Mechanism of Electromagnetic Flow Control Enhanced by Electro-Discharge in Water

Pulsed discharge utilized to achieve large current density in the electromagnetic flow control is numerically studied. A mathematic discharge model is established to calculate the plasma channel, and an actuator is designed to generate the Lorentz force in the micro plasma channel. During the discharge process, the resistance in the channel decreases rapidly and a large current density appears between the discharge electrodes. After the actuator is applied in the leading edge of a flat plate, the separation region and downstream turbulent boundary layer on the plate disappear. Meanwhile, a skin-friction drag force reduction is achieved.

Natural Graphene Plasmonic Nano-Resonators for Highly Active Surface-Enhanced Raman Scattering Platforms

Highly sensitive and uniform three-dimensional(3D)hybrid heterogeneous structures for use in surface-enhanced Raman scattering(SERS)experiments were fabricated by sequentially decorating high-quality,ultra-clean,graphene quantum dots(GQDs)and Ag nanoparticles(Ag-NPs)onto 3D-graphene.Finite-difference time-domain calculations and scanning Kelvin probe microscopy were used to verify that the Ag-NPs/GQDs/3D-graphene system facilitates substantial electromagnetic enhancement(due to the occurrence of two kinds of"gaps"between the Ag-NPs that form 3D"hot spots")and additional chemical enhancement(in detecting someπ-conjugated molecules).The SERS mechanism was explored in further detail via experimental analysis and confirmed by performing theoretical calculations.The large surface area of the 3D substrate(due to the large specific surface areas of the GQDs and 3D-graphene)results in a better enrichment effect which helps produce lower detection limits.In particular,the detection limits obtained using the Ag-NPs/GQDs/3D-graphene platform can reach 10^(-11)M for rhodamine 6G,10^(-10)M for methylene blue and dopamine,and 10^(-7)M for tetramethylthiuram disulfide and methyl parathion in apple juice(these are superior to most of the results reported using graphene-based SERS substrates).In summary,the 3D-platform Ag-NPs/GQDs/3D-graphene/Si shows outstanding SERS performance.It therefore has excellent application prospects in biochemical molecular detection and food safety monitoring.

Selective synthesis of three-dimensional ZnO@Ag/SiO2@Ag nanorod arrays as surface-enhanced Raman scattering substrates with tunable interior dielectric layer

We describe the synthesis of three-dimensional(3D) multilayer ZnO@Ag/SiO2@Ag nanorod arrays by the physico–chemical method. The surface-enhanced Raman scattering(SERS) performance of the 3D multilayer Zn O@Ag/SiO2@Ag nanorod arrays is studied by varying the thickness of dielectric layer SiO2 and outer-layer noble Ag. The 3D Zn O@Ag/SiO2@Ag nanorod arrays create a huge number of SERS "hot spots" that mainly contribute to the high SERS sensitivity. The great enhancement of SERS results from the electron transfer between ZnO and Ag and different electromagnetic enhancements of Ag nanoparticles(NPs) with different thicknesses. Through the finite-difference time-domain(FDTD) theoretical simulation, the enhancement of SERS signal can be ascribed to a strong electric field enhancement produced in the 3D framework. The simplicity and generality of our method offer great advantages for further understanding the SERS mechanism induced by the surface plasmon resonance(SPR) effect.

Ultralow-noise single-photon detection based on precise temperature controlled photomultiplier with enhanced electromagnetic shielding

We demonstrate an ultralow-noise single-photon detection system based on a sensitive photomultiplier tube（PMT） with precise temperature control, which can capture fast single photons with intervals around 10 ns.By improvement of the electromagnetic shielding and introduction of the self-differencing method, the dark counts（DCs） are cut down to ~1%. We further develop an ultra-stable PMT cooling subsystem and observe that the DC goes down by a factor of 3.9 each time the temperature drops 10°C. At -20°C it is reduced 400 times with respect to the room temperature（25°C）, that is, it becomes only 2 counts per second, which is on par with the superconducting nanowire detectors. Meanwhile, despite a 50% loss, the detection efficiency is still 13%. Our detector is available for ultra-precise single-photon detection in environments with strong electromagnetic disturbances.

UV-light-assisted synthesis of CeB_(6)@Ag nano-trees for SERS application

The conventional methods of using surfactants to synthesize noble metal nanoparticles usually introduce residues on the surface,which inevitably decreases nanoparticles’ surface enhanced Raman scattering(SERS) performance.Herein,we propose a surfactant-free and feasible approach of preparing cerium hexaboride-Ag nano-trees hybrids(CeB_(6)@Ag nano-trees) as the SERS substrate.First,the CeB_(6)was synthesized by a one-pot ionothermal method.Secondly,the CeB_(6)powder and silver nitrate were dispersed in an aqueous solution.Thereafter,the Ag+was reduced by the UV-light assisted photoreaction and deposited on the surface of the CeB_(6).The SERS performance of the CeB_(6)@Ag nano-trees was evaluated by using the Rhodamine 6 G as the Raman reporter.It shows that CeB_(6)@Ag nano-trees exhibit good SERS sensitivity with the enhancement factor of 2.45 × 10^(7) and detection limit of 10^(-10) mol/L.Moreover,uniformity evaluation of the SERS signal intensity on the substrate also shows that relatively good relative standard deviation values of 12.6%(Raman peak@612 cm^(-1)) and 14.1%(Raman peak@1652 cm^(-1))can be achieved.Finally,finite element simulation evidences that excellent SERS performance of the CeB_(6)@Ag nano-trees is produced by the strong coupled localized surface plasmon resonance generated under the Raman laser irradiation.

Adhesive surface-enhanced Raman scattering Cu-Au nanoassembly for the sensitive analysis of particulate matter

Surface-enhanced Raman scattering(SERS)has been used in atmospheric aerosol detection as it enables the high-resolution analysis of particulate matter.However,its use in the detection of historical samples without damaging the sampling membrane while achieving effective transfer and the high-sensitivity analysis of particulate matter from sample films remains challenging.In this study,a new type of SERS tape was developed,consisting of Au nanoparticles(NPs)on an adhesive double-sided Cu film(DCu).The enhanced electromagnetic field generated by the coupled resonance of the local surface plasmon resonances of AuNPs and DCu led to an enhanced SERS signal with an experimental enhancement factor of 10^(7).The AuNPs were semi-embedded and distributed on the substrate,and the viscous DCu layer was exposed,enabling particle transfer.The substrates exhibited good uniformity and favorable reproducibility with relative standard deviations of 13.53%and 9.74%respectively,and the substrates could be stored for 180 days with no signs of signal weakening.The application of the substrates was demonstrated by the extraction and detection of malachite green and ammonium salt particulate matter.The results demonstrated that SERS substrates based on AuNPs and DCu are highly promising in real–world environmental particle monitoring and detection.