Project description:Understanding the nature of charge carriers at the LaAlO3/SrTiO3 interface is one of the major open issues in the full comprehension of the charge confinement phenomenon in oxide heterostructures. Here, we investigate thermopower to study the electronic structure in LaAlO3/SrTiO3 at low temperature as a function of gate field. In particular, under large negative gate voltage, corresponding to the strongly depleted charge density regime, thermopower displays high negative values of the order of 10(4)-10(5) μVK(-1), oscillating at regular intervals as a function of the gate voltage. The huge thermopower magnitude can be attributed to the phonon-drag contribution, while the oscillations map the progressive depletion and the Fermi level descent across a dense array of localized states lying at the bottom of the Ti 3d conduction band. This study provides direct evidence of a localized Anderson tail in the two-dimensional electron liquid at the LaAlO3/SrTiO3 interface.
Project description:Nonaqueous potassium-ion hybrid capacitors (KIHCs) are faced with limited redox reaction kinetics of electrodes for accommodation of large-sized K+. Here, dipotassium terephthalate (K2TP) is applied as an organic negative electrode to provide comparable reaction kinetics with a non-faradaic activated carbon (AC) positive electrode to boost the electrochemical performance of KIHCs. It is revealed that the large exchange current density and fast two-dimensional (2D) diffusion pathways of K+ in K2TP determined by density functional theory (DFT) calculations ensure its fast redox reaction and transport kinetics. The as-constructed KIHC presents both high energy and power densities of 101 W h kg-1 and 2160 W kg-1 based on the mass of the two electrodes (41.5 W h kg-1 and 885.2 W kg-1 based on the mass of the two electrodes and electrolyte), respectively, and a superior capacity retention of 97.7% after 500 cycles. The excellent electrochemical performance is attributed to the fast kinetics, good structural flexibility, and small volume change (9.4%) of K2TP upon K+ insertion/extraction, and its good compatibility with the AC positive electrode in 1,2-dimethoxyethane (DME)-based electrolyte. This will promote application of organic materials in hybrid capacitors and the development of KIHCs.
Project description:Flexible power supply devices provide possibilities for wearable electronics in the Internet of Things. However, unsatisfying capacity or lifetime of typical batteries or capacitors seriously limit their practical applications. Different from conventional heat-to-electricity generators, zinc ion thermal charging cells has been a competitive candidate for the self-power supply solution, but the lack of promising cathode materials has restricted the achievement of promising performances. Herein, we propose an attractive cathode material by rational heterostructure engineering of hydrated vanadium pentoxide. Owing to the integration of thermodiffusion and thermoextraction effects, the thermopower is significantly improved from 7.8 ± 2.6 mV K-1 to 23.4 ± 1.5 mV K-1. Moreover, an impressive normalized power density of 1.9 mW m-2 K-2 is achieved in the quasi-solid-state cells. In addition, a wearable power supply constructed by three units can drive the commercial health monitoring system by harvesting body heat. This work demonstrates the effectiveness of electrodes design for wearable thermoelectric applications.
Project description:We report here on a new generation of optical ion-selective sensors benefiting from cubosomes or hexosomes-nanostructural lipid liquid phase. Cubosome as well as hexosome optodes offer biocompatibility, self-assembly preparation, high stability in solution, and unique, tunable analytical performance. The temperature trigger reversibly changes the lipid nanoparticle internal structure-changing analyte access to the bulk of the probe and ultimately affecting the response pattern. Thus, cubosome or hexosome optodes are highly promising alternatives to conventional polymeric based optical nanoprobes.
Project description:Shaping soft and conductive materials into sophisticated architectures through 3D printing is driving innovation in myriad applications, such as robotic counterparts that emulate the synergic functions of biological systems. Although recently developed multi-material 3D printing has enabled on-demand creation of intricate artificial counterparts from a wide range of functional viscoelastic materials. However, directly achieving complementary functionalities in one ink design remains largely unexplored, given the issues of printability and synergy among ink components. In this study, an easily accessible and self-regulating tricomponent ionogel-based ink design to address these challenges is reported. The resultant 3D printed objects, based on the same component but with varying ratios of ink formulations, exhibit distinct yet complementary properties. For example, their Young's modulus can differ by three orders of magnitude, and some structures are rigid while others are ductile and viscous. A theoretical model is also employed for predicting and controlling the printing resolution. By integrating complementary functionalities, one further demonstrates a representative bioinspired prototype of spiderweb, which mimics the sophisticated structure and multiple functions of a natural spiderweb, even working and camouflaging underwater. This ink design strategy greatly extends the material choice and can provide valuable guidance in constructing diverse artificial systems by 3D printing.
Project description:We demonstrate that the giant magnetoresistance can be switched off (on) in even- (odd-) width zigzag graphene-like nanoribbons by an atomistic gate potential or edge disorder inside the domain wall in the antiparallel (ap) magnetic configuration. A strong magneto-thermopower effect is also predicted that the spin thermopower can be greatly enhanced in the ap configuration while the charge thermopower remains low. The results extracted from the tight-binding model agree well with those obtained by first-principles simulations for edge doped graphene nanoribbons. Analytical expressions in the simplest case are obtained to facilitate qualitative analyses in general contexts.
Project description:Nonaqueous emulsions are crucial for a range of applications based on water-sensitive systems such as controlled polymerizations requiring anhydrous reaction conditions and the stabilization of readily hydrolyzable reagents or pharmacologically active components. However, defined molecular surfactants to stabilize such nonaqueous emulsions are scarce. We introduce a self-assembled coordination cage, decorated with cholesterol functionalities, to serve as a molecular surfactant for various oil-in-oil emulsions of immiscible organic solvents. While the positively charged cage forms the amphiphile's polar moiety, the non-polar cholesterol appendices can bend in a common direction to stabilize the emulsion. Templated by the droplets, polycondensation reactions were carried out to produce microstructured polyurethane and polyurea materials of different particle sizes and morphologies. Further, the amphiphilic cage can encapsulate a guest molecule and the resulting host-guest assembly was also examined as a surfactant. In addition, the aggregation behavior of the amphiphilic cage in an aqueous medium was examined.
Project description:Solid-contact ion-selective electrodes (SC-ISEs) exhibit great potential in the detection of routine and portable ions which rely on solid-contact (SC) materials for the transduction of ions to electron signals. Carbon-based materials are state-of-the-art SC transducers due to their high electrical double-layer (EDL) capacitance and hydrophobicity. However, researchers have long searched for ways to enhance the interfacial capacitance in order to improve the potential stability. Herein, three representative carbon-based SC materials including nitrogen-doped mesoporous carbon (NMC), reduced graphene oxide (RGO), and carbon nanotubes (CNT) were compared. The results disclose that the NMC has the highest EDL capacitance owing to its mesopore structure and N-doping while maintaining high hydrophobicity so that no obvious water-layer effect was observed. The Ca2+-SC-ISEs based on the SC of NMC exhibited high potential stability compared with RGO and CNT. This work offers a guideline for the development of carbon-material-based SC-ISEs through mesoporous and N-doping engineering to improve the interfacial capacitance. The developed NMC-based solid-contact Ca2+-SC-ISE exhibited a Nernstian slope of 26.3 ± 3.1 mV dec-1 ranging from 10 μM to 0.1 M with a detection limit of 3.2 μM. Finally, a practical application using NMC-based SC-ISEs was demonstrated through Ca2+ ion analysis in mineral water and soil leaching solutions.