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Fe-based nanoparticles are promising oxygen evolution reaction (OER) electrocatalysts. However, they often suffer from serious agglomeration during the electrocatalytic process, which leads to significant attenuation of catalytic performance. Herein, highly dispersed Fe nanoparticles with small sizes of ∼7 nm are confined in amorphous carbon matrix by pulsed laser deposition technology. Based on this, a simple N2 radio frequency plasma strategy is proposed to introduce N doping in the Fe nanoparticles. Electrochemical measurements suggest that N-doped Fe nanoparticles exhibit enhanced OER activity and stability, which offers a low overpotential of 246 mV at 10 mA cm−2 and the Tafel slope of 50 mV dec−1 in 1 M KOH solution. Based on experimental measurements combined with first-principles calculations, the outstanding OER performance of N-doped Fe nanoparticles can be attributed to the synergistic effect of the unique confined structure and N doping, which not only enhances the electrochemical surface area and improves electrical conductivity but also weakens the adsorption of intermediates and reduces the energy barrier of OER reaction. This work provides a facile method for the construction of metal nanoparticles with confined nanostructure and controlled N doping, which will greatly promote the development of OER electrocatalysts.

High efficiency, lightweight, and tunable microwave absorbing materials have drawn tremendous attention. Here, we have synthesized layered GeP5 bulk at high temperature and high pressure. Then, the GeP5 nanosheets are obtained by an efficient liquid-phase exfoliation method and display excellent microwave absorption performance as a microwave absorber. The reflection loss (RL) can achieve below −10 dB in a wide range of thicknesses and microwave frequencies. For further meeting the lightweight demand of microwave absorption materials, porous germanium (GeP5-570) is obtained from GeP5 via the annealing treatment. Microwave absorption characteristics can be significantly improved after annealing treatment. The minimum RL values of porous germanium (GeP5-570) can reach −37.8 dB at a microwave frequency of 4.7 GHz under a thickness of 2.9 mm. The effective absorption bandwidth (RL< −10 dB) of GeP5-570 is 11.8–14.3 GHz with a thickness of 1.2 mm. In addition, the RL value can attain −20 dB in the frequency range of 3.8–16.1 GHz with various thicknesses from 1.0 to 3.5 mm.

The gap mode enhancement of metal nanoparticles is introduced into wide-field Raman microscopic imaging, where it produces a more efficient Raman scattering map compared with the scanning mechanism based on a single nanoparticle. Patterned surface plasmon illumination technique is employed to extend spatial resolution of the wide-field Raman imaging to 133 nm achieved by a modified total internal reflection microscope. The images by different Raman shifts are extracted by using narrow band pass dielectric filters. The technique can serve as a robust tool for wide-field surface enhanced Raman imaging.

Au:CdS nanocomposite film was investigated using femtosecond pump–probe measurement at 800 nm. Time dependence of transmittance shows a two-photon absorption followed by a saturable absorption and recovery process, which clearly demonstrates that resonant energy transfer between CdS and Au nanocomposite systems occur with excitation at 800 nm. In addition, enhancement of the two-photon absorption coefficient in Au:CdS nanocomposite with a factor of more than 6 was observed compared to that of bulk CdS.

Recent experiments showed that irreversible structural change or plasticity could occur in metallic glasses (MGs) even within the apparent elastic limit after a sufficiently long waiting time. To explain this phenomenon, a stochastic shear transformation model is developed based on a unified rate theory to predict delayed yielding in MGs, which is validated afterwards through extensive atomistic simulations carried out on different MGs. On a fundamental level, an analytic framework is established in this work that links time, stress, and temperature altogether into a general yielding criterion for MGs.

Two strong violet-blue luminescence emissions at 390 and 440 nm under excitation at room temperature have been observed in the ordered mesoporous zirconium oxide post-treated with phosphoric acid. The oxide was characterized by powder x-ray diffraction, nitrogen adsorption, diffuse reflectance UV-vis spectroscopy, x-ray fluorescence analysis, and time-resolved photoluminescence decay spectra. It is concluded that these photoluminescence responses are related to the presence of P–O–Zr lumophores in tetrapodal framework due to the post-treatment with phosphoric acid, and are also related to the defects of oxygen vacancies in the mesoporous zirconia itself. The significant optical properties of this material may be very interesting for further application.

We presented a quantitative study on the Fe-doping concentration dependence of optical nonlinearities and ultrafast carrier dynamics in Fe-doped GaN (GaN:Fe) single crystals using picosecond Z-scan and femtosecond pump-probe with phase object techniques under two-photon excitation. In contrast to the two-photon absorption that was found to be independent on the Fe-doping, the nonlinear refraction decreased with the Fe concentration due to the fast carrier trapping effect of Fe3+/Fe2+ deep acceptors, which simultaneously acted as an efficient non-radiative recombination channels for excess carriers. Remarkably, compared to that of Si-doped GaN bulk crystal, the free-carrier refraction effect in GaN:Fe crystals was found to be enhanced considerably since Fe-doping and the effective carrier lifetime (∼10 ps) could be tuned over three orders of magnitude at high Fe-doping level of 1 × 1019 cm−3.

We reported a systematic investigation on the three-photon absorption (3PA) spectra and wavelength dispersion of Kerr refraction of bulk m-plane GaN crystal with both polarization E⊥c and E//c by femtosecond Z-scan technique in the near-infrared region from 760 to 1030 nm. Both 3PA spectra and Kerr refraction dispersion were in good agreement with two-band models. The calculated nonlinear figure of merit and measured ultrafast nonlinear refraction dynamics via femtosecond pump-probe with phase object method revealed that m-plane GaN would be a promising candidate for ultrafast all-optical switching and autocorrelation applications at telecommunication wavelengths.

Optical nonlinearities and transient dynamics of Fe doped GaN (GaN:Fe) were studied by Z-scan and pump-probe with phase object techniques under picosecond and nanosecond at 532 nm. From the pump-probe results, an additional decay pathway subsequent to two photon excitation was observed due to the carrier trapping of Fe3+/Fe2+ deep acceptors. The trapping state in the band gap results in a pronounced modulation to nonlinear responses of GaN:Fe compared to that of undoped GaN. With an effective three-level model as well as carrier trapping effect we described the photo-physical dynamics in GaN:Fe unambiguously.

Metallic glasses (MGs) or other amorphous materials often yield macroscopically with the instantaneous formation of shear bands under the applied stresses. Here, through microcompression tests, we showed that, below the conventional yield stress, shear banding can still be activated but requires an incubation time. The incubation or delay time is found to be closely related to the level of the applied stress. From a dynamic evolution model entailing the plastic deformation units in MGs, the delayed shear banding behavior is modeled as a result of the spatial evolution of the local internal plastic flow.

Yielding in crystalline metals is well known to be governed by dislocation dynamics; however, the structural origin of yielding in metallic glasses (MGs) still remains as an issue of intense debate despite that substantial research efforts have been expended. In this Letter, based on well-designed cyclic microcompression tests, we provide compelling experimental evidence revealing that yielding of MGs is essentially a stress-induced viscous flow process, during which the measured viscosity ranges from 1014 Pa·s to 1011 Pa·s and decreases with the increase of applied stress, resembling the “shear-thinning” behavior of non-Newtonian liquids. This stress-induced non-Newtonian flow finally leads to shear instability, which manifests itself as the phenomenon of delayed yielding common to a variety of MGs.

A patterned LiFePO4 nanorod with a pristine amorphous LiFePO4 surface layer was fabricated by controlling the temperature gradient from the interior to the exterior layer in high-temperature annealing process through designing hierarchical multilayer electrode structure. The three dimensional patterned LiFePO4 nanorods were prepared using tobacco mosaic virus nanoforest arrays. The results indicate that the nano-electrodes nearly reached the theoretical capacity at a very low C rate even without conductive coatings. The amorphous LiFePO4 can fast transport the Li-ion to inside crystal LiFePO4, thus enhancing the rate capability.

Under 980 nm excitation, high multi-photon upconversion (UC) emission from the 2H11/2/4S3/2 (green) and 4F9/2 (red) levels of Er3+ ions were observed from Er3+ singly doped BiOCl microcrystals. These high-energy excited states were populated by a three to ten photon UC process conditionally, which depended on the pump power density and the Er3+ ion doping concentration, characterizing as a hetero-looping enhanced energy transfer avalanche UC process. UC emission lifetime and Raman analysis suggest that the unusual UC phenomena are initiated by the new and intense phonon vibration modes of BiOCl lattices due to Er3+ ions doping.

High crystalline anatase TiO2 and Nb:TiO2 thin films were fabricated on LaAlO3 (100) substrates by pulsed laser deposition. Room temperature ferromagnetism was obtained in Nb:TiO2 but absent in pure TiO2. The Kondo effect and anomalous Hall effect observed in metallic Nb:TiO2 strongly confirmed the existence of exchange interaction between intrinsic local magnetic moments and carriers. High energy resolution x-ray photoelectron spectroscopy studies of the Nb:TiO2 thin film revealed clear signals of Ti3+ and Nb4+ ions, which had one unpaired d electron responsible for the local magnetic moments. This result consisted quite well with the spin polarized first principle calculation.

We studied and demonstrated optical trapping capabilities of an Airy beam generated with a cubic phase plate incorporated into a conventional optical tweezer system. The power efficiency and damage threshold of the cubic phase plate were found to be much higher when spatial light modulators were employed in beam generation.

In this letter, we report an important experimental finding and theoretical analysis of the shear-band speed measured in a variety of bulk metallic-glasses. Unlike the prior work, in which the shear-band speed was regarded as a constant, our current study, based on carefully designed loading-holding cyclic tests, reveals that the speed of a shear band correlates with its resultant shear offset. Such a correlation arises as a “size” effect, which could be rationalized with the energy balance principle and shear-banding dynamics entailing initial shear softening and subsequent materials recovery.

An increased absorption of regioregular poly(3-hexylthiophene) due to surface plasmons (SPs) has been studied by steady state fluorescence spectra measurements and femtosecond transient absorption (TA) technique. The SPs were excited by periodic Ag grating structures transferred from the photoresist gratings which were fabricated by two-beam laser interference. The steady state fluorescence measurements show a maximum enhanced fluorecence of about 16 times larger arising from the absorption enhancement. Further investigation by TA technique reveals that the yield of the polaron pairs on Ag gratings significantly increase, much bigger than that of the pure sample, which also confirms the enhanced absorption efficiency as resulting from the excited SPs.

In this letter, the anelastic deformation of a Zr-based metallic glass (MG) at ambient temperature is revealed through spherical nanoindentation. A general rheological model, which is linked with the atomic structure of MGs, is proposed to explain the observed anelasticity. The experimental and theoretical results clearly indicate the existence of structural inhomogeneity intrinsic to MGs, which causes the anelastic deformation upon mechanical loading under high loading rates before shear banding. The outcome of the current research provides an important insight into the property-structure relation of MGs.

The electronic density of states of two-dimensional (2D) Au quantum dot superlattice are explored by using cryogenic scanning tunneling microscopy and scanning tunneling spectroscopy. The 2D Au superlattice opens up a gap in its electronic density of states. The single-electron transfer of a single Au quantum dot can be effectively inhibited by this “artificial” forbidden gap. This finding opens a route toward modulating electronic energy band of solid on the basis of 2D metal quantum dot superlattice, which may generate materials with electronic properties for possible future electronic devices.

The electronic local density of states of a single Co3O4 semiconductor nanowire with the diameter of 3 nm is explored using low-temperature scanning tunneling microscopy and spectroscopy. The energy gap between the conduction band and valence band of the nanowire is about 1.7 eV, which is slightly enhanced compared to the bulk value, ∼1.5 eV, due to the quantum confinement effect. Two surface states are observed locating near the Fermi level in the band gap.

In this letter, we propose a unified theory for the size-dependent plasticity of bulk metallic glasses (BMGs) at room temperature. Based on the principle of energy balance and the shear-banding kinetics, two characteristic length scales are derived. One is a sample-geometry dependent variable related to the elastic energy released to drive shear-band propagation and the other is a material-dependent constant related to the internal resistance to brittle fracture. It is shown that this unified theory is effective in explaining many unusual deformation and fracture behaviors of BMGs.

Anatase thin films of pure TiO2 and 6% niobium doped TiO2 (Nb:TiO2) were fabricated on LaAlO3(100) by pulsed laser deposition. The electrical properties of Nb:TiO2 films are grain-size dependent, i.e., the larger grain size, the higher conductivity, and mobility. For all TiO2 and for Nb:TiO2 with small mean grain size (d 15 nm), particularly, a blueshift in Nb:TiO2 is governed by the Burstein–Moss effect.

We have presented a detailed experimental investigation of the effects of disorder on the electron-phonon interaction in semiconducting InN system. Both the temperature (T) and disorder (electron mean free path l) dependences of the electron-phonon scattering time τe-ph have been determined from the weak localization analysis. It is found that τe-ph−1 exhibits a tendency to change gradually from the characteristic dependence τe-ph−1∝T3l0 in the pure limit to the form of T2l−1 as the films become disordered. Our observation gives clear evidence for the substantial enhancement of the electron-phonon coupling in semiconductor structures due to elastic electron scattering.

Linear- and parallel-aligned gold nanorods (GNRs) were self-assembled on glass substrates and their surface-enhanced Raman scattering effect was investigated. GNRs were prepared by seed-mediated growth method and self-assembled to form linear and parallel aggregation on the substrate. The parallel-aligned GNRs showed weak optical absorption intensities in the visible to infrared wavelength region. On the other hand, the linear-aligned GNRs exhibited strong optical absorption bands peaking at 830 and 2200nm, which are assigned to the weakly coupled surface plasmons of the GNRs. When Rhodamine-6G molecules were adsorbed on the linear-aligned GNRs, strong surface-enhanced Raman scattering spectra were observed.

Linear chains of SiO2-coated Au nanoparticles, exhibiting large third-order nonlinearity at multiple wavelengths ranging from visible to near infrared, were successfully synthesized and self-assembled on glass substrates using a reduction of HAuCl4 and chemical surfactant modification. The optical absorption spectra peaking at 530, 620, 715, 830, and 1100nm wavelengths were measured to the transverse and longitudinal surface plasmon resonance modes of 2, 3, 4, and 5 Au particles, respectively. Greatly enhanced third-order nonlinear optical responses have been observed at multiple wavelengths.