Theoretical investigation on optical properties of Möbius carbon nanobelts in one-and two-photon absorption

The first successful synthesis of fully fused and fully conjugated Möbius carbon nanobelts(CNBs)has attracted considerable attention.However,theoretical calculations based on suchπ-conjugated Möbius CNB are still insufficient.Herein,we theoretically investigated molecular spectroscopy of Möbius CNBs without and with n-butoxy groups via visualization methods.The results show that the presence of n-butoxy groups can significantly affect Möbius CNBs’optical performance,changing electron-hole coherence and enhancing two-photon absorption cross-sections.Our work provides a deeper understanding of photophysical mechanisms of Möbius CNBs in one-and two-photon absorption and reveals possible applications on optoelectronic devices.

Nanoplasmonic waveguides: towards applications in integrated nanophotonic circuits

The properties of propagating surface plasmon polaritons(SPPs)along one-dimensional metal structures have been investigated for more than 10 years and are now well understood.Because of the high confinement of electromagnetic energy,propagating SPPs have been considered to represent one of the best potential ways to construct next-generation circuits that use light to overcome the speed limit of electronics.Many basic plasmonic components have already been developed.In this review,researches on plasmonic waveguides are reviewed from the perspective of plasmonic circuits.Several circuit components are constructed to demonstrate the basic function of an optical digital circuit.In the end of this review,a prototype for an SPP-based nanochip is proposed,and the problems associated with building such plasmonic circuits are discussed.A plasmonic chip that can be practically applied is expected to become available in the near future.

Remotely excited Raman optical activity using chiral plasmon propagation in Ag nanowires

We experimentally investigated remotely excited Raman optical activity(ROA)using propagating surface plasmons in chiral Ag nanowires.Using chiral fmoc-glycyl-glycine-OH(FGGO)molecules,we first studied the local surface plasmon-enhanced ROA.We found that the Raman intensity can be excited by left-and right-circularly polarized lights and that the circular intensity difference(CID)can be significantly enhanced.Second,by selecting vibrational modes with large Raman and ROA intensities that are not influenced by chemical enhancements,we studied remotely excited ROA imaging and the CID of FGGO molecules by propagating a plasmonic waveguide using Ag chiral nanostructures.When laser light was radiated on one of the Ag terminals,the measured CID of the FGG at the other terminal showed little change compared to the local excited CID.Meanwhile,when the laser light was radiated on the Ag nanowires(not on the terminals)and was coupled to the nearby nanoantenna,the CID of the ROA could be manipulated by altering the coupling angle between the Ag nanowires.To directly demonstrate the propagation of ROA along the nanowire and its remote detection,we also measured the remotely excited ROA spectra.Our experimental method has the potential to remotely determine the chirality of molecular structures and the absolute configuration or conformation of a chiral live cell.

Nanowire-supported plasmonic waveguide for remote excitation of surface-enhanced Raman scattering

Due to its amazing ability to manipulate light at the nanoscale,plasmonics has become one of the most interesting topics in the field of light–matter interaction.As a promising application of plasmonics,surface-enhanced Raman scattering(SERS)has been widely used in scientific investigations and material analysis.The large enhanced Raman signals are mainly caused by the extremely enhanced electromagnetic field that results from localized surface plasmon polaritons.Recently,a novel SERS technology called remote SERS has been reported,combining both localized surface plasmon polaritons and propagating surface plasmon polaritons(PSPPs,or called plasmonic waveguide),which may be found in prominent applications in special circumstances compared to traditional local SERS.In this article,we review the mechanism of remote SERS and its development since it was first reported in 2009.Various remote metal systems based on plasmonic waveguides,such as nanoparticle–nanowire systems,single nanowire systems,crossed nanowire systems and nanowire dimer systems,are introduced,and recent novel applications,such as sensors,plasmon-driven surface-catalyzed reactions and Raman optical activity,are also presented.Furthermore,studies of remote SERS in dielectric and organic systems based on dielectric waveguides remind us that this useful technology has additional,tremendous application prospects that have not been realized in metal systems.

Transition metal dichalcogenides (TMDCs) heterostructures: Optoelectric properties

Transition metal dichalcogenides(TMDCs)have suitable and adjustable band gaps,high carrier mobility and yield.Layered TMDCs have attracted great attention due to the structure diversity,stable existence in normal temperature environment and the band gap corresponding to wavelength between infrared and visible region.The ultra-thin,flat,almost defect-free surface,excellent mechanical flexibility and chemical stability provide convenient conditions for the construction of different types of TMDCs heterojunctions.The optoelectric properties of heterojunctions based on TMDCs materials are summarized in this review.Special electronic band structures of TMDCs heterojunctions lead to excellent optoelectric properties.The emitter,p-n diodes,photodetectors and photosensitive devices based on TMDCs heterojunction materials show excellent performance.These devices provide a prototype for the design and development of future high-performance optoelectric devices.

Tip-enhanced photoluminescence spectroscopy of monolayer MoS_2

Probing the optical properties of molybdenum disulfide(MoS_2) is vital to its application in plasmon-enhanced spectroscopy, catalysts, sensing, and optoelectronic devices. In this paper, we theoretically studied the Raman and fluorescence properties of monolayer MoS_2 using tip-enhanced spectroscopy(TES). In the strong-coupling TES system, the Raman and fluorescence enhancement factors can be turned to as high as 4.5 × 10~8 and 3.3 × 10~3,respectively, by optimizing the tip–MoS_2-film distance. Our theoretical results not only help to deeply understand the TES properties of monolayer MoS_2, but also provide better guidance on the applications of the novel two-dimensional material.