Shigang Hu

Multicolor upconversion NaLuF4 fluorescent nanoprobe for plant cell imaging and detection of sodium fluorescein

Multicolor upconversion NaLuF4 nanocrystals with strong upconversion luminescence and biocompatibility were synthesized by a general solvothermal method and subsequent surface modification. The emission color of these NaLuF4 upconversion nanoparticles can be easily modulated by the doping. These multicolor NaLuF4 upconversion nanocrystals can be employed as fluorescent probes for in vivo biological imaging for living beings, without the need of a slicing process. Importantly, the upconversion nanoprobes (UCNPs) with an acidic ligand can quickly capture the basic sodium fluorescein (SF) in plant cells and form a close UCNPs@SF system. The UCNPs@SF system can emit cyan light due to luminescence resonant energy transfer (LRET) from UCNPs to SF under the excitation of 980 nm infrared light, which is actually composed of the blue emission of NaLuF4:18%Yb3+/0.5%Tm3+ nanoprobes and the green emission of SF. According to the Integral Intensity Ratio of Green to Blue fluorescent signals (IIRGB), the concentration of SF can be easily addressed. The detection limit of sodium fluorescein for this upconversion fluorescent nanoprobe can reach upto 0.14 μg cm−3 in plant cells.

Upconversion NaLuF4 fluorescent nanoprobes for jellyfish cell imaging and irritation assessment of organic dyes

Upconversion NaLuF4 nanoparticles (UCNPs) with intense visible fluorescence and good biocompatibility were successfully synthesized by the solvothermal method and subsequent surface modification, of which the upconversion emission can be tuned by Zn2+ doping. These UC fluorescent nanoprobes with oleic acid–PEG hybrid ligands can efficiently capture Rhodamine B (RhB) and sodium fluorescein (SF) in jellyfish to image their excretion in vivo and simultaneously present background-free cell morphologies and efficient luminescence resonant energy transfer (LRET) processes. The irritation of RhB and SF is assessed in jellyfish cells using NaLuF4 nanoparticles as probes and based on the combination of cell fluorescent imaging with emission spectra from LRET processes. It is clearly determined that RhB presents recoverable physical injury to the cells and SF presents unrecoverable biochemical injury to the cells. This procedure, based on surface controlled UCNPs and the LRET process, supplies background-free imaging and spectrum signals, so that the detecting limitations of conventional ultraviolet excitation are overcome and rapid optical detection of trace organic dyes becomes possible.

A kind of coating method of GaN-MOCVD graphite susceptor

A novel coatingmethod for the GaN-MOCVD graphite susceptor is proposed in the paper, whichmeans that the upper surface and sides of the graphite susceptor are covered with a low emissivity material coating, and the surface under the susceptor is covered with a high emissivity SiC coating. By using finite element analysis software COMSOL Multiphysics, the temperature field of the susceptors without coating, with common SiC coating, and with improved coating is obtained and compared, which shows that the susceptor with the improved coating not only increases the heating efficiency of the heater, but also improves the temperature uniformity of the substrate, which can be of great benefit to the film growth. In addition, this improved coating for the susceptor has the same heating sensitivity as the common SiC coating.

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.

Novel compact dual-band-notched ultra-wideband printed antenna with a parasitic circular ring strip

A simple and compact printed ultra-wideband antenna with dual-band-notched characteristics is presented. The proposed antenna is composed of a rectangular patch and a modified ground plane. The rectangular patch is etched onto a lossy FR4 substrate. A circular ring strip parasitizes the rectangular patch embedded by a U-shaped slot. Two inverted-L slits and a rectangular slit are embedded onto the ground plane. Some bandwidth enhancement and band-notched techniques are applied in the antenna structure for broadening the bandwidth and generating notches. The simulated and measured results show that the proposed antenna offers a very wider bandwidth ranging from 3.04 to 17.30 GHz, defined by the return loss less than −10 dB, with dual-notched bands of 3.30–4.20 and 5.10–5.85 GHz covering the 3.3/3.7 GHz WiMAX, 3.7/4.2 GHz C-band, and 5.2/5.8 GHz wireless local area network systems. Furthermore, the proposed antenna presents relatively high antenna gain and quasi-omnidirectional radiation patterns.

Upconversion NaYF 4 nanoparticles for size dependent cell imaging and concentration dependent detection of Rhodamine B

Upconversion nanoparticles (UCNPs) based on NaYF4 nanocrystals with strong upconversion luminescence are synthesized by the solvothermal method. The emission color of these NaYF4 upconversion nanoparticles can be easily modulated by the doping. These NaYF4 upconversion nanocrystals can be employed as fluorescence donors to pump fluorescent organic molecules. For example, the efficient luminescence resonant energy transfer (LRET) can be achieved by controlling the distance between NaYF4:Yb3+/Er3+ UCNPs and Rhodamine B (RB). NaYF4:Yb3+/Er3+ UCNPs can emit green light at the wavelength of ∼540 nm while RB can efficiently absorb the green light of ∼540 nmto emit red light of 610 nm. The LRET efficiency is highly dependent on the concentration of NaYF4 upconversion fluorescent donors. For the fixed concentration of 3.2 µg/mL RB, the optimal concentration of NaYF4:Yb3+/Er3+ UCNPs is equal to 4mg/mL which generates the highest LRET signal ratio. In addition, it is addressed that the upconversion nanoparticles with diameter of 200 nm are suitable for imaging the cells larger than 10 µm with clear differentiation between cell walls and cytoplasm.

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.

Upconversion nanoparticle arrays for detecting glycated hemoglobin with high sensitivity and good reusability

Lanthanide-doped upconversion nanoparticles (UCNPs) have attracted extensive interest in bio-applications due to their unique optical properties by converting near infrared excitation to visible emission. Here, we show that NaGdF4:48% Yb3+,2% Er3+ upconversion nanoparticle arrays could be used as a high-sensitive, reusable, and stable device for detecting glycosylated hemoglobin (HbA1c), based on the luminescent resonance energy transfer (LRET) from UCNPs to HbA1c. Importantly, the upconversion nanoparticle arrays present a much higher sensitivity to the concentration variation of HbA1c than the direct detection in the solution, which is ascribed to the extinction effect of the arrays.

Upconversion Luminescence and Magnetic Turning of NaLuF4

Fluorescent and magnetic bifunctional NaLuF4:Yb3+/Tm3+/Gd3+ nanocrystals were synthesized by the solvothermal method and subsequent surface modification. By changing the doping concentration of Gd3+, the shape, size, luminescent properties, and magnetic properties of the nanoparticles can be modulated. These NaLuF4:Yb3+/Tm3+/Gd3+ nanocrystals present efficient blue upconversion fluorescence and excellent paramagnetic property at room temperature. Based on the luminescence resonance energy transfer LRET, upconversion nanoparticles UCNPs were confirmed to be an efficient fluorescent nanoprobe for detecting acriflavine. It is easy to derive the concentration of acriflavine from the Integral Intensity Ratio of Green emission from acriflavine to Blue emission from UCNPs fluorescent signals. Based on this upconversion fluorescent nanoprobe, the detection limit of acriflavine can reach up to 0.32 μg/mL.

Low-Complexity robust capon beamforming based on reduced-rank technique

Existing robust Capon beamformers achieve robustness against steering vector errors at a high cost in terms of computational complexity. Computationally efficient robust Capon beamforming approach based on the reduced-rank technique is proposed in this paper. Theproposed method projects the received data snapshots onto a lower dimensional subspace consisting of the matched filters of the multistage Wiener filter (MSWF). The subsequent adaptive beamforming will then be performed within this subspace. The combination of the benefit of the robust adaptive beamforming and the reduced-rank technique improves the performance on combating steering vector errors and lowering the computational complexity.