China is a country with many lakes, about one-third of which are freshwater mainly distributed in the middle and lower reaches of the Yangtze River. Currently most of the lakes are mesotrophic or eutrophic. Lake eutrophication has become one of the major ecological and environmental problems faced by lakes in China and can lead to a series of abnormal ecosystem responses, including extinction of submerged plants, frequent occurrence of cyanobacterial blooms, increased microbial biomass and productivity, decreased biodiversity, accelerated cycles, and a change in the efficient use of nutrients. With development of eutrophication, the whole lake ecosystem suffers decreased biodiversity, simplification of biotic community structure, instability of the ecosystem, and ultimately the clear-water, macrophyte-dominated ecosystem gradually shifts to a turbid-water, algae-dominated ecosystem. This ecosystem succession mechanism is speculated to be caused by different nutrient utilization efficiencies of macrophytes and phytoplankton. The ultimate ecosystem succession trend of seriously eutrophic lakes is that a phytoplankton-dominated autotrophic lake shifts to a heterotrophic lake dominated by micro-organisms, protozoans. Today, eutrophication generally refers to trophic state arising from increased nitrogen and phosphorus input, specifically, increased discharge of plant nutrients (mainly nitrogen and phosphorus) from industrialization, agricultural modernization, and urbanization.Nitrogen, phosphorus, and some other elements are essential for plant growth; however, if a water body receives more nitrogen and phosphorus than necessary, the ecosystem can experience changes such as algal blooms; therefore, eutrophication can be considered as a biological or ecological concept. In this sense, using nitrogen, phosphorus, or other environmental factors is not the most appropriate way to evaluate the trophic level of a lake or reservoir; instead, the evaluation should be based on primary productivity of macrophytes and phytoplankton, but these indicators are difficult to assess. Alternatively, nitrogen, phosphorus, transparency, and chlorophyll a are commonly used as indicators for evaluation of eutrophication.OECD proposed the following thresholds of eutrophication in 1982: average total phosphorus concentration >0.035 mg/L; average chlorophyll a concentration >0.008 mg/L; and average transparency <3 m [2]. According to these thresholds, many lakes in China have become eutrophic. An assessment of the trophic status of lakes in the middle and

Abstract:The interaction of exciton-plasmon coupling and the conversion of exciton-plasmon-photon have been widely investigated experimentally and theoretically. In this review, we introduce the exciton-plasmon interaction from basic principle to applications. There are two kinds of exciton-plasmon coupling, which demonstrate different optical properties. The strong exciton-plasmon coupling results in two new mixed states of light and matter separated energetically by a Rabi splitting that exhibits a characteristic anticrossing behavior of the exciton-LSP energy tuning. Compared to strong coupling, such as surface-enhanced Raman scattering, surface plasmon (SP)-enhanced absorption, enhanced fluorescence, or fluorescence quenching, there is no perturbation between wave functions; the interaction here is called the weak coupling. SP resonance (SPR) arises from the collective oscillation induced by the electromagnetic field of light and can be used for investigating the interaction between light and matter beyond the diffraction limit. The study on the interaction between SPR and exaction has drawn wide attention since its discovery not only due to its contribution in deepening and broadening the understanding of SPR but also its contribution to its application in light-emitting diodes, solar cells, low threshold laser, biomedical detection, quantum information processing, and so on.

In this work, an electro-optical device based on a graphene-Ag nanoparticle hybrid is fabricated as the substrate of graphene mediated surface enhanced Raman scattering (G-SERS) manipulated by the gate and bias voltages. Plasmon-exciton coupling promotes co-driven surface catalytic reactions, where the density of states (DOS) of holes and electrons on graphene is well controlled by the gate voltage, and the kinetic energy of holes and electrons is driven by the bias voltage (or current). Our experimental results reveal that the hot holes on graphene mainly contribute to plasmon-exciton co-driven oxidation reactions. The contribution of hot electrons to oxidation reactions is less important. Our novel electro-optical device can be potentially applied in controlling plasmon-exciton co-driven oxidation or reduction reactions by tuning the gate and bias voltages.

A single-sheeted potential energy surface is reported for the electronic ground-state of H(2)S by fitting accurate multireference configuration interaction energies calculated using aug-cc-pVTZ and aug-cc-pVQZ basis sets with extrapolation of the electron correlation energy to the complete basis set limit, plus extrapolation to the complete basis set limit of the complete-active-space self-consistent field energy. A switching function formalism has been used to warrant the correct behavior at the H(2)(X (1)Sigma(g) (+))+S((1)D) and SH(X (2)Pi)+H((2)S) dissociation limits. The topographical features of the novel global potential energy surface are examined in detail, with the former being used for exploratory quasiclassical trajectory calculations of the thermal rate constant for the S((1)D)+H(2), S((1)D)+D(2), and S((1)D)+HD reactions at room temperature. A comparison with other available potential energy surfaces as well as kinetics data is also provided.

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The monolayer graphene–Ag nanoparticles hybrid system is fabricated as the electrooptical‐coordinated controlled substrate for surface‐enhanced Raman scattering spectroscopy. Plasmon–exciton interactions in this hybrid system are systemically investigated and applied in the field of surface catalytic reactions, manipulated by the electrooptical synergy. Experimental results demonstrate that the surface catalytic reactions can not only be controlled by plasmon–exciton coupling, but also be affected by the gate voltages and electric currents (or bias voltages). The gate voltage can tune the density of state of electrons, and electric current can make the hot electrons near the Fermi level with higher kinetic energy. Both of gate voltages and electric currents can significantly promote the efficiency and probability of plasmon–exciton‐codriven surface catalytic reactions. The electrooptical device based on plasmon–exciton coupling can be potentially applied in the fields of sensor, catalysis, energy, and environment.

Surface plasmons, the free electrons' collective oscillations, have been used in the signal detection and analysis of target molecules, where the local surface plasmon resonance (LSPR) can produce a huge EM field, thus enhancing the SERS signal.

In this study, density functional theory (DFT) and time‐dependent DFT (TD‐DFT) theory are use to shed light on how the number of thiophene rings in π‐conjugated system influence the absorption spectra and non‐linear optical (NLO) properties of dyes. The results of theoretical computation show that the absorption spectra are gradually broadened and red‐shifted (384–542 nm) with increasing number of thiophene units. The theoretical examination on non‐linear optical properties was performed on the key parameters of polarizabilty and hyperpolarizability. A remarkable increase in non‐linear optical response was observed on insertion of thiophene rings in π‐spacer. Copyright © 2015 John Wiley & Sons, Ltd.