Chemical Enhancement on Surface-Enhanced Resonance Raman Scattering of Au3-1,4-BenzenedithioI-Au3 Junction

Surface-enhanced Raman scattering （SERS） and surface-enhanced resonance Raman scattering （SERRS） spectra of the 1,4-benzenedithiol molecule in the junction of two Au3 clusters have been calculated using density functional theory （DFT） and time-dependent DFT method. In order to investigate the contribution of charge transfer （CT） enhancement, the wavelengths of incident light are chosen to be at resonance with four representative excited states, which correspond to CT in four different forms. Compared with SERS spectrum, SERRS spectra are enhanced enormously with distinct enhancement factors, which can be attributed to CT resonance in different forms.

Surface-enhanced resonance Raman scattering spectroscopy of single R6G molecules

Surface-enhanced resonance Raman scattering （SERRS） of Rhodamine 6G （R6G） adsorbed on colloidal silver clusters has been studied. Based on the great enhancement of the Raman signal and the quench of the fluorescence, the SERRS spectra of R6G were recorded for the samples of dye colloidal solution with different concentrations. Spectral inhomogeneity behaviours from single molecules in the dried sample films were observed with complementary evidences, such as spectral polarization, spectral diffusion, intensity fluctuation of vibrational lines and even ＂breathing＂ of the molecules. Sequential spectra observed from a liquid sample with an average of 0.3 dye molecules in the probed volume exhibited the expected Poisson distribution for actually measuring 0, 1 or 2 molecules. Difference between the SERRS spectra of R6G excited by linearly and circularly polarized light were experimentally measured.

A mini review and hypothesis for coronavirus detection using photonics: surface enhanced Raman scattering and fluorescence resonance energy transfer

COVID-19 has devastated numerous nations around the world and has overburdened numerous healthcare systems,which has also caused the loss of livelihoods due to prolonged shutdowns and further led to a cascading effect on the global economy.COVID-19 infections have an incubation period of 2–7 days,but 40 to 45%of cases are asymptomatic or show mild to moderate respiratory symptoms after the period due to subclinical lung abnormalities,making it more likely to spread the pandemic disease.To restrict the spread of the virus,on-site diagnosis methods that are quicker,more precise,and easily accessible are required.Rapid Antigen Detection Tests and Polymerase Chain Reaction tests are currently the primary methods used to determine the presence of COVID-19 viruses.These tests are typically time-consuming,not accurate,and,more importantly,not available to everyone.Hence,in this review and hypothesis,we proposed equipment that employs the properties of photonics to improve the detection of COVID-19 viruses by taking the advantage of typical binding of coronavirus with angiotensin-converting enzyme 2(ACE2)receptors.This hypothetical model would combine Surface-Enhanced Raman Scattering(SERS)and Fluorescence Resonance Energy Transfer(FRET)to provide great flexibility,high sensitivities,and enhanced accessibility.

Resonance Raman Spectra of Purified PS Ⅱ Core Antenna Complexes CP43 and CP47

PSⅡ core antenna complexes, CP43 and CP47, were purified from spinach (Spinacia oleracea L.) by DEAE Fractogel TSK 650S anion exchange chromatography. Their normal temperature (298 K) resonance Raman spectra were measured. The results suggest that all β carotenoids bound to CP43 and CP47 are in all trans configuration and likely in twisted conformations.

Surface-enhanced Raman Scattering of Aflatoxin B1 on Silver by DFT Method

The structure, electrostatic properties, and Raman spectra of aflatoxin B1 （AFB1） and AFB1-Ag complex are studied by density functional theory with B3LYP/6- 311G（d,p）/Lan12dz basis set. The results show that the surface-enhanced Raman scattering （SERS） and pre-resonance Raman spectra of AFB1-Ag complex strongly depend on the adsorption site and the excitation wavelength found to enhance 102-103 order compared to of the incident light. The SERS factors are normal Raman spectrum of AFB1 molecule due to the larger static polarizabilities of the AFB1-Ag complex, which directly results in the stronger chemical enhancement in SERS spectra. The pre-resonance Raman spectra of AFB1-Ag complex are explored at 266, 482, 785, and 1064 nm incident light wavelength, in which the enhancement factors are about 10^2-10^4, mainly caused by the charge-transfer excitation resonance. The vibrational modes are analyzed to explain the relationship between the vibrational direction and the enhanced Raman intensities.

The effect of an anti-hydrogen bond on Fermi resonance： A Raman spectroscopic study of the Fermi doublet v1-v12 of liquid pyridine

The effects of an anti-hydrogen bond on the v1 v12 Fermi resonance （FR） of pyridine are experimentally investigated by using Raman scattering spectroscopy. Three systems, pyridine/water, pyridine/formamide, and pyridine/carbon tetrachloride, provide varying degrees of strength for the diluent-pyridine anti-hydrogen bond complex. Water forms a stronger anti-hydrogen bond with pyridine than with formamide, and in the case of adding non-polar solvent carbon tetrachloride, which is neither a hydrogen bond donor nor an acceptor and incapable of forming a hydrogen bond with pyridine, the intermolecular distance of pyridine will increase and the interaction of pyridine molecules will reduce. The dilution studies are performed on the three systems. Comparing with the values of the Fermi coupling coefficient W of the ring breathing mode v1 and triangle mode v12 of pyridine at different volume concentrations, which are calculated according to the Bertran equations, in three systems, we find that the solution with the strongest anti-hydrogen bond, water, shows the fastest change in the v1-v12 Fermi coupling coefficient W with the volume concentration varying, followed by the formamide and carbon tetrachloride solutions. These results suggest that the stronger anti-hydrogen bond-forming effect will cause a greater reduction in the strength of the v1-v12 FR of pyridine. According to the mechanism of the formation of an anti-hydrogen bond in the complexes and the FR theory, a qualitative explanation for the anti-hydrogen bond effect in reducing the strength of the v1 - v12 FR of pyridine is given.

Comparison of Surface-enhanced Raman Scattering Spectra of Two Kinds of Silver Nanoplate Films

Surface-enhanced Raman scattering（SERS） spectra of different silver nanoplate selt-assembled tllmS at different excitation wavelengths were fairly compared. Shape conversion from silver nanoprisms to nanodisks on slides was in situ carried out. The SERS spectra of 4-mercaptopyridine（4-MPY） on these anisotropic silver nanopar- ticle self-assembled films present that strong enhancement appeared when the excitation line and the surface plasmon resonance（SPR） band of silver substrate overlapped. In this model, the influence of the crystal planes of silver na- noplates on SERS enhancement could be ignored because the basal planes were nearly unchanged in two kinds of silver nanoplate self-assembled films.

Surface-enhanced Raman scattering on dielectric microspheres with whispering gallery mode resonance

Conventionally, metallic nanostructures are used for surface-enhanced Raman spectroscopy(SERS), but recently there has been increasing interest in the enhancement of Raman scattering from dielectric substrates due to their improved stability and biocompatibility compared with metallic substrates. Here, we report the observation of enhanced Raman scattering from rhodamine 6 G molecules coated on silica microspheres. We excite the whispering gallery modes(WGMs) supported in the microspheres with a tapered fiber coupler for efficient WGM excitation, and the Raman enhancement can be attributed to the WGM mechanism. Strong resonance enhancement in pump laser intensity and modified Raman emission from the Purcell effect in the microsphere resonator are observed from the experiment and compared with theoretical results. A total Raman enhancement factor of 1.4 × 10~4 is observed, with contribution mostly from the enhancement in pump laser intensity. Our results show that, with an efficient pumping scheme, dielectric microspheres are a viable alternative to metallic SERS substrates.

Surface-enhanced Raman scattering(SERS)based on surface plasmon resonance coupling techniques

Surface plasmon resonance(SPR)can provide a remarkably enhanced electromagetic field around metal surface.It is one of the enhancement models for explaining surface-enhanced Raman scattering(SERS)phonomenon.With the development of SERS theories and techniques,more and more studies referred to the configurations of the optical devices for coupling the excitation and radiation of SERS,including the prism-coupling,waveguide-coupling,and grating-coupling modes.In this review,we will summarize the recent experimental improvements on the surface plasmoncoupled SERS.

A dual-functional membrane for bisphenol A enrichment and resonance amplification by surface-enhanced Raman scattering

Bisphenol A （BPA） was one of the environmental hormones that would cause endocrine and metabolic disorders in human or wildlife. This paper proposed a method to detect the trace amounts of BPA in water samples by fully utilizing the enrichment and resonance amplification functions of a new dual-functional membrane. In this work, gold nanoparticles （AuNPs） modified by 3-amino-5-mercapto-1,2,4-triazole （AMT） were embedded in nylon66 membrane to produce a dual-functional membrane which could carry out sample enrichment by capturing BPA molecules from water and achieve resonance amplification by connecting BPA to the surfaces of AuNPs. By designing an automatic sampler for large-volume enrichment, the SERS enhancement factor （EF） of the method was further improved to 1.2 × 105. The present method had been successfully applied to detect BPA in drinking water and environmental water by SERS with the detection limit of 0.012 μg/L. It had the potential for on-site detecting of BPA in various water samples.

四苯基卟啉二酸H_4TPP^(2+)的共振Raman光谱研究

本文研究了四苯基卟啉二酸H_4TPP^(2+)在固体和溶液状态下的共振Raman光谱。并结合红外光谱指出H_4TPP^(2+)分子可能存在对称中心。退偏振比测量发现H_4TPP^(2+)有两个反常退偏带。H_4TPP^(2+)分子近似具有D_(14)对称性。

菌紫质在银膜表面的共振增强Raman光谱

本文用表面共振增强Raman方法,研究了菌紫质在不同条件下吸附在镀银玻璃上的Raman光谱,结果表明菌紫质吸附在银膜上,代表菌紫质分子循环中间体M412特征谱带的1565cm-1Raman位移明显增强,说明银膜对M412态有一定表面共振增强作用。

半导体纳米材料SPR特性及其在SERS中的应用

表面增强拉曼光谱(Surface enhanced Raman spectroscopy,SERS)由于其高灵敏度,高选择性获得了广泛的关注。目前可作为SERS基底的材料主要为贵金属纳米材料。贵金属纳米材料的表面等离子共振频率一般在可见光区范围,具有较高的SERS增强因子,但贵金属材料存在的一些问题限制其应用。人们希望设计并合成出适用于多种检测分子的更多样化的SERS基底,同时期望与金属类似地,通过材料自身就能实现较高的增强效应。而对于大多数半导体材料而言,由于很难在拉曼激发光波长范围内(可见区)获得表面等离激元共振(Surface plasmon resonance,SPR)诱导的增强效应,需要通过调控SPR来实现其SERS应用。基于半导体本身的物理增强研究,尤其是SPR效应的协同增强机理方向获得了越来越多的关注。本文将重点总结各类半导体SPR调控手段,以及近些年基于半导体SPR的SERS应用。

Modulating carrier density of the(Ag)_(x)(MoO_(3))_(y)system to enhance SERS:Localized surface plasmon resonance contribution

Semiconductors typically exhibit long-wavelength LSPR absorption in the infrared region due to lower carrier density.Tuning the carrier density of semiconductors and blue-shifting their LSPR absorption to the visible and near-infrared region has always been a great challenge.Herein,we discussed how the controllable carrier of(Ag)x(MoO_(3))y composite influences the LSPR based on SERS test and UVeViseNIR absorption spectra.We were surprised to find that the LSPR absorption wavelength can be easily tuned from 950 to 735 nm by changing the sputtering power of MoO_(3)of the(Ag)x(MoO_(3))_(y)composite.This shows that LSPR can be precisely adjusted by increasing the semiconductor content and even the carrier density.In addition,the carrier density was measured by Hall effect to investigate the SERS intensity change caused by electromagnetic(EM)enhancement,and obtain the relationship between the two.The findings of this work provide an idea for tunable LSPR and the research of EM contributions to SERS.

Laser irradiation induced spectral evolution of the surface-enhanced Raman scattering(SERS) of 4-tert-butylbenzylmercaptan on gold nanoparticles assembly

The spectral evolution of the surface-enhanced Raman scattering (SERS) of 4-tert-butylbenzylmer-captan (4-tBBM) on gold nanoparticles assembly under laser irradiation is reported. The relative intensities of typical peaks in the spectrum of 4-tBBM gradually change with irradiation time. Comparison of the rate of spectral changes under several experimental conditions indicates that the surface plasmon resonance (SPR) induced heat in the gold nanoparticles assembly is the origin of the spectral evolution. During the process of self-assembly, 4-tBBM molecules do not form a compact ordered monolayer because of the spatial hindrance of the 4-tert-butyl end group. The heat induced by laser irradiation drives the 4-tBBM molecules to rearrange to a more stable orientation.

Silver-coated elevated bowtie nanoantenna arrays： Improving the near-field enhancement of gap cavities for highly active surface-enhanced Raman scattering

Improving hot-spot intensity is a key issue in surface-enhanced Raman scattering （SERS）. The bowtie nanoantenna （BNA） is an effective device used to concentrate light energy into a nanoscale volume and produce strong hot spots. Nanosphere lithography （NSL） is a large-area and low-cost technique to produce BNA arrays; however, the SERS activity of NSL-fabricated BNAs is limited. In this paper, we present a simple method to improve the SERS activity of conventional NSL-fabricated BNAs by modifying their geometry. The new configuration is termed ＂silver-coated elevated bowtie nanoantenna＂ （SCEBNA）. SCEBNAs perform intensive near-field enhancement in the gap cavities owing to the integrated contribution of the ＂lightning rod＂ effect, resonance coupling, and the formation of the plasmonic Fabry-Perot cavity. Experimental measurements and finite-difference time-domain simulations revealed that the hot-spot intensity and the substrate enhancement factor can be optimized by adjusting the silver thickness. The optimal sample has the capability of trace-amount detection with fine reproducibility.

Single-site surface-enhanced Raman scattering beyond spectroscopy

Recent progress in the observation of surface-enhanced Raman scattering （SERS） is reviewed to examine the possibility of finding a novel route for the effective photoexcitation of materials. The importance of well-controlled SERS experiments on a single molecule at a single site is discussed based on the difference in the information obtained from ensemble SERS measurements using mul- tiple active sites with an uncontrolled number of molecules. A single-molecule SERS observation performed at a mechanically controllable breaking junction with a simultaneous conductivity mea- surement provides clear evidence of the drastic changes both in the intensity and in the Raman mode selectivity of the electromagnetic field generated by localized surface plasmon resonance. Careful con- trol of the field at a few-nanometer-wide gap of a metal nanodimer results in the modification of the selection rule of electronic excitation of an isolated single-walled carbon nanotube. The examples shown in this review suggest that a single-site SERS observation could be used as a novel tool to find, develop, and implement applications of plasmon-induced photoexcitation of materials.

自适应随机共振算法用于微弱信号检测

An adaptive algorithm for extracting weak signal based on the theory of stochastic resonance(SR) was proposed. It was implemented by investigating the self correlation of the outputs of the bistable system(with different μ ). The results show that the self correlation will reach maximum when a sudden change of output occurs, and hence prove that SR is sensitive sharply to the change of the parameters μ , and also provide one novel method to express the outputs which hasnt been solved till now. The adaptive algorithm was also applied to analyze the weak Laser Raman spectrum of a CCl 4 sample(liquid in capillary) which was measured with SPEX 1403 Laser Raman spectrometer from 250 cm -1 to 418 cm -1 on 5 mW(output power of laser) . The spectrum was analyzed with the adaptive algorithm by varying the data to (-4 13, 3 50) and declining μ from 2 0 with step 0 01. The results obtained show that the adaptive algorithm was able to detect the weak signal automatically and correctly.

共振隧穿二极管的压阻特性测试与研究

设计并搭建了检测共振隧穿二极管(RTD)压阻特性的实验系统,测试了RTD结构在不同应力状态下I-V特性曲线的漂移.实验结果表明RTD结构压阻特性的灵敏度大于1×10-8Pa-1.为了更精确地定量表达其压阻特性,研究了同一RTD结构I-V特性的一致性,得到相同环境条件下RTD电阻的最大相对漂移量小于3%,其中1%由测试仪器造成.

基于周期调节的随机共振算法对化学弱信号的检测研究

提出了一种新的随机共振算法 ,通过对系统的周期进行调节以实现系统的共振 .讨论了实现共振的系统参数 ,并对模拟信号和拉曼光谱实验信号进行了处理 .结果表明 ,该方法不仅可方便地用于弱化学信号的处理 ,克服检出信号的滞后现象 。