Ultrasensitive Detection Of Hg2 Research Articles

Fluorescent nanocomposites of Ag nanoclusters grown in anionic polymer layers grafted to plastic substrate: Preparation, characterization and evaluation in Hg2+ sensing and white light generation

AbstractFluorescent noble metal nanoclusters (NCs) are emerging optical nanomaterials with properties similar to those of quantum dots. Their applications can be expanded by combining them with polymer matrices to obtain flexible and transparent light‐emitting nanocomposites. However, achieving highly fluorescent nanocomposites of this type remains challenging due to phase separation and aggregation of NCs in polymer hosts leading to a strong reduction in fluorescence efficiency. We address this key issue by covalently grafting a layer of a specifically selected matrix polymer onto a transparent plastic film and photochemically synthesizing the fluorescent metal NCs directly in the grafted layer. The surface‐grafted matrix polymer effectively captures the noble metal (Ag) ions, photo‐reduces them to atoms, acts as a capping ligand for the growing Ag NCs, and immobilizes them on the substrate surface. The Ag NCs were produced by both wet and dry synthesis, and effects of synthesis method, reaction time, and matrix polymer layer thickness on the fluorescence properties of the resulting nanocomposites were investigated and discussed. Importantly, the fluorescence intensity of these nanocomposite films is sensitive to submicromolar concentrations of aqueous Hg2+ that makes them useful as fluorescent sensing materials for selective and ultrasensitive detection of Hg2+ ions in water. Besides, the nanocomposite films obtained by the dry synthesis of NCs exhibit an intensive emission covering the whole green to red range of the visible spectrum and, hence, produce bright white light under illumination with a blue LED that makes them attractive as down‐conversion materials in one‐phosphor‐converted white LEDs.

Dual recognition strategy for ultra-sensitive fluorescent detection of Hg2+ at femto-molar level based on aptamer functionalized sulfur quantum dots

In the present study, a dual recognition strategy for ultrasensitive detection of Hg 2+ was successfully developed for the first time based on aptamer functionalized sulfur quantum dots (Apt-SQDs). The developed Apt-SQDs not only retained the good fluorescence properties of quantum dots but also overcame the problem of poor selectivity of SQDs for heavy metal ions. This system used the dual recognition strategy, including the combination of S x 2− and Hg 2+ and T-Hg 2+ -T structures to excellently identify and capture Hg 2+ , and an ultrahigh sensitivity fluorescent aptasensor was fabricated. The fluorescent aptasensor had a good response to Hg 2+ at concentrations ranging of 10 −15 to 10 −7 M with an ultralow limit of detection of 0.3 fM, and the response to other metal ions was far less than that to Hg 2+ . It was successfully applied to detect Hg 2+ in nearby environmental water samples (tap water, lake water and river water) with a good recovery rate. Moreover, portable test papers that would be useful for Hg 2+ monitoring in environmental water were designed. The dual recognition strategy not only achieves ultrasensitive fluorescent detection of Hg 2+ but also provides a new insight into the further expansion of the application of SQDs.

Intelligent multicolor nano-sensor based on nontoxic dual fluoroprobe and MOFs for colorful consecutive detection of Hg2+ and cysteine

Ultrasensitive detection of Hg2+ in aquatic ecosystems is of great significance due to its high toxicity and ubiquity in water. Herein, using a one-step in-situ synthesis method, blue fluorescent carbon dots (CDs), red fluorescent InP/ZnS quantum dots (InPQDs), and MOFs (ZIF-8) integrated multicolor nano-sensor CDs/InPQDs@ZIF-8 was constructed for consecutive visual detection of Hg2+ and Cys. The InPQDs can act as the response unit for Hg2+ and Cys, with the limit of detection (LOD) of 8.68 and 37.96 nM, respectively. Significantly, the low detection limit combines with good specificity and accuracy of the nano-sensor meet the requirement for the safety monitoring and control of Hg2+ in drinking and environmental water. Moreover, the color recognition and processing software installed on smart phone can realize the real-time and rapid sensing of Hg2+ and Cys. A logic gate circuit was also devised, providing the possibilities for the application of the nano-sensor in the field of intelligent devices. As far as we know, this was the first example to apply InPQDs to the continuous multicolor visual detection of Hg2+ and Cys, which provided reference for the construction of environmentally-friendly dual emission fluorescent sensors for hazardous substance monitoring.

A dual-emission fluorescence sensor for ultrasensitive sensing mercury in milk based on carbon quantum dots modified with europium (III) complexes

A dual-emission fluorescence sensor was developed for Hg2+detection based on carbon quantum dots (CQDs) and Europium (III, Eu3+) complexes. The CQDs modified with Eu3+ complexes displayed dual-emission wavelengths of 443 and 617 nm. The dual-emission fluorescence intensity was significantly increased in the presence of Hg2+. The developed sensor displayed excellent selectivity and sensitivity with the detection range of 1–20 nM and detection limit of 0.2 nM. With increasing Hg2+ concentrations, developed sensor showed clear and regular color alternations from strong blue, light blue, lavender to deep purple observed by the naked eyes. The dual-emission method was successfully used for visual and ultrasensitive detection of Hg2+ in drinking water and milk samples with satisfied recovery from 97.6 % to 105.4 %. The sensor provides a generalizable platform for dual-emission fluorescence detection of Hg2+ based on rare earth ions-modified CQDs.

Highly durable covalent organic framework for the simultaneous ultrasensitive detection and removal of noxious Hg2+

Designed porous materials, such as covalent organic frameworks (COFs), are promising materials for the removal of toxic metals from wastewater. To assess the contamination and removal of toxic metal ions, their ultrasensitive detection is extremely important. However, to date, there have been very few reports on the ultrasensitive (picomolar) detection of toxic metal ions using highly porous COFs. Therefore, in this study, we synthesized a highly porous and durable COF containing amine and sulfonyl groups using the hydrothermal method. We demonstrated the impressive performance of obtained COF for the selective and ultrasensitive detection of Hg2+. Owing to its excellent luminescence properties and highly p-conjugated system, this metal-free COF can be used as a signal transducer for the selective and sensitive detection of Hg2+ at the picomolar level (640 pM). We studied the influence of various factors (e.g., pH, concentration, and temperature) on the sensitive detection of Hg2+. Owing to excellent luminescence properties and ultrasensitive detection of Hg2+, COF works as highly adsorbent materials for Hg2+ with the effective removal capacity of 99.8% at neutral pH. The obtained COF was also applied as a probe for the simultaneous detection and removal of Hg2+ in a natural river water sample. The results indicate a new path toward metal-free chemical sensors for toxic pollutants.

Colorimetric determination of Hg2+ based on the mercury-stimulated oxidase mimetic activity of Ag3PO4 microcubes.

Fourkinds of Ag3PO4 materials were prepared by controlling the experimental conditions, which were developed as oxidase mimics. Experimental results showed that different synthesis methods led to distinct crystal structures, morphologies, and surface properties, which contributed to diverse oxidase-like activities of Ag3PO4 materials. Among them, Ag3PO4 microcubes (APMCs) can efficiently catalyze the oxidation of colorless 3,3',5,5'-tetramethylbenzidine in the presence of dissolved oxygen to form a blue-colored oxide, presenting the best intrinsic oxidase mimetic ability. The higher-energy [110] facets with more oxygen vacancies exposed and more active sites coupled with more negative charge and larger specific surface area of APMCs contributed to its enhanced oxidase mimetic performance. Besides, mercury ions were proved to remarkably and selectively stimulate the oxidase-like ability of APMCs owing to the formation of Ag-Hg amalgam on its surface. Based on the stimulating effect of Hg2+ towards APMCs, a simple and rapid method for colorimetric determination of Hg2+ was thus established via the significant signal amplification and megascopic color variation. Under the optimal conditions, the sensing system showed a good linear relationship ranging from 0.1 to 7.0μM and a detection limit of 20nM for Hg2+, exhibiting high selectivity and good colour stability. Moreover, the colorimetric method was successfully applied to determine Hg2+ in real water samples. Considering these advantages, the developed colorimetric sensing system is expected to hold bright prospects for trace determinationof Hg2+ in biological, environmental, and food samples. Graphical abstract The preparation process of Ag3PO4 materials and Hg2+-stimulated enhanced oxidase-like ability of Ag3PO4 microcubes in catalyzing the oxidation of TMB to generate a typical blue color, which can be applied in rapid and ultrasensitive detection of Hg2+ visually.

Ultrasensitive colorimetric detection of Hg2+ in urine based on single hairpin DNA-based self-propelled dual-cycle targets recycling amplification strategy

ABSTRACT This work reported a label-free single hairpin DNA-based self-propelled dual-cycle targets recycling strategy for ultra sensitive detection of Hg2+ based on T-Hg2+-T structure, exonuclease Ш (Exo Ш)-assisted self-propelled dual-cycle targets recycling and haemin/G-quadruplex (DNAzyme) signal amplification. The hairpin DNA probe with G-quadruplex fragment and continuously repeated sequences was specially designed for this strategy. Hg2+ could assist the combination between Hg2+ binding probe and free 3ʹ-terminus of hairpin DNA probe by T-Hg2+-T coordination to form the blunt 3ʹterminus that triggered Exo III-assisted digestion, and set free Hg2+, Hg2+ binding probe, and free G-quadruplex fragment. The released Hg2+ and Hg2+ binding probe is recycled through cycle 1. The released free G-quadruplex fragments are recycled through cycle 2. Single hairpin DNA-propelled dual-cycle targets recycling triggered by ultra-trace Hg2+ produce massive G-quadruplex fragments that bind haemin to yield G-quadruplex−haemin DNAzymes, which can efficiently catalyse ABTS-H2O2 system and convert ABTS2- to the coloured products. This ultra-sensitive colorimetric assay successfully achieved Hg2+ analysis in urine as low as 0.07 pmol/L with a linear calibration range from 0.1 pmol/L to 50 pmol/L (R2 = 0.992), and was amenable to quantification of Hg2+ in complex biological matrixes. This proposed single hairpin DNA-propelled signal amplification strategy displayed excellent sensitivity, remarkable specificity, high capacity of resisting disturbance, simplicity, low-cost, and was successfully applied for colorimetric detection of Hg2+ in urine samples with good recovery and accuracy.

Ultrasensitive colorimetric aptasensor for Hg2+ detection using Exo-III assisted target recycling amplification and unmodified AuNPs as indicators

Facile and ultrasensitive detection of Hg2+ in water environment remains challenging. Exonuclease III (Exo-III)-assisted target recycling is one of the most popular amplification strategies. Although the magnesium (II) ions are widely acting as cofactors of Exo-III, we recognized that Mg2+ cofactors would strongly disturb the charge distribution on citrate-stablized gold nanoparticles (in the general sense, unmodified AuNPs) surface, thus generate false positive colorimetric signals. To address this issue, we first put forward the view that the cobalt (II) ions can function as the Exo-III cofactor and successfully construct a novel label-free colorimetric aptasensor for facile and ultrasensitive detection of Hg2+ using Hg2+-triggered Exo-III-assisted signal amplification and unmodified AuNPs as indicators. A hairpin-looped DNA probe was rationally designed with thymine-rich recognition termini and specifically recognized trace Hg2+ by a stable T–Hg2+–T structure. A blue-to-red color change of AuNPs with the addition of Hg2+ provided the quantitative detection of Hg2+ with a limit of detection of 0.2 nM and a linear working range from 0.5 nM to 5.0 nM. The whole testing time for one assay was approximately 40 min. Real water samples, even containing Hg2+ at 1 nM, could be determined by the aptasensor with recovery rates from 97% to 103%.

Ultrasensitive Silicon Nanoparticle Ratiometric Fluorescence Determination of Mercury(II)

ABSTRACTA novel ratiometric fluorescence sensing system for the ultrasensitive detection of Hg2+ was developed. It used aminofunctionalized silicon nanoparticles and rhodamine B, which exhibit two distinct fluorescence emission peaks at 449 and 581 nm, respectively, under a single excitation wavelength (350 nm). The fluorescence of the amino-functionalized silicon nanoparticles was selectively quenched by Hg2+, while that of rhodamine B was insensitive to Hg2+. The ratio of fluorescence intensities at 449–581 nm linearly decreased with increasing concentrations of Hg2+ from 0.005–0.1 and 0.1–7 µM within 0.5 min, and a detection limit as low as 3.3 nM was achieved. Moreover, the ratiometric fluorescence sensing system exhibited good selectivity toward Hg2+ over other metal ions with relatively low background interference, even in a complex matrix such as lake water. Most importantly, the practical use of this sensing system for Hg2+ detection in real water samples was also demonstrated.

Ellagic acid-functionalized fluorescent carbon dots for ultrasensitive and selective detection of mercuric ions via quenching

The authors report on a strategy for the fabrication of water soluble carbon quantum dots (CDs) functionalized with ellagic acid. They also demonstrate highly selective detection of Hg2+ ions in aqueous media via fluorescence quenching. The CDs were prepared via a one-step technique using tannic acid as the carbon source and directly surface functionalized during nanoparticle synthesis. Following photoexcitation at 210nm they exhibit excitation-independent emission that peaks at 340nm. The CDs display strong affinity for Hg2+ and binding result in quenching of fluorescence. This effect can be used to quantify Hg2+ in concentration down to 10pM and with detection limit as low as 0.24pM. The ultrasensitive detection of Hg2+ ions is demonstrated by analyzing Hg2+-spiked water and tap-water samples.

A SERS biosensor with magnetic substrate CoFe2O4@Ag for sensitive detection of Hg2+

Mercuric ion (Hg2+) is one toxic metal ion existed in aquatic ecosystems which would seriously damage human central nervous system and other organs. So developing an approach to sensitively detect Hg2+ in our living environment is urgent and important. In this work, a novel surface enhancement Raman spectrum(SERS) sensor is fabricated for high selective and ultrasensitive detection of Hg2+ in aqueous solution, based on a stable thymine-Hg2+-thymine (T-Hg2+-T) structure and the π-π interaction between single-stranded DNA (ssDNA) and single walled carbon nanotubes (SWCNTs). Herein, SWCNTs act as Raman labels to produce characteristic Raman peaks which can be a beacon to quantitative detect Hg2+. In the presence of Hg2+, the ssDNA can capture Hg2+ forming T-Hg2+-T structure, which makes SWCNTs leave the hot spots of the SERS-based biosensor. With this design, the Raman intensity of SWCNTs decreased with the increasing concentration of Hg2+. At the same time, CoFe2O4@Ag as active SERS substrates can effectively enhance sensitivity and uniformity of the biosensor through aggregation by magnet. Under optimal conditions, this proposed biosensor can detect Hg2+ at a range from 1pM to 100nM with a detection limit of 0.84pM. With the advantages of good sensitivity, selectivity, simplicity and rapidity, the biosensor is potentially suitable for monitoring of Hg2+ in environmental applications.

Ultratrace Naked-Eye Colorimetric Detection of Hg2+ in Wastewater and Serum Utilizing Mercury-Stimulated Peroxidase Mimetic Activity of Reduced Graphene Oxide-PEI-Pd Nanohybrids.

Herein, we developed a general strategy for rapid, highly selective, and ultratrace naked-eye colorimetric detection of Hg2+ in aqueous solutions. Two dimensional rGO/PEI/Pd nanohybrids, where rGO, PEI, and Pd were referred to as reduced graphene oxide, polyethylenimine, and Pd nanoparticles, respectively, were synthesized and used as mimetic peroxidase for selective and ultrasensitive detection of Hg2+ in water and human serum samples. In the presence of mercury ions, the peroxidase mimetic activity of rGO/PEI/Pd nanohybrids was found to be stimulated and enhanced significantly, which promoted the effective oxidation and color change of 3,3',5,5'-tetramethylbenzidine (TMB) in solution to dark blue that was detected by the naked-eye and the absorption spectroscopic method. The proposed sensing strategy coupled with spectroscopic detection method showed an ultralow detection limit of 0.39 nM for Hg2+ in ddH2O and ∼1 nM in wastewater as well as serum samples, respectively. On the basis of the colorimetric assay, a minimum concentration of ∼10 nM for Hg2+ in wastewater and human serum can be detected with the naked-eye. The naked-eye-based colorimetric assay for sensitive and selective detection of mercury is expected to hold huge potentials in applications such as environmental monitoring, clinical diagnosis, and pharmaceutical analysis.

Bright far-red/near-infrared gold nanoclusters for highly selective and ultra-sensitive detection of Hg2+

In this paper, we developed a simple one-pot method, employing inexpensive chicken egg white (EW) as a reducing/capping reagent, for microwave-assisted synthesis of water-soluble and well-dispersed chicken egg white-protected gold nanoclusters (EW@AuNCs) with far-red/near-infrared (FR/NIR) emission. The resultant AuNCs showed strong emission at 667nm with a quantum yield of 7.23%. The excellent photostability, large Stokes shift (>350nm), microsecond-scale lifetime and strong emission endowed EW@AuNCs potential as a sensing probe. The photoluminescence of EW@AuNCs could be quenched upon addition of either Hg2+ or Cu2+ ion. After ethylenediamine (En) was used as a masking agent, the EW@AuNCs offered highly selective for determination of Hg2+ ion. Also, the resultant EW@AuNCs probe exhibited ultra-high sensitivity toward Hg2+ ion with a detection limit as low as 20 pM, which is 500 times lower than the limit value (10nM) defined by the U.S. Environmental Protection Agency in drinkable water. The proposed AuNCs probe for Hg2+ ion has a linear range of 0.0446–5.90nM and good repeatable response to 2.0nM Hg2+ with a relative standard deviation of 2.8% (n=5). Additionally, the applicability of the sensing system was also verified by analysis of Hg2+ ion in tap water and pond water samples.

Ultrasensitive detection of mercury with a novel one-step signal amplified lateral flow strip based on gold nanoparticle-labeled ssDNA recognition and enhancement probes

A novel one-step signal amplified lateral flow strip (SA-LFS) is described for direct ultrasensitive and on-site detection of Hg2+ based on the specific recognition system of thymine–Hg2+–thymine using gold nanoparticles (AuNPs) as labeling tags. The signal was also amplified by hybridization induced dual labeling of AuNPs, which increased signal intensity of test line on strips. The presence of both probes on the LFS enabled both sensing and signal amplification to be achieved in a single step. The resulting SA-LFS is capable of rapid and ultrasensitive detection of Hg2+ with LODs of 0.005ppb and 0.0015ppb by visual observation and quantitative analysis, respectively. At least 40-fold improvement in sensitivity of the traditional LFS was achieved through this signal amplification process. The successful application of the method to the determination of Hg2+ in water sample is reported. The proposed signal amplification process may also be applicable to other LFS-based methods.

Highly selective and ultrasensitive detection ofHg2+ based on fluorescence quenching of Au nanoclusters by Hg2+–Au+ interactions

A simple label-free method for the detection of Hg(2+) ions with high selectivity and sensitivity has been developed by using fluorescent Au NCs in aqueous media. The sensing mechanism was based on the high-affinity metallophilic Hg(2+)-Au(+) interactions, which effectively quenched the fluorescence of Au NCs.