Quantification Of Ions Research Articles

LIFs-Based Fluorescent Analysis of Silver Ions in Water Using AIEgen-Embedded PVA Hydrogel.

The detection and quantification analysis of silver ions is important to protect human health and improve the level of wastewater treatment. In this work, a polyvinyl alcohol (PVA) hydrogel-based sensing material based on an aggregation-induced emission strategy was developed and combined with a portable laser-induced fluorescence spectroscopy (LIFs) device for the direct detection and quantification of silver ions in water. Considering the requirements of environmental water analysis regarding portability, reliability, and convenience, this fluorescence turn-on strategy was optimized accordingly to ensure the accuracy and stability of the analysis in complex natural water environmental. This sensing method showed operational excellence and good sensitivity (down to 1 ppb) and may provide a stable and convenient strategy for the on-site, real-time analysis of environmental water samples.

H19 lncRNA triggers ferroptosis, exacerbating ox-LDL-induced artery endothelial cell damage in vitro.

The precise association between lncRNA H19 and ferroptosis in the context of atherosclerosis remains uncertain. This study is to clarify the underlying process and propose novel approaches for the advancement of therapeutic interventions targeting atherosclerosis. Assessment of ferroptosis, which entails the evaluation of cell viability using CCK-8 and the quantification of intracellular MDA, GSH, and ferrous ions. Simultaneously, the protein expression levels of assessed by western blot analysis, while the expression level of lncRNA H19 was also determined. Furthermore, HAECs that were cultured with ox-LDL were subjected to Fer-1 interference. HAECs were exposed to ox-LDL and then transfected with H19 shRNA and H19 overexpression vector pcDNA3.1. The level of ferroptosis in the cells was then measured. Then, HAECs were subjected to incubation with ox-LDL, followed by transfection with H19 shRNA and treated with Erastin to assess the levels of ferroptosis, cell viability, and inflammatory factor production. and the ability for blood vessel development. The survival rate of HAECs in the ox-LDL group was much lower. Ox-LDL resulted in an upregulation of ACSL4 expression in HAECs, while the expression of SLC7A11 and GPX4 decreased. lncRNA H19 enhances ferroptosis and exacerbates arterial endothelial cell damage induced by LDL.

A fluorescence-electrochemical dual-mode aptasensor for ultrasensitive detection of lead based on exonuclease-catalyzed recycling and hybridization chain reaction amplification

To improve the accuracy and reliability of the detection system, this study combined the exonuclease-assisted autocatalytic target cycling fluorescence strategy with an electrochemical platform to establish a dual-mode fluorescence-electrochemical aptasensor for the ultra-sensitive quantification of lead ion (Pb2+). In the fluorescence detection strategy, ssDNA could hybridize with the aptamer to form double-stranded DNA. With the addition of Pb2+, the aptamer dissociated from the double-stranded DNA to capture Pb2+ and trigger the enzymatic digestion process, leading to the target recirculation to achieve the first signal amplification. The free ssDNA could then hybridize with S1, and the released S2 was able to trigger a hybridization chain reaction (HCR) in the electrochemical system, achieving the second signal amplification. The quantification of Pb2+ was realized by measuring both the fluorescence and the differential pulse voltammetry signals with detection limits of 0.028ng/mL and 0.788pg/mL, respectively. This fluorescence-electrochemical dual-mode aptasensor overcame the limitations of complex matrices and environmental interference, and provided a valuable reference for the development of reliable multi-signal sensors in water, tea and vegetable safety monitoring.

Smartphone-enabled composite of cellulose nanocrystals for rapid and selective mercury detection in cosmetics and water: insights from density functional theory studies

ABSTRACT The pervasive contamination of cosmetics and water with mercury ions (Hg(II)) poses severe health risks, driving the need for efficient methods for in situ detection and removal of it. Our study showcases a groundbreaking composite material that combines cellulose nanocrystals (CNCs) and smartphones for the purpose of rapid and selective mercury detection. The CNCs exhibit a distinctive rod-like morphology, presenting a high surface area that facilitates the accommodation of the Hg(II) ion probe, 4-(dimethylamino)phenyl)methanethione (DPM). This interaction leads to a distinct colour change from yellow to green, visible to the naked eye, enabling straightforward visual detection. Our composite is highly sensitive, with a limit of detection (LOD) of 1.76 × 10 − 8 M using digital image analysis and 3.6 × 10 − 8 M using spectrophotometric methods. These values are significantly below the safe drinking water guidelines set by the World Health Organization (WHO). Density functional theory (DFT) calculations were used to understand how Hg(II) ions interact with the DPM-CNC composite. These calculations confirmed that the material has a strong affinity for Hg(II) ions and demonstrated its selective detection capabilities. The DPM-CNC composite’s low detection threshold, rapid response time, and ease of regeneration make it a potent candidate for practical applications in mercury monitoring. This composite is a robust and reusable solution for real-time visualisation and quantification of mercury ions. It only requires 10 mg of material for effective measurements. It enhances safety in cosmetic products and water.

Smartphone-assisted colorimetric sensor arrays based on nanozymes for high throughput identification of heavy metal ions in salmon

The rapid, precise, and high-throughput identification of multiple heavy metals ions holds immense importance in ensuring food safety and promoting public health. This study presents a novel smartphone-assisted colorimetric sensor array for the rapid and precise detection of multiple heavy metals ions. The sensor array is based on three signal recognition elements (AuPt@Fe-N-C, AuPt@N-C, and Fe-N-C) and the presence of different heavy metal ions affects the nanozymes-chromogenic substrate (TMB) catalytic color production, enabling the differentiation and quantification of various heavy metal ions. Combined with a smartphone-based RGB mode, the colorimetric sensor array can successfully identify five different heavy metal ions (Hg2+, Pb2+, Co2+, Cr6+, and Fe3+) as low as 0.5 μM and different ratios of binary and ternary mixed heavy metal ions in just 5 min. The sensor array successfully tested seawater and salmon samples with a total heavy metal content of 10 μM in the South China Sea (Haikou and Wenchang). Overall, this study highlights the potential of smartphone-assisted colorimetric sensor arrays for the rapid and precise detection of multiple heavy metal ions, which could significantly contribute to food safety and public health monitoring.

Highly sensitive disposable test strips for sweat chloride detection using silver nanoparticles decorated reduced graphene oxide

The quantification of chloride ions in sweat by a point-of-care test system is a useful strategy in the early screening of cystic fibrosis. In this context, silver nanoparticles decorated reduced graphene oxide were synthesized by one-pot reduction method in this work. This reaction in situ produces silver nanoparticles spread across thin sheets of rGO with high surface area. This helps in the electrochemical detection of chloride ions by conversion of silver to silver chloride and formation of a thin layer of silver chloride on the surface of nanocomposite. The validity of this strategy has been demonstrated by voltammetric analysis of chloride ions using the screen-printed Ag-rGO nanocomposite. For electrodes tested in buffer, the sensitivity was 37.66 ± 0.99 mA (log mM)−1 cm−2 with a high selectivity and detection range from 30 to 400 mM chloride concentration. The lower detection limit is 1.02 mM (S/N = 3), and the relative standard deviation (RSD) of sensor response is 4.77 %. Disposable sensor test strips fabricated with screen printing of the catalyst followed by layer by layer array of electrolyte and hydrophilic membrane shows a sensitivity of 165.2 ± 4.3 µA mM−1 cm−2, a linear detection range upto 210 mM, and a LOD of 2.46 ± 0.06 µM. The quantification of the developed sensor strips were confirmed by comparing the values from clinical laboratories. This finding confirms the potentiality of the developed method and its possible application in the rapid and easy-to-use point-of-care devices. Notable advantages of the Ag-rGO nanocomposite is its reversibility due to the regeneration of fresh silver nanoparticles on the rGO surface and increased electrochemical response. This feature realizes a high stability even at multiple trials with a RSD of 2.63 % and long-time storage tested upto 3 months. Using this superior performance, the developed sensor test strip demonstrates a disposable, non-invasive, reproducible, reversible, highly selective, and sensitive monitoring of chloride ions.

Quantification of Ions in Human Urine-A Review for Clinical Laboratories.

Urine is an organic fluid produced by the kidney, and its analysis is one of the most requested laboratory tests by clinicians. The ionic composition of urine has been shown to be a good health indicator: it is useful for the diagnosis of several diseases, as well as monitoring therapeutics. This review considers laboratorial techniques that have been used throughout time for the quantification of ions in urine, and also considers some methodologies that can potentially be used in clinical laboratories for this kind of analysis. Those methods include gravimetry, titration, flame emission spectrophotometry (flame photometry), fluorimetry, potentiometry (ion selective electrodes), ion chromatography, electrophoresis, kinetic colorimetric tests, enzymatic colorimetric tests, flow cytometry, atomic absorption, plasma atomic emission spectrometry, and paper-based devices. Sodium, potassium, chloride, calcium, and magnesium are among the most important physiological ions, and their determination is frequently requested in hospitals. There have been many advances regarding the analysis of these ions in 24 h urine. However, there is still some way to go concerning the importance of intracellular ions in this type of sample as well as the use of occasional urine for monitoring these parameters.

Schiff base-stabilized electron-deficient copper species on MOFs as durable sensor of nitrate in water

The electrochemical sensor has been considered an efficient and portable platform for the rapid quantification of nitrate ions in industrial wastewater and natural water bodies. Albeit of the high sensitivity to NO3−, the electron-deficient copper sites (Cuδ+) were unstable under the negative working potentials for detection (Cuδ+ was readily reduced to Cu0). Herein, the Schiff base was grafted on MIL-125 (Ti) via covalent binding to stabilize the Cuδ+, leading to a composite Cuδ+/Schiff base/MIL-125 (Ti) material (abbreviated as CuSM) for NO3− sensing. Moreover, the unique porous structure of CuSM can speed up the diffusion rate of NO3− from the bulk solution to the surface of the modified electrode, enhancing the sensitivity of NO3− assay. As a result, the CuSM-based sensor not only exhibited a wide linear range from 1.18 µM to 58.8 mM and a low detection limit (S/N = 3) of 0.253 µM but also possesses high specificity, excellent reproducibility (the RSD of the five inter-batch sensors was 1.138%) and the ability to detect real water samples.

In situ-floating organic dispersive solid-phase extraction based on putrescine as a new adsorbent for the extraction of ions from crude oil prior to ICP-MS

ABSTRACT Quantification of ions in complex matrices like crude oil is an outstanding issue because of the high complexity of the sample. Herein, a facile, reliable, and precise floating dispersive solid-phase extraction procedure was introduced for the extraction of several ions (B, Ca, Cd, Cu, Cr, Ag, Fe, Mn, Ni, Na, Ba, Mg, Al, Si, Sn, Ti, Mo, V, Pb, Zn, P, and K) in which the need for adding complexing agent for the extraction of ions, centrifugation for separation of adsorbent, and shaker to enhance the contact area of the sample solution with absorbent was eliminated. These advantages were provided by using putrescine as the absorbent for the extraction of the analytes. To reach this goal, a proper amount of putrescine was dissolved in ethanol and injected into a diluted crude oil solution. During this step, putrescine formed stable complexes with the ions and extracted them from the solution and collected on top of the solution easily. The floated phase was collected by a spatula, and the extracted ions were determined by inductively coupled plasma mass spectrometry. Validation parameters of this method showed that low limits of detection (0.003–3.62 ng g−1) and quantification (0.009–12.0 ng g−1), broad linear range (12.0–80,000 ng g−1), acceptable relative standard deviation (≤5.3%) for intra- and inter-day precisions and high extraction recovery (72–90%) were the features of the method. The method was successful in the determination of the analytes in real crude oil samples.

Single-bubble sonoluminescence of itterbium(II or III) and thulium(II or III) chloride nanoparticles colloidal suspensions in dodecane

Colloidal suspensions of nanoparticles of di- and trivalent ytterbium and thulium chloride crystals in dodecane were prepared by ultrasonic dispersion. The average nanoparticle size in the suspensions was 20–35 nm. During single-bubble sonolysis with the bubble moving at the standing wave antinode, identical bands with a maximum at 550 nm appeared in the sonoluminescence spectra with spectral resolution Δλ = 15 nm for suspensions of both Yb(II) and Yb(III) salts. Bands with a maximum at 600 nm were found for suspensions of Tm(II) and Tm(III) salts. These sonoluminescence bands coincide with the photoluminescence bands of Yb(II) (550 nm) or Tm(II) (600 nm) salts, respectively. For suspensions of divalent lanthanide salts, these sonoluminescence bands appear when nanoparticles get into a moving bubble, because of collisional excitation of Yb(II) or Tm(II) in the bubble plasma, which periodically appears during acoustic oscillations: [Ln(II)]suspension → [Ln(II)]bubble → [Ln(II)]plasma → [Ln(II)*]plasma → Ln(II) + hνLn(II). The presence of analogous bands for suspensions of trivalent lanthanide salts is caused, in particular, by also their reduction in the plasma after they get into a bubble: [Ln(III)]suspension → [Ln(III)]bubble → [Ln(III)]plasma → [Ln(II), Ln(II)*]plasma → [Ln(II)*]plasma → Ln(II) + hνLn(II). The reduction of lanthanide ions in the bubble plasma is not limited to the reaction Ln(III) → Ln(II), Ln(II)*, but can proceed further giving singly charged lanthanide cations and lanthanide atoms: Ln(II) → Ln(I), Ln(I)* → Ln(0), Ln(0)*. The single-bubble sonoluminescence spectra with Δλ = 1.5 nm for a suspension of Yb(III) salt showed characteristic lines of Yb(I) and Yb(0). These characteristic lines and bands for ytterbium and thulium atoms and ions are suitable for sonoluminescent spectroscopic analysis, that is, identification and quantification of ions in solutions and suspensions and determination of electronic temperature in bubble plasma.

Evaluation of the immunotoxicity potential of nanomaterials using THP-1 cells.

With the expansion of nanomaterials (NMs) usage, concerns about their toxicity are increasing, and the wide variety of NMs makes it difficult to assess their toxicity. Therefore, the development of a high-throughput, accurate, and certified method to evaluate the immunotoxicity of NMs is required. In this study, we assessed the immunotoxicity potential of various NMs, such as nanoparticles of silver, silica, and titanium dioxide, using the human Cell Line Activation Test (h-CLAT) at the cellular level. After exposure to silver nanoparticle dispersions, the expression levels of CD86 and CD54 increased, suggesting the activation of antigen-presenting cells (APCs) by silver nanoparticles. Quantification of silver ions eluted from silver nanoparticles and the activation of APCs by silver ions suggested that it was due to the release of silver ions. Silica nanoparticles also increased the expression of CD86 and/or CD54, and their activation ability correlated with the synthesis methods and hydrodynamic diameters. The ability of titanium dioxide to activate APCs differed depending on the crystal type and hydrodynamic diameter. These results suggest a potential method to evaluate the immunotoxicity potential of various NMs based on their ability to activate APCs using human monocytic THP-1 cells. This method will be valuable in assessing the immunotoxicity potential and elucidating the immunotoxic mechanisms of NMs.

A fluorescent sensor array based on a single cucurbit[5]uril-truxene probe for simultaneous identification of five heavy metal ions.

There is a need to develop simple and effective strategies for the rapid detection of heavy metal ions (HMIs) in order to protect the environment and human health. A simple fluorescent sensor array based on a single cucurbit[5]uril-truxene probe was proposed to simultaneously identify five HMIs (Pb2+, Cu2+, Ag+, Fe2+ and Fe3+). This probe was synthesized using monohydroxyl cucurbit[5]uril and monobromohexyl truxene by a substitution reaction between them. It could be observed that the fluorescence response of this synthesized probe to HMIs was closely related to the pH of the aqueous solution, exhibiting different fluorescence intensities at pH 3.0, 7.0, and 9.0. Based on this phenomenon, a fluorescent sensor array based on a single cucurbit[5]uril-truxene probe was then constructed by simply altering the pH in the sensor element. These unique fluorescence responses were analyzed using linear discriminant analysis (LDA) to identify metal ions. A concentration limit classification of 0.1 μM was applied to the above five HMIs. Moreover, the quantification of metal ions was implemented even at low concentrations of 48-121 nM. This array showed good results in the recognition of metal ions in real water samples (lake water and tap water samples), which shows its broad application prospects in many fields, including monitoring of the environmental water quality and so on.

Ion-selective paper-based chromogenic strip and electrochemical sensor for the detection of ammonium ions

The fraudulent practice of adding ammonium salts to milk in order to enhance the nitrogen content has serious health implications including renal failure. Ammonium ion detection has been targeted through the conventional analytical methods however, lack of portability and complex operation limits their use for field applications. In this scenario, paper-based test strips and electrochemical sensors can provide strategies for point-of-test applications. Here, an ion-selective paper-based chromogenic strip and an electrochemical sensor has been developed for detection and quantification of ammonium ions. The developed paper-based chromogenic strip showed detection limit of 0.008 % (w/v) for ammonium ions, whereas, electrochemical sensor showed an LOD of 0.0062 ± 0.0023 % (w/v) with a sensitivity of 1.6 × 10−5 A.% −1.mm−2. The developed paper-based chromogenic strip and electrochemical sensor can be employed by regulatory bodies and dairy industries to ensure the safety and quality of milk.

NP3 MS Workflow: An Open-Source Software System to Empower Natural Product-Based Drug Discovery Using Untargeted Metabolomics.

Natural products (or specialized metabolites) are historically the main source of new drugs. However, the current drug discovery pipelines require miniaturization and speeds that are incompatible with traditional natural product research methods, especially in the early stages of the research. This article introduces the NP3 MS Workflow, a robust open-source software system for liquid chromatography-tandem mass spectrometry (LC-MS/MS) untargeted metabolomic data processing and analysis, designed to rank bioactive natural products directly from complex mixtures of compounds, such as bioactive biota samples. NP3 MS Workflow allows minimal user intervention as well as customization of each step of LC-MS/MS data processing, with diagnostic statistics to allow interpretation and optimization of LC-MS/MS data processing by the user. NP3 MS Workflow adds improved computing of the MS2 spectra in an LC-MS/MS data set and provides tools for automatic [M + H]+ ion deconvolution using fragmentation rules; chemical structural annotation against MS2 databases; and relative quantification of the precursor ions for bioactivity correlation scoring. The software will be presented with case studies and comparisons with equivalent tools currently available. NP3 MS Workflow shows a robust and useful approach to select bioactive natural products from complex mixtures, improving the set of tools available for untargeted metabolomics. It can be easily integrated into natural product-based drug-discovery pipelines and to other fields of research at the interface of chemistry and biology.

Mediating sequential turn-on and turn-off fluorescence signals for discriminative detection of Ag+ and Hg2+ via readily available CdSe quantum dots

Realizing the accurate recognition and quantification of heavy metal ions is pivotal but challenging in the environmental, biological, and physiological science fields. In this work, orange fluorescence emitting quantum dots (OQDs) have been facilely synthesized by one-step method. The participation of silver ion (Ag+) can evoke the unique aggregation-induced emission (AIE) of OQDs, resulting in prominent fluorescence enhancement, which is scarcely reported previously. Moreover, the Ag+-triggered turn-on fluorescence can be continuously shut down by mercury ion (Hg2+). This intriguing sequential fluorescence variation exhibits great sensing potency for discrimination and quantification of Ag+ and Hg2+. Meanwhile, our OQDs also exhibit good selectivity, sensitivity, and rapid response toward Ag+ and Hg2+ detection. Due to their high performance, OQDs have been applied to the determination of Ag+ and Hg2+ levels in daily necessities and water samples with satisfactory results. Moreover, a portable smartphone-assisted sensing platform based on chromatic change has been constructed, facilitating the real-time and naked-eye visualization in the resource-confined scene. We anticipate that the discovery of these OQDs would be advantageous for exploring novel QDs materials for fluorescence detection.

Fluorescent multichannel sensor array based on three carbon dots derived from Tibetan medicine waste for the quantification and discrimination of multiple heavy metal ions in water.

Afluorescent multichannel sensor array has been establishedbased on three carbon dots derived from Tibetan medicine waste for rapid quantification and discrimination of six heavy metal ions. Due to the chelation between metal ions and carbon dots (CDs), this fluorescence "turn off" mode sensing array can quantify six metal ions as low as "μM" level. Moreover, the six heavy metal ions display varying quenching effects on these three CDs owing to diverse chelating abilities between each other, producing differential fluorescent signals for three sensing channels, which can be plotted as specific fingerprints and converted into intuitive identification profiles via principal component analysis (PCA) and hierarchical cluster analysis (HCA) technologies to accurately distinguish Cu2+, Fe3+, Mn2+, Ag+, Ce4+, and Ni2+ with the minimum differentiated concentration of 5μM. Valuably, this sensing array unveils good sensitivity, exceptional selectivity, ideal stability, and excellent anti-interference ability for both mixed standards and actual samples. Our contribution provides a novel approach for simultaneous determination of multiple heavy metal ions in environmental samples, and it will inspire the development of other advanced optical sensing array for simultaneous quantification and discrimination of multiple targets.

Electrodeposition of Co-Mo Alloys and Its Applications in Electrochemical Sensing of Phosphate

Quantification of phosphate ions in water ecosystems is crucial for maintaining a healthy aquatic environment and optimizing aquaculture parameters. While cobalt (Co) thin film modified electrodes are widely used as phosphate sensors, their selectivity and stability often require improvements for on-site measurement. The present work addresses this challenge by introducing a novel phosphate sensing platform utilizing Cobalt-Molybdenum (Co-Mo) alloy film deposited on copper substrate. The developed Co-Mo thin film sensor exhibited a good thermal stability (up to 60 °C) and significantly improved the detection ranges (10−6 M to 10−2 M). The influence of electrolyte pH and temperature toward potentiometric sensing of phosphate were investigated and the conditions were optimized to improve the sensor sensitivity. The sensor showed a sensitivity of −56 mV.dec−1 with a good correlation coefficient (0.988). The detection limit was determined to be 0.987 μM and the relative standard deviation (RSD) was 1.3% (n = 3). The Co-Mo thin film sensor exhibited negligible interference even in the presence of 10-fold excess concentrations of common interfering analytes, demonstrating its robust performance in real-world environment. To validate the field practicality, the sensor’s performance was successfully tested in real shrimp culture water samples, demonstrating its compatibility with complex environmental matrices.

A capillary-aided microfiber Bragg grating pH sensor for hydrovoltaic technology

Hydrovoltaic is an emerging technology that aims to harvest energy from water flow and evaporation, in which the plasmonic hydrogen ions are generated by the interaction between water and hydrovoltaic device. However, the volume of the water sample for the interaction is usually ultra-small due to the compact size of hydrovoltaic device, making the quantification and characterization of the hydrogen ions in such water sample an elusive goal. To address this issue, a miniature fiber-optic pH probe is proposed using a unilaterally tapered-microfiber Bragg grating. The microfiber Bragg grating has an intrinsic Bragg reflection signal with a narrow linewidth. The fiber probe is functionalized by coating the sodium alginate, which can respond to the variation of pH mediated by the alteration of the hydrophilicity. The rigidity and robustness of microfiber Bragg grating facilitates the encapsulation of the sensor into a sampling capillary, allowing for the detection of trace aqueous sample less than 2 μL. The pH sensitivity of the tapered-μFBG-based sensor is 62.8 p.m./pH (R2 = 0.995) with a limit resolution of 0.096 pH. The sensor performed a practical application in the monitoring and characterization of the hydrovoltaic microdevice, which can generate microcurrent as soaked in the water. This work demonstrates a promising technology in the fields of materials, energy, biology and medicine, in which the detection of the microsamples is inevitable.

Laser-induced graphene electrochemical sensor for quantitative detection of phytotoxic aluminum ions (Al3+) in soils extracts

Aluminum in its Al3+ form is a metal that inhibits plant growth, especially in acidic soils (pH < 5.5). Rapid and accurate quantitative detection of Al3+ in agricultural soils is critical for the timely implementation of remediation strategies. However, detecting metal ions requires time-consuming preparation of samples, using expensive instrumentation and non-portable spectroscopic techniques. As an alternative, electrochemical sensors offer a cost-effective and minimally invasive approach for in situ quantification of metal ions. Here, we developed and validated an electrochemical sensor based on bismuth-modified laser-induced graphene (LIG) electrodes for Al3+ quantitative detection in a range relevant to agriculture (1–300 ppm). Our results show a linear Al3+ detection range of 1.07–300 ppm with a variation coefficient of 5.3%, even in the presence of other metal ions (Pb2+, Cd2+, and Cu2+). The sensor offers a limit of detection (LOD) of 0.34 ppm and a limit of quantification (LOQ) of 1.07 ppm. We compared its accuracy for soil samples with pH < 4.8 to within 89–98% of spectroscopic methods (ICP-OES) and potentiometric titration. This technology's portability, easy to use, and cost-effectiveness make it a promising candidate for in situ quantification and remediation of Al3+ in agricultural soils and other complex matrices.

Dual detection and quantification of hypochlorite and sulfite ions via SERS spectroscopy by utilizing the redox reaction of tetramethylbenzidine

We developed a highly efficient, ultra-sensitive, and selective dual detection sensor for hypochlorite (ClO–) and sulfite (SO32–) ions based on surface-enhanced Raman scattering (SERS) spectroscopy. 3,3′,5,5′-Tetramethylbenzidine (TMB) is oxidized by ClO– under acidic conditions to diazotized oxTMB that, when electrostatically adsorbed onto Au nanoparticles (NPs), produces a strong Raman signal at 1605 cm−1. Meanwhile, oxTMB is reduced to TMB by SO32–, which significantly reduces the Raman signal. The linear detection range of the proposed sensor is 10–10 to 10–6 M with a detection limit of 59 pM for ClO– and 10–9 to 10–5 M with a detection limit of 5.4 nM for SO32–. In addition, the sensor was successfully applied to detect ClO– and SO32– in water samples.