Browsing by Author "Darshika Jauhari"

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A dual-ion imprinted polymer embedded in sol-gel matrix for the ultra trace simultaneous analysis of cadmium and copper
(Elsevier B.V., 2014) Bhim Bali Prasad; Darshika Jauhari; Archana Verma
In simultaneous determination of group of elements, there are inter-metallic interactions which result in a non-linear relationship between the peak current and ionic concentration for each of the element, at bare (unmodified) electrode. To resolve this problem, we have resorted, for the first time, to develop a modified pencil graphite electrode using a typical ion imprinted polymer network (dual-ion imprinted polymer embedded in sol-gel matrix (inorganic-organic hybrid nano-material)) for the simultaneous analysis of a binary mixture of Cd(II) and Cu(II) ions, without any complication of inter-metallic interactions and competitive bindings, in real samples. The adequate resolution of differential pulse anodic stripping voltammetry peaks by 725 mV (cf, 615 mV with unmodified electrode), without any cross-reactivity and the stringent detection limits as low as, 0.050 and 0.034 ng mL-1 (S/N=3) for Cd(II) and Cu(II) ions, respectively by the proposed sensor can be considered useful for the primitive diagnosis of several chronic diseases in clinical settings. © 2013 Elsevier B.V.
A dual-template biomimetic molecularly imprinted dendrimer-based piezoelectric sensor for ultratrace analysis of organochlorine pesticides
(Elsevier B.V., 2015) Bhim Bali Prasad; Darshika Jauhari
A double-template imprinted biomimetic dendritic nano-fibers based piezoelectric sensor was developed for the analysis of dichlorodiphenyltrichloroethane and hexachorobenzene prevalent together as organo-chlorinated pesticide residues in real samples, without any cross reactivity and false positives. For this, the immobilization of 2,5-thiophene dicarbonyl dichloride molecules was initially carried out on the surface of gold quartz crystal via Au-S links. Latter, these molecules were covalently attached to dendron molecules (monomer) followed by the free-radical polymerization at 65 °C, in the presence of both target analytes, cross-linker and initiator, leading to the development of self-assembled molecularly imprinted dendrimer nano-fibers on the gold surface. The method of analysis necessarily involved a typical 'saturation approach' in this work. Accordingly, one of the molecular cavities was completely saturated with an authentic amount of the respective analyte, whereas the cavity specific for other analyte was exposed to rebinding resulting in the frequency change in accordance with the mass of the analyte in question. Detection limits of dichlorodiphenyltrichloroethane and hexachorobenzene were realized as low as 0.75 and 0.69 ng mL-1 (S/N = 3), and linearity observed in the concentration ranges 5.0-150.0 and 5.0-75.0 ng mL-1, respectively. © 2014 Elsevier B.V. All rights reserved.
A dual-template imprinted polymer-modified carbon ceramic electrode for ultra trace simultaneous analysis of ascorbic acid and dopamine
(2013) Bhim Bali Prasad; Darshika Jauhari; Mahavir Prasad Tiwari
A dual-template imprinted polymer film containing dispersed multiwalled carbon nanotubes was exploited in the fabrication of a typical, reproducible, and rugged carbon ceramic electrode, adopting "surface grafting from" approach for the growth of a nanometer thin coating on its surface. For this, chloro groups were first introduced at the exterior surface of silica-carbon composite electrode through sol-gel modification using (3-chloropropyl)-trimethoxysilane, followed by an iniferter (sodium diethyl dithiocarbamate) initiated photopolymerization of functional monomer (2,4,6-trisacrylamido-1,3,5-triazine), mixed templates (ascorbic acid and dopamine), and cross-linker (ethylene glycol dimethacrylate), in the presence of multiwalled carbon nanotubes. The modified sensor was validated for the simultaneous analysis of ascorbic acid and dopamine in aqueous, blood serum, cerebrospinal fluid, and pharmaceutical samples, using differential pulse anodic stripping voltammetric technique. The oxidation peak potentials for both analytes were found to be well apart approximately by 300mV, which was large enough to allow selective and sensitive analysis of one in the presence of other, without any cross reactivity, interferences and false-positives. The detection limits realized by the proposed sensor, under optimized conditions, were found to be as low as 2.24ngmL-1 for ascorbic acid and 0.21ngmL-1 for dopamine (S/N=3). Such stringent limits could be considered suitable for the primitive diagnosis of several chronic diseases, in clinical settings. © 2013 Elsevier B.V.
Double imprinting in a single molecularly imprinted polymer format for the determination of ascorbic acid and dopamine
(2011) Mahavir Prasad Tiwari; Rashmi Madhuri; Deepak Kumar; Darshika Jauhari; Bhim Bali Prasad
A new molecularly imprinted polymer - carbon composite fiber is constructed using reversible addition-fragmentation chain transfer polymerization technique. The fiber was evaluated as a sensor for the simultaneous determination of ascorbic acid and dopamine at ultratrace level, in aqueous samples, without any cross-reactivity. The binding characteristics of ascorbic acid and dopamine were also evaluated by differential pulse cathodic stripping voltammetry. © 2011 VBRI press.
Double-ion imprinted polymer @magnetic nanoparticles modified screen printed carbon electrode for simultaneous analysis of cerium and gadolinium ions
(Elsevier B.V., 2015) Bhim Bali Prasad; Darshika Jauhari
A typical, reproducible, and rugged screen printed carbon electrode, modified with dual-ion imprinted beads, was fabricated employing the "surface grafting from" approach. For this, the acyl chloride functionalized magnetic nanoparticles were first immobilized and chemically attached with a typical functional monomer (but-2-enedioic acid bis-[(2-amino-ethyl)-amide]) on the electrode surface. This was subsequently subjected to the thermal polymerization in the presence of template ions (Ce(IV) and Gd(III)), cross-linker (ethylene glycol dimethacrylate), initiator (AIBN), and multiwalled carbon nanotubes. The modified sensor was used for the simultaneous analysis of both template ions in aqueous, blood serum, and waste-water samples, using differential pulse anodic stripping voltammetry which revealed two oxidation peaks for respective templates with resolution as much as 950mV, without any cross reactivity, interferences and false-positives. The detection limits realized by the proposed sensor, under optimized conditions, were found to be as low as 0.07ngmL-1 for Ce(IV) and 0.19ngmL-1 for Gd(III) (S/N=3) that could eventually be helpful for lanthanide estimation at stringent levels. © 2015 .
Doubly imprinted polymer nanofilm-modified electrochemical sensor for ultra-trace simultaneous analysis of glyphosate and glufosinate
(Elsevier Ltd, 2014) Bhim Bali Prasad; Darshika Jauhari; Mahavir Prasad Tiwari
A rapid, selective, and sensitive double-template imprinted polymer nanofilm-modified pencil graphite electrode was fabricated for the simultaneous analysis of phosphorus-containing amino acid-type herbicides (glyphosate and glufosinate) in soil and human serum samples. Since both herbicides respond overlapped oxidation peaks and only glyphosate is prone to nitrosation, n-nitroso glyphosate and glufosinate were used as templates for obtaining the well-resolved quantitative differential pulse anodic stripping voltammetric peaks on the proposed sensor. Toward sensor fabrication, a nano-structured polymer film was first grown directly on the electrode via initial immobilization of gold nanoparticles at its surface. This was followed by linking of monomeric (N-methacryloyl-l-cysteine) molecules through S-Au bonds. Subsequently, these molecules were subjected to free radical polymerization, in the presence of templates, cross linker, initiator, and multiwalled carbon nanotubes as pre-polymer mixture. The modified sensor observed wide linear ranges (3.98-176.23ngmL-1 and 0.54-3.96ngmL-1) of simultaneous analysis with detection limits as low as 0.35 and 0.19ngmL-1 (S/N=3) for glyphosate and glufosinate, respectively, in aqueous samples. The respective oxidation peak potentials of both analytes were found to be substantially apart by 265mV. This enabled the simultaneous determination of one target in the presence of other, without any cross reactivity, interferences, and false-positives, in real samples. © 2014 Elsevier B.V.