Nitrite Sensor Research Articles

Innovative dual-mode miniaturized nitrite sensor: Incorporating colorimetric and electrochemical detectors for comprehensive monitoring on a single platform

This study introduces a novel, miniaturized analytical platform for a comprehensive range of founded nitrite concentrations on a single, portable device. Nitrites, essential for extending shelf life and enhancing color, are commonly found in both natural and industrial environments. In environmental settings, it is important to detect low nitrite concentrations, industrial applications, such as in the food industry, require handling higher concentrations effectively. This groundbreaking approach combines colorimetry and electrochemical detection for nitrite monitoring in a single portable paper-based device (PAD). Utilizing potassium permanganate (KMnO4) as a chromogenic agent, the device enables rapid, visual detection and quantification of high nitrite concentrations via smartphone-based color intensity analysis. For sensitive detection of low-level nitrite, it incorporates a cellulose acetate-modified screen-printed electrode (CA/SPCE) with differential pulse voltammetric detection. Under optimal conditions, the proposed dual-detection platform effectively detects nitrite concentrations ranging from 0.05 to 12.5 mM. Specifically, it covers (0.05 to 0.6 mM using electrochemical detection and 0.5 to 12.5 mM through colorimetric analysis. High nitrite levels produce a faded color in the test zone, while low or undetectable color changes trigger electrochemical analysis for enhanced precision. This PAD platform is portable, cost-effective, and minimizes reagent usage. Importantly, the method’s detection limit aligns with the World Health Organization’s acceptable daily nitrite intake in drinking water (3 mg L−1, approximately 65 µM), making it a practical tool for nitrite screening.

Nano-sized gold particles driven interfacial reaction for the enhanced electrochemical nitrite sensing

Nitrite is a typical food additive and chemical fertilizer, which could pose toxicity to human and aquatic organisms when it is excessive. Therefore, it is meaningful to develop reliable analytical methods for nitrite detection. In this work, an innovative electrochemical nitrite sensor has been fabricated using In2O3 decorated with high-activity nano-sized Au particles (Au/In2O3), which were synthesized through a two-step synthetic method combining hydrothermal reaction and deposition-precipitation, resulting in an excellent sensing performance for the nitrite. Specifically, the electrochemical nitrite sensor based on Au/In2O3 exhibits high sensitivity with a linear detection range from 10 μM to 5 mM at pH 7.38. Additionally, the Au/In2O3 based nitrite sensor shows a detection limit of 0.46 μM and presents impressive selectivity and stability. The extraordinary nitrite sensing performance can be attributed to the excellent catalytic activity of nano-sized Au particles and the strong interfacial reaction between Au/In2O3 and nitrite. Furthermore, theoretical calculations reveal the interfacial reactions mechanism driven by Au particles, which enhance the charge transfer between Au/In2O3 and nitrite and thus improve its electrochemical sensing performance. This work presents a novel approach towards fabricating high-performance electrochemical nitrite sensor and reveals the enhanced interfacial reaction mechanism of nano-sized Au particles.

An Ultra‐Sensitive Electrochemical Sensor for Nitrite Based on Green Synthesized Gold Nanoparticles Using Colocasia Esculenta Extract

AbstractSeeking to establish a novel, eco‐friendly and ultra‐ sensitive electrochemical nitrite sensor, we have fabricated fluorine doped tin oxide (FTO) electrode with green synthesized gold nanoparticles (AuNPs) from gold salt and taro plant (Colocasia esculenta) extract (Taro_AuNPs/FTO). Different morphological and elemental analysis were conducted to undermine morphological condition and shapes of AuNPs. Further, electrochemical studies were performed for enabling observation on the modification as well as interaction between nitrite ion and AuNPs on the modified FTO. Furthermore, the performance of Taro_AuNPs/FTO sensor was evaluated using DPV technique and the limit of detection (LOD) was 0.923 nmol L−1 (S/N=3) having sensitivity of 0.00503 μA mM−1 cm−2 within 5–500 μmol L−1. Additionally, an insightful mechanistic overview was highlighted about interacting nitrite on the modified electrode surface. Finally, interference test, stability, reproducibility and real sample analysis were conducted to establish the effectiveness of Taro_AuNPs/FTO electrochemical senor for environmental application.

Rational design of carbon dot nanozymes for ratiometric dual-signal and smartphone-assisted visual detection of nitrite in food matrices

Developing reliable nitrite (NO2−) sensors is essential for food safety and reducing health risks from NO2− exposure. In this study, we strategically designed nitrogen-doped carbon dot (N-CD) nanozymes to establish an accessible dual-signal ratiometric sensing system for detecting NO2− in food matrices. This system utilizes the photoluminescence and enzyme-like properties of N-CD nanozymes combined with NO2−-triggered diazotization reactions of substrates such as o-phenylenediamine (OPD) or 3,3',5,5'-tetramethylbenzidine (TMB). The resulting N-CD/OPD and N-CD/TMB composites provide dual-mode detection—fluorescence and colorimetric—with high selectivity for NO2− and excellent resistance to interference. These sensors exhibit clear color changes under both ultraviolet and visible light, and can be combined with smartphones for visual, on-site detection of NO2−. By incorporating a ratiometric strategy, dual-signal output, and smartphone compatibility, our system achieved a low detection limit (≤ 1.92μM) and satisfactory recovery rates (85.6~115%) in environmental water and food samples. This highlights the potential of smartphone-assisted sensors for environmental monitoring and food safety applications. Our carbon dot-based platform offers a practical and effective solution for on-site NO2− detection, contributing valuable insights to the field.

In2O3 electrochemical transistors based on PtAu4/RGO nanocomposites functionalized gate for highly sensitive nitrite detection

Nitrite is commonly found in the environment, but its overuse and potential toxicity pose serious health risks. There is a strong need to develop robust and reliable methods for detecting nitrite. Herein, a novel In2O3 solution-gated electrochemical transistor (SGET) nitrite sensor was designed and fabricated for highly sensitive detection of nitrite. Different thicknesses of In2O3 thin films were prepared by sol–gel method, which were used as the channel of transistors and optimized through evaluating the electronic and electrochemical properties. To improve the catalytic oxidation of nitrite, PtAu4 nanoparticles modified reduced graphene oxide nanocomposites (PtAu4/RGO) were fabricated on the gate of transistors through electrodeposition approach. The developed sensor exhibited exceptional sensing performance in nitrite detection, which featured with low detection limit (0.1 nM nitrite) and ultra-wide linear range from 0.1 nM to 1 mM. The developed In2O3 SGET sensor displayed excellent stability and high resistance to common interfering ions, thereby demonstrating superior anti-interference performance. Nitrite in real samples of natural lake water has been accurately measured, suggesting that the designed sensor could act as an ideal transducer platform for highly sensitive and selective nitrite detection in food and environmental fields.

Efficient nitrite determination by electrochemical approach in liquid phase with ultrasonically prepared gold-nanoparticle-conjugated conducting polymer nanocomposites.

An electrochemical nitrite sensor probe is introduced herein using a modified flat glassy carbon electrode (GCE) and SrTiO3 material doped with spherical-shaped gold nanoparticles (Au-NPs) and polypyrrole carbon (PPyC) at a pH of 7.0 in a phosphate buffer solution. The nanocomposites (NCs) containing Au-NPs, PPyC, and SrTiO3 were synthesized by ultrasonication, and their properties were thoroughly characterized through structural, elemental, optical, and morphological analyses with various conventional spectroscopic methods, such as field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller method. The peak currents due to nitrite oxidation were characterized in detail and analyzed using conventional cyclic voltammetry (CV) as well as differential pulse voltammetry (DPV) under ambient conditions. The sensor response increased significantly from 0.15 to 1.5mM of nitrite ions, and the sensor was fabricated by coating a conducting agent (PEDOT:PSS) on the GCE to obtain the Au-NPs/PPyC/SrTiO3 NCs/PEDOT:PSS/GCE probe. The sensor's sensitivity was determined as 0.5μA/μM∙cm2 from the ratio of the slope of the linear detection range by considering the active surface area (0.0316cm2) of the flat GCE. In addition, the limit of detection was determined as 20.00 ± 1.00 µM, which was found to be satisfactory. The sensor's stability, pH optimization, and reliability were also evaluated in these analyses. Overall, the sensor results were found to be satisfactory. Real environmental samples were then analyzed to evaluate the sensor's reliability through DPV, and the results showed that the proposed novel electrochemical sensor holds great promise for mitigating water contamination in the real samples with the lab-made Au-NPs/PPyC/SrTiO3 NC. Thus, this study provides valuable insights for improving sensors for broad environmental monitoring applications using the electrochemical approach.

Fabrication of Highly Sensitive and Selective Nitrite Colorimetric Sensor Based on the Enhanced Peroxidase Mimetic Activity of Using Acetic Acid Capped Zinc Oxide Nanosheets.

Nitrite ions (NO2-), as one of the leading type-A inorganic-anion, showing significant-effects in the aquatic environment and also to humans health. Whereas, the higher uptake causes detrimental threat to human health leading to various chronic diseases, thus demanding efficient, reliable and convenient method for its monitoring. For this purpose, in the present research study we have fabricated the mimetic nonozyme like catalyst based colorimetric nitrite sensor. The acetic acid capped Zinc Oxide (ZnO) nanosheets (NSs) were introduce as per-oxidase mimetic like catalyst which shows high efficiency towards the oxidative catalysis of colorless tetramethylbenzidine (TMB) to oxidized-TMB (blue color) in the presence of Hydrogen-peroxide (H2O2). The present nitrite ions will stimulate the as formed oxidized-TMB (TMBox), and will caused diazotization reaction (diazotized-TMBox), which will not only decreases the peak intensity of UV-visible peak of TMBox at 652nm but will also produces another peak at 446nm called as diazotized-TMBox peak, proving the catalytic reaction between the nitrite ions and TMBox. Further, the prepared colorimetric sensor exhibits better sensitivity with a wider range of concentration (1 × 10-3-4.50 × 10-1 µM), lowest limit of detection (LOD) of 0.22 ± 0.05 nM and small limit of quantification (LOQ) 0.78 ± 0.05 nM having R2 value of 0.998. Further, the colorimetric sensor also manifest strong selectivity towards NO2- as compared to other interference in drinking water system. Resultantly, the prepared sensor with outstanding repeatability, stability, reproducibility, re-usability and its practicability in real water samples also exploit its diverse applications in food safety supervision and environmental monitoring.

Controllable synthesis of cross-linked 3D ZnO nanosheet toward a nitrite electrochemical sensor

A 3D cross-linked ZnO (cl-ZnO) nanosheets were prepared via a simple one-pot hydrothermal approach, and then characterized by a series of modern advanced technique including XRD, SEM, TEM and XPS. This nanomaterial was used to modify the glass carbon electrode (GCE), obtaining an electrochemical sensor (cl-ZnO/GCE) of which the electrochemical properties were studied using various electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The sensor exhibited remarkably enhanced electrocatalytic activity for nitrite ions (NO2-) in comparison to that of the commercially available ZnO-modified GCE. Two electrochemical techniques, including chronoamperometry (CA) and linear sweep voltammetry (LSV) were adopted to test the determination performance of the sensor for nitrite, it exhibited a good linear relationship within the range of 0.8 μmol·L-1 - 0.462 mmol·L-1 and 0.608 - 7.84 mmol·L-1 evaluated by CA, the limit of detection (LOD) and sensitivity for NO2- were 0.26 μmol·L-1 (S/N = 3) and 824.6 µA (mmol·L-1)-1cm-2, respectively. For LSV, the two linearity responses of 0.95 μmol·L-1- 0.515 mmol·L-1 and 0.667 mmol·L-1- 5.41 mmol·L-1, high sensitivity of 1336.1 µA (mmol·L-1)-1cm-2 with low LOD of 0.32 μmol·L-1 were gained. This sensor can be employed to detect trace amount of NO2- in ham sausage and pickled vegetables successfully, supporting an insight and strategy for more sensitive nitrite electrochemical sensor.

MnCo2O4 Spinel Nanorods for Highly Sensitive Electrochemical Detection of Nitrite.

The rational design of nitrite sensors has attracted significant research interest due to their widespread use and the associated risks of methemoglobinemia and carcinogenicity. The undisclosed nitrite-sensing performance of the spinel cobaltite MnCo2O4 (MCO) prepared by an oxalate-assisted coprecipitation method is reported in this study. Spectroscopy and microscopy investigations revealed the formation of uniform MCO nanorods with a high aspect ratio. The electrocatalytic nitrite oxidation at the MCO-coated glassy carbon electrode (MCO/GCE) indicated the promising performance of the synthesized material for nitrite sensing. MCO/GCE detects nitrite in a concentration range of 5 μM to 3 mM and has a limit of detection of 0.95 μM with a higher sensitivity of 857 μA mM-1 cm-2 in a response time of 4 s. In MCO, the mixed-valence states of Co2+/Co3+ confer a high electrical conductivity, and higher valent redox couples of Mn and Co impart remarkable electrocatalytic activity toward nitrite oxidation. MCO spinel undergoes facile and ultrafast faradaic reactions to mediate nitrite oxidation. Additionally, the mesopores of MCO nanorods facilitate the rapid diffusion of electrolyte and nitrite ions. Employing the electrode in sensing nitrite in milk, lake, and tap water samples further validates its potential application in real-life testing. MCO spinel nanorods showcase promising scope for utilization in the electrochemical sensing of nitrite and inspire further exploration of transition-metal oxide-based mixed-spinel materials.

An Electroanalytical Enzymeless α-Fe2O3-ZnO Hybrid Nanostructure-Based Sensor for Sensitive Quantification of Nitrite Ions.

Nitrite monitoring serves as a fundamental practice for protecting public health, preserving environmental quality, ensuring food safety, maintaining industrial safety standards, and optimizing agricultural practices. Although many nitrite sensing methods have been recently developed, the quantification of nitrite remains challenging due to sensitivity and selectivity limitations. In this context, we present the fabrication of enzymeless iron oxide nanoparticle-modified zinc oxide nanorod (α-Fe2O3-ZnO NR) hybrid nanostructure-based nitrite sensor fabrication. The α-Fe2O3-ZnO NR hybrid nanostructure was synthesized using a two-step hydrothermal method and characterized in detail utilizing x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). These analyses confirm the successful synthesis of an α-Fe2O3-ZnO NR hybrid nanostructure, highlighting its morphology, purity, crystallinity, and elemental constituents. The α-Fe2O3-ZnO NR hybrid nanostructure was used to modify the SPCE (screen-printed carbon electrode) for enzymeless nitrite sensor fabrication. The voltammetric methods (i.e., cyclic voltammetry (CV) and differential pulse voltammetry (DPV)) were employed to explore the electrochemical characteristics of α-Fe2O3-ZnO NR/SPCE sensors for nitrite. Upon examination of the sensor's electrochemical behavior across a range of nitrite concentrations (0 to 500 µM), it is evident that the α-Fe2O3-ZnO NR hybrid nanostructure shows an increased response with increasing nitrite concentration. The sensor demonstrates a linear response to nitrite concentrations up to 400 µM, a remarkable sensitivity of 18.10 µA µM-1 cm-2, and a notably low detection threshold of 0.16 µM. Furthermore, its exceptional selectivity, stability, and reproducibility make it an ideal tool for accurately measuring nitrite levels in serum, yielding reliable outcomes. This advancement heralds a significant step forward in the field of environmental monitoring, offering a potent solution for the precise assessment of nitrite pollution.

Electronic modulation caused by interfacial Fe-O-Co-O-Fe bonding for boosting highly efficient non-enzymic nitrite sensing

Rational electronic modulation of metal–organic frameworks (MOFs) derived electrocatalysts is an effective strategy for rendering them capable of enhanced sensing performance, but rather challenging. Herein, we propose a combination strategy of self-templated transformation and carbonization pyrolysis for elaborately synthesizing a MOF-derived non-planar FeCo hierarchical nest-like networks (n-FeCo-HNNs) heterojunction catalyst. Owing to the excellent electrical conductivity and active site density of n-FeCo-HNNs, such non-enzymic nitrite sensor displays a wide broad detection range, excellent sensitivity, and ultralow limit of detection. Experimental and theoretical calculations clarified the electrons are extracted and rapidly transferred to the surface-active sites through the Fe-O-Co-O-Fe bridge, and then improve the reaction kinetics and boost the sensing performance for nitrite. The synergistic effect of this chemical bond established in the heterostructure unveils a new avenue for efficient electrochemical sensing.

Nano-palladium-decorated bismuth sulfide microspheres on a disposable electrode integrated with smartphone-based electrochemical detection of nitrite in food samples

Nitrite (NO2−) is widely used as an additive to extend the shelf life of food products. Excessive nitrite intake not only causes blood-related diseases but also has the potential risk of causing cancers. A disposable screen-printed electrode was modified with nano‑palladium decorated bismuth sulfide microspheres (nanoPd@Bi2S3MS/SPE), and integrated with a smartphone-interfaced potentiostat to develop a portable, electrochemical nitrite sensor. NanoPd@Bi2S3MS was prepared by the hydrothermal reduction of a Bi2S3MS and Pd2+ dispersion and drop cast on the SPE. The nanoPd@Bi2S3MS/SPE was coupled with a smartphone-controlled portable potentiostat and applied to determine nitrite in food samples. The linear range of the sensor was 0.01–500 μM and the limit of detection was 0.0033 μM. The proposed system showed good repeatability, reproducibility, catalytic stability, and immunity to interferences. The proposed electrode material and a smartphone-based small potentiostat created a simple, portable, fast electrochemical sensing system that accurately measured nitrite in food samples.

The electrochemical fabrication of Cu@CeO2-rGO electrode for high-performance electrochemical nitrite sensor

The synthesis of cerium oxide-reduced graphene oxide (CeO2−rGO) and Cu nanoparticles decorated−CeO2−rGO (Cu@CeO2−rGO) nanocomposites based on electrochemical deposition technique and their nitrite sensor application are presented as the first report. CeO2−rGO nanocomposites were prepared via a one-pot and one-step technique on the pencil graphite electrode (PGE) surface. To increase the activity toward nitrite, the CeO2−rGO surface was also decorated with metallic Cu nanoparticles using electrochemical deposition. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction spectroscopy (XRD), and energy dispersive spectroscopy (EDS) techniques were used for structural characterization. Morphological analysis was performed using the SEM technique. The electrocatalytic properties of fabricated electrodes for nitrite detection were investigated by cyclic voltammetry (CV), amperometry, and electrochemical impedance spectroscopy (EIS). The detection limit, the sensitivity, and the linear range of nitrite on the Cu@CeO2 − rGO electrode were determined as 10.1 nM, 1963.2 μA μM cm−2, and 10–2000 μM, respectively. Moreover, the Cu@CeO2−rGO electrode exhibited high selectivity toward nitrite in the presence of interfering species. The results in the salami sample showed that the Cu@CeO2−rGO electrode could also be used successfully in food analysis.

Novel nitrogen‐rich anchored nickel (II) phthalocyanine with composite of multiwalled carbon nanotubes on modified glassy carbon electrode: Sensitive and selective electrocatalytic activity of nitrite

This work describes the synthesis of novel nickel tetra substituted 6‐bromobenzothiazole carboxamide nickel (II) phthalocyanine (NiTBBTCAPc) and confirmed by spectroscopic‐microscopic methods and as well as electrochemical analysis. The electrochemical oxidation of nitrite was studied on NiTBBTCAPc‐multiwalled carbon nanotube (MWCNTs)/glassy carbon electrode (GCE) due to its better electron transferring ability than bare GCE and NiTBBTCAPc/GCE. As there is acceleration in surface area of GCE by multiwalled carbon nanotubes, a cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometric techniques utilized for nitrite sensor were developed. The sensor exhibited a fast response towards nitrite with a detection limit of 3.012 nM and a linear concentration range of 50–900 nM by the CV method. The fabricated sensor shows excellent electrocatalytic activity compared with the modified electrode with Pc with a composite of MWCNTs towards oxidation of nitrite. The NiTBBTCAPc‐MWCNTs/GCE shows good repeatability, stability, and high selectivity even in the presence of excess ascorbic acid (AA), dopamine (DA), uric acid (UA), paracetamol (PA), glucose, Pb (II), Cd (II), Ca (II), and Mg (II). Finally, for usage in practical applications, the modified electrode was employed to achieve quantitative detection of nitrite in drinking water and cabbage vegetable samples, respectively.

A novel boat‐based field application of a high‐frequency conductometric ammonium analyzer to characterize spatial variation in aquatic ecosystems

AbstractDocumenting dissolved inorganic nitrogen (DIN) concentrations and forms at appropriate temporal and spatial scales is key to understanding aquatic ecosystem health, particularly because DIN fuels primary productivity. In addition to point and nonpoint source nutrient inputs, factors such as hydrology, geomorphology, temperature, light, and biogeochemical transformations influence nutrient dynamics in surface waters, allowing for the formation of steep spatial gradients and patchiness. Documenting nutrient variability is also necessary to identify sources, quantify transformation rates, and understand drivers. Because of logistical and cost constraints, it is often unfeasible to measure concentrations of nutrients in surface waters using discrete sampling followed by laboratory analysis at a resolution high enough to identify steep spatial gradients and patchiness. Because of these constraints, data generated from discrete sampling are limited in space and time, often missing key variabilities. Recent advancements of in situ nitrate plus nitrite ( and ) sensor technology have enabled highly temporally and spatially resolved concentration measurements in aquatic ecosystems. However, comparable information about ammonium () concentrations remains unavailable. To address this need, US Geological Survey collaborated with Timberline Instruments to modify their commercially available benchtop TL‐2800 ammonia analyzer to operate in flow‐through mode, enabling rapid continuous concentration measurements at a micromolar (0.5 μM) resolution while receiving water pumped from a moving boat. Although the utility of this method is described for spatial surveys, we anticipate that it would be adaptable to installation at a fixed station for continuous monitoring of concentration.

Trimetallic zeolitic imidazolate framework-derived hollow structure as a sensing material for nitrite electrochemical detection

A hollow structure is characterized by well-defined inner voids, high surface area, and numerous active sites, exhibiting great potential in electrochemical sensing. Herein, a trimetallic zeolitic imidazolate framework (ZnCoMn ZIF-67) was synthesized and then treated with dopamine (DA) to produce hollow ZnCoMn ZIF-67@DA (H-ZnCoMn ZIF-67@DA). Hollow Co, Mn, N-doped-porous carbons (H-CoMnN-PCs) were prepared through a pyrolysis treatment, and the resulting material retained the hollow structure of the precursor. The structural characteristics of the prepared material were evaluated through different techniques. Under optimized conditions, the nitrite sensor prepared using H-CoMnN-PCs exhibited two linear working ranges of 0.1–1500 and 1500–12000 μM, with a low detection limit of 0.097 μM. Moreover, the sensor featured high selectivity, stability, and reproducibility, making it a suitable candidate for various practical applications.

Novel biogenic preparation of gold nanoparticles decorated on sepiolite clay and evaluation of anti-cancer effect on gastric cancer cell and electrochemical sensing of nitrite

An environmentally friendly strategy was used in this study to synthesize gold nanoparticles decorated on sepiolite clay (GNPs-SC) using Heracleum persicum grass extract. The physicochemical characters of the prepared composite were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). A GNPs-SC modified carbon pate electrode (CPE) was used to study the electrochemical oxidation of nitrite. The proposed nitrite sensor exhibits excellent performance, including a broad linear range (1.0–150 μM), a low limit of detection (0.4 μM), and acceptable reproducibility (RSD = 2.6%). As well, the prepared GNPs-SC was tested for its effectiveness against human gastric adenocarcinoma (AGS) cell line. The MTT assay protocol revealed that the bio-synthesized product displayed significant cytotoxic activity against gastric cancer in human subjects. The findings of this study indicate that GNPs-SC, synthesized using environmentally friendly protocol, exhibit great potential for use in electrochemical sensing and treatment of human cancer.

Nanocomposite of nickel phthalocyanine nanoparticles and detonation nanodiamonds for enhanced electrocatalysis

This work reports on nickel phthalocyanines nanoparticles (NPs)-detonation nanodiamonds (DNDs) as potential platforms for electrocatalytic detection of nitrite in 0.2 M sodium hydroxide solution. The electrode surfaces were analysed using cyclic voltammetry and electrochemical impedance which showed enhanced electron transfer after modification, with (1)-NPs-DNDs showing relatively better electron tranter ability. The electrocatalytic performance of modified surfaces was investigated towards nitrite electrooxidation. The results demonstrated that tetrakis [4-(4-(4,5-dichloro-1H-benzo[d]imidazole-2-yl) phenoxy] phthalocyanato nickel (II) (1)-NPs-DNDs gave more negative oxidation potential (0.87 V), highest background corrected current (120.3 μA), highest electrocatalytic rate constant (2.84 × 104 M−1 s−1) and lowest limit of detection of (0.098 nM). These factors rendered (1)-NPs-DNDs electrode surface better than others studied here making it a promising sensor for nitrite.

A new design of a fiber optic sensor based on balloon shaped bending and flattening sensing probe: Application towards an ultra specific and sensitive detection of nitrite using g-C3N4/ZrPO4 nanocomposites coating

The fabrication and characterization of a flattened balloon shaped fiber optic nitrite sensor using zirconium phosphate supported on graphitic carbon nitrite nanocomposites (g-C3N4/ZrPO4) as a cladding material have been reported. To design the sensing probe, a small portion of the fiber is mechanically hot pressed for flattening and then structured into a balloon shape. The improved sensitivity of the proposed design is ascribed to the better light extraction efficiency to the cladding in the flattened region of the balloon shaped fiber compared with a similar non flattened structure which is explained using numerical simulation. To demonstrate the sensing behavior of the proposed design, a NO2− ion sensing probe is fabricated by coating g-C3N4/ZrPO4 nanocomposite over the flattened portion of the balloon shaped fiber. Experimental results on sensing exhibit a limit of detection (LOD) of 182 ppb and sensitivity 0.03204 µA/µM for NO2− ion. Further, the study is extended towards showing high specificity and fair temperature invariance of the proposed sensor which indicates its improved performance.

In situ fabrication of copper oxide nanoparticles decorated carbon cloth for efficient electrocatalytic detection of nitrite

In this work, a simple and efficient electrochemical sensor for nitrite based on in situ fabrication of copper oxide nanoparticles decorated carbon cloth (CuO NPs/CC) has been fabricated by efficient electrodeposition and calcination route. Owing to the synergistic effect of high conductivity, fast electron transfer kinetics, excellent electrocatalytic activity and large electroactive specific surface area, the CuO NPs/CC electrode has exhibited brilliant ability in nitrite detection, including wide linear ranges of 0.5–3000 μM, low detection limit of 0.043 μM (S/N = 3), the fast response time of 0.9 s and high sensitivity of 1656 μA mM−1 cm−2. Additionally, CuO NPs/CC electrode has been successfully used to determine nitrite in real samples of drinking water and sauerkraut with satisfactory recoveries.