Manas Roy

Nanoceria based electrochemical sensor for hydrogen peroxide detection

Oxidative stress is a condition when the concentration of free radicals and reactive molecular species rise above certain level in living systems. This condition not only perturbs the normal physiology of the system but also has been implicated in many diseases in humans and other animals. Hydrogen peroxide (H2O2) is known to be involved in induction of oxidative stress and has also been linked to a variety of ailments such as inflammation, rheumatoid arthritis, diabetes, and cancer in humans. It is one of the more stable reactive molecular species present in living systems. Because of its stability and links with various diseases, sensing the level of H2O2 can be of great help in diagnosing these diseases, thereby easing disease management and amelioration. Nanoceria is a potent candidate in free radical scavenging as well as sensing because of its unique redox properties. These properties have been exploited, in the reported work, to sense and quantify peroxide levels. Nanoceria has been synthesized using different capping agents: Hexamethylene-tetra-amine (HMTA) and fructose. CeO2-HMTA show rhombohedral and cubic 6.4 nm particles whereas CeO2-fructose are found to be spherical with average particle diameter size 5.8 nm. CeO2-HMTA, due to the better exposure of the active (200) and (220) planes relative to (111) plane, exhibits superior electrocatalytic activity toward H2O2 reduction. Amperometric responses were measured by increasing H2O2 concentration. The authors observed a sensitivity of 21.13 and 9.6 μA cm(-2) mM(-1) for CeO2-HMTA and CeO2-fructose, respectively. The response time of 4.8 and 6.5 s was observed for CeO2-HMTA and CeO2-fructose, respectively. The limit of detection is as low as 0.6 and 2.0 μM at S/N ratio 3 for CeO2-HMTA and CeO2-fructose, respectively. Ceria-HMTA was further tested for its antioxidant activity in an animal cell line in vitro and the results confirmed its activity.

Cerium oxide nanoparticles promote neurogenesis and abrogate hypoxia-induced memory impairment through AMPK–PKC–CBP signaling cascade

Structural and functional integrity of the brain is adversely affected by reduced oxygen saturation, especially during chronic hypoxia exposure and often encountered by altitude travelers or dwellers. Hypoxia-induced generation of reactive nitrogen and oxygen species reportedly affects the cortex and hippocampus regions of the brain, promoting memory impairment and cognitive dysfunction. Cerium oxide nanoparticles (CNPs), also known as nanoceria, switch between +3 and +4 oxidation states and reportedly scavenge superoxide anions, hydrogen peroxide, and peroxynitrite in vivo. In the present study, we evaluated the neuroprotective as well as the cognition-enhancing activities of nanoceria during hypobaric hypoxia. Using polyethylene glycol-coated 3 nm nanoceria (PEG-CNPs), we have demonstrated efficient localization of PEG-CNPs in rodent brain. This resulted in significant reduction of oxidative stress and associated damage during hypoxia exposure. Morris water maze-based memory function tests revealed that PEG-CNPs ameliorated hypoxia-induced memory impairment. Using microscopic, flow cytometric, and histological studies, we also provide evidences that PEG-CNPs augmented hippocampus neuronal survival and promoted neurogenesis. Molecular studies revealed that PEG-CNPs promoted neurogenesis through the 5′-adenine monophosphate-activated protein kinase–protein kinase C–cyclic adenosine monophosphate response element-binding protein binding (AMPK-PKC-CBP) protein pathway. Our present study results suggest that nanoceria can be translated as promising therapeutic molecules for neurodegenerative diseases.

Seed treatment with iron pyrite (FeS2) nanoparticles increases the production of spinach

Certain nano-materials are known to have plant growth promoting effects, which could find applications in agriculture. We drew inspiration from the nano-factories of deep-sea hydrothermal vents; where iron pyrite nanoparticles serve as fertilizer to sustain chemoautotrophic life forms. We synthesized such iron pyrite nanoparticles in a controlled environment and used them as seed treatment agent (Pro-fertilizer). For us, the term ‘pro-fertilizers’ represents those materials that cause enhanced plant growth with minimum interference to the soil ecosystem when used for seed treatment. We conducted multi-location field trials on spinach crops, since it is a globally popular crop, consumed as both fresh (salads) and processed food. The spinach seeds were treated for 14 hours in an aqueous suspension of iron pyrite nanoparticle (FeS2 + H2O) and thereafter directly sown in the field setup for the experiment. The control seeds were only treated in water for the same duration and sown directly in the field. After 50 days, the crop yields from iron-pyrite nanoparticle treated seeds and control seeds were evaluated. The plants developed from iron pyrite nanoparticle treated seeds exhibited significantly broader leaf morphology, larger leaf numbers, increased biomass; along with higher concentration of calcium, manganese and zinc in the leaves when compared to the plants developed from control seeds. We further investigated the possible mechanism resulting in the biomass enhancement following seed-treatment. Our results indicate that there is an enhanced breakdown of stored starch in the iron pyrite treated seeds resulting in significantly better growth. This raises the possibility of developing iron pyrite nanoparticles as a commercial seed-treatment agent (pro-fertilizer) for spinach crops.

Nano iron pyrite (FeS2) exhibits bi-functional electrode character

Sustainable charge storage devices require materials that are environmentally benign, readily moldable, easily synthesizable, and profitable for applications in the electronics industry. Nano iron pyrite (FeS2) is one such material, which is applicable in diverse areas like photovoltaic devices to seed dressing in agriculture. In this work, we propose an innovative application of nano FeS2viz., as a symmetric charge storage device that is flexible, portable, and lightweight; along with its fabrication details. The device consists of a (H3PO4)/polyvinyl alcohol (PVA) electrolyte gel sandwiched between two similar electrodes made up of FeS2/poly-aniline (PA), upon which graphite sheets are used as current collectors. Electrodes were characterized by XRD, FTIR and SEM. The device was calibrated by cyclic voltammetry and charge–discharge cycle. In its present laboratory prototype form, it powers solid-state electronic devices and electric motors. Further refinements of this device will open up new avenues in the field of sustainable charge storage devices and low power electronics.

Nanodomain cubic cuprous oxide as reusable catalyst in one-pot synthesis of 3-alkyl/aryl-3-(pyrrole-2-yl/indole-3-yl)-2-phenyl-2,3-dihydro-isoindolinones in aqueous medium

An environmentally benign one-pot protocol has been developed for the syntheses of 3-alkyl/aryl-3-(pyrrole/indole-2/3-yl)-2-phenyl-2,3-dihydro-isoindolinones via a multi-component one-pot reaction involving 2-iodo-N-phenylbenzamides, terminal alkyne and substituted indoles/pyrroles in aqueous medium using cubic cuprous oxide nanoparticles as catalyst. It involves domino Sonogashira-5-exo-dig-cyclization followed by regioselective nucleophilic addition of indoles or pyrroles, in aqueous medium without using any surfactants or additional ligands.

Soft magnetic memory of silk cocoon membrane.

Silk cocoon membrane (SCM), a solid matrix of protein fiber, responds to light, heat and moisture and converts these energies to electrical signals. Essentially it exhibits photo-electric and thermo-electric properties; making it a natural electro-magnetic sensor, which may influence the pupal development. This raises the question: ‘is it only electricity?’, or ‘it also posses some kind of magnetic memory?’ This work attempted to explore the magnetic memory of SCM and confirm its soft magnetism. Fe, Co, Ni, Mn, Gd were found in SCM, in traces, through energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma mass spectrometry (ICP-MS). Presence of iron was ascertained by electron paramagnetic resonance (EPR). In addition, EPR-spectra showed the presence of a stable pool of carbon-centric free radical in the cocoon structure. Carbon-centric free radicals behaves as a soft magnet inherently. Magnetic-Hysteresis (M-H) of SCM confirmed its soft magnetism. It can be concluded that the soft bio-magnetic feature of SCM is due to the entrapment of ferromagnetic elements in a stable pool of carbon centric radicals occurring on the super-coiled protein structure. Natural soft magnets like SCM provide us with models for developing eco-friendly, protein-based biological soft magnets.

The seed stimulant effect of nano iron pyrite is compromised by nano cerium oxide: regulation by the trace ionic species generated in the aqueous suspension of iron pyrite

A brief seed pretreatment of 12 hours, in an aqueous suspension of synthesized nano iron pyrite (FeS2), significantly increases the yield of spinach and other crops. The effector mechanism is not clear. An aqueous suspension of FeS2, produces very trace amounts of H2O2, Fe2O3, FeS, FeSO4, Fe(SO4)3, SO2, S and H+ ionic species. Thus for 12 hours, seeds are exposed to this complex aqueous suspension. Among these trace species, H2O2 and Fe2O3 are known seed stimulants and plant growth promoters respectively. In this work, an attempt has been made to quench one of these trace compounds generated in the aqueous suspension of FeS2, viz., H2O2; and the long-term effect on the mature plant was monitored. To test this, along with FeS2, an agriculturally relevant inorganic peroxide scavenger viz., nano cerium oxide (CeO2) was introduced into this system. Four seed pretreatment regimens were followed for the spinach viz., (i) control (water), (ii) FeS2 + water, (iii) CeO2 + water, (iv) FeS2 + CeO2 + water; and growth was monitored for the next 80 days. It was found that, at maturity, CeO2 and FeS2 + CeO2, resulted in significantly smaller leaves, as compared to the control and FeS2; furthermore, FeS2 resulted in leaves with increased chlorophyll and carbohydrate. Thus, the data indicates that by quenching the H2O2, the seed-stimulant effect of FeS2 is compromised. So, while the FeS2 + water suspension functions as a seed vigor enhancer, CeO2 + water on the contrary, functions as a ‘seed vigor reducer’. It is noteworthy, that CeO2 is used by Chinese farmers, as a micro-nutrient to increase crop production. Current data indicates that, it delays germination of seeds, whereas FeS2 hastens germination. Thus such an approach could be used for hastening or delaying germination, manipulating weed population, seed storage in critical conditions, timing the life-cycle of a plant and developing more energy-efficient plants, especially in regions, where there is limited sunlight during significant parts of the year.

Homolytic displacement at saturated carbon centre: Synthesis of benzylsulphones

Abstract The reactions of benzyl cobaloximes with p-substituted benzenesulphonyl chlorides under photochemical conditions form benzyl sulphones by novel S H 2 process.

Nano-iron pyrite seed dressing: a sustainable intervention to reduce fertilizer consumption in vegetable (beetroot, carrot), spice (fenugreek), fodder (alfalfa), and oilseed (mustard, sesamum) crops

AbstractContinuous agricultural innovations are required to feed the exploding human population through natural or artificial resources. Though light is ample on earth, two-third of unavailable ocean and one-third of available soil are major limiting factors to free growth. Excessive fertilizer usage is irreversibly altering the chemical ecology of soil, further reducing the available area. Seed metabolism might be a potential answer to this resource crunch. Without genetic modification and thus maintaining the existing biodiversity, manipulation of seed metabolism at the very onset of germination is a sustainable alternative. The current work presents seed priming with iron pyrite (FeS2) prior to sowing as one such sustainable and innovative intervention to reduce fertilizer consumption in vegetable (beetroot, carrot), spice (fenugreek), fodder (alfalfa), and oilseed (mustard, sesamum) crops. A 12-h seed pretreatment in an aqueous suspension of nano-iron disulfide/pyrite (FeS2) resulted in significant yield increase in the above crops. While agriculturists aim to restore the natural genomic diversity of different domesticated crops, environmental engineers require technologies to reduce fertilizer consumption without compromising agricultural yields, thereby making the planet more sustainable. This nanoscale seed pretreatment approach using FeS2, otherwise a benign earth abundant mineral, suggests the sustainable opportunity to translate this technology to other crops thereby enhancing the global agricultural production.