Differential 3ω calorimeter

We have developed a new dynamic calorimeter using the differential 3ω detection method. The differential 3ω calorimeter is capable of measuring dynamic heat capacity of liquid samples. The new calorimeter consists of a Wheatstone bridge made of two identical heater/sensors, and is based on the sensitive null detection method. The balancing is done automatically at all frequencies and is independent of temperature; once a sample is placed on one heater/sensor, a third harmonic signal is produced due to the difference in the two arms of the bridge. The differential 3ω calorimeter provides enhancements over traditional dynamic methods in dynamic range (up to 30 kHz), resolution, and ease of operation.     

Bio-Templated Chiral Zeolitic Imidazolate Framework for Enantioselective Chemoresistive Sensing

Chiral metal–organic frameworks (MOFs) have gained rising attention as ordered nanoporous materials for enantiomer separations, chiral catalysis, and sensing. Among those, chiral MOFs are generally obtained through complex synthetic routes by using a limited choice of reactive chiral organic precursors as the primary linkers or auxiliary ligands. Here, we report a template-controlled synthesis of chiral MOFs from achiral precursors grown on chiral nematic cellulose-derived nanostructured bio-templates. We demonstrate that chiral MOFs, specifically, zeolitic imidazolate framework (ZIF), unc -[Zn(2-MeIm)₂, 2-MeIm=2-methylimidazole], can be grown from regular precursors within nanoporous organized chiral nematic nanocelluloses via directed assembly on twisted bundles of cellulose nanocrystals. The template-grown chiral ZIF possesses tetragonal crystal structure with chiral space group of P4₁, which is different from traditional cubic crystal structure of I-43 m for freely grown conventional ZIF-8. The uniaxially compressed dimensions of the unit cell of templated ZIF and crystalline dimensions are signatures of this structure. We observe that the templated chiral ZIF can facilitate the enantiotropic sensing. It shows enantioselective recognition and chiral sensing abilities with a low limit of detection of 39 μM and the corresponding limit of chiral detection of 300 μM for representative chiral amino acid, D- and L- alanine.     

Morphology-Directed Selective Production of Ethylene or Ethane from CO2 on a Cu Mesopore Electrode

The electrocatalytic conversion of CO₂ to value-added hydrocarbons is receiving significant attention as a promising way to close the broken carbon-cycle. While most metal catalysts produce C₁ species, such as carbon monoxide and formate, the production of various hydrocarbons and alcohols comprising more than two carbons has been achieved using copper (Cu)-based catalysts only. Methods for producing specific C₂ reduction outcomes with high selectivity, however, are not available thus far. Herein, the morphological effect of a Cu mesopore electrode on the selective production of C₂ products, ethylene or ethane, is presented. Cu mesopore electrodes with precisely controlled pore widths and depths were prepared by using a thermal deposition process on anodized aluminum oxide. With this simple synthesis method, we demonstrated that C₂ chemical selectivity can be tuned by systematically altering the morphology. Supported by computational simulations, we proved that nanomorphology can change the local pH and, additionally, retention time of key intermediates by confining the chemicals inside the pores.     

Thermal stability of ester linkage in the presence of 1,2,3‐Triazole moiety generated by click reaction

The copper(I)‐catalyzed alkyne‐azide cycloaddition (CuAAC), so‐called “click” reaction, is one of most useful synthetic strategies to connect two polymer chains. 1,2,3‐Triazole ring (TA) produced by the click reaction has good thermal and chemical stability. However, we observed that block copolymers synthesized by the click reaction showed thermal degradation to give homopolymers when they are thermally annealed at high temperature, which is required for obtaining equilibrium microdomain structure. To investigate the origin of thermal instability of block copolymers, we synthesized model polystyrenes (PSs) using systematically designed bi‐functional atom transfer radical polymerization (ATRP) initiators containing TA. PS including both ester and TA groups showed thermal decomposition at relatively low temperature (e.g., 140 °C). MALDI‐TOF analysis clearly demonstrated that the cleavage site is the ester group adjacent to TA. We also found that the bromine group located at the polymer chain end plays an important role in pyrolysis of ester groups at low temperature. The pyrolysis occurs by syn‐elimination of the ester group. This result implies that the phase behavior of block copolymer synthesized by click reaction should be carefully investigated when high temperature thermal annealing is required. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 427–436     

Hydrophobic Poly(tert‐butyl acrylate) Photonic Crystals towards Robust Energy‐Saving Performance

Photonic crystals (PCs) have been widely applied in optical, energy, and biological fields owing to their periodic crystal structure. However, the major challenges are easy cracking and poor structural color, seriously hindering their practical applications. Now, hydrophobic poly(tert‐butyl acrylate) (P(t‐BA)) PCs have been developed with relatively lower glass transition temperature (T_g), large crack‐free area, excellent hydrophobic properties, and brilliant structure color. This method based on hydrophobic groups (tertiary butyl groups) provides a reference for designing new kinds of PCs via the monomers with relatively lower T_g. Moreover, the P(t‐BA) PCs film were applied as the photoluminescence (PL) enhanced film to enhance the PL intensity of CdSe@ZnS QDs by 10‐fold in a liquid‐crystal display (LCD) device. The new‐type hydrophobic force assembled PCs may open an innovative avenue toward new‐generation energy‐saving devices.     

Preparation and ionic conductivities of the plasticized polymer electrolytes based on poly(methyl methacrylate-co-alkali metal methacrylate)

Ionic conductivities of the polymer electrolytes prepared from the ionomer (poly(methyl methacrylate-co-alkali metal methacrylate)), lithium perchlorate, and ethylene carbonate as a plasticizer, were studied as a function of the ion content and the alkali-metal cation of the ionomer. It was possible to obtain tough films with room-temperature ionic conductivities of ∼ 10^-3 S/cm. The maximum ion conductivities of the polymer electrolytes were obtained at the ion content of 5 mol % for both Li and Na ionomer. The effects of the ion content of the ionomer on the ionic conductivities of the polymer electrolytes were mainly interpreted in terms of the characteristics of the ion aggregate formed in the polymer electrolytes. The thermal dependence of the ionic conductivity was shown to be a non-VTF pattern in some of the polymer electrolytes investigated, which is expected to be due to the presence of the ion aggregate. © John Wiley & Sons, Inc.     

Efficient chemoselective deprotection of silyl ethers using catalytic 1-chloroethyl chloroformate in methanol

Fast and chemoselective desilylation of silyl-protected alcohols was achieved using a catalytic amount of 1-chloroethyl chloroformate in methanol. With a minimal amount of 1-chloroethyl chloroformate as the source for anhydrous HCl, extremely efficient cleavage of silyl ethers of primary and secondary alcohols was accomplished, and chemoselective deprotection of one silyl ether in the presence of another silyl or other acid-labile group was possible through controlling the amount of the chloroformate and reaction time.     

Study on new typical ionic clusters K+ (KNO3)n and NO3‐(KNO3)m

The sample solution of KNO₃ is ejected into the gas phase and the ionic dusters of K⁺(KNO₃)_n and NO₃ (KNO₃)_m are formed and observed by electrospray ionization mass spectrometry (ESIMS). Hie full mass spectra of both the positive ion and the negative ion show that the differences between each peak nearby are all about 101 (m/z), which correspond to the molecular weight of KNO₃. The general formula of the ionic clusters can be assigned as K⁺(KNO₃)_n and NO₃′‐(KNO₃)_m..     

TEMPO-Assisted Free Radical-Initiated Peptide Sequencing Mass Spectrometry (FRIPS MS) in Q-TOF and Orbitrap Mass Spectrometers: Single-Step Peptide Backbone Dissociations in Positive Ion Mode

The present study demonstrates that one-step peptide backbone fragmentations can be achieved using the TEMPO [2-(2,2,6,6-tetramethyl piperidine-1-oxyl)]-assisted free radical-initiated peptide sequencing (FRIPS) mass spectrometry in a hybrid quadrupole time-of-flight (Q-TOF) mass spectrometer and a Q-Exactive Orbitrap instrument in positive ion mode, in contrast to two-step peptide fragmentation in an ion-trap mass spectrometer (reference Anal. Chem. 85, 7044–7051 (30)). In the hybrid Q-TOF and Q-Exactive instruments, higher collisional energies can be applied to the target peptides, compared with the low collisional energies applied by the ion-trap instrument. The higher energy deposition and the additional multiple collisions in the collision cell in both instruments appear to result in one-step peptide backbone dissociations in positive ion mode. This new finding clearly demonstrates that the TEMPO-assisted FRIPS approach is a very useful tool in peptide mass spectrometry research.

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