Xihong Guo

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.

Novel Carbon Nanohybrids As Highly Efficient Magnetic Resonance Imaging Contrast Agents

Novel carbon nanohybrids based on unmodified metallofullerenes have been successfully fabricated for use as a new magnetic resonance imaging (MRI) contrast agent. The nanohybrids showed higher R1 relaxivity and better brightening effect than Gd@C82(OH)X, in T1-weighted MR images in vivo. This is a result of the proton relaxivity from the original gadofullerenes, which retained a perfect carbon cage structure and so might completely avoid the release of Gd3+ ions. A “secondary spin-electron transfer” relaxation mechanism was proposed to explain how the encaged Gd3+ ions of carbon nanohybrids interact with the surrounding water molecules. This approach opens new opportunities for developing highly efficient and low toxicity MRI contrast agents.

Enhancement of Au nanoparticles formed by in situ electrodeposition on direct electrochemistry of myoglobin loaded into layer-by-layer films of chitosan and silica nanoparticles.

In the present work, a new kind of myoglobin (Mb)/Au nanoparticles composite film was fabricated on pyrolytic graphite (PG) electrodes. Oppositely charged chitosan (CS) and silica (SiO(2)) nanoparticles were alternately adsorbed on the PG surface by the electrostatic interaction between them, forming {CS/SiO(2)}(5) layer-by-layer films. Mb and HAuCl(4) in solution were then simultaneously loaded into {CS/SiO(2)}(5) films. The loaded Au(III) in the films were electrochemically reduced into Au nanoparticles, forming nanocomposite films, designated as {CS/SiO(2)}(5)-Mb-Au. Various techniques such as cyclic voltammetry (CV), square wave voltammetry (SWV), quartz crystal microbalance (QCM), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis were used to characterize the films. Compared with {CS/SiO(2)}(5)-Mb films without Au nanoparticles inside, the {CS/SiO(2)}(5)-Mb-Au films exhibited much better behavior in electrochemistry and electrocatalysis of Mb, mainly because the Au nanoparticles formed inside the films were located in proximity to Mb and acted as electron bridges between Mb molecules, making more Mb molecules in the films become electroactive. In addition, the permeability or porosity of the films also played an important role in realizing the direct electrochemistry of Mb. This system provides a novel platform to develop electrochemical biosensors based on the direct electron transfer of redox enzymes without using mediators.

Enhanced performance of inverted organic photovoltaic cells using CNTs-TiOX nanocomposites as electron injection layer

In this study, we fabricated inverted organic photovoltaic cells with the structure ITO/carbon nanotubes (CNTs)-TiO(X)/P3HT:PCBM/MoO₃/Al by spin casting CNTs-TiO(X) nanocomposite (CNTs-TiO(X)) as the electron injection layer onto ITO/glass substrates. The power conversion efficiency (PCE) of the 0.1 wt% single-walled nanotubes (SWNTs)-TiO(X) nanocomposite device was almost doubled compared with the TiO(X) device, but with increasing concentration of the incorporated SWNTs in the TiO(X) film, the performance of the devices appeared to decrease rapidly. Devices with multi-walled NTs in the TiO(X) film have a similar trend. This phenomenon mainly depends on the inherent physical and chemical characteristics of CNTs such as their high surface area, their electron-accepting properties and their excellent carrier mobility. However, with increasing concentration of CNTs, CNTs-TiO(X) current leakage pathways emerged and also a recombination of charges at the interfaces. In addition, there was a significant discovery. The incorporated CNTs were highly conducive to enhancing the degree of crystallinity and the ordered arrangement of the P3HT in the active layers, due to the intermolecular π-π stacking interactions between CNTs and P3HT.

Supercritical synthesis and characterization of SWNT-based one dimensional nanomaterials

The present study developed a novel, fast and efficient method to synthesize one dimensional nanotube-based materials via supercritical reactions and supercritical fluids. It was proved that supercritical organic fluids were good media to take materials into the nanocavity, not only as solvents but also as reaction agents. Different kinds of metals (Ni, Cu, Ag) and fullerenes (C(60), C(70), C(78), C(84), Gd@C(82), Er@C(82), Ho@C(82), Y@C(82)) were successfully inserted into nanotubes with small diameters by this technique, with various supercritical fluids such as C(2)H(5)OH, CH(3)OH or C(6)H(5)CH(3). The filling rates were proved to be more than 90%. The high filling efficiency and the properties of the as-generated materials were characterized by TEM, Raman, EDS and XPS. In principle, this technique can be applied to construct new types of nanomaterials, if we choose the appropriate supercritical reaction and fluid in the CNTs.

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.

Synthesis of a UCNPs@SiO2@gadofullerene nanocomposite and its application in UCL/MR bimodal imaging

Multimodal imaging provides more complementary information than single mode imaging. Herein, we have developed a novel bimodal imaging agent (GdF–UCNPs) through conjugating paramagnetic water-soluble polyhydroxy Gd@C82-PCBM with silica coated NaYF4:Yb,Er nanoparticles. In the new contrast agent, the stable silica shell and the carbon cage structure protect the encaged inner rare earth ions, which results in low toxicity. The resulting nanoconjugates exhibit strong luminescence and present efficient MRI contrast (r1 = 11.89 mM−1 s−1). Ex vivo and in vivo bimodal imagings were carried out in a mouse model. The results prove that the nanocomposites are useful as bimodal imaging agents for luminescence/MR imaging in biomedical research.

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.

An Electrochemical Immunosensor for Fullerenol Detection Based on the Generated Antibody

As the nanomaterial fullerenol has attracted much attention in various fields, there is a need to develop convenient and effective detection methods for its determination. In this paper, the polyclonal antibody against fullerenol was obtained by immunization of rabbits with the fullerenol protein conjugate. Based on this new antibody against fullerenol, an electrochemical immunosensor was constructed by employing the redox couple to sense the generated antibody and fullerenol interaction. The peak current decreased after the interaction of fullerenol with the immunosensor. Using this strategy, the concentration of fullerenol in the range of 1 × 10−5 to 1 mg mL−1 was detected with a good linear relationship, and the lowest detection limit was about 3 × 10−6 mg mL−1. This immunosensor was used to detect and quantify fullerenol.

Structural change of metallofullerene: an easier thermal decomposition

We have studied for the first time the structural change of high-purity metallofullerene (Gd@C(82)) upon heat treatment in an ultra-high vacuum system (10(-10) Torr) and examined the decomposition product through successive analysis with MS, IR, Raman, TEM, EDS and XPS. It was found that metallofullerene (Gd@C(82)) had fully collapsed at 580 °C which was lower than that for the complete destruction of C(60). The easier decomposition should be ascribed to the encapsulated metal in the carbon cage which could induce the deformation of the C-C bond. The analysis indicated that the broken metallofullerene (Gd@C(82)) became a kind of graphite-like material with a lot of defects. The Gd atoms leaked out from the carbon cage and aggregated together to form a regular arrangement.