Detection Of Silver Ions Research Articles

Three-dimensional DNA Walker-mediated polarity switching biosensor based on the heterostructure of COFs and CuO nanocube for the sensitive photoelectrochemical detection of silver

Herein, a novel photocurrent polarity switchable photoelectrochemical (PEC) biosensor was fabricated based on the formation of a heterojunction between CuO nanocubes and two-dimensional crystalline covalent organic frameworks (COFs) by cyano-substituted buta-1,3-diene linkage for the detection of silver ion (Ag+), exhibiting an excellent anti-interference capability toward redox substances. Different from most of the COFs that were crystallized by condensation of two components, the proposed PTP-COF was generated by two competitive reversible reactions between the three components 4,4′,4″,4′′′-(pyrene-1,3,6,8-tetrayl)tetrabenzaldehyde (PTBD), 2,2′-(1,4-phenylene)-diacetonitrile (PDT) and acetaldehyde, which not only increased the conjugated π system of framework to accelerate the charge transfer efficiency, but also had strong acid and alkali resistance and bioavailability. Impressively, by combining with Mg2+ DNAzyme triggered DNA walker amplification strategy, the designed PEC biosensor exhibited excellent detection performance for Ag+ range from 100 fM to 1 μM with a limit of detection as low as 35 fM. This work puts forward a new idea for eliminating negative background signals for sensing and expands the application of COFs in the PEC system.

Utilization of Schiff base ligands to chelate Ag+ for highly specific and sensitive Hg2+/Ag+ immunoassay

In this study, a planar benzothiazole Schiff base derivative ZX1 was designed and synthesized to selectively precipitate silver ions, in conjunction with the immunoassay detection of Hg2+ ions. The silver chelation process was highly effective in the pH range of 7–10, with a silver ion precipitation ratio of 99.9 %. The coordination behavior of ZX1 with Ag+ was studied using a series of spectroscopic measurements, topography analysis and DFT calculation. The shortest bond distances were 2.251 and 2.254 Å between nitrogen atom of thiazole and Ag+. Weak interactions were analyzed using the interaction region indicator (IRI) method and VMD. The immunoassay was developed through an anti-Hg2+/Ag+ monoclonal antibody, which showed similar sensitivities for Ag+ and Hg2+. The selectivity and anti-interference ability of the Schiff base ligands were tested for some hard metal ions and several anions. With co-existence of interference ion Ag+, Hg2+ was detected in rice matrix solution with 77 %∼123.5 % recovery by addition of ZX1 as the masking reagent and 90.3 %∼115 % for wheat matrix. This research provides a promising immunoassay strategy for simultaneous detection of silver ions and mercury ions in food matrix by utilization of Schiff base ligands. This novel Schiff base ligand was then used as the pre-treatment reagent to remove silver ions within 5 min for detection of Hg2+ or detection of both Ag+ and Hg2+ based on a novel bi-specific heavy metal antibody.

Silver induced self-assembly of a rhodanine derived reversible fluorescent chemosensor: Applications in smart-phone color assist app, logic gate, real sample analysis and bio-imaging

An innovative chemosensor, Rhodanine-appended benzaldehyde (RB), was developed and analyzed using spectroscopic methods to detect silver ions (Ag+) in a THF–H2O buffer solution via fluorimetry. The RB probe exhibited low fluorescence due to C-N free rotation and inhibition of electron transfer. However, interaction with Ag+ ions resulted in a noteworthy redshift of approximately 6 nm and increased fluorescence intensity owing to the chelation-enhanced fluorescence (CHEF) effect, which hindered the Intramolecular Charge Transfer (ICT) process. The binding ratio between RB and Ag+ ions was determined to be 2:1 using the job plot method. The association constant (Ka) was calculated to be 4.84 × 105 M−1 and further confirmed through ESI-TOF spectroscopic and DFT analyses. The limit of detection (LOD) and quantification (LOQ) for RB in binding with Ag+ ions were found to be 1.7 × 10−8 M and 5.4 × 10−8 M, respectively. Additionally, the color changes of RB when binding with Ag+ ions were effectively leveraged in an RGB-assisted smartphone color analysis app for precise sample analysis for Ag+ ion detection. Most importantly, the RB probe’s ability to detect silver ions in the E. coli pathogen was successfully demonstrated, providing reassurance about its practical application, using a confocal scanning electron microscope via the green channel.

Thiazole-derived pyrazin-2-carbohydrazide chemosensors: Colorimetric & photoluminescent detection of silver ions for theoretical, environmental, and cell imaging

In this work, a simple and versatile chemosensor receptor TZPYZ was synthesized through the combination of thiazole with pyrazine-2-carbohydrazide, resulting in a confirmed chemical structure via various analytical techniques including FT-IR, 1H, and 13C Nuclear Magnetic Resonance Spectroscopy, as well as High-Resolution Mass Spectroscopy analysis. TZPYZ exhibits specific colorimetric and photoluminescent responses to Ag+ ions in a solvent solution consisting of DMSO and H2O (7:3, v/v). Upon addition of Ag+ ions, noticeable changes in absorption spectra occur, resulting in a visible color change from pale yellow to blue. Additionally, an enhanced emission intensity with wavelength at 523 nm, when excited at 410 nm. Notably, TZPYZ demonstrated exceptional selectivity for Ag+ ions over other metal cations, achieving a detection limit (LOD) of 10.6 × 10−9 M and 6.74 × 10−9 M and using the UV–visible & photoluminescent titration method. Interference studies indicated minimal disruption from other metal ions on emission at 523 nm, highlighting TZPYZ discerning capability for Ag+ ions. With a binding affinity of 3.622 × 10−11 M−1, TZPYZ proved effective in detecting Ag+ ions across various water samples, showcasing its practical utility. The mechanism of interaction between TZPYZ and Ag+ ions was investigated using various experimental techniques, including Job’s plot, Benesi-Hildebrand investigations, 1H NMR, and HRMS analysis. Test strips coated with TZPYZ showed selective detection of Ag+ ions, indicating its potential for on-site applications. Furthermore, DFT computations provided insights into the structural and electronic properties of TZPYZ and its complex with Ag+ ions, further elucidating the binding mechanism and stability of the complex. In addition, TZPYZ demonstrated compatibility with biological systems, as fluorescence imaging tests on MCF-7 breast cancer cells confirmed both its non-cytotoxic nature and its proficiency in detecting intracellular silver ions. Based on these findings, TZPYZ is highlighted as a highly sensitive and selective chemosensor for Ag+ ions, with promising applications in environmental analysis and bioimaging.

Development of an innovative colorimetric optical sensor for the detection of silver ions in environmental and biological samples

ABSTRACT A recently developed optical chemical sensor for silver assessment relies on polymer inclusion membranes (PIM) and avoids the use of plasticisers. This innovative optical sensor is constructed through a physical immobilisation process known as the encapsulation technique, resulting in an optical chemical membrane. The suggested PIM integrates 2-(2`-hydroxynaphthylazo)benzo-thiazole (HNABT) was used as a colorimetric reagent, polyvinyl chloride (PVC) as the foundational polymer, and dinonyl naphthalene sulphonic acid (DNNS) as an extractant. The created PIM demonstrates heightened responsiveness within the described approach, credited to the sensor membrane, in contrast to the optical sensor without PIM. The achieved results demonstrated that the sensor response was based on some factors such as plasticiser, film thickness, stirring effect, HNABT concentration, DNNS concentration and pH of the aqueous solution. Within the measurement range spanning from 7.5 to 250 ng mL−1 of Ag+ at pH 7.75, the absorbance response exhibits a notable correlation, achieving detection and quantification limits of 2.3 and 7.3 ng mL−1, respectively. The λmax for the PIM-based sensor registers at 577 nm. Additionally, the reproducibility and repeatability of the system are characterised by RSD of 2.25% and 1.13%, respectively, with a swift response time of approximately 3.0 min. The optode membrane’s selectivity is scrutinised in pH-buffered solutions concerning Ag+ ions. The proposed sensor is effectively applied for Ag+ assessment in food, water, environmental, and biological samples. The obtained results are corroborated by the FAAS procedure.

Colorimetric Silver Ion Detection Based on Silver Metallization of Gold Nanorods

AbstractDespite the use of silver in various industries, this heavy metal can pose serious risks to living organisms and the environment. Therefore, the development of simple measurement strategies for detection of silver ions (Ag+) with high sensitivity is of great importance. In this research, gold nanorods (AuNRs) have been used as indicator element in colorimetric sensor, which provides the possibility of facile and visual detection of silver by forming gold@silver core‐shell nanostructures (Au@Ag NRs). The basis of this sensor is the metallization of silver on AuNRs through ascorbic acid (AA) as a reducing agent, which forms Au@Ag NRs. During this mechanism, Ag+ is converted to silver atom (Ago) in the presence of AA and the surface of AuNRs is coated by inducing metallization. Any changes in composition and dimensions of AuNRs will cause color changes in the detection solution and subsequently spectral changes. The obtained results showed a good correlation between silver concentration and probe response (λo–λ) in the range of 2.5 to 30.0 μmol L−1 with a detection limit of 1.3 μmol L−1. In addition, the evaluation of the sensor in water and soil samples showed that it has acceptable accuracy in detecting silver ions in real conditions.

Analyte-perturbed balance between reducibility and fluorescence of Ti3C2 MXene quantum dots for label-free, dual-mode detection of silver ions

BackgroundAs an emerging and attractive low-dimensional functional materials, Ti3C2 MXene quantum dots (QDs) enlarge the toolbox of fluorescence sensing. However, monochromatic fluorescence, which only provide one single signal, is often beset by challenges such as false-positive readouts and limitations in selectivity. Consequently, to improve the sensing accuracy by means of cross-verified dual-signal authentication, the endeavor to engineer dual-mode nanoprobes based on Ti3C2 QDs, incorporating both the capability of fluorescence and an alternative sensing mechanism, emerges as a compelling avenue. ResultsHere, based on the alterations in colorimetric and fluorescent signals of Ti3C2 QDs with the addition of Ag+, we propose a dual-mode sensor obviating the necessity for nanoprobe labeling. Owing to the decent reducibility of Ti3C2 QDs, Ag+ is adsorbed and reduced, resulting in the generation of plasmonic Ag nanoparticles (NPs), which simultaneously trigger colorimetric responses of the solution and enhance the fluorescent emission of Ti3C2 QDs. The confluence of colorimetry and fluorometry within this strategy optimally harnesses the modulating role of the acquired Ag NPs on the reducing capability and fluorescence characteristics of Ti3C2 QDs. The equilibrium imparts versatility and promising prospects to this analyte-triggered label-free method, which enables a remarkable specificity and an excellent detecting limit (0.45 μM) for Ag+. SignificanceThe balance between reducibility and fluorescence of Ti3C2 QDs for dual-mode detection is inventively demonstrated. With the exemplification of a direct influence of both features of the nanoprobe via the introduction of analytes, this study opens the feasibility of the analyte-perturbed felicitous equilibrium, which endows label-free methods with versatility and promising prospects. This design may evoke more biosensing strategies with the function of double-signal mutual verification.

SYNTHESIS, CHARACTERIZATION AND APPLICATION OF A FERROCENYL AZO-BASED LIGAND AS AG+- DETECTOR IN AN AQUEOUS SYSTEM

Over the years, humans and the environment have been exposed to various toxic ionic species that emanated, majorly, from anthropogenic sources. In this study, a new ferrocenyl-azo based chemosensor, ferrocenyl 1-(2-phenylazo)-2-naphtholate (FPN) for the determination of silver ions was developed via catalytic reduction and diazotization routes. The structural features were confirmed by spectroscopic methods involving proton NMR, GC/MS and FTIR. Having exposed the product to different metal solutions, Ag+ was distinctively recognized, revealing FPN as an effective and sensitive chemosensor. The binding behavior of FPN towards the sensitive silver ion was investigated using Job’s plot, and a metal:ligand ratio of 1:1 was revealed. The study showed a bathochromic shift and a new peak band was observed at 275 nm in the absorption spectra of FPN. The absorption experiments demonstrate that FPN as a rapid and reliable sensor capable of determining silver and ferric ions. Therefore, ferrocenyl 1-(2-phenylazo)-2-naphtholate ligand is highly recommended as an alternative route in detecting silver ions in both organic and aqueous media.

Expression of concern: Water-soluble pyridine-based colorimetric chemosensor for naked eye detection of silver ions: design, synthesis, spectral and theoretical investigation

Expression of concern for ‘Water-soluble pyridine-based colorimetric chemosensor for naked eye detection of silver ions: design, synthesis, spectral and theoretical investigation’ by B. Annaraj and M. A. Neelakantan, Anal. Methods, 2014, 6, 9610–9615, https://doi.org/10.1039/C4AY01592D.

Cytosine-rich mismatched DNA aptamer combined with superparamagnetic photonic crystal sensing material for the specific visual detection of silver ions

DNA aptamer superparamagnetic photonic crystals (DSPCs), enriched with a highly selective cytosine-rich mismatched single-stranded DNA aptamer (CRDA), were successfully employed in a novel visual detection strategy for the detection of silver ions (Ag+). The technologies of superparamagnetic colloidal nanospheres (SCNs), DNA aptamer, and photonic crystals were combined to fabricate DPSCs. The aptamer was immobilized via electrostatic adsorption with amino groups that were chemically introduced on the surface of the SCNs, forming D–NH–SCNs. The detection is achieved by forming an Ag+ complex (C–Ag+–C) between Ag+ and D–NH–SCN. The DSPCs assembled under a magnetic field by D–NH–SCNs effectively detected Ag+ in the range of 1 μg/L to 5 mg/L, corresponding to the critical concentration range for heavy metals in drinking water. During the detection, the DSPC exhibited a wavelength blueshift from 652.8 nm to 626.4 nm (26.4 nm), as well as changes in reflection intensity. Notably, when detecting Ag+, a change in DSPC color from orange to yellow was observed. In summary, the developed visual detection material facilitates direct Ag + sensing. In the future, different DNA aptamers will be modified further to detect various targets in the fields of medicine, environmental monitoring, and food safety.

Vortex-assisted hydrophobic natural deep eutectic solvent liquid-liquid microextraction for the removal of silver ions from environmental water.

This study presents a novel approach for the quantification of silver ions in environmental water through the utilization of liquid-liquid microextraction, employing natural deep eutectic solvents in conjunction with inductively coupled plasma emission spectroscopy. The extracted solvent was characterized by Fourier transform infrared spectroscopy (FT-IR). The impact of various extractant types, extractant molar ratio, extractant volume, extraction time, and salt concentration on the efficacy of silver ion extraction was investigated. The findings indicate that the optimal extraction efficiency was attained by utilizing a 5-mL aqueous solution volume, containing 1000 μL thymol/lactic acid NADES 1:3, a salt concentration of 1 mg mL-1, a pH value of 4, and a vortex time of 4 min. Upon implementing the optimized experimental conditions, the recovery of target metal ions was from 96.9 to 101.0%. The relative standard deviations were observed to be within the range of 1.5 to 2.7%. The present study demonstrates the reproducibility, accuracy, and reliability of the method for detecting silver ions in environmental water, with linear range of 5~1000 ng mL-1 and limits of detection (LOD) and limits of quantification (LOQ) of 1.52 ng mL-1 and 5.02 ng mL-1, respectively.

Phenazine-based fluorescence probes for simultaneous sensing of silver and iodide ions

The selective and sensitive detection of silver ions (Ag+) and iodide ions (I−) is of paramount importance in various scientific and industrial domains. In this paper, we present phenazine-based fluorescence probes, synthesized through a scalable and straightforward procedure, for the simultaneous sensing of Ag+ and I−ions in solution phase. The introduction of Ag+ led to ratiometric changes, manifesting in alterations of both solution color (from colorless to yellow) and fluorescence signal (from blue to cyan). Mechanistic investigations unveil that Ag+ coordinate with the phenazine nitrogen ends, forming self-assembled nanostructures characterized by significant charge-transfer properties. Moreover, we observed that the nature of the terminal alkyl residue played a pivotal role in governing the binding interaction with Ag+, with aliphatic residues featuring positively charged quaternary nitrogen ends exhibiting notably reduced responses. Additionally, the in-situ formed metal complex, comprising 1.Ag+, proved to be highly effective in selectively analyzing I− ions. The exceptional binding affinity of Ag+ for I− ions, marked by an exceptionally low solubility product constant, facilitated the sequestration of Ag+, ultimately leading to the formation of free probe in the reaction medium. Our research showcases the capability of phenazine-based probes in selective ion sensing applications, and their adjustable properties position them as promising options for a range of analytical and diagnostic uses.

Dual-Channel Fluorescent/Colorimetric-Based OPD-Pd/Pt NFs Sensor for High-Sensitivity Detection of Silver Ions.

Silver ions (Ag+) exist widely in various areas of human life, and the food contamination caused by them poses a serious threat to human health. Among the numerous methods used for the detection of Ag+, fluorescence and colorimetric analysis have attracted much attention due to their inherent advantages, such as high sensitivity, simple operation, short time, low cost and visualized detection. In this work, Pd/Pt nanoflowers (NFs) specifically responsive to Ag+ were synthesized in a simple way to oxidize o-phenylenediamine (OPD) into 2,3-diaminophenazine (DAP). The interaction of Ag+ with the surface of Pd/Pt NFs inhibits the catalytic activity of Pd/Pt NFs towards the substrate OPD. A novel dual-channel nanosensor was constructed for the detection of Ag+, using the fluorescence intensity and UV-vis absorption intensity of DAP as output signals. This dual-mode analysis combines their respective advantages to significantly improve the sensitivity and accuracy of Ag+ detection. The results showed that the limit of detection was 5.8 nM for the fluorescence channel and 46.9 nM for the colorimetric channel, respectively. Moreover, the developed platform has been successfully used for the detection of Ag+ in real samples with satisfactory recoveries, which is promising for the application in the point-of-care testing of Ag+ in the field of food safety.

Dual colorimetric detection and chemical reduction toward silver ions of imidazole-conjugated poly(diacetylenes)

In this article, we reported a new poly(diacetylenes)-based sensor (PDA-IBA) for silver ion detection and reduction through the chelation of imidazole moiety. The poly(diacetylenes) polymer functionalized with imidazole groups. As the concentration of silver ions in the solution increased, the PDA surface underwent oxidation concurrently with the reduction of silver ions was demonstrated through imidazole receptor. This chemical reaction resulted in a noticeable change in the color of the solution, shifting from blue to dark red. The limit of detection (LOD) was determined to be 0.034 mM. Zeta potential data analysis and electrochemical measurements further confirmed the PDA-IBA was capable to reduce Ag+ into Ag0. Moreover, the silver species produced were validated through inductively coupled plasma optical emission spectrometry (ICP-OES). Additionally, the color change observed in PDA-IBA as a response to silver ions was effectively demonstrated by integrating it into a paper-based sensor. This study introduces an innovative and promising approach for enhancing the capabilities of chemosensors in detecting and reducing Ag+.

Highly selective and sensitive photoelectrochemical detection of silver ions in complex industrial wastewater

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.

Quinoline scaffolds as fluorescent symmetric dipodal molecular cleft for swift and efficient Ag+ ion detection: Applications in real samples and bioimaging

Two elegantly designed cleft-like dipodal receptors based on amino quinoline scaffolds (AQP &AQM) has been synthesized and characterized by usual spectroscopic data for fluorimetric detection of silver ions in DMSO-H2O (1:1, v/v) solution. The fluorimetry investigations revealed that the inhibition of the Photoinduced Electron Transfer process (PET) and the Intra molecular Charge transfer (ICT) process are accounted as the detection mechanisms. The association constants were obtained as Ka = 1.7 × 104 M−1 for AQP and Ka = 2.02 × 104 M−1 for AQM with silver ions respectively. Also, the limit of detection (LOD) values obtained were appreciably at a lower level of 1.7 × 10-2 µM for AQP and 7.9 × 10-2 µM for AQM. As a practical utility of the receptors, real sample analysis of water, rice flour, banana flower extract were demonstrated along with the E.Coli. cell imaging studies.

An ultrahigh-resolution multicolor sensing platform via target-induced etching of gold nanorods for multi-colorimetric analysis of trace silver ions

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 (H2O2) decomposition. This inhibition enables the Fenton reaction between H2O2 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.

Imidazole appended rotatable hydroxy quinoline scaffold as dual signaling fluorescent chemosensor: Detection of silver ions with hypsochromic shift and hydroxide ions with bathochromic shift and their LFP’s, anticounterfeiting, soil analysis and bio-imaging

An imidazole conjugated hydroxy quinoline based chemosensor (QBI) was developed for the specific dual detection of silver (Ag+) and hydroxide (OH−) ions by fluorimetric technique. QBI had weak fluorescent emission, upon binding with Ag+ and OH−, fluorescence intensity enhanced with a large hypsochromic shift for Ag+ ion and notable bathochromic shift for OH− ions respectively. Three modes of possible mechanistic pathways accounts for the detection of the Ag+ ions, restriction of the C–C free rotation between the quinoline and imidazole scaffolds, blocking of photoinduced electron transfer (PET) process assisted by the Intramolecular charge transfer (ICT) process. On other hand, the –OH moiety of QBI gets deprotonated during the process of detecting OH− ions. The binding stoichiometry of complexations was confirmed by Jobs plot, Benesi-hildebrand, 1H NMR titration, DFT analysis and ESI-TOF. The limit of detection (LOD) of QBI with Ag+ and OH− was found to be 3.53 × 10−8 M for Ag+ and 1.5 × 10−7 M respectively. Latent fingerprintvisualization (LFP), anti-counterfeiting applications, and soil analysis are merely a few instances of where QBI has been effectively put to use in the real world for the specific detection of Ag+ and OH− ions. Furthermore, receptor QBI was utilized in bacterial imaging against E.coli and pseudomonas pathogens for the detection of both ions.

A multimode detection of silver ions based on peroxidase-like activity and photothermal effect of Prussian blue nanoparticles

Silver ion (Ag+), as a heavy metal ion easily absorbed by organisms, can be enriched through the food chain. This study present a novel multimodal detection system for Ag+ using Prussian blue nanoparticles (PB NPs) with excellent photothermal effect and peroxidase-like activity. The PB NPs undergo a dissolution-precipitation equilibrium, converting blue PB NPs into colourless silver ferrocyanide ions in the presence of Ag+. The color, photothermal effect, and peroxidase-like activity of the PB NPs change with the concentration of Ag+, making them an effective probe for detecting Ag+. The key parameters that affect the performance of multimode detection assay were optimized. Under optimal conditions, the detection limit of visual detection was estimated to be 2.94 μM. Based on catalytic color development and the photothermal effect of PB NPs, the detection limit of color development detection and photothermal analysis were reduced to 0.57 μM and 0.23 μM, respectively. And the detection range was also broadened than visual direct detection. Besides, the multimode detection of Ag+ improves the accuracy of detection by mutual verification. The promising multimode system exhibited good repeatability and specificity of Ag+ in different sample implementations, which has great potential for applications in food safety regulation and environmental monitoring.

Development and analysis of a universal label-free micro/nano component for three-channel detection of silver ions, mercury ions, and tetracycline

In this paper, an enzyme-free and label-free fluorescent nanomodule is proposed for rapid, simple and sensitive detection of Ag+, Hg2+ and tetracycline (TC). The strategy is cleverly designed to enable multiple-purpose detection with as little as 31 nt of ssDNA. Both the embedded dye SYBR Green I and the nanomaterial graphene oxide (GO) are able to distinguish single-stranded DNA from double-stranded DNA; thus, the combination of the two instead of using traditional molecular beacon (MB)-labeled fluorophores and quencher groups can effectively reduce the cost of experiments while efficiently reducing the background noise. Performance testing experiments confirmed the stability and selectivity of the platform; the limits of detection (LODs) of Ag+ and Hg2+ were 1.41 nM and 1.79 nM, respectively, and the detection range were within the WHO standards. In addition, only some base sequences in the flexible functional domain of the nanoloop needed to be programmed to build a universal platform, which was feasible using TC as a target. Therefore, the designed nanomodule has the potential to detect various types of targets, such as antibiotics, proteins, and target genes, and has broad application prospects in environmental monitoring, food testing, and disease diagnosis.