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The elongation of metallic nanoparticles (NPs) embedded in a dielectric matrix after irradiation with swift heavy ions is a phenomenon that has been known for several years. However, the precise mechanism behind this deformation process is still not fully understood, primarily due to the dearth of information during intermediate stages of deformation. In this study, we report the continuation of our previous work [Peña-Rodríguez et al., Sci. Rep. 7(1), 922 (2017)], exploiting the strong dependence of the localized surface plasmon resonance on the aspect ratio of elongated metal NPs to study the elongation kinetics in situ. In situ optical absorption spectra were measured using a polarizing beam splitter to separate the longitudinal and transverse plasmon modes of the anisotropic NPs. Then, the detailed geometrical and compositional parameters were determined from a fit of these spectra. The use of linearly polarized light allowed for a more accurate analysis of the elongation kinetics, particularly useful in the first stages, where longitudinal and transverse modes overlap. [ABSTRACT FROM AUTHOR]

We report on the irradiation of gold rod–sphere assemblies with ultrashort laser pulses, producing structures that are very difficult to obtain by other methods. The optical response of these assemblies displays several peaks arising from the interaction of the plasmon modes of the individual particles, offering thus great flexibility to control the energy deposited on the individual particles. Judicious selection of the wavelength and fluence of the laser pulses allow fine control over the changes produced: the particles can be melted, welded and/or the organic links cleaved. In this way, it is possible to generate structures “à la carte” with a degree of control unmatched by other synthetic protocols. The method is exemplified with gold nanoparticles, but it can be easily implemented on particles composed of different metals, widening considerably the range of possibilities. The final structures are excellent candidates for surface-enhanced spectroscopies or plasmonic photothermal therapy as they have a very intense electric field located outside the structure, not in the gaps.

The compaction process of calf thymus DNA by cationic liposomes formed by a 1:1 mixture of cationic lipid and zwitterionic lipid is studied using conductometry, cryo-TEM and fluorescence spectroscopy. The results show that when the charge ratio between the cationic liposome and DNA reaches 1, the liposome membranes fuse and cause the lead DNA to collapse onto condensed structures together with the liposomes.

A study was conducted to analyze artificial beta-sheets in competitive solvents. The bruker DRX500 spectrometer was utilized to perform nuclear magnetic resonance experiments. A spin locking field strength of 5 kHz was utilized to collect points in the f2 dimension. Results indicated that artificial beta-sheet is partially folded in methanol and aqueous methanol solutions. Findings also showed that the diurea turn unit can influence the structure of the beta-sheet.

Thermodynamic analyses of the binding of a series of p-nitrophenyl glycosides (PNPGly) of different stereochemistry to alpha-cyclodextrin were performed at three different temperatures utilizing a microcalorimetric procedure. Findings indicated that the thermodynamic values were close in magnitude to those obtained for the binding of monosaccharides to proteins, the complex formation was enthalpy driven, the enthalpy of binding was provided primarily by the PNP moiety, and that the chemical nature and the stereochemistry of the substituents in the carbohydrate had a differential effect on the thermodynamics of binding in aqueous solution.

The lipophilic interaction between carbohydrate surfaces regulates the stability of glycophane and various 4-nitrophenyl and 2,4-dinitrophenyl glycoside complexes. The hydroxy group at the position 5 and the hydroxyl group at position 2 of the axial derivative exerts a destabilizing effect on the glycophane complex. All glucose units exhibit a stable C1 chair conformation. Alterations in the chemical nature of the substituents of the incoming group cause differential changes in the free energy of binding of the complexes.

An easy, inexpensive, fast experiment has been developed for junior-level physical chemistry students to use to determine the equilibrium constants of an acid-base pair, both free and complexed with a molecular receptor. Easy pH experiments are used. Supramolecular systems are increasingly important and should be introduced to students for that reason. Topics include van't Hoff analysis.

The theory of mixed micellization is used for studying the micellization of an aqueous mixture of sodium dodecanoate (SDD) and sodium 10-undecenoate (SUD). The phenomenon is interpreted on the basis of the interaction between the vinyl group and water by hydrogen bonding.