本文通过分析不同几何配置下的偏振拉曼光谱对非线性光学晶体的晶格振动模式进行了研究.首先根据因子群分析,将晶体的振动模按晶体对称群的不可约表示进行分类,其次测量了晶体在10—1600 cm 1范围内,不同几何配置下的偏振拉曼光谱,并在...本文通过分析不同几何配置下的偏振拉曼光谱对非线性光学晶体的晶格振动模式进行了研究.首先根据因子群分析,将晶体的振动模按晶体对称群的不可约表示进行分类,其次测量了晶体在10—1600 cm 1范围内,不同几何配置下的偏振拉曼光谱,并在此基础上指认了晶体的晶格振动模式.300 cm 1以下的振动峰,归结为晶体的外振动,来自[BiO6],[ZnO4],[BO4]和[BO3]原子基团的平动和转动;300cm 1以上为晶体的内振动,主要与Bi-O,和Zn-O键振动有关.晶体拉曼光谱中最高振动频率达到1407 cm 1,被指认为[BO3]三角形中B-O键的伸缩振动,体现了[BO3]基团中高的电子非局域化程度.展开更多
Molecular self-assembly is extremely important in many fields, but the characterization of their corresponding intermolecular interactions is still lacking. The C-H stretching Raman band can reflect the hydrophobic in...Molecular self-assembly is extremely important in many fields, but the characterization of their corresponding intermolecular interactions is still lacking. The C-H stretching Raman band can reflect the hydrophobic interactions during the self-assembly process of sodium dodecyl sulfate （SDS） in aqueous solutions. However, the Raman spectra in this region are seriously overlapped by the OH stretching band of water. In this work, vertically polarized Raman spectra were used to improve the detection sensitivity of spectra of C-H region for the first time. The spectral results showed that the first critical micelle concentration and the second critical micelle concentration of SDS in water were 8.5 and 69 mmol/L, respectively, which were consistent with the results given by surface tension measurements. Because of the high sensitivity of vertically polarized Raman spectra, the critical micelle concentration of SDS in a relatively high concentration of salt solution could be obtained in our experiment. The two critical concentrations of SDS in 100 mmol/L NaCl solution were recorded to be 1.8 and 16.5 mmol/L, respectively. Through comparing the spectra and surface tension of SDS in water and in NaCl solution, the self-assembly process in bulk phase and at interface were discussed. The interactions among salt ions, SDS and water molecules were also analyzed. These results demonstrated the vertically polarized Raman spectra could be employed to study the self-assembly process of SDS in water.展开更多
Deleterious chlorine fluorescence was found to occur at the same frequency as the Raman scattering of 02 （1 A） and 02 （3 E）, seriously affecting the 02 （1 A） yield measurement in the reaction of chlorine with ba...Deleterious chlorine fluorescence was found to occur at the same frequency as the Raman scattering of 02 （1 A） and 02 （3 E）, seriously affecting the 02 （1 A） yield measurement in the reaction of chlorine with basic hydrogen peroxide by use of the Raman spectroscopy technique. To solve this problem we have taken advantage of the fact that Raman radiation is always strongly polarized while fluorescence is essentially non-polarized in a gaseous medium. When chlorine utilization of a singlet oxygen generator is 88%, 02（1A） yield reaches （42.4±7.4）% with the effect of chlorine fluorescence completely eliminated.展开更多
In situ strain photoluminescence （PL） and Raman spectroscopy have been employed to exploit the evolutions of the electronic band structure and lattice vibrational responses of chemical vapor deposition （CVD）-grown...In situ strain photoluminescence （PL） and Raman spectroscopy have been employed to exploit the evolutions of the electronic band structure and lattice vibrational responses of chemical vapor deposition （CVD）-grown monolayer tungsten disulphide （WS2） under uniaxial tensile strain. Observable broadening and appearance of an extra small feature at the longer-wavelength side shoulder of the PL peak occur under 2.5% strain, which could indicate the direct-indirect bandgap transition and is further confirmed by our density-functional-theory calculations. As the strain increases further, the spectral weight of the indirect transition gradually increases. Over the entire strain range, with the increase of the strain, the light emissions corresponding to each optical transition, such as the direct bandgap transition （K-K） and indirect bandgap transition （F-K, ≥2.5%）, exhibit a monotonous linear redshift. In addition, the binding energy of the indirect transition is found to be larger than that of the direct transition, and the slight lowering of the trion dissociation energy with increasing strain is observed. The strain was used to modulate not only the electronic band structure but also the lattice vibrations. The softening and splitting of the in-plane E＇ mode is observed under uniaxial tensile strain, and polarization-dependent Raman spectroscopy confirms the observed zigzag-oriented edge of WS2 grown by CVD in previous studies. These findings enrich our understanding of the strained states of monolayer transition-metal dichalcogenide （TMD） materials and lay a foundation for developing applications exploiting their strain-dependent optical properties, including the strain detection and light-emission modulation of such emerging two-dimensional TMDs.展开更多
文摘本文通过分析不同几何配置下的偏振拉曼光谱对非线性光学晶体的晶格振动模式进行了研究.首先根据因子群分析,将晶体的振动模按晶体对称群的不可约表示进行分类,其次测量了晶体在10—1600 cm 1范围内,不同几何配置下的偏振拉曼光谱,并在此基础上指认了晶体的晶格振动模式.300 cm 1以下的振动峰,归结为晶体的外振动,来自[BiO6],[ZnO4],[BO4]和[BO3]原子基团的平动和转动;300cm 1以上为晶体的内振动,主要与Bi-O,和Zn-O键振动有关.晶体拉曼光谱中最高振动频率达到1407 cm 1,被指认为[BO3]三角形中B-O键的伸缩振动,体现了[BO3]基团中高的电子非局域化程度.
基金supported by the National Natural Science Foundation of China(20673004,20725307,50821061)National Key Basic Research Program of China(973)(2006CB932701,2006CB932403,2007CB936203)~~
基金This work is supported by the National Natural Science Foundation of China （No.21473171 and No.21573208）, the Pundamental Research Funds for the Central Universities （No.JB160508）, and the Huashan Mountain Scholar Program.
文摘Molecular self-assembly is extremely important in many fields, but the characterization of their corresponding intermolecular interactions is still lacking. The C-H stretching Raman band can reflect the hydrophobic interactions during the self-assembly process of sodium dodecyl sulfate （SDS） in aqueous solutions. However, the Raman spectra in this region are seriously overlapped by the OH stretching band of water. In this work, vertically polarized Raman spectra were used to improve the detection sensitivity of spectra of C-H region for the first time. The spectral results showed that the first critical micelle concentration and the second critical micelle concentration of SDS in water were 8.5 and 69 mmol/L, respectively, which were consistent with the results given by surface tension measurements. Because of the high sensitivity of vertically polarized Raman spectra, the critical micelle concentration of SDS in a relatively high concentration of salt solution could be obtained in our experiment. The two critical concentrations of SDS in 100 mmol/L NaCl solution were recorded to be 1.8 and 16.5 mmol/L, respectively. Through comparing the spectra and surface tension of SDS in water and in NaCl solution, the self-assembly process in bulk phase and at interface were discussed. The interactions among salt ions, SDS and water molecules were also analyzed. These results demonstrated the vertically polarized Raman spectra could be employed to study the self-assembly process of SDS in water.
基金This work was supported by the Knowledge Innovation Program of the Chinese Academy of Sciences （No.K2009F02） and the National Natural Science Foundation of China-Youth Science Foundation （No.20603039）. The authors thank Dr. Jing Leng, Shn-yan Du, Wen-ming Tian, and Jun-hui Wang for their helpful discussions in the experiment.
文摘Deleterious chlorine fluorescence was found to occur at the same frequency as the Raman scattering of 02 （1 A） and 02 （3 E）, seriously affecting the 02 （1 A） yield measurement in the reaction of chlorine with basic hydrogen peroxide by use of the Raman spectroscopy technique. To solve this problem we have taken advantage of the fact that Raman radiation is always strongly polarized while fluorescence is essentially non-polarized in a gaseous medium. When chlorine utilization of a singlet oxygen generator is 88%, 02（1A） yield reaches （42.4±7.4）% with the effect of chlorine fluorescence completely eliminated.
基金This work is supported by the Singapore National Research Foundation NRF RF Award No. NRFRF2010- 07, MOE Tier 2 MOE2012-T2-2-049, A＇Star SERC PSF grant No. 1321202101, and MOE Tier 1 MOE2013- T1-2-235. W. Huang acknowledges the support of the National Basic Research Program of China （973 Program） （No. 2015CB932200）, the National Natural Science Foundation of China （NSFC） （Grant Nos. 21144004, 20974046, 21101095, 21003076, 20774043, 51173081, 50428303, 61136003, and 50428303）, the Ministry of Education of China （No. IRT1148）, the NSF of Jiangsu Province （Grant Nos. SBK201122680, 11KJB510017, BK2008053, 11KJB510017, BK2009025, 10KJB510013, and BZ2010043）, and NUPT （Nos. NY210030 and NY211022）. J. R Wang is grateful for the NSFC （No. 11474164）, NSF of Jiangsu province （No. BK20131413）, and the Jiangsu Specially-Appointed Professor program. Y. L. Wang thanks Luqing Wang, Dr. Xiaolong Zou, and Dr. Alex Kutana for the constructive discussion.
文摘In situ strain photoluminescence （PL） and Raman spectroscopy have been employed to exploit the evolutions of the electronic band structure and lattice vibrational responses of chemical vapor deposition （CVD）-grown monolayer tungsten disulphide （WS2） under uniaxial tensile strain. Observable broadening and appearance of an extra small feature at the longer-wavelength side shoulder of the PL peak occur under 2.5% strain, which could indicate the direct-indirect bandgap transition and is further confirmed by our density-functional-theory calculations. As the strain increases further, the spectral weight of the indirect transition gradually increases. Over the entire strain range, with the increase of the strain, the light emissions corresponding to each optical transition, such as the direct bandgap transition （K-K） and indirect bandgap transition （F-K, ≥2.5%）, exhibit a monotonous linear redshift. In addition, the binding energy of the indirect transition is found to be larger than that of the direct transition, and the slight lowering of the trion dissociation energy with increasing strain is observed. The strain was used to modulate not only the electronic band structure but also the lattice vibrations. The softening and splitting of the in-plane E＇ mode is observed under uniaxial tensile strain, and polarization-dependent Raman spectroscopy confirms the observed zigzag-oriented edge of WS2 grown by CVD in previous studies. These findings enrich our understanding of the strained states of monolayer transition-metal dichalcogenide （TMD） materials and lay a foundation for developing applications exploiting their strain-dependent optical properties, including the strain detection and light-emission modulation of such emerging two-dimensional TMDs.
