Search

The portable detection of trace mercury ions (Hg2+) in water is crucial for preventing and controlling mercury pollution. In this study, graphitic carbon nitride nanoparticles (CNNPs) with green fluorescence as the self-calibration signal were synthesized by a one-pot solvothermal method. Cadmium telluride sulfide quantum dots (CdTe 0.16 S 0.84 QDs) with red fluorescence as a response signal were prepared using an oxidation-reduction method. Thus, a new ratiometric fluorescence sensor based on CNNPs-CdTe 0.16 S 0.84 QDs was constructed for the visual detection of trace Hg2+. The linear range of the sensor was from 0.05 to 2525 nM, with a detection limit of 0.009 nM. The sensor displayed higher sensitivity to Hg2+ compared to copper ions and silver ions. The fluorescence quenching behavior and the source of sensitivity for the three metal ions were investigated using the Stern-Volmer equation and density functional theory. The results suggest that the high sensitivity to Hg2+ may arise from electron transfer and electrostatic interactions between Hg2+ and CdTe 0.16 S 0.84 QDs. Building on this proposed strategy, a new smartphone-assisted CNNPs-CdTe 0.16 S 0.84 QDs hydrogel-based fluorescence sensor was constructed for portable on-site analysis of trace Hg2+. This new method will facilitate the on-site monitoring of hazardous substances in environmental water. [Display omitted] • A new ratiometric fluorescent sensor based on C 3 N 4 -CdTe 0.16 S 0.84 QDs is constructed. • The sensor shows high sensitivity for Hg2+ with a low detection limit of 9 pmol L−1. • The sensitive detection for Hg2+ is studied by Stem-Volmer equation, DFT and MCR-ALS. • The hydrogel sensor and APP platform can portable analysis of Hg2+ under UV lamp. [ABSTRACT FROM AUTHOR]

Substandard discharge of industrial wastewater leads to abundant silver ions (Ag+) emission into water and soil, causing serious environmental threat. Precise and reliable detection of Ag+ is vital for environmental surveillance, while it remains a great challenge in complex actual environment. Herein, a lab-to-factory adoptable photoelectrochemical (PEC) approach for highly selective and sensitive detection of Ag+ in industrial wastewater has been first demonstrated. BiOI nanosheets (NSs) were prepared as photocathode and showed a spontaneous and selective ion-exchange process with Ag+ ions when it immersed into complicated industrial wastewater. The in situ generated AgI/Ag exhibits unique localized surface plasmonic resonance (LSPR) effect to modulate PEC signals for highly selective and sensitive Ag+ detection. As a result, the prepared photocathode delivers an ultralow detection limit (0.21 nM) and a broad linear range (up to 300 μM), outperforming most reported results. This work opens a feasible avenue for Ag+ monitoring in actual environment. • BiOI photocathode can selectively recognize and ion-exchange with Ag+ in complex industrial wastewater. • In situ generated AgI/Ag exhibits unique localized surface plasmonic resonance effect to realize Ag+ detection. • Superior detection property with ultralow detection limit of 0.21 nM and wide linear range up to 300 μM is achieved. • The stable BiOI photocathode show promising potential for practical industrial application. [ABSTRACT FROM AUTHOR]

Apurinic/apyrimidinic endonuclease 1 (APE1) plays an essential part in the base excision repair whose abnormal expression is closely correlated to the occurrence of tumors. Therefore, a sensitive assay of APE1 is crucial for the early diagnosis of cancer. Herein, we developed a simplified rolling circle amplification (RCA) strategy to drive in situ production of electrochemiluminescent (ECL) silver nanoclusters (Ag NCs) for APE1 activity monitoring. Unlike conventional RCA, which required locker DNA and padlock to form the circular template and hybridize with primer to initiate amplification, we proposed a simplified RCA that employed hairpin (HP) and padlock to directly form the circular template to initiate the amplification. Through reasonable design of the amplification templates, the RCA products were cytosine-rich (C-rich) sequences for silver ions adsorption, which were electrochemically reduced to Ag NCs. Combined with Cu-based metal-organic frameworks (Cu-MOFs) as co-reaction accelerator to facilitate the reduction of S 2 O 8 2-, the ternary ECL system (Ag NCs/S 2 O 8 2-/Cu-MOFs) demonstrated strong ECL intensity. The simplified RCA strategy combined with the ternary ECL sensing platform achieved the sensitive analysis of APE1 with a linear range of 1 × 10−8 to 1 × 10−2 U/μL and a detection limit of 2.29 × 10−9 U/μL, which presented a novel approach for sensitive monitoring of APE1 activity. [Display omitted] • Simplified RCA that integrates loop and hybridization of hairpin and padlock. • Ag NCs generated by electrochemical in-situ reduction. • Cu-MOFs enhance ECL signal of in situ electrochemical generated Ag NCs. • A ternary ECL biosensor realizes the activity monitoring of APE1. [ABSTRACT FROM AUTHOR]

Heavy metal ion pollution is a pressing global concern with detrimental effects on the environment and human health. To address this issue, we have developed an ultrahigh-resolution multicolor sensing platform for the specific detection of silver ions (Ag(I)). The method employs the nanozyme of platinum nanoparticles (PtNPs) as a link to control the etching of gold nanorods (AuNRs). Through specific binding with Ag(I), the PtNPs hinder the catalase-like activity responsible for hydrogen peroxide (H 2 O 2) decomposition. This inhibition enables the Fenton reaction between H 2 O 2 and ferrous ions, generating highly oxidizing hydroxyl free radicals (·OH). The resulting etching of AuNRs induces a blue-shift in their local surface plasmon resonance (LSPR) absorption spectra. The degree of blue-shift is directly proportional to the Ag(I) concentration, facilitating trace-level detection. Furthermore, the aspect ratio change of the AuNRs yields distinguishable colors. In contrast to common multicolor sensors relying on nanozyme horseradish peroxidase (HRP) activity, which exhibits an inverse relationship between AuNR etching and target concentration, our approach demonstrates a proportional response. This unique characteristic enables ultrahigh-resolution multicolor detection of Ag(I) visible to the naked eye. We anticipate that this innovative sensing platform will pave the way for nanosensor development in environmental monitoring and food safety detection. • An ultrahigh-resolution multicolor detector via reverse etching of AuNRs was developed. • The multicolor assay displays a multi-color change for analysis of trace silver ions. • The reverse etching of AuNRs exhibits a proportional response to the silver ion concentration. • The platform was demonstrated with high assay ability and practicability for Ag(I) analysis. [ABSTRACT FROM AUTHOR]

A new, distinctive, and inexpensive colorimetric sensor for the detection of phosphate ions (Pi) performed on paper-based analytical devices (PADs) based on the anti-aggregation of 2-mercaptoethanesulfonate (MS)-modified silver nanoplates is proposed. An aggregation of MS-AgNPls due to the electrostatic interaction between the negatively charged sulfonate group on MS-AgNPls and europium ions (Eu3+) causes a color change. Conversely, the color of MS-AgNPls remains unchanged in the presence of premixed Eu3+ with Pi because of the higher binding affinity that Eu3+ has towards Pi, leaving the AgNPls dispersed. An apparent color change from brown to red with the increasing amount of Pi can be observed by the naked eye on PADs and can be used for quantification by the measurement of color intensity using ImageJ software and determined with the color comparator. The aggregation and anti-aggregation of MS-AgNPls were characterized by TEM, UV–vis spectroscopy, and FT-IR to confirm the mechanism. This method can detect Pi in the range of 1–30 mg L−1, with a detection limit of 0.33 mg L−1 (3SD/slope) and a limit of quantification equal to 1.01 mg L−1 (10SD/slope). The optimum parameters, including pH, MS and Eu3+ concentrations, reaction time, and interference effects, were studied. This method can be applied with the detection of Pi in real samples collected from soils, and the results agree with those of the standard method (UV–vis spectroscopy). [ABSTRACT FROM AUTHOR]

Highlights • Simultaneously detection of Ag+ and Pb2+ by dual reference ion imprinted ratiometric fluorescence probe was first proposed. • The detection process was simplified, and the time and cost was saved. • The detection sensitivity was improved by ratiometric fluorescence signal output and mesoprous structure. Abstract We describe a dual reference ion-imprinted ratiometric fluorescence probe for simultaneous detection of Ag+ and Pb2+. Carbon dots (CDs) and gold nanoclusters (AuNCs) were adopted for fluorescence signal output. To improve the conversion efficiency from molecular recognition to fluorescence signal output, functional groups on the surface of fluorescence nanoparticles were used to form a chelate with template ions during polymerization. During the detection of Ag+, the CDs were quenched, while AuNCs remained stable as the reference. For Pb2+ detection, AuNCs were the response signal, and CDs were the reference. Under optimal conditions, (I CDs) 0 /(I AuNCs) displayed a good linear relationship with the concentration of Pb2+ from 50 to 900 nM with detection limits of 26 nM; (I AuNCs) 0 /(I CDs) had a good linear relationship with the concentration of Ag+ from 0.2–12.5 μM with a detection limit of 86 nM. Using this dual reference strategy, Ag+ and Pb2+ can be detected simultaneously in real water samples with satisfactory recoveries. This work enables high-throughput detection based on fluorescence signal output, which saves detection time and costs. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Facile electrochemical impedance sensing for HCHO was first constructed. • The sensor fabricated by the exchange of silver ions with trapped ammonium ions. • The mechanism is the decrement of resistance resulted from the Ag nanoparticles. • This strategy provides a new insight into the gas sensor at room temperature. Abstract Formaldehyde is a highly reactive and toxic compound in air pollutants, exposure to even a low concentration of formaldehyde will do harm to human health. Herein, a novel electrochemical impedance sensor for formaldehyde has been developed based on Ag+-SiO 2 microspheres prepared by the exchange of silver ions with trapped ammonium ions. The probe of silver ion is easily and selectively reduced by formaldehyde, then the silver nanoparticles would be generated. Exposure to more concentration of formaldehyde, more proportionate silver nanoparticles would be loaded on the surface of silica microspheres, and then the decrement of interface charge transfer resistance (R ct) would be obtained accordingly. The decrement of R ct was linear with the concentration of formaldehyde in the range from 2 to 6000 pmol L−1 with a detection limit of 0.5 pmol L−1. Enabled by such a unique sensing mechanism, the fabricated sensor has been successfully applied for the detection of formaldehyde in real samples with high performance in selectivity, low power consumption, sensitivity, cost-effectiveness, facility, and portability. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Ease of preparation for gold nanoparticles (AuNPs) using gallotannin (GT). • Sensitive, selective and rapid naked eye colorimetric detection of Ag+ only. • GT-AuNPs interacts with Ag+ forms nano clusters (GT-AuNPs-AgNPs). • Lower detection limit for Ag+ = 0.22 ng/mL (2.05 nM). • Prepared GT-AuNPs explored for Ag+ detection in real environmental samples. Abstract We have prepared gallotannin (GT) capped gold nanoparticles (AuNPs) for rapid, sensitive and naked eye colorimetric detection of silver ion (Ag+) in aqueous medium. Amongst the 21 different metal ion studied for absorption titration, only Ag+ ion induces the change in color and spectral properties of GT capped AuNPs. The formation of GT capped AuNPs and its interaction with Ag+ were discussed with change in pink to yellowish brown color, hypsochromic spectral shift in absorption maximum wavelength, decrease in zeta potential and increase in particle size. The sequential addition of Ag+ to the colloidal suspension of GT capped AuNPs simultaneously increases the absorbance along with hypsochromic shift in wavelength maxima. The absorption titration results were fits well to calibration plot in linearity range of 0–1 ng/mL of Ag+ showing correlation coefficient (R2) of 0.9983. The lower detection limit estimated for Ag+ is 0.22 ng/mL (2.05 nM) that shows sensitivity and selectivity of present analytical method towards detection of Ag+ in aqueous solution. The present method includes practical application for quantitative determination of Ag+ in real environmental water samples. Thus, the present study offers simple, cost-effective, selective, sensitive, speedy, profitable and naked eye detection of Ag+ in aqueous medium. [ABSTRACT FROM AUTHOR]

Highlights • A new supramolecular polymer was fabricated by crown ether-based host‒guest interaction and Ag-coordination. • The supramolecular polymer displayed sensitive property to H 2 S. • The supramolecular polymer was made into a thin film and used as a convenient test kit for detecting H 2 S. • The thin film was more stable under moisture and sunlight than simple silver ion. Abstract A supramolecular polymer was fabricated via crown ether-based host–guest interaction and Ag-coordination. It displayed hydrogen sulfide sensitive property. In addition, the supramolecular polymer was made into a thin film which can be used to detect hydrogen sulfide. [ABSTRACT FROM AUTHOR]

The silver ions (Ag + ) and hydrogen sulfide (H 2 S) play extremely an important role in the organism and the environment, while there lack a novel probe with biodegradability, good water solubility, and good biocompatibility to detect Ag + and H 2 S individually. Herein, a novel fluorescence chemosensor DP (Dansyl-Leu-Leu-Cys-Acp-Asp-OH) based on biomolecular peptide has been designed and synthesized, which can be used in the detection of intracellular and environmental Ag + and H 2 S. The DP exhibited high selectivity and sensitivity, excellent cell permeation, biodegradability, good water solubility, and pH insensitivity over a biologically relevant range, with detection limits of 61.7 nM and 74.0 nM for Ag + and H 2 S, respectively. This work can inspire the design of multi-functional fluorescence sensor based on beacon peptides by modifying lateral and terminal groups for imaging applications in physiological and pathological events. [ABSTRACT FROM AUTHOR]

A novel colorimetric and ratiometric fluorescent probe CHa based on Ag + -induced hydrolysis of hydrazone was designed and synthesized. To the best of our knowledge, this is the first time the ratiometric sensing of Ag + based on a chemical reaction has been accomplished. When Ag + was added to a solution of CHa , a visible color change from yellow to colorless and a fluorescence color change from yellow to blue were observed. Probe CHa displayed a 203-fold enhancement of the fluorescence intensity ratio (I 450nm /I 520nm ) toward Ag + with outstanding sensitivity, high selectivity and a low detection limit (LOD 61 nM). Moreover, CHa was successfully applied to the ratiometric imaging of Ag + in HepG2 and HeLa cells. [ABSTRACT FROM AUTHOR]

Keratins are a group of cysteine-rich structural proteins found abundant in hair, wool, feathers, etc. In this work, a highly luminescent gold nanocluster (AuNCs-Ag@Keratin) was synthesized for the first time by using keratin as the template, followed by a simple modification with silver(I) ions. The prepared AuNCs-Ag@Keratin could exhibit dramatically enhanced red fluorescence (λ em  = 725 nm), which was about 5-folds higher than that of common AuNCs@Keratin. The interactions of AuNCs with silver(I) ions were systematically characterized by fluorescence measurements, fluorescence correlation spectroscopy (FCS) and X-ray photoelectron spectroscopy (XPS). It was demonstrated that the “silver effect” could not only enhance the fluorescence intensity of AuNCs, but also improved the particles’ dispersion and stability. The as-prepared AuNCs-Ag@Keratin was applied to detect Hg 2+ in a wide detection range (2.44–2500 nM) and low detection limit (2.31 nM). [ABSTRACT FROM AUTHOR]

With the extensive application of silver containing materials in industry, the issue of release of silver ions has attracted increasing attention due to toxic effect of silver ions on the human health and environment. Traditionally, silver ions can be detected by atomic absorption spectroscopy, atomic emission spectrometry etc. , which needed expensive and elaborate instruments and were high energy consumption. Therefore, economic and convenient methods are required for the effective determination of silver ions. Herein, two types of carbon dots (CDs-1 and CDs-2) have been prepared through a solvothermal synthesis method by using sucrose or citric acid and tris(hydroxymethyl)aminomethane as precursor, respectively. Then, CDs-1 were developed for the detection of silver ions through a colorimetric method. The detection mechanism was based on the reduction of silver ions and the formation of silver nanoparticles, which possess unique surface plasma resonance properties. CDs-1 could both act as reductants and stabilizers during the reaction for determination of silver ions. This CDs-1 based detection system could quantitatively determine silver ions in 3 min with a limit of detection (LOD) of 26 nmol/L (2.81 ppb). Interestingly, this strategy could also realize the detection of silver ions by CDs-2. Furthermore, the sensing assay is applicable to detecting silver ions in lake water and silver sulfadiazine cream samples. [ABSTRACT FROM AUTHOR]

In this work, a novel bifunctional fluorescent sensor ( FQ ) was developed for simultaneous detection and removal of Ag + in aqueous solutions by grafting a naphthalimide-based fluorescent probe onto the surface of the mesoporous silica nanoparticles. FQ exhibited good selectivity towards Ag + in water samples, and showed 2.5-fold enhancement of fluorescence intensity with the addition of Ag + . Meanwhile, FQ showed a very good linearity at a low concentration of Ag + with a detection limit of 7.2 × 10 −6  M. In addition, FQ can also serve as an adsorbent for the removal of Ag + in water samples with the maximal adsorption capacity of 14.8 mg g −1 . FQ can be regenerated easily by modulating the pH value of the aqueous solution, and can be recycled at least eight times. All results demonstrate that FQ has potential applications for the detection and removal of Ag + in aqueous samples. [ABSTRACT FROM AUTHOR]

Green fluorescent protein (GFP) becomes one of the most important imaging tools in biology and biomedicine. To simplify usage, expand the application and avoid complicated operations, a kind of artificial fluorescent protein (AFP) is inspired and fabricated by lighting up human serum albumin (HSA) with loading microenvironment-sensitive fluorescent dye DMAR , which could be applied in HSA assay in human urine and serum samples as a physiological indicator of diagnosis in clinical. Besides, the AFP, DMAR /HSA, could act as a nanosensor for Ag + sensing with good selectivity by a new relay recognition strategy. [ABSTRACT FROM AUTHOR]

In this study, we employed CupR protein in the construct of a fluorescence resonance energy transfer (FRET)-based protein biosensor for the detection of silver ions. We fused the CFP and the YPet through a truncated CupR protein (containing a dimerization helix and a metal binding domain) to create a FRET-based biosensor for the detection of silver ions. Various aqueous media (including tap water and pond water) were examined to determine the matrix effects and agarose gel was used to increase the feasibility of this portable biosensors. The resulting biosensor has demonstrated high sensitivity and selectivity to silver ions. [ABSTRACT FROM AUTHOR]

In the present report a dihydropyrimidine-based Biginelli compound 1 was engineered into stable organic nanoparticles via reprecipitation method. The organic nanoparticles, N1 acted as an efficient fluorescent nanosensor for selective detection of Ag (I) ions via fluorescence quenching with a detection limit of 7.9 nM. Furthermore, successful detection of spermidine (an important biogenic amine) was realized through an indirect metal ion mediated approach where the quenched fluorescence of complex, C was recovered with a red-shift on addition of spermidine. The lowest detection limit for spermidine was found to be 3.2 nM. The nanosensor found applicability in a wide pH range from 3 to 12, which is appropriate for evaluation in environmental and physiological conditions. The selectivity for Ag (I) ions and spermidine was further confirmed with competitive binding studies which demonstrated no interference from other analytes. Moreover, real sample analysis established the practical applicability of the developed probes. The proposed strategy provides a facile, non-invasive, sensitive and economic platform for the estimation of Ag (I) ions in environmental samples (river water) and spermidine in biological samples (urine). [ABSTRACT FROM AUTHOR]

We described a rapid and highly sensitive colorimetric method for the detection and quantification of silver ions employing glutathione (GSH)-mediated MnO 2 nanosheets as an artificial oxidase. In this assay,the absorption intensity of the chromogenic reaction system enabled the quantification of silver ions. Under the optimum conditions, the linear response ranged for Ag + was from 10 nM to 800 nM with a correlation coefficient of 0.996. Remarkably, limit of detection in aqueous solutions was 4.23 nM, which was well below United States Environmental Protection Agency (USEPA) permissible limit in drinking water (460 nM). This sensing assay had highly specificity because no significant interference occurred with 10-fold concentration of other metal ions. Moreover, the approach also could be employed to the Ag + detection in real samples. And the recovery of Ag + spiked in tap water ranged from 99.62% to 108.01%. Importantly, the oxidation reaction of TMB to oxTMB by MnO 2 nanosheets completed instantaneously even by naked-eye readout. Therefore, the assay based on GSH-mediated MnO 2 nanosheets is simple, rapid, highly sensitive and selective for the quantification of Ag + in water and practical samples. [ABSTRACT FROM AUTHOR]

A luminescent Eu-complex is synthesized with the use of Eu(NO 3 ) 3 ·6H 2 O, zinc acetate dihydrate, biphenyl-4,4-dicarboxylic acid (BPDC) and adenine. Ag + is further fabricated with the complex by stirring the Eu-complex in silver nitrate solution at dark for 6 h. Both of the two complexes show the similar framework structure to Bio-MOF-1. Subsequently, the resulting complex (labeled as Ag + @Eu-complex) is developed as a fluorescence probe for aspartic acid. The existence of aspartic acid can make the emission intensity of ligand enhance a lot while Eu 3+ decrease gradually, which is different from other 19 kinds of common amino acids. We also examine the luminescent properties of Ag + @Eu-complex in varying concentration of aspartic acid, which show the favorable linear relationship between luminescent intensity and concentration of aspartic acid as well low detection limit (calculated as 0.46 μM). The results indicate that the material can be a good sensor for aspartic acid. [ABSTRACT FROM AUTHOR]

A ratiometric fluorescent nanosensor was reported for the first time for the sensitive and selective analysis of Ag + ions by employing graphene quantum dots (GQDs) as the reference fluorophore and o -phenylenediamine (OPD) as the specific recognition probe. Upon the addition of Ag + ions, OPD could be oxidized to produce 2,3-diaminophenazine (DAP) with a strong fluorescence emission at 557 nm, whereas the fluorescence of GQDs at 445 nm would be simultaneously quenched by the so generated DAP through fluorescence resonance energy transfer (FRET). A ratiometric fluorescent Ag + nanosensor was thus developed. The fluorescence intensity ratios of DAP to GQDs linearly increased with the increasing of Ag + concentrations in the range of 0–115.2 μM, with a detection limit down to 250 nM. Furthermore, the feasibility of practical applications of the developed detection strategy for probing Ag + ions in real water samples was demonstrated. [ABSTRACT FROM AUTHOR]

Pesticides abuse has drawn considerable attention in agriculture, environment and food safety in recent years. How to selective and on-site detection of pesticide residues with rapid operation and low cost is still a hot topic. In this work, we report a novel method for the detection of pesticide thiram using phosphorescent Mn-doped ZnS quantum dots (ZnS:Mn 2+ QDs) combined by an affinity reaction between thiram and Ag + ions. On the one hand, the phosphorescence of as-prepared ZnS:Mn 2+ QDs at 590 nm can be effectively quenched by Ag + ions due to the direct cation-exchange reaction at the surface of QDs. On the other hand, the presence of thiram can inhibit phosphorescence quenching through the formation of stable Ag-thiram complex. This inhibition resulted in a linear recovery in emission intensity with increasing the amount of thiram, which enables thiram residues to be identified under the UV light illumination. In buffer condition, thiram could be detected within the concentration range of 50 nM–2.5 μM with a detection limit of 25 nM. Moreover, the proposed method has been successfully applied to thiram residues identification at fresh fruit peels. The investigation provides a profile for instant and visual detection of surface residues using doped quantum dots. [ABSTRACT FROM AUTHOR]

The bis-imidazolium salt 1,4-bis[ N -(9′-anthracenyl-methyl)imidazoliumyl]butane hexafluorophosphate ( L 1 H 2 ·(PF 6 ) 2 ) and its N -heterocyclic carbene (NHC) silver(I) macrometallocycle [(L 1 Ag) 2 ](PF 6 ) 2 ( 1 ) have been prepared and characterized. 18-Membered macrometallocycle of 1 is formed via two ligands ( L 1 ) and two silver(I) ions. The selective recognition of m -dinitrobenzene (DNB) using 1 as a host was studied on the basis of fluorescence titrations, 1 H NMR titrations, HRMS spectra and IR spectra. The results indicate that 1 can distinguish effectively m -dinitrobenzene with other aromatic compounds. [ABSTRACT FROM AUTHOR]

Silver ion (Ag + ) is a highly toxic heavy metal ion to aquatic organisms and accumulates in the human body via the food chain. Therefore, fast and accurate detection of Ag + in water and food resources has become a critical issue within the scope of human health. Herein, we developed an ultrasensitive electrochemical biosensor for detection of Ag + based on magnetic Fe 3 O 4 @gold core-shell nanoparticles (Fe 3 O 4 @Au NPs) labeling with hybridization chain reaction (HCR) amplification strategy. In this sensing strategy, the magnetic Fe 3 O 4 @Au NPs were selected for labeling with HCR product and enrichment on the surface of magnetic gold electrode. Thiolated-oligonucleotide (S1) was firstly immobilized on the surface of Fe 3 O 4 @Au NPs through Au–S chemical bond. In the presence of Ag + , cytosine-rich DNA oligonucleotide S2 hybridized with S1 to form an intramolecular duplex, in which Ag + can selectively bind to cytosine–cytosine mismatches forming C–Ag + –C complex. The exposed stem of the C–Ag + –C complex opened two alternating ferrocene-labeled DNA hairpins (H 1 and H 2 ) in turn and triggered HCR to form a supersandwich DNA structure on the surface of Fe 3 O 4 @Au NPs. The HCR products modified Fe 3 O 4 @Au NPs were brought to the surface of magnetic gold electrode for direct electrochemical measurements. The proposed strategy led to a low detection limit of 0.5 fM and a wide dynamic range of 1 fM–100 pM for target Ag + . The developed biosensor was highly selective and its practical applicability in tap water and lake water samples was also investigated with a satisfactory result. [ABSTRACT FROM AUTHOR]

Adenosine (AD) is a biomarker for monitoring the progress of lung cancer and its analysis in biological fluids of patients is significant. Here, we report a novel signal amplification platform for the sensitive and selective monitoring of AD in the biological fluids on the basis of silver ions-assisted cation exchange reaction with CdTe quantum dots (QDs). The AD aptamer was engineered to consist of two pieces of ssDNA which were respectively attached to Fe 3 O 4 magnetic nanoparticles and CdTe QDs. In the presence of AD, it would reassemble the two pieces of ssDNA into the intact aptamer tertiary structure, and then form the stable nanoparticle sandwich structure. After magnetic separation, the final fluorescence signal with amplification process based on silver ions-assisted twice cation exchange reactions would make AD detection more sensitive, compared with directly measuring the fluorescence intensity of sandwich structure. The platform exhibits excellent sensitivity and high specificity, with a detection limit of 0.217 nM for AD. Moreover, the present platform was successfully applied to the determination of AD in urine samples of lung cancer patients and the range of the recoveries was from 90％ to 106％. The results revealed that the developed platform may provide a promising analytical platform for various target molecules in the biomedical field and clinical diagnosis. [ABSTRACT FROM AUTHOR]

The development of Ag + detection system with high sensitivity, selectivity and quantitatively accurate analysis is crucial because of the potential risk of Ag ion increasingly applied in various fields. As synthetic oligodeoxyribonucleotides are available to use, there have been few studies reported in the literature regarding techniques for electrochemical biosensors based on cytosine-enriched DNA used as the capture material of Ag ion. The high price and complex process for connecting NH 2 -terminal to DNA make it expensive to fabricate the Ag detecting system. In this study, we investigated the Ag ion detection system with single-cytosine (SC) used in the place of DNA with a functional group. The proposed system can guarantee the effect of span increase, price reduction of detection system, and lower detection limit due to the increase of immobilization efficiency by using SC as a capture probe. Three-electrode system was microfabricated on a glass wafer. SC was immobilized on the working electrode surface, and then this electrode was exposed to a solution with Ag ions and other SC for mismatching cytosine-Ag + -cytosine. Before detecting Ag ion, cyclic voltammetry and energy-dispersive X-ray spectroscopy were used for the identification of stable immobilization of SC on the surface of the functionalized Au electrode. The electrochemical analysis for increasing Ag ion concentration and the Ag + selectivity of the SC probe were performed by square wave voltammetry. The resulted current increase is linear with the logarithmic concentration of Ag ion from 0.5 nM to 1 mM with ∼20 pM of detection limit. The slope of in a target concentration range mentioned above are 9.14 × 10 −2 per concentration decade with R 2 value of 0.9814. The reason why our system has a lower detection limit than the previous studies is because the bound each single Ag ion performs a path role for electron transfer. Moreover, the proposed electrochemical assay has good selectivity to other environmentally relevant metal ions. [ABSTRACT FROM AUTHOR]

A novel near infrared (NIR) fluorescent hybrid system ( PD-SQ ⊂ BSA ) assembled from squaraine dye PD-SQ and bovine serum albumin (BSA) was developed for selective detection of Ag + over other metal ions in absolute PBS. The detection limit of PD-SQ ⊂ BSA for Ag + is calculated to be about 8.99 × 10 −8 M, which is lower than the guidelines for drinking water set by the WHO. PD-SQ alone shows very weak fluorescence due to aggregation-caused quenching (ACQ) property. BSA can cause PD-SQ to partially disaggregate through electrostatic and hydrophobic interactions, but various metal ions including Ag + cannot do. Interestingly, the presence of both BSA and Ag + can trigger PD-SQ to almost completely disaggregate through synergic binding of multiple S-Ag linkings derived from the biothiol moieties in BSA and PD-SQ with Ag + , resulting in obvious turn-on fluorescence change. Absorption and field emission scanning electron microscope (FESEM) spectra have been used to prove the conversion of PD-SQ from aggregates to monomers. In addition, based on the fluorescence spectra changes of PD-SQ ⊂ BSA system upon addition of Hg 2+ and ethylenediaminetetraacetic acid (EDTA), logic circuits including AND and INHIBIT logic gates with reset function were successfully constructed. This type of fluorescent system shows great potential for disease diagnosis, environmental protection, and information protection at the molecular scale. [ABSTRACT FROM AUTHOR]

An organic/inorganic hybrid L@SBA-15 was constructed by the intermolecular hydrogen bond. XRD, TEM, FT-IR and TGA were used to characterize the grafting process. The results proved that L-Cl was successfully anchored into the channel of SBA-15 and that the primary ordered mesoporous structure of SBA-15 was well preserved. L@SBA-15 was utilized for Ag + determination in aqueous media. The correlative fluorescence signals are linearly proportional to log[Ag + ] in the concentration region of 1 × 10 −6 ∼ 4 × 10 −5 mol/L, showing a low detection limit of 1.26 × 10 −7 mol/L. A high sensitivity parameter of 0.97 was found. The competitive experiment confirmed that this sensor exhibited a high selectivity to Ag + . The high selectivity towards Ag + is mainly attributed to the spatial factor in the channel of SBA-15. The most attractive feature of this sensor is the excellent recovery, which indicates L@SBA-15 would be a promising candidate for practical application. [ABSTRACT FROM AUTHOR]

Sulfur-doped graphene quantum dots (S-GQDs) with bright blue emission have been prepared by a facile one-pot hydrothermal treatment. A specific compound, 1,3,6-trinitropyrene, which has a mother nucleus structure similar with graphene, was chosen as the carbon source and 3-mercaptopropionic acid (MPA) was employed for S-doping and carboxyl groups modification. The synthesized S-GQDs were characterized by atomic force microscopy (AFM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and fluoscence (FL) spectrum. Results indicated that S-GQDs possessed single layer graphene structure with mean size of about 2.5 nm and presented an excitation-independent photoluminescence behavior with maximum excitation/emission wavelength at 360/450 nm, respectively. The sulfur-doping of GODs drastically improved their electronic and chemical properties, which afforded the S-GQDs a sensitive response to Ag + ions. Furthermore, the S-GQDs were successfully explored as a sensing probe for Ag + detection with high sensitivity and selectivity. A wide linear range of 0.1-130.0 μM with a low detection limit of 30 nM was obtained. The facile preparation method and the high performace of the as-prepared S-GQDs present promising potential for their applications in sensing, biological imaging and catalysis. [ABSTRACT FROM AUTHOR]

A colorimetric assay with excellent selectivity is reported for detecting silver ion in aqueous solutions. The system works based on the competitive interaction of gold nanoparticles (AuNPs) and Ag + with tris(hydroxymethyl) aminomethane (tris). The sensing strategy is quite simple, fast, convenient and the detection is by the naked eye. The aggregation of AuNPs with tris was inhibited in the presence of Ag + ions resulting in a significant hypsochromic spectral shift of the surface plasmon resonance (SPR) of AuNPs and a color change from blue to red. The interaction between tris and Ag + ion was investigated with cyclic voltammetry. The effect of Ag + concentration on the aggregation of AuNPs by tris was monitored by UV–vis spectroscopy with the dynamic range of 1–9 μM and detection limit of 0.41 μM. The recovery analysis of river water and wastewater samples proved that this colorimetric sensor is successfully operational in environmental monitoring. [ABSTRACT FROM AUTHOR]

In this work, a new phenazine-based derivative ( L-1 ) which based on 2,3-diamino-phenazine and 5-(4-chlorphenyl)-2-furaldehyde was designed to act efficiently in a chemodosimeter approach for the rapid and selective detection of silver ion in aqueous solution over a wide pH range. The addition of Ag + to an aqueous solution of L-1 induced a change in the solution color from yellow to shallow orange and fluorescent quenching, indicating that L-1 could act as an excellent ON−OFF-type fluorescent chemosensor for Ag + . With a detection limit of 3.25 × 10 −7 M, the chemosensor shows great potential to monitor Ag + in environmental analysis systems. Furthermore, this sensor can serve as a recyclable component in sensing materials. These properties make L-1 act as an accurate Ag + controlled ON−OFF−ON fluorescence switch and implication (IMP) function logic gate. In addition, the actual usage of sensor L-1 was further demonstrated by test kits and silica gel plates. Notably, the stoichiometry of the complexes between the sensor and Ag + is indicative of a 2:1 ratio which was determined by a Job's plot yielded from fluorescence titrations. And the mode of interaction between Ag + ions and L-1 has been supported by 1 H NMR spectroscopy and mass spectrometry studies. [ABSTRACT FROM AUTHOR]

Herein, an assembly of a new synthesized lariat ether ( Pc ) was demonstrated as a novel fluorescent indicator for the determination of silver ions in aqueous solution. The silver-specific receptor Pc was constructed by incorporating an azacrown[N,S,O] moiety into a picoline fluorophore. The UV–vis spectra revealed that the self-assembly of the stacked Pc molecules is initially in a form of J- aggreate ( Pc J-agg ), whereas it gradually converts to a form of H -aggregate ( Pc H-agg ), driven by the π-π stacking and hydrophobic effects. Under ultrasonic oscillation, the transformation of the aggregated forms from Pc J-agg to Pc H-agg would be disturbed while a formation of a new stable assembled form of Pc molecules denoted as Pc NS was initiated. The morphology and nanosheeted structure of the new Pc NS were revealed by atomic force microscopy and dynamic light-scattering measurement. As for the investigation of its emission property, the fluorescence spectroscopy was used and an evidently blue-shifted fluorescence was observed. When used as a stimuli-responsive fluorescent indicator, the Pc NS assembly was degraded upon the addition of silver ions, accompanying a 44 nm bathochromic shift in its fluorescence emission spectrum. Investigation of its selectivity for various cations confirmed that the Pc NS nanosheet assembly could be efficiently used for the detection of silver ions. [ABSTRACT FROM AUTHOR]

Accurate detection and localization of micrometastases are extremely important for tumor diagnosis and comprehensive treatment. However, it is clinically difficult to finely localize micrometastases, especially focal lesions smaller than 1 mm. To that purpose, this work designed a tumor microenvironment factor (glutathione, GSH)-activated second near-infrared transparency window (NIR-II) fluorescent probe for visualization of micrometastases. It is constructed by complexing copper ions with 3-mercaptopropionic acid-modified silver sulfide (Ag 2 S-MPA) quantum dots. The experimental results showed that the probe has good and stable GSH activation properties and can achieve tumor-specific NIR-II fluorescence imaging. Further, in vivo imaging experiments demonstrated that the probe can precisely localize melanomas with a diameter of < 0.1 mm in lung micrometastases. This work provides a potential strategy for the development of novel tools for localization and visualization of micrometastases. • Detection of micrometastases is the key to grading and treating tumors. • Glutathione-activated NIR-II fluorescent probes for micrometastases visualization. • The probe was designed by complexing Cu2+ ions with silver sulfide quantum dots. • Precise fluorescence localization of lung micrometastases < 0.1 mm was achieved with this probe. [ABSTRACT FROM AUTHOR]

For surface-enhanced Raman scattering (SERS) analytical technology, the rational design of efficient substrate and effective internal standard is the key issue to implement the reliable detection. In this paper, a novel three-dimensional (3D) silver(I)-polyoxometalate complex of Ag 2 [Ag(trz) 2 ][H 6 CrMo 6 O 24 ]·2H 2 O (Ag 3 CrMo 6 , trz = 1, 2, 4-triazole) has been designed and synthesized, which can be used for the quantitative detection of formaldehyde (FA). Structural analysis reveals that the [H 6 CrMo 6 O 24 ]3- polyoxoanions link Ag+ by diverse Ag−O (Mo−O) bonds to form a stable 3D framework. When Ag 3 CrMo 6 is exposed to FA, the Ag+ can be partially reduced to Ag0 species to become the label-free SERS active substrate and and present the enhanced signals ascribed to the Mo−O vibrations. Due to that the reduced Ag0 species is only close to Mo−O groups, the Raman signals for Cr−O bonds are almost constant and can be used as internal standards. Therefore, the I Mo−O /I Cr−O values can be used as ratiometric SERS signals to fulfill the elusive SERS quantitative analysis for FA with the detection limit of 0.05 ng/L. This work opens up an innovative way to the rational design of label-free SERS substrate based on polyoxoanions and silver ions, by which the quantitative detection can be realized via the ratiometric Raman signals. [Display omitted] • A 3D Ag-polyoxometalate crystalline compound of Ag 3 CrMo 6 is rationally designed and synthesized. • Ag 3 CrMo 6 can be used as ultra-sensitive SERS substrate with response to formaldehyde. • The polyoxoanion in Ag 3 CrMo 6 is unveiled to act as both internal standard and signal labels. • It extends a rational design of label-free SERS substrate based on polyoxoanions and silver ions. [ABSTRACT FROM AUTHOR]

A label free difunctional electrochemiluminescence (ECL) sensor for the ultrasensitive detection of mercury ions (Hg2+) and silver ions (Ag+) was constructed based on Ru(bpy) 3 2+-functionalized metal-organic frameworks (Ru-MOFs) and the strand-displacement-amplification (SDA) reaction. Electrodeposited Ru-MOFs not only overcome the disadvantage of poor stability of traditional Ru2+ in aqueous solution, but also serve as an excellent carrier for hairpin DNA H1 during sensor construction. The SDA technology can transform extremely low concentrations of Hg2+ and Ag+ into a large number of the same alternative target DNA (tDNA). By combining SDA with Ru-MOFs, the detection sensitivity of the sensor is further improved. Meanwhile, the generated same alternative target tDNA can realize the detection of Hg2+ and Ag+ ions on this same sensing platform, which is beneficial to solve the common problems of high cost, long time and complicated operation in the detection of metal ion. The detection limits for Hg2+ and Ag+ are as low as 0.00032 pM and 0.00298 pM, respectively. And the corresponding linear detection range (LDR) is 0.001–1000 pM and 0.01–10000 pM, respectively. This ECL sensor has also been successfully used in the determination of Hg2+ and Ag+ in seawater, indicating an ideal platform for the simultaneous detection of trace heavy metal ions. [Display omitted] • A novel Ru-MOF with high luminous efficiency and good stability is synthesized. • A difunctional sensor is constructed for ultrasensitive detection of Hg2+ and Ag+. • ECL sensor based on strand-displacement-amplification reaction is constructed. • ECL sensor shows good sensitivity, stability and selectivity for real samples. [ABSTRACT FROM AUTHOR]

A simple dual sensing of CN − and Ag + was first time reported by naphthalene based lab-on-a-molecule containing benzothiazole in DMF buffered aqueous solution. With CN − and Ag + , probe 1 showed highly selective and sensitive responses towards CN − and Ag + in both UV–Vis and fluorescence channels over other tested ions. Meanwhile, the sensing mechanism of both title ions was further studied by NMR titration and XPS experiments. [ABSTRACT FROM AUTHOR]

The hyperbranched polyethylenimine (HPEI) derivative with thiol (SH) terminals was synthesized and used as multidentate ligand to stabilize AuNPs/analyte composites. A facile and rapid colorimetric method for the sensitive and selective detection of Ag + based on the formation of Au-Ag core-shell NPs with three color changes (red through brown to green) was developed. Successive multiple color changes can greatly improve the specificity and selectivity of this colorimetric sensor owing to the lower possibility of false positive results. Other environmentally relevant metal ions did not interfere with the determination of Ag + . The response (i.e., the absorbance at 600 nm, A 600 nm ) was linearly proportional to the Ag + concentration in a range from 8.76 × 10 −9 to 1.27 × 10 −4 M with a detection limit of 8.76 × 10 −8 M by the naked eyes and 8.76 × 10 −9 M by the UV–vis spectra. For the first time, this novel colorimetric sensor based on multiple color changes was developed and successfully applied to detect Ag + in real samples. [ABSTRACT FROM AUTHOR]

Two fluorophores, SPF-TNS and SPF-TBB , with electron-rich triphenylamine groups and Ag + receptor units on the respective biphenyl branches of 9,9′-spirobifluorene were synthesized. They exhibit strong one- and two-photon excited fluorescence, and the two-photon absorption cross-section values are 665 GM for SPF-TNS and 355GM for SPF-TBB . The probing behaviors toward metal ions were investigated via UV/Vis absorption spectra as well as one-photon fluorescence changes. The results indicated that SPF-TNS and SPF-TBB exhibit distinct fluorescent quenching in the presence of silver ions that can be used for highly sensitive and selective naked-eye detection of Ag + . The one-photon excited fluorescence of SPF-TBB can be made to measure water content of organic solvents. The detection limits were calculated to be 0.04% for THF and 0.03% for 1,4-dioxane. The two-photon scanning microscopy experiments suggest that SPF-TNS is a promising label potentially applicable for the tracking of biomolecules. [ABSTRACT FROM AUTHOR]

A novel colorimetric method for the detection of acetylcholinesterase (AChE) and its inhibitor by taking utilization of Ag [I] ion–3,3′,5,5′-tetramethylbenzidine (TMB) detection system has been proposed. Ag [I] ion could oxidize TMB to induce a blue color and an absorption peak centered at 652 nm. In the presence of AChE, acetylthiocholine (ACh) was hydrolyzed to thiocholine. Ag [I] ion could interact with thiocholine and thiocholine can reduce the oxidized TMB (oxTMB) to TMB, both of which suppressed the oxidation capacity of Ag [I] ion, resulting in a blue color fading and a decrease of the absorbance at 652 nm. The developed assay is highly sensitive with a low detection limit of 4.3 μU/mL. Moreover, the method was also applied in AChE inhibitor sensing. The obtained assay is fairly simple, inexpensive and sensitive without the utilization of nanomaterials, which may be not only used for the sensing of other hydrolytic enzyme activities with properly selected substrates, but also used for the screening of potential inhibitor drugs. [ABSTRACT FROM AUTHOR]

The main problem in preparing stable and printable inks for the inkjet printing of textile substrates is in overcoming their roughness and high sintering temperature. In this study, the modified Tollens’ process for the preparation of a suitable water-soluble ink containing silver for the inkjet printing of textile substrates as a tool for textronic applications was adopted. The choice of this type of ink ensured inkjet printability of textile surfaces with simultaneous sintering at low temperature not exceeding 90 °C. The surface resistance of the inkjet-printed silver layers on all the textile fabrics studied steadily decreased with the number of silver layers deposited. In the case of 8 prints on synthetic textiles made of polyacrylonitrile, polypropylene, polyester and basalt fibres the surface resistance in the range 0.155–0.235 Ω/sq. was achieved. For some textile substrates made of natural fibres and their blends with synthetic fibres, to achieve the proper conductivity an interlayer of acrylic copolymer containing resin was applied. The surface resistance for the same number of prints was in the range of 0.389–0.622 Ω/sq. The study confirmed the usefulness of ink applied in printing silver electrodes and their resistance to bending, washing and dry-cleaning processes. On the basis of these findings, some potential applications in textronic systems, e.g., capacitors, textile heating actuators, textile patch antennas, and high-frequency transmission lines were proposed. [ABSTRACT FROM AUTHOR]

A new fluorescent multi-functional monomer (E)-3′,6′-bis (allyloxy)-2-((thiazol-2-ylmethylene)amino)-4a′,9a′-dihydrospiro[isoindoline-1,9′-xanthen]-3-one (ATMIX) was successfully synthesized for the first time. The obtained ATMIX not only exhibited fluorescence on–off characteristics toward Ag(I), but also could produce radical polymerization with cross-linkers. Based on ATMIX, a novel ion-imprinted fluorescent on–off sensor (IIFOS) was fabricated successfully for selective recognition of Ag(I). The morphology, structure and fluorescent property of IIFOS was characterized by infrared spectroscopy, scanning electron microscopy (SEM) and fluorescent spectrometry. The results indicated that the obtained IIFOS exhibited high selective fluorescence on–off characteristics toward Ag(I) based on the mechanism of photoinduced electron transfer. What is more, the IIFOS is reusable and has been applied to detect Ag(I) in water sample with satisfactory recoveries. [ABSTRACT FROM AUTHOR]

In this work, a facile approach to sensitively detect sulfide ions is developed. The proposed method is based on the findings that silver ions could oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) to induce a blue color and an absorption peak centered at 652 nm. The introduction of sulfide ions leads to the formation of Ag 2 S nanoparticles which act as catalyst to enhance the oxidation capacity of silver ions, resulting in a blue color burning and increase of the absorbance at 652 nm. Based on the above facts, a facile method is developed to qualitatively and quantitatively detect sulfide ions by naked eyes and UV–vis spectroscopy, respectively. The color changes of the detection system in the presence of nanomolar level of sulfide ions could be distinguished by naked-eyes, demonstrating the high sensitivity of the method. Highly sensitive detection of sulfide ions can be achieved in the range of 1.0 × 10 −9 M to 8.0 × 10 −8 M, with a detection limit of 0.2 nM. In addition, this method shows excellent selectivity toward sulfide ions detection and has been successfully applied to detect sulfide ions in tap water and lake water samples. Moreover, this method is simple without the preparation of nanomaterials and the need of complex readout instruments. [ABSTRACT FROM AUTHOR]

A new coumarin-based probe 1 was prepared for the detection of Cu 2+ and Ag + in aqueous solutions. Probe 1 shows highly selective and sensitive chromogenic recognition toward Cu 2+ and Ag + , before and after exposure to natural sunlight, respectively. The selectivity toward Cu 2+ or Ag + was not interfered with by other metal ions. The detection limits for Cu 2+ and Ag + ion were determined as (7.99 ± 0.04) × 10 −6 M and (8.60 ± 0.04) × 10 −10 M, respectively. Thus, the probe 1 can be used as a practical, highly sensitive chromogenic probe for the determination of Cu 2+ and Ag + in aqueous medium. [ABSTRACT FROM AUTHOR]

Silver ion (Ag+) is one of the most toxic and dangerous heavy metal pollutants. Therefore, finding a simple, sensitive and selective approach to detect Ag+ is very urgent for environmental protection and risk reduction to human health. In this work, water-soluble red-emitting micellized phosphorescent silver nanoclusters (Ag 29 @Na micelles) with a large stokes shift of 380 nm are prepared and used as sensitive and selective phosphorescent probes to realize the rapid and simple detection of Ag+. Upon adding Ag+, the phosphorescence of Ag 29 @Na micelles is quenching, and the phosphorescence quenching ratio is linearly proportional to the Ag+ concentration over the range from 1 nM to 100 nM with the detection limit of 0.8 nM (S / N = 3). The Ag 29 @Na micelles exhibit high selectivity for Ag+ over other potentially interfering metal ions. The quenching mechanism of Ag 29 @Na micelles by Ag+ is studied in details using various analytical characterizations including UV–vis absorption spectroscopy, photoluminescence lifetime, X-ray photoelectron spectroscopy, transmission electron microscopy, and zeta potential, and the results denote that the aggregation between Ag 29 @Na micelles and Ag+ is responsible for the phosphorescence quenching. The Ag 29 @Na micelles-based phosphorescence probes are successfully applied to detect Ag+ in lake water samples with good recoveries of 98 %−108 %. [Display omitted] • The red-emitting Ag 29 @Na micelles with a large stokes shift were used as phosphorescent probes. • The Ag 29 @Na micelles can be used for ultrasensitive and highly selective detection of Ag+ ions. • The quenching mechanism of Ag 29 @Na micelles by Ag+ ions was studied in details. • The proposed method was used to detect Ag+ ions in water samples. [ABSTRACT FROM AUTHOR]

In the present study, we report on a simple, sensitive and selective chemosensor for the recognition and monitoring of silver ions in aqueous solutions. It is based on the inhibitory effect of Ag(I) ion on the chemiluminescence signal of H 2 O 2 –luminol system, which could be improved by at least 10-folds in the presence of cobalt ferrite (CoFe 2 O 4 ) magnetic nano-particles. The structure and morphology of the synthesized CoFe 2 O 4 nano-particles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The as-prepared CoFe 2 O 4 nano-particles were then used as catalysts for H 2 O 2 –luminol chemiluminescence system. The enhanced chemiluminescence signal was dramatically decreased by adding trace levels of Ag(I) ion into the solution. The possible mechanism to explain this finding was discussed. Several parameters affecting the analytical signal such as the pH value, the concentrations of H 2 O 2 , luminal and CoFe 2 O 4 nano-particles, incubation time and interfering ions were investigated and optimized. Under the optimized experimental conditions, chemiluminescence intensity of luminol–H 2 O 2 –CoFe 2 O 4 versus Ag(I) concentration gave a linear response within the range of 0.5–100 ng mL −1 with a detection limit of 0.15 ng mL −1 . The method was successfully applied to monitoring Ag(I) in various water samples. [ABSTRACT FROM AUTHOR]

In this paper, the flexible capacitive humidity sensors using the polyimide foils as the substrate together with the moisture sensitive materials had been investigated. A simple and low cost inkjet-printing method had been developed to form silver interdigitated electrodes on PI foils. Two kinds of capacitive humidity sensors with Ag IDEs were constructed. And the humidity sensor characteristics such as sensitivity and hysteresis were analyzed. The results indicated that the metallization of Ag on PI is potential for various future flexible applications. [ABSTRACT FROM AUTHOR]

Berberine ( Bn ), an important traditional medicinal herb with anticancer, antitumour and antidiabetic activities, is effectively utilized as a sensing probe for silver ion with good sensitivity and selectivity, using absorbance and fluorescence studies. The effect of presence of other metal ions with Bn is also investigated and Bn is found to be selective towards Ag + ion over other metal ions such as Cu 2+ , Zn 2+ , Sn 2+ , Ni 2+ , Ba 2+ , Bi 2+ , Pb 2+ , Co 3+ , In 3+ , Mn 2+ , Fe 2+ , Fe 3+ , Li + , Hg 2+ and Ca 2+ with a detection limit of 0.1 × 10 −4 mol L −1 . The colour changes from yellow to orange when Ag + ion is added and other metal ions failed to show any visible colour change. The effective quenching of Bn upon binding with Ag + ion is attributed to suppression of intramolecular charge transfer (ICT). [ABSTRACT FROM AUTHOR]

A simple, signal-on electrochemical biosensor for sensitive detection of Ag+ was developed based on the three components of alkanethiol, single-walled carbon nanotube (SWNT) and silver ion-specific oligonucleotide (SSO) layer-by-layer modified electrode where square wave voltammetry (SWV) response of K3[Fe(CN)6] at the modified electrode was used for signal transduction. A gold electrode was first assembled with 1-dodecanethiol (C12H25SH) monolayer to which SWNTs were attached. The SWNT surfaces were further noncovalently bound with SSO probes to obtain the sensor interface. The negatively charged SSO probe acts as a physical obstacle and electrostatic repulsion barrier to block the SWNT-mediated long-distance electron transfer of K3[Fe(CN)6] across the -SC12H25 monolayer. Upon Ag+ binding, the SWNT surface-bound SSO probe forms an unimolecular duplex through C-Ag+-C interaction-mediated intramolecular hybridization and departs from the SWNT surface, resulting in decreased electron transfer resistance and increased SWV current of K3[Fe(CN)6] at the modified electrode. This current enhancement effect provides a signal-on mechanism for sensitive transduction of Ag+ recognition and the resulted current increase is linear with the logarithmic concentration of Ag+ from 2.0 nM to 100 nM. The developed biosensor was highly selective and its practical applicability in tap water was also tested with a satisfactory result. [ABSTRACT FROM AUTHOR]

A novel carbon paste ion selective electrode which was based on a newly synthesized N,N'-bis(benzophenone imine)formamidine (b-BPEF) as an ionophore was prepared for the determination of silver ion. (b-BPEF) was characterized by elemental analysis, FT-IR, ¹H NMR, 13C NMR spectroscopy and X-ray single crystal diffraction. The modified electrode with optimum composition, exhibited an excellent Nernstian response to Ag+ ion ranging from 2.2 x 10-7 to 2.2 x 10-2 mol L-1 with a detection limit of 5.0 x 10-8 mol L-1 and a slope of 59.54 ± 0.2 mV decade-1 over a wide pH range (2.0-9.0) with a fast response time (<10 s) at 25 °C. The interaction between (b-BPEF) and Ag+ was studied spectrophotometrically exhibiting the stoichiometry of the complex (1:1) in methanol solution. The proposed electrode showed a fairly good selectivity toward Ag+ ion in comparison with some alkali, alkaline earth, transition and heavy metal ions. This carbon paste electrode was applied as an indicator electrode in potentiometric titration of Ag+ and in direct determination of silver (I) ion in the mineral water and medicinal sample. [ABSTRACT FROM AUTHOR]

Abstract: A sensitive and selective colorimetric Ag+ detection method was developed by using N-1-(2-mercaptoethyl)adenine functionalized gold nanoparticles (MEA-AuNPs). The presence of Ag+ immediately induced aggregation of MEA-AuNPs, yielding a color change from red to blue. This Ag+-induced aggregation of MEA-AuNPs was monitored by bare eye and UV–vis spectroscopy with a detection limit of 3.3nM. MEA-AuNPs showed excellent selectivity toward Ag+ compared with other metal ions through interaction between adenine and Ag+. The best detection of Ag+ was achieved at pH 6–9. Furthermore, MEA-AuNPs were applied to detect Ag+ in lake water with low interference. [Copyright &y& Elsevier]

Abstract: Three conjugated polymers comprised of 9,9-didodecyl-2,7-diethynyl-9H-fluorene and 2-pyridine-1H-benzo[d]imidazole units, which are alternatively linked to 4,7-position (P1) and 5,5′-position (P2, P3), respectively, have been synthesized via Sonogashira reaction. P2 and P3 with the twisted conjugated backbones were proved to show selectivity for nickel ion. By contrast, P1 with the linear conjugated backbone exhibited highly selectivity for silver ion. The results suggest that the metal ion recognition feature of the chemosensors based on the conjugated polymers can be adjusted by fine-tuning the linkage pattern between the recognition group and the conjugated backbone. Thus, a selective chemosensor for detection of nickel ion was developed. [Copyright &y& Elsevier]