Controllable Synthesis of Au NRs and Its Flexible SERS Optical Fiber Probe with High Sensitivity

The surface-enhanced Raman scattering(SERS) optical fiber probes were successfully prepared by self-assembling on polyelectrolyte multilayers. Gold nanorods(Au NRs) were used as SERS enhancement material to give excellent biological affinity and stability to the SERS optical fiber probes. Au NRs were synthesized by seed growth method. The synergistic effect between AgNO_(3) and surfactant was investigated, and the highest yield was found when AgNO_(3) was 500 uL. Meanwhile, different SERS optical fiber probes were obtained by selecting silane coupling agent, polyelectrolyte multilayer and graphene oxide(GO) to treat quartz fiber. It was found that the SERS optical fiber probes obtained by the self-assembled on polyelectrolyte multilayers method performed better than those by other methods. In addition, Mapping was combined with finite element simulation to analyze the electromagnetic field distribution at the fiber end face.The electromagnetic field distribution of Au NRs was investigated, the difference of electromagnetic field intensity around the Au NRs with different arrangements was compared, the strongest signal was obtained when the Au NRs were head-to-head. Finally, sensitivity of the optimized SERS optical fiber probes could reach 10^(-9)mol/L, with excellent stability and repeatability.

Au@Ag Core-shell Nanorods Self-assembled on Polyelectrolyte Multilayers for Ultra-High Sensitivity SERS Fiber Probes

We demonstrated a chemical process in the fabrication of a SERS fiber probe with an ultrahigh sensitivity.The synthesis was carried out by preparing Au@Ag core-shell nanorods (Au@Ag-NRs) selfassembled on polyelectrolyte (PE) multilayers,for which Au@Ag-NRs were controlled by adjusting the silver layer thickness.The effect of silver layer thickness of Au@Ag-NRs on the SERS performance of the fiber probe was investigated.The SERS fiber probe shows the best performance when the silver layer thickness is controlled at 8.57 nm.Under the condition of optimizing silver layer thickness,the fiber probe exhibits ultra-high sensitivity (i e,10^(-10) M crystalline violet,CV),good reproducibility (i e,RSD of 3.5%) and stability.Besides,electromagnetic field distribution of the SERS fiber probe was also investigated.The strongest enhancement is found within the core of fiber,whereas a weakened electromagnetic field exists in the fiber cladding layer.The SERS fiber probe can be a good candidate in ultra-trace detection for biomedical and environmental areas.

The Fabrication and SERS Performance of Multi-layer Hollow Au-Ag Alloy Nano Urchins Structure-based SERS Fiber Probe

Novel hollow Au Ag alloy nano urchins were synthesized via Ag seeds growth method,and self-assembly coated on the wall and end-tip of silica fiber for fiber probe fabrication.The nano urchins homogeneously distributed on fiber surface because of fiber silanization.The sizes and tip sharpness of the nano-urchins could be controlled by Ag seeds.The elements distribution analysis indicated there was high Ag content in tip-top for better surface enhance Raman scattering performance.The detectable concentration could be as low as 10-8 M using crystal violet molecules as analyte.Moreover,the fiber probes were stable in air,due to Au in the alloy.This fiber probe could be used for low content single molecular analysis.

Transmission Properties of Fiber Probes

Transmission properties of tapered fiber including right cone fiber and bend optical fiber are discussed.The transmission efficiency of the tapered fiber is measured.The curve of transmission efficiency versus taper cone angle is given.By the scalar wave equation and Gaussian approximation,transmission properties of the two kinds of tapered fibers are analyzed,the power losses caused by taper cone angle and by the bending are also calculated.From the experiments and theoretical analysis,it could come to a conclusion that the wider the taper cone angle is,the higher the transmission efficiency will be.

Optical trapping and orientation of Escherichia coli cells using two tapered fiber probes

We report on the optical trapping and orientation of Escherichia coli(E.coli) cells using two tapered fiber probes.With a laser beam at 980 nm wavelength launched into probe I, an E. coli chain consisting of three cells was formed at the tip of probe I. After launching a beam at 980 nm into probe II, the E.coli at the end of the chain was trapped and oriented via the optical torques yielded by two probes. The orientation of the E. coli was controlled by adjusting the laser power of probe II. Experimental results were interpreted by theoretical analysis and numericalsimulations.

Fabrication method of ultra-small gradient-index fiber probe

Fabrication method and device of ultra-small gradient-index （GRIN） fiber probe were investigated in order to explore the development of ultra-small probes for optical coherence tomography （OCT） imaging. The beam- expanding effect of no-core fiber （NCF） and the focusing properties of the GRIN fiber lens were analyzed based on the model of GRIN fiber probe consisting of single-mode fiber （SMF）, NCF and GRIN fiber lens. A stereo micro- scope based system was developed to fabricate the GRIN fiber probe. A fiber fusion splicer and an ultrasonic cleaver were used to weld and cut the fiber respectively. A con- focal microscopy was used to measure the dimensions of probe components. The results show that the sizes of probe components developed are at the level of millimeter. Therefore, the proposed experimental system meets the fabrication requirements of an ultra-small self-focusing GRIN fiber probe. This shows that this fabrication device and method can be employed in the fabrication of ultra- small self-focusing GRIN fiber probe and applied in the study of miniaturized optical probes and OCT systems.

Microball lens integrated fiber probe for optical frequency domain imaging

An integrated microball lens fiber catheter probe is demonstrated, which has better lateral resolution and longer working distance than a corresponding bare fiber probe with diverging beam for Fourier domain optical coherence tomography （FDOCT）. Simulation results are shown to gain the effect of the distance between the mieroball lens and the bare fiber to the focusing plane and beam width. The freedom of modifying the working distance and lateral resolution is shown. This is achieved by changing the gap distance between the single-mode fiber and the microball lens within the packaged surgical needle catheter without using an additional beam expander having a fixed length. The probe successfully acquired crosssectional images of ocular tissues from an animal sample with the proposed miniaturized imaging probe.

Zemax-Based Optimum Structural Design of Probe of an Optical-Fiber Sensor

Bubble plumes are important during the process of air-sea exchange,and optical-fiber phase detection is a suitable way to observe bubble plumes entrained by breaking waves.This paper designs a new optical-fiber probe(OFP)made of sapphire to overcome the limitations of existing materials(e.g.,high brittleness,poor corrosion resistance,and narrow bandwidth)and thereby enhance the detection performance of the OFP by improving its structure.Based on total internal reflection and light refraction,a simulation model of the probe is established in the Zemax optical design software to optimize the probe tip and matching mode of the two probe tips.The results show that the optimum OFP tip is a conical sapphire one with a cone angle of 35°.Tests are then conducted on a bespoke OFP sensor,the results of which are consistent with those predicted theoretically.The simulation results lay the foundation for the integrated design of OFP sensors and the optimization of their internal optics.The findings could also be applied to OFPs with multiple tips.

Fiber lenses for ultra-small probes used in optical coherent tomography

We present a design, construction and characterization of different variations of GRIN and ball fiber lenses, which were recently proposed for ultra-small biomedical imaging probes. Those fiber lens modules are made of a single mode fiber and a GRIN or ball fiber lens with or without a fiber spacer between them. The lens diameters are smaller than 0.3 mm. We discuss design methods, fabrication techniques, and measuring performance of the fiber lenses. The experimental results are compared to their modeling results. The fabrication of a high quality beam director for both lens types is presented as well. These fiber integrated beam directors could be added on the tips of the fiber lenses for side-view probes. A needle probe made by these fiber lenses is demonstrated as a sample of the ultra-small probe for biomedical imaging application. In vivo human finger images acquired by a swept source optical coherence tomography using the fiber lenses with different beam profiles were shown, which indicates the important impact of

基于光纤镀膜探针的固体介质中应力波粒子速度测量技术

粒子速度是分析固体介质中应力波传播规律的一个重要参数。结合激光多普勒效应和全光纤干涉测速系统,提出了一种基于光纤镀膜探针的固体介质中应力波粒子速度的测量方法。将光纤镀膜探针嵌入有机玻璃(PMMA)中,距爆心同一半径处,采用0.125 g TNT当量的微型炸药球作为爆炸源,进行填实爆炸产生应力波,通过采集光纤探针端面的运动信息,基于短时傅里叶变换的时频分析方法,解调出端面运动速度,进而反推出粒子速度。实验结果表明:不同光纤镀膜探针测得的速度分别为22.648 m/s、23.505 m/s,将反推的粒子速度与传统的圆环型电磁粒子速度计方法获取到的数据进行对比,两者的相对偏差低于5.00%,验证了光纤镀膜探针测量固体介质中应力波粒子速度的可行性。

大孔柚子型微结构光纤探针的表面增强拉曼散射性能研究

随着光纤制备工艺以及纳米材料制备技术的发展,光纤探针已成为一种新型的表面增强拉曼散射(SERS)基底,通过在普通单模光纤或多模光纤上制备不同的结构并修饰相应的纳米材料,可以得到多种类型的光纤表面增强拉曼散射探针,并实现较好的检测效果。但受限于光纤本身的结构,普通光纤仅能利用端面或侧表面提供拉曼检测的“热点”区域,限制了其SERS性能的进一步提高。因此制备了大孔柚子型微结构光纤(MSF)表面增强拉曼散射(SERS)探针,其中大孔柚子型MSF SERS探针结构通过一段阶跃多模光纤与柚子型微结构光纤熔接制得。实验分别对自制的纳米银溶胶基底以及大孔柚子型MSF SERS探针的SERS性能进行检测。采用溶胶自组装法制备负载银纳米颗粒的MSF SERS探针,通过控制自组装时间制备不同光纤SERS探针(Ag/MSF-x,其中x为自组装时间,分别为15、30、45、60 min)。采用溶液检测方法,利用Ag/MSF-x探针对10^(-3) mol·L^(-1)的亚甲基蓝(MB)探针分子进行检测,通过比较相同条件下的增强效果筛选得到Ag/MSF-45探针。为进一步检测Ag/MSF-45探针的SERS性能,制备不同浓度的MB溶液,分别利用纳米银溶胶基底和Ag/MSF-45探针对其进行检测。实验结果表明,纳米银溶胶基底对MB的检测限(LOD)为10^(-6) mol·L^(-1),Ag/MSF-45探针对MB的检测限(LOD)为10^(-7) mol·L^(-1);拉曼信号的再现性结果表明纳米银溶胶基底以及Ag/MSF-45探针在各个特征峰处的RSD值均在合理范围内;在1619 cm^(-1)拉曼位移处对纳米银溶胶基底以及Ag/MSF-45探针检测MB的拉曼强度和浓度进行对数转换拟合,纳米银溶胶基底的拟合优度R2达0.91628,Ag/MSF-45探针的拟合优度R2达0.98848;纳米银溶胶基底和Ag/MSF-45探针的再现性结果表明,其在各个特征峰处的RSD值均处于合理范围,但Ag/MSF-45探针的各特征峰RSD值均小于纳米银溶胶基底,最大为13.89%;利用10^(-6) mol·L^(-1)的MB对Ag/MSF-45探针的增强因子(AEF)进行计算,Ag/MSF-45探针的AEF达到6.09×10^(6),表现出良好的增强效果。因此,基于大孔柚子型MSF SERS探针凭借独特的空气孔结构使其具有较高的灵敏度以及良好的再现性,且其SERS性能均优于纳米银溶胶基底,在农业、化学分析、生物检测等领域及大分子物质检测等方面应用前景广泛。

光纤拉曼生化传感器研究进展

光纤拉曼生化传感器是一种基于拉曼散射原理的光纤传感器,它结合了拉曼散射光谱技术和光纤传输的优势,具有体积小、无需标记、高灵敏度和特异性,能够实现实时快速检测的特点,可以广泛应用于生化检测领域低浓度分析物的检测。对光纤拉曼生化传感器的基本原理、结构和工作方式进行相关介绍,以它在食品安全、环境监测和生物医学等多个领域的实际应用为切入点,重点介绍了不同结构光纤拉曼探针的制备过程和对实际分析物的检测限。此外,总结了当前光纤拉曼生物传感器面临的挑战和未来的发展方向,进一步就如何提高光纤拉曼传感器的性能进行了相关讨论。

加热光纤法同步测定土壤水热参数误差分析

土壤水热参数是研究土壤水热传输的基本物理参数。当前热脉冲探针法(HPP)可同步测定土壤水热参数,但该方法仅限于在点尺度下测定。与其具有相同理论基础的加热光纤法(SPHP-DTS),可将测定尺度增大至田间千米尺度,但其测定精度尚未得到有效验证。为了探知SPHP-DTS法的误差,本研究进行了SPHP-DTS法与HPP法测定土壤水热参数的对比试验。结果表明,以HPP为标准,加热光纤法测定热导率的精度RMSE为0.13 W×m^(-1)×℃^(-1)。SPHP-DTS法测定的热导率显著高于HPP法,主要原因在于加热光纤时产生的温度效应。通过热导率法测定土壤含水率时,在热导率测定误差的影响下,SPHP-DTS法的测定精度明显低于HPP法。SPHP-DTS法测定土壤水热参数的其他误差来源包括光纤与土壤之间多个界面的接触热阻、光纤的温度敏感性、噪音干扰以及温度梯度驱动下的水分迁移。本研究可为SPHP-DTS法提升土壤水热参数测定精度提供理论参考。

New Fluoroptic Therm ometer with Optical Fiber

A new optical fiber fluoroptic thermometer based on the temperature—fluoroptic characteristic of fluoroptic materials is presented.The ratio technique of intensities of fluorescent emission lines of certain rare earth phosphors is used,making the measurement of temperatures of the system to 0.5 ℃ precision. The characteristics of thermometer are discussed and the experiment results of temperature are given.

小型探针式FBG流量温度复合传感器

针对光纤布拉格光栅流量温度复合传感器存在压损大、量程窄、结构复杂的问题,提出了一种基于光纤布拉格光栅的小型探针式流量温度复合传感器。基于悬臂梁弯曲变形理论和光纤布拉格光栅传感机理,结合管道内流体流速分布特性,建立探针式流量温度复合传感模型,揭示了光纤布拉格光栅中心波长漂移量与流量温度的映射关系;采用有限元分析法研究了探针结构应变分布特性,确定了光纤布拉格光栅的最优粘贴位置;搭建实验系统平台,进行了温度和流量实验。温度实验结果表明,传感器的灵敏度为25 pm/℃,是裸光纤布拉格光栅的2.3倍,重复性误差为3.621%;流量实验结果表明,传感器测量范围为2~30 m^(3)/h,重复性误差为2.141%。与现有光纤光栅流量温度复合传感器相比,复合传感器压损更小、量程更宽。

光纤预制棒中元素的线分析定量化方法

采用电子探针显微分析法对光纤预制棒进行元素线分析定量化,光纤预制棒心部Yb和Al等元素的含量较低、基体效应的复杂影响以及测试条件的差异等因素导致线分析定量化结果误差较大。采用多点法的测试结果对光纤预制棒中Yb、Al元素的线分析定量化结果进行校正。结果表明:在两点法的基础上引入修正因子,可以简化测试过程,快速、准确地得到元素线分析定量化结果。

基于荧光寿命与热辐射测温的30℃至800℃的光纤温度传感器

通过研究荧光型光纤温度传感和热辐射型光纤温度传感,该文设计了一种结合荧光寿命与热辐射测温的光纤温度传感器,适用温度为30~800℃。首先,改进了传统的荧光传感探针,采用石英玻璃棒代替光纤,可避免高温下光纤吸收和散射损耗导致的光传输效率下降。其次,利用耐高温的Y(P,V)O_(4):Eu^(3+)荧光材料进行中、低温段(低于400℃)的荧光寿命测温,获得材料荧光寿命与温度的关系;在中、高温段(高于300℃),使用光功率计测得1490 nm波长下光纤探针的热辐射功率与温度的关系,并拟合得到热辐射功率与温度的四阶表达式;然后,在两种测温方法都有效的温度重叠区(300~360℃),使用荧光寿命测温值标定热辐射的功率与温度关系式,确保高温段的测温精度;最后,将荧光寿命测温与热辐射测温相结合,实现30~800℃范围内的温度测量。

近红外漫射光相关断层成像的乳腺光纤探头设计

为获得稳定的光学信号,提高近红外漫射光相关断层成像技术(diffuse correlation tomography,DCT)的诊断效率,本研究结合阵列式光开关,设计了一种适用于DCT的弧面式光学乳腺探头,可将DCT检测部位扩展到人体乳腺组织。为验证该乳腺探头的有效性及实用性,本研究设计了相应的乳腺仿体,并进行了仿体实验。结果表明,该乳腺探头可较好地契合DCT设备,并能捕捉微弱的血流变化,有望促进DCT技术在早期乳腺恶性肿瘤筛查中的临床应用。

用于油井相含率测量的光纤探针传感器研究

针对地面成熟三相流相含率测量传感器无法适应井下高温高压腐蚀的复杂环境,现有井下测量设备复杂,需要多种传感器和探头联合才能实现三相流相含率测量的问题,设计了一种光纤探针传感器。以蓝宝石作为光纤探针的前端敏感材料,利用气相和液相对光的折射率不同,通过检测探针反射光的光强来分辨光纤探针处于气相还是液相。通过检测经探针耦合进光纤的荧光光强分辨水相还是油相,从而实现单一探针传感器对油井内油相、水相、气相三相相含率的测量。

基于光纤探头的光电图像径向畸变校正方法

随着光电图像的广泛应用,图像畸变所带来的弊端日渐突显,为减少图像畸变影响,提升光电图像径向畸变校正效果,降低校正后失真程度,提出一种基于光纤探头的光电图像径向畸变校正方法。分析光纤探头的成像原理,确定被拍摄物体理想位置与发生畸变后位置的映射关系,根据径向RAC的摄像机标定方法构建光电图像畸变模型,根据畸变模型求逆解算得光电图像的径向畸变程度,光电图像畸变损失的计算,根据直线投影不变性原理构建光电图像的畸变损失函数,采用Levenberg-Marguardt算法对函数求解,获得最优畸变系数,实现光电图像径向畸变校正。实验结果表明,所提方法校正时图像旋转角度小,校正后失真程度小,更符合人眼的视觉习惯。