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Bi1−xBaxFeO3 (BBFO, x = 0, 0.03, 0.1) thin films were epitaxially grown on SrRuO3-buffered SrTiO3 (001) substrates by pulsed laser deposition. With increasing Ba content, the BBFO thin films show significantly reduced leakage currents but suppressed ferroelectric polarization. X-ray diffraction reciprocal space mappings and Raman spectra indicate a structural evolution from a rhombohedral-like to tetragonal-like phase in the BBFO thin films. Optical absorption and photoelectron spectroscopy measurements demonstrate a modulation of energy band structures in the BBFO thin films. With A-site Ba acceptor doping, the BBFO thin films exhibit a blue-shift of optical bandgap and an increase in work function. The energy positions of conduction and valence bands of the BBFO thin films have been modulated, and the Fermi level shifts down to the center of the forbidden band, but acceptor-doped BFO thin films still show n-type conduction. The presence of extra oxygen vacancies by acceptor doping is supposed to make contribution to conduction behavior. This study provides a method to manipulate the functional properties and gives insights into the physics of Ba doping in BFO thin films. [ABSTRACT FROM AUTHOR]

Ultralong organic phosphorescence (UOP) is essential for potential applications in bioelectronics and optoelectronics. However, the precise design of UOP materials remains a formidable challenge. Herein, a facile strategy is presented to confine dimeric chromophores for triggering UOP emission, based on the manipulation of the carbonyl, sulfonyl, and amino groups within organic phosphors. The experimental data reveal that saccharin analogs in crystals containing dimeric chromophores, confined by the (3D) hydrogen‐bonded networks, exhibit ultralong emission lifetime of up to 635 ms under ambient conditions. Whereas for saccharin analogue crystals lacking dimeric chromophores, the lifetime decreases to 54 ms, resulting in the absence of UOP emission. Moreover, the non‐toxic saccharin crystals with UOP have succeeded in drug anti‐counterfeiting. These findings will open a novel avenue for the design UOP materials and broaden the domain of UOP to diverse applications. [ABSTRACT FROM AUTHOR]

Repairing infected bone defects remains a severe challenge due to antibiotic abuse and recurrence. Hence, we modified magnetocaloric Fe3O4 nanoparticles and added them to magnesium calcium phosphate bone cement (MCPC) to fabricate multifunctional magnetic composites for sequential bacterial inhibition, angiogenesis and osteogenesis. Nevertheless, high doses of Mg ions and Fe ions were released from MCPC, which adversely affected osteogenesis. Thus, Fe3O4 was modified using gelatin according to the emulsification crosslinking method, which exhibited a controllable magnetocaloric effect and degradation behavior, and favorable anti-bacterial ability under the action of an alternating magnetic field (AMF). In the early stage, the residual MgO created a local strong alkaline microenvironment by hydrolysis, which inhibited the function and activity of S. aureus and E. coli. At the later stage, the MCPC composites were controllably degraded under the function of gelatin and maintained a long-term local slight alkaline microenvironment that promoted the osteogenic differentiation and mineralization of BMSCs. In vivo subcutaneous implantation experiments further indicated that MCPC composites showed good biocompatibility and facilitated angiogenesis, presenting a promising future in magnetic materials design and infectious bone defect repair. [ABSTRACT FROM AUTHOR]

The substituent effect is a ubiquitous tool to improve the room temperature phosphorescence (RTP) of organic materials, but it remains unclear as to how to rationally manipulate the RTP performance. However, we establish a π-orbital model to unravel the substituent effect on the organic RTP materials, by using the hybrid quantum mechanics/molecular mechanics (QM/MM) model and N-Electron Valence State Perturbation Theory (NEVPT2). With the substitution of electron-donating groups (EDGs), the increase of the π-orbital energy level separates the hybrid or adjacent n/π-orbitals, converting S1 from (n, π*) to (π, π*) that produces the Tn-dependent intersystem crossing process, accounting for the diverse RTP efficiency caused by EDGs. Moreover, this change also transforms T1 (n, π*) to T1 (π, π*), suppressing the nonradiative relaxation of triplet excitons, thereby prolonging the RTP lifetime. Experimental validation was further performed for the predicted organic RTP molecule based on the π-orbital model. This model provides new guidelines to manipulate the RTP performance in organic materials. [ABSTRACT FROM AUTHOR]

The magnetic resonance sounding (MRS) method is a non-invasive, efficient and advanced geophysical method for groundwater detection. However, the MRS signal received by the coil sensor is extremely susceptible to electromagnetic noise interference. In MRS data processing, random noise suppression of noisy MRS data is an important research aspect. We propose an approach for intensive sampling sparse reconstruction (ISSR) and kernel regression estimation (KRE) to suppress random noise. The approach is based on variable frequency sampling, numerical integration and statistical signal processing combined with kernel regression estimation. In order to realize the approach, we proposed three specific sparse reconstructions, namely rectangular sparse reconstruction, trapezoidal sparse reconstruction and Simpson sparse reconstruction. To solve the distortion of peaks and valleys after sparse reconstruction, we introduced the KRE to deal with the processed data by the ISSR. Further, the simulation and field experiments demonstrate that the ISSR-KRE approach is a feasible and effective way to suppress random noise. Besides, we find that rectangular sparse reconstruction and trapezoidal sparse reconstruction are superior to Simpson sparse reconstruction in terms of noise suppression effect, and sampling frequency is positively correlated with signal-to-noise improvement ratio (SNIR). In one case of field experiment, the standard deviation of noisy MRS data was reduced from 1200.80 nV to 570.01 nV by the ISSR-KRE approach. The proposed approach provides theoretical support for random noise suppression and contributes to the development of MRS instrument with low power consumption and high efficiency. In the future, we will integrate the approach into MRS instrument and attempt to utilize them to eliminate harmonic noise from power line. [ABSTRACT FROM AUTHOR]

Interfaces between complex oxides provide a unique opportunity to discover novel interfacial physics and functionalities. Here, we fabricate the multilayers of itinerant ferromagnet SrRuO 3 (SRO) and multiferroic BiFeO 3 (BFO) with atomically sharp interfaces. Atomically resolved transmission electron microscopy reveals that a large ionic displacement in BFO can penetrate into SRO layers near the BFO/SRO interfaces to a depth of 2-3 unit cells, indicating the ferroelectric proximity effect. A topological Hall effect is indicated by hump-like anomalies in the Hall measurements of the multilayer with a moderate thickness of the SRO layer. With magnetic measurements, it can be further confirmed that each SRO layer in the multilayers can be divided into interfacial and middle regions, which possess different magnetic ground states. Our work highlights the key role of functional heterointerfaces in exotic properties and provides an important guideline to design spintronic devices based on magnetic skyrmions.

Amorphous purely organic phosphorescence materials with long-lived and color-tunable emission are rare. Herein, we report a concise chemical ionization strategy to endow conventional poly(4-vinylpyridine) (PVP) derivatives with ultralong organic phosphorescence (UOP) under ambient conditions. After the ionization of 1,4-butanesultone, the resulting PVP-S phosphor showed a UOP lifetime of 578.36 ms, which is 525 times longer than that of PVP polymer itself. Remarkably, multicolor UOP emission ranging from blue to red was observed with variation of the excitation wavelength, which has rarely been reported for organic luminescent materials. This finding not only provides a guideline for developing amorphous polymers with UOP properties, but also extends the scope of room-temperature phosphorescence (RTP) materials for practical applications in photoelectric fields., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Exploring and manipulating domain configurations in ferroelectric thin films are of critical importance for the design and fabrication of ferroelectric heterostructures with a novel functional performance. In this study, BiFeO 3 (BFO) ultrathin films with various Bi/Fe ratios from excess Bi to deficient Bi have been grown on (La 0.7 Sr 0.3 )MnO 3 (LSMO)-covered SrTiO 3 substrates by a laser molecular beam epitaxy system. Atomic force microscopy and piezoresponse force microscopy measurements show that both the surface morphology and ferroelectric polarization of the films are relevant to Bi nonstoichiometry. More significantly, a Bi-excess thin film shows an upward (from substrate to film surface) uniform ferroelectric polarization, whereas a Bi-deficient thin film exhibits a downward uniform polarization, which means the as-grown polarization of BFO thin films can be controlled by changing the Bi contents. Atomic-scale structural and chemical characterizations and second-harmonic generation measurements reveal that two different kinds of structural distortions and interface atomic configurations in the BFO/LSMO heterostructures can be induced by the change of Bi nonstoichiometry, leading to the two opposite as-grown ferroelectric polarizations. It has also been revealed that the band gap of BFO thin films can be modulated via Bi nonstoichiometry. These results demonstrate that Bi nonstoichiometry plays a key role on the ferroelectric domain states and physical properties of BFO thin films and also open a new avenue to manipulate the structure and ferroelectric domain states in BFO thin films.