Compression of dry lysozyme targets: The target preparation pressure as a new parameter in protein thin film production by pulsed laser deposition
Compression of dry lysozyme targets: The target preparation pressure as a new parameter in protein thin film production by pulsed laser deposition
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DOI：
10.1016/j.apsusc.2019.03.089
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发表时间：
2019-07
影响因子：
6.7
通讯作者：
C. Constantinescu;A. Matei;M. Tabetah;M. Dinescu;L. Zhigilei;J. Schou
中科院分区：
文献类型：
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作者：
C. Constantinescu;A. Matei;M. Tabetah;M. Dinescu;L. Zhigilei;J. Schou
研究了由干法脉冲激光沉积(PLD)技术生产的鸡溶菌酶在压缩粉末靶材中的薄膜生长与靶材制备压力的关系。PLD是一种用于制造高质量无机材料薄膜的通用技术，但激光通常会在靶材中产生分子碎片，随后在沉积的薄膜中产生分子碎片。我们证明了在激光照射前压实靶材的压力是决定沉积速率和沉积分子碎裂程度的重要参数。沉积过程是在真空中进行的，使用压制压力在10-160 bar范围内制备的干靶。溶菌酶分子口袋中的残留水分会将碎片或完整的溶菌酶赶出靶标。在2 J/cm~2的中间注量下，随着压实压力从10 巴增加到160 巴，材料(碎片或完整分子)的沉积速度从每枪3到9 ngN/cm2。然而，在相同的压力范围内，完整分子的数量几乎下降了两个数量级。这是因为在较高的压缩压力下制备的目标材料具有更强的内聚力，因此需要更多的能量，从而需要更高的温度来启动材料喷射。在最高压缩压力下，这意味着没有完整的分子在喷射中幸存下来。结果表明，在一定的压力范围内，既可以获得合理的沉积速率，又可以获得相当一部分完整的分子。这些实验观察结果与粗粒分子动力学模拟的结果是一致的，在粗粒分子动力学模拟中，观察到完整的溶菌酶分子的比例随着辐照靶中最高温度的增加而消失。
Film growth of the well-known protein, chicken lysozyme, produced by the dry technique, pulsed laser deposition (PLD), from a compressed powder target has been investigated as a function of the target preparation pressure. PLD is a versatile technique for fabricating high quality films of inorganic materials, but the laser beam will typically produce fragments of molecules in the target and subsequently in the deposited films. We demonstrate that the pressure applied to compact the target prior to the laser irradiation is an important parameter that determines the deposition rate as well as the extent of fragmentation of the deposited molecules. The deposition process was carried out in vacuum using dry targets prepared with compaction pressure in the range 10–160 bar. The residual water in pockets of the lysozyme molecules drives fragments or intact lysozyme out of the target. At the intermediate fluence of 2 J/cm2, the deposition rate of the material (fragments or intact molecules) rises from 3 to 9 ng/cm2per shot as the compaction pressure increases from 10 to 160 bar. However, the number of intact molecules falls down by almost two orders of magnitude in the same pressure range. This is explained by a stronger cohesion of the target material prepared at higher compression pressure, such that more energy and thus a higher temperature are required for the onset of material ejection. At the highest compression pressure, it means that no intact molecules survive the ejection. The results indicate that there is a pressure range where both a reasonable deposition rate and a considerable fraction of intact molecules in the films can be achieved. These experimental observations are consistent with the results of coarse-grained molecular dynamics simulations, where the fraction of intact lysozyme molecules is observed to vanish as the maximum temperature in the irradiated target increases.