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Magnetic–plasmonic nanoparticles (NPs) have attracted great interest in many fields because they can exhibit more physical and chemical properties than individual magnetic or plasmonic NPs. In this work, we synthesized Au- or Ag-decorated Fe3O4 nanoparticles coated with PEI (Fe3O4-PEI-M (M = Au or Ag) NPs) using a simple method. The influences of the plasmonic metal NPs' (Au or Ag) coating density on the magnetic and plasmonic properties of the Fe3O4-PEI-M (M = Au or Ag) NPs were investigated, and the density of the plasmonic metal NPs coated on the Fe3O4 NPs surfaces could be adjusted by controlling the polyethyleneimine (PEI) concentration. It showed that the Fe3O4-PEI-M (M = Au or Ag) NPs exhibited both magnetic and plasmonic properties. When the PEI concentration increased from 5 to 35 mg/mL, the coating density of the Au or Ag NPs on the Fe3O4 NPs surfaces increased, the corresponding magnetic intensity became weaker, and the plasmonic intensity was stronger. At the same time, the plasmonic resonance peak of the Fe3O4-PEI-M (M = Au or Ag) NPs was red shifted. Therefore, there was an optimal coverage of the plasmonic metal NPs on the Fe3O4 NPs surfaces to balance the magnetic and plasmonic properties when the PEI concentration was between 15 and 25 mg/mL. This result can guide the application of the Fe3O4-M (M = Au or Ag) NPs in the biomedical field. [ABSTRACT FROM AUTHOR]

Herein, three self‐assembling materials (SAMs), (pyridine‐4‐ylmethyl)phosphonic acid (PyPA), benzylphosphonic acid (BnPA), and pentafluorobenzyl phosphonic acid (F5BnPA), are selected as hole‐injecting layers in organic light‐emitting diodes (OLEDs) and the effects of the aromatic ring of SAMs on indium tin oxide (ITO) work function (WF), hole injection, and device performances are investigated. After assembling them on ITO, the X‐ray photoemission spectroscopy data suggest that three samples have a similar binding mode, and the ultraviolet photoemission spectroscopy shows the effective change of ITO WF gradually enlarged along the order of PyPA, BnPA, and F5BnPA, resulting in increase in hole‐injecting capability in turn. The calculated molecule dipole of pyridine is 2.65 Debye, clearly larger than that of phenyl (0.32 Debye) and pentafluorophenyl (1.88 Debye), but PyPA presents minimum ITO WF change. Such differentiated WF changes are not only contributed by the molecular dipole of aromatic ring but also their titling angles. In OLEDs based on tris(8‐hydroxyquinoline) aluminum (III) (Alq3), the device modified by PyPA affords the highest external quantum efficiency (EQE) of 1.45% and current efficiency (CE) of 4.62 cd A−1. However, in the device using 9‐[4‐(4,6‐diphenyl‐1,3,5‐triazine‐2‐yll)phenyl]‐N,N,N′,N′‐tetraphenyl‐9H‐carbazole‐3,6‐diamine as emitters, the OLEDs modified by F5BnPA show the best EQE of 24.85% and CE of 81.88 cd A−1. [ABSTRACT FROM AUTHOR]

A novel molecular scaffold, dibenzo[f,h]furo[2,3-b]quinoxaline (diBFQ), and its derivatives, 3,6-bis(4-isopropylphenyl)-11-phenyldibenzo[f,h]furo[2,3-b]quinoxaline (dP-diBFQ) and furo[2′,3′:5,6]pyrazino[2,3-f][1,10]phenanthroline (FPPhen), were designed and synthesized, showing highly efficient pure and deep blue emission. The unsubstituted molecular scaffolds diBFQ and FPPhen exhibit emission from 424–445 nm with PLQYs of ∼70%, and the disubstituted derivative of diBFQ, dP-diBFQ, shows a PLQY of 79.1%. Our experimental and theoretical investigations revealed that the additional N atoms in FPPhen facilitate the electron distribution of the HOMO orbital localizing on a smaller π-conjugate fragment compared with diBFQ, which resulted in the emission peak blue-shifting from 445 nm for diBFQ to 424 nm for FPPhen. Furthermore, introducing the steric substituent isopropylphenyl into the diBFQ scaffold would help to suppress aggregates of dP-diBFQ molecules and improve the fluorescence efficiency. OLEDs using dP-diBFQ as dopants show pure blue emission with CIE coordinates of (0.154, 0.102) and an EQE of 2.28%. Upon increasing the dopant concentration, the EQE and current efficiency could be improved to 2.63% and 4.7 cd A−1, but aggregate emission with a peak from 472–476 nm was clearly observed due to molecular aggregation. Our studies clearly suggested that diBFQ and FPPhen scaffolds are promising fluorescence cores for deep and pure-blue emission. [ABSTRACT FROM AUTHOR]

Metallic films are widely used in many micro-cavities or as electrodes. However, the quenching of fluorescent molecules and the large absorption loss of metallic films are generally considered fatal for lasing. In this article, we present the enhanced lasing of an organic gain medium in a planar waveguide, assisted by the plasmonic hybrid structure of an Ag nanoparticles (NPs)–Ag film. Compared to the devices of gain media deposited on glass, Ag film, and Ag NPs island film, the lowest lasing threshold was achieved by the gain medium deposited on the Ag NPs–Ag film hybrid structure. This is attributed to the hybrid plasmonic coupling between the localized surface plasmons of Ag NPs and the delocalized surface plasmon polariton of the Ag film, leading a more intense localized electric field. In addition, the reinjection and confinement of the leaking photons into the gain medium by the external feedback of the Ag film also contributes to the enhanced lasing. Our results could provide us with a unique approach to effectively avoid the negative effect of the metallic film, enhance the lasing gain of organic dye molecules, and realize a lower pumped threshold and stronger lasing. [ABSTRACT FROM AUTHOR]

High-performance and wavelength-tunable random lasing has a wide application prospect. We developed an enhanced-performance and wavelength-tunable magnetically controlled random lasing system based on R6G solution doped with Fe 3 O 4 /Au nanoparticles (NPs), in which Fe 3 O 4 /Au NPs could exhibit both magnetic and plasmonic characteristics. Compared to the Fe 3 O 4 NPs, Fe 3 O 4 /Au NPs could more effectively lower the random lasing threshold, which was 37.6% of that of the net gain medium. This is because the Fe 3 O 4 /Au NPs exhibit the plasmonic effect and larger scattering cross section than the Fe 3 O 4 NPs. In addition, the distribution of the Fe 3 O 4 /Au NPs in the R6G solution could be effectively regulated by an external magnetic field; thus the random lasing emission modes could be tuned in real-time, and a switch between the random lasing and amplified spontaneous emission can be achieved by removing or applying the external magnetic field. This work provides a simple method to enhance the lasing properties and tune the emission wavelength simultaneously.

All-inorganic halide perovskite quantum dots (QDs) have recently received much attention due to their excellent optoelectronic properties. And their emission properties still need to be improved for further applications. Here, we demonstrated a remarkable emission enhancement of the CsPbBr 3 QDs based on an Ag nanoparticle-Ag film plasmonic coupling structure. Through precise control of the gap distance between Ag nanoparticle and Ag film, the localized surface plasmon resonance (LSPR) peak was tuned to match the emission wavelength of the CsPbBr 3 QDs. We achieved a 30-fold fluorescence intensity enhancement and a lower lasing threshold, which is 25% of that of the CsPbBr 3 QDs without plasmonic coupling structure. It is attributed to that the plasmonic coupling structure exhibits an extremely strong local electric field owing to the coupling between LSPR of Ag nanoparticle and surface plasmon polariton of Ag film. This work provides an effective way to enhance the optical emission of perovskite QDs and promotes the further exploration of on-chip light source.

All-inorganic halide perovskite CsPbX 3 (X = Br/Cl/I)quantum dots have gained a considerable attention in the optoelectronic fields. However, the high cost and poor stability of the prepared CsPbX 3 quantum dots (QDs) are inevitable challenges for their future practical applications. And the high-performance CsPbX 3 QDs are always needed. Herein, a facile and low-cost synthesis scheme was adopted to prepare the CsPbBr 3 QDs modified by lead bromide (PbBr 2 ) and tetraoctylammonium bromide (TOAB) ligands at room temperature in open air. The prepared CsPbBr 3 QDs exhibited a high photoluminescence quantum yield (PLQY) of 96.6% and a low amplified spontaneous emission (ASE) threshold of 12.6 µJ/cm 2 . Stable ASE intensity with little degradation was also realized from the CsPbBr 3 QDs doped with PMMA. Furthermore, the enhanced ASE properties of the CsPbBr 3 QDs-doped PMMA based on distributed feedback (DFB) substrate was achieved with a lower threshold of 3.6 µJ/cm 2 , which is 28.6% of that of the (PbBr 2  + TOAB)-treated CsPbBr 3 QDs without PMMA. This work exhibits a promising potential in the on-chip light source.