ReS2 Nanoflowers-Assisted Confined Growth of Gold Nanoparticles for Ultrasensitive and Reliable SERS Sensing.

ReS2, as a new member of transition metal dichalcogenides (TMDCs), has emerged as a promising substrate for semiconductor surface-enhanced Raman spectroscopy (SERS) due to its unique optoelectronic properties. Nevertheless, the sensitivity of the ReS2 SERS substrate poses a significant challenge to its widespread application in trace detection. In this work, we present a reliable approach for constructing a novel ReS2/AuNPs SERS composite substrate, enabling ultrasensitive detection of trace amounts of organic pesticides. We demonstrate that the porous structures of ReS2 nanoflowers can effectively confine the growth of AuNPs. By precisely controlling the size and distribution of AuNPs, numerous efficient and densely packed "hot spots" were created on the surface of ReS2 nanoflowers. As a result of the synergistic enhancement of the chemical and electromagnetic mechanisms, the ReS2/AuNPs SERS substrate demonstrates high sensitivity, good reproducibility, and superior stability in detecting typical organic dyes such as rhodamine 6G and crystalline violet. The ReS2/AuNPs SERS substrate shows an ultralow detection limit of 10-10 M and a linear detection of organic pesticide molecules within 10-6-10-10 M, which is significantly lower than the EU Environmental Protection Agency regulation standards. The strategy of constructing ReS2/AuNPs composites would contribute to the development of highly sensitive and reliable SERS sensing platforms for food safety monitoring.

Magnetic tuning of upconversion luminescence in Au/NaGdF4:Yb3+/Er3+ nanocomposite.

Lanthanide-doped upconversion nanoparticles (UCNPs) NaGdF4:Yb3+/Er3+ have received increasing attention due to their unique optical-magnetic bifunctional properties. Here, we show that the luminescent intensity from NaGdF4:Yb3+/Er3+ nanoparticles decreases monotonously with increasing the applied magnetic field from 0 to 37.1 T, while plasmon-enhanced upconversion luminescence in Au/NaGdF4:Yb3+/Er3+ nanocomposite is independent of a magnetic field lower than 6 T. The surface plasmon resonances could compensate for the energetic mismatching between the excitation light and the energy-level gaps induced by magnetic field and enhance the radiative efficiency, which is the main factor for achieving this stable upconversion emission in this nanocomposite under a magnetic field not higher than 6 T. These findings provide a novel route for exploring the magnetic control of upconversion luminescence in lanthanide-doped bifunctional nanoparticles.

Mechanistic Analysis of Embedded Copper Oxide in Organic Thin-Film Transistors with Controllable Threshold Voltage.

The modulation of threshold voltage (V TH) of organic thin-film transistors (OTFTs) was investigated by embedding a thin CuO layer between the two semiconductor layers. The results showed that the V TH of OTFTs with a CuO layer can be effectively tuned by controlling the positive gate-to-source voltage (V GS0) under stress of gate-to-source voltages. The V TH shifts from -3.67 to -0.82 V when the positive V GS0 varies from 30 to 50 V. This can be explained by the mechanism of trapping electrons at the interface between the CuO charge-separation layer and the active layer. To confirm the role of the CuO layer acting as the charge-separation source, two organic thin-film diodes, indium-tin oxide(ITO)/tris (8-quinolinolato) aluminum(III) (Alq3)/pentacene/Al (inverted-stack diode) and ITO/Alq3/CuO/pentacene/Al (inverted-stack diode with a CuO layer), were fabricated and their diode current characteristics were measured. For the second device, a large current flow was observed at positive bias on the ITO electrodes, which is ascribed to the internal bipolar charge separation within the added CuO zone.

Core/shell upconversion nanoparticles with intense fluorescence for detecting doxorubicin in vivo.

Doxorubicin (Dox) is a chemotherapy medication used to treat cancer. Herein, we report a rapid and efficient method for detecting Dox in vivo based on a NaGdF4:Yb3+,Er3+@NaYF4 core/shell upconversion nanoparticles (UCNPs) probe. We found that the intensity ratio of green to red emission (IGVRE) bands of the core/shell NaGdF4:Yb3+,Er3+@NaYF4 nanoparticles was sensitive to Dox in blood samples, and drops as the concentration of Dox increases. In addition, the proposed UCNPs probe possessed the advantage that no nanoparticles leaked into the living body, thus overcoming the intrinsic defect (difficulty in removing UCNPs from blood vessels) of the fluorescence resonance energy transfer (FRET) approach. This proposed UCNP probe design and results may provide some guidance for the real-time and efficient detection of Dox, and can be helpful in biomedical applications.

Correction: Core/shell upconversion nanoparticles with intense fluorescence for detecting doxorubicin in vivo.

[This corrects the article DOI: 10.1039/C8RA02928H.].