Theoretical investigation on electron transfer-based antioxidant activity of melinjo resveratrol

We employ density functional calculations to study the electron transfer-based antioxidant activity of resveratrol derivatives from melinjo. The derivatives are monomer resveratrol which is trans-resveratrol, and dimer resveratrol which are gnetin C, gnetin L, and gnemonoside C. The results show that gnetin C has the lowest adiabatic ionization potential both in gas phase and water environment. Furthermore, our results demonstrate that dimer resveratrol is consistent to have better electron transfer ability than its monomer. This may due to the destabilization of the high occupied molecular orbital energy of resveratrol. However, the presence of glucoside in gnemonoside C does not affect the electron transfer-based antioxidant activity of dimer resveratrol

Synthesis of zeolite and y-alumina nanoparticles as ceramic membranes for desalination applications

Development of ceramic membrane for desalination is gaining interest in order to provide fresh water for human's life. In this work, a ceramic membrane was developed by coating of porous geopolymer with nanoparticles of gamma alumina (γ-Al2O3) (Al membrane), zeolite (Z membrane), and its combination (Al-Z membrane) which were synthesized through a sol-gel method. Nanoparticles of γ-Al2O3 exhibit rod structures with 10-20 nm in diameter and 40-70 nm in length, a surface area of 326.26 m2/g, total pore volume of 0.10 cm3/g, and an average pore diameter of 2.10 nm. Zeolite nanoparticles were obtained from a composition of 6Na2O: 0.55Al2O3: SiO2: 150H2O having particle sizes in the range from 100 to 400 nm, a surface area of 97.32 m2/g, total pore volume of 0.80 cm3/g, and an average pore diameter of 11.19 nm. The performance of membranes was evaluated by measuring the salt rejection and the flux of NaCl 1% (w/v) solution that was passed through the membrane. The Z membrane demonstrated the highest salt rejection, up to 87.88%, whereas the Al-Z membrane reached 68%. The Al membrane exhibited the lowest salt rejection rate, amounted to 57.14%. The highest flux was obtained using Al membrane, which was to 3.43 × 103 L/m2h on the 54.29% rejection value; whereas the Z membrane reached 3.28 × 103 L/m2h on the 87.88% salt rejection value, and the lowest flux of 2.91 × 103 L/m2h showed by the Al-Z membrane at the 62% salt rejection value. It is promising to use the synthesized γ-Al2O3 and zeolite nanoparticles as alternative ceramic membrane materials to be applied in the desalination

Oxygen reduction reaction mechanism on a phosporus-doped pyrolyzed graphitic Fe/N/C catalyst

The oxygen reduction reaction (ORR) mechanism on the active sites of a phosphorus-doped pyrolyzed Fe/N/C catalyst is examined by using density functional theory based calculations. The introduction of the phosphorus dopant creates three initial possible active sites for the ORR i.e., FeN4, C–N and P-doped sites. In the presence of O2, the P-doped sites become passivated while the rest of the catalyst sites are still functional. The ORR profile for the associative mechanism (the O2 molecule is reduced from its molecular form) on the FeN4 site is practically unaffected by the presence of the neighboring P[double bond, length as m-dash]O site. However, the ORR profile for the dissociative mechanism (the O2 molecule is reduced from its dissociated form) on the FeN4 site is significantly improved as compared to that on the undoped Fe/N/C catalyst system. This phenomenon is mainly induced by the distortion of C–C networks due to the presence of the neighboring FeN4 and P[double bond, length as m-dash]O sites, which leads to the stabilization of the *OH adsorption state on the C atoms next to the FeN4 site

Theoretical exploration on free radical scavenging mechanism of curcumin analogues in water solvent

One way to improve curcumin's possibility in preventing lipid peroxidation is through modification of carbon linker, β-diketone group and aromatic rings. However, there remains a need to explore the role of carbon linker on the free radical scavenging mechanisms of curcumin. This study uses density functional theory to explore two descriptors of free radical scavenging mechanisms, which are bond dissociation enthalpy (BDE) and adiabatic ionization potential (AIP) of curcumin and its analogues. Five analogues with different amount of carbon atoms in the linker in the presence / absence of β-diketone group are chosen. Our result shows that decreasing the amount of carbon atom from 7 to 5 atoms in the linker decreases the BDE at β-diketone group of the curcumin analogue. Moreover, increasing the amount of carbon atoms in the linker decreases the AIP of the analogues

Ab initio study for structure, electric properties and light emission of linear-trans-quinacridone

The structure, electric properties and emission rate of linear-trans-quinacridone are investigated within the density functional theory (DFT) calculations. We find the structure of the molecule to be planar with an energy gap of 3.06 eV. The emission lifetime from the lowest unoccupied molecular orbital (LUMO) to the highest occupied molecular orbital (HOMO) of this material is found to be 24 ns, which is in good agreement with experimental results

Ab initio study for structure, electric properties and light emission of linear-trans-quinacridone

The structure, electric properties and emission rate of linear-trans-quinacridone are investigated within the density functional theory (DFT) calculations. We find the structure of the molecule to be planar with an energy gap of 3.06 eV. The emission lifetime from the lowest unoccupied molecular orbital (LUMO) to the highest occupied molecular orbital (HOMO) of this material is found to be 24 ns, which is in good agreement with experimental results