Guoming Lin

An organic–inorganic hybrid perovskite logic gate for better computing

A practicable means of significantly reducing the energy consumption and speeding up the operating rate of computer chips is to place the processor and memory into one device, which processes and stores information simultaneously like the human brain. Here we demonstrate a novel sandwich architecture where organic–inorganic hybrid perovskite materials could be used as building-block materials for non-volatile memristors, accompanied with photoresponsive performance. Owing to the distinct photo-response of the two resistance states of the memristor, it is feasible to utilize the device as a logic OR gate by employing an electrical field and light illumination as input sources. This study provides potential applications in logic circuits, optical digital computation and optical quantum information for beneficial supplementation of the von Neumann architecture, or even for computing beyond it.

Adaption of the structure of carbon nanohybrids toward high-relaxivity for a new MRI contrast agent

Water-soluble GO–Gd@C82 nanohybrids exhibit high relaxivities and could be explored as potential magnetic resonance imaging (MRI) contrast agents. To better understand the relaxation mechanism in the novel carbon nanohybrids, in the present paper, after layers of in-depth analysis and exploration, we propose that the structure and the physicochemical properties of the carbon nanohybrids contribute significantly to the enhanced relaxivity. Better electron transfer from Gd@C82 to the GO nanosheet, appropriate electric conductivity and size of the GO used, an increased number of H proton exchange sites and an adequate concentration of Gd3+ should result in optimal equilibrium for high relaxivity of the GO–Gd@C82. These results are important for constructing and optimizing novel nanoscale architectures with higher relaxivity.

Magnetic evolution of spinel Mn1−xZnxCr2O4 single crystals

Mn1−xZnxCr2O4 (0 ≤ x ≤ 1) single crystals have been grown using the chemical vapor transport (CVT) method. The crystallographic, magnetic, and thermal transport properties of the single crystals were investigated by room-temperature X-ray diffraction, magnetization M(T) and specific heat CP(T) measurements. Mn1−xZnxCr2O4 crystals show a cubic structure, the lattice constant a decreases with the increasing content x of the doped Zn2+ ions and follows the Vegard law. Based on the magnetization and heat capacity measurements, the magnetic evolution of Mn1−xZnxCr2O4 crystals has been discussed. For 0 ≤ x ≤ 0.3, the magnetic ground state is the coexistence of the long-range ferrimagnetic order (LFIM) and the spiral ferrimagnetic one (SFIM), which is similar to that of the parent MnCr2O4. When x changes from 0.3 to 0.8, the SFIM is progressively suppressed and spin glass-like behavior is observed. When x is above 0.8, an antiferromagnetic (AFM) order presents. At the same time, the magnetic specific heat (Cmag.) was also investigated and the results are coincident with the magnetic measurements. The possible reasons based on the disorder effect and the reduced molecular field effect induced by the substitution of Mn2+ ions by nonmagnetic Zn2+ ones in Mn1−xZnxCr2O4 crystals have been discussed.

Eu3+:Y2O3@CNTs—a rare earth filled carbon nanotube nanomaterial with low toxicity and good photoluminescence properties

Red-emission phosphor europium-doped yttria (Eu3+:Y2O3) nanoparticles have been successfully filled into the nanocavity of carbon nanotubes (CNTs) via supercritical reaction and supercritical fluids followed by calcination. The existence of Eu3+:Y2O3 nanoparticles inside CNTs was characterized by TEM, EDS and XRD. The as-prepared nanomaterials (Eu3+:Y2O3@CNTs) exhibited strong red-emission at 610 nm, which corresponded to 5D0 → 7F2 transition within Eu3+ ions. It showed that the existence of the walls of the CNTs did not quench the luminescence of Eu3+:Y2O3. Due to the surface modification with Tween 80, Eu3+:Y2O3@CNTs had good water solubility. In vitro cytotoxicity studies showed that the as-prepared nanomaterials had low toxicity on HeLa cells at concentrations of 10–1000 μg mL−1. And their use as luminescence probes for live cell imaging was demonstrated by using inverted fluorescence microscopy. With the advantages of the easy dispersion in water, low toxicity, and good photoluminescence (PL) properties, the as-prepared Eu3+:Y2O3@CNTs could potentially be used as nanophosphors in bio-imaging.

Effects of hydrostatic pressure on spin-lattice coupling in two-dimensional ferromagnetic Cr2Ge2Te6

Spin-lattice coupling plays an important role in both formation and understanding of the magnetism in two-dimensional magnetic semiconductors (2DMS). In this paper, the steady pressure effects on the lattice structure, Raman resonances, and magnetization of a 2DMS Cr2Ge2Te6 have been studied by both experiments and first principles calculations. It is found that the bond length of Cr-Cr decreases, the angle of Cr-Te-Cr diverges from 90°, and the Raman modes Eg3 and Ag1 show an increase with the application of external pressure. Consequently, the magnetic phase transition temperature TC decreases from 66.6 K to 60.6 K (∼9%) as the pressure increases from 0 to 1 GPa. These pressure effects not only confirm the existence of strong spin-lattice coupling but also reveal the detailed information about the lattice deformation effect on the magnetic properties in such 2DMS, which would be a benefit for the further understanding and manipulation of the magnetism in 2D materials.

Critical behavior of two-dimensional intrinsically ferromagnetic semiconductor CrI3

CrI3, which belongs to a rare category of two-dimensional (2D) ferromagnetic semiconductors, is of great interest for spintronic device applications. Unlike CrCl3 whose magnetism presents a 2D-Heisenberg behavior, CrI3 exhibits a larger van der Waals gap, smaller cleavage energy, and stronger magnetic anisotropy which could lead to a 3D magnetic characteristic. Hence, we investigate the critical behavior of CrI3 in the vicinity of magnetic transition. We use the modified Arrott plot and Kouvel-Fisher method, and conduct critical isotherm analysis to estimate the critical exponents near the ferromagnetic phase transition. This shows that the magnetism of CrI3 follows the crossover behavior of a 3D-Ising model with mean field type interactions where the critical exponents \b{eta}, {\gamma}, and {\delta} are 0.323, 0.835, and 3.585, respectively, at the Curie temperature of 64 K. We propose the crossover behavior can be attributed to the strong uniaxial anisotropy and inevitable interlayer coupling. Our experiment demonstrates the applicability of crossover behavior to a 2D ferromagnetic semiconductor.

Anomalous Hall effect in two-dimensional non-collinear antiferromagnetic semiconductor Cr0.68Se

Cr0.68Se single crystals with two-dimensional (2D) character have been grown, and the detailed magnetization M(T), electrical transport properties (including longitudinal resistivity and Hall resistivity and thermal transport ones (including heat capacity Cp(T) and thermoelectric power (TEP) S(T)) have been measured. There are some interesting phenomena: (i) Cr0.68Se presents a non-collinear antiferromagnetic (AFM) semiconducting behavior with the Neel temperature TN = 42 K and the activated energy Eg=3.9 meV; (ii) It exhibits the anomalous Hall effect (AHE) below TN and large negative magnetoresistance (MR) about 83.7% (2 K, 8.5 T). The AHE coefficient RS is 0.385 cm-3/C at T=2 K and the AHE conductivity {\sigma}H is about 1 ohm-1cm-1 at T=40 K, respectively; (iii) The scaling behavior between the anomalous Hall resistivity and the longitudinal resistivity is linear and further analysis implies that the origin of the AHE in Cr0.68Se is dominated by the skew-scattering mechanism. Our results may be helpful for exploring the potential application of these kind of 2D AFM semiconductors.