohexane have also been functionalized with poly(St‐co‐MAA), based on a designed oil‐in‐water microemulsion system. These polymer‐coated nanospheres are water‐soluble and bioconjugable. Unlike semiconductor quantum dots, the as‐prepared lanthanum fluoride nanocrystals possess non‐size‐dependent emissions and completely stable photocycles. With functionalized LaF₃ nanospheres as fluorescence probes, a fluorescence method was developed for the rapid quantitative analysis of DNA, due to the quenching effect of fluorescence by the DNA. Under optimum conditions, the fluorescence intensity was proportional to the concentration of the introduced DNA over the range 2.5–35 µg/mL for calf thymus DNA (ctDNA) and 2.5–30 µg/mL for fish sperm DNA (fsDNA), respectively. Copyright © 2008 John Wiley & Sons, Ltd.     

构建一种检测水中As3+的敏感型大肠杆菌

为构建一种敏感性强、特异性好的检测砷离子的大肠杆菌荧光报告菌株,本研究利用基因敲除技术,敲除了大肠杆菌中负责向胞外转运砷离子的ars B基因,构建对As~(3+)敏感的菌株;利用egfp基因作为报告基因,构建融合检测载体p ET28b-Pars-ars R-egfp。然后将检测载体p ET28b-Pars-ars R-egfp转化至ars B基因敲除菌中完成敏感型As~(3+)检测菌株的构建。接着对此微生物传感器进行了检测条件的优化,以及线性检测范围、最低检出限、特异性等性能的确定。研究结果表明,与利用野生大肠杆菌作为检测宿主相比,此敏感型砷检测菌株对检测As~(3+)的灵敏度有显著提高,最适检测As~(3+)浓度范围为0.013-42.71μmol/L,最低检出下限为5.13 nmol/L。因此,本研究利用基因敲除技术对大肠杆菌进行改造,成功地提高了砷检测微生物传感器的灵敏度,为重金属微生物传感器的优化研究工作提供了有用方案。     

A highly selective aggregation‐induced emission fluorogen for sensitive detection of Al3+ in living cells

A Schiff's base derivative was synthesized using a condensation reaction between 8‐formyl‐7‐hydroxy‐4‐methylcoumarin and furan‐2‐carbohydrazide that produced marked aggregation‐induced emission and had excellent ability to specifically recognize aluminium ions (Al³⁺). This compound displayed faint fluorescence in the benign solvent dimethyl formamide, and exhibited obvious green fluorescence following addition of specific amounts of water. Moreover, it exhibited strong blue fluorescence after combination with Al³⁺ even in the presence of other interfering ions. These experimental results demonstrated that this derivative could be used as a fluorescence probe for Al³⁺. The advantages, including significant fluorescence change, high selectivity and sensitivity, and fast response, meant that this probe could be used both to detect Al³⁺ in water samples and for fluorescence imaging in living cells.     

‘Turn‐on’ fluorescent chemosensors based on naphthaldehyde‐2‐pyridinehydrazone compounds for the detection of zinc ion in water at neutral pH

A series of naphthaldehyde‐2‐pyridinehydrazone derivatives were discovered to display interesting ‘turn‐on’ fluorescence response to Zn²⁺ in 99% water/DMSO (v/v) at pH 7.0. Mechanism study indicated that different substituent groups in the naphthaldehyde moiety exhibited significant influence on the detection of Zn²⁺. The electron rich group resulted in longer fluorescence wavelengths but smaller fluorescence enhancement for Zn²⁺. Among these compounds, 1 showed the highest fluorescence enhancement of 19‐fold with the lowest detection limit of 0.17 μmol/L toward Zn²⁺. The corresponding linear range was at least from 0.6 to 6.0 μmol/L. Significantly, 1 showed an excellent selectivity toward Zn²⁺ over other metal ions including Cd²⁺.     

Carbon nanoparticle for highly sensitive and selective fluorescent detection of mercury(II) ion in aqueous solution

In this article, carbon nanoparticles (CNPs) were used as a novel fluorescent sensing platform for highly sensitive and selective Hg(2+) detection. To the best of our knowledge, this is the first example of CNPs obtained from candle soot used in this type of sensor. The general concept used in this approach is based on that adsorption of the fluorescently labeled single-stranded DNA (ssDNA) probe by CNP via π-π stacking interactions between DNA bases and CNP leads to substantial dye fluorescence quenching; however, in the presence of Hg(2+), T-Hg(2+)-T induced hairpin structure does not adsorb on CNP and thus retains the dye fluorescence. A detection limit as low as 10nM was achieved. The present CNP-based biosensor for Hg(2+) detection exhibits remarkable specificity against other possible metal ions. Furthermore, superior selectivity performance was observed when Hg(2+) detection was carried out in the presence of a large amount of other interference ions. Finally, in order to evaluate its potential practical application, Hg(2+) detection was conducted with the use of lake water other than pure buffer and it is believed that it holds great promise for real sample analysis upon further development.     

Determination of chromium(III) in aqueous solution using CePO4:Tb3+ nanocrystals in a fluorescence resonance energy transfer system

Trivalent chromium is an essential element required for normal carbohydrate, lipid and protein metabolism in humans and animals. This article describes an efficient fluorescence resonance energy transfer (FRET) system between CePO₄:Tb³⁺ nanocrystals as the donor and chromium(III) as the acceptor. CePO₄:Tb³⁺ nanocrystals were synthesized in aqueous solution, and characterized by transmission electron microscopy. Under optimum conditions, a linear calibration graph was obtained (R² = 0.996). The linear range and detection limit of chromium(III) were 0.01–2.2 μM, and 9.1 nM, respectively. The proposed method had a wide linear range and proved to be very sensitive, rapid and simple. Moreover, the method was applied successfully to the determination of chromium(III) in synthetic samples and tap water. Copyright © 2013 John Wiley & Sons, Ltd.     

Carbon dots-modified paper-based chemiluminescence device for rapid determination of mercury (II) in cosmetics

Here, a simple and portable paper-based analytical device (PAD) based on the inherent capability of carbon quantum dots (CQDs) to serve as a great emitter for the bis(2,4,6-trichlorophenyl)oxalate (TCPO)–hydrogen peroxide (H₂O₂) chemiluminescence (CL) reaction is introduced for the detection of harmful mercury ions (Hg²⁺). The energy is transferred from the unstable reaction intermediate (1,2-dioxetanedione) to CQDs, as acceptors, and an intensive orange-red CL emission is generated at ~600 nm, which is equal to the fluorescence emission wavelength of CQDs. The analytical applicability of this system was examined for the determination of Hg²⁺. It was observed that Hg²⁺ could significantly quench the produced emission, which can be attributed to the formation of a stable and nonluminescent Hg²⁺–CQDs complex. Accordingly, a simple and rapid PAD was established for monitoring Hg²⁺, with a limit of detection of 0.04 μg ml⁻¹. No interfering effect on the signal was found from other examined cations, indicating the acceptable specificity of the method. The designed assay was appropriately utilized to detect Hg²⁺ ions in cosmetic samples with high efficiency. It was characterized by its low cost, ease of use, and was facile but accurate and high selective for the detection of Hg²⁺ ions. In addition, the portability of this probe makes it suitable for on-site screening purposes.