201766(火)

Experimental techniques

We show that the experimental results can be satisfactorily fitted by equation (3), shown by the solid lines in Fig. 5a,c,d, from which values can be extracted and are plotted in Fig. 5b as a function of temperature. By using the well-known g-factor ge=?0.44 for GaAs, we found that increases with increasing temperature and has a value around 60?ps at 80?K. The deduced values fall within the range of 20–150?ps typically reported for electron spin lifetime in GaAs bulk and quantum well structures27,28,29. The observed temperature dependence of the spin lifetime is also consistent with what is expected from the D’yakonov–Perel’ spin relaxation mechanism29,30. (We point out that deduced from the fitting is an effective averaged value, as the experimental results were obtained from ensemble electrons in GaAs with a distribution of depending on their proximity to the Bi2Te3/GaAs interface.) The fact that the surface spin current of the TI can be significantly altered and controlled by the spin injection from GaAs suggests that the TI can greatly benefit from the adjacent GaAs in such hetero or hybrid structures where one can exploit GaAs for its longer electron spin lifetime, improved performance at elevated temperatures and control of spin current in TI.



The bare substrates used in the growth of the TI film in Samples S1 and S2, namely the semi-insulating GaAs (111)B and GaAs (100) 2° off-cut substrate that are denoted as Sub.1 and Sub.2, respectively, were also studied as the reference samples.

Experimental techniques
Photocurrent was measured independently for both x and y directions without electric bias, under optical excitation with a wavelength-tunable, cw Ti-sapphire laser. The excitation T8 Fluorescent Lamps was modulated either in intensity by a mechanic chopper to generate helicity-independent photocurrent or in helicity by using a broadband electro-optic amplitude modulator to generate helicity-dependent photocurrent. Both helicity-independent and helicity-dependent photocurrent could be separately and selectively registered with the standard lock-in technique as described in Supplementary Note 9 and Supplementary Fig. 9. In the helicity-dependent photocurrent measurements, electro-optic amplitude modulator introduced a periodic variation of the laser polarization with each cycle starting from σ+ (left circularly polarized) to σy (linearly polarized along the y direction), then to σ? (right circularly polarized) and finally back to σ+ via σy. In cw-PL experiments, the samples were excited by the same laser beam as that used in the photocurrent measurements under the normal incident condition. The resulting PL emission from the GaAs substrate was collected in a backscattering geometry by a cooled Ge detector through a 0.8-m double grating monochromator. In the TR-PL experiments, a pulsed Ti-sapphire laser with a repetition rate of 76?MHz and a pulse duration of ~2?ps was employed. Transient PL was detected by a streak camera in combination with a 0.5-m single grating monochromator. The time resolution of the whole TR-PL system is 2?ps.



201766(火)

significant injection of photo-excited

Fourth, significant injection of photo-excited carriers from GaAs to TI. The evidence for injection of photo-generated carriers from GaAs to TI is directly provided by a substantial increase of PTE current when . (For the measurements of , an imbalanced geometry was employed to provide a non-vanishing that can directly monitor injection of hot carriers from GaAs and its relative contribution as compared with the PTE current component arising from the photoexcitation of the Bi2Te3 film alone.) Carrier injection gives rise to an increase of ~40% in as compared with that observed with , as shown in Fig. 3a. As the contribution to from photo-generation of hot electrons within Bi2Te3 itself should be smoothly varying with near , which is well above the Bi2Te3 bandgap energy , the observed abrupt increase of when must arise from a different source of hot electrons other than Bi2Te3. The possibility that the observed 40% increase in is merely due to reabsorption of the PL emission Led SMD Bulbs from the GaAs substrate by the TI film can be safely excluded here as the DAP intensity from the substrate was experimentally measured to be at least six orders of magnitude weaker than the laser light. This leaves the injection of photo-generated electrons from GaAs to TI, driven by a large bandgap mismatch between them (), as the only plausible explanation for the observed sharp increase of in Bi2Te3.

Figure 3: Carrier and spin injection from GaAs to TI.
Figure 3
(a) PTE current in the S1 sample, generated intentionally under an imbalanced excitation condition. The current rise observed when the photon energy is tuned above the bandgap energy of GaAs (), with the onset around 1.52?eV, is a result of carrier injection from the GaAs substrate to TI. (b) Helicity-dependent photocurrent as a function of excitation photon energy at the normal incidence measured at 5?K from both S1 and S2 samples. The error bars were estimated from the statistics of 300 data points collected in steady-state measurements.
Full size image
To further confirm <a href="">carrier </a>injection from GaAs to Bi2Te3, we have conducted time-resolved PL (TR-PL) experiments to examine carrier/exciton lifetime in GaAs that could be affected by the injection process. As band-edge excitons in GaAs are formed by binding photo-generated electron–hole pairs and free excitons additionally have a chance to diffuse to the GaAs/TI interface, thereby contributing to carrier injection, the exciton emission X was closely monitored in our TR-PL studies. It is clearly seen from the results shown in Fig. 2c that the exciton lifetime of the GaAs substrate is significantly shorter in the Bi2Te3/GaAs structure (for example, Sample S2) than that in the reference sample of the bare GaAs substrate (for example, Sample Sub.2). Besides the radiative and non-radiative recombination processes common to GaAs in both the Bi2Te3/GaAs structure and the bare GaAs substrate, a major difference between the two structures that can affect the GaAs exciton lifetime is the presence of an additional loss channel for carriers/excitons in GaAs due to their injection to Bi2Te3 in the former structure. This finding thus provides further evidence for efficient carrier/exciton injection that tends to deplete the carriers/excitons in GaAs at and near the TI/GaAs interface.



201766(火)

Immunocytochemistry and fluorescence microscopy

Immunocytochemistry and fluorescence microscopy
All washes and incubation steps were performed in PBS with 0.01% w/v sodium azide (PBS-NaN3) unless otherwise stated. Cell cultures were fixed for 15?min at RT in 4% w/v paraformaldehyde (PFA) in PBS. Fixed cells were blocked and permeabilized with 0.1% Triton X-100 with 10% v/v goat serum (Vector Laboratories; UK) in PBS for 1?hour at RT. Primary and secondary antibody sources and dilutions are shown in Table 1. Primary antibody incubations were overnight at 4°?C, followed with PBS wash, secondary antibody incubations at RT for 1?hour followed with PBS wash, stained for 10?min at RT with DAPI or Hoechst-33342 (Life Technologies; UK) followed with PBS wash prior to mounting in Mowiol with 2.5% w/v DABCO. Omission of primary antibodies was used to verify specificity as control in all experiments. Photo-micrographs were taken with using Leica SP5 confocal or Leica DM inverted microscopes (Leica; UK).


Binarised images of MBP and IB4 were used to calculate fraction areas with ImageJ v1.48, and normalized to controls for each biological replicate. For Sholl analysis, GFAP images were binarised and branches manually traced using the NeuronJ plugin in ImageJ followed with Sholl Analysis v3.4.1 plugin in ImageJ55. Sholl parameters were 10?μm starting radius with 2.5?μm steps. Viability was calculated as cell numbers with DAPI and cell specific marker (NG2 or β-III-tubulin) minus those with PI, and values normalized to control conditions.

Calcium Imaging
Coverslips with OPCs were placed in either DMEM?+?SATO or MEMO?+?SOS with mitogens for ~24?hrs, prior to loading LED Candle Lights with 4?μM Fura2-AM (Life Technologies; UK) for 1?hour at 37?°C. Coverslips were placed on an Olympus IX71 microscope superfused with buffered Ringer’s solution containing the following (in mM) 124 NaCl, 2.5 KCl, 2 MgCl2, 1 NaH2PO4, 26 NaHCO3, 10 Glucose and 2.5 CaCl2 and bubbled with 95% O2, 5% CO2. Fluorescent images from 340?nm and 380?nm excitations were collected, on average from all experiments (n?=?10), for 83.9?±?1.54?minutes at an average of ~1 frame per second (0.78?±?0.02), with an exposure time of 200?ms. The emission of Fura2-AM is measured at 510?nm after excitation at 340?nm and 380?nm and the ratio of these emission intensities correlates with the calcium concentration within the cell.

Statistical Analysis
Numbers of experiments are indicated on bargraphs, data shown as mean?±?standard error of the mean (s.e.m.), and assumed to follow normal distribution. P values from Student’s two tailed unequal variance t-tests?<?0.05 were considered significant.

Additional Information
Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.



201765(月)

The entanglement can be evaluated in terms of sinuosity

The entanglement can be evaluated in terms of sinuosity (S), defined as L/d, wherein d is the shortest distance between the two ends of a given fibre with the length L. The value of S for a perfectly straight fibre (S=1.0) increases upon increasing the degree of entanglement. Histograms of L, d and S values for randomly chosen fibres of SPspiral, (SPlinear)UV and (SPrandom)Vis are shown in Supplementary Fig. 12. The L of the above three SPs are widely distributed in the range of 100–1,500 nm, and the distribution showed no arguable difference before and after light irradiation. In contrast, the distribution of d displayed a great change before and after light irradiation. While the d of most SPspiral and (SPrandom)Vis fibres are in the range of 100–500 nm, those of (SPlinear)UV fibres are distributed in a wider range up to 1,200 nm due to extension. As a result, most of the (SPlinear)UV fibres have S values in the range of 1.0–3.0, which illustrates their extended form, whereas those of SPspiral and (SPrandom)Vis are more widely distributed in the range of 2–20, which illustrate the substantial difference in entanglement well.



201765(月)

There were a number of reports on the growth of NR

Additional Information
Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

There were a number of reports on the growth of NR using several kinds of growth techniques. Inorganic nanowires can be synthesized by various methods such as VLS, CVD, thermal oxidation and hydrothermal (Supplementary Table 3). However, VLS, CVD and the thermal oxidation methods required high temperature (greater than 400 °C), which would damage a polymer substrate. The hydrothermal method can grow NRs at low temperatures (about 100 °C), but the growth rate is too slow (less than 1 nm min-1). The high process temperatures and slow rates of the previous methods are serious disadvantages for application to polymer substrates. In this work, we found a way to use a Cl2 plasma source to grow the single-crystalline and vertically well-aligned AgCl NRs. The advantages of this technique are low temperature process (room temperature) and high-growth rate (about 2,000 nm min-1). Such process condition allows the AgCl NRs to implement the R2R process shown in Fig. 1.

To confirm the applicability of the method to R2R process, we designed a virtual roll-to-roll (R2R) system (Supplementary Fig. 10). The plasma exposure time is a critical factor for application to R2R process. The plasma time of 45 s is sufficient to get the NRs (Fig. 2). Because the deposition rate of Ag layer did not have a significant effect on morphology or growth rate of AgCl NRs (Supplementary Fig. 11), the deposition rate was set to be 20 Å s-1.

When the plasma chamber was 90 cm long, and the Ag-deposition chamber was 300 cm long, the feed rate of R2R process was 1.2 m min-1, which could be used in a commercial process. As a result, the plasma-induced AgCl NRs could be rapidly fabricated using an R2R process over a large area on several kinds of polymer film because the method does not require lithography, mask moulds or thermal processes. These size-tunable and plasma-induced AgCl NRs can promote the commercialization of highly efficient, inexpensive flexible optoelectronic devices.

Methods
Fabrication of AgCl NRs
The colourless PI films were ultrasonically cleaned with isopropyl alchol for 5 min, then dried under blowing N2 gas and baked at 110 °C for 10 min. The Ag layer was deposited at 1 Å s-1 on the PI film by using an e-beam evaporator under 1 × 10-6 Torr. Then PI films with Ag layers were treated using Cl2 plasma. The plasma was induced using 350-W RF power in Cl2 ambient. The chamber pressure was maintained at 10 mTorr during treatment.

Characterized instrument
The total and diffused transmittance of the AgCl/PI sample were measured using a ultraviolet–visible–NIR spectrophotometer (Cary 4000, Agilent) with a diffuse reflectance accessory. The surface morphology of the AgCl was measured using a field-emission scanning electron microscope (XL30S FEG, PHILIPS) with an 5 kV acceleration voltage and 6 mm working distance, and an atomic force microscope operated in tapping mode on a Veeco nanoscope III. XPS was measured using a synchrotron radiation photoemission spectroscopy with the incident X-ray source at 650 eV and a base pressure of 5 × 10-10 Torr at the 4D beam line at the Pohang Accelerator Laboratory (PAL). The chemical bonding states were separated using a combination of Gaussian and Lorentzian functions. The XRD patterns were measured using a house X-ray source (D2 phaser, Bruker) at 30 kV and 10 mA. Off-axis phi scans using synchrotron radiation were performed at the 3D beamline at PAL. The HRTEM (JEM 2200FS, JEOL) was conducted at 200 kV with a Cs-corrector. The AgCl NRs were sonicated in ethanol and put in a Cu grid. To prevent e-beam decomposition of the AgCl, 10 nm of carbon was deposited on both sides of the Cu grid.



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