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pH-Regulated Heterostructure Porous Particles Enable Similarly Sized Protein Separation
No full textPorous particles are frequently used for various healthcare applications that involve protein separation processes. However, conventional porous particles, either homogeneous particles or those subjected to surface modification with a layer of specific molecules, often encounter bottlenecks in separating proteins with similar size. Here, it is reported that heterostructure-enabled separation particles (HESP), synthesized by a double emulsion interfacial polymerization process, can effectively and rapidly separate similarly sized proteins. Double emulsion interfacial polymerization endows the HESP with a nanoscale carboxylic layer outside the particles and inside the pores, allowing pH-regulated selective adsorption of proteins. Thus, by optimizing the environmental pH, proteins with similar size can be effectively and rapidly separated. These HESP are expected to show potential in widespread applications ranging from biomolecule adsorption, encapsulation, and separation to controlled release and other biomedical fields
Characterization of tunnel oxide passivated contact with n-type poly-Si on p-type c-Si wafer substrate
No full textThe junction properties of tunnel silicon oxide (SiOx) passivated contact (TOPCon) with n-type poly-Si on p-type c-Si wafer are characterized using current-voltage (J-V) and capacitance-voltage (C-V) measurements. The dark J-V curves show a standard diode characteristic with a turn-on voltage of similar to 0.63 V, indicating a p-n junction is formed. While the C-V curve displays an irregular shape with features of 1) a slow C increase with the decrease of the magnitude of reverse bias voltage, being used to estimate the built-in potential (V-bi), 2) a significant increase at a given positive bias voltage, corresponding to the geometric capacitance crossing the ultrathin SiOx, and 3) a sharp decrease to negative values, resulting from the charge tunneling through the SiOx layer. The C of depleting layer deviates from the normal linear curve in the 1/C-2-V plot, which is caused by the diffusion of P dopants from the n-type poly-Si into the p-type c-Si wafer as confirmed by the electrochemical capacitance-voltage measurements. However, the 1/C2+gamma-V plots with gamma > 0 leads to linear curves with a proper gamma and the V-bi can still be estimated. We find that the V-bi is the range of 0.75-0.85 V, increases with the increase of the doping ratio during the poly-Si fabrication process, and correlates with the passivation quality as measured by the reverse saturated current and implied open circuit voltage extracted from transient photoconductivity decay
One-pot conversion of lysine to caprolactam over Ir/H-Beta catalysts
No full textAmino acid lysine could serve as an ideal bio-based feedstock for the synthesis of caprolactam (CPL), which is currently a petroleum-derived monomer. Herein, we report the one-pot conversion of L-lysine to CPL via hydrogenolysis over bifunctional metal supported catalysts. Among the various hydrogenation metals and different supports, the combination of Ir and HB zeolite gave the best performance. Under optimal conditions, a 30% yield of CPL from L-lysine and a 58% yield from the reaction intermediate a-dimethyl amino caprolactam (DMAC) were obtained over a 2Ir/HB-124 catalyst at 250 degrees C in an autoclave or fixed-bed reactor. The reaction solvent dramatically affected the reaction selectivity, and methanol was found to be the best due to its unique contribution towards the formation of a-dimethyl amino caprolactam (DMAC) as well as the following C-N breakage of the C-N(CH3)(2) bond. The acid sites on the catalyst accelerate lactam formation, and the synergy between the acid sites and hydrogenation sites favours C-N bond hydrogenolysis to produce CPL. Besides the acidity, the large pore size of HB is able to accommodate big reaction intermediate molecules inside the pores further ensures the superior performance of Ir/HB. The reaction route was identified, i. e., L-lysine first undergoes cyclization and N-methylation to DMAC, and then C-N(CH3)(2) bond hydrogenolysis to form CPL. The Ir/HB catalyst has reasonably good stability and high selectivity, making this one-pot conversion process a novel and environmentally benign way of producing CPL from easily available renewable feedstocks
A H-bond strategy to develop acid-resistant photoswitchable rhodamine spirolactams for super-resolution single-molecule localization microscopy
No full textRhodamine spirolactam based photoswitches have been extensively applied in super-resolution single-molecule localization microscopy (SMLM). However, the ring-opening reactions of spirolactams are cross-sensitive to acid, limiting their photoswitch use to neutral pH conditions. In addition, the ring-closing reactions of spirolactams are environment-sensitive and slow (up to hours), virtually making rhodamine spirolactams caged fluorescent dyes instead of reversible photoswitches in SMLM. Herein, by introducing hydrogen bonds to stabilize spirolactams, we report a series of acid-resistant rhodamine spirolactams with accelerated ring-closing reactions from fluorescent xanthyliums to non-fluorescent spirolactams, endowing them with good photoswitchable properties even in acidic environments. By further substitution of 6-phenylethynyl naphthalimide on the spirolactam, we shifted the photoactivation wavelength into the visible region (>400 nm). Subsequently, we have successfully applied these dyes in labeling and imaging the cell surface of Bacillus subtilis at pH 4.5 using SMLM
Chabazite Architecture Dominates the Structure of SAPO-34's Surface Methoxy Species
No full textFour types of SAPO-34's surface methoxy species (CH3-SAPO-34) structures have been studied by periodic density functional theory calculations. The most stable CH3-SAPO-34 structure is the methyl cation locating on the framework oxygen anion site O(z1), which is at the middle position of a cha composite building unit.
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Reverse-Graded 2D Ruddlesden-Popper Perovskites for Efficient Air-Stable Solar Cells
No full text2D Ruddlesden-Popper perovskites (RPPs) have emerged as a promising solar cell material. A group of novel RPPs with cyclohexane methylamine (CMA) as a spacer cation is presented. Unlike previously reported RPPs, the deposited films of (CMA)(2)(MA)(n-1)PbnI3n+1 (MA is CH3NH3+, n = 1, 2, 3, horizontal ellipsis ) exhibit multiple phases with reverse-graded quantum well (QW) distribution; small n (n = 2) RPPs are located at the surface and large n (n >= 10) RPPs at the bottom. This has three advantages: (a) The outer, more moisture resistant, small n RPPs create a stable barrier that protects the vulnerable large n RPP lattice from being attacked by water molecules. (b) It forms a type-II band alignment between different phases, which favors self-driven charge transport. (c) The natural structure of graded QWs expands the range of photon collection. Attributed to these properties, the best efficiency of 15.05%, with high open-circuit voltage (V-oc) of 1.10 V for a first-generation solar cell containing (CMA)(2)(MA)(8)Pb9I28, is achieved. A notable enhancement in short wavelength is observed in the Incident photon-to-current conversion efficiency spectra. This device shows significantly improved long-term stability, retaining approximate to 95% of the initial efficiency after 4600 h exposure in ambient conditions with 40-70% relative humidity
