Anish Khan

Preparation and characterization of a new organic-inorganic nano-composite poly-o-toluidine Th(IV) phosphate: Its analytical applications as cation-exchanger and in making ion-selective electrode.

An organic-inorganic hybrid poly-o-toluidine Th(IV) phosphate was chemically synthesized by mixing ortho-tolidine into the gel of Th(IV) phosphate in different mixing volume ratios, concentration of inorganic reactant with a fixed mixing volume ratios of organic polymer. The physico-chemical characterization was carried out by elemental analysis, TEM, SEM, XRD, FTIR and simultaneous TGA-DTA studies. The ion-exchange capacity, chemical stability, effect of eluant concentration, elution behavior and pH titration studies were also carried out to understand the ion-exchange capabilities. The distribution studies revealed that the cation-exchange material is highly selective for Hg(2+), which is an important environmental pollutant. Due to selective nature of the cation-exchanger ion-selective membrane electrode was fabricated for the determination of Hg(II) ions in solutions. The analytical utility of this electrode was established by employing it as an indicator electrode in electrometric titrations.

Photocatalytic degradation of a widely used insecticide Thiamethoxam in aqueous suspension of TiO2: Adsorption, kinetics, product analysis and toxicity assessment

This paper deals with the study of photocatalyzed degradation of an insecticide, Thiamethoxam in aqueous suspension of TiO2. The adsorption of Thiamethoxam on TiO2 surface under dark conditions was also investigated in order to find out equilibrium adsorption constant. The degradation kinetics was studied using spectrophotometric method under various conditions such as substrate concentration, type of catalyst, catalyst dosage, pH, and in the presence of electron acceptors such as hydrogen peroxide, potassium bromate, and ammonium persulphate under continuous purging of atmospheric oxygen, and the degradation rates were found to be strongly influenced by these parameters. The results manifested that the photocatalysis of Thiamethoxam follows pseudo-first-order kinetics. The toxicity assessments of the irradiated samples were carried out using human erythrocytes as a model system under in vitro conditions. GC-MS study showed the formation of several intermediate products which were characterised based on their molecular mass and mass fragmentation pattern. A probable mechanism for the formation of various products formed during the photocatalytic process of Thiamethoxam was also proposed.

Electrical conductivity and cation exchange kinetic studies on poly-o-toluidine Th(IV) phosphate nano-composite cation exchange material

An advanced organic-inorganic cation exchange material poly-o-toluidine Th(IV) phosphate nano-composite was synthesized by a modified sol-gel technique by incorporating Th(IV) phosphate precipitate with the matrix of poly-o-toluidine. The material showed good ion-exchange behavior and used successfully in separation of metal ions. The conductivity of the composite was found within the range of 10(-2) to 10(-3)S/cm; measured by 4-in-line-probe dc electrical conductivity measuring technique. The conductivity is at the border of metallic and semiconductor region. Ion-exchange kinetics for few divalent metal ions was evaluated by particle diffusion-controlled ion-exchange phenomenon at four different temperatures. The particle diffusion mechanism is confirmed by the linear tau (dimensionless time parameter) versus t (time) plots. The exchange processes thus controlled by the diffusion within the exchanger particle for the systems studies herein. Some physical parameters like self-diffusion coefficient (D(0))(,) energy of activation (E(a)) and entropy of activation (DeltaS(0)) have been evaluated under conditions favoring a particle diffusion-controlled mechanism.

Multienzyme microbiosensor based on electropolymerized o-phenylenediamine for simultaneous in vitro determination of acetylcholine and choline

The electrochemical biosensors based on poly(o-phenylenediamine) (PoPD) and acetylcholinesterase (AChE) and choline oxidase (ChO) enzymes were fabricated on carbon fibre (CF) substrate. The electropolymerized PoPD was used to reduce the interfering substances. The electrode assembly was completed by depositing functionalized carbon nano tubes (FCNTs) and Nafion (Naf). Amperometric detection of acetylcholine (ACh) and choline (Ch) were realized at an applied potential of +750 mV vs Ag/AgCl (saturated KCl). At pH 7.4, the final assembly, Naf-FCNTs/AChE-ChO((10:1))/PoPD/CF(Elip), was observed to have high sensitivity towards Ch (6.3±0.3 μA mM(-1)) and ACh (5.8±0.3 μA mM(-1)), linear range for Ch (K(M)=0.52±0.03 mM) and ACh (K(M)=0.59±0.07 mM), and for Ch the highest ascorbic acid blocking capacity (97.2±2 1mM AA). It had a response time of <5s and with 0.045 μM limit of detection. Studies on different ratio (ACh/Ch) revealed that 10:1, gave best overall response.

Lead sensors development and antimicrobial activities based on graphene oxide/carbon nanotube/poly(O-toluidine) nanocomposite.

Graphene oxide/carbon nanotube/poly (O-toluidine) (GO-CNT-POT) nanocomposite was prepared by a situ polymerization method and characterized by X-ray powder diffractometry (XRD) and scanning electron microscopy (SEM). The antibacterial activity of the obtained GO-CNT-POT nanocomposite was also evaluated against Gram positive bacteria Bacillus subtilis, Gram negative bacteria Escherichia coli and antibiotics (Amoxicillin) using the agar plate. The antibacterial study showed that the GO-CNT-POT was found to be most effective against both B. subtilis and E. coli respectively which was significant compared to the amoxicillin and the simultaneously GO-CNT-POT nanocomposite were fabricated onto glassy carbon electrode (GCE) using conducting coating binders by I-V technique, where the total analytical parameters were measured for the development of sensitive lead sensors (Pb(2+)). The GO-CNT-POT nanocomposite were deposited on flat-GCE (surface area: ∼0.0316cm(2)) to result in a sensor that has a fast response to selective Pb(2+) ions in buffer system. Features including sensitivity, detection limit, reproducibility, linear dynamic range, selectivity, and electrochemical performances were investigated in details with the GO-CNT-POT nanocomposite fabricated GCE electrodes. The calibration plot is linear (r(2): 0.9907) over the large concentration range (0.1nM to 1.0mM). The sensitivity and detection limit is calculated as 8.53164μAcm(-2)μM(-1) and 89.0 pM (at a signal-to-noise-ratio, SNR of 3) respectively.

Ion-exchange studies on poly-o-anisidine Sn(IV) phosphate nano composite and its application as Cd(II) ion-selective membrane electrode

An organic-inorganic composite, poly-o-anisidine Sn(IV) phosphate, was chemically synthesized by mixing ortho-anisidine into gels of Sn(IV) phosphate with different mixing volume ratios. Studies on the effect of eluant concentration, elution behavior and separation of metal ions were carried out to understand the ion-exchange capabilities. Due to Cd(II) selective nature of composite, revealed by distribution studies, Cd(II) ion selective membrane electrode was fabricated. The analytical utility of the electrode was established by employing it as an indicator electrode in electrometric titrations having fast response time, 3–5s, and long life span of six months. Some physical parameters like self-diffusion coefficient (D0), activation energy (Ea) and entropy of activation (ΔS0) have been evaluated under conditions favoring a particle diffusion-controlled mechanism by studying ion-exchange kinetics.

Mixed micellization of gemini surfactant with nonionic surfactant in aqueous media: a fluorometric study

Herein we report on the study of the interactions between alkanediyl-α,ω-type cationic dimeric (gemini) surfactant and the nonionic Triton X-100 in aqueous medium. The critical micelle concentrations of binary mixtures were determined by fluorometric study. Using the regular solution theory for the analysis of the experimental data, the attractive nature of interactions and synergistic behavior of gemini surfactant and Triton X-100 mixture were demonstrated. The micelle aggregation number was measured using steady state fluorescence quenching method. The micropolarity, binding constant and dielectric constant of mixed systems were determined from the ratio of peak’s intensity (I1/I3) in the pyrene fluorescence emission spectrum.

Chemical sensor development based on poly(o-anisidine)silverized–MWCNT nanocomposites deposited on glassy carbon electrodes for environmental remediation

A poly(o-anisidine)/silverized multiwall carbon nanotube (POAS–Ag/MWCNT) nanocomposite was synthesized by adsorption between POAS and MWCNTs using a solution technique. In this approach, an extended study on the potential development of a chemical sensor was done with the nanocomposites. The sensor was prepared by a simplistic and facile route from the POAS–Ag/MWCNT composites. Here, a thin layer of the POAS–Ag/MWCNT nanocomposites was deposited onto a glassy carbon electrode (GCE) with conducting coating agents to fabricate a selective 3-methoxyphenol sensor with a short response time in a phosphate buffer phase. The fabricated chemi-sensor also exhibited higher sensitivity, large dynamic concentration ranges, long-term stability, and improved electrochemical performance towards 3-methoxyphenol. The calibration plot is linear (r2 = 0.9938) over a large 3-methoxyphenol concentration range (0.4 nM to 40.0 mM). The sensitivity and detection limit are ∼3.829 μA cm−2 mM−1 and ∼0.36 ± 0.05 nM (signal-to-noise ratio at an SNR of 3), respectively. This novel effort initiates a well-organized method of using nanocomposites for efficient sensor improvement towards toxic pollutants in environmental and health-care fields on large scales.

Photocatalytic degradation of herbicide Bentazone in aqueous suspension of TiO2: mineralization, identification of intermediates and reaction pathways

Semiconductor-mediated hydrogen peroxide-assisted photocatalytic degradation of a selected herbicide, Bentazone (1) has been investigated in aqueous suspensions of TiO2 under a variety of conditions. The degradation was studied by monitoring the depletion in total organic carbon content as a function of irradiation time. The degradation kinetics was investigated under different conditions such as type of TiO2 (Anatase/Anatase-Rutile mixture), reaction pH, catalyst dosage and hydrogen peroxide (H2O2) concentration. The degradation rates were found to be strongly influenced by all the above parameters. Titanium dioxide Degussa P25 was found to be more efficient as compared with other two commercially available TiO2 powders like Hombikat UV100 and PC500 from Millennium Inorganic Chemicals. Gas Chromatography-Mass Spectrometry (GC-MS) analysis of the irradiated mixture of Bentazone (1) indicates the formation of several intermediate products which have been characterized on the basis of molecular ion/mass fragmentation pattern and also on comparison with the National Institute of Standards and Technology (NIST) library. Plausible mechanism for the formation of different products during photocatalytic treatment of Bentazone in the presence of TiO2 has been proposed. The use of H2O2 substantially increased the efficiency of TiO2 photocatalytic degradation.

Sensor development of 1,2 Dichlorobenzene based on polypyrole/Cu-doped ZnO (PPY/CZO) nanocomposite embedded silver electrode and their antimicrobial studies

Cu-doped ZnO nanopowders and their composites of polypyrole (PPY)/CZO were prepared by a gel combustion method and an in-situ polymerization process, respectively. The synthesized nanocomposite are characterized by X-ray powder diffractometry (XRD), scanning electron microscopy (SEM), FTIR, and TGA studies. Then the PPY/CZO/AgE nanocomposites were used for potential application in chemical sensing by easy and reliable I-V method, where 1,2 dichlorobenzene (1,2-DCB) is considered as a model target compound. The chemical sensor performances are exhibited the higher sensitivity, good stability, and repeatability of the sensor enhanced significantly using PPY/CZO/AgE of thin-film with conducting binders on silver electrodes (AgE; Surface area: 0.0216cm2). The calibration plot is linear over the large dynamic range (0.35nM∼3.5mM), where the sensitivity (∼2.702μAmM-1cm-2) and detection limit (∼0.34nM) is calculated based on signal/noise ratio (∼3N/S) in short response time. Finally, it is concluded that the structural and optical characteristics could be encompassed to a broad-scale in PPY/CZO/AgE composites and efficient chemical sensor applications for environmental fields. Simultaneously PPY/CZO composites was also evaluated against Gram positive bacteria Bacillus subtilis, Gram negative bacteria Escherichia coli and antibiotics (Amoxicillin) using the agar plate.