Determination of Synchronous Fluorescence Scan Parameters for Certain Petroleum Products

300-305Synchronous fluorescence scan (SFS) technique is a promising tool for polycyclic aromatic hydrocarbon analysis. For analytical purposes the SFS parameters that are needed to be optimized are Δλ (λex ~ λem) and synchronous fluorescence maximum. In the present work, conventional petroleum products available in Indian market like kerosene and petrol, and added lubricant namely 2T oil have been studied with respect to their SFS parameters. For these multifluorophoric systems conventional electronic absorption and fluorescence spectroscopy is of limited use. The effect of dilution (5 - 100 per cent, v/v in cyclohexane) on the SFS parameters has been examined. In these multifluorophoric systems, excitation energy transfer results in shifting of synchronous fluorescence maxima with increasing concentration of the petroleum product. The correlation of this shift with concentration shows the possibility of using it as an analytical method to quantify the petroleum products in the environment

Characterization and investigation of polycyclic aromatic compounds present in petrol, diesel, kerosene and 2T oil using excitation emission matrix fluorescence

374-379Excitation emission matrix fluorescence fingerprint has been used for characterization of motor oils like diesel, petrol , kerosene and lubricant oil (2T oil). Heavy oil like diesel and 2T oil contain mostly higher membered polycycl ic aromatic compounds, whereas lighter oils like petrol and kerosene contain intermediate polycyclic aromatic compounds along with their lower membered aromatics. Analysis of synthetic mixture of diesel and kerosene has been carried out to check contamination of diesel qualitatively by kerosene. A multivariate method to estimate kerosene and diesel in their mixture comprising their dilute solutions has been used, which gives a satisfactory result. Estimation of 2T oil (0- 10%, v/v) in petrol has been successfully carried out using this technique

Synthesis of Au Nanorods through Prereduction with Curcumin: Preferential Enhancement of Au Nanorod Formation Prepared from CTAB-Capped over Citrate-Capped Au Seeds

Despite seed-mediated growth approach being the state of art method for synthesis of gold nanorods, the mechanism of gold nanorod formation to control final aspect ratio of the nanorods is not yet well understood. In this work, formation of Au nanorods has been investigated using curcumin, a hydrophobic molecule, as secondary reducing agent, instead of popularly used hydrophilic ascorbic acid. It is found that the nature of the secondary reducing agent plays a crucial role in preferential enhancement of Au nanorod formation. Although in the seed-mediated growth approach the concentration of curcumin has similar effect on Au nanorod formation as observed for ascorbic acid earlier, the combination of the nature of the capping agent of seed particles as well as that of the secondary reducing agent determines the final aspect ratio of the nanorods. Hydrophobic (secondary) reducing agent, curcumin, prefers CTAB capped seed solution compared with citrate capped seed solution. The mechanism of nanorod formation has been explored. AgNO₃ is known to enhance the aspect ratio of the nanorod formation when the ascorbic acid and citrate capped seed method is used; however, in contrast when curcumin is used, AgNO₃ encourages nanorod formation for only CTAB capped seed solution but discourages nanorod formation for citrate capped seed solution. A mechanism has been suggested for this discrepancy. Present results help to gain more understanding of the formation process by bringing new insight in the mechanism of Au nanorod formation through seed-mediated growth approach, which may trigger better design of nanomaterials

Ionic Liquid Expedites Partition of Curcumin into Solid Gel Phase but Discourages Partition into Liquid Crystalline Phase of 1,2-Dimyristoyl-<i>sn</i>-glycero-3-phosphocholine Liposomes

The hydrolysis of curcumin in alkaline and neutral buffer conditions is of interest because of the therapeutic applicability of curcumin. We show that hydrolysis of curcumin can be remarkably suppressed in 1,2-dimyristoyl-<i>sn</i>-glycero-3-phosphocholine (DMPC) liposomes. The fluorescence of curcumin sensitively detects the phase transition temperature of liposomes. However, at greater concentrations, curcumin affects the phase transition temperature, encouraging fusion of two membrane phases. The interaction of curcumin with DMPC is found to be strong, with a partition coefficient value of <i>K</i>_p = 2.78 × 10⁵ in the solid gel phase, which dramatically increases in the liquid crystalline phase to <i>K</i>_p = 1.15 × 10⁶. The importance of ionic liquids as green solvents has drawn interest because of their toxicological effect on human health; however, the impact of ionic liquids (ILs) on liposomes is not yet understood. The present study establishes that ILs such as 1-methyl-3-octylimidazolium chloride (moic) affect the permeability and fluidity of liposomes and thus influence parition of curcumin into DMPC liposomes, helping in the solid gel phase but diminishing in the liquid crystalline phase. The <i>K</i>_p value of curcumin does not change appreciably with moic concentration in the solid gel state but decreases with moic concentration in the liquid crystalline phase. Curcumin, a rotor sensitive to detect phase transition temperature, is applied to investigate the influence of ionic liquids such as 1-methyl-3-octylimidazolium chloride, 1-buytl-3-methyl imadazolium tetrafluoroborate, and 1-benzyl-3-methyl imidazolium tetrafluoroborate on DMPC liposome properties. 1-Methyl-3-octylimidazolium chloride lowers the phase transition temperature, but 1-buytl-3-methyl imidazolium tetrafluoroborate and 1-benzyl-3-methyl imidazolium tetrafluoroborate do not perceptibly modify the phase transition temperature; rather, they broaden the phase transition

Thermal and mechanical properties of epoxy resin reinforced with modified iron oxide nanoparticles

Epoxy polymers, having good mechanical properties and thermal stability, are often used for engineering applications. Their properties can be further enhanced by the addition of iron oxide (Fe3O4) nanoparticles (NPs) as fillers to the resin. In this study, pristine Fe3O4 NPs were functionalized with polydopamine (PDA), (3-glycidoxypropyl)trimethoxysilane (GPTMS), and (3-aminopropyl)trimethoxysilane (APTES). X-ray diffraction and scanning electron microscopy (SEM) were used to study any changes in the crystal structure and size of the NPs while Fourier-Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA) were used to ensure the presence of functional groups on the surface. The mechanical properties of the Fe3O4-based nanocomposites generally improved except when reinforced with Fe3O4/PDA. The maximum improvement in tensile strength (∼34%) and fracture toughness (∼13%) were observed for pristine Fe3O4-based nanocomposites. Dynamic mechanical analysis (DMA) showed that the use of any of the treated NPs improved the material's initial storage modulus and had a substantial impact on its dissipation potential. Also, it was observed that the glass transition temperature measurements by DMA and differential scanning calorimetry were below that of pure epoxy. SEM of the cracked surfaces shows that the incorporation of any NPs leads to an enhancement in its thermal and mechanical properties.Peer reviewe