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Flexible electronics has recently captured extensive attention due to its intriguing functionalities and great potential for influencing our daily life. In addition, with the increasing demand for green energy, photoelectrochemical (PEC) water splitting is a clean process that directly converts solar energy to chemical energy in the form of hydrogen. Thus the development of flexible green energy electronics represents a new domain in the research field of energy harvesting. In this work, we demonstrate the BiVO4 (BVO)/WO3/ITO/muscovite heterostructure photoelectrode for water splitting with flexible characteristics. The performance of BVO was modified by specific crystal facets, and the BVO/WO3 bilayer exhibited superior performance of 33% enhanced PEC activity at 1 V vs Ag/AgCl compared with pure BVO due to the proper staggered band alignment. Moreover, excellent mechanical stability was verified by a series of bending modes. This study demonstrates a pathway to a flexible photoelectrode for developing innovative devices for solar fuel generation.

Epitaxial CoFe2O4(CFO)/CoO bilayers were fabricated by pulsed laser deposition on flexible muscovite mica substrate. Samples with different CFO thicknesses were employed to study the phenomenon of ...

The ability of band offsets at multiferroic/metal and multiferroic/electrolyte interfaces in controlling charge transfer and thus altering the photoactivity performance has sparked significant attention in solar energy conversion applications. Here, we demonstrate that the band offsets of the two interfaces play the key role in determining charge transport direction in a downward self-polarized BFO film. Electrons tend to move to BFO/electrolyte interface for water reduction. Our experimental and first-principle calculations reveal that the presence of neodymium (Nd) dopants in BFO enhances the photoelectrochemical performance by reduction of the local electron–hole pair recombination sites and modulation of the band gap to improve the visible light absorption. This opens a promising route to the heterostructure design by modulating the band gap to promote efficient charge transfer.

In the era of Internet of Things, the demand for flexible and transparent electronic devices has shifted to the forefront of materials science research. However, the radiation damage to key performance of transparent devices under radiative environment remains as a critical issue. Here, we present a promising technology for nonvolatile transparent electronic devices based on flexible oxide heteroepitaxy. A direct fabrication of epitaxial lead lanthanum zirconate titanate on transparent flexible mica substrate with indium tin oxide electrodes is presented. The transparent flexible ferroelectric heterostructures not only retain their superior performance, thermal stability, reliability, and mechanical durability, but also exhibit remarkably robust properties against to a strong radiation exposure. Our study demonstrates an extraordinary concept to realize transparent flexible nonvolatile electronic devices for the design and development of next-generation smart devices with potential application in electronics, automotive, aerospace, and nuclear systems.

Chemical modification of engineered microenvironments surrounding living cells represents a means for directing cellular behaviors through cell-matrix interactions. Presented here is a temporally controlled method for modulating the properties of biomimetic, synthetic extracellular matrices (ECM) during live cell culture employing the rapid, bioorthogonal tetrazine ligation with trans-cyclooctene (TCO) dienophiles. This approach is diffusion-controlled, cytocompatible, and does not rely on light, catalysts, or other external triggers. Human bone-marrow-derived mesenchymal stem cells (hMSCs) were initially entrapped in a hydrogel prepared using hyaluronic acid carrying sulfhydryl groups (HA-SH) and a hydrophilic polymer bearing both acrylate and tetrazine groups (POM-AT). Inclusion of a matrix metalloprotease (MMP)-degradable peptidic cross-linker enabled hMSC-mediated remodeling of the synthetic environment. The resultant network displayed dangling tetrazine groups for subsequent conjugation with TCO derivatives. Two days later, the stiffness of the matrix was increased by adding chemically modified HA carrying multiple copies of TCO (HA-TCO) to the hMSC growth media surrounding the cell-laden gel construct. In response, cells developed small processes radially around the cell body without a significant alteration of the overall shape. By contrast, modification of the 3D matrix with a TCO-tagged cell-adhesive motif caused the resident cells to undergo significant actin polymerization, changing from a rounded shape to spindle morphology with long cellular processes. After additional 7 days of culture in the growth media, quantitative analysis showed that, at the mRNA level, RGD tagging upregulated cellular expression of MMP1, but downregulated the expression of collagen I/III and tenascin C. RGD tagging, however, was not sufficient to induce the classic osteoblastic, chondrogenic, adipogenic, or fibroblastic/myofibroblastic differentiation. The modular approach allows facile manipulation of synthetic ECM to modulate cell behavior, thus potentially applicable to the engineering of functional tissues or tissue models.

Because of the nontargeting release of anticancer drugs, conventional chemotherapy results in serious side effects and poor therapeutic outcomes. In addition, hypoxia situation in the tumor microenvironment also promotes the growth and metastasis of tumors. Multifunctional nanocarriers with stimuli-activation and hypoxia-relieving properties can help overcome some of these limitations. In this study, we have constructed a nanocarrier which is named PBMn-DOX@RBC. A Prussian blue/manganese dioxide (PBMn) nanoparticle is used as an oxygen precursor or catalyzer for H2O2 activation, and a red blood cell (RBC) membrane is used to increase the loading capacity of doxorubicin (DOX) and prolong the circulation time in vivo. H2O2 is overproduced in tumor tissues and tumor cells. It can be used as a stimulus to activate drug release. In the presence of H2O2, the hypoxia inside the tumors is relieved by the administration of PBMn-DOX@RBC. The generated oxygen disrupts the RBC coated on the surface of PBMn, which accelerates the release of DOX. RBCs also prolong the circulation time of the nanometer system in vivo. By combining the photothermal therapy (PTT) and chemotherapy, the tumor growth inhibition mediated by PBMn-DOX@RBC is further enhanced. PBMn-DOX@RBC fulfills the demands to relieve tumor hypoxia and enhance cancer chemotherapy/PTT.

A bimorph composed of ferrimagnetic cobalt ferrite (CoFe2O4, CFO) and flexible muscovite was fabricated via van der Waals epitaxy. The combination of X-ray diffraction and transmission electron microscopy was conducted to reveal the heteroepitaxy of the CFO/muscovite system. The robust magnetic behaviors against mechanical bending were characterized by hysteresis measurements and magnetic force microscopy, which maintain a saturation magnetization (Ms) of ∼120–150 emu/cm3 under different bending states. The large magnetostrictive response of the CFO film was then determined by digital holographic microscopy, where the difference of magnetostrction coefficient (Δλ) is −104 ppm. The superior performance of this bimorph is attributed to the nature of weak interaction between film and substrate. Such a flexible CFO/muscovite bimorph provides a new platform to develop next-generation flexible magnetic devices.

Spintronics has captured a lot of attention since it was proposed. It has been triggering numerous research groups to make their efforts on pursuing spin-related electronic devices. Recently, flexible and wearable devices are in a high demand due to their outstanding potential in practical applications. In order to introduce spintronics into the realm of flexible devices, we demonstrate that it is feasible to grow epitaxial Fe3O4 film, a promising candidate for realizing spintronic devices based on tunneling magnetoresistance, on flexible muscovite. In this study, the heteroepitaxy of Fe3O4/muscovite is characterized by X-ray diffraction, high-resolution transmission electron microscopy, and Raman spectroscopy. The chemical composition and magnetic feature are investigated by a combination of X-ray photoelectron spectroscopy and X-ray magnetic circular dichroism. The electrical and magnetic properties are examined to show the preservation of the primitive properties of Fe3O4. Furthermore, various bending tests are performed to show the tunability of functionalities and to confirm that the heterostructures retain the physical properties under repeated cycles. These results illustrate that the Fe3O4/muscovite heterostructure can be a potential candidate for the applications in flexible spintronics.

Materials with high spin-polarization play an important role in the development of spintronics. Co-based Heusler compounds are a promising candidate for practical applications because of their high Curie temperature and tunable half-metallicity. However, it is a challenge to integrate Heusler compounds into thin film heterostructures because of the lack of control on crystallinity and chemical disorder, critical factors of novel behaviors. Here, muscovite is introduced as a growth substrate to fabricate epitaxial Co

Benefiting from the advances made in well-controlled materials synthesis techniques, nanocomposites have drawn considerable attention due to their enthralling physics and functionalities. In this work, we report a new heteroepitaxial mesocrystal-perovskite nanocomposite, (NiFe2O4)0.33:(La0.67Ca0.33MnO3)0.67. Elaborate structural studies revealed that tiny NiFe2O4 nanocrystals aggregate into ordered octahedral mesocrystal arrays with {111} facets together with a concomitant structural phase transition of the La0.67Ca0.33MnO3 matrix upon postannealing process. Combined magnetic and X-ray absorption spectroscopic measurements show significant enhancement in the magnetic properties at room temperature due to the structural evolution of magnetic NiFe2O4 and the consequent magnetic coupling at the heterointerfaces mediating via well connected octahedrons of Mn-O6 in La0.67Ca0.33MnO3 and (Ni,Fe)-O6 in NiFe2O4. This work demonstrates an approach to manipulate the exciting physical properties of material systems by integrating desired functionalities of the constituents via synthesis of a self-assembled mesocrystal embedded nanocomposite system.

Magnetic refrigeration, resulting from the magnetocaloric effect of a material around the magnetic phase-transition temperature, is a topic of great interest as it is considered to be an alternate energy solution to conventional vapor-compression refrigeration. The viability of a magnetic refrigeration system for magnetic cooling can be tested by exploiting materials in various forms, from bulk to nanostrucutres. In this study, magnetocaloric properties of self-assembled Mn3O4-La(0.7)Sr(0.3)MnO3 nanocomposites, with varying doping concentrations of Mn3O4 in the form of nanocrystals embedded in the La(0.7)Sr(0.3)MnO3 matrix, are investigated. The temperatures corresponding to the paramagnetic-to-ferromagnetic transitions are higher, and the values of change in magnetic entropy under a magnetic field of 2 T show an enhancement (highest being ∼130%) for the nanocomposites with low doping concentrations of Mn3O4, compared to that of pure La(0.7)Sr(0.3)MnO3 thin films. Relative cooling power remain close to those of La(0.7)Sr(0.3)MnO3. The enhanced magnetic phase-transition temperature and magnetocaloric effect are interpreted and evidenced in the framework of interfacial coupling between Mn3O4 and La(0.7)Sr(0.3)MnO3. This work demonstrates the potentiality of self-assembled nanostructures for magnetic cooling near room temperature under low magnetic fields.