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The nonlinear optical microscopies of coherent two-photon excited fluorescence and anti-Stokes Raman scattering are strongly enhanced by multiple surface plasmon resonances (MSPRs). The Au@Ag nanorods presented strong MSPRs peaks at 800 and 400 nm, and can enhance nonlinear optical microscopy at fundamental and double frequencies, respectively. A two-dimensional (2D) material of g-C3N4 is employed to study the plasmon-enhanced nonlinear optical microscopy by the femtosecond laser. The electric analysis reveals that the MSPRs of the Au@Ag nanorod can significantly enhance the signals of two-photon excited fluorescence and anti-Stokes Raman scattering by up to the orders of 104 and 1016, respectively. The results demonstrate the great advantages of plasmon-enhanced nonlinear optical microscopy for the optical analysis on 2D materials, thus providing a new adventure for increasing the optical resolutions of nonlinear optical microscopy.

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Single-particle fluorescent probe for copper ion detection based on fluorescence quenching.

Localized surface plasmon has been extensively studied and used for the photocatalysis of various chemical reactions. However, the different contributions between plasmon resonance and interband transition in photocatalysis has not been well understood. Here, we study the photothermal and hot electrons effects for crystal transformation by combining controlled experiments with numerical simulations. By photo-excitation of NaYF4 : Eu3+ @Au composite structure, it is found that the plasmonic catalysis is much superior to that of interband transition in the experiments, owing to the hot electrons generated by plasmon decay more energetic to facilitate the reaction. We emphasize that the energy level of hot electrons plays an essential role for improving the photocatalytic activity. The results provide guidelines for improving the efficiency of plasmonic catalysis in future experimental design.

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Colloidal nanocrystals (NCs) play an important role in the field of optoelectronic devices such as photovoltaic cells, photodetectors, and light-emitting diodes (LEDs). The properties of NC films are strongly affected by ligands attached to them, which constitute a barrier for charge transport between adjacent NCs. Therefore, the method of surface modification by ligand exchange has been used to improve the electrical conductivity of NC films. However, surface modification to NCs in LEDs can also affect emission characteristics. Among NCs, nanorods have unique properties, such as suppression of nonradiative Auger recombination and linearly polarized light emission. In this work, CdSe/CdS nanorods (NRs) were prepared by the hot injection method. To increase the charge transport into CdSe/CdS NRs, we adopted ligand modification to CdSe/CdS NRs. Using this technique, we could shorten the injection barrier length between CdSe/CdS NRs and adjacent layers. It leads to a more balanced charge injection of electron/hole and a greatly increased current efficiency of CdSe/CdS NR-LEDs. In the NR-LEDs, the ligand exchange boosted the electroluminance, reaching a sixfold increase from 848 cd/m 2 of native surfactants to 5600 cd/m 2 of the exchanged n-octanoic acid ligands at 12 V. The improvement of CdSe/CdS NR-LED performance is closely correlated to the efficient control of charge balance via ligand modification strategy, which is expected to be indispensable to the future NR-LED-based optoelectronic system.

Plasmonic nanostructures with sharp tips are widely used for optical signal enhancement because of their strong light-confining abilities. These structures have a wide range of potential applications, for example, in sensing, bioimaging, and surface-enhanced Raman scattering. Au nanoparticles, which are important plasmonic materials with high photothermal conversion efficiencies in the visible to near-infrared region, have contributed greatly to the development of photothermal catalysis. However, the existing methods for synthesizing nanostructures with tips need the assistance of poly(vinylpyrrolidone), thiols, or biomolecules. This greatly hinders signal detection because of stubborn residues. Here, we propose an efficient binary surfactant–mediated method for controlling nanotip growth on Au nanoparticle surfaces. This avoids the effects of surfactants and can be used with other Au nanostructures. The Au architecture tip growth process can be controlled well by adjusting the ratio of hexadecyltrimethylammonium bromide to hexadecyltrimethylammonium chloride. This is due to the different levels of attraction between Br−/Cl− and Au3+ ions. The surface-enhanced Raman scattering and catalytic abilities of the synthesized nanoparticles with tips were evaluated by electromagnetic simulation and photothermal catalysis experiments (with 4-nitrothiophenol). The results show good potential for use in surface-enhanced Raman scattering applications. This method provides a new strategy for designing plasmonic photothermal nanostructures for chemical and biological applications.