The fluorescence enhancement of Rhodamine 6G(Rh6G) fluorophore in the close vicinity of porous alumina film with ordered nanohole arrays is investigated.Experimental observations show that the nonmetallic substrate with hole arrays enhances the fluorescence intensity.By comparing the fluorescence emissions that are excited with 325 nm and 532 nm,better fluorescence enhancement is obtained with excitation at a shorter wavelength.The study suggests that higher fluorescence excitation efficiency due to the energy transfer from oxygen vacancies to Rh6G fluorophore molecules is responsible for better fluorescence enhancement.The contribution of the scattering of nanohole arrays to the fluorescence enhancement is also proposed based on the intensity increase and reduced lifetime when the energy transfer from oxygen vacancy is absent.The result of the current study is useful for developing non-metal substrates in the study of spectroscopic enhancement,and is expected to advance the applications of porous alumina to microanalysis.
We present a study of electronic properties of zigzag graphene nanoribbons(ZGNRs) substitutionally doped with nitrogen atoms at a single edge by first principle calculations. We find that the two edge states near the Fermi level separate due to the asymmetric nitrogen-doping. The ground states of these systems become ferromagnetic because the local magnetic moments along the undoped edges remain and those along the doped edges are suppressed. By controlling the charge-doping level, the magnetic moments of the whole ribbons are modulated. Proper charge doping leads to interesting half-metallic and single-edge conducting ribbons which would be helpful for designing graphene–nanoribbon-based spintronic devices in the future.
Plasmonics is a rapidly developing field concerning light manipulation at the nanoscale with many potential applications, of which plasmonic circuits are promising for future information technology. Plasmonic waveguides are fundamental elements for constructing plasmonic integrated circuits. Among the proposed different plasmonic waveguides, metallic nanowires have drawn much attention due to the highly confined electromagnetic waves and relatively low propagation loss. Here we review the recent research progress in the waveguiding characteristics of metallic nanowires and nanowire-based nanophotonic devices. Plasmon modes of both cylindrical and pentagonal metallic nanowires with and without substrate are discussed. Typical methods for exciting and detecting the plasmons in metallic nanowires are briefly summarized. Because of the multimode characteristic, the plasmon propagation and emission in the nanowire have many unique properties, benefiting the design of plasmonic devices. A few nanowire-based devices are highlighted, including quarter-wave plate, Fabry-Prot resonator, router and logic gates.
室温常压下,以氢化铝锂为还原剂在溶液中还原烯丙基三氯硅烷和四氯化硅体系,制备了烯丙基功能基团修饰的正六边形硅单晶.采用透射电子显微镜（Transmission Electron Microscopy,TEM）和傅里叶变换红外光谱（Fourier Transform Infrared,FTIR）对产物进行表征.研究了硅晶体的尺寸分布、晶面取向及表面组成,推测了可能的反应机理.结果表明,三氯硅烷与四氯化硅浓度比为1：3时经过还原可生成尺寸为20~50nm,表面有烯丙基基团的（111）晶向的单晶硅.
We used a thin-film thermocouple to detect the thermal effect of surface plasmons excited in Au nanohole array structures.We found that the thermal electromotive force of Au film with periodic nanohole structures is three times greater than that of a bare Au film for 785-nm laser excitation at a given power.This effect is caused by the resonant excitation of localized surface plas- mons in the nanoholes.In addition,we found that the thermal electromotive force(EMF)of the Au film with dumbbell-like na- nohole arrays depends strongly on the incident polarization.The thermal EMF is the greatest when the excitation light is polarized perpendicular to the long axis of the dumbbell.
Noble metal nanostructures possess novel optical properties because of their collective electronic oscillations,known as surface plasmons(SPs).The resonance of SPs strongly depends on the material,surrounding environment,as well as the geometry of the nanostructures.Complex metal nanostructures have attracted research interest because of the degree of freedom in tailoring the plasmonic properties for more advanced applications that are unattainable by simple ones.In this review,we discuss the plasmonic properties of several typical types of complex metal nanostructures,that is,electromagnetically coupled nanoparticles(NPs),NPs/metal films,NPs/nanowires(NWs),NWs/NWs,and metal nanostructures supported or coated by dielectrics.The electromagnetic field enhancement and surface-enhanced Raman scattering applications are mainly discussed in the NPs systems where localized SPs have a key role.Propagating surface plasmon polaritons and relevant applications in plasmonic routers and logic gates using NWs network are also reviewed.The effect of dielectric substrates and surroundings of metal nanostructures to the plasmonic properties is also discussed.
Using numerical simulation,we investigate the high-order plasmon resonances in individual nanostructures of an Ag nanorice core surrounded by an Al2O3shell.The peak positions of localized surface plasmon resonances(LSPRs)are red-shifted exponentially with the increase of the dielectric shell thickness.This is due to the exponential decay of electromagnetic field intensity in the direction perpendicular to the interface.This exponential red-shift depends on the wavelength of the resonance peak instead of the resonance order.In addition,we find that the LSPRs in an Ag nanorice of 60-nm width can be perfectly described by a single linear function.These features make nanorice an ideal platform for sensing applications.
