A sensitive and high-performance electrochemical detection of nitrite in water samples based on Sonochemical synthesized Strontium Ferrite Nanochain architectures

Design of an injectable magnetic hydrogel with porous structure and electrocatalytic activity for the sensitive electrochemical detection of nitrite in foods

Herein, we synthesized a novel injectable porous magnetic hydrogel (MHG) at room temperature using carboxymethyl chitosan (CMCS), polydopamine (PDA), sodium alginate (SA), polyethyleneimine (PEI) and copper ferrite (CuFe2O4) as building blocks. The CMCS and SA as monomers provided good film-forming and anti-fouling properties for MHG. The PDA-coated CuFe2O4 as a cross-linking agent improved the homogeneity, adsorption and electrocatalytic performance of MHG, but also generated a macroporous hydrogel structure which was beneficial for sensing applications. The positive PEI enhanced the adsorption of nitrite (NO2-) via electrostatic attraction. The MHG modified glassy carbon electrode (MHG/GCE) sensor offered a wide linear range (0.02-2250.00 μM) and a low limit of detection (3.60 nM) for NO2-. Recovery tests in crispy fried pork and roast chicken yielded excellent recoveries (91.01 %-107.68 %). Analyses of commercial chicken sausage and canned luncheon meat were conducted using the MHG/GCE sensor and an ultraviolet spectrophotometry method, with the results being near identical.

A strontium ferrite modified separator for adsorption and catalytic conversion of polysulfides for excellent lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) have emerged as one of the ideal contenders for the upcoming generation of high energy storage devices due to their superb energy density. Nonetheless, the shuttle effect generated by intermediate lithium polysulfides (LiPSs) during cell cycling brings about capacity degradation and poor cycling stability of LSBs. Here, a versatile SrFe₁₂O₁₉ (FSO) and acetylene black (AB) modified PP separator is first presented to inhibit the shuttle effect. Thanks to the strong chemical interaction of Fe and Sr with polysulphides in FSO, it can trap LiPSs and provide catalytic sites for their conversion. Therefore, the cell using the FSO/AB@PP separator has a high initial discharge specific capacity (930 mA h g^-1) at 2 C and lasts for 1000 cycles with a remarkably low fading rate (0.036% per cycle), while those using PE and AB@PP separators have inferior initial specific capacities (255 mA h g^-1 and 652 mA h g^-1, respectively) and fail within 600 cycles. This work proposes a novel approach for addressing the shuttle of LiPSs from a bimetallic oxide modified separator.

Investigation of structural, morphological and magnetic properties of nanostructured strontium hexaferrite through co-precipitation technique: Impacts of annealing temperature and Fe/Sr ratio

M-type strontium hexaferrite (SrM) were successfully synthesized from Sr²⁺ and Fe³⁺ precursor salt through co-precipitation technique. Different higher sintering temperatures (800-1000 °C) were used to get the desired SrM with variation of Fe³⁺/Sr²⁺ mole ratio as well. The characterization of SrM and its properties were investigated using modern instrumental techniques viz. X-ray diffraction (XRD), Fourier Transform Infrared Spectrometer, Scanning Electron Microscopy, Vibrating Sample Magnetometer, UV-Visible NIR Spectrometer, Impedance Analyzer and Thermal Conductivity Meter. The phase of the synthesized SrM were confirmed by comparing the XRD patterns with the standard ICDD data and Reitvelt Refinement for the SrM having Fe³⁺/Sr²⁺ ratio 10 and SrM with distinct annealing temperature were performed. The structural parameters, particle size (75 nm-318 nm) and shape of the as prepared samples were changed with calcination temperature as well as mole ratio. The saturation magnetization (73.77-24.27 emu/g), coercivity (3732.28-642.10 Oe) and remanant magnetization (39.15-8.86 emu/g) were varied with calcination temperature and composition. The dielectric properties, optical properties and thermophysical properties were measured for the SrM keeping Fe³⁺/Sr²⁺ ratio 10 calcined at 1000 °C. The synthesized SrM can be applied in magnetic recording media and as photocatalyst due to its low coercivity (2764.48 Oe), high saturation magnetization (73.77 emu/g) and low band gap energy (Eg-2.04 eV) respectively.

Appraising the electrocatalytic performance of beta-cyclodextrin embellished supramolecular recognition system for pernicious food colorants

The current research presents the evaluation of supramolecular proficiency of the designed platform for electrocatalytic determination of pernicious food colorants, amaranth and fast green. The approach involving surface modification of glassy carbon electrode with beta cyclodextrin decorated strontium ferrite reduced graphene oxide nanocomposite (SFrGO-βCD) to ensure fast and reversible electro-oxidation of hydroxyl groups of the colorant molecules. The synergy between SF and rGO facilitated the sensor with enhanced surface area and conductivity through faradic redox reaction. Tremendous decrease in the obtained values of peak separation potential and impedance as manifested in CV and EIS analysis, enabled by electrostatic interactions between surface functionalities of rGO and βCD has resulted in the significant augmentation of sensitivity. The value of charge transfer coefficient, number of electrons involved, nature of electron transport process at electrode electrolyte interface during the analysis of electrochemical detection were explored through CV experiments. Food samples analysis (without spiking) utilizing screen printed electrode manifested the sensor as portable device for real time monitoring. Outstanding detection limit (0.022 nM for amaranth and 0.051 nM for fast green), excellent regenerability (Relative standard deviation less than 3%) and apparent recovery rate (above 90%) of the modified electrode presented a colossal potential for the development of sustainable and commercially competitive electrochemical sensor in food sector.

Preparation of highly sensitive electrochemical sensor for detection of nitrite in drinking water samples

Nitrite is both an environmental contaminant and a food additive. Excessive intake of nitrites not only causes blood diseases, but also has the potential risk of causing cancer. Therefore, rapid detection of nitrite in water is necessary. In this work, we propose an electrochemical sensor for the sensing of nitrite. Glassy carbon electrodes modified with noble metal nanomaterials have been widely used in the preparation of sensors, but the surface properties of noble metals largely affect the sensing performance. This work proposes the biosynthesis of Au nanoparticles using the pollen extract of Lycoris radiata as a reducing agent. Flavonoids rich in pollen can be used as weak reducing agents for the reduction of chloroauric acid, and slowly synthesize uniformly dispersed Au nanoparticles. These Au nanoparticles do not agglomerate because they contain small biological molecules on the surface and can form a homogeneous sensing interface on the electrode surface. The electrochemical sensor assembled with biosynthesized Au nanoparticles provides linear detection of nitrite between 0.01 and 3.8 mM. The sensor also has excellent immunity to interference. In addition, the proposed sensor was also successfully used for the detection of nitrite in drinking water.

Prostate cancer biomarker citrate detection using triaminoguanidinium carbon dots, its applications in live cells and human urine samples

Citrate is a tricarboxylate, plays vital role in prostate cancer (PC) and the level of citrate is an indicator for PC identification. Herein, triaminoguanidine carbon dots (TAG-CDs) prepared by one step hydrothermal method and used as a citrate receptor. Notably the TAG-CDs without alkaline treatment were highly fluorescent at pH 7 with high quantum yield (11.3%). TAG-CDs were characterized through TEM, XRD, FT-IR, UV-vis and spectrofluorimetry. It is noted that the average size was of 2.8 nm, the presence of highly disordered carbon, retain the functionality of TAG. The absorbance maxima obtained at 294 nm and good emitting response observed at 396 nm. The Y-aromaticity of receptor guanidinium moiety acts as Lewis acid and have peculiar interaction with Lewis base citrate via electrostatic interaction and also protons in the TAG participate hydrogen bonds with citrate, which causes quenching of TAG-CDs. From the obtained linear quenching equation the LOD was found to be 4 nM. The probe expressed high selectivity, high interference tolerance (500 - fold), fast response in 15 mins and good biocompatible. Finally, TAG-CDs utilized for the intracellular imaging of citrate in live MCF-7 cells, it showed good cytotoxicity and delivered contrast images in presence, absence of citrate. TAG-CDs detected the citrate level in human urine samples, the obtained results are validated with HPLC method.

Fabricating BiOI nanostructures armed catalytic strips for selective electrochemical and SERS detection of pesticide in polluted water

We have constructed a dual mode catalytic strip equipped with 2D BiOI nanostructures and deployed for dual mode detection sensing of hazardous trichlorophenol (TCP). Synthesized BiOI nanostructures are investigated for its crystal architecture, morphology and chemical composition. The BiOI are loaded onto the catalytic strips with the assistance of gravity offered drying process. The BiOI nanostructures offers a very less charge transfer resistance indicating its superior catalytic properties upon the electrochemical impedance studies. It reflected on providing an excellent limit of detection (LOD) and linear sensing range for TCP in electrochemical mode. For SERS, a thin plasmonic Au layer is sputter coated on BiOI equipped catalytic strips (Au@BiOI) for the TCP detection. An impressive enhancement factor of 10⁷ is obtained for SERS detection of TCP with good LOD of 10^-10 M. Fabricated dual mode BiOI based strips are thoroughly examined for operational stability and performance in real time conditions. The fabricated high performance dual mode platform for the detection of hazardous pesticides appears to be a promising prospect for the on-the-spot investigation.

Development of a simplified spectrophotometric method for nitrite determination in water samples

A new eco-friendly, rapid, and sensitive spectrophotometric method was developed to determine small quantities of nitrite, based on a diazotization mechanism. In an acidic solution, sulfathiazole was first diazotized with sodium nitrite, followed by adding phosphate buffer to form a yellow-colored compound, which showed maximum absorption at 450 nm, without the need for the addition of coupling agents such as N-(1-naphthyl) ethylenediamine. The effects of reagents amount and the optimal experimental conditions were examined by Central composite design. The simplified method presented a wide linear range of nitrite between 0.091 μg mL^-1 and 1.47 μg mL^-1, a sensitivity of 0.447 Abs mL µg^-1, a determination coefficient of 0.998, and a low limit of detection of 0.053 μg mL^-1. The simplified method was found to be comparable to the Griess method. It was evaluated for the measurements of nitrite using the accuracy profile approach. The validation procedure results established that 80% of the future results would be within the acceptability limit of 10% over the validation domain ranging from 0.174 μg mL^-1 to 1.37 μg mL^-1. The developed method was furtherly applied in the determination of nitrite using a developed paper-based analytical device that detected a nitrite concentration of 3 μg mL^-1 which is considered by the World Health Organization to be the maximal permissible limit of nitrite in drinking water.