Optical activation of material properties illustrates the potentials held by tuning light-matter interactions with impacts ranging from basic science to technological applications. Here, we demonstrate for the first time that composite nanostructures providing nonlocal environments can be engineered to optically trigger photoinduced charge transfer dynamic (CTD) modulations in the solid state. The nanostructures herein explored lead to unprecedented out-of-phase behaviour between charge separation and recombination dynamics, along with linear CTD variations with the optical-field amplitude. Using transient absorption spectroscopy, up to 270 % increase in charge separation rate is obtained in organic semiconductor thin films. We provide evidences that composite nanostructures allow for surface photovoltages to be created, which kinetics vary with the composite architecture and last beyond optical pulse temporal characteristics. Furthermore, by generalizing Marcus theory framework, we explain why CTD modulations can only be unveiled when optic field effects are enhanced by nonlocal image dipole interactions. Demonstrating that composite nanostructures can be designed to use optical fields as CTD remote actuators opens the path for their use in practical and original applications ranging from photochemistry to optoelectronics.
Nanostructured and architectured copper niobium composite wires are excellent candidates for the generation of intense pulsed magnetic fields (>90T) as they combine both high strength and high electrical conductivity. Multi-scaled Cu-Nb wires are fabricated by accumulative drawing and bundling (a severe plastic deformation technique), leading to a multiscale, architectured, and nanostructured microstructure exhibiting a strong fiber crystallographic texture and elongated grain shapes along the wire axis. This paper presents a comprehensive study of the effective elastic behavior of this compos…
2D MoS2 attracts increasing attention for its application in flexible electronics and photonic devices. For 2D material optoelectronic devices, light absorption of the molecularly thin 2D absorber would be one of the key limiting factors in device efficiency, and conventional photon management techniques are not necessarily compatible with them. In this paper, we show two semimetal composite nanostructures for synergistic photon management and strain-induced band gap engineering of 2D MoS2: (1) pseudo-periodic Sn nanodots, (2) conductive SnOx (x<1) core-shell nanoneedle structures. Without sop…
We investigate - both experimentally and theoretically - the inelastic interaction between fast electrons and the electromagnetic field scattered by metallic apertures and nanostructures on dielectric membranes using photon induced near-field electron microscopy. The experiments - performed in a high brightness ultrafast transmission electron microscope - on gold apertures on silicon nitride membranes reveal strong modulations of the electron-light coupling strength. We demonstrates that this effect results from the combined action of the electric field scattered by the aperture edges and the …
A recent preprint arXiv:1807.08572 reported the observation of a transition in Ag/Au nanoparticle composites near room temperature and at ambient pressure, to a vanishingly small four-probe resistance, which was tentatively identified as a percolating superconducting transition. In this brief comment, I point out that a vanishing four-probe resistance may also emerge in non-superconducting systems near conductance percolation threshold.
The viability of ultrasonic sonochemistry is investigated in the context of delivering air-stable metallic Al rich-PVP composite. The parameters investigated are; sono-(1) process intensification, (2) crystallization, (3) agglomeration, and (4) fragmentation, respectively. The conventional solvent of n-hexadecane is employed as the sonotrode generated pressure transmitting medium to carry out the above experiments. Two precursors, (1) Poly (vinylpyrrolidone) (PVP) and (2) Aluminum chloride (AlCl3) are chosen to evaluate and demonstrate the viability of the ultrasonic induced processing. Temper…
Current-modulation annealing to control microwave permittivity in composites with melt-extracted microwires
研究了采用电流调制退火（CCMA）技术制备的CoFeBSiNb微丝/环氧树脂复合材料的微波性能。当外加磁场增加时，我们观察到含有退火25 mm Nb掺杂微丝的复合材料样品的有效介电常数谱中的共振峰的位移。这一观察结果与厚微丝的吸收主导阻抗和铁磁共振现象是一致的。结果表明，CCMA是一种合适的技术，以释放内部残余应力。因此，对于含有少量Nb的样品，我们观察到CCMA允许我们抑制在含有铸态线材的样品中观察到的高频共振峰。然而，对于含有大量Nb的样品，尽管进行了CCMA处理，高频峰仍然存在。在这种情况下，在介电常数谱中的双峰特征的观察归因于共存的非晶相和少量的纳米微晶分布在导线表面。然而，由于长（35 mm）和短（15 mm）的铸态导线和不完美的导线-环氧树脂键合的大的静磁能，可以检测到的谐振峰和特征双峰的介电常数谱没有移动。总体而言，CCMA出现作为一个有前途的策略，以控制微波介电常数的复合材料与熔融提取的微丝。
We propose a mechanism to drive singlet-triplet spin transitions electrically, in a wide class of graphene nanostructures that present pairs of in-gap zero modes, localized at opposite sublattices. Examples are rectangular nanographenes with short zigzag edges, armchair ribbon heterojunctions with topological in-gap states and graphene islands with sp$^3$ functionalization. The interplay between the hybridization of zero modes and Coulomb repulsion leads to symmetric exchange interaction that favors a singlet ground state. Application of an off-plane electric field to the graphene nanostructur…
External magnetic fields are known to attract and orient magnetically responsive colloidal particles. In the case of 2D microplatelets, rotating magnetic fields are typically used to orient them parallel to each other in a brick-and-mortar fashion. Thanks to this microstructure, the resulting composites achieve enhanced mechanical and functional properties. However, parts with complex geometry require their microstructure to be specifically tuned and controlled locally in 3D. Although the tunability of the microstructure along the vertical direction has already been demonstrated using magnetic…
Magnetic Skyrmions and multiferroics are the most interesting objects in nanostructure science that have great potential in future spin-electronic technology. The study of multiferroic Skyrmions has attracted much interest in recent years. This article reports magnetic Bloch Skyrmions induced by an electric driving field in a composite bilayer (chiral-magnetic/ferroelectric bilayer) lattice. By using the spin dynamics method, we use a classical magnetic spin model and an electric pseudospin model, which are coupled by a strong magnetoelectric coupling in the dynamical simulations. Interestingl…
Effect of 1-D photonic crystals on optical transmission of VO2 is studied by depositing thin films of VO2 nanoparticles on SiO2/TiO2 distributed Bragg reflectors (DBR) in the near infrared (IR) spectrum as per earlier theoretical predictions of J. Phys. D: Appl. Phys. 51 375102 (2018). Monoclinic VO2 nanoparticles with tuned crystallinity were synthesized by a facile solution processing method. Moderately crystalline (MC) and highly crystalline (HC) VO2 nanostructures were obtained by varying its synthesis temperature and post growth annealing conditions. Both MC VO2 and HC VO2 films exhibit e…
This study is focused on the mechanical properties and stress transfer behavior of multiscale composites containing nano- and micro-scale reinforcements. The distinctive feature of construction of this composite is such that the carbon nanostructures (CNS) are dispersed in the matrix around the continuous microscale fiber to modify microfiber-matrix interfacial adhesion. Such CNS are considered to be made of aligned CNTs (A-CNTs). Accordingly, multiscale models are developed for such hybrid composites. First, molecular dynamics simulations in conjunction with the Mori-Tanaka method are used to…
An analytical model of the spin-diode effect induced by resonant spin-transfer torque in a ferromagnetic bilayer with strong dipolar coupling provides the resonance frequencies and the lineshapes of the magnetic field spectra obtained under field or laser-light modulation. The effect of laser irradiation is accounted for by introducing the temperature dependence of the saturation magnetization and anisotropy, as well as thermal spin-transfer torques. The predictions of the model are compared with experimental data obtained with single Co/Cu/Co spin valves, embedded in nanowires and produced by…
Amongst the wide spectrum of potential applications of graphene, ranging from transistors and chemical-sensors to nanoelectromechanical devices and composites, the field of photonics and optoelectronics is believed to be one of the most promising. Indeed, graphene's suitability for high-speed photodetection was demonstrated in an optical communication link operating at 10 Gbit/s\cite. However, the low responsivity of graphene-based photodetectors compared to traditional III-V based ones is a potential drawback. Here we show that, by combining graphene with plasmonic nanostructures, the efficie…
