Combining selection valve and mixing chamber for nanoflow gradient generation: Toward developing a liquid chromatography cartridge coupled with mass spectrometer for protein and peptide analysis

Toward developing a micro HPLC cartridge, we have recently built a high-pressure electroosmotic pump (EOP). However, we do not recommend people to use this pump to deliver an organic solvent directly, because it often makes the pump rate unstable. We have experimented several approaches to address this issue, but none of them are satisfactory. Here, we develop an innovative approach to address this issue. We first create an abruption (a dead-volume) within a fluid conduit. We then utilize an EOP to withdraw, via a selection valve, a train of eluent solutions having decreasing eluting power into the fluid conduit. When these solutions are further aspirated through the dead-volume, these solutions are partially mixed, smoothening concentration transitions between two adjacent eluent solutions. As these solutions are pushed back, through the dead-volume again, a smooth gradient profile is formed. In this work, we characterize this scheme for gradient formation, and we incorporate this approach with a high-pressure EOP, a nanoliter injection valve, and a capillary column, yielding a micro HPLC system. We then couple this micro HPLC with an electrospray ionization – mass spectrometer for peptide and protein separations and identifications.     

Statistics of polymer capture by a nanopore: A Brownian dynamics simulation study

We investigate the statistics of polymer capture by a nanopore using Brownian dynamics simulations. It is found that when the velocity flux is greater than a critical velocity flux, the capture picture is a random selection process, otherwise it tends to a statistical process governed by energetic considerations. In addition, the chain ends capture probability decreases as the chain length increases and satisfies a power-law scaling of P0(N)~N-0.8.     

Polypyrrole Shell@3D‐Ni Metal Core Structured Electrodes for High‐Performance Supercapacitors

Three‐dimensional (3D) nanometal films serving as current collectors have attracted much interest recently owing to their promising application in high‐performance supercapacitors. In the process of the electrochemical reaction, the 3D structure can provide a short diffusion path for fast ion transport, and the highly conductive nanometal may serve as a backbone for facile electron transfer. In this work, a novel polypyrrole (PPy) shell@3D‐Ni‐core composite is developed to enhance the electrochemical performance of conventional PPy. With the introduction of a Ni metal core, the as‐prepared material exhibits a high specific capacitance (726 F g^?1 at a charge/discharge rate of 1 A g^?1), good rate capability (a decay of 33 % in C_sp with charge/discharge rates increasing from 1 to 20 A g^?1), and high cycle stability (only a small decrease of 4.2 % in C_sp after 1000 cycles at a scan rate of 100 mV s^?1). Furthermore, an aqueous symmetric supercapacitor device is fabricated by using the as‐prepared composite as electrodes; the device demonstrates a high energy density (≈21.2 Wh kg^?1) and superior long‐term cycle ability (only 4.4 % and 18.6 % loss in C_sp after 2000 and 5000 cycles, respectively).     

Geometric Phase for High-Temperature Master Equation

Geometric phase of mixed state is investigated for three-level system obeying a high-temperature master equation. The results show the Berry phase of mixed phase is strongly dependent on the initial condition. For the different initial angle, the turning region is different. In addition, the decrease of Berry phase is most slow around the coupling strength α=5 with an increasing of evolving time.     

Thermogravimetric analysis of carbide slag

Potential of carbide slag as transesterification catalyst is validated. Combined with X-ray fluorescence for ingredient determination, X-ray diffraction for textural phase analysis, scanning electron microscope for surface morphology observation and Hammett indicator for basic strength mensuration, thermal event of carbide slag is investigated through thermogravimetric analysis to estimate the potential of this calcium-based industrial waste as transesterification catalyst. Further, kinetic parameters are calculated through model-free method, where the experiments are conducted at temperature heating rates of 5, 10, 15, and 20 K min^?1. As for activation energy and reaction order, Vyazovkin method and Avrami theory are respectively mentioned. Meanwhile, catalytic performance of carbide slag is labeled by transesterification efficiency and calcium hydroxide is conditionally mentioned for comparison. In conclusion, potential of carbide slag as transesterification catalyst is adequately validated.     

Solvothermal synthesis of PbTe/SnTe hybrid nanocrystals

PbTe/SnTe hybrid nanocrystals with designed shape, chemical composition and narrow size distribution were synthesized by an efficient solvothermal approach. This approach enables mass and economical synthesis of PbTe-based nanocrystals. The organic ligands were completely removed by pretreatment with a super-hydride solution, making it possible to fabricate fully dense and robust thermoelectric devices with increased electrical conductivity.     

Synthesis and selective recognition toward zinc ion of chiral poly(imine‐triazole)

A novel AB type of clickable monomer, (S)‐2‐[(2‐azido‐1‐phenylethylimino)methyl]‐5‐propargyloxyphenol (AMPP) was designed and polymerized to yield a class of main‐chain chiral poly(imine‐triazole)s through the metal‐free click reaction. With the thermally induced polymerization, the desired polytriazoles can be easily prepared in high yields by a stepwise heating‐up process and have the number‐average molecular masses ranging from 5.1 × 10³ to 58.1 × 10³ (polydispersity indices = 1.38?1.68). The polymers were characterized by Fourier Transform Infrared spectroscopy (FTIR), ¹H Nuclear Magnetic Resonance (NMR), and gel permeation chromatography, and their optical properties were studied by fluorescence and circular dichroism (CD) spectroscopies. As a chemosensor, these polymers exhibited a selective “turn‐on” fluorescence enhancement response toward Zn²⁺ ion over other cations such as Na⁺, K⁺, Mg²⁺, Ca²⁺, Ag⁺, Pb²⁺, Cd²⁺, Hg²⁺, Mn²⁺, and Ni²⁺ in dimethyl sulfoxide. However, the Zn²⁺‐induced fluorescence signal was subject to serious interference by Al³⁺, Cu²⁺, Cr³⁺, and Fe³⁺ ions. Interestingly, the chiral polymer showed distinctive changes in the CD spectra on complexation with Zn²⁺, which allowed for the discrimination of this ion in the presence of other species tested including those interfering ions observed in the fluorescent detection. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2248–2257