电场对溶液相变过程影响的热刺激去极化电流分析

Thermally-stimulated Depolarization Current Analysis on the Phase Transition of Biological Solution Under Electric Field

为了研究电场对冰晶形成及冰晶结构影响的内部机理,采用热刺激去极化电流(TSDC)测量方法对生物溶液进行了热刺激去极化电流特性的研究,从而根据热刺激去极化电流峰值位置与大小判断电场在溶液相变过程中的作用。以去离子水和氯化钠NaCl生理盐水(其中NaCl质量分数为0.9%)为试样,对比测量了对试样加电场和不加电场条件下的热刺激去极化电流特性。结果表明,在生物溶液低温冷冻过程中施加电场会影响冰晶的结构组成并宏观表现为微小热刺激去极化电流。去离子水冰的热刺激去极化电流曲线上分别在125 K和213 K温度附近出现2个明显的电荷释放峰,其中低温峰是由于玻璃态下水分子偶极转向极化而产生的,高温峰则源于陷阱中空间电荷的释放。而对于生理盐水,只能观察到在138 K温度附近有1个峰,然后随着温度的升高而呈不断增大趋势,可能是由于生理盐水冰中Na+、Cl-热离子极化电导所致。研究表明热刺激去极化电流测量方法可以作为一个分析外加电场对生物溶液低温保存影响机理的有效手段。

In order to investigate the underlying mechanism of icecrystallization influenced by electric field, we per formed thermally stimulated current depolarization（TSDC） measurements on specimens of doubledistilled water and NaC1 aqueous solution （the mass fraction of NaC1 is 0.9%） to determine the role of electric field in the solutions＇ crystal lization according to the position and magnitude of the obtained depolarization current. The experimental results indicate that, with decreasing temperature, the crystallization structure of the tested solutions will be influenced by the ap plied electric field, and this influence can be detected as a tiny thermallystimulated depolarization current. Two chargerelease peaks are observed in pure ice, of which the highertemperature peak at around 215 K results from the re lease of trapped space charges and the lowertemperature one at about 125 K is attributed to the relaxation of orientation depolarization of the water molecules. However, only one peak at near 138 K is observed in saline ice, and the peak ele vates with the increase of temperature. This could be possibly induced by the polarization conductance of Na＋ and C1 ions in saline. It is concluded that TSDC may he an effective tool to elucidate some unrevealed principles of cryopreser vation controlled by electric field.