Continuous Percolation Transition in Random Cluster Growth Model

A random cluster growth model is developed in terms of two parameters, the initial seed concentration ρ and the growth probability g of individual clusters. The model is studied on a two dimensional square lattice. For every ρ value, a critical value of g = gc is determined at which a percolation transition is observed. A scaling theory for this model is developed and numerically verified. The scaling functions are found to scale with ρ, g as well as the system size L with appropriate critical exponents. The values of the critical exponents are found to belong to the same universality class of percolation. Finally a phase diagram is developed in the ρ − g parameter space for percolating and non-percolating regions separated by a line of second order phase transition points. (doi: 10.5562/cca2313

Isolation and identification of poly beta hydroxybutyric acid accumulating bacteria of Staphylococcal sp. and characterization of biodegradable polyester

250-256Staphylococcus sp. strain BP/SU1, capable of degrading the biopolymer and utilize it as a source of carbon and energy, was isolated from activated sludge using METABOLIX (MBX D411G). It was found that this strain was capable of accumulating poly(3-hydroxybutyric acid) P(3-HB), as granule poly (3-hydroxybutyric acid), p(3-HB), inclusion bodies when grown under suitable nutrient conditions. These strains could sustain cell growth up to a dry mass of 9.24 g/l with a doubling time of 8 to 10 hr and could accumulate P(3-HB) as granular inclusion bodies to a cell dry weight of more than 12%. P(3-HB) accumulated by this organism was isolated and characterized through NMR, FT- IR spectroscopy, UV Spectroscopy, Mass spectroscopy and Differential Scanning Calorimetry. P(3-HB) granules so isolated showed physical and chemical properties that should be possessed by a superior quality thermoplastic biopolymer

pH and anion sensitive silver(I) coordinated melamine hydrogel with dye absorbing properties: metastability at low melamine concentration

Ag(I)-melamine coordination polymer produces a metastable hydrogel at 1:1 molar ratio but 1:2 molar ratio produces a stable gel which has the helical fibrillar morphology, the ability of selective dye absorption and is highly sensitive to pH and addition of anions

Bi-component hydrogel of perylene-3, 4, 9, 10-tetracarboxylic potassium salt and L-tyrosine

Potassium perylene-3,4,9,10-tetracarboxylate (P) and L-tyrosine (T) produces supramolecular PT complexes viz. PT11, PT12, PT13 and PT14 where the numbers indicate respective molar ratios. PT11 does not produce a hydrogel but the other three produce hydrogels with a minimum gelation concentration of 1.30% (w/v). All PT gels exhibit a fibrillar morphology and the gel melting temperature follows the order PT14 > PT13 > PT12. The frequency independent G' (G' > G'') for PT12, PT13 and PT14 systems characterize them as a gel and the critical yield stress values are 6.0, 3.18 and 0.76 Pa for PT14, PT13 and PT12, respectively. The presence of H-bonding and electrostatic interactions in PT complexes is evident from the FTIR spectra. NMR spectra suggest p-p stacking in both gels and in the PT11 complex, however, there is less p-stacking in the latter. The red shift of the absorption peaks of PT gels compared to that of P is attributed to the J-aggregate formation. The emission peaks also show red shifts and the emission intensity increases significantly. The average life time value decreases in the gels. With increasing temperature, PL-intensity gradually decreases due to the de-stacking of the J-aggregates but the emission peak position shows a step like increase due to batch-wise slipping of PT motifs from J-aggregates

Melamine sensing through riboflavin stabilized gold nanoparticles

Melamine (M) sensing has been achieved through supramolecular assembly with riboflavin (R) via H-bonding in the platform of R stabilized gold nanoparticles (R-Au NPs), by colorimetric as well as UV-vis techniques

Selective colorimetric sensing of mercury(II) using turn off-turn on mechanism from riboflavin stabilized silver nanoparticles in aqueous medium

A simple Hg<SUP>2+</SUP> sensor has been developed using the vitamin B2 (riboflavin) stabilized Ag nanoparticle via a "turn off"-"turn on" mechanism; both the colour and photoluminescence properties of the riboflavin solution are used as sensitizing tools showing a sensitivity up to 5 nM Hg<SUP>2+</SUP> concentration

Effect of complementary small molecules on the properties of bicomponent hydrogel of riboflavin

Three new bicomponent hydrogels of riboflavin (R) with salicylic acid (S), dihydroxybenzoic acid (B) and acetoguanamine (D) in 1:1 molar ratio have been reported. FTIR and UV-vis spectra suggest formation of H-bonded complexes in 1:1 molar ratio of the components. The network consists of tape, bar and helical tubes for RB11, RS11 and RD11 systems, respectively. Reversible first order phase transition and invariant storage modulus (G') with angular frequency (ω) characterise the systems as forming thermoreversible hydrogels. The RD11 gel has the highest gel melting temperature and highest critical strain compared to other gels. WAXS study indicates different crystal structures for different gels. NMR spectra reveals higher shielding of protons in RD11 gel suggesting better p-stacking compared to RS11 and RB11 gels. RD11 gel shows two-fold enhancement of photoluminescence (PL) intensity with a substantial red shift of emission peak but RB11 and RS11 gels show PL-quenching. The gels exhibit a small decrease in lifetime and the PL property is very much temperature and pH dependent. So the complementary molecules have a pronounced effect on morphology, structure, stability and optical property of riboflavin gels