Mingwang Shao

Upconversion and Downconversion Fluorescent Graphene Quantum Dots: Ultrasonic Preparation and Photocatalysis

A facile ultrasonic route for the fabrication of graphene quantum dots (GQDs) with upconverted emission is presented. The as-prepared GQDs exhibit an excitation-independent downconversion and upconversion photoluminescent (PL) behavior, and the complex photocatalysts (rutile TiO(2)/GQD and anatase TiO(2)/GQD systems) were designed to harness the visible spectrum of sunlight. It is interesting that the photocatalytic rate of the rutile TiO(2)/GQD complex system is ca. 9 times larger than that of the anatase TiO(2)/GQD complex under visible light (λ > 420 nm) irradiation in the degradation of methylene blue.

Multifunctional nanoparticles for upconversion luminescence/MR multimodal imaging and magnetically targeted photothermal therapy.

Theranostics, the combination of diagnostics and therapies, has become a new concept in the battles with various major diseases such as cancer. Herein, we develop multifunctional nanoparticles (MFNPs) with highly integrated functionalities including upconversion luminescence, superparamagnetism, and strong optical absorption in the near-infrared (NIR) region with high photostability. In vivo dual modal optical/magnetic resonance imaging of mice uncovers that by placing a magnet nearby the tumor, MFNPs tend to migrate toward the tumor after intravenous injection and show high tumor accumulation, which is ~8 folds higher than that without magnetic targeting. NIR laser irradiation is then applied to the tumors grown on MFNP-injected mice under magnetic tumor-targeting, obtaining an outstanding photothermal therapeutic efficacy with 100% of tumor elimination in a murine breast cancer model. We present here a strategy for multimodal imaging-guided, magnetically targeted physical cancer therapy and highlight the promise of using multifunctional nanostructures for cancer theranostics.

Excellent photocatalysis of HF-treated silicon nanowires.

HF-treated silicon nanowires exhibited excellent photocatalysis, which were even better than some noble metal-modified ones, such as palladium, gold, silver, and rhodium. This phenomenon was critical in the application of silicon-related materials as they are normally employed as a catalyst carrier. These HF-treated silicon nanowires were also stable in solution over 1 week; consequently, a possible explanation for the stability was proposed.

Flexible Nanogenerators Based on Graphene Oxide Films for Acoustic Energy Harvesting

Graphene oxide (GO), a derivative of graphene, consists of a hexagonal ring of carbon network having both sp 2 - and sp 3 -hybridized carbon atoms bearing hydroxyl and epoxide functional groups on basal planes, as well as carbonyl and carboxyl groups at the edges of the sheet. [8, 9] Those functional groups can extensively modify the electronic structure and chemical properties of GO, [10–12] enabling various applications. [14–24] Here, we report the exciting application of GO as a flexible, high-efficiency nanogenerator, realized through oxygen-containing functional groups which enable GO to store charges and harvest acoustic energy. In this study, GO exfoliated from a modified Hummer method [13, 14] was used to fabricate a nanogenerator, which could convert acoustic energy to electricity at a high conversion efficiency of 12.1 %. The induced mean current is sensitively dependent on the pH values of the suspensions used to prepare the GO films. The findings reveal the exciting potential of GO for fabricating nanogenerators for energy harvesting, as well as a novel avenue for nanoelectronic

Network-like mesoporous NiCo2O4 grown on carbon cloth for high-performance pseudocapacitors

Network-like mesoporous NiCo2O4 arrays were grown on flexible carbon cloth via a hydrothermal method first assisted by polyethylene oxide – polypropylene oxide – polyethylene oxide and ethylene glycol followed by thermal treatment. These arrays were made up of nanoflakes (thickness varies from 5 to 15 nm) and multilevel pores, giving a vast specific surface area of 130.2 m2 g−1. The as-prepared products were fabricated into electrodes to conduct electrochemical experiments. The results showed a high capacitance of 1843.3 F g−1 (volume capacitance of 33.8 F cm−3) at 1 A g−1, satisfied constant rate performance of 80% shifting from 1 to 32 A g−1 (1481 F g−1), and only a 10% loss of its capacitance even after 4000 recycles at a consistent current density of 10 A g−1. A symmetric supercapacitor based on NWM NiCo2O4 was assembled and it exhibited a high specific capacitance of 269 F g−1 at 1 A g−1 and a preferable energy density of 38.3 W h kg−1 at a power density of 396 W kg−1. The optimum overall performance of both high rate capability and cycle stability make the network-like mesoporous NiCo2O4 the prime candidate for application in electrochemical supercapacitors.

The Effect of Dielectric Constants on Noble Metal/Semiconductor SERS Enhancement: FDTD Simulation and Experiment Validation of Ag/Ge and Ag/Si Substrates

The finite-difference time-domain (FDTD) method was employed to simulate the electric field distribution for noble metal (Au or Ag)/semiconductor (Ge or Si) substrates. The simulation showed that noble metal/Ge had stronger SERS enhancement than noble metal/Si, which was mainly attributed to the different dielectric constants of semiconductors. In order to verify the simulation, Ag nanoparticles with the diameter of ca. 40u2005nm were grown on Ge or Si wafer (Ag/Ge or Ag/Si) and employed as surface-enhanced Raman scattering substrates to detect analytes in solution. The experiment demonstrated that both the two substrates exhibited excellent performance in the low concentration detection of Rhodamine 6G. Besides, the enhancement factor (1.3 × 109) and relative standard deviation values (less than 11%) of Ag/Ge substrate were both better than those of Ag/Si (2.9 × 107 and less than 15%, respectively), which was consistent with the FDTD simulation. Moreover, Ag nanoparticles were grown in-situ on Ge substrate, which kept the nanoparticles from aggregation in the detection. To data, Ag/Ge substrates showed the best performance for their sensitivity and uniformity among the noble metal/semiconductor ones.

Catalytic degradation of dye molecules and in situ SERS monitoring by peroxidase-like Au/CuS composite

In this paper, Au/CuS composites were fabricated by a two-step method based on a facile solvothermal approach combined with the in situ reduction. It was demonstrated that the Au/CuS composite not only exhibited excellent peroxidase-like catalytic activity in the oxidation of the typical peroxidases (o-phenylenediamine and diaminobenzidine), but also showed promising SERS performance with remarkable sensitivity and high reproducibility. Based on these properties, the bi-functional Au/CuS composite was employed both as a catalyst for degrading a pollutant (Rhodamine 6G) and a SERS substrate for real-time monitoring of the degradation process quantitatively.

Silicon nanowires with permanent electrostatic charges for nanogenerators.

Electrets are dielectric materials possessing a quasi-permanent electric charge or dipole polarization. Frequently, the electrets are adversely affected by environmental temperature and humidity, leading to charge instability, which severely restricts applications. Here we show that silicon nanowires (SiNWs) via modified oxide-assisted growth can surprisingly serve as electrets with permanent electrostatic charges and surface potential up to 7.7 mV. Significantly, the extraordinary electret behavior of SiNWs is extremely robust, remaining stable against immersion in water for over 2 months. The SiNWs were utilized to fabricate a nanogenerator, which yielded an output electrical power of 2.19 × 10(-11) W with a conversion efficiency of 2.2%. The nanogenerator consists of only one movable part, giving highly sustainable and stable output signals, and thus holds promise for various self-powered applications. The permanent electrostatic charges on SiNWs are attributed to the formation of α-quartz in SiNWs.

The mutual promotional effect of Au–Pd bimetallic nanoparticles on silicon nanowires: A study of preparation and catalytic activity

Au–Pd nanoparticles were synthesized on the surface of silicon nanowires and used in the degradation of the p-nitroaniline, which exhibited the mutual promotional effect compared with Au/Si and Pd/Si catalysts. This synergistic effect factor was calculated as 2.35. The Au–Pd/Si catalysts might be recycled and used again. The catalytic rate of the catalysts only decreased by 20% after recycling for five times.

High capacitance and rate capability of a Ni3S2@CdS core–shell nanostructure supercapacitor

Hierarchical Ni3S2@CdS core–shell nanostructures on nickel foam were synthesized by a one-step hydrothermal method for the first time. As supercapacitor materials, the Ni3S2@CdS core–shell nanostructures exhibited a high capacitance of 3.15 F cm−2 (2100 F g−1) at a current density of 2 mA cm−2, and 86.7% of the original capacitance was retained even at a high current density of 15 mA cm−2, suggesting excellent rate capability. An asymmetric supercapacitor based on Ni3S2@CdS as the positive electrode, porous carbon as the negative electrode and KOH as the electrolyte can work steadily at a voltage of 1.5 V, and presented excellent electrochemical performance. After 4000 charge–discharge cycles at a current density as large as 6 mA cm−2, 130% of the initial capacitance was maintained. The asymmetric supercapacitor exhibited a high energy density of 127.5 W h kg−1 at a current density of 2 mA cm−2 and with a corresponding power density of 0.995 kW kg−1. The above-mentioned results indicate that Ni3S2@CdS could be a potential candidate for supercapacitors.