Highly selective SERS probe for Hg(II) detection using tryptophan-protected popcorn shaped gold nanoparticles

Contamination of the environment with toxic Hg(II) is becoming a huge concern throughout the world now. Driven by the need, this communication reports for the first time a tryptophan protected popcorn shaped gold nanomaterials based SERS probe for rapid, easy and highly selective recognition of Hg(II) ions in the 5 ppb level from aqueous solution, with high sensitivity and selectivity over competing analytes. We demonstrate that our SERS assay is capable of measuring the amount of Hg(II) in alkaline battery.     

Gold nanoparticles functionalized with Ru(II)bipyridyl labeled DNA as a luminescent probe for the sensitive determination of DNase I

Microchimica Acta - The authors describe a fluorometric method for the determination of the activity of the enzyme DNase I. Gold nanoparticles were functionalized with a Ru(II)bipyridyl complex to...     

A selective, sensitive probe for mercury(II) ions based on oxazine-thione

A selective, sensitive probe for Hg(II) ions, 7-(diethylamino)-3-methyl-2H-benzo[b][1,4] oxazine-2-thione (1), is developed. Compound 1 behaves as a ratiometric probe, exhibiting a large blue shift of 100 nm in its absorption spectra upon exposure to Hg(II) ions. The dramatic color change of the solution made ‘naked-eye’ detection of Hg(II) ions possible. Emission spectra of 1 displayed a selective enhancement in intensity in the presence of Hg(II) ions. ESI⁺-MS analysis indicated that Hg²⁺-induced desulfurization caused the large absorption response.     

Aptameric SERS sensor for Hg~(2+) analysis using silver nanoparticles

Aptamer–silver nanoparticles (AgNPs) based surface-enhanced Raman scattering (SERS) sensor has been developed for Hg²⁺ detection by employing the structure-switching aptamer in the presence of spermine. This simple method shows excellent sensitivity and selectivity owing to the sensitive SERS detection technique and high specificity of aptamer for binding Hg²⁺.     

Highly sensitive microRNA quantification with zero background signal from silver nanoparticles

MicroRNAs are a class of noncoding RNAs, which play vital roles in numerous cellular processes. Recent studies have confirmed their significance in the theranostics of various diseases. We herein fabricate an electrochemical approach for microRNA quantification. DNA/microRNA/DNA hybridization and electrochemical signals from silver nanoparticles (AgNPs) are employed in this work. DNA1 immobilized on a gold electrode interacts with target microRNA, along with amino group labeled DNA2, to form the sandwich hybrid. The adjacent DNA1 and DNA2 are then ligated, which can keep DNA2 on the electrode surface during the denaturation. Amino group modified at the 5′ end of DNA2 captures AgNPs on the electrode surface, which provide sharp stripping peaks for microRNA quantification. This electrochemical approach offers a simple and sensitive platform for the detection of microRNA, which shows great utility in biomedical research and clinical diagnosis.     

A sensitive optical element for mercury(II)

A transparent polymethacrylate matrix modified with copper dithizonate was used to determine mercury(II). Optimum conditions for modifying the polymethacrylate matrix with copper dithizonate were found, and its reaction with mercury(II) in model solutions was studied.     

Highly sensitive and selective voltammetric detection of mercury(II) using an ITO electrode modified with 5-methyl-2-thiouracil, graphene oxide and gold nanoparticles

We have developed an electrochemical sensor for highly selective and sensitive determination of Hg(II). It is based on the specific binding of 5-methyl-2-thiouracil (MTU) and Hg(II) to the surface of an indium tin oxide (ITO) electrode modified with a composite made from graphene oxide (GO) and gold nanoparticles (AuNPs). This leads to a largely enhanced differential pulse voltammetric response for Hg(II). Following optimization of the method, a good linear relationship (R?=?0.9920) is found between peak current and the concentration of Hg(II) in the 5.0–110.0 nM range. The limit of detection (LOD) is 0.78 nM at a signal-to-noise ratio of 3. A study on the interference by several metal ions revealed no interferences. The feasibility of this method was demonstrated by the analyses of real water samples. The LODs are 6.9, 1.0 and 1.9 nM for tap water, bottled water and lake water samples, respectively, and recoveries for the water samples spiked with 8.0, 50.0 and 100.0 nM were 83.9–96.8 %, with relative standard deviations ranging from 3.3 % to 5.2 %.

SERS spectroscopy and SERS imaging of Shewanella oneidensis using silver nanoparticles and nanowires

Facile and reproducible SERS signals from Shewanella oneidensis were obtained utilizing silver nanoparticles (AgNPs) and silver nanowires (AgNWs). Additionally, SERS images identify the distribution of SERS hot-spots. One important observation is the synergistically enhanced SERS signal when AgNPs and AgNWs are used in conjunction, due to constructively enhanced electromagnetic field.     

Highly sensitive and selective determination of copper(II) based on a dual catalytic effect and by using silicon nanoparticles as a fluorescent probe

The authors describe a silicon nanoparticle-based fluorometric method for sensitive and selective detection of Cu²⁺. It is based on the catalytic action of Cu²⁺ on the oxidation of cysteine (Cys) by oxygen to form cystine and the by-product H₂O₂. The generated H₂O₂ is catalytically decomposed by Cu²⁺ to generate hydroxyl radicals which oxidize and destroy the surface of SiNPs. As a result, the blue fluorescence of the SiNPs is quenched. The method has excellent selectivity due to the dual catalytic effects of Cu²⁺, which is much better than most previously reported nanomaterial-based assays for Cu²⁺. Under the optimal conditions, the method has low detection limit (29 nM) and a linear response in a concentration range from 0.05 μM to 15 μM. The method has been successfully applied to the determination of Cu²⁺ in spiked real water samples, and the results agreed well with those obtained by the Chinese National Standard method (GB/T 7475-1987; AAS).

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Graphical abstract Schematic presentation of a fluorometric method for the determination of Cu²⁺ based on the dual catalytic effects of Cu²⁺, and the oxidative effect of hydroxy radicals on the surface of silicon nanoparticles (SiNPs). The method has a 29 nM detection limit and good selectivity.

     

An ultrasensitive conformation-dependent colorimetric probe for the detection of mercury(II) using exonuclease III-assisted target recycling and gold nanoparticles

An ultrasensitive conformation-dependent colorimetric assay has been developed for the detection of mercury(II) ions. It is based on the use of exonuclease III (Exo III)-assisted target recycling and gold nanoparticles (AuNPs). In the absence of Hg(II), the hairpin-shaped DNA probe (H-DNA) binds to AuNPs and stabilizes them in solutions of high ionic strength. In the presence of Hg(II), on the other hand, the sticky termini of the H-DNA form a rigid DNA duplex stem with a blunt 3′-terminus. Thus, Exo III is activated as a biocatalyst for selective and stepwise removal of mononucleotides from the 3′-terminus of the H-DNA. As a result, Hg(II) is released from the T?Hg(II)?T complexes. The guanine-rich sequences released from the H-DNA are then self-assembled with potassium ion to form a stable G-quadruplex conformation. In solutions of high ionic strength, this results in aggregation of AuNPs and a color change from red to blue which can be seen with bare eyes. The method is highly sensitive and selective. It has a linear response in the 10 pM to 100 nM Hg(II) concentration range, and the detection limit is as low as 3.2 pM (at an S/N ratio of 3). The relative standard deviation at a level of 0.5 nM of Hg(II) is 4.9% (for n?=?10). The method was applied to the detection of Hg(II) in spiked environment water samples, with recoveries ranging from 92% to 106%.

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Graphical abstract A conformation-dependent colorimetric system was fabricated for label-free detection of mercury(II) by utilizing exonuclease III(Exo III)-assisted target recycling and gold nanoparticles (AuNPs).

     

Highly sensitive detection of mercury (II) in aqueous media by tetraphenylporphyrin with a metal ion receptor

We provide a highly sensitive and selective assay to detect Hg²⁺ in aqueous solutions using a novel β-functionalised porphyrin-based chemosensor 5 at room temperature. The binding properties of the chemosensor 5 for cations were examined by UV–vis spectroscopy and ¹H NMR. The results indicate that a 1:1 stoichiometric complex is formed between chemosensor 5 and mercury (II) ion. The recognition mechanism between chemosensor 5 and metal ion was discussed based on their absorbance changes and the chemical shift changes when they interact with each other. Control experiments revealed that chemosensor 5 has a selective response to mercury (II) ion compared with other metal ions.     

A functionalized gold nanoparticles and Rhodamine 6G based fluorescent sensor for high sensitive and selective detection of mercury(II) in environmental water samples

A gold-nanoparticles (Au NPs)-Rhodamine 6G (Rh6G) based fluorescent sensor for detecting Hg (II) in aqueous solution has been developed. Water-soluble and monodisperse gold nanoparticles (Au NPs) has been prepared facilely and further modified with thioglycolic acid (TGA). Free Rh6G dye was strongly fluorescent in bulk solution. The sensor system composing of Rh6G and Au NPs fluoresce weakly as result of fluorescence resonance energy transfer (FRET) and collision. The fluorescence of Rh6G and Au NPs based sensor was gradually recovered due to Rh6G units departed from the surface of functionalized Au NPs in the presence of Hg(II). Based on the modulation of fluorescence quenching efficiency of Rh6G-Au NPs by Hg(II) at pH 9.0 of teraborate buffer solution, a simple, rapid, reliable and specific turn-on fluorescent assay for Hg(II) was proposed. Under the optimum conditions, the fluorescence intensity of sensor is proportional to the concentration of Hg(II). The calibration graphs are linear over the range of 5.0 × 10⁻¹⁰ to 3.55 × 10⁻⁸ mol L⁻¹, and the corresponding limit of detection (LOD) is low as 6.0 × 10⁻¹¹ mol L⁻¹. The relative standard deviation of 10 replicate measurements is 1.5% for 2.0 × 10⁻⁹ mol L⁻¹ Hg(II). In comparison with conventional fluorimetric methods for detection of mercury ion, the present nanosensor endowed with higher sensitivity and selectivity for Hg(II) in aqueous solution. Mercury(II) of real environmental water samples was determined by our proposed method with satisfactory results that were obtained by atomic absorption spectroscopy (AAS).     

Highly sensitive fluorescence determination of silver ions based on functionalized cadmium telluride nanorods

Microchimica Acta - Water-soluble fluorescent CdTe nanorods (NRs) capped with L-cysteine (Cys) and thioglycolic acid (TGA) were prepared for optical determination of silver ions. These NRs are...     

Colorimetric detection of manganese(II) ions using alginate-stabilized silver nanoparticles

Research on Chemical Intermediates - Marine algal polysaccharides have been recognized as the most effective and promising substrates for reduction and stabilization of metal nanoparticles....     

Highly sensitive electrochemical detection of mercury (II) via single ion-induced three-way junction of DNA

A “signal-on” electrochemical sensing strategy was designed for highly sensitive and selective detection of mercury (II) via its induction to three-way junction of DNA (DNA-TWJ). The TWJ consisted of the capture probe that was self-assembled on a gold electrode surface through SAu bond, the signal probe that was labeled with ferrocene (Fc) and contained single T–T mismatch to capture probe, and an assistant probe for the formation of DNA-TWJ upon the presence of mercury (II). This process caused the Fc tag approaching the electrode for fast electron transfer and thus increased the oxidation current. The “signal-on” sensing method could detect Hg^2 + ranging from 0.005 to 100 nM. The assay was simple and fast. It showed potential application in on-site and real-time Hg^2 + detection.