Size dependent effects of antifungal phytogenic silver nanoparticles on germination,growth and biochemical parameters of rice (Oryza sativa L), maize (Zea mays L) and peanut (Arachis hypogaea L)

Advancement in materials synthesis largely depends up on their diverse applications and commercialisation. Antifungal effects of phytogenic silver nanoparticles (AgNPs) were evident, but the reports on the effects of the same on agricultural crops are scant. Herein, we report for the first time, size dependent effects of phytogenic AgNPs (synthesised using Stevia rebaudiana leaf extract) on the germination, growth and biochemical parameters of three important agricultural crops viz., rice (Oryza sativa L), maize (Zea mays L) and peanut (Arachis hypogaea L). AgNPs with varied sizes were prepared by changing the concentration and quantity of the Stevia rebaudiana leaf extract. As prepared AgNPs were characterized using the techniques, such as high‐resolution transmission electron microscopy, particle size and zeta potential analyser. The measured (dynamic light scattering technique) average sizes of particles are ranging from 68.5 to 116 nm. Fourier transform infrared studies confirmed the participation of alcohols, aldehydes and amides in the reduction and stabilisation of the AgNPs. Application of these AgNPs to three agricultural crop seeds (rice, maize and peanut) resulted in size dependent effects on their germination, growth and biochemical parameters such as, chlorophyll content, carotenoid and protein content. Further, antifungal activity of AgNPs also evaluated against fungi, Aspergillus niger.Inspec keywords: antibacterial activity, silver, nanoparticles, nanomedicine, biochemistry, crops, transmission electron microscopy, Fourier transform infrared spectra, electrokinetic effects, organic compounds, particle size, plant diseases, microorganismsOther keywords: fungi, Aspergillus niger, size 68.5 nm to 116 nm, silver particles, phytoextract, amide functional groups, aldehydes, alcohols, Fourier transform infrared studies, zeta potential analyser, particle size, high‐resolution transmission electron microscopy, Stevia plant leaf extract, agricultural crops, antifungal effects, materials synthesis, Arachis hypogaea L, peanut, Zea mays L, maize, Oryza sativa L, rice, biochemical parameters, growth, germination, antifungal phytogenic silver nanoparticles, size dependent effects     

Accumulation and residue of napropamide in alfalfa (Medicago sativa) and soil involved in toxic response

Napropamide belongs to the amide herbicide family and widely used to control weeds in farmland. Intensive use of the herbicide has resulted in widespread contamination to ecosystems. The present study demonstrated an analysis on accumulation of the toxic pesticide napropamide in six genotypes of alfalfa (Medicago sativa), along with biological parameters and its residues in soils. Soil was treated with napropamide at 3 mg kg(-1) dry soil and alfalfa plants were cultured for 10 or 30 d, respectively. The maximum value for napropamide accumulation is 0.426 mg kg(-1) in shoots and 2.444 mg kg(-1) in roots. The napropamide-contaminated soil with alfalfa cultivation had much lower napropamide concentrations than the control (soil without alfalfa cultivation). Also, the content of napropamide residue in the rhizosphere was significantly lower than that in the non-rhizosphere soil. M. sativa exposed to 3 mg kg(-1) napropamide showed inhibited growth. Further analysis revealed that plants treated with napropamide accumulated more reactive oxygen species (O(2)(-) and H(2)O(2)) and less amounts of chlorophyll. However, not all cultivars showed oxidative injury, suggesting that the alfalfa cultivars display different tolerance to napropamide.     

Kinetic and equilibrium studies on the removal of Cd2+ ions from water using polyacrylamide grafted rice (Oryza sativa) husk and (Tectona grandis) saw dust

The increase in the use of heavy metals has resulted in an increased flux of metallic substances into the aquatic environment which poses a danger to human health. The present work relates to the removal of cadmium ions by treatment with polyacrylamide grafted rice (Oryza sativa) husk/saguan (Tectona grandis) saw dust. The drinking water guideline value recommended by WHO for cadmium is 0.005 ppm.The adsorbent has been prepared by treatment of rice husk/saw dust with acrylamide. Removal has been studied at various pH values for different times of contact and adsorbate concentrations and is found to be pH-dependent, maximum removal occurs at pH 9 and at a contact time of 180 min for both the adsorbents. The results were found to be consistent with both the Langmuir and Freundlich isotherm models. The value of n (rate constant) determined at pH 9 has been found to be 1 (within experimental limits). This is further substantiated by applying the Lagergren model. The intra-particle diffusion constants were determined by the Morris-Weber model. Continuous flow column studies have also been undertaken and the breakthrough characteristics were determined. Desorption has been affected with 0.5M HCl. The results suggest that both polyacrylamide grafted rice husk/saw dust can be used as efficient and cost effective adsorbents for cadmium ion removal.     

Detection of chemically induced DNA damage in layered films by catalytic square wave voltammetry using Ru(bpy)3(2+).

A sensor constructed by alternate layer-by-layer adsorption of PDDA cations and double-stranded (ds)-DNA on oxidized pyrolytic graphite electrodes was evaluated for detection of chemical damage to ds-DNA from known damage agent styrene oxide. Films made with PDDA ions of structure (PDDA/DNA)2 were approximately 6 nm thick and contained 0.23 microg of ds-DNA. Catalytic oxidation using 50 microM Ru(bpy)3(2+) (bpy = 2,2'-bipyridine) and square wave voltammetry (SWV) provided more sensitive detection of DNA damage than direct SWV oxidation. The catalytic peaks increased linearly with time during incubations with styrene oxide, but only minor changes were detected during incubation with nonreactive toluene. For best sensitivity, the outer layer of the film must be ds-DNA, and analysis should be done at low salt concentration. Studies of DNA and polynucleotides in solutions and films suggested that oxidation of guanine and chemically damaged adenine in partly unraveled, damaged DNA were the most likely contributors to the catalytic peak.     

Use of rice straw as biosorbent for removal of Cu(II), Zn(II), Cd(II) and Hg(II) ions in industrial effluents

Adsorption experiments were carried out using waste rice straw of several kinds as a biosorbent to adsorb Cu(II), Zn(II), Cd(II) and Hg(II) ions from aqueous solutions at room temperature. To achieve the best adsorption conditions the influence of pH and contact time were investigated. The isotherms of adsorption were fitted to the Freundlich equation. Based on the experimental data and Freundlich model, the adsorption order was Cd(II) > Cu(II) > Zn(II) > Hg(II) on the rice straw. This quick adsorption process reached the equilibrium before 1.5 h, with maximum adsorptions at pH 5.0. Thermodynamic aspects of the adsorption process were investigated. The biosorbent material was used in columns for the removal of ions Cu, Zn, Cd and Hg of real samples of industrial effluent and its efficiency was studied.     

Radiation induced damage and recovery in poly(3-hexyl thiophene) based polymer solar cells

Polymer solar cells have been characterized during and after x-ray irradiation. The open circuit voltage, dark current and power conversion efficiency show degradation consistent with the generation of defect states in the polymer semiconductor. The polymer solar cell device remained functional with exposure to a considerable dose (500?krad?(SiO(2))) and showed clear signs of recovery upon removal of the irradiation source (degraded from 4.1% to 2.2% and recovered to 2.9%). Mobility-relaxation time variation, derived from J-V measurement, clearly demonstrates that radiation induced defect generation mechanisms in the organic semiconductor are active and need to be further studied. Optical transmission results ruled out the possibility of reduced light absorption and/or polymer crystallinity. The results suggest that organic solar cells are sufficiently radiation tolerant to be useful for space applications.     

Health risk assessment by measuring plasma malondialdehyde (MDA), urinary 8-hydroxydeoxyguanosine (8-OH-dG) and DNA strand breakage following metal exposure in foundry workers

Silica particles and metals are important occupational hazards in foundry workers, and exposure may result in DNA damage and lipid peroxidation through oxidative stress. This study aimed to compare oxidative damage by measuring the levels of plasma malondialdehyde (MDA), urinary 8-hydroxydeoxyguanosine (8-OH-dG) and DNA strand breakage in workers at two foundry plants (exposure group) and in town hall employees (control group) in central Taiwan. Air samples for metals analysis in the workplace were also collected to assess the health risk to foundry workers.Significantly higher MDA levels (4.28 μM versus 1.64 μM), DNA strand breakage (6.63 versus 1.22), and 8-OH-dG levels (5.00 μg/g creatinine versus 1.84 μg/g creatinine) were found in exposure group compared with the control group. Higher levels of these parameters were also found in workers involved in manufacturing than in workers involved in administration. Higher air respirable dust concentrations were found in manufacturing departments (0.99 mg/m³) than in administrative departments (0.34 mg/m³). The health risk assessment on metals exposure showed that the cancer risk for Cd, Cr and Ni were all above 1 × 10⁻⁶. Future studies are necessary to determine whether metals exposure can contribute to oxidative damage in foundry workers.     

Voltammetric sensor for chemical toxicity using [Ru(bpy)2poly(4-vinylpyridine)10Cl)+ as catalyst in ultrathin films. DNA damage from methylating agents and an enzyme-generated epoxide

Films containing presynthesized [Ru(bpy)2poly(4-vinylpyridine)10Cl)]Cl and ds-DNA grown layer by layer by alternate electrostatic assembly were used to detect DNA damage from an epoxide metabolite and methylating agents on a reaction time scale of minutes. The redox polymer [Ru(bpy)2poly(4-vinylpyridine)10Cl)]Cl was used as an inner layer in films 14-25 nm thick to catalyze the voltammetric oxidation of guanine bases of ds-DNA in the outer layers. This film architecture provides a self-contained, reagentless sensor for toxicity screening based on detection of DNA damage. Films were incubated with reactants and washed, and then DNA damage was analyzed by square wave voltammetry (SWV). Bioactivation of styrene to its metabolite styrene oxide was accomplished by incorporating the protein myoglobin into the films to catalyze the conversion. DNA damage caused the catalytic SWV peaks at approximately 0.75 V vs SCE to increase nearly linearly over the first 10-20 min of reaction, depending on the damage agent employed. Such prototype toxicity biosensors hold promise for in vitro screening of new agricultural chemicals and drugs for potential genotoxicity.     

Effect of the structural and electronic changes induced in poly(3-methylthiophene), PMeT, by the monomer concentration on the characteristics of sprayed CdS(Al)–PMeT based photovoltaic junctions

The direct electrodeposition of 3-methylthiophene (MeT) into poly(3-methylthiophene) (PMeT) on aluminium-doped cadmium sulphide, CdS(Al), in the form of sprayed thin films, leads to a Schottky solid-state junction PMeT–CdS(Al) when PMeT is in its highly doped metal-like state. Attention has been focused on the effect of the parameters of electropolymerization of PMeT. The concentration of the monomer produced significant changes in the photovoltaic parameters of the junction, such as ideality factor (n), saturation current density (J0), barrier height (ΦB), fill factor (FF), series and shunt resistances (Rs, Rsh), and conversion efficiency (η). This revised version was published online in July 2006 with corrections to the Cover Date.