Amino-calixarene-modified graphitic carbon as a novel electrochemical interface for simultaneous measurement of lead and cadmium ions at picomolar level

Amino-calixarene-derivatized graphitic carbon electrode has been used in the simultaneous quantification of lead and cadmium ions at picomolar level. The graphitic carbon has been chemically modified using amino-calixarene as an indicator molecule through microwave irradiation, and it has been characterized by NMR, mass, and Fourier transform infrared spectroscopy (FTIR) techniques. The proposed sensor has shown linearity in the concentration range 10–120 pM with detection limits of 3.3 and 3.5 pM for lead and cadmium, respectively. The proposed sensor has been successfully applied to quantify lead and cadmium levels in battery effluents, alloy materials, and sewage water sample matrices. The results obtained by the proposed sensor are in agreement with the results of the standard protocols.     

Graphene oxide/copper terephthalate composite as a sensing platform for nitrite quantification and its application to environmental samples

Journal of Solid State Electrochemistry - A robust electrochemical sensing platform based on graphene oxide-copper terephthalate (GO/Cu-tpa) composite has been fabricated. The prepared composite...     

Optical studies in gamma irradiated Mg doped CaF2 single crystals

Pure and Mg doped CaF₂ single crystals grown by the Bridgman method were irradiated with gamma rays (γ-rays) for doses ranging from 97 Gy to 9.72 KGy. The pristine samples showed minimal absorption indicating the purity of the samples. The γ-irradiated pure CaF₂ crystals showed prominent and strong absorption with a peak at ~ 374 nm besides three weak ones at ~ 456, 523 and 623 nm. However γ-rayed Mg doped crystals showed a prominent absorption with a strong peak at ~ 370 nm and a broad one at ~ 530 nm. The absorption indicated the generation of F and F-aggregate centers in the irradiated crystals. The photoluminescence (PL) emission spectrum of both pure and Mg doped crystals showed prominent emission at ~ 390 nm when they were excited at ~ 250 nm. Also, when the samples were excited at 323 and 363 nm strong emissions were observed at ~ 430 and 422 nm respectively. The optical absorption and PL intensities were found to increase with increase in dose.     

Optical studies of samarium-doped fluoride nanoparticles

Samarium-doped calcium fluoride (CaF₂) nanoparticles were synthesized by the co-precipitation method and characterized by powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), optical absorption and photoluminescence (PL) techniques. The PXRD patterns confirmed the cubic crystallinity of the synthesized nanoparticles. The average particle size estimated using Scherer's formula was ～20?nm. The purity of the synthesized nanoparticles was confirmed by the FTIR spectrum. The morphological features studied using SEM revealed that the nanoparticles were agglomerated and porous. The optical absorption spectrum showed a strong and prominent absorption peak at ～264?nm and a weak one at ～212?nm. The PL spectrum showed broad and prominent emissions with peaks at ～387 and 532?nm along with weak emissions at 573 and 605?nm.     

A binderless,covalently bulk modified electrochemical sensor: Application to simultaneous determination of lead and cadmium at trace level

A new type of covalent binderless bulk modified electrode has been fabricated and used in the simultaneous determination of lead and cadmium ions at nanomolar level. The modification of graphitic carbon with 4-amino salicylic acid was carried out under microwave irradiation through the amide bond formation. The electrochemical behavior of the fabricated electrode has been carried out to decipher the interacting ability of the functional moieties present on the modifier molecules toward the simultaneous determination of Pb²⁺ and Cd²⁺ ions using cyclic and differential pulse anodic stripping voltammetry. The possible mode of interaction of functional groups with metal ions is proposed based on the pKa values of the modifier functionalities present on the surface of graphitic carbon particles. The analytical utility of the proposed sensor has been validated by measuring the lead and cadmium content from pretreated waste water samples of lead acid batteries.     

Surfactant mediated sulfide estimation at trace level: Application to environmental samples

A simple spectrophotometric method has been developed for the quantification of dissolved sulfide based on its reaction with ferric iron and the subsequent reaction of ferrous iron with 1-nitroso-2-naphthol in alkaline medium. The insoluble iron(II)-ligand complex has been solubilized in micellar medium using neutral surfactant which facilitates the non extraction step. The method obeys Beer??s law in the concentration range 0.5?C8 ??g in 10 mL of aqueous phase. The complex showed an absorption maximum at 710 nm with ?? value of 4.11 × 10⁴ L/mol cm. The detection limit has been found to be 0.0036 ??g/mL. The interference of common cations and anions has been studied and the proposed method has been successfully applied to determine the sulfide in different sewage water samples.     

Morphology and optical properties of Mg and Sr doped CaF2 nanocrystals

Magnesium (Mg) and Strontium (Sr) doped Calcium fluoride nanocrystals were synthesized by co-precipitation method. The cubic structure of the samples was confirmed by Powder X-ray diffraction. The average crystallite size of Mg doped samples was found to be ~ 25 nm whereas in Sr doped one it was ~ 35 nm. The morphological features revealed that the nanocrystals were agglomerated, crispy and porous. The as-prepared samples showed the presence of hydroxyl groups. The optical absorption spectrum of as-prepared Mg doped samples showed a strong absorption band peaked at ~ 233 nm whereas the Sr doped one showed a prominent absorption peak at 248 nm. A strong PL emission was observed at ~ 300 nm in Mg doped samples. However, the Sr doped samples showed two prominent emissions at ~ 345 and 615 nm.     

CeO<Subscript>2</Subscript> nanoparticle-modified electrode as a novel electrochemical interface in the quantification of Zn<Superscript>2+ </Superscript>ions at trace level: application to real sample analysis

A simple strategy has been proposed to quantify Zn²⁺ ions using CeO₂ nanoparticle-modified glassy carbon electrode. The CeO₂ nanoparticles were prepared by sucrose-nitrate decomposition method, and it was characterized by X-ray diffraction (XRD), FT-IR, TEM, and surface area analyzer. The synthesized CeO₂ nanoparticles were used as modifier molecules as a thin film on glassy carbon electrode (GCE) in the trace level quantification of Zn²⁺ by using cyclic voltammetry (CV) and differential pulse anodic stripping voltammetry (DPASV) techniques. The fabricated sensor exhibited a good analytical response towards Zn²⁺ ions. The modified electrode showed a wide linearity in the concentration range 20–380 μg L^?1 with a limit of detection 0.36 μg L^?1. The proposed electrochemical sensor was successfully applied to trace level Zn²⁺ quantification from real sample matrices.     

Microwave-assisted functionalization of glassy carbon spheres: electrochemical and mechanistic studies

Functionalization of glassy carbon spheres have been carried out by microwave irradiation in the presence of modifier molecules through oxidation followed by amidation reaction. The glassy carbon spheres were initially catalyzed by treating with concentrated nitric acid to introduce surface-bound carboxylic groups, and its subsequent amidation reaction in the presence of p-nitroaniline yields p-nitroanilide-functionalized substrate materials. These derivatized glassy carbon spheres have been electrochemically characterized by immobilizing them on bppg electrode and studying its voltammetric behavior. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy studies have revealed that the modifying molecules are surface bound and covalently attached on the carbon substrate.