INVESTIGASI EKSTRAK BAHAN ALAM SEBAGAI INHIBITOR KOROSI HIJAU PADA BAJA MENGGUNAKAN TEORI FUNGSIONAL KERAPATAN

Salah satu material yang ketahanannya terhadap korosi rendah adalah baja ketika berinteraksi dengan lingkungan korosif. Penggunaan green inhibitor mampu memberikan kinerja penghambatan korosi yang baik dengan efisiensi inhibisi yang tinggi pada baja. Green inhibitor yang dalam struktur senyawanya mengandung gugus heteroatom (seperti O, N, S, P) dan cincin aromatik efisien digunakan sebagai inhibitor korosi pada baja. Makalah ini memberikan tinjauan komparatif penting bagi pengembangan green inhibitor ekstrak bahan alam pada baja. Kajian DFT pada level atomik berdasarkan orbital molekuler, parameter kuantum kimia, dan karakteristik adsorpsi menunjukkan hasil yang sesuai dengan hasil eksperimen. Distribusi kerapatan elektron melalui plot Frontier Molecular Orbitals (FMO) menggambarkan prediksi situs aktif melalui distribusi daerah HOMO-LUMO molekul inhibitor yang berinteraksi dengan permukaan baja. Untuk mendapatkan korelasi antara sifat elektronik molekul inhibitor dengan potensi penghambatan (inhibisi) korosi, kalkulasi parameter kimia kuantum seperti potensial ionisasi (I), afinitas elektron (A), kekerasan global (η), elektronegativitas absolut (χ), kelembutan global (σ), fraksi elektron yang ditransfer (ΔN), elektrofilisitas global (ɷ) dan donasi balik elektron (ΔEback-donation) menunjukkan reaktivitas molekul inhibitor yang berpotensi sangat baik untuk dapat berinteraksi dan berikatan kuat dengan permukaan logam, sehingga berpotensi menghasilkan efisiensi inhibisi yang tinggi. Mekanisme inhibisi korosi dapat melalui adsorpsi kimia dan/atau adsorpsi fisika dengan membentuk senyawa kompleks antara molekul inhibitor dengan permukaan baja untuk melindungi dari lingkungan korosif. Pengembangan kajian ke depan harus dapat menampilkan mekanisme interaksi dan inhibisi dari molekul inhibitor secara lebih detail dan sistematis pada level atomik pada beberapa permukaan logam seperti Fe, Al, Cu, dan lainnya.

Interaction of a conical carbon scaffold with the thio-substituted model of fluorouracil towards approaching the drug delivery purposes

A representative FeN4-doped conical carbon (C) scaffold was investigated for participating in interactions with the thio-substituted fluorouracil (SFU) anticancer drug by performing density functional theory (DFT) calculations. In this regard, all possible relaxation configurations of SFU at the doped tip of C scaffold were examined, in which three models were obtained including one horizontal relaxation configuration (FC1) and two vertical relaxation configurations (FC2 and FC3). The results indicate the highest stability and strength for FC1 model. Examining formations and strengths of interactions showed two medium strength interactions in each of FC1, FC2, and FC3 models. Moreover, the evaluated electronic molecular orbitals features indicated availability of sensor function for the proposed C scaffold towards the interacting SFU substance. As a consequence, the models were determined to work in dual functions of sensor and carrier towards drug delivery purpose of SFU anticancer drug.

“Like-Likes-Like” strategy for the design of electron transport materials and emitters with facilitated interlayer electron transport and improved efficiency

A novel strategy, named as “Like-Likes-Like” due to the resembled characters of structures, molecular orbitals, and ground/excited-states, is proposed for the design of electron transport materials (ETMs) and emitters with...

Investigating drug delivery of 5-fluorouracil by assistance of an iron-modified graphene scaffold: Computational studies

This computational work was performed to investigate drug delivery of 5-fluorouracil (FU) anti-cancer by assistance of an iron(Fe)-modified graphene (G) scaffold. The models were optimized to reach the minimized energy structures in both of singular and bimolecular models. Two models of FU@G complex were obtained including O2@G and O4@G by relaxation of FU through O2 and O4 atoms towards the Fe-atom region of G surface. The obtained results of energies indicated a higher stability and strength for the O2@G model in comparison with the O4@G model. The quantitative and qualitative features of electronic molecular orbitals indicated the investigated G surface could work as a carrier of FU by reducing the unwanted side effects and also playing the sensor role. As a final remark of this work, the investigated G model could be proposed for employing in the targeted drug delivery of FU in both of carrier and sensor agents.

A conversation on the quartic equation of the secular determinant of methylenecyclopropene

The Hückel method (HM) is based on quantum mechanics and it is used for calculating the energies of molecular orbitals of π electrons in conjugated systems. The HM involves the setting up of the secular determinant which is expanded to obtain a polynomial which is to be solved. In general, the polynomial is one which may be factorized. However, in May 2020, students brought to my attention that the secular determinant of methylenecyclopropene could not be factorized completely. As a result of this, we used a combination of online tools, technology and visualization to calculate the roots of the secular determinant. This write-up, in a playwriting format, describes the conversation between the facilitator and the students.

Application of computational chemistry in chemical reactivity: a review

Molecular orbitals are vital to giving reasons several chemical reactions occur. Although, Fukui and coworkers were able to propose a postulate which shows that highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) is incredibly important in predicting chemical reactions. It should be kept in mind that this postulate could be a rigorous one therefore it requires an awfully serious attention in order to be understood. However, there has been an excellent breakthrough since the introduction of computational chemistry which is mostly used when a mathematical method is fully well built that it is automated for effectuation and intrinsically can predict chemical reactivity. At the cause of this review, we’ve reported on how HOMO and LUMO molecular orbitals may be employed in predicting a chemical change by the utilization of an automatic data processing (ADP) system through the utilization of quantum physics approximations.

Electromechanical Characteristics by a Vertical Flip of C70 Fullerene Prolate Spheroid in a Single-Electron Transistor: Hybrid Density Functional Methods

In this study, the B3LYP hybrid density functional theory was used to investigate the electromechanical characteristics of C70 fullerene with and without point charges to model the effect of the surface of the gate electrode in a C70 single-electron transistor (SET). To understand electron tunneling through C70 fullerene species in a single-C70 transistor, descriptors of geometrical atomic structures and frontier molecular orbitals were analyzed. The findings regarding the node planes of the lowest unoccupied molecular orbitals (LUMOs) of C70 and both the highest occupied molecular orbitals (HOMOs) and the LUMO of the C70 anion suggest that electron tunneling of pristine C70 prolate spheroidal fullerene could be better in the major axis orientation when facing the gate electrode than in the major (longer) axis orientation when facing the Au source and drain electrodes. In addition, we explored the effect on the geometrical atomic structure of C70 by a single-electron addition, in which the maximum change for the distance between two carbon sites of C70 is 0.02 Å.