Li Nb O 3 -doped (Na,K)NbO3 lead-free piezoelectric ceramics were prepared by normal sintering, and the electrical properties were investigated with a special emphasis on the influence of sintering temperature. The ceramics synthesized at 1020–1080°C showed a phase transition from orthorhombic to tetragonal symmetry, which is similar to the morphtropic phase boundary (MPB). Because of such MPB-like behavior, a high piezoelectric coefficient d33 (314pC∕N) was obtained in the nominal composition 0.058LiNbO3–0.942[(Na0.535K0.480)NbO3] ceramic sintered at 1060°C; however, this high d33 value was reported previously only in the Li-modified (Na,K)NbO3-based ceramics with codopants of Ta and Sb to B site.

Articles you may be interested inImproved temperature stability of CaTiO 3 -modified [ ( K 0.5 Na 0.5 ) 0.96 Li 0.04 ] ( Nb 0.91 Sb 0.05 Ta 0.04 ) O 3 lead-free piezoelectric ceramics J. Appl. Phys.

Carbon dots have a wide range of applications in biological and medical fields as an alternative to quantum dots because of their low toxicity and excellent luminescence properties. To date, a large number of carbon dots have been prepared and they were consequently reviewed according to their synthetic method, luminescence properties and related applications. The dispersibility of carbon dots in aqueous and/or organic solvents could actually play a significant role in the properties and various application fields, however, such a perspective is ignored by most of the reviewed literature studies. Thus in this minireview, we focus on the surfactant groups of carbon dots which could be classified as hydrophilic, hydrophobic and amphiphilic types. They have accordingly a marked impact on the dispersibility of carbon dots in different solvents as well as the further advantage in those imaging studies in vitro and in vivo.

CH-π interaction-assisted alignment of organic conjugated systems has played an important role to regulate molecular electronic and photophysical properties, whereas harnessing such a smart noncovalent interaction into the tuning of unimolecular complex emissive bands covering a wide spectral region remains a challenging research topic. Since the tuning for visible and near-infrared emissive properties in a single π-functional platform relates to its multicolor luminescent behaviors and potential superior application in analysis, bioimaging, and sensing, herein, we report a proportional control of the singlet and triplet emissions that cover visible and near-infrared spectral regions, respectively, can be straightforwardly achieved by CH-π interaction-assisted self-assembly at the unimolecular level. Employing an octathionaphthalene-based single luminophore as a prototype, we find that a strength-adjustable CH-π interaction-assisted self-assembly can be established in mixed DMF/HO and in the film state. The hybridization of planar local excited and intramolecular charge transfer transitions occurs on the basis, allowing a competitive inhibition to the intersystem crossing process to generate a complex emission composed of visible fluorescence and near-infrared phosphorescence. Furthermore, reversible mechanochromic and mechanoluminescent conversions of the corresponding solid sample can both be observed to rely on a corresponding self-assembly alternation. These results can probably provide new visions for the development of future intelligent and multifunctional luminescent materials.

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Here we report a chemical strategy that uses rigid molecules to straightforwardly construct amphiphilic carbon dots (ACDs) with high luminescence quantum yields (QYs).

chiefly exhibited on those ferromagnetic systems or specific liquid-crystalline phase, [4] the effective alignment of organic polymers within a magnetic field is not easy to be achieved because of their weak magnetic response. Raising magnetic intensity with high-cost setup is currently a routine approach for addressing the issue. A simple and general chemical strategy that can take advantage of an easily accessible magnetic control is still challenging but desirable.The directed self-assembly (DSA) of block copolymers (BCPs) has been of significant interest as a typical route to produce ordered nanostructures. [5] While those thermodynamically stable structures obtained by BCP self-assembly are usually ordered at the nanometer scale, a macroscopic BCP sample is generally made up of mixed-orientation BCP grains, thus limiting their practical utility in large-area producing. [6] Electric fields, shear and surface-induced alignments have been used to control the orientation of the nanostructures and long-range orderliness in classical polymer systems. Nevertheless, all these techniques require restrictive geometry and direct contact with the polymer surface for alignment. [7] Once the magnetic field can be employed for BCP self-assembly, the entirely exposed BCP interfaces could be rearranged along with the field direction. Therefore, to overcome the poor magnetic response of BCPs, chemists have introduced mesogen into BCPs to form smectic species in response to a magnetic field. [8] Normally the alignment of these samples needs high electromagnetic field (5-10 Tesla), and the expensive facilities remain a big challenge and considerably prevent the application of the BCP self-assembly method. There remains a great challenge to achieve controlled alignment of BCPs with low-intensity magnetic field in an easily accessible way. Specifically, it is keenly interesting to control the DSA of BCPs by a single commercial magnet.We aim to create high magnetostatic energy on BCPs through a smart chemical strategy, thus they will be capable of high sensitivity to weak magnetic field and can be controlled by a commercial neodymium permanent magnet (0.35 Tesla) for DSA (Figure 1). Metal containing paramagnetic polymers with a room temperature ferromagnetic property have attracted great attention. [9] Inspired by these findings, we eventually found that the electrostatical coupling between quaternary ammonium based polystyrene-block-poly(diethyl-aminoethylmethacrylate) (PS-b-PA) and tetrabromoferrate (FeBr 4 − )Magnetic control has been a prosperous and powerful contactless approach in arraying materials into high-order nanostructures. However, it is tremendously difficult to control organic polymers in this way on account of the weak magnetic response. The preparation of block copolymers (BCPs) with high magnetostatic energy is reported here, relying on an effective electrostatic coupling between paramagnetic ions and polymer side chains. As a result, the BCPs undergo a magnetically directed self-assembly to form microphase...

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