Hybrid Plasmonic–Aerogel Materials as Optical Superheaters with Engineered Resonances

Solar radiation is a versatile source of energy, convertible to different forms of power. A direct path to exploit it is the generation of heat, for applications including passive building heating, but it can also drive secondary energy‐conversion steps. We present a novel concept for a hybrid material which is both strongly photo‐absorbing and with superior characteristics for the insulation of heat. The combination of that two properties is rather unique, and make this material an optical superheater. To realize such a material, we are combining plasmonic nanoheaters with alumina aerogel. The aerogel has the double function of providing structural support for plasmonic nanocrystals, which serve as nanoheaters, and reducing the diffusion rate of the heat generated by them, resulting in large local temperature increases under a relatively low radiation intensity. This work includes theoretical discussion on the physical mechanisms impacting the system's balanced thermal equilibrium.     

Inverse Peptide Synthesis via Activated α‐Aminoesters

A mild, practical, and simple procedure for peptide‐bond formation is reported. Instead of activation of the carboxylic acid functionality, the reaction involves an unprecedented use of activated α‐aminoesters. The method provides a straightforward entry to dipeptides and was effective when a sensitive cysteine residue was used, as no epimerization was detected in this case. The applicability of this method to iterative peptide synthesis was illustrated by the synthesis of a model tetrapeptide in the challenging reverse N→C direction.     

Iridium Complexes Containing Mesoionic C Donors: Selective C(sp3)H versus C(sp2)H Bond Activation,Reactivity Towards Acids and Bases,and Catalytic Oxidation of Silanes and Water

Metalation of a C2‐methylated pyridylimidazolium salt with [IrCp*Cl₂]₂ affords either an ylidic complex, resulting from C(sp³)?H bond activation of the C2‐bound CH₃ group if the metalation is performed in the presence of a base, such as AgO₂ or Na₂CO₃, or a mesoionic complex via cyclometalation and thermally induced heterocyclic C(sp²)?H bond activation, if the reaction is performed in the absence of a base. Similar cyclometalation and complex formation via C(sp²)?H bond activation is observed when the heterocyclic ligand precursor consists of the analogous pyridyltriazolium salt, that is, when the metal bonding at the C2 position is blocked by a nitrogen rather than a methyl substituent. Despite the strongly mesoionic character of both the imidazolylidene and the triazolylidene, the former reacts rapidly with D⁺ and undergoes isotope exchange at the heterocyclic C5 position, whereas the triazolylidene ligand is stable and only undergoes H/D exchange under basic conditions, where the imidazolylidene is essentially unreactive. The high stability of the Ir?C bond in aqueous solution over a broad pH range was exploited in catalytic water oxidation and silane oxidation. The catalytic hydrosilylation of ketones proceeds with turnover frequencies as high as 6 000 h^?1 with both the imidazolylidene and the triazolylidene system, whereas water oxidation is enhanced by the stronger donor properties of the imidazol‐4‐ylidene ligands and is more than three times faster than with the triazolylidene analogue.     

Stereocontrol in Dinuclear Triple Lithium‐Bridged Titanium(IV) Complexes: Solving Some Stereochemical Mysteries

Compounds 1 a – f ‐H₂ form “monomeric” triscatecholate titanium(IV) complexes [Ti( 1 a – f )₃]^2?, which in the presence of Li cations are in equilibrium with the triple lithium‐bridged “dimers” [Li₃(Ti( 1 a – f )₃)₂]^?. The equilibrium strongly depends on the donor ability of the solvent. Usually, in solvents with high donor ability, the stereochemically labile monomer is preferred, whereas in nondonor solvents, the dimer is the major species. In the latter, the stereochemistry at the complex units is “locked”. The configuration at the titanium(IV) triscatecholates is influenced by addition of chiral ammonium countercations. In this case, the induced stereochemical information at the monomer is transferred to the dimer. Alternatively, the configuration at the metal complexes can be controlled by enantiomerically pure ester side chains. Due to the different orientation of the ester groups in the monomer or dimer, opposite configurations of the triscatecholates were observed by circular dichroism (CD) spectroscopy for [Ti( 1 c – e )₃]^2? or [Li₃(Ti( 1 c – e )₃)₂]^?. A surprising exception was found for the dimer [Li₃(Ti( 1 f )₃)₂]^?. Herein, the dimer is the dominating species in weak donor (methanol), as well as strong donor (DMSO), solvents. This is due to the bulkiness of the ester substituent destabilizing the monomer. Due to the size of the substituent in [Li₃(Ti( 1 f )₃)₂]^? the esters have to adopt an unusual conformation in the dimer resulting in a stereocontrol of the small methyl group. Following this, opposite stereocontrol mechanisms were observed for the central metal‐complex units of [Li₃(Ti( 1 c – e )₃)₂]^? or [Li₃(Ti( 1 f )₃)₂]^?.     

Chirality and Polarity in the f‐Block Borates M4[B16O26(OH)4(H2O)3Cl4] (M=Sm,Eu, Gd,Pu, Am,Cm, and Cf)

The reactions of trivalent lanthanides and actinides with molten boric acid in high chloride concentrations result in the formation of M₄[B₁₆O₂₆(OH)₄(H₂O)₃Cl₄] (M=Sm, Eu, Gd, Pu, Am, Cm, Cf). This cubic structure type is remarkably complex and displays both chirality and polarity. The polymeric borate network forms helical features that are linked via two different types of nine‐coordinate f‐element environments. The f–f transitions are unusually intense and result in dark coloration of these compounds with actinides.     

Lactate biosensors: current status and outlook

Many research efforts over the last few decades have been devoted to sensing lactate as an important analytical target in clinical care, sport medicine, and food processing. Therefore, research in designing lactate sensors is no longer in its infancy and now is more directed toward viable sensors for direct applications. In this review, we provide an overview of the most immediate and relevant developments toward this end, and we discuss and assess common transduction approaches. Further, we critically describe the pros and cons of current commercial lactate sensors and envision how future sensing design may benefit from emerging new technologies.     

Quantitative monitoring of yeast fermentation using Raman spectroscopy

Compared to traditional IR methods, Raman spectroscopy has the advantage of only minimal interference from water when measuring aqueous samples, which makes this method potentially useful for in situ monitoring of important industrial bioprocesses. This study demonstrates real-time monitoring of a Saccharomyces cerevisiae fermentation process using a Raman spectroscopy instrument equipped with a robust sapphire ball probe. A method was developed to correct the Raman signal for the attenuation caused by light scattering cell particulate, hence enabling quantification of reaction components and possibly measurement of yeast cell concentrations. Extinction of Raman intensities to more than 50 % during fermentation was normalized with approximated extinction expressions using Raman signal of water around 1,627 cm^?1 as internal standard to correct for the effect of scattering. Complicated standard multi-variant chemometric techniques, such as PLS, were avoided in the quantification model, as an attempt to keep the monitoring method as simple as possible and still get satisfactory estimations. Instead, estimations were made with a two-step approach, where initial scattering correction of attenuated signals was followed by linear regression. In situ quantification measurements of the fermentation resulted in root mean square errors of prediction (RMSEP) of 2.357, 1.611, and 0.633 g/L for glucose, ethanol, and yeast concentrations, respectively.     

A General Method for Computer-Assisted Proofs of Periodic Solutions in Delay Differential Problems

Journal of Dynamics and Differential Equations - In this paper we develop a general computer-assisted proof method for periodic solutions to delay differential equations. The class of problems...     

On the mechanism of the144Nd(p, α)141Pr reaction

Zeitschrift für Physik A Hadrons and nuclei - Experimental evidence is presented that the144Nd(p, α)141Pr reaction excites residual nucleus levels with a dominant single proton...