A dipeptide-based synthetic amphiphile bearing a myristyl chain has been found to form hydrogels ... more A dipeptide-based synthetic amphiphile bearing a myristyl chain has been found to form hydrogels in the pH range 6.9-8.5 and organogels in various organic solvents including petroleum ether, diesel, kerosene, and petrol. These organogels and hydrogels have been thoroughly studied and characterized by different techniques including high-resolution transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and rheology. It has been found that the xerogel obtained from the peptide gelator can trap various toxic organic dyes from wastewater efficiently. Moreover, the hydrogel has been used to remove toxic heavy metal ions Pb2+ and Cd2+ from wastewater. Dye adsorption kinetics has been studied, and it has been fitted by using the Freundlich isotherm equation. Interestingly, the gelator amphiphilic peptide gels fuel oil, kerosene, diesel, and petrol in a biphasic mixture of salt water and oil within a few seconds. This indicates that these gels not only may find application in oil spill recovery but also can be used to remove toxic organic dyes and hazardous toxic metal ions from wastewater. Moreover, the gelator can be recycled several times without significant loss of activity, suggesting the sustainability of this new gelator. This holds future promise for environmental remediation by using peptide-based gelators.
A histidine based amphiphile containing a C14 fatty acyl chain, N-histidyl N-myristry ethyl amin... more A histidine based amphiphile containing a C14 fatty acyl chain, N-histidyl N-myristry ethyl amine (AM1, 14.7mM) forms hydrogels in the presence of Fe 3+ (within the range 1.47 to 4.41mM) and Hg 2+ (within the range 3.67 to 11.02 mM) ions in aqueous dispersions at pH 6.6 (27C). The imidazole ring of the histidine residue plays a vital role to interact with these metalions. The thermal and mechanical stability of these metallo-hydrogels can be tuned by changing the proportion of amphiphile to metal ion ratio (1:0.1 to 1:0.3 for Fe 3+ containing gel and 1:0.25 to 1:0.75 for Hg 2+ containing gel). The metallo-hydrogels were characterized by different spectroscopic and microscopic techniques, low-and wide-angle powder X-ray diffraction and small-angle X-ray scattering studies. FT-IR and NMR spectroscopic studies indicate the participation of the imidazole ring in metal-ion binding. Low-and wide-angle powder X-ray diffraction and small-angle X-ray scattering data are in favour of a layered structure of the supramolecular assembly of the AM1 in presence of metal-ions. Both, the amphiphiles and the metal ion induced hydrogels reveal catalytic activity of p-nitrophenyl esters hydrolysis for the acetyl, n-butyl and n-octyl esters. Ferric ion containing metallo-hydrogel exhibits higher catalytic activity than the corresponding AM1 aggregate in the absence of metal-ions.
A rigid pyridine-3,5-bis(5-azabenzimidazole) ligand (L) and linear dicarboxylate sodium terephtha... more A rigid pyridine-3,5-bis(5-azabenzimidazole) ligand (L) and linear dicarboxylate sodium terephthalate (TPA) with Cd(II), Zn(II), and Co(II) under solvothermal conditions afforded water stable and nitrogen-rich MOFs with general formulas [Cd2L2(TPA)2]·12H2O}n, 1, {[Zn4L4(TPA)4]·(DMF)·16H2O}n, 2, and {[Co2L2(TPA)2]·12H2O}n, 3, respectively. These MOFs are found to contain doubly interpenetrated pcu networks with hydrophilic channels. The networks are propagated by M2(CO2)2 SBUs (intermetallic distances 4.0 A) which leads to the formation of a two-dimensional grid structure of metal-terephthalate. The shape of grids varies from rhomboidal to squaric depending on the presence of a metal center. The channels of these MOFs are occupied by the one-dimensional water cages. In the pcu network, each cuboid is found to have dimensions of ∼12.5 A as width and 18.5 A as length. They have shown an excellent ability for water vapor sorption (180–225 cc/g at 298 K). Further, CO2 is found to be the preferred sorbent (70 c...
Copper(I) iodide-catalyzed oxidative C(sp(2))-H functionalization of pyridines and isoquinolines ... more Copper(I) iodide-catalyzed oxidative C(sp(2))-H functionalization of pyridines and isoquinolines for the synthesis of imidazo[1,2-a]pyridines and 2-phenylimidazo[2,1-a]isoquinolines with vinyl azides under mild aerobic conditions is reported. Good selectivity for 3-substituted pyridines and single isomer formation with isoquinolines were observed.
A histidine-containing peptide-based amphiphile (P1) forms a transparent hydrogel within a pH ran... more A histidine-containing peptide-based amphiphile (P1) forms a transparent hydrogel within a pH range of 5.5 to 8.5 in phosphate buffer solution. Interestingly, thermal stability and mechanical stiffness are modulated by incorporating different types of dicarboxylic acids into the hydrogels. Inclusion of succinic acid with the molar ratio 2:1 (peptide:dicarboxylic acid) yields improved properties compared to the other tested dicarboxylic acids such as oxalic, glutaric and octanedioic acids. Transmission electron microscopic (TEM) images show the assembly of nanospheres is responsible for the hydrogel obtained from the assembly of native peptide. However, a morphological transformation takes place from nanosphere to nanofibers, when the peptide gels with succinic acid. XRD and FT-IR studies reveal interactions between peptide amphiphiles and the acids are responsible for the formation of a two-component hydrogel. Gel stiffness is enhanced considerably upon the addition of succinic acid...
A dipeptide-based synthetic amphiphile bearing a myristyl chain has been found to form hydrogels ... more A dipeptide-based synthetic amphiphile bearing a myristyl chain has been found to form hydrogels in the pH range 6.9-8.5 and organogels in various organic solvents including petroleum ether, diesel, kerosene, and petrol. These organogels and hydrogels have been thoroughly studied and characterized by different techniques including high-resolution transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and rheology. It has been found that the xerogel obtained from the peptide gelator can trap various toxic organic dyes from wastewater efficiently. Moreover, the hydrogel has been used to remove toxic heavy metal ions Pb2+ and Cd2+ from wastewater. Dye adsorption kinetics has been studied, and it has been fitted by using the Freundlich isotherm equation. Interestingly, the gelator amphiphilic peptide gels fuel oil, kerosene, diesel, and petrol in a biphasic mixture of salt water and oil within a few seconds. This indicates that these gels not only may find application in oil spill recovery but also can be used to remove toxic organic dyes and hazardous toxic metal ions from wastewater. Moreover, the gelator can be recycled several times without significant loss of activity, suggesting the sustainability of this new gelator. This holds future promise for environmental remediation by using peptide-based gelators.
A histidine based amphiphile containing a C14 fatty acyl chain, N-histidyl N-myristry ethyl amin... more A histidine based amphiphile containing a C14 fatty acyl chain, N-histidyl N-myristry ethyl amine (AM1, 14.7mM) forms hydrogels in the presence of Fe 3+ (within the range 1.47 to 4.41mM) and Hg 2+ (within the range 3.67 to 11.02 mM) ions in aqueous dispersions at pH 6.6 (27C). The imidazole ring of the histidine residue plays a vital role to interact with these metalions. The thermal and mechanical stability of these metallo-hydrogels can be tuned by changing the proportion of amphiphile to metal ion ratio (1:0.1 to 1:0.3 for Fe 3+ containing gel and 1:0.25 to 1:0.75 for Hg 2+ containing gel). The metallo-hydrogels were characterized by different spectroscopic and microscopic techniques, low-and wide-angle powder X-ray diffraction and small-angle X-ray scattering studies. FT-IR and NMR spectroscopic studies indicate the participation of the imidazole ring in metal-ion binding. Low-and wide-angle powder X-ray diffraction and small-angle X-ray scattering data are in favour of a layered structure of the supramolecular assembly of the AM1 in presence of metal-ions. Both, the amphiphiles and the metal ion induced hydrogels reveal catalytic activity of p-nitrophenyl esters hydrolysis for the acetyl, n-butyl and n-octyl esters. Ferric ion containing metallo-hydrogel exhibits higher catalytic activity than the corresponding AM1 aggregate in the absence of metal-ions.
A rigid pyridine-3,5-bis(5-azabenzimidazole) ligand (L) and linear dicarboxylate sodium terephtha... more A rigid pyridine-3,5-bis(5-azabenzimidazole) ligand (L) and linear dicarboxylate sodium terephthalate (TPA) with Cd(II), Zn(II), and Co(II) under solvothermal conditions afforded water stable and nitrogen-rich MOFs with general formulas [Cd2L2(TPA)2]·12H2O}n, 1, {[Zn4L4(TPA)4]·(DMF)·16H2O}n, 2, and {[Co2L2(TPA)2]·12H2O}n, 3, respectively. These MOFs are found to contain doubly interpenetrated pcu networks with hydrophilic channels. The networks are propagated by M2(CO2)2 SBUs (intermetallic distances 4.0 A) which leads to the formation of a two-dimensional grid structure of metal-terephthalate. The shape of grids varies from rhomboidal to squaric depending on the presence of a metal center. The channels of these MOFs are occupied by the one-dimensional water cages. In the pcu network, each cuboid is found to have dimensions of ∼12.5 A as width and 18.5 A as length. They have shown an excellent ability for water vapor sorption (180–225 cc/g at 298 K). Further, CO2 is found to be the preferred sorbent (70 c...
Copper(I) iodide-catalyzed oxidative C(sp(2))-H functionalization of pyridines and isoquinolines ... more Copper(I) iodide-catalyzed oxidative C(sp(2))-H functionalization of pyridines and isoquinolines for the synthesis of imidazo[1,2-a]pyridines and 2-phenylimidazo[2,1-a]isoquinolines with vinyl azides under mild aerobic conditions is reported. Good selectivity for 3-substituted pyridines and single isomer formation with isoquinolines were observed.
A histidine-containing peptide-based amphiphile (P1) forms a transparent hydrogel within a pH ran... more A histidine-containing peptide-based amphiphile (P1) forms a transparent hydrogel within a pH range of 5.5 to 8.5 in phosphate buffer solution. Interestingly, thermal stability and mechanical stiffness are modulated by incorporating different types of dicarboxylic acids into the hydrogels. Inclusion of succinic acid with the molar ratio 2:1 (peptide:dicarboxylic acid) yields improved properties compared to the other tested dicarboxylic acids such as oxalic, glutaric and octanedioic acids. Transmission electron microscopic (TEM) images show the assembly of nanospheres is responsible for the hydrogel obtained from the assembly of native peptide. However, a morphological transformation takes place from nanosphere to nanofibers, when the peptide gels with succinic acid. XRD and FT-IR studies reveal interactions between peptide amphiphiles and the acids are responsible for the formation of a two-component hydrogel. Gel stiffness is enhanced considerably upon the addition of succinic acid...
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