应用表面等离激元提高有机发光器件效率的研究进展

表面等离激元（SPP）存在于金属和介质界面,是光场和金属表面自由电子相互作用而产生的电子集体振荡行为.一方面,由于在金属纳米颗粒表面会形成局域的SPP震荡（LSP）,可以调控金属表面附近分子的发光性质,因此,很多研究者尝试在有机电致发光器件（OLED）中引入金属纳米颗粒,利用LSP改善OLED器件性能;另一方面,在传统发光器件中,由于金属表面等离激元的波矢量和自由光波的波矢量不匹配,无法辐射成自由光波,最终只能以热能的形式耗散掉.通过改变金属表面形貌,如附加光栅结构等方法,使得SPP的能量能够耦合成自由光,从而提高发光器件的外量子效率.利用SPP来提高有机发光器件的效率,已经引起广泛的关注,本文着重综述以下两个方面的工作：一是采用金属纳米颗粒的LSP提高荧光分子辐射跃迁的几率,从而提升发光器件的内量子效率;二是利用有序或无序光栅结构使得SPP与自由光的波矢匹配来提高器件的耦合出光,从而提升外量子效率.     

Pure surface plasmon resonance enhancement of the first hyperpolarizability of gold core-silver shell nanoparticles

We report the optical second harmonic (SH) response from gold core-silver shell nanoparticles supported at a liquid-liquid interface in the spectral region where the second harmonic generation (SHG) frequency is resonant with the surface plasmon (SP) resonance excitation of the nanoparticles. We compare these results with that obtained by classical linear optical absorption spectroscopy and show that the nonlinear optical response is dominated by the SP resonance enhancement with negligible contributions from the interband transitions. As a result, the SH spectrum exhibits two clear SP resonance bands attributed to the two SP resonances of the composite nanostructure formed by the gold core-silver shell nanoparticles. Absolute values of the hyperpolarizabilities are measured by hyper Rayleigh scattering (HRS) and compared that of pure gold nanoparticles. The hyperpolarizability measured at a harmonic energy of 3.0 eV, enhanced through excitation of the high energy SP resonance of the nanoparticle, increases with the silver content whereas the hyperpolarizability measured at a harmonic energy of 2.4 eV, enhanced through the excitation of the low energy SP resonance of the nanoparticle, decreases because of the shift of this resonance away from the harmonic frequency. The hyperpolarizability determined by HRS and the square root of the SHG intensities, scaling with the nanoparticle hyperpolarizability, have similar trends with respect to the silver content indicative of closely related adsorption properties yielding similar surface concentrations at the liquid-liquid interface.     

CO2Laser Photochemical Hole Burning in the IR Reflection Spectra of Crystalline Natural Silicates

Structural and chemical transformations induced on the surface of crystalline natural silicates by pulse ₂laser radiation with a pulse length of 200 ns and an energy per pulse of 2 J were examined. The IR reflection spectra of nepheline KNa₃[AlSiO₄]₄and rhodonite CaMn₄[Si₅O₁₅] were measured before and after exposure to laser radiation. An increase in the reflectance at the laser frequency used was observed, which was named hole burning in the IR reflection spectra of specimens. A 50-cm^–1wide hole was shown to be burnt at a frequency coinciding with that of a laser radiation line within this width. At the incident laser frequency, a narrow, 5-cm^–1wide hole is also burnt in the IR spectra of the irradiated samples. The burning of the 50-cm^–1hole was assumed to be due to the selective sublimation of Si_mO_ncomplexes. The burning of the narrow hole of 5 cm^–1width is associated with the laser-induced selective dissociation of Si–O bonds in the near-surface layer at the frequency employed.     

BaF（Cl,Br）：Sm^2＋的光谱烧孔与光激励发光过程

Ｘ射线辐照前后，在ＢａＦ（Ｃｌ，Ｂｒ）：Ｓｍ＾２＋中以５６０ｎｍ的Ｎｄ：ＹＡＧ脉冲光在液氮温度下进行了双光子烧孔实验和光激励发光实验，结果表明，Ｓｍ＾２＋掺杂的碱土金属氟卤化物光谱烧孔过程中伴随着光激励发光过程，这一过程直接影响光谱烧孔过程的进行。     

光化学烧孔及其在频域光存储中的应用

光化学光谱烧孔是近年来发展起来的一种高新技术,在超高密度光学存储中有着光明的应用前景。本文着重从材料科学的角度介绍了其基本原理、材料特性及其在频域光存储技术中应用的最新进展情况。     

Ag Nanowire‐Ag Nanoparticle Hybrids for the Highly Enhanced Fluorescene Detection of Protoporphyrin IX Based on Surface Plasmon‐Enhanced Fluorescence

In this study, we developed an approach to fabricate novel 1D Ag NWs‐Ag NPs hybrid substrate for enhanced fluorescene detection of protoporphyrin IX (PpIX) based on surface plasmon‐enhanced fluorescence. The Ag NWs‐Ag NPs hybrid was synthesized by combining the hydrothermal method and self‐assembly method with the asisstance of polyvinylpyrrolidone (PVP). When the Ag NWs‐Ag NPs hybrid was deposited on the glass substrate and employed as active substrate to detect PpIX, the fluorescence intensity of PpIX was enhanced greatly due to the coupling effect of localized surface plasmon‐localized surface plasmon (LSP‐LSP) and localized surface plasmon‐surface plasmon propagation (LSP‐SPP) which induced great enhancement of the electromagnetic field. Furthermore, the enhancement effect was approximately linear when the concentration of PpIX was ranged from 1×10^?7 mol/L to 2×10^?5 mol/L, and the photobleaching phenomenon of PpIX was reduced greatly, indicating that the fabricated Ag NWs‐Ag NPs hybrid substrate had well performance for PpIX imaging. This work provides an effective approach to prepare highly sensitive and stable fluorescence enhancement substrate, and has great potential application in fluorescence imaging.     

Enhancement of the SPR Effect in an Optical Fiber Device Utilizing a Thin Ag Layer and a 3092A Liquid Crystal Mixture

This paper is a continuation of previous work and shows the enhancement of the surface plasmon resonance effect in a tapered optical fiber device. The study investigated liquid crystal cells containing a tapered optical fiber covered with a silver nanolayer, surrounded by a low refractive index liquid crystal in terms of the properties of light propagation in the taper structure. Silver films with a thickness of d = 10 nm were deposited on the tapered waist area. Measurements were performed at room temperature; liquid crystal steering voltage U from 0 to 200 V, with and without any amplitude modulation with a frequency of f = 5 Hz, and the wavelength λ ranged from 550 to 1200 nm. A significant influence of the initial arrangement of liquid crystals molecules on light propagation was observed. Three types of liquid crystal cells—orthogonal, parallel, and twist—were considered. During the measurements, resonant peaks were obtained—the position of which can also be controlled by the type of liquid crystal cells and the steering voltage. Based on the obtained results, the best parameters, such as highest peak’s width reduction, and the highest SNR value were received for twisted cells. In addition, the present work was compared with the previous work and showed the possibility of improving properties of the manufactured probes, and consequently, the surface plasmon resonance effect. In the presented paper, the novelty is mainly focused on the used materials as well as suitable changes in applied technological parameters. In contrast to gold, silver is characterized by different optic and dielectric properties, e.g., refractive index, extension coefficient, and permittivity, which results in changes in the light propagation and the SPR wavelengths.     

Photochromic coumarin spiropyrans

New photochromic spiropyrans (SPP) derived from 4-methyl-7-hydroxy-8-formylcoumarin have been synthesized. The effect of the heterene fragment on the spectral and photochromic properties of the SPP was examined. The photoproduct of the benzodithiolane SPP had the absorption with longest wavelength. Indoline SPP were found to have the most efficient photocoloring. Fluorescence of the cyclic form was found for the SPP.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 601–604, May, 1992     

Electron transfer reaction of meso-phenyl-tetrabenzo-porphyrinato-zinc and dicyanobenzene at low temperature

The behavior of photon-gated spectral hole burning with meso-phenyl-tetrabenzoporphyrinato-zinc as electron donor and dicyanobenzene as electron acceptor dispersed in polymethylmethacrylate was investigated.The data of absorption spectrum of the photoproduct acquired through photon-gated hole burning process by high power density and long hole burning time at 20 K were given The mechanism of photomduced donor-acceptor electron transfer for the iarget system in photon-gated spectral hole burning was demonstrated.     

Fabrication of an Anti-Reflective Microstructure on ZnS by Femtosecond Laser Bessel Beams

As an important mid-infrared to far-infrared optical window, ZnS is extremely important to improve spectral transmission performance, especially in the military field. However, on account of the Fresnel reflection at the interface between the air and the high-strength substrate, surface optical loss occurs in the ZnS optical window. In this study, the concave antireflective sub-wavelength structures (ASS) on ZnS have been experimentally investigated to obtain high transmittance in the far-infrared spectral range from 6 μm to 10 μm. We proposed a simple method to fabricate microhole array ASS by femtosecond Bessel beam, which further increased the depth of the microholes and suppressed the thermal effects effectively, including the crack and recast layer of the microhole. The influence of different Gaussian and Bessel beam parameters on the microhole morphology were explored, and three ASS structures with different periods were prepared by the optimized Bessel parameters. Ultimately, the average transmittance of the sample with the ASS microhole array period of 2.6 μm increased by 4.1% in the 6 μm to 10 μm waveband, and the transmittance was increased by 5.7% at wavelength of 7.2 μm.     

Persistent spectral hole‐burning study on dendrimer porphyrins

We report the first results of persistent spectral hole burning of dendrimer porphyrins having three‐, four‐, or five‐layered aryl ether dendritic arrays. We evaluate structural relaxations of dendrimer framework around the porphyrin core at low temperatures. A large environmental change around the porphyrin core, as evaluated from the hole area, was suppressed in dendrimer porphyrins of higher generation numbers, whereas a small environmental change, as evaluated from hole width, showed no dependence on the number of generations. The dendrimer porphyrins showed sharp holes at 20 K, suggesting a long dephasing time and the suppression of spontaneous spectral diffusion. The results of dendrimer‐embedded polymer sample indicated that the structural relaxation of polymer chain outside the dendrimer does not have an influence on the resonant frequency of the porphyrin core. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 210–215, 2002     

表面等离子体波共振与常规检测技术的联用

表面等离子体波共振(SPR)是被入射电磁波所激发、存在于金属和电介质界面上电荷密度振动的谐振波.SPR是一种消逝场光学成功应用的典范,它具有体积小、分辨率高、无需标记、抗电磁干扰能力强等特点.本文介绍了SPR与电化学方法(循环伏安法、溶出伏安法)、光学方法(荧光光谱、红外光谱)、质谱和石英晶体微天平等其它常规检测技术联用的研究进展,与其它常规方法联用能进一步提高分析能力,可弥补彼此的不足.本文还特别详细说明了部分电化学方法、干涉测量法与表面等离子体波共振联用的优势及不足.     

Total (elastic + inelastic) cross sections for electron scattering with bound and free germanium and lead atoms

Spherical complex optical potential (SCOP) approach has been used to compute the differential, total (elastic + inelastic) and momentum transfer cross sections for electrons scattering from the bound and free germanium and lead atoms in the energy range from 100–5000 eV. We find that the present calculated differential scattering cross sections (DCS) exhibit all important features (such as forward peaking, dip at middle angles and enhanced backward scattering) observed in other theoretical calculations and experimental measurements. The effect of absorption potential is generally to reduce the elastic cross section.     

Alkyl‐Chain‐Regulated Charge Transfer in Fluorescent Inorganic CsPbBr3 Perovskite Solar Cells

Improved charge extraction and wide spectral absorption promote power conversion efficiency of perovskite solar cells (PSCs). The state‐of‐the‐art carbon‐based CsPbBr₃ PSCs have an inferior power output capacity because of the large optical band gap of the perovskite film and the high energy barrier at perovskite/carbon interface. Herein, we use alkyl‐chain regulated quantum dots as hole‐conductors to reduce charge recombination. By precisely controlling alkyl‐chain length of ligands, a balance between the surface dipole induced charge coulomb repulsive force and quantum tunneling distance is achieved to maximize charge extraction. A fluorescent carbon electrode is used as a cathode to harvest the unabsorbed incident light and to emit fluorescent light at 516 nm for re‐absorption by the perovskite film. The optimized PSC free of encapsulation achieves a maximum power conversion efficiency up to 10.85 % with nearly unchanged photovoltaic performances under 80 %RH, 80 °C, or light irradiation in air.     

Conformational reduction of DOPA in the gas phase studied by laser desorption supersonic jet laser spectroscopy

The conformational reduction in catecholamine neurotransmitters was studied by resonance enhanced multi photon ionization (REMPI), ultraviolet-ultraviolet (UV-UV) hole burning and infrared (IR) dip spectroscopy with applying a laser desorption supersonic jet technique to DOPA, which is one of the catecholamine neurotransmitters and has one more phenolic OH group than tyrosine. It is concluded that DOPA has a single observable conformer in the gas phase at low temperature. Quantum chemical calculations at several levels with or without the dispersion correction were also carried out to study stable conformations. From the comparison between the computational IR spectra and the experimental ones, the most stable structure was determined. It is strongly suggested that the conformational reduction is caused by electrostatic interactions, such as a dipole-dipole interaction, between the chain and OH groups.     

Room Temperature Persistent Spectral Hole-Burning in Sol-Gel-Derived Glasses Doped with Eu3+ Ions

Persistent spectral hole burning was investigated for the Eu³⁺ ions-doped glasses prepared by a sol-gel method. For the glasses containing OH bonds, persistent spectral hole is burned by the laser-induced rearrangement of the OH bonds surrounding the Eu³⁺ ions, which is thermally unstable to erase up to 200 K. On the other hand, the Eu³⁺-doped Al₂O₃-SiO₂ glasses which are heated under H₂ gas or irradiated with X-ray exhibit room temperature PSHB. The depth of the burnt hole increases as the Al₂O₃ content increases. The hole-formation could be explained by a model of the excitation of the Eu³⁺ ions and subsequent electron transfer with the excited [Eu³⁺]^– or oxygen-defect centers in the Al—O bonds. The burnt holes are more stable compared with those burned by the rearrangement of the OH bonds.     

Investigation of the adsorption of 4-cyanopyridine on Au(111) by in situ visible–infrared sum frequency generation

We have investigated the configuration of 4-cyanopyridine on Au(111) electrodes in perchlorate solution by in situ visible–IR sum frequency generation (SFG). Thanks to the use of two IR tunable lasers (the free electron laser CLIO and a table laser based on an optical parametric oscillator) we have obtained SFG spectra of the system in the spectral range of both the aromatic cycle and the CN stretching modes. We present herein the first SFG spectra ever obtained under electrochemical conditions in the 9–12 μm range. Our results show a potential-dependent orientation of the adsorbed 4-cyanopyridine from a configuration where the molecule is adsorbed perpendicular to the electrode via the nitrogen of the pyridine ring at negative potentials, to a flat adsorption configuration at intermediate potentials, and finally a perpendicular orientation again where the molecule is bound through the nitrogen of the cyanide end.     

Influence of temperature and pressure on shape and shift of impurity optical bands in polymer glasses

The shape, broadening, and shift of optical absorption spectra of molecular impurity centers in polymer glasses are considered in terms of inhomogeneous energy distributions and coupling of electronic transitions to vibrations. Persistent spectral hole burning was applied for frequency-selective probing of zero-phonon lines. The shift and broadening of spectral holes were studied between 5 and 50 K and by applying a hydrostatic He gas pressure up to 200 bar. Broadband absorption spectra were recorded between 5 and 300 K in poly(methyl methacrylate) and polyethylene. In addition to "normal" thermal broadening, due to the first- and second-order electron phonon coupling, several narrowing components were predicted on the basis of frequency dependent hole behavior. Thermal expansion of the matrix and the relaxation of local strains, previously accumulated on cooling below the glass temperature can lead to shrinking of the inhomogeneous width. A Voigt treatment of absorption band shapes reveals that the Gaussian component can indeed suffer remarkable narrowing. Inhomogeneous band shapes and the frequency-dependent thermal and baric line shifts were rationalized with the aid of a pair of two-body Lennard-Jones potentials. The shift of potential well minima is a crucial factor influencing solvent shifts, inhomogeneous band shapes, pressure shift coefficients, and quadratic electron phonon coupling constants.     

The alkali metal cation effect on the surface-enhanced Raman spectra of phosphate anions adsorbed at silver electrodes

The interaction of adsorbed phosphate anions with alkali metal cations at the Ag|aqueous solution interface has been investigated by surface-enhanced Raman spectroscopy (SERS). Formation of ion pairs at the interface was evident from the cation-induced perturbations in the SER spectra of anions. The frequency of the external vibration, silver–oxygen (Ag---O′), was not sensitive to the nature of cation, while the relative intensity of this mode was cation-dependent and was explored as a sensitive probe for the monitoring of coadsorption of ions at the interface. From the internal phosphate vibrations, both asymmetric modes, δ_as(PO) and ν_as(PO), were found to be the most sensitive to the nature of the cation. At a relatively positive potential (0.00 V vs. Ag | AgCl) the spectral parameters for the Cs⁺ and K⁺ cations were very similar indicating the same bonding type with anions. A more inhomogeneous chemical environment for the phosphate oxygen atoms was detected in the case of Na⁺ and Li⁺ cations. An increase in ν_as(PO) frequency by ca. 10 cm⁻¹ was the characteristic spectral signature for the interaction of phosphates with Li⁺. The formation of water-shared ion pairs at the interface was suggested based on the absence of splitting in the ν_as(PO) mode and the previously observed frequency sensitivity of this band to solvent H₂O substitution by D₂O. At negative potential (−0.80 V), a stabilization effect of Cs⁺ on the phosphate adlayer was detected based on the twofold increase in intensity of the ν(Ag---O′) mode compared with Li⁺. Splitting of the ν_as(PO) mode suggested the contact interaction of anions with specifically adsorbed Cs⁺ cations.     

Raman-spectroscopy and -imaging with surface-plasmon polaritons

We report on surface plasmon field—enhanced Raman imaging investigations of Langmuir—Blodgett multilayer assemblies of cadmium arachidate. This new method is a combination of Plasmon surface polariton field—enhanced Raman scattering with an optical multichannel detection scheme. The imaging capabilities of a CCD—camera are used to spatially resolve the Raman—spectral information of a heterogenous sample.