Multipole plasmon resonances of submicron silver particles

Single crystal, silver particles of 215 +/- 10 nm size were synthesized in solution using the hydrogen reduction method and were characterized by UV-visible extinction spectroscopy and electron microscopy. The extinction spectra reveal the presence of higher order multipoles of the plasmon resonance, such as quadrupole, octupole, and hexadecapole, in addition to the dipole. The formation of higher order multipoles was continuously monitored during the particles growth. Mie extinction calculations were performed and are in good agreement with the measured extinction spectra. The frequency shift of all plasmon modes was measured as a function of the refractive index of the surrounding dielectric medium.     

Interaction of plasmon and molecular resonances for rhodamine 6G adsorbed on silver nanoparticles

Localized surface plasmon resonance (LSPR) is a key optical property of metallic nanoparticles. The peak position of the LSPR for noble-metal nanoparticles is highly dependent upon the refractive index of the surrounding media and has therefore been used for chemical and biological sensing. In this work, we explore the influence of resonant adsorbates on the LSPR of bare Ag nanoparticles (lambda(max,bare)). Specifically, we study the effect of rhodamine 6G (R6G) adsorption on the nanoparticle plasmon resonance because of its importance in single-molecule surface-enhanced Raman spectroscopy (SMSERS). Understanding the coupling between the R6G molecular resonances and the nanoparticle plasmon resonances will provide further insights into the role of LSPR and molecular resonance in SMSERS. By tuning lambda(max,bare) through the visible wavelength region, the wavelength-dependent LSPR response of the Ag nanoparticles to R6G binding was monitored. Furthermore, the electronic transitions of R6G on Ag surface were studied by measuring the surface absorption spectrum of R6G on an Ag film. Surprisingly, three LSPR shift maxima are found, whereas the R6G absorption spectrum shows only two absorption features. Deconvolution of the R6G surface absorption spectra at different R6G concentrations indicates that R6G forms dimers on the metal surface. An electromagnetic model based on quasi-static (Gans) theory reveals that the LSPR shift features are associated with the absorption of R6G monomer and dimers. Electronic structure calculations of R6G under various conditions were performed to study the origin of the LSPR shift features. These calculations support the view that the R6G dimer formation is the most plausible cause for the complicated LSPR response. These findings show the extreme sensitivity of LSPR in elucidating the detailed electronic structure of a resonant adsorbate.     

多模式结合教学在分析化学课程中的探索

This article aims at how to cultivate top talents through analytical chemistry teaching by following the philosophy of teaching student to fish rather than giving them a fish. Throughout the course, multimode teaching practice was implemented via combining "large-size lecture classes" with "seminar and small-size learn-by-doing classes". It is hoped that through these efforts, the students will, at least in the analytical chemistry field, enhance the abilities to obtain and evaluate scientific references and research achievements, improve oral and written expression skills, and have hands-on DIY experience in assembling and disassembling analytical instruments. The multimode teaching practice is expected to make contribution to establish high-quality education system for top talents to stand out.     

Multimode Self-Oscillating Vesicle Transformers

Engineering synthetic materials that mimic the complex rhythmic oscillatory behavior of living cells is a fundamental challenge in science and technology. Up to now, the reported synthetic model system still cannot compete with nature in oscillatory modes and amplitudes. Presented here is a novel alternating copolymer vesicle that exhibits drastic and multimode shape oscillations in real time, which are controlled by polymer concentrations and driven by the Belousov—Zhabotinsky oscillatory reaction, including swelling/deswelling, twisting/detwisting, stretching/shrinking, fusion/fission, and multiple division. Some of them, especially the fission oscillation, have not been observed before. In addition, the oscillation magnitude with regard to diameter is much larger than that of previously reported self-oscillating vesicles. Such a self-oscillating vesicle transformer would extend the complexity and capacity of membrane deformations in synthetic systems, approaching those of natural cells.     

Multimode effects and vibronic borrowing

The effects of a large multidimensional vibrational subspace on the Herzberg-Teller (HT) theory of vibronic borrowing are explored. It is found that under certain circumstances significant vibronic intensity can be induced at the OO transition of a weakly allowed electronic excitation. Complete breakdown of the HT theory for large polyatomic systems is discussed.     

Surface plasmon resonances of silver triangle nanoplates: graphic assignments of resonance modes and linear fittings of resonance peaks

The extinction spectra of five silver equilateral triangle plates with a fixed thickness of 10 nm and side lengths of 50, 100, 150, 200 ,and 250 nm, respectively, have been simulated by the discrete dipole approximation (DDA) method in which a geometric object of interest is meshed and represented by a lattice of spatial dipoles. Irradiated by an incident plane wave with a given propagation direction and polarization state, each triangle nanoplate presents three surface plasmon resonance (SPR) peaks in the range of 300 to 1200 nm. At a given peak, every complex spatial oscillatory vector derived by DDA (corresponding to a certain dipole in the meshed target) is orthogonally resolved into three basic oscillations. Each basic component can be subsequently expressed by two parameters, amplitude (P) and phase angle (varphi). The distributions of six such physical parameters of all the dipoles in the selected cross plane of the target are illustrated colorfully in plots as a graphic characterization and assignment of the SPR modes. The graphic method is applied to reveal the local fine features of SPR modes. And it provides direct evidence for classifying SPR peaks which belong to different triangle nanoplates and appear at different wavelengths. Three SPR modes are recognized graphically and the wavelengths of SPR peaks are found to have linear relationships with the side lengths of the triangle nanoplates.     

Multimode approach to hydrogen tunneling

A procedure is developed to improve the quantitative evaluation of hydrogen transfer rates in polyatomic molecules and solids. The aim is to introduce a dynamical model that includes explicitly all vibrations participating in the transfer. This aim favors adoption of the golden-rule approach, since it treats all vibrational modes equally. To simplify the resulting multidimensional transfer integrals, two basic assumptions are introduced: (i) adiabatic separability of the hydrogenic modes directly involved in the tunneling from the other modes, and (ii) negligible anharmonicity for the latter. The number of effectively participating modes can then be reduced drastically by transformation to an appropriate local representation which allows analytical integration over most of these other modes. Those that remain involve vibrations of the atoms between which the hydrogen is transferred. Their frequency, reduced mass and displacement are expressed in terms of the harmonic force field of the system before and after transfer and can be unambiguously evaluated if these force fields are available. These modes replace the empirical effective modes used previously. The theory is applied successfully to single hydrogen transfer in dimethyl-glyoxime and double hydrogen transfer in porphine.     

Autoionization resonances in triatomic molecules

Review is made of the different types of information becoming available by the combined use of photoelectron spectroscopy and fluorescence excitation spectroscopy coupled to synchrotron radiation for the study of the dynamics of the triatomic molecules CO₂, OCS and CS₂. In particular, importance is layed on the decay pattern of the autoionization resonances associated with the valence shell excitations, their selectivity and possibly their coupling with dissociation.     

Surface plasmon resonances, optical properties, and electrical conductivity thermal hystersis of silver nanofibers produced by the electrospinning technique

In the present study, silver metal nanofibers have been successfully prepared by using the electrospinning technique. Silver nanofibers have been produced by electrospinning a sol-gel consisting of poly(vinyl alcohol) and silver nitrate. The dried nanofiber mats have been calcined at 850 degrees C in an argon atmosphere. The produced nanofibers do have distinct plasmon resonance compared with the reported silver nanoparticles. Contrary to the introduced shapes of silver nanoparticles, the nanofibers have a blue-shifted plasmon resonance at 330 nm. Moreover, the optical properties study indicated that the synthesized nanofibers have two band gap energies of 0.75 and 2.34 eV. An investigation of the electrical conductivity behavior of the obtained nanofibers shows thermal hystersis. These privileged physical features greatly widen the applications of the prepared nanofibers in various fields.     

Behaviour of silver—silver malonate and silver—silver succinate electrodes in aqueous media

The silver—silver oxalate electrode has been employed by many workers^1–3 in aqueous media as the second order reference electrode, but no work seems to have been done so far on the study of the behaviour of silver—silver malonate and silver—silver succinate electrodes. The present work deals with the study of these electrodes in ionic equilibria of malonate and succinate ions in aqueous media. These electrodes, in conjunction with a saturated calomel electrode, have been employed in the poten- tiometric determination of malonate and succinate ions in aqueous media. In additon, the effect of the added salts, such as, potassium nitrate and sucrose on the behaviour of these electrodes has also been examined in this media.     

Multipole plasmon resonances in gold nanorods

The optical properties of gold rods electrochemically deposited in anodic aluminum oxide templates have been investigated. Homogeneous suspensions of rods with an average diameter of 85 nm and varying lengths of 96, 186, 321, 465, 495, 578, 641, 735, and 1175 nm were fabricated. The purity and dimensions of these rod nanostructures allowed us to observe higher-order multipole resonances for the first time in a colloidal suspension. The experimental optical spectra agree with discrete dipole approximation calculations that have been modeled from the dimensions of the gold nanorods.     

Vibrational Fano resonances in dipole-bound anions

This paper explores Fano resonances due to non-adiabatic coupling of vibrational modes and the electron continuum in dipole-bound anions. We adopt a simple one-electron model consisting of a point dipole and an auxiliary potential to represent the electron interaction with the neutral core. Nuclear motion is added by assuming that harmonic vibrations modulate the dipole moment. When the model is parameterized to simulate key features of the water tetramer anion, the resultant photodetachment lineshape closely resembles that observed experimentally and analyzed as a Fano resonance with a parameter q close to -1. Other parameterizations are explored for the model and it is found that large changes in the auxiliary potential are required to change the sign of q. This is consistent with the experimental finding that q is negative for all water cluster sizes studied.     

Existence of nonlinear resonances in polyethylene

In this paper, we demonstrate that the internal dynamics and vibrational spectra of polyethylene are influenced by Fermi and other nonlinear resonances. In previous work, the first semiclassical theory and quantum numbers (in parabolic coordinates) appropriate for this type of resonance were developed. We find from detailed molecular dynamics simulations that the same types of quantum numbers are applicable for polyethylene stretch-bend mode interactions. In addition, a one-to-one resonance is found to exist from one local C H stretch to another C H stretch along the polymer chain.     

Time delay for resonances

Time evolution of wave packets is analyzed for the case of resonances. It is shown that time delay of wave packets is entirely determined by the background phase and it is not affected by the width of resonances. Various definitions of long lived states are discussed.     

Multimode hydriding/dehydriding reactions of CaPd

Combined thermodynamical and structural studies have confirmed the occurrence of multimode hydriding/dehydriding reactions of CaPd that vary depending on temperature, and that these reactions proceed via hydrogen solution/dissolution in the temperature range 273-523 K and via phase decomposition/recombination in the temperature range 523-773 K.     

Multimode Self‐Oscillating Vesicle Transformers

Engineering synthetic materials that mimic the complex rhythmic oscillatory behavior of living cells is a fundamental challenge in science and technology. Up to now, the reported synthetic model system still cannot compete with nature in oscillatory modes and amplitudes. Presented here is a novel alternating copolymer vesicle that exhibits drastic and multimode shape oscillations in real time, which are controlled by polymer concentrations and driven by the Belousov—Zhabotinsky oscillatory reaction, including swelling/deswelling, twisting/detwisting, stretching/shrinking, fusion/fission, and multiple division. Some of them, especially the fission oscillation, have not been observed before. In addition, the oscillation magnitude with regard to diameter is much larger than that of previously reported self‐oscillating vesicles. Such a self‐oscillating vesicle transformer would extend the complexity and capacity of membrane deformations in synthetic systems, approaching those of natural cells.     

Multimode process monitoring based on Bayesian method

Multimode process monitoring has recently attracted much attention both in academy and industry. Conventional methods assume that either the process data are Gaussian in each operation mode, or some process knowledge should be incorporated, thus making the methods supervised. In this paper, a new unsupervised method is developed for multimode process monitoring, which is based on Bayesian inference and two‐step independent component analysis–principal component analysis (ICA–PCA) feature extraction strategy. ICA–PCA is first introduced for feature extraction and dimension reduction. By transferring the traditional monitoring statistic to fault probability in each operation mode, monitoring results in different operation modes can be easily combined by the Bayesian inference. Another contribution of the present paper is the development of a new fault identification method. Through analyses of the posterior probability and the joint probability for the monitored data sample, the correct operation mode or fault scenario can be identified. Three case studies are demonstrated to evaluate the feasibility and efficiency of the proposed method. Copyright © 2009 John Wiley & Sons, Ltd.