Detection Of Silver Ions Research Articles

A high selective colorimetric fluorescent probe for detection of silver ions in vitro and in vivo and its application on test strips

To detect silver ions conveniently and rapidly in vitro and in vivo, a selective fluorescent probe with a wide measurement range, AgP, was developed. This probe exhibits a bright green fluorescence with an emission wavelength of 532 nm under 390 nm excitation, and its detection of Ag+ is stable in the pH range of 4–10 with a quench-type fluorescence response. Specially, the probe and its easily prepared test strips can be directly used for the colorimetric detection of Ag+ in aqueous samples with simple and convenient characteristics, the color change can be observed within a few seconds. The recovery rate of AgP detection water samples was between 117.6% and 98.3%, and the relative standard deviation (RSD) was between 0.41% and 2.06%. AgP is also suitable for in vivo imaging of Ag+ in the classical model plant, Arabidopsis thaliana, and 50 μM Ag+ can completely quench its fluorescence, which will provide a new detection tool for studying the distribution of Ag+ in the environment and live plants.

Rapid sonochemical synthesis of copper nanoclusters with red fluorescence for highly sensitive detection of silver ions

In this study, fluorescent copper nanoclusters (Cu NCs) have been efficiently synthesized in a novel strategy via sonochemical method, using N-acetyl-L-cysteine (NAC) as reducing and stabilizing reagent. The preparation of Cu NCs could complete within 15 min due to the ultrasonic radiation treatment. The obtained NAC-Cu NCs exhibited red fluorescence at λem 630 nm. Silver ions could significantly induce fluorescence quenching of NAC-Cu NCs. Subsequently, a detection method for Ag+ with high response sensitivity and selectivity was constructed. The proposed method displayed a good linear relationship in the Ag+ concentration range of 1.64 × 10-10-1.16 × 10-8 M. The limit of detection (LOD) was as low as 7.76 × 10-11 M (signal/noise = 3). In addition, the practical application was further evaluated with environmental water samples, and the tested results were compared with those obtained by the inductively coupled plasma mass spectrometry (ICP-MS) method. The satisfactory recoveries (98.50%-101.6%) showed that the fluorescent detection method had potential application in environmental monitoring field.

Design and synthesis of a combined meso-adsorbent/chemo-sensor for extraction and detection of silver ions

We synthesized a new pH-dependent meso-captor/sensor for the visual monitoring and selective sequestering of Ag(I) ions from wastewater. The SBA-16 microspheres were successfully synthesized via a direct hydrothermal treatment through surfactant-assisted cooperative self-assembly. The meso-captor/sensor was designed via the direct immobilization of the chromogenic Acid Blue 90 (AB90) chelate into cubical large, open mesoporous SBA-16 carriers and investigate of its ability to detect and retain silver ions from aqueous solutions. Results show that the synthesized SBA-16 microspheres were retained after modification and the AB90 functional groups were immobilized hierarchically inside the mesopore channels. This was evidenced by the N2 adsorption, X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared (FTIR), Scanning Electron Microscope (SEM), High-Resolution Transmission Electron Microscope (HR-TEM), and elemental analyses. Batch adsorption experiments were carried out and the effects of various parameters on Ag(I) ions removal and detection were determined. The optimum adsorption/detection of Ag(I) ions were recorded at a pH of 6.2 within 30 min with color change from a brilliant blue to a pale blue-gray. The spectral response for [SBA-16@AB90 → Ag(I)] complex showed a maximum reflectance at λmax = 385 nm within 2.5 min response time (tR); the LOD was close to 3.87 µg/L while the LOQ approached 12.83 µg/L, this was attributed to the concentration range at which a linear signal has been observed against Ag(I) analyte concentration (i.e., 5 to 1000 µg/L) at pH 6.2 with standard deviation (SD) of 0.077 (RSD% = 9.5 at n = 8).

Photoelectrochemical assay based on CdS nanocrystal\hexagonal carbon-nitrogen tube nanocomposite for detection of silver ions.

A photochemical assay was reported based on CdS nanocrystal (NC)\hexagonal carbon-nitrogen tube (HCNT) nanocomposite for the detection of Ag+. When CdS NCs were combined with HCNT, the photocurrent intensity was increased extensively. After incubation of Ag+ with CdS NC\HCNT nanocomposite-modified electrode, Ag2S was formed on the electrode by the ion-change reaction. As the band gap of Ag2S cannot match well with HCNT, the photogenerated electron-hole pairs cannot separate efficiently, so the photocurrent intensity decreases. A good linear relationship between the concentration of Ag+ in the range from 0.01 to 3μM and the corresponding photocurrent intensity was obtained with a detection limit of 3.3nM (S/N = 3). The assay was employed to detect Ag+ in lake water and human serum with satisfactory results, which indicated that it might have a broad application in different areas. Photoelectrochemical assay was reported based on CdS nanocrystal\hexagonal carbon-nitrogen tube nanocomposite for detection of Ag.

Speciation analysis of silver ions and silver nanoparticles in commercial antibacterial products by a self-constructed fluorescent spectrophotometer

A miniaturized fluorescent spectrophotometer was constructed in this work with a cheap light-emitting diode (LED) as the light source and a handheld charge coupled device (CCD) as the detector. The developed system was utilized to accurately detecting silver ions (Ag+) and silver nanoparticles (AgNPs) without any pre-concentration and chromatographic separation operations. The principle of this speciation analysis was that Ag+ can quench the fluorescent of CdTe QDs, while AgNPs cannot. Under the optimal conditions, the limit of detection (LOD) was found to be 0.06 μg mL−1 for both Ag+ and AgNPs, and the relative standard deviation (RSD, n = 7) was calculated to be 2.9% for 1 μg mL−1 of Ag+. The proposed system was demonstrated for the speciation analysis in commercial antibacterial products with satisfactory results.

Preparation of Copper/Silver Bimetallic Nanoclusters Stabilized by Penicillamine and Their Application in Silver Ion Detection

Preparation of Copper/Silver Bimetallic Nanoclusters Stabilized by Penicillamine and Their Application in Silver Ion Detection

Study on the interactions between melamine-cored Schiff bases with cucurbit[n]urils of different sizes and its application in detecting silver ions.

Three different complexes, TMeQ[6]-TBT, Q[7]-TBT, and Q[8]-TBT are constructed by three different cucurbiturils and synthesized by guest melamine-cored Schiff bases (TBT) through outer-surface interaction and host–guest interactions. TBT forms a TMeQ[6]-TBT complex with TMeQ[6] through outer-surface interaction, while Q[7]-TBT and Q[8]-TBT form complexes with Q[7,8] through host–guest interactions. Among them, Q[7]-TBT is selected as a UV detector for the detection of silver ions (Ag+). This work makes full use of the characteristics of each cucurbituril and melamine-cored Schiff base to construct a series of complexes and these are applied to metal detection.

A fluorescent nanoprobe based on AIEgen: Visualization of silver ions and sensing applications in cancer cells and S. aureus

We have developed a fluorescent nanoprobe (AgP-1) that can detect silver ions (Ag+) in biological media. For the first time, a hybridized structure based on AIEgen (tetraphenylethylene; TPE) and 2-(methylthio)aniline (MTA) moiety has been designed, and its unique sensing properties toward silver ions were systematically analyzed. The nanoprobe AgP-1 has an aggregated form with weak fluorescence and showed significant fluorescence enhancement (3.7-fold) upon forming complex with silver ions. AgP-1 has high selectivity, high sensitivity (detection limit 6.6 ppb), a fast response time (fluorescence enhancement within 10 s), and superior biocompatibility. Visualization of silver ions in cancer cells (U87 glioblastoma) and bacteria (S. aureus) was also successfully demonstrated. We believe AgP-1 holds a great potential to serve as a practical sensor for silver ions detection in biomedical applications.

Design of smartphone platform by ratiometric fluorescent for visual detection of silver ions

In this work, a smartphone platform based on ratiometric fluorescence signals was reported, which can achieve fast, sensitive, and on-site visual detection of silver ions. The ratiometric fluorescent probe was constructed with fluorescein isothiocyanate (FITC) and telluride quantum dots (CdTe QDs) through electrostatic interaction. Silver ions will interact with -SH on the surface of CdTe QDs, which can cause the decrease of the fluorescence intensity at 680 nm, while the fluorescence of FITC at 522 nm remains unchanged. It displays the obvious color changes from orange-red to light yellow to green. Based on the changes, the portable smartphone platform was used to identify the RGB values of the system. Then, an analysis model was established according to the variation of RGB values for the visual analysis of Ag+. Under the best experimental conditions, the detection limit of Ag+ by fluorescence spectrometer analysis can be as low as 3.65 nM, the linear range was 12.50 nM to 500 nM. Additionally, the linear range of smartphone platform was 0.125–12.5 μM, and the detection limit was 40 nM. Therefore, visual on-site analysis of Ag+ in environmental water samples can be achieved by capturing the obvious color changes of the system on a smartphone platform.

A rapid fluorescent ratiometric Ag+ sensor based on synthesis of a dual-emission ternary nucleotide/terbium complex probe

To develop a fast, isothermal, enzyme-free and visible method for the on-site detection of silver ions (Ag+), a ratiometric Ag+ sensor was constructed based on a dual-emission ternary nucleotide terbium probe, fabricated by synthesizing the luminescent nanomaterial Luminol-GMP-Tb (LGT). We repositioned the fluorescent properties of the nanomaterial from the perspective of the inherent optical properties of two signal reporters (luminol and Tb3+) through highlighting the absorption, fluorescence steady-state measurement and time-resolved properties. Furthermore, based on the ingenious coordination interaction and energy transfer among Ag+, luminol and GMP-Tb, we hypothesized and confirmed that Ag+ induced morphology and luminescence changes of LGT through scanning electron microscopy and lifetime changes as well as fluorescence changes. Meanwhile, by means of a portable ultraviolet detector with dual wavelengths, based on the fluorescence excitation characteristics of each component, different photoluminescence color phenomena presented at different excitation wavelengths. Therefore, visual qualitative detection could be realized under a portable UV lamp with 254 nm for mainly visible green color change while 365 nm as built-in reference for blue-emitting luminol. The ratio calculation method and the enhanced luminescence ratio mechanism made LGT exhibited extremely high selectivity to Ag+. Quantitative detection Ag+ was realized in two ranges of 0.1 μM ~ 6 μM and 6 μM ~ 100 μM with a minimum detection limit of 65 nM. The method has been successfully exploited in real water samples with recovery rate between 99.7% and 106.38%, showing broad application prospects in food safety and environmental monitoring for the on-site detection of Ag+.

Photocatalytic synthesis of BSA-Au nanoclusters with tunable fluorescence for highly selective detection of silver ion

A new photocatalytic synthesis strategy for rapid preparation of BSA-Au nanoclusters (NCs) with tunable fluorescence was developed and used for the highly selective detection of silver ion. In this strategy, the silver ion was firstly photo-reduced to Ag NCs under UV light illumination. Then, the produced Ag NCs would further reduce HAuCl4 to Au NCs stabilized in BSA molecules. In this process, silver ion not only acted as a photocatalyst to accelerate the formation of fluorescent Au nanocluster but also as a regulator to tune the fluorescence emission color of the BSA-Au NCs from orange to red. The maximum emission peak of BSA-Au NCs fluorescence could be tuned from 570 to 620 nm in different experimental conditions. Furthermore, a fluorescence emission peak red-shifts of the as-prepared BSA-Au NCs could also be observed by subsequent adding of silver ion. Thus, a quantitative analytical method for silver ion detection could be established in the range from 5.0 to 60.0 μM with a detection limit (LOD) of 0.226 μM (3σ). The method had high selectivity that other common metal ions and small biological molecules did not have similar phenomena. It had great potential for applying for environmental water sample analysis.

Detection of silver through amplified quenching of fluorescence from polyvinyl pyrrolidone-stabilized copper nanoclusters.

Silver ion detection with ultra-high sensitivity was established. We synthesized copper nanoclusters (CuNCs) with blue fluorescence through a one-pot process. Instead of a direct quencher toward the CuNCs, silver ions activated the strong oxidation from persulfate and subsequently converted divalent manganese ion into manganese dioxide (MnO2). The surface charges of MnO2 and the CuNCs brought them together and quenched the fluorescence from the latter. Due to silver ions' role as the catalyst in the process, it cycled and even a small amount leads to a significant fluorescence change. This signaling provided the determination of silver ions in the range 5 pM~1nM, with a detection limit of 1.2 pM. The method is selective, and its applicability was validated through practical water sample analyses.

Creatinine assembled on dithiobis(succinimidylpropionate) modified gold nanoparticles as a sensitive and selective colorimetric nanoprobe for silver ion detection

A sensitive and selective colorimetric assay for silver ion (Ag+) detection is demonstrated, based on creatinine (CRN) assembled on dithiobis(succinimidylpropionate) modified gold nanoparticles (DSP-AuNPs) as an optical probe. DSP was firstly modified on AuNPs to generate DSP-AuNPs through the highly efficient Au-S covalent interaction. Under pH 8.4 phosphate buffer, CRN can be assembled on DSP-AuNPs surface through the amine coupling reaction between the carboxyl group of DSP and the amino group of CRN, with the formation of an amide bond. Thus, CRN assembled on DSP-AuNPs denoted as DSP-AuNPs@CRN was used for Ag+ detection. The morphology of DSP-AuNPs@CRN was found to be highly dispersed and spherical particles with Dh of 41.5 ± 2.8 nm. When adding Ag+, progressive particle clustering of the nanoparticles was observed, Dh increased up to 324.7 ± 2.7 nm and naked eye color changed from red to blue-grey within 30 min, arising from particle aggregation. The absorption peak of dispersed and aggregated DSP-AuNPs@CRN was at 522 and 680 nm, respectively. The calibration curve plotted between the absorbance ratio (A680/A522) and Ag+ concentration was linear with two concentration ranges (0.50–3.00 µM and 3.00–35.00 µM Ag+). The assay detection limit of 0.13 µM is far below the USEPA maximum acceptable limit of Ag+ in drinking water at 0.93 μM. Finally, the assay has been successfully applied to Ag+ detection in water sample with good accuracy and precision.

A label-free Exonuclease I-assisted fluorescence aptasensor for highly selective and sensitive detection of silver ions

Based on the specific interaction of Ag+ and cytosine-cytosine (C-C) base mismatch and using berberine (Ber) as the fluorescent probe and Exonuclease I (Exo I) as the background fluorescence reducing tool, a label-free Exo I-assisted fluorescence aptamer sensing platform was established for the detection of silver ions with high sensitivity and selectivity. Exo I reduced the fluorescence background of the Ber/Ag+-aptamer complex to a level similar to that of Ber itself in the absence of Ag+. After introducing Ag+ into the sensing system, it induces the aptamer rich in base C to form C-Ag+-C i-motif structure which are resistant to degradation mediated by Exo I. The concentration of Ber, Ag+-aptamer, Exo I and the temperature and reaction time for Exo I were all optimized. Under the optimal experimental conditions, the detection limit of Ag+ was 4.4 nM and the linear range was from 0.0059 μM to 235.48 μM with a coefficient of determination (R2) > 0.99. Moreover, the proposed strategy had been successfully applied to the detection of Ag+ in tap water and human serum with a good recovery ranging from 88.4% to 106.9%.

Reagent free electrochemical-based detection of silver ions at interdigitated microelectrodes using in-situ pH control

• Applying 1.65 V to a protonator electrode lowered the pH at the sensor electrode to pH 3, optimal for silver ion detection. • In-situ pH control eliminated the need for the addition of mineral acids to a solution before analysis. • Chlorine present in tap water helped in detection, causing a sharpening of the silver stripping peak due to formation of silver chloride. • Detection of 250 nM of silver ions in tap water in less than 3 min was possible without the need for additional electrolytes. Herein we report on the development of an electrochemical sensor for silver ions detection in tap water using anodic sweep voltammetry with in-situ pH control; enabled by closely spaced interdigitated electrode arrays. The in-situ pH control approach allowed the pH of a test solution to be tailored to pH 3 (experimentally determined as the optimal pH) by applying 1.65 V to a protonator electrode with the subsequent production of protons, arising from water electrolysis, dropping the local pH value. Using this approach, an initial proof-of-concept study for silver detection in sodium acetate was undertaken where 1.25 V was applied during deposition (to compensate for oxygen production) and 1.65 V during stripping. Using these conditions, calibration between 0.2 and 10 μM was established with the silver stripping peak ∼0.3 V. The calculated limit of detection was 13 nM. For the final application in tap water, 1.65 V was applied to a protonator electrode for both deposition and stripping of silver. The chloride ions, present in tap water (as a consequence of adding chlorine during the disinfection process) facilitated silver detection and caused the striping peak to shift catholically to ∼0.2 V. The combination of the complexation of silver ions with chloride and in-situ pH control resulted in a linear calibration range between 0.25 and 2 μM in tap water and a calculated limit of detection of 106 nM without the need to add acid or supporting electrolytes.

Modulating fluorescence emission of l-methionine-stabilized Au nanoclusters from green to red and its application for visual detection of silver ion

Gold nanoclusters (Au NCs) have been considered as novel heavy metal ions sensors due to their ultrafine size, photo-stability and excellent fluorescent properties. This work not only demonstrated a novel strategy to modulate the emission color of l-methionine stabilized Au NCs based on a unique manner of Ag(Ⅰ) adding, but successfully applied this strategy for visual detection of Ag(Ⅰ) in environmental water samples. The Au NCs prepared here had yellow-green fluorescence with emission peaks at 536 nm. When Ag(Ⅰ) was added, the emission peak showed a clear shift from 538 nm to 590 nm and the color showed a change from yellow-green to orange. The Ag(Ⅰ) of concentration from 18.0 to 210.0 μM could be linearly detected using this method with a limit of detection (LOD) of 8.54 μM. The formation mechanisms of these Au NCs was discussed and the strategy proposed here was promising for preparing new types of fluorescent metal nanoclusters and a new analytical method.

One-Step Synthesis of Water-Soluble CdS Quantum Dots for Silver-Ion Detection.

To realize fast synthesis of cadmium sulfide (CdS) quantum dots with a low-toxic material, a one-step synthesis method is investigated and conducted. Potato extract is used as a stabilizer and modifier, by which aqueous CdS quantum dots can be prepared at a lower temperature with a shorter time. Through systematic characterization and analysis, a green and fast synthesis mechanism is demonstrated in detail. And the nanoscale CdS quantum dots are uniform in size and dispersity. With low cost and high sensitivity, the prepared CdS quantum dots show promising application in silver-ion detection. This method shows great significance for an environmentally friendly and facile synthesis of CdS quantum dots.

The functionalization of gold nanoparticles as a novel platform for the highly efficient electrochemical detection of silver ions.

Herein, a novel electrochemical biosensor was constructed for the highly efficient detection of silver ions. A porous platform constructed with functionalized gold nanoparticles (AuPP) was electropolymerized on the gold electrode surface. The obtained polymer, analogous to a metal-organic framework, was used as the sensing platform together with cytosine-Ag+-cytosine interaction for dual signal amplification. The scanning electron microscopy (SEM) image of the AuPP platform exhibited a porous structure and considerable binding sites for C-riched single stranded DNA, leading to predictable silver ion preconcentration. Based on this strategy, the biosensor showed that the peak current in differential pulse voltammetry rose linearly as the concentration of silver ion increased from 0.005 to 3 μM with a detection limit of 1.3 nM. In addition, in the presence of other metal ions, such as Pb2+, Mn2+, Ni2+, Co2+, Cu2+, Zn2+, Na+, Ca2+, and Cd2+, at the same concentration, the current signal remained almost unchanged, manifesting high selectivity for Ag+. This proposed sensor might exhibit a novel fabrication method for metal ion detection with the aid of multiple AuPP materials by designing ligands with different functional groups.

Application of Biomimetic Nanomaterials in Biological Detection and the Intelligent Recognition Method of Nanoparticle Images

New nanomaterials (metal nanoclusters, graphene, etc.) are favored by researchers due to their unique properties and are widely used in biomedical detection. The excellent fluorescence characteristics of gold nanoclusters are utilized to develop a fast and highly sensitive bionic nanomaterial with non-label and dual functions, which can detect silver ions and mercury ions and study the particularity of TEM nanoparticle images. The particle segmentation of TEM nanoparticle images is studied to compare the traditional watershed algorithm and watershed transformation algorithm. The experiment results show that silver ions can enhance the fluorescence of gold nanoclusters to form gold-silver nanoclusters with strong yellow fluorescence, and mercury ions can quickly weaken the fluorescence of gold-silver nanoclusters. Based on the biomimetic nanomaterials, a dual-function fluorescent probe is designed to detect silver ions and mercury ions in lake with detection accuracy of 8 nM and 33 nM respectively; the sensing excitation of the fluorescent probe is further analyzed. Because the metal-enhanced fluorescence (MEF) effect enables the silver element and Au nanoparticles to form fluorescence-enhancing effect, the high metalphilic interaction between mercury ions and silver ions quenches the fluorescence effect of gold nanocluster; the rapid watershed transformation/region fusion method can achieve better particle image segmentation combined with the image segmentation algorithms of different TEM nanoparticles, which can be better applied to the characterization analysis of the preparation of gold nanomaterials.

Rapid detection of silver ions based on luminescent carbon nanodots for multicolor patterning, smartphone sensors, and bioimaging applications.

Photoluminescent nitrogen and sulfur co-doped carbon nanodots (N,S-CNDs) were prepared via single-step hydrothermal carbonization using 2,4-diaminobenzenesulfonic acid (2,4-DABSA) as the sole precursor. The synthesized N,S-CNDs are easily dispersed in aqueous solution and have an average particle size of 5.0 ± 0.2 nm, showing a high quantum yield of 23.1% with excellent stability. The surface states of the N,S-CNDs were confirmed by Fourier-transform infrared spectroscopy, powder X-ray diffractometry, Raman spectroscopy, and X-ray photoelectron spectroscopy techniques. These N,S-CNDs were applied for the rapid visual sensing detection of Ag+ ions, which can be identified by their photoluminescent color change under ultraviolet (UV) light illumination at 365 nm within 5 s. Furthermore, a linear correlation coefficient between P0/P and Ag+ ions was observed in the linear range of 0-1.2 μM with a detection limit of 7.88 nM. The proposed method was successfully used for the sensitive detection of Ag+ ions in real samples with satisfactory recoveries and relative standard deviation. The photoluminescence properties of N,S-CND and N,S-CNDs/Ag+ aqueous solutions were demonstrated by their invisible inks that can only be seen when irradiated with UV light. The RGB values of N,S-CND and N,S-CNDs/Ag+ aqueous solutions were measured using a color selector smartphone application. In addition, N,S-CND and N,S-CNDs/Ag+ aqueous solutions were further used for the multicolor imaging of HCT-116 cancer cells due to the low toxicity of N,S-CNDs.