电场诱导水的太赫兹透射特性研究

Terahertz Transmission Characteristics of Water Induced by Electric Field

许多生物分子自身的转动、振动或分子团的整体振动模式都位于太赫兹波段内,因此可以利用太赫兹光谱技术对生物分子进行检测。同时又由于太赫兹波的光子能量仅为毫电子伏量级,不会对分子的内部结构造成破坏,所以太赫兹时域光谱技术在生物检测方面具有良好的应用前景。众所周知,绝大多数的生物分子只有在液体条件下才能发挥其生物活性,所以研究液体环境下生物分子之间的相互作用就非常必要。然而水分子的转动模式、振动模式以及和氢键有关的能量均处于太赫兹波段,从而对其产生强烈的吸收;另外,水分子为极性分子,而极性分子对太赫兹波有强烈的共振吸收,这就使利用太赫兹技术对生物分子活性进行动态表征产生了困难。因此在研究溶液中的生物分子与太赫兹波的相互作用时,最大限度地减小水分子对太赫兹波的吸收就成为近年来的研究热点。目前,减少水对太赫兹波吸收的主要方法有:在溶液样品中加入抑制氢键缔合的离子来减小水对太赫兹的吸收;通过改变溶液的温度来调节水对太赫兹的吸收;利用微流控芯片技术,通过减小被测样品与太赫兹波的作用距离来减小水对太赫兹波的吸收。另外,激光的激励、电场或磁场的处理,也能改变水对太赫兹波的吸收,将盛有去离子水的微流控芯片放于电场中,研究经电场处理不同时间的去离子水对太赫兹吸收强度的影响。结果发现,太赫兹波的透射强度随着去离子水在电场当中静置时间的增加而增强,当在电场中静置60 min时,太赫兹的频谱强度达到最大,与空气的频谱强度接近。由此可以推断外加电场使水分子的偶极矩发生了变化,从而对整体水分子的振动和转动产生了影响,并且改变了水中的氢键结构,导致了太赫兹透射光谱强度的增强。

Many biomolecules’rotation,vibration or the whole vibration mode of the molecular group are located in the terahertz band,so we can use terahertz spectrum technology to detect biomolecules.At the same time,because the photon energy of the terahertz wave is only millivolts,it will not damage the internal structure of molecules,so terahertz time-domain spectroscopy technology has a good application prospect in biological detection.As we all know,most biomolecules can only play their biological activities in the liquid environment,so it is necessary to study the interaction between biomolecules in the liquid environment.However,the rotation mode,vibration mode and the energy related to hydrogen bond of water molecules are all in the terahertz band,so they have strong absorption;in addition,water molecules are polar molecules,and polar molecules have strong resonance absorption for terahertz wave,which makes it difficult to use terahertz technology to characterize the activity of biomolecules dynamically.Therefore,in the study of the interaction between biomolecules and terahertz wave in solution,it has become a research hotspot in recent years to minimize water molecules’absorption to terahertz wave.At present,the main methods to reduce the absorption of THz wave by water are:adding ions that inhibit hydrogen bond association in solution samples to reduce the absorption of THz wave by water;adjusting the absorption of THz wave by water by changing the temperature of the solution;reducing the absorption of THz wave by water by reducing the distance between the sample and THz wave by using microfluidic chip technology.In addition,the excitation of laser,the treatment of electric field or magnetic field can also change the absorption of THz wave by water.In this paper,a microfluidic chip containing deionized water is put into the electric field to study the influence of deionized water treated by electric field for different time on THz wave’s absorption intensity.The results show that THz wave’s transmission intensity increases with the increase of the standing time of deionized water in the electric field.When standing in the electric field for 60 minutes,the spectrum intensity of the THz wave reaches the maximum,close to that of air.It can be concluded that the applied electric field changes the dipole moment of water molecules,which affects the vibration and rotation of water molecules as a whole,and changes the hydrogen bond structure in water,resulting in the enhancement of the THz transmission spectrum.