Current Physical Chemistry - Volume 10, Issue 3, 2020

Aim: Pitting corrosion is a very serious problem for mild steel when it comes in contact with the dilute sulfuric acid medium. Specialized corrosion inhibitors are essentially required to minimize pitting and uniform types of corrosion in mild steel. Background: Most of the corrosion inhibitors discovered so far protects the mild steel from uniform type of corrosion. But pitting corrosion is more fatal than a uniform type of corrosion because it immediately makes mild steel unfit for use as leakage starts from the pit. Objective: The objective was to protect the mild steel alloys from pitting corrosion when comes in contact with dilute sulfuric acid by the use of organic corrosion inhibitor. Methods: Cetyl Trimethyl Ammonium Bromide (CTAB) is tested as a corrosion inhibitor for mild steel in 0.1 N H2SO4 as corroding medium at 25.0, 30.0 and 35.0°C by weight loss, electrochemical polarization, and Impedance spectroscopy methods. Surface study of corroded and un-corroded specimens of mild steel was carried out by Metallurgical Research Microscopy (MRM) and Scanning Electron Microscopy (SEM) techniques. Results: Surface study confirms that the adsorption of CTAB takes place through nitrogen atom resulting in the formation of uniform, nonporous, passive film confirmed by decrease in Warburg Impedance (Zw), decrease in Faradaic current, increase in Capacitive current, an increase in charge transfer resistance, Rct (41 to 401 Ω cm2) and significant increase in capacitive loop in Nyquist plot with increase in concentration of CTAB which results in significant decrease in corrosion rate of mild steel in 0.1N H2SO4 medium (percentage corrosion inhibition efficiency: 95.0%) especially eradicating pitting type of corrosion. Conclusion: CTAB was proved to be a very good anti-pit agent for mild steel in 0.1N sulfuric acid medium. Pitting and uniform type of corrosion was significantly reduced by the use of CTAB as corrosion inhibitor for mild steel in the dilute sulfuric acid medium at 25.0, 30.0 and 35.0°C.

Background: Understanding the interaction between different organic dyes and carbon quantum dots helps us to understand several photo physical processes like electron transfer, energy transfer, molecular sensing, drug delivery and dye degradation processes etc. Objective: The primary objective of this study is to whether the carbon quantum dots can act as an electron donor and can participate in the different photo physical processes. Methods: In this work, Carbon Quantum Dots (CQDLs) are synthesized in most economical and simple carbonization method where petals of Nelumbo nucifera L. are used as a carbon precursor. The synthesized CQDLs were characterized by using experimental techniques like UV−Vis absorption, FT-IR, Transmission Electron Microscopy (TEM), steadystate and time-resolved fluorescence spectroscopy. Results: The spectral analysis shows that the so synthesized CQDLs are spherical in shape and its diameter is around 4.2 nm. It shows the fluorescence emission maximum at 495 nm with a quantum yield of 4%. In this work the interaction between Carbon Quantum Dots (CQDLs) and an organic dye Malachite Green (MG) is studied using fluorescence spectroscopic technique under ambient pH condition (At pH 7). The quenching mechanism of CQDLs with MG was investigated using Stern-Volmer equation and time-resolved fluorescence lifetime studies. The results show that the dominant process of fluorescence quenching is attributed to Forster Resonance Energy Transfer (FRET) having a donor acceptor distance of 53 Å where CQDLs act as a donor and MG acts as an acceptor. Conclusion: This work has a consequence that CQDLs can be used as a donor species for different photo physical processes such as photovoltaic cell, dye sensitized solar cell, and also for antioxidant activity study.

Background: The liquid molar volume (V) and the heat of vaporization (ΔH^VAP) of four fatty acids (n-Heptanoic acid, Hexadecanoic acid, n-Hexanoic acid and n- Dodecanoic acid) have been estimated. Objective: This paper aims to calculate the liquid molar volume and the heat of vaporization of four fatty acids under the critical point using two traditional equations of state: Peng-Robinson (PR) [21] and Soave-Redlich-Kwong. Methods: The area rules method applicable to obtaining the saturation pressure of the compounds has been used. The properties of the acids investigated in this work have been compared with those provided by literature. For molar volumes, the equations of state have given improved predictions when compared to traditional equations such as Rackett equation and so on. According to the vapor enthalpy calculations, no reference value was required. Results: In general, the Clausius-Clapeyron equation provides a better estimation of the vaporization enthalpy of fatty acids when Soave-Redlich-Kwong (SRK) equation was used. The heat of vaporization for fatty acids can be calculated with good reliability in comparison with the Watson equation if suitable equation of state is used. Conclusion: Accurate results for heat of vaporization can be reached in comparison with the Watson equation if the reliable equation of state is used.

Background: Non-Covalent Interactions (NCIs) play a vital role in the chemical process. Certain Experimental and theoretical approaches provide information about the stronger and weaker interactions. In the present work, we have implemented Hirshfeld charges based surface mapping to find the weaker interactions between the molecules of busulfan. Objective: The main objective of this work is to recognize the non-covalent interactions which are not simply drawn from the experimental and conventional theoretical approach. It aims to provide more insightful information into the crystallographic structure. Methods: In the present work, we have implemented a Hirshfeld surface mapping which incorporates periodic boundary conditions of the crystalline geometry. Each point of the isosurface is defined by two distances i.e. de, the distance from the point to the nearest atom outside to the surface and di, the distance to the nearest atom inside the surface. Also, for precise identification of intermolecular interactions, mapping by normalized contact distance dnorm is also considered. Fingerprint plot di vs de for various types of interactions were also provided. Results: The Hirshfeld surface and fingerprint plot show the very weak H···H interactions in addition to the O···H interactions. This enables the visualization of very weak interactions. Conclusion: This proposed work on Hirschfeld surface analysis accounts for the solidstate environment of the busulfan, crystallographic parameters and packing information. Hence, the interactions obtained for monomer and extended molecular framework in this work are more reliable to study the intermolecular interactions. The 2D finger print plots revealed the predominant OH interactions within the crystal packing. In addition to OH interactions, HH interaction were also identified.

Aim: To study the temperature stability of TGS doped with ZnSO4, CdCl2, BaCl2, and compare it with that of pure TGS. Objectives: Synthesizing pure and doped TGS and studying their temperature dependence using TGA, DTA, and DSC analysis. Methods: Slow cooling solution growth was used to grow single crystals of pure and doped TGS. The TGA, DTA and DSC analysis was conducted for determining the temperature stability. Results: The thermal analysis of pure and doped TGS shows that the doped samples show a similar dependence on temperature as pure TGS. The temperature of decomposition of pure and doped samples (BTGS, ZTGS, CdTGS) was 226.60°C, 228.38°C, 229.13°C, and 239.13°C respectively. The melting onset of these samples was 214.51°C, 216.04°C, 217.69°C and 216.04°C respectively. Conclusion: The study shows that doping TGS with the above three described materials did not alter their temperature stability considerably. It is a good result as doping TGS, for varying its characteristics like absorbance, reflectance, bandgap energy, etc., which did not alter its temperature stability. Therefore, TGS doped with the above three dopants can be used at the same temperature ranges as of pure TGS but with much-improved efficiency.

Background: Thermal degradation has attracted the attention of scientific community throughout the world due to its multiple applications in environment, energy, waste water treatment, pollution control, green chemistry, etc. Objective: The present work deals with the study of synthesis and characterization of thermal and biological properties of novel copper complex. Methods: Chemical structures of copper (II) sesame 2-amino-6-ethoxy benzothiazole complex were confirmed by IR, NMR, and ESR techniques. Thermal and biological properties were analysed by Thermogravimetry (TGA) and antimicrobial activity determination against Staphylococcus aureus. Results: The TGA study reveals that copper (II) sesame 2-amino-6-ethoxy benzothiazole complex undergoes stepwise thermal degradation of ligand-soap bond of complex and unsaturated and saturated fatty acid components of edible oils. The complex exhibit significant antimicrobial activities against Staphylococcus aureus. Conclusion: This study provides relevant basic information on the thermal and antimicrobial properties of new copper (II) bio-based surfactants, as well as an explicit relationship structure-biological activity for their potential use as safe and green chemicals.

Aims: The aim of this research work is to synthesise, study and analyse photocatalytic degradation, kinetics. Background: Copper(II) mustard thio urea complex has been synthesized and characterized through FT-IR, NMR, ESR studies. Objective: Photocatalytic degradation of copper(II) mustard thio urea complex was studied in the presence of ZnO as a catalyst in the solution form, using a non polar solvent benzene and a polar solvent methanol with different compositions. Antibacterial activities of copper(II) complex have also been studied against Staphylococcus aureus. Method: O.D. was measured after different time intervals spectrophotometrically to measure the degradation of the complex. Mueller-Hinton agar medium was used for antimicrobial activity of the synthesized compound at different concentrations by disk/ well diffusion susceptibility testing. Result: Plot of 2+ log O.D. (absorbance) versus time was plotted and found to be linear. The heterogeneous photocatalysis followed pseudo-first-order reaction kinetics. The present study suggests that the CMT complex shows antibacterial activity at different concentrations. Conclusion: The rate of photocatalytic degradation of CMT complex was studied and analyzed. It has been found that the rate of degradation varies with different parameters like the concentration of complex, the amount of catalyst, light intensity, solvent polarity etc. The CMT complex derived from natural mustard oil has shown an inhibitory effect on the growth of S. aureus which may cause skin diseases.