Anupama Singh

Novel cross linked guar gum-g-poly(acrylate) porous superabsorbent hydrogels: Characterization and swelling behaviour in different environments

A new series of eco-friendly cross linked guar gum-g-poly(acrylate) porous superabsorbent hydrogels was prepared by in situ grafting polymerization and cross-linking on to a natural guar gum employing N,N-methylene bis acrylamide as cross linker. Morphological and structural characterization of the prepared hydrogels (SPHs) done by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and solid state C(13) NMR spectroscopy confirmed formation of porous grafted and crosslinked hydrogel structure. Increase in cross linker concentration in the feed mass exhibited decrease in porosity and increase in density of the hydrogels. Swelling of an optimized hydrogel (SPH) in response to external stimuli namely, salt solutions, fertilizer solutions, temperature, and pH exhibited high swelling ratios in various environments. Swelling rate of the SPH was faster than the corresponding nonporous superabsorbent hydrogel. The prepared hydrogels can serve as excellent carriers of pesticides, fertilizers and agriculturally important microbes. Biocontrol formulations based on a representative SPH exhibited excellent shelf-life characteristics and bioefficacy against phytopathogenic fungus Pythium aphanidermatum.

Synthesis and Characterization of Poly (CMC-g-cl-PAam/Zeolite) Superabsorbent Composites for Controlled Delivery of Zinc Micronutrient: Swelling and Release Behavior

A series of novel superabsorbent hydrogel composites, poly(CMC-g-cl-PAam/Zeolite) (ZSAPC) were prepared by in situ graft polymerization using a cellulosic backbone, acrylamide and natural zeolite. The swelling and deswelling behavior of the prepared composites was evaluated and analyzed by different empirical models. The composite with optimum water absorption capacity were impregnated with ZnSO4 in situ during polymerization reaction. Zincated composites showed less water absorption capacity as compared to non-zincated ones. Zinc release behavior of zincated test hydrogel composites was studied in water and soil. All the test compositions exhibited non-Fickian or anomalous transport (0.43 < n < 0.84) and behaved as slow release products. GRAPHICAL ABSTRACT

Base triggered release of insecticide from bentonite reinforced citric acid crosslinked carboxymethyl cellulose hydrogel composites

Biopolymeric clay hydrogels composites, synthesized from crosslinking of carboxymethyl cellulose with citric acid in the presence of bentonite, were used to develop base triggered release formulations (TRFs) of thiamethoxam (3-(2-chloro-1,3-thiazol-5-ylmethyl)-5-methyl-1,3,5-oxadiazinan-4-ylidene(nitro)amine) through an ex-situ encapsulation technique. Hydrogels, hydrogel-bentonite composites and their formulations were characterized by 1H NMR, IR spectroscopy, XRD, and SEM-EDS. Triggered release of thiamethoxam from the developed formulations was studied in water (pH 7-11) with the help of HPLC and subjected to kinetics analysis using different models. The kinetics study showed the release from developed TRFs followed Gallagher-Corrigan equation with an immediate burst release phenomena and higher release rate of thiamethoxam was observed at alkaline pH than neutral condition (pH 7.0). These TRFs of thiamethoxam may be useful for the efficient control of insects which are having alkaline pH in their gut.

Release behavior and bioefficacy of imazethapyr formulations based on biopolymeric hydrogels

ABSTRACT Controlled release formulations of imazethapyr herbicide have been developed employing guar gum-g-cl-polyacrylate/bentonite clay hydrogel composite (GG-HG) and guar gum-g-cl-PNIPAm nano hydrogel (GG-NHG) as carriers, to assess the suitability of biopolymeric hydrogels as controlled herbicide release devices. The kinetics of imazethapyr release from the developed formulations was studied in water and it revealed that the developed formulations of imazethapyr behaved as slow release formulations as compared to commercial formulation. The calculated diffusion exponent (n) values showed that Fickian diffusion was the predominant mechanism of imazethapyr release from the developed formulations. Time for release of half of the loaded imazethapyr (t1/2) ranged between 0.06 and 4.8 days in case of GG-NHG and 4.4 and 12.6 days for the GG-HG formulations. Weed control index (WCI) of GG-HG and GG-NHG formulations was similar to that of the commercial formulation and the herbicidal effect was observed for relatively longer period. Guar gum-based biopolymeric hydrogels in both macro and nano particle size range can serve as potential carriers in developing slow release herbicide formulations.

Investigating Transient Thermal Effects in Flash-Lamp-Pumped Heat Capacity Nd:YAG Rod Laser

Transient thermal effects induced in the laser medium under heat capacity (HC) mode of operation and its influence on the output laser performance is presented. Thermal loading and the resulting negative lensing effects are shown to be different under lasing and nonlasing conditions. Negative refractive power of laser rod affecting the laser resonator stability was observed to be the major cause for the decline in the output power in HC mode. An active resonator model based on measured thermal refractive power is discussed and impact of resonator design parameters on laser beam quality is investigated. An output power of 152 W in HC mode for a run time of 5 s has been obtained. Comparative performance results in conventional continuously cooled (CC) mode is also discussed to highlight the characteristic differences in the two operating modes. Nearly 2-3 times better output beam quality was obtained in HC mode as compared to CC mode.

pH-triggered Release of Boron and Thiamethoxam from Boric Acid Crosslinked Carboxymethyl Cellulose Hydrogel Based Formulations

ABSTRACT Boric acid crosslinked carboxymethyl cellulose hydrogels were synthesized to develop pH-triggered release formulations (pH-TRFs) of boron and thiamethoxam. The developed hydrogels showed pH sensitive water absorption capacity (16.75 to 110.80 g/g xerogel). Entrapment of thiamethoxam was done through an ex-situ loading technique. The boron and thiamethoxam release was studied in pH buffer solutions (4.0, 7.0 and 9.2). Release kinetics analysis using mathematical models showed fast release in high pH solution as compared to acidic pH. These pH-TRFs may find usefulness in selective release of nutrients and pesticides in plant rhizospheric zone of problem soils viz. acidic soils and alkaline soils. GRAPHICAL ABSTRACT

Nanotechnology Prospects and Constraints in Agriculture

Particles at nanoscale has lead revolutionary developments in all major sectors like medicine, pharmaceuticals, drug delivery, electronics and including agriculture and food due to expression of different properties like optical, mechanical, magnetic and other physical properties than their bulk counterparts. The technology deals with study of nanoscale particles and their behavior is called nanotechnology. With increase in demand for feeding the growing population has leading to adopt newer, stable and ecofriendly technologies for sustainable agriculture. Among the advanced technologies, nanotechnology has finding the applications in agricultural and allied sectors. Application of nanotechnology in agriculture has great potential and enhances the quality of life. Increasing applications of nanotechnology in agriculture and allied areas is due to enhanced quality of produce, food quality and safety. Issues leads to utilize nanotechnology in agriculture are climate change, urbanization, sustainable use of natural resources and environmental issues like runoff and accumulation of pesticides and fertilizers. Nanotechnological applications agriculture ranges from nanopesticides, nanofertilizers, controlled delivery devices, water management, soil management, aquaculture, poultry, veterinary, detecting of pathogens, precise agriculture etc. Nanotechnology plays a pivotal role in agriculture from field to plate stage. Different types of nanoparticles which varies in size, shape and chemical nature are utilized at different stages and phases of agriculture, water management, soil management and post-harvest. Like every technology, nanotechnological approaches has its own pros and cons. Emphasis is going on to make nanotechnology safer to humans and environment by increasing its potential and utilizing greener nanomaterials and nanotechnology. This chapter provides a detailed overview potential of nanotechnology in the field of agriculture as different types of nanopesticides, nanoformulations, nanofertilizers, nanosensors, entry and uptake of nanomaterials of utilized nanoparticles in plants, involvement in plant functioning, risks associated with nanotechnology and greener options to overcome the risks. Uptake, translocation and mechanism of action of nanomaterials has been discussed along with its potential. Conventional nanomaterials has finding its potential in almost every phase of agriculture but due to smaller in size its entry into plant, environment and humans is very easy which have risks associated with it and synthesis of nanoparticles involves generation of huge hazardous waste. In order to reduce these risks and toxicological effects in nanotechnology, adoption of greener methods for synthesis of existing nanoparticles, green nanomaterials usage is research trend in present. In this context, present article has given reference of need of green nanotechnology and some of the key points involved in it which aims for nutritional security in agriculture along with safer and sustainable environment.

Hydrogel based formulations of Tagetes patula root extract and MgSO4 to control Meloidogynae incognita in cucumber

Root knot nematode (Meloidogynae incognita) infestation and low magnesium use efficiency are serious constraints in polyhouse cultivation of cucumber. Novel combination formulations of Tagetes patula root extract containing the nematicidal alpha terthienyl (α-T) and magnesium sulfate were prepared, using the biopolymeric hydrogel as carrier. The test products slowly released the nematicidal α-T with half life (t1/2) of 22.97 and 36.87 days, in water and soil, respectively. Magnesium showed fast release till 3 Day. Compared with commercial formulations (carbofuran, Furadan 3G®), these formulations showed significantly higher mortality of M. incognita population under in vivo and polyhouse conditions. In 3-months polyhouse study conducted on cucumber crop during 2011-12, the application of formulations containing Mg alone or Mg in combination with root extract significantly increased the crop yield and showed 83% correlation with the magnesium content of leaves. Besides the morphological and physiological parameters of the crop were also improved.