scholarly journals Optical Feedback for Sensitivity Enhancement in Direct Raman Detection of Liquids

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Miao Liu ◽  
Yunyun Mu ◽  
Jingyun Hu ◽  
Jiajun Li ◽  
Xinping Zhang

Detection of low-concentration molecules in liquids has been a challenge in sensing technologies. Raman spectroscopy is an effective approach for trace detection, which is in fact a “volume-excitation” and “volume-collection” technique in the analysis of liquid samples. However, for the commonly employed one-pass excitation and back-scattering detection scheme, a large portion of both the excitation laser energy and the Raman-scattering light energy is wasted without efficient reuse or collection. In this consideration, we demonstrate a broadband optical feedback scheme by a curved high-reflection mirror for both the excitation and the Raman-scattering light, so that the excitation and the forward-propagating Raman signal can be back-reflected and collected with a high efficiency. Using the “F+2f” design, where F and f are the focal lengths of the focusing lens and curved reflection mirror, respectively, we were able to not only produce two focuses of the excitation laser beam but also extend the Raman interaction by a doubled distance. For the detection of pure ethanol molecules and the R6G molecules in water with a concentration of 10−3 M, the Raman signal was enhanced by a factor of about 5.6. The optical feedback scheme and discovered optical mechanisms supply effective improvements to the Raman spectroscopic measurements on liquid samples.

Foods ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 483
Author(s):  
Francisco J. Rivero ◽  
Leonardo Ciaccheri ◽  
M. Lourdes González-Miret ◽  
Francisco J. Rodríguez-Pulido ◽  
Andrea A. Mencaglia ◽  
...  

Overripe seeds from sun-dried grapes submitted to postharvest dehydration constitute a scarcely investigated class of vinification byproduct with limited reports on their phenolic composition and industrial applications. In this study, Raman spectroscopy was applied to characterize a selection of overripe seed byproducts from different white grapes (cv. Moscatel, cv. Pedro Ximénez and cv. Zalema) submitted to postharvest sun drying. The Raman measurements were taken using a 1064 nm excitation laser in order to mitigate the fluorescent effect and the dispersive detection scheme allowed a compactness of the optical system. Spectroscopic data were processed by a principal component analysis to reduce the dimensionality and partner recognition. The evolution of the Raman spectrum during the overripening process was compared with the phenolic composition of grape seeds, which was determined by rapid resolution liquid chromatography/mass spectrometry (RRLC/MS). A multivariate processing of the spectroscopic data allowed the classification of overripe seeds according to the grape variety and the monitoring of stages of the postharvest sun drying process.


Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1359
Author(s):  
Anindya-Sundar Jana ◽  
Hwa-Dong Liu ◽  
Shiue-Der Lu ◽  
Chang-Hua Lin

The traditional perturbation and observation (P&O) maximum power point tracking (MPPT) algorithm of a structure is simple and low-cost. However, the P&O algorithm is prone to divergence under solar radiation when the latter varies rapidly and the P&O algorithm cannot track the maximum power point (MPP) under partial shading conditions (PSCs). This study proposes an algorithm from the P&O algorithm combined with the solar radiation value detection scheme, where the solar radiation value detection is based on the solar photovoltaic (SPV) module equivalent conductance threshold control (CTC). While the proposed algorithm can immediately judge solar radiation, it also has suitable control strategies to achieve the high efficiency of MPPT especially for the rapid change in solar radiation and PSCs. In the actual test of the proposed algorithm and the P&O algorithm, the MPPT efficiency of the proposed algorithm could reach 99% under solar radiation, which varies rapidly, and under PSCs. However, in the P&O algorithm, the MPPT efficiency was 96% under solar radiation, which varies rapidly, while the MPPT efficiency was only 80% under PSCs. Furthermore, in verifying the experimental results, the proposed algorithm’s performance was higher than the P&O algorithm.


2015 ◽  
Vol 2015 ◽  
pp. 1-5 ◽  
Author(s):  
Li Yuan ◽  
Jinghuai Fang ◽  
Yonglong Jin ◽  
Chaonan Wang ◽  
Tian Xu

We fabricated a simple, cheap, and functional surface enhanced Raman scattering substrate for biomedical application. Hot spots between two close silver nanoparticles distributed in the skeleton of a three-dimensional porous membrane, especially in the pores, were formed. The dual poles of micropores in the membrane were discussed. The pores could protect the silver nanoparticles in the pores from being oxidized, which makes the membrane effective for a longer period of time. In addition,Staphylococcus aureuscells could be trapped by the micropores and then the Raman signal became stronger, indicating that the functional surface enhanced Raman scattering substrate is reliable.


2021 ◽  
Author(s):  
Zohreh Hosseinaee ◽  
Ben Ecclestone ◽  
Nicholas Pellegrino ◽  
Layla Khalili ◽  
Lyazzat Mukhangaliyeva ◽  
...  

2004 ◽  
Vol 818 ◽  
Author(s):  
Vitaliy N. Pustovit ◽  
Tigran V. Shahbazyan

AbstractWe study the role of a strong electron confinement on the surface-enhanced Raman scattering from molecules adsorbed on small noble-metal nanoparticles. We describe a novel enhancement mechanism which originates from the different effect that confining potential has on s-band and d-band electrons. We demonstrate that the interplay between finite-size and screening efects in the nanoparticle surface layer leads to an enhancement of the surface plasmon local field acting on a molecule located in a close proximity to the metal surface. Our calculations show that the additional enhancement of the Raman signal is especially strong for small nanometer-sized nanoparticles.


2013 ◽  
Vol 40 (3) ◽  
pp. 0317001 ◽  
Author(s):  
何滔 He Tao ◽  
杨苏辉 Yang Suhui ◽  
张海洋 Zhang Haiyang ◽  
赵长明 Zhao Changming ◽  
徐鹏 Xu Peng ◽  
...  

Nanoscale ◽  
2020 ◽  
Vol 12 (46) ◽  
pp. 23768-23779
Author(s):  
Yitian Zeng ◽  
Steven J. Madsen ◽  
Andrew B. Yankovich ◽  
Eva Olsson ◽  
Robert Sinclair

Correlation of surface plasmon resonance and surface enhanced Raman scattering: maximum enhancement achieved when excitation laser match with plasmon resonance.


2020 ◽  
Vol 8 ◽  
Author(s):  
Yao Zhao ◽  
Suming Weng ◽  
Zhengming Sheng ◽  
Jianqiang Zhu

Stimulated Raman scattering (SRS) in plasma in a non-eigenmode regime is studied theoretically and numerically. Different from normal SRS with the eigen electrostatic mode excited, the non-eigenmode SRS is developed at plasma density $n_{e}>0.25n_{c}$ when the laser amplitude is larger than a certain threshold. To satisfy the phase-matching conditions of frequency and wavenumber, the excited electrostatic mode has a constant frequency around half of the incident light frequency $\unicode[STIX]{x1D714}_{0}/2$ , which is no longer the eigenmode of electron plasma wave $\unicode[STIX]{x1D714}_{pe}$ . Both the scattered light and the electrostatic wave are trapped in plasma with their group velocities being zero. Super-hot electrons are produced by the non-eigen electrostatic wave. Our theoretical model is validated by particle-in-cell simulations. The SRS driven in this non-eigenmode regime is an important laser energy loss mechanism in the laser plasma interactions as long as the laser intensity is higher than $10^{15}~\text{W}/\text{cm}^{2}$ .


2014 ◽  
Vol 912-914 ◽  
pp. 633-637
Author(s):  
Ping He ◽  
Chao Liu ◽  
Ying Li ◽  
Zhi Qiang Zhao

Actuator is the main executive mechanism for the attitude control of aircraft in the aerospace industry and aviation field. With the further development of technology, higher quality of product research and detection has been required. According to the test requirements, the actuator nonlinear parameter testing system is designed to realise the automatic detection for actuator transmission mechanism on the basis of the research in nonlinear measured parameter of tranmission accuracy. Firstly, the principle and detection scheme of the system was presented. Then the overall structure of the system was designed. After that, the hardware circuit of the system which used TMS320F2812 as main control chip was designed. It mainly consisted of the function of each module and the working process of the system. Finally, the software of the image acquisition system was presented. With the experimental verification, the system realises the automatic detection for tranmission accuracy and has advantages of low cost, high efficiency and strong resistance to interference. The functions and indexes achieved the design requirements..


Sign in / Sign up

Export Citation Format

Share Document