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The investigation of the fluorescence mechanism of carbon dots (CDs) has attracted significant attention, particularly the role of the oxygen-containing groups. Dual-CDs exhibiting blue and green emissions are synthesized from glucose via a simple ultrasonic treatment, and the oxidation degree of the CDs is softly modified through a slow natural oxidation approach, which is in stark contrast to that aggressively altering CDs’ surface configurations through chemical oxidation methods. It is interesting to find that the intensity of the blue fluorescence gradually increases, eventually becoming the dominant emission after prolonging the oxidation periods, with the quantum yield (QY) of the CDs being enhanced from ~0.61% to ~4.26%. Combining the microstructure characterizations, optical measurements, and ultrafiltration experiments, we hypothesize that the blue emission could be ascribed to the surface states induced by the C–O and C=O groups, while the green luminescence may originate from the deep energy levels associated with the O–C=O groups. The distinct emission states and energy distributions could result in the blue and the green luminescence exhibiting distinct excitation and emission behaviors. Our findings could provide new insights into the fluorescence mechanism of CDs.

In this paper, a physical model is established to reveal the relationship between polarization phase of incident light and in-plane spin splitting (IPSS) of reflected beam, and the impact of polarization phase on the IPSS is systematically investigated. Three interesting features of the effect of polarization phase on IPSS were discovered. Furthermore, it is found that the IPSS can be effectively enhanced and suppressed by adjusting the polarization phase near ±π/2. The enhanced IPSS shift can almost reach its upper limit (that is, half of the beam waist) and the suppressed IPSS shift can be reduced to zero. In addition, it is also found that the spin cumulative direction of spin components can be reversed adjusting the polarization phase at ±π/2. These findings not only provide a deeper insight into photonic spin Hall effect, but also open a path for the photon manipulation, precision metrology and the manufacture of photonic spin switching devices.

Oxygen is not only important which people rely on but also one type of important industrial gas. Considering that there are some disadvantages of traditional methods to measure the oxygen concentration, the tunable diode laser absorption spectroscopy is researched in this paper combined with the phase-lock amplify technique. This method combines the high power, good monochrome, wavelength tuned with the drive current or temperature of laser and the advantage of phase-lock amplifier to improve the signal and noise ratio and the measure precision. Based on designing the detect system, the quantitative relation between the oxygen absorption cross-section and temperature at 760.26 nm is deduced. Moreover the linear bias of the detect result is 1%, and there is no interference caused by the other components mixed in the measured gas. So it can be seen that this technology has many advantages and can meet the application of industry very well. [ABSTRACT FROM AUTHOR]