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The temperature alarm system is self-powered by luminescent solar concentrators based on a single green-emitted PEA2MnBr2I2with a backward energy transfer process.

Exploring the origin of emission is fundamental in the field of carbon dots (CDs). Due to the lack of suitable in situprobing techniques, it is necessary to explore effective alternative methods that can accurately reflect the relationship between the emission and the composition of the functional groups of CDs. Herein, we propose a new method of post-synthetic treatment of CDs by photo-oxidation to investigate the origin of emission for CDs. After the addition of a photo-oxidant into pre-prepared CDs under UV irradiation, the fluorescence of CDs can be regulated from the original orange emission to the final green emission due to the damage of original functional groups and the formation of new functional groups on CDs during the post-treatment process. The abundant dynamic information about the functional groups and emissions of CDs during the visible and ready-to-monitor post-treatment process makes it possible to quantitatively analyze the origin of the emission of CDs. Our results suggest that the emission sub-peaks at 560 nm and 600 nm relate to the CD surface-state-associated –NH3+groups, while the emission sub-peak at 537 nm or 494 nm is associated with the CD surface-state-associated –OH groups or the CD surface-state-associated carbonyl groups (CO). Under UV irradiation, the CD surface-state-associated –NH3+groups can be continuously converted into the CD surface-state-associated –OH groups and the CD surface-state-associated carbonyl groups (CO), leading to the changed emission color of CDs.

The coherent random laser (CRL) from dye-doped polydimethylsiloxane (PDMS) has been investigated in both nanoparticle-doped (NP-doped) thin films and pure dye thin films. Compared with the literature, the pump threshold is only 1.5 mJ/cm2in the pure dye thin film with a low dye concentration. The spontaneously formed micro-/nanocrystals of Pyrromethene 597 (PM597) dye support both gain and random feedback in the bulk of the PDMS during the sample preparation. When the SiO2NPs were doped, the pump threshold was reduced to 0.75 mJ/cm2. The threshold increased after the film was peeled off from glass, which indicates that the photon localization effect of the leaky-waveguide structure plays an important role in the reduction of the CRL threshold. By a change in the pump stripe length or the thickness of the film, the peak wavelength red-shifts 6.7 or 5.93 nm, respectively. The PM597 dye molecule solubility changes, and they spontaneously aggregate in the process of toluene volatilization; the PDMS cures, which is the reason for the formation of PM597 micro-/nanocrystals. This thin film random laser with a low dye concentration can be used in integrated optoelectronics and display imaging.

The multiexciton states in semiconductor quantum dots (QDs) have obtained increasing attention because of their extensive potential applications. Here, the pump-intensity-dependent multiexciton process in phase-pure wurtzite CdSe/CdS QDs is revealed by analyzing a fast photoluminescence (PL) decay component. The experimental results show that the PL decay traces can be fitted well by a superradiance decay function. The average number of excitons per QD (⟨N⟩), obtained by fitting PL decay traces, is proportional to the power density, which is consistent with their theoretical calculations. However, the ⟨N⟩ starts to exhibit the saturation trends when the exciton number reaches about 6, which maybe result from the increased nonradiative losses of excitons at higher pump levels. The results give us deeper insights into the multiexciton dynamics process of CdSe/CdS QDs from the viewpoint of PL decay mechanism. Moreover, the fitting results are further confirmed by the multiband amplified stimulated emission measurements. Finally, we fabricate QD microlasers based on the microdisk resonator, indicating that CdSe/CdS QDs will be a promising lasing gain material for prospective applications in practical QD lasers.

The random laser from sheared dye-doped polymer-dispersed liquid crystal (DDPDLC) is investigated. As the emission intensity weakens, the threshold of random laser from DDPDLC increases from 2.0 mJ/pulse to 4.0 mJ/pulse, and the degree of polarization (DOP) increases from 0.1 to 0.78, obviously when the shear distance increases from 0 mm to 4 mm. As the liquid crystal droplets are gradually oriented in the shear direction caused by alignment direction of polymer chain and anisotropy of droplet shape, the scattering intensity perpendicular to the shear direction gradually decreases and that parallel to the shear direction gradually increases. The anisotropic absorption of the laser dye also plays a certain role as the shear distance is 0 mm. The controllable intensity and polarization degree of random laser have a huge potential for sensing applications.

“Giant” semiconductor quantum dots (GQDs) have tremendous potential for applications in laser devices. Here, CdSe/CdS core–shell GQDs (11 monolayers) have been synthesized as lasing gain material. The photoluminescence decay of the GQD ensemble is single-exponential, and the two-photon absorption cross-section is above 105GM. This article presents a versatile method for fabrication of CdSe/CdS GQD distributed feedback (DFB) lasers by laser interference ablation. A high-quality surface-relief grating structure can be readily created on the GQD thin films, and the relationship between laser beam intensity and surface modulation depth is studied. With appropriate periods, single-mode lasing emission has been detected from these devices under excitation wavelengths of 400 and 800 nm. The laser thresholds are as low as 0.028 and 1.03 mJ cm–2, with the lasing Q-factors of 709 and 586, respectively. Lasing operation is realized from the direct laser interference-ablated QD DFB structures for the first time.

The atmospheric vertical structure and changed characteristics of boundary layer parameters, as well as their relations with sea ice and temperature changes in the center of Arctic Ocean (80°–88°N) are presented by adopting GPS sounding data obtained by the 4th–6th Arctic expeditions of China and NCEP (National Centre for Environmental Prediction) reanalysis data. Obvious differences are observed regarding the tropopause, boundary layer height, temperature inversion, and vertical structure of wind speed and direction in the center Arctic Ocean in the summer of 2012, 2010, and 2014. These differences can be explained by the relations between temperature and changes in sea ice extent in September from 1979 to 2014. In September 2012, the Arctic sea ice extent decreased by 44% an with obvious warming process. In September 2010 and 2014, it decreased by 22.6% and 17% with an obvious cooling process, respectively. A comparison of the two processes shows that sea ice change has a significant influence on the structure of the atmospheric boundary layer. In the recent 30 years, the temperature changes of 1000 and 850 hPa in the center of the Arctic Ocean have displayed an obvious warming trend and negative correlation with sea ice extent. These changes indicate that the continuous reduction of Arctic sea ice will continue the warming of the troposphere middle layer.

In this article, three truexene-based dyes with 2-cyanoacrylic acid as acceptor and starburst triarylamine as donor (S5, S6, and S7) were conveniently synthesized and used for dye-sensitized solar cells (DSSCs). A compact sensitizer layer is molecular interfacially engineered on the TiO2surface via cone-shaped sensitizers. As a result, the approach of the electrolyte to the TiO2surface is blocked significantly by the compact sensitizer layer formed and the charge recombination in the DSSCs is proved to be retarded effectively. The monochromatic incident photon-to-current conversion efficiency of these sensitizers is near 90%. In addition, S7-sensitized solar cells yield an open-circuit voltage of 752 mV and a fill factor of 0.70, which are even higher than those of N719 under the same conditions.

Two-, three-, and four-photon-pumped stimulated emission (cavityless lasing) properties of ten novel stilbazolium dyes in solution phase have been comprehensively studied. These newly synthesized multiphoton active dye compounds have the same molecular backbone but differ either in their electron donors or in their electron acceptors and can be utilized to generate highly directional stimulated emissions over a broad visible spectral range (from 490 to 618 nm) under multiphoton-pump conditions. The pump source was a powerful Ti:sapphire oscillator-amplifier system associated with an optical-parametric generator, which could specifically provide ∼160 fs duration and ∼775, 1320, and 1890 nm laser pulses for two-, three-, and four-photon excitation, respectively. The spectral, spatial, and temporal properties as well as the efficiency of multiphoton-pumped lasing output from different dye-solution samples have been studied. Based on the measured results, two salient features have been found: (i) the threshold pump-energy values for two-, three-, and four-photon-pumped lasing were quite close (within a factor of 3-4); and (ii) there was an obvious wavelength difference (10-30 nm) between the forward and backward lasing output under three- and four-photon-pump conditions.

The synthesis and characterization of two novel fluorene-containing ferrocene derivatives were reported. The two-photon absorption spectra and three-photon absorption cross-section values in the IR region for these two chromophores were studied. Together with their thermal stabilities, their linear absorption and emission properties were also investigated. The results show that the ferrocene derivatives have large two-photon and three-photon absorption in IR region as well as excellent thermal stabilities. The three-photon absorption based optical limiting properties of these two ferrocene derivatives were investigated by using sub-picosecond IR laser pulses.

We report the experimental generation and dynamic trajectory control of plasmonic Airy beams (PABs). The PABs are created by directly coupling free-space Airy beams to surface plasmon polaritons through a grating coupler on a metal surface. We show that the ballistic motion of the PABs can be reconfigured in real time by either a computer addressed spatial light modulator or mechanical means.

The synthesis of some novel perylene bisimide derivatives was reported and their linear absorption, emission, and two-photon properties were measured and discussed. Two-photon cross-sections for these compounds were determined to be 8735 GM maximum (nonlinear transmittance, ≈7 ns, 10 Hz and 850 nm). The frequency upconversion fluorescence was observed under the excitation of 850-nm-nanoseconds laser pulses with the peaks located around 669 nm.