Formation and characterization of leaf waste into organic compost.

In solid waste management, pollution-free disposal of leaf waste in urban areas is still not standardized and adopted. According to the World Bank report, 57% of wastes generated in South East Asia are consisted of food and green waste, which can be recycled into valuable bio-compost. The present study shows a method of leaf litter waste management by composting it using essential microbe (EM) method. Different parameters, such as pH, electrical conductivity, macronutrients, micronutrients, and potentially toxic elements (PTE) were measured at zero to 50 days of composting using appropriate methods. The microbial composting was shown to mature within 20 to 40 days, and its maturity could be evaluated by the attainment of stable pH (8), electrical conductivity (0.9 mS/cm), and C:N ratio ≥ 20. The analysis was also performed on other bio-composts viz. kitchen waste compost, vermicompost, cow dung manure, municipal organic waste compost, and neem cake compost. The fertility index (FI) was evaluated based on six parameters viz. total carbon, total nitrogen, N ratio, phosphorus, potassium, and sulphur contents. The PTE values were used to calculate their clean index (CI). The results showed that leaf waste compost has a higher fertility index (FI = 4.06) than other bio-composts, except the neem cake compost (FI = 4.44). The clean index of the leaf waste compost (CI = 4.38) was also higher than other bio-composts. This indicates that leaf waste compost is a valuable bio-resource with high nutritive value and low PTE contamination, with a favourable prospective to be used in organic farming.

Contrasting reactions of hydrated electron and formate radical with 2-thio analogues of cytosine and uracil.

2-Thiocytosine (TC) and 2-thiouracil (TU) were subjected to hydrated electron (eaq-), formate radical (CO2˙-) and 2-hydroxypropan-2-yl radical ((CH3)2˙COH) reactions in aqueous medium. Transients were characterized by absorption spectroscopy and the experimental findings were rationalized by DFT calculations at LC-ωPBE and M06-2X levels using a 6-311+G(d,p) basis set and SMD solvation. In eaq- reactions, a ring N-atom protonated radical of TC and an exocyclic O-atom protonated radical of TU were observed via addition of eaq- and subsequent protonation by solvent molecules. However, two competing but simultaneous mechanisms are operative in CO2˙- reactions with TC and TU. The first one corresponds to formations of N(O)-atom protonated radicals (similar to eaq- reactions); the second mechanism led to 2 center-3 electron, sulfur-sulfur bonded neutral dimer radicals, TCdim˙ and TUdim˙. DFT calculations demonstrated that H-abstraction by CO2˙- from TC(TU) results in S-centered radical which upon combination with TC(TU) provide the dimer radical. In some cases, DFT energy profiles were further validated by CBS-QB3//M06-2X calculations. This is the first time report for a contradictory behavior in the mechanisms of eaq- and CO2˙- reactions with any pyrimidines or their thio analogues.

Effect of Molecular Interactions on Electron-Transfer and Antioxidant Activity of Bis(alkanol)selenides: A Radiation Chemical Study.

Understanding electron-transfer processes is crucial for developing organoselenium compounds as antioxidants and anti-inflammatory agents. To find new redox-active selenium antioxidants, we have investigated one-electron-transfer reactions between hydroxyl ((.) OH) radical and three bis(alkanol)selenides (SeROH) of varying alkyl chain length, using nanosecond pulse radiolysis. (.) OH radical reacts with SeROH to form radical adduct, which is converted primarily into a dimer radical cation (>Se∴Se<)(+) and α-{bis(hydroxyl alkyl)}-selenomethine radical along with a minor quantity of an intramolecularly stabilized radical cation. Some of these radicals have been subsequently converted to their corresponding selenoxide, and formaldehyde. Estimated yield of these products showed alkyl chain length dependency and correlated well with their antioxidant ability. Quantum chemical calculations suggested that compounds that formed more stable (>Se∴Se<)(+) , produced higher selenoxide and lower formaldehyde. Comparing these results with those for sulfur analogues confirmed for the first time the distinctive role of selenium in making such compounds better antioxidants.

Binding of a cyclic organoselenium compound with gold nanoparticles (GNP) and its effect on electron transfer properties.

Binding of a cyclic organoselenium compound, DL-trans-3,4-dihydroxy-1-selenolane (DHSred) with gold nanoparticles (GNP) of different sizes was studied by absorption spectroscopy, dynamic light scattering (DLS), transmission electron microscope (TEM), surface enhanced Raman spectroscopy (SERS) and zeta-potential (ζ) measurements. GNP of different size were synthesized by varying the reaction conditions and their size was determined by DLS and TEM techniques. The absorption spectral data showed red shift in the surface plasmon resonance (SPR) band indicating increase in the size of GNP on binding to DHSred. SERS studies confirmed that the binding of DHSred with GNP is through selenium center with planar orientation of DHSred on the GNP surface. The product of the number of binding sites (n) in GNP and the binding constant (K) was estimated for GNP of different particle size. The zeta potential (ζ) value of GNP decreased marginally in the presence of DHSred. Further, the binding of DHSred with GNP was found to enhance its reactivity with 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radicals (ABTS(·-)) and the reactivity increased with decrease in the GNP size. Such enhancement in the reducing ability may have a greater impact on the antioxidant activity of DHSred.