Effect of head group polarity and spacer chain length on the aggregation properties of gemini surfactants in an aquatic environment

The aggregation behavior of cationic gemini surfactants with respect to variation in head group polarity and spacer length is studied through conductance, surface tension, viscosity, and small-angle neutron-scattering (SANS) measurements. The critical micellar concentration (cmc), average degree of micelle ionization (beta(ave)), minimum area per molecule of surfactant at the air-water interface (A(min)), surface excess concentration (gamma(max)), and Gibb's free energy of micellization (delta G(mic)) of the surfactants were determined from conductance and surface tension data. The aggregation numbers (N), dimensions of micelles (b/a), effective fractional charge per monomer (alpha), and hydration of micelles (h(E)) were determined from SANS and viscosity data, respectively. The increasing head group polarity of gemini surfactant with spacer chain length of 4 methylene units promotes micellar growth, leading to a decrease in cmc, beta(ave), and delta G(mic) and an increase in N and b/a. This is well supported by the observed increase in hydration (h(E)) of micelles with increase in aggregation number (N) and dimension (b/a) of micelle.     

Improved time efficiency and accuracy in diffusion tensor microimaging with multiple-echo acquisition

In high-field NMR microscopy rapid single-shot imaging methods, for example, echo planar imaging, cannot be used for determination of the apparent diffusion tensor (ADT) due to large magnetic susceptibility effects. We propose a pulse sequence in which a diffusion-weighted spin-echo is followed by multiple gradient-echoes with additional diffusion weighting. These additional echoes can be used to calculate the ADT and maps. We show here that this results in modest but consistent improvements in the accuracy of ADT determination within a given total data acquisition time. The method is tested on excised, chemically fixed rat spinal cords.     

Coupling between helix-coil and coil-globule transitions in helical polymers

We explore the coupling between the helix-coil and coil-globule transitions of a helical polymer using Monte Carlo simulations. A very rich state diagram is found. Each state is characterized by a specific configuration of the chain which could be a helix, a random coil, an amorphous globule, or one of various other globular states which carry residual helical strands. We study the boundaries between states and provide further insight into the physics of the system with a detailed analysis of the order parameter and other properties.     

Synthesis of GaN phase by ion implantation

GaN phase is synthesized using systemic implantation of nitrogen ions of multiple energies (290, 130 and 50 keV) into Zn-doped GaAs (1 0 0) at room temperature and subsequent annealing at 850 °C for 30 min in Ar + H₂ atmosphere. The implanted doses of nitrogen ions are 5 × 10¹⁶ and 1 × 10¹⁷ ions-cm⁻². Glancing angle X-ray diffraction studies show that hexagonal phase of GaN were formed. The photoluminescence studies show the emission from the band edge as well as from point defects.     

Synthesis and biological evaluation of new 2-aryl-4-((4-aryl-1H-1,2,3-triazol-1-yl)methyl)thiazole derivatives

Research on Chemical Intermediates - A series of 2-aryl-4-((4-aryl-1H-1,2,3-triazol-1-yl)methyl)thiazole derivatives (8a–p) have been synthesized. The structure of the newly synthesized...     

Deposition of CTAB-terminated nanorods on bacteria to form highly conducting hybrid systems

Gold nanorods and nanospheres capped with positively charged CTAB are deposited on the surface of gram-positive bacterium having negatively charged teichoic acid brushes. The deposition rate is more than an order of magnitude faster than that for peptide and nucleic acid capped nanoparticles. For the nanorods, never been reported before, the strong electrostatic attraction causes the rods to bend conformally over the curved bacterium surface in random orientations. This leads to formation of an efficient percolating cluster (i.e., low contact resistance and high radius of gyration) with 104-fold higher current at 3-fold lower coverage compared to a monolayer from nanospheres. The high monolayer conductivity at only approximately 10% coverage for nanorods has potential for fabricating a novel class of bioelectronic devices by coupling electronic "nanocircuitry" at the surface to the biological function of microorganisms.     

Facile synthesis of layered reduced graphene oxide–copper sulfide (rGO-CuS) hybrid electrode for all solid-state symmetric supercapacitor

A straightforward process for synthesis of hybrid porous electrode material composed of reduced graphene oxide (rGO) and copper sulfide (CuS) with layered structure on the stainless steel substrate is developed. As-synthesized hybrid electrode shows hexagonal crystal structure of CuS with 77 m² gm⁻¹ specific surface area and 22 nm average pore size. The specific capacitance obtained with rGO-CuS5 hybrid electrode is 1201 F g⁻¹ at the sweep rate of 5 mV s⁻¹ in 1 M LiClO₄ aqueous electrolyte. The majority of charge stored by diffusion-controlled process indicates benefits of layered structures for solid-state energy storage. The rGO-CuS5-based hybrid symmetric supercapacitor delivers a specific capacitance (C_s) as high as 109 F g⁻¹ at a sweep rate of 5 mV s⁻¹ with polyvinyl alcohol (PVA)-LiClO₄ gel electrolyte. Also, the specific energy of 44 Wh kg⁻¹ and specific power of 1.4 kW kg⁻¹ with 87% stability after 6000 cycles at an applied current of 5 mA are obtained. The simple process of synthesis of layered hybrid electrode material for flexible supercapacitor promises its use in smart textile and wearable electronic devices.

Graphical abstract

     

Synthesis and Antimicrobial Activities of Novel 2‐[substituted‐1H‐pyrazol‐4‐yl] Benzothiazoles,Benzoxazoles, and Benzimidazoles

In an endeavor to find a new class of antimicrobial agents, a series of novel substituted benzimidazole, benzoxazole, and benzothiazole derivatives 6 containing pyrazole moiety have been synthesized by reaction of 3‐aryl‐4‐formyl pyrazole 4 with substituted phenylenediamine or o‐aminophenol or o‐aminothiophenol 5 . Reaction of phenyl hydrazine or 2‐hydrazinopyridine 1 with substituted acetophenones 2 gave the corresponding hydrazones 3 , which on Vilsmeier–Haack reaction with POCl₃–DMF gave substituted 3‐aryl‐4‐formyl pyrazoles 4 . All final compounds 6a , 6b , 6c , 6d , 6e , 6f , 6g , 6h , 6i , 6j , 6k were evaluated for in vitro antibacterial activities against Escherichia coli and Staphylococcus aureus strains and in vitro antifungal activity against Candida albicans and Aspergillus niger strains by using serial dilution method. The antimicrobial activities were expressed as the minimum inhibitory concentration in µg/mL. The compound containing benzimidazole and benzoxazole moiety gave better antibacterial and antifungal activities than benzothiazole compounds.     

A comparative study of chiral separation of proton pump inhibitors by supercritical fluid chromatography and high-performance liquid chromatography

A comparative study of chiral separation of pantoprazole and rabeprazole is carried out using supercritical fluid chromatography and high-performance liquid chromatography. The columns used were Chiralpak IA and Chiralpak IE. The best mobile phase in supercritical fluid chromatography was carbon dioxide-0.2% triethylamine in methanol (60:40) and 0.1% triethylamine in n-hexane-ethanol (50:50) in high-performance liquid chromatography. For supercritical fluid chromatography, values of the retention factor of pantoprazole enantiomers were 3.97 and 4.88. These values for rabeprazole enantiomers were 6.10 and 7.52. The values of separation and resolution factor for pantoprazole and rabeprazole were 1.23 and 1.23 and 2.20 and 3.36, respectively. Similarly, for high-performance liquid chromatography, the values of retention factor for enantiomers of pantoprazole were 4.02 and 7.32. These values for rabeprazole enantiomers were 5.32 and 7.88, respectively. The values of separation and resolution factor for pantoprazole and rabeprazole were 1.82 and 1.48 and 9.22 and 6.58, respectively. A comparison was carried out, which confirmed supercritical fluid chromatography as the best method due to its fastness, eco-friendly, and inexpensiveness. The reported methods are effective, efficient, and reproducible and may be used to separate and identify pantoprazole and rabeprazole in any unknown samples.     

Investigation of Physicochemical Properties of Plasma Activated Water and its Bactericidal Efficacy

Plasma Chemistry and Plasma Processing - Presently, the world is using different types of disinfectants for various applications such as disinfecting instrument surfaces in the medical field,...