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Promoting core/surface homogeneity during flash sintering of 3YSZ ceramic by current path management: experimental and modelling studies
No full textDuring flash sintering (FS) of ceramics, the heat loss by surface radiation is the main cause of temperature gradient between core and surface, which induces inhomogeneity in microstructure. To solve this problem, the judicious designing of sample geometry and electrodes configuration is proposed. Experimental and simulation results show that the application of dogbone shape, forked electrodes, and lower cross-section aspect ratio effectively shifts the current path in 3YSZ samples from core to near-surface during FS, compared to bar-shape samples with a single electrode at each end. Consequently, the temperature distribution becomes more uniform throughout the 3YSZ sample, resulting in increase in relative density from 92.7 % to 99.7 % and improved core/ surface homogeneity in microstructure. These optimizations enable 3YSZ ceramics to obtain significant increase in flexural strength from 1203 +/- 17 MPa to 1501 +/- 15 MPa. A multiphysics model is implemented and compared with experimental results, which reveals the underlying mechanisms of improved sample homogeneity
Large magnetic anisotropy in Tetraoxa[8]circulene-based organometallic nanosheet
No full textExploring magnetic anisotropy (MA) in single-atom-doped two-dimensional (2D) materials is greatly needed for the development of nanomagnetic devices. Taking full advantage of the natural hollow sites of 2D Tetraoxa[8] circulene-based nanosheet (TOC), we systemically study the MA of the TOC doped by single 3d tradition metal (TM) atoms (V, Cr, Mn, Fe, Co and Ni) via first-principles calculations. Specifically, we find that the Co@TOC system has large perpendicular magnetic anisotropy (PMA), up to 1.76 meV/atom, which originates from the hybridization of Co-(dxz, dyz) and O-pz orbitals with strong spin-orbit splitting near Fermi level. Furthermore, the PMA of Co@TOC can be enhanced up to 7.28 meV/atom by applying biaxial tensile strain of 9%. The large PMA provides a practical single-atom magnetic system for potential spintronic applications
Ti3C2Tx/PEDOT:PSS Composite Interface Enables over 17% Efficiency Non-fullerene Organic Solar Cells
No full textMetal carbide Ti3C2Tx as a new two-dimensional material with excellent metallic conductivity, good water solubility, and superior transmittance in the visible light range shows great potential for applications in optoelectronic devices. Herein, Ti3C2Tx/PEDOT:PSS composite films were fabricated by a simple solution process and employed as an anode interfacial layer in organic solar cells. By introducing the Ti3C2Tx/PEDOT:PSS composite interface into the devices, the highest power conversion efficiency (PCE) of 17.26% was achieved while using PM6:Y6 as the active layer, with a high short-circuit current (J(sc)) of 26.52 mA/cm(2) and a fill factor of up to 0.76. The PCE is much higher than 15.89% for the pure PEDOT:PSS interfacial layer-based device without doping. The dramatically improved performance was attributed to the increased conductivity of the Ti3C2Tx/PEDOT:PSS composite interface and the increased charge extraction and collection efficiency of the devices. This work presents an effective method to prepare the Ti3C2Tx/PEDOT:PSS composite interface and high-performance organic solar cells
Biomimetic self-assembly of lipase-zeolitic imidazolate frameworks with enhanced biosensing of protox inhibiting herbicides
No full textProtox inhibiting herbicides such as nitrofen have detrimental effects on the environment and human health. The current work aims to fabricate a Candida rugosa lipase (CRL)-based electrochemical sensor for rapid and sensitive detection of protox inhibiting herbicides (nitrofen). We proposed the use of poly(vinylpyrrolidone) (PVP) and amino-acids to promote accumulation of Zn2+ ions at the surfaces of Candida rugosa lipase (CRL) and subsequently induce self-assembly of a CRL-zeolitic imidazolate framework (ZIF) structure. This process can be easily and rapidly achieved via a one-pot facile self-assembly method. Steady-state fluorescence spectroscopy indicated that CRL has undergone a conformational change following encapsulation within the ZIF structure. This conformational change is beneficial as the prepared PVP/Glu/CRL@ZIF-8 exhibited enhanced catalytic activity (207% of native CRL), and higher substrate affinity (lower K-m than native CRL) and showed high stability under harsh denaturing conditions. PVP/Glu/CRL@ZIF-8 was finally used for electrochemical biosensing of nitrofen. The fabricated biosensor has a wide linear detection range (0-100 mu M), a lower limit of detection and a good recovery rate
MC2 (M = Y, Zr, Nb, and Mo) monolayers containing C-2 dimers: prediction of anode materials for high-performance sodium ion batteries
No full textSeeking novel high performance anode materials for sodium ion batteries (SIBs) is an attractive theme in developing energy storage devices. In this work, by means of density functional theory computations, we predicted a family of MC2 (M = Y, Zr, Nb, and Mo) monolayers containing C-2 dimers to be promising anode materials for SIBs. The stability, electronic structure, and adsorption/diffusion/storage behavior of sodium atoms in MC2 (M = Y, Zr, Nb, and Mo) monolayers were explored. Our computations revealed that Na adsorbed MC2 (M = Y, Zr, Nb, and Mo) monolayers show metallic characteristics that give rise to excellent electrical conductivity and Na mobility with low activation energies for diffusion (0.21, 0.04, 0.20, and 0.22 eV, respectively) in these materials, indicative of a high charge/discharge rate. In addition, the theoretical capacities of Na-adsorbed on YC2, ZrC2, NbC2, and MoC2 monolayers are 478, 697, 687, and 675 mA h g(-1), respectively, higher than that of commercial graphite (284 mA h g(-1)), and the open-circuit voltages are moderate (0.11-0.25 V). Our results suggest that MC2 (M = Y, Zr, Nb, and Mo) monolayers have great potential to serve as anode materials for SIBs
Homointerface covalent organic framework membranes for efficient desalination
No full textCovalent organic frameworks (COFs) are an emergent class of crystalline porous polymers featuring a long-range regular pore structure, high porosity and excellent chemical stability. Bilayer COF membranes with tunable interfaces hold great promise in ionic and molecular separations. Herein, we designed a series of bilayer COF membranes with homointerface and heterointerface, which achieved efficient desalination performance through manipulating the interface confinement effect. COF membranes were prepared on a porous support through successively regulating the growth of imine-based 2D COF layers by in situ growth and counter-diffusion approach at ambient temperature. Narrowed sub-nanometer interlaced channels were created at the interface of the two adjacent COF layers. The rejection rate of homointerface COF membrane toward Na2SO4 was higher than that of heterointerface COF membranes, which was due to the synergistic enhancement of interface-confined size sieving and Donnan effect. The homointerface TpPa-SO3H/TpPa-SO3H/MPAN membrane exhibits a rejection rate of 98.3% for Na2SO4 and water flux of 13.1 L m(-2) h(-1) bar(-1), which is the highest performance among COF desalination membranes ever reported
Ultra-smooth and robust graphene-based hybrid anode for high-performance flexible organic light-emitting diodes (vol 9, pg 2106, 2021)
No full textCorrection for 'Ultra-smooth and robust graphene-based hybrid anode for high-performance flexible organic light-emitting diodes' by Zhikun Zhang et al., J. Mater. Chem. C, 2021, 9, 2106-2114, DOI: 10.1039/D0TC05213B
Highly sensitive flexible tactile perceptual interactive platform with functions of Braille code recognition
No full textImitation of tactile perception activities is crucial to the developments of advanced interactive neuromorphic platforms. However, it is a challenge to develop such a platform using a low-cost manufacturing process and with low-power consumption. Here, a low-cost, highly sensitive flexible tactile perceptual interactive platform is proposed, composed of polydimethylsiloxane-based flexible tactile sensors and a flexible chitosan-gated oxide neuromorphic transistor. The flexible tactile sensors made with alkaline textured silicon molds are used as skin receptors that convert pressure signals into electrical signals. The flexible indium-tin-oxide neuromorphic transistor fabricated with a single-step mask process can process electrical signals from the tactile sensor. The neuromorphic transistor exhibits good electrical performances against bending stress. Basic synaptic functions, including excitatory postsynaptic current and paired-pulse facilitation, are demonstrated. Thus, the tactile perceptual platform successfully imitates tactile perception activities in our body. Moreover, when loading a low pressure of similar to 1.4 Pa, the flexible tactile perceptual platform demonstrates a high S/N value and sensitivity of similar to 4.93 and similar to 6.9 dB, respectively. As a proof-of-concept, recognition of Braille codes is demonstrated on the platform by integrating two tactile sensors. The results show the widespread potential of the present interactive platform in wearable flexible cognitive electronics. It has potential applications, including but not limited to human-computer interaction technology and intelligent robot technology
In-situ growth of MAX phase coatings on carbonised wood and their terahertz shielding properties
No full textElectromagnetic interference (EMI) shielding materials have received considerable attention in recent years. The EMI shielding effectiveness (SE) of materials depends on not only their composition but also their microstructures. Among various microstructure prototypes, porous structures provide the advantages of low density and high terahertz wave absorption. In this study, by using carbonised wood (CW) as a template, 1-mm-thick MAX@CW composites (Ti2AlC@CW, V2AlC@CW, and Cr2AlC@CW) with a porous structure were fabricated through the molten salt method. The MAX@CW composites led to the formation of a conductive network and multilayer interface, which resulted in improved EMI SE. The average EMI SE values of the three MAX@CW composites were > 45 dB in the frequency of 0.6-1.6 THz. Among the composites, V2AlC@CW exhibited the highest average EMI SE of 55 dB
Peptide nucleic acid-assisted colorimetric detection of single-nucleotide polymorphisms based on the intrinsic peroxidase-like activity of hemin-carbon nanotube nanocomposites
No full textHere, taking the advantage of single-stranded (ss) DNA specific nuclease (S1) and peptide nucleic acid (PNA), we demonstrated a novel, rapid, and label-free colorimetric nanosensor for the sensitive and accurate detection of SNPs based on the intrinsic peroxidase-like activity of hemin-functionalized single-walled carbon nanotubes (hemin-SWCNTs). PNA, a man-made mimic of DNA with extraordinary stability toward enzymatic degradation, can effectively protect DNA in the fully matched DNA/PNA duplexes from nuclease digestion. While the DNA in DNA/PNA duplexes containing a mismatch can be cleaved into small fragments. This difference can be visually monitored from the specific color change of TMB/H2O2 system by employing the peroxidase activity of hemin-SWCNTs because of its different aggregation states responding to ssPNA or DNA/PNA duplex. Under optimized conditions, the SNPs in the human tumor suppressor gene TP53 have been successfully genotyped in a linear range of 50-1000 nM with a detection limit of 0.11 nM. Moreover, this platform can effectively discriminate a series of single-base mismatches. This assay avoids the assistance of sophisticated instruments and complicated modifications of probes or nanomaterials, and function well for both cell lysate samples and PCR amplicons from standard cell lines, implying its potential practical applications for bioanalysis and biosensors