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Spontaneous Raman scattering is an attractive optical technique for the analysis of gases and liquids; however, their low densities and notoriously weak scattering cross sections demand an enhancement of the spontaneous Raman scattering signal for detection. Here, we have developed a simple but highly effective and fast technique to enhance the signal of spontaneous Raman scattering from gases and liquids. The technique is developed based on the principle of an integrating sphere, which realizes the multiple pass actions of low-energy pump light and the collection of all Raman scattered light for a sample volume of 2 mL. By measuring the ambient air sample with an exposure time of 180 s, we found the experimental detection limit of our spontaneous Raman scattering setup can reach 3 ppm. CH4(<2 ppm) in air can be also examined by increasing the exposure time to 300 s. The performance of our setup used for the analysis of trace gases is further illustrated by characterizing ethane, propane, butane, and pentane in methane as well as isotopes of carbon dioxide. The results reveal that the detection limit of our setup for liquids can be improved by nearly 4 orders of magnitude compared to that of confocal Raman scattering spectroscopy with the same experimental conditions.

Nanosecond laser-induced breakdown (LIB) in liquids (e.g., water) can produce dynamic high pressure and high temperature. However, since high pressure needs to negate the effect of high temperature to some degree, it is only partially effective. As a result, it is difficult to directly measure the effective pressure due to the transient and complex LIB process. Here, we presented a simple method based on Raman spectroscopy to indirectly determine the effective pressure caused by LIB in liquid pure H_2O and low concentration H_2O−H_2O_2 mixtures. By comparing the Raman shifts of the ice-VII mode for pure H_2O and H_2O−H_2O_2 mixtures under laser pumping and static high pressure, the LIB effective pressure can be first estimated. The empirical equation was then derived base on the correlation of the LIB effective pressure to ice-VII-point stimulated Raman scattering thresholds for pure and mixture water solutions, which can be used to estimate the LIB effective pressures for other different mixture water solutions with the uncertainty of 0.14–0.25 Gpa. Hopefully, our study here would advance the measurements of effective pressure in the LIB process.

Elasticity and stability play a crucial role in phase change fibers (PCFs), ensuring both comfort and effective thermal management in fabrics. In this study, we present the development of an elastic and shape-stable phase change fiber through coaxial wet spinning. The fiber consists of a paraffin wax (PW) core encapsulated in a thermoplastic polyurethane (TPU) sheath, providing reliable protection against leakage during use. The obtained PCFs exhibit a PW loading capacity of up to 64.9 wt% and a heating enthalpy of 117.0 J/g. Notably, these fibers maintain their morphological and thermal stability even after undergoing 50 cycles of heating and cooling treatments. By integrating the PCFs into a fabric and coating the surface with CNTs, the PCFs-based fabric achieves an outstanding photothermal conversion efficiency of 95.1 % under a light intensity of 250 mW/cm2and an electrothermal conversion efficiency of 73.2 % at a power level of 0.9 W. Furthermore, the fabric, woven with uniformly broken PW core, exhibits excellent tensile resilience in various conditions, including room temperature and during photothermal and electrothermal conversion processes. This study introduces a promising avenue for the development of innovative PCFs, offering significant potential for their application in the realm of personal smart fabrics, particularly in the field of advanced thermal management.

Stimulated Raman scattering (SRS) of silicon quantum dots (Si QD) water solutions of different sizes (2 and 5 nm) are investigated using Nd:YAG laser. Since strong and weak hydrogen bonds are formed by the charge transfer between water molecules and Si QDs, two SRS peaks of OH stretching vibrations of Si QDs solutions are observed in the forward direction. Simultaneously, characteristic feature peaks related to the interaction between OH groups and excess electrons are obtained in the backward SRS of 2 nm Si QDs solutions. The excess electrons induce a strong electrostatic field, leading to the transformation from water to an ice-VIII structure.