A two component thermoreversible hydrogel of riboflavin and melamine: Enhancement of photoluminescence in the gel form

A new thermoreversible hydrogel of riboflavin and melamine supramolecular complex (> or =0.02%, w/v) shows enhanced photoluminescence properties through H-bonding.     

Enhanced performance of a wide-aperture copper vapour laser with hydrogen additive in neon buffer gas

A wide-aperture copper vapour laser was demonstrated at ∼10 kHz rep-rate with hydrogen additive in its buffer gas. Maximum power in excess of ∼50 W (at 10 kHz) was achieved by adding 1.96% hydrogen to the neon buffer gas at 20 mbar total gas pressure. This increase in output power was about 70% as compared to ∼30 W achieved with pure neon at 5.5 kHz rep-rate. The 70% enhancement achieved was significantly higher than the maximum reported value of 50% so far in the literature. The enhancement was much higher (about 150%) as compared to its 20 W power at 10 kHz rep-rate using pure neon as the standard CVL operation.     

Deciphering the evolution of supramolecular nanofibers in solution and solid-state: a combined microscopic and spectroscopic approach

Supramolecular self-assembly of small organic molecules has emerged as a powerful tool to construct well-defined micro- and nanoarchitecture through fine-tuning a range of intermolecular interactions. The size, shape, and optical properties of these nanostructures largely depend on the specific assembly of the molecular building units, temperature and polarity of the medium, and external stimuli. The engineering of supramolecular self-assembled nanostructures with morphology-dependent tunable emission is in high demand due to the promising scope in nanodevices and molecular machines. However, probing the evolution of molecular aggregates from the solution and directing the self-assembly process in a pre-defined fashion are challenging. In the present study, we have deciphered the sequential evolution of supramolecular nanofibers from solution to spherical and oblong-shaped nanoparticles through the variation of solvent polarity, tuning the hydrophobic–hydrophilic interactions. An intriguing case of molecular self-assembly has been elucidated employing a newly designed π-conjugated thiophene derivative (TPAn) through a combination of steady-state absorption, emission measurements, fluorescence correlation spectroscopy (FCS), and electron microscopy. The FCS analysis and microscopy results revealed that the small-sized nanofibers in the dispersion further agglomerated upon solvent evaporation, resulting in a network of nanofibers. Stimuli-responsive reversible interconversion between a network of nanofibers and spherical nanoaggregates was probed both in dispersion and solvent-evaporated state. The evolution of organic nanofibers and a subtle control over the self-assembly process demonstrated in the current investigation provide a general paradigm to correlate the size, shape, and emission properties of fluorescent molecular aggregates in complex heterogeneous media, including a human cell.

Supramolecular nanofiber evolution in solution and solid-state, including stimuli-responsive reversible interconversion among diverse nanoarchitectures, was probed through a combined spectroscopic and microscopic approach.     

Exceptional CO2 Adsorbing Materials under Different Conditions

In this article we discuss those materials that have recorded the highest adsorption capacities for the greenhouse gas CO₂ under ambient conditions as well as at different temperatures and pressures. For convenience, the materials have been categorized under four categories, viz., porous carbon, metal–organic, zeolite and mesoporous silica, and porous organic frameworks. It has been found that the gas adsorption property significantly relies on several factors such as high surface area and pore volume and the presence of N‐, O‐ and S‐containing moieties. The presence of a microporous structure and strong interaction between the CO₂ molecules with the framework through H‐bonding or dipole–quadrupole interactions facilitates adsorption of the gas.     

Development and optimization of an integrated PDMS based‐microdialysis microchip electrophoresis device with on‐chip derivatization for continuous monitoring of primary amines

An all‐PDMS on‐line microdialysis‐microchip electrophoresis with on‐chip derivatization and electrophoretic separation for near real‐time monitoring of primary amine‐containing analytes is described. Each part of the chip was optimized separately, and the effect of each of the components on temporal resolution, lag time, and separation efficiency of the device was determined. Aspartate and glutamate were employed as test analytes. Derivatization was accomplished with naphthalene‐2,3,‐dicarboxyaldehyde/cyanide (NDA/CN^?), and the separation was performed using a 15‐cm serpentine channel. The analytes were detected using LIF detection.     

Single crystal HPGe (80%) versus BGO shielded CLOVER detector for high precision decay rate measurements: a comparative study

In this study, various detector configurations have been investigated in order to explore the optimal condition for decay rate measurements of radioactive samples using gamma spectroscopy technique. A limitation of detecting low energy gamma rays from decaying radioactive nuclei, is the Compton background which can be significantly reduced by rejecting Compton scattered events through active Bismuth germanate (BGO) shielding. On the other hand, for a CLOVER detector without BGO shielding, one can place the radioactive samples very close to the detector for enhancing geometrical efficiency. A single crystal High Purity Germanium (HPGe) detector can also be used for decay rate measurements. In order to measure the decay rate of nuclei decaying via gamma emission with reasonable intensity, optimal close geometry options have been investigated for various HPGe detector configurations.

     

A freely falling magneto-optical trap drop tower experiment

We experimentally demonstrate the possibility of preparing ultracold atoms in the environment of weightlessness at the earth-bound short-term microgravity laboratory Drop Tower Bremen, a facility of ZARM – University of Bremen. Our approach is based on a freely falling magneto-optical trap (MOT) drop tower experiment performed within the ATKAT collaboration (“Atom-Catapult”) as a preliminary part of the QUANTUS pilot project (“Quantum Systems in Weightlessness”) pursuing a Bose–Einstein condensate (BEC) in microgravity at the drop tower [1, 2]. Furthermore we give a complete account of the specific drop tower requirements to realize a compact and robust setup for trapping and cooling neutral rubidium ⁸⁷Rb atoms in microgravity conditions. We also present the results of the first realized freely falling MOT and further accomplished experiments during several drops. The goal of the preliminary ATKAT pilot project is to initiate a basis for extended atom-optical experiments which aim at realizing, observing and investigating ultracold quantum matter in microgravity. PACS 67.85.-d     

Nanoaggregate shapes at the air/water interface

Chiral interfaces and molecular recognition phenomena are of special interest not only for the understanding of biological recognition processes but also for the potential application in material science. Langmuir monolayers at the air-water interface have successfully been used as simple models to mimic biological phenomena. Recent experimental studies revealed that both chirality and molecular recognition processes of amphiphiles are controlling the features of the nano-aggregates at the air/water interface. The objective of experimental studies has been to gain information about the properties of mesoscopic length scale aggregates obtained on the basis of chiral discrimation effects and the formation of supramolecular entities by molecular recognition of non-surface active species dissolved in the aqueous subphase. Differences in the two-dimensional morphology and lattice structures of the nano-aggregates cannot be explained by macroscopic theories and needed information about the detailed orientation and distance dependence of the intermolecular interaction within the aggregates. First new bottom-up studies have been directed toward understanding the driving forces for the aggregation processes of monolayers. Different types of interactions have been successfully considered using semi-empirical quantum chemical methods. The possibilities of Langmuir-Blodgett (LB) patterning to be an alternative paradigm for large-area patterning with mesostructured features are discussed.     

Regioselective synthesis of tetrahydrothiochromen-5-ones via a one-pot three-component solvent-free domino protocol

A highly efficient one-pot three-component regioselective synthesis of 4-aryl-3-aroyl-2-methylsulfanyl-4,6,7,8-tetrahydrothiochromen-5-ones has been developed by annulation of β-oxodithioesters with aldehydes and cyclic 1,3-diketones under solvent-free conditions promoted by P(2)O(5). No cocatalyst or activator is needed in this protocol. The merit of this process is highlighted by its high efficiency of producing three new bonds and a stereocenter in one operation.