Sharif Ahmad

Iron oxide nanoparticles–chitosan composite based glucose biosensor

Iron oxide (Fe(3)O(4)) nanoparticles prepared using co-precipitation method have been dispersed in chitosan (CH) solution to fabricate nanocomposite film on indium-tin oxide (ITO) glass plate. Glucose oxidase (GOx) has been immobilized onto this CH-Fe(3)O(4) nanocomposite film via physical adsorption. The size of the Fe(3)O(4) nanoparticles estimated using X-ray diffraction (XRD) pattern and transmission electron microscopy (TEM) has been found to be approximately 22 nm. The CH-Fe(3)O(4) nanocomposite film and GOx/CH-Fe(3)O(4)/ITO bioelectrode have been characterized using UV-visible and Fourier transform infrared (FTIR) spectroscopic and scanning electron microscopy (SEM) techniques, respectively. This GOx/CH-Fe(3)O(4)/ITO nanocomposite bioelectrode has response time of 5s, linearity as 10-400 mgdL(-1) of glucose, sensitivity as 9.3 microA/(mgdLcm(2)) and shelf life of about 8 weeks under refrigerated conditions. The value of Michaelis-Menten (K(m)) constant obtained as 0.141 mM indicates high affinity of immobilized GOx towards the substrate (glucose).

A nanostructured cerium oxide film-based immunosensor for mycotoxin detection

Rabbit-immunoglobulin antibodies (r-IgGs) and bovine serum albumin (BSA) have been immobilized onto sol-gel-derived nanostructured cerium oxide (nanoCeO(2)) film fabricated onto an indium-tin-oxide (ITO) coated glass plate to detect ochratoxin-A (OTA). Broad reflection planes obtained in x-ray diffraction (XRD) patterns reveal the formation of CeO(2) nanostructures. Electrochemical studies reveal that nanoCeO(2) particles provide an increased electroactive surface area for loading of r-IgGs with desired orientation, resulting in enhanced electron communication between r-IgGs and electrode. BSA/r-IgGs/nano CeO(2)/ITO immunoelectrode exhibits improved characteristics such as linear range (0.5-6 ng dl(-1)), low detection limit (0.25 ng dl(-1)), fast response time (30 s) and high sensitivity (1.27 microA ng(-1) dl(-1) cm(-2)). The high value of the association constant (K(a), 0.9 x 10(11) l mol(-1)) indicates the high affinity of the BSA/r-IgGs/nanoCeO(2)/ITO immunoelectrode to OTA.

Studies on ambient cured polyurethane modified epoxy coatings synthesized from a sustainable resource

Abstract Polyurethane resins are a class of thermosetting polymers largely used in high performance surface coatings and paints. Fast depletion of petroleum stock and increase in their cost puts limit to their use in future for production of petroleum-based resins. Consequently the need for utilization of renewable resources as substitute to petrochemical is pressing. We have attempted to synthesize polyurethane (PU) from linseed oil epoxy and have developed from it an anticorrosive coating. Trans hydroxylation of linseed oil epoxy was carried out in situ after a reported method. It was further reacted with toluylene diisocyanate to synthesize polyurethane. Physico-chemical characterization of the synthesized resin was carried out as per standard methods. Structural elucidation was carried out using IR, NMR spectral data. Physico-mechanical and weather resistance performance of the coated samples were also studied. It was found that the synthesized resin showed good performance in various corrosion tests. These studies show that the material holds promise for use as an effective anticorrosive coating compound.

Cerium oxide-chitosan based nanobiocomposite for food borne mycotoxin detection

Cerium oxide nanoparticles (NanoCeO2) and chitosan (CH) based nanobiocomposite film deposited onto indium-tin-oxide coated glass substrate has been used to coimmobilize rabbit immunoglobin (r-IgGs) and bovine serum albumin (BSA) for food borne mycotoxin [ochratoxin-A (OTA)] detection. Electrochemical studies reveal that presence of NanoCeO2 increases effective electro-active surface area of CH-NanoCeO2/indium tin oxide (ITO) nanobiocomposite resulting in high loading of r-IgGs. BSA/r-IgGs/CH-NanoCeO2/ITO immunoelectrode exhibits improved linearity (0.25–6.0 ng/dl), detection limit (0.25 ng/dl), response time (25 s), sensitivity (18 μA/ng dl−1 cm−2), and regression coefficient (r2∼0.997).

Development of Novel Bio-Based Soybean Oil Epoxy Resins as a Function of Hardener Stoichiometry

Bio-based epoxy materials were prepared from epoxidized soybean oil (ESO) with an anhydride-curing agent. Variation of anhydride/epoxy ratio (R) was found to have significant effect on the resulting properties of the materials. The properties were studied and compared by dynamic mechanical analysis (DMA), izod impact, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The glass transition temperature reaches the maximum at stoichiometric ratio related to the cross-link density of the formed networks. These materials are thermally stable but exhibit a rapid decrease as the anhydride/epoxy ratio was increased.

Physico-mechanical and electrochemical corrosion behavior of soy alkyd/Fe3O4 nanocomposite coatings

The present article reports the synthesis of butylated melamine formaldehyde (BMF) cured soy alkyd (SA-BMF) and nanoferrite (Fe3O4) dispersed SA-BMF (SA-BMF–Fe3O4) nanocomposite anticorrosive coatings. The structural elucidation of SA-BMF and SA-BMF–Fe3O4 was performed by Fourier transform infra-red (FT-IR) spectroscopy. Physico-mechanical properties such as impact resistance, bend test, scratch hardness, cross hatch adhesion test of these coatings were analyzed by standard protocols. Thermogravimetric analysis (TGA) was used to evaluate the thermal stability of the coating material. The corrosion resistance performance of SA-BMF and SA-BMF–Fe3O4 coated CS was evaluated by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques in 3.5 wt% NaCl solution. The salt spray test for coated and uncoated carbon steel (CS) strips in 5 wt% NaCl solution was also performed. Study revealed that the presence of Fe3O4 nanoparticles played a prominent role in the performance of SA-BMF matrix as reflected by high thermal stability, good hydrophobicity, enhanced physico-mechanical properties and higher corrosion resistance performance. Among different compositions, SA-BMF–Fe3O4-2.5 coatings exhibited far superior physico-mechanical and corrosion inhibition properties than SA-BMF coatings and other similar reported systems. The possible mechanisms of corrosion inhibition by nanocomposite coatings are also discussed.

Synthesis, characterization and the effect of the s-triazine ring on physico-mechanical and electrochemical corrosion resistance performance of waterborne castor oil alkyd

The sustainable resource based volatile organic content (VOC) free coatings with superior anticorrosive properties are some of the most in demand in the surface coating industry. In the present investigation, we report the synthesis of butylated melamine formaldehyde (BMF) cured waterborne castor alkyd (WCA-BMF) using environmentally friendly solvent for anticorrosion applications. The cured resin was characterized by spectroscopic techniques, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The molecular weight of the resin was determined by gel permeation chromatography (GPC). The corrosion protection performance of the coatings on carbon steel strips (CS) was investigated by potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) and the salt spray test. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) examinations were carried out to study the morphology of bare CS and coated CS before and after exposure to a salt spray chamber. The results showed the prominent role played by the amount of BMF in the performance of the castor alkyd, as reflected by the high thermal stability, good adhesion, bending ability (1/8 inch bend test), impact resistance (>100 cm), scratch hardness (7.50 kg), along with good hydrophobicity and high corrosion protection performance. Thus, this study revealed that the presence of the s-triazine moiety in waterborne castor alkyd can produce a high performance corrosion protection coating material via a green route.

Facile green synthesis of nickel nanostructures using natural polyol and morphology dependent dye adsorption properties

Ni nanostructures were synthesized using only castor oil (CSO), a natural polyol through green chemistry. CSO acts as multifunctional reagent (solvent, reducing agent, template, surface modifier) for the synthesis of the Ni nanostructures and imparts dye adsorption ability. The morphology of the nanostructures was found to be influenced by variations in the precursor concentration. A three molar concentration resulted in the formation of nanorods (ca. 11 × 75 nm) due to a higher nucleation rate as compared to growth rate, while a six molar concentration produces nanospheres (ca. 15 nm) due to a higher growth rate. The progress of the reaction, synthesis mechanism and surface functionalization of the Ni nanostructures were analyzed by Fourier transform infrared (FT-IR) spectroscopy. The interaction of Ni2+ with electron rich sites in the CSO resulted in the reduction of Ni2+ to Ni(0). The cubic lattice of the synthesized nanostructures, phase and preferred growth direction of the nanorods along the [200] plane were determined by correlation of X-ray diffraction (XRD) results with that of transmission electron microscopy (TEM) analysis. The adsorption ability of the magnetic Ni nanostructures was analyzed using parameters such as the adsorption kinetics (rate and order of adsorption), maximum adsorption capacity (250 mg g−1 (nanospheres) and 142 mg g−1 (nanorods)), effect of initial concentration of dye/adsorbent and contact time. The Langmuir and Freundlich adsorption isotherms were employed for an understanding of the nature (chemisorption or physisorption) of the dye adsorption. The magnetic nature of the adsorbent helps in the fast, economical separation of an adsorbed particle in comparison to non-magnetic dye adsorbents. The better and favorable adsorption (RL value) of the dye on the synthesized Ni nanostructures, makes them a potential adsorbent for the removal of toxic dyes from industrial effluents.

Effect of Dopant on the Nanostructured Morphology of Poly (1-naphthylamine) Synthesized by Template Free Method

The study reports some preliminary investigations on the template free synthesis of ascantly investigated polyaniline (PANI) derivative—poly (1-naphthylamine) (PNA) by template free method in presence as well as absence of hydrochloric acid (HCl) (dopant), using ferric chloride as oxidant. The polymerization was carried out in alcoholic medium. Polymerization of 1-naphthylamine (NPA) was confirmed by the FT-IR as well as UV–visible studies. The morphology and size of PNA particles was strongly influenced by the presence and absence of acid which was confirmed by transmission electron microscopy (TEM) studies.

Ambient Cured Tartaric Acid Modified Oil Fatty Amide Anticorrosive Coatings

A novel tartaric acid modified fatty amide diol (TAFA) was synthesized through the condensation polymerization of N,N‐bis(2‐hydroxy ethyl) linseed oil fatty amide and tartaric acid (TA).The structural elucidation of the TAFA resin was carried out by FT‐IR,1H‐NMR, and 13C‐NMR spectroscopic techniques. The physico‐mechanical and physico‐chemical characterization of the resin were done by standard methods. TAFA, when further reacted with butylated melamine formaldehyde (BMF) in different phr (part per hundred part of resin) (TAFA‐BMF) was found to cure at room temperature. The TAFA‐BMF cured system was subjected to spectroscopic analysis to ascertain the structure and curing scheme of the same. The thermal studies of these resins were carried out by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The physico‐mechanical properties and anticorrosive performance of TAFA‐BMF coatings were evaluated by standard methods. The effect of TA and BMF on thermal stability, physico‐mechanical and anticorrosive properties of resins was also investigated.