Defect-induced room temperature ferromagnetism in Cu-doped In2S3 QDs.

The practical application of existing diluted magnetic semiconductors (DMSs) depends crucially on improving their room temperature ferromagnetism. Doping, as an effective method, can be used to modulate the physical properties of semiconducting materials. Herein, we report on the observation of significant RTFM in a III-VI semiconductor compound doped with nonmagnetic impurities, Cu-doped In2S3 quantum dots (QDs) grown by a gas-liquid phase chemical deposition method. The effect of Cu doping on the electronic structure and optical and magnetic properties of In2S3 is studied systematically. The UV-vis and photoluminescence (PL) spectra reveal that Cu-doped In2S3 can moderately benefit the optical properties of pristine In2S3. Magnetic measurements show that the pristine In2S3 and Cu-doped In2S3 QDs exhibit obvious RTFM, which is ascribed to the role of intrinsic defects in accordance with the bound-magnetic-polaron (BMP) theory. Furthermore, first-principles calculations based on the spin density functional theory indicate that In vacancies and their complexes with Cu dopants play a crucial role in inducing ferromagnetism. These results suggest that the Cu-doped In2S3 QDs are promising candidates for spintronics and magneto-optical applications.

Intraoperative Transcranial Doppler Monitoring Predicts the Risk of Cerebral Hyperperfusion Syndrome After Carotid Endarterectomy.

OBJECTIVE: Cerebral hyperperfusion syndrome (CHS) is a rare but serious complication following carotid endarterectomy (CEA). The aim of this study was to identify intraoperative transcranial Doppler (TCD) hemodynamic predictors of CHS after CEA. METHODS: Between January 2013 and December 2018, intraoperative TCD monitoring was performed for 969 patients who underwent CEA. The percentage increase in the mean velocity of the middle cerebral artery (MCAV%) at 3 postdeclamping time points (immediately after declamping, 5 minutes after declamping, and after suturing the skin) over baseline was compared between CHS and non-CHS patients. RESULTS: CHS was diagnosed in 31 patients (3.2%), including 11 with intracranial hemorrhage. The MCAV% values at the 3 postdeclamping time points over baseline were 177% (81%-275%), 90% (41%-175%), and 107% (55%-191%) in the CHS group, significantly higher than those in the non-CHS group (40% [14%-75%], 15% [1%-36%], and 18% [3%-41%], respectively, all P < 0.001). Receiver operating characteristic curve analysis showed that the 3 intraoperative MCAV% parameters all had excellent accuracy in identifying CHS (areas under the curve: 0.854, 0.839, and 0.858, respectively, all P < 0.001). The predictive value of the model consisting only of preoperative parameters was significantly increased by adding the intraoperative TCD hemodynamic parameters (area under the curve: 0.747 vs. 0.858, P = 0.006). Multivariate analyses identified the intraoperative MCAV% immediately after declamping (odds ratio: 9.840, 95% confidence interval: 2.638-36.696, P < 0.001) as an independent predictor of CHS. CONCLUSIONS: Our results indicate that intraoperative TCD monitoring helps predict CHS after CEA at an early stage.

High growth per cycle thermal atomic layer deposition of Ni films using an electron-rich precursor.

An efficient process for thermal atomic layer deposition (ALD) of Ni film with high growth per cycle (GPC) value is developed in this study using an electron-rich compound (N,N,N',N'-tetramethylethylenediamine) (bis(2,4-pentanedionato)) nickel(ii) and anhydrous hydrazine as the reactants. The thermal properties and adsorption behavior of selected compounds were studied. Significantly, a high film GPC value of 2.1 Å per cycle for ALD was achieved, and the deposited film exhibited high purity, low resistivity and a smooth surface. We believe that such an efficient method for high GPC thermal ALD of Ni and even other transition metals will benefit ALD technology development.

The first atomic layer deposition process for FexN films.

An efficient process for ALD FexN films was reported in this study for the first time. Bis(N,N'-di-tert-butylacetamidinato)iron(ii) (Fe(tBu-amd)2) and anhydrous hydrazine (N2H4) were used as reactants. Ideal self-limiting growth behavior was confirmed through the effect of the reactant dose and deposition cycle number on the growth rate (film thickness). Besides, these pure FexN films were able to grow into trench substrates with an aspect ratio of 2.5 : 1 conformally and uniformly, highlighting the potential of this ALD process for complex 3D or porous structures. The possible mechanism was proposed by investigating the reaction between Fe(tBu-amd)2 and N2H4 in toluene, and performing first-principles calculations. Our ALD process is expected to promote the development of FexN-based nanoengineering for its broad applications.

One-step detonation-assisted synthesis of Fe3O4-Fe@BCNT composite towards high performance lithium-ion batteries.

An Fe3O4-Fe@BCNT composite was successfully synthesized via detonation of a mixture of hexogen (C3H6N6O6) and ferrocene (C10H10Fe), in which bamboo-like carbon nanotubes encapsulating iron nanoparticles attached to Fe3O4 flakes (up to 58.1%) were formed. In the detonation process, hexogen was used to generate high temperature and high pressure, while ferrocene was used as a carbon source and catalyst. The recovered Fe3O4-Fe@BCNT composite was characterized by TEM, SEM, XRD, XPS, and Raman spectroscopy. The results indicate that multi-walled carbon tubes with a bamboo-like structure are formed, in which iron nanoparticles are encapsulated. The length of the multi-layered nanotubes (about 18-20 layers) is over 600 nm with diameters in the range of 20-30 nm. The content of Fe3O4 flakes dispersed into the carbon tubes is affected by the atomic ratio of C to Fe. In addition, the Fe3O4-Fe@BCNT composite exhibits excellent electrochemical performance as an anode material in Li-ion batteries. The charge-discharge coulombic efficiency is up to 81.1% in the first cycle. After 100 cycles, the discharge capacity steadily increases up to nearly 800 mA h g-1 due to activation. The rate capability of the Fe3O4-Fe@BCNT composite is also excellent at current densities ranging from 100 to 2000 mA g-1.