【作者】 陈敏；

【导师】 谢丽娟；

【作者基本信息】 浙江大学 ， 生物系统工程， 2018， 博士

【摘要】 四环素因疗效好、成本低,被广泛应用于养殖业中动物疾病预防与治疗。但四环素分子极不稳定,在生产和贮存过程中容易生成差向四环素、脱水四环素和差向脱水四环素等有害降解物。许多不法商家为了尽可能降低动物疾病风险和成本,将四环素生产过程中含大量降解物的发酵残液制成的粉末制剂直接作为饲料添加剂用于动物日常养殖中,导致动物体内四环素及其降解物残留,对消费者健康造成极大危害,因此对四环素及其有害降解物进行快速检测十分重要。太赫兹光谱技术,尤其太赫兹时域光谱(THz-TDS)技术,是近年来新兴的一种检测手段,与传统技术相比,具有安全、无损、快速等优点,目前已被广泛应用于生物及化学分子检测中。但由于技术上的不成熟,该技术的检测灵敏度较低,且由于水对太赫兹波的强烈吸收,对高吸收性液体检测较为困难。超材料是一种人工复合结构或材料,具有独特的电磁响应特性,可显著提高太赫兹光谱技术检测的灵敏度,已被广泛应用于太赫兹传感中。但由于水对太赫兹波的强烈吸收,对高吸收性液态样品中微量物质的检测仍是一大挑战。本文以食品中常见的盐酸四环素(TetracylineHydrochloride,TCH)及其降解物盐酸差向四环素(EpitetracylineHydrochloride,ETCH)、盐酸脱水四环素(Anhydrotetracyline Hydrochloride,ATCH)和盐酸差向脱水四环素(Epianhydrotetracyline Hydrochloride,EATCH)为研究对象,通过研究这4种物质的太赫兹特征谱并对其特征吸收峰进行解析,探索THz-TDS技术对这4种物质进行定性鉴别的可行性,并建立基于非对称双杆谐振器(ADWR)结合THz-TDS技术的TCH及其降解物水溶液检测方法体系,为液态食品中四环素及其降解物残留、其他抗生素残留的快速测定提供新思路。主要研究内容、结果和结论如下:(1)分析了 TCH及其降解物在常温下的太赫兹吸收光谱,并利用密度泛函(DFT)方法对它们的特征吸收峰的振动模式进行解析,结果表明:1)在0.2-1.8THz频段,TCH具有两个明显的特征吸收峰,分别位于0.77THz和1.40THz。ETCH具有5个较弱的特征吸收峰,分别位于 0.61THz、1.01THz、1.17THz、1.32THz 和 1.59THz 处。ATCH在0.88 THz和1.17 THz处具有两个较强特征吸收峰,在1.30 THz处有一个较弱特征吸收峰。EATCH则未观察到特征吸收峰。且整体而言,EATCH的吸收系数最高,TCH和ATCH次之,ETCH最低。同时,EATCH的折射率最大,TCH次之,ATCH再次之,ETCH最小。2)DFT分析结果表明,TCH在0.77THz处的特征吸收峰来自于分子内振动模式,实验测得而DFT计算未得到的1.40 THz处的特征吸收峰则可能来自于分子间相互作用如氢键结合作用引起的分子间振动模式或声子模式。ETCH在0.61 THz、1.01 THz、1.17 THz、1.32 THz和1.59 THz处的特征吸收峰来自于分子内振动模式。ATCH在0.88 THz处的特征吸收峰来自于分子内振动模式,实验测得而DFT计算未得到的1.17 THz和1.30 THz处的特征吸收峰则可能来自于分子间相互作用如氢键结合作用引起的分子间振动模式或声子模式。EATCH在0.2-1.8THz频段无特征吸收峰。结果表明,TCH及其降解物具有明显不同的太赫兹光谱特征,可利用这些光谱特征对其进行定性鉴别,且DFT方法能在一定程度上解析太赫兹特征吸收峰,为后续研究打下理论基础。(2)分析了不同温度下TCH及其降解物的太赫兹吸收光谱,结合DFT结果,进一步对这4种物质特征吸收峰的振动模式进行解析,结果表明:1)随着温度降低,TCH在0.2-1.8THz频段内的两个特征吸收峰发生频率移动,且1.40THz处的特征吸收峰的频率与温度的关系符合声子的频率-温度经验公式,结合DFT分析结果说明,TCH在0.77THz处的特征吸收峰来自于分子内振动模式,在1.40THz处的特征吸收峰则来自于分子间氢键振动势的非谐性引起的声子-声子散射。2)随着温度降低,ETCH在0.2-1.8 THz频段内的5个特征吸收峰发生频率移动,且所有特征吸收峰的频率与温度的关系均不符合声子的温度-频率经验公式,结合DFT分析结果说明,ETCH的这5个特征峰均来自于分子内振动模式。3)随着温度降低,ATCH在0.2-1.8 THz频段内的3个特征吸收峰发生频率移动,且1.17 THz处的特征吸收峰的频率与温度的关系符合声子的频率-温度经验公式。结合DFT分析结果说明,ATCH在0.88 THz处的特征吸收峰来自于分子内振动模式,1.17 THz处的特征吸收峰来自于分子间氢键振动势的非谐性引起的声子-声子散射,1.30 THz处的振动模式则来自于普通分子间振动模式。4)随着温度降低,EATCH在0.2-1.8THz频段均未发现可以辨别的特征吸收峰,说明EATCH在该频段无特征吸收峰,验证了 DFT分析结果。结果表明,研究TCH及其降解物的特征吸收峰随温度变化情况可进一步对其太赫兹特征吸收峰进行解析,揭示各自特征吸收峰的来源,为后续研究提供理论依据。(3)以简单的金属杆阵列作为基本研究结构,以Mylar薄膜作为基底,借助CST仿真软件分析了金属杆阵列的结构尤其相邻两杆的非对称度对其电磁响应特性的影响,并对其结构参数进行优化,以期获得在TCH及其降解物可定性鉴别的太赫兹频段具有多重共振模式、高共振强度和高灵敏度的超材料,并通过高吸收性水-甲醇混合溶液的实际检测验证其用于高吸收性液体太赫兹检测的可行性,结果表明:1)通过打破相邻金属双杆的对称性,可获得具有多重共振模式包括Fano共振、Fano透射峰和Dipole共振的非对称双杆谐振器(Asymmetric Dual-Wire Resonator,ADWR)结构。且随着双杆非对称度增加,Fano共振和Fano透射峰的灵敏度降低,Dipole共振的灵敏度增加,同时,Fano共振的强度增加。综合考虑共振强度和灵敏度,选择双杆长度分别为60μm和106μm的ADWR作为最终所用结构。所选择的ADWR的Dipole共振灵敏度最高,Fano透射峰次之,Fano共振灵敏度最低。2)随着水-甲醇混合液中水的浓度增加,ADWR的Fano共振、Fano透射峰及Dipole共振均发生红移,并伴随Fano透射峰的透过率逐渐降低,Fano共振、Fano透射峰及Dipole共振结合THz-TDS技术可实现的水-甲醇混合溶液的检测灵敏度分别达到93GHz/RIU、105GHz/RIU和160GHz/RIU。结果表明,所设计的ADWR结构具有多重共振模式、较高共振强度和灵敏度,且可有效用于高吸收性液体的太赫兹检测,为后续TCH及其降解物水溶液的高灵敏、高准确性太赫兹检测提供方法。(4)以太赫兹超材料检测常用的滴样干燥法制样,分析了基于滴样干燥法的ADWR结合THz-TDS技术的TCH及其降解物水溶液间接检测效果,结果表明:1)随着TCH及其降解物浓度增加,ADWR的3种共振模式均发生红移,并伴随Fano透射峰的透过率值降低,且Dipole共振发生的频移最大,Fano透射峰次之,Fano共振最小,与本文第四章所得的这3种共振模式的理论结果一致。同时,EATCH引起的3种共振模式的频移和Fano透射峰的透过率变化最大,TCH和ATCH次之,ETCH最小,与本文第二章所获得的这4种物质的折射率和吸收系数大小一致。2)PCA结果表明,ADWR的Fano共振、Fano透射峰和Dipole共振结合THz-TDS可检测到的TCH水溶液的最低浓度分别为0.1 mg/L,0.01 mg/L和0.01 mg/L,可检测到的ATCH和EATCH水溶液的最低浓度分别与TCH 一致,可检测到的ETCH水溶液的最低浓度则分别为0.1 mg/L,0.1 mg/L和0.1 mg/L,比法律规定的动物源性食品中四环素类抗生素的最高残留限量(0.1-0.6mg/L)更低,且可同时利用ADWR的3种共振模式进行检测提高TCH及其降解物检测的准确性。结果表明,基于滴样干燥法的ADWR结合THz-TDS技术在TCH及其降解物水溶液的间接高灵敏、商准确性太赫兹检测上具有一定的应用前景。(5)借助光程较小的液体池作为样品池,分析了基于液体池法的ADWR结合THz-TDS技术的TCH及其降解物水溶液直接检测效果,结果表明:1)对液体进行检测时,ADWR的3种共振模式尤其Dipole共振的共振强度明显降低,且3种共振模式尤其低频处的Fano共振和Fano透射峰随着样品浓度增加而发生蓝移,并伴随Fano透射峰的透过率值增加,与基于滴样干燥法获得的规律相反。对TCH和ATCH水溶液进行检测时,Fano共振发生的频移最大,Fano透射峰次之,Dipole共振最小。而对ETCH和EATCH水溶液进行检测时,Fano透射峰发生的频移最大,Fano共振次之,Dipole共振最小。2)PCA结果表明,ADWR的Fano共振、Fano透射峰和Dipole共振结合THz-TDS技术可直接检测到的TCH、ETCH、ATCH和EATCH水溶液的最低浓度均分别为10mg/L,10 mg/L和100mg/L,虽然没有达到动物源性食品中四环素类抗生素的最高残留限量(0.1-0.6 mg/L),但明显低于文献报道的基于普通液体池法(730 mg/L)和衰减全反射方法(450mg/L)得到的四环素类抗生素溶液的检测限,且可同时利用ADWR的3种共振模式进行检测提高TCH及其降解物水溶液检测的准确性。结果表明,基于液体池法的ADWR结合THz-TDS技术在TCH及其降解物水溶液直接、快速、较高灵敏度和商准确性太赫兹检测上具有一定的应用前景。更多还原

【Abstract】 Tetracycline is widely used to prevent and treat animal disease in animal breeding industry due to its good curative effect and low cost.However,tetracycline is seriously instable and can produce harmful degradation products including epitetracycline,anhydrotetracycline,and epianhydrotetracycline during its producing and reserving process.In order to reduce the risk of animal diseases and costs as much as possible,powder made from residual fermented liquid derived from tetracycline production process is used as feed additive for daily animals feeding by some illegal businessmen,which leads to the residual of tetracycline,epitetracycline,anhydrotetracycline,and epianhydrotetracycline in animal body and does great harm to human health.Therefore,it is very important to realize the fast detection of tetracycline and its degradation products.Terahertz spectroscopy,especially terahertz time-domain spectroscopy(THz-TDS),has been a newly developed detection method in recent years.Compared with traditional techniques,THz-TDS is safe,non-destructive and fast.It has been widely used in detection of biology and chemistry molecule.However,the sensitivity of THz-TDS is not very high due to the technical immaturity.Besides,water has strong absorption which causes the big difficulty of highly absorptive liquid detection using THz-TDS.Metamaterial is an artificial composite structure or material with unique electromagnetic response characteristics,which can significantly improve the sensitivity of terahertz spectroscopy detection and has been widely used in terahertz sensing.Nevertheless,the detection of highly absorptive solution remains a big challenge due to the strong absorption of water.In this study,common tetracyclines in food including tetracycline hydrochloride(TCH)and its degradation products including epitetracycline hydrochloride(ETCH),anhydrotetracycline hydrochloride(ATCH)and epianhydrotetracycline hydrochloride(EATCH)were used as research objects,we aim to prove the feasibility of qualitative identification of them using THz-TDS by studying their terahertz absorption spectra,and build a method system for their aqueous solutions detection based on asymmetric dual-wire resonator(ADWR)and THz-TDS,providing a new idea for the detection of tetracycline and its degradation product and other antibiotics residues in liquid foods.The main contents,results and conclusions are summarized as follows:(1)The terahertz spectra of TCH and its degradation products at room temperature were analyzed.The vibration modes of their characteristic absorption peaks,mainly the intramolecular vibration modes,were analyzed using density function theory(DFT)method.The results indicated:1)in 0.2-1.8 THz,TCH had two strong characteristic absorption peaks at 0.77 and 1.40 THz,respectively.ETCH had five weak characteristic absorption peaks at 0.61 THz,1.01 THz,1.17 THz,1.32 THz,and 1.59 THz,respectively.ATCH had two strong and one weak characteristic absorption peaks,which were located at 0.88 THz,1.17 THz and 1.30 THz,respectively.EATCH had no characteristic absorption peaks at 0.2-1.8 THz.And overall,the absorption coefficient of EATCH was the highest,followed by TCH and ATCH,and then ETCH.Besides,EATCH had the highest refractive index,followed by TCH,ATCH,and then ETCH.2)DFT results indicated the characteristic absorption peak of TCH at 0.77 THz was from intramolecular vibration,while the characteristic absorption peak at 1.40 THz was possible from intermolecular vibration modes.All the characteristic absorption peaks of ETCH were from intramolecular vibration modes.The characteristic absorption peak of ATCH at 0.88 THz is from intramolecular vibration,those of 1.17 THz and 1.30 THz are possible from the intermolecular vibration.EATCH has a lot of intramolecular vibration modes with close resonance intensity,and does not show characteristic absorption peaks.The results indicated that TCH and its degradation products had distinctly different terahertz spectra signatures,which allowed qualitative identification of them,and DFT could explain origin of terahertz characteristic absorption peaks in part,which built theoretical basis for follow-up studies.(2)The terahertz spectra of TCH and its degradation products under different temperatures were analyzed.Combined with DFT results,the vibrational modes of their characteristic absorption peaks,especially the intermolecular vibration modes,were further analyzed.The results indicated:1)with the decrease of temperature,the two characteristic absorption peaks of TCH in 0.2-1.8 THz moved,and the relationship between the frequency of characteristic absorption peak at 1.40 THz and temperature accorded with the empirical formula of resonant frequency and temperature of phonons.Combined with the result of the DFT analysis,the characteristic absorption peak at 0.77 THz of TCH was from intramolecular vibrational modes,and that at 1.40 THz was from the phonon-phonon scatting caused by the anharmonicity vibration potential of intermolecular hydrogen bond.2)with the decrease of temperature,the five characteristic absorption peaks of ETCH in 0.2-1.8 THz moved.And the relationship between the frequency of the five characteristic absorption peaks and temperature were not compl:iant with the empirical formula of frequency and temperature of phonons.Combined with the result of the DFT,the five characteristic absorption peaks of ETCH were all from intramolecular vibration modes.3)The characteristic absorption peaks of ATCH in 0.2-1.8 THz moved with decreasing temperature,and the relationship between the frequency of the characteristic absorption peak at 1.17 THz and temperature accorded with the phonon frequency-temperature empirical formula.Combined with the DFT results,the characteristic absorption peak of ATCH at 0.88 THz came from the intramolecular vibrational mode.The characteristic absorption peak at 1.17 THz resulted from the phonon-phonon scattering caused by anharmonicity vibration potential of intermolecular hydrogen bond.The vibrational mode at 1.3 THz came from the common mode of intermolecular vibration;4)No discernible characteristic absorption peak of EATCH is found in 0.2-1.8 THz under different temperature,which validated the DFT results.The results indicated that the origin of each characteristic absorption peak of TCH and its degradation products could be further analyzed and clarified by studying the temperature dependence of characteristic absorption peak,which provided theoretical foundation for follow-up studies.(3)Using simple metal-wire array as basic research structure and Mylar as the substrate,structure of metal-wire arry,especially asymmetry between adjacent wires on its electromagnetic characteristics was analyzed using CST simulaition software.The structure parameters of the metal-wire structure was optimized to obtain metamaterial which had multiple resonance modes,high resonance intensity,high sensitivity,and could be used for detection of highly absorptive solution in terahertz region where TCH and its degradation products could be qualitatively identified.And the optimal structure was used to detect the highly absorptive water-methanol mixed solution to verify the feasibility of terahertz detection of highly absorptive liquid using it.The results indicated:1)asymmetric dual-wire resonator(ADWR)with multiple resonances,including a Fano resonance dip,a Fano transmittance peak,and a Dipole resonance dip in 0.5-2.0 THz was obtained once the structural symmetry was breaking.With the asymmetry increased,the sensitivity of Fano resonance dip and Fano transmittance peak were decreased,that of Dipole resonance dip was increased,and the amplitude transmission of Fano transmittance peak was increased.After comprehensive consideration of resonance intensity and sensitivity,the ADWR with the length of the two wires to be 60 μm and 106μm were selected to be the final used structure.And the sensitivity of Dipole resonance dip of the selected ADWR was the highest,followed by Fano transmittance peak,and Dipole resonance dip.2)With the increase of water concentration in water-methanol mixture,the Fano resonance dip,Fano transmittance peak,and Dipole resonance of ADWR exhibited red shifts,and the transmittance of Fano transmittance peak decreased.And sensitivities of the Fano resonance dip,Fano transmittance peak,and dipole resonance dip for detection of TCH and its degradation products aqueous solution turned out to be 93 GHz/RIU,160 GHz/RIU,and 305 GHz/RIU.The results indicated that the designed ADWR had multiple resonances,higher resonance intensity,higher sensitivity,and could be effectively used for terahertz detection of highly absorptive liquid,which provided a method for following terahertz detection of TCH and its degradation products aqueous solution with high sensitivity and accuracy.(4)Using dropping-drying method,the common used sample preparation method in terahertz metamaterial detection to prepare sample,the indirect detection efficiency of aqueous solutions of TCH and its degradation products using ADWR combined with THz-TDS were analyzed.The results indicated:1)all resonance modes showed red shifts and the amplitude transmission of Fano transmittance peak decreased in terahertz absorption spectra with the increase of TCH and its degradation products concentration.And dipole resonance dip exhibited the largest frequency shift,followed by Fano transmittance peak and Fano resonance dip,which was in accord with their simulation results in Chapter 4 of this paper.Besides,EATCH caused the largest frequency shifts for the three resonance modes of ADWR and biggest transmittance change for the Fano transmittance peak,followed by TCH and ATCH,then ETCH,which related to the size of the refractive indices and absorption coefficients of these four substances in Chapter 2 of this paper.2)The PCA results indicated that the lowest detectable concentration of TCH aqueous solution using Fano resonance dip,Fano transmittance peak and dipole resonance dip combined with THz-TDS were 0.1 mg/L,0.01 mg/L and 0.01 mg/L,respectively,that of ATCH and EATCH was the same with TCH,and the lowest detectable concentration of ETCH aqueous were 0.1 mg/L,0.1 mg/L,and 0.1 mg/L,respectively.These results were smaller than the maximum residue limit(MRL)of tetracyclines in animal-origin food from international regulations(0.1-0.6 mg/L).Furthermore,the detection accuracy could be improved using all resonance modes of ADWR to detect TCH and its degradation products at the same time.The results indicated that dropping-drying method-based ADWR combined with THz-TDS had a certain application prospect in indirect teraherz detection of TCH and its degradation products aqueous solutions with high sensitivity and accuracy.(5)Using liquid cuvette with small pathlength as the sample cell,the direct detection efficiency of aqueous solutions of TCH and its degradation products using ADWR combined with THz-TDS were analyzed.The results indicated:1)the resonance intensity of the three resonance modes of ADWR decreased obviously,especially the Dipole resonance dip in detection of solutions.Besides,the three resonance modes,especially the Fano Resonance and Fano transmission peak in lower frequency region exhibited blue shifts,and the amplitude transmission of Fano transmittance peak increased with the increase of the concentration of sample solution,which was contrary to the results of the solid film.For TCH and ATCH aqueous solution detection,the frequency shift of Fano resonance dip was the most,followed by the Fano transmission peak and Dipole resonance dip.For ETCH and EATCH aqueous solution detection,the frequency shift of Fano transmittance peak was the most,followed by the Fano resonance dip and Dipole resonance dip.2)The PCA results indicated that the lowest detectable concentrations of TCH,ETCH,ATCH and EATCH aqueous solution using Fano resonance dip,Fano transmission peak and Dipole resonance dip of ADWR combined with THz-TDS were 10 mg/L,10 mg/L and 100 mg/L,respectively.Although it did not reach the MRL(0.1-0.6 mg/L)of the tetracycline antibiotic in animal-origin food from international regulations,it was significantly lower than reported limit of detection of tetracycline antibiotic solution by conventional liquid cuvette method(730 mg/L)and the attenuated total reflection method(450 mg/L).Besides,the detection accuracy could be improved using all resonance modes of ADWR to detect TCH and its degradation products at the same time.The results indicated that liquid cuvette-based ADWR combined with THz-TDS had a certain application prospect in direct,fast,higher sensitive and accurate teraherz detection of TCH and its degradation products aqueous solutions.更多还原