Unveiling the molecular interactions and antimicrobial activity of cetyl pyridinium bromide in ternary systems with short tetraalkylammonium bromide salts.

Physicochemical properties of a surfactant cetyl pyridinium bromide (CPB) (0.2-2 mmol kg-1) has been investigated by the addition of greener additives, that is, aqueous tetraalkylammonium bromide (TAAB) salts at different concentrations (0.005, 0.010 and 0.015 mol kg-1) by employing techniques viz: conductivity, fluorescence and UV-visible spectra. In contrast to spectroscopic analysis, which was conducted at room temperature (298.15 K), conductivity measurements were made at various temperatures (298.15, 303.15, 308, and 313.15 K). The obtained electrical conductivity data has been used to compute the critical micelle concentration (cmc), which was also obtained from the UV-Visible and fluorescence methods. It is important to mention that the cmc values obtained from these methods are found to be in good agreement. Various thermodynamic parameters (ΔGmo, ΔHmo, and ΔSmo) have been calculated using conductivity data, the interpretation of which reveals that the interactions between CPB and TAAB are found to be both electrostatic and hydrophobic, however, hydrophobic interactions are found to be dominant in the ternary system. Additionally, the impact of TAAB on the antimicrobial activities of CPB has been evaluated by measuring the zone of inhibition, which explains why the CPB-TAAB system is more effective against gram-positive bacteria (Bacillus cereus and Staphylococcus aureus) than gram-negative bacteria (Escherichia coli and Salmonella typhi).Communicated by Ramaswamy H. Sarma.

Study on Volumetric, Compressibility and Viscometric Behavior of Cationic Surfactants (CTAB and DTAB) in Aqueous Glycyl Dipeptide: A Thermo-Acoustic Approach.

This study aims to understand how glycyl dipeptide affected the compressibility, volumetric behavior and viscometric behavior of the cationic surfactants CTAB (Cetyltrimethylammonium bromide) and DTAB (dodecyltrimethylammonium bromide). Information on solute-solute, solute-solvent, and solvent-solvent interactions has been inferred using the quantification of density (ρ), speed of sound (u) and viscosity in aqueous media containing glycyl dipeptide in the temperature range 293.15-313.15 K at an interval of 5 K. The data from the aforementioned research have been used to enumerate numerous volumetric and compressibility metrics that aid in the collection of information about the interactional behavior of the system under consideration. The study suggests that CTAB interacts strongly compared to DTAB with dipeptide, and it also significantly dehydrates glycyl dipeptide. The difference in water-water interactions caused by the loss of hydrophobic hydration of the surfactant molecules upon the addition of cationic surfactants may be the cause of the variation in determined parameters with surfactant concentration. Consideration of the structural rearrangement of molecules that may occur in the system has been used to explain the results of viscosity and computed factors related to viscosity. The patterns of competitive intermolecular interactions in the ternary (dipeptide + water + surfactant) system have been used to analyze the trends of all the parameters. The study may be helpful to understand the stability and structural changes in protein-surfactant systems mediated through various interactions that may be present in the system.

Volumetric, Compressibility and Viscometric Approach to Study the Interactional Behaviour of Sodium Cholate and Sodium Deoxycholate in Aqueous Glycyl Glycine.

Viscosity, speed of sound (u), and density (ρ) have been measured in aqueous glycyl glycine solution over a temperature range from 293.15 to 313.15 K with a 5 K interlude to evaluate the volumetric and compressibility properties of bio-surfactants, namely sodium cholate (NaC; 1-20 mmol∙kg-1) and sodium deoxycholate (NaDC; 1-10 mmol∙kg-1). Density and viscosity findings provide information on both solute-solute and solute-solvent types of interactions. Many other metrics, such as apparent molar adiabatic compression (κS,φ), isentropic compressibility (κS), and apparent molar volume (Vφ), have been calculated from speed of sound and density measurements, utilising experimental data. The results show that the zwitterionic end group in the glycyl glycine strongly interacts with NaDC and NaC, promoting its micellization. Since the addition of glycyl glycine causes the bio-surfactant molecules to lose their hydrophobic hydration, the observed concentration-dependent changes in apparent molar volume and apparent molar adiabatic compression are likely attributable to changes in water-water interactions. Viscous relaxation time (τ) increases significantly with a rise in bio-surfactant concentration and decreases with increasing temperature, which may be because of structural relaxation processes resulting from molecular rearrangement. All of the estimated parameters have been analysed for their trends with regard to the different patterns of intermolecular interaction present in an aqueous glycyl glycine solution and bio-surfactant system.

Conductometric and Fluorescence Probe Analysis to Investigate the Interaction between Bioactive Peptide and Bile Salts: A Micellar State Study.

The present work deals with the micellar state study of sodium cholate and sodium deoxycholate in the aqueous solution of a bioactive peptide, namely glycyl dipeptide, having different concentrations through conductivity and fluorescence methods at different temperatures. The data obtained from conductivity is plotted against the concentration of Bile salts, and CMC (critical micelle concentration) values are calculated. The results realized have been elucidated with reference to Glycyl dipeptide-bile salts hydrophobic/hydrophilic interactions existing in solution. In addition, the CMC values converted to mole fraction (Xcmc) values have been used to evaluate the standard thermodynamic factors of micellization viz., enthalpy H, free energy ΔGm0, and entropy (ΔSm0) which extract information regarding thermodynamic feasibility of micellar state, energy alteration, and the assorted interactions established in the existing (bile salts-water-glycyl dipeptide) system. Furthermore, the pyrene fluorescence spectrum has also been utilized to study the change in micro polarity induced by the interactions of bile salts with glycyl dipeptide and the aggregation action of bile salts. The decrease in modification in the ratio of intensities of first and third peaks i.e., (I1/I3) for the pyrene molecules in aqueous bile salts solution by the addition of dipeptide, demonstrates that the micelle polarity is affected by glycyl dipeptide. This ratio has also been utilized to determine CMC values for the studied system, and the results have been found to be in good correlation with observations made in conductivity studies.

Synthesis, Characterization, Photocatalytic and Sensing Properties of Mn-Doped ZnO Nanoparticles.

In this paper, Mn-doped ZnO nanoparticles (0 to 10 mol% Mn) were synthesized by facile low-temperature aqueous solution process and characterized by several techniques such as field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-visible and Raman-scattering spectroscopy. The SEM studies confirmed that the synthesized nanoparticles are grown in high density and increase in Mn content was found to have a significant effect on the morphologies of ZnO nanoparticles. The XPS studies established the structural variation of the samples with the change in dopant concentration and its oxidation state. XPS probe the existence of impurity phases in the as-synthesized samples. The results indicate further that hexagonal wurtzite structure of ZnO undergoes distortion with the increase in the dopant concentration. Also, with the increase in the dopant concentration, the blue-shift was observed in the UV-vis. spectra. Photocatalytic and chemicals sensing performances of these nanomaterials have been investigated by subjecting them to photocatalytic degradation of methyl orange (MO) under UV irradiation and for the detection of picric acid (PA) in aqueous solutions. Mn doped ZnO samples were found to be more efficient in catalyzing the MO degradation than pure ZnO. 5 mol% Mn doped ZnO nanomaterials were studied to use as fluorescence sensor for the detection of PA and the observed detection limit was found to be 2.5 µM.

Iron Oxide Nanoparticles as Potential Scaffold for Photocatalytic and Sensing Applications.

Herein, we report photocatalytic and fluorescence sensing applications of iron oxide (α-Fe2O3) nanoparticles synthesized by facile low-temperature simple solution process. The synthesized nanoparticles were characterized by several techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) attached with energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), UV-visible spectroscopy and fluorescence spectroscopy. The detailed analysis revealed that the synthesized nanoparticles were well-crystalline, grown in very high density and possessing rhombohedral α-Fe2O3 crystal structure. The prepared nanoparticles were used as efficient scaffold for photocatalytic and sensing applications. The detailed photocatalysis results revealed that in presence of an appropriate amount of α-Fe2O3 nanoparticles as photocatalyst, a significant dye degradation of methyl orange (MO) was observed in 140 min. In addition, the fabricated florescence sensor based on α-Fe2O3 nanoparticles exhibited a low detection limit of ∼3.33 µM/L towards picric acid. The observed results clearly confirmed that the synthesized α-Fe2O3 nanoparticles are potential scaffold for photocatalysis and sensing applications.

Hexagonal cadmium oxide nanodisks: Efficient scaffold for cyanide ion sensing and photo-catalytic applications.

Herein, we report the large-scale low-temperature aqueous solution based synthesis of hexagonal-shaped cadmium oxide (CdO) nanodisks. The synthesized nanodisks were characterized in detail to investigate the morphological, structural, optical and compositional properties using various analytical tools. The detailed characterizations revealed that the synthesized CdO nanodisks are grown in high-density, possessing well-crystallinity with cubic crystal phase and exhibiting good optical properties. Further, the prepared CdO nanodisks were used as efficient scaffold for cyanide ion sensor and photocatalyst applications. A luminescent sensor for the determination of cyanide ion in aqueous solution was fabricated based on synthesized CdO nanodisks. The fabricated luminescent sensor exhibited an extremely low detection limit (~1.40µmolL(-1)) towards cyanide ion which is significantly lower than the maximum permitted value of cyanide ion by United States Environmental Protection Agency (EPA) for drinking water (7.69µmolL(-1)). The interference studies of the fabricated sensor also demonstrate excellent selectivity towards cyanide ions compared to other coexisting ions. As a photocatalyst, the synthesized CdO nanodisks exhibited high photodegradation (~99.7%) of toxic methyl orange dye just in 90min using 0.25g of CdO nanodisks.

Ag-doped ZnO nanoellipsoids: potential scaffold for photocatalytic and sensing applications.

Well-crystalline Ag-doped ZnO nanoellipsoids (NEs) were synthesized in large quantity and used as effective photocatalyst for the photocatalytic degradation of methyl orange (MO) and efficient electron mediator for the fabrication of highly sensitive, reliable and robust hydrazine chemical sensor. The Ag-doped NEs were synthesized by facile low-temperature (~60°C) solution process and characterized in detail using various characterization techniques. The characterizations revealed that the synthesized nanostructures are well-crystalline, possessing ellipsoidal shapes and were grown in very high density. The photocatalytic activities of these Ag-doped NEs were evaluated by measuring the rate of photodegradation reaction of hazardous methyl orange (MO) dye under UV light irradiation. By comparing the photocatalytic performance of Ag-doped ZnO NEs with those of ZnO nanoflowers, the former was found to be a much superior photocatalyst than the later. Further, Ag-doped ZnO NEs based hydrazine sensor exhibited a high sensitivity of ~9.46 µA/cm(2)µM and detection limit of 0.07 µM in a response time of <10s. Thus we find that Ag-doped ZnO nanomaterials synthesized by simple solution process holds potential as efficient photocatalysts and efficient electron mediators for the fabrication of robust and highly sensitive chemical sensors.