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.

3D printed fiber-optic nanomechanical bioprobe

Ultrasensitive nanomechanical instruments,e.g.atomic force microscopy(AFM),can be used to perform delicate biomechanical measurements and reveal the complex mechanical environment of biological processes.However,these instruments are limited because of their size and complex feedback system.In this study,we demonstrate a miniature fiber optical nanomechanical probe(FONP)that can be used to detect the mechanical properties of single cells and in vivo tissue measurements.A FONP that can operate in air and in liquids was developed by programming a microcantilever probe on the end face of a single-mode fiber using femtosecond laser two-photon polymerization nanolithography.To realize stiffness matching of the FONP and sample,a strategy of customizing the microcantilever’s spring constant according to the sample was proposed based on structure-correlated mechanics.As a proof-of concept,three FONPs with spring constants varying from 0.421 N m^(−1)to 52.6 N m^(−1)by more than two orders of magnitude were prepared.The highest microforce sensitivity was 54.5 nmμN^(−1)and the detection limit was 2.1 nN.The Young’s modulus of heterogeneous soft materials,such as polydimethylsiloxane,muscle tissue of living mice,onion cells,and MCF-7 cells,were successfully measured,which validating the broad applicability of this method.Our strategy provides a universal protocol for directly programming fiber-optic AFMs.Moreover,this method has no special requirements for the size and shape of living biological samples,which is infeasible when using commercial AFMs.FONP has made substantial progress in realizing basic biological discoveries,which may create new biomedical applications that cannot be realized by current AFMs.

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.

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.

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

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.

Mapping an on-chip terahertz antenna by a scanning near-field probe and a fixed field-effect transistor

In the terahertz（THz） regime,the active region for a solid-state detector usually needs to be implemented accurately in the near-field region of an on-chip antenna.Mapping of the near-field strength could allow for rapid verification and optimization of new antenna/detector designs.Here,we report a proof-of-concept experiment in which the field mapping is realized by a scanning metallic probe and a fixed AlGaN/GaN field-effect transistor.Experiment results agree well with the electromagnetic-wave simulations.The results also suggest a field-effect THz detector combined with a probe tip could serve as a high sensitivity THz near-field sensor.

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.

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。

EFFECTIVE DETECTION DEPTH OF NEEDLE-LIKE OPTICAL PROBE

The effective detection depth of the needle-like optical probe is studied. The light transport model in highly scattering tissue is the diffusion equation and the boundary is Neuman. The sensitivity matrix is related to the position of the light source and the detector. It can be used to evaluate the effective detection depth. The sensitivity matrix is defined as the multiplication of the source and detector hght distribution. Six different groups about ix parameters including the source diameter and detector fibers, the core-to-core distance between the source and detector fibers, the opotode depth, the absorption, and reduced scattering coefficient, are used as experimental models. The relationship between the six parameters and the effective detection depth is analyzed. Resuits can be used to study the spatial resolution and the depth of multi-fibers.

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。

Particle Velocity Sensor and Its Application in Near-Field Noise Scanning Measurement

The Particle Velocity Sensor (PVS) is a kind of acoustic transducer which measures the particle velocity directly with figure-of-eight directivity. This paper proposes a near-field noise scanning technology based on the research of PVS, pressure-particle velocity (P-U) probe, and its application in noise source identification. Firstly, the principle and characteristics of PVS are presented. Secondly, a P-U probe is designed on the basis of PVS development. Finally, the noise measurement experiment for a single source is arranged and conducted. The result shows that the proposed P-U probe performs well in near-field noise source identification and localization.

Review of reflective fiber optic sensors for surface topography measurement

Different from the traditional contact surface topography measurement,reflective intensity-modulated fiber optic sensor(RIM-FOS)has the unique advantages of non-contact nondestructive detection.This paper briefly introduces the principle and performance of RIM-FOS for surface topography measurement and compares with several other methods of topography measurement.Based on the review of its development process,this paper summarizes and analyses the hot issues of RIM-FOS in the surface topography measurement,then predicts the future trend for a guidance of the further study.

New Optical Fiber Pressure Sensor with Reflection Capsule

The ratio measurement by means of the sensing optical fiber and the reference fiber with different beginning positions, and the technique to improve the stability of the sensor are first described. Then the ability to restrain and compensate the interference of the same nature through the double channel ratio measurement is illustrated. Finally, the performance of sensor and its engineering design are discussed.

New Measuring Temperature Setup with Optical Probe

Abstract: A new setup of measuring temperature is developed, which the probe is a micro- power consumptive one with CMOS circuit and is driven by optical power. For transmitting the measured signal and optical power signal in a long distance, the fiber technology is applied in this setup.

Far-Field Pattern Reconstruction from Positioning Errors Affected Near-Field Data Acquired via Helicoidal Scanning

In this paper, an effective technique to compensate the positioning errors in a near-field—far-field (NF-FF) transformation with helicoidal scanning for elongated antennas is presented and validated both numerically and experimentally. It relies on a nonredundant sampling representation of the voltage measured by the probe, obtained by considering the antenna as enclosed in a cylinder ended in two half-spheres. An iterative scheme is used to reconstruct the helicoidal NF data at the points fixed by the representation from the acquired irregularly spaced ones. Once the helicoidal data have been retrieved, those needed by a classical NF-FF transformation with cylindrical scanning are efficiently evaluated by using an optimal sampling interpolation algorithm. Some numerical tests, assessing the accuracy of the approach and its stability with respect to random errors affecting the data, are reported. Experimental tests performed at the Antenna Characterization Lab of the University of Salerno further confirm the validity of the proposed technique.

Spherical Near-Field - Far-Field Transformation for Quasi-Planar Antennas from Irregularly Spaced Data

An effective near-field - far-field (NF - FF) transformation with spherical scanning for quasi-planar antennas from irregularly spaced data is developed in this paper. Two efficient approaches for evaluating the regularly spaced spherical samples from the nonuniformly distributed ones are proposed and numerically compared. Both the approaches rely on a nonredundant sampling representation of the voltage measured by the probe, based on an oblate ellipsoidal modelling of the antenna under test. The former employs the singular value decomposition method to reconstruct the NF data at the points fixed by the nonredundant sampling representation and can be applied when the irregularly acquired samples lie on nonuniform parallels. The latter is based on an iterative technique and can be used also when such a hypothesis does not hold, but requires the existence of a biunique correspondence between the uniform and nonuniform samples, associ- ating at each uniform sampling point the nearest irregular one. Once the regularly spaced spherical samples have been recovered, the NF data needed by a probe compensated NF - FF transformation with spherical scanning are efficiently evaluated by using an optimal sampling interpolation algorithm. It is so possible to accurately compensate known posi- tioning errors in the NF - FF transformation with spherical scanning for quasi-planar antennas. Some numerical tests assessing the accuracy and the robustness of the proposed approaches are reported.

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.